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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>
DFSS 기법에 의한 운전자 체형을 고려한 인간공학적 차량설계의 연구
최태현(Taehyun Choi),서상열(Sangyeol Seo),심준엽(Junyoub Shim),정원석(Wonsuk Jung) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
The aim of this study is to suggest ergonomic vehicle design method through optimization of driver’s space about various driver body types (tall, middle, short). Recently, many drivers consistently demand ergonomic factors as well as driving performance when they choose their vehicle. So, there have been a lot of efforts to improve habitability and comfortability through optimizing vehicle interior in advanced design stage. The procedure of this study is as follows. (1)VOC: Driver’s needs of vehicle interior system are collected to select the factors which determine driving posture. (2)QFD: The VOC is converted to engineering words to optimize driving posture in QFD stage. (3)Pugh: The pugh matrix is used to determine optimal concept based on the priority about vehicle interior items. (4)Robust Design: The robust design method is used to select the most compromised group of design factors to minimize discomfort level that is simulated by RAMSIS. And vehicle interior items are optimized to satisfy various body types in this process. The result of optimization from robust design satisfy DFSS target except extremely tall body type (German man 95percentile). It is reasonable to use DFSS in package design stage for ergonomic vehicle. The results of the vehicle design considering driver’s body types can help to determine composition of vehicle interior systems and develop new vehicle.
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>
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.
벼 조생흑찰의 시비조건에 따른 생육 및 안토시아닌 함량변이
오성환,김상열,최원영,서종호,황정동,이휘종,조준현,권영업,남민희,이철원 忠北大學校 農業科學硏究所 2015 農業科學硏究 Vol.31 No.2
Anthocyanin production of black pigmented rice is generally influenced by cultivation environments like transplanting date, cultivation location and fertilization method. This study was carried out to establish an optimum fertilizer application method for production of black pigmented rice with high anthocyanin content. Eight fertilization treatments(NPK, NPK+Si, NPK+Compost, PK, NK, NP, Compost, No Fertilizer) were evaluated with a back pigmented rice cultivar, Josaengheugchal, from 2013 to 2014. Heading date of Josaengheugchal in most fertilization treatments was August 6 to 9 but heading date of NK(P0) treatment was late on August 16. Anthocyanin content was fluctuated between 2013 to 2014. Anthocyanin content of Josaengheugchal in 2014 was higher than that of 2013 because average temperature of ripening stage in 2014 was lower by about 3.2oC than that of 2013. In 2013, anthocyanin content of Josaengheugchal during 30 days after heading(DAH) was decreased by 15.6 mg with increasing average temperature of 1oC. However, temperature effect on anthocyanin content of Josaengheuchal was not observed in 2014 because no significant correlation between average temperature and application treatments was observed. On the other hand, anthocyanin content was significantly influenced by fertilization treatments. Anthocyanin content of Josaengheuchal was highest at the NPK+Compost treatment showing about 17% and 62% higher than NPK, No-Fertilizer treatments, respectively. Total amount of anthocyanin production was also highest with NPK+Compost, higher about 30%, 288% than NPK, No-Fertilizer, respectively.