电镀金刚石线锯切割单晶硅的试验研究

本文利用电镀金刚石线锯对单晶硅进行了切割试验,研究了锯丝运动速度、工件进给力对材料加工质量、加工效率、锯切力的影响。研究发现,单晶硅加工表面存在划痕和凹坑,材料为脆性去除。加工效率随锯丝运动速度、工件进给力的增大而提高。锯丝运动速度增加,锯切力减小;工件进给力增大,锯切力也增加。最后通过正交实验对工艺参数进行了优化。     

模具零件高速走丝电火花线切割加工方法研究

通过对模具零件高速走丝电火花线切割加工中加工穿丝孔、装夹工件、电极丝的找正、选择切割路线、计算走丝轨迹、校验程序、加工质量与精度的提高等方面进行研究,形成了一套较为完整的工艺方法,加工效果良好。     

浅谈数控电火花线切割加工

电火花加工是在一定介质中通过工具电极和工件电极间的脉冲放电的电蚀作用,对工件进行加工的方法。因电火花加工具有其他加工方法无可替代的特最,它已成为模具制造中较为先进的加工方法。本文阐述了数控电火花切割加工的基本原理,主要对设备、电极丝及应用范围进行了分析。     

螺纹加工工艺方法探讨

主要针对螺纹加工工艺方法进行探讨,以便于用最简单的方法加工出合格的螺纹件.螺纹加工工艺方法主要分两个大部分,即切削螺纹和滚压螺纹.螺纹切削一般指用成形刀具或磨具在工件上加工螺纹,主要有车削、铣削、攻丝、套丝等.螺纹滚压是指用成形滚压模具使工件产生塑性变形以获得螺纹的加工方法,它是利用冷挤压的原理,用滚压的方法加工外螺纹.     

关于线切割"花丝"现象的探讨

大多数从事线切割加工和实训教学的教师,在加工较厚工件时都碰上对这种情况.经过一段时间的加工后,钼丝出现一段一段黑斑,出现这种黑斑后钼丝很快就会断掉,而钼丝的使用时间远远没达到正常的寿命.黑斑按一定规律排列形成花纹,故称为"花丝".     

模糊控制线切割机脉冲电源

在数控电火花线切割机生产过程中,为了提高切割速度,又要保证加工精度和光洁度,对步进电机进给频率要实时地进行模糊控制,使钼丝和工件的间隙处于最佳状态;同时控制的脉宽和脉冲间隔度在电腐蚀中也处于最佳状态,均在PLC中采用模糊控制器。     

影响金属切削加工表面质量的因素

在金属切削加工中,很多因素影响工件表面质量,如何使工件的表面质量达到粗糙度要求,如何减小各因素对工件表面质量的影响,就成为加工前必须考虑的问题,通过对影响金属切削加工表面质量的因素进行分析,并对提出提高工件表面质量的措施。     

螺纹铣削方法分析与应用

壳体类零件上的内螺纹、非旋转工件上的内外螺纹、旋转工件上不与零件轴心同心的内外螺纹等,传统方式只能利用手工、钻床和加工中心等利用丝锥来攻丝,或者利用螺纹铣刀来铣螺纹。随着数控技术的不断发展,数控螺纹铣削加工的诸多优势,大批量螺纹生产已较广泛地采用了铣削工艺。本文就螺纹铣削方法进行了相关研究和分析。     

模态分析对提高加工质量的作用

针对盘类工件采用循环对称算法进行模态分析，对比了工件工作状态和加工状态的固有频率和振型，提出了在工件设计中不能仅仅考虑工作状态的振动特性，而应全面考虑工作和加工过程两种状态的振动特性，避免工件在加工过程由于振动引起的加工质量问题，提高工件加工质量。     

减少机械加工误差提高机械加工精度

机械误差现象一般来说是不可避免的,因为在加工生产时机械工件不能够完全的可以做到一丝不差,所以说出现机械误差的现象是必然的。虽然说机械误差是必然存在的,但是这对工件质量的提升是没有影响的,并且我们可以通过各种方法来减少机械误差,提高机械加工精度。也许没有办法能够的完全消除误差,但是我们可以在机械的加工中可以通过去实验、去分析等等各种方法来减少误差,提高精度。本文将指出一些导致机械加工误差的原因,以及一些解决误差,提高精度的办法,希望通过本文可以得到精度更好的工件。     

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.