Microstructure and Strength of Laser Welds of Sub-micron Particulate-reinforced Aluminum Matrix Composite Al_2O_(3p)/6061Al

The microstructure of laser welds of sub-micron particulate-reinforced aluminum matrix composite Al_2O_(3p)/6061Al and the weldability of the material were studied. Experimental results indicated that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement was re- strained intenslvely at elevated temperature and pulsed laser beam. The main factor affecting the weldability of the com- posite was the reinforcement segregation in the weld resulting from the push of the liquid/solid interface during the soli- dification of the molten pool. The laser pulse frequency directly affected the reinforcement segregation and the reinfor- cement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. On the basis of this, a satisfactory welded joint of sub-micron paniculate-reinforced aluminum matrix com- posite Al_2O_(3p)/6061Al was obtained by using appopriate welding parameters.

Gradient-Based Iterative Algorithm for a Coupled Complex Conjugate and Transpose Matrix Equations

Gradient-based iterative algorithm is suggested for solving a coupled complex conjugate and transpose matrix equations. Using the hierarchical identification principle and the real representation of a complex matrix, a convergence proof is offered. The necessary and sufficient conditions for the optimal convergence factor are determined. A numerical example is offered to validate the efficacy of the suggested algorithm.

Applications of AuNRs@SiO₂Matrix Nanocomposites

Gold nanorods (AuNRs/GNR) have unique, controllable and anisotropic local surface plasmon resonance (SPR) properties, which have been widely used in biochemistry, electronics and catalysis. It is of great value and significance to study the synthesis, properties, surface modification and structural regulation of AuNRs. This paper introduces AuNRs and AuNRs@SiO2. The synthesis of AuNRs@SiO2 composite nanomaterials with quantum dots, graphene, rare earth materials and magnetic materials is described. The applications of nanocomposites in optics, biomedicine and biosensors are also discussed. The future development of nanocomposites is proposed.

H∞ Control for Externally Excited Building Structures with Active Mass Damper under Actuator Saturation

This paper investigates the application of active mass dampers to mitigate the vibrations of building structures subjected to unknown external excitations under controller saturation conditions. By utilizing an H∞ control strategy, the optimal state feedback controller is derived by solving the linear matrix inequality problem for controller saturation. Case studies show that the proposed controller is capable of stabilizing the closed-loop system with good control performance and effectively suppressing vibrations in building structures under unknown external excitation. When compared to controllers that do not consider saturation, the proposed controller requires lower gain and results in reduced energy consumption. The research findings provide valuable insights for addressing real-world building structure control problems, contributing to both theoretical significance and practical applications.

基于特征值的动态数字信道化子带检测算法

动态数字信道化接收结构通过检测所有子带,判断信号是否存在,为综合滤波器组处理提供依据,因此子带检测在接收结构中起着关键作用。针对传统检测算法存在低信噪比(signal-to-noise ratio,SNR)下检测性能不高的问题,依据随机矩阵理论,提出了基于最大最小特征值之差与平均特征值之比的检测算法,利用平均特征值和最小特征值的极限分布规律来推导算法的检测门限。其次,根据所有子带数据获取的特征值信息对所提算法进行了优化。最后,在动态数字信道化接收结构中,分析不同因素下算法的性能,表明了所提算法能够克服低SNR的影响,子带检测的性能更好。

Flex-DMA:支持多模式高效传输的DMA系统设计

随着数据密集型科学和高通量应用的迅速发展,专用集成电路设计不断涌现,传输系统不再只有数据传输的需求。现有的一些直接存储器访问(Data Memory Access,DMA)设计可以支持高效的矩阵转置传输,但这些设计不能满足复杂的访存模式,也不具有灵活的可配置性,从而降低计算效率。针对这些问题设计了一种可配置的多模式传输系统Flex-DMA,该系统包含可配置的寄存器以及传输通道,拥有基础模式和单指令多数据(Single Instruction Multiple Data,SIMD)模式。因此,Flex-DMA可根据不同的数据传输需求选择不同的传输模式,灵活配置数据规模和数据格式,支持数据向量化转换、矩阵转置传输等功能。在大规模并行模拟框架中对Flex-DMA做性能评估,其结果表明,Flex-DMA在数据向量化处理中可以获得平均5.14倍的加速比。此外,与MT-DMA结构相比,Flex-DMA在矩阵转置传输中可以获得平均2.52倍性能提升。实验证明:Flex-DMA能满足复杂的访存模式和传输需求,在低传输时延下实现数据的重组和预处理。

