finding core for coalition structure utilizing dual solution when forming the grand coalition is not possible or optimal agents need to create a coalition structure the idea of the core can be extended to such a case in this paper we propose an innovative exact algorithm called cored to check core non emptiness for coalition structures a more straightforward exact algorithm based on existing techniques which we call corep first obtains the value of optimal coalition structure by solving an integer programming problem then it checks whether that value can be divided without making a blocking dissatisfied coalition in contrast cored first finds a minimal value of the optimal coalition structure so that there exists no blocking coalition next it checks whether the optimal value equals the minimal value we empirically show that when the core is empty cored is by far superior to corep also to find a second best payoff vector when the core is empty we propose a new solution concept called the weak e core which can utilize the approximate value of the optimal coalition structure based on the idea of cored we further develop an algorithm for checking the non emptiness of the weak e core

on the physical interpretation of proper orthogonal modes in vibrations abstract the authors relate the proper orthogonal modes as applied in discrete vibration systems to normal modes of vibration in systems with a known mass matrix in the case of undamped free vibration the proper orthogonal modes converge to the linear normal modes as the amount of data increases this interpretation is also practical for lightly modally damped systems forced resonances lead to proper orthogonal modes which approximate vibration modes a particular case of non linear normal modes are looked at in which the motion of a single mode follows a curve in the co ordinate space in this case the proper orthogonal modes represent the principal axes of inertia formed by the distribution of data on the modal co ordinate curve more generally the proper orthogonal modes represent the principal axes of inertia of the data

application of the karhunen loeve procedure for the characterization of human faces the use of natural symmetries mirror images in a well defined family of patterns human faces is discussed within the framework of the karhunen loeve expansion this results in an extension of the data and imposes even and odd symmetry on the eigenfunctions of the covariance matrix without increasing the complexity of the calculation the resulting approximation of faces projected from outside of the data set onto this optimal basis is improved on average

constrained coalition formation on valuation structures coalition structure generation is the problem of partitioning the agents of a given environment into disjoint and exhaustive coalitions so that the whole available worth is maximized while this problem has been classically studied in settings where all coalitions are allowed to form it has been recently reconsidered in the literature moving from the observation that environments often forbid the formation of certain coalitions by following this latter perspective a model for coalition structure generation is proposed where constraints of two different kinds can be expressed simultaneously indeed the model is based on the concept of valuation structure which consists of a set of pivotal agents that are pairwise incompatible plus an interaction graph prescribing that a coalition c can form only if the subgraph induced over the nodes agents in c is connected it is shown that valuation structures can be used to model a number of relevant problems arising in real world application domains then the complexity of coalition structure generation over valuation structures is studied by assuming that the functions associating each coalition with its worth are given as input according to some compact encodingrather than explicitly listing all exponentially many associations in particular islands of tractability are identified based on the topological properties of the underlying interaction graphs and on suitable algebraic properties of the given worth functions finally stability issues over valuation structures are studied too by considering the core as the prototypical solution concept

density matrix renormalization for model reduction in nonlinear dynamics we present an approach for model reduction of nonlinear dynamical systems based on proper orthogonal decomposition pod our method derived from the density matrix renormalization group provides a significant reduction in computational effort for the calculation of the reduced system compared to a pod the efficiency of the algorithm is tested on the one dimensional burgers equations and a one dimensional equation of the fisher type as nonlinear model systems

proper orthogonal decomposition pod of a class of vibroimpact oscillations abstract this study employs the method of proper orthogonal decomposition pod also known as the karhunen loeve k l method to extract dominant coherent structures modes that approximate the system behavior from time series data these mode shapes can be used in a galerkin reconstruction process to obtain lower dimensional models for the structural systems under consideration the mode shapes and the energies obtained by this process can also be used to predict certain kinds of periodic or non periodic non linear motions the k l method has been applied successfully to fluid dynamical thermal processes and signal processing however only a handful of works exist in the area of vibration analysis and structural mechanics an extensive k l analysis is performed numerically for two vibroimpacting systems a beam and a rotor lower dimensional models are created and used to study non linear energy transmission from low to higher k l modes extensive reconstructions are also performed to prove the efficacy of the k l method to provide accurate low dimensional dynamical models in addition experimental investigations are presented for the case of the overhung impacting rotor and qualitative comparisons with the theoretical analysis are presented

