a stochastic continuation approach to piecewise constant reconstruction we address the problem of reconstructing a piecewise constant 3 d object from a few noisy 2 d line integral projections more generally the theory developed here readily applies to the recovery of an ideal n d signal n ges 1 from indirect measurements corrupted by noise stabilization of this ill conditioned inverse problem is achieved with the potts prior model which leads to a challenging optimization task to overcome this difficulty we introduce a new class of hybrid algorithms that combines simulated annealing with deterministic continuation we call this class of algorithms stochastic continuation sc we first prove that under mild assumptions sc inherits the finite time convergence properties of generalized simulated annealing then we show that sc can be successfully applied to our reconstruction problem in addition we look into the concave distortion acceleration method introduced for standard simulated annealing and we derive an explicit formula for choosing the free parameter of the cost function numerical experiments using both synthetic data and real radiographic testing data show that sc outperforms standard simulated annealing

vibration of twisted and curved cylindrical panels with variable thickness abstract a numerical procedure with an exact strain displacement relationship of twisted and curved cylindrical panels having variable thickness derived by considering the green strain tensor on general shell theory is presented using the principle of virtual work and the rayleigh ritz method with algebraic polynomials as in plane and transverse displacement functions the accuracy and applicability of the procedure are verified by comparing the present results with previous experimental and theoretical results for several panels the effects of variation ratio of thickness in chordwise and lengthwise directions twist and curvature both in two directions aforementioned on vibrations of cylindrical panels are studied in detail and typical vibration mode shapes are plotted to demonstrate the effects

the convergence of stochastic algorithms solving flow shop scheduling abstract in the paper we apply logarithmic cooling schedules of simulated annealing based algorithms to flow shop scheduling in our problem setting the objective to minimize the overall completion time which is called the makespan we prove a lower bound for the number of steps that are sufficient to approach an optimum solution with a certain probability the result is related to the maximum escape depth from local minima of the underlying energy landscape in our approach we need n o log o 1 1 steps to be in an optimum solution with probability 1 where n denotes the total number of tasks the auxiliary computations are of polynomial complexity since the model cannot be approximated arbitrarily closely in the general case unless p np the approach can be used to obtain approximation algorithms that work well in the average case

cooling schedules for optimal annealing a monte carlo optimization technique called simulated annealing is a descent algorithm modified by random ascent moves in order to escape local minima which are not global minima the level of randomization is determined by a control parameter t called temperature which tends to zero according to a deterministic cooling schedule we give a simple necessary and sufficient condition on the cooling schedule for the algorithm state to converge in probability to the set of globally minimum cost states in the special case that the cooling schedule has parametric form tt c log1 t the condition for convergence is that c be greater than or equal to the depth suitably defined of the deepest local minimum which is not a global minimum state

axisymmetric vibration of thick conical shells determination des frequences propres de coques coniques d epaisseur variable analyse de vibrations libres a symetrie axiale en utilisant une technique d equations integrales etudes en fonction de la deformation de cisaillement transversal et de l inertie de rotation etude parametrique dans le cas d une coque encastree aux deux extremites

theory of genetic algorithms ii models for genetic operators over the string tensor representation of populations and convergence to global optima for arbitrary fitness function under scaling we present a theoretical framework for an asymptotically converging scaled genetic algorithm which uses an arbitrary size alphabet and common scaled genetic operators the alphabet can be interpreted as a set of equidistant real numbers and multiple spot mutation performs a scalable compromise between pure random search and neighborhood based change on the alphabet level we discuss several versions of the crossover operator and their interplay with mutation in particular we consider uniform crossover and gene lottery crossover which does not commute with mutation the vose liepins version of mutation crossover is also integrated in our approach in order to achieve convergence to global optima the mutation rate and the crossover rate have to be annealed to zero in proper fashion and unbounded power law scaled proportional fitness selection is used with logarithmic growth in the exponent our analysis shows that using certain types of crossover operators and large population size allows for particularly slow annealing schedules for the crossover rate in our discussion we focus on the following three major aspects based upon contraction properties of the mutation and fitness selection operators i the drive towards uniform populations in a genetic algorithm using standard operations ii weak ergodicity of the inhomogeneous markov chain describing the probabilistic model for the scaled algorithm iii convergence to globally optimal solutions in particular we remove two restrictions imposed in theorem 8 6 and remark 8 7 of theoret comput sci 259 2001 1 where a similar type of algorithm is considered as described here mutation need not commute with crossover and the fitness function which may come from a coevolutionary single species setting need not have a single maximum

