Map
WeChat
Email alert
RSS2021 Vol. 45, No. 4
Display Method:
[Abstract]
[PDF 260KB]
2021, 45(4): 405-410.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.001
[FullText HTML]
Abstract:
In order to explore the characteristics of the state change of micro-nano particles during the laser plasma shock wave cleaning process, cleaning experiments were carried out for Al micro-nano particles on the surface of single crystal silicon; combined with the plasma propagation law and finite element method, the internal stress and temperature changes of the particles were simulated under the circumstances, and the law of phase transition and evolution of particles was obtained. The results show that the number of large and medium particles is significantly reduced, and the size is changed from 0.5μm~3μm to 0.1μm~1μm; the change in the state of the particles is mainly caused by the instantaneous high temperature and high pressure of the shock wave, and the maximum stress in the particles reaches 1GPa. The maximum temperature reaches 1100K; therefore, the particles break and phase change under the action of the shock wave, and the number of fine particles increases and adheres to the sample surface, which increases the difficulty of cleaning. This research can provide reference for the theory and application of laser cleaning particles.
In order to explore the characteristics of the state change of micro-nano particles during the laser plasma shock wave cleaning process, cleaning experiments were carried out for Al micro-nano particles on the surface of single crystal silicon; combined with the plasma propagation law and finite element method, the internal stress and temperature changes of the particles were simulated under the circumstances, and the law of phase transition and evolution of particles was obtained. The results show that the number of large and medium particles is significantly reduced, and the size is changed from 0.5μm~3μm to 0.1μm~1μm; the change in the state of the particles is mainly caused by the instantaneous high temperature and high pressure of the shock wave, and the maximum stress in the particles reaches 1GPa. The maximum temperature reaches 1100K; therefore, the particles break and phase change under the action of the shock wave, and the number of fine particles increases and adheres to the sample surface, which increases the difficulty of cleaning. This research can provide reference for the theory and application of laser cleaning particles.
2021, 45(4): 411-416.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.002
Abstract:
In order to explore the choice of white balance point in laser display, the influence of white balance point change on the color gamut in three primaries laser display was studied based on the color mixing theory and stereoscopic color gamut algorithm. Taking D65 color gamut as the standard, the appropriate white balance point selection range of laser display system was obtained by combining with color gamut coverage. The results show that when the white balance point is on the blackbody locus, the best choice of color temperature is around 6500K under different wavelength combinations. Further, considering the situation that the white point deviates from the blackbody locus, the appropriate selection range of white balance point of laser display system under different wavelength combinations can be obtained. These results can provide theoretical basis and reference for the selection of white balance point of display system.
In order to explore the choice of white balance point in laser display, the influence of white balance point change on the color gamut in three primaries laser display was studied based on the color mixing theory and stereoscopic color gamut algorithm. Taking D65 color gamut as the standard, the appropriate white balance point selection range of laser display system was obtained by combining with color gamut coverage. The results show that when the white balance point is on the blackbody locus, the best choice of color temperature is around 6500K under different wavelength combinations. Further, considering the situation that the white point deviates from the blackbody locus, the appropriate selection range of white balance point of laser display system under different wavelength combinations can be obtained. These results can provide theoretical basis and reference for the selection of white balance point of display system.
2021, 45(4): 417-428.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.003
Abstract:
Glass materials are widely used in semiconductor, micro-electromechanical system, microfluidic chip, optical communication, optical storage, and other emerging fields due to its excellent and unique physical and chemical properties. As a new non-contact machining method, laser technology can carry out high-precision and high-efficiency micro-machining on the surface and inside of glass materials, which shows great development potential in the field of glass material processing. In this paper, the basic principle and key problems of four typical laser machining glass processes: Laser etching, laser drilling, laser welding, and laser fabrication of functional structures were reviewed. And the latest research progress, technological level, and application status of laser processing of glass materials were pointed out. Laser etching includes laser direct-writing etching, laser-induced plasma-assisted ablation, and laser-induced backside wet etching; laser drilling includes far-infrared CO2 laser drilling, ultrafast laser drilling, and improved new drilling methods; laser welding includes far-infrared CO2 laser welding, nanosecond laser welding, and ultrafast laser welding; while laser fabrication of functional structures was divided into surface functional structures fabrication and internal functional structures fabrication. At the same time the advantages and disadvantages of four kinds of laser machining glass processes were summarized, and the bottleneck problems were analyzed. On this basis, the development prospect of laser processing technology for glass materials is summarized and prospected.
