seismic response of underwater members of variable cross section abstract this paper is concerned with a method for solving seismic response problems of a pile of variable cross section with a tip inertia subjected to a sea bottom seismic displacement the analysis developed here is based on an elastodynamic theory in which the effects of the continuously distributed mass and rigidity of the pile are included the method includes use of fourier series expansion the laplace transform the transfer matrix method and the residue theorem in order to deal with the complex seismic displacement and arbitrarily shaped piles considerable simplification of the calculations is thus achieved the theoretical results given are applicable to seismic response problems for a pile of arbitrary shape with a tip inertia excited by arbitrary displacements as an application of the present theoretical results the dynamic response has been calculated for hollow piles of curved conical shape with tip inertias and double taper beams subjected to seismic displacements

hydroelastic vibrations of flexible rectangular tanks partially filled with liquid in this paper the three dimensional vibratory characteristics of flexible rectangular tanks partially filled with liquid are studied the surface waves of the liquid are taken into account in the analysis both the bulging modes of the tank wall vibration and the sloshing modes of the liquid oscillation are investigated the vibrating modes of the liquid tank system are divided into four distinct categories double symmetric modes ss antisymmetric symmetric modes as symmetric antisymmetric modes sa and double antisymmetric modes aa each of these categories is separately investigated the velocity potential of the liquid is analytically deduced by using a combination of the superposition method and the method of separation of variables according to the liquid tank interface conditions and the orthogonality of trigonometric functions the coefficients in the solution of liquid velocity potential are expressed in the integral forms including the tank wall dynamic deflection a set of reasonable static beam functions is constructed as the admissible functions of the tank wall vibration the eigenfrequency equation of the liquid tank system is derived by using a combination of the rayleigh ritz method and the galerkin method convergence study demonstrates the high accuracy and small computational cost of the proposed approach finally some numerical results are presented for the first time copyright 2006 john wiley sons ltd

lagrangean decomposition a model yielding stronger lagrangean bounds given a mixed integer programming problem with two matrix constraints it is possible to define a lagrangean relaxation such that the relaxed problem decomposes additively into two subproblems each having one of the two matrices of the original problem as its constraints there is one lagrangean multiplier per variable we prove that the optimal value of this new lagrangean dual dominates the optimal value of the lagrangean dual obtained by relaxing one set of constraints and give a necessary condition for a strict improvement we show on an example that the resulting bound improvement can be substantial we show on a complex practical problem how lagrangean decomposition may help uncover hidden special structures and thus yield better solution methodology

vibration of circular plates on a free fluid surface effect of surface waves the effect of free surface waves on free vibrations of circular plates resting on a free fluid surface is studied the solution is achieved by using a perturbation technique and the hankel transformation method which give a couple of dual integral equations of titchmarsh type the fluid is considered inviscid and incompressible and the velocity potential describes its motion the kirchhoff theory of plates is used to model the elastic thin plate the theory is suitable for all axisymmetric plate boundary conditions numerical results are given in non dimensional form for modes up to five nodal circles and diameters for clamped simply supported and free edge plates to be ready to use in applications the effect of free surface waves on the plate s natural frequencies is significant only when bluging and sloshing modes of the system have close natural frequencies

mapping tori of free group automorphisms are coherent the mapping torus of an endomorphism of a group g is the hnnextensiong g with bonding maps the identity and we show that a mapping torus of an injective free group endomorphism has the property that its flnitely generated subgroups are flnitely presented and moreover these subgroups are of flnite type

an efficient tabu search approach for the 0 1 multidimensional knapsack problem abstract in this paper we describe a new approach to tabu search ts based on strategic oscillation and surrogate constraint information that provides a balance between intensification and diversification strategies new rules needed to control the oscillation process are given for the 0 1 multidimensional knapsack 0 1 mkp based on a portfolio of test problems from the literature our method obtains solutions whose quality is at least as good as the best solutions obtained by previous methods especially with large scale instances these encouraging results confirm the efficiency of the tunneling concept coupled with surrogate information when resource constraints are present

