anti periodic solutions for bam neural networks with time delays in the paper bidirectional associative memory neural networks with time delays are studied by using the fundamental solution matrix of coefficients and lyapunow function sufficient conditions are obtained for the existence and global exponential stability of the anti periodic solution of the model an example and numerical simulations are also given to illustrate the theoretical results

exponential p convergence analysis for stochastic bam neural networks with time varying and infinite distributed delays we discuss exponential p convergence for stochastic bam neural networks the delays here are multiple time varying and infinite distributed delays we establish a new l operator delay differential integral inequality delay dependent criteria ensuring exponential p convergence are obtained giving the detail estimations of the exponential p convergence ball this paper is concerned with the problem of global exponential p convergence for stochastic bam neural networks with time varying and infinite distributed delays by constructing a new delay differential integral inequality and a novel l operator differential integral inequality and coupling with stochastic analysis techniques some delay dependent sufficient conditions are derived to guarantee exponential p convergence and the state variables of the discussed stochastic bam neural networks are globally exponentially convergent to a ball in the state space with a pre specified convergence rate meanwhile the exponential p convergent balls are also estimated here the existence and the uniqueness of the equilibrium point needs not to be considered finally two examples with numerical simulations are given to illustrate the effectiveness of the theoretical results

time stepping schemes for systems of volterra integro differential equations linear volterra type systems of integro differential equations sides with kernels in the form of sums of complex exponentials are considered such systems arise for example in the semi discrete finite element model of dynamic viscoelasticity and of some dispersive wave equations and in the representation of dynamic subsystems on interfaces several new families of time stepping schemes are proposed here for the solution of this class of sides the accuracy stability and efficiency properties of these schemes are demonstrated via both theoretical analysis using a scalar model problem and numerical experiments applied to first and second order sides

high modal density approximations for equipment in the time domain this article considers modeling the effect of complex subsystems on the dynamics of the main structure to which they are attached it is proposed that the substructure say a piece of equipment be replaced by an equivalent set of forces which react back on the main structure these forces are given as time convolutions of the displacements at the equipment attachment points the convolution integral which represents a time domain dtn dirichlet to neumann map is approximated in the high modal density limit with determined error bounds this approximation leads to a family of equipment representations the simplest requires few measured equipment properties though more information can lead to greater accuracy our approximate dtns are demonstrated numerically in finite element simulations

which are the important modes of a subsystem a linearly behaving vibrational substructure or more generally a linear dynamic subsystem attached to a main structure or a main dynamic system is considered after discretization the substructure is represented by afinite typically large number of degrees of freedom n and hence also by n s eigenmodes in order to reduce the computational effort it is common to apply modal reduction to the subsystem such that only n r modes out of the total number of n modes are retained where n r n s the following question then arises which n r modes should be retained in structural dynamics it is traditional to retain those modes associated with the lowest frequencies in this paper the question is answered by solving an appropriate optimization problem the most important modes of the subsystem are shown to be those whose coupling matrices which are defined in a particular way have the highest norm this leads to a simple and effective algorithm for optimal modal reduction the new criterion for modal importance is explained both mathematically and physically and is demonstrated by numerical examples

computing the aspect graph for line drawings of polyhedral objects an algorithm for computing the aspect graph for polyhedral objects is described the aspects graph is a representation of three dimensional objects by a set of two dimensional views the set of viewpoints on the gaussian sphere is partitioned into regions such that in each region the qualitative structure of the line drawing remains the same at the boundaries between adjacent regions are the accidental viewpoints where the structure for the line drawing changes it is shown that for polyhedral objects there are two fundamental visual events 1 the projections of an edge and a vertex coincide and 2 the projections of three nonadjacent edges intersect at a point the geometry of the object is reflected in the locus of the accidental viewpoints the algorithm computes the partition together with a representative view for each region of the partition

