利用FPGA器件实现非线性图象处理器

非线性图象处理中有许多操作以逻辑运算为主,并且结构简单、规则、有重复性,非常适于FPGA器件实现。本文以堆栈滤波器为例,研究了利用XC6216器件实现椎栈滤波器的方法以及得到的性能和代价指标。     

Subharmonic Resonance Behavior for the Classical Hydrogen Atomic System

Previously unexplored resonance conditions are shown to exist for the classical hydrogen atomic system, where the electron is treated as a classical charged point particle following the nonrelativistic Lorentz-Dirac equation of motion about a stationary nucleus of opposite charge. For circularly polarized (CP) light directed normal to the orbit, very pronounced subharmonic resonance behavior is shown to occur with a variety of interesting properties. In particular, only if the amplitude of the CP light exceeds a critical value, will the resonance continue without radius and energy decay. A perturbation analysis is carried out to illustrate the main features of the behavior. The present phenomena adds to a growing list of other nonlinear dynamical behaviors of this simple system, that may well be important for more deeply understanding classical and quantum connections.     

A nonlinear analytical model for the squeeze-film dynamics of parallel plates subjected to axial flow

In this paper, we develop a theoretical model to predict the nonlinear fluid-structure interaction forces and the dynamics of parallel vibrating plates subjected to an axial gap flow. The gap is assumed small, when compared to the plate dimensions, the plate width being much larger than the length, so that the simplifying assumptions of 1D bulk-flow models are adequate. We thus develop a simplified theoretical squeeze-film formulation, which includes both the distributed and singular dissipative flow terms. This model is suitable for performing effective time-domain numerical simulations of vibrating systems which are coupled by the nonlinear unsteady flow forces, for instance the vibro-impact dynamics of plates with fluid gap interfaces. A linearized version of the flow model is also presented and discussed, which is appropriate for studying the complex modes and linear stability of flow/structure coupled systems as a function of the average axial gap velocity. Two applications of our formulation are presented: (1) first we study how an axial flow modifies the rigid-body motion of immersed plates falling under gravity; (2) then we compute the dynamical behavior of an immersed oscillating plate as a function of the axial gap flow velocity. Linear stability plots of oscillating plates are shown, as a function of the average fluid gap and of the axial flow velocity, for various scenarios of the loss terms. These results highlight the conditions leading to either the divergence or flutter instabilities. Numerical simulations of the nonlinear flow/structure dynamical responses are also presented, for both stable and unstable regimes. This work is of interest to a large body of real-life problems, for instance the dynamics of nuclear spent fuel racks immersed in a pool when subjected to seismic excitations, or the self-excited vibro-impact motions of valve-like components under axial flows.     

非线性失真对场倒置加扰信号的影响

文章通过分析非线性失真对场倒置加扰信号的影响，指出了非线性失真是引起解忧后图象色度闪烁的一个不容忽视的原因。它的大小，将直接影响此类加扰方式的效果。     

NEW PERTURBATION TECHNIQUE FOR TRANSIENT ANALYSIS AND ITS APPLICATIONS IN DC-DC PWM SWITCHING POWER CONVERTERS

An improved perturbation technique proposed in a recent paper (Int. J. Electronics, vol. 63, pp.403-414) has been successfully applied to steady-state analysis of PWM switching converters. This paper extends the algorithm to transient analysis of a broader class of non-linear systems. As an example, the transient response of a Boost PWM switching converter is analyzed to demonstrate its simplicity and accuracy.     

Gas bubble dynamics—experiment and fractal analysis

In the paper, nonlinear features of the air bubbling from a submerged glass nozzles are discussed. The air bubbles were emitted from glass nozzles of different diameters submerged in distilled water at a depth of 15 cm in a cylindrical tank of 30 cm in diameter and 37 cm height. The air volume flow rate was changed from 1 l/h to 45 l/h. A laser-photodiode and an acoustic technique system have been used. Also photographic study of bubbles departure has been carried out. Measured data have been analysed using the fractal analysis method. It has been shown that bubbles dynamics is of deterministic chaos nature and behaviours of such system can be chaotic or periodic depending on the volume flow rate. The map of chaos appearance has been constructed. Data recorded by acoustic system has been used to analysis of bubble wall movement.     

自主机器人直线行进过程的数字PID控制

针对自主机器人的直线行进过程，提出一种通过硬件电路确定直流电机模型的方法，即利用光电编码器测得机器人驱动轮电机转速信号，经硬件电路将每个周期时间内的脉冲数记录下来，从而得到电机输出转速响应曲线，确定电机的数学模型。在电机模型确定的基础上，实现了自主机器人直线行进过程的数字PID控制。数字PID参数的确定采用Ziegler—Nichols法，同时借助Matlab／Simulink仿真软件对所得PID参数进行了进一步的整定，取得了良好的控制效果。     

RAPID APPROXIMATE SOLUTIONS FOR ADSORPTION BED CONCENTRATION PROFILE AND BREAKTHROUGH CURVE BEHAVIOR: FAVORABLE ISOTHERMS AND BOTH PHASE RESISTANCES IMPORTANT

A simple method is presented for determining fluid-phase and solid-phase solute concentration profiles, and solute breakthrough curves, for fixed bed adsorbers when both the fluid-phase and solid-phase mass transfer resistances are important. The method applies to any nonlinear isotherm of the “favorable” type. Freundlich and Langmuir isotherms are used as specific examples in the present paper. Constant-pattern behavior and linear-driving-force rate laws are assumed.     

A survey on nonlinear analog-to-digital converters

This paper presents a survey on Nonlinear Analog-to-Digital converters (ADC). This class of converters is extremely relevant in applications where there is a need for non-uniform quantization characteristic, for example, some specific applications in the areas of light detection, hearing aid, nuclear physics, image acquisition, communication systems, etc. This survey outlines the state-of-the-art Nonlinear ADC topologies, such as, floating point, logarithmic, piecewise linear and oversampled nonlinear converters, and discusses their performance and advantages in terms of their applications.     

无人机空中加油自主会合导引律研究

针对自主空中加油技术中的会和阶段的理论研究,提出一种带有终端偏航角约束的导引问题。通过对三维空间中重新设计偏置项,来同时约束俯仰与偏航角,将期望的会合点作为跟踪目标,并在制导末端结合纯追踪法,实现终端航向的控制。最后,以匀速直线运动和作U型机动的加油机为例,对无人机（UAV）选取不同的初始位置和航向来检验所提出的制导律实现会合的能力。仿真结果表明,所设计的自主会合制导律有效实现无人机空中加油自主会合,解决了现有一类自主会合制导律设计复杂、需预先已知加油机轨迹及大量在线规划计算的问题。