new developments in the primal dual column generation technique abstract the optimal solutions of the restricted master problems typically leads to an unstable behavior of the standard column generation technique and consequently originates an unnecessarily large number of iterations of the method to overcome this drawback variations of the standard approach use interior points of the dual feasible set instead of optimal solutions in this paper we focus on a variation known as the primal dual column generation technique which uses a primal dual interior point method to obtain well centered non optimal solutions of the restricted master problems we show that the method converges to an optimal solution of the master problem even though non optimal solutions are used in the course of the procedure also computational experiments are presented using linear relaxed reformulations of three classical integer programming problems the cutting stock problem the vehicle routing problem with time windows and the capacitated lot sizing problem with setup times the numerical results indicate that the appropriate use of a primal dual interior point method within the column generation technique contributes to a reduction of the number of iterations as well as the running times on average furthermore the results show that the larger the instance the better the relative performance of the primal dual column generation technique

language stability and stabilizability of discrete event dynamical systems this paper studies the stability and stabilizability of discrete event dynamical systems dedss modeled by state machines stability and stabilizability are defined in terms of the behavior of the dedss i e the language generated by the state machines sms this generalizes earlier work where they were defined in terms of legal and illegal states rather than strings the notion of reversal of languages is used to obtain algorithms for determining the stability and stabilizability of a given system the notion of stability is then generalized to define the stability of infinite or sequential behavior of a deds modeled by a buchi automaton the relationship between the stability of finite and stability of infinite behavior is obtained and a test for stability of infinite behavior is obtained in terms of the test for stability of finite behavior an algorithm of linear complexity for computing the regions of attraction is presented which is used for determining the stability and stabilizability of a giv

diagnosability of discrete event systems subject to permanent sensor failures this paper considers a failure diagnosis problem for discrete event systems subject to permanent sensor failures a notion of diagnosability subject to permanent sensor failures is introduced with respect to a certain nondeterministic observation mask for its verification an aggregated mealy automaton with a deterministic and state dependent observation mask is defined it is shown that the diagnosability of the aggregated mealy automaton is equivalent to the diagnosability of the original system subject to permanent sensor failures then a method for verifying the diagnosability of the aggregated mealy automaton is presented moreover the delay bound within which the occurrence of any failure string can be detected subject to permanent sensor failures is computed

supervisory control of partially observable marked graphs this note presents a control synthesis approach for discrete event systems modeled by marked graphs with unobservable transitions it solves forbidden state problems characterized by a set of general mutual exclusion constraints we prove that for any sequence of observable transitions there exist a unique marking from which all other possible current markings can be reached unobservably this salient feature allows us to design efficient control policies based on proper separation of observation and control

permanence and global attractivity of a discrete multispecies lotka volterra competition predator prey systems in this paper we propose a discrete multispecies lotka volterra competition predator prey systems for general non autonomous case sufficient conditions which ensure the permanence and the global stability of the system are obtained for periodic case sufficient conditions which ensure the existence of a globally stable positive periodic solution of the system are obtained

a branch and cut algorithm without binary variables for nonconvex piecewise linear optimization we give a branch and cut algorithm for solving linear programs lps with continuous separable piecewise linear cost functions plfs models for plfs use continuous variables in special ordered sets of type 2 sos2 traditionally sos2 constraints are enforced by introducing auxiliary binary variables and other linear constraints on them alternatively we can enforce sos2 constraints by branching on them thus dispensing with auxiliary binary variables we explore this approach further by studying the inequality description of the convex hull of the feasible set of lps with plfs in the space of the continuous variables and using the new cuts in a branch and cut scheme without auxiliary binary variables we give two families of valid inequalities the first family is obtained by lifting the convexity constraints the second family consists of lifted cover inequalities finally we report computational results that demonstrate the effectiveness of our cuts and that branch and cut without auxiliary binary variables is significantly more practical than the traditional mixed integer programming approach

branch and price column generation for solving huge integer programs we discuss formulations of integer programs with a huge number of variables and their solution by column generation methods i e implicit pricing of nonbasic variables to generate new columns or to prove lp optimality at a node of the branch and bound tree we present classes of models for which this approach decomposes the problem provides tighter lp relaxations and eliminates symmetry we then discuss computational issues and implementation of column generation branch and bound algorithms including special branching rules and efficient ways to solve the lp relaxation we also discuss the relationship with lagrangian duality

