generalizing the hough transform to detect arbitrary shapes abstract the hough transform is a method for detecting curves by exploiting the duality between points on a curve and parameters of that curve the initial work showed how to detect both analytic curves 1 2 and non analytic curves 3 but these methods were restricted to binary edge images this work was generalized to the detection of some analytic curves in grey level images specifically lines 4 circles 5 and parabolas 6 the line detection case is the best known of these and has been ingeniously exploited in several applications 7 8 9 we show how the boundaries of an arbitrary non analytic shape can be used to construct a mapping between image space and hough transform space such a mapping can be exploited to detect instances of that particular shape in an image furthermore variations in the shape such as rotations scale changes or figure ground reversals correspond to straightforward transformations of this mapping however the most remarkable property is that such mappings can be composed to build mappings for complex shapes from the mappings of simpler component shapes this makes the generalized hough transform a kind of universal transform which can be used to find arbitrarily complex shapes

adaptive artificial boundary condition for the two level schrodinger equation with conical crossings in this paper we present an adaptive approach to design the artificial boundary conditions for the two level schrodinger equation with conical crossings on the unbounded domain we use the windowed fourier transform to obtain the local wave number information in the vicinity of artificial boundaries and adopt the operator splitting method to obtain an adaptive local artificial boundary condition then reduce the original problem into an initial boundary value problem on the bounded computational domain which can be solved by the finite difference method by this numerical method we observe the surface hopping phenomena of the two level schrodinger equation with conical crossings several numerical examples are provided to show the accuracy and convergence of the proposed method

artificial boundary conditions for one dimensional cubic nonlinear schrodinger equations this paper addresses the construction of nonlinear integro differential artificial boundary conditions for one dimensional nonlinear cubic schrodinger equations several ways of designing such conditions are provided and a theoretical classification of their accuracy is given semidiscrete time schemes based on the method developed by duran and sanz serna ima j numer anal 20 2000 pp 235 261 are derived for these unusual boundary conditions stability results are stated and several numerical tests are performed to analyze the capacity of the proposed approach

the relationship between frequency selectivity and pitch discrimination sensorineural hearing loss this study tested the relationship between frequency selectivity and the minimum spacing between harmonics necessary for accurate fo discrimination fundamental frequency difference limens fo dls were measured for ten listeners with moderate sensorineural hearing loss snhl and three normal hearing listeners for sine and random phase harmonic complexes bandpass filtered between 1500 and 3500 hz with fo s ranging from 75 to 500 hz or higher all listeners showed a transition between small good fo dls at high fo s and large poor fo dls at low fo s although the fo at which this transition occurred fo tr varied across listeners three measures thought to reflect frequency selectivity were significantly correlated to both the fo tr and the minimum fo dl achieved at high fo s 1 the maximum fo for which fo dls were phase dependent 2 the maximum modulation frequency for which amplitude modulation and quasi frequency modulation were discriminable and 3 the equivalent rectangular bandwidth of the auditory filter estimated using the notched noise method these results provide evidence of a relationship between fo discrimination performance and frequency selectivity in listeners with snhl supporting spectral and spectro temporal theories of pitch perception that rely on sharp tuning in the auditory periphery to accurately extract fo information

absorbing boundary conditions for one dimensional nonlinear schrodinger equations we construct two families of absorbing boundary conditions for the nonlinear schrodinger equation the first one relies on the pseudodifferential calculus and the second one relies on the paradifferential calculus we show that some of the corresponding initial boundary value problems are well posed we finally present numerical experiments illustrating the efficiency of these methods

absorbing boundary conditions for the schrodinger equation a large number of differential equation problems which admit traveling waves are usually defined on very large or infinite domains to numerically solve these problems on smaller subdomains of the original domain artificial boundary conditions must be defined for these subdomains one type of artificial boundary condition which can minimize the size of such subdomains is the absorbing boundary condition the imposition of absorbing boundary conditions is a technique used to reduce the necessary spatial domain when numerically solving partial differential equations that admit traveling waves such absorbing boundary conditions have been extensively studied in the context of hyperbolic wave equations in this paper general absorbing boundary conditions will be developed for the schrodinger equation with one spatial dimension using group velocity considerations previously published absorbing boundary conditions will be shown to reduce to special cases of this absorbing boundary condition the well posedness of the initial boundary value problem of the absorbing boundary condition coupled to the interior schrodinger equation will also be discussed extension of the general absorbing boundary condition to higher spatial dimensions will be demonstrated numerical simulations using initial single gaussian double gaussian and a narrow gaussian pulse distributions will be given with comparision to exact solutions to demonstrate the reflectivity properties of various orders of the absorbing boundary condition

