In order to improve the bioactivity of 316L stainless steel,a titanium layer was prepared on the surface of 316L by laser cladding(LC),followed by plasma electrolytic oxidation(PEO)to form a porous ceramic coating on ...In order to improve the bioactivity of 316L stainless steel,a titanium layer was prepared on the surface of 316L by laser cladding(LC),followed by plasma electrolytic oxidation(PEO)to form a porous ceramic coating on titanium layer.The morphologies,microstructure and compositions of the coated samples were characterized by 3D surface profiler,SEM,EDS,XRD and XPS.The corrosion resistance and bioactivity of the coatings were evaluated by potentiodynamic polarization and immersion test in simulated body fluid(SBF),respectively.The results showed that the porous ceramic coating mainly consisted of anatase and rutile,and highly crystalline HA was also detected.The main elements of the PEO coating are Ca,P,Ti and O.The LC+PEO composite bio-coating has more excellent corrosion resistance than the 316L substrate in simulated body fluid.Furthermore,the composite coating could effectively improve the bioactivity of 316L stainless steel.展开更多
Pulse-burst 1064-nm picosecond azimuthal polarization beam amplification up to an average power of 16.32 W using side-pumped Nd: YAG amplifiers has been demonstrated. The maximum envelop energy as much as 16.32 mJ, co...Pulse-burst 1064-nm picosecond azimuthal polarization beam amplification up to an average power of 16.32 W using side-pumped Nd: YAG amplifiers has been demonstrated. The maximum envelop energy as much as 16.32 mJ, corresponding to a power amplification factor of 299.5%. A simple criterion was defined to help estimate the amount of depolarization in Nd:YAG amplifier stages. The degree of depolarization of the beam was 7.1% and the beam quality was measured to be M2= 3.69. The reason for the azimuthal polarization depolarization and beam quality degradation were explained theoretically and experimentally during the amplification process.展开更多
In order to study the depolarization properties of an improved Lyot depolarizer with monochromatic light, the theory of multi-beam superposition is adopted. The dependences of degree of depolarization (D) on vibration...In order to study the depolarization properties of an improved Lyot depolarizer with monochromatic light, the theory of multi-beam superposition is adopted. The dependences of degree of depolarization (D) on vibration azimuth angle (VAA) and total retardation (TR) are analyzed. The results show that D is ideal for any VAA when TR is δ=(N+1/2)π (N is an integer) on the basis of wedge angle large enough. And when δ=Nπ, VAA makes the most significant impact on D. When δ is assigned to the other values, the impact on D made by VAA is between the former two. Using a 405 nm semiconductor laser, experiments for measuring D of the sample with wedge angle of 6° are conducted. The theo-retical results are well verified by experiments. D is over 98.8% when TR is nearly δ=(N+1/2)π by changing the incident angle.展开更多
To obtain a stable amplified spontaneous emission（ASE） source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperature...To obtain a stable amplified spontaneous emission（ASE） source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperatures.We optimize the structure of the ASE source to flatten the ASE spectrum, and study the output characteristics in terms of output power and optical spectrum under different pump powers. Then the performance of the ASE source is investigated in the temperature range from-18.9°C to 50°C. A stable-power and flat-spectrum ASE source can be obtained by structural optimization and pump control.展开更多
For high performance manufacturing of micro parts and features,a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refi...For high performance manufacturing of micro parts and features,a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition.The strategy,namely UVlight and IR-laser hybrid chemical modification(UVIR-CM)strategy,includes two steps,an ultraviolet light(UV-light)catalytic advanced oxidation and an infrared laser(IR-laser)assisted selective modification based on Fenton liquid–solid reaction for monocrystalline silicon.The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation,crosssection transmission electron microscopy(TEM)observation,Raman spectroscopy analysis and nanoindentation test.Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples’IR-laser scanned area.And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium.But for the UVIR-CM strategy,a uniform and amorphous silicate layer is detected in a certain boundary.The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step.Attributing to synergism of photochemical,photothermal and kinetic effects induced by IR-laser,the modified layer displays layered structure with about 600 nm thickness,(2.7±0.60)GPa nanohardness,and(93.7±22.9)GPa indentation modulus.And the layered structure is amorphous layer,nanocrystal and micro-twins layer from the surface to the interior of sample.Consequently,it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area.Meanwhile,its original excellent mechanical properties also are maintained under a certain depth.The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.展开更多
