旋翼/机身非线性气弹耦合配平及稳定性分析

根据Hamilton原理,采用中等变形梁理论,将桨叶离散为15自由度梁单元,用准定常气动模型建立旋翼/刚性机身耦合的有限元非线性方程,用时间有限元法进行气弹耦合配平计算,得到桨叶和机身运动的周期解．在此基础上,引入Peters动态入流模型分析耦合系统的稳定性．并研制相应的计算程序,可用于桨叶响应、桨叶和桨毂载荷、旋翼操纵等方面的分析计算．算例分析结果与相关文献吻合较好,且同时满足桨叶响应和配平方程的收敛性要求．     

基于Bagging 算法的神经网络在粒子鉴别中的应用

分析了神经网络方法和bagging 算法在实验高能物理和核物理数据分析中的应用现状。分别对神经网络方法和bagging 算法的基本原理进行了介绍。以蒙特卡罗产生器产生的夸克胶子喷注样本为例,详细讨论了神经网络方法以及bagging 算法与神经网络结合对粒子鉴别中信号和背景区分问题的应用过程,并对结果进行了讨论和分析。实验结果表明,应用bagging 算法后,神经网络能够较大幅度地提高实验高能物理和核物理数据分析中粒子鉴别的精度,以及能够得到较高的信噪比。The paper presents the application of neural network and bagging algorithm in experimental high-energy physics and nuclear physics data analysis. Paper also introduces the basic principles of neural network method and bagging algorithm. We use the data samples of quark-gluon jets, which are generated by Monte Carlo generator, to solve the problem of discriminating signal events and background events by the combined algorithm of bagging algorithm and neural network. Experimental results show that, to apply bagging algorithm, neural networks can greatly improve the accuracy of the identification of particles in the experiments of high energy physics and nuclear physical data analysis,and also obtains a larger SNR (Signal to Noise Ratio).     

色重组负关联效应的起源

最近提出W⁺W^－强子衰变过程中的负关联效应可能是色重组的信号.采用随机级联a模型研究这一效应.在模型中假设色重组导致W⁺W^－衰变形成的两个未态系统之间的粒子发生交换.根据这一物理图象可以再现Pythia事件产生器所得到的负关联.     

A Monte Carlo Study on the Identification of Quark and Gluon Jets

Three-jet events in e^ e^- collisions at 91.2 GeV are investigated using both HERWIG and JETSET Monte Carlo generators.The angles among the three jets are used to identify the quark and gluon jets.An analysis at the parton level is carried out to ensure the reasonableness of this method and an angular cut is utilized to improve the purity of this identification.The multiplicity inside the identified quark or gluon jets agrees with the quantum chromodynamic predictions qualitatively.     

胶子喷注和夸克喷注性质的蒙特卡洛研究

用蒙特卡洛方法研究了91.2GeV e⁺e^－碰撞产生的3喷注事件.用3个喷注之间的夹角来标识各个喷注,分别计算了3个喷注的能量及能量分布,并在相同能量下计算了3个喷注的多重数,横动量及其分布.通过与能量相同的2喷注事件中单夸克喷注的上述性质的比较,得到了从3喷注事件中挑选胶子喷注和夸克喷注的一种简便方法.这样挑选出来的胶子和夸克喷注在性质上与QCD的理论预言一致,并且胶子和夸克喷注的平均多重数比值的计算结果与实验观测值符合     

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简要介绍工程力学课程为适应新型人才培养模式和工程界技术需求应采取的一些具 体革新措施,以供同类课程参考.     

Nonlinear aeroelastic coupled trim and stability analysis of rotor-fuselage

Based on the Hamilton principle and the moderate deflection beam theory, discretizing the helicopter blade into a number of beam elements with 15 degrees of freedora, and using a quasi-steady aero-model, a nonlinear coupled rotor/fuselage equation is established. A periodic solution of blades and fuselage is obtained through aeroelastic coupled trim using the temporal finite element method （TEM）. The Peters dynamic inflow model is used for vehicle stability. A program for computation is developed, which produces the blade responses, hub loads, and rotor pitch controls. The correlation between the analytical results and related literature is good. The converged solution simultaneously satisfies the blade and the vehicle equilibrium equations.     

Critical behavior of a dynamical percolation model

The critical behavior of the dynamical percolation model,which realizes the molecular-aggregation conception and describes the crossover between the hadronic phase and the partonic phase,is studied in detail. The critical percolation distance for this model is obtained by using the probability P∞ of the appearance of an infinite cluster. Utilizing the finite-size scaling method the critical exponents γ/ν and τ are extracted from the distribution of the average cluster size and cluster number density. The influences of two model related factors,i.e. the maximum bond number and the definition of the infinite cluster,on the critical behavior are found to be small.     

施肥方案对作物、蔬菜的影响

对土豆和生菜,分别建立了产量与施肥水平之间的多元二次回归模型.运用SAS/STAT 软件依次采用全回归、逐步回归和二次响应面回归.在确认模型具完美适度性基础上,进行线性相关、交互作用、最佳响应水平、强影响变量、回归曲面形状等分析.同时,将两种作物进行比较,得出一系列颇有实用价值的结论.分析结果表明:土豆的产量对 N 具有强线性依赖性,而生菜是对 P;施肥的交互作用对土豆影响较大,对生菜则无强影响;最佳施肥方案中 N,P,K 的用量土豆为292,246,542(公斤/公顷),生菜为213,667,427(公斤/公顷)对应产量为45.18和23.13吨/公顷,且均在试验范围内达到,可信性强;对土豆,强影响因子依次为 N→K→P,对生菜为 P→N→K;回归曲面上凸,沿(N,P,K)=(1,0,0)方向下降迅速.因此,施肥中应特别注意 N 的使用量.