Sparse vector heterogeneous autoregressive model with nonconvex penalties

Shin, Jaeho Sungkyunkwan University 2022 국내석사

High dimensional time series is gaining considerable attention lately and its temporal and spatial dependency could be considered by vector autogressrive(VAR) model. In this research, we propose a nonconvex penalized estimation for estimating sparse vector het-erogeneous Autoregressive(VHAR) model for realized volatility forecasting. Estimation of sparse VHAR model using convex penalties(e.g. adaptive lasso) are proposed by Baek and park(2020). Based on this research, we further propose sparse VHAR model estimation with nonconvex penalties such as SCAD and MCP and compare them with adaptive lasso procedure. Also, some theoretical properties are provided and empirical analysis are also provided. 고차원 시계열은 최근 큰 관심을 받고 있고 시간과 공간 의존성은 백터 자기회귀(VAR) 모형으로 설명될 수 있다. 이 연구는 RV 예측을 위한 성근 VHAR 비볼록 벌점 추정을 제안한다. 볼록 벌점함수를 이용한 성근 VHAR 모형의 추정은 Baek and Park(2020)이 제안했다. 이 연구를 기반으로 SCAD와 MCP와 같은 비볼록 벌점함수를 이용한 VHAR 모형 추정을 제안하고, adaptive lasso 방법과 비교연구를 한다. 또한 이론적 성질과 경험 분석을 제시한다.

Software-defined mobility management and base station control for green cellular networks

Shin, Sunae ProQuest LLC 2016 국내박사

Edge-iodine/sulfonic acid functionalized graphene nanoplatelets as an efficient electrocatalyst for oxygen reduction reaction

Jong Yeol Baek Graduate school of UNIST 2015 국내석사

Development of electrocatalysts, along with cheap and available materials to facilitate oxygen reduction reaction (ORR) in fuel cells to replace Pt-based catalyst is an important issue in the development of fuel cells and other electro-chemical energy devices. The graphene provides good substitutes for electrode catalyst and some research have done to apply graphene nano-material into an cathodic catalyst as an ORR performance owing to its large surface area, the excellent conductivity, freely selectable functional groups such as atoms, molecules involved. It also can be noted that well-defined theoretical design of graphene-based nano-material with specific structure can perform important electro-chemical property in fuel cells ORR. Many studies have made for various hetero-atom based graphene nano-material or graphene-based nano-composites to reach goals which is its extraordinary characteristics for applications (ORR) in the fuel cells. It is reported that the synthesis of edge-iodine/sulfonic acid functionalized graphene nanoplatelets (ISGnP) via two-step sequential ball-milling graphite and their use as electrocatalyst for oxygen reduction reaction (ORR) in fuel cells. Graphite was ball-milled in presence of iodine to produce edge-iodine functionalized GnP (IGnP) in the first step and subsequently IGnP was ball-milled with sulfur trioxide to yield ISGnP. The resultant ISGnP was highly dispersible in various polar solvents, allowing the fabrication of electrodes for ORR using solution processing. The ORR performance of ISGnP in an alkaline medium was superior to commercial Pt/C in terms of electrocatalytic activity and cycle stability.

(The) scope of prolonged responsibility of the architect in incremental housing : based upon two case studies

Marinovic, Goran Ivo Seoul National University 2016 국내박사

Advancing microbial electrosynthesis through gas diffusion cathode and vapor-fed anode-membrane integrated system

