The transport processes of plasmas in grid systems of krypton（Kr） ion thrusters at different acceleration voltages were simulated with a 3 D-PIC model, and the result was compared with xenon（Xe） ion thrusters. The...The transport processes of plasmas in grid systems of krypton（Kr） ion thrusters at different acceleration voltages were simulated with a 3 D-PIC model, and the result was compared with xenon（Xe） ion thrusters. The variation of the screen grid transparency, the accelerator grid current ratio and the divergence loss were explored. It is found that the screen grid transparency increases with the acceleration voltage and decreases with the beam current, while the accelerator grid current ratio and divergence loss decrease first and then increase with the beam current. This result is the same with Xe ion thrusters. Simulation results also show that Kr ion thrusters have more advantages than Xe ion thrusters, such as higher screen grid transparency, smaller accelerator grid current ratio, larger cut-off current threshold, and better divergence loss characteristic. These advantages mean that Kr ion thrusters have the ability of operating in a wide range of current. Through comprehensive analyses, it can be concluded that using Kr as propellant is very suitable for a multimode ion thruster design.展开更多
High-resolution absorption spectra of atomic krypton in the range of 11870-12700 cm-1 were recorded by employing concentration modulation absorption spectroscopy technique with a tunable single-mode cw Ti:Sapphire las...High-resolution absorption spectra of atomic krypton in the range of 11870-12700 cm-1 were recorded by employing concentration modulation absorption spectroscopy technique with a tunable single-mode cw Ti:Sapphire laser. The krypton atoms were excited to the absorbing energy states by discharge-burning in a mixture of helium and krypton. A total of 120 lines of neutral krypton were observed, among them 33 lines had already been classified in previous studies, 45 lines were newly classified with the known energy levels, and 42 lines cannot be classified. These unclassified lines indicate that up to now unknown energy levels of Kr must exist. Further, an analysis of the unclassified lines to get possible new energy levels with a classification program is reported.展开更多
The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence...The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ←4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. （Phys. Rev. A 67 022703 （2003））. The differences between the experimental results and theoretical calculations show that more studies are needed.展开更多
Electron cyclotron resonance radio frequency （ECR-rf） hybrid krypton-diluted oxygen plasmas were used to pattern the surfaces of diamond films with the assistance of a physical mask, while optical emission spectrosc...Electron cyclotron resonance radio frequency （ECR-rf） hybrid krypton-diluted oxygen plasmas were used to pattern the surfaces of diamond films with the assistance of a physical mask, while optical emission spectroscopy was employed to characterize the plasma. It was found that with krypton dilution the etching rate decreased, and also the aspect ratios of nanotips formed in micro-holes were significantly modified. The oxygen atomic densities were estimated by oxygen atom optical emission and argon actinometry. Under a microwave power of 300 W and rf bias of-300 V, the absolute density of ground-state oxygen atoms decreased from 1.3×10^12 cm^-3 to 1.4×10^11 cm^-3 as the krypton dilution ratio increased to 80%, accompanied by the decrease in the plasma excitation temperature. It is concluded that oxygen atoms play a dominant role in diamond etching. The relative variations in the horizontal and vertical etching rates induced by the addition of krypton are attributed to the observations of thicker nanotips at a high krypton dilution ratio.展开更多
