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
Learning With Errors (LWE) is one of the Non-Polynomial (NP)-hard problems applied in cryptographic primitives against quantum attacks.However,the security and efficiency of schemes based on LWE are closely affected b...Learning With Errors (LWE) is one of the Non-Polynomial (NP)-hard problems applied in cryptographic primitives against quantum attacks.However,the security and efficiency of schemes based on LWE are closely affected by the error sampling algorithms.The existing pseudo-random sampling methods potentially have security leaks that can fundamentally influence the security levels of previous cryptographic primitives.Given that these primitives are proved semantically secure,directly deducing the influences caused by leaks of sampling algorithms may be difficult.Thus,we attempt to use the attack model based on automatic learning system to identify and evaluate the practical security level of a cryptographic primitive that is semantically proved secure in indistinguishable security models.In this paper,we first analyzed the existing major sampling algorithms in terms of their security and efficiency.Then,concentrating on the Indistinguishability under Chosen-Plaintext Attack (IND-CPA) security model,we realized the new attack model based on the automatic learning system.The experimental data demonstrates that the sampling algorithms perform a key role in LWE-based schemes with significant disturbance of the attack advantages,which may potentially compromise security considerably.Moreover,our attack model is achievable with acceptable time and memory costs.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
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(Nos.61572521 and U1636114)the National Key Project of Research and Development Plan(No.2017YFB0802000)+1 种基金the Innovative Research Team Project of Engineering University of PAP(No.KYTD201805)the Fundamental Research Project of Engineering University of PAP(No.WJY201910)。
文摘Learning With Errors (LWE) is one of the Non-Polynomial (NP)-hard problems applied in cryptographic primitives against quantum attacks.However,the security and efficiency of schemes based on LWE are closely affected by the error sampling algorithms.The existing pseudo-random sampling methods potentially have security leaks that can fundamentally influence the security levels of previous cryptographic primitives.Given that these primitives are proved semantically secure,directly deducing the influences caused by leaks of sampling algorithms may be difficult.Thus,we attempt to use the attack model based on automatic learning system to identify and evaluate the practical security level of a cryptographic primitive that is semantically proved secure in indistinguishable security models.In this paper,we first analyzed the existing major sampling algorithms in terms of their security and efficiency.Then,concentrating on the Indistinguishability under Chosen-Plaintext Attack (IND-CPA) security model,we realized the new attack model based on the automatic learning system.The experimental data demonstrates that the sampling algorithms perform a key role in LWE-based schemes with significant disturbance of the attack advantages,which may potentially compromise security considerably.Moreover,our attack model is achievable with acceptable time and memory costs.
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.
