Laser multipass welding techniques for thick section steels have been developed using a new type of UV combined narrow groove. The shape and sizes at the bottom of groove are determined by analyzing the plasma behavio...Laser multipass welding techniques for thick section steels have been developed using a new type of UV combined narrow groove. The shape and sizes at the bottom of groove are determined by analyzing the plasma behavior using high speed photographic equipment. A stable autogenous CO2 laser welding process and greater penetration are generated at the root pass because of strong reduction of the plasma volume. According to the waveforms of welding current and arc voltage, and the interaction between the arc and the laser induced plasma, a suitable groove angle is obtained. Laser-double MIG hybrid welding process is studied and the optimum distances between the laser and two arcs are determined. By using autogenous CO2 laser welding, CO2 laser-MIG hybrid welding and laser-double MIG hybrid welding, 28 mm thick steel plates are welded with four passes. The welds produced are assessed by X-ray. No crack is found and there is only a small amount of pores. The experimental results show that the multipuss welding procedures proposed can realize the joining of thick section steels with high efficiency and good quality.展开更多
We simulate some laser output patterns observed in our previous experiment employing superposition of Laguerre- Gaussian modes. The rotating pattern is qualitatively analysed from the point of contemporary spatial bur...We simulate some laser output patterns observed in our previous experiment employing superposition of Laguerre- Gaussian modes. The rotating pattern is qualitatively analysed from the point of contemporary spatial burning hole effect of the lasing crystal.展开更多
Results in the air-breathing propulsion experiments with a parabolic light craft and a self-made UV-preionized 100 J TEA CO2 laser device are presented. Air disturbance and the spectrum of the plasma after the interac...Results in the air-breathing propulsion experiments with a parabolic light craft and a self-made UV-preionized 100 J TEA CO2 laser device are presented. Air disturbance and the spectrum of the plasma after the interaction of pulsed laser radiation with the light craft were studied. It was found that the focal length of the parabolic light craft had a significant effect on the air-disturbance. Two shock waves were detected for the longer focal length, while only one shock wave detected for the short focal length. The spectrum of the laser-induced plasma, the distribution of the characteristic lines, and the temporal behaviors of the air plasma were studied in detail. The results showed that, the evolution of the laser-induced plasma lasted 20μs, and the plasma spectrum would reach the maximum intensity at 7μs.展开更多
A grazing incidence flat-field spectrograph using a concave grating was constructed to measure extreme ultraviolet （EUV） emission from a CO 2 laser-produced tin plasma throughout the wavelength region of 5 nm to 20 ...A grazing incidence flat-field spectrograph using a concave grating was constructed to measure extreme ultraviolet （EUV） emission from a CO 2 laser-produced tin plasma throughout the wavelength region of 5 nm to 20 nm for lithography. Spectral efficiency of the EUV emission around 13.5 nm from plate, cavity, and thin foil tin targets was studied. By translating the focusing lens along the laser axis, the dependence of EUV spectra on the amount of defocus was investigated. The results showed that the spectral efficiency was higher for the cavity target in comparison to the plate or foil target, while it decreased with an increase in the defocus distance. The source＇s spectra and the EUV emission intensity normalized to the incident pulse energy at 45 from the target normal were characterized for the in-band （2% of bandwidth） region as a function of laser energy spanning from 46 mJ to 600 mJ for the pure tin plate target. The energy normalized EUV emission was found to increase with the increasing incident pulse energy. It reached the optimum value for the laser energy of around 343 mJ, after which it dropped rapidly.展开更多
The work is devoted to the choice of optimal parameters of laser controlled thermocracking (LСT) when cutting products with a complex curvilinear contour. With this purpose the LCT mathematical model is considered wh...The work is devoted to the choice of optimal parameters of laser controlled thermocracking (LСT) when cutting products with a complex curvilinear contour. With this purpose the LCT mathematical model is considered when a laser beam and coolant transfer from a rectilinear site to a non-rectilinear contour with given radius R. The obtained findings allow proper adjustment of LCT modes to ensure a higher quality of cutting the glass.展开更多
