extension of a binaural cross correlation model by contralateral inhibition i simulation of lateralization for stationary signals running interaural cross correlation is a basic assumption to model the performance of the binaural auditory system although this concept is particularly suited to simulate psychoacoustic localization phenomena there exist some localization effects which cannot be explained by pure cross correlation in this paper a model of interaural cross correlation is extended by a contralateral inhibition mechanism and by monaural detectors in order to simulate a wide range of psychoacoustic lateralization data the extended model explains lateralization of pure tones with interaural time differences as well as with interaural level differences multiple images are predicted for tones with characteristic combinations of interaural signal parameters and for noise signals with different degrees of interaural cross correlation the model is also capable of simulating dynamic lateralization phenomena such as the law of the first wave front which is dealt with in a companion paper lindemann j acoust so

monaural and binaural loudness of 5 and 200 ms tones in normal and impaired hearing the difference in level required to match monaural and binaural loudness of 5 and 200 ms tones was measured for listeners with normal and impaired hearing stimuli were 1 khz tones presented at levels ranging from 10 to 90db sensation level sixteen listeners eight normal and eight with losses of primarily cochlear origin made loudness matches between equal duration monaural and binaural tones using an adaptive 2afc procedure the present results corroborate existing data for 200 ms tones in normal listeners and provide new data for 5 ms tones on average the binaural level difference required for equal loudness of monaural and binaural tones is about the same for 5 and 200 ms tones of equal level and changes as a function of level the group data for normal and impaired listeners are in reasonable agreement with data in the literature however the data from some of the impaired listeners deviate markedly from the average indicating that group data do not accurately represent the behavior of all im

harmonic oscillator with multiplicative noise nonmonotonic dependence on the strength and the rate of dichotomous noise the output signal of a undamped linear oscillator with a random frequency subject to a periodic force shows nonmonotonic dependence on the strength and the rate of color noise stochastic resonance the effect is absent for white noise

effect of time delay on pattern dynamics in a spatial epidemic model time delay accounting for constant incubation period or sojourn times in an infective state widely exists in most biological systems like epidemiological models however the effect of time delay on spatial epidemic models is not well understood in this paper spatial pattern of an epidemic model with both nonlinear incidence rate and time delay is investigated in particular we mainly focus on the effect of time delay on the formation of spatial pattern through mathematical analysis we gain the conditions for hopf bifurcation and turing bifurcation and find exact turing space in parameter space furthermore numerical results show that time delay has a significant effect on pattern formation the simulation results may enrich the finding of patterns and may well capture some key features in the epidemic models

rising relative fluctuation as a warning indicator of discontinuous transitions in symbiotic metapopulations abstract the long time limit behavior of the stochastic lotka volterra model of a symbiotic metapopulation subjected to generalized verhulst self regulation is considered the influence of a time variable environment on the carrying capacities of subpopulations is modeled as a periodic deterministic part and a symmetric dichotomous noise relying on the mean field approach it is established that at certain parameter regimes the mean field average subpopulations size exhibits hysteresis in respect to the noise correlation time manifested in the appearance of colored noise induced discontinuous transitions especially it is shown that the relative fluctuation of the subpopulation sizes exhibits accelerated increase prior to abrupt transitions of the metapopulation state moreover in certain cases the autocorrelation function of the population sizes demonstrates anticorrelation at some values of the lag time

effect of multiplicative noise on stationary stochastic process an open system that can be analyzed using the langevin equation with multiplicative noise is considered the stationary state of the system results from a balance of deterministic damping and random pumping simulated as noise with controlled periodicity the dependence of statistical moments of the variable that characterizes the system on parameters of the problem is studied a nontrivial decrease in the mean value of the main variable with an increase in noise stochasticity is revealed applications of the results in several physical chemical biological and technical problems of natural and humanitarian sciences are discussed

influence of strong noise on the decline and propagation of population in the delayed malthus verhulst model abstract the effects of strong noise on the decline and propagation processes of a population in the malthus verhulst model with time delay are investigated by a stochastic simulation time delays in two different processes are concurrent in ecosystems the simulation results indicate that the stability of the population is enhanced by the decreasing multiplicative noise intensity and the increasing delay time the replacement of old individuals with young ones is accelerated by an increasing multiplicative noise intensity an increasing additive noise intensity and a decreasing delay time an increasing multiplicative noise intensity will drive the population of species to fluctuate more largely