response surface bandits in this paper we define a response surface bandit as the sequential design problem that maximizes an expected bandit utility but where the outcomes y n are continuous and can be related through a response surface to a set of controllable variables x n x 1n x 2n x kn we link this problem to other traditional optimization problems from industrial engineering and to the traditional bandit problem we consider two approaches to the problem the first is based on a myopic sequential design the second approach uses the best design out of a family of designs related to upper bounds for the predicted surface the family includes myopic and sequential versions of d optimal designs these approaches can be generalized to more broadly defined sequential problems

convergence to global minima for a class of diffusion processes abstract we prove that there exists a gain function t t t 0 such that the solution of the sde d x t t grad u x t d t t d b t settles down on the set of global minima of u in particular the existence of a gain function t t 0 so that yt satisfying d y t t grad u y t d t d b t converges to the set of the global minima of u is verified then we apply the results to the robbins monro and the kiefer wolfowitz procedures which are of particular interest in statistics

phase transition and landscape statistics of the number partitioning problem the phase transition in the number partitioning problem npp i e the transition from a region in the space of control parameters in which almost all instances have many solutions to a region in which almost all instances have no solution is investigated by examining the energy landscape of this classic optimization problem this is achieved by coding the information about the minimum energy paths connecting pairs of minima into a tree structure termed a barrier tree the leaves and internal nodes of which represent respectively the minima and the lowest energy saddles connecting those minima here we apply several measures of shape balance and symmetry as well as of branch lengths barrier heights to the barrier trees that result from the landscape of the npp aiming at identifying traces of the easy hard transition we find that it is not possible to tell the easy regime from the hard one by visual inspection of the trees or by measuring the barrier heights only the difficulty measure given by the maximum value of the ratio between the barrier height and the energy surplus of local minima succeeded in detecting traces of the phase transition in the tree in addition we show that the barrier trees associated with the npp are very similar to random trees contrasting dramatically with trees associated with the p spin glass and random energy models we also examine critically a recent conjecture on the equivalence between the npp and a truncated random energy model

on the rational derivation of a hierarchy of dynamic equations for a homogeneous isotropic elastic plate abstract flexural equations of motion for a homogeneous isotropic elastic plate are derived by an antisymmetric expansion in the thickness coordinate of the displacement components all but the lowest order expansion functions are eliminated with the help of the three dimensional equations of motion and are plugged into the boundary conditions eliminating between these an equation is obtained for the mean plane vertical displacement which also includes arbitrary loading on the plate surface this equation can be truncated to any order in the thickness and it is in particular noted that the corresponding dispersion relation seems to correspond to a power series expansion of the exact rayleigh lamb dispersion relation to all orders various truncations of the equation are discussed and are compared numerically with each other the exact three dimensional solution and mindlin s plate equation both the dispersion relation and the corresponding displacement components as well as an excitation problem are used for the comparisons the theories are reasonably close to each other and in order to be on the safe side none of them should in fact be used for frequencies above the cutoff of the second flexural mode

a ritz vibration analysis of doubly curved rectangular shallow shells using a refined first order theory integral expressions for strain and kinetic energies in vibration analysis of shear deformable doubly curved shallow shells are presented although the formulation follows the first order shear deformation theory the consideration of lame parameters for the transverse shear strain through shell thickness which have been hitherto neglected by other researchers shows linear distribution functions instead of constant values if the lame parameters were dropped finite higher order two dimensional orthogonal polynomials pb 2 functions previously used in thin shell analyses 3 6 have been generalized from three to five degrees to account for the additional rotation fields of a moderately thick shell these global shape functions satisfy the kinematic boundary conditions at the outset the excellent performance and versatility of the computational methodology of the pb 2 ritz method are illustrated in representative numerical simulations the resultant matrix size is far smaller than other discretization methods and yet accurate solutions can be obtained the validity of the results is verified through direct comparisons the discrepancy of various formulations with and without the lame parameters is presented and discussed

