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Electrical and Electronics Engineering publications abstract of: 06-2010 sorted by title, page: 35
» Solution processed tetrasubstituted zinc phthalocyanine as an active layer in organic field effect transistors
Abstract:
Spun films of liquid crystalline peripheral-tetrasubstituted zinc (II) phthalocyanine (Pc) derivatives have been employed as active organic semiconducting layers in the fabrication of organic field effect transistors. The Pc molecules in the thin film formulation are stacked perpendicular to the substrate. Values of 1.8×10-4 cm2V-1s-1 and 103 were estimated for the field-effect mobility and on/off ratio, respectively, from the hysteresis-free transistor characteristics. The transistor can be switched on and off at a relatively low value of 3.7 V for threshold voltage. The carrier transport is believed to be largely determined by the multidomain Pc film structure.
Autors: Chaure, Nandu B.;Basova, Tamara;Zahedi, Marjan;Ray, Asim K.;Sharma, Ashwani K.;Durmus, Mahmut;Ahsen, Vefa;
Appeared in: Journal of Applied Physics
Publication date: Jun 2010, volume: 107, issue:11, pages: 114503 - 114503-5
Publisher: IEEE
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» Solution-processed zinc–tin oxide thin-film transistors with low interfacial trap density and improved performance
Abstract:
Solution-processed amorphous oxide semiconductors are attractive channel materials in thin-film transistors (TFTs) for low-cost electronics. We demonstrate improved performance and uniformity of solution-processed zinc–tin oxide (ZTO) TFTs by optimizing the prebake process for the ZTO precursor film. ZTO prebake process prearranges the dielectric/semiconductor interface and minimizes the performance variation caused by the uneven thermal distribution during annealing process. Prearranging the interface also reduces interfacial trap density and results in improved performance. A mobility of 27.3 cm2/Vs, an on/off ratio of ∼107, and a subthreshold swing of 122 mV/decade have been obtained. Significant improvement in operational stability has also been observed.
Autors: Lee, Chen-Guan;Dodabalapur, Ananth;
Appeared in: Applied Physics Letters
Publication date: Jun 2010, volume: 96, issue:24, pages: 243501 - 243501-3
Publisher: IEEE
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» Solving optimal power flow problems using a probabilistic α-constrained evolutionary approach
Abstract:
One of the most difficult tasks in any population-based approach is to deal with large-scale constrained systems without losing computational efficiency. To achieve such goal, a methodology based on two different techniques is presented. First, an evolutionary algorithm based on a cluster-and-gradient-based artificial immune system (CGbAIS) is used to improve computational time. For that, the CGbAIS uses the numerical information provided by the electrical power system and a clustering strategy that eliminates redundant individuals to speed up the convergence process. Second, to increase the capacity of dealing with constraints, a probabilistic a-level of relaxation is used. This approach treats separately the constraints and objective functions. It generates a lexicographic comparison process meaning that, if two individuals have their constraints below the current a-level, the one with the better objective function has a probability of winning the comparison. Otherwise, the individual with the lower penalty is selected regardless the value of the objective function. Combining these concepts together generates a computational framework capable of finding optimal solutions within a very interesting computational time. Applications using a mixed integer and continuous variables will illustrate the performance of the proposed method.
Autors: Honorio, L.M.;Leite da Silva, A.M.;Barbosa, D.A.;Delboni, L.F.N.;
Appeared in: IET Generation, Transmission & Distribution
Publication date: Jun 2010, volume: 4, issue:6, pages: 674 - 682
Publisher: IEEE
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» Some extremal properties of daubechies filters and other orthonormal filters
Abstract:
New extremal properties of Daubechies 4-tap orthonormal filters are given: They maximize a certain functional, have the largest gain in (0, ?/2), and allow maximum energy compaction in [0, ?/2]. These properties do not carry over to Daubechies filters of arbitrary length. They complement what is known about Daubechies filters and highlight the specific role of the 4-tap filter. Moreover, we demonstrate that these properties cannot be fulfilled by any other orthonormal lowpass filter, regardless of its length.
Autors: María Elena, Domínguez-Jiménez , Paulo J.S.G., Ferreira
Appeared in: Signal Processing
Publication date: Jun 2010
Publisher: Elsevier B.V.
Full litterature document
 
» Some New Developments on the Al-Alaoui and the Pei and Hsu s-to-z Transforms
Abstract:
This brief refocuses on three classes of s-to-z transforms. For each class, a closed-form expression is proposed, and a particular element, having an imaginary part of its frequency response very close to the ideal value, is presented. These s-to-z transforms are then related to all-pass infinite-impulse-response fractional delay filters, allowing another way to choose their degree of freedom.
Autors: Auger, F.;
Appeared in: IEEE Transactions on Circuits and Systems II: Express Briefs
Publication date: Jun 2010, volume: 57, issue:6, pages: 471 - 475
Publisher: IEEE
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» Some Superconducting Magnets at IMP
Abstract:
Some superconducting magnets research at IMP (Institute of Modern Physics, CAS, Lanzhou) will be described in this paper. Firstly, a superconducting electron cyclotron resonance ion source (SECRAL) was successfully built to produce intense beams of highly charged heavy ions for Heavy Ion Research Facility in Lanzhou (HIRFL). An innovation design of SECRAL is that the three axial solenoid coils are located inside of a sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. For 28 GHz operation, the magnet assembly can produce peak mirror fields on axis of 3.6 T at injection, 2.2 T at extraction, and a radial sextupole field of 2.0 T at plasma chamber wall. Some excellent results of ion beam intensity have been produced and SECRAL has been put into operation to provide highly charged ion beams for HIRFL since May 2007. Secondly, a super-ferric dipole prototype of FAIR Super-FRS is being built by FCG (FAIR China Group) in cooperation with GSI. Its superconducting coils and cryostat is made and tested in the Institute of Plasma Physics (IPP, Hefei), and it more 50 tons laminated yoke was made in IMP. This super-ferric dipole static magnetic field was measured in IMP, it reach to the design requirement, ramping field and other tests will be done in the future. Thirdly, a 3 T superconducting homogenous magnetic field solenoid with a 70 mm warm bore has been developed to calibrate Hall sensor, some testing results is reported. And a penning trap system called LPT (Lanzhou Penning Trap) is now being developed for precise mass measurements.
Autors: Yuan, P.;Zhao, H. W.;Leibrock, H.;Ma, L. Z.;Sun, L. T.;Zhang, X. Q.;Zhang, B.;Guo, B. L.;Wu, W.;Yao, Q. G.;Wu, W. Y.;Wang, Q. L.;Wu, X.;Han, S. F.;He, Y.;Zhang, S. L.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 214 - 217
Publisher: IEEE
Full litterature document
 
» Son of Carterfone: Network Neutrality or Regulation?
Abstract:
Ending network neutrality would benefit ISPs at the expense of Internet vendors, but would probably disadvantage users in general and could pose risks for privacy and innovation.
Autors: Lesk, Michael;
Appeared in: IEEE Security & Privacy
Publication date: Jun 2010, volume: 8, issue:3, pages: 77 - 82
Publisher: IEEE
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» Sorting Genomes by Reciprocal Translocations, Insertions, and Deletions
Abstract:
The problem of sorting by reciprocal translocations (abbreviated as SBT) arises from the field of comparative genomics, which is to find a shortest sequence of reciprocal translocations that transforms one genome Pi into another genome Gamma, with the restriction that Pi and Gamma contain the same genes. SBT has been proved to be polynomial-time solvable, and several polynomial algorithms have been developed. In this paper, we show how to extend Bergeron's SBT algorithm to include insertions and deletions, allowing to compare genomes containing different genes. In particular, if the gene set of Pi is a subset (or superset, respectively) of the gene set of Gamma, we present an approximation algorithm for transforming Pi into Gamma by reciprocal translocations and deletions (insertions, respectively), providing a sorting sequence with length at most OPT + 2, where OPT is the minimum number of translocations and deletions (insertions, respectively) needed to transform Pi into Gamma; if Pi and Gamma have different genes but not containing each other, we give a heuristic to transform Pi into Gamma by a shortest sequence of reciprocal translocations, insertions, and deletions, with bounds for the length of the sorting sequence it outputs. At a conceptual level, there is some similarity between our algorithm and the algorithm developed by El Mabrouk which is used to sort two chromosomes with different gene contents by reversals, insertions, and deletions.
Autors: Qi, Xingqin;Li, Guojun;Li, Shuguang;Xu, Ying;
Appeared in: IEEE/ACM Transactions on Computational Biology and Bioinformatics
Publication date: Jun 2010, volume: 7, issue:2, pages: 365 - 374
Publisher: IEEE
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» Source and Boundary Implementation in Vector and Scalar DGTD
Abstract:
We summarize the boundary and source implementation for the several formulations of the discontinuous Galerkin time domain method (DGTD). Since DGTD with zeroth-order scalar basis functions using the upwind flux, coincides with the finite volume time domain (FVTD), many of the concepts developed for FVTD can be ported to DGTD in any of its different formulations (scalar/vector basis, upwind/centered flux). Numerical examples illustrate the different alternatives.
Autors: Alvarez, J.;Angulo, L. D.;Pantoja, M. F.;Bretones, A. R.;Garcia, S. G.;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Jun 2010, volume: 58, issue:6, pages: 1997 - 2003
Publisher: IEEE
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» Source Camera Identification Using Enhanced Sensor Pattern Noise
Abstract:
Sensor pattern noises (SPNs), extracted from digital images to serve as the fingerprints of imaging devices, have been proved as an effective way for digital device identification. However, as we demonstrate in this work, the limitation of the current method of extracting SPNs is that the SPNs extracted from images can be severely contaminated by details from scenes, and as a result, the identification rate is unsatisfactory unless images of a large size are used. In this work, we propose a novel approach for attenuating the influence of details from scenes on SPNs so as to improve the device identification rate of the identifier. The hypothesis underlying our SPN enhancement method is that the stronger a signal component in an SPN is, the less trustworthy the component should be, and thus should be attenuated. This hypothesis suggests that an enhanced SPN can be obtained by assigning weighting factors inversely proportional to the magnitude of the SPN components.
Autors: Li, C.-T.;
Appeared in: IEEE Transactions on Information Forensics and Security
Publication date: Jun 2010, volume: 5, issue:2, pages: 280 - 287
Publisher: IEEE
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» Source-channel rate optimization for progressive image transmission over block fading relay channels [Transactions Papers]
Abstract:
In this paper, we are concerned with the design and analysis of joint source-channel coding schemes for block fading channels with relay-assisted distributed spatial diversity. Assuming a progressive image coder with a constraint on the transmission bandwidth, we formulate a joint source-channel rate allocation scheme that maximizes the expected source throughput. Specifically, using Gaussian as well as BPSK inputs on flat Rayleigh fading channels, we lower bound the average packet error rate by the corresponding mutual information outage probability, and derive the average throughput expression as a function of channel code rates as well as channel SNR for both a frequency-division multiplexing-based baseline system without relaying, and a half-duplex relay system with a decodeand- forward protocol. At high signal-to-noise ratio (SNR), for the systems considered in this paper, we show that our rate optimization problem is a convex function of the channel code rates, and we show that a known recursive algorithm can be used to predict the performance of both systems.
Autors: Kim, H.;Annavajjala, R.;Cosman, P.C.;Milstein, L.B.;
Appeared in: IEEE Transactions on Communications
Publication date: Jun 2010, volume: 58, issue:6, pages: 1631 - 1642
Publisher: IEEE
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» Sovietization of Czechoslovakian Computing: The Rise and Fall of the SAPO Project
Abstract:
After World War II, Antonín Svoboda returned to Czechoslovakia with experience in building analog computers, a keen interest in digital computing technology, and aspirations to establish a computer industry in his homeland. Svoboda's original ideas were further developed by his students and colleagues and reflected in the design of SAPO, the first Czechoslovakian computer, in the 1950s.
