层状地基端承桩扭转动力阻抗研究

本文采用Novak薄层法推导粘弹性地基的扭转动力阻抗,并将其用于考虑桩土相互作用的单桩扭转动力阻抗,又通过传递矩阵法将此公式推广到求取层状地基单桩扭转动力阻抗。而且本文以工程中常用的端承桩为例,推导了层状地基中端承桩扭转动力阻抗的简化计算公式。根据此公式,分析了频率、上覆软土层厚度、上覆软土层刚度等因素对单桩扭转动力阻抗的影响,分析结果表明,随着振动频率提高,层状地基中端承单桩的扭转动力阻抗的实部有缓慢下降的趋势,而虚部则增大;随着上覆土层厚度的增加,层状地基中端承单桩的扭转动力阻抗的实部和虚部均减小;随着上覆土层刚度的减小,层状地基中端承单桩的扭转动力阻抗的实部减小,虚部在低频段减小,而在较高频率段则增大。     

协调大集合模拟下全球海表面温度对北极对流层早冬增暖的影响

本文使用六个不同的最新大气模式进行了协调数值集合实验,评估和量化了全球海表面温度(SST)对1982-2014年冬季早期北极变暖的影响.本研究设计了两组实验:在第一组(EXP1)中,将OISSTv2逐日变化的海冰密集度和SST数据作为下边界强迫场;在第二组(EXP2)中,将逐日变化的SST数据替换为逐日气候态.结果表明...     

Effect of land‐use changes on nonpoint source pollution in the Xizhi River watershed,Guangdong, China

The Annualized Agricultural Non‐point Source (AnnAGNPS) pollution model has been widely used to assess and predict runoff, soil erosion, sediment and nutrient loading with a geographic information system. This article presents a case study of the effect of land‐use changes on nonpoint source (NPS) pollution using the AnnAGNPS model in the Xizhi River watershed, eastern Pearl River Delta of Guangdong province, China. The land‐use changes in the Xizhi River watershed between 1998 and 2003 were examined using the multitemporal remote sensing data. The runoff, soil erosion, sediment transport and nutrient loading 1998 and 2003 were assessed using AnnAGNPS. The effects of land‐use changes on NPS were studied by comparing the simulation results of each year. Our results showed that (i) the NPS loadings increased when forest and grass land converted into paddy, orchard and farmland land, and population size and gross domestic product size as well as the usage amounts of fertilizer and pesticide in the entire watershed were firmly correlated with the NPS loadings; (ii) the land‐use change during fast urbanization in particular when other land types were converted into the development land and buildup land led to increasing of NPS pollution; and (iii) urban land expansion showed more important effects on total organic carbon (TOC) loading compared with nitrogen and phosphorus loadings. Copyright © 2012 John Wiley & Sons, Ltd.     

标准系列制备的一种简单方法

一些新的稀释装置已用于原子发射光谱法和原子吸收分光光度法中,改变了以往预先配制浓度依次变化的标准系列的习惯做法。Ko(?)cielniak提出的一种非连续稀释方法,所配制溶液的浓度与稀释次数成指数关系。本文采用了这种技术对稀释装置作了改进,只需要一个小锥形瓶,添加或稀释同一个原始溶液便可制备出一系列标准溶液。设备简单、操作方便,用于原子吸收分光光度法测定钾长石中的钠、钾并与常规法对照结果满意。     

青藏高原与落基山背风气旋的对比分析(一)——天气结构

本文分别选用了一个东亚(EA)和北美(NA)的背风气旋进行对比分析.分析了两者的天气形势、动力和热力结构的差异.由于青藏高原和落基山地形对气流的不同影响,北美水汽从墨西哥湾向北输送,东亚水汽从南海向东北输送,因而,NA的对流不稳定区成南北带状分布;而EA的则成东西带状分布.EA的初生时,正压不稳定作用是主要的;在发展中,起主导作用的是斜压不稳定.     

青藏高原与落基山背风气旋的对比分析(二)——诊断分析

本文对第一部分所选的东亚和北美的背风气旋个例继续进行诊断分析。利用Q矢量诊断了两者的锋生函数和垂直运动,同时对两者进行了涡度收支、热量和水汽收支的计算,对比分析了两者物理量的分布特征。结果表明:北美的锋生与落基山地形影响有关,在落基山东侧,对流活跃;而东亚的锋生与海洋上感热和水汽蒸发有关,气旋入海后,对流作用加强。     

青藏高原和落基山对气旋的动力影响

本文利用北京气象中心的业务预报模式(B模式),采用全风速调整方案,进行了绕流、爬坡等各种数值试验,研究青藏高原和落基山对气旋的动力影响。结果表明,气流绕青藏高原而行,产生的散度场与东亚的气旋生成区和路径匹配;在青藏高原主体下游,高层辐合,抑制了我国大陆东部的气旋发展。在北美,落基山对大气的动力影响以爬坡为主,由于气流在迎风坡上升,空气绝热冷却,在背风面大规模下沉增温,对流层低层形成暖脊,这对背风锋生和背风气旋的发生发展有着直接的影响;另外爬坡作用也是美国中西部干线形成的主要原因。     

Mixture of populations

A simple example simulating a mixture of two normal populations results in some important observations, nonnormality and nonsymmetry of the mixture conditional pdf, nonlinearity of the conditional mean as a function of the conditioning data, heteroscedasticity of the conditional variance and its nonmonotonicity as a function of distance of the unknown to the conditioning data. A comparison of the mixture statistics with those predicted by traditional models ignoring the mixture reveals the inadequacy and inappropriateness of these traditional approaches. A mixture of two multivariate normal populations is illustrated through the analytical expressions of its conditional distribution and moments.     

用专家系统技术确定地图要素的地图符号类型

地图要素与地图符号类型之间的关系长期被人们忽略。但它确是专题地图设计专家系统中不可缺少的重要环节,是地图符号设计的基础。本文给出了地图要素类型和地图符号类型的定义,详细阐述了两者之间的关系;作者用Turbo Prolog2.0语言在COMPAQ 386微机上建立的地图要素的地图符号类型确定专家系统模块,可以对一幅地图上各种类型的地图要素确定其地图符号类型,为下一步具体的符号设计工作打下了良好的基础。