• Title/Summary/Keyword: A first principles study

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Band Structure Engineering of Monolayer MoS2 by Surface Ligand Functionalization

  • Lee, Sang Yoon;Ramzan, Sufyan
    • Proceeding of EDISON Challenge
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    • 2015.03a
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    • pp.367-370
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    • 2015
  • Monolayer transition metal dicalcogenide (TMDC) materials are currently attracting extensive attention due to their distinctive electronic, transport, and optical properties. For example, monolayer $MoS_2$ exhibits a direct band gap in the visible frequency range, which makes it an attractive candidate for the photocatalytic water splitting. For the photoelectrochemical water splitting, the appropriate band edge positions that overlap with the water redox potential are necessary. Similarly, appropriate band level alignments will be crucial for the light emitting diode and photovoltaic applications utlizing heterojunctions between two TMDC materials. Carrying out first-principles calculations, we here investigate how the band edges of $MoS_2$ can be adjusted by surface ligand functionalization. This study will provide useful information for the realization of ligand-based band engineering of monolayer $MoS_2$ for various electronic, energy, and bio device applications.

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Electronic Structure and Magnetism of CrP/SrBi Interface: A First Principles Study

  • Bialek, Beata;Lee, Jae-Il
    • Journal of Magnetics
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    • v.12 no.3
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    • pp.93-96
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    • 2007
  • We investigated the electronic structure and magnetic properties of zinc-blende CrP/SrBi interface by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. It is found that the half-metallicity is destroyed when the two half-metals are in contact. Magnetic moments of the atoms forming the supercell differ considerably from the respective values obtained for the bulk structures of the two materials. Cr atoms being and not being in contact with Bi atoms have magnetic moment 3.43 and $2.69{\mu}_B$, respectively. Bi atoms lose their majority electrons which results in their negative polarization. Alkaline Sr atoms are very weakly negatively polarized. The spin distribution within the supercell is such that well separated regions of positive and negative polarization are seen, especially around the layer of P atoms being in contact with the layer of Sr atoms.

A First-principles Study on the Oscillation of Magnetic Moments in the Nonmagnetic 4d and 5d Transition Metal (Rh, Pd, and Pt) Thin Films with an Inserted Ni Monolayer (Ni 단층이 삽입된 비자성 4d 및 5d 전이금속 Rh, Pd 과 Pt 박막에서 자기모멘트 진동에 관한 제1원리 연구)

  • 김인기;김선희;위선미;이재일;이상조
    • Proceedings of the Korean Magnestics Society Conference
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    • 2002.12a
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    • pp.192-193
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    • 2002
  • 비자성 금속에 자성 불순물이 첨가되었을 경우 비자성 전이금속의 전도전자들이 불순물에서 멀어지면서 감쇠 진동하는 형태로 스핀분극 된다는 사실은 매우 잘 알려져 있으며, 그 진동주기는 Fermi 파동벡터 크기(k$_{F}$ )의 역수의 절반이다[1]. 비자성 금속 내의 자성 불순물사이의 상호작용은 전도성 전자의 감쇠 진동하는 스핀 분극에 바탕을 둔 RKKY 교환 상호작용[2]으로 잘 기술된다. (중략)

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Understanding the Mapping Principle of One Syllable One Character as a Predictor of Word Reading Development in Chinese

  • Lin, Dan;Shiu, Ling-Po;Liu, Yingyi
    • Child Studies in Asia-Pacific Contexts
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    • v.6 no.2
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    • pp.73-85
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    • 2016
  • Speech-print mapping awareness is defined as the awareness of the principles underpinning how speech sound is matched to print symbols. Chinese is unique in that it follows the one syllable one character mapping principle. The present study examined the predictive power of speech-print mapping awareness in young children's word reading. Seventy-four Hong Kong children from the first and second kindergarten years were tested with phonological awareness, visual skills, syllable-level mapping awareness, and Chinese reading ability at Time 1. Chinese reading abilities were tested again 1 year later. It was found that syllable-level mapping awareness predicted Chinese word reading abilities 12 months later. Further, it seemed that the link of syllable mapping to Chinese reading is particularly significant for beginning readers. The findings suggest that understanding the language-specific speech-print mapping principle is critical for reading acquisition at the early stage of reading development.

Metamagnetism in $Fe_3$Al Alloy

  • Rhee, Joo-Yull;Lee, Young-Pak
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.60-62
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    • 2003
  • In this study we report the results of ab initio first-principles calculations to investigate the possibility of metamagnetic behavior in Fe$_3$Al alloy. We used the WIEN2k package of full-potential linearized-augmented- plane-wave method within the local-spin-density approximation to the density-functional theory. The exchange-correlation functional is the generalized-gradient approximation of Perdew-Burke-Ernzerhof. The theoretical lattice constant, which is about 0.5% smaller than the experimental one, is obtained by minimizing the total energy. If the volume decreases about 9 % from the equilibrium, the total magnetic moment decreases abruptly from 4.6 $\mu_{B}$/f.u. to 4.0 $\mu_{B}$/f.u. Since this change is considerably large (∼14%), it is possible to measure by a simple high-pressure experiment at about 180 kbar.

