h 2 h control for stochastic systems with delay this paper is concerned with the h2 h control problem for stochastic linear systems with delay in state control and external disturbance dependent noise a necessary and sufficient condition for the existence of a unique solution to the control problem is derived the resulting solution is characterised by a kind of complex generalised forward backward stochastic differential equations with stochastic delay equations as forward equations and anticipated backward stochastic differential equations as backward equations especially we present the equivalent feedback solution via a new type of riccati equations to explain the theoretical results we apply them to a population control problem

a new car following model with consideration of the velocity difference between the current speed and the historical speed of the leading car in this study a new car following model is proposed based on taking the effect of the leading vehicle s velocity difference between the current speed and the historical speed into account the model s linear stability condition is obtained via the linear stability theory the time dependent ginzburg landau tdgl equation and the modified korteweg de vries mkdv equation are deduced through the nonlinear analysis the kink antikink soliton can interpret the traffic jams near the critical point in addition the connection between the tdgl and the mkdv equations is also given numerical simulation shows that the new model can improve the stability of traffic flow which is consistent with the theoretical analysis correspondingly

a finite axiomatization of conditional independence and inclusion dependencies we present a complete finite axiomatization of the unrestricted implication problem for inclusion and conditional independence atoms in the context of dependence logic for databases this result implies a finite axiomatization of the unrestricted implication problem for inclusion functional and embedded multivalued dependencies in the unirelational case we also indicate the generality of our approach by showing the analogous result for inclusion and embedded join dependencies

stochastic h2 h control with x u v dependent noise finite horizon case in this paper the finite horizon mixed h 2 h control problem is studied for the systems governed by ito type nonlinear stochastic differential equations with state control and external disturbance dependent noise it is shown that the mixed h 2 h control under consideration is associated with the four cross coupled hamilton jacobi equations a discrete approximation algorithm is presented for solving the coupled generalized differential riccati equations arising from linear stochastic h 2 h control a necessary condition and a sufficient condition for the existence of the finite horizon stochastic h 2 h control are derived in particular some previous results on deterministic and stochastic h 2 h control can be viewed as corollaries of our main theorems

a delayed feedback control method for the lattice hydrodynamic model caused by the historic density difference effect abstract a delayed feedback control pattern is brought forward for lattice hydrodynamic model of traffic flow with the consideration of the historic density difference effect we utilize the modern control theory to obtain the linear stability conditions with the consideration of feedback control signal which shows that the stability of traffic flow is closely related to the information of the historic density difference furthermore numerical simulations affirm that the delayed feedback control signal can suppress the traffic congestion efficiently

the implication problem for functional and inclusion dependencies is undecidable the implication problem for a class of dependencies is the following given a finite set of dependencies determine if they logically imply another dependency we show that the implication problem is undecidable for the class of functional and inclusion dependencies this holds true even if the inclusion dependencies are restricted to be binary it may be noted that the implication problem is known to be decidable for functional and unary inclusion dependencies and also for inclusion dependencies without functional dependencies

a nash game approach to mixed h sub 2 h sub spl infin control the established theory of nonzero sum games is used to solve a mixed h sub 2 h sub spl infin control problem our idea is to use the two pay off functions associated with a two player nash game to represent the h sub 2 and h sub spl infin criteria separately we treat the state feedback problem and we find necessary and sufficient conditions for the existence of a solution both the finite and infinite time problems are considered in the infinite horizon case we present a full stability analysis the resulting controller is a constant state feedback law characterized by the solution to a pair of cross coupled riccati equations which may be solved using a standard numerical integration procedure we begin our development by considering strategy sets containing linear controllers only at the end of the paper we broaden the strategy sets to include a class of nonlinear controls it turns out that this extension has no effect on the necessary and sufficient conditions for the existence of a solution or on the nature of the controllers

non finite specifiability of projections of functional dependency families abstract a functional dependency fd implicational dependency id family is a family of relational database instances consisting of all instances which satisfy a given set of fds ids an id family is finitely specifiable if it can be defined using a finite set of ids it is known that all fd families are finitely specifiable id families and also that each projection of each fd family while not necessarily an fd family is an id family it is shown here that if the projection of an fd family is not an fd family then it is not a finitely specifiable id family

brief paper maximum principle for the stochastic optimal control problem with delay and application in this paper we consider an optimal control problem for the stochastic system described by stochastic differential equations with delay we obtain the maximum principle for the optimal control of this problem by virtue of the duality method and the anticipated backward stochastic differential equations our results can be applied to a production and consumption choice problem the explicit optimal consumption rate is obtained

