credibilistic markov decision processes the average case using a concept of random fuzzy variables in credibility theory we formulate a credibilistic model for unichain markov decision processes under average criteria and a credibilistically optimal policy is defined and obtained by solving the corresponding non linear mathematical programming also we give a computational example to illustrate the effectiveness of our new model

optimal multinational capital budgeting under uncertainty this paper discusses the multinational capital budgeting problem when there are some candidate foreign projects which project s should the investor choose in the paper special cash flows and value sources of foreign projects are introduced regarding project parameters such as construction costs annual net operating cash flows terminal values of the projects as well as the foreign exchange rates as uncertain variables the paper proposes one new uncertain zero one integer model for optimal multinational project selection to solve the problem a hybrid intelligent algorithm integrating the 99 methods and genetic algorithm is provided as an illustration an application example is also presented

discrete time credibilistic processes construction and convergences in this paper we discuss a method of constructing a credibilistic process which is a family of fuzzy variables on credibility space applying the extension theorem in credibility theory the finite or infinite horizon credibilistic process is made up from a family of credibilistic kernels also for the markov case convergence theorems are given and credibilistic risk models for reward processes are considered whose risk is completed by the recursive equation

energy decay for timoshenko systems of memory type abstract linear systems of timoshenko type equations for beams including a memory term are studied the exponential decay is proved for exponential kernels while polynomial kernels are shown to lead to a polynomial decay the optimality of the results is also investigated

a boundary element method for solving 2 d and 3 d static gradient elastic problems part i integral formulation abstract a boundary element formulation is developed for the static analysis of two and three dimensional solids and structures characterized by a linear elastic material behavior taking into account microstructural effects the simple gradient elastic theory of aifantis expressed in the framework of mindlin s general theory is used to model this material behaviour a variational statement is established to determine all possible classical and non classical due to gradient terms boundary conditions of the general boundary value problem the gradient elastic fundamental solution for both two and three dimensional cases is explicitly derived and used to construct the boundary integral representation of the solution with the aid of the reciprocal integral identity especially established for the gradient elasticity considered here it is found that for a well posed boundary value problem in addition to a boundary integral representation for the displacement a second boundary integral representation for its normal derivative is also necessary explicit expressions for interior displacements and stresses in integral form are also presented all the kernels in the integral equations are explicitly provided

necessity constraint in two plant optimal production problem with imprecise parameters the purpose of this paper is to present and solve a real life problem of two plants producing the same item under fuzzy stochastic environment here an item alongwith random defective units is produced at two different plants situated in different locations under a single management the rates of demand production and defectiveness at these places are different demands of the item are primarily met locally from the respective plants but if a stock out situation occurs in a plant immediately some stock from the other plant if available is rushed to the stock out plant the demands are known but production rates are unknown functions of time are taken as control variables the available budget for the management house is imprecise the holding shortage and transportation costs are assumed to be imprecise and represented by fuzzy numbers which are transformed to corresponding interval numbers following interval mathematics and nearest interval approximation the objective function is changed to respective multi objective functions and thus the single objective fuzzy problem is reduced to a crisp multi objective decision making modm problem the modm problem is then again transformed to a single crisp objective function with the help of weighted sum method using fuzzy relations the imprecise budget constraint expressed in the form of necessity constraint is transformed into an equivalent crisp one then total cost consisting of production holding shortage and transportation from one plant to another costs is expressed as an optimal control problem and solved using weighted sum method the kuhn tucker conditions pontryagin s optimal control principle and generalized reduced gradient grg technique the model has been illustrated by numerical data the optimum results are presented in both tabular and graphical forms

uniform stability for the timoshenko beam with tip load abstract in this paper we consider a hybrid elastic model consisting of a timoshenko beam and a tip load at the free end of the beam we show that uniform stabilization of the model which includes the rotary inertia of the tip load can be obtained when feedback boundary moment and force controls are applied at the point of contact between the beam and the tip load however in the presence of the load stabilization is slower and subject to a restriction on the boundary data at the free end of the beam

