global stability analysis of a compressible turbulent flow around a high lift configuration the stability of flow over a complex high lift configuration with significant regions of separated flow is analyzed current state of the art flow solvers encounter difficulties in predicting both the onset of flow separation over similar configurations and the progression of the separated region when the angle of attack is increased the present analysis provides useful insights into the mechanisms responsible for limiting the maximum lift on multielement wing configurations by relating flow separation with the onset of flow instability a steady solution based on a finite volume discretization is used as the basic state for the linear stability analysis the resulting generalized eigenvalue problem has been solved using a krylov subspace projection technique in the form of the arnoldi iterative method this methodology is first applied to a naca0012 test case at subsonic and transonic conditions then for the first time the stability of flow over an industrial multicomponent geometry involving the a31

existence of positive solutions for a system of generalized lidstone problems in this paper we study the existence of positive solutions for the system of generalized lidstone problems for ordinary differential equations 1 mu 2 m f 1 t u u 1 m 1u 2 m 2 v v 1 n 1v 2 n 2 1 nv 2 n f 2 t u u 1 m 1u 2 m 2 v v 1 n 1v 2 n 2 a 0u 2 i 0 b 0u 2 i 1 0 a 1u 2 i 1 b 1u 2 i 1 1 0 i 0 1 m 1 a 0v 2 j 0 b 0v 2 j 1 0 a 1v 2 j 1 b 1v 2 j 1 1 0 j 0 1 n 1 here f 1 f 2 c 0 1 xr m n r r 0 our hypotheses imposed on the nonlinearities f 1 and f 2 are formulated in terms of nonnegative matrices we use fixed point index theory to establish our main results based on a priori estimates of positive solutions

asymmetric temporal envelope encoding implications for within and across ear envelope comparison separating sound sources in acoustic environments relies on making ongoing highly accurate spectro temporal comparisons however listeners with hearing impairment may have varying quality of temporal encoding within or across ears which may limit the listeners ability to make spectro temporal comparisons between places of stimulation in this study in normal hearing listeners depth of amplitude modulation am for sinusoidally amplitude modulated sam tones was manipulated in an effort to reduce the coding of periodicity in the auditory nerve the ability to judge differences in am rates was studied for stimuli presented to different cochlear places of stimulation within or across ears it was hypothesized that if temporal encoding was poorer for one tone in a pair then sensitivity to differences in am rate of the pair would decrease results indicated that when the depth of am was reduced from 50 to 20 for one sam tone in a pair sensitivity to differences in am rate decreased sensitivity was greatest for am rates near 90 hz and depended upon the places of stimulation being compared these results suggest that degraded temporal representations in the auditory nerve for one place of stimulation could lead to deficits comparing that temporal information with other places of stimulation separating sound sources in acoustic environments relies on making ongoing highly accurate spectro temporal comparisons however listeners with hearing impairment may have varying quality of temporal encoding within or across ears which may limit the listeners ability to make spectro temporal comparisons between places of stimulation in this study in normal hearing listeners depth of amplitude modulation am for sinusoidally amplitude modulated sam tones was manipulated in an effort to reduce the coding of periodicity in the auditory nerve the ability to judge differences in am rates was studied for stimuli presented to different cochlear places of stimulation within or across ears it was hypothesized that if temporal encoding was poorer for one tone in a pair then sensitivity to differences in am rate of the pair would decrease results indicated that when the depth of am was reduced from 50 to 20 for one sam tone in a pair sensitivity to differences in am rate decreased sensitivity was

adjustment and discrimination measurements of the precedence effect a simple model to summarize the precedence effect is proposed that uses a single metric to quantify the relative dominance of the initial interaural delay over the trailing interaural delay in lateralization this model is described and then used to relate new measurements of the precedence effect made with adjustment and discrimination paradigms in the adjustment task subjects matched the lateral position of an acoustic pointer to the position of a composite test stimulus made up of initial and trailing binaural noise bursts in the discrimination procedure subjects discriminated interaural time differences in a target noise burst in the presence of another burst either trailing or preceding the target experimental parameters were the delay between initial and trailing stimuli and the overall level of the stimulus the model parameters the metric c and the variability of lateral position judgments were estimated from the results of the matching experiment and used to predict results of the discrimination task with good success finally the observed values of the metric were compared to values derived from previous studies

