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The optical diagnosis of Underwater Positive Sparks and Corona Discharges

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Plasma Science and Technology 2014年第12期16卷 1100-1105页

作者：陈聃曾新吾王一博 College of Opto-Electric Science and Engineering National University of Defense Technology

In this paper, two types of underwater discharges, spark discharge and corona discharge, are investigated by optical diagnosis using a high speed framing camera （HSFC） with the framing time within nanoseconds under the same experimental conditions. In order to capture the photographs of streamer propagation, the influence of the randomicity of the prebreakdown duration is taken into consideration. By increasing the conductivity of water, the randomicity reduces effectively. Experimental results show that, for a spark discharge, the process can be separated into three stages： the generation and propagation of a streamer, the generation and expansion of the discharge channel, and the development and annihilation of the plasma. The streamers do not directly move to the opposite electrode, but form a bush-like figure. With the increase of the number of branches, the velocity of streamer propagation slows down. The trajectory of the initial channel between electrodes is not straight. However, with the channel expanding, its shape transforms into a straight column. For a corona discharge, there are two stages： the generation and propagation of a streamer, and the stagnation and annihilation of the streamer. The initial streamer in a corona discharge is generated later than in a spark discharge. The forms of streamers for both kinds of discharge are similar; however, streamers generated by a corona discharge propagate with a slower velocity and the number of branches is less compared with a spark discharge. When the energy injection stops, the luminescence of plasma inside the discharge channel （spark discharge） or streamers （corona discharge） becomes weaker and weaker, and finally disappears.

关键词： spark discharge corona discharge optical diagnosis HSFC

Photographic Analysis and optical diagnosis of Kilowatt Microwave Plasma Torch with Air Carrier Gas

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Chemical Research in Chinese Universities 2023年第6期39卷 1051-1057页

作者： YU Dengjie YU Bingwen ZHANG Xuchen HUANG Shiluo YING Yangwei YAN Yuwei JIN Yining JIN Wei Research Center for Analytical Instrumentation Institute of Cyber-Systems and ControlCollege of Control Science and EngineeringZhejiang UniversityHangzhou 310058P.R.China Research Center for Analytical Instruments and Intelligent Systems Huzhou Institute of Zhejiang UniversityHuzhou 313002P.R.China Faculty of Engineering University of Alberta116 St.and 85 Ave.EdmontonAlbertaCanada

The spatiotemporal motion characteristics of the kilowatt argon microwave plasma torch with the air carrier gas(kW-AC-ArMPT)and the behavior of the plasma filaments are investigated with a digital single-lens reflex(SLR)camera and a high-speed *** with the introduction of the air,both the volume of the central channel and the rotational frequency of the plasma filament are ***,the excitation temperature(Texc),rotational temperature(Trot),and density of electron number(ne)of the kW-AC-ArMPT are measured with optical *** is clearly shown that the introduction of air contributed to the rise of Trot and ne of the plasma,which is beneficial to improving the analytical performance of the *** the detection limits of some heavy metal elements are measured by kW-AC-ArMPT,which are in the ppb *** experimental results show that the kW-ArMPT has a high tolerance to air injection at least 1.0 L/min,which allows the direct extraction of air from the environment for analysis and therefore has the potential for online and in-situ detection of ambient air quality and industrial exhaust gases.

关键词： Air carrier gas Microwave plasma torch Photographic analysis optical diagnosis

optical detection method of discharge mode transition of inductively coupled plasma in an atmosphere-breathing electric propulsion system

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Chinese Journal of Aeronautics 2024年第10期37卷 172-183页

作者： Yuxuan ZHONG Yu ZHANG Jianjun WU Peng ZHENG College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China

Plasma discharge stability is an important problem in atmosphere-breathing electric propulsion system when maintaining long-term missions at ultra-low earth *** paper designed an inductively coupled plasma source to imitate the ionization *** effect of inflow rate and Radio Frequency(RF)power on the plasma discharge mode transition is experimentally studied.A discharge mode detection method is proposed,which determines the discharge mode by identifying the morphology of the plasma *** using the method,the discharge mode transition is quantified and a control model based on the parameter sensitivity is *** verify the method,the spectra are measured and the electron temperature spatial distribution is *** the method has been proven *** results show that the inductively coupled discharge contains capacitive components affected by the mass flow rate and the radio frequency *** plasma characteristics can be maintained stably by controlling the radio frequency power when the mass flow rate randomly changes in a certain *** is demonstrated that the application of detection method effectively identifies the discharge mode,which is a promising active control method for the plasma discharge mode.

