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951.
围海造陆工程项目往往具有投资规模大、工程周期长、技术比较复杂以及工程参与人员众多等特点。本文运用风险管理的理论,分析了 T 市临港工业区围海造陆工程项目的特点,提出了该项目在实施过程中的风险监控和应对的具体措施。 相似文献
952.
随着经济社会的发展,高层建筑日益增多,高层建筑防排烟设计问题逐渐引起人们的关注。文章通过分析高层防排烟设计中存在的问题,对高层建筑防排烟系统的设计方法进行了深入地探讨。 相似文献
953.
近年来,由于高速公路的损坏而导致的交通事故越来越多,所以逐渐引起了人们的重视。水泥混凝土桥面板破损往往是面积最大的、也是最严重的,其他比较常见的病害有桥面铺装层破损、开裂、错台、麻面和磨光等。 相似文献
954.
955.
In this paper, we propose and analyze the integration of source and jammer for a decode-and-forward two-way scheme under physical layer security where the source nodes not only transmit data signals, but also transmit jamming signals to degrade the quality of eavesdropping links, and a selected relay forwards the combined data signals using an XOR operation. In this proposed protocol, the best relay is chosen by the maximum end-to-end achievable secrecy rate, and the secrecy system performance is evaluated by the exact and asymptotic secrecy outage probability over flat and block Rayleigh fading channels. The Monte-Carlo results are presented to verify the theoretical analysis. 相似文献
956.
The increasing use of relays in wireless communication systems is a driving force to explore innovative techniques that can improve the quality of service as well as enhance the coverage in wireless systems. In this article, we propose a two-step approach for subcarrier allocation and power allocation in the downlink of an OFDM-based amplify-and forward relaying system. In the first step, the total power is allocated to mobile users and relays based on the optimum power ratio derived for the single-relay system. In the second step, subcarriers are assigned to the users based on cooperative subcarrier allocation algorithms. Compared to the non-cooperative algorithm with flat power allocation, the total throughput is shown to improve by applying the two-step cooperative subcarrier allocation and power allocation algorithms. 相似文献
957.
Exploitation of Diversity in Cooperative Spectrum Sharing with the Four-way Relaying AF Transmission
This paper investigates a cooperative spectrum sharing model where both the primary and secondary systems are two-way relaying-based systems. This model is also known as four-way relaying-based cooperative spectrum sharing. In the scenario of multiple relays, we propose a transmission scheme that enables a degradation-free primary system, exploitation of spatial diversity without using any interference constraint at the primary receivers. In this scheme, both of the primary and secondary systems employ the two-way amplify-and-forward (AF) relaying-based transmission (TW-AF-RT) within two timeslots and with the help of \(M\) relays \(R_1,\ldots ,R_M\) . The system operates in three modes: simultaneous sharing (SimS) mode, primary-single-access (PSA) mode, and secondary-single-access (SSA) mode. The SimS mode is a four-way AF relaying-based transmission, and it is prioritized when at least one relay node satisfies that both systems are not in outage. In this mode, the pulse-amplitude-modulation (PAM) signal is employed to present the information messages of the sources. As a result, the best relay selection method, which is based on the max–min rule, is still applicable for the exploitation of spatial diversity in this mode. Only the primary system accesses the spectrum in the PSA mode while only the secondary system does this in the SSA mode. In both the PSA and SSA modes, complex signals are used to present the information messages of the related sources instead of PAM signals. These modes are used when the SimS mode is not available. The analysis and simulation results are conducted to validate the advantages of the proposed scheme. 相似文献
958.
针对传统手工查找PCB设计辅助信息效率低、工作强度大的问题,文章运用Excel VBA二次开发功能,实现了PCB设计辅助信息的自动查询。与传统方法相比,本方法能显著提高工作效率,减少工作量,有效保证数据准确性,达到事半功倍的效果。 相似文献
959.
介绍了均衡技术的基本原理、均衡器的发展现状、盲均衡器算法的分类、均衡器算法的评价标准等,并对均衡技术的研究前景进行了展望。 相似文献
960.
Bo Kong Ti-Xian Zeng Zhu-Wen Zhou De-Liang Chen Xiao-Wei Sun 《Bulletin of Materials Science》2014,37(3):549-552
The structure and pressure-induced phase transitions for CdSe are investigated using first-principles calculations. The pressure-induced phase transition sequence WZ/ZB → Rs → Cmcm → CsCl for CdSe is drawn reasonably for the fist time, the corresponding transition pressures are 3.8, 29 and 107 GPa, respectively and the intermediate states between the Cmcm structure and the CsCl structure should exist. 相似文献