Margin optimization algorithm for digital subscriber lines based on particle swarm optimization*

The margin maximization problem in digital subscriber line (DSL) systems is investigated. The particle swarm optimization (PSO) theory is applied to the nonconvex margin optimization problem with the target power and rate constraints. PSO is a new evolution algorithm based on the social behavior of swarms, which can solve discontinuous, nonconvex and nonlinear problems efficiently. The proposed algorithm can converge to the global optimal solution, and numerical example demonstrates that the proposed algorithm can guarantee the fast convergence within a few iterations.     

Design of complex FIR filters with arbitrary magnitude and group delay responses

To design approximately linear-phase complex coefficient finite impulse response (FIR) digital filters with arbitrary magnitude and group delay responses, a novel neural network approach is studied. The approach is based on a batch back-propagation neural network algorithm by directly minimizing the real magnitude error and phase error from the linear-phase to obtain the filter’s coefficients. The approach can deal with both the real and complex coefficient FIR digital filters design problems. The main advantage of the proposed design method is the significant reduction in the group delay error. The effectiveness of the proposed method is illustrated with two optimal design examples.     

DDFS spurious signals due to amplitude quantization in absence of phase-accumulator truncation

Spurious signals in direct digital frequency synthesizers (DDFSs) are partly caused by amplitude quantization and phase truncation, which affect their application to many wireless telecommunication systems. Thee signals are deterministic and periodic in the time domain, so they appear as line spectra in the frequency domain. Two types of spurious signals due to amplitude quantization are exactly formulated and compared in thetime and frequency domains respectively. Then the frequency spectra and power levels of the spurious signals due to amplitude quantization in the absence of phase-accumulator truncation are emphatically analyzed, and the effects of the DDFS parameter variations on the spurious signals are thoroughly studied by computer simulation. And several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.     

综合航电任务机仿真系统的设计与实现

介绍了航空电子综合化仿真系统中任务计算机子系统的设计与实现,详细讨论了此系统的功能、组成以及具体的硬件与软件设计方法.仿真系统的设计采用某型飞机的总线拓扑结构,将各个子系统连接起来,以达到综合显示、综合处理、综合控制、数据综合传输、资源共事的目的,并在综合航电仿真系统的联合调试中,验证了此系统的可行性和正确性.     

基于遗传算法的嵌入式仿真的系统辨识与控制优化

数字随动(伺服)系统因具有非线性、不确定性和时变性,难以精确地建立系统的数学模型,由此对设计高性能的控制器造成困难.遗传算法因其隐含并行性、全局搜索等优点,在优化问题领域得到了很好的应用,但遗传算法简单应用于如数字随动系统这样的控制系统在线闭环辨识或参数优化时,会面临大量重复实验成本高、实验时间过长引起系统不稳定等实际问题.针对以上困难,提出一种基于嵌入式仿真的系统辨识方法,采用遗传算法进行数字随动系统同步在线闭环模型参数辨识与控制参数寻优.经过在数字随动系统实物环境下实验,证明了该方法的有效性.     

面向数字孪生的动态数据驱动建模与仿真方法

信息物理系统(cyber-physical system, CPS)是支撑信息化和工业化深度融合的综合技术体系,传统的建模与仿真方法难以满足其应用需求。因此,提出面向数字孪生的动态数据驱动建模与仿真方法,通过随机有限集对CPS中的物理实体和传感器进行数据驱动建模,并使用基于贝叶斯推理的预测与校正过程支持数据驱动的仿真模型运行。该方法能够很好地实现数字孪生机制下虚实结合的仿真运行,并实现数据驱动的CPS仿真模型解算,通过以实利虚的方式有效提高了仿真结果的准确性和可信性。最后,通过水面舰艇作战应用案例,验证了该方法的可行性和有效性。     

两种数字生命的Swarm仿真研究

数字生命的概念是托马斯·雷最早在计算机上模拟实验提出的,以此为指导,介绍了复杂适应系统、Agent建模等理论知识,利用Swarm仿真平台构建了两种异类数字生命及共同生存的环境,模拟自然界生命体最基础的繁殖歼灭等生命现象,通过可视化窗口观察生命体个体及群体间的交互行为,得到结果的不可测性和突现性,实现了两种数字生命的Swarm仿真。     

一种新的对地定位方法及其精度分析与仿真

提出一种新的无人空中载体对地定位方法。该方法根据GPS／INS组合导航系统测量的载体坐标与姿态角、光轴稳定平台相对于载体的姿态角以及激光测距数据，计算地面目标点的三维维坐标，克服了共线条件方程对地形鲁棒性差和DEM迭代定位算法容易发散的缺点。为分析此方法的定位性能，给出了定位误差分析模型，并通过仿真算例验证了该定位方法的有效性，仿真结果表明目标定位精度满足舰炮作战要求。     

A FRAMEWORK FOR REAL-VALUED CIPHER SYSTEMS

Most cipher systems designed thus far are binary-valued or integer-valued cipher systems. Their security relies on the assumption that one-way functions exist. Though the existence of one-way functions has not been proved yet, most cryptographic researchers believe that one-way functions exist. In addition, many candidates for one-way functions have been proposed. Therefore, the key step for developing real-valued cipher systems is to define real one-way functions and to propose candidates for them. In this paper, based on computational complexity theory over the real field, we give two definitions of real one-way functions; one is for digital one-way functions and the other is for general one-way functions. Candidates for these two classes of one-way functions are also proposed. Moreover, we present two examples to demonstrate that the candidates for both digital one-way functions and general one-way functions can be applied to construct secure real-valued cipher systems.     

论数字生命的实在特性

数字生命是人工生命的一种,在人工生命研究领域中具有重要地位。关于数字生命是否具有实在论地位,形成了数字生命强实在论、数字生命反实在论和数字生命弱实在论三个阵营。分析三种主张及其论证方式并给予新的解释,有助于深化对数字生命的实在性质的理解。