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NONSTATIONARY LEARNING CHARACTERISTICS OF THE LMS ALGORITHM

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 1987年第10期34卷 1199-1207页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis USA

Upper and lower bounding first-order linear recursions for the mean-squared error realized with the LMS algorithm subjected to a sequence of independent nonstationary training vectors are derived. These bounds coincide to give the exact evolution of mean-squared error for the problem of identification of a nonrecursive time-varying system with white-noise excitation. This leads to an exact formula for time-averaged mean-squared error that is used to study optimization of the step-size parameter for minimum time-average misadjustment. New results on dependence of the minimal step size and the minimum misadjustment on the degree of nonstationarity are obtained.

关键词： Least squares approximation System identification Adaptive filters Algorithm design and analysis Vectors Time varying systems Gaussian distribution signal processing Image processing

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A LAYER STRIPPING FAST ALGORITHM FOR THE TWO-DIMENSIONAL DIRECT-CURRENT INVERSE RESISTIVITY PROBLEM

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 1987年第5期25卷 558-563页

作者： YAGLE, AE Communications and Signal Processing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The inverse problem of reconstructing the resistivity of the earth, varying both laterally and with depth, from direct current measurements is considered. The problem is formulated as a multidimensional inverse scattering problem and solved using a layer stripping algorithm. This algorithm recursively reconstructs the resistivity and electrical potential on horizontal planes of increasing depth by downward continuation. This is the first exact solution to the inverse resistivity problem for resistivity varying laterally as well as with depth. The algorithm is an extension of an algorithm proposed by Levy for resistivity varying in one dimension.

关键词： Conductivity Inverse problems signal processing algorithms Earth Electric potential Multidimensional systems Integral equations Current measurement Surface reconstruction Partial differential equations

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A LAYER-STRIPPING FAST ALGORITHM FOR RECONSTRUCTING AN ELASTIC MEDIUM FROM ITS compressionAL WAVE REFLECTION RESPONSE

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IEEE JOURNAL OF OCEANIC engineering 1987年第2期12卷 423-432页

作者： YAGLE, AE Department of Electrical Engineering and Computer Science Communications and Signal Processing Laboratory Ann Arbor MI USA

A fast algorithm for recovering profiles of density and compressional (P) and shear-vertical (SV) wave speeds as functions of depth for the inverse seismic problem in a continuous layered elastic medium is obtained. This algorithm differs from previous fast algorithms for this problem since it requires only the compressional wave P-P reflection response at the surface of the medium, for three different slownesses or angles of incidence. Previous algorithms have required shear stress data in the form of the P-SV and SV-SV reflection responses, making them unsuitable for an ocean environment. This algorithm is thus much more suitable for reconstructing the ocean floor from pressure data taken in the ocean. The algorithm is exact, and it includes the effects of multiple reflections and mode conversions. A computer run illustrates the performance of the algorithm on synthetic data.

关键词： Oceans Inverse problems signal processing algorithms Integral equations Acoustic reflection Acoustic propagation Surface waves Sea surface Probes Response surface methodology

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IMPLEMENTATION OF DIGITAL FILTERING ALGORITHMS USING PIPELINED VECTOR PROCESSORS

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PROCEEDINGS OF THE IEEE 1987年第9期75卷 1293-1303页

作者： SUNG, W MITRA, SK Signal Processing Laboratory Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

The implementation of digital filtering algorithms using pipelined vector processors is investigated. Modeling of vector processors and vectorization methods are explained, and then the performances of several implementation methods are evaluated based on the model. Vector processor implementation of FIR filtering algorithms using the outer product method and the indirect convolution method is evaluated. Recursive and adaptive filtering algorithms, which lead to dependency problems in direct vector processor implementations, are implemented very efficiently using a newly developed vectorization method. The proposed method computes multiple output samples at a time, making the vector length independent of the filter order. Illustrative examples comparing theoretical results with Cray X-MP simulation results are included.

关键词： Filtering algorithms Vector processors signal processing algorithms Finite impulse response filter Adaptive filters Supercomputers Computational modeling Multidimensional signal processing signal processing Pipeline processing

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MULTIDIMENSIONAL INVERSE SCATTERING - AN ORTHOGONALIZATION FORMULATION

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JOURNAL OF MATHEMATICAL PHYSICS 1987年第7期28卷 1481-1491页

作者： YAGLE, AE Communications and Signal Processing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor Michigan 48109

The three‐dimensional Schrödinger equation inverse scattering problem is solved using an orthogonalization approach. The plane waves propagating in free space are orthogonalized with respect to an inner product defined in terms of a Jost operator. The resulting integral equation is identical to the generalized Gel’fand–Levitan equation of Newton, although the present derivation is simpler and more physical than that of Newton. Newton’s generalized Marchenko equation is derived from the defining integral equation for the Jost operator. These integral equations are shown to be solved by fast algorithms derived directly from the properties of their solutions. This paper thus presents a simple interpretation of Newton’s two integral equations, two fast algorithms for solving these integral equations, and relations between the various approaches. This is a generalization of previously obtained results, which are also reviewed here, for the one‐dimensional inverse scattering problem.

