800 V급 4H-SiC DMOSFET 전력 소자 구조 최적화 시뮬레이션

최창용,강민석,방욱,김상철,김남균,구상모,Choi, Chang-Yong,Kang, Min-Seok,Bahng, Wook,Kim, Sang-Cheol,Kim, Nam-Kyun,Koo, Sang-Mo 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8

In this work, we demonstrate 800 V 4H-SiC power DMOSFETs with several structural alterations to obtain a low threshold voltage ($V_{TH}$) and a high figure of merit ($V_B\;^2/R_{SP,ON}$), To optimize the device performance, we consider four design parameters; (a) the doping concentration ($N_{CSL}$) of current spreading layer (CSL) beneath the p-base region, (b) the thickness of p-base ($t_{BASE}$), (c) the doping concentration ($N_J$) and width ($W_J$) of a JFET region, (d) the doping concentration ($N_{EPI}$) and thickness ($t_{EPI}$) of epi-layer. These parameters are optimized using 2D numerical simulation and the 4H-SiC DMOSFET structure results in a threshold voltage ($V_{TH}$) below $^{\sim}$3.8 V, and high figure of merit ($V_B\;^2/R_{SP,ON}$>$^{\sim}$200 $MW/cm^2$) for a power MOSFET in $V_B\;^{\sim}$800 V range.

원형 덕트유동에서의 Graetz 문제에 대한 이중교환 경계요소 해석

최창용,Choi, Chang Yong 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.2

The dual reciprocity boundary element method (DRBEM) is used to solve the Graetz problem of laminar flow inside circular duct. In this method the domain integral tenn of boundary integral equation resulting from source term of governing equation is transformed into equivalent boundary-only integrals by using the radial basis interpolation function, and therefore complicate domain discretization procedure Is completely removed. Velocity profile is obtained by solving the momentum equation first and then, using this velocities as Input data, energy equation Is solved to get the temperature profile by advancing from duct entrance through the axial direction marching scheme. DRBEM solution is tested for the uniform temperature and heat flux boundary condition cases. Local Nusselt number, mixed mean temperature and temperature profile inside duct at each dimensionless axial location are obtained and compared with exact solutions for the accuracy test Solutions arc in good agreement at the entry region as well as fully developed region of circular duct, and their accuracy are verified from error analysis.

G 방정식을 이용한 실린더 챔버 내부 둔각물체 주위의 난류 예 혼합 화염 해석

최창용,박남섭,고상철,Choi Chang-Yong,Park Nam-Seob,Ko Sang-Cheol 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.4

In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.

SOI-MOSFET의 고온 동작에 관한 연구

최창용,문경숙,구상모,Choi, Chang-Yong,Moon, Kyung-Sook,Koo, Sang-Mo 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.8

The substrate bias effect on the current level of SOI-MOSFETs for high temperature operation has been investigated. In this work, we demonstrate the current level of SOI-MOSFETs can be controlled at different temperatures by applying a control bias to the substrate, showing that all current levels below T=150$^{\circ}C$ can be adjusted to a constant current level. 2D numerical simulation results show that substrate bias effectively controls the current conduction; as the substrate bias effectively lower the potential of the channel, inversion carrier generation is effectively controlled and consequently a constant current conduction level is achieved up to T=150$^{\circ}C$. We also demonstrate that the device simulated in this work has same operation at any temperature below T=150$^{\circ}C$ through mixed mode simulation.

후두부에 발생한 유피낭종의 특징

최환준,탁민성,최창용,강상규,이영만,Choi, Hwan-Jun,Tark, Min-Seong,Choi, Chang-Yong,Kang, Sang-Gue,Lee, Young-Man 대한성형외과학회 2010 Archives of Plastic Surgery Vol.37 No.4

Purpose: Congenital dermoid cysts develop during the fusion of the embryo when the ectodermal tissue gets trapped in the line of fusion. Dermoid cysts of the head are rare lesions comprised of epidermal and mesodermal elements. Furthermore, dermoid cysts in the occipital area are extremely rare. Only a few cases of dermoid cysts in the posterior scalp have been reported. Especially, A bilateral, synchronous presentation in this location has not been reported previously in the literature. Methods: All 5 cases had a gradually enlarging mass of the posterior aspect of the scalp. The cysts were mobile, noncompressible, and non-tender, without evidence of an associated sinus tract, skin dimpling, discoloration, or communication with adjacent structures. The CT scan displayed a hypodense cystic lesions about -87 to +24 HU (Housefield units, average +3.2 HU) with hypodense capsule and no postcontrast enhancement. All tumors were found just under the skin, and were well encapsulated, so they were completely removed the mass with adjacent periosteum. Results: On gross findings, all tumors were oval-or round-shaped, and when the cystic tumor was cut open it presented a greasy and caseous substance. Histologically, all specimens contain desquamated squamous epithelium and keratin in the lumen and are encapsulated and lined by keratinized stratified squamous epithelium. And, all cases of posterior mass are the presence of adnexal structures. Conclusion: Appropriate diagnosis requires not only an index of suspicion for this rare tumor a very careful history and search for skin changes. Especially, CT can reveal the exact location of the cyst, its relationship with the adjacent structures. We think that occipital dermoids divide into superficial and deep type. In our cases, because they did not have intra-cranial involvement or fistula formation, they are superficial type. This report describes the clinical and operative aspects of the superficial dermoid cysts and provides a review of the literatures.

WPAN에서 거리별 측정오차 패턴을 적용한 위치인식 보정 알고리즘의 성능 분석

최창용(Choi, Chang-Yong),이동명(Lee, Dong-Myung) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.5

본 논문에서는 거리별 측정오차 패턴을 적용한 보정 알고리즘(DCA1)의 위치인식 성능특성과 문제점을 분석 하고 이를 개선한 알고리즘인 WPAN에서 거리별 측정오차 패턴을 적용한 위치인식 보정 알고리즘(<I>DCA</I>2)을 제안하 였다. 위치인식 실험결과, 평균적으로 <I>DCA</I>1 및 <I>DCA</I>2는 각각 위치인식 지점의 60%이상, 75% 이상에서 SDS-TWR 보다 위치인식 성능이 더 우수하였고, 특히 15m×15m의 실험공간에서는 <I>DCA</I>2는 SDS-TWR 보다 위치인식 지점의 91%에서 위치인식 정확도가 더 우수함을 확인하였다. 또한 10m×10m 및 15m×15m의 실험공간에서 <I>DCA</I>2는 <I>DCA</I>1 보다 각각 16%, 22%의 위치인식 지점에서 위치인식 정확도가 더 우수하였고, <I>DCA</I>1 및 <I>DCA</I>2의 평균 위치인식 오 차는 SDS-TWR보다 각각 7~12%, 20% 감소함을 확인하였다. 이와 같은 결과를 볼 때 <I>DCA</I>2가 SDS-TWR 및 <I>DCA</I>1 보다 위치인식 정확도가 가장 우수함을 알 수 있다. The performance characteristics and the disadvantages in the compensation algorithm based on the Measured Error Patterns of Distance that is already developed are analyzed, and the localization compensation algorithm(<I>DCA</I>2) based on measured error patterns of distance in WPAN that is the enhanced version of <I>DCA</I>1 is supposed in this paper. From the experimental results, it is confirmed that the localization performance of <I>DCA</I>1 and <I>DCA</I>2 is superior than SDS-TWR as each average above 60% and 75% of the total localizing measurement points in 2 experimental regions, and the localization performance of <I>DCA</I>2 is especially better than SDS-TWR as 91% of the points in 15m×15m experimental region. In addition to this, it is confirmed that <I>DCA</I>2 is better than <I>DCA</I>1 as each 16% and 22% of the total localizing measurement points in 10m×10m and 15m×15m scaled experimental regions, and the average localization errors of <I>DCA</I>1 and <I>DCA</I>2 are lower than SDS-TWR to each 7~12% and 20%. Thus, it can be inferred that <I>DCA</I>2 is the best localization algorithm among 3 localization algorithms SDS-TWR, <I>DCA</I>1 and <I>DCA</I>2.