Glass materials are widely used in semiconductor, micro-electromechanical system, microfluidic chip, optical communication, optical storage, and other emerging fields due to its excellent and unique physical and chemical properties. As a new non-contact machining method, laser technology can carry out high-precision and high-efficiency micro-machining on the surface and inside of glass materials, which shows great development potential in the field of glass material processing. In this paper, the basic principle and key problems of four typical laser machining glass processes: Laser etching, laser drilling, laser welding, and laser fabrication of functional structures were reviewed. And the latest research progress, technological level, and application status of laser processing of glass materials were pointed out. Laser etching includes laser direct-writing etching, laser-induced plasma-assisted ablation, and laser-induced backside wet etching; laser drilling includes far-infrared CO2 laser drilling, ultrafast laser drilling, and improved new drilling methods; laser welding includes far-infrared CO2 laser welding, nanosecond laser welding, and ultrafast laser welding; while laser fabrication of functional structures was divided into surface functional structures fabrication and internal functional structures fabrication. At the same time the advantages and disadvantages of four kinds of laser machining glass processes were summarized, and the bottleneck problems were analyzed. On this basis, the development prospect of laser processing technology for glass materials is summarized and prospected.
2021, 45(4): 429-435.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.004
Abstract:
As a new type of subtractive processing technology, femtosecond laser has unique advantages in material micromachining. The mechanism of femtosecond laser processing was introduced, and the factors that influence the femtosecond laser processing efficiency and processing quality were analysed. The prediction method of femtosecond laser processing parameters and surface quality was expounded. The combined application of the femtosecond laser and additive manufacturing was thenprospected. There are many factors affecting the efficiency and accuracy of femtosecond laser processing. To truly apply this fine technology on a large scale in the field of metal processing, more in-depth study of the system of femtosecond laser and its interaction with the different properties of the metal material is still needed.
As a new type of subtractive processing technology, femtosecond laser has unique advantages in material micromachining. The mechanism of femtosecond laser processing was introduced, and the factors that influence the femtosecond laser processing efficiency and processing quality were analysed. The prediction method of femtosecond laser processing parameters and surface quality was expounded. The combined application of the femtosecond laser and additive manufacturing was thenprospected. There are many factors affecting the efficiency and accuracy of femtosecond laser processing. To truly apply this fine technology on a large scale in the field of metal processing, more in-depth study of the system of femtosecond laser and its interaction with the different properties of the metal material is still needed.
2021, 45(4): 436-440.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.005
Abstract:
In order to avoid the nonlinear effect of the optical fiber and the insensitivity of the front-end vibration under the high power pulse, a new fiber sensing structure method of composite fiber was adopted, which was analyzed theoretically and verified experimentally. By using the hybrid of multi-mode fiber and single-mode fiber as the sensing fiber method, the distance data of the optical fiber sensing was obtained by processing the sensing signals under different power pulses. The results show that the new composite optical fiber sensor structure can detect the vibration signal of 30km. At the same time, the sensing function of multi-mode fiber in Raman system was further studied, and the sensing characteristics of multi-mode fiber were discussed. The new sensor structure provides an important reference for the scientific research and engineering application of the multimode fiber in the field of phase-sensitive optical time-domain sensing.
In order to avoid the nonlinear effect of the optical fiber and the insensitivity of the front-end vibration under the high power pulse, a new fiber sensing structure method of composite fiber was adopted, which was analyzed theoretically and verified experimentally. By using the hybrid of multi-mode fiber and single-mode fiber as the sensing fiber method, the distance data of the optical fiber sensing was obtained by processing the sensing signals under different power pulses. The results show that the new composite optical fiber sensor structure can detect the vibration signal of 30km. At the same time, the sensing function of multi-mode fiber in Raman system was further studied, and the sensing characteristics of multi-mode fiber were discussed. The new sensor structure provides an important reference for the scientific research and engineering application of the multimode fiber in the field of phase-sensitive optical time-domain sensing.
2021, 45(4): 441-447.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.006
Abstract:
In order to study the microstructure evolution and mechanical properties of laser cladding coatings of high temperature alloy, a nickel-based NiCrFeMo high temperature alloy coating was prepared on the surface of 2Cr25Ni20 heat-resistant austenitic stainless steel using laser cladding technology. The cladding technology prepares a nickel-based NiCrFeMo high-temperature alloy coating on the surface of 2Cr25Ni20 heat-resistant austenitic stainless steel. Scanming electron microscope, X-ray diffraction, energy dispersive spectrometer, micro-hardness tester and other micro-analysis test methods were used to analyze the microstructure morphology, phase types, interface element distribution and segregation, and hardness of each area of the nickel-based superalloy coating. The results show that the bonding position of the base material and the cladding layer to the top of the cladding layer is sequentially generated from a variety of crystal grain morphologies. The Nb and Mo elements diffuse to the substrate under the action of the molten metal liquid convection, and the other elements basically have no diffusion. The cladding layer has phases: γ-Ni and Cr2Fe14C, while the bonding position of the cladding layer contains phases: Fe2Ni3, γ-(Fe, Ni), and Ni0.9Nb0.1. The average microhardness of the substrate is about 252HV0.3, and the average microhardness of the cladding layer is about 285HV0.3. In normal temperature tensile test, compared with the mechanical properties of 2Cr25Ni20 steel, the tensile strength of 2Cr25Ni20 steel repaired parts increases, the strength increases, the elongation after fracture decreases significantly, and the plasticity decreases. Therefore, this study provides a feasible plan for the subsequent repair of the steel furnace shaft.