enhancing an algorithm for set covering problems abstract in this note we present enhancements to a previously published algorithm for the optimal solution of set covering problems these enhancements relate to the use of a langrangean heuristic feasible solution exclusion constraints gomory f cuts and an improved branching strategy computational results for problems involving up to 400 rows and 4000 columns indicate that the enhanced algorithm gives better computational results than the original algorithm

a fast approximation algorithm for solving the complete set packing problem we study the complete set packing problem cspp where the family of feasible subsets may include all possible combinations of objects this setting arises in applications such as combinatorial auctions for selecting optimal bids and cooperative game theory for finding optimal coalition structures although the set packing problem has been well studied in the literature where exact and approximation algorithms can solve very large instances with up to hundreds of objects and thousands of feasible subsets these methods are not extendable to the cspp since the number of feasible subsets is exponentially large formulating the cspp as an milp and solving it directly using cplex for example is impossible for problems with more than 20 objects we propose a new mathematical formulation for the cspp that directly leads to an efficient algorithm for finding feasible set packings upper bounds we also propose a new formulation for finding tighter lower bounds compared to lp relaxation and develop an efficient method for solving the corresponding large scale milp we test the algorithm with the winner determination problem in spectrum auctions the coalition structure generation problem in coalitional skill games and a number of other simulated problems that appear in the literature

a rank correlation coefficient resistant to outliers abstract in this article a nonparametric correlation coefficient is defined that is based on the principle of maximum deviations this new correlation coefficient rg is easy to compute by hand for small to medium sample sizes in comparing it with existing correlation coefficients it was found to be superior in a sampling situation that we call biased outliers and hence appears to be more resistant to outliers than the pearson spearman and kendall correlation coefficients in a correlational study not included in this article of some social data consisting of five variables for each of 51 observations rg was compared with the other three correlation coefficients there was agreement on 8 of the 10 possible correlations but in one case rg was significant when the others were not and in yet another case rg was not significant when the others were a further analysis of this data set indicated that there were three to six data points that were anomalies and had a severe effect on the other cor

on nonparametric measures of dependence for random variables in 1959 a renyi proposed a set of axioms for a measure of dependence for pairs of random variables in the same year a sklar introduced the general notion of a copula this is a function which links an n dimensional distribution function to its one dimensional margins and is itself a continuous distribution function on the unit n cube with uniform margins we show that the copula of a pair of random variables x y is invariant under a s strictly increasing transformations of x and y and that any property of the joint distribution function of x and y which is invariant under such transformations is solely a function of their copula exploiting these facts we use copulas to define several natural nonparametric measures of dependence for pairs of random variables we show that these measures satisfy reasonable modifications of renyi s conditions and compare them to various known measures of dependence e g the correlation coefficient and spearman s rho

a layer stripping solution of the inverse problem for a one dimensional elastic medium a fast algorithm for recovering profiles of density and lame parameters as functions of depth for the inverse seismic problem in an elastic medium is obtained the medium is probed with planar impulsive p and sv waves at oblique incidence and the medium velocity components are measured at the surface the interconversion of p and sv waves defines reflection coefficients from which the medium parameter profiles are obtained recursively the algorithm works on a layer stripping principle and it is specified in both differential and recursive forms a physical interpretation of this procedure is given in terms of a lattice filter where the first reflections of the downgoing waves in each layer yield the various reflection coefficients for that layer a computer run of the algorithm on the synthetic impulsive plane wave responses of a twenty layer medium shows that the algorithm works satisfactorily

ordinal measures for image correspondence we present ordinal measures of association for image correspondence in the context of stereo linear correspondence measures like correlation and the sum of squared difference between intensity distributions are known to be fragile ordinal measures which are based on relative ordering of intensity values in windows rank permutations have demonstrable robustness by using distance metrics between two rank permutations ordinal measures are defined these measures are independent of absolute intensity scale and invariant to monotone transformations of intensity values like gamma variation between images we have developed simple algorithms for their efficient implementation experiments suggest the superiority of ordinal measures over existing techniques under nonideal conditions these measures serve as a general tool for image matching that are applicable to other vision problems such as motion estimation and texture based image retrieval

