• Carbon letters
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• 제27권
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• pp.42-49
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• 2018

A citric acid functionalized graphene oxide nanocomposite was successfully synthesized and the structure and morphology of the nanocatalyst were comprehensively characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, X-ray diffraction patterns, atomic force microscopy images, scanning electron microscopy images, transmission electron microscopy images, and thermogravimetric analysis. The application of this nanocatalyst was exemplified in an important condensation reaction to give imidazole derivatives in high yields and short reaction times at room temperature. The catalyst shows high catalytic activity and could be reused after simple work up and easy purification for at least six cycles without significant loss of activity, which indicates efficient immobilizing of citrate groups on the surface of graphene oxide sheets.

• 한국표면공학회지
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• 제29권5호
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• pp.467-473
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• 1996

Heteroepitaxial growth of cubic silicon carbide films on Si(001) and Si(111) substrates at temperatures 900-$1000^{\circ}C$ has been achieved by high vacuum chemical vapor deposition using the single precursor 1, 3-disilabutane without carrying out the carbonization process of the substrate surfaces. The deposition temperature range is much lowered compared with conventiontional chemical vapor deposition where separate sources for silicon and carbon are employed. The deposition procedure is quite simple and safe. The qualities of the films were found to be very good judging from the results obtained by various characterization techniques including reflection high energy electron diffraction, X-ray diffraction, X-ray pole figure analysis, Rutherford backscattering spectrometry, Auger depth profiling, and transmission electron diffraction.

• 한국전기전자재료학회논문지
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• 제24권3호
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• pp.256-260
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• 2011

ZnO nanostructures with tetrapod, needle and multipod shapes were synthesized without catalysts through a simple thermal oxidation of metallic Zn powder in alumina crucible under air atmosphere. X-ray diffraction data revealed that the ZnO nanostructures had wurtzite structure of hexagonal phase. Energy dispersive X-ray (EDX) spectra showed that the ZnO was of high purity. After the oxidation of Zn powder, white colored product was mainly observed and yellow colored product was observed only a very little on the surface of the oxidized source materials. The white product consisted of tetrapods, while yellow product was composed of needles and multipods. Cathodoluminescece spectra showed that the crystalline quality of tetrapods was better that those of needles and multipods.

• Bulletin of the Korean Chemical Society
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• 제12권5호
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• pp.525-529
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• 1991

A simple route is described for the selective functionalization of calixarene at the para positions of phenyl rings. Calix[4]arene tetraacetate 2, obtained from the treatment of calix[4]arene with acetic anhydride, undergoes Fries rearrangement to yield the diametrically para substituted p-diacetylcalix[4]arene 3 in 80% yield. The crystal and molecular strucutre has been determined by X-ray diffraction method. The crystals are orthorhombic, space group Pna21, with a = 11.121 (3), b = 10.374 (3), c = 21.690 (6) $\AA$ and Z = 4. The structure was solved by direct method and refined by full-matrix least-squares methods to final R of 0.036 for 1795 observed reflections. Each hydroxyl hydrogen atom is disordered over two positions. The macrocycle exists in the cone conformation which is determined by the strong circular intramolecular flip-flop type hydrogen bonds of phenolic OH, while crystal packing effects of the diametrically para-acetyl substituents seem to be responsible for the distortion of the cone conformation.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.38-43
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• 2013

In this study, we propose a simple and indirect method to determine the optical constants of Mo and ITO thin films in the extreme ultraviolet (EUV) wavelength region by using X-ray reflectometry (XRR) and Rutherford backscattering spectrometry (RBS). Mo and ITO films were deposited on silicon substrates by using an RF magnetron sputtering method. The density and the composition of the deposited films were evaluated from the XRR and RBS analysis, respectively and then the optical constants of the Mo and ITO films were determined by an indirect optical method. The results suggest that the indirect method by using the XRR and RBS analysis will be useful to search for suitable high absorbing EUVL mask material quickly.

