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Breaking barriers by interfacial charge transfer
No full textThe issue of ohmic contact in WSe2 has been effectively addressed through a significant charge transfer mechanism enabled by the RuCl3/WSe2 heterostructure. © Springer Nature Limited 2024.FALSEsciescopu
Magnon Characteristics in Metallic Bilayers through Unidirectional Magnetoresistance
No full textMagnon, quasi-particles arising from collective mode of spin excitations in magnetic materials, play an important role in understanding many spin-related phenomena, such as ultrafast spin dynamics and current-induced magnetic auto-oscillation. In particular, the concept of magnon current has been proposed as a potential replacement for electronic systems, offering data technology solutions without Joule heating-induced power dissipation. Therefore, the identification of magnon characteristics is highly demanded for realizing future magnonic applications. In this study, we investigate magnon characteristics in metallic bilayers using unidirectional magnetoresistance (UMR), a magnon-related phenomenon observed in ferromagnet/heavy metal bilayer structures. Through experiments focused on crystallographic dependence and non-local UMR measurement configurations, our results demonstrate that magnon can be efficiently generated in a system with I-sing type exchange interaction and the high energy magnons are much more efficient for spin pumping and spin current generation. Our results shed light on the underlying mechanism of energy-dependent magnonic phenomena and suggest a route to enhance the efficiency of magnon generation in the magnonic devices
Mechanothermal-milling-assisted removal of native passivation layer for refreshing lithium metal anodes
No full textSecuring the stable and reliable operation of high-energy lithium (Li) metal batteries (LMBs) is crucial for fundamental studies and practical applications. However, commercial Li metal anodes (LMAs) suffer from unreliable pre-passivation during vendor-specific manufacturing, which deteriorates their surface quality and compromises the reproducibility of novel post-treatments and new electrolytes. To avoid chemical and structural degradation originating from the initial LMA, this study presents a mechanothermal milling (MTM) method using heating blades to smoothly peel off the native passivation layer (NPL) on the LMA surface, thereby exposing near-fresh Li. Compared to as-received LMA, the LMA revitalized by the MTM process (MTM-Li) exhibited faster kinetics and less interfacial resistance, promoting spatially uniform, dendrite-less Li plating and pit-less Li stripping. The MTM-guided surface equalization of the LMA enables an accurate comparison of the electrolyte-derived SEI properties, which is essential for identifying an electrolyte that is genuinely compatible with freshly exposed Li. By combining it with highly stable electrolytes, MTM-Li can regulate the structural evolution of LMAs, effectively securing cycling stability for LMBs, even under stringent conditions. © 2024 Elsevier B.V.FALSEsciescopu
The effect of avian eggshell membrane structure on microbial penetration: A simulation study
