共查询到20条相似文献，搜索用时 15 毫秒
1.
Relay-assisted transmission could effectively enhance the performance of Device-to-Device (D2D) communications when D2D user equipments (UEs) are too far away from each other or the quality of D2D channel is not good enough for direct communications. Meanwhile, security is one of the major concerns for proximity services. The secure relay selection problem for D2D communications underlaying cellular network is studied in this paper. Firstly, we define a relay selection area and derive the closed-form of outage probability in D2D links using a Poisson Point Process (PPP) method. Next, in the defined relay selection area, we propose a secure relay selection scheme for the relay-assisted D2D communication system by exploiting the social relation as a security factor. Simulation results show that the scheme based on social relation can greatly improve the security performance of relay-assisted D2D communications. 相似文献
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探讨了玻璃基片上毛细管区带电泳集成系统的进样及其对分离效率的影响 ,在本实验模型中 ,分离管道长 4cm ,10 0V/cm电场下的理论塔板数可至 4 50 0 0。 相似文献
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对单锚腿系泊系统的构成进行了分析,根据系统中零部件的结构尺寸作了约束的定义,并据此对系统中零部件作了约束分析,简化了系统参数化设计的复杂性,使得系统结构的约束分析条理清晰;在约束的定义和分析后,对系统的各零部件进行了关联分析,确定了建模顺序,在SolidWorks平台上开发出单锚腿系泊的参数化设计系统. 相似文献
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本文从摄影过程理论出发,以感光材料的感光特性曲线为工具对“负-正”系统中采取前期增加曝光量并和后期洗印工艺相结合来改善画面暗部影像质量的方法进行了分析和研究,并进行了相应的实拍验证。 相似文献
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Domain switching in PMN-PT single crystal and PZT-5 ceramics under electromechanical loading were studied in two different ways. For the single crystal, domain switching was in situ investigated with polarized light microscopy. A 90° domain-switching zone was observed near the crack tip and the size of the switching zone changed with the acuity of the crack tip. For PZT-5 ceramics, domain switching under orthogonal electromechanical loading (E3 and compressive stress σ11) was studied by measuring the hysteresis loops, butterfly curves and reversed butterfly curves (11 versus E3). Experimental results show that 90° domain switching is suppressed in the planes parallel to the compression direction. A domain-switching model dividing each 180° switching to two successive 90° switching was proposed to explain the experimental results. 相似文献
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This paper considers the zone automated order fulfilment systems with a number of zones linked by a main conveyor. Each zone has a number of dispensers and a buffer. Each dispenser holds one type of item and dispenses the items for an order into a buffer before the items are merged to the main conveyor. Due to variability of the mix of item types and number of items for each type in successive orders, idle time or open space on the conveyor can occur if the buffers merge the items to the conveyor sequentially. The idle time prolongs the order fulfilment duration. This paper aims to provide a solution to reduce the idle time or open space by optimising the merging sequences among zones. A model is developed to find merging sequences with minimum order fulfilment time. However, the model is strongly NP-hard. A greedy heuristic-based solution approach is thus developed. Experiment performance shows that the presented solution can reduce the order fulfilment time approximately 5% with both empirical data and simulation data. Moreover, the sensitivity analysis is conducted to measure the effect of the solution under the variation of zone numbers and order structures. Although the idle time reduction can be achieved with any number of zones and order structures, it was most significant in certain range of zone numbers and appropriate order structures. 相似文献
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The speech recognition technology has been increasingly common in our lives. Recently, a number of commercial smart speakers containing the personal assistant system using speech recognition came out. While the smart speaker vendors have been concerned about the intelligence and the convenience of their assistants, but there have been little mentions of the smart speakers in security aspects. As the smart speakers are becoming the hub for home automation, its security vulnerabilities can cause critical problems. In this paper, we categorize attack vectors and classify them into hardware-based, network-based, and software-based. With the attack vectors, we describe the detail attack scenarios and show the result of tests on several commercial smart speakers. In addition, we suggest guidelines to mitigate various attacks against smart speaker ecosystem. 相似文献
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Zinatul A. ZainolAuthor Vitae Wan M.H.W. HussainAuthor VitaeNoor Inayah YaakubAuthor Vitae 《World Patent Information》2011,33(3):275-281
The Uniform Dispute Resolution Policy (UDRP) is a unique process that resolves domain name disputes effectively and inexpensively. This paper, through an analysis of the UDRP three-prong test, revealed that even though the UDRP affords a great degree of discretion to the WIPO Panels deciding any given case, there is some consistency and predictability inherent in the UDRP process. 相似文献