psychometric functions for frequency discrimination from listeners with sensorineural hearing loss psychometric functions for pulsed pure tone frequency discrimination were obtained from hearing impaired listeners at frequencies with normal hearing and at frequencies with mild or moderate hearing losses the general form of psychometric functions at hearing impaired frequencies was found to be the same as at normal hearing frequencies i e d was linear with the frequency difference between tones in hz for all but one psychometric function the addition of an intercept term to the fitting equation did not account for significantly more variance than did the slope term alone therefore it was concluded that psychometric functions for frequency discrimination can be adequately described with only one parameter the slope of the psychometric function deficits in discrimination at hearing loss frequencies were manifested by more gradual slopes of psychometric functions procedures for normalizing psychometric functions are presented which facilitate comparisons of normal and impaired frequency discrimination data across studies and frequencies comparisons of dlf s difference limen for frequency obtained with adaptive and fixed procedures show a bias toward larger dlf s with adaptive procedures but only at higher frequencies a discussion of equal interval and equal ratio adaptive stepping rules indicates that an equal ratio rule may be preferable

on the stability of boundary conditions for molecular dynamics we study the stability of boundary conditions for molecular dynamics simulations a general stability criterion is established we first consider a one dimensional model with nearest neighbor interaction and multiple neighbor interactions we then generalize the results to more realistic models in 3d with nonlinear atomic interaction

absorbing boundary conditions for general nonlinear schrodinger equations this paper addresses the construction of different families of absorbing boundary conditions for the one and two dimensional schrodinger equations with a general variable nonlinear potential various semidiscrete time schemes are built for the associated initial boundary value problems finally some numerical simulations give a comparison of the various absorbing boundary conditions and associated schemes to analyze their accuracy and efficiency

accurate boundary treatment for transient schrodinger equation under polar coordinates abstract a new local boundary condition is designed for the two dimensional schrodinger equation under polar coordinates based on an approximate linear relation among the kernel functions for a free one dimensional schrodinger equation of a new variable it takes a simple form of ordinary differential equation that relates the neighboring grid points numerical tests and comparisons demonstrate the effectiveness of the proposed boundary treatment

frequency resolution and discrimination of constant and dynamic tones in normal and hearing impaired listeners frequency resolution and three tasks of frequency discrimination were measured at 500 and 4000 hz in 12 normal and 12 hearing impaired listeners a three interval two alternative forced choice procedure was used frequency resolution was measured with an abbreviated psychoacoustical tuning curve frequency discrimination was measured for 1 a fixed frequency standard and target 2 a fixed frequency standard and a frequency transition target and 3 frequency transition standard and a frequency transition target the 50 ms frequency transitions had the same final frequency as the standards but the initial frequency was lowered to obtain about 79 discrimination performance there was a strong relationship between poor frequency resolution and elevated pure tone thresholds but only a very weak relationship between poor frequency discrimination and elevated pure tone thresholds several hearing impaired listeners had normal discrimination performance together with pure tone thresholds of 80 90 db hl a slight correlation was found between word recognition and frequency discrimination but a detailed comparison of the phonetic errors and either the frequency discrimination or frequency resolution tasks failed to suggest any consistent interdependencies these results are consistent with previous work that has suggested that frequency resolution and frequency discrimination are independent processes

transparent boundary condition for numerical modeling of intense laser molecule interaction this article addresses the problem of constructing transparent boundary conditions for the schrodinger maxwell system where the interacting electromagnetic field is treated classically in the dipole approximation the problem essentially boils down to constructing transparent boundary condition for the schrodinger equation with time dependent linear potential the transparent boundary maps obtained are not purely of the convolution type however they are amenable to numerical methods like convolution quadrature for implementation

on detection of multiple object instances using hough transforms hough transform based methods for detecting multiple objects use nonmaxima suppression or mode seeking to locate and distinguish peaks in hough images such postprocessing requires the tuning of many parameters and is often fragile especially when objects are located spatially close to each other in this paper we develop a new probabilistic framework for object detection which is related to the hough transform it shares the simplicity and wide applicability of the hough transform but at the same time bypasses the problem of multiple peak identification in hough images and permits detection of multiple objects without invoking nonmaximum suppression heuristics our experiments demonstrate that this method results in a significant improvement in detection accuracy both for the classical task of straight line detection and for a more modern category level pedestrian detection problem

theoretical quantification of shape distortion in fuzzy hough transform we present a generalization of classical hough transform in fuzzy set theoretic framework called fuzzy hough transform or fht in order to handle the impreciseness ill definedness in shape description in addition to identifying the shapes the methodology can quantify the amount of distortion present in each shape by suitably characterizing the parametric space we extended fht to take care of gray level images gray fht in order to handle the gray level variation along with shape distortion the gray fht gives rise to a scheme for image segmentation based on the a priori knowledge about the shapes

