transparent acoustic source condition applied to the euler equations it can be concluded from the present calculations that the transparent source model proposed here is useful to numerically simulate an acoustic source in the computational domain that is located far downstream thus it is possible to simulate a complex acoustic problem such as the reflection and transmission of an incident wave

a time domain method for duct acoustics this paper reports the development of a time accurate method for prediction of acoustics in lined ducts the multi dimensional euler equations are dimensionally split into a system of uni directional simple wave equations which are discretized and solved using an implicit compact high order finite difference scheme the split equations are closed and coupled through the concept of impedance at domain boundaries time domain extensions of the impedance boundary condition and their efficient implementation are introduced for broadband and monotone waves the method is benchmarked by the modal solution of a monopole in the lined duct and used to investigate wall interference on the acoustic fields of realistic sources excellent agreement is found in the comparison with classical solutions and the discrepancy found in the comparison with experiment is ascribable to experimental uncertainty

multigrid acceleration of a high resolution computational aeroacoustics scheme a multigrid method is applied to a fourth order accurate spatially and temporally nite difference runge kutta time marching scheme thisisusedto solvethenonlineareulerequationsfortheef cientprediction ofnoise radiation from turbofan engine inlets this noise prediction approach computes a steady state solution rst and thenasourceisturnedonandtheunsteadysolutioniscomputed thishastheadvantageofusingthesamenumerical scheme to evaluate the residuals of the governing equations in both the steady and unsteady calculations which meansthatthesteady statesolutionissmoothand nonumericalerrorscontaminatetheacousticsolution thehigh

a new norm relaxed method of strongly sub feasible direction for inequality constrained optimization combining the norm relaxed method of feasible direction mfd with the idea of strongly sub feasible direction method we present a new convergent algorithm with arbitrary initial point for inequality constrained optimization at each iteration the new algorithm solves one direction finding subproblem dfs which always possesses a solution some good properties of the new algorithm are that it can unify automatically the operations of initialization phase i and optimization phase ii and the number of the functions satisfying the inequality constrains is nondecreasing particularly a feasible direction of descent can be obtained by solving dfs whenever the iteration point gets into the feasible set under some mild assumptions without the linear independence the global and strong convergence of the algorithm can be obtained

broadband time domain impedance models the modeling of a set of impedance values given either experimentally or heuristically for implementation as a time domain impedance equivalent boundary condition tdibc is discussed it is shown that impedance as defined by the reflection of plane harmonic waves when extended for broadband time domain applications can correspond to mathematically feasible but physically unacceptable noncausal reflection processes given a set of impedance data on a finite positive and real frequency range it is possible to construct causal time domain models that render efficient implementation of tdibc for broadband reflections however these models defined by measurement of harmonic waves may not be valid for the reflection of impulses for which measurement of transient reflections is warranted

statistical spectrum of the non markovity parameter for simple model systems the spectra of the non markovity parameter for three model systems are found an ideal gas weakly non ideal gas and a medium in hydrodynamic limits it is shown that the non markovian effects play the dominant role in all three above mentioned cases the effects of molecular memory are connected with the statistical appearance of intermolecular interactions in statistical systems

modified newton methods for solving a semismooth reformulation of monotone complementarity problems in this paper we propose a newton type method for solving a semismooth reformulation of monotone complementarity problems in this method a direction finding subproblem which is a system of linear equations is uniquely solvable at each iteration moreover the obtained search direction always affords a direction of sufficient decrease for the merit function defined as the squared residual for the semismooth equation equivalent to the complementarity problem we show that the algorithm is globally convergent under some mild assumptions next by slightly modifying the direction finding problem we propose another newton type method which may be considered a restricted version of the first algorithm we show that this algorithm has a superlinear or possibly quadratic rate of convergence under suitable assumptions finally some numerical results are presented

a new qp free globally convergent locally superlinearly convergent algorithm for inequality constrained optimization in this paper we propose a new qp free method which ensures the feasibility of all iterates for inequality constrained optimization the method is based on a nonsmooth equation reformulation of the kkt optimality condition by using the fischer burmeister nonlinear complementarity problem function the study is strongly motivated by recent successful applications of this function to the complementarity problem and the variational inequality problem the method we propose here enjoys some advantages over similar methods based on the equality part of the kkt optimality condition for example without assuming isolatedness of the accumulation point or boundedness of the lagrangian multiplier approximation sequence we show that every accumulation point of the iterative sequence generated by this method is a kkt point if the linear independence condition holds and if the second order sufficient condition and the strict complementarity condition hold the method is superlinearly convergent some preliminary numerical results indicate that this new qp free method is quite promising