evaluation of queries in independent database schemes a simple characterization of independent database schemes is proved an algorithm is given for translating a tableau t posed as a query on a representative instance to a union of tableaux that is equivalent to t but can be applied directly to database relations the algorithm may take exponential time in the size of t and the database scheme and it is applicable only to independent database schemes if t is a just a projection of a representative instance then the algorithm has a simpler form which is still exponential in the worst case and is polynomial in some cases

formal systems for join dependencies we investigate whether a sound and complete formal system for join dependencies can be found we present a system that is sound and complete for tuple generating dependencies and is strong enough to derive join dependencies from join dependencies using only generalized join dependencies in the derivation we also present a system that sound and complete for tuple generating dependencies and is complete for extended join dependencies which are a special case of generalized join dependencies finally we construct a gentzen style system that is sound and complete for join dependencies the last two systems have unbounded inference rules

a new car following model considering the related factors of a gyroidal road abstract a novel car following model was proposed to describe the motion of the vehicles on a single lane gyroidal road we explore the related effects of gyroidal road upon uniform traffic flow analytically and numerically the analytical result shows that the related factors of gyroidal road including the friction coefficient radius of curvature and slope have great influences on the stability of the uniform flow respectively the modified kdv korteweg de vries equation is derived in the unstable area and the kink solution is obtained near the critical point a series of simulations are conducted to verify the effects upon uniform traffic flow under different road conditions it is shown that the amplitudes of the headway oscillation wave were affected by the friction coefficient radius of curvature and slope respectively the numerical results are in good agreement with the analytical results

notions of dependency satisfaction two notions of dependency satisfaction consistency and completeness are introduced consistency is the natural generalization of weak instance satisfaction and seems appropriate when only equality generating dependencies are given but disagrees with the standard notion in the presence of tuple generating dependencies completeness is based on the intuitive semantics of tuple generating dependencies but differs from the standard notion for equality generating dependencies it is argued that neither approach is the correct one but rather that they correspond to different policies on constraint enforcement and each one is appropriate in different circumstances consistency and completeness of a state are characterized in terms of the tableau associated with the state and in terms of logical properties of a set of first order sentences associated with the state a close relation between the problems of testing for consistency and completeness and of testing implication of dependencies is established leading to lower and upper bounds for the complexity of consistency and completeness the possibility of formalizing dependency satisfaction without using a universal relation scheme is examined

analysis of social optimum for staggered shifts in a single entry traffic corridor with no late arrivals abstract this paper investigates the traffic flow dynamics under the social optimum so principle in a single entry traffic corridor with staggered shifts from the analytical and numerical perspectives the lwr lighthill whitham and richards model and the greenshield s velocity density function are utilized to describe the dynamic properties of traffic flow the closed form so solution is analytically derived and some numerical examples are used to further testify the analytical solution the optimum proportion of the numbers of commuters with different desired arrival times is further discussed where the analytical and numerical results both indicate that the cumulative outflow curve under the so principle is piecewise smooth

finite axiomatization of languages for representations of system properties axiomatization of dependencies abstract the existence of full consistent and finite systems of inference rules for several languages is discussed these languages are used for the description of system classes the system being given by a multiplace relation the same languages types of dependencies are used in relational database theory for describing integrity constraints the absence of finite axiomatization for different types of dependencies including join dependencies is proved

polynomial time implication problems for unary inclusion dependencies unary inclusion dependencies are database constraints expressing subset relationships the decidability of implication for these dependencies together with embedded implicational dependencies such as functional dependencies are investigated as shown by casanova et al the unrestricted and finite implication problems are different for the class of functional and unary inclusion dependencies also for this class and for any fixed k finite implication has no k ary complete axiomatization for both of these problems complete axiomatizations and polynomial time decision procedures are provided linear time for unrestricted implication and cubic time for finite implication it follows that functional and unary inclusion dependencies form a semantically natural class of first order sentences with equality which although not finitely controllable is efficiently solvable and docile generalizing from these results it is shown that the interaction between functionaland inclusion dependencies characterizes 1 unrestricted implication of unary inclusion and all embedded implicational dependencies 2 finite implication of unary inclusion and all full implicational dependencies 3 finite implication of unary inclusion and all embedded tuple generating dependencies as a direct consequence of this analysis most of the applications of dependency implication are extended within polynomial time to database design problems involving unary inclusion dependencies such examples are tests for lossless joins and tests for complementarity of projective views finally if one additionally requires that

