共查询到20条相似文献，搜索用时 43 毫秒
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《科技通报》2017,(12)
关于二维结构面粗糙度系数的分形维数评价方法,目前比较常用的方法之一是码尺法。由于采样间距r和长度L(r)对二维轮廓曲线的分形维数D值的影响不容忽视。本文以Barton给出的十条标准轮廓曲线为研究对象,首先,分析分形维数D和变异系数CV随采样间距区间的变化规律,得出采样间距区间为0.1~1.2 mm时,D值有较好的稳定性,其变异系数不大于0.05;其次,设置不同采样间距间隔,分析分形维数D值的变化规律进行分析,得出最佳采样间距;最后,提出一种新的与采样间距有关的粗糙度系数JRC的分形维数评价方法。通过与JRC试验反算值结果对比表明该方法可以较为准确地预测结构面粗糙度系数JRC值,具有较强的适用性。 相似文献
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《中国科学院院刊》2005,20(2):134-148
基础科学研究1 数学与系统科学研究 数 学与 系统 科学 研 究院 建立 了 有重 要 应用价值具有二次特征标的 Siegel权公式;给出了 Hausdorff 维数下界的一个非常有 用的估计方法,解决了 Hausdorff 维数渐进公 式的一个猜测;完满地解决了非对称狄氏型与 半狄氏型Beurling-Deny 分 解 这 一 重 要 的 公 开 问 题 ;在超大 规模集 成电 路设 计中的 若干 新 互连 结 构模型 的研究 中,获 多项重 要成 果;首 次提 出 了广义 Stewart 平台的概念,系统地提 出机构组成的 新方法 ,并综 合出大 量的 新机 构;在 反 馈能力研究方面,证明了多参数… 相似文献
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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。 相似文献
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薄膜材料的表面形貌直接影响到它的电阻率、介电常数等物理性能,描述薄膜材料的表面形貌对了解其可能产生的物理性能具有重要意义。由于分形盒维数能够综合反映出晶体大小,晶体的不规则程度、晶体排列的致密性等表面形貌结构特征,因而本文的研究拟运用计算机图像分析技术,从分形的角度综合描述薄膜材料表面形貌,并将其分形维数的大小和其电阻率的大小关联起来。本文的研究将有助于阐明晶体排列等结构与物理性能的关系,有助于指导材料制备。 相似文献
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在整体解唯一存在的基础上,研究了广义Boussinesq方程的整体吸引子和有限维的Hausdorff维数和分形维数. 相似文献
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基于因素计点法和IAHP的企业管理类岗位价值评价 总被引：2，自引：0，他引：2
系统地阐述了如何提取有效的薪酬要素,构建了企业管理类岗位价值评价递阶层次结构模型;提出了基于因素计点法和区间层次分析法(IAHP)的管理类岗位价值评价方法;用区间数代替传统层次分析法判断矩阵中的点值,合理地解决了薪酬要素两两比较结果的不确定性和模糊性问题,提高了岗位评价结果的可信度;运用实例,展示了基于因素计点法和IAHP的岗位价值评价的具体操作过程。 相似文献
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深基坑施工中重要的测量设备除深层沉降仪与测斜仪外,还有振弦式钢筋应力计、土压力盒、孔隙水压力计等,分别适用于不同的专门需求。 相似文献
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相空间重构参数选择方法的研究 总被引：2，自引：0，他引：2
基于目前相空间重构中常用的参数选择方法,提出了一种新的相空间重构的联合算法,联合算法以时间窗口法和互信息法为基础,在综合考虑嵌入窗宽的基础上,可同时确定嵌入延迟和嵌入维数.仿真实验表明,用该算法计算Lorenz混沌时间序列关联维相对误差由传统算法的0.83%降低到0.44%,有效地提高了计算相空间重构中不变量的精度. 相似文献
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《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
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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
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《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
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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
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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
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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
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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
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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
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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
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Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献