目的比较CO2激光鼓膜造孔术及鼓膜置管术治疗儿童分泌性中耳炎(Otitis media with effusion,OME的临床疗效,探讨CO2激光鼓膜造孔术能否替代鼓膜置管术。方法79例(139耳)OME患儿随机分为两组:激光组:40例(73耳)采用CO2激光鼓膜造孔术;置...目的比较CO2激光鼓膜造孔术及鼓膜置管术治疗儿童分泌性中耳炎(Otitis media with effusion,OME的临床疗效,探讨CO2激光鼓膜造孔术能否替代鼓膜置管术。方法79例(139耳)OME患儿随机分为两组:激光组:40例(73耳)采用CO2激光鼓膜造孔术;置管组:39例(66耳)采用鼓膜置管术。比较两种手术方法的有效率、复发率、并发症发生率以及浆液型、粘液型鼓室积液的治疗效果。结果术后6月激光组治疗有效率63.01%,置管组治疗有效率84.85%,两组差异有统计学意义(χ^2=8.460,P=0.004);激光组鼓膜穿孔平均愈合时间为19.49±5.774天;激光组的复发率为31.5%,置管组的复发率为9.09%,两组差异有统计学意义(χ^2=10.549,P=0.001);激光组并发症发生率为2.74%,置管组并发症发生率为13.64%,两组差异有统计学意义(χ^2=5.648,P=0.017);浆液型积液耳激光组与置管组治疗有效率比较差异无统计学意义(χ^2=1.801,P=0.180),粘液型积液耳激光组与置管组治疗有效率比较差异有统计学意义(χ^2=5.064,P=0.024),置管组有效率优于激光组。结论CO2激光鼓膜造孔术是治疗儿童OME的一种安全、有效的术式,但并未能因此代替鼓膜置管术,需根据患儿是否伴发合并症情况及鼓室积液类型选择合适的手术方法,对于鼓室积液粘稠、同时合并有腺样体肥大、慢性鼻-鼻窦炎或过敏性鼻炎等合并症患者,鼓膜置管术仍为最有效的手术方式。展开更多
Purpose: The purpose of this study was to evaluate a new procedure aimed at lengthening the palpebral fissure to facilitate femtosecond laser-assisted cataract surgery in patients with small eyes. Method: A quick proc...Purpose: The purpose of this study was to evaluate a new procedure aimed at lengthening the palpebral fissure to facilitate femtosecond laser-assisted cataract surgery in patients with small eyes. Method: A quick procedure using the CO2 laser was adapted for patients with small eyes undergoing laser-assisted cataract surgery using the Catalys system. The UniPulse CO2 laser (Nidek) was used for laser lateral canthotomy on patients with small palpebral fissures to allow fitting of the Liquid OpticTM Interface eyepiece. Results: Lateral canthotomies were performed on 19 women and 7 men (ages ranged from 45 to 93 years) with lower eyelid lengths equal to or shorter than 32 mm who then underwent femtosecond laser-assisted cataract surgery. A total of 33 eyelids received laser lateral canthotomy with the CO2 laser;only one eyelid had lateral canthotomy with cold-steel tenotomy scissors. Dockings were completed for all 34 eyes with eyelids receiving lateral canthotomies. The 33 eyes with eyelids that received laser canthotomy with the CO2 laser had successful femtosecond laser-assisted cataract surgery. The one eye with the eyelid that received cold-steel canthotomy could not have femtosecond laser-assisted cataract surgery despite successful docking because of pupillary constriction. The findings were statistically significant;Fisher Exact Test showed a p-value of 0.0294. Conclusion: Laser lateral canthotomy with CO2 laser is a safe and effective method to allow docking and completion of femtosecond laser-assisted cataract surgery.展开更多
文摘Laser multipass welding techniques for thick section steels have been developed using a new type of UV combined narrow groove. The shape and sizes at the bottom of groove are determined by analyzing the plasma behavior using high speed photographic equipment. A stable autogenous CO2 laser welding process and greater penetration are generated at the root pass because of strong reduction of the plasma volume. According to the waveforms of welding current and arc voltage, and the interaction between the arc and the laser induced plasma, a suitable groove angle is obtained. Laser-double MIG hybrid welding process is studied and the optimum distances between the laser and two arcs are determined. By using autogenous CO2 laser welding, CO2 laser-MIG hybrid welding and laser-double MIG hybrid welding, 28 mm thick steel plates are welded with four passes. The welds produced are assessed by X-ray. No crack is found and there is only a small amount of pores. The experimental results show that the multipuss welding procedures proposed can realize the joining of thick section steels with high efficiency and good quality.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10534020 and 60478009.
文摘We simulate some laser output patterns observed in our previous experiment employing superposition of Laguerre- Gaussian modes. The rotating pattern is qualitatively analysed from the point of contemporary spatial burning hole effect of the lasing crystal.
基金National Key Basic Research Special Foundation of China
文摘Results in the air-breathing propulsion experiments with a parabolic light craft and a self-made UV-preionized 100 J TEA CO2 laser device are presented. Air disturbance and the spectrum of the plasma after the interaction of pulsed laser radiation with the light craft were studied. It was found that the focal length of the parabolic light craft had a significant effect on the air-disturbance. Two shock waves were detected for the longer focal length, while only one shock wave detected for the short focal length. The spectrum of the laser-induced plasma, the distribution of the characteristic lines, and the temporal behaviors of the air plasma were studied in detail. The results showed that, the evolution of the laser-induced plasma lasted 20μs, and the plasma spectrum would reach the maximum intensity at 7μs.