boundary element formulation for plane problems in couple stress elasticity summary couple stresses are introduced to account for the microstructure of a material within the framework of continuum mechanics linear isotropic versions of such materials possess a characteristic material length l that becomes increasingly important as problem dimensions shrink to that level e g as the radius a of a critical hole reduces to a size comparable to l consequently this size dependent elastic theory is essential to understand the behavior at micro and nano scales and to bridge the atomistic and classical continuum theories here we develop an integral representation for two dimensional boundary value problems in the newly established fully determinate theory of isotropic couple stress elastic media the resulting boundary only formulation involves displacements rotations force tractions and moment tractions as primary variables details on the corresponding numerical implementation within a boundary element method are then provided with emphasis on kernel singularities and numerical quadrature afterwards the new formulation is applied to several computational examples to validate the approach and to explore the consequences of size dependent couple stress elasticity copyright 2011 john wiley sons ltd

boundary control of the timoshenko beam it is shown that the timoshenko beam can be uniformly stabilized by means of a boundary control a numerical study on the spectrum is also presented

an evaluation of the eigenvalue approach for determining the membership values in fuzzy sets abstract the membership values of the elements of a fuzzy set of key importance in any theoretical or practical application of fuzzy set theory although there are many methods that evaluate membership values the methd proposed by saaty 8 9 based on matrix of pairwise comparisons and eigenvalue theory is the backbone of many other methods in this paper we evaluate the above method by using a forward error analysis approach with the assumption that the true membership values in a fuzzy set are continuous in the interval 0 1 the results reveal that the eigenvalue method is dramatically inaccurate even for fuzzy sets with few members

stability to weak dissipative bresse system in this paper we study the bresse system with frictional dissipation working only on the angle displacement our main result is to prove that this dissipative mechanism is enough to stabilize exponentially the whole system provided the velocities of waves propagations are the same this result is significative only from the mathematical point of view since in practice the velocities of waves propagations are always different in that direction we show that when the velocities are not the same the system is not exponentially stable and we prove that the solution in this case goes to zero polynomially with rates that can be improved by taking more regular initial data finally we give some numerical result to verify our analytical results

exponential and polynomial stability of an elastic bresse system with two locally distributed feedbacks in this paper we study the energy decay rate for the elastic bresse system in one dimensional bounded domain the physical system consists of three wave equations the two wave equations about the rotation angle and the longitudinal displacement are damped by two locally distributed feedbacks at the neighborhood of the boundary then indirect damping is applied to the equation for the transverse displacement of the beam through the coupling terms we will establish the exponential stability for this system in the case of the same speed of propagation in the equation for the vertical displacement and the equation for the rotation angle of the system when the wave speeds are different nonexponential decay rate is proved and a polynomial type decay rate is obtained the frequency domain method and the multiplier technique are applied

solving multi period project selection problems with fuzzy goal programming based on topsis and a fuzzy preference relation project portfolio managers are multi objective decision makers dms who are expected to select the best mix of projects by maximizing profits and minimizing risks over a multi period planning horizon however project portfolio decisions are complex multi objective problems with a high number of projects from which a subset has to be chosen subject to various constraints and a multitude of priorities and preferences we propose a goal programming gp approach for project portfolio selection that embraces conflicting fuzzy goals with imprecise priorities a fuzzy goal with an aspiration level and a predefined membership function is defined for each objective the impreciseness in the priorities of the membership values of the fuzzy goals is modeled with fuzzy relations this leads to type ii fuzzy sets since fuzzy relations are organized between the membership values of the fuzzy goals which are themselves fuzzy sets the proposed model is based on the technique for order preference by similarity to ideal solution topsis and fuzzy preference relations topsis is used to reduce the multi objective problem into a bi objective problem the resulting bi objective problem is solved with fuzzy gp fgp the fuzzy preference relations are used to help dms express their preferences with respect to the membership values of the fuzzy goals the proposed approach is used to solve a real life problem characterized as a fuzzy multi objective project selection with multi period planning horizon mops mpph the performance of the proposed approach is compared with a competing method in the literature we show that our approach generates high quality solutions with minimal computational efforts