No full textAvian eggshells exhibit excellent antimicrobial properties. In this study, we conducted simulation experiments to explore the defense mechanisms of eggshell membranes with regards to their physical features. We developed a mathematical model for the movement of microorganisms and estimated their penetration ratio into eggshell membranes based on several factors, including membrane thickness, microbial size, directional drift, and attachment probability to membrane fibers. These results not only suggest that an eggshell membrane with multiple layers and low porosity indicates high antimicrobial performance, but also imply that the fibrous network structure of the membrane might contribute to effective defense. Our simulation results aligned with experimental findings, specifically in measuring the penetration time of Escherichia coli through the eggshell membrane. We briefly discuss the significance and limitations of this pilot study, as well as the potential for these results, to serve as a foundation for the development of antimicrobial materials. © 2024 Elsevier B.V.FALSEsciescopu
Study of Weight Quantization Associations over a Weight Range for Application in Memristor Devices
Get PDFThe development of hardware-based cognitive computing systems critically hinges upon the integration of memristor devices capable of versatile weight expression across a spectrum of resistance levels while preserving consistent electrical properties. This investigation aims to explore the practical implementation of a digit recognition system utilizing memristor devices with minimized weighting levels. Through the process of weight quantization for digits represented by 25 or 49 input signals, the study endeavors to ascertain the feasibility of digit recognition via neural network computation. The integration of memristor devices into the system architecture is poised to streamline the representation of the resistors required for weight expression, thereby facilitating the realization of neural-network-based cognitive systems. To minimize the information corruption in the system caused by weight quantization, we introduce the concept of “weight range” in this work. The weight range is the range between the maximum and minimum values of the weights in the neural network. We found that this has a direct impact on weight quantization, which reduces the number of digits represented by a weight below a certain level. This was found to help maintain the information integrity of the entire system despite the reduction in weight levels. Moreover, to validate the efficacy of the proposed methodology, quantized weights are systematically applied to an array of double-layer neural networks. This validation process involves the construction of cross-point array circuits with dimensions of 25 × 10 and 10 × 10, followed by a meticulous examination of the resultant changes in the recognition rate of randomly generated numbers through device simulations. Such endeavors contribute to advancing the understanding and practical implementation of hardware-based cognitive computing systems leveraging memristor devices and weight quantization techniques. © 2024 by the authors.TRUEsciescopu
Unlocking solar energy: Photocatalysts design for tuning the CO2 conversion into high-value (C2+) solar fuels