existence of weighted pseudo anti periodic solutions to some non autonomous differential equations abstract in this paper we first introduce two new concepts called respectively weighted pseudo periodicity and weighted pseudo anti periodicity which generalize respectively the well known notions of periodicity and that of anti periodicity basic properties of these new functions are discussed furthermore the existence of weighted pseudo anti periodic solutions to some damped non autonomous second order differential equations will be investigated to illustrate our abstract results the existence of weighted pseudo anti periodic solutions to a plate like equation is discussed

anti periodic solutions for high order hopfield neural networks in this paper high order hopfield neural networks hhnns with time varying delays are considered sufficient conditions for the existence and exponential stability of anti periodic solutions are established which are new and complement previously known results

mean and mean square responses of a prototypical master fuzzy structure analytical estimates are made for mean and mean square transient responses of a single degree of freedom master oscillator attached to an undamped n degree of freedom random substructure the ensemble averaged response is found to be asymptotically for a large number of substructural degrees of freedom in accord with the predictions of the pierce sparrow russell theory in particular the mean response of the master oscillator manifests an apparent damping corrections to this behavior are also predicted but are found to lie well below the root mean square level of the fluctuations the corrections are therefore for practical purposes unimportant the ensemble average of the square of the response is also investigated and found to take a value at later times that is in accord with simple equipartition arguments advanced in an earlier paper the power spectral density of the late time behavior is shown to be proportional to the square of the power spectrum of the early time response and thus to be a n

existence and exponential stability of anti periodic solutions of hopfield neural networks with impulses in this paper we investigate a class of hopfield neural networks subject to periodic impulses first we give sufficient conditions to ensure existence and exponential stability of the anti periodic solutions which are new and complementary to previously known results then we present an example to demonstrate our results

exponential stability of delayed bi directional associative memory networks some sufficient conditions are derived for the global exponential stability in delayed bi directional associative memory bam networks by constructing suitable lyapunov functional and the inequality 2ab

an output sensitive algorithm for computing visibility the visibility graph of a set of nonintersecting polygonal obstacles in the plane is an undirected graph whose vertex set consists of the vertices of the obstacles and whose edges are pairs of vertices u v such that the open line segment between u and v does not intersect any of the obstacles the visibility graph is an important combinatorial structure in computational geometry and is used in applications such as solving visibility problems and computing shortest paths this paper presents an algorithm that computes the visibility graph of a set of obstacles in time o e n log n where e is the number of edges in the visibility graph and n is the total number of vertices in all the obstacles

visibility occlusion and the aspect graph this chapter studies the ways in which the topology of the image of a polyhedron changes with changing viewpoint we catalog the ways that the topological appearance or aspect can change this enables us to find maximal regions of viewpoints of the same aspect we use these techniques to construct the viewpoint space partition vsp a partition of viewpoint space into maximal regions of constant aspect and its dual the aspect graph here we present tight bounds on the maximum size of the vsp and the aspect graph and give algorithms for their construction first in the convex case and then in the general case in particular we give bounds on the maximum size of n 2 and n 6 under an orthographic projection viewing model and of n 3 and n 9 under a perspective viewing model the algorithms make use of a new representation of the appearance of polyhedra from all viewpoints called the aspect representation or asp we believe that this representation is one of the significant contributions of this paper

statistical energy analysis and structural fuzzy the concepts and derivations of the effects of a minor or secondary structure on the dynamics of a well defined major or primary structure have been recently presented as a fuzzy structure interacting with a deterministic one on the face of it this appears like a halfway sea system in that one of the two systems is well defined while the other is probabilistic in the sea sense it is therefore interesting to see if a full sea treatment of the system would lead to difference in at least some of the quoted results the second and more important purpose of this paper is to relate the dynamics of potential minor structures to the properties of the fuzzy system since these properties have been presented in some of the fuzzy literature in rather general terms