expected value of fuzzy variable and fuzzy expected value models this paper will present a novel concept of expected values of fuzzy variables which is essentially a type of choquet integral and coincides with that of random variables in order to calculate the expected value of general fuzzy variable a fuzzy simulation technique is also designed finally we construct a spectrum of fuzzy expected value models and integrate fuzzy simulation neural network and genetic algorithms to produce a hybrid intelligent algorithm for solving general fuzzy expected value models

exponential stability for a timoshenko type system with history in this paper we consider hyperbolic timoshenko type vibrating systems that are coupled to a heat equation modeling an expectedly dissipative effect through heat conduction we use the semigroup method to prove the exponential stability result with assumptions on past history relaxation function g exponentially decaying for the equal wave speed case

the lack of exponential stability of the hybrid bresse system abstract in this paper we consider the dissipative bresse system with an attached hollow tip body that contains granular material the resulting model being called hybrid system our main result is to show that the corresponding model is not exponentially stable moreover we show that the solution decays polynomially to zero as 1 t 1 2 when t

gradient elasticity in statics and dynamics an overview of formulations length scale identification procedures finite element implementations and new results in this paper we discuss various formats of gradient elasticity and their performance in static and dynamic applications gradient elasticity theories provide extensions of the classical equations of elasticity with additional higher order spatial derivatives of strains stresses and or accelerations we focus on the versatile class of gradient elasticity theories whereby the higher order terms are the laplacian of the corresponding lower order terms one of the challenges of formulating gradient elasticity theories is to keep the number of additional constitutive parameters to a minimum we start with discussing the general mindlin theory that in its most general form has 903 constitutive elastic parameters but which were reduced by mindlin to three independent material length scales further simplifications are often possible in particular the aifantis theory has only one additional parameter in statics and opens up a whole new field of analytical and numerical solution procedures we also address how this can be extended to dynamics an overview of length scale identification and quantification procedures is given finite element implementations of the most commonly used versions of gradient elasticity are discussed together with the variationally consistent boundary conditions details are provided for particular formats of gradient elasticity that can be implemented with simple linear finite element shape functions new numerical results show the removal of singularities in statics and dynamics as well as the size dependent mechanical response predicted by gradient elasticity

a heuristic self tuning fuzzy controller abstract in this paper a self tuning fuzzy controller based on the tuning of scaling factors is presented the tuning schemes are tuning the scaling factors is individual tuning rules the tuning rules are transformed into numeric tuning tables by applying suitable membership functions so that the adjustings of the scaling factors are merely matrix mappings since the tuning rules are constructed with the control signal and the output error and change in output error of the plant as their antecedent parts the tuning processes have the advantage of real time property simulation results with a perturbed servo and the inverted pendulum system as the controlled plants show the performance and adaptivity of the proposed controller

transportation projects selection process using fuzzy sets theory government transportation agencies are faced with the problem of efficiently selecting a subset of transportation projects for implementation this selection process is based on multiple objectives which are often measured in incommensurable units usually the problem is treated by neglecting or biasing the qualitative characteristics of the various projects moreover the usual selection methods cannot deal effectively with the decision makers preferences or vagueness fuzzy sets theory is able to cope with inexact information and therefore is believed to be an appropriate tool for use in the projects selection process this work presents an efficient technique for the selection of transportation projects using fuzzy sets theory the selection procedure is a multiple objectives process and projects are rated both on a quantitative and qualitative basis using linguistic variables in order to describe appropriately a given transportation policy both fuzzy weighted average and noncompensatory fuzzy decision rules are used in the proposed approach in addition this work contains a case study of a selection process of interurban road projects in israel the results of the proposed method obtained by a fuzzy expert system are compared with the results obtained by an ordinary crisp process

model reference adaptive fuzzy control a linguistic space approach in this paper a model reference adaptive fuzzy controller with the adaptivity achieved by tuning both the scaling factors and the control rules is presented the proposed tuning strategy includes two parts 1 by referring a reference trajectory created in the linguistic space to tune the scaling factors and 2 by applying an auxiliary correction matrix generated by specific tuning rules to compensate the control rules since only the control signal the output error and change in output error of the plant are needed in the construction of the reference trajectory and the tuning rules the tuning strategy has the advantage of real time property simulation results with a damping process and an oscillating process as the controlled plants show the performance and adaptivity of the proposed controller

