Influence of Mg Flux on the Photoelectrochemical Properties of p-Type GaN for Hydrogen Production

Bae, Hyojung,Kim, Eunsook,Park, Jun-Beom,Fujii, Katsushi,Lee, Sanghyun,Lee, Hyo-Jong,Ryu, Sang-Wan,Lee, June Key,Ha, Jun-Seok American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10

<P>This study investigates the effects of the doping flux of magnesium (Mg) on the photoelectrochemical (PEC) properties of p-type GaN. The Mg-doped GaN samples were deposited directly on c-plane Al2O3 substrates by metalorganic chemical vapor deposition (MOCVD). The Mg flux during growth was controlled by a mass flow controller at flows of 50, 100, 200, and 500 sccm. Optical property analysis revealed band-gaps for the films between 3.2 eV and 3.4 eV. The PEC properties of the films were examined by potentiostat with a three-electrode configuration. The photocurrent density of the 200 sccm sample was the highest, which would be attributed to vacancies or other intrinsic defects, such as interstitials and antisites, giving n-type conductivity.</P>

Highly Stable Bulk GaN Photoanode Grown by Hydride Vapor-Phase Epitaxy for Photoelectrochemical Water Splitting

Bae, Hyojung,Kim, Haseong,Ju, Jin-Woo,Jeon, Dae-Woo,Ryu, Sang-Wan,Moon, Youngboo,Ha, Jun-Seok The Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.4

<P>Photoelectrochemical (PEC) characteristics of GaN grown by hydride vapor-phase epitaxy (HVPE) with different polarizations were studied and compared. The polar GaN used a (0001)-oriented plane and the semipolar GaN used a (20-21)-oriented plane. The photocurrent density of polar GaN exhibited a two-fold increase over that of semipolar GaN. Bulk GaN sustained water splitting up to 400 h at 0 V versus the reference electrode. To the best of our knowledge, this is the highest value reported for PEC water-splitting stability. This demonstrates the potential of GaN thin films grown by HVPE for application in large-scale solar-fuel conversion.</P>

The Effect of Rapid Temperature Annealing with N₂ and H₂ on Photoelectrochemical Properties of u-TiO₂

Bae, Hyojung,Park, Seung Hwan,Nakamura, Akihiro,Koike, Kayo,Fujii, Katsushi,Park, Hyung-Jo,Lee, Hyo-Jong,Oh, Tae-Sung,Ha, Jun-Seok The Electrochemical Society 2013 Journal of the Electrochemical Society Vol.160 No.11

<P>The effects of annealing with H<SUB>2</SUB> and N<SUB>2</SUB> on the photoelectrochemical (PEC) properties of annealed Nb-doped TiO<SUB>2</SUB> (ann-TNO) film were investigated. The photocurrent density of the ann-TNO film was 2 to 3 orders of magnitude higher than that of u-TiO<SUB>2</SUB> film. To understand this phenomenon, ann-TNO film was investigated by comparing u-TiO<SUB>2</SUB> and Nb-doped TiO<SUB>2</SUB> (TNO) films. An investigation was conducted using Hall effect estimation, photoluminescence (PL) analysis, and band-gap calculation.</P>

Improvement of efficiency in graphene/gallium nitride nanowire on Silicon photoelectrode for overall water splitting

Bae, Hyojung,Rho, Hokyun,Min, Jung-Wook,Lee, Yong-Tak,Lee, Sang Hyun,Fujii, Katsushi,Lee, Hyo-Jong,Ha, Jun-Seok Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.422 No.-

<P><B>Abstract</B></P> <P>Gallium nitride (GaN) nanowires are one of the most promising photoelectrode materials due to their high stability in acidic and basic electrolytes, and tunable band edge potentials. In this study, GaN nanowire arrays (GaN NWs) were prepared by molecular beam epitaxy (MBE); their large surface area enhanced the solar to hydrogen conversion efficiency. More significantly, graphene was grown by chemical vapor deposition (CVD), which enhanced the electron transfer between NWs for water splitting and protected the GaN NW surface. Structural characterizations of the prepared composite were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocurrent density of Gr/GaN NWs exhibited a two-fold increase over pristine GaN NWs and sustained water splitting up to 70min. These improvements may accelerate possible applications for hydrogen generation with high solar to hydrogen conversion efficiency.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pristine GaN NWs were grown on n-type Si (111) substrates using radio-frequency plasma-assisted MBE. </LI> <LI> The graphene grown by CVD was coated on surface of GaN nanowires (Gr/GaN NWs). </LI> <LI> The photoelectrochemical properties of these structures were investigated. </LI> <LI> The saturated photocurrent density increased in Gr/GaN NWs than ref GaN NWs. </LI> <LI> We reported the reason for this difference. </LI> </UL> </P>