In order to study the microstructure evolution and mechanical properties of laser cladding coatings of high temperature alloy, a nickel-based NiCrFeMo high temperature alloy coating was prepared on the surface of 2Cr25Ni20 heat-resistant austenitic stainless steel using laser cladding technology. The cladding technology prepares a nickel-based NiCrFeMo high-temperature alloy coating on the surface of 2Cr25Ni20 heat-resistant austenitic stainless steel. Scanming electron microscope, X-ray diffraction, energy dispersive spectrometer, micro-hardness tester and other micro-analysis test methods were used to analyze the microstructure morphology, phase types, interface element distribution and segregation, and hardness of each area of the nickel-based superalloy coating. The results show that the bonding position of the base material and the cladding layer to the top of the cladding layer is sequentially generated from a variety of crystal grain morphologies. The Nb and Mo elements diffuse to the substrate under the action of the molten metal liquid convection, and the other elements basically have no diffusion. The cladding layer has phases: γ-Ni and Cr2Fe14C, while the bonding position of the cladding layer contains phases: Fe2Ni3, γ-(Fe, Ni), and Ni0.9Nb0.1. The average microhardness of the substrate is about 252HV0.3, and the average microhardness of the cladding layer is about 285HV0.3. In normal temperature tensile test, compared with the mechanical properties of 2Cr25Ni20 steel, the tensile strength of 2Cr25Ni20 steel repaired parts increases, the strength increases, the elongation after fracture decreases significantly, and the plasticity decreases. Therefore, this study provides a feasible plan for the subsequent repair of the steel furnace shaft.
2021, 45(4): 448-455.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.007
Abstract:
In order to achieve blood glucose concentration detection with ultra-low sample volume and high sensitivity, the influence of the wall thickness and diameter of liquid-core microtube cavity(MTC) on whispery gallery mode(WGM) resonance property was analyzed based on finite-difference time-domain(FDTD) method. The MTC was fabricated by melt-taping method. High-precision coupling of MTC and tapered fiber and the excitation of WGM resonance spectrum were realized by high-precision electronically controlled displacement platform. The surface functionalization and over-coupling methods of MTC were carried out to improve sensitivity and stability. Theoretical analysis and experimental verification have been carried out. The experimental results show that the linearity and sensitivity of the surface functionalized liquid-core MTC sensor are 0.988 and 0.911pm/(mmol· L-1), respectively. The low-concentration blood glucose optical sensor has high sensitivity and stability. This result is helpful for real-time and rapid monitoring of blood sugar during training of athletes, and for ensuring the safety and durability of sports.
In order to achieve blood glucose concentration detection with ultra-low sample volume and high sensitivity, the influence of the wall thickness and diameter of liquid-core microtube cavity(MTC) on whispery gallery mode(WGM) resonance property was analyzed based on finite-difference time-domain(FDTD) method. The MTC was fabricated by melt-taping method. High-precision coupling of MTC and tapered fiber and the excitation of WGM resonance spectrum were realized by high-precision electronically controlled displacement platform. The surface functionalization and over-coupling methods of MTC were carried out to improve sensitivity and stability. Theoretical analysis and experimental verification have been carried out. The experimental results show that the linearity and sensitivity of the surface functionalized liquid-core MTC sensor are 0.988 and 0.911pm/(mmol· L-1), respectively. The low-concentration blood glucose optical sensor has high sensitivity and stability. This result is helpful for real-time and rapid monitoring of blood sugar during training of athletes, and for ensuring the safety and durability of sports.
2021, 45(4): 456-462.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.008
Abstract:
In order to realize the on-line accurate measurement of turbidity of traditional Chinese medicine (TCM), the spectrum characteristics analysis method was used to establish the relationship between the spectrum characteristics and turbidity of the transmitted and scattered light signals. A near-infrared LED was employed as the light source of the sensor. The transmitted light and scattered light signals were converted into weak current signals by FDS100 photodiodes, then conditioned by a trans-impedance amplifier and a low-pass filter. The processed signals then were converted by A/D converters to digital signals. A MCU (STM32F405) was used to calculate fast Fourier transformation and turbidity. Finally, sixteen groups of standard turbidity solution (Formazin) ranging from 0NTU to 1000NTU were prepared using gradient dilution method to calibrate our sensor and make further verification, in addition, the sensor was applied for determination of the turbidity of angelica essential oil. The results show that the related coefficients of linear fitting of a ratio of the third and fifth harmonics components of the transmitted signal amplitude and the scattered signal amplitude are 0.9883 and 0.9946, respectively. And the minimum error and maximum error of our sensor are 0.471% and 3.768%, respectively. A good linear fitting degree of the turbidity of angelica essential oil is 0.99176, which satisfies real-time and on-line measurement requirements of essential oil extraction, concentration and drying. Therefore, the sensor has certain application filed for manufacturing and quality monitoring of TCM.
