Most of the previous studies concerning checking the integrity constraints in distributed database derive simplified forms of the initial integrity constraints with the sufficiency property, since the sufficient test ...Most of the previous studies concerning checking the integrity constraints in distributed database derive simplified forms of the initial integrity constraints with the sufficiency property, since the sufficient test is known to be cheaper than the complete test and its initial integrity constraint as it involves less data to be transferred across the network and can always be evaluated at the target site （single site）. Their studies are limited as they depend strictly on the assumption that an update operation will be executed at a site where the relation specified in the update operation is located, which is not always true. Hence, the sufficient test, which is proven to be local test by previous study, is no longer appropriate. This paper proposes an approach to checking integrity constraints in a distributed database by utilizing as much as possible the local information stored at the target site. The proposed approach derives support tests as an alternative to the existing complete and sufficient tests proposed by previous researchers with the intention to increase the number of local checking regardless the location of the submitted update operation. Several analyses have been performed to evaluate the proposed approach, and the results show that support tests can benefit the distributed database, where local constraint checking can be achieved.展开更多
The extensions for logic-based knowledge bases with integrity constraints are rather popular. We put forward an alternative criteria for analysis of integrity constraints in Web ontology language （OWL） ontology unde...The extensions for logic-based knowledge bases with integrity constraints are rather popular. We put forward an alternative criteria for analysis of integrity constraints in Web ontology language （OWL） ontology under the closed world assumption. According to this criteria, grounded circumscription is applied to define integrity constraints in OWL ontology and the satisfaction of the integrity constraints by minimizing extensions of the predicates in integrity con- straints. According to the semantics of integrity constraints, we provide a modified tableau algorithm which is sound and complete for deciding the consistency of an extended ontol- ogy. Finally, the integrity constraint validation is converted into the corresponding consistency of the extended ontology. Comparing our approach with existing integrity constraint validation approaches, we show that the results of our approach are more in accordance with user requirements than other approaches in certain cases.展开更多
Integrity constraint is a formula that checks whether all necessary information has been explicitly provided. It can be added into ontology to guarantee the data-centric application. In this paper,a set of constraint ...Integrity constraint is a formula that checks whether all necessary information has been explicitly provided. It can be added into ontology to guarantee the data-centric application. In this paper,a set of constraint axioms called IC-mapping axioms are stated. Based on these axioms,a special ontology with integrity constraint,which is adapted to map ontology knowledge to data in relational databases,is defined. It＇s generated through our checking and modification. Making use of the traditional mapping approaches,it can be mapped to relational databases as a normal ontology. Unlike what in the past,a novel mapping approach named IC-based mapping is proposed in accordance with such special ontology. The detailed algorithm is put forward and compared with other existing approaches used in Semantic Web applications. The result shows that our method is advanced to the traditional approaches.展开更多
This paper investigates the robust tracking control problcm for a class of nonlinear networked control systems （NCSs） using the Takagi-Sugeno （T-S） fuzzy model approach. Based on a time-varying delay system transf...This paper investigates the robust tracking control problcm for a class of nonlinear networked control systems （NCSs） using the Takagi-Sugeno （T-S） fuzzy model approach. Based on a time-varying delay system transformed from the NCSs, an augmented Lyapunov function containing more useful information is constructed. A less conservative sufficient condition is established such that the closed-loop systems stability and time-domain integral quadratic constraints （IQCs） are satisfied while both time-varying network- induced delays and packet losses are taken into account. The fuzzy tracking controllers design scheme is derived in terms of linear matrix inequalities （LMIs） and parallel distributed compensation （PDC）. Furthermore, robust stabilization criterion for nonlinear NCSs is given as an extension of the tracking control result. Finally, numerical simulations are provided to illustrate the effectiveness and merits of the proposed method.展开更多
