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Enhancing ABS performance through integrated control of regenerative braking and hydraulic braking
No full text학위논문(석사) - 한국과학기술원 : 기계공학과, 2025.2,[v, 55 p. :]자동차 산업의 발전과 차량의 전반적인 성능 향상에 따라, 차량의 안전성 보장을 위한 기술 개발은 필수적 요소로 자리 잡고 있다. 특히 사고 예방에서 중요한 역할을 하는 잠김 방지 제동 시스템(Anti-lock Braking System, ABS)은 차량의 안전 기술의 핵심적인 부분이다. 기존 ABS는 규칙 기반 제어 방식에 의존하고 있으며, 유압 제동 시스템으로 인한 지연과 불확실성의 한계를 지닌다. 이에 비선형 제어 기법을 활용하여 ABS 성능 향상을 보인 연구들이 제안되어 왔으나, 실제 차량에서 얻기 어려운 정보에 의존하는 한계가 존재한다. 또한, 전기차 및 하이브리드 차량에 탑재되는 회생 제동 시스템의 정확한 토크 값을 활용하여 ABS의 성능을 향상시킨 연구들 역시, 실제로 얻기 어려운 정보를 가정하거나 회생 제동의 최대 토크 제한과 유압 제동 토크의 불확실성과 같은 제동 시스템들의 한계를 충분히 반영하지 못했다. 이에 본 학위논문에서는 회생 제동 시스템과 유압 제동 시스템의 상호 보완적인 관계를 활용한 통합 제어 알고리즘을 통해, 기존 ABS 및 관련 연구들의 한계를 극복한 실용적인 ABS를 제안한다. 정확한 회생 제동 토크 정보와 센서 데이터를 기반으로 각 타이어의 종, 횡, 수직 방향의 힘을 추정하고, 이를 바탕으로 한 실시간 노면 마찰계수 추정 및 타이어 힘 기반 슬라이딩 모드 제어를 통해 ABS 성능의 향상을 보인다.한국과학기술원 :기계공학과
전고체전지용 Argyrodite 황화물 고체전해질의 SbO 도핑에 의한 화학적 안정성 향상에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2025.2,[vi, 69 p. :]LiPSCl with an argyrodite structure is a promising sulfide electrolyte for next-generation all-solid-state batteries due to its high ionic conductivity at room temperature and excellent ductility, which makes it easy to process. Nevertheless, its high reactivity leads to interfacial issues with lithium metal and the HS gas generation in the air, requiring further research. Here, to address the above issues, this study proposes SbO doping to LiPSCl for enhancement of stability at the lithium metal interface and in air. SbO doping improves the ionic conductivity of the solid electrolyte and enhances its chemical stability, including at the lithium metal interface. These improvements also contribute to enhanced air stability, positively affecting the overall performance of all-solid-state batteries, including their capacity and cycle life. Based on these findings, this study suggests the potential application of SbO doped LiPSCl for all-solid-state batteries with improved chemical stability.한국과학기술원 :신소재공학과
전기화학적 이산화탄소 환원을 위한 구리 이성분계 합금 촉매에서의 구리와 금속 간의 상호관계 분석
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2025.2,[v, 46 p. :]Electrochemical carbon dioxide reduction (CORR) is an economical reaction that not only reduces carbon dioxide concentrations, but also produces useful compounds such as carbon monoxide, methane, ethylene, and the liquid products ethanol and propanol. Cu catalyst is the only metal capable of producing multi-carbon (C) products. However, tailoring Cu catalyst is crucial due to its low selectivity towards products. Among various approaches, investigating Cu alloy catalysts for a deep understanding of the intrinsic properties of the elements is imperative. While d-block metals are commonly used for copper alloy catalysts, the understanding of p-block metals is still lacking. However, there has been reported that Al was active in the form of metal-organic framework (MOF) or single-atom electron catalysts, although Al film was reported to be unactive to CORR. Accordingly, we investigated the Cu-Al alloy with dilute concentration of Al to create atomic-scale active sites. The results showed that the Faraday efficiency of the Cu-Al 6.5% catalyst for C products in neutral electrolyte achieved 59.32%, exceeding the value of 44.32% for pure Cu. Even when the current density of C products were normalized by electrochemically active surface area (ECSA), the value of Cu-Al was 1.7 times greater at maximum than that of Cu (-1.1 VRHE). The surface valence electron spectra (UPS) and surface photoelectron spectroscopy (XPS) showed that when Cu was doped with Al, the d-band center of Cu shifted towards the fermi level, and the electron density increased around Cu, experimentally confirming that Al doping can lead to an optimized electronic structure for C compounds.한국과학기술원 :신소재공학과