stochastic relaxation on partitions with connected components and its application to image segmentation we present a new method of segmentation in which images are segmented in partitions with connected components we give computationally inexpensive algorithms for probability simulation and simulated annealing on the space of partitions with connected components of a general graph in particular hastings algorithms 1970 and generalized metropolis algorithms are defined to avoid heavy computation to achieve segmentation we propose a hierarchical approach which at each step minimizes a cost function on the space of partitions with connected components of a graph the algorithm is applied to segment gray level color and textured images

approximate dynamic boundary conditions for a thin piezoelectric layer abstract approximate dynamic boundary conditions of different orders are derived for the case of a thin piezoelectric coating layer bonded to an elastic material the approximate boundary conditions are derived using series expansions of the elastic displacements and the electric potential in the thickness coordinate of the layer all the expansion functions are then eliminated with the aid of the equations of motion and boundary interface conditions of the layer this results in boundary conditions on the elastic material that may be truncated to different orders in the thickness of the layer to obtain approximate boundary conditions the approximate boundary conditions may be used as a replacement for the piezoelectric layer and thus simplify the analysis significantly numerical examples show that the approximate boundary conditions give good results for low frequencies and or thin piezoelectric layers

dynamic cylindrical shell equations by power series expansions the dynamics of an infinite circular cylindrical shell is considered the derivation process is based on power series expansions of the displacement components in the radial direction by using these expansions in the three dimensional equations of motions a set of recursion relations is identified expressing higher displacement coefficients in terms of lower order ones the new approximate shell equations are hereby obtained from the boundary conditions resulting in a set of six partial differential equations these equations are believed to be asymptotically correct and it is in principle possible to go to any order equations of order up to and including the square of the thickness h2 are presented explicitly this set of six equations are reduced to five as well as three equations and compared to classical theories dispersion curves together with the eigenfrequencies for a 2d case are calculated using exact classical and expansion theories it is shown that the approximate equations containing order h2 are in general as good as or better than the established theory of the same order

fluctuations of empirical means at low temperature for finite markov chains with rare transitions in the general case the integrated autocovariance and autocorrelation time are essential tools to understand the dynamical behavior of a markov chain we study here these two objects for markov chains with rare transitions with no reversibility assumption we give upper bounds for the autocovariance and the integrated autocorrelation time as well as exponential equivalents at low temperature we also link their slowest modes with the underline energy landscape under mild assumptions our proofs will be based on large deviation estimates coming from the theory of wentzell and freidlin and others 4 3 12 and on coupling arguments see 6 for a review on the coupling method

simulated annealing acceleration techniques and image restoration typically the linear image restoration problem is an ill conditioned underdetermined inverse problem here stabilization is achieved via the introduction of a first order smoothness constraint which allows the preservation of edges and leads to the minimization of a nonconvex functional in order to carry through this optimization task we use stochastic relaxation with annealing we prefer the metropolis dynamics to the popular but computationally much more expensive gibbs sampler still metropolis type annealing algorithms are also widely reported to exhibit a low convergence rate their finite time behavior is outlined and we investigate some inexpensive acceleration techniques that do not alter their theoretical convergence properties namely restriction of the state space to a locally bounded image space and increasing concave transform of the cost functional successful experiments about space variant restoration of simulated synthetic aperture imaging data illustrate the performance of the resulting class of algorithms and show significant benefits in terms of convergence speed

stochastic local search for the feature set problem with applications to microarray data we prove a m o na time bound for finding minimum solutions smin of feature set problems where n is the total size of a given feature set problem smin m equals the number of non target features a is a relatively small constant and 1 is the confidence that the solution is of minimum length in terms of parameterized complexity of np complete problems our time bound differs from an fpt type bound by the factor mo for fixed the algorithm is applied to a prominent microarray dataset the classification of gene expression data related to acute myeloid leukaemia aml and acute lymphoblastic leukaemia all from the set of potentially significant features calculated by the algorithm we can identify three genes d88422 m92287 l09209 that produce zero errors on the test set by using a simple straightforward evaluation procedure performing the test on the single gene m84526 produces only one error