The study considers issues of elaborating and validating a technique of autonomous vehicle motion planning based on sequential trajectory and speed optimization.This method includes components such as representing sou...The study considers issues of elaborating and validating a technique of autonomous vehicle motion planning based on sequential trajectory and speed optimization.This method includes components such as representing sought-for functions by finite elements(FE),vehicle kinematic model,sequential quadratic programming for nonlinear constrained optimization,and Gaussian N-point quadrature integration.The primary novelty consists of using the inverse approach for obtaining vehicle trajectory and speed.The curvature and speed are represented by integrated polynomials to reduce the number of unknowns.For this,piecewise functions with two and three degrees of freedom(DOF)are implemented through FE nodal parameters.The technique ensures higher differentiability compared to the needed in the geometric and kinematic equations.Thus,the generated reference curves are characterized by simple and unambiguous forms.The latter fits best the control accuracy and efficiency during the motion tracking phase.Another advantage is replacing the nodal linear equality constraints with integral nonlinear ones.This ensures the non-violation of boundary limits within each FE and not only in nodes.The optimization technique implies that the spatial and time variables must be found separately and staged.The trajectory search is accomplished in the restricted allowable zone composed by superposing an area inside the external and internal boundaries,based on keeping safe distances,excluding areas for moving obstacles.Thus,this study compares two models that use two and three nodal DOF on optimization quality,stability,and rapidity in real-time applications.The simulation example shows numerous graph results of geometric and kinematic parameters with smoothed curves up to the highest derivatives.Finally,the conclusions are made on the efficiency and quality of prognosis,outlining the similarities and differences between the two applied models.展开更多
In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security mode...In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security model for database systems is pro- posed. According to this method, an analysis by using Coq proof assistant to ensure the correctness and security of the extended model is introduced. Our formal security model has been verified secure. This work demonstrates that our verification method is effective and sufficient.展开更多
This paper proposes the concept of transaction-type covert storage channels, which are caused by database storage resources. It also proposes that the mode of auditing those channels be based on the transactions. Next...This paper proposes the concept of transaction-type covert storage channels, which are caused by database storage resources. It also proposes that the mode of auditing those channels be based on the transactions. Next, the paper analyzes and resolves the two problems arising from auditing the use of transaction-type covert storage channels in database systems: namely, the relationship between channel variables, which are altered (or viewed) by the transaction and satisfy integrity constraints in DBMS, and database states; and the circumvention of covert storage channel audit in DBMS.展开更多
Stability perturbation bounds problem for systems with mixed uncertainties is discussed. It is supposed that the linear part in the forward loop is of parametric uncertainties described by interval perturbation mode, ...Stability perturbation bounds problem for systems with mixed uncertainties is discussed. It is supposed that the linear part in the forward loop is of parametric uncertainties described by interval perturbation mode, and that the nonlinear part in the feedback loop is characterized by an integral quadratic constraint (IQC). The definition of stability margin under the interval perturbation mode is given by using the Minkowski functional. The infinite stability checking problem of the mixed uncertain system can be converted to finite or one dimensional stability checking for different structures of the IQC multipliers based on the concepts of biconvex and convex-concave junctions and their properties. The result is illustrated to be efficient through an example.展开更多
This paper proposes an effective algorithm to work out the linear parameter-varying (LPV) framework autopilot for the air defense missile so as to simultaneously guarantee the closed-loop system properties globally an...This paper proposes an effective algorithm to work out the linear parameter-varying (LPV) framework autopilot for the air defense missile so as to simultaneously guarantee the closed-loop system properties globally and locally, which evidently reduces the number of unknown variables and hence increases the computational efficiency. The notion of 'robust quadratic stability' is inducted to meet the global properties, including the robust stability and robust performance, while the regional pole placement scheme together with the adoption of a model matching structure is involved to satisfy the dynamic performance, including limiting the 'fast poles'. In order to reduce the conservatism, the full block multiplier is employed to depict the properties, with all specifications generalized in integral quadratic constraint frame and finally transformed into linear matrix inequalities for tractable solutions through convex optimization. Simulation results validate the performance of the designed robust LPV autopilot and the proposed framework control method integrating with the full block multiplier approach and the regional pole placement scheme, and demonstrate the efficiency of the algorithm. An efficient algorithm for the air defense missile is proposed to satisfy the required global stability and local dynamical properties by a varying controller according to the flight conditions, and shows sufficient promise in the computational efficiency and the real-time performance of the missile-borne computer system.展开更多
