Constructing G~2 Continuous Curve on Freeform Surface with Normal Projection

This article presents a new method for G～2 continuous interpolation of an arbitrary sequence of points on an implicit or parametric surface with prescribed tangent direction and curvature vector,respectively,at every point.First,a G～2 continuous curve is constructed in three-dimensional space.Then the curve is projected normally onto the given surface.The desired interpolation curve is just the projection curve,which can be obtained by numerically solving the initialvalue problems for a system of first-order ordinary differential equations in the parametric domain for parametric case or in three-dimensional space for implicit case.Several shape parameters are introduced into the resulting curve,which can be used in subsequent interactive modification so that the shape of the resulting curve meets our demand.The presented method is independent of the geometry and parameterization of the base surface.Numerical experiments demonstrate that it is effective and potentially useful in numerical control (NC) machining,path planning for robotic fibre placement,patterns design on surface and other industrial and research fields.     

一种矩形件优化排样算法的研究

针对在具有一定长宽尺寸的板材上进行矩形件排样的问题,结合遗传算法,设计了一种矩形件优化排样算法。该算法考虑到排样高度不超过板材长度的要求,可以实现换板,使剩余待排矩形件在新板材上继续排放。通过算例验证了该算法的有效性和合理性。     

一种精确计算航天器本体对太阳电池阵遮挡的方法

针对航天器太阳电池阵电设计和热设计中需要准确考虑阴影影响的问题,提出了一种可以精确计算太阳电池阵阴影的方法。首先使用三角网格来建立3D模型,其次考虑了航天器本体构件间的相对运动,然后用一个“包围盒”去截取模型上的三角网格点,再把这些点投射到太阳电池阵上,最后把太阳电池阵分成小方格,分别使用逐点比较法和最小矩形法来生成阴影图形。给出了月球车遮挡计算的实例,仿真分析表明生成阴影图形时,最小矩形法具有更高的速度。使用本文所述的方法,可计算结构复杂、构件间有相对运动的航天器本体对太阳电池阵造成的遮挡,能生成精确的阴影图形,为后续计算受遮挡的太阳电池阵的输出特性奠定了基础。     

基于弹丸直径和速度的靶板击穿判据

文章提出了基于弹丸直径和速度的靶板毁伤二次函数模型,其特点是毁伤函数的正值意味着靶板已被击穿,其负值意味着靶板未被击穿;还推导出了用试验数据确定靶板毁伤函数的方法,通过令该毁伤函数为0而得到了基于弹丸直径和速度的靶板击穿判据,并给出了作为靶板击穿判据的曲线形状辨识方法;最后,用一组模拟数据验证了该方法的实现过程,证明了该方法的可行性。     

改进的EMD方法在车辆振动信号提取中的应用(英文)

为了能在强噪声背景下准确地进行振动信号的特征提取,对经验模式分解进行了研究和改进,并将其应用于车辆振动信号的特征提取中。首先对系统中各输入信号进行了多次自相关处理,有效地降低信号中的噪声。然后对处理的信号进行经验模式分解,得到了各固有模态函数分量。最后对感兴趣的固有模态函数分量进行希尔伯特变换和谱分析,从而得到信号的特征信息。仿真和试验分析说明了改进的经验模式分解方法的可行性,并且对同类工程问题具有一定的参考价值。     

O2 evolution and cyclic electron flow around photosystem I in long-term ground batch culture of Euglena gracilis

Based on the purpose of better exploring the function of green producers in the closed aquatic biological life support system, the condition of dynamic O₂ evolution and performance of cyclic electron flow around photosystem I (CEF-PSI) in long-term ground batch culture of Euglena gracilis were studied, the relationship between linear electron flow (LEF) and CEF-PSI was revealed, the function of CEF-PSI was investigated. Excellent consistency in O₂ evolution pattern was observed in cultures grown in both closed and open containers, O₂ evolution was strictly suppressed in phase 1, but the rate of it increased significantly in phase 2. CEF-PSI was proposed to be active during the whole course of cultivation, even in the declining phase 3, it still operated at the extent of 47–55%. It is suggested that the relationship between LEF and CEF-PSI is not only competition but also reciprocity. CEF-PSI was proposed to contribute to the considerable growth in phase 1; it was also suggested to play an important protective role against photosystem II (PSII) photoinhibition at the greatly enhanced level (approximately 80–95%) on the 2nd day. Our results in this research suggest that E. gracilis had very particular photosynthetic characteristics, the strict O₂ evolution suppression in the initial culture phase might be a special light acclimation behavior, and CEF-PSI could be an important mechanism involved in this kind of adaptation to the changeable light environment.     

非对称转捩对横向偏离稳定的影响

为研究非对称转捩对横向偏离稳定的影响,采用指定位置的强制转捩方法,对典型升力体外形进行非对称转捩的的数值模拟,包含全层流、全湍流及斜线转捩情况的计算与分析,得到非对称转捩对横向偏离稳定性影响的结论。结果表明：极端转捩会使飞行器航向稳定性变差,斜线转捩甚至会使飞行器航向稳定性的极性发生改变。     

同轴喷嘴自发激励高频燃烧不稳定性试验研究

为增进对液氧煤油火箭发动机同轴离心喷嘴燃烧不稳定性过程的理解,在大气环境下进行了同轴离心喷嘴的自发激励燃烧不稳定性试验。试验采用单喷嘴敞口模拟燃烧室,高温的氧气和空气混合物从同轴喷嘴的直流喷嘴喷注,高温的煤油蒸气从同轴喷嘴的离心喷嘴喷注。通过逐步改变氧化剂流量使模拟燃烧室内产生自发激励高频燃烧不稳定性,使用脉动压力传感器和黑白高速相机记录稳定和不稳定燃烧工况下的脉动压力和火焰。研究发现：气气同轴离心喷嘴的自发激励高频燃烧不稳定过程呈现“滞后”现象;不稳定工况下的火焰均为脱口火焰,火焰特征长度约等于喷嘴出口到脱口火焰团上沿的距离;气气同轴离心喷嘴燃烧不稳定性的发生原因可以被认为是因混合特征时间与声学特征时间相关。     

基于形态学的多级滤波背景抑制算法

传统的形态学单一结构元素,对云杂波背景滤波常留下强云层边缘及类似于目标的噪声,增加了后续处理的复杂程度.针对这一问题,提出了一种多级滤波思想.采用不同方向的线性结构元素进行形态学滤波,通过滤波尽可能准确地保留图像背景,然后与原图差分,将得到的图像再用矩形结构元素进行形态学开运算.仿真结果表明,该算法对云杂波背景抑制效果好,提高了图像的信噪比.     

数据链人机界面设计及仿真

随着现代空中交通控制技术的发展,数据链的应用逐渐显得更为重要。然而,数据链应用的有效性是个重要问题。为了满足飞行任务实时性的要求,必须考虑人机界面,特别在CPDLC(Controller Pilot Data Link Communication)通信中。本文采用面向任务的设计思想,对指令进行分类整理,通过综合人机界面显示单元的设计来实现数据链(Data link)人机界面的仿真设计。