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101.
102.
PROBLEM: There is a growing concern with the safety of school-aged children. This study identifies the locations of pedestrian/bicyclist crashes involving school-aged children and examines the conditions when these crashes are more likely to occur. METHOD: The 5-year records of crashes in Orange County, Florida where school-aged children were involved were used. The spatial distribution of these crashes was investigated using the Geographic Information Systems (GIS) and the likelihoods of crash occurrence under different conditions were estimated using log-linear models. RESULTS: A majority of school-aged children crashes occurred in the areas near schools. Although elementary school children were generally very involved, middle and high school children were more involved in crashes, particularly on high-speed multi-lane roadways. Driver's age, gender, and alcohol use, pedestrian's/bicyclist's age, number of lanes, median type, speed limits, and speed ratio were also found to be correlated with the frequency of crashes. DISCUSSION: The result confirms that school-aged children are exposed to high crash risk near schools. High crash involvement of middle and high school children reflects that middle and high schools tend to be located near multi-lane high-speed roads. IMPACT ON INDUSTRY: The pedestrian's/bicyclist's demographic factors and geometric characteristics of the roads adjacent to schools associated with school children's crash involvement are of interest to school districts. 相似文献
103.
Zhenghong Tang Ruopu Li Xu Li Weiguo Jiang Aaron Hirsh 《Journal of the American Water Resources Association》2014,50(1):234-245
The digital elevation model data from traditional stereo photogrammetric methods are inadequate in providing accurate vertical parameters to feed hydrologic models for low‐lying, extremely flat areas. High‐resolution light detection and ranging (LiDAR) data provide the robust capability of capturing small variations in low‐relief playa wetlands. The Rainwater Basin in south‐central Nebraska includes a complex of seasonally shallow playa wetlands that attract millions of migratory waterfowl every spring and fall. This research focuses on the development of a procedure with applicable protocols to produce LiDAR‐derived three‐dimensional wetland maps and to extract the critical surface parameters (i.e., watershed boundaries, flow direction, flow accumulation, and drainage lines) for playa wetlands. The topo‐hydrologic conditions of playa wetlands were evaluated at the watershed level. The results show that in the Rainwater Basin, 70.7% of the historic hydric soil footprints identified in the Soil Survey Geographic (SSURGO) database were not functioning as topographically depressional wetlands. This finding was confirmed by a recent five‐year Annual Habit Survey showing that 69.8% of the historic hydric soil footprints did not function during the spring migratory bird seasons between 2004 and 2009. The majority of playa wetlands' topographic conditions have been substantially changed and the SSURGO data cannot fully reflect current topographic reality in the Rainwater Basin. 相似文献
104.
基于循环修正模式的云南省水资源短缺程度分析 总被引:1,自引:0,他引:1
区域水资源短缺评价是水资源风险研究的基础。前期的研究多采用单一评价方法进行,致使评价结果存在差异。论文提出采用循环修正模式对单一评价方法得出的不同评价结果进行组合修正。通过构建云南省水资源短缺综合评价指标体系,利用模糊物元、模糊识别等多种单一评价方法进行评价,最后运用平均值法、Boarda法和Compeland法三种组合评价方法对单一评价方法得到的不同结果进行组合评价,建立了基于循环修正模式的水资源短缺程度评价模型并加以应用,给出了云南省16个地、市、州的水资源短缺程度的排序及其缺水类型的划分。 相似文献
105.
加氢装置属甲类火灾、爆炸危险生产装置。为了在设计阶段尽可能消除或控制潜在风险,本文总结了多套加氢装置HAZOP分析报告中的设备类别及其分析内容,提出了基于危险与可操作性(HAZOP)分析的加氢装置工程设计方法。在传统工程设计方法的基础上增加了参数敏感性工程设计方法,依据分析报告中的设计建议,利用ASPEN软件计算过程参数变化对目标参数的影响程度,确定参数稳定操作区域;建立了数据库管理界面实现了加氢装置工程安全设计经验知识的有序管理。应用基于HAZOP分析的加氢装置工程设计方法,有助于将安全隐患问题在设计阶段消除或加以控制,可为降低石化装置改造成本和提高装置的安全水平提供方法依据。 相似文献
106.
Eimear M. Nic Lughadha Vanessa Graziele Staggemeier Thais N. C. Vasconcelos Barnaby E. Walker Cátia Canteiro Eve J. Lucas 《Conservation biology》2019,33(3):511-522
The value of natural history collections for conservation science research is increasingly recognized, despite their well-documented limitations in terms of taxonomic, geographic, and temporal coverage. Specimen-based analyses are particularly important for tropical plant groups for which field observations are scarce and potentially unreliable due to high levels of diversity-amplifying identification challenges. Specimen databases curated by specialists are rich sources of authoritatively identified, georeferenced occurrence data, and such data are urgently needed for large genera. We compared entries in a monographic database for the large Neotropical genus Myrcia in 2007 and 2017. We classified and quantified differences in specimen records over this decade and determined the potential impact of these changes on conservation assessments. We distinguished misidentifications from changes due to taxonomic remodeling and considered the effects of adding specimens and georeferences. We calculated the potential impact of each change on estimates of extent of occurrence (EOO), the most frequently used metric in extinction-risk assessments of tropical plants. We examined whether particular specimen changes were associated with species for which changes in EOO over the decade were large enough to change their conservation category. Corrections to specimens previously misidentified or lacking georeferences were overrepresented in such species, whereas changes associated with taxonomic remodeling (lumping and splitting) were underrepresented. Among species present in both years, transitions to less threatened status outnumbered those to more threatened (8% vs 3%, respectively). Species previously deemed data deficient transitioned to threatened status more often than to not threatened (10% vs 7%, respectively). Conservation scientists risk reaching unreliable conclusions if they use specimen databases that are not actively curated to reflect changing knowledge. 相似文献
107.
