Electrical and Electronics Engineering publications abstract of: 11-2017 sorted by title, page: 17

» Sketch-Based Articulated 3D Shape Retrieval
Abstract:
Sketch-based queries are a suitable and superior alternative to traditional text- and example-based queries for 3D shape retrieval. The authors developed an articulated 3D shape retrieval method that uses easy-to-obtain 2D sketches. In contrast to existing sketch-based retrieval systems that lower the 3D database models to 2D, their algorithm implicitly lifts the 2D query to 2.5D by inferring depth information from possibly self-intersecting sketches using a good continuation rule. It does not require 3D example models to initiate queries, but results show that it achieves accuracy comparable to a state-of-the-art example-based 3D shape retrieval method.
Autors: Yusuf Sahillioğlu;Metin Sezgin;
Appeared in: IEEE Computer Graphics and Applications
Publication date: Nov 2017, volume: 37, issue:6, pages: 88 - 101
Publisher: IEEE
 
» Slack Inspection Method of High-Tension Bolt Using Electromagnetic Field Without Influence of Lift-Off Between Bolt Head and Inspection Sensor
Abstract:
In the automobile industry, the simple inspection method of detecting the slack of the high-tension bolt in the engine section is desired. Since the permeability of the compression direction inside the steel is decreased when the steel material is compressed, the permeability of the compressed domain in the bolt is decreased when the fastened force of the bolt is increased. Therefore, the evaluation of the slack of the bolt is possible by detecting the difference of the magnetic characteristics near the compressed position in the bolt. However, the detection signal is also influenced by the change of distance (lift-off) between the bolt and an electromagnetic sensor. In this paper, the inspection method for measuring the slack of the bolt taking account of the lift-off is proposed using the 3-D edge-based hexahedral nonlinear finite element method and the experimental verification.
Autors: Yuji Gotoh;Nozomi Shigematsu;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Small Curvature Sensor Based on Butterfly-Shaped Mach–Zehnder Interferometer
Abstract:
A novel and small curvature sensor based on the butterfly-shaped Mach–Zehnder interferometer is proposed and experimentally demonstrated. The sensing element is a tapered hollow-core fiber sandwiched between two single-mode fibers. The fusion-collapsed region around the first fusion interface excites the high-order modes, and the butterfly-shaped structure couples the high-order modes back into the core and interferes with the fundamental mode in the second fusion-collapsed interface. Simulation of the butterfly-shaped structure is carried out by the beam propagation method to determine an optimized size of sensing element. The experimental results show that the light intensity variation of the interference spectrum is almost linearly proportional to the change of curvature, and the curvature sensitivity and resolution of the proposed sensor can be up to −10.9041 dB/m−1 and 0.000917 m−1, respectively, in the range from 0.387 to 1.285 m−1. The proposed curvature sensor is compact in size, high sensitive, and inexpensive. The excellent electromagnetic interference resistance and fabrication simplicity make the device an attractive candidate for curvature measurement in harsh environments.
Autors: Yong Zhao;Mao-qing Chen;Feng Xia;Lu Cai;Xue-Gang Li;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Nov 2017, volume: 64, issue:11, pages: 4644 - 4649
Publisher: IEEE
 
» Small-Signal Model for 2D-Material Based FETs Targeting Radio-Frequency Applications: The Importance of Considering Nonreciprocal Capacitances
Abstract:
A small-signal equivalent circuit of 2D-material based FETs is presented. Charge conservation and nonreciprocal capacitances have been assumed, so the model can be used to make reliable predictions at both device and circuit levels. In this context, explicit and exact analytical expressions of the main radio-frequency figures of merit of these devices are given. Moreover, a direct parameter extraction methodology is provided based on S-parameter measurements. In addition to the intrinsic capacitances, transconductance and output conductance, our approach allows extracting the series combination of drain–source metal contact and access resistances. Accounting for these extrinsic resistances is of upmost importance when dealing with low dimensional FETs.
Autors: Francisco Pasadas;Wei Wei;Emiliano Pallecchi;Henri Happy;David Jiménez;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Nov 2017, volume: 64, issue:11, pages: 4715 - 4723
Publisher: IEEE
 
» Smart Grid Simulations and Their Supporting Implementation Methods
Abstract:
In this tutorial we present the state-of-the-art as well as new methods for simulating various planning, operation, stability, reliability, and economic models of electric power systems. The discussion is driven by both first-principle models and empirical models. First-principle models result from the fundamental physics and engineering principles that govern the behavior of various components of a grid. Empirical models, on the other hand, are models that result from statistics and data analysis. We overview a wide spectrum of applications starting from planning models with a time-scale of simulation in years to real-time models where the time-scale can be in the order of milliseconds. We present a list of simulation software popularly used by the power engineering research community across the world. The increasingly important roles of power electronics, communication and computing, model aggregation, hybrid simulation, faster-than-real-time simulation, and co-simulation in emulating the daily operation of a grid are enumerated. The importance of research testbeds for testing, verification and validation of complex grid models at various temporal and spatial scales is also highlighted. The overall goal is to provide a vision on how simulations and their supporting implementation methods can help us in understanding the evolving behavior of tomorrow’s power networks as a truly intelligent cyber-physical system.
Autors: Aranya Chakrabortty;Anjan Bose;
Appeared in: Proceedings of the IEEE
Publication date: Nov 2017, volume: 105, issue:11, pages: 2220 - 2243
Publisher: IEEE
 
» Smartphone-Based Gait Recognition: From Authentication to Imitation
Abstract:
This work evaluates the security strength of a smartphone-based gait recognition system against zero-effort and live minimal-effort impersonation attacks under realistic scenarios. For this purpose, we developed an Android application, which uses a smartphone-based accelerometer to capture gait data continuously in the background, but only when an individual walks. Later, it analyzes the recorded gait data and establishes the identity of an individual. At first, we tested the performance of this system against zero-effort attacks by using a dataset of 35 participants. Later, live impersonation attacks were performed by five professional actors who are specialized in mimicking body movements and body language. These attackers were paired with their physiologically close victims, and they were given live audio and visual feedback about their latest impersonation attempt during the whole experiment. No false positives under impersonation attacks, indicate that mimicry does not improve chances of attackers being accepted by our gait authentication system. In 29 percent of total impersonation attempts, when attackers walked like their chosen victim, they lost regularity between their steps which makes impersonation even harder for attackers.
Autors: Muhammad Muaaz;René Mayrhofer;
Appeared in: IEEE Transactions on Mobile Computing
Publication date: Nov 2017, volume: 16, issue:11, pages: 3209 - 3221
Publisher: IEEE
 
» Snowpack Density Retrieval Using Fully Polarimetric TerraSAR-X Data in the Himalayas
Abstract:
This paper focuses on the development of a novel algorithm for deriving snowpack density over the snow-covered region of the Himalayas. The analysis utilizes fully polarimetric TerraSAR-X synthetic aperture radar data sets, field observations, and other ancillary information for the retrieval of snowpack density. The algorithm involves the development of a new generalized hybrid decomposition model. The generalized volume scattering parameter from the decomposition model is inverted for snow density estimation. A few field data measurements’ campaigns were carried out, within near-real time of satellite passing over the area, to collect various parameters such as temperature, water content, and the density of the snowpack at varying depths. These field observations are further used for validation of the results obtained from the inversion algorithm. It is also found that the model-estimated snowpack density is highly congruent with the field-measured snowpack density. The mean absolute error of snowpack density, root-mean-square error, and index of agreement are found to be 9.9 kg/, 10 kg/, and 0.96, respectively, which are well within the acceptable range.
Autors: Gulab Singh;Ashutosh Verma;Sanjeev Kumar; Snehmani;Ashwagosha Ganju;Yoshio Yamaguchi;Anil V. Kulkarni;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6320 - 6329
Publisher: IEEE
 
» Social-Aware Rate Based Content Sharing Mode Selection for D2D Content Sharing Scenarios
Abstract:
Device-to-device (D2D) content sharing has become a promising solution to support the growing popularity of multimedia contents for local services. Considering the randomness of content location, the limited storage and transmission capability of devices, and the coexistence of altruistic and selfish user behaviors, how to optimally match the demanders to the providers of contents and how to stimulate an efficient cooperation are of importance for achieving the full benefits of D2D content sharing. Especially when the base-station-to-device (B2D), D2D, and novel multi-D2D sharing modes coexist, the issue of content sharing mode selection plays the predominant role in such matching. In this paper, we introduce a notion of social-aware rate, which combines the social selfishness from the social knowledge with the link rate to ensure the physical link quality and the effective cooperation together. Then, the social-aware rate-based content sharing mode selection problem is modeled as a maximum weighted mixed matching problem, which can be computationally reduced to a submodular welfare problem subject to a matroid constraint. Subsequently, we develop a best-effort distributed algorithm framework, which displays alternatives of various computation complexities and approximation ratios to satisfy the diverse practical needs.
Autors: Dan Wu;Liang Zhou;Yueming Cai;
Appeared in: IEEE Transactions on Multimedia
Publication date: Nov 2017, volume: 19, issue:11, pages: 2571 - 2582
Publisher: IEEE
 
» Soft Magnetic Properties of Thin Nanocrystalline Particles Due to the Interplay of Random and Coherent Anisotropies
Abstract:
We investigated coercive fields of 200 nm nm nm rectangular nanocrystalline thin films as a function of grain size using finite-element simulations. To this end, we created granular finite-element models with grain sizes ranging from 5 to 60 nm, and performed micromagnetic hysteresis calculations along the -axis (easy direction) as well as along the -axis (hard direction). We then used an extended random anisotropy model to interpret the results and to illustrate the interplay of random anisotropy and shape-induced anisotropy, which is coherent on a much larger scale, in thin films.
Autors: Anton Bachleitner-Hofmann;Bernhard Bergmair;Thomas Schrefl;Armin Satz;Dieter Suess;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 6
Publisher: IEEE
 
» Soft Prosthetic Forefinger Tactile Sensing via a String of Intact Single Mode Optical Fiber
Abstract:
We report a prosthetic forefinger with distributed tactile sensing capability based on an embedded single mode fiber (SMF) sensor. We developed a human-size prosthetic forefinger by using soft silicon rubber via a fast wax-casting procedure. A strand of SMF was directly embedded along the palmar side of the prosthetic forefinger. For the first time to our knowledge, an SMF sensor is embedded in a soft silicon rubber-made prosthetic forefinger for distributed tactile sensing that eases the fabrication processes and affords judicious way in large-area, high-resolution applications. Our tactile sensor is interrogated with a distributed Rayleigh backscattering-based optical frequency domain reflectometry system. A series of experiments were conducted to verify the proposed tactile sensor. The reported soft silicon rubber-made prosthetic forefinger with built-in fiber optic sensors opens up promising possibilities for the development of sensing abilities and feedback strategies in artificial intelligence.
Autors: Yang Du;Qingbo Yang;Jie Huang;
Appeared in: IEEE Sensors Journal
Publication date: Nov 2017, volume: 17, issue:22, pages: 7455 - 7459
Publisher: IEEE
 
» Software Toolbox for Low-Frequency Conductivity and Current Density Imaging Using MRI
Abstract:
Objective: Low-frequency conductivity and current density imaging using MRI includes magnetic resonance electrical impedance tomography (MREIT), diffusion tensor MREIT (DT-MREIT), conductivity tensor imaging (CTI), and magnetic resonance current density imaging (MRCDI). MRCDI and MREIT provide current density and isotropic conductivity images, respectively, using current-injection phase MRI techniques. DT-MREIT produces anisotropic conductivity tensor images by incorporating diffusion weighted MRI into MREIT. These current-injection techniques are finding clinical applications in diagnostic imaging and also in transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and electroporation where treatment currents can function as imaging currents. To avoid adverse effects of nerve and muscle stimulations due to injected currents, conductivity tensor imaging (CTI) utilizes B1 mapping and multi-b diffusion weighted MRI to produce low-frequency anisotropic conductivity tensor images without injecting current. This paper describes numerical implementations of several key mathematical functions for conductivity and current density image reconstructions in MRCDI, MREIT, DT-MREIT, and CTI. Methods: To facilitate experimental studies of clinical applications, we developed a software toolbox for these low-frequency conductivity and current density imaging methods. This MR-based conductivity imaging (MRCI) toolbox includes 11 toolbox functions which can be used in the MATLAB environment. Results: The MRCI toolbox is available at http://iirc.khu.ac.kr/software.html . Its functions were tested by using several experimental datasets, which are provided together with the toolbox. Conclusion: Users of the toolbox can focus on experimental designs and interpretations of reconstructed images instead of developing their own image reconstruction softwares. We expect more toolbox functions to be added from future research outcomes.
Autors: Saurav Z. K. Sajib;Nitish Katoch;Hyung Joong Kim;Oh In Kwon;Eung Je Woo;
Appeared in: IEEE Transactions on Biomedical Engineering
Publication date: Nov 2017, volume: 64, issue:11, pages: 2505 - 2514
Publisher: IEEE
 
» Solar Photovoltaic and Thermal Energy Systems: Current Technology and Future Trends
Abstract:
Solar systems have become very competitive solutions for residential, commercial, and industrial applications for both standalone and grid connected operations. This paper presents an overview of the current status and future perspectives of solar energy (mainly photovoltaic) technology and the required conversion systems. The focus in the paper is put on the current technology, installations challenges, and future expectations. Various aspects related to the global solar market, the photovoltaic (PV) modules cost and technology, and the power electronics converter systems are addressed. Research trends and recommendations for each of the PV system sectors are also discussed.
Autors: Mariusz Malinowski;Jose I. Leon;Haitham Abu-Rub;
Appeared in: Proceedings of the IEEE
Publication date: Nov 2017, volume: 105, issue:11, pages: 2132 - 2146
Publisher: IEEE
 
» Solving the 5G Mobile Antenna Puzzle: Assessing Future Directions for the 5G Mobile Antenna Paradigm Shift
Abstract:
Advances in antenna technologies for cellular hand-held devices have been synchronous with the evolution of mobile phones over nearly 40 years. Having gone through four major wireless evolutions [1], [2], starting with the analog-based first generation to the current fourth-generation (4G) mobile broadband, technologies from manufacturers and their wireless network capacities today are advancing at unprecedented rates to meet our unrelenting service demands. These ever-growing demands, driven by exponential growth in wireless data usage around the globe [3], have gone hand in hand with major technological milestones achieved by the antenna design community. For instance, realizing the theory regarding the physical limitation of antennas [4]-[6] was paramount to the elimination of external antennas for mobile phones in the 1990s. This achievement triggered a variety of revolutionary mobile phone designs and the creation of new wireless services, establishing the current cycle of cellular advances and advances in mobile antenna technologies.
Autors: Wonbin Hong;
Appeared in: IEEE Microwave Magazine
Publication date: Nov 2017, volume: 18, issue:7, pages: 86 - 102
Publisher: IEEE
 