• 방사선산업학회지
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• 제10권1호
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• pp.29-35
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• 2016

Radiation generating devices must be properly shielded for their safe application. Although institutes such as US National Bureau of Standards and National Council on Radiation Protection and Measurements (NCRP) have provided guidelines for shielding X-ray tube of various purposes, industry people tend to rely on 'Half Value Layer (HVL) method' which requires relatively simple calculation compared to the case of those guidelines. The method is based on the fact that the intensity, dose, and air kerma of narrow beam incident on shielding wall decreases by about half as the beam penetrates the HVL thickness of the wall. One can adjust shielding wall thickness to satisfy outside wall dose or air kerma requirements with this calculation. However, this may not always be the case because 1) The strict definition of HVL deals with only Intensity, 2) The situation is different when the beam is not 'narrow'; the beam quality inside the wall is distorted and related changes on outside wall dose or air kerma such as buildup effect occurs. Therefore, sometimes more careful research should be done in order to verify the effect of shielding specific radiation generating device. High energy X-ray tubes which is operated at the voltage above 400 kV that are used for 'heavy' nondestructive inspection is an example. People have less experience in running and shielding such device than in the case of widely-used low energy X-ray tubes operated at the voltage below 300 kV. In this study, Air Kerma value per week, outside concrete shielding wall of various thickness surrounding 450 kVp X-ray tube were calculated using MCNP simulation with the aid of Geometry Splitting method which is a famous Variance Reduction technique. The comparison between simulated result, HVL method result, and NCRP Report 147 safety goal $0.02mGy\;wk^{-1}$ on Air Kerma for the place where the public are free to pass showed that concrete wall of thickness 80 cm is needed to achieve the safety goal. Essentially same result was obtained from the application of HVL method except that it suggest the need of additional 5 cm concrete wall thickness. Therefore, employing the result from HVL method calculation as an conservative upper limit of concrete shielding wall thickness was found to be useful; It would be easy, economic, and reasonable way to set shielding wall thickness.

• Journal of Biosystems Engineering
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• 제28권1호
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• pp.45-52
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• 2003

Red ginsengs are inspected manually by examining those in the dark room with back light illumination. Manual inspection is often influenced by physical condition of inspectors. Sometimes. the best grade, heaven. has some inner holes though it was inspected by a specialist. In order to resolve this problem, this study was performed to develop image processing algorithm to detect the inner holes in the x-ray image of ginseng. Because of little gray value difference between background and ginseng in the image. simple thresholding method was not appropriate. Modified watershed algorithm was used to differentiate the inner holes from background and normal ginseng body. Inner hole edge region detected by watershed algorithm consists of many number of blobs including normal portions. With line profile analysis with scanning one line at a time beginning the starting point. it shelved two peaks both ends representing extracting each blobs. in which setting threshold value as of lower peak value enabled us to obtain inner hole image. Once this procedure has to be done till the finishing point it is completing inner hole detection for one blob. Thus. conducting ail blobs by this procedure is completing inner detection of one whole ginseng. Detection results of the inner holes fer various size of red ginsengs were good even though there was small detection variation. 6.2%. according to position of x-rat tube.

• Tuberculosis and Respiratory Diseases
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• 제39권1호
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• pp.15-23
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• 1992

