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Electrochemically Fabricated Alloys and Semiconductors Containing Indium
Chung, Yonghwa,Lee, Chi-Woo The Korean Electrochemical Society 2012 Journal of electrochemical science and technology Vol.3 No.3
Although indium (In) is not an abundant element, the use of indium is expected to grow, especially as applied to copper-indium-(gallium)-selenide (CI(G)S) solar cells. In future when CIGS solar cells will be used extensively, the available amount of indium could be a limiting factor, unless a synthetic technique of efficiently utilizing the element is developed. Current vacuum techniques inherently produce a significant loss of In during the synthetic process, while electrodeposition exploits nearly 100% of the In, with little loss of the material. Thus, an electrochemical process will be the method of choice to produce alloys of In once the proper conditions are designed. In this review, we examine the electrochemical processes of electrodeposition in the synthesis of indium alloys. We focus on the conditions under which alloys are electrodeposited and on the factors that can affect the composition or properties of alloys. The knowledge is to facilitate the development of electrochemical means of efficiently using this relatively rare element to synthesize valuable materials, for applications such as solar cells and light-emitting devices.
Fabrications and photoluminescence of Sm2+ -doped aluminosilicate thin films
Yonghwa Chung,Kiwan Jang,Eunjin Cho,HyoJin Seo,Ilgon Kim,Sangsu Kim,Seongtae Park,Weiping Qin,Yong-Ill Lee 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.I
Sm2+-doped 10Al2O390SiO2 thin lms were prepared by coating on Al-deposited Si(100) wafers with a sol solution and heating in air, as well as in a H2 atmosphere. The prepared thin films were examined with a scanning electron microscope for observing their morphologies, and the photoluminescence spectra of Sm2+ ions were measured. The morphologies of the thin lms were found to be highly dependent upon the samarium precursors and the emission peaks due to the 5D0 ! 7F0 transitions of Sm2+ ions were highly dependent on the reduction processes of the Sm3+ ions and the samarium precursors.
Nucleation Process of Indium on a Copper Electrode
Chung, Yonghwa,Lee, Chi-Woo The Korean Electrochemical Society 2013 Journal of electrochemical science and technology Vol.4 No.3
The electrodeposition of indium onto a copper electrode from an aqueous sulfate solution containing $In^{3+}$ was studied by means of cyclic voltammetry and chronoamperometry. Reduction and oxidation of indium on copper were investigated by using cyclic voltammograms at different negative limiting potentials and at different scan rates in cumulative cycles. Cyclic voltammograms indicated that reduction and oxidation processes of indium could involve various reactions. Chronoamperometry was carried out to analyze the nucleation mechanism of indium in the early stage of indium electrodeposition. The non-dimensional plot of the current transients at different potentials showed that the shape of the plot depended on the applied potential. The nucleation of indium at potential step of -0.6~-0.8 V was close to progressive nucleation limited by diffusion. However the non-dimensional plot of current transients for the indium nucleation showed different behaviors from theoretical curves at the potential step lower than -0.8 V.
Chung, Yonghwa,Lee, Chi-Woo The Korean Electrochemical Society 2013 Journal of electrochemical science and technology Vol.4 No.1
Gallium is an important element in the production of a variety of compound semiconductors for optoelectronic devices. Gallium has a low melting point and is easily oxidized to give oxides of different compositions that depend on the conditions of solutions containing Ga. Gallium electrode reaction is highly irreversible in acidic media at the dropping mercury electrode. The passive film on a gallium surface is formed during anodic oxidation of gallium metal in alkaline media. Besides, some results in published reports have not been consistent and reproducible. An increase in the demand of intermetallic compounds and semiconductors containing gallium gives rise to studies on electrosynthesis of them and an increase of gallium concentration in the environment with various application of gallium causes the development of electroanalysis tools of Ga. It is required to understand the electrochemistry of Ga and to predict the electrochemical behavior of Ga to meet these needs. Any review papers related to the electrochemistry of gallium have not been published since 1978, when the review on the subject was published by Popova et al. In this study, the redox behavior, anodic oxidation, and electrodeposition of gallium, and trace determination of gallium by stripping voltammetries will be reviewed.
Charge Transfer between STM Tip and Au(100) in Dry, H<sub>2</sub>O, and D<sub>2</sub>O Atmospheres
Utami, Anggi,Chung, Yonghwa,Lee, Chi-Woo The Korean Electrochemical Society 2013 Journal of electrochemical science and technology Vol.4 No.4
Charge transfer between STM tip and Au(100) has been investigated by using a Scanning Tunneling Microscopy (STM) technique in dry, $H_2O$, and $D_2O$ atmospheres. Dry atmosphere was indicated by humidity as low as 5 % and high humidity as high as 98% was managed by injecting $H_2O$ and $D_2O$ to the chamber. The current decayed more slowly in high humidity than in dry atmosphere. The plateau currents were found to appear at separations larger than ca. $5{\AA}$ where the current decay stopped depending on applied bias voltages. The polarity dependence was observed at the STM junction between Pt-Ir tip and the gold. On the contrary, little dependence was seen at the one between Au tip and the substrate electrode.