With the rapid growth in electronic device performance,there has been an increasing demand for thermally conductive polymer composites to handle the thermal management issue,thus contributing to the great importance t...With the rapid growth in electronic device performance,there has been an increasing demand for thermally conductive polymer composites to handle the thermal management issue,thus contributing to the great importance to develop the graphene framework,which is evaluated as the most promising reinforcements for enhancing the thermal conductivity of polymer.Vacuum filtration is a common method to fabricate graphene framework,whereas,it is available to prepare a framework with centimeter-scale thickness by filtrating the graphene-water dispersion,due to the fact of sample cracking caused by the mismatch of surface tension between graphene and water.In this work,a surfactantassisted strategy was proposed by adjusting the surface tension of the water close to that of graphene first,then performing a conventional filtration process,to fabricate graphene framework.As a result,a thick graphene framework(thickness:3 cm)was successfully prepared,and after embedding into epoxy,the framework endows the composite(13.6 wt%)with a high in-plane thermal conductivities of12.4 W/mK,which is equivalent to≈64 times higher than that of neat epoxy.Our method is simple and compatible with the conventional filtration process,suggesting great potential for the mass-production of graphene framework to meet the practical application requirements.展开更多
The retardation of wave plate has the sensitivity to the incident angle.We design a new kind of tunable Lyot filter based on the sensitivity.The method of tuning is rotating the wave plate by the axial direction paral...The retardation of wave plate has the sensitivity to the incident angle.We design a new kind of tunable Lyot filter based on the sensitivity.The method of tuning is rotating the wave plate by the axial direction parallel to the optical axis.It is proved that this kind of tunable Lyot filter has the properties of favorable tenability,wide tunable range.展开更多
In order to gain circularly polarized light of left-handed and right-handed rotation by using a fixed device, a left-handed and right-handed rotation double function circular polarizer is designed with two λ/4 retard...In order to gain circularly polarized light of left-handed and right-handed rotation by using a fixed device, a left-handed and right-handed rotation double function circular polarizer is designed with two λ/4 retarders and one polarizer, and its operating principle is analysed by matrix optical means. The result indicates that when the monochromatic light enters this circular polarizer in the positive direction and the negative direction,the emergent light should be circularly polarized light,of left-handed and right-handed rotation respectively. The testing system has been established to verify the above results.展开更多
A design of coating on the entrance surface of the beam splitters with a transparent thin film of certain refractive index and thickness was presented.For this kind of beam splitters,it was possible to realize polariz...A design of coating on the entrance surface of the beam splitters with a transparent thin film of certain refractive index and thickness was presented.For this kind of beam splitters,it was possible to realize polarization-independent beam-splitting for chosen wavelength λ with incident angle .In addition,the simulation results using the coating designable software(Auto film) were consistent with the theoretical results,and the beam splitters are not sensitive to the small errors of film-thickness and film refractive-index over a broad spectra.展开更多
A distributed feedback diode laser （DFB-DL） based hygrometer combined with a long-path-length Herriot gas cell and waterless optical components was proposed and investigated. The main function of this sensor was to ...A distributed feedback diode laser （DFB-DL） based hygrometer combined with a long-path-length Herriot gas cell and waterless optical components was proposed and investigated. The main function of this sensor was to simultaneously improve the measurement reliability and resolution. A comparison test between a 10-cm normal transmission-type gas cell and a 3-m Herriot gas cell was carried out to demonstrate the improvement. Reliability improvement was achieved by influence suppression of water vapor inside optical components （WVOC） through combined action of the Herriot gas cell and waterless optical components. The influence of WVOC was suppressed from 726ppmv to 25ppmv using the Herriot gas cell. Moreover, combined with waterless optical components, the influence of WVOC was further suppressed to no more than 4ppmv. Resolution improvement from l l.7ppmv to 0.32ppmv was achieved mainly due to the application of the long-path-length Herriot gas cell. The results show that the proposed sensor has a good performance and considerable potential application in gas sensing, especially when probed gas possibly permeates into optical components.展开更多