auditory spatial resolution in horizontal vertical and diagonal planes minimum audible angle maa and minimum audible movement angle mama thresholds were measured for stimuli in horizontal vertical and diagonal 60 degrees planes a pseudovirtual technique was employed in which signals were recorded through kemar s ears and played back to subjects through insert earphones thresholds were obtained for wideband high pass and low pass noises only 6 of 20 subjects obtained wideband vertical plane maas less than 10 degrees and only these 6 subjects were retained for the complete study for all three filter conditions thresholds were lowest in the horizontal plane slightly but significantly higher in the diagonal plane and highest for the vertical plane these results were similar in magnitude and pattern to those reported by perrott and saberi j acoust soc am 87 1728 1731 1990 and saberi and perrott j acoust soc am 88 2639 2644 1990 except that these investigators generally found that thresholds for diagonal planes were as good as those for the horizontal plane the present results are consistent with the hypothesis that diagonal plane performance is based on independent contributions from a horizontal plane system sensitive to interaural differences and a vertical plane system sensitive to pinna based spectral changes measurements of the stimuli recorded through kemar indicated that sources presented from diagonal planes can produce larger interaural level differences ilds in certain frequency regions than would be expected based on the horizontal projection of the trajectory such frequency specific ild cues may underlie the very good performance reported in previous studies for diagonal spatial resolution subjects in the present study could apparently not take advantage of these cues in the diagonal plane condition possibly because they did not externalize the images to their appropriate positions in space or possibly because of the absence of a patterned visual field

singular nonlinear boundary value problems for second order ordinary differential equations abstract the boundary value problem y f x y 0 y 0 y 0 0 y 1 y 1 0 is studied under conditions which are modeled on the problem y a x y p 0y 0 y 1 0 or y 0 y 1 0 which occurs in a number of applications the technical arguments involve properties of solutions i e concavity and the use of iterative techniques a new fixed point theorem for cones for decreasing mappings is proved and used it is of interest in its own right since most such theorems are for monotone increasing mappings

travelling waves for reaction diffusion equations with time depending nonlinearities abstract the existence of travelling wave with given end points for parabolic system of nonlinear equations is proven the nonlinear term depends also on a x ct where x is the multidimensional space variable t time c the speed of the wave and a the direction of travel

two point higher order bvps with singularities in phase variables the existence of solutions for singular higher order differential equations with the lidstone or the n p boundary conditions is proved the right hand sides of differential equations can have singularities in the zero value of their phase variables and so higher derivatives of solutions changing their signs can pass through these singularities proofs are based on the method of a priori estimates the degree theory arguments and on vitali s convergence theorem

existence result for the lidstone boundary value problem at resonance abstract in this paper we consider the existence problem to some type of the lidstone boundary value problem at resonance with discontinuity of the caratheodory type we prove that a solution exists if the conditions similar to the landesman lazer ones are satisfied

finite element methods for viscous incompressible biglobal instability analysis on unstructured meshes viscous linear 3 d biglobal instability analyses of incompressible flows have been performed using finite element numerical methods with a view to extend the scope of application of this analysis methodology to flows over complex geometries the initial value problem ivp based on the linearized navier stokes equations lnse as well as the real and the complex partial differential equation based generalized eigenvalue problems evp have been solved a mixed p 2 p 1 finite element spatial discretization on unstructured meshes for both the lnse and the evp approaches has been used for the time discretization of the lnse a characteristics method has been used for the first time in the context of flow stability analysis the complex biglobal evp has also been solved for the first time in the context of a finite element numerical discretization in either its real or its complex form the evp has been solved without the need to introduce pseudocompressibility into the incompressible equations which has simplified the systems to be solved without sacrificing accuracy an arnoldi approach has been used to recover the most significant eigenvalues in this context the associated solutions to the resulting linear systems were obtained by iterative methods generalized minimal residual with incomplete lower upper preconditioning or conjugate gradient with i cholesky preconditioning depending on whether the coefficient matrix was symmetric or not the 3 d instability of the classic 2 d lid driven cavity flow and that of the rectangular duct flow were used as validation cases for the real and complex evp respectively new results have been obtained for the 3 d biglobal instability of two closed and one open flow namely the regularized lid driven cavity of rectangular and triangular shape and flow in the wake of a model bluff body

