The supervisory control problem for discrete event system(DES) under control involves identifying the supervisor, if one exists, which, when synchronously composed with the DES,results in a system that conforms to the...The supervisory control problem for discrete event system(DES) under control involves identifying the supervisor, if one exists, which, when synchronously composed with the DES,results in a system that conforms to the control specification. In this context, we consider a non-deterministic DES under complete observation and control specification expressed in action-based propositional μ-calculus. The key to our solution is the process of quotienting the control specification against the plan resulting in a new μ-calculus formula such that a model for the formula is the supervisor. Thus the task of control synthesis is reduced a problem of μ-calculus satisfiability. In contrast to the existing μ-calculus quotienting-based techniques that are developed in deterministic setting, our quotienting rules can handle nondeterminism in the plant models. Another distinguishing feature of our technique is that while existing techniques use a separate μ-calculus formula to describe the controllability constraint(that uncontrollable events of plants are never disabled by a supervisor), we absorb this constraint as part of quotienting which allows us to directly capture more general state-dependent controllability constraints. Finally, we develop a tableau-based technique for verifying satisfiability of quotiented formula and model generation. The runtime for the technique is exponential in terms of the size of the plan and the control specification. A better complexity result that is polynomial to plant size and exponential to specification size is obtained when the controllability property is state-independent. A prototype implementation in a tabled logic programming language as well as some experimental results are presented.展开更多
The spectrum allocation for cognitive radio networks(CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes i...The spectrum allocation for cognitive radio networks(CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes is time-varied due to primary user/secondary user(PU/SU) activity and mobility, which result in non-determinacy. This paper studies the spectrum allocation for CRNs with non-deterministic bandwidth of spectrum holes. We present a novel probability density function(PDF) through order statistics as well as its simplified form to describe the statistical properties of spectrum holes, with which a statistical spectrum allocation model based on stochastic multiple knapsack problem(MKP) is formulated for spectrum allocation with non-deterministic bandwidth of spectrum holes. To reduce the computational complexity, we transform this stochastic programming problem into a constant MKP through exploiting the properties of cumulative distribution function(CDF), which can be solved via MTHG algorithm by using auxiliary variables. Simulation results illustrate that the proposed statistical spectrum allocation algorithm can achieve better performance compared with the existing algorithms when the bandwidth of spectrum holes is time-varied.展开更多
In this paper, we study the supervisory control problem of discrete event systems assuming that cyber-attacks might occur. In particular, we focus on the problem of liveness enforcement and consider a sensor-reading m...In this paper, we study the supervisory control problem of discrete event systems assuming that cyber-attacks might occur. In particular, we focus on the problem of liveness enforcement and consider a sensor-reading modification attack(SM-attack) that may disguise the occurrence of an event as that of another event by intruding sensor communication channels. To solve the problem, we introduce non-deterministic supervisors in the paper, which associate to every observed sequence a set of possible control actions offline and choose a control action from the set randomly online to control the system. Specifically, given a bounded Petri net(PN) as the reference formalism and an SMattack, an algorithm that synthesizes a liveness-enforcing nondeterministic supervisor tolerant to the SM-attack is proposed for the first time.展开更多
Modeling and forecasting of the groundwater water table are a major component of effective planning and management of water resources. One way to predict the groundwater level is analysis using a non-deterministic mod...Modeling and forecasting of the groundwater water table are a major component of effective planning and management of water resources. One way to predict the groundwater level is analysis using a non-deterministic model. This study assessed the performance of such models in predicting the groundwater level at Kashan aquifer. Data from 36 piezometer wells in Kashan aquifer for 1999 to 2010 were used. The desired statistical interval was divided into two parts and statistics for 1990 to 2004 were used for modeling and statistics from 2005 to 2010 were used for valediction of the model. The Akaike criterion and correlation coefficients were used to determine the accuracy of the prediction models. The results indicated that the AR(2) model more accurately predicted ground water level in the plains;using this model, the groundwater water table was predicted for up to 60 mo.展开更多
