排序方式: 共有91条查询结果,搜索用时 15 毫秒
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阐述太原市山洪沟河及排退水渠的现状及发展 ,研讨河道及排水渠道的规划和复盖中应遵循的原则和存在的一些问题 相似文献
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针对哈尔滨至牡丹江电气化改造工程季节性冻土分布的实际工程特点,结合季节性冻土条件下接触网基础的设计理念,对本项目选用的扩大型钢柱基础和不带扩底的拉线基础进行切向冻胀应力计算分析,并考虑影响切向冻胀力的水分、土质、负温以及基础侧表面的粗糙度等主要因素,提出了对钢柱基础采用换填加扩大型基础的处理措施,对接触网的下锚拉线基础提出了换填及加大埋深等防冻胀处理措施以抵抗季节性冻土的上拔力。 相似文献
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Short period traffic counts (SPTCs) are conducted routinely to estimate the annual average daily traffic (AADT) at a particular site. This paper uses Indian traffic volume data to methodically and extensively study the effect of four aspects related to the design of SPTCs. These four aspects are: (i) for how long, (ii) on which days should SPTCs be carried out, (iii) how many times, and (iv) on which months should SPTCs be carried out? The analyses indicate that the best durations for conducting SPTCs are 3 days (starting with a Thursday) and 7 days, for total traffic and truck traffic, respectively. Further, these counts should be repeated twice a year keeping a separation of two months between the counts to obtain good estimates of AADT at minimal cost. An additional outcome of this study has been the determination of seasonal factor values for roads in developing economies, like India. 相似文献
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This paper reviews the existing procedures to compute the seasonal factors, growth factors, and the number of automatic traffic recorder stations (ATRs) for developing a statistically reliable traffic counting program. The review is based on, (i) theoretical evaluation of the procedures, (ii) analysis of the results obtained from applying these procedures to extensive real life data, and (iii) experience of past researchers with these methods. The paper primarily deals with existing statistical procedures for determining seasonal factors, since it is believed that these factors play the most important role in estimating Annual Average Daily Traffic (AADTs) from short counts. The procedure of cluster analysis (which is most commonly used to determine seasonal factors) is critically reviewed. The shortcomings of this method motivated the development of a different statistical procedure, based on regression analysis, to determine seasonal factors. It is shown that this newly developed method gives better results than the cluster analysis techniques. Furthermore, separate sections are dedicated to a thorough analysis of determination of number of ATR stations and computation of growth factors. 相似文献
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探讨了山区河流航道整治建筑物水毁灾害过程中各物相 (固态、液态、气态 )之间耦合破坏作用的特征 ,耦合作用物理模型及仿真模型的概念和关系 ,为深入研究整治建筑物水毁机理提供理论依据 相似文献
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随着国家与公众对乡村生态环境的日益重视,如何对乡村河道进行有效修复成为当前的研究热点.现以闵行区浦锦街道为例,在对其水生态现状调研基础上,解析河道污染特征与污染物来源.并基于绿色生态修复的原则提出了在空间上通过生态缓冲区、河道及植物种植的方式构建河道生态系统的修复思路.进一步根据水体污染特性,制定了底质改良、紫外催化、沉水曝气、底部生物载体、生态浮岛、漂浮草垫、点源净化的内源污染防治技术措施.对比治理前后河道踏勘与水质检测结果显示:治理后河道水生态恢复较好、溶解氧浓度大幅提升、总磷得到了有效控制.后期可根据水体溶解氧浓度对曝气调控以促进对氨氮的去除效果. 相似文献
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利用声学多普勒流速剖面仪(ADCP)的声反向散射强度(ABS),估算悬移质浓度(SSC)的相关技术日臻成熟,其原理是利用走航式声学多普勒流速剖面仪(ADCP),采集足够频次的流速和声反向散射强度,以替代流量和悬移质浓度(SSC)的数据,在一定程度上破解了在复杂水流环境中测定和估算水体悬移质输沙率的难题。简要介绍利用声学多普勒流速剖面仪(ADCP)估算悬移质输沙率的基本原理和方法,并结合在连云港徐圩海域水文观测中的应用实例,验证该方法的可行性、可靠性和精度。 相似文献
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Modelling nutrient fluxes from sub-arctic basins: Comparison of pristine vs. dammed rivers 总被引:1,自引:0,他引:1
Agata Sferratore Gilles Billen Josette Garnier Erik Smedberg Christoph Humborg Lars Rahm 《Journal of Marine Systems》2008,73(3-4):236
The deterministic Riverstrahler model of river functioning is applied for the first time to sub-arctic catchments. Seasonal nutrient (N, P, Si) deliveries to the coastal zone are simulated, and nutrient annual fluxes are established for the nearly pristine river Kalix (hereafter called Kalixälven) and the heavily dammed river Lule, (hereafter called Luleälven) both located in Northern Sweden and draining into the Bothnian Bay, Baltic Sea.For Kalixälven simulations are performed with a runoff calculated from precipitation, evapo-transpiration and temperature data for the period 1990–1999, using a hydrological model calibrated on observed monthly discharges at the river outlet. The same hydrological parameters are used to calculate specific runoff for the Luleälven basin in absence of dam regulation. Reservoir filling and emptying are simulated using a simplified representation of their management rules. Diffuse sources of nutrient are evaluated according to land cover of the catchment. The simulated seasonal trends are within the range of the observed data, in particular for discharge, dissolved silica, total phosphorus, inorganic nitrogen and total organic carbon. Specific runoff is 50% higher in the Luleälven than in the Kalixälven watershed due to higher altitudes and precipitations. Average silica, nitrate and phosphorus concentrations are much lower in Luleälven than in Kalixälven. Comparison of model results for the Luleälven with and without dams shows a reduction of respectively 25% and 30% in silica and phosphorus fluxes delivered at the outlet, while nitrogen delivery is increased by 10% in the dammed vs. undammed river system. The model allows assessing the respective role of reservoir trapping of nutrient in the reservoir through algal uptake and sedimentation, and of changes in the vegetation induced by flooding the valley formerly covered by forests and wetlands. 相似文献