国际地球参考框架2000(ITRF2000)的定义及其参数

对国际地球参考框架2000(ITRF2000)的定义、主要参数及其应满足的条件进行了研究,重点指出了它和历史上的各个ITRFyy的不同,并阐述了各个ITRFyy的联系和区别,给出了它们之间相互转换的参数。     

关于国家高精度GPS B级网成果的使用问题

本文简要地介绍了国家高精度GPS网[1]情况,对GPSB级网与2000国家GPS大地控制网[3]重合点的成果进行了比较与分析,在2000国家大地坐标系下,如何处理以B网成果为基准建立的GPSC级网或城市基础控制网成果问题进行了讨论,提出了解决办法,并进行了试算、分析和比较。     

Effects of jpeg 2000 compression on automated dsm extraction: evidence from aerial photographs

This paper evaluates the effects of JPEG 2000 compression on automated digital surface model (DSM) extraction, using the area-based matching technique. Two stereopairs of aerial photographs, which have different photo scale, pixel size, and topographic type, are used as the images for the experiments. In the experiments, the DSM generated from the uncompressed image is set as the reference, and the elevation accuracy is computed for a range of compression ratios (2:1 to 100:1). The results show that the employed indices of image quality based on the JPEG 2000 compression are clearly superior to the commonly used JPEG compression technique—especially for high compression ratios. However, the elevation accuracy varies with the compression ratios. Also, JPEG 2000 compression does not have a significant influence on the percentage of the successful matching rate. In addition, a near linear fall-off is observed in extracted DSM accuracy with increasing compression ratios.     

2000年Jerk存在吗

从分布在欧亚美太平洋几个质量较好的台站的dY/dt变化曲线看,2000年或2001年似乎没出现新的Jerk(Y)。     

在EBEX-2000实验资料中湍流谱和局地各向同性特征

采用2000年8月在美国加州棉花地两个高度上应用超声三分量仪、快速响应050206 温度和湿度仪进行的EBEX-2000 (International Energy Balance Experiment,2000,EBEX-2000)风速三分量、温度和湿度湍流实验观测数据,计算分析了湍流速度、温度和湿度谱在不同稳定度下的特征.对湍流的局地各向同性进行了讨论并与Kansas和长白山原始森林湍流实验得到的结果进行了比较,得到了一些湍流特征量在不同下垫面情况下的一些有意义的特征.     

常见网络故障浅析

在我们安装好一个局域网后，你是否经常为如何排除网络的故障而烦恼呢？遇到该如何解决呢？在这里向大家介绍怎样使用win95/98/NT/2000操作系统内置的一些实用的工具来解决一些网络故障，以及在使用windows2000的过程中遇到的一些实际问题。     

水稻高温热害风险评估方法研究

以衡阳地区的水稻生长为研究对象,对ORYZA2000水稻模型的相应参数进行了本地化,模拟了该地区常年气候条件、设定高温条件及各年高温条件下的一季稻产量,并计算了各年实况及设定条件下的产量灾损率,在此基础上建立了两种水稻产量灾损率评估模型.研究发现: 46 a来衡阳地区水稻开花灌浆期平均日最高气温为34.98 ℃,高于水稻生产的最适温度5 ℃以上;相对常年产量,由高温热害导致的产量灾损率最高为67.2%,历年灾损中2003年的灾损率接近最高值,达67.0%;高温造成的产量灾损率受高温程度及持续时间的共同影响,二者缺一不可;根据多元回归建立的灾损率评估模型,F计算值＞＞F查表值,方程有意义.其趋势预测完全一致,灾损率精确度＞72%;根据高温指标建立的灾损率评估模型通过了46 a的大样本检验,在高温热害风险评估方面具有一定的实际应用价值.     

Characteristics of Temperature Change in China over the Last 2000 years and Spatial Patterns of Dryness/Wetness during Cold and Warm Periods

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3℃ and 0.7℃, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56°± 0.42℃(100 yr)~(-1); however, temperatures recorded in the 20 th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20 th century warming can primarily be attributed to a mega El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.     

惯性力影响下的渠道倒虹吸水力计算

从能量角度出发,分析了管渠结合一维非恒定流系统中倒虹吸进出口断面能量损失,对是否考虑惯性力的影响进行了分析比较,并结合南水北调中线工程某段实例进行了对比计算,结果说明考虑惯性力计算出的结果更符合实际情况.     

基于C#和SQL的校园短信信息系统的探讨

短消息,俗称短信,已经成为现代人交流的常用手段之一。但是在实际使用中,存在着诸如手机屏幕小,影响短信的阅读以及手机键盘小,影响短信的输入等问题。针对这些问题,本文设计并开发了基于C#语言和SQL数据库的校园短信信息系统。该系统经过需求分析和数据库设计,在建立的用户表和短信表的基础上,编程实现了功能设计中的登录验证功能、简单查询功能、复合查询功能和发送短信功能,并在某大学里进行了实际的使用。