direct numerical simulation of the glottal jet and vocal fold dynamics in a three dimensional laryngeal model an immersed boundary method based flow solver coupled with a finite element solid dynamics solver is employed in order to conduct direct numerical simulations of phonatory dynamics in a three dimensional model of the human larynx the computed features of the glottal flow including mean and peak flow rates and the open and skewness quotients are found to be within the normal physiological range the flow induced vibration pattern shows the classical convergent divergent glottal shape and the vibration amplitude is also found to be typical for human phonation the vocal fold motion is analyzed through the method of empirical eigenfunctions and this analysis indicates a 1 1 modal entrainment between the adduction abduction mode and the mucosal wave mode the glottal jet is found to exhibit noticeable cycle to cycle asymmetric deflections and the mechanism underlying this phenomenon is examined

chaotic component obscured by strong periodicity in voice production system the effect of glottal aerodynamics in producing the nonlinear characteristics of voice is investigated by comparing the outputs of the asymmetric composite model and the two mass model the two mass model assumes the glottal airflow to be laminar nonviscous and incompressible in this model when the asymmetric factor is decreased from 0 65 to 0 35 only 1 1 and 1 2 modes are detectable however with the same parameters four vibratory modes 1 1 1 2 2 4 2 6 are found in the asymmetric composite model using the navier stokes equations to describe the complex aerodynamics in the glottis moreover the amplitude of the waveform is modulated by a small amplitude noiselike series the nonlinear detection method reveals that this noiselike modulation is not random but rather it is deterministic chaos this result agrees with the phenomenon often seen in voice in which the voice signal is strongly periodic but modulated by a small amplitude chaotic component the only difference between the two mass model and the composite model is in their descriptions of glottal airflow therefore the complex aerodynamic characteristics of glottal airflow could be important in generating the nonlinear dynamic behavior of voice production including bifurcation and a small amplitude chaotic component obscured by strong periodicity

correlation dimension of electroglottographic data from healthy and pathologic subjects this paper considers the effects of nonstationarity noise and finite data sets on the estimation of the correlation dimension of time series data characterizing the vibratory behavior of the vocal folds the electroglottographic signal of sustained a phonations from 10 healthy subjects and 20 subjects with vocal fold pathologies were used to reconstruct the state space in successively higher embeddings using the method of lags the dimension values were calculated from the scaling region the level area of the slope plots which did not increase for higher embeddings reasonably defined scaling regions were found in all of the data from the healthy subjects and from five of the pathologic subjects with values saturating between the first and second embeddings the egg data from those five pathologic subjects were nearly periodic from the remaining 15 subjects the scaling regions were highly constricted with nonconstant slopes so that dimension values could not be confidently estimated the results suggest that the correlation dimension is a highly subjective measure which is not usefully applied to abnormal egg data it is recommended that if used correlation dimension statistics need to be presented cautiously and graphical presentation of the data should be included

new results on the synthesis of pid controllers this paper considers the problem of stabilizing a first order plant with dead time using a proportional integral derivative pid controller using a version of the hermite biehler theorem that is applicable to quasi polynomials the complete set of stabilizing pid parameters is determined for both open loop stable and unstable plants the range of admissible proportional gains is first determined in closed form for each proportional gain in this range the stabilizing set in the space of the integral and derivative gains is shown to be either a trapezoid a triangle or a quadrilateral for the case of an open loop unstable plant a necessary and sufficient condition on the time delay is determined for the existence of stabilizing pid controllers

brief paper all stabilizing pid controllers for time delay systems this paper presents a method to compute the entire set of stabilizing pid controller parameters for an arbitrary including unstable linear time delay system the main contribution is to handle the infinite number of stability boundaries in the k d k i plane for a fixed proportional gain k p for retarded open loops it is shown that the stable region in the k d k i plane consists of convex polygons concerning neutral loops a new phenomenon is introduced for certain systems and certain k p the exact stable region in the k d k i plane can be described by the limit of a sequence of polygons with an infinite number of vertices this sequence may be well approximated by convex polygons moreover the paper describes a necessary condition for k p intervals potentially having a stable region in the k d k i plane thus the set of stabilizing controller parameters can be calculated after gridding k p in these intervals a matlab tool implementing the presented method is available