Autors: Durnova, Helena;
Appeared in: IEEE Annals of the History of Computing
Publication date: Jun 2010, volume: 32, issue:2, pages: 21 - 31
Publisher: IEEE
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» Space Charge Distribution Measurement in Complex Insulating Structures
Abstract:
Electrical insulation involves more and more complex structures in which the electric field or the material can be heterogeneous. For testing space charge buildup in such structures, one-dimensional measurements are still often used owing to their simplicity. The sample complexity may, however, induce spurious effects that can be confused with space charge. In this paper, from the underlying physics of the pressure-wave propagation (PWP) and the electro-acoustic (PEA) methods, limitations of the one-dimensional model are shown and an analysis procedure is given. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Autors: Stéphane Holé
Appeared in: IEEJ Transactions on Electrical and Electronic Engineering
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Space Charge Measurement in MgO/LDPE Nanocomposite up to Breakdown under DC Ramp Voltage
Abstract:
To understand the basic electric properties of nanosized magnesium oxide (MgO)/low-density polyethylene (LDPE) nanocomposites under an applied DC voltage, the DC breakdown strength and space charge up to the breakdown under a DC ramp voltage were investigated. Compared to that of the LDPE sample, the sample containing a MgO nanofiller (hereafter, called a nanocomposite) had a higher DC breakdown strength. In the case of the LDPE sample, the homo charges, which contained a large negative charge and a small positive charge, were only observed near the electrodes just prior to breakdown. However, in the case of the nanocomposite sample, the positive charge increased as the average field increased until the average field reached a certain value. After that, the positive charge decreased as the average field increased until breakdown occurred. The field enhancement rate (=maximum field/average field) of the nanocomposite sample increased with the average field, until it became saturated. After peaking, the field enhancement rate of the nanocomposite sample decreased as the average field increased. These observations suggest that, instead of the MgO nanofiller suppressing the electronic avalanche, it suppresses the conduction current, which was determined by the space charge, leading to the higher DC breakdown strength. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Autors: Yoshinobu Murakami, Shunsuke Okuzumi, Masayuki Nagao, Masumi Fukuma, Yoitsu Sekiguchi, Manabu Goshowaki, Yoshinao Murata
Appeared in: IEEJ Transactions on Electrical and Electronic Engineering
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Space Vectors Modulation for Nine-Switch Converters
Abstract:
Recently, nine-switch inverter and nine-switch-z-source inverter have been proposed as dual output inverters. In this paper, the space vector modulation (SVM) of nine-switch inverter and nine-switch-z-source inverter is proposed. The proposed method increases the sum of modulation indices up to 15% in contrast with the conventional, scheme in which the sum of modulation indices is equal or less than one. The extra voltage available for a given input dc-voltage, translates to a higher torque–-a critical factor for defining the capacity of products in marketplace. Also, in order to further reduce the cost of power devices and also thermal heat effect, and to reduce the number of semiconductor switching, specific SVM switching pattern is presented. This feature will be advantageous for high-power inverter applications where cost and efficiency are key decision factors. Furthermore, a novel SVM is proposed for minimizing total harmonic distortion. The performance of the proposed SVM for both nine-switch inverter and nine-switch-z-source inverter is verified by simulation. Experimental results validate the simulation results as well as the superiority of the proposed SVM.
Autors: Dehghan Dehnavi , S. M.;Mohamadian, M.;Yazdian, A.;Ashrafzadeh, F.;
Appeared in: IEEE Transactions on Power Electronics
Publication date: Jun 2010, volume: 25, issue:6, pages: 1488 - 1496
Publisher: IEEE
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» Space-time clutter rejection and target passive detection using the APES method
Abstract:
A new method to reject ground clutter using the Amplitude and Phase EStimation (APES) method is proposed. The theoretical approach is followed by the application of this method to the rejection of such an interference in the frameof a bistatic passive radar using digital video broadcasting - terrestrial (DVB-T) transmitters.
Autors: Raout, J.;Santori, A.;Moreau, E.;
Appeared in: IET Signal Processing
Publication date: Jun 2010, volume: 4, issue:3, pages: 298 - 304
Publisher: IEEE
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» SPARE—A Scalable Algorithm for Passive, Structure Preserving, Parameter-Aware Model Order Reduction
Abstract:
This paper describes a flexible and efficient new algorithm for model order reduction of parameterized systems. The method is based on the reformulation of the parameterized system as a perturbation-like parallel interconnection of the nominal transfer function and the nonparameterized transfer function sensitivities with respect to the parameter variations. Such a formulation reveals an explicit dependence on each parameter which is exploited by reducing each component system independently via a standard nonparameterized structure preserving algorithm. Therefore, the resulting smaller size interconnected system retains the structure of the original system with respect to parameter dependence. This allows for better accuracy control, enabling independent adaptive order determination with respect to each parameter and adding flexibility in simulation environments. It is shown that the method is efficiently scalable and preserves relevant system properties such as passivity. The new technique can handle fairly large parameter variations on systems whose outputs exhibit smooth dependence on the parameters, also allowing design space exploration to some degree. Several examples show that besides the added flexibility and control, when compared with competing algorithms, the proposed technique can, in some cases, produce smaller reduced models with potential accuracy gains.
Autors: Villena, J. F.;Silveira, L. M.;
Appeared in: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
Publication date: Jun 2010, volume: 29, issue:6, pages: 925 - 938
Publisher: IEEE
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» Sparse Approximation Through Boosting for Learning Large Scale Kernel Machines
Abstract:
Recently, sparse approximation has become a preferred method for learning large scale kernel machines. This technique attempts to represent the solution with only a subset of original data points also known as basis vectors, which are usually chosen one by one with a forward selection procedure based on some selection criteria. The computational complexity of several resultant algorithms scales as in time and in memory, where is the number of training points and is the number of basis vectors as well as the steps of forward selection. For some large scale data sets, to obtain a better solution, we are sometimes required to include more basis vectors, which means that is not trivial in this situation. However, the limited computational resource (e.g., memory) prevents us from including too many vectors. To handle this dilemma, we propose to add an ensemble of basis vectors instead of only one at each forward step. The proposed method, closely related to gradient boosting, could decrease the required number of forward steps significantly and thus a large fraction of computational cost is saved. Numerical experiments on three large scale regression tasks and a classification problem demonstrate the effectiveness of the proposed approach.
Autors: Sun, P.;Yao, X.;
Appeared in: IEEE Transactions on Neural Networks
Publication date: Jun 2010, volume: 21, issue:6, pages: 883 - 894
Publisher: IEEE
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» Sparse Bayesian Learning of Filters for Efficient Image Expansion
Abstract:
We propose a framework for expanding a given image using an interpolator that is trained in advance with training data, based on sparse Bayesian estimation for determining the optimal and compact support for efficient image expansion. Experiments on test data show that learned interpolators are compact yet superior to classical ones.
Autors: Kanemura, A.;Maeda, S.-I.;Ishii, S.;
Appeared in: IEEE Transactions on Image Processing
Publication date: Jun 2010, volume: 19, issue:6, pages: 1480 - 1490
Publisher: IEEE
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» Sparse Non-Gaussian Component Analysis
Abstract:
Non-Gaussian component analysis (NGCA) introduced in offered a method for high-dimensional data analysis allowing for identifying a low-dimensional non-Gaussian component of the whole distribution in an iterative and structure adaptive way. An important step of the NGCA procedure is identification of the non-Gaussian subspace using principle component analysis (PCA) method. This article proposes a new approach to NGCA called sparse NGCA which replaces the PCA-based procedure with a new the algorithm we refer to as convex projection.
Autors: Diederichs, E.;Juditsky, A.;Spokoiny, V.;Schutte, C.;
Appeared in: IEEE Transactions on Information Theory
Publication date: Jun 2010, volume: 56, issue:6, pages: 3033 - 3047
Publisher: IEEE
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» Sparse Recovery Using Sparse Matrices
Abstract:
In this paper, we survey algorithms for sparse recovery problems that are based on sparse random matrices. Such matrices has several attractive properties: they support algorithms with low computational complexity, and make it easy to perform incremental updates to signals. We discuss applications to several areas, including compressive sensing, data stream computing, and group testing.
Autors: Gilbert, A.;Indyk, P.;
Appeared in: Proceedings of the IEEE
Publication date: Jun 2010, volume: 98, issue:6, pages: 937 - 947
Publisher: IEEE
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» Sparse Representation for Computer Vision and Pattern Recognition
Abstract:
Techniques from sparse signal representation are beginning to see significant impact in computer vision, often on nontraditional applications where the goal is not just to obtain a compact high-fidelity representation of the observed signal, but also to extract semantic information. The choice of dictionary plays a key role in bridging this gap: unconventional dictionaries consisting of, or learned from, the training samples themselves provide the key to obtaining state-of-the-art results and to attaching semantic meaning to sparse signal representations. Understanding the good performance of such unconventional dictionaries in turn demands new algorithmic and analytical techniques. This review paper highlights a few representative examples of how the interaction between sparse signal representation and computer vision can enrich both fields, and raises a number of open questions for further study.
Autors: Wright, J.;Ma, Y.;Mairal, J.;Sapiro, G.;Huang, T. S.;Yan, S.;
Appeared in: Proceedings of the IEEE
Publication date: Jun 2010, volume: 98, issue:6, pages: 1031 - 1044
Publisher: IEEE
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» Sparse Representations in Audio and Music: From Coding to Source Separation
Abstract:
Sparse representations have proved a powerful tool in the analysis and processing of audio signals and already lie at the heart of popular coding standards such as MP3 and Dolby AAC. In this paper we give an overview of a number of current and emerging applications of sparse representations in areas from audio coding, audio enhancement and music transcription to blind source separation solutions that can solve the “cocktail party problem.” In each case we will show how the prior assumption that the audio signals are approximately sparse in some time-frequency representation allows us to address the associated signal processing task.
Autors: Plumbley, M. D.;Blumensath, T.;Daudet, L.;Gribonval, R.;Davies, M. E.;
Appeared in: Proceedings of the IEEE
Publication date: Jun 2010, volume: 98, issue:6, pages: 995 - 1005
Publisher: IEEE
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» Sparsity and Compressed Sensing in Radar Imaging
Abstract:
Remote sensing with radar is typically an ill-posed linear inverse problem: a scene is to be inferred from limited measurements of scattered electric fields. Parsimonious models provide a compressed representation of the unknown scene and offer a means for regularizing the inversion task. The emerging field of compressed sensing combines nonlinear reconstruction algorithms and pseudorandom linear measurements to provide reconstruction guarantees for sparse solutions to linear inverse problems. This paper surveys the use of sparse reconstruction algorithms and randomized measurement strategies in radar processing. Although the two themes have a long history in radar literature, the accessible framework provided by compressed sensing illuminates the impact of joining these themes. Potential future directions are conjectured both for extension of theory motivated by practice and for modification of practice based on theoretical insights.
Autors: Potter, L. C.;Ertin, E.;Parker, J. T.;Cetin, M.;
Appeared in: Proceedings of the IEEE
Publication date: Jun 2010, volume: 98, issue:6, pages: 1006 - 1020
Publisher: IEEE
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» Spatial Harmonics and Homogenization of Negative-Refractive-Index Transmission-Line Structures
Abstract:
In this paper, we discuss negative-refractive-index transmission-line (NRI-TL) metamaterial structures with respect to spatial harmonics. The power in the fundamental spatial harmonic is shown to yield a measure that relates to the homogeneity of the metamaterial. It is shown that NRI-TL metamaterials yield highly homogeneous field distributions if both the unit cell is short compared to the guided wavelength, and if the unloaded unit cell is short compared to the “free space” wavelength. Based on the homogeneity, we provide practical design choices for NRI-TL metamaterial unit cells. Under the restriction of a high homogeneity we derive expressions for extracting an effective permittivity and permeability. Circuit theory results and full-wave eigenmode simulations of two NRI-TL structures are presented.