chirality in isotropic linear gradient elasticity abstract chirality is generally speaking the property of an object that can be classified as left or right handed though it plays an important role in many branches of science chirality is encountered less often in continuum mechanics so most classical material models do not account for it in the context of elasticity for example classical elasticity is not chiral leading different authors to use cosserat elasticity to allow modelling of chiral behaviour gradient elasticity can also model chiral behaviour however this has received much less attention than its cosserat counterpart this paper shows how in the case of isotropic linear gradient elasticity a single additional parameter can be introduced that describes chiral behaviour this additional parameter directly linked to three dimensional deformation can be either negative or positive with its sign indicating a discrimination between the two opposite directions of torsion two simple examples are presented to show the practical effects of the chiral behaviour

expert fuzzy controller abstract we describe a fuzzy controller based on our general purpose fuzzy expert system shell flops we take a decision theoretic view in designing an optimal fuzzy controller the variables in the decision problem are 1 the defuzzification rules 2 the fuzzification rules and 3 the fuzzy control rules the objective function is composed of fuzzy goals specified for each system output we differentiate between decision making under certainty risk or uncertainty depending whether or not random elements are present in the system an example is presented illustrating varying the defuzzification rules to improve system performance

a fuzzy dynamic learning controller for chemical process control a fuzzy dynamic learning controller is proposed and applied to control of time delayed non linear and unstable chemical processes the proposed fuzzy dynamic learning controller can self adjust its fuzzy control rules using the external dynamic information from the process during on line control and it can create the new fuzzy control rules autonomously using its learning capability from past control trends the proposed controller shows better performance than the conventional fuzzy logic controller and the fuzzy self organizing controller

a model reference control structure using a fuzzy neural network in this paper we present a design method for a model reference control structure using a fuzzy neural network we study a simple fuzzy logic based neural network system knowledge of rules is explicitly encoded in the weights of the proposed network and inferences are executed efficiently at high rate two fuzzy neural networks are utilized in the control structure one is a controller called the fuzzy neural network controller fnnc the other is an identifier called the fuzzy neural network identifier fnni adaptive learning rates for both the fnnc and fnni are guaranteed to converge by a lyapunov function the on line control ability robustness learning ability and interpolation ability of the proposed model reference control structure are confirmed by simulation results

fuzzy self organizing controller and its application for dynamic processes abstract this paper deals with a self organizing controller used in real time and its application for dynamic processes the control policy of the controller is able to develop and improve automatically a new self organizing control algorithm which modifies the fuzzy control decision table is presented in this paper the control algorithm needs much less computation time and memory of the computer this paper provides two examples of the fuzzy self organizing control a set of experiment results is described it shows that the controller can be applied to some processes such as processes with time lag and non linearity or one whose parameter or running conditions are varied which were usually not controlled very well with a conventional controller

credibility based chance constrained integer programming models for capital budgeting with fuzzy parameters in this paper we discuss a problem of capital budgeting in a fuzzy environment two types of models are proposed using credibility to measure confidence level since the proposed optimization problems are difficult to solve by traditional methods a fuzzy simulation based genetic algorithm is applied two numerical experiments demonstrate the effectiveness of the proposed algorithm

uniform decay in a timoshenko type system with past history abstract fernandez sare and rivera h d fernandez sare j e munoz rivera stability of timoshenko systems with past history j math anal appl 339 1 2008 482 502 considered the following timoshenko type system 1 t t k x x 0 2 t t b x x 0 g t x x t s d s k x 0 where g is a positive differentiable exponentially decaying function they established an exponential decay result in the case of equal wave speed propagation and a polynomial decay result in the case of nonequal wave speed propagation in this paper we study the same system for g decaying polynomially and prove polynomial stability results for the equal and nonequal wave speed propagation our results are established under conditions on the relaxation function weaker than those in h d fernandez sare j e munoz rivera stability of timoshenko systems with past history j math anal appl 339 1 2008 482 502

minimax chance constrained programming models for fuzzy decision systems abstract the existing chance constrained programming for fuzzy decision systems is essentially a kind of maximax models optimistic models which maximize the maximum possible return this paper presents a spectrum of minimax models as opposed to maximax models based on chance constrained programming as well as chance constrained multi objective programming and chance constrained goal programming in which the minimax models will select the alternative that provides the best of the worst possible return finally a fuzzy simulation based genetic algorithm will be designed for solving minimax models and illustrated by some numerical examples