on the nucleolus of the basic vehicle routing game in the vehicle routing cost allocation problem the aim is to find a good cost allocation method i e a method that according to specified criteria allocates the cost of an optimal route configuration among the customers we formulate this problem as a co operative game in characteristic function form and give conditions for when the core of the vehicle routing game is nonempty one specific solution concept to the cost allocation problem is the nucleolus which minimizes maximum discontent among the players in a co operative game the class of games we study is such that the values of the characteristic function are obtained from the solution of a set of mathematical programming problems we do not require an explicit description of the characteristic function for all coalitions instead by applying a constraint generation approach we evaluate information about the function only when it is needed for the computation of the nucleolus

characteristic function games with restricted agent interactions in many real world settings the structure of the environment constrains the formation of coalitions among agents these settings can be represented by characteristic function games also known as coalitional games equipped with interaction graphs an interaction graph determines the set of all feasible coalitions in that a coalition c can form only if the subgraph induced over the nodes agents in c is connected our work analyzes stability issues arising in such environments by focusing on the core as a solution concept and by considering the coalition structure viewpoint that is without assuming that the grand coalition necessarily forms the complexity of the coalition structure core is studied over a variety of interaction graph structures of interest including complete graphs lines cycles trees and nearly acyclic graphs formally having bounded treewidth the related stability concepts of the least core and the cost of stability are also studied results are derived for the setting of compact coalitional games i e for games that are implicitly described via a compact encoding and where simple calculations on this encoding are to be performed in order to compute the payoff associated with any coalition moreover specific results are provided for compact games defined via marginal contribution networks an expressive encoding mechanism that received considerable attention in the last few years

simple full field method for the elastic characterization of orthotropic composite plates a speckle shearing interferometer with a simple setup is designed and tested for full field characterization of the elastic properties of isotropic and orthotropic composite plates the technique is straightforward and provides comparable results obtained by standard methods the proposed method has the advantages of being noncontact and full field in nature beam specimens cut from the plate were loaded under the standard four point bending configuration gradients of bending deformation are measured by the speckle shearing interferometer directly curvature of each bended beam is calculated from the slope of the fitted line of the gradient data the elastic moduli and poisson s ratios of the plate material are determined from the curvature of the beam specimens comparing the present approach to other full field techniques reported in literature that are mostly based on deformation measurement of a specimen subjected to a complicated load field the present method is much easier to apply and the image analysis procedure is much simpler

a new approach for modeling and solving set packing problems in recent years the unconstrained quadratic binary program has emerged as a unified modeling and solution framework for a variety of combinatorial optimization problems experience reported in the literature with several problem classes has demonstrated that this unified approach works surprisingly well in terms of solution quality and computational times often rivaling and sometimes surpassing special purpose methods in this paper we report on the application of this unified framework to set packing problems with a variety of coefficient distributions computational experience is reported illustrating the attractiveness of the approach in particular our results highlight both the effectiveness and robustness of our approach across a wide array of test problems

inversion of acoustic material signature of layered solids the simplex inversion technique is applied to the acoustic material signature ams of layered solids to obtain thickness and material properties of layers it is shown in this paper that by careful application of the simplex technique it is possible to extract much information about a multilayered specimen from its ams a brief review of different inversion techniques is also given in the paper from which the relative advantages of using the simplex alogrithm over other techniques are derived

coalitions among computationally bounded agents abstract this paper analyzes coalitions among self interested agents that need to solve combinatorial optimization problems to operate efficiently in the world by colluding coordinating their actions by solving a joint optimization problem the agents can sometimes save costs compared to operating individually a model of bounded rationality is adopted where computation resources are costly it is not worthwhile solving the problems optimally solution quality is decision theoretically traded off against computation cost a normative application and protocol independent theory of coalitions among bounded rational agents is devised the optimal coalition structure and its stability are significantly affected by the agents algorithms performance profiles and the cost of computation this relationship is first analyzed theoretically then a domain classification including rational and bounded rational agents is introduced experimental results are presented in vehicle routing with real data from five dispatch centers this problem is np complete and the instances are so large that with current technology any agent s rationality is bounded by computational complexity