the energy transformation method for the metropolis algorithm compared with simulated annealing we present and analyze a new speed up technique for monte carlo optimization the iterated energy transformation algorithm where the metropolis algorithm is used repeatedly with more and more favourable energy functions derived from the original one by increasing transformations we show that this method allows a better speed up than simulated annealing when convergence speed is measured by the probability of failure of the algorithm after a large number of iterations we study also the limit of a large state space in the special case when the energy is made of a sum of independent terms we show that the convergence time of the i e t algorithm is polynomial in the size number of coordinates of the problem but with a worse exponent than for simulated annealing this indicates that the i e t algorithm is well suited for moderate size problems but not for too large ones the independent component case is a good model for the end of many optimization processes when at low temperature a neighbourhood of a local minimum is explored by small and far apart modifications of the current solution we show that in this case both global optimization methods simulated annealing and the i e t algorithm are less efficient than repeated local stochastic optimizations using the general concept of slow stochastic optimization algorithm we show that any slow global optimization scheme should be followed by a local one to perform the last approach to a minimum

approximate boundary conditions for a fluid loaded elastic plate approximate boundary conditions for an infinite elastic layer immersed in a fluid are derived by using series expansions in the thickness coordinate of the plate fields the displacements fields are eliminated adopting the three dimensional equations of motion the sums and differences of the boundary pressure fields and their normal derivatives are related through a set of approximate boundary conditions one symmetric and one antisymmetric these equations involve powers in the layer thickness together with partial derivatives with respect to time as well as the spatial variables in the plate plane the approximate boundary conditions can be truncated to an arbitrary order and explicit relations are presented including terms of order five comparisons are made with effective boundary conditions using classical plate theories the numerical examples involve reflection and transmission of plane waves incident on the plate at different angles as well as the pressure fields due to a line force three fluid loading cases are studied modest heavy and light loadings the results using truncated approximate boundary conditions are compared to exact and classical plate solutions the examples show that the accuracies of the power series approximations of order three and higher are very good in the frequency interval considered

on the convergence rate of annealing processes for the class of inhomogeneous markov processes arising from simulated annealing it is shown that lim t to infty p x t i exp u i t t exists and is positive for each state i where t t is the temperature and u i is the energy level at i assuming that min u i 0 the method used is to consider the forward equations associated with such processes

free vibration of a conical shell with variable thickness abstract an analysis is presented for the free vibration of a truncated conical shell with variable thickness by use of the transfer matrix approach the applicability of the classical thin shell theory is assumed and the governing equations of vibration of a conical shell are written as a coupled set of first order differential equations by using the transfer matrix of the shell once the matrix has been determined by quadrature of the equations the natural frequencies and the mode shapes of vibration are calculated numerically in terms of the elements of the matrix under any combination of boundary conditions at the edges the method is applied to truncated conical shells with linearly parabolically or exponentially varying thickness and the effects of the semi vertex angle truncated length and varying thickness on the vibration are studied

asymptotical behaviour of several interacting annealing processes we prove that the optimal convergence speed exponent for parallel annealing based on periodically interacting multiple searches with time periodr is always worse than for independent multiple searches whenever the cost function has only one global minimum our proofs will be based on large deviation estimates coming from the theory of generalized simulated annealing g s a

solution of vibration problems for shallow shells of arbitrary form by the r function method an effective method for the free vibration of arbitrary plan form shallow shells is proposed the algorithm is based on the r function theory and variational ritz method the effectiveness of the method offered is illustrated by examples of shallow shells of a complex plan form at different boundary conditions three types of curvatures are considered which are the spherical circularly cylindrical and of hyperbolic paraboloid shape a number of the test problems were solved to check the veracity of the proposed method the comparison between the obtained results and those available in the literature was carried out

