基于动力特性的工程结构损伤识别技术(一)

基于动力特性的损伤识别技术是结构损伤识别的有效方法.介绍了基于动力特性的损伤识别技术研究现状,对基于结构振动响应和系统动态特性参数进行损伤识别的方法和原理进行了评述,提出了结构动力特性的损伤识别技术有待于研究的问题.     

基于振动的结构损伤识别研究综述

提供了结构基于振动的损伤识别现状综述,并结合国内现状总结出一般建筑的通用框架.首先介绍了损伤识别的基本原理并总结出基于振动的损伤识别对应于损伤响应、损伤定位、损伤量化以及损伤预测的一般流程.接下来按照损伤识别流程分别介绍了各个步骤的最新进展及应用方法.最后讨论了基于振动的损伤识别的研究方向.     

用振动参数识别技术对混凝土框架进行破损评估

本文提出了采用振动参数识别技术对混凝土平面框架结构进行破损评估的新方法.该方法是首先采用“残余力向量”识别结构的损伤部位,然后再用振动理论中的加权灵敏度分析的方法识别结构的物理参数,由此识别结构的损伤严重程度.经三榀钢筋混凝土框架的试验结果表明,本文的方法是可行的.     

论土木工程结构的振动损伤识别

随着信息技术的不断发展,传感技术、信号采集与处理技术随着应用领域的拓宽得到了充分的发展空间,土木工程结构的振动损伤识别技术研究经过多年研究已取得了一些成就,相应的技术也在实际工程中广泛应用,但是应用过程还存在着许多的问题与不足,针对当前国内的土木工程结构的振动损伤识别技术发展现状,本文主要论述土木工程结构的振动损伤识别技术应用过程中所遇到的问题以及其发展状况,并提出了结构振动损伤识别的发展趋势。     

基于自适应人工鱼群算法的钢梁结构损伤识别

桥梁在投入使用后,在环境因素和荷载作用下,常常会产生结构上的损伤,伴随损伤状态运作的桥梁存在很大的安全隐患。本文介绍一种基于自适应步长的人工鱼群算法,首先介绍了人工鱼群算法的基本原理,并在此基础上对算法进行了改进,寻优过程中采用自适应步长。然后,通过基于MATLAB自行开发的有限元分析程序和锤击振动试验,得到各损伤工况下的理论和试验模态参数。最后将实际损伤和算法识别结果进行了对比分析。研究结果表明,本文的自适应人工鱼群算法能较准确找到损伤位置,并识别出损伤程度,与原算法相比在识别损伤位置和损伤的大小程度判断方面都有所提高,说明本文方法准确有效,可应用于实际结构的损伤识别。     

有模型损伤诊断技术研究进展

归纳总结了现阶段各种有模型损伤诊断方法,并对其各自的特点及适用性进行了分析介绍,最后对复杂结构的损伤诊断方法进行了阐述,指出基于结构振动损伤识别技术具有广阔的研究背景,值得大力推广应用。     

木梁基于曲率模态技术的损伤识别

利用有限元分析软件建立了木梁的损伤模型,获取了不同损伤参数的曲率模态;基于结构动力学中梁自由振动的理论,推导了木梁基于曲率模态的损伤程度判定理论;对人工模拟的损伤木梁进行了模态试验.结果 表明:曲率模态对损伤识别非常敏感,损伤位置可通过曲率模态图的突变判定,损伤程度可以根据突变程度判定;模态分析试验结果与有限元分析结果吻合较好;有限元算例和模态试验验证了损伤程度判定理论公式的适用性,采用曲率模态技术对木梁进行损伤检测是有效可行的.     

