跨声速风洞斜孔壁非线性流动试验

为分析跨声速风洞斜孔壁近壁区域的流动特性，评估气流偏角-压力系数的非线性关联，在0.6 m跨超声速风洞中开展了基于七孔探针的流动特性测量试验。通过气流偏角和压力系数分布分析了斜孔壁流动的差阻特性，以及马赫数、模型升力对斜孔壁流动的影响，最后基于试验结果发展了计算斜孔壁特性参数的微分法，并与经验方法结果进行对比。结果表明，斜孔壁流动呈现出明显的差阻性和非线性，在负压差范围内，近壁流动仍以出流为主；高亚声速时，空风洞模型区孔壁流动特性趋于实壁；安装模型后，随着升力的增大，升力面对应的孔壁区域流动向入流发展，孔壁流动特性趋于开口边界。     

Indicators of black-hole mass and Eddington accretion ratio from QSO X-ray and UV spectra

The evolution of luminous QSOs is linked to the evolution of massive galaxies. We know this because the relic black-holes found locally have masses dependent on the properties of the host galaxy’s bulge. An important way to explore this evolution would be to measure dependences of black-hole masses and Eddington accretion ratios over a range of redshifts, i.e., with cosmological age. For low redshift QSOs (and their lower luminosity Seyfert galaxy counterparts) it has been possible to infer black-hole masses from the luminosities and velocity dispersions of their host-galaxy bulges. These masses agree with those virial black-hole masses calculated from the Doppler widths of the broad Hβ emission lines. The latter method can then be extended to more distant and luminous QSOs, up to redshifts of 0.6 with ground-based optical observations. We discuss ways to extend these explorations to higher redshifts – up to 3 using the widths of QSOs’ broad UV emission lines, and in principle, and to redshifts near 4 from ground-based infrared observations of rest-frame Hβ at 2.5 μm. We discuss the possibility of investigating the accretion history of the higher redshift QSOs using measures of Eddington accretion ratio – the soft X-ray spectral index and the eigenvectors of Principal Components Analyses of QSOs’ UV emission-line spectra.     

Overview of QPOs in neutron-star low-mass X-ray binaries

Some aspects of the rapid X-ray variability of low magnetic-field neutron stars in low-mass X-ray binaries are briefly summarized.     

高精度旋转密集钻孔方法

采用预先计算和定点钻孔的方法,用普通分度头钻出位置度要求很高的旋转密集孔。     

Visual inspection of aircraft skin: Automated pixel-level defect detection by instance segmentation

Skin defect inspection is one of the most significant tasks in the conventional process of aircraft inspection. This paper proposes a vision-based method of pixel-level defect detection, which is based on the Mask Scoring R-CNN. First, an attention mechanism and a feature fusion module are introduced, to improve feature representation. Second, a new classifier head—consisting of four convolutional layers and a fully connected layer—is proposed, to reduce the influence of information around the area of the defect. Third, to evaluate the proposed method, a dataset of aircraft skin defects was constructed, containing 276 images with a resolution of 960 × 720 pixels. Experimental results show that the proposed classifier head improves the detection and segmentation accuracy, for aircraft skin defect inspection, more effectively than the attention mechanism and feature fusion module. Compared with the Mask R-CNN and Mask Scoring R-CNN, the proposed method increased the segmentation precision by approximately 21% and 19.59%, respectively. These results demonstrate that the proposed method performs favorably against the other two methods of pixel-level aircraft skin defect detection.     

基于合成卷积层网络结构的焊缝X射线图片缺陷筛选技术

焊接技术应用于多个领域,近些年焊缝缺陷自动检测技术成为了重要的研究方向。本文基于VGG-16卷积神经网络的良好分类性能,提出一种SC-VGG网络结构,利用合成卷积层替换了单个卷积层,同时改进了训练过程中的损失函数,使网络结构更为关注焊缝缺陷类型预测的结果。经过实验测试,SC-VGG网络结构在训练过程中损失函数曲线可以很好的收敛,与其他网络结构相比对焊缝缺陷特征的提取性能更好,平均准确率和召回率达到了95.86%和98.33%,为焊缝缺陷自动化识别提供了算法支撑。     

地磁Ap指数滞后太阳周循环分析

把1932-2006年地磁Ap指数12个月流动均值分解成为(Ap)R和(Ap)I.其中(Ap)R为太阳黑子数R的线性函数,与太阳黑子数R相位相同,可能对应于日冕物质抛射(CME)等地磁控制因素. (Ap)I分量与太阳黑子数R相位相差约180°,该分量可能对应于极冕洞变化(从太阳峰年开始,由日面极区逐渐向赤道延伸).以地磁Ap指数与太阳黑子数R滞后非常严重的第20太阳周为例,证实了(Ap)I分量与极冕洞向赤道延伸循环变化相对应.因此极冕洞循环变化可能是导致地磁扰动指数与太阳周循环相位不一致,出现滞后现象的一个十分重要原因.      

缺陷对高温合金蜂窝板弯曲力学性能的影响

采用预埋缺陷的方法,制备含有面芯脱焊缺陷的高温合金蜂窝板,进行了三点弯曲试验,研究了缺陷形状、大小、位置和蜂窝芯取向对蜂窝板三点弯曲损伤模式和承载能力的影响.研究发现,含面芯脱焊缺陷的蜂窝板在缺陷受压部位产生反向鼓包,并沿着宽度方向扩展为完全破坏;随着缺陷尺寸的增大,蜂窝板承载能力逐渐降低;当缺陷位于三点弯曲受拉面时,蜂窝板具有更高的三点弯曲极限载荷,且矩形缺陷试样的弯曲极限载荷要高于相同缺陷面积的圆形试样.最后,利用LS-DYNA对含圆形缺陷高温合金蜂窝板的三点弯曲性能进行了数值模拟分析,得到其三点弯曲过程中的应力分布状态.     

高温下DD6单晶气冷叶片模拟试样拉伸性能试验

通过选晶法制备DD6单晶薄壁圆管模拟试样,对850℃和980℃两种温度下[001]晶体取向含与不含气膜孔的薄壁试管进行拉伸性能试验研究.结果表明:在850℃条件下,[001]取向含气膜孔的拉伸性能比[001]取向不含气膜孔的拉伸性能降低10.5%;在980℃条件下,[001]取向含气膜孔的拉伸性能与[001]取向不含气膜孔的拉伸性能水平相当,这表明温度越高,气膜孔对薄壁件拉伸性能的影响越不显著;但在980℃ 条件下,[001]取向通气状态的拉伸强度比不通气状态下的拉伸强度提高16%.同时,发现圆管表面状态及通气状态是影响单晶薄壁试样高温性能的重要因素,特别是通气状态的存在显著提高了其高温力学性能.      

各向同性热解炭材料中的缺陷分析和超声检测技术

利用偏光金相显微镜和超声探伤仪对高性能机械密封用块体各向同性热解炭材料中的缺陷进行表征和无损检测.偏光显微观察发现,各向同性热解炭材料中的主要缺陷主要包括三种:各向异性夹杂、裂纹和各向同性夹杂.超声实验研究表明,利用脉冲反射法超声波检测技术可有效检出各向同性热解炭制件中存在的上述缺陷.目前该技术已成功地用于各向同性热解...