• Journal of the Korean Society of Radiology
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• v.3 no.2
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• pp.27-31
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• 2009

Now a days, the Medical X-ray equipments has become digitalized from analog type such as film, cassette to CR, DR. And many scientists are still researching and developing the Medical X-ray equipment. In this study, we used the Bismuth tri-iodide to conversion material for digital X-ray equipments and we couldn't get the satisfying result than previous study, but it opened new possibility to cover the disadvantage of a-Se is high voltage aplly and difficultness of make. In this paper, we use $BiI_3$ powder(99.99%) as x-ray conversion material and make films that have thickness of 200um and the film size is $3cm{\times}3cm$. Also, we deposited an ITO(Indium Tin Oxide) electrode as top electrode and bottom electrode using a Magnetron Sputtering System. To evaluate a characteristics of the produced films, an electrical and structural properties are performed. Through a SEM analysis, we confirmed a surface and component part. And to analyze the electrical properties, darkcurrent, sensitivity and SNR(Signal to Noise Ratio) are measured. Darkcurrent is $1.6nA/cm^2$ and sensitivity is $0.629nC/cm^2$ and this study shows that the electrical properties of x-ray conversion material that made by screen printing method are similar to PVD method or better than that. This results suggest that $BiI_3$ is suitable for a replacement of a-Se because of the reduced manufacture processing and improved yield.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.262-266
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• 2007

Polycrystalline $Mn_xFe_{3-x}O_4$ thin films were synthesized on Si(100) substrates using sol-gel method and the effects of Mn substitution on the structural, magnetic, and magnetotransport properties were analyzed. X-ray diffraction revealed that cubic structure is maintained up to x = 1.78 with increasing lattice constant for increasing x. Such increase of the lattice constant is attributable to the substitution of $Mn^{2+}$ (with larger ionic radius) ions into tetrahedral $Fe^{3+}$(with smaller ionic radius) sites. VSM measurements revealed that $M_s$ does not vary significantly with x, qualitatively explainable by comparing spin magnetic moments of Mn and Fe ions. On the other hand, $H_c$ was found to decrease with increasing x, attributable to the decrease of magnetic anisotropy due to the decrease of $Fe^{2+}$ density through $Mn^{2+}$ substitution. Magnetoresistance (MR) of the $Mn_xFe_{3-x}O_4$ films was found to decrease with increasing x. Analysis of the MR data in comparison with the VSM results gives an indication of the tunneling of spin-polarized carriers through the grain boundaries of the polycrystalline samples at low external field and spin-flip of the carriers at high external field.

• Analytical Science and Technology
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• v.18 no.4
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• pp.355-361
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• 2005

The objective of this paper is to compare the surface features of two kinds of activated caron fiber (ACF) treated with potassium and the variation of their properties by phosphoric acid pre-treatment. X-ray diffraction (XRD) patterns indicate that activated carbon fiber containing potassium species show better performance for metal and metal salts by pre-treatment with phosphoric acid. In order to present the causes of the differences in surface properties and specific surface area after the samples were treated with phosphoric acid, pore structure and surface morphology were investigated by adsorption analysis and SEM. For the chemical composition microanalysis for potassium leading of the activated carbon fibers pre-treated with phosphoric acid, samples were analyzed by EDX. Finally, the type and quality of oxygen groups were determined from the method proposed by Boehm.

• Journal of Radiation Protection and Research
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• v.18 no.1
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• pp.63-70
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• 1993

Double ionization of the K- shell accompanying K- shell electron capture of the 0.035 MeV transition of $^{125}I$ has been studied by counting coincidences between $K_{\alpha}$ hypersatellite X-rays and Ka satellite X-rays emitted when double vacancies are filled. The $^{125}I\;and\;^{125}Te^m$ source materials were used in the measurement. We obtained the coincidence spectrum using two NaI(T1) detectors and a Ge(Li) detector and TAC(Time-to-Amplitude Converter), and then analysed the measured coincidence number $N(K_{\alpha}^{II},\;K_{\alpha}^s)$, the total number $N(K_{\alpha})$ of K X-ray. The probability per K-shell electron capture that a double vacancy is formed, $P_{KK}$ is formed, $P_{KK}$ is found to be $2.15{\times}10^{-4}$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.61.2-61.2
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• 2013

