3차원의 회로 모델링을 이용한 청색 GaN/InGaN LED의 전류 확산 효과에 관한 연구

황성민,심종인,Hwang, Sung-Min,Shim, Jong-In 한국광학회 2007 한국광학회지 Vol.18 No.2

본 논문에서는 GaN/InGaN 다중양자우물(MQW)의 청색 발광 다이오드(LED)에서의 3차원적인 전류 및 2차원적인 광 분포를 보여 주기 위해 새롭고 간단한 3차원 회로 모델링과 해석이 처음으로 제안되었으며 이를 실험적으로 검증하였다. LED의 회로 파라미터들은 금속 및 에피 박막의 저항과 다이오드만으로 이루어져 있으며 각각의 파라미터는 전송선 모델(TLM) 및 전압-전류의 특성으로부터 얻을 수 있다. 제안된 방법과 회로 파라미터를 상부로 발광하는(top-surface emitting) LED에 적용하여 금속 및 에피 박막의 각 저항 변화에 따라 활성층을 지나가는 전류 분포의 효과를 정량적으로 해석하였다. 그리고 제작된 청색 LED 소자의 발광 분포는 p-전극 주위에서 어두운 발광 분포를 보이는 해석 결과와 유사한 경향을 보여주었다. A new and simple method of 3-dimensional circuit modeling and analysis is proposed and verified experimentally for the first time by determining 3-dimensional current flow and 2-dimensional light distribution in blue InGaN/GaN multi-quantum well (MQW) light emitting diode (LED) devices. Circuit parameters of the LED consist of the resistance of the metallic film and epitaxial layer, and the intrinsic diode which represents the active region emitting the light. The circuit parameters are extracted from the transmission line model (TLM) and current-voltage relation. We applied the >> proposed method and extracted circuit parameters to obtain the light emission pattern in a top-surface emitting-type LED. The current spreading effect is analyzed theoretically and quantitatively with a variation of the resistance of metallic and epitaxial layers. The emitting-light distribution of the fabricated blue LED showed a good agreement with the analyzed result, which shows the dark emission intensity at the corner of the p-electrode.

SQUID 센서 기반의 극저자장 자기공명 장치를 위한 사전자화코일 전류구동장치 개발

황성민,김기웅,강찬석,이성주,이용호,Hwang, S.M.,Kim, K.,Kang, C.S.,Lee, S.J.,Lee, Y.H. 한국초전도학회 2011 Progress in superconductivity Vol.13 No.2

SQUID sensor-based ultra low-field magnetic resonance apparatus with ${\mu}T$-level measurement field requires a strong prepolarization magnetic field ($B_p$) to magnetize its sample and obtain magnetic resonance signal with a high signal-to-noise ratio. This $B_p$ needs to be ramped down very quickly so that it does not interfere with signal acquisition which must take place before the sample magnetization relaxes off. A MOSFET switch-based $B_p$ coil driver has current ramp-down time ($t_{rd}$) that increases with $B_p$ current, which makes it unsuitable for driving high-field $B_p$ coil made of superconducting material. An energy cycling-type current driver has been developed for such a coil. This driver contains a storage capacitor inside a switch in IGBT-diode bridge configuration, which can manipulate how the capacitor is connected between the $B_p$ coil and its current source. The implemented circuit with 1.2 kV-tolerant devices was capable of driving 32 A current into a thick copper-wire solenoid $B_p$ coil with a 182 mm inner diameter, 0.23 H inductance, and 5.4 mT/A magnetic field-to-current ratio. The measured trd was 7.6 ms with a 160 ${\mu}F$ storage capacitor. trd was dependent only on the inductance of the coil and the capacitance of the driver capacitor. This driver is scalable to significantly higher current of superconducting $B_p$ coils without the $t_{rd}$ becoming unacceptably long with higher $B_p$ current.