symmetry adapted equilibrium matrices a number of authors have previously used group representation theory to block diagonalise the stiffness matrix of a symmetric structure this paper describes how similar techniques can be used to block diagonalise the equilibrium matrix of a symmetric structure this is shown to provide useful insight into the static and kinematic response of such systems in particular it simplifies finding and classifying states of self stress and mechanisms as well as reducing the computational effort required for a force method analysis

perturbation free measurement of the harmonics to noise ratio in voice signals using pitch synchronous harmonic analysis the measurement of the harmonics to noise ratio hnr in speech signals gives an indication of the aperiodicity of the speech waveform this may be due to the presence of jitter shimmer additive noise waveshape change or some unknown combination of these factors in order to estimate the hnr as a measure of the additive noise component only the contaminating effects of the other contributory components must first be removed a pitch synchronous harmonic analysis is proposed to overcome this problem the procedure takes advantage of the time scale compression frequency expansion property of the fourier series in order to eliminate jitter and shimmer successive spectra are added by harmonic number as opposed to frequency location and perturbation is removed due to the fact that the relative heights of the harmonic components remain the same for scaled signals the technique is examined on synthetically generated voice signals a discussion of the results is given in terms of human voice signals characterization of jitter vocal tract filtering effects perturbation mechanisms nonlinear dynamics and the possibility of developing the method for use with inverse filtering strategies

nonlinear analysis of irregular animal vocalizations animal vocalizations range from almost periodic vocal fold vibration to completely atonal turbulent noise between these two extremes a variety of nonlinear dynamics such as limit cycles subharmonics biphonation and chaotic episodes have been recently observed these observations imply possible functional roles of nonlinear dynamics in animal acoustic communication nonlinear dynamics may also provide insight into the degree to which detailed features of vocalizations are under close neural control as opposed to more directly reflecting biomechanical properties of the vibrating vocal folds themselves so far nonlinear dynamical structures of animal voices have been mainly studied with spectrograms in this study the deterministic versus stochastic dvs prediction technique was used to quantify the amount of nonlinearity in three animal vocalizations macaque screams piglet screams and dog barks results showed that in vocalizations with pronounced harmonic components adult macaque screams certain piglet screams and dog barks deterministic nonlinear prediction was clearly more powerful than stochastic linear prediction the difference termed low dimensional nonlinearity measure lnm indicates the presence of a low dimensional attractor in highly irregular signals such as juvenile macaque screams piglet screams and some dog barks the detectable amount of nonlinearity was comparatively small analyzing 120 samples of dog barks it was further shown that the harmonic to noise ratio hnr was positively correlated with lnm it is concluded that nonlinear analysis is primarily useful in animal vocalizations with strong harmonic components including subharmonics and biphonation or low dimensional chaos

determination of parameters for lumped parameter models of the vocal folds using a finite element method approach to study the mechanical behavior of the vocal folds lumped parameter models of the vocal folds have been developed in the past coupling with a model of the aerodynamics in the glottis provides the possibility of simulating glottal waves a new method is presented to obtain values for the masses and springs of the lumped parameter models by using a finite element method model of the vocal folds this finite element method model is based on geometry and material data from the literature resulting in a model that describes the vocal fold in a realistic way requiring the dynamic behavior of the lumped parameter model of the vocal fold to be equal to the dynamic behavior of the finite element method model of the vocal fold parameter values are obtained that are purely based on dynamic considerations therefore the behavior of the vocal folds is described in a realistic way by these parameters these values are compared with the values used by previous authors and are implemented in lumped parameter models self sustained oscillation is achieved with the new values for masses and springs

subject specific computational modeling of human phonation a direct numerical simulation of flow structure interaction is carried out in a subject specific larynx model to study human phonation under physiological conditions the simulation results compare well to the established human data the resulting glottal flow and waveform are found to be within the normal physiological ranges the effects of realistic geometry on the vocal fold dynamics and the glottal flow are extensively examined it is found that the asymmetric anterior posterior laryngeal configuration produces strong anterior posterior asymmetries in both vocal fold vibration and glottal flow which has not been captured in the simplified models it needs to be pointed out that the observations from the current numerical simulation are only valid for the flow conditions investigated the limitations of the study are also discussed