Autors: Zedler, M.;Eleftheriades, G. V.;
Appeared in: IEEE Transactions on Microwave Theory and Techniques
Publication date: Jun 2010, volume: 58, issue:6, pages: 1521 - 1531
Publisher: IEEE
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» Spatial stability of non-steady Stokes flow along a pipe
Abstract:
Estimates for the growth and decay of the cross-section total energy flux in the form of exponential lower and upper bounds are obtained for non-steady Stokes flow in a semi-infinite three-dimensional pipe of uniform star-shaped cross-section. The method depends upon the derivation and integration of a first-order differential inequality.
Autors: R.J., Knops , C., Lupoli
Appeared in: International Journal of Engineering Science
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Spatial-Temporal Color Video Reconstruction From Noisy CFA Sequence
Abstract:
Single-sensor digital video cameras use a color filter array (CFA) to capture video and a color demosaicking (CDM) procedure to reproduce the full color sequence. The reproduced video frames suffer from the inevitable sensor noise introduced in the video acquisition process. This paper presents a spatial-temporal denoising and demosaicking scheme that works without explicit motion estimation. We first perform patch based denoising on the mosaic CFA video. For each CFA patch to be denoised, similar patches are selected within a local spatial-temporal neighborhood. The principal component analysis is performed on the selected patches to remove noise. We then apply an initial single-frame CDM to the denoised CFA data, and subsequently post-process the demosaicked frames by exploiting the spatial-temporal redundancy to reduce the color artifacts. The experimental results on simulated and real noisy CFA sequences demonstrate that the proposed spatial-temporal CFA video denoising and demosaicking scheme can significantly reduce the noise-caused color artifacts and effectively preserve the image edge structures.
Autors: Zhang, L.;Dong, W.;Wu, X.;Shi, G.;
Appeared in: IEEE Transactions on Circuits and Systems for Video Technology
Publication date: Jun 2010, volume: 20, issue:6, pages: 838 - 847
Publisher: IEEE
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» Spatio-Temporal Data Fusion for 3D+T Image Reconstruction in Cerebral Angiography
Abstract:
This paper provides a framework for generating high resolution time sequences of 3D images that show the dynamics of cerebral blood flow. These sequences have the potential to allow image feedback during medical procedures that facilitate the detection and observation of pathological abnormalities such as stenoses, aneurysms, and blood clots. The 3D time series is constructed by fusing a single static 3D model with two time sequences of 2D projections of the same imaged region. The fusion process utilizes a variational approach that constrains the volumes to have both smoothly varying regions separated by edges and sparse regions of nonzero support. The variational problem is solved using a modified version of the Gauss–Seidel algorithm that exploits the spatio-temporal structure of the angiography problem. The 3D time series results are visualized using time series of isosurfaces, synthetic X-rays from arbitrary perspectives or poses, and 3D surfaces that show arrival times of the contrasted blood front using color coding. The derived visualizations provide physicians with a previously unavailable wealth of information that can lead to safer procedures, including quicker localization of flow altering abnormalities such as blood clots, and lower procedural X-ray exposure. Quantitative SNR and other performance analysis of the algorithm on computational phantom data are also presented.
Autors: Copeland, A. D.;Mangoubi, R. S.;Desai, M. N.;Mitter, S. K.;Malek, A. M.;
Appeared in: IEEE Transactions on Medical Imaging
Publication date: Jun 2010, volume: 29, issue:6, pages: 1238 - 1251
Publisher: IEEE
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» Speak to Win (Tracy, B.; 2008) [Book Review]
Abstract:
In 12 chapters, the author moves through topics such as the art of speaking, preparation and planning, the strong opening, platform mastery, vocal mastery, the strong conclusion, and a few other tips on negotiation thrown in along the way. While the book could provide ideas for an accomplished or experienced speaker, it could also serve as a quick reference for someone embarking on a new career or career enhancement.
Autors: Floyd, R.E.;
Appeared in: IEEE Transactions on Professional Communication
Publication date: Jun 2010, volume: 53, issue:2, pages: 183 - 184
Publisher: IEEE
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» Speak to Win Book Review
Abstract:
Autors: Tracy, B.;
Appeared in: IEEE Transactions on Professional Communication
Publication date: Jun 2010, volume: 53, issue:2, pages: 183 - 184
Publisher: IEEE
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» Special Section on Relay Communications
Abstract:
Autors: Yuen, C.;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Jun 2010, volume: 59, issue:5, pages: 2118 - 2119
Publisher: IEEE
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» Spectral dependency of superconducting single photon detectors
Abstract:
We investigate the effect of varying both incoming optical wavelength and width of NbN nanowires on the superconducting single photon detectors (SSPD) detection efficiency. The SSPD are current biased close to critical value and temperature fixed at 4.2 K, far from transition. The experimental results are found to verify with a good accuracy predictions based on the “hot spot model,” whose size scales with the absorbed photon energy. With larger optical power inducing multiphoton detection regime, the same scaling law remains valid, up to the three-photon regime. We demonstrate the validity of applying a limited number of measurements and using such a simple model to reasonably predict any SSPD behavior among a collection of nanowire device widths at different photon wavelengths. These results set the basis for designing efficient single photon detectors operating in the infrared (2–5 μm range).
Autors: Maingault, L.;Tarkhov, M.;Florya, I.;Semenov, A.;Espiau de Lamaestre, R.;Cavalier, P.;Goltsman, G.;Poizat, J.-P.;Villegier, J.-C.;
Appeared in: Journal of Applied Physics
Publication date: Jun 2010, volume: 107, issue:11, pages: 116103 - 116103-3
Publisher: IEEE
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» Spectral Reflectance Imaging for a Multiplexed, High-Throughput, Label-Free, and Dynamic Biosensing Platform
Abstract:
There are a number of emerging optical biosensing techniques utilizing interferometric and resonant characteristics of light. We have recently demonstrated an interferometric technique, the spectral reflectance imaging biosensor (SRIB) that uses optical wave interference to detect changes in the optical path length as a result of capture of biological material on the microarray surface without the need for labels and secondary reagents. In this paper, we review the principles and performance of the SRIB technique in the context of label-free biosensors and demonstrate its high-throughput, quantitative and calibrated, versatile, and dynamic (kinetic) capabilities. A unique aspect of the SRIB system is that the measurement technique is independent of surface conformation and allows for utilization of novel polymeric coatings for surface binding, thus providing a versatile and high-density platform. We present experimental results on multiplexed antibody/antigen arrays and DNA hybridization in real time, as well as specific binding of whole virus particles. The simplicity of the overall system, its high sensitivity and compatibility with glass surface chemistries, and a linear dynamic range of nearly four orders of magnitude makes SRIB a promising platform for multiplexed detection of different biological analytes in a complex sample, with potential impact in research and clinical applications.
Autors: Ozkumur, E.;Lopez, C. A.;Yalcin, A.;Connor, J. H.;Chiari, M.;Unlu, M. S.;
Appeared in: IEEE Journal of Selected Topics in Quantum Electronics
Publication date: Jun 2010, volume: 16, issue:3, pages: 635 - 646
Publisher: IEEE
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» Spectrum sensing with active cognitive systems
Abstract:
Spectrum sensing is critical for cognitive systems to locate spectrum holes. In the IEEE 802.22 proposal, short quiet periods are arranged inside frames to perform a coarse intra-frame sensing as a pre-alarm for fine inter-frame sensing. However, the limited sample size of the quiet periods may not guarantee a satisfying performance and an additional burden of quiet-period synchronization is required. To improve the sensing performance, we first propose a quiet-active sensing scheme in which inactive customer-provided equipments (CPEs) will sense the channels in both the quiet and active periods. To avoid quiet-period synchronization, we further propose to utilize (optimized) active sensing, in which the quiet periods are replaced by `quiet samples¿ in other domains, such as quiet sub-carriers in OFDMA systems. By doing so, we not only save the need for synchronization, but also achieve selection diversity by choosing quiet sub-carriers based on channel conditions. The proposed active sensing scheme is also promising for spectrum sharing applications where both the cognitive and primary systems can be active simultaneously.
Autors: Song, S.H.;Hamdi, K.;Letaief, K.B.;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jun 2010, volume: 9, issue:6, pages: 1849 - 1854
Publisher: IEEE
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» Spectrum Shaping for Heterodyne Detection of Wavelength-Swept WDM Signal: Feasibility Study of Mach–Zehnder Interferometer-Type Periodic Filter
Abstract:
In this paper, we investigate the performance of a spectrum shaping technique for the suppression of image-induced crosstalk during the heterodyne detection of wavelength-swept wavelength-division-multiplexed (WDM) signals. In particular, we focus on a Mach–Zehnder interferometer (MZI) filter as a promising candidate for a spectrum shaping filter. We calculate the relationship between the power penalty, signal-to-crosstalk ratio (SCR) and free spectral range (FSR) of the MZI filter, the bandwidth of an IF filter, and the bit rate per channel, taking into consideration three tandem configurations of plural MZIs with different FSRs. And, to clarify the tolerance to the wavelength drift that occurs in actual systems, we investigate the impact of the wavelength mismatch between a WDM signal and a local light. The calculated results provide the criteria for suppressing the image-induced penalty quantitatively, and the SCR improvements that are realized when the tandem configurations are used. The results also indicate that each type of MZI tandem configuration has merits and demerits, depending on the ratio of the bit rate per channel to the channel spacing and the reception quality requirements. Furthermore, we also describe experiments that we performed with respect to the generation, spectrum shaping, and selective heterodyne detection of a three-channel super-dense WDM signal with a channel spacing of 25 GHz transmitted at 1.0 Gb/s per channel, by using tandem configurations of three MZI filters ( , 12.5, and 6.25 GHz). The experimental results agreed well with the calculated results, which are based on the consideration discussed in Sections III and IV , and the results confirmed that the image rejection was well performed. Moreover, we confirmed that we can suppress the SCR degradation b- - y using the tandem configurations for a spectrum shaper. The allowable normalized wavelength mismatch for a degradation of 1.0 dB can be enhanced from 0.012 for 1-MZI to 0.016 and 0.04 for 2-MZI and 3-MZI configurations, respectively.
Autors: Taniguchi, T.;Sakurai, N.;Kimura, H.;Hadama, H.;
Appeared in: Journal of Lightwave Technology
Publication date: Jun 2010, volume: 28, issue:11, pages: 1693 - 1702
Publisher: IEEE
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» Spectrum shaping: a new perspective on cognitive radio¿part I: coexistence with coded legacy transmission
Abstract:
A new approach to cognitive radio based on the premise that the legacy link is not fully loaded by the legacy service is presented. The assumption implies that there is a non-negligible margin to accommodate a cognitive transmission; this accommodation is achieved by spectrum shaping of the cognitive user. Much prior work on cognitive systems captures the effect of interference by the interference power level. In contrast, the current work characterizes interference by its induced degradation on the legacy user. Despite ignorance of the legacy user¿s message, the spectrum shaped cognitive user can always operate at its full available power. As a result, logarithmic growth of the cognitive transmission rate is achievable. In Part I of this two-part paper, analysis is provided for both scalar and vector system models where the legacy system employs coded transmission (Part II examines analog legacy users). The logarithmic growth rates, i.e., the prelog coefficients, of cognitive transmission rates in the high-power regime, are established for both the scalar and vector system models considered.
Autors: Zhang, W.;Mitra, U.;
Appeared in: IEEE Transactions on Communications
Publication date: Jun 2010, volume: 58, issue:6, pages: 1857 - 1867
Publisher: IEEE
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» Speedup of FEM Micromagnetic Simulations With Graphical Processing Units
Abstract:
We have adapted our finite element micromagnetic simulation software to the massively parallel architecture of graphical processing units (GPUs) with double-precision floating point accuracy. Using the example of Standard Problem #4 with different numbers of discretization points, we demonstrate the high speed performance of a single GPU compared with an OpenMP-parallelized version of the code using eight CPUs. The adaption of both the magnetostatic field calculation and the time integration of the Landau-Lifshitz-Gilbert equation routines can lead to a speedup factor of up to four. The gain in computation performance of the GPU code increases with increasing number of discretization nodes. The computation time required for high-resolution micromagnetic simulations of the magnetization dynamics in large magnetic samples can thus be reduced effectively by employing GPUs.
