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이정수(Jungsoo Lee),박용민(Yongmin Park),장진혁(Jinhyuck Chang) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6
In general, Mass-produced vehicles that are not High-performance vehicles will be developed with a focus on CD(Coefficient Drag) in aerodynamics for improved fuel efficiency rather than CL(Coefficient Lift). However, Highperformance vehicles require downforce for ground grip force, and Drag reduction is also required to improve overtaking, max. speed, and high speed fuel efficiency. Lift force improving is often accompanied by increased drag. Some High performance vehicles can be equipped with active devices such as variable spoiler to adjust lift and drag according to driving conditions. But, active devices add weight and cost to the vehicle. In this study, the aerodynamic performance improvement of a vehicle was studied with optimization using CFD(Computational Fluid Dynamics) to simultaneously lift and drag force improvement, rather than minimizing the trade-off relationship between lift and drag.
woongkyo Jeong,Jeonghun choe,Geunwoo Park,Jinhyuck Lee,Wonjik Juh 대한견주관절의학회 2021 대한견주관절학회 학술대회논문집 Vol.2021 No.3
Introduction and Background Ultrasonography has been increasingly used to investigate the postoperative condition in patients with rotator cuff tear. Recently, several studies show the usefulness of sonoelastography in evaluating state of rotator cuff muscles, but there is no consensus about the stiffness of repaired rotator cuff tendon and postoperative muscle function. The purpose of this study is to evaluate the relation between muscle strength and neuromuscular control and stiffness of repaired tendon through serial sonoelastography after surgery in patients with rotator cuff tear. Material and Method From 2017 to 2019, in retrospective analysis, 50 patients(average age : 58.76 ± 7.73) with rotator cuff tear underwent arthroscopic rotator cuff repair(ARCR) were enrolled. The stiffness ratio of repaired rotator cuffs(repaired tendon site and normal portion of tendon) were evaluated using sonoelastography at 4 weeks, 3 months, 6 months, 1 year after surgery. Additionally, isokinetic muscle performance testing including muscle strength(peak torque/body weight, total work) and neuromuscular control(time to peak torque and acceleration time) was performed at 1 year postoperatively. Results In correlation analysis, the stiffness ratio at 6 months after ARCR was significantly correlated with the acceleration time of the external rotation(R=-0.285, P=0.045) and total work of extension of shoulder(R=0.423, P=0.003).? Conclusions The elasticity of repaired rotator cuff tendon at 6 months after surgery was associated between neuromuscular control activity of the external rotation and strength of shoulder extension.