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261.
目的构建适用于高强度铝合金在某工业海洋性气候地区的加速腐蚀试验方法。方法选用飞机结构用典型高强度铝合金7B04-T6为试验材料,进行实验室加速腐蚀试验与某工业地区海洋大气环境曝晒试验,并对试验后的试样进行疲劳性能评价。通过平均腐蚀速率测试、腐蚀形态特征观察、疲劳断口特征分析,腐蚀加速倍率计算,对两种形式腐蚀铝合金的腐蚀机理和疲劳破坏行为等进行综合对比。结果经历实验室加速腐蚀试验与海洋大气环境曝晒试验后,7B04-T6铝合金的质量损失率基本相等,腐蚀形貌相近,疲劳断口特征一致,因而两种腐蚀模式一致,机理相同。结论所编制的实验室加速环境谱与试验方法,能够较好地用于某工业海洋性气候地区高强度铝合金材料和结构的环境损伤加速试验,实验室与外场海洋大气环境曝晒试验的加速比为97.64。 相似文献
262.
现代社会大量化学品的生产与广泛使用造成了地表水、地下水、沉积物、土壤等环境受到污染,并对人体健康和生态系统构成威胁。基于毒性效应的关键致毒物质鉴别技术(effect directed analysis,EDA)已经在水体、沉积物的致毒物筛选方面得到了一定的应用。但是由于污染物组成复杂、范围广、基质干扰高、同分异构体广泛存在、人工合成标样缺少等问题,非目标致毒化合物的鉴别成为了EDA的瓶颈技术。逐渐发展的色谱与质谱技术、数据库指标在化合物筛选识别中发挥了重要作用。本文综述了基于高分辨质谱,数据库搜索,色谱保留特征,模型构建来筛选识别化合物的方法,总结了近年来化合物筛选识别方法在环境新型污染物及药物筛选等方面的应用并分析了化合物筛选识别所存在的问题与应用前景。这些方法可以提高非目标化合物筛选的准确性和通量,减少样品复杂性和基质干扰带来的负面影响,从而有利于未知化合物的确定。 相似文献
263.
This work provides insights on the solubilization products after a simultaneous combination of alkaline and ultrasonic (ALK + ULS) pre-treatment of sewage sludge. Soluble chemical oxygen demand (SCOD) increased from 1200 to 11,000 mg/L after such treatment. Organics with molecular weight around 5.6 kDa were solubilized because of the synergistic effect of ultrasound and alkali. Organics with molecular weight larger than 300 kDa increased from 7.8% to 60%, 16% and 42.3% after ULS, ALK and ALK + ULS treatment, respectively. Excitation emission matrix fluorescence spectroscopy analysis identified soluble microbial product-like and humic acid-like matters as the main solubilization products. Sludge anaerobic biodegradability was significantly enhanced with the simultaneous application of ALK + ULS pre-treatment. ALK + ULS pre-treatment resulted in 37.8% biodegradability increase compared to the untreated sludge. This value was higher compared to the biodegradability increase induced by individual ALK pre-treatment (5.7%) or individual ULS pre-treatment (20.7%) under the same conditions applied. 相似文献
264.
Lucie Flache Sezin Czarnecki Rolf-Alexander Dring Uwe Kierdorf Jorge A. Encarnao 《环境科学学报(英文版)》2015,27(5):184-193
Metal-contaminated soils and sediments are widespread in urbanized areas due to atmospheric deposition close to emission sources. These metals are bio-available for organisms, e.g., insects, and accumulate in food chains of insectivorous mammals. Especially bats, which live in urban regions and ingest large amounts of food relative to their body mass, are at risk of being poisoned due to the accumulation of trace metals. To determine species-specific trace metal contents in bats from urban environments, hair samples were analyzed by ICP-OES. Observed trace metal concentrations were related to species-specific foraging habitat, prey spectrum and degree of synanthropy. The species studied were Pipistrellus pipistrellus, Myotis daubentonii and Nyctalus noctula. P. pipistrellus showed the highest concentrations of lead and zinc and slightly higher concentrations of cadmium than the other two species, which was related to its high degree of synanthropy with foraging habitat mostly located in cities. In contrast, N. noctula displayed the highest contents of manganese and copper. The reason might be found in its prey spectrum, as N. noctula feeds mainly on beetles that are caught in cultured areas. Trace metal concentrations determined in hair samples of M. daubentonii ranged between the values of P. pipistrellus and N. noctula, probably reflecting an intermediate level of synanthropy. Positive correlations were observed between the concentrations of cadmium and lead and those of manganese and copper. Hair samples from bats are suitable monitoring tools to study trace metal exposure and can be used to determine differences in trace metal levels between species. 相似文献
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268.