on acyclic database decompositions given a universal relation scheme presented as a set of attributes and a set of dependencies it may be advantageous to decompose it into a collection of schemes each with its own sets of attributes and dependencies that has some desired properties a basic requirement for such a decomposition to be useful is that the corresponding decomposition map on universal relations be injective a central problem in database theory is to find the reconstruction map i e the inverse map of an injective decomposition map it is proved here that when the decomposition viewed as a hypergraph is acyclic and the given dependencies are full implicational dependencies then the reconstruction map is the natural join based on this it is shown that there is a polynomial time algorithm to test for injectiveness of decompositions

equivalence of linear response among extended optimal velocity models we investigate the property of extended optimal velocity ov models of traffic flow in which a driver looks at arbitrary number of vehicles that precede we prove an equivalence of linear response among extended models this equivalence provides a natural understanding of the improvement of the stability of traffic flow

size and treewidth bounds for conjunctive queries this article provides new worst case bounds for the size and treewith of the result q d of a conjunctive query q applied to a database d we derive bounds for the result size q d in terms of structural properties of q both in the absence and in the presence of keys and functional dependencies these bounds are based on a novel coloring of the query variables that associates a coloring number c q to each query q intuitively each color used represents some possible entropy of that variable using this coloring number we derive tight bounds for the size of q d in case i no functional dependencies or keys are specified and ii simple functional dependencies keys are given these results generalize recent size bounds for join queries obtained by atserias et al 2008 in the case of arbitrary compound functional dependencies we use tools from information theory to provide lower and upper bounds establishing a close connection between size bounds and a basic question in information theory our new coloring scheme also allows us to precisely characterize both in the absence of keys and with simple keys the treewidth preserving queries the queries for which the treewidth of the output relation is bounded by a function of the treewidth of the input database finally we give some results on the computational complexity of determining the size bounds and of deciding whether the treewidth is preserved

kink soliton characterizing traffic congestion we study traffic congestion by analyzing a one dimensional traffic flow model developing an asymptotic method to investigate the long time behavior near a critical point we derive the modified korteweg de vries mkdv equation as the lowest order model there is an infinite number of kink solitons to the mkdv equation while it has been found by numerical simulations that the kink pattern arising in traffic congestion is uniquely determined irrespective of initial conditions in order to resolve this selection problem we consider higher order corrections to the mkdv equation and find that there is a kink soliton that can deform continuously with the perturbation represented by the addition of these corrections with numerical confirmation we show that this continuously deformable kink soliton characterizes traffic congestion we also discuss the relationship between traffic congestion and the slugging phenomenon in granular flow

formal systems for tuple and equality generating dependencies we develop several formal systems for tuple and equality generating dependencies there are three kinds of systems based upon substitution tuple elimination and transitivity we specialize our systems to several subclasses total dependencies template dependencies and binary dependencies we also show that finding a formal system for embedded multivalued dependencies is equivalent to solving the implication problem for that class

tools for template dependencies template dependencies td s are a class of data dependencies that include multivalued and join dependencies and embedded versions of these a collection of techniques examples and results about td s are presented the principal results are 1 finite implication implication over relations with a finite number of tuples is distinct from unrestricted implication for td s 2 there are for td s over three or more attributes infinite chains of increasingly weaker and increasingly stronger full td s 3 however there are weakest nontrivial and strongest full td s over any given set of attributes 4 over two attributes there are only three distinct td s 5 there is no weakest not necessarily full td over any set of three or more attributes 6 there is a finite relation that obeys every strictly partial td but no full td 7 the conjunction of each finite set of full td s is equivalent to a single full td however the conjunction of a finite set of not necessarily full td s is not necessarily e

a novel lattice hydrodynamic model considering the optimal estimation of flux difference effect on two lane highway abstract the optimal estimation of flux difference effect is introduced to construct a new lattice hydrodynamic model for two lane highway through linear stability analysis it is found that the new consideration plays an important influence upon the stability of two lane traffic flow moreover the mkdv equation near the critical point is derived from nonlinear analysis which describes the propagation behavior of traffic jam in two lane traffic system simulation results show that the stability of two lane traffic system can be increased and the emergence of traffic jams are effectively relieved by the optimal estimation of flux difference effect which is in good agreement with theoretical analysis

on bounded database schemes and bounded horn clause programs a lossless database scheme with full implicational dependencies is considered the following condition is necessary in order that restricted projections of the representative instance could be expressed in relational algebra i e in first order logic the dependencies of the database scheme are equivalent to a single join dependency and some equality generating dependencies an important special case is when the database scheme has only full tuple generating dependencies in this case restricted projections of the representative instance can be expressed in relational algebra if and only if the following condition is true the dependencies of the database scheme are equivalent to a single join dependency testing this condition is decidable this result also applies to the class of horn clause programs consisting only of typed rules with one predicate symbol r and without function symbols a program consisting of rules of this form is equivalent to a nonrecursive program if and only if it is equival