液晶调控下的亚波长金光栅反射相位

空间光调制器(Spatial Light Modulator,SLM)是实现光场调控的关键器件。本文研究了一种将亚波长金光栅嵌入硅基液晶(Liquid Crystal on Silicon,LCoS)构成的SLM(G-LCoS)器件模型的反射相位特性,该器件模型以ITO透明导电层和液晶构成G-LCoS中亚波长金光栅的非对称边界。首先运用散射矩阵原理给出了亚波长金光栅反射相位的计算表达式,其次给出了下表面液晶的有效折射率计算公式。在此基础上,利用TechWiz 3D软件模拟加电情况下金光栅下表面液晶指向矢的变化,给出金光栅下表面液晶有效折射率的变化值。将得到的有效折射率数据导入到FDTD Solutions软件,对该器件结构开展了相关的仿真实验和结果分析。综合考虑了上表面的ITO色散情况、金光栅高度变化以及不同电压下液晶有效折射率值,实现了可见光范围内多波长的近2π相位调制。本文研究的器件也为AR/VR显示系统以及全息视频显示的优化提供了一种新思路。

浅谈方阵及其转置矩阵的特征向量之间的关系

刻画了方阵和其转置矩阵的特征向量的关系.一方面,当方阵是可相似对角化时,给出了利用方阵特征向量求其转置矩阵的特征向量的方法;另一方面,从约当标准型的角度给出了方阵及其转置矩阵的特征向量的求解方法,这些结果丰富了特征值和特征向量的理论和方法.

伴随矩阵性质证明的一种新方法

定义了矩阵的旋转运算和矩阵的加符号因子运算,证明这两种运算的若干性质。利用这些性质定理研究了伴随矩阵,得到了伴随矩阵的一些重要性质。推广和改进了关于伴随矩阵的已有结论,丰富和完善了伴随矩阵的相关理论。

Optimal Estimation of High-Dimensional Covariance Matrices with Missing and Noisy Data

The estimation of covariance matrices is very important in many fields, such as statistics. In real applications, data are frequently influenced by high dimensions and noise. However, most relevant studies are based on complete data. This paper studies the optimal estimation of high-dimensional covariance matrices based on missing and noisy sample under the norm. First, the model with sub-Gaussian additive noise is presented. The generalized sample covariance is then modified to define a hard thresholding estimator , and the minimax upper bound is derived. After that, the minimax lower bound is derived, and it is concluded that the estimator presented in this article is rate-optimal. Finally, numerical simulation analysis is performed. The result shows that for missing samples with sub-Gaussian noise, if the true covariance matrix is sparse, the hard thresholding estimator outperforms the traditional estimate method.

Matrices That Commute with Their Conjugate and Transpose

It is known that if A∈Mn is normal (AA*=A*A) , then AA￣=A￣A if and only if AAT=ATA. This leads to the question: do both AA￣=A￣A and AAT=ATA?imply that A?is normal? We give an example to show that this is false when n=4, but we show that it is true when n=2?and n=3.

基于线圈子单元的永磁同步电机健康与定子绕组短路故障数学模型

针对相绕组为基本单元的永磁同步电机定子绕组短路故障数学模型,存在故障空间位置影响无法计及、不同短路故障需要重新建模,且无法研究健康状态时线圈对电机性能的贡献等问题,该文提出一种基于线圈子单元的永磁同步电机健康与定子绕组短路故障数学模型(APM)。首先,将每个线圈分割为多个线圈子单元,分别建立各子单元的电压、阻抗和空载反电动势等物理量的矩阵方程,利用基尔霍夫电压定律建立所有子单元的电压方程,建立电机的电磁功率和转矩方程。其次,利用有限元法和拟合法建立考虑槽内空间位置关系的线匝电感矩阵,通过矩阵变换得到计及位置信息的子单元电感矩阵。然后,在Matlab/Simulink中建立APM的仿真模型和图形化界面,通过修改抽头编号及图形化界面中短路电阻模块的连接位置,计算电机健康和不同类型定子绕组短路故障下的电磁特性。最后,有限元仿真和实验结果验证了模型的正确性和准确性,表明APM不仅可以精细地分析健康状态时线圈对电机性能的贡献,也可以高效、准确地分析线圈内部不同位置短路故障对电机性能的影响。该文研究可以为永磁同步电机的设计、故障诊断和容错控制提供依据。

Effects of Mg content on aging behavior of sub-micron Al_2O_(3p)/Al-Cu-Mg composites

30%Al2O3p/Al-Cu-2.0Mg composite and Al2O3p/Al-Cu-2.5Mg composite with 0.3μm-Al2O3 particles were fabricated. Age-hardening behaviors of two composites and the related matrix alloys were studied by means of Brinell-hardness measurement, DSC and TEM. The results show that the hardness of the composite is improved obviously because of the addition of sub-micron Al2O3 particles. But the hardness increment of Al2O3p/Al composite after aging is lower than that of the related matrix alloy. Moreover, the formation of GP region is suppressed by the addition of sub-micron Al2O3 particles, which broadens the exothermic peak of S' phase. The increment of Mg content has a different influence on accelerating the aging processes of aluminum alloys and the composites, and the hardness also increases.

