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황성진(Hwang, Seongjin),정현상(Jung, Hyunsang),전재승(Jeon, Jaeseung),김형순(Kim, Hyungsun) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06
Dye-sensitized solar cells (DSSC) show great promise as an inexpensive alternative to conventional p-n junction solar cells. Investigations into the various factors influencing the photovoltaic efficiency have recently been intensified. The conventional absorber electrode in DSSC is composed of compacted or sintered TiO₂ nanopowder that carries an anchored organic dye. The absorbance of incident light in the DSC is realized by specifically engineered dye molecules placed on the semiconductor electrode surface (TiO₂). The dye absorbs light at wavelengths up to about 920nm, the energy of the exited state of the molecule should be about 1.35eV above the electronic ground state corresponding to the ideal band gap of a single band gap solar cell. The dye molecules ar adhered onto the nanostrutured TiO₂ electrode by immersing the sintered electrode into a dye solution, typically 3mM in alcohol, for a long enough period to fully impregnate the electrode. However, the concentrations of the dye is slightly changed due to the evaporation of the alcohol. The dye is more expensive than other materials in DSSC and related to the efficiency of DSSC. Therefore, the concentrations of the dye should be carefully measured. In this study, we investigated to the dye loading on fired TiO₂ powder as a function of temperature by the TG-DTA and the dye solution by UV-visible spectroscopy after the impregnation process. The dye loading is related to the porosity of the nanostructured TiO₂ electrode.
Sungsoo Hwang,Taewoo Nam,Hyunsang Ha 한국행정학회 2021 International Review of Public Administration Vol.26 No.3
This study proposes a framework of data-driven administration built on both data and value dimensions and thereby suggests four possible types arising from cases (data-rich and value neutral, data-rich and value-controversial, data-poor and value-neutral, and data-poor and value-controversial). Using an exploratory case study approach, we discuss data-driven administration in the perspective of evidence-based policy-making. Following the tradition of evidence-based policy-making, the advancement of data analytics promotes data-driven administration to solve social problems and innovate government operations. We review relevant cases in Korea and then illustrates how the combinations of two dimensions make practices of data-driven administration successful or not. There is little study pointing out to be mindful of values embedded with social issues in certain domains, even when approached with data-driven administration. The framework of data-driven administration can be used for the better understanding of increasing data analytics practices in the public sector with guiding principles of data readiness and value controversy.
공간정보 융복합 산업 창출을 위한 R&D 혁신 로드맵 수립에 관한 연구
황정래(JungRae Hwang ),송기성(KiSung Song),권회윤(HoeYun Kwon),이수지(SooJi Lee),최현상(HyunSang Choi) 대한공간정보학회 2017 한국지형공간정보학회 학술대회 Vol.2017 No.10
최근 공간정보가 자율주행차, 드론, AR/VR 등 신산업 발전을 지원하는 기반 인프라로서 기술발전에 대한 필요성이 증대되고 있다. 이에, 본 논문은 제4차 산업혁명 등 급변하는 대내외 환경변화를 반영하고 공간정보 활용 수요자 중심의 공간정보 중장기 R&D 발전방향을 제시한다. 이를 위해 국내외 공간정보 관련 기술, 정책, 시장 동향 분석을 통한 공간정보분야 최신 트렌드를 조사·분석하고, 기술수요조사를 통해 공간정보 융복합 산업 창출 지원에 필요한 핵심기술을 도출하며, 이를 기반으로 공간정보 중장기 R&D 혁신 로드맵을 수립한다.
전극 형상에 따른 저비중 경량강판의 저항 점 용접 특성
황인성(Insung Hwang),윤현상(Hyunsang Yoon),김동철(Dongcheol Kim),강문진(Munjin Kang),김재도(Jae Do Kim),김영민(Young-Min Kim) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.2
In this study, resistance spot weldability of lightweight steel with high Al contents was evaluated using various electrode shapes. The six types of electrode shape were prepared with different electrode face diameter and radius. The tensile shear tests were carried out to investigate the failure behaviors. Also, the nugget size and hardness were measured and compared with various electrode shapes. The experimental results show that the acceptable weld current region for low density lightweight steel could be obtained with 10mm electrode face diameter and 76mm electrode face radius.