almost exact boundary condition for one dimensional schrodinger equations an explicit local boundary condition is proposed for finite domain simulations of the linear schr odinger equation on an unbounded domain based on an exact boundary condition in terms of the bessel functions it takes a simple form with 16 neighboring grid points and it involves no empirical parameter while the computing load is rather low the proposed boundary condition is effective in reflection suppression comparable to the exact convolution treatments an extension to nonlinear schr odinger equations is also proposed numerical comparisons clearly demonstrate the effectiveness of this almost exact alex boundary condition for both the linear and the cubic nonlinear schr odinger equations

relations between frequency selectivity temporal fine structure processing and speech reception in impaired hearing frequency selectivity temporal fine structure tfs processing and speech reception were assessed for six normal hearing nh listeners ten sensorineurally hearing impaired hi listeners with similar high frequency losses and two listeners with an obscure dysfunction od tfs processing was investigated at low frequencies in regions of normal hearing through measurements of binaural masked detection tone lateralization and monaural frequency modulation fm detection lateralization and fm detection thresholds were measured in quiet and in background noise speech reception thresholds were obtained for full spectrum and lowpass filtered sentences with different interferers both the hi listeners and the od listeners showed poorer performance than the nh listeners in terms of frequency selectivity tfs processing and speech reception while a correlation was observed between the monaural and binaural tfs processing deficits in the hi listeners no relation was found between tfs processing and frequency selectivity the effect of noise on tfs processing was not larger for the hi listeners than for the nh listeners finally tfs processing performance was correlated with speech reception in a two talker background and lateralized noise but not in amplitude modulated noise the results provide constraints for future models of impaired auditory signal processing

using selective correlation coefficient for robust image registration a new method is proposed for robust image registration named selective correlation coefficient in order to search images under ill conditioned illumination or partial occlusion a correlation mask image is generated for selecting pixels of an image before matching the mask image can be derived from a binary coded increment sign image defined from any object image and the template the mask rate of occluded regions is theoretically expected to be 0 5 while unoccluded regions have much lower rate than 0 5 robustness for ill conditioned environment can be realized since inconsistent brightness of occluded regions can be omitted from the mask operation furthermore the mask enhancement procedure is proposed to get more stable robustness the effectiveness of masking increases by the procedure resulting in the rate around 0 7 for masking of occluded regions this paper includes a theoretical modeling and analysis of the proposed method and some experimental results with real images

ordinal measures for image correspondence we present ordinal measures of association for image correspondence in the context of stereo linear correspondence measures like correlation and the sum of squared difference between intensity distributions are known to be fragile ordinal measures which are based on relative ordering of intensity values in windows rank permutations have demonstrable robustness by using distance metrics between two rank permutations ordinal measures are defined these measures are independent of absolute intensity scale and invariant to monotone transformations of intensity values like gamma variation between images we have developed simple algorithms for their efficient implementation experiments suggest the superiority of ordinal measures over existing techniques under nonideal conditions these measures serve as a general tool for image matching that are applicable to other vision problems such as motion estimation and texture based image retrieval

a finite difference method for the one dimensional time dependent schrodinger equation on unbounded domain a finite difference scheme is proposed for the one dimensional time dependent schrodinger equation we introduce an artificial boundary condition to reduce the original problem into an initial boundary value problem in a finite computational domain and then construct a finite difference scheme by the method of reduction of order to solve this reduced problem this scheme has been proved to be uniquely solvable unconditionally stable and convergent some numerical examples are given to show the effectiveness of the scheme

fuzzy cognitive maps for stereovision matching this paper outlines a method for solving the stereovision matching problem using edge segments as the primitives in stereovision matching the following constraints are commonly used epipolar similarity smoothness ordering and uniqueness we propose a new matching strategy under a fuzzy context in which such constraints are mapped the fuzzy context integrates both fuzzy clustering and fuzzy cognitive maps with such purpose a network of concepts nodes is designed each concept represents a pair of primitives to be matched each concept has associated a fuzzy value which determines the degree of the correspondence the goal is to achieve high performance in terms of correct matches the main findings of this paper are reflected in the use of the fuzzy context that allows building the network of concepts where the matching constraints are mapped initially each concept value is loaded via the fuzzy clustering and then updated by the fuzzy cognitive maps framework this updating is achieved through the influence of the remainder neighboring concepts until a good global matching solution is achieved under this fuzzy approach we gain quantitative and qualitative matching correspondences this method works as a relaxation matching approach and its performance is illustrated by comparative analysis against some existing global matching methods

