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JEONGWOON HWANG,CHANGWON PARK,최근수,MOON-HYUN CHA,라제브아후자,DONG WOOK KIM,DONG OK KIM,KIL SAGONG,UI GAB JOUNG,HOGYUN JEONG,임지순 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.6
We investigate the hydrogen storage capacity of the light transition metal (TM)-decorated metal organic frameworks (MOFs) by performing ab initio density functional theory calculations. We ¯nd that among all the light TM elements, divalent Ti and Fe are suitable for decorating MOFs to enhance the hydrogen uptake, considering the H2 binding energy on the TM atom and the reversibly usable number of H2 molecules attached to the metal site. In general, the magnetization of metal atoms undergoes a high-spin to low-spin state transition when H2molecules are adsorbed, which helps to stabilize the system energetically. By analyzing the projected density of states on each TM atom, it is shown that the d-level shift induced by the ligand ¯eld of the adsorbed H2 molecules contributes substantially to the H2 binding strength. We also study the stability of selected TM-decorated nanostructures against the attack of foreign molecules by examining the energetics of those contaminating molecules around the metal sites.
물리교육과 신임교수의 교사교육자로서 역할에 관한 셀프스터디
황정운(Jeongwoon Hwang),최재혁(Jaehyeok Choi) 한국물리학회 2022 새물리 Vol.72 No.10
본 연구는 사범대학 물리교육과 신임교수인 물리학자가 교사교육자로서 역할을 구체화하는 과정에 관한 셀프스터디이다. 사범대학의 교사양성 교육과정은 이에 대한 경험이 전무한 ‘나’에게 낯설었고, 처음 하게 되는 물리학 강의는 물리학 연구자로서 내가 가진 경험을 바탕으로 준비하였다. 한편, 임용 직후부터 교사교육자로서 막연히 예비교사들에게 좋은 롤 모델이 되고자 하였다. 본 연구에서 낯섦은 나와 전공과목 강의자로서 나, 교사교육자로서 나의 역할을 분명하게 하는 중요한 출발점이었다. 낯선 환경은 내가 교사교육과정을 비판적으로 보고 이를 개선하는 방향을 모색하게 했으며, 내가 나와 학생들을 깊이있게 이해하고자 노력하게 하는 계기를 주었다. 이를 통해 나의 학생인 예비교사들에 대한 이해가 분명해지면서 스스로 정한 교사교육자로서의 역할도 구체화되었다. This is a self-study on specifying the role of a teacher educator who was a junior faculty in a department of physics education at the college of education. I was unfamiliar with the curriculum for physics preservice teachers owing to having no prior relevant experience. I prepared my first physics lecture at the university based on my experience as a physics researcher. Meanwhile, as a teacher educator, I wanted to be a good role model for the preservice teachers. In this study, the unfamiliarity became an critical starting point for me to clarify my role as a physics major lecturer and as a teacher educator. The unfamiliar environment allowed me to critically evaluate the curriculum of the department of physics education and explore different ways to improve it. Additionally, it has provided me the opportunity to understand myself as well as my students in depth. This made my understanding of students as a preservice teacher clear, thus allowing me to embody the self-appointed role of a teacher educator.
이정운(JeongWoon Lee),황효석(Hyoseok Hwang) 한국방송·미디어공학회 2023 한국방송공학회 학술발표대회 논문집 Vol.2023 No.6
최근 디지털 트윈,자율주행,로봇의 발달로 산업에서 3D Reconstruction의 쓰임이 다양해지고 있다.본 연구에서는 3D Reconstruction의 품질을 높이는 최적화 방법중에 하나인 Bundle Adjustment의 초기값 추정에서 발생하는 오차를 줄이는 Separated Bundle Adjustment를 구현한다.