singular boundary value problems for superlinear second order ordinary and delay differential equations abstract existence criteria are established for singular boundary value problems for nonlinear second order ordinary and delay differential equations the theorems obtained are very general and complement previous known results

a new continuation method for the study of nonlinear equations at resonance abstract a new continuation theorem for the existence of solutions to an equation lu n u where n is a nonlinear continuous operator and l a linear fredholm noninvertible one is proved the continuation which makes n collapse is replaced by a deformation of l to an invertible linear operator this implies results concerning sublinear n n having a linear growth at infinity and superlinear n these generalize the classical theorems on the solvability of semilinear elliptic bvp s at resonance the periodic solutions of lienard equations are studied

intensity perception xiii perceptual anchor model of context coding in our preliminary theory of intensity resolution e g see n i durlach and l d braida j acoust soc am 46 372 383 1969 two modes of memory operation are postulated the trace mode and the context coding mode in this paper we present a revised model of the context coding mode which describes explicitly a process by which sensations are coded relative to the context and which predicts a resolution edge effect l d braida and n i durlach j acoust soc am 51 483 502 1972 j e berliner l d braida and n i durlach j acoust soc am 61 1256 1267 1977 the sensation arising from a given stimulus presentation is coded by determining its distance from internal references or perceptual anchors the noise in this process combined with the sensation noise constitutes the limitation on resolution in the model in the revised model the probability density functions of the decision variable are not precisely gaussian and cannot be expressed analytically in closed form this p

lidstone polynomials and boundary value problems abstract we define lidstone polynomials provide their explicit representations give their relations with bernoulli polynomials obtain best possible error estimates in lidstone interpolation and establish several best possible sharp inequalities which compare favourably with the known results next we use these results to study even order differential equations together with lidstone boundary conditions

on solvability of boundary value problems for higher order nonlinear hyperbolic equations abstract in the rectangle 0 a 0 b for the nonlinear hyperbolic equation u m n i 0 m 1 h 1 i x u i n k 0 n 1 h 2 k y u m k f x y u u m 1 n 1 the boundary value problems of the type l 1 i u y 0 i 1 m l 2 k u x 0 k 1 n are considered where l 1 i c m 1 0 a r i 1 m and l 2 k c n 1 0 b r k 1 n are linear bounded functionals sufficient conditions of solvability and unique solvability of the general problem and its particular cases nicoletti type dirichlet lidstone and periodic problems are established

time dependent algorithms for the simulation of viscoelastic flows with spectral element methods applications and stability this paper presents the development of spectral element methods to simulate unsteady flows of viscoelastic fluids using a closed form differential constitutive equation the generation and decay poiseuille planar flows are considered as benchmark problems to test the abilities of our computational method to deal with truly time dependent flows satisfactory results converging toward steady state regimes have been obtained for the flow through a four to one planar abrupt contraction with unsteady algorithms time dependent simulations of viscoelastic flows are prone to numerical instabilities even for simple geometrical configurations possible methods to improve the numerical stability of the computational algorithms are discussed in view of the results carried out with numerical simulations for the flows through a straight channel and the four to one contraction

