蔬菜种子的电传导和介电特性

本文介绍一种能在任意频率下测定种子电阻率和介电常数等电参量的测试系统和方法,研究了蔬菜种子的含水量和测试频率对种子电传导和介电特性的影响,莸得相互之间的回归方程。     

The effect of micro-heterogeneity and capillary number on capillary pressure and relative permeability curves of soils

The determination of the two-phase flow coefficients (such as the capillary pressure, P_c, and relative permeabilities, k_rw, k_ro) is of a key importance to model the two-phase flow processes taking place during contaminant transport in subsurface. In the present work, transient immiscible displacement experiments are performed at various flow rates on long disturbed soil columns. The capillary pressure-saturation-relative permeability relationships of soils characterized by narrow and broad grain size distributions are estimated with inverse modeling from rate-controlled displacement experiments and are correlated with the grain size variability and ratio of viscous to capillary forces (capillary number). A soil core holder assembled with electrodes is constructed to monitor the axial distribution of water saturation. A new technique is developed to determine the water saturation averaged over successive segments of the soil column by measuring the transient responses of the electrical resistance between vertical ring electrodes. The transient responses of the average oil (water) saturation in five segments along with the total pressure drop across the soil column are introduced into an inverse modeling numerical solver of the macroscopic two-phase flow equations to estimate simultaneously the capillary pressure and relative permeability curves under dynamic conditions. The water and oil relative permeabilities increase drastically with the capillary number, while the capillary pressure curve of soils with broad grain (pore) size distribution is wider than that of soils with narrow grain (pore) size distribution. For soils with high variability of grain sizes, the irreducible wetting phase saturation is higher, the relative permeability curves are sharper and the end oil relative permeability is higher compared to soils with low variability of grain sizes.     

Electromagnetic shielding efficiency of the electric field of charcoal from six wood species

Six wood species were carbonized under various carbonization temperatures and nonoxygen conditions to obtained charcoal. The effects of wood species, rate of temperature rise, and carbonization temperature on the electromagnetic shielding efficiency (ESE) of the electric field were investigated. The wood species used in this study were Japanese cedar, China fir, western hemlock, red oak, fortune paulownia, and Taiwan acacia. Tested materials were carbonized in a high-temperature oven under the following conditions: rate of temperature rise 1°–5°C/min; carbonization temperature 500°–1100°C, with temperature intervals of 100°C; maximum temperature maintained for 1h; and flow rate of nitrogen 300ml/min. The electromagnetic insulation strength system was used to detect the ESE of the electric field of charcoal. It was found that western hemlock and fortune paulownia charcoal showed maximum ESE values of of 36 and 61dB generated at a carbonization temperature of 1000°C. The charcoals derived from four other wood species showed maximum ESE values of 28dB for Japanese cedar, 23dB for China fir, 32dB for red oak, and 38dB for Taiwan acacia, respectively, at a carbonization temperature of 1100°C. The ESE value for fortune paulownia charcoal was similar to those of metal nets. The relations between ESE and logarithmic values of resistivity (log) could be represented by a negatively exponential formula.Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

云南地方油菜种质资源抗(耐)病毒病、菌核病和霜霉病的鉴定研究

 对云南油菜种质资源317份的抗(耐)病毒病、菌核病、霜霉病进行鉴定研究,结果为:云南省的地方油菜种质资源中虽无对病毒病、菌核病、霜霉病免疫的品种,但存在着高抗(耐)病毒病、菌核病和霜霉病的种质资源。其中,在芥菜型油菜中鉴定出高抗(耐)病毒病种质资源11份(高抗3份,高耐8份)、高抗(耐)菌核病的种质资源有3份、高抗(耐)霜霉病种质资源1份;在白菜型油菜中鉴定出高抗(耐)病毒病种质资源1份;甘蓝型油菜无高抗(耐)3类病的种质资源。云南省大部份油菜种质资源对3类病的抗性为低感至高感,占油菜资源总数的89.4%。     

电极接触与间距对土壤电阻率测量的影响

电阻率法在土壤测试的精确性方面存在较多不足,而电极是影响精度的重要原因,尤其是二极法。若能确定电极与土壤的接触程度及两电极间距离对测试结果的影响,将最大程度避免电极的干扰。基于米勒盒(Millersoil-box)测试模型,采用锌污染砂作为模拟土壤,以测试其交流电阻为例,进行系统的试验研究,建立了新的串联导电模型,分析了电极接触与间距对电阻的影响,又通过COMSOL软件仿真进行核准和补充,量化了测试误差。结果表明:试验研究和数值仿真能够相互验证和补充,说明建立的导电测试模型是正确的。导电模型划分了导电正常段与受电极影响的过渡段串联,过渡段长度随接触程度的增大而减小;过渡段中电流流网的变化产生了收缩电阻,随接触程度的增大而减弱,但二者不受电极间距的影响。过渡段长度与电流偏离程度又可借助仿真得出的径向电流密度精确表达,进而从数值上得出过渡段与正常段电阻率的偏差情况。误差分析中,测试所得的综合电阻率随着接触程度的增大和电极间距的增加而逐渐接近正常电阻率。上述研究可有效分析出因电极接触与间距而引起的测试偏差,得出正常电阻率,为测试中完善电极布置与提高测试精度提供合理建议。     

