Dynamic Motion Resistance for Tracked Vehicle

Based on previous achievements,a dynamic pressure-sinkage equation for saturated clay is established.First,aquasi-static penetration rate is selected,and the ratio of the dynamic penetration rate to the quasi-static rate is used to characterize the degree of dynamic effect,then theβth power of the ratio is used to quantify the dynamic effect of sinkage.The dynamic effect exponentβis obtained using penetration tests with different penetration rates.Then,a dynamic motion resistance equation for a tracked vehicle is established based on the dynamic pressure-sinkage equation.The equation incorporates both penetration and bulldozing resistance.Finally,a series of simulation experiments with varying travel speeds and slip rates is carried out.The results show that an increase in the speed leads to stronger terrain stiffness,resulting in a decrease in sinkage and motion resistance.However,the enhancement effect becomes weaker with an increase in the travel speed.     

Prediction on Deflection of Inflated Beam

The bending stiffness of the inflated beam is considered as a constant before wrinkles appear, and it decreases obviously as wrinkles propagate. The formula of the bending stiffness is obtained based on the membrane theory in this paper. Furthermore, the definition of dimensionless bending stiffness factor is presented; the relationship of bending stiffness factor and wrinkling factor is derived; the bending stiffness factor is simplified as different linear functions with wrinkling factor, and the simplified model of bending stiffness of inflated beam under bending is also obtained. The bending stiffness including expression of wrinkling factor is substituted into the deflection differential equation, and then the slope and deflection equation of the inflated beam is deduced by integrating the deflection differential equation. Finally, the load-deflection curve is obtained, which is compared with the experimental data in a previous paper. It has a good agreement with each other.     

Experimental Study on Nitrogen Solubility in Molten Iron and Denitrification during Hot Metal Pretreatment

Rollback smoke is one kind of familiar turbulent flow during mine fire and may cause serious damage and injury. The rollback law of reversal smoke flow is significant to mine fire rescue. The theories of environmental fluid mechanics and heat transfer are applied to study on the rollback law of the reversal smoke flow in a horizontal airway during mine fire. The heat transfer process between the rever- sal smoke and the airway wall is analyzed. Through the analysis above, the rollback distance equation of the reversal smoke is formed. The mass flux of the re- versal smoke flow at the reverse point above the fire source and under the roof and the temperature at the point before smoke reverse again are the key points of working out the equation. At the stagnation before smoke reverse again, namely at the stagnant point oft he reversal smoke, the pressure between smoke flow and airflow is equal and thus a pressure equilibrium equation is built up. Combined with the smoke plume model and gas state equation, the mass flux of the re- versal smoke and the temperature at the stagnant point are worked out. At a result, the function of rollback distance of the reversal smoke is educed and simplified in order to be used in practice.     

Design and Analysis of a Horizontal Quasi-Zero Stiffness Vibration Isolator by Combining Rolling-Ball and Disk Springs in Parallel

Combining disk springs having negative stiffness with a rolling-ball in parallel is proposed in this paper.It is used to reduce the system stiffness and the positioning error in a non-ideal environment.The characteristics of a disk spring are analyzed.The dynamic equation of its motion has been obtained based on Newton's second law.After definition of a error margin,the dynamic equation of the motion can be treated as a Duffimg oscillator,and the influences of non-dimensional parameters on the stiffness and transmissibility are studied.The natural frequency and transmissibility are achieved in a linearization range,where the ratio of linear to nonlinear items is small enough.The influence of mass ratio and non-dimensional parameters on natural frequency are analyzed.Finally,a comparison of numerical example demonstrates that the QZS system can realize a lower stiffness within an increased range.     

Numerical Simulation of Methane Distribution and Sensor Placement in 2-Dimension Roadway

In order to provide a theoretical basis for methane sensor placement in the vertical direction of a tunnel, the software Fluent was used to simulate methane distribution. A geometric roadway model was established and divided by grids. Methane distribution in both level and vertical sections was simulated using a realizable k-ε model with the Fluent software according to a conservation equation in a turbulent state, a turbulent kinetic energy equation and a turbulent dissipation rate equation. The realizable k-ε model and the Fluent software were used to simulate methane distribution according to the principle of the conservation equation in a state of turbulent flow. The results show that after overflowing, a methane level with a certain thickness is formed. Methane density curves at three specific levels were internally consistent and methane density at higher levels is denser than that at lower levels. Methane distribution becomes thinner in the direction of wind and methane in the vertical direction becomes uniform if wind speed is high. The distance be- tween sensors and roof should be less than 300 mm which is in agreement with mine safety regulations.     