단일필라멘트와 다중필라멘트 초전도 코일의 교류 전류에 의한 발열 특성 비교 평가

황성민,김기웅,강찬석,이성주,이용호,Hwang, S.M.,Kim, K.,Kang, C.S.,Lee, S.J.,Lee, Y.H. 한국초전도학회 2011 Progress in superconductivity Vol.13 No.2

Since superconducting wires have no resistance, electromagnets based on the superconducting wires produce no resistive heating with DC current as long as the current does not exceed the critical current of the wire. However, unlike resistive wires, superconducting wires exhibit AC heat loss. Embedding fine superconducting filaments inside copper matrix can reduce this AC loss to an acceptable level and opens the way to AC-capable superconducting coils. Here, we introduce an easy and accurate method to measure AC heat loss from sample superconducting coils by measuring changes in the rate of gas helium outflow from the liquid helium dewar in which the sample coil is placed. This method provides accurate information on total heat loss of a superconducting coil without any size limit, as long as the coil can fit inside the liquid helium dewar. With this method, we have evaluated AC heat loss of two superconducting solenoids, a 180-turn solid NbTi wire with 0.127 mm diameter (NbTi coil) and a 100-turn filamented wire with 1.4 mm diameter where 7 NbTi filaments were embedded in a copper matrix with copper to NbTi ratio of 6.7:1 (NbTi-Cu coil). Both coils were wound on 15 mm-diameter G-10 epoxy tubes. The AC heat losses of the NbTi and NbTi-Cu coils were evaluated as $53{\pm}4.7\;{\mu}W/A^2Hzcm^3$ and $0.67{\pm}0.16\;{\mu}W/A^2Hzcm^3$, respectively.

SAW Self-Aligned Selectively Grown W-GAte) MOSFETs (SAW (Self-Algined Selectively Grown W-Gate) MOSFETs의 제작 및 특성 분석

황성민,노광명,정명준,허민,정하풍,서정원,박찬광,고요환,이대훈,Hwang, Seong-Min,Rho, Kwang-Myoung,Chung, Myung-Jun,Huh, Min,Jeong, Ha-Poong,Suh, Jeong-Won,Park, Chan-Kwang,Koh, Yo-Hwan,Lee, Dai-Hoon 대한전자공학회 1995 전자공학회논문지-A Vol.32 No.6

We proposed SAW (Self-Algined Selectively Grown W-Gate) MOSFET structure, and strudied electrical characteristics of the fabricated SAW MOSFETs. The threshold volgate of 0.21${\mu}$m SAW NMOSFET was 0.18 V and that of 0.24 ${\mu}$m SAW PMOSFET was -0.16 V. The subthreshold slope was 74 mV/decade for NMOSFET and 82 mV/decade for PMOSFET. The maximum transconductance of NMOSFET and PMOSFET, at V$_{GS}$=2.5 V and V$_{DS}$=1.5 V, were260 mS/mm and 122 mS/mm. The measured saturation drain current at V$_{GS}$=V$_{DS}$ =2.5 V was 0.574 mA/${\mu}$m for NMOSFET and -0.228 mA/${\mu}$m for PMOSFET. The gate resistance of SAW MOSFET was about m$\Omega$cm and the n+-p junction capacitance of SAW MOSFET was about 10% lowas than that of the conventional MOSFET's.

Improvement of Transglycosylation Efficiency using a Glycosynthase Mutant derived from Thermoplasma acidophilum ${\alpha}$-Glucosidase

황성민,서성화,박인명,최경화,김도만,차재호,Hwang, Sung-Min,Seo, Seong-Hwa,Park, In-Myoung,Choi, Kyoung-Hwa,Kim, Do-Man,Cha, Jae-Ho The Korean Society for Microbiology and Biotechnol 2012 한국미생물·생명공학회지 Vol.40 No.2