Hydrothermal Synthesis of CaMn2O4·xH2O Nanorods as Co-Catalysts on GaN Nanowire Photoanode

Bae Hyojung,Kim Hyunggu,Burungale Vishal,Min Jung‐Wook,Cha An‐na,Rho Hokyun,Ryu Sang‐Wan,Kang Soon Hyung,Ha Jun‐Seok 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.6

Co-catalysts play a crucial role in photoelectrochemical (PEC) water splitting reactions by improving slow kinetics and reducing surface recombination, thereby enhancing PEC performance. However, achieving a well-defined interface between low-dimensional semiconductors and co-catalysts is challenging due to difficulties in depositing a uniform co-catalyst layer and attaining mixed and disordered states. CaMn2O4 xH2O has been extensively studied for the purpose of decreasing the overpotential in the oxygen evolution reaction. In this study, CaMn2O4xH2O was synthesized via a hydrothermal method, and loaded onto a GaN nanowire (NW) photoanode. Optimized CaMn2O4xH2O layers were decorated on GaN NWs to create CaMn2O4@GaN, which delivered a maximum photocurrent of 0.4 mA/cm2 at 0 V vs. the Ag/AgCl reference electrode under an AM 1.5 G solar simulator, 1.6-fold higher than that (0.25 mA/cm2) of bare GaN NWs. Thus, highly efficient and stable PEC water splitting was achieved on the GaN NW photoanode.