a pb 2 ritz formulation for flexural vibration of shallow cylindrical shells of rectangular planform abstract this paper presents a free flexural vibration analysis of shallow cylindrical shells of rectangular planform with arbitrary combinations of free simply supported and clamped boundaries the pb 2 ritz method previously used in the plate analysis by one of the authors is now extended to shallow shell studies the ritz approach along with the in plane and transverse displacements assumed in the form of orthogonal polynomials is used to formulate the problems numerical results for the vibration frequencies for wide ranges of aspect ratio shallowness ratio and thickness ratio are presented several selected contour plots of the mode shapes for six different combinations of boundary conditions are presented as usual the accuracy of the present method is illustrated by convergence tests and comparison with the well established results from the literature

the deterioration of hearing with age frequency selectivity the critical ratio the audiogram and speech threshold the frequency selectivity of the auditory system was measured by masking a sinusoidal signal 0 5 2 0 or 4 0 khz or a filtered speech signal with a wideband noise having a notch or stopband centered on the signal as the notch was widened performance improved for both types of signal but the rate of improvement decreased as the age of the 16 listeners increased from 23 to 75 years indicating a loss in frequency selectivity with age auditory filter shapes derived from the tone in noise data show a that the passband of the filter broadens progressively with age and b that the dynamic range of the filter ages like the audiogram that is the range changes little with age before 55 but beyond this point there is an accelerating rate of loss the speech experiment shows comparable but smaller effects the filter width measurements show that the critical ratio is a poor estimator of frequency selectivity because it confounds the tuning of the system with the efficiency of the signal detection and speech processing mechanisms that follow the filter an alternative one point measure of frequency selectivity which is both sensitive and reliable is developed via the filter shape model of masking

comparing the perceptual contributions of cochlear scaled entropy and speech level cochlear scaled entropy cse has been suggested to be a reliable predictor of speech intelligibility previous studies showed that speech segments with high root mean square rms levels h levels contained primarily vowels which carry important information for speech recognition the present work compared the contributions of high cse h entropy and h level segments to speech intelligibility the natural speech was edited to generate two types of noise replaced stimuli which preserved the same percentages of largest cse segments and highest rms level segments and played to normal hearing listeners in a recognition experiment experimental results showed that the nature of the noise replaced stimulus h entropy and h level made a small difference in intelligibility performance cses and rms levels showed a moderately high correlation r 0 79 suggesting that many speech segments may have both large cses and high rms levels which might account partially for the small intelligibility difference between the two types of stimuli in addition the vowel duration proportion differed between h entropy and h level segments of the same length suggesting that vowels play different roles in contributing to the intelligibility of h entropy and h level stimuli

dynamic equations for a fully anisotropic elastic plate a hierarchy of dynamic plate equations is derived for a fully anisotropic elastic plate using power series expansions in the thickness coordinate for the displacement components recursion relations are obtained among the expansion functions adopting these in the boundary conditions on the plate surfaces and along the edges a set of dynamic equations with pertinent edge boundary conditions are derived on implicit form these can be truncated to any order and are believed to be asymptotically correct for the special case of an orthotropic plate explicit plate equations are presented and compared analytically and numerically to other approximate theories given in the literature these results show that the present theory capture the plate behavior accurately concerning dispersion curves eigenfrequencies as well as stress and displacement distributions

cochlea scaled spectral entropy predicts rate invariant intelligibility of temporally distorted sentences some evidence mostly drawn from experiments using only a single moderate rate of speech suggests that low frequency amplitude modulations may be particularly important for intelligibility here two experiments investigated intelligibility of temporally distorted sentences across a wide range of simulated speaking rates and two metrics were used to predict results sentence intelligibility was assessed when successive segments of fixed duration were temporally reversed exp 1 and when sentences were processed through four third octave band filters the outputs of which were desynchronized exp 2 for both experiments intelligibility decreased with increasing distortion however in exp 2 intelligibility recovered modestly with longer desynchronization across conditions performances measured as a function of proportion of utterance distorted converged to a common function estimates of intelligibility derived from modulation transfer functions predict a substantial proportion of the variance in listeners responses in exp 1 but fail to predict performance in exp 2 by contrast a metric of potential information quantified as relative dissimilarity change between successive cochlear scaled spectra is introduced this metric reliably predicts listeners intelligibility across the full range of speaking rates in both experiments results support an information theoretic approach to speech perception and the significance of spectral change rather than physical units of time

an asymptotic theory for circular cylindrical shells we derive the two dimensional shell equations for a circular cylindrical shell by means of an asymptotic expansion of the three dimensional elastic state the assumptions involved are of mathematical character only and concern the continuity differentiability and convergence of the series used a numerical comparison between the frequencies obtained by the two dimensional shell equations and the three dimensional state in the case of free vibrations is presented in a few examples

a hierarchy of dynamic equations for micropolar plates this work considers homogeneous isotropic micropolar plates adopting a power series expansion method in the thickness coordinate variationally consistent equations of motion and end boundary conditions are derived in a systematic fashion up to arbitrary order for extensional and flexural displacement cases the plate equations are asymptotically correct to all studied orders numerical results are presented for various orders of the present method other approximate theories as well as the exact three dimensional theory the results illustrate that the present approach may render benchmark solutions provided higher order truncations are used and act as engineering plate equations using low order truncation

dynamic equations for an isotropic spherical shell using the power series method and surface differential operators dynamic equations for an isotropic spherical shell are derived by using a series expansion technique the displacement field is split into a scalar radial part and a vector tangential part surface differential operators are introduced to decrease the length of the shell equations the starting point is a power series expansion of the displacement components in the thickness coordinate relative to the mid surface of the shell by using the expansions of the displacement components the three dimensional elastodynamic equations yield a set of recursion relations among the expansion functions that can be used to eliminate all but the four of lowest order and to express higher order expansion functions in terms of these of lowest orders applying the boundary conditions on the surfaces of the spherical shell and eliminating all but the four lowest order expansion functions give the shell equations as a power series in the shell thickness after lengthy manipulations the final four shell equations are obtained in a more compact form which can be represented explicitly in terms of the surface differential operators the method is believed to be asymptotically correct to any order the eigenfrequencies are compared to exact three dimensional theory and membrane theory

speech intelligibility is best predicted by intensity not cochlea scaled entropy cochlea scaled entropy cse is a measure of spectro temporal change that has been reported to predict the contribution of speech segments to overall intelligibility this paper confirms that cse is highly correlated with intensity making it impossible to determine empirically whether it is cse or simply intensity that determines speech importance a more perceptually relevant version of cse that uses db scaled differences rather than differences in linear amplitude failed to predict speech intelligibility overall a parsimonious account of the available data is that the importance of speech segments to overall intelligibility is best predicted by their relative intensity not by cse

dsc ritz method for high mode frequency analysis of thick shallow shells this paper addresses a challenging problem in computational mechanics the analysis of thick shallow shells vibrating at high modes existing methods encounter significant difficulties for such a problem due to numerical instability a new numerical approach dsc ritz method is developed by taking the advantages of both the discrete singular convolution dsc wavelet kernels of the dirichlet type and the ritz method for the numerical solution of thick shells with all possible combinations of commonly occurred boundary conditions as wavelets are localized in both frequency and co ordinate domains they give rise to numerical schemes with optimal accurate stability and flexibility numerical examples are considered for mindlin plates and shells with various edge supports benchmark solutions are obtained and analyzed in detail experimental results validate the convergence stability accuracy and reliability of the proposed approach in particular with a reasonable number of grid points the new dsc ritz method is capable of producing highly accurate numerical results for high mode vibration frequencies which are hitherto unavailable to engineers moreover the capability of predicting high modes endows us the privilege to reveal a discrepancy between natural higher order vibration modes of a mindlin plate and those calculated via an analytical relationship linking kirchhoff and mindlin plates copyright 2004 john wiley sons ltd

a hierarchy of dynamic equations for solid isotropic micropolar circular cylinders this work considers the derivation procedure and evaluation of dynamic equations for isotropic micropolar circular cylinders by adopting a power series expansion method in the radial coordinate variationally consistent equations of motion together with pertinent sets of boundary conditions are expressed in a systematic fashion up to arbitrary order the numerical results cover eigenfrequencies mode shapes and field distributions over cross sections for axisymmetric and flexural motion adopting different sets of end boundary conditions for equations of different truncation orders of the present method the results illustrate that the present approach may render benchmark solutions provided that higher order equations are used and act as accurate approximate engineering solution for lower order equations

