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31.
32.
房屋结构损伤及安全性评估实例分析 总被引:1,自引:0,他引:1
随着我国部分房屋建筑使用年限接近设计期限,或者说结构进入老化阶段,结构的健康状况和安全性评估逐步引起人们的关注。现代测试技术和计算机信息处理方法的结合,结构工程损伤检测方法、技术的规范化和科学化,基于时域和频域分析的结构参数辨识理论和技术、人工智能技术和专家系统也开始应用于结构健康监测和评估。简要评述了结构损伤检测方法进展和理论分析方法,并结合某体育场馆的结构安全性评估为实例,从结构设计、材料强度检测和实际结构状态进行全面检测和分析,并对其健康状况和安全性进行评估。 相似文献
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针对搅拌桩施工会引起周围土体的位移及产生很高的超静孔隙水压力的工程现象,首先分析了搅拌桩施工中固化剂的注入体积与膨胀压力、成桩直径的关系。结果表明,5%~10%的注入浆液的体积可以对周围土体产生1.8~3.0倍不排水抗剪强度的膨胀压力,成桩直径比搅拌叶片的名义直径大5%~10%。然后量测室内模型桩、现场搅拌桩的成桩直径,分析了注入浆液的体积与成桩直径的关系。结果表明,对于深度不太大的水泥土搅拌桩,有约45%的注入体积会通过上浮隆起的土体损失掉;大约5%的注入体积通过劈裂裂缝渗入到周围土体中;大约50%的注入体积会转化为成桩直径,使桩体膨胀5%~10%,即实测桩径比搅拌叶片的名义直径大5%~10%。 相似文献
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对实验室污染问题的思考和建议 总被引:10,自引:0,他引:10
余华 《中国环境管理干部学院学报》2005,15(1):58-60
分析了目前实验室存在的污染种类及危害,阐明实验室是一种不容忽视的污染源,且污染种类复杂,毒害较大.提出实验室污染防治措施. 相似文献
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随着城市生活水平的提高,室内装修装饰日益普及.各种新材料的引入,使得室内的各种有害气体总量日益增加.长期生活在这样的环境下,会对人体健康产生极为不利的影响.居民生活用煤气,在给人们生活带来便利的同时,作为一种可燃性、有毒气体,也具有极强的危害性.因此,研制一种能检测多种有害气体的实用仪器,具有很大的应用价值.本仪器为便携式多功能仪器,采用可充电电池供电,可以检测ppb的挥发性气体,显示气体浓度值,也可检测煤气,并具有声光报警功能. 相似文献
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Annemieke Farenhorst Inoka Amarakoon Lindsey Andronak 《Journal of environmental science and health. Part. B》2017,52(8):564-569
Mineralization studies of natural steroid hormones (e.g., 17β-estradiol, E2) are performed in environmental incubators, usually under a constant temperature such as 20°C. In this paper, we present a microcosm protocol that quantified the mineralization of E2 in soils under field temperatures. The nine agricultural soils tested had a wide range of soil organic carbon (1.1 to 5.2%) and clay (9 to 57%) contents. The calculated time over which half of the applied E2 was mineralized (E2-½) ranged from 299 to 910 d, and total E2 mineralization at 48 d (E2-TOT48) ranged from 4 to 13%. In subsequent laboratory incubations, the same soils were incubated under a constant temperature of 20°C, as well as under cyclic temperatures of 14.5°C (14 h) and 11.5°C (10h), which was within the temperature extremes observed in the field microcosms. E2-½ ranged from 157 to 686 d at 20°C and from 103 to 608 d at the cyclic temperatures, with the E2-TOT48 ranging from 6 to 21% at 20°C and from 7 to 30% under cyclic temperatures. Despite the overall 6.75°C lower mean temperatures under the cyclic versus constant temperatures, E2 mineralization was stimulated by the temperature cycles in three soils. Regardless of the incubation, the same loamy sand soil always showed larger E2 mineralization than the other eight soils and this loamy sand soil also had the smallest E2 sorption. Current modeling approaches do not take into consideration the effects of temperature fluctuations in the field because the input parameters used to describe degradation are derived from laboratory incubations at a constant temperature. Across the eight soils, E2-½ was on average 1.7 times larger and E2-TOT48 was on average 0.8 times smaller under field temperatures than under a constant 20°C. Hence, we conclude that incubations at 20°C give a reasonable representation of E2 mineralization occurring under field conditions to be expected in a typical Prairie summer season. 相似文献
39.
Johan Svensson Jon Andersson Per Sandström Grzegorz Mikusiński Bengt Gunnar Jonsson 《Conservation biology》2019,33(1):152-163
Loss of natural forests by forest clearcutting has been identified as a critical conservation challenge worldwide. This study addressed forest fragmentation and loss in the context of the establishment of a functional green infrastructure as a spatiotemporally connected landscape-scale network of habitats enhancing biodiversity, favorable conservation status, and ecosystem services. Through retrospective analysis of satellite images, we assessed a 50- to 60-year spatiotemporal clearcutting impact trajectory on natural and near-natural boreal forests across a sizable and representative region from the Gulf of Bothnia to the Scandinavian Mountain Range in northern Fennoscandia. This period broadly covers the whole forest clearcutting period; thus, our approach and results can be applied to comprehensive impact assessment of industrial forest management. The entire study region covers close to 46,000 km2 of forest-dominated landscape in a late phase of transition from a natural or near-natural to a land-use modified state. We found a substantial loss of intact forest, in particular of large, contiguous areas, a spatial polarization of remaining forest on regional scale where the inland has been more severely affected than the mountain and coastal zones, and a pronounced impact on interior forest core areas. Salient results were a decrease in area of the largest intact forest patch from 225,853 to 68,714 ha in the mountain zone and from 257,715 to 38,668 ha in the foothills zone, a decrease from 75% to 38% intact forest in the inland zones, a decrease in largest patch core area (assessed by considering 100-m patch edge disturbance) from 6114 to 351 ha in the coastal zone, and a geographic imbalance in protected forest with an evident predominance in the mountain zone. These results demonstrate profound disturbance of configuration of the natural forest landscape and disrupted connectivity, which challenges the establishment of functional green infrastructure. Our approach supports the identification of forests for expanded protection and conservation-oriented forest landscape restoration. 相似文献
40.
微生物是威胁饮用水安全的首要问题,水环境微生物快速检测技术的开发和应用是推动饮用水源微生物快速检测和水质安全预警技术发展的保障。随着对水质微生物污染快速检测和准确预警新要求的提出,水环境中微生物在线检测和预警技术得到了越来越多的开发和应用。笔者总结了水环境常见微生物检测方法和技术的发展,重点讨论了饮用水源微生物快速检测技术的发展和应用,根据各项技术的应用和推广使用程度,将其归纳为常用快速检测技术、潜在适用快速检测技术和新型快速检测技术等类别,并详细阐述了一些应用较广的技术,以期为构建水质微生物污染早期预警系统提供参考。 相似文献