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Task-based Data Visibility using eBPF in Container-based Cluster Environments
No full textAI산업의 발전에 따라 대규모 데이터셋이 많이 활용되면서, 학습 데이터셋에 포함된 개인정보와 프라이버시 문제에 대한 대중의 불안감이 증가하였다. 이에 따라, 데이터의 사용처를 소명할 수 있는 방법이 필요하다. 이러한 문제에 대해, 데이터 분산 처리 시스템에서 활용되는 원본 데이터를 작업 단위로 묶고, 작업과 관련된 데이터 흐름을 식별하고자 하였다. 이를 위해, 시스템에 eBPF 기반 사이드카를 부착하여 작업 중 발생하는 트래픽 로그를 수집하고, 이를 작업 정보와 결합하여 데이터 이동 경로를 작업 단위로 식별하였다. 단순화된 분산 처리 시스템에서 유효성을 확인한 결과, 작업 단위의 데이터 흐름을 식별할 수 있음을 보였다.FALSEkc
Ultrathin infrared bolometric photodetector based on MoTe2
No full textA fast thermal response time is crucial as it directly influences imaging speed and sensitivity. This is particularly important for military applications, such as night vision systems, where precise temperature measurement and high thermal contrast are required. While quantum-type sensors provide rapid detection, their use of hazardous materials and high costs restrict their industrial use. In contrast, bolometers are more cost-effective but have slower response times and face difficulties maintaining absorption rates as thickness decreases. Our study introduces an innovative approach featuring a simple design and an ultra-thin bolometer with over twice the thinness and an impressive absorption efficiency, achieved using materials with high absorption coefficients like TiN and Fabry-Perot resonance. The proposed structure includes a thermoresistive sensing layer (MoTe2-2H, 11 nm), a leakage current blocking layer (HfO2, 10 nm), and infrared absorption layers (TiN, 10 nm). We measured the temperature coefficient of resistance (TCR) of the suspended MoTe2, with a TCR of -0.1 %K-1, which shows feasibility as a sensor. Additionally, we executed the photoresponse of the suspended MoTe2/HfO2/TiN, which needs to be additional fine tuning of the thickness due to leakage current. Our research aims to broaden the application of high-speed sensors based on 2D materials, addressing critical industry needs.MasterList of Contents
Abstract (English) i
Abstract (Korean) ii
List of Contents iii
List of Tables vi
List of Figures vii
I. Introduction
1.1 Bolometer 1
1.2 2D materials 4
1.2.1 Transition metal dicalcogenides (TMDs) 4
1.3 Titanium nitride (TiN) 6
1.4 Objective 8
II. Sample Preparation and Measurement Method
2.1 Device fabrication 9
2.2 MoTe2 fabrication 10
2.2.1 Raman spectroscopy 11
2.2.2 X-ray photoelectron spectroscopy (XPS) 12
2.3 HfO2/TiN deposition 13
2.3.1 Atomic force microscopy (AFM) 14
2.3.2 Transmission electron microscopy (TEM) 15
2.3.3 Fourier-transform infrared spectroscopy (FT-IR) 17
2.4 Micro-blade patterning 18
2.4.1 2D material transfer setup 19
2.5 Dry transfer 20
2.5.1 Nitrocellulose (NC) strip transfer 21
2.5.2 Critical point dryer (CPD) 22
2.6 Resistance measurement 23
2.6.1 Electrical setup 24
2.6.2 IR setup 25
III. Results and Discussion
3.1 TCR of suspended thin MoTe2 26
3.2 Photoresponse 28
IV. Conclusion
4.1 Summary 29
4.2 Future work 30
References 3
Role of electronic modulation of Ni-Pr bimetallic catalyst for low-temperature CO2 methanation
No full textCO2 methanation has gained increasing attention as a viable strategy for carbon recycling and renewable energy storage. While Ni-based catalysts are widely used due to their cost-effectiveness and intrinsic activity, they often suffer from limited low-temperature performance. This work reports a superior catalytic activity of bimetallic Ni–Pr supported on silica (Ni‒Pr/SiO2) catalysts (XCO2 = 82.6% and SCH4 = 99% at 350 °C), significantly outperforming the monometallic Ni/SiO2. We investigated how the Ni‒Pr interaction modulates the electronic structure of Ni active sites to enhance CO2 activation and methanation efficiency. By systematically comparing various Ni:Pr compositions, we identified an optimal ratio (10:1) that maximizes this interaction. The Ni‒Pr interface sites directly influenced the CO2 adsorption strength and activation, leading to increased conversion and CH4 selectivity at low temperatures. DFT analysis further revealed that the electronic structure of these bimetallic sites lowers the energy barrier for C[dbnd]O bond cleavage, providing a more favorable reaction pathway. This study presents key mechanistic insights into the role of bimetallic electronic interactions in CO2 methanation and presents a rational design strategy for optimizing Ni‒based catalyst systems. © 2025 Elsevier B.V.FALSEsciescopu
Grain-size-dependent Terahertz Conductivity of MAPbI3 Perovskite