In order to realize the on-line accurate measurement of turbidity of traditional Chinese medicine (TCM), the spectrum characteristics analysis method was used to establish the relationship between the spectrum characteristics and turbidity of the transmitted and scattered light signals. A near-infrared LED was employed as the light source of the sensor. The transmitted light and scattered light signals were converted into weak current signals by FDS100 photodiodes, then conditioned by a trans-impedance amplifier and a low-pass filter. The processed signals then were converted by A/D converters to digital signals. A MCU (STM32F405) was used to calculate fast Fourier transformation and turbidity. Finally, sixteen groups of standard turbidity solution (Formazin) ranging from 0NTU to 1000NTU were prepared using gradient dilution method to calibrate our sensor and make further verification, in addition, the sensor was applied for determination of the turbidity of angelica essential oil. The results show that the related coefficients of linear fitting of a ratio of the third and fifth harmonics components of the transmitted signal amplitude and the scattered signal amplitude are 0.9883 and 0.9946, respectively. And the minimum error and maximum error of our sensor are 0.471% and 3.768%, respectively. A good linear fitting degree of the turbidity of angelica essential oil is 0.99176, which satisfies real-time and on-line measurement requirements of essential oil extraction, concentration and drying. Therefore, the sensor has certain application filed for manufacturing and quality monitoring of TCM.
2021, 45(4): 463-469.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.009
Abstract:
In order to obtain intense and broad harmonic spectral plateau, by numerical solution of time-dependent Schrödinger equation, the half-cycle waveform control for producing the optimal half-cycle harmonic emission conditions was proposed by using multi-color combined field. The results show that, by controlling the chirps of two-color field, the optimal negative half-cycle waveform can be obtained; while, by controlling the chirp delay, the optimal positive half-cycle waveform can be produced. Driven by the above waveforms, the harmonic cutoffs can be extended. Further, with the introduction of ultraviolet pulse, due to the ultraviolet resonance enhanced ionization, the harmonic intensity can be enhanced. Furthermore, when the ultraviolet energy meets the single and two photon resonance enhanced ionization, the harmonic intensity is remarkably enhanced. With the decrease of ultraviolet photon energy, the enhancement of harmonic intensity decreases. Finally, the single attosecond pulses of sub-50as can be obtained by superposing harmonics on the harmonic spectral plateau. The results are helpful for the control of high-order harmonic generation and the production of attosecond pulses.
In order to obtain intense and broad harmonic spectral plateau, by numerical solution of time-dependent Schrödinger equation, the half-cycle waveform control for producing the optimal half-cycle harmonic emission conditions was proposed by using multi-color combined field. The results show that, by controlling the chirps of two-color field, the optimal negative half-cycle waveform can be obtained; while, by controlling the chirp delay, the optimal positive half-cycle waveform can be produced. Driven by the above waveforms, the harmonic cutoffs can be extended. Further, with the introduction of ultraviolet pulse, due to the ultraviolet resonance enhanced ionization, the harmonic intensity can be enhanced. Furthermore, when the ultraviolet energy meets the single and two photon resonance enhanced ionization, the harmonic intensity is remarkably enhanced. With the decrease of ultraviolet photon energy, the enhancement of harmonic intensity decreases. Finally, the single attosecond pulses of sub-50as can be obtained by superposing harmonics on the harmonic spectral plateau. The results are helpful for the control of high-order harmonic generation and the production of attosecond pulses.
2021, 45(4): 470-474.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.010
Abstract:
In order to meet the requirements of the virtual reality head-mounted display with large field of view, large exit pupil, and high imaging quality, a three-piece virtual reality head-mounted display optical system was designed using aspheric lenses, and the tolerance analysis of the optical system was carried out.The results show that the average modulation transfer function (MTF) value of the optical system meets the transfer function requirements. The field of view of the system is 90°, the exit pupil diameter is 8mm, the system weight is 33.67g, the total length is less than 60mm, the MTF value at 9.31lp/mm is better than 0.272, the maximum distortion is 8.17%, and the maximum vertical chromatic aberration is 36.2μm that less than a pixel size, respectively. Compared with the literature, the field of view, exit pupil diameter, and exit pupil distance is respectively increased, and the imaging quality is improved. This study can provide a reference for the optical design of immersive head-mounted displays.
