静态安全约束下基于Benders分解算法的可用传输容量计算

在电力市场环境下，可用传输容量(ATC)是反映输电线路可用于交易的剩余容量的重要指标。文中以最优潮流为基础，采用Benders分解方法将考虑静态安全约束的ATC计算问题分解为一个基态主问题和一系列与各预想事故有关的子问题。主问题用来处理基态潮流和相应约束以及由子问题所返回的Benders割(cut)约束，而各子问题用来处理各预想事故和形成相应的静态安全约束。文章给出了相应的数学模型，并提出了两种改进的求解策略。4节点和IEEE30节点系统的计算结果表明了该方法和求解策略的有效性。     

考虑周期特性的电力市场稳定性分析

研究了电力市场的稳定性问题。并根据电力市场的物理特性，在模型中考虑了电能供需的同时性、市场需求的周期性以及市场中非连续的投标竞价方式，将市场稳定问题转化为一个非线性、非自治的周期差分系统的稳定问题。为了研究市场的稳定条件，证明了差分系统收敛于唯一有界周期解的条件，并据此提出了系统最终收敛边界的估计公式。基于文中提出的模型和引理，给出了电力市场稳定的一个充分条件以及电价最终收敛边界的估计公式，并以算例仿真验证了其结论的正确性。     

A framework for capacity planning and machine configuration in flexible assembly systems

We consider the problem of simultaneously determining the number of machines (and/or workers), the assignment of tasks (and related tools and components) to these machines, and the number of jobs circulating in a flexible assembly system (FAS), to satisfy steady-state throughput requirements for a family of similar products at minimum cost. We focus on situations where there are precedence relations among the various tasks, as is common in assembly systems. We present a framework for solving this problem based on a heuristic decomposition approach which involves the solution of only a few types of sub-problems. We demonstrate the efficiency and effectiveness of the overall procedure using a number of example problems.     

Simulation modeling for comparative evaluation of supply chain management strategies

Supply chain management (SCM) has become one of the most important strategies for achieving competitive advantage in different industries in the last decade. Researchers have investigated various processes in the planning and development of supply chains. However, increasing attention has been placed on performance, design and analysis of supply chain models. A supply chain is a complex model that is very difficult to analyze, in particular, with respect to performance. Simulation is one of the effective tools to evaluate the control mechanism for a supply chain. In this paper, five common supply chain models have been built and tested with the aid of simulation. Various performance measures such as transportation cost, resources utilization, inventory level, and order cycle time will be calculated for comparative indications. The methodology that is presented in this paper can be extended to any real life applications in SCM.     

Energy Efficient Cloud Service Provisioning: Keeping Data Center Granularity in Perspective

The cost of power and its associated delivery are becoming significant factors in the total expenditure of large-scale data centers. Numerous techniques have been proposed to address the energy efficiency issue in cloud systems. Recently, some efforts have been made to decentralize the cloud via distributing data centers in diverse geographical positions, at different scales. In this paper, we elaborate on the energy effectiveness of service provisioning on different cloud architectures, from a mega-data center to a nano data center, which provides the extreme decentralization in terms of cloud architecture, as well as P2P-clouds or community network clouds. We study the energy consumption through an analytical and simulation framework for video streaming and MapReduce applications.     

Managing incidents in a complex system: a railway case study

The authors of this paper review how complex entities, composed of many interdependent subsystems, such as international rail operators, can improve their ability to recover from incidents through the better management of key interfaces. The principles of Normal Accident Theory and resilience engineering are discussed, and the case study of the Eurostar incident of 18–19 December 2009 is considered in detail. Lessons learnt from resilience engineering are applied to the case study to extract recommendations by which incident management for open access international rail transport may be improved.