세법상 신뢰보호 원칙의 해석 - 대법원 2023. 12. 7. 선고 2020두42668 판결의 평석을 중심으로 -

배효정(Hyojung Bae) 한국법학원 2024 저스티스 Vol.- No.202

‘신뢰보호 원칙’이란 국민에게 국가작용에 대한 예측가능성과 신뢰를 보장하는 헌법상 원칙으로 법치국가의 원리와 법적 안정성에 근거한다. 납세의무자에게 불리한 내용의 세법 개정이 있는 상황에서 판례를 중심으로 헌법상, 행정법상, 세법상 신뢰보호 원칙에 대한 판단이 이루어지는 경우 세부 요건에 관하여 판시한 내용에 일부 차이는 발견되지만, 큰 틀에서 보호가치 있는 납세의무자의 신뢰가 있는지를 판단하고, 구법에 대한 납세의무자의 신뢰와 신법이 추구하는 공익적 목적 사이의 이익형량을 하는 과정을 거친다는 점에서 동일하다. 한편, 대법원은 세법상 신뢰보호 원칙이 문제된 사건에서 경과규정을 두고 있는지 여부와 더불어 종전 규정에서 비과세 내지 조세 감면과 같이 유리한 구법에 따른 납세의무자의 신뢰를 보호한다는 내용이 명시적으로 포함되어 있는지 여부를 살펴, 종전 규정에 그러한 내용이 포함된 경우에만 납세의무자의 구법에 대한 신뢰에 관한 보호가치성을 인정하는 입장이다. 대법원은 평석대상 사건에서 첫째, 종전 규정에 명시적으로 납세의무자에게 유리한 비과세 내지 면세 규정을 두고 있는지를 살폈고, 이러한 명시적 내용이 없다는 이유를 들어 납세의무자의 구법의 비과세 내지 면세에 따른 신뢰가 보호받을 가치가 있는 신뢰가 아니라 단순한 기대권에 불과하다고 판단하였다. 둘째, 납세의무자의 (보호가치 있는) 신뢰의 토대가 되는 구법인, ‘종전’ 규정의 범위에 대해서 ‘개정 대상이 된’ 구 지방세법 ‘본칙’만을 가리킨다고 보고, 이 사건에서 납세의무자가 가지는 신뢰의 토대는 연구개발비에 대한 이월공제를 허용하는 구 조특법 제144조 제1항의 경우 개정 대상도 아니고 본칙도 아니라는 점에서, 구 지방세법 제89조 제1항, 제94조 제1항의 경우 애초에 직접 지방소득세 법인세분에 대한 조세 감면을 명시한 규정이 아니라는 점을 들어 보호가치 없는 신뢰로 보았다. 그러나 헌법, 행정법, 세법상 신뢰보호 원칙의 적용례에 비추어 볼 때 위와 같은 해석은 납세의무자가 가지는 신뢰의 대상을 지나치게 형식적으로 제한하는 해석이고, 이 사건에서는 오히려 ‘종전 규정’에 대한 판단은 법체계상 개정법률인지 아니면 다른 법률인지, 아니면 부과 및 감면 규정 그 자체인지 아니면 세액의 산정방식에 관한 규정 그 자체인지와 같은 형식적 기준이 아니라 신뢰의 대상이 된 납세의무의 범위에 영향을 미치는지 여부라는 실질적 기준을 가지고 판단되어야 한다. 이러한 점에서 검토하면 이 사건에서 납세의무자의 신뢰는 보호가치 있는 신뢰로 볼 수 있다. 다만, 이러한 해석에 의하는 경우라고 하더라도 신법에 대한 공익과 구법에 대한 납세의무자의 신뢰 사이 이익형량을 하는 절차는 필요하고, 이 사건의 경우 여러 사실관계에 비추어 볼 때 조세법률의 특성상 일반적으로 인정되는 공익에 우선하여 납세의무자의 신뢰를 보호할 특별한 이유는 발견하기 어렵다고 판단된다. The “principle of trust protection(Estoppel)” is a fundamental aspect of constitutional law, ensuring citizens’ assertiveness in the predictability and reliability of government actions, thereby upholding the principles of a rule of law and legal stability. When confronted with amendments to tax laws that may adversely affect taxpayers, the judiciary, particularly the Constitutional Court and the Supreme Court, play a pivotal role in interpreting and applying the principle of trust protection as enshrined in constitutional, administrative, and tax laws. While there may be variations or adjustments in the specific criteria emphasized in judiciary precedents, the overarching jurisprudence remains consistent; to ascertain the presence of trustworthiness in the beliefs of taxpayers, determining whether there exists substantial reliance by taxpayers on the previous tax laws and assessing the balance of interests between the trust of taxpayers vested in previous rules and the public welfare pursued by recent one. In cases where the principle of trust protection in tax laws is challenged, the Supreme Court meticulously examines whether statutory provisions explicitly safeguard taxpayers’ trust in advantageous provisions of previous tax regulations. Notably, if such explicit provisions are found within the previous one, the Court acknowledges the value of protecting taxpayers’ reliance on those laws. In the same vein, recent judicial decisions have punctuated the importance of explicit statutory in conferring protection on taxpayers’ trust, highlighting that mere expectations without explicit provisions may not warrant significant protection. However, the Court need to consider the interpretative scope of previous laws and their impact on taxpayers’ trust, moving beyond formalistic criteria as used it above, to evaluate the substantive implications on the range of trust vested in taxpayers. In terms of material criteria favoring taxpayers’ trust, which are related to the tax liability and vested into the previous laws, it should be acknowledged as a worthy of safeguarding, given its implications for taxpayers’ assertion in the legal system. Nevertheless, even following with such recognition, the courts face challenges in prioritizing taxpayer trust over the broader public interest, particularly in the context of tax law where considerations of public welfare often prevail. Therefore, while the principle of trust protection remains integral to legal interpretation and application, determining its applicability requires a careful balance between safeguarding taxpayer trust and upholding the broader objectives of public policy within the framework of tax laws.

복합환승센터 주변 가로의 보행·자전거 중심 정비에 따른 접근성 변화 분석에 관한 연구

배효정(BAE, Hyojung),엄홍민(EOM, Hongmin),서민호(SEO, Minho) 한국도시설계학회 2014 도시설계 : 한국도시설계학회지 Vol.15 No.5