stable periodic solution of a discrete periodic lotka volterra competition system abstract this paper discusses a discrete lotka volterra competition system we first obtain the persistence of the system assuming that the coefficients in the system are periodic we obtain the existence of a periodic solution moreover under some additional conditions this periodic solution is globally stable our results not only reduce to those for the scalar equation when there is no coupling but also improve and complement some in the literature

language convergence in controlled discrete event systems discrete event systems modeled as state machines in the framework of ramadge and wonham are considered in this paper convergence of the language generated or marked by the system to a specified legal language is investigated the convergence property is studied both with respect to open loop uncontrolled systems and with respect to controlled systems in the latter case both questions of existence and synthesis of supervisors that force convergence are examined algorithms for verification of convergence and for synthesis of stabilizing supervisors are provided finally the concept of asymptotic behavior of systems is defined and questions related to this concept are investigated

on a weaker notion of controllability of a language k with respect to a language l a necessary and sufficient condition for a prefix closed language k contained in sigma to be controllable with respect to another prefix closed language l contained in sigma is that k contained in l a weaker notion of controllability where it is not required that k contained in l is considered here if l is the prefix closed language generated by a plant automaton g then essentially there exists a supervisor theta that is complete with respect to g such that l theta mod g k intersection l if and only if k is weakly controllable with respect to l for an arbitrary modeling formalism it is shown that the inclusion problem is reducible to the problem of deciding the weaker notion of controllability therefore removing the requirement that k contained in l from the original definition of controllability does not help the situation from a decidability viewpoint this observation is then used to identify modeling formalisms that are not viable for supervisory control of the untimed behaviors of discrete event dynamic systems

global periodic solutions of a generalized n species gilpin ayala competition model abstract in this paper we investigate a generalized n species gilpin ayala competition system with several deviating arguments in periodic environment which is more general and more realistic than the classical lotka volterra competition systems by using the method of coincidence degree a set of easily verifiable sufficient conditions are derived for the existence of at least one strictly positive componentwise periodic solution some new results are obtained as applications we also apply our main results to some special cases of the system we consider here including the classical n species lotka volterra competition systems and n species gilpin ayala competition model which have been studied extensively in the literature some known results are improved and generalized the examples show that our criteria are new general and easily verifiable

permanence for a delayed discrete ratio dependent predator prey system with holling type functional response abstract sufficient conditions are established for the permanence in a delayed discrete predator prey model with holling type iii functional response n 1 k 1 n 1 k exp b 1 k a 1 k n 1 k 1 1 k n 1 k n 2 k n 1 2 k m 2 n 2 2 k n 2 k 1 n 2 k exp b 2 k 2 k n 1 2 k 2 n 1 2 k 2 m 2 n 2 2 k 2 our investigation confirms that when the death rate of the predator is rather small as well as the intrinsic growth rate of the prey is relatively large the species could coexist in the long run

supervisory control of a class of discrete event processes this paper studies the control of a class of discrete event processes i e processes that are discrete asynchronous and possibly nondeter ministic the controlled process is described as the generator of a formal language while the controller or supervisor is constructed from the grammar of a specified target language that incorporates the desired closed loop system behavior the existence problem for a supervisor is reduced to finding the largest controllable language contained in a given legal language two examples are provided

the persistence and global attractivity in general nonautonomous discrete single species kolmogorov model with delays in this paper general nonautonomous discrete time single species kolmogorov model with delays is studied some sufficient conditions on the boundedness persistence permanence and global attractivity of solutions are established as application the discrete time nonautonomous delayed allee effect model is discussed the sufficient conditions on the permanence and global attractivity are obtained

robust and nonblocking supervisor for discrete event systems with model uncertainty under partial observation addresses a robust and nonblocking supervisory control problem based on a framework of discrete event systems with model uncertainty under partial observation the uncertainty introduced in the paper is associated with internal and unobservable events occurring in systems the paper presents a systematic method for modeling uncertainty described as a spl delta transition representing the internal and unobservable events in particular at a state with the assigned positive integer value p a system is assumed to experience at most a p step state transition by the internal and unobservable event under the framework for model uncertainty the paper presents necessary and sufficient conditions for the existence of a robust supervisor with the nonblocking property