intensity approximation of random fluctuation in complex systems abstract the markov and non markov processes in complex systems are examined with the help of dynamical information shannon entropy method here we consider the essential role of two mutually independent channels of entropy involving creation of correlation and annihilation of correlation the developed method has been used to analyze the intensity fluctuation of the complex systems of various nature in psychology to analyze numerical and pattern short time human memory to study the effect of stress on the parameters of the dynamical taping test and in cardiology to analyze the random dynamics of rr intervals in human ecg s and to diagnose various diseases of human cardiovascular systems the received results show that the application of intensity approximation allows to improve essentially the diagnostics of parameters in the evolution of human dynamic states

design of broadband time domain impedance boundary conditions using the oscillatory diffusive representation of acoustical models a methodology to design broadband time domain impedance boundary conditions tdibcs from the analysis of acoustical models is presented the derived tdibcs are recast exclusively as first order differential equations well suited for high order numerical simulations broadband approximations are yielded from an elementary linear least squares optimization that is for most models independent of the absorbing material geometry this methodology relies on a mathematical technique referred to as the oscillatory diffusive or poles and cuts representation and is applied to a wide range of acoustical models drawn from duct acoustics and outdoor sound propagation which covers perforates semi infinite ground layers as well as cavities filled with a porous medium it is shown that each of these impedance models leads to a different tdibc comparison with existing numerical models such as multi pole or extended helmholtz resonator provides insights into their suitability additionally the broadly applicable fractional polynomial impedance models are analyzed using fractional calculus

quantification of heart rate variability by discrete nonstationary non markov stochastic processes we develop the statistical theory of discrete nonstationary non markov random processes in complex systems the objective of this paper is to find the chain of finite difference non markov kinetic equations for time correlation functions tcf in terms of nonstationary effects the developed theory starts from careful analysis of time correlation through nonstationary dynamics of vectors of initial and final states and nonstationary normalized tcf using the projection operators technique we find the chain of finite difference non markov kinetic equations for discrete nonstationary tcf and for the set of nonstationary discrete memory functions mf s the last one contains supplementary information about nonstationary properties of the complex system on the whole another relevant result of our theory is the construction of the set of dynamic parameters of nonstationarity which contains some information of the nonstationarity effects the full set of dynamic spectral and kinetic parameters and kinetic functions tcf short mf s statistical spectra of non markovity parameter and statistical spectra of nonstationarity parameter has made it possible to acquire the in depth information about discreteness non markov effects long range memory and nonstationarity of the underlying processes the developed theory is applied to analyze the long time holter series of rr intervals of human ecg s we had two groups of patients the healthy ones and the patients after myocardial infarction in both groups we observed effects of fractality standard and restricted self organized criticality and also a certain specific arrangement of spectral lines the received results demonstrate that the power spectra of all orders n 1 2 mf m n t exhibit the neatly expressed fractal feat ures we have found out that the full sets of non markov discrete and nonstationary parameters can serve as reliable and powerful means of diagnosis of the cardiovascular system states and can he used to distinguish healthy data from pathologic data

on the robust flexible and consistent implementation of time domain impedance boundary conditions for compressible flow simulations the accurate simulation of compressible flows requires the appropriate modeling of the reflection of acoustic waves at the boundaries in the present study we discuss time domain impedance boundary conditions tdibc the formulation proposed allows to impose a desired reflection coefficient at the inflow and outflow boundaries our formulation is an extension of the well known navier stokes characteristic boundary conditions the frequency dependent reflections at the boundaries are implemented with a state space model in the time domain we provide a comprehensive discussion on how such state space models can be constructed and interpreted this discussion shows that the state space description allows a robust and flexible implementation it allows to consider complex reflection coefficients and account for non constant cfd time steps in a straight forward manner furthermore we prove analytically and demonstrate numerically that the formulation proposed is consistent i e the formulation ensures that the flow simulation exhibits the reflection coefficient imposed accurately as long as the waves impinging on the boundary are plane and it prohibits drift of the mean flow variables finally the boundary conditions are tested successfully for laminar and turbulent flows

frequency domain prediction of turbofan noise radiation this paper describes a frequency domain numerical method for predicting noise radiation from ducted fans including acoustic treatment and non uniform background flow effects the method solves the euler equations linearized about a mean flow in the frequency domain a pseudo time derivative term is added to the frequency domain equations so that a time marching technique can be employed to drive the acoustic field to steady state explicitly this approach makes distributed parallel computing more viable for equations of this type and will allow for future use of well known convergence acceleration techniques such as multigrid to obtain the solutions efficiently simulations of the jt15d static test inlet are performed including the effects of liners and the results are compared with experimental data a generic engine geometry is used for demonstrating further the prediction capability of the code calculating the attenuation effects of different liner impedances and liner installation locations on the radiated sound fields