proliferation assisted transport in a random environment we investigate the competition between barrier slowing down and proliferation induced superdiffusion in a model of population dynamics in a random force field numerical results in d 1 suggest that a new intermediate diffusion behaviour appears we introduce the idea of proliferation assisted barrier crossing and give a flory like argument to understand qualitatively this non trivial diffusive behaviour a renormalization group analysis close to the critical dimension dc 2 confirms that the random force fixed point is unstable and flows towards an uncontrolled strong coupling regime

the mechanism of stochastic resonance it is shown that a dynamical system subject to both periodic forcing and random perturbation may show a resonance peak in the power spectrum which is absent when either the forcing or the perturbation is absent

addendum to colored noise induced discontinuous transitions in symbiotic ecosystems a symbiotic ecosystem with gompertz self regulation and with adaptive competition between populations is studied by means of a n species lotka volterra stochastic model the influence of fluctuating environment on the carrying capacity of a population is modeled as a dichotomous noise the study is a follow up of previous investigations of symbiotic ecosystems subjected to the generalized verhulst self regulation phys rev e 69 061106 2004 65 051108 2002 in the framework of mean field approximation the behavior of the solutions of the self consistency equation for a stationary system is examined analytically in the full phase space of system parameters depending on the mutual interplay of symbiosis and competition of species variation of noise parameters amplitude correlation time can induce doubly unidirectional discontinuous transitions as well as single unidirectional discontinuous transitions of the mean population size

double stochastic resonance in an insect ecosystem with time delays abstract considering additive and multiplicative periodic signals we have investigated the stochastic resonance sr phenomenon in an insect ecosystem with two different types of time delays at which the insect dynamics is assumed to be disturbed by both additive and multiplicative noises the signal to noise ratio snr is calculated when two different weak periodic signals are added to the insect system it is shown from the snr that the additive and multiplicative periodic signals can cause the sr and double sr in the case of time delays in the stochastic and deterministic force respectively a detailed study of the snr depending on various noise characteristics is performed and the main results about sr are compared for two different cases of time delays

role of the noise on the transient dynamics of an ecosystem of interacting species abstract we analyze the transient dynamics of an ecosystem described by generalized lotka volterra equations in the presence of a multiplicative noise and a random interaction parameter between the species we consider specifically three cases i two competing species ii three interacting species one predator two preys iii n interacting species the interaction parameter in case i is a stochastic process which obeys a stochastic differential equation we find noise delayed extinction of one of two species which is akin to the noise enhanced stability phenomenon other two noise induced effects found are temporal oscillations and spatial patterns of the two competing species in case ii the noise induces correlated spatial patterns of the predator and of the two preys concentrations finally in case iii we find the asymptotic behavior of the time average of the ith population when the ecosystem is composed of a great number of interacting species

effects of time delay on symmetric two species competition subject to noise noise and time delay act simultaneously on real ecological systems the lotka volterra model of symmetric two species competition with noise and time delay was investigated in this paper by means of stochastic simulation we find that i the time delay induces the densities of the two species to periodically oscillate synchronously ii the stationary probability distribution function of the two species densities exhibits a transition from multiple to single stability as the delay time increases iii the characteristic correlation time for the sum of the two species densities squared exhibits a nonmonotonic behavior as a function of delay time our results have the implication that the combination of noise and time delay could provide an efficient tool for understanding real ecological systems

cross correlated bounded noises induced the population extinction and enhancement of stability in a population growth model abstract the bounded noises as a new typed non gaussian noise have important practical significance in this paper the steady state and transient dynamical properties of the population growth model subjected to the cross correlated sine wiener bounded noise are investigated based on the approximate fokker planck equation the analytical expressions of stationary probability distribution function and extinction time of the population growth model are obtained the results show that the bounded noise intensity and the cross correlated bounded noise intensity can cause the population extinction in particular the population density are sensitive to the environmental fluctuation multiplicative noise and the self correlated time on the other hand the effects of noise intensities on the extinction time are discussed the results indicate that the extinction time can be decreased with the intrinsic stochasticity additive noise and the self correlated time increasing for the positive correlated case the result is similar to the additive noise and the self correlated time however for the negative correlated case the extinction time can be increased with the intensity increasing in particular the environmental fluctuation multiplicative noise causes noise enhanced stability for the negative correlated case and the extinction time firstly decreases for the small environmental fluctuation and then increases for the large environmental fluctuation for the positive correlated case the numerical results are in basic agreement with the theoretical predictions