acceleration techniques for reduced order models based on proper orthogonal decomposition this paper presents several acceleration techniques for reduced order models based on the proper orthogonal decomposition pod method the techniques proposed herein are i an algorithm for splitting the database of snapshots generated by the full order model ii a method for solving quasi symmetrical matrices iii a strategy for reducing the frequency of the projection the acceleration techniques were applied to a pod based reduced order model of the two phase flows in fluidized beds this reduced order model was developed using numerical results from a full order computational fluid dynamics model of a two dimensional fluidized bed using these acceleration techniques the computational time of the pod model was two orders of magnitude shorter than the full order model

a genetic algorithm for the set covering problem abstract in this paper we present a genetic algorithm based heuristic for non unicost set covering problems we propose several modifications to the basic genetic procedures including a new fitness based crossover operator fusion a variable mutation rate and a heuristic feasibility operator tailored specifically for the set covering problem the performance of our algorithm was evaluated on a large set of randomly generated problems computational results showed that the genetic algorithm based heuristic is capable of producing high quality solutions

solving coalitional resource games coalitional resource games crgs are a form of non transferable utility ntu game which provide a natural formal framework for modelling scenarios in which agents must pool scarce resources in order to achieve mutually satisfying sets of goals although a number of computational questions surrounding crgs have been studied there has to date been no attempt to develop solution concepts for crgs or techniques for constructing solutions in this paper we rectify this omission following a review of the crg framework and a discussion of related work we formalise notions of coalition structures and the core for crgs and investigate the complexity of questions such as determining nonemptiness of the core we show that while such questions are in general computationally hard it is possible to check the stability of a coalition structure in time exponential in the number of goals in the system but polynomial in the number of agents and resources as a consequence checking stability is feasible for systems with small or bounded numbers of goals we then consider constructive approaches to generating coalition structures we present a negotiation protocol for crgs give an associated negotiation strategy and prove that this strategy forms a subgame perfect equilibrium we then show that coalition structures produced by the protocol satisfy several desirable properties pareto optimality dummy player and pseudo symmetry

inverse calculation of material parameters for a thin layer system using transient elastic waves the inverse calculation of material parameters of a thin layer system is investigated using transient elastic waves the inverse problem is formulated as an optimization problem in which the norm of the discrepancies between the calculated and measured normal surface displacements is minimized through the simplex algorithm the theoretical result is first solved using the laplace transform and the transient response is then implemented analytically by cagniard s method in the experiment the source time function is generated by the brittle fracture of a pencil lead on the surface of the thin layer system and a national bureau of standards nbs conical transducer is used to record the surface responses to obtain reliable inverse results for material parameters a two step inverse calculation procedure is proposed the recovered material parameters of the specimens agree well with the theoretical values and experimental results

karhunen loeve decomposition of the transient dynamics of a multibay truss we compute the transient dynamics of an impulsively loaded multibay truss in computing the transient responses we avoid numerical instabilities due to exponential dichotomy of the bay transfer matrices by employing the direct global matrix approach this method eliminates the need of transfer matrix multiplications that are prone to numerical instabilities and instead requires a numerically stable inversion of a global transfer matrix of large dimension the transient responses at multiple points of the truss are used to perform system identification of the dynamics using karhunen loeve k l decomposition this analysis computes dominant coherent structures proper orthogonal modes of the truss under specific transient excitations together with the energy of each identified coherent structure the identified k l modes can be used to develop accurate low order models of the truss dynamics for control or substructure synthesis purposes

inverse evaluation of material constants for composite plates by optical interferometry method electronic speckle pattern interferometry espi is a powerful tool for the full field noncontact and real time measurement method of surface displacements for deformed bodies as compared with the conventional film recording and optical reconstruction procedures used for holographic interferometry the interferometric fringes of espi are produced instantly by a video recording system in this study the amplitude fluctuation espi af espi optical system is used for measuring the resonant frequencies and mode shapes of vibrating composite plates by making use of the resonant frequencies for free plates obtained experimentally an inverse evaluation for the material constants is developed using the rayleigh ritz technique and the simplex method for function minimization finally finite element calculation is used to construct the mode shapes from the obtained material constants by inverse evaluation and the results are compared with the experimental observations the experimental method based on optical af espi setup and the inverse algorithms proposed might become a reliable and self consistent methodology for evaluating material constants of composite plates