Kim, Myeonggyun Sungkyunkwan University 2026 국내석사

미생물전기합성(Microbial electrosynthesis; MES)은 이산화탄소를 메탄 또는 아세테이트와 같은 고부가가치 생산물로 전환하는 지속가능한 바이오 플랫폼으로써 최근 부상하였다. 그러나 유망한 잠재력에도 불구하고, 장기 운전 시 이온 이동으로 인한 pH의 불균형과 생물막으로의 낮은 이산화탄소 전달률은 바이오음극 성능에 부정적인 영향을 미치며 MES의 실제 적용을 제한하고 있다. 이러한 MES의 본질적인 문제를 타파하고자 본 연구에서는 플래티넘으로 촉매화된 티타늄 펠트와 양이온 교환 막을 접합한 Membrane-Electrode Assembly(MEA) 활용과 함께 pH 불균형을 해소하기 위해 양극에 증기를 공급하는 디자인을 설계하였으며, 또한 CO₂의 바이오필름 전달률 향상을 위해 가스확산전극(Gas diffusion electrode; GDE)을 음극으로 활용하여 새로운 디자인의 통합형 MES 반응기를 개발 및 운전하였다. 음극 전위를 –1.0 V (Ag/AgCl)로 인가한 MES에서 GDE의 음극 적용 시, 음극액에 직접 CO₂를 분사하는 기존 방식의 MES보다 전류 밀도는 최대 1.35배, 아세테이트 생산 속도는 1.8배 높은 생산률을 달성하였다. 또한 전체 산물 중 90%가 CO₂에서 아세테이트로 환원되었으며, 이는 음극 바이오필름에서의 전자 이용 효율과 기질 가용성이 향상되었음을 나타낸다. 구조적 특성 분석 결과, 소수성 기체 확산층은 전해질의 침수를 효과적으로 방지하는 반면, 친수성 촉매층은 미생물 부착과 전기화학적 활성을 촉진함과 동시에 바이오필름으로의 CO₂ 전달을 강화하는 것으로 확인되었다. 미생물 군집 분석 결과, Malaciobacter, Trichlorobacter, Oryzomicrobium을 포함한 전기 활성 속이 활성 바이오필름 내에서 우점하였으며, 이는 아세테이트 생산을 위한 활발한 직접 전자 전달과 탄소 흐름이 이루어졌음을 시사한다. 또한, 기체 공급 양극-막 접합체의 활용은 운전 기간 동안 pH 안정성에 기여하였으며, 이는 미생물 활성과 반응기 성능 유지에 필수적이었다. 결론적으로, 본 연구 결과는 MES 시스템에 GDE 기반 환원전극과 기체 공급식 양극-막 접합체 시스템을 통합함으로써 나타나는 결합 효과를 입증하였으며, CO₂ 환원 공정에서 기체-액체 물질 전달, 전자 전달 효율 및 생체촉매 안정성을 향상시키기 위한 전략적 반응기 설계 방안을 제시하였다. Microbial electrosynthesis (MES) has emerged as a sustainable technology for the bioconversion of CO₂ into value-added organic compounds such as acetate. Despite its promise, the practical implementation of MES remains constrained by the limited solubility of CO₂ in aqueous media and pH imbalances arising from ion migration during long-term operation. To address these challenges, this study developed a novel three-chamber MES reactor configuration integrating a gas diffusion electrode (GDE) at the cathode and a vapor-fed anode-membrane assembly. Compared to the non-GDE configuration, the GDE phase achieved significantly higher current densities (up to 1.35-fold increase) and acetate production rates (1.8-fold increase), indicating improved electron utilization and substrate availability at the cathodic biofilm. Structural characterization confirmed that the hydrophobic gas diffusion layer effectively prevented electrolyte flooding, while the hydrophilic catalyst layer facilitated microbial attachment and electrochemical activity, with enhanced CO₂ delivery to biofilm. Microbial community analysis revealed that electroactive genera, including Malaciobacter, Trichlorobacter, and Oryzomicrobium, dominated the active biofilm, suggesting robust interspecies electron transfer and carbon flux toward acetate production. The use of the vapor-fed anode also contributed to pH stability throughout the experimental period, which was critical for sustaining microbial activity and reactor performance. Collectively, the results of this study demonstrated the combined effects of integrating GDE-based cathodes and vapor-fed anodes in MES systems, providing a strategic reactor design framework for improving gas–liquid mass transfer, electron delivery efficiency, and biocatalyst stability in CO₂ reduction processes.

Study on patterning processes and supercapacitors using dually responsive materials and electrodeposition

정경옥 Korea Advanced Institute of Science and Technology 2017 국내박사

Commuting involution graphs of linear groups

한창혁 Korea Advanced Institute of Science and Technology 2017 국내석사

Applications of compressive sensing in wireless sensor networks

위샤오한 Korea University 2015 국내박사

(A) comparative study on newspaper coverage of ‘Pyeongchang olympic games’ between Chinese newspaper and Korean newspaper

He, Qian Sungkyunkwan University 2019 국내석사

When reporting on sports, differences in audience and media perceptions often give viewers a specific perception, and then these perceptions will extend to the impressions and attitudes of specific countries. The Olympic Games is the biggest sports event in the world. It has received the attention of the people of the world. The purpose of this study was to find out the similarities and differences in the news reports of China and Korea. The authors collected data from two representative news media: People's Daily from China and the Chosun Ilbo from South Korea. As mainstream media in China and Korea, People's Daily and the Chosun Ilbot influence worldwide. The two newspapers have the ability to represent the authoritative media in China and the Korea. This article selected the news reports of the People’s Daily and the Chosun Ilbo during the Pyeongchang Olympics as the contents of the analysis. This study applied the following semiotic approaches to analyze the news reports: Categorization Analysis, Over-lexicalization Analysis and Presupposition Analysis. These methods were used to figure out the news patterns, different discourses and in-depth meanings of the two different news coverages on the Pyeongchang Olympics. This study can help to explore the different coverage patterns of news media on Pyeongchang Winter Olympics between China and Korea and to find out the advantages and disadvantages of newspaper reports in both countries and promote the development of sports news.

Advanced fabrication of micro-macro complex part by metal injection molding

Tirta, Andy Yeungnam University 2015 국내박사