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991.
Jean E. Weber Chester C. Kisiel Lucien Ducksteiri 《Journal of the American Water Resources Association》1973,9(6):1075-1088
ABSTRACT: Many difficulties exist in the matching of models with data. This paper identifies elements of this problem and discusses considerations involved in model evaluation. The well known multivariate linear regression model is used to illustrate the distinctions between accuracy and precision and between estimation and prediction (because the model is commonly misused.) No amount of additional data will improve the accuracy of a poor model. A high R2, while indicative of a good matching between the observed data and model estimates, is a poor criterion for judging adequacy of the model to make good predictions of future events. Model evaluation also includes the problem of introducing secondary data and proxy variables into a model. Secondary data frequently enter, for example, the mass, energy and water budget equations because of difficulties in measuring the primary variables. Proxy variables arise because of a desire to collapse a vector of incomparable values, say, of water quality into a single number. Review of the above issues indicates that model evaluation is a multi-criterion problem, often imbedded in a larger framework where models are intended to meet multiple objectives. The mismatch of models and data has increasing legal and social consequences. 相似文献
992.
PROBLEM: Accidents involving temporary access systems, particularly temporary scaffolds, account for a large proportion of injuries in the construction industry worldwide. METHOD: This paper outlines the development of a prototype decision aid (SCAFPASS, an abbreviation for Scaffold Planning Aid for System Safety) to promote access scaffold safety. It was guided by an examination of the root-causes and management deficiencies apparent in: (a) paper-based files of 186 access-related incidents held by the Health and Safety Executive (HSE) in the UK; and (b) computer-based files of 2,910 incidents appearing in the HSE database between 1997 to 2000. RESULTS: The more frequent root-causes included the fitting of defective components, unauthorized modification of the structure, omission of barriers, and errors resulting in simple, readily detectable structural faults. Common managerial deficiencies included failure to control risk, unsafe methods and procedures, and inadequate training and supervision. IMPACT ON INDUSTRY: SCAFPASS aims to avoid these root-causes by improving safety management from the outset and throughout all phases of a project. 相似文献
993.
Paolo Fiorucci Riccardo Minciardi Michela Robba Roberto Sacile 《Resources, Conservation and Recycling》2003,37(4):301-328
A decision support system (DSS) developed to assist the planner in decisions concerning the overall management of solid waste at a municipal scale is described. The DSS allows to plan the optimal number of landfills and treatment plants, and to determine the optimal quantities and the characteristics of the refuse that has to be sent to treatment plants, to landfills and to recycling. The application of the DSS is based on the solution of a constrained non-linear optimization problem. Various classes of constraints have been introduced in the problem formulation, taking into account the regulations about the minimum requirements for recycling, incineration process requirements, sanitary landfill conservation, and mass balance. The cost function to be minimized includes recycling, transportation and maintenance costs. The DSS has been tested on the municipality of Genova, Italy, and the results obtained are presented. 相似文献
994.
Jianbiao Lu Ge Sun Steven G. McNulty Devendra M. Amatya 《Journal of the American Water Resources Association》2003,39(4):886-896
ABSTRACT: About 50 to 80 percent of precipitation in the southeastern United States returns to the atmosphere by evapotranspiration. As evapotranspiration is a major component in the forest water balances, accurately quantifying it is critical to predicting the effects of forest management and global change on water, sediment, and nutrient yield from forested watersheds. However, direct measurement of forest evapotranspiration on a large basin or a regional scale is not possible. The objectives of this study were to develop an empirical model to estimate long‐term annual actual evapotranspiration (ART) for forested watersheds and to quantify spatial AET patterns across the southeast. A geographic information system (GIS) database including land cover, daily streamflow, and climate was developed using long term experimental and monitoring data from 39 forested watersheds across the region. Using the stepwise selection method implemented in a statistical modeling package, a long term annual AET model was constructed. The final multivariate linear model includes four independent variables—annual precipitation, watershed latitude, watershed elevation, and percentage of forest coverage. The model has an adjusted R2 of 0.794 and is sufficient to predict long term annual ART for forested watersheds across the southeastern United States. The model developed by this study may be used to examine the spatial variability of water availability, estimate annual water loss from mesoscale watersheds, and project potential water yield change due to forest cover change. 相似文献
995.
996.
将农业气象灾害的防灾减灾成果与智能化的计算机系统相结合,建立了东北地区低温冷害防御决策支持系统的概念模型,以提高灾害决策分析水平.概述了概念模型的基本结构,介绍了其数据库、知识库和模型库的组成,以及基于这三大库结构的查询分析功能和对低温冷害发生可能性的预测防御功能,最后对今后防灾减灾智能化的决策系统的发展进行了讨论. 相似文献
997.
