• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.234.1-234.1
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• 2015

Molybdenum disulfide (MoS2)는 van der Waals 결합을 통한 층상구조의 물질로써 뛰어난 물리화학적, 기계적 특성으로 Field Effect Transistors (FETs), Photoluminescence, Photo Detectors, Light Emitters 등의 많은 분야에서 연구가 보고 되어지고 있는 차세대 2D-materials이다. 이처럼 MoS2 가 다양한 범위에 응용될 수 있는 이유는 layer 수가 증가함에 따라 1.8 eV의 direct band gap 에서 1.2 eV 의 indirect band-gap으로 특성이 변화할 뿐만 아니라 다양한 고유의 전기적 특성을 지니고 있기 때문이다. 그러나 MoS2 는 원자층 단위의 layer control 이 어렵다는 이유로 다양한 전자소자 응용에 많은 제약이 보고 되어졌다. 본 연구에서는 MoS2 의 layer를 control 하기 위해 ICP system 에서 mesh grid 를 삽입하여 Cl2 radical을 효과적으로 adsorption 시킨 뒤, Ion beam system 에서 Ar+ Ion beam 을 통해 한 층씩 제거하는 방식의 atomic layer etching (ALE) 공정을 진행하였다. ALE 공정시 ion bombardment 에 의한 damage 를 최소화하기 위해 Quadruple Mass Spectrometer (QMS) 를 통한 에너지 분석으로 beam energy 를 20 eV에서 최적화 할 수 있었고, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy(AFM) 분석을 통해 ALE 공정에 따른 MoS2 layer control 가능 여부를 증명할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3244-3248
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• 2014

Two ethylenediamine cobalt(II) oxalate complexes Co(ox)(en), 1 and $Co(ox)(en){\cdot}2H_2O$, 2 have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, IR spectrum, TG analysis, and magnetic measurements. In 1, Co atoms are coordinated by two bis-bidentate oxalate ions in transconfiguration to form Co(ox) chains, which are further bridged by ethylenediamine molecules to produce 2D grid layers, Co(ox)(en). In 2, Co atoms are coordinated by bridging oxalate ions in cis-configuration to form Co(ox) chains, and the additional chelation of ethylenediamine to Co atoms completes 1D zigzag chain, Co(en)(ox). Two lattice water molecules stabilize the chains through hydrogen bonding. Magnetic susceptibility measurements indicate that both complexes exhibit weak antiferromagnetic coupling between cobalt(II) ions with the susceptibility maxima at 23 K for 1 and 20 K for 2, respectively. In 1 and 2, the oxalate ligands afford a much shorter and more effective pathway for the magnetic interaction between cobalt ions compared to the ethylenediamine ligands, so the magnetic behaviors of both complexes could be well described with 1D infinite magnetic chain model.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3743-3748
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• 2013

A tetradentate ligand of 2-phenyl-4,6-di(pyridin-2-yl)pyrimidine (L) has been synthesized and its complexes with $ZnI_2$ and CuI have been obtained by hydrothermal method. single crystal X-ray diffraction analysis indicates that ligand L coordinates with Zn(II) ions to form a simple four-coordinate di-nuclear complex, while the complexation of L with Cu(I) constructs a one-dimensional chain polymer. The existence of $I^-$ ion hampers the L to assemble grid-type complexes with Zn(II) and Cu(I). Fluorescence spectra show that the L emits blue fluorescence while its Cu(I) polymer decrease the fluorescence intensity and Zn(II) complex quenches the fluorescence.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.348-351
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• 1995

A modified silicon direct bonding method has been developed alloying an intimate contact between grooved and smooth mirror-polished oxide-free silicon wafers. A regular set of grooves was formed during preparation of heavily doped $p^+$-type grid network by oxide-masking und boron diffusion. Void-free bonded interfaces with filing of the grooves were observed by x-ray diffraction topography, infrared, optical. and scanning electron microscope techniques. The presence of regularly formed grooves in bending plane results in the substantial decrease of dislocation over large areas near the interface. Moreover two strongly misoriented waters could be successfully bonded by new technique. Diodes with bonded a pn-junction yielded a value of the ideality factor n about 1.5 and the uniform distribution of series resistance over the whole area of horded pn-structure. The suitability of the modified technique was confirmed by I - V characteristics of power diodes and reversly switched-on dynistor(RSD) with a working area about $12cm^2$. Both devices demonstrated breakdown voltages close to the calculation values.