This paper presents the integration methods for vacco dynmmies equations of nonlinear nonholononic system,First.vacco dynamies equations are written in the canonical form and the field form.second the gradient methods...This paper presents the integration methods for vacco dynmmies equations of nonlinear nonholononic system,First.vacco dynamies equations are written in the canonical form and the field form.second the gradient methods the single-componentmethods and the field method are used to integrate the dynamics equations of the corresponding holonomic system respectively.And considering the restriction of nonholonomic construint to the initial conditions the solutions of Vacco dynamics cquations of nonlinear nonholonomic system are obtained.展开更多
In this paper,we analyze the blow-up behavior of sequences{uk}satisfying the following conditionsΔuk=｜x｜2αk V k eukinΩ,（0.1）whereΩR2,V k→V in C1,｜Vk｜≤A,0
Matching dependencies （MDs） are used to declaratively specify the identification （or matching） of cer- tain attribute values in pairs of database tuples when some similarity conditions on other values are satisfie...Matching dependencies （MDs） are used to declaratively specify the identification （or matching） of cer- tain attribute values in pairs of database tuples when some similarity conditions on other values are satisfied. Their en- forcement can be seen as a natural generalization of entity resolution. In what we call the pure case of MD enforce- ment, an arbitrary value from the underlying data domain can be used for the value in common that is used for a match- ing. However, the overall number of changes of attribute val- ues is expected to be kept to a minimum. We investigate this case in terms of semantics and the properties of data clean- ing through the enforcement of MDs. We characterize the in- tended clean instances, and also the clean answers to queries, as those that are invariant under the cleaning process. The complexity of computing clean instances and clean query an- swering is investigated. Tractable and intractable cases de- pending on the MDs are identified and characterized.展开更多
In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this app...In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this approach, inconsistency is viewed as a property of data and described with annotations. To be more precise, every piece of data in a relation can have zero or more annotations with it and annotations are propagated along with queries from the source to the output. With annotations, inconsistent data in both input tables and query answers can be marked out but preserved, instead of being filtered in most previous work. Thus this approach can avoid information loss, a vital and common deficiency of most previous work in this area. To calculate query answers on an annotated database, we propose an algorithm to annotate the input tables, and redefine the five basic relational algebra operations （selection, projection, join, union and difference） so that annotations can be correctly propagated as the valid set of functional dependency changes during query processing. We also prove the soundness and completeness of the whole annotation computing system. Finally, we implement a prototype of our system, and give some performance experiments, which demonstrate that our approach is reasonable in running time, and excellent in information preserving.展开更多
In this paper we formulate a continuous-time behavioral （4 la cumulative prospect theory） portfolio selection model where the losses are constrained by a pre-specified upper bound. Economically the model is motivate...In this paper we formulate a continuous-time behavioral （4 la cumulative prospect theory） portfolio selection model where the losses are constrained by a pre-specified upper bound. Economically the model is motivated by the previously proved fact that the losses Occurring in a bad state of the world can be catastrophic for an unconstrained model. Mathematically solving the model boils down to solving a concave Choquet minimization problem with an additional upper bound. We derive the optimal solution explicitly for such a loss control model. The optimal terminal wealth profile is in general characterized by three pieces： the agent has gains in the good states of the world, gets a moderate, endogenously constant loss in the intermediate states, and suffers the maximal loss （which is the given bound for losses） in the bad states. Examples are given to illustrate the general results.展开更多
Based on the Hybrid Coordinate Ocean Model （HYCOM）, this article presents simulations of the three-dimensional dynamic and thermal structure of the North Pacific Ocean （NPO） in the time domain from January 1991 to...Based on the Hybrid Coordinate Ocean Model （HYCOM）, this article presents simulations of the three-dimensional dynamic and thermal structure of the North Pacific Ocean （NPO） in the time domain from January 1991 to December 2000. The baroclinic current field and its interannual variability in Northwest Pacific Ocean （NWPO）, especially, the Kuroshio Current （KC） and the Japan/East Sea （JES） are analyzed and discussed. The results show that the HYCOM covers a complete dynamic and thermo process with adequate representations of the eddy fields and variability in main spatial and temporal scales. The model is used to simulatethe strong interanual variability of the KC, which may affect the strength of the eastern bifurcation of the Tsushima Warm Current （TSWC）, named the Nearshore Branch （NB） in the JES. When the KC is strong and its axis is close to the Japan Island, the TSWC and its bifurcations in the JES would intensify accordingly. Our results confirm once again the hypothesis of Yang et al. that the KC determines the annual mean NB in the JES via the ＂island integral constraint＂. This article further extends this hypothesis to study the KC role in the NB on a time dependent scale.展开更多