The Influence of Atmospheric N Deposition on Nitrous Oxide and Nitric Oxide Fluxes and Soil Ammonium and Nitrate Concentrations 总被引:2,自引:0,他引:2
U. Skiba C. Pitcairn L. Sheppard V. Kennedy D. Fowler 《Water, Air, & Soil Pollution: Focus》2004,4(6):37-43
The deposition of atmospheric N to soils provides sources of available N to the nitrifying and denitrifying microbial community and subsequently influences the rate of NO and N2O emissions from soil. We have investigated the influence of three different sources of enhanced N deposition on NO and N2O emissions 1) elevated NH3 deposition to woodlands downwind of poultry and pig farms, 2) increased wet cloud and occult N deposition to upland forest and moorland and 3) enhanced N deposition to trees as NO
3
–
and NH
4
+
aerosol. Flux measurements of NO and N2O were made using static chambers in the field or intact and repacked soil cores in the laboratory and determination of N2O by gas chromatography and of NO by chemiluminescence analysis. Rates of N deposition to our study sites were derived from modelled estimates of N deposition, NH3 concentrations measured by passive diffusion and inference from measurements of the 210Pb inventory of soils under tree canopies compared with open grassland. NO and N2O emissions and KCl-extractable soil NH
4
+
and NO
3
–
concentrations all increased with increasing N deposition rate. The extent of increase did not appear to be influenced by the chemical form of the N deposited. Systems dominated by dry-deposited NH3 downwind of intensive livestock farms or wet-deposited NH
4
+
and NO
3
–
in the upland regions of Britain resulted in approximately the same linear response. Emissions of NO and N2O from these soils increased with both N deposition and KCl extractable NH
4
+
, but the relationship between NH
4
+
and N deposition (ln NH
4
+
= 0.62 ln Ndeposition + 0.21, r
2 = 0.33, n = 43) was more robust than the relationship between N deposition and soil NO and N2O fluxes. 相似文献
998.
In 1990 the Environmental Protection Agency (EPA) began sponsoring several pilot projects in its regional offices to examine
the potential benefits of adopting a multimedia approach to facility management. This approach differs from traditional practices
at EPA in that facilities (dischargers regulated under permits issued by the agency) are managed based upon their cumulative
impacts to all media: air, water, and land. Currently, facilities are managed by separate programs at EPA that evaluate environmental
impacts from a single-media perspective.
One aspect of discharger management is the necessity to allocate limited financial resources in a way that will minimize risk
to human health and the environment. A careful, risk-based prioritization of facilities is one means of providing insight
to the most effective strategy of allocating monitoring, inspection, and enforcement resources. Prioritization from a multimedia
perspective is particularly difficult, however, since it requires translation and integration of medium-specific facility
performances, management objectives, and perceptions of risk into a cumulative rating.
A computerized decision support system (DSS) designed to guide management through the prioritization process from a multimedia
perspective was identified as a potentially valuable tool for use in the pilot projects. This article describes the development
of such a prototype, outlines the features of the completed system, and discusses its potential for use at EPA. 相似文献
999.
K C. Gan T A. McMahon I. C. O'Neill 《Journal of the American Water Resources Association》1990,26(3):443-450
ABSTRACT: For a set of 81 catchments in southeast Victoria, Australia, predictive equations were developed by least squares regression of the mean and coefficient of variation of annual Streamflow against a variety of rainfall and physiographic parameters. The data were also divided into subsets according to catchment size, subregion, or record length of investigate if the relationships differed significantly between subsets. Only the catchment area and some rainfall statistical parameters were found to be significant. Streamflow parameters predicted by the regression equations were used to estimate storage requirements in ungauged catchments. The influence of errors in the Streamflow parameters on the storage error was examined. 相似文献
1000.
Ecological limitations and appropriation of ecosystem support by shrimp farming in Colombia 总被引:4,自引:0,他引:4
Shrimp farming in mangrove areas has grown dramatically in Asia and Latin America over the past decade. As a result, demand
for resources required for farming, such as feed, seed, and clean water, has increased substantially. This study focuses on
semiintensive shrimp culture as practiced on the Caribbean coast of Colombia. We estimated the spatial ecosystem support that
is required to produce the food inputs, nursery areas, and clean water to the shrimp farms, as well as to process wastes.
We also made an estimate of the natural and human-made resources necessary to run a typical semiintensive shrimp farm. The
results show that a semiintensive shrimp farm needs a spatial ecosystem support—the ecological footprint—that is 35–190 times
larger than the surface area of the farm. A typical such shrimp farm appropriates about 295 J of ecological work for each
joule of edible shrimp protein produced. The corresponding figure for industrial energy is 40:1. More than 80% of the ecological
primary production required to feed the shrimps is derived from external ecosystems. In 1990 an area of 874–2300 km2 of mangrove was required to supply shrimp postlarvae to the farms in Colombia, corresponding to a total area equivalent to
about 20–50% of the country’s total mangrove area. The results were compared with similar estimates for other food production
systems, particularly aquacultural ones. The comparison indicates that shrimp farming ranks as one of the most resource-intensive
food production systems, characterizing it as an ecologically unsustainable throughput system. Based on the results, we discuss
local, national, and regional appropriation of ecological support by the semiintensive shrimp farms. Suggestions are made
for how shrimp farming could be transformed into a food production system that is less environmentally degrading and less
dependent on external support areas. 相似文献