黑龙江省东部地区对外贸易通道研究

本文对黑龙江省东部地区外港──俄罗斯远东南部港群的能力与现状,“中东”铁路的历史、能力现状与运能潜力等作了深入的研究,并运用路线比较模型与重力模型对哈尔滨──绥芬河──海参崴铁路通道条件的吸引力进行了分析。笔者认为,中俄公路运输的发展是其对外通道的新优势。     

ALTERATIONS OF RIVER MORPHOLOGY DUE TO VEGETATION ON SLOPES AND FLOOD PLAINS

LRESEarCHACTIVITIESCharaCtCriedcofunlinedalluvialriVersisthe~linteractionbettVeenwaterflowandmovableriVerbed.Sedimenttransport,bedresistanceandriVermorphologydecisivelydependontheflowconditionsandviceversathesefactorsgovernthehydraulicprocesses.EVenundersimplifiedconditions,e.g.inlaboratorytests,theseillteractionsareeXtremelycomplexandrelldsraliZationmakesengineeringproblemsevenmored~.TomaketheseprocessesmoreunderstandablecomprehensiVeresearchprojectswereconductedatseveralGermanuniv…     

COARSE-PARTICLE TRANSPORT IN A GRAVEL-BED RIVER

ＣＯＡＲＳＥ－ＰＡＲＴＩＣＬＥＴＲＡＮＳＰＯＲＴＩＮＡＧＲＡＶＥＬ－ＢＥＤＲＩＶＥＲＷｉｌｌｉａｍＷ．ＥＭＭＥＴＴ１，ＲｏｂｅｒｔＬ．ＢＵＲＲＯＷＳ２，ａｎｄＥｄｗａｒｄＦ．ＣＨＡＣＨＯ，Ｊｒ３．（１Ｕ．Ｓ．ＧｅｏｌｏｇｉｃａｌＳｕｒｖｅｙ，Ｗａｔｅ...     

改进的MM4模式暴雨实例对比试验

本文利用改进了水汽输送方案的中尺度模式ＭＭ４对三次暴雨过程作了试验。这三次过程包括两次长江中下游特大暴雨和一次华并暴雨。把三次暴雨过程的降水实况和采用不同水汽输送方案所得到的模拟降水结果进行了对比，并主要分析了“８２．６”湖北特大暴雨过程。     

包含正定水汽输送算法改进的MM4中尺度模式与暴雨实例数值试验

暴雨预报是一个既重要又十分困难的问题。水汽条件是产生暴雨的关键，水汽的平流输送在模式的水汽方程中占有重要地位，模式对暴雨的预报能力必然涉及到水汽输送的计算精度问题；本文以著名的中尺度模式ＭＭ４为基础，理论测试和分析为依据，以引入新的正定高精度水汽输送算法作为消除模式水汽负值和改进中尺度模式预报能力的途径，研制了取名为改进的ＭＭ４中尺度模式，该模式除仍保留原ＭＭ４模式的所有功能外，增加了５种水汽输送算法的改进与选择，这５种算法是：１）Ｂ网格二阶守恒中心差（原ＭＭ４平流格式），２）上游差分，３）Ｂｏｔ（２阶），４）Ｂｏｔ（４阶），５）Ｐｒａｔｈｅｒ格式。多个暴雨、台风个例试验表明模式预报能力对水汽输送算法精度有显著的依赖性，采用高精度的水汽输送算法水汽保证正值并提高了模式对暴雨区、降水结构、雨团活动的预报能力。改进水汽输送算法的精度是提高中尺度模式对暴雨预报能力的重要途径。     

Statistical aspects of flow in a random network of channels

This paper presents a detailed statistical analysis of Hagen-Poiseuille flow in plane random isotropic networks of interconnected channels. The emphasis is on statistico-geometrical features of networks that affect macroscopic permeability. It is shown that permeability of a network depends on its average co-ordination number, the first two moments of the channel length distribution and other explicitly identifiable geometrical features. Distributions of flow rates in channels and average flow rates are established by minimization of the rate of energy dissipation. Theoretical developments are interpreted in the context of classical statistical mechanics. Analytical results are illustrated and verified using numerical analysis of flow in a simulated random network.     

