为了提高积云模式对雷暴云内电过程的模拟能力,将Mansell提出的放电参数化方案在起始击穿阈值和闪电通道感应电荷的分配过程上进行改进,耦合了已有的三维强风暴动力—电耦合模式中。对STEPS(Severe Thunderstorm Electrification and Pr...为了提高积云模式对雷暴云内电过程的模拟能力,将Mansell提出的放电参数化方案在起始击穿阈值和闪电通道感应电荷的分配过程上进行改进,耦合了已有的三维强风暴动力—电耦合模式中。对STEPS(Severe Thunderstorm Electrification and Precipitation Study)试验中一次雷暴个例以及对中纬度地区理想雷暴个例的模拟表明,引入了新放电参数化方案的模式模拟出闪电在发展特性和几何结构上和观测结果有较好的一致性。模拟结果还表明:闪电的类型与极性取决于背景电荷结构以及闪电的起始位置,只有底部存在正电荷堆时才会产生负地闪,且负地闪的起始点均具有较高的负电势。闪电通道上感应电荷的沉降会改变通道附近水成物粒子上携带的电荷,这对雷暴云内复杂电荷结构的形成有重要作用。经统计,模拟的地闪和云闪通道的分形维数平均值分别为1.47和1.69。对起始击穿阈值的敏感性试验表明,随着起始击穿阈值的增大,首次闪电时间会向后推迟,当采用逃逸击穿时首次闪电产生的时间最早;闪电数量随起始击穿阈值的增大而减少;当使用固定击穿阈值(100,150和200 k V)时得到的云地闪比均小于使用逃逸击穿时得到的云地闪比,使用逃逸击穿时得到的云地闪比与观测结果最为接近。展开更多
In this paper,the mechanical behavior of sand,was systematically described and modeled with a elastoplastic model proposed by Zhang et al.[1].Without losing the generality of the sand,a specific sand called as Toyoura...In this paper,the mechanical behavior of sand,was systematically described and modeled with a elastoplastic model proposed by Zhang et al.[1].Without losing the generality of the sand,a specific sand called as Toyoura sand,a typical clean sand found in Japan,has been discussed in detail.In the model,the results of conventional triaxial tests of the sand under different loading and drainage conditions were simulated with a fixed set of material parameters.The model only employs eight parameters among which five parameters are the same as those used in Cam-clay model.Once the parameters are determined with the conventional drained triaxial compression tests and undrained triaxial cyclic loading tests,then they are fixed to uniquely describe the overall mechanical behaviors of the Toyoura sand,without changing the values of the eight parameters irrespective of what kind of the loadings or the drainage conditions may be.The capability of the model is discussed in a theoretical way.展开更多
Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,mak...Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,making it difficult to machine functional surface structures through mechanical and chemical methods.This study investigated the fundamental characteristics of laser-induced periodic surface structures(LIPSSs)on RB-SiC via femtosecond pulsed laser irradiation at a wavelength of 1028 nm.Low-spatial-frequency LIPSS(LSFL)and high-spatial-frequency LIPSS(HSFL)formed on the surface along directions perpendicular to the laser polarization.SiC grains surrounded by a large amount of Si show a reduced threshold for LIPSS formation.By varying laser fluence and scanning speed,HSFL-LSFL hybrid structures were generated on the SiC grains.Transmission electron microscopy observations and Raman spectroscopy were carried out to understand the formation mechanism of the hybrid LIPSS.A possible mechanism based on the generation of multiple surface electromagnetic waves due to the nonlinear response of SiC was proposed to explain the hybrid structure formation.Furthermore,the direction of laser scanning with respect to laser polarization affects the uniformity of the generated LIPSS.展开更多
Blast-induced traumatic brain injury(b-TBI)is a kind of significant injury to soldiers in the current military conflicts.However,the mechanism of b-TBI has not been well understood,and even there are some contradictor...Blast-induced traumatic brain injury(b-TBI)is a kind of significant injury to soldiers in the current military conflicts.However,the mechanism of b-TBI has not been well understood,and even there are some contradictory conclusions.It is crucial to reveal the dynamic mechanism of brain volume and shear deformations under blast loading for better understanding of b-TBI.In this paper,the numerical simulation method is adopted to carry out comprehensive and in-depth researches on this issue for the first time.Based on the coupled Eulerian-Lagrangian method,the fluid-structure coupling model of the blast wave and human head is developed to simulate two situations,namely the head subjected to the frontal and lateral impacts.The simulation results are analyzed to obtain the underlying dynamic mechanisms of brain deformation.The brain volume deformation is dominated by the local bending vibration of the skull,and the corresponding frequency for the forehead skull under the frontal impact and the lateral skull faced to the lateral impact is as high as 8 kHz and 5 kHz,respectively.This leads to the high-frequency fluctuation of brain pressure and the large pressure gradient along the skull,totally different from the dynamic response of brain under head collisions.While the brain shear deformation mainly depends on the relative tangential displacement between the skull and brain and the anatomical structure of inner skull,being not related to the brain pressure and its gradient.By further comparing the medical statistics,it is inferred that diffuse axonal injury and brain contusion,the two most common types of b-TBI,are mainly attributed to brain shear deformations.And the von Mises stress can be adopted as the indicator for these two brain injuries.This study can provide theoretical guidance for the diagnosis of b-TBI and the development of protective equipment.展开更多
