直升机紧急医疗救援服务(Helicopter emergency medical service,HEMS)作为院外急救的重要补充,在欧美发达国家已开展了近半个世纪并积累了丰富的实践经验。随着我国经济发展和综合国力的提升,开展HEMS是必然趋势并受到社会各界的广泛...直升机紧急医疗救援服务(Helicopter emergency medical service,HEMS)作为院外急救的重要补充,在欧美发达国家已开展了近半个世纪并积累了丰富的实践经验。随着我国经济发展和综合国力的提升,开展HEMS是必然趋势并受到社会各界的广泛关注。由于国情不同,我国HEMS仍处于起步探索阶段。因此,非常有必要参考借鉴国外HEMS发展经验和教训,结合我国各地区实际情况开展实践,探索出适合我国基本国情的HEMS发展模式。笔者以学习为目的检索了国外HEMS相关文献,现将直升机紧急医疗救援的特殊性和存在的问题综述如下。展开更多
Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of...Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.展开更多
Study of electrochemical behavior of chromium （molybdenum, tungsten） and silicon containing melts allowed defining conditions for synthesis of silicides of chromium, molybdenum and tungsten in the form of fine powde...Study of electrochemical behavior of chromium （molybdenum, tungsten） and silicon containing melts allowed defining conditions for synthesis of silicides of chromium, molybdenum and tungsten in the form of fine powders by electrolysis of halide-oxide melts. Sequence of stages of electrosynthesis of silicides of molybdenum and tungsten was found as follows： deposition of more electroposifve metal （molybdenum or tungsten）, deposition of the second component （silicon） on the surface of metal deposited previously, and reaction diffusion of silicon into the deep of the metal-salt ＂pear＂ with the formation of silicide phases of different compositions up to the higher silicides. In contrast, during the electrodeposition of chromium silicides, one of the components （chromium） is deposited not in elemental form, but in oxide form, and the other （silicon） acts as a reducing agent for this oxide to form binary compounds. Duration of the synthesis first stage （deposition of refractory metal or of its oxide） depends on the refractory metal compound content in the system and on the cathode current density. Synthesis of silicides is possible due to retention of powders of molybdenum （tungsten） or chromium oxide at the cathode without scaling. Optimal values of concentrations ratio, current density, temperature, and duration of electrosynthesis were found. Phase composition of products were obtained, as well as their chemical and thermal stability, were studied.展开更多
This paper presents experimental studies on bypass transition of separated boundary layer on low-pressure turbine airfoils,focusing on the effects of freestream turbulence on the transition process.Hot-wire probe meas...This paper presents experimental studies on bypass transition of separated boundary layer on low-pressure turbine airfoils,focusing on the effects of freestream turbulence on the transition process.Hot-wire probe measurements are performed on the suction side of an airfoil in the low-pressure linear turbine cascade at several Reynolds number conditions.Freestream turbulence is enhanced by use of turbulence grid located upstream of the cascade.The results of this experimental study show that the location of boundary layer separation does not strongly de-pend on the freestream turbulence level.However,as the freestream turbulence level increases,the size of separa-tion bubble becomes small and the location of turbulent transition moves upstream.The size of separation bubble becomes small as the Reynolds number increases.At low freestream turbulence intensity,the velocity fluctuation due to Kelvin-Helmholtz instability is observed clearly in the shear layer of the separation bubble.At high frees-tream turbulence intensity,the streak structures appear upstream of the separation location,indicating bypass transition of attached boundary layer occurs at high Reynolds number.展开更多
The structural, electronic and magnetic properties of La0.55Ca0.45MnO3 were measured. A rapid change of lattice parameters appeared around 190 K associated with the az2 orbital ordering and charge ordering （CO） stat...The structural, electronic and magnetic properties of La0.55Ca0.45MnO3 were measured. A rapid change of lattice parameters appeared around 190 K associated with the az2 orbital ordering and charge ordering （CO） states that were reflected by both magnetization and resistivity. Great difference of magnetizations between the field-cooling （FC） and zero-field-cooling （ZFC） modes below the charge ordering temperature Too in high magnetic field （H〉4 T） was clearly seen. A field of 5 T （threshold field） is sufficient to completely destroy the antiferromagnetic （AFM） CO state for FC mode in magnetization while it is not the case for ZFC mode. A much larger field （larger than 10 T from ZFC resistivity data） is needed to destroy the CO state for ZFC mode. This could be explained by the coexistence and transformation of two phases reported by Huang et al. For ZFC mode, with increasing H, Tco gradually moves to low temperature regime and the relationship between the critical field Hc （0） to destroy CO state and Tco conforms to a power law Hc = Hc（0）（1 - T/Tco（0））^γ, where Hc （0） is the critical field to destroy the CO state at 0 K, and Too （0） is the CO temperature in zero field.展开更多
文摘直升机紧急医疗救援服务(Helicopter emergency medical service,HEMS)作为院外急救的重要补充,在欧美发达国家已开展了近半个世纪并积累了丰富的实践经验。随着我国经济发展和综合国力的提升,开展HEMS是必然趋势并受到社会各界的广泛关注。由于国情不同,我国HEMS仍处于起步探索阶段。因此,非常有必要参考借鉴国外HEMS发展经验和教训,结合我国各地区实际情况开展实践,探索出适合我国基本国情的HEMS发展模式。笔者以学习为目的检索了国外HEMS相关文献,现将直升机紧急医疗救援的特殊性和存在的问题综述如下。
文摘Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.
