共查询到20条相似文献，搜索用时 125 毫秒
1.
2.
磁流变阻尼器虽具有良好的阻尼力特性,但是其强非线性的特点却使得力学模型相当复杂,如何有效地识别磁流变阻尼器力学模型中的参数是急需解决的问题。本文选取Bouc-Wen模型用以描述磁流变阻尼器的非线性滞回特性,为了准确的识别出Bouc-Wen模型中的未知参数,通过采用无迹卡尔曼滤波算法(UKF)对Bouc-Wen模型参数进行在线识别。识别结果表明:由UKF算法识别出的参数的精度较高,且识别出的阻尼力与时间、速度以及位移的关系曲线与原曲线吻合度高;可以说明UKF算法在磁流变阻尼器Bouc-Wen模型参数识别中的有效性。 相似文献
3.
4.
由于对车辆的舒适性要求越来越高,发动机的隔振越来越受到关注,通过试验对某柴油发动机在橡胶垫和磁流变阻尼器上隔振特性研究,并且在不同转速的情况下,对橡胶和磁流变阻尼器的隔振性能进行对比分析,从而得出不同阻尼器的隔振特性,为对发动机进行相应的隔振措施提供一定的依据。 相似文献
5.
当前,汽车变速器中使用摩擦式离合器实现动力切换的比较多,但摩擦式离合器在接合时存在机械摩擦,这就会产生机械磨损严重、降低零件使用寿命以及噪音大等缺陷,而随着磁流变液的兴起,它逐渐引起了国内外学者和工业界的广泛研究,并取得了显著进展。但磁流变液剪切屈服应力不足问题从磁流变技术诞辰时起就一直困扰着磁流变液材料和技术的发展,依据现有的磁流变液剪切应力设计的磁流变液离合器,不但体积较大,而且所能传递的扭矩很小,根本无法适应工业生产。在总结、分析国内外相关技术发展及应用现状的基础上,本论文提出一种基于磁流变液挤压—剪切混合模式下的汽车离合器,这种离合器的优势在于:1)传递更大转矩(不单纯是在剪切模式下工作,不完全依赖于磁流变液自身的剪切屈服强度);2)结构简单、体积小(锥形结构增大了有效剪切面积);3)密封性好(磁流变液被挤压后其颗粒不会因离心力作用甩向圆盘外径边缘处)。 相似文献
6.
主要以双喷嘴挡板电液伺服阀为研究对象,推导出其数学模型;根据电液伺服阀目标结构参数,使用SIMULINK仿真软件对数学模型进行仿真,得出电液伺服阀的闭环阶跃响应图和伯德图。通过改变静态参数得出不同的伯德图;分析电液伺服阀动态性能的变化,从而达到动态参数优化的目的。 相似文献
7.
8.
9.
为研究斜靠式钢管混凝土拱桥的结构受力特点,以一座拟建的90m斜靠式拱桥为例,分析了其主要结构参数(矢跨比、吊杆间距、斜拱倾角)对结构静力性能的影响。经过结构参数对比计算分析发现:当矢跨比由1/5变化至1/6时,内力值将出现较大幅度增加;吊杆间距的增大对斜拱受力不利;倾角的减小对主拱、系梁和斜拱受力不利。分析结果为斜靠拱设计提供了结构参数选取的建议,为此类桥梁的设计提供有利的参考。 相似文献
10.
11.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
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. 相似文献
12.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US 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 the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
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. 相似文献
13.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
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. 相似文献
14.
《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
15.
《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
16.
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. 相似文献
17.
Puay Tang 《The Information Society》1998,14(1):19-31
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. 相似文献
18.
Milton Mueller 《The Information Society》2001,17(3):151-163
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. 相似文献
19.
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.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
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. 相似文献
20.
Leah A. Lievrouw 《The Information Society》1998,14(2):83-96
The main premise of this article is that in information societies generally, and in virtual social contexts particularly, a distinctive style of interaction to facilitate the communication of difference, heterotopic communication , has emerged. It rests on two cultural foundations: an ideological belief in the positive, socially integrating power of communication, and a prevailing ethic of instrumental rationality, subjective individualism, and strategically practiced self-interest. The former is demonstrated by the use of simulation and spectacle as sources of information; exhibitionism/voyeurism as a communicative style; and the awareness of surveillance. The latter is seen in the competitive use of knowledge as a commodity; a surface globalism masking deep parochialism; lateral as well as vertical information inequity; and the use of public versus private as strategies for engagement rather than as spaces. Those who engage in heterotopic communication resort to their 'own devices' both in the sense of personal agendas, strategies, interests, and interpretations, and in the form of the telecommunication tools that help realize them. These personal and technological devices allow individuals with the right educational and technical resources to avoid exposure to disagreement, difference, or other information that does not serve their direct purposes or reflect their particular views of the world; yet they also help convey the appearance of openness, availability, and cooperation. This style of interaction is used strategically in combination with information and communication technologies to gain social or economic advantages, but it may encourage social separatism and parochialism, inhibit the negotiation of disputes, and emphasize competing interests. 相似文献