백금-코발트 금속간화합물 산소환원반응용 촉매를 위한 황 도핑 탄소 담지체에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2025.2,[iv, 52 p. :]Enhancing catalysts for the oxygen reduction reaction (ORR) is a critical step toward the widespread adoption of proton exchange membrane fuel cells (PEMFCs), as the ORR at the cathode exhibits slow reaction kinetics. However, existing ORR catalysts have issues that the noble metals for the catalysts are expensive and their durability need to be improved. A common approach to improve catalyst activity is alloying Pt with transition metals (M) to control the oxygen binding energy. Instead of the disordered PtM, high ordered Pt intermetallic compounds show enhanced ORR activity and improved stability. Also, doping carbon supports with heteroatoms such as nitrogen and phosphorous is a feasible strategy to increase the interaction between metal nanoparticles of the catalysts and the supports, which leads to improved performance and stability of the catalysts. In this study, we synthesized intermetallic PtCo nanoparticles supported on sulfur-doped carbon. Catalysts with high metal loading offer significant benefits for practical applications of PEMFCs by enhancing mass transport and reducing voltage losses, particularly at high current densities. In this study, sulfur was doped on commercial carbon support uniformly when synthesizing intermetallic PtCo nanoparticles. Since the sulfur sites anchor metal nanoparticles even during a harsh heat treatment, the sintering issues are suppressed. Also, the sulfur sites improve the electrochemical performance. By applying this strategy, sub-5 nm PtCo intermetallic nanoparticles with a high loading (52.5 wt%) and a Pt-enriched shell (PtCo@Pt/S-C) were successfully synthesized. Their morphology and properties were characterized using various analytical techniques, such as XPS, XRD, TEM, ICP-OES, EDS mapping, and HAADF-STEM In the rotating disk electrode (RDE) measurement, mass activity and specific activity of PtCo@Pt/S-C was enhanced compared to commercial Pt/C and PtCo@Pt/C. Moreover, the catalyst retained its performance even after 50,000 cycles, attributed to the thermodynamically stable intermetallic phase and the protective Pt-enriched shell. This synthesis approach offers a viable route for advancing Pt-based catalysts for practical PEMFC applications.한국과학기술원 :신소재공학과
블록 공중합체 템플릿을 이용한 MoS 나노닷 지지체 제작 및 고정된 단원자 촉매의 수전해 특성에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2025.2,[iii, 44 p. :]Over the past decade, efforts to overcome the limitations of fossil fuel-based energy sources have led to significant advancements in the development of environmentally friendly energy solutions. Among these, hydrogen has garnered attention as a clean energy carrier due to its environmentally friendly nature and high energy density. Electrolysis is a widely adopted method for hydrogen production, with noble metals such as platinum and iridium serving as the primary catalysts. However, the high cost of these noble metals poses a significant barrier to commercialization, driving extensive research into alternative catalytic systems.
Single-atom catalyst (SAC) technology has emerged as a promising approach to maximize catalyst utilization by achieving superior performance with minimal amounts of noble metals. In particular, two-dimensional materials such as molybdenum disulfide (MoS) have drawn significant interest as supports for single-atom catalysts. MoS provides a high surface area due to its two-dimensional structure, enabling the dispersion of single metal atoms and maximizing the number of active sites. Furthermore, it forms strong interactions with single metal atoms, preventing their aggregation and ensuring stability even under harsh reaction conditions. These interactions also allow for the electronic properties of the single-atom catalysts to be finely tuned, optimizing their catalytic performance for specific reactions.
However, a major limitation of MoS lies in its catalytic activity, which is predominantly concentrated at the edge sites, leaving the basal planes relatively inactive. This reduces the overall efficiency of MoS as a catalytic material.
