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 coincid...
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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.
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 scatte...
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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.
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. T...
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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.
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 impleme...
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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.
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 ...
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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 algorithms are recursive in nature and are shown to be sensitive to initial condition estimates.
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 complem...
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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.
A method for recognition of speech of the nonverbal is presented. Results of the application of the procedure to simple utterances by cerebral palsied individuals and implications for an overall communications device ...
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A method for recognition of speech of the nonverbal is presented. Results of the application of the procedure to simple utterances by cerebral palsied individuals and implications for an overall communications device are addressed.
The three‐dimensional Schr?dinger equationinverse scattering problem is solved using an orthogonalization approach. The plane waves propagating in free space are orthogonalized with respect to an inner product define...
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The three‐dimensional Schr?dinger equationinverse 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.
The theory of set membership (SM) identification is formulated, and applied to linear prediction (LP) analysis of speech. The LP parameters of a simulated vowel are identified as an illustration. The SM strategy resul...
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The theory of set membership (SM) identification is formulated, and applied to linear prediction (LP) analysis of speech. The LP parameters of a simulated vowel are identified as an illustration. The SM strategy results in a significant computational savings due to rejection of data which are informationless in the SM sense.
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 r...
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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.
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