基于电阻率静力触探的海相黏土成因特性分析

土的电阻率是表征土体导电性的基本参数,也是反映土体固有物性的一个综合性指标。众所周知,土的电阻率影响因素较多,因此电阻率随深度的变化可以反映出土体的许多性状。电阻率静力触探(RCPT)作为一种新型的原位测试技术,除可测锥尖阻力、侧壁摩阻力和孔隙水压力以外,还可以同时测试土的电阻率。首先简要介绍了RCPT测试技术,采用电阻率静力触探(RCPT)在连云港海相黏土场地进行了试验,得到土的原位电阻率测试值。结合连云港海相黏土的室内物理化学分析试验,研究了其矿物成分、沉积化学特征,分析了该海相软黏土的电阻率指标与矿物成分、离子含量、胶结特性和氧化环境间的关系。分析表明:基于RCPT测试成果是可以充分反映出连云港海相黏土的成因特性的。

基于电阻率孔压静力触探的浅层气可靠度识别

地下浅层气的存在会对地铁项目的勘察、施工以及后期正常运营构成安全隐患。采用基于地质统计学和可靠性分析的概率方法,对杭州某地铁站场地的电阻率静力触探测试数据进行分析。通过回归分析移除电阻率数据的趋势项,以变差函数为工具,描述电阻率残差在竖向和水平向上的各向异性,采用克里格插值对未采样点参数值进行最优线性无偏估计,采用一阶可靠度方法获取基于电阻率的地下浅层气分布三维概率图。分析表明:电阻率残差具有显著的各向异性,在竖直和水平方向的自相关距离分别为5.1 m和55.6 m。在考虑不同土体电阻率背景值不同的前提下,采用一阶可靠度方法建立了浅层气三维概率分布图。该场地竖直方向上浅层气分布于25m附近及30~35m深度区间内,水平方向上则集中分布于RCPTU1点位附近。可基于该结果提出针对性的防治对策,为布设排气孔、浅层气监测等治理措施提供依据。

电阻应变式力传感器低频冲击频率测量电路设计

针对采用压电式力传感器、冲击力传感器测量冲击频率存在成本高、安装不便等问题,设计了一种电阻应变式力传感器低频冲击频率测量电路。该电路根据电阻应变式力传感器的工作原理,首先采用放大电路将传感器输出信号放大,然后运用电压比较电路产生方波信号,最后采用单稳态触发电路对方波信号整形,从而得到标准的方波信号。实际应用表明,该电路工作稳定,测量精度较高。

基于电阻率静力触探的膨胀土膨胀性原位评价应用研究

现行的膨胀土膨胀性能评价手段费时、复杂且难以反映膨胀土场地地基的真实状况,亟需发展先进的原位测试方法和技术,实现现场快速、准确的膨胀土膨胀特性评价。结合前期研究,本文以电阻率静力触探(RCPT)作为原位评价技术,采用商用高岭土和膨润土按质量比拌合配置人工膨胀土进行定量分析,并以两种天然膨胀土进行验证。开展室内四电极法电阻率测试,探明膨胀土自由膨胀率随电阻率的变化规律,通过电阻率影响因素之含水量变化指数b作为中间参数,构建了基于电阻率指标的膨胀土膨胀性能评价模型。采用自主研发的电阻率CPT标定罐贯入系统,研究了原位实测电阻率参数评价膨胀土膨胀性能的适用性,并验证了室内四电极法和原位电阻率CPT测得的电阻率之间呈1∶1的线性关系,电阻率CPT可以作为原位膨胀土膨胀性能评价技术。研究表明,膨胀土的电阻率参数随自由膨胀率的增加而增加;膨胀土电阻率与自由膨胀率之间呈指数定量关系;电阻率指标可以作为原位膨胀土膨胀性能表征指标。