In order to meet the requirements of the virtual reality head-mounted display with large field of view, large exit pupil, and high imaging quality, a three-piece virtual reality head-mounted display optical system was designed using aspheric lenses, and the tolerance analysis of the optical system was carried out.The results show that the average modulation transfer function (MTF) value of the optical system meets the transfer function requirements. The field of view of the system is 90°, the exit pupil diameter is 8mm, the system weight is 33.67g, the total length is less than 60mm, the MTF value at 9.31lp/mm is better than 0.272, the maximum distortion is 8.17%, and the maximum vertical chromatic aberration is 36.2μm that less than a pixel size, respectively. Compared with the literature, the field of view, exit pupil diameter, and exit pupil distance is respectively increased, and the imaging quality is improved. This study can provide a reference for the optical design of immersive head-mounted displays.
2021, 45(4): 475-484.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.011
Abstract:
In this paper, the current research hotspots and related research progress of laser additive manufacturing technology were analyzed from the aspects of material, technology, equipment, and application. And the main development directions in the future were combed. In terms of materials and processes, the related research was mainly focused on the laser additive manufacturing of lightweight alloy and high-value alloy. From the point of view of forming equipment, large-scale equipment, high-speed, and composite processing were the main development direction in the future, while the application was it mainly focuses on the laser additive manufacturing of high performance, high value parts, and biological implants. Generally speaking, high quality, high performance, and high efficiency will be the focus of laser additive manufacturing in the future.
In this paper, the current research hotspots and related research progress of laser additive manufacturing technology were analyzed from the aspects of material, technology, equipment, and application. And the main development directions in the future were combed. In terms of materials and processes, the related research was mainly focused on the laser additive manufacturing of lightweight alloy and high-value alloy. From the point of view of forming equipment, large-scale equipment, high-speed, and composite processing were the main development direction in the future, while the application was it mainly focuses on the laser additive manufacturing of high performance, high value parts, and biological implants. Generally speaking, high quality, high performance, and high efficiency will be the focus of laser additive manufacturing in the future.
2021, 45(4): 485-491.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.012
Abstract:
In order to analyze the influence of high contrast grating(HCG) parameters and incident wavelength on beam deflection angle, the rigorous coupled wave method was used to design a deflectable non-periodic triangular HCG, and it is proved that 30.3° beam deflection can be achieved in the designed non-periodic triangular HCG by the finite-difference time-domain (FDTD). At the same time, it is found that when the refractive index of the low refractive index material increases from 1 to 1.4, the deflection angle of the transmission beam can achieve 11° tuning, and when the incident wavelength increases from 1.5μm to 1.6μm, the aperiodic triangular HCG can achieve 3.527° transmission beam deflection angle tuning. The results can provide theoretical guidance for the fabrication of high-performance beam deflection gratings in the future.
In order to analyze the influence of high contrast grating(HCG) parameters and incident wavelength on beam deflection angle, the rigorous coupled wave method was used to design a deflectable non-periodic triangular HCG, and it is proved that 30.3° beam deflection can be achieved in the designed non-periodic triangular HCG by the finite-difference time-domain (FDTD). At the same time, it is found that when the refractive index of the low refractive index material increases from 1 to 1.4, the deflection angle of the transmission beam can achieve 11° tuning, and when the incident wavelength increases from 1.5μm to 1.6μm, the aperiodic triangular HCG can achieve 3.527° transmission beam deflection angle tuning. The results can provide theoretical guidance for the fabrication of high-performance beam deflection gratings in the future.
2021, 45(4): 492-499.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.013
Abstract:
Paleoclimatology is a discipline that studies the past climate of the earth, and its purpose is to predict the future climate change, to solve problems related to the environment, resources and so on. Based on laser-induced breakdown spectroscopy(LIBS), the complex and diverse large area paleoclimatology samples can be quickly, accurately and in situ analyzed by the element imaging technology, and the element information that can be linked with the climate can be obtained. LIBS thus has a good application prospect in climate change research. This paper first introduces the basic principles of element imaging technology based on LIBS. Secondly, it reviews the instrument configuration of the currently commonly used imaging system, including laser light source, focusing system and spectral detection system. Finally, typical cases of analyzing paleoclimate agents based on LIBS element imaging technology at home and abroad is introduced. Therefore, this paper has a good guiding role for the application of element imaging technology based on LIBS in paleoclimate research.
Paleoclimatology is a discipline that studies the past climate of the earth, and its purpose is to predict the future climate change, to solve problems related to the environment, resources and so on. Based on laser-induced breakdown spectroscopy(LIBS), the complex and diverse large area paleoclimatology samples can be quickly, accurately and in situ analyzed by the element imaging technology, and the element information that can be linked with the climate can be obtained. LIBS thus has a good application prospect in climate change research. This paper first introduces the basic principles of element imaging technology based on LIBS. Secondly, it reviews the instrument configuration of the currently commonly used imaging system, including laser light source, focusing system and spectral detection system. Finally, typical cases of analyzing paleoclimate agents based on LIBS element imaging technology at home and abroad is introduced. Therefore, this paper has a good guiding role for the application of element imaging technology based on LIBS in paleoclimate research.
