Double-pulse LIBS is a promising technique for deep-sea applications.LIBS measurements in shallow water with up to 400 mJ each pulse were done to select laser parameters which promote optimized spectral line emission ...Double-pulse LIBS is a promising technique for deep-sea applications.LIBS measurements in shallow water with up to 400 mJ each pulse were done to select laser parameters which promote optimized spectral line emission from plasma even at elevated pressures,where line broadening until loss of most of the spectral information can occur.Optical emission spectroscopy,using a Czerny-Turner spectrometer,has been applied to investigate the dependence of the emitted radiation on laser parameters and hydrostatic pressure.It has been found,that higher laser pulse energies,especially with short pulse delay as required in high water pressure,can also have an adverse effect on the measured spectrum.展开更多
Welding voltage and current in arc signals are directly related to arc stability and welding quality.Process experiments with different parameters were organized according to the orthogonal experimental design method ...Welding voltage and current in arc signals are directly related to arc stability and welding quality.Process experiments with different parameters were organized according to the orthogonal experimental design method by constructing an aluminum alloy double-pulse metal inert gas(MIG)welding arc electric signal test platform.The data acquisition system of the aluminum alloy MIG welding process was established to obtain real-time arc signal information reflecting the welding process.The aluminum alloy’s collected double-pulse arc current signals are decomposed adaptively by broadband mode decomposition(BMD).The direct current(DC)signal,pulse signal,distortion signal,ripple signal,and noise signal are separated and extracted,and the composite multiscale fuzzy entropy(CMFE)is calculated for the component set of the electrical signal.The experimental results show that the current waveform obtained by the double-pulse MIG welding current signal is consistent with the corresponding weld forming diagram.Simultaneously,the composite multiscale fuzzy entropy is calculated for the arc characteristic parameters.The rationality of matching process parameters and arc stability of aluminum alloy’s double-pulse MIG welding were evaluated.展开更多
目的探讨良性阵发性位置性眩晕(BPPV)患者SRM-IV眩晕诊疗系统治疗后眩晕残障现状的影响因素。方法采用前瞻性队列研究,选取2022年4月至2023年4月于西宁市第一人民医院进行SRM-IV眩晕诊疗系统治疗的BPPV患者100例为研究对象,分析治疗后...目的探讨良性阵发性位置性眩晕(BPPV)患者SRM-IV眩晕诊疗系统治疗后眩晕残障现状的影响因素。方法采用前瞻性队列研究,选取2022年4月至2023年4月于西宁市第一人民医院进行SRM-IV眩晕诊疗系统治疗的BPPV患者100例为研究对象,分析治疗后患者的眩晕残障现状及相关影响因素。结果与治疗前相比,BPPV患者治疗后眩晕残障程度量表(DHI)评分较低(68.36±13.14 vs 45.29±8.20)分。与治疗有效的BPPV患者相比,治疗无效的BPPV患者治疗后DHI评分较高(43.32±7.01 vs 67.89±14.01)分。单因素分析显示,≥60岁、病程≥3个月、有头部外伤史、有高血压、高血脂、高血糖、半规管轻瘫CP值≥20%、25羟维生素D3[25-(OH)-D3]<30μg/L、同型半胱氨酸(Hcy)≥13μmol/L、嵴帽型、雌二醇(E2)<100 pmol/L的BPPV患者SRM-IV眩晕诊疗系统治疗后DHI评分较高。多因素Logistics回归分析显示,年龄、病程、头部外伤史、高血压、高血脂、高血糖、半规管轻瘫CP值、25-(OH)-D3、Hcy、疾病类型、E2为影响BPPV患者SRM-IV眩晕诊疗系统治疗后眩晕残障现状的主要因素。结论BPPV患者经SRM-IV眩晕诊疗系统治疗后眩晕残障现状改善,合并症、病情严重程度、外伤史等均与眩晕残障现状相关。展开更多
The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas（DP-MIG） welding process was investigated by simulation and experiment.A three-dimensional finite element model and the DP-...The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas（DP-MIG） welding process was investigated by simulation and experiment.A three-dimensional finite element model and the DP-MIG heat source of double-ellipsoidal volumetric model were developed to simulate the temperature and stress fields under different welding conditions.The macro-morphology and microstructure of welding joints at the corresponding currents were observed in the experiment.The results show that the best condition is at an average current of 90 A and current difference of 40 A,when the maximum temperature is 200 °C higher than the fusion points,with the temperature difference of about 100 °C and stress change of 10 MPa between thermal pulse and thermal base.Under these conditions,Al alloy T-joint with proper fusion condition has smooth fish-scale welding appearance and finer microstructure.Furthermore,the thermal curves and stress distribution in the experiment are consistent with those in the simulation,verifying the precision of the welding simulation.展开更多
