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

on sparse hard sets for counting classes abstract in this paper we study one word decreasing self reducible sets which are introduced by lozano and toran 1991 these are the usual self reducible sets with the peculiarity that the self reducibility machine makes at most one query and this is lexicographically smaller than the input we show first that for all counting classes defined by a predicate on the number of accepting paths there exist complete sets which are one word decreasing self reducible using this fact we can prove that for any class k chosen from pp np c p mod2p mod3 p it holds that 1 if there is a sparse pbtt hard set for k then k p and 2 if there is a sparse snbtt hard set for k then k np co np this generalizes the result of ogiwara and watanabe 1991 to the mentioned complexity classes

piecewise convex maximization approach to multiknapsack we refine the reverse convex approach to binary programs into a piecewise convex maximization problem with only two pieces as a vital lead we address the multiknapsack problem the results of computational experiments are presented in contrast with the best known solutions found by heuristics and by the reverse convex approach

nonuniform proof systems a new framework to describe nonuniform and probabilistic complexity classes the concept of non uniform proof systems is introduced this notion allows a uniform description of non uniform complexity classes 10 probabilistic classes e g bpp 8 15 27 32 am 2 3 and language classes defined by simultaneous non uniform and nondeterministic time bounds non uniform proof systems provide a better understanding of many results concerning these classes particularly their connections to uniform complexity measures we give an uniform approach to lowness results 19 20 for various complexity classes for instance we show that co np poly np is contained in the third level of the low hierarchy and that np c np co np poly implies that the polynomial time hierarchy collapses to its second level see also 1 finally some evidence is given that the low hierarchy cannot be extended beyond its third level by the current techniques

sparse sets lowness and highness we develop the notions of generalized lowness for sets in ph the union of the polynomial time hierarchy and of generalized highness for arbitrary sets also we develop the notions of extended lowness and extended highness for arbitrary sets these notions extend the decomposition of np into low sets and high sets developed by schoning 15 and studied by ko and schoning 9 we show that either every sparse set in ph is generalized high or no sparse set in ph is generalized high further either every sparse set is extended high or no sparse set is extended high in both situations the former case corresponds to the polynomial time hierarchy having only finitely many levels while the latter case corresponds to the polynomial time hierarchy extending infinitely many levels

development of a fast method for determining psychophysical tuning curves a psychophysical tuning curve ptc is usually measured by determining the level of a narrowband noise required to mask a fixed low level tone for several masker center frequencies ptcs could be useful clinically for assessing frequency selectivity and for the diagnosis of dead regions in the cochlea when the signal frequency falls in a dead region the tip of the ptc is shifted away from the signal frequency however ptcs determined in the traditional way are too time consuming for use in clinical practice a fast method for determining ptcs is being developed and evaluated this uses a band of noise that sweeps in center frequency a bekesy method is used to track the masker level required for threshold for normally hearing subjects the new method gives stable results and ptcs similar in shape to those determined in the traditional way when the masker sweeps over a 2 octave range in about 4 minutes and the level changes by 1 2 db s preliminary results using hearing impaired subjects also show a good agreement with the traditional method however further work is required to determine optimum values for the noise bandwidth and rate of change of frequency and level

state variable planning under structural restrictions algorithms and complexity abstract computationally tractable planning problems reported in the literature so far have almost exclusively been defined by syntactical restrictions to better exploit the inherent structure in problems it is probably necessary to study also structural restrictions on the underlying state transition graph the exponential size of this graph though makes such restrictions costly to test hence we propose an intermediate approach using a state variable model for planning and defining restrictions on the separate state transition graphs for each state variable we identify such restrictions which can tractably be tested and we present a planning algorithm which is correct and runs in polynomial time under these restrictions the algorithm has been implemented and it outperforms graphplan on a number of test instances in addition we present an exhaustive map of the complexity results for planning under all combinations of four previously studied syntactical restrictions and our five new structural restrictions this complexity map considers both the optimal and non optimal plan generation problem

