检索结果-南通市图书馆

laser-induced damage threshold in HfO_2/SiO_2 multilayer films irradiated by β-ray

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2019年第2期28卷 294-298页

作者： Mei-Hua Fang Peng-Yu Tian Mao-Dong Zhu Hong-Ji Qi Tao Fei Jin-Peng Lv Hui-Ping Liu College of Astronautics Nanjing University of Aeronautics&Astronautics Laboratory of Thin Film Optics Key Laboratory of Materials for High Power LaserShanghai Institute of Optics and Fine MachanicsChinese Academy of Sciences Institute of Modern Physics Chinese Academy of Sciences

Post-processing can effectively improve the resistance to laser damage in multilayer films used in a high power laser system. In this work, HfO_2/SiO_2 multilayer films are prepared by e-beam evaporation and then β-ray irradiation is employed as the post-processing method. The particle irradiation affects the laser induced damage threshold(LIDT),which includes defects, surface roughness, packing density and residual stress. The residual stress that is relaxed during irradiation changes from compressive stress into tensile stress. Our results indicate that appropriate tensile stress can improve LIDT remarkably. In view of the fact that LIDT rises from 8 J/cm^2 to 12 J/cm^2, i.e., 50% increase, after the film has been irradiated by 2.2×10^(13)/cm^2 β-ray, the particle irradiation can be used as a controllable and desirable postprocessing method to improve the resistance to laser induced damage.

关键词： β-ray irradiation HfO2/SiO2 multilayer film residual stress laser-induced damage threshold

laser-induced spark ignition of H_2/O_2/Ar mixtures

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2007年第6期50卷 797-806页

作者： WANG ChangJian XU ShengLi JIA GuangMing Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei 230026 China Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei 230026 China Department of Mechanics and Mechanical Engineering University of Science and Technology of China Hefei 230026 China

laser-induced spark ignition of hydrogen-oxygen-argon mixtures was experimen- tally investigated using a Q-swiched Nd:YAG laser to break down the gas at 532 nm. The laser-based high-speed schlieren system was employed to record flame front evolution for the gas mixtures with different initial pressure or laser output energy or argon dilution. The results show that the breakdown of the gas leads to the generation of ellipsoidal plasma. The rarefaction waves create the toroidal rings at the leading and trailing edges of the plasma, which provides a reasonable explana- tion for inward wrinkle of the plasma and the resultant flame. The toroidal rings at leading edge decays more rapidly and a gas lobe is generated that moves towards the laser. The hot gas in the plasma induces the generation of the spark kernel. Affected by the very weak shock wave or compression waves reflected off the wall, the initial laminar flame decelerates. The arc flame front interactions with the wall, reversed shock wave or compression waves, rarefaction waves, etc. induce the transition from laminar flame to turbulent one. These induce the transition from laminar flame to turbulent flame. For stoichiometric hydrogen-oxygen mixtures diluted by 76.92% argon at an initial pressure of 53.33 kPa, the minimum output energy of the laser is 15 mJ for successful laser-induced spark ignition. With in- creasing initial pressure or the output energy of the laser, or decreasing argon di- lution, the speed of the flame front increases.

关键词： laser-induced spark ignition, high-speed schlieren photography, plasma, rarefaction waves, laminar flame,turbulent fame

Quantitative analysis of steel and iron by laser-induced breakdown spectroscopy using GA-KELM

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2019年第3期21卷 167-173页

作者： Yaguang MEI Shusen CHENG Zhongqi HAO Lianbo GUO Xiangyou LI Xiaoyan ZENG Junliang GE School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Wuhan National Laboratory for Optoelectronics Laser and Tera-Hertz Technology Division Huazhong University of Science and Technology Institute for Science and Technology Information and Strategy Central Iron and Steel Research Institute

According to the multiple researches in the last couple of years, laser-induced breakdown spectroscopy(LIBS) has shown a great potential for rapid analysis in steel ***, the accuracy and precision may be limited by complex matrix effect and selfabsorption effect of LIBS seriously. A novel multivariate calibration method based on genetic algorithm-kernel extreme learning machine(GA-KELM) is proposed for quantitative analysis of multiple elements(Si, Mn, Cr, Ni, V, Ti, Cu, Mo) in forty-seven certified steel and iron ***, the standardized peak intensities of selected spectra lines are used as the input of ***, the genetic algorithm is adopted to optimize the model parameters due to its obvious capability in finding the global optimum solution. Based on these two steps above, the kernel method is introduced to create kernel matrix which is used to replace the hidden layer's output matrix. Finally, the least square is applied to calculate the model's output weight. In order to verify the predictive capability of the GA-KELM model, the R-square factor(R^2), Root-meansquare Errors of Calibration(RMSEC), Root-mean-square Errors of Prediction(RMSEP) of GAKELM model are compared with the traditional PLS algorithm, respectively. The results confirm that GA-KELM can reduce the interference from matrix effect and self-absorption effect and is suitable for multi-elements calibration of LIBS.