one dimensional finite element method in hydrodynamic stability the stability of plane poiseuille flow and circular couette flow are examined with respect to linear azimuthally periodic disturbances by the finite element method in the case of couette motion solutions are obtained for a narrow gap a wide gap and a dilute polymer solution with an elongational viscosity in the narrow gap limit when both cylinders rotate at almost equal speed in the same direction results are in good agreement with previous calculations by other numerical methods

positive solutions of fourth order boundary value problems with two parameters abstract in this paper the existence results of positive solutions are obtained for fourth order boundary value problem u 4 u u f t u 0 where f 0 1 r r is continuous r and satisfy

minimum audible angle thresholds obtained under conditions in which the precedence effect is assumed to operate two experiments were conducted to examine the ability of human listeners to localize the lag or echo source in a precedence effect paradigm a 5 ms noise burst was presented from a source located between 554 279 cm from the subject this lead source was always located at 0 azimuth at the same time one of two sources located at a distance of 610 cm from the subject was also activated with the same 5 ms noise burst the subject s task was to identify which lag source had been active across sessions the angular distance between the lag sources was varied so as to allow a determination of the minimum audible angle maa that could be resolved tests were run in a room designed to minimize reflections and in a hallway that was acoustically quite complex no systematic differences in maa thresholds were observed as a function of the environment employed maa thresholds obtained without the signal from the lead speaker were less than 1 for four of the five subjects tested the precedence effec

sound localization precision under conditions of the precedence effect effects of azimuth and standard stimuli minimum audible angles maas were estimated for single noise bursts and for burst pairs that satisfied the conditions of the precedence effect that is produced fused images in one burst pair condition the bursts to be discriminated differed in lead location in the other they differed in lag location sounds were presented over loudspeakers maas were lowest for single bursts slightly higher for lead discrimination and much higher for lag discrimination presence of a standard reference burst had no reliable effect on performance the data are interpreted using a model of shinn cunningham et al j acoust soc am 93 2923 2932 1993 in which discrimination of precedence effect burst pairs is based on the lateral position of the auditory image which is a weighted average of the positions of the leading and lagging bursts

some new results for singular problems with sign changing nonlinearities we present some general existence theorems for second order boundary value problems with sign changing nonlinearities both the upper and lower solution approach and the growth restriction approach are discussed

eigenmodes of a counter rotating vortex dipole highly resolved solutions of the two dimensional incompressible navier stokes and continuity equations describing the evolution of a counter rotating pair of vortices have been obtained accurately and efficiently by spectral collocation methods and an eigenvalue decomposition algorithm such solutions have formed the basic state for subsequent three dimensional biglobal eigenvalue problem linear instability analyses which monitor the modal response of these vortical systems to small amplitude perturbations periodic along the homogeneous axial spatial direction without the need to invoke an assumption of azimuthal spatial homogeneity a finite element methodology gonzalez l m theofilis v and gomez blanco r finite element numerical methods for viscous incompressible biglobal linear instability analysis on unstructured meshes aiaa journal vol 45 no 4 2007 pp 840 855 has been adapted to study the instability of vortical flows and has been validated on the batchelor vortex mayer e w and powell k g viscous and inviscid instabilities of a trailing vortex journal of fluid mechanics vol 245 1992 pp 91 114 subsequently the instability of the counter rotating dipole has been analyzed aspects monitored have been the dependence of the results on the reynolds number the value of the nonzero axial velocity considered and the time at which the quasi steady basic flow has been monitored essential to the success of the analysis has been the appropriate design of a calculation mesh as well as exploitation of the symmetries of the basic state the spatial structure of the amplitude functions of all unstable eigenmodes reflects the inhomogeneity of the basic state in the azimuthal spatial direction thus providing a posteriori justification for the use of the biglobal eigenvalue problem concept

