共查询到20条相似文献，搜索用时 70 毫秒
1.
2.
在毒气泄漏事故的应急处理中,根据泄漏源强度、气象条件、以及扩散模型就能够确定下风向污染物浓度,划定受影响范围,因而泄漏源强度的快速确定是事故应急救援的基础.文中结合瞬时泄漏的高斯点源扩散模型和下风向浓度测量数据,将计算浓度与测量浓度的误差平方和作为目标函数,利用模式搜索算法来优化,以确定源强;并通过模拟的测量浓度数据进行算法有效性验证,结果表明算法对于污染源强的反算研究是可行的. 相似文献
3.
4.
室内建筑污染区域会受到空气对流作用的影响,导致污染物的扩散方向和扩散速度都发生无序变化,污染区域呈散乱分布。传统的室内建筑污染扩散程度计算是基于污染物均匀分布的区域进行计算的,忽略了空气对流作用对污染区域均匀分布的影响,导致无法准确计算室内建筑污染扩散面积。为了避免传统方法的弊端,提出一种基于移动区域优化算法的室内建筑污染扩散面积的计算方法。利用对室内污染物区域边缘的空间位置提取数据建立模型,利用模型计算出污染物扩散过程中的污染区域面积,对扩散过程中的污染面积误差进行补偿处理,实现了对室内建筑污染扩散面积的准确计算。仿真实验表明,利用该算法能够对室内建筑污染扩散面积进行准确计算,从而准确判断出室内污染扩散的程度。 相似文献
5.
《科学中国人》2022,(2):10-15
福岛核废水在太平洋的扩散机理研究清华大学深圳国际研究生院海洋工程研究院张建民院士、胡振中副教授团队从宏观和微观两种角度分别建立了海洋尺度下放射性物质的扩散模型,实现了福岛核废水排放计划的长期模拟。相关成果发表于National Science Review。宏观模拟结果表明,核废水在排放后240天就会到达我国沿岸海域,1200天后将到达北美沿岸并污染几乎整个北太平洋。随后,污染物一边在赤道洋流的作用下沿着美洲海岸向南太平洋快速扩散,另一边通过澳大利亚北部海域向印度洋转移。此外,研究人员还从微观角度进行了氚的扩散模拟,微观扩散分析更加关注污染物个体的行为,能够支持污染物的扩散路径分析。 相似文献
6.
ADMS-Urban在机动车尾气扩散上的应用研究 总被引：1，自引：0，他引：1
ADMS_Urban (UrbanAirQualityManagementSystem)是一套城市大气质量管理系统。本文首先简单介绍了ADMS_Urban ,然后用ADMS_Urban模拟广州市天河区机动车尾气排放的ONX 的扩散过程 ,并将模拟结果与实测值、机动车尾气污染扩散数值模型的模拟结果进行对比。结果表明 ,风速对NOX 浓度分布有很大的影响 ,路网结构对浓度分布有一定的影响。ADMS_Urban能够很好地模拟有风 (风速≥ 1m/s)条件下NOX 的扩散过程 ,但只能近似模拟静风 (风速 <1m/s)条件下的NOX 扩散过程。 相似文献
7.
8.
风洞模拟相似参数的实用探讨 总被引：1，自引：0，他引：1
要计算高架点源对周围环境的污染,唯一可靠的方法,就是要进行现场测试和风洞模拟实验。对于风洞模拟而言,一个较根本的问题就是模拟的结果,能否代表实际大气扩散情况。相似性定律作了比较明确地回答。只要满足一系列无量纲参数,则风洞中模拟烟羽的扩散和大气中实际扩散情况一致。反之,模拟不符合相似参数的要求,其结果不能应用于实际大气的扩散。本文对模拟相似参数的实用性进行了初步探讨。 相似文献
9.
范海娇 《内蒙古科技与经济》2013,(24):103-103,105
阐述了遥感与GIS在土地覆盖分类中的应用原理。遥感自动分类主要依赖地物的光谱特性,采用数理统计的方法,基于单个像元来进行,主要有监督分类和非监督分类的方法。GIS可以使分类结果更加精确,在GIS的支持下对遥感数据分类结果进行叠加分析,使分类图像与土地利用分区信息集合起来,可以很大程度上提高精确度。 相似文献
10.
《软科学》2018,(1)
构建政府、企业、学研机构间的生态技术合作创新博弈模型,重点考察合作创新过程中各博弈方决策的演化机理与影响因素;引入Lotka-Voltrra模型,探究竞争系数、政府行为对其合作创新成果扩散的具体影响,运用Matlab进行仿真模拟。研究发现,生态合作创新的超额收益、竞争系数分别是产学研生态合作创新决策与成果扩散状态的决定因素,政府规制则间接促进双方选择生态合作创新,提升创新扩散效率;政府高额征收污染税,适度给予生态合作创新补偿激励,能有效调节产学研双方的利益分配,促进实现"帕累托最优"均衡;政府规制下"强污染惩处,适度环保宣传"的政策组合,对产学研生态合作创新成果扩散的促进效果最为明显。 相似文献
11.
A research 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 in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
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. 相似文献
12.
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
13.
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
14.
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
15.
Active biological molecules 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 therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
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. 相似文献
16.
《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
17.
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
18.
《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
19.
Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献
20.
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