电阻率静力触探技术在软土地区水土污染调查中的应用

电阻率法是水土污染调查的重要物探方法之一,针对软土地区浅部土层导电性好、土体受污染前后导电性差异较小的问题,统计了覆盖上海地区73个钻孔套管以下首层软土的电阻率平均值分布区间,分析了浅部土层电阻率变化趋势,评价了电阻率法在上海地区对于不同水土污染类型探测的适用性,最后介绍了电阻率静力触探技术在上海某化厂场地水土污染快速调查中的应用。结果表明:上海地区深度20 m以内土层电阻率总体在5Ω·m左右,靠杭州湾、长江口的近海区域,土体电阻率在2Ω·m以下,故电阻率法在上海地区油烃类有机物污染调查适用性更好;电阻率静力触探技术可快速获得软土地区电阻率随深度的变化曲线,对浅部有机污染引起的高阻异常、深部无机污染引起的低阻异常均有良好反映。

减小电阻应变式力敏传感器的零点漂移探讨

电阻应变式力敏传感器的零点漂移是生产过程中必须重视的问题之一。本文介绍了解决零点漂移问题对提高产品使用性能和市场竞争力的重要性,分析了传感器零点漂移的规律和产生原因,提出了减小电阻应变式力敏传感器零点漂移的工艺措施和思路方法。

用表面电渗法减少煤与外物的切向阻力

分析了煤的含水量及所受的正压力对煤与工作部件切向阻力的影响 ,并应用表面电渗技术减少煤的切向阻力。结果表明 ,煤的含水量与所受的正压力对煤切向阻力的影响有明显的交互作用。当正压力较小时 ,切向阻力随含水量的增加而增加 ;当正压力较大时 ,切向阻力与含水量呈抛物线关系。表面电渗法可有效地减少煤的切向阻力 ,但电极分布对电渗效果有很大影响。当正负极面积比为 1∶3时 ,最佳减阻值为 8 8%。

基于电阻率综合测试的污染场地快速诊断方法研究

通过地球物理探测方法测试土层电阻率,利用电阻率的异常判别筛查场地污染分布范围,是国内环境岩土工程领域关注的热点问题。本文基于现场试验与工程应用,探讨高密度电法、电阻率CT、电阻率静力触探(RCPT)对污染土诊断的适用性。结果表明,电阻率测试可快速诊断场地潜在污染区域,操作简单、结果可靠、成本较低,在污染场地初步调查中有较高的应用价值与优势。

电阻率CPTU在某农药厂污染场地评价中的应用

电阻率孔压静力触探(RCPTU)除了包含常规的孔压静力触探测试功能之外,还可以提供连续的电阻率变化曲线,因而在环境岩土工程领域具有广阔的应用前景。电阻率是表征土体导电性的基本参数,是土的固有物性之一,每种类型的土都有固有的电阻率,其变异可能意味着受到污染。本文根据某农药厂污染场地的RCPTU试验结果,分析了不同污染物类型对电阻率的影响,并初步研究了基于电阻率指标的污染物分布与污染程度的鉴别。考虑到孔隙比或相对密实度对土体积电阻率也会产生较大影响,利用RCPTU可测相对密实度的优点,本文提出可将实测电阻率值等效至某一特定的相对密实度下,再将等效电阻率值与相应的背景值进行对比分析,根据等效电阻率值与背景值的偏差量与偏差率进行污染范围与污染程度的确定。结果表明电阻率指标能够精确反应污染物的存在与受污染的程度。

Microstructure evolution of Al-Zn-Mg-Cu alloy during non-linear cooling process

The microstructure evolution and properties of an Al-Zn-Mg-Cu alloy were investigated under different non-linear cooling processes from the solution temperature, combined with in-situ electrical resistivity measurements, selected area diffraction patterns （SADPs）, transmission electron microscopy （TEM）, and tensile tests. The relative resistivity was calculated to characterize the phase transformation of the experimental alloy during different cooling processes. The results show that at high temperatures, the microstructure evolutions change from the directional diffusion of Zn and Mg atoms to the precipitation of S phase, depending on the cooling rate. At medium temperatures, q phase nucleates on A13Zr dispersoids and grain boundaries under fast cooling conditions, while S phase precipitates under the slow cooling conditions. The strength and ductility of the aged alloy suffer a significant deterioration due to the heterogeneous precipitation in medium temperature range. At low temperatures, homogeneously nucleated GP zone, η′ and η phases precipitate.