robust image registration by increment sign correlation abstract a novel and robust statistic as a similarity measure for robust image registration is proposed the statistic is named as increment sign correlation because it is based on the average evaluation of incremental tendency of brightness in adjacent pixels it is formalized to be a binary distribution or a gaussian distribution for a large image size through statistical analysis and modeling by utilizing the proposed statistical model for example we can theoretically determine a reasonable value of threshold for verification of matching this sign correlation can also be proved to expectedly have the constant value 0 5 for any uncorrelated images to a template image and then the property of the constancy can be utilized to analyze the high robustness for occlusion the good performance for the case of saturation or highlight can also be proved through theoretical analysis and fundamental experiments a basic algorithm for image scanning search and registration over a large scene is represented with a technique for a fast version by the branch and bound approach many experimental evidences with real images are provided and discussed

perfectly matched absorbing layers for the paraxial equations a new absorbing boundary technique for the paraxial wave equations is proposed and analyzed numerical results show the efficiency of the method

a high order finite element discretization with local absorbing boundary conditions of the linear schrodinger equation the goal of this paper is to obtain a high order full discretization of the initial value problem for the linear schrodinger equation in a finite computational domain for this we use a high order finite element discretization in space together with an adaptive implementation of local absorbing boundary conditions specifically obtained for linear finite elements and a high order symplectic time integrator the numerical results show that it is possible to obtain simultaneously a very good absorption at the boundary and a very small error in the interior of the computational domain

extracting straight lines this paper presents a new approach to the extraction of straight lines in intensity images pixels are grouped into line support regions of similar gradient orientation and then the structure of the associated intensity surface is used to determine the location and properties of the edge the resulting regions and extracted edge parameters form a low level representation of the intensity variations in the image that can be used for a variety of purposes the algorithm appears to be more effective than previous techniques for two key reasons 1 the gradient orientation rather than gradient magnitude is used as the initial organizing criterion prior to the extraction of straight lines and 2 the global context of the intensity variations associated with a straight line is determined prior to any local decisions about participating edge elements

similarity measures for image matching despite occlusions in stereo vision in the context of computer vision matching can be done with similarity measures this paper presents the classification of these measures into five families in addition 18 measures based on robust statistics previously proposed in order to deal with the problem of occlusions are studied and compared to the state of the art a new evaluation protocol and new analyses are proposed and the results highlight the most efficient measures first near occlusions the smooth median powered deviation and second near discontinuities a non parametric transform based measure census

a fast discrete approximation algorithm for the radon transform this paper addresses fast parallel methods for the computation of the radon or hough transform the radon transform of an image is a set of projections of the image taken at different angles its computation is important in image processing and computer vision for problems such as pattern recognition and reconstruction of medical images a unique new method for combining partial results is presented from which an algorithm is constructed that computes a provably good approximation to the discrete radon transform the approximate discrete radon transform adrt algorithm computes 4 n 4 projections through an n times n image in time o n 2 mathrm lg n the majority of previous algorithms are o n 3 the method is quite simple and easy to parallelize a parallel version of the adrt requires only o mathrm lg n parallel steps on o n 2 processors ignoring communication time an additional property of the algorithm is that it can be applied directly to compute the backprojection step of the inverse rt

face contour extraction from front view images abstract facial feature detection is crucial for visual recognition of human faces this paper reports on a study in detecting face contours from front view id type pictures based on the eye and mouth positions which can be detected by the algorithms proposed in ref 1 g chow and x li pattern recognition 26 1739 1755 1993 a simplified adaptive hough transform aht technique is used to identify straight cheek lines which are approximately vertical from the edge image independently parabolas forming the chin are detected by another aht procedure the location and curvature of the chin line together with the cheek lines characterize the shape of the face this method was tested on over 70 different face images and is shown to produce results with a high degree of accuracy we discuss in detail the specific issues involved in the detections such as the definition of relevant subimage parameter ranges resolution of the accumulator array peak cells and end point determination

radiation boundary conditions for the numerical solution of the three dimensional time dependent schrodinger equation with a localized interaction exact radiation boundary conditions on the surface of a sphere are presented for the single particle time dependent schr odinger equation with a localized interaction with these boundary conditions numerical computations of spatially unbounded outgoing wave solutions can be restricted to the finite volume of a sphere the boundary conditions are expressed in terms of the free particle green s function for the outside region the green s function is analytically calculated by an expansion in spherical harmonics and by the method of laplace transformation for each harmonic number a discrete boundary condition between the function values at adjacent radial grid points is obtained the numerical method is applied to quantum tunneling through a spherically symmetric potential barrier with different angular momentum quantum numbers l calculations for l 0 are compared to exact theoretical results