hydroelastic vibration of two identical rectangular plates a theoretical study is presented on the hydroelastic vibration of two identical rectangular plates coupled with a bounded fluid it is assumed that the plates are clamped along the plate edges and an ideal fluid is surrounded by the two rectangular plates and a rigid rectangular container the velocity potential satisfying the fluid boundary conditions is expanded in terms of a finite fourier series and the modal displacements of the plates are also expanded by the finite fourier series for the compatibility requirement along the contacting surface between the plates and the fluid two transverse vibration modes in phase and out of phase are observed in the symmetric fluid coupled structure each in phase mode is assumed as a combination of the beam modes in air but every out of phase mode is assumed as a combination of polynomials satisfying the plate boundary condition and fluid volume conservation the coupled natural frequencies are obtained from the relationship between the reference kinetic energy of the structure including the fluid and the maximum strain energy of the two plates the proposed analytical method was found to be in good agreement with the results of a three dimensional finite element analysis

an exact algorithm for the two constraint 0 1 knapsack problem we consider a knapsack problem in which each item has two types of weight and the container has two types of capacity we discuss the surrogate lagrangian and continuous relaxations and give an effective method to determine the optimal lagrangian and surrogate multipliers associated with the continuous relaxation of the problem these results are used to obtain an exact branch and bound algorithm which also includes heuristic procedures and a reduction technique the performance of bounds and algorithms is evaluated through extensive computational experiments

asymmetric vibration of a heavily fluid loaded circular plate using variational principles as an initial step in the extension of the surface variational principle svp to an assumed modes analysis of vibratory displacement and surface pressure on submerged axisymmetric structures subjected to arbitrary nonsymmetric loading the present study considers an arbitrary harmonic excitation of an elastic plate two configurations in which the supporting baffle is a thin rigid disk or an infinite plane are considered fourier series expansions of the azimuthal dependence of pressure and displacement are shown to be uncoupled with each harmonic being governed by equations that are similar in form to those for the analogous axisymmetric problem recursion relations using coefficients developed in the course of solving the axisymmetric problem are shown to substantially expedite the evaluation of the additional azimuthal harmonics results for a force located at r a 2 when ka 3 35 where a is the radius of the plate are presented in terms of the radial variation associated with each harmonic as wel

vibration of a plate with arbitrary shape in contact with a fluid this paper is concerned with a method for solving vibration problems of arbitrarily shaped plates in contact with a fluid expressions of natural frequencies displacements and pressures for arbitrary plates in contact with a fluid are obtained with consideration of viscosity of fluid the analysis applies the exact solution of the equations of motion and the fourier expansion collocation method for satisfying the boundary conditions numerical calculations have been carried out for elliptical plates and rectangular plates with round corners in contact with a fluid

axisymmetric vibration of circular plates in contact with fluid abstract this paper is concerned with the effect of fluid on the natural frequencies of circular plates vibrating axisymmetrically in contact with fluid the ratio between the natural frequencies in fluid and the natural frequencies in air is a function of so called added virtual mass incremental avmi factor which reflects the increase of inertia due to the presence of fluid in this paper the non dimensionalized added virtual mass incremental navmi factor for circular plates having simply supported clamped and free edges is obtained by employing the integral transformation technique in conjunction with the dual integral equation method it is shown that the effect of fluid on the natural frequencies decreases with order

hydroelastic vibration of a circular plate submerged in a bounded compressible fluid abstract an analytical method for the linear free vibration of a circular plate submerged in a fluid was developed by the rayleigh ritz method based on the fourier bessel series expansion it is assumed that the plate is clamped at an offcenter location of a rigid cylindrical container and the fluid bisected by the plate in the container is non viscous and compressible since a combination of the dry modal functions of the circular plate can approximate the wet vibration modes the functions were used to form a set of linearly independent functions of the rayleigh ritz method it was found that the theoretical results could predict well the fluid coupled natural frequencies with excellent accuracy compared with the finite element analysis results the effects of the fluid compressibility and the offcenter distance on the natural frequencies were also observed

