automatic mesh generation over intersecting surfaces a fully automatic general scheme is proposed to determine and analyse the intersections between two groups of surfaces composed of triangular facets by carefully maintaining the spatial position of the lines of intersection in regenerating mesh locally around surface intersections pieces of surfaces can be arbitrarily combined and merged a great variety of objects can be easily created by selectively putting together different surface parts derived from surface intersections the new algorithm is best applied in conjunction with an existing surface mesh generator to enhance its general capability in dealing with objects built from intersecting surfaces in fact it is a powerful surface mesh manipulator and through the repeated use of the process complex structures can be rapidly and accurately constructed

a new mesh generation scheme for arbitrary planar domains this paper describes a new algorithm to generate interior nodes within any arbitrary multi connected regions the boundary nodes and the interior nodes are then linked up to form the best possible triangular elements by a completely revised technique in an efficient and stable manner owing to the generality of the central generation program the global domain is allowed to be divided into as many irregular subdomains as desired in order to model closely the actual physical situation moreover the boundaries of the sub domains are updated from time to time when necessary to include the possibilities of progressive refinement around a sharp corner generating radiating mesh from a prescribed node generating mesh between two circular arcs etc despite its flexibility and capabilities data for triangulation have been kept to a minimum by a logical input module no connectivity information between subregions is needed and common boundaries are defined once only all these features have contributed to a powerful method to generate 3 node or 6 node triangular element meshes of great variety within the most irregular heterogeneous regions

average adjacencies for tetrahedral skeleton regular partitions for any conforming mesh the application of a skeleton regular partition over each element in the mesh produces a conforming mesh such that all the topological elements of the same dimension are subdivided into the same number of child elements every skeleton regular partition has associated special constitutive recurrence equations in this paper the average adjacencies associated with the skeleton regular partitions in 3d are studied in three dimensions different values for the asymptotic number of average adjacencies are obtained depending on the considered partition in contrast with the two dimensional case j comput appl math 140 2002 673 in addition a priori formulae for the average asymptotic adjacency relations for any skeleton regular partition in 3d are provided

effects of degradation of intensity time or frequency content on speech intelligibility for normal hearing and hearing impaired listeners many hearing impaired listeners suffer from distorted auditory processing capabilities this study examines which aspects of auditory coding i e intensity time or frequency are distorted and how this affects speech perception the distortion sensitivity model is used the effect of distorted auditory coding of a speech signal is simulated by an artificial distortion and the sensitivity of speech intelligibility to this artificial distortion is compared for normal hearing and hearing impaired listeners stimuli speech plus noise are wavelet coded using a complex sinusoidal carrier with a gaussian envelope 14 octave bandwidth intensity information is distorted by multiplying the modulus of each wavelet coefficient by a random factor temporal and spectral information are distorted by randomly shifting the wavelet positions along the temporal or spectral axis respectively measured were 1 detection thresholds for each type of distortion and 2 speech reception thresholds for various degrees

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

nonmonotonicity of informational masking neff and green percept psychophys 41 409 415 1987 report that the masking of single tones by random frequency multitone maskers varies nonmonotonically with number of masker components peaking at 10 50 components in this paper it is shown that such results are well predicted by a model the component relative entropy model core wherein thresholds increase linearly with the ensemble variance of masker spectra smoothed by peripheral auditory filters r a lutfi j acoust soc am 94 748 758 1993 three experiments were conducted in the first the nonmonotonic relation was replicated for 9 of 11 listeners in conditions similar to those of neff and green in the second the frequencies of masker components were fixed and the levels of components were varied randomly across presentations to simulate gaussian noise in this case the nonmonotonicity and the total amount of masking for these listeners were shown to be significantly reduced in the third experiment masked thresholds for the signal were found to vary monotonically with the frequency spacing of masker components for a fixed number of masker components large individual differences among listeners were obtained in some experimental conditions individual as well as mean thresholds were well predicted by the core model with an appropriate selection of the values of the two free parameters of the model for each listener

factors affecting masking release for speech in modulated noise for normal hearing and hearing impaired listeners the speech reception threshold for sentences in stationary noise and in several amplitude modulated noises was measured for 8 normal hearing listeners 29 sensorineural hearing impaired listeners and 16 normal hearing listeners with simulated hearing loss this approach makes it possible to determine whether the reduced benefit from masker modulations as often observed for hearing impaired listeners is due to a loss of signal audibility or due to suprathreshold deficits such as reduced spectral and temporal resolution which were measured in four separate psychophysical tasks results show that the reduced masking release can only partly be accounted for by reduced audibility and that when considering suprathreshold deficits the normal effects associated with a raised presentation level should be taken into account in this perspective reduced spectral resolution does not appear to qualify as an actual suprathreshold deficit while reduced temporal resolution does temporal resolution and age are shown to be the main factors governing masking release for speech in modulated noise accounting for more than half of the intersubject variance their influence appears to be related to the processing of mainly the higher stimulus frequencies results based on calculations of the speech intelligibility index in modulated noise confirm these conclusions

finite element transport modeling using analytic element flow solutions 1 finite element methods for solute transport simulation typically use a discrete representation of the flow domain obtained from a finite element solution of the associated groundwater flow problem velocity saturated thickness and components of the dispersion coefficient tensor are represented as a set of nodal and or element averaged values in contrast the analytic element method aem provides continuous mesh independent solutions for these variables in this paper a set of techniques for using two dimensional aem flow solutions as the basis of finite element solute transport models is introduced first a general aem based discretization approach is presented that addresses the existence of curved boundaries singularities and discontinuities in vertically averaged concentration second residual integration methods that handle continuous parameters with internal and boundary singularities are developed and evaluated third an approach is introduced for handling internal discontinuities in concentration across certain analytic elements this new approach uses a nonstandard mesh topology and a new formulation for internal coupled boundary conditions the aem based transport simulation methods introduced in this paper are demonstrated to be robust and accurate for a variety of test problems

a combined octree delaunay method for fully automatic 3 d mesh generation fully automatic three dimensional mesh generation is a fundamental requirement for automating the numerical solution of partial differential equations two techniques in particular the octree and delaunay approaches have been used towards this end a method that combines both approaches to fully automatic mesh generation is presented here the resulting algorithm provides the linear growth rate and divide and conquer approach of the octree method with the simplicity and optimal properties of the delaunay triangulation

mid node admissible spaces for quadratic triangular 2d finite elements with one edge curved a robust element distortion metric based on the new concept of mid node admissible spaces for two dimensional quadratic triangular finite elements is developed the metric is based on the jacobian determinant over the entire element without requiring that it actually be computed everywhere on the element the metric is relatively inexpensive to compute especially for mildly distoted elements the metric is able to detect elementsof poor quality that other distortion metrics fall to detect it also has the ability to approve elements of good quality regardless of the extent to which they may appear geometrically distorted copyright 2001 john wiley sons ltd

automated adaptive time discontinuous finite element method for unsteady compressible airfoil aerodynamics an adaptive finite element methodology for unsteady compressible aerodynamics is presented the automated adaptive environment consists of the finite quadtree automatic mesh generator a time discontinuous galerkin least squares finite element flow solver an error indicator based on interpolation estimates and a mesh enrichment procedure specifically a linear space time wedge element formulation was developed and implemented for two dimensional problems with relative body motion the mesh enrichment procedure is developed to enable the solution process to be spatially adaptive h refinement is edge based and stores no mesh enrichment history