연구배경 : 폐암은 가장 흔한 암중의 하나로 예후가 좋지 않아 폐암의 조기진단은 매우 중요하다. 폐암의 조기진단에는 객담세포진검사와 단순흉부 X-선 촬영이 쓰이고 있으나 이런 방법들에는 한계점들이 있다. 따라서 연구자들은 단순흉부 X-선 촬영상 종괴가 없었던 폐암환자들을 분석함으로써 폐암의 조기진단에 도움을 얻고자 본 연구를 시행하였다. 방법 : 1986년 8월부터 1989년 6월까지 서울대학교병원에서 폐암으로 진단 받은 환자중 단순흉부 X-선 촬영상 종괴가 없었던 11명의 환자들을 대상으로 후향적 연구를 시행하였다. 결과 : 11명중 10명이 남자였고, 8명에서 흡연력이 있었고, 증상으로는 가래, 기침, 그리고 각혈이 많았으며, 이학적 검사상 천명음이나 천음이 들렸던 환자는 3예였다. 단순흉부 X-선 촬영에서 3예에서 확실한 종괴는 없었으나 후에 폐암으로 밝혀진 부위에 불명확한 침윤, 주사열의 비후, 폐결핵증의 소견이 있었으며, 그리고 1예에서는 늑골에 종괴가 가려져 있었던 경우가 있었다. 또 1예에서는 단순흉부 X-선 촬영에서는 종괴가 없었으나 흉부 측면촬영상 종괴가 보였던 경우가 있었다. 폐암의 위치확인의 방법으로는 기관지내시경검사와 흉부 전산화 단층촬영이 유용하였다. 병리학적으로는 11명중 7예가 편평상피세포암이었다. 이들의 병기는 제 2기이하가 5예로서 비교적 조기에 발견된 경우가 많았으며, 11명중 4명이 수술후 2년반에서 4년동안 병의 재발의 증거없이 본원외래를 다니고 있다. 결론 : 호흡기증상이 있고 폐암의 가능성을 배제하지 못하는 환자들에서는 흉부 측면사진과 객담세포진검사 등이 필요할 것이고, 폐암이 의심되면 흉부 전산화 단층촬영과 기관지 내시경 등의 검사들이 적극적으로 시행되어 폐암의 조기진단에 도움을 주어야 한다고 생각된다.

• 한국방사선학회논문지
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• 제9권7호
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• pp.501-508
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• 2015

무릎 과간와 X선 촬영법은 Holmblad법, Camp-Coventry법, Beclere법의 다양한 방법들이 임상에서 시행되고 있다. 무릎관절의 과간와 촬영은 단순 골절과 십자인대와 관련한 진단에 기본검사로 많이 시행되고 있으며 환자의 상태와 통증을 고려하여 안전한 방법을 선택하게 되는데, Holmblad법은 카세트에 밀착되는 무릎 부위에서 통증을 유발할 수 있으므로 쉽게 사용하지 않고 있다. 본 연구에서는 자체 제작한 평면 원형 cone을 카세트에 부착하여 Holmblad법 자세에서 통증 경감에 대한 인식을 파악하기 위해 100명의 자원자의 설문지를 비교 분석하였고, 산란선에 의한 영상화질의 농도는 인체 팬텀을 X선으로 촬영하여 농도계로 측정 하였다. 그 결과 Holmblad법 자세에서 통증에 대한 인식은 평균 99% 경감되었으며, 팬텀을 이용하여 촬영한 X선 필름에 대한 농도는 자체 제작한 평면 원형 cone을 사용하지 않은 카세트에 비교하여 산란선에 의한 농도변화가 통계적으로 유의하게 감소되어 임상에서 유용하게 사용될 수 있을 것으로 사료된다.

• Journal of Magnetics
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• 제4권3호
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• pp.102-106
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• 1999

Ce exhibits the intermediate valence (IV) state both as an element and in its compounds. In the present review characteristic behavior of the materials showing the IV state are described. Then the methods of producing this state : the application of the external pressure, temperature and magnetic field as well as the alloying are being discussed. An identification of the IV state is frequently not a simple goal and the best results can be obtained using a combination of various independent methods. Particular attention is paid to the X-ray spectroscopy, lattice parameters and the magnetic properties. As the examples of the IV state in the Ce compounds the properties of following materials are reported : CeRhSb, $CeCu_5In_7, CeAg_6In_6, Sc_{1-x}Ce_xFe_4Al_8 $and for comparison Sc1-xYbxFe4Al8.