我国农村居民茶叶消费特点之实证分析

本文利用扩展线性支出系统等计量经济模型,求出茶叶的边际消费倾向和需求收入弹性并进行比较分析,揭示我国农村居民茶叶消费的现状和特点,为茶叶经营策略的制订提供参考依据。     

左权县1961—2015年降水变化特征及对农业生产的影响

为了掌握左权县降水变化规律,笔者利用左权县1961—2015年逐月降水资料,采用线性趋势、5年滑动平均、M-K检验和滑动t检验等方法,分析左权县年及季节降水量变化趋势和突变特征。结果表明：左权县年降水量总体以-12.6 mm/10 a速率下降,20世纪60—90年代呈减少趋势,21世纪以来呈增加趋势,且在1968年发生了减少突变;季节降水量变化,春、夏、秋季呈减少趋势,冬季则呈微弱增加趋势,夏、秋季降水年代际变化与年降水变化趋势一致,冬、春季降水年代际变化起伏较大,秋季在1970年发生了减少突变,春季在2005年发生了由少到多的跃变,冬季在1976年和2003年分别发生了由多到少和由少到多的转变;干旱和暴雨是影响当地农业生产主要气象灾害。     

Delesse principle and statistical fractal sets: 2. Unified Fractal Model for soil porosity

Self-similar fractals are useful models of the soil solid and pore sets along lines, across areas and inside volumes. The scaling properties of these sets, analysed by the divider method within the known scale range over which the fractal extends, were described by three parameters, the solid (D_s) and pore (D_p) linear box or capacity empirical fractal dimensions, and the total number of rulers that covered the line (N_t). The empirical fractal model for soil porosity was developed and compared with the more commonly used theoretical one, and the Unified Fractal Model (UFM) for soil porosity was proposed. This model extracts the soil linear (NL), areal (AP) and volumetric (VP) porosity from the solid and pore distributions along the lines. The accuracy of the empirical model was tested for NL, AP and VP, within the scale range from 0.008 to 3 mm, by using the real macro and micromorphological images of soils and sediments with contrasting genesis, available from field experiments and published by other researchers. It was shown that the proposed model offers a rapid and statistically coherent solution to porosity estimation. The UFM for soil porosity was derived starting from the theoretical and empirical ones. The UFM is useful to solve the relationship between NL, AP and VP, and to estimate the alternative space filling ability of solid and pore sets along a line, across an area and inside a volume.     

家具制造厂板材综合下料问题的研究

介绍了在家具制造过程中采用线性规划数学方法,通过MicrosoftExcel来计划家具厂板材最优下料,从而达到节约用料、降低成本的目的。     

六安地区农作物种植结构优化模型及其应用

利用线性规划方法,对六安地区农作物种植结构进行优化模拟,优化调整后的农作物种植系统的社会、经济、生态效益均优于现实系统结构,系统净总收益增加9629．19万元。该模型可为当前区域性农业结构调整提供定量分析方法和决策依据。     

Effect of vegetation removal on airflow patterns and dune dynamics in the southwest Kalahari desert

Vegetation is a major control of dune surface activity. To assess the effect of removing vegetation from otherwise largely inactive sand-dune surfaces, two field experiments were undertaken in the southwest Kalahari Desert of southern Africa. In the first, wind velocity profiles were measured on two flat surfaces, one vegetated and one where vegetation had been removed by fire. In the second, levels of dune surface activity were measured on burnt and vegetated sites over a ten week period. The data indicate a striking increase in the near-surface wind velocity allied to a decrease in shear stress after the destruction of the vegetation canopy as a result of burning, grazing or drought. Measurements on the consequences of such changes in the airflow patterns on dune dynamics suggest a three-fold increase in dune surface activity after vegetation clearance. The dunes therefore have a staggered response to the contemporary environment, being largely inactive relicts for much of the time, but becoming more active as vegetation is episodically removed.     

基于正交线性判别分析的植物分类方法

首先计算数据的类内和类间散度矩阵,得到差形式的目标函数;然后进行特征值分解,得到映射矩阵;最后利用实际植物叶片数据集进行植物分类试验。结果表明,该算法对植物分类是有效可行的。     

漂移式线性规划在农业生产中的应用初探

为解决普通线性规划在农业生产中的应用的局限性,文中以灰色系统和普通线性规划的理论为依据,提出了漂移式线性规划的特点、数学模型和基本解法及其在农业生产中的应用举例。漂移式线性规划作为灰色规划的一种方法,比普通线性规划更适合于农业系统的“灰色”特点。     

SAS软件在回归分析中的应用

SAS软件是目前世界上应用最广泛的数据分析软件之一,它具有强大的统计功能和较好的人面交互性。本文通过实例介绍了如何用SAS软件进行农业试验的直线回归分析和多重线性回归分析。     

Partitioning soil respiration in a temperate desert steppe in Inner Mongolia using exponential regression method

Accurately partitioning soil respiration into autotrophic and heterotrophic components is important for understanding how ecosystem carbon budgets will respond to climate change. Usually, heterotrophic respiration can be estimated by a linear relationship between soil respiration and root biomass. In this study, however, we found that an exponential relationship was more appropriate than a linear relationship for relating soil respiration to root biomass in a temperate desert steppe in Inner Mongolia, China.