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641.
Tamie L. Veith Mary Leigh Wolfe Conrad D. Heatwole 《Journal of the American Water Resources Association》2003,39(6):1331-1343
ABSTRACT: A combinatorial optimization procedure for best management practice (BMP) placement at the watershed level facilitates selection of cost effective BMP scenarios to control non point source (NFS) pollution. A genetic algorithm (GA) was selected from among several optimization heuristics. The GA combines an optimization component written in the C++ language with spatially variable NFS pollution prediction and economic analysis components written within the Arc View geographic information system. The procedure is modular in design, allowing for component modifications while maintaining the basic conceptual framework. An objective function was developed to lexicographically optimize pollution reduction followed by cost increase. Scenario cost effectiveness is then calculated for scenario comparisons. The NPS pollutant fitness score allows for evaluation of multiple pollutants, based on prioritization of each pollutant. The economic component considers farm level public and private costs, cost distribution, and land area requirements. Development of a sediment transport function, used with the Universal Soil Loss Equation, allows the optimization procedure to run within a reasonable timeframe. The procedure identifies multiple near optimal solutions, providing an indication of which fields have a more critical impact on overall cost effectiveness and flexibility in the final solution selected for implementation. The procedure was demonstrated for a 1,014‐ha watershed in the Ridge and Valley physiographic region of Virginia. 相似文献
642.
643.
基于遗传算法与人工神经网络相结合的玉米估产研究 总被引:6,自引:0,他引:6
在遗传算法 (GeneticAlgorithm )与误差反传 (BackPropagation)网络结构模型相结合的基础上 ,设计了用遗传算法训练神经网络权重的新方法 ,并对吉林省梨树县的玉米进行了估产研究 ,同时与BP算法和灰色系统理论模型进行了比较。经检验 ,计算值与实际值接近 ,并优于灰色理论模型 ,具有良好的预测效果 ,从而为农作物估产提供了新方法 相似文献
644.
Predicting the Range of Chinese Mitten Crabs in Europe 总被引:1,自引:0,他引:1
LEIF-MATTHIAS HERBORG† DEBORAH A. RUDNICK‡ YANG SILIANG§ DAVID M. LODGE† HUGH J. MacISAAC 《Conservation biology》2007,21(5):1316-1323
Abstract: Ecological niche modeling provides a means for predicting the potential future distribution of a nonindigenous species based on environmental characteristics of the species' native range. We applied this method to the Chinese mitten crab (Eriocheir sinensis) , a catadromous crustacean with a long history of invasion in Europe. We used genetic algorithm for rule-set prediction to predict the potential European distribution of mitten crab based on its distribution in 42 locations in its native Asia. The climatic variables, air temperature, number of days, amount of precipitation, and wetness index, contributed significantly to predictions of native distribution limits. Although the genetic algorithm for rule-set prediction model was developed for the native range, the species' extensive distribution in Europe ( n = 434) allowed independent validation of the predictions. Application of the model to Europe was successful, with 84% of occurrences in regions predicted to be suitable by >80% of the models and <4% of occurrences in areas predicted suitable by <50% of the models (mainly along the northern range). At the watershed scale, areas with established mitten crab populations had significantly higher habitat matching than sites that were not invaded. The independent validation of the Asian-based model by the European distribution revealed that predictions were highly accurate. The model also identified large areas of Europe, particularly along the Mediterranean coast, as vulnerable to future invasion. These predictions can be used to develop strategies to control the spread of mitten crab by preventing introductions into vulnerable areas. 相似文献
645.
结构抗连锁倒塌问题研究 总被引:1,自引:0,他引:1
如何保证结构的整体性,并防止其局部破坏所造成的结构连锁倒塌问题,已经得到工程设计和研究者的广泛重视。近年来,欧美国家颁布了结构抗连锁倒塌设计标准,并提出抗连锁倒塌设计是结构多灾害防治的一种手段。改善结构的整体强劲性,是抗连锁倒塌设计主要解决的问题。通过对国内外连锁倒塌和结构整体强劲性研究发展状况的简要评述,主要介绍了连锁倒塌分析与整体强劲性的定义,讨论了整体强劲性分析和评价的不同方法以及改善整体强劲性的措施。最后,探讨了结构抗连锁倒塌与整体强劲性分析有待研究的问题。 相似文献
646.
Kostas Bithas 《Environment, Development and Sustainability》2008,10(3):373-390
The operational designing of Environmentally Sustainable Economic Development (ESED) emerges as an urgent and demanding task.
Even though ESED has paved the way for thought-provoking and constructive scientific dialogue, appeal for designing an operational
ESED is still lagging behind the needs of contemporary societies, leaving much to be desired. With this in mind, the present
paper will aim at delineating principles for the operational application of ESED. First, the preservation of crucial properties
of environmental functions and ecosystems, emerges as a prime condition of ESED. The second condition concerns the provision
of the economic process with sufficient natural inputs; in this context, the paper intends to trace certain operational tenets
governing the use of natural resources. Finally, the appropriate institutional settings for the operational design of ESED
are traced.
Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue 相似文献
647.
Area-Based Refinement for Selection of Reserve Sites with the Benefit-Function Approach 总被引:1,自引:0,他引:1
Abstract: Optimization of resource use is necessary for efficient conservation planning. Many reserve-selection algorithms aim to identify representative but inexpensive networks, which may lead to selecting small sites due to their lower costs and collectively higher species richness. Nevertheless, larger sites would be preferable regarding species' long-term persistence. An area-based refinement can be used to overcome this problem. We used a reserve-planning framework in which continuous benefit functions valued representation (numbers of populations), and differential species weights were based on a species' local rarity and threatened status. We introduced a refinement based on the species-area relationship that provides relatively higher values for larger sites. We applied the proposed method to rich fen vegetation in southern Finland. The species-area refinement resulted in a network of significantly larger sites with minor trade-offs with representation (numbers of populations). Giving endangered species higher weights ensured that the trade-off occurred mostly between site size and representation of low-priority species. We recommend using a species-area refinement for practical, maximum-coverage conservation planning. 相似文献
648.
649.
基于矿井中低频噪声突出,存在时间长、危害大,尤其周期性噪声比重较大,而传统降噪技术对其降噪效果并不明显,提出了基于fxlms
算法的自适应有源降噪耳罩降低矿井中的低频周期性信号,并采用离线建模方法建立了次级通道模型,利用MATLAB8.0拟合了64阶的滤波器,对
矿井中具有代表性的1kHz低频周期噪声和伴有随机噪声的1kHz低频周期性噪声进行了降噪仿真研究。结果表明:1kHz低频周期性噪声的降噪量
达到了30dB。而且在本模型下,随机噪声对低频周期性噪声的降噪效果几乎没有影响。 相似文献
650.
旨在为煤矿安全风险预控管理提供一种适用的风险评价模型或方法。研究过程中,介绍了人工神经网络自适应共振理论的ART-2算法;在安全系统工程理论及相关研究基础上,结合调研分析建立了风险评价指标体系;选取山西9家煤矿作为研究样本进行实证研究。该算法仿真识别结果与煤矿实际安全风险情况一致性程度达到77.78%,表明针对煤矿安全风险预控管理过程中的安全风险评价,ART-2神经网络具有较好的适用性。 相似文献