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排序方式: 共有283条查询结果,搜索用时 15 毫秒
221.
222.
人工神经网络结构对径流预报精度的影响分析 总被引:15,自引:0,他引:15
建立了基于径流形成机理的以时段降水量与前期径流量为预报因子的前向多层人工神经网络径流预报模型;分析了网络结构对月径流预报精度的影响,发现随网络结构的复杂化,网络训练误差减小,模型评定的确定性系数增大,并均趋于稳定,预报检验的确定性系数总趋势是减小;发现影响模型精度的决定因素是网络输入单元数,亦即径流影响因素;提出了以模型评定与预报检验共同高效或等效的模型选择的折衷方法,以及按模型适宜预报域进行多模型组合预报的最佳预报域组合法。 相似文献
223.
Removal of cadmium using MnO2 loaded D301 resin 总被引:6,自引:0,他引:6
MnO2 loaded weak basic anion exchange resin D301 (Anion exchange resin, macroreticular weak basic styrene) as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2+ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2+ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm. 相似文献
224.
本文根据多年从事监测工作的体会和对各类监测站的调查研究,评述了当前地方监测工作和行业、企业监测工作中存在的一些问题,提出了用切实运转的监测网来深化和开拓监测工作的建议,并对监测网的组建和运转作了较为可行的建议和设想。 相似文献
225.
Laura E. Coristine Sheila Colla Nathan Bennett Anja M. Carlsson Christina Davy Kimberley T.A. Davies Brett Favaro D.T. Tyler Flockhart Kevin Fraser Diane Orihel Sarah P. Otto Wendy Palen Jean L. Polfus Oscar Venter Adam T. Ford 《Conservation biology》2019,33(5):1219-1223
Current conservation templates prioritize biogeographic regions with high intensity ecosystem values, such as exceptional species richness or threat. Intensity-based targets are an important consideration in global efforts, but they do not capture all available opportunities to conserve ecosystem values, including those that accrue in low intensity over large areas. We assess six globally-significant ecosystem values—intact wilderness, freshwater availability, productive marine environments, breeding habitat for migratory wildlife, soil carbon storage, and latitudinal potential for range shift in the face of climate change—to highlight opportunities for high-impact broadly-distributed contributions to global conservation. Nations can serve as a cohesive block of policy that can profoundly influence conservation outcomes. Contributions to global ecosystem values that exceed what is predicted by a nation's area alone, can give rise to countries with the capacity to act as ‘conservation superpowers’, such as Canada and Russia. For these conservation superpowers, a relatively small number of national policies can have environmental repercussions for the rest of the world. 相似文献
226.
Elizabeth H. Boakes Richard A. Fuller Georgina M. Mace Philip J.K. McGowan 《Conservation biology》2018,32(1):229-239
Over half of globally threatened animal species have experienced rapid geographic range loss. Identifying the parts of species’ distributions most vulnerable to local extinction would benefit conservation planning. However, previous studies give little consensus on whether ranges decline to the core or edge. We built on previous work by using empirical data to examine the position of recent local extinctions within species’ geographic ranges, address range position as a continuum, and explore the influence of environmental factors. We aggregated point‐locality data for 125 Galliform species from across the Palearctic and Indo‐Malaya into equal‐area half‐degree grid cells and used a multispecies dynamic Bayesian occupancy model to estimate rates of local extinctions. Our model provides a novel approach to identify loss of populations from within species ranges. We investigated the relationship between extinction rates and distance from range edge by examining whether patterns were consistent across biogeographic realm and different categories of land use. In the Palearctic, local extinctions occurred closer to the range edge than range core in both unconverted and human‐dominated landscapes. In Indo‐Malaya, no pattern was found for unconverted landscapes, but in human‐dominated landscapes extinctions tended to occur closer to the core than the edge. Our results suggest that local and regional factors override general spatial patterns of recent local extinction within species’ ranges and highlight the difficulty of predicting the parts of a species’ distribution most vulnerable to threat. 相似文献
227.
228.
N. V. Lapshin 《Russian Journal of Ecology》2009,40(3):199-205
Annual cycle phenomena taking place in the nesting part of the range, such as dates of migration and breeding and molting pattern, have been studied in the wood warbler in northwestern Russia, at the boundary of its nesting range. The results provide evidence that the annual cycle of long-distance migrant birds living at the boundary of their nesting range has certain specific features. 相似文献
229.
吹扫捕集/气相色谱/质谱法测定水体中54种常见挥发性有机物的研究 总被引:2,自引:0,他引:2
运用吹扫捕集/气相色谱/质谱(P&T/GC/MS)法对水体中54种常见的挥发性有机物(VOCs)进行了测定.结果表明,VOCs的色谱分离情况较好,平均加标回收率为88.5%~117.0%,相对标准偏差为0.71%~8.50%,准确度和精密度均符合有关分析测试的要求;方法检出限为0.10~0.61μg/L,远低于<地表水环境质量标准>(GB 3838-2002)、<生活饮用水卫生标准>(GB3838-2002)及国外相关标准的限值;54种VOCs的线性范围不同,低沸点的VOCs线性范围较宽,高沸点的VOCs的线性范围较窄,因此在分析VOCs样品配制标准工作曲线时,应注意不同沸点VOCs的线性范围. 相似文献
230.
Ceren Boa 《Journal of environmental psychology》2009,29(2):267-278
This paper examines issues arising from the involuntary relocation of Turkish Cypriot refugees from the southern to the northern portion of the island of Cyprus. After the ceasefire in 1974, participants in this study were relocated into homes originally built and occupied by Greek Cypriots. Using data obtained from questionnaires, semi-structured interviews and drawings, the study analyses their place attachment under the unusual circumstances of their own forced relocation coupled with their occupation of homes abandoned by residents also displaced by war and interethnic hostility. The study compares the place attachment of refugees to their children, who were born and brought up in the new community. The results of this study suggest that participants' future expectations shaped their attachment to their new homes and community, whilst their degree of attachment to their previous environments also played an important role in the attachment process. Younger generations, on the other hand, were more attached to their current environment than older generations; however they did not wish to be identified with their current environment. 相似文献