Computing Optimal Beams in Two and Three Dimensions

The problem of computing an optimal beam among weighted regions (called the optimal beam problem) arises in several applied areas such as radiation therapy, stereotactic brain surgery, medical surgery, geological exploration, manufacturing, and environmental engineering. In this paper, we present computational geometry techniques that enable us to develop efficient algorithms for solving various optimal beam problems among weighted regions in two and three dimensional spaces. In particular, we consider two types of problems: the covering problems (seeking an optimal beam to contain a specified target region), and the piercing problems (seeking an optimal beam of a fixed shape to pierce the target region). We investigate several versions of these problems, with a variety of beam shapes and target region shapes in 2-D and 3-D. Our algorithms are based on interesting combinations of computational geometry techniques and optimization methods, and transform the optimal beam problems to solving a collection of instances of certain special non-linear optimization problems. Our approach makes use of interesting geometric observations, such as utilizing some new features of Minkowski sums.     

论土地承包经营权的完善及相关制度建设

本文以《农村土地承包法》〔1〕存在的缺陷为切入点,以土地利用制度的价值追求———公平和效率的统一为向标,对土地承包经营权的进一步完善进行了探讨,提出了农村土地“三田制”的构想;并考虑到土地利用权利安排的特殊性和复杂性,就三个密切相关的制度建设:改革农地征用制度、建立农地登记制度、建立农地融资制度进行了思索。     

树立和落实科学发展观促进经济社会协调发展

十六届三中全会明确提出:以人为本,树立全面协调、可持续发展的发展观。对科学发展观的理论、背景形成和科学发展观的内涵进行分析,可得出现阶段实施科学发展观的具体步骤,即五个坚持和五个统筹。坚持以人为本,树立全面协调可持续发展的发展观,可促进经济、社会和人的全面发展。     

合同违约责任法律救济措施的经济学思考

合同违约责任的救济措施主要有实际履行与损害赔偿两种,大陆法系强调实际履行的重要性,而英美法系更注重损害赔偿的救济功能,从我国国情和微观经济学的角度出发,我国合同违约救济措施应采纳大陆法系“严格的效率违约”理论,即原则上应以实际履行为主要救济措施,在实际履行明显不符合效率原则时强调损害赔偿的救济功能。只有这样才能使双方当事人付出的成本最低,而收益最大。     

关于师专体育专业学分制课程设置的探讨

就体育专业课程设置的原则和依据，课程设置结构等问题提出了一些看法。     

Rota-Risk-Profile-Analysis

In this article an update of the Rota-Risk-Profile-Analysis (RRPA) is presented. This RRPA is based on 9 rota-risk criteria that are central to a more encompassing rota theory. The RRPA allows coherent assessment of the physical and social risks of a working-time schedule (rota). comparison of schedules with one another in quantitative terms and interpretations of possible differential effects more adequately. First, a closer look at the instrument-a computer program-is taken. Afterwards the criteria and their way of implementation are discussed briefly. To get an impression of the way that RRPA functions an example will be given by applying the instrument to the working rotas from a study on shiftwork in the Netherlands.     

Organizing the Global Value Chain

We develop a property‐rights model of the firm in which production entails a continuum of uniquely sequenced stages. In each stage, a final‐good producer contracts with a distinct supplier for the procurement of a customized stage‐specific component. Our model yields a sharp characterization for the optimal allocation of ownership rights along the value chain. We show that the incentive to integrate suppliers varies systematically with the relative position (upstream versus downstream) at which the supplier enters the production line. Furthermore, the nature of the relationship between integration and “downstreamness” depends crucially on the elasticity of demand faced by the final‐good producer. Our model readily accommodates various sources of asymmetry across final‐good producers and across suppliers within a production line, and we show how it can be taken to the data with international trade statistics. Combining data from the U.S. Census Bureau's Related Party Trade database and estimates of U.S. import demand elasticities from Broda and Weinstein (2006), we find empirical evidence broadly supportive of our key predictions. In the process, we develop two novel measures of the average position of an industry in the value chain, which we construct using U.S. Input–Output Tables.     

约定竞业禁止的法律问题探讨

约定竞业禁止是以限制劳动者劳动权的手段来保护用人单位的商业秘密权的制度.为有效保护用人单位的商业秘密,约定竞业禁止有其存在的必要性;另一方面,约定竞业禁止实施的结果又会导致对劳动者劳动权的限制,因此,有必要在用人单位商业秘密权与劳动者劳动权之间达成平衡.