우리나라 최초의 거대과학 장치인 포항방사광가속기(PLS)는 지난 16년(1994~2010) 동안 국내외 이용자에게 제3세대 방사광을 제공했다. 최초 2기의 빔라인을 시작으로 꾸준하게 빔라인 증설과 성능개선을 위해 노력해 왔다. 지속해서 늘어나는 방사광 이용자 수와 더욱더 좋은 수준의 방사광 요구에 부응하기 위하여 2009년부터 3년 동안 가속장치의 성능향상사업(PLS-II)을 마쳤다. PLS-II는 PLS 대비에너지와 빔전류는 3 GeV, 400 mA로 늘리는 반면 빔의 크기는 크게 줄이고 빔안정성을 개선한 고품질 X-선 방사광 발생장치이다. 2012년부터 16기의 삽입장치 빔라인을 포함한 30기의 빔라인을 가동하여 이용자 지원을 하고 있으며 초전도케비티 설치를 포함한 목표 성능의 확보에도 많은 노력을 기울이고 있다. 현재는 6 nm-rad의 빔에 미턴스, 3-GeV전자빔, 약 0.5 ${\mu}m-rms$ 빔안정도를 가진 200 mA Top-up 운전으로 빔을 제공 하고 있으며 2014년 말에는 저장전류 400 mA급의 PLS-II 목표치로 운전할 계획이다. 본 발표에서는 포항가속기의 25년 역사를 돌아보고 가속장치의 건설에 얽힌 이야기, 중요장치 그리고 운전과 빔제공에 관한 내용, 특히 핵심 운전가치인 빔안정성을 개선하고 유지하기 위한 노력을 빔운전 측면과 진공을 포함한 엔지지어링 측면에서 언급하고자 한다. PLS 건설부터 현재 운용 중인 30기의 빔라인에서 수행된 연구 성과의 통계에 대하여 훑어보고 X-선 산란과 광전자분광을 이용한 구조, 성분 및 물성분석, 그리고 이미징 등의 분야에서 나온 탁월한 연구 결과를 살펴본다. 앞으로 건설될 신규 빔라인과 빔라인의 향후 운영 방향을 소개한다. 마지막으로 지금 포항가속기연구소에서 건설 중인 제4세대 가속기(X-선 자유전자레이저) 프로젝트의 개요 및 건설 현황과 함께 앞으로 기대되는 새로운 과학에 대하여도 소개하고자 한다.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.329-337
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• 2010

Purpose: The surfaces and compositions of rigid gas permeable (RGP) contact lenses were analyzed with the consistent methods, and the basic informations for the composition design of lens materials were suggested. Methods: The bulk structures were analyzed by using Fourier infrared spectroscopy (FTIR), the compositions of surface components were observed by using x-ray photoelectron spectroscopy (XPS), the surface morphology and roughness were observed using atomic force microscopy (AFM), and the wettabilities were estimated by the surface wetting angles. The relations and trends of those results were analyzed. Results: The high oxygen permeability RGP lenses showed the trend that the fluorine decreases and the silicon increases. As the silicon and fluorine contents increased, the carbon and oxygen contents of RGP lens materials decreased at a constant ratio. The decreasing ratio of the carbon contents was three times larger than the decreasing ratio of oxygen contents. The composition of the surface treated lens was far from these tendency line. When the silicon contents increased, the rough surface was formed with the cohered particles. When the fluorine contents increased, the rough surface was formed with the deep flaws. The surface roughness increased and then wettabilities decreased as the silicon and fluorine contents increased. For the surface roughness changes, the increasing ratio of the silicon contents was two times larger than the increasing ratio of fluorine contents. The surface of RGP lens materials appeared the hydrophobic character of which the wettabilities decreased when the roughnesses increased. Conclusions: The surfaces and compositions of RGP contact lenses were measured by the same methods. Those results and relationships were compared and analysed. It is considered that these research results will be applied with the basic data for the composition design of lens materials.

• Journal of the Mineralogical Society of Korea
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• v.25 no.2
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• pp.77-84
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• 2012

Anatase, one of the $TiO_2$ polymorphs, is known to show different phase transition paths depending on its crystalline and shape. Particle size of 15~25 nm anatase has been subjected to high-pressure Raman spectroscopy and X-ray diffraction studies using a diamond anvil cell. We observe that the starting sample transforms to an amorphous phase above approx. 20 GPa, which is retained upon pressure release to ambient condition. This is in contrast to previously established transition to baddeleyite phase and we suspect difference in the particle distribution state trigger phase instability of nanoparticles and hence amorphization.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.205-215
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• 2012

Metal ions, toxic or potentially toxic to biota and human beings, can be immobilized by sorption onto the mineral surfaces in soils and sediments. This article briefly explains theories regarding the chemical properties of mineral surfaces to sorb metal ions and processes of extended X-ray absorption fine structure (EXAFS) analysis for sorption study, and reviews atomic-scale findings on metal sorption on mineral surfaces. The theoretical understanding on the chemistry of mineral surfaces and metal sorption is fundamental to the proper analysis of the atomic-scale spectroscopy to determine the sorption phases. Atomic-scale findings on metal sorption phases discussed here include co-precipitation, ternary complexation, aging effects, and desorption possibilities, as well as outer-sphere complexation, inner-sphere complexation, and surface precipitation.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.2
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• pp.190-200
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• 2021

Purpose. The aim of this study was to evaluate biaxial flexural strength and hardness of colored monolithic zirconia after dipping in different time intervals of coloring solution. Materials and Methods. Disk shaped specimens were prepared from monolithic zirconia (Eclipse V2.0, AMS, Gimpo, Korea). Four experimental groups were categorized (n = 12) due to coloring time (PU (0