reasoning about functional and full hierarchical dependencies over partial relations we study the implication problem for the combined class of functional and full hierarchical dependencies in the presence of sql s not null constraints two different notions of implication are addressed one where a dependency is implied by the given set of dependencies plus the underlying schema and one where a dependency is implied by the given set of dependencies alone we establish axiomatizations for both notions of implication and reveal deep relationships between them

equivalence of relational database schemes we investigate the question of when two database schemes embody the same information we argue that this question reduces to the equivalence of the sets of fixed points of the project join mappings associated with the two database schemes in question when data dependencies are given we need only consider those fixed points that satisfy the dependencies a polynomial algorithm to test the equivalence of database schemes when there are no dependencies is given we also provide an exponential algorithm to handle the case where there are functional and or multivalued dependencies furthermore we give a polynomial time test to determine whether a project join mapping preserves a set of functional dependencies and a polynomial time algorithm for equivalence of database schemes whose project join mappings do preserve the given set of functional dependencies lastly we introduce the update sets approach to database design as an application of these results

stabilization effect of traffic flow in an extended car following model based on an intelligent transportation system application an extended car following model is proposed by incorporating an intelligent transportation system in traffic the stability condition of this model is obtained by using the linear stability theory the results show that anticipating the behavior of more vehicles ahead leads to the stabilization of traffic systems the modified korteweg de vries equation the mkdv equation for short near the critical point is derived by applying the reductive perturbation method the traffic jam could be thus described by the kink antikink soliton solution for the mkdv equation from the simulation of space time evolution of the vehicle headway it is shown that the traffic jam is suppressed efficiently with taking into account the information about the motion of more vehicles in front and the analytical result is consonant with the simulation one

a new lattice model accounting for multiple optimal current differences anticipation effect in two lane system abstract this paper extends a two lane lattice hydrodynamic traffic flow model to take into account the driver s anticipation effect in sensing the multiple optimal current differences based on the proposed model we derive analytically the effect of driver s anticipation of multiple optimal current differences on the instability of traffic dynamics the phase diagrams have been plotted and discussed that the stability region enhances with anticipation effect in sensing multiple optimal current differences through simulation it is found that the oscillation of density wave around critical density decreases with an increase in lattice number and anticipation time for transient and steady state the simulation results are in good agreement with the theoretical analysis which show that considering the driver s anticipation of multiple optimal current differences in two lane lattice model stabilizes the traffic flow and suppresses the traffic jam efficiently

on a general class of data dependencies in the relational model and its implication problems abstract the present paper deals with an important problem of the relational database theory with analysis of dependencies in the first part of the paper it is shown that a sufficiently large class of dependencies hypothesis conclusion type of dependencies can be expressed as first order sentences in the second part of the paper we deal with implication problems for egd ttgd tgd types of dependencies of relational databases wich are generalizations of dependencies introduced by beeri vardi 2 for these implication problems we give a generalized version of the proof procedure called chase we introduce exchangeability generating dependencies xgd and analyze the structure of relational database classes satisfying a system of xgds ex

xml queries and constraints containment and reformulation starting from the xquery language we define xbind an xml analog of relational conjunctive queries as well as a related class of xml integrity constraints dependencies we identify a fragment of xbind for which containment is decidable in fact 2p complete and a further fragment for which containment is np complete we extend the containment algorithm to take xml dependencies into account we give an algorithm for the reformulation of xbind queries under combinations of gav and lav xquery views as well as additional dependencies we prove a completeness theorem which guarantees that under certain conditions our algorithm will find a minimal reformulation if one exists moreover we identify conditions when this algorithm achieves optimal complexity bounds our results on containment and reformulation depend on certain restrictions on the query and constraint languages we calibrate the results by showing that lifting these restrictions significantly changes the complexity of the problems

on characterizing boundedness of database schemes with bounded dependencies abstract we investigate the effect of bounded dependencies on the boundedness of database schemes the following results are proved a database scheme with only bounded equality generating dependencies is always bounded with respect to dependencies a lossless database scheme with bounded full implicational dependencies is bounded w r t dependencies if and only if the implicational dependencies are equivalent to a single join dependency and some equality generating dependencies by a known method this condition can be tested effectively these results are relevant in database theory in that they determine in a rather general case whether queries under the representative instance approach can be expressed in relational algebra