Organic fluorophores with dynamic conformations in the excited state have played a significant role in applications of organic functional dyes.Among them,dihydrophenazine-based dynamic fluorophores involving a photoin...Organic fluorophores with dynamic conformations in the excited state have played a significant role in applications of organic functional dyes.Among them,dihydrophenazine-based dynamic fluorophores involving a photoinduced structural planarization process in the excited state exhibited large Stokes shifts and conformation-dependent multicolor emissions.With the developments of synthetic strategies,precise modifications on dihydrophenazinebased scaffolds have successfully afforded a variety of precise molecular structures of varying sizes and compositions,which have delicately modulated their photophysical properties.Herein,this Perspective summarizes the precise modulations of dihydrophenazine-based dynamic fluorophores,including the development of the synthetic methodologies,and tailor-made molecular models to reveal the luminescence−structure relationships.展开更多
Due to the easy coarsening caused by poor thermal stability,the verified annealing-induced hardening in nanograined metals can only maintain at a relatively low-temperature range.In this study,a nanolam-inated(CrCoNi)...Due to the easy coarsening caused by poor thermal stability,the verified annealing-induced hardening in nanograined metals can only maintain at a relatively low-temperature range.In this study,a nanolam-inated(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)medium-entropy alloy with an average lamellae thickness of∼20 nm embedded by thinner nanotwins was fabricated by severe cold rolling to achieve superior thermal stability.Compared with the conventional nanotwinned CrCoNi with nanotwins inside ultra-fined grains,the hier-archical nanolaminated-nanotwinned(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8) exhibits a significant annealing-induced hard-ening effect,i.e.,hardness increasing from∼250 HV in the original specimen to∼500 HV in the cold-rolled status and finally∼630 HV after annealing at 600℃for 1 h.Detailed microstructure characterizations reveal that the reduced dislocation density and formation of L1_(2)ordered domain are mainly responsible for such hardening effect,which is facilitated by the effectively suppressed coarsening with annealing temperature,i.e.,slow detwinning process and well-retained low-angle nanolamellar structure.The coarsening mechanisms from the cold-rolled nanolamellae to the fully recrystallized micro-equiaxed structures under the annealing temperatures ranging from 400 to 800℃ were also elucidated by atomic observations.展开更多
In this paper,an effective method is proposed to generate specific periodical surface structures.A 532 nm linearly polarized laser is used to irradiate the silicon with pulse duration of 10 ns and repetition frequency...In this paper,an effective method is proposed to generate specific periodical surface structures.A 532 nm linearly polarized laser is used to irradiate the silicon with pulse duration of 10 ns and repetition frequency of 10 Hz.Laser-induced periodic surface structures(LIPSSs) are observed when the fluence is 121 mJ/cm;and the number of pulses is 1000.The threshold of fluence for generating LIPSS gradually increases with the decrease of the number of pulses.In addition,the laser incident angle has a notable effect on the period of LIPSS,which varies from 430 nm to 1578 nm,as the incident angle ranges from10° to 60° correspondingly.Besides,the reflectivity is reduced significantly on silicon with LIPSS.展开更多