parametric surface meshing using a combined advancing front generalized delaunay approach an indirect method for meshing parametric surfaces conforming to a user specifiable size map is presented first from this size specification a riemannian metric is defined so that the desired mesh is one with unit length edges with respect to the related riemannian space the so called unit mesh then based on the intrinsic properties of the surface the riemannian structure is induced into the parametric space finally a unit mesh is generated completely inside the parametric space such that it conforms to the metric of the induced riemannian structure this mesh is constructed using a combined advancing front delaunay approach applied within a riemannian context the proposed method can be applied to mesh composite parametric surfaces several examples illustrate the efficiency of our approach copyright 2000 john wiley sons ltd

speech intelligibility is best predicted by intensity not cochlea scaled entropy cochlea scaled entropy cse is a measure of spectro temporal change that has been reported to predict the contribution of speech segments to overall intelligibility this paper confirms that cse is highly correlated with intensity making it impossible to determine empirically whether it is cse or simply intensity that determines speech importance a more perceptually relevant version of cse that uses db scaled differences rather than differences in linear amplitude failed to predict speech intelligibility overall a parsimonious account of the available data is that the importance of speech segments to overall intelligibility is best predicted by their relative intensity not by cse

simulation of the effect of threshold elevation and loudness recruitment combined with reduced frequency selectivity on the intelligibility of speech in noise the effect of loudness recruitment and threshold elevation together with reduced frequency selectivity have been simulated to examine the combined effect of the two major consequences of cochlear hearing loss on the intelligibility of speech in speech shaped noise in experiment 1 four conditions were simulated a moderate flat loss with auditory filters broadened by a factor of three b3r2 a moderate to severe sloping loss with auditory filters broadened by a constant factor of three b3rx and these conditions with linear amplification applied prior to the simulation processing b3r2 b3rx for conditions b3r2 and b3rx performance was markedly worse than for a control condition normal hearing condition r1 tested in a previous study for conditions b3r2 and b3rx linear amplification improved performance considerably however performance remained below that for condition r1 by between 5 and 19 in experiment 2 the broadening of the auditory filters was made more realistic by making it a function of the absolute threshold at the center frequency of the auditory filter three different hearing losses were simulated a moderate to severe sloping loss with variable broadening of the auditory filters bxrx the same moderate to severe sloping loss with linear amplification bxrx and the same broadening of the auditory filters but without the simulation of loudness recruitment and threshold elevation bx for condition bxrx performance was markedly worse than in condition r1 while performance in condition bx was somewhat worse than for condition r1 for condition bxrx linear amplification according to the nal procedure improved performance to a large extent but it remained worse than for condition r1 the results are consistent with previous evidence indicating that only part of the decrease of performance produced by actual cochlear hearing loss can be compensated by conventional linear hearing aids

improved vector fem solutions of maxwell s equations using grid pre conditioning the time domain vector finite element method is a promising new approach for solving maxwell s equations on unstructured triangular grids this method is sensitive to the quality or condition of the grid in this study grid pre conditioning techniques such as edge swapping laplacian smoothing and energy minimization are shown to improve the accuracy of the solution and also reduce the overall computational effort 1997 john wiley sons ltd

informational masking by everyday sounds tone in noise detection is severely degraded when only a few spectral components of the noise are presented at random on each trial neff and green percept psychophys 41 409 415 1987 the elevations in threshold are attributed to uncertainty regarding the noise caused by sparse sampling of noise components informational masking is the term used to describe the result the present experiment was undertaken to determine how informational masking is affected when sparse sampling is from a set of common everyday sounds instead of noise on each presentation a different masker waveform of constant total power was synthesized from the magnitude and phase of a fixed number m of spectral components m 2 921 across blocks of trials the components were selected at random from 1 of 50 common environmental sounds e g baby crying door slamming phone ringing or 1 of 50 samples of gaussian noise masked thresholds for a 1 0 khz signal in the presence of both types of maskers were obtained using an adaptive two interval forced choice procedure results with noise replicated earlier results showing largest elevations in threshold for 10 20 sampled components results with everyday sounds showed a similar pattern with thresholds elevated above those for noise by as much as 10 db at the larger values of m the differences in masked thresholds were systematically related to differences in the ensemble variance of masker spectra as predicted by a model previously applied to noise lutfi j acoust soc am 94 748 758 1993 not predicted was the result of a subsequent trial by trial analysis in which 9 11 db less masking was observed for samples from everyday sounds rated as easily recognized by listeners the results suggest that listeners fail to exploit lawful dependencies among spectral components of everyday sounds to aid detection unless enough information is available for the sound to be easily recognized

an approach to the generation of triangular grids possessing few obtuse triangles a triangular mesh generator is presented which makes extensive use of side swapping and mesh smoothing to create a grid with few obtuse triangles to perform the above task a data structure is presented which holds full adjacency information both for nodes and elements it is shown how this data structure is employed in the process mesh generation and how the methods of computational geometry such as region decomposition are used not only to decompose a complex region but also to reflect the boundary grading into the interior the region algorithms are provided to show the mechanism of these processes and practical examples are given to support the approach

effective and practical h p version adaptive analysis procedures for the finite element method two practical and effective h p type finite element adaptive procedures are presented the procedures allow not only the final global energy norm error to be well estimated using hierarchic p refinement but in addition give a nearly optimal mesh the design of this is guided by the local information computed on the previous mesh the desired accuracy can always be obtained within one or at most two h p refinements the rate of convergence of the adaptive h p version analysis procedures has been tested for some examples and found to be very strong the presented procedures can easily be incorporated into existing p or h type code structures

contributions of cochlea scaled entropy and consonant vowel boundaries to prediction of speech intelligibility in noise recent evidence suggests that spectral change as measured by cochlea scaled entropy cse predicts speech intelligibility better than the information carried by vowels or consonants in sentences motivated by this finding the present study investigates whether intelligibility indices implemented to include segments marked with significant spectral change better predict speech intelligibility in noise than measures that include all phonetic segments paying no attention to vowels consonants or spectral change the prediction of two intelligibility measures normalized covariance measure ncm coherence based speech intelligibility index csii is investigated using three sentence segmentation methods relative root mean square rms levels cse and traditional phonetic segmentation of obstruents and sonorants while the cse method makes no distinction between spectral changes occurring within vowels consonants the rms level segmentation method places more emphasis on the vowel consonant boundaries wherein the spectral change is often most prominent and perhaps most robust in the presence of noise higher correlation with intelligibility scores was obtained when including sentence segments containing a large number of consonant vowel boundaries than when including segments with highest entropy or segments based on obstruent sonorant classification these data suggest that in the context of intelligibility measures the type of spectral change captured by the measure is important

robust boundary triangulation and delaunay triangulation of arbitrary planar domains a simple and robust boundary triangulation algorithm is proposed and based on it completely automatic delaunay mesh generation procedures are developed the algorithm is equally applicable to convex non convex and multiply connected planar domains in this approach given the nodes the number of triangles formed is precisely known and any desired control over mesh generation is possible

selective refinement derefinement algorithms for sequences of nested triangulations the construction of changing sequences of irregular and nested triangulations based on the use of conforming refinement derefinement algorithms for triangulations is presented and discussed this strategy is particularly appropriate to combine adaptivity and full multigrid algorithms for dealing with moving fronts or fluid dynamics problems it is shown that the quality of all the triangulations iteratively generated depends only on the geometric characteristics of the initial grid a data structure suitable to create manage and modify series of nested triangulations as well as the main features of the deref prototype package are described and numerical examples are given

