CNGI青海湖系统建设中的若干技术问题

CNGI 青海湖系统支撑青海湖区域的生态保护和多学科交叉融合的科研协作。针对青海湖基础设施种类众多的特点,我们发展了 IPv6 相关关键技术,应用于基础网络环境建设、数据传输、设备管理与状态监控等多个层面,并充分考虑了由此带来的安全隐患,制定了相应安全策略。这些技术可以支持多种传感器构成的 IPv6 网络,并支持 IPv6 的相关应用软件研发,促进大规模、跨领域复杂科学问题研究工作。     

散景效果的真实感绘制

针对现有方法绘制的散景效果真实感较差的问题,提出一种基于几何光学理论的散景效果真实感绘制方法.该方法以光线传播的折射定律为基础,利用序列光线追踪方法对相机镜头的光学成像特性进行精确建模;对相机镜头的内部结构进行精确模拟,包括孔径光阑和渐晕光阑,以绘制出由孔径形状和渐晕共同作用的散景效果;利用几何光学理论和序列光线追踪方法精确计算出出射光瞳的位置和大小,以辅助光线采样,提高光线追踪效率.绘制结果表明,利用该方法能够绘制出较为逼真的散景效果,正确模拟了孔径形状和渐晕对散景效果的影响,并具有较高的光线追踪效率.     

景深效果绘制技术综述

景深效果能够增强计算机生成图像的真实感,因此关于这类效果的绘制已成为计算机图形学中的重要研究方向。针对景深效果的绘制问题,首先研究和分析各种相机镜头模型的光学成像原理,比较各类镜头模型的特点和模拟景深效果的能力;然后分类总结景深效果绘制的基本原理和典型算法,比较各类景深绘制方法的优缺点。最后指出景深效果绘制技术的应用价值,并展望未来的研究方向。     

ScienceWord+PagePlayer模式电子教案设计与实现——《多面体和棱柱》课题教案制作

随着教学办公自动化的发展,针对"Word+PowerPoint模式"电子教案模式中的一些不足,应用ScienceWord和PagePlayer设计制作的电子教案不仅能够方便制作出各种几何图形,还能快速制作出各种教学需要的特效文字,实现更简便高效的电子教案制作。     

探究式教学法在中职网页设计制作课程中的应用

网页设计制作是一门集设计技术、资源、美学等为一体的综合设计课程。本文阐述了探究式教学法的概念和探究式教学法的过程结构步骤,其次,从多方面就探究式教学法在中职网页设计制作课程中的应用进行探讨,同时,就运用探究式教学模式需要注意的几个问题提出了自己的看法和建议。     

在Debian上用DRBD实现MySQL群集

本文旨在Debian系统上,创建一个基于DRBD磁盘镜像技术的MySQL群集及故障转移方法,同时使用了负载均衡技术来完善系统。     

Evaluating MODIS data for mapping wildlife habitat distribution

Habitat distribution models have a long history in ecological research. With the development of geospatial information technology, including remote sensing, these models are now applied to an ever-increasing number of species, particularly those located in areas in which it is logistically difficult to collect habitat data in the field. Many habitat studies have used data acquired by multi-spectral sensor systems such as the Landsat Thematic Mapper (TM), due mostly to their availability and relatively high spatial resolution (30 m/pixel). The use of data collected by other sensor systems with lower spatial resolutions but high frequency of acquisitions has largely been neglected, due to the perception that such low spatial resolution data are too coarse for habitat mapping. In this study we compare two models using data from different satellite sensor systems for mapping the spatial distribution of giant panda habitat in Wolong Nature Reserve, China. The first one is a four-category scheme model based on combining forest cover (derived from a digital land cover classification of Landsat TM imagery acquired in June, 2001) with information on elevation and slope (derived from a digital elevation model obtained from topographic maps of the study area). The second model is based on the Ecological Niche Factor Analysis (ENFA) of a time series of weekly composites of WDRVI (Wide Dynamic Range Vegetation Index) images derived from MODIS (Moderate Resolution Imaging Spectroradiometer – 250 m/pixel) for 2001. A series of field plots was established in the reserve during the summer–autumn months of 2001–2003. The locations of the plots with panda feces were used to calibrate the ENFA model and to validate the results of both models. Results showed that the model using the seasonal variability of MODIS-WDRVI had a similar prediction success to that using Landsat TM and digital elevation model data, albeit having a coarser spatial resolution. This suggests that the phenological characterization of the land surface provides an appropriate environmental predictor for giant panda habitat mapping. Therefore, the information contained in remotely sensed data acquired with low spatial resolution but high frequency of acquisitions has considerable potential for mapping the habitat distribution of wildlife species.     

Thermodynamic modeling of the V–Si system supported by key experiments

The V–Si system is reassessed based on a critical literature review involving recently reported data and the present experimental data. These new data include the thermodynamic stability of V ₆Si₅ and the enthalpies of formation for the compounds calculated by first-principles method. Two alloys were prepared in the region of (Si)+V Si₂ and annealed at 1273 K for 14 days. After X-ray diffraction (XRD) and chemical analysis of these alloys were performed, the eutectic reaction (L⇔(Si)+V Si₂) temperature was determined by differential thermal analysis (DTA). Self-consistent thermodynamic parameters for the V–Si system were obtained by optimization of the selected experimental values. The calculated phase diagram and thermodynamic properties agree well with the experimental ones. Noticeable improvements have been made, compared with the previous assessments.     

Thermodynamic description of the Mg–Eu binary system

Thermodynamic assessment of the Mg–Eu binary system has been carried out by combining first-principles calculations and Miedema’s theory with CALPHAD method. Firstly, the mixing enthalpy of the liquid alloys was calculated by using Miedema’s theory, and formation enthalpies of the intermetallic compounds were calculated by using the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA). Subsequently, the liquid phase was described employing a simple substitutional model, of which the excess Gibbs energy was formulated with a Redlich-Kister expression. And the solubility of Eu in HCP_(Mg) and Mg in BCC_(Eu) were neglected. While the intermetallic compounds Mg₁₇Eu₂, Mg₅Eu, Mg₄Eu, Mg₂Eu and MgEu, were treated as stoichiometric compounds. Consequently, a set of self-consistent thermodynamic parameters for all stable phases in the Mg–Eu binary system were obtained, which can reproduce most of the thermodynamic and phase boundary data.     

基于模板法的网页英语试卷自动抽取技术的研究

为解决在线考试系统中建立海量数据库的问题,采用基于模板法的Web信息抽取方法,提取相似网页中的正文内容。并根据包含英文试卷的网页特点,制定正文抽取规则,最终可获得完整的英语试卷及其答案。实验结果表明,该方法具有较高的准确率和提取速度。