金属电阻率模型

修正了Burgess电阻率模型中的错误公式和算法流程,获得了与文献中结果完全相同的电阻率曲 线。采用Burgess电阻率对Z装置上的磁驱动飞片实验进行数值模拟,计算的自由面速度曲线与实验结果相 差较大。由于液体到达汽化点时,是气液混合体,因此从汽化点到临界温度的Burgess电阻率公式不应采用 气体计算公式,应改为气液混合体的计算公式。采用从汽化点到临界温度阶段修改为气液混合体的电阻率公 式进行数值模拟,计算的自由面速度曲线与实验结果、文献计算结果相吻合。     

电阻率测试技术在沉积物-盐水-甲烷水合物体系中的应用

利用自制的一维天然气水合物(NGH)开采模拟实验系统,通过对NGH生成过程中电阻率、温度、压力等的变化规律进行分析,验证了在海洋沉积物体系中用电阻率法测试NGH的可行性。实验结果表明,电阻率可以清楚地反映NGH的成核及生长过程。NGH开始成核时消耗了溶液中的水分和甲烷气体,增加了离子之间的连通性,使电阻率降低;晶核开始生长为NGH后,由于生成的NGH类似于绝缘体,并且使得孔隙连通性变差,电阻率逐步升高,NGH大量生成后电阻率保持稳定。然后进行NGH降压分解实验,随着NGH的分解,NGH饱和度下降,电阻率也逐渐下降。     

电阻率法在地基处理工程中的应用探讨

土的电阻率相关参数指标与土的工程力学指标紧密相连,并可反映土的一些特殊性质,如土的污染特征、地基液化特征等。本文首先简要介绍了土的电阻率理论,分析了土电阻率的室内外测试原理与方法。在归纳相关文献与工作的基础上,探讨土电阻率法在地基处理及其相关领域中的应用。深入分析了电阻率法在水泥土搅拌桩质量评价、地基处理效果评价、地基液化评判、压实土质量评价以及地基污染中的应用特征以及评价方法。并讨论了土的电阻率理论研究中存在的问题,展望了土电阻率理论的研究与应用前景。     

电阻率法探测黄土滑坡滑动面(带)的试验研究

根据滑体与滑床土的结构差异特性,其中电阻率特性也有显著不同,利用WDJD-1型多功能数字直流激电仪和改进的探测电极装置,分别在滑坡后壁原状黄土地层、探槽及钻孔中测试黄土滑坡滑面上下各层土的电阻率值。试验结果显示电阻率测试曲线在滑动带位置出现异常跃变现象,而曲线在未滑动过的黄土地层之间变化差异不明显。这一异常突变特性,在实践中可作为鉴别滑动面位置的特征标志。该探测方法充分利用现有的勘探技术条件,操作简便,试验结果直观,可在黄土滑坡勘察实践中推广使用。     

气相生长碳纤维作为润滑脂导电填料的摩擦学性能研究

以聚环氧乙烷聚环氧丙烷单丁基醚(PAG)为基础油和聚四氟乙烯为稠化剂,分别以气相生长碳纤维(VGCF)、银粉和铜粉作为导电填料,制备了电力复合脂.采用GEST-121型体积表面电阻率测试仪测定了润滑脂的体积电阻率,往复摩擦磨损试验机考察三种导电填料对润滑脂摩擦磨损性能的影响,用扫描电镜(SEM)和能谱仪(EDS)观察并分析了磨痕表面形貌和主要元素.结果表明:在室温和100℃下,含有VGCF的电力复合脂均具有较低的体积电阻率;这种润滑脂还具有优异的润滑性能,当VGCF添加质量分数为1.5%时,具有最优的减摩和抗磨性能.     

碳纳米管在润滑脂中的导电性和摩擦学性能研究

碳纳米管(CNTs)作为添加剂,制备了以油溶性聚醚为基础油,聚四氟乙烯(PTFE)作稠化剂的导电润滑脂.用体积表面电阻测定仪测定其体积电阻率,用扫描电子显微镜(SEM)观察钢盘磨斑表面形貌,EDS能谱仪分析磨损表面元素组成.结果表明:含碳纳米管的润滑脂与含导电炭黑的润滑脂相比较,不但具有优异的润滑性能,还具有低的体积电阻率.     

电爆炸断路开关综述

叙述了金属导体电爆炸的物理过程，分析了金属导体电爆炸时电阻率的影响因素，从而确定电爆炸断路开关的一般设计原则。     

改进的佐迪反演方法及在考古中的应用研究

高密度电阻率法应用于考古中可提高对地电结构的分辩率。文中简述了改进的佐迪反演方法,给出了数值模拟的实例,并用该方法对商丘周朝古城遗址的两条高密度探测剖面进行了处理,反演后得到了与考古资料较为接近的结果,展现了良好的应用前景。     

多种物探方法在湘潭城区活断层勘探中的应用

杨梅洲—木鱼湖断裂位于湘潭城区,要查明其位置和性质,地球物理勘探干扰因素多,施工条件不好。调查中分别采用天然电场选频法、高密度电阻率法和地质雷达等方法进行勘探,并通过开挖等方式进行验证,3种物探方法各有特点:天然电场选频法仪器轻便、勘探线布置灵活,干扰因素较少,工作效率高,特别是利用其动态信息确定断层平面位置准确;高密度电阻率法勘探结果比较直观,特别是对断层性质的确定形象,但勘探布极的工作量较大,受地形等因素影响较大,在城区很多地方无法正常开展工作;地质雷达勘探成果形象直观,但设备成本高,勘探受地形等因素影响大,勘探深度有限,一般对表层效果较好。     

Unsymmetrical nonlinear bending problem of circular thin plate with variable thickness