friction coefficient and radius of curvature effects upon traffic flow on a curved road abstract we investigate the friction coefficient and radius of curvature effects upon traffic flow analytically and numerically a new model is proposed to describe the motion of vehicles running on a curved road the stability condition is obtained by the use of control theories the nonlinear analysis method is taken to derive the modified kdv korteweg de vries equation and the kink antikink solution is obtained near the critical point simulations are carried out to verify the double effects upon traffic flow the flux increases but the stability decreases with an increase of the two parameters numerical results are in good agreement with the analytical results

stabilization and enhancement of traffic flow by the next nearest neighbor interaction the car following model of traffic is extended to take into account the car interaction before the next car ahead the next nearest neighbor interaction the traffic behavior of the extended car following model is investigated numerically and analytically it is shown that the next nearest neighbor interaction stabilizes the traffic flow the jamming transition between the freely moving and jammed phases occurs at a higher density than the threshold of the original car following model by increasing the maximal velocity the traffic current is enhanced without jam by the stabilization effect the jamming transition is analyzed with the use of the linear stability and nonlinear perturbation methods the traffic jam is described by the kink solution of the modified korteweg char21 de vries equation the theoretical coexisting curve is in good agreement with the simulation result

membership problem for embedded multivalued dependencies under some restricted conditions abstract it is known that there is no finite set of inference rules that is complete for embedded multivalued dependencies this paper considers the problem called membership problem of deciding whether a given embedded multivalued dependency x v on u or functional dependency x v is implied by a given set d of functional and embedded multivalued dependencies a new inference rule for embedded multivalued dependencies is presented and the following results about membership problems are shown let u be a set of attributes and let w n w 0 u let d f e e 1 e n where 1 i f is a set of functional dependencies y z satisfying y w 0 or z w 0 2 ii e is a set of embedded multivalued dependencies y z on t satisfying at least one of y w 0 t z w 0 and t y z w 0 and 3 iii each e 1 i n is a set of embedded multivalued dependencies on w 1 1 if x v u w 0 then the membership problem is solaable that is it is decidable whether x v on u or x v is implied by d 2 2 if x v u w n then the membership problem cah be solved in o d v x time where d is the size of the description of d 3 3 if x w n and x v u w 0 then the membership problem can be solved in o d 2 w n x n t 1 w 1 w 1 l 1 time

on rules with existential variables walking the decidability line we consider positive rules in which the conclusion may contain existentially quantified variables which makes reasoning tasks such as conjunctive query answering or entailment undecidable these rules called email protected rules have the same logical form as tuple generating dependencies in databases and as conceptual graph rules the aim of this paper is to provide a clearer picture of the frontier between decidability and non decidability of reasoning with these rules previous known decidable classes were based on forward chaining on the one hand we extend these classes on the other hand we introduce decidable classes based on backward chaining a side result is the definition of a backward mechanism that takes the complex structure of email protected rule conclusions into account we classify all known decidable classes by inclusion then we study the question of whether the union of two decidable classes remains decidable and show that the answer is negative except for one class and a still open case this highlights the interest of studying interactions between rules we give a constructive definition of dependencies between rules and widen the landscape of decidable classes with conditions on rule dependencies and a mixed forward backward chaining mechanism finally we integrate rules with equality and negative constraints to our framework

study on the interval integration effect of vehicle s self delayed velocity on traffic stability in micro traffic modeling abstract a new car following model is proposed in this paper to study the interval integration effect of vehicle s self delayed velocity information on traffic flow the stability condition of the new model is derived through linear analysis and the result shows that the traffic stability can be improved when a longer interval of vehicle s self delayed velocity information is taken into account also it is revealed that the traffic information in the time interval which is far from the present time is more positive in stabilizing traffic flow comparing to the traffic information in the time interval which is close to the present time through nonlinear analysis the mkdv equation is derived to describe the propagation properties of density wave in the unstable region finally the theoretical results are confirmed by numerical simulation

probabilistic data exchange the work reported here lays the foundations of data exchange in the presence of probabilistic data this requires rethinking the very basic concepts of traditional data exchange such as solution universal solution and the certain answers of target queries we develop a framework for data exchange over probabilistic databases and make a case for its coherence and robustness this framework applies to arbitrary schema mappings and finite or countably infinite probability spaces on the source and target instances after establishing this framework and formulating the key concepts we study the application of the framework to a concrete and practical setting where probabilistic databases are compactly encoded by means of annotations formulated over random boolean variables in this setting we study the problems of testing for the existence of solutions and universal solutions materializing such solutions and evaluating target queries for unions of conjunctive queries in both the exact sense and the approximate sense for each of the problems we carry out a complexity analysis based on properties of the annotation for various classes of dependencies finally we show that the framework and results easily and completely generalize to allow not only the data but also the schema mapping itself to be probabilistic

