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RSS2001 Vol. 25, No. 1
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2001, 25(1): 1-6.
[Abstract]
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Abstract:
A lot of experiments have shown that there is an obvious relation between surface qualities of specimen after laser shock-processing(LSP) and its fatigue life.Consequently,the LSP effects can be evaluated by surface qualities in LSP areas.In this paper,an artificial neural network(ANN) is utilized to study the surface qualities of specimen after LSP.Based on the data obtained in the experiment,an ANN is established.The trained ANN could acquire the relations between surface qualities and laser parmeters.From the verification of aluminium alloy 2024-T62,it is proved that the neural network can successfully predict the surface quality grades of specimen after LSP,and easily determine the laser parameters under different production conditions.The research and experimental results show that the ANN has not only the accuracy and good stability,but also the intelligent improving control ability during process.
A lot of experiments have shown that there is an obvious relation between surface qualities of specimen after laser shock-processing(LSP) and its fatigue life.Consequently,the LSP effects can be evaluated by surface qualities in LSP areas.In this paper,an artificial neural network(ANN) is utilized to study the surface qualities of specimen after LSP.Based on the data obtained in the experiment,an ANN is established.The trained ANN could acquire the relations between surface qualities and laser parmeters.From the verification of aluminium alloy 2024-T62,it is proved that the neural network can successfully predict the surface quality grades of specimen after LSP,and easily determine the laser parameters under different production conditions.The research and experimental results show that the ANN has not only the accuracy and good stability,but also the intelligent improving control ability during process.
2001, 25(1): 7-10.
Abstract:
A precision approach utilizing fiber grating as elements to measure height of liquid is presented and experimented and the basic issues of the sensor system design are discussed. This type of sensor can be used in precision measurement of medium measurement ranges. The sensitivity of 0.15mm/pm for measuring the height of water has been obtained.
A precision approach utilizing fiber grating as elements to measure height of liquid is presented and experimented and the basic issues of the sensor system design are discussed. This type of sensor can be used in precision measurement of medium measurement ranges. The sensitivity of 0.15mm/pm for measuring the height of water has been obtained.
2001, 25(1): 11-14.
Abstract:
Three laser bending mechanisms,temperature mechanism,buckling mechanism and upsetting mechanism,are introduced.After being scanned,the sheet that isn't pre-bent can still obtain the bending towards the laser beam.Aiming at this phenomenon,temperature fields and strain fields in laser bending are numerically analyzed by finite element method,it is preserted that its forming mechanism still belongs to buckling mechanism,and the reason is explained.The relationship between bending angles and scanning velocity of the laser beam is studied numerically and experimentally.
Three laser bending mechanisms,temperature mechanism,buckling mechanism and upsetting mechanism,are introduced.After being scanned,the sheet that isn't pre-bent can still obtain the bending towards the laser beam.Aiming at this phenomenon,temperature fields and strain fields in laser bending are numerically analyzed by finite element method,it is preserted that its forming mechanism still belongs to buckling mechanism,and the reason is explained.The relationship between bending angles and scanning velocity of the laser beam is studied numerically and experimentally.
2001, 25(1): 15-18.
Abstract:
A sensitive intracavity photoacoustic spectrometer,which consists of a CO/CO2 laser, a longitudinal resonant photoacoustic cell, a plant gas sampling system and a computer control and data processing system, is able to measure many kinds of gases relevant to plant trace gas exchange. The sensitivity limit of the system for ethylene measurement is 2×10-11.The system is applied to the study of stress reaction of nectarine fruit exposed to O3 by monitoring the variation of the ethylene production. The measurement is helpful for the study of fruit postharvest biology and preservation technique.
A sensitive intracavity photoacoustic spectrometer,which consists of a CO/CO2 laser, a longitudinal resonant photoacoustic cell, a plant gas sampling system and a computer control and data processing system, is able to measure many kinds of gases relevant to plant trace gas exchange. The sensitivity limit of the system for ethylene measurement is 2×10-11.The system is applied to the study of stress reaction of nectarine fruit exposed to O3 by monitoring the variation of the ethylene production. The measurement is helpful for the study of fruit postharvest biology and preservation technique.
2001, 25(1): 18-22.
Abstract:
In this paper, solidification process of laser pool for composite coating system is studied, using numerical technology. The results demonstrate that solidification process may be divided into two stages: quasi-state stage and accelerating stage. At quasi-state stage, the depth and radius of laser pool have small changes, but the highest surface temperature and velocity of molten pool decease rapidly. At the accelerating stage, those are on the contrary. Because of highly overheating in upper molten pool, post molten phenomenon is produced in down molten pool, during solidification quasi-state stage. The key factors to produce post molten region are the overheating and the latent heat released during solidification process in upper molten pool.
