Performance analysis of multi‐antenna relay communication systems with MRC

The performance of multi‐antenna relay communication systems is investigated in this letter. The source broadcasts the signal to all the relays and the destination. Decode‐and‐forward scheme is adopted at the relays, and the destination employs maximum ratio combining (MRC) technique to maximize the received signal‐to‐noise ratio. Closed‐form expressions of outage probability are derived in the MRC case and minimum routes MRC case. An adaptive grouping algorithm of relay antennas is also presented under the constraint of total antenna number. Simulation results show that the analytical curves agree with the simulated ones very well, and the performance of the proposed grouping algorithm is very close to the upper bound mentioned in other papers. Copyright © 2012 John Wiley & Sons, Ltd.     

热处理工艺绿色性评价系统的研究

我国的热处理工艺污染大、能耗高,与世界先进水平有着一定的差距.说明实现热处理工艺绿色性的重要性,并建立热处理工艺的清单分析表及IPO模型,建立模糊度数学评价模型,对其进行资源、环境等方面的分析和评价.     

控制注入/压降试井测试时间因素分析

为了减少注入/压降试井对整个煤层气井施工进度的影响,基于对煤层气注入/压降试井测试理论及实际操作的研究,提出控制试井测试时间长短的几个因素,应用实例说明其解决方案,结果表明在煤层气井况、设备等基本固定的情况下,对于中高渗煤层,通过提高地面注入压力增大注入量是缩短试井测试时间的重要手段。     

Understanding the diffusion of mobile digital content: a growth curve modelling approach

While the sales of mobile digital content have been growing exponentially, the understanding of its diffusion remains limited in the literature. In this study, we set out to enrich this understanding using a growth curve modelling approach. We applied four widely used growth curve models of innovation diffusion and compared their performance in explaining the diffusion of mobile digital content empirically. Analysis based on the data collected on a product adopted by nearly 30 million mobile phone users over a 149-week period in 31 regions in China revealed that the Gompertz model was the most effective model in depicting the diffusion process, with more than 99 % of the variance explained. Moreover, we found that population, urbanization, education level, and mobile technology usage were significant determinants of various parameters such as the diffusion rate and inflection point of the diffusion process, respectively. Implications for both researchers and practitioners are discussed.     

Linear tracking-differentiator and application to online estimation of the frequency of a sinusoidal signal with random noise perturbation

A simple linear tracking-differentiator is proposed and the convergence proved for any differentiable signal with random perturbation to be tracked. This enables us to design a relatively simple globally convergent online estimator of the frequency of a sinusoidal signal under small random perturbation. The polynomial convergent rate is obtained.     

电磁波衰减系数特性分析

为了探索勘探深度大且分辨率高的电磁勘探技术,采用数值计算的方法研究了电磁波在1~1015Hz整个波谱范围内的衰减规律。计算了多种模型下,电磁波衰减系数的频率响应曲线,得到了电阻率分别为50、100、150、200、250、300、350、400、450、500Ω·m共10条曲线。这些曲线共同揭示了一个规律,从低频到高频,衰减系数随频率的增大而急剧增大;到一定频率后,波衰减系数趋于稳定;频率增大到某个阀值后,衰减系数急剧下降。在任意给定的电阻率下,频率超过某一阀值频率后,电磁波呈慢衰减或基本不衰减特性。因此,大于阀值的高频电磁波可进行大深度高分辨率勘探。     

项目管理方法在油气输送钢管驻厂监理中的应用探讨

本文概述了项目管理体系和油气输送钢管驻厂监理发展情况，详细探讨了如何采用项目管理标准科学方法实施驻厂监理项目管理，并介绍了油气输送钢管驻厂监理项目如何启动、规划、执行、监控、收尾以及变更，为油气输送管道工程项目监理提供依据或参考。     

机会式频谱接入问题基于事件的优化方法

研究机会式频谱接入技术中次用户对可利用频谱进行探测和接入策略的优化问题. 通过引入事件的概念, 将含有可数无限状态的原问题转化为包含有限个事件的决策问题. 从性能灵敏度的角度出发, 分析不同策略下平均传输率的差异, 给出了基于事件策略的性能差分公式. 以此为基础, 通过合理的近似, 设计了基于事件的策略迭代算法. 仿真示例验证了所提出算法的有效性和近似处理的合理性.

     

长沙地区通信基站通风冷却技术节能分析

基于长沙地区气象条件,采用建筑环境与能耗模拟软件DeST对通风冷却技术应用于通信基站的节能效益进行研究,并验证其可行性。结果表明：换气次数为40次/时,全年累计冷负荷指标下降76%;长沙地区全年约有74.4%的时间适合应用通风冷却技术,节能效果明显;该技术在长沙地区通信基站中的应用可以满足基站内温度、相对湿度和洁净度的要求,带来良好的经济和社会效益。