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排序方式: 共有289条查询结果,搜索用时 15 毫秒
281.
Cluster analysis of structural stage classes to map wildland fuels in a Madrean ecosystem 总被引:2,自引:0,他引:2
Miller JD Danzer SR Watts JM Stone S Yool SR 《Journal of environmental management》2003,68(3):239-252
Geospatial information technology is changing the nature of fire mapping science and management. Geographic information systems (GIS) and global positioning system technology coupled with remotely sensed data provide powerful tools for mapping, assessing, and understanding the complex spatial phenomena of wildland fuels and fire hazard. The effectiveness of these technologies for fire management still depends on good baseline fuels data since techniques have yet to be developed to directly interrogate understory fuels with remotely sensed data. We couple field data collections with GIS, remote sensing, and hierarchical clustering to characterize and map the variability of wildland fuels within and across vegetation types. One hundred fifty six fuel plots were sampled in eight vegetation types ranging in elevation from 1150 to 2600 m surrounding a Madrean 'sky island' mountain range in the southwestern US. Fuel plots within individual vegetation types were divided into classes representing various stages of structural development with unique fuel load characteristics using a hierarchical clustering method. Two Landsat satellite images were then classified into vegetation/fuel classes using a hybrid unsupervised/supervised approach. A back-classification accuracy assessment, which uses the same pixels to test as used to train the classifier, produced an overall Kappa of 50% for the vegetation/fuels map. The map with fuel classes within vegetation type collapsed into single classes was verified with an independent dataset, yielding an overall Kappa of 80%. 相似文献
282.
Richard E. Barlow 《Environment international》1978,1(6):345
A four-cell model to analyze dependent lifetimes by using the generalized multivariate Gumbel distribution is described. 相似文献
283.
284.
N. Jay Bassin 《Journal of the American Water Resources Association》1985,21(1):145-150
ABSTRACT: Dinosaur National Monument, in northwestern Colorado, has become a test case in the establishment of a federal reserved water right to instream flows. For the first time, the Interior Department was forced to rigorously defend its claims in a watershed where the federal government did not control the upstream reaches. Inadequate quantification of minimum flow requirements, court orders, and an apparent Congressional ban on the spending of Water Resources Program funds by the Park Service to quantify its water rights have already placed the Service in a difficult position to protect instream flows for maintaining the ecological integrity of the Monument. As late as 1983, administrators of the Park Service were divided over their legal strategy, many wanting to pursue a policy of claiming “natural, historic” flows rather than “minimum” flows. The conditional right to instream flows panted to the Park Service in 1978 was subject to quantification within five years. That deadline has been extended, but it is not likely that the case will reach final settlement this decade. Until the design and conduct of federal water rights quantifications better integrate public policy and law with science, the principle lesson from Dinosaur may have to be repeated. 相似文献
285.
Jay R. Stauffer Jr. David K. Vann Charles H. Hocutt 《Journal of the American Water Resources Association》1984,20(5):771-775
Acclimation to varying salinities did not affect the preferred temperature of Saratherodon melanotheron, which had a final preferred temperature of 33.5 C. However, fish acclimated to 25 C and 0, 15, and 30 o/oo salinities had lower lethal temperatures of 15, 13, and 15 C, respectively, and an upper lethal temperature of 37 C. The thermal zone of tolerance for fish acclimated in freshwater was 17-35 C, and was not dependent upon acclimation temperatures. Data suggest this species could expand its range in North America. 相似文献
286.
ABSTRACT: At a time when productive water resources research is essential to protecting the quality of and wisely using our limited water resources, pervasive trends toward consumerism, fiscal restraint, centralized management, and using research for other social objectives threaten research productivity. The research prioritization and management structure that these trends have created was examined in the microcosm of its application at the Utah Water Research Laboratory. The result indicated that ephemeral prioritization and the failure of research users to target researchers to their own particular needs is diluting productivity. Incremental research prioritization and greater use of advisory councils in facilitating user-researcher interaction are suggested as corrective approaches, but the only firm conclusion at this point in time must be that empirical studies of the performance of alternatives in research management structure are solely needed. 相似文献
287.
Jay R. Stauffer 《Journal of the American Water Resources Association》1981,17(3):504-507
The bluespotted sunfish, Enneacanthus gloriosus (Holbrook), had a final temperature preferendum of 31.5 C. Fish acclimated to 30 C avoided 36 C. The analysis of acute temperature preference data and the relationship between final temperature preferendum and upper avoidance temperatures are discussed. 相似文献
288.
Jay?K.?Goldberg Alisa?K.?Wallace Stacey?L.?WeissEmail author 《Die Naturwissenschaften》2017,104(9-10):81
Sex pheromones can perform a variety of functions ranging from revealing the location of suitable mates to being honest signals of mate quality, and they are used in the mate selection process by many species of reptile. In this study, we determined whether the skin lipids of female striped plateau lizards (Sceloporus virgatus) can predict the reproductive quality of females, thereby having the potential to serve as pheromones. Using gas chromatography/mass spectrometry, we identified 17 compounds present in skin lipids of female lizards. Using principal component analysis to compare the skin lipid profile of receptive and non-receptive females, we determined that an uncharacterized compound may allow for chemical identification of receptive mates. We also compared extracted principal components to measures of female fitness and reproductive qualities and found that the level of two 18 carbon fatty acids present in a female’s skin lipids may indicate her clutch size. Finally, we compared the information content of the skin lipids to that of female-specific color ornaments to assess whether chemical and visual cues transmit different information or not. We found that the chroma of a female’s orange throat patch is also related to her clutch size, suggesting that chemical signals may reinforce the information communicated by visual ornamentation in this species which would support the “backup signals” hypothesis for multiple signals. 相似文献
289.
Jay N. Meegoda Wiwat Kamolpornwijit 《Frontiers of Environmental Science & Engineering in China》2011,5(2):159-166
As species we humans generate excessive amounts of waste and hence for sustainability we should explore innovative ways to
recover them. The primary objective of this study is to demonstrate an efficient and optimum way to recover chromium and iron
from chromite ore processing residues (COPR) for the production of chrome steel and stainless steel. In Hudson County, New
Jersey, there are more than two million tons of leftover COPR. Part of COPR was used as fill materials for construction sites,
which spread the problem to a larger area. With high solubility along with their toxicity leached chromate from COPR is threatening
the environment as well as human health. In this research, COPR was thermally treated to recover iron with chromium by applying
techniques used in steel manufacturing. An extensive experimental program was performed using a Thermo-Gravimetric Analyzer
(TGA) and bench scale tests to thermally treat the processed chromium contaminated soils with carbon and sand at varying temperatures
and under reducing environment. The optimum chemical composition of COPR and additives to be used in the melts were evaluated
based upon the thermodynamic properties of the mixture to ensure good phase separation, least amounts of iron and chromium
oxides in the slag and minimum variability of final product (steel or iron with chromium). The impact of other oxides on the
steel making process was evaluated to minimize the adverse impact on the process. The research demonstrated the feasibility
of recovering a valuable construction material (chrome steel) from a waste (COPR). 相似文献