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881.
Knowledge of the historical responses of animal species to climate changes is critical for understanding their evolutionary history and conservation.During the late Quaternary period,Southeast Asia had a larger land area than today due to lower sea levels,and its terrestrial landscape was covered by extensive forests and savannah.To date,however,the general fluctuations in landscape distribution and their impacts on the demographics history of native species during the late Quaternary periods are still disputed.Specifically,the responses of animals on Hainan Island,which is located in the northernmost region of Southeast Asia,to historical climate changes,are poorly understood.Here,we performed a series of demographic analyses based on mitochondrial DNA genes to examine the response of the resident Hainan Peacock Pheasant(Polyplectron katsumatae) to climate change.Unlike the pattern of population collapse during the ice age and expansion during the warming period,we detected a historical expansion pattern in the demographic history of Hainan Peacock Pheasant through the late Quaternary period.It was concluded that the Hainan Peacock Pheasant survived through the late Quaternary periods,despite of its currently limited distribution and population size on Hainan Island.Anthropogenic influences must be considered in conservation planning due to their impacts on currently fragmented habitats and populations.  相似文献   
882.
提出一种基于DFT的自适应循环电力系统信号分析算法,该算法将插值算法和相位差校正算法进行融合.首先使用插值算法估计被检测信号的频率,计算出最佳的信号整数倍周期的截断长度,然后利用相位差校正算法纠正测量分量的频率、相位和幅度等参数,信号中各频率分量在迭代循环中进行分离.仿真实验中,通过添加海明窗、汉宁窗、布莱克曼窗和莱夫-文森特窗等来展示该文方法的效果.实验结果表明,该方法相比其他算法具有较高的计算精度.  相似文献   
883.
首次将自蔓延高温合成法(self-propagating high-temperature synthesis,SHS)用于锰铝中间合金的制备。采用Miedema生成热模型、金属间化合物的双参数模型估算了锰铝中间合金的标准生成焓、标准熵及比热容。通过理论计算确定了Mn3O4-Mn2O3-CaO-Al反应体系的绝热温度。以Mn2O3、Mn3O4和CaO、金属Al为原料,进行了锰铝中间合金的自蔓延反应合成试验,采用化学滴定、X射线衍射以及光学显微镜的方法对产物进行分析。理论计算和实验结果表明:反应体系的绝热温度为3 160 K,确定了该体系进行自蔓延反应的可行性。采用自蔓延合成法制备出了锰含量高达78%以上的锰铝中间合金,拓宽了锰铝中间合金的生产工艺。  相似文献   
884.
As the avian influenza virus H5N1 swept from Asia across Russia to Europe, Nigeria was the first country in Africa to report the emergence of this highly pathogenic virus. Here we analyse H5N1 sequences in poultry from two different farms in Lagos state and find that three H5N1 lineages were independently introduced through routes that coincide with the flight paths of migratory birds, although independent trade imports cannot be excluded.  相似文献   
885.
Based on the non-Archimedian infinite model C^2R of the Data Envelopment Analysis, combined with characteristics of Chinese mainland banks' inputs and outputs, the paper sets up an index system of inputs and outputs as well as an overall technical efficiency evaluation model for Chinese banks, which considers not only the profit ability, but also the control capacity of banks risk. The overall technical efficiency values of Chinese banks are given respectively based on the samples of state owned banks and 14 integrated samples both state owned banks and shareholding banks. The input redundancy of labor, net value fixed assets, operating expenses, owner's equity, branch number and output deficiency of operating income, total increase in deposits, total increase in loans, ROE, decrease in bad debts ratio, are also calculated. The pertinence policy suggestions of efficiency improvement of banks are put forward. The results show that the efficiencies of new shareholding banks are far higher than non-shareholding bank and the all four state owned banks are commonly lower in overall technical efficiency. The overall technical efficiency of Agriculture Bank of China is the lowest one in all banks, and Bank of Communications is the efficiency lowest in all shareholding banks. The contributions and characteristics of the paper are: 1) the bad debit ratio is used to reflect the quality of the outputs, which is an improvement to the current literature of neglecting the difference in loans quality. 2) The inefficiency reasons of banks are list out by quantity analysis, and the pertinent macro strategies and concrete measures on improving banks efficiency are given, which is another improvement to current research that tend to give the efficiency value, but not ignore giving improving strategy from quantities analysis. 3) Banks overall technical efficiency values under several portfolios of inputs and outputs are given respectively, which not only overcomes the restraints that the sample size is at least the 2 times of the number of inputs and outputs indexes, but also measures banks overall technical efficiency from several directions. 4) It makes the efficiency values estimation more comparable by extracting four state owned banks for another efficiency evaluation. Combining both state owned banks and shareholding banks as a whole group of efficiency evaluation shows the real overall technical efficiency distance between two different kinds of bank and provide realistic basis for the bank reform of China.  相似文献   
886.
四川省的城市化水平较低,在一定程度上阻碍了区域经济发展水平的提高.本文分析了现阶段四川省城市化水平及其制约因素,并探讨了推动城市化进程的对策措施.  相似文献   
887.
RSPUDT滤波器通过引入声谐振腔 ,改善了普通SPUDT(单相单向换能器 )滤波器的形状因子和通带特性 .但由于它结构复杂 ,加权和优化很困难 .提出一种改进型RSPUDT结构 ,将原来集中的声谐振腔均一地分布在换能器中 ,成为许多相同的谐振腔单元 .这种结构使得RSPUDT可以采用基本的加权方法 ,优化过程更加简单 .34°ST切割石英基片上RSPUDT滤波器的计算和实验表明 :改进型RSPUDT较之于原型具有更好的形状因子和更平坦的通带 .改进型RSPUDT的这些优点将使其在低插损中频滤波器的设计中得到广泛应用 .  相似文献   
888.
分析了国内外关于技术定价的多种理论 ,探讨了影响技术价格的多种因素 ,在此基础上 ,结合铁路工业的特点 ,提出了铁路高新技术产品的定价原则 ,并在借鉴国内外经验模式的基础上研究提出了适合铁路工业高新技术产品系统的多元化定价模式 ,最后深入研究了成本效益模式中主要参数的确定方法  相似文献   
889.
鉴定锌离子的一种新方法   总被引:1,自引:1,他引:0  
在罗丹明B和亚铁氰化钾存在下,用N-烯丙基-N′-(对苯磺酸钠)硫脲鉴定锌离子,其灵敏度m=1.5ug,c=45ug.ml^-1,实验了鉴定条件和应用。  相似文献   
890.
In order to provide short‐run forecasts of headline and core HICP inflation for France, we assess the forecasting performance of a large set of economic indicators, individually and jointly, as well as using dynamic factor models. We run out‐of‐sample forecasts implementing the Stock and Watson (1999) methodology. We find that, according to usual statistical criteria, the combination of several indicators—in particular those derived from surveys—provides better results than factor models, even after pre‐selection of the variables included in the panel. However, factors included in VAR models exhibit more stable forecasting performance over time. Results for the HICP excluding unprocessed food and energy are very encouraging. Moreover, we show that the aggregation of forecasts on subcomponents exhibits the best performance for projecting total inflation and that it is robust to data snooping. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
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