oscillation criteria for nonlinear damped dynamic equations on time scales abstract we present new oscillation criteria for the second order nonlinear damped delay dynamic equation r t x t p t x t q t f x t 0 our results generalize and improve some known results for oscillation of second order nonlinear delay dynamic equation our results are illustrated with examples

the oscillation and asymptotically monotone solutions of second order quasilinear differential equations abstract we offer sufficient conditions for the oscillation of all solutions of the perturbed quasilinear differential equation a t y 1 y q t y p t y y as well as for the existence of a positive monotone solution of the damped differential equation a t y 1 y b t y 1 y h t y 0 where 0 examples that dwell upon the importance of our results are also included

existence of uncountably many bounded nonoscillatory solutions and their iterative approximations for second order nonlinear neutral delay difference equations in this paper the banach fixed point theorem is employed to establish several existence results of uncountably many bounded nonoscillatory solutions for the second order nonlinear neutral delay difference email protected n dx n b n x email protected email protected n x h 1 n x h 2 n x h k n f n x f 1 n x f 2 n x f k n c n n n 0 where t email protected n n email protected n 0 a b c n n 0 r with a n 0 for email protected n n 0 h f n n 0xr k r and h l f l n n 0 z withlimn h l n limn f l n email protected 1 2 k a few mann type iterative approximation schemes with errors are suggested and the errors estimates between the iterative approximations and the nonoscillatory solutions are discussed seven nontrivial examples are given to illustrate the advantages of our results

refinable bounds for large markov chains a method to bound the steady state solution of large markov chains is presented it integrates the concepts of eigen vector polyhedron and of aggregation and is iterative in nature the bounds are obtained by considering a subset only of the system state space this makes the method specially attractive for problems which are too large to be dealt with by traditional methods the quality of the bounds depends on the locality of the system which is studied when the system spends most of its time in a small subset of states tight bounds can be obtained by considering this subset only finally the bounds are refinable in the sense that the tightness of the bounds can be improved by enlarging the subset of states which is considered the method is illustrated on a model of a repairable fault tolerant system with 16 million states tight bounds on its availability are obtained by considering less than 0 1 percent of its state space

on polyhedra of perron frobenius eigenvectors abstract this paper deals with the positive eigenvectors of nonnegative irreducible matrices which are merely characterized by a given upper bound u on their spectral radius and by a given matrix l of lower bounds for their elements for any such matrix the normalized positive left right eigenvector is shown to belong to the polyhedron the vertices of which are given by the normalized rows columns of the matrix u i l 1 this polyhedron is proven to be also the smallest closed set which is guaranteed to contain the positive left right normalized eigenvector its vertices are therefore the best componentwise bounds one can obtain on the positive eigenvectors of these matrices a less general result has also been obtained for the symmetrical case when the matrices are only characterized by a given lower bound l on their spectral radius and by a given matrix u of upper bounds for their elements

oscillation theorems for higher order nonlinear delay difference equations abstract some new oscillation results for difference equations of the form 1 1 and forced difference equations of the form 1 2 are established the results obtained are discrete analogues of some known results for delay differential equations

relative contributions of specific frequency bands to the loudness of broadband sounds listeners with normal hearing nh and sensorineural hearing loss snhl were asked to compare pairs of noise stimuli and choose the louder noise in each pair each noise was made up of 15 two erbn equivalent rectangular bandwidth wide frequency bands that varied independently over a 12 db range from one presentation to the next mean levels of the bands followed the long term average speech spectrum ltass or were set to 43 51 or 59 db sound pressure level spl the relative contribution of each band to the total loudness of the noise was determined by computing the correlation between the difference in levels for a given band on every trial and the listener s decision on that trial weights for snhl listeners were governed by audibility and the spectrum of the noise stimuli with bands near the spectral peak of the ltass noise receiving greatest weight nh listeners assigned greater weight to the lowest and highest bands an effect that increased with overall level but did not assign greater weight to bands near the ltass peak additional loudness matching and paired comparison studies using stimuli missing one of the 15 bands showed a significant contribution by the highest band but properties other than loudness may have contributed to the decisions

spectral shape discrimination by hearing impaired and normal hearing listeners the ability to discriminate between sounds with different spectral shapes was evaluated for normal hearing and hearing impaired listeners listeners discriminated between a standard stimulus and a signal stimulus in which half of the standard components were decreased in level and half were increased in level in one condition the standard stimulus was the sum of six equal amplitude tones equal spl and in another the standard stimulus was the sum of six tones at equal sensation levels re audiometric thresholds for individual subjects equal sl spectral weights were estimated in conditions where the amplitudes of the individual tones were perturbed slightly on every presentation sensitivity was similar in all conditions for normal hearing and hearing impaired listeners the presence of perturbation and equal sl components increased thresholds for both groups but only small differences in weighting strategy were measured between the groups depending on whether the equal spl or equal sl condition was tested the average data suggest that normal hearing listeners may rely more on the central components of the spectrum whereas hearing impaired listeners may have been more likely to use the edges however individual weighting functions were quite variable especially for the hi listeners perhaps reflecting difficulty in processing changes in spectral shape due to hearing loss differences in weighting strategy without changes in sensitivity suggest that factors other than spectral weights such as internal noise or difficulty encoding a reference stimulus also may dominate performance

oscillation and asymptotic behavior of second order difference equations abstract the oscillation of the second order difference equation c n y n p n y v n 1 0 n 0 1 2 1 1 is investigated where yn yn 1 yn v is a quotient of odd positive integers some necessary and sufficient conditions for oscillation of 1 1 with v 1 and v

periodic solutions for nonlinear second order difference equations abstract this paper is devoted to introduce a new approach to investigate the existence of periodic solutions for nonlinear difference equations transforming a second order nonlinear difference equation on a finite discrete segment with periodic boundary conditions into a continuous system we obtain the existence conditions of periodic solutions of the equation the proof relies on coincidence degree theory and matrix theory without using green s function

informational processing of complex sound normal hearing listeners discriminated among complex nonspeech sounds in which the difference to be discriminated was randomly varied from trial to trial all other physical parameters of the sounds were fixed within a block of trials on each trial the listener heard two sounds e g tone complexes the values of the variable parameter e g tone frequencies were drawn from two normal distributions differing only in mean the listener s task was to identify the sound having the higher mean value of the variable parameter discrimination performance was found to be largely independent of the particular physical dimensions along which the sounds varied rather performance appeared to depend primarily on information content of the sounds information content was defined in terms of a stimulus equivocation factor that was derived from the data based on this model transmitted information was estimated to be between 1 0 3 0 bits work supported by afosr

variation in spectral shape discrimination weighting functions at different stimulus levels and signal strengths this study evaluated whether weights for spectral shape discrimination depend on overall stimulus level and signal strength the degree of spectral shape change between two stimuli five listeners discriminated between standard stimuli that were the sum of six equal amplitude tones and signal stimuli created by decreasing the amplitudes of three low frequency components and increasing the amplitudes of three high frequency components weighting functions were influenced by stimulus level in that the relative contribution of the low frequency decremented components to the high frequency incremented components decreased with increasing stimulus level although individual variability was present a follow up experiment suggested that the level dependence was due to greater reliance on high frequency components rather than incremented components excitation pattern analyses indicated that the level dependence is primarily but not solely driven by cochlear factors in general different signal strengths had no effect on the weighting functions when normalized but two of the five listeners showed variability in the shape of the weighting function across signal strengths results suggest that the effects of stimulus level on weighting functions and individual variability in the shapes of the weighting functions should be considered when comparing weighting functions across conditions and groups that might require different stimulus levels and signal strengths

measuring decision weights in recognition experiments with multiple response alternatives comparing the correlation and multinomial logistic regression methods psychophysical reverse correlation methods allow researchers to gain insight into the perceptual representations and decision weighting strategies of individual subjects in perceptual tasks although these methods have gained momentum until recently their development was limited to experiments involving only two response categories recently two approaches for estimating decision weights in m alternative experiments have been put forward one approach extends the two category correlation method to m 2 alternatives the second uses multinomial logistic regression mlr in this article the relative merits of the two methods are discussed and the issues of convergence and statistical efficiency of the methods are evaluated quantitatively using monte carlo simulations the results indicate that for a range of values of the number of trials the estimated weighting patterns are closer to their asymptotic values for the correlation method than for the mlr method moreover for the mlr method weight estimates for different stimulus components can exhibit strong correlations making the analysis and interpretation of measured weighting patterns less straightforward than for the correlation method these and other advantages of the correlation method which include computational simplicity and a close relationship to other well established psychophysical reverse correlation methods make it an attractive tool to uncover decision strategies in m alternative experiments

comparing markov chains aggregation and precedence relations applied to sets of states with applications to assemble to order systems solving markov chains is in general difficult if the state space of the chain is very large or infinite and lacking a simple repeating structure one alternative to solving such chains is to construct models that are simple to analyze and provide bounds for a reward function of interest we present a new bounding method for markov chains inspired by markov reward theory our method constructs bounds by redirecting selected sets of transitions facilitating an intuitive interpretation of the modifications of the original system we show that our method is compatible with strong aggregation of markov chains thus we can obtain bounds for an initial chain by analyzing a much smaller chain we illustrate our method by using it to prove monotonicity results and bounds for assemble to order systems

spectral weights for overall level discrimination in listeners with sensorineural hearing loss a conditional on a single stimulus coss analysis procedure b g berg j acoust soc am 86 1743 1746 1989 was used to measure the weight or relative reliance that normal hearing and hearing impaired listeners give to different frequencies in the discrimination of the overall level of a multitone complex on each trial two multitone tone complexes comprised of six octave frequencies from 250 to 8000 hz were presented to subjects the levels of the frequencies for each complex were randomly varied the listeners task was to identify the complex with the higher overall intensity level normal hearing listeners used a variety of listening strategies to perform the task showing no general preference to weight one component over another hearing impaired listeners however showed a general tendency to give greatest weight to the spectral information in the region of their hearing loss thirteen of the 14 hearing impaired listeners all of whom had a high frequency sensorineural hearing loss weighted one or more of the high frequency components in the complex the greatest

oscillation for nonlinear second order dynamic equations on a time scale abstract we obtain some oscillation criteria for solutions to the nonlinear dynamic equation x q t x p t f x 0 on time scales in particular no explicit sign assumptions are made with respect to the coefficients p t q t we illustrate the results by several examples including a superlinear emden fowler dynamic equation

the information divergence hypothesis of informational masking in recent years there has been growing interest in masking that cannot be attributed to interactions in the cochlea so called informational masking im similarity in the acoustic properties of target and masker and uncertainty regarding the masker are the two major factors identified with im these factors involve quite different manipulations of signals and are believed to entail fundamentally different processes resulting in im here however evidence is presented that these factors affect im through their mutual influence on a single factor the information divergence of target and masker given by simpson fitter s da lutfi et al 2012 j acoust soc am 132 el109 113 four experiments are described involving multitone pattern discrimination multi talker word recognition sound source identification and sound localization in each case standard manipulations of masker uncertainty and target masker similarity including the covariation of target masker frequencies are found to have the same effect on performance provided they produce the same change in da the function relating d performance to da moreover appears to be linear with constant slope across listeners the overriding dependence of im on da is taken to reflect a general principle of perception that exploits differences in the statistical structure of signals to separate figure from ground

observer efficiency and weights in a multiple observation task a sequence of seven tones sampled from one of two distributions differing in mean frequency is presented to observers who try to report which distribution was sampled estimates are obtained of the weight or importance given to each tone as a function of its temporal position in five experiments the reliability of the information is varied by changing the variance of the distributions tones with high reliability are sampled from distributions with relatively small variance whereas tones with low reliability are sampled from distributions with relatively large variance results show that the observations are weighted more efficiently when the tones have equal rather than unequal reliability and when the most reliable tones have the greater intensity additional results show that the most intense tones often receive the greatest weight even when those tones have the least reliability

informational processing of complex sound ii cross dimensional analysis a series of experiments investigated listeners ability simultaneously to process information across different acoustic dimensions on each trial the listener heard a pair of brief n tone sequences n 1 to 12 the frequency intensity and duration of each tone in the sequence varied randomly from trial to trial on average the values of these three parameters were greater for one sequence the target than the other the nontarget the listener s task was to identify the target on each trial for an ideal observer in this task d performance grows as the square root n obtained d grew at a rate slightly less than the square root of n close to cube root of n growth was observed when the average difference occurred in only one of the three tone parameter values within a block of trials although performance fell short of ideal optimum weights were consistently given to each tone and each parameter the results are consistent with a model in which performance depends predominantly on the information content of the sounds regardless of how the information is packaged in the stimulus transmitted information is estimated to be 0 9 2 0 bits within a single acoustic dimension 2 1 3 0 bits when distributed across dimensions

global solvability for a second order nonlinear neutral delay difference equation this paper studies the global existence of solutions of the second order nonlinear neutral delay difference equation d a email protected x n bx n t f n x n d 1 n x n d 2 n x n d k n c n n n 0 with respect to all email protected r a few results on global existence of uncountably many bounded nonoscillatory solutions are established for the above difference equation several nontrivial examples which dwell upon the importance of the results obtained in this paper are also included

oscillation criteria for second order nonlinear differential equations involving general means consider the second order nonlinear differential equation e y a t f y 0 where a t c 0 f y c1 f y 0 and yf y 0 for y 0 furthermore f y also satisfies either a superlinear or a sublinear condition which covers the nonlinear function f y y y 1 with 1 and 0 1 respectively commonly known as the emden fowler case here the coefficient function a t is allowed to be negative for arbitrarily large values of t kamenev type oscillation criteria involving integral averages for the linear equations l y a t y 0 are extended to the nonlinear equation e by using more general means the results extend similar results on general means by philos for the linear equation l and also results based upon kamenev s integral averaging method concerning the nonlinear equation e

intensity discrimination in the presence of random frequency multicomponent maskers and broadband noise this study examined the effects of multicomponent random frequency maskers and broadband noise maskers on intensity discrimination at 1000 hz maskers and signals were 200 ms presented simultaneously in the first set of conditions thresholds were measured for the detection of a 1000 hz tone in the presence of 40 or 60 db spl random frequency or noise maskers with extensive training of listeners with the random frequency masker to assure stable effects of masker frequency uncertainty the random frequency maskers had two six or ten components chosen at random from a large frequency range 300 3000 hz excluding a 160 hz band around 1000 hz for these maskers performance across the four listeners was very similar showing large effects of masker frequency uncertainty for noise maskers performance matched predictions for energy based masking in the second and third sets of conditions intensity discrimination was measured at 1000 hz for pedestals ranging from 40 to 80 db spl first in isolation and then in the presence of the maskers the pattern of results for intensity discrimination in quiet showed the expected near miss to weber s law but poorer performance than typically observed the addition of broadband noise maskers had little effect on performance however random frequency maskers degraded performance in nearly all conditions with the size of the effect dependent on the level of the pedestal relative to the masker considering the pedestal as a tonal masker the data were fitted with various models of combined masking a simple power law model provided excellent fits with exponents ranging from 0 24 to 0 35 for the multicomponent maskers but 1 0 linear for the noise the results support models positing that the effects of individual maskers undergo nonlinear transformation before they are added independent of the mechanisms which produce these effects because random frequency maskers presumably produce informational uncertainty based masking the nonlinearity in this case appears central rather than peripheral

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

asymptotic and oscillatory behavior of solutions of certain second order nonlinear difference equations mingshu peng department of applied mathematics beijing institute of technology beijing 100081 p r china qianli xu department of mathematics yiyang teachers college yiyang 413049 p r china lihong huang department of applied mathematics hunan university changsha 410082 p r china weigao ge

auditory discrimination of force of impact the auditory discrimination of force of impact was measured for three groups of listeners using sounds synthesized according to first order equations of motion for the homogenous isotropic bar morse and ingard 1968 theoretical acoustics pp 175 191 the three groups were professional percussionists nonmusicians and individuals recruited from the general population without regard to musical background in the two interval forced choice procedure listeners chose the sound corresponding to the greater force of impact as the length of the bar varied from one presentation to the next from the equations of motion a maximum likelihood test for the task was determined to be of the form log a log f 0 where a and f are the amplitude and frequency of any one partial and 0 5 relative decision weights on log f were obtained from the trial by trial responses of listeners and compared to percussionists generally outperformed the other groups however the obtained decision weights of all listeners deviated significantly from and showed variability within groups far in excess of the variability associated with replication providing correct feedback after each trial had little effect on the decision weights the variability in these measures was comparable to that seen in studies involving the auditory discrimination of other source attributes

spectral weights for sample discrimination as a function of overall level doherty and lutfi 1996 spectral weights for overall level discrimination in listeners with sensorineural hearing loss j acoust soc am 99 1053 1058 examined the weights assigned to individual components of a six tone complex during a sample discrimination task and reported that hearing impaired subjects gave the most weight to components in the region of their high frequency hearing loss in contrast weighting patterns varied for normal hearing subjects in the current study the same six tone complex comprised of the octave frequencies from 0 25 to 8 khz was presented to three subjects with normal hearing in high pass noise in low pass noise and in quiet at two overall levels consistent with doherty and lutfi subjects assigned more weight to the 4 khz component in the high pass noise condition but roughly equal weight to all components in the lower level quiet condition weights in the low pass noise and higher level quiet conditions however were similar to those in the high pass no

oscillatory behavior of second order half linear damped dynamic equations by refining the generalized riccati transformation technique we obtain new oscillation criteria for a class of second order half linear delay dynamic equations with damping on a time scale assumptions in our theorems are less restrictive these results complement and improve related contributions to the subject in particular the results obtained amend related results reported in the literature

