Collision criterion for two satellites on Keplerian orbits

This paper analyzes the collision possibility for two satellites on Keplerian orbits. Coplanar and noncoplanar cases are considered, respectively. For each case, the problem of collision possibility analysis can be solved through two steps: First, to determine whether there is any intersection point of the two orbits; if there is no intersection point, the conclusion can be given directly that collision never happens. Secondly, if the two orbits do intersect, the collision possibility in the given time-scale can be studied in terms of the relationship between the two orbital periods and time. Numerical simulations for both cases, each including several situations, are given to prove the validity of the proposed collision criterion.     

基于Altera IP核的RS译码器的设计与实现

介绍了一种基于Altera公司提供的Reed-Solomon IP（intellectual property）核来实现RS译码功能的设计方法,该方法具有开发周期短、系统成本低以及稳定可靠特点。主要分析了Altera公司提供的IP核工作原理、参数配置以及接口设计,最后通过时序仿真验证了该设计的正确性。该设计方法已经成功应用于BPL长波接收机数据解调模块中。     

遥感影像三维可视化的实现及应用初探

三维可视化是众多GIS应用中的重要组成部分。本文就如何利用地形图和遥感图像等多源数据实现三维可视化的技术路线及相关原理作了详尽阐述并对其在地质中的应用做了初步探究,对野外地质区调工作部署有一定的辅助指导意义。     

矿床学研究思路的变化与进展综述

矿床学的发展突破在很大程度上取决于其研究思路的发展变化上。矿床学从传统的对单一矿种、单一矿床和单一成矿模式的研究发展到对成矿系列、成矿系统的全面探讨和整体认识,妥善处理了局部与整体、片面与全面、个体与群体、定性与定量、时间与空间等种种复杂关系,这种研究思路上的变化体现了系统的、辨证的哲学思维方法。     

The response of soil CO<Subscript>2</Subscript> efflux to desertification on alpine meadow in the Qinghai–Tibet Plateau

Assessing the global C budget requires a better understanding of the effect of environmental factors on soil CO₂ efflux from both experiments and theoretical research, especially in different desertified lands in the Qinghai–Tibet Plateau. Based on the enclosed chamber method, soil CO₂ efflux in four different desertified lands and one control [alpine meadow (AM)] were measured in June, August and September, 2008, respectively. Soil CO₂ efflux rates at the top, the middle, the bottom of a slope and the flat in front of the slope were obtained at Maduo County. The results showed that average daily soil CO₂ efflux rates were 3.72, 2.65, 2.68, 0.59 and 0.37 g m⁻² day⁻¹ in the AM, lightly (LDL), moderately (MDL), severely (SDL) and very severely desertified lands (VSDL) during the growing season, respectively. Soil CO₂ efflux decreased with the change of desertification. The response of soil CO₂ efflux to environmental factors was adequately described by the linear model; models accounted for 76, 65, 72, 59 and 71% of the variability on soil CO₂ efflux in the AM, LDL, MDL, SDL and VSDL, respectively. Any environmental factor, however, was insufficient to explain the soil CO₂ efflux; the common influence could perfectly reflect soil CO₂ efflux response to the desertification change.     

Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first model intercomparison experiment

This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models’ (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among models in simulating spatial correlation, intensity, and variance of precipitation compared with observations. Furthermore, the majority of models fail to produce proper intensities of the African Easterly Jet (AEJ) and the tropical easterly jet. AMMA Land Surface Model Intercomparison Project (ALMIP) data are used to analyze the association between simulated surface processes and the WAM and to investigate the WAM mechanism. It has been identified that the spatial distributions of surface sensible heat flux, surface temperature, and moisture convergence are closely associated with the simulated spatial distribution of precipitation; while surface latent heat flux is closely associated with the AEJ and contributes to divergence in AEJ simulation. Common empirical orthogonal functions (CEOF) analysis is applied to characterize the WAM precipitation evolution and has identified a major WAM precipitation mode and two temperature modes (Sahara mode and Sahel mode). Results indicate that the WAMME models produce reasonable temporal evolutions of major CEOF modes but have deficiencies/uncertainties in producing variances explained by major modes. Furthermore, the CEOF analysis shows that WAM precipitation evolution is closely related to the enhanced Sahara mode and the weakened Sahel mode, supporting the evidence revealed in the analysis using ALMIP data. An analysis of variability of CEOF modes suggests that the Sahara mode leads the WAM evolution, and divergence in simulating this mode contributes to discrepancies in the precipitation simulation.     

中国东部夏季降水与东亚垂直环流结构及其预测试验

本文在分析中国东部夏季降水的时空分布特征基础上, 从东亚高、中、低层大尺度环流异常着手, 选取对中国东部夏季降水异常有显著影响的大气环流预报因子, 分别应用逐步回归和最优子集回归法两种统计降尺度方法, 以动力气候模式CAM3.1预报输出的大气环流预报因子为基础, 以中国东部夏季降水的典型空间分布型为预报对象, 建立动力与统计相结合的中国东部夏季降水预测模型, 并对1981～2000年的中国东部夏季降水进行回报试验。结果表明: 中国东部夏季降水具有4类典型的空间分布型式, 且具有显著的准2年和年代际尺度振荡周期; 东亚高、中、低层大气环流异常的特定配置, 对东部夏季降水的空间分布型有显著影响; 使用两种降尺度方案建立的动力与统计相结合的预测模型对中国东部夏季降水异常具有一定的预报技巧, 可以在一定程度上提高动力模式对中国东部夏季降水的预报效果。     

三峡水库蓄水后巴东地区波速比( Vp/ Vs)研究

采用固定台站法计算了三峡水库蓄水后湖北省巴东地区 ML2.0以上地震的波速比值,并给出了各自的相关系数.结果显示,巴东地区地震波速比值变化与水库地震的震源浅,裂隙发育,水的渗入作用等有关,并存在扩容期间波速比降低,震前波速比回升的现象.     

湖北随州ML4.7地震序列基础资料分析

依据随州三里岗ML4.7地震序列的地震监测和宏观调查所获得的基础资料,对此次地震序列的时空强特征及地震成因机理进行了分析。为使地震资料准确可靠,对混淆在序列中的爆破波形与地震波形进行了鉴别和剔除。结合这些基础资料和震源机制解结果。分析认为随州地震序列在成因上与该地区存在的北东和北西向两组断裂构造有关,但主发震构造是北西向断裂。