predicates and predicate transformers for supervisory control of discrete event dynamical systems discrete event systems are studied treating the state space as the fundamental modeling concept the control of discrete event systems using predicates and predicate transformers is treated predicates have the advantage that they can concisely characterize an infinite state space the notion of controllability of a predicate is defined and the supervisory predicate control problem is solved a closed form expression for the weakest controllable predicate is obtained the problem of controlling discrete event systems under incomplete state observation is also considered and observability of predicates is defined techniques for finding extremal solutions of boolean equations are used to derive minimally restrictive supervisors

feedback stabilization of some event graph models the authors introduce several notions of stability for event graph models timed or not the stability is similar to the boundedness notion for petri nets the event graph models can be controlled by an output feedback which takes information from some observable transitions and can disable some controllable transitions the controller itself is composed of an event graph in this framework the authors solve the corresponding stabilization problems i e they wonder if such a controller may prevent the explosion of the number of tokens

selected topics in column generation dantzig wolfe decomposition and column generation devised for linear programs is a success story in large scale integer programming we outline and relate the approaches and survey mainly recent contributions not yet found in textbooks we emphasize the growing understanding of the dual point of view which has brought considerable progress to the column generation theory and practice it stimulated careful initializations sophisticated solution techniques for the restricted master problem and subproblem as well as better overall performance thus the dual perspective is an ever recurring concept in our selected topics

supervisory control of hybrid systems within a behavioural framework abstract this contribution addresses the synthesis of supervisory control for hybrid systems with discrete external signals such systems are in general neither l complete nor can they be represented by finite state machines we find an l complete approximation abstraction l for represent it by a finite state machine and investigate the control problem for the approximation if a solution exists we synthesize the maximally permissive supervisor for l we show that it also solves the control problem for the hybrid system if no solution exists approximation accuracy can be increased by computing a k complete abstraction k k l this paper is entirely set within the framework on willems behavioural systems theory

stabilized dynamic constraint aggregation for solving set partitioning problems abstract dynamic constraint aggregation dca and dual variable stabilization dvs are two methods that can reduce the negative impact of degeneracy when solving linear programs the first uses a projection to reduce the primal space whereas the second acts in the dual space in this paper we develop a new method called stabilized dynamic constraint aggregation sdca that combines dca and dvs for solving set partitioning problems it allows to fight degeneracy from both primal and dual perspectives simultaneously to assess the effectiveness of sdca we report computational results obtained for highly degenerate multi depot vehicle scheduling problem instances solved by column generation these results indicate that sdca can reduce the average computational time of the master problem by a factor of up to 7 with respect to the best of the two combined methods furthermore they show that its performance is robust with regard to increasing levels of degeneracy in test problems

permanence of a delayed non autonomous gilpin ayala competition model abstract in this paper we consider a delayed non autonomous n species gilpin ayala competitive system which is more general and more realistic then classical lotka volterra competition model by means of ahmad and lazer s definitions of lower and upper averages of a function we give the average conditions for the permanence of the system it is shown that our result is the generalization of those of zhao et al j d zhao j f jiang a c lazer the permanence and global attractivity in a nonautonomous lotka volterra system nonlinear analysis real world applications 5 4 2004 265 276 our results also supplement the results of fan and wang m fan k wang global periodic solutions of a generalized n species gilpin ayala competition model computer and mathematics with applications 40 2000 1141 1151

a comparison of mixed integer programming models for nonconvex piecewise linear cost minimization problems we study a generic minimization problem with separable nonconvex piecewise linear costs showing that the linear programming lp relaxation of three textbook mixed integer programming formulations each approximates the cost function by its lower convex envelope we also show a relationship between this result and classical lagrangian duality theory

some tractable supervisory control problems for discrete event systems modeled by buchi automata discrete event systems des are modeled by buchi automata together with a means of online control in this setting the concept of a controllable language is extended to infinite strings and conditions for the existence of a supervisor controller to implement a prescribed closed loop behavior are derived the focus is on a class of des called product systems these are des composed of a finite set of asynchronous components a control problem for such a system typically requires the synthesis of an online controller so as to achieve some prescribed coordinated behavior of the component subsystems one of the principal difficulties in this task is that the size of the state space increases exponentially with the number of components it is shown that despite this fact several interesting control synthesis problems for such systems are computationally feasible and algorithms are developed for solution