大华matrix 120

matrix 120是国内品牌第一次采用TI DM320方案的。视频上，matrix 120支持MPEG1／2／4、DIVX4／5、XVID等视频编码格式，并支持SUB字幕显示。音频上，matrix 120支持MPEG1／2、LAYER1／2／3、WMA、PCM等音频编码格式，并且支持电视录制／输出功能。

Robust Finite-Time H∞ Filtering for ItôStochastic Systems

This paper investigates the problem of robust finite-time H∞ filter design for Itô stochastic systems. Based on linear matrix inequalities (LMIS) techniques and stability theory of stochastic differential equations, stochastic Lyapunov function method is adopted to design a finite-time H∞ filter such that, for all admissible uncertainties, the filtering error system is stochastic finite-time stable (SFTS). A sufficient condition for the existence of a finite-time H∞ filter for the stochastic system under consideration is achieved in terms of LMIS. Moreover, the explicit expression of the desired filter parameters is given. A numerical example is provided to illustrate the effectiveness of the proposed method.

Optimal Management of the Pension Contribution Rate Using the H∞-Control Theory

In this paper, we construct a general model for a pension fund when there are time delays in the valuation process. Actually, we use the standard structure of the basic reserve equation in order to rebuild a more sophisticated approach based on the theory of H∞ control. Our model evaluates the incomplete information from the delayed fund valuations—due to the oscillatory pattern for benefit claims and investment experience of the past years—within the context of uncertainty additionally to the randomness which certainly exists. So, we construct estimations for the optimal proposed contribution rates based on a feedback mechanism which is a robust stabilization controller, using typical linear matrix inequalities. Finally, a numerical application is fully investigated to obtain further insight into the problem.

关于复矩阵(A^(T)A)^(m)的秩及其推广

设A为复矩阵,A为A的共轭矩阵,A^(T)为A的转置,m为任意正整数,R(A)为A的秩.证明了R((A^(T)A)^(m))=R((A^(T)A)^(m)A^(T))=R(A(A^(T)A)^(m))=R(A).

Winograd转置卷积快速实现方法研究

Winograd转置卷积算法是现场可编程门阵列中广泛使用的卷积加速方法,可通过分组后执行Winograd卷积来解决转置卷积的零填充问题。然而该方法需要对输入特征映射和卷积核进行分组运算,且需要对运算结果进行重组,以生成完整的输出特征映射,复杂的元素坐标计算增加了设计的复杂度。针对上述问题,提出一种采用统一转换矩阵计算Winograd转置卷积的方法,使用统一的转换矩阵代替对输入特征映射和卷积核进行分组,有效解决了重叠求和、零填充、卷积核翻转、分解和重组等问题。并在该方法的指导下,结合数据重用、双缓冲区设计和流水线等方法,完成了现场可编程门阵列上转置卷积的加速器的设计。选择高斯-泊松生成对抗网络进行实验验证,并与主流的转置卷积设计方法进行了综合比较。实验结果表明,提出的方法可有效降低资源消耗和功耗,加速器的有效性能比现有的转置卷积方法提高了约1.13至23.92倍。

Robust Optimal H∞ Control for Uncertain 2-D Discrete State-Delayed Systems Described by the General Model

This paper investigates the problem of robust optimal H∞ control for uncertain two-dimensional (2-D) discrete state-delayed systems described by the general model (GM) with norm-bounded uncertainties. A sufficient condition for the existence of g-suboptimal robust H∞ state feedback controllers is established, based on linear matrix inequality (LMI) approach. Moreover, a convex optimization problem is developed to design a robust optimal state feedback controller which minimizes the H∞ noise attenuation level of the resulting closed-loop system. Finally, two illustrative examples are given to demonstrate the effectiveness of the proposed method.

Delay-Dependent Robust H∞ Control for Uncertain 2-D Discrete State Delay Systems Described by the General Model

This paper considers the problem of delay-dependent robust optimal H∞ control for a class of uncertain two-dimensional (2-D) discrete state delay systems described by the general model (GM). The parameter uncertainties are assumed to be norm-bounded. A linear matrix inequality (LMI)-based sufficient condition for the existence of delay-dependent g-suboptimal state feedback robust H∞ controllers which guarantees not only the asymptotic stability of the closed-loop system, but also the H∞ noise attenuation g over all admissible parameter uncertainties is established. Furthermore, a convex optimization problem is formulated to design a delay-dependent state feedback robust optimal H∞ controller which minimizes the H∞ noise attenuation g of the closed-loop system. Finally, an illustrative example is provided to demonstrate the effectiveness of the proposed method.