基于振动传递率的损伤识别仿真研究

为研究基于振动传递率的损伤识别方法的可行性,以一钢悬臂梁为例,进行了多种仿真试验,分别研究了振动传递率的可重复性、损伤敏感性和损伤位置敏感性。仿真试验结果显示:振动传递率不依赖于结构激励荷载;对损伤具有较强的敏感性;能识别结构损伤位置。相对于多位置损伤识别相比,其对于单位置损伤识别具有更好的效果。     

基于D-S证据理论的结构多损伤识别结果融合研究

考虑噪声影响时,无论基于刚度矩阵损伤因子的损伤识别方法,还是基于模态应变能的方法对结构多损伤识别的效果均不太理想,容易造成误判。为此,采用信息融合技术的D-S证据理论将基于刚度矩阵损伤因子和基于模态应变能的损伤识别结果进行融合。平面桁架数值仿真结果表明,融合后能提高结构多损伤识别的准确性。     

基于动静力参数的结构损伤识别研究进展

基于振动的识别方法是损伤识别应用较为广泛的一种方法,而基于静力参数的识别方法较为直观,也是目前普遍使用的方法。本文综述了基于结构动静力参数的损伤识别方法研究现状,对模态参数、模型修正等方法做了一定程度的介绍,分析了各种方法的优点与不足,并展望了损伤识别的发展方向。     

Afterword—gendering religious objects: placing them as agents in matrices of power

ABSTRACT

The articles in this special issue demonstrate how objects can be interpreted as agents, as gendered images that make a statement, and how their impacts can be understood and assessed by human actors. They are differentially placed in matrices of power, and they can be manipulated to shift genders, to play with gendered combinations, to expand the limits of a particular gendered domain, to creatively play with reproductive imagery, and even to sell commodities in new and enticing ways in the mass media. Gendered religious objects are “statements” addressed not only to the eye but to the emotions, and part of a complex cultural field in which things can play important roles in people's lives. The links that connect ritual power to other forms of agency and biographical significance are perhaps the most significant links that we need to examine to understand them better in a world of many diverse cultural forms.     

材料的重要性

《材料的重要性》是《景观设计理论》的一段节选。《景观设计理论》旨在不使用专业术语或其他领域假说的前提下,结合景观设计过程向学生介绍内在理论思想。《材料的重要性》是本书的五章之一。每一章针对特定理论,解释了其基础和来源,探讨了它对设计的重要性,列举了20—21世纪与其相关的设计案例,整理了该理论的辩论(尤其是有关现代和后现代思想),最后还有相关阅读材料清单和需要学生们思考的问题。本文分为如下3个部分：第一部分,物质性,介绍“辩证唯物主义”“媒介即信息”“物质实践”和“编码”等理论及其在设计中的运用;第二部分,通过“建构表达”“地貌代理人策略”“石材的面层”“材料的暗示”“人造,但不是伪造”等理论,介绍材料的真实性及其在设计中的运用;第三部分,复写理论及应用,包括“剩余物”“复写的展示性”“未来的复写”和“虚构的复写”等内容。     

Urban soil characteristics and limitations for landscape planting in Hong Kong

Soils in urban areas have not received adequate attention in relation to landscape planting. Recent urban tree surveys in Hong Kong identified many arboricultural problems related to stressful habitat conditions including edaphic ones. Soil constraints in the crowded city are acute and yet relevant data are lacking. This project evaluated in the field and laboratory 100 soil samples obtained from sites of varied natural and disturbance history at difficult roadside tree-pit sites in urban Hong Kong. An extensive range of physical and chemical properties were assessed to establish baseline information on soil limitations to amenity-vegetation growth. Most soils have lost natural soil horizons with morphological features of fill materials such as poor structure and artificial layering. They are excessively stony and coarse-textured, with abundance of building rubble and other foreign substances. The extensive soil compaction, associated with structural degradation and loss of porosity, is inimical to aeration, drainage, storage of plant-available moisture, and root growth. Release of carbonate from the calcareous construction waste has induced alkaline pH, with consequences on micronutrient and phosphorus deficiency. Organic matter contents, and the related supply of essential nitrogen and phosphorus, are all meager. The capacity to hold nutrient bases and the amount held in available forms are both inadequate for vigorous plant performance. There are signs of pollution by heavy metals, especially lead, which are derived from air-borne sources related to vehicular traffic. The results help to ascertain the need for soil tests in landscaping endeavors, to reinforce a weak link in landscaping programs, to establish a package of recommendations to improve urban soil management, to enhance the cost-effectiveness of greening programs, and to augment urban-tree performance so as to reduce recurrent management liability and burden.     