The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×10^5 to 6.81×10^5, and the position of guide vane is determine...The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×10^5 to 6.81×10^5, and the position of guide vane is determined by publications. The turbulent flow in the piping elbow is simulated with large eddy simulation （LES）. Following this, a hybrid method of combining LES and Lighthill＇s acoustic analogy theory is used to simulate the hydrodynamic noise and sound sources are solved as volume sources in code Actran. In addition, the flow-induced vibration of the piping elbow is investigated based on a fluid-structure interaction （FSI） code. The LES results indicate that the range of vortex zone in the elbow without the guide vane is larger than the case with the guide vane, and the guide vane is effective in reducing flow-induced noise and vibration in the 90° piping elbow at different Reynolds numbers.展开更多
Computational fluid dynamics(CFD)and the finite element method(FEM)are used to investigate the wind-driven dynamic response of cantilever traffic signal support structures as a whole.By building a finite element model...Computational fluid dynamics(CFD)and the finite element method(FEM)are used to investigate the wind-driven dynamic response of cantilever traffic signal support structures as a whole.By building a finite element model with the same scale as the actual structure and performing modal analysis,a preliminary understanding of the dynamic properties of the structure is obtained.Based on the two-way fluid-structure coupling calculation method,the wind vibration response of the structure under different incoming flow conditions is calculated,and the vibration characteristics of the structure are analyzed through the displacement time course data of the structure in the crosswind direction and along-wind direction.The results show that the maximum response of the structure increases gradually with the increase of wind speed under 90°wind direction angle,showing a vibration dispersion state,and the vibration response characteristics are following the vibration phenomenon of galloping;under 270°wind direction angle,the maximum displacement response of the structure occurs at the lower wind speed of 5 and 6m/s,and the vibration generated by the structure is vortex vibration at this time;the displacement response of the structure in along-wind direction increaseswith the increase of wind speed.The along-wind displacement response of the structure will increase with increasing wind speed,and the effective wind area and shape characteristics of the structurewill also affect the vibration response of the structure.展开更多
Motivated by the recent experimental work,the pressure-induced structural transition of well-known two-dimensional(2D)1T-Hf Te_(2)was investigated up to 50 GPa through the advanced CALYPSO structure search technique c...Motivated by the recent experimental work,the pressure-induced structural transition of well-known two-dimensional(2D)1T-Hf Te_(2)was investigated up to 50 GPa through the advanced CALYPSO structure search technique combined with the first-principles calculations.Our calculations suggested that the 1T-Hf Te_(2)will first transform to C2/m phase at 3.6 GPa with a volume reduction of 7.6%and then to P62m phase at 9.6 GPa with a volume collapse of 4.6%.The occurrences of 3D C2/m and P62m phases mainly originated from the enhanced Te-Te interlayer coupling and the drastic distortions of Hf-Te polyhedrons in P3m1 phase under compression.Concomitantly,the coordination number of Hf atoms increased from six in P3m1 to eight in C2/m and eventually to nine in P62m at elevated pressure.The metallic and semimetallic nature of C2/m and P62m phases were characterized,and the evidence of the reinforced covalent interactions of Te-Hf and Te-Te orbitals in these two novel high-pressure phases were manifested by the atom-projected electronic DOS and Bader charge.展开更多
The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film ...The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film changed a little with the increase in annealing temperature. Analysis of the optical properties indicated that excellent antireflection behavior of the film in the range of 200-400 nm can be obtained by the samples coated with MgF2 film. The refractive index increased and the extinction coefficient decreased with increasing annealing temperature. Compared with the asdeposited films, the laser-induced damage threshold was improved after annealing process and decreased with the increase in annealing temperature, which was probably due to the denser film and more absorption centers under higher annealing temperature.展开更多
