1 Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China
2 Songshan Lake Materials Laboratory, Dongguan 523830, Guangdong, China
3 Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
4 Jiaxing Research Institute, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China
5 High Performance Computing Department, National Supercomputing Center, Shenzhen 518055, Guangdong, China
Ti-6Al-4V is a benchmark Ti alloy. Laser wire additive manufacturing (LWAM) offers advanced manufacturing capability to the alloy for applications possibly including exploration of outer space. As a typical multiple-variable process, LWAM is complex, which, however, can be analyzed, predicated or even optimized by artificial intelligence (AI) methods such as machine learning (ML). In this study, printing parameters of the Ti-6Al-4V is firstly optimized using single-track-single-layer experiments, and then single-track-multiple-layer samples are printed, whose properties in terms of hardness and compressive strength are analyzed subsequently by both experiments and ML. The two ML approaches, artificial neural network (ANN) and support vector machine (SVM), are employed to predict the experimental results, whose coefficients of determination R2 show good values. Further optimized properties are realized by adopting genetic algorithm (GA) and simulated annealing (SA) approaches, which contribute to high mechanical properties achieved, for instance, an engineering compressive strength of about 1694 MPa. The results here indicate that important mechanical properties of the LWAM-prepared Ti alloys can be well predicted and enhanced using suitable ML approaches.
laser technique laser wire additive manufacturing (LWAM) Ti-6Al-4V machine learning mechanical properties support vector machine (SVM) artificial neural network (ANN)
1 安徽大学 物质科学与信息技术研究院, 合肥 230601
2 中国科学技术大学 近代力学系, 合肥 230027
为了解决常规数字图像相关法应用于高温工况下热应变测量时, 人工制作的散斑受高热载荷冲击容易出现变色、熔化、脱落的问题, 采用激光散斑作为数字图像相关法特征纹理的方法, 计算温度变化前后散斑图像相关性来测量金属热应变, 进行了非真空环境下加热试件的实验, 以及在管式加热炉中分别对铝试件和钨试件进行人工散斑和激光散斑的真空加热实验对比, 取得了相应的散斑图像, 并计算出平均应变曲线数据。结果表明, 在非真空环境下, 由于热流扰动导致激光散斑图像抖动较大, 测量出的热应变曲线存在较大的干扰噪声; 铝从室温升至450 ℃和钨从室温升至800 ℃的热应变与人工散斑结果相对一致; 激光散斑数字图像相关法在类似聚变堆偏滤器高真空、高热流条件下, 可以有效地测出金属壁面的动态热应变。该研究为聚变堆偏滤器第一壁材料的损伤诊断提供了新思路。
测量与计量 热应变 激光散斑 数字图像相关法 人工散斑 measurement and metrology thermal strain laser speckle digital image correlation method artificial speckle
安徽大学，物质科学与信息技术研究院，合肥 230601
以六水合氯化铝和尿素为原料，甲醇为溶剂，在NH3气氛下通过湿化学法制备AlN粉体，并采用X射线衍射仪、扫描电子显微镜和激光粒度仪对产物进行表征。结果表明：煅烧温度在900 ℃以上可获得六方AlN粉体；煅烧温度为1 000 ℃时获得的AlN粉体具有球形特征，粉体的平均晶粒尺寸为17.0 nm，平均粒径为159.5 nm。使用透射电子显微镜进一步表征了AlN粉体的微观结构。拉曼光谱结合能谱分析表明，存在于AlN粉体中的非晶杂质不是残留的含碳副产物，而是粉体表面水解产生的氢氧化铝。
氮化铝 尿素 六水合氯化铝 湿化学法 煅烧温度 氨气 水解 aluminum nitride urea aluminium chloride hexahydrate wet chemical method calcination temperature ammonia hydrolysis
1 特种环境复合材料技术国家级重点实验室(哈尔滨工业大学)，哈尔滨 150001
2 哈尔滨工业大学分析测试中心，哈尔滨 150001
3 微系统与微结构制造教育部重点实验室(哈尔滨工业大学)，哈尔滨 150001
微机电系统、深空、深海探测任务等对于长效、便携电源提出了更高的要求。同位素电池由于其能量密度高、功率输出稳定，可以在高低温、无太阳光照等极端环境下持续不断地为月球车、海底探测器等提供能量。作为同位素电池中的主要类型，辐射伏特效应同位素电池由于其理论能量转换效率高、易于微型化被广泛研究，并已经成功应用于心脏起搏器。宽禁带的半导体换能结器件制作的同位素电池能够获得更高的能量转换效率。宽禁带半导体中的代表金刚石具有5.5 eV的禁带宽度与耐辐射的特性，使其成为制作辐射伏特效应同位素电池换能结器件的最佳选择。随着化学气相沉积技术的发展，金刚石晶体的外延技术突飞猛进，为金刚石半导体器件的发展打下了材料基础。本文对比了常见的同位素电池换能结用半导体材料和辐射源材料的特性，介绍了辐射伏特效应的基本原理，接着对辐射伏特效应同位素电池的关键参数进行了分析，并汇总了有关金刚石辐射伏特效应同位素电池研究的文献，通过各个参数，如开路电压、转换效率等的对比，指出了目前金刚石同位素电池发展的状态与存在的问题。通过分析金刚石与其他n型半导体材料组成的异质pn结目前的性能与应用情况，给出了基于金刚石异质pn结的高性能同位素电池的结构设计，并进行了总结与展望。
同位素电池 辐射伏特效应 金刚石 肖特基器件 开路电压 半导体换能结 转换效率 isotope battery radio-voltaic effect diamond Schottky diode open circuit voltage semiconductor material for energy converter conversion efficiency