2021, 45(4): 500-506.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.014
Abstract:
In order to study the influence of laser process parameters on the cleaning quality of carbon steel surface contaminant layer, the Nd∶ YAG quasi continuous laser was used to clean the surface rust contaminant of Q235 steel sample. The effect of laser cleaning on the sample surface was observed, and the working mechanism of laser cleaning contaminant ablation was analyzed. Then the cleaning effects and the cleaning quality with different process parameters such as laser energy density, cleaning rate, scanning width, defocusing amount, and repetition frequency were studied experimentally, and based on this, the orthogonal test was carried out to obtain the optimum laser process parameters to the Q235 steel; three-dimensional morphology, scanning electron microscopy, and energy spectrum were conducted to analyse the cleaning effect. And the optimal process parameters were obtained: Laser cleaning rate is 900mm/min, defocusing amount is 1mm, energy density is 7.6J/cm2, scanning width is 30mm respectively. Research shows that the surface roughness and three-dimensional morphology of the laser cleaning samples are improved, the roughness value of the laser cleaning samples is close to that of the rust-free samples, and the morphology of the laser cleaning samples is basically the same as that of the rust-free samples; after laser cleaning, the rust layer on the surface of the material is basically removed, and there are remelted microstructures on the surface. It can be concluded that laser cleaning can meet the cleaning quality requirements for carbon steel.
In order to study the influence of laser process parameters on the cleaning quality of carbon steel surface contaminant layer, the Nd∶ YAG quasi continuous laser was used to clean the surface rust contaminant of Q235 steel sample. The effect of laser cleaning on the sample surface was observed, and the working mechanism of laser cleaning contaminant ablation was analyzed. Then the cleaning effects and the cleaning quality with different process parameters such as laser energy density, cleaning rate, scanning width, defocusing amount, and repetition frequency were studied experimentally, and based on this, the orthogonal test was carried out to obtain the optimum laser process parameters to the Q235 steel; three-dimensional morphology, scanning electron microscopy, and energy spectrum were conducted to analyse the cleaning effect. And the optimal process parameters were obtained: Laser cleaning rate is 900mm/min, defocusing amount is 1mm, energy density is 7.6J/cm2, scanning width is 30mm respectively. Research shows that the surface roughness and three-dimensional morphology of the laser cleaning samples are improved, the roughness value of the laser cleaning samples is close to that of the rust-free samples, and the morphology of the laser cleaning samples is basically the same as that of the rust-free samples; after laser cleaning, the rust layer on the surface of the material is basically removed, and there are remelted microstructures on the surface. It can be concluded that laser cleaning can meet the cleaning quality requirements for carbon steel.
2021, 45(4): 507-510.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.015
Abstract:
To realize the double-mode absorption, the graphene ribbon was embedded into the defective photonic crystal. Based on the rigorous coupled wave method, it is found that the system achieves two perfect absorption modes at 5.1537THz and 5.1970THz, due to the Fabry-Pérot resonance and surface plasmon polariton resonance. At the same time, the impedance of the whole structure was equal to that of the free space. Analysis of key parameters indicate that both modes number and modes-coupling extent can be changed by tuning the chemical potential of graphene electrically. When the chemical potential is 0.7eV, two absorption modes are coupled wholly. Also, the coupling extent can be controlled by adjusting the geometry of graphene ribbon. When the incident light deviates from the normal incidence, the modes number is directly affected by the deflection. This study is helpful to reconstruct the absorption spectrum of terahertz devices.
To realize the double-mode absorption, the graphene ribbon was embedded into the defective photonic crystal. Based on the rigorous coupled wave method, it is found that the system achieves two perfect absorption modes at 5.1537THz and 5.1970THz, due to the Fabry-Pérot resonance and surface plasmon polariton resonance. At the same time, the impedance of the whole structure was equal to that of the free space. Analysis of key parameters indicate that both modes number and modes-coupling extent can be changed by tuning the chemical potential of graphene electrically. When the chemical potential is 0.7eV, two absorption modes are coupled wholly. Also, the coupling extent can be controlled by adjusting the geometry of graphene ribbon. When the incident light deviates from the normal incidence, the modes number is directly affected by the deflection. This study is helpful to reconstruct the absorption spectrum of terahertz devices.