Cha, Eunho,Patel, Mumukshu D.,Park, Juhong,Hwang, Jeongwoon,Prasad, Vish,Cho, Kyeongjae,Choi, Wonbong Nature Publishing Group UK 2018 Nature nanotechnology Vol.13 No.4
Among the candidates to replace Li-ion batteries, Li–S cells are an attractive option as their energy density is about five times higher (~2,600 Wh kg<SUP>−1</SUP>). The success of Li–S cells depends in large part on the utilization of metallic Li as anode material. Metallic lithium, however, is prone to grow parasitic dendrites and is highly reactive to several electrolytes; moreover, Li–S cells with metallic Li are also susceptible to polysulfides dissolution. Here, we show that ~10-nm-thick two-dimensional (2D) MoS<SUB>2</SUB> can act as a protective layer for Li-metal anodes, greatly improving the performances of Li–S batteries. In particular, we observe stable Li electrodeposition and the suppression of dendrite nucleation sites. The deposition and dissolution process of a symmetric MoS<SUB>2</SUB>-coated Li-metal cell operates at a current density of 10 mA cm<SUP>−2</SUP> with low voltage hysteresis and a threefold improvement in cycle life compared with using bare Li-metal. In a Li–S full-cell configuration, using the MoS<SUB>2</SUB>-coated Li as anode and a 3D carbon nanotube–sulfur cathode, we obtain a specific energy density of ~589 Wh kg<SUP>−1</SUP> and a Coulombic efficiency of ~98% for over 1,200 cycles at 0.5 C. Our approach could lead to the realization of high energy density and safe Li-metal-based batteries.
Band Structure Engineering of Layered WSe<sub>2</sub><i>via</i> One-Step Chemical Functionalization
Park, Jun Hong,Rai, Amritesh,Hwang, Jeongwoon,Zhang, Chenxi,Kwak, Iljo,Wolf, Steven F.,Vishwanath, Suresh,Liu, Xinyu,Dobrowolska, Malgorzata,Furdyna, Jacek,Xing, Huili Grace,Cho, Kyeongjae,Banerjee, S American Chemical Society 2019 ACS NANO Vol.13 No.7
<P>Chemical functionalization is demonstrated to enhance the p-type electrical performance of two-dimensional (2D) layered tungsten diselenide (WSe<SUB>2</SUB>) field-effect transistors (FETs) using a one-step dipping process in an aqueous solution of ammonium sulfide [(NH<SUB>4</SUB>)<SUB>2</SUB>S(aq)]. Molecularly resolved scanning tunneling microscopy and spectroscopy reveal that molecular adsorption on a monolayer WSe<SUB>2</SUB> surface induces a reduction of the electronic band gap from 2.1 to 1.1 eV and a Fermi level shift toward the WSe<SUB>2</SUB> valence band edge (VBE), consistent with an increase in the density of positive charge carriers. The mechanism of electronic transformation of WSe<SUB>2</SUB> by (NH<SUB>4</SUB>)<SUB>2</SUB>S(aq) chemical treatment is elucidated using density functional theory calculations which reveal that molecular “SH” adsorption on the WSe<SUB>2</SUB> surface introduces additional in-gap states near the VBE, thereby, inducing a Fermi level shift toward the VBE along with a reduction in the electronic band gap. As a result of the (NH<SUB>4</SUB>)<SUB>2</SUB>S(aq) chemical treatment, the p-branch ON-currents (<I>I</I><SUB>ON</SUB>) of back-gated few-layer ambipolar WSe<SUB>2</SUB> FETs are enhanced by about 2 orders of magnitude, and a ∼6× increase in the hole field-effect mobility is observed, the latter primarily resulting from the p-doping-induced narrowing of the Schottky barrier width leading to an enhanced hole injection at the WSe<SUB>2</SUB>/contact metal interface. This (NH<SUB>4</SUB>)<SUB>2</SUB>S(aq) chemical functionalization technique can serve as a model method to control the electronic band structure and enhance the performance of devices based on 2D layered transition-metal dichalcogenides.</P> [FIG OMISSION]</BR>