mixed integer models for nonseparable piecewise linear optimization unifying framework and extensions we study the modeling of nonconvex piecewise linear functions as mixed integer programming mip problems we review several new and existing mip formulations for continuous piecewise linear functions with special attention paid to multivariate nonseparable functions we compare these formulations with respect to their theoretical properties and their relative computational performance in addition we study the extension of these formulations to lower semicontinuous piecewise linear functions

uniform persistence and periodic solutions for a discrete predator prey system with delays abstract in this paper we deal with a discrete predator prey system with delay we first give a sufficient condition for the uniform persistence of the system assuming that the coefficients in the system are periodic by generalizing the yoshizawa s theorem on the existence of periodic solution for ordinary differential equations to the difference equations with delays we obtain the existence of a periodic solution basing on the uniform persistence result

nonconvex piecewise linear knapsack problems this paper considers the minimization version of a class of nonconvex knapsack problems with piecewise linear cost structure the items to be included in the knapsack have a divisible quantity and a cost function an item can be included partially in the given quantity range and the cost is a nonconvex piecewise linear function of quantity given a demand the optimization problem is to choose an optimal quantity for each item such that the demand is satisfied and the total cost is minimized this problem and its close variants are encountered in manufacturing planning supply chain design volume discount procurement auctions and many other contemporary applications two separate mixed integer linear programming formulations of this problem are proposed and are compared with existing formulations motivated by different scenarios in which the problem is useful the following algorithms are developed 1 a fast polynomial time near optimal heuristic using convex envelopes 2 exact pseudo polynomial time dynamic programming algorithms 3 a 2 approximation algorithm and 4 a fully polynomial time approximation scheme a comprehensive test suite is developed to generate representative problem instances with different characteristics extensive computational experiments show that the proposed formulations and algorithms are faster than the existing techniques

similarity based supervisory control of discrete event systems due to the appearance of uncontrollable events in discrete event systems one may wish to replace the behavior leading to the uncontrollability of pre specified language by some quite similar one to capture this similarity we introduce metric to traditional supervisory control theory and generalize the concept of original controllability to spl lambda controllability where spl lambda indicates the similarity degree of two languages a necessary and sufficient condition for a language to be spl lambda controllable is provided we then examine some properties of spl lambda controllable languages and present an approach to optimizing a realization

a minimal algorithm for the multiple choice knapsack problem abstract the multiple choice knapsack problem is defined as a 0 1 knapsack problem with the addition of disjoined multiple choice constraints as for other knapsack problems most of the computational effort in the solution of these problems is used for sorting and reduction but although o n algorithms which solve the linear multiple choice knapsack problem without sorting have been known for more than a decade such techniques have not been used in enumerative algorithms in this paper we present a simple o n partitioning algorithm for deriving the optimal linear solution and show how it may be incorporated in a dynamic programming algorithm such that a minimal number of classes are enumerated sorted and reduced computational experiments indicate that this approach leads to a very efficient algorithm which outperforms any known algorithm for the problem

permanence in nonautonomous multi species predator prey system with feedback controls a nonautonomous multi species predator prey system with feedback controls is proposed in this paper where the competition among the predator species and among the prey species is considered also some important factors such as the effect of toxins and the age structure are also considered average conditions are obtained for permanence and global attractivity in the system the results obtained here generalized the main results of zhao and jiang j d zhao j f jiang permanence in nonautonomous lotka volterra system with predator prey appl math computat 152 2004 99 109

on a periodic multi species ecological model a periodic predator prey model with m predators and n preys is proposed in this paper which can be seen as the modification of the traditional lotka volterra model by using comparison theorem the ultimately bounded region of the system is obtained by using comparison theorem and brouwer fixed point theorem sufficient conditions with guarantee the existence of a positive periodic solution of the system is obtained finally by constructing a suitable lyapunov function some sufficient conditions are obtained for the existence of a unique globally attractive periodic solution of system the results obtained here generalized the main results of j d zhao w c chen global asymptotic stability of a periodic ecological model applied mathematics and computation 147 3 2004 881 892