individual differences in simultaneous masking with random frequency multicomponent maskers individual differences were examined for 49 listeners in a simultaneous masking task with random frequency multicomponent maskers and a 1000 hz signal across conditions the maskers were broadband noise or complexes of 2 100 sinusoids whose frequencies were randomly chosen with each presentation maskers were equal rms waveforms presented at 60 db spl thresholds for the multicomponent maskers spanned a range of up to 59 db across listeners within conditions without distinct groupings when divided into quartiles mean thresholds for listeners in the lowest quartile increased monotonically with the number of masker components and peaked below values produced by broadband noise listeners in the upper quartile had nonmonotonic functions with a broad peak around 10 20 components with values above those produced by broadband noise quiet thresholds and masked thresholds for the broadband noise masker did not distinguish high from low threshold groups lowering masker uncertainty frequencies randomized between but not within trials or introducing temporal differences by shortening the signal both improved performance by as much as 40 db dependent on the masking produced with maximum uncertainty training effects within experiment excluding an initial training period were examined for all listeners and for five listeners across two consecutive experiments eleven of forty nine listeners 22 showed systematic improvement averaging 12 db within experiment independent of high or low original thresholds for the five tested longer four improved by 5 db or more in at least one condition but the change in performance occurred primarily during initial training for the second experiment the large individual differences documented present a challenge to the development of models for masking produced by masker frequency uncertainty

material identification of real impact sounds effects of size variation in steel glass wood and plexiglass plates identification of the material of struck objects of variable size was investigated previous studies on this issue assumed recognition to be based on acoustical measures of damping this assumption was tested comparing the power of a damping measure in explaining identification data with that of several other acoustical descriptors listeners performance was perfect with respect to gross material categories steel glass and wood plexiglass comprising materials of vastly different mechanical properties impaired performance was observed for materials within the same gross category identification being based on the size of the objects alone the damping descriptor accounted for the identification of the gross categories however other descriptors such as signal duration explained the results equally well materials within the same gross category were identified mainly on the basis of signal frequency overall poor support for the relevance of damping to material perception was found an analysis of the acoustical support for perfect material identification was carried out sufficient acoustical information for perfect performance was found thus procedural biases for the origin of the effects of size could be discarded pointing toward their cognitive rather than methodological nature identification performance was explained in terms of the regularities of the everyday acoustical environment

forward masking as a function of frequency masker level and signal delay the forward masking of a sinusoidal signal by a sinusoid of the same frequency was investigated for frequencies ranging from 125 to 4000 hz forward masking in db is proportional to both masker level and log signal delay at each frequency more forward masking occurs at very low frequencies than at high frequencies given equal sensation level maskers and masked thresholds are greater at low frequencies than at high frequencies given equal spl maskers the data can be described equally well by assuming that the difference in forward masking as a function of frequency is due to a change in the time course of recovery from masking or to a change in the growth of masking at each signal delay the frequency effect is not large enough to change the interpretation of forward masking data in studies of suppression or psychophysical tuning curves

a second order nonlinear difference equation oscillation and asymptotic behavior discrete analogues are investigated for well known results on oscillation growth and asymptotic behavior of solutions of y q t y 0 for q t 0 and for q t 0 the analogue of atkinson s oscillation criterion is shown to be true for 2yn 1 qn yn 0 but the analogue for atkinson s nonoscillation criterion is shown to be false

oscillation criteria for two dimensional difference systems of first order linear difference equations sufficient conditions are established for the oscillation of the linear two dimensional difference system dx n p ny n dy n 1 q nx n n n n 0 n 0 n 0 1 where p n q n are nonnegative real sequences our results extend the results in the literature

a molecular description of profile analysis decision weights and internal noise systematic inefficiencies and internal noise in a spectral profile discrimination task were investigated listeners detected a 1000 hz sinusoid added in phase to the central component of a complex consisting of 11 equal intensity sinusoids parameters for a channel model that employs decision weights and internal noise were estimated with molecular psychophysical techniques maximum likelihood predictions of the model were generally within a few decibels of observed thresholds the degree to which an assumption of ideal weights leads to overestimation of internal noise was also assessed

estimates of internal templates for the detection of sequential tonal patterns in this experiment listeners detected sequential tonal patterns embedded in multitone multiburst random maskers the maskers consisted of eight 30ms bursts of random frequency tones the signal when present occupied the central six bursts and was centered at 1000hz the six sequential signal tones formed several spectro temporal patterns an equal frequency pattern three ascending patterns with frequency ranges spanning 0 5 1 and 2 equivalent rectangular bandwidths erbs and a random pattern with frequencies drawn at random from the range of 925 1075hz the total number of tones in each burst m was varied to determine detection threshold the detectability of the signal pattern declined as the frequency range of the signal pattern increased and when the signal was random relative weights as a function of time and frequency interpreted as listeners internal templates depended systematically on the properties of the signal pattern tested the templates indicated that when sensitivity was po

on the existence of maximum likelihood estimates in logistic regression models summary the problems of existence uniqueness and location of maximum likelihood estimates in log linear models have received special attention in the literature haberman 1974 chapter 2 wedderburn 1976 silvapulle 1981 for multinomial logistic regression models we prove existence theorems by considering the possible patterns of data points which fall into three mutually exclusive and exhaustive categories complete separation quasicomplete separation and overlap our results suggest general rules for identifying infinite parameter estimates in log linear models for frequency tables