Electronic Structures and Physical Properties of the Ordered and Disordered $Ni_2$MnGa Alloy Films

  • Kim, K. W.;Lee, N. N.;Y. Y. Kudryavtsev;Lee, Y. P.
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.104-106
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    • 2003
  • In this study, the electronic structures and physical properties of Ni$_2$MnGa alloy films and their dependence on the order-disorder structural transitions were investigated. The results show that the ordered films behave nearly the same as the bulk $Ni_2$MnGa alloy, including the martensitic transformation at 200 K. Unexpectedly, the disordering in $Ni_2$MnGa alloy films does not lead to any appreciable magnetic ordering down to 4 K. An annealing of the disordered films restores the ordered structure with an almost full recovery of the magnetic and the transport properties of the ordered $Ni_2$MnGa alloy films. A possible explanation of the disappearance of magnetic moment in the disordered film is given by using the ab initio first-principles electronic-structure calculations.

First Principles Study of spin polarization in Fe-doped monolayer C2N-h2D

  • Lee, Sang Yoon;Jeong, Geumbi
    • Proceeding of EDISON Challenge
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    • 2016.03a
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    • pp.336-338
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    • 2016
  • Recent multifunctional two-dimensional material research has triggered huge interests in various modifications for substitution of atoms. Instead of novel metals used as the most popular catalysts, nonprecious transition metals are promising candidates for efficient oxidation-reduction transfers. The recent discovery of $Co@C_2N$ has an alternate possiblity as catalysts for the ORR(Oxygen Reduction Reaction) in DSSc(Dye Sensitized Solar Cell) and OER(Oxygen evolution cobalt oxides). Here we report spin-polarized DFT calculations of the structure doped Iron that is one of ferromagnetism atoms like Co to provide a basic desciption of the ferromagnetism of the elemental metals. The spin-density-funtional results present the most stable state energetically is when having pairwise up/down spin.

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A Study on the Characteristics by Design Component Elements of the Facade in Elementary School Buildings in the 2000's (2000 년대 초등학교 교사 입면의 디자인 구성요소에 의한 특성 연구)

  • Seo, Hee-Sook
    • Korean Institute of Interior Design Journal
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    • v.19 no.5
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    • pp.38-47
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    • 2010
  • The purpose of this study is to examine the characteristics by design component elements of the facade in elementary school buildings after the 7th educational curriculum. This study choose twenty five elementary school as the subjects of the study. And among many elevations of building, an elevation that is alongside of the schoolyard is chosen because this elevation has the highest visual influence on passers-by. To begin with, this elevation is divided into the roof and the surface of a wall, The roof is divided into roof styles, existence of roof and materials. The surface of a wall is divided into design principles(balance, contrast, rhythm), the formal organization(basic elements and form, and transformation of form), the ornamental composition, materials and colors. The results of the research are summarized as follows: First of all, motifs of classical architecture were well expressed in this period and postmodern tendency had been shown until 2005. After Build Transfer Lease(BTL), however, tendency of classical architecture, contrast by the size of the form and base element by point disappeared. Instead, asymmetrical and flat tendency is expressed. Also, emphasized design of the building elevation appear by basic colors of Munsell, not motifs of classical architecture.

Visuality and Hapticity in Acupoints: A Study on Benshu Chapter in Huangdi Neijng Lingshu (경혈의 시각성과 촉각성: 『영추·본수』의 한 연구)

  • Song, Seok Mo
    • Korean Journal of Acupuncture
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    • v.38 no.4
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    • pp.290-307
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    • 2021
  • Objectives : Perceptual experiences have a causal relationship with reality. If there exists something corresponding to acupoints, there should be perceptual experiences for that something. The purpose of this study is to identify and to analyze the perceptual experiences for acupoints within 『LingShu·BenShu』. Methods : First, we briefly propose a perceptual anatomy in order to describe the perceived human body parts, and their perceived directions and places. Second, we analyze the ways of identifying acupoints in the original text of 『LingShu·BenShu』. Results : From 『LingShu·BenShu』, the procedures of identifying total 64 acupoints were recognized. It was clarified that they are by way of visual and haptic explorations in body regions and partial regions. Conclusions : Perceptual explorations for acupoints follow three major principles: of gradual narrowing down, of determination of direction or place, of relative distance. At the final stages, categories of form and location are encountered by observers. The forms have either concavities or convexities. They are determinate indicators of where acupoints are, while the locations are indetermanate. Haptic forms of acupoints are newly discovered from textual analysis with perceptual anatomy. These properties will shed new light both on study of acupoints and on study of meridians.

A Study on the Plausible Application of Coaching in the Field of Family Resource Management (가족자원경영의 관점에서 본 코칭(Coaching)의 적용가능성에 관한 연구)

  • Kim, Hye-Yeon;Kim, Sung-Hee;Rhee, Kyung-Hee;Kwak, In-Sook
    • Journal of Families and Better Life
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    • v.26 no.1
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    • pp.137-147
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    • 2008
  • This study aimed to explore the plausible application of Coaching in the major of family resource management. For this purpose, first, this study reviewed the historical background of the coaching. In the contents, the concepts and principles of coaching were identified. Second, The recent application of coaching to the various areas such as finns, centers, occupation and the academical fields in Korea as well other countries were investigated. Finally, this study connected the nature and emphasis of the family resource management with the philosophy of coaching, which focuses on the internal strength of his/their own change and development in an/a individual/organization. Also, the process of family resource management and coaching models which were regarded as the similar ones in the phases consisted of situation perception, exploring alternatives, planning, implementing and feedback. On the basis of these contexts, this study suggested the plausible classes applied coaching which are able to be introduced in the under-graduated and graduated courses.