• Title/Summary/Keyword: First-principles

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Applying First Principles of Instruction to Flipped Classroom in Engineering Education: Model and Instructional Strategies (공학교육에서 교수 으뜸원리를 적용한 플립러닝 모델 및 교수 전략에 관한 연구)

  • Lim, JiYoung;Kim, Seyoung
    • Journal of Engineering Education Research
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    • v.22 no.1
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    • pp.39-47
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    • 2019
  • This study aims to suggest a model and instructional strategies for a flipped classroom using First Principles of Instruction in engineering education in order to organize teaching and learning activities in a flipped classroom. For this purpose, the authors analyzed the literature on the flipped classroom in engineering education and on applying First Principles of Instruction in designing flipped classroom. Then, a framework of flipped classroom employing First Principles of Instruction and instructional strategies were suggested. Two experts examined the validity of the model and of the instructional strategies, and the final version was completed reflecting on those feedback. Since engineering education aims to teach procedural knowledge as well as conceptual knowledge, different instructional strategies upon two types of knowledge were presented. The implication of our work is to illustrate the model and tactics for flipped classroom based on the Merrill's deeply rooted pedagogical approach. This study may contribute to practice in engineering education.

First-Principles Calculations for Design of Efficient Electrocatalysts (제일원리 계산을 활용한 전기화학 촉매 연구)

  • Kim, Dong Yeon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.6
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    • pp.393-400
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    • 2021
  • As the recent climate problems are getting worse year after year, the demands for clean energy materials have highly increased in modern society. However, the candidate material classes for clean energy expand rapidly and the outcomes are too complex to be interpreted at laboratory scale (e.g., multicomponent materials). In order to overcome these issues, the first-principles calculations are becoming attractive in the field of material science. The calculations can be performed rapidly using virtual environments without physical limitations in a vast candidate pool, and theory can address the origin of activity through the calculations of electronic structure of materials, even if the structure of material is too complex. Therefore, in terms of the latest trends, we report academic progress related to the first-principles calculations for design of efficient electrocatalysts. The basic background for theory and specific research examples are reported together with the perspective on the design of novel materials using first-principles calculations.

The First-principles View of Nanometal Alloy Catalysts

  • Ham, Hyung Chul;Hwang, Gyeong S.
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.129-129
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    • 2013
  • Nanometal alloy catalysts have been found to significantly increase catalytic efficiency, compared to the monometallic counterparts. This enhancement can be attributed to various alloying effects: i) the existence of uniquemixed-metal surface sites [the so called ensemble (geometric) effect]; ii) electronic state changes due to metal-metal interactions [the so called ligand (electronic) effect]; and iii) strain caused by lattice mismatch between the alloy components [the socalled strain effect]. In addition, the presence of low-coordination surface atoms and preferential exposure of specific facets [(111), (100), (110)] in association with the size and shape of nanoparticle catalysts [the so called shape-size-facet effect] can be another important factor for modifying the catalytic activity. However, mechanisms underlying the alloying effect still remain unclear owing to the difficulty of direct characterization. Computational approaches, particularly the prediction using first-principles density functional theory (DFT), can be a powerful and flexible alternative for unraveling the role of alloying effects in catalysis since those can give us quantitative insights into the catalytic systems. In this talk, I will present the underlying principles (such as atomic arrangement, facet, local strain, ligand interaction, and effective atomic coordination number at the surface) that govern catalytic reactions occurring on Pd-based alloys using the first-principles calculations. This work highlights the importance of knowing how to properly tailor the surface reactivity of alloy catalysts for achieving high catalytic performance.

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First Principles Computational Study of Surface Reactions Toward Design Concepts of High Functional Electrocatalysts for Oxygen Reduction Reaction in a Fuel Cell System

  • Hwang, Jeemin;Noh, Seunghyo;Kang, Joonhee;Han, Byungchan
    • Journal of the Korean institute of surface engineering
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    • v.50 no.1
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    • pp.1-9
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    • 2017
  • Design of novel materials in renewable energy systems plays a key role in powering transportation vehicles and portable electronics. This review introduces the research work of first principles-based computational design for the materials over the last decade to accomplish the goal with less financial and temporal cost beyond the conventional approach, especially, focusing on electrocatalyst toward a proton exchange membrane fuel cell (PEMFC). It is proposed that the new method combined with experimental validation, can provide fundamental descriptors and mechanical understanding for optimal efficiency control of a whole system. Advancing these methods can even realize a computational platform of the materials genome, which can substantially reduce the time period from discovery to commercialization into markets of new materials.