Effects of argon, krypton and their mixed pressure treatments on the quality of white mushrooms were studied during 9 days of storage at 4℃. Among all treatments in this study, the minimum respiration rate, polypheno...Effects of argon, krypton and their mixed pressure treatments on the quality of white mushrooms were studied during 9 days of storage at 4℃. Among all treatments in this study, the minimum respiration rate, polyphenoloxidase activity, retained color change, antioxidants and delayed pseudomonas growth were observed with pressure argon (5 MPa) followed by mixing argon and krypton (2.5 MPa each) treatments. Respiration rates after 9 days of storage were 5.35%, 6.20%, 7.50%, 7.60%, 7.91% and 8.95% for HA5, HAK, HA2, HK5, HK2 and control, respectively. DPPH inhibition percentages of free radical for HA5, HAK, HK5, HA2, HK2 and control mushrooms were 28.03%, 25.24%, 24.96%, 21.87%, 20.56% and 19.06%, respectively, after 9 days of storage. The pressurized argon treatment was the most effective compared to pressurized krypton. Thus, application of pressurized argon and krypton treatments could extend the storage life of white mushrooms to 9 days at 4℃.展开更多
The inert gas radioactive isotope ^(85)Kr(with a half-life of 10.74 years), due to its stable physical and chemical properties, is an ideal tracer for shallow groundwater dating. In such a dating application, first th...The inert gas radioactive isotope ^(85)Kr(with a half-life of 10.74 years), due to its stable physical and chemical properties, is an ideal tracer for shallow groundwater dating. In such a dating application, first the dissolved gas is extracted from groundwater in the field, then krypton is separated from the gas sample, and finally the isotopic abundance ^(85)Kr/Kr will be determined by an ATTA instrument. According to the atmospheric input curve of ^(85)Kr, the ^(85)Kr age of groundwater is determined. We conducted ^(85)Kr analysis in three wells in Zhengding County on the plains in front of the Taihang Mountains, and made a comparison with tritium(~3H) method.展开更多
Purpose:To investigate the association between high anisometropia and the area of choroidal neovascularization (CNV) induced by krypton laser in guinea pigs and better understand the pathogenesis and prevention of myo...Purpose:To investigate the association between high anisometropia and the area of choroidal neovascularization (CNV) induced by krypton laser in guinea pigs and better understand the pathogenesis and prevention of myopic CNV. Methods:.Nine 3-week old male guinea pigs with anisometropia > 6.00D were randomly assigned to three groups according to examination date after laser photocoagulation (7d, 14d and 28d). All animals underwent refraction. The eye with higher myopia was used as the experimental eye, and the other as the control eye..All eyes received repeated multi-wavelength krypton laser photocoagulation treatments (wavelength: 532 nm; laser power: 400 mW; spot diameter: 50 μm; exposure time: 0.1s). Fundus photography and indocyanine green angiography (ICGA) were performed. Afterwards, the animals were sacrificed immediately,.and the eyes were enucleated and processed for histopathologic examination and flat mounts. Results: CNV appeared at 7d after laser treatment. The area of CNV peaked at 14d, and decrease in area and the presence of scarring was noted at 28 d..CNV was present in 66.7% of eyes by ICGA at 14 d..CNV could be observed under light microscopy at all three time points..At 14 d,.flat mount showed the neovascular plexus around the lesion. Semi-quantitative analysis revealed that the area of CNV in treated eyes was greater than that of control eyes. Conclusion:.Since the mechanism of CNV in this study resembles that of CNV in pathological myopia, this model can be used to investigate the etiology, pathogenesis and treatment of CNV in pathological myopia.展开更多
ZrCoRE(RE denotes rare earth elements)non-evaporable getter films have significant applications in vacuum packaging of micro-electro mechanical system devices because of their excellent gas adsorption performance,low ...ZrCoRE(RE denotes rare earth elements)non-evaporable getter films have significant applications in vacuum packaging of micro-electro mechanical system devices because of their excellent gas adsorption performance,low activation temperature and environmental friendliness.The films were deposited using DC magnetron sputtering with argon and krypton gases under various deposition pressures.The effects of sputtering gas type and pressure on the morphology and hydrogen adsorption performance of ZrCoRE films were investigated.Results show that the films prepared in Ar exhibit a relatively dense structure with fewer grain boundaries.The increase in