long range memory and non markov statistical effects in human sensorimotor coordination in this paper the non markov statistical processes and long range memory e ects in human sensorimotor coordination are investigated the theoretical basis of this study is the statistical theory of non stationary discrete non markov processes in complex systems phys rev e 62 6178 2000 the human sensorimotor coordination was experimentally studied by means of standard dynamical tappingtest on the g roup of 32 youngpeoples with tap numbers up to 400 this test was carried out separately for the right and the left hand according to the degree of domination of each brain hemisphere the numerical analysis of the experimental results was made with the help of power spectra of the initial time correlation function the memory functions of low orders and the 7rst three points of the statistical spectrum of non markovity parameter our observations demonstrate that with the regard to results of the standard dynamic tapping test it is possible to divide all examinees into 7ve di erent dynamic types we have introduced the con ict coe cient to estimate quantitatively the order disorder e ects underlying life systems the last one re ects the existence of disbalance between the nervous and the motor human coordination the suggested classi7cation of the neurophysiological activity represents the dynamic generalization of the well known neuropsychological types and provides the new approach in a modern neuropsychology c

a strongly sub feasible primal dual quasi interior point algorithm for nonlinear inequality constrained optimization in this paper a primal dual quasi interior point algorithm for inequality constrained optimization problems is presented at each iteration the algorithm solves only two or three reduced systems of linear equations with the same coefficient matrix the algorithm starts from an arbitrarily initial point then after finite iterations the iteration points enter into the interior of the feasible region and the objective function is monotonically decreasing furthermore the proposed algorithm is proved to possess global and superlinear convergence under mild conditions including a weak assumption of positive definiteness finally some encouraging preliminary computational results are reported

possibility between earthquake and explosion seismogram differentiation by discrete stochastic non markov processes and local hurst exponent analysis the basic scientific point of this paper is to draw the attention of researchers to new possibilities of differentiation of similar signals having different nature one example of such kinds of signals is presented by seismograms containing recordings of earthquakes eq s and technogenic explosions te s eq s are among the most dramatic phenomena in nature we propose here a discrete stochastic model for possible solution of a problem of strong eq forecasting and differentiation of te s from the weak eq s theoretical analysis is performed by two independent methods by using statistical theory of discrete non markov stochastic processes phys rev e 62 6178 2000 and the local hurst exponent the following earth states have been considered among them before ib and during i strong eq during weak eq ii and during te iii and in a calm state of earth s core iv the estimation of states i ii and iii has been made on the particular examples of turkey 1999 eq s state iv has been taken as an example of earth s state before underground te time recordings of seismic signals of the first four dynamic orthogonal collective variables six various planes of phase portrait of four dimensional phase space of orthogonal variables and the local hurst exponent have been calculated for the dynamic analysis of states of systems i char21 iv the analysis of statistical properties of seismic time series i char21 iv has been realized with the help of a set of discrete time dependent functions time correlation function and first three memory functions their power spectra and the first three points in the statistical spectrum of non markovity parameters in all systems studied we have found a bizarre combination of the following spectral characteristics the fractal frequency spectra adjustable by phenomena of usual and restricted self organized criticality spectra of white and color noises and unusual alternation of markov and non markov effects of long range memory detected earlier j phys a 27 5363 1994 only for hydrodynamic systems our research demonstrates that discrete non markov stochastic processes and long range memory effects play a crucial role in the behavior of seismic systems i char21 iv the approaches permitting us to obtain an algorithm of strong eq forecasting and to differentiate te s from weak eq s have been developed

fundamental problems with the model of uniform flow over acoustic linings abstract the walls of ducts containing flow are often acoustically lined in order to reduce sound many simple models of acoustic linings assume the lining to be linear and locally reacting examples considered here include the three parameter mass spring damper helmholtz resonator and enhanced helmholtz resonator models all of these models have been found to have stability issues with uniform mean grazing flow and there has been some confusion over the existence of hydrodynamic instability surface waves over such linings mathematically the standard proven briggs bers stability analysis is not applicable computationally the hydrodynamic modes are routinely ignored in the frequency domain and instabilities filtered out in the time domain this confusion also causes significant problems for mode matching green functions and scattering analyses in this paper it is shown that any situation not capable of being analysed using the briggs bers criterion is illposed and that this is the root cause of the confusion over hydrodynamic instabilities a large class of lining models including all those mentioned above are shown to be illposed with uniform mean flow an explanation is given of the effects of this illposedness in practice and it is argued that illposed models should not be used an alternative stability criterion to briggs bers has been occasionally used in the literature this alternative criterion involving analytic continuation to purely imaginary frequencies was recently christened the crighton leppington stability criterion however this stability criterion is incorrect and several counter examples are given here