Watson Crick automata are finite automata working on double strands. Extensive research work has already been done on non deterministic Watson Crick automata and on deterministic Watson Crick automata. Parallel Commun...Watson Crick automata are finite automata working on double strands. Extensive research work has already been done on non deterministic Watson Crick automata and on deterministic Watson Crick automata. Parallel Communicating Watson Crick automata systems have been introduced by E. Czeziler et al. In this paper we discuss about a variant of Watson Crick automata known as the two-way Watson Crick automata which are more powerful than non-deterministic Watson Crick automata. We also establish the equivalence of different subclasses of two-way Watson crick automata. We further show that recursively enumerable (RE) languages can be realized by an image of generalized sequential machine (gsm) mapping of two-way Watson-Crick automata.展开更多
The recently experienced hype concerning the so-called “4<sup>th</sup> Industrial Revolution” of production systems has prompted several papers of various subtopics regarding Cyber-Phdysical Production S...The recently experienced hype concerning the so-called “4<sup>th</sup> Industrial Revolution” of production systems has prompted several papers of various subtopics regarding Cyber-Phdysical Production Systems (CPPS). However, important aspects such as the modelling of CPPS to understand the theory regarding the performance of highly non-ergodic and non-deterministic flexible manufacturing systems in terms of Exit Rate (ER), Manufacturing Lead Time (MLT), and On-Time Delivery (OTD) have not yet been examined systematically and even less modeled analytically. To develop the topic, in this paper, the prerequisites for modelling such systems are defined in order to be able to derive an explicit and dedicated production mathematics-based understanding of CPPS and its dynamics: switching from explorative simulation to rational modelling of the manufacturing “physics” led to an own and specific manufacturing theory. The findings have led to enouncing, among others, the Theorem of Non-Ergodicity as well as the Batch Cycle Time Deviation Function giving important insights to model digital twin-based CPPS for complying with the mandatory OTD.展开更多
The non-probabilistic approach to fatigue life analysis was studied using the convex models-interval, ellipsoidal and multiconvex models. The lower and upper bounds of the fatigue life were obtained by using the secon...The non-probabilistic approach to fatigue life analysis was studied using the convex models-interval, ellipsoidal and multiconvex models. The lower and upper bounds of the fatigue life were obtained by using the second-order Taylor series and Lagrange multiplier method. The solving process for derivatives of the implicit life function was presented. Moreover, a median ellipsoidal model was proposed which can take into account the sample blind zone and almost impossibility of concurrence of some small probability events. The Monte Carlo method for multi-convex model was presented, an important alternative when the analytical method does not work. A project example was given. The feasibility and rationality of the presented approach were verified. It is also revealed that the proposed method is conservative compared to the traditional probabilistic method, but it is a useful complement when it is difficult to obtain the accurate probability densities of parameters.展开更多
保证服务质量的QoS路由(Quality of Service Routing)是网络中解决QoS问题的一项关键技术。QoS路由的主要目标是为接入的业务选择满足服务质量要求的传输路径,同时保证整个网络资源的有效利用。度量参数选择问题、寻路问题和路由信息不...保证服务质量的QoS路由(Quality of Service Routing)是网络中解决QoS问题的一项关键技术。QoS路由的主要目标是为接入的业务选择满足服务质量要求的传输路径,同时保证整个网络资源的有效利用。度量参数选择问题、寻路问题和路由信息不准确问题是QoS路由中的几个主要研究内容。多约束QoS路由算法通常是NPC问题,本文先对QoS路由中的问题进行分类,再对当前研究的一些多约束QoS路由算法进行了归纳与分析。这些算法对于在Internet中实现QoS有着重要的指导意义。展开更多
This paper investigates the maximal achievable multi-rate throughput problem of a multicast ses-sion at the presence of network coding. Deviating from previous works which focus on single-rate network coding, our work...This paper investigates the maximal achievable multi-rate throughput problem of a multicast ses-sion at the presence of network coding. Deviating from previous works which focus on single-rate network coding, our work takes the heterogeneity of sinks into account and provides multiple data layers to address the problem. Firstly formulated is the maximal achievable throughput problem with the assumption that the data layers are independent and layer rates are static. It is proved that the problem in this case is, unfortunately, Non-deterministic Polynomial-time (NP)-hard. In addition, our formulation is extended to the problems with dependent layers and dynamic layers. Furthermore, the approximation algorithm which satisfies certain fair-ness is proposed.展开更多
QoS(Quality of Service)路由算法是解决QoS问题的关键,也是当前网络领域里的一大研究热点。QoS路由算法的主要目的是为接入的业务选择满足服务质量要求的传输路径,同时保证整个网络资源的有效利用。改文深入探讨了QoS路由问题的实质,...QoS(Quality of Service)路由算法是解决QoS问题的关键,也是当前网络领域里的一大研究热点。QoS路由算法的主要目的是为接入的业务选择满足服务质量要求的传输路径,同时保证整个网络资源的有效利用。改文深入探讨了QoS路由问题的实质,并对以往的QoS路由算法进行了归纳总结。基于已有的QoS路由算法的研究,该文对QoS路由算法的发展方向进行了预测。展开更多