文摘为了提高积云模式对雷暴云内电过程的模拟能力,将Mansell提出的放电参数化方案在起始击穿阈值和闪电通道感应电荷的分配过程上进行改进,耦合了已有的三维强风暴动力—电耦合模式中。对STEPS(Severe Thunderstorm Electrification and Precipitation Study)试验中一次雷暴个例以及对中纬度地区理想雷暴个例的模拟表明,引入了新放电参数化方案的模式模拟出闪电在发展特性和几何结构上和观测结果有较好的一致性。模拟结果还表明:闪电的类型与极性取决于背景电荷结构以及闪电的起始位置,只有底部存在正电荷堆时才会产生负地闪,且负地闪的起始点均具有较高的负电势。闪电通道上感应电荷的沉降会改变通道附近水成物粒子上携带的电荷,这对雷暴云内复杂电荷结构的形成有重要作用。经统计,模拟的地闪和云闪通道的分形维数平均值分别为1.47和1.69。对起始击穿阈值的敏感性试验表明,随着起始击穿阈值的增大,首次闪电时间会向后推迟,当采用逃逸击穿时首次闪电产生的时间最早;闪电数量随起始击穿阈值的增大而减少;当使用固定击穿阈值(100,150和200 k V)时得到的云地闪比均小于使用逃逸击穿时得到的云地闪比,使用逃逸击穿时得到的云地闪比与观测结果最为接近。
文摘In this paper,the mechanical behavior of sand,was systematically described and modeled with a elastoplastic model proposed by Zhang et al.[1].Without losing the generality of the sand,a specific sand called as Toyoura sand,a typical clean sand found in Japan,has been discussed in detail.In the model,the results of conventional triaxial tests of the sand under different loading and drainage conditions were simulated with a fixed set of material parameters.The model only employs eight parameters among which five parameters are the same as those used in Cam-clay model.Once the parameters are determined with the conventional drained triaxial compression tests and undrained triaxial cyclic loading tests,then they are fixed to uniquely describe the overall mechanical behaviors of the Toyoura sand,without changing the values of the eight parameters irrespective of what kind of the loadings or the drainage conditions may be.The capability of the model is discussed in a theoretical way.
文摘Reaction-bonded silicon carbide(RB-SiC)is an excellent engineering material with high hardness,stiffness,and resistance to chemical wear.However,its widespread use is hindered due to the properties mentioned above,making it difficult to machine functional surface structures through mechanical and chemical methods.This study investigated the fundamental characteristics of laser-induced periodic surface structures(LIPSSs)on RB-SiC via femtosecond pulsed laser irradiation at a wavelength of 1028 nm.Low-spatial-frequency LIPSS(LSFL)and high-spatial-frequency LIPSS(HSFL)formed on the surface along directions perpendicular to the laser polarization.SiC grains surrounded by a large amount of Si show a reduced threshold for LIPSS formation.By varying laser fluence and scanning speed,HSFL-LSFL hybrid structures were generated on the SiC grains.Transmission electron microscopy observations and Raman spectroscopy were carried out to understand the formation mechanism of the hybrid LIPSS.A possible mechanism based on the generation of multiple surface electromagnetic waves due to the nonlinear response of SiC was proposed to explain the hybrid structure formation.Furthermore,the direction of laser scanning with respect to laser polarization affects the uniformity of the generated LIPSS.
文摘Blast-induced traumatic brain injury(b-TBI)is a kind of significant injury to soldiers in the current military conflicts.However,the mechanism of b-TBI has not been well understood,and even there are some contradictory conclusions.It is crucial to reveal the dynamic mechanism of brain volume and shear deformations under blast loading for better understanding of b-TBI.In this paper,the numerical simulation method is adopted to carry out comprehensive and in-depth researches on this issue for the first time.Based on the coupled Eulerian-Lagrangian method,the fluid-structure coupling model of the blast wave and human head is developed to simulate two situations,namely the head subjected to the frontal and lateral impacts.The simulation results are analyzed to obtain the underlying dynamic mechanisms of brain deformation.The brain volume deformation is dominated by the local bending vibration of the skull,and the corresponding frequency for the forehead skull under the frontal impact and the lateral skull faced to the lateral impact is as high as 8 kHz and 5 kHz,respectively.This leads to the high-frequency fluctuation of brain pressure and the large pressure gradient along the skull,totally different from the dynamic response of brain under head collisions.While the brain shear deformation mainly depends on the relative tangential displacement between the skull and brain and the anatomical structure of inner skull,being not related to the brain pressure and its gradient.By further comparing the medical statistics,it is inferred that diffuse axonal injury and brain contusion,the two most common types of b-TBI,are mainly attributed to brain shear deformations.And the von Mises stress can be adopted as the indicator for these two brain injuries.This study can provide theoretical guidance for the diagnosis of b-TBI and the development of protective equipment.
