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作者： B.M. Howe S.G. Anderson A. Baggeroer J.A. Colosi K.R. Hardy D. Horwitt F.W. Karig S. Leach J.A. Mercer K. Metzger L.O. Olson D.A. Peckham D.A. Reddaway R.R. Ryan R.P. Stein K. von der Heydt J.D. Watson S.L. Weslander P.F. Worcester Applied Physics Laboratory University of Washington Seattle WA USA Massachusetts Institute of Technology Cambridge MA USA Scripps Institution of Oceanography University of California San Diego Seattle WA USA Scripps Institution of Oceanography University of California San Diego La Jolla CA USA Communications and Signal Processing Laboratory Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI USA Woods Hole Oceanographic Institution Seattle WA USA Applied Physics Laboratory University of Washington Woods Hole MA USA

The prototype Pacific Ocean network for the Acoustic Thermometry of Ocean Climate (ATOC) program consists of two shore-cabled acoustic sources, two autonomous vertical hydrophone receiving arrays, and 16 U.S. Navy hydrophone arrays. The sources, receivers, and signaling strategy are designed to be capable of up to 10-megameter transmissions on a routine basis. A new broadband, low-frequency (75 Hz), acoustic source was designed and built by Alliant Techsystems. The bender-bar/barrel-stave transducer is pressure compensated for operation to 1000-m depth. signal waveform shaping is employed to broaden the effective bandwidth of the source to 37.5 Hz (Q=2; time resolution of 27 ms). Four-element vertical hydrophone arrays are attached to the sources to permit reciprocal transmissions and ambient noise monitoring. Autonomous vertical hydrophone arrays consisting of 40 elements at 35-m spacing (1400-m aperture) were developed to resolve low-order acoustic modes. The autonomous arrays are designed for deployments of up to 1 year, with intermediate readout of the data via ship-recoverable pop-up data modules. The U.S. Navy hydrophone arrays were instrumented with 80486-based data acquisition and processing systems, with communications links for transmitting the data in near real time to a central site for further processing and archiving.

关键词： Instruments Oceans Sonar equipment Acoustic arrays Prototypes signal design Acoustic transducers Bandwidth signal resolution Acoustic noise

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A class of order statistics learning vector quantizers

A class of order statistics learning vector quantizers

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： I. Pitas C. Kotropoulos N. Nikolaidis R. Yang M. Gabbouj Department of Electrical & Computer Engineering University of Thessaloniki Thessaloniki Greece Signal Processing Laboratory Tampere University of Technology Tampere Finland

A novel class of Learning Vector Quantizers (LVQs) based on multivariate order statistics is proposed in order to overcome the drawback that the estimators for obtaining the reference vectors in LVQ do not have robustness either against erroneous choices for the winner vector or against the outliers that may exist in vector-valued observations. The performance of the proposed variants of LVQ is demonstrated by experiments. In the case of marginal median LVQ, its asymptotic properties are derived as well.< >

关键词： Statistics Vectors Robustness Artificial neural networks signal processing algorithms signal processing Laboratories Neural networks Network topology Error correction codes

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Design of limit-cycle-free recursive transfer functions for fixed-point direct form implementation

Design of limit-cycle-free recursive transfer functions for ...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T.I. Laakso M. Lang T. Saramaki Nokia Research Center Helsinki Finland Electrical and Computer Engineering Department Rice University TX USA Signal Processing Laboratory Tampere University of Technology Tampere Finland

An approach for the design of limit-cycle-free digital fixed-point filters is proposed. By constraining the transfer function already in the design phase, it is guaranteed that the filter will be free from limit cycles and overflow oscillations in the direct form implementation. The design strategy also guarantees low roundoff noise. The proposed approach is illustrated with design examples. The examples show that typically a 50-100% increase in the filter order (as compared to standard elliptic design) is needed for the limit-cycle-free implementation of a lowpass filter with the direct form (DF) structure. Since the DF structure is very efficient to implement in signal processors, the proposed filters are very attractive for such environment, whereas dedicated filter structures (wave digital, state-space, etc.) easily result in a 3 to 4-fold implementation complexity.< >

关键词： Transfer functions Limit-cycles Electronic mail Digital filters Stability criteria Algorithm design and analysis Design engineering Laboratories Elliptic design signal processing

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Bayesian techniques for equalization of rapidly fading frequency selective channels

Bayesian techniques for equalization of rapidly fading frequ...

