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玄武,是中国古代最令妖邪胆战且法力无边的神兽之一,与白虎、朱雀、玄武并称中国古代四大神兽。玄武,本意就是玄冥。武、冥,古音相通。玄,是＂黑＂的意思。冥,就是＂阴＂的意思。玄冥,起初是对龟卜的形容。龟背是黑色的,龟卜就是请龟到冥间去询问祖先,将答案带回来,以卜兆的形式显给世人。因此,最早的玄武就是乌龟。以后,玄冥的含义不断扩大。 相似文献
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一、加快人才开发是乡镇企业发展的客观要求 现代经济社会发展的客观规律表明,任何企业的生存和发展都离不开人才。人才是企业发展的决定因素。激烈的市场竞争,表面看来是产品质量,价格的角逐,实质上是人才的竞争。因为只有占据人才优势,才会有高质量的产品,才会有运用自如,灵活多变的价格对策,才会在竞争中立于不败之地。而目前的实际情况是,乡镇企业普遍存在着较为严重的人才缺乏问题。首先,人才数量严重不足。其次,人才构成不合理。其三,人才专业结构不合理。这就使许多占有较大资源优势的行业,不能形成发展优势,从而造成乡镇企业发展中的畸形状态。 相似文献
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特殊的地质环境,孕育了这里神秘的湖光山色。泸沽湖,以它的质朴秀美,勾画出一幅美丽的“世外桃源”。泸沽湖,意即“山沟里的湖”,以湖心为界,西部属云南宁蒗县,东部属四川盐源县,海拔约2700米,面积50平方千米,是由断层陷落而形成的高原湖泊。整个湖泊,状若马蹄,平均深度40米,最深处93米。由于泸沽湖地处偏僻,保持了良好的生态环境,水质纯净,具有原始的朴素美。“泸沽秋水阔,隐隐浸芙蓉。并峙波问鼎,连排海上峰。倒涵天一碧,横锁树千重。应识仙源近,乘槎访赤松”。泸沽湖,清潋幽深,一日四时,姿色各异。周围山峦起伏,使人流连忘返。湖光山色,… 相似文献
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针对城市环境地质研究现状,做了简单的论述。首先,分析了城市环境地质研究现状。其次,围绕城市环境地质研究需要注意的问题,展开了论述。最后,提出了城市环境地质研究开展建议。现阶段,各地区积极开展生态文明建设,加快城市化建设。地质环境状况如何,直接影响着城市规划和建设。基于此,加强此课题的研究,明确研究需要注意的问题,为城市建设提供更多的数据信息,有着必要性。 相似文献
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鄂尔多斯高原农业开发和生态变迁的回顾与反思 总被引：1，自引：0，他引：1
历史时期,鄂尔多斯高原的农业开发,以汉、唐、清三代最为恢宏。从唐代开始,该区的生态环境明显恶化,渐向沙漠生态转变。不合理的农业开发通过直接与间接的作用,诱发、促进了沙化的发生发展。鄂尔多斯高原的现代农业开发,应以史为鉴,走治理与开发相结合的道路,重新分配人口,安排生产。同时,要充分发挥、协调各种科学技术的生态、经济作用。在缺乏灌溉条件的地区,可发展径流农业。 相似文献
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正每一个城市大都有属于自己地标式的风景,或建筑,或遗迹,或园林,亦或自然景观。比如北京,有天安门、故宫、长城。比如南京,有中山陵、雨花台、长江大桥不一而足。这些就像城市的名片,承载着城市的历史以及它所赋予给城市的厚重和内涵。当然,作为一个异地旅人,乍去一个陌生的城市,首先想到的就是城市的地标。春节期间,我去了一趟澳门。去澳门看看,是我多年的梦想。这个梦想由于多种原因直到今年终于成行。说实在的,这应该感谢在深圳工作的儿子。要不是在深圳欢度春节,期间呆上半个 相似文献
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扩散模拟型流域地貌汇流模型 总被引：12，自引：0，他引：12
根据概念性流域地貌汇流模型的一般理论，以概念性元素“扩散模拟河段”模拟各级单元河道的汇流作用，建立 以洪水波的波速和扩散系数为参数的扩散模拟型流域地貌汇流模型。 相似文献
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在地貌瞬时单位线中作者假定沿任一“路径”的等待时间密度函数成Γ型分布。本文讨论了Γ型地貌瞬时单位线的推导、参数确定和特点。并取蛇家口、三川口流域的突测资料验证,计算洪峰值和涨洪历时与实测值十分接近。 相似文献
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Tomas Crols Roger White Inge Uljee Guy Engelen Lien Poelmans Frank Canters 《International journal of geographical information science》2013,27(10):1757-1781
Urban growth and population growth are used in numerous models to determine their potential impacts on both the natural and the socio-economic systems. Cellular automata (CA) land-use models became popular for urban growth modelling since they predict spatial interactions between different land uses in an explicit and straightforward manner. A common deficiency of land-use models is that they only deal with abstract categories, while in reality, several activities are often hosted at one location (e.g. population, employment, agricultural yield, nature…). Recently, a multiple activity-based variable grid CA model was proposed to represent several urban activities (population and economic activities) within single model cells. The distance-decay influence rules of the model included both short- and long-distance interactions, but all distances between cells were simply Euclidean distances. The geometry of the real transportation system, as well as its interrelations with the evolving activities, were therefore not taken into account. To improve this particular model, we make the influence rules functions of time travelled on the transportation system. Specifically, the new algorithm computes and stores all travel times needed for the variable grid CA. This approach provides fast run times, and it has a higher resolution and more easily modified parameters than the alternative approach of coupling the activity-based CA model to an external transportation model. This paper presents results from one Euclidean scenario and four different transport network scenarios to show the effects on land-use and activity change in an application to Belgium. The approach can add value to urban scenario analysis and the development of transport- and activity-related spatial indicators, and constitutes a general improvement of the activity-based CA model. 相似文献
