Contact duration aware evaluation for content dissemination delay in mobile social network

Groups of people with mobile phones using short‐range connections such as WiFi and Bluetooth to propagate messages can be modeled as, with regard to regular absence of end‐to‐end connection, mobile social networks (MSNs), which can be exploited to offload a significant amount of mobile content from the overloaded infrastructure networks such as 3G. The study of content transmission delay for the applications of mobile content dissemination in MSNs is an important problem, because to enhance the network capacity, the traffic is offloaded at the cost of inducing longer delay. In contrast to existing works, which ignore the factors of contact duration limits and large content size, we present a contact duration aware framework to model the content dissemination process in MSNs, give an explicit expression for the average content dissemination delay, and reveals its relationship with various system parameters of content size, users’ selfishness, number of involved subscribers, infecting ratio, and so on. We apply our proposed model to real‐life traces to assess its reliability by comparing the theoretical results with measured statistics and present extensive upshots to evaluate the influence of various parameters on system performance. The results demonstrate the accuracy of our proposed framework and reveal that system parameters of content size, system infecting ratio and intragroup transmission are the most important factors to influence the content dissemination delay. Copyright © 2013 John Wiley & Sons, Ltd.     

Numerical study on PM10 collection efficiency in a wire-cylinder electrostatic precipitator under multi-field coupling

The PM10 collection efficiency of a wire-cylinder electrostatic precipitator (ESP) was studied by means of a developed mathematical model, including the multi-field coupling between the gas flow field, the particle dynamic field and the electric field, and applying the Deutsch–Anderson Equation. The diffusion charging mechanism was considered due to the diameter range of PM10. The investigated variables were the applied potential, the gas velocity and the particle distribution. Numerical results indicate that the diffusion charging has significant influence on PM10 removal performance and the effect is more obvious with the decreasing diameter, and that the PM10 collection efficiency increases with the increasing applied potential and the increment of collection efficiency is more significant at lower voltage. Moreover, as the gas velocity at inlet decreases, collection efficiency of PM10 will increase. Finally, the overall efficiency increases with increasing the mean diameter of particle distribution. The research results can provide theoretical and technical references for the design of novel ESP aiming at economy and environment protection.     

生物质多联供系统在农村应用的可行性分析

某乡村拥有猪粪、秸秆等大量生物质能,为降低该地区玻璃厂的能源成本及污染物排放量,提出建立生物质多联供系统的改造方案。对改造前后生物质处理利用方式及玻璃厂用能方式进行探讨,比较改造前后玻璃厂二氧化硫、温室气体排放量。生物质多联供系统具有较高的环保、经济效益,在农村地区具有可行性。     

矿区岩质斜坡稳定性评价与研究

以某矿为例,采用不平衡推力法和统计矩法等方法对矿区斜坡稳定性进行了评价,给出了各种算法下斜坡的安全系数和可靠指标;同时采用FLAC3D有限差分数值计算方法,对斜坡的位移场、速度场和稳定性做出综合评价,得出了斜坡安全系数;最后运用瑞典法、Bishop法、Janbu法等其他方法也对斜坡的安全系数进行了计算;比较研究结果表明:工程地质环境等随机变量对斜坡稳定性影响较大;FLAC3D与其他方法计算值基本一致,在矿区特殊的地质环境下,统计矩法能够有效地避免不确定因素过多产生的误差,其简便的计算和合理的结果显示了很大的优越性;对斜坡稳定性分析要求严格时,应采用多种方法进行综合比较.     

钢-混凝土混合结构的阻尼比取值

钢-混凝土混合结构在我国高层与超高层建筑中已经广泛应用,但国内外对混合结构体系的抗震设计中一些关键技术问题还存在争议。介绍了现行规范关于混合结构抗震计算中关键问题之阻尼比取值的相关规定,讨论了其不近完善之处。结合工程实例,推荐了混合结构简化计算时的等效阻尼比的合理取值,提出了适合复杂混合结构的阻尼比的实用计算方法。     

建设方造价专业人员在工程设计和实施中的地位及作用

从工程建设方出发,结合具体实例,针对工程设计方案、施工组织设计、工程建设实施三个阶段中的工程造价管理问题,论述造价专业人员的地位和作用.建设方应在整个工程建设周期内始终占主导地位,在工程造价管理工作中有意识地组织协调设计方、施工方和造价咨询方,正确处理造价合理与技术先进两者之间的统一关系.     

纤维增韧泡沫玻璃的制备及性能

以高硅氧玻璃纤维为增韧材料,SiC为发泡剂,废弃的钠钙硅平板玻璃粉为主要原料,采用烧结法成功制备了纤维增韧高强泡沫玻璃.通过DTA、SEM及力学性能测试,分析了试样的特性,定义了泡沫玻璃的比强度特性,应用比强度分析了泡沫玻璃基体中玻璃纤维掺量与试样机械性能的关系.结果表明,基体中加入质量为5％～25％、长度为10～30mm、长径比为100～300的高硅氧玻璃纤维,在790～815℃发泡烧结后,可以制备出比抗折强度为10.45～22.26MPa/(g/cm3),比抗压强度为30.45～34.34MPa/(g/cm3)的纤维增韧泡沫玻璃.所用纤维高强度,高弹性模量,以及纤维在泡沫玻璃基体中纵横交错的结构特征,是构成纤维增强泡沫玻璃机械性能优良的关键因素.     

动载荷作用下应用高强度螺栓连接时应注意的问题

针对深圳地铁站自动扶梯主驱动链轮连接螺栓松脱引发的停机故障,通过计算与分析得知,施工时因预紧力矩不足导致其连接方式由摩擦型连接向承压型连接转变,最终致使连接螺栓松脱。引发了故障。针对承受动载荷作用的重要结构或机构使用高强度螺栓连接,在设计．安装等环节提出了一些建议。     

框架填充墙的等效弹簧斜撑模型

填充墙的破坏形式较为复杂,为了有效地模拟填充墙的非线性性能,在对恢复力模型研究的基础上,提出静力非线性分析方法.由于SAP2000软件中无法直接模拟填充墙的非线性性能,本文结合填充墙的破坏特征,使用LINK单元建立填充墙等效模型,通过与试验结果对比,验证了该模型的合理性.在此基础上,以某5层框架填充墙结构为算例,建立考虑填充墙和不考虑填充墙的分析模型,分别进行了模态分析和Pushover分析.分析结果表明,考虑填充墙影响的周期折减系数为0.4 ～0.5,填充墙对框架结构中塑性铰的出铰顺序、塑性铰的发展情况都会产生重要影响.     

烟气冷凝热回收装置的节能与净化烟气效果的工程试验

基于燃气锅炉房排烟冷凝余热利用节能改造工程,并模拟电厂工况,试验研究了不同过剩空气系数条件下烟气冷凝热回收装置的节能与净化烟气效果。研究表明,烟气冷凝热回收装置不仅提高了燃气利用热效率,产生的烟气冷凝水量可观,且净化烟气效果显著,烟气冷凝水呈强酸性,设备的防腐至关重要。