localization dominance in the median sagittal plane effect of stimulus duration localization dominance is an aspect of the precedence effect pe in which the leading source dominates the perceived location of a simulated echo lagging source it is known to be robust in the horizontal azimuthal dimension where binaural cues dominate localization however little is known about localization dominance in conditions that minimize binaural cues and most models of precedence treat the phenomena as belonging to the binaural system here localization dominance in the median sagittal plane was studied where binaural cues are greatly reduced and monaural spectral level cues are thought to be the primary cues used for localization lead lag pairs of noise bursts were presented from locations spaced in 15 increments in the frontal median sagittal plane with a 2 ms delay in their onsets for source durations of 1 10 25 and 50 ms intermixed with these trials were single speaker trials in which lead and lag were summed and presented from one speaker listeners identified the speaker that was nearest to the perceived source location with single speaker stimuli localization improves as signal duration is increased furthermore evidence of elevation compression was found with a dependence on duration with lead lag pairs localization dominance occurs in the median plane and becomes more robust with increased signal duration these results suggest that accurate localization of a co located lead lag pair is necessary for localization dominance to occur when the lag is spatially separated from the lead

a direct method for computation of simple bifurcations in the present study we focus on the computational analysis of partial differential equations with emphasis on the stability of the equilibrium states and on their bifurcations in practical applications it is not sufficient to obtain an equilibrium solution at a point in the parameter space the equilibrium solution branches their stability characteristics and particularly the critical points of transition from one state to another e g bifurcation points are required for understanding the physics of the problem in principle the linear stability of an equilibrium state can be investigated by solving an eigenvalue problem and consequently the points of bifurcations can be detected we review alternative techniques for detecting bifurcation points which are direct and numerically efficient and therefore more practical starting with a large dimension dynamical system which represents a projection of a set of coupled partial differential equations onto a basis function we discuss the relative effectiveness of the time evolution approach the test function approach and the direct method we will then extend the direct method for a more practical and efficient implementation with this technique we compute the sequence of transitions from steady state to chaotic flow in a two dimensional lid driven cavity of aspect ratio 0 8 1 0 and 1 5 we demonstrate the effectiveness of this technique by computing interesting new dynamics in this relatively simple hydrodynamic system in particular we show that depending on the aspect ratio the first transition from steady state could be through a supercritical or a subcritical hopf bifurcation leading the system to a time periodic state we construct the destabilizing disturbance structure and conclude that the first bifurcation of the primary steady state is due to the centrifugal instability of the primary eddy the mechanism of transition to chaos is low dimensional the transition to chaos occurs after a secondary hopf bifurcation

the influence of broadband noise on the precedence effect this study examined the influence of background noise on the localization of lead lag noise burst pairs and on echo threshold for the same stimuli experiments were conducted in an anechoic chamber with a leading stimulus delivered from a loudspeaker at 45 degrees to the right of center and a lagging stimulus from 45 degrees left lead and lag stimuli were 4 ms bursts of gaussian noise in experiment 1 with lead and lag at equal levels and the lag delay fixed at 2 ms the perceived location of the image produced by the lead lag stimulus was estimated from subjects left right judgments relative to bursts from a comparitor loudspeaker whose position could be adjusted in experiment 2 the dominance of the leading burst on perceived location was measured by determining the increase in level of the lagging burst necessary to produce an image estimated to be centered at 0 degree azimuth experiment 3 was concerned with echo threshold subjects reported whether or not they heard a sound in the vicinity of the lagging loudspeaker as the lag burst delay was varied in all three experiments data were obtained for four to five stimulus levels in quiet and for three levels of background white noise from a loudspeaker at 180 degrees the results revealed a substantial weakening effect of background noise on the precedence effect in experiments 2 and 3 and a nonsignificant effect in experiment 1

intensity discrimination for precedence effect stimuli when two identical stimuli are presented from two loudspeakers with a brief delay between them a single image is heard near the source of the leading sound the delayed sound or echo appears to be suppressed whereas the preceding sound determines perceived location hence the name the precedence effect this study investigated normal hearing listeners sensitivity to changes in the intensity of the lagging sound pairs of 2 ms white noise bursts with a 2 ms delay between the onsets of lead and lag were presented from two loudspeakers 45 left and right of midline in an anechoic chamber a 2afc procedure was used to test discrimination of intensity changes in the lead lag and both sounds together the untreated results showed discrimination to be poorest for changes in the lag stimulus however when the intensity differences were transformed into predictions of equivalent monaural level based on kemar measurements and binaural loudness summation discrimination for the lag was equal to the other two

