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.

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.

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.

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.

태양열 냉난방 부하산정을 위한 TRNSYS 동적 시뮬레이션

최창용(Choi Chang-Yong),고상철(Ko Sang-Cheol),곽희열(Kwak Hee-Youl) 한국태양에너지학회 2006 한국태양에너지학회 논문집 Vol.26 No.1

This paper presents the heating and cooling load estimations for the library of a cultural center building located in Gwangju Korea by TRNSYS with Type 56 of multi-zone building components. In this study, energy rate control mode is selected and the design temperatures for heating and cooling are specified respectively as 20oC and 26oC. Reading rooms of the library are located on the third floor of the cultural center building, and this third floor space is modeled as the five thermal zones for the TRNSYS simulation. Among the five zones, attention is given to the two zones which are the reading rooms 1 and 2. Since these two zones are to be heated and cooled by the solar thermal system which is planned to be installed in the building, dynamic thermal behaviors of the two zones are analyzed by the heating and cooling load estimations.

대학생 참여 CSR유형에 따른 기업이미지, 기업평판 및 구매의도의 영향력 분석

최창용 ( Chang Yong Choi ),김형재 ( Hyung Jae Kim ) 국제지역학회 2015 국제지역연구 Vol.19 No.1

본 연구의 목적은 대학생 참여 CSR 유형에 따라 해당 변수들에 미치는 영향이 차이가 있는지를 분석하고 해당 사업에 대한 대학생들의 참여의도가 기업이미지, 기업평판 및 구매의도에 어떠한 영향을 주는지를 실증적으로 분석하고자 하는 것이다. 해당 연구의 실증적 연구결과를 도출해내기 위해 서울지역 대학생 468명을 대상으로 설문조사를 실시하였다. 연구결과 대학생 참여 CSR 유형에 따라 해당 변수(참여의도, 기업이미지, 기업평판 및 구매의도)에 미치는 영향은 유의미한 수준에서 차이가 있는 것으로 나타났다. 참여의도와 기업이미지 부분은 외부 타 단체나 기업 등과의 파트너쉽을 통한 외부 사업형태를 기업주도로 했을 경우 보다 긍정적인 반응이 발생되었다. 반면, 기업평판과 구매의도 변수에서는 앞선 참여 의도나 기업이미지와 달리 기업이 직접 CSR 사업을 추진하는 직접사업형태를 기업주도로 추진했을 경우보다 긍정적인 영향을 미친다는 것이 확인되었다. 이는 참여의도, 기업이미지, 기업평판 및 구매의도와 같은 변수들이 서로 상관성이 있는 변수임에도 불구하고 CSR 유형에 따라 반응을 보이는 패턴이 상이하므로 기업들이 대학생 참여 CSR 사업을 구상할 때 사업을 통해 궁극적으로 얻고자 하는 목적에 따라 사업형태를 전략적으로 선택해야 한다는 것을 의미한다. 마지막으로 CSR 유형 및 종속변수 관계에서 참여하는 대학생들의 의도(의지)정도가 높을수록 해당 기업의 CSR 사업 등에 관심도가 상승되고 긍정적인 평가가 형성되었다. In the past, the CSR in Korea used to be a simple type such as donating money to NPO(Non-Profit Organization)s, but the recent CSR for the companies seems to be more active such as forming their own CSR team. The recent trend in CSR which many companies has focused on is the CSR type which university students are involved in. The aim of this study is to analyze whether factors(participant intention, corporate image, corporate reputation and purchase intention) can be affected by the type of CSR involving university students. To get more empirical result from the study, the survey has been carried for 468 university students in Seoul. We found out the fact that there were some differences for the four factors depending on the type of CSR. For participant intention and corporate image, the type of external partnership leading by a corporation can be more positive. On the other hand, the type of direct CSR business leading by a corporation can affect to the factors affirmatively in corporate reputation and purchase intention. It means that we have to consider the different type of CSR as marketing method seriously when we plan the CSR which university students are involved in due to the relationship between the type of CSR and the factors. Lastly, more positive interest and reputation can be, the higher participant intention for university students is getting. Therefore we have to think deeply when choosing the type of CSR for an individual case.

