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.     

Turned trochoidal disturbance on a liquid jet surface

This paper shows that a turned trochoidal function disturbance may lead to peripheral drops production. The resulting model is used to describe that a turned trochoidal disturbance leads to peripheral drops production on the liquid jet surface without the necessity for superimposed disturbances. The trochoid is a non-unique parametric function. Only non-unique parametric functions disturbances may lead to peripheral drops production. The trochoidal function disturbance is decomposed to Fourier series. Every Fourier element receives an amplification factor in accordance to the Rayleigh inviscid jet model. Peripheral drops are received on the jet surface. The paper shows that all trochoidal disturbance functions, prolate cycloid, cycloid and curtate cycloid have a capability of peripheral drops producing. A limited capability of peripheral drops production is introduced for the trochoidal curtate cycloid. Produced drops size are reduced for increasing the jet velocity and wave number. Smaller drops are also received by transition from the prolate cycloid to curtate cycloid disturbance.     

Modelling corn production in China using AVHRR‐based vegetation health indices

Weather‐related crop losses have always been a concern for farmers, governments, traders and policy makers for the purpose of balanced food supplies, demands, trade, and distribution of aid to nations in need. Therefore, early crop loss assessment in response to weather fluctuations is an important issue. This paper discusses the utility of Advanced Very High Resolution Radiometer (AVHRR)‐based vegetation health indices as a proxy for modelling corn yield and for early warning of drought‐related losses of agricultural production in China. The indices were tested in Jilin province on corn yield during 1982–2001 using correlation and regression analysis. A strong correlation between corn yield and the vegetation health indices were found during the critical period of corn growth, which starts 2–3 weeks before and 2–3 weeks after corn tassel. Following the results of correlation analysis, several regression equations were constructed where vegetation health indices were used as independent variables. The estimates of corn yield can be carried out well in advance of harvest and the errors of the estimates are 7–10%. The errors become smaller when the estimations are related to losses in corn yield due to drought.