关键词： Atmosphere-breathing electric propulsion Inductively coupled plasma Discharge mode transition optical diagnosis Ultra-low earth orbit

Shock wave velocity measurement in the Al_2O_3 under ultrahigh pressure

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Chinese Physics B 2011年第6期20卷 307-312页

作者：王峰彭晓世刘慎业李永升蒋小华丁永坤 Research Centre of Laser Fusion Chinese Academy of Engineering Physics Institute of Applied Physics and Computational Mathematics

in indirect-drive experiment, the blank effect caused by X-rays from Hohlraum will show the dark area in time scale of optical streak camera （OSC）. This blank effect, which was a serious problem in indirect-drive shock wave experiments, has been explained by the semiconductor model. The X-rays cause the band to band transition and the probe laser is absorbed by the intraband transition, which leads to a dark region in time scale of the OSC image. In the experiment, the reflectivity of shock wave front was measured to be about 50% at shock wave velocity 32 km/s and was compared to the theoretical calculations with the Drude free electron model. From the experimental data, it is found that the blank effect can be avoided at radiation temperature of 170 eV if the Al layer is thicker than 60μm.

关键词： shock wave optical diagnosis interfere meter semiconductor model

Comparative study of pulsed breakdown processes and mechanisms in self-triggered four-electrode pre-ionized switches

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Plasma Science and Technology 2022年第11期24卷 114-125页

作者： Tianchi WANG Chuyu SUN Youheng YANG Haiyang WANG Linshen XIE Tao HUANG Yingchao DU Wei CHEN Key Laboratory of Particle&Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084People’s Republic of China State Key Laboratory of Intense Pulsed Radiation Simulation and Effect Northwest Institute of Nuclear TechnologyXi’an 710024People’s Republic of China State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong UniversityXi’an 710049People’s Republic of China

This work investigates the pulsed breakdown processes and mechanisms of self-triggered preionized switches with a four-electrode structure in nitrogen through intensified charge coupled device *** diameter of the trigger plane hole mainly determines the switch’s electric field *** configurations with minimum and maximum trigger plane holes are adopted for *** the switch with a minimum trigger plane hole,the maximum electric field distributes at the surfaces of the main *** charged particles in the triggering spark channel cannot drift out,homogeneous discharges can be stimulated from both the cathode and anode surfaces through ultraviolet *** sub-gaps are likely to break down *** the switch with a maximum trigger plane hole,the maximum electric field locates near the trigger *** in both sub-gaps initiate from the trigger electrodes in the form of a positive or negative *** to the lower breakdown voltage and electric field threshold for discharge initiation,the cathode side sub-gap breaks down *** analysis of two extreme examples can be referenced in the future design and improvement of self-triggered four-electrode switches with different trigger electrode structures.

关键词： gas switch optical diagnosis pre-ionization pulsed breakdown

This research was supported by ***6 Integrated Project“Molecular Imaging”LSHG-CT-2003-503259 and ***7 Collaborative Project“FMT-XCT”.*** support from the Marie Curie Program EST-MolecImag Early Stage Training MEST-CT-2004-007643.

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Journal of Innovative optical Health Sciences 2009年第4期2卷 365-374页

作者： MAHSA RANJI SHOKO NIOKA HE N.XU BAOHUA WU LIN Z.LI DWIGHT L.JAGGARD BRITTON CHANCE Biophotonics Laboratory Department of Electrical Engineering and Computer Science University of Wisconsin-Milwaukee MilwaukeeWI 53211USA Department of Electrical and Systems Engineering University of Pennsylvania PhiladelphiaPA 19104USA Department of Biochemistry and Biophysics University of Pennsylvania PhiladelphiaPA 19104USA Department of Radiology University of Pennsylvania PhiladelphiaPA 19104USA

We have imaged mitochondrial oxidation-reduction states by taking a ratio of mitochondrial fluorophores:NADH(reduced nicotinamide adenine dinucleotide)to Fp(oxidized flavoprotein).Although NADH has been investigated for tissue metabolic state in cancer and in oxygen deprived tissues,it alone is not an adequate measure of mitochondrial metabolic state since the NADH signal is altered by dependence on the number of mitochondria and by blood *** redox ratio,NADH/(Fp+NADH),gives a more accurate measure of steady-state tissue metabolism since it is less dependent on mitochondrial number and it compensates effectively for hemodynamic *** ratio provides important diagnostic information in living *** this study,the emitted fluorescence of mouse colon in situ is passed through an emission filter wheel and imaged on a CCD *** ratio images of the healthy and hypoxic mouse intestines clearly showed significant ***,the corrected redox ratio indicated an increase from an average value of 0.51±0.10 in the healthy state to 0.92±0.03 in dead tissue due to severe ischemia(N=5).We show that the CCD imaging system is capable of displaying the metabolic differences in normal and ischemic tissues as well as quantifying the redox ratio in vivo as a marker of these changes.

关键词： optical diagnosis NADH flavoprotein in vivo ischemia fluorescence.