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IEEE Conference on Vehicular Technology (VTC)

作者： Gen-Kwo Lee M.P. Fitz S.B. Gelfand Vides Signal Processing Department Computer & Communication Research Laboratory Industrial Technology and Research Institute Hsinchu Taiwan School of Electrical Engineering Purdue University West Lafayette IN USA

This paper applies the Bayesian conditional decision feedback estimator (BCDFE) to rapidly fading frequency selective channels. The BCDFE is a model-based deconvolution algorithm which jointly estimates the transmitted data and channel parameters. The BCDFE applies joint symbol-by-symbol MAP demodulation and channel estimation to equalize channels, and consequently provides robust performance in rapidly fading channels. We provide a brief derivation of the BCDFE and characterize the performance on the land mobile radio channel. We assess the BCDFE's principle design characteristics and the resulting performance in both transient and steady-state operation. The effects of delay spread, Doppler spread, and co-channel interference on the BEP performance are also presented. The BCDFE demonstrates many of the desirable characteristics of an equalizer for mobile radio.< >

关键词： Bayesian methods Fading Frequency estimation Land mobile radio Feedback Deconvolution Demodulation Channel estimation Robustness Steady-state

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On the methodology for comparing learning algorithms: a case

On the methodology for comparing learning algorithms: a case

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Australian and New Zealand Conference on Intelligent Information Systems

作者： A. Bradley B. Lovell M. Ray G. Hawson Department of Electrical and Computer Engineering University of Queensland Brisbane Australia Cooperative Research Centre for Sensor Signal and Information Processing Australia Haemostatis Research Laboratory The Prince Charles Hospital Queensland Health Brisbane Australia

We explore several issues relevant to the benchmarking and comparison of machine learning algorithms. We illustrate those issues with a case study using the decision tree induction algorithms C4.5 (J. Quinlan, 1993) and multiscale classification (MSC) (A.P. Bradley and B.C. Lovell, 1994), multilayer perceptrons (MLP) and multivariable regression (MVR). Then for a "real world" problem we compare estimates of the true error rates for each classifier, first on a single train and test partition, and then using cross validated subsampling techniques. The relevance of the /spl chi//sup 2/ test is then discussed in relation to comparing the classifier accuracies. The paper concludes by evaluating the performance of these four fundamentally different approaches to the solution of this regression problem.< >

关键词： computer aided software engineering Decision trees Classification tree analysis Hospitals Machine learning algorithms multilayer perceptrons Error analysis Blood Australia signal processing

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TECHNICAL ISSUES REGARDING SATELLITE PACKET-SWITCHING

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INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS 1994年第3期12卷 257-267页

作者： IVANCIC, WD CHU, P SHYY, DJ National Aeronautics and Space Administration Lewis Research Center Cleveland Ohio 44135 USA. A design engineer in the Digital Technology Branch of the Space Electronics Division. He has extensive experience in satellite communications systems modulation and coding on-board switching and routeing and high speed digital design. Since joining NASA in 1982 Mr. Ivancic has been responsible for the development of a variety of matrix switch controllers ground terminal equipment numerous pieces of special test equipment a beacon controller for the SARSAT program (Search and Rescue Satellite) and a time-shared decoder for a processing satellite. In addition Mr. Ivancic has been technical contract monitor on a number of advanced communications technology contracts including the Advanced Modulation Technology Development a 5 GHz fibre-optic link and multi-programmable modem study. He was awarded the B.S.E.E. and M.S.E.E. degrees by Cleveland State University in 1982 and 1986 respectively. Cleveland State University Cleveland Ohio 44115 USA. Currently an assistant professor of Electrical Engineering Department at Cleveland State University. He obtained the M.S. and Ph.D. degrees from Iowa State University majoring in Electrical and Computer Engineering. His research interests include high-speed computer networks digital systems and neural networks applications. He is a member of Sigma Xi Phi Kappa Phi as well as the IEEE and ACM. ComSearch Reston Virginia 22091 USA. Received the B.S. degree in electrical engineering from National Chiao-Tung University Hsin-Chu Taiwan in 1983 and the M.S. and Ph.D. degrees in electrical engineering from Georgia Institute of Technology Atlanta GA in 1986 and 1990 respectively. From June 1987 to October 1987 he worked for the Department of Neurology Emory University Atlanta as a Programmer. From September 1989 to December 1989 he worked for the Advanced Development Laboratory. AMP Inc. Atlanta as a Test Engineer. From February 1990 to August 1993 he wor

