Modeling Microibril Angle with Mixed Models for Dahurian Larch

In this study,the sample data was based on 2 790 samples of 9 trees from dahurian larch （Larix gmelinii） plantations located in Qitaihe Forest Bureau in Heilongjiang Province.The modified Logistic model y = b₁ /[1 + exp（b₂ x）]+ b₃ was selected to modeling microfibril angle from six models based on nonlinear regression.Then,the logistic model was fitted using nonlinear mixed-effect modeling approach based on NLME of S-PLUS software.Evaluation statistics,such as AIC,BIC, Log Likelihood and Likelihood ratio test were used for model comparisons.The results showed that the Logistic model with parameters b₁,b₂,b₃ as mixed effects showed the best performance.Correlation structures included compound-symmetry structure （CS）,first-order autoregressive correlation structure AR（1）,moving average correlation structure MA（1） and autoregressive-moving average correlation structure[ARMA（1,1）]were incorprated into the best microfibril angle mixed model.[ARMA（1,1）]significantly improved the precision of mixed model.Validation confirmed that the mixed model with calibration of random parameters could provide more accurate and precise prediction.Therefore,the application of mixed model not only showed the mean trends of microfibril angle,but also showed the individual difference based on variance-covariance structure and correlation structure.     

Pipe-model ratio distributions and branch foliage biomass: differences between two sympatric spruce species

The foliage biomass–sapwood relationship (the pipe model) is critical for tree growth and is used in tree growth models for understanding the implications of this structural relationship on the allocation of resources. In this research, we compared this relationship for two commercially important and sympatric species, black spruce (Picea mariana (Mill.) B.S.P.) and white spruce (Picea glauca (Moench) Voss). At locations in eastern Canada, 57 black and 50 white spruce trees were destructively sampled to obtain foliage biomass, crown structure, and tree stem measures. Using a model-based approach, we compared foliage biomass–branch basal area and foliage biomass–sapwood relationships at the tree and disk (i.e. along the tree stem) levels (i.e. pipe-model ratios) between these two species. We found that (i) branch foliage biomass–branch basal area was greater for black spruce than white spruce and (ii) pipe-model ratios along the tree stem given tree size were greater for black spruce than for white spruce. We attributed these differences to: (i) greater shade tolerance and leaf longevity of black spruce; (ii) slower growth rates of black spruce; and (iii) differing hydraulic strategies and mechanical requirements.     

非线性随机干扰系统轨迹跟踪预测自适应控制

针对一类受到随机干扰的非线性系统,研究了基于预测控制的轨迹跟踪自适应控制算法,该方法考虑了随机性的干扰,在控制过程中,系统不断修正非线性预测模型来提高预测精度,同时根据二次性能指标确定当前时刻的控制动作,即先预测后控制,明显地优于经典的反馈控制系统.matlab仿真结果表明,所设计的非线性模型预测自适应控制能较好的实现轨迹跟踪.相比于经典的比例积分控制算法,该算法克服不确定干扰的能力提高,动态性能更好,超调现象得到改善.     

油松林下种子更新过程格局模型的初步研究

从数学模型层面上对油松天然林更新与林下种子萌生的关系进行深入研究,提出一系列的理论模型,并对种子领地分布模型进行引例数据拟合模型。结果表明,种子的超氧化物歧化酶和丙二醛随着频次增加呈负指数关系。非线性参数拟合分析表明:提出的模型能较好地模拟油松林下种子的空间分布状况,为油松林下种子空间分布状况的估计提供参考。     

Analysis of Basal Area for Chinese Fir Plantation Using Two Kinds of Nonlinear Mixed Effects Model(Two Levels)

