基于DEM的东江湖风景区水文分析研究

DEM(Digital Elevation Model)是流域分析的主要数据源,提供了丰富的地质地貌、水文信息。详细介绍了利用DEM数据提取水文特征的方法,包括洼地填充、水流方向、汇流累积量、水流长度和水文分析。以东江湖流域为例,采用ArcGIS软件的Hydrology模块提供的D8算法以确定水流方向,通过汇流累积量的计算和相关阈值的设定,提取东江湖水文特征。结果表明,研究区最大水流长度为113651 m;采用该算法模拟的流域数字水系与水利部门提供的地形数据基本相符,真实反映了研究区水系的空间分布规律,为进一步研究东江湖流域的植被生态环境演变提供基础数据和参考。     

食品行业粉体材料流动性研究的新仪器——PFT

奶粉、面粉、糖、盐、调味品等原料和添加剂粉体的流动性研究是目前很多材料行业的难点,现有常见的一些方法不能满足实际的需求。简单介绍了Brookfield公司根据ASTM D 6128推出的PFT粉体流体测试仪的基本功能,介绍了粉体流动函数、壁面摩擦、松装密度、时间固结、拱架、鼠孔、料斗半角的测量和计算。     

基于DEM的河网水系分形特征研究——以常德市桃源县为例

为了给流域的治理实践及理论研究提供基础性数字地形信息,以常德市桃源县为例,利用ArcGIS软件的水文分析扩展模块,探讨了DEM的制作处理,获取了研究区域水流流向、汇流累积量、河网水系等流域特征信息,同时用计盒维数和Horton定理2种水系分维数估算方法来估算水系分维数。结果表明：（1）运用DEM和ArcGIS的水文分析模块提取的水系连续完整,且与实际水系特征吻合性较好,是一种进行流域水文分析的优良方法;（2）利用DEM提取水系的分维值,与原水系分维值基本一致,说明利用DEM提取水系分维值的方法具有可行性;（3）根据分维值可以判定研究流域地貌处于幼年期,此时水系尚未充分发育。     

LPI插值参数对泥石流冲沟DEM构建的影响

研究旨在利用局部多项式插值(LPI)对地震造成滑坡而形成的泥石流冲沟进行DEM建模,分析其插值参数对插值精度的影响,并提取最佳插值参数。以彭州市银厂沟谢家店滑坡体泥石流冲沟为例,以平均误差(ME)、中误差(RMSE)、最大正负误差(MPE, MNE)及正负误差百分比(PPE, PNE)作为DEM内插结果的精度评价指标,对不同阶数(P)、核函数[K(x)]、带宽(H)以及搜索扇区类型的DEM插值精度进行比较提取出最佳插值参数。结果表明：在其他参数默认的情况下,P为2时插值精度最高;K(x)为Exponential时拟合精度最高;4种搜索扇区类型的插值结果各项精度指标差异不大;插值试验中H=2为最优选择;所有设定参数的插值结果的正负误差大致都呈对半分布。利用LPI构建谢家店泥石流冲沟DEM结果可以满足大比例尺DEM精度要求,参数P、K(x)、H对插值精度影响较大,而搜索扇区类型对插值结果影响较小,插值参数的优选有助于泥石流冲沟地形进行DEM构建。     

Behavior of Loose Sand-structure Interface Undergoing High Frequency Cycle Shearing

The behavior of loose sand-structure interface under the high frequency cycle shearing is analyzed by using Particle Discrete Element Method (DEM).The changes of sand box porosities of DEM model and sand volume strains are examined in detail.The results show that sand volumetric shrinkage due to shearing is not obvious in spite of the larger loose sand particle friction coefficients and particle stiffness.The particle stiffness ratio has a little effect on the mechanical properties of sands.In addition,the decrease in volume of sand under shearing is more obvious with the increase of the confining pressures.Moreover,the decrease in volume of loose sand under shearing is greater with the increase of the high frequency cycle shear amplitude and the shear frequency.     

一种高质量的数字高程模型（DEM）建立方法 ——ANUDEM法

建立高质量的数字高程模型（DEM）是正确计算坡度、坡向、提取流域地形特征、进行水文分析的前提，因而在研究土壤侵蚀、植被建设和土地利用规划与评价中都具有重要意义。ANUDEM采用迭代有限微分内插技术和地形强化算法，自动去除伪下陷点和生成输入数据错误文件，便于查错改善DEM质量，并减少了去除伪下陷点的编辑或DEM的后处理过程。本文以黄土高原丘陵沟壑区典型小流域为例，利用大比例尺（1:10000）数字化地形图，利用ANUDEM建立DEM，从DEM光照模拟图、回放等高线、提取水系、坡度等方面对建立的DEM的质量进行了评价。研究表明，ANUDEM建立的DEM表面光滑；回放等高线与原等高线符合度高，能更准确地表现地形起伏；由其提取的坡度准确；水系连续完整与地形图上河流一致，适宜水文分析，是一种建立高质量DEM的优良方法。     

Energy-absorbing Properties and Crushing Flow Stress Equation of Lightweight Foamed Concrete