efficient nonlinear solvers for laplace beltrami smoothing of three dimensional unstructured grids the laplace beltrami system of nonlinear elliptic partial differential equations has utility in the generation of computational grids on complex and highly curved geometry discretization of this system using the finite element method accommodates unstructured grids but generates a large sparse ill conditioned system of nonlinear discrete equations the use of the laplace beltrami approach particularly in large scale applications has been limited by the scalability and efficiency of solvers this paper addresses this limitation by developing two nonlinear solvers based on the jacobian free newton krylov jfnk methodology a key feature of these methods is that the jacobian is not formed explicitly for use by the underlying linear solver iterative linear solvers such as the generalized minimal residual gmres method do not technically require the stand alone jacobian instead its action on a vector is approximated through two nonlinear function evaluations the preconditioning required by gmres is also discussed two different preconditioners are developed both of which employ existing algebraic multigrid amg methods further the most efficient preconditioner overall for the problems considered is based on a picard linearization numerical examples demonstrate that these solvers are significantly faster than a standard newton krylov approach a speedup factor of approximately 26 was obtained for the picard preconditioner on the largest grids studied here in addition these jfnk solvers exhibit good algorithmic scaling with increasing grid size

estimates of effective frequency selectivity based on the detection of a tone added to complex maskers in experiment 1 the validity of parameters associated with the roex p r auditory filter shape was examined for three different types of maskers a a noise masker b a random 12 tone masker whose frequencies varied on a burst by burst basis multiple burst different mbd and c a random 12 tone masker whose frequencies were the same across bursts multiple burst same mbs first the power spectrum model of masking was used to estimate auditory filter shapes for four observers second the resulting auditory filter shapes were used in a computer simulation that provided an estimate of internal noise for each observer third relative weights across frequency were estimated for each observer and each masker type for the noise masker these analyses provided predictions and relative weights that were consistent across the three analyses for the mbd and mbs maskers there was little consistency neither the estimated internal noise nor the estimated relative weights reliably supported a single f

plotting of contours in a natural way a simple and straightforward scheme for plotting contours is introduced for any function the appropriate contours are traced on the paths of constant function values disclosing the information contained in the shape functions the exactness of the contours matches that of the finite element analysis extreme value considerations must be carried out to decide whether contours appear in an element at all three co ordinate systems are dealt with the local the global and the screen co ordinate system and the necessary mutual transformations a short section deals with the treatment of contour discontinuities across element borders which frequently occur with stresses and heat fluxes finally some examples are shown

relations between intelligibility of narrow band speech and auditory functions both in the 1 khz frequency region relations between perception of suprathreshold speech and auditory functions were examined in 24 hearing impaired listeners and 12 normal hearing listeners the speech intelligibility index sii was used to account for audibility the auditory functions included detection efficiency temporal and spectral resolution temporal and spectral integration and discrimination of intensity frequency rhythm and spectro temporal shape all auditory functions were measured at 1 khz speech intelligibility was assessed with the speech reception threshold srt in quiet and in noise and with the speech reception bandwidth threshold srbt previously developed for investigating speech perception in a limited frequency region around 1 khz the results showed that the elevated srt in quiet could be explained on the basis of audibility audibility could only partly account for the elevated srt values in noise and the deviant srbt values suggesting that suprathreshold deficits affected intelligibility in these conditions sii predictions for the srbt improved significantly by including the individually measured upward spread of masking in the sii model reduced spectral resolution reduced temporal resolution and reduced frequency discrimination appeared to be related to speech perception deficits loss of peripheral compression appeared to have the smallest effect on the intelligibility of suprathreshold speech

detection and intensity discrimination of gaussian shaped tone pulses as a function of duration j acoust soc am 105 3425 3435 1999 proposed that the auditory system partitions the spectro temporal domain into frequency time f t windows and that the characteristics of these windows could be explored by measuring intensity discrimination for gaussian shaped tone pulses presented just above their detection threshold in noise they reasoned that for a long duration tone pulse the auditory representation would be maximally compact in the frequency domain but would spread across several f t windows in the time domain for a very short duration tone pulse the auditory representation would be maximally compact in the time domain but would spread across several f t windows in the frequency domain there should be some intermediate duration at which the auditory representation is compact in both the time and frequency domains and for which intensity discrimination performance should worsen due to the limited opportunity for multiple looks their data for signal frequencies of 1 and 4 khz were consistent with this expectation intensity discrimination was poorest at a duration of about 3 5 ms at 1 khz and 1 ms at 4 khz durations are specified between 6 8 db down points on the envelope this experiment attempted to replicate those results and to extend them to a wider range of frequencies and levels intensity discrimination of gaussian shaped tone pulses was measured at three levels 10 db above absolute threshold or above masked threshold in a pink noise with a spectrum level of either 15 or 40 db at 1 khz the signal frequency was 0 25 khz durations from 2 to 320 ms 1 khz durations from 0 5 to 80 ms or 4 khz durations from 0 1 to 20 ms three normally hearing subjects were tested at 1 and 4 khz performance was poorest overall for the 15 db pink noise level and thresholds showed a peak at intermediate durations about 3 5 ms at 1 khz and 1 ms at 4 khz such peaks were still apparent but smaller in the no noise condition and were almost absent at the higher noise level for the 0 25 khz signal frequency peaks were not observed consistently at any level although two subjects showed small peaks for durations around 10 ms an explanation is offered for the results in terms of the level and frequency dependence of basilar membrane input output functions

parallel two step w methods with peer variables a new class of methods for the solution of stiff initial value problems is introduced that is parallel by design it has a two step character and propagates s different peer solution variables with essentially identical characteristics from step to step the main work lies in the solution of s independent linear stage equations which may be solved in parallel convergence of order s 1 and stability for general stepsize sequences are proved conditions for order s and stronger stability criteria are addressed as well promising methods up to order 7 are identified by numerical tests with some widely used stiff test problems some of these are competitive with existing software even in sequential computations

unstructured grid generation and a simple triangulation algorithm for arbitrary 2 d geometries using object oriented programming this paper describes the logic of a dynamic algorithm for a general 2d delaunay triangulation of arbitrarily prescribed interior and boundary nodes the complexity of the geometry is completely arbitrary the scheme is free of specific restrictions on the input of the geometrical data the scheme generates triangles whose associated circumcircles contain no nodal points except their vertices there is no predefined limit for the number of points and the boundaries the direction of generation of the triangles cannot be determined a priori as opposed to the moving front techniques an automatic node placement scheme reflecting the initial boundary point spacings is used the successive refinement scheme results in such a point distribution that the triangulation algorithm need not perform any geometric intersection check for overlapped triangles and penetrated boundaries further computational saving is provided by using a special binary tree adt in which the points are ordered such that contiguous points in the list are neighbours in physical space the method consists of a set of simple rules to understand the dynamic nature of the object oriented programming oop of the algorithms provides efficient memory management on the insertion deletion and searching processes the computational effort bears a linear relation ship between the cpu time and the total number of nodes some of the existing methods in the literature regarding triangular mesh generation are discussed in context 1997 by john wiley sons ltd