shot noise in the leaky integrate and fire neuron we study the influence of noise on the transmission of temporal information by a leaky integrate and fire neuron using the theory of shot noise the model includes a finite number of synapses and has a membrane potential variance de facto modulated by the input signal the phenomenon of stochastic resonance in spiking neurons is analytically exhibited using an inhomogeneous poisson process model of the spike trains and links with the traditional ornstein uhlenbeck process obtained by a diffusion approximation are given it is shown that the modulated membrane potential variance inherent to the model gives better signal processing capabilities than the diffusion approximation

classical locally finite tits chamber systems of rank 3 a chamber system v 9 j zi is over some index set z is a set of chambers together with partitions in z of v if ze z and c e v then bj is the join of all partitions fijzi e z and d c is the element of fij containing c d c is again a chamber system over j with fij restricted to z we say q is connected if d c furthermore 111 is the rank of v the most important examples of chamber systems are those obtained from groups if g is a group b a subgroup of g and xi ie z are subgroups of g containing b then 5 g b xi icl has as chambers the cosets bg g e g two such cosets bg bh being i adjacent if and only if xi g xih then g acts chamber transitively on with kernel b n bg and is connected if and only if g x 1 i e z furthermore each chamber system with transitive automorphism group g can be obtained in this way by setting b g and xi gd cr a rank 2 chamber system u hi fi is called a classical generalized ma gon mq 3 if is isomorphic to g b pi p where g is an essentially simple rank 2 group of lie type in the sense of cl b is a bore1 subgroup and p pj are the two maximal parabolic subgroups of g containing b here md is given by the relation vu wj wiw g 1 defined by the weyl group of g a rank 2 chamber system is a generalized digon if is isomorphic to v g pin p pi p where pi p are different proper subgroups of g satisfying g pipj pjpi a connected chamber system over z is called a classical tits chamber system if for each ce and i j c z di j c is either a generalized digon or a classical generalized m gon for some mi e n is focally finite if all d c are finite for motivation to consider such classical locally finite tits chamber systems see 15 and 16 if is a classical tits chamber system then the diagram d z is defined in 9 0021 8693 89 3 00

enhancement of stochastic resonance the role of non gaussian noises abstract we have analyzed the phenomenon of stochastic resonance in a double well potential driven by a colored non gaussian noise using a path integral approach we have obtained a consistent markovian approximation that enables us to get through the two state theory analytical expressions for the signal to noise ratio finding an enhancement of this quantity when the system departs from gaussian behavior this finding is supported by extensive numerical simulations we discuss the relation of these results to some experiments in sensory systems

stochastic resonance in a mono stable system with multiplicative and additive noise the stochastic resonance in a biased mono stable system subject to multiplicative and additive noise is investigated based on the adiabatic approximation theory the analytic expression of the signal to noise ratio snr is obtained it is shown that the snr is a non monotonic function of the intensities of the multiplicative and additive noise as well as the parameters of the mono stable system

relaxation dynamics in the presence of pulse multiplicative noise sources with different correlation properties the relaxation dynamics of a system described by a langevin equation with pulse multiplicative noise sources with different correlation properties is considered the solution of the corresponding fokker planck equation is derived for gaussian white noise moreover two pulse processes with regulated periodicity are considered as a noise source the dead time distorted poisson process and the process with fixed time intervals which is characterized by an infinite correlation time we find that the steady state of the system is dependent on the correlation properties of the pulse noise an increase of the noise correlation causes the decrease of the mean value of the solution at the steady state the analytical results are in good agreement with the numerical ones