a branch cut and price algorithm for the piecewise linear transportation problem abstract in this paper we present an exact solution method for the transportation problem with piecewise linear costs this problem is fundamental within supply chain management and is a straightforward extension of the fixed charge transportation problem we consider two dantzig wolfe reformulations and investigate their relative strength with respect to the linear programming lp relaxation both theoretical and practical through tests on a number of instances based on one of the proposed formulations we derive an exact method by branching and adding generalized upper bound constraints from violated cover inequalities the proposed solution method is tested on a set of randomly generated instances and compares favorably to solving the model using a standard formulation solved by a state of the art commercial solver

global attractivity of the periodic lotka volterra system a lotka volterra periodic model withm predators andn preys is studied in this paper a set of easily verifiable sufficient conditions that guarantee the existence uniqueness and global attractivity of the positive periodic solutions is obtained finally a suitable example is given to illustrate that the conditions of the main theorem are feasible

positive periodic solutions of discrete n species food chain systems discrete periodic n species food chain systems with holling types ii and iii functional responses and time delays are investigated respectively by using gaines and mawhin s continuation theorem of coincidence degree theory sufficient conditions are obtained for the existence of positive periodic solutions of the systems

a note on the properties of the supremal controllable sublanguage in pushdown systems consider an event alphabet sigma the supervisory control theory of ramadge and wonham asks the question given a plant model g with language lm g sube sigma and another language k sube lm g is there a supervisor phi such that lm phi g k ramadge and wonham showed that a necessary condition for this to be true is the so called controllability of k with respect to lm g they showed that when g is a finite state automaton and k is a regular language also generated by a finite state automaton then there is a regular supremal controllable sublanguage supc k sube k that is effectively constructable from generators of k and g in this paper we show 1 there is an algorithm to compute the supremal controllable sublanguage of a prefix closed k accepted by a deterministic pushdown automaton dpda when the plant language is also prefix closed and accepted by a finite state automaton and 2 in this case we show that this supremal controllable sublanguage is also accepted by a dpda

control of networked discrete event systems dealing with communication delays and losses in this paper we investigate supervisory control of networked discrete event systems such systems are now widely used in practice the key feature of a networked discrete event system is communication delays and losses in observation and control without addressing communication delays and losses in networked systems no control will be effective we propose to use some special observation mappings to deal with observation delays and losses based on these mappings we define network observability we also consider control delays and losses in networked discrete event systems and define network controllability we show that these definitions capture precisely the requirements on effective supervisory control in networked discrete event systems in the sense that a networked supervisor exists if and only if both network controllability and network observability are satisfied

robust supervisory control of a class of timed discrete event systems under partial observation this paper studies robust supervisory control of timed discrete event systems proposed by brandin and wonham given a set of possible models which includes the exact model of the plant the objective is to synthesize a robust supervisor such that it achieves legal behavior for all possible models we show that controllability for each possible model and observability for a suitably defined aggregate model are necessary and sufficient conditions for the existence of a solution to the robust supervisory control problem moreover when there does not exist a solution a maximally permissive robust supervisor is synthesized under the assumption that all controllable events are observable

on optimal attraction in discrete event processes abstract the concept of attraction has been shown to play a basic role in the synthesis of supervisors for stabilizing discrete event processes in this paper we define and investigate optimal attraction in the sense that the cost or distance of the convergent path is minimized with respect to some distance measure we find conditions for the existence of supervisors achieving optimal attraction and provide efficient algorithms for their synthesis

on supervisory control of sequential behaviors the authors address the supervisory synthesis problem of controlling the sequential behaviors of discrete event dynamical systems dedss under complete and partial information through the use of synchronous composition of the plants and the supervisors the authors present the notion of complete languages discuss some of its algebraic properties and show its close relation to omega languages the authors prove that the supremal closed complete and controllable sublanguage of a given language exists and present an algorithm to compute it they present a closed form expression for the supremal omega controllable sublanguage of a given omega language in terms of the supremal closed complete and controllable sublanguage this closed form expression suggests that certain operations on a given omega language can alternatively be achieved by performing certain other similar operations on its prefix which is a finite language and then taking the limit to obtain the desired omega language a necessary and sufficient condition for the existence of a supervisor in case of partial observation is presented in terms of omega observability notion of omega normality is also introduced and a closed form expression for the supremal omega normal sublanguage in terms of the supremal closed complete and normal sublanguage is presented

