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空化器形状对超空泡射弹尾拍运动影响的数值研究 被引量:16
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作者 陈伟善 郭则庆 +1 位作者 刘如石 黄振贵 《工程力学》 EI CSCD 北大核心 2020年第4期248-256,共9页
为研究空化器形状对超空泡射弹尾拍航行时运动特性的影响,基于有限体积法和Mixture多相流模型,结合动网格技术构建了三维自由尾拍运动仿真模型,在两种长径比下比较了平头弹、凹口弹、锥头弹的尾拍运动特性,并分析了其水动力影响因素。... 为研究空化器形状对超空泡射弹尾拍航行时运动特性的影响,基于有限体积法和Mixture多相流模型,结合动网格技术构建了三维自由尾拍运动仿真模型,在两种长径比下比较了平头弹、凹口弹、锥头弹的尾拍运动特性,并分析了其水动力影响因素。结果表明:较小长径比下,平头弹可以保持运动稳定,凹口弹和锥头弹易失稳,主要是由于空化器产生的空泡尺寸差异导致其临界失稳攻角依次降低。较大长径比下,临界失稳攻角消失,三种头型射弹均能保持尾拍稳定,锥头弹在速度较高时以“单侧尾拍”保持稳定,速度降低后以“双侧尾拍”保持稳定,而平头弹和凹口弹始终以“双侧尾拍”保持稳定;锥头弹由于“单侧尾拍”会产生与初始扰动方向相反的垂直位移,而平头弹和凹口弹由于弹头升力产生与初始扰动方向相同的垂直位移。 展开更多
关键词 超空泡射弹 尾拍运动 数值模拟 空化器 多相流
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Changes in the expression of platelet-derived growth factor in astrocytes in diabetic rats with spinal cord injury 被引量:5
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作者 WU Qiong-hua chen wei-shan +2 位作者 chen Qi-xin WANG Jian-hong ZHANG Xiao-ming 《Chinese Medical Journal》 SCIE CAS CSCD 2010年第12期1577-1581,共5页
Background Prospective mortality studies in the United States revealed that the mortality was elevated in diabetics compared to normal individuals following chronic spinal cord injury (SCI). Our study was conducted ... Background Prospective mortality studies in the United States revealed that the mortality was elevated in diabetics compared to normal individuals following chronic spinal cord injury (SCI). Our study was conducted to investigate the levels of platelet-derived growth factor (PDGF) of astrocytes in SCI in streptozotocin (STZ)-induced diabetic rats. Methods Thirty male Sprague-Dawley (SD) rats were randomly divided into 3 groups: SCI group, diabetic SCI group, and sham operation control group. We employed STZ-induced diabetic SD rats and a weight-drop contusion SCI model. The rats were sacrificed on day 7 after the induction of SCI. Immunohistochemistry and Western blotting analysis were used to detect the PDGF expression level. Basso, Beattie and Bresnahan locomotor rating scale (BBB) was also used to evaluate the neurological recovery level of the rats. Results PDGF positive astrocyte numbers were significantly higher and PDGF staining was more intensive in astrocytes in the SCI group than in the diabetic SCI group (P〈0.05). The diabetic SCI group showed a slower recovery of motor function with a lower BBB score 7 days after acute spinal injury. Conclusions PDGF is an important factor for the recovery of neurological function after acute spinal injury and hyperglycemia in diabetic rats could depress the expression of PDGF in injured spinal cord. This may help to explain the slower recovery and higher mortality in diabetics after SCI. 展开更多
关键词 platelet-derived growth factor spinal cord injury diabetes mellitus RAT
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