Lightweight foamed concrete is a new arresting material for arresting overrun aircraft. To reveal its compression properties and mechanism of deformation and destruction, a study on lightweight foamed concrete with different density, 0.21 and 0.31 g/cm 3 respectively, has been carried out. Experiment system include CSS4410 electronic universal testing machine and Dynatup9250 drop-hammer testing machine and VHS8800 high strain rate system. Then, extrusion strength under different indenter area is predicted with a theoretical model, and a crushing flow stress constitutive equation is proposed. The results show that it is characterized by the movement of crushing driving interface during the process of deformation, crush to compaction of the material, and the deformation is notably in local. The compression strength is relevant to density and impact velocity. Moreover, theoretical model can predict the extrusion strength under different indenter area exactly, and the crushing flow stress equation can describe mechanic properties of compression well.     

Water/oil radial flow behavior near well bore zones in oil reservoir

The flow behavior of water and oil near well bore zones in oil reservoir is radial flow. Based on the fluid displacement experiments in radial systems, the equation describing radial flow is investigated and analytical solution about the relationship between relative permeability ratio and saturation is obtained. The analytical solution is used to treat the experiment results and the two phase flow behavior of water and oil is characterized. The results show that the analytical solution can characterize the actual flow of water and oil near well bore zone. According to the radial experiments, the saturation scope in which the relative permeability ratio and saturation is linear is smaller. The flow behavior of water and oil near well bore zones is complex and nonlinear.     

Pressure driven flow of the MR fluids in the cylindrical pipe

Herschel-Bulkley model is used to describe rheological behavior of the Magnetorheological (MR) fluids subject to an applied magnetic field. Based on momentum equation, the effect of the applied magnetic field on the pressure driven flow of the MR fluids in the cylindrical pipe is analyzed theoretically. The expressions for the velocity and the volumetric flow rate in viscoplastic flow are derived to provide a theoretical foundation for the design of cylindrical pipe MR devices. The results indicate the MR fluids have the properties of both viscosity and viscoplasticity. The flow of the MR fluids in the cylindrical pipe exhibits viscoplastic flow behavior. The velocity exhibits the distributions of both parabolic curve and straight line with the magnetic field direction. The volumetric flow rate can be continuously adjusted by an external magnetic field.     

Control of compaction on the farm a personal view

Compaction of soils under agricultural use is widespread. Its effects on crops and soil properties are complex. The author's experience has suggested that cultivation to break up compaction of rutted surfaces immediately after the harvest of many crops, particularly of potatoes and root crops, can reduce the risk of further serious compaction. Deep cultivation (subsoiling) can have adverse effects and its use should be confined of land where examination of the soil has shown that a layer of compact soil is present, and that the soil is dry enough for fracturing to take place.     

基于点云构建干热河谷典型冲沟DEM的参数优选—以析取克里格插值方法为例

为了探索析取克里格插值算法中的插值参数对构建DEM精度的影响,以云南元谋干热河谷典型冲沟为例,基于野外实测点云数据,改变析取克吕格插值中的核函数、搜索点数、搜索方向和光滑因子参数构建DEM,运用交叉检验和验证数据集检验评价DEM插值精度。研究结果表明：（1）在不同的核函数中,Stable 函数的插值效果最佳;（2）搜索点数为2~5 个是最佳的选择;（3）在搜索方向的对比中,有方向搜索比无方向搜索误差小,且四方向比八方向的误差小;（4）当光滑因子≥0.8 时,DEM插值精度的误差明显增大。通过对析取克里格插值参数的优选,在研究样区构建出0.08 m的高精度DEM,为该区域的冲沟研究提供资料。     

机载 LiDAR生成DEM的一些关键问题评述

提取DEM是机载LiDAR技术应用研究关键内容之一,从LiDAR数据滤波、DEM模型选择、内插、误差控制和数据压缩等几个方面,分析当前利用机载激光雷达数据提取DEM的主要研究进展.着重讨论插值滤波、倾角滤波和形态学滤波算法,定量分析滤波算法的性能;分析比较确定性内插方法和地学统计内插方法,并指出内插方法在提高精度同时也要考虑稳定性和序同构性;论述DEM格网压缩和三角网压缩方法,并指出在满足地形可视化需要的同时提高压缩效率;并进行了总结展望,为相关研究提供参考.     

Density Distribution of Sand Packing in Vacuum Suction Molding Process and its Influential Factors

By means are measured of the direct observation of the packing behavior of sand in the vacuum suction molding process.The air and powder pressure,density distribution of sand core.The packing mechanisms are studied based on these experimental results.It found that the density distribution of sand core is elucidated by powder pressure theory,and the density distribution is decided by air flowing,sand chocking and shearing.     

