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991.
为了正确评估钢筋混凝土矩形梁在实际火灾条件下的承载力,以一般室内火灾轰燃后的房间平均温度一时间曲线为火作用,以热传导和建筑结构耐火理论为基础,以梁在实际和标准火灾下的承载力相等为等效准则,用数值计算方法研究梁的当量耐火时间,并用最小二乘法导出其计算公式.火灾房间火灾荷载越大,开口因子越小,梁的当量耐火时间越长;反之越短.所给梁的当量耐火时间可用于建筑结构性能化耐火设计与评估:当火灾荷载密度较大,开口因子较小时加大梁的截面参数以获得安全性,反之,减小截面参数以获得经济性. 相似文献
992.
钢筋混凝土矩形梁在实际火灾下正截面承载力数值计算 总被引:1,自引:1,他引:0
为了正确评估钢筋混凝土矩形梁在实际火灾条件下的承载力,以一般室内火灾轰燃后的房间平均温度-时间曲线为火作用,以建筑结构耐火理论为基础,采用数值计算方法研究钢筋混凝土矩形梁的正截面承载力.研究结果表明:梁的承载力随火灾房间温度升高而变小,在温度达到最大值后承载力达到最小值.火灾房间火灾荷载越大,开口因子越小,火作用越大,梁的最小承载力越小;反之相反.相同条件下梁支座截面的承载力要大于跨中截面. 相似文献
993.
994.
Triclosan in Fresh Water Fish Gibelion Catla from the Kaveri River,India, and Its Consumption Risk Assessment 总被引:1,自引:0,他引:1
Govindaraj Shanmugam Karthik Ramasamy Krishna Kumar Selvaraj Srimurali Sampath 《Environmental Forensics》2014,15(3):207-212
Triclosan is a common antimicrobial agent that is found in significant levels in the aquatic environment and may elicit effects on aquatic organisms through unexpected modes of action. In this study, triclosan was quantified in fish from the Kaveri River, India, by using the gas chromatography and mass spectrometry technique and it was found in the range of 0.73–50 ng/g wet weight (ww). The mean bioaccumulation factor based on water (BAFw 820) and sediment (BAFs 2.12) in the Kaveri River showed that triclosan is accumulative in fish, and reflects its feeding behavior. The bioaccumulation indicates triclosan's persistence or prevalence throughout the river stretch. Human risk assessment through dietary intake demonstrated that the triclosan exposure is five orders of magnitude lower than the acceptable daily intake (50 μg/kg bw) and US EPA reference dose (300 μg/kg bw/day). This investigation is the first to report the bioaccumulation of triclosan in freshwater fish from India. Further, the results indicate that this fish acts as a biomarker of exposure for triclosan and thus shall be used to report triclosan pollution in the future. 相似文献
995.
啶虫脒属于一种新型的氯化烟碱类杀虫剂,被认为是替代有机磷农药的重要品种之一,在世界范围内已经得到了广泛的应用,其在环境中的残留备受关注,利用微生物修复异源污染物是一种有效的措施。在实验室条件下,研究了高效降解菌D-2(噬染料菌属,Pigmentiphaga sp.)对被啶虫脒污染土壤的修复作用及其影响因素。结果表明,降解菌株在未灭菌土壤中的降解效果要略好于灭菌土壤,在土壤外源添加降解菌2×108 cfu/g,温度20~40℃,弱碱性(pH 7.5)的条件下,该菌株能有效降解土壤中1~200 mg/kg的啶虫脒。啶虫脒施用对土壤种群结构有一定的影响,可以刺激细菌和真菌的生长,从而使土壤微生物群落结构发生改变,而降解菌的施用可缓解啶虫脒对土壤微生物的影响,修复受污染土壤。因此,人工接种降解菌D-2可提高土壤中啶虫脒的降解率,有效降低其在土壤中的残留。 相似文献
996.
Tetsuo Yasutaka Yumi Iwasaki Shizuka Hashimoto Wataru Naito Kyoko Ono Atsuo Kishimoto Kikuo Yoshida Michio Murakami Isao Kawaguchi Toshihiro Oka Junko Nakanishi 《Chemosphere》2013
Despite the enormous cost of radiation decontamination, there has been almost no quantitative discussion on how much it would reduce the long-term external radiation exposure in the Evacuation Zone and Planned Evacuation Zone (restricted zone) in Fukushima. The aim of this study is to assess the effectiveness of decontamination and return options and to identify important parameters for estimating the long-term cumulated effective dose (CED) during 15, 30 and 70 year period using data on land-use, population and decontamination in the restricted zone (about 1100 km2) in Fukushima. 相似文献
997.
Polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) are organic contaminants that tend to accumulate in fish. Estuaries are exposed to high anthropogenic activities, therefore tending to accumulate more contaminants than the adjacent coastal waters. Platichthys flesus, a fish with high economic value, was analysed for PCBs and HCB along its different age groups, in liver, gills, gonads and muscle. Younger fishes were caught in the estuary, whereas older fishes were caught in the adjacent coastal waters and acquired at Figueira da Foz Regional Office of Docapesca-Portos e Lotas, SA. Both contaminants concentrations follow the pattern: liver > gills > muscle. Hepatosomatic index had the lowest values in younger fishes and the highest values in older fishes. Condition factor values remain stable with age. Younger fishes had higher PCBs concentrations than the older fishes. In opposition HCB was only detected in fish from 3+ to 5+ and its concentration tended to increase with age. Overall P. flesus is considered safe for human intake. 相似文献
998.
分析比较了相关分析法、多元线性回归法与逐步回归法在环境影响因子辨识中的功能异同点。以甘肃省白银市为例 ,用 3种统计学方法对城郊土壤 -作物系统重金属污染影响因子进行判别 ,提出了研究区土壤污染修复方案选择指标的建议 相似文献
999.
Panichayapichet P Nitisoravut S Simachaya W 《Environmental monitoring and assessment》2007,135(1-3):181-193
The aim of this study was to investigate the spatial distribution of heavy metal in soil and evaluate the dissolution of metal
from soil to ponded-surface water, leaching through soil profiles and metal uptake in grass as related to different land-use
practices. The data provided a scientific basis for best-management practices for land use in Khli Ti watershed. The watershed
has a Pb-contamination problem from the previous operation of a Pb-ore concentrator and abandoned Zn–Pb mine. Sampling sites
were selected from a land-use map, with land-use types falling into the following four categories: forest, agricultural land,
residential area and road. Soil, ponded-surface water, grass samples and soil profiles were collected. The study related soil
characteristics from different land-use practices and locations with observed metal concentrations in ponded-surface water
and soil. High enrichment factors of Pb and As in soil were found. Partitioning coefficient, Kd values were in the order: Cr > Pb > Ni > Cu > Cd > Zn. Soil disturbance from land-use activities including tillage and traffic
increased leaching of trace metal from soils. Pb in soil was significantly taken up by grass even though the Transfer Factor,
TF values were rather low. Agricultural activities in the watershed must be limited. Moreover, land encroachments in the upper
and middle part of the watershed which have high potential of Pb must be strictly controlled in order to reduce the Pb contamination
from non-point sources. 相似文献
1000.