distortion product otoacoustic emission suppression tuning curves in hearing impaired humans distortion product otoacoustic emission dpoae suppression tuning curves stcs were measured in 65 hearing impaired hi subjects at f2 frequencies of 2 0 2 8 4 0 and 5 6 khz and l2 levels relative to sensation level sl from 10 db to as much as 50 db best frequency cochlear amplifier gain tip to tail difference t t and tuning qerb were estimated from stcs as with normal hearing nh subjects t t differences and qerb decreased as l2 increased t t differences and qerb were reduced in hi ears compared to normal for conditions in which l2 was fixed relative to behavioral threshold db sl when stcs were compared with l2 at constant sound pressure levels db spl differences between nh and hi subjects were reduced the large effect of level and small effect of hearing loss were both confirmed by statistical analyses therefore the magnitude of the differences in dpoae stcs between nh and hi subjects is mainly dependent on the manner in which level l2 is specified although this conclusion may appear to be at odds with previous invasive measures of cochlear response gain and tuning the apparent inconsistency may be resolved when the manner of specifying stimulus level is taken into account

new collapse consequences of np having small circuits we show that if a self reducible set has polynomial size circuits then it is low for the probabilistic class zpp np as a consequence we get a deeper collapse of the polynomial time hierarchy ph to zpp np under the assumption that np has polynomial size circuits this improves on the well known result in karp and lipton proceedings of the 12th acm symposium on theory of computing acm press new york 1980 pp 302 309 stating a collapse of ph to its second level sigmap 2 under the same assumption furthermore we derive new collapse consequences under the assumption that complexity classes like up fewp and c p have polynomial size circuits finally we investigate the circuit size complexity of several language classes in particular we show that for every fixed polynomial s there is a set in zpp np which does not have o s n size circuits

the computational complexity of propositional strips planning abstract i present several computational complexity results for propositional strips planning i e strips planning restricted to ground formulas different planning problems can be defined by restricting the type of formulas placing limits on the number of pre and postconditions by restricting negation in pre and postconditions and by requiring optimal plans for these types of restrictions i show when planning is tractable polynomial and intractable np hard in general it is pspace complete to determine if a given planning instance has any solutions extremely severe restrictions on both the operators and the formulas are required to guarantee polynomial time or even np completeness for example when only ground literals are permitted determining plan existence is pspace complete even if operators are limited to two preconditions and two postconditions when definite horn ground formulas are permitted determining plan existence is pspace complete even if operators are limited to zero preconditions and one postcondition one of the interesting tractable problems is if each operator is restricted to positive preconditions and one postcondition only ground literals the blocks world problem slightly modified is a subproblem of this restricted planning problem these results in combination with previous analyses are not encouraging for domain independent planning

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

planning for conjunctive goals abstract the problem of achieving conjunctive goals has been central to domain independent planning research the nonlinear constraint posting approach has been most successful previous planners of this type have been complicated heuristic and ill defined i have combined and distilled the state of the art into a simple precise implemented algorithm tweak which i have proved correct and complete i analyze previous work on domain independent conjunctive planning in retrospect it becomes clear that all conjunctive planners linear and nonlinear work the same way the efficiency and correctness of these planners depends on the traditional add delete list representation for actions which drastically limits their usefulness i present theorems that suggest that efficient general purpose planning with more expressive action representations is impossible and suggest ways to avoid this problem

robustness of probabilistic computational complexity classes under definitional perturbations various types of probabilistic algorithms play an increasingly important role in computer science especially in computational complexity theory probabilistic polynomial time complexity classes are defined and compared to each other emphasizing some structural relationships to the known complexity classes p np pspace the classes r and zpp corresponding to the so called las vegas polynomial time bounded algorithms are given special attention it is shown that many definitions that arise naturally from different types of algorithms are equivalent in defining the same class r or zpp resp these robustness results justify finally the tractability of the above probabilistic classes

complexity of finite horizon markov decision process problems controlled stochastic systems occur in science engineering manufacturing social sciences and many other cntexts if the systems is modeled as a markov decision process mdp and will run ad infinitum the optimal control policy can be computed in polynomial time using linear programming the problems considered here assume that the time that the process will run is finite and based on the size of the input there are mny factors that compound the complexity of computing the optimal policy for instance there are many factors that compound the complexity of this computation for instance if the controller does not have complete information about the state of the system or if the system is represented in some very succint manner the optimal policy is provably not computable in time polynomial in the size of the input we analyze the computational complexity of evaluating policies and of determining whether a sufficiently good policy exists for a mdp based on a number of confounding factors including the observability of the system state the succinctness of the representation the type of policy even the number of actions relative to the number of states in almost every case we show that the decision problem is complete for some known complexity class some of these results are familiar from work by papadimitriou and tsitsiklis and others but some such as our pl completeness proofs are surprising we include proofs of completeness for natural problems in the as yet little studied classes np pp