This thesis aims to address these challenges by utilizing the self-assembly properties of block copolymers to fabricate MoS nanodots, thereby maximizing the edge sites. Single metal atoms, such as platinum and iron, are anchored onto these MoS nanodots to leverage both the edge and basal plane catalytic activities. The electrochemical properties of these systems were investigated in the context of hydrogen evolution and oxygen reduction reactions한국과학기술원 :신소재공학과
구리/폴리머 하이브리드 접합 공정을 위한 폴리머의 화학적 기계적 연마 공정 호환성 향상에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2025.2,[v, 49 p. :]The advent of the Fourth Industrial Revolution has led to a significant increase in demand for real-time processing of vast amounts of data, including applications such as AI, big data analytics, and autonomous driving. This has positioned 2.5D/3D semiconductor packaging technologies as crucial solutions. Conventional methodologies entail the utilisation of vertical interconnects, encompassing through-silicon via (TSV), copper bumps, and Sn/Ag solder. This is followed by the introduction of underfill and non-conductive film (NCF) for the purpose of gap filling. However, the use of solder can give rise to reliability issues, such as the formation of inter-metallic compounds and solder bridging, particularly at ultra-fine pitches. In response to these challenges, hybrid bonding technology has emerged as a solution. This approach enables the simultaneous bonding of copper and dielectric layers without the use of solder. In the context of hybrid bonding, it is of paramount importance to achieve an appropriate surface through chemicalmechanical polishing (CMP). However, in Cu/Polymer hybrid bonding, where polymers are employed as dielectric layers, the elevated toughness and viscoelastic characteristics of polymers present challenges to CMP compatibility. This study aims to enhance CMP compatibility by employing Ar plasma treatment on divinylsiloxane-bis-benzocyclobutene (DVS-BCB) surfaces, thereby enabling precise control over mechanical properties and surface morphology. The underlying mechanisms were investigated through an analysis of the mechanical properties and chemical composition of Ar plasma-treated DVS-BCB. Additionally, Cu/Polymer hybrid bonding was demonstrated through thermal-compression bonding. Furthermore, the structural reliability was assessed through cross-sectional analysis post-bonding, confirming the successful outcomes of this research.한국과학기술원 :신소재공학과
가상 전시 공간에서 벽체 곡선 유형이 미적 감정에 미치는 영향
No full text학위논문(석사) - 한국과학기술원 : 메타버스대학원, 2025.2,[iv, 33 p. :]As virtual reality (VR) technology fundamentally transforms the way art is experienced, increasing attention has been drawn to the significant influence of curvilinear structures in exhibition spaces, such as museums, on viewers' emotional responses and aesthetic appreciation. Consequently, understanding the interaction between VR environments and curvilinear spaces is essential for optimizing virtual exhibition design. This study investigates how different types of curves (circle, ellipse, semicircle, semi-ellipse, parabola, hyperbola) in a virtual exhibition space affect visitors’ aesthetic emotions and how these responses differ between expert and general audiences. Because curved spatial design in exhibitions greatly influences visitors’ emotional immersion beyond a mere aesthetic variation, the findings from this research provide essential theoretical and practical insights for the development of future virtual exhibitions and user-centric exhibition design. Six types of curved virtual spaces—each displaying a single artwork—were constructed. Expert and general visitor groups experienced these spaces wearing VR headsets, and their emotional responses were measured and analyzed using the AESTHEMOS and SAM questionnaires. Results indicate that parabolic spaces generally elicited stronger aesthetic emotions of awe, surprise, and interest, while hyperbola and semicircle spaces tended to evoke higher uneasiness. Expert visitors exhibited more complex emotional reactions to deeper spaces (e.g., parabola, hyperbola), whereas general visitors’ emotions were more influenced by instinctive factors such as stability and threat perception. By systematically clarifying the relationship between various curved spatial forms and visitors’ aesthetic emotions—and distinguishing between expert and general audiences—this study fills a significant gap regarding the multi-layered emotional responses elicited by the spatial form in exhibition design research. These findings offer concrete strategies for curators and designers seeking to harness specific emotional responses through curved spatial designs in virtual exhibitions, enabling greater immersion and satisfaction by tailoring exhibit spaces to their audiences' characteristics and expertise levels.한국과학기술원 :메타버스대학원
풀비등 조건 외벽냉각 상관식 개발을 위한 스테인리스 스틸 가열면 표면의 임계열유속에 대한 실험적 연구