关键词： laser-induced breakdown spectroscopy(LIBS) alloy elements calibration genetic algorithm-kernel extreme learning machine(GA-KELM)

Small-invasive determination of iron content in coating of galvanized steel sheets by laser-induced breakdown spectroscopy

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2019年第10期26卷 1137-1146页

作者： Lan-xiang Sun Wei-ye Wang Mei-ting Guo Xue-yong Tian Peng Zhang Li-feng Qi Hai-bin Yu Peng Zeng Shenyang Institute of Automation Chinese Academy of SciencesShenyang 110016LiaoningChina Key Laboratory of Networked Control Systems Chinese Academy of SciencesShenyang 110016LiaoningChina Northeastern University Shenyang 110819LiaoningChina Central Research Institute SIASUN Robot&Automation Co.Ltd.Shenyang 110168LiaoningChina University of the Chinese Academy of Sciences Beijing 100049China

A new method was presented to determine the iron content in the coating of galvanized steel sheet based on laser-induced breakdown *** zinc-iron coating was characterized with a series of single laser pulses irradiated on the traversing sheet steel,each on a different steel sheet *** influences of laser fluence and elemental depth distribution were studied and *** protect the corrosion performance of the coating and meet requirements for small-invasive measurement,the ablation size of the crater under different laser fluences was *** the optimized experimental parameters,the diameter of ablation craters is about 50μm,and then,the Fe content in the coating was calibrated and analyzed by the linear standard calibration *** calibration result,however,is not *** that the Zn content in the coating was high and relatively constant,curve calibration was then carried out with the intensity ratio(IFe404.58/Izn468.01)instead of the net line intensity of Fe,and then,the determination coefficient of calibration curve increases from 0.7713 to 0.9511,and the root-mean-square error decreases from 0.4832%to 0.1509%.The results prove that the laser-induced breakdown spectroscopy is an effective way for the analysis of the Fe content in the coating of galvanized steel sheet.

关键词： laser-induced breakdown spectroscopy Galvanized steel sheet Quantitative analysis Small-invasive analysis Iron content

Identification of heavy metal-contaminated Tegillarca granosa using laser-induced breakdown spectroscopy and linear regression for classification

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2020年第8期22卷 151-159页

作者： Zhonghao XIE Liuwei MENG Xi'an FENG Xiaojing CHEN Xi CHEN Leiming YUAN Wen SHI Guangzao HUANG Ming YI School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072People's Republic of China College of Physical and Electronic Information Engineering Wenzhou UniversityWenzhou 325035People's Republic of China Research and Development Department Hangzhou Goodhere Biotechnology Co.LtdHangzhou 311100People's Republic of China Research and Development Department Hangzhou Weizan Technology Co.LtdHangzhou 311100People's Republic of China

Tegillarca granosa(***)is susceptible to heavy metals,which may pose a threat to consumer ***,healthy and polluted *** should be distinguished *** study aimed to rapidly identify heavy metal pollution by using laser-induced breakdown spectroscopy(LIBS)coupled with linear regression classification(LRC).Five types of *** were studied,namely,Cd-,Zn-,Pb-contaminated,mixed contaminated,and control *** method was applied to extract the significant variables from LIBS ***,LRC was used to classify the different types of *** classification models and feature selection methods were used for *** was the best model,achieving an accuracy of 90.67%.Results indicated that LIBS combined with LRC is effective and feasible for *** heavy metal detection.

关键词： shellfish laser-induced breakdown spectrometry heavy metal linear regression classification

Study of pressure effects on ocean in-situ detection using laser-induced breakdown spectroscopy

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2019年第3期21卷 182-187页

作者： Jinjia GUO Nan LI Jiaojian SONG Ronger ZHENG Optics and Optoelectronics Laboratory Ocean University of China

laser-induced breakdown spectroscopy(LIBS) has attracted extensive attention as a new technique for in-situ marine application. In this work, the influence of deep-sea high pressure environment on LIBS signals was investigated by using a compact LIBS-sea system developed by Ocean University of China for the in-situ chemical analysis of seawater. The results from the field measurements show that the liquid pressure has a significant effect on the LIBS signals. Higher peak intensity and larger line broadening were obtained as the pressure increases. By comparing the variations of the temperature and salinity with the LIBS signals, a weak correlation between them can be observed. Under high pressure conditions, the optimal laser energy was higher than that in air environment. When the laser energy exceeded 17 mJ, the effect of laser energy on the signal intensity weakened. The signal intensity decreases gradually at larger delays. The obtained results verified the feasibility of the LIBS technique for the deep-sea in-situ detection, and we hope this technology can contribute to surveying more deep-sea environments such as the hydrothermal vent regions.