» SonoNet: Real-Time Detection and Localisation of Fetal Standard Scan Planes in Freehand Ultrasound
Abstract:
Identifying and interpreting fetal standard scan planes during 2-D ultrasound mid-pregnancy examinations are highly complex tasks, which require years of training. Apart from guiding the probe to the correct location, it can be equally difficult for a non-expert to identify relevant structures within the image. Automatic image processing can provide tools to help experienced as well as inexperienced operators with these tasks. In this paper, we propose a novel method based on convolutional neural networks, which can automatically detect 13 fetal standard views in freehand 2-D ultrasound data as well as provide a localization of the fetal structures via a bounding box. An important contribution is that the network learns to localize the target anatomy using weak supervision based on image-level labels only. The network architecture is designed to operate in real-time while providing optimal output for the localization task. We present results for real-time annotation, retrospective frame retrieval from saved videos, and localization on a very large and challenging dataset consisting of images and video recordings of full clinical anomaly screenings. We found that the proposed method achieved an average F1-score of 0.798 in a realistic classification experiment modeling real-time detection, and obtained a 90.09% accuracy for retrospective frame retrieval. Moreover, an accuracy of 77.8% was achieved on the localization task.
Autors: Christian F. Baumgartner;Konstantinos Kamnitsas;Jacqueline Matthew;Tara P. Fletcher;Sandra Smith;Lisa M. Koch;Bernhard Kainz;Daniel Rueckert;
Appeared in: IEEE Transactions on Medical Imaging
Publication date: Nov 2017, volume: 36, issue:11, pages: 2204 - 2215
Publisher: IEEE
 
» Spaceborne Observations of the Diurnal Variation of Shortwave Aerosol Direct Radiative Effect at Top of Atmosphere Over the Dust-Dominated Arabian Sea and the Atlantic Ocean
Abstract:
The ScaRaB payload onboard the low-inclination Megha-Tropiques (MT) satellite has been making observations of radiative fluxes at the top of the atmosphere (TOA) for different local times (LTs) of the day over the tropics since October 2011. This provides a unique opportunity to investigate the diurnal variation of the regional instantaneous aerosol direct radiative effect efficiency (IADREE) at TOA, which is otherwise not possible using the available long-term satellite observations carried out using similar sensors onboard polar sun-synchronous satellites. In this paper, the diurnal variations of the IADREE over the Arabian Sea and the Atlantic Ocean during June–September, when both these regions are engulfed by large-scale mineral dust plumes transported from the adjoining deserts, are investigated using collocated multiyear (2012–2014) observations of the MT-ScaRaB measured shortwave fluxes and MODIS-derived aerosol optical depth. The estimates of the IADREE made using the MT-ScaRaB data at 13:30 LT are found to be in agreement with those derived from the Cloud and the Earth’s Radiant Energy System data at this LT, at which the latter observations are carried out. The IADREE derived from the MT-ScaRaB shows diurnal peak value of −53 ± 10 Wm and −40 ± 3 Wm at solar zenith angle of ~40° over the Arabian Sea and the Atlantic Ocean, respectively. Diurnal mean aerosol direct radiative effect efficiency at TOA during June–September is −22 ± 4.5 Wm over the Arabian Sea and −18 ± 3.6 Wm over the Atlantic Ocean.
Autors: Manoj Kumar Mishra;Ashok Kumar Gupta;K. Rajeev;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6610 - 6616
Publisher: IEEE
 
» SPACF: A Secure Privacy-Preserving Authentication Scheme for VANET With Cuckoo Filter
Abstract:
Vehicular ad-hoc networks (VANETs) have been emerging based on the state-of-art technologies in wireless and network communications. The message authentications between vehicles and roadside units are essential for the security of VANETs. Messages should be signed and verified before they could be trusted. The real identity of vehicles should not be revealed, but which is only traceable by authorized parties. Existing solutions either rely heavily on a tamper-proof hardware device or cannot satisfy the security requirement. Communication overhead as another issue has also not been well addressed in previously reported studies. To address these issues, in this paper, we propose the SPACF scheme that is based on software without relying on any special hardware. We use the Cuckoo filter and the binary search methods to achieve higher success rate than the previous schemes in the batch verification phase. In order to guarantee that it can satisfy message authentication requirement, existential unforgeability of underlying signature against adaptively chosen-message attack is proved under the elliptic curve discrete logarithm problem in the random oracle model. The evaluation results show that our proposed scheme is more efficient than the previous schemes since it is pairing free and does not use map-to-point hash functions, and it satisfies security and privacy requirements of vehicular ad hoc networks.
Autors: Jie Cui;Jing Zhang;Hong Zhong;Yan Xu;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Nov 2017, volume: 66, issue:11, pages: 10283 - 10295
Publisher: IEEE
 
» Sparse Array Quiescent Beamformer Design Combining Adaptive and Deterministic Constraints
Abstract:
In this paper, we examine sparse array quiescent beamforming for multiple sources in interference-free environment. To maximize the output signal-to-noise ratio (SNR), the beamformer design comprises two intertwined stages, the determination of beamforming weights and the reconfiguration of array structure. The SNR maximization may produce high sidelobe levels, making the receiver vulnerable to interferences. We consider the problem of achieving maximum SNR beamforming subject to specified quiescent pattern constraints and, as such, combine both adaptive and deterministic approaches for sparse array configurations. We employ two convex relaxation methods and an iterative linear fractional programming algorithm to solve the nonconvex antenna selection problem for sparse array beamformers. Simulation examples demonstrate that the array configuration plays a vital role in determining the beamforming performance in interference-free scenarios.
Autors: Xiangrong Wang;Moeness Amin;Xianghua Wang;Xianbin Cao;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Nov 2017, volume: 65, issue:11, pages: 5808 - 5818
Publisher: IEEE
 
» Sparse Bayesian Learning-Based Seismic Denoise by Using Physical Wavelet as Basis Functions
Abstract:
Attenuating random noise is a fundamental yet necessary step for subsequent seismic image processing and interpretation. We introduce a sparse Bayesian learning (SBL)-based seismic denoise method by using the physical wavelet as the basis function. The physical wavelet estimated from seismic and well logging data can appropriately describe the characteristics of the seismic data. Thus, it is an appropriate choice of basis function. Moreover, the tradeoff regularization parameter for determining denoise quality can be adaptively estimated according to the updated data misfit and sparseness degree during the iterative process of the SBL algorithm. The motivation behind the denoise method using sparse representations is that seismic signals can be sparsely represented by using several physical wavelets, whereas noise cannot. Both synthetic and real seismic data examples are adopted to demonstrate the effectiveness of the method.
Autors: Li Deng;Sanyi Yuan;Shangxu Wang;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Nov 2017, volume: 14, issue:11, pages: 1993 - 1997
Publisher: IEEE
 
» Sparse Bayesian Learning-Based Time-Variant Deconvolution
Abstract:
In seismic exploration, the wavelet-filtering effect and -filtering (amplitude attenuation and velocity dispersion) effect blur the reflection image of subsurface layers. Therefore, both wavelet- and -filtering effects should be reduced to retrieve a high-quality subsurface image, which is significant for fine reservoir interpretation. We derive a nonlinear time-variant convolution model to sparsely represent nonstationary seismograms in time domain involving these two effects and present a time-variant deconvolution (TVD) method based on sparse Bayesian learning (SBL) to solve the model to obtain a high-quality reflectivity image. The SBL-based TVD essentially obtains an optimum posterior mean of the reflectivity image, which is regarded as the inverted reflectivity result, by iteratively solving a Bayesian maximum posterior and a type-II maximum likelihood. Because a hierarchical Gaussian prior for reflectivity controlled by model-dependent hyper-parameters is adopted to approximately represent the fact that reflectivity is sparse, SBL-based TVD can retrieve a sparse reflectivity image through the principled sequential addition and deletion of -dependent time-variant wavelets. In general, strong reflectors are acquired relatively earlier, whereas weak reflectors and deep reflectors are imaged later. The method has the capacity to avoid false artifacts represented by sequential positive or negative reflectivity spikes with short two-way travel time, which typically occur within stationary deconvolution outcomes. Synthetic, laboratorial, and field data examples are used to demonstrate the effectiveness of the method and illustrate its advantages over SBL-based stationary deconvolution and TVD using an -norm or an -norm regularization. The results show that SBL-based TVD is a potentially effective, stable, and high-quality imaging tool.
Autors: Sanyi Yuan;Shangxu Wang;Ming Ma;Yongzhen Ji;Li Deng;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6182 - 6194
Publisher: IEEE
 
» Sparse Distributed Multitemporal Hyperspectral Unmixing
Abstract:
Blind hyperspectral unmixing jointly estimates spectral signatures and abundances in hyperspectral ima-ges (HSIs). Hyperspectral unmixing is a powerful tool for analyzing hyperspectral data. However, the usual huge size of HSIs may raise difficulties for classical unmixing algorithms, namely, due to limitations of the hardware used. Therefore, some researchers have considered distributed algorithms. In this paper, we develop a distributed hyperspectral unmixing algorithm that uses the alternating direction method of multipliers and sparse regularization. The hyperspectral unmixing problem is split into a number of smaller subproblems that are individually solved, and then the solutions are combined. A key feature of the proposed algorithm is that each subproblem does not need to have access to the whole HSI. The algorithm may also be applied to multitemporal HSIs with due adaptations accounting for variability that often appears in multitemporal images. The effectiveness of the proposed algorithm is evaluated using both simulated data and real HSIs.
Autors: Jakob Sigurdsson;Magnus O. Ulfarsson;Johannes R. Sveinsson;José M. Bioucas-Dias;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6069 - 6084
Publisher: IEEE
 
» Spatial Downscaling of SMAP Soil Moisture Using MODIS Land Surface Temperature and NDVI During SMAPVEX15
Abstract:
The Soil Moisture Active Passive (SMAP) mission provides a global surface soil moisture (SM) product at 36-km resolution from its L-band radiometer. While the coarse resolution is satisfactory to many applications, there are also a lot of applications which would benefit from a higher resolution SM product. The SMAP radiometer-based SM product was downscaled to 1 km using Moderate Resolution Imaging Spectroradiometer (MODIS) data and validated against airborne data from the Passive Active L-band System instrument. The downscaling approach uses MODIS land surface temperature and normalized difference vegetation index to construct soil evaporative efficiency, which is used to downscale the SMAP SM. The algorithm was applied to one SMAP pixel during the SMAP Validation Experiment 2015 (SMAPVEX15) in a semiarid study area for validation of the approach. SMAPVEX15 offers a unique data set for testing SM downscaling algorithms. The results indicated reasonable skill (root-mean-square difference of 0.053 m3/m3 for 1-km resolution and 0.037 m3/m3 for 3-km resolution) in resolving high-resolution SM features within the coarse-scale pixel. The success benefits from the fact that the surface temperature in this region is controlled by soil evaporation, the topographical variation within the chosen pixel area is relatively moderate, and the vegetation density is relatively low over most parts of the pixel. The analysis showed that the combination of the SMAP and MODIS data under these conditions can result in a high-resolution SM product with an accuracy suitable for many applications.
Autors: Andreas Colliander;Joshua B. Fisher;Gregory Halverson;Olivier Merlin;Sidharth Misra;Rajat Bindlish;Thomas J. Jackson;Simon Yueh;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Nov 2017, volume: 14, issue:11, pages: 2107 - 2111
Publisher: IEEE
 
» Spatial Group Sparsity Regularized Nonnegative Matrix Factorization for Hyperspectral Unmixing
Abstract:
In recent years, blind source separation (BSS) has received much attention in the hyperspectral unmixing field due to the fact that it allows the simultaneous estimation of both endmembers and fractional abundances. Although great performances can be obtained by the BSS-based unmixing methods, the decomposition results are still unstable and sensitive to noise. Motivated by the first law of geography, some recent studies have revealed that spatial information can lead to an improvement in the decomposition stability. In this paper, the group-structured prior information of hyperspectral images is incorporated into the nonnegative matrix factorization optimization, where the data are organized into spatial groups. Pixels within a local spatial group are expected to share the same sparse structure in the low-rank matrix (abundance). To fully exploit the group structure, image segmentation is introduced to generate the spatial groups. Instead of a predefined group with a regular shape (e.g., a cross or a square window), the spatial groups are adaptively represented by superpixels. Moreover, the spatial group structure and sparsity of the abundance are integrated as a modified mixed-norm regularization to exploit the shared sparse pattern, and to avoid the loss of spatial details within a spatial group. The experimental results obtained with both simulated and real hyperspectral data confirm the high efficiency and precision of the proposed algorithm.
Autors: Xinyu Wang;Yanfei Zhong;Liangpei Zhang;Yanyan Xu;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6287 - 6304
Publisher: IEEE
 
» Spatial Power Combiner With Low-Impedance Inputs and Increased Isolation
Abstract:
A 2.5-, 8-way, 1–6 GHz spatial power combiner with increased isolation is presented. Insertion losses are better than 1.8 dB on the 1–6 GHz, except on a few peaks. Isolation is better than −10 dB for 45° inputs pairs and better than −15 dB for other pairs. This power combiner provides wide bandwidth, high isolation, and low input impedance at the same time.
Autors: Hadrien Theveneau;Christophe Gaquière;Romain Lenglet;Matthieu Werquin;Jean-Christophe Joly;Stèphane Tortel;
Appeared in: IEEE Microwave and Wireless Components Letters
Publication date: Nov 2017, volume: 27, issue:11, pages: 956 - 958
Publisher: IEEE
 
» Spatial-Aware Hierarchical Collaborative Deep Learning for POI Recommendation
Abstract:
Point-of-interest (POI) recommendation has become an important way to help people discover attractive and interesting places, especially when they travel out of town. However, the extreme sparsity of user-POI matrix and cold-start issues severely hinder the performance of collaborative filtering-based methods. Moreover, user preferences may vary dramatically with respect to the geographical regions due to different urban compositions and cultures. To address these challenges, we stand on recent advances in deep learning and propose a Spatial-Aware Hierarchical Collaborative Deep Learning model (SH-CDL). The model jointly performs deep representation learning for POIs from heterogeneous features and hierarchically additive representation learning for spatial-aware personal preferences. To combat data sparsity in spatial-aware user preference modeling, both the collective preferences of the public in a given target region and the personal preferences of the user in adjacent regions are exploited in the form of social regularization and spatial smoothing. To deal with the multimodal heterogeneous features of the POIs, we introduce a late feature fusion strategy into our SH-CDL model. The extensive experimental analysis shows that our proposed model outperforms the state-of-the-art recommendation models, especially in out-of-town and cold-start recommendation scenarios.
Autors: Hongzhi Yin;Weiqing Wang;Hao Wang;Ling Chen;Xiaofang Zhou;
Appeared in: IEEE Transactions on Knowledge and Data Engineering
Publication date: Nov 2017, volume: 29, issue:11, pages: 2537 - 2551
Publisher: IEEE
 
» Spatially Adaptive Sparse Representation for Target Detection in Hyperspectral Images
Abstract:
As sparse representation gradually obtains better and better results in the analysis of hyperspectral imagery and sparsity-based algorithms are becoming more and more popular, especially in target detection. However, these methods mostly assume an absolute equal contribution by all neighboring pixels while detecting the central pixel. There is no doubt that this approach is unsuitable for pixels located in heterogeneous areas. In this letter, to address this problem, spatially adaptive sparse representation for target detection in hyperspectral images (HSIs) is proposed. Neighboring spatial information is utilized by considering the different contributions of the distinct neighborhood pixels. The different weights are determined according to the similarity between the neighboring pixels and the central test pixel. The proposed algorithm was tested on two HSIs and demonstrated outstanding detection performance when compared with other commonly used detectors.
Autors: Yiming Zhang;Bo Du;Yuxiang Zhang;Liangpei Zhang;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Nov 2017, volume: 14, issue:11, pages: 1923 - 1927
Publisher: IEEE
 