a rule self regulating fuzzy controller abstract the most effective way to improve the performance of a fuzzy controller may be to optimize the fuzzy control rules usually fuzzy control rules are generated by 1 translating the operators experience into fuzzy linguistic form directly 2 monitoring and summarizing the control behaviour of the operators 3 modelling the process to be controlled using fuzzy set theory 4 self organizing in running of the control systems different from the above means the authors in 10 have proposed a method to regulate fuzzy control rules where the control rules are represented by an analytic expression with a regulating factor the authors in this paper employ such a method and use a simplified fuzzy control algorithm which allows fuzzy control rules to be regulated on line thus constructing a rule self regulating fuzzy controller rsfc simulation results demonstrate that the performance of rsfc is better than that of a non rule regulating fuzzy controller

building a model based fuzzy controller a new form of fuzzy model based controller is introduced the new controller is based on a conventional predictive controller design but utilises a fuzzy relational model the controller is described and compared with existing fuzzy controllers practical advice is given on generating suitable relational models for control purposes and an appropriate identification algorithm is recommended the controller is tested on a liquid level process and its performance compared to another fuzzy model based controller which has been previously reported

relations among convergence concepts of uncertain sequences uncertainty theory is a generalization of probability theory and credibility theory the purpose of this paper is to investigate various convergence concepts of uncertain sequences in uncertainty spaces sufficient and necessary conditions for convergence of uncertain sequences are given the relations among various convergence concepts of uncertain sequences are established

control of dynamical processes using an on line rule adaptive fuzzy control system abstract in this paper we present a detailed discussion on the design of a rule adaptive fuzzy control system along with simulation analysis demonstrating its usefulness in controlling plants of various dynamical natures conceived first by wang and further clarified in 8 the rule adaptive fuzzy controller considered here generates the fuzzy control signal as a convex combination of the standard fuzzy inputs to the controller the error and the error rate such a combination is automatically adjusted on line in response to the varying control situations with certain updating scheme this paper considers two different updating schemes the first one is based on a fuzzy relationship and is a revision of the rule presented in 11 the present paper also proposes the second updating rule that is essentially a nonlinear differential equation both of the rules are applied to the simulations of several selected dynamical plants the simulation results show that the controller is effective in controlling a wide range of dynamical plants especially it shows better performance in controlling the plants found difficult to be controlled by the conventional means the simulation also shows that the controller can be used to curb the effect of load disturbance in the control process

asymptotic behavior of timoshenko beam with dissipative boundary feedback abstract this paper is concerned with the stabilization problem of timoshenko beam in the presence of linear dissipative boundary feedback controls using c 0 semigroups theory we establish the existence and the uniqueness of solution of the proposed closed loop system in order to consider the asymptotic behavior of the closed loop system we first discuss the existence of nonzero solution of a closely related boundary value problem then we derive various necessary and sufficient conditions for the system to be asymptotically stable finally we prove the equivalence between the exponential stability and the asymptotic stability for the closed loop system

bresse system with indefinite damping abstract we consider the bresse system in a bounded domain 0 l r 1 the system has an indefinite damping mechanism i e with a damping function a a x possibly changing sign presented only in the equation for the rotation angle we shall prove that the system is still exponentially stable under the same conditions as in the positive constant damping case and provided a 1 l 0 l a x d x 0 and a a l 2 for small enough in the arguments we shall also give a new proof of exponential stability for the constant case a a

generating rules for fuzzy logic controllers by functions abstract in this paper we introduce a method of generating control rules for fuzzy logic controllers called parametric functions method by this method we can obtain control rules by adjusting several parameters

