复杂运动目标ISAR成像技术进展与展望

逆合成孔径雷达成像是宽带雷达实现目标信 息获取和精细描述的重要途径,但在成像过程中存在复杂运动导致散焦和成像分辨率不高两 个难题。针对目标复杂运动导致成像散焦问题,本文总结了微动对雷达波调制、进动目标成 像、 三维运动成像、分离部件成像等技术现状;针对成像分辨率不高问题,分析了多频段宽带回 波相参配准、融合成像等技术进展。本文介绍了雷达成像新技术,为解决上述两个难题带来 新的思路和途径,其中,雷达关联成像不依赖于雷达与目标的相对运动,可避免成像的复杂 运动补偿;太赫兹雷达成像容易实现大带宽和窄波束,获得目标精细雷达像。最后对新兴技 术的难点和发展趋势进行了展望。     

基于双天线GNSS/SINS组合的风速测量运动补偿方案设计

以基于浮标平台的动态风速测量为背景,根据运动姿态补偿的原理和实际需要,设计了一套双天线GNSS/SINS组合姿态测量系统,采用卡尔曼滤波实现信息融合,通过在卡尔曼滤波的观测量中引入双天线GNSS输出的航向角信息,解决了惯性系统航向角可观测性较弱的问题,并通过实验验证了系统的有效性。实验结果表明,该运动补偿设计方案能够提高平台姿态测量的精度和稳定性,准确测量平台的姿态信息,并有效降低平台运动对风速测量的影响,风速测量误差低于4%,满足了海洋浮标观测的需求。     

A visual study on flame behavior in tone-excited non-premixed jet flames

A visualization study on the effect of forcing amplitude in tone-excited jet diffusion flames has been conducted. Visualization techniques are employed using optical schemes, which are a light scattering photography. Flame stability curve is attained according to Reynolds number and forcing amplitude at a fuel tube resonant frequency. Flame behavior is globally grouped into two from attached flame to blown-out flame according to forcing amplitude; one sticks the tradition flame behavior which has been observed in general jet diffusion flames and the other shows a variety of flame modes such as the flame of a feeble forcing amplitude where traditionally well-organized vortex motion evolves, a fat flame, an elongated flame, and an in-burning flame. Particular attention is focused on an elongation flame, which is associated with a turnabout phenomenon of vortex motion, and on a reversal of the direction of vortex roll-up. It is found that the flame length with forcing amplitude is the direct outcome of the evolution process of the formed inner flow structure. Especially the negative part of the acoustic cycle under the influence of a strong positive pressure gradient causes the shapes of the fuel stem and fuel branch part and even the direction of vortex roll-up to dramatically change.     

Controlling aliased dynamics in motion systems? An identification for sampled-data control approach

Sampled-data control systems occasionally exhibit aliased resonance phenomena within the control bandwidth. The aim of this paper is to investigate the aspect of these aliased dynamics with application to a high performance industrial nano-positioning machine. This necessitates a full sampled-data control design approach, since these aliased dynamics endanger both the at-sample performance and the intersample behaviour. The proposed framework comprises both system identification and sampled-data control. In particular, the sampled-data control objective necessitates models that encompass the intersample behaviour, i.e., ideally continuous time models. Application of the proposed approach on an industrial wafer stage system provides a thorough insight and new control design guidelines for controlling aliased dynamics.     

Explicit solution of relative entropy weighted control

We consider the minimization over probability measures of the expected value of a random variable, regularized by relative entropy with respect to a given probability distribution. In the general setting we provide a complete characterization of the situations in which a finite optimal value exists and the situations in which a minimizing probability distribution exists. Specializing to the case where the underlying probability distribution is Wiener measure, we characterize finite relative entropy changes of measure in terms of square integrability of the corresponding change of drift. For the optimal change of measure for the relative entropy weighted optimization, an expression involving the Malliavin derivative of the cost random variable is derived. The theory is illustrated by its application to several examples, including the case where the cost variable is the maximum of a standard Brownian motion over a finite time horizon. For this example we obtain an exact optimal drift, as well as an approximation of the optimal drift through a Monte-Carlo algorithm.     

基于十二烷基衣康酸甘油酯的光电双响应传感器

该文制备了一种利用结构色水凝胶作为导电电极的光电双响应传感器。以十二烷基衣康酸甘油酯(DGI)、丙烯酰胺、十二烷基硫酸钠(SDS)、氯化钠等为原料,通过双分子层自组装的方法,制备了结构色水凝胶。将这种结构色水凝胶与传统电容型传感器相结合,得到了光电双响应传感器。采用SEM、LCR数字电桥、拉力试验机、光纤光谱仪等对器件进行了结构、光学、电学及机械性能的表征。结果表明:传感器在拉伸状态(0～100%)和压缩状态(0～60.9k Pa)下,传感器的电容分别变化了31%和44%,其自身颜色在可见光光谱内可以动态可逆地从红色变化到紫色。经历15000次循环拉伸后,传感器性能依旧保持稳定。利用传感器颜色的刺激响应性,传感器在发生形变时,其表面可以清楚地显示出应变源的位置和形状,这样传感器在检测时就可以实现可视化效果。     

探究Flash CS6之“创建补间动画”

随着Flash软件版本的不断升级,传统的一些功能也有了颠覆性的改变。2013年底在建设课题《艺术设计网络辅助教学平台的开发研究》(项目编号12535201)过程中,为《Flash动画制作》网络课程录制微课视频时,比平时执教中更深切地体会到了这一点。其中感触最深的就是"动作补间动画"的全新突破。本文从老版本与新版本的使用对比,最终得出结论,是执教者的经验总结。     

基于半监督距离学习的运动相似性度量算法

人体运动捕获技术的发展使得运动捕获数据不断积累,人体运动的检索技术成为运动数据管理和重用过程中的关键环节。由于逻辑相似的运动在数值上并不一定相似,使用欧式距离度量2个运动间的逻辑相似性难以取得理想的结果。为此,提出一种半监督的距离度量学习算法,利用带标记的运动和未标记运动进行训练以得到运动间的马氏距离度量,从而判断2个运动之间的逻辑相似性,实现运动检索。实验结果表明,与现有的大部分检索算法相比,该算法能够得到更高的查询精度,且没有任何人工干预,可应用于自动检索领域。     

采用截面流量统计的高密度人群行人计数

利用摄像头实现行人计数在智能视频监控领域有着重要的价值,但是行人互相遮挡、噪声、摄像机透视效果和图像背景等问题影响了人群计数的准确性.针对高密度人群场景的行人计数准确率的问题,提出了基于截面流量统计的行人计数方法,该方法基于梯度运动历史图像检测前景,并用有效运动图像改进了基于特征提取的行人计数方法,结合运动速度提取方法实现了行人计数.实验结果表明,提出的计数方法在高密度人群场景中具有较高的准确率和实时性,是一种针对高密度人群有效的行人计数方法.