nonlinear analysis of traffic flow on a gradient highway abstract we investigate the slope effects upon traffic flow on a single lane gradient uphill downhill highway analytically and numerically the stability condition neutral stability condition and instability condition are obtained by the use of linear stability theory it is found that stability of traffic flow on the gradient varies with the slopes the burgers korteweg de vries kdv and modified korteweg de vries mkdv equations are derived to describe the triangular shock waves soliton waves and kink antikink waves in the stable meta stable and unstable region respectively a series of simulations are carried out to reproduce the triangular shock waves kink antikink waves and soliton waves results show that amplitudes of the triangular shock waves and kink antikink waves vary with the slopes the soliton wave appears in an upward form when the average headway is less than the safety distance and a downward form when the average headway is more than the safety distance moreover both the kink antikink waves and the solitary waves propagate backwards the numerical simulation shows a good agreement with the analytical result

car following model for autonomous vehicles and mixed traffic flow analysis based on discrete following interval abstract in this paper a discrete car following interval model for autonomous vehicles is proposed with the steady following and dynamic following intervals and the range of the steady following interval is established the stability conditions of the model are explored using linear stability analysis theory numerical simulation is used to verify the influence of the discrete following interval model on mixed traffic flow under small perturbations and hard braking the research results show that with the increase in the proportion of autonomous vehicles the stability of traffic flow is gradually enhanced in particular in the small perturbation condition the autonomous vehicle has a speed maintenance period in the steady following interval thereby reducing the influence of the preceding vehicle perturbations with the increase of the steady following interval the stability of traffic flow first increases and then decreases moreover when the length of steady following interval is constant with the increase of the minimum safety time headway the stability of traffic flow is gradually enhanced

feedback and optimal sensitivity model reference transformations multiplicative seminorms and approximate inverses in this paper the problem of sensitivity reduction by feedback is formulated as an optimization problem and separated from the problem of stabilization stable feedback schemes obtainable from a given plant are parameterized salient properties of sensitivity reducing schemes are derived and it is shown that plant uncertainty reduces the ability of feedback to reduce sensitivity the theory is developed for input output systems in a general setting of banach algebras and then specialized to a class of multivariable time invariant systems characterized by n times n matrices of h infty frequency response functions either with or without zeros in the right half plane the approach is based on the use of a weighted seminorm on the algebra of operators to measure sensitivity and on the concept of an approximate inverse approximate invertibility of the plant is shown to be a necessary and sufficient condition for sensitivity reduction an indicator of approximate invertibility called a measure of singularity is introduced the measure of singularity of a linear time invariant plant is shown to be determined by the location of its right half plane zeros in the absence of plant uncertainty the sensitivity to output disturbances can be reduced to an optimal value approaching the singularity measure in particular if there are no right half plane zeros sensitivity can be made arbitrarily small the feedback schemes used in the optimization of sensitivity resemble the lead lag networks of classical control design some of their properties and methods of constructing them in special cases are presented

guaranteeing no interaction between functional dependencies and tree like inclusion dependencies functional dependencies fds and inclusion dependencies inds are the most fundamental integrity constraints that arise in practice in relational databases a given set of fds does not interact with a given set of inds if logical implication of any fd can be determined solely by the given set of fds and logical implication of any ind can be determined solely by the given set of inds the set of tree like inds constitutes a useful subclass of inds whose implication problem is polynomial time decidable we exhibit a necessary and sufficient condition for a set of fds and tree like inds not to interact this condition can be tested in polynomial time

null inclusion dependencies in relational databases abstract functional dependencies fds and inclusion dependencies inds are the most fundamental integrity constraints that arise in practice in relational databases we introduce null inclusion dependencies ninds to cater for the situation when a database is incomplete and contains null values we show that the implication problem for ninds is the same as that for inds we then present a sound and complete axiom system for null functional dependencies nfds and ninds and prove that the implication problem for nfds and ninds is decidable and exptime complete by contrast when no nulls are allowed this implication problem is undecidable this undecidability result has motivated several researchers to restrict their attention to fds and noncircular inds in which case the implication problem was shown to be exptime complete our results imply that when considering nulls in relational database design we need not assume that ninds are noncircular