a self tuning fuzzy controller abstract the aim of a fuzzy controller is to compensate the dynamic characteristics of the controlled system it is the same purpose as for the fuzzy logic controller flc now the best design of the flc is required for achievement of this purpose but such a controller has not yet been completely designed because the fuzzy controller is constructed of control rules which are ambiguously described by conventional controller strategies and expert knowledge and because its structure theory is not well established yet that is in order to construct the best rules a highly skilled technique and a tuning technique using trial and error are required as a way to easily design a flc a method which improves a given standard flc is considered in this paper we propose a self tuning algorithm of the flc it has two functions in adjusting the scaling factors which are the parameters of the flc and in improving the control rules of flc by evaluating the control response at real time and the control results after operations we add these functions to the flc and design the self tuning fuzzy controller stfc this makes the flc a good controller

stabilization of the nonuniform timoshenko beam in this paper we consider a timoshenko beam with variable physical parameters we prove that the model can be stabilize by one control force for both internal and boundary cases

general energy decay in a timoshenko type system of thermoelasticity of type iii with a viscoelastic damping in this paper we consider a one dimensional linear thermoelastic system of timoshenko type where the heat conduction is given by green and naghdi theories we prove a general decay result from which the exponential and polynomial decays are only special cases

fuzzy quadratic minimum spanning tree problem in this paper a fuzzy quadratic minimum spanning tree problem is formulated as expected value model chance constrained programming and dependent chance programming according to different decision criteria then the crisp equivalents are derived when the fuzzy costs are characterized by trapezoidal fuzzy numbers furthermore a simulation based genetic algorithm using prufer number representation is designed for solving the proposed fuzzy programming models as well as their crisp equivalents finally a numerical example is provided for illustrating the effectiveness of the genetic algorithm

fuzzy capital budgeting fuzzy equivalents of all the classical capital budgeting investment choice methods are generalised or proposed these equivalents can be used to evaluate and compare projects in which the cash ows duration time and required rate of return cost of capital are given imprecisely in the form of a fuzzy number c 2000 elsevier science b v all rights reserved

energy decay in a timoshenko type system of thermoelasticity of type iii in this paper we consider a one dimensional linear thermoelastic system of timoshenko type where the heat conduction is given by green and naghdi theories we prove the exponential stability by using the energy method

fuzzy adaptive control of a first order process abstract fuzzy adaptive control of a first order process with a varying gain and time constant is demonstrated the fuzzy adaptive controller is based on a fuzzy model based controller that uses an explicit fuzzy model of the process adaptation is achieved by the addition of on line identification of the fuzzy process model starting with a crude initial model the adaptive controller matches the model to the process to self tune the controller the model is further modified when the operating point is changed to adapt the controller to the new process conditions two different fuzzy identification algorithms are both shown to provide a successful fuzzy adaptive controller the robustness of the algorithms in the presence of process noise is investigated and improved by the addition of weighting factors

chance constrained programming with fuzzy parameters this paper extends chance constrained programming from stochastic to fuzzy environments analogous to stochastic programming some crisp equivalents of chance constraints in fuzzy environments are presented we also propose a technique of fuzzy simulation for the chance constraints which are usually hard to be converted to their crisp equivalents finally a fuzzy simulation based genetic algorithm is designed for solving this kind of problems and some numerical examples are discussed

an advanced boundary element method for solving 2d and 3d static problems in mindlin s strain gradient theory of elasticity an advanced boundary element method bem for solving two 2d and three dimensional 3d problems in materials with microstructural effects is presented the analysis is performed in the context of mindlin s form ii gradient elastic theory the fundamental solution of the equilibrium partial differential equation is explicitly derived the integral representation of the problem consisting of two boundary integral equations one for displacements and the other for its normal derivative is developed the global boundary of the analyzed domain is discretized into quadratic line and quadrilateral elements for 2d and 3d problems respectively representative 2d and 3d numerical examples are presented to illustrate the method demonstrate its accuracy and efficiency and assess the gradient effect on the response the importance of satisfying the correct boundary conditions in gradient elastic problems is illustrated with the solution of simple 2d problems copyright 2010 john wiley sons ltd

risk curve and fuzzy portfolio selection in stochastic environment variance semivariance and probability of a bad outcome are three popular definitions of risk for portfolio selection in fuzzy environment variance is carried on as the definition of risk however in real life risk is understood in many different ways in this paper we propose a new definition of risk for portfolio selection in fuzzy environment based on this new definition a new type of model is provided to give a general solution to the new model problem a hybrid intelligent algorithm is designed one numerical example is also presented to illustrate the optimization idea and the effectiveness of the designed algorithm