Many concepts for advanced communication satellite networks have recently been proposed. Critical technical issues relating to satellite packet switching for meshed very small aperture terminal networks and broadband ... 详细信息

关键词： FAST PACKET SWITCH BISDN MESHED VSAT ON-BOARD processing

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A new adaptive image contrast enhancement method

A new adaptive image contrast enhancement method

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Image and Video processing 1993

作者： Yu, Tian-Hu Mitra, S.K. Department of Electrical and Computer Engineering Signal and Image Processing Laboratory University of California Santa BarbaraCA93106 United States

In direct methods of contrast enhancement, a contrast measure is first defined, which is then modified by a mapping function to generate the pixel value of the enhanced image. Various mapping functions such as the square root function, the exponential function, etc., have been introduced for the contrast measure modification. However, these functions do not produce satisfactory contrast enhancement results and are usually sensitive to noise and digitization effects. In addition, they are computationally complex from the point of view of implementation. In this paper, we propose a simple polynomial mapping function for the contrast measure modification. The polynomial function is easy to implement on digital computers and provides very satisfactary contrast enhancement. We also introduce an adaptive clipping technique to control the dynamic range of the output image. © 1993 SPIE. All rights reserved.

关键词： Exponential functions

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ONE-BIT SPECTRAL-CORRELATION ALGORITHMS

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IEEE TRANSACTIONS ON signal processing 1993年第1期41卷 423-427页

作者： GARDNER, WA ROBERTS, RS Signal Processing Group Department of Electrical and Computer Engineering University of California Davis CA USA Los Alamos National Laboratory Los Alamos NM USA Signal Processing Group. Department of Electrical and Computer Engineering University of California Davis CA USA

A technique that greatly simplifies the computational complexity of digital cyclic spectral analysis algorithms is presented. The technique, which is based on Bussgang's theorem, replaces complex multiplications in spectral correlation operations with simple sign-change and data-multiplexing operations. Moreover, the technique is applicable to both time- and frequency-averaging algorithms. A simulation study that compares the computed results obtained using the new technique with results from standard time- and frequency-averaging algorithms shows that the new technique is very promising, particularly for frequency-averaging algorithms.

关键词： signal processing algorithms Frequency estimation Spectral analysis signal analysis Instruments signal processing Bandwidth Aging Phase measurement Laboratories

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Histogram-shape preserving algorithm for image enhancement

Histogram-shape preserving algorithm for image enhancement

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： T.-H. Yu S.K. Mitra Department of Electrical and Computer Engineering Signal and Image Processing Laboratory University of California Santa Barbara CA USA

A new direct contrast enhancement algorithm is proposed. It can be used to enhance the contrast of an image without increasing the dynamic range of the pixel values. A distinctive property of the proposed method is that it yields results matching the characteristic of the human visual system. The histogram of the enhanced image has almost the same shape as that of the original image.< >

关键词： Image enhancement Dynamic range Pixel Histograms Shape Humans Visual system Displays Computational complexity signal processing

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Nonlinear filters for image sharpening and smoothing

Nonlinear filters for image sharpening and smoothing

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IEEE International Conference on Systems engineering

作者： Mitra Yu Signal and Image Processing Laboratory Department of Electrical & Computer Engineering University of California Santa Barbara CA USA

A general approach to the transform-magnitude-shaping-based image enhancement method is advanced. In the method, the magnitude of the input image transform is modified using a nonlinear mapping expressible as a power series, while its phase is kept invariant. The inverse transform of the modified image transform results in a sharpening or smoothing depending on the choice of the power series coefficients. Further improvement in the overall enhancement is achieved by a two-channel processing scheme which is implemented by applying different transform amplitude shaping methods to the low-frequency and high-frequency components. Examples the proposed enhancement method are included.< >

关键词： Filtering Image processing Transforms

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