摘要：In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi-body dynamics, considering the gravitational forces of the Sun, Earth, and Moon. It is proposed that an electric-propulsion spacecraft initially parking in a circular 200-kin-altitude low Earth orbit is expected to rendezvous with an asteroid and carry as much sample as possible back to the Earth in a 10-year time frame. The team from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences has reported a solution with an asteroid sample mass of 328 tons, which is ranked first in the competition. In this article, we will present our design and optimization methods, primarily including overall analysis, target selection, escape from and capture by the Earth-Moon system, and optimization of impulsive and low-thrust trajectories that are modeled in multi-body dynamics. The orbital resonance concept and lunar gravity assists are considered key techniques employed for trajectory design. The reported solution, preliminarily revealing the feasibility of returning a hundreds-of-tons asteroid or asteroid sample, envisions future space missions relating to near-Earth asteroid exploration.

摘要：为了研究民机侧壁板结构抗鸟撞性能,基于Abaqus建立了航空铆钉动态弹塑性损伤模型,并通过模拟铆钉动态加载试验、民机侧壁板鸟撞试验和仿真分析,研究了铆钉紧固件动态模型的准确性和民机侧壁板的鸟撞动态响应。结果表明:民机侧壁板结构鸟撞冲击下主要表现为铆钉紧固件的大量破坏导致加强肋脱离。结构纵框、加强肋和蒙皮均未出现撕裂破坏。基于Abaqus的铆钉动态弹塑性损伤模型能够很好地描述其动态加载下的应变率强化效应,能够较为准确地模拟拉剪耦合加载下的损伤破坏行为,并且应用该模型能够准确模拟鸟撞冲击下铆钉紧固件的失效形式,从而获得与试验较为一致的应变结果;可见该铆钉模型能够为民机结构抗鸟撞问题研究提供基于Abaqus的铆钉紧固件建模方法。

摘要：In order to improve the utilization rate of foam,an arc jet nozzle was designed for precise dust *** theoretical analysis,the different demands of foam were compared amongst arc jets,flat jets and full cone jets when the dust source was covered identically by *** is proved that foam consumption was least when an arc jet was *** production capability of an arc jet nozzle under different conditions was investigated through *** results show that with the gas liquid ratio(GLR)increasing,the spray state of an arc jet nozzle presents successively water jet,foam jet and *** a reasonable working condition range of foam production and a fixed GLR,foam production quantity increases at first,and then decreases with the increase of liquid supply *** the inner diameter of the nozzle is 14 mm,the best GLR is 30 and the optimum liquid supply quantity is0.375 m^3/*** results of field experiments show that the total dust and respirable dust suppression efficiency of arc jet nozzles is 85.8%and 82.6%respectively,which are 1.39 and 1.37 times higher than the full cone nozzles and 1.20 and 1.19 times higher than the fiat nozzles.

摘要：针对航天器燃料最优可变周期绕飞轨迹的求解问题,提出了一种以推力幅值为延拓参数的延拓方法.问题求解从最为简单的双脉冲绕飞轨迹出发,首先利用有限推力替代脉冲推力,设定推力序列为"开—关—开",然后逐步减小推力幅值,最终得到最小推力绕飞轨迹;此后,再逐步增加推力幅值,结合主矢量曲线判断最优推力开关序列,将最小推力解延拓至有限推力以及脉冲推力燃料最优解.该方法通过对推力幅值的延拓,实现了有限推力bang-bang控制与脉冲推力燃料最优绕飞轨迹优化问题的一并求解,同时避免了最优控制问题中协态变量的随机猜测.慢速与快速绕飞算例的优化结果验证了所提出方法的有效性.