基于海相粘土沉积化学特性的RCPT测试影响因素分析

首先简要回顾了土的电阻率影响因素,介绍了电阻率静力触探(RCPT)测试技术和操作方法,采用RCPT在连云港海相粘土场地进行了现场试验,获得土的原位电阻率测试值.结合连云港海相粘土的沉积特性与物理化学分析试验,对RCPT电阻率测试数据进行了基于矿物成分、离子浓度、Fe3+含量影响因素分析.研究发现:土的电阻率随着粘土矿物含量和离子浓度的增加而减小,并且Fe3+对电阻率测试值也具有明显的影响.分析表明:连云港海相粘土的沉积特征和化学特性对其电阻率测试参数具有显著的影响.

Anodic behavior and microstructure of Al/Pb-Ag anode during zinc electrowinning

Anodic behaviors and oxygen evolution kinetics of Pb-0.8%Ag and Al/Pb-0.8%Ag anodes during the initial 24 h zinc electrowinning were investigated with cyclic voltammetry （CV） curves and electrochemical impedance spectroscopy （EIS）. The results reveal that the anodic behaviors and reaction kinetics of the two anodes vary a lot during the anodic polarization which indicate the formation and stabilization of anodic layer. Compared with conventional Pb-0.8%Ag anode, A1/Pb-0.8%Ag anode has longer time of anodic polarization. At the very beginning of anodic polarization, the two anodes all exhibit higher potential of oxygen evolution reaction （OER） since the reaction is controlled by the transformation step of intermediates. Then, its OER potential is largely diminished and OER rate is deduced from the formation and adsorption of the first intermediate （S-OHms）. In the prolonged anodie polarization, the anodie potential of A1/Pb-0.8%Ag gradually decreases and the final value is more stable than that of conventional Pb-0.8%Ag anode. On the anodic layer after 24 h of anodic polarization, the OER potential is controlled by the formation and adsorption of intermediate. The microstructures of A1/Pb-0.8%Ag and Pb-0.8%Ag anodes after 24 h of anodie polarization were analyzed by scanning electron microscope （SEM）.

Microstructure characterization and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy

The microstructure, microhardness and quasi-static failure behavior of resistance spot welds of AA6111-T4 aluminum alloy were experimentally investigated. Optical metallography and high-resolution hardness traverses were utilized to characterize the weld nugget, heat affected zone and base metal. The AA6111 spot welds displayed a softer nugget and hardened heat affected zone, compared with the base metal. The through-thickness hardness of the base metal sheet was not constant and had to be carefully considered to determine the effect of welding on material properties. Quasi-static lap-shear tensile tests were used to determine the failure load and failure mode. All tensile specimens failed through the interfacial fracture. This failure mode is consistent with the observed reduced hardness in the weld nugget.

变压器突发短路时电流的危害及防范措施

主要讨论了变压器二次突然短路过电流现象和电磁力对变压器本身的危害，以及变压器在制造过程中应采取的相应措施。在电网运行过程中，发生突然短路的现象并不少见。特别是变压器在短路瞬间，电场和磁场的能量发生较大变化，可能会使绕组中的电流和电压超过额定数值许多倍，即出现所谓的过电流和过电压现象，使变压器遭到破坏，因此在变压器制造过程中应采取相应措施提高变压器抗短路能力。

RESEARCH ON MEMBRANE BIOREACTOR TREATING DOMESTIC WASTEWATER AND RELATED MECHANISMS

Experiments on treatment of domestic wastewater by membrane bioreactors were carried out.The results showed that this process could produce good quality effluent with low COD,turbidity and total count of bacteria.With intermittent operation and continuous aeration,the membrane flux was kept steady.The mechanisms of removing COD through membrane,the structure of membrane and filtration resistance were also discussed.

Study on the resistance spot welding technology of 22MnMoB hot stamping quenched steel

In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we have obtained the optimal spot welding technological parameter condition. According to the results, the relations among spot welding technological parameter, welding nugget, mechanical property and fracture mode were discussed. The effects of all the welding parameters such as welding current, welding time and electrode force on the quality of joint can be boiled down to one thing--the diameter of welding nugget. The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation. There are two typical fracture models of 22MnMoB hot stamping quenched steel sheet, i.e., interracial fracture and nugget pullout. Other than mild steel or normal high strength steel, in the shearing tensile test, hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure, welding soft zone and the porosity level of fusion zone.