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PHASE RECONSTRUCTION IN THE TRISPECTRUM DOMAIN

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IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND signal PROCESSING 1987年第6期35卷 895-897页

作者： PAN, R NIKIAS, CL Communications and Digital Signal Processing Laboratory Department of Electrical and Computer Engineering Northeastern University Boston MA USA

The phase reconstruction problem in the trispectrum domain is addressed in this correspondence. In particular, three different reconstruction algorithms are discussed and their performance is evaluated. The first two ... 详细信息

关键词： Radar detection Reconstruction algorithms Clutter signal processing algorithms Equations Nonlinear filters Detectors Data processing signal processing Recursive estimation

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A CLASS OF MAGNITUDE COMPLEMENTARY LOUDSPEAKER CROSSOVERS

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IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND signal PROCESSING 1987年第11期35卷 1509-1516页

作者： REGALIA, PA MITRA, SK Signal Processing Laboratory Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

Necessary and sufficient conditions are developed for a pair of transfer functions to have magnitude responses which sum to a constant. If, in addition, the transfer function pair is constrained to be all-pass complementary, the transfer function pair so obtained is well suited for loudspeaker crossover applications. Such crossover systems are characterized by a pair of transfer functions which exhibit the same phase angle at all frequencies. This property has twofold implications: i) in active crossover biamplified audio systems, whereby the low frequencies and high frequencies are reproduced using separate power amplifiers, in-phase crossover transfer functions require less power in subsequent amplifier stages than other designs to achieve a given acoustic sound pressure level; and ii) the summed acoustic magnitude response is least sensitive to noncoincidental mounting of the low- and high-frequency transducers when the crossover transfer functions exhibit the same phase angle at all frequencies. The class of transfer functions realizable is quite wide, and includes squared versions of Butterworth, Chebyshev, and elliptic transfer functions of all orders.

关键词： Loudspeakers Transfer functions Frequency Delay Acoustic distortion High power amplifiers Chebyshev approximation Filters Phase distortion Ear

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AN ALTERNATIVE ADAPTIVE SEQUENTIAL REGRESSION ALGORITHM AND ITS APPLICATION TO THE RECOGNITION OF CEREBRAL-PALSY SPEECH

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 1987年第7期34卷 782-787页

作者： DELLER, JR DONG, H Digital Signal Processing Laboratory Speech Processing Sector Department of Electrical and Computer Engineering Northeastern University Boston MA USA

An algorithm is presented which can be used to compute a temporally adaptive, recursive solution to the problem of estimating the linear prediction parameters of speech. The method is theoretically equivalent to conventional adaptive sequential regression, but is slightly more efficient and computationally much more straightforward. Application to the problem of recognition of speech of the profoundly disabled is discussed.

关键词： Speech recognition Birth disorders Equations signal processing algorithms Recursive estimation Speech analysis Least squares methods Speech processing Parameter estimation

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Non-casual autoregressive bispectrum estimation and deconvolution

Non-casual autoregressive bispectrum estimation and deconvol...

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International Conference on Acoustics, Speech, and signal Processing (ICASSP)

作者： C. Nikias Hsing-Hsing Chiang Communications and Digital Signal Processing Laboratory Department of Electrical and Computer Engineering Northeastern University Boston MA USA

In this paper we propose a new method for non-minimum phase wavelet estimation and deconvolution based on non-causal autoregressive (AR) modeling of third moments of the output seismic trace. The magnitude and phase response of the wavelet are expressed in terms of the parameters of the noncausal AR model. The set of the AR parameters is obtained by solving an overdetermined linear system of equations which is formed using third moment estimates of the output data. A comparison of the non-causal AR bispectrum approach against more conventional approaches for wavelet magnitude and phase reconstruction is a major component of the paper. It is demonstrated by means of standard example that the proposed procedure achieves improved performance.

关键词： Deconvolution Phase estimation Reflectivity Digital signal processing Wavelet domain Laboratories Linear systems Equations Autocorrelation Nonlinear systems

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Nonminimum phase system identification via cepstrum modeling of higher-order cumulants

Nonminimum phase system identification via cepstrum modeling...

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International Conference on Acoustics, Speech, and signal Processing (ICASSP)

作者： C. Nikias Renlong Pan Communications and Digital Signal Processing Laboratory Department of Electrical and Computer Engineering Northeastern University Boston MA USA

A new computationally efficient identification procedure is proposed for a non-Gaussian white noise driven linear, time-invariant, non-minimum phase system. The method is based on the idea of computing the complex cepstrum of higher-order cumulants of the system output. In particular, the differential cepstrum parameters of the system's impulse response are computed directly from higher-order cumulants via least-squares solution. The method is flexible enough to reconstruct the minimum and maximum phase components of the impulse response of MA, AR or ARMA systems without any prior knowledge of the type of the system. It does not require model order selection criteria and is shown to provide estimates with small bias and variance even with "short" length data records.

关键词： System identification Cepstrum White noise Transfer functions Digital signal processing Laboratories signal processing Convolution Frequency signal reconstruction

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