stochastic multiresonance and correlation time controlled stability for a harmonic oscillator with fluctuating frequency the long time behavior of the first two moments and the correlation function for the output signal of a harmonic oscillator with fluctuating frequency subjected to an external periodic force and an additive thermal noise is considered analytically the colored fluctuations of the oscillator frequency are modeled as a three level markovian noise using the shapiro loginov formula the exact expressions of several stochastic resonance sr characteristics such as the spectral amplification the variance of the output signal the signal to noise ratio and the sr gain have been calculated the nonmonotonic dependence of the sr characteristics versus the noise parameters as well as versus the input signal frequency and also the conditions for the appearance of energetic instability are analyzed in particular the multiresonancelike behavior of the variance and the signal to noise ratio as functions of the noise correlation time are observed and the connection between the occurrence of energetic instability and the phenomenon of stochastic multiresonance is established some unexpected effects such as the hypersensitive response of the spectral amplification to small variations of the noise amplitude encountered in the case of a large flatness of the colored noise are also discussed

stochastic resonance in a trapping overdamped monostable system the response of a trapping overdamped monostable system to a harmonic perturbation is analyzed in the context of stochastic resonance phenomenon we consider the dynamics of a brownian particle moving in a piecewise linear potential with a white gaussian noise source based on linear response theory and laplace transform technique analytical expressions of signal to noise ratio snr and signal power amplification spa are obtained we find that the snr is a nonmonotonic function of the noise intensity while the spa is monotonic theoretical results are compared with numerical simulations

saturated fusion systems with parabolic families abstract let g be a group a finite p subgroup s of g is a sylow p subgroup if every finite p subgroup of g is conjugate to a subgroup of s in this paper we examine the relations between the fusion system over s which is given by conjugation in g and a certain chamber system c on which g acts chamber transitively with chamber stabilizer n g s next we introduce the notion of a fusion system with a parabolic family and we show that a chamber system can be associated to such a fusion system we determine some conditions the chamber system has to fulfill in order to assure the saturation of the underlying fusion system we give an application to fusion systems with parabolic families of classical type

the loudness of sounds whose spectra differ at the two ears moore and glasberg 2007 j acoust soc am 121 1604 1612 developed a model for predicting the loudness of dichotic sounds the model gave accurate predictions of data in the literature except for an experiment of zwicker and zwicker 1991 j acoust soc am 89 756 764 in which sounds with non overlapping spectra were presented to the two ears the input signal was noise with the same intensity in each critical band bark this noise was filtered into 24 bands each 1 bark wide the bands were then grouped into wider composite bands consisting of 1 2 4 or 12 successive sub bands and each composite band was presented either to one ear or the other loudness estimates obtained using a scaling procedure decreased somewhat as the number of composite bands increased and their width decreased but the predictions of the model showed the opposite pattern this experiment was similar to that of zwicker and zwicker except that the widths of the bands were based on the erb n number scale and a loudness matching procedure was used the pattern of the results was consistent with the predictions of the model showing an increase in loudness as the number of composite bands increased and their spacing decreased

pattern transitions and complexity for a nonlocal logistic map abstract we examine the pattern solutions in a generalized nonlocal logistic map that includes spatial kernels in both growth and competition terms we show that this map includes as a particular case the nonlocal fisher kolmogorov equation and we demonstrate the existence of three kinds of stationary nonlinear solutions one uniform one cosine type that we refer to as wavelike solution and another in the form of gaussian we also obtain analytical expressions that describe the nonlinear pattern behavior in the system and we establish the stability criterion we define thermodynamics quantities such as entropy and the order parameter based on this the pattern no pattern and pattern pattern transitions are properly analyzed we show that these pattern solutions may be related to the recently observed peak adding phenomenon in nonlinear optics

self regulation mechanism of an ecosystem in a non gaussian fluctuation regime we study a dynamical model for an ecological network of many interacting species we consider a malthus verhulst type of self regulation mechanism in the framework of the mean field theory we study the nonlinear relaxation in three different cases a towards the equilibrium state b towards the absorbing barrier c at the critical point we obtain asymptotic behavior in all different cases for the time average of the process the dynamical behavior of the system in the limit of infinitely many interacting species is investigated in the stability and instability conditions and theoretical results are compared with numerical simulations textcopyright 1996 the american physical society