基金financially supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.21790361 and 21871084)Shanghai Municipal Science and Technology Major Project(Grant No.2018SHZDZX03)+3 种基金the Fundamental Research Funds for the Central Universities,the Programme of Introducing Talents of Discipline to Universities(Grant No.B16017)Program of Shanghai Academic/Technology Research Leader(19XD1421100)the Shanghai Science and Technology Committee(Grant No.17520750100)the China Postdoctoral Science Foundation(2020M671018).
文摘Organic fluorophores with dynamic conformations in the excited state have played a significant role in applications of organic functional dyes.Among them,dihydrophenazine-based dynamic fluorophores involving a photoinduced structural planarization process in the excited state exhibited large Stokes shifts and conformation-dependent multicolor emissions.With the developments of synthetic strategies,precise modifications on dihydrophenazinebased scaffolds have successfully afforded a variety of precise molecular structures of varying sizes and compositions,which have delicately modulated their photophysical properties.Herein,this Perspective summarizes the precise modulations of dihydrophenazine-based dynamic fluorophores,including the development of the synthetic methodologies,and tailor-made molecular models to reveal the luminescence−structure relationships.
基金supported by the National Natural Science Foundation of China Project(No.51971187)Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011322)+2 种基金PolyU Fund(No.G-YBZ3)funding support to the State Key Laboratories in Hong Kong from the Innovation and Technology Commission of the Government of the HKASR,ChinaSY and LQ were supported by grants from the Research Committee of PolyU under student account codes RK2J and RK2U,respectively.
文摘Due to the easy coarsening caused by poor thermal stability,the verified annealing-induced hardening in nanograined metals can only maintain at a relatively low-temperature range.In this study,a nanolam-inated(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)medium-entropy alloy with an average lamellae thickness of∼20 nm embedded by thinner nanotwins was fabricated by severe cold rolling to achieve superior thermal stability.Compared with the conventional nanotwinned CrCoNi with nanotwins inside ultra-fined grains,the hier-archical nanolaminated-nanotwinned(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8) exhibits a significant annealing-induced hard-ening effect,i.e.,hardness increasing from∼250 HV in the original specimen to∼500 HV in the cold-rolled status and finally∼630 HV after annealing at 600℃for 1 h.Detailed microstructure characterizations reveal that the reduced dislocation density and formation of L1_(2)ordered domain are mainly responsible for such hardening effect,which is facilitated by the effectively suppressed coarsening with annealing temperature,i.e.,slow detwinning process and well-retained low-angle nanolamellar structure.The coarsening mechanisms from the cold-rolled nanolamellae to the fully recrystallized micro-equiaxed structures under the annealing temperatures ranging from 400 to 800℃ were also elucidated by atomic observations.
基金supported by the National Natural Science Foundation of China (No. 61805279)
文摘In this paper,an effective method is proposed to generate specific periodical surface structures.A 532 nm linearly polarized laser is used to irradiate the silicon with pulse duration of 10 ns and repetition frequency of 10 Hz.Laser-induced periodic surface structures(LIPSSs) are observed when the fluence is 121 mJ/cm;and the number of pulses is 1000.The threshold of fluence for generating LIPSS gradually increases with the decrease of the number of pulses.In addition,the laser incident angle has a notable effect on the period of LIPSS,which varies from 430 nm to 1578 nm,as the incident angle ranges from10° to 60° correspondingly.Besides,the reflectivity is reduced significantly on silicon with LIPSS.
