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Issue 2 • Date Mar 1989

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Displaying Results 1 - 25 of 3910804
  • Characteristics of high-transmission-probability tunnel junctions for use as particle detectors

    Page(s): 1343 - 1346
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Interest in the problem of the galactic dark matter has stimulated development of particle detectors sensitive to very low energies. The authors describe superconducting tunnel junctions with thin barriers which may be suitable for this purpose. They present I-V (current-voltage) characteristics and data on the temperature dependence of the subgap tunneling current. They examine the barrier transmission probability and the resistance of the null junction. They also present some scanning-electron-microscope observations of the thin films of the tunnel junctions, which show that faster deposition produces smaller grains and increasing film thickness results in larger grains from an apparent fusing of smaller grains View full abstract»

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  • A fastwidely-linear QR-decomposition least-squares (FWL-QRD-RLS) algorithm

    Page(s): 4169 - 4172
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    This paper considers the development of fast widely-linear (FWL) recursive Least-squares (RLS) algorithm well suited for processing non-circular signals. The proposed algorithm makes use of covariance and modified covariance matrices which take full advantage of second order statistics of non-circular data. Further, the proposed algorithm is based on the fast QR-decomposition recursive least-squares (QRD-RLS) algorithm. Therefore, its computational complexity is of O(N) as compared to O(N2) of conventionalWL-RLS and is numerically more stable in finite precision environment. Simulation results have been presented to test the proposed FWL-QRD-RLS algorithm in two adaptive filtering scenarios: system identification and uniform array beamformer. View full abstract»

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  • Author index

    Page(s): A-1 - A-12
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    Freely Available from IEEE
  • Nonuniform polar grid algorithm for fast field evaluation

    Page(s): 142 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB)  

    A novel algorithm to efficiently compute time-harmonic fields produced by known two-dimensional source constellations is proposed. The algorithm relies on domain decomposition and comprises two steps to be repeated for each subdomain. In the first step, phase, and amplitude compensated fields, produced by currents residing within each subdomain are computed over a sparse set of points surrounding the observation domain. During the second step, total fields in the observer domain are evaluated by interpolation, phase and amplitude restoration and aggregation of subdomain fields. The proposed approach is applied to the fast iterative analysis of scattering phenomena using the method of moments. View full abstract»

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  • Phonon-mediated detection of X-rays in silicon crystals using superconducting transition edge phonon sensors

    Page(s): 1347 - 1350
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The authors present data on the operation of thin-film superconducting strips of titanium as phonon sensors on the surface of silicon crystals. The superconducting films are biased at the foot of the resistive transition in temperature and below the critical latching current (the current above which a normal region in the film grows from self-heating). The interaction of an incident X-ray in the Si crystal generates a phonon source which propagates to the surface at the speed of sound. Such an event produces a several-microsecond-long self-terminating voltage pulse which is proportional to the amount of the sensor area driven normal. It is shown that these Ti superconducting transition edge sensors operated at 0.3 K have sufficient resolution for detecting particles with energy deposition above several keV, which makes them good candidates for use in neutrino (and other) experiments View full abstract»

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  • Robust beamforming via FIR filtering for GNSS multipath mitigation

    Page(s): 4173 - 4177
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    This paper addresses the problem of multipath mitigation with GNSS antenna arrays. A beamformer that is able to cancel the multipath components regardless of their relative delay and directions of arrival is proposed. The weights are obtained from a set of spatial correlation matrices that allows us to estimate the multipath subspace. These matrices are generated after a FIR filter that reduces the correlation between the multipath components and the line-of-sight signal, and it is only used for spatial processing. Some representative simulation results show the multipath attenuation provided by the proposed method under different conditions. View full abstract»

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  • Polytope codes against adversaries in networks

    Page(s): 2423 - 2427
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    Network coding is studied when an unknown subset of nodes in the network is controlled by an adversary. To solve this problem, a new class of codes called Polytope Codes is introduced. Polytope Codes are linear codes operating over bounded polytopes in real vector fields. The polytope structure creates additional complexity, but it induces properties on marginal distributions of code vectors so that validities of codewords can be checked by internal nodes of the network. It is shown that a cut-set bound for a class planar networks can be achieved using Polytope Codes. It is also shown that this cut-set bound is not always tight, and a tighter bound is given for an example network. View full abstract»