No full textThe carbon dioxide (CO2) conversion to useful chemicals is a promising technique to address global environmental issues and ensure a renewable energy supply. Despite the efforts to enhance product yield with different catalysts, most studies focused on improving efficiency with less emphasis on the selectivity of higher hydrocarbon (C2+) products. Hence, CO, CH4, and HCOOH are the commonly obtained products during CO2 photoreduction according to most literature. C2+ hydrocarbons have a higher market value compared to C1 products. Therefore, research on photocatalytic CO2-to-C2+ conversion has received significant attention in recent years. This review discusses the progress of CO2-to-C2+ photoconversions. First, the insights into CO2 reduction, kinetics, critical challenges, and underlying mechanisms involved in the conversion of CO2-to-C2+ are highlighted. Further, the progress on strategies such as defect engineering, heteroatom doping, cocatalysts deposition, single or dual-atom catalysts, heterostructured combinations, and morphological modulations to improve the selectivity of CO2 reduction towards C2+ formation has been discussed. Factors affecting the performance of CO2-to-C2+ are discussed throughout, focusing on aspects like the interaction of reactants with the catalyst surface, various reaction conditions, intermediate formation, *C1 stabilization, and C–C coupling. Finally, a summary and outlook on recent trends in CO2 utilization are discussed. © 2024 Elsevier LtdFALSEscopu
Conceptual Design of an Automated Wall Painting-masking System
No full text기존 노무 집약적 페인팅 공정은 오늘날 건설 현안의 일환으로 기능인력 고령화 및 부족, 그에 따른 노무 생산성 및 품질의 저하 및 안전사고 증가의 문제점을 가지고 있다. 이 문제를 해결하기 위해 건설 현장 내 로봇 및 자동화 기술 도입이 국내외 건설사를 통해 진행되고 있으며, 특히 본 연구에서는 현장 환경과 사용자 요구사항을 충족하는 로봇 H/W 기술, 기능공 신체 기능 구현을 위한 로봇 간 협업, 주변 환경 인지, 자율주행 로봇 S/W 기술을 포함하는 입체 이동형 협동로봇 기반 페인팅-마스킹 자동화 시스템(Automated Wall Painting-masking System, AWPS) 개발을 목표 로 한다. 상기 시스템의 장점은 각 구성 모듈 간 교체 및 변경이 용이한 구조로 향후 기술 고도화, 적용 분야 다각 화 및 유지보수가 용이하다. 또한 상기 시스템 중 로봇 간 협업 기술은 2 개의 로봇 팔들, 즉 베이스가 고정된 페인 팅용 로봇팔과 마스킹용 로봇 팔이 공간좌표 상 자유도를 가지고 협동 작업을 수행하여 페인팅 공정 상 세부 공정 을 동시에 수행함으로써 작업 시간 단축에 따른 건설 생산성 향상이 기대되며 본 논문에서는 상기 페인팅-마스킹 자동화 시스템의 개념설계를 다룬다
Development of Performance Evaluation Methods for Power Assistive Exo-suit Operated in Human-Contac Environment
No full text근력보조용 의복형 착용로봇은 착용자와 접촉하는 환경에서 운용되기 때문에 위험에 노출될 수밖에 없다. 따라서 이러한 형태의 로봇이 사용자에게 미치는 위험 요소에 대하여 평가하고 저감하기 위한 방법에 대한 연구가 필요하다. 본 논문에서는 의복형 착용로봇이 착용자의 신체에 영향을 미칠 수 있는 요인들을 분석하고 이를 기반으로 성능을 평가하기 위한 방법에 대하여 기술한다. 의복형 착용로봇은 착용자에게 근력을 보조하기 위한 동작 시 인체 체결부를 통해 신체에 국부적인 압력을 줄 수 있으며, 국부적인 압력은 착용자에게 통증을 유발하는 원인으로써 지속적인 노출은 인체상해를 유발시킬 수 있다. 그리고 의복형 착용로봇의 구동력은 착용자의 관절에 보조적인 힘으로 사용됨과 동시에 다른 형태로는 동작을 방해하는 부하로도 작용될 수 있어 착용자의 신체에 부담으로 작용할 수 있다. 또한, 착용자와 착용로봇의 동작이 동기화되지 않을 경우 착용자는 이질감을 가지게 되며, 심각하게는 신체 균형에 영향을 미칠 수 있다. 본 연구에서는 의복형 착용로봇을 사용할 때 인체 착용부의 국부적인 압력과 관절에 작용하는 토크 및 착용자와 로봇의 동기화를 정량적으로 평가하기 위한 방법과 그 시험과정의 개발을 목적으로 한다. 본 연구에서 개발되는 평가방법들을 검증하기 위하여 무릎 근력 보조용 의복형 착용로봇 과 인체 다리 형상을 가지는 테스트 시스템을 구축하였으며, 실험을 통한 검증을 수행하였다
일산화질소의 전기화학적 환원으로부터 암모니아의 생산을 위한 전기촉매 개발
No full textNitric Oxide Reduction Reaction, Ammonia Production, Core-shell Nanostructure, Metal Phosphide Nanocluster, Non-noble Metal CatalystsList of Contents
Abstract i
List of Contents ii
List of Tables v
List of Figures vi
CHAPTER 1. INTRODUCTION 1
1.1. Background 1
1.1.1. Nitric Oxide 1
1.1.2. Ammonia 2
1.2. Conventional Haber-Bosch Process 3
1.3. Electrochemical Ammonia Synthesis from Nitric Oxide 4
1.4. Nitric Oxide Reduction Reaction Mechanisms 5
1.5. Types of Cell Configurations for Nitric Oxide Reduction Reaction 7
1.5.1. H-type Batch Cell 7
1.5.2. Zn-NO Battery 8
1.6. Literature Survey and Current Issues 9
1.7. Objectives of This Research Work 12
CHAPTER 2. EXPERIMENTAL SECTION 14
2.1. Synthesis of Core-Shell Ni@NC Electrocatalyst 14
2.1.1. Materials 14
2.1.2. Synthesis of Covalent Organic Framework (RIO-12) 14
2.1.3. Synthesis of Ni@RIO-12 15