Transfer and water-retention properties of seed-pelleting materials

Until now, the choice of materials for seed pelleting has been mostly empirical. We have analysed coating materials (silicate powder A, clay B and hydrophobic clay C) and their water-transfer properties. Seed-pelleting materials were studied with conventional soil-analysis techniques. An original device for studying water transfer through a thin layer of powder was designed to simulate the transfer of water from the soil to the seed, through the pelleting material. Different parameters were studied: particle-size distribution, water-retention curve of materials, thickness of powder, influence of concentration of adhesive in pelleting, etc. The sintered glass on which the powders were placed in the device constituted a limiting factor. The major component, a silicate powder (A), consisting of large particles, is responsible for the general structure of the pelleting. Introduction of clay (B) gave intermediate properties between A and C to water-transfer capacity. Hydrophobic clay (C) can be used to control the incoming flow. The particle-size distribution and wettability of materials have a direct impact on the transfer capacity of the powder. High adhesive concentration had a negative effect on water transfer. These parameters and the formulation have a direct impact on imbibition of pelleting materials. Objective tools, like the analytical methods used in this study, enable water-transfer parameters and consequences on imbibition of coated seed to be understood.     

DEM模拟解析二元混合颗粒粒径偏析分布规律

颗粒粒径偏析分布是高炉炉顶布料过程中不可避免的现象,易造成炉喉处局部料层的空隙度降低和压差升高,影响煤气流的均匀分布,继而间接影响炉况的顺行。通过DEM离散单元法模拟研究二元混合颗粒的偏析分布规律,同时,提出一个偏析指数T,用以表征粒径偏析分布的相对程度。研究结果表明：同一T值图中,相邻区域颗粒的T值相差越大,则该区域颗粒的粒径偏析程度越大;不同T值图中,所有相邻T值之差的平均绝对值越大,则颗粒堆积整体粒径偏析程度越为严重。     

黄土区土地整理压实土壤物理性状的初步研究

【研究目的】拟了解黄土丘陵土地整理区的土壤压实情况,从而制定相应的改良措施,促进土地资源的优化配置和有效利用。【研究方法】以闻喜县后宫乡的土地整理项目为研究对象,调查了压实地土壤的容重、紧实度、含水量以及渗水速率。【研究结果】结果表明：（1）与一般农田土壤相比,整理区土壤容重平均增高1.34倍、紧实度平均高484倍。（2）压实土壤的初始渗透速率为1.21mm/10min,稳渗速率为0.7 mm/10min,约相当于一般农田土壤的16%和28%。【研究结论】这些物理性状表明土地整理区内土壤压实程度非常严重,必须采取相应措施改良压实的土壤,迅速提高土地的生产力。     

基于DEM 的重庆长江流域水系分维估算

摘要：基于数字高程模型,本文利用ArcGIS9.3的水文分析模块,根据不同的集水面积阈值, 提取了重庆长江流域河网信息,通过网格法计算了相应的水系分维。根据集水面积阈值与水系分维的相互关系, 确定该流域水系分维值为1. 036,经计算得到的河网特征以及流域信息与实际河流水系特征及流域信息基本吻合。     

土壤机械压实及其对作物生长的影响

在生产中农业机械替代人畜力从事农业生产劳动是必然的趋势。随着农业机械化水平的快速提高,土壤机械压实问题越来越突出。通过分析土壤机械压应力传递模型,以及土壤压实后土壤容重、坚实度增加,孔隙度、含水量降低,土壤的渗透性变差等土壤质量恶化现象,发现土壤压实可导致土壤质量下降,抑制作物的根系生长发育,对作物吸收土壤中的水分、养分产生不利影响。可造成玉米减产9.5%～14.4%,小麦减产4.0%～20.0%,大豆减产3.8%～13.4%,甜菜根产量降低5.81%～24.13%,含糖率降低0.49～0.81oZ。因此,在农业生产中必须要重视土壤压实问题,采取切实可行的技术措施,减轻农业机械化作业对土壤造成的负面影响,促进作物生长,提高农艺综合效益。     

Experimental Study on the Compressive Property of Luojiashan Clay

This paper carried out an experimental study on the compressive property of Luojiashan Clay at Wuhan University. In order to investigate the influence of compaction degree, compaction water content and saturation state of compacted soil on the compressive property of clayey fill, compression tests were done on the samples compacted to different water content around optimum moisture content by different degrees of compaction. The theory of compacted soil structure was used to explain mechanism of the influence, and it was the change of soil structure that caused the variation of compresSive property. The results of the tests show that it was at agiven range of stress that degree of compaction and compaction water content have influence on the compressive prop- erty of clayey fill. Around optimum moisture content with degree of compaction decreasing or compaction water content increasing, the compressive deformation of clayey fill increased. When compacted fill was saturated by water soaking, the compressive deformation increased much, and the clayey fill compacted at greater water con- tent than optimum moisture content showed smaller compressive deformation caused by saturation at other conditions the same.     

Transport of Anion Towards Root as Influenced by Soil Compaction

This experiment was conducted in metal container of 2 liters capacity in the glass house to find out the effect of different bulk densities on the movement of non-adsorbed anion (Cl) towards the root. It is inferred from the study that at low moisture content, compaction to a certain degree can increase movement of nutrients to the root due to increase in moisture content per unit volume of soil, further increase in compaction may however affect nutrient availability to the roots. This has a far greater significance in No₃ movement. But from the salinity point of view, plant roots in soil containing salt will be exposed to a much higher salt concentration than that may be obtained from the analysis of the bulk soil.