efficient algorithms for solving multiconstraint zero one knapsack problems to optimality the multiconstraint 0 1 knapsack problem is encountered when one has to decide how to use a knapsack with multiple resource constraints even though the single constraint version of this problem has received a lot of attention the multiconstraint knapsack problem has been seldom addressed

forward and simultaneous masked thresholds in bandlimited maskers in subjects with normal hearing and cochlear hearing loss forward and simultaneous masked thresholds were measured at 0 5 and 2 0 khz in bandpass maskers as a function of masker bandwidth and in a broadband masker with the goal of estimating psychophysical suppression suppression was operationally defined in two ways 1 as a change in forward masked threshold as a function of masker bandwidth and 2 as a change in effective masker level with increased masker bandwidth taking into account the nonlinear growth of forward masking subjects were younger adults with normal hearing and older adults with cochlear hearing loss thresholds decreased as a function of masker bandwidth in forward masking which was attributed to effects of suppression thresholds remained constant or increased slightly with increasing masker bandwidth in simultaneous masking for subjects with normal hearing slightly larger estimates of suppression were obtained at 2 0 khz rather than at 0 5 khz for hearing impaired subjects suppression was reduced in regions of hearing loss the magnitude of suppression was strongly correlated with the absolute threshold at the signal frequency but did not vary with thresholds at frequencies remote from the signal the results suggest that measuring forward masked thresholds in bandlimited and broadband maskers may be an efficient psychophysical method for estimating suppression

psychophysical suppression measured with bandlimited noise extended below and or above the signal effects of age and hearing loss the objectives of this study were to measure suppression with bandlimited noise extended below and above the signal at lower and higher signal frequencies between younger and older subjects and between subjects with normal hearing and cochlear hearing loss psychophysical suppression was assessed by measuring forward masked thresholds at 0 8 and 2 0 khz in bandlimited maskers as a function of masker bandwidth bandpass masker bandwidth was increased by introducing noise components below and above the signal frequency while keeping the noise centered on the signal frequency and also by adding noise below the signal only and above the signal only subjects were younger and older adults with normal hearing and older adults with cochlear hearing loss for all subjects suppression was larger when noise was added below the signal than when noise was added above the signal consistent with some physiological evidence of stronger suppression below a fiber s characteristic frequency than above for subjects

exploring relaxation induced neighborhoods to improve mip solutions given a feasible solution to a mixed integer programming mip model a natural question is whether that solution can be improved using local search techniques local search has been applied very successfully in a variety of other combinatorial optimization domains unfortunately local search relies extensively on the notion of a solution neighborhood and this neighborhood is almost always tailored to the structure of the particular problem being solved a mip model typically conveys little information about the underlying problem structure this paper considers two new approaches to exploring interesting domain independent neighborhoods in mip the more effective of the two which we call relaxation induced neighborhood search rins constructs a promising neighborhood using information contained in the continuous relaxation of the mip model neighborhood exploration is then formulated as a mip model itself and solved recursively the second which we call guided dives is a simple modification of the mip tree traversal order loosely speaking it guides the search towards nodes that are close neighbors of the best known feasible solution extensive computational experiments on very difficult mip models show that both approaches outperform default cplex mip and a previously described approach for exploring mip neighborhoods local branching with respect to several different metrics the metrics we consider are quality of the best integer solution produced within a time limit ability to improve a given integer solution of both good and poor quality and time required to diversify the search in order to find a new solution

global optimization and multi knapsack a percolation algorithm abstract since the standard multi knapsack problem may be rewritten as a reverse convex problem we present a global optimization approach it is known from solving high dimensional nonconvex problems that pure cutting plane methods may fail and branch and bound is impractical due to a large duality gap on the other hand a strategy based on some sufficient optimality condition does not help much because it requires generating all level set points an intractable problem therefore we propose to combine both a cutting plane method and a sufficient optimality condition together with a random generation of level set points where the number of points is limited by a tabu list to prevent re examination of the same level set area experiments show that we end up with a small duality gap allowing a subsequent branch and bound approach to prove optimality

