The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angl...The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angle errors of BLGFU,in this paper,the contact stress and deformation mechanics between the ball and rail is analyzed. Based on Hertz theory of contact and theory of the multi-body system,a model of the contact stiffness considering the changes in contact angle is established. With the increasing of the external load,the varying trend of the contact deformation can be obtained. Therefore, the motion accuracy degradation of the BLGFU can be analyzed. By using a special experimental device and test system of the rolling linear guide worktable,the horizontal contact stiffness and the vertical linear stiffness are obtained,respectively. By comparing the contact stiffness of the experiment dates and the simulation results,the variation tendency of two curves is consisted and the difference between the measured values and the theoretical values is less than 18%. It is obvious that the model of the contact stiffness considering changes of contact angle has accuracy and feasibility. Thus,while external force point locating at different positions; the contact stiffness and the accuracy analysis of the BLGFU are proved validity by simulations.展开更多
背景如何保证呼吸科重症监护室(intensive care unit,ICU)患者肠内营养治疗安全性及有效性成为研究热点.胃残余量为肠内营养重要评估指标,可指导后续干预但近年来临床对胃残余量的评估准确性、科学性存在一定争议.目的探讨腹内压联合24 ...背景如何保证呼吸科重症监护室(intensive care unit,ICU)患者肠内营养治疗安全性及有效性成为研究热点.胃残余量为肠内营养重要评估指标,可指导后续干预但近年来临床对胃残余量的评估准确性、科学性存在一定争议.目的探讨腹内压联合24 h胃残余量监测调适的肠内营养方案在呼吸科ICU鼻饲患者中的应用效果.方法选取2019-02/2020-12我院呼吸科ICU鼻饲患者82例,依据随机数字表法分为研究组(n=41)及对照组(n=41).对照组采取常规营养支持,研究组采取腹内压联合24 h胃残余量监测调适的肠内营养方案干预.统计两组治疗情况、干预前后营养状态指标[转铁蛋白(transferrin,TF)、前白蛋白(prealbumin,PA)、白蛋白(albumin,ALB)]水平、T细胞亚群指标(CD3^(+)、CD4^(+)、CD4^(+)/CD8^(+))水平、不良事件发生情况.结果(1)研究组达目标喂养用时、ICU住院时间短于对照组(P<0.05);(2)干预后两组TF、PA、ALB水平较干预前增高(P<0.05),但研究组干预后TF、PA、ALB水平虽略高于对照组,但二者比较无显著差异;(3)两组CD3^(+)、CD4^(+)、CD4^(+)/CD8^(+)干预后水平增高(P<0.05),但研究组干预后CD3^(+)、CD4^(+)、CD4^(+)/CD8^(+)水平虽略高于对照组,但二者比较无显著差异;(4)研究组营养达标率较对照组高,营养支持中断发生率较对照组低(P<0.05);(5)研究组腹胀、呕吐的发生率(4.88%)明显低于对照组(21.95%)(P<0.05).但两组吸入性肺炎及腹泻的发生率比较无显著差异.结论腹内压联合24 h胃残余量监测调适的肠内营养方案在呼吸科ICU鼻饲患者中具有较高应用价值,可改善患者机体营养状态及免疫功能,提高生存质量,减少不良事件发生.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51505012 and 51575014)the Natural Science Foundation of Beijing(Grant No.KZ201410005010)+2 种基金the Important National Science&Technology Specific Projects of China(Grant No.2012ZX04010021-001-004)the China Postdoctoral Science Foundation Funded Project(Grant No.2016M591033)the Beijing Postdoctoral Research Foundation(Grant No.2015ZZ-13)
文摘The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angle errors of BLGFU,in this paper,the contact stress and deformation mechanics between the ball and rail is analyzed. Based on Hertz theory of contact and theory of the multi-body system,a model of the contact stiffness considering the changes in contact angle is established. With the increasing of the external load,the varying trend of the contact deformation can be obtained. Therefore, the motion accuracy degradation of the BLGFU can be analyzed. By using a special experimental device and test system of the rolling linear guide worktable,the horizontal contact stiffness and the vertical linear stiffness are obtained,respectively. By comparing the contact stiffness of the experiment dates and the simulation results,the variation tendency of two curves is consisted and the difference between the measured values and the theoretical values is less than 18%. It is obvious that the model of the contact stiffness considering changes of contact angle has accuracy and feasibility. Thus,while external force point locating at different positions; the contact stiffness and the accuracy analysis of the BLGFU are proved validity by simulations.
