1 北京理工大学光电成像技术与系统教育部重点实验室, 北京 100081
2 北京智慧共享技术服务有限公司, 北京 100125
3 中国石油集团安全环保技术研究院有限公司, 北京 102206
基于热成像的气体泄漏检测技术以其检测效率高、直观可视等优点,已成为石油天然气泄漏检测的重要手段,但常规的气体泄漏热成像检测方法需要检测人员从视频图像中主观地判断泄漏气体痕迹,容易发生漏检、误检。研究了一种基于尺度不变特征变换(SIFT)和支持向量机(SVM)的泄漏气体云团热成像检测算法,采用帧间差分法从红外图像序列中筛选目标区域;分别提取泄漏气体和干扰物的SIFT特征;使用SVM对候选区域进行目标判别,提取泄漏气体云团目标。针对真实复杂场景中包含乙烯、甲烷等的气体泄漏图像和运动人员、漂动树木、野草等干扰图像,建立了1000个典型目标图像数据库,通过图像检测仿真,可得所提算法对距10~150 m处的泄漏气体云团的分类准确率可达92.5%。结果表明,采用该检测方法可自动排除其他运动物体的干扰,有效检测出泄漏气体云团。
成像系统 热成像 气体泄漏检测 气体云团 尺度不变特征变换 支持向量机
Author Affiliations
Abstract
1 Institute of Chemical Materials China Academy of Engineering Physics Mianyang 621999 China
2 Shaanxi Applied Physics-Chemistry Research Institute Xi’an 710061 China
3 Department of Chemical Engineering Nanjing University of Science and Technology Nanjing 210094 China
The laser-driven flyer plate is an important loading technology in high energy physics, shock wave physics, and explosive initiation application. How to generate a high-velocity and intact flyer plate by using the laser is a matter of concern for laser driving. In this study, the multilayer flyer plates (MFPs) of Al/Al2O3/Al and TiO2/Al/Al2O3/Al with adjustable performance were designed and fabricated by magnetron sputtering and analyzed by scanning electron microscopy (SEM), laser reflectance spectrometer, and differential thermal analysis (DTA). The effects of the structure and material on the output performance of MFPs were analyzed by photon Doppler velocimetry (PDV) and ultrahigh-speed video. The morphology results showed that the structure of MFPs had uniform and clear boundaries between side-by-side layers. The MFP velocity was controlled in the range of 4.0–6.0 km/s by adjusting the film thickness, structure, and thermite material with 43.1 J/cm2 laser ablation. Among them, the energetic flyers with the thermite ablation layer had the highest final velocity of 5.38 km/s due to the prestored energy of TiO2/Al. By appropriately increasing the thickness of Al2O3 from 0.4 μm to 0.8 μm, the complete flight of the flyer plate to 3.72 mm can be realized. In addition, TiO2/Al thermite film had characteristics of reaction heat release and lower laser reflectivity (72.13%) than the Al layer (80.55%), which explained the velocity enhancement effect of energetic flyer plates. This work provides facile strategy to enhance the output performance of MFPs, which may facilitate the practical applications of laser driving technology.
Laser and Particle Beams
2022, 2022(1): 4546178
武汉工程大学材料科学与工程学院, 湖北省等离子体化学与新材料重点实验室, 湖北 武汉 430073
采用微波等离子体化学气相沉积法,在半开放式样品台上通过调整种晶在样品台中的凸出高度(Δh)实现了对微波等离子体中基团分布的调控,并进行了单晶金刚石的侧向外延扩大生长研究。将发射光谱与金刚石样品的傅里叶变换红外光谱、Raman光谱、白光干涉测试结果及光学形貌表征结果结合起来,分析了种晶在样品台中的凸出高度对侧向外延生长单晶金刚石的影响。结果表明:随着凸出高度增大,等离子体中的C2(516.08 nm)基团在中心区域(-2~2 mm)的相对浓度增加,当凸出高度为0.6 mm时,中心区域碳源基团的浓度相对较高,导致该区域的纵向生长速率略高于周围区域的纵向生长速率,有利于生长面自主形成偏离(100)晶面一定角度的倾斜结构,进而侧向扩大生长出无多晶金刚石外圈且红外光学透过性能优异的单晶金刚石。顶部生长面自主形成一定角度的倾斜结构,是实现单晶金刚石侧向外延扩大生长的关键。继续增大凸出高度至0.8 mm,就会导致中心区域C2(516.08 nm)基团的相对浓度过高,形成金字塔丘状体,反而不利于高质量单晶金刚石的外延生长。
材料 单晶金刚石 发射光谱 基团分布 微波等离子体 光学学报
2021, 41(20): 2016001
Author Affiliations
Abstract
1 School of Physics, Northwest University, Xi’an 710127, China
2 Department of Electrical and Electronic Engineering, Joint Appointment with School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
In this Letter, we developed a robust method for integrating nanodiamonds (NDs) to optical fiber. The NDs, containing nitrogen-vacancy (NV) centers, were uniformly mixed with UV adhesive before coating the end surface of a multimode fiber as a hemispherical film. The excitation and collection efficiency of NV fluorescence can be enhanced by increasing the thickness of UV adhesive film and additional aluminum film deposition. The fiber-based quantum sensor was also experimentally demonstrated for all-optical thermometry application. The variation of the refractive index of UV adhesive under different temperatures will also affect the NV collection efficiency by changing the light confinement. The demonstrated facile integration approach paves the way for developing fiber-based quantum thermometry and magnetometry.
