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一个图的自同构群通常反映了该图的对称性,讨论一个图的自同构群构造是代数图论中的基本问题之一。直观上可以看出,圈Cn的自同构群是2n阶的,但对于其具体构造目前还没有形式化的证明。作者基于群作用的思想,利用群的轨道方程对此问题研究,得出Cn的自同构群是一个二面体群的结论。通过严格的推证,表明该结论是可靠的。 相似文献
166.
集成和互操作一直是GIS发展的热点问题,而在互联网时代背景下产生的Web服务(Web Service)技术为GIS的集成和互操作提供了全新的、有效的解决途径。在介绍和分析Web服务技术的基础上,提出并实践了一种将地图服务的基本功能包装成Web服务进行发布的思路。通过将GIS的基本功能包装成Web服务,可以实现使用一种标准的协议来实现各GIS应用系统的交互和集成,屏蔽了系统间软、硬件平台的不同。 相似文献
167.
塔克拉玛干沙漠石油公路沿线风沙活动的气候环境 总被引:5,自引:2,他引:3
塔克拉玛干沙漠石油公路沿线风沙活动是由塔木盆地内热能释放与冷空气入侵相互作用的结果。冷期,盆地内冷高压逆温作用较强,地面热能不足,使得风力和风沙活动强度弱;暖期,盆地内热源剧增,每当热能源饱和遇到冷空气入侵诱导,导致了强风及强风沙活动天气。可见,区内风沙活动及风成景观的塑造过程,主要是在暖干期进行的。 相似文献
168.
NEAR-FAULT DISPLACEMENT AND DEFORMATION OBTAINED FROM ONE-KILOMETER-LONG FAULT-CROSSING BASELINE MEASUREMENTS-A PRELIMINARY EXPERIMENT AT 2 SITES ON THE EASTERN BOUNDARY OF THE SICHUAN-YUNNAN BLOCK
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The current and conventional fault-crossing short baseline measurement has a relatively high precision, but its measurement arrays usually fail to or cannot completely span major active fault zones due to the short length of the baselines, which are only tens to 100 meters. GNSS measurement has relatively low resolution on near-fault deformation and hence is not suitable for monitoring those faults with low motion and deformation rates, due to sparse stations and relatively low accuracy of the GNSS observation. We recently built up two experimental sites on the eastern boundary of the active Sichuan-Yunnan block, one crossing the Daqing section of the Zemuhe Fault and the other crossing the Longshu section of the Zhaotong Fault, aiming to test the measurement of near-fault motion and deformation by using fault-crossing arrays of one-kilometer-long baselines. In this paper, from a three-year-long data set we firstly introduce the selection of the sites and the methods of the measurement. We then calculate and analyze the near-field displacement and strain of the two sites by using three hypothetical models, the rigid body, elastic and composed models, proposed by previous researchers. In the rigid body model, we assume that an observed fault is located between two rigid blocks and the observed variances in baseline lengths result from the relative motion of the blocks. In the elastic model, we assume that a fault deforms uniformly within the fault zone over which a baseline array spans, and in the array baselines in different directions may play roles as strainmeters whose observations allow us to calculate three components of near-fault horizontal strain. In the composed model, we assume that both displacement and strain are accumulated within the fault zone that a baseline array spans, and both contribute to the observed variances in baseline lengths. Our results show that, from the rigid body model, variations in horizontal fault-parallel displacement component of the Zemuhe Fault at the Daqing site fluctuate within 3mm without obvious tendencies. The displacement variation in the fault-normal component keeps dropping in 2015 and 2016 with a cumulative decrease of 6mm, reflecting transverse horizontal compression, and it turns to rise slightly(suggesting extension)in 2017. From the elastic model, the variation in horizontal fault-normal strain component of the fault at Daqing shows mainly compression, with an annual variation close to 10-5, and variations in the other two strain components are at the order of 10-6. For the Longshu Fault, the rigid-body displacement of the fault varies totally within a few millimeters, but shows a dextral strike-slip tendency that is consistent with the fault motion known from geological investigation, and the observed dextral-slip rate is about 0.7mm/a on average. The fault-parallel strain component of the Longshu Fault is compressional within 2×10-6, and the fault-normal strain component is mainly extensional. Restricted by the assumption of rigid-body model, we have to ignore homolateral deformation on either side of an observed fault and attribute such deformation to the fault displacement, resulting in an upper limit estimate of the fault displacement. The elastic model emphasizes more the deformation on an observed fault zone and may give us information about localizations of near-fault strain. The results of the two sites from the composed model suggest that it needs caution when using this model due to that big uncertainty would be introduced in solving relevant equations. Level surveying has also been carried out at the meantime at the two sites. The leveling series of the Daqing site fluctuates within 4mm and shows no tendency, meaning little vertical component of fault motion has been observed at this site; while, from the rigid-body model, the fault-normal motion shows transverse-horizontal compression of up to 6mm, indicating that the motion of the Zemuhe Fault at Daqing is dominantly horizontal. The leveling series of the Longshu site shows a variation with amplitude comparable with that observed from the baseline series here, suggesting a minor component of thrust faulting; while the baseline series of the same site do not present tendencies of fault-normal displacement. Since the steep-dip faults at the two sites are dominantly strike-slip in geological time scale, we ignore probable vertical movement temporarily. In addition, lengths of homolateral baselines on either side of the faults change somewhat over time, and this makes us consider the existence of minor faults on either side of the main faults. These probable minor faults may not reach to the surface and have not been identified through geological mapping; they might result in the observed variances in lengths of homolateral baselines, fortunately such variations are small relative to those in fault-crossing baselines. In summary, the fault-crossing measurement using arrays with one-kilometer-long baselines provides us information about near-fault movement and strain, and has a slightly higher resolution relative to current GNSS observation at similar time and space scales, and therefore this geodetic technology will be used until GNSS networks with dense near-fault stations are available in the future. 相似文献
169.
In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations. 相似文献
170.
医疗设施布局的GIS优化评价——以翔安区医疗设施为例 总被引:2,自引:0,他引:2
开展现有医疗设施布局的分析与评价,对解决公众医疗需求与医疗服务供给的矛盾,以及政府部门决策具有重要意义。本文在厦门市第一次全国地理国情普查试点的背景下,以翔安区医疗设施为研究对象,在地理国情普查数据结果的基础上,结合卫生等专业部门的统计数据,从医疗设施的现状、服务水平和空间布局优化3个角度,构建了医疗设施布局的评价指标体系。从医疗卫生角度分析医疗资源现状特征;基于GIS网络分析开展医疗设施服务水平的分析与评价;利用GIS"位置分配模型"对医疗设施空间布局进行优化。最后,本文对医疗设施布局提出改善建议和措施。研究结果表明:(1)翔安区医疗资源总量不足,分布不均衡;(2)城乡医疗设施差异明显,医疗服务水平不高;(3)翔安区需新增4家医院,5家卫生院才能满足居民就医需求。本研究可以为今后翔安区医疗设施布局决策提供借鉴和参考,为医疗设施布局评价提供一个可行的方法。 相似文献