基金supported by the Scientific Research Foundation of the Education Department of Hubei Province (No.Q20131512)National Natural Science Foundation of China (No.61078024)
文摘A grazing incidence flat-field spectrograph using a concave grating was constructed to measure extreme ultraviolet （EUV） emission from a CO 2 laser-produced tin plasma throughout the wavelength region of 5 nm to 20 nm for lithography. Spectral efficiency of the EUV emission around 13.5 nm from plate, cavity, and thin foil tin targets was studied. By translating the focusing lens along the laser axis, the dependence of EUV spectra on the amount of defocus was investigated. The results showed that the spectral efficiency was higher for the cavity target in comparison to the plate or foil target, while it decreased with an increase in the defocus distance. The source＇s spectra and the EUV emission intensity normalized to the incident pulse energy at 45 from the target normal were characterized for the in-band （2% of bandwidth） region as a function of laser energy spanning from 46 mJ to 600 mJ for the pure tin plate target. The energy normalized EUV emission was found to increase with the increasing incident pulse energy. It reached the optimum value for the laser energy of around 343 mJ, after which it dropped rapidly.
文摘The work is devoted to the choice of optimal parameters of laser controlled thermocracking (LСT) when cutting products with a complex curvilinear contour. With this purpose the LCT mathematical model is considered when a laser beam and coolant transfer from a rectilinear site to a non-rectilinear contour with given radius R. The obtained findings allow proper adjustment of LCT modes to ensure a higher quality of cutting the glass.
文摘目的比较CO2激光鼓膜造孔术及鼓膜置管术治疗儿童分泌性中耳炎(Otitis media with effusion,OME的临床疗效,探讨CO2激光鼓膜造孔术能否替代鼓膜置管术。方法79例(139耳)OME患儿随机分为两组:激光组:40例(73耳)采用CO2激光鼓膜造孔术;置管组:39例(66耳)采用鼓膜置管术。比较两种手术方法的有效率、复发率、并发症发生率以及浆液型、粘液型鼓室积液的治疗效果。结果术后6月激光组治疗有效率63.01%,置管组治疗有效率84.85%,两组差异有统计学意义(χ^2=8.460,P=0.004);激光组鼓膜穿孔平均愈合时间为19.49±5.774天;激光组的复发率为31.5%,置管组的复发率为9.09%,两组差异有统计学意义(χ^2=10.549,P=0.001);激光组并发症发生率为2.74%,置管组并发症发生率为13.64%,两组差异有统计学意义(χ^2=5.648,P=0.017);浆液型积液耳激光组与置管组治疗有效率比较差异无统计学意义(χ^2=1.801,P=0.180),粘液型积液耳激光组与置管组治疗有效率比较差异有统计学意义(χ^2=5.064,P=0.024),置管组有效率优于激光组。结论CO2激光鼓膜造孔术是治疗儿童OME的一种安全、有效的术式,但并未能因此代替鼓膜置管术,需根据患儿是否伴发合并症情况及鼓室积液类型选择合适的手术方法,对于鼓室积液粘稠、同时合并有腺样体肥大、慢性鼻-鼻窦炎或过敏性鼻炎等合并症患者,鼓膜置管术仍为最有效的手术方式。
文摘Purpose: The purpose of this study was to evaluate a new procedure aimed at lengthening the palpebral fissure to facilitate femtosecond laser-assisted cataract surgery in patients with small eyes. Method: A quick procedure using the CO2 laser was adapted for patients with small eyes undergoing laser-assisted cataract surgery using the Catalys system. The UniPulse CO2 laser (Nidek) was used for laser lateral canthotomy on patients with small palpebral fissures to allow fitting of the Liquid OpticTM Interface eyepiece. Results: Lateral canthotomies were performed on 19 women and 7 men (ages ranged from 45 to 93 years) with lower eyelid lengths equal to or shorter than 32 mm who then underwent femtosecond laser-assisted cataract surgery. A total of 33 eyelids received laser lateral canthotomy with the CO2 laser;only one eyelid had lateral canthotomy with cold-steel tenotomy scissors. Dockings were completed for all 34 eyes with eyelids receiving lateral canthotomies. The 33 eyes with eyelids that received laser canthotomy with the CO2 laser had successful femtosecond laser-assisted cataract surgery. The one eye with the eyelid that received cold-steel canthotomy could not have femtosecond laser-assisted cataract surgery despite successful docking because of pupillary constriction. The findings were statistically significant;Fisher Exact Test showed a p-value of 0.0294. Conclusion: Laser lateral canthotomy with CO2 laser is a safe and effective method to allow docking and completion of femtosecond laser-assisted cataract surgery.
