Back Frame Optimization of a Large Radio Telescope Based on Force Cone Method

A new research perspective is proposed to optimize the topology of truss structure by force cone method,which involves force cone drawing rules and growth rules.Through the comparison with the mature variable density topology optimization method,the effectiveness of force cone method is verified.This kind of new method is simple and easy to understand(no need to master complex structural optimization design theory).Besides,it is time-saving in finite element calculations,and can obtain an optimized truss layout easily.By drawing the force cone,its application on a large radio telescope’s back frame structure shows that,compared with the existing one in terms of structural stiffness,Root Mean Square(RMS)precision,and beam stress distribution,the optimized back frame using the force cone method has higher stiffness,better RMS,more uniform stress,and lighter weight.

Application of the method of equivalent edge currents to composite scattering from the cone-cylinder above a dielectric rough sea surface

Compared with scattering from a rough surface only, composite scattering from a target above a rough surface has become so practical that it is a subject of great interest. At present, this problem has been solved by some numerical methods which will produce an enormous calculation amount. In order to overcome this shortcoming, the reciprocity theorem （RT） and the method of equivalent edge currents （MEC） are used in this paper. Due to the advantage of RT, the difficulty in computing the secondary scattered fields is reduced. Simultaneously, MEC, a high-frequency method with edge diffraction considered, is used to calculate the scattered field from the cone-cylinder target with a high accuracy and efficiency. The backscattered field and the polarization currents of the rough sea surface are evaluated by the Kirchhoff approximation （KA） method and physical optics （PO） method, respectively. The effects of the backscattering radar cross section （RCS） and the Doppler spectrum on the size of the target and the windspeed of the sea surface for different incident angles are analysed in detail.

Some Approximation in Cone Metric Space and Variational Iterative Method

In this paper, we give some new results of common fixed point theorems and coincidence point case for some iterative method. By using of variation iteration method and an effective modification of He’s variation iteration method discusses some integral and differential equations, we give out some new conclusion and more new examples.

新一代评估方法——锥形量热仪(CONE)法在材料阻燃研究中的应用

利用新一代评估方法———锥形量热仪法对材料阻燃机理、材料危险性等级划分、烟毒释放评价、材料燃烧性及阻燃性评价等方面的应用进行了分析讨论 ,结果表明锥形量热仪法对阻燃剂、阻燃制品的研究开发及阻燃剂在火灾中的行为研究具有重要意义。

CONE模型与地基动力液化的非线性有效应力分析

在分析建筑物地基的地震(或振动)液化时,为了简化分析土壤-地基的动力相互作用,引入Cone模型,在总应力分析的方法基础上,结合了Martin等提出的孔隙水压力发展模型,并且考虑土壤发生液化的动力非线性过程中材料刚度退化的影响,提出了可以直接求解各区域的孔隙水压力的有效应力简化分析法,并进行液化可能性判别。

EXISTENCE RESULTS FOR DEGENERATE ELLIPTIC EQUATIONS WITH CRITICAL CONE SOBOLEV EXPONENTS

In this paper, we study the existence result for degenerate elliptic equations with singular potential and critical cone sobolev exponents on singular manifolds. With the help of the variational method and the theory of genus, we obtain several results under different conditions.

Modeling natural convection boundary layer flow of micropolar nanofluid over vertical permeable cone with variable wall temperature

This paper discusses the natural convection boundary layer flow of a micropo- lax nanofluid over a vertical permeable cone with variable wall temperatures. Non-similax solutions are obtained. The nonlineaxly coupled differential equations under the boundary layer approximations governing the flow axe solved numerically using an efficient, itera- tive, tri-diagonal, implicit finite difference method. Different experimental correlations for both nanofluid effective viscosity and nanofluid thermal conductivity are considered. It is found that as the vortex-viscosity parameter increases, both the velocity profiles and the local Nusselt number decrease. Also, among all the nanoparticles considered in this investigation, Cu gives a good convection.

Time-optimal rendezvous transfer trajectory for restricted cone-angle range solar sails

The advantage of solar sails in deep space exploration is that no fuel consumption is required. The heliocentric distance is one factor influencing the solar radiation pressure force exerted on solar sails. In addition, the solar radiation pressure force is also related to the solar sail orientation with respect to the sunlight direction. For an ideal flat solar sail, the cone angle between the sail normal and the sunlight direction determines the magnitude and direction of solar radiation pressure force. In general, the cone angle can change from 0° to 90°. However, in practical applications, a large cone angle may reduce the efficiency of solar radiation pressure force and there is a strict requirement on the attitude control. Usually, the cone angle range is restricted less more than an acute angle （for example, not more than 40°） in engineering practice. In this paper, the time-optimal transfer trajectory is designed over a restricted range of the cone angle, and an indirect method is used to solve the two point boundary value problem associated to the optimal control problem. Relevant numerical examples are provided to compare with the case of an unrestricted case, and the effects of different maximum restricted cone angles are discussed. The results indicate that （1） for the condition of a restricted cone-angle range the transfer time is longer than that for the unrestricted case and （2） the optimal transfer time increases as the maximum restricted cone angle decreases.