automatic quadrilateral triangular free form mesh generation for planar regions automation of finite element mesh generation holds great benefits for mechanical product development and analysis in addition to freeing engineers from mundane tasks automation of mesh generation reduces product cycle design and eliminates human related errors most of the existing mesh generation methods are either semi automatic or require specific topological information a fully automatic free form mesh generation method is described in this paper to alleviate some of these problems the method is capable of meshing singly or multiply connected convex concave planar regions these regions can be viewed as crosssectional areas of 2 1 2 d objects analysed as plane stress plane strain or axisymmetric stress problems in addition to being fully automatic the method produces quadrilateral or triangular elements with aspect rations near one moreover it does not require any topological constraints on the regions to be meshed i e it provides free form mesh generation the input to the method includes the region s boundary curves the element size and the mesh grading information the method begins by decomposing the planar region to be meshed into convex subregions each subregion is meshed by first generating nodes on its boundaries using the input element size the boundary nodes are then offset to mesh the subregion the resulting meshes are merged together to form the final mesh the paper describes the method in detail algorithms developed to implement it and sample numerical examples results on parametric studies of the method performance are also discussed

the advancing front mesh generation method revisited this paper presents a mesh generation method of the advancing front type which is designed in such a way that the well known difficulties of the classical advancing front method are not present the retained solution consists of using the first steps of a voronoi delaunay method to construct a background mesh which is then used to govern the algorithm the two dimensional case is considered in detail and possible extensions to adaption problems and three dimensions are indicated

iterated function systems and the global construction of fractals iterated function systems i f ss are introduced as a unified way of generating a broad class of fractals these fractals are often attractors for i f ss and occur as the supports of probability measures associated with functional equations the existence of certain p balanced measures for i f ss is established and these measures are uniquely characterized for hyperbolic i f ss the hausdorff besicovitch dimension for some attrac tors of hyperbolic i f ss is estimated with the aid of p balanced measures what appears to be the broadest framework for the exactly computable moment theory of p balanced measures that of linear i f ss and of probabilistic mixtures of iterated riemann surfaces is presented this extensively generalizes earlier work on orthogonal polynomials on julia sets an example is given of fractal reconstruction with the use of linear i f ss and moment theory

delaunay triangulation of non convex planar domains this paper investigates the possibility of integrating the two currently most popular mesh generation techniques namely the method of advancing front and the delaunay triangulation algorithm the merits of the resulting scheme are its simplicity efficiency and versatility with the introduction of non delaunay line segments the concept of using delaunay triangulation as a means of mesh generation is clarified an efficient algorithm is proposed for the construction of delaunay triangulations over non convex planar domains interior nodes are first generated within the planar domain these interior nodes and the boundary nodes are then linked up together to produce a valid triangulation in the mesh generation process the delaunay property of each triangle is ensured by selecting a node having the smallest associated circumcircle in contrast to convex domains intersection between the proposed triangle and the domain boundary has to be checked this can be simply done by considering only the non delaunay segments on the generation front through the study of numerous examples of various characteristics it is found that high quality triangular element meshes are obtained by the proposed algorithm and the mesh generation time bears a linear relationship with the number of elements nodes of the triangulation

level dependence of auditory filters in nonsimultaneous masking as a function of frequency auditory filter bandwidths were measured using nonsimultaneous masking as a function of signal level between 10 and 35db sl for signal frequencies of 1 2 4 and 6khz the brief sinusoidal signal was presented in a temporal gap within a spectrally notched noise two groups of normal hearing subjects were tested one using a fixed masker level and adaptively varying signal level the other using a fixed signal level and adaptively varying masker level in both cases auditory filters were derived by assuming a constant filter shape for a given signal level the filter parameters derived from the two paradigms were not significantly different at 1khz the equivalent rectangular bandwidth erb decreased as the signal level increased from 10to20db sl after which it remained roughly constant in contrast at 6khz the erb increased consistently with signal levels from 10to35db sl the results at 2 and 4khz were intermediate showing no consistent change in erb with signal level overall the results sugge

a quadratic plane triangular element immune to quadratic mesh distortions under quadratic displacement fields abstract a quadratic plane triangular element is developed extending the concepts of us quad8 element the element belongs to the broad class of petrov galerkin formulation which is characterized by the choice of test and trial functions from different spaces the performance of the proposed element has been studied for typical static and free vibration problems the element exhibits a high degree of tolerance to mesh distortions as compared to the classical isoparametric quadratic triangular element for undistorted meshes however the performance is similar to that of the classical element

mesh smoothing using a posteriori error estimates we develop a simple mesh smoothing algorithm for adaptively improving finite element triangulations the algorithm makes use of a posteriori error estimates which are now widely used in finite element calculations in this paper we derive the method present some numerical illustrations and give a brief analysis of the issue of uniqueness

a close look at valences in hexahedral element meshes this paper discusses using valences in objective functions for topological modification of 3d hexahedral meshes for topological optimization of 2d quadrilateral meshes node valence i e number of element edges attached to each node is used to maximize the number of regular nodes i e nodes with four attached edges difficulties in developing 3d hexahedral local topology modifications have limited the success of hexahedral topology optimization although published literature suggests using an object function based on node valence however in this paper we show that node valence is not a consistent measure of good hexahedral element topology and objective functions based on node valence can lead to element topology which will only admit concave element shapes instead we propose that objective functions based on edge valence i e number of quadrilateral faces attached to each element edge will provide a consistent measure of element topology copyright 2010 john wiley sons ltd

comparing the perceptual contributions of cochlear scaled entropy and speech level cochlear scaled entropy cse has been suggested to be a reliable predictor of speech intelligibility previous studies showed that speech segments with high root mean square rms levels h levels contained primarily vowels which carry important information for speech recognition the present work compared the contributions of high cse h entropy and h level segments to speech intelligibility the natural speech was edited to generate two types of noise replaced stimuli which preserved the same percentages of largest cse segments and highest rms level segments and played to normal hearing listeners in a recognition experiment experimental results showed that the nature of the noise replaced stimulus h entropy and h level made a small difference in intelligibility performance cses and rms levels showed a moderately high correlation r 0 79 suggesting that many speech segments may have both large cses and high rms levels which might account partially for the small intelligibility difference between the two types of stimuli in addition the vowel duration proportion differed between h entropy and h level segments of the same length suggesting that vowels play different roles in contributing to the intelligibility of h entropy and h level stimuli

auditory filters and the benefit measured from spectral enhancement algorithms designed to improve speech intelligibility for those with sensorineural hearing loss snhl by enhancing peaks in a spectrum have had limited success since testing of such algorithms cannot separate the theory of the design from the implementation itself the contribution of each of these potentially limiting factors is not clear therefore psychophysical paradigms were used to test subjects with either normal hearing or snhl in detection tasks using well controlled stimuli to predict and assess the limits in performance gain from a spectrally enhancing algorithm a group of normal hearing nh and hearing impaired hi subjects listened in two experiments auditory filter measurements and detection of incremented harmonics in a harmonic spectrum the results show that nh and hi subjects have an improved ability to detect incremented harmonics when there are spectral decrements surrounding the increment various decrement widths and depths were compared against subjects equivalent rectangula

an automatic adaptive refinement finite element procedure for 2d elastostatic analysis an automatic adaptive refinement procedure for finite element analysis is presented the procedure is applied to two dimensional elastostatic problems to obtain solutions of prescribed accuracy through the combined use of new mesh generator using contour developed by lo1 and the concept of strain energy concentration high quality graded finite element meshes are generated the whole process is fully automatic and no user intervention is required during the successive cycles of the mesh refinements the zienkiewicz and zhu2 error estimator is found to be effective and has been adopted for the present implementation in the numerical examples tested the error estimator gives an accurate error norm estimation and the effectivity index of the estimator converges to a value close to unity

mesh rezoning of 2d isoparametric elements by inversion the method uses techniques from elimination theory to solve the parametric inversion problem for each node on the new undistorted mesh these parameter values are then used in the elemental shape functions to transfer the nodal state variables from the distorted mesh to each node in the new mesh by interpolation the method has been implemented for bilinear and biquadratic elements the method is based on fundamental finite element approximations since the interpolation functions which define the element are also used to perform rezoning