Effects of dimethyl ether and ethanol additions on soot transition in ethylene counterflow diffusion flames

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Science China(Technological Sciences) 2024年第4期67卷 1094-1112页

作者： GUO LinGe YING YaoYao CHEN Chen ZHAO Xuan LIU Dong MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China Advanced Combustion Laboratory School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China

This paper investigates the effect of blending dimethyl ether(DME)and ethanol on the soot transition periods in ethylene counterflow diffusion flames by using a novel optical diagnostic *** soot critical transition point in different conditions is identified experimentally and *** kinds of flames are carried out to gain the soot critical transition point in counterflow diffusion flames by changing oxygen fraction(Xo)and changing volume flow rates of fuel and oxidizer(Qv).The red-green-blue(RGB)ratio method is used to precisely identify the soot critical transition point,and chemical kinetic simulations are performed to analyze the detailed reaction *** results show that compared to the ethylene flame,the soot critical transition point occurs at a higher Xoand a lower Qvwhen DME or ethanol is *** addition of DME and ethanol can inhibit soot formation,due to the degree of soot formation reaction being lower than the degree of the oxidation reaction in the blending flames.

关键词： optical diagnosis sooting tendency counterflow diffusion flame dimethyl ether ethanol

Non-optical polyp-based resect and discard strategy:A prospective clinical study

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World Journal of Gastroenterology 2022年第19期28卷 2137-2147页

作者： Mahsa Taghiakbari Celia Hammar Mira Frenn Roupen Djinbachian Heiko Pohl Erik Deslandres Simon Bouchard Mickael Bouin Daniel von Renteln Department of Gastroenterology Montreal University Hospital Research Center(CRCHUM)Montréal H2X 0A9QuebecCanada Department of Gastroenterology University of MontrealFaculty of MedicineMontreal H2X 0A9QuebceCanada Department of Internal Medicine University of Montreal Hospital Center(CHUM)Montreal H2X 0A9QuebecCanada Department of Medicine Veterans Affairs Medical CenterWhite River JunctionVT 05009United States Department of Gastroenterology Dartmouth Geisel School of Medicine and The Dartmouth InstituteHanoverNH 03755United States

BACKGROUND Post-polypectomy surveillance intervals are currently determined based on pathology *** To evaluate a polyp-based resect and discard model that assigns surveillance intervals based solely on polyp number and *** Patients undergoing elective colonoscopies at the Montreal University Medical Center were enrolled *** polyp-based strategy was used to assign the next surveillance interval using polyp size and *** intervals were also assigned using optical diagnosis for small polyps(optical diagnosis,and the pathology-based reference standard using the 2020 United States Multi-Society Task Force *** outcomes included the proportion of reduction in required histopathology evaluations and proportion of immediate post-colonoscopy recommendations provided to *** Of 944 patients(mean age 62.6 years,49.3%male,933 polyps)were *** surveillance interval agreement for the polyp-based strategy was 98.0%[95%confidence interval(CI):0.97-0.99]compared with pathology-based *** diagnosis-based intervals achieved 95.8%(95%CI:0.94-0.97)agreement with *** using the polyp-based strategy and optical diagnosis,the need for pathology assessment was reduced by 87.8%and 70.6%,*** polyp-based strategy provided 93.7%of patients with immediate surveillance interval recommendations vs 76.1%for optical *** The polyp-based strategy achieved almost perfect surveillance interval agreement compared with pathology-based assignments,significantly reduced the number of required pathology evaluations,and provided most patients with immediate surveillance interval recommendations.

关键词： Colonoscopy Colorectal pathology Colorectal adenomas Endoscopy Surveillance optical diagnosis

Autofluorescence excitation-emission matrices for diagnosis of colonic cancer

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World Journal of Gastroenterology 2005年第25期11卷 3931-3934页

作者： Bu-HongLi Shu-SenXie BiomedicalOpticsLaboratory InstituteofLaserandOptoelectronicsTechnologyFujianNormalUniversityFuzhou350007FujianProvinceChina

AIM: To investigate the autofluorescence spectroscopic differences in normal and adenomatous coionic tissues and to determine the optimal excitation wavelengths for subsequent study and clinical application. METHODS: Normal and adenomatous coionic tissues were obtained from patients during surgery. A FL/FS920 combined TCSPC spectrofluorimeter and a lifetime spectrometer system were used for fluorescence measurement. Fluorescence excitation wavelengths varying from 260 to 540 nm were used to induce the autofluorescence spectra, and the corresponding emission spectra were recorded from a range starting 20 nm above the excitation wavelength and extending to 800 nm. Emission spectra were assembled into a three-dimensional fluorescence spectroscopy and an excitation-emission matrix (EEM) to exploit endogenous fluorophores and diagnostic information. Then emission spectra of normal and adenomatous coionic tissues at certain excitation wavelengths were compared to determine the optimal excitation wavelengths for diagnosis of coionic cancer. RESULTS: When compared to normal tissues, low NAD (P)H and FAD, but high amino acids and endogenous phorphyrins of protoporphyrin IX characterized the high-grade malignant coionic tissues. The optimal excitation wavelengths for diagnosis of coionic cancer were about 340, 380, 460, and 540 nm. CONCLUSION: Significant differences in autofluorescence peaks and its intensities can be observed in normal and adenomatous coionic tissues. Autofluorescence EEMs are able to identify coionic tissues.

关键词： Autofluorescence spectroscopy Excitation-emission matrix optical diagnosis Colonic cancer