interaural correlation and the binaural summation of loudness the effect of interaural correlation on the loudness for noisebands was measured using a loudness matching task in naive listeners the task involved a sequence of loudness comparisons for which the intensity of one stimulus in a given comparison was varied using a one up one down adaptive rule the task provided an estimate of the level difference in decibels for which two stimulus conditions have equal loudness giving measures of loudness difference in equivalent decibel units dbequiv concurrent adaptive tracks measured loudness differences between 1 0 and 1 and between these binaural stimuli and the monaural case for various noisebands for all noisebands monaural stimuli required approximately 6db higher levels than 1 for equal loudness for most noisebands 1 and 1 were almost equal in loudness with 1 being slightly louder in the majority of measurements while 0 was about 2dbequiv louder than 1 or 1 however noisebands with significant high frequency energy showed smaller differences for 3745 4245hz 0 was only about 0 85dbequiv louder than 1 and for 100 5000hz it was non significantly louder perhaps 0 7dbequiv

stability in a system subject to noise with regulated periodicity the stability of a simple dynamical system subject to multiplicative one side pulse noise with hidden periodicity is investigated both analytically and numerically the stability analysis is based on the exact result for the characteristic functional of the renewal pulse process the influence of the memory effects on the stability condition is analyzed for two cases i the dead time distorted poissonian process and ii the renewal process with pareto distribution we show that for fixed noise intensity the system can be stable when the noise is characterized by high periodicity and unstable at low periodicity

parabolic systems the gf 3 case parabolic systems defined over gf q have been classified by timmesfeld for q 4 and by stroth for q 2 see references we deal with the case q 3

an application of mean escape time and metapopulation on forestry catastrophe insurance abstract a forestry catastrophe insurance model due to forestry pest infestations and disease epidemics is developed by employing metapopulation dynamics and statistics properties of mean escape time met the probability of outbreak of forestry catastrophe loss and the catastrophe loss payment time with met are respectively investigated forestry loss data in china is used for model simulation experimental results are concluded as 1 the model with analytical results is shown to be a better fit 2 within the condition of big area of patches and structure of patches high system factor low extinction rate high multiplicative noises and additive noises with a high cross correlated strength range an outbreak of forestry catastrophe loss or catastrophe loss payment due to forestry pest infestations and disease epidemics could occur 3 an optimal catastrophe loss payment time met due to forestry pest infestations and disease epidemics can be identified by taking proper value of multiplicative noises and limits the additive noises on a low range of value and cross correlated strength at a high range of value

trichotomous noise controlled signal amplification in a generalized verhulst model abstract the long time limit of the probability distribution and statistical moments for a population size are studied by means of a stochastic growth model with generalized verhulst self regulation the effect of variable environment on the carrying capacity of a population is modeled by a multiplicative three level markovian noise and by a time periodic deterministic component exact expressions for the moments of the population size have been calculated it is shown that an interplay of a small periodic forcing and colored noise can cause large oscillations of the mean population size the conditions for the appearance of such a phenomenon are found and illustrated by graphs implications of the results on models of symbiotic metapopulations are also discussed particularly it is demonstrated that the effect of noise generated amplification of an input signal gets more pronounced as the intensity of symbiotic interaction increases

system size stochastic resonance in a model for opinion formation we study a model for opinion formation which incorporates three basic ingredients for the evolution of the opinion held by an individual imitation influence of fashion and randomness we show that in the absence of fashion the model behaves as a bistable system with random jumps between the two stable states with a distribution of times following kramer s law we also demonstrate the existence of system size stochastic resonance by which there is an optimal value for the number of individuals n for which the average opinion follows better the fashion

interaural correlation and loudness when the same sound is presented to both ears rather than to just one a phenomenon called binaural summation occurs in which the overall loudness is greater than when either ear is individually stimulated the present investigation focused on the effect of interaural correlation on this phenomenon an adaptive matching paradigm was used to measure the difference in intensity between monotic diotic uncorrelated and anticorrelated bands of noise needed to equate them in loudness the results for 460 540 hz bands showed 1 consistent with binaural summation diotic noise was matched to monotic noise that was 4 6 db more intense and 2 uncorrelated noise was matched to diotic noise that was 2 0 db more intense anticorrelated and diotic noises did not differ significantly in intensity when matched in loudness similar results were observed for 100 900 hz bands 1 was extended to 6 5 db and 2 remained at 2 0 db but anticorrelated noise was now matched to diotic noise that was 1 0 db more intense f