» Spatially and spectrally flexible scheduling with time-slotted lightpath-switching
Abstract:
Optical wavelength-routed networks enable parallel transmission of massive datasets on nonover-lapping wavelength channels. However, as the sizes of scientific workflows increase, the availability of multi-wavelength resources will fall short of supporting application needs. Rather, these resources must be allocated intelligently, efficiently, and flexibly to bear the burden of high-volume science. We propose lightpath-switching to support modification to the set of wavelength/route resources used to carry and transmit a lightpath signal intermittently throughout its lifetime. Lightpath-switching exposes the scheduler to flexible consumption of unused, fragmented resources during the request schedule but requires neither underlying network technology nor equipment enhancement. We explore the efficacy of lightpath-switching in terms of wavelength-switching, path-switching, and a combination of the two techniques. We prove these problems are NP-complete and develop optimization models and efficient heuristics to quantitatively and qualitatively evaluate the solution space against optimality benchmarks. Our evaluations consider cross-dimension resource consumption from the time, space, and spectrum domains, and our findings indicate great potential for increasing network-wide resource savings, particularly via wavelength-switching. Furthermore, evidence is presented to defend the claim that spectral flexibility has a greater impact on resource utilization efficiency than spatial flexibility.
Autors: Jeremy M. Plante;Vinod M. Vokkarane;
Appeared in: IEEE/OSA Journal of Optical Communications and Networking
Publication date: Nov 2017, volume: 9, issue:11, pages: 945 - 959
Publisher: IEEE
 
» Spatially Consistent Street-by-Street Path Loss Model for 28-GHz Channels in Micro Cell Urban Environments
Abstract:
This paper considers a fundamental issue of path loss (PL) modeling in urban micro cell (UMi) environments, namely the spatial consistency of the model as the mobile station moves along a trajectory through street canyons. This paper is motivated by the observed non-stationarity of the PL. We show that the traditional model of power law PL plus log-normally distributed variations can provide misleading results that can have serious implications for system simulations. Rather, the PL parameters have to be modeled as random variables that change from street to street and also as a function of the street orientation. Variations of the PL, taken over the ensemble of the whole cell (or multiple cells), thus consist of the compound effect of these PL parameter variations together with the traditional shadowing variations along the trajectory of movement. Ray-tracing results demonstrate that ignoring this effect can lead to a severe overestimation of the local standard deviation in a given area. Then, a spatially consistent stochastic street-by-street PL model is established, and a parameterization for 28-GHz UMi cells is given. The model correctly describes the PL as a function of the street orientation as well as the large variance observed for all the PL model parameters.
Autors: Aki Karttunen;Andreas F. Molisch;Sooyoung Hur;Jeongho Park;Charlie Jianzhong Zhang;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Nov 2017, volume: 16, issue:11, pages: 7538 - 7550
Publisher: IEEE
 
» Spatio-Temporal Analysis of Passenger Travel Patterns in Massive Smart Card Data
Abstract:
Metro systems have become one of the most important public transit services in cities. It is important to understand individual metro passengers’ spatio-temporal travel patterns. More specifically, for a specific passenger: what are the temporal patterns? what are the spatial patterns? is there any relationship between the temporal and spatial patterns? are the passenger’s travel patterns normal or special? Answering all these questions can help to improve metro services, such as evacuation policy making and marketing. Given a set of massive smart card data over a long period, how to effectively and systematically identify and understand the travel patterns of individual passengers in terms of space and time is a very challenging task. This paper proposes an effective data-mining procedure to better understand the travel patterns of individual metro passengers in Shenzhen, a modern and big city in China. First, we investigate the travel patterns in individual level and devise the method to retrieve them based on raw smart card transaction data, then use statistical-based and unsupervised clustering-based methods, to understand the hidden regularities and anomalies of the travel patterns. From a statistical-based point of view, we look into the passenger travel distribution patterns and find out the abnormal passengers based on the empirical knowledge. From unsupervised clustering point of view, we classify passengers in terms of the similarity of their travel patterns. To interpret the group behaviors, we also employ the bus transaction data. Moreover, the abnormal passengers are detected based on the clustering results. At last, we provide case studies and findings to demonstrate the effectiveness of the proposed scheme.
Autors: Juanjuan Zhao;Qiang Qu;Fan Zhang;Chengzhong Xu;Siyuan Liu;
Appeared in: IEEE Transactions on Intelligent Transportation Systems
Publication date: Nov 2017, volume: 18, issue:11, pages: 3135 - 3146
Publisher: IEEE
 
» Special Photonic Crystal Modal Interferometer for Highly Sensitive Biosensing
Abstract:
We present an all-fiber Mach–Zehnder modal interferometer based on a special photonic crystal fiber taper and its performance as a transducer for biological sensing. The sensor showed refractive index sensitivity around 722.3 nm/RIU for measurements between 1.30864 and 1.32014 RIU We investigated the interferometer as a transducer for an immunosensor system after immobilization of an antigen over the activated taper waist, where it detected the interaction between antigen and antibody achieving a record detection limit of 125 pg/ml of antibody concentration. This extra low detection limit allows the modal interferometer to be used in biosensing applications, such as disease diagnosis, or in the food industry.
Autors: Juan Esteban Betancur-Ochoa;Vladimir P. Minkovich;Yeison Javier Montagut-Ferizzola;
Appeared in: Journal of Lightwave Technology
Publication date: Nov 2017, volume: 35, issue:21, pages: 4747 - 4751
Publisher: IEEE
 
» Special Section on the 2017 International Conference on Compound Semiconductor Manufacturing Technology (CS-MANTECH)
Abstract:
As guest editors for the special section on the 2017 International Conference on Compound Semiconductor Manufacturing Technology (CS-MANTECH), we are pleased to present IEEE Transactions on Semiconductor Manufacturing readers with a selection of papers based on work presented at this year’s conference. The CS-MANTECH conference provides a technical forum for presenting advances in compound semiconductor devices and associated manufacturing technologies. The high performance of devices based on compound semiconductors has long made them the material of choice in RF, microwave, and millimeter-wave systems. While advances continue to be made in these traditional applications, compound semiconductors are increasingly finding their way into power systems via SiC and GaN device technologies, and are also increasingly integrated with silicon-based technologies to provide enhanced system-level performance and functionality. In addition, narrow-gap III-Vs are being explored as alternative-channel materials for aggressively-scaled logic.
Autors: Celicia Della-Morrow;Drew Hanser;Patrick Fay;
Appeared in: IEEE Transactions on Semiconductor Manufacturing
Publication date: Nov 2017, volume: 30, issue:4, pages: 448 - 449
Publisher: IEEE
 
» Spectra Measurements Using Piezoelectric Diaphragms to Detect Burn in Grinding Process
Abstract:
Researchers have evaluated a great number of monitoring techniques in order to control the surface condition of ground parts. Piezoelectric diaphragms of lead zirconate titanate are used in many fields, but these sensors are not common in the monitoring of the machining processes. This paper proposes a method for monitoring the workpiece surface condition (normal grinding and burn) by using a piezoelectric diaphragm and feature extraction techniques. A comparison is made with a conventional acoustic emission sensor, which is a traditional sensor in the monitoring of the machining processes. Grinding tests were performed in a surface-grinding machine with Society of Automotive Engineers (SAE) 1045 steel and cubic boron nitride (CBN) grinding wheel, where the signals were collected at 2 MHz. The workpieces were thoroughly analyzed through visual inspection, surface roughness and hardness measurements, and metallographic analyses. Study on the frequency content of both signals was carried out in order to select bands closely related to the workpiece surface condition. Digital filters were applied to the raw signals and features were extracted and analyzed. The root mean square values filtered in the selected bands for both sensors presented a better fitting to the linear regression, which is highly desirable for setting a threshold to detect burn and implementing into a monitoring system. Also, the basic damage index results show an excellent behavior for grinding burn monitoring for both sensors. The method was verified by using a different grinding wheel, which clearly shows its effectiveness and demonstrates the potential use of the low-cost piezoelectric diaphragm for grinding burn monitoring.
Autors: Danilo M. S. Ribeiro;Paulo R. Aguiar;Luiz F. G. Fabiano;Doriana M. D’Addona;Fabricio Guimarães Baptista;Eduardo C. Bianchi;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Publication date: Nov 2017, volume: 66, issue:11, pages: 3052 - 3063
Publisher: IEEE
 
» Spectral Efficiency Analysis for Downlink NOMA Aided Spatial Modulation With Finite Alphabet Inputs
Abstract:
As the conventional spatial modulation (SM) system lacks an efficient downlink multiple access scheme, this paper proposes a novel downlink nonorthogonal multiple access aided multiple-input multiple-output SM system with finite alphabet inputs. Mutual information (MI) is used to characterize the system's achievable spectral efficiency (SE). Because the MI lacks a closed-form formulation, in this paper we propose a computational-efficient lower bound to provide an approximation to the simulated MI. Besides, preprocessing is also designed at the receiver to mitigate the detrimental effect of channel correlation, which leads to striking a higher SE performance. Simulation results not only confirm the accuracy of our SE analysis, but also substantiate the superior SE performance achieved by the proposed preprocessing.
Autors: Xuesi Wang;Jintao Wang;Longzhuang He;Jian Song;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Nov 2017, volume: 66, issue:11, pages: 10562 - 10566
Publisher: IEEE
 
» Spectral-Element Method With Divergence-Free Constraint for 2.5-D Marine CSEM Hydrocarbon Exploration
Abstract:
Rapid simulations of large-scale low-frequency subsurface electromagnetic measurements are still a challenge because of the low-frequency breakdown phenomenon that makes the system matrix extremely poor-conditioned. Hence, significant attention has been paid to accelerate the numerical algorithms for Maxwell’s equations in both integral and partial differential forms. In this letter, we develop a novel 2.5-D method to overcome the low-frequency breakdown problem by using the mixed spectral element method with the divergence-free constraint and apply it to solve the marine-controlled-source electromagnetic systems. By imposing the divergence-free constraint, the proposed method considers the law of conservation of charges, unlike the conventional governing equation for these problems. Therefore, at low frequencies, the Gauss law guarantees the stability of the solution, and we can obtain a well-conditioned system matrix even as the frequency approaches zero. Several numerical experiments show that the proposed method is well suited for solving low-frequency electromagnetic problems.
Autors: Yuanguo Zhou;Mingwei Zhuang;Linlin Shi;Guoxiong Cai;Na Liu;Qing Huo Liu;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Nov 2017, volume: 14, issue:11, pages: 1973 - 1977
Publisher: IEEE
 
» Spectrally Efficient Channel Estimation for Asynchronous Amplify-and-Forward Two-Way Relay Networks
Abstract:
In this paper, we consider the problem of channel estimation for asynchronous amplify-and-forward (AF) two-way relay networks. We propose a novel semi-blind channel estimation algorithm for this problem based on the expectation-maximization (EM) framework. The proposed EM algorithm has low complexity, and only a small number of EM iterations are needed to achieve convergence. The semi-blind Cramer-Rao bound (CRB) for channel estimation in asynchronous AF two-way relay networks is also obtained. Using simulations, we show that the proposed EM algorithm significantly outperforms pilot-based estimation by using only a limited number of received data samples in addition to the pilot samples. Furthermore, the achieved mean-squared error performance almost overlaps with the obtained CRB. Finally, a semi-blind generalized likelihood ratio testing (GLRT) method is proposed to tackle sequence arriving order (SAO) detection at the terminals and is shown to yield a higher probability of detection than the pilot-based GLRT for SAO detection.
Autors: Saeed Abdallah;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Nov 2017, volume: 16, issue:11, pages: 7333 - 7347
Publisher: IEEE
 
» Spelling With a Small Mobile Brain-Computer Interface in a Moving Wheelchair
Abstract:
Research into brain-computer interfaces (BCIs), which spell words using brain signals, has revealed that a desktop version of such a speller, the edges paradigm, offers several advantages: This edges paradigm outperforms the benchmark row-column paradigm in terms of accuracy, bitrate, and user experience. It has remained unknown whether these advantages prevailed with a new version of the edges paradigm designed for a mobile device. This paper investigated and evaluated in a rolling wheelchair a mobile BCI, which implemented the edges paradigm on small displays with which visual crowding tends to occur. How the mobile edge paradigm outperforms the mobile row-column paradigm has implications for understanding how principles of visual neurocognition affect BCI speller use in a mobile context. This investigation revealed that all the advantages of the edges paradigm over the row-column paradigm prevailed in this setting. However, the reduction in adjacent errors for the edges paradigm was unprecedentedly limited to horizontal adjacent errors. The interpretation offered is that dimensional constraints of visual interface design on a smartphone thus affected the neurocognitive processes of crowding.
Autors: Qasem T. Obeidat;Tom A. Campbell;Jun Kong;
Appeared in: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Publication date: Nov 2017, volume: 25, issue:11, pages: 2169 - 2179
Publisher: IEEE
 
» Spin Diffusion Length in Ferromagnet/Superconductor Bilayers
Abstract:
We report a systematic study on the bilayers of ferromagnetic Sm1–xSrxMnO3 (SSMO) and superconducting YBa2Cu3O7 (YBCO). The bilayer structure is composed of one SSMO layer of 10-nm thickness and one layer of YBCO of various thicknesses. The measurements of X-ray diffraction/reflectivity, resistivity, and magnetization were carried out for determining the crystalline properties and the superconducting temperatures of bilayers. A significant suppression of superconducting temperature is observed in all bilayers, indicating that the spin-polarized quasi-particles of SSMO are efficiently injected into the YBCO layer. The experimental results will be discussed in term of the spin diffusion length of polarized quasi-particles with a model of inverse proximity.
Autors: S. L. Cheng;T. H. Chuang;J. G. Lin;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Spin-Current Manipulation of Photo-Induced Magnetization Dynamics in Heavy Metal/Ferromagnet Double Layer-Based Nanostructures
Abstract:
Spin currents offer a way to control static and dynamic magnetic properties, and therefore, they are crucial for the next-generation magnetoresistive random access memory devices or spin-torque oscillators. Manipulating the dynamics is especially interesting within the context of photo-magnonics. In typical 3d transition metal ferromagnets, such as CoFeB, the lifetime of light-induced magnetization dynamics is restricted to about 1 ns, which, e.g., strongly limits the opportunities to exploit the wave nature in a magnonic crystal filtering device. Here, we investigate the potential of spin currents to increase the spin-wave lifetime in a functional bilayer system, consisting of a heavy metal [8 nm of -Tantalum (Platinum)] and 5 nm CoFeB. Due to the spin Hall effect, the heavy metal layer generates a transverse spin current when a lateral charge current passes through the strip. Using time-resolved all-optical pump-probe spectroscopy, we investigate how this spin current affects the magnetization dynamics in the adjacent CoFeB layer. We observed a linear spin-current manipulation of the effective Gilbert damping parameter for the Kittel mode from which we were able to determine the system’s spin Hall angles. Furthermore, we measured a strong influence of the spin current on a high-frequency mode. We interpret this mode as an exchange dominated higher order spin-wave resonance. Thus, we infer a strong dependence of the exchange constant on the spin current.
Autors: Steffen Wittrock;Dennis Meyer;Markus Müller;Henning Ulrichs;Jakob Walowski;Maria Mansurova;Ulrike Martens;Markus Münzenberg;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Spin-Transfer-Driven Dynamics of Magnetic Vortices and Antivortices in Dots With Crystalline Cubic Anisotropy
Abstract:
We study the magnetization dynamics of a vortex- or antivortex-containing nanodot driven by an out-of-plane polarized electric current within micromagnetic simulations. The dot is an ultra-thin structure created using a material with strong crystalline cubic anisotropy. It is in-plane ordered with an effective fourfold anisotropy. In the case of the antivortex, we consider astroid-shaped dots, while in the case of the vortex, the circular dots and the astroid-shaped ones. Unlike in the soft-magnetic dots, the vortex (antivortex) textures in thin layers with sufficiently strong fourfold anisotropy consist of four closure domains independent of the dot shape. The magnetization in the domain walls (DWs) deviates from the dot plane under the action of the out-of-plane polarized electric current normal to the dot, which drives the DW propagation—a rotation of the texture around the vortex (antivortex) center. The DW velocity is dependent on the distance from the vortex (antivortex) core; thus, the DWs deform under the current creating a fourfold spiral shape. For sufficiently hard cubic magnets, we find a regime of the oscillatory dynamics of the dot [a cyclic switching between the spiral state and the closure-domain vortex (antivortex) state]. For softer magnets, we consider a spin-transfer-driven fast magnetization reversal of the vortex state mediated by the creation of the spiral state.
Autors: Andrzej Janutka;Przemysław Gawroński;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 6
Publisher: IEEE
 