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

symmetric space bounded computation abstract a symmetric turing machine is one such that the yields relation between configurations is symmetric the space complexity classes for such machines are found to be intermediate between the corresponding deterministic and nondeterministic space complexity classes certain natural problems are shown to be complete for symmetric space complexity classes and the relationship of symmetry to determinism and nondeterminism is investigated

some consequences of non uniform conditions on uniform classes we obtain some results of the form if certain complexity classes satisfy a non uniform condition then some unlikely consequences follow more precisely 1 1 if the non uniform polynomial time hierarchy collapses at level i 0 i e ipoly ipoly then the meyer stockmeyer hierarchy collapses at level i 2 i e i 2 i 2 this strengthens a generalization of a result of karp and lipton 1980 2 2 if co np is conjunctively reducible to a sparse set then p np this generalizes a theorem of fortune 1979 3 3 if np is conjunctively and disjunctively reducible to a sparse np complete set then p np this is a partial generalization of a result of mahaney 1980 conjuctive and disjunctive reducibility were introduced by ladner lynch and selman 1975 4 4 if co np is reducible to a sparse set then np co np reducibility was introduced 5 by adleman and manders 1977

comparisons of frequency selectivity in simultaneous and forward masking for subjects with unilateral cochlear impairments two experiments are described in which frequency selectivity was estimated in simultaneous and forward masking for each ear of subjects with moderate 25 60 db hl unilateral cochlear hearing losses in both experiments the signal level was fixed for a given ear and type of masking simultaneous or forward and the masker level was varied to determine threshold using an adaptive two alternative forced choice procedure in experiment i the masker was a noise with a spectral notch centered at the signal frequency either 1 0 or 1 5 khz threshold was determined as a function of notch width signal levels were chosen so that the noise level required at threshold for a notch width of zero was similar for the normal and impaired ear of each subject in both simultaneous and forward masking the function relating threshold to notch width had a steeper slope for the normal ear than for the impaired ear of each subject for the normal ears these functions were steeper in forward masking than in simultaneous masking this difference was interpreted as resulting from suppression for the impaired ears significant differences in the same direction were observed for three of the five subjects but the differences were smaller in experiment ii psychophysical tuning curves ptcs were determined in the presence of a fixed notched noise centered at the signal frequency 1 0 khz for the normal ears the ptcs were sharper in forward masking than in simultaneous masking for the impaired ears the ptcs were similar in simultaneous and forward masking but those in forward masking tended to be sharper at masker frequencies far removed from the signal frequency overall the results suggest that suppression is reduced but not completely absent in cases of moderate cochlear hearing loss

expressive equivalence of planning formalisms abstract a concept of expressive equivalence for planning formalisms based on polynomial transformations is defined it is argued that this definition is reasonable and useful both from a theoretical and from a practical perspective if two languages are equivalent then theoretical results carry over and more practically we can model an application problem in one language and then easily use a planner for the other language in order to cope with the problem of exponentially sized solutions for planning problems an even stronger concept of expressive equivalence is introduced using the novel esp reduction four different formalisms for propositional planning are then analyzed namely two variants of strips ground tweak and the sas formalism although these may seem to exhibit different degrees of expressive power it is proven that they are in fact expressively equivalent under esp reduction this means that neither negative goals partial initial states nor multi valued state variables increase the expressiveness of standard propositional strips

towards efficient universal planning a randomized approach one of the most widespread approaches to reactive planning is schoppers universal plans we propose a stricter definition of universal plans which guarantees a weak notion of soundness not present in the original definition and isolate three different types of completeness that capture different behaviors exhibited by universal plans we show that universal plans which run in polynomial time and are of polynomial size cannot satisfy even the weakest type of completeness unless the polynomial hierarchy collapses by relaxing either the polynomial time or the polynomial space requirement the construction of universal plans satisfying the strongest type of completeness becomes trivial as an alternative approach we study randomized universal planning by considering a randomized version of completeness and a restricted but nontrivial class of problems we show that there exists randomized universal plans running in polynomial time and using polynomial space which are sound and complete for the restricted class of problems we also report experimental results on this approach to planning showing that the performance of a randomized planner is not easily compared to that of a deterministic planner

a trust branching path heuristic for zero one programming abstract for 0 1 problems we propose an exact branch and bound procedure where branching strategy is based on empirical distribution of each variable within three intervals 0 1 1 1 under the linear relaxation model we compare the strategy on multiknapsack and maximum clique problems with other heuristics