Model for Long-Rod Penetration into Semi-Infinite Targets

Based on the equation of momentum conservation, an improved equation for the quisi-steady penetration of a long rod into homogeneous semi-infinite targets has been derived, assuming that the flow interface between the rod material and the target material is hemispherical and that the normal pressure on the interface is defined by the dynamic spherical cavity expansion. The equation has a form similar to the Tate equation, and the parameters in this equation have definite physical senses and practical values.     

Analysis of unsteady supercavitating flow around a wedge

Supercavitating flow around a slender symmetric wedge moving at variable velocity in static fluid has been studied. Singular integral equation for the flow has been founded through distributing the sources and sinks on the symmetrical axis. The supercavity length at each moment is determined by solving the singular integral equation with finite difference method. The supercavity shape at each moment is obtained by solving the partial differential equation with variable coefficient. For the case that the wedge takes the impulse and uniformly variable motion,numerical results of time history of the supercavity length and shape are presented. The calculated results indicate that the shape and the length of the supercavity vary in a similar way to the case that the wedge takes variable motion,and there is a time lag in unsteady supercavitating flow induced by the variation of wedge velocity.     

Numerical Simulation of Interaction Between Tributary Debris Flow and Main River

Based on two-phase flow theory and shallow water flow assumption,a mathematical model is applied to simulate debris flow.The model considers a two-phase mixture of sediments and water fluid.Assuming that the sediments and the water fluid move downstream with the same velocity,the flow of the mixture is described using a two dimensional depth averaged model with a unique 2-D momentum equation and two mass balance e- quations for the mixture and the sediments,respectively.The finite volume method is used for the iterative so- lution of the mathematical model,and upwind schemes (Roe's approximate Riemann solver or Van Leer's flux splitting) are used to compute convection fluxes.The pressure-velocity coupling is obtained from the combina- tion of the continuity equation and the equations of momentum by the SIMPLE algorithm.     

New Variational Solution for the Space Contact Problem

In the recent thirty years,a great of investigations have been made in the Wiener-Hopf equations and variational inequalities as two mutually independent problems.In this paper,we investigate the equivalence of the solution of variational inequality and the inversion of the Toeplitz operator when the projection operators P,Q are linear.The solution of general Wiener-Hopf equation is concluded as the solution of a variational problem.Thus an approximation method of obtaining the maximum value by variational is proposed to obtain the approximation of general Wiener-Hopf equation and apply it to the space contact problems in the elasticity theory.Especially,the solution representation is given in case that the projection of contact surface is round.The closing-form solution is also given when the known displacement is a polynomial of even power.     

Active suspension with optimal control based on a full vehicle model

The 7-DOF model of a full vehicle with an active suspension is developed in this paper. The model is written into the state equation style. Actuator forces are treated as inputs in the state equations. Based on the basic optimal control theory, the optimal gains for the control system are figured out. So an optimal controller is developed and implemented using Matlab/Simulink, where the Riccati equation with coupling terms is deduced using the Hamilton equation. The all state feedback is chosen for the controller. The gains for all vehicle variables are traded off so that majority of indexes were up to optimal. The active suspension with optimal control is simulated in frequency domain and time domain separately, and compared with a passive suspension. Throughout all the simulation results, the optimal controller developed in this paper works well in the majority of instances. In all, the comfort and ride performance of the vehicle are improved under the active suspension with optimal control.     