on a nonlinear nonautonomous predator prey model with diffusion and distributed delay in this paper a nonlinear nonautonomous predator prey model with diffusion and continuous distributed delay is studied where all the parameters are time dependent the system which is composed of two patches has two species the prey can diffuse between two patches but the predator is confined to one patch we first discuss the uniform persistence and global asymptotic stability of the model after that by constructing a suitable lyapunov functional some sufficient conditions for the existence of a unique almost periodic solution of the system are obtained an example shows the feasibility of our main results

a language measure for partially observed discrete event systems recent literature has introduced and validated a signed real measure of regular languages for quantitative analysis and synthesis of discrete event supervisory des control systems where all events are assumed to be observable this paper presents a modification of the language measure for supervisory control under partial observation and shows how to generalize the analysis when some of the events may not be observable at the supervisory level in the context of des control synthesis the language measure of partially observable discrete event processes is expressed in a closed form which is structurally similar to that of completely observable discrete event processes examples are provided to elucidate the concept of des control under partial observation

global attractivity in an almost periodic multi species nonlinear ecological model abstract a nonlinear almost periodic predator prey model with n preys and m predators is studied in this paper which can be seen as the modification of the traditional multi species lotka volterra predator prey model for general nonautonomous case by using the differential inequality theory we obtain the sufficient conditions which guarantee the uniform persistence and nonpersistence of the system after that by constructing a suitable lyapunov function some sufficient conditions are obtained which ensure the global attractivity of the system for almost periodic case by constructing a suitable lyapunov function sufficient conditions which guarantee the existence of an unique globally attractive positive almost periodic solution of the system are obtained examples together with their numeric simulations show the feasibility of our main results

positive periodic solutions of neutral lotka volterra system with feedback control with the help of a continuation theorem based on gaines and mawhin s coincidence degree easily verifiable criteria are established for the global existence of positive periodic solutions of neutral lotka volterra system with periodic delays and feedback control our results extend and improve existing results and have further applications in population dynamics

on the supermal controllable sublanguage of a given language the concept of controllable language has been shown to play a basic role in the existence theory of supervisory controls for discrete event processes in this paper the supremal controllable sublanguage s of a given language l is characterized as the largest fixpoint of a monotone operator omega in the case where the languages involved are regular it is shown that the fixpoint s can be computed as the limit of the finite sequence k j given by k j 1 omega k j k 0 l an effective computational algorithm is developed and three examples are provided for illustration

global asymptotic stability of a periodic ecological model the periodic lotka volterra model with m predators and n preys is considered in this paper under the suppose that the intrinsic growth rate of the prey species may be negative while the total intrinsic growth rate in a period are positive sufficient conditions are obtained for existence and global asymptotic stability of the periodic solution of this model

permanence and global attractivity of the discrete gilpin ayala type population model in this paper we propose a discrete gilpin ayala competition model and a discrete gilpin ayala type multispecies competition predator model for general nonautonomous case sufficient conditions which ensure the permanence and the global stability of the system are obtained for periodic case sufficient conditions which ensure the existence of an unique globally stable positive periodic solution of the system are obtained an example together with its numeric simulations shows the feasibility of the main results

the stability of a class of discrete event systems using markov chains this paper presents a stability concept of a class of discrete event systems dess using markov chains the dess under consideration are modelled as state machines adopted from ramadge wonham which represent the hybrid dynamic models of constrained motion systems by identifying the probability of firing enabled events of the des p convergence is proposed some properties of p convergence are investigated including the fact that p convergence is a generalization of the convergence proposed by brave and heymann yet it is less restrictive the application of p convergence is shown for a robotic assembly des

control of discrete event systems modeled as hierarchical state machines discrete event systems dess are systems in which state changes take place in response to events that occur discretely asynchronously and often nondeterministically a class of dess modeled as hierarchical state machines hsms a special case of the statecharts formalism introduced recently is considered an efficient algorithm is provided for solving reachability problems in the hsm framework it utilizes the hierarchical structure of hsms this efficient solution is used extensively in control applications where controllers achieving a desired behavior are synthesized online

