线性规划在利润最大化和成本最小化问题中的应用

本文从线性规划模型的建立和求解、对偶理论、灵敏度分析等方面阐述了线性规划的基本理论,并针对实际问题建立模型说明了线性规划方法在利润最大化和成本最小化问题中的应用。     

线性规划问题最优解之探究

线性规划最优问题的解决在众多学科领域内具有广泛的应用,本文通过多元函数的图像解法、单纯形法和对偶规划问题等,对如何寻求线性规划问题的最优解进行探究。     

基于GIS的震后物流配送中心运输与指派问题研究

根据地震的突发性、不确定性、非常规性以及弱经济性等特点,应用GIS定位系统对灾区物资需求点和配送中心进行定位。以时间最快为目标,建立最短路模型解决应急物流的运输与指派问题。应用WinQSB软件操作,得出应急物流配送中心运输与配送救援方案,通过举例对此模型进行说明。     

在线双边匹配在网络广告分配问题中的应用

如何分配关键词给广告厂商以使得搜索引擎公司收入最大实际上是一个在线双边匹配问题.贪婪算法只考虑到厂商出价,竞争比只有1/2.本文分配方案不仅考虑到每个厂商的出价,而是通过引入平衡函数综合考虑厂商出价和未使用的预算,然后将关键词分配给能够使得出价和平衡函数乘积最大的厂商.最后将问题转化为一个线性规划族,通过求解其对偶规划族算出平衡函数的具体形式,并得出本文的分配方案能使得竞争比达到1-1/e,优于其他任意随机算法的竞争比.     

基于线性规划的对偶算法求解最小费用流问题

首先描述了线性规划对偶性和最小费用流问题,提出了最小费用流的对偶算法。简单的证明了此算法的正确性,并说明通过此算法可以获得最小费用流问题的最优解。最后通过一个实例说明了利用对偶算法求解最小费用流问题的步骤。     

利用线性规划技术估计回归系数

线性规划技术已被应用于许多学科。有一类统计问题,根据其实质可视为线性规划问题,或者说可转化为线性规划问题进行求解。本文讨论在回归分析中利用线性规划技术对线性模型中的回归系数进行估计。最小二乘法通常用作最优拟合的准则。其优点在于消除了正负误差相互抵消的问题,突出了大的拟合误差的作用以及计算上方便。我们能求解普通的线性方程组     

线性规划法在运输问题中的应用

随着我国市场经济的不断完善,同地区、不同地区、甚至跨国间的企业交易活动更加频繁。因此,在运输中如何降低运输费用、减少运输路线等问题,已成为交易活动的重点,而线性规划主要应用于解决最优化问题。本文根据运输问题的基本特征,通过实例对运输问题进行了优化分析,建立了运输问题的线性规划数学模型,并借助于计算机进行求解,从而得到最优化的方案,提高了实际运输工作中的经济效益。     

含模糊变量的两层多目标线性规划方法

为了求出在线性规划中模糊变量的最优解或比较优越的解为多少,需要对含模糊变量的两层多目标线性规划方法进行研究。但当前方法是将IMOLP作为参数规划,通过变量转化为多目标的线性规划,然后利用齐墨尔曼方法对此进行求解,得出含多目标函数的总变量的线性规划,最终将其转化为单目标的线性规划,并求出各目标函数的最优值区间,但该方法存在准确性较低的问题。为此,提出一种含模糊变量的两层多目标线性规划方法。该方法首先利用新的假设模糊数序关系将其先转化为一个多目标线性规划问题,然后再转化为两层多目标的线性规划问题,结合两层目标函数的含模糊变量的多目标线性规划数学模型转换为线性规划问题对此进行求解,由此完成对含模糊变量的两层多目标线性规划进行求解。数值实例证明,可求出含模糊变量的两层多目标性规划的最优解。     

铁路货物门到门运输相关问题研究

传统铁路运输中最大的问题是铁路与公路之间的衔接问题。因为两种运输之间存在较大的区别,不仅给运输带来了麻烦,也影响了整个物流过程的顺畅。为了改善这种状况,人们提出了一种创新理念,即铁路"门对门"运输理念。铁路"门对门"运输充分体现现代物流思想,然而这种新思路也存在很多问题急需解决,例如运输部门间的利益分配和运输风险控制问题等。     

城市中的综合运输枢纽研究

伴随经济和运输化进程的发展,运输业发展的重点已经逐渐从城市与地区之间的衔接转化为城市内节点之间的问题。运输节点的设置决定了运输网的通行效率。目前,我国综合运输体系已逐渐规模化,运输体系也从单一的各自为政,转变为综合型的枢纽运输转变。高效率的综合型运输将是运输生产力发展到一定阶段的必然转变。     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.     

Prevalence of soft neurological signs in Chinese people

Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence