Carbon isotope ratios of C4 plants in loess areas of North China

Carbon isotope ratios (δ ¹³C) of 89 C₄ plant samples were determined from the loess area in North China. δ ¹³C values vary between −10.5‰ and −14.6‰ with a mean of −12.6‰. Along a precipitation gradient from the semi-moist area to the semiarid area, then to the arid area, the δ ¹³C values of C₄ plants show a slight decreasing trend. The δ ¹³C values of C₄ plants in the dry season are found lower than those in the wet season. These trends are opposite to those observed for C₃ species.     

基于小波分解和布谷鸟搜索算法的小波神经网络风速预测（英文）

风速预测是风电场运行和风电并网过程中的关键技术之一。由于风速序列呈现出明显的间歇性和波动性,使用单一模型进行时预测难以取得满意的结果。本文发展了三种混合多步预测模型,并将他们与已有的风速预测模型相比较。这三个模型结合了小波分解、布谷鸟搜索算法和小波神经网络,分别记为CS-WD-ANN,CS-WNN和CS-WD-WNN。研究采用中国山东省两个风电场的实测数据进行模拟试验和模型比较,结果显示CS-WD-WNN表现最佳,具有最低的统计误差。     

南京市近地层气象要素与大气真菌浓度分布规律的调查研究

本文以1998年7月的观测资料为例,分析了南京市某地气象要素的变化规律以及该地区大气真菌浓度的分布特征,对二者之间的相互关系进行了初步探讨,发现一天内气象要素及真菌浓度均呈周期变化,且二者有一定的相关性。     

数字海淀智能平台开发

本文着重介绍数字海淀智能平台开发框架的主要内容和功能。即数字海淀智能平台总体设计方案及技术规范研制 ;基础信息平台的数据更新与扩建 ;数字海淀智能管理信息系统开发 ;公众服务信息系统开发 ;数字海淀技术支持系统的软件开发与建设。功能开发集中在实现各子系统的可视性 ;辅助决策系统的规划、分析和决策能力等。     

基于克里金法重力数据插值的研究

分析了变异函数的五种理论模型,采用了各种模型进行插值计算,实现了对我国某区域重力异常数据进行空间插值。     

温室效应对未来长江中下游地区温度和降水变化的影响

使用全球海气耦合模式和区域气候模式,对人类活动影响导致的温室气体和气溶胶增加引起的长江中下游地区的气候变化进行了分析研究.全球模式部分使用的是IPCC数据分发中心提供的5个模式模拟结果,包括IS92a中未来温室气体增加(GG)以及温室气体和硫化物气溶胶共同增加(GS)和A2、B2共4种排放情景.分析表明在温室气体增加的情况下,这里未来的地面气温变化与全球和全国一样,都呈增加趋势.以GG和GS为例,GG情景下,这一地区的变暖幅度在21世纪末期达到4.2℃, GS情景下达到3.1℃.但总体来说这里的变暖幅度较全球和中国其它大部分地区小.各个季节中,冬春季的增温幅度大于夏秋季.对降水的分析表明,GG情景下长江中下游地区是中国降水增加较少的地区之一,而在GS情景下,降水将出现微弱的减少.区域气候模式的模拟,在气温变化方面得到的结果和全球模式类似.但降水与全球模式的结果有所差别,主要表现在降水增加的季节分布不同上,模拟结果中降水增加最多的是冬季和夏季(增加值分别为44%和23%),而春秋季的降水将减少.     

深水顶张式立管全耦合动力响应及参数敏感性分析

通过建立双套管与油管的全耦合运动控制方程,使用Newmark-β法,运用Matlab软件进行编程,对模型进行非线性时域动力耦合响应分析,分析在一定波浪环境,不同扶正器布置间距下,立管各层相同节点处耦合动力响应,研究各层管之间发生碰撞和摩擦的最大扶正器布置间距;分析相同扶正器布置间距下,不同顶张力系数对耦合动力响应的影响。结果表明:在波浪作用下,全耦合动力响应分析比等效管更能展现各层管的实际动力响应;扶正器布置间距与顶张力系数的取值不同,会影响各层立管的耦合响应与相对位移,取值不当时,立管会发生碰撞。     

试论砖瓦粘土企业的现状与发展趋势

本文阐述了廊坊市砖瓦粘土企业的发展现状,分析了其发展趋势,提出了加快地方经济发展的合理化建议。     

一维大气边界层二阶闭合的有限元数值模式 I. 对流边界层模拟

利用有限元法用于二阶湍流闭合大气对流边界层模式,并模拟了Wangara试验33天的对流边界层的发展过程,计算结果表明,该模式能真实的模拟出对流边界层的发展过程,并且准确地反映对流边界层中湍流扩散和输送过程。     

Environmental process and convergence belt of atmospheric NO2 pollution in North China

Both surface environmental monitoring and satellite remote sensing show that North China is one of the regions that are heavily polluted by NO₂. Using the NO₂ monitoring data from 18 major cities in the region, the tropospheric NO₂ column density data from the Ozone Monitoring Instrument (OMI) on the Aura satellite, and the observations from the China Meteorological Administration network, this paper analyzes a regional NO₂ pollution event in February 2007 over North China, examines the convergence of the pollutant, and identies its correlation with the atmospheric background conditions. The results show that daily mean NO₂ concentrations derived from surface observations are consistent with the mean values of the OMI measurements, with their correlation coeficient reaching 0.81. The correlations of NO₂ concentration with general weather patterns and sequential changes of temperature structure from 925 hPa down to the surface indicate that the weather fronts, high pressure and low pressure systems in the atmosphere play a role in changing the temporal and spatial evolutions of NO₂ through removing, accumulating or converging of the pollutant, respectively. It is also found that the eastern Taihang Mountains is most heavily polluted by NO₂ in North China. Based on a model that correlates NO₂ column density with surface wind vector, the relation of the NO₂ concentrations in six major cities in North China to the surrounding wind field is analyzed. The results show that the maximum wind field is associated with the highest frequency of pollution events, and under certain large-scale atmospheric conditions together with the topographic effect, small- and meso-scale wind fields often act to transport and converge pollutants, and become a major factor in forming the heaviest NO₂ pollution event in North China. Analysis of the causes for the severe NO₂ pollution event in this study may shed light on understanding, forecasting, and mitigating occurrences of heavy NO₂ pollution.