거리측정의 오차비율 오프셋을 적용한 보정알고리즘 연구

최창용(Choi, Chang-Yong),이동명(Lee, Dong-Myung) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.3

CSS(Chirp Spread Spectrum)기반에서 SDS-TWR(Symmetric Double Side-Two-Way Ranging)의 거리측정 정확 도는 실험에 의하면 전파환경 간섭으로 인해 일부 레인징 구간에서 매우 큰 오차가 발생함을 확인하였다. 본 논문에 서는 이러한 문제를 해결하기 위해 레인징 오차를 감소시킬 수 있는 측정거리의 오차비율 오프셋을 적용한 SDS-TWR의 보정 알고리즘(<I>CA</I>d)을 제안하였다. <I>CA</I>d는 두 노드를 LOS(Line Of Sight)환경에서 1~25m까지 1m 간 격으로 SDS-TWR으로 거리 값을 측정하여, 거리보정에 필요한 각 파라미터의 값을 계산한 후 이를 사용하여 거리 값을 보정한다. 제안한 보정 알고리즘의 성능분석 결과, <I>CA</I>d는 SDS-TWR에 비해 오차가 평균 95cm, 최대 오차가 526cm 감소하였고, 는 25m에서 약 60cm의 오차가 발생함을 확인하였다. 이러한 결과를 볼 때 제안한 <I>CA</I>d는 LOS 환경에서 SDS-TWR에 비해 매우 정밀한 정확도를 가진 것으로 판단된다. It is confirmed that as the distance measurements accuracy of the SDS-TWR(Symmetric Double-Sided Two-Way Ranging) based on CSS(Chirp Spread Spectrum) is considerably degraded due to frequency interference and it causes to severe errors in the localization applications. In this paper, the compensation algorithm based on error rate offset of distance measurement (<I>CA</I>d) is proposed for the purpose to reduce the ranging errors due to by the SDS-TWR ranging problems. The <I>CA</I>d measures the distance values between two nodes by means of 1m interval about 1~25m distances in the SDS-TWR, and compensates the distance values using the parameters related to the distance compensation. From the experiments, it is analyzed that the <I>CA</I>d have reduced the distance error to average 95cm and maximum 526cm, and the distance error by the <I>CA</I>d was below about 60cm in the 25m distances. In particular, the performance of the distance measurements accuracy by the <I>CA</I>d is very high in LOS(Line Of Sight) environments.