In this paper is demonstrated a method for reduction of integer factorization problem to an analysis of a sequence of modular elliptic equations. As a result, the paper provides a non-deterministic algorithm that comp...In this paper is demonstrated a method for reduction of integer factorization problem to an analysis of a sequence of modular elliptic equations. As a result, the paper provides a non-deterministic algorithm that computes a factor of a semi-prime integer n=pq, where prime factors p and q are unknown. The proposed algorithm is based on counting points on a sequence of at least four elliptic curves y2=x(x2+b2)(modn) , where b is a control parameter. Although in the worst case, for some n the number of required values of parameter b that must be considered (the number of basic steps of the algorithm) substantially exceeds four, hundreds of computer experiments indicate that the average number of the basic steps does not exceed six. These experiments also confirm all important facts discussed in this paper.展开更多
For better applications of fuzzy automata on target tracking, this paper presents an associated method of fuzzy automata by discussing the relation between fuzzy automata. The equivalence is mainly discussed regarding...For better applications of fuzzy automata on target tracking, this paper presents an associated method of fuzzy automata by discussing the relation between fuzzy automata. The equivalence is mainly discussed regarding these fuzzy automata. The target tracking based on the associated method of fuzzy automata is given. Moreover, the simulation result shows that the associated method is better than single fuzzy automaton relatively. The development of these researches in this paper in turn can quicken the applications of the fuzzy automata in various fields.展开更多
The Balanced Academic Curriculum Problem （BACP） is a constraint satisfaction problem classified as （Non-deterministic Polynomial-time Hard） NP-Hard. This problem consists in the allocation of courses in the period...The Balanced Academic Curriculum Problem （BACP） is a constraint satisfaction problem classified as （Non-deterministic Polynomial-time Hard） NP-Hard. This problem consists in the allocation of courses in the periods that are part of a curriculum such that the prerequisites are satisfied and the load of courses is balanced for the students. This paper presents the solution for a modified BACP where the academic loads and number of curses may be the same or different for each one of the periods and allows having some courses in a specific period. This problem is modeled as an integer programming problem and is proposed the use of Tabu search with short-term memory for its solution because it is not possible to find solutions for all the instances of this modified problem with an exact method.展开更多
In present paper,the mathematic background of intrusive polynomial chaos (IPC) method and coupling process with one dimension Euler equation were introduced. The IPC method was implemented for the 2D compressible stoc...In present paper,the mathematic background of intrusive polynomial chaos (IPC) method and coupling process with one dimension Euler equation were introduced. The IPC method was implemented for the 2D compressible stochastic Navier-Stokes equations to simulate the non-deterministic behavior of a lid driven cavity flow under the influence of uncertainties. The driven velocity and fluid viscosity were supposed respectively to be the uncertain variable which has Gaussian probability distribution. Based on the validation with benchmark results,discussions were mainly focused on the statistic properties of velocity distribution. The results indicated the effect of IPC method on the simulation of propagation of uncertainty in the flow field. For the simulated results of 2D cavity flow,influence of the driven velocity uncertainty is larger than that of viscosity.展开更多
The controlled islanding for the power system is an effective method to deal with the emergent situations caused by large disturbances. The size of the solution space would increase exponentially as the scale of the p...The controlled islanding for the power system is an effective method to deal with the emergent situations caused by large disturbances. The size of the solution space would increase exponentially as the scale of the power grid increases. The goal of our controlled islanding strategy is to divide the system into several islands quickly. Meanwhile, the generator coherency and the power-flow disruption have to be taken into consideration carefully. This paper proposed a two-stage fast islanding strategy for large power networks, which is on the basis of large power grid graph theories. In the first stage, the Stoer-Wagner algorithm is employed to obtain the grouping cluster of coherent generators in the dynamic undirected liaison graph. In the second stage, the improved Dinic max-flow method is proposed to search the optimal splitting boundary so as to acquire the minimum power flow impact. Our two-stage islanding strategy does not need to reduce the whole power network. Simulations on IEEE 118-bus and162-bus power systems showed that the proposed strategy can acquire high quality solutions effectively and efficiently.展开更多
