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91.
92.
Martha L. Crouch 《Journal of Agricultural and Environmental Ethics》1995,8(2):98-111
Biotechnology increases commercialization of food production, which competes with food for home use. Most people in the world grow their own food, and are more secure without the mediation of the market. To the extent that biotechnology enhances market competitiveness, world food security will decrease. This instability will result in a greater gap between rich and poor, increasing poverty of women and children, less ability and incentive to protect the environment, and greater need for militarization to maintain order. Therefore, biotechnology should be discouraged. An active program to protect and strengthen local food production and to decrease reliance on industrial agriculture should be promoted. 相似文献
93.
本文研究了基于综合应用人工神经网络和演化算法的位移反演分析方法,并将此方法应用于三峡茅坪溪沥青混凝土心墙堆石坝的变形反演分析中。以茅坪溪一期工程原型观测成果为依据,反演出能够正确反映坝体变形特性的邓肯-张EB模型参数,从而预测了施工期末和蓄水期末该坝的变形特性,并基于总应力法研究了心墙水力劈裂破坏发生的可能性,为茅坪溪堆石坝运行期的安全生产提供依据。研究结果表明,茅坪溪心墙堆石坝不会发生水力劈裂破坏,该坝蓄水后虽然水压上升,但心墙仍是安全的。 相似文献
94.
慢生花生根瘤菌的遗传多样性研究 总被引:6,自引:0,他引:6
用REP1R1和REP21DNA为引物,对22株四川土著慢生花生根瘤菌染色体DNA的基因外回文重复序列(RepetitiveExtrogenicpalindromicsequenceREP)进行了PCR扩增和凝胶电泳,并对电泳结果的指纹图型进行了相似性聚类分析.结果表明了四川土著慢生花生根瘤菌的遗传多样性.指纹图形是根瘤菌多样性研究中一种简便而有效的方法 相似文献
95.
神经网络及其在水库调洪演算中的应用 总被引:8,自引:0,他引:8
结合洪水灾害管理的特点建立了水库调洪演算的人工神经网络模型,阐述了其基本原理及算法,并结合某水库调洪演算实例说明了其应用。 相似文献
96.
Chao‐Hsien Liaw Yao‐Lung Tsai Mow‐Soung Cheng 《Journal of the American Water Resources Association》2006,42(2):311-322
The Keelung River Basin in northern Taiwan lies immediately upstream of the Taipei metropolitan area. The Shijr area is in the lower basin and is subject to frequent flooding. This work applies micromanagement and source control, including widely distributed infiltration and detention/ retention runoff retarding measures, in the Wudu watershed above Shijr. A method is also developed that combines a genetic algorithm and a rainfall runoff model to optimize the spatial distribution of runoff retarding facilities. Downstream of Wudu in the Shijr area, five dredging schemes are considered. If 10‐year flood flows cannot be confined in the channel, then a levee embankment that corresponds to the respective runoff retarding scheme will be required. The minimum total cost is considered in the rule to select from the regional flood mitigation alternatives. The results of this study reveal that runoff retarding facilities installed in the upper and middle parts of the watershed are most effective in reducing the flood peak. Moreover, as the cost of acquiring land for the levee embankment increases, installing runoff retarding measures in the upper portion of the watershed becomes more economical. 相似文献
97.
The Value of Biodiversity in Reserve Selection: Representation, Species Weighting, and Benefit Functions 总被引:7,自引:0,他引:7
ANNI ARPONEN§ RISTO K. HEIKKINEN† CHRIS D. THOMAS‡ ATTE MOILANEN 《Conservation biology》2005,19(6):2009-2014
Abstract: The limited availability of resources for conservation has led to the development of many quantitative methods for selecting reserves that aim to maximize the biodiversity value of reserve networks. In published analyses, species are often considered equal, although some are in much greater need of protection than others. Furthermore, representation is usually treated as a threshold: a species is either represented or not, but varying levels of representation over or under a given target level are not valued differently. We propose that a higher representation level should also have higher value. We introduce a framework for reserve selection that includes species weights and benefit functions for under- and overrepresentation (number of locations for each species). We applied the method to conservation planning for herb-rich forests in southern Finland. Our use of benefit functions and weighting changed the identity of about 50% of the selected sites at different funding levels and improved the representation of rare and threatened species. We also identified a small area of additional land that would substantially enhance the existing reserve network. We suggest that benefit functions and species weighting should be considered as standard options in reserve-selection applications. 相似文献
98.
Maintenance of biodiversity through seed banks and botanical gardens, where the wealth of species’ genetic variation may be preserved ex situ, is a major goal of conservation. However, challenges can persist in optimizing ex situ collections if trade-offs exist among cost, effort, and conserving species evolutionary potential, particularly when genetic data are not available. We evaluated the genetic consequences of population preservation informed by geographic (isolation by distance [IBD]) and environmental (isolation by environment [IBE]) distance for ex situ collections for which population provenance is available. We used 19 genetic and genomic data sets from 15 plant species to assess the proportion of population genetic differentiation explained by geographic and environmental factors and to simulate ex situ collections prioritizing source populations based on pairwise geographic distance, environmental distance, or both. Specifically, we tested the impact prioritizing sampling based on these distances may have on the capture of neutral, functional, or putatively adaptive genetic diversity and differentiation. Individually, IBD and IBE explained limited population genetic differences across all 3 genetic marker classes (IBD, 10–16%; IBE, 1–5.5%). Together, they explained a substantial proportion of population genetic differences for functional (45%) and adaptive (71%) variation. Simulated ex situ collections revealed that inclusion of IBD, IBE, or both increased allelic diversity and genetic differentiation captured among populations, particularly for loci that may be important for adaptation. Thus, prioritizing population collections based on environmental and geographic distance data can optimize genetic variation captured ex situ. For the vast majority of plant species for which there is no genetic information, these data are invaluable to conservation because they can guide preservation of genetic variation needed to maintain evolutionary potential within collections. 相似文献
99.
大型公共场所动态引导人移动路径设计方法 总被引:1,自引:3,他引:1
针对方向式动态引导在大型公共场所安全疏散中的重要作用,以及对动态引导人移动路径研究不足的现状,提出利用比值函数设计动态引导人移动路径的方法。并借鉴TSP(旅行商问题)方法的求解思路,提出可用于动态引导人移动路径优化的禁忌搜索算法。以一个内部布局较为复杂的大型公共场所模拟场景为例,利用MA-ESM疏散模型,分别模拟了引导人最优移动路径、最短移动路径和影响面积最大路径3种不同情景下疏散效果。结果表明,利用影响面积和路径长度比值最大的优化算法计算得出的引导人移动路径,既可满足在相同时间内引导更多的人员进行疏散,又可节省总体的疏散时间,充分保证疏散效果,验证了笔者所提出的动态引导人移动路径优化算法的合理性。 相似文献
100.
R. Saura W. Traore L. Taine Z. Q. Wen D. Roux B. Maugey-Laulom M. Ruffie A. Vergnaud J. Horovitz 《黑龙江环境通报》1995,15(7):609-614
Six prenatally diagnosed cases of trisomy 9 are reported and 22 previously reported cases are reviewed; the difficulty of genetic counselling for such cases and the variation in the percentage of trisomic cells in different tissues, thus making accurate diagnosis of trisomy 9 difficult, are emphasized. In addition to karyotyping results, ultrasound findings are important in achieving diagnoses. Finally, a course of action when prenatal trisomy 9 is detected is proposed. 相似文献