Evaluation of differences in potassium availability in soils of the same exchangeable potassium level

Abstract

Potassium availability was determined by growing corn (Zea mays L.) in pots of soil in a controlled environment chamber. Comparison of K uptake rate per unit root area indicated differing degrees of K availability. The differences in availability among soils were not predicted by differences in cation exchange capacities. The K concentration in solution and the average rate of diffusion more nearly reflected differences in K availability, particularly when the kinetic rate factors of diffusion and mass flow were integrated with root growth and uptake factors in the Cushman mathematical model of K uptake. Utilization of this model demonstrated the importance of using rate factors for ion movement in soil along with plant factors of root growth in predicting K availability.     

Local water vapor diffusion coefficient when drying Norway spruce sapwood

In this article, a one-dimensional and a two-dimensional approach to the evaluation of local diffusion coefficients for Norway spruce sapwood from measured moisture content (MC) values are presented. A studied wood sample was dried from the initial green condition to about 15% mean MC, but here only the diffusive part of the drying process between approximately 25% and 15% mean MC was treated. Measured local MC values were based on nondestructive X-ray computed tomography data. Finite element calculations were performed with two alternative diffusion coefficients to test the appropriateness of the diffusion coefficients that were evaluated from the measured MC values. The evaluated diffusion coefficients show interesting dependence on MC and distance from the evaporation surface. The advantage of using the methods presented is that the diffusion coefficient is calculated on a local level without having to define a function for the diffusion coefficient’s dependency on other parameters.     

The Approximate Method of Quadratic Function With Mixed Constraint

A reduced method to solve the problem with equality constraints is given. Based on the reference we use nonlinear equality constraints, the approximate algorithm is obtained. The nonlinear programming of quadratic function with equality and unequality constraints is discussed by Wang kairong. We transform unequality constraints into equality constraints by add to relaxation variable, the quadratic programming is obtained by linear approximation, and approximate calculation is done by means of reduced method. The result of numerical calculation shows the method is feasible.     

表面电荷性质对离子在土壤胶体界面扩散的影响

采用动力学方法测定了中性紫色土胶体和砖红壤胶体的电荷性质,研究了不同pH、电解质体系、浓度条件下离子在带电土壤胶体中的扩散过程,分析了两种土壤胶体在不同条件下离子扩散通量和扩散系数的特点。结果表明:1)中性紫色土胶体和砖红壤胶体中离子平衡扩散量为2.6～3.1 mg g-1和0.26～0.51 mg g-1,前者的扩散平衡量是后者的6倍～10倍;2)中性紫色土胶体不同温度条件下,离子扩散系数为1.17×10-9～1.91×10-9cm2s-1,砖红壤胶体中在与其对应温度条件下,离子扩散系数为0.23×10-9～0.45×10-9cm2s-1,前者是后者的4倍～5倍。表面电荷性质对离子在带电土壤胶体界面扩散的影响起决定性作用。     

Orlicz空间中的单隐层神经网络逼近

本文研究了Orlicz空间中的单隐层神经网络逼近问题,以单隐层神经网络为工具,借助最佳多项式逼近,以构造性的方法研究了单隐层神经网络对Orlicz空间内函数的逼近问题以及稠密性问题.     

木材结合水扩散的非平衡态热力学研究

本文从非平衡热力学观点,推导了驱动力和通量的普遍表达式,并与Siau等所得到的结果作了比较,简单评述了关于木材中结合水扩散过程的研究,主要侧重于驱动力和通量讨论的进展。内容涉及木材水分输运中驱动力、化学势、蒸汽相的作用以及等温和非等温扩散模型。     

子阵约束下矩阵方程AX=B反问题的实反对称解及其最佳逼近

利用矩阵的奇异值分解及广泛逆，给出了子矩阵约束下矩阵方程AX＝B反问题有实反对称解的充分必要条件及其通解的表达式，另外，给出了解集合中与给定矩阵的最佳逼近解的表达式以及求解最佳逼近解的一个数值算法和一个数值例子。     

基于切比雪夫最佳逼近意义下的CPI指数变化通道的原理与方法

中国2000-2015年的186组CPI指数所体现的变化规律，可以用通道原理来描述.通道类似于交通图中的道路，依据切比雪夫最佳逼近原理，以CPI函数为中心线，以极小化最大正负误差为边界线，包含了所有的CPI数据，是一条具有最大安全范围意义的数据通道.假设端点数据是建立在零误差基础上的最大权重数据，未来短期内CPI指数的变化不存在突变，或存在突变但其误差不大于通道内的最大正负误差，则通道的延伸可以预测未来CPI指数的变化，以及变化的波动范围.介绍了CPI通道的基本原理与方法、适用范围、判别法则、具体算法等.通过多个数据处理实例，说明了直线通道具有简单易懂、直观性强、计算方便、适用范围广、符合性较好等特点，验证了未来短期CPI指数变化基本是可知与可控的.     

拟Shannon区间小波的构造及其在数值逼近中的应用

为克服拟Shannon小波变换边界效应明显，导致计算精度下降的缺点，根据插值小波的概念构造了拟Shannon区间小波，给出了在对连续函数进行数值逼近时，配置点参数j=4，5时的数值计算结果。随着j的增大x=0处的误差越来越突出，且逼近精度越来越高，而边界处的逼近误差并不大，即使j=4时，边界处也没有明显的震荡现象。与拟Shannon小波相比，拟Shannon区间小波不仅精确度更高，而且能有效消除边界效应。     

多维函数逼近的核方法

n维空间中连续函数逼近问题的数值方法,一直是计算科学中研究的热点。本文考虑利用一种新兴的逼近方法棗核方法,以解决NR中连续函数的逼近问题。在给出核方法解决函数逼近问题的详细数学表示之后,我们通过具体的实例说明了核方法在函数逼近问题中的有效性与优越性。