Modern nuclear power plants, both newly designed generation 3 and existing generation 2 reactors, make use of passive safety systems for significant and measurable improvements in safety and reliability. Medium Pressu...Modern nuclear power plants, both newly designed generation 3 and existing generation 2 reactors, make use of passive safety systems for significant and measurable improvements in safety and reliability. Medium Pressure Safety Injection System (MP-SIS) in Tianwan Nuclear Power Plant is a typical and very important nuclear safety passive system. This paper discusses the reliability of MP-SIS on the basis of Fault Tree Analysis (FTA) with unavailability and Minimal Cut Set (MCS) calculated as two important indicators. The result illustrates that the passive MP-Safety Injection Tank barely contributes to the system’s unavailability and human interactions with Manual Valves and Motor Operated Valves have great negative impact on the reliability.展开更多
On the basis of Ref.\, the M x/G(M/G)/1 repairable queueing system with single delay vacation is discussed again. The following reliability problems of the service station are studied: (a) The probability that it fai...On the basis of Ref.\, the M x/G(M/G)/1 repairable queueing system with single delay vacation is discussed again. The following reliability problems of the service station are studied: (a) The probability that it fails at time t , i.e. its unavailability; (b) The expected failure number during the time interval (0,t\];; (c) The expected failure number during the ″server busy period″; (d) The expected downtime during the time interval (0,t\]. Some reliability results of the service station are obtained. These results would be interest to reliability analysts.展开更多
In this paper, two mixed integer programming models integrating production scheduling and preventive maintenances are proposed to derive the optimal solutions for the identical machine scheduling problem with unavaila...In this paper, two mixed integer programming models integrating production scheduling and preventive maintenances are proposed to derive the optimal solutions for the identical machine scheduling problem with unavailability constraints. In the first model, the maintenance activities are performed periodically and the objective is to minimize the makespan. In the second model, the maintenance activities are flexible and the machines' continuous working time cannot exceed a maximum allowed time T; the objective is to minimize the total completion time of jobs. For the first problem, we propose a heuristic longest batch time(LBT) and prove that the worst case error bound of LBT is 2. For the second problem, we develop a heuristic modified smallest processing time(MSPT) based on some properties of the optimal solutions. Computational experiments show that both of the heuristics are effective and efficient compared with the results obtained by CPLEX and the other algorithms.展开更多
This paper systematically studies the two machine flow-shop scheduling problems with no-wait and deterministic unavailable interval constraints.To minimize the makespan,three integer programming mathematical models ar...This paper systematically studies the two machine flow-shop scheduling problems with no-wait and deterministic unavailable interval constraints.To minimize the makespan,three integer programming mathematical models are formulated for two-machine flow-shop with no-wait constraint,two-machine flow-shop with resumable unavailable interval constraint,and two-machine flow-shop with no-wait and non-resumable unavailable interval constraints problems,respectively.The optimal conditions of solv-ing the two-machine flow-shop with no-wait constraint problem by the permutation schedules,the two-machine flow-shop with resumable unavailable interval constraint problem by the Johnson algorithm,and two-machine flow-shop with no-wait and non-resumable unavailable interval constraints problem by the Gilmore and Gomory Algorithm(GGA)are presented,respectively.And the tight worst-case performance bounds of Johnson and GGA algorithms for these problems are also proved to be 2.Several instances are generated to demonstrate the proposed theorems.Based on the experimental results,GGA obtains the optimal solution for the two-machine flow-shop with no-wait constraint problem.Although it cannot reach the optimal solution for the two-machine flow-shop with resumable unavailable interval constraint problem,the optimal gap is 0.18%on average when the number of jobs is 100.Moreover,under some special conditions,it yields the optimal solution for the two-machine flow-shop with no-wait and non-resumable unavailable interval constraints problem.Therefore,GGA is an efficient heuristic to solve these problems.展开更多
A new species, Belisana cas sp. nov. is reported based on description of B. ＂xtbg＂. B. ＂xtbg＂ mentioned by Yao et al.（2018） is unavailable after the ICZN（article 11.3）.