蒽酮法研究烷基多苷(APG)的初级生物降解性 总被引:1,自引:0,他引:1
用蒽酮分光光度法对 5种不同碳链APG的初级生物降解性进行了研究。结果表明 ,直链醇APG和碳链较短的支链醇APG能完全降解 ,但碳链为 1 4~ 1 5的支链醇APG不能被降解。探讨了结构对降解性的影响 :疏水基的结构对其降解性有较大影响 ,直链醇APG的降解性优于支链醇对APG的降解性 ,碳链较短的降解性优于碳链长的 ,链支化度影响支链醇APG的降解性 ;对其降解曲线的研究表明 :C8~ 1 0 直链、C1 4~ 1 5支链等APG的降解曲线存在降解度随时间下降的特殊现象 ;提出了APG一条可能的降解途径。 相似文献
108.
Alexandridis TK Lazaridou E Tsirika A Zalidis GC 《Journal of environmental management》2009,90(7):2243-2251
The European Habitats Directive 92/43/EEC has defined the need for the conservation of habitats and species with the adoption of appropriate measures. Within the Natura 2000 ecological network of special areas of conservation, natural habitats will be monitored to ensure the maintenance or restoration of their composition, structure and extent. The European Space Agency's GlobWetland project has provided remotely sensed products for several Ramsar wetlands worldwide, such as detailed land cover-land use, water cycle and inundated vegetation maps. This paper presents the development and testing of an operational methodology for updating a wetland's habitat map using the GlobWetland products, and the evaluation of the extent to which GlobWetland products have contributed to the habitat map updating. The developed methodology incorporated both automated and analyst-supervised techniques to photo-interpret, delineate, refine, and evaluate the updated habitat polygons. The developed methodology was proven successful in its application to the wetland complex of the Axios-Loudias-Aliakmon delta (Greece). The resulting habitat map met the European and Greek national requirements. Results revealed that GlobWetland products were a valuable contribution, but source data (enhanced satellite images) were necessary to discriminate spectrally similar habitats. Finally, the developed methodology can be modified for original habitat mapping. 相似文献
109.
The dual goals of the Organic Act of 1916 and Wilderness Act of 1964 are to protect natural resources and provide quality
visitor experiences. Park managers need metrics of trail conditions to protect park resources and quality of visitor experiences.
A few methods of sampling design for trails have been developed. Here, we describe a relatively new method, spatially balanced
sampling, and compare it to systematic sampling. We evaluated the efficiency of sampling designs to measure recreation-related
impacts in Rocky Mountain National Park. This study addressed two objectives: first, it compared estimates of trail conditions
from data collected from systematic versus spatially balanced sampling data; second, it examined the relationship between
sampling precision and sampling efficiency. No statistically significant differences in trail condition were found between
the 100-m interval and the spatially balanced datasets. The spatially balanced probability-based dataset was found to be a
good estimate of trail conditions when analyses were conducted with fewer sample points. Moreover, spatially balanced probability-based
sampling is flexible and allows additional sample points to be added to a sample. 相似文献
110.
Agricultural non–point source (NPS) pollution poses a severe threat to water quality and aquatic ecosystems. In response,
tremendous efforts have been directed toward reducing these pollution inputs by implementing agricultural conservation practices.
Although conservation practices reduce pollution inputs from individual fields, scaling pollution control benefits up to the
watershed level (i.e., improvements in stream water quality) has been a difficult challenge. This difficulty highlights the
need for NPS reduction programs that focus efforts within target watersheds and at specific locations within target watersheds,
with the ultimate goal of improving stream water quality. Fundamental program design features for NPS control programs—i.e.,
number of watersheds in the program, total watershed area, and level of effort expended within watersheds—have not been considered
in any sort of formal analysis. Here, we present an optimization model that explores the programmatic and environmental trade-offs
between these design choices. Across a series of annual program budgets ranging from $2 to $200 million, the optimal number
of watersheds ranged from 3 to 27; optimal watershed area ranged from 29 to 214 km2; and optimal expenditure ranged from $21,000 to $35,000/km2. The optimal program configuration was highly dependent on total program budget. Based on our general findings, we delineated
hydrologically complete and spatially independent watersheds ranging in area from 20 to 100 km2. These watersheds are designed to serve as implementation units for a targeted NPS pollution control program currently being
developed in Wisconsin. 相似文献