The E×B drift instability is studied in Hall thruster using one-dimensional particle in cell(PIC)simulation method.By using the dispersion relation,it is found that unstable modes occur only in discrete bands in ...The E×B drift instability is studied in Hall thruster using one-dimensional particle in cell(PIC)simulation method.By using the dispersion relation,it is found that unstable modes occur only in discrete bands in k space at cyclotron harmonics.The results indicate that the number of unstable modes increases by increasing the external electric field and decreases by increasing the radial magnetic field.The ion mass does not affect the instability wavelength.Furthermore,the results confirm that there is an instability with short wavelength and high frequency.Finally,it is shown that the electron and ion distribution functions deviate from the initial state and eventually the instability is saturated by ion trapping in the azimuthal direction.Also for light mass ion,the frequency and phase velocity are very high that could lead to high electron mobility in the axial direction.展开更多
Objective： To describe mortality pattern and to determine undiagnosed fatal injuries according to autopsy findings among road traffic accident victims in Yazd, Iran. Methods： In this retrospective study, 251 victims...Objective： To describe mortality pattern and to determine undiagnosed fatal injuries according to autopsy findings among road traffic accident victims in Yazd, Iran. Methods： In this retrospective study, 251 victims of road traffic accidents who were admitted to a tertiary trauma hospital over a two-year period （2006 and 2007） and received medical cares were included. Hospital records were reviewed to gather demographic characteristics, road user type, and medical data. Autopsy records were also reviewed to determine actual causes of death and possible undiagnosed injuries occurred in the initial assessment of the emergency unit or during hospitalization. Results： There were 202 males （80.5%） and 49 females （19.5%）. The mean （＋SD） age of fatalities was 34.1 （＋21.5） years. Pedestrian-vehicle accidents were the most common cause of trauma （100 cases, 39.8%）. The most common cause of death was central nervous system injury （146 cases, 58.1%）. The other causes were skull base fractures （10%）, internalbleeding （8%）, lower limb hemorrhage （8%）, skull vault fractures （4%）, cervical spinal cord injury （3.6%）, airway compromise （3.2%）, and multifactor cases （5.1%）, respectively. Thirty-six fatal injuries in 30 victims （12%） mainly contributed to death according to autopsy, but were not diagnosed in initial assessments. The head （72.2%） and cervical spine （13.8%） regions were the two most common sites for undi- agnosed injuries. Conclusion： Training courses for emergency unit medical staff with regard to interpreting radiological findings of head and neck and high clinical suspicion for cervical spine injuries are essential to improve the quality of early hospital care and reduce the mortality and morbidity of traffic accident patients.展开更多
文摘The E×B drift instability is studied in Hall thruster using one-dimensional particle in cell(PIC)simulation method.By using the dispersion relation,it is found that unstable modes occur only in discrete bands in k space at cyclotron harmonics.The results indicate that the number of unstable modes increases by increasing the external electric field and decreases by increasing the radial magnetic field.The ion mass does not affect the instability wavelength.Furthermore,the results confirm that there is an instability with short wavelength and high frequency.Finally,it is shown that the electron and ion distribution functions deviate from the initial state and eventually the instability is saturated by ion trapping in the azimuthal direction.Also for light mass ion,the frequency and phase velocity are very high that could lead to high electron mobility in the axial direction.
文摘Objective： To describe mortality pattern and to determine undiagnosed fatal injuries according to autopsy findings among road traffic accident victims in Yazd, Iran. Methods： In this retrospective study, 251 victims of road traffic accidents who were admitted to a tertiary trauma hospital over a two-year period （2006 and 2007） and received medical cares were included. Hospital records were reviewed to gather demographic characteristics, road user type, and medical data. Autopsy records were also reviewed to determine actual causes of death and possible undiagnosed injuries occurred in the initial assessment of the emergency unit or during hospitalization. Results： There were 202 males （80.5%） and 49 females （19.5%）. The mean （＋SD） age of fatalities was 34.1 （＋21.5） years. Pedestrian-vehicle accidents were the most common cause of trauma （100 cases, 39.8%）. The most common cause of death was central nervous system injury （146 cases, 58.1%）. The other causes were skull base fractures （10%）, internalbleeding （8%）, lower limb hemorrhage （8%）, skull vault fractures （4%）, cervical spinal cord injury （3.6%）, airway compromise （3.2%）, and multifactor cases （5.1%）, respectively. Thirty-six fatal injuries in 30 victims （12%） mainly contributed to death according to autopsy, but were not diagnosed in initial assessments. The head （72.2%） and cervical spine （13.8%） regions were the two most common sites for undi- agnosed injuries. Conclusion： Training courses for emergency unit medical staff with regard to interpreting radiological findings of head and neck and high clinical suspicion for cervical spine injuries are essential to improve the quality of early hospital care and reduce the mortality and morbidity of traffic accident patients.