three dimensional solutions of trailing vortex flows using parabolized equations flows of practical significance exist like systems of trailing vortices which are inhomogeneous in two directions and weakly dependent along the third spatial direction exploiting these characteristics an integration of the navier stokes equations using the parabolic navier stokes concept is proposed for the recovery of steady solutions that might be used subsequently in the scope of primary instability analyses the parabolic navier stokes equations are first formulated in a cylindrical coordinate frame and used to calculate the solution of an isolated axisymmetric nonparallel axially developing vortex then the fully three dimensional flow corresponding to a counter rotating pair of nonparallel vortices is obtained by parabolic navier stokes formulated in cartesian coordinates stable high order finite difference based numerical schemes are used for the spatial discretization to exploit the benefits of using a sparse direct solver for the inversion of the large matrices resulting from the discre

singular lidstone boundary value problem with given maximal values for solutions abstract the singular problem 1 nx 2n f t x x 2n 2 x 2j 0 x 2j t 0 0 j n 1 max x t 0 t t a depending on the parameter is considered here the positive caratheodory function f may be singular at the zero value of all its phase variables the paper presents conditions which guarantee that for any a 0 there exists a 0 such that the above problem with a has a solution x ac2n 1 0 t which is positive on 0 t the proofs are based on the regularization and sequential techniques and use the leray schauder degree and vitali s convergence theorem

linear stability of incompressible flow using a mixed finite element method we analyzed the linear stability for incompressible flow using the mixed finite element method first by means of the fractional step finite element method the two dimensional base flows were numerically computed over a range of reynolds numbers and then they were perturbed with three dimensional disturbances by using linear stability and normal mode analysis we obtained the partial differential equations governing the evolution of perturbation from linearized navier stokes equations with slight compressibility in terms of the mixed finite element discretization in which six node quadratic lagrange triangular elements with quadratic interpolation for velocities p2 and three node linear lagrange triangular elements for pressure p1 were used a nonsingular generalized eigenproblem was formulated from these equations whose solution gives the dispersion relationship between the complex growth rate and the wave number we examined the stability of lid driven cavity flow in this study the stability results obtained from thep2p1elements were compared with those fromp1p1elements the spatial distribution of the pressure disturbance can be smoothed by using ap2p1element such as that in the simulation of incompressible flows by the mixed finite element method however the choice of elemental type has little influence on the stability results this study presents stability curves to identify the critical reynolds number and the critical wavelength of the neutral mode and discusses the instability mechanism the taylor goertler like vortices in the cavity were obtained by means of the reconstruction of three dimensional flows the stability results and the reconstructed three dimensional flows were in agreement with the observed ones and the other numerical stability results respectively

eigenvalues of lidstone boundary value problems we consider the following boundary value problem 1 ny 2 n lf t y n 1 t 0 1 y 2 i 0 y 2 i 1 0 0 0 the values of l are characterized so that the boundary value problem has a positive solution in addition we derive explicit intervals of l such that for any l in the interval existence of a positive solution of the boundary value problem is guaranteed several examples are also included to dwell upon the importance of the results obtained

existence multiplicity and dependence on a parameter for a periodic boundary value problem the authors consider the boundary value problem y 2 y g t f y 0 0 t 2 y 0 y 2 y 0 y 2

