Rainfall spectrum change in North China and its possible mechanism

The seasonal distribution of the rainfall in North China has changed greatly since 1977, with more rainfall in spring and less in July, August, and September (JAS). Wavelet analysis showed that the JAS rainfall underwent an abrupt spectrum change in the mid-1960s. Its interannual variability has declined while the interdecadal component has become the dominant mode, associated with the dry climate. Correlation analysis found that the JAS rainfall is negatively correlated with the departures of the 500 hPa geopotential height significantly over the northwest and southwest of China, and positively correlated with the suer monsoon over eastern China. Therefore, the interdecadal ascending of the air pressure in northwestern China and the monsoon decaying over East Asia in the past 20 years may be the two major causes of North China drought.     

一种GIS中不规则曲线数字化的精度评定方法

通过分析GIS中曲线数字化的特征点与非特征点的性质,提出用曲率变化比较法建立由特征点组成的数学模型,分别对特征点进行拟合,并与其数字化的值比较,以此来分析GIS中不规则曲线数字化的精度。根据试验结果,得出不规则曲线数字化中误差为±0.28～±0.35mm,符合对手扶数字化线状目标的理论分析和模拟试验的±0.24～±0.32mm的结果。     

归一化测量多用表设计

介绍将电压、电流、电阻归一化测量的自动量程转换电路及主要软件流程。通过多路模拟开关与比例放大器的组合设置了多个电压、电流量程 ,利用恒流源电路实现了电阻 /电压归一化测量。应用单片机软件资源实现了数字滤波、误差校正、量程判断、标度变换等功能 ,研制的多用表具有交直流自动测量、测量范围宽等优点。     

篮球攻守转换的训练

现代篮球运动正朝着高技术、高速度、高强度的方向迅速发展,由于运动员的身高、身体素质和个人技术的不断提高,进攻与防守的对抗更加剧烈.因此,攻守转换的速度愈来愈快,攻守转换已成为现代篮球的重要特点之一.     

当代资本主义的新变化与"两个必然"

当代资本主义发生了一系列深刻变化：生产力快速发展，资本社会化，政府职能强化和经济运行有序化，阶级关系缓和化，收入分配制度社会化，从而延缓了资本主义的生命。但是，千变万变，资本主义的基本矛盾没有变，资本主义必然灭亡、社会主义必然胜利的论断不可变。     

高温相变容器的传热分析

吸热 /蓄热器是空间太阳能热动力发电系统的一个关键部件 ,其中的高温蓄热容器的传热性能会直接影响到整个系统的性能。本文利用焓法建立了吸热 /蓄热器中高温相变容器的传热数学模型 ,分析了计算结果     

Evidence for cold events in the early Holocene from the Guliya ice core, Tibetan Plateau, China

Evidence for the “8.2 ka cold event” has been provided mostly from the circum-North Atlantic area. However, whether this cold event occurred in other places is a key to understanding its cause. Here, we provide the evidence for the “8.2 ka cold event” from the Guliya ice core in the northwest Tibetan Plateau, and it was found that the peak cooling (~8.3—8.2 ka) in this ice core was about 7.8—10℃, which was larger than the cooling in the North Atlantic region. The primary causes for this episode were diminished solar activity and weakened thermohaline circulation. Moreover, another weak cold event, centered about 9.4 ka, was also recorded in the Guliya ice core record. These two cold events were concurrent with the ice-rafting episodes in the North Atlantic during the early Holocene, which implies that the millennial-scale climatic cyclicity might exist in the Tibetan Plateau as well as in the North Atlantic.     

临沂市耕地数量变化分析

利用52a耕地长序列统计资料，研究揭示了临沂市土地开发的特征和耕地数量变化的过程，剖析了耕地数量变化的主要驱动因子及其作用，提出了耕地资源可持续利用的对策。     

电流电弧作用下触头表面热过程的数值计算

在电弧热源正态分布于触头表面的情况下，根据正态分布的数学特征确定了电弧能量与电弧形状关系，并建立了触头传热模型；阐明了如何利用焓法处理相变过程，如何运用无量纲化的焓H和温度θ的关系简化求解温度的过程，同时运用传热模型对电流下的触头熔化过程进行了仿真。仿真结果显示：触头熔化的体积几乎随弧根半径的增加而线性增加。     

唐末五代词人心态与词风的嬗变

通过全面考察唐末五代词人心态与词风的嬗变轨迹,揭示出儒道传统的丧失、家国观念的淡漠以及无可奈何的乱世心态,为五代词创作的初兴提供了历史和文化的契机。通过多角度考察认为"花间词风"早在王建时代就已完全成熟,王衍、孟昶虽不免豪侈淫逸,却与"花间词风"关系不大。南唐一代是词体创作产生转折的关键时期,雅逸好学的社会风气,词人群体的学者化,以君臣欢会、高朋宴集为主的创作氛围,共同造就了南唐词从容淡雅的诗化景象。针对前人关于五代词创作与乱世君臣荒淫生活关系的论述,明确指出:放诞荒淫本身绝难造就五代词创作的初步繁荣。