free vibration of two identical circular plates coupled with bounded fluid abstract this paper examines the hydroelastic vibration of two identical circular plates coupled with a bounded fluid an analytical method based on the finite fourier bessel series expansion and the rayleigh ritz method is suggested in the theory it is assumed that a rigid cylindrical container is filled with the ideal fluid and the two plates are clamped along the container edges the proposed method is verified by finite element analysis using commercial software with excellent accuracy two transverse vibration modes in phase and out of phase are observed alternately in the fluid coupled system when the number of nodal circles increases for the fixed nodal diameter it is found that the normalized natural frequency of the system monotonically increases with an increase in the number of nodal diameters and circles by virtue of a decrease in relative hydrodynamic mass

heuristics for the 0 1 multidimensional knapsack problem abstract two heuristics for the 0 1 multidimensional knapsack problem mkp are presented the first one uses surrogate relaxation and the relaxed problem is solved via a modified dynamic programming algorithm the heuristics provides a feasible solution for mkp the second one combines a limited branch and cut procedure with the previous approach and tries to improve the bound obtained by exploring some nodes that have been rejected by the modified dynamic programming algorithm computational experiences show that our approaches give better results than the existing heuristics and thus permit one to obtain a smaller gap between the solution provided and an optimal solution

exploiting nested inequalities and surrogate constraints abstract the exploitation of nested inequalities and surrogate constraints as originally proposed in glover glover f 1965 a multiphase dual algorithm for the zero one integer programming problem operations research 13 879 919 glover f 1971 flows in arborescences management science 17 568 586 has been specialized to multidimensional knapsack problems in osorio et al osorio m a glover f hammer p 2002 cutting and surrogate constraint analysis for improved multidimensional knapsack solutions annals of operations research 117 71 93 we show how this specialized exploitation can be strengthened to give better results this outcome results by a series of observations based on surrogate constraint duality and properties of nested inequalities the consequences of these observations are illustrated by numerical examples to provide insights into uses of surrogate constraints and nested inequalities that can be useful in a variety of problem settings

three dimensional vibration analysis of rectangular thick plates on pasternak foundation the free vibration characteristics of rectangular thick plates resting on elastic foundations have been studied based on the three dimensional linear and small strain elasticity theory the foundation is described by the pasternak two parameter model the ritz method is used to derive the eigenvalue equation of the rectangular plate by augmenting the strain energy of the plate with the potential energy of the elastic foundation the chebyshev polynomials multiplied by a boundary function are selected as the admissible functions of the displacement functions in each direction the approach is suitable for rectangular plates with arbitrary boundary conditions convergence and comparison studies have been performed on square plates on elastic foundations with different boundary conditions it is shown that the present method has a rapid convergent rate stable numerical operation and very high accuracy parametric investigations on the dynamic behaviour of clamped square thick plates on elastic foundations have been carried out in detail with respect to different thickness span ratios and foundation parameters some results found for the first time have been given and some important conclusions have been drawn

dynamics of a rectangular plate resting on an elastic foundation and partially in contact with a quiescent fluid abstract in this study a method of analysis is presented for investigating the effects of elastic foundation and fluid on the dynamic response characteristics natural frequencies and associated mode shapes of rectangular kirchhoff plates for the interaction of the kirchhoff plate pasternak foundation a mixed type finite element formulation is employed by using the g teaux differential the plate finite element adopted in this study is quadrilateral and isoparametric having four corner nodes and at each node four degrees of freedom are present one transverse displacement two bending moments and one torsional moment therefore a total number of 16 degrees of freedom are assigned to each element a consistent mass formulation is used for the eigenvalue solution in the mixed finite element analysis the plate structure considered is assumed clamped or simply supported along its edges and resting on a pasternak foundation furthermore the plate is fully or partially in contact with fresh water on its one side for the calculation of the fluid structure interaction effects generalized fluid structure interaction forces a boundary element method is adopted together with the method of images in order to impose an appropriate boundary condition on the fluid s free surface it is assumed that the fluid is ideal i e inviscid incompressible and its motion is irrotational it is also assumed that the plate elastic foundation system vibrates in its in vacuo eigenmodes when it is in contact with fluid and that each mode gives rise to a corresponding surface pressure distribution on the wetted surface of the structure at the fluid structure interface continuity considerations require that the normal velocity of the fluid is equal to that of the structure the normal velocities on the wetted surface of the structure are expressed in terms of the modal structural displacements obtained from the finite element analysis by using the boundary integral equation method the fluid pressure is eliminated from the problem and the fluid structure interaction forces are calculated in terms of the generalized hydrodynamic added mass coefficients due to the inertial effect of fluid to asses the influences of the elastic foundation and fluid on the dynamic behavior of the plate structure the natural frequencies and associated mode shapes are presented furthermore the influence of the submerging depth on the dynamic behavior is also investigated