time domain numerical simulation of a flow impedance tube an efficient method has been developed for the application of the surface acoustic impedance condition in time domain solutions of aeroacoustic problems such as the broadband frequency simulation of a flow impedance tube the basis for this method is the standard impedance condition stated in the frequency domain as the particle displacement continuity equation the development of the time domain impedance condition follows the relations among the frequency z and discrete time domains and a rational function representation of the impedance in thez domain the resultant impedance condition consists of finite infinite impulse response type digital filter operations in the time domain which is very suitable to computational aeroacoustics algorithms this paper describes the present approach and discusses the time domain numerical simulations of the nasa langley flow impedance tube with a constant depth ceramic tubular liner both single and broadband frequency simulations are performed excellent agreement is shown with experimental data at various frequencies and flow conditions

acoustics in variable area duct finite element and finite difference comparisons to experiment plane wave sound propagation without flow in a rectangular duct with a converging diverging area variation is studied experimentally and theoretically the area variation was of sufficient magnitude to produce large reflections and induce modal scattering the rms pressure and phase angle on both the flat and curved surface were measured and tabulated the steady state finite element theory of astley and eversman and the transient finite difference theory of white are in good agreement with the data it is concluded that numerical finite difference and finite element theories appear ideally suited for handling duct propagation problems which encounter large area variations f h j k l p p p0 s t u

a controllable canonical form implementation of time domain impedance boundary conditions for broadband aeroacoustic computation a new method which can be effectively and efficiently applied in the simulations of broadband noise problems is proposed for time domain impedance boundary condition implementations by using the so called controllable canonical form that is well known in linear system usually the impedance boundary condition can be defined in frequency domain as a rational polynomial function with poles in the negative half of the complex plane to guarantee stability otherwise causality might be violated in the corresponding time domain implementation to address this issue various methodologies have been proposed previously that usually lead to complicated polynomials whose numerical implementations are often indirect and intricate the proposed method with a controllable canonical form on the other hand directly transforms the frequency domain transfer function a quotient of rational polynomials to an equivalent state space model which consists of a series of first order ordinary differential equations that can be numerically implemented in a straightforward way the proposed method is demonstrated by using two benchmark problems a two dimensional gaussian pulse propagating in a uniform flow with a lined wall and the test cases from the nasa langley grazing incidence tube experiments good agreements demonstrate the potential of the proposed computational method

stochastic dynamics of time correlation in complex systems with discrete time in this paper we present the concept of description of random processes in complex systems with discrete time it involves the description of kinetics of discrete processes by means of the chain of finite difference non markov equations for time correlation functions tcfs we have introduced the dynamic time dependent information shannon entropy s i t where i 0 1 2 3 ellipsis as an information measure of stochastic dynamics of time correlation i 0 and time memory i 1 2 3 ellipsis the set of functions s i t constitute the quantitative measure of time correlation disorder i 0 and time memory disorder i 1 2 3 ellipsis in complex system the theory developed started from the careful analysis of time correlation involving dynamics of vectors set of various chaotic states we examine two stochastic processes involving the creation and annihilation of time correlation or time memory in details we carry out the analysis of vectors dynamics employing finite difference equations for random variables and the evolution operator describing their natural motion the existence of tcf results in the construction of the set of projection operators by the usage of scalar product operation harnessing the infinite set of orthogonal dynamic random variables on a basis of gram shmidt orthogonalization procedure tends to creation of infinite chain of finite difference non markov kinetic equations for discrete tcfs and memory functions mfs the solution of the equations above thereof brings to the recurrence relations between the tcf and mf of senior and junior orders this offers new opportunities for detecting the frequency spectra of power of entropy function s i t for time correlation i 0 and time memory i 1 2 3 ellipsis the results obtained offer considerable scope for attack on stochastic dynamics of discrete random processes in a complex systems application of this technique on the analysis of stochastic dynamics of rr intervals from human ecg s shows convincing evidence for a non markovian phenomemena associated with a peculiarities in short and long range scaling this method may be of use in distinguishing healthy from pathologic data sets based in differences in these non markovian properties

efficient implementation of tam and auriault s time domain impedance boundary condition a new and efficient time domain implementation is proposed for the impedance model originally introduced by tam and auriault tam c k w and auriault l time domain impedance boundary conditions for computational aeroacoustics aiaa journal vol 34 no 5 may 1996 pp 917 923 in the frequency domain the pressure can be calculated from the product of the impedance with the normal velocity in the time domain a convolution is needed which may become a costly operation present solutions for this problem involve either a full convolution and storage of a time history of data or a translation of the frequency domain models to time domain formulations involving time derivatives the former approach is very costly in terms of memory and cpu time the latter makes the implementation discretization specific and vulnerable to stability issues a new formulation based on recursive convolution results in an efficient implementation that stores only one accumulator which can be updated at each time step with minimal addition and multiplication it allows for the exact representation of the impedance at a given frequency the formulation is validated by a comparison with the measurement data from the nasa langley grazing flow impedance tube the simulations are performed by introducing a plane wave at a single frequency in the tube and this is done for six frequencies and five different mean flow speeds