基金Supported by the Independent Innovation Foundation for National Defense of Huazhong University of Science and Technology(No.01-18-140019)
文摘The effect of a guide vane installed at the elbow on flow-induced noise and vibration is investigated in the range of Reynolds numbers from 1.70×10^5 to 6.81×10^5, and the position of guide vane is determined by publications. The turbulent flow in the piping elbow is simulated with large eddy simulation （LES）. Following this, a hybrid method of combining LES and Lighthill＇s acoustic analogy theory is used to simulate the hydrodynamic noise and sound sources are solved as volume sources in code Actran. In addition, the flow-induced vibration of the piping elbow is investigated based on a fluid-structure interaction （FSI） code. The LES results indicate that the range of vortex zone in the elbow without the guide vane is larger than the case with the guide vane, and the guide vane is effective in reducing flow-induced noise and vibration in the 90° piping elbow at different Reynolds numbers.
基金funded by the National Natural Science Foundation of China(Grant No.51578512)the Cultivating Fund Project for Young Teachers of Zhengzhou University(Grant No.JC21539028).
文摘Computational fluid dynamics(CFD)and the finite element method(FEM)are used to investigate the wind-driven dynamic response of cantilever traffic signal support structures as a whole.By building a finite element model with the same scale as the actual structure and performing modal analysis,a preliminary understanding of the dynamic properties of the structure is obtained.Based on the two-way fluid-structure coupling calculation method,the wind vibration response of the structure under different incoming flow conditions is calculated,and the vibration characteristics of the structure are analyzed through the displacement time course data of the structure in the crosswind direction and along-wind direction.The results show that the maximum response of the structure increases gradually with the increase of wind speed under 90°wind direction angle,showing a vibration dispersion state,and the vibration response characteristics are following the vibration phenomenon of galloping;under 270°wind direction angle,the maximum displacement response of the structure occurs at the lower wind speed of 5 and 6m/s,and the vibration generated by the structure is vortex vibration at this time;the displacement response of the structure in along-wind direction increaseswith the increase of wind speed.The along-wind displacement response of the structure will increase with increasing wind speed,and the effective wind area and shape characteristics of the structurewill also affect the vibration response of the structure.
基金Project supported by the National Natural Science Foundation of China(Grant No.11964026)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant Nos.2023-JC-YB-021,2022JM-035,and 2022JQ-008)。
文摘Motivated by the recent experimental work,the pressure-induced structural transition of well-known two-dimensional(2D)1T-Hf Te_(2)was investigated up to 50 GPa through the advanced CALYPSO structure search technique combined with the first-principles calculations.Our calculations suggested that the 1T-Hf Te_(2)will first transform to C2/m phase at 3.6 GPa with a volume reduction of 7.6%and then to P62m phase at 9.6 GPa with a volume collapse of 4.6%.The occurrences of 3D C2/m and P62m phases mainly originated from the enhanced Te-Te interlayer coupling and the drastic distortions of Hf-Te polyhedrons in P3m1 phase under compression.Concomitantly,the coordination number of Hf atoms increased from six in P3m1 to eight in C2/m and eventually to nine in P62m at elevated pressure.The metallic and semimetallic nature of C2/m and P62m phases were characterized,and the evidence of the reinforced covalent interactions of Te-Hf and Te-Te orbitals in these two novel high-pressure phases were manifested by the atom-projected electronic DOS and Bader charge.
基金financially supported by the Research Fund of the State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,China(Grant No.155-QP-2016)the Fundamental Research Funds for the Central Universities(No.3102014JCQ01032)the 111 Project(No.B08040)
文摘The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film changed a little with the increase in annealing temperature. Analysis of the optical properties indicated that excellent antireflection behavior of the film in the range of 200-400 nm can be obtained by the samples coated with MgF2 film. The refractive index increased and the extinction coefficient decreased with increasing annealing temperature. Compared with the asdeposited films, the laser-induced damage threshold was improved after annealing process and decreased with the increase in annealing temperature, which was probably due to the denser film and more absorption centers under higher annealing temperature.