Effects of Nitrogen Defect on Magnetism of Cu-doped InN: First-principles Calculations

  • Kang, Byung-Sub;Chae, Kwang-Pyo;Lee, Haeng-Ki
    • Journal of Magnetics
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    • v.18 no.2
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    • pp.81-85
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    • 2013
  • We investigate the electronic and magnetic properties in Cu-doped InN with the N vacancy ($V_N$) from first principles calculations. There is the long-range ferromagnetic order between two Cu atoms, attributed to the hole-mediated double exchange through the strong p-d interaction between the Cu atom and neighboring N atom. The system of $V_N$ defect in Cu-doped InN has the lowest formation energy. Due to the hybridization between the Cu-3d and $V_N$ states, the spin-polarization on the Cu atoms in the InN lattice is reduced by $V_N$ defect. So, it shows a weak ferromagnetic behavior.

First-Principles Study on Thermodynamic Stability of UO2 with He Gas Incorporation via Alpha-Decay

  • Kwon, Choa;Lee, Kwanpyung;Han, Byungchan
    • Korean Chemical Engineering Research
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    • v.57 no.3
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    • pp.368-371
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    • 2019
  • Using first principles calculations we investigated the thermomechanical stability of spent nuclear fuels (SNF), especially how mechanical properties of $UO_2$, such as, bulk, shear and Young's moduli and Poisson's ratio vary through alpha-decay of U into Th with generation of He gas. Our results indicate that substitution of U by Th through alpha decay ($U_{1-x}Th_xO_2$) does not significantly affect the stability of the grain in a fuel matrix. In addition, we studied the transport properties of He in and boundaries of the $U_{1-x}Th_xO_2$ grain. Helium preferentially resides at the grain boundaries through diffusion. Our study can contribute to substantial reduction of environmentally risk and enhancement of our sustainability by safe control of radioactive materials.

A First-principles Study on Magnetism of Al Impurity in bcc Fe

  • Rahman, Gul;Kim, In-Gee
    • Journal of Magnetics
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    • v.16 no.1
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    • pp.1-5
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    • 2011
  • The magnetism and electronic structure of bcc $Al_1Fe_{26}$ was investigated by means of first-principles calculations with and without spin-orbit coupling (SOC). From the calculated total energy, the SOC corrected system is shown to be approximately 5 meV per atom lower than the SOC uncorrected system. The induced spin magnetic moment at the Al site was -0.125 ${\mu}_B$ without SOC and -0.124 ${\mu}_B$ with SOC. The orbital magnetic moments were calculated to be 0.002 ${\mu}_B$ in [$\overline{1}$00] direction for Al. The electronic structures showed the nearest neighbor antiferromagnetic interaction between Fe and Al to be essential for determining the magnetism of the $Al_1Fe_{26}$ system.

A First Principles Calculation of the Coherent Interface Energies between Group IV Transition Metal Nitrides and bcc Iron (IV족 천이금속 질화물과 bcc Fe간 계면 에너지의 제일원리 연구)

  • Chung, Soon-Hyo;Jung, Woo-Sang;Byun, Ji-Young
    • Korean Journal of Materials Research
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    • v.16 no.8
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    • pp.473-478
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    • 2006
  • The coherent interface energies and misfit strain energies of Fe/XN (X=Ti, Zr, Hf) systems were calculated by first principles method. The interface energies in Fe/TiN, Fe/ZrN and Fe/HfN systems were 0.343, 0.114, and 0.030 $J/m^2$, respectively. Influence of bond energy was estimated using the discrete lattice plane/nearest neighbor broken bond(DLP/NNBB) model. It was found that the dependence of interface energy on the type of nitride was closely related to changes of the bond energies between Fe, X and N atoms before and after formation of the Fe/XN interfaces. The misfit strain energies in Fe/TiN, Fe/ZrN, and Fe/HfN systems were 0.239, 1.229, and 0.955 eV per 16 atoms(Fe; 8 atoms and XN; 8 atoms). More misfit strain energy was generated as the difference of lattice parameters between the bulk Fe and the bulk XNs increased.

Study of Pd substitution in orthorhombic-NiSi/Si (010) structure: First principles calculation (Orthorhombic-NiSi/Si (010) 구조의 Pd 치환 연구: 제 1 원리 계산)

  • Kim, Dae-Hee;Kim, Dae-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Semiconductor & Display Technology
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    • v.7 no.4
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    • pp.41-44
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    • 2008
  • NiSi is less stable than the previously-used $CoSi_2$ at high temperature. Some noble metals, such as Pd and Pt, have been added to NiSi to improve its thermal stability. We employed a first principles calculation to understand the Pd segregation at the interface. An orthorhombic structure of NiSi was used to construct an orthorhombic-NiSi/Si (010). Lattice parameters along a- and c-axes in orthorhombic-NiSi were matched with those of Si for epitaxy contact. The optimized $1\times4\times1$ orthorhombic-NiSi (010) and $1\times2\times1$ Si (010) superstructures were put together to construct the orthorhombic-NiSi/Si (010), and the superstructure was relieved in calculation to minimize its total free energy. The optimized interface thickness of the superstructure was $1.59\AA$. Pd atom was substituted in Ni and Si sites located near interface. Both Ni and Si sites located at the interface were favorable for Pd substitution.

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