目的 通过自动寻优制定冲击环境后峰锯齿脉冲试验条件,避免冲击“过试验”。方法 根据冲击响应谱的基本原理和谱型特征,提出利用对数距离量化评价2条谱型的吻合度。对冲击环境和后峰锯齿脉冲分别进行冲击响应谱分析,将2条冲击响应谱之间的对数距离最小作为优化目标,将后峰锯齿脉冲的波形参数作为优化参数,基于自适应差分进化算法,提出冲击环境后峰锯齿脉冲试验条件自动寻优方法。结果 将所提方法分别应用于模拟冲击环境和实测冲击环境,均获得了合理的后峰锯齿脉冲试验条件,验证了所提方法的正确性。结论 提出的基于自适应差分进化算法的冲击环境后峰锯齿脉冲试验条件自动寻优方法正确可行。 相似文献
269.
Wusi Yue Charles Meneveau Marc B. Parlange Weihong Zhu Hyung Suk Kang Joseph Katz 《Environmental Fluid Mechanics》2008,8(1):73-95
A comparative study of turbulence in a wind-tunnel model canopy is performed, using Large eddy simulation (LES) and experimental
data from PIV and hot-wire anemometry measurements. The model canopy is composed of thin cylindrical stalks. In the LES, these
are represented using a plant-scale approach, while the scale-dependent Lagrangian dynamic model is used as subgrid-scale
model. LES predictions of turbulence statistics and energy spectra are found to be in good agreement with the experimental
data. Turbulent kinetic energy (TKE) budgets from the LES simulation are analyzed to provide more information absent in the
measurements. Results confirm that sloshing motions at the low levels of the canopy are mainly driven by pressure fluctuations.
A difference between the energy flux obtained from the energy spectrum and the SGS dissipation rate is observed, consistent
with a spectral bypass mechanism in which the real spectral flux due to cascade is smaller than that implied by the energy-spectrum
level, due to direct drain by the canopy. 相似文献
270.
The selection and establishment of the structure (number and compartments, aggregation criteria, and trophic links) of the food webs is a critical task in trophic modelling. The present work proposes a systematic method to structure trophic networks in pelagic food webs. The biomass-size spectrum (BSS) is a well-established approach to analyze the structure of pelagic communities, and the body size is especially related to the ecological role of the organisms in the pelagic environment. To structure food webs, this work uses detailed arrangements of the community in size classes with increasing widths (like Sheldon-type BSS) as first aggregation criteria, and BSS theory as a framework to integrate the available knowledge about feeding selectivity in order to obtain a method to identify the trophic links between compartments. Diet composition matrices were estimated through the combination of a probability of encounter for each food type and a specific probability of ingestion related to the food size selectivity and other food quality characteristics (e.g., morphology and nutritional quality). The feasibility of this approach has been illustrated through data of size-structured communities extracted from the literature including different planktonic predator guilds (nanoflagellates, cladoceran-dominated zooplankton and copepod-dominated zooplankton) in a high mountain lake (La Caldera, Spain), two subtropical wetland lakes (meso-oligotrophic Laguna Galarza and eutrophic Laguna Iberá, Argentina) and a marine microcosm (Alborán Sea, Mediterranean). The identification of “who eats whom” and “by how much” also allows for more accurate analyses of the trophic control in the BSS. Extensive analyses of the balance between top-down and bottom-up controls were developed for the feeding interactions of the study cases. 相似文献