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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. 相似文献
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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。 相似文献
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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。 相似文献
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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。 相似文献
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邓君子 《建筑·建材·装饰》2014,(18)
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。 相似文献
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《Material Religion》2013,9(1):110-120
ABSTRACTThe 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. 相似文献
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《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。 相似文献
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C.Y Jim 《Landscape and urban planning》1998,40(4):771
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. 相似文献
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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. 相似文献
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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. 相似文献
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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。 相似文献
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Public health and economic impact of dampness and mold 总被引:1,自引:0,他引:1
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. 相似文献
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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. 相似文献
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