• 대한방사선기술학회지:방사선기술과학
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• 제19권1호
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• pp.41-49
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• 1996

We have been used super sensitive screen/film system which is thought to be the limit of sensitivity, however, we think this method is not satisfactory. As a general radiographic rule, reduction of exposure is inconsistent with improvement of image quality, but it is necessary to challenge this rule to get better method. We tried air gap method for minimal diffuse lung shadow which is difficult to find out by our routine method. As a result, air gap method with super sensitive screen/film system(SRO 1000/TMH) showed lower exposure dose, 50% of our routine system(SRO 750/SRH with grid), and better image quality for pulmonary pattern in the lower lung field.

• Bulletin of the Korean Chemical Society
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• 제25권12호
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• pp.1801-1806
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• 2004

Ligand-based quantitative structure-activity relationship (QSAR) studies were performed on indolinones derivatives as a potential inhibitor of the protein tyrosine kinase of fibroblast growth factor receptor (FGFR) by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) implemented in the SYBYL packages. The initial X-ray structure of docked ligand (Su5402) to FGFR was used to minimize the 27 training set molecules using TRIPOS force field. Seven models were generated using CoMFA and CoMSIA with grid spacing 2 ${\AA}$. After the PLS analysis the best predicted CoMSIA model with hydrophobicity, hydrogen bond donor and acceptor property showed that a leave-one out(LOO) cross validated value $({r^2}_{cv})^$ and non-cross validated conventional value $({r^2}_{ncv})^$ are 0.543 and 0.938, respectively.

• 한국방사선학회논문지
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• 제13권5호
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• pp.749-755
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• 2019

본 연구에서는 관전압과 관전류량이 디지털 방사선영상에서 적용되고 있는 노출 지수에 미치는 영향을 알아보고자 하였다. 방사선발생장치는 인버터방식의 디지털 X선 발생장치를 사용했으며 영상검출체는 포터블 형태의 무선 디텍터를 그리드 없이 사용하였다. 방사선영상은 3D 프린터를 이용하여 제작한 원뿔형 피라미드 팬텀을 이용하여 획득하였다. X선의 관전압 조사조건은 40 kVp부터 120 kVp까지 10 kVp 씩 증가시켰고 각 관전압에서 관전류량은 1 mAs에서부터 128 mAs까지 배수적으로 증가시켰다. 그 결과 관전압이 EI와 높은 $R^2$ 값으로 로그 함수적 관계가 있었으며 관전류량이 매우 높은 선형적인 관계가 있었다. 또한 영상 검출체의 면적선량과 EI도 $R^2$ 값이 0.76 이상으로 높은 상관관계가 있었다. 결론적으로 관전류량이 EI에 선형적으로 영향을 주었으며, 적절한 영상품질 유지를 위해서는 예측이 용이한 관전류량을 주로 조절하는 것이 유리하다고 판단된다.

• 방사성폐기물학회지
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• 제19권2호
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• pp.161-176
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• 2021

In this study, the electrochemical behavior of Sm on the binary liquid Al-Ga cathode in the LiCl-KCl molten salt system is investigated. First, the co-reduction process of Sm(III)-Al(III), Sm(III)-Ga(III), and Sm(III)-Ga(III)-Al(III) on the W electrode (inert) were studied using cyclic voltammetry (CV), square-wave voltammetry (SWV) and open circuit potential (OCP) methods, respectively. It was identified that Sm(III) can be co-reduced with Al(III) or Ga(III) to form Al_zSm_y or Ga_xSm_y intermetallic compounds. Subsequently, the under-potential deposition of Sm(III) at the Al, Ga, and Al-Ga active cathode was performed to confirm the formation of Sm-based intermetallic compounds. The X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analyses indicated that Ga₃Sm and Ga₆Sm intermetallic compounds were formed on the Mo grid electrode (inert) during the potentiostatic electrolysis in LiCl-KCl-SmCl₃-AlCl₃-GaCl₃ melt, while only Ga₆Sm intermetallic compound was generated on the Al-Ga alloy electrode during the galvanostatic electrolysis in LiCl-KCl-SmCl₃ melt. The electrolysis results revealed that the interaction between Sm and Ga was predominant in the Al-Ga alloy electrode, with Al only acting as an additive to lower the melting point.