fiber optics sensors fiber optics quantum optics Chinese Optics Letters
2021, 19(12): 120601
Author Affiliations
Abstract
1 Huazhong University of Science and Technology, School of Physics and Wuhan National Laboratory for Optoelectronics, Wuhan, China
2 Wuhan Institute of Technology, Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan, China
Tunneling ionization of atoms and molecules induced by intense laser pulses contains the contributions of numerous quantum orbits. Identifying the contributions of these orbits is crucial for exploring the application of tunneling and for understanding various tunneling-triggered strong-field phenomena. We perform a combined experimental and theoretical study to identify the relative contributions of the quantum orbits corresponding to the electrons tunneling ionized during the adjacent rising and falling quarter cycles of the electric field of the laser pulse. In our scheme, a perturbative second-harmonic field is added to the fundamental driving field. By analyzing the relative phase dependence of the signal in the photoelectron momentum distribution, the relative contributions of these two orbits are unambiguously determined. Our results show that their relative contributions sensitively depend on the longitudinal momentum and modulate with the transverse momentum of the photoelectron, which is attributed to the interference of the electron wave packets of the long orbit. The relative contributions of these orbits resolved here are important for the application of strong-field tunneling ionization as a photoelectron spectroscopy for attosecond time-resolved measurements.
tunneling ionization quantum orbits photoelectron holography attosecond electron dynamics Advanced Photonics
2021, 3(3): 035001
1 国网电力科学研究院, 江苏 南京 211106
2 国网电力科学研究院 武汉南瑞有限责任公司, 湖北 武汉 430074
3 西安电子科技大学 先进材料与纳米科技学院, 陕西 西安 710071
采用传统固相法制备稀土氧化物La2O3掺杂的ZnO压敏陶瓷。采用X线衍射(XRD)、扫描电子显微镜(SEM)和压敏电阻直流参数仪对样品的物相、显微组织及电性能进行分析。结果表明, 随着La2O3掺杂量的增加, ZnO压敏陶瓷电位梯度单调递增, 非线性系数先增加后减小, 而漏电流呈现先减小后增大的变化趋势。综合衡量ZnO压敏电阻的各项性能指标发现, 在1 000 ℃烧结温度下, La2O3的质量分数为0.25%时, ZnO压敏电阻的综合性能最好, 其电位梯度为532.2 V/mm, 非线性系数为41.6, 漏电流为3.3 μA。
ZnO压敏陶瓷 稀土氧化物La2O3 电位梯度 电性能 ZnO varistor ceramics rare earth oxide La2O3 potential gradient electric property
武汉工程大学材料科学与工程学院, 湖北省等离子体化学与新材料重点实验室, 湖北 武汉 430205
反应腔作为微波等离子体化学气相沉积法制备光纤预制棒的核心, 其结构直接影响到反应腔内的电磁场分布, 进而影响到等离子体状态, 因此对反应腔的结构进行研究是十分有必要的。 为了在反应腔中获得较高密度和较好均匀性的等离子体, 提出了一种双路微波耦合反应腔结构, 首先模拟计算了不同反应腔结构参数下反应腔内的电场分布规律, 并以氧气作为工作气体, 通过等离子体发射光谱探究了反应腔结构和工作气压对石英管内的等离子体分布的影响。 研究结果表明: 双路微波输入方式在石英管中心区域产生了很强的电场耦合增强效果。 反应腔的内径对电场分布状态影响较大, 在反应腔内径为86 mm时, 石英管内的电场分布出现轴对称性, 且轴向中心区域的等离子体密度最大。 在两路矩形波导的距离为61.2 mm和反应腔的长度为202 mm时, 反应腔内等离子体的强度和均匀性具有最佳分布。 另外还发现, 当气压从1.8 kPa上升到2.8 kPa时, 反应腔内等离子体光谱强度减小, 但靠近石英管内壁处的变化不明显, 这与等离子体中粒子碰撞几率增加造成的能量损失和管壁存在的高温有关。
双路微波耦合反应腔 发射光谱 微波等离子体 Two-way microwave coupled reaction cavity Emission spectrum Microwave plasma 光谱学与光谱分析
2020, 40(11): 3613
Author Affiliations
Abstract
1 Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK
2 State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China
3 Silicon Technologies Centre of Excellence, Nanyang Technological University, Singapore 639798, Singapore
4 Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N—Palaiseau, 91120 Palaiseau, France
We report mid-infrared Ge-on-Si waveguide-based PIN diode modulators operating at wavelengths of 3.8 and 8 μm. Fabricated 1-mm-long electro-absorption devices exhibit a modulation depth of >35 dB with a 7 V forward bias at 3.8 μm, and a similar 1-mm-long Mach–Zehnder modulator has a Vπ·L of 0.47 V·cm. Driven by a 2.5Vpp RF signal, 60 MHz on-off keying modulation was demonstrated. Electro-absorption modulation at 8 μm was demonstrated preliminarily, with the device performance limited by large contact separation and high contact resistance.
Photonics Research
2019, 7(8): 08000828
1 武汉邮电科学研究院，武汉 430074
2 武汉光迅科技股份有限公司，武汉 430205
3 光纤和网络技术国家重点实验室，武汉 430074
可调谐激光器已经成为相干光传输系统中最重要的器件之一。文章基于现有的集成可调谐激光器模块，提出了一种新型的基于硅基光波导芯片实现器件高稳定性的小型化结构，基于该结构设计的微环可调谐激光器的外腔主要由一个半导体光放大器和两个透镜组成。针对器件进行了外置波锁分析和芯片的耦合分析，芯片与半导体光放大器之间的耦合采用双透镜和模斑转换器，因此大大提高了耦合效率，减小了腔内损耗，提高了输出功率。实验结果表明，该装置的输出功率可达14 dBm，调谐范围可覆盖整个C波段。
硅基微环 可调谐激光器 相干光传输 silicon micro-ring tunable laser coherent optical transmission