» Spin-Valve Junction With Transfer-Free MoS2 Spacer Prepared by Sputtering
Abstract:
The prospects of spintronic devices based on 2-D materials originate from their outstanding spin-related properties. Fabrication of such devices typically involves transfer processes that yield inferior interfaces due to trapped contaminants or cavities at 2-D material/electrode interfaces. Here, we report a transfer-free fabrication process of MoS2 films by RF magnetron sputtering, and demonstrate its application in the La0.7Sr0.3MnO3/MoS2/Ni0.8Fe0.2 spin-valve structure. The Raman spectroscopy shows and vibration modes of MoS2, suggesting the growth of crystalline MoS2 layers. A giant magnetoresistance ratio of 0.8% at 20 K was observed. The results suggest a scalable route for fabricating MoS2-based electronic and spintronic devices with a transfer-free process for obtaining reliable contacts.
Autors: W. C. Wong;S. M. Ng;H. F. Wong;C. L. Mak;C. W. Leung;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 5
Publisher: IEEE
 
» Spin-Wave Switching in the Side-Coupled Magnonic Stripes
Abstract:
This study of the spin waves coupling in the magnonic coupler, formed by the laterally coupled magnonic stripes, is performed by the means of finite-element and micromagnetic simulations. The efficiency of the spin-wave coupling is improved by the geometry design and choice of the appropriate magnetization direction inside each magnonic stripe. The proposed side-coupled magnetic stripes enable the improvement of performance of the advanced integrated magnonic devices and offer a range of further opportunities in planar magnonics.
Autors: Alexandr V. Sadovnikov;Sergey A. Odintsov;Evgeniy N. Beginin;Svetlana E. Sheshukova;Yurii P. Sharaevskii;Sergey A. Nikitov;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Splitting of Ferromagnetic Resonance Spectra in Periodically Modulated 1-D Magnonic Crystal
Abstract:
In this paper, we present a systematic study of a series of 1-D magnonic crystals defined as periodic arrays of grooves in a Permalloy thin film. Thin films of Ni80Fe20 with dimensions by and thickness 40 nm were prepared on the top of signal line of coplanar waveguides by a combination of photolithography, e-beam lithography and lift-off processing. Starting from thin films, stripe-type periodic structures (grooves) with a depth of 4 nm were created in a controlled manner by focused ion beam. By changing the dimensions of the distance between the grooves, it was possible to systematically tune single, double, triple, and quadruple ferromagnetic resonance (FMR) absorption modes. Broadband FMR experiments were carried out to collect the frequency and field-dependent FMR spectra. The experimental results are corroborated with micromagnetic simulations.
Autors: Shankar Khanal;Pemba Sherpa;Leonard Spinu;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Splitting of Spin Waves in Strain Reconfigurable Magnonic Stripe
Abstract:
We report on the study of the spin wave (SW) propagation in the magnonic waveguide which consists of an irregular magnetic thin film and a piezoelectric layer. We demonstrate that the use of a finite-width piezoelectric layer on the top of a magnetic waveguide leads to controllable SW splitting. By means of numerical simulation, we demonstrate the functionality of the proposed structure. We show that the switching of SW power is possible due to electric field variation and thus the proposed structure can act as a frequency-selective multichannel SW splitter and multiplexer.
Autors: Alexander V. Sadovnikov;Andrey A. Grachev;Evgeniy N. Beginin;Svetlana E. Sheshukova;Yurii P. Sharaevsky;Alexey A. Serdobintsev;Dmitry M. Mitin;Sergey A. Nikitov;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» SRTM DEM-Aided Mapping Satellite-1 Image Geopositioning Without Ground Control Points
Abstract:
A Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM)-aided geopositioning method is proposed to solve the problem of geopositioning without ground control points for Mapping Satellite-1 imagery. The method comprises coarse and accurate correction stages, and it compensates errors gradually. DEM extraction and DEM matching are important steps in both the stages, the objectives of which are to compensate the relative and absolute errors in an image, respectively. The SRTM DEM is integrated into all the processes to take full advantage of its consistent and high accuracy. Experimental results showed that this method could greatly improve geometry accuracy and obtain stable and highly accurate geopositioning for Mapping Satellite-1 images, regardless of the land area proportion (LAP) or the production mode. The planimetric and vertical accuracies were better than 8.1 and 5.2 m, respectively, which could satisfy the accuracy requirements of mapping at 1:50 000 scale. The computational efficiency depends on the LAP and target DEM resolution.
Autors: Xiaowei Chen;Baoming Zhang;Minyi Cen;Haitao Guo;Tonggang Zhang;Chuan Zhao;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Nov 2017, volume: 14, issue:11, pages: 2137 - 2141
Publisher: IEEE
 
» Stability Analysis of Polynomially Dependent Systems by Eigenvalue Perturbation
Abstract:
In this technical note we present a stability analysis approach for polynomially-dependent one-parameter systems. The approach, which appears to be conceptually appealing and computationally efficient and is referred to as an eigenvalue perturbation approach, seeks to characterize the analytical and asymptotic properties of eigenvalues of matrix-valued functions or operators. The essential problem dwells on the asymptotic behavior of the critical eigenvalues on the imaginary axis, that is, on how the imaginary eigenvalues may vary with respect to the varying parameter. This behavior determines whether the imaginary eigenvalues cross from one half plane into another, and hence plays a critical role in determining the stability of such systems. Our results reveal that the eigenvalue asymptotic behavior can be characterized by solving a simple generalized eigenvalue problem, leading to numerically efficient stability conditions.
Autors: Jie Chen;Peilin Fu;César-Fernando Méndez-Barrios;Silviu-Iulian Niculescu;Hongwei Zhang;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Nov 2017, volume: 62, issue:11, pages: 5915 - 5922
Publisher: IEEE
 
» Stability of Excitation of Traveling Waves in Gyrotrons With Low-Relativistic Electron Beams
Abstract:
A number of application require compact low-power gyrotrons with relatively low operating currents. In order to provide the start of such gyrotrons, one should use long-length operating cavities with high diffraction Q-factors, and, therefore, with significant losses of the radiated wave power due to Ohmic heating of the cavity wall. In this paper, we demonstrate that in low-voltage gyrotrons there is a possibility for stable operation at higher order axial modes possessing relatively low diffraction Q-factors. An enhanced efficiency of the beam-wave interaction is provided due to the excitation of such modes in the traveling-wave-tube regime.
Autors: Yuriy K. Kalynov;Ivan V. Osharin;Andrey V. Savilov;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Nov 2017, volume: 64, issue:11, pages: 4693 - 4699
Publisher: IEEE
 
» Stability Properties of Coupled Impedance Passive LTI Systems
Abstract:
We study the stability of the feedback interconnection of two impedance passive linear time-invariant systems, of which one is finite dimensional. The closed-loop system is well known to be impedance passive, but no stability properties follow from this alone. We are interested in two main issues: 1) the strong stability of the operator semigroup associated with the closed-loop system, 2) the input–output stability (meaning transfer function in ) of the closed-loop system. Our results are illustrated with the system obtained from the nonuniform SCOLE (NASA Spacecraft Control Laboratory Experiment) model representing a vertical beam clamped at the bottom, with a rigid body having a large mass on top, connected with a trolley mounted on top of the rigid body, via a spring and a damper. Such an arrangement, called a tuned mass damper (TMD), is used to stabilize tall buildings. We show that the SCOLE-TMD system is strongly stable on the energy state space and that the system is input–output stable from the horizontal force input to the horizontal velocity output.
Autors: Xiaowei Zhao;George Weiss;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Nov 2017, volume: 62, issue:11, pages: 5769 - 5779
Publisher: IEEE
 
» Stack Structure Dependence of Magnetic Properties of PtMn/[Co/Ni] Films for Spin-Orbit Torque Switching Device
Abstract:
We investigate the stack structure dependence of magnetic properties on thin films that consist of an antiferromagnetic PtMn and a ferromagnetic Co/Ni multilayer for field-free spin-orbit torque-induced magnetization switching devices. Magnetic parameters, such as the spontaneous magnetization, effective and interfacial magnetic anisotropies, and exchange bias field are quantified as a function of stack structure. Engineering of the stack allows the improvement of current-induced magnetization switching characteristics compared with a previous work, which is confirmed using patterned Hall cross devices.
Autors: William A. Borders;Shunsuke Fukami;Hideo Ohno;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Stack-Size Sensitive On-Chip Memory Backup for Self-Powered Nonvolatile Processors
Abstract:
Wearable devices gain increasing popularity since they can collect important information for healthcare and well-being purposes. Compared with battery, energy harvesting is a better power source for these wearable devices due to many advantages. However, harvested energy is naturally unstable and program execution will be interrupted frequently. Nonvolatile processors demonstrate promising advantages to back up volatile state before the system energy is depleted. However, it also introduces non-negligible energy and area overhead. In this paper, we aim to reduce the amount of data that need to be backed up during a power failure. Based on the observation that stack size varies along program execution, we propose to analyze the application program and identify efficient backup positions, by which the stack content to back up can be significantly reduced. The evaluation results show an average of 45.7% reduction on nonvolatile stack size for stack backup, with 0.58% storage overhead. In the mean time, with the proposed schemes, the energy utilization and program forward progress can be greatly improved compared with instant backup.
Autors: Mengying Zhao;Chenchen Fu;Zewei Li;Qingan Li;Mimi Xie;Yongpan Liu;Jingtong Hu;Zhiping Jia;Chun Jason Xue;
Appeared in: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
Publication date: Nov 2017, volume: 36, issue:11, pages: 1804 - 1816
Publisher: IEEE
 
» Staggered SAR: Performance Analysis and Experiments With Real Data
Abstract:
Synthetic aperture radar (SAR) remote sensing allows high-resolution imaging independent of weather conditions and sunlight illumination and is therefore very attractive for the systematic observation of dynamic processes on the earth’s surface. Conventional SAR systems are, however, limited in that a wide swath can only be imaged at the expense of a degraded azimuth resolution. This limitation can be overcome by using systems with multiple receive subapertures displaced in along-track, but a very long antenna is required to map a wide swath. If a relatively short antenna with a single aperture in along-track is available, it is still possible to map a wide area: multiple subswaths can simultaneously be imaged using digital beamforming in elevation, but “blind ranges” are present between adjacent swaths, as the radar cannot receive while it is transmitting. Staggered SAR overcomes the problem of blind ranges by continuously varying the pulse repetition interval (PRI). A proper selection of the PRIs, together with moderate oversampling in azimuth, allows an accurate interpolation of the nonuniformly sampled raw data into a uniform grid, so that resampled data can then be focused with a conventional SAR processor. This approach thereby allows high-resolution imaging of a wide continuous swath without the need for a long antenna with multiple subapertures. In this paper, the performance of staggered SAR is thoroughly discussed and novel methods for the evaluation of the range and azimuth ambiguity-to-signal ratios in staggered SAR are proposed. An L-band design example based on a reflector antenna with multiple feeds shows that outstanding ambiguity performance is obtained, provided that data are moderately oversampled in azimuth. As an additional benefit, the energy of range and azimuth ambiguities is spread over large areas: ambiguities therefore appear in the image as a noise-like disturbance rather than loca- ized artifacts. The impact of staggered SAR operation on image quality is furthermore assessed with experiments using real data. As the first step, highly oversampled F-SAR airborne data have been used to generate equivalent staggered SAR data sets and to evaluate the performance for different oversampling factors and interpolation methods. Then, the radar instrument of the German satellite TerraSAR-X has been commanded to acquire data over the lake Constance in staggered SAR mode. Measurements on these data show very good agreement with predictions from simulations. Staggered SAR is currently being considered as the baseline acquisition mode for Tandem-L, a proposal for a polarimetric and interferometric spaceborne SAR mission to monitor dynamic processes on the earth’s surface with unprecedented accuracy and resolution.
Autors: Michelangelo Villano;Gerhard Krieger;Marc Jäger;Alberto Moreira;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6617 - 6638
Publisher: IEEE
 
» State and Unknown Input Observers for Nonlinear Systems With Bounded Exogenous Inputs
Abstract:
A systematic design methodology for state observers for a large class of nonlinear systems with bounded exogenous inputs (disturbance inputs and sensor noise) is proposed. The nonlinearities under consideration are characterized by an incremental quadratic constraint parameterized by a set of multiplier matrices. Linear matrix inequalities are developed to construct observer gains, which ensure that a performance output based on the state estimation error satisfies a prescribed degree of accuracy. Furthermore, conditions guaranteeing estimation of the unknown inputs to arbitrary degrees of accuracy are provided. The proposed scheme is illustrated with a numerical example, which does not satisfy the so-called “matching conditions.”
Autors: Ankush Chakrabarty;Martin J. Corless;Gregery T. Buzzard;Stanisław H. Żak;Ann E. Rundell;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Nov 2017, volume: 62, issue:11, pages: 5497 - 5510
Publisher: IEEE
 