optimal polynomial decay of functions and operator semigroups we characterize the polynomial decay of orbits of hilbert space c 0 semigroups in resolvent terms we also show that results of the same type for general banach space semigroups and functions obtained recently in batty and duyckaerts j evol eq 8 765 780 2008 are sharp this settles a conjecture posed in batty and duyckaerts 2008

a boundary element method for solving 2 d and 3 d static gradient elastic problems part ii numerical implementation the boundary element formulation for the static analysis of two dimensional 2 d and three dimensional 3 d solids and structures characterized by a gradient elastic material behavior developed in the first part of this work is treated numerically in this second part for the creation of a highly accurate and efficient boundary element solution tool the discretization of the body is restricted only to its boundary and is accomplished by the use of quadratic isoparametric three noded line and eight noded quadrilateral boundary elements for the 2 d and 3 d cases respectively advanced algorithms are presented for the accurate and efficient numerical computation of the singular integrals involved numerical examples involving a cylindrical bar in tension and a cylinder and a sphere in radial deformation are solved by the proposed boundary element method and the results are found in excellent agreement with the derived by the authors analytical solutions the bar and sphere problems are solved in a 3 d context while the cylinder problem is solved in a 2 d context plane strain both the exterior and interior versions of the cylinder and sphere problems are considered

stability of timoshenko systems with past history we consider vibrating systems of timoshenko type with past history acting only in one equation we show that the dissipation given by the history term is strong enough to produce exponential stability if and only if the equations have the same wave speeds otherwise the corresponding system does not decay exponentially as time goes to infinity in the case that the wave speeds of the equations are different which is more realistic from the physical point of view we show that the solution decays polynomially to zero with rates that can be improved depending on the regularity of the initial data

an empirical analysis of the use of the analytic hierarchy process for estimating membership values in a fuzzy set abstract the analytic hierarchy process ahp is now a popular multicriteria decision making method and has been applied in many diverse areas despite the debate on its theoretical foundations many researchers have been using the pairwise comparison matrix and the eigenvector method suggested by saaty for obtaining priority ratings of the decision alternatives in an ahp hierarchy these priority ratings have been used as estimates of fuzzy membership values of the elements called alternatives in ahp of a fuzzy set triantaphyllou and mann have argued that saaty s scale and the eigenvector method are inadequate for estimating fuzzy membership values this paper points out the limitations in the arguments of triantaphyllou and mann about the eigenvector method it primarily concentrates on two aspects the first pertains to saaty s condition on deleting or combining two alternatives which are near copies alternatives whose priority values are close to each other within a 10 range over all criteria the second aspect concerns the use of the eigenvector method for estimating the membership values of elements of a fuzzy set the use of the eigenvector method for estimating fuzzy membership values in a fuzzy set has been justified using the empirical analysis together with theoretical support it has been amply demonstrated in this paper that the problem lies in saaty s scale and not in the eigenvector method

asymptotic stability for bresse systems abstract in this paper consider a vibrating system of bresse type in a one dimensional bounded domain with a nonlinear damping acting in the equation of the shear angle displacement and nonlinear localized damping in other equations we show the asymptotic stability without imposing conditions about the equal speed wave propagation using a method developed by lasiecka and tataru 9

boundary element analysis of mode i and mixed mode i and ii crack problems of 2 d gradient elasticity abstract a boundary element method is developed for fracture analysis of gradient elastic planar solids under static loading a simple version of mindlin s general theory of gradient elastic materials is employed and the two required boundary integral equations one for the displacement vector and the other for its normal derivative are presented use is made of the fundamental solution of the problem and this leads to a formulation that requires only a boundary discretization two representative numerical examples are presented to illustrate the method demonstrate its accuracy and efficiency and assess the gradient effect on the response the first deals with a mode i crack while the second with a mixed mode i ii crack for the second case the proposed method is used in conjunction with the method of subregions the method is employed with regular and special near the crack tip boundary elements the gradient effect consists of modifying both the displacement and the stress field around the crack tip and resulting in a response which is more physically acceptable than the one coming from the classical theory of elasticity