developmental changes in the precedence effect estimates of minimum audible angle the precedence effect refers to an auditory phenomenon which occurs when two similar sounds are presented from different locations with a brief delay and only one sound is heard whose perceived location is dominated by the first source although the lagging source is not localized as an independent event under some conditions adults are able to extract its directional cues developmental studies suggest that this ability changes during development however those studies have used stimulus configurations which minimize the measurement of that ability in the present study adults were first tested under several conditions and the one which produced optimal performance was chosen for testing children using the minimum audible angle maa task in the azimuthal plane performance was compared for a single source condition and two precedence conditions in lag discrimination the lagging source changed location while the lead remained at midline and in lead discrimination the reverse occurred subjects were 18 months old 5 years old and adult significant improvements in maa occurred with an increase in age especially in the precedence conditions within each group performance was significantly better in single source condition followed by the lead and the lag discrimination

order 104 speedup in global linear instability analysis using matrix formation abstract a unified solution framework is presented for one two or three dimensional complex non symmetric eigenvalue problems respectively governing linear modal instability of incompressible fluid flows in rectangular domains having two one or no homogeneous spatial directions the solution algorithm is based on subspace iteration in which the spatial discretization matrix is formed stored and inverted serially results delivered by spectral collocation based on the chebyshev gauss lobatto cgl points and a suite of high order finite difference methods comprising the previously employed for this type of work dispersion relation preserving drp and pade finite difference schemes as well as the summation by parts sbp and the new high order finite difference scheme of order q fd q have been compared from the point of view of accuracy and efficiency in standard validation cases of temporal local and biglobal linear instability the fd q method has been found to significantly outperform all other finite difference schemes in solving classic linear local biglobal and triglobal eigenvalue problems as regards both memory and cpu time requirements results shown in the present study disprove the paradigm that spectral methods are superior to finite difference methods in terms of computational cost at equal accuracy fd q spatial discretization delivering a speedup of o 10 4 consequently accurate solutions of the three dimensional triglobal eigenvalue problems may be solved on typical desktop computers with modest computational effort

multiple solutions of some nonlinear fourth order beam equations abstract several new existence theorems on three solutions and infinitely many solutions for the following fourth order beam equation are obtained u 4 f t u t t 0 1 u 0 u 1 u 0 u 1 0 where f c 1 0 1 r 1 r 1 the morse theory is employed to discuss this problem

dynamic processes in the precedence effect three experiments were conducted to investigate the dependence of echo suppression on the auditory stimulation just prior to a test stimulus subjects sat in an anechoic chamber between two loudspeakers one which presented the lead sound and the other the delayed lag sound in the first experiment subjects reported whether or not they heard an echo coming from the vicinity of the lag loudspeaker during a test click pair in seven of nine listeners perception of the lagging sound was strongly diminished by the presence of a train of conditioning clicks presented just before the test click echo threshold increased subjects were less sensitive to echoes as the number of clicks in the train increased from 3 to 17 for a fixed number of clicks the effect was essentially independent of click rate from 1 s through 50 s and duration of the train from 0 5 through 8 s a second experiment demonstrated a similar buildup of echo suppression with white noise bursts regardless of whether the bursts in the conditioning train were repeated samples of frozen noise or were independent samples of noise using an objective procedure for measuring echo threshold the third experiment demonstrated that both lead and lag stimuli must be presented during the conditioning train in order to produce the buildup of suppression when only the lead sound was presented during the conditioning train the perceptibility of the lag sound during the test burst appeared to be enhanced

existence and uniqueness of positive solutions for a higher order boundary value problem the goal of this paper is to study the existence and uniqueness of positive solutions for the 2nth order boundary value problem 1 nu 2 n f t u u 1 n 1u 2 n 2 a 0u 2 i 0 email protected 0u 2 i 1 0 0 i 0 1 n 1 a 1u 2 i 1 email protected 1u 2 i 1 1 0 i 0 1 n 1 the krein rutman theorem and the krasnoselskii zabreiko fixed point theorem are the main tools that have been used to develop our work