文摘Modern nuclear power plants, both newly designed generation 3 and existing generation 2 reactors, make use of passive safety systems for significant and measurable improvements in safety and reliability. Medium Pressure Safety Injection System (MP-SIS) in Tianwan Nuclear Power Plant is a typical and very important nuclear safety passive system. This paper discusses the reliability of MP-SIS on the basis of Fault Tree Analysis (FTA) with unavailability and Minimal Cut Set (MCS) calculated as two important indicators. The result illustrates that the passive MP-Safety Injection Tank barely contributes to the system’s unavailability and human interactions with Manual Valves and Motor Operated Valves have great negative impact on the reliability.
基金supported in part by Special Fund of the National Priority Basic Research of China(No.2004CB217908)National Science Foundation of China(No.50?07013).
基金the Supporing Program of the National Education Ministry for ChineseUniversity Excellent Teachers([2 0 0 0 ]65 )
文摘On the basis of Ref.\, the M x/G(M/G)/1 repairable queueing system with single delay vacation is discussed again. The following reliability problems of the service station are studied: (a) The probability that it fails at time t , i.e. its unavailability; (b) The expected failure number during the time interval (0,t\];; (c) The expected failure number during the ″server busy period″; (d) The expected downtime during the time interval (0,t\]. Some reliability results of the service station are obtained. These results would be interest to reliability analysts.
基金the National Natural Science Foundation of China(No.71171130)
文摘In this paper, two mixed integer programming models integrating production scheduling and preventive maintenances are proposed to derive the optimal solutions for the identical machine scheduling problem with unavailability constraints. In the first model, the maintenance activities are performed periodically and the objective is to minimize the makespan. In the second model, the maintenance activities are flexible and the machines' continuous working time cannot exceed a maximum allowed time T; the objective is to minimize the total completion time of jobs. For the first problem, we propose a heuristic longest batch time(LBT) and prove that the worst case error bound of LBT is 2. For the second problem, we develop a heuristic modified smallest processing time(MSPT) based on some properties of the optimal solutions. Computational experiments show that both of the heuristics are effective and efficient compared with the results obtained by CPLEX and the other algorithms.
基金supported in part by the National Natural Sci-ence Foundation of China(NSFC)under Grant No.71801051.
文摘This paper systematically studies the two machine flow-shop scheduling problems with no-wait and deterministic unavailable interval constraints.To minimize the makespan,three integer programming mathematical models are formulated for two-machine flow-shop with no-wait constraint,two-machine flow-shop with resumable unavailable interval constraint,and two-machine flow-shop with no-wait and non-resumable unavailable interval constraints problems,respectively.The optimal conditions of solv-ing the two-machine flow-shop with no-wait constraint problem by the permutation schedules,the two-machine flow-shop with resumable unavailable interval constraint problem by the Johnson algorithm,and two-machine flow-shop with no-wait and non-resumable unavailable interval constraints problem by the Gilmore and Gomory Algorithm(GGA)are presented,respectively.And the tight worst-case performance bounds of Johnson and GGA algorithms for these problems are also proved to be 2.Several instances are generated to demonstrate the proposed theorems.Based on the experimental results,GGA obtains the optimal solution for the two-machine flow-shop with no-wait constraint problem.Although it cannot reach the optimal solution for the two-machine flow-shop with resumable unavailable interval constraint problem,the optimal gap is 0.18%on average when the number of jobs is 100.Moreover,under some special conditions,it yields the optimal solution for the two-machine flow-shop with no-wait and non-resumable unavailable interval constraints problem.Therefore,GGA is an efficient heuristic to solve these problems.
文摘A new species, Belisana cas sp. nov. is reported based on description of B. ＂xtbg＂. B. ＂xtbg＂ mentioned by Yao et al.（2018） is unavailable after the ICZN（article 11.3）.
