薯类收获机振动筛伤薯机理计算机模拟与分析

分析目前马铃薯机械化收获中筛分方面的技术难题,建立关于振动筛运动的数学模型,使用Visual Basic6.0程序语言编程,利用计算机辅助分析（CAA）开发新部件的设计思想和手段,对薯块与筛面相互作用的过程进行分析,研究它的运动规律,模拟运动过程,认识薯块在振动筛面上的运动机理,以及薯块在筛面上的运动状况.从提高筛分效率、降低伤薯率的角度对其进行参数优化和性能分析,提高了整机工作性能和效率.     

基于NSGA-Ⅱ悬架参数优化设计

基于车辆系统动力学分析与最优化设计,提出了混合多目标客车悬架系统优化的数学模型。以车辆乘坐舒适性、结构空间、行驶安全性为优化目标,选择悬架系统的弹簧刚度和减振器阻尼作为优化参数,建立多目标优化函数。以四分之一车辆模型为例,采用最近发展起来的具有优良性能的多目标遗传算法NSGA-Ⅱ为优化方法来求全局最优解。通过比较优化前后的仿真结果,可以看出优化后客车的各项性能都有了不同程度的提高,表明该遗传算法在悬架参数优化方面具有较好的效果。     

VE型分配泵检修与调试试验研究

对ＶＥ型分配泵进行检修与调试试验研究，提出了ＶＥ型分配泵调试参数的确定方法及检验，调试与评价调试质量的标准，为正确检修与提高调试质量，提供了理论依据与规范参数。     

姬松茸保鲜影响因素分析及参数优化

以提高姬松茸的保鲜品质为目的 ,采用不同处理进行保鲜对比试验。采用正交实验方法 ,分析了不同处理对姬松茸的褐变程度及膳食纤维素的影响。结果表明 ,姬松茸经处理后进行保鲜 ,可有效减缓贮存过程中的褐变程度和品质变化。在相同条件下 ,以 0 2 5 %NaHSO3水溶液渗析 30min ,捞出沥水后再放入 0 15 %VC与 0 5 %柠檬酸混合的水溶液中渗析 10min进行处理 ,保鲜效果最好。此外 ,还对该处理的状态参数进行了分析和优化     

Hassell-Rogers模型参数的简化回归计算

本文提出了Hasscll-Rogers模型中参数计算的一种简便方法。即先用Beddington提出的亚模型计算出a’和T_h,代入Hasscll-Rogers公式,再用一元回归求出m和c值。文中以玉米螟赤眼蜂在不同自身密度和寄主密度下寄生的实验数据作实例,用上述方法求出了Hasscll-Rogcrs模型的理论公式。对原数据的拟合效果经x~2检验显著适合。该算法与用Marquardt法在IBM-PC微机上计算所得结果也十分接近。     

Modelling stand structure in young Scots pine dominated stands

The purpose of this study was to construct models for predicting the structure of young Scots pine (Pinus sylvestris L.) stands. The two-parameter Weibull function characterized the height distribution of the stands. In young stands height was preferred to dbh as a random variable because of its continuous feature. Tree diameters were predicted using a multiplicative model, fitted as a linearized mixed-effect model. The modelling data consisted of repeatedly measured Scots pine dominated juvenile stands, carried out on a sub-sample of the 7th National Forest Inventory. The data covered a dominant height range from 0.2 up to 17 m. Two independent data sets were used to validate the models. The Weibull function was fitted using the maximum likelihood method. Four methods for predicting the distributions were compared: (1) parameter prediction models (PPM) consisting of seemingly unrelated regression equations, (2) a generalized linear model (GLM) which was a one-stage distribution and model fitting procedure, (3) a hybrid method including PPM for the shape parameter together with moment-based parameter recovery for the scale parameter, and (4) inclusion of moment-based parameter recovery for the scale parameter in the estimated GLM. Goodness-of-fit were tested in terms of Kolmogorov–Smirnov and error index statistics. Parameter recovery showed no improvement when used with PPM, but it improved GLM and gave the overall best performance for this new method. The constructed diameter–height model showed quite flexible and unbiased behaviour. Models are recommended as practical tools for Finnish forest management planning purposes.     

Identification of the hydraulic conductivity using a global optimization method

A method to determine the soil hydraulic conductivity via an internal drainage experiment is presented. Identifying the parameters of the hydraulic conductivity is achieved by solving an inverse global optimization problem that uses the water contents measured at different depths and times as matching flow variables. The optimization procedure is combined with a recently developed analytical model for the water content propagation, which essentially assumes that the flow is gravity-driven. A crucial (from the identification point of view) parameter of such a model is the initial position z_W of the draining front, determining the interface between the wetted and dried zone. By using an evolutionary algorithm specifically developed for this problem, it is shown that if information upon z_W is not a priori available, the identification of the hydraulic conductivity is not possible. However, assuming that z_W is known (i.e. measured), and by dividing the model variables by z_W, the optimization is able to fully identify the soil hydraulic conductivity. Finally, in order to show the robustness of the proposed approach, it is shown that the method leads to very good estimates of the hydraulic conductivity even if data are noise-affected, provided that the optimization procedure is coupled to the (Tikhonov) regularization approach.     

福建省年极端低温的分布及其参数估计

利用福建省67个气象站50a(1961-2010年)最低气温资料,分析了福建省极端低温的时空分布规律,并应用耿贝尔分布函数对各站的年极端气温进行了概率计算,计算过程中耿贝尔分布函数分别采用了2种参数估计方法:矩法和耿贝尔法,结合2种表征参数估计优良性的指标,对不同的参数估计方法进行了比较。结果表明:大多数情况下采用矩法时拟合效果较好;在推算不同重现期的年极端最低气温时,用耿贝尔法较好。     

依赖于参数的泛函微分方程正周期解的存在性

考虑依赖于参数的泛函微分方程x′(t)=-a(t)g(x(t))x(t)+λb(t)f(t,x(t-τ_1(t)),x(t-τ_2(t)),…,x(t-τ_n(t))).利用不动点定理,得到了上述方程正周期解存在的充分条件。