인터넷 게시물에서 ‘참새구이’로 나타나는 국내의 소규모 산새류 포획 및 소비 실태

최창용(Chang-Yong Choi),남현영(Hyun-Young Nam) 한국조류학회II 2020 한국조류학회지 Vol.27 No.1

국내에서 가장 널리 행해지는 산새류의 포획 및 상업적 거래 대상종은 참새(Passer montanus)로서, 현재에도 ‘참새구이’라는 형태로 유통과 소비가 이루어지고 있다. 본 연구에서는 상업적 포획과 거래와는 별도로 개인에 의해 일어나고 있는 산새류의 소규모 포획 및 소비 현황을 파악하기 위해, 인터넷 게시물을 검색하고 분석하여 소형 산새류 포획 행위와 대상 종, 방법 등을 파악하였다. 지난 15년간 게시된 총 4,500여 건의 인터넷 게시물 중에서 48건 571개체에 대한 포획 및 소비 사례가 확인되었으며, 21건 325개체가 확인된 참새 외에도 8종의 소형 산새류도 함께 혼획되어 희생되는 것이 확인되었다. 소규모 밀렵행위는 산새류가 무리를 이루는 겨울철(12-2월)에 닭장과 같은 개인 사유지에서 가장 흔히 발생하였으며, 특히 새그물을 이용한 포획이 6건으로 나타났다. 전체 사례 중 39건이 무허가 포획으로 추정되었으나, 이런 행위가 밀렵이라는 게시자의 인식은 낮은 것으로 판단된다. 본 연구를 통해 국내 농촌지역에서 여전히 여러 종의 산새류에 대한 소규모 포획 활동이 지속되고 있음이 확인되었으나, 이런 소규모 밀렵이 국내의 산새류 개체군이나 다양성이 미치는 영향은 파악하기 어려운 실정이다. 이런 행위로 인한 산새류의 피해를 줄이기 위해 밀렵행위에 대한 인식 증진, 새그물의 판매와 사용 대한 법적 규제 강화 등이 필요한 것으로 판단된다. The most common target songbird for trapping and trade in Korea is the Tree Sparrow (Passer montanus) because ‘grilled sparrows’ are still regarded as a commercially-available delicacy in the market. To understand how small-scale trapping and self-consumption of songbirds occur by individuals in Korea, along with the commercial trade, we searched for and analyzed such cases from internet posts using a Korean keyword meaning the ‘grilled sparrow’. As a result, we found 571 victims from 48 of 4,500 internet posts published over the past 15 years; Tree Sparrows (325 birds in 21 cases) were the most common victims, while 8 more songbird species were also bycatch. Trapping and self-consumption of songbirds frequently occurred at personal properties in rural areas, like hencoops, especially in winter (December to February), and mist-nets were the most common tools for poaching (6 cases). Illegal trapping without proper permits was suspected in 39 cases, but the recognition of their activities as poaching was seemed to be low. This study confirms that the small-scale trapping and self-consumption of songbirds still exists in rural areas of Korea, though its impact on songbird populations and diversity is unknown. In addition to public awareness programs on the songbird conservation, new legislation about and law enforcement against mist-net use and trade are required to mitigate the impact on songbirds in Korea.

검은꼬리사막딱새(Oenanthe deserti)의 국내 최초 기록

최창용(Chang-Yong Choi),남현영(Hyun-Young Nam) 한국조류학회II 2008 한국조류학회지 Vol.15 No.1

2008년 1월 26일 경상북도 포항시 장기면 양포항 인근(N 35˚ 52' 37", E 129˚ 31' 07")에서 검은꼬리사막딱새(Oenanthe deserti) 1개체를 확인하였으며, 이는 국내 첫 관찰기록에 해당한다. 관찰된 개체는 l년생 겨울깃의 어린 수컷이었으며, 몸집의 크기나 깃털의 특징, 각 아종의 분포 등을 고려할 때 Oenanthe deserti atrogularis에 해당되는 것으로 판단된다. On 26 January 2008, one young male of the Desert Wheatear (Oenanthe deserti) was observed at Yangpo harbor (N 35˚ 52' 37", E 129˚ 31' 07'), Janggi-myeon, Pohang, Gyeongbuk Province, and this is the first record of this species for the Korean peninsula. The wheatear was in 1st winter plumage and was possibly the Oenanthe deserti atrogularis based on size, plumage and distribution of subspecies.

탈황, 재생공정 및 흡착속도 추정을 포함한 디젤용 탈황반응기 설계

최창용 ( Chang Yong Choi ),임도진 ( Do Jin Im ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.6

In this study, we performed numerical simulation of the adsorptive desulfurization reactor for a 100 kW fuel cell. Using experimental results and the adsorption kinetics theory, the adsorption rate of sulfur in diesel was estimated and verified by numerical analysis. By analyzing the performance of desulfurization according to reactor size, the optimal reactor size was determined. By maximizing processed diesel amount, optimal diesel flow rate was determined. Regenera-tion process was also confirmed for the obtained optimal reactor size. The present work will be utilized to design a die-sel desulfurization reactor for a fuel cell used in a ship by further process modeling and economic analysis.