A novel algorithm for layout optimization of injection process with random demands and sequence dependent setup times

Injection molding is an ideal manufacturing process for producing high volumes of products from both thermoplastic and thermo setting materials. Nevertheless, in some cases, this type of manufacturing process decelerates the production rate as a bottleneck. Thus, layout optimization plays a crucial role in this type of problem in terms of increasing the efficiency of the production line. In this regard, a novel computer simulation–stochastic data envelopment analysis (CS-SDEA) algorithm is proposed in this paper to deal with a single row job-shop layout problem in an injection molding process. First, the system is modeled with discrete-event-simulation as a powerful tool for analyzing complex stochastic systems. Then, due to lack of information about some operational parameters, theory of uncertainty is imported to the simulation model. Finally, an output-oriented stochastic DEA model is used for ranking the outputs of simulation model. The proposed CS-SDEA algorithm is capable of modeling and optimizing non-linear, stochastic, and uncertain injection process problems. The solution quality is illustrated by an actual case study in a refrigerator manufacturing company.     

双渠道供应链中服务对定价和需求的影响研究

研究了集中式决策和基于Stackelberg博弈这两种情况下的双渠道供应链的定价、服务及需求的关系。制造商和零售商提供的服务对价格、需求会产生影响,渠道商改善服务有利于本渠道价格的提高,同时会影响到另一渠道的定价,影响程度与双渠道决策模式相关。与服务对定价的影响不同,渠道商提供的服务对本渠道需求产生的影响是双向的,当服务水平在一定的范围内,改善服务可以增加本渠道市场需求,降低另一渠道需求;当服务水平过高,继续改善服务不仅不能增加需求反而减少需求,同时对另一渠道的需求产生影响,这种影响与消费者市场类型存在密切关系。当消费者市场属于价格敏感型时,服务水平存在一个帕累托区间,任一渠道商改善服务都会促进双渠道需求的增加。     

考虑出行方向的广州出租车时空可达性研究

出行方向是可达性研究中的一个关键要素, 因此, 提出一种考虑出行方向的出租车时空可达性分析方法。根据出租车经验路径分方向构建经验等级路网, 采用基于分层路网的Dijkstra算法计算得到各OD对之间的行程时间, 作为可达性评价指标, 并采用网格法和反距离加权插值法绘制得到广州市中心商业区等时线及其渲染图, 分方向、分时段对其时空可达性进行分析。结果证明了不同出行方向下, 特别是处于高峰时段, 可达性有较大的不同。     

纺织企业的原料库存控制模型研究

合理控制库存量,降低原料库存成本对纺织企业提高市场竞争力具有重大的意义。通过建立原料库存的不定量不定期控制模型,并采用遗传算法求解,给出了满足平均库存成本最小的(s,S)控制策略,并通过实例验证算法的有效性。     

基于需求更新的救灾品配送公平与效率协调模型

鉴于需求准确度与救灾品配送效率之间的悖反关系,研究了基于需求更新的救灾品配送效率与公平问题.通过对某市民政局进行调研,了解到台风灾害发生时的需求变化规律,设计一种通过已知需求灾区对未知需求灾区的需求进行贝叶斯更新的需求更新方式,由此建立救灾品配送模型.将该模型应用于某台风救灾实例,通过实例分析表明了该模型的求解速率与精度,并找到了最优"决策点",实现了救灾品配送公平与效率的平衡.     

Hybrid systems in seawater desalination—practical design aspects, present status and development perspectives