A standard assumption when modelling linked sample data is that the stochastic properties of the linking process and process underpinning the population values of the response variable are independent of one another.T...A standard assumption when modelling linked sample data is that the stochastic properties of the linking process and process underpinning the population values of the response variable are independent of one another.This is often referred to as non-informative linkage.But what if linkage errors are informative?In this paper,we provide results from two simulation experiments that explore two potential informative linking scenarios.The first is where the choice of sample record to link is dependent on the response;and the second is where the probability of correct linkage is dependent on the response.We focus on the important and widely applicable problem of estimation of domain means given linked data,and provide empirical evidence that while standard domain estimation methods can be substantially biased in the presence of informative linkage errors,an alternative estimation method,based on a Gaussian approximation to a maximum likelihood estimator that allows for non-informative linkage error,performs well.展开更多
基金supported in part by the National Sci-ence Foundation (NSF-ECCS-1509420, NSF-CSSI-2004766)。
文摘The supervisory control problem for discrete event system(DES) under control involves identifying the supervisor, if one exists, which, when synchronously composed with the DES,results in a system that conforms to the control specification. In this context, we consider a non-deterministic DES under complete observation and control specification expressed in action-based propositional μ-calculus. The key to our solution is the process of quotienting the control specification against the plan resulting in a new μ-calculus formula such that a model for the formula is the supervisor. Thus the task of control synthesis is reduced a problem of μ-calculus satisfiability. In contrast to the existing μ-calculus quotienting-based techniques that are developed in deterministic setting, our quotienting rules can handle nondeterminism in the plant models. Another distinguishing feature of our technique is that while existing techniques use a separate μ-calculus formula to describe the controllability constraint(that uncontrollable events of plants are never disabled by a supervisor), we absorb this constraint as part of quotienting which allows us to directly capture more general state-dependent controllability constraints. Finally, we develop a tableau-based technique for verifying satisfiability of quotiented formula and model generation. The runtime for the technique is exponential in terms of the size of the plan and the control specification. A better complexity result that is polynomial to plant size and exponential to specification size is obtained when the controllability property is state-independent. A prototype implementation in a tabled logic programming language as well as some experimental results are presented.
基金supported by the National Natural Science Foundation of China (No.61501065, 91438104,No.61571069 and No.61601067)the Fundamental Research Funds for the Central Universities (No.106112015CDJXY160002,No.106112016CDJXY160001)the Chongqing Research Program of Basic Research and Frontier Technology (No.CSTC2016JCYJA0021)
文摘The spectrum allocation for cognitive radio networks(CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes is time-varied due to primary user/secondary user(PU/SU) activity and mobility, which result in non-determinacy. This paper studies the spectrum allocation for CRNs with non-deterministic bandwidth of spectrum holes. We present a novel probability density function(PDF) through order statistics as well as its simplified form to describe the statistical properties of spectrum holes, with which a statistical spectrum allocation model based on stochastic multiple knapsack problem(MKP) is formulated for spectrum allocation with non-deterministic bandwidth of spectrum holes. To reduce the computational complexity, we transform this stochastic programming problem into a constant MKP through exploiting the properties of cumulative distribution function(CDF), which can be solved via MTHG algorithm by using auxiliary variables. Simulation results illustrate that the proposed statistical spectrum allocation algorithm can achieve better performance compared with the existing algorithms when the bandwidth of spectrum holes is time-varied.
基金supported in part by the Public Technology Research Plan of Zhejiang Province (LGJ21F030001)the National Natural Science Foundation of China (62302448)the Zhejiang Provincial Key Laboratory of New Network Standards and Technologies (2013E10012)。
文摘In this paper, we study the supervisory control problem of discrete event systems assuming that cyber-attacks might occur. In particular, we focus on the problem of liveness enforcement and consider a sensor-reading modification attack(SM-attack) that may disguise the occurrence of an event as that of another event by intruding sensor communication channels. To solve the problem, we introduce non-deterministic supervisors in the paper, which associate to every observed sequence a set of possible control actions offline and choose a control action from the set randomly online to control the system. Specifically, given a bounded Petri net(PN) as the reference formalism and an SMattack, an algorithm that synthesizes a liveness-enforcing nondeterministic supervisor tolerant to the SM-attack is proposed for the first time.
