• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1187-1192
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• 2000

Ternary (Mo-Ru-Pd) and binary (Mo-Ru, Mo-Pd) alloys have been prepared using an Ar arc melting furnace. Mo and the noble metals, Ru and Pd, are the constituents of metallic insoluble residues, which were found in the early days of post-irradiation studies on uranium oxide fuels. In the present study, the structure of the alloys was evaluated using a powder X-ray diffractometer. Unit cell parameters were determined by least squares refinements of powder X-ray diffraction data. Scanning electron microscopic analyses of the surface of the alloys indicated that surface morphology was dependent on the crystallographic structure as well as its composition. Measurements of the magnetic susceptibility of the alloys showed evidence of superconducting transition from 3 to 9.2 K. Among the ternary and binary alloys, the ${\sigma}-phase$ showed the highest superconducting transition temperature,~9.2 K.

• 대한영상의학회지
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• 제82권1호
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• pp.173-181
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• 2021

목적 대퇴골 경부 골절 환자를 대상으로 골다공증 평가를 위해 다중검출 전산화단층촬영(multidetector computed tomography; 이하 MDCT)에서의 감쇠 계수(Hounsfield unit; 이하 HU)와 이중 에너지 X선 흡수 계측법(dual energy X-ray absorptiometry; 이하 DXA)을 비교하였다. 대상과 방법 2016년 6월부터 12월까지 MDCT와 DXA를 모두 시행한 42명의 대퇴골 경부 골절 환자가 본 연구의 대상으로 포함되었다. MDCT에서는 정상 대퇴골 경부의 해면골에서 HU를 측정하였으며 DXA에서는 동 부위의 골밀도 및 T 값을 얻었다. HU와 골밀도 및 T 값의 상관관계를 Spearman 상관계수를 이용하여 분석하였다. 결과 대퇴골 경부 골절 환자의 골밀도와 T 값의 평균은 각각 0.650 g/cm²과 -2.4이었다. 정상, 골감소증, 골다공증 환자 군의 HU의 평균은 각각 131.9, 98.9, 41.3이었다. HU는 골밀도(r² = 0.670; p < 0.001) 및 T 값(r² = 0.676; p < 0.001) 모두와 양의 상관관계를 보였다. 결론 다중검출 전산화단층촬영에서 감쇠계수의 측정은 골다공증 선별검사를 위한 유용한 진단적 도구가 될 수 있다.

• 한국콘텐츠학회논문지
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• 제15권11호
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• pp.298-306
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• 2015

본 연구는 진단용 X선 검사 시 사용하고 있는 부가필터의 재질(Cu, Ni, CaWO4, Gd+Ba)을 다양화하여 그에 따른 검사실 내의 공간선량을 평가 한 후 적합한 재질을 찾아 제시하고자 하였다. 실험은 몬테칼로 기법을 바탕으로 하는 MCNPX 프로그램을 사용하여 흉부와 복부검사를 선택하여 모의실험을 진행하였다. 그 결과 각 재질별 선량은 모의피폭체가 위치한 곳을 중심으로 반경 50 cm 인 지점의 평균 산란선량은 모의피폭체 표면선량의 약 62%, 반경 100 cm인 지점은 평균 약 47% 정도 측정되었다. 결과에 따라 현재 상용화 되어 있는 Al 재질을 Cu, Ni 재질이 충분히 대체가능 할 것으로 판단된다. 다만 원자번호와 밀도의 차이로 인하여 그 두께를 Al의 약 1/10 정도로 조정을 해서 사용하면 적합할 것이다.

• 대한디지털의료영상학회논문지
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• 제10권2호
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• pp.23-31
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• 2008