a generalized super memory gradient projection method of strongly sub feasible directions with strong convergence for nonlinear inequality constrained optimization in this work combining the properties of the generalized super memory gradient projection methods with the ideas of the strongly sub feasible directions methods we present a new algorithm with strong convergence for nonlinear inequality constrained optimization at each iteration the proposed algorithm can sufficiently use the information of the previous t steps iterations to generate a new iterative point particularly the intervals of parameters in the super memory gradient projection direction are adjustable the main properties of the new algorithm are described as follows i the improving super memory gradient projection direction is a combination of the generalized gradient projection and the t steps super memory gradients which include both the previous t steps search directions and gradients moreover only the gradients associated with a generalized active constrained set are dealt with rather than the gradients of all constraints ii the initial point can be chosen arbitrarily and at each iteration the number of the functions satisfying the inequality constraints is nondecreasing especially once a feasible iteration is obtained then the subsequent iterations are also feasible iii under suitable assumptions it possesses global and strong convergence finally some preliminary numerical results show that the proposed algorithm is promising

inflow outflow boundary conditions for two dimensional acoustic waves in channels with flow an analysis of the number and form of the required inflow outflow boundary conditions for the full two dimensional time dependent nonlinear acoustic system in subsonic mean flow is performed the analysis is performed in a rectangular channel with rigid walls and is extendable to more complicated geometries and wall conditions the explicit predictor corrector method of maccormack is used to integrate the acoustic system coupled with the derived boundary conditions the methodology is tested on both uniform and sheared mean flows with plane and nonplanar sources

possible generalization of boltzmann gibbs statistics with the use of a quantity normally scaled in multifractals a generalized form is postulated for entropy namelys q k 1 i 1 w p i q q 1 whereq characterizes the generalization andp i are the probabilities associated withw microscopic configurations w the main properties associated with this entropy are established particularly those corresponding to the microcanonical and canonical ensembles the boltzmann gibbs statistics is recovered as theq 1 limit

dynamics of the information entropy in random processes abstract the problem of the description of temporal evolution of the random variables in terms of the information shannon entropy of correlation processes has been considered the influence and important role of the two mutually dependent channels of the entropy alternation correlation creation or the generation of correlations and anti correlation decay or the annihilation of correlation have been discussed the method developed is used for the analysis of chaotic dynamics of the long range fluctuation in the short time human memory

stabilization of time domain acoustic boundary element method for the interior problem with impedance boundary conditions the time domain boundary element method bem is associated with numerical instability that typically stems from the time marching scheme in this work a formulation of time domain bem is derived to deal with all types of boundary conditions adopting a multi input multi output infinite impulse response structure the fitted frequency domain impedance data are converted into a time domain expression as a form of an infinite impulse response filter which can also invoke a modeling error in the calculation the response at each time step is projected onto the wave vector space of natural radiation modes which can be obtained from the eigensolutions of the single iterative matrix to stabilize the computation unstable oscillatory modes are nullified and the same decay rate is used for two nonoscillatory modes as a test example a transient sound field within a partially lined parallelepiped box is used within which a point source is excited by an octave band impulse in comparison with the results

time domain impedance boundary conditions for computational aeroacoustics it is an accepted practice in aeroacoustics to characterize the properties of an acoustically treated surface by a quantity known as impedance impedance is a complex quantity as such it is designed primarily for frequency domain analysis time domain boundary conditions that are the equivalent of the frequency domain impedance boundary condition are proposed both single frequency and model broadband time domain impedance boundary conditions are provided it is shown that the proposed boundary conditions together with the linearized euler equations form well posed initial boundary value problems unlike ill posed problems they are free from spurious instabilities that would render time marching computational solutions impossible

parallel computation of forward radiated noise of ducted fans with acoustic treatment forward radiated noise of ducted fans is computed numerically on parallel processors solving the three dimensional time dependent euler equations in body conformed coordinates with a fourth order accurate finite difference runge kutta time integration scheme sound attenuation effects of inlet wall acoustic treatment are included in computations employing a time discrete form of the standard impedance condition a distributed computing approach with domain decomposition is used for integrating the equations in parallel using the message passing interface library routines the abilities of the method are demonstrated with hard and soft wall simulations of the jt15d inlet including flow effects

nonequilibrium statistical operator method in renyi statistics abstract the generalization of the zubarev nonequilibrium statistical operator nso method for the case of renyi statistics is proposed when the relevant statistical operator or distribution function is obtained based on the maximum entropy principle for the renyi entropy the nonequilibrium statistical operator and corresponding generalized transport equations for the reduced description parameters are obtained a consistent description of the kinetic and hydrodynamic processes in a system of interacting particles is considered as an example