Introduction Manystructuralelements(pole,plate,shell)withunevenandvariablethicknessarewidely usedinallkindsofengineeringfields.Engineerscansavematerialswhentheydesignbecause theseelementshavebetteroptimizedshapeofstructuralfeature,butthisaddsdifficultytotheanalysisoftheirmechanicalcapability.Manypreviouspapers[1-4]havesolvedtheproblemof symmetricalaxis,butnobodyhassolvedtheunsymmetricalnonlineardeformationproblemof circularthinplatewithvariablethicknessandunsymmetricalaxisuptonow,afewworkonly …     

Influence of root resistivity on plant water uptake mechanism,part I: numerical solution

The issue of water flow through the root zone of field crops represents a complex problem requiring knowledge of a large spectrum of phenomena from various disciplines. Although many investigations have been devoted to gain better understanding of water dynamics in the root zone, the problem is still insufficiently understood. The main objective of the presented work was to analyze the importance of root water resistivity in the plant water extraction process. The problem was solved numerically for a wide range of the soil–root conductivity ratio (SRCR). Two different types of root water uptake (RWU) mechanisms were obtained. The first one is related to low root resistivity or low SRCR, and, thus, exhibits a so-called “moving uptake front” (MUF) effect observed previously in several experimental studies. The second one is inherent in large values of root resistivity or high values of SRCR (larger than 10⁴), and is strongly dependent on the root density distribution. Deceased.     

Determination of Capillary Pressure Function from Resistivity Data

A model has been derived theoretically to correlate capillary pressure and resistivity index based on the fractal scaling theory. The model is simple and predicts a power law relationship between capillary pressure and resistivity index (P _c = p _e · I ^β) in a specific range of low water saturation. To verify the model, gas-water capillary pressure and resistivity were measured simultaneously at a room temperature in 14 core samples from two formations in an oil reservoir. The permeability of the core samples ranged from 0.028 to over 3000 md. The porosity ranged from less than 8 to over 30. Capillary pressure curves were measured using a semi-permeable porous-plate technique. The model was tested against the experimental data obtained in this study. The results demonstrated that the model could match the experimental data in a specific range of low water saturation. The experimental results also support the fractal scaling theory in a low water saturation range. The new model developed in this study may be deployed to determine capillary pressure from resistivity data both in laboratories and reservoirs, especially in the case in which permeability is low or it is difficult to measure capillary pressure.     

Pore Network Analysis of Resistivity Index for Water-Wet Porous Media

Pore network analysis is used to investigate the effects of microscopic parameters of the pore structure such as pore geometry, pore-size distribution, pore space topology and fractal roughness porosity on resistivity index curves of strongly water-wet porous media. The pore structure is represented by a three-dimensional network of lamellar capillary tubes with fractal roughness features along their pore-walls. Oil-water drainage (conventional porous plate method) is simulated with a bond percolation-and-fractal roughness model without trapping of wetting fluid. The resistivity index, saturation exponent and capillary pressure are expressed as approximate functions of the pore network parameters by adopting some simplifying assumptions and using effective medium approximation, universal scaling laws of percolation theory and fractal geometry. Some new phenomenological models of resistivity index curves of porous media are derived. Finally, the eventual changes of resistivity index caused by the permanent entrapment of wetting fluid in the pore network are also studied.Resistivity index and saturation exponent are decreasing functions of the degree of correlation between pore volume and pore size as well as the width of the pore size distribution, whereas they are independent on the mean pore size. At low water saturations, the saturation exponent decreases or increases for pore systems of low or high fractal roughness porosity respectively, and obtains finite values only when the wetting fluid is not trapped in the pore network. The dependence of saturation exponent on water saturation weakens for strong correlation between pore volume and pore size, high network connectivity, medium pore-wall roughness porosity and medium width of the pore size distribution. The resistivity index can be described succesfully by generalized 3-parameter power functions of water saturation where the parameter values are related closely with the geometrical, topological and fractal properties of the pore structure.     

考虑弹性地基切向抗力的变截面圆弧壳梁分析

本文根据弹性薄壳理论,考虑了弹性地基径向和切向抗力的影响,解决了变截面圆弧壳地基梁的难题,作者所提出的近似解析法和加权余量法、传递矩阵法较有限单元法简便.     

三峡工程地质勘察研究的理论与实践

举世瞩目的三峡工程目前已进入关键的建没阶段。本文从区域稳定与地震危险性、水库区工程地质与环境地质、水库诱发地震、坝址及建筑物工程地质以及天然建筑材料等五个方面论述三峡工程长期以来所进行的工程地质勘察研究工作,并着重对三峡工程区的地质地震问题作了较为详细的探讨。最后对这一巨型工程的地质勘察工作进行了经验总结。     

Pore Network Modelling of Electrical Resistivity and Capillary Pressure Characteristics

In order to model petrophysical properties of hydrocarbon reservoir rocks, the underlying physics occurring in realistic rock pore structures must be captured. Experimental evidence showing variations of wetting occurring within a pore, and existence of the so-called 'non-Archie' behaviour, has led to numerical models using pore shapes with crevices (for example, square, elliptic, star-like shapes, etc.). This paper presents theoretical derivations and simulation results of a new pore space network model for the prediction of petrophysical properties of reservoir rocks. The effects of key pore geometrical factors such as pore shape, pore size distribution and pore co-ordination number (pore connectivity) have been incorporated into the theoretical model. In particular, the model is used to investigate the effects of wettability and saturation history on electrical resistivity and capillary pressure characteristics. The petrophysical characteristics were simulated for reservoir rock samples. The use of the more realistic grain boundary pore (GBP) shape allows simulation of the generic behaviour of sandstone rocks, with various wetting scenarios. The predictions are in close agreement with electrical resistivity and capillary pressure characteristics observed in experiments.