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951.
烟草行业的火灾特点及其监测方法的讨论 总被引:1,自引:0,他引:1
烟厂是火灾危险性较大的部门,加强其火灾的早期探测报警是防止火灾发生、减少火灾损失的重要方面。本文对烟厂中各主要生产环节的火灾特点作了分析,指出应针对各部分的特殊性采取适当的火灾探测方法并对现在常用的一些火灾探测技术在烟厂中的适用性作了讨论,认为现有的光束式火灾探测器较适用于内部空间较大的烟厂仓库和厂房。对安装了电视监控系统的企业,建议将其与计算机图象分析技术相结合,增加其防火监视功能。 相似文献
952.
953.
Sheryl Luzzadder-Beach 《Environmental management》1995,19(3):383-392
What size sample is sufficient for spatially sampling ambient groundwater quality? Water quality data are only as spatially accurate as the geographic sampling strategies used to collect them. This research used sequential sampling and regression analysis to evaluate groundwater quality spatial sampling policy changes proposed by California's Department of Water Resources. Iterative or sequential sampling of a hypothetical groundwater basin's water quality produced data sets from sample sizes ranging from 2.8% to 95% coverage of available point sample sites. Contour maps based on these sample data sets were compared to an original (control), mapped hypothetical data set, to determine at which point map information content and pattern portrayal are not improved by increasing sample sizes. Comparing series of contour maps of ground water quality concentration is a common means of evaluating the geographic extent of groundwater quality change. Comparisons included visual inspection of contout maps and statistical tests on digital versions of these map files, including correlation and regression products. This research demonstrated that, down to about 15% sample site coverage, there is no difference between contour maps produced from the different sampling strategies and the contout map of the original data set. 相似文献
954.
A hierarchical approach to fisheries planning and modeling in the Columbia River Basin 总被引:1,自引:0,他引:1
The Columbia River Basin is the scene of a massive effort to restore populations of Pacific salmon (Oncorhynchus spp.) and steelhead (O. mykiss). Efficient restoration is confounded by a high level of complexity, competing sociopolitical goals and values, and uncertainty
about key system properties. Simulation models and other tools of systems analysis are important to development of a comprehensive,
regionally acceptable strategy. Hierarchy theory provides a useful paradigm for organized complexity within the Columbia Basin
and the basis for a trilevel hierarchical structure for organizing and integrating models. Life-stage models compose the most
basic simulation units at the lowest level in the proposed hierarchical modeling structure. Each life-stage model simulates
a distinct period in the life cycle of anadromous salmonids. Population models at the intermediate level simulate the complete
life cycles of salmon and steelhead populations. At the highest level in the hierarchy, interpopulation models simulate extensive,
long-term processes that affect multiple species and stocks. A hierarchical system of models is preferable to a single model
or to a group of models lacking formal structure. A principal advantage is that models have the correct spatial and temporal
resolution for analyzing questions at different scales. A hierarchical structure also facilitates the flow of information
among models, and aids in understanding the impacts of uncertainty. Constructing a hierarchy of models should involve both
bottom-up and top-down perspectives that maintain logical consistency among models, while allowing unique model structures
appropriate for each level in the hierarchy. 相似文献
955.
956.
Carol B. Griffin 《Journal of the American Water Resources Association》1995,31(6):1041-1050
ABSTRACT: The effectiveness of urban Best Management Practices (BMPs) in achieving the No-Net-Increase Policy (NNTP), a policy designed to limit nonpoint nitrogen loading to Long Island Sound (US), is analyzed. A unit loading model is used to simulate annual nitrogen exported from the Norwalk River watershed (Connecticut) under current and future conditions. A probabilistic uncertainty analysis is used to incorporate uncertainty in nitrogen export coefficients and BMP nitrogen removal effectiveness. The inclusion of uncertainty in BMP effectiveness and nitrogen export coefficients implies that additional BMPs, or BMPs with a greater effectiveness in nitrogen removal, will be required to achieve the NNIP. Even though including uncertainty leads to an increase in BMP implementation rates or BMP effectiveness, this type of analysis provides the decision maker with a more realistic assessment of the likelihood that implementing BMPs as a management strategy will be successful. Monte Carlo simulation results indicate that applying BMPs to new urban developments alone will not be sufficient to achieve the NNIP since BMPs are not 100 percent effective in removing the increase in nitrogen caused by urbanization. BMPs must also be applied to selected existing urban areas. BMPs with a nitrogen removal effectiveness of 40–60 percent, probably the highest level of removal that can be expected over an entire watershed, must be applied to at least 75 percent of the existing urban area to achieve the NNIP This high rate of application is not likely to be achieved in urbanized watersheds in the LIS watershed; therefore, additional point source control will be necessary to achieve the NNIP 相似文献
957.