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Geographic variations in spatial accessibility to public resources, such as health care services, raise important questions about the efficiencies and inequities of the processes that determine where these services are located. Spatial accessibility can be measured many different ways, but many of methods in use today involve some measure of travel cost (in time or distance). In this study we explore a simple methodological question: how much are models of spatial accessibility influenced by the precise metric of travel cost? We address this question by comparing spatial accessibility to primary care physicians for two different methods of calculating travel cost (in time) on a street network: free-flow travel time and congested with turn penalties travel time—which augments free-flow travel times with the burden of traffic congestion and traffic intersection controls. We consider the effect of these two metrics of travel cost on a gravity-based measure of spatial accessibility to primary health care services in Edmonton, Alberta, Canada. Our results suggest that while travel times between locations of demand and locations of primary care providers greatly differ based on how travel cost is calculated, the gravity-based measure of spatial accessibility provides similar information for both travel cost metrics. Using congested with turn penalties travel time can be an onerous addition to the analysis of spatial accessibility, and is more useful for measuring absolute travel time rather than modeling relative spatial accessibility. 相似文献
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Bi Yu Chen Donggen Wang Shih-Lung Shaw Hui-Ping Chen 《International journal of geographical information science》2017,31(4):783-804
Travel time uncertainty has significant impacts on individual activity-travel scheduling, but at present these impacts have not been considered in most accessibility studies. In this paper, an accessibility evaluation framework is proposed for urban areas with uncertain travel times. A reliable space-time service region (RSTR) model is introduced to represent the space-time service region of a facility under travel time uncertainty. Based on the RSTR model, four reliable place-based accessibility measures are proposed to evaluate accessibility to urban services by incorporating the effects of travel time reliability. To demonstrate the applicability of the proposed framework, a case study using large-scale taxi tracking data is carried out. The results of the case study indicate that the proposed accessibility measures can evaluate large-scale place-based accessibility well in urban areas with uncertain travel times. Conventional place-based accessibility indicators ignoring travel time reliability can significantly overestimate the accessibility to urban services. 相似文献
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基于家庭的城市居民出行需求理论与验证模型 总被引：8，自引：2，他引：6
西方的城市居民出行需求研究已经由基于出行的分析转向基于活动的分析, 而国内的相关研究几乎空白, 特别是基于家庭的分析。基于出行的交通需求理论在交通规划中的不足, 强调活动分析法的理论基础和应用优势, 提出了基于家庭的活动-移动行为的理论并进行模 型验证。采用天津市居民时间利用日志调查的第一手数据, 以家庭为研究单元, 建立结构方 程模型, 在解读天津市民工作日的活动-移动模式的基础上, 验证了基于家庭的活动分析法 的理论。结果表明, 出行来源于相应的活动参与, 且活动分析法很好地解决了四阶段法等基 于出行的模型的一些不足。男女家长之间存在明显的活动-移动联系, 并且在非工作活动上存在联合参与行为。在考虑活动和家庭成员的间接效应时, 社会经济属性对居民出行时间的的总体效应和直接效应显著程度不一, 验证了基于家庭的活动分析法在出行行为研究上比传统基于出行的分析更加全面和深入。 相似文献