文摘Study of electrochemical behavior of chromium （molybdenum, tungsten） and silicon containing melts allowed defining conditions for synthesis of silicides of chromium, molybdenum and tungsten in the form of fine powders by electrolysis of halide-oxide melts. Sequence of stages of electrosynthesis of silicides of molybdenum and tungsten was found as follows： deposition of more electroposifve metal （molybdenum or tungsten）, deposition of the second component （silicon） on the surface of metal deposited previously, and reaction diffusion of silicon into the deep of the metal-salt ＂pear＂ with the formation of silicide phases of different compositions up to the higher silicides. In contrast, during the electrodeposition of chromium silicides, one of the components （chromium） is deposited not in elemental form, but in oxide form, and the other （silicon） acts as a reducing agent for this oxide to form binary compounds. Duration of the synthesis first stage （deposition of refractory metal or of its oxide） depends on the refractory metal compound content in the system and on the cathode current density. Synthesis of silicides is possible due to retention of powders of molybdenum （tungsten） or chromium oxide at the cathode without scaling. Optimal values of concentrations ratio, current density, temperature, and duration of electrosynthesis were found. Phase composition of products were obtained, as well as their chemical and thermal stability, were studied.
文摘This paper presents experimental studies on bypass transition of separated boundary layer on low-pressure turbine airfoils,focusing on the effects of freestream turbulence on the transition process.Hot-wire probe measurements are performed on the suction side of an airfoil in the low-pressure linear turbine cascade at several Reynolds number conditions.Freestream turbulence is enhanced by use of turbulence grid located upstream of the cascade.The results of this experimental study show that the location of boundary layer separation does not strongly de-pend on the freestream turbulence level.However,as the freestream turbulence level increases,the size of separa-tion bubble becomes small and the location of turbulent transition moves upstream.The size of separation bubble becomes small as the Reynolds number increases.At low freestream turbulence intensity,the velocity fluctuation due to Kelvin-Helmholtz instability is observed clearly in the shear layer of the separation bubble.At high frees-tream turbulence intensity,the streak structures appear upstream of the separation location,indicating bypass transition of attached boundary layer occurs at high Reynolds number.
基金supported by the National Natural Science Foundation of China (Grant No. 50772111)the 211 Project of Anhui University (Grant No. 06130221)
文摘The structural, electronic and magnetic properties of La0.55Ca0.45MnO3 were measured. A rapid change of lattice parameters appeared around 190 K associated with the az2 orbital ordering and charge ordering （CO） states that were reflected by both magnetization and resistivity. Great difference of magnetizations between the field-cooling （FC） and zero-field-cooling （ZFC） modes below the charge ordering temperature Too in high magnetic field （H〉4 T） was clearly seen. A field of 5 T （threshold field） is sufficient to completely destroy the antiferromagnetic （AFM） CO state for FC mode in magnetization while it is not the case for ZFC mode. A much larger field （larger than 10 T from ZFC resistivity data） is needed to destroy the CO state for ZFC mode. This could be explained by the coexistence and transformation of two phases reported by Huang et al. For ZFC mode, with increasing H, Tco gradually moves to low temperature regime and the relationship between the critical field Hc （0） to destroy CO state and Tco conforms to a power law Hc = Hc（0）（1 - T/Tco（0））^γ, where Hc （0） is the critical field to destroy the CO state at 0 K, and Too （0） is the CO temperature in zero field.