Nonlinear mixed effects model（NLMEM） is based on the relationship between the fixed and random effects in the regression function.The NLMEM has a competitive advantage in analyzing repeated measures data,the longitudinal data and multilevel data.This paper chose two kinds of two-level nonlinear mixed model to analyze basal area growth for Chinese Fir（Cunninghamia lanceolata）. Model 1 is a general two-level NLMEM and Model 2 is based on Model 1 to further consider the fixed effects parameters changes with a specific factor. Firstly,through the analysis of these two models, this paper defined the basic model to build the two-level NLMEM.Secondly,665 kinds of models derived from Model 1 and 2 703 kinds of models derived from Model 2 were calculated and compared. The results showed that:for Model 1,there were 57 kinds of models converging,and when the formal parameter b₀ considered the block effects and plot effects,b₁ and b₄ only considered the block effects, the model fitted the best;and for Model 2,there were 24 kinds of model converging,and when the formal parameter bs considered the block effects and plot effects,b₁ only considered block effects and the fixed effects b₀ changed with any level of block level, Model 2 fitted the best.Finally,by comparing the traditional nonlinear regression model,Model 1 and Model 2,the results showed that Model 1 and Model 2 fitted better than the traditional nonlinear regression, and Model 2 was best fitting model.     

The Parameter Analysis of the Hydraulic Viscous Dampers in Ground-Anchored Suspension Bridge with Single Tower

Ground-anchored suspension bridge owns a neat structure as well as can use the stiff rock condition at the ends of the bridge to share the forces. While under the effects of earthquake motion, the large longitudinal displacement of the girder poses great threat on the safety and serviceability of the bridge. By the way of nonlinear time-history analysis, this paper emphasizes the effect of hydraulic viscous damper on the seismic reduction of ground-anchored Suspension Bridge with single tower and the damper parameter analysis based on Tongmai Bridge. The study indicates that the hydraulic viscous damper can effectively control the longitudinal displacement of the girder. And when the damping index coefficient a remains constant, the longitudinal displacement of the girder decreases with the increase of the damping coefficient C, but the decreasing magnitude is small. On the other hand, the variations of the coefficients of the hydraulic damper have little influence on the forces of critical sections of the tower and foundation.     

基于时变非线性特征和状态变量的农田灌溉节水控制方法

常规的农田灌溉节水控制,主要采用影响因子分析模拟农田灌溉精度得出农田灌溉节水控制方案,忽略了实际农田土壤的液限和塑限变量对控制方案造成的影响,导致节水控制结果的节水系数较低。提出了基于时变非线性特征和状态变量的农田灌溉节水控制方法。该方法计算农田土壤的基础参数分析时变非线性特征,根据分析所得的特征计算约束条件,建立目标约束函数,构建出农田灌溉的节水控制模型,计算农田土壤液限和塑限的状态变量重新演化模型的目标约束条件,得出最终的农田灌溉节水控制方案。试验结果表明,所提方法应用后得出的节水控制结果,表现出节水系数较高,均值达到0.477,节水效果较好,满足农田灌溉的现实应用需求。     

玉米籽粒灌浆与积温关系的非线性动态模型

分别用线性与非线性模型建立了描述１９８９年和１９９０年８至１０月份内不同时段积温变化规律的运动模型。验证结果表明，此方法提高了数据拟合的精度。     

求解非线性方程组的一种改进的ABS算法

给出了非线性方程组分量方程的一种非线性度量,根据这种度量,提出了求解非线性方程组的一种改进的ＡＢＳ算法,用该算法将较少的计算量用于非线性程度较低的分量方程,将较多的计算量用于非线性程度较高的方程。初步的数值试验结果表明,与原来的非线性ＡＢＳ算法相比,大多数情况下,改进后的算法收敛速度较快。     

摇杆操控型农机的转向控制策略研究*

根据小型电动农机的摇杆操控模式,本文针对遥杆电压与驱动轮转速,及与导向轮转向偏角间关系,建立遥杆电压与驱动轮的“电压-转速”模型,及与导向轮的“电压-转向”模型。基于电子差速原理与Ackermann Jeantand模型,探讨了电压,转速与转向偏角间关系,获得车轮转速与车身转向偏角,进而获取导向轮转向偏角,采用非线性拟合建立“电压-转速”与“电压-转向”模型,“电压-转速”模型中Adj R-square校正拟合结果分别为0.9546与0.9744,“电压-转向”模型中Adj R-square校正拟合结果为0.8690,该模型可实现电动农机在行进和转向过程中实时获取车轮转速与车身转向偏角,按照预设方案稳定前进。电动农机是当前农业机械的发展方向,对农业的发展有着重要意义。