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951.
Blocksom KA 《Environmental management》2003,31(5):0670-0682
When biological metrics are combined into a multimetric index for bioassessment purposes, individual metrics must be scored
as unitless numbers to be combined into a single index value. Among different multimetric indices, methods of scoring metrics
may vary widely in the type of scaling used and the way in which metric expectations are established. These differences among
scoring methods may influence the performance characteristics of the final index that is created by summing individual metric
scores. The Macroinvertebrate Biotic Integrity Index (MBII), a multimetric index, was developed previously for first through
third order streams in the Mid-Atlantic highlands of the United States. In this study, six metric scoring methods were evaluated
for the MBII using measures related to site condition and index variability, including the degree of overlap between impaired
and reference distributions, relationships to a stressor gradient, within-sample index variability, temporal variability,
and the minimum detectable difference. Measures of index variability were affected to a greater degree than those of index
responsiveness by both the type of scaling (discrete or continuous) and the method of setting expectations. A scoring method
using continuous scaling and setting metric expectations using the 95th percentile of the entire distribution of sites performed
the best overall for the MBII. These results showed that the method of scoring metrics affects the properties of the final
index, particularly variability, and should be examined in developing a multimetric index because these properties can affect
the number of condition classes (e.g., unimpaired, impaired) an index can distinguish. 相似文献
952.
Age differences in safety attitudes and safety performance in Hong Kong construction workers 总被引:1,自引:0,他引:1
PROBLEM: Safety in the construction industry is a major issue in Hong Kong, representing about 46% of all occupational injuries in 1998. This study explored linear and curvilinear relations between age and safety performance (accident rates and occupational injuries), as well as safety attitudes, in construction workers in Hong Kong. METHOD: A Chinese version of the Safety Attitude Questionnaire (SAQ by Donald & Canter) was developed and administered to a sample of Chinese construction workers (N=374, 366 males, 8 females) from 27 construction sites. RESULTS: Accident rates were not related to age. Occupational injuries were related to age in a curvilinear manner, with injuries at first increasing with age, then decreasing. Two safety attitude scales were related to age with older workers exhibiting more positive attitudes to safety. If age and tenure are controlled, some attitude scales are predictors of safety performance. IMPACT ON INDUSTRY: Management/supervisors, team leaders, and workers are all responsible for safety, and any negative bias toward older construction workers is unfounded. 相似文献
953.
详细介绍了战斗机飞行员新型YM9915加压供氧面罩和TK - 11飞行保护头盔配套的高空供氧防护性能生理评价实验结果。分析讨论了新型加压供氧面罩与飞行保护头盔配套的供氧防护性能特点 ,并针对其不足提出改进建议 相似文献
954.
活性粉末混凝土 (ReactivePowderConcrete ,简称RPC)是一种具有超高性能和超高强度的水泥基复合材料。本文首先论述了这一材料应用于结构抗震领域中的潜力 ,然后通过 4个小比例RPC矩形截面柱的拟静力试验 ,研究了RPC配筋柱的延性性能、滞回曲线及其破坏机理 ,分析了配箍率对RPC配筋柱延性的影响。 相似文献
955.
物流配送中心防火设计初探 总被引:1,自引:0,他引:1
系统分析了物流配送中心防火设计所面临的问题,讨论了如何利用性能化的方法来研究配送中心的防火设计,提出了配送中心防火设计的相关对策. 相似文献
956.
ABSTRACT: The performance of a hydrological model is usually assessed first by visual inspection of the measured and computed hydrographs. Numerous statistical criteria are available for numerical evaluations of model accuracy in each single year, in a particular season of the year, or in a sequence of years or seasons. In the last case, the problem of computing the overall result has to be considered. If too many criteria are used and the criteria are switched frequently, an assessment of a model's performance becomes difficult for a potential user. Therefore, this paper concentrates on just three criteria and their combined evaluation: The Nash-Sutcliffe coefficient, which compares the model computed discharge with the average measured discharge; the “coefficient of gain from daily means” in which a uniform average discharge is replaced by daily average discharges; and the volumetric difference between the total measured and computed runoff. The three criteria are combined in a three dimensional representation that allows intercomparisons of model performance in a single diagram. 相似文献
957.
Using data from a study conducted in the Cranberry Wilderness Area of West Virginia, United States, this paper describes how
a modified importance—performance approach can be used to prioritize wilderness indicators and determine how much change from
the pristine is acceptable. The approach uses two key types of information: (1) indicator importance, or visitor opinion as
to which wilderness indicators have the greatest influence on their experience, and (2) management performance, or the extent
to which actual indicator conditions exceed or are within visitor expectations. Performance was represented by calculating
indicator performance estimates (IPEs), as defined by standardized differences between actual conditions and visitor preferences
for each indicator. The results for each indicator are then presented graphically on a four-quadrant matrix for objective
interpretation. Each quadrant represents a management response: keep up the good work, concentrate here, low priority, or
possible overkill. The technique allows managers to more systematically and effectively utilize information routinely collected
during the limits of acceptable change wilderness planning process.
This paper is submitted with the approval of the Director of the West Virginia Agricultural and Forestry Experiment Station
as Scientific Article No. 541. The study was funded in part, through a grant from the USDA Forest Service, Monongahela National
Forest. 相似文献
958.
David Seckler R. K. Sampath S. K. Raheja 《Journal of the American Water Resources Association》1988,24(4):855-860
ABSTRACT: This paper presents a statistically valid index for measuring the performance of irrigation systems. The index is applied to a sample of 39 farms on a watercourse under the warabandi system of irrigation management in India. It is found that while the farmers in fact irrigated almost exactly the total amount of irrigated area as designed, inter-farm variations were considerable. The index shows that the degree of error of managerial effectiveness of irrigation on this watercourse is 20 percent. Therefore it is concluded that the system is performing at 80 percent effectiveness. 相似文献
959.
针对提速后的小唐河大桥,运用动力检测方法,对其梁跨中的动挠度、横向振幅、横向及竖向加速度、振动频率,梁端横向振幅,墩顶横向振幅、加速度、振动频率,桥墩基础顶(承台顶)横向振幅等进行了测量。根据测量的结果对其进行安全性评价,评价结果表明:提速条件下各跨梁体的最大横向振幅均不满足规范的要求,墩顶、桥墩横向振幅值较大,承台顶的横向振幅也偏大,梁墩体系横向自振频率低,而各墩墩顶和梁体跨中的横向加速度值、梁体跨中竖向振动加速度值仍能满足规范的要求;梁跨具有足够的竖向刚度。根据评价的结果对小唐河大桥的加固提出了建议。 相似文献
960.
本文从生态安全角度提出了矿产资源开发应遵循可持续发展的理念,并结合外部性理论,运用生态足迹和生态演替理论模型量化矿产资源开发外部性最优化时的生态承载力关系,通过对湖南湘西州钒矿开采区进行实证研究,推导出湘西州钒矿开发外部性最优条件下的生态承载力平衡等式以及开矿条件,即同时达到社会经济效益和环境保护最优化的条件。该研究可为探讨实现矿产资源开发外部性最优化的路径提供借鉴。 相似文献