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81.
82.
流速仪法测流最小水深计算公式推导 总被引:3,自引:1,他引:2
在<河流流量测验规范>中,规定了流速仪法测流垂线、流速测点的分布位置和布置测点时的最小水深,[1]也有这方面的刊载,并列举了部分计算公式,但公式考虑不够全面,而且还不符合规范要求.本文依据规范,按流速仪测点布置情况,分析推导出了具体完整的计算公式,并对测点布置方案选择提出了相应的建议. 相似文献
83.
According to the connotation and structure of science and technology resources and some relevant data of more than 286 cities at prefecture level and above during 2001–2010, using modified method—Data Envelopment Analysis(DEA), science and technology(ST) resource allocation efficiency of different cities in different periods has been figured out, which, uncovers the distributional difference and change law of ST resource allocation efficiency from the time-space dimension. Based on that, this paper has analyzed and discussed the spatial distribution pattern and evolution trend of ST resource allocation efficiency in different cities by virtue of the Exploratory Spatial Data Analysis(ESDA). It turned out that:(1) the average of ST resource allocation efficiency in cities at prefecture level and above has always stayed at low levels, moreover, with repeated fluctuations between high and low, which shows a decreasing trend year by year. Besides, the gap between the East and the West is widening.(2) The asymmetrical distribution of ST resource allocation efficiency presents a spatial pattern of successively decreasing from Eastern China, Central China to Western China. The cities whose ST resource allocation efficiency are at higher level and high level take on a cluster distribution, which fits well with the 23 forming urban agglomerations in China.(3) The coupling degree between ST resource allocation efficiency and economic environment assumes a certain positive correlation, but not completely the same. The differentiation of ST resource allocation efficiency is common in regional development, whose existence and evolution are directly or indirectly influenced by and regarded as the reflection of many elements, such as geographical location, the natural endowment and environment of ST resources and so on.(4) In the perspective of the evolution of spatial structure, ST resource allocation efficiency of the cities at prefecture level and above shows a notable spatial autocorrelation, which in every period presents a positive correlation. The spatial distribution of ST resource allocation efficiency in neighboring cities seems to be similar in group, which tends to escalate stepwise. Meanwhile, the whole differentiation of geographical space has a diminishing tendency.(5) Viewed from LISA agglomeration map ofST resource allocation efficiency in different periods, four agglomeration types have changed differently in spatial location and the range of spatial agglomeration. And the continuity of ST resource allocation efficiency in geographical space is gradually increasing. 相似文献
84.
基于GIS的合肥市BRT和Metro交通可达性研究 总被引:1,自引:0,他引:1
评价了合肥市中心城区的BRT和在建Metro线路对可达性的影响。基于GIS网络分析模拟复杂的多模式交通网络,应用修正潜能模型指标度量了居民区与CBD、与商业金融中心、与行政中心以及与工业区的可达性,对比有无BRT和Metro两种情景下的可达性变化。研究结果表明:在有BRT和Metro时,居民区至CBD的可达性均值变化幅度为45.8%,出行时间从65.5min减至35.5min;居民区至商业金融中心的可达性均值变化幅度为45.7%,时间从74.8min减至40.6min;居民区至行政中心的可达性均值变化幅度为18.9%,时间从104.7min减至84.9min;居民区至工业区的可达性均值变化幅度为37.4%,时间从92.1min减至57.7min。BRT和Metro线路显著地节省了居民出行时间,改善了城市边缘区域的交通可达性,其中经开区的可达性变化幅度最高,其次是滨湖新区、高新区和东区、老城区、南区、西区和北区。 相似文献
85.
目前,针对地学对象的非结构化六面体网格生成问题仍未得到很好的解决。为满足相关地学研究对六面体网格的需求,促进地学模拟及传统GIS空间分析的进一步发展,本文对传统栅格法进行扩展,提出了一种面向地学研究的六面体网格生成的改进栅格法。通过提取实体模型表面的几何特征,考虑内部孔、洞约束生成骨干网格,在此基础上构建一套特征约束模板来处理复杂的特征约束,使之既能保持地学研究对象的几何形态特征,又能实现加密区域与非加密区域的平滑过渡,从而满足地学分析与模拟的需求。 相似文献
86.
