论摆动从动件长度变化对凸轮机构工作性能之影响

通过对两个几何相似摆动从动件盘形凸轮机构的力学研究以及对摆动从动件长度与凸轮机构工作性能之关系的分析,本文提出一系列合理选择凸轮机构几何相似系数及摆动从动件长度的简易原则.按本文推荐的原则选择凸轮机构的几何相似系数及摆动从动件长度可使凸轮机构的工作性能得到明显的改善.     

基于ADAMS凸轮机构的动态分析

采用Pro/E和ADAMS完成了直动滚子从动件平面回转凸轮机构虚拟样机建模,应用ADAMS/Flex模块对刚体从动件进行柔性化处理,实现了实际凸轮机构的动态仿真,对凸轮机构进行动态分析研究。仿真方法及仿真结果为凸轮的优化设计提供了可靠依据。     

基于Pro/ENGINEER的凸轮造型与仿真设计

凸轮机构是机械工程中广泛应用的传动结构。文章根据凸轮机构从动件的运动规律,提出了利用Pro/ENGINEER软件中图形基准与可变截面扫描功能相结合进行凸轮轮廓精确造型的一种比较快捷的方法,同时利用Pro/ENGINEER软件CAE功能对凸轮机构设计进行了仿真和分析,对凸轮机构的精确及优化设计有一定的启示。     

自动盖章机的研制

目前,无论是在医院、银行还是在一些大型企业中均采用手工的盖章方式,但是其不仅消耗人力物力,同时对人体也会造成一定的伤害,基于此,设计了一种自动盖章机,本盖章机通过偏置的曲柄滑块机构以及摩擦轮实现送纸的动作,采用凸轮机构带动连杆机构来完成自动盖章和蘸印泥的工作。     

高速马芬纸杯成型机储纸给纸机构设计

基于马芬纸杯成型原理及所用原料纸张的分析与研究,本文指出了该类成型机的储纸给纸机构的设计方法,介绍了其纸张和精确给纸的原理,给出了在纸杯成型过程中储纸给纸结构工作结构与特点,经实例应用证明,该机构设计合理有效,精度高。     

基于AVL-Excite Timing Drive对发动机配气机构运动学和动力学分析与改进

配气机构作为发动机的重要部件之一,直接影响发动机的动力、油耗、排放以及工作稳定性和可靠性。以某国产发动机凸轮顶置直接驱动气门式配气机构为研究对象,利用AVL-Excite TimingDrive软件分析了其运动学和动力学特性,针对存在的问题和不足提出改进方案,并对改进后的凸轮型线进行研究,验证改进方案的正确性。     

双键槽铣槽设备研究

用于传递扭矩及动力的轴类零件,一般采用平键或花键联接。在重型机械中,常采用对称双键实现轴与轴上零件的联接,是机械制造业中的重要联接方式。在机械制造及修理中,180°对称双键槽的加工并非易事,而且现有方法均有不足。例如,用插削法受结构限制,用刨削法效率低,用拉削法制造成本高等等。铣槽机因铣削精度高,质量好,自动化程度好等优点,已在机械制造行业中得到广泛应用,成为机械制造行业的关键设备之一。现有铣槽机只适用于加工单键槽,若加工双键槽需要更换零件位置,找正工序麻烦,耗费时间长,生产效率低,键槽的对称度误差大,致使使用寿命缩短。为此,设计了一种对称双键槽自动铣槽机。完成铣槽机总体传动方案设计,主轴与分配轴的设计,凸轮机构的设计,电动机、减速器的合理选择以及操作装置的设计。     

基于Pro/E的凸轮机构运动仿真分析

凸轮机构是各类机器中广泛使用的传动机构,本文通过Pro/E软件对凸轮机构的实体建模和运动仿真分析,得到了摆杆的位移、速度、加速度的运动曲线,简化了设计过程,提高了设计效率.     

移栽机凸轮机构建模和仿真研究

文章运用三维建模软件结合动力学仿真软件,对农作物移栽机凸轮机构建模和仿真,提高了凸轮设计的科学性和可靠性,缩短了设计周期.     

基于子图的科学家合作网络家族辨识

对科学家合作网络宏观全局结构的研究多表明其小世界和无标度共性特征,而就其微观子图分布特性即网络家族的认知较少。研究基于复杂网络家族辨识的子图比剖面方法、子图组合强度和子图浓度排序方法,系统辨识了若干规模和不同领域的科学家合作网络的家族分类及特征。研究表明,具有宏观全局结构共性的上述科学家合作网络,在微观子图的分布、组合或排序上依次具有一种形式、三种规则及五种模式的特性,因而划分为相应家族类别,并表征了理论型、实验型及理论实验型合作网络家族特征。相关方法可用于系统分析和比较科研合作家族行为特性和演化机理。     

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.     

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.     

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     

Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels

<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese     

More than Skin Deep – Understand Skin Biology by Means of Dermatogenomics

<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages.