考虑网架覆盖率与分散度的网架重构优化

大停电后的网架重构过程中需要选择合理的恢复路径,尽快建立系统的骨干网架。提出了网架覆盖率和网架分散度指标,分别用于衡量骨干网架对系统原网络的覆盖程度以及重构过程中出现过长支路的风险,并综合恢复时间和线路充电电容等因素,建立了网架重构优化模型,利用简化模型寻找最优目标节点,采用改进的交叉粒子群算法优化目标节点恢复顺序,进而得到网架重构最优方案,其中考虑了非电源目标节点的同步恢复机制,提高重构效率。最后,以IEEE30节点系统算例验证了所提的网架重构方法的有效性。     

Performance analysis of hexagonal cellular networks in fading channels

This paper analyzes the location‐dependent performance metrics of coverage probability and spectral efficiency in hexagonal cellular networks under Rayleigh fading with a general distribution for shadowing and also including two special cases of no shadowing and lognormal shadowing. The effects of system parameters such as frequency reuse factor, transmission probability of base stations, and signal‐to‐interference‐plus‐noise ratio gap from Shannon capacity are accurately characterized. The proposed approach is applied to fractional frequency reuse (FFR) scheme where the impact of FFR on spectral efficiency is evaluated. Numerical results show that (i) in a lognormal‐shadowed Rayleigh fading channel with the shadowing standard deviation of 12 dB, the cell area wide spectral efficiency is degraded by approximately 40% compared with when there is Rayleigh fading without shadowing; (ii) the improvement in spectral efficiency achieved by FFR over the universal frequency reuse increases as the transmission probability increases and the shadowing becomes less severe; and (iii) in Rayleigh fading without shadowing environment where all the base stations are actively transmitting, FFR achieves approximately 20% improvement in spectral efficiency in the cell edge area. Interestingly, this improvement increases to about 30% if a 3‐dB signal‐to‐interference‐plus‐noise ratio gap from Shannon capacity is further accounted. Copyright © 2015 JohnWiley & Sons     

Coverage‐aware connectivity‐constrained unattended sensor deployment in underwater acoustic sensor networks

Careful deployment of nodes in underwater acoustic sensor networks in a distributed manner with the goal of maximized coverage and guaranteed connectivity is a challenging problem because it is very difficult and costly to access the 3D underwater environment. This paper presents a novel algorithm for self‐deployment of nodes in underwater acoustic sensor networks assuming that the nodes are randomly dropped to the water surface and form a densely populated connected network at the water surface. The idea of the algorithm is based on calculating an optimized depth for each node in the network in such a way that the possible sensing coverage overlaps are minimized and the connectivity of final topology is guaranteed. The algorithm has three main phases. In the first phase, nodes are organized in a tree structure that is rooted at the surface station. In the second phase, the depths for all nodes are computed iteratively at surface station. In the final phase, the calculated depths are distributed to nodes so that the nodes start sinking. The performance of the proposed approach is validated through simulation. We observed that the proposed approach performs at least 10% better in terms of network coverage than contemporary schemes in the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

采用配体交换法制备贵金属纳米粒子修饰电极的研究

选择8个碳链长度的烷基双硫醇分子在电极表面自组装构筑Au-SHSAM模板,然后将由弱保护剂四辛基溴化铵(TOAB)稳定的小尺寸Au、Ag、Pd和Pt纳米粒子通过纳米粒子与电极上巯基之间的强相互作用(M-S)将其表面的弱保护剂TOAB替换的方式,成功实现了贵金属纳米粒子在巯基模板电极表面的自组装,利用循环伏安法(CV)和扫描隧道显微镜(STM)对纳米粒子修饰电极在H2SO4溶液中的电化学行为以及纳米粒子在电极表面的形貌进行了表征,发现可以通过调节浸泡时间控制纳米粒子在电极表面的覆盖度。该方法新颖、简单而且具有一定的普适性。     