Glycosynthase는 친핵성 아미노산을 비친핵성 아미노산으로 치환하여 당전이 산물의 가수분해를 막아서 당전이 효율을 증가시킬 수 있다. 이전 연구에서 본 실험실은 열에 안정하고 산에 강한 Thermoplasma acidophilum 유래의 ${alpha}$-glucosidase (AglA)가 당전이 활성이 있음을 입증하였으나 시간이 지남에 따라 당전이 산물이 가수분해 되었다. 이러한 AglA의 당전이 효율을 개선하기 위하여 친핵성 아미노산인 아스파라긴산을 글리신으로 치환하였다. 이 치환된 glycosynthase는 니켈 친화력 크로마토그래피를 통하여 정제되었으며, 정제된 돌연변이 단백질의 배당체를 합성하는 능력이 말토오스를 공여체로 그리고 p-nitrophenyl-${alpha}$-D-glucopyranoside($pNP{\alpha}G$)를 수용체로, 그리고 $pNP{\alpha}G$가 당공여체 및 수용체로 이용될 수 있는지 검사하였다. Glycosynthase를 이용한 당전이 산물의 수율은 약 42.5%를 보였으며 시간이 지남에 따라서 가수분해되지 않았다. 박막 크로마토그래피법을 이용한 반응산물의 분석은 수용체의 높은 농도에서 기존의 효소보다 많은 양의 배당체를 합성할 수 있음을 보여주었고, 특히 중성보다 낮은 pH 영역에서 가장 높은 활성을 보여줌을 확인하였다. 이러한 결과는 glycosynthase가 산업적으로 배당체를 합성하는데 유용성이 크다는 것을 나타낸다. Glycosynthase is an active site nucleophile mutant enzyme, prepared from glycosidase, which is capable of synthesizing oligosaccharide derivatives without the hydrolysis of the product. Thermoacidophilic ${\alpha}$-glucosidase of Thermoplasma acidophilum (AglA) exhibits a transglycosylating activity yielding various glycosides. AglA was converted to glycosynthase by the substitution of the catalytic nucleophile Asp-408 residue into non-nucleophile glycine in order to increase its ability to synthesize various glycosides by transglycosylation. The glycosynthase mutant was purified by Ni-NTA chromatography and its glycoside-synthesizing activity was measured by using an external nucleophile, sodium formate buffer, providing maltose as a donor and p-nitrophenyl-${\alpha}$-D-glucopyranoside ($pNP{\alpha}G$) as an acceptor, respectively. In addition, $pNP{\alpha}G$ was examined for its feasibility to act as both a donor and an acceptor, and products were compared with those of the wildtype enzyme. The mutant enzyme was found to catalyze the formation of a specific product from $pNP{\alpha}G$ with a yield of 42.5% without further hydrolysis, while the wild-type enzyme produced two $pNP{\alpha}G$ products at low yields. The results demonstrate the possibility of satisfactory yields for the reactions in the presence of small amounts of acceptor, and demonstrate that the high activity of the mutant, at pHs below neutrality, was applicable in the transfer of glucose from the natural donor.

견섬유의 염색에 있어서 첨가용제의 영향(Ⅰ)

황성민(Sung Min Hwang),윤남식(Nam Sik Yoon),임용진(Yong Jin Lim),이동수(Dong Soo Lee),이인전(In Jeon Rhee) 한국염색가공학회 1989 韓國染色加工學會誌 Vol.1 No.1

Thermoplasma acidophilum 유래 α-glucosidase로 부터 생산된 glycosynthase 돌연변이 단백질의 개선된 당전이 효율

황성민 ( Sung Min Hwang ),서성화 ( Seong Hwa Seo ),박인명 ( In Myoung Park ),최경화 ( Kyoung Hwa Choi ),김도만 ( Do Man Kim ),차재호 ( Jae Ho Cha ) 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 2012 한국미생물·생명공학회지 Vol.40 No.2

Glycosynthase는 친핵성 아미노산을 비친핵성 아미노산으로 치환하여 당전이 산물의 가수분해를 막아서 당전이 효율을 증가시킬 수 있다. 이전 연구에서 본 실험실은 열에 안정하고 산에 강한 Thermoplasma acidophilum 유래의 α-glucosidase (AglA)가 당전이 활성이 있음을 입증하였으나 시간이 지남에 따라 당전이 산물이 가수분해 되었다. 이러한 AglA의 당전이 효율을 개선하기 위하여 친핵성 아미노산인 아스파라긴산을 글리신으로 치환하였다. 이 치환된glycosynthase는 니켈 친화력 크로마토그래피를 통하여 정제되었으며, 정제된 돌연변이 단백질의 배당체를 합성하는 능력이 말토오스를 공여체로 그리고 p-nitrophenyl-α-D-glucopyranoside(pNPαG)를 수용체로, 그리고 pNPαG가 당공여체 및 수용체로 이용될 수 있는지 검사하였다. Glycosynthase를 이용한 당전이 산물의 수율은 약 42.5%를 보였으며 시간이 지남에 따라서 가수분해되지 않았다. 박막 크로마토그래피법을 이용한 반응산물의 분석은 수용체의 높은 농도에서 기존의 효소보다 많은 양의 배당체를 합성할 수 있음을 보여주었고, 특히 중성보다 낮은 pH 영역에서 가장 높은 활성을 보여줌을 확인하였다. 이러한 결과는 glycosynthase가 산업적으로 배당체를 합성하는데 유용성이 크다는 것을 나타낸다. Glycosynthase is an active site nucleophile mutant enzyme, prepared from glycosidase, which is capable of synthesizing oligosaccharide derivatives without the hydrolysis of the product. Thermoacidophilic α-glucosidase of Thermoplasma acidophilum (AglA) exhibits a transglycosylating activity yielding various glycosides. AglA was converted to glycosynthase by the substitution of the catalytic nucleophile Asp-408 residue into non-nucleophile glycine in order to increase its ability to synthesize various glycosides by transglycosylation. The glycosynthase mutant was purified by Ni-NTA chromatography and its glycoside-synthesizing activity was measured by using an external nucleophile, sodium formate buffer, providing maltose as a donor and pnitrophenyl- α-D-glucopyranoside (pNPαG) as an acceptor, respectively. In addition, pNPαG was examined for its feasibility to act as both a donor and an acceptor, and products were compared with those of the wildtype enzyme. The mutant enzyme was found to catalyze the formation of a specific product from pNPαG with a yield of 42.5% without further hydrolysis, while the wild-type enzyme produced two pNPαG products at low yields. The results demonstrate the possibility of satisfactory yields for the reactions in the presence of small amounts of acceptor, and demonstrate that the high activity of the mutant, at pHs below neutrality, was applicable in the transfer of glucose from the natural donor.