In this paper, solidification process of laser pool for composite coating system is studied, using numerical technology. The results demonstrate that solidification process may be divided into two stages: quasi-state stage and accelerating stage. At quasi-state stage, the depth and radius of laser pool have small changes, but the highest surface temperature and velocity of molten pool decease rapidly. At the accelerating stage, those are on the contrary. Because of highly overheating in upper molten pool, post molten phenomenon is produced in down molten pool, during solidification quasi-state stage. The key factors to produce post molten region are the overheating and the latent heat released during solidification process in upper molten pool.
2001, 25(1): 23-26.
Abstract:
Many methods for fabricating periodic gratings (including standing-wave coherent method,transverse holographic method, point-by-point method, phase mask method) and chirped gratings are introduced. The advantages and disadvantages of these methods are compared.
Many methods for fabricating periodic gratings (including standing-wave coherent method,transverse holographic method, point-by-point method, phase mask method) and chirped gratings are introduced. The advantages and disadvantages of these methods are compared.
2001, 25(1): 27-31.
Abstract:
In view of the crystal structure,this paper reports the character of single crystal growth of germanate and the properties as medium of laser crystal.The study and progress in germanate crystals used as widely tunable laser crystal, self-doubling-frequency crystal and highly efficient and low pumping threshold laser crystal are introduced.
In view of the crystal structure,this paper reports the character of single crystal growth of germanate and the properties as medium of laser crystal.The study and progress in germanate crystals used as widely tunable laser crystal, self-doubling-frequency crystal and highly efficient and low pumping threshold laser crystal are introduced.
2001, 25(1): 32-34.
Abstract:
In view of the crystal structure,this paper reports the character of single crystal growth of germanate and the properties as medium of laser crystal.The study and progress in germanate crystals used as widely tunable laser crystal, self-doubling-frequency crystal and highly efficient and low pumping threshold laser crystal are introduced.
In view of the crystal structure,this paper reports the character of single crystal growth of germanate and the properties as medium of laser crystal.The study and progress in germanate crystals used as widely tunable laser crystal, self-doubling-frequency crystal and highly efficient and low pumping threshold laser crystal are introduced.
2001, 25(1): 35-39.
Abstract:
In this paper,the losses of novel sine-Gaussian and cosine-Gaussian beams propagating through a hard aperture are calculated in detail. The results are analyzed and compared. The effect of modulation parameter α is discussed.
In this paper,the losses of novel sine-Gaussian and cosine-Gaussian beams propagating through a hard aperture are calculated in detail. The results are analyzed and compared. The effect of modulation parameter α is discussed.
2001, 25(1): 39-42.
Abstract:
This paper describes the status of cladding with high power density beam. The main problems and the solutions of them in this field are presented. The development tendency of cladding with high power density beam is pointed out.
This paper describes the status of cladding with high power density beam. The main problems and the solutions of them in this field are presented. The development tendency of cladding with high power density beam is pointed out.
2001, 25(1): 43-47.
Abstract:
In the paper,the constructions of a few optical packet switching systems are described.A 2.5 Gbits/s optical ATM switching system is successfully manufactured by ourselves.Its construction,operation principle and the waveform are shown in the paper.
In the paper,the constructions of a few optical packet switching systems are described.A 2.5 Gbits/s optical ATM switching system is successfully manufactured by ourselves.Its construction,operation principle and the waveform are shown in the paper.
2001, 25(1): 48-54.
Abstract:
The developing procedure of laser welding technology is presented in this paper.The current situation of laser welding and future perspective is also clarified.The emphasis is focused on the characteristics of laser welding process and its problems to be studied.The comparisons of laser welding with other welding techniques,including electron beam welding,inert gas tungsten arc welding,gas metal arc welding and resistance welding,are performed roundly and deeply.The advantages and disadvantages of laser welding are summed up.
The developing procedure of laser welding technology is presented in this paper.The current situation of laser welding and future perspective is also clarified.The emphasis is focused on the characteristics of laser welding process and its problems to be studied.The comparisons of laser welding with other welding techniques,including electron beam welding,inert gas tungsten arc welding,gas metal arc welding and resistance welding,are performed roundly and deeply.The advantages and disadvantages of laser welding are summed up.
2001, 25(1): 54-59.
Abstract:
This paper describes the thermal effects of a coaxial RF-excited CO2 laser,based on the balance equations of electron density and energy,current continuity equation,and heat conduction equationDependencies of the spatial distributions of gas temperature on some discharge parameters are discussed.
