Spline Boundary Element Method for Calculating Three-Dimensional Electrostatic Fields

Based on [l].this paper presents a new spline-BEM for calculating 3-D electrostatic fields,in which bi-cubic B-splines are used as basis functions. The corner problem in BEM and the extreme conditions for splines are circumvented. The numerical results presented show that the global approximation .convergence and stability of the method are satisfactory.     

The Stability of Quaternion Metrices and Their Judging Criteria

Some conceptions of stable quaternion matrices and some judging criteria are given.The Robrach theorem,Taussky theorem,Ostrowski Schneider theorem and Gerschgorin theorem are generalized to quaternion field.The conclusion about two quaternion matrices,i.e.,inferior positive matrices are unstable,interior negative matrices are stable and some other results are pointed out.     

FDTD Method''s Application in the Research of Television Interference From High Voltage Transmission Line

The mechanism of television interference is discussed from High voltage transmission line. Then the computational model is established, and scattering fields are calculated with the finite-difference time-domain(FDTD) method, and the results are visualized. The scattering effects of High voltage transmission lines on horizontal polarization waves (corresponding to TM mode) are greater than on vertical polarization waves (corresponding to TE mode).     

Nonlinear Finite Element Analysis of RC Deep Flexural Simply Supported Beams Using Disturbed Stress Field Model

A nonlinear finite element analysis of 4 RC deep flexural simply supported beams with the program VT2 is presented. Crack development and failure modes , longitudinal reinforcement strain distributions and load -deflection curves were compared as a result in order to evaluate the validity of the disturbed stress field model to analyse such deep simply supported beam.     

北方旱地土壤氮素平衡

北方大部分地区的旱地土壤中,农业氮素一般表现亏损,平衡强度约87%;园田土壤氮素略有盈余,平衡强度约123%.~(15)示踪研究表明,旱地土壤主要作物氮素利用率平均为27.04%,土壤残留24.79%,亏缺损失48.17%.园田主要蔬菜氮素和用率平均为29.11%,土壤残留22.67%,亏缺损失48.23%,其间差异很小.北方旱地施用铵态氮化肥主要损失是氨的挥发.影响氨挥发的因素有风速、温度、土壤水分、土壤质地、化肥品种.氮肥深施是防止氨挥发的有效方法.     

切线泵流动特征的整流场数值模拟

对单级切线泵在设计工况进行了定常流动数值模拟，分析了叶轮流道及蜗壳内的液体流动情况。结果表明，切线泵内流场非常复杂，叶轮进口有明显冲击，叶轮各流道的速度、压力差异很大，环形蜗壳内流动呈现旋涡推进特征，上、下游流动有强烈的相互作用，整机流场不具有对称性；环形蜗壳的几何结构以及流场上、下游的相互作用是导致整机流场非对称特性的主要原因。计算结果为进一步改进结构、提高性能、减小水力损失提供了理论依据。     

高压静电场处理对葡萄鲜度保持的影响

以巨丰葡萄为材料,研究了在20kV/m,40kV/m,60kV/m,80kV/m,100kV/m不同高压静电场处理1h对葡萄的质量损失率、腐烂率、掉果率的影响.试验结果表明:高压静电场处理对葡萄质量损失有明显的抑制作用;并且能够延迟葡萄采后的衰老过程,葡萄的腐烂率、掉果率明显低于对照;在相同贮藏条件下,利用60kV/m的高压静电场处理,葡萄的保鲜效果好于其它高压静电场处理,葡萄贮藏70天,好果率达80%.     

基于最小二乘支持向量机模型预测田面糙率

田面糙率是影响地面灌溉质量的重要参数。基于最小二乘支持向量机建立了两类4个田面糙率预测模型,并进行了验证。结果表明第一类模型预测值(即作物地采用LSSVM-N-I3、裸地采用LSSVM-N-I1,翻耕地采用LSSVM-N-I2)相对误差最大值为9.7%;第二类模型预测值(即LSSVM-N-II模型)相对误差最大值为10.5%,由此可见两类模型都具有较高的预测精度,可以用于田面糙率的预测。     

水稻田间育秧精密播种机设计与试验

为提高田间育秧播种机的播种合格率和播种稳定均匀性,设计了一种适用于南方水稻田间育秧的精密播种机。在深入分析螺旋勺轮式播种器的播种原理,以及播种器行走控制系统的基础上,采用正交试验方法,研究了螺旋勺轮的凹槽深度、螺旋升角、播种器行走速度对播种合格率和空穴率的影响规律,得出杂交稻播种合格率和空穴率影响因素的最佳参数组合:凹槽深度h为3 mm、螺旋升角α为81.73°、播种器行走速度v为0.35 m/s。试验表明,采用闭环控制系统后的播种机播种杂交稻2~6粒/格合格率由87.14%提升到93.21%,常规稻3~8粒/格的播种合格率为92.14%,播种性能满足常规稻和杂交稻精密播种育秧的技术要求。