복합환승센터는 교통수단간 환승연계시설과 상업·업무·문화시설을 복합하는 계획개념으로 역세권 정비를 촉진할 수 있는 새로운 대안이다. 그러나 대형 상업시설 입점과 승용차 중심 주변 가로 정비에 따른 상권 빨대효과와 이용자 접근성 저하가 우려되고 있다. 본 연구에서는 복합환승센터 주변의 보행?자전거 중심 가로 정비가 이용자 접근성에 어떤 변화를 가져올 수 있는지 분석하여 정책 개선대안을 모색하고자 하였다. 동대구역을 대상으로 보행·자전거 중심의 네트워크와 가로 정비 대안을 상정하고 통행수단별 이동경로 및 시간, 직접 연결도 등 접근수준, 이용자 분포가 어떻게 변화하는지 GIS를 통해 분석하였다. 분석 결과, 10분 이동권역 내 보행 접근성은 33.6%, 자전거 접근성은 29%, 가로 직결도는 15.7% 증가하였으며, 보행 및 자전거 이용자는 11~91% 증가할 수 있는 것으로 추정되었다. 따라서 복합환승센터 구축 시 주변 가로를 보행·자전거 중심으로 동시에 정비하는 패키지형 정책을 추진하여 복합환승센터의 보행·자전거 접근성 제고와 이용자 증대는 물론, 주변 상권 활성화를 도모하는 노력이 필요할 것으로 판단된다. Transit centers, transport hubs that gather transit facilities and commercial, business, and cultural facilities, are a new TOD development alternative. However, large commercial complexes and car-dominated streets are threatening user accessibility and bringing the straw effect to local commerce. This research aims to propose a street refurbishment plan for the transit center development near East Daegu Station to promote walking and cycling, and to measure its impact on accessibility levels. Pedestrian and bicycle networks are built and a street refurbishment plan is postulated. GIS is used for analyzing networks, travel time, and accessibility levels, such as directiveness and number of users. Under the refurbishment plan, pedestrian accessibility increases by 33.6% for 10-minute travel, bicycle accessibility by 29%, and route directiveness by 15.7%. The number of pedestrians and bicycle users increases by 11-91%. In order to improve accessibility, we argue that it is necessary to establish a transit center development plan, including a street refurbishment plan for walking and cycling.

YAG:Ce<SUP>3+</SUP>@ beta-SiALON 형광체를 이용한 InGaN 광전극의 효과적인 물분해

배효정(Hyojung Bae),이대장(Daejang Lee),차안나(An-Na Cha),주진우(Jin-Woo Ju),문영부(Youngboo Moon),하준석(Jun-Seok Ha) 한국태양광발전학회 2020 Current Photovoltaic Research Vol.8 No.2

GaN based photoelectrode has shown good potential owing to its better chemical stability and tunable bandgap with materials such as InN and AlN. Tunable bandgap allows GaN to make the maximum utilization of solar spectrum, which could improve photoelectrode performance. However, the problems about low photoelectrode performance and photo-corrosion still remain. In this study, we attempt to investigate the photoelectrochemical (PEC) properties of phosphor application to InGaN photoelectrode. Experimental result shows YAG:Ce<SUP>3+</SUP> and beta-SiALON phosphor result in the highest photoelectrode performance of InGaN.

Rapid Fabrication of Cu/Cu2O/CuO Photoelectrodes by Rapid Thermal Annealing Technique for Efficient Water Splitting Application

Minjeong Lee(Minjeong Lee),Hyojung Bae(Hyojung Bae),Hokyun Rho(Hokyun Rho),Vishal Burungale(Vishal Burungale ),Pratik Mane(Pratik Mane ),Chaewon Seong(Chaewon Seong),Jun-Seok Ha(Jun-Seok Ha) 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.4

The Cu/Cu2O/CuO photoelectrode has been successfully fabricated by Rapid Thermal Annealing technique. The structural characterization of fabricated photoelectrode was performed using X-Ray diffraction, while elemental composition of the prepared material has been checked with X-Ray Photoelectron Spectroscopy. The synthesis parameters are optimized on the basis of photoelectrochemical performance. The best photoelectrochemical performance has been observed for the Cu/Cu2O/CuO photoelectrode fabricated at 550 ℃ oxidation temperature and oxidation time of 50 seconds with highest photocurrent density of -3 mA/㎠ at -0.13 V vs. RHE.

Marketing Applications of Big Data and Visual Analytics in Neonatal Intensive Care Units in Korea and Beyond

HyoJung Kim,SooYeop Kim,Hongjae Lee,Michael Cardinale,SeungJoo Choi,Yongtae Shin,Jong-Bae Kim 보안공학연구지원센터 2016 International Journal of Software Engineering and Vol.10 No.10

This plan explores the marketing potential for the use of Big Data along with visual analytics in neonatal intensive care units. The goal of this technology is to provide more efficient and streamlined data collection and display methods for an extremely vulnerable segment of the population. The applicability of this technology is explored through various business models which address the short, medium, and long term marketing goals, such as SWOT, TOWS, and a Strategic Road Map. The results provide strong support for potential market application in Korea as well as abroad.