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排序方式: 共有419条查询结果,搜索用时 31 毫秒
181.
基于遗传算法的洪水灾情评估神经网络模型探讨 总被引:26,自引:2,他引:24
洪水灾情评估实际上是一种模式识别问题,而人工神经网络模型具有逼近有界闭子集上任意非线性映射的特性,且模型更新方便。本文邮基于遗传算法的洪水灾情评估神经网络模型,阐述了其基本原理和算法,实例研究表明其实用性、客观性和通用性。 相似文献
182.
基于清洁生产、产业生态学和循环经济等可持续发展理论,结合产业园区现有指标体系、评价标准和相关文献资料,通过评价指标频度统计分析,筛选出重点关注指标,经专家咨询补充完善相关指标,构建了产业园区清洁生产水平评价指标体系(包含7项一级指标和26项二级指标)。通过层次分析法确定了各项指标权重,参考已发布相关标准及研究成果,确定了指标评价标准。以苏州国家环保高新技术产业园为例,应用该指标体系评价其清洁生产水平,结果为合格,与实际情况相符。指出,该指标体系能够合理反映产业园区清洁生产水平,判断其是否建成清洁生产园区,并在园区层面提出清洁生产审核重点及改进建议,从而进一步发掘产业园区清洁生产潜力。 相似文献
183.
对新安江水体(含新安江、千岛湖)DO浓度偏低进行了研究分析,结果表明新安江水电站的建造是主要影响因素. 相似文献
184.
张光贵 《环境监测管理与技术》2000,12(5):27-29
针对单项生物指数评价水质的片面性不确定性,提出了用综合生物指数法评价水质。实验结果表明,该方法在综合各种生物指数评价结果的基础上,能对某一水体水质作出明确的评价结论,且与用理化监测结果评价水质的结论相吻合。 相似文献
185.
为解决农村地下水源受到污染,直接影响农村生态环境和居民健康的问题。采用物元可拓法对广东省粤东地区典型农村地下水饮用水源地开展了水质评价研究,并提出了地下水水质保护策略。结果表明:该饮用水源污染较为严重,锰、硝酸盐氮、亚硝酸盐氮、氨氮和菌落的含量较高,其中,锰的超标最为严重。"三氮"中氨氮的污染最严重。经分析,锰超标主要由于地区地质条件背景值超标导致的,而氨氮污染主要由当地农业活动引起。最后,研究提出划分地下水水源地保护区,加强农村生活垃圾管理及科学使用化肥等保护对策。 相似文献
186.
Amid growing effort to move towards implementation of climate change adaptation, serious interest is emerging about how to use indicators and metrics (I&M) to evaluate adaptation success. Cities are among the leading experimenters developing I&M, but many other entities also view I&M as a tool for providing clarity and accountability about the goals and progress of adaptation. The current landscape of this work is scattered: I&M examples, frameworks, and guidance documents reflect motivations, contexts, and approaches as diverse as the field of adaptation itself. This study systematically surveys the “growth industry” of I&M, including a special focus on I&M approaches developed for cities anywhere and by US cities in particular. We classify these I&M efforts into four domains: those developed in academia, by program sponsors, boundary organizations, and on-the-ground implementers. With attention to theory on (program) evaluation and on science-practice interaction, we reveal a broad range of I&M evaluation purposes and collaboration practices. We conclude that evaluation of adaptation progress and effectiveness – if it is to usefully inform the work of cities or other implementers – would benefit from greater attention to the best practices and guidance offered in the related, but largely still separate, fields of evaluation and science-practice interaction. 相似文献
187.
沈阳市土地生态适宜性初步评价 总被引:10,自引:0,他引:10
主要通过运用生态学、土壤学、环境科学、系统科学和计算机科学的理论、手段与方法。根据行政区划和自然地理条件,对沈阳市土地进行评价单元的划分,运用特尔菲法对预选评价指标集进行筛选,建立评价指标体系并确定各评价因子的权重值,通过加权指数和法计算各评价单元的综合评价值,确立土地生态适宜性分级标准,划分沈阳市土地生态适宜性分区,确定划分区域的土地用途,建立沈阳市土地利用适宜生态发展的模式,为沈阳市土地利用规划提供科学依据。 相似文献
188.
P. Zanis E. Katragkou I. Tegoulias A. Poupkou D. Melas P. Huszar F. Giorgi 《Atmospheric environment (Oxford, England : 1994)》2011,45(36):6489-6500
This study aims to evaluate near surface ozone simulated with the modelling system RegCM3/CAMx against ozone measurements from the EMEP database for the recent decade 1991–2000. The RegCM3/CAMx simulations were performed on a 50 km × 50 km grid over Europe driven either by ERA-40 reanalysis (hereafter referred as ERA simulation) or the global circulation model (GCM) ECHAM5 (hereafter referred as ECHAM simulation). A set of statistical metrics is used for the model evaluation, including temporal correlation coefficient, the ratio of the standard deviations and the bias of simulated versus observed values. Overall, a good agreement is found for both ERA and ECHAM simulations at the majority of the selected EMEP stations in all metrics throughout the year based either on monthly or daily ozone values. Based on these results, it is assessed that the modelling system RegCM3/CAMx is suitable to be used for present and future regional climate-air quality simulations with emphasis on near surface ozone. The ERA simulations reproduce more accurately the observed ozone values in comparison to ECHAM simulations because the meteorology of the ERA experiment is closer to real atmospheric conditions than the GCM based experiment. On a seasonal basis, both ERA and ECHAM simulations exhibit a seasonally dependent bias, with winter and spring ozone values being generally under-estimated by the model and summer and autumn values being slightly overestimated. This seasonally dependent bias is also evident from median and peak midday ozone values. However, the highest observed midday ozone peaks in summer, with values higher than 80 ppbv, could not be captured either by ERA or ECHAM simulations. An analysis of day-time and night-time ERA and ECHAM modelled ozone values shows that CAMx performs better during the day-time. 相似文献
189.
为了解大口子水库水质的污染状况及污染趋势,淮安市环境监测中心站于“九五”期间对大口子水库进行了生物分析指标的监测和生物学评价。结果表明,“九五”期间,大口子水库的水质呈典型富营养化状态,且营养化程度有加重趋势;底栖动物群落的调查结果显示,化学毒性污染稍有好转,有机物污染占主导地位。提出,该水域不宜继续作为养殖基地进行水产养殖,对其污染的治理已刻不容缓。 相似文献
190.
Lindenmann HP 《Journal of Safety Research》2006,37(4):395-400
INTRODUCTION: The significance of the influence of poor pavement skid resistance values on accident frequency in wet pavement conditions has been the object of many studies over several years. The various investigations have produced very diverse findings. Only seldom, however, has detailed consideration been given to the central question of whether pavement skid resistance is a decisive parameter in the occurrence of local accident "black spots." Until now, the focus has been more on describing a relationship between pavement skid resistance and accident frequency. METHOD AND RESULTS: In the course of the network-wide survey of the states of pavements and of accident occurrence on Switzerland's freeways from 1999 to 2003, it emerged that a relationship with inadequate pavement skid resistance was provable for only a small proportion of accident black spots. These findings were used to frame a guideline for authorities and highway operators about how to treat skid resistance when assessing pavements and accident occurrence on freeways. 相似文献