Effect of carbon fibre on properties of TiB_2/C composite cathode coating for aluminum electrolysis

The tensile strength,compressive strength and electrical resistivity of TiB2/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device,and the effects of carbon fibre content and carbon fibre length on tensile strength,compressive strength and electrical resistivity were investigated.The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre(length of 3 mm)content ranges from 0 to 4.0%;at the carbon fibre content of 1.5%,the tensile strength of coating reaches the maximum,25.6 MPa.For the coating with carbon fibre content of 1.5%,the carbon fibre length has a great influence on tensile strength and compressive strength of coating;when the carbon fibre length is 6 mm,the tensile strength and compressive strength of coating reach the maximum,27.6 MPa and 39.2 MPa,respectively.The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre,and the influence of carbon fibre length on electrical resistivity of coating at low temperature(30-200℃)is more obvious than that at high temperature(960℃).

Hydraulic Resistance and Capacitance in the Soil-Plant System

In this paper, the hydraulic resistances and capacitances were evaluated. based on the development of non-(?) model of water flow in the soil-plant system and the simulating experiment work.The results show that the mean hydraulic resistance in the soil-plant system is 6.79×109 MPa·S·m-3; the mean hydraulic capacitance in the system is 5.2×107m3·MPa-1. In the components of hydraulic capacitance in the system, the capacitance in soil (81.8×10-6m3·MPa ) is the biggest and its variability with suii water potential is extremely strong, the capacitance in plant (5.3×10-7m3·MPa-1) is much smaller than that in soil, and the capacitance in shoots (15.5×10-7m3·2MPa-1) is bigger than that in roots (8.4×10-7m3·2MPa-1). An interesting result is that the capacitance in plant is almost equivalent to that in the soil-plant system.

Numerical investigation of influence of pantograph parameters and train length on aerodynamic drag of high-speed train

This study investigates the influence of different pantograph parameters and train length on the aerodynamic drag of high-speed train by the delayed detached eddy simulation(DDES) method. The train geometry considered is the high-speed train with pantographs, and the different versions have 3, 5, 8, 10, 12, 16 and 17 cars. The numerical results are verified by the wind tunnel test with 3.6% difference. The influences of the number of cars and the position, quantity and configuration of pantographs on flow field around high-speed train and wake vortices are analyzed. The aerodynamic drag of middle cars gradually decreases along the flow direction. The aerodynamic drag of pantographs decreases with its backward shift, and that of the first pantograph decreases significantly. As the number of pantographs increases, its effect on the aerodynamic drag decrease of rear cars is more significant. The engineering application equation for the aerodynamic drag of high-speed train with pantographs is proposed. For the 10-car and 17-car train, the differences of total aerodynamic drag between the equation and the simulation results are 1.2% and 0.4%, respectively. The equation generalized in this study could well guide the design phase of high-speed train.

Imaging technologies in oilfield applications

In this paper, we describe some recent imaging technologies developed by Schlumberger for oilfield downhole mul- tiphase flow production logging (PL) and cross-well electromagnetic (EM) survey applications. FloScan Imager (FSITM) has been introduced as a 3-phase oil/gas/water flow PL tool for deviated and horizontal wells. FSI sensors can map fluid velocity and holdup profiles along a vertical diameter of the wellbore at every survey depth, enabling a robust estimate of the individual phase flow rates in complex flow regimes. The cross-well EM survey is based on cross-borehole induction logging technique and provides resistivity distribution at a reservoir scale. It is a useful tool for reservoir management and is most effective in dynamic fields where fluid saturations are variable in time and space. The tool can be used to identify (water or steam) flooded and bypassed regions. By monitoring changes in the resistivity spatial distribution with time, cross-well EM survey is very effective at mapping inter-well temperature and structure. Some field examples are shown for both FloScan Imager PL tool and cross-well resistivity imaging survey.