wavelet transform analysis of time series generated by the stimulated neuronal activity abstract we have studied the stimulated discharge dynamics of fusimotor neurons by applying the wavelet transform technique and by adopting that the neuronal discharge dynamics is manifested by the random time series of interspike intervals we found two different power law type behaviors along interspike intervals isi time scale which implies existence of two different types of neuronal noise which are separated by a crossover region our results reveal that complex neuronal dynamics in the presence of external stimulation is manifested with long range correlated noise in the region before the crossover on the isi time scale

a pushing up result and some consequences for the embedding of 2 constrained subgroups let m m1 be maximal 2 locai subgroups of some finite group g with o g 1 satisfying qi o mi f mi for i 0 1 is it possible in this situation that q1 qo the bulk of the proof of l consists of showing that there exists no k group g of characteristic 2 type satisfying these and certain non generational conditions for mi which by results of g seitz strongly restrict the structure of mr if one tries to consider this problem more generally one realizes that it splits naturally into two cases

the availability of logical operation induced by dichotomous noise for a nonlinear bistable system instead of a continuous system driven by gaussian white noise logical stochastic resonance will be investigated in a nonlinear bistable system with two thresholds driven by dichotomous noise which shows a phenomenon different from gaussian white noise we can realize two parallel logical operations by simply adjusting the values of these two thresholds besides to quantify the reliability of obtaining the correct logic output we numerically calculate the success probability and effects of dichotomous noise on the success probability are observed these observations show that the reliability of realizing logical operation in the bistable system can be improved through optimizing parameters of dichotomous noise

stochastic resonance and noise delayed extinction in a model of two competing species abstract we study the role of the noise in the dynamics of two competing species we consider generalized lotka volterra equations in the presence of a multiplicative noise which models the interaction between the species and the environment the interaction parameter between the species is a random process which obeys a stochastic differential equation with a generalized bistable potential in the presence of a periodic driving term which accounts for the environment temperature variation we find noise induced periodic oscillations of the species concentrations and stochastic resonance phenomenon we find also a nonmonotonic behavior of the mean extinction time of one of the two competing species as a function of the additive noise intensity

exact probability distribution for the bernoulli malthus verhulst model driven by a multiplicative colored noise we report an exact result for the calculation of the probability distribution of the bernoulli malthus verhulst model driven by a multiplicative colored noise we study the conditions under which the probability distribution of the malthus verhulst model can exhibit a transition from a unimodal to a bimodal distribution depending on the value of a critical parameter also we show that the mean value of x t in the latter model always approaches asymptotically the value 1

dynamics of two competing species in the presence of levy noise sources we consider a lotka volterra system of two competing species subject to multiplicative stable levy noise the interaction parameter between the species is a random process which obeys a stochastic differential equation with a generalized bistable potential in the presence both of a periodic driving term and an additive stable levy noise we study the species dynamics which is characterized by two different regimes exclusion of one species and coexistence of both we find quasiperiodic oscillations and stochastic resonance phenomenon in the dynamics of the competing species analyzing the role of the levy noise sources

theory of frequency and phase synchronization in a rocked bistable stochastic system we investigate the role of noise in the phenomenon of stochastic synchronization of switching events in a rocked overdamped bistable potential driven by white gaussian noise the archetype description of stochastic resonance we present an approach to the stochastic counting process of noise induced switching events starting from the markovian dynamics of the nonstationary continuous particle dynamics one finds upon contraction onto two states a non markovian renewal dynamics a proper definition of an output discrete phase is given and the time rate of change of its noise average determines the corresponding output frequency the phenomenon of noise assisted phase synchronization is investigated in terms of an effective instantaneous phase diffusion the theory is applied to rectangular shaped rocking signals versus increasing input noise strengths in this case for an appropriate choice of the parameter values the system exhibits a noise induced frequency locking accompanied by a very pronounced suppression of the phase diffusion of the output signal precise numerical simulations corroborate very favorably our analytical results the novel theoretical findings are also compared with prior ones

