履带车辆模拟器转向盘系统的力特性研究

建立了一种应用于履带车辆模拟器转向盘模拟系统中的力特性函数,将Vortex动力学软件中的车辆动力学参数、状态参数引入到该函数中。提出了"广义地面阻力系数"的概念,并给出了利用车辆状态角来对其进行构造的方法。在Vortex软件中虚拟驾驶履带车辆,对不同影响参数与力特性函数的变化关系进行了仿真分析,在不同路面状况下实时计算驾驶员转向盘力感,结果表明所设计的力特性函数能够很好的满足要求。

Oblique Wave Motion over Multiple Submerged Porous Bars near a Vertical Wall

This study examines oblique wave motion over multiple submerged porous bars in front of a vertical wall. Based on linear potential theory, an analytical solution for the present problem is developed using matched eigenfunction expansions. A complex dispersion relation is adopted to describe the wave elevation and energy dissipation over submerged porous bars. In the analytical solution, no limitations on the bar number, bar size, and spacing between adjacent bars are set. The convergence of the analytical solution is satisfactory, and the correctness of the analytical solution is confirmed by an independently developed multi-domain BEM （boundary element method） solution. Numerical examples are presented to examine the reflection and transmission coefficients of porous bars, CR and Cv, respectively, for engineering applications. The calculation results show that when the sum of widths for all the porous bars is fixed, increasing the bar number can significantly improve the sheltering function of the bars. Increasing the bar height can cause more wave energy dissipation and lower CR and Cr. The spacing between adjacent bars and the spacing between the last bar and the vertical wall are the key parameters affecting CR and Ct. The proposed analytical method may be used to analyze the hydrodynamic performance of submerged porous bars in preliminary engineering designs.

Numerical Investigation on Power Outputs of a Wind Turbine Sited over Continuous Hilly Terrain

The location of wind turbines on a continuous hilly terrain has an influence on its power outputs.A CFDbased approach is developed to investigate the complex aerodynamic interference between two wind turbines and the hilly terrain.In this approach,a new three-dimensional model of hilly terrain is established to analyze its viscous effect,and a wind shear is modelled through logarithmic function.They are coupled into the aerodynamics of wind turbine based on“FLUENT”software.Then we apply the proposed method to the NREL Phase VI wind turbines and compare with an experiment in the atmospheric boundary layer(ABL)wind tunnel to validate its accuracy.The simulation also investigates the power outputs of wind turbines on the flat ground and the continuous hilly terrain by changing the location of the wind turbine related to the hilly terrain and the shape of the 1st hill.The results show that the wind turbine located on the top of the 2nd hill has the maximum power;and that when the wind turbine is located on the downstream of the hill,the stall zone should be avoided,and the power of the wind turbine located on the side of the hill is higher than that of the wind turbine located on the front and rear of the hilly terrain.

Comments on “double—Wave Theory”

Some falsehoods of the so-called double-wave theory (DWT) are pointed out. The logic and the origin of the DWT, and three of the four fundamental hypotheses of DWT are criticized. It is expounded that the hypothesis of two wave functions is unreasonable, the hypothesized Hamiltonian differs from the actually used Hamiltonian, and the hypothesized expression of measured values or mean values of mechanical quantities is wrong and does not express the measured values or mean values at all.

Pedotransfer Functions for Estimating Soil Hydraulic Properties： A Review

Characterization of soil hydraulic properties is important to environment management; however, it is well recognized that it is laborious, time-consuming and expensive to directly measure soil hydraulic properties. This paper reviews the development of pedotransfer functions （PTFs） used as an alternative tool to estimate soil hydraulic properties during the last two decades. Modern soil survey techniques like satellite imagery/remote sensing has been used in developing PTFs. Compared to mechanistic approaches, empirical relationships between physical properties and hydraulic properties have received wide preference for predicting soil hydraulic properties. Many PTFs based on different parametric functions can be found in the literature. A number of researchers have pursued a universal function that can describe water retention characteristics of all types of soils, but no single function can be termed generic though van Cenuchten （VG） function has been the most widely adopted. Most of the reported parametric PTFs focus on estimation of VG parameters to obtain water retention curve （WRC）. A number of physical, morphological and chemical properties have been used as predictor variables in PTFs. Conventionally, regression algorithms/techniques （statistical/neurM regression） have been used for calibrating PTFs. However, there are reports of utilizing data mining techniques, e.g., pattern recognition and genetic algorithm. It is inferred that it is critical to refine the data used for calibration to improve the accuracy and reliability of the PTFs. Many statistical indices, including root mean square error （RMSE）, index of agreement （d）, maximum absolute error （ME）, mean absolute error （MAE）, coefficient of determination （r2） and correlation coefficient （r）, have been used by different researchers to evaluate and validate PTFs. It is argued that being location specific, research interest in PTFs will continue till generic PTFs are developed and validated. In future studies, improved methods will be required to extract information from the existing database.

Generation of optical vortices by apodized photon sieves

As a novel diffractive optical element, photon sieve has good focusing properties. We propose a method to verify the focusing properties by using apodized photon sieves. The apodized photon sieve is obtained by using a Gaussian window function to modulate the general photon sieve. Focusing properties of apodized photon sieve are studied by numerical simulations and experiments. It shows that photon sieves have good focusing ability, and the focusing ability of the photon sieve on the focal plane is stronger than that on other image planes. The experimental results also demonstrate that photon sieves can be used to generate optical vortices. The existence of optical vortices is confirmed by the formation of fork fringes. This apodized photon sieve is expected to have some practical applications in focusing analysis, optical imaging, and optical communication.