关键词： laser-induced breakdown spectroscopy deep-sea in-situ detection pressure effect plasma emission

Signal processing for real-time identification of similar metals by laser-induced breakdown spectroscopy

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2019年第3期21卷 84-91页

作者： Sungho SHIN Youngmin MOON Jaepil LEE Hyemin JANG Euiseok HWANG Sungho JEONG School of Mechanical Engineering Gwangju Institute of Science and Technology

laser-induced breakdown spectroscopy(LIBS) is regarded as a promising technique for realtime sorting of scrap metals due to its capability of fast multi-elemental and in-air analysis. This work reports a method for signal processing which ensures high accuracy and high speed during similar metal sorting by LIBS. Similar metals such as aluminum alloys or stainless steel are characterized by nearly the same constituent elements with slight variations in elemental concentration depending on metal type. In the proposed method, the original data matrix is substantially reduced for fast processing by selecting new input variables(spectral lines) using the information for the constituent elements of similar metals. Specifically, principal component analysis(PCA) of full-spectra LIBS data was performed and then, based on the loading plots, the input variables of greater significance were selected in the order of higher weights for each constituent element. The results for the classification test with aluminum alloy, copper alloy,stainless steel and cast steel showed that the classification accuracy of the proposed method was nearly the same as that of full-spectra PCA, but the computation time was reduced by a factor of 20 or more. The results demonstrated that incorporating the information for constituent elements can significantly accelerate classification speed without loss of accuracy.

关键词： laser-induced breakdown spectroscopy classification similar metal reduced number of spectral lines

Investigation of cavitation erosion caused by laser-induced single bubble collapse near alloy coating surface

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2023年第5期35卷 876-886页

作者： Hai-gang Wen Zhi-feng Yao Qin Wu Yu-rong Sun Chen-xi Yang Qiang Zhong College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing100083China School of Mechanical Engineering Beijing Institute of TechnologyBeijing100081China

To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd: YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse under different conditions. We analyzed the generation of collapse microjets and the emission of collapse shock waves and explored the cavitation erosion characteristics caused by laser-induced single bubble collapse. We discovered that even on surfaces of highly hard and corrosion-resistant alloy coatings, severe cavitation erosion occurred, and there was a phenomenon of mismatch between the cavitation erosion location and the bubble projection position. The intensity of cavitation erosion depended on the energy self-focusing effect of the collapse shockwaves. In the experiments, we also observed the self-focusing phenomenon of collapse shockwaves under different conditions. The self-focusing effect of collapse shockwaves weakened as the distance between the bubble and the material surface increased, which may be the cause of cavitation erosion induced by a laser-induced single bubble.

关键词： Cavitation erosion bubble collapse laser-induced shock wave self-focusing effect

Investigation of the factors affecting the limit of detection of laser-induced breakdown spectroscopy for surface inspection

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2019年第3期21卷 174-181页

作者： Tadatake SATO Kenichi TASHIRO Yoshizo KAWAGUCHI Hideki OHMURA Haruhisa AKIYAMA Electronics and Photonics Research Institute National Institute of Advanced Science and Technology (AIST) Research Institute for Sustainable Chemistry National Institute of Advanced Science and Technology (AIST)

laser-induced breakdown spectroscopy(LIBS) was examined to detect a trace substance adhered onto Al alloys for the surface inspection of materials to be adhesively bonded. As an example of Si contamination, silicone oil was employed and sprayed onto substrates with a controlled surface concentration. LIBS measurements employing nanosecond UV pulses(λ?=?266 nm) and an off-axis emission collection system with different detecting heights were performed. Because surface contaminants are involved in the plasma formed by laser ablation of the substrates, the relative contribution of the surface contaminants and the substrates to the plasma emission could be changed depending on the conditions for plasma formation. The limit of detection(LOD) was evaluated under several detecting conditions for investigating the factors that affected the LOD. A significant factor was the standard deviation values of signal intensities obtained for the clean substrates. This value varied depending on the measurement *** the Al alloy(A6061), the smallest LOD obtained was 0.529 μg?·?cm^(-2). Furthermore, an improved LOD(0.299 μg?·?cm^(-2)) was obtained for the Al alloy with a lower Si content.

关键词： laser-induced breakdown spectroscopy adhesive bonding surface contamination detection pre-bond surface inspection