• 한국의학물리학회지:의학물리
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• 제22권4호
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• pp.163-171
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• 2011

본 연구에서는 피사체에 의한 산란, 초점에 의한 흐림, 기하학적 확대도 그리고 검출기의 특성이 반영된 유효검출양자효율(effective detective quantum efficiency, eDQE)과 유효선량을 평가하여 소아 흉부 X선 촬영 시 선량의 최적화를 위한 조사조건의 영향을 평가하였다. 100, 110, 120, 150, 180 cm의 FDD (focus-to-detector distance)일 때 관전압을 40 kVp에서 90 kVp까지 10 kVp씩 증가시켜가며 동일한 유효선량일 때 eDQE를 평가하였다. 그 결과 eDQE는 다른 관전압과 비교 시60 kVp에서 가장 높은 값을 보였다. 특히, 동일한 유효선량일 때 그리드가 없을 경우 상대적으로 매우 높은 eDQE를 나타냈다. 이는 그리드에 의한 산란선의 감소가 그리드에서 흡수된 유효 광자의 손실을 보상하지 못하기 때문이다. 그리드 가 없을 경우 FDD가 증가할수록 향상된 유효변조전달함수(effective modulation transfer function, eMTF)로 인하여 eDQE는 증가하였다. 국내 대형병원들의 대부분은 15개월 소아의 흉부 X선 촬영 시 그리드와 함께 100 cm의 짧은 FDD를 사용하고 있다. 그 결과 대부분의 경우는 국내 환자선량권고량(diagnostic reference level, DRL) $100{\mu}Gy$을 초과하였다. 이는 5세 소아 흉부 X선 촬영 시 150 cm에서 180 cm 사이의 긴 FDD를 사용하지만, 15개월을 모사하고 있는 표준 소아팬텀의 흉부 X선 촬영의 경우 100 cm의 짧은 FDD를 사용했기 때문이다. 따라서, 나이에 따른 소아의 흉부 X선 촬영을 시행하기 위한 적절한 조사조건이 확립되어야 한다. 본 연구 결과는 나이에 따른 소아 선량의 권고량을 설립하는데 기초자료로 활용될 수 있을 것이다.

• 대한디지털의료영상학회논문지
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• 제14권2호
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• pp.1-8
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• 2012

Purpose : We aim at presenting the optimum radiologic factor through the evaluation of dose variation and of image quality through the use of a grid in Humerus examination and the change of dose because of the change of radiologic factor. Materials and Methods : We divided it in 3 cases: when using a grid or not and when using IP(Image Plate) in a digital system. Also, as fixing kVp to 70kVp it changed mAs, and fixing mAs to 10 it changed kVp, we put up resolution chart and Burger rose phantom on the acrylic phantom of 7cm (the same level of Humerus) to evaluate the dose and image. We used Image J program to evaluate the quantitative resolution of the obtained image, and made the qualitative evaluation and statistical analysis of the image saved in PACS for 20 radiologic technologist with more than 10 years of experience in order of evaluate its contrast. We used SPSS10(SPSS Inc. Chicago, Illinois) for statistical analysis. Results : We observed the analytic result of resolution by the change of kVp that it was $4.539dGycm^2$ in 60kVp and $757.472dGycm^2$ in 75kVp, which increased about 64.6% of dose, while for the resolution it had the pixel value 30.7% better with 851 in 60kVp than 651 in 75kVp. Also, we analyzed the result of resolution by the change of mAs that it was $3.106dGycm^2$ in 5mAs, and $12.470dGycm^2$ in 20mAs, which increased about 400% of dose, while for the resolution DR had 678 in 5mAs, and 724 in 20mAs that increased about 6.8% of resolution. We made the qualitative evaluation of contrast by the change of kVp that DR showed the higher quality than CR, but the contrast by the change of kVp had no special different at the moment of visual evaluation, nor statistically significant difference(P>0.05). We observed the qualitative evaluation of contraste by the change of mAs that the contrast increased as DR increased mAs, and had statistically significant difference(P<0.05). On the other hand, CR had no significant difference for more than 10mAs nor statistically significant difference(P>0.05). Conclusion : In case of some patients with radiographic exposure by the repeated examination such as emergent patient or Follow up patient, they are considered to try to limit the use of a grid, to set kVp under 65kVp in fixed mode, to select less than 10mAs and to reduce the possibility of patient being bombed.