the element free kp ritz method for free vibration analysis of conical shell panels in this paper the free vibration of conical panels is analyzed by the mesh free kp ritz method both 1 d and 2 d versions of the kp ritz approach are formulated for conical panels for conical panels with two simply supported straight edges the 1 d kp ritz version is used where the kernel particle estimation is employed in hybridized form with harmonic functions to approximate the 2 d displacement field for conical panels having arbitrary boundary conditions the displacement field is approximated by the 2 d kp ritz version with 2 d form of kernel particle functions employed the classical thin shell theory based on love s hypothesis is employed in the present analyses and based on the kernel particle concept and ritz technique the eigenequations of the frequencies of the conical panels are obtained to validate the accuracy of stability of the present method convergence studies were carried out based on the influences of the support size and the number of nodes comparisons were also made with existing results available in the open literature this study also examines in detail the effects of variation in the semi vertex angle and boundary conditions on the frequency characteristics of conical panels

vibratory characteristics of cantilevered rectangular shallow shells of variable thickness in this paper a comprehensive study on the modeling of vibratory response of variable thickness cantilevered shallow cylindrical shells of rectangular planform is carried out through the principle of minimum total energy the equations of stretching and bending strain energies kinetic energy and the associated boundary conditions of the shells are derived the present model is developed based on the ritz formulation with the assumption of sets of mathematicall y complete admissible two dimensional polynomials to approximate the in plane and transverse displacement amplitude functions a basic function is introduced in the approximate method to enforce automatic satisfaction of the kinematic boundary conditions sets of comprehensive reasonably accurate vibration frequencies of the shallow shells are presented for wide ranges of aspect ratio thickness variation ratios and shallowness ratio these results where possible are verified by comparing with other established experimental and theoretical solutions few selected contour plots for the first known mode shapes of these cylindrical shells of variable thickness are included

spectral tilt change in stop consonant perception there exists no clear understanding of the importance of spectral tilt for perception of stop consonants it is hypothesized that spectral tilt may be particularly salient when formant patterns are ambiguous or degraded here it is demonstrated that relative change in spectral tilt over time not absolute tilt significantly influences perception of b vs d experiments consisted of burstless synthesized stimuli that varied in spectral tilt and onset frequency of the second formant in experiment 1 tilt of the consonant at voice onset was varied in experiment 2 tilt of the vowel steady state was varied results of these experiments were complementary and revealed a significant contribution of relative spectral tilt change only when formant information was ambiguous experiments 3 and 4 replicated experiments 1 and 2 in an aba ada context the additional tilt contrast provided by the initial vowel modestly enhanced effects in experiment 5 there was no effect for absolute tilt when consonant an

a bayesian approach to dynamic contours through stochastic sampling and simulated annealing in many applications of image analysis simply connected objects are to be located in noisy images during the last 5 6 years active contour models have become popular for finding the contours of such objects connected to these models are iterative algorithms for finding the minimizing energy curves making the curves behave dynamically through the iterations these approaches do however have several disadvantages the numerical algorithms that are in use constrain the models that can be used furthermore in many cases only local minima can be achieved in this paper the author discusses a method for curve detection based on a fully bayesian approach a model for image contours which allows the number of nodes on the contours to vary is introduced iterative algorithms based on stochastic sampling is constructed which make it possible to simulate samples from the posterior distribution making estimates and uncertainty measures of specific quantities available further simulated annealing schemes making the curve move dynamically towards the global minimum energy configuration are presented in theory no restrictions on the models are made in practice however computational aspects must be taken into consideration when choosing the models much more general models than the one used for active contours may however be applied the approach is applied to ultrasound images of the left ventricle and to magnetic resonance images of the human brain and show promising results

on the vibration of shells with timoshenko mindlin type shear deflections and rotatory inertia equations of motion of shells are formulated in curvilinear co ordinates that are consistent with assumptions made in the timoshenko beam and also the mindlin plate equations this consistency is proven by obtaining the timoshenko and mindlin equations from the derived shell equations by geometrical reduction the implication of the timoshenko type shear is illustrated by constrasting the free vibration behavior of the special case of a cylindrical shell with the behavior of the timoshenko beam and the mindlin plate