online set packing in online set packing osp elements arrive online announcing which sets they belong to and the algorithm needs to assign each element upon arrival to one of its sets the goal is to maximize the number of sets that are assigned all their elements a set that misses even a single element is deemed worthless this is a natural online optimization problem that abstracts allocation of scarce compound resources e g multipacket data frames in communication networks we present a randomized competitive online algorithm for the weighted case with general capacity namely where sets may have different values and elements arrive with different multiplicities we prove a matching lower bound on the competitive ratio for any randomized online algorithm our bounds are expressed in terms of the maximum set size and the maximum number of sets an element belongs to we also present refined bounds that depend on the uniformity of these parameters

a polynomial case of unconstrained zero one quadratic optimization unconstrained zero one quadratic maximization problems can be solved in polynomial time when the symmetric matrix describing the objective function is positive semidefinite of fixed rank with known spectral decomposition

karhunen loeve decomposition of coupled axial bending vibrations of beams subject to impacts abstract this work presents a study of the oscillations of a vertical slender beam clamped in its upper extreme pinned in its lower one and constrained inside an outer cylinder in its lower portion the beam is subject to distributed axial loads due to its own weight leading to geometric softening of its lower portion and thus yielding a large number of vibroimpacts with the outer cylinder this is due to the axial bending coupling often called geometric stiffening and largely discussed in the last two decades here it is accounted for by using a non linear finite element model proposed in a previous work in which non linear strain displacement relations are considered to help understand this non linear coupled vibro impact problem the karhunen loeve decomposition also known as the proper orthogonal decomposition is applied to its simulated dynamics the results show that the micro impacts accompanying the beam hole impacts and mainly due to the beam compressive softening and the reaction forces at the top and bottom positions are well represented only when using a non linear axial bending coupling it is also shown that 15 proper orthogonal modes are sufficient to reconstruct the dynamics of the impacting beam under a 3 error margin

algorithmic aspects of the core of combinatorial optimization games we discuss an integer programming formulation for a class of cooperative games we focus on algorithmic aspects of the core one of the most important solution concepts in cooperative game theory central to our study is a simple but very useful observation that the core for this class is nonempty if and only if an associated linear program has an integer optimal solution based on this we study the computational complexity and algorithms to answer important questions about the cores of various games on graphs such as maximum flow connectivity maximum matching minimum vertex cover minimum edge cover maximum independent set and minimum coloring

a linear approximation method for the shapley value the shapley value is a key solution concept for coalitional games in general and voting games in particular its main advantage is that it provides a unique and fair solution but its main drawback is the complexity of computing it e g for voting games this complexity is p complete however given the importance of the shapley value and voting games a number of approximation methods have been developed to overcome this complexity among these owen s multi linear extension method is the most time efficient being linear in the number of players now in addition to speed the other key criterion for an approximation algorithm is its approximation error on this dimension the multi linear extension method is less impressive against this background this paper presents a new approximation algorithm based on randomization for computing the shapley value of voting games this method has time complexity linear in the number of players but has an approximation error that is on average lower than owen s in addition to this comparative study we empirically evaluate the error for our method and show how the different parameters of the voting game affect it specifically we show the following effects first as the number of players in a voting game increases the average percentage error decreases second as the quota increases the average percentage error decreases third the error is different for players with different weights players with weight closer to the mean weight have a lower error than those with weight further away we then extend our approximation to the more general k majority voting games and show that for n players the method has time complexity o k 2n and the upper bound on its approximation error is o k 2 n

