分布式数据挖掘研究

首先简单介绍了分布式数据挖掘的定义、重要性、研究现状以及数据源 ,然后详细介绍了两个典型的分布式数据挖掘系统。最后探讨了分布式数据挖掘系统应该具有的特点     

电大尺寸目标电磁散射的区域分解计算

提出了电大尺寸目标电磁散射的有限元区域分解计算方法。分析了子区域的有限元解法,建立了区域分解耦合的边界方程,导出了相应的耦合矩阵,并采用了内视法还原了耦合矩阵对称、稀疏的特征,最后研究了不同类型大尺寸目标的雷达散射截面问题并与公开文献结果进行了分析比较。     

ILS与VOR分析仪数字中频处理技术研究与实现

本文对仪表着陆与全向信标分析仪中航向信标信号基于FPGA的数字中频处理技术进行了研究,提出了一种基于数据分离滤波的数字中频处理方案.与传统的数字中频处理方案相比,对LOC多频调制信号进行了分离测量,提高了测试的精度,对仪表着陆与全向信标分析仪广泛应用于机场校飞、日常监测和设备维护有着重要的意义.     

一种改进的基于排序的区域匹配算法

兴趣匹配是分布仿真中兴趣管理的关键环节,其速度和精度影响着兴趣管理的性能。基于排序的区域匹配算法是针对HLA／DDM的有效算法,但它只是利用了对范围界点排序而带来的空间关系启发信息,其匹配效率还有值得改进的地方。本文首先分析了匹配算法的实质,然后研究了实际分布仿真系统中实体运行时的局部性,并利用这种局部性对匹
匹配算法进行改进,给出了改进算法,进而对改进算法和原算法进行了比较测试,最后给出了结论和进一步的工作展望。     

Parallel FETI‐DP algorithm for efficient simulation of large‐scale EM problems

An efficient parallelization of the dual‐primal finite‐element tearing and interconnecting (FETI‐DP) algorithm is presented for large‐scale electromagnetic simulations. As a nonoverlapping domain decomposition method, the FETI‐DP algorithm formulates a global interface problem, whose iterative solution is accelerated with a solution of a global corner problem. To achieve a good load balance for parallel computation, the original computational domain is decomposed into subdomains with similar sizes and shapes. The subdomains are then distributed to processors based on their close proximity to minimize inter‐processor communication. The parallel generalized minimal residual method, enhanced with the iterative classical Gram‐Schmidt orthogonalization scheme to reduce global communication, is adopted to solve the global interface problem with a fast convergence rate. The global corner‐related coarse problem is solved iteratively with a parallel communication‐avoiding biconjugate gradient stabilized method to minimize global communication, and its convergence is accelerated by a diagonal preconditioner constructed from the coarse system matrix. To alleviate neighboring communication overhead, the non‐blocking communication approach is employed in both generalized minimal residual and communication‐avoiding biconjugate gradient stabilized iterative solutions. Three numerical examples are presented to demonstrate the accuracy, scalability, and capability of the proposed parallel FETI‐DP algorithm for electromagnetic modeling of general objects and antenna arrays. Copyright © 2016 John Wiley & Sons, Ltd.     

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…     

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.     

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。     

低渗透油气藏水平井分段多簇压裂簇间距优化新方法

水平井分段多簇压裂中簇间距的大小是决定水平井分段多簇压裂成败的关键因素。为提高低渗透油气藏储层压裂改造效果,需建立合理的簇间距优化模型,而现有的优化方法多以应力反转半径作为最佳间距,并未定量化表征压裂后的储层改造效果。为此,基于弹性力学基础理论和位移不连续法建立了考虑水力裂缝干扰模式下的复杂地应力场计算模型,研究了天然裂缝在复杂地应力场条件下发生张开和剪切破裂形成复杂裂缝网络的规律,再以获得最大缝网波及区域面积为优化目标,形成一种新的簇间距优化方法。研究结果表明:(1)张开的水力裂缝会在其周围产生诱导应力,压裂液的滤失则会导致地层孔隙压力变化,相应的地层孔隙弹性应力也会发生变化;(2)天然裂缝剪切破裂区域与张开破裂区域重叠,且前者要远大于后者,可采用天然裂缝剪切破裂区域面积来表征复杂裂缝网络波及区域的大小。采用该方法指导了现场水平井的簇间距优化设计,实验井压裂后取得了理想的增产效果,为低渗透油气藏水平井分段多簇压裂的簇间距优化设计提供了借鉴和指导。