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1.
为了提升无人机机群间的通信频谱利用效率,认知无线电技术被应用在无人机机群中。由于传统频谱感知算法易受到噪声干扰、受通信时延干扰、需要累积信号长,无法适应无人机机群间通信,本文提出了一种基于长短期记忆神经网络(LSTM)的双门限无人机机群频谱感知算法。首先利用所有次级用户对频谱信号进行感知收集,随后将所有次级用户信号传入无人机融合节点,最后利用长短期记忆(LSTM)神经网络进行感知判断。在仿真实验条件下与传统单门限能量协作算法、双门限能量协作算法比较,仿真结果表明在不同信噪比和虚警概率下,所提方法的检测性能均优于传统算法。 相似文献
2.
《科技通报》2015,(9)
在对数字电路中非正常跳变信号进行检测的过程中,容易出现干扰信号,影响非正常跳变信号的检测,导致传统的基于交错正交幅度调制的正交频分复用系统采用迫零均衡器进行非正常跳变信号检测时,不能完全消除干扰,无法有效实现数字电路中非正常跳变信号的检测,提出一种基于傅里叶转换的非正常跳变信号检测方法,对数字电路中的干扰进行分析及处理,理想情况下,利用频谱在信号变化频率范围内进行搜寻,获取频率同时对其进行锁定。实际应用中,将信号与一个矩形窗相乘,获取矩形窗的幅度谱,通过无限长信号的理想幅度谱和矩形窗幅度谱的卷积求出有限长信号的幅度谱。对信号进行模拟低通滤波后,对其进行采集,求出非正常跳变信号实际频率的估计值,通过牛顿迭代法向实际频率进行逼近后,实际信号进行恢复。仿真实验结果表明,所提方法具有很高的检测精度。 相似文献
3.
工频50HZ的电流信号是电机故障检测中的干扰信号,尤其在电机运行时严重影响故障信号的判断,本文通过MATLAB仿真工具软件,设计采用自适应陷波器对工频分量进行自适应陷波处理和快速傅里叶变换(FFT),以此来消除工频分量对故障特征分量的检测干扰,以便能更好的采集到故障信号,对故障信号做出分析。本文通过MATLAB的仿真编程,可以消除干扰信号突出故障信号。 相似文献
4.
《科技通报》2016,(4)
无线传感器网络在强干扰环境下,通信节点受到干扰影响和能耗限制,导致节点之间的通信信道失衡,需要对无线传感器网络通信节点进行鲁棒性选择,提高网络通信的覆盖和均衡能力。传统方法中对无线传感器网络鲁棒性通信节点选择采用节点间互助转包轮换路由分发协议,由于邻居节点的自私性导致对节点通信的抗干扰性不强。提出一种基于自适应分层能量均衡的强干扰下的无线传感器网络鲁棒性通信节点选择模型。构建无线传感器网络的通信节点布局模型,然后进行通信节点的最优节点密度分布设计,基于自适应分层能量均衡方法实现对强干扰下的无线传感器网络鲁棒性通信节点选择模型改进。仿真实验结果表明,采用该模型进行强干扰下的无线传感器网络鲁棒性通信节点优化部署和选择,降低了数据传输丢包率和延迟,减少了计算开销,提高了网络的连通性和覆盖度,性能优越。 相似文献
5.
《科技通报》2015,(8)
新型的网络病毒的入侵和传播以正态谐振方式进行连续攻击,检测困难,需要对病毒攻击进行有效检测。传统的检测方法采用干扰攻击定位状态转移特征提取的层次性检测算法实现对病毒连续攻击的检测,算法没能自适应求解连续攻击下的特征选择参数,检测性能不好。提出一种基于窄带信号频谱偏移修正的正态谐振网络病毒连续攻击下的重叠检测算法。采用链重叠检测和向量化运算模拟正态谐振网络病毒的攻击特征和相关性质,实现对病毒的检测,通过Langevin方程描述,正态谐振网络的病毒连续攻击表现为一种双稳态非线性驱动多频共振模型,采用窄带信号频谱偏移修正方法,计算得到病毒节点连接概率以及个体的感染率,提高检测性能。仿真结果表明,该算法对病毒传播有较好的抑制性,提高了对网络病毒连续攻击下的检测性能和重叠检测能力。 相似文献
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7.
《科技通报》2015,(8)
通过对自组织网络动态融合,提高复杂应用环境下的无线传感网络的稳定性和通信能力。传统方法中对自组织网络动态融合采用时延-多普勒域动态重组的融合机制,导致相邻节点功率均衡偏差,融合性能不好。提出一种基于分布传感的容迟自组织网络动态融合算法。构建无线传感自组织网络的网络模型,设计短距离通信的主从式无线传输信道自适应跟踪技术和冲激响应特性分析模型,使用分段副本相关检测器对分布频段内频谱进行分段滤波和检测,进行无线传输信道自适应均衡设计,通过相关处理后,可消除这种多径干扰的影响,得到分布传感的容迟自组织网络动态融合结果,实验得出,该算法的融合精度较高,信号保真度较好,优于传统算法,展示了较好的应用价值。 相似文献
8.
高速移动场景下的无线网络覆盖已经成为移动网络建设的重要组成部分,传统的移动节点衰减模型,由于其在计算的准确性和反应速度方面存在着一定的局限性,无法得到理想的衰减信道。为此,提出建立高速环境下移动节点衰减性能检测模型。新型高速环境下移动节点衰减性能检测模型通过测算大差分衰落特性,对高速移动环境下通信节点接收信号幅值强度进行计算,为高速铁路建网前期通信节点的建设规划和后期网络运行提供准确的基础数据。通过提高外置车顶天线的接收性能,减少测量过程中因速度的改变和场景的变化而造成的通信节点衰减性能的下降幅度。通过对高速移动场景下多尺度、多角度衰落系数的修订,消除地貌环境的影响,最终推衍出综合检测模型。仿真结果表明,新型的通信节点性能检测模型最终可将高速移动环境下的移动通信节点衰减性能检测参数计算的精准率提高20%。 相似文献
9.
计算机通信节点部署随机性较大,热点周边存在随机的窄带干扰信号。其中,较强的窄带干扰会严重影响计算机正常通信。为解决这一问题,提出了一种基于通信信息模糊一致的计算机优化通信算法,设计了通信中的模糊矩阵,利用矩阵一致性判断方法,在变换域实现对干扰信号的识别与滤除,并且无失真地恢复出原始信号。仿真分析结果表明,该算法下,计算机能够实现识别并滤除窄带干扰,很大程度上降低计算机通信的误码率。 相似文献
10.
移动卫星通信信道的多普勒效应会产生强烈的发生码间干扰和相位失衡,导致移动通信质量降低。传统方法采用单模判决神经模糊系统对信道进行盲均衡处理,虽然能克服卫星信道的幅度畸变,但无法消除码间干扰和相位偏转畸变。提出一种具有判决反馈结构的模糊控制下多模移动卫星信道盲均衡算法,通过模糊控制自适应调整变量因子抽头系数,保证了算法快速收敛,并纠正了相位偏转,抑制码间干扰。仿真实验表明,采用该算法进行移动卫星通信盲均衡信道优化设计,移动通信质量提高明显。 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.
《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
16.
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
17.
《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
18.
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
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