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内燃式水平对动空气压缩机的平衡设计
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作者 王庆前 张继忠 +2 位作者 于祥 薛耀勇 巩健 《青岛大学学报(工程技术版)》 CAS 2017年第1期94-98,共5页
针对传统内燃式空气压缩机工作过程中存在振动和噪声较大并且动不平衡的问题,本文提出了新型的内燃式水平对动空气压缩机。该设计以178F柴油机曲轴系相关参数为基础,通过平衡理论对内燃式水平对动空气压缩机进行了平衡设计,然后在Adams... 针对传统内燃式空气压缩机工作过程中存在振动和噪声较大并且动不平衡的问题,本文提出了新型的内燃式水平对动空气压缩机。该设计以178F柴油机曲轴系相关参数为基础,通过平衡理论对内燃式水平对动空气压缩机进行了平衡设计,然后在Adams中建立了刚性体模型,施加相应约束并定义新材料与驱动,最后选取3种典型工况(曲轴转速分别为1 500,2 000,2 400r/min)进行动力学仿真,并将仿真结果进行对比研究。研究结果表明,方案1中,随着曲轴平均转速的增大,曲轴自由端轴承支点力的平均值一直增大,而且靠近动力活塞端的轴承支点处受力平均值大约是自由端的1.7倍;方案2中,输出端轴承支点力平均值先减小后增大;曲轴自由端轴承支点处受力平均值与曲轴输出端相同。该研究具有广阔的应用前景。 展开更多
关键词 内燃式 水平对动 空气压缩机 平衡 力学仿真
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Performance on the Functional Movement Screen in older active adults 被引量:3
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作者 Ulrike H.Mitchell A.Wayne Johnson +2 位作者 Pat R.Vehrs J.Brent Feland Sterling C.Hilton 《Journal of Sport and Health Science》 SCIE 2016年第1期119-125,共7页
Background:The Functional Movement Screen(FMS^(TM)) has become increasingly popular for identifying functional limitations in basic functional movements.This exploratory and descriptive study was undertaken to confirm... Background:The Functional Movement Screen(FMS^(TM)) has become increasingly popular for identifying functional limitations in basic functional movements.This exploratory and descriptive study was undertaken to confirm feasibility of performing the FMS^(TM) in older active adults,assess prevalence of asymmetries and to evaluate the relationship between functional movement ability,age,physical activity levels and body mass index(BMI).Methods:This is an observational study;97 men(n = 53) and women(n = 44) between the ages of 52 and 83 participated.BMI was computed and self-reported physical activity levels were obtained.Subjects were grouped by age(5-year intervals),BMI(normal,over-weight,and obese)and sex.Each participant's performance on the FMS^(TM) was digitally recorded for later analysis.Results:The youngest age group(50–54 years) scored highest in all seven tests and the oldest age group(75+) scored lowest in most of the tests compared to all other age groups.The subjects in the 'normal weight' group performed no different than those who were in the 'overweight' group;both groups performed better than the 'obese' group.Of the 97 participants 54 had at least one asymmetry.The pairwise correlations between the total FMS^(TM) score and age(r =-0.531),BMI(r =-0.270),and the measure of activity level(r = 0.287) were significant(p < 0.01 for all).Conclusion:FMS^(TM) scores decline with increased BMI,increased age,and decreased activity level.The screen identifies range of motion-and strength-related asymmetries.The FMS^(TM) can be used to assess functional limitations and asymmetries.Future research should evaluate if a higher total FMS^(TM) score is related to fewer falls or injuries in the older population. 展开更多
关键词 Age BMI Fitness level FMS^(TM) Functional fitness Functional limitations
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Role of Downward Momentum Transport in the Formation of Severe Surface Winds 被引量:3
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作者 LIU Xiang-E GUO Xue-Liang 《Atmospheric and Oceanic Science Letters》 2012年第5期379-383,共5页
The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan ... The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan and Shandong Provinces of China. The results show that there was a strong westerly jet belt with a wind speed greater than 30 m s 1 and a thickness of 5 km at an altitude of 11-16 km. The jet belt was accelerated, and it descended while the squall line convective system occurred. It was found that the appearance of strong negative perturbation pressure accompanied by the squall line caused the acceleration of the upper-level westerly jet and increased the horizontal wind speed by a maximum of 18%. Meanwhile, the negative buoyancy due to the loading, melting, and evaporation of cloud hydrometeors induced the downward momentum transport from the upper levels. The downward momentum transport contributed approximately 70% and the surface cold pool 30% to the formation of severe surface winds. 展开更多
关键词 downward momentum transport severe surface winds WRF model
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