Ever since seawater desalination has been applied on an industrial scale, and particular in the countries of the Arabian Gulf, the application of desalination processes in dual-purpose facilities—water and power—as a hybrid configuration has been discussed in many feasibility investigations and also planning concepts. It is above all the combination of reverse osmosis with thermal processes that has found increasing interest with the aim of ensuring, as economically as possible, uniform water supplies under the specific, greatly varying load conditions in the Gulf countries. Such design concepts for hybrid configurations encompass straightforward structures with a low degree of coupling between membrane and thermal desalination processes, but range up to very complex configurations with strong interconnections on both the water side and thermally, as well as with several desalination processes connected in series or in parallel. Classical hybrid concepts in which the permeate from an RO desalination component is mixed with distillate from thermal desalination have already been implemented in Saudi Arabian dual-purpose plants, like Jeddah and Yanbu-Medina. Although hybrid systems of greater complexity have been addressed in many design studies and publications, up to now none has been brought to fruition. Coming into consideration asthe design basis for determining the capacity shares of the various desalination processes operated in a hybrid configuration are: arrangement of thermal cycle of the power plant component; water/power ratio of the dual-purpose seawater desalination and power plant; provision of undiminished water production of the desalination plant as electricity generation varies; provision of a specified drinking water quality with regard to composition and salt content; combination of all these aspects. Also gaining in importance are concerns of environmental pollution and sustainable development when selecting seawater desalination and power plant configurations, as well as their optimization when considering desalination and electricity generation as a whole. In the practical design of hybrid membrane and thermal systems, aspects come to light, though, that restrict linking of the two systems and joint utilization of facilities, as conceived in studies and conceptual design investigations. This applies both for common utilization of intakes and the use of heated up cooling water from thermal processes as a feed stream for the RO part of the desalination process. Additionally, requirements of drinking water composition, particularly chloride content, TDS and compliance with a specific residual content of boron, influence specifically the design of the membrane process part and its share in the total desalination capacity. Such practical aspects have greatly influenced the design and configuration of the Fujairah hybrid plant for which, from a total desalination capacity of 100 MIGD (454,600 m³/d), the share of 37.5 MIGD (170,500 m³/d) makes its seawater RO plant the biggest currently being constructed anywhere in the world. From the findings of the engineering of this plant and the idea that, by increasing interconnection between the two processes on the water side, it is possible to advance a hybrid configuration of this type with regard to cost optimization in the membrane installation, but also by joint utilization of the intake equipment, perspectives result for applied research efforts over the near and long terms, for example: long-term behavior of membranes at elevated temperatures; tendency for biofouling in membrane process with common utilization of cooling water and brine; influences of such interconnections on the overall availability of the facility. But also for the operation and maintenance organization of such large facilities, consequences can be foreseen for the future development of hybrid plants, particularly for operation management and organisation of the interplay of the different power plant and desalination systems, monitoring of SWRO membrane replacement and cleaning, as well as controlling water quality.     

基于最大偏差相似性准则的BP神经网络短期电力负荷预测算法

针对企业电力负荷随机性强、稳定性低、预测精度不理想等问题,提出了一种基于最大偏差相似性准则的BP神经网络短期电力负荷预测算法。首先对最大偏差相似性准则算法进行修改,并提出使用预测日的负荷特征向量与最大偏差相似性准则算法聚类之后的类中心负荷特征的距离来确定预测日的相似日类别;然后将聚类后的相似日类别负荷数据作为BP网络的训练数据,输出预测日起始的连续三天96整点负荷值。实验表明,该方法提出的短期电力负荷预测方法在精度和网络训练时间上都有较大的提升,具有较高的有效性和实用性。     

全自动液压压砖机CAD/CAE信息集成系统数据库的研究与开发

对全自动液压压砖机CAD CAE信息集成系统中的工程数据库的设计和实施进行了研究 ,分析了系统对数据信息的需求 ,提出了该系统数据库的E -R数据模型以及表的定义和结构关系 ,实现了压砖机CAD CAE信息集成系统。     

邻苯二甲酸酐的生产与市场

2005年全球邻苯二甲酸酐(PA)的生产能力约为450万t/a,需求量可达到350万~360万t,用于增塑剂占57%、醇酸树脂占17%、不饱和聚酯树脂占17%。未来5年全球PA需求将以年均3.0%~3.5%的速率增长,其中亚太地区将继续引领全球PA市场快速增长,其年均增速将达到4.0%~4.5%,美国仅以1.5%~2.0%的速率增长,西欧仅以1.0%的速率增长。我国产能和产量快速增长,2004年国内生产能力约为864 kt/a,消费量约为873 kt,用于邻苯二甲酸酯类增塑剂约占总消耗的60%,醇酸树脂约占22%,不饱和聚酯树脂占10%。     

甲醇市场分析及发展甲醇工业应注意的问题

分析和预测了国内外甲醇消费用户目前和今后几年的需求情况,从新建装置的布局、产品深加工、生产成本和市场价格等方面提出了发展甲醇工业应注意的问题。