2021, 45(4): 511-515.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.016
Abstract:
In order to realize the identification of jadeite species and rubber-injected jadeite, theoretical analysis and experimental verification were carried out by using microscope combined with shifted-excitation Raman difference spectroscopy(SERDS), and SERDS data of 112 jadeite samples were obtained. The SERDS and ordinary Raman spectrum of jade were compared, and the Raman characteristic peaks of jade and the identification basis of B jade were statistically analyzed. The results show that the SERDS can effectively filter out the fluorescence and has a significant advantage in identifying the characteristic peaks of high-fluorescence jadeite samples. The peaks at 378cm-1, 698cm-1, and 1037cm-1 are relatively strong and have sharp peak shapes. They are the characteristic peaks with the highest frequency when detecting jadeite, which can be used to identify sample species. The cracks, pits and the organic matter filled by the pickling of the B jadeite can be observed by microscopic magnification. The Raman characteristic peaks of the organic matter can be detected here, of which 1114cm-1, 1188cm-1, 1611cm-1 appear most frequently, jade goods A and B can be identified through this method is simple to operate and the identification efficiency can be improved. This method can provide a reference for the rapid identification of jadeite.
In order to realize the identification of jadeite species and rubber-injected jadeite, theoretical analysis and experimental verification were carried out by using microscope combined with shifted-excitation Raman difference spectroscopy(SERDS), and SERDS data of 112 jadeite samples were obtained. The SERDS and ordinary Raman spectrum of jade were compared, and the Raman characteristic peaks of jade and the identification basis of B jade were statistically analyzed. The results show that the SERDS can effectively filter out the fluorescence and has a significant advantage in identifying the characteristic peaks of high-fluorescence jadeite samples. The peaks at 378cm-1, 698cm-1, and 1037cm-1 are relatively strong and have sharp peak shapes. They are the characteristic peaks with the highest frequency when detecting jadeite, which can be used to identify sample species. The cracks, pits and the organic matter filled by the pickling of the B jadeite can be observed by microscopic magnification. The Raman characteristic peaks of the organic matter can be detected here, of which 1114cm-1, 1188cm-1, 1611cm-1 appear most frequently, jade goods A and B can be identified through this method is simple to operate and the identification efficiency can be improved. This method can provide a reference for the rapid identification of jadeite.
2021, 45(4): 516-521.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.017
Abstract:
In order to effectively reduce the motion artifacts generated by the pulse wave signal in the severe environment, the pulse signal collected by the photoelectric sensor composed of photonic devices in the mimic database was used, and the gyro signal and the three-axis acceleration complementary filtering were used to correct the three-axis acceleration. Singular spectrum analysis was used to group the corrected three-axis acceleration signals into signals with different frequency components, which were used as the reference signal of the three-stage fast transverse recursive least square (FTRLS) algorithm to adaptively eliminate motion artifacts. Compared and analyzed with the least mean square algorithm and recursive least square method, the signal-to-noise ratio increased by 12.2% and 6.7%, the root mean square error was reduced by 30% and 11%, respectively, and the calculation speed was increased. The experimental results show that this research is helpful to remove the pulse wave motion interference spectrum peak in the frequency domain and retain the information of the heavy wave.
In order to effectively reduce the motion artifacts generated by the pulse wave signal in the severe environment, the pulse signal collected by the photoelectric sensor composed of photonic devices in the mimic database was used, and the gyro signal and the three-axis acceleration complementary filtering were used to correct the three-axis acceleration. Singular spectrum analysis was used to group the corrected three-axis acceleration signals into signals with different frequency components, which were used as the reference signal of the three-stage fast transverse recursive least square (FTRLS) algorithm to adaptively eliminate motion artifacts. Compared and analyzed with the least mean square algorithm and recursive least square method, the signal-to-noise ratio increased by 12.2% and 6.7%, the root mean square error was reduced by 30% and 11%, respectively, and the calculation speed was increased. The experimental results show that this research is helpful to remove the pulse wave motion interference spectrum peak in the frequency domain and retain the information of the heavy wave.
2021, 45(4): 522-529.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.018
Abstract:
In order to study the modal intensity of partially coherent Airy vortex beams in the non-Kolmogorov turbulence, based on the generalized Huygens-Fresnel principle and the Rytov approximation theory, the analytical expressions of modal probability of partially coherent Airy vortex beams carrying orbital angular momentum were derived and the numerical simulation was carried out with MATLAB. The influence of turbulent parameters and beam parameters on the intensity of the vortex mode when partially coherent Airy vortex beams propagate in a non-Kolmogorov turbulence were investigated, the influence of the coherence width of partially coherent Airy vortex beams on the modal intensity during transmission was theoretically studied. The results indicate that partially coherent Airy vortex beams with a smaller topological charge, larger main ring radius and longer wavelength can effectively mitigate the influence of turbulence effect and reduce the crosstalk between modes in strong turbulence; larger non-Kolmogorov spectrum parameter and smaller detector aperture diameter can improve the modal intensity of partially coherent Airy vortex beams. Furthermore, compared with fully coherent vortex beams, partially coherent vortex beams have stronger turbulence resistance and better transmission performance in atmospheric turbulence. While poor coherence will lead to dispersion of spiral spectrum. The research results provide reference for the application of partially coherent Airy vortex beams in free space optical communication.
