低矮房屋风致结构响应极值不确定性分析

风致结构响应极值估算在结构抗风的可靠度设计中十分重要。在整个极值估算过程中,由于许多不定或随机的因素存在(如：极值自身、估算方法、样本采集、极值概率模型等),得到的极值通常存在不确定性。在各种影响因素中,该文将考虑结构响应极值变量本身的随机特性,对任意分位点处响应极值的不确定性进行分析。首先,利用有限元软件对低矮房屋模型进行框架结构设计并优化,加载风压荷载得到结构响应时程数据。然后,基于Hermite多项式模型(HPM)转换过程方法,估算得到响应的极值Ⅰ型分布(Gumbel);基于该极值估算方法,提出时程样本偏度、峰度、零超越次数与Gumbel分布两个参数之间的经验公式。接着,考虑前四阶矩的不确定性,利用经验公式以及多步概率分析,对任意分位点处响应极值的不确定性进行估计。最后,给出相关结论。     

Rural Migrants’ Residential Mobility: Housing and Locational Outcomes of Forced Moves in China

This paper analyses the residential mobility of China’s rural–urban migrants in light of evidence from Yangzhou, a medium-sized city in Jiangsu province. To evaluate the effects of forced moves induced by demolition-led redevelopment, these outcomes are compared to those of voluntary moves. The evaluation is specifically concerned with dwelling attributes and location characteristics. Dwelling attributes consist of tenure and housing facilities, while commuting distance, distance to the city centre and the length of a child’s trip to school comprise the location characteristics. Logistic regression of data from a 2012–2013 survey shows that a voluntary relocation and the intention to move prior to notification of intended demolition are likely to result in positive outcomes. The migrants’ relocation strategy involves making a trade-off between better dwelling attributes and a better location. When housing improvement is their major concern, they tend to move to peripheral areas. However, it seems that children’s educational opportunities are being factored into the trade-off. In that case, migrants purchase an apartment in a specific school district or at least move closer to it. For the sake of their children, they relegate other motives to second place.     

Vulnerability Mitigation of Multiple Spatially Localized Attacks on Critical Infrastructure Systems

Recently, many studies have analyzed critical infrastructure vulnerability under spatially localized attack (SLA), which is modeled as the failure of a set of infrastructure components, distributed in a spatially localized area, due to malicious attacks, while other components outside of the area do not directly fail. However, existing studies have only considered one single attack area, and multiple SLAs (MSLAs) with more than one attack area have been seldom investigated. This article addresses this issue and studies vulnerability mitigation of critical infrastructure systems (CISs) against the worst‐case MSLAs. The problem is mathematically formulated as a tri‐level defender‐attacker‐defender model, the exact solution of which is solved by a proposed decomposition algorithm. Case studies on the adapted IEEE 24 bus system and the power transmission systems in Shelby County and Harris County, U.S., indicate that (1) system vulnerability under 2*M localized attack areas might be much larger than two times of the vulnerability under M localized attack areas; (2) small preevent defense investment might mitigate the worst‐case vulnerability by more than 40%; and (3) MSLAs might cause larger vulnerability than nonproximity‐based malicious attacks.     

城市燃气施工数字化管理应用

针对目前燃气施工管理数字化应用平台功能不全,精细化不足等问题,本文介绍了一套完整的工程管理数字化系统。系统的应用,实现了工程质量管理的标准化、全面化,工程进度控制的精准化,施工后处理的高效化,办公的移动化以及监管的数字化、动态化,提高了工程各方的工作效能。最后分析了系统的优势与不足,探讨了下一步的升级方向,将燃气工程的数字化应用水平提升到了一个新的高度。     

红粘土地质开口管桩上浮特性的模型试验

针对红粘土上硬下软地层中开口管桩上浮问题,分别进行了三类不同桩径的开口管桩室内沉桩模型试验,研究单桩和群桩静压沉桩试验中上浮量变化规律和土塞效应对开口管桩上浮的影响。结果表明:单桩上浮量主要由静压沉桩引起的管桩弹性压缩经卸荷回弹产生的变形提供;群桩静压上浮与施工顺序、桩间距以及位置有关,先压入的管桩上浮量大于后压入的管桩上浮量,且先压入桩的上浮速度随着后压入桩的桩间距减小而增加;桩位对桩上浮的影响强度顺序由高到低依次是中心桩位、边桩位、角桩位;当开口管桩从硬塑层压入至可塑层一定深度后,由于土塞完全闭塞的影响,导致挤土效应增强,有别于闭口管桩静压至在软硬交界面处出现的短暂上浮量增长休止的状况,开口管桩群桩挤土上浮量表现出显著上升趋势。     

潜江市现代测绘基准体系建设

介绍了潜江市现代测绘基准体系建设的总体情况,详细分析了QJCORS系统、高精度GNSS控制网、二等水准网、区域似大地水准面精化等的数据处理、测试情况,总结分析了现代测绘基准体系建设的现实意义和应用前景。     

倾斜摄影测量技术在三维建模中的应用

三维建模已经成为测绘数字化过程中不可缺少的重要一环。Smart3D软件在快速低成本实现精细三维模型的构建、大比例尺DOM的制作以及三维模型的可视化展示等方面拥有巨大优势。本文借助倾斜摄影测量技术和Smart3D软件实现精细三维模型的快速构建,规范和分析了数据获取的主要流程和数据处理的关键技术,对比和探讨了利用点云和影像数据建模的精度和优缺点,总结了三维建模过程中相关数据的质量要求和评价标准。最后指出了影像建模仍面临的一些问题,仍需要进一步研究。     

“半城市化”与“市民化”——新型城镇化背景下的城市正式移民问题研究

新型城镇化的人本主义内涵之一即是强调城镇化水平由数量型增长向质量型增长的转变。"半城市化"指已取得城市户籍的正式迁移人口在居住就业、社会行为和社会心理等层面尚未完全融入城市社会的状态。这一现象的长期存在不利于新型城镇化的实现与推进。研究选择一部分在南京城区内种菜的人为调查对象,通过与城市普通居民在居住和生活方式方面的比较,以及他们对自我身份的认同和周边居民对他们的认同情况来印证城市正式移民中"半城市化"状态的存在。从社会融合的视角构建了一个评价指标体系,借以测量他们的"市民化"程度,并指出经济收入水平与城市正式移民的"市民化"程度正相关。     

《建设项目交通影响评价技术标准》的规范与创新

《建设项目交通影响评价技术标准》是国内首部颁布实施的交通影响评价行业技术标准。研究简要介绍了该标准的编制背景、总体思路和主要内容构成,重点阐述了编制中的技术难点和技术创新点,对标准颁布后的实施情况和存在的问题进行了回顾与小结,并对未来交通影响评价的发展趋势进行了展望。     

基于主体功能区划思想的荆州市国土空间划分研究

研究探讨了荆州市国土空间划分的基本思路和主导因素,设定"县域"为分析评价单元,通过定性分析判定一部分区域的国土功能区的类型划分,采用多指标综合评判法最终形成国土功能区划方案,并对不同功能分区发展的政策导向进行了深入分析。研究表明,对于荆州市这样自然环境条件区域分异明显、人口集聚和经济发展水平差异显著、市域内交通指向主导经济布局的地区,在划分国土功能区时,应综合考虑应用市域单元、乡镇单元两种尺度,避免"一刀切"。