No full textIn recent years, hybrid organic–inorganic halide perovskites have attracted extensive attention due to their potential in low-cost fabrication across a broad spectrum of photovoltaic applications, particularly in perovskite-based solar cells. To increase the efficiency of the photovoltaic effect, grain size plays a pivotal role, and it must be reduced for the realization of a large charge diffusion length. In this study, we investigate the grain-size-dependent optical conductivity of CH3NH3PbI3 perovskite (MAPbI3) in the terahertz frequency range. The grain sizes examined are 100, 500, 1,000, and 2,000 nm. There are two distinct phonon features in the optical conductivity spectra, which show no discernible variations with respect to grain size. In contrast, spectral features associated with free carrier dynamics show a noticeable evolution as grain size is varied. We interpret these spectral changes arising from free-carrier dynamics as resulting from grain-size-dependent carrier trapping, which is consistently supported by pump-probe measurements. Our comprehensive experimental investigation indicates that increasing the grain size to approximately 1,000 nm is necessary to achieve a carrier scattering rate comparable to that of ideal MAPbI 3 crystals without grain boundaries.TRUEsciescopuskc
SpinTexture: Exploring Scanning Realism from Concentric to Uni-directional Slip Feedback Using a Spinning Textured Disk
No full textIn providing realistic texture scanning experiences, the recent concentric rotation mechanism contributed to its small form factor, but its realism was not validated compared with the typical uni-directional slip feedback. Therefore, we investigated differences in tactile perception between concentric rotation and uni-directional feedback by implementing SpinTexture, which rotates a textured disk in sync with users' scanning speed. We configured five distances between the centers of the fingerpad and the disk (0.00, 0.25, 0.50, 0.75, and 1.00 cm) and two materials (sandpaper and silk). We first established rotation gain functions to provide perceptually similar sensations to real texture scanning. In 2D (Study 2) and 3D object (Study 3) interaction scenarios, our results showed that scanning realism (Study 2, 3) and enjoyment (Study 3) were insignificantly affected by the different center distances while the sandpaper interaction rated higher realism than silk. Our study bridges the gap between uni-directional and concentric methods. © 2025 Elsevier B.V., All rights reserved.FALSEsciescopu
San Francisco World: Leveraging Structural Regularities of Slope for 3-DoF Visual Compass
No full textWe propose the San Francisco world (SFW) model, a novel structural model inspired by San Francisco's hilly terrain, enabling 3D inter-floor navigation in urban areas rather than being limited to 2D intra-floor navigation of various robotics platforms. Our SFW consists of a single vertical dominant direction (VDD), two horizontal dominant directions (HDDs), and four sloping dominant directions (SDDs) sharing a common inclination angle. Although SFW is a more general model than the Manhattan world (MW), it is a more compact model than the mixture of Manhattan world (MMW). Leveraging the structural regularities of SFW, such as uniform inclination angle and geometric patterns of the four SDDs, we design an efficient and robust DD/vanishing point estimation method by aggregating sloping line normals on the Gaussian sphere. We further utilize the structural patterns of SFW for the 3-DoF visual compass, the rotational motion tracking from a single line and plane, which corresponds to the theoretical minimal sampling for 3-DoF rotation estimation. Our method demonstrates enhanced adaptability in more challenging inter-floor scenes in urban areas and the highest rotational tracking accuracy compared to state-of-the-art methods. We release the first dataset of sequential RGB-D images captured in San Francisco world (SFW) and open source codes at: https://SanFranciscoWorld.github.io/. © 2016 IEEE.FALSEsciescopu
Enhancing Sustainable Resource Circulation through pH Swing-Assisted Carbon Mineralization: Integrating CO₂ storage, Utilization, and valuable Metal Recovery
No full textEx-situ carbon mineralization has emerged as a promising method for permanently sequestering carbon dioxide (CO₂) by transforming it into stable solid carbonates (CaCO₃, MgCO₃) through reactions with alkaline metals (Ca, Mg). Industrial by-products from iron and steelmaking processes have been evaluated as a suitable feedstock due to their high CO₂ storage potential and ability to reduce landfill burdens while recovering valuable resources. However, the unpredictable physicochemical properties of these by-products, low valuable metal recovery efficiency, and limited value of the final products pose commercialization challenges. Low leaching efficiency further reduces carbonation performance, making it difficult to implement. To address these issues, this dissertation proposes a pH swing-assisted carbon mineralization process to recover valuable metals and store CO₂, evaluating its feasibility and offering specific solutions for overcoming commercialization challenges.
In chapter 1, the background of ex-situ carbon mineralization technology and its potential application to iron and steelmaking by-products were introduced. Key challenges such as improving metal recovery, enhancing the value of final products, and boosting leaching efficiency for better carbonation were discussed, with proposed strategies outlined in Chapters 2, 3, and 4.
In chapter 2, pH swing-based carbon mineralization was applied to six domestic by-products from various generation processes, and their physicochemical characteristics were investigated. The results revealed significant variations in leaching, precipitation, and carbonation behaviors depending on the generation process. The simultaneous application of a reductant and organic acid to steel slag demonstrated a synergistic effect, improving both leaching efficiency and metal recovery.
In chapter 3, the formation conditions and mechanisms of CaCO₃ polymorphs, the final product, were explored to enhance its value. Spectroscopy and transmission electron microscopy (TEM) were employed to characterize the crystallographic properties of each polymorph. The findings indicated that Nuclear Magnetic Resonance (NMR) bulk analysis could offer greater efficiency for commercial applications, and two distinct crystal structures within vaterite were thoroughly confirmed.
In chapter 4, CaO/CaCO₃ composites were developed for high-value applications as thermochemical storage sorbents. Doping with transition metal additives provided excellent photo-to-thermal and thermo-to-chemical energy conversion performance, which was further enhanced by co-doping with CaCl₂ to improve reactivity. Overall, this dissertation demonstrated the feasibility of ex-situ carbon mineralization for CO₂ storage and metal recovery, providing a foundation for the conversion of by-products into high-value products. These results could significantly contribute to the commercialization of carbon mineralization and resource circularity.DoctorAbstract i
Contents ii
List of Figures v
List of Tables viii
Chapter 1. Introduction 1
1.1. Global climate change and transition toward a carbon circular economy 2
1.2. Carbon mineralization for carbon capture, utilization, and storage (CCUS) technologies 2
1.2.1. Iron and steelmaking by-products for ex-situ carbon mineralization 6
1.2.2. Challenges for ex-situ carbon mineralization 8
1.3. References 21
Chapter 2. Integrated approach to carbon mineralization and valuable element recovery from iron and steelmaking by-products 28
2.1. Investigation of iron and steelmaking by-products via pH swing-assisted carbon process 29
2.1.1. Motivation 29
2.1.2. Materials and methods 30
2.1.2.1. Materials 30
2.1.2.2. Multi-step pH swing procedure for carbon process 30
2.1.2.3. Characterizations 31
2.1.3. Results and discussion 32
2.1.3.1. Characterization of iron and steelmaking slag 32
2.1.3.2. Leaching behavior of major elements 34
2.1.3.3. pH swing precipitation behavior of major elements 35
2.1.3.4. Carbonation capacity and high purity CaCO3 38
2.1.4. Conclusion 40
2.1.5. References 54
2.2. Enhancement of metal extraction from steelmaking slag via synergistic effect of biogenic volatile
organic acids and reductants 57
2.2.1. Motivation 57
2.2.2. Materials and methods 57
2.2.2.1. Materials 57
2.2.2.2. Leaching experiment for reductant and ligand effect 58
2.2.2.3. Multi-step pH swing procedure for carbonation process 59
2.2.2.4. Characterizations 59
2.2.3. Results and discussion 60
2.2.3.1. Characterization of electric arc furnace slag (EAF) 60
2.2.3.2. Leaching behavior in model chemical: the effect of reductants 61
2.2.3.3. Leaching behavior in EAF: synergistic effect of reductants and ligands 62
2.2.3.4. pH swing precipitation and carbonation behavior in EAF 64
2.2.4. Conclusion 67
2.2.5. References 80
Chapter 3. Polymorph-controlled synthesis and structural validation of calcium carbonate polymorphs for high value-added production 82
3.1. Polymorph-controlled synthesis of calcium carbonate: formation conditions of calcite, aragonite,
vaterite 83
3.1.1. Motivation 83
3.1.2. Mechanism and formation condition for calcium carbonate polymorphs 84
3.1.3. Physicochemical properties and applications of calcite, aragonite, vaterite 87
3.1.4. Conclusion 88
3.1.5. References 92
3.2. Crystallographic investigation of calcium carbonate polymorphs: focus on two crystal structures of
vaterite 95
3.2.1. Motivation 95
3.2.2. Materials and methods 96
3.2.2.1. Materials 96
3.2.2.2. Synthesis for calcium carbonate based on three polymorphs 96
3.2.2.3. Characterizations for synthesized calcium carbonate 97
3.2.2.4. 13C solid-state NMR spectroscopy 97
3.2.3. Results and discussion 98
3.2.3.1. Crystalline structure of polymorph-controlled calcium carbonate 98
3.2.3.2. The two crystalline structures of vaterite 99
3.2.4. Conclusion 103
3.2.5. References 119
Chapter 4. Application of high value-added calcium carbonate: thermochemical energy storage sorbent 122
4.1. Effect of Co and Mn doping on CaO/CaCO3-based sorbent for enhanced photo-to-thermal energy
conversion in concentrated solar power systems 123
4.1.1. Motivation 123
4.1.2. Materials and methods 125
4.1.2.1. Materials 125
4.1.2.2. Synthesis of CaO/CaCO3-based sorbents 125
4.1.2.3. Characterizations 126
4.1.2.4. Optical absorption analysis 126
4.1.2.5. Photo-to-thermal energy conversion efficiency measurement 127
4.1.2.6. Iterative carbonation-calcination reaction stability analysis 128
4.1.3. Results and discussion 129
4.1.3.1. Characterizations of synthesized CaO/CaCO3-based sorbents 129
4.1.3.2. Optical absorbance and photo-to-thermal energy conversion efficiency 129
4.1.3.3. Reaction stability analysis 131
4.1.4. Conclusion 132
4.1.5. References 143
4.2. Effect of CaCl2 addition to CaO/CaCO3-based sorbent on iterative reaction and absorbance for
thermochemical energy storage 148
4.2.1. Motivation 148
4.2.2. Carbonation-calcination reaction mechanism and deactivation phenomena 149
4.2.3. Materials and methods 151
4.2.3.1. Materials 151
4.2.3.2. Synthesis of CaCl2 addition to CaO/CaCO3-based sorbents 151
4.2.4. Results and discussion 152
4.2.4.1. Enhancement of reactivity and optical absorbance CaCl2 addition 152
4.2.5. Conclusion 154
4.2.6. References 161
Chapter 5. Conclusion 165
Curriculum Vitae 16
Multi-Solid-Electrolyte Systems for All-Solid-State Batteries: Current Status and Future Prospects
No full textAll-solid-state batteries (ASSBs) are considered a groundbreaking solution to next-generation energy storage, offering enhanced safety, higher energy density, and longer cycle life than conventional lithium-ion batteries (LIBs). A key component of ASSBs are single-solid-electrolyte systems, which include sulfide-, oxide-, halide-, and hydride-based solid electrolytes. However, these single solid electrolytes often fail to simultaneously meet all of the necessary criteria, such as sufficient ionic conductivity, strong chemical stability, and robust interfaces with both high-voltage cathodes and low-voltage metal anodes. Therefore, multi-solid-electrolyte systems, which integrate two or more solid electrolytes to overcome these limitations, have been gaining increasing importance. When solid electrolytes are strategically combined, multi-solid-electrolyte systems can effectively mitigate interfacial reactions, enhance ionic transport, and improve electrochemical performance. Approaches include coating the cathode with a solid electrolyte, using solid electrolytes as the catholyte and anolyte, and employing mixed and multilayered solid electrolytes. These methods have been proven to reduce side reactions at both electrodes and enable stable cycling at high voltages and with metallic anodes. Furthermore, future perspectives focus on refining interfacial engineering and optimizing design strategies to fully unlock the potential of multi-solid-electrolyte systems. These advancements will provide deeper insights into the fundamental mechanisms governing ion transport and interfacial stability, thereby guiding the further development of next-generation ASSBs. © 2025 American Chemical Society.FALSEsciescopu
Lithium Ion-dependent Energy Conservation System in Rhodobacter nitrogen fixation (Rnf) Complex-possessing Acetogen, Eubacterium callanderi KIST612
No full textAcetogens are anaerobic bacteria that convert one-carbon substrates such as carbon dioxide (CO₂) or carbon monoxide (CO) into acetate through the Wood–Ljungdahl pathway. These organisms rely on chemiosmotic energy conservation rather than substrate-level phosphorylation to produce ATP. The Na⁺- translocating Rhodobacter nitrogen fixation (Rnf) complex plays a central role in this process by coupling electron transfer with the translocation of Na⁺ across the membrane to generate an electrochemical gradient, which drives ATP synthesis via ATP synthase. Although Na⁺-translocating Rnf complexes are typically considered to utilize Na⁺, Li⁺ has been reported as a substitutable ion in certain Na⁺ transport proteins, including the homologous Na⁺-NQR complex. In Acetobacterium woodii DSM 1030T, Li⁺ utilization via the Rnf complex has been experimentally confirmed, however, whether this is strain-specific or conserved remains unclear. In this study, Eubacterium callanderi KIST612 was selected as a model strain because it is a representative acetogen with clearly characterized Na⁺-translocating Rnf complex. Proteomic analysis revealed significant upregulation of the Rnf complex and ATP synthase under autotrophic conditions, indicating potential activation of the chemiosmotic energy conservation system. Based on these data, acetate production was evaluated under H₂/CO₂ conditions supplemented with Na⁺, Li⁺, or K⁺. The results showed that acetate production was enhanced under both Na⁺ and Li⁺ conditions compared to the control, suggesting that Li⁺ could be utilized for ion gradient necessary for ATP synthesis and carbon fixation via the Wood–Ljungdahl pathway. Growth profiling further supported this observation, with robust growth under Na⁺ and Li⁺ conditions and no growth under K⁺ or control conditions, confirming functional ATP generation with Li⁺. Additionally, structural analysis of six representative Na⁺-translocating Rnf complex-possessing acetogens, including A. woodii DSM 1030T and E. callanderi KIST612, revealed conserved Na⁺-binding residues (T111RnfA and V106RnfE) and four cysteine ligands coordinating the [2Fe–2S] cluster essential for ion translocation. These features were preserved not only in the Li⁺-utilizing strains but also in other examined acetogens, suggesting that the ability to utilize Li⁺ could be a conserved characteristic of Na⁺-translocating Rnf complexes. This study expands our understanding of ion selectivity in Na⁺-translocating Rnf complexes and experimentally demonstrates that acetogenic energy conservation systems could utilize Li⁺. These findings provide foundational insights for the future design of bioenergy production systems and emerging ion-based bioelectrochemical energy storage technologies.MasterI. INTRODUCTION 1
1.1. Needs to alternative energy 1
1.2. Acetogen 1
1.3. The Wood-Ljungdahl pathway 2
1.4. Chemiosmotic energy conservation in acetogen 4
1.5. Possibility of Li+-utilization in Na+-translocating Rnf complex 4
1.6. Insights into the Na+-binding and translocation mechanism of Na+-translocating Rnf complex 7
1.7. Model strain for the study: Eubacterium callanderi KIST612 8
1.8. Objective and hypothesis 8
II. MATERIALS AND METHODS 9
2.1. Used strains and cultivation 9
2.2. Bioinformatics 9
2.3. Heterologous expression of Rnf complex 9
2.3.1. Plasmid construction 9
2.3.2. Transformation 10
2.3.3. Protein expression 10
2.3.4. SDS-PAGE and Western blot 10
2.4. Measurement of acetate in resting cells 12
2.4.1. Preparation of resting cells 12
2.4.2. Sampling and determination of acetate 12
2.5. Grow profiling 13
III. RESULTS AND DISCUSSION 14
3.1. Sequence similarity analysis of Rnf complex 14
3.2. Co-expression of Rnf complex 15
3.3. Upregulation of the CEC system under autotrophic conditions 20
3.4. Acetate production in resting cells under autotrophic conditions 20
3.5. Growth on Li+-containing defined medium 28
3.6. Conserved Na+-binding site and Na+-binding switch in Na+-translocating Rnf complex 31
IV. CONCLUSION 35
SUMMARY 37
Acknowledgement 39
References 4