摘要：为实现卷积混合信号的盲分离,提出了一种基于斜投影的子空间方法,首先设计"过去"、"现在"和"未来"的观测数据空间,并通过斜投影将卷积混合转化成为线性瞬时混合;然后采用静态分离算法重构源信号。该方法利用了观测数据矩阵的结构信息直接获得线性瞬时混合的数据模型,不需要进行高维子空间代价函数的优化,运算量相对小。计算机仿真验证了算法的有效性。

摘要：当前的程序设计都是人工设计执行流程,这种方法具有被动性、机械性、缺乏灵活性等缺点。提出一种基于强化学习的程序设计机制,并实现了相应的算法。根据环境情况和问题要求让计算机自主选择执行流程,通过学习使结果达到最优,同时能实现分层调用。采用这种方法,程序执行可以自主决策,较好地实现了自适应,减少了对设计者的依赖。结果显示,这种方法能取得较好的运行效率。

摘要：A method of predicting design pressure and burn-through of in-service welding pipes was established. Temperature distributions of in-service welding under variable parameters were simulated by FEM. The effect of flowing of internal media was regarded as forced convection. Based on the numerical results, design pressure of the pipe can be obtained and burn-through can be predicted. It can be concluded that the design pressure decreases with the increasing of heat input. RSF and design pressure of the pipe increase with the increasing of flow rate. There is a range in which the increase changes greatly. For in-service welding, the range should be considered adequately to determine operating condition optimally. RSF increases with the increasing of pipe wall thickness. While the thickness increases to an extent, RSF shows little increase. Accord- ing to the curves of design pressure versus different parameters, safe working pressure can be achieved.

摘要：实时服装动画生成技术能够为三维虚拟角色实时地生成逼真的服装动态效果,在游戏娱乐、虚拟服装设计展示等领域有着广泛的应用前景.其难点在于如何建立服装动画计算模型,在实时计算的前提下获得最佳的服装动画生成效果.在对服装模型与人体模型在运动过程中发生的位置冲突(collision,也称碰撞)进行分析的基础上,研究并提出了一种基于混合模型的实时虚拟人服装动画计算模型.首先,根据服装动画样本数据中服装与人体发生位置冲突的信息,对服装与人体的运动相关性进行分析;在此基础上,提出并实现一种新的混合策略,将具有较好服装动态模拟效果的动力学计算模型与具有较高计算效率的几何变形方法进行混合,建立支持实时计算且效率可动态控制的服装动画计算模型.实验结果表明,该计算模型能够实时地生成具有较好视觉逼真性的服装动画.

摘要：冲突检测是人体-服装动画研究的核心技术之一,已有的层次冲突检测方法在处理服装变形时需要对层次节点进行大量更新,计算复杂度高,难以满足实时检测的要求.针对人体和服装的特殊位置关系和运动规律,提出一种基于双层候选集的实时冲突检测方法.首先为服装模型的每个顶点建立可能发生位置冲突的人体模型面片候选集,利用候选集的母子双层结构剔除绝大多数不可能发生冲突的图元.该候选集相对于已有的层次方法具有更快的更新速度且具有较好的独立性,便于并行处理;在确定可能冲突的图元后,采用GPU片段程序来加速大规模图元间的相交测试.实验结果表明,该方法检测迅速准确,对一般人体-服装模型(10000面以下)能达到30～75帧/s的实时处理.

摘要：针对我国玉米收获机智能化水平较低,玉米收获机参数的调节多通过机械操纵杆,玉米收获时含水率较高,高含水率玉米收获籽粒破碎率和夹带损失率较高等问题,对国内某纵轴流籽粒收获机进行了智能化改装,并设计了基于CAN总线的高含水率玉米低损脱粒智能控制系统。根据玉米收获机工作过程的需要,设计了手动控制和自动控制两种控制模式,提出了自动控制策略,并结合离散化PID控制算法实现了高含水率玉米低损脱粒。对系统进行了控制策略测试和田间试验,系统测试结果表明,各工作参数可按控制策略调节并稳定在设定的阈值内;田间试验结果表明,在高含水率玉米收获时,本系统可使籽粒破碎率和夹带损失率达到国家标准要求,其中籽粒破碎率最低为3.35%,最高为4.05%,平均为3.75%,夹带损失率最低为1.56%,最高为2.08%,平均为1.77%。