Photo-Bleaching Eect in Divalent Samarium-Doped Alkaline-Earth Fluorohalides
Weiping Qin,Kiwan Jang,Changdae Kim,Hynngab Cho,Seongtae Park,Yonghwa Chung,Yong-ill Lee 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2
When a CW laser was focused on a sample of divalent samarium-doped alkaline-earth uorohalides (Mg0:5Sr0:5FCl0:5Br0:5 : Sm2+ or BaFCl0:5Br0:5 : Sm2+), the uorescence intensity of Sm2+ ions decreased rapidly. Under irradiation from a 488-nm laser with a power density of 10 W/cm2, the intensity of the 5D0 ! 7F0 (Sm2+) emission decreased as much as 96 % of its initial intensity in 30 minutes (for an X-ray-reduced sample). The so-called photo-bleaching eect can be in uenced by the processes used for sample synthesis, such as the reduction method, the grinding process or X-ray irradiation. The decreasing curves obtained in the photo-bleaching experiments were tted, a biexponential decreasing mode was found, which included a fast decrease (time constant tens of seconds) and a slow decrease (time constant hundreds of seconds). There was no evidence to support the divalent samarium ions being photo-ionized into trivalent samarium ions in the photobleaching process. The most probable mechanism for the photo-bleaching eect involves structural defects and color centers in the samples.
Audio-visual 멀티모달 정보 기반의 비정상 활성 돼지 탐지 시스템
채희찬 ( Heechan Chae ),이준희 ( Junhee Lee ),이종욱 ( Jonguk Lee ),정용화 ( Yonghwa Chung ),박대희 ( Daihee Park ) 한국정보처리학회 2022 한국정보처리학회 학술대회논문집 Vol.29 No.1
양돈을 관리하는 데에 있어 비정상 개체를 식별하고 사전에 추적하거나 격리할 수 있는 양돈업 시스템을 구축하는 것은 효율적인 돈사관리를 위한 필수 요소이다. 그러나 돈사내의 이상 상황을 탐지하는 연구는 보고되었지만, 이상 상황이 발생한 돼지를 특정하여 식별하는 연구는 찾아보기 힘들다. 따라서, 본 연구에서는 소리를 활용하여 이상 상황이 발생함을 탐지한 후 영상을 활용하여 소리를 낸 특정 돼지를 식별할 수 있는 시스템을 제안한다. 해당 시스템의 주요 알고리즘은 활성 화자 탐지 문제에서 착안하여 이를 돈사에 맞게 적용하여, 비정상 소리를 내는 활성 돼지를 식별 가능하도록 구현하였다. 제안한 방법론은 모의 실험을 통해 돈사 내의 이상 상황이 발생한 돼지를 식별할 수 있음을 확인하였다.
Alkyl Chain Length Dependence of the Field-Effect Mobility in Novel Anthracene Derivatives
Back, Jang Yeol,An, Tae Kyu,Cheon, Ye Rim,Cha, Hyojung,Jang, Jaeyoung,Kim, Yebyeol,Baek, Yonghwa,Chung, Dae Sung,Kwon, Soon-Ki,Park, Chan Eon,Kim, Yun-Hi American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.1
<P>We report six asymmetric alkylated anthracene-based molecules with different alkyl side chain lengths for use in organic field-effect transistors (OFETs). Alkyl side chains can potentially improve the solubility and processability of anthracene derivatives. The crystallinity and charge mobility of the anthracene derivatives may be improved by optimizing the side chain length. The highest field-effect mobility of the devices prepared here was 0.55 cm<SUP>2</SUP>/(V s), for 2-(<I>p</I>-pentylphenylethynyl)anthracene (PPEA). The moderate side chain length appeared to be optimal for promoting self-organization among asymmetric anthracene derivatives in OFETs, and was certainly better than the short or long alkyl side chain lengths, as confirmed by X-ray diffraction measurements.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-1/am5063103/production/images/medium/am-2014-063103_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5063103'>ACS Electronic Supporting Info</A></P>
키워드 네트워크를 이용한 구제역 파급효과의 트렌드 분석
노병준 ( Byeongjoon Noh ),서정순 ( Zhenshun Xu ),이종욱 ( Jonguk Lee ),박대희 ( Daihee Park ),정용화 ( Yonghwa Chung ) 한국정보처리학회 2016 한국정보처리학회 학술대회논문집 Vol.23 No.2
최근 구제역의 발생으로 인해 농·축산업계 및 관련 산업분야에 막대한 피해를 야기함에 따라, 구제역의 발병에 따른 다양한 사회적 파급효과의 분석이 필요하다. 본 논문에서는 온라인 뉴스를 대상으로 텍스트 마이닝 방법들을 사용하여 구제역으로 인한 경제적, 환경적, 그리고 정책적 파급효과를 분석하는 공학적 방법론을 제안한다. 제안하는 시스템은 먼저, 구제역 관련 온라인 뉴스를 수집한 후, 토픽 모델링의 대표적인 방법 중 하나인 LDA(Latent Dirichlet Allocation)를 활용하여 뉴스 기사로부터 키워드들을 추출한다. 둘째, 추출된 키워드들로부터 구제역으로 인한 파급효과의 분석을 위해 동시출현 키워드 네트워크를 구성한다. 셋째, 키워드 네트워크 타임라인을 통해 각 파급효과들의 변화를 분석한다. 마지막으로, 사례분석을 통해 2010년 7월부터 2011년 12월까지 한국에서 발생한 구제역으로 인한 사회적 파급효과의 분석을 수행하였다.