Autors: Kakay, A.;Westphal, E.;Hertel, R.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2303 - 2306
Publisher: IEEE
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» SPICE Macromodel of Spin-Torque-Transfer-Operated Magnetic Tunnel Junctions
Abstract:
The electrical behavior of a magnetic tunnel junction (MTJ) using spin-torque-transfer (STT) switching was modeled using a SPICE subcircuit. The subcircuit is a two-terminal device that exhibits the electrical characteristics of an STT-MTJ. These characteristics include all the major transient characteristics of an MTJ, including the hysteresis, bias voltage dependence of the resistance, and the critical switching current versus the critical switching time. The model was designed to work over a wide range of operating conditions. Simulation and analysis of an MTJ-based D flip-flop are presented to demonstrate possible applications of the model.
Autors: Harms, J. D.;Ebrahimi, F.;Yao, X.;Wang, J.-P.;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Jun 2010, volume: 57, issue:6, pages: 1425 - 1430
Publisher: IEEE
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» Spin Accumulation in Cr Nanoparticles in Single Electron Tunneling Regime
Abstract:
We have studied spin-dependent single electron tunneling in Cr nanoparticles with a diameter of 4 nm using Fe/MgO/Cr-nanoparticles/MgO/Fe double tunnel junctions. The transport properties are governed by the Coulomb blockade, showing suppression of current at low bias voltages. Magnetoresistance is clearly observed at a bias voltage over 0.25 V, and the magnetoresistance ratio increases with increasing bias voltage. These results suggest that the magnetoresistance is due to the spin accumulation in Cr nanoparticles. With some assumption, the minimum value of spin relaxation time in Cr nanoparticles is roughly estimated to be on the order of tens of nanoseconds .
Autors: Koda, T.;Mitani, S.;Mizuguchi, M.;Takanashi, K.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2060 - 2062
Publisher: IEEE
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» Spin Coulomb Drag in a One-Dimensional Spin-Polarized Conductor
Abstract:
The spin Coulomb drag is a distinctive feature of spin-polarized transport. The current of majority spins can induce a current of minority spin carriers via the transconductivity. The friction is caused by the Coulomb interaction between up- and down-spin. This interaction reduces the current but does not change the spin-polarization. We calculate the conductivities and the transconductivity for a spin-polarized interacting 1-D electron gas for a lattice without inversion symmetry in the presence of nonmagnetic impurities. Due to the Luttinger liquid properties, the temperature dependence of the transport correlation functions follows power laws of with nonuniversal exponents.
Autors: Schlottmann, P.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 1346 - 1349
Publisher: IEEE
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» Spin injection and circular polarized electroluminescence from InAs-based spin-light emitting diode structures
Abstract:
We have investigated circularly polarized electroluminescence (EL) from hybrid II-Mn-VI/III–V light emitting diodes (LED’s) at low temperatures in magnetic fields upto 10 T. Both magnetic (the Brillouin paramagnet Cd1-xMnxSe) and nonmagnetic (CdSe) injectors were studied. Electrons, spin unpolarized (n-CdSe) or spin-polarized (n-CdMnSe), were injected into wide InAs quantum wells, where they recombined with unpolarized holes injected from p-type InAs/AlAsSb layers. Detailed measurements and modeling of the circular polarization of the resulting midinfrared EL were carried out to explore and quantify the additional complexities of this materials system compared with the extensively studied GaAs-based spin-LED structures. We show that optical and spin polarization in narrow gap semiconductors such as InAs are not simply related to each other. To analyze the complex relationship, we have developed and used a detailed rate equation model, which incorporates the band-structure of electrons and holes in a magnetic field, a finite ratio of recombination and spin-flip times, and the spin polarization of the CdMnSe spin-aligner as a function of injection current. The latter was determined in situ by circular polarized photoluminescence measurements on the injector material. Experimentally, the circular polarization degrees of magnetic and nonmagnetic structures are observed to be very similar, when the magnetic samples have low effective Mn incorporation. This results from a combination of the consequently low spin polarization of the aligner and comparable spin and recombination life times in InAs.
Autors: Meining, C. J.;Stier, A. V.;McCombe, B. D.;Chado, I.;Grabs, P.;Schmidt, G.;Molenkamp, L. W.;
Appeared in: Journal of Applied Physics
Publication date: Jun 2010, volume: 107, issue:11, pages: 114510 - 114510-10
Publisher: IEEE
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» Spin Torque Oscillator With Negative Magnetic Anisotropy Materials for MAMR
Abstract:
Microwave assisted magnetic recording (MAMR) has recently emerged as a candidate to solve the trilemma in magnetic recording. In MAMR the magnetizations of recording medium can be switched with much lower magnetic field by magnetic resonance, which however requires a higher frequency oscillator than 20 GHz. In this paper, it is described that spin torque oscillator (STO) using a magnetic material with a large negative uniaxial anisotropy has a possibility to generate higher frequency and stable magnetic field and it might be preferable to a conventional oscillator with soft magnetic materials.
Autors: Yoshida, K.;Yokoe, M.;Ishikawa, Y.;Kanai, Y.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2466 - 2469
Publisher: IEEE
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» Spin Torques in Point Contacts to Exchange-Biased Ferromagnetic Films
Abstract:
Hysteretic magneto-resistance of point contacts formed between non-magnetic tips and single ferromagnetic films exchange-pinned by antiferromagnetic films is investigated. The analysis of the measured current driven and field driven hysteresis agrees with the recently proposed model of the surface spin-valve, where the spin orientation at the interface can be different from that in the bulk of the film. The switching in magneto-resistance at low fields is observed to depend significantly on the direction of the exchange pinning, which allows identifying this transition as a reversal of interior spins of the pinned ferromagnetic films. The switching at higher fields is thus due to a spin reversal in the point contact core, at the top surface of the ferromagnet, and does not exhibit any clear field offset when the exchange-pinning direction or the magnetic field direction is varied. This magnitude of the switching field of the surface spins varies substantially from contact to contact and sometimes from sweep to sweep, which suggests that the surface coercivity can change under very high current densities and/or due to the particular microstructure of the point contact. In contrast, no changes in the effect of the exchange biasing on the interior spins are observed at high currents, possibly due to the rapid drop in the current density away from nanometer sized point contact cores.
Autors: Yanson, I. K.;Naidyuk, Y. G.;Balkashin, O. P.;Fisun, V. V.;Triputen, L. Y.;Andersson, S.;Korenivski, V.;Yanson, Y. I.;Zabel, H.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2094 - 2096
Publisher: IEEE
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» Spin Transfer on Low Resistance-Area MgO-Based Magnetic Tunnel Junctions Prepared by Ion Beam Deposition
Abstract:
This work reports spin transfer switching results on nano-sized MgO-based magnetic tunnel junctions (MTJs) prepared by Ion Beam deposition (IBD). Nano-devices with areas down to 60 nm 180 nm have been successfully nanofabricated. The MgO deposition conditions were optimized aiming at reducing the resistance-area (RA) product, and RA value as low as 0.8 could be successfully obtained for 0.75 nm thick MgO barriers. The average switching current density of 5.45 can be obtained for a MTJ nanopillar with the dimension of 225 nm 730.3 nm with low RA of 1.47 .
Autors: Yang, J.;Macedo, R.;Debs, M. G.;Ferreira, R.;Cardoso, S.;Freitas, P. J. P.;Teixeira, J. M.;Ventura, J. O.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2002 - 2004
Publisher: IEEE
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» Spin Transfer Switching and MR Properties of Co/Pt Multilayered Free Layers for Submicron Sized Magneto-Optical Light Modulation Device
Abstract:
Co/Pt multilayered films show strong perpendicular magnetic anisotropy and have a large magneto-optical Kerr effect in the short wavelength side. To use these films with submicron spatial light modulators driven by spin transfer switching (STS), we fabricated current perpendicular to plane giant magnetoresistance (CPP-GMR) and tunnel magnetoresistance (TMR) devices with Co/Pt multilayers for free layers and investigated the MR properties, the STS characteristics, and the Kerr effects. A Kerr hysteresis loop was clearly observed in the CPP-GMR device, which was 125 180 nm . Full magnetization reversal of the Co/Pt multilayered film by spin transfer torque was demonstrated for a CPP-GMR device with a Cu-based top electrode. On the other hand, there was hardly any resistance change in a CPP-GMR with a transparent top electrode due to the low MR ratio of the device. A TMR stack with a Ag buffer layer showed a strong perpendicular magnetic anisotropy. An MR curve was detected for a TMR device with a transparent top electrode.
Autors: Machida, K.;Furukawa, K.;Funabashi, N.;Aoshima, K.-I.;Kuga, K.;Ishibashi, T.;Shimidzu, N.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2171 - 2174
Publisher: IEEE
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» Spin wave assisted current induced magnetic domain wall motion
Abstract:
The interaction between the propagating spin waves and the current driven motion of a transverse domain wall in magnetic nanowires is studied by micromagnetic simulations. If the speed of domain walls due to current induced spin transfer torque is comparable to the velocity driven by spin waves, the speed of domain wall is improved by applying spin waves. The domain wall velocity can be manipulated by the frequency and amplitude of spin waves. The effect of spin waves is suppressed in the high current density regime in which the domain wall is mostly driven by current induced spin transfer torque.
Autors: Jamali, Mahdi;Yang, Hyunsoo;Lee, Kyung-Jin;
Appeared in: Applied Physics Letters
Publication date: Jun 2010, volume: 96, issue:24, pages: 242501 - 242501-3
Publisher: IEEE
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» Spin- and Spray-Deposited Single-Walled Carbon-Nanotube Electrodes for Organic Solar Cells
Abstract:
Organic bulk-heterojunction solar cells using thin-film single-walled carbon-nanotube (SWCNT) anodes deposited on glass are reported. Two types of SWCNT films are investigated: spin-coated films from dichloroethane (DCE), and spray-coated films from deionized water using sodium dodecyl sulphate (SDS) or sodium dodecyl benzene sulphonate (SDBS) as the surfactant. All of the films are found to be mechanically robust, with no tendency to delaminate from the underlying substrate during handling. Acid treatment with HNO3 yields high conductivities >1000 S cm-1 for all of the films, with values of up to 7694 ± 800 S cm-1 being obtained when using SDS as the surfactant. Sheet resistances of around 100 [Omega] sq-1 are obtained at reasonable transmission, for example, 128 ± 2 [Omega] sq-1 at 90% for DCE, 57 ± 3 [Omega] sq-1 at 65% for H2O:SDS, and 68 ± 5 [Omega] sq-1 at 70% for H2O:SDBS. Solar cells are fabricated by successively coating the SWCNT films with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS), a blend of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxy-carbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM), and LiF/Al. The resultant devices have respective power conversions of 2.3, 2.2 and 1.2% for DCE, H2O:SDS and H2O:SDBS, with the first two being at a virtual parity with reference devices using ITO-coated glass as the anode (2.3%).
Autors: Sungsoo Kim, Jonghyuk Yim, Xuhua Wang, Donal D.C. Bradley, Soonil Lee, John C. deMello
Appeared in: Advanced Functional Materials
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Spin-Flipping Associated With the Antiferromagnet IrMn
Abstract:
We have used current-perpendicular-to-plane magnetoresistance measurements of Py-based exchange-biased spin-valves containing IrMn inserts of thickness to estimate the spin-flipping probability of the antiferromagnet IrMn. From to 1 nm, we find a rapid decrease in , by about a factor of 50—here is the area through which the CPP current flows, and and are the resistances with the moments of the two Py layers oriented anti-parallel (AP) or parallel (P) to each other. We attribute this decrease to very strong spin-flipping in the IrMn/Cu interfacial region, with effective spin diffusion length 0.24 nm, only about 1 monolayer (ML). But for from 2 to 5 nm, the decrease of with increasing IrMn thickness is much slower. The reason for this slowing is not yet clear.