2.1.4. Synthesis of COF-derived Core-Shell Electrocatalysts 16
2.1.5. Synthesis of Nickel Nanoparticle Electrocatalysts 16
2.1.6. Synthesis of NC Electrocatalysts 17
2.2. Synthesis of Atomically Dispersed Cu3P embedded in N-doped carbon nanorods
(Cu3P/NCNR) Catalyst 17
2.2.1. Chemicals and Materials 17
2.2.2. Preparation of Cu3P Catalyst by Electrospinning method 18
2.2.3. Preparation of Control Samples 19
CHAPTER 3. CHARACTERIZATION 20
3.1. Instrumentation 20
3.2. Electrochemical Measurements 20
3.3. Zn-NO Battery. 22
3.4. Fabrication of Electrode 22
3.5. Nafion Membrane Pretreatment 23
3.6. Electrochemical Active Surface Area 23
3.7. Product Quantification 23
3.8. Quantification of NH3 (Indophenol Blue Method) 24
3.8.1. Quantification of NH2OH 25
3.8.2. Quantification of N2H4 (Watt and Chrisp method) 26
3.8.3. 1H NMR Quantification of NH3 27
3.8.4. Quantification of H2 29
3.9. Equations used for the Calculation 30
3.9.1. NH3 yield rate 30
3.9.2. Faradaic Efficiency 30
3.9.3. Turnover Frequency 31
CHAPTER 4. RESULT AND DISCUSSION 32
4.1. Development of Core-shell Nanostructures as High-performance Electrocatalysts for
NH3 Synthesis at Low Overpotentials 32
4.1.1. Physicochemical Characterization 32
4.1.2. Morphology Analysis 33
4.1.3. Surface Composition and Electronic Structure (XPS Analysis) 36
4.1.4. Raman Analysis 38
4.1.5. Electrochemical Characterization 39
4.1.6. Elucidating the Nature of the Active Site 45
4.1.7. Identification of N-source and Optimization of Catalyst Loading 47
4.1.8. Stability Performance 48
4.1.9. Post-NORR Study for Ni@NC-700 to Evaluate the Chemical and Morphological
Features. 50
4.1.10. Summary. 52
4.2. Efficient Electrosynthesis of NH3 from NO Reduction Over Atomically Dispersed
Cu3P Nanocluster in N-doped Carbon Nanorod Catalysts 53
4.2.1. Structural Analysis 53
4.2.2. Morphological Analysis 54
4.2.3. Surface Chemical Composition and Nature of Carbon 59
4.2.4. Elemental Analysis 63
4.2.5. Electrochemical NORR Activity of Cu3P/NCNR catalyst 64
4.2.6. GC Quantification of H2 70
4.2.7. 1H NMR Quantification of H2 70
4.2.8. Investigation of Intrinsic Catalyst Property 73
4.2.9. Elucidating the Nature of the Active Site and Identification of N-Source 74
4.2.10. Effect of Catalyst Loading on GDE 77
4.2.11. Robustness of Cu3P/NCNR-2 and Post-Analysis Study 78
4.2.12. Zn-NO Battery Performance 84
4.2.13. Summary. 87
CHAPTER 5. CONCLUSION 88
References 90MasterdCollectio
Surface Defect Recovery in Perovskite Nanocrystals with Excess Halide for Core-Shell Structure
No full textWe present a method to synthesize stable and uniform high-quality perovskite nanocrystals (PNCs) by using excess halide to recover surface defects in CsPbBr3/ZnS core/shell nanocrystals. Use of N-bromosuccinimide as a halide donor recovered surface halide vacancies of bare CsPbBr3 PNCs during the growth of the ZnS shell, as confirmed by DFT calculations. This approach achieves a high photoluminescence quantum yield of nearly 1, and significantly increases the stability of PNCs under adverse conditions such as high humidity and elevated temperature. CsPbBr3/ZnS PNC light-emitting diodes demonstrated outstanding luminous characteristics, with a remarkable external quantum efficiency of 12.77% and a maximum luminance of 1449 cd m-2 at 517 nm. These characteristics of the PNCs will have a wide variety of applications and will help enable development of highly efficient optoelectronic devices. © 2024 American Chemical Society.FALSEsciescopu