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  • A design for a two-dimensional coupled oscillator beam-steering antenna array

    Page(s): 360 - 362
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    A two-dimensional coupled oscillator beam-steering array without phase-shifters is presented for several design considerations. The 20 GHz 4/spl times/4 array has a triple-layer tile architecture. Mutually coupled oscillators on the bottom layer generate steered phase by edge-element tuning, which drives a 4/spl times/4 microstrip patch antenna array located on the top layer. The circuit measures 1.2 inch long and 1.2 inch wide. Near-field and far-field measurement results show that the main beam of the antenna array can be steered off broadside from -26/spl deg/ to +30/spl deg/ in azimuth and from -24/spl deg/ to +30/spl deg/ in elevation. A frequency multiplication technique is employed to increase the array beam-steering range. View full abstract»

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  • Characterization of talker radiation pattern using a microphone array

    Page(s): II/257 - II/260 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    A microphone array has the capability of capturing the properties of a significant portion of a talker's radiation pattern. In this paper, potential implications of measuring the radiation pattern of a talker for the recognition and enhancement of speech are discussed. Current applications of microphone arrays entail their installation in small enclosures such as a conference room or an automobile, typically placing a talker in the array's near field. Fitting a nominal acoustic model to a sparse sampling of the radiation pattern yields parameter estimates which should prove useful as features for speech recognition. Parameter-estimation results using fixed-radius sources (loudspeakers) are presented. Other considerations unique to placement of a talker in close proximity to an array are discussed View full abstract»

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  • Robust evolving cloud-based PID control adjusted by gradient learning method

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB) |  | HTML iconHTML  

    In this paper an improved robust evolving cloud-based controller (RECCo) for a class of nonlinear processes is introduced. The controller is based on parameter-free premise (IF) part. The consequence in this case is given in the form of PID-type controller. The three adjustable parameters of PID controller are updated on-line with a stable adaptation mechanism based on Lyapunov approach such that the output of the process tracks the desired model-reference trajectory. The proposed algorithm has also ability to add new rules or new clouds when this is necessary to improve the whole behaviour of the controlled process. This means that RECCo controller evolves the control structure and adjusts at the same time the parameters of the controller in an on-line manner, while performing the control of the plant. This approach is an example of almost parameter-free approach, because it does not use any off-line pre-training nor the explicit model of the plant and requires almost no parameter tuning. The proposed algorithm is tested on an artificial nonlinear first-order process and on a simulated hydraulic plant. View full abstract»

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  • Modeling of {311} facets using a lattice kinetic Monte Carlo three-dimensional model for selective epitaxial growth of silicon

    Page(s): 153111 - 153111-3
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    Using lattice kinetic Monte Carlo, we provide a quantitative physically based atomistic model for the selective grown of Si-based materials, and explain {311} facet formation while remaining computationally efficient. Descriptions of the local atomistic configurations critical for the developing of {100}, {110}, {111}, and {311} facets are given. The model also introduces (a) three different microscopic growth rates for local {100} planes, needed to properly simulate the formation of perfect {100} terraces in miscut substrates and (b) a break-up energy to account for bonding during {311} facet formation. The model has been verified against experimental results. View full abstract»

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  • Detecting Virulent Cells of Cryptococcus Neoformans Yeast: Clustering Experiments

    Page(s): 1112 - 1115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    The yeast cryptococcus neoformans can cause dangerous infections such as meningitis. The presence of a thick capsule is shown to be correlated with virulence of a yeast cell. This paper reports on our approach towards developing a classifier for detecting virulent cells in images. We present our methods for creating samples, collecting images, preprocessing the images, identifying cells and creating features for each cell. Unsupervised clustering experiments have provided preliminary evidence that our methods results in features that can successfully be used to group and distinguish virulent from normal cells. In our future work we plan to use the same methods and feature set to build supervised classification models View full abstract»