Autors: Acharyya, R.;Nguyen, H. Y. T.;Pratt, W. P.;Bass, J.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 1454 - 1456
Publisher: IEEE
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» Spiral periodic structure inside chaotic region in parameter-space of a Chua circuit
Abstract:
In this letter we investigate, via numerical simulations, the parameter-space of the set of autonomous first-order differential equations of a Chua circuit. We show that this parameter-space presents self-organized periodic structures immersed in a chaotic region, forming a single spiral structure that coils up around a focal point. Additionally, bifurcation diagrams are used to show that those periodic structures also organize themselves in period-adding cascades, along specific directions that point towards this same focal point. Copyright © 2010 John Wiley & Sons, Ltd.
Autors: Holokx A. Albuquerque, Paulo C. Rech
Appeared in: International Journal of Circuit Theory and Applications
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Spontaneous long and short-range ferroelectric ordering in Pb0.55La0.30TiO3 ceramics
Abstract:
In this work, we investigated the temperature dependence of short and long-range ferroelectric ordering in Pb0.55La0.30TiO3 relaxor composition. High-resolution x-ray powder diffraction measurements revealed a clear spontaneous macroscopic cubic-to-tetragonal phase transition in the PLT relaxor sample at ∼60 K below the maximum of the dielectric constant peak (Tm). Indeed, the x-ray diffraction (XRD) data showed that at 300 K (above Tm but below the Burns temperature, TB) the long-range order structure corresponds to a macroscopic cubic symmetry, space group number 221 (Pm-3m), whereas the data collected at 20 K revealed a macroscopic tetragonal symmetry, space group number 99 (P4mm) with c/a=1.0078, that is comparable to that of a normal ferroelectric. These results show that for samples with tetragonal composition, the long-range ferroelectric order may be recovered spontaneously at cryogenics temperatures, in contrast to ferroelectric samples with rhombohedral symmetry. On the other hand, x-ray absorption spectroscopy investigations intriguingly revealed the existence of local tetragonal disorder around Ti atoms for temperatures far below Tm and above TB, for which the sample presents macroscopic tetragonal and cubic symmetries, respectively.
Autors: Mastelaro, V. R.;Mascarenhas, Y. P.;Neves, P. P.;Mir, M.;Doriguetto, A. C.;Michalowicz, A.;Moscovici, J.;Lente, M. H.;Eiras, J. A.;
Appeared in: Journal of Applied Physics
Publication date: Jun 2010, volume: 107, issue:11, pages: 114103 - 114103-9
Publisher: IEEE
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» Sputtered Ru-Ti, Ru-N and Ru-Ti-N films as Cu diffusion barreier
Abstract:
Ultrathin Ru-Ti alloy, Ru-N and Ru-Ti-N films were fabricated as diffusion barriers to Cu metallization. The thermal stability, phase formation surface morphology and atomic depth profile of the Cu/Ru-Ti(10nm)/Si, Cu/Ru-N(10nm)/Si and Cu/Ru-Ti-N(10nm) /Si structures after annealing at different temperatures were investigated. Comparing to the single Ru layer, both N doping and Ti alloying improve the thermal stability and diffusion barrier properties to Cu. The Cu on the Ru-Ti layer has better morphology than Cu on the Ru-N layer, while the Ru-Ti-N layer has the best thermal stability and has great potential to be applied as a single layer diffusion barrier.
Autors: Ji, Li , Hai-Sheng, Lu , Yong-Wei, Wang , Xin-Ping, Qu
Appeared in: Microelectronic Engineering
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Square-root second-order extended Kalman filter and its application in target motion analysis
Abstract:
In this study, a new non-linear filter based on second-order extended Kalman technology and squareroot Kalman algorithm is proposed and applied to the problem of target motion analysis (TMA). By orthogonalising the state vectors with the square root of covariance matrix, the authors reduce the computational complexity in the second-order extended Kalman algorithm, and then we deduce a secondorder extended Kalman algorithm based on square-root Kalman technology, which is more numerically stable and can guarantee positive and semi-definiteness of the state covariance. The authors apply the new algorithm to a TMA problem, and prove with both numerical simulation and actual experimentation that their algorithm performs well in the significant non-linear systems.
Autors: Daowang, F.;Teng, L.;Tao, H.Z.;
Appeared in: IET Radar, Sonar & Navigation
Publication date: Jun 2010, volume: 4, issue:3, pages: 329 - 335
Publisher: IEEE
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» SRAM Read/Write Margin Enhancements Using FinFETs
Abstract:
Process-induced variations and sub-threshold leakage in bulk-Si technology limit the scaling of SRAM into sub-32 nm nodes. New device architectures are being considered to improve control and reduce short channel effects. Among the likely candidates, FinFETs are the most attractive option because of their good scalability and possibilities for further SRAM performance and yield enhancement through independent gating. The enhancements to read/write margins and yield are investigated in detail for two cell designs employing independently gated FinFETs. It is shown that FinFET-based 6-T SRAM cells designed with pass-gate feedback (PGFB) achieve significant improvements in the cell read stability without area penalty. The write-ability of the cell can be improved through the use of pull-up write gating (PUWG) with a separate write word line (WWL). The benefits of these two approaches are complementary and additive, allowing for simultaneous read and write yield enhancements when the PGFB and PUWG designs are used in combination.
Autors: Carlson, A.;Guo, Z.;Balasubramanian, S.;Zlatanovici, R.;King Liu, T.-J.;Nikolic, B.;
Appeared in: IEEE Transactions on Very Large Scale Integration Systems
Publication date: Jun 2010, volume: 18, issue:6, pages: 887 - 900
Publisher: IEEE
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» Ssecrett and NeuroTrace: Interactive Visualization and Analysis Tools for Large-Scale Neuroscience Data Sets
Abstract:
Data sets imaged with modern electron microscopes can range from tens of terabytes to about one petabyte. Two new tools, Ssecrett and NeuroTrace, support interactive exploration and analysis of large-scale optical-and electron-microscopy images to help scientists reconstruct complex neural circuits of the mammalian nervous system.
Autors: Won-Ki Jeong;Beyer, J.;Hadwiger, M.;Blue, R.;Law, C.;Vazquez-Reina, A.;Reid, R.C.;Lichtman, J.;Pfister, H.;
Appeared in: IEEE Computer Graphics and Applications
Publication date: Jun 2010, volume: 30, issue:3, pages: 58 - 70
Publisher: IEEE
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» SSRF Phase-I Insertion Devices
Abstract:
Shanghai Light Source (SSRF) is a third generation synchrotron radiation facility with the intermediate energy of 3.5 GeV. Two wigglers W80 and W140, one elliptically polarizing undulator EPU100 of the APPLE-II type with 4.3 meters long and two in-vacuum undulators IVU25-1,2 with 2 meters long have been built in the phase-I of SSRF project. This paper describes the design parameters, the magnet configurations and the magnetic field performances of these five IDs. The electron trajectories, the phase errors and the predicated on-axis spectral fluxes with the measured magnetic fields of two in-vacuum undulators are also presented. The R.M.S. phase errors of less than 4 are obtained for the EPU100 in the horizontal polarization mode as well as in the vertical polarization mode. The maximum R.M.S. phase errors for two in-vacuum undulators are 3.1 and 2.2 respectively and the ratio of the photon flux to the ideal case is larger than 80% on the 11th harmonic.
Autors: Zhou, Q.;Zhang, W.;Zhang, M.;Wang, H.;Lu, J.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 254 - 257
Publisher: IEEE
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» Stability Analysis of a Wave-Energy Conversion System Containing a Grid-Connected Induction Generator Driven by a Wells Turbine
Abstract:
This paper presents the dynamic-stability analyzed results of both dynamic simulations and steady-state performance of a wave-energy power generation system containing a grid-connected induction generator (IG) driven by a Wells turbine. The stator windings of the IG are connected directly to a power grid through a step-up transformer and a transmission line. A dq axis equivalent-circuit model is employed to establish the IG, the transmission line, and the grid to derive the complete dynamic equations of the studied system under three-phase balanced loading conditions. A frequency-domain approach based on eigenvalue analysis and a time-domain scheme based on nonlinear-model simulations are both carried out to systematically determine the dynamic stability of the studied system under various operating conditions. It can be concluded from the simulation results that the studied wave-energy power generation system subject to different disturbance conditions can maintain stable operation.
Autors: Wang, L.;Chen, Z.-J.;
Appeared in: IEEE Transactions on Energy Conversion
Publication date: Jun 2010, volume: 25, issue:2, pages: 555 - 563
Publisher: IEEE
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» Stability and Protection of Coils Wound With YBCO Bundle Conductor
Abstract:
The thermal behavior of a high-temperature superconducting (HTS) coil is significantly different from that of a low-temperature superconducting (LTS) coil. A HTS conductor has a greater volumetric heat capacity at the operating temperature envisaged for practical applications. Therefore, a HTS coil is much less likely to be quenched than a LTS coil by mechanical disturbances such as the heat generated by the cracking of the impregnation material or by the friction resulting from wire movements. However, the HTS conductor is cyclically subjected to tensile strain because electrical charging and discharging are repeated in real applications involving the Superconducting Magnetic Energy Storage (SMES) system. The superconducting characteristics may locally deteriorate due to this cyclic strain. Therefore, to enhance the reliability and safety of the HTS coil, a quench protection scheme is needed. Because the normal-zone propagation velocity is quite low, detecting a non-recovering normal zone is difficult in HTS coils, and quenching produces excessive overheating that may cause the conductor to melt. In this study, we focus on a coil wound with a YBCO bundle conductor used in SMES applications and investigate the redistribution characteristics of the transport current in and the thermal behavior of the coil during a quench; we use a newly developed computer code based on the finite element method (FEM) and an equivalent circuit. We also discuss a protection scheme to dump the magnetic energy stored in the coils on an external resistance connected in parallel.
Autors: Ueda, H.;Ishiyama, A.;Shikimachi, K.;Hirano, N.;Nagaya, S.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 1320 - 1323
Publisher: IEEE
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» Stability and Quench Test for NbTi CIC Conductor of JT-60SA Equilibrium Field Coil
Abstract:
The EF coil conductors of JT-60SA are designed with the NbTi cable in conduit conductor because the maximum magnetic field goes up to 6.2 T. The prototype NbTi conductor was developed and tested to confirm the capability of the real conductor. The prototype conductor was proven to have enough Tcs margin under the operating conditions investigated in previous test. In this study, the quench test was operated to measure the stability margin and the normal state propagation. Firstly, the MQE under the Tcs margin of 0.2 K was found to be 80 mJ/cc-strand which is almost the same as that of the previous CIC conductor to result in enough stability margins on EF coil operation. Secondly, the propagation velocity to upstream direction and downstream direction were found to be about 0.47 m/s and 0.54 m/s, respectively. Finally, the quench analysis was conducted to calculate the maximum temperature during quench. The analysis results showed that the maximum temperature reached about 70 K, which is within the permissible value of 150 K for the EF coils.
Autors: Murakami, H.;Ichige, T.;Kizu, K.;Tsuchiya, K.;Yoshida, K.;Obana, T.;Hamaguchi, S.;Takahata, K.;Mito, T.;Imagawa, S.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 512 - 516
Publisher: IEEE
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» Stability and stabilization of aperiodic sampled-data control systems using robust linear matrix inequalities?