This paper is concerned with the robustness analysis and distributed output feedback control of a networked system with uncertain time-varying communication delays.This system consists of a collection of linear time-i...This paper is concerned with the robustness analysis and distributed output feedback control of a networked system with uncertain time-varying communication delays.This system consists of a collection of linear time-invariant subsystems that are spatially interconnected via an arbitrary directed network.Using a dissipation inequality that incorporates dynamic hard lQCs(integral quadratic constraints)for the delay uncertainties,we derive some sufficient robustness conditions in the form of coupled linear matrix inequalities,in which the couplld parts reflect the interconnection structure of the system.We then provide a procedure to construct a distributed controller to ensure the robust stability of the closed-loop system and to achieve a prescribed lzgain performance.The effectiveness of the proposed approach is demonstrated by some numerical examples.展开更多
In this paper,we present a technique for ensuring the stability of a large class of adaptively controlled systems.We combine IQC models of both the controlled system and the controller with a method of filtering contr...In this paper,we present a technique for ensuring the stability of a large class of adaptively controlled systems.We combine IQC models of both the controlled system and the controller with a method of filtering control parameter updates to ensure stable behavior of the controlled system under adaptation of the controller.We present a specific application to a system that uses recurrent neural networks adapted via reinforcement learning techniques.The work presented extends earlier works on stable reinforcement learning with neural networks.Specifically,we apply an improved IQC analysis for RNNs with time-varying weights and evaluate the approach on more complex control system.展开更多
文摘Most of the previous studies concerning checking the integrity constraints in distributed database derive simplified forms of the initial integrity constraints with the sufficiency property, since the sufficient test is known to be cheaper than the complete test and its initial integrity constraint as it involves less data to be transferred across the network and can always be evaluated at the target site （single site）. Their studies are limited as they depend strictly on the assumption that an update operation will be executed at a site where the relation specified in the update operation is located, which is not always true. Hence, the sufficient test, which is proven to be local test by previous study, is no longer appropriate. This paper proposes an approach to checking integrity constraints in a distributed database by utilizing as much as possible the local information stored at the target site. The proposed approach derives support tests as an alternative to the existing complete and sufficient tests proposed by previous researchers with the intention to increase the number of local checking regardless the location of the submitted update operation. Several analyses have been performed to evaluate the proposed approach, and the results show that support tests can benefit the distributed database, where local constraint checking can be achieved.
基金Acknowledgements This work was supported in part by the National Natural Science Foundation of China （Grant Nos. 61133011, 41172294, 61003101, 61170092） Jilin Province Science and Technology Development Plan （20101501, 20100185, 201101039）+2 种基金 Doctoral Fund of Ministry of Edu- cation of China （20100061110031） Opening Fund of Top Key Discipline of Computer Software and Theory in Zhejiang Provincial Colleges at Zhejiang Normal University （ZSDZZZZXK12） Jilin University Doctoral Interdisci- plinary Research Funded Project （2012JC012）.
文摘The extensions for logic-based knowledge bases with integrity constraints are rather popular. We put forward an alternative criteria for analysis of integrity constraints in Web ontology language （OWL） ontology under the closed world assumption. According to this criteria, grounded circumscription is applied to define integrity constraints in OWL ontology and the satisfaction of the integrity constraints by minimizing extensions of the predicates in integrity con- straints. According to the semantics of integrity constraints, we provide a modified tableau algorithm which is sound and complete for deciding the consistency of an extended ontol- ogy. Finally, the integrity constraint validation is converted into the corresponding consistency of the extended ontology. Comparing our approach with existing integrity constraint validation approaches, we show that the results of our approach are more in accordance with user requirements than other approaches in certain cases.