Ar pressure results in more grain boundaries and gap structures in the films.In contrast,films deposited in Kr display a higher density of grain boundaries and cluster structures,and the films have an obvious columnar crystal structure,with numerous interfaces and gaps distributed between the columnar structures,providing more paths for gas diffusion.As Kr pressure increases,the film demonstrates more pronounced continuous columnar structure growth,accompanied by deeper and wider grain boundaries.This structural configuration provides a larger specific surface area,which significantly improves the hydrogen adsorption speed and capacity.Consequently,high Ar and Kr pressures are beneficial to improve the adsorption performance.展开更多
This letter reports an all-optical measurement of laser electric field based on strong field ionization.By measuring the attosecond transient absorption spectra of krypton ions subjected to strong laser fields,we obta...This letter reports an all-optical measurement of laser electric field based on strong field ionization.By measuring the attosecond transient absorption spectra of krypton ions subjected to strong laser fields,we obtain the time-dependent effective valence-hole population,from which the driving laser waveform is retrieved with particle swarm optimization and genetic algorithm under strong-field approximation.展开更多
针对国内测量85Kr探测下限较高的现状,本文通过探测其衰变产生的β射线,设计并优化探测系统的本底和探测效率,实现对85Kr极低放射性浓度的测量。在探测器设计中,采用国产正比计数管作为4π主探测器,辅以铅铜屏蔽,以塑料闪烁体作为反符...针对国内测量85Kr探测下限较高的现状,本文通过探测其衰变产生的β射线,设计并优化探测系统的本底和探测效率,实现对85Kr极低放射性浓度的测量。在探测器设计中,采用国产正比计数管作为4π主探测器,辅以铅铜屏蔽,以塑料闪烁体作为反符合探测器。通过Geant4模拟研究正比计数管的探测效率,分析了其尺寸、工作气压对探测下限的影响,提出了优化方案。模拟结果表明,最佳的正比计数管参数为半径30 mm、长度100 mm,并在压强大于1 atm的条件下可有效提高探测效率至92%以上。塑料闪烁体反符合效率达90.29%,铅铜屏蔽厚度优化为外层8 cm、内层2 cm,屏蔽效率达99.5%。根据优化得到的主探测器的探测效率和探测系统的本底,计算出理论探测下限可达16.08 m Bq/m~3,比国内正比计数管的探测下限180 m Bq/m~3降低一个数量级。本研究为开发一种成本低、结构简单、性能可靠的^(85)Kr实时监测系统提供了重要的模拟参考和理论依据。展开更多
Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in...Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0＋ states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes （except the ground state of 72Kr）, the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.展开更多
基金co-supported by the National Natural Science Foundation of China (No. 11675040)the Fundamental Research Funds for the Central Universities of China (Nos. 3102014KYJD005 and 1191329723)
文摘The transport processes of plasmas in grid systems of krypton（Kr） ion thrusters at different acceleration voltages were simulated with a 3 D-PIC model, and the result was compared with xenon（Xe） ion thrusters. The variation of the screen grid transparency, the accelerator grid current ratio and the divergence loss were explored. It is found that the screen grid transparency increases with the acceleration voltage and decreases with the beam current, while the accelerator grid current ratio and divergence loss decrease first and then increase with the beam current. This result is the same with Xe ion thrusters. Simulation results also show that Kr ion thrusters have more advantages than Xe ion thrusters, such as higher screen grid transparency, smaller accelerator grid current ratio, larger cut-off current threshold, and better divergence loss characteristic. These advantages mean that Kr ion thrusters have the ability of operating in a wide range of current. Through comprehensive analyses, it can be concluded that using Kr as propellant is very suitable for a multimode ion thruster design.
基金supported by the National Natural Science Foundation of China (No.11674096)
文摘High-resolution absorption spectra of atomic krypton in the range of 11870-12700 cm-1 were recorded by employing concentration modulation absorption spectroscopy technique with a tunable single-mode cw Ti:Sapphire laser. The krypton atoms were excited to the absorbing energy states by discharge-burning in a mixture of helium and krypton. A total of 120 lines of neutral krypton were observed, among them 33 lines had already been classified in previous studies, 45 lines were newly classified with the known energy levels, and 42 lines cannot be classified. These unclassified lines indicate that up to now unknown energy levels of Kr must exist. Further, an analysis of the unclassified lines to get possible new energy levels with a classification program is reported.