Environmental aspects of the use of NTA as a detergent builder

The behaviour, fate and significance of the detergent builder nitrilotriacetic acid (NTA) has been reviewed with particular reference to the removal of NTA during wastewater treatment and the effects of NTA on heavy metal solubility both during treatment and in the receiving environment. It is concluded that NTA removal during secondary biological treatment is subject to considerable variation, both temporal and between works as a result of changes in NTA load, temperature, water hardness and treatment process parameters. As a result of such variability, effluent NTA concentrations may be sufficient to mobilise heavy metals resulting in metal contamination of receiving waters and potable waters, particularly in areas of low effluent dilution and high water re-use. Removal of NTA during primary sedimentation and septic tank treatment is concluded to be predominantly due to adsorption to the sludge solids while removal in anaerobic sludge digestion is subject to operational characteristics of the treatment works. Disposal of NTA contaminated sludge to land may contaminate groundwaters and affect heavy metal speciation, while the disposal of contaminated sludge or sewage to sea may result in toxic algal blooms, in addition to effects on metal speciation.     

Use of iodide to enhance the phytoextraction of mercury-contaminated soil

Low bioavailability of mercury (Hg) in soil is a restricting factor in phytoextraction of Hg-contaminated soil. Iodide is known to mobilize Hg in soil and, therefore, the aim of this study was to investigate the possibility to use iodide to increase phytoextraction of Hg. The sensitivity of willow to iodide was investigated in both hydroponics with 0-10 mM KI and in soil with 0.2 and 1 mM KI addition. The capacity to accumulate HgI(2) was compared with that of Hg(NO(3))(2) in hydroponics. Soil extractions with 0-2 mM KI were used to study mobilization of Hg in aged Hg-spiked soil. Additions of KI (0.2-1 mM) were used in pot tests with aged Hg-spiked soil as well as in field trials in an industrial Hg-contaminated soil to study whether iodide addition increased the accumulation of Hg from contaminated soil and the translocation of Hg to the shoots. The total Hg contents in plants, soils and extracts were analyzed by CVAAS. The results showed that too high KI concentration was toxic to plants. Moreover, KI was toxic to plants at lower concentrations in hydroponics than in soil additions. KI (85 microM) in hydroponics gave 50% growth decrease in terms of dry weight of shoot biomass, whereas 0.2 mM KI in soil addition could be tolerated by the plant without growth disturbance. Willow accumulated Hg from HgI(2) solution slower than that from Hg(NO(3))(2) solution. KI mobilized Hg in contaminated soil and thereby increased the bioavailability of Hg in soil. Up to 1 mM KI addition increased the Hg concentrations to about 5, 3 and 8 times, respectively, in the leaves, branches and roots. However, the Hg translocation to the shoots did not show an increase with KI addition. Only less than 1% of the total Hg accumulated in the plant was distributed in the shoots. We may conclude that iodide addition enhances the phytoextraction of Hg, however, the translocation of Hg to the shoots is still too low and therefore it will not be realistic to use this method for phytoextraction of Hg-contaminated soil in practice.     

中国规划的政治依附性之辩——转型中国规划的角色认识

在经济增速放缓、政治体制变革的转型背景中,中国城市规划专业应该怎样"转型"成为热题。其中,城市规划附庸于政治而需要被动地应对政治转变是隐含的"常识",但这一认识带来了规划转型的现实压力——受制于无法改变的体制。规划是否的确依附于政治体制,如果不是,又应该怎样看待规划与政治的关系,进而认识规划转型的核心?本文从论述方式、论证视角两个方面解读和反思了中国规划的政治依附性的判断过程,发现城市规划不仅没有长期固化依附政治的角色,反而在不同时代发挥了专业价值。再从解构主义思维反思政治经济结构凌驾于其他结构之上的观点。最后认为,转型中国规划求变的核心并不在于规划要怎样适应政治体制这一或其他外因,而在于反思与自省内因,沉淀与重拾专业价值,进而期待一个多元多维的规划前景。     

