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81.
Results of a fault test performed in the unsaturated zone of Yucca Mountain, Nevada, were analyzed using a three-dimensional numerical model. The fault was explicitly represented as a discrete feature and the surrounding rock was treated as a dual-continuum (fracture-matrix) system. Model calibration against seepage and water-travel-velocity data suggests that lithophysal cavities connected to fractures can considerably enhance the effective fracture porosity and therefore retard water flow in fractures. Comparisons between simulation results and tracer concentration data also indicate that matrix diffusion is an important mechanism for solute transport in unsaturated fractured rock. We found that an increased fault-matrix and fracture-matrix interface areas were needed to match the observed tracer data, which is consistent with previous studies. The study results suggest that the current site-scale model for the unsaturated zone of Yucca Mountain may underestimate radionuclide transport time within the unsaturated zone, because an increased fracture-matrix interface area and the increased effective fracture porosity arising from lithophysal cavities are not considered in the current site-scale model. 相似文献
82.
胶带输送机运输事故树可靠性的计算机模拟 总被引:3,自引:2,他引:1
以胶带输送机运输事故树的计算机模拟过程为例 ,介绍了对事故树可靠性进行计算机模拟的原理、算法以及程序运行步骤 ,编制了模拟程序。用笔者提出的理论、方法及模拟程序 ,对平顶山煤业集团一矿胶带输送机运输事故进行了事故树分析与求解 ,同时将模拟程序运行结果与最小割集法求得的理论值进行了对比 ,计算结果误差小 ,所得结论准确可靠 ,为类似事故的模拟分析提供了一种新的方法和途径 相似文献
83.
铁路安全预警系统的研究和实现 总被引:4,自引:2,他引:2
结合哈尔滨铁路局实际运营系统 ,基于事故树分析理论 ,探讨了铁路安全预警系统的实现。首先论述了事故树的建立方法和以事故树分析法为基础的铁路安全预警系统的核心算法 ,然后讨论了具体实现的数据结构和事故树编码方法 ,最后简要提出了铁路安全预警系统的系统设计思想 相似文献
84.
Summary. Detection of heterospecific predators and prey
via chemical cues is well known, but only a few studies have
examined the potential for such discrimination in cannibalistic
systems. In newts, Notophthalmus viridescens, adults are
opportunistic predators of conspecific larvae. I used a laboratory
bioassay to determine whether larvae and adults distinguish
between chemical stimuli from members of the
different age classes. Larvae distinguished between chemical
stimuli from larvae and adults by decreasing their activity
only following exposure to stimuli from adults. Decreased
activity is consistent with an antipredator response in many
prey species, including larval newts. In contrast, adults
increased their activity and increased time spent in open
areas in response to stimuli from larvae, but not to stimuli
from adults. Increased activity is consistent with a feeding
response; adults also showed increased activity and
increased time in open areas in response to chemical stimuli
from familiar heterospecific prey (brine shrimp). The proximate
cue that allowed the newts to distinguish between the
different age classes is not associated with short-term
dietary differences because all stimulus animals were fed the
same prey. Stimulus strength was controlled by diluting the
stimulus solutions according to the volume of the stimulus
animal. Therefore, there appear to be intrinsic differences in
the chemical signatures of larval and adult newts. 相似文献
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Roy W. Koch Thomas G. Sanders H. J. Morel-Seytoux 《Journal of the American Water Resources Association》1982,18(5):815-821
ABSTRACT: The detection of change in a hydrologic varaible, particularly water quality, is a current problem. A method is presented for testing whether there has been a shift in the mean of a hydrologic variable based on the well established bivariate normal distribution theory. In this technique, the dependent, or target, and the independent, or control, variables are formed as weighted linear combinations of the mean values at a number of locations in a selected target and control area. The weighting factors are determined based on a mathematical programming technique which minimizes the conditional coefficient of variation thereby minimizing the number of observations required to detect a change of a preselected magnitude in the mean of the target area. The result is a situation where a savings in the number of observations required to detect a change is a consequence of adding more stations: the space-time tradeoff. Two applications of the technique are presented, the first using electrical conductivity (EC) data from two sets of river basins and the second using EC data from a set of basins as the target variable and annual discharge as the control. The results indicate that a significant savings in time can be achieved by using this method. 相似文献
88.
Summary. We investigated the hypothesis that aggregation signals produced by male webbing clothes moths (WCM), Tineola bisselliella (Hum.) (Lepidoptera: Tineidae), and close-range male attractant signals produced by females have a pheromonal basis, at least
in part. Gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses of bioactive methanolic
extracts of male WCM disclosed three candidate pheromone components: hexadecanoic acid methyl ester (16:Ester), (Z)-9-hexadecenoic acid methyl ester (Z9—16:Ester), and octadecanoic acid methyl ester (18:Ester). In bioassay experiments in a large Plexiglas™ arena, a blend of
synthetic 16:Ester plus Z9—16:Ester was attractive to male and virgin (but not mated) female WCM; the 18:Ester was inactive.
GC-EAD analyses of pheromone gland extracts from female WCM revealed (E,Z)-2,13-octadecadienal (E2Z13—18:Ald) and (E,Z)-2,13-octadecadienol (E2Z13—18:OH) as candidate sex pheromone components. In arena bioassay experiments, 1—5 female equivalents of synthetic E2Z13—18:Ald (0.2 ng) and E2Z13—18:OH (0.1 ng) were more attractive to male WCM than were two virgin female WCM. We anticipate that the combination of
aggregation and sex pheromones, male-produced sonic aggregation signals, and habitat-derived semiochemicals will be highly
effective in attracting male and female WCM to commercial traps.
Received 12 January 2001; accepted 8 June 2001. 相似文献
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