基金Project supported by the National Natural Science Foundation of China （Grant No 10474089）.
文摘The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ←4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. （Phys. Rev. A 67 022703 （2003））. The differences between the experimental results and theoretical calculations show that more studies are needed.
基金supported by National Natural Science Foundation of China (No. 10635010)National Basic Research Program of China (No. 2008CB717800)
文摘Electron cyclotron resonance radio frequency （ECR-rf） hybrid krypton-diluted oxygen plasmas were used to pattern the surfaces of diamond films with the assistance of a physical mask, while optical emission spectroscopy was employed to characterize the plasma. It was found that with krypton dilution the etching rate decreased, and also the aspect ratios of nanotips formed in micro-holes were significantly modified. The oxygen atomic densities were estimated by oxygen atom optical emission and argon actinometry. Under a microwave power of 300 W and rf bias of-300 V, the absolute density of ground-state oxygen atoms decreased from 1.3×10^12 cm^-3 to 1.4×10^11 cm^-3 as the krypton dilution ratio increased to 80%, accompanied by the decrease in the plasma excitation temperature. It is concluded that oxygen atoms play a dominant role in diamond etching. The relative variations in the horizontal and vertical etching rates induced by the addition of krypton are attributed to the observations of thicker nanotips at a high krypton dilution ratio.
文摘Effects of argon, krypton and their mixed pressure treatments on the quality of white mushrooms were studied during 9 days of storage at 4℃. Among all treatments in this study, the minimum respiration rate, polyphenoloxidase activity, retained color change, antioxidants and delayed pseudomonas growth were observed with pressure argon (5 MPa) followed by mixing argon and krypton (2.5 MPa each) treatments. Respiration rates after 9 days of storage were 5.35%, 6.20%, 7.50%, 7.60%, 7.91% and 8.95% for HA5, HAK, HA2, HK5, HK2 and control, respectively. DPPH inhibition percentages of free radical for HA5, HAK, HK5, HA2, HK2 and control mushrooms were 28.03%, 25.24%, 24.96%, 21.87%, 20.56% and 19.06%, respectively, after 9 days of storage. The pressurized argon treatment was the most effective compared to pressurized krypton. Thus, application of pressurized argon and krypton treatments could extend the storage life of white mushrooms to 9 days at 4℃.
基金supported by the National Natural Science Foundation of China (41102151)Public Science and Technology Research Funds Projects of Ministry of Land and Resources(201511046)
文摘The inert gas radioactive isotope ^(85)Kr(with a half-life of 10.74 years), due to its stable physical and chemical properties, is an ideal tracer for shallow groundwater dating. In such a dating application, first the dissolved gas is extracted from groundwater in the field, then krypton is separated from the gas sample, and finally the isotopic abundance ^(85)Kr/Kr will be determined by an ATTA instrument. According to the atmospheric input curve of ^(85)Kr, the ^(85)Kr age of groundwater is determined. We conducted ^(85)Kr analysis in three wells in Zhengding County on the plains in front of the Taihang Mountains, and made a comparison with tritium(~3H) method.