Effect of Hartmann Number on Free Convective Flow of MHD Fluid in a Square Cavity with a Heated Cone of Different Orientation

This paper presents the effect of magnetic field, indicated by Hartmann number (Ha), on the free convective flow of Magneto-hydro-dynamic (MHD) fluid in a square cavity with a heated cone of different orientation. Although similar studies abound, the novelty of this work lies in the presence of the heated cone, whose orientation is varied at different angles. The mathematical model includes the system of governing mass, momentum and energy equations. The system is solved by finite element method. The calculations are performed for Prandtl number Pr = 0.71;the Rayleigh number Ra = 10, 1000, 100,000;and for Hartmann number Ha = 0, 20, 50, 100. The results are illustrated with streamlines, velocity profiles and isotherms. From the results, it is found that for the present configuration, magnetic field (Hartmann number) has no effect on the shape of the streamlines for low Rayleigh numbers. However, for high values of Ra, the effect of Ha becomes quite visible. Magnetic field affects the flow by retarding the fluid movement, and thus affects convective heat transfer. At low Ra, the fluid movement and heat transfer rate are already slowing, thus impressing a magnetic field does not produce much effect. At high Ra, fluid particles move at high velocity and change the stream lines, in absence of any magnetic force. Impressing magnetic field in this situation produced noticeable effect by slowing down the fluid movement and changing the streamlines back to low Ra situations. It is noted that a combination of low Ra with zero or low Ha produces similar effects with the combination of high Ra and high Ha. It can be concluded that with increasing Ha, heat transfer mode in MHD fluid gradually changes toward conduction from convection. It can be surmised that sufficiently large Ha can potentially stop the fluid movement altogether. In that case, heat transfer would be fully by conduction.

SMOOTHING NEWTON ALGORITHM FOR THE CIRCULAR CONE PROGRAMMING WITH A NONMONOTONE LINE SEARCH

In this paper, we present a nonmonotone smoothing Newton algorithm for solving the circular cone programming(CCP) problem in which a linear function is minimized or maximized over the intersection of an affine space with the circular cone. Based on the relationship between the circular cone and the second-order cone(SOC), we reformulate the CCP problem as the second-order cone problem(SOCP). By extending the nonmonotone line search for unconstrained optimization to the CCP, a nonmonotone smoothing Newton method is proposed for solving the CCP. Under suitable assumptions, the proposed algorithm is shown to be globally and locally quadratically convergent. Some preliminary numerical results indicate the effectiveness of the proposed algorithm for solving the CCP.

EXTENSION OF SMOOTHING FUNCTIONS TO SYMMETRIC CONE COMPLEMENTARITY PROBLEMS

The paper uses Euclidean Jordan algebras as a basic tool to extend smoothing functions, which include the Chen-Mangasarian class and the Fischer-Burmeister smoothing functions, to symmetric cone complementarity problems. Computable formulas for these functions and their Jacobians are derived. In addition, it is shown that these functions are Lipschitz continuous with respect to parameter # and continuously differentiable on J × J for any μ 〉 0.

Analysis of Unsteady Supercavitating Flow Around a Cone Cavitator

Based on an integral equation method,the unsteady supercavitating flow around a slender cone cavitator is studied.The shape and length of supercavity is calculated respectively by using a finite difference time discrete method.Their characteristics varying with the cone angle and cavitation number are investigated respectively.It can be seen obviously that the change of supercavity is characterized by retardation and waviness.

基于净能力及二阶锥规划的分布式光储多场景协同优化策略

针对现有配电网中分布式光储调度模型存在资源协同不足、求解复杂等问题,提出了一种基于净能力及二阶锥规划的分布式光储多场景协同优化调度策略。通过引入储能接入配电网后的功率转移分布因子,提出一种基于系统净能力的储能最优选址计算方法;综合考虑储能的运行特性和分布式光伏的出力不确定性,建立以系统日综合成本和削峰填谷为目标的分布式光储多场景协同优化调度模型;利用二阶锥松弛和Big-M法对潮流约束、储能运行约束进行处理,将原规划模型转化为混合整数二阶锥规划问题。以IEEE 33节点系统和西北某实际系统为算例进行仿真分析,结果表明所提方法能在降低负荷峰谷差和日综合成本、平抑负荷波动的同时,显著提高对分布式光伏的消纳能力,验证了所提方法的有效性和可行性。

某小口径火炮弹丸挤进过程动力学特性分析

为研究某小口径火炮不同坡膛结构下弹丸挤进过程的动力学特性,建立了考虑挤进阻力变化的内弹道方程组并通过vuamp子程序引入到有限元求解中,实现了挤进过程中内弹道计算与弹丸挤进有限元仿真耦合求解。通过对弹丸全膛运动的仿真分析验证了模型的可行性,随后得到并分析不同坡膛锥度、膛线深度及阴线宽度下挤进过程中弹丸的速度、加速度、挤进阻力和膛压曲线及变化影响规律。结果表明,坡膛锥度对挤进过程中弹丸的动力学参数影响不是单调的,而膛线深度及阴线宽度的改变则单调地影响弹丸动力学参数,对优化坡膛结构及弹带设计具有一定的指导意义。