planar mesh refinement cannot be both local and regular we show that two desirable properties for planar mesh refinement techniques are incompatible mesh refinement is a common technique for adaptive error control in generating unstructured planar triangular meshes for piecewise polynomial representations of data local refinements are modifications of the mesh that involve a fixed maximum amount of computation independent of the number of triangles in the mesh regular meshes are meshes for which every interior vertex has degree 6 at least for some simple model meshing problems optimal meshes are known to be regular hence it would be desirable to have a refinement technique that if applied to a regular mesh produced a larger regular mesh we call such a technique a regular refinement in this paper we prove that no refinement technique can be both local and regular our results also have implications for non local refinement techniques such as delaunay insertion or rivara s refinement

relationship between frequency selectivity and frequency discrimination measured in subjects with unilateral and bilateral cochlear impairments frequency selectivity refers to the filtering processes which underlie our ability to detect a sound of one frequency in the presence of another sound with a different frequency frequency discrimination is our ability to detect changes in frequency over time it is a basic tenet of the place theory that frequency discrimination depends upon frequency selectivity in this paper we describe an experimental test of a place model put forward by zwicker 1956 in which frequency discrimination is explained in terms of excitation patterns the model is illustrated schematically in fig 1 which shows excitation patterns calculated using the method described by moore and glasberg 1983 for two sinusoids with frequencies 1180 and 1220 hz zwicker assumed that the frequencies of the two sinusoids can be discriminated if their excitation patterns differ at any point by more than a criterion amount he assumed a criterion of 1 db

mesh relaxation a new technique for improving triangulations summary given a list of points defining a domain boundary a three stage process is often used to triangulate a domain first an appropriate distribution of interior points is generated next the points are connected to form triangles and finally the connectivity data are used to reposition the interior points using the laplacian smoothing technique thereby usually improving the shapes of the triangles this paper describes a new technique for mesh improvement adjusting the connection structure during the second stage of this process the new scheme which we call mesh relaxation consists of a procedure for iteratively making the mesh topology more regular by edge swapping for each interior edge a relaxation index is computed that depends on the degrees of its end points and adjacent points any edge for which this index exceeds a prescribed threshold will be swapped i e replaced by a new edge connecting the adjacent points of the original edge after all edge swaps are completed laplacian smoothing is applied to the mesh examples show that when the mesh point density varies smoothly and due care is taken in the vicinity of the boundary mesh relaxation can dramatically increase the regularity of the mesh and produce improved triangle shapes

algorithms for refining triangular grids suitable for adaptive and multigrid techniques two general algorithms for refining triangular computational meshes based on the bisection of triangles by the longest side are presented and discussed the algorithms can be applied globally or locally for selective refinement of any conforming triangulation and always generate a new conforming triangulation after a finite number of interactions even when locally used the algorithms also ensure that all angles in subsequent refined triangulations are greater than or equal to half the smallest angle in the original triangulation the shape regularity of all triangles is maintained and the transition between small and large triangles is smooth in a natural way proofs of the above properties are presented the second algorithm is a simpler improved version of the first which retains most of the properties of the latter the algorithms can be used either for constructing irregular computational meshes or for locally refining any given triangulation in this sense they can be adequately combined with adaptive and or multigrid techniques for solving finite element systems examples of the application of the algorithms are given and two possible generalizations are pointed out

a grid generator based on 4 triangles conforming mesh refinement algorithms a procedure to generate 2d meshes of triangles in a quite general fashion allowing for local and selective mesh refinement is presented and discussed the grid generator is based on the iterative application of 4 triangles conforming mesh refinement algorithms for triangulations which are also introduced in this paper these algorithms are modified versions of those proposed in int j numer methods eng 20 745 756 1984 and they can be used for global refinement of a grid as well as for local refinement the grid generator works in the following way given any initial coarse triangulation which properly defines the geometry of the problem a set of user defined refinement subregions ri i 1 2 n and an associated set of tolerance parameters hi an irregular and conforming final triangulation is automatically constructed in such a way that the diameter of all the triangles contained in ri is smaller than hi i 1 2 n moreover all angles in the final triangulation are greater than or equal to half the smallest angle in the initial coarse one the refinement is propagated only to assure the conformity and smoothness of the grid and consequently the number of involved nodes will be minimized the refinement of the final mesh will be determined by the subregions ri and the parameters ni and will be essentially independent of the initial coarse grid the 4 triangles conforming mesh refinement algorithms are presented and their properties discussed the implementation of these techniques is discussed and examples of the application of the grid generator are given

automatic mesh generation and adaptation by using contours a general and efficient remeshing algorithm is presented for the discretization of arbitrary planar domains into triangular elements in consistency with the given node spacing funstion the contour lines of the node spacing function at suitable calculated levels provide the natural lines of division of the problem domain into subregions where finite elements meshes of different element sizes zre generated using the available general purpose mesh generators

auditory filter nonlinearity in mild moderate hearing impairment sensorineural hearing loss has frequently been shown to result in a loss of frequency selectivity less is known about its effects on the level dependence of selectivity that is so prominent a feature of normal hearing the aim of the present study is to characterize such changes in nonlinearity as manifested in the auditory filter shapes of listeners with mild moderate hearing impairment notched noise masked thresholds at 2 khz were measured over a range of stimulus levels in hearing impaired listeners with losses of 20 50 db growth of masking functions for different notch widths are more parallel for hearing impaired than for normal hearing listeners indicating a more linear filter level dependent filter shapes estimated from the data show relatively little change in shape across level the loss of nonlinearity is also evident in the input output functions derived from the fitted filter shapes reductions in nonlinearity are clearly evident even in a listener with only 20 db hearing loss

indices of frequency and temporal resolution as a function of level several investigators have suggested that between subject variations in hearing aid benefit may be related to between subject variations in auditory resolution evaluation of this relationship is complicated by the need to assess resolution at several frequencies and levels in hearing impaired listeners who may not tolerate lengthy test procedures this paper reports data from normal hearing listeners for abbreviated indices of frequency and temporal resolution for a particular frequency stimulus level combination both indices may be derived from three pure tone thresholds obtained with different masking stimuli norms are reported as a function of masker level for each index at four test frequencies changes in the indices as a function of masker level were consistent with expectations based on related studies by other investigators norms were obtained using a supra aural earphone comparison of results from supra aural and insert earphones suggested that low frequency sound leakage substantially affected the norms for 500 hz reliability of individual indices was good to excellent

using longest side bisection techniques for the automatic refinement of delaunay triangulations in this paper we discuss study and compare two linear algorithms for the triangulation refinement problem the known longest side triangle bisection refinement algorithm as well as a new algorithm that uses longest side bisection techniques for refining delaunay triangulations we show that the automatic point insertion criterion taken from the fractal property of optimal linear longest side bisection algorithms assures the construction of good quality delaunay triangulations in linear time numerical evidence showing that the practical behaviour of the new algorithm is in complete agreement with the theory is included 1997 by john wiley sons ltd

imex extensions of linear multistep methods with general monotonicity and boundedness properties for solving hyperbolic systems with stiff sources or relaxation terms time stepping methods should combine favorable monotonicity properties for shocks and steep solution gradients with good stability properties for stiff terms in this paper we consider implicit explicit imex multistep methods suitable methods will be constructed based on explicit methods with general monotonicity and boundedness properties for hyperbolic equations numerical comparisons are made with several implicit explicit runge kutta methods