拉格朗日方程平面展开式在机构动力学中的应用

针对利用拉格朗日方程建立平面机构动力学方程的问题,进行了新的探讨和分析,首先对多构件多自由度系统的动能提出了新的表达形式,在此研究过程中,引出了类速度,类角速度,慢性系数等重要概念,而后在此基础上推导出了拉格朗日方程平面展开式,最后做为一个实例,用拉格朗日方程展开式建立了开式链二杆机构的运动方程,本文所谈到的内容,可供深入研究拉格朗日方程及对平面机构多自由度系统和平面开式链机器人的动力学研究,提出     

光纤声光互作用耦合波方程

从参量互作用基本方程出发,导出微扰形式的光纤耦合模方程;视超声波为微扰,推导出光纤声光互作用耦合波方程组,它包括前向波和后向波两个方程．通过求解耦合波方程组,得到后向波效率计算公式,并证明在弱声光互作用的条件下,后向波的光强与超声波功率近似成正比．该研究为光纤声光强度调制器的研制打下了理论基础,这种新型调制器将在光纤通信领域中有广泛的应用前景．     

扩散方程的回溯时间积分格式

大量数值结果已表明自记忆方程具有很高的精度和很好的稳定性 .将它纳入差分方程的框架进行研究 ,针对扩散方程建立了基于自记忆方程的单参数回溯时间积分格式 ,导出了它的稳定性条件     

矩阵论在解线性定常系统状态方程中的应用

本文讨论了线性定常系统的状态方程求解,得到了在特殊条件下,状态方程的求解方法,并且研究了线性定常系统状态方程的解在李雅普诺夫意义下的稳定性,得到了构造李雅普诺夫函数的新方法以及在一定条件下对线性定常连续系统和离散系统的李雅普诺夫方程的求解方法,该求解方法适合在计算机上编程运算。     

P-R方程在天然气热物性计算中的应用

在天然气管道的水力、热力计算中需要进行热物性参数的计算,详细地介绍了用P-R方程求解天然气各物性参数的方法及其求解过程。分别采用范德瓦尔斯方程、RKS方程、P-R方程和BWRS方程求氮气的压缩因子,通过与已知实验数据比较表明P-R方程作为两参数立方型方程,计算气体物性参数精度高于范德瓦尔斯方程和RKS方程,略低于BWRS方程。P-R方程参数数目少,参数确定简洁,计算简单,可以在天然气物性计算领域广泛应用。     

二维铸造充型过程数值模拟的特征分数步长法

铸造充型过程的数学模型是包括连续性方程和动量方程的偏微分方程组．利用分数步长法将动量方程分裂成两部分，对第一个方程采用特征差分法进行处理，对第二个方程结合连续性方程进行处理后得到压力的泊松方程，用迭代法进行求解，给出了收敛性分析和稳定性条件．     

4n-2阶发展方程的算子半群

针对高价发展方程的形式解,将二阶发展方程扩展为时滞分布参数系统标准型中的4n-2阶发展方程,同时构造内积形成4n-2维Hilbert空间。将4n-2阶发展方程转化为一阶发展方程组,求得4n-2阶发展方程的生成算子和在一定的条件下生成半群。构造出半群的结构式并证明其具有的基本特征。当n=1时为二阶发展方程型的Golstein算子半群。     

关于熵函数的探讨

提出了一种从熵函数的引入、定义、揭示其物理意义,推导其计算公式以及熵判据的方法。该方法具有普遍性,且环环相扣,连通一贯,有助于加强对熵函数及熵判据的理解,有助于了解玻尔兹曼熵公式和克劳修斯熵公式的内在联系。     

二维铸造充型过程数值模拟的特征分数步长法

铸造充型过程的数学模型是包括连续性方程和动量方程的偏微分方程组.利用分数步长法将动量方程分裂成两部分，对第一个方程采用特征差分法进行处理，对第二个方程结合连续性方程进行处理后得到压力的泊松方程，用迭代法进行求解，给出了收敛性分析和稳定性条件.     

Fitzhugh-Nagumo方程在非齐次边界条件下解的动力学分析

Hodgkin-Huxley方程描述了生物神经的放电活动,Fitzhugh-Nagumo方程是Hodgkin-Huxley方程的简化模型.讨论了Fitzhugh-Nagumo神经传导方程在非齐次边界条件下的初边值问题,利用Galerkin方法证明了Fitzhugh-Nagumo方程在非齐次边界条件下整体解的存在性和唯一性;运用Lyapunov稳定性理论对Fitzhugh-Nagumo方程进行了稳定性分析.