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Jean-Jacques Corre 《Landscape Ecology》1991,6(1-2):65-75
The Golfe du Lion is mainly bordered by low and narrow sand dunes. Since about four decades, 1/3 of its shoreline has been receding, while 1/3 has been prograding and another 1/3 is stable. Several types of dunes may be described mainly depending on storms, high wind frequencies and sand grain size. Vegetation on dune system is distributed along a primary gradient according to sand stability and soil development, and a secondary gradient along slope of dune according to a seasonal cycle of fresh and salt phreatic water level.Global changes in climate may influence these geomorphological and biological structures mainly through:- Winter minimum temperatures changing the distribution of several plant species, especially in the middle part of the Golfe du Lion.- Frequent high storms which cause damages to the front of the dune systems and disrupt the shore. Changes in dune ecosystems will be cyclic so these tendencies will be obvious only upon a long term period. 相似文献
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基于粒子群优化算法的农田多目标控制排水模型 总被引：3，自引：2，他引：1
该文研究内容包括2个方面： 1）针对南方丘陵地区地表排水方式,通过田间排水试验,探求控制排水中氮、磷浓度的变化规律,拟合了累计入渗量Philip公式的参数,建立了排涝、除渍和减少氮、磷流失的多目标控制排水模型。2）在分析多目标优化问题Pareto最优解的基础上,运用MATLAB编制计算程序,针对控制排水模型的具体特点,分别定义了粒子的适应值、个体极值和全局极值的计算公式,利用粒子群优化算法对模型进行了求解。结果表明,运用基于粒子群的多目标优化算法求解农田多目标控制排水模型,所求得的控制排水时间与实际控制排水时间基本一致,为农田排水的科学管理提供参考。 相似文献
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为了提高水库和河流中长期径流预测精度,针对粒子群算法存在的缺陷,提出了动态调整粒子群算法（DAPSO）。借助霍尔特-温特斯线性季节性模型的预测功能,应用DAPSO算法求解和优化霍尔特-温特斯线性季节性模型组合参数,形成动态调整粒子群-霍尔特-温特斯线性季节性模型组合算法,对石泉水库进行中长期径流预测。仿真计算表明,动态调整粒子群-霍尔特-温特斯线性季节性模型算法收敛速度快于霍尔特-温特斯线性季节性模型算法、粒子群-霍尔特-温特斯线性季节性模型算法。该组合算法克服了按梯度试算法搜索质量差和精度不高的缺点,输出稳定性好,预报精度显著提高,置信度为95%时的预测相对误差小于6%。该算法可应用于水库和河川中长期径流预测。 相似文献
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B.M. Croes P.J. Funston G. Rasmussen R. Buij A. Saleh P.N. Tumenta H.H. de Iongh 《Biological conservation》2011,144(12):3064-3072
In West and Central Africa large carnivores have become increasingly rare as a consequence of rapid habitat destruction and lack of resources for protected area management. The Bénoué Complex (23,394 km2) in northern Cameroon is a regionally critical area for large mammal conservation. In the complex lions (Panthera leo), leopards (Panthera pardus) and spotted hyenas (Crocuta crocuta) are formally protected in three national parks and 28 hunting zones. Over-hunting may be having a strong additive effect precipitating declines in large carnivore numbers across the complex. We used a coarse level track index method to estimate the relative abundance of these three species both in hunting zones and national parks. The results were interpreted with respect to ungulate abundance, and hunting impact. There was no significant difference between the densities of medium to larger species of ungulates in the hunting zones and the national parks, and no difference in leopard and spotted hyena densities in the respective areas. However, lions occurred at significantly lower densities in the hunting zones, and even in the national parks occurred at significantly lower densities than prey biomass would predict. 相似文献
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我国犬瘟热病毒的生态学调查研究 总被引：25，自引：0，他引：25
本研究应用电子显微镜技术检查了１７个毛皮动物和野生动物的６７６份材料,从犬,貂,貉,狐熊,小熊猫,大熊猫,狼,狮,虎,猞狮、金猫等１２种动物病料中,检出含有ＣＤＶ材料４８７份。应用间接ＥＬＩＳＡ、免疫荧光和中和试验等技术检测了８种动物１５８份血清,其中从犬,狐,小熊猫、虎、金猫,狼等６种动物的１０６份血清中检出了抗ＣＤＶ抗体。应用ＲＴ－ＰＣＲ和基因探针检查了４种动物的３７份材料,其中有２９份阳性。 相似文献
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Lilenbaum W Varges R Moraes IA Ferreira AM Pissinatti A 《Veterinary journal (London, England : 1997)》2005,169(3):237-464
Serum samples from 73 lion tamarins of three species living at the Centro de Primatologia do Rio de Janeiro were tested for antibodies against serovars of Leptospira interrogans by microscopic agglutination test. Antibodies were detected in serum samples of 15% of tested samples. Seroreactivity prevalence was lower than that described in other non-human primates and could be explained by the arboreal behaviour of these animals. Icterohaemorrhagiae was the most common serogroup. 相似文献
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E. Bollo M. Tursi G. Degiorgi S. Capella D. Bellis 《Research in veterinary science》2011,91(1):116-118
An 18-year-old female lion (Panthera leo) was referred to the Department of Animal Pathology of the University of Turin (Italy). At necropsy, multiple nodular, 4-20-mm, confluent white firm nodules were scattered throughout the pleural surfaces of the thoracic wall and of the lungs. Histological lesions were represented by proliferations of papillary structures lined by cuboidal basophilic mesothelial cells with large, oval nuclei and abundant granular eosinophilic cytoplasm. Immunohistochemistry revealed immunoreactivity for pancytokeratin and vimentin. None of the cells expressed calretinin antigen. Asbestos fibers and asbestos bodies were not detected respectively by light microscopy and by Scanning Electron Microscope-Energy Dispersive Spectrometer investigations. On the contrary, chrysotile asbestos were identified in samples from shelter material. Histological and immunohistochemical findings were consistent with the diagnosis of an epithelial malignant mesothelioma. To our best knowledge, this is the first report of a pleural mesothelioma in a lion. 相似文献
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采用三维定点高速摄像机对北狮“高台180°飞跃直接站腿”动作进行200帧/s频率的拍摄。首先,用视讯系统进行分段解析,得出腾空阶段中狮尾不同环节、不同时间的三维空间数据;然后,对数据应用Q-TOOLS、EXCEL等软件进行解析、计算;最后,根据计算结果分析狮尾在腾空阶段运动的运动学特征。 相似文献
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提出了在用粒子群算法求解水库优化调度问题时,将模拟退火因子引入罚函数,可以克服不变罚因子的缺陷.采用动态规划法和PSO算法优化调度程序,结果发现PSO算法计算结果更优于动态规划结果.实例计算表明,粒子群算法原理简单,易于编程,占用内存少,求解精度高,适合求解具有复杂约束的水库优化调度问题. 相似文献