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Scattering coefficient for S wave incident in a random medium characterized by exponential correlation function

GEOPHYSICAL JOURNAL INTERNATIONAL 2002年第2期150卷 415-421页

作者： Tripathi, JN Univ Allahabad Dept Earth & Planetary Sci Allahabad 211002 Uttar Pradesh India

Analytical expressions for scattering coefficients for S -wave incidence have been derived for the medium defined by the exponential correlation function. Low- and high-frequency asymptotic characteristics of the total scattering coefficients have also been investigated. The scattered energy of the converted waves reaches a maximum value in the high-frequency range for the case of an exponential correlation function. The meridional component of the scattered energy for common-mode scattering has a second-power frequency dependence for the high-frequency range, while the latitude component of the scattered energy for common-mode scattering has a fourth-power frequency dependence for the high-frequency range. A comparison of the scattering coefficient for P - and S -wave incidence is also discussed. Mode-conversion for P -wave incidence is greater than that for S -wave incidence. On the other hand, for the common-mode case the scattered energy for S -wave incidence is greater than that for P -wave incidence.

关键词： exponential correlation function inhomogeneity random medium scattering

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ULTRASONIC CHARACTERIZATION OF FRACTAL MEDIA

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PROCEEDINGS OF THE IEEE 1993年第10期81卷 1523-1533页

作者： CHANDRA, K THOMPSON, C Dept. of Electr. Eng. Massachusetts Univ. Lowell MA

Ultrasonic scattering in inhomogeneous fluid media is examined. Of particular interest are those media having a compressibility that varies on a continuum of spatial scales. It is shown that the internal features of such media can be extracted by an analysis of the forward scattered field. The angular distribution of scattered pressure intensity is found to vary with frequency and compressibility contrast. The scattered field data can be rendered stationary to arch variations by an application of a similarity transformation. Examples are given for cases where the spatial variation in the compressibility of the media obeys either a power law or exponential correlation function. When these similarity transformations are applied, an estimate of the characteristic radius of the scatterers and the fractal dimension of the medium can be directly obtained.

关键词： angular distribution characteristic radius compressibility compressibility compressibility contrast exponential correlation function forward scattered field fractal dimension fractal models fractals inhomogeneous fluid media internal features power law similarity transformation spatial variation ultrasonic propagation ultrasonic scattering

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Bacterial genomes lacking long-range correlations may not be modeled by low-order Markov chains: The role of mixing statistics and frame shift of neighboring genes

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COMPUTATIONAL BIOLOGY AND CHEMISTRY 2014年第PartA期53卷 15-25页

作者： Cocho, Germinal Miramontes, Pedro Mansilla, Ricardo Li, Wentian Univ Nacl Autonoma Mexico Inst Fis Dept Sistemas Complejos Mexico City 04510 DF Mexico Univ Nacl Autonoma Mexico Fac Ciencias Mexico City 04510 DF Mexico Univ Nacl Autonoma Mexico Ctr Invest Interdisciplinarias Ciencias & Hamanid Mexico City 04510 DF Mexico North Shore LIJ Hlth Syst Robert S Boas Ctr Genom & Human Genet Feinstein Inst Med Res Manhasset NY USA

We examine the relationship between exponential correlation functions and Markov models in a bacterial genome in detail. Despite the well known fact that Markov models generate sequences with correlation function that decays exponentially, simply constructed Markov models based on nearest-neighbor dimer (first-order), trimer (second-order), up to hexamer (fifth-order), and treating the DNA sequence as being homogeneous all fail to predict the value of exponential decay rate. Even reading-frame-specific Markov models (both first- and fifth-order) could not explain the fact that the exponential decay is very slow. Starting with the in-phase coding-DNA-sequence (CDS), we investigated correlation within a fixed-codon-position subsequence, and in artificially constructed sequences by packing CDSs with out-of-phase spacers, as well as altering CDS length distribution by imposing an upper limit. From these targeted analyses, we conclude that the correlation in the bacterial genomic sequence is mainly due to a mixing of heterogeneous statistics at different codon positions, and the decay of correlation is due to the possible out-of-phase between neighboring CDSs. There are also small contributions to the correlation from bases at the same codon position, as well as by non-coding sequences. These show that the seemingly simple exponential correlation functions in bacterial genome hide a complexity in correlation structure which is not suitable for a modeling by Markov chain in a homogeneous sequence. Other results include: use of the (absolute value) second largest eigenvalue to represent the 16 correlation functions and the prediction of a 10-11 base periodicity from the hexamer frequencies. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Bacterial genomes exponential correlation function Markov model Second largest eigenvalue Hexamer Periodicity of 10-11 bases Heterogeneity Codon positions

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On the Accurate Modeling of Analog Circuits via the Kriging Metamodeling Technique 14

On the Accurate Modeling of Analog Circuits via the Kriging ...

