求凸多边形最小面积包围盒算法的比较

当前许多工程应用中都需要对区域最小面积包围盒进行研究、计算,通常有三角形包围盒、矩形包围盒、凸四边形包围盒等等方法,本文对各包围盒算法进行了综述,并通过其中的遗传算法对各包围盒最小面积进行比较,来证明凸多边形最小面积凸四边形包围盒算法的优越性,从而表明该算法的实用性和有效性.     

层次包围盒的碰撞检测算法研究

基于包围盒的碰撞检测算法是应用广泛的碰撞检测算法。本文对基于包围盒的碰撞检测算法中的球形包围盒法、轴向包围盒法、方向包围盒法和离散多面体法的检测原理和方法进行了分析和比较。     

碰撞检测技术在颗粒混合中的应用

采用图形引擎OSG和物理引擎Bullet,设计了片理颗粒混合碰撞仿真系统。在该系统实现过程中,首先对AABB、OBB、包围球及K—DOP算法进行对比研究,然后选择较为合适的AABB包围算法进行应用。该系统通过解决片理颗粒的控制、碰撞检测、OSG图形引擎与Bullet物理引擎结合以及场景渲染优化等关键技术问题,最后实现仿真模拟程序。     

基于包围盒碰撞检测算法研究

为了提高碰撞检测的速度,提出了基于包围盒碰撞检测改进算法。算法将碰撞检测分为两个阶段,第一阶段快速排除不相交的物体,第二阶段利用时空关联性原理,提高层次包围盒树的遍历速度。如果检测的是叶子节点,那将省略包围盒直接进行三角形碰撞检测,进一步提高系统的碰撞检测效率。算法可行性已经被实验初步证实。     

基于古建筑BIM模型单体构件的实时碰撞检测研究

碰撞检测技术在三维虚拟漫游中起着非常重要的作用,传统的碰撞检测算法大多基于模型对象整体进行检测,主要通过漫游对象与建筑模型整体包围盒进行碰撞检测,进而将漫游对象与具体的建筑模型每个三角网面片进行碰撞检测,这种针对于古建筑奇特复杂结构模型而言并不适用,复杂的计算使得碰撞检测很难达到实时性。为解决这一问题,提出了一种基于古建筑BIM模型单体构件的实时碰撞检测算法,首先将漫游对象与建筑模型整体包围盒进行碰撞检测,进而与属于该建筑整体的构件模型包围盒进行并行碰撞检测,从而实现实时的碰撞检测。     

数控加工仿真中的碰撞干涉检测算法研究

论述了碰撞干涉产生的条件,分析比较了碰撞干涉检测的常用算法,重点研究了应用于数控加工仿真中的基于包围盒进行碰撞干涉检测的算法。此算法将碰撞干涉检测分为粗检、细检和精检等三个步骤,简化了计算难度,提高了检测效率。     

虚拟视觉的Mesh方法与包围球方法研究

虚拟现实（VE）中虚拟视觉的实现方法大多采用基于信息表的查询,一般对静态物体的检测采用包围盒的办法。信息表的查询方法在一定程度上保证了处理速度,但是违背了视觉的工作原理。基于包围球的方法比包围盒方法精确,Mesh方法对动态物体轮廓的获取不但遵循了生物仿生学原理,而且也在信息处理速度和仿真度上折中得到了最优结果。     

城域景观仿真系统开发中层次包围盒结构的研究与应用

在面向城市/区域虚拟场景仿真系统中,模型的组织和管理方式直接决定了系统的性能。本文引入了层次包围盒的方法来组织和管理场景模型,介绍了沿坐标轴的包围盒(AABB)树的构造和其在可见性剔除、层次细节技术(LOD)优化、以及在碰撞检测中的应用。     

积云的建模与渲染技术研究

积云的形状和颜色千变万化,形成过程复杂,传统的云模拟方法建模困难,真实性,实时性差。本文根据积云的形成特点,采用粒子系统的建模方法,生成粒子云,并利用Impostor技术采用包围盒算法计算纹理图像,提高渲染速度,在OpenGL上实现积云的渲染效果。     

DES算法的S盒分析

S盒是DES算法中的一个关键部分,它的设计好坏直接影响DES的加密性能.这里就DES的算法、S盒的设计原理及规律,以及使用VHDL(甚高速集成电路硬件描述语言)设计对S盒作了一些分析.     

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