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원자층 증착된 ZnO를 전구체로 사용한 PIM-1 기질의 ZIF-8 분리막을 통한 프로필렌/프로페인 분리
No full text학위논문(석사) - 한국과학기술원 : 생명화학공학과, 2025.2,[iv, 43 p. :]Propylene is a highly valuable material widely utilized in industry. However, its separation from propane is challenging due to their similar boiling points and molecular sizes, leading to significant energy and cost consumption in conventional separation methods. As an alternative, membrane-based separation has gained considerable attention, with Zeolitic Imidazolate Framework-8 (ZIF-8) being recognized as one of the most promising materials due to its outstanding performance. Nevertheless, traditional ZIF-8 studies have faced limitations, such as the need for large amounts of toxic solvents during synthesis and challenges in large-scale production. To overcome these limitations, this study developed a scalable method for fabricating ZIF-8 membranes on polymeric supports using a vapor-phase process. First, a thin layer of polymer of intrinsic microporosity (PIM-1) was coated onto an alumina substrate via spin coating, followed by the deposition of ZnO using Atomic Layer Deposition (ALD). Subsequently, the ZnO precursor was exposed to vapor-phase 2-methylimidazole, converting it into ZIF-8. As a result, a ZIF-8 membrane with excellent propylene permeability, outstanding propylene/propane selectivity was successfully fabricated.한국과학기술원 :생명화학공학과
라이다 인지 향상을 위한 근적외선 반사 콜로이드 광결정 설계
No full text학위논문(석사) - 한국과학기술원 : 생명화학공학과, 2025.2,[iii, 31 p. :]Conventional dark-tone paints absorb both visible light and near-infrared (NIR) wavelengths, posing a challenge for light detection and ranging (LiDAR) recognition in autonomous driving. To overcome this issue, various chemical and structural coating materials have been explored to selectively reflect NIR. In this study, we newly propose colloidal photonic crystals with a stopband in the NIR range, fabricated through the spontaneous formation of crystalline arrays of silica particles dispersed in a photocurable resin, as a potential solution. The stopband position is finely adjusted by controlling the volume fraction of particles, and the translucent films are rendered black by incorporating carbon black nanoparticles into the interstitial regions. By optimizing the concentration of carbon black, we achieve a balance of low visible lightness and high LiDAR intensity. These black photonic films demonstrate superior LiDAR intensity compared to commercial dark-tone paints and perform on par with perylene black-deposited white coating, one of the most promising LiDAR-assistive materials currently available, under normal reflection conditions. Additionally, the photonic films are highly durable, thermally stable, non-toxic, and environmentally friendly, making them promising candidates for LiDAR-assistive coatings.한국과학기술원 :생명화학공학과
기질 이질성이 Methylosinus trichosporium OB3b 메탄영양성장 및 Polyhydroxybutyrate 합성에 미치는 영향
No full text학위논문(석사) - 한국과학기술원 : 건설및환경공학과, 2025.2,[iv, 63 p. :]Type II methanotrophs are a promising solution to pressing environmental challenges, as they can utilize methane (CH4), a potent greenhouse gas, to synthesize polyhydroxybutyrate (PHB), a biodegradable plastic. However, CH4 released from both natural and anthropogenic sources often coexists with other gas components rather than being present in a high-purity, standalone form. To effectively utilize CH4-based gas mixtures as substrates for methanotrophic PHB synthesis, it is essential to investigate how substrate heterogeneity within such mixtures influences the growth and PHB accumulation of methanotrophs. Accordingly, this thesis examines the effects of substrate heterogeneity in representative CH4-based gas mixtures—biogas [CH4 + carbon dioxide (CO2)] and natural gas [CH4 + ethane (C2H6)]—on Methylosinus trichosporium OB3b, a representative type II methanotroph.
In the first study, to investigate the impacts of biogas compositions, methanotrophs were cultivated under artificial biogas conditions with varying CH4-to-CO2 ratios. The results revealed that as the CO2 concentration in biogas increased, both the maximum specific growth rate and the maximum specific CH4 consumption rate improved. However, PHB accumulation was largely unaffected by the CH4-to-CO2 ratio, with consistent PHB content observed across all conditions. This indicates that M. trichosporium OB3b can drive composition-independent application of biogas in PHB production.
In the second study, the impacts of C2H6, a nongrowth co-metabolic substrate for type II obligate methanotroph, was analyzed. Addition of C2H6 and increasing its concentration under various CH4 and/or O2 availability consistently resulted in reduced cell growth, decreased CH4 consumption, and increased PHB content. To elucidate the mechanisms underlying these effects, three hypotheses were tested. The findings suggested that C2H6-derived acetate inhibits cell growth during nutrient-balanced growth phases but enhances PHB production during nutrient-imbalanced PHB accumulation phases. Furthermore, C2H6 addition during the growth phase was found to suppress the expression of key enzymes essential for CH4 oxidation, likely contributing to the observed reduction in CH4 uptake in C2H6-supplemented conditions.한국과학기술원 :건설및환경공학과
구리 기반 나노다이오드의 표면 플라즈몬에 의한 광전기화학적 특성에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 화학과, 2025.2,[iii, 25 p. :]Hydrogen, a significant energy source, can be generated through water splitting using sunlight. The transformation of solar energy into electrical energy and its application in photoelectrochemical (PEC) water splitting are crucial areas of interest in renewable energy research. Localized surface plasmon resonance (LSPR) occurs when electrons vibrate in a localized area with light. Hot electrons and holes excited by the LSPR effect can be separated through the metal-semiconductor Schottky junction and utilized as an energy source in PEC systems. While several studies have been conducted using gold and silver, which are plasmonic metals, as photocatalysts, the application of copper has been less active due to its susceptibility to oxidation. This thesis analyzes the photoelectrical characteristics of nanodiodes depending on the oxidation state of the copper layer and presents the applicability of copper-based nanodiodes. Furthermore, we confirm enhanced hot carrier-based oxygen evolution reaction (OER) via surface plasmon in the copper layer and show significant advancement.한국과학기술원 :화학과
다성분계 합금 나노입자-페로브스카이트 복합 촉매가 기능화된 금속산화물 가스 센서 제조 방법
No full textProvided are a composite structure, in which metal nanoparticle-perovskite oxide is bound to metal oxide supports (i.e., sensing materials), and a preparation method thereof. The composite structure has improved durability, in which metal nanoparticles uniform in size are evenly distributed on the surface of perovskite oxide. Provided is also a high-performance gas sensor having excellent target gas detection performances by including the composite structure
Quantifying Haptic Affection of Car Door Through Data-Driven Analysis of Force Profile
No full textHaptic affection plays a crucial role in user experience, particularly in the automotive industry where the tactile quality of components can influence customer satisfaction. This study aims to accurately predict the affective property of a car door by only watching the force or torque profile of it when opening. To this end, a deep learning model is designed to capture the underlying relationships between force profiles and user-defined adjective ratings, providing insights into the door-opening experience. The dataset employed in this research includes force profiles and user adjective ratings collected from six distinct car models, reflecting a diverse set of door-opening characteristics and tactile feedback. The model's performance is assessed using Leave-One-Out Cross-Validation, a method that measures its generalization capability on unseen data. The results demonstrate that the proposed model achieves a high level of prediction accuracy, indicating its potential in various applications related to haptic affection and design optimization in the automotive industry.
From Vision to Motion: Translating Large-Scale Knowledge for Data-Scarce IMU Applications
No full textPre-training representations acquired via self-supervised learning could achieve high accuracy on even tasks with small training data. Unlike in vision and natural language processing domains, pre-training for IMU-based applications is challenging, as there are few public datasets with sufficient size and diversity to learn generalizable representations. To overcome this problem, we propose IMG2IMU that adapts pre-trained representation from large-scale images to diverse IMU sensing tasks. We convert the sensor data into visually interpretable spectrograms for the model to utilize the knowledge gained from vision. We further present a sensor-aware pre-training method for images that enables models to acquire particularly impactful knowledge for IMU sensing applications. This involves using contrastive learning on our augmentation set customized for the properties of sensor data. Our evaluation with four different IMU sensing tasks shows that IMG2IMU outperforms the baselines pre-trained on sensor data by an average of 9.6%p F1-score, illustrating that vision knowledge can be usefully incorporated into IMU sensing applications where only limited training data is available.
Essential dimension of reductive groups via generically free representations
No full textWe provide a simple method to compute upper bounds on the essential dimension of split reductive groups with finite or connected center by means of their generically free representations. Combining our upper bound with previously known lower bound, the exact value of the essential dimension is calculated for some types of reductive groups. As an application, we determine the essential dimension of a semisimple group of classical type or E6, and its strict reductive envelope under certain conditions on its center. This extends previous works on simple simply connected groups of type B or D by Brosnan-Reichstein-Vistoli and Chernousov-Merkurjev, strict reductive envelopes of groups of type A by Cernele-Reichstein, and semisimple groups of type B by the authors to any classical type and type E6 in a uniform way.
Multi-repetition-rate mode-locking of a Yb:LuGG waveguide laser
No full textWe report on the development of a continuous-wave modelocked Yb:LuGG waveguide laser fabricated via femtosecond laser inscription. The laser operates near 1036 nm with tunable repetition rates of 192 MHz and 532 MHz, utilizing a single-walled carbon nanotube saturable absorber mirror for mode-locking. By precisely adjusting a piezo-driven air gap between the output coupler and the waveguide facet, and fine-tuning the laser mode area on the absorber using an intracavity lens pair, we achieved stable mode-locked operation at both repetition rates without Q-switching instabilities. The optimized laser delivers maximum average output powers of 113 mW with a pulse duration of 1.18 ps at 192 MHz, and 115 mW with a pulse duration of 968 fs at 532 MHz, demonstrating robust and efficient ultrafast pulse generation in a compact configuration. (c) 2025 Optica Publishing Group. All rights, including for text and data mining are reserved.
A mirrored pair of optimal non-decomposable entanglement witnesses for two qudits does exist
No full textTwo approaches can be utilized to handle the separability problem, finding out whether a given bipartite qudit state is separable or not: a direct procedure on the state space or the effective tool of entanglement witnesses (EWs). This contribution studies the structure of EWs. Exploiting the very concept of mirrored EWs, increasing the detection power, we show, in contrast to the conjecture in a recent paper (Bera et al. in Sci Rep 13:10733, 2023), there exist pairs of optimal EWs, which are both non-decomposible, i.e. can detect bound/PPT-entangled states in an optimal way. Since we show that the structure also extends to higher dimensions, our results reveal a further structure of entanglement witnesses.