Abstract:
Stability analysis of an aperiodic sampled-data control system is considered for application to networked and embedded control. The stability condition is described in a linear matrix inequality to be satisfied for all possible sampling intervals. Although this condition is numerically intractable, a tractable sufficient condition can be constructed with the mean value theorem. Special attention is paid to tightness of the sufficient condition for less conservative stability analysis. A region-dividing technique for the reduction of conservatism and generalization to stabilization are also discussed. An example demonstrates the efficacy of the approach.
Autors: Yasuaki, Oishi , Hisaya, Fujioka
Appeared in: Automatica
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Stability and Stabilization of Two Time Scale Switched Systems in Discrete Time
Abstract:
In this technical note, stability and stabilization of two time scale switched linear systems in the singular perturbation form are addressed in discrete time. We show that, under an arbitrary switching rule, stability of the slow and fast switched subsystems is not sufficient to assess stability of the original two time scale switched system, even if the singular perturbation parameter tends to zero. Therefore, we propose LMI based conditions that guarantee the asymptotic stability of the two time scale switched system using switched quadratic Lyapunov functions. These conditions express the fact that the coupling between fast and slow subsystems has to be taken into account in addition to stability properties of the two subsystems, when the switching rule is arbitrary. The presented conditions are extended to state feedback control design. A numerical example illustrates the features of the proposed approach.
Autors: Malloci, I.;Daafouz, J.;Iung, C.;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Jun 2010, volume: 55, issue:6, pages: 1434 - 1438
Publisher: IEEE
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» Stability Investigation of a LTS/HTS Hybrid Conductor
Abstract:
A new concept of LTS/HTS hybrid conductor was recently proposed. However, little theoretical and experimental research has been done in aspects of its stability. Based on the electromagnetic model of the hybrid conductors, current redistribution between LTS and HTS is numerically investigated in transient process. Furthermore, temperature distribution, quench velocity and minimum quench energy are also simulated by solving thermal-magnetic coupling equivalent equations. Comparing with conventional superconducting conductor, the simulated results show that the stability of the hybrid conductor can be greatly improved and it has potential application in large scale and conduction cooled superconducting magnet.
Autors: Liu, H.;Wang, Y.;Zhang, H.;Qu, Y.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 2176 - 2179
Publisher: IEEE
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» Stability of Domain Walls in Ferromagnetic Nanorings
Abstract:
The stability of domain walls in ferromagnetic nanorings is investigated via calculation of the minimum energy path that separates a domain wall from the vortex state of a ferromagnetic nanoring. Trapped domains are stable when they exist between certain types of transverse domain walls, i.e., walls in which the edge defects on the same side of the magnetic strip have equal sign and thus repel. Here the energy barriers between these configurations and vortex magnetization states are obtained using the string method. Due to the geometry of a ring, two types of walls must be distinguished that differ by their overall topological index and exchange energy. The minimum energy path corresponds to the expulsion of a vortex. The energy barrier for annihilation of a wall is compared to the activation energy for transitions between the two ring vortex states.
Autors: Chaves-O'Flynn, G. D.;Bedau, D.;Vanden-Eijnden, E.;Kent, A. D.;Stein, D. L.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2272 - 2274
Publisher: IEEE
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» Stability of Domain Walls in Ferromagnetic Nanorings
Abstract:
The stability of 2¿ domain walls in ferromagnetic nanorings is investigated via calculation of the minimum energy path that separates a 2¿ domain wall from the vortex state of a ferromagnetic nanoring. Trapped domains are stable when they exist between certain types of transverse domain walls, i.e., walls in which the edge defects on the same side of the magnetic strip have equal sign and thus repel. Here the energy barriers between these configurations and vortex magnetization states are obtained using the string method. Due to the geometry of a ring, two types of 2¿ walls must be distinguished that differ by their overall topological index and exchange energy. The minimum energy path corresponds to the expulsion of a vortex. The energy barrier for annihilation of a 2¿ wall is compared to the activation energy for transitions between the two ring vortex states.
Autors: Chaves-O'Flynn, G.D.;Bedau, D.;Vanden-Eijnden, E.;Kent, A.D.;Stein, D.L.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2272 - 2274
Publisher: IEEE
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» Stability of a time-delayed aeroelastic system with a control surface
Abstract:
This paper investigates the effects of time delay on the flutter instability of an actively controlled airfoil in an incompressible flow field. Firstly, in view of the presence of time delays in the actual control system, multiple time delays in feedback loop are introduced to the present flutter suppression system. Next, the stability boundaries of the closed-loop system with multiple time delays are obtained by solving a polynomial eigenvalue problem, and are validated by numerical simulations. The results demonstrate that time delays in control loop have strong effects on the stability of controlled aeroelastic systems and should not be ignored...
Autors: Y.H., Zhao
Appeared in: Aerospace Science and Technology
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Stability of General Coupled Inertial Agents
Abstract:
We investigate the stability of a system of multiple inertial agents, using the decomposition approach, in which the velocity/position coupling can be generally non-balanced. The stability of the system is determined by two sorts of factors: the velocity/position coupling and the damping/stiffness gains. We indicate all possibly invariant quantities of the system and give sufficient conditions for stability. Also, our result gives a less conservative estimate to design the damping/stiffness gains of the system for stability than some other recent results.
Autors: Li, W.;Spong, M. W.;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Jun 2010, volume: 55, issue:6, pages: 1411 - 1416
Publisher: IEEE
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» Stability preservation analysis in direct discretization of fractional order transfer functions
Abstract:
In this paper, a class of the direct methods for discretization of fractional order transfer functions is studied in the sense of stability preservation. The stability boundary curve is exactly determined for these discretization methods. Having this boundary helps us to recognize whether the original system and its discretized model are the same in the sense of stability. Finally, some illustrative examples are presented to evaluate achievements of the paper.
Autors: Milad, Siami , Mohammad, Saleh Tavazoei , Mohammad, Haeri
Appeared in: Signal Processing
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Stability region bifurcations of nonlinear autonomous dynamical systems: Type-zero saddle-node bifurcations
Abstract:
The behavior of stability regions of nonlinear autonomous dynamical systems subjected to parameter variation is studied in this paper. In particular, the behavior of stability regions and stability boundaries when the system undergoes a type-zero sadle-node bifurcation on the stability boundary is investigated in this paper. It is shown that the stability regions suffer drastic changes with parameter variation if type-zero saddle-node bifurcations occur on the stability boundary. A complete characterization of these changes in the neighborhood of a type-zero saddle-node bifurcation value is presented in this paper. Copyright © 2010 John Wiley & Sons, Ltd.
Autors: F. M. Amaral, L. F. C. Alberto
Appeared in: International Journal of Robust and Nonlinear Control
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Stability Test of a Superconducting W7-X Coil With Respect to Mechanical Disturbances
Abstract:
The superconducting magnet system of the Wendelstein 7-X (W7-X) stellarator experiment consists of 50 non-planar and 20 planar coils which are supported by the central support structure and inter-coil structure elements. This highly loaded support system is prone to mechanical disturbances like stick-slip effects. On the other hand, the coils are built up from cable-in-conduit-conductors (CICC) whose strands are highly compressed by Lorentz forces during operation. Residual elastic energy release within a cable can be triggered by shock waves and corresponding frictional heat generation may occur. The released energy might come into the order of the conductor stability limit and possibly cause a quench. An experiment was performed to simulate the impact of such mechanical disturbances on W7-X coils with stability margins corresponding to different operation conditions. A non-planar coil installed within the magnet test facility was energized and then hit by a pendulum via a stainless steel transfer rod. The test has shown that mechanical disturbances expected in W7-X are not able to induce a quench in any of the foreseen W7-X operation scenarios.
Autors: Hathiramani, D.;Bergmann, T.;Bykov, V.;Chen, P.;Danner, W.;Dudek, A.;Fellinger, J.;Freundt, S.;Genini, L.;Hochel, K.;Kallmeyer, J. P.;Lingertat, J.;Viebke, H.;Weber, S.;Schauer, F.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 543 - 546
Publisher: IEEE
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» Stabilization of controlled positive discrete-time T-S fuzzy systems by state feedback control
Abstract:
This paper deals with sufficient conditions of asymptotic stability and stabilization for nonlinear discrete-time systems represented by a Takagi-Sugeno-type fuzzy model whose state variables take only nonnegative values at all times t for any nonnegative initial state. This class of systems is called positive systems. The conditions of stabilizability are obtained with state feedback control. This work is based on multiple Lyapunov functions. The results are presented in linear matrix inequalities form. A real plant is studied to illustrate this technique. Copyright © 2010 John Wiley & Sons, Ltd.
Autors: Abdellah Benzaouia, Abdelaziz Hmamed, Ahmed EL Hajjaji
Appeared in: International Journal of Adaptive Control and Signal Processing
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Stabilization of networked control systems with nonuniform random sampling periods
Abstract:
In this paper, a new linear delayed delta operator switched system model is proposed to describe networked control systems with packets dropout and network-induced delays. The plant is a continuous-time system, which is sampled by time-varying random sampling periods. A general delta domain Lyapunov stability criterion is given for delta operator switched systems with time delays. Sufficient conditions for asymptotic stability of closed-loop networked control systems with both packets dropout and network-induced delays are presented in terms of linear matrix inequalities (LMIs). A verification theorem is given to show the solvability of the stabilization conditions by solving a class of finite LMIs. Both the case of data packets arrive instantly and the case of invariant sampling periods in delta operator systems are given, respectively. Three numerical examples are given to illustrate the effectiveness and potential of the developed techniques. Copyright © 2010 John Wiley & Sons, Ltd.
Autors: Hongjiu Yang, Yuanqing Xia, Peng Shi
Appeared in: International Journal of Robust and Nonlinear Control
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Stabilization of sets with application to multi-vehicle coordinated motion?
Abstract:
In this paper, we develop stability and control design framework for time-varying and time-invariant sets of nonlinear dynamical systems using vector Lyapunov functions. Several Lyapunov functions arise naturally in multi-agent systems, where each agent can be associated with a generalized energy function which further becomes a component of a vector Lyapunov function. We apply the developed control framework to the problem of multi-vehicle coordinated motion to design distributed controllers for individual vehicles moving in a specified formation. The main idea of our approach is that a moving formation of vehicles can be characterized by a time-varying set in the state...
Autors: Sergey G., Nersesov , Parham, Ghorbanian , Amir G., Aghdam
Appeared in: Automatica
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Stabilizing Vehicle Lateral Dynamics With Considerations of Parameter Uncertainties and Control Saturation Through Robust Yaw Control
Abstract:
This paper presents a robust yaw-moment controller design for improving vehicle handling and stability with considerations of parameter uncertainties and control saturation. The parameter uncertainties dealt with are the changes of vehicle mass and moment of inertia about the yaw axis and the variations of cornering stiffnesses. The control saturation considered is due to the physical limitations of actuators and tires. Both polytopic and norm-bounded approaches are used to describe parameter uncertainties, and a norm-bounded approach is applied to handle the saturation nonlinearity. The conditions for designing such a controller are derived as linear matrix inequalities (LMIs). A nonlinear vehicle model is utilized to validate the effectiveness of the proposed approach. The simulation results show that the designed controller can improve vehicle handling and stability, regardless of the changes in vehicle mass and moment of inertia and the variations of road surfaces and saturation limitations.
Autors: Du, H.;Zhang, N.;Dong, G.;
Appeared in: IEEE Transactions on Vehicular Technology
Publication date: Jun 2010, volume: 59, issue:5, pages: 2593 - 2597
Publisher: IEEE
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» Stable Inverted Polymer/Fullerene Solar Cells Using a Cationic Polythiophene Modified PEDOT:PSS Cathodic Interface
Abstract:
A cationic and water-soluble polythiophene [poly[3-(6-pyridiniumylhexyl)thiophene bromide] (P3PHT+Br-)] is synthesized and used in combination with anionic poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) (PEDOT:PSS)- to produce hybrid coatings on indium tin oxide (ITO). Two coating strategies are established: i) electrostatic layer-by-layer assembly with colloidal suspensions of (PEDOT:PSS)-, and ii) modification of an electrochemically prepared (PEDOT:PSS)- film on ITO. The coatings are found to modify the work function of ITO such that it could act as a cathode in inverted 2,5-diyl-poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) polymer photovoltaic cells. The interfacial modifier created from the layer-by-layer assembly route is used to produce efficient inverted organic photovoltaic devices (power conversion efficiency [sim]2%) with significant long-term stability in excess of 500 h.