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  • Characteristics of Nb-based Josephson junctions at a temperature below 1 K

    Page(s): 1354 - 1357
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A lithographic technique for Josephson LSI (large scale integrated) circuits was applied to the production of a superconducting tunnel junction for radiation detection. Nb-Al/aluminum oxide/Nb tunnel junctions with different junction sizes and barrier oxidation times have been fabricated. The current-voltage curves were measured in the temperature range from 4.2 to 0.45 K. The junctions showed some amounts of leakage current, which remained below 2 K. The behavior of the leakage current was successfully understood from its experimental dependence on the junction size View full abstract»

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  • Canonical Polyadic decomposition of complex-valued multi-way arrays based on Simultaneous Schur Decomposition

    Page(s): 4178 - 4182
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    In this paper, we propose a new semi-algebraic algorithm to compute the Canonical Polyadic (CP) decomposition of complex-valued multi-way arrays. The proposed algorithm is based on the Simultaneous Schur Decomposition (SSD) of particular matrices derived from the array to process. This CP algorithm solves some convergence problems of classical iterative techniques and its identifiability assumptions are less restrictive than those of other semi-algebraic methods. We also propose a new Jacobi-like algorithm to calculate the SSD of several complex-valued matrices. Finally the usefulness of the proposed method is illustrated in the context of fluorescence spectroscopy and epileptic source localization. View full abstract»

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  • Security of concatenated encoders for wiretap channels

    Page(s): 2558 - 2562
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (197 KB) |  | HTML iconHTML  

    Upper bounds on the `information leakage' of concatenated encoders for wiretap channels are presented. An illustrative implication of this result is that for a wide class of wiretap channels, there exists a sequence of encoder-decoder pairs such that the sequence achieves any rate below the secrecy capacity and each encoder in the sequence is constructible in polynomial time in its block length. View full abstract»

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  • Mobile P2P Fast Similarity Search

    Page(s): 1 - 2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (318 KB) |  | HTML iconHTML  

    In informal data sharing environments, misspellings cause problems for data indexing and retrieval. This is even more pronounced in mobile environments, in which devices with limited input devices are used. In a mobile environment, similarity search algorithms for finding misspelled data need to account for limited CPU and bandwidth. This demo shows P2P fast similarity search (P2PFastSS) running on mobile phones and laptops that is tailored to uncertain data entry and uses available resources efficiently. In this demo, users publish and search for textual content containing misspellings without relying on query logging, as done by Google, and with a minimum distributed indexing infrastructure. Similarity search is supported by using the concept of deletion neighborhood to evaluate the edit distance metric of string similarity. View full abstract»

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  • A discussion of the WSCC 2 July 1996 outages

    Page(s): 60 - 61
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    A criterion to distinguish between voltage instability and angle instability is presented. Analysis of the WSCC outage of 2 July 1996 is given. By applying the criteria, it is recognized that the Pacific Intertie outage was caused by angle instability. To avoid similar cascading outages, some related issues and suggestions are discussed. These include application of single phase tripping and reclosing, and improvements in dynamic performance monitoring. View full abstract»

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  • Robust controller design of uncertain nonlinear systems using singular perturbation

    Page(s): 1473 - 1476
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (190 KB) |  | HTML iconHTML  

    The problem of robust controller Design for uncertain nonlinear systems is considered. Based on singularly perturbed theory, we have proven that the states will enter the positively invariant subset within finite time under some definite initial conditions, and the controller is robust to all uncertain terms that belong to a known compact set. The simulation results show the controller can recur the performance of the state feedback. View full abstract»

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  • Schÿssler¿elliptic low-pass filters

    Page(s): 33 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (201 KB)  

    It is proposed that the approximation problem for low-pass filters with a good transient response should be solved by adding zeros to transfer functions which were obtained by Neirynck and van Bastelaer in the time domain, using a method devised by Schÿssler. The order of the solution and the number of zeros required are calculated from the well known elliptic solution for a low-pass response. View full abstract»