on controllability and normality of discrete event dynamical systems abstract this paper studies the supervisor synthesis problem of discrete event dynamical systems deds s through the use of synchronous composition of the plant and the supervisor and discusses some of the simplifications achieved by using the synchronous composition to model supervisory control an alternate definition of controllability is presented this definition of controllability is then used to derive an algorithm that is computationally more efficient than previously existing ones for the construction of the supremal controllable sublanguage the algorithm is also shown to be optimal the observability and normality issues arising due to the partial observation of the system dynamics under an arbitrary mask are then investigated closed form representations of the supremal normal and supremal closd and normal sublanguages are derived in the more general setting of arbitrary mask and nonclosed languages thus extending earlier results of the authors and others

a framework for state attraction of discrete event systems under partial observation state attraction for discrete event systems des addresses the problem of reaching a desired subset of the plant state space after a bounded number of event occurrences the problem of state attraction arises for example in fault tolerant supervisory control or in the control of reconfigurable manufacturing systems and is also applicable to systems biological problems such as the control of gene regulatory networks state attraction is investigated with the assumption of full event observation in the existing literature this paper extends the concept of state attraction to the case of partial observation the notion of weak attraction under partial observation wapo is introduced and necessary and sufficient conditions for the existence of a supervisor under partial observation that achieves wapo are derived furthermore a solution algorithm is proposed that finds such supervisor whenever it exists it is shown that such supervisor can always be realized as a subautomaton of the observer automaton of the des plant an application example from systems biology illustrates the obtained results

optimal supervisory control of discrete event dynamicalsystems the notion of optimal supervisory control of discrete event dynamical systems dedss is formalized in the framework of ramadge and wonham a deds is modeled as a state machine and is controlled by disabling some of its transitions two types of cost functions are defined a cost of control function corresponding to disabling transitions in the state machine and a penalty of control function corresponding to reaching some undesired states or not reaching some desired states in the controlled system the control objective is to design an optimal control mechanism if it exists so that the net cost is minimized since a deds is represented as a state machine a directed graph network flow techniques are naturally applied for designing optimal supervisors it is also shown that our techniques can be used to solve supervisory control problems under complete as well as partial observation in particular for the first time techniques for computing the supremal controllable and normal sublanguage and the infimal controllable and normal observable superlanguage without having to perform alternate computations of controllable and normal observable languages are obtained

a necessary and sufficient condition for permanence of a lotka volterra discrete system with delays abstract in this paper we consider the permanence of the following lotka volterra discrete competition system with delays k1 k2 l1 and l2 x n 1 x n exp r1 1 x n k1 1y n k2 y n 1 y n exp r2 1 2x n l1 y n l2 we show the system is permanent for all nonnegative integers k1 k2 l1 and l2 if and only if 1

periodicity in a logistic type system with several delays with the help of a continuation theorem based on gaines and mawhin s coincidence degree easily verifiable criteria are established for the global existence of positive periodic solutions of the following several delays logistic type system du t dt u t a t j 1mb j t u t t j t q j where a t b j t are positive periodic continuous functions with periodic w 0 t j t are nonnegative continuous periodic functions with periodic w 0 after that by constructing a suitable lyapunov functional some sufficient conditions which guarantee the stability of the positive periodic solutions are obtained

existence uniqueness and stability of positive periodic solution for a nonlinear prey competition model with delays a nonlinear periodic predator prey model with m preys and n m predators and delays is proposed in this paper which can be seen as the modification of the traditional lotka volterra prey competition model sufficient conditions which guarantee the existence of a unique globally attractive positive periodic solution of the system are obtained

formulas for calculating supremal controllable and normal sublanguages abstract supremal controllable and normal sublanguages have been shown to play an important role in supervisor synthesis in this paper we discuss the computation of supremal controllable and normal sublanguages we derive formulas for both supremal controllable sublanguages and supremal normal sublanguages when the languages involved are closed as a result those languages can be computed without applying recursive algorithms we also discuss those aspects of these formulas