In this study, a stand-off and collinear double pulse laser-induced breakdown spectroscopy （DP LIBS） system was designed, and the magnesium alloy samples at a distance of 2.5 m away from the LIBS system were measure...In this study, a stand-off and collinear double pulse laser-induced breakdown spectroscopy （DP LIBS） system was designed, and the magnesium alloy samples at a distance of 2.5 m away from the LIBS system were measured. The effect of inter-pulse delay on spectra was studied, and the signal enhancement was observed compared to the single pulse LIBS （SP LIBS）. The morphology of the ablated crater on the sample indicated a higher efficiency of surface pretreatment in DP LIBS. The calibration curves of Ytterbium （Y） and Zirconium （Zr） were investigated. The square of the correlation coefficient of the calibration curve of element Y reached up to 0.9998.展开更多
In this paper, we present a study on the effect of inter-pulse delay using femtosecond double-pulse laser-induced breakdown spectroscopy in a collinear geometry. The temporal evolution of spectral intensity is perform...In this paper, we present a study on the effect of inter-pulse delay using femtosecond double-pulse laser-induced breakdown spectroscopy in a collinear geometry. The temporal evolution of spectral intensity is performed for the lines of Fe I 423.60 nm, Fe I 425.08 nm and Fe I 427.18 nm. It is found that, by selecting appropriate inter-pulse delay, the signal enhancement can be significantly increased compared with the single-pulse case. A three-fold enhancement in the current experiment is obtained. The plasma temperature and electron density are also investigated based on the theory of Boltzmann plot and Stark broadening. We attribute the main mechanism for emission enhancement to the plasma re-heating effect.展开更多
New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd：YAG laser beams（266＋1064 nm） are optimized to focus on the sample in air. Optimization of the exper...New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd：YAG laser beams（266＋1064 nm） are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.展开更多
基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)–Project No.454848899。
文摘Double-pulse LIBS is a promising technique for deep-sea applications.LIBS measurements in shallow water with up to 400 mJ each pulse were done to select laser parameters which promote optimized spectral line emission from plasma even at elevated pressures,where line broadening until loss of most of the spectral information can occur.Optical emission spectroscopy,using a Czerny-Turner spectrometer,has been applied to investigate the dependence of the emitted radiation on laser parameters and hydrostatic pressure.It has been found,that higher laser pulse energies,especially with short pulse delay as required in high water pressure,can also have an adverse effect on the measured spectrum.
基金The 2024 University-level Higher Education Teaching Reform Project of Guangzhou Xinhua University,“Teaching Reform and Practice Based on OBE Concept”:A Case Study of“University Physics Experiment”(Project No.2024J044)。
文摘Welding voltage and current in arc signals are directly related to arc stability and welding quality.Process experiments with different parameters were organized according to the orthogonal experimental design method by constructing an aluminum alloy double-pulse metal inert gas(MIG)welding arc electric signal test platform.The data acquisition system of the aluminum alloy MIG welding process was established to obtain real-time arc signal information reflecting the welding process.The aluminum alloy’s collected double-pulse arc current signals are decomposed adaptively by broadband mode decomposition(BMD).The direct current(DC)signal,pulse signal,distortion signal,ripple signal,and noise signal are separated and extracted,and the composite multiscale fuzzy entropy(CMFE)is calculated for the component set of the electrical signal.The experimental results show that the current waveform obtained by the double-pulse MIG welding current signal is consistent with the corresponding weld forming diagram.Simultaneously,the composite multiscale fuzzy entropy is calculated for the arc characteristic parameters.The rationality of matching process parameters and arc stability of aluminum alloy’s double-pulse MIG welding were evaluated.
