针对机载应用的H.264编码器评估方法

本文针对机载图像实时压缩的应用需求,讨论了一种H.264编码器性能的评估方法.该方法以典型的机载视频画面为测试序列,对编码器设定一组恒定QP值进行编码,将压缩后码流比特率与标准算法对比,评判编码器性能的优劣.通过对三种不同编码器的测试对比,证明了该评估方法的有效性.     

飞行原理实验教学现状调查研究及对策

飞行原理实验教学是飞行技术专业教学工作的重要组成部分.本文对普通高校飞行技术专业飞行原理实验课教学现状进行了问卷调查,分析了目前飞行原理实验课教学存在的问题,并提出了相关的措施与建议.     

一种Ka频段波导微带鳍线转换结构

为使波导微带转换的尺寸和性能更优,采用HFSS高频仿真软件里的样条曲线做波导微带转换的鳍线渐变曲线,使波导微带转换的过渡长度与采用其他渐变曲线在相同指标情况下相比更短一些。转换模型中的介质基片向标准矩形波导宽边两侧延伸四分之一波长并在其上各打一行孔径和间距合适的金属填充通孔,这样既便于固定基片,又能提高鳍线电路的隔离度。使用HFSS软件对该模型进行仿真优化分析后的结果为：在28．5～39GHz频带内得到大于25dB的回波损耗和小于0．1dB的插入损耗,基本达到预期目的。     

数字图像相关方法在土木测试领域中的实验研究

针对传统接触式测试方法(如电测法等)在土木工程领域中的局限性,开展了数字图像相关(Digital image correlation,DIC)方法在该测试领域的应用研究.采用橡胶带的拉伸实验来验证DIC方法的测量精度,具体的实验测试内容包括:基于空域和频域相结合的混合相关法,开展了建筑膜材的双轴拉伸实验,测量了膜材的力学参数;基于仿射变换的相关迭代法,开展了钢管混凝土框架梁柱连接模型的转角测量与分析实验,测量了加强环式连接的弯矩转角关系;基于时间序列DIC和高速摄影成像技术,开展了自由振动状态下拉索模型的动力学参数识别的实验研究.实验结果验证了这一新型检测手段用于测试建筑材料及结构的力学性能的可靠性与精度.     

磁粉检测课程改革的探索

分析磁粉检测课程能力培养目标,明确课程教学目标,提出课程改革的方案,包括实行教学做合一、推行案例教学、改革课程考核方法。     

空间TDICCD相机动态信噪比计算方法研究

信噪比是空间光学相机系统的主要设计指标之一,可用于表征相机的辐射性能。文章通过建立遥感卫星轨道模型,分析计算一年中任意时刻用太阳高度角和卫星观测角描述太阳、卫星、地面目标点之间的相对位置关系,并将计算得到的卫星观测角和太阳高度角等参数导入大气传输软件MODTRAN,输出在相机入瞳处的地面目标光谱辐亮度,再根据信噪比的计算方法,最后完成TDICCD相机动态的信噪比计算值。通过该方法,可以计算任一时刻任一观测目标的信噪比,这将有利于判断在某一时刻的能量是否满足观测要求,以随时改变TDICCD的探测器级数,使得成像像质达到最佳。     

激光参数对光船性能影响分析

采用三温度11组元热化学非平衡空气模型计算了激光能量在等离子体中的沉积过程,并在激光脉冲作用结束8 μs后采用平衡空气模型,完成激光推进光船工作过程的数值模拟,研究了不同入射激光能量和脉冲宽度对光船推进性能的影响。结果表明:当脉冲宽度相同时,入射激光能量越大,所得冲量耦合系数越大;当入射激光脉冲能量相同时,脉冲宽度越小,所得冲量耦合系数越大。将计算所得冲量耦合系数与Schall实验所得结果进行比较,结果非常吻合。     

Earth remote sensing as an effective tool for the development of advanced innovative educational technologies

Current educational system is facing a contradiction between the fundamentality of engineering education and the necessity of applied learning extension, which requires new methods of training to combine both academic and practical knowledge in balance. As a result there are a number of innovations being developed and implemented into the process of education aimed at optimizing the quality of the entire educational system. Among a wide range of innovative educational technologies there is an especially important subset of educational technologies which involve learning through hands-on scientific and technical projects. The purpose of this paper is to describe the implementation of educational technologies based on small satellites development as well as the usage of Earth remote sensing data acquired from these satellites. The increase in public attention to the education through Earth remote sensing is based on the concern that although there is a great progress in the development of new methods of Earth imagery and remote sensing data acquisition there is still a big question remaining open on practical applications of this kind of data. It is important to develop the new way of thinking for the new generation of people so they understand that they are the masters of their own planet and they are responsible for its state. They should desire and should be able to use a powerful set of tools based on modern and perspective Earth remote sensing. For example NASA sponsors “Classroom of the Future” project. The Universities Space Research Association in United States provides a mechanism through which US universities can cooperate effectively with one another, with the government, and with other organizations to further space science and technology, and to promote education in these areas. It also aims at understanding the Earth as a system and promoting the role of humankind in the destiny of their own planet. The Association has founded a Journal of Earth System Science Education. Authors describe an effective model of educational technology developed in the Center for Earth Remote Sensing of Bauman Moscow State Technical University and based on scientific and educational organizations integration in the field of applied studies. The paper also presents how students are being trained to acquire and process satellite imagery data from Terra and Aqua satellites. It also reveals the results of space monitoring for Russia's ecologically complex regions conducted by Bauman Moscow State Technical University students in cooperation with specialists from the Laboratory for Aerospace Methods of Moscow State University named after M. Lomonosov.     

Multi-objective output-feedback control for microsatellite attitude control: An LMI approach

Mixed H₂/H_∞ output-feedback controller with pole placement constraints against the internal uncertainty of moment-of-inertia variation and space environmental disturbances is proposed for mircosatellite attitude control. The multi-objective controller is designed based on linear model of attitude dynamics. The H_∞ performance takes into account both robustness stability against moments-of-inertia uncertainty and the disturbance rejection aspect. H₂ performance takes into account the LQG aspect which avoids the undesirable wheels’ saturation effect. In addition, the closed-loop poles can be forced into some sector of the stable half-plane to obtain well-damped transient responses. The problem is then reduced to a convex optimization involving linear matrix inequalities (LMIs), so it can be efficiently solved. The simulation results demonstrate that the presented mixed H₂/H_∞ control system is robust stable and optimal in the sense of H₂ norm, and has good steady-state and dynamic performances against the parameter uncertainties and various disturbances for the microsatellite attitude control system.     

大跨域条件下的自适应滚转稳定容错控制方法

制导弹药在执行大跨域飞行任务时,其滚转扰动系数随速度、高度和攻角高频大幅值非线性变化,对制导弹药滚转通道稳定性造成了恶劣的影响。此外,时间滞后与控制失效等执行机构动力学特性进一步增加了滚转通道稳定性的控制难度。针对上述问题,设计了一种强鲁棒性的自适应滚转稳定容错控制方法。首先,在考虑执行机构失效动力学特性条件下建立了制导弹药滚转通道的数学模型,将系统不确定性和扰动项视为外部扰动,设计一种基于自适应滑模控制理论的强鲁棒滚转稳定控制方法,以补偿非线性变化项及执行机构失效。在此基础上,进一步考虑了执行机构动力学滞后特性,利用反步法设计了一种考虑执行机构动力学的控制方法,以补偿执行机构动力学滞后特性,提高弹体的响应速度。仿真结果表明所设计控制方法对气动扰动有较强鲁棒性以及在故障处理方面的优势。