Autors: David A. Rider, Brian J. Worfolk, Kenneth D. Harris, Abeed Lalany, Kevin Shahbazi, Michael D. Fleischauer, Michael J. Brett, Jillian M. Buriak
Appeared in: Advanced Functional Materials
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Stable, Glassy, and Versatile Binaphthalene Derivatives Capable of Efficient Hole Transport, Hosting, and Deep-Blue Light Emission
Abstract:
Organic light-emitting diodes (OLEDs) have great potential applications in display and solid-state lighting. Stability, cost, and blue emission are key issues governing the future of OLEDs. The synthesis and photoelectronics of a series of three kinds of binaphthyl (BN) derivatives are reported. BN1-3 are "melting-point-less" and highly stable materials, forming very good, amorphous, glass-like films. They decompose at temperatures as high as 485-545 °C. At a constant current density of 25 mA cm-2, an ITO/BN3/Al single-layer device has a much-longer lifetime (>80 h) than that of an ITO/NPB/Al single-layer device (8 h). Also, the lifetime of a multilayer device based on BN1 is longer than a similar device based on NPB. BNs are efficient and versatile OLED materials: they can be used as a hole-transport layer (HTL), a host, and a deep-blue-light-emitting material. This versatility may cut the cost of large-scale material manufacture. More importantly, the deep-blue electroluminescence (emission peak at 444 nm with CIE coordinates (0.16, 0.11), 3.23 cd A-1 at 0.21 mA cm-2, and 25200 cd m-2 at 9 V) remains very stable at very high current densities up to 1000 mA cm-2.
Autors: Bin Wei, Ji-Zhong Liu, Yong Zhang, Jian-Hua Zhang, Hua-Nan Peng, He-Liang Fan, Yan-Bo He, Xi-Cun Gao
Appeared in: Advanced Functional Materials
Publication date: Jun 2010
Publisher: Wiley InterScience
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» Stacking fault formation in the long wavelength InGaN/GaN multiple quantum wells grown on m-plane GaN
Abstract:
Nonpolar GaN-based light emitting diodes (LEDs) and laser diodes (LDs) show great promise. However, long wavelength emitters (λ>500 nm) have reduced performance in comparison with violet and blue nonpolar emitters. We present results of transmission electron microscopy studies of long wavelength (1100) m-plane GaN LED series and m-plane GaN LDs grown on high quality bulk GaN substrates. I1 basal plane stacking faults form in the high In content InxGa1-xN quantum wells (x∼0.26) for thicker wells. The I1 faults are bounded by sessile Frank–Shockley partial dislocations that likely limit the radiative efficiency of long wavelength m-plane emitters.
Autors: Wu, Feng;Lin, You-Da;Chakraborty, Arpan;Ohta, Hiroaki;DenBaars, Steven P.;Nakamura, Shuji;Speck, James S.;
Appeared in: Applied Physics Letters
Publication date: Jun 2010, volume: 96, issue:23, pages: 231912 - 231912-3
Publisher: IEEE
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» State estimation in Multi-Microgrids
Abstract:
In this paper, a Multi-Microgrid state estimator is proposed, following the concept of distribution state estimators, where a limited number of real-time measurements are available. Since state estimation (SE) solution is impossible with these limited measurements, forecasted values of load injections at buses remote from the substations are needed, for a given period that coincides with the real-time measurements. The proposed state estimator is based on the traditional WLS algorithm and uses few real-time measurements, mainly at the primary (MV) or secondary (LV) substations and DG locations, and pseudo-measurements for the load bus estimates. The impact of the accuracy of distributed generation (DG) voltage magnitude measurements and load pseudo measurements on the bus voltage estimates is also investigated. Grid-connected and islanded modes are simulated and monitored. Topology errors at the main substations and feeders, where there is sufficient measurement redundancy, are also examined. Test results are given for a 55-bus distribution network including DG. Copyright © 2010 John Wiley & Sons, Ltd.
Autors: George N. Korres, Nikos D. Hatziargyriou, Petros J. Katsikas
Appeared in: European Transactions on Electrical Power
Publication date: Jun 2010
Publisher: Wiley InterScience
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» State-of-the-Art Intelligent Mechatronics in Human–Machine Interaction [Guest Introduction]
Abstract:
Intelligent mechatronics is a machine system that has its own entity and equips humanlike or creaturelike smart abilities. The concept of intelligence is, however, ambiguous; hence, there is no clear definition because the meanings and nuances are modified according to the individual intention of a designer who deals with the concept. In this column, the characteristics and system structure of intelligent mechatronics are briefly mentioned. Several types of state-of-the-art intelligent mechatronics, such as communicative, network, human-assistive, and cognitive types, are introduced.
Autors: Harashima, F.;Suzuki, S.;
Appeared in: IEEE Industrial Electronics Magazine
Publication date: Jun 2010, volume: 4, issue:2, pages: 9 - 13
Publisher: IEEE
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» Statistical Evaluation of Process Damage Using an Arrayed Test Pattern in a Large Number of MOSFETs
Abstract:
Evaluating the statistical variations of MOSFETs is important for realizing accurate analog circuits and large-scale-integration devices. A new evaluation method for the statistical variation of the electrical characteristics of MOSFETs is presented. We have developed a test circuit for understanding the statistical and local variations of MOSFETs in a very short time. We demonstrate that the electrical characteristics in more than one million MOSFETs, such as the threshold voltage and the subthreshold swing (S-Factor), are measured in 30 min and that the measured results are very efficient in developing the fabrication process, the process equipment, and the device structure to reduce the statistical and local characteristic variation.
Autors: Watabe, S.;Teramoto, A.;Abe, K.;Fujisawa, T.;Miyamoto, N.;Sugawa, S.;Ohmi, T.;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Jun 2010, volume: 57, issue:6, pages: 1310 - 1318
Publisher: IEEE
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» Statistics of Optical Coherence Tomography Data From Human Retina
Abstract:
Optical coherence tomography (OCT) has recently become one of the primary methods for noninvasive probing of the human retina. The pseudoimage formed by OCT (the so-called B-scan) varies probabilistically across pixels due to complexities in the measurement technique. Hence, sensitive automatic procedures of diagnosis using OCT may exploit statistical analysis of the spatial distribution of reflectance. In this paper, we perform a statistical study of retinal OCT data. We find that the stretched exponential probability density function can model well the distribution of intensities in OCT pseudoimages. Moreover, we show a small, but significant correlation between neighbor pixels when measuring OCT intensities with pixels of about 5 . We then develop a simple joint probability model for the OCT data consistent with known retinal features. This model fits well the stretched exponential distribution of intensities and their spatial correlation. In normal retinas, fit parameters of this model are relatively constant along retinal layers, but varies across layers. However, in retinas with diabetic retinopathy, large spikes of parameter modulation interrupt the constancy within layers, exactly where pathologies are visible. We argue that these results give hope for improvement in statistical pathology-detection methods even when the disease is in its early stages.
Autors: Grzywacz, N. M.;de Juan, J.;Ferrone, C.;Giannini, D.;Huang, D.;Koch, G.;Russo, V.;Tan, O.;Bruni, C.;
Appeared in: IEEE Transactions on Medical Imaging
Publication date: Jun 2010, volume: 29, issue:6, pages: 1224 - 1237
Publisher: IEEE
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» Status of Resistive Magnets in the LHC Injectors Chain
Abstract:
About 4650 normal conducting magnets are presently installed in the CERN accelerators complex, more than 3000 of them belonging to the LHC injector chain and 163 installed in the LHC. The oldest magnets have been in operation for 50 years, and some of them are submitted to aggressive conditions, either in terms of radiation, extreme water cooling conditions or temperature. The smallest magnets in the linacs weigh a few kilograms, whilst each of the main magnets of the Proton Synchrotron weighs 33 tons. The paper reviews the status of these magnets and gives some examples of findings and relevant recent actions undertaken to ensure their reliable operation in the coming years.
Autors: Tommasini, D.;Bauche, J.;Bodart, D.;Lopez, R.;Newborough, A.;Sgobba, S.;Thonet, P.;Zickler, T.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 348 - 351
Publisher: IEEE
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» Status of the EDIPO Project
Abstract:
The aim of this paper is to present an up to date review of the status of the European DIPOle (EDIPO) project whose objective is to build a new facility to perform both DC and AC tests of large superconductor samples in high magnetic background field (up to 12.5 T). EDIPO was designed by EFDA, is being built by BNG (Babcock-Noell) and, once completed, it shall be installed near the existing SULTAN facility at the Paul-Scherer-Institute, (CRPP, Villigen, Switzerland). The results presented focus on the manufacture of the dummy coil (which is a 1:1 model of one of the EDIPO poles) that was completed in spring 2009. Details are given about the dummy coil winding results, coil reaction heat treatment, impregnation and acceptance tests. Moreover, a progress status is provided about the manufacturing of the other parts of the EDIPO magnet assembly, in particular with respect to the manufacturing of the test-well, AC coils, yoke sheets cutting and assembly, the outer cylinder production and welding (316 LN steel, 35 mm thick) and the coils ends preparation. Some results regarding the R&D studies are also reported about the winding trials carried out to improve the winding accuracy and the numerical simulations made to support coil winding (e.g. conductor spring back).
Autors: Portone, A.;Baker, B.;Combescure, D.;Fernandez-Cano, E.;Salpietro, E.;Testoni, P.;Theisen, E.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 600 - 603
Publisher: IEEE
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» Status Quo—The Silent Killer
Abstract:
In a slow economy, most firms find themselves in a "status quo" stance. After taking organization-wide cost-cutting measures, executives often look to IT to create value. This expectation during a down cycle isn't typically aligned with the retrenchment stance. Taking certain steps, including developing and discussing a series of diagrams, can improve IT management in the down market and position IT and the organization for the future uptick.
Autors: Costello, Tom;
Appeared in: IT Professional
Publication date: Jun 2010, volume: 12, issue:3, pages: 61 - 64
Publisher: IEEE
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» Status Report of the SULTAN Test Facility
Abstract:
One year of operation and test activity of the SULTAN test facility at CRPP-Villigen, from October 2008 to October 2009 is reviewed. The main improvements of the facility include a new control system for the cryo-plant and a new electric motor for the helium compressor. The range of operation for the SULTAN samples has been improved in terms of cyclic loading rate. The test campaigns from October 2008 to October 2009 include eight ITER TF conductor samples, two JT60SA samples and a number of other developmental samples. The highlights of the test campaign and the statistical data about cool-downs, warm-ups and test duration are reported. For the eight ITER TF samples, more detail is given about the joint development, the standard test program and the data reduction for the assessment of the results. Eventually, an outlook in the next operation period is also discussed.
Autors: Bruzzone, P.;Stepanov, B.;Wesche, R.;Bagnasco, M.;Cau, F.;Herzog, R.;Calvi, M.;Vogel, M.;Jenni, M.;Holenstein, M.;Rajainmaki, H.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 455 - 457
Publisher: IEEE
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» Status Report on the Toroidal Field Coils for the ITER Project
Abstract:
The magnet system for ITER comprises 18 Toroidal Field (TF) Coils using cable-in-conduit superconductor, which operate at 4.5 K in supercritical helium.