dynamical shannon entropy and information tsallis entropy in complex systems abstract in this work we offer a new approach to the concept of the information entropy for the description of the dynamic behaviour of complex systems on the basis of the unification of the known information approach to the shannon entropy submitted in works of authors phys rev e 62 5 2000 6178 physica a 303 2002 427 and generalization of the boltzman gibbs entropy offered by tsallis braz j phys 29 1 1999 1 we have received a new representation of the dynamic information entropy here we present concrete applications of the received equations to the study of complex systems related to the electric signals of ecgs of healthy people and patients with myocardial infarction mi as an example various modifications of the non markovity parameter are also submitted they were received with the help of the new approach to the information entropy we have received detailed information about markov quasi markov and non markov characteristics of the rr interval fluctuations of the ecgs with the help of the chain of zwanzig mori s discrete kinetic equations and dynamical tsallis entropy

numerical study of sound generation due to a spinning vortex pair a numerical approach for the calculation of an acoustic field is applied to the case of a spinning vortex pair to investigate the sound generation by quadrupole sources in unsteady vortical flows based on the unsteady hydrodynamic information from the known incompressible flowfield the perturbed compressible acoustic terms derived from the euler equations are calculated nonreflecting boundary conditions are developed to obtain highly stable solutions calculated results are compared with analytical solutions obtained by the method of matched asymptotic expansions the possibility of predicting the effect of convective mean flow is also tested it is concluded that the sound generated by the quadrupole sources of unsteady vortical flows without a sound generating body or surface can be calculated by using the source terms of hydrodynamic flow fluctuations

time domain numerical computation of noise reduction by diffraction and finite impedance of barriers a new time domain numerical method is presented for the estimation of noise reduction by the diffraction and finite impedance of barriers high order finite difference schemes conventionally used for computational aeroacoustics and time domain impedance boundary conditions are utilized for the development of the time domain method compared with other methods this method can be applied more easily to the problems related to nonlinear noise propagation such as impulsive noise and broadband noise linearized euler equations in cartesian co ordinates are considered and solved numerically straight and t shaped barriers with and without surface admittance are calculated in order to assess the accuracy of this time domain method comparison with the results of sysnoise software ver 5 3 are made there are very good agreements between the results of the present time domain numerical method and the boundary element method of the sysnoise software

a finite element propagation model for extracting normal incidence impedance in nonprogressive acoustic wave fields a propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented the method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function a finite element propagation model is combined with a coarse fine grid impedance plane search technique to extract the impedance of the material results are presented for three different materials for which the impedance is known for each material the input data required for the prediction scheme were computed from modal theory and then contaminated by random error the finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments thus the method developed here provides a means for determining the impedance of materials in a nonprogressive wave environment such as that usually encountered in a commercial aircraft engine and in most laboratory settings

two step method for evolving nonlinear acoustic systems to a steady state a two step method for evolving two dimensional nonlinear acoustic systems with flow to a periodic steady state is presented in the first step of the method the full nonlinear system governing acoustic disturbances is integrated numerically starting with arbitrary initial conditions using the explicit predictor corrector method developed by maccormack in the second step the fourier time transform of the computed field is calculated to determine its frequency components the transient wave field is then filtered from the spectrum and the inverse transform taken to provide an approximation to the steady state wave field this approximate field provides a new initial condition for subsequent iterations on the method the method is tested on a benchmark acoustic problem for which exact steady state solutions are known and on a nonlinear problem for which a steady state solution has not been given before excellent agreement with the benchmark acoustic solution was obtained within four iterations for planar and nonplanar sources convergence to a steady state for the nonlinear problem occurred in six iterations the two step method eliminates the need to develop nonreflecting boundary conditions in order to obtain periodic steady state solutions of two dimension al acoustic problems and is easily extended to any number of spatial dimensions and to other hyperbolic systems the procedure is shown to be numerically stable and may provide the only alternative for obtaining steady state solutions to problems for which nonreflecting boundary conditions are not known or are physically incorrect

a two stage feasible directions algorithm for nonlinear constrained optimization we present a feasible directions algorithm based on lagrangian concepts for the solution of the nonlinear programming problem with equality and inequality constraints at each iteration a descent direction is defined by modifying it we obtain a feasible descent direction the line search procedure assures the global convergence of the method and the feasibility of all the iterates we prove the global convergence of the algorithm and apply it to the solution of some test problems although the present version of the algorithm does not include any second order information like quasi newton methods these numerical results exhibit a behavior comparable to that of the best methods known at present for nonlinear programming