국제회의 용역 입찰에 있어 선정기준에 대한 인식 비교: 주최자와 국제회의 기획사(PCO) 중심으로

황성민 ( Sung Min Hwang ),김철원 ( Chul Won Kim ) (사)한국마이스관광학회(구 한국컨벤션학회) 2011 MICE관광연구 Vol.11 No.3

The main purpose of this study was to compare the perception or recognition of the bidding of labor services in international conferences. We create a survey upon our research of current bidding practices of international conferences and interviewed professional convention hosts and convention project planners. Upon reviewing the results of the survey, it was seen that especially within the labor force, project proposals, and pricing categories, there was a great difference in the perception between PCOs and project planners. After reviewing the results, the reseachers proposed a new selection criteria by rearranging the contents of each category and changing the project evaluation scoring methods.

SA 해쉬 알고리즘을 이용한 중복파일 업로드 방지 시스템 설계

황성민(Sung-Min Hwang),김석규(Seog-Gyu Kim) 한국컴퓨터정보학회 2014 韓國컴퓨터情報學會論文誌 Vol.19 No.10

본 논문에서는 서버로의 중복파일을 업로드 방지를 위하여 SA 해쉬 알고리즘을 제안하고 이를 이용하여 서버시스템을 설계한다. SA 해쉬 값으로 동일한 파일이 서버에 있는 지 검사하고 존재한다면 클라이언트에게 업로드를 받지 않고 기존 파일을 이용하는 방법으로 효율적인 시스템 설계를 할 수 있게 되는 것이다. 중복파일 검사를 할 수 있는 SA 해쉬 알고리즘은 출력하고자 하는 비트 수 n을 한 블록으로 하고 원본 파일을 블록 단위로 나누게 된다. 원본 파일의 mod i 비트와 출력 해쉬 값의 i 비트를 XOR 연산을 하게 된다. 이렇게 반복적으로 원본 파일 길이까지 XOR연산을 하는 것이 SA 해쉬 알고리즘의 메인 루틴이다. 기존 해쉬 함수인 MD5, SHA-1, SHA-2보다 중복파일 업로드 방지 서버 시스템에 적합한 해쉬 함수인 SA 해쉬 알고리즘을 통해 시간 및 서버 스토리지 용량의 절약을 도모할 수 있다. In this paper, we propose SA hash algorithm to avoid upload identical files and design server system using proposed SA hash algorithm. Client to want to upload file examines the value of SA hash and if the same file is found in server system client use the existing file without upload. SA hash algorithm which is able to examine the identical-file divides original file into blocks of n bits. Original file’s mod i bit and output hash value’s i bit is calculated with XOR operation. It is SA hash algorithm’s main routine to repeat the calculation with XOR until the end of original file. Using SA hash algorithm which is more efficient than MD5, SHA-1 and SHA-2, we can design server system to avoid uploading identical file and save storage capacity and upload-time of server system.

하드웨어 배치 정규화 기능의 플래시 메모리 기반 이진 신경망

황성민(Sungmin Hwang),이왕주(Wangjoo Lee),박정우(Jeong Woo Park),서동우(Dongwoo Suh) 대한전자공학회 2022 대한전자공학회 학술대회 Vol.2022 No.11