Autors: Savary, F.;Bonito-Oliva, A.;Gallix, R.;Knaster, J.;Koizumi, N.;Mitchell, N.;Nakajima, H.;Okuno, K.;Sborchia, C.;
Appeared in: IEEE Transactions on Applied Superconductivity
Publication date: Jun 2010, volume: 20, issue:3, pages: 381 - 384
Publisher: IEEE
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» Steady-State Analysis of a Permanent-Magnet-Assisted Salient-Pole Synchronous Generator
Abstract:
This paper presents a simple mathematical model for the steady-state analysis of a permanent-magnet-assisted salient-pole synchronous generator (PMa-SG). The PMa-SG is a new type of salient-pole SG that has PMs between the adjacent pole shoes. The developed model takes into account the magnetic saturation and core loss, and enables quantitative predictions of load characteristics from the no-load test data. The validity of the developed model is confirmed experimentally. The effect of the PMs on the performance characteristics of the PMa-SG is also investigated.
Autors: Fukami, T.;Hayamizu, T.;Matsui, Y.;Shima, K.;Hanaoka, R.;Takata, S.;
Appeared in: IEEE Transactions on Energy Conversion
Publication date: Jun 2010, volume: 25, issue:2, pages: 388 - 393
Publisher: IEEE
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» Steady-State Stability of Current Mode Active-Clamp ZVS DC–DC Converters
Abstract:
Active-clamp dc–dc converters are pulsewidth-modulated converters having two switches featuring zero-voltage switching at frequencies beyond 100 kHz. Generalized equivalent circuits valid for steady-state and dynamic performance have been proposed for the family of active-clamp converters. The active-clamp converter is analyzed for its dynamic behavior under current control in this paper. The steady-state stability analysis is presented. On account of the lossless damping inherent in the active-clamp converters, it appears that the stability region in the current-controlled active-clamp converters get extended for duty ratios, a little greater than 0.5, unlike in conventional hard-switched converters. The conventional graphical approach fails to assess the stability of current-controlled active-clamp converters due to the coupling between the filter inductor current and resonant inductor current. An analysis that takes into account the presence of the resonant elements is presented to establish the condition for stability. This method correctly predicts the stability of the current-controlled active-clamp converters. A simple expression for the maximum duty cycle for subharmonic free operation is obtained. The results are verified experimentally.
Autors: Masihuzzaman, M.;Lakshminarasamma, N.;Ramanarayanan, V.;
Appeared in: IEEE Transactions on Power Electronics
Publication date: Jun 2010, volume: 25, issue:6, pages: 1546 - 1555
Publisher: IEEE
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» Steady-state transport characteristics of photoconductor based on dye-sensitized solar cell
Abstract:
In the present work, three photoconductors based on dye-sensitized nanocrystalline TiO2 are designed with two dye-sensitized solar cells (DSSCs) connected together using a common counter electrode but different connecting approaches for electrolytes and TiO2 film. DC steady-state transport measurements on source and drain corresponding to the photoanodes of two constituent DSSC units, respectively, show that the three photoconductive devices exhibit similar transistor characteristics, regardless of their different electronic connecting approaches. It is revealed that their transport characteristics are determined by the effective areas of the photoanode and the counter electrode, rather than the connection of electrolytes and TiO2 film. Furthermore, it is demonstrated that the dominant factor of transport behavior is the imbalanced energy band caused by the match of intrinsic potential within two constituent DSSC units. Due to unique mechanism and relatively simple fabrication process, the present phototransistors have potentials for an economical and efficient light-operated switch as well as an emerged optical communication device.
Autors: Xu, J.;Wang, X. Q.;Lu, Y. M.;Liu, Z. Y.;Cai, C. B.;
Appeared in: Journal of Applied Physics
Publication date: Jun 2010, volume: 107, issue:11, pages: 114511 - 114511-5
Publisher: IEEE
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» Steganalysis by Subtractive Pixel Adjacency Matrix
Abstract:
This paper presents a method for detection of steganographic methods that embed in the spatial domain by adding a low-amplitude independent stego signal, an example of which is least significant bit (LSB) matching. First, arguments are provided for modeling the differences between adjacent pixels using first-order and second-order Markov chains. Subsets of sample transition probability matrices are then used as features for a steganalyzer implemented by support vector machines. The major part of experiments, performed on four diverse image databases, focuses on evaluation of detection of LSB matching. The comparison to prior art reveals that the presented feature set offers superior accuracy in detecting LSB matching. Even though the feature set was developed specifically for spatial domain steganalysis, by constructing steganalyzers for ten algorithms for JPEG images, it is demonstrated that the features detect steganography in the transform domain as well.
Autors: Pevny, T.;Bas, P.;Fridrich, J.;
Appeared in: IEEE Transactions on Information Forensics and Security
Publication date: Jun 2010, volume: 5, issue:2, pages: 215 - 224
Publisher: IEEE
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» Steganography Development Offers Promise
Abstract:
Topics include a new Bluetooth version that uses less energy, an innovative steganography approach, a proposed specification that promises to enable rich typography on the Web, and a social network for scientists.
Autors: Paulson, Linda Dailey;
Appeared in: Computer
Publication date: Jun 2010, volume: 43, issue:6, pages: 18 - 21
Publisher: IEEE
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» Stiffness and Damping in Fe, Co, and Ni Nanowire-Based Magnetorheological Elastomeric Composites
Abstract:
The stiffness and damping properties of the aligned magnetorheological (MR) elastomer composites filled with 10 wt% Fe, Co, and Ni nanowires were investigated under normalized strain amplitude of 1, 2, and 3%, cyclic deformation frequency of 1 Hz, and magnetic flux density of 0, 0.1, and 0.2 T. The highest values of the dynamic stiffness are observed for the Ni- and the lowest for the Fe-based composites within the whole range of strain amplitude and magnetic flux density. The MR effect on the dynamic stiffness is the most significant for 1% strain amplitude and it almost completely disappears for 3% amplitude for all composites. The equivalent damping coefficient values have maxima for 1% strain amplitude for all composites. These values abruptly drop with an increase of strain amplitude to 2% and only slightly change as strain amplitude is further increased to 3%. The MR effect on the equivalent damping coefficient is high for all composites and strain amplitudes.
Autors: Padalka, O.;Song, H. J.;Wereley, N. M.;Filer II, J. A.;Bell, R. C.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 2275 - 2277
Publisher: IEEE
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» Stochastic ellipsoid methods for robust control: Multiple updates and multiple cuts?
Abstract:
Efficient randomized algorithms are developed for solving robust feasibility problems with multiple parameter-dependent convex constraints. Two complementary strategies are presented, both of which exploit the multiplicity to achieve fast convergence. One is the stochastic ellipsoid method with multiple updates. In each iteration of this algorithm, an ellipsoid which describes a candidate of the solution set is updated many times via the multiple constraints with one random sample, while at most one update is allowed in the original method. The other is the stochastic ellipsoid method with multiple cuts. Here, a new update rule is presented to construct a smaller ellipsoid...
Autors: Takayuki, Wada , Yasumasa, Fujisaki
Appeared in: Automatica
Publication date: Jun 2010
Publisher: Elsevier B.V.
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» Stochastic Modular Robotic Systems: A Study of Fluidic Assembly Strategies
Abstract:
Modular robotic systems typically assemble using deterministic processes where modules are directly placed into their target position. By contrast, stochastic modular robots take advantage of ambient environmental energy for the transportation and delivery of robot components to target locations, thus offering potential scalability. The inability to precisely predict component availability and assembly rates is a key challenge for planning in such environments. Here, we describe a computationally efficient simulator to model a modular robotic system that assembles in a stochastic fluid environment. This simulator allows us to address the challenge of planning for stochastic assembly by testing a series of potential strategies. We first calibrate the simulator using both high-fidelity computational fluid-dynamics simulations and physical experiments. We then use this simulator to study the effects of various system parameters and assembly strategies on the speed and accuracy of assembly of topologically different target structures.
Autors: Tolley, M. T.;Kalontarov, M.;Neubert, J.;Erickson, D.;Lipson, H.;
Appeared in: IEEE Transactions on Robotics
Publication date: Jun 2010, volume: 26, issue:3, pages: 518 - 530
Publisher: IEEE
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» Stop-band and band-pass filters in coplanar waveguide technology implemented by means of electrically small metamaterial-inspired open resonators
Abstract:
In this study, coplanar waveguide (CPW) stop-band filters based on open split ring resonators (OSRRs) are presented for the first time. The filters consist on a cascade of transmission line sections, acting as impedance inverters, alternating with shunt connected OSRRs. An order-3 Butterworth stop-band filter is presented as an illustrative example. The second part of the study deals with the application of these stop-band filters to improve the out-of-band rejection (through spurious suppression) of wideband band-pass filters implemented by means of open complementary split ring resonators (OCSRRs). The combination of OCSRRs (the complementary counterparts of OSRRs) and OSRRs for the design of CPW band-pass filters is used for the first time in the proposed prototype device example. The achieved results are promising and are indicative of the possibilities of these electrically small open resonators (OSRRs and OCSRRs).
Autors: Velez, A.;Aznar, F.;Duran-Sindreu, M.;Bonache, J.;Martin, F.;
Appeared in: IET Microwaves, Antennas & Propagation
Publication date: Jun 2010, volume: 4, issue:6, pages: 712 - 716
Publisher: IEEE
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» Strain and crystal defects in thin AlN/GaN structures on (0001) SiC
Abstract:
High-resolution x-ray diffraction was used to compare strain relaxation and defect populations in thin GaN/AlN heterostructures (total thickness ≈480 nm) grown on (0001) SiC using metalorganic chemical vapor deposition (MOCVD) and hydride vapor epitaxy (HVPE) techniques. The results of high-resolution x-ray diffraction measurements (rocking curves and reciprocal space mapping) were corroborated using transmission electron microscopy. Differently grown films exhibited dissimilar strain relaxation and defect populations that were related to specific growth conditions. In the MOCVD films, grown under lower deposition rates, the elastic strain in the AlN and GaN layers was fully relaxed at the initial stages of the epitaxial growth yielding nearly similar densities of threading dislocation segments (TDS) in layer volumes. Additional, “secondary” elastic stresses in these layers were attributed to the excess of point defects. In the HVPE films, grown under higher (five to ten times) deposition rates, these layers were over relaxed and the density of TDS in the GaN layer was an order of magnitude larger than that in AlN. The MOCVD-grown sample was devoid of planar defects whereas the HVPE film contains significant densities of stacking faults in both GaN and AlN layers. Formation of “secondary” extended defects was interpreted in terms of creation and structural transformation of point defects during epitaxial growth. Differences in strain levels, types, and defect populations/distributions for the two heterostructures were attributed to the different growth rates for MOCVD and HVPE.
Autors: Faleev, N.;Levin, I.;
Appeared in: Journal of Applied Physics
Publication date: Jun 2010, volume: 107, issue:11, pages: 113529 - 113529-7
Publisher: IEEE
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» Strain Effects on the Electric and Magnetic Properties of the Magnetoresistive Films
Abstract:
We have synthesized (100) films on , , , and MgO substrates using pulsed laser deposition and investigated their electric and magnetic properties. The structural, electric and magnetic properties of the LBMO films seemed to be dependent on lattice mismatch between LBMO and the substrate. The characteristics of the LBMO film on STO with negligible lattice mismatch were close to those of the bulk LBMO. Interestingly, the uniaxial-type stress acting on the LBMO film by the NGO substrate induced a distinctive difference in the magnetic hysteresis and the magnetoresistance curves measured for two orthogonal in-plane directions. A sudden drop of 0.6% in the low field magnetoresistance curve of the LMBO on the NGO is probably related to spin dependent scattering of charge carriers going through magnetic domains or grains. On the other hand, the LAO and the MgO substrates with a large lattice mismatch of 5% did not effectively induced homogeneous lattice strain to the LBMO film.
Autors: Jeong, D.;Dho, J.;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jun 2010, volume: 46, issue:6, pages: 1883 - 1885
Publisher: IEEE
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