文摘目的探讨良性阵发性位置性眩晕(BPPV)患者SRM-IV眩晕诊疗系统治疗后眩晕残障现状的影响因素。方法采用前瞻性队列研究,选取2022年4月至2023年4月于西宁市第一人民医院进行SRM-IV眩晕诊疗系统治疗的BPPV患者100例为研究对象,分析治疗后患者的眩晕残障现状及相关影响因素。结果与治疗前相比,BPPV患者治疗后眩晕残障程度量表(DHI)评分较低(68.36±13.14 vs 45.29±8.20)分。与治疗有效的BPPV患者相比,治疗无效的BPPV患者治疗后DHI评分较高(43.32±7.01 vs 67.89±14.01)分。单因素分析显示,≥60岁、病程≥3个月、有头部外伤史、有高血压、高血脂、高血糖、半规管轻瘫CP值≥20%、25羟维生素D3[25-(OH)-D3]<30μg/L、同型半胱氨酸(Hcy)≥13μmol/L、嵴帽型、雌二醇(E2)<100 pmol/L的BPPV患者SRM-IV眩晕诊疗系统治疗后DHI评分较高。多因素Logistics回归分析显示,年龄、病程、头部外伤史、高血压、高血脂、高血糖、半规管轻瘫CP值、25-(OH)-D3、Hcy、疾病类型、E2为影响BPPV患者SRM-IV眩晕诊疗系统治疗后眩晕残障现状的主要因素。结论BPPV患者经SRM-IV眩晕诊疗系统治疗后眩晕残障现状改善,合并症、病情严重程度、外伤史等均与眩晕残障现状相关。
基金Project(51475156)supported by the National Natural Science Foundation of China
文摘The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas（DP-MIG） welding process was investigated by simulation and experiment.A three-dimensional finite element model and the DP-MIG heat source of double-ellipsoidal volumetric model were developed to simulate the temperature and stress fields under different welding conditions.The macro-morphology and microstructure of welding joints at the corresponding currents were observed in the experiment.The results show that the best condition is at an average current of 90 A and current difference of 40 A,when the maximum temperature is 200 °C higher than the fusion points,with the temperature difference of about 100 °C and stress change of 10 MPa between thermal pulse and thermal base.Under these conditions,Al alloy T-joint with proper fusion condition has smooth fish-scale welding appearance and finer microstructure.Furthermore,the thermal curves and stress distribution in the experiment are consistent with those in the simulation,verifying the precision of the welding simulation.
基金supported by National Natural Science Foundation of China(No.61473279)the National High-Tech Research and Development Program of China(863 Program)(No.2012AA040608)Equipment Development Programs of the Chinese Academy of Sciences(No.YZ201247)
文摘In this study, a stand-off and collinear double pulse laser-induced breakdown spectroscopy （DP LIBS） system was designed, and the magnesium alloy samples at a distance of 2.5 m away from the LIBS system were measured. The effect of inter-pulse delay on spectra was studied, and the signal enhancement was observed compared to the single pulse LIBS （SP LIBS）. The morphology of the ablated crater on the sample indicated a higher efficiency of surface pretreatment in DP LIBS. The calibration curves of Ytterbium （Y） and Zirconium （Zr） were investigated. The square of the correlation coefficient of the calibration curve of element Y reached up to 0.9998.
基金supported by the National Basic Research Program of China(No.2013CB922200)the China Postdoctoral Science Foundation(No.2014M551169)National Natural Science Foundation of China(Nos.11674128,11474129 and 11504129)
文摘In this paper, we present a study on the effect of inter-pulse delay using femtosecond double-pulse laser-induced breakdown spectroscopy in a collinear geometry. The temporal evolution of spectral intensity is performed for the lines of Fe I 423.60 nm, Fe I 425.08 nm and Fe I 427.18 nm. It is found that, by selecting appropriate inter-pulse delay, the signal enhancement can be significantly increased compared with the single-pulse case. A three-fold enhancement in the current experiment is obtained. The plasma temperature and electron density are also investigated based on the theory of Boltzmann plot and Stark broadening. We attribute the main mechanism for emission enhancement to the plasma re-heating effect.
文摘New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd：YAG laser beams（266＋1064 nm） are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.