基金supported by the National Natural Science Foundation of China (60973089, 60873148)the Jilin Province Science and Technology Development Plan (20101501, 20100185)+1 种基金the Erasmus Mundus External Cooperation Window’s Project (EMECW): Bridging the Gap (155776-EM-1-2009-1-IT-ERAMUNDUS-ECW-L12)the Foundation of Key Laboratory of SCKE of Ministry of Education (450060326019)
文摘Integrity constraint is a formula that checks whether all necessary information has been explicitly provided. It can be added into ontology to guarantee the data-centric application. In this paper,a set of constraint axioms called IC-mapping axioms are stated. Based on these axioms,a special ontology with integrity constraint,which is adapted to map ontology knowledge to data in relational databases,is defined. It＇s generated through our checking and modification. Making use of the traditional mapping approaches,it can be mapped to relational databases as a normal ontology. Unlike what in the past,a novel mapping approach named IC-based mapping is proposed in accordance with such special ontology. The detailed algorithm is put forward and compared with other existing approaches used in Semantic Web applications. The result shows that our method is advanced to the traditional approaches.
基金supported by National Natural Science Foundation of China (No. 60574014, No. 60425310)Doctor Subject Foundation of China (No. 200805330004)+2 种基金Program for New Century Excellent Talents in University (No. NCET-06-0679)Natural Science Foundation of Hunan Province of China (No. 08JJ1010)Science Foundation of Education Department of Hunan Province (No. 08C106)
文摘This paper investigates the robust tracking control problcm for a class of nonlinear networked control systems （NCSs） using the Takagi-Sugeno （T-S） fuzzy model approach. Based on a time-varying delay system transformed from the NCSs, an augmented Lyapunov function containing more useful information is constructed. A less conservative sufficient condition is established such that the closed-loop systems stability and time-domain integral quadratic constraints （IQCs） are satisfied while both time-varying network- induced delays and packet losses are taken into account. The fuzzy tracking controllers design scheme is derived in terms of linear matrix inequalities （LMIs） and parallel distributed compensation （PDC）. Furthermore, robust stabilization criterion for nonlinear NCSs is given as an extension of the tracking control result. Finally, numerical simulations are provided to illustrate the effectiveness and merits of the proposed method.
基金supported by the Natural Sciences and Engineering Research Council of Canada(RGPIN-2020-04667).
文摘The study considers issues of elaborating and validating a technique of autonomous vehicle motion planning based on sequential trajectory and speed optimization.This method includes components such as representing sought-for functions by finite elements(FE),vehicle kinematic model,sequential quadratic programming for nonlinear constrained optimization,and Gaussian N-point quadrature integration.The primary novelty consists of using the inverse approach for obtaining vehicle trajectory and speed.The curvature and speed are represented by integrated polynomials to reduce the number of unknowns.For this,piecewise functions with two and three degrees of freedom(DOF)are implemented through FE nodal parameters.The technique ensures higher differentiability compared to the needed in the geometric and kinematic equations.Thus,the generated reference curves are characterized by simple and unambiguous forms.The latter fits best the control accuracy and efficiency during the motion tracking phase.Another advantage is replacing the nodal linear equality constraints with integral nonlinear ones.This ensures the non-violation of boundary limits within each FE and not only in nodes.The optimization technique implies that the spatial and time variables must be found separately and staged.The trajectory search is accomplished in the restricted allowable zone composed by superposing an area inside the external and internal boundaries,based on keeping safe distances,excluding areas for moving obstacles.Thus,this study compares two models that use two and three nodal DOF on optimization quality,stability,and rapidity in real-time applications.The simulation example shows numerous graph results of geometric and kinematic parameters with smoothed curves up to the highest derivatives.Finally,the conclusions are made on the efficiency and quality of prognosis,outlining the similarities and differences between the two applied models.
基金the National High Technology Research and Development Program of China (2006AA01Z430)
文摘In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security model for database systems is pro- posed. According to this method, an analysis by using Coq proof assistant to ensure the correctness and security of the extended model is introduced. Our formal security model has been verified secure. This work demonstrates that our verification method is effective and sufficient.
