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脉动顶张力作用下输流立管涡激振动主共振研究
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作者 秦营 李世博 常学平 《中国海洋大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第7期72-78,共7页
为定量描述海洋工程中输流立管受脉动顶张力作用时的涡激振动响应,本文研究了海洋输流立管受到内部流体、脉动顶张力和涡流激励作用时的参数主共振问题。首先建立了该问题的数学模型,运用Galerkin法和多重尺度法对其进行求解,引入调谐... 为定量描述海洋工程中输流立管受脉动顶张力作用时的涡激振动响应,本文研究了海洋输流立管受到内部流体、脉动顶张力和涡流激励作用时的参数主共振问题。首先建立了该问题的数学模型,运用Galerkin法和多重尺度法对其进行求解,引入调谐参数描述输流立管第一阶固有频率同顶张力脉动频率和涡流频率的接近程度,通过改变调谐参数,研究输流立管的动力学响应。结果表明:定常顶张力作用下,立管的振幅为单值,随着调谐参数增大,立管振幅先增大后减小,且出现明显的跳跃现象,内部流体速度和张力幅值的竞争机制也会影响立管振幅;脉动顶张力作用时,在一阶锁频的条件下,随着调谐参数变化,立管的振幅呈现“多值—单值—多值”的变化规律,顶张力均值或脉动幅值越大,立管振幅的变化范围越宽。 展开更多
关键词 海洋输流立管 张力 涡激振 主参数共振 调谐参数 响应
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环锭细纱机上纱条张力分析与应用 被引量:11
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作者 赵健 唐文辉 《纺织器材》 2013年第5期1-8,共8页
为了稳定纱条张力,提高成纱质量,降低纺纱断头,分析了细纱机加捻卷绕过程中纱条张力的分布规律,纱条张力与基本卷绕工艺的关系,重点阐述了纺纱张力曲线的变化,纱条张力测试方法、设备、一落纱中典型位置纺纱张力测定示例,及其在细纱变... 为了稳定纱条张力,提高成纱质量,降低纺纱断头,分析了细纱机加捻卷绕过程中纱条张力的分布规律,纱条张力与基本卷绕工艺的关系,重点阐述了纺纱张力曲线的变化,纱条张力测试方法、设备、一落纱中典型位置纺纱张力测定示例,及其在细纱变速上的应用。指出:①卷绕过程中纱条张力分布一般规律为TW>T0>TR>TS;②纱条张力与基本卷绕工艺的关系是TR与锭子速度平方(ns2)、钢丝圈重力Gt、钢领半径R(直径DR)成正比;③纺纱张力不是恒值,而是一个不断波动的变量,张力波动和张力脉动是管纱卷装型式客观条件决定的;④由高速摄影记录曲线发现,当纱条转到机台正前方、脱开导纱钩孔眼而悬空时,Tsmax=T0,即在纺纱张力测试时,同时也可测得气圈顶端张力;⑤细纱机上变频调速装置可降低毛羽,调节范围广且节电,纺纱效益好。 展开更多
关键词 卷绕张力 纺纱张力 气圈张力 钢丝圈 钢领 管纱 张力 张力脉动 突变张力 变速装置
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VEGFmRNA and eNOSmRNA expression in immature rabbits with bleomycin-induced pulmonary hypertension
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作者 龚方戚 林幼敏 +3 位作者 汤宏峰 顾伟忠 汪伟 康曼丽 《Journal of Zhejiang University Science》 CSCD 2004年第8期995-1000,共6页
Objective: To investigate the evolution of pulmonary hypertension, the pathological changes of pulmonary arteries, and the expression of VEGFmRNA and eNOSmRNA of pulmonary arterial endothelial cells in immature rabbit... Objective: To investigate the evolution of pulmonary hypertension, the pathological changes of pulmonary arteries, and the expression of VEGFmRNA and eNOSmRNA of pulmonary arterial endothelial cells in immature rabbits treated with intratracheal bleomycin (BLM). Methods: Immature rabbits were divided into control and BLM group. Two and four weeks after intratracheal normal saline or BLM injection, the systolic, diastolic and mean pulmonary artery pressure (PASP, PADP, MPAP) were measured by micro-catheter; the pathological changes and the expression of VEGFmRNA and eNOSmRNA of endothelial cells in pulmonary arteries were evaluated by HE and in situ hybridization.Results: Two and four weeks after intratracheal injection of BLM, the PASP, PADP and MPAP increased 53%, 49%, 52%in 2 weeks, and 43%, 89%, 56% in 4 weeks; the wall thickness increased and the cavity in middle and small pulmonary arteries became narrow; the Thickness Index (TI) and Area Index (AI) increased 25%, 14% in 2 weeks, and 22%, 24% in 4 weeks; the level of VEGFmRNA and eNOSmRNA expression decreased 46%, 43% in 2 weeks, and 43%, 51% in 4 weeks.There was no significant difference between 2 weeks and 4 weeks BLM groups. Conclusion: The pulmonary artery pressure was elevated, the thickness of wall increased and the cavity became narrow in middle and small pulmonary arteries, and the level of VEGFmRNA and eNOSmRNA expression in pulmonary arterial endothelial cells decreased in immature rabbits after 2 weeks and 4 weeks of intratracheal 4 U/kg BLM injection. 展开更多
关键词 BLEOMYCIN Pulmonary hypertension VEGF ENOS MRNA
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