The effect of the matrix temperature on laser-induced plasma generated in bulk water by using a532 nm pulsed laser beam has been studied.Ca Ⅰ and Ⅱ emission line intensities were recorded for an aqueous solution of ...The effect of the matrix temperature on laser-induced plasma generated in bulk water by using a532 nm pulsed laser beam has been studied.Ca Ⅰ and Ⅱ emission line intensities were recorded for an aqueous solution of CaCl2 in the temperature range of 7℃-70℃.The emission line intensities did not follow the matrix temperature in our experiments.Maximum intensities were observed at ~18℃ for both lines.Herein,a possible mechanism responsible for the observed variation in intensity is suggested,in which laser-produced bubbles play important roles.Bubble formation is essential to ignite plasma in the liquid and more feasible at the higher liquid temperature.However,the abundant bubbles at the higher temperature can scatter the incident laser beam more effectively to decrease the energy delivered for the laser-induced plasma.Thus,these two roles have effects on the optical emission intensities in opposite ways.The validity of the suggested mechanism is discussed based on the plasma temperature,temperature dependence of the refractive index of water,plasma electron density,scattered light intensity,and plasma ignition threshold energy.Our result indicates that the temperature of the liquid is also an important parameter to be considered in the laser-induced breakdown spectroscopy analysis of bulk liquid samples and its application in deep-sea exploration.展开更多
Theoretical investigation on the propagation characteristics of a new class of laser beams known as multi Gaussian(M.G)laser beams has been presented.To investigate the linear characteristics,propagation of the laser ...Theoretical investigation on the propagation characteristics of a new class of laser beams known as multi Gaussian(M.G)laser beams has been presented.To investigate the linear characteristics,propagation of the laser beam in vacuum has been considered.Whereas,the nonlinear characteristics have been investigated in plasmas.Optical nonlinearity of the plasma has been modeled by relativistic mass nonlinearity of the plasma electrons in the field of laser beam.Formulation is based on finding the semi analytical solution of the wave equation for the slowly varying envelope of the laser beam.Particularly,the dynamical evolutions of the beam width and longitudinal phase of the laser beam have been investigated in detail.展开更多
The cellulosic bast fibers are recognized as a justifiable and biodegradable substitute for producing moderate strength polymer composite materials because of their characteristics of renewability,ecofriendliness,and ...The cellulosic bast fibers are recognized as a justifiable and biodegradable substitute for producing moderate strength polymer composite materials because of their characteristics of renewability,ecofriendliness,and higher specific strength.Hence the aim of this research work is to fabricate Himalayan bast fibers(Nettle fiber(NF)/bauhinia vahlii fiber(BF)) based mono/hybrid epoxy composites at varying weight percentage of 2-6 wt% and evaluate the physical(void fraction and water absorption),mechanical(tensile strength,flexural strength,hardness) and sliding wear properties of as-fabricated composites.The 6 wt% NBF reinforced composites exhibited higher mechanical properties as compared to NF and BF composites with tensile strength of 34.04 MPa,flexural strength of 42.45 MPa,and hardness of 37.01 Hv respectively.The influence of various control factors(sliding velocity,NF/BF/NBF contents,normal load and sliding distance) on specific sliding wear rate of composites was evaluated by Taguchi(three factors at three levels) experimental design and the percentage contribution of these selected parameters on sliding wear performance was examined by Analysis of variance(ANOVA).The sliding wear property of as-developed composites was found to be greatly influenced by sliding velocity and the wear resistance was observed to be improved with the NF/BF/NBF contents.The wear mechanism of the as-fabricated composites has been elucidated by scanning electron microscopy analysis.The research outcomes demonstrated that the hybridization of Bauhinia vahlii fiber with Nettle fiber led to improve the mechanical and wear properties of epoxy composites.展开更多
基金supported by the Korea Basic Science Institute(KBSI)National Research Facilities&Equipment Center(NFEC)grant funded by the Korean government(Ministry of Education)(No.2019R1A6C1010005)。
文摘The effect of the matrix temperature on laser-induced plasma generated in bulk water by using a532 nm pulsed laser beam has been studied.Ca Ⅰ and Ⅱ emission line intensities were recorded for an aqueous solution of CaCl2 in the temperature range of 7℃-70℃.The emission line intensities did not follow the matrix temperature in our experiments.Maximum intensities were observed at ~18℃ for both lines.Herein,a possible mechanism responsible for the observed variation in intensity is suggested,in which laser-produced bubbles play important roles.Bubble formation is essential to ignite plasma in the liquid and more feasible at the higher liquid temperature.However,the abundant bubbles at the higher temperature can scatter the incident laser beam more effectively to decrease the energy delivered for the laser-induced plasma.Thus,these two roles have effects on the optical emission intensities in opposite ways.The validity of the suggested mechanism is discussed based on the plasma temperature,temperature dependence of the refractive index of water,plasma electron density,scattered light intensity,and plasma ignition threshold energy.Our result indicates that the temperature of the liquid is also an important parameter to be considered in the laser-induced breakdown spectroscopy analysis of bulk liquid samples and its application in deep-sea exploration.
文摘Theoretical investigation on the propagation characteristics of a new class of laser beams known as multi Gaussian(M.G)laser beams has been presented.To investigate the linear characteristics,propagation of the laser beam in vacuum has been considered.Whereas,the nonlinear characteristics have been investigated in plasmas.Optical nonlinearity of the plasma has been modeled by relativistic mass nonlinearity of the plasma electrons in the field of laser beam.Formulation is based on finding the semi analytical solution of the wave equation for the slowly varying envelope of the laser beam.Particularly,the dynamical evolutions of the beam width and longitudinal phase of the laser beam have been investigated in detail.
文摘The cellulosic bast fibers are recognized as a justifiable and biodegradable substitute for producing moderate strength polymer composite materials because of their characteristics of renewability,ecofriendliness,and higher specific strength.Hence the aim of this research work is to fabricate Himalayan bast fibers(Nettle fiber(NF)/bauhinia vahlii fiber(BF)) based mono/hybrid epoxy composites at varying weight percentage of 2-6 wt% and evaluate the physical(void fraction and water absorption),mechanical(tensile strength,flexural strength,hardness) and sliding wear properties of as-fabricated composites.The 6 wt% NBF reinforced composites exhibited higher mechanical properties as compared to NF and BF composites with tensile strength of 34.04 MPa,flexural strength of 42.45 MPa,and hardness of 37.01 Hv respectively.The influence of various control factors(sliding velocity,NF/BF/NBF contents,normal load and sliding distance) on specific sliding wear rate of composites was evaluated by Taguchi(three factors at three levels) experimental design and the percentage contribution of these selected parameters on sliding wear performance was examined by Analysis of variance(ANOVA).The sliding wear property of as-developed composites was found to be greatly influenced by sliding velocity and the wear resistance was observed to be improved with the NF/BF/NBF contents.The wear mechanism of the as-fabricated composites has been elucidated by scanning electron microscopy analysis.The research outcomes demonstrated that the hybridization of Bauhinia vahlii fiber with Nettle fiber led to improve the mechanical and wear properties of epoxy composites.