文摘Modeling and forecasting of the groundwater water table are a major component of effective planning and management of water resources. One way to predict the groundwater level is analysis using a non-deterministic model. This study assessed the performance of such models in predicting the groundwater level at Kashan aquifer. Data from 36 piezometer wells in Kashan aquifer for 1999 to 2010 were used. The desired statistical interval was divided into two parts and statistics for 1990 to 2004 were used for modeling and statistics from 2005 to 2010 were used for valediction of the model. The Akaike criterion and correlation coefficients were used to determine the accuracy of the prediction models. The results indicated that the AR(2) model more accurately predicted ground water level in the plains;using this model, the groundwater water table was predicted for up to 60 mo.
文摘Watson Crick automata are finite automata working on double strands. Extensive research work has already been done on non deterministic Watson Crick automata and on deterministic Watson Crick automata. Parallel Communicating Watson Crick automata systems have been introduced by E. Czeziler et al. In this paper we discuss about a variant of Watson Crick automata known as the two-way Watson Crick automata which are more powerful than non-deterministic Watson Crick automata. We also establish the equivalence of different subclasses of two-way Watson crick automata. We further show that recursively enumerable (RE) languages can be realized by an image of generalized sequential machine (gsm) mapping of two-way Watson-Crick automata.
文摘The recently experienced hype concerning the so-called “4<sup>th</sup> Industrial Revolution” of production systems has prompted several papers of various subtopics regarding Cyber-Phdysical Production Systems (CPPS). However, important aspects such as the modelling of CPPS to understand the theory regarding the performance of highly non-ergodic and non-deterministic flexible manufacturing systems in terms of Exit Rate (ER), Manufacturing Lead Time (MLT), and On-Time Delivery (OTD) have not yet been examined systematically and even less modeled analytically. To develop the topic, in this paper, the prerequisites for modelling such systems are defined in order to be able to derive an explicit and dedicated production mathematics-based understanding of CPPS and its dynamics: switching from explorative simulation to rational modelling of the manufacturing “physics” led to an own and specific manufacturing theory. The findings have led to enouncing, among others, the Theorem of Non-Ergodicity as well as the Batch Cycle Time Deviation Function giving important insights to model digital twin-based CPPS for complying with the mandatory OTD.
基金supported by the Program for New Century Excellent Talents in University of Chinathe Advanced Research Foundation of China (Grant No. 9140A27050109JB1112)
文摘The non-probabilistic approach to fatigue life analysis was studied using the convex models-interval, ellipsoidal and multiconvex models. The lower and upper bounds of the fatigue life were obtained by using the second-order Taylor series and Lagrange multiplier method. The solving process for derivatives of the implicit life function was presented. Moreover, a median ellipsoidal model was proposed which can take into account the sample blind zone and almost impossibility of concurrence of some small probability events. The Monte Carlo method for multi-convex model was presented, an important alternative when the analytical method does not work. A project example was given. The feasibility and rationality of the presented approach were verified. It is also revealed that the proposed method is conservative compared to the traditional probabilistic method, but it is a useful complement when it is difficult to obtain the accurate probability densities of parameters.
文摘保证服务质量的QoS路由(Quality of Service Routing)是网络中解决QoS问题的一项关键技术。QoS路由的主要目标是为接入的业务选择满足服务质量要求的传输路径,同时保证整个网络资源的有效利用。度量参数选择问题、寻路问题和路由信息不准确问题是QoS路由中的几个主要研究内容。多约束QoS路由算法通常是NPC问题,本文先对QoS路由中的问题进行分类,再对当前研究的一些多约束QoS路由算法进行了归纳与分析。这些算法对于在Internet中实现QoS有着重要的指导意义。
基金Supported by the National 863 High-tech Program of China (No.2003AA121560) and High-tech Project of Jiangsu Province (No.BG2003001).
文摘This paper investigates the maximal achievable multi-rate throughput problem of a multicast ses-sion at the presence of network coding. Deviating from previous works which focus on single-rate network coding, our work takes the heterogeneity of sinks into account and provides multiple data layers to address the problem. Firstly formulated is the maximal achievable throughput problem with the assumption that the data layers are independent and layer rates are static. It is proved that the problem in this case is, unfortunately, Non-deterministic Polynomial-time (NP)-hard. In addition, our formulation is extended to the problems with dependent layers and dynamic layers. Furthermore, the approximation algorithm which satisfies certain fair-ness is proposed.