mesh generation refinement using fractal concepts and iterated function systems a novel method of mesh generation is proposed which is based on the use of fractal concepts to derive contractive affine transformations the transformations are constructed in such a manner that the attractors of the resulting maps are a union of the points lines and surfaces in the domain in particular the mesh nodes may be generated recursively as a sequence of points which are obtained by applying the transformations to a coarse background mesh constructed from the given boundary data a delaunay triangulation or similar edge connection approach can then be performed on the resulting set of nodes in order to generate the mesh local refinement of an existing mesh can also be performed using the procedure the method is easily extended to three dimensions in which case the delaunay triangulation is replaced by an analogous 3 d tesselation

excitation based and informational masking of a tonal signal in a four tone masker this study examined contributions of peripheral excitation and informational masking to the variability in masking effectiveness observed across samples of multi tonal maskers detection thresholds were measured for a 1000 hz signal presented simultaneously with each of 25 four tone masker samples using a two interval forced choice adaptive task thresholds were measured with each sample fixed throughout trial blocks for ten listeners average thresholds differed by as much as 26 db across samples an excitation based model of partial loudness moore b c j et al 1997 j audio eng soc 45 224 237 was used to predict thresholds these predictions accounted for a significant portion of variance in the data of several listeners but no relation between the model and data was observed for many listeners moreover substantial individual differences on the order of 41 db were observed for some maskers the largest individual differences were found for maskers predicted to produce minimal excitat

bayesian adaptive estimation of the auditory filter a bayesian adaptive procedure for estimating the auditory filter shape was proposed and evaluated using young normal hearing listeners at moderate stimulus levels the resulting quick auditory filter qaf procedure assumed the power spectrum model of masking with the auditory filter shape being modeled using a spectrally symmetric two parameter rounded exponential roex function during data collection using the qaf procedure listeners detected the presence of a pure tone signal presented in the spectral notch of a noise masker dependent on the listener s response on each trial the posterior probability distributions of the model parameters were updated and the resulting parameter estimates were then used to optimize the choice of stimulus parameters for the subsequent trials results showed that the qaf procedure gave similar parameter estimates to the traditional threshold based procedure in many cases and was able to reasonably predict the masked signal thresholds additional measurements suggested that occasional failures of the qaf procedure to reliably converge could be a consequence of incorrect responses early in a qaf track the addition of a parameter describing lapses of attention reduced the likelihood of such failures

extrapolation based implicitexplicit peer methods with optimised stability regions in this paper we investigate a new class of implicitexplicit imex two step methods of peer type for systems of ordinary differential equations with both non stiff and stiff parts included in the source term an extrapolation approach based on already computed stage values is applied to construct imex methods with favourable stability properties optimised imex peer methods of order p 2 3 4 are given as result of a search algorithm carefully designed to balance the size of the stability regions and the extrapolation errors numerical experiments and a comparison to other implicitexplicit methods are included

rapid estimation of high parameter auditory filter shapes a bayesian adaptive procedure the quick auditory filter qaf procedure was used to estimate auditory filter shapes that were asymmetric about their peaks in three experiments listeners who were naive to psychoacoustic experiments detected a fixed level pure tone target presented with a spectrally notched noise masker the qaf procedure adaptively manipulated the masker spectrum level and the position of the masker notch which was optimized for the efficient estimation of the five parameters of an auditory filter model experiment i demonstrated that the qaf procedure provided a convergent estimate of the auditory filter shape at 2 khz within 150 to 200 trials approximately 15 min to complete and for a majority of listeners excellent test retest reliability in experiment ii asymmetric auditory filters were estimated for target frequencies of 1 and 4 khz and target levels of 30 and 50 db sound pressure level the estimated filter shapes were generally consistent with published norms especially at the low target level it is known that the auditory filter estimates are narrower for forward masking than simultaneous masking due to peripheral suppression a result replicated in experiment iii using fewer than 200 qaf trials

masked threshold difference due to masker harmonicity uniform modulation rates of auditory filter outputs versus periodicity in waveform fine structure in a previous paper treurniet and boucher j acoust soc am 109 306 320 2001 a model was presented which successfully accounted for the lower threshold obtained using a harmonic masker instead of a similar inharmonic masker for the harmonic masker the frequencies of partials were equally spaced so the envelope modulation rates of auditory filter outputs were invariant across filters however for the inharmonic masker the intervals between adjacent partials were not equal and this resulted in a decreased uniformity of modulation rates across filters the model proposed that the lower uniformity interferes with detection of a probe induced change in the modulation rates thus accounting for the masked threshold difference this paper shows that an inharmonic masker yields thresholds similar to a harmonic masker provided that the modulation rates are uniform across the auditory filters involved in processing the masker and probe thus the lowered threshold associated with a harmonic masker appears to arise from uniform modulation rates across auditory filters and does not require periodicity in the fine structure of the waveform produced by partial frequencies that are integer multiples of a fundamental

a stitching method for the generation of unstructured meshes for use with co volume solution techniques abstract the successful implementation of co volume time domain solution techniques requires the use of high quality smooth dual meshes the generation of delaunay voronoi diagrams with these properties for two dimensional domains of complicated geometrical shape is considered in the adopted approach near boundary regions are discretised according to prescribed criteria and the remainder of the computational domain is discretised using an ideal mesh the two meshes are stitched together to provide a consistent mesh for the complete domain after smoothing the resulting mesh is found to be of a quality which exceeds that of meshes produced by standard automatic unstructured mesh generation methods examples involving electromagnetic wave scattering are included to demonstrate the computational performance that can be achieved with a co volume time domain solution algorithm on these meshes

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

the deterioration of hearing with age frequency selectivity the critical ratio the audiogram and speech threshold the frequency selectivity of the auditory system was measured by masking a sinusoidal signal 0 5 2 0 or 4 0 khz or a filtered speech signal with a wideband noise having a notch or stopband centered on the signal as the notch was widened performance improved for both types of signal but the rate of improvement decreased as the age of the 16 listeners increased from 23 to 75 years indicating a loss in frequency selectivity with age auditory filter shapes derived from the tone in noise data show a that the passband of the filter broadens progressively with age and b that the dynamic range of the filter ages like the audiogram that is the range changes little with age before 55 but beyond this point there is an accelerating rate of loss the speech experiment shows comparable but smaller effects the filter width measurements show that the critical ratio is a poor estimator of frequency selectivity because it confounds the tuning of the system with the efficiency of the signal detection and speech processing mechanisms that follow the filter an alternative one point measure of frequency selectivity which is both sensitive and reliable is developed via the filter shape model of masking

rapid efficient encoding of correlated complex acoustic properties early sensory processing is long thought to extract and exploit redundancy and regularity in the input but perceptual evidence supporting this hypothesis has been limited experiments are reported demonstrating efficient encoding of multiple acoustic attributes resulting in the reduction of perceptual dimensionality stimuli varied across two complex independent dimensions attack decay ad and spectral shape ss a subset of 24 stimuli captured a near perfect correlation between these dimensions r2 0 95 participants passively listened to 25 presentations of these correlated stimuli over 7 5 min before discriminating sound pairs in axb trials without feedback for trials where both ss and ad varied listeners successfully discriminated sounds consistent with the correlation of ss and ad during exposure but they were at chance discriminating pairs varying orthogonal to the correlation presented in exposure after exposure participants were also significantly poorer at detecting differences among s