dispersive waves and pml performance for large stencil differencing in the parabolic equation the discrete reflection absorption performance of perfectly matched layer pml boundary conditions is a function of the field discretization scheme throughout the computational domain and the form of the complex coordinate extension that characterizes the pml region most previous work analyzing pml reflection performance has assumed use of low order second or fourth small stencil three or five point spatial discretizations whose dispersion is poor outside a narrow low wavenumber band large stencil differencing schemes regardless of order are easily created with physically realistic wide band dispersive characteristics but the effect their adoption has on pml performance has not been analyzed previously in the context of a semi discrete approximation to the parabolic paraxial equation this work derives the analytic form of the discrete pml reflection coefficient for an arbitrary order arbitrary stencil interior differencing scheme coupled to an arbitrary order arbitrary stencil pml region this result is then used to show that the absorption performance of the pml regions is largely insensitive to changes in interior differencing as a consequence the benefits of superior dispersion characteristics provided by use of large stencil differencing in the interior physical domain can be had without incurring discrete reflection penalties at the pml

absorbing boundary conditions for relativistic quantum mechanics equations this paper is devoted to the derivation of absorbing boundary conditions for the klein gordon and dirac equations modeling quantum and relativistic particles subject to classical electromagnetic fields microlocal analysis is the main ingredient in the derivation of these boundary conditions which are obtained in the form of pseudo differential equations basic numerical schemes are derived and analyzed to illustrate the accuracy of the derived boundary conditions

adaptive time varying cancellation of wideband interferences in spread spectrum communications based on time frequency distributions the paper proposes an adaptive method for suppressing wideband interferences in spread spectrum ss communications the proposed method is based on the time frequency representation of the received signal from which the parameters of an adaptive time varying interference excision filter are estimated the approach is based on the generalized wigner hough transform as an effective way to estimate the instantaneous frequency of parametric signals embedded in noise the performance of the proposed approach is evaluated in the presence of linear and sinusoidal fm interferences plus white gaussian noise in terms of the snr improvement factor and bit error rate ber

on the rate of convergence of schwarz waveform relaxation methods for the time dependent schrodinger equation this paper is dedicated to the analysis of the rate of convergence of the classical and quasi optimal schwarz waveform relaxation swr method for solving the linear schrodinger equation with space dependent potential the strategy is based on i the rewriting of the swr algorithm as a fixed point algorithm in frequency space and ii the explicit construction of contraction factors thanks to pseudo differential calculus some numerical experiments illustrating the analysis are also provided

relation between derived band auditory brainstem response latencies and behavioral frequency selectivity derived band click evoked auditory brainstem responses abrs were obtained for normal hearing nh and sensorineurally hearing impaired hi listeners the latencies extracted from these responses as a function of derived band center frequency and click level served as objective estimates of cochlear response times for the same listeners auditory filter bandwidths at 2 khz were estimated using a behavioral notched noise masking paradigm generally shorter derived band latencies were observed for the hi than for the nh listeners only at low click sensation levels prolonged latencies were obtained for some of the hi listeners the behavioral auditory filter bandwidths accounted for the across listener variability in the abr latencies cochlear response time decreased with increasing filter bandwidth consistent with linear system theory the results link cochlear response time and frequency selectivity in human listeners and offer a window to better understand how hearing impairment affects the spatiotemporal cochlear response pattern

a comparison of transparent boundary conditions for the fresnel equation abstract we consider two numerical transparent boundary conditions that have been previously introduced in the literature the first condition bpp was proposed by baskakov and popov 1991 wave motion 14 121 128 and papadakis et al 1992 j acoust soc am 92 2030 2038 while the second sdy is that of schmidt and deuflhard 1995 comput math appl 29 53 76 and schmidt and yevick 1997 j comput phys 134 96 107 the latter procedure is explicitly tailored to the form of the underlying numerical propagation scheme and is therefore unconditionally stable and highly precise here we present a new derivation of the sdy approach as a result of this analysis we obtain a simple modification of the bpp method that guarantees accuracy and stability for long propagation step lengths

discrete transparent boundary conditions for the numerical solution of fresnel s equation the paper presents a construction scheme of deriving transparent i e reflection free boundary conditions for the numerical solution of fresnel s equation being formally equivalent to schrodinger s equation in contrast to previous suggestions the method advocated here treasts the discrete problem after discretization of the time like variable i e in a rothe method which leads to a sequence of coupled boundary value problems the thus obtained boundary conditions appear to be of a nonlocal cauchy type as it turns out each kind of linear implicit discretization induces its own discrete transparent boundary conditions numerical experiments on technologically relevant examples from integrated optics are included