文摘Purpose:To investigate the association between high anisometropia and the area of choroidal neovascularization (CNV) induced by krypton laser in guinea pigs and better understand the pathogenesis and prevention of myopic CNV. Methods:.Nine 3-week old male guinea pigs with anisometropia > 6.00D were randomly assigned to three groups according to examination date after laser photocoagulation (7d, 14d and 28d). All animals underwent refraction. The eye with higher myopia was used as the experimental eye, and the other as the control eye..All eyes received repeated multi-wavelength krypton laser photocoagulation treatments (wavelength: 532 nm; laser power: 400 mW; spot diameter: 50 μm; exposure time: 0.1s). Fundus photography and indocyanine green angiography (ICGA) were performed. Afterwards, the animals were sacrificed immediately,.and the eyes were enucleated and processed for histopathologic examination and flat mounts. Results: CNV appeared at 7d after laser treatment. The area of CNV peaked at 14d, and decrease in area and the presence of scarring was noted at 28 d..CNV was present in 66.7% of eyes by ICGA at 14 d..CNV could be observed under light microscopy at all three time points..At 14 d,.flat mount showed the neovascular plexus around the lesion. Semi-quantitative analysis revealed that the area of CNV in treated eyes was greater than that of control eyes. Conclusion:.Since the mechanism of CNV in this study resembles that of CNV in pathological myopia, this model can be used to investigate the etiology, pathogenesis and treatment of CNV in pathological myopia.
基金National Natural Science Foundation of China(62171208)Natural Science Foundation of Gansu Province(23JRRA1355)。
文摘ZrCoRE(RE denotes rare earth elements)non-evaporable getter films have significant applications in vacuum packaging of micro-electro mechanical system devices because of their excellent gas adsorption performance,low activation temperature and environmental friendliness.The films were deposited using DC magnetron sputtering with argon and krypton gases under various deposition pressures.The effects of sputtering gas type and pressure on the morphology and hydrogen adsorption performance of ZrCoRE films were investigated.Results show that the films prepared in Ar exhibit a relatively dense structure with fewer grain boundaries.The increase in Ar pressure results in more grain boundaries and gap structures in the films.In contrast,films deposited in Kr display a higher density of grain boundaries and cluster structures,and the films have an obvious columnar crystal structure,with numerous interfaces and gaps distributed between the columnar structures,providing more paths for gas diffusion.As Kr pressure increases,the film demonstrates more pronounced continuous columnar structure growth,accompanied by deeper and wider grain boundaries.This structural configuration provides a larger specific surface area,which significantly improves the hydrogen adsorption speed and capacity.Consequently,high Ar and Kr pressures are beneficial to improve the adsorption performance.
基金supported by the National Natural Science Foundation of China(Grant Nos.12234020,12450403,and 12374263)。
文摘This letter reports an all-optical measurement of laser electric field based on strong field ionization.By measuring the attosecond transient absorption spectra of krypton ions subjected to strong laser fields,we obtain the time-dependent effective valence-hole population,from which the driving laser waveform is retrieved with particle swarm optimization and genetic algorithm under strong-field approximation.
文摘针对国内测量85Kr探测下限较高的现状,本文通过探测其衰变产生的β射线,设计并优化探测系统的本底和探测效率,实现对85Kr极低放射性浓度的测量。在探测器设计中,采用国产正比计数管作为4π主探测器,辅以铅铜屏蔽,以塑料闪烁体作为反符合探测器。通过Geant4模拟研究正比计数管的探测效率,分析了其尺寸、工作气压对探测下限的影响,提出了优化方案。模拟结果表明,最佳的正比计数管参数为半径30 mm、长度100 mm,并在压强大于1 atm的条件下可有效提高探测效率至92%以上。塑料闪烁体反符合效率达90.29%,铅铜屏蔽厚度优化为外层8 cm、内层2 cm,屏蔽效率达99.5%。根据优化得到的主探测器的探测效率和探测系统的本底,计算出理论探测下限可达16.08 m Bq/m~3,比国内正比计数管的探测下限180 m Bq/m~3降低一个数量级。本研究为开发一种成本低、结构简单、性能可靠的^(85)Kr实时监测系统提供了重要的模拟参考和理论依据。
基金Supported by National Key Basic Research Program of China(2013CB83440)''National Natural Science Foundation of China(11235001,11320101004)
文摘Total Routhian Surface （TRS） calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0＋ states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes （except the ground state of 72Kr）, the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.
