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581.
模糊回归分析和数据融合方法 总被引:8,自引:2,他引:8
傅惠民 《中国安全科学学报》2002,12(6):73-76
提出一种新的模糊回归分析和数据融合方法 ,该方法能够将多种不同条件 (不同仪器、人员、环境条件等 )下的测量数据进行融合 ,特别是可以将不同量纲的测量值进行数据融合。实际应用表明 ,模糊回归分析能够很好地消除工程测量中无法通过仪器校准的系统误差 ,数据融合方法可以减小其偶然误差 ,大大提高测量精度 相似文献
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根据语言测试的发展历程,指出了语言测试在外语教学过程中发挥的作用。当前高职英语测试存在学期测试与等级测试脱节、测试模式陈旧、形式单一、等级测试题型死板等问题。结合高职英语教学现状和学生素质水平,对高职英语的常规测试模式提出改革,构建了形成性评价与终结性评价相结合、重技能、寓考于乐的高职英语的新测试体系。 相似文献
584.
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承德市室内环境质量污染现状调查与研究 总被引:1,自引:1,他引:0
对承德市160家宾馆、饭店、歌舞厅等公共场所,80个民用建筑工程项目,80余家个人家庭装修进行室内环境检测,发现不同场所室内主要超标污染物不同。新建公共场所和个人家装室内空气主要污染物为总挥发性有机物、甲醛、苯、氨,已建成的重点公共场所空气超标污染物主要为二氧化碳、菌落总数,民用建筑工程超标污染物主要为氨。 相似文献
586.
Partial stroke testing of process shutdown valves: How to determine the test coverage 总被引:1,自引:0,他引:1
Mary Ann Lundteigen Marvin Rausand 《Journal of Loss Prevention in the Process Industries》2008,21(6):579-588
Partial stroke testing (PST) has recently been introduced as a semi-automatic means to test process shutdown valves. Normally, this type of testing does not disturb the process and can detect many of the failures that traditionally have been revealed only by functional testing. The fraction of all dangerous failures that are detected by PST is called the PST coverage and is decisive for the effectiveness of the PST. So far, limited guidance on how to determine the PST coverage has been given. This paper discusses the application and limitations of PST and suggests a new procedure for how to determine the PST coverage factor. 相似文献
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Kocí V Ocelka T Dragoun D Vit M Grabic R Sváb M 《Environmental science and pollution research international》2007,14(2):94-101
Background, Aim and Scope
The article is focused on dioxin, furan, PCB and organochlorine pesticide monitoring in the surface waters of the Central
European, protected natural reserve Krivoklatsko, under the UNESCO programme Man and Biosphere. Persistent compounds are presently
transported via different means throughout the entire world. This contamination varies significantly between sites. This raises
the question of what constitutes the naturally occurring background levels of POPs in natural, unpolluted areas, but which
are close to industrialised regions. Information of real background POP contamination can be of high value for risk assessment
management of those sites evidently polluted and for the defining of de-contamination limits.
Preserved areas should not be seen as isolated regions in which the impacts of human activities and natural factors are either
unexpected or overlooked. Every ambient region, even those protected by a law or other means, are still closely connected
to neighbouring human developed and impacted areas, and are therefore subject to this anthropogenic contamination. These areas
adjacent to natural reserves are sources of diverse substances, via entry of air, water, soil and/or biota. After an extended
period of industrial activities, organochlorine pollutants, even those emitted in trace concentrations have reached detectable
levels. For future research and for the assessment of environmental changes, present levels of contamination would be of high
importance. This work publishes data of the contamination with organochlorine pollutants of this natural region, where biodiversity
and ecological functions are of the highest order.
Materials and Methods:
Semipermeable membrane devices (SPMDs) were utilised as the sampling system. SPMDs were deployed in two small creeks and one
water reservoir selected in the central part of the Krivoklatsko Natural Reserve, where it could be expected that any possible
contamination by POPs would be lowest. The exposed SPMDs were analysed both for chemical contents of POPs and for toxicity
properties. The chemical analyses of dibenzo-dioxins, dibenzo-furans, PCBs and OCPs were analysed by GC/MS/MS on GCQ or PolarisQ
(Thermoquest). Toxicity bioassays were performed on the alga Desmodesmus subspicatus, bacteria Vibrio fischeri and crustacean
Daphnia magna. All toxicity data were expressed as the effective volume Vtox. Vtox is a toxicity parameter, the determination
of which is independent of SPMD deployment time and pre-treatment dilution (unlike, for example, the EC50 of the SPMD extract).
Results:
The following chemical parameters were monitored: 1) tetra, penta, hexa and hepta dibenzo-p-dioxins and furans; 2) all those
detectable from tri- through deca-polychloriated biphenyls (PCBs) and 3) a group of organochlorine pesticides: hexachlorobenzene
and isomers of hexachlorocyclohexane, DDE, DDD and DDT. The concentrations of dioxins and furans on the assessed sites varied
from under detection levels up to 7 pg.l-1; PCBs were detected in a sum concentration up to 2.8 ng.l-1; and organochlorine
pesticides up to 346 pg.l-1. The responses of bioassays used were very low, with the values obtained for Vtox being under
0.03 l/d.
Discussion:
Toxicity testing showed no toxicity responses, demonstrating that the system used is in coherence with the ecological status
of the assessed sites. Values of Vtox were under the critical value – showing no toxicity. The PCA of chemical analysis data
and toxicity responses resulted in no correlations between these two groups of parameters. This demonstrated that the present
level of contamination has had no direct adverse effects on the biota.
Conclusions:
The concentration values of six EPA-listed, toxic dioxins and sums of tetra-hepta dioxins; nine EPA toxic dibenzofurans and
the sums of tetra-hepta bibenzofurans are presented together with all tri-deka PCBs and organochlorine pesticides (alfa-,
beta-, gama-, delta-HCH, HCB, opDDE, ppDDE, opDDD, ppDDD, opDDT, ppDDT). These values represent possible current regional
natural background values of these substances monitored within the Central European region, with no recorded adverse effects
on the freshwater ecosystem (up until the present time).
Recommendations and Perspectives:
Assessment of dioxins, furans and other organochlorine compounds within natural reserves can be important for the monitoring
of human-induced impacts on preserved areas. No systematic monitoring of these substances in areas not directly affected by
industry has generally been realised. There is a paucity of data of the presence of any of these substances within natural
regions. Further monitoring of contamination of both soil and biota by dioxins and furans in preserve regions is needed and
can be used for future monitoring of man-made activities and/or accidents.
Semipermeable membrane devices proved to be a very good sampling system for the monitoring of trace concentrations of ambient
organochlorine compounds. Toxicity evaluation using the Vtox concept demonstrated that those localities assessed expressed
no toxicity. 相似文献
590.