a model and numerical method in the medium frequency range for vibroacoustic predictions using the theory of structural fuzzy in linear dynamical analysis of complex mechanical systems the structural fuzzy is defined as the set of minor subsystems that are connected to the master structure but are not accessible by classical modeling the notion of master structure is presently extended to others elements such as an external dense compressible fluid strongly coupled with the primary structure for the low frequency lf dynamical analysis the modeling of the structural fuzzy is commonly made with a system of masses if the lf modeling of the structural fuzzy is applied in the medium frequency mf domain there are some large differences between calculations and experiment it is therefore necessary to take into account internal degrees of freedom of the structural fuzzy a global probabilistic modeling of the structural fuzzy is proposed to improve the calculated estimates of the mf vibrations into the master structure and of the far field radiated by itself in or out of context of the acoustic scattering this paper reviews the author s previous work and introduces the type ii probabilistic constitutive law in this paper 1 a probabilistic modeling of the structural fuzzy is presented 2 two probabilistic constitutive laws of the structural fuzzy are constructed 3 the modeling in the mf range for vibroacoustic predictions using theory of structural fuzzy is developed 4 the fuzzy solution in the mf range is studied and 5 numerical simulations on standard structures and on a submerged complex industrial structure are shown

on the standard deviation of change in impedance due to fuzzy subsystems the effects of attached multiple subsystems of uncertain properties on the behavior of a main system are investigated by modeling the natural frequencies of the subsystems as random points in the frequency domain both the mean and the standard deviation of the change in impedance attributable to the subsystems are computed without the usual assumption of modal overlap it is shown that the standard deviation which has been overlooked by most authors on this subject can sometimes be greater than the mean thus the knowledge of the mean alone is inadequate to make engineering decisions

three dimensional weak visibility complexity and applications abstract in this paper we study the complexity of 3d weak visibility we obtain an o n 8 time and n 6 space algorithm to compute the weakly visible region of a triangle f from another triangle g among general scenes which are a set of n disjoint triangles we also consider the cases when the scenes are rectilinear objects and polyhedral terrains we show that in these special situations the weakly visible regions can be computed much faster in o n 6 time and o n 4 space with these results we obtain the first known polynomial time algorithm to decide whether or not a simple polyhedron is weakly internally or externally visible

estimation of fuzzy structure parameters for continuous junctions the fuzzy structure theory introduced 15 years ago is designed to predict the frequency response functions of structures and structural acoustic systems with structural complexity in the low and medium frequency ranges this paper constitutes a first validation of the fuzzy structure theory for continuous junctions between the master structure and the fuzzy substructures in addition a method to estimate the fuzzy structure parameters introduced in the fuzzy structure theory is presented and it is validated for the case of continuous junctions this validation obtained by numerical simulations opens the field of experimental identifications

efficiently computing and representing aspect graphs of polyhedral objects an efficient algorithm and a data structure for computing and representing the aspect graph of polyhedral objects under orthographic projection are presented the aspect graph is an approach to representing 3 d objects by a set of 2 d views for the purpose of object recognition in this approach the viewpoint space is partitioned into regions such that in each region the qualitative structure of the line drawing does not change the viewing data of an object is the partition of the viewpoint space together with a representative view in each region the algorithm computes the viewing data for line drawings of polyhedral objects under orthographic projection

exponential stability and periodic oscillatory solution in bam networks with delays both exponential stability and periodic oscillatory solution of bidirectional associative memory bam networks with axonal signal transmission delays are considered by constructing suitable lyapunov functional and some analysis techniques some simple sufficient conditions are given ensuring the global exponential stability and the existence of periodic oscillatory solutions of bam with delays these conditions are presented in terms of system parameters and have important leading significance in the design and applications of globally exponentially stable and periodic oscillatory neural circuits for bam with delays in addition two examples are given to illustrate the results

fat triangles determine linearly many holes the authors show that for every fixed delta 0 the following holds if f is a union of n triangles all of whose angles are at least delta then the complement of f has o n connected components and the boundary of f consists of o n log log n straight segments where the constants of proportionality depend on delta this latter complexity becomes linear if all triangles are of roughly the same size or if they are all infinite wedges