On the Irrotational Approximation to the 2-Dimensional Isothermal Euler System

The author mainly studies the difference of the weak solutions generated by a wave front tracking algorithm to the steady Euler system and the isothermal Euler system. Under the hypothesis that the initial data are of sufficiently small total variation, it is proved that the difference between the solutions of the steady Euler system and the system of isothermal supersonic flow can be bounded by the cube of the total variation of the initial perturbation.     

在探究中发现,在发现中探究

数学综合与实践活动课,是数学课程的重要组成部分,是新课改的一个突出亮点．综合实践活动强调学生活动;强调转变学生的学习方式;强调学生的主动参与和自主学习;强调通过小组学习、合作探究等手段解决实际问题．笔者现以苏科版八年级上册《数学综合与实践活动》中的《数格点,算面积》为例,展现学生在探究中发现,在发现中探究的风采．     

基于永磁同步电机的光电设备新型驱动研究

针对目前光电设备中直流电机的惯量大、成本高、需要维护等问题,提出了交流伺服控制系统,以适应新型光电设备的发展要求或替代目前的直流控制系统。以永磁同步电机为控制对象,分析了永磁同步电机的磁场定向矢量控制原理,以获得类似直流电动机的控制效果。通过复合式光电编码器确定永磁同步电动机转子的初始位置,设计了永磁同步电机伺服控制系统的硬件电路。以id-0的矢量控制方法实现了永磁同步电机位置闭环伺服控制,能够满足新型光电设备跟踪控制系统的快速与稳定性要求。     

Bounded consensus tracking of second-order multi-agent systems with sampling delay under directed networks

The bounded consensus tracking problems of second-order multi-agent systems under directed networks with sam- pling delay are addressed in this paper. When the sampling delay is more than a sampling period, new protocols based on sampled-data control are proposed so that each agent can track the time-varying reference state of the virtual leader. By using the delay decomposition approach, the augmented matrix method, and the frequency domain analysis, necessary and sufficient conditions are obtained, which guarantee that the bounded consensus tracking is realized. Furthermore, some numerical simulations are presented to demonstrate the effectiveness of the theoretical results.     

Approximation-error-ADP-based optimal tracking control for chaotic systems with convergence proof

In this paper, an optimal tracking control scheme is proposed for a class of discrete-time chaotic systems using the approximation-error-based adaptive dynamic programming （ADP） algorithm. Via the system transformation, the optimal tracking problem is transformed into an optimal regulation problem, and then the novel optimal tracking control method is proposed. It is shown that for the iterative ADP algorithm with finite approximation error, the iterative performance index functions can converge to a finite neighborhood of the greatest lower bound of all performance index functions under some convergence conditions. Two examples are given to demonstrate the validity of the proposed optimal tracking control scheme for chaotic systems.     

采用栅格特征及可视化技术感知跟踪中目标的遮挡状态

针对监控视频中运动目标跟踪问题,提出了一种栅格划分的梯度朝向直方图特征对目标进行描述,并通过可视化技术来实时观测目标局部区域特征量的变化,通过变化来感知目标在运动中可能发生的遮挡等异常情况.利用感知到的状态自适应调整参加融合计算的子模板的个数,指导跟踪过程,以防止异常情况对跟踪结果的影响,实现了对视频目标准确、稳健的跟踪.实验结果表明,提出的目标局部特征能够较准确地感知目标及周围环境发生的变化,对于提高跟踪算法的鲁棒性和准确性具有积极的作用.     

基于形态学与遗传粒子滤波器的红外小目标检测与跟踪算法

针对复杂背景下红外小目标的检测与跟踪,提出了一种融合了top-hat算法、遗传算法以及粒子滤波器的新方法.该方法首先采用提取副帧的方法去除目标周围部分的背景和噪音,有效地减少了参与运算的像素数目;其次,将具有不同边缘特性的多个结构体应用于top-hat检测算法中,提高了副帧中预目标的有效性;接着,利用目标时空运动的相关性,结合阈值判断来去除虚假目标,增强了目标检测的可靠性;最后,将遗传算法引入粒子滤波算法,较好地改善了粒子的多样性,在保障跟踪实时性的同时,提高了粒子滤波的准确度.实验结果表明,该算法在检测准确度、跟踪准确度和鲁棒性都具有一定的优越性.     

分层次提高高中生物理自主学习能力的策略研究

基于当前理科课时少,内容多的矛盾,许多学校采取了自主学习模式嵌入传统教学模式中.然而,自主学习模式的有效性推进是个难点.笔者通过三年的实践探索,研究出了分层次提高学生物理自主学习能力的策略,能使自主学习模式得到更好地发挥.     

一种结合室内空间剖分的声线跟踪法

声线跟踪法是应用于室内声场预测的几何声学模拟经典方法之一,但该方法的计算效率随着室内空间布局复杂度的增加而降低。为了高效地应用于各种室内空间布局,提出了一种结合室内空间剖分的声线跟踪法,该方法将整个室内空间剖分成有限个凸多面体子空间,以减少在声线跟踪过程中与声线求交点的墙面数量,并省略了碰撞点有效性判断,显著提高了计算效率,尤其适用于大型复杂的室内空间布局。