Boundary-fitted grid in landscape modeling     

Kang-Ren Jin  Yegang Wu 《Landscape Ecology》1997,12(1):19-26

Landscape modeling requires the delineation of system boundaries and interior features. Quite often, these components are complex and difficult to accurately represent. A rectangular grid is used to represent the study and adjacent non-study areas in most cases. When the non-study area occupies a large portion of the grid, computer memory is wasted, and computational time increases. An elliptical grid generator for non-orthogonal curvilinear coordinates is used to generate a boundary-fitted grid for a landscape model. In a boundary-fitted grid coordinate system, one coordinate axis follows the landscape domain boundary and is non-orthogonal to the second axis. The boundary-fitted grid uses elliptic partial differential equations to distribute grid points inside the landscape domain. Although the boundary-fitted grid follows the domain boundary, the grid pattern and point allocation remain structured. Thus, a landscape model can use a boundary-fitted grid without changing the model’s data structure or the computational scheme. In this study, a boundary-fitted grid and a raster-based grid were applied to the Everglades Landscape Fire Model. Use of the boundary-fitted grid decreased model simulation time by about one fifth and computer storage by 58% relative to the raster-based grid. Also, the linear characteristics of interior geographical features such as rivers and airboat trails were preserved by the boundary-fitted grid, but not by the raster-based grid. This preservation provided a more reasonable base map for simulating ecological processes, such as fire across heterogenous landscapes.  相似文献   

春小麦蛋白质、脂肪、淀粉含量间的相关与回归分析   总被引：2，自引：0，他引：2  

孙继堂  司爱香 《甘肃农业大学学报》1989,(4):44-56

本文通过对20个春小麦品种(或品系)蛋白质、脂肪、淀粉百分含量间的相关、回归、协方差分析,表明蛋白质百分含量与淀粉百分含量间为极显著的负相关;脂肪百分含量与淀粉百分含量间为极显著的负相关;蛋白质百分含量与脂肪百分含量间为极显著的正相关。并建立了淀粉、脂肪、蛋白质百分含量间的回归方程。在同一试验条件下,各品种(或品系)蛋白质、脂肪、淀粉百分含量变异系数的大小,在一定程度上反映出各品种在品质性状上的纯合程度。变异系数愈小,表明纯合程度愈高;变异系数愈大,表明纯合程度愈低。因此,在那些变异系数较大的品种(或品系)中,可选出表型性状与原品种(或品系)基本相似,而在品质性状上却有较大提高的优质新品系。  相似文献   

电导法测定林木种子活力的研究   总被引：4，自引：0，他引：4  

郑郁善 《福建林学院学报》1989,9(2):199-202

本文研究了林木种子电导法测定条件和测定电导率或相对电导率,通过回归分析建立电导率或相对电导率与种子活力指数的相关方程,找出了电导法测定林木种子活力的方法。  相似文献   

三阶时滞泛函微分方程解的渐近性     

庾建设 《湖南农业大学学报(自然科学版)》1990,17(3)

本文讨论一类三阶时滞泛函微分方程解的渐近性质,给出了若干解的有界性及解趋于零的判定准则.  相似文献   

角形区域的Teichmuler极值映照     

程金发  诸玉明  顾广泽 《湖南农业大学学报(自然科学版)》1996,23(5)

采用二次微分的方法，得到了角形区域Ω１的Ａｆｆｉｎｅ变换关于其边界值不是极值映照．并明确给出在边界同伦下唯一极值的Ｔｅｉｃｈｍｕｌｅｒ映照．  相似文献   

Yield Stability of Winter Wheat (Triticum sp.) Cultivars and Lines     

M. Özgen 《Journal of Agronomy and Crop Science》1991,166(5):318-325

The purpose of this study was to compare responsiveness to environment as well as the stability of newly developed promising lines with traditional commercial cultivars. Subject research was conducted in Ankara between 1983-1989 on common and durum wheat cultivars and lines. Regression coefficient (b) was used as the criterion of genotypes' responsiveness to environment whereas deviation from regression (S²d) and coefficient of determination (r²) were used as stability parameters. Each experiment year was regarded as an environment and yield average of each year was used as the environmental index.
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions.  相似文献   

落桦混交林幼龄期Ⅰ级木分布规律研究     

刘群舫  刘国英  徐士瑞 《河北林果研究》1996,(1)

利用３６块落叶松一样树混交林标准地调查资料，研究其幼龄期林分Ⅰ级木单位面积株数与林分密度之间的关系，结果表明：Ⅰ级木的株数并非随密度的增加而直线递增，而是趋向“二阶常数”分布，且在同一年龄阶段，在较低的密度范围（２３２５～４８００株／ｈｍ２）或较高的密度范围（４８０１～６７５０株／ｈｍ２）．Ⅰ级木的株数变动幅度不太大。  相似文献   

推求合理畦宽的方法及应用     

孙雪峰 《中国农村水利水电》1993,(1)

为了寻求合理的节水省时畦宽,以更好地利用现有水源,在1990、1991年试验和实践的基础上,用统计回归分析方法对大城县农田畦田规格进行了分析,求出了合理畦宽,并从灌水持续时间、用电量、提水量等方面对合理畦宽的节水、节能效果进行了分析。  相似文献   

二阶拟线性椭圓型Euler方程组解的Pohozaev型恒等式及其应用     

徐海祥 《湖南农业大学学报(自然科学版)》1989,16(1)

本文对于二阶椭圆型Euler方程组 -∑D_αF_(q_α~i)(x,u,Du)+F_(ui)(x,u,Du)=0得到了一些积分恒等式,利用这些恒等式证明了某些方程组非平凡解的不存在性。  相似文献   

黄淮夏大豆主要农艺性状的遗传分析     

贺春林  段贵娥  柴建新 《中国油料作物学报》1993,(4)

利用黄淮地区的12个高产夏大豆品种(系),通过NCⅡ交配设计,对12个主要农艺性状的遗传进行了分析。结果表明,所有性状的加性方差大于显性方差。主茎节数、株高、每簇荚数和主茎荚数的加性成分占绝对优势,遗传力较高。分枝荚数、单株粒数和单株粒重的显性成分比例大,遗传力较低,其中单株粒重趋于完全显性。主茎节数的显性成分很少,其它性状均为部分显性。建立了单株产量与产量因子之间的逐步回归方程。  相似文献