steady viscous flow in a triangular cavity by efficient numerical techniques abstract accurate and efficient calculations of the flow inside a triangular cavity are presented for high reynolds numbers the navier stokes equations expressed in a stream function and vorticity formulation are solved numerically using finite differences on a transformed geometry second order numerical boundary conditions are derived and newton s iteration is employed to solve the nonlinear system resulting from the finite difference discretization aside from solving the equilateral triangular cavity problem we have also been able to compute numerical solutions for scalene triangular cavity problems our coarse mesh results for the equilateral triangular cavity problem are compared with finer mesh results in the literature and the agreement is good

minimum audible angle for clicks with simulated echoes effects of azimuth and standard minimum audible angle maa was measured in free field with a center position at 0 and 25 or 50 on the right stimuli were 6 ms wide band noise bursts presented as single bursts or noise pairs under precedence effect conditions in the single noise condition one burst was presented from the right or left in precedence lead discrimination a leading sound was presented from the left or right speaker and a lagging sound from a speaker at center in precedence lag discrimination the lagging sound was on the right or left and the leading sound was at center the test stimulus was either presented in isolation or was preceded by a single standard noise at center maas were lowest for the single condition slightly higher for lead discrimination and much higher for lag discrimination presence of a standard yielded a benefit in lag discrimination especially at 0 thresholds at 50 were significantly higher than at 0 and 25 especially in lag discrimination the data can be described by a model in wh

symmetric positive solutions of nonlinear boundary value problems abstract we study the nonlinear boundary value problem u 2 m f t u u u 2 m 2 t 0 1 u 2 i 0 u 2 i 1 0 i 0 m 1 the existence of symmetric positive solutions of the above problem is discussed sufficient conditions are obtained for the problem to have one any finite number and a countably infinite number of such solutions our results extend some recent work in the literature on boundary value problems of ordinary differential equations we illustrate our results by two examples none of which can be handled using the existing results

different modes of rayleigh benard instability in two and three dimensional rectangular enclosures the article describes a complete numerical solution of a recently formulated benchmark problem devoted to the parametric study of rayleigh benard instability in rectangular two and three dimensional boxes the solution is carried out by the spectral galerkin method with globally defined three dimensional divergent free basis functions which satisfy all boundary conditions the general description of these three dimensional basis functions which can be used for a rather wide spectrum of problems is presented the results of the parametric calculations are presented as neutral curves showing the dependence of the critical rayleigh number on the aspect ratio of the cavity the neutral curves consist of several continuous branches which belong to different modes of the most dangerous perturbation the patterns of different perturbations are also reported the results obtained lead to some new conclusions about the patterns of the most dangerous perturbations and about the similarities between two and three dimensional models some extensions of the considered benchmark problem are discussed

on a generalization of the miranda theorem and its application to boundary value problems abstract in this paper we have proved a multi valued version of the miranda theorem involving an admissible map in the sense of gorniewicz examples of its application to boundary value problems have been given

positive solutions of singular dirichlet and periodic boundary value problems let a and t be positive numbers the singular differential equation r x x q t f t x is considered here r 0 on 0 a may be singular at x 0 and f t x 0 may be singular at x 0 and x a effective sufficient conditions imposed on r q and f are given for the existence of a solution x to the above equation satisfying either the dirichlet conditions x 0 x t 0 or the periodic conditions x 0 x t x 0 x t and in addition 0 x a on 0 t

positive solutions of a 2nth order boundary value problem involving all derivatives via the order reduction method this paper is mainly concerned with the existence multiplicity and uniqueness of positive solutions for the 2nth order boundary value problem 1 nu 2 n f t u u 1 i 2 u i 1 n 1u 2 n 1 u 2 i 0 u 2 i 1 1 0 i 0 1 n 1 where n 2 and f c 0 1 xr 2 n r r 0 we first use the method of order reduction to transform the above problem into an equivalent initial value problem for a first order integro differential equation and then use the fixed point index theory to prove the existence multiplicity and uniqueness of positive solutions for the resulting problem based on a priori estimates achieved by developing spectral properties of associated parameterized linear integral operators finally as a byproduct our main results are applied for establishing the existence multiplicity and uniqueness of symmetric positive solutions for the lidstone problem involving all derivatives