含电动汽车的主动配电网多目标分层优化调度

为了协调电动汽车车主和主动配电网2个不同主体之间的利益关系,针对电动汽车接入后主动配电网的优化调度问题,文中提出一种考虑电动汽车充电综合满意度和主动配电网运行效益的多目标分层优化方法。上层模型注重最大化电动汽车车主的充电利益,采用归一化法向约束法求解电动汽车的最优充放电计划,并将其输入下层优化模型。下层模型旨在最大化主动配电网的运行效益,根据电动汽车的充放电计划调整可控分布式电源的输出功率,采用二阶锥松弛转换法和带权极小模理想点法求解该非线性多目标问题。仿真结果表明,所提含电动汽车的主动配电网多目标分层优化方法能够在促使电动汽车充电综合满意度超过0.9的同时,减少有功网损约94.12%、运行成本约30.90%,实现电动汽车车主和主动配电网的双赢。

变胞工程机器人设计及其稳定性探究

为使变胞工程机器人能够应对更复杂的地形,研究通过轮腿式和滑槽式魔方机构增大机器内部空间,实现躯干各层转动和子块位置互换的功能,从而设计了一种新型的变胞工程机器人。结果表明:变胞工程机器人改进后的滑槽式结构加工难度降低,子块不易脱离。该机器人构型的前后转动层由电机驱动,在越障时左右转动层可以自适应旋转。当其最小稳定角为25.69°、重心高度为56.45 mm时,运动的稳定性最好,不易发生倾翻。此外,机器人采用的三足步态可以保持快速移动,并具有较小的位移偏移量。新型的变胞工程机器人具有较高的稳定性,在地域探险中具有较高的应用价值。

某大口径火炮不同坡膛锥角弹丸挤进过程

为对某大口径火炮不同坡膛锥角时弹丸挤进过程进行对比分析,通过光滑粒子流体动力学法仿真某装药条件下弹带挤进过程。仿真得到挤进阻力和导转力矩,分析产生力矩波动的原因,并提出减轻力矩波动、缓解膛线受力的改进措施。结果表明,该研究能为坡膛锥角对弹带刻槽影响的研究提供参考。

土壤对军用越野车辆机动性能影响分析

在软地面上的机动性能是军用高机动性越野车辆的主要性能之一,对于其野外作业有重要的战略意义。为了探究不同类型松软土壤地面路况对越野车辆机动性能的影响,基于离散元法对土壤进行建模,通过土壤堆积角测试试验以及土壤圆锥指数试验进行土壤刚度对标测试。通过DEM-MBD联合仿真方法,利用精确的土壤模型,对不可压缩干燥土壤、不可压缩湿润土壤、可压缩干燥土壤、可压缩湿润土壤4种不同类型土壤进行仿真分析,通过对比越野车辆平均速度、牵引力、驱动扭矩、轮胎沉陷量,探究土壤类型对越野车辆机动性能的影响。越野车在湿润土壤上比在干燥土壤上牵引力减少了6.98%,在不可压缩土壤上的稳定行驶速度比在可压缩土壤上稳定行驶速度高34.2%,在湿润的土壤路面上速度更加稳定。研究成果弥补了国内车辆地面力学领域土壤对整车机动性影响的空白,可为军车野外复杂地形(如沙地、雪地、泥泞等)作战时选择最优的行驶路面,提高作战效率。

基于田口算法的锥形氢气减压阀结构优化

为了研究锥形氢气减压阀内的能量损失,阐明减压阀几何结构与能耗之间的相互作用机理,以平均湍流耗散率为评价指标,基于田口算法设计了16种新型氢气减压阀结构。通过计算流体力学对不同的减压阀方案进行了数值计算,并分析了不同几何因素对响应的影响。结果表明,1级进口细管(D1=2.5 mm)、1级出口细管(D2=2.5 mm)和1级阀芯锥角(β=66°)是最优的几何参数组合;最优组合平均湍流耗散率比其他试验方案降低5%~27%,可以有效地降低氢气减压阀的能量损失;D2对氢气减压阀内的平均湍流耗散率影响最大;随着D1,D2,β的增大,减压阀的平均湍流耗散率增大。研究结果可为氢气减压阀设计和改进提供参考。

拉伸法制备微纳光纤的设计与研究

微纳光纤通常采用光纤拉锥法制备.对原有装置进行改进,增加电机和控制器搭建火焰加热电机拉伸法制备微纳光纤的实验平台,实现了微纳光纤的自动化制备.探究了光纤直径与拉伸距离、拉伸速度、火焰高度等的关系.理论推导出单侧拉伸过程中锥区直径与拉伸长度的关系,通过对不同速度下锥区形状的测量,解释了拉伸速度影响光纤直径的原因.