the use of the karhunen loegve procedure for the calculation of linear eigenfunctions abstract it is shown that the karhunen loeve decomposition may be used to determine the eigenfunctions of a general class of linear operators from an ensemble of realizations that are derived from that system given a moderate size data set either numerical or experimental from a linear system good approximations to the eigenfunctions that characterize the underlying equations can be computed by performing the karhunen loeve procedure two numerical examples are presented the vibration of a thin membrane in a rectangular domain and in a stadium these are used to determine the convergence and accuracy of the method it is found that this method yields accurate results for the first few eigenfunctions with relatively few realizations eigenfunctions with less energy are accurately resolved as the size of the ensemble increase the method is shown to be an efficient and practical procedure for determining the eigenfunctions of systems in complex geometries and in cases where the governing equations are not known a priori the effect of random noise contamination of the data set is also investigated and it is found that the karhunen loeve procedure can still achieve accurate results despite the presence of substantial background noise

double link expandohedra a mechanical model for expansion of a virus double link expandohedra are introduced each is constructed from a parent polyhedron by replacing all faces with rigid plates adjacent plates being connected by a pair of spherically jointed bars powerful symmetry techniques are developed for mobility analysis of general double link expandohedra and when combined with numerical calculation and physical model building they demonstrate the existence of generic finite breathing expansion motions in many cases for icosahedrally symmetric trivalent parents with pentagonal and hexagonal faces only fullerene polyhedra the derived expandohedra provide a mechanical model for the experimentally observed swelling of viruses such as cowpea chlorotic mottle virus ccmv a fully symmetric swelling motion a finite mechanism is found for systems based on icosahedral fullerene polyhedra with odd triangulation number t 31 and is conjectured to exist for all odd triangulation numbers

a symmetry extension of maxwell s rule for rigidity of frames a symmetry extension of maxwell s rule for rigidity of frames is found this rule subsumes and strengthens maxwell s 1864 rule by requiring that the internal and external degrees of freedom of a pin jointed structure are not only numerically equal but are also equisymmetric a number of special cases of maxwell s original rule are studied to show the improved insight that the symmetry adapted version can give

detection of finite mechanisms in symmetric structures abstract using group representation theory it is possible to block diagonalise the equilibrium matrix of a symmetric structure this analysis can identify the symmetry properties of any states of self stress or mechanisms present in the structure this paper will show that in some cases this linear analysis combined with symmetry arguments can show that particular mechanisms of a symmetric structure must be finite

the emergence of coherent structures in coupled map lattices we show how increasing spatial interaction leads to the merging of coherent structures from chaos in some systems of coupled map lattices this phenomenon reflects the arising of new ground states in the corresponding model of statistical mechanics if we further increase the coupling then new ground states appear showing the coexistence of a large scale coherent structure with a small scale chaotic motion this allows us to propose a generalization of the notion of spatial intermittency

spatiotemporal analysis of complex signals theory and applications we present a space time description of regular and complex phenomena which consists of a decomposition of a spatiotemporal signal into orthogonal temporal modes that we call chronos and orthogonal spatial modes that we call topos this permits the introduction of several characteristics of the signal three characteristic energies and entropies one temporal one spatial and one global and a characteristic dimension although the technique is general we concentrate on its applications to hydrodynamic problems specifically the transition to turbulence we consider two cases of application a coupled map lattice as a dynamical system model for spatiotemporal complexity and the open flow instability on a rotating disk in the latter we show a direct relation between the global entropy and the different instabilities that the flow undergoes as reynolds number increases

an in vitro setup to test the relevance and the accuracy of low order vocal folds models an experimental setup and human vocal folds replica able to produce self sustained oscillations are presented the aim of the setup is to assess the relevance and the accuracy of theoretical vocal folds models the applied reduced mechanical models are a variation of the classical two mass model and a simplification inspired on the delayed mass model for which the coupling between the masses is expressed as a fixed time delay the airflow is described as a laminar flow with flow separation the influence of a downstream resonator is taken into account the oscillation pressure threshold and fundamental frequency are predicted by applying a stability analysis to the mechanical models the measured frequency response of the mechanical replica together with the initial rest area allows us to determine the model parameters spring stiffness damping geometry masses validation of theoretical model predictions to experimental data shows the relevance of low order models in gaining a qualitative understanding of phonation however quantitative discrepancies remain large due to an inaccurate estimation of the model parameters and the crudeness in either flow or mechanical model description as an illustration it is shown that significant improvements can be made by accounting for viscous flow effects

