Equipment replacement under continuous and discontinuous technological change

Technological change is a major motivator for replacing equipment.Models in the literature generally assume that technology evolvescontinuously according to some known function or that thereare breakthroughs in technology in a given (or uncertain) futuretime period. We model the situation where breakthroughs occurperiodically, providing a new vintage of challenger and eachchallenger within a vintage evolves according to a known function.We examine the economic life of an asset with respect to modelsthat only assume continuous or discontinuous technological change.For the case of exponential technological change, we illustratethat the economic life tends to be shorter in our models andthat significantly different solutions can occur when breakthroughsare ignored. We believe this work leads to new questions inreplacement analysis which examine the combined effect of continuousand discontinuous technological change.     

技术创新的评价模型研究

国内外至今未对技术创新形成严格统一的定义，如何界定技术创新成为理论界争论的焦点，尤其是对技术创新中“技术”的限定和技术创新成功实现的标准与界定方面存在着分歧。为了淡化技术创新的神秘性和推进技术创新的社会化，本从界定技术创新是否成功的角度出发，通过对比技术创新前后的经济效益和社会效益的差异，利用SAVAGE的期望效用理论和方法，提出了技术创新的评价模型。通过该评价模型，对技术创新的界定有一个定量的评判，对任何一种简单的技术进步和方法的改进都可以进行评价和界定，从而促进技术创新的不断发展。     

大学物理实验项目的系统设计

根据工科院校不同院系对物理实验的要求，基于培养学生用脑动手能力、综合分析能力、发明创造能力的“三能”目标，从基础实验、综合实验、科研及毕业设计等方面论述了大学物理实验项目系统设计的重要性。     

提高数控车床加工质量的措施

提高数控车床加工质量，第一要合理考虑工艺因素；第二要掌握数控车床的三大操作技巧，即一刀多尖、刀具圆弧半径补偿和刀具磨损参数的有效运用。     

Fiber‐forming blend polypropylene‐polyvinyl alcohol

The preparation of a fiber‐forming blend consisting of polypropylene and polyvinyl alcohol mixed with glycerol and with polypropylene grafted with maleic anhydride were studied. The physical and mechanical properties of blend fibers were also studied. The rheological measurements for semiquantitative evaluation of technological compatibility of the components and for processing the polymeric material in extruding and spinning process were carried out. The experimental results revealed the technological compatibility of the polypropylene‐polyvinyl alcohol blend in the presence of glycerol and polypropylene grafted with maleic anhydride. The colloidal structure of interface layer is assumed to be in a three‐ or four‐component system. The mixture of polyvinyl alcohol with glycerol allows for the preparation of well spun fiber‐forming polypropylene blends. Polypropylene‐polyvinyl alcohol blend fibers consisting of up to 20% polyvinyl alcohol with sufficient mechanical properties, higher porosity and significantly higher sorption of water than polypropylene fibers alone were prepared. Copyright © 2001 John Wiley & Sons, Ltd.     

浅谈三相异步电动机软起动器的性能及应用

介绍了软起动的工作原理、技术特点、产品及应用．并把软起动与相关设备进行了比较．说明了软起动是集电动机软起动和多种保护功能于一体的电机控制装置，具有传统起动方式所不具备的优点．     

跨国公司与国内企业之间的非对称研发竞争

同跨国公司相比，国内企业的融资能力受到资本市场的限制，这削弱了其参与研发竞争的能力。本文建立了一个动态博弈模型来分析这一状况。研究表明，跨国公司存在一种研发竞争策略，即通过更激进的产品市场攻势，来对国内企业施加融资限制，进而扩大其研发竞争优势。这一策略增加了跨国公司垄断技术产品市场的可能性。     

Optimal replacement policy for obsolete components with general failure rates

Identical components are considered, which become obsolete once new‐type ones are available, more reliable and less energy consuming. We envision different possible replacement strategies for the old‐type components by the new‐type ones: either purely preventive, where all old‐type components are replaced as soon as the new‐type ones are available; either purely corrective, where the old‐type ones are replaced by new‐type ones only at failure; or a mixture of both strategies, where the old‐type ones are first replaced at failure by new‐type ones and next simultaneously preventively replaced after a fixed number of failed old‐type components. To evaluate the respective value of each possible strategy, a cost function is considered, which represents the mean total cost on some finite time interval [0, t]. This function takes into account replacement costs, with economical dependence between simultaneous replacements, and also some energy consumption (and/or production) cost, with a constant rate per unit time. A full analytical expression is provided for the cost function induced by each possible replacement strategy. The optimal strategy is derived in long‐time run. Numerical experiments conclude the paper. Copyright © 2008 John Wiley & Sons, Ltd.     

An evaluation of continuous assessment in statistics courses for social scientists

This paper reports on the use of continuous assessment in a statistics course for social scientists, in which assignments are open‐ended and use real data. The students' performance in the assignments and a formal examination are compared, and it is found that when students are assessed by a combination of continuous assessment and examination, those students who carry out the majority of the assignments score higher examination marks than do the rest.     

Conceptual and technological evolutions of particle accelerators

We give here an ordered list of all types of particle accelerators and exhibit how each type evolves conceptually and/or technologically from the preceding. This is in contrast to the usual ``history of particle accelerators" in which unrelated accelerator types are listed in the chronological order. It is hoped that this discussion and understanding of the rationale and logic in the evolution of one accelerator type to the next will help to educe future inventions.