an equivalence between relational database dependencies and a fragment of propositional logic it is known that there is an eqmvalence between functional dependencies m a relatmonal database and a certain fragment of proposmonal logic thins eqmvalence is extended to include both functional and multivalued dependencmes thus for each dependency there is a corresponding statement m proposmonal logic it ms then shown that a dependency funcuonal or multivalued is a consequence of a set of dependencies ff and only ff the corresponding proposiuonal statement s a consequence of the corresponding set of proposmonal statements examples are given to show that these techniques are valuable mn provmdmg much shorter proofs of theorems about dependencies than have been obtained by more tradmonal means it is shown that this eqmvalence cannot be extended to include either join dependencies or embedded multmvalued dependencies

on the decidability and axiomatization of query finiteness in deductive databases a database query is finite if its result consists of a finite sets tuples for queries formulated as sets of pure horn rules the problem of determining finiteness is in general undecidable in this paper we consider superfiniteness a stronger kind of finiteness which applies to horn queries whose function symbols are replaced by the abstraction of infinite relations with finiteness constraints abbr fc s we show that superfiniteness is not only decidable but also axiomatizable and the axiomatization yields an effective decision procedure although there are finite queries that are not superfinite we demonstrate that superfinite queries represent an interesting and nontrivial subclass within the class of all finite queries the we turn to the issue of inference of finiteness constraints an important practical problem that is instrumental in deciding if a query is evaluable by a bottom up algorithm although it is not known whether fc entailment is decidable for sets of function free horn rules we show that super entailment a stronger form of entailment is decidable we also show how a decision procedure for super entailment can be used to enhance tests for query finiteness

a proof procedure for data dependencies definition d une classe de dependances dependances generant l equalite et les triples et generalisation du processus de poursuite pour traiter ces dependances on montre quelques cas pour lesquels il y a une procedure de decision redondance de l egalite pour decider de l implication des dependances generant les triples et presque redondance pour decider de l implication des dependances generant l egalite

finitely specifiable implicational dependency families une famille de dependance d implication id est une famille d exemples de base de donnees relationnelles composee de tous les cas qui satisfont un ensemble donne d ids dans cet article on montre que la collection de familles de dependances d implication specifiable de maniere finie n est pas bloquee sous les dependances de jointure ou de projection

extending inclusion dependencies with conditions this paper introduces a class of conditional inclusion dependencies cinds which extends inclusion dependencies inds by enforcing patterns of semantically related data values we show that cinds are useful not only in data cleaning but also in contextual schema matching we give a full treatment of the static analysis of cinds and show that cinds retain most desired properties of traditional inds a cinds are always satisfiable b cinds are finitely axiomatizable i e there exists a sound and complete inference system for the implication analysis of cinds and c the implication problem for cinds has the same complexity as its traditional counterpart namely pspace complete in the absence of attributes with a finite domain but it is exptime complete in the general setting in addition we investigate the interaction between cinds and conditional functional dependencies cfds as well as two practical fragments of cinds namely acyclic cinds and unary cinds we show the following d the satisfiability problem for the combination of cinds and cfds becomes undecidable even in the absence of finite domain attributes e in the absence of finite domain attributes the implication problem for acyclic cinds and for unary cinds retains the same complexity as its traditional counterpart namely np complete and ptime respectively but in the general setting it becomes pspace complete and conp complete respectively and f the implication problem for acyclic unary cinds remains in ptime in the absence of finite domain attributes and conp complete in the general setting

the implication problem for functional and inclusion dependencies there are two implication problems for functional dependencies and inclusion dependencies general implication and finite implication given a set of dependencies the problems are to determine whether holds in all databases satisfying or all finite databases satisfying contrary to the possibility suggested in casanova fagin and papadimitriou proceedings 1st acm conf on principles of database system pp 171 176 1982 there is a natural complete axiom system for general implication however a simple observation shows that both implication problems are recursively unsolvable it follows that there is no recursively enumerable set of axioms for finite implication

the impact of the density difference memory integral on traffic stability in two lane lattice hydrodynamic model abstract the density difference memory integral ddmi term can be applied to describe traffic density information of the driver s historical memory during a continuous period of time in this paper a new lattice model is provided with the consideration of the ddmi effect for two lane freeway the linear stability condition of two lanes has been derived by considering the ddmi effect through linear stability theory which shows that the ddmi effect can improve traffic stability under lane changing according to the observation of simulation the ddmi effect conduces to the stability of traffic flow for two lane freeway