modeling of chaotic vibrations in symmetric vocal folds the chaos mechanism of above range phonation was examined in symmetrically modeled vocal folds by using the traditional two mass model assumption the poincare map technique was used to display chaotic attractors this method provided an effective description of irregular vocal fold movements the power spectrum lyapunov exponent and kaplan yorke dimension were employed to describe chaotic vibrations in the vocal fold model these nonlinear dynamic analyses suggested that for the positive lyapunov exponent chaotic attractors contribute to irregular vocal fold vibrations descriptions of complicated irregular vibrations of the vocal fold yielded evidence of chaos to investigate the effects of independent parameters such as subglottal pressure coupling stiffness and phonation neutral area bifurcation diagrams based on the poincare map were discussed the results confirmed that the dynamics of the two mass model was strongly influenced by independent parameters nonlinear dynamic methods were expecte

mobility of n loops bodies cyclically connected by intersecting revolute hinges the mobilities of many objects from toys and molecular models to large scale deployable structures can be understood in terms of n loops sets of n bodies cyclically connected by pairs of intersecting revolute hinges a symmetry extended version of the grubler criterion for counting kinematic degrees of freedom is used to explain and rationalize the observed mobilities of n loops with small n compared with simple counting the symmetry based approach gives improved detection and visualization of mechanisms and states of self stress it can also give a better account of the differing mobilities of conformers occupying different regions of the phase space such as the rigid chair and flexible boat forms of cyclohexane

reducing the number of vocal fold mechanical tissue properties evaluation of the incompressibility and planar displacement assumptions the incompressibility and planar displacement assumptions were used to reduce the number of independent tissue parameters required for the characterization of a structural model of the vocal folds the influence of these simplifying assumptions on the vibratory properties of the model was investigated the purpose was to provide estimates of the error introduced by these assumptions the variability in human tissue properties was accounted for through systematic variation of several material parameters the modal properties of a vocal fold structural model were computed with each assumption and in turn were relaxed to determine their respective effects the results indicated that the incompressibility assumption introduces little error errors introduced by the planar displacement assumption were found to depend on the ratio of the longitudinal stiffness and the transverse stiffness criteria for determining the compatibility of tissue property values from independent studies are also presented

stable polyhedra in parameter space a typical uncertainty structure of a characteristic polynomial is p s a s q s b s with a s and b s fixed and q s uncertain in robust controller design q s may be a controller numerator or denominator polynomial an example is the pid controller with q s k i k ps k ds 2 in robustness analysis q s may describe a plant uncertainty for fixed imaginary part of q email protected it is shown that hurwitz stability boundaries in the parameter space of the even part of q email protected are hyperplanes and the stability regions are convex polyhedra a dual result holds for fixed real part of q email protected also s stability with the real parts of all roots of p s smaller than s is treated under the above conditions the roots of p s can cross the imaginary axis only at a finite number of discrete singular frequencies each singular frequency generates a hyperplane as stability boundary an application is robust controller design by simultaneous stabilization of several representatives of a s and b s by a pid controller geometrically the intersection of convex polygons must be calculated and represented tomographically for a grid on k p

comments on new results on the synthesis of pid controllers silva datta and bhattacharyya in the above paper have studied the feedback control system provided with a proportional integral derivative pid controller and relative to a first order plant with a time delay and have determined the range of the pid controller parameters suitable for the stability by means of a version of the hermite biehler theorem the purpose of this note is to find the same results in a simpler way by means of the classical nyquist s stability criterion

brief fast calculation of stabilizing pid controllers a fast method for the computation of stabilizing pid controllers is proposed it is shown in particular that for a fixed value of the proportional term k p the resulting stabilizing pid compensators form a finite set of disjoint polyhedral sets in the parameter space a complete characterization and a practical way of finding such stabilizing regions are given moreover the bounds on stabilizing k p parameters are derived the method therefore has several advantages over recent results and is very promising for real time and or robust control applications

technical communique stability of pid controlled second order time delay feedback systems in the previous papers the stability of pid controlled first order time delay systems has been investigated by means of several methods of which the nyquist criterion a generalization of the hermite biehler theorem and the root location method are well known explicit expressions of the boundaries of the stability region which is the set of controller parameters that give stable closed loop systems have been determined from these studies one can verify that not all plants can be made stable and then obtain the set of process parameters that allow stable closed loop systems with this set one can implement the stability region of the process parameters in a recent paper the stability conditions based on pontryagin s studies and valid for arbitrary order plants have been presented the procedure deduced for the controller parameters is exhaustive but that deduced for the process parameters requires further mathematical evaluations whose complexity is proportional to the number of process time constants in the aforementioned recent paper these evaluations have been performed for a second order time delay plant whose transfer function has no zero the aim of this paper is to execute these calculations for a second order plant whose transfer function has one zero and to provide the related stability region