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Li-Sha Zhu Hao Lu Yi-Min Zhang 《Quality and Reliability Engineering International》2021,37(6):2950-2969
Despite many advances in the field of computational system reliability analysis, estimating the joint probability distribution of correlated non-normal state variables on the basis of incomplete statistical data brings great challenges for engineers. To avoid multidimensional integration, system reliability estimation usually requires the calculation of marginal failure probability and joint failure probability. The current article proposed an integrated approach for estimating system reliability on the basis of the high moment method, saddle point approximation, and copulas. First, the statistic moment estimation based on the stochastic perturbation theory is presented. Thereafter, by constructing CGF (concise cumulant generating function) for the state variable with its first four statistical moments, a fourth moment saddle point approximation method is established for the component reliability estimation. Second, the copula theory is briefly introduced and extensively utilized two-dimensional copulas are presented. The best fit copula for estimating the probability of system failure is selected according to the AIC (Akaike Information Criterion). Finally, the derived method is applied to three numerical examples for the sake of a comprehensive validation. 相似文献
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钛合金生体材料及其表面改性 总被引：4，自引：0，他引：4
介绍了新型钛合金生体材料的研究开发,探讨了人工关节的失效机理,综述了对钛合金在表面生物活性、耐磨性、耐蚀性三个方面的表面改性的研究进展。 相似文献
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本文分析了一种静态随机存储器单比特位失效的机理.通过纳米探针测量,发现该比特位写操作失败是由负责存取的N型晶体管的驱动力较弱导致.TEM分析显示该晶体管的多晶硅栅中晶粒尺寸较大,这有可能导致栅的功函数变化以及靠近栅介质层区域的掺杂较轻.我们用SPICE模拟证实了晶体管驱动力变弱的原因是局域的多晶栅耗尽. 相似文献
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悬浮区域熔炼法制备REB6（LaB6、CeB6）单晶体及其表征 总被引：1，自引：0，他引：1
采用区域熔炼法成功制备出了高质量、高纯度、大尺寸的LaB6、CeB6单晶体。系统分析了制备过程中每个参数对晶体生长的影响,确定了晶体成长最佳工艺:(1)LaB6:转速为30r/min,生长速度为8～10mm/h,两次区熔;(2)CeB6:转速为30r/min,生长速度15～20mm/h,一次区熔。然后对晶体进行表征,主要方法有单晶衍射、断面扫描、拉曼衍射、摇摆曲线。由此可知悬浮区域熔炼法是制备高质量、高纯度、大尺寸REB6的最佳方法。 相似文献
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电梯安全保护系统一般由机械安全保护装置和电气安全保护装置两大部分组成。机械安全保护装置主要有限速器和安全钳、缓冲器、制动器、层门门锁与轿门电气联锁装置、门的安全保护装置、轿顶安全窗、轿顶防护栏杆、护脚板等;.电气安全保护有直接触电的防护、间接触电的防护、电气故障的防护、电气安全装置等,其中一些机械安全装置往往需要电气方面的配合和联锁装置才能完成其动作和可靠的效果。文章从各个装置的功能及其设置要求作了简要论述。 相似文献
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李建英 《成组技术与生产现代化》2007,24(1):57-59
信息网络安全状况直接影响信息化发展的进程和计算机网络的正常运行.本文从烟机企业网络安全的需求、存在的问题、以及相应的技术措施等几个方面入手,对烟机企业信息网络系统的安全防护体系进行探讨. 相似文献
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Composite joints are often the weakest elements in composite structures. In this paper, we propose a modified version of the damage zone theory based on the yield strain ratio. We use this framework to predict failure loads for various adhesive joints. Thick aluminum-to-aluminum joint specimens with eight different adhesive lengths and four adhesive thicknesses were manufactured and tested. The strengths of different adhesive lengths could be predicted to within 15.4% using the damage zone ratio method. In addition, the strengths of joints that feature different adhesive thicknesses were predicted to within 16.3% using the damage zone ratio method. 相似文献
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针对单站无源跟踪系统非线性较强、传统跟踪滤波方法收敛速度慢且容易发散的问题,提出了一种基于自适应因子化 H∞滤波的单站无源跟踪算法.该算法利用 sigma 点转换和鲁棒 H∞滤波能够减小观测方程的线性化误差和降低观测误差不确定性的特点,通过新息控制减小野值对滤波的干扰,利用比例因子和渐消因子自适应调整采样点到中心点的距离和状态预报误差的协方差,从而克服基于 UT 变换的 H∞滤波采样时的非局部效应问题,增强了单站无源跟踪系统对噪声的鲁棒性.仿真实验结果表明,本文方法通过对 UT 变换进行简化,在自适应因子化的同时,算法的计算量与基于 UT 变换的 H∞滤波基本持平,且跟踪精度优于基于 UT 变换的 H∞滤波算法.该算法在保持高精度估计能力的同时,具有较强的鲁棒性,是解决非线性系统状态估计问题的一种有效方法. 相似文献
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Marcello Braglia Roberto Gabbrielli Leonardo Marrazzini 《Quality and Reliability Engineering International》2021,37(2):433-450
In this paper, a novel integrated tool for failure mode and effects analysis (FMEA), opportunely named Risk Failure Deployment (RFD), which is able to evaluate the most critical failure modes and provide analyst with a practical and step-by-step guidance by selecting the most effective corrective actions for removal/mitigation process of root causes, is presented. Thanks to the modification of the framework of the Manufacturing cost deployment (MCD) and to its well-structured use of matrices, the novel RFD is able both to handle the dependencies and interactions between different and numerous failures and to evaluate the most critical ones on the basis of the risk priority number (RPN). Thereafter, the logical relationship between root causes and failure modes is assessed. Successively, the prioritization of corrective actions that are the most suitable for root causes is executed using not only the RPN but also other criteria, such as the economic aspect and the ease of implementation, that are unavoidable to execute a rational and effective selection of improvement activities. The effectiveness and usefulness in practice of the original tool for the prioritization of corrective actions to mitigate the risks due to failure modes collected during FMEA are presented in a case study. 相似文献