In the field of oil well logging, real-time monitoring of the fluid flow parameter provides a scientific basis for oil and gas optimization exploration and increase in reservoir recovery, so a non-intrusive flow test ...In the field of oil well logging, real-time monitoring of the fluid flow parameter provides a scientific basis for oil and gas optimization exploration and increase in reservoir recovery, so a non-intrusive flow test method based on turbulent vibration was proposed. The specific length of the sensor fiber wound tightly around the outer wall of the pipe was connected with the optical fiber gratings at both ends, and the sensor fiber and the optical fiber gratings composed the flow sensing unit. The dynamic pressure was generated by the turbulence when fluid flows through the pipe, and the dynamic pressure resulted in the light phase shift of the sensor fiber. The phase information was demodulated by the fiber optic interferometer technology, time division multiplexing technology, and phase generated carrier modulation and demodulation techniques. The quadratic curve relationship between the phase change and flow rate was found by experimental data analysis, and the experiment confirmed the feasibility of the optical fiber flow test method with non-intrusion and achieved the real-time monitoring of the fluid flow.展开更多
A novel laser-electro magnetic acoustic transducer （EMAT） system for nondestructive testing NDT surface crack of continuous casting billet （CCB） is provided. Rayleigh wave generated by line laser source is used to...A novel laser-electro magnetic acoustic transducer （EMAT） system for nondestructive testing NDT surface crack of continuous casting billet （CCB） is provided. Rayleigh wave generated by line laser source is used to detect the surface crack of CCB. According to the principle of mode conversion from Rayleigh wave to shear wave, the defect signal is received using the shear wave EMAT sensor in a non-contact way. Experiments are carried out on the steel sample with size 30 × 0.2 ×0.2 （mm） of crack. Further, the influences of life off value and distance between EMAT sensor and laser beam on the testing sensitivity are discussed, respectively. It is found that the life off value is the main factor that effects sensitivity of the proposed method. There is a clear prospect of the method applied to test continuously cast bloom at high temperature.展开更多
Spontaneous combustion of the coal mine goaf is one of the main disasters in the coal mine. The detection technology based on symbolic gas is the main means to realize the spontaneous combustion prediction of the coal...Spontaneous combustion of the coal mine goaf is one of the main disasters in the coal mine. The detection technology based on symbolic gas is the main means to realize the spontaneous combustion prediction of the coal mine goaf, and ethylene gas is an important symbol gas of spontaneous combustion in the coal accelerated oxidation stage. In order to overcome the problem of current coal ethylene detection, the paper presents a mine optical fiber multi-point ethylene concentration sensor based on the tunable diode laser absorption spectroscopy. Based on the experiments and analysis of the near-infrared spectrum of ethylene, the system employed the 1.62 μm （DFB） wavelength fiber coupled distributed feedback laser as the light source. By using the wavelength scanning technique and developing a stable fiber coupled Herriot type long path gas absorption cell, a ppm-level high sensitivity detecting system for the concentration of ethylene gas was realized, which could meet the needs of coal mine fire prevention goaf prediction.展开更多
An optimum design of static Fourier-transform spectrometer based on Savert prisms is presented in this paper. A new method of increasing path difference and resolution of spectrometer is given. When the angle between ...An optimum design of static Fourier-transform spectrometer based on Savert prisms is presented in this paper. A new method of increasing path difference and resolution of spectrometer is given. When the angle between the crystal optical axis of the first Savert prism and the incident interface is 58° and the angle between the crystal optical axis of the second Savert prism and the incident interface is 28°, the maximum path difference will be 0.63 mm, the maximum resolution will be 15.8 cm-1, and the whole field-of-view will reach 6°.展开更多