This paper describes the thermal effects of a coaxial RF-excited CO2 laser,based on the balance equations of electron density and energy,current continuity equation,and heat conduction equationDependencies of the spatial distributions of gas temperature on some discharge parameters are discussed.
2001, 25(1): 60-63.
Abstract:
In this paper, we report a kind of holographic wave-guided optical interconnect based on a glass substrate and transmission volume gratings in photopolymer. An experimental curve of diffraction efficiency for each output grating was plotted. Maximum diffraction efficiency of output grating tends to 50%. The angular deviation of output light from the surface-normal is 0.43° and the relative intensity fluctuation of output light is 11% while the wavelength is 632.8nm.
In this paper, we report a kind of holographic wave-guided optical interconnect based on a glass substrate and transmission volume gratings in photopolymer. An experimental curve of diffraction efficiency for each output grating was plotted. Maximum diffraction efficiency of output grating tends to 50%. The angular deviation of output light from the surface-normal is 0.43° and the relative intensity fluctuation of output light is 11% while the wavelength is 632.8nm.
2001, 25(1): 63-66.
Abstract:
In the miniature Cr4+:YAG passive Q-switched conductive cooling repetitive(Nd,Ce):YAG lasers,replacement of the 100% reflector of its plane-parallel resonator with a TIR(total internal reflection)prism,gives better thermal stability characteristic and the repetitive frequency reaches 5pps. Single laser pulse output gets to 20～25mJ with pulse width smaller than 15ns.The operation ambient temperature range reaches -40℃～+55℃.
In the miniature Cr4+:YAG passive Q-switched conductive cooling repetitive(Nd,Ce):YAG lasers,replacement of the 100% reflector of its plane-parallel resonator with a TIR(total internal reflection)prism,gives better thermal stability characteristic and the repetitive frequency reaches 5pps. Single laser pulse output gets to 20～25mJ with pulse width smaller than 15ns.The operation ambient temperature range reaches -40℃～+55℃.
2001, 25(1): 67-70.
Abstract:
The influence of the delivery distance on the focus quality of laser beam in large field laser processing machine has been discussed and analyzed theoretically. Several kinds of international leading methods for improving the focus quality of laser beam have been described in this paper.
The influence of the delivery distance on the focus quality of laser beam in large field laser processing machine has been discussed and analyzed theoretically. Several kinds of international leading methods for improving the focus quality of laser beam have been described in this paper.
2001, 25(1): 70-72.
Abstract:
A method of focal length measurement by calculating Fourier transform spectrum interference fringes of symmetric double circular apertures with small distance is presented.The setup is simple with high accuracy.The principle is described and the error is analyzed.The consistent experimental results are also given in the paper.
A method of focal length measurement by calculating Fourier transform spectrum interference fringes of symmetric double circular apertures with small distance is presented.The setup is simple with high accuracy.The principle is described and the error is analyzed.The consistent experimental results are also given in the paper.
2001, 25(1): 73-76.
Abstract:
By calculating the mode volume of the Gaussian fundamental mode in the steady zone, the gain mode volume for two-rod Nd:YAG laser in symmetric interval setting is compared with that in equal interval setting. It is found that two-rod resonator in equal interval setting can get higher output power.
By calculating the mode volume of the Gaussian fundamental mode in the steady zone, the gain mode volume for two-rod Nd:YAG laser in symmetric interval setting is compared with that in equal interval setting. It is found that two-rod resonator in equal interval setting can get higher output power.
2001, 25(1): 76-79.
Abstract:
The characteristics of gain spectrum of a semiconductor optical amplifier(SOA) are analyzed and the output extinction ratio of wavelength conversion based on cross-gain modulation(XGM) is studied numerically in this paper. Moreover,we investigate the causes of the degradation of extinction ratio,which provides the theoretical basis for improving the characteristic of wavelength converters.
The characteristics of gain spectrum of a semiconductor optical amplifier(SOA) are analyzed and the output extinction ratio of wavelength conversion based on cross-gain modulation(XGM) is studied numerically in this paper. Moreover,we investigate the causes of the degradation of extinction ratio,which provides the theoretical basis for improving the characteristic of wavelength converters.
2001, 25(1): 80-81.
Abstract:
This paper introduces a method for cauterization treatment of salivary glands cyst with Nd:YAP laser.In 120 treatment cases,the cure rate is high up to 100%.Therefore the method is better than any others.
This paper introduces a method for cauterization treatment of salivary glands cyst with Nd:YAP laser.In 120 treatment cases,the cure rate is high up to 100%.Therefore the method is better than any others.
