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排序方式: 共有546条查询结果,搜索用时 15 毫秒
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Michael Adam Steve Comfort Daniel Snow David Cassada Matthew Morley Wilson Clayton 《Canadian Metallurgical Quarterly》2006,132(12):1580-1588
Years of wastewater discharge at the Department of Energy’s Pantex Plant have contaminated the vadose zone and underlying perched aquifer with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone (27?mg?L?1; 150?mL?min?1) was effective in mineralizing 80% of the RDX (30?mg?RDX?L?1) provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 day and >80% within 7 day. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35 versus <0.3% cumulative mineralization). These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex facility. 相似文献
3.
本文介绍6例在苏联切尔诺贝利核电站事故期间受到放射性铯内污染的我国驻外人员,在本实验室接受活体测量和服用普鲁士蓝促排的观察结果。6例内污染者分两组分别于受污染后的第114天和第272天开始用药,在大约一个月期间,每人共服药54g(给药方式:每次服1g,每日3次,6天为一个疗程,间隔6天,共用药3个疗程)。观测结果表明,在促排期间,6例内污染者体内铯的生物半排期均明显缩短,~(131)Cs 的生物半排期由对照期(用药前)的54—123d 缩短到28—65d,~(134)Cs 由对照期的42—117d 缩短到23—69d;6例体内放射性铯的累积活度相对于同期未用药条件下的累积活度减少2—21%。 相似文献
4.
滑阀污染敏感尺寸的确定 总被引:1,自引:0,他引:1
本文根据滑阀运动副发生污染卡紧与污染磨损的污染物尺寸条件,给出了滑阀污染敏感尺寸范围。试验结果很好地证明理论分析的正确性。这对于确定液压系统中滑阀所需要的过滤精度具有重要价值。 相似文献
5.
Bilayer SiO2 Nanorod Arrays as Omnidirectional and Thermally Stable Antireflective Coating
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Sadaf B. Khan Hui Wu Jianghao Li Limin Chen Zhengjun Zhang 《Advanced Engineering Materials》2018,20(5)
6.
Treatment of lead-contaminated material focuses on the reduction of leached lead concentrations in laboratory leaching tests. There has been little study on the chemical stability of treated materials after waste disposal. To investigate the effects of weathering on several solidification/stabilization chemistries, lead-contaminated soil was treated with various agents (cement, phosphates, dithiocarbamate, calcium hydroxide, calcium carbonate, and metallic iron) and subjected to natural weathering for one year. Lead concentrations and pH values in field percolates and leachates from toxicity characteristic leaching procedure (TCLP) and water leaching tests were used to evaluate changes in the treatment effectiveness. Weathering altered the treatment chemistry of several additives—alkaline additives were neutralized, while reduced additives were oxidized. Lead concentrations in field percolates from the untreated soil were around 1.0?mg/L, and did not vary over one year of weathering time. After one year of weathering, lead concentrations in field percolates from most samples were reduced to low levels (<0.15 mg/L). Weathering also affected lead concentrations in the TCLP and water leach test leachates from the treated wastes. Treated wastes in which the alkaline additives were neutralized or reduced additives oxidized gave higher TCLP lead concentrations after weathering than before, in contrast to the decreasing lead concentrations in the field percolates. Water leaching tests on the alkaline treated wastes had lower lead concentrations after weathering than before. 相似文献
7.
8.
As the demand for large capacity storage drives has increased, the flying height of near-field recording (NFR) sliders becomes
as small as 100 nm for super high storage density. Accordingly contamination problems have been a concern of information storage
industry because it may cause a serious damage to solid immersion lens (SIL) of optical flying head. Sub-micro contaminants
in air bearing of the NFR slider may affect the flyability and stability of the optical slider. In addition, the cleaning
of small particles becomes more difficult as the contaminant particle size decreases because the adhesion force increases
very much as the particle size decreases. Recently developed high-frequency ultrasonic (megasonic) cleaning technique have
made it possible to remove sub-micron particles less than 100 nm without surface erosion and many remarkable results have
been reported. In this paper, the megasonic technique is applied and tested for the cleaning of the flying head of NFR drive.
1 MHz ultrasound with maximum 100 W was used to remove polystyrene latex (PSL) particles and alumina particles deposited on
the surface of the slider. Effective cleaning performance was observed without any damages on the slider surface using optical
microscope and AFM at different ultrasonic energy levels and cleaning times.
Received: 20 June 2002 / Accepted: 9 September 2002 相似文献
9.
Minimizing the spread of infections is a challenging problem, and it is the subject matter in many different fields such as epidemiology and cyber-security. In this paper, we investigate link removal as an intervention strategy and study the relative effectiveness of different link removal methods in minimizing the spread of infections in a network. With that in mind, we develop four connectivity-based network interdiction models and formulate these models as mixed integer linear programs. The first model minimizes the number of connections between infected and susceptible nodes; the second the number of susceptible nodes having one or more connections with infected nodes; the third the total number of paths between infected and susceptible nodes; and the fourth the total weight of the paths between infected and susceptible nodes. We also propose heuristic algorithms to solve the models. The network interdiction models act as link removal methods, i.e., each return a solution consisting of a set of links to remove in the network. We compare the effectiveness of these four methods with the effectiveness of an existing link removal method [25], a method based on link betweenness centrality [18], and random link removal method. Our results show that complete isolation of susceptible nodes from infected nodes is the most effective method in reducing the average number of new infections (reduce occurrence) under most scenarios, and the relative effectiveness of the complete isolation method increases with transmission probability. In contrast, removing the highest probability transmission paths is the most effective method in increasing the average time to infect half of the susceptible nodes (reduce speed) under most scenarios, and the relative effectiveness of this method decreases with transmission probability. 相似文献
10.
M. Villalobos C. Merino-Sánchez J. Grieshop M.A. Handley 《The Science of the total environment》2009,407(8):2836-2844
An interdisciplinary investigation, involving environmental geochemists, epidemiologists, nurses, and anthropologists, was undertaken to determine the contamination source and pathway of an on-going outbreak of lead poisoning among migrants originating from Zimatlán, Oaxaca, Mexico and living in Seaside, California, and among their US-born children. An initial investigation in Seaside identified grasshopper foodstuff (“chapulines”) imported from Mexico and consumed as snacks, as containing alarmingly high lead concentrations (up to 2300 mg/kg). The focus in the present work concentrates on the Oaxacan area of origin of the problem in Mexico, and two potential sources of contamination were investigated: wind-borne dusts from existing mine residues as potential contaminants of soil, plant, and fauna; and food preparation practices using lead-glazed ceramic cookware.Over a three year period, sampling was conducted in Oaxaca using community-level sampling and also targeted sampling with families of cases with lead poisoning in California. In addition to fresh field chapulines, we analyzed for total lead: soil, water, mine residues, and plant materials, both from areas adjacent to or at an abandoned waste site containing mine tailings, and from fields where chapulines are collected; foodstuffs gathered in community markets or in a food transport business; and foodstuffs and cookware gathered from relatives of case families in California. Also, selected new and used lead-glazed clay cookware was extracted for lead, using 0.02 M citric acid and with 4% acetic acid.The results indicated significant presence of lead in mine wastes, in specific foodstuffs, and in glazed cookware, but no extensive soil contamination was identified. In-situ experiments demonstrated that lead incorporation in food is made very efficient through grinding of spices in glazed cookware, with the combination of a harsh mechanical action and the frequent presence of acidic lime juice, but without heating, resulting in high but variable levels of contamination. 相似文献