首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6篇
  免费   1篇
大气科学   2篇
地质学   2篇
综合类   1篇
自然地理   2篇
  2021年   1篇
  2013年   3篇
  2012年   1篇
  2009年   1篇
  1997年   1篇
排序方式: 共有7条查询结果,搜索用时 15 毫秒
1
1.
《The Journal of geography》2012,111(6):233-242
Abstract

Concern about the health of American democracy mounts as a result of the large body of literature documenting chronically low levels of voter turnout among young people in particular. A volunteer, nonprofit organization called “Kids Voting, USA” was formed in the late 1980s to try to tackle the specific problem of encouraging young adults to vote. In cooperation with school districts, the program includes some grade-specific curricula and culminates on Election Day with kids voting in polling booths set up alongside official ones. Existing assessments of the program's impact have been very positive. Particularly hopeful is one study that concludes that the program's strongest effects are found in mobilizing those least advantaged in terms of the customary correlates of political participation. Our ecological analysis, based on the actual turnout rates in the Kids Voting elections for participating schools in Erie County, NY (N = 222), suggests that such conclusions are perhaps overly optimistic. Patterns in the geography and social ecology of participation in Kids Voting elections unfortunately look quite similar to those related to variations in the official electoral process. Although Kids Voting programs may have a salutary effect stimulating political involvement among the young, further reforms seem necessary if they are to reach their full potential.  相似文献   
2.
Abstract

A primary goal of the NERC/ESRC Land Use Programme (NELUP) was to design and build a decision support system (DSS) to model rural land use and its change due to environmental and agricultural policy. The effects of policies are measured in terms of economic, ecological and hydrological parameters, with land use and land cover being the uniting factors. The DSS incorporates access to a large database and a suite of complex models. The DSS is user-friendly, produces meaningful graphics, and is almost entirely mouse-driven. This paper describes the NELUP view of policy making and DSS, the NELUP database and the DSS models and interface philosophy and design. The results of workshops, conducted with potential users of the DSS, are discussed and summarised.  相似文献   
3.
卡尔曼滤波的初值计算方法及其应用   总被引:26,自引:2,他引:26       下载免费PDF全文
文章从气象应用角度论述了卡尔曼滤波在天气预报业务系统中应用的理论原理和计算方法。介绍了不同季节的试验结果,并分析了卡尔曼滤波的适应数值模式变化的能力和它的稳定性、可用性,展示了它的优越性和应用前景。  相似文献   
4.
Deuterium, δ 18O, major ions and dissolved silica in groundwater from semi-arid Mayo-Tsanaga river basin in the Far North Province, Cameroon were used to trace hydrogeochemical processes that control their concentrations and to explore for usability of the water. Electrical conductivity ranges from 57–2,581 μs/cm with alternating low and high values along the hydraulic gradient. Waters from piedmont alluvium show low concentrations in major cations, which peak in Mg within basalt, Na within plain alluvium, and Ca within basalt and the sandy Limani-Yagoua ridge. The initial dominant groundwater composition is CaHCO3, which did not evolve within the basalt and piedmont alluvium, but evolved to NaHCO3 in the granite and plain alluvium. The main processes controlling the major ions composition include the following: (1) dissolution of silicates and fluorite; (2) precipitation of fluorite and carbonate; (3) cation exchange of Ca in water for Na in clay; (4) and anthropogenic activities. The δD and δ 18O ratios vary from −35 to 0.7 and −5.3 to 1.1‰, respectively. The lowest and highest isotope ratios are observed in groundwater within the downstream sandy Limani-Yagoua ridge and the upstream graintes respectively. Variation in isotope ratios depends on altitude effect of −0.48‰ per 100 m between 600 and 850 m asl, and on evaporation, which had insignificant effect on the water salinity. Seventy percent of the groundwater shows poor drinking quality and 90% is suitable for irrigation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
5.
总结了东胜煤田延安组煤的两种主要成煤模式,结合煤质分析数据,探讨成煤环境条件对煤质的控制作用。研究结果显示,河流成煤模式的煤层,煤岩类型以暗淡型为主,煤中富丝质组,煤层中矿物质含量较高,灰分含量多大于10%,煤类以不粘煤为主。湖泊三角洲成煤模式的煤层,煤岩类型以光亮煤和半亮煤为主,煤中富镜质组,煤层中矿物质含量低,灰分含量少于10%,煤类以长焰煤为主。经对比两种成煤模式煤的工艺性质,认为富丝质组煤利于气化、动力燃烧、制吸附剂,富镜质组煤则首选液化和配焦。  相似文献   
6.
While scenarios are used extensively for communication about climate change mitigation, little is known about the interpretation of these scenarios by citizens. We conducted a cross-country empirical evaluation of scenario visualizations for global mitigation, using online surveys in Germany (N = 379), Poland (N = 223), and France (N = 225). Each respondent received visualizations of the required changes in global carbon dioxide emissions and composition of electricity supply (fossil fuels, nuclear, and renewable sources) for limiting global warming to 1.5 °C. We evaluated the effects of respondents’ demographics, prior beliefs, numeracy, and graph literacy on the reading accuracy and knowledge gains from the visualizations. We also included an experimental between-groups design on visualization format, where four groups received different graph formats (steep or gradual graphs with depictions of uncertainty ranges or scenario ensembles) and the fifth group received a table. Results showed that higher education level, numeracy, and graph literacy increased reading accuracy in all countries, while age reduced them. Respondents with prior beliefs about climate change mitigation that matched the information in the visualizations had also higher reading accuracy and knowledge gains. While the effects of different visualization formats were comparatively minor, customizing formats according to demographic and country differences was used to reduce adverse effects from these differences. These results emphasize the need to design visualizations that match characteristics of the intended audience and could inform better communication of climate change mitigation scenarios to non-expert audience.  相似文献   
7.
地理信息服务是地理信息产业从“专业化”发展到“公众化、社会化”的必然,地理空间数据网络服务是开展地理信息服务的基础和前提。本文系统总结了网络环境下地理空间数据服务的特点,即规范化,大众化,多元化,个性化,实时化,动态化;提出了地理空间数据网络服务的关键技术,地理空间数据可用性评价,地理空间数据共享与互操作,地理空间数据网络服务的安全管理。  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号