In order to study the modal intensity of partially coherent Airy vortex beams in the non-Kolmogorov turbulence, based on the generalized Huygens-Fresnel principle and the Rytov approximation theory, the analytical expressions of modal probability of partially coherent Airy vortex beams carrying orbital angular momentum were derived and the numerical simulation was carried out with MATLAB. The influence of turbulent parameters and beam parameters on the intensity of the vortex mode when partially coherent Airy vortex beams propagate in a non-Kolmogorov turbulence were investigated, the influence of the coherence width of partially coherent Airy vortex beams on the modal intensity during transmission was theoretically studied. The results indicate that partially coherent Airy vortex beams with a smaller topological charge, larger main ring radius and longer wavelength can effectively mitigate the influence of turbulence effect and reduce the crosstalk between modes in strong turbulence; larger non-Kolmogorov spectrum parameter and smaller detector aperture diameter can improve the modal intensity of partially coherent Airy vortex beams. Furthermore, compared with fully coherent vortex beams, partially coherent vortex beams have stronger turbulence resistance and better transmission performance in atmospheric turbulence. While poor coherence will lead to dispersion of spiral spectrum. The research results provide reference for the application of partially coherent Airy vortex beams in free space optical communication.
2021, 45(4): 530-534.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.019
Abstract:
In order to construct a model for identifying printing and copying toners, X-ray fluorescence spectroscopy was used for theoretical analysis and experimental verification. The experiment data was obtained through quantitatively analyzing of the element content of 28 common brands toner samples. According to the preliminary grouping based on the presence or absence of specific elements, improved power k-means algorithm was used to perform clustering analysis to divide samples into 7 groups. After the verification by the Pearson coefficient, the result was testified, and the samples were well distinguished. The samples within the group were significantly correlated at the level of 0.001.The experiment provides new ideas which is fast and easy for the identification of printing and copying toners in judicial practice.
In order to construct a model for identifying printing and copying toners, X-ray fluorescence spectroscopy was used for theoretical analysis and experimental verification. The experiment data was obtained through quantitatively analyzing of the element content of 28 common brands toner samples. According to the preliminary grouping based on the presence or absence of specific elements, improved power k-means algorithm was used to perform clustering analysis to divide samples into 7 groups. After the verification by the Pearson coefficient, the result was testified, and the samples were well distinguished. The samples within the group were significantly correlated at the level of 0.001.The experiment provides new ideas which is fast and easy for the identification of printing and copying toners in judicial practice.
2021, 45(4): 535-540.
doi: 10.7510/jgjs.issn.1001-3806.2021.04.020
Abstract:
In order to realize the area division of point cloud data, a segmentation algorithm (SPFCM) combining supervoxels and particle swarm optimization fuzzy C-means (PFCM) was proposed. A random sampling consensus algorithm was used to remove the point cloud plane. According to the spatial position, curvature and fast point feature histogram characteristics of the 3-D point cloud, the octree voxelization point cloud was used to obtain the supervoxel. The PFCM algorithm was used to preliminarily divide the superbody and subdivide the connected point cloud, which overcomes the shortcomings of the PFCM algorithm for stacking objects and over-segmentation of larger objects. The performance test of the SPFCM algorithm was performed on the OSD-v0.2 data set. The experimental results show that compared with the PFCM algorithm, it not only retains its advantages such as fewer parameters and simple operation, but also the index has been greatly improved, and the accuracy is up to 86%, while the recall rate reaches 83%. This research provides help and reference for the accurate segmentation of complex scenes in 3-D point clouds.
In order to realize the area division of point cloud data, a segmentation algorithm (SPFCM) combining supervoxels and particle swarm optimization fuzzy C-means (PFCM) was proposed. A random sampling consensus algorithm was used to remove the point cloud plane. According to the spatial position, curvature and fast point feature histogram characteristics of the 3-D point cloud, the octree voxelization point cloud was used to obtain the supervoxel. The PFCM algorithm was used to preliminarily divide the superbody and subdivide the connected point cloud, which overcomes the shortcomings of the PFCM algorithm for stacking objects and over-segmentation of larger objects. The performance test of the SPFCM algorithm was performed on the OSD-v0.2 data set. The experimental results show that compared with the PFCM algorithm, it not only retains its advantages such as fewer parameters and simple operation, but also the index has been greatly improved, and the accuracy is up to 86%, while the recall rate reaches 83%. This research provides help and reference for the accurate segmentation of complex scenes in 3-D point clouds.