the effect of hearing loss on the resolution of partials and fundamental frequency discrimination the relationship between the ability to hear out partials in complex tones discrimination of the fundamental frequency f0 of complex tones and frequency selectivity was examined for subjects with mild to moderate cochlear hearing loss the ability to hear out partials was measured using a two interval task each interval included a sinusoid followed by a complex tone one complex contained a partial with the same frequency as the sinusoid while in the other complex that partial was missing subjects had to indicate the interval in which the partial was present in the complex the components in the complex were uniformly spaced on the erbn number scale performance was generally good for the two edge partials but poorer for the inner partials performance for the latter improved with increasing spacing f0 discrimination was measured for a bandpass filtered complex tone containing low harmonics the equivalent rectangular bandwidth erb of the auditory filter was estimated using the notched noise

an adaptive method for computing invariant manifolds in non autonomous three dimensional dynamical systems abstract we present a computational method for determining the geometry of a class of three dimensional invariant manifolds in non autonomous aperiodically time dependent dynamical systems the presented approach can be also applied to analyse the geometry of 3d invariant manifolds in three dimensional time dependent fluid flows the invariance property of such manifolds requires that at any fixed time they are given by surfaces in r 3 we focus on a class of manifolds whose instantaneous geometry is given by orientable surfaces embedded in r 3 the presented technique can be employed in particular to compute codimension one invariant stable and unstable manifolds of hyperbolic trajectories in 3d non autonomous dynamical systems which are crucial in the lagrangian transport analysis the same approach can also be used to determine evolution of an orientable material surface in a fluid flow these developments represent the first step towards a non trivial 3d extension of the so called lobe dynamics a geometric invariant manifold based framework which has been very successful in the analysis of lagrangian transport in unsteady two dimensional fluid flows in the developed algorithm the instantaneous geometry of an invariant manifold is represented by an adaptively evolving triangular mesh with piecewise c 2 interpolating functions the method employs an automatic mesh refinement which is coupled with adaptive vertex redistribution a variant of the advancing front technique is used for remeshing whenever necessary such an approach allows for computationally efficient determination of highly convoluted evolving geometry of codimension one invariant manifolds in unsteady three dimensional flows we show that the developed method is capable of providing detailed information on the evolving lagrangian flow structure in three dimensions over long periods of time which is crucial for a meaningful 3d transport analysis

towards a more efficient dynamic mesh adaptation methodology for continuum discretization in complex engineering problems a novel and efficient method of adaptive mesh generation for dynamically adaptive unstructured grids is proposed a locally refined triangulation is constructed on a coarse background mesh subdividing each triangle in the refinement region r into four congruent sub triangles iteratively by connecting edge midpoints until triangles of a prescribed lengthscale are obtained the unavoidable propagation outside the refinement region r is restricted to a single triangle in the coarse background mesh the triangles in the immediate vicinity of region r are broken down using the concept of iterated function systems widely used in fractal modeling by recursive generation of sub triangles with a gradation towards the region r triangles a quantitative assessment of the present algorithm proves its superiority over other comparable models reported in the literature the time cost of the algorithm is linear and the method can be easily extended to three dimensions

sample discrimination of frequency differences with distracters this study examined the effect of the type and frequency range of remote frequency distracters on sample discrimination of frequency differences sd f for baseline sd f conditions normal hearing listeners judged frequency differences between pairs of target tones drawn from gaussian frequency distributions near 2000 hz in experiment 1 the distracters were pairs of random frequency tones fixed frequency tones or noise bands with one distracter above and one below the target region three frequency separations of targets and distracters were tested none overlapping the target region effects of fixed frequency or noise band distracters were small compared to that of random frequency distracters which drove performance to near chance in experiment 2 dominance of the low frequency distracter was supported by the effects of changing distracter level by presenting only the higher or lower frequency distracter and by the pattern of weights derived from trial by trial responses performance recovered only when the lower frequency distracter was attenuated 40 50 db relative to the targets in experiment 3 all stimulus distributions were shifted 2 octaves higher in frequency the stronger influence of the distracter frequency below the target remained the results demonstrate the importance of both stimulus variability and frequency relationships in the interaction of targets and distracters for sd f

auditory filter shapes of cba caj mice behavioral assessments auditory filter shape and frequency tuning may be derived by measuring changes in pure tone thresholds as a function of the bandwidth of notched noise maskers when these psychophysical methods were applied to cba caj mice the resulting filter shapes were well fit by roex p r functions originally developed for human subjects the equivalent rectangular bandwidths erbs of the filter shapes ranged from 16 to 19 of test frequencies between 8 to 16khz these erbs correspond well to the performance of humans at high frequencies and the limited number of mammalian species that have been characterized with notched noise procedures frequency tuning was maintained throughout most of the adult lifespan and then showed a selective high frequency loss at ages beyond 2 years these results suggest that auditory filtering effects in adult cba caj mice are similar to normal processes in other mammalian species and provide an excellent model of human presbycusis when they begin to degrade in aging individuals

a class of data structures for 2 d and 3 d adaptive mesh refinement a family of tree data structures for adaptive mesh refinement is described and details concerning the associated logic are provided the data structures encompass triangular elements and quadrilateral elements in two dimensions and quadrilateral bricks in three dimensions furthermore both linear bilinear and quadratic biquadratic element types respectively are developed representative refinement results are given for the bilinear trilinear and biquadratic types and associated performance studies made for the refinement procedure

local bisection refinement for n simplicial grids generated by reflection a simple local bisection refinement algorithm for the adaptive refinement of n simplicial grids is presented the algorithm requires that the vertices of each simplex be ordered in a special way re

a compressive gammachirp auditory filter for both physiological and psychophysical data a gammachirp auditory filter was developed by irino and patterson j acoust soc am 101 412 419 1997 to provide a level dependent version of the linear gammatone auditory filter with which to explain the level dependent changes in cochlear filtering observed in psychophysical masking experiments in this analytical gammachirp filter the chirp varied with level and there was no explicit representation of the change in filter gain or compression with level subsequently carney et al j acoust soc am 105 2384 2391 1999 reviewed carney and yin s j neurophysiol 60 1653 1677 1988 reverse correlation revcor data and showed that the frequency glide of the chirp does not vary with level in their data in this article the architecture of the analytical gammachirp is reviewed with respect to cochlear physiology and a new form of gammachirp filter is described in which the magnitude response the gain and the compression vary with level but the chirp does not this new compressive gammachirp filter is used to fit the level dependent revcor data reported by carney et al 1999 and the level dependent masking data reported by rosen and baker hear res 73 231 243 1994

automatic mesh generation with tetrahedron elements to reduce the manual work involved in the application of the fem in practice preprocessors can be applied for the construction of network structures which are complicated in generation strategy and do not form any optimum discrete structure the time necessary for generation can be minimized even more by the application of only one element type within the whole network structure a technique for the automatic generation of 3d network structures with tetrahedron elements is presented in this paper in this proposed technique the nodal points of the network structure must be defined manually before the generation procedure since a random positioning of points is usually undesirable for fem calculation the nodal points are connected by a program to a network structure consisting of tetrahedron elements which have optimum form for the numerical computation of the element matrices after the generation the element sides forming any part of the boundary surface of the network structure can be automatically identified if necessary the network structure can be automatically refined