a model of auditory pattern analysis based on component relative entropy recently results from detection and information theory have been used to predict performance of human observers in experiments involving the discriminability of changes in individual components of unfamiliar or uncertain tone patterns r a lutfi j acoust soc am 91 3391 3401 1992 in this paper the theoretical analysis is expanded to yield a general rule of pattern analysis that accounts for nearly all of the major results of such experiments conducted over the last 18 years the rule can be stated as follows component discriminability in an unfamiliar tone pattern profile or sequence is a linearly increasing function of the component s relative entropy core in the pattern ancillary the threshold for detection of a change decreases by one order of magnitude factor of 10 for each one bit increase in core this precise relation of threshold to core is demonstrated repeatedly in a review of past studies and is shown to account for the relative effects of a variety of important variables and their interactions such variables include the total duration of the pattern the number of tones in the pattern the number of tones subject to change the relative level and duration of individual tones in the pattern the relative variability and the physical dimension of the tones parameters that are subject to change the number and position of targets in the pattern the psychophysical procedure used method of adjustment versus same different the type of discrimination task frequency versus intensity discrimination and the manner of presentation of the tones simultaneous or sequential the core rule seems to reflect a general property of auditory analysis wherein the perception of patterns in an ensemble is dominated by those features that dominate the variance of the ensemble

structural analysis of a queueing system with multiclasses of correlated arrivals and blocking in assemble to order production systems and others of a similar flavor it is often the case that orders for components of various types are placed simultaneously but that these components are manufactured or assembled at separate facilities t he order process introduces correlation among the jobs at separate facilities the purpose of this paper is to study the effect of this correlation on a variety of system performance measures consider a system that consists of s parallel servers where e ach server has a finite buffer and is dedicated to a separate job type multiple classes of customer orders arrive to the system where each class is composed of one or more unique job types upon the arrival of an order each job in the order is separately routed to its designated buffer if the buffer is full that job is blocked and lost otherwise it enters the buffer and is served according to the fcfs discipline under markovian assumptions we systematically examine the impact of arrival correlati ons on system based performance measures such as the queue length vector and the workload vector and class based performance measures such as the waiting time vector and the order response time among other things we establish several stochastic orders between performance vectors with different degrees of arrival correlations we also show that greater arrival correlation can stochastically improve the worst component in a performance vector e g the longest queue the heaviest workload reduce the expected sum of the j longest queues 1 j s and for any given order type increase its entering probability and reduce its order response time our results can also be extended to the compound poisson arrival process where each order contains multiple units of several job types

temporal limits of level dominance in a sample discrimination task level dominance refers to the effect where attention is automatically directed to the loudest part of an auditory display in a sample discrimination task the frequencies of five 50ms tones were sampled from normal distributions with means of 1000 and 1100hz and presented sequentially with the tones alternating in intensity observers decide from which distribution the sample was drawn the informativeness of the even numbered tones d 2 was greater than the informativeness of the odd numbered tones d 1 estimates of decision weights and performance levels d show that when the more informative tones were less intense observers attended to the louder tones rather than the more informative tones this effect extends well beyond the temporal limits expected from forward masking studies

algorithms for an irreducible and lumpable strong stochastic bound despite considerable works the numerical analysis of large chains remains a difficult problem fortunately enough while modeling computer networks it is often sufficient to check if the studied mechanism satisfies the requirements of the quality of service qos we expect and exact values of the performance indices are not necessary so we advocate a new method based on the algorithmic derivation of a lumpable stochastic bounding matrix to analyze large state space problems because of the lumpability the numerical analysis deals with smaller matrices the stochastic bounds provide upper bounds for performance indices defined as reward functions our work is purely algorithmic and algebraic and does not require proofs based on the sample path theorem and coupling see stoyan comparison methods for queues and other stochastic models wiley 1983 for some examples we present the algorithms time complexity memory requirements and an example

computational complexity of loss networks abstract in this paper we examine the theoretical limits on developing algorithms to find blocking probabilities in a general loss network we demonstrate that exactly computing the blocking probabilities of a loss network is a p complete problem we also show that a general algorithm for approximating the blocking probabilities is also intractable unless rp np which seems unlikely according to current common notions in complexity theory given these results we examine implications for designing practical algorithms for finding blocking probabilities in special cases

level dominance in sound source identification impact sounds were synthesized according to standard textbook equations given for the motion of simply supported metal plates in a two interval forced choice procedure highly practiced listeners identified from these sounds a predefined class of target plates based on their particular material and geometric properties the effects of two factors on identification were examined the relative level of partials comprising the sounds and the relative amount of information given as the difference in d each partial provided for identification in different conditions one factor was fixed while the other either increased or decreased with frequency the effect on listener identification in each case was determined from a logistic discriminant analysis of trial by trial responses yielding a vector of listener decision weights on the frequency and decay of individual partials the weights increased proportionally with relative level but were largely uninfluenced by relative information content a result exactly opposite to that expected from a maximum likelihood observer the dominant effect of relative level was replicated for other sound sources clamped bars and stretched membranes and was not diminished by randomizing the relative level of partials across trials the results are taken to underscore the importance of relative level in the identification of rudimentary sound sources

auditory detection of hollowness the airborne sounds produced by freely vibrating hollow and solid bars were synthesized according to the equations of bar motion from theoretical acoustics and were presented to listeners over headphones in a two interval forced choice task listeners were asked to distinguish between the hollow and solid bar sounds as bar length was varied at random from one presentation to the next all other physical properties of the bar were held constant across trials listener decision strategies for detecting hollowness in iron aluminum and wood bars were determined from regression weights describing the relation between the listener s response and the frequency intensity and decay modulus of the individual partials comprising these sounds the obtained weights were compared to those of a hypothetical listener that bases judgments on the acoustic relations intrinsic to hollowness as determined from the equations for motion results indicate that listeners adopt roughly one of two decision strategies either basing judgments on the appropriate acoustic relations or basing judgments predominantly on frequency alone the decision strategy of some listeners also changed from one type to the other with a change in bar material or upon replication of the same condition the results are interpreted in terms of the vulnerability of the intrinsic acoustic relations to small perturbations in acoustic parameters as would be associated with listener internal noise they demonstrate that basic limits of human sensitivity can have a profound effect on the identification of rudimentary source attributes from sound even in conditions where acoustic variation is largely dictated by physical variation in the source