treatment of frequency dependent admittance boundary conditions in transient acoustic finite infinite element models the paper addresses the handling of frequency dependent local admittance boundary conditions in acoustic transient finite infinite element models the proposed approach avoids the evaluation of a convolution integral along the related boundary based on a similar technique developed in an aeroacoustic finite difference context the spatially local boundary condition is rewritten in a discrete form that involves normal accelerations and pressure time derivatives at the current time step and few steps before the incorporation of such a discrete in time boundary condition in a finite infinite element context is addressed the infinite element scheme selected for that purpose relies on the conjugated astley leis formulation implementation aspects cover the handling of frequency dependent boundary conditions along both finite and infinite element edges numerical examples waveguide single source in a half space bounded by an impedance plane diffraction by an acoustically treated screen are presented in order to demonstrate the efficiency of the proposed approach

energy analysis and discretization of nonlinear impedance boundary conditions for the time domain linearized euler equations time domain impedance boundary conditions tdibcs can be enforced using the impeda nce the admittance or the scattering operator this article demonstrates the computational advantage of the last even for nonlinear tdibcs with the linearized euler equations this is achieved by a systematic semi discrete energy analysis of the weak enforcement of a generic nonlinear tdibc in a discontinuous galerkin finite element method in particular the analysis highlights that the sole definition of a discrete model is not enough to fully define a tdibc to support the analysis an elementary physical nonlinear scattering operator is derived and its computational properties are investigated in an impedance tube then the derivation of time delayed broadband tdibcs from physical reflection coefficient models is carried out for single degree of freedom acoustical liners a high order discretization of the derived time local formulation which consists in composing a set of ordinary differential equations with a transport equation is applied to two flow ducts

a new super memory gradient method with curve search rule in this paper we propose a new super memory gradient method with curve search rule for unconstrained optimization problems the method uses previous multi step iterative information and some curve search rules to generate new iterative points at each iteration this makes the new method converge stably and be more suitable for solving large scale optimization problems than other similar methods we analyze the global convergence and convergence rate under some mild conditions numerical experiments show that some new algorithms are available and effective in practical computation

frequency dependent fdtd methods using z transforms the frequency dependent finite difference time domain method fd sup 2 td method has been shown to be capable of correctly calculating electromagnetic propagation through media whose dielectric properties are frequency dependent however as researchers search for more elaborate applications the formulation of the fd sup 2 td methods becomes more complex in this work the mathematics of the fd sup 2 td method is developed using z transform theory this has the advantages of presenting a clearer formulation and allowing researchers to draw on the literature of systems analysis and signal processing disciplines

impedance and its time domain extensions the classical concept of impedance as a means to characterize the ree ectivity and absorption of a surface to the incident waves has always been a complex valued quantity akin to plane harmonic waves and the analysis of their ree ections a new look at this classical quantity irrespective of the type of incident waves is presented it points out that a direct operational inversion of impedance into time domain boundary operators will in general lead to an unstable system whereas the inversion of the corresponding ree ection coefe cient will result in stable easily implementable boundary operators for time domain prediction of wave ree ection it reveals the equivalent pulselike causal process of time convoluting the incident wave into the ree ected wave excellent agreement with analytical solutions derived here and from other sources supports the validity of the approach and demonstrates the accuracy of the implementations

quadratically constraint quadratical algorithm model for nonlinear minimax problems abstract in this paper a quadratically approximate algorithm framework for solving general constrained minimax problems is presented the framework contains the idea of the sequential quadratic programming method the sequential quadratically constrained quadratic programming method norm relaxed method and strong sub feasible method the global convergence of the algorithm framework is obtained under the mangasarian fromovitz constraint qualification mfcq and the conditions for superlinear convergence of the algorithm framework are presented under the mfcq the constant rank constraint qualification crcq as well as the strong second order sufficiency conditions ssosc and quadratic convergence rate is obtained under the mfcq and ssosc

effect of nonstationarities on detrended fluctuation analysis detrended fluctuation analysis dfa is a scaling analysis method used to quantify long range power law correlations in signals many physical and biological signals are noisy heterogeneous and exhibit different types of nonstationarities which can affect the correlation properties of these signals we systematically study the effects of three types of nonstationarities often encountered in real data specifically we consider nonstationary sequences formed in three ways i stitching together segments of data obtained from discontinuous experimental recordings or removing some noisy and unreliable parts from continuous recordings and stitching together the remaining parts a cutting procedure commonly used in preparing data prior to signal analysis ii adding to a signal with known correlations a tunable concentration of random outliers or spikes with different amplitudes and iii generating a signal comprised of segments with different properties e g different standard deviations or different correlation exponents we compare the difference between the scaling results obtained for stationary correlated signals and correlated signals with these three types of nonstationarities we find that introducing nonstationarities to stationary correlated signals leads to the appearance of crossovers in the scaling behavior and we study how the characteristics of these crossovers depend on a the fraction and size of the parts cut out from the signal b the concentration of spikes and their amplitudes c the proportion between segments with different standard deviations or different correlations and d the correlation properties of the stationary signal we show how to develop strategies for preprocessing raw data prior to analysis which will minimize the effects of nonstationarities on the scaling properties of the data and how to interpret the results of dfa for complex signals with different local characteristics