文摘This paper proposes the concept of transaction-type covert storage channels, which are caused by database storage resources. It also proposes that the mode of auditing those channels be based on the transactions. Next, the paper analyzes and resolves the two problems arising from auditing the use of transaction-type covert storage channels in database systems: namely, the relationship between channel variables, which are altered (or viewed) by the transaction and satisfy integrity constraints in DBMS, and database states; and the circumvention of covert storage channel audit in DBMS.
文摘Stability perturbation bounds problem for systems with mixed uncertainties is discussed. It is supposed that the linear part in the forward loop is of parametric uncertainties described by interval perturbation mode, and that the nonlinear part in the feedback loop is characterized by an integral quadratic constraint (IQC). The definition of stability margin under the interval perturbation mode is given by using the Minkowski functional. The infinite stability checking problem of the mixed uncertain system can be converted to finite or one dimensional stability checking for different structures of the IQC multipliers based on the concepts of biconvex and convex-concave junctions and their properties. The result is illustrated to be efficient through an example.
基金supported by the National Natural Science Foundation of China(11532002)
文摘This paper proposes an effective algorithm to work out the linear parameter-varying (LPV) framework autopilot for the air defense missile so as to simultaneously guarantee the closed-loop system properties globally and locally, which evidently reduces the number of unknown variables and hence increases the computational efficiency. The notion of 'robust quadratic stability' is inducted to meet the global properties, including the robust stability and robust performance, while the regional pole placement scheme together with the adoption of a model matching structure is involved to satisfy the dynamic performance, including limiting the 'fast poles'. In order to reduce the conservatism, the full block multiplier is employed to depict the properties, with all specifications generalized in integral quadratic constraint frame and finally transformed into linear matrix inequalities for tractable solutions through convex optimization. Simulation results validate the performance of the designed robust LPV autopilot and the proposed framework control method integrating with the full block multiplier approach and the regional pole placement scheme, and demonstrate the efficiency of the algorithm. An efficient algorithm for the air defense missile is proposed to satisfy the required global stability and local dynamical properties by a varying controller according to the flight conditions, and shows sufficient promise in the computational efficiency and the real-time performance of the missile-borne computer system.
文摘This paper presents the integration methods for vacco dynmmies equations of nonlinear nonholononic system,First.vacco dynamies equations are written in the canonical form and the field form.second the gradient methods the single-componentmethods and the field method are used to integrate the dynamics equations of the corresponding holonomic system respectively.And considering the restriction of nonholonomic construint to the initial conditions the solutions of Vacco dynamics cquations of nonlinear nonholonomic system are obtained.
基金Supported by the German Research Foundation Collaborative Research Center Collaborative Research/Tran-sregio 71
文摘In this paper,we analyze the blow-up behavior of sequences{uk}satisfying the following conditionsΔuk=｜x｜2αk V k eukinΩ,（0.1）whereΩR2,V k→V in C1,｜Vk｜≤A,0
文摘Matching dependencies （MDs） are used to declaratively specify the identification （or matching） of cer- tain attribute values in pairs of database tuples when some similarity conditions on other values are satisfied. Their en- forcement can be seen as a natural generalization of entity resolution. In what we call the pure case of MD enforce- ment, an arbitrary value from the underlying data domain can be used for the value in common that is used for a match- ing. However, the overall number of changes of attribute val- ues is expected to be kept to a minimum. We investigate this case in terms of semantics and the properties of data clean- ing through the enforcement of MDs. We characterize the in- tended clean instances, and also the clean answers to queries, as those that are invariant under the cleaning process. The complexity of computing clean instances and clean query an- swering is investigated. Tractable and intractable cases de- pending on the MDs are identified and characterized.