global and local dimensions of vocal dynamics the global embedding dimension de and the local dynamical dimension dl are calculated from the microphone and electroglottographic egg signals elicited from five healthy subjects and seven dysphonic subjects with laryngeal pathology during phonation of sustained a the data from each pathologic subject contain at least one bifurcation and are divided into periodic and irregular segments for analysis the de values from both the microphone and egg signals elicited from the healthy subjects indicate that a relatively small coordinate space can be used to reconstruct the attractor with little residual noise consistent across all healthy subjects three dominant degrees of freedom dl are found to govern local dynamics of the trajectories on the attractor from the pathologic subjects many of the de values suggest the presence of a high dimensional component in the signals however the noise does not completely obscure the deterministic dynamics of the source signal or prevent extraction of an optimal global embedding dimension the data do not reveal consistent differences in degrees of freedom between healthy and pathologic phonation or between different modes of pathologic phonation however the dl values suggest that the pathologic vocal fold vibration of these subjects even highly irregular vibration is governed locally by a low number of dominant degrees of freedom sometimes no greater than those calculated from the signals of healthy subjects only in the cases of severe breathiness are the microphone and egg signals sufficiently contaminated by noise to obscure any deterministic component

low dimensional dynamics for the complex ginzburg landau equation abstract a method is presented which results in low dimensional dynamical systems for situations in which low dimensional attractors are known to exist the method is based on the use of the karhunen loeve procedure for the determination of an optimal basis and the subsequent use of the galerkin procedure to generate the dynamical system the method is applied to two problems for the ginzburg landau equation for which large databases have been obtained in each instance a dynamical system is generated which has roughly twice the number of degrees of freedom as the hausdorff dimension of the exact case it is also demonstrated that the approximations are robust in that they are accurate over a wide range of parameter space

singular spectrum analysis a toolkit for short noisy chaotic signals abstract singular spectrum analysis ssa is developed further based on experience with applications to geophysical time series it is shown that ssa provides a crude but robust approximation of strange attractors by tori in the presence of noise the method works well for short noisy time series the lagged covariance matrix of the processes studied is the basis of ssa we select subsets of eigenelements and associated principal components pcs in order to provide i a noise reduction algorithm ii a detrending algorithm and iii an algorithm for the identification of oscillatory components reconstructed components rcs are developed to provide optimal reconstruction of a dynamic process at precise epochs rather than averaged over the window length of the analysis ssa is combined with advanced spectral analysis methods the maximum entropy method mem and the multi taper method mtm to refine the interpretation of oscillatory behavior a combined ssa mem method is also used for the prediction of selected subsets of rcs the entire toolkit is validated against a set of four prescribed time series generated by known processes quasi periodic or chaotic it is also applied to a time series of global surface air temperatures 130 years long which has attracted considerable attention in the context of the global warming issue and provides a severe test for noise reduction and prediction

a class of expandable polyhedral structures a class of expandable polyhedral structures the expandohedra consisting of prismatic faces linked along edges by hinged plates provides a model for the swelling of viruses the finite breathing mode of the expandohedra apparent in the model and from geometric arguments is not however detected by elementary counting techniques symmetry extended mobility criteria show that the breathing motion is part of a set of face mechanisms for many expandohedra numerical analysis using the singular value decomposition of the compatibility matrix confirms the completeness of the deductions from general symmetry theorems derived for expandohedra

controller design for delay systems via eigenvalue assignment on a new result in the distribution of quasi polynomial roots this paper considers the eigenvalue distribution of a linear time invariant lti system with time delays and its application to some controllers design for a delay plant via eigenvalue assignment first a new result on the root distribution for a class of quasi polynomials is developed based on the extension of the hermite biehler theorem then such result is applied to proportional integral pi controller parameter design for a first order plant with time delay through pole placement the complete region of pi gains can be obtained so that the rightmost eigenvalues in the infinite eigenspectrum of the closed loop system with delay plant are assigned to desired positions in the complex plane furthermore on the basis of the previous result this paper also extended the pi control to the proportional integral derivative pid control it is worth pointing out that this work aims to improve the performance of the closed loop system on the premise of guaranteeing the stability