Modelling seasonal variations in nitrate and sulphate concentrations in a vulnerable alluvial aquifer

The Eisden–Meeswijk region in Belgium has been affected by mining subsidence due to the deep coal mining activities. Groundwater levels in the alluvial plain of the Meuse River are maintained below the ground surface by drainage installations and municipal well fields. A correlation between the water level in the Meuse River and the variation in nitrate and sulphate concentrations in the aquifer has been observed. A transient groundwater model is developed for the period May 1998–May 2002 and advective transport simulations have been carried out using this model. During dry periods, the major groundwater flow is directed towards the Meuse River, thereby feeding the river. During wet periods, however, groundwater flows in the opposite direction. Due to these variations in groundwater flow direction and to the extraction of groundwater, zones of higher solute concentration exist of which the position and extension vary both spatially and temporally.     

Abflußereignisse,eine skalenabhängige multiple Antwort von Einzugsgebieten auf Niederschläge

Flood Events, a Multiple Basin Response to Precipitation Events at Different Scales Results in the small catchment of the Kartelbornsbach have shown that summer events lead to typical types of flood waves that can be classified according to their response patterns. Differences to this pattern are due to the precipitation amount and duration and in some times to the pre-event moisture of the soil. The results show further that the Kartelbornsbach catchment can be considered as a block system where spatial differences are responsible for the basic pattern of the reaction but not for differences between flood events. Small catchments are excellent tools for relatively inexpensive hydrological and hydrochemical research on streamflow generation mechanisms. With increasing size of the basin the response becomes less clear, because the spatial distribution of rainfall and the distance of delivering areas from the sampling station mask or modify the type of response. Although the main flow components may not change, there is a considerable shift in the composition of water quality, because the increase of travel time does not affect all flow components at the same rate.     

On the mechanisms of the saltating motion of bedload

Saltation of sediment particles is an important pattern of bedload transport.Based on force analysis for sediment particles,a Lagrangian model was proposed for the saltating motion of bedload in river flows,which was then solved with numerical method.Simulation results on the saltating trajectories neglecting particle rotation and turbulence effects compare fairly well with experimental observations.The mean values of the saltation parameters (saltation height,length and velocity) also agree well with the previous experimental data.Based on the numerical results,regression equations for the dimensionless saltation height,length and velocity were presented.Using the numerically achieved characteristics of the sediment saltation,we also obtained mathematical expression for the sediment transport rate.The studies in this paper are significant for its contribution to mechanism of the bedload motion and the computation of sediment transport rate.     

Estimation of Longshore Sediment Transport Rate for a Typical Pocket Beach Along West Coast of India

Estimation of Longshore Sediment Transport Rate (LSTR) in the littoral zone is essential for managing and developing any coastal zone. Numerical models are powerful tool to understand and investigate various processes responsible for LSTR in a systematic manner since direct measurement of LSTR is a difficult task. A one dimensional LITDRIFT model was implemented along the Vengurla coast for estimation of LSTR and to analyze the sensitivity of each input parameters towards the computation of LSTR. Major input parameters required for the estimation of LSTR are nearshore wave climate, bathymetry, and sediment characteristics. The nearshore wave data at a depth of 15 m were collected using wave rider buoy in 2015 is used in the present study. Field observations were carried out to survey the regional bathymetry and sediment characteristics. Annual net LSTR along Vengurala coast is relatively less and varies from ?7778 to ?9015 m³ with an average of ?8511 m³. The net direction of LSTR is towards south and gross LSTR is 1.18 × 10⁵ m³/year. The LSTR reveals more sensitivity to coastline orientation and wave direction. A 1° changes in coastline angle and wave direction causes approximately 3000 m³/month difference in LSTR. Moreover, wave height, wave period, and bed roughness has an important role for controlling LSTR. The model results help to identify the role of each parameter contributing towards LSTR estimation and a similar model approach can be applied to other coasts for estimating LSTR in an accurate way.