Computed radiography(CR) has been widely used in the field of diagnostic radiography since digital X-ray image was introduced. The imaging performance of CR system was studied by analyzing the digital image data of the CR images which are the outcomes of the whole imaging system composed of image plate(IP), laser digitizer, analoge-digital convertor, and a given image processing unit. In this study, we used a conventional CR system made by Agfa. From the flat field image of 150$\times$150 image pixels, signal-to-noise ratio(SNR) was calculated. SNR of the CR image increases in proportion to logarithm value of the X-ray exposure irradiated on the IP. SNR is less than about 6 at the exposure below 0.2mR and is more than 10 at the exposure above 0.54mR. In our study, most of images obtained by the smaller exposures less than 2.0mR can not be readable. In general, the minimum value of the SNR ranges from 3 to 5. We obtained modulation transfer function(MTF) by analyzing the bar pattern image which was made under conditions as follows: X-ray tube potential was 55kVp, the IP exposure was 0.54 mR, and the distance between X-ray source to IP was 2m, where bar pattern was located on the IP. MTF is 23% at 2.5lp/mm spatial frequency. Provided that the MTF of noise equivalent modulation is 10%, the CR system has the limiting spatial resolution of 3.2lp/mm. If the image sharpness is evaluated by the spatial frequency where MTF is 50%. the corresponding spatial frequency is 0.5$\sim$0.75lp/mm. MTFA(Modulation Transfer Function Area) is 1.0lp/mm. Compared with the Fuji CR whose MTFA is 1.1lp/mm, Agfa CR in this study shows almost same MTFA performance.

• Imaging Science in Dentistry
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• 제42권4호
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• pp.237-242
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• 2012

Purpose: The objectives of this study were to survey the radiographic exposure parameters, to measure the patient doses for intraoral dental radiography nationwide, and thus to establish the diagnostic reference levels (DRLs) in intraoral dental X-ray examination in Korea. Materials and Methods: One hundred two intraoral dental radiographic machines from all regions of South Korea were selected for this study. Radiographic exposure parameters, size of hospital, type of image receptor system, installation duration of machine, and type of dental X-ray machine were documented. Patient entrance doses (PED) and dose-area products (DAP) were measured three times at the end of the exit cone of the X-ray unit with a DAP meter (DIAMENTOR M4-KDK, PTW, Freiburg, Germany) for adult mandibular molar intraoral dental radiography, and corrections were made for room temperature and pressure. Measured PED and DAP were averaged and compared according to the size of hospital, type of image receptor system, installation duration, and type of dental X-ray machine. Results: The mean exposure parameters were 62.6 kVp, 7.9 mA, and 0.5 second for adult mandibular molar intraoral dental radiography. The mean patient dose was 2.11 mGy (PED) and 59.4 $mGycm^2$ (DAP) and the third quartile one 3.07 mGy (PED) and 87.4 $mGycm^2$ (DAP). Doses at university dental hospitals were lower than those at dental clinics (p<0.05). Doses of digital radiography (DR) type were lower than those of film-based type (p<0.05). Conclusion: We recommend 3.1 mGy (PED), 87.4 $mGycm^2$ (DAP) as the DRLs in adult mandibular molar intraoral dental radiography in Korea.

• Biodesign
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• 제6권4호
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• pp.92-95
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• 2018

API5 is a unique oncogenic, non-BIR type IAP nuclear protein and is up-regulated in several cancers. It exerts several functions, such as apoptosis inhibition, cell cycle progression, cancer immune escape, and anticancer drug resistance. Although structural studies of API have revealed that API5 mediates protein-protein interactions, its detailed molecular functions remain unknown. Since FGF2 is one of API5's major interacting proteins, structural studies of the API5-FGF2 complex will provide insight into both proteins' molecular function. We overexpressed and purified API5 and FGF2 in Escherichia coli and crystallized the API-FGF2 complex using polyethylene glycol (PEG) 6000 as a precipitant. Diffraction data were collected to a $2.7{\AA}$ resolution using synchrotron X-rays. Preliminary diffraction analysis revealed that the API5-FGF2 complex crystal belongs to the space group $P2_12_12_1$ with the following unit cell parameters: a = 46.862, b = 76.523, $c=208.161{\AA}$. One asymmetric unit with 49.9% solvent contains one API5-FGF2 complex. Molecular replacement calculation, using API5 and FGF2 coordinates, provided a clear electron density map for an API5-FGF2 complex.

