试论网络时代高校大学生思想教育工作的机遇与困惑

随着计算机和通讯技术的迅猛发展,人类社会开始全面迈进网络时代.互联网作为信息传播的新媒体,不仅为高校大学生思想教育工作提供了丰富的信息来源和快捷的传播方式,拓展了教育空间,使教育工作更趋人性化,同时在舆论导向、价值取向、民族文化传承、学风建设等方面也给高校大学生思想教育工作带来了严峻的的挑战和困惑.     

读书的经济学分析与对策

文章分析了当前读书无用论的成因,包括学费过高、就业形势不好、工作待遇不高等现象,指出教学实用性不强是形成这一现象的原因,并且提出了一些解决措施,如加大科研投入和提高对研究开发的重视程度,让知识分子有用武之地,提高教学质量,加大教育投入,通过社会保障来调节工作待遇.     

基于CAN总线的星载软件测试系统设计

对基于CAN总线的星载软件测试系统设计进行了研究。系统硬件包括PXI工控机和CAN高速板卡,应用LabVIEW编程模拟各下位机,实现了与星载软件的通信,具有下位机的状态检测、遥测数据分析、注数数据监测和计算机内存下卸等功能。实际应用表明:该基于CAN总线的星载软件测试系统满足第三方测试要求,运行稳定可靠。     

Minimum sliding mode error feedback control for fault tolerant small satellite attitude control

This paper proposes a new control strategy (which we call “minimum sliding mode error feedback control, MSMEFC”) for small satellite attitude control. As we know, the attitude control algorithm plays a significant role in the whole performance of the satellite, especially under the existence of uncertain disturbances from the space. Without loss of generality, the MSMEFC is presented based on the sliding mode theory. It is assumed that the equivalent control error is defined to offset the uncertain disturbances to improve the control performance. Hence, in order to estimate the optimal equivalent control error, a cost function is derived on the basis of the principle of minimum sliding mode error. Then, the equivalent control error wills feedback to the conventional sliding mode control to obtain the final MSMEFC. According to the theoretical analyzes, the sliding mode after the MSMEFC will approximate to the ideal sliding mode, resulting in enhancing the control performance. Moreover, an adaptive non-singular terminal sliding mode is employed to compare with the performance of MSMEFC. Several simulations are performed to verify the effectiveness of proposed MSMEFC in the presence of serious perturbations, even in some fault-tolerant scenarios.     

Leading-edge flow separation control over an airfoil using a symmetrical dielectric barrier discharge plasma actuator

In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode excitation, an experimental investigation of an SC(2)-0714 supercritical airfoil with a symmetrical DBD plasma actuator was performed in a closed chamber and a low-speed wind tunnel. The plasma actuator was mounted at the leading edge of the airfoil.Time-resolved Particle Image Velocimetry(PIV) results of the near-wall region in quiescent air suggested that the symmetrical DBD plasma actuator could induce some coherent structures in the separated shear layer, and these structures were linked to a dominant frequency of f0= 39 Hz when the peak-to-peak voltage of the plasma actuator was 9.8 kV. In addition, an analysis of flow structures without and with plasma actuation around the upper side of the airfoil at an angle of attack of18° for a wind speed of 3 m/s(Reynolds number Re = 20000) indicated that the dynamic process of leading-edge flow separation control over an airfoil could be divided into three stages. Initially, this plasma actuator could reinforce the shedding vortices in the separated shear layer. Then, these vortical structures could deflect the separated flow towards the wall by promoting the mixing between the outside flow with a high kinetic energy and the flow near the surface. After that, the plasma actuator induced a series of rolling vortices in the vicinity of the suction side of the airfoil, and these vortical structures could transfer momentum from the leading edge of the airfoil to the separated region, resulting in a reattachment of the separated flow around the airfoil.     

放宽静稳定度飞机时间延迟稳定边界

针对飞机初步设计阶段其放宽静稳定度（RSS）与电传飞控系统时间延迟边界之间的定量关系求解问题，以战斗机纵向短周期方程为基础，分析了飞控系统中的时间延迟因素，描述了放宽静稳定度与方程参数间的关系。并以等效输入延迟的形式构建了含飞控系统时间延迟的闭环系统特征方程，通过根轨迹趋势理论和数值计算方法确定了放宽静稳定度与飞控系统时间延迟边界的定量数值关系，同时探讨了舵效与动导的参数不确定性对所求时间延迟边界的影响。本文方法对飞机初步设计阶段飞控系统时间延迟指标和可放宽静稳定度边界的确定具有一定的工程实践意义。     

基于学习的中段反导拦截时间和拦截点预测方法

弹道导弹实时、准确地预测拦截弹的拦截点与拦截时间，是实现中段突防的有效手段。针对弹道导弹中段突防中的拦截点坐标及拦截时间的预测问题，提出了一种基于监督学习的在线预测方法。以拦截弹的主动段关机参数和关机时刻为输入量，建立拦截时间和拦截点预测模型。在多层感知机神经网络的基础上构建有监督学习算法，通过攻防仿真获取拦截弹的参数制作训练数据集，在线下完成网络训练。仿真结果表明:神经网络能够有效在线预测拦截时间和拦截点坐标，预测结果的相对误差分别为0.124 3%和0.128 5%，拦截时间预测结果误差的平均值为0.224 0 s，拦截点预测结果距离误差平均值为2 016.48 m，均满足精度要求。      

水陆两栖飞机静力试验优化机翼变形的载荷配平

水陆两栖飞机全机静力试验的浮筒着水工况试验中，在试验允许的常规载荷配平方案下，压向大量级水载荷作用于浮筒结构引起机翼较大变形，影响试验精度，因此进行以减少机翼变形为目标的载荷配平研究。将机翼近似为悬臂梁结构，在构建的机翼力学模型基础上应用Green函数建立机翼的挠度曲线方程。首次以考核区域边界肋的挠度和转角为优化目标并建立多目标函数，通过层次分析法和极差变换标准化处理方法将其转化为单目标函数后，采用引入交叉和变异因子的改进蚁群算法进行载荷配平方案优化运算。有限元分析及试验结果显示，优化得到的载荷配平方案可以显著地减少机翼变形，配平载荷不影响考核区域的真实变形，证明了该优化方案的正确性和可行性。     

基于微分进化算法的二自由度PID控制器参数优化

针对二自由度PID控制器参数多、调节困难等问题,提出了一种基于微分进化算法参数调节优化方法。证明了微分进化算法能够收敛到平稳点,并具有概率全局收敛性。研究了二自由度PID控制器参数与抑制特性、跟踪特性的关系,并将微分算法与遗传算法、粒子群算法的参数优化结果进行了比较。仿真验证表明,微分算法能够更好地实现二自由度PID控制器参数的调节,具有优异的跟踪特性和抑制特性。     

弹射救生系统大迎角大侧滑角气动特性工程计算方法研究

对弹射救生系统的气动特性进行了分析,发展了一套快速获取其气动特性的工程计算方法,并对某战斗机弹射救生系统的大迎角大侧滑角气动力特性进行了计算.结果表明,工程计算结果与风洞试验数据一致性良好.