木材介质损耗参数的研究

在频率100 kHZ-26MHz,含水率0-100％,温度0-100℃范围内,对50个树种木材的介质损耗参数进行了测计,并着重对华山松、油松、木荷、青岗栎、栓皮栎等5个树种进行了研究。结果表明:木材介质损耗正切角和损耗因子随含水率增大而增大,随温度升高而降低。一般轴向大于横向;损耗因子与密度呈正相关(r=0.42)。木材并联等效交流。电阻率γ随频率、含水率升高而降低,并与密度呈负相关γ=-O.59);轴向r值小于横向r值,方差分析表明,频率、含水率、温度、纹理方向和密度对木材介质损耗参数的影响显著。     

电阻率法确定土壤水分特征曲线初探

以取自青岛市郊区的田间土样为研究对象,通过自制的室内土壤电阻率测量装置,测定了土壤的电阻率及对应的含水量,建立了电阻率-含水量关系模型。基于Ku/pF非饱和导水率测量系统测定的土壤水分特征曲线,借助含水量这一中间量,推求出了土壤电阻率-基质吸力关系模型,从而可以根据电阻率计算出对应的土壤基质吸力。耦合土壤电阻率-含水量关系模型与土壤电阻率-基质吸力关系模型,达到了预测土壤水分特征曲线的目的,为电阻率法在区域尺度空间和时间上预测土壤水分特征曲线提供了新的途径。     

六盘山香水河小流域典型坡面的土壤电阻率空间变异

为了解坡面土壤水文特征的空间分布,采用多电极电阻仪法(ERT),于2009年5月初在宁夏六盘山香水河小流域一个长约600 m的华北落叶松人工林典型坡面上,设置了从坡顶至坡底的1条纵向样线及处于不同坡位的水平分布的3条横向样线,多点测定了多层土壤的电阻率值并分析其空间变异特征。结果表明,土壤电阻率在纵向样线上总体有较好的空间连续性及一定的空间变异性,随着坡位下降,电阻率呈现出由坡上至坡中上逐渐减小和然后又恢复性增大的过程。由于局部特殊的土壤特征、地貌及植被分布差异,使土壤电阻率沿坡面纵向变异程度大于不同坡位的横向变异程度。在土层垂直方向上,由于石砾含量和岩石比例随深度逐渐增多,电阻率表现为随深度增加逐渐增大。电阻率与土壤总孔隙度和体积含水率相关最紧密,尤其与体积含水率相关较好,说明通过测定坡面电阻率推求土壤水分等土壤特性的坡面变化是可行的。     

云雾山和叠叠沟草坡土壤电阻率和含水率空间差异

为了解不同土质坡面土壤含水率的空间分布差异,选择固原黄土区云雾山和石质山区叠叠沟为研究区域,采用多电极电阻仪法,在长约400 m的坡面上设置纵向样线,多点同步连续测定了土壤含水率和电阻率.结果表明:黄土区云雾山土壤电阻率和含水率的相关性较好(R2=0.78),说明通过测定坡面电阻率推求土壤含水率的坡面变化是可行的.云雾山土壤电阻率沿坡面表现为由坡上至坡中逐渐增大,到坡下部又逐渐减小;而固原石质山区叠叠沟坡面从坡上到坡下电阻率逐渐减小.土壤干层特征方面,云雾山草坡在1～3m土层出现轻度于层,3～4m出现中度干层,6～17m出现重度干层;叠叠沟坡面在3 m土层才出现轻度干层,在6m以及更深层处出现重度干层.     

海水入侵-地下水位变化-土壤盐渍化自动监测实验研究

利用国家863课题支持研制的电阻率探杆自动监测系统,分别进行了海水入侵、地下水位升降、土壤盐渍化过程的动态监测室内模拟实验,旨在探讨该系统用于海水入侵、地下水位变化、土壤盐渍化等环境过程自动监测的可行性。结果表明,海水入侵形成的咸-淡水界面及海水弥散带,地下水位位置上下及包气带,及不同含盐量的土体,均具有显著的电阻率探杆测试结果特征差异。该系统可为海水入侵,地下水位变化,土壤盐渍化,土壤地下污染等环境过程的原位连续实时自动监测提供数据资料及技术支持。