» Static and Dynamic Magnetic Properties of Sputtered Fe–Ga Thin Films
Abstract:
We present the measurements of the static and dynamic properties of polycrystalline iron–gallium films, ranging from 20 to 80 nm and sputtered from an Fe0.8Ga0.2 target. Using a broadband ferromagnetic resonance setup in a wide frequency range, perpendicular standing spin-wave resonances were observed with the external static magnetic field applied in-plane. The field corresponding to the strongest resonance peak at each frequency is used to determine the effective magnetization, the -factor, and the Gilbert damping. Furthermore, the dependence of spin-wave mode on field-position is observed for several frequencies. The analysis of broadband dynamic properties allows determination of the exchange stiffness pJ/m and Gilbert damping for 40 and 80 nm thick films. These values are approximately consistent with values seen in epitaxially grown films, indicating the potential for the industrial fabrication of magnetostrictive FeGa films for microwave applications.
Autors: Daniel B. Gopman;Vimal Sampath;Hasnain Ahmad;Supriyo Bandyopadhyay;Jayasimha Atulasimha;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Statistical Anomaly Detection in Human Dynamics Monitoring Using a Hierarchical Dirichlet Process Hidden Markov Model
Abstract:
Understanding of human dynamics has drawn attention to various areas. The wide spread of positioning technologies, such as GPS facilitates location information to be obtained with high spatio-temporal resolution as well as at low costs. By collecting individual location information in real time, monitoring of human dynamics has recently become possible and is expected to the area of dynamic traffic control. In this monitoring, detecting anomalous states of human dynamics become important. This research aims to define an anomaly detection problem of the human dynamics monitoring with time-series gridded population data and develop an anomaly detection method for this problem. According to the result of a review we have conducted, we discussed the characteristics of the anomaly detection in human dynamics monitoring and categorized our problem to a semi-supervised anomaly detection problem that detects contextual anomalies behind time-series data. We developed an anomaly detection method based on a sticky hierarchical Dirichlet process hidden Markov model, which is able to estimate the number of latent states according to the input data. Results of the experiment with synthetic data showed that our proposed method has good fundamental performance with respect to the detection rate. Through the experiments with real gridded population data, anomalies were detected when and where an actual social event had occurred.
Autors: Takashi Fuse;Keita Kamiya;
Appeared in: IEEE Transactions on Intelligent Transportation Systems
Publication date: Nov 2017, volume: 18, issue:11, pages: 3083 - 3092
Publisher: IEEE
 
» Stator Shape Design Method for Improving Power Density in PM Motor
Abstract:
In this paper, we propose a stator shape design method for improving power density in a small permanent magnet motor. In order to calculate iron loss correctly, we analyze a motor by using 2-D finite element method (FEM) in which an E&S model is introduced. Moreover, external circuit equations are solved coupled with equations in electromagnetic field by FEM to calculate copper loss correctly. It is possible to calculate power density correctly by evaluating loss and weight of a motor correctly whether stator shape is changed. As a result, we show that our analysis technique is useful as a shape design method of a motor’s stator for improving power density.
Autors: Naoya Soda;Masato Enokizono;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» STC: A Simple to Complex Framework for Weakly-Supervised Semantic Segmentation
Abstract:
Recently, significant improvement has been made on semantic object segmentation due to the development of deep convolutional neural networks (DCNNs). Training such a DCNN usually relies on a large number of images with pixel-level segmentation masks, and annotating these images is very costly in terms of both finance and human effort. In this paper, we propose a simple to complex (STC) framework in which only image-level annotations are utilized to learn DCNNs for semantic segmentation. Specifically, we first train an initial segmentation network called Initial-DCNN with the saliency maps of simple images (i.e., those with a single category of major object(s) and clean background). These saliency maps can be automatically obtained by existing bottom-up salient object detection techniques, where no supervision information is needed. Then, a better network called Enhanced-DCNN is learned with supervision from the predicted segmentation masks of simple images based on the Initial-DCNN as well as the image-level annotations. Finally, more pixel-level segmentation masks of complex images (two or more categories of objects with cluttered background), which are inferred by using Enhanced-DCNN and image-level annotations, are utilized as the supervision information to learn the Powerful-DCNN for semantic segmentation. Our method utilizes 40K simple images from Flickr.com and 10K complex images from PASCAL VOC for step-wisely boosting the segmentation network. Extensive experimental results on PASCAL VOC 2012 segmentation benchmark well demonstrate the superiority of the proposed STC framework compared with other state-of-the-arts.
Autors: Yunchao Wei;Xiaodan Liang;Yunpeng Chen;Xiaohui Shen;Ming-Ming Cheng;Jiashi Feng;Yao Zhao;Shuicheng Yan;
Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence
Publication date: Nov 2017, volume: 39, issue:11, pages: 2314 - 2320
Publisher: IEEE
 
» Stereo Image Retrieval Using Height and Planar Visual Word Pairs
Abstract:
The wide availability of high-resolution satellite stereo images has created a surging demand for effective stereo image retrieval methods. Recently, few retrieval methods have been designed specifically for stereo images having unique characteristics (e.g., viewing number and viewing angles), and often have insufficient retrieval accuracy. A new content-based stereo image retrieval method is achieved with height and planar visual word pairs, which are generated from the stereo extracted digital surface models and orthoimages. Experimental results of the International Society for Photogrammetry and Remote Sensing stereo benchmark test data set show that our method outperforms the state-of-the-art methods in terms of accuracy and stability. Our method achieves a high retrieval precision of 0.9, and has a high efficiency. Our method is stable for two stereo pairs, covering the same scene from different sensors, which usually have a small ranking difference in the returned ranking list. Our method is helpful to quickly and accurately locate desired stereo images from large quantities of multisensor stereo images.
Autors: Feifei Peng;Jing Luo;Gaoqiang Wang;Kunlun Qi;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Nov 2017, volume: 14, issue:11, pages: 2082 - 2086
Publisher: IEEE
 
» Stochastic Phase Synchronization of Perpendicularly Magnetized Spin-Torque Oscillators With the Second-Order Uniaxial Anisotropy
Abstract:
Stochastic phase synchronization is investigated for spin-torque oscillators (STOs) with perpendicularly magnetized free layer with the first- and second-order magnetic anisotropy. We numerically calculated the magnetization dynamics for the pair of STOs receiving a dc current with Gaussian noise through common current source, and found that the STOs with the second-order magnetic anisotropy synchronized more effectively than that without the second-order magnetic anisotropy. We analyzed the response of the oscillation phase to a perturbative current, i.e., phase resetting curve, and also found that the STO with the second-order uniaxial anisotropy performs better with stochastic phase synchronization.
Autors: Hiroko Arai;Hiroshi Imamura;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 5
Publisher: IEEE
 
» Strain Effects on the Interaction Between NO2 and the Mo-Edge of the MoS2 Zigzag Nanoribbon
Abstract:
Density functional theory based theoretical studies on the interaction of NO2 molecule with the Mo-edge of MoS2 zigzag nanoribbon have been presented in this paper. Effects from uniaxial tensile strain on the structure and physical properties of the nanoribbon and the adsorption process are discussed in detail. Without strain, NO2 dissociates and adsorbs onto the Mo-edge, with an adsorption energy of –0.91 eV, and the nanoribbon is metallic. With strain and without the presence of NO2, the nanoribbon remains metallic. However, with the presence and interaction from NO2, the nanoribbon under strain shows a band gap opening. Meanwhile, there is an increase in the magnitude of the adsorption energy, indicating more stable adsorbed structures with strain.
Autors: Xiaowei Wang;Junxia Shi;
Appeared in: IEEE Transactions on Nanotechnology
Publication date: Nov 2017, volume: 16, issue:6, pages: 982 - 990
Publisher: IEEE
 
» Strain-Mediated Magnetization Reversal Through Spin-Transfer Torque
Abstract:
Recent experiments have shown the ability to introduce an anisotropy energy to the energy landscape of a thin-film nanomagnet through the use of mechanical strain. Assuming this strain-induced anisotropy is large enough, the low-energy state of the nanomagnet is altered and can be used to initialize the magnetization along a given axis. Utilizing this effect, we propose a more energy efficient method of nanomagnet reversal through spin-transfer torque (STT). This is accomplished by first initializing the magnetization to a high-energy state and then applying a short current pulse to nudge the magnetization in the appropriate energy basin. Using extensive numerical simulations, we qualitatively analyze this type of reversal and find the optimal parameters for reliable functionality while in the presence of thermal noise. We demonstrate that despite negating the initial portion of nominal STT reversal, where the STT must fight against the damping torque of the initial energy-basin, the magnitude of spin current required for our proposed strain-mediated reversal is equivalent to the nominal case. However, the strain-meditated reversal is beneficial by minimizing the spin-current pulsewidth necessary for reliable operation allowing for large energy savings. Assuming the strain-anisotropy is significantly larger than the nanomagnet’s internal free-axis anisotropy, strain-mediated reversals offer a energy reduction over nominal STT reversals.
Autors: Nickvash Kani;John T. Heron;Azad Naeemi;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 8
Publisher: IEEE
 
» Strained Germanium Gate-All-Around pMOS Device Demonstration Using Selective Wire Release Etch Prior to Replacement Metal Gate Deposition
Abstract:
Strained Ge p-channel gate-all-around (GAA) devices with Si-passivation are demonstrated on high-density 45-nm active pitch starting from 300-mm SiGe strain relaxed buffer wafers. While single horizontal Ge nanowire (NW) devices are demonstrated, the process flow described in this paper can be adjusted to make vertically stacked horizontal Ge NWs to increase the drive per footprint. The demonstrated short-channel devices have round Ge NWs with 9-nm diameter and are the Ge GAA devices with the smallest channel and gate dimensions ( nm) published to date. Electrostatics and off-state leakage are maintained down to the shortest gate lengths studied, showing drain-induced barrier lowering of 30 mV/V and sub-20 nA/ at V and nm. The short-channel device subthreshold slope SS and performance can be further improved by use of high-pressure annealing in hydrogen, yielding the best SSLIN and SSSAT of 71 and 76 mV/dec reported so far for any -nm Ge pMOS channel device.
Autors: L. Witters;H. Arimura;F. Sebaai;A. Hikavyy;A. P. Milenin;R. Loo;A. De Keersgieter;G. Eneman;T. Schram;K. Wostyn;K. Devriendt;A. Schulze;R. Lieten;S. Bilodeau;E. Cooper;P. Storck;E. Chiu;C. Vrancken;P. Favia;E. Vancoille;J. Mitard;R. Langer;A. Opdebee
Appeared in: IEEE Transactions on Electron Devices
Publication date: Nov 2017, volume: 64, issue:11, pages: 4587 - 4593
Publisher: IEEE
 
» Strategies to Empower Existing Automated Material Handling Systems to Rising Requirements
Abstract:
Due to reasons like higher flexibility demands, smaller lot sizes in production, and tool upgrades leading to higher throughputs, existing automated material handling systems are facing ever rising requirements. At the same time, the potential to upgrade transport system hardware is limited due to technical reasons as well as its interconnected nature. This paper, therefore, focuses on new possibilities regarding the integration of already existing but not yet used information into automated material handling system (AMHS) control, and presents three different approaches for improvement: 1) improving empty vehicle management strategies by incorporating near-future transports demands; 2) balancing track utilization by adjusting path selection processes; and 3) interaction between AMHS and scheduling/dispatching, in order to consider potential bottle-necks. Each of these approaches improves AMHS performance; in combination they have the potential to empower the system to handle future demands with little or no hardware manipulations.
Autors: Robert Schmaler;Christian Hammel;Thorsten Schmidt;Matthias Schoeps;Joerg Luebke;Ralf Hupfer;
Appeared in: IEEE Transactions on Semiconductor Manufacturing
Publication date: Nov 2017, volume: 30, issue:4, pages: 440 - 447
Publisher: IEEE
 
» Stray gassing of transformer insulating oils: impact of materials, oxygen content, additives, incubation time and temperature, and its relationship to oxidation stability
Abstract:
For many years, dissolved gas analysis (DGA) has been considered worldwide as the most important technique for evaluating the state of health of oil-filled power transformers. Based on regular analysis and trending of the dissolved gases extracted from insulating oil samples, an assessment can be made whether internal transformer abnormalities are present and how critical these abnormalities are [1], [2].
Autors: Steve Eeckhoudt;Stijn Autru;Luc Lerat;
Appeared in: IEEE Electrical Insulation Magazine
Publication date: Nov 2017, volume: 33, issue:6, pages: 27 - 32
Publisher: IEEE
 
» StreaMon: A Data-Plane Programming Abstraction for Software-Defined Stream Monitoring
Abstract:
The fast evolving nature of modern cyber threats and network monitoring needs calls for new, “software-defined”, approaches to simplify and quicken programming and deployment of online (stream-based) traffic analysis functions. StreaMon is a carefully designed data-plane abstraction devised to scalably decouple the “programming logic” of a traffic analysis application (tracked states, features, anomaly conditions, etc.) from elementary primitives (counting and metering, matching, events generation, etc), efficiently pre-implemented in the probes, and used as common instruction set for supporting the desired logic. Multi-stage multi-step real-time tracking and detection algorithms are supported via the ability to deploy custom states, relevant state transitions, and associated monitoring actions and triggering conditions. Such a separation entails platform-independent, portable, online traffic analysis tasks written in a high level language, without requiring developers to access the monitoring device internals and program their custom monitoring logic via low level compiled languages (e.g., C, assembly, VHDL). We validate our design by developing a prototype and a set of simple (but functionally demanding) use-case applications and by testing them over real traffic traces.
Autors: Marco Bonola;Giuseppe Bianchi;Giulio Picierro;Salvatore Pontarelli;Marco Monaci;
Appeared in: IEEE Transactions on Dependable and Secure Computing
Publication date: Nov 2017, volume: 14, issue:6, pages: 664 - 678
Publisher: IEEE
 
» Strong Dynamic Interactions of Grid-Connected DFIGs With Power Systems Caused by Modal Coupling
Abstract:
This paper establishes a closed-loop interconnected dynamic model of a power system with a doubly fed induction generator (DFIG) for wind power generation, wherein, the DFIG and power system are modeled as two open-loop interconnected subsystems. The established model indicates that the impact of the dynamic interactions introduced by the DFIG on the power system's small-signal angular stability is the difference between the closed-loop and open-loop electromechanical oscillation modes (EOMs). The analysis conducted in this study reveals that when an open-loop DFIG oscillation mode (DOM) is close to an open-loop EOM on the complex plane, the modal coupling of the open-loop EOM and DOM can cause strong dynamic interactions between the DFIG and the power system; thus, the DFIG has a significant impact on the power system's small-signal angular stability. An example multimachine power system with grid-connected DFIGs is presented to demonstrate and validate the analysis and conclusions made in the paper.
Autors: Wenjuan Du;Xiao Chen;H. F. Wang;
Appeared in: IEEE Transactions on Power Systems
Publication date: Nov 2017, volume: 32, issue:6, pages: 4386 - 4397
Publisher: IEEE
 