a finite element model of vocal fold vibration a finite element model of the vocal fold is developed from basic laws of continuum mechanics to obtain the oscillatory characteristics of the vocal folds the model is capable of accommodating inhomogeneous anisotropic material properties and irregular geometry of the boundaries it has provisions for asymmetry across the midplane both from the geometric and tension point of view which enables one to simulate certain kinds of voice disorders due to vocal fold paralysis it employs the measured viscoelastic properties of the vocal fold tissues the detailed construction of the matrix differential equations of motion is presented followed by the solution scheme finally typical results are presented and validated using an eigenvalue method and a commercial finite element package abaqus

reliable computation of pid gain space for general second order time delay systems abstractthis paper addresses the problem of determining the stability gain space of a pid controller for general second order time delay systems first a review of existing results and the associated drawbacks is presented subsequently a new algorithm to compute the entire pid stability gain space is developed the new algorithm is based upon existing results on the relationship between the stability of a quasi polynomial and its derivatives an extended version of the hermit biehler theorem and also the nyquist criterion the algorithm entails extraction of an admissible range for the pid parameter kp and then based on this range a stability region in the ki kd plane is computed well known examples are studied to demonstrate the reliability and accuracy of the results

phase space analysis of bursting behavior in kolmogorov flow abstract pde simulations for the kolmogorov flow are analyzed in terms of phase space concepts the tool used is the proper orthogonal decomposition method which extracts coherent structures and prominent features of a random or turbulent dataset we analyze a quasiperiodic regime and an intermittent regime we derive two eigenfunctions that determine the dynamics and structure of the quasiperiodic case and find a third one associated with the unstable manifold of the bursts of the intermittent regime calculations are performed for streamfunction data and vorticity data which show substantial differences it is argued that the streamfunction data demonstrate the low dimensional phase space dynamics of the large scales whereas the vorticity data show an enstrophy cascade

nonlinear dynamics of phonations in excised larynx experiments nonlinear dynamic methods including correlation dimension and lyapunov exponents are applied to quantitatively analyze phonations in excised larynx experiments irregular phonations are typically characterized by aperiodic waveforms and broadband spectra finite correlation dimensions and positive lyapunov exponents of irregular phonations demonstrate the existence of chaos in excised larynx phonations furthermore the correlation dimension maximal lyapunov exponent jitter shimmer and peak prominence ratio are used to statistically distinguish irregular phonations from normal phonations the correlation dimension and maximal lyapunov exponent indicate a significant difference between irregular and normal phonations however jitter shimmer and peak prominence ratio do not reveal such a significant difference and thus are unsuitable to differentiate between irregular phonations and normal phonations these findings might potentially assist investigators in understanding rough phonations and developing clinically valuable methodologies for the diagnosis of voice disorders

ranking vocal fold model parameters by their influence on modal frequencies the purpose of this study was to identify using computational models the vocal fold parameters which are most influential in determining the vibratory characteristics of the vocal folds the sensitivities of vocal folds modal frequencies to variations model parameters were used to determine the most influential parameters a detailed finite element model of the human vocal fold was created the model was defined by eight geometric and six material parameters the model included transitional boundary regions to idealize the complex physiological structure of real human subjects parameters were simultaneously varied over ranges representative of actual human vocal folds three separate statistical analysis techniques were used to identify the most and least sensitive model parameters with respect to modal frequency the results from all three methods consistently suggest that a set of five parameters are most influential in determining the vibratory characteristics of the vocal folds

further results on the synthesis of pid controllers this note focuses on a graphical approach to determine the stability region in the parameter space of pid controlled second order plants with dead time this work is the extension of and further results on the same topic of the previous paper in the literature on first order plants with dead time the main characterization of the new method is the utilization of a graphical stability criterion in the parameter space which releases a necessary and sufficient stability condition once the range of proportional gain is known the complete stabilizing set in the plain of integral derivative gains can be drawn and identified immediately not to be computed mathematically a practical algorithm of drawing the stabilizing boundaries in the integral derivative space is proposed

