T 市临港工业区围海造陆工程项目的风险监控和应对措施研究

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。     

解析防排烟设计技术在高层建筑中的应用

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。     

浅谈桥面铺装层裂缝产生的原因与修补措施

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。     

已通车高速公路软基沉降病害侧向辐射注浆处治技术

针对江苏省沿海已通车高速公路试验段(K865+220—K865+280)存在的沉降病害,提出了既有高速公路运用侧向辐射注浆法进行沉降病害处治的设计方法和施工工艺。通过现场注浆试验,确定注浆过程控制参数,通过理论分析和现场沉降观测进行了效果评价,最后对其经济性进行了分析。实践表明,此方法能有效控制既有高速公路沉降病害,且具有施工简便、振动小、不影响正常通车等优点。     

An Integration of Source and Jammer for a Decode-and-Forward Two-way Scheme Under Physical Layer Security

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.     

Cooperative Subcarrier Allocation and Power Allocation in the Downlink of an Amplify-and-Forward OFDM Relaying System

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.     

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.     

Excel VBA在PCB设计辅助信息查询中的应用

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。     

数字通信系统中均衡器研究综述

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。     

Effects of particle size and properties on the microstructures,mechanical properties,and fracture mechanisms of 7075Al hybrid composites prepared by squeeze casting

To investigate the effects of particle size and properties on the mechanical properties of 7075Al matrix composites, hybrid composites reinforced using three different reinforcement combinations, 40 vol. % 7 μm SiC_p with 5 vol. % 7 μm SiC_p, 35 μm SiC_p, and 35 μm Ti, were prepared using squeeze casting. The failure mechanisms and the microstructure–property relationships of hybrid composites were studied using SEM, TEM, and tensile tests. The composite containing Ti particles achieved the highest tensile strength of 626 MPa and an elongation of 1.2 %. Fracture mechanism analyses imply that the reduced strength for the 35 μm SiC_p-containing composite are caused by the inefficient load transfer capability resulting from the preferential breakage of larger-sized SiC_p particles during the deformation process. In contrast, micro-zones formed by Ti particles at the center and matrix alloy with few dislocations around release stress and deform synergistically during deformation, which decreases the breakage of SiC_p and improves the plastic deformation ability of the matrix alloy, resulting in a good combination of strength and ductility.