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Nebojša Dedovi? Sne?ana Mati?-Keki? Ondrej Ponji?an Branislav Karad?i? 《Computers and Electronics in Agriculture》2011,79(1):94-101
In many processes of heat exchange, as well as in other processes of biomaterial handling, physical properties of fruit such as dimensions, shape, surface area and volume are of crucial importance. The objective of this work was to find a function which approximates pear border line, as precisely as possible, in order to calculate the surface area and volume of a pear by means of integral calculus. Previously described estimation of an average pear border line was based on the sixth order polynomial and proposed algorithm. Two new ways to calculate the Williams pear border line are the focus of this study. The first way includes spline functions as an estimation of a pear border line (i.e. four third order polynomials), while the second one uses regression function obtained by nonlinear regression method. The regression function has two independent variables, length and total length of a pear. The most precise approximation of a pear border line was obtained by nonlinear regression with R2 = 97.48. This was more obvious when total pear length was smaller or greater than average total pear length. Border lines of all tested pears were determined by one regression function with large precision. Therefore, it is safe to calculate surface area and volume of a pear based on regression function and total pear length, only. Calculated volumes of the pears were compared with volumes measured by Archimedes’ method. The smallest relative error has been obtained when the volumes were calculated using the regression function as approximation of pear border line. 相似文献
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裂隙岩体渗流场与应力场耦合分析方法 总被引:4,自引:0,他引:4
高海鹰 《云南农业大学学报(自然科学版)》1997,12(2):137-142
从工程观点出发,忽略不计完整岩块的渗透系数,借助于层面缝隙流运动规律(立方定律)和变分基本原理,建立了三维裂隙岩体渗流场和应力场耦合模型。并推出了耦合的有限元支配方程,提出了运用同一套单元网络对两场进行区域离散的观点。以重力坝坝基渗流场与应力场耦合计算为例,验证了模型的可行性。 相似文献
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林地面积量算方法的比较研究 总被引:7,自引:1,他引:6
为解决林地面积测量计算的难题 ,作者通过对各种面积量算方法的比较研究 ,总结了各种量算方法的优缺点和适应性 ,比较了仪器实测与图上量测林地面积精度之间的关系 ,得知图上量测林地面积的精度因存在不可避免的系统误差而比仪器实测林地面积的精度低 .最后 ,该文着重推导了利用三次样条法测定林地面积的数学原理 ,并对梯形公式法、辛普生法、等距三次样条法和三次样条法对于林地面积边界不规则曲线的拟合原理进行了分析比较 .结合对中国科协北京绿化基地地块同精度的GPS测量试验结果 ,与运用上述 4种方法量算面积的精度结果进行比较 ,得知三次样条法量算林地面积的精度最高 ,且便于实时差分GPS(RTDGPS)作业 . 相似文献
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基于非线性PLSR模型的气候变化对粮食产量的影响分析 总被引:1,自引:0,他引:1
考虑气候因子间多重共线性及其与粮食产量间复杂的非线性关系,本文在HP滤波分离出气候产量的基础上,尝试引入基于三次B样条变换(Spline-PLSR)和内部嵌入GRNN的两种非线性偏最小二乘模型(GRNN-PLSR),利用1961-2008年气候因子数据建立气候产量计算模型,以2009—2013年数据进行拟合检验,并与常用的C-D生产函数法计算的气候产量进行比较。结果表明,Spline-PLSR法在拟合气候因子变化对粮食产量影响时预测精度较高。而且,与C-D生产函数法相比,Spline-PLSR所需要素较少,操作简单,相对误差最高仅为13.6%;与GRNN-PLSR法拟合结果相比,Spline-PLSR相对误差波动较小,因此,基于三次B样条变换的非线性偏最小二乘法建模较适合拟合气候产量。 相似文献
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本文介绍了多分辨率分析的基本概念,用分段三次B样条函数作为尺度函数建立了一种多分辨率梁单元。这种新单元除了能象一般梁单元使用之外,还可用于自适应分析法去求解梁的局部动力特征。它列式简单,在用直接法求解的系统中长法效率较高。 相似文献
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