基金Supported by the National Natural Science Foundation of China under Grant No. 60603043the Program of Shanghai Municipal Education Commission under Grant No.06FZ030
文摘In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this approach, inconsistency is viewed as a property of data and described with annotations. To be more precise, every piece of data in a relation can have zero or more annotations with it and annotations are propagated along with queries from the source to the output. With annotations, inconsistent data in both input tables and query answers can be marked out but preserved, instead of being filtered in most previous work. Thus this approach can avoid information loss, a vital and common deficiency of most previous work in this area. To calculate query answers on an annotated database, we propose an algorithm to annotate the input tables, and redefine the five basic relational algebra operations （selection, projection, join, union and difference） so that annotations can be correctly propagated as the valid set of functional dependency changes during query processing. We also prove the soundness and completeness of the whole annotation computing system. Finally, we implement a prototype of our system, and give some performance experiments, which demonstrate that our approach is reasonable in running time, and excellent in information preserving.
文摘In this paper we formulate a continuous-time behavioral （4 la cumulative prospect theory） portfolio selection model where the losses are constrained by a pre-specified upper bound. Economically the model is motivated by the previously proved fact that the losses Occurring in a bad state of the world can be catastrophic for an unconstrained model. Mathematically solving the model boils down to solving a concave Choquet minimization problem with an additional upper bound. We derive the optimal solution explicitly for such a loss control model. The optimal terminal wealth profile is in general characterized by three pieces： the agent has gains in the good states of the world, gets a moderate, endogenously constant loss in the intermediate states, and suffers the maximal loss （which is the given bound for losses） in the bad states. Examples are given to illustrate the general results.
基金supported by the National Basic Research Program of China(973 Program,Grant Nos.2005CB422302,2005CB422303,2007CB411804)the National Natural Science Foundation of China(Grant Nos.40706006,40930844)+2 种基金the key project of International Science and Technology Cooperation Program of China(Grant No.2006DFB21250)the Ministry of Education's 111 Project(Grant No.B07036)the Program for New Century Excellent Talents in University(Grant No.NECT-07-0781)
文摘Based on the Hybrid Coordinate Ocean Model （HYCOM）, this article presents simulations of the three-dimensional dynamic and thermal structure of the North Pacific Ocean （NPO） in the time domain from January 1991 to December 2000. The baroclinic current field and its interannual variability in Northwest Pacific Ocean （NWPO）, especially, the Kuroshio Current （KC） and the Japan/East Sea （JES） are analyzed and discussed. The results show that the HYCOM covers a complete dynamic and thermo process with adequate representations of the eddy fields and variability in main spatial and temporal scales. The model is used to simulatethe strong interanual variability of the KC, which may affect the strength of the eastern bifurcation of the Tsushima Warm Current （TSWC）, named the Nearshore Branch （NB） in the JES. When the KC is strong and its axis is close to the Japan Island, the TSWC and its bifurcations in the JES would intensify accordingly. Our results confirm once again the hypothesis of Yang et al. that the KC determines the annual mean NB in the JES via the ＂island integral constraint＂. This article further extends this hypothesis to study the KC role in the NB on a time dependent scale.
基金This work was supported by the National Natural Science Foundation of China(Nos.61573209,61733008).
文摘This paper is concerned with the robustness analysis and distributed output feedback control of a networked system with uncertain time-varying communication delays.This system consists of a collection of linear time-invariant subsystems that are spatially interconnected via an arbitrary directed network.Using a dissipation inequality that incorporates dynamic hard lQCs(integral quadratic constraints)for the delay uncertainties,we derive some sufficient robustness conditions in the form of coupled linear matrix inequalities,in which the couplld parts reflect the interconnection structure of the system.We then provide a procedure to construct a distributed controller to ensure the robust stability of the closed-loop system and to achieve a prescribed lzgain performance.The effectiveness of the proposed approach is demonstrated by some numerical examples.
基金supported by the National Natural Science Foundation (No.0245291)
文摘In this paper,we present a technique for ensuring the stability of a large class of adaptively controlled systems.We combine IQC models of both the controlled system and the controller with a method of filtering control parameter updates to ensure stable behavior of the controlled system under adaptation of the controller.We present a specific application to a system that uses recurrent neural networks adapted via reinforcement learning techniques.The work presented extends earlier works on stable reinforcement learning with neural networks.Specifically,we apply an improved IQC analysis for RNNs with time-varying weights and evaluate the approach on more complex control system.