» Structural and Ferromagnetic Properties of Sputtered FeCoB/AlN Soft Magnetic Multilayers for GHz Applications
Abstract:
Owing to their large saturation magnetization and low hysteresis loss, soft magnetic layers based on amorphous alloys currently receive great attention for their potential for gigahertz frequencies applications. In this paper, we studied the structural and magnetic properties of amorphous FeCoB/AlN multilayered thin films with in-plane uniaxial magnetic anisotropy based on the Fe-28%Co-20%B (at. %) alloy, deposited on 8” Si/200 nm-thermal-SiO2 wafers in an industrial, high-throughput magnetron sputtering system. Depending on the process conditions and hardware configuration, the multilayers exhibit structural anisotropy consisting of surface ripples elongated perpendicular to the incident flux direction, which replicate through the entire multilayer stack. By varying the AlN interlayer thickness and sputter process parameters the anisotropy field of these films was tuned in the range of 25–130 Oe, while the coercivity along the magnetic easy axis was kept low, 0.2–0.3 Oe. The ferromagnetic resonance frequency of the multilayered structures was ~2 GHz, and the experimental behavior of the magnetization dynamics was described by the classical Landau–Lifschitz–Gilbert model. Magnetic domain imaging confirmed a strong coupling between the adjacent FeCoB layers, in agreement with the edge-curling wall model.
Autors: Claudiu Valentin Falub;Rachid Hida;Mojmír Meduňa;Josef Zweck;Jean-Philippe Michel;Henri Sibuet;Daniel Schneider;Martin Bless;Jan H. Richter;Hartmut Rohrmann;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 6
Publisher: IEEE
 
» Structural and Magnetic Properties in Mn2VAl Full-Heusler Epitaxial Thin Films
Abstract:
Epitaxially grown Mn2VAl full-Heusler thin films were fabricated on single crystalline MgO (001) substrates by using an ultra-high-vacuum magnetron sputtering technique. X-ray diffraction revealed that epitaxial Mn2VAl films with a highly -ordered structure were obtained by annealing around 600 °C. For the films deposited without a buffer layer and annealed at 500 °C–600 °C, the saturation magnetization was about 240 emu/cm3 at 300 K, which was close to the theoretical value. The effective magnetic damping constant of Mn2VAl thin films was investigated using the ferromagnetic resonance technique. The effective damping constant was much larger than expected due to the inhomogeneity in the Mn2VAl films.
Autors: Kenji Fukuda;Mikihiko Oogane;Yasuo Ando;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Structure, Magnetic, and Electrical Properties of La2NiO $_{4+delta }$ Compounds
Abstract:
We have investigated the structure, magnetic, and electrical properties, and the resistance switching effect (RSE) of La2NiO compounds with different excess oxygen levels of . Our results showed the structure changes from tetragonal I4/mmm to orthorhombic Fmmm when reducing value from 0.011 to 0.006. The curves measured at several temperatures exhibit a coexistence of the weak ferromagnetic and antiferromagnetic interactions. Two shoulders on curves related to the spin and charge ordering have also been observed. These ordering temperatures depend strongly on value and they shift toward lower temperature with decreasing . All the samples exhibit a semiconductor behavior and their temperature dependences of the resistivity obey the variable-range-hoping model. Interestingly, the typical current–voltage characteristics of the samples show a hysteresis, which suggests an existence of the RSE. We have observed two different states of the resistance corresponding to high () and low () values. The resistance change ratio of the samples defined as 100% is found to be about 18�- 25;–57%, which depends on the value of in the samples.
Autors: Tran Dang Thanh;H. T. Van;D. T. A. Thu;L. V. Bau;Nguyen Van Dang;D. N. H. Nam;L. V. Hong;Seong-Cho Yu;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Structure-Exploiting Delay-Dependent Stability Analysis Applied to Power System Load Frequency Control
Abstract:
Linear matrix inequality (LMI) based delay-dependent stability analysis/synthesis methods have been applied to power system load frequency control (LFC) which has communication networks in its loops. However, the computational burden of solving large-scale LMIs poses a great challenge to the application of those methods to real-world power systems. This paper investigates the computational aspect of delay-dependent stability analysis (DDSA) of LFC. The basic idea is to improve the numerical tractability of DDSA by exploiting the chordal sparsity and symmetry of the graph related to LFC loops. The graph-theoretic analysis yields the structure restrictions of weighting matrices needed for the LMIs to inherit the chordal sparsity of the control loops. By enforcing those structure restrictions on weighting matrices, the positive semidefinite constraints in the LMIs can be decomposed into smaller ones, and the number of decision variables can be greatly reduced. Symmetry in LFC control loops is also exploited to reduce the number of decision variables. Numerical studies show the proposed structure-exploiting techniques significantly improves the numerical tractability of DDSA at the cost of the introduction of acceptable minor conservatism.
Autors: Chao Duan;Chuan-Ke Zhang;Lin Jiang;Wanliang Fang;Wei Yao;
Appeared in: IEEE Transactions on Power Systems
Publication date: Nov 2017, volume: 32, issue:6, pages: 4528 - 4540
Publisher: IEEE
 
» Structure-Property Correlations of Carbon and Nitrogen Incorporated NiFe2O4
Abstract:
In this paper, carbon (C) and nitrogen (N) were incorporated into the interstitial sites of nickel (Ni) ferrite lattice. Structural studies of the incorporated NiFe2O4 (NFO) samples (C-NFO and N-NFO) using X-ray diffraction revealed changes in the values of the lattice parameter, bond angle, and bond length. Raman spectroscopic studies revealed shifts in peak positions of and (3) vibrational modes of the spectra. Magnetization measurements at 20 and 300 K using vibrating sample magnetometer showed decrease in the values of upon incorporation of C/N (/f.u. of C-NFO and /f.u. of N-NFO from /f.u. of NFO, at 20 K). An increase in intrinsic coercive field () value (18.2 Oe of C-NFO and 14.2 Oe of N-NFO from 5.2 Oe of NFO, at 20 K) was also observed. However, a reduction in the value of first-order cubic magnetocrystalline anisotropy constant () was observed upon incorporation of C/N. Microstructural analysis using scanning electron microscopic images revealed modifications in the shape and the size of the grains. The average grain size was found to be reduced upon C/N incorporation (~600 nm of NFO, while ~550 nm of C-NFO and ~400 nm of N-NFO).
Autors: K. B. Anoop Baby;Lijin George;Manu Jaiswal;G. Markandeyulu;A. Subrahmanyam;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 5
Publisher: IEEE
 
» Structured Projection-Based Model Reduction With Application to Stochastic Biochemical Networks
Abstract:
The chemical master equation (CME) is well known to provide the highest resolution models of a biochemical reaction network. Unfortunately, even simulating the CME can be a challenging task. For this reason, simpler approximations to the CME have been proposed. In this paper, we focus on one such model, the linear noise approximation (LNA). Specifically, we consider implications of a recently proposed LNA time-scale separation method. We show that the reduced-order LNA converges to the full-order model in the mean square sense. Using this as motivation, we derive a network structure-preserving reduction algorithm based on structured projections. We discuss when these structured projections exist and we present convex optimization algorithms that describe how such projections can be computed. The algorithms are then applied to a linearized stochastic LNA model of the yeast glycolysis pathway.
Autors: Aivar Sootla;James Anderson;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Nov 2017, volume: 62, issue:11, pages: 5554 - 5566
Publisher: IEEE
 
» Students’ Task Interpretation and Conceptual Understanding in an Electronics Laboratory
Abstract:
Task interpretation is a critical first step for students in the process of self-regulated learning, and a key determinant when they set goals in their learning and select strategies in assigned work. This paper focuses on the explicit and implicit aspects of task interpretation based on Hadwin’s model. Laboratory activities improve students’ conceptual understanding, as they utilize cognitive ability to integrate the new experiences these provide. The purpose of this paper is to investigate how students’ interpretation of a task assigned during laboratory work may change during the task process, and how this relates to their conceptual understanding. A total of 143 students enrolled in an electronics course participated in this paper. Instruments to measure task interpretation and conceptual understanding were created, piloted, and applied before and after selected laboratory activities over the semester. Findings suggest that while students’ task interpretation changes during the task process, increasing after the completion of the laboratory activity levels of task interpretation are low. Previous research findings—that students generally have an incomplete understanding of the assigned tasks and struggle to establish a connection between laboratory activities and the theory—were confirmed. Lastly, this paper reports a significant relationship between students’ task interpretation and their conceptual understanding in laboratory work. Further investigation is necessary to unveil other factors related to these constructs in order to engage students in laboratory work.
Autors: Presentacion Rivera-Reyes;Oenardi Lawanto;Michael L. Pate;
Appeared in: IEEE Transactions on Education
Publication date: Nov 2017, volume: 60, issue:4, pages: 265 - 272
Publisher: IEEE
 
» Study for Phosphorus Contamination to High Voltage Transistors
Abstract:
Threshold voltage () needs to be well controlled to determine the switching point of the transistors. However, variation was observed on high voltage transistor during development phase. Investigations show that the variation was caused by phosphorus contamination from wafer backside. Various wet chemical cleaning methods were evaluated to understand the effectiveness for the phosphorus decontamination. Good result was achieved with improved cleaning solution.
Autors: Liang Li;Qiong Luo;Zeng Yuan Wu;Yun Ling Tan;Alex See;Soo Cheng Chua;Troy Zhu;Chor Shu Cheng;
Appeared in: IEEE Transactions on Semiconductor Manufacturing
Publication date: Nov 2017, volume: 30, issue:4, pages: 323 - 327
Publisher: IEEE
 
» Study of Electronic Switching Between Multiple Backward-Wave Modes in a W-Band Extended Interaction Oscillator
Abstract:
The performance of electronic switching between multiple backward-wave modes is studied in a designed extended interaction oscillator (EIO) based on a ladder circuit with finite number of periods to overcome electronic tuning range limits of EIOs operated in standing-wave mode. The dispersion characteristic of the circuit with finite number of periods, which is constructed by a series of discrete modes, is investigated. The mode separation is analyzed and reduced to support continuous switching between multiple different modes by increasing the number of periods as compared with the standing-wave EIO approach. An output circuit is designed to extract the power of backward wave. The electronic switching between nine backward-wave modes has been achieved by changing the beam voltage from 4.1 to 10.5 kV, where the maximum output power over 58 W is obtained at 5.3 kV from the simulation prediction. The EIO can operate over an electronic tuning range of 3.53 GHz from 89.65 to 93.18 GHz in ensuring the output power no less than 20 W. This technique can be extensively applied to increase operating band for extended interaction klystrons (EIKs) and electronic tuning range for EIOs, making them more suitable for many potential applications.
Autors: Liangjie Bi;Yong Yin;Changpeng Xu;Zhang Zhang;Zhiwei Chang;Fanbo Zeng;Ruibin Peng;Wen Zhou;Abdur Rauf;Safi Ullah;Bing Wang;Hailong Li;Lin Meng;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Nov 2017, volume: 64, issue:11, pages: 4686 - 4692
Publisher: IEEE
 
» Study of the Effect of Annealing on the Properties of Mn2RuxGa Thin Films
Abstract:
The effect of vacuum annealing thin films of the compensated ferrimagnetic half-metal Mn2RuxGa at temperatures from 250 °C to 400 °C is investigated. The 39.3 nm films deposited on (100) MgO substrates exhibit perpendicular magnetic anisotropy due to a small ~ 1% tetragonal elongation induced by the substrate strain. The main change on annealing is a modification in the compensation temperature , which first increases from 50 K for the as-deposited film to 185 K after annealing at 250 °C, and then falls to 140 K after annealing at 400 °C. There are minor changes in the atomic order, coercivity, resistivity, and anomalous Hall effect (AHE), but the net magnetization measured by SQUID magnetometry with the field applied in-plane or perpendicular-to-the-plane changes more significantly. It saturates at 20 –30 kA at room temperature, and a small soft component is seen in the perpendicular SQUID loops, which is absent in the square AHE hysteresis loops. This is explained by the half-metallic nature of the compound; the AHE probes only the 4c Mn sublattice that provides the spin-polarized electrons at the Fermi level, whereas the SQUID measures the sum of the oppositely aligned 4c and 4a sublattice magnetizations.
Autors: K. E. Siewierska;G. Atcheson;K. Borisov;M. Venkatesan;K. Rode;J. M. D. Coey;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 5
Publisher: IEEE
 
» Study on Electromagnetic Force Characteristics Acting on Levitation/Guidance Coils of a Superconducting Maglev Vehicle System
Abstract:
Superconducting Maglev has been developed as a high-speed transport system. Superconducting coils (SC coils) are installed on the vehicle, and levitation/guidance coils (LG coils) are installed on the ground. A null-flux-type electrodynamic suspension system provided by electromagnetic interaction between SC coils and LG coils serves as the levitation and guidance functions of the vehicle system. Electromagnetic forces acting on SC coils are related to levitation and guidance functions of the vehicle. These forces were studied in previous research, and characteristics of levitation and guidance forces were revealed with respect to parameters of the design of the vehicle. On the other hand, electromagnetic forces acting on LG coils also exist as action–reaction pairs with the forces acting on SC coils. The forces act on LG coils in every levitated run of the vehicle, and stress is applied on the conductor and molded resin of the LG coils. In conventional studies, the vehicle design has been decided mainly by the electromagnetic forces acting on SC coils, and not by the forces acting on LG coils. The aim of the study is to establish an improved method to design the vehicle system with the objective of not only optimization of characteristics of the vehicle, but also consideration of stress on LG coils. As a preliminary study to establish the improved method, a study by computer simulation on characteristics of electromagnetic forces acting on LG coils with respect to the parameters of the vehicle is described in this paper.
Autors: Takenori Yonezu;Ken Watanabe;Erimitsu Suzuki;Takashi Sasakawa;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 5
Publisher: IEEE
 
» Study on Pattern Distortion and DOA Estimation Performance of Crossed-Loop/Monopole Antenna in HF Radar
Abstract:
Crossed-loop (CL)/monopole antenna has been widely used in high-frequency ground-wave radar for ocean surface remote sensing owing to its compact size. The multiple signal classification (MUSIC) algorithm is commonly adapted to achieve a favorable angular resolution for this broad beam antenna. However, the direction of arrival (DOA) estimation is always troubled by the frequently occurring distortion of antenna pattern. Previous studies are mainly focused on the calibration by using the actual pattern or other assistant algorithms. In this paper, theoretical analysis is made to illustrate the reason for pattern distortion, which draws a conclusion that the distortion is essentially due to the different influence of environmental obstacles upon the electric field part and magnetic field part. This also implies that there is nearly no distortion between the two loops, which is validated by three different experiments. Based on this conclusion, the DOA estimation performance of the MUSIC algorithm is studied by creating a numerical relationship associating the estimation error with distortion level. Furthermore, a new method using ideal pattern is proposed to improve the estimation performance by removing the amplitude information of monopole and relying on the CL processing. Both simulation and experimental results are given to prove its validity.
Autors: Yingwei Tian;Biyang Wen;Jian Tan;Ziyan Li;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Nov 2017, volume: 65, issue:11, pages: 6095 - 6106
Publisher: IEEE
 