Steven R. Greb David J. Graczyk 《Journal of the American Water Resources Association》1995,31(3):431-438
ABSTRACT: Historically, dissolved-oxygen (DO) data have been collected in the same manner as other water-quality constituents, typically at infrequent intervals as a grab sample or an instantaneous meter reading. Recent years have seen an increase in continuous water-quality monitoring with electronic dataloggers. This new technique requires new approaches in the statistical analysis of the continuous record. This paper presents an application of frequency-duration analysis to the continuous DO records of a cold and a warm water stream in rural southwestern Wisconsin. This method offers a quick, concise way to summarize large time-series data bases in an easily interpretable manner. Even though the two streams had similar mean DO concentrations, frequency-duration analyses showed distinct differences in their DO-concentration regime. This type of analysis also may be useful in relating DO concentrations to biological effects and in predicting low DO occurrences. 相似文献
958.
本文以定量分析为主要手段,详细研究了吉林省农业病虫害发生的时间过程规律和空间分布规律,深入探讨了环境因子对农业病虫害的影响,综合评价了病虫害防治工作的效果。 相似文献
959.
Results of breeding bird censuses in 1979 and 1980 were used to compare the relationships of both species and guilds to forest habitats in the White Mountains of New Hampshire. Several age classes of 11 forest cover types were studied: northern hard-woods (Fagus-Betula-Acer), spruce (Picea), spruce-fir (Picea-Abies), birth (Betula), swamp hardwoods (Acer-Pinus-Tsuga), pine (Pinus strobus andP. resinosa), balsam fir (Abies), aspen (Populus tremuloides andP. grandidentata), northern red oak (Quercus), oak-pine (Quercus-Pinus), and hemlock (Tsuga). All types were even-aged; only northern hardwoods had an additional uneven-aged condition. Forest cover types were also pooled to consider generalized habitats: hardwoods, mixed forest, or softwoods. Results of ordinations based on censuses of 74 bird species indicate that foraging guilds are more related to general cover types than are nesting substrate guilds, but bird species reflect habitat differences to a greater degree than do either guild scheme. Also, considerable overlap occurs in bird species distribution between hardwoods and mixed forests; softwoods show little overlap with other types. Discriminant function and classification analyses revealed that bird species composition can be used to correctly classify general forest habitats more accurately (83.8%) than either foraging (63.2%) or nesting substrate guilds (58.4%). These results indicate that, of the habitats studied, avian species compositions are more characteristic than are foraging or nesting substrate guild composition, which tend to be similar across forest habitats. 相似文献
960.
The proposed restoration of an abandoned hydroelectric dam on the Quinebaug River, Connecticut, is studied using energy analysis. The analysis considers the effects of alternative minimum flow releases, ranging from 0 to 34 cubic meters per second (cms), on the total energy flow of the affected system. The principal system components affected by differing minimum flows are hydroelectric power generation, aquatic habitat, and gross aquatic ecosystem productivity.The minimum flow alternative resulting in the highest annual energy flow in the affected system is considered optimal. From this purely analytical point of view, the optimum minimum flow is 0 cms, due to the short length and low productivity of the regulated reach, and the lack of floodplain interactions.Simulations of longer and more productive river reaches were conducted. For very short, unproductive reaches, in the absence of a floodplain, the contribution of aquatic community productivity to total system energy flow is negligible compared to hydroelectric generation. Optimum minimum flows are higher for longer and more productive reaches. For such cases the operation of hydroelectric dams could reduce total system energy flow because the energy supplied by hydroelectric generation may be offset by losses in aquatic productivity due to diminished riverine habitat. 相似文献