PBA／PMMA型核壳弹性粒子增韧环氧树脂研究

合成了一系列的ＰＢＡ／ＰＭＭＡ核壳型复合弹性粒子,并用于增韧双酚Ａ环氧树脂ＤＥＧＭＡ／ＤＤＭ体系。研究表明,适宜的ＰＢＡ／ＰＭＭＡ核壳比是核壳型复合弹性粒子增韧环氧树脂的先决条件,添加合适核壳比的复合粒子能提高改性体系的冲击强度、剪切强度、降低固体化系的内应力。随着核壳粒子橡胶相尺寸的减小,改性体系的冲击强度逐渐增加,内应力降低,但对体系的剪切强度影响并不显著。在外作用下观察到核壳粒子空穴化引起剪切屈服增韧。核壳粒子的形态由透射电镜观测（ＴＥＭ）。,改性试样的断裂表面扫描电镜观测（ＳＥＭ）。改性体系中分散相的尺寸由预测结构的核的核壳复合粒子控制。     

变尺度动态网格法在数据分发管理中的研究

在分析高层体系结构下数据分发管理机制实现的各种静态和动态方法的基础上,指出了仿真过程中时间开销与数据过滤率是一对矛盾的因素,提高数据过滤率必然导致时间开销的增加。一个仿真系统不能只采用一种固定的网格单元尺寸,而要随系统的不同动态改变网格的单元尺寸,以达到在最短时间消耗情况下得到最高的数据过滤率。由此提出了一种变尺度动态网格法,在深入分析网格单元尺寸与更新时间、数据过滤率、接收时间及排队时间的关系后,给出了该算法的数据方程及实现过程;最后在一个应用实例中对该算法进行了验证,说明了该算法的有效性。     

基于DDM技术的FEM/PO-PTD方法在深腔导体目标RCS分析中的应用

采用一种基于区域分解法(DDM)的混合方法——FEM/PO—PTD法，分析带有深腔的三维电大尺寸导体目标的电磁散射特性。应用DDM将原有深腔分成若干个较小的子域。对于腔体开口面所在子域，应用等效原理，结合物理光学法(PO)与物理绕射理论(PTD)，得到腔体开口面的边界积分方程；对于其它子域，通过传输条件实现各子域间的耦合。在各子域内推导出此边值问题的等价泛函。应用基于棱边的有限元法(Edge—based FEM)进行分析。理论分析与计算结果表明，该混合方法与其它计算同类问题的方法相比，有较高的计算精度，同时能减少对计算机内存的需求     

三维散射体宽带RCS频率响应的快速算法:渐进波形估计技术加速的区域分裂法

本文基于渐近波形估计(AWE)技术和区域分裂法(DDM)快速预测有限长三维柱体RCS的频率响应.首先采用区域分裂法结合频域有限差分(FDFD-DDM)计算柱体表面等效电流和磁流在某一给定频率展开的Taylor级数,然后通过Padè逼近将Taylor级数转化为有理函数,由此可获得柱体在任一频率入射波照射下的表面等效电流和磁流,进而计算出RCS频率响应特性.本文结果和文献结果吻合较好,证明了本文方法的正确性,另外相对于直接采用FDFD-DDM法而言,计算效率得到了显著的提高.     

Computation of the gradient and sensitivity coefficients in sum of squares minimization problems with differential equation models

In parameter estimation problems where the system model consists of differential equations, methods for minimizing a sum of squares of residuals objective function require derivatives of the residuals with respect to the parameters being estimated (sensitivity coefficients) or the gradient of the objective function (depending on the numerical optimization method). This paper considers two methods for generating such derivatives: (1) the adjoint equation — gradient formula; and (2) complimentary sensitivity coefficient differential equations. Particular attention is given to the consistency between the method used to solve the model equations and the proper formulation of the additional equations required by the two methods. Two example problems illustrate computational experience using a modified quasi-Newton method with the adjoint method used to generate gradients and applying a modified Gauss-Newton approach with the sensitivity coefficient equations to calculate both the Gauss-Newton matrix and the objective function gradient. Results indicate the superiority of the sensitivity coefficient approach. When comparing the computational effort required by the two methods and the results from the simple examples, it appears that the use of complimentary sensitivity coefficient equations is much more efficient than using only the gradient of the sum of squares function.     

海杂波环境中运动目标电磁散射的数值模拟

提出用广义前后向迭代方法(GFBM)与谱加速算法(SAA)结合的数值方法,求解PM谱粗糙导体海面与船目标散射的电磁场积分方程,数值模拟海杂波中船目标双站与后向散射,给出观测条件变化时的海杂波与目标回波、及其与环境和目标各特征参数关系的模拟.提出有限元-区域分解法(FEM-DDM)的双级准静态方法,数值模拟风驱动态海面上低飞目标的Doppler(DP)频谱.分析了不同海况、有无舰船目标的情况下海面上低空飞行目标的时域回波、DP频谱及其与目标飞行高度、观测角等特征参数的关系.     

A PARTITIONING PARALLEL PROCEDURE FOR NUMERICAL SIMULATION OF GAS FLOW IN A CYCLONE SEPARATOR

1. INTRODUCTIONIt is difficult to deal with most problems of fluid flow because of the complexity of its geometry and performance characteristics. To avoid geometrical complexity of the computational zone, most of numerical strategies are based on the coo…     

Direct digital manufacturing of three-dimensional functionally graded material objects

Among the different types of direct digital manufacturing (DDM) technologies, some of them can be used for making functionally graded material (FGM) objects. Apart from specific characteristics of the DDM process being employed, one problem in FGM object fabrication is the generation of the corresponding information complete format so that the functionally graded material information can be realized. In this paper, this issue is addressed and the three-dimensional printing (3DP) process is considered as the DDM technology employed for making a FGM prototype. The property of printing a 3D prototype in color is adopted and a methodology is proposed for representing the mechanical properties of an FGM object by color information. In this methodology, an object is considered as “functionally graded” if its mechanical strength is gradually changed within the object and the mechanical strength arisen from gluing powdered material by binders in 3DP is assumed to be proportional to the concentrations of the binders applied in it. If the concentration of each primary color binder is different and a pixel of color is printed in the appropriate proportion, the resultant pixel would have a corresponding binder concentration value. To determine the binder concentration requirements, a computer-aided engineering (CAE) analysis is first carried out and the concentration requirements in different parts of the object are inferred from the CAE analysis result. These requirements are then converted to color information by applying the proposed methodology. As the binder concentrations of different colors are different, a colorful prototype would also be an FGM one.     

对KIVA程序中粒子跟踪数学模型的修正

在应用中发现ＫＩＶＡ、ＫＩＶＡ－Ⅱ程序中的粒子跟踪数学模型存在错误，该错误将导致在某些情况下较大的绝对误差，甚至预测完全失真的结果。本文分析了原模型产生错误的原因，并进行了修正。计算表明修正后的模型彻底根除了原模型的错误对预测结果的影响。     

对ILS小功率干扰的效能评估与仿真研究

在电子对抗中,小功率干扰技术是近几年研究的焦点,本文研究了小功率干扰对仪表着陆系统(instrument landing system,ILS)性能的影响,为ILS干扰环境的效能评估提供参考。首先,推导了ILS的测量参数调制度差(difference of degree of modulation,DDM)受干扰影响的数学表达式; 其次,以干扰源的功率、位置等关键参数为参变量,通过计算机仿真分析了在着陆引导区域内DDM产生的误差。理论分析与仿真结果表明,小功率干扰对ILS性能影响明显,必须采取相应的干扰抑制技术,以改善系统的引导性能。