Public health and economic impact of dampness and mold

The public health risk and economic impact of dampness and mold exposures was assessed using current asthma as a health endpoint. Individual risk of current asthma from exposure to dampness and mold in homes from W.J. Fisk, Q. Lei-Gomez & M.J. Mendell [(2007) Indoor Air, [corrected] 17, 284-296], and [corrected] asthma risks calculated from additional studies that reported the prevalence of dampness and mold in homes were used to estimate the proportion of US current asthma cases that are attributable to dampness and mold exposure at 21% (95% confidence internal 12-29%). An examination of the literature covering dampness and mold in schools, offices, and institutional buildings, which is summarized in the Appendix, suggests that risks from exposure in these buildings are similar to risks from exposures in homes. Of the 21.8 million people reported to have asthma in the USA, approximately 4.6 (2.7-6.3) million cases are estimated to be attributable to dampness and mold exposure in the home. Estimates of the national cost of asthma from two prior studies were updated to 2004 and used to estimate the economic impact of dampness and mold exposures. By applying the attributable fraction to the updated national annual cost of asthma, the national annual cost of asthma that is attributable to dampness and mold exposure in the home is estimated to be $3.5 billion ($2.1-4.8 billion). Analysis indicates that exposure to dampness and mold in buildings poses significant public health and economic risks in the USA. These findings are compatible with public policies and programs that help control moisture and mold in buildings. PRACTICAL IMPLICATIONS: There is a need to control moisture in both new and existing construction because of the significant health consequences that can result from dampness and mold. This paper demonstrates that dampness and mold in buildings is a significant public health problem with substantial economic impact.     

Analysis of household access to drinking water,sanitation, and waste disposal services in urban areas of Nepal

In recent years, researchers have paid increasing attention to the provision of access to clean and sufficient drinking water, sanitation facilities, and proper waste management in developing countries. This paper examines household access to these services in urban areas of Nepal by studying the comprehensive data of the Nepal Living Standard Survey (NLSS) for the 1995-1996, 2003–2004, and 2010–2011 periods. Multinomial logit models are employed to identify and analyse potentially influential factors. We find that education levels, household wealth, and distance to markets are among the significant determinants of household access to safe and secure drinking water, flush toilets connected to septic tanks, and proper liquid and solid waste disposal. Households located in relatively developed regions, such as the Midwest and Far West, tend to have better access to these services compared to households located in the ecologically sensitive mountainous regions. Education and employment opportunities are also relevant to service access in urban areas of Nepal. Stakeholder involvement and effective governmental intervention are also necessary.     

道隐天地，咫尺情韵 ——以云南凤庆石洞寺浅观中国理想人居

中国人对山水之迷恋已是极致,一则因山水媾和万物阴阳两态之流变认识;二可借山纹水脉暗通昆仑神话之时空不尽。前者构建其认知世界之方法,后者为维稳其文化溯源所求之本源归属感,以及忘化时空、死生之界域囿限。亘古亘今,隐处丘园者,究其思想,多染映于道佛之法,而返窥宗教名山,素于山林最胜处,得居游自足之洞庭妙所,何也？遂凭托云南石洞寺,借境生文,以其“行望居游”之体验品判,引发今之园构,师法何式之问;究源古之隐者,生死流变之忧;承启当下居境,适宜理式之思。     

关于项目代建方工作职责的思考

根据代建制的内涵,在代建实践工作中的认识,分析了建设项目前期、设计、施工各阶段的主要工作职责,即设计方案及图纸优化,创造和谐的工作氛围,做好参建各方之间的协调工作,加强合同管理,监督各方切实履行各自职责,严格控制工程质量、投资、进度,竣工验收后移交使用方。