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声自导技术的基础是波束形成技术,对波束形成技术的研究能够让我们更好地提高水下航行器的自动导引能力。本文首先对声自导系统的模型和基本职能进行了简单介绍,然后对波束形成技术和方位估计（参数估计）技术在无人水下航行器声自导技术上的应用进行了初步的研究,为我们将来发展新型无人水下航行器提供了一定的理论基础。 相似文献
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《科技风》2021,(21)
水下无人航行器是在对传统潜艇设备的升级基础下完成的,相较于传统潜艇具备更高的安全性,并且体积小巧,在水下进行常规作业隐蔽性极强,可以在海洋探索与海湾战争中占据有利地位。但水下无人航行器缺乏人员配置,在遇到故障时难以进行自我检修,加之维修成本高昂、水下作业难度大等问题,使得水下无人航行器的故障检测研究刻不容缓。本文根据水下无人航行器的构件构成为出发点,论述PHM技术在水下无人航行器中的适用性问题,从而总结出能够对水下无人航行器进行故障预测与管理的健康管理框架,针对应用中的相关科技进行PHM数据信息的优化升级,为水下无人航行器的故障预测管理打下坚实的理论实验基础。 相似文献
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提出一种基于自适应控制理论的机电控制系统算法设计,以某型智能水下航行器控制系统为例,设计出并联参考模型自适应控制系统。设计出基于自适应控制理论的机电设备控制系统,设计了控制系统的硬件电路图,对某型智能水下航行器控制系统的俯仰、偏航和横滚三个通道单独进行设计,分别设计出控制算法,得到俯仰、偏航和横滚控制三个通道的控制系统输出信号仿真结果和软件系统。控制系统的设计和仿真结果显示控制性能实时稳定,软件系统具有较高的人机交互性和友好性,能有效应用与某型水下智能航行器的控制系统中。 相似文献
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针对水下自主航行器的三维轨迹跟踪问题,本文介绍一种基于无线通信的水下自主航行器主被动跟踪技术。主要介绍了系统的总体方案、直线阵测向技术、无线网络通信技术和目标跟踪算法等几项关键技术。通过这几项关键技术的研究,对于提高水下自主航行器的跟踪能力,突破基于特征声源的动态目标跟踪技术难题,揭示水下目标的三维运动规律等都具有重要意义。 相似文献
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航行器的的水下驾驶技术是其先进性能的重要因素。没有电力推进技术的支持,许多先进的战斗思路和战术是无法实现的。无轴推进技术消除了传统的推进驱动轴,这将促进电机和螺旋桨的整合,可以充分利用电气和海水接触,散热效果好,有效地节省了水下机舱空间,地面和水下航行器的动力推进系统。 相似文献
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航行器的的水下驾驶技术是其先进性能的重要因素。没有电力推进技术的支持,许多先进的战斗思路和战术是无法实现的。无轴推进技术消除了传统的推进驱动轴,这将促进电机和螺旋桨的整合,可以充分利用电气和海水接触,散热效果好,有效地节省了水下机舱空间,地面和水下航行器的动力推进系统。 相似文献
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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
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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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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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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
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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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《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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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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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
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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