almost exact boundary conditions for transient schrodinger poisson system for the schrodinger poisson system we propose an almost exact alex boundary condition to treat accurately the numerical boundaries being local in both space and time the alex boundary conditions are demonstrated to be effective in suppressing spurious numerical reflections together with the crank nicolson scheme we simulate a resonant tunneling diode the algorithm produces numerical results in excellent agreement with those in mennemann et al 1 yet at a much reduced complexity primary peaks in wave function profile appear as a consequence of quantum resonance and should be considered in selecting the cut off wave number for numerical simulations

the role of stimulus complexity spectral overlap and pitch for gap detection thresholds in young and old listeners thresholds for detecting a gap between two complex tones were determined for young listeners with normal hearing and old listeners with mild age related hearing loss the leading tonal marker was always a 20 ms 250 hz complex tone with energy at 250 500 750 and 1000 hz the lagging marker also tonal could differ from the leading marker with respect to fundamental frequency f0 the presence versus absence of energy at f0 and the degree to which it overlapped spectrally with the leading marker all stimuli were presented with steeper 1 ms and less steep 4 ms envelope rise and fall times f0 differences decreases in the degree of spectral overlap between the markers and shallower envelope shape all contributed to increases in gap detection thresholds age differences for gap detection of complex sounds were generally small and constant when gap detection thresholds were measured on a log scale when comparing the results for complex sounds to thresholds obtained for pure tones in a previous study by heinrich and schneider 2006 j acoust soc am 119 2316 2326 thresholds increased in an orderly fashion from markers with identical within channel pure tones to different between channel pure tones to complex sounds this pattern of results was true for listeners of both ages although younger listeners had smaller thresholds overall

discrete transparent boundary conditions for wide angle parabolic equations in underwater acoustics this paper is concerned with transparent boundary conditions tbcs for wide angle parabolic equations wapes in the application to underwater acoustics assuming cylindrical symmetry existing discretizations of these tbcs introduce slight numerical reflections at this artificial boundary and also render the overall crank nicolson finite difference method only conditionally stable here a novel discrete tbc is derived from the fully discretized whole space problem that is reflection free and yields an unconditionally stable scheme while we shall assume a uniform discretization in range the interior depth discretization i e in the water column may be nonuniform and we shall discuss strategies for the best exterior discretization i e in the sea bottom the superiority of the new discrete tbc over existing discretizations is illustrated on several benchmark problems in the literature different wapes or wape and the standard parabolic equation have been coupled in the water and the sea bottom we analyze under which conditions this yields a hybrid model that is conservative for the acoustic field

on image analysis by moments research has been performed investigating the use of moments for pattern recognition in recent years the basic problem of the influence of discretization and noise on moment accuracy as object descriptors has been barely investigated in this paper the detailed error analysis involved in the moment method is discussed several new techniques to increase the accuracy and efficiency of moment descriptor are proposed we utilize these results for the problem of image reconstruction from the orthogonal legendre moments computed from discrete and noisy data the automatic selection of an optimal number of moments is also discussed

least median of squares regression abstract classical least squares regression consists of minimizing the sum of the squared residuals many authors have produced more robust versions of this estimator by replacing the square by something else such as the absolute value in this article a different approach is introduced in which the sum is replaced by the median of the squared residuals the resulting estimator can resist the effect of nearly 50 of contamination in the data in the special case of simple regression it corresponds to finding the narrowest strip covering half of the observations generalizations are possible to multivariate location orthogonal regression and hypothesis testing in linear models

suppression and comodulation masking release in normal hearing and hearing impaired listeners the detectability of a sinusoidal signal embedded in a masker at the signal frequency can be improved by simultaneously presenting additional maskers in off frequency regions if the additional maskers and the on frequency masker component have the same temporal envelope this effect is commonly referred to as comodulation masking release cmr recently it was hypothesized that peripheral nonlinear processes such as suppression may play a role in cmr over several octaves when the level of the off frequency masker component is higher than the level of the on frequency masker component the aim of the present study was to test this hypothesis by measuring suppression and cmr within the same subjects for various frequency level combinations of the off frequency masker component experimental data for normal hearing listeners show a large overlap between the existence regions for suppression and cmr hearing impaired subjects with a sensorineural hearing loss show on average negligible suppression and cmr the data support the hypothesis that part of the cmr in experiments with large spectral distances and large level differences between the masker components is due to the nonlinear processing at the level of the cochlea