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  • Fuzzy logic: issues, contentions and perspectives

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    There has been a rapid growth in the number and variety of applications of fuzzy logic. The successes of fuzzy logic have also generated a skeptical reaction. Most of the criticisms directed at fuzzy logic are rooted in a misunderstanding of what it is and/or a lack of familiarity with it. In many cases, what is not recognized is that the term fuzzy logic (FL) is actually used in two different senses. In a narrow sense, fuzzy logic (FLn) is a logical system which is an extension of multivalued logic and is intended to serve as a logic of approximate reasoning. But in a wider sense, fuzzy logic (FLw) is more or less synonymous with the theory of fuzzy sets (FST). Today the term fuzzy logic is used predominantly in its wider sense. It is in this sense that any field X can be fuzzified-and hence generalized by replacing the concept of a crisp set in X by a fuzzy set. What is gained through fuzzification is greater generality, higher expressive power, an enhanced ability to model real-world phenomena and a methodology for exploiting the tolerance for imprecision. Most of the applications of fuzzy logic relate to control in the context of industrial systems and consumer products. What is discernible, however, is (a) the trend toward the use of fuzzy logic in task-oriented-rather than set-point-oriented-control; and (b) the incorporation of fuzzy logic and neural network techniques in the conception and design of complex systems in which control and expert system techniques are used in combination View full abstract»

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  • Time series forecasting using Artificial Neural Networks vs. evolving models

    Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (626 KB) |  | HTML iconHTML  

    Time series forecasting plays an important role in many fields such as economics, finance, business intelligence, natural sciences, and the social sciences. This forecasting task can be achieved by using different techniques such as statistical methods or Artificial Neural Networks (ANN). In this paper, we present two different approaches to time series forecasting: evolving Takagi-Sugeno (eTS) fuzzy model and ANN. These two different methods will be compared taking into account the different characteristic of each approach. View full abstract»

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  • Determination of the critical interspacing for the noninteracting magnetic nanoparticle system

    Page(s): 153112 - 153112-3
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    The dipole–dipole interactions of monodisperse Fe3O4 nanoparticles (NPs) can be directly controlled by a uniform SiO2 shell with different thickness, i.e., different interspacings. Thus, the interacting strength of a serial of Fe3O4SiO2 NPs system can be revealed by fitting the blocking temperature TB measured at ac fields to the Vogel–Fulcher law. The interspacing over five times of diameter for less than 8.0 nm Fe3O4 NPs is the critical value to achieve a noninteracting system. Furthermore, a general equation to evaluate critical interspacing for noninteracting magnetic NPs systems with different sizes and saturation magnetizations was calculated by Monte Carlo method. View full abstract»

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  • Honeybees as an Intelligent based Approach for 3D Reconstruction

    Page(s): 1116 - 1119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    This work is about the communication system used by honeybees with the idea of designing a new intelligent approach for 3D reconstruction. A new framework is proposed to allow the communication between 3D points in order to achieve an improved quasi-dense reconstruction. We have presented a novel bioinspired evolutionary algorithm based on the honeybee search behavior. The advantage of using the honeybee search algorithm is the robustness against outliers. Moreover, this work opens the avenue towards new intelligent reconstruction that we are planning to use as a sonar in a mobile robot View full abstract»

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  • An aerodynamic characteristic measurement method for fixed-pitch wind turbine

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    Non-grid-connected wind power theory, which is defined as the optimized integration of grid-connected and stand-alone wind power generation forms, avoids the technical issue of integrating wind power into utilities, and creates a new solution to wind power generation. In order to describe the characteristic of the non-grid-connected wind power generation, this paper discusses a kind of power control strategy that suits the large-scale, non-grid-connected wind power system with electrochemistry loads. Then, with the help of LABVIEW, an experimental and testing platform is designed to meet the special requirement of the fixed-pitch wind turbine and high-energy -consuming simulated loads. The results of wind tunnel experiments verify the feasibility of the presented system and control strategy. View full abstract»

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