智能复合开关在航天地面供电设备中的应用分析

针对航天系统地面供电设备在供电瞬间出现的大量冲击性负荷对试验造成影响的问题,提出采用无功补偿的解决方案,结果表明：通过在供电设备上选用智能复合开关,能够避免供电电源在投或切的瞬间造成的设备损伤或数据失真。     

一种基于DSP组合式中频逆变电源的设计

针对设计的电源要求有很强的带不平衡负载能力,提出一种组合式400 Hz中频电源的设计方案,其优点在于在三相不平衡负载的情况下,能保持三相电压的平衡。给出主电路及控制电路设计,分析基于DSP的同步信号的接收和发送的处理以及正弦脉宽调制的实现。仿真及试验结果验证了该方案的可行性。     

A single-period analysis of a two-echelon inventory system with dependent supply uncertainty

Disruptions and random supplies have been important sources of uncertainty that should be considered in the design and control of supply chains. There have been many real world examples in which a single catastrophic event has simultaneously degraded the capabilities of several suppliers leading to considerable erosion of profits and goodwill for a company. However, the literature on analytical models that account for the dependence nature of disruptions and its impact on supply chain performance is sparse.In this paper, we consider an m-manufacturer, 1-retailer, newsvendor inventory system with stochastically dependent manufacturing capacities, caused by random disruptions that may simultaneously inflict damages to the capacities of the manufacturers. We develop the structural/analytical properties of key performance measures and optimal inventory policies for the multi-source and assembly inventory systems. We show that stochastic dependence in disruptions can have opposite effects on system performance in the multi-source and assembly systems. While risk diversification is preferred in the multi-source system, risk concentration is preferred in the assembly system. Our results also suggest that, if the retailer ignores the effect of dependent disruptions, then in the multi-source structure, it would underestimate the cost, overestimate the fill rate, and order more units than the optimum; however, in the assembly structure, the opposite would happen. We perform a comprehensive numerical study to validate our analytical results and generate useful managerial and operational insights for effective risk management of supply chains in the presence of dependent supply uncertainty.     

Competition and disruption in a dynamic urban supply chain

Rapid changes and complexities in business environments have stressed the importance of interactions between partners and competitors, leading supply chains to become the most important element of contemporary business environments. There is a concomitant need for foresight in describing supply chain performance in all operating environments, including those involving punctuated disruptions. Furthermore, the urban metropolis is now widely recognized to be an environment which is especially vulnerable to supply chain disruptions and for which integrated supply chain decisions can produce very substantial net benefits. Accordingly, this paper presents a dynamic supply chain network model formulated as a differential variational inequality; the model is fashioned to allow consideration of supply chain disruption threats to producers, freight carriers, and retail enterprises. The DVI is solved using a fixed-point algorithm, and a simple numerical example, introduced to illustrate how the impacts of supply chain disruptions may be quantified, is presented.     

有限经济批量和库存的模拟退火算法

研究在一个简单供应链中的生产批量和配送计划问题。解决在供应链中减少单位时间库存、设备和运输的平均成本生产批量及运送计划。假设所有影响因素如产品需求率都已限定在有限的计划范围内,利用模拟退火算法具有的较强局部搜索能力特性弥补传统算法的不足,计算结果表明SA算法能够找到问题的最优解或近似最优解,是解决该问题的有效方法。     

模拟退火算法在供应链生产调度中的应用

研究一个简单供应链中的生产调度问题,目的是找到一个合理生产排序使得单位时间的成本最小,建立该问题的单目标非线性规划模型。运用模拟退火算法,结合邻域搜索进行求解,最后举例验证算法的有效性。     

灰色模型在中长期用水量预测中的应用

为实现供水管网经济、可靠、科学的规划改扩建,给出一种基于记录时间较短、历史数据较少的用水量序列的GM(1,1)预测方法。该预测方法把原始用水量序列累加处理生成新序列后,用指数关系式拟合,通过构造参数矩阵,确定辩识参数,建立灰色模型的微分方程。通过对灰色预测方法建模机理的研究建立城市用水量预测GM(1,1)模型,并以东北某大型城市用水量为原始数据进行实际预测,模型精度检验的结果表明该模型的预测等级为高精度预测。该预测方法应用于S市的中长期用水量预测,为S市供水规划改扩建提供有效依据。     

铁路瓦斯隧道施工特点及问题探讨

通过对铁路瓦斯隧道现有施工规范分析,并参考《煤矿安全规程》,对铁路瓦斯隧道施工特点进行总结;同时通过对相关条款的分析、研究,并对照国内已发生的瓦斯隧道施工、低瓦斯矿井生产事故,对现有规范中存在的问题进行探讨,提出以下建议：1) 进一步明确进洞管理系统的标准和要求;2) 进一步明确和细化瓦斯隧道电力供应原则;3) 进一步明确和改进瓦斯隧道机电设备防爆性配备的原则和相关条款。     

Minimum Efficient Scale (MES) and preferred scale of container terminals

The decision on the scale of a port terminal affects the terminal’s managerial, operational and competitive position in all the phases of its life. It also affects competition structures in the port in which the terminal is operating, and has a potential impact on other terminals. Port authorities and terminal operators need to know the scale of the terminal when engaging in concession agreements. In economic theory the scale of a plant/firm is typically defined in relation to the Minimum Efficient Scale (MES), the long-run output where the internal economies of scale are fully exploited. However, there are a number of theoretical and empirical indications that in ports the scale of a terminal is commonly guided by a combination of the MES and other determining factors. The “preferred” scale is the result of a complex interaction between the MES, the port governance framework and objectives, the market size and structure, technological change and operational considerations, physical and geographical limitations, and the business patterns of shipping lines. This study analyses the factors resulting in a preferred container terminal scale that in most of the times is different from the MES. The analysis of the technical, market-related and governance-related factors is supported by theoretical and empirical insights that illustrate the presence of a range of actual ”preferred” scales of terminal concessions that usually are different, below or above, MES.     

码头船用岸电供电系统技术

船用岸电系统代替原有的燃油发电,大大降低了靠泊船舶的废气排放及对环境的污染,是节能减排、建设“绿色港口”的有效途径。分析国、内外船用岸电技术发展现状及发展方向,结合我国国情,探讨船用岸电供电系统在应用过程中需重点解决的技术问题。