frozen gaussian approximation based domain decomposition methods for the linear schrodinger equation beyond the semi classical regime the paper is devoted to develop efficient domain decomposition methods for the linear schrodinger equation beyond the semiclassical regime which does not carry a small enough rescaled planck constant for asymptotic methods e g geometric optics to produce a good accuracy but which is too computationally expensive if direct methods e g finite difference are applied this belongs to the category of computing middle frequency wave propagation where neither asymptotic nor direct methods can be directly used with both efficiency and accuracy motivated by recent works of the authors on absorbing boundary conditions antoine et al 2014 13 and yang and zhang 2014 43 we introduce semiclassical schwarz waveform relaxation methods sswr which are seamless integrations of semiclassical approximation to schwarz waveform relaxation methods two versions are proposed respectively based on herman kluk propagation and geometric optics and we prove the convergence and provide numerical evidence of efficiency and accuracy of these methods

matching by monotonic tone mapping in this paper a novel dissimilarity measure called matching by monotonic tone mapping mmtm is proposed the mmtm technique allows matching under non linear monotonic tone mappings and can be computed efficiently when the tone mappings are approximated by piecewise constant or piecewise linear functions the proposed method is evaluated in various template matching scenarios involving simulated and real images and compared to other measures developed to be invariant to monotonic intensity transformations the results show that the mmtm technique is a highly competitive alternative of conventional measures in problems where possible tone mappings are close to monotonic

absorbing boundary conditions for the two dimensional schrodinger equation with an exterior potential four families of abcs where built in antoine et al math models methods appl sci 22 10 2012 for the two dimensional linear schrodinger equation with time and space dependent potentials and for general smooth convex fictitious surfaces the aim of this paper is to propose some suitable discretization schemes of these abcs and to prove some semi discrete stability results furthermore the full numerical discretization of the corresponding initial boundary value problems is considered and simulations are provided to compare the accuracy of the different abcs

absorbing boundary conditions for the one dimensional schrodinger equation with an exterior repulsive potential mathematical constructions and comparisons of accurate absorbing boundary conditions for the one dimensional schrodinger equation with a general variable repulsive potential are developed stable semi discretization schemes are built for the associated initial boundary value problems finally some numerical simulations give a comparison of the various absorbing boundary conditions and show that they yield accurate computations

a local high order doubly asymptotic open boundary for diffusion in a semi infinite layer a high order open boundary for transient diffusion in a semi infinite homogeneous layer is developed the method of separation of variables is used to derive a relationship between the modal function and the flux at the near field far field boundary in the fourier domain the resulting equation in terms of the modal impedance coefficient is solved by expanding the latter into a doubly asymptotic series of continued fractions as a result the open boundary condition in the fourier domain is represented by a system of algebraic equations in terms of i w this corresponds to a system of fractional differential equations of degree a 0 5 in the time domain this temporally global formulation is transformed into a local description by introducing internal variables the resulting local high order open boundary condition is highly accurate as is demonstrated by a number of heat transfer examples a significant gain in accuracy is obtained in comparison with existing singly asymptotic formulations at no additional computational cost

analysis of multicomponent lfm signals by a combined wigner hough transform the aim of the paper is the performance evaluation of a method for the analysis of mono or multicomponent linear frequency modulation lfm signals based on the hough transform of the wigner ville distribution of the signals a closed form expression is found for the signal to noise ratio and the parameter estimation accuracy the overall method as any nonlinear method exhibits a threshold effect nevertheless it is shown to be asymptotically efficient and offers a good rejection capability of the cross terms

the contracting curve density algorithm fitting parametric curve models to images using local self adapting separation criteria the task of fitting parametric curve models to the boundaries of perceptually meaningful image regions is a key problem in computer vision with numerous applications such as image segmentation pose estimation object tracking and 3 d reconstruction in this article we propose the contracting curve density ccd algorithm as a solution to the curve fitting problem the ccd algorithm extends the state of the art in two important ways first it applies a novel likelihood function for the assessment of a fit between the curve model and the image data this likelihood function can cope with highly inhomogeneous image regions because it is formulated in terms of local image statistics the local image statistics are learned on the fly from the vicinity of the expected curve they provide therefore locally adapted criteria for separating the adjacent image regions these local criteria replace often used predefined fixed criteria that rely on homogeneous image regions or specific edge properties the second contribution is the use of blurred curve models as efficient means for iteratively optimizing the posterior density over possible model parameters these blurred curve models enable the algorithm to trade off two conflicting objectives namely heaving a large area of convergence and achieving high accuracy we apply the ccd algorithm to several challenging image segmentation and 3 d pose estimation problems our experiments with rgb images show that the ccd algorithm achieves a high level of robustness and sub pixel accuracy even in the presence of severe texture shading clutter partial occlusion and strong changes of illumination

on image analysis by the methods of moments various types of moments have been used to recognize image patterns in a number of applications a number of moments are evaluated and some fundamental questions are addressed such as image representation ability noise sensitivity and information redundancy moments considered include regular moments legendre moments zernike moments pseudo zernike moments rotational moments and complex moments properties of these moments are examined in detail and the interrelationships among them are discussed both theoretical and experimental results are presented

