In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted....In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted. The relationships between the above three characteristics have been researched. The evolution of the cavity can be divided into three processes according to its shape characteristics. The first liquid spurt occurred in Process Ⅱ and the rest of it occurred in Process Ⅲ. The duration of the second liquid spurt is longer than the first liquid spurt. When the impact velocity of the fragment is less than996 m/s, the velocity of the second liquid spurt is the highest. When the velocity of the fragment is greater than 996 m/s, the velocity of the first liquid spurt is the highest. The maximum velocities of the first and second liquid spurt are 111 m/s and 94 m/s respectively. The pressure fluctuated sharply in Processes Ⅰ and Ⅲ. The maximum peak pressures in the shock and the cavity oscillation phases are15.51 MPa and 7.96 MPa respectively. The time interval of the two adjacent pressure pulses increases with the increase of the fragment velocity.展开更多
基金the National Natural Science Foundation of China(Grant No.11572159)the National Defense Science and Technology Foundational Enhancement Program Technology Field Foundation(No.2020-JCJQ-JJ-401)for providing the financial support for this study.
文摘In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted. The relationships between the above three characteristics have been researched. The evolution of the cavity can be divided into three processes according to its shape characteristics. The first liquid spurt occurred in Process Ⅱ and the rest of it occurred in Process Ⅲ. The duration of the second liquid spurt is longer than the first liquid spurt. When the impact velocity of the fragment is less than996 m/s, the velocity of the second liquid spurt is the highest. When the velocity of the fragment is greater than 996 m/s, the velocity of the first liquid spurt is the highest. The maximum velocities of the first and second liquid spurt are 111 m/s and 94 m/s respectively. The pressure fluctuated sharply in Processes Ⅰ and Ⅲ. The maximum peak pressures in the shock and the cavity oscillation phases are15.51 MPa and 7.96 MPa respectively. The time interval of the two adjacent pressure pulses increases with the increase of the fragment velocity.
基金supported by Key Basic Research Program of Ministry of Science and Technology of China(No.2006FY110300)National Key Technology Research and Development Program,China(No.2008BAI52B02)
文摘本文旨在研究儿童青少年去脂体重(fat free mass,FFM)、脂肪体重(fat mass,FM)和肺通气功能的关系。随机抽取黑龙江省10～18岁健康儿童青少年1174人(男性583人,女性591人),测量身高、体重和腰臀比(waist to hip ratio,WHR),使用身体成分测量仪和肺功能仪分别测量FFM、FM和肺通气功能,采用独立样本t检验、偏相关和多元逐步回归分析FFM、FM和肺通气功能的关系。结果显示,无论性别,受试者年龄与去脂体重指数(FFM index,FFMI)呈正相关(P<0.001)。男性年龄和脂肪体重指数(FM index,FMI)呈负相关(P<0.001),女性年龄和FMI呈正相关(P<0.001)。无论性别,受试者FFMI与用力呼气肺活量(forced vital capacity,FVC)、用力呼气一秒量(forced expiratory volume in one second,FEV1)、最大呼气流量(peak expiratory flow,PEF)、用力呼出25%肺活量时呼气流量(forced expiratory flow at25%of forced vital capacity,FEF25%)、FEF50%和最大呼气中段流量(maximum mid-expiratory flow,MMEF)都呈正相关(P<0.05),与FEV1/FVC呈负相关(P<0.01)。男性FFMI与FEF75%正相关(P<0.05),女性FFMI与FEF75%不相关。男性FMI与FEV1、FEV1/FVC、PEF、FEF25%、FEF50%、FEF75%和MMEF呈负相关(P<0.05),而与FVC不相关。女性FMI与肺通气功能的指标均不相关。除男性FEV1/FVC和FEF75%外,无论性别,FFMI对肺通气功能指标的预测作用大于FMI。FFMI对男性肺通气功能预测作用大于女性。男性肺功能突增发生在12～15岁:FVC较前一个年龄段分别增加10.05%、20.41%、11.75%和9.00%,FEV1分别较前一年龄段增加11.38%、20.07%、12.01%和9.14%。女性肺功能突增发生在12、13和18岁:FVC较前一年龄段分别增加13.73%、9.07%和9.76%,FEV1较前一年龄段分别增加13.17%、11.12%和10.62%。在肺功能突增期,无论性别,FFMI对肺功能的预测作用大于年龄的预测作用。综上所述,无论性别,反映骨骼肌力的FFM与肺通气功能呈正相关,对男性肺通气功能的预测作用大于女性。FM与男性肺通气功能呈负相关,而与女性肺通气功能不相关。在肺功能突增期,身高和FFM的快速增长可能是造成肺功能快速增长的主要原因。