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When geographically aggregated data are included in hedonic models, the resulting coefficients are biased by the spatial scale and spatial configuration of variable measurement. We explore the effects of this modifiable areal unit problem (MAUP) within the context of hedonic price models with an individual-level dependent variable. Specifically, we developed standard and spatial hedonic regression models in order to examine the effects of the MAUP on model fit and coefficient estimates. Our empirical analysis documents several significant scale and zoning effects in the hedonic modeling framework. First, neighborhood characteristics are clearly important in efforts to improve model fit—and they are more significant contributors in the standard model than in the spatial hedonic model. For aggregation scale, the model fit change of the standard model is relatively large, whereas the change is more modest for spatial models. The patterns of change in model fit for standard and spatial hedonic models clearly diverge from one another, implying the existence of a scale level showing a maximum functional range of the submarket on which scale dependencies are expected to have an impact. Regarding the zoning effect, the model fits for both standard and spatial hedonic models vary according to the submarket systems. 相似文献
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Accurate estimation of evapotranspiration (ET), especially at the regional scale, is an extensively investigated topic in the field of water science. The ability to obtain a continuous time series of highly precise ET values is necessary for improving our knowledge of fundamental hydrological processes and for addressing various problems regarding the use of water. This objective can be achieved by means of ET data assimilation based on hydrological modeling. In this paper, a comprehensive review of ET data assimilation based on hydrological modeling is provided. The difficulties and bottlenecks of using ET, being a non-state variable, to construct data assimilation relationships are elaborated upon, with a discussion and analysis of the feasibility of assimilating ET into various hydrological models. Based on this, a new easy-to-operate ET assimilation scheme that includes a water circulation physical mechanism is proposed. The scheme was developed with an improved data assimilation system that uses a distributed time-variant gain model (DTVGM), and the ET-soil humidity nonlinear time response relationship of this model. Moreover, the ET mechanism in the DTVGM was improved to perfect the ET data assimilation system. The new scheme may provide the best spatial and temporal characteristics for hydrological states, and may be referenced for accurate estimation of regional evapotranspiration. 相似文献
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据加拿大Carnation Creek生态试验站20a的森林水文观测资料,应用回归分析和协方差检验,研究了森林砍伐以前、道路修筑、砍伐中和砍伐后各时期洪水参数的变化,统计结果表明,森林砍伐后,洪峰和洪量有显著的增大,一般增幅在20％～30％之间,年径流量增长15％～20％,但洪峰滞时和洪水形态变化不大。 相似文献
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《地理学报(英文版)》2016,(2)
Accurate estimation of evapotranspiration(ET),especially at the regional scale,is an extensively investigated topic in the field of water science. The ability to obtain a continuous time series of highly precise ET values is necessary for improving our knowledge of fundamental hydrological processes and for addressing various problems regarding the use of water. This objective can be achieved by means of ET data assimilation based on hydrological modeling. In this paper,a comprehensive review of ET data assimilation based on hydrological modeling is provided. The difficulties and bottlenecks of using ET,being a non-state variable,to construct data assimilation relationships are elaborated upon,with a discussion and analysis of the feasibility of assimilating ET into various hydrological models. Based on this,a new easy-to-operate ET assimilation scheme that includes a water circulation physical mechanism is proposed. The scheme was developed with an improved data assimilation system that uses a distributed time-variant gain model(DTVGM),and the ET-soil humidity nonlinear time response relationship of this model. Moreover,the ET mechanism in the DTVGM was improved to perfect the ET data assimilation system. The new scheme may provide the best spatial and temporal characteristics for hydrological states,and may be referenced for accurate estimation of regional evapotranspiration. 相似文献