1 国防科技大学电子科学学院 ATR重点实验室，湖南长沙 410073
2 昆明物理研究所，云南昆明 650233
为解决基于卷积神经网络的目标检测算法对预训练权重的过度依赖，特别是数据稀缺条件下的红外场景目标检测，提出了融入注意力模块来缓解不进行预训练所带来的检测性能下降的方法。本文基于 YOLO v3算法，在网络结构中融入模仿人类注意力机制的 SE和 CBAM模块，对提取的特征进行通道层面和空间层面的重标定。根据特征的重要程度，自适应地赋予不同权重，最终提升检测精度。在构建的红外车辆目标数据集上，注意力模块能够显著提升无预训练卷积神经网络的检测精度，融入了 CBAM模块的网络检测精度为 86.3 mAP。实验结果证明了注意力模块能够提升网络的特征提取能力，使网络摆脱对预训练权重的过度依赖。
目标检测 红外目标 深度学习 卷积神经网络 target detection, infrared target, deep learning,
Author Affiliations
Abstract
1 Institute of Plasma Physics, Hefei Institutes of Physical Sciences, Chinese Academy of Sciences, Hefei 230031, China
2 Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230031, China
3 College of Liberal Arts and Sciences, National University of Defense Technology, Changsha 410073, China
4 Institute of Applied Physics, Army Academy of Artillery and Air Defense, Hefei 230031, China
5 Institute of Physical Science and Information Technology, Anhui University, Hefei 230031, China
6 e-mail: whwang@ipp.ac.cn
7 e-mail: xjli@nudt.edu.cn
A concise, efficient, and practical direct-view scheme is presented to generate arbitrary cylindrical vector (CV) beams, including CV beams, vortex beams, and cylindrical vector vortex (CVV) beams, by a vortex half-wave plate (VHP). Six kinds of first-order and other high-order CV beams, such as azimuthally polarized (AP) beams, antivortex radial polarization mode beams, and three-order AP beams, are formed by simply rotating a half-wave plate. The Stokes parameters and double-slit interference of multitype CV beams are investigated in detail. The polarization parameters, including degree of polarization, polarization azimuth, and ellipticity, are obtained, which demonstrates the efficient generation of CV beams. In addition, the double-slit interference experiment is introduced in the setup, and fringe misplacement and tilt appear for CVV beams, in which the misplacement number is for and for , where is the polarization order number, and the fringe tilt offset is positively related to the topological charge number of CVV beams. In addition, new types of VHPs can be formed by cascading two or more VHPs when the types of available VHPs are limited, assisting in more flexible generation of multitype CV beams. It is experimentally demonstrated that arbitrary CV beams with high quality are effectively achieved by the proposed setup, and the double-slit interference method can be utilized to determine and analyze CV beams rapidly and concisely by practical performance, which shows the potential to be implemented as a commercial device.
Photonics Research
2021, 9(5): 05000803
微波等离子体化学气相沉积(MPCVD)技术被认为是制备大尺寸高品质单晶金刚石的理想手段之一。然而其较低的生长速率(～10 μm/h)以及较高的缺陷密度(103~107 cm-2)是阻碍MPCVD单晶金刚石应用的主要因素, 经过国内外研究团队数十年的不懈努力, 在高速率生长和高品质生长两个方面都取得了众多成果。但是除此之外还需解决高速率与高品质生长相统一的问题, 才能实现MPCVD单晶金刚石的高端应用价值。
MPCVD单晶金刚石 高速率 高品质 MPCVD single crystal diamond high growth rate high growth quality
为了满足低轨道航天器姿态轨道控制系统对小型化地球敏感器的需求, 对广角长波红外地球敏感器光学系统设计及成像畸变校正技术进行了研究。广角长波红外光学系统采用反远距结构形式, 由三片锗透镜实现140°的视场角, 光学系统工作波段为 14 μm～16.25 μm, F数为0.8。广角长波红外光学系统体积小、结构简单, 并且成像质量良好, 实现了红外地球敏感器光学系统的小型化高精度设计。采用分视场区间分别建立畸变校正公式的方法来实现光学系统成像畸变校正, 校正精度优于像元尺寸的1/5, 可满足敏感器产品姿态测量的需求。
地球敏感器 光学系统 广角 畸变校正 earth sensor optical system wide angle distortion correction
基于多个圆环嵌套结构单元, 设计、加工与测试了一种对偏振无依赖以及大角度入射稳定的三波段超材料宽带带通滤波器(BPF)。仿真结果表明该滤波器存在三个通带, 中心频率分别为7.22, 10.10, 14.46 GHz, 3 dB相对带宽分别为17.5%, 20.2%和17.4%, 中心频率处透射率分别为-0.85 dB, -0.69 dB和-1.73 dB。单元结构具有旋转对称性, 使得该滤波器对电磁波偏振不敏感, 并且在入射角达到40°时, 三个波段依然维持较好的稳定性。通过监测谐振频点处的表面电流分布情况, 分析了三波段滤波的物理机理。这种带通滤波器具有多波段滤波、偏振无依赖以及大角度入射稳定等特性, 有望在多频谱成像技术、信息通信等领域发挥一定的作用。
光学器件 带通滤波器 超材料 三波段