oscillation criteria for half linear dynamic equations on time scales this paper is concerned with oscillation of the second order half linear delay dynamic equation r t x p t x t 0 on a time scale t where 1 is the quotient of odd positive integers p t and t t are positive rd continuous functions on t r t is positive and delta differentiable t t and limt t we establish some new sufficient conditions which ensure that every solution oscillates or converges to zero our results in the special cases when t r and t n involve and improve some oscillation results for second order differential and difference equations and when t hn t q n 0 and t n 2 our oscillation results are essentially new some examples illustrating the importance of our results are also included

oscillation of second order superlinear dynamic equations with damping on time scales this paper concerns the oscillation of solutions to the second order superlinear dynamic equation with damping r t x d t d p t x d t q t f x s t 0 on a time scale t which is unbounded above no sign conditions are imposed on r t p t and q t the function f c r r is assumed to satisfy xf x 0 and f x 0 for x 0 we illustrate the results by several examples

level discrimination of single tones in a multitone complex by normal hearing and hearing impaired listeners a conditional on a single stimulus coss analysis procedure j acoust soc am 86 1743 1746 1989 was used to estimate how well normal hearing and hearing impaired listeners selectively attend to individual spectral components of a broadband signal in a level discrimination task on each trial two multitone complexes consisting of six octave frequencies from 250 to 8000 hz were presented to listeners the levels of the individual tones were chosen independently and at random on each presentation the target tone was selected within a block of trials as the 250 1000 or 4000 hz component on each trial listeners were asked to indicate which of the two complex sounds contained the higher level target as a group normal hearing listeners exhibited greater selectivity than hearing impaired listeners to the 250 hz target while hearing impaired listeners showed greater selectivity than normal hearing listeners to the 4000 hz target which is in the region of their hearing loss both groups of listeners displayed large variability in their ability to selectively weight the 1000 hz target trial by trial analysis showed a decrease in weighting efficiency with increasing frequency for normal hearing listeners but a relatively constant weighting efficiency across frequency for hearing impaired listeners interestingly hearing impaired listeners selectively weighted the 4000 hz target which was in the region of their hearing loss more efficiently than did the normal hearing listeners

new criteria for the oscillation and existence of monotone solutions of second order nonlinear difference equations we obtain sufficient conditions for the oscillation of the perturbed difference equation d a n 1 dy n 1 s f n y n g n y n dy n n 1 as well as for the existence of monotone solutions of the nonlinear difference equation d a n 1 dy n 1 s k nf y r n 0 n 1 where 0 s p q with p even and q odd integers and some incorrect results in a recent paper are pointed out examples which illustrate the importance of our results are also included

an examination of procedures for determining the number of clusters in a data set a monte carlo evaluation of 30 procedures for determining the number of clusters was conducted on artificial data sets which contained either 2 3 4 or 5 distinct nonoverlapping clusters to provide a variety of clustering solutions the data sets were analyzed by four hierarchical clustering methods external criterion measures indicated excellent recovery of the true cluster structure by the methods at the correct hierarchy level thus the clustering present in the data was quite strong the simulation results for the stopping rules revealed a wide range in their ability to determine the correct number of clusters in the data several procedures worked fairly well whereas others performed rather poorly thus the latter group of rules would appear to have little validity particularly for data sets containing distinct clusters applied researchers are urged to select one or more of the better criteria however users are cautioned that the performance of some of the criteria may be data dependent

oscillation of second order perturbed nonlinear difference equations using the riccati transformation techniques we will establish some new oscillation criteria for the second order perturbed nonlinear difference equation d a n 1 dx n 1 c f n x n g n x n dx n n 1where c 0 is a quotient of odd positive integers some comparison between our theorems and those previously known results are indicated examples are interested in the text to illustrate the relevance of our results

relative dominance of individual partials in determining the pitch of complex tones these experiments were conducted to determine the dominance of each partial in determining the residue pitch of a complex tone subjects were required to make pitch matches to a complex tone which had one partial slightly mistuned from its correct harmonic value the shift in residue pitch was measured as a function of the frequency shift of the harmonic for each harmonic in turn for mistunings up to 2 3 the shift in residue pitch was approximately a linear function of the shift in the harmonic but for greater mistunings the shift in residue pitch was reduced the degree to which a given harmonic can influence residue pitch gives a measure of the dominance of that harmonic the dominant harmonics were always contained within the lowest six harmonics for fundamental frequencies of 100 200 and 400 hz but there were marked individual differences in the exact distribution of dominance across harmonics the level of a harmonic relative to adjacent harmonics can have a significant effect on its dominance the implications of the results for theories of pitch perception are discussed

level dominance for the detection of changes in level distribution in sound streams sound streams were generated by randomly choosing the levels of tone pips from two different distributions a and b of the 18 tone pips the first nine were drawn from distribution a and the second nine from distribution b or the opposite the listeners task was to indicate order a b or b a in two conditions the a and b distributions differed in mean condition 1 or variance condition 2 in contrast to an ideal observer listeners strategies were consistent across the two conditions analyses suggest that listeners relied primarily on the more intense tone pips in making their decisions

correlation coefficients and correlation ratios as estimates of observer weights in multiple observation tasks advantages of correlational methods are described for estimating the relative reliance or weight observers give to different elements of a complex display when performing auditory or visual discriminations correlational methods differ from other such methods by providing a least squares estimate of weights rather than a maximum likelihood estimate based on a presumed model the main benefit is that these methods can be generally applied in cases where the statistical properties of elements are unknown where correlations exist between elements or where it is necessary to evaluate decision models that are inherently nonlinear

perceptual weights for loudness judgments of six tone complexes subjects with normal hearing nh and with sensorineural hearing loss snhl judged the overall loudness of six tone complexes comprised of octave frequencies from 0 25 to 8 khz the level of each tone was selected from a normal distribution with a standard deviation of 5 db and subjects judged which of two complexes was louder overall level varied across conditions in the loudness task there was no difference in mean level across the two stimuli in the sample discrimination task the two complexes differed by an average of 5 db for both tasks perceptual weights were derived by correlating the differences in level between matched frequency tones in the complexes and the loudness decision on each trial weights obtained in the two tasks showed similar shifts from low to high frequency components with increasing overall level simulation of these experiments using a model of loudness perception moore and glasberg 2004 hear res 188 70 88 yielded predicted weights for these stimuli that were highly correlated with predicted specific loudness but not with the observed weights