time dependent wave envelope finite difference analysis of sound propagation a transient finite difference wave envelope formulation is presented for sound propagation without steady flow before the finite difference equations are formulated the governing wave equation is first transformed to a form whose solution tends not to oscillate along the propagation direction this transformation reduces the required number of grid points by an order of magnitude physically the transformed pressure represents the amplitude of the conventional sound wave the derivation for the wave envelope transient wave equation and appropriate boundary conditions are presented as well as the difference equations and stability requirements to illustrate the method example solutions are presented for sound propagation in a straight hard wall duct and in a two dimensional straight soft wall duct the numerical results are in good agreement with exact analytical results

an adjoint based method for liner impedance eduction validation and numerical investigation abstract an inverse method for liner acoustic impedance eduction in a duct is presented the determination of adjoint equations allows to make explicit the directional derivatives of the objective function needed by the search algorithm direct and adjoint system of equations are spatially discretized by a discontinuous galerkin scheme the propagation model and the eduction process are successfully validated on nasa benchmark data extracted from literature in a no flow configuration objective functions written in terms of acoustic pressure and acoustic velocity are considered successively special attention is given to the possibilities offered by the method such as multiparameter identification with the study of a non homogeneous liner convergence history of the process is also examined revealing interesting properties for the velocity based objective function compared to the pressure based objective function in further developments the method is planned to be used with acoustic velocity fields obtained by laser doppler velocimetry

a nonsmooth version of newton s method newton s method for solving a nonlinear equation of several variables is extended to a nonsmooth case by using the generalized jacobian instead of the derivative this extension includes the b derivative version of newton s method as a special case convergence theorems are proved under the condition of semismoothness it is shown that the gradient function of the augmented lagrangian forc2 nonlinear programming is semismooth thus the extended newton s method can be used in the augmented lagrangian method for solving nonlinear programs

a new efficient algorithm for computational aeroacoustics on parallel processors one of the great challenges in computational physics is the prediction of flow associated noise where the quantities of interest namely the sound waves can be at high frequencies and are usually orders of magnitude smaller in magnitude than the mean quantities in order to numerically resolve such small scales governed by the fluid dynamics equations high resolution schemes are required thus solutions of flow noise problems are computationally intensive an efficient hybrid data parallel computational aeroacoustics algorithm has been developed for the prediction of noise radiation and scattering from three dimensional geometries the algorithm solves the euler navier stokes equations in the interior and nonreflecting boundary conditions on the outer boundaries a moving surface kirchhoff method is coupled to the flow solver for far field predictions the algorithm uses standard time and spatial discretization techniques but utilizes several new optimization strategies that are highly suitable for single zone solutions on data parallel processors one strategy for example enables simultaneous residual evaluations of the interior and far field nonreflecting boundary conditions equations reducing the computational effort spent on them by approximately 60 cpu time savings the algorithms for the flow solver and the kirchhoff method and their coupling are described in this paper and results for some example radiation and scattering problems are presented

a qp free globally convergent locally superlinearly convergent algorithm for inequality constrained optimization an algorithm is proposed for the minimization of a smooth function subject to smooth inequality constraints unlike sequential quadratic programming type methods this algorithm does not involve the solution of quadratic programs but merely that of linear systems of equations locally the iteration can be viewed as a perturbation of a quasi newton iteration on both the primal and dual variables for the solution of the equalities in the kuhn tucker first order conditions of optimality it is observed that provided the current iterate is feasible and the current multiplier estimates are strictly positive the primal component of the quasi newton direction is a direction of descent for the objective function this fact is used to induce global convergence without the need of a surrogate merit function a careful bending of the search direction prevents any maratos like effect and local superlinear convergence is proven while the algorithm requires that an initial feasible point be available the succe

broadband impedance boundary conditions for the simulation of sound propagation in the time domain an accurate and practical surface impedance boundary condition in the time domain has been developed for application to broadband frequency simulation in aeroacoustic problems to show the capability of this method two kinds of numerical simulations are performed and compared with the analytical experimental results one is acoustic wave reflection by a monopole source over an impedance surface and the other is acoustic wave propagation in a duct with a finite impedance wall both single frequency and broadband frequency simulations are performed within the framework of linearized euler equations a high order dispersion relation preserving finite difference method and a low dissipation low dispersion runge kutta method are used for spatial discretization and time integration respectively the results show excellent agreement with the analytical experimental results at various frequencies the method accurately predicts both the amplitude and the phase of acoustic pressure and ensures the well posedness of the broadband time domain impedance boundary condition