有压隧洞围岩最小覆盖层厚度弹塑性力学分析

水工隧洞的最小覆盖层厚度受到多方面因素的影响,如何确定最小覆盖层厚度是水工隧洞设计中必须重视的关键点之一。针对传统的最小覆盖层厚度算法的不足,本文提出了基于采用弹塑性力学方法的优化算法。该优化算法综合考虑了黏聚力、内摩擦角、地质强度指标、施工扰动等因素的影响,得到的最小覆盖层厚度更加符合实际情况。根据水工隧洞运行期的受力情况,运用Mohr-Coulomb与Hoek-Brown破坏准则,对无限大均质体中圆形水工隧洞在有无衬砌两种情况下的最小覆盖层厚度进行了弹塑性力学分析。并且与采用Tresca准则的分析结果进行了比较。结果表明:有衬砌时最小覆盖层厚度计算值小于无衬砌计算值。无衬砌时,由Mohr-Coulomb准则与Tresca准则计算所得最小覆盖层厚度随黏聚力的增大而逐渐减小;由Mohr-Coulomb准则计算结果随内摩擦角增大而逐渐减小。当m_i为一定值时,由Hoek-Brown准则计算结果随GSI值增大而减小。有衬砌时,当弹塑性界面在衬砌内时,最小覆盖层厚度随着衬砌黏聚力增大而增大,随着衬砌内摩擦角增大而减小。当弹塑性界面位于岩体内时,最小覆盖层厚度随着岩体和衬砌黏聚力增大而减小,随着围岩内摩擦角增大而增大,衬砌内摩擦角的增大而减小。     

公园绿化覆盖率对人群情感恢复的影响研究

公园绿化覆盖率对人群情感恢复起到重要影响作用,但关于情感恢复的具体结果及效果的细化研究较为匮乏。选取重庆市沙坪公园中的6处空间为研究样本,以归一化植被指数(NDVI)区分空间绿化覆盖率,结合生态瞬时评估(EMA)以精确测度人群情感的恢复结果,并分析两者之间的关系,结果表明:1)以硬质铺地为主、绿化覆盖率相对较低(0.38≤NDVI≤0.45)的公园空间,对人群外向情感恢复起主要影响作用;以软质绿化为主、绿化覆盖率相对较高(0.58≤NDVI≤0.72)的公园空间,对人群内向情感恢复起主要影响作用,且随绿化覆盖率提升,人群对应形成的外向或内向情感恢复效果均显著提升;2)公园绿化覆盖差异将诱导人群形成外向或内向2条情感恢复路径;3)在硬质铺地类空间中,丰富植被色彩及群落层次搭配,完善配置功能设施,有助于提升人群外向情感的恢复效果;在软质绿化类空间中,提升绿化覆盖率、植被丰富度,降低空间视野开阔度,有助于提升人群内向情感的恢复效果。研究结论可为公园恢复性环境理论体系的完善及实际项目建设提供思路借鉴。     

The performance of a sequential procedure for the estimation of the median survival time with specified accuracy

A bound on the order of convergence of the remainder term in the coverage probability of a fixed quantile of the survival distribution is obtained as the prescribed tolerance on the width of the interval shrinks to zero.     

建筑面积计算对工程造价的影响案例分析

针对具体工程结算中建筑面积计算的差异导致工程结算造价差异的情况，提出在招投标、签订合同及施工期间工程变更中对建筑面积需明确的事项，并给出面积计算依据，从而保证建筑面积计算的合理性。     

Femtocell技术的由来、优势和市场前景

Femtocell是用于增强室内无线覆盖的一项新技术,近年来受到了业界的广泛注意,发展十分迅速。本文叙述了Femtocell技术的由来和发展;讨论了Femtocell系统的优越性和需解决的关键技术;介绍了国外业界对Femtocell市场的预测。     

海能达无线通信解决方案在民用建筑中的应用

针对民用建筑通信需求、规模．结合无线通信产品与技术的发展趋势，介绍海能达为物业小区、大型商场、博物馆、展览馆等民用建筑提供的弱场覆盖解决方案，以及海能达数字无线互联系统在局域网和广域网中的应用。