dynamic responses of reissner mindlin plates with free edges resting on tensionless elastic foundations abstract dynamic response analysis is presented for a reissner mindlin plate with four free edges resting on a tensionless elastic foundation of the winkler type and pasternak type the mechanical loads consist of transverse partially distributed impulsive loads and in plane static edge loads while the temperature field is assumed to exhibit a linear variation through the thickness of the plate the material properties are assumed to be independent of temperature the two cases of initially compressed plates and of initially heated plates are considered the formulations are based on reissner mindlin first order shear deformation plate theory and include the plate foundation interaction and thermal effects a set of admissible functions is developed for the dynamic response analysis of moderately thick plates with four free edges the galerkin method the gauss legendre quadrature procedure and the runge kutta technique are employed in conjunction with this set of admissible functions to determine the deflection time and bending moment time curves as well as shape mode curves an iterative scheme is developed to obtain numerical results without using any assumption on the shape of the contact region the numerical illustrations concern moderately thick plates with four free edges resting on tensionless elastic foundations of the winkler type and pasternak type from which results for conventional elastic foundations are obtained as comparators the results confirm that the plate will have stronger dynamic behavior than its counterpart when it is supported by a tensionless elastic foundation

computing subgroup presentations using the coherence arguments of mccammond and wise abstract we describe an algorithm which may be used to compute a finite presentation of a finitely generated subgroup of a finitely presented group g provided that g satisfies appropriate hypotheses the algorithm is based on an algorithm of mccammond and wise but is extended to cover a wider class of groups including all those satisfying the path reduction or weak 2 cell reduction hypotheses of mccammond and wise the proofs of correctness of our algorithm emerge from mccammond and wise own proofs that their hypotheses imply coherence of the groups satisfying them we also demonstrate that the algorithm may be extended further to cover groups satisfying appropriate conditions on fans strings of 2 cells within disc diagrams the core of this work originally appeared in the phd thesis of the first author

the forced vibration of a thin plate floating on an infinite liquid abstract in this paper a solution is presented for the harmonically forced vibration of an arbitrary thin plate floating on the surface of an infinite liquid the full linear potential problem for the liquid is solved by the use of the appropriate green s function a variational equation which the plate liquid system must satisfy is derived and a solution by the rayleigh ritz method is presented examples of possible calculations are given for a square and a rectangular plate

hydroelastic vibration of circular plates abstract this paper is concerned with the virtual mass effect due to the presence of water on the natural frequencies of circular plates which are placed into a hole of an infinite rigid wall with one side exposed to water this classical problem was solved by lamb but he provided limited theoretical results to obtain the complete theoretical results the so called non dimensionalized added virtual mass incremental factors are obtained by employing the integral transformation technique in conjunction with the fourier bassel series approach it is found that the non dimensionalized added virtual mass incremental factors for circular plates vibrating in an infinite rigid wall with one side exposed to water are larger than those for circular plates which rest on a free surface this is due to the fact that the rigid wall constrains the motion of the water thus resulting in an increase in the kinetic energy of the water it is also observed that the effect of water on the natural frequencies generally decreases with order

