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Brake disk cooling performance optimization with DFSS
Sangyeol Choi(최상열),Semoon Choi(최세문),Younghoon Kim(김영훈),Yongsuk Kim(김용석) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
The cooling performance of ventilated brake disk of vehicle which depends on convective heat transfer rate governed by air flow entering into brake system is the main property to determine the brake disk size. To achieve competitive brake disk size will contribute the mass reduction that is one of most significant challenges for fuel economy in recent automotive industry. To improve the cooling performance of brake disk without disk size increasing, it is obvious that the cooling air flow should be induced to brake system inside wheel rim effectively by design optimization of vehicle front end and underbody configurations. However, there are little correlation studies between vehicle geometry and brake cooling performance. So, it is necessary that it should be preceded to find the correlation with each geometric change. In the present study, DFSS method is used for analyzing which design parameter affect on brake cooling performance and how it works on. According to the results, brake cooling performance is proportional to mass flow rate into wheel and it should be controlled to achieve desired brake sizing and cooling performance.
홍최상열(Sangyeol Choi),이동현(Donghyun Lee),하종백(Jongpaek Ha) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
Recently, wheels in road vehicle are being developed to be stiffed and lighten from the standpoint of vehicle dynamics and fuel economy, respectively. In addition, design and shape of wheels are being diversified more and more. So, understanding air flow characteristics by those changes of wheel design and shape are very important on production vehicle, because it affect on not only aerodynamic performance which can be sensitized by geometric complexity near wheel, but also thermal performance which can be depended on convective heat transfer rate governed by cooling air flow entering into thermal objectives inside wheel rim like a brake assembly. The objective of this investigation is to analyze aerodynamic performances on the wheel spokes which were designed virtually using NACA airfoil. According to the results, air flow through the wheel opening area could be controlled by NACA airfoil spokes with angle of attack, and also drag coefficient and lift coefficient were changed by the changes of air flow patterns. The results are intended to be used in guiding the establishment of optimum wheel design for future aerodynamic friendly vehicle.
차량 형상에 따른 브레이크 냉각성능과 공기역학적 성능과의 상관관계에 관한 수치해석적 사례연구
최상열(Sangyeol Choi),백봉범(Bongbum Baek),하종백(Jongpaek Ha) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The cooling performance of ventilated brake disk of vehicle depends on convective heat transfer rate governed by air flow entering to brake system. To improve the cooling performance, it is obvious that heat released area of objectives should be larger and cooling air flow should be induced to brake system effectively by design optimization of vehicle front end and underbody configurations. However, increasing the brake disk size which is related with heat release causes not only poor fuel economy by increment of vehicle weight and also development cost increases. In addition, it could be concerned about aerodynamic performances due to the geometric changes. Accordingly, it would be more competitive to precede and optimize the co-relation with each performance. Therefore, the aims of this case study with CFD are to support the effect of additional parts and design changes on the brake cooling performance and to provide the advanced backups for the further development.
Vertical Split Ring Resonator Using Vias With Wide Bandwidth and Small Electrical Size
Choi, Jongwon,Oh, Sangyeol,Jo, Sangjin,Yoon, Won-Sang,Lee, Jaehoon THE INSTITUTE OF ELECTRICAL ENGINEERS 2017 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS Vol.27 No.1
<P>In this letter, we propose a vertically inserted split ring resonator (SRR) in microstrip lines. Since the top and bottom layers of the resonator are electrically connected by using via holes and it has a 3-D shape, it occupies a small electrical size. Through numerical simulations and measurement, it is shown that it can provide a wider range variation of bandwidth than conventional planar SRRs and the resonant frequency and the bandwidth can be adjusted by its length and width, respectively.</P>
최용길(Yonggil Choi),이상열(Sangyeol Lee) 물리치료재활과학회 2021 Physical therapy rehabilitation science Vol.10 No.2
Objective: The purpose of this study was to find out how the back instability during clam exercise (CE) causes changes in pelvicrotation and hip joint abductor muscle activity, and to find out the effects with different methods of application of pressurebiofeedback. Design: Comparative study using repeated measures. Methods: Each subjects performed the clam exercise (CE) without pressure biofeedback, the clam exercise with pressurebiofeedback applied to the back (CE-PBU to back), and the clam exercise with pressure biofeedback applied to the side (CE-PBUto side). The amount of pelvic rotation was measured using myomotion. And the muscle activity of the muscle gluteus medius andthe tensor fasciae latae was measured using EMG device. One-way repeated measures ANOVA followed by the Bonferroni posttest were used to compare the EMG activity in each muscle and pelvic rotation angle during the CE, CE-PBU to back, CE-PBU toside. Results: The amounts of pelvic rotation was the lowest in CE-PBU to back (p< 0.05) and the ratio of muscle activity of the musclegluteus / tensor fasciae latae was the highest in CE-PBU to back (p< 0.05). Conclusions: It is thought that, in order to stabilize the waist-pelvis and increase hip joint muscle strength in subjects with backinstability, applying clam exercise with pressure biofeedback applied to the lower back is effective in improving waist-pelvicmovements and selectively strengthening the muscle gluteus medius.
A CPW-Fed Rectangular Ring Monopole Antenna for WLAN Applications
Jo, Sangjin,Choi, Hyunjin,Shin, Beomsoo,Oh, Sangyeol,Lee, Jaehoon Hindawi Limited 2014 International journal of antennas and propagation Vol.2014 No.-
<P>We present a simple coplanar waveguide- (CPW-) fed rectangular ring monopole antenna designed for dual-band wireless local area network (WLAN) applications. The antenna is based on a simple structure composed of a CPW feed line and a rectangular ring. Dual-band WLAN operation can be achieved by controlling the distance between the rectangular ring and the ground plane of the CPW feed line, as well as the horizontal vertical lengths of the rectangular ring. Simulated and measured data show that the antenna has a compact size of21.4×59.4 mm<SUP>2</SUP>, an impedance bandwidths of 2.21–2.70 GHz and 5.04–6.03 GHz, and a reflection coefficient of less than −10 dB. The antenna also exhibits an almost omnidirectional radiation pattern. This simple compact antenna with favorable frequency characteristics therefore is attractive for applications in dual-band WLAN.</P>
최수홍(Suhong Choi),이상열(Sangyeol Lee) 물리치료재활과학회 2021 Physical therapy rehabilitation science Vol.10 No.2
Objective: This study was conducted to apply skin mobilization to patients with Axillary web syndrome following breast cancer resection and to see the resulting changes in pain and joint range of motion. Design: Single case study,pre-post comparison. Methods: The subject was a female patient in her 40s who performed a mastectomy after being diagnosed with breast cancer, andthen complained of uncomfortable pain from the shoulder joint to the axilla and limited range of motion. To implement a skinmobilization, the palms were adhered to the inner half of the arm, the arms were raised to a pain-free extent, and skin mobilization was performed. The skin was pulled in the direction of axilla and kept for 5 seconds 10 times for a total of 2 sets. Immediatechanges in range of motion and pain were identified. Results: Following skin mobilization, there was an immediate increase in range of motion (pre 116°, post 140°) and a decrease inpain (NRS pre 5, post 2). And also uncomfortable pain, which is hard to define in words, also seems to have improved. Conclusions: Skin mobilization, which considers skin mobility for patients with Axillary web syndrome, can be considered forimproving range of motion and restoring function in patients with pain due to fibrous bands around veins and lymphatic vessels,and is recommended as a new intervention method not used as a conventional treatment.