on the direct determination of invariant parameters governing anisotropic plate bending problems abstract many papers deal with the determination of flexural rigidities of anisotropic plates from only one specimen subjected to one or several loading conditions in such a problem one of the main questions is the best identification of the unknown parameters according to the type of material the shape of the specimen and the loading conditions it seems that no general rule giving the best configuration leading to an accurate determination has been established one of the main reasons is the anisotropic nature of the tested plates which leads the mechanical configuration to be dependent on the material itself this problem would be avoided by the direct measurement of invariant parameters from which the rigidities are easily deduced these invariant parameters reveal the intrinsic elastic behavior of the tested plate contrary to the rigidities usually considered which are directional quantities this paper describes a procedure for the identification of invariant parameters governing the bending of anisotropic plates it is shown that the whole displacement field processing of the surface strain fields obtained in two particular loading cases directly provides those parameters a numerical simulation shows the stability of the present method

coalition structure generation with worst case guarantees coalition formation is a key topic in multiagent systems one may prefer a coalition structure that maximizes the sum of the values of the coalitions but often the number of coalition structures is too large to allow exhaustive search for the optimal one furthermore finding the optimal coalition structure is np complete but then can the coalition structure found via a partial search be guaranteed to be within a bound from optimum we show that none of the previous coalition structure generation algorithms can establish any bound because they search fewer nodes than a threshold that we show necessary for establishing a bound we present an algorithm that establishes a tight bound within this minimal amount of search and show that any other algorithm would have to search strictly more the fraction of nodes needed to be searched approaches zero as the number of agents grows if additional time remains our anytime algorithm searches further and establishes a progressively lower tight bound surprisingly just searching one more node drops the bound in half as desired our algorithm lowers the bound rapidly early on and exhibits diminishing returns to computation it also significantly outperforms its obvious contenders finally we show how to distribute the desired search across self interested manipulative agents 1999 elsevier science b v all rights reserved

grasp for set packing problems abstract the principles of the greedy randomized adaptative search procedure grasp metaheuristic are instantiated for the set packing problem we investigated several construction phases and evaluated improvements based on advanced strategies these improvements include a self tuning procedure using reactive grasp an intensification procedure using path relinking and a procedure involving the diversification of the selection using a learning process two sets of various numerical instances were used to perform the computational experiments the first set contains randomly generated instances while the second includes instances relating to real problems in railway planning no metaheuristic has previously been applied to this combinatorial problem consequently we have discussed grasp s performances both in relation to lower upper bounds and to the results obtained with cplex when such results are available our analysis based on the average performances observed shows the impact of the suggested strategies and indicates the configuration that produces the best results

an algorithm for set covering problem in this paper we present an algorithm for the set covering problem that combines problem reduction tests with dual ascent subgradient optimisation and linear programming computational results are presented for problems involving up to 400 rows and 4000 columns

synchronization in oscillator networks with delayed coupling a stability criterion we derive a stability criterion for the synchronous state in networks of identical phase oscillators with delayed coupling the criterion applies to any network whether regular or random low dimensional or high dimensional directed or undirected in which each oscillator receives delayed signals from k others where k is uniform for all oscillators

analytical sensitivities of principal components in time series analysis of dynamical systems original method for calculating the analytical sensitivities of the principal components of dynamical systems is developed methods for analytical sensitivity calculations are developed for both the singular value decomposition and eigenanalysis based approaches for principal component calculation sensitivities with respect to state initial conditions and system parameters are enabled by state transition matrix calculations for augmented state and parameter differential equations a novel approach to compute principal component sensitivities with respect to transient forcing function parameters isintroduced bytransforming nonhomogenous differential equations forced system into homogenous differential equations unforced system these new developments are applied to several example problems in dynamics analysis with an emphasis on structural dynamics analysis analytical sensitivities provide the necessary derivatives for gradient based optimization algorithms and provide an analytical framework for evaluating structural modifications based on principal components analysis

