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191.
基于BP神经网络优化制备Cu-Ce/TiO_2及其光催化活性研究 总被引:1,自引:1,他引:0
采用Cu和Ce对TiO2进行改性,基于正交实验设计和BP神经网络研究了Cu-Ce/TiO2中Cu-Ce对TiO2的摩尔百分数、Cu-Ce/TiO2中CuCe摩尔比及Cu-Ce/TiO2烧结温度对Cu-Ce/TiO2光催化降解甲醛溶液性能的影响.同时,对Cu-Ce/TiO2制备方案进行了优化,并运用X射线衍射仪、扫描电子显微镜和紫外-可见分光光度计对最佳条件下制备的Cu-Ce/TiO2进行表征.结果表明,优化的制备条件为Cu-Ce/TiO2中Cu-Ce对TiO2的摩尔百分数为2.88%,Cu-Ce/TiO2中Cu-Ce的摩尔比为1∶1,Cu-Ce/TiO2的烧结温度为570℃.共掺杂Cu离子和Ce离子能有效避免掺杂TiO2晶格内部表层和近表层产生较多的位错,从而抑制晶格畸变增大;诱导TiO2中锐钛矿型晶体向金红石型晶体转变的能力增强,有效抑制电子-空穴对的复合,产生介电局域效应. 相似文献
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Cost-efficient sample designs for collection of ground data and accurate mapping of variables are required to monitor natural
resources and environmental and ecological systems. In this study, a sample design and mapping method was developed by integrating
stratification, model updating, and cokriging with Landsat Thematic Mapper (TM) imagery. This method is based on the spatial
autocorrelation of variables and the spatial cross-correlation among them. It can lead to sample designs with variable grid
spacing, where sampling distances between plots vary depending on spatial variability of the variables from location to location.
This has potential cost-efficiencies in terms of sample design and mapping. This method is also applicable for mapping in
the case in which no ground data can be collected in some parts of a study area because of the high cost. The method was validated
in a case study in which a ground and vegetation cover factor was sampled and mapped for monitoring soil erosion. The results
showed that when the sample obtained with three strata using the developed method was used for sampling and mapping the cover
factor, the sampling cost was greatly decreased, although the error of the map was slightly increased compared to that without
stratification; that is, the sample cost-efficiency quantified by the product of cost and error was greatly increased. The
increase of cost-efficiency was more obvious when the cover factor values of the plots within the no-significant-change stratum
were updated by a model developed using the previous observations instead of remeasuring them in the field. 相似文献
195.
An Interpretive Study of Yosemite National Park Visitors’ Perspectives Toward Alternative Transportation in Yosemite Valley 总被引:1,自引:0,他引:1
White DD 《Environmental management》2007,39(1):50-62
The National Park Service (NPS) is increasingly focusing on alternative transportation systems in national parks to address
environmental and social problems arising from a historical reliance on personal automobiles as the primary means of visitor
access. Despite the potential advantages, alternative transportation may require a reorientation in the way that Americans
have experienced national parks since the advent of auto-tourism in the early twentieth century. Little research exists, however,
on visitor perspectives towards alternative transportation or the rationale underlying their perspectives. It remains unclear
how transportation systems affect visitors’ experiences of the park landscape or the factors influencing their travel behavior
in the parks. This report presents an interpretive study of visitor perspectives toward transportation management in the Yosemite
Valley area of Yosemite National Park, California. Qualitative analysis of 160 semi-structured interviews identified individual
psychological factors as well as situational influences that affect visitors’ behavior and perspectives. Individual psychological
factors include perceived freedom, environmental values and beliefs, prior experience with Yosemite National Park and other
national parks, prior experience with alternative transportation in national parks, and sensitivity to subjective perceptions
of crowding. Situational factors included convenience, access, and flexibility of travel modes, as well as type of visit,
type of group, and park use level. Interpretive communication designed to encourage voluntary visitor use of alternative transportation
should focus on these psychological and situational factors. Although challenges remain, the results of this study suggest
approaches for shaping the way Americans visit and experience their national parks to encourage environmental sustainability. 相似文献
196.
某钢铁企业高炉炼铁车间的出铁场在生产过程中产生大量高浓度的烟尘,对厂区的大气环境及周边的环境造成严重污染,同时直接危害了职工的身体健康。通过对整个出铁场除尘工艺系统及通风状况的分析及实际应用情况,总结出了适合该场合的系统除尘方案。 相似文献
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198.
本文介绍了基于任务成功率的装备综合保障工作体系框架,提出了可靠性、维修性、测试性、保障性、安全性协同设计环境要求,从而为进行可靠性、维修性、测试性、保障性、安全性综合优化设计奠定基础。 相似文献
199.
SCR脱硝装置中整流格栅的优化设计 总被引:1,自引:0,他引:1
基于CFD模拟软件对某选择性催化还原(SCR)脱硝装置进行数值模拟,分析了不同整流格栅间距、形式对反应器上部流场的影响。以不同高度截面的烟气速度变异系数CV和最大烟气入射角为定量评价指标,给出了满足性能要求的整流格栅设计参数范围以及最优设计方案。 相似文献
200.
民用飞机的发动机转子非包容性失效给飞机的安全运行带来巨大的风险,为了将这种转子非包容性失效可能带来的危害降至最小,需要合理的评估碎片的危害水平,以及采取合理的安全预防措施。尽管在FAA(Federal Aviation Administration)用于评估碎片危害水平的UEDDAM(Uncontained Engine Debris Damage Analysis Model)软件工具中采用了加强防护设计以减少碎片危害,但是没有对具体的分析流程和碎片能量衰减的计算模型进行说明。为此,在现有的碎片危害分析方法的基础上,考虑到碎片在侵彻过程中会有能量衰减,分析了降低碎片危害的三种安全预防措施,通过对比确定了加强防护设计对于降低碎片危害的重要意义及其分析的流程。通过对飞机结构中关键区域定义的理解,明确了在飞机的不同部位需要采取不同的加强防护设计,并详细介绍了整体加强防护设计和局部加强防护设计的流程。 相似文献