landscapes on spaces of trees combinatorial optimization problems defined on sets of phylogenetic trees are an important issue in computational biology for instance the problem of reconstructing a phylogeny using maximum likelihood or parsimony approaches the collection of possible phylogenetic trees is arranged as a so called robinson graph by means of the nearest neighborhood interchange move the coherent algebra and spectra of robinson graphs are discussed in some detail as their knowledge is important for an understanding of the landscape structure we consider simple model landscapes as well as landscapes arising from the maximum parsimony problem focusing on two complementary measures of ruggedness the amplitude spectrum arising from projecting the cost functions onto the eigenspaces of the underlying graph and the topology of local minima and their connecting saddle points

vibration of shallow conical shells with shear flexibility a first order theory a formulation of shear deformation theory implemented numerically for the prediction of vibratory characteristics of shallow conical shell panels is presented the derivation of thickness shear is assumed in a linear approximation the lame parameter for the transverse shear strain component which has previously been neglected is considered this consideration accounts for the replacement of a term in transverse strain distribution through the shell thickness which results in linear transverse shear strain distribution in contrast to the constant distribution hitherto known to researchers in this field the energy integral which incorporates the shear deformation and rotary inertia is minimized to derive the governing eigen matrix equation a set of benchmark frequency solutions is presented for two exemplary conical shells the cantilever and the fully clamped shells some selected mode shapes in terms of mid surface contour plots and three dimensional meshes are also illustrated

solving scheduling problems by simulated annealing we define a general methodology to deal with a large family of scheduling problems we consider the case where some of the constraints are expressed through the minimization of a loss function we study in detail a benchmark example consisting of some jigsaw puzzle problem with additional constraints we discuss some algorithmic issues typical of scheduling problems such as the apparition of small unused gaps or the representation of proportionality constraints we also carry on an experimental comparison between the metropolis algorithm simulated annealing and the iterated energy transformation method to see whether asymptotical theoretical results are a good guide towards practically efficient algorithms

method of initial functions for thick shells abstract in the present work for circular cylindrical shells three dimensional elasticity equations are solved by assuming taylor series expansions in the radial direction for the stresses and displacements depending upon the number of terms retained in the expansion different order shell theories are derived classical theories referred to as eighth order the shear deformation transverse normal stress theories referred to as tenth order and higher order theories referred to as twelfth order in each case by carrying out the symbolic algebra using the digital computer partial differential equations are derived the procedure was carried out in detail for the case of a circular cylindrical shell with no loading on the interior surface and a given pressure distribution on the exterior surface then numerical comparisons are made between the current theories and various shell theories as well as the exact three dimensional theory thus using this method with its associated computer programs one can realize a spectrum of approximate shell theories ranging from the classical thin shell through all current thick shell theories right up to the three dimensional elastic theories

free vibrations of doubly curved in plane non homogeneous shells a method for investigating free vibrations rectangular non homogeneous shells is proposed by non homogeneity we define a chage of stiffness of shell bending caused by an introduction of another material or change of a shell thickness is defined it is assumed that a shell possesses an arbitrary value of rectangular parts with different bending stiffness

a global continuum ritz formulation for flexural vibration of pretwisted trapezoidal plates with one edge built in abstract the development of a continuum ritz model for twisted plate vibration on the basis of minimization of the energy functional is presented this method involves the use of a set of orthogonally generated pb 2 shape functions to approximate the transverse and in plane deflections in this paper a two dimensional recurrence formula is proposed to generate this set of functions during the orthogonalization process a basic function is introduced to each transverse and in plane displacement to ensure the automatic satisfaction of the essential boundary conditions the whole process can be easily implemented numerically and the accuracy of the method can be achieved by increasing the number of terms used in the polynomial functions following the above procedures a governing eigenvalue equation is derived this equation is solved to determine the vibration response of trapezoidal plates with initial twist in order to verify the validity and reliability of this method in addition to the convergence study the present results are compared with the available values from the literature where possible