karhunen loeve decomposition approach to analyzing complex network synchronization in this paper the approach of the karhunen lo ve decomposition known also as the proper orthogonal modes poms is taken to analyze phase synchronization of various complex networks with different topologies namely the classic kuramoto model coupled chaotic maps with gaussian delays and a chain of diffusively coupled bistable oscillators in the case of the kuramoto model the poms reveal the tendency and the level of synchronization with the increase of the coupling strength for globally coupled networks and scale free networks while periodic poms are found in nearest neighbor coupled networks furthermore for cluster networks on the kuramoto model the first leading poms based on different time intervals reveal that different sub groups of nodes synchronize gradually to different levels eventually leading to the complete phase synchronization in the case of coupled chaotic maps some properties of phase synchronization change with the coupling strength value in the case of the chain of diffusively coupled bistable oscillators several main poms not only determine the network phase synchronization but also provide good reconstruction of the network responses

physical interpretation of the proper orthogonal modes using the singular value decomposition abstract proper orthogonal decomposition is a statistical pattern analysis technique for finding the dominant structures called the proper orthogonal modes in an ensemble of spatially distributed data while the proper orthogonal modes are obtained through a statistical formulation they can be physically interpreted in the field of structural dynamics the purpose of this paper is thus to provide some insights into the physical interpretation of the proper orthogonal modes using the singular value decomposition

on the computational complexity of coalitional resource games we study coalitional resource games crgs a variation of qualitative coalitional games qcgs in which each agent is endowed with a set of resources and the ability of a coalition to bring about a set of goals depends on whether they are collectively endowed with the necessary resources we investigate and classify the computational complexity of a number of natural decision problems for crgs over and above those previously investigated for qcgs in general for example we show that the complexity of determining whether conflict is inevitable between two coalitions with respect to some stated resource bound i e a limit value for every resource is co np complete we then investigate the relationship between crgs and qcgs and in particular the extent to which it is possible to translate between the two models we first characterise the complexity of determining equivalence between crgs and qcgs we then show that it is always possible to translate any given crg into a succinct equivalent qcg and that it is not always possible to translate a qcg into an equivalent crg we establish some necessary and some sufficient conditions for a translation from qcgs to crgs to be possible and show that even where an equivalent crg exists it may have size exponential in the number of goals and agents of its source qcg

anytime coalition structure generation in multi agent systems with positive or negative externalities much of the literature on multi agent coalition formation has focused on characteristic function games where the effectiveness of a coalition is not affected by how the other agents are arranged in the system in contrast very little attention has been given to the more general class of partition function games where the emphasis is on how the formation of one coalition could influence the performance of other co existing coalitions in the system however these inter coalitional dependencies called externalities from coalition formation play a crucial role in many real world multi agent applications where agents have either conflicting or overlapping goals against this background this paper is the first computational study of coalitional games with externalities in the multi agent system context we focus on the coalition structure generation csg problem which involves finding an exhaustive and disjoint division of the agents into coalitions such that the performance of the entire system is optimized while this problem is already very challenging in the absence of externalities due to the exponential size of the search space taking externalities into consideration makes it even more challenging as the size of the input given n agents grows from o 2 n to o n n our main contribution is the development of the first csg algorithm for coalitional games with either positive or negative externalities specifically we prove that it is possible to compute upper and lower bounds on the values of any set of disjoint coalitions building upon this we prove that in order to establish a worst case guarantee on solution quality it is necessary to search a certain set of coalition structures which we define we also show how to progressively improve this guarantee with further search since there are no previous csg algorithms for games with externalities we benchmark our algorithm against other state of the art approaches in games where no externalities are present surprisingly we find that as far as worst case guarantees are concerned our algorithm outperforms the others by orders of magnitude for instance to reach a bound of 3 given 24 agents the number of coalition structures that need to be searched by our algorithm is only 0 0007 of that needed by sandholm et al 1999 1 and 0 5 of that needed by dang and jennings 2004 2 this is despite the fact that the other algorithms take advantage of the special properties of games with no externalities while ours does not

direct identification of elastic constants of anisotropic plates by modal analysis experimental results abstract the determination of the six elastic stiffnesses of thin anisotropic plates from vibration tests is usually performed with numerical procedures based on the finite element or the rayleigh ritz method which both require assumptions concerning the studied mode shapes the present paper describes a method based on the measurement and the processing of natural frequencies as well as mode shapes of the vibrating tested plate as a result the unknown stiffnesses are determined directly without any iterative calculations the experimental aspects of the method are presently described and several results illustrate the relevance of the approach