hydroelastic analysis of fluid storage tanks by using a boundary integral equation method abstract this paper presents a boundary integral equation method in conjunction with the method of images in order to investigate the dynamic behaviour wet frequencies and associated mode shapes of fluid containing structures in the analysis of the linear fluid structure system it is assumed that the fluid is ideal and fluid forces are associated with inertial effects of the contained fluid this implies that the fluid pressure on the wetted surface of the structure is in phase with the structural acceleration the in vacuo dynamic properties of the dry structure are obtained by using standard finite element software in the wet part of the analysis the fluid structure interaction effects are calculated in terms of the generalized added mass coefficients by use of the boundary integral equation method together with the method of images in order to impose the 0 boundary condition on the free surface in this study three different test cases are considered i a clamped free cylindrical tank with a rigid bottom ii a flexible circular plate in a rigid cylindrical tank and iii a flexible cylindrical shell with flexible end plates hermetic can the fluid storage tanks in this investigation are assumed partially or completely filled with water to assess the influence of the contained fluid on the dynamic characteristics the wet natural frequencies and associated mode shapes are calculated the predictions compare well with available experimental and numerical data

free vibration of a partially liquid filled and submerged horizontal cylindrical shell abstract the dynamic characteristics i e natural frequencies and mode shapes of a partially filled and or submerged horizontal cylindrical shell are examined in this investigation it is assumed that the fluid is ideal and fluid forces are associated with inertial effects only namely the fluid pressure on the wetted surface of the structure is in phase with the structural acceleration the in vacuo dynamic characteristics of the cylindrical shell are obtained using standard finite element software in the wet part of the analysis it is assumed that the shell structure preserves its in vacuo mode shapes when in contact with the contained and or surrounding fluid and that each mode shape gives rise to a corresponding surface pressure distribution of the shell the fluid structure interaction effects are calculated in terms of generalized added masses using a boundary integral equation method together with the method of images in order to impose an appropriate boundary condition on the free surface to assess the influence of the contained and or surrounding fluid on the dynamic behaviour of the shell structure the wet natural frequencies and associated mode shapes were calculated and compared with available experimental measurements

a theoretical and empirical investigation on the lagrangian capacities of the 0 1 multidimensional knapsack problem abstract we present a novel lagrangian method to find good feasible solutions in theoretical and empirical aspects after investigating the concept of lagrangian capacity which is the value of the capacity constraint that lagrangian relaxation can find an optimal solution we formally reintroduce lagrangian capacity suitable to the 0 1 multidimensional knapsack problem and present its new geometric equivalent condition including a new associated property based on the property we propose a new lagrangian heuristic that finds high quality feasible solutions of the 0 1 multidimensional knapsack problem we verify the advantage of the proposed heuristic by experiments we make comparisons with existing lagrangian approaches on benchmark data and show that the proposed method performs well on large scale data

effect of fluid depth on the hydroelastic vibration of free edge circular plate abstract this paper is concerned with the effect of water depth on the free vibration of free edge circular plates resting on a free fluid surface the problem addressed is formulated by using the hankel transformation method which leads to dual integral equations the solution of dual integral equations is solved numerically by using fourier bessel series the fluid is assumed to be inviscid and incompressible the kirchhoff theory of plates is used to model the elastic thin plate numerical results are given in non dimensional form for free edge circular plates in order to be ready to use in applications to validate the theoretical results experiments were carried out experimental results are in good agreement with theoretical results it is found that the effect of the fluid depth can be neglected when the fluid depth is greater than the diameter of the circular plates but becomes significant as the water depth decreases it is also observed in the experimental results that the fluid damping increases as the water depth decreases

an exact search for the solution of the surrogate dual of the 0 1 bidimensional knapsack problem abstract the surrogate dual of the 0 1 bidimensional knapsack problem is exactly solved by an algorithm with a modified dichotomic search the primal or dual optimality is proved with a finite number of iterations a lot of numerical experiments show the efficiency of our method its reduced number of iterations is revealed to be independent of the size of the instances

efficient algorithms for solving multiconstraint zero one knapsack problems to optimality the multiconstraint 0 1 knapsack problem is encountered when one has to decide how to use a knapsack with multiple resource constraints even though the single constraint version of this problem has received a lot of attention the multiconstraint knapsack problem has been seldom addressed

asymptotic formulas for the acoustic radiation impedance of an elastically supported annular plate this paper deals with the normalized acoustic radiation impedance of an elastically supported annular plate in axisymmetric vibrations cauchy s theorem about residues and the stationary phase method have been used to approximate the corresponding integrals as a result elementary asymptotic formulas valid for axisymmetric boundary configurations of clamped guided simply supported and free annular plates as well as for all the intermediate boundary configurations have been obtained

