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851.
QTM地址码与经纬度坐标的快速转换算法 总被引:11,自引:2,他引:11
球面四元三角网(QTM——Quarternary Triangular Mesh)结构是目前研究全球海量数据管理的有效方法之一。但是,在现有的QTM地址码与经纬度的转换算法中,“ZOT投影法”的转换速度快,但生成的编码缺乏方向性;“ETP投影法”生成的编码具有固定的方向性,但转换速度慢。为解决这个矛盾,提出一个新的转换算法——“行列逼近法”(CAM——Cavalcade Approach Method),其算法的基本原理是根据QTM的行和列,按一定的方向递归逼近地址码。文章给出了算法的详细步骤,并在实验中应用不同点数在不同层次对几种典型的转换算法进行了对比分析,结果表明:“行列逼近法”在保证所生成的地址码具有固定方向性的同时,时间消耗仅为“等三角投影法”的7%~20%左右。 相似文献
852.
853.
An engineering approach is proposed for representing both site effects and soil-structure interaction in extended alluvial valleys, by using the one-dimensional model of shear were propagation corrected empirically to account for lateral heterogeneities and generated surface waves. The peak structural response is expressed by means of spectral contours that are a function of the predominant period of the site and the fundamental period of the structure. Variations of the peak spectral ordinates with the prevailing site period can be deduced from these contours. A number of events of firm ground, representative of the most dangerous earthquakes expected in Mexico City, are assumed as design earthquakes. Making use of the resulting spectral contours, the provisions for site effects recommended in the Mexican seismic code are evaluated. Also, considering as control motion the 1985 Michoacan earthquake recorded at a representative firm site, spectral contours with soil-structure interaction are obtained which allow one to identify the significant interaction effects originating in the Valley of Mexico for medium- and long-period structures. The influence and relative importance of the critical parameters involved are examined within practical ranges of interest. 相似文献
854.
Chin-Hsiung Loh Chau-Shen Hwang Wen-Yu Jean 《Soil Dynamics and Earthquake Engineering》1998,17(5):335-345
The Park and Ang damage model was used as the "Structural Damage Control Model" to study the seismic design parameters. This damage control model included the displacement ductility and hysteretic energy in the analysis of elastic-perfect-plastic single-degree-of-freedom system. Based on this damage control model, the reduction factor and yield base shear coefficient are discussed. Seismic data collected from Taipei basin were used to examine the code-provided yield base shear coefficient which reflects the influence of using a damage control model in the seismic design parameter. Effects of seismic source as well as Taipei basin topography are also considered in examining the variation of yield base shear coefficient. 相似文献
855.
A barotropic model containing large-scale topography and zonal mean flow is established to discuss the effects of large-scale topography on the low-frequency waves. The results show that what affects low-frequency waves mostly is maximal height of topography and topographic slope. The former makes frequency of topographic Rossby waves decrease, the latter makes Rossby waves instable. Moreover, when topographic slope is appropriate, it can also make Rossby waves turn into low-frequency waves. 相似文献
856.
采用伴随码方法构造了数值天气预报的伴随模式系统,并对其正确性进行了检验,发现伴随码推导伴随模式是很有价值的工具。用理想场和实际资料进行的试验发现:权重函数和尺度因子选取的不同及不同的网格距对伴随模式同化系统会产生不同的影响。试验表明伴随模式系统有较强的同化能力。 相似文献
857.
H.263视频编解码器在TM1300上的实现与优化 总被引:6,自引:0,他引:6
介绍了ITU-T.H263编解码算法原理和TM1300定点DSP芯片。针对该芯片的硬件结构特点,设计了一套设计TM1300之上的实时视频信号采集、视频编码、视频输出系统的可行方案。讨论了H.263实时视频编码在TM1300上定点实现的关键技术和难点问题,详细论述了H.263编解码算法的代码优化技术。测试表明,本文的实现及优化技术是可行的。 相似文献
858.
中国海图符号发展特点研究 总被引:1,自引:0,他引:1
海图符号又称为海图语言,是制图者和用图者通过海图进行信息传输和交流的工具和桥梁,是连接符号学与海图制图学的有机知识整体。本文在分析海图符号的概念、特征与功能的基础上,提出了当前海图符号的三个主要发展特点,即相对稳定性、国际性、变异性;指出了目前海图符号系统需要改进的几个问题。本文研究的主题对于设计与应用海图符号系统具有重要的参考作用。 相似文献
859.
Yoshimitsu Fukushima Onur Köse Tekin Yürür Philippe Volant Edward Cushing Richard Guillande 《Journal of Seismology》2002,6(3):379-396
The 17 August 1999 Kocaeli earthquake in Turkey produced a majorsurface rupture. We traced this surface rupture from Gölcük toDüzce and located it accurately by using GPS. The closest distancefrom the surface rupture to the strong motion observation sites weredetermined. Then the attenuation characteristics of the observed peakground acceleration were compared with the attenuation relation given byFukushima and Tanaka (1992), which is suitable for the near-fault zone inJapan and gives results that closely match data recorded during the 1995Hyogo-ken Nanbu earthquake in Japan. Although this attenuation relationwas developed for Japan, we found that it agreed well with the KOCAELIearthquake. Furthermore, the observed spectral acceleration of 5%damping was compared with the building design code of Turkey and theobserved level was lower than the code. 相似文献
860.