unconditionally stable discretization schemes of non reflecting boundary conditions for the one dimensional schrodinger equation this paper addresses the problem of the construction of stable approximation schemes for the one dimensional linear schrodinger equation set in an unbounded domain after a study of the initial boundary value problem in a bounded domain with a transparent boundary condition some unconditionally stable discretization schemes are developed for this kind of problem the main difficulty is linked to the involvement of a fractional integral operator defining the transparent operator the proposed semi discretization of this operator yields with a very different point of view the one proposed by yevick friese and schmidt j comput phys 168 2001 433 two possible choices of transparent boundary conditions based on the dirichlet neumann dn and neumann dirichlet nd operators are presented to preserve the stability of the fully discrete scheme conform galerkin finite element methods are employed for the spatial discretization finally some numerical tests are performed to study the respective accuracy of the different schemes

structural indexing efficient 3 d object recognition the authors present an approach for the recognition of multiple 3 d object models from three 3 d scene data the approach uses two different types of primitives for matching small surface patches where differential properties can be reliably computed and lines corresponding to depth or orientation discontinuities these are represented by splashes and 3 d curves respectively it is shown how both of these primitives can be encoded by a set of super segments consisting of connected linear segments these super segments are entered into a table and provide the essential mechanism for fast retrieval and matching the issues of robustness and stability of the features are addressed in detail the acquisition of the 3 d models is performed automatically by computing splashes in highly structured areas of the objects and by using boundary and surface edges for the generation of 3 d curves the authors present results with the current system 3 d object recognition based on super segments and discuss further extensions

discrete transparent boundary conditions for schrodinger type equations we present a general technique for constructing nonlocal transparent boundary conditions for one dimensional schrodinger type equations our method supplies boundary conditions for the family of implicit one step discretizations of schrodinger s equation in time the use of mikusi ski s operator approach in time avoids direct and inverse transforms between time and frequency domains and thus implements the boundary conditions in a direct manner

adaptive absorbing boundary conditions for schrodinger type equations application to nonlinear and multi dimensional problems we propose an adaptive approach in picking the wave number parameter of absorbing boundary conditions for schrodinger type equations based on the gabor transform which captures local frequency information in the vicinity of artificial boundaries the parameter is determined by an energy weighted method and yields a quasi optimal absorbing boundary conditions it is shown that this approach can minimize reflected waves even when the wave function is composed of waves with different group velocities we also extend the split local absorbing boundary slab method z xu h han phys rev e 74 2006 037704 to problems in multi dimensional nonlinear cases by coupling the adaptive approach numerical examples of nonlinear schrodinger equations in one and two dimensions are presented to demonstrate the properties of the discussed absorbing boundary conditions

focused color intersection with efficient searching for object extraction we propose focused color intersection with efficient searching for identifying and extracting the objects in a complex scene based on color similarity the method matches the models against different parts of a scene called focus regions using normalized color histogram intersection the best matching focus region is determined by an efficient search strategy employing upper bound pruning this search strategy called active search concentrates its effort on parts of the scene having high similarity with the object consequently it achieves a large reduction in computational effort without sacrificing accuracy an efficient algorithm for evaluating the color histogram intersection between a model and a focus region is also given experiments conducted demonstrate that multiple known objects in complex scenes can be extracted by this process the method is stable against scale changes two dimensional rotation moderate changes in shape and partial occlusion

robust regression methods for computer vision a review regression analysis fitting a model to noisy data is a basic technique in computer vision robust regression methods that remain reliable in the presence of various types of noise are therefore of considerable importance we review several robust estimation techniques and describe in detail the least median of squares lmeds method the method yields the correct result even when half of the data is severely corrupted its efficiency in the presence of gaussian noise can be improved by complementing it with a weighted least squares based procedure the high time complexity of the lmeds algorithm can be reduced by a monte carlo type speed up technique we discuss the relationship of lmeds with the ransac paradigm and its limitations in the presence of noise corrupting all the data and we compare its performance with the class of robust m estimators references to published applications of robust techniques in computer vision are also given

transparent boundary conditions for iterative high order parabolic equations recently a new approach to the construction of high order parabolic approximations for the helmholtz equation was developed these approximations have the form of the system of iterative parabolic equations where the solution of the n th equation is used as an input term for the n 1 th equation in this study the transparent boundary conditions for such systems of coupled parabolic equations are derived the existence and uniqueness of the solution of the initial boundary value problem for the system of iterative parabolic equations with the derived boundary conditions are proved the well posedness of this problem is also established and an unconditionally stable finite difference scheme for its solution is proposed