Considering the discontinuous characteristics of sea ice on various scales,a modified discrete element model(DEM) for sea ice dynamics is developed based on the granular material rheology.In this modified DEM,a soft sea ice particle element is introduced as a self-adjustive particle size function.Each ice particle can be treated as an assembly of ice floes,with its concentration and thickness changing to variable sizes under the conservation of mass.In this model,the contact forces among ice particles are calculated using a viscous-elastic-plastic model,while the maximum shear forces are described with the Mohr-Coulomb friction law.With this modified DEM,the ice flow dynamics is simulated under the drags of wind and current in a channel of various widths.The thicknesses,concentrations and velocities of ice particles are obtained,and then reasonable dynamic process is analyzed.The sea ice dynamic process is also simulated in a vortex wind field.Taking the influence of thermodynamics into account,this modified DEM will be improved in the future work. 相似文献
87.
利用Copula函数建立各分区洪水的联合分布,基于联合概率密度最大原则,推导得到最可能地区组成法的计算通式,并用来推求梯级水库下游断面的设计洪水。选择清江流域水布垭-隔河岩-高坝洲梯级水库为例,开展了验证和方法比较研究。结果表明:最可能地区组成法计算得到的设计洪水值位于同频率地区组成法多方案计算结果的区间之内;受清江梯级水库调洪的影响,宜都断面设计洪水的削峰率十分显著,最可能地区组成法推求100年一遇设计洪水的削峰率达到30.2%。该法具有较强的统计基础,组成方案唯一,结果合理可行,为复杂梯级水库设计洪水的计算提供了一种新途径。 相似文献
88.
89.
A modified global model for predicting the tritium concentration in precipitation has been developed using the dataset of International Atomic Energy Agency/the World Meteorological Organization (IAEA/WMO) over the period from 1960 to 2005. The tritium concentration in precipitation and its history can be estimated at any location using the model. The modified global model of tritium in precipitation (MGMTP) here presented has higher accuracy than the global model of tritium in precipitation (GMTP) developed by Doney et al. ( 1992 ). The new model is not only more appropriate for a particular station but also applicable for the un‐normalized observations directly. Another advantage of MGMTP is that it can estimate a longer history (from 1960 to 2005) of tritium content in precipitation than GMTP (from 1960 to 1986). The seasonal cycle of tritium in precipitation has also been modelled in the form of a simple cosine function with five parameters. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
90.
《水文科学杂志》2013,58(6)
Abstract Abstract Evaporation is one of the fundamental elements in the hydrological cycle, which affects the yield of river basins, the capacity of reservoirs, the consumptive use of water by crops and the yield of underground supplies. In general, there are two approaches in the evaporation estimation, namely, direct and indirect. The indirect methods such as the Penman and Priestley-Taylor methods are based on meteorological variables, whereas the direct methods include the class A pan evaporation measurement as well as others such as class GGI-3000 pan and class U pan. The major difficulty in using a class A pan for the direct measurements arises because of the subsequent application of coefficients based on the measurements from a small tank to large bodies of open water. Such difficulties can be accommodated by fuzzy logic reasoning and models as alternative approaches to classical evaporation estimation formulations were applied to Lake Egirdir in the western part of Turkey. This study has three objectives: to develop fuzzy models for daily pan evaporation estimation from measured meteorological data, to compare the fuzzy models with the widely-used Penman method, and finally to evaluate the potential of fuzzy models in such applications. Among the measured meteorological variables used to implement the models of daily pan evaporation prediction are the daily observations of air and water temperatures, sunshine hours, solar radiation, air pressure, relative humidity and wind speed. Comparison of the classical and fuzzy logic models shows a better agreement between the fuzzy model estimations and measurements of daily pan evaporation than the Penman method. 相似文献