• 한국방사선학회논문지
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• 제10권1호
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• pp.1-6
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• 2016

현재 CCD 및 TFT LCD 기반의 평판형 디지털 X선 센서를 이용한 많은 디지털 X선 영상장치가 활용되고 있으며, 특히 포톤계수형 센서 기술에 대한 많은 연구가 수행되고 있다. 본 연구에서는 포톤계수형 센서의 정량적 성능 평가 항목인 포톤계수효율을 측정하기 위해 포톤계수형 센서 물질에 입사되는 X선 플루엔스 측정하였다. IEC 61223-1-2 권고안의 RQA-M2 Radiation beam quality를 이용하여 포톤 플루엔스를 측정한 결과, $10{\mu}m$ 핀홀 영역에서 입사 광자 플루엔스는 $4photon/unit\;area{\cdot}{\mu}Gy$, $30{\mu}m$ 핀홀 영역에서 약 $50photons/unit\;area{\cdot}{\mu}Gy$, $100{\mu}m$ 핀홀 영역에서 $698photons/unit\;area{\cdot}{\mu}Gy$의 플루엔스로 규정할 수 있었다. 셋업된 입사 플루엔스를 이용하여 포톤계수형 센서 물질에서의 X선 조사시 출력파형을 측정함으로써 실제 포톤계수효율을 측정할 수 있을 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제19권10호
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• pp.1095-1099
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• 1998

The crystal structure of an acetylene sorption complex of dehydrated fully Mn(Ⅱ)-exchanged zeolite X, Mn46Si100Al92O384·30C2H2 (a=24.705(3) Å) has been determined by single-crystal X-ray diffraction techniques. The structure was solved and refined in the cubic space group Fd3 at 21(l) ℃. The complex was prepared by dehydration at 380 ℃ and 2 x 10-6 Torr for 2 days, followed by exposure to 300 Torr of acetylene gas for 2 h at 24 ℃. The structure was refined to the final error indices, R1=0.060 and R2=0.054 with 383 reflections for which I > 3σ(Ⅰ). In the structure, Mn2+ ions are located at two different crystallographic sites; sixteen Mn2+ ions at site I are located at the centers of the double six rings and thirty Mn2+ ions are found at site Ⅱ in the supercage, respectively. Each of these latter Mn2+ ions is recessed ca. 0.385(2) Å into the supercage from its three-oxygen plane. Thirty acetylene molecules are sorbed per unit cell. Each Mn2+ ion at site Ⅱ lies on a threefold axis in the supercage of the unit cell, close to three equivalent trigonally arranged zeolite framework oxygen atoms (Mn(Ⅱ)-O=2.135(9) Å) and symmetrically to both carbon atoms of a C2H2 molecules. At these latter distances, the Mn(Ⅱ)-C interactions are weak (Mn(Ⅱ)-C=2.70(5) Å), probably resulting from electrostatic attractions between the divalent cations and the polarizable π-electron density of the acetylene molecules.

• 한국세라믹학회지
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• 제31권1호
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• pp.62-68
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• 1994

It is compared the structures of the S-block in the Ba-Co-Zn Y-type hexagonal ferrites (Ba2Co2-xZnxFe12O22, x=0~2) and the Co-Zn spinel ferrites (Co1-xZnxFe2O4, x=0~1) expressed by a hexagonal axis system (space group R3m). The structures have been refined with a Rietveld analysis of the powder X-ray diffraction pattern with high precision (Rwp<0.13, RI<0.03). The overal dimension of the S-block is slightly different from the 1/3 of a hexagonal spinel unit cell as follow: 1.6~2.0% longer c-axis, 1.3~1.6% shorter a-axis and about 1% smaller volume. Upto Zn:Co=1:1 in the Ba-Co-Zn Y-type hexagonal ferrites, the zinc substitute primarily the tetrahedral sites in the S-block. Beyond that the zinc seems to go into the T-block as well.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.64-74
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• 1994

The nonstoichiometric chalcogenides with NaCl-type structure were prepared and the physical and structural properties were studied. The homogeneous range and the structural change were studied based on X-ray powder diffractions using Rietveld-type full-profile fitting technique. Wide homogeneous ranges were observed in Y-S and Y-Se systems, and relatively narrow homogeneous ranges were observed in Yb-S and Yb-Se systems. Both in $Yb_{1-x}S\;and\;Yb_{1-x}Se$, a vacancy ordering transition occurred in (111) plane direction. The ordered superstructure had cubic symmetry(Fm$\bar{3}m) with doubled unit cell "a" parameter compared to the original NaCl-type. The superlattice developed in a continuous second-order transitiion was characterized by the reduced waved vector k= $(a^*+b^*+c^*)/2$. Y-S system had metallic, and YSe, YbSe system had semiconducting properties in their homogeneous ranges. It was observed that the change of electronic transport properties in extended homogeneous range did not depend on the relativeratio of metal to nonmetal, but on the quantities of vacancies.