dynamic response of circular plates in contact with a fluid subjected to general dynamic pressures on a fluid surface abstract this paper is concerned with a method for solving dynamic response problems of a circular plate in contact with a fluid whose surface is excited by general dynamic pressures by utilizing the fourier expansion and the laplace transform methods the expression for the dynamic response of displacement is obtained in a general form which is applicable to general dynamic pressures as applications numerical calculations have been carried out for three types of sinusoidal trapezoidal and explosive pressures the results obtained in a certain type of impact pressure are compared with the exact ones

topology of finite graphs this paper derives from a course in group theory which i gave at berkeley in 1982 i wanted to prove the standard theorems on free groups and discovered that after a few preliminaries the notion of locally injective map or immersion of graphs was very useful this enables one to see in an effective easy algorithmic way just what happens with finitely generated free groups one can understand in this way 1 howson s theorem that if a and b are finitely generated subgroups of a free group then a b is finitely generated and 2 m hall s theorem that finitely generated subgroups of free groups are closed in the profinite topology during this course s m gersten came up with a simple proof of h neumann s inequality on the ranks in howson s theorem one of the ideas in gersten s proof was to use core graphs graphs with no trees hanging on subsequently i found that some consequences of a paper of greenberg s could be proved using core graphs and covering translations of immersions the most striking such result is that if a and b are finitely generated subgroups of a free group and if a c b is of finite index in both a and b then a b is of finite index in a v b the subgroup generated by a ub

surrogate upper bound sets for bi objective bi dimensional binary knapsack problems the paper deals with the definition and the computation of surrogate upper bound sets for the bi objective bi dimensional binary knapsack problem it introduces the optimal convex surrogate upper bound set which is the tightest possible definition based on the convex relaxation of the surrogate relaxation two exact algorithms are proposed an enumerative algorithm and its improved version this second algorithm results from an accurate analysis of the surrogate multipliers and the dominance relations between bound sets based on the improved exact algorithm an approximated version is derived the proposed algorithms are benchmarked using a dataset composed of three groups of numerical instances the performances are assessed thanks to a comparative analysis where exact algorithms are compared between them the approximated algorithm is confronted to an algorithm introduced in a recent research work

buckling and vibration of polar orthotropic circular plate resting on winkler foundation buckling and vibrational behavior of polar orthotropic circular plates of linearly varying thickness is presented on the basis of classical plate theory the plate is resting on winkler type foundation an approximate solution has been obtained by ritz method which employs basis functions based upon static deflection of polar orthotropic plates the effect of elastic foundation and that of orthotropy on the natural frequency of plate has been illustrated for different values of taper parameter flexibility parameter in plane force and nodal diameter the critical buckling load for clamped and simply supported plates have been obtained a comparison of results with those available in literature has been presented

the effects of coefficient correlation structure in two dimensional knapsack problems on solution procedure performance this paper presents the results of an empirical study of the effects of coefficient correlation structure and constraint slackness settings on the performance of solution procedures on synthetic two dimensional knapsack problems 2kp the population correlation structure among 2kp coefficients the level of constraint slackness and the type of correlation product moment or rank are varied in this study representative branch and bound and heuristic solution procedures are used to investigate the influence of these problem parameters on solution procedure performance population correlation structure and in particular the interconstraint component of the correlation structure is found to be a significant factor influencing the performance of both the algorithm and the heuristic in addition the interaction between constraint slackness and population correlation structure is found to influence solution procedure performance

pspace complete problems for subgroups of free groups and inverse finite automata we investigate the complexity of algorithmic problems on finitely generated subgroups of free groups margolis and meakin showed how a finite monoid synt h can be canonically and effectively associated with such a subgroup h we show that h is pure that is closed under radical if and only if synt h is aperiodic we also show that testing for this property of h is pspace complete in the process we show that certain problems about finite automata which are pspace complete in general remain pspace complete when restricted to injective and inverse automata with single accept state whereas they are known to be in nc for permutation automata with single accept state