세라믹 여재를 활용한 상향류식 여과형 비점오염저감시설의 최적 운전 및 역세척 조건
황유훈(Yuhoon Hwang),서영교(Younggyo Seo),김효원(Hyowon Kim),노건완(Kunwan Roh),신현상(Hyunsang Shin),김도군(Dogun Kim) 대한환경공학회 2017 대한환경공학회지 Vol.39 No.8
도로변 등에 여과형 강우유출수 처리시설이 많이 이용되고 있으나, 유지관리의 최소화, 성능의 검증 및 최적 조건의 수립이 선행되어야 한다. 본 연구에서는 강도가 우수하고 성형이 용이한 세라믹 여재를 사용하고, 하단 지지부와 상단의 여과조로 이루어진 상향류식 여과 시스템을 구성하고, SS 제거능과 역세척 조건을 검토하여, 최적 운전 조건을 설정하였다. 여과 선속도 20-40 m/h 조건에서 운전하였을 때, 총 고형물 부하 30 kg/m² 에 이르는 조건에서도 최대 수두 손실 상승이 3 cm 내외이었으며, SS 처리 효율이 96% 이상으로, 안정적인 운전이 가능하였다. 운전 중의 손실수두와 여재층 공극률은 급수 모델에 의해 모사가 가능하였다. 특히, 하단 지지부에서 일정 입도 이상의 SS가 상당량 제거되어, 여과조에 부하를 감소시킬 수 있음을 확인하였다. 최적의 역세척 조건을 설정하기 위하여 공기 및 수세척의 시간과 유량, 그리고 정체수 배출 공정의 유무에 따른 영향을 확인하였으며, 실험한 모든 조건에서 만족할 만한 손실수두의 회복을 달성할 수 있었다. 다만, 역세척 직후 SS의 배출을 최소화하기 위해서는 공기세척과 수세척 공정 사이에 정체수 배출 공정의 도입이 효과적인 것으로 파악되었다. 본 연구에서 설정한 역세척 조건을 적용하였을 때, SS 부하 400-450 kg/m² 의 여재층이 성공적으로 세척될 수 있어, 장기운전이 충분히 가능할 것으로 판단된다. Stormwater filtration is widely used for the urban runoff treatment. However, intensive maintenance and lack of information about the performance have resulted in an increased need of proper evaluation. In this study, the performance of an upflow stormwater runoff filtration system, consisting of a supporting unit and a filtration unit filled with a ceramic media, was investigated. The maximum head loss increase was about 3 cm under the suspended solid (SS) load of 30 kg/m² and the SS removal was more than 96%, when the filtration velocity was 20-40 m/h. The head loss and the porosity of the media can successfully be described by a power model. It was confirmed that the a significant amount of SS can effectively be removed at supporting unit, minimizing SS load to the filter media bed. Several backwashing strategies have been tested to establish the optimum condition. It was found that the stagnant water discharge is important to minimize the SS release immediately after backwashing. Also, the filter bed loaded with 400-450 kg/m² SS can almost completely be washed to reduce the head loss to the that of empty bed. The results in this study indicate that the upflow ceramic media filter is an excellent alternative to stormwater treatment, with high SS removal and long lifespan.
A Materials Approach to Resistive Switching Memory Oxides
Musarrat Hasan,Hyunsang Hwang,Rui Dong,Dongsoo Lee,Dong-jun Seong,Hye jung Choi,Myeongbum Pyun 대한전자공학회 2008 Journal of semiconductor technology and science Vol.8 No.1
Several oxides have recently been reported to have resistance-switching characteristics for nonvolatile memory (NVM) applications. Both binary and ternary oxides demonstrated great potential as resistive-switching memory elements. However, the switching mechanisms have not yet been clearly understood, and the uniformity and reproducibility of devices have not been sufficient for gigabit-NVM applications. The primary requirements for oxides in memory applications are scalability, fast switching speed, good memory retention, a reasonable resistive window, and constant working voltage. In this paper, we discuss several materials that are resistive-switching elements and also focus on their switching mechanisms. We evaluated non-stoichiometric polycrystalline oxides (Nb₂O5, and ZrOx) and subsequently the resistive switching of CuxO and heavily Cu-doped MoOx film for their compatibility with modern transistor-process cycles. Single-crystalline Nb-doped SrTiO₃ (NbSTO) was also investigated, and we found a Pt/single-crystal NbSTO Schottky junction had excellent memory characteristics. Epitaxial NbSTO film was grown on an Si substrate using conducting TiN as a buffer layer to introduce single-crystal NbSTO into the CMOS process and preserve its excellent electrical characteristics.
Woo, Jiyong,Hwang, Hyunsang The Electrochemical Society 2016 ECS journal of solid state science and technology Vol.5 No.3
<P>We show that the motion of Ag atoms in an Ag2S-based conductive bridge RAM system can be utilized for threshold-type selector applications. We found that the instability of an Ag filament could be increased in low current operation, where only few limited Ag ions are allowed to form a filament, and this resulting small filament enables the transition of a non-volatile memory system to a volatile mode. Furthermore, the enhanced activity of Ag atoms at elevated temperatures promotes the self-dissolution process when the bias is removed. As a result, threshold switching behavior with suppressed hysteresis can be achieved. (c) 2016 The Electrochemical Society. All rights reserved.</P>