No full text학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2025.2,[iv, 44 p. :]In this study, a critical heat flux (CHF) correlation for evaluating external reactor vessel cooling (ERVC) in innovative small modular reactor (i-SMR) was developed using stainless steel heater under pool boiling conditions. The experiments were designed to explore various factors affecting CHF, including material effect, hysteresis effect, and the geometric differences between 2D plates and 3D hemispherical surfaces, considering the actual conditions of ERVC in the i-SMR. The correlation was developed based on experimental data derived from heating conditions and stainless steel surfaces, and it demonstrated predictions within a ±20% error margin for CHF values from previous studies using 3D hemispherical surfaces.한국과학기술원 :원자력및양자공학과
소형 장주기 해양용 용융염고속로의 반사체온도계수 연구
No full text학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2025.2,[vii, 122 :]This thesis introduces research on the reflector temperature coefficient (RTC) of a small long-life maritime molten salt fast reactor (MSFR) employing a moderating reflector. The use of a moderator as a reflector maintains the advantages of the MSFR while enabling miniaturization and long-term operation. However, this results in a positive reflector temperature coefficient (RTC), which limits the miniaturization of the reactor. To reveal the underlying mechanism of the positive RTC induced by the usage of moderating reflector in the MSFR, neutronic analyses were conducted which consist of quantitative evaluation of the local spectrum hardening due to the enhanced up-scattering, as well as neutron flux, neutron current and reaction rates. Furthermore, factors influencing the positive RTC, such as the size of the active core, effect of structure material and various reflector materials were assessed. Additionally, the contributions to the positive RTC from different internal regions of the reflector were evaluated, and the impact of the positive RTC on reactor transient behavior was analyzed by applying a simplified thermohydraulic and heat conduction model combined with a reactor transient model. The neutronics analysis was performed using the continuous energy Monte Carlo code Serpent 2.2.1 with the ENDF/B-Ⅶ.1 nuclear cross-section library.한국과학기술원 :원자력및양자공학과
액체 고순도저농축우라늄(HALEU) 연료를 사용하는 열추진 원자로 핵설계 개념 연구
No full text학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2025.2,[xi, 120 p. :]This master's thesis explores the feasibility of enhancing Nuclear Thermal Rocket (NTR) performance using a liquid uranium fuel. The proposed approach offers key advantages over traditional solid-core designs. Liquid fuel eliminates the temperature constraints of solid fuels, enabling higher operational temperatures and improved specific impulse. It also mitigates fission product poisoning, particularly from Xe-135, by allowing fission products to diffuse out of the reactor core, to maintain stable reactivity, and support long-term operation. Additionally, liquid fuel promotes uniform burnup along the reactor’s axial direction despite variations in the axial power profile. The study begins with a review of nuclear thermal rocket fundamentals and performance parameters. Design goals for the liquid-fuel NTR system are established by limiting reactor mass to under 3,000 kg and achieving exhaust temperatures exceeding 3,000 K, resulting in specific impulse values above 900 seconds. Liquid Uranium Manganese (UMn) fuel with High-Assay Low-Enriched Uranium (HALEU) enrichment of 19.75% is selected to improve neutron economy and ensure proliferation resistance. A novel moderator configuration of graphite, Beryllium Oxide (BeO), and Synthetic Diamond (SD) is adopted to enhance thermalization. To address hydrogen attack on the graphite moderator, a protective graphite coating using ZrC or NbC is applied. The NTR thermal power shape is designed to sustain liquid fuel without preheating. Four NTR models are developed based on annular and cylindrical channel configurations and various synthetic diamond loadings and graphite coatings. Nuclear performance parameters are analyzed to satisfy design constraints, including criticality, neutron spectrum, power distributions, reactivity coefficients, depletion, and shutdown margin. Then, neutronics results inform the subsequent thermal-hydraulic analysis to ensure compliance with temperature, pressure, velocity, and Mach number requirements. Iterative optimization processes are employed to maximize performance in both domains, before the rocket’s performance is evaluated in terms of specific impulse, thrust, and thrust-to-weight ratio. Finally, comparisons between the proposed designs and baseline core are conducted to identify the best design. We conclude that the adoption of liquid uranium fuel significantly enhances NTR performance, offering exceptional specific impulse and extended operational lifetimes.한국과학기술원 :원자력및양자공학과