free vibration analysis of a circular plate partially in contact with a liquid abstract this paper provides a theoretical method for a hydroelastic vibration of a clamped circular plate partially in contact with a liquid it is assumed that the liquid is inviscid and incompressible while the thickness of the plate is small compared to the plate radius and the gravity effect on the system is neglected the wet dynamic displacement of the plate is approximated by combining the orthogonal modal functions of a dry circular plate with a clamped boundary condition the liquid displacement potential satisfying the boundary conditions is derived and the wet dynamic modal functions of the plate are derived by using a compatibility requirement along the contacting surface between the plate and the liquid the eigenvalue equation for the system is obtained by using the rayleigh ritz method in order to calculate the wet natural frequencies and the mode shapes for the symmetric and the asymmetric modes the proposed method is verified by observing a good agreement with three dimensional finite element analysis results the effects of the liquid thickness and the liquid depth on the natural frequencies are also discussed

dynamic programming and strong bounds for the 0 1 knapsack problem two new algorithms recently proved to outperform all previous methods for the exact solution of the 0 1 knapsack problem this paper presents a combination of such approaches where in additi on valid inequalities are generated and surrogate relaxed and a new initial core problem is adopted the algorithm is able to solve all classical test instances with up to 10 000 variables in less than 0 2 seconds on a hp9000 735 99 computer the c language implementation of the algorithm is available on the internet

the surface variational principle applied to an acoustic cavity this paper presents the development and application of the surface variational principle svp for the evaluation of axisymmetric interior acoustic domains the interior form of the svp is first developed in the same manner as the existing exterior form then the surface pressure and normal velocity are represented with a ritz expansion using basis functions that span the entire wetted surface of the object of interest the resultant formulation is used to analyze the interior acoustic response of a harmonically forced right circular elastic cylinder this validation model was chosen as both the structural and acoustic responses can be solved analytically results are presented for two models one with a length to radius ratio of 2 4 and another with a ratio of 12 3 the svp is shown to well reproduce the analytical solution for this geometry and displays the asymptotic convergence expected of its variational formulation the svp formulation developed here is not restricted to right circular cylindrical geometries and may indeed be readily applied to any axisymmetric body

natural frequencies and modes of free edge circular plates vibrating in vacuum or in contact with liquid abstract the influence of poisson s ratio upon the free vibrations of free edge circular plates is studied both when in vacuum and in contact with liquid in the latter case the liquid structure interaction is evaluated by applying the added virtual mass approach the frequency and mode shape parameters as well as the non dimensionalized added virtual mass incremental navmi factors are given for modes having up to seven nodal diameters and five nodal circles and the full range of possible poisson s ratios

new trends in exact algorithms for the 0 1 knapsack problem abstract while the 1980s were focused on the solution of large sized easy knapsack problems kps this decade has brought several new algorithms which are able to solve hard large sized instances we will give an overview of the recent techniques for solving hard kps with special emphasis on the addition of cardinality constraints dynamic programming and rudimentary divisibility computational results comparing all recent algorithms are presented

the multidimensional 0 1 knapsack problem an overview abstract the multidimensional 0 1 knapsack problem is one of the most well known integer programming problems and has received wide attention from the operational research community during the last four decades although recent advances have made possible the solution of medium size instances solving this np hard problem remains a very interesting challenge especially when the number of constraints increases this paper surveys the main results published in the literature the focus is on the theoretical properties as well as approximate or exact solutions of this special 0 1 program

a soft table for the natural frequencies and modal parameters of uniform circular plates with elastic edge support abstract the paper introduces a soft table for the natural frequencies and modal parameters of uniform circular plates with elastic edge support in contrast to conventional tabulations on paper the soft table allows to save space and display parameters for required number of vibration modes the soft table is realized in a collection of matlab codes that calculate natural frequencies and mode shape parameters for a given set of translational and rotational constraints and modifiable poisson ratio calculations of natural frequencies and modal parameters for a wide range of constraints revealed distinctive regions where the frequencies and parameters could change considerably knowing position and extension of these regions could be essential for design and vibration control of structures incorporating circular plates