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。     

用无网格局部Petrov-Galerkin方法分析Winkler弹性地基板

利用Winkler弹性地基板控制微分方程的等效积分对称弱形式，同时对变量(挠度)采用移动最小二乘近似函数进行插值，研究了无网格局部Petrov-Galerkin方法在弹性地基板弯曲问题中的应用．它不需要任何形式的网格划分，所有的积分都在规则形状的子域及其边界上进行，并用罚因子法施加本质边界条件．数值算例说明，无网格局部Petrov-Galerkin法不但能够求解弹性静力学问题，而且在求解弹性地基板问题时仍具有收敛快、稳定性好和精度高的特点．     

PIN管正偏注入的载流子在Ⅰ层中分布的研究

本文认为,Ⅰ层中不会有电子浓度和空穴浓度处处相等的电中性近似,这两种浓度都要随扩散距离的增加而衰减.本文用准中性条件来求解电子和空穴的连续性方程,导出这两种浓度都按扩散距离的负指数函数在Ⅰ层中分布.这样,其载流子一载流子散射效应可忽略不计,其俄歇复合较小,比用电中性近似求得的载流子分布的俄歇复合要小许多倍.     

一类Holling型时滞扩散捕食-食饵系统的持久性

研究一类Holling型时滞三种群捕食．食饵扩散系统的持久性。应用微分方程比较原理，得到保证系统持久性的充分条件，所得结果推广了相应文献的主要结果．     

湖泊沉积物中磷释放的研究进展

沉积物是湖泊营养物质的重要蓄积库,也是湖泊内源性P的主要来源。沉积物中部分固定的P可通过分解或溶解作用而释放磷酸盐到沉积物间隙水中,然后通过扩散作用或表层沉积物的再悬浮作用而释放到上覆水体中。本文就目前对沉积物P释放的影响因素及释放机制的研究进展作一简要概述。     

土壤磷扩散规律及其能量特征的研究Ⅱ.施磷量及水肥温相互作用对磷扩散的影响

非饱和土壤在施磷量０－４００ｍｇ／ｋｇ下的磷自扩散系数随施磷量近线性增加,但增加的幅度以缓冲性能小的轻质土壤最高。不同土壤磷扩散受土壤水分,施磷量和温度等因素相互作用的影响程度不同,为表征这种差异利用其多元非线性拟合方程的偏微分,本文提出了磷扩散率的水分系数,肥料系数和温度系数等概念。     

Moisture modulates rhizosphere effects on C decomposition in two different soil types

While it is well known that soil moisture directly affects microbial activity and soil organic matter (SOM) decomposition, it is unclear if the presence of plants alters these effects through rhizosphere processes. We studied soil moisture effects on SOM decomposition with and without sunflower and soybean. Plants were grown in two different soil types with soil moisture contents of 45% and 85% of field capacity in a greenhouse experiment. We continuously labeled plants with depleted ¹³C, which allowed us to separate plant-derived CO₂-C from original soil-derived CO₂-C in soil respiration measurements. We observed an overall increase in soil-derived CO₂-C efflux in the presence of plants (priming effect) in both soils. On average a greater priming effect was found in the high soil moisture treatment (up to 76% increase in soil-derived CO₂-C compared to control) than in the low soil moisture treatment (up to 52% increase). Greater plant-derived CO₂-C and plant biomass in the high soil moisture treatment contributed to greater priming effects, but priming effects remained significantly higher in the high moisture treatment than in the low moisture treatment after correcting for the effects of plant-derived CO₂-C and plant biomass. The response to soil moisture particularly occurred in the sandy loam soil by the end of the experiment. Possibly, production of root exudates increased with increased soil moisture content. Root exudation of labile C may also have become more effective in stimulating microbial decomposition in the higher soil moisture treatment and sandy loam soil. Our results indicate that moisture conditions significantly modulate rhizosphere effects on SOM decomposition.     

The SAHGA model to calculate the Spatial Ammoniacal Heterogeneity at the soil surface after fertiliser Granule Application

After dissolution of fertiliser granules, a high nitrogen concentration is recovered in the immediate vicinity of granules, which may enhance damaging processes like nitrite accumulation or ammonia volatilisation. Based on the diffusion equations of Cranck, the granule-soil microsite was modelled to obtain the actual fertilised surface plot and the effective rate of N application on this surface. Parameterisation of the diffusion coefficient of solutes consisted of a temperature and soil texture correction. The model was tested against an experimental data set obtained from soil incubations at two soil water contents (21.2% m³ m^–3 and 28.3% m³ m^–3) and two temperatures (4°C and 25°C) by comparing NH₄⁺ recovery at various distances from the granules. The simulated radius of the granule-soil microsite was more affected by the water content than by the temperature. The model is very accurate because 95–100% of total NH₄⁺ applied was recovered in the modelled surface depending on the experimental conditions (temperature and water content). The model was simple enough to be easily integrated into larger models dealing with surface-applied granule fertilisers.     

APPROXIMATION OF INVOLUTE PROFILE BY PEACH-SHAPED RING SECTION

By using the least pth min-max method, we find the best approximation of involute ptofile by peach-shaped ring section. The error of approximation is less than that of [ 1 ] and [2]. Thus we provide a new direction for dressing of a wheel for involute gear forming-grinding. In order to simplify calculation, we define the error function according to implicit equation of curve and as a result its rationalization is proved.