붉은배새매(Accipiter soloensis)의 번식기 세력권 추정

최창용 ( Chang Yong Choi ),남현영 ( Hyun Young Nam ),이우신 ( Woo Shin Lee ) 한국환경생태학회 2012 한국환경생태학회지 Vol.26 No.2

붉은배새매(Accipiter soloensis)는 국내에서 가장 흔히 번식하는 맹금류에 해당함에도 불구하고, 이 종의 번식기 공간이용에 대한 정보는 부족한 실정이다. 붉은배새매의 번식기 세력권과 행동권을 파악하기 위하여 국내에서 번식하는 6쌍(2005년 4쌍, 2006년 2쌍)의 수컷을 6월부터 7월까지 관찰하였다. 이를 통해 수컷이 3회 이상 반복적으로 이용하는 주요 지점과 명확한 세력권 방어 행동을 보이는 지점을 확인하고, 이를 GIS 프로그램으로 분석하였다. 확인된 25.2±5.3 개 지점을 중심으로 100% 최소다각형법(minimum convex polygon)을 이용하여 분석한 결과, 붉은배새매의 번식기 세력권은 4.62±0.90 ha, 행동권은 22.57±5.12 ha에 해당하는 것으로 나타났다. 본 연구에서 확인된 붉은배새매의 세력권과 행동권은 비록 기존에 보고된 값보다 넓었으나, 전체 번식기에 걸쳐 이용하는 절대적인 공간 규모가 여전히 작다는 점을 보여준다. 이는 붉은배새매가 먹이를 제공할 수 있는 좁은 서식지, 특히 0.6-2.0 ha에 불과한 논에서 발생할 수있는 환경 변화나 자원 고갈에도 상당히 취약할 수 있다는 것을 의미한다. 본 연구는 관찰을 통한 세력권 추정에 해당하지만, 붉은배새매의 보전과 관리, 향후 연구를 위한 기초연구로서의 중요성이 있다고 판단된다. The Chinese Sparrowhawk(Accipiter soloensis) is the most common breeding raptor in Korea, but its spatial use in the breeding season has been poorly documented. Therefore, to estimate the territory and home range sizes of breeding sparrowhawks, six territorial males(four in 2005 and two in 2006) were observed from June to July in Gyeonggi Province, the Republic of Korea. Main perches, which were used repeatedly(more than three times) or where apparent territorial behaviors were observed, were identified and the locations were analyzed by GIS software. According to the 100% Minimum Convex Polygons which were identified from 25.2±5.3 perches, Chinese Sparrowhawks occupied 4.62±0.90 ha for breeding territories and used 22.57±5.12 ha for their home ranges. These estimates showed larger spatially occupied areas than those in one previous report, but this study suggests that Chinese Sparrowhawks intensively use small areas throughout the breeding season. This result also implies that the sparrowhawks have the potential to be significantly affected by any habitat changes and resource exploitation in the small areas(particularly in small rice paddies of 0.6-2.0 ha) which they largely rely on for food. Although this study was based on observations solely for territory size estimations, this study may be worthwhile as preliminary pilot research for Chinese Sparrowhawk conservation, management, and further studies.

키토산과 PVP를 이용한 미소구체의 제조 및 특성 분석

최창용 ( Chang Yong Choi ),홍웅길 ( Woong-gil Hong ),정경원 ( Gyeong-won Jeong ),이현수 ( Hyun-su Lee ),최선주 ( Sun-ju Choi ),김원석 ( Won-seok Kim ),나재운 ( Jae-woon Nah ) 한국키틴키토산학회 2016 한국키틴키토산학회지 Vol.21 No.1

The oral drug delivery system using polymeric micelle was limited due to its instability caused by the gastric acid and various enzymes. To overcome these problems, we prepared chitosan/PVP (Polyvinypyrrolydone) (CPM) microspheres according to the stirring speed by W/O emersion method. The physicochemical characterization of CPMs were analyzed by scanning electron microscope (SEM), dynamic light scattering (DLS), thermo-gravimetric analyzer (TGA) and FT-IR, The SEM results showed that the morphology of CPM was fine spherical shape. Furthermore, SEM and DLS results showed that the size and surface area of CPM were decrease to the increment of stirring speed. The thermal stability of CPM was enhanced than raw chitosan andPVP. These results revealed that CPMs are expected to good candidate in the oral delivery system fields.

태양열 구동 흡수식 냉난방시스템 TRNSYS 모델링

최창용(Choi Chang-Yong),조성환(Cho Sung-Hwan),곽희열(Kwak Hee-Youl),신우철(Shin U-Cheul) 한국태양에너지학회 2006 한국태양에너지학회 학술대회논문집 Vol.- No.-

This paper presents the simulation modeling and its results of the solar thermal driven absorption heating and cooling system for the library reading rooms of a cultural center building located in Gwangju Korea. In this study, single efficiency LiBr-H2O absorption chiller of the rated capacity 10 RT, and 0.7 COP with a evacuated tubular solar collector system is used for the solar cooling facility. A complete system composed of solar collectors, thermal storage tanks, absorption chiller, and auxiliary gas boiler is modelled, and the yearly solar energy supply rate of the system is predicted with the TRNSYS simulation results.