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13th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME) / 14th International Conference on Synthesis, Modeling, Analysis and Simulation Methods and Application to Circuit Design (SMACD)

作者： Garbaya, Amel Kotti, Mouna Fakhfakh, Mourad Tlelo-Cuautle, Esteban Univ Sfax Sfax Tunisia Univ Sousse Sousse Tunisia INAOE Cholula Mexico CINVESTAV Mexico City DF Mexico

ISBN: (纸本)9781509050529

This work deals with the application of the Kriging technique for the accurate modeling of analog circuits, namely, a CMOS second generation current conveyor, and a CMOS voltage follower. Three types of correlation functions are used for this purpose: the Spline, the Gaussian and the exponential correlation functions. A comparative study is given. Two metrics are used;Root Mean Square Error and the Maximum Absolute Error. Obtained results show that the Gaussian correlation function provides better results regarding the accuracy of the constructed models, when compared to the other functions.

关键词： Surrogate Modeling Kriging Model Spline correlation function Gaussian correlation function exponential correlation function Analog Circuit Design CCII VF RMSE MAE

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Propagation of Random Waves in Elastic Media with Microheterogeneities

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Taiwan-Russia Symposium on Deformation and Fracture in Technological Processes

作者： Belyaev, Alexander K. Russian Acad Sci Inst Problems Mech Engn St Petersburg 199178 Russia

ISBN: (纸本)9783037855003

Propagation of elastic waves in heterogeneous linear 1-D media is considered. The scalar wave equation is transformed by the Liouville substitution and the Dyson integral equation is applied for a statistically homogeneous field of heterogeneities. The result is the mean wave field which is analysed in detail for the exponential correlation functions. The general case of the random elastic medium with an arbitrary heterogeneity of small scale is considered and simple closed form expressions for the mean field and attenuation are derived.

关键词： elastic solid random mass density random elasticity modulus Dyson integral equation exponential correlation function mean field spatial decay

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Research on the Microwave Scattering from Bare Land Based on IEM 3

Research on the Microwave Scattering from Bare Land Based on...

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3rd IEEE International Conference on Integrated Circuits and Microsystems (ICICM)

作者： Wang, Tong Tong, Chuang-Ming Chen, Bin Air Force Engn Univ Xian Shaanxi Peoples R China

ISBN: (纸本)9781538683118

With the development of remote sensing for the land environment, the microwave scattering of bare land attracts more attention. Comparing Gauss rough surface, the surface with exponential correlation function shows better agreement with natural environment. In this paper, the scattering characteristics of rough surface with exponential correlation function are investigated. The monostatic and bistatic scattering results simulated with integral equation method (IEM). By comparing the results of desert, gobi and soil environment at X and Ku band, the effects of key parameters on the scattering characteristics are analyzed. The research in this paper is expected to possess an application value in the microwave remote sensing for the land environment.

关键词： microwave scattering exponential correlation function integral equation method remote sensing

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On the Design of Linear Arrays of Fixed Length for Diversity Reception in Rayleigh Fading and Cochannel Interference

On the Design of Linear Arrays of Fixed Length for Diversity...

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IEEE Wireless Communications and Networking Conference (WCNC)

作者： Rahimzadeh, Payam Dehghani Beaulieu, Norman C. Univ Alberta Dept Elect & Comp Engn Edmonton AB T6G 2V4 Canada

ISBN: (纸本)9781612842547

The problem of optimizing the placement of the antennas for an optimum combining receiver equipped with a linear antenna array of fixed length is addressed. A Rayleigh fading model is considered where the complex channel gains of both the desired user and the interfering users are assumed to be correlated due to the mutual proximity of the antennas. The average output signal-to-interference-plus-noise ratio is adopted as a measure of the system's performance and is maximized over the number and the arrangement of the antennas in the array. The optimization problem is formulated as a quadratic convex optimization problem in an infinite dimensional space where finite dimensional approximations of the problem are numerically solved using a convex optimization method. For the special case of an exponential correlation function the optimal arrangement is also derived analytically. It is shown for an exponential correlation model that the optimal number of antennas is infinite meaning that adding more antennas is always beneficial. Perhaps unexpectedly, the best arrangement of antennas in this case is not uniform, in general. On the contrary, it is shown through numerical results that for a two dimensional omnidirectional scattering correlation model the optimal number of antennas is a finite number and the optimum placement is uniform.

关键词： Antenna arrays correlation MIMO Optimization Rayleigh channels Rayleigh fading model Receivers Signal to noise ratio antenna placement optimization average output signal-to-interference-plus-noise ratio cochannel interference cochannel interference convex programming diversity reception diversity reception exponential correlation function finite dimensional approximation infinite dimensional space linear antenna array linear antenna arrays linear array design omnidirectional antennas omnidirectional scattering correlation model optimum combining receiver quadratic convex optimization problem quadratic programming

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