decision strategies of hearing impaired listeners in spectral shape discrimination the ability to discriminate between sounds with different spectral shapes was evaluated for normal hearing and hearing impaired listeners listeners detected a 920 hz tone added in phase to a single component of a standard consisting of the sum of five tones spaced equally on a logarithmic frequency scale ranging from 200 to 4200 hz an overall level randomization of 10 db was either present or absent in one subset of conditions the no perturbation conditions the standard stimulus was the sum of equal amplitude tones in the perturbation conditions the amplitudes of the components within a stimulus were randomly altered on every presentation for both perturbation and no perturbation conditions thresholds for the detection of the 920 hz tone were measured to compare sensitivity to changes in spectral shape between normal hearing and hearing impaired listeners to assess whether hearing impaired listeners relied on different regions of the spectrum to discriminate between sounds spectral weights were estimated from the perturbed standards by correlating the listener s responses with the level differences per component across two intervals of a two alternative forced choice task results showed that hearing impaired and normal hearing listeners had similar sensitivity to changes in spectral shape on average across frequency correlation functions also were similar for both groups of listeners suggesting that as long as all components are audible and well separated in frequency hearing impaired listeners can use information across frequency as well as normal hearing listeners analysis of the individual data revealed however that normal hearing listeners may be better able to adopt optimal weighting schemes this conclusion is only tentative as differences in internal noise may need to be considered to interpret the results obtained from weighting studies between normal hearing and hearing impaired listeners

auditory correlates of perceived mallet hardness for a set of recorded percussive sound events a psychophysical investigation of timbre was undertaken with the intent of deriving quantitative results that could be useful in musical applications recordings of metal objects being struck with percussion mallets were rated by subjects on a unidimensional perceptual scale of perceived mallet hardness four acoustical parameters of the attack portion first 325 ms were defined and evaluated as predictors of perceived mallet hardness rating to measure these parameters a critical band filter bank was employed two curves were extracted from the filter bank output 1 spectral level log of area under spectrum over time and 2 spectral centroid over time for each curve two parameters were measured the mean and the slope of the spectral level curve and the mean and the time weighted average of the spectral centroid curve multiple regression analysis was used to relate the perceptual ratings to these four acoustical parameters and a good fit was achieved multiple r squared 0 725 f 1135 8 p 0

molecular analysis of the effect of relative tone level on multitone pattern discrimination molecular psychophysics attempts to model the observer s response to stimuli as they vary from trial to trial the approach has gained popularity in multitone pattern discrimination studies as a means of estimating the relative reliance or decision weight listeners give to different tones in the pattern various factors affecting decision weights have been examined but one largely ignored is the relative level of tones in the pattern in the present study listeners detected a level increment in a sequence of 5 100 ms 2 0 khz tone bursts alternating in level between 40 and 80db spl the level increment was made largest on the 40 db tones yet despite this all four highly practiced listeners gave near exclusive weight to the 80 db tones the effect was the same when the tones were replaced by bursts of broadband gaussian noise alternating in level it was reduced only when the level differences were made 10db and it was entirely reversed only when the low level tones alternated with louder bursts of ga

bounds for the positive eigenvectors of nonnegative matrices and for their approximations by decomposition cet article traite des vecteurs propres positifs des matrices irreductibles non reparties qui sont simplement caracterisees par une limite superieure donnee sur leur rayon spectral et par une matrice l donnee de limites inferieures pour leurs elements analyse du cas particulier des matrices stochastiques et on donne un exemple numerique

discrimination of the spectral density of multitone complexes spectral density d defined as the number of partials comprising a sound divided by its bandwidth has been suggested as cue for the identification of the size and shape of sound sources few data are available however on the ability of listeners to discriminate differences in spectral density in a cue comparison forced choice procedure with feedback three highly practiced listeners discriminated differences in the spectral density of multitone complexes varying in bandwidth w 500 1500 hz center frequency fc 500 2000 hz and number of tones n 6 31 to reduce extraneous cues for discrimination the overall level of the complexes was roved and the frequencies were drawn at random uniformly over a fixed bandwidth and center frequency for each presentation psychometric functions were obtained relating percent correct discrimination to d in each condition for d 0 02 hz 1 they increased with d

an oscillation theorem for second order superlinear dynamic equations on time scales in this paper the oscillatory behavior of the second order superlinear dynamic equation 0 1 r t x d t d p t x a s t 0 a 1 is studied under the email protected email protected t 0 t in our main theorem is assumed to be a regular time scale a is the quotient of odd positive integers when the coefficient function p t is allowed to be negative for arbitrarily large values of t we establish a sufficient condition for oscillation of all solutions of eq 0 1 as special cases we get that the superlinear differential equation r t x t p t x a t 0 a 1 is oscillatory email protected r a t p t dt r t email protected t dsr s and the superlinear difference email protected r n dx n p n x a n 1 0 a 1 is oscillatory email protected r a n 1 p n r n email protected k n 1r k

relative weights for frequency glide detection using narrowband noise narrowband noise stimuli were used to derive relative weights for detecting frequency glides in a yes no procedure one stimulus set was restricted to the duration of the glide for the second stimulus set there were fringe noise bands preceding and following the glide for both sets the center frequency of the linear glide was either fixed at 1000hz or randomly chosen on each trial from the range of 800 1200hz relative weights as a function of time were derived using a linear model and the linear classification method a ahumada j vis 2 121 131 2002 sensitivity was better for the fixed than random frequency conditions and weight patterns from the random frequency conditions were less reliable than those obtained from the fixed frequency conditions the magnitudes of the relative weights tended to be larger for the second half of the stimulus suggesting that subjects paid more attention to the later than the earlier parts of stimuli in the random frequency conditions the linear model failed to account for subjects performance unless the stimuli were expressed in terms of relative changes in frequency rather than absolute frequency