» Study on Requirements for Load Emulation of the Vehicle With an Electric Braking System
Abstract:
For different configurations of the electric braking systems (EBS) in the vehicle, requirements for the emulation of their dynamic load on the test bench are studied in this paper, in order to determine appropriate parameters of the test equipment. First, models of three kinds of EBS as well as the test bench are built and characteristics of the transmission system including elasticity and backlash nonlinearity with their influences on the braking performance are fully considered. Two normal braking strategies, namely the maximum-motor-torque strategy and the good-pedal-feel strategy, are designed and the antilock braking strategy that includes the regenerative and friction blended torque control of the wheel slip ratio, the sliding mode control of the backlash, and the PID closed-loop control for elasticity compensation in the emergency condition is proposed. With these methods, motor and frictional braking torque are under the coordinated control to make the most of the EBS. Then, the scheme and control methods of load emulation including the PI method and the feedforward method on the test bench are put forward. Based on the models and control methods, vehicle braking results that indicate the emulation effects and requirements of different kinds of EBS in the MATLAB/Simulink environment are shown; and meanwhile, the dynamic performance parameters of the test bench containing the moment of inertia and the time constant of torque response are obtained for the selection of the test equipment. Finally, experiments on the real bench are carried out. The loading and motion of the vehicle EBS under various braking conditions can be accurately emulated on the proposed test bench and the reliable test results make it possible to investigate the EBS safely, economically, and time-efficiently in the laboratory.
Autors: Zhongshi Zhang;Lifang Wang;Junzhi Zhang;Ruihai Ma;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Nov 2017, volume: 66, issue:11, pages: 9638 - 9653
Publisher: IEEE
 
» Study on the Heat Transfer of GaN-Based High Power HEMTs
Abstract:
In this paper, study on the heat transfer of GaN-based high electron mobility transistors (HEMTs) on SiC substrate was carried out utilizing transient thermal analysis method. Gate-source voltage () is used as the temperature sensitive parameter. Linear relationship ( factor) between and temperature is obtained. It is found that the factor is proportional with drain-source current and does not change with the variation of drain-gate voltage in the linear region of HEMT. We proposed and proved that the factor should be calibrated with HEMT working at linear region to insure the accuracy of subsequent thermal evaluation. Moreover, the temperature rise and thermal resistance keeps as constant when factors were calibrated within the linear region. Transient thermal measurement turns out to be a non-destructive, fast, and precise method for the thermal performance analysis and quality control of the power HEMTs.
Autors: Lianqiao Yang;Zhangfu Chen;Xiaoxue Xu;Jianhua Zhang;
Appeared in: IEEE Transactions on Semiconductor Manufacturing
Publication date: Nov 2017, volume: 30, issue:4, pages: 526 - 530
Publisher: IEEE
 
» Studying the Reliability Implications of Line Switching Operations
Abstract:
This paper proposes a method for studying the reliability implications of line switching operations in power systems. Two case studies are conducted on RTS and IEEE 118-bus system to illustrate this method. This method is designed to explore previously overlooked areas in reliability evaluation of line switching operations. Line removal test is proposed to obtain simulation data of the system, and then with risk analysis and impact analysis, six reliability indices are used to evaluate reliability performance of each transmission line in the system. Instead of the traditionally used mean value, this method introduces variance into analysis. Weibull distribution is used to reconstruct distributions of reliability indices which provide worst case scenario comparisons in reliability evaluation. Eventually, with results obtained from the proposed reliability evaluation method, categorization for line switching operations is introduced to classify all transmission lines based on their reliability performance. The categories provide reliability implications of line switching operations and can be used for guidance in actual operations.
Autors: Shijia Zhao;Chanan Singh;
Appeared in: IEEE Transactions on Power Systems
Publication date: Nov 2017, volume: 32, issue:6, pages: 4614 - 4625
Publisher: IEEE
 
» Sub-Nyquist SAR via Fourier Domain Range-Doppler Processing
Abstract:
Conventional synthetic aperture radar (SAR) systems are limited in their ability to satisfy the increasing requirement for improved spatial resolution and wider coverage. The demand for high resolution requires high sampling rates, while coverage is limited by the pulse repetition frequency. Consequently, sampling rate reduction is of high practical value in SAR imaging. In this paper, we introduce a new algorithm, equivalent to the well-known range-Doppler method, to process SAR data using the Fourier series coefficients of the raw signals. We then demonstrate how to exploit the algorithm features to reduce sampling rate in both range and azimuth axes and process the signals at sub-Nyquist rates, by using compressive sensing (CS) tools. In particular, we demonstrate recovery of an image using only a portion of the received signal’s bandwidth and also while dropping a large percentage of the transmitted pulses. The complementary pulses may be used to capture other scenes within the same coherent processing interval. In addition, we propose exploiting the ability to reconstruct the image from narrow bands in order to dynamically adapt the transmitted waveform energy to vacant spectral bands, paving the way to cognitive SAR. The proposed recovery algorithms form a new CS-SAR imaging method that can be applied to high-resolution SAR data acquired at sub-Nyquist rates in range and azimuth. The performance of our method is assessed using simulated and real data sets. Finally, our approach is implemented in hardware using a previously suggested Xampling radar prototype.
Autors: Kfir Aberman;Yonina C. Eldar;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Nov 2017, volume: 55, issue:11, pages: 6228 - 6244
Publisher: IEEE
 
» Sub/Supraliminal Stimulus With Pseudo-“Blindsight” Under Exposure to Extremely Low-Frequency Fields
Abstract:
This paper was conducted to examine whether subliminal/supraliminal stimulus with phosphene as pseudo-blindsight under exposure to extremely low-frequency magnetic fields can control retinal activities through changes in the receptivity of the flicker sensation. Eight healthy male subjects ranging in age from 21 to 66 participated in the visual stimulus experiments. For the measurement on the effects of subliminal stimuli, we investigated the threshold variations after the pre-stimuli at 80% of the threshold at 20 Hz. The subliminal stimuli for 30 s and 45 s reduced the standard threshold value (9.8 mT) of the following phosphene by about 3.9% and 8.9%, respectively. In evaluating the supraliminal effects, we measured recovery times at around the threshold (test stimuli: 150–110% threshold) for the phosphene after pre-stimulus of 47 mT at 20 Hz for 30s. Judging from the result of the recovery times, we took notice of the possibility that there might be a latent threshold in the range of 20.8–22.4 mT for the phosphene re-perception. We strongly propose the idea that subliminal/supraliminal control with pseudo-blindsight can gradually activate synaptic plasticity and might be an effective medical treatment for the aged and the handicapped with lost visual functions. Besides, it is perfectly painless.
Autors: Hidenori Nakagawa;Shoogo Ueno;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 4
Publisher: IEEE
 
» Submodular Attribute Selection for Visual Recognition
Abstract:
In real-world visual recognition problems, low-level features cannot adequately characterize the semantic content in images, or the spatio-temporal structure in videos. In this work, we encode objects or actions based on attributes that describe them as high-level concepts. We consider two types of attributes. One type of attributes is generated by humans, while the second type is data-driven attributes extracted from data using dictionary learning methods. Attribute-based representation may exhibit variations due to noisy and redundant attributes. We propose a discriminative and compact attribute-based representation by selecting a subset of discriminative attributes from a large attribute set. Three attribute selection criteria are proposed and formulated as a submodular optimization problem. A greedy optimization algorithm is presented and its solution is guaranteed to be at least (1−1/e)-approximation to the optimum. Experimental results on four public datasets demonstrate that the proposed attribute-based representation significantly boosts the performance of visual recognition and outperforms most recently proposed recognition approaches.
Autors: Jingjing Zheng;Zhuolin Jiang;Rama Chellappa;
Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence
Publication date: Nov 2017, volume: 39, issue:11, pages: 2242 - 2255
Publisher: IEEE
 
» Subsynchronous Interaction Between Direct-Drive PMSG Based Wind Farms and Weak AC Networks
Abstract:
Recently, sustained power oscillation at subsynchronous frequency was captured in direct-drive permanent magnetic synchronous generator (PMSG) based wind farms in Xinjiang Uygur Autonomous Region, China. This new type of subsynchronous interaction (SSI) detected in practical systems has never been reported and analyzed before. Therefore, its mechanism and characteristics are not yet clearly clarified. In this paper, a simplified but representative system model with multiple PMSGs interfaced with AC networks is established first based on the actual system and the PMSG model provided by the manufacturer. Then, small-signal eigenanalysis, time-domain simulation, and impedance model analysis are carried out to investigate the interactive dynamics between them. The results show that such interaction between direct-drive PMSG wind farms and weak ac grids characterized by low short-circuit ratio would cause negative-resistance effect for the SSI mode, leading to unstable oscillation. In such cases, the controller of PMSG would saturate soon, resulting in sustained power oscillation in the system. If unfortunately the oscillation frequency matches the torsional mode of any nearby turbogenerator, severe torsional vibration would be excited on the shaft of the latter. The analysis results are finally validated with field measurements of an actual SSI event. To address the problem, a supplementary subsynchronous damping control loop is attached to the controllers of PMSGs to reshape the impedance and thus to stabilize the SSI.
Autors: Huakun Liu;Xiaorong Xie;Jingbo He;Tao Xu;Zhao Yu;Chao Wang;Chuanyu Zhang;
Appeared in: IEEE Transactions on Power Systems
Publication date: Nov 2017, volume: 32, issue:6, pages: 4708 - 4720
Publisher: IEEE
 
» Sum-Power Minimization Problem in Multisource Single-AF-Relay Networks: A New Revisit to Study the Optimality
Abstract:
For multisource single amplify-and-forward (AF) relay networks, the optimality of power allocation is revisited from different solution aspect, and a universal optimization framework is proposed. The proposed framework can be used to solve problems that have some common specific structure. As a baseline of the optimization framework, two theorems are proposed to obtain the extreme value of the problem, which is general to realize the optimal resource allocation under some system-specific constraints. Then, based on the proposed theorems, for multiuser single-AF-relay cooperative networks without direct links between sources and destinations, optimal power allocation strategies with low computational complexity are proposed to minimize sum-source-power consumption and sum-system-power consumption. When the number of mobile user is , the overall complexity of both power allocation schemes is , which is lower than or same as the existing strategies. While comparing with the traditional methods to solve this type of problem, extensive numerical simulation has been conducted for different system setups to justify the effectiveness and efficacy of our proposed power allocation schemes.
Autors: Shiguo Wang;Rukhsana Ruby;Victor C. M. Leung;Zhiqiang Yao;Xianru Liu;Zhetao Li;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Nov 2017, volume: 66, issue:11, pages: 9958 - 9971
Publisher: IEEE
 
» Sum-Rate Analysis for Multi-User MIMO Systems With User Exposure Constraints
Abstract:
Fifth generation (5G) and beyond cellular systems are expected to support multiple uplink transmit antennas. Previous research demonstrates that designing waveforms satisfying near field user exposure constraints affects the far-field data rates achievable by portable devices using multiple transmit antennas. Therefore, user exposure constraints need to be taken into account in the uplink transmission covariance matrix design (e.g., precoder design) for 5G. Specific absorption rate (SAR) is a widely accepted user exposure measurement used in wireless communication regulations throughout the world. In this paper, we perform sum-rate analysis for a multi-user multiple-input multiple-output (MIMO) system with SAR constraints enforced at each user. The maximum achievable sum rates for various channel state information at the transmitter scenarios are studied in this paper. The SAR-aware MIMO transmission methods are based on the modified waterfilling algorithm. Simulation results show our proposed methods outperform the conventional transmission strategy for the two user case.
Autors: Dawei Ying;David J. Love;Bertrand M. Hochwald;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Nov 2017, volume: 16, issue:11, pages: 7376 - 7388
Publisher: IEEE
 
» Sum-Rate Capacity of Poisson MIMO Multiple-Access Channels
Abstract:
In this paper, we analyze the sum-rate capacity of two-user Poisson multiple input multiple output multiple-access channels (MACs), when both the transmitters and the receiver are equipped with multiple antennas. Although the sum-rate capacity of Poisson MISO MAC when the receiver is equipped with a single antenna has been characterized by us, the inclusion of multiple antennas at the receiver makes the problem more challenging and requires the development of new analytical tools. We first characterize the sum-rate capacity of the Poisson MAC when each transmitter has a single antenna and the receiver has multiple antennas. We obtain the optimal input that achieves the sum-rate capacity by solving a non-convex optimization problem. We show that, for certain channel parameters, it is optimal for a single user to transmit to achieve the sum-rate capacity, and for certain channel parameters, it is optimal for both users to transmit. We then characterize the sum-rate capacity of the channel where both the transmitters and the receiver are equipped with multiple antennas. We show that the sum-rate capacity of the Poisson MAC with multiple transmit antennas is equivalent to a properly constructed Poisson MAC with a single antenna at each transmitter, and has thus been characterized by the former case. We show this by developing a novel channel transformation argument.
Autors: Ain-ul Aisha;Lifeng Lai;Yingbin Liang;Shlomo Shamai Shitz;
Appeared in: IEEE Transactions on Communications
Publication date: Nov 2017, volume: 65, issue:11, pages: 4765 - 4776
Publisher: IEEE
 
» Summarizing Unconstrained Videos Using Salient Montages
Abstract:
We present a novel method to summarize unconstrained videos using salient montages (i.e., a “melange” of frames in the video as shown in Fig. 1), by finding “montageable moments” and identifying the salient people and actions to depict in each montage. Our method aims at addressing the increasing need for generating concise visualizations from the large number of videos being captured from portable devices. Our main contributions are (1) the process of finding salient people and moments to form a montage, and (2) the application of this method to videos taken “in the wild” where the camera moves freely. As such, we demonstrate results on head-mounted cameras, where the camera moves constantly, as well as on videos downloaded from YouTube. In our experiments, we show that our method can reliably detect and track humans under significant action and camera motion. Moreover, the predicted salient people are more accurate than results from state-of-the-art video salieny method [1] . Finally, we demonstrate that a novel “montageability” score can be used to retrieve results with relatively high precision which allows us to present high quality montages to users.
Autors: Min Sun;Ali Farhadi;Ben Taskar;Steve Seitz;
Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence
Publication date: Nov 2017, volume: 39, issue:11, pages: 2256 - 2269
Publisher: IEEE
 
» Super-accurate GPS coming to smartphones in 2018 [News]
Abstract:
We've all been there. You're driving down the highway, just as your navigation app instructed, when Siri tells you to "proceed east for one-half mile, then merge onto the highway." But you're already on the highway. After a moment of confusion and perhaps some rude words about Siri and her extended AI family, you realize the problem: Your GPS isn't accurate enough for your navigation app to tell if you're on the highway or on the road beside it. Those days are nearly at an end. At the Institute of Navigation GNSS+ conference in Portland, Ore., in September, Broadcom announced that it is providing customers samples of the first mass-market chip to take advantage of a new breed of global navigation satellite signals. This new chip will give the next generation of smartphones 30‑centimeter accuracy as opposed to today’s 5 meters. Even better, it works in a city's concrete canyons, and it consumes half the power of today's generation of chips. The chip, the BCM47755, has been included in the design of some smartphones slated for release in 2018, but Broadcom would not reveal which.
Autors: Samuel K. Moore;
Appeared in: IEEE Spectrum
Publication date: Nov 2017, volume: 54, issue:11, pages: 10 - 11
Publisher: IEEE
 
