Polarization comparison between on-axis and off-axis dual reflector telescopes: Zemax and Grasp8 simulations

The cross-polarization performance for an off-axis dual reflector telescope is shown to be equivalent to an on-axis telescope when used for a large-format focal plane array. The need for low sidelobes forces the on-axis designs to high curvature, which in turn leads to high cross-polarization at the edge of the field. A scheme for correcting instrumental-polarization is presented, as well as a full design for a polarization-pure optical system capable of supporting a 1000-element focal plane array.     

传统村落分布的“边缘化”特征——以湖南省为例

传统村落伴随快速城市化、城进乡退的进程,呈现出“边缘化”分布趋势。以湖南省723个传统村落为实证对象,借助ArcGIS 10.0技术平台,选取影响传统村落的农业资源、经济、空间及交通等四类因素,以县域为统计单元,对湖南省域进行核心—边缘区评价。将评价结果与传统村落分布进行叠加,结果显示湖南省传统村落分布呈现农业资源边缘化、经济边缘化、空间边缘化和交通边缘化特征,并分析传统村落分布“边缘化”特征形成机理,提出保护开发建议。     

Real-time implementation of `propagator' bearing estimationalgorithm by use of neural network

A neural network for implementing the Marcos `propagator' bearing estimation algorithm is presented. It is shown both analytically and by simulations that this neural network is guaranteed to be stable and to provide the results arbitrarily close to the accurate propagator operator and the orthogonal projection operator on the noise subspace within an elapsed time of only a few characteristic time constants of the network. The parameters such as the interconnection strengths and bias currents of this proposed network can be obtained from the cross-spectral matrix without any computations     

UNRAVELING ECOTOURISM PRACTICE：PROBLEM ANALYSIS BASED ON STAKEHOLDERS

Despite the considerable literatures defined what Ecotourism is or should be, it is experiencing various practices with different features. Now the term “Ecotourism” is almost applied to all tourism activities which are based on nature. Faced to the flooding of those unqualified Ecotourism, it is of great necessity to put forward professional claim. The present writer holds that the key to the realization of rigorous Ecotourism chiefly lies in the relationships among the different interest groups involved in it. So the focus of this paper is just on giving a special analysis to the interest relations between those stakeholders which include local government, tour-operators, local residents and eco-tourists, and thus helping to find out what wrong is in those unqualified Ecotourism and the roots of those problems.     

A Statistical Study of Transequatorial Loops

We identify 356 transequatorial loops (TLs) from the data set of Yohkoh Soft X-Ray Telescope (SXT) in the period of solar cycles 22 and 23. The classification of the TLs can be made on two bases. One is according to the magnetic polarities of the footpoints of TLs, and the other is according to the number of TLs in the same region. Based on the first criterion, TLs fall into two categories: PTLs in which the magnetic polarities of the footpoints are the same as the preceding polarities and FTLs in which the footpoint polarities are the same as the following polarities of active regions, respectively. It is found that PTLs have a preference; about 66% of the TLs are PTLs, and this preference of PTLs is independent of the solar cycle. The percentage of FTLs is about 34%. Based on the second criterion, TLs are also divided into two categories: the number of TLs in a region is either single (STLs) or multiple (MTLs). In addition, we find that the number of TLs, PTLs, and FTLs have good correlations with solar cycle indices. By comparing the number of TLs and the number of active regions in each year, we obtain the ratio between them. The separation of footpoints and their yearly variations are calculated, and we find that our result is consistent with spörer's law.     

Expansion properties and creep tests for a new type of solidified expansive sealing material for gas drainage boreholes in underground mines

This study was conducted to find the optimal expansion for a new type of solidified expansive sealing (SES) material. The aim was to better meet the requirements for sealing gas extraction boreholes in underground coal mines by examining the expansion and creep properties of the material. The effect of different proportions of expansion agent on expansion time, expansion mechanisms, and creep properties of the SES material was investigated using an electronic universal testing machine and other systems. Based on the results of step loading creep tests, the Kelvin–Voigt viscoelastic model was selected to further analyze the mechanical properties of the material. The analysis showed that when the proportion of expansion agent in the SES is increased to 2.0%, the final expansion percentage increases to 11.5%, and the rapid expansion time and expansion preparation time quickly decreases to 18 and 12 min, respectively. In addition, the step loading displacement and constant force load displacement increase sharply. The creep parameters E₀, E₁, and η₁ of the Kelvin–Voigt model reflect the gradually weakening of the compressive capacity and anti-deformation ability of the SES material. Based on the analysis of the experimental results and field application on sealing boreholes using SES material, it was possible to establish the optimum amount of expansion agent that should be added to the SES material. The optimized proportions can meet the requirements of good flowability, high compressive capacity, and anti-deformation ability for borehole sealing in a mine.     

伴有区域暴雨的重庆秋季连阴雨及其暴雨特征

利用降水实测资料、1°×1°的NCEP格点再分析资料对2000年以来的伴有区域暴雨的重庆秋季连阴雨过程进行统计分析。结果表明：伴有区域暴雨的重庆秋季连阴雨过程主要发生在9月份,重庆西部地区为伴有区域暴雨的连阴雨过程的多发区;可将连阴雨期间区域暴雨就有无台风西进登陆我国分为两类,两类暴雨的影响系统的差异表现为,没有台风登陆时700hPa/850hPa的主要影响系统为切变线或者西南涡;有台风登陆时的主要影响系统则为台风倒槽;24小时变温、低层涡度、假相当位温、整层水汽通量以及比湿对连阴雨期间暴雨的预报有较好的指示意义,同样表征水汽条件的相对湿度的指示意义较差。     

上海城市雾理化特性的研究

通过3年冬季雾的理化特性观测和分析，首次探讨上海城市雾的物理特性、微结构、酸度和化学成分等，从而了解上海雾的生成、发展、消散原因及理化结构。为提高雾的预报准确率和人工局部消雾提供物理背景。     

地质过程动力学体系、研究层次及认识论

本文根据作者个人的观点讨论了地质过程动力学的本质特征,根据地质过程动力学广泛的研究对象和研究内容归纳了地质过程动力学的分支体系,并依据地质过程动力学的不同研究水平和研究方法把地质过程动力学划分成3个不同的层次,分别讨论了各层次动力学的研究方法。最后,作者讨论了有关地质过程动力学研究中经常遇到的几个认识问题,期望对地质过程动力学研究起到推动作用。