文摘QoS(Quality of Service)路由算法是解决QoS问题的关键,也是当前网络领域里的一大研究热点。QoS路由算法的主要目的是为接入的业务选择满足服务质量要求的传输路径,同时保证整个网络资源的有效利用。改文深入探讨了QoS路由问题的实质,并对以往的QoS路由算法进行了归纳总结。基于已有的QoS路由算法的研究,该文对QoS路由算法的发展方向进行了预测。
文摘In this paper is demonstrated a method for reduction of integer factorization problem to an analysis of a sequence of modular elliptic equations. As a result, the paper provides a non-deterministic algorithm that computes a factor of a semi-prime integer n=pq, where prime factors p and q are unknown. The proposed algorithm is based on counting points on a sequence of at least four elliptic curves y2=x(x2+b2)(modn) , where b is a control parameter. Although in the worst case, for some n the number of required values of parameter b that must be considered (the number of basic steps of the algorithm) substantially exceeds four, hundreds of computer experiments indicate that the average number of the basic steps does not exceed six. These experiments also confirm all important facts discussed in this paper.
文摘For better applications of fuzzy automata on target tracking, this paper presents an associated method of fuzzy automata by discussing the relation between fuzzy automata. The equivalence is mainly discussed regarding these fuzzy automata. The target tracking based on the associated method of fuzzy automata is given. Moreover, the simulation result shows that the associated method is better than single fuzzy automaton relatively. The development of these researches in this paper in turn can quicken the applications of the fuzzy automata in various fields.
文摘The Balanced Academic Curriculum Problem （BACP） is a constraint satisfaction problem classified as （Non-deterministic Polynomial-time Hard） NP-Hard. This problem consists in the allocation of courses in the periods that are part of a curriculum such that the prerequisites are satisfied and the load of courses is balanced for the students. This paper presents the solution for a modified BACP where the academic loads and number of curses may be the same or different for each one of the periods and allows having some courses in a specific period. This problem is modeled as an integer programming problem and is proposed the use of Tabu search with short-term memory for its solution because it is not possible to find solutions for all the instances of this modified problem with an exact method.
基金supported by the National Natural Science Foundation of China(Grant No.90718025)the EU Six Frame Project(Grant No.AST5-CT-2006-030959)
文摘In present paper,the mathematic background of intrusive polynomial chaos (IPC) method and coupling process with one dimension Euler equation were introduced. The IPC method was implemented for the 2D compressible stochastic Navier-Stokes equations to simulate the non-deterministic behavior of a lid driven cavity flow under the influence of uncertainties. The driven velocity and fluid viscosity were supposed respectively to be the uncertain variable which has Gaussian probability distribution. Based on the validation with benchmark results,discussions were mainly focused on the statistic properties of velocity distribution. The results indicated the effect of IPC method on the simulation of propagation of uncertainty in the flow field. For the simulated results of 2D cavity flow,influence of the driven velocity uncertainty is larger than that of viscosity.
基金supported by National Natural Science Foundation of China(No.51507116)the Project of State Grid Corporation of China(Active Power Islanding Technology of Large Power Grid Based on Multi Source Information and Trajectory Trend Prediction)
文摘The controlled islanding for the power system is an effective method to deal with the emergent situations caused by large disturbances. The size of the solution space would increase exponentially as the scale of the power grid increases. The goal of our controlled islanding strategy is to divide the system into several islands quickly. Meanwhile, the generator coherency and the power-flow disruption have to be taken into consideration carefully. This paper proposed a two-stage fast islanding strategy for large power networks, which is on the basis of large power grid graph theories. In the first stage, the Stoer-Wagner algorithm is employed to obtain the grouping cluster of coherent generators in the dynamic undirected liaison graph. In the second stage, the improved Dinic max-flow method is proposed to search the optimal splitting boundary so as to acquire the minimum power flow impact. Our two-stage islanding strategy does not need to reduce the whole power network. Simulations on IEEE 118-bus and162-bus power systems showed that the proposed strategy can acquire high quality solutions effectively and efficiently.
文摘A standard assumption when modelling linked sample data is that the stochastic properties of the linking process and process underpinning the population values of the response variable are independent of one another.This is often referred to as non-informative linkage.But what if linkage errors are informative?In this paper,we provide results from two simulation experiments that explore two potential informative linking scenarios.The first is where the choice of sample record to link is dependent on the response;and the second is where the probability of correct linkage is dependent on the response.We focus on the important and widely applicable problem of estimation of domain means given linked data,and provide empirical evidence that while standard domain estimation methods can be substantially biased in the presence of informative linkage errors,an alternative estimation method,based on a Gaussian approximation to a maximum likelihood estimator that allows for non-informative linkage error,performs well.
