星舰-超重体系与开发的范式变革探究

为了梳理和分析星舰-超重体系与开发的模式,及其相比以往航天运输体系的变革,本文首先回顾星舰-超重的宏观演化与微观验证历程,而后评估基于星舰-超重的太空新物流体系优势与挑战,最后探讨资本驱动下航天运输系统价值网升维与开发范式变革的内在逻辑。研究发现:星舰-超重的开发理念是“创新引领,市场运作;宏观演化,微观验证”,本质是资本内在增值需求推动新技术、新平台的快速集成和应用。     

A novel method for solving shortest tool length based on compressing 3D check surfaces relative to tool postures

Solving the shortest tool length quickly under a known tool trajectory in multi-axis machining of complex channel parts is an urgent problem in industrial production. To solve this problem, a novel and efficient method is proposed which is featured by extracting only a few necessary curves from the check surface instead of sampling the entire surface. By rotating and compressing the 3D check surface relative to all tool postures, the boundaries of the area occupied by the 2D compressed surfaces are the essential elements for determining the shortest tool length. A tracking-based numerical algorithm is introduced to efficiently solve the silhouette curves which are formed in compressing. To define the multi-taper shaped tool holding system (THS) which is commonly used in production, a characterization model for THS profile is established. A model for solving the shortest tool length is finally constructed based on the critical interference relationship between the THS profile and all compressed boundary curves. For acceleration, the boundary splines are segmented according to their knot vectors. Then a new concept called the axis-aligned tool length box (AATB) is introduced, which can provide a conservative range of tool length for a spline segment. By scanning the AATBs of all spline segments, the very few effective spline segments that may ultimately determine the shortest tool length are filtered out. This acceleration method makes the solution for the shortest tool length more focused and efficient. The results of experimental examples are also reported to validate the efficiency and accuracy of the proposed algorithm.     

柱面气相散心爆轰波胞格演化规律研究

本文采用二阶精度NND格式,应用改进的二阶段化学反应模型,通过求解二维Euler方程对柱面气相散心爆轰波胞格演化过程进行了数值模拟.计算结果表明在传播过程中,空间尺度的扩张导致了散心爆轰波后气流的自然膨胀,使得多波结构的爆轰阵面呈现出显著的胞格自组织特性.根据计算结果与理论分析,本文归纳了五种胞格演化模式,分别命名为内凹波阵面会聚、波阵面扭结、褶皱波面失稳、胞格自合并和三波点滑移,并定义了各种模式的物理特征,分析了其相关的演化机制和规律.     

一种改进的地形轮廓预测匹配辅助导航算法

传统的地形轮廓匹配 (TERCOM )辅助导航系统 ,由于其实时性差 ,已不能满足飞行器超低空高速的导航需要。本文引入预测控制的思想 ,提出了一种基于高度特征的地形轮廓预测匹配方法 ,减少了计算量 ,提高了导航系统的实时性和机动性。     

直面未来挑战——德国空军训练变革情况介绍

介绍了德刚空军未来任务能力对其训练发展提m的新要求，分析了德刚空军训练机构的编制体制变革，详细阐述了其训练体制新发展，最后对其变革方向进行了总结。     

基于双目视觉的多型号电连接器检测技术

通过双目视觉平台捕获图像反馈PC机,采用基于支持向量机（SVM）的机器学习方法对目标进行分类。判定型号并为每个型号加载图像处理检测方案及参数矩阵,实现电连接器针脚的柔性定位预处理,之后执行针顶轮廓的精确拟合算法,结合插针排列模版实现其三项检测工作。最后,通过实例验证与重复精度实验,结果表明本文方法具备面向多型号的柔性检测能力,并且稳定性,精度,效率满足低频连接器的检验要求。     

用于原木材积检测的图像处理与分析算法

基于原木材积自动化检测系统的检测原理,研究并设计了关键的图像处理与分析算法.针对原木端面为类圆形状这一特点,对其进行Hough变换,然后结合数学形态学中的骨架提取算法,在骨架极值对应的最大圆盘中搜索Hough变换的峰值,使每一峰值对应一个原木端面,从而实现了原木端面图像的粗略分割.将活动轮廓模型变换到极坐标系中,以梯度的极值作为端面轮廓的候选点,可以利用动态规划法来获得能量泛函的全局极值,从而实现了精确提取端面轮廓.实验结果表明所提出的算法具有实用性.     

Tool wear during high speed turning in situ TiCp/TiBw hybrid reinforced Ti-6Al-4V matrix composite

Chipping, adhesive wear, abrasive wear and crater wear are prevalent for both the polycrystalline diamond(PCD) and the carbide tools during high speed turning of TiC_p/TiB_w hybrid reinforced Ti-6Al-4V(TC4) matrix composite(TMCs). The combined effects of abrasive wear and diffusion wear caused the big crater on PCD and carbide tool rake face. Compared to the PCD, bigger size of crater was found on the carbide tool due to much higher cutting temperature and the violent chemical reaction between the Ti element in the workpiece and the WC in the tool.However, the marks of the abrasive wear looked much slighter or even could not be observed on the carbide tool especially when low levels of cutting parameters were used, which attributes to much lower hardness and smaller size of WC combined with more significant chemical degradation of carbide. When cutting TC4 using PCD tool, notch wear was the most significant wear pattern which was not found when cutting the TMCs. However, chipping, adhesive wear and crater wear were much milder when compared to the cutting of titanium matrix composite. Due to the absence of abrasive wear when cutting TC4, the generated titanium carbide on the PCD protected the tool from fast wear, which caused that the tool life for TC4 was 6–10 times longer than that for TMCs.     

An improved sea level retrieval method using the differential evolution of GNSS SNR data

This paper presents an improved new method with differential evolution and the cubic spline approach is proposed to retrieve sea level height based on GNSS SNR observations from a single geodetic receiver. Considering the B-spline function is unstable at the beginning or end, and the feature that B-spline functions do not pass through nodes may introduce errors. Thus, the cubic spline is applied to the retrieval process and accounts for a continuous and smooth in sea level retrieval time series. Besides, the biases caused by tropospheric delay and dynamic sea level are considered and corrected. Testing data from two stations with different tidal range and the final solution agrees well with measurements from co-located tide gauges, reaching the RMSE of 3.67 cm at Friday Harbor, Washington, and 1.36 cm at Onsala, Sweden. Comparison of the nonlinear least squares, this method leads to a clear increase in precision of the sea level retrievals within 50%. Additionally, referring to the result of Purnell et al. (2020) and the IAG inter-comparison campaign, the results of this paper show more potential.     

Blasius边界层C－型失稳的理论分析

本文用空间模式的二次失稳理论分析了Ｂｌａｓｉｕｓ边界层转转捩实验￣［１］中Ｃ－型失稳后扰动演化过程。其幅值演化曲线与实验曲线符合较好。