numerical simulation of soliton and kink density waves in traffic flow with periodic boundaries abstract the soliton and kink antikink density waves are simulated with periodic boundaries by adding perturbation in the initial condition on single lane road based on a car following model they are reproduced in the form of the space time evolution of headway both of which propagate backwards it is found that the solitons appear only near the neutral stability line regardless of the boundary conditions and they exhibit upward form when the initial headway is smaller than the safety distance otherwise they exhibit downward form comparison is made between the numerical and analytical results about the amplitude of kink antikink wave and the underlying mechanism is analyzed besides it is indicated that the maximal current of traffic flow increases with decreasing safety distance the numerical simulation shows a good agreement with the analytical results

the stochastic maximum principle for optimal control problems of delay systems involving continuous and impulse controls this paper is concerned with a pontryagin s maximum principle for stochastic optimal control problems of delay systems with random coefficients involving both continuous and impulse controls this kind of control problems is motivated by some interesting phenomena arising from economics and finance we establish a necessary maximum principle and a sufficient verification theorem by virtue of the duality and the convex analysis to explain the theoretical results we apply them to a production and consumption choice problem

anticipated backward stochastic differential equations in this paper we discuss new types of differential equations which we call anticipated backward stochastic differential equations anticipated bsdes in these equations the generator includes not only the values of solutions of the present but also the future we show that these anticipated bsdes have unique solutions a comparison theorem for their solutions and a duality between them and stochastic differential delay equations

cellular automaton for migration in ecosystem application of traffic model to a predator prey system in most cases physicists have studied the migration of biospecies by the use of random walk in the present article we apply cellular automaton of traffic model for simplicity we deal with an ecosystem contains a prey and predator and use one dimensional lattice with two layers preys stay on the first layer but predators uni directionally move on the second layer the spatial and temporal evolution is numerically explored it is shown that the migration has the important effect on populations of both prey and predator without migration the phase transition between a prey phase and coexisting phase occurs in contrast the phase transition disappears by migration this is because predator can survive due to migration we find another phase transition for spatial distribution in one phase prey and predator form a stripe pattern of condensation and rarefaction while in the other phase they uniformly distribute the self organized stripe may be similar to the migration patterns in real ecosystems

stability of the car following model on two lanes in the case of two lane traffic vehicle drivers always worry about the lane changing actions from neighbor lane this paper studies the stability of a car following model on two lanes which incorporates the lateral effects in traffic the stability condition of the model is obtained by using the linear stability theory the modified korteweg de vries equation is constructed and solved and three types of traffic flows in the headway sensitivity space stable metastable and unstable are classified both analytical and simulation results show that the anxiousness about lane changing from neighbor lane indeed has influence upon people s driving behavior and the consideration of lateral effects could stabilize the traffic flows on both lanes

nonlinear analysis of a differential difference equation with next nearest neighbour interaction for traffic flow we analyse the newell whitham type car following model described by a differential difference equation with a generalized optimal velocity function which depends not only on the headway of each car but also on the headway of the immediately preceding one linear stability analysis shows that the model is stabilized for larger delay time by taking into account the headway of the immediately preceding car from the nonlinear analysis the propagating kink solution for traffic jams is obtained the fundamental diagram and the relation between the headway and the delay time are examined by numerical simulation we find that the result from the nonlinear analysis is in good agreement with that obtained from the numerical simulation

density waves in a traffic flow model with reaction time delay abstract density waves are investigated analytically and numerically in the optimal velocity model with reaction time delay of drivers the stability condition of this model is obtained by using the linear stability theory the results show that the decrease of reaction time delay of drivers leads to the stabilization of traffic flow the burgers korteweg de vries kdv and modified korteweg de vries mkdv equations are derived to describe the density waves in the stable metastable and unstable regions respectively the triangular shock waves soliton waves and kink antikink waves appearing respectively in the three distinct regions are derived to describe the traffic jams the numerical simulations are given

full velocity difference model for a car following theory in this paper we present a full velocity difference model for a car following theory based on the previous models in the literature to our knowledge the model is an improvement over the previous ones theoretically because it considers more aspects in car following process than others this point is verified by numerical simulation then we investigate the property of the model using both analytic and numerical methods and find that the model can describe the phase transition of traffic flow and estimate the evolution of traffic congestion

effect of looking backward on traffic flow in an extended multiple car following model abstract in this paper a new car following model is proposed by incorporating the backward looking effect under certain conditions and multiple information of preceding cars in traffic flow and the neutral stability condition of this model can be obtained by using the linear stability theory numerical simulation shows that the proposed model is theoretically an improvement over previous ones