prediction of absolute thresholds and equal loudness contours using a modified loudness model the loudness model described by moore et al j audio eng soc 45 224 240 1997 forms the basis for a recent ansi standard for the calculation of the loudness of steady sounds however the model does not give accurate predictions of the absolute thresholds published in a recent iso standard here it is described how the assumed middle ear transfer function in the model can be modified to give more accurate absolute threshold predictions the modified model also gives reasonably accurate predictions of the equal loudness contours published in a recent iso standard

stochastic dynamic balance of a bi stable vegetation model with pulse control abstract the stochastic vegetation model with the pulse control is established and the related dynamic mechanisms are explored the stationary responses of the system can be detected by the stationary probability density function and the mean vegetation biomass and the transient properties of the system are investigated by the mean first exit time of the attraction basin and the time series of the attractor due to the special discontinuity of the pulse control these indexes are analyzed through numerical simulations alone specially for the uncontrolled case the analytical expressions of the stationary probability density and mean first exit time can be derived and relative errors of the two proposed methods can be ignored as a whole it turns out that the strong environmental disturbance such as the random climate change can influence the vegetation ecosystem balance which can be effectively controlled by the pulse control

relation between optimal nonlinearity and non gaussian noise enhancing a weak signal in a nonlinear system in the study of stochastic resonance it is often mentioned that nonlinearity can enhance a weak signal embedded in noise in order to give a systematic proof of the signal enhancement in nonlinear systems we derive an optimal nonlinearity that maximizes a signal to noise ratio snr the obtained optimal nonlinearity yields the maximum unbiased signal estimation performance which is known in the context of information theory it is found that a linear system is optimal for a gaussian noise but for a non gaussian noise there exist nonlinear systems that can achieve an snr higher than that obtained from linear systems this analysis refers to a system subjected to an additive non gaussian noise with a small signal input

an approach for measuring corporation financial stability by econophysics and bayesian method abstract corporation financial stability was investigated by the method of econophysics and bayesian approach in this paper a stochastic predator prey model was built to describe the corporation financial condition the mean limiting extinction time was proposed to measure the corporation financial stability the model parameters were estimated by using bayesian approach with real corporation financial data experimental results show that i an increase of system risk corresponds to a decrease of the corporation stability ii the optimal initial financial condition enhances the corporation stability to its maximum extent iii under the optimal initial financial condition the optimal system parameters and system risk strength can be observed

different delays induced regime shifts in a stochastic insect outbreak dynamics abstract considering time delays in the deterministic and stochastic forces we construct stochastic delayed differential equations to investigate the regime shifts in an insect ecosystem the stationary probability distribution spd and mean first passage time mfpt are obtained respectively our main results show i the multiplicative noise positive cross correlation noise between two noises and time delays can induce the regime shifts from the boom outbreak state to the bust one but the additive noise and negative cross correlation can induce the regime shifts from the bust outbreak state to the boom one ii for the negative cross correlation the mfpt as a function of noise strengths exhibits one maximum which shows the characteristic of the noise delayed switching for the boom outbreak state but for the no cross correlation or positive cross correlation the mfpt decreases with the noise strengths iii two different types of time delays play same roles on the maximal mfpt with additive noise and play opposite roles on the maximal mfpt with multiplicative noise the mechanisms for noises and delays induced regime shifts between two states can be explained physically through the effective potential of ecological model

colored noise induced discontinuous transitions in symbiotic ecosystems a symbiotic ecosystem is studied by means of the lotka volterra stochastic model using the generalized verhulst self regulation the effect of fluctuating environment on the carrying capacity of a population is taken into account as dichotomous noise the study is a follow up of our investigation of symbiotic ecosystems subjected to three level trichotomous noise r mankin a ainsaar a haljas and e reiter phys rev e 65 051108 2002 relying on the mean field theory an exact self consistency equation for stationary states is derived in some cases the mean field exhibits hysteresis as a function of noise parameters it is established that random interactions with the environment can cause discontinuous transitions the dependence of the critical coupling strengths on the noise parameters is found and illustrated by phase diagrams predictions from the mean field theory are compared with the results of numerical simulations our results provide a possible scenario for catastrophic shifts of population sizes observed in nature