External calibrator in global signal experiment for detection of the epoch of reionization

We present a conceptual design study of external calibrators in the 21 cm experiment towards detecting the globally averaged radiation of the epoch of reionization(EoR). Employment of external calibrator instead of internal calibrator commonly used in current EoR experiments allows removing instrumental effects such as beam pattern, receiver gain and instability of the system if the conventional three-position switch measurements are implemented in a short time interval. Furthermore, in the new design the antenna system is placed in an underground anechoic chamber with an open/closing ceiling to maximally reduce the environmental effect such as RFI and ground radiation/reflection. It appears that three of the four external calibrators proposed in this paper, including two indoor artificial transmitters and one outdoor celestial radiation(the Galactic polarization), fail to meet our purpose. Diurnal motion of the Galactic diffuse emission turns out to be the most probable source as an external calibrator, for which we have discussed the observational strategy and the algorithm of extracting the EoR signal.     

基于数值解与解析解耦合的SSI体系地震反应分析方法

基于子结构分析方法,提出了土-结构相互作用体系中数值解和解析解耦合的地震反应分析方法。此方法中,数值解是用有限元方法来模拟上部结构的非线性动力行为;而弹性结构-刚性基础-半无限大弹性地基中频域内的解析解,是通过离散时间递归滤波方法得到时域内的解来等效,且在整个体系中,利用土、结构两个子结构边界上的力和位移协调求解。本文提出的方法用有限元程序Opensees来实现,并用于一个线弹性单层框架结构的动力分析中。这种耦合的分析方法得到的结果,与土-结构相互作用单自由度体系的解析解进行了比较,验证此方法的精度、稳定性和工程实用性。     

基于虚拟化的“天地图?四川”网站集群设计与实现

本文通过对服务器集群和虚拟化技术的研究,设计了一种基于虚拟化的地理信息服务器集群架构,在此基础上,对地理信息服务软件系统进行了优化,并应用于天地图?四川的建设。通过相应的性能测试对比分析,采用虚拟化的“天地图?四川”服务器集群架构,能有效提高地理信息服务功能的可用性和性能。     

An improved direction relation detection model for spatial objects

Direction is a common spatial concept that is used in our daily life. It is frequently used as a selection condition in spatial queries. As a result, it is important for spatial databases to provide a mechanism for modeling and processing direction queries and reasoning. Depending on the direction relation matrix, an inverted direction relation matrix and the concept of direction pre- dominance are proposed to improve the detection of direction relation between objects. Direction predicates of spatial systems are also extended. These techniques can improve the veracity of direction queries and reasoning. Experiments show excellent efficiency and performance in view of direction queries.     

Distribution characteristics of Geo-hazards in Ganxi Valley after the Wenchuan earthquake

A devastating earthquake of Ms 8.0 struck the Wenchuan area on May 12, 2008. The quake triggered numerous landslides and avalanches in Ganxi Valley. Aerial photo interpretation indicates that the landslides and avalanches, presently in a stable state, are concentrated in 91 subregions of the valley, occupying 10.42 km², about 29% of the valley area. Some laws have been found on the gradient, aspect, elevation, distance of rupture, and formation lithology of geo-hazards in Ganxi Valley: (1) They are mainly situated on slopes between 30° and 50° and increase in number with increasing slope; (2) Failures are mainly in a southerly direction; and most occurred between 1,000 and 1,600 m, especially between 1,000 and 1,400 m; (3) Most are within 2,000 m of the Beichuan fault or within 1,000 m of other major faults; (4) most failures occurred from the T₁f + t formation in the study area. The geo-hazards status quo of Ganxi Valley provides foundation for the scheme of hazard reducing in the future.     

交错齿槛槽排导粘性泥石流的试验

排导槽是一种结构简单、效果明显、用途广泛的泥石流防治措施,在总结东川槽、V型槽等现有排导槽槽型优缺点的基础上,结合一种新槽型——交错齿槛型泥石流排导槽展开试验研究。提出排导槽排导指数概念,即直接反应排导槽排泄能力的参数。利用室内水槽模型试验,通过改变交错槽纵比降、齿槛间距、夹角等参数,得出排导指数与上述参数的关系,试验结果表明:1.与东川槽相比,交错齿槛槽的排导能力有大幅度的提升,最大增幅达74%,表明交错齿槛有较强的挑流排泄能力,能有效解决东川槽等存在的淤积难题;2.不同比降下,交错槽主要设计参数组合存在差异,其中10%与15%比降下,60°齿槛间距为30 cm时,交错槽的排导指数最大,排导能力最强;而12%比降下,60°齿槛间距为40 cm为最优组合;3.小角度齿槛(60°)齿槛挑流排导能力较大角度(80°)更强,更适合坡降较小的排导槽;齿槛角度越大,齿槛的挑流能力有限,阻流作用越明显,对需控制流速及洪峰流量的泥石流,可考虑采用大角度齿槛。     

利用特色叠前深度偏移技术消除崎岖海底影响——以珠江口盆地番禺—流花地区应用为例

叠前深度偏移技术可有效地进行复杂构造成像,针对不同的地质条件,需要应用不同的处理技术。针对陆架坡折带崎岖海底造成的地震成像差、构造畸变等问题,选择使用了如下叠前深度偏移技术:通过海平面叠前深度偏移技术得到精确的海底成像;通过约束速度反演、加入断层控制建立初始速度模型;采用百分比扫描速度分析对速度模型进行迭代修改,进而快速得到较为收敛的速度体;在此基础上再采用Kirchhoff积分法进行偏移。在珠江口盆地番禺—流花地区应用上述技术,基本消除了崎岖海底对下伏地层的影响,改善了断层和地层成像,并落实了该地区的构造圈闭。     

西北干旱区荒漠生态系统通量贡献区模型研究

涡度相关仪通量值所代表的通量贡献区范围,对于通量观测塔的选址、仪器安装高度的确定以及通量观测数据的质量控制等具有重要的指导意义。利用通量贡献区模型对位于古尔班通古特沙漠试验场通量观测资料的空间代表性进行初步分析。结果表明：该荒漠区在大气稳定条件下90%的通量贡献区最远可以达到686.40 m,通量贡献函数最大点的位置在162.50 m;大气稳定时各风向的通量贡献区范围在生长末期均达到最大,生长初期和中期的源区变化因受到各风向风速和植被下垫面的影响而有差异;大气不稳定时不同生长时期各风向通量贡献区没有固定变化规律;通量源区大约有58.71%的信息来自于荒漠区通量观测塔西南至西北方,整个生长季生长末期通量贡献最多,所占比例为40.16%。由FSAM模型测得的通量贡献区范围可以较准确地反映荒漠生态系统下垫面的通量信息。