石蜡的国内外市场

石蜡在国际市场上相对稳定，预计２０００年的需求量为３５０万ｔ，价格仍将维持在目前的水平。１９９５年我国石蜡的产量为８４．５万ｔ，预计２０００年国内需求量约６０万ｔ，出口量将达５０万ｔ     

Maximum quasi-likelihood estimation for the near(2) model

Abstract.  Maximum quasi-likelihood estimation is investigated for the NEAR(2) model, an autoregressive time series model with marginal exponential distributions. In certain regions of the parameter space, simulations indicate that maximum quasi-likelihood estimators perform better than two-stage conditional least squares estimators in terms of the per cent of estimates falling in the parameter space. The problem of out-of-range estimates is shown to be caused by the lack of information in the data rather than the characteristics of the method of estimation.     

基于LS-SVM逆系统的无轴承异步电机解耦控制

无轴承异步电机具有非线性、多变量和强耦合的特点,要实现电机稳定悬浮和旋转运行,必须对其进行非线性动态解耦控制。为了克服逆系统方法精确建模难的局限性,采用基于最小二乘支持向量机(LS-SVM)α阶逆系统方法对无轴承异步电机进行动态解耦控制的研究。首先利用最小二乘支持向量机辨识出无轴承异步电机的逆模型,然后将它串联在原系统前,将无轴承异步电机解耦成四个独立的伪线性子系统-2个径向位移子系统、一个速度子系统和一个磁链子系统。为保证鲁棒性能,最后对解耦后的系统采用非线性内模控制策略。研究表明,LS-SVMα阶逆系统方法能够实现无轴承异步电机径向悬浮力和旋转力之间的动态解耦控制,控制系统具有良好的静态和动态性能。     

基于 IFPUG功能点分析方法改进特征值因子的应用研究*

论文阐述了功能点分析方法的计算步骤,并采用IFPUG分析方法对一个接近完成的软件开发项目进行了评估,并结合国内标准提出了改进后的系统特征值评估模型,用六个特性的参数来确定一个系统特征值,以此取代IFPUG功能点分析方法中的调整因子。结果表明：改进后的功能点分析方法在对所开发的软件项目的度量上具有更高的精确度,更接近项目开发的实际。     

局部表面改性紫铜方柱阵列池沸腾传热特性和机理

以局部表面改性的紫铜直方柱和梯度方柱阵列为研究对象，实验研究了表面润湿性、表面形貌和表面活性剂对池沸腾换热性能和气泡生长特性的影响。实验工质为去离子水，浓度分别为100、200、400、800 mg·L^-1的异丙醇溶液和正庚醇溶液。实验结果表明：方柱阵列表面镀银之后润湿性变差，表面产生的气泡数量减少。向去离子水中添加异丙醇或正庚醇后，在热通量为66.1～202 kW·m^-2时，气泡脱离直径变小、数目减少，而当热通量增至413 kW·m^-2时，活性剂能够有效阻碍气泡合并，故池沸腾传热系数随着浓度增加先减小后增大。上下层宽分别0.5 mm和1 mm、间距为2 mm的梯度方柱阵列结构有助于气泡的合并，但由于促进了固体表面气膜的形成，从而降低了沸腾换热性能。     

Measurement of soybean fatty acids by near-infrared spectroscopy: Linear and nonlinear calibration methods

A key element of successful development of new soybean cultivars is availability of inexpensive and rapid methods for measurement of FA in seeds. Published research demonstrated applicability of NIR spectroscopy for FA profiling in oilseeds. The objectives of this study were to investigate the applicability of NIR spectroscopy for measurement of FA in whole soybeans and compare performance of calibration methods. Equations were developed using partial least squares (PLS), artificial neural networks (ANN), and support vector machines (SVM) regression methods. Validation results demonstrated that (i) equations for total saturates had the highest predictive ability (r ²=0.91–0.94) and were usable for quality assurance applications, (ii) palmitic acid models (r ²=0.80–0.84) were usable for certain research applications, and (iii) equations for stearic (r ²=0.49–0.68), oleic (r ²=0.76–0.81), linoleic (r ²=0.73–0.76), and linolenic (r ²=0.67–0.74) acids could be used for sample screening. The SVM models produced significantly more accurate predictions than those developed with PLS. ANN calibrations were not different from the other two methods. Reduction in the number of calibration samples reduced predictive ability of all equations. The rate of performance degradation of SVM models with sample reduction was the lowest.     

基于图像反馈的标靶面与光轴垂直调节系统

介绍了摄像机标定的内部参数,阐述了标靶面与光轴垂直可以简化标定的过程.当标靶面与光轴垂直时,利用标靶面上特征圆在CCD成像面上成像也是圆的特点,提出了基于图像反馈的标靶面与光轴垂直的调节方法.一般情况下,标靶面与光轴不垂直,标靶面上特征圆在CCD成像面上成像为椭圆.通过图像处理和最小二乘椭圆拟合法计算出成像椭圆的长短轴及偏角,设计了调整控制策略.实验结果表明,该方法是有效可行的.     

非负线性最小二乘问题的一种严格可行内点算法

给出了非负线性最小二乘问题的一个新算法。首先,把非负线性最小二乘转化为线性互补问题,结合牛顿方向和中心路径方向,通过求解一个线性方程组得到搜索方向;进而获得了求解非负线性最小二乘问题的一种严格可行内点算法,并证明该算法经过多项式次迭代之后收敛到原问题的一个最优解,数值实验表明此方法是有效的。     

基于Hoek-Brown准则的深部岩体力学参数及其应用

基于Hoek-Brown经验强度准则,采用最小二乘法拟合出岩体力学强度参数,并与H-B_02ed推荐的等面积拟合结果进行对比,结果发现两种拟合方法得出的岩体内摩擦角数值相差很小,但等面积拟合法得出的黏聚力强度远高于最小二乘拟合法。将两种强度参数拟合结果应用于深部矿体开采的数值模拟,发现采用最小二乘拟合法的岩体强度参数其模拟结果更接近工程实际。该方法对深部岩体力学参数的确定具有一定的借鉴意义。