anterior posterior biphonation in a finite element model of vocal fold vibration in this paper a finite element model is used to simulate anterior posterior biphonation neubauer et al j acoust soc am 110 6 3179 3192 2001 the anterior posterior stiffness asymmetric factor and the anterior posterior shape asymmetric factor describe the asymmetry properties of vocal folds spatiotemporal plot spectral analysis anterior posterior fundamental frequency ratio cross covariation function and correlation length quantitatively estimate the spatial asymmetry of vocal fold oscillations calculation results show that the anterior posterior stiffness asymmetry decreases the spatial coherence of vocal fold vibration when the stiffness asymmetry reaches a certain level the drop in spatial coherence desynchronizes the vibration modes the anterior and posterior sides of the vocal fold oscillate with two independent fundamental frequencies fa and fp the complex spectral characteristics of vocal fold vibration under biphonation conditions can be explained by the linear combination

structural computations with the singular value decomposition of the equilibrium matrix abstract the singular value decomposition of the equilibrium matrix makes it possible to answer any question of a static kinematic or static kinematic nature for any structural assembly within a unified computational framework the paper introduces this decomposition relates it to the physical properties of a given assembly and derives formulae for stresses displacements etc a simple example illustrates the calculations

normal modes in a continuum model of vocal fold tissues the ritz method is used to calculate eigenmodes and eigenfrequencies in a continuum model of the vocal folds the investigation represents a rectification and extension of previous studies emphasizing the indispensability of utilizing natural boundary conditions when computing the characteristic modes of a system concurring with previous assertions two of the lower order eigenmodes are theorized to play a major role in facilitating self oscillation of the folds during phonation one mode related to vertical phasing is shown to have a more direct control over glottal convergence divergence than indicated in previous calculations unlike lumped element models the continuum model predicts that the eigenfrequencies of the two modes are closely spaced over an extensive range of tissue sizes and stiffnesses this finding may help explain why the two modes entrain so naturally over a wide range of phonatory adjustments in human phonation

brief synthesis of h pid controllers a parametric approach this paper considers the problem of synthesizing proportional integral derivative pid controllers for which the closed loop system is internally stable and the h norm of a related transfer function is less than a prescribed level for a given single input single output plant it is shown that the problem to be solved can be translated into simultaneous stabilization of the closed loop characteristic polynomial and a family of complex polynomials it calls for a generalization of the hermite biehler theorem applicable to complex polynomials it is shown that the earlier pid stabilization results are a special case of the results developed here then a linear programming characterization of all admissible h pid controllers for a given plant is obtained this characterization besides being computationally efficient reveals important structural properties of h pid controllers for example it is shown that for a fixed proportional gain the set of admissible integral and derivative gains lie in a union of convex sets

spatio temporal analysis of irregular vocal fold oscillations biphonation due to desynchronization of spatial modes this report is on direct observation and modal analysis of irregular spatio temporal vibration patterns of vocal fold pathologies in vivo the observed oscillation patterns are described quantitatively with multiline kymograms spectral analysis and spatio temporal plots the complex spatio temporal vibration patterns are decomposed by empirical orthogonal functions into independent vibratory modes it is shown quantitatively that biphonation can be induced either by left right asymmetry or by desynchronized anterior posterior vibratory modes and the term ap anterior posterior biphonation is introduced the presented phonation examples show that for normal phonation the first two modes sufficiently explain the glottal dynamics the spatio temporal oscillation pattern associated with biphonation due to left right asymmetry can be explained by the first three modes higher order modes are required to describe the pattern for biphonation induced by anterior posterior vibrations spatial irregularity is

interpretation of biomechanical simulations of normal and chaotic vocal fold oscillations with empirical eigenfunctions empirical orthogonal eigenfunctions are extracted from biomechanical simulations of normal and chaotic vocal fold oscillations for normal phonation two dominant empirical eigenfunctions capture the vibration patterns of the folds and exhibit a 1 1 entrainment the eigenfunctions show some correspondence to theoretical low order normal modes of a simplified three dimensional elastic continuum and to the normal modes of a linearized two mass model the eigenfunctions also facilitate a physical interpretation of energy transfer mechanisms in vocal fold dynamics subharmonic regimes and chaotic oscillations are observed during simulations of a lax cover in which case at least three empirical eigenfunctions are necessary to capture the resulting vocal fold oscillations these chaotic oscillations might be understood in terms of a desynchronization of a few of the low order modes and may be related to mechanisms of creaky voice or vocal fry furthermore some of the empirical eigenfunctions captured during complex oscillations correspond to higher order normal modes described in earlier theoretical work the empirical eigenfunctions may also be useful in the design of lower order models valid over the range for which the empirical eigenfunctions remain more or less constant and may help facilitate bifurcation analyses of the biomechanical simulation