液相过渡扩散焊

重点介绍液相过渡扩散焊的特点及国外近年的研究和应用情况。     

某型飞机导航误差对CCD稳瞄系统目标搜索域的影响

分析了DG-1型多普勒／GPS组合导航系统，在不同工作方式下导航误差所引起的搜索方位角的误差；讨论了由于搜索方位角的变化引起的搜索域的变化。通过对机理的研究提出了解决办法。     

双翼金属圆柱体散射场的整体计算

本文利用keller的几何绕射理论（GTD）推求出双翼金属圆柱体散射场高频快收敛整体解，弥补了传统分离解（把系统分解为一个金属圆柱和两个金属半平面，分别求解再简单迭加）的不足之处，最后，给出了整体解和分离解的散射电场的模值数值计算结果。     

电子回旋共振中和器内静磁场及微波电磁场的数值计算

为了研究电子回旋共振中和器内静磁场和微波电磁场的分布规律,设计合理的磁路结构以形成电子回旋共振区,并使微波强电场区与电子回旋共振区重合,采用有限元分析软件对中和器内的静磁场和微波电磁场进行了数值计算。计算结果表明:永磁体及磁轭的尺寸均影响电子回旋共振区的分布;天线伸入长度越长,微波电场越强。微波频率为4.2GHz时,六块相同的长12mm,宽8mm,高5mm的条形永磁铁与磁轭组成的磁路结构,可以产生合理的电子回旋共振区。L型天线伸入长度为5mm时微波强电场区可与电子回旋共振区重合。     

温度场对转子系统响应特性影响的分析

建立了一个轴向可自由伸缩的单转子系统计算模型,采用有限元法分析了温度场对单转子系统响应特性的影响。参考发动机转子系统的加热对流的边界条件,利用 ANSYS 软件构造了该转子系统的瞬态温度场。分别在常温状态下和考虑温度场情况下,计算了转子系统的不平衡响应并进行了对比分析。结果表明,随着温度的升高,第三阶共振频率的相对误差最大达到11.2％。     

混合场积分方程在开放结构散射分析中的应用

针对复合开放闭合结构电磁散射问题的矩量法求解,通过修改混合场积分方程的建立方式,将混合场积分方程扩展应用到这类开放结构,大大提高了求解效率,数值算例证明了该方法的精度和效率。     

轴对称拉瓦尔喷管流场分析

采用一维管流理论分析了轴对称拉瓦尔喷管典型工作状态,结合理论分析对喷管流场进行CFD仿真计算。经研究表明：（1）结合理论分析的流场初始化、以及FMG和外推计算方法,CFD计算效率明显提高;（2）不同拉瓦尔喷管工作状态,需采取不同的壁面函数法来处理近壁区;（3）一维管流理论分析中,将管内强激波简化为正激波的常规做法,计算误差较大,不尽合理。     

A fault-tolerant triple-redundant voice coil motor for direct drive valves: Design, optimization, and experiment

A direct drive actuator (DDA) with direct drive valves (DDVs) as the control device is an ideal solution for a flight actuation system. This paper presents a novel triple-redundant voice coil motor (TRVCM) used for redundant DDVs. The TRVCM features electrical/mechanical hybrid triple-redundancy by securing three stators along with three moving coils in the same frame. A permanent magnet (PM) Halbach array is employed in each redundant VCM to simplify the system structure. A back-to-back design between neighborly redundancies is adopted to decouple the magnetic flux linkage. The particle swarm optimization (PSO) method is implemented to optimize design parameters based on the analytical magnetic circuit model. The optimization objective function is defined as the acceleration capacity of the motor to achieve high dynamic performance. The optimal geometric parameters are verified with 3D magnetic field finite element analysis (FEA). A research prototype has been developed for experimental purpose. The experimental results of magnetic field density and force output show that the proposed TRVCM has great potential of applications in DDA systems.     

Extension of the low diffusion particle method for near-continuum two-phase flow simulations

The low diffusion (LD) particle method, proposed by Burt and Boyd, is modified for the near-continuum two-phase flow simulations. The LD method has the advantages of easily coupling with the direct simulation Monte Carlo (DSMC) method for multi-scale flow simulations and dramatically reducing the numerical diffusion error and statistical scatter of the equilibrium particle methods. Liquidor solid-phase particles are introduced in the LD method. Their velocity and temperature updating are respectively, calculated from the motion equation and the temperature equation according to the local gas properties. Coupling effects from condensed phase to gas phase are modeled as momentum and energy sources, which are respectively, equal to the negative values of the total momentum and energy increase in liquid or solid phase. The modified method is compared with theoretical results for unsteady flows, and good agreements are obtained to indicate the reliability of the one-way gas-to-particle coupling models. Hybrid LD-DSMC algorithm is implemented and performed for nozzle discharging gas-liquid flow to show the prospect of the LD-DSMC scheme for multi-scale two-phase flow simulations.     

Temporal evolution of statistical features of the sunspot cycles

Analysis of the general statistical features of the sunspot cycles in the period 1700–1996 AD, including the Gnevyshev–Ohl rule, Waldmeier rule and an amplitude–period effect, was performed for both Wolf numbers and group sunspot numbers. It was shown that for both solar indices all the statistical effects are weaker over the time interval 1700–1855 AD than over the time interval 1856–1996 AD. Possible causes of this difference are discussed.