Non-line-of-sight (NLOS) imaging has emerged as a prominent technique for reconstructing obscured objects from images that undergo multiple diffuse reflections. This imaging method has garnered significant attention in diverse domains, including remote sensing, rescue operations, and intelligent driving, due to its wide-ranging potential applications. Nevertheless, accurately modeling the incident light direction, which carries energy and is captured by the detector amidst random diffuse reflection directions, poses a considerable challenge. This challenge hinders the acquisition of precise forward and inverse physical models for NLOS imaging, which are crucial for achieving high-quality reconstructions. In this study, we propose a point spread function (PSF) model for the NLOS imaging system utilizing ray tracing with random angles. Furthermore, we introduce a reconstruction method, termed the physics-constrained inverse network (PCIN), which establishes an accurate PSF model and inverse physical model by leveraging the interplay between PSF constraints and the optimization of a convolutional neural network. The PCIN approach initializes the parameters randomly, guided by the constraints of the forward PSF model, thereby obviating the need for extensive training data sets, as required by traditional deep-learning methods. Through alternating iteration and gradient descent algorithms, we iteratively optimize the diffuse reflection angles in the PSF model and the neural network parameters. The results demonstrate that PCIN achieves efficient data utilization by not necessitating a large number of actual ground data groups. Moreover, the experimental findings confirm that the proposed method effectively restores the hidden object features with high accuracy.

A novel experimental method is proposed for observing plasma dynamics subjected to magnetic fields based on a newly developed cylindrical theta-pinch device. By measuring simultaneously the temporal profiles of multiple parameters including the drive current, luminosity, plasma density, and plasma temperature, it provides a basis for observing the plasma dynamics of the theta pinch, such as shock transport and magnetohydrodynamic instability. We show that the plasma evolution can be distinguished as three phases. First, in the radial implosion phase, the trajectories of the current sheath and shock wave are ascertained by combining experimental data with a snowplow model (Lee model) in a self-consistent way. Second, in the axial flow phase, we demonstrate that m = 0 (sausage) instability associated with the plasma axial flow suppresses the plasma end-loss. Third, in the newly observed anomalous heating phase, the lower-hybrid-drift instability may develop near the current sheath, which induces anomalous resistivity and enhanced plasma heating. The present experimental data and novel method offer better understanding of plasma dynamics in the presence of magnetic fields, thereby providing important support for relevant research in magneto-inertial fusion.

现有方法常将相机从下至上拍摄标记物图像，当桨叶扭转幅度较大时，相机主光轴与标记物平面法向量存在明显夹角，导致拍摄图像存在透视畸变现象，从而引发较大测量误差。为解决上述问题，提出一种基于透视变换的直升机桨根扭转角测量方法。首先，将靶标垂直固定在桨叶下方，相机正对桨毂拍摄图像。其次，计算桨叶在低速拉平状态下待测方位与正方位靶标图像中的四个顶点坐标，并求解待测方位的透视变换矩阵，然后利用透视变换矩阵对桨叶高速运动状态下待测方位拍摄的畸变图像进行校正。最后，求得基准图像与校正后图像中的圆心坐标，进而计算出待测方位扭转角。实验结果表明，各方位测量误差均小于0.2°。该方法不但测量精度高，而且具有多方位动态测量的优点，在直升机旋翼桨叶运动参数测量领域具有良好的应用前景。

采用飞秒激光加工4H-SiC压力敏感膜片，研究了飞秒激光深度方向步进间距、扫描路径方向、单脉冲能量、扫描线间距等参数对4H-SiC烧蚀形貌和烧蚀速率的影响。实验结果表明，飞秒激光加工4H-SiC样品表面孔洞的形成主要与激光诱导微沟槽的重叠有关，激光能量分布更均匀能够有效减少4H-SiC被烧蚀表面的激光诱导微沟槽的数量，增大激光扫描路径与激光偏振方向的夹角能够有效降低激光诱导微沟槽的重叠概率，从而抑制孔洞的形成。采用优化后的飞秒激光加工工艺参数，制备出直径为1 600 μm、厚度为100 μm的4H-SiC压力敏感膜片。所制备的4H-SiC压力敏感膜片表面无明显孔洞，边缘过烧蚀深度小于10 μm，实现了4H-SiC压力敏感膜片的低损伤飞秒激光加工。

火花发射光谱分析钢中单一夹杂物的研究已有文献报导, 但用火花光谱分析钢中复合夹杂物一直是个难题。 钢中复合夹杂物是一种单一夹杂物包裹另外一种单一夹杂物组成的复合体, 或由两个及以上单一夹杂物紧密相邻结合体。 如何区分材料中同时存在但不相邻的两种单一夹杂物和二者复合夹杂物, 用火花发射光谱技术难于实现。 该工作采用火花光谱原位统计分布分析(OPA)进行高铁车轮截面的夹杂物分析, OPA通过对经连续扫描的火花放电激发所产生的元素光谱信号进行采集和分析, 可实现大尺度金属材料的成分及夹杂物统计分布表征, 在同一激发位置下, 当既有Al₂O₃夹杂物光谱信号, 也有MnS夹杂物光谱信号, 通过对Al₂O₃夹杂物和MnS夹杂物的火花光谱强度时序耦合处理, 获得此时序对应位置处的复合夹杂物信息。 根据超过阈值以上的火花光谱强度和夹杂物平均面积之间的良好线性关系, 在同一位置下, 分别获得Al₂O₃/MnS复合夹杂物中Al₂O₃夹杂物和MnS夹杂物的面积, 将Al₂O₃夹杂物面积和MnS夹杂物面积加和, 得到Al₂O₃/MnS复合夹杂物的面积。 同时结合扫描电镜(SEM)分析小区域内的复合夹杂物, 将每一个扫描电镜复合夹杂物面积对应一个OPA分析夹杂物的归一化面积, 建立SEM 和OPA两种分析方法获得的复合夹杂物面积的关系曲线, 二者具有良好线性关系, 线性相关系数大于0.99。 取高铁车轮截面中另外两部分进行验证实验, 得到的结果也与扫描电镜结果基本一致, 即在分析小面积区域内Al₂O₃/MnS复合夹杂物, OPA分析的归一化结果也能够满足表征需要。 除此之外, 由于 OPA可以进行部件全域分析, 可检测到更多的较大Al₂O₃/MnS复合夹杂物颗粒, 可有效避免扫描电镜(SEM)因分析区域有限造成大尺寸夹杂物漏检问题, 为大尺寸金属构件的夹杂物分析特别是Al₂O₃/MnS复合夹杂物的分析提供了一种有效手段。