» Superpixels by Bilateral Geodesic Distance
Abstract:
We present a novel superpixel generation algorithm based on a new definition of geodesic distance, called bilateral geodesic distance. In contrast to the traditional geodesic distance, the new bilateral geodesic distance of two pixels considers the distance between their positions as well as their color difference. Superpixel generation is essentially a problem of clustering image pixels with respect to a set of properly selected seeds. We first use an adaptive hexagonal subdivision method to determine the initial seed-based image gradient. Then, we use the bilateral geodesic distance to measure the similarity between the pixels and the seeds. We apply an improved fast marching method to generate superpixels’ contour regions with the expansion velocities dependent on a new gradient formulation that depends on the seeds’ properties. The experimental results indicate that our algorithm is not only much faster than the structure-based method, which uses conventional geodesic distance, but also outperforms the existing methods in terms of region compactness and region boundary regularity.
Autors: Yuanfeng Zhou;Xiao Pan;Wenping Wang;Yilong Yin;Caiming Zhang;
Appeared in: IEEE Transactions on Circuits and Systems for Video Technology
Publication date: Nov 2017, volume: 27, issue:11, pages: 2281 - 2293
Publisher: IEEE
 
» Superposition Modulation-Based Cooperation for Oversampled OFDM Signals
Abstract:
This paper proposes an iterative detector for uncoded OFDM signals in cooperative networks, where the information symbols are simply partitioned through a time-domain matrix at the OFDM transmitter. We analytically show that our proposed iterative detector at the partner node converges and can completely recover the user’s data from its partitioned version, if sufficient redundancy is inserted in the user’s data. For efficient use of the redundancy in the user’s data, a coded cooperative transmission based on superposition modulation is proposed. Additionally, a closed-form input–output relationship for the partitioning and reconstruction algorithm in the proposed cooperative scenario is derived. We also obtain closed-form expressions for symbol error rate performance of the proposed coded cooperative scenario over Rayleigh frequency-selective fading channels. Numerical comparisons shed light on the relative merits of the proposed coded cooperation under various inter-user and uplink channel conditions.
Autors: Alireza Rahmati;Kaamran Raahemifar;Alagan Anpalagan;Theodoros A. Tsiftsis;Paeiz Azmi;Nikolaos I. Miridakis;
Appeared in: IEEE Transactions on Communications
Publication date: Nov 2017, volume: 65, issue:11, pages: 4791 - 4802
Publisher: IEEE
 
» Superposition Signaling in Broadcast Interference Networks
Abstract:
It is known that superposition signaling in Gaussian interference networks is capable of improving the achievable rate region. However, the problem of maximizing the rate gain offered by superposition signaling is computationally prohibitive, even in the simplest case of two-user single-input single-output interference networks. This paper examines superposition signaling for the general multiple-input multiple-output broadcast Gaussian interference networks. The problem of maximizing either the sum rate or the minimal user’s rate under superposition signaling and dirty paper coding is solved by a computationally efficient path-following procedure, which requires only a convex quadratic program for each iteration but ensures convergence at least to a locally optimal solution. Numerical results demonstrate the substantial performance advantage of the proposed approach.
Autors: Hoang Duong Tuan;Ho Huu Minh Tam;Ha H. Nguyen;Trung Q. Duong;H. Vincent Poor;
Appeared in: IEEE Transactions on Communications
Publication date: Nov 2017, volume: 65, issue:11, pages: 4646 - 4656
Publisher: IEEE
 
» Support Vector Motion Clustering
Abstract:
We present a closed-loop unsupervised clustering method for motion vectors extracted from highly dynamic video scenes. Motion vectors are assigned to nonconvex homogeneous clusters characterizing direction, size and shape of regions with multiple independent activities. The proposed method is based on support vector clustering. Cluster labels are propagated over time via incremental learning. The proposed method uses a kernel function that maps the input motion vectors into a high-dimensional space to produce nonconvex clusters. We improve the mapping effectiveness by quantifying feature similarities via a blend of position and orientation affinities. We use the Quasiconformal Kernel Transformation to boost the discrimination of outliers. The temporal propagation of the clusters’ identities is achieved via incremental learning based on the concept of feature obsolescence to deal with appearing and disappearing features. Moreover, we design an online clustering performance prediction algorithm used as a feedback that refines the cluster model at each frame in an unsupervised manner. We evaluate the proposed method on synthetic data sets and real-world crowded videos and show that our solution outperforms state-of-the-art approaches.
Autors: Isah A. Lawal;Fabio Poiesi;Davide Anguita;Andrea Cavallaro;
Appeared in: IEEE Transactions on Circuits and Systems for Video Technology
Publication date: Nov 2017, volume: 27, issue:11, pages: 2395 - 2408
Publisher: IEEE
 
» Supporting One-Time Point Annotations for Gesture Recognition
Abstract:
This paper investigates a new annotation technique that reduces significantly the amount of time to annotate training data for gesture recognition. Conventionally, the annotations comprise the start and end times, and the corresponding labels of gestures in sensor recordings. In this work, we propose a one-time point annotation in which labelers do not have to select the start and end time carefully, but just mark a one-time point within the time a gesture is happening. The technique gives more freedom and reduces significantly the burden for labelers. To make the one-time point annotations applicable, we propose a novel BoundarySearch algorithm to find automatically the correct temporal boundaries of gestures by discovering data patterns around their given one-time point annotations. The corrected annotations are then used to train gesture models. We evaluate the method on three applications from wearable gesture recognition with various gesture classes (10-17 classes) recorded with different sensor modalities. The results show that training on the corrected annotations can achieve performances close to a fully supervised training on clean annotations (lower by just up to 5 percent F1-score on average). Furthermore, the BoundarySearch algorithm is also evaluated on the ChaLearn 2014 multi-modal gesture recognition challenge recorded with Kinect sensors from computer vision and achieves similar results.
Autors: Long-Van Nguyen-Dinh;Alberto Calatroni;Gerhard Tröster;
Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence
Publication date: Nov 2017, volume: 39, issue:11, pages: 2270 - 2283
Publisher: IEEE
 
» Surface Plasmon Resonance Refractive Index Sensor Based on Tapered Coreless Optical Fiber Structure
Abstract:
In this paper, we announce the surface plasmon resonance (SPR) refractive index (RI) sensor based on tapered coreless fiber (TCF) structure. We take full advantage of the transmission characteristics of the coreless fiber, and the experimental results evidence that TCF is able to excite surface plasmon wave effectively. Compared with common SPR sensors, this sensor is easier to fabricate, has better mechanical stability, and offers a comparable sensitivity. The wavelength interrogation sensitivity of the proposed sensor is 2278.4 nm/RIU in the RI range of 1.33-1.391. As the structure of the proposed sensor can lead to multimode interference (MMI), and the gold film is only coated on one side of TCF, MMI spectra appear in the visible light band instead of in the near-infrared. When surrounding RI increases, the resonance wavelength shifts to shorter wavelengths. We get an ultrahigh wavelength interrogation sensitivity, 866.1 nm/RIU, compared with common MMI RI sensors, in the RI range of 1.3864-1.416. Because both SPR and MMI are sensitive to the change of surrounding RI, this sensor can achieve a wide detection range when we use these two phenomena together.
Autors: Zhe-Wen Ding;Ting-Ting Lang;Yu Wang;Chun-Liu Zhao;
Appeared in: Journal of Lightwave Technology
Publication date: Nov 2017, volume: 35, issue:21, pages: 4734 - 4739
Publisher: IEEE
 
» Surface Water Mapping by Deep Learning
Abstract:
Mapping of surface water is useful in a variety of remote sensing applications, such as estimating the availability of water, measuring its change in time, and predicting droughts and floods. Using the imagery acquired by currently active Landsat missions, a surface water map can be generated from any selected region as often as every 8 days. Traditional Landsat water indices require carefully selected threshold values that vary depending on the region being imaged and on the atmospheric conditions. They also suffer from many false positives, arising mainly from snow and ice, and from terrain and cloud shadows being mistaken for water. Systems that produce high-quality water maps usually rely on ancillary data and complex rule-based expert systems to overcome these problems. Here, we instead adopt a data-driven, deep-learning-based approach to surface water mapping. We propose a fully convolutional neural network that is trained to segment water on Landsat imagery. Our proposed model, named DeepWaterMap, learns the characteristics of water bodies from data drawn from across the globe. The trained model separates water from land, snow, ice, clouds, and shadows using only Landsat bands as input. Our code and trained models are publicly available at http://live.ece.utexas.edu/research/deepwatermap/.
Autors: Furkan Isikdogan;Alan C. Bovik;Paola Passalacqua;
Appeared in: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Publication date: Nov 2017, volume: 10, issue:11, pages: 4909 - 4918
Publisher: IEEE
 
» Surface-Oxidized Amorphous Alloy Powder/Epoxy-Resin Composite Bulk Magnetic Core and Its Application to Megahertz Switching LLC Resonant Converter
Abstract:
To realize a compact, lightweight and high-efficiency megahertz (MHz) switching DC–DC converter using SiC/GaN power device, inductor/transformer core must have small core loss at such high frequency to maintain high efficiency of the converter. This paper focuses on Fe-based amorphous (Fe-AMO) alloy powder used in metal composite bulk magnetic core for MHz switching DC–DC converter, where fine Fe-AMO powder with a mean diameter of was used to suppress MHz band eddy current inside the Fe-AMO powder body. When applying Fe-AMO powder to the closely packed composite core together with epoxy resin, high electrical-resistivity layer must be formed on the Fe-AMO powder surface in order to suppress the overlapped eddy current between adjacent Fe-AMO powders. In this paper, about 10 nm-thick oxidized layer of the Fe-AMO powder surface was successfully formed by using annealing in dry air. This paper describes on the surface-oxidized Fe-AMO powder/epoxy-resin composite bulk core transformer and its application to GaN power device MHz switching LLC resonant DC–DC converter. By using the Fe-AMO composite core transformer, the fabricated 48 V-input/24 V-output LLC resonant converter exhibited 90% over efficiency in the output power range of 24 to 120 W, which was higher efficiency when using the Ni–Zn ferrite core transformer.
Autors: Kanako Sugimura;Daisuke Shibamoto;Naoki Yabu;Tatsuya Yamamoto;Makoto Sonehara;Toshiro Sato;Tsutomu Mizuno;Hideaki Mizusaki;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 6
Publisher: IEEE
 
» Survivability-Aware Connectivity Restoration for Partitioned Wireless Sensor Networks
Abstract:
In this letter, we propose a survivability-aware connectivity restoration strategy for partitioned wireless sensor networks with mobile nodes. Our main contributions lie in two aspects. First, we design a load equilibrium mechanism, in which the partitioned segments are connected according to an in-order connection pattern rather than conventional factors, so as to enhance the network lifespan. Second, we design a reliability enhancement measure, in which the stopping points of mobile nodes are selected according to the surrounding node distribution status rather than conventional factors, so as to reduce the connectivity failure probability for the second destruction. In the end, simulations are conducted to demonstrate the effectiveness and advantages of our connectivity restoration scheme.
Autors: Xuxun Liu;
Appeared in: IEEE Communications Letters
Publication date: Nov 2017, volume: 21, issue:11, pages: 2444 - 2447
Publisher: IEEE
 
» Switching Controller Design With Dwell-Times and Sampling
Abstract:
We consider the problem of obtaining state dependent switching strategies for switching linear time-invariant systems which satisfy prespecified dwell-time constraints. Continuous-time strategies which yield exponential stability and a guaranteed level of performance are presented. We also consider discrete-time strategies in which the sampling time is independent of the dwell-times. A numerical example is included to validate the developed theory.
Autors: Matheus Souza;André R. Fioravanti;Martin Corless;Robert N. Shorten;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Nov 2017, volume: 62, issue:11, pages: 5837 - 5843
Publisher: IEEE
 
» Symmetric Channel Hopping for Blind Rendezvous in Cognitive Radio Networks Based on Union of Disjoint Difference Sets
Abstract:
In order to exchange control information without relying on any fixed control channel, neighboring cognitive users (CUs) in a multichannel cognitive radio network (CRN) can tune their transceivers to hop among a common set of spectrum channels and communicate when they rendezvous at a common channel in the blind fashion. Based on the combinatorial concept of the union of disjoint difference sets ( UDDS), the present paper proposes two novel symmetric channel hopping (CH) schemes, namely UDDS-SCH and UDDS-ACH, for CUs with or without a synchronized time clock, respectively, to achieve blind rendezvous. By deriving their performance metrics, we then point out that both UDDS-SCH and -ACH can be optimized by adopting a special UDDS, which can be partitioned into mutually disjoint minimal difference sets (MDSs) as many as possible. This stimulates us to further develop exhaustive and heuristic solutions for searching the optimal and suboptimal numbers of mutually disjoint MDSs at high and low computational complexities, respectively. Based on these searching results, we finally show that both UDDS-SCH and -ACH can achieve better performance metrics than most existing symmetric CH schemes and remedy one major shortcoming of the best known ones, i.e., incapability to rendezvous at an arbitrary number of spectrum channels. Numerical simulation demonstrates that, when primary users may appear at part of or all rendezvous channels, the proposed CH schemes will outperform the existing ones in terms of the average transmission throughput and time of the CRN.
Autors: Xuesong Jonathan Tan;Chao Zhou;Jie Chen;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Nov 2017, volume: 66, issue:11, pages: 10233 - 10248
Publisher: IEEE
 
» Synchronization of Pulse-Coupled Oscillators and Clocks Under Minimal Connectivity Assumptions
Abstract:
Populations of flashing fireflies, claps of applauding audience, cells of cardiac and circadian pacemakers reach synchrony via event-triggered interactions, referred to as pulse couplings. Synchronization via pulse coupling is widely used in wireless sensor networks, providing clock synchronization with parsimonious packet exchanges. In spite of serious attention paid to networks of pulse coupled oscillators, there is a lack of mathematical results, addressing networks with general communication topologies and general phase-response curves of the oscillators. The most general results of this type (Wang et al., 2012, 2015) establish synchronization of oscillators with a delay-advance phase-response curve over strongly connected networks. In this technical note we extend this result by relaxing the connectivity condition to the existence of a root node (or a directed spanning tree) in the graph. This condition is also necessary for synchronization.
Autors: Anton V. Proskurnikov;Ming Cao;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Nov 2017, volume: 62, issue:11, pages: 5873 - 5879
Publisher: IEEE
 
» Synchronization of Spin Torque Oscillators through Spin Hall Magnetoresistance
Abstract:
Spin torque oscillators placed onto a nonmagnetic heavy metal show synchronized auto-oscillations due to the coupling originating from spin Hall magnetoresistance effect. Here, we study a system having two-spin torque oscillators under the effect of the spin Hall torque, and show that switching the external current direction enables us to control the phase difference of the synchronization between in-phase and antiphase.
Autors: Tomohiro Taniguchi;
Appeared in: IEEE Transactions on Magnetics
Publication date: Nov 2017, volume: 53, issue:11, pages: 1 - 7
Publisher: IEEE
 

Publication archives by date

  2017:   January     February     March     April     May     June     July     August     September     October     November     December    

  2016:   January     February     March     April     May     June     July     August     September     October     November     December    

  2015:   January     February     March     April     May     June     July     August     September     October     November     December    

  2014:   January     February     March     April     May     June     July     August     September     October     November     December    

  2013:   January     February     March     April     May     June     July     August     September     October     November     December    

  2012:   January     February     March     April     May     June     July     August     September     October     November     December    

  2011:   January     February     March     April     May     June     July     August     September     October     November     December    

  2010:   January     February     March     April     May     June     July     August     September     October     November     December    

  2009:   January     February     March     April     May     June     July     August     September     October     November     December    

 
0-C     D-L     M-R     S-Z