spectral and temporal cues for perception of material and action categories in impacted sound sources in two experiments similarity ratings and categorization performance with recorded impact sounds representing three material categories wood metal glass being manipulated by three different categories of action drop strike rattle were examined previous research focusing on single impact sounds suggests that temporal cues related to damping are essential for material discrimination but spectral cues are potentially more efficient for discriminating materials manipulated by different actions that include multiple impacts e g dropping rattling perceived similarity between material categories across different actions was correlated with the distribution of long term spectral energy spectral centroid similarity between action categories was described by the temporal distribution of envelope energy temporal centroid or by the density of impacts moreover perceptual similarity correlated with the pattern of confusion in categorization judgments listeners tended to confuse materials with similar spectral centroids and actions with similar temporal centroids and onset densities to confirm the influence of these different features spectral cues were removed by applying the envelopes of the original sounds to a broadband noise carrier without spectral cues listeners retained sensitivity to action categories but not to material categories conversely listeners recognized material but not action categories after envelope scrambling that preserved long term spectral content

auditory discrimination of material changes in a struck clamped bar the principles of theoretical acoustics were applied to approximately reconstruct the sound pressure waveform at the ear as would be generated by an idealized struck clamped bar the result is an inharmonic sum of damped sinusoids whose individual acoustic parameters frequency intensity and decay modulus are for a fixed geometry and fixed driving force uniquely determined by the material composition of the bar in the standard 2ifc procedure listeners were asked to discriminate changes in material composition based on their perception of the acoustic waveform listener strategies for discriminating such changes were estimated by perturbing slightly the individual acoustic parameters from trial to trial and computing correlations with the listener s response cf r a lutfi and e oh j acoust soc am 95 2963 a 1994 in general the correlations reveal that listeners fail to make optimal use of the information in the acoustic waveform by tending to give undue weight for a given material change to changes in component frequency in some case the accompanying reduction in performance efficiency amounted to 80

informational processing of complex sound i intensity discrimination this paper reports on some initial experiments using the sample discrimination paradigm to investigate normal hearing listeners ability to process information in complex nonspeech sounds an important feature of the sample discrimination experiment is that the value of the d i f f e r e n c e to be discriminated randomly varies from trial to trial it is this variation that yields potential information in the present study listeners heard a pair of multitone complexes or sequences on each trial the individual levels of the tones were drawn from two normal distributions differing only in mean the listener s task was to identify the sound having the higher mean tone level for an ideal observer in these experiments performance in d grows as the square root n where n is the number of tones obtained d grew more nearly as the cube root of n regardless of whether the tones were played sequentially or simultaneously or whether they were increased in number from high frequencies to low or from low frequencies to high a preliminary model is proposed in which discrimination performance depends predominantly on the information content of the sounds and is largely independent of the physical dimensions along which the sounds vary information content is defined in terms of the variance of the underlying stimulus distributions and a stimulus equivocation factor that is derived from the data based on this model transmitted information is estimated to be between 1 0 and 2 6 bits

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

oscillation and asymptotic behavior of two dimensional difference systems this paper is concerned with the oscillation behavior of solutions of the nonlinear two dimesional difference system dx n b ng y n dy n 1 a nf x n n n n 0 n 0 n 0 1 some necessary and sufficient conditions are given for the oscillation of all solution of the system our result improve and generalize some results in the literature examples to illustrate the result are included

bounding availability of repairable systems markov models are widely used for the analysis of availability of computer communication systems realistic models often involve state space cardinalities that are so large that it is impractical to generate the transition rate matrix let alone solve for availability measures an approximation technique is presented for determining steady state availability of particular interest is that the method also provides bounds on the error examples are given to illustrate the method

the effect of onset asynchrony on relative weights in profile analysis decision weights were estimated in a profile analysis task to determine whether onset asynchronies between the signal component and the nonsignal components encourage the segregation of the signal relative to the other components the signal component onset was either synchronous or asynchronous with respect to the nonsignal components in the asynchronous conditions thresholds were higher and the decision weights were less efficient than in the synchronous conditions these data are largely consistent with a segregation hypothesis onset asynchrony encourages subjects to shift strategies from one of spectral shape discrimination toward one of intensity discrimination

sample discrimination of frequency by hearing impaired and normal hearing listeners in a multiple observation sample discrimination experiment normal hearing nh and hearing impaired hi listeners heard two multitone complexes each consisting of six simultaneous tones with nominal frequencies spaced evenly on an erbn logarithmic scale between 257 and 6930hz on every trial the frequency of each tone was sampled from a normal distribution centered near its nominal frequency in one interval of a 2ifc task all tones were sampled from distributions lower in mean frequency and in the other interval from distributions higher in mean frequency listeners had to identify the latter interval decision weights were obtained from multiple regression analysis of the between interval frequency differences for each tone and listeners responses frequency difference limens an index of sensorineural resolution and decision weights for each tone were used to predict the sensitivity of different decision theoretic models results indicate that low frequency tones were given much greater perceptu

sensory constraints on auditory identification of the material and geometric properties of struck bars a computational formula is derived for estimating the constraints limited auditory sensitivity imposes on auditory identification of the material and geometric properties of struck bars the formula combines a model of the transverse motion of the bar with empirical psychometric functions to map out null regions in the bar s physical parameter space where changes in the frequency amplitude and decay of partials are likely below threshold for detection parameters of the physical space include bar density young s modulus fluid and viscoelastic damping factors bar length and bar cross sectional area as related to bar shape and hollowness the formula is used to estimate the possible effect of limited sensitivity in past studies on the auditory identification of bar attributes the results suggest that sensitivity may indeed have played a role in some studies and that apparent discrepancies in results may be understood based on whether the predominant source of damping was internal or external to the bar the formula identifies conditions representing an expected bound on identification performance and thereby may be used to aid in the design of future studies for which the struck bar is the sound source of choice