3d delaunay mesh generation coupled with an advancing front approach abstract this paper describes a fully automatic mesh generation method suitable for domains of any shape in r 3 initially a so called boundary mesh is generated wherein internal points are created using advancing front point placement and inserted using a delaunay method the algorithm combines the advantages of efficiency and nice mathematical properties of a delaunay approach with advancing front high quality point placement strategy several three dimensional examples are presented to demonstrate the overall efficiency and the relevance of the combined procedure the present method can be extended to isotropic or anisotropic adaptive mesh generation

on the adjacencies of triangular meshes based on skeleton regular partitions for any 2d triangulation the 1 skeleton mesh of is the wireframe mesh defined by the edges of while that for any 3d triangulation the 1 skeleton and the 2 skeleton meshes respectively correspond to the wireframe mesh formed by the edges of and the surface mesh defined by the triangular faces of a skeleton regular partition of a triangle or a tetrahedra is a partition that globally applied over each element of a conforming mesh where the intersection of adjacent elements is a vertex or a common face or a common edge produce both a refined conforming mesh and refined and conforming skeleton meshes such a partition divides all the edges and all the faces of an individual element in the same number of edges faces we prove that sequences of meshes constructed by applying a skeleton regular partition over each element of the preceding mesh have an associated set of difference equations which relate the number of elements faces edges and vertices of the nth and n 1 th meshes by using these constitutive difference equations we prove that asymptotically the average number of adjacencies over these meshes number of triangles by node and number of tetrahedra by vertex is constant when n goes to infinity we relate these results with the non degeneracy properties of longest edge based partitions in 2d and include empirical results which support the conjecture that analogous results hold in 3d

a new concept in two dimensional auto adaptative mesh generation the new method presented here is capable of building finite element meshes and managing their adaptation simultaneously to the object load case and geometry before any calculations i e an a priori mesh adaptation is conducted the principle relies on an analogy between a finite element mesh and the equilibrium position of a network of branches each branch is adequately sized by setting force length ratios called force densities starting from these data the nodal co ordinates are obtained through the solution of a linear system which describes the equilibrium state of the net this method seems very attractive since the only given data are a connectivity table the number of boundary and interior nodes and a geometrical description of the boundaries

comparison of the roex and gammachirp filters as representations of the auditory filter although the rounded exponential roex filter has been successfully used to represent the magnitude response of the auditory filter recent studies with the roex p w t filter reveal two serious problems the fits to notched noise masking data are somewhat unstable unless the filter is reduced to a physically unrealizable form and there is no time domain version of the roex p w t filter to support modeling of the perception of complex sounds this paper describes a compressive gammachirp cgc filter with the same architecture as the roex p w t which can be implemented in the time domain the gain and asymmetry of this parallel cgc filter are shown to be comparable to those of the roex p w t filter but the fits to masking data are still somewhat unstable the roex p w t and parallel cgc filters were also compared with the cascade cgc filter patterson et al j acoust soc am 114 1529 1542 2003 which was found to provide an equivalent fit with 25 fewer coefficients moreover the fits were stable the advantage of the cascade cgc filter appears to derive from its parsimonious representation of the high frequency side of the filter it is concluded that cgc filters offer better prospects than roex filters for the representation of the auditory filter

cochlea scaled spectral entropy predicts rate invariant intelligibility of temporally distorted sentences some evidence mostly drawn from experiments using only a single moderate rate of speech suggests that low frequency amplitude modulations may be particularly important for intelligibility here two experiments investigated intelligibility of temporally distorted sentences across a wide range of simulated speaking rates and two metrics were used to predict results sentence intelligibility was assessed when successive segments of fixed duration were temporally reversed exp 1 and when sentences were processed through four third octave band filters the outputs of which were desynchronized exp 2 for both experiments intelligibility decreased with increasing distortion however in exp 2 intelligibility recovered modestly with longer desynchronization across conditions performances measured as a function of proportion of utterance distorted converged to a common function estimates of intelligibility derived from modulation transfer functions predict a substantial proportion of the variance in listeners responses in exp 1 but fail to predict performance in exp 2 by contrast a metric of potential information quantified as relative dissimilarity change between successive cochlear scaled spectra is introduced this metric reliably predicts listeners intelligibility across the full range of speaking rates in both experiments results support an information theoretic approach to speech perception and the significance of spectral change rather than physical units of time

an automatic procedure with a control of accuracy for finite element analysis in 2d elasticity abstract this paper gives a procedure for an automation of the entire finite element analysis for 2d or axisymmetric elastic structures with a control of accuracy the user describes the problem and the level of desired accuracy the procedure then provides an approximate solution for a minimal computation cost this procedure uses an error measure based on the constitutive relation 1 5 and an efficient adaptive technique 6 which automatically take account of the regions of stress concentration examples are presented for discretizations using 3 or 6 node triangular elements

an analysis of metal forming processes using large deformation elastic plastic formulations a concise survey of the literature related to the large deformation elasto plasticity problems including unilateral contact and friction is presented together with an extension of the friction law for large deformation analysis starting from the principle of virtual work the so called total lagrangian and updated lagrangian formulations are derived based on some fundamental assumptions in linearizing the nonlinear equations by introducing the zaremba jaumann co rotational increment to the cauchy stress tensor the classical prandtl reuss equations are generalized for describing the elastic plastic material behavior to allow a proper consideration of the contact conditions in the incremental analysis a general friction law with an associated isotropic coulomb sliding rule is obtained by the similarity between dry friction and plasticity finite element discretizations and approximations are applied to the resulting formulation of the updated lagrangian approach four example problems are solved to test the formulations developed in this paper the emphasis is made toward the numerical accuracy of the finite element solutions

the effects of frequency region and bandwidth on the temporal modulation transfer function temporal modulation transfer functions tmtfs were measured using narrow band am and qfm noises with upper spectral edges from 0 6 to 4 8 khz and spectrum levels of 10 and 40 db spl the cutoff frequency of the tmtf increases as the upper spectral edge is increased up to 4 8 khz at low levels and is constant at higher levels sensitivity increases with bandwidth if frequency region is constant in a second experiment these results were compared to predictions of a model incorporating peripheral and central limitations to modulation detection to obtain an estimate of peripheral filtering frequency selectivity was measured using the notched noise method with probe frequencies and levels chosen to parallel those in the first experiment the tmtf data were then predicted using the model predicted cutoff frequencies as a function of the upper spectral edge of the test stimulus were lower than but parallel to those of the subjects at the lower stimulus level the model predicted only a slight increase in cutoff frequency with level and thus predicted an increase in cutoff frequency with frequency region at the higher level as well in contrast to the measured data these results suggest that there are peripheral and central limitations to temporal resolution but the psychoacoustically derived auditory filter may be only an indirect measure of peripheral filtering and or a more complex model may be needed

effects of spectral smearing and temporal fine structure degradation on speech masking release this study assessed the effects of spectral smearing and temporal fine structure tfs degradation on masking release mr the improvement in speech identification in amplitude modulated compared to steady noise observed for normal hearing listeners syllables and noise stimuli were processed using either a spectral smearing algorithm or a tone excited vocoder the two processing schemes simulated broadening of the auditory filters by factors of 2 and 4 simulations of the early stages of auditory processing showed that the two schemes produced comparable excitation patterns however fundamental frequency f0 information conveyed by tfs was degraded more severely by the vocoder than by the spectral smearing algorithm both schemes reduced mr but for each amount of spectral smearing the vocoder produced a greater reduction in mr than the spectral smearing algorithm consistent with the effects of each scheme on f0 representation moreover the effects of spectral smearing on mr produced by the two schemes were different for manner and voicing finally mr data for listeners with moderate hearing loss were well matched by mr data obtained for normal hearing listeners with vocoded stimuli suggesting that impaired frequency selectivity alone may not be sufficient to account for the reduced mr observed for hearing impaired listeners