By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reco...By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reconstructed results. Some problems concerning with the digital hologram recording and reconstruction of the diffractive object at a short distance are discussed. The experimental result shows that the resolution of the reconstructed image is better than 10μm, which is the limit by using this experimental arrangement.展开更多
We analyze the random disturbance in the transmission of light through a spinning Glan-Thompsontype prism polarizer.The disturbance makes the dependence of the transmission on the rotation angle significantly deviates...We analyze the random disturbance in the transmission of light through a spinning Glan-Thompsontype prism polarizer.The disturbance makes the dependence of the transmission on the rotation angle significantly deviates from the Malus cosine-squared law and severely spoils the output light quality.Slight vibration of the polarizer as it rotates combing the multi-beam-interference effect raises the disturbance. Further analysis reveals the sensitive dependence of the disturbance on the composing material of the prism gap,and the appropriate selection of such material can make the disturbance minimize to very desirable levels.The model results show quite good agreement with experiments.展开更多
The main refractive indices of calcite crystal are measured by the means of auto-collimation, and the thermo-optical coefficients are calculated. The coefficient expression of Sellmeier equation is obtained by solving...The main refractive indices of calcite crystal are measured by the means of auto-collimation, and the thermo-optical coefficients are calculated. The coefficient expression of Sellmeier equation is obtained by solving Sellmeier equation strictly and the refractive indices of different wavelengths are calculated, which accord with experimental results very well. The measured main refractive indices of calcite at 488-nm wavelength are identical with the values obtained bv Sellmeier equation.展开更多
A large lateral shearing distance of parallel beam-splitting prism is often needed in laser modulation and polarization interference. In this letter, we present an optimized design of parallel beam-splitting prism and...A large lateral shearing distance of parallel beam-splitting prism is often needed in laser modulation and polarization interference. In this letter, we present an optimized design of parallel beam-splitting prism and list some different cases in detail. The optimized design widens the use range of parallel beam-splitting prism. At the wavelength of 632.8 nm, the law that the enlargement ratio changes with the refractive index and the apex angle is verified.展开更多
基金financial support from the National Natural Science Foundation of China (No. 51975533)National Safety Academic Fund, China (No. U2130122)Public Projects of Zhejiang Province, China (Nos. LGJ22E050002, LGJ20E050002)
文摘In order to improve the bioactivity of 316L stainless steel,a titanium layer was prepared on the surface of 316L by laser cladding(LC),followed by plasma electrolytic oxidation(PEO)to form a porous ceramic coating on titanium layer.The morphologies,microstructure and compositions of the coated samples were characterized by 3D surface profiler,SEM,EDS,XRD and XPS.The corrosion resistance and bioactivity of the coatings were evaluated by potentiodynamic polarization and immersion test in simulated body fluid(SBF),respectively.The results showed that the porous ceramic coating mainly consisted of anatase and rutile,and highly crystalline HA was also detected.The main elements of the PEO coating are Ca,P,Ti and O.The LC+PEO composite bio-coating has more excellent corrosion resistance than the 316L substrate in simulated body fluid.Furthermore,the composite coating could effectively improve the bioactivity of 316L stainless steel.
基金Project supported by the National Natural Science Foundation of China(Grant No.U1631240)the Education Commission Program of BeijingBeijing Natural Science Foundation(Grant No.KZ201510005001)
文摘Pulse-burst 1064-nm picosecond azimuthal polarization beam amplification up to an average power of 16.32 W using side-pumped Nd: YAG amplifiers has been demonstrated. The maximum envelop energy as much as 16.32 mJ, corresponding to a power amplification factor of 299.5%. A simple criterion was defined to help estimate the amount of depolarization in Nd:YAG amplifier stages. The degree of depolarization of the beam was 7.1% and the beam quality was measured to be M2= 3.69. The reason for the azimuthal polarization depolarization and beam quality degradation were explained theoretically and experimentally during the amplification process.
基金the Young Scientists Fund of the National Natural Science Foundation of China (No.11104161)
文摘In order to study the depolarization properties of an improved Lyot depolarizer with monochromatic light, the theory of multi-beam superposition is adopted. The dependences of degree of depolarization (D) on vibration azimuth angle (VAA) and total retardation (TR) are analyzed. The results show that D is ideal for any VAA when TR is δ=(N+1/2)π (N is an integer) on the basis of wedge angle large enough. And when δ=Nπ, VAA makes the most significant impact on D. When δ is assigned to the other values, the impact on D made by VAA is between the former two. Using a 405 nm semiconductor laser, experiments for measuring D of the sample with wedge angle of 6° are conducted. The theo-retical results are well verified by experiments. D is over 98.8% when TR is nearly δ=(N+1/2)π by changing the incident angle.
基金Supported by the National Natural Science Foundation of China under Grant No 11504320
文摘To obtain a stable amplified spontaneous emission（ASE） source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperatures.We optimize the structure of the ASE source to flatten the ASE spectrum, and study the output characteristics in terms of output power and optical spectrum under different pump powers. Then the performance of the ASE source is investigated in the temperature range from-18.9°C to 50°C. A stable-power and flat-spectrum ASE source can be obtained by structural optimization and pump control.
基金supported by the National Natural Science Foundation of China(52075161,51875192).
文摘For high performance manufacturing of micro parts and features,a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition.The strategy,namely UVlight and IR-laser hybrid chemical modification(UVIR-CM)strategy,includes two steps,an ultraviolet light(UV-light)catalytic advanced oxidation and an infrared laser(IR-laser)assisted selective modification based on Fenton liquid–solid reaction for monocrystalline silicon.The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation,crosssection transmission electron microscopy(TEM)observation,Raman spectroscopy analysis and nanoindentation test.Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples’IR-laser scanned area.And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium.But for the UVIR-CM strategy,a uniform and amorphous silicate layer is detected in a certain boundary.The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step.Attributing to synergism of photochemical,photothermal and kinetic effects induced by IR-laser,the modified layer displays layered structure with about 600 nm thickness,(2.7±0.60)GPa nanohardness,and(93.7±22.9)GPa indentation modulus.And the layered structure is amorphous layer,nanocrystal and micro-twins layer from the surface to the interior of sample.Consequently,it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area.Meanwhile,its original excellent mechanical properties also are maintained under a certain depth.The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.
基金financial support by the National Key R&D Program of China (No.2017YFB0406000)Scientific Instrument Developing Project of the Chinese Academy of Sciences (No.YZ201640)+6 种基金the Project of the Chinese Academy of Sciences (No.KFZD-SW-409)Science and Technology Major Project of Ningbo (Nos.2016S1002 and 2016B10038)International S&T Cooperation Program of Ningbo (No. 2017D10016) for financial supportthe Chinese Academy of Sciences for Hundred Talents ProgramChinese Central Government for Thousand Young Talents Program3315 Program of Ningbothe Key Technology of Nuclear Energy (CAS Interdisciplinary Innovation Team,2014)
文摘With the rapid growth in electronic device performance,there has been an increasing demand for thermally conductive polymer composites to handle the thermal management issue,thus contributing to the great importance to develop the graphene framework,which is evaluated as the most promising reinforcements for enhancing the thermal conductivity of polymer.Vacuum filtration is a common method to fabricate graphene framework,whereas,it is available to prepare a framework with centimeter-scale thickness by filtrating the graphene-water dispersion,due to the fact of sample cracking caused by the mismatch of surface tension between graphene and water.In this work,a surfactantassisted strategy was proposed by adjusting the surface tension of the water close to that of graphene first,then performing a conventional filtration process,to fabricate graphene framework.As a result,a thick graphene framework(thickness:3 cm)was successfully prepared,and after embedding into epoxy,the framework endows the composite(13.6 wt%)with a high in-plane thermal conductivities of12.4 W/mK,which is equivalent to≈64 times higher than that of neat epoxy.Our method is simple and compatible with the conventional filtration process,suggesting great potential for the mass-production of graphene framework to meet the practical application requirements.
文摘The retardation of wave plate has the sensitivity to the incident angle.We design a new kind of tunable Lyot filter based on the sensitivity.The method of tuning is rotating the wave plate by the axial direction parallel to the optical axis.It is proved that this kind of tunable Lyot filter has the properties of favorable tenability,wide tunable range.
文摘In order to gain circularly polarized light of left-handed and right-handed rotation by using a fixed device, a left-handed and right-handed rotation double function circular polarizer is designed with two λ/4 retarders and one polarizer, and its operating principle is analysed by matrix optical means. The result indicates that when the monochromatic light enters this circular polarizer in the positive direction and the negative direction,the emergent light should be circularly polarized light,of left-handed and right-handed rotation respectively. The testing system has been established to verify the above results.
文摘A design of coating on the entrance surface of the beam splitters with a transparent thin film of certain refractive index and thickness was presented.For this kind of beam splitters,it was possible to realize polarization-independent beam-splitting for chosen wavelength λ with incident angle .In addition,the simulation results using the coating designable software(Auto film) were consistent with the theoretical results,and the beam splitters are not sensitive to the small errors of film-thickness and film refractive-index over a broad spectra.
基金This work was supported by the National Natural Science Foundation of China （60977058 ＆ 61475085）, the Science and Technology Development Project of Shandong Province （2014GGX101007）, and the Fundamental Research Funds of Shandong University （2014YQ011）.
文摘A distributed feedback diode laser （DFB-DL） based hygrometer combined with a long-path-length Herriot gas cell and waterless optical components was proposed and investigated. The main function of this sensor was to simultaneously improve the measurement reliability and resolution. A comparison test between a 10-cm normal transmission-type gas cell and a 3-m Herriot gas cell was carried out to demonstrate the improvement. Reliability improvement was achieved by influence suppression of water vapor inside optical components （WVOC） through combined action of the Herriot gas cell and waterless optical components. The influence of WVOC was suppressed from 726ppmv to 25ppmv using the Herriot gas cell. Moreover, combined with waterless optical components, the influence of WVOC was further suppressed to no more than 4ppmv. Resolution improvement from l l.7ppmv to 0.32ppmv was achieved mainly due to the application of the long-path-length Herriot gas cell. The results show that the proposed sensor has a good performance and considerable potential application in gas sensing, especially when probed gas possibly permeates into optical components.
文摘In the field of oil well logging, real-time monitoring of the fluid flow parameter provides a scientific basis for oil and gas optimization exploration and increase in reservoir recovery, so a non-intrusive flow test method based on turbulent vibration was proposed. The specific length of the sensor fiber wound tightly around the outer wall of the pipe was connected with the optical fiber gratings at both ends, and the sensor fiber and the optical fiber gratings composed the flow sensing unit. The dynamic pressure was generated by the turbulence when fluid flows through the pipe, and the dynamic pressure resulted in the light phase shift of the sensor fiber. The phase information was demodulated by the fiber optic interferometer technology, time division multiplexing technology, and phase generated carrier modulation and demodulation techniques. The quadratic curve relationship between the phase change and flow rate was found by experimental data analysis, and the experiment confirmed the feasibility of the optical fiber flow test method with non-intrusion and achieved the real-time monitoring of the fluid flow.
基金This work was supported by the National Natural Science Foundation of China （No. 51205240）, Outstanding Young Scientists Program of Shandong （No. BS2011ZZ016）, and Youth Science Funds of Shandong Academy of Sciences （No. 2012-02）.
文摘A novel laser-electro magnetic acoustic transducer （EMAT） system for nondestructive testing NDT surface crack of continuous casting billet （CCB） is provided. Rayleigh wave generated by line laser source is used to detect the surface crack of CCB. According to the principle of mode conversion from Rayleigh wave to shear wave, the defect signal is received using the shear wave EMAT sensor in a non-contact way. Experiments are carried out on the steel sample with size 30 × 0.2 ×0.2 （mm） of crack. Further, the influences of life off value and distance between EMAT sensor and laser beam on the testing sensitivity are discussed, respectively. It is found that the life off value is the main factor that effects sensitivity of the proposed method. There is a clear prospect of the method applied to test continuously cast bloom at high temperature.
基金This work was supported by the National Natural Science Foundation of China （60977058 ＆ 61475085） and Fundamental Research Funds of Shandong University （2014YQ011）.
文摘Spontaneous combustion of the coal mine goaf is one of the main disasters in the coal mine. The detection technology based on symbolic gas is the main means to realize the spontaneous combustion prediction of the coal mine goaf, and ethylene gas is an important symbol gas of spontaneous combustion in the coal accelerated oxidation stage. In order to overcome the problem of current coal ethylene detection, the paper presents a mine optical fiber multi-point ethylene concentration sensor based on the tunable diode laser absorption spectroscopy. Based on the experiments and analysis of the near-infrared spectrum of ethylene, the system employed the 1.62 μm （DFB） wavelength fiber coupled distributed feedback laser as the light source. By using the wavelength scanning technique and developing a stable fiber coupled Herriot type long path gas absorption cell, a ppm-level high sensitivity detecting system for the concentration of ethylene gas was realized, which could meet the needs of coal mine fire prevention goaf prediction.
文摘An optimum design of static Fourier-transform spectrometer based on Savert prisms is presented in this paper. A new method of increasing path difference and resolution of spectrometer is given. When the angle between the crystal optical axis of the first Savert prism and the incident interface is 58° and the angle between the crystal optical axis of the second Savert prism and the incident interface is 28°, the maximum path difference will be 0.63 mm, the maximum resolution will be 15.8 cm-1, and the whole field-of-view will reach 6°.
文摘By using a spherical wave as the reference wave, we recorded the in-line phase-shifting digital hologram of the 25th element of Chinese standard No. 3 resolution test pattern, and gave the corresponding numerical reconstructed results. Some problems concerning with the digital hologram recording and reconstruction of the diffractive object at a short distance are discussed. The experimental result shows that the resolution of the reconstructed image is better than 10μm, which is the limit by using this experimental arrangement.
基金supported by the Nanjing University of Science and Technology Scientific Research & Development and Start-Up Foundations(Nos.AB96230 and AB41897)Partial support was also from the Teaching and Research Foundation for the Outstanding Young Faculty of Southeast University(No.4007021037)
文摘We analyze the random disturbance in the transmission of light through a spinning Glan-Thompsontype prism polarizer.The disturbance makes the dependence of the transmission on the rotation angle significantly deviates from the Malus cosine-squared law and severely spoils the output light quality.Slight vibration of the polarizer as it rotates combing the multi-beam-interference effect raises the disturbance. Further analysis reveals the sensitive dependence of the disturbance on the composing material of the prism gap,and the appropriate selection of such material can make the disturbance minimize to very desirable levels.The model results show quite good agreement with experiments.
文摘The main refractive indices of calcite crystal are measured by the means of auto-collimation, and the thermo-optical coefficients are calculated. The coefficient expression of Sellmeier equation is obtained by solving Sellmeier equation strictly and the refractive indices of different wavelengths are calculated, which accord with experimental results very well. The measured main refractive indices of calcite at 488-nm wavelength are identical with the values obtained bv Sellmeier equation.
文摘A large lateral shearing distance of parallel beam-splitting prism is often needed in laser modulation and polarization interference. In this letter, we present an optimized design of parallel beam-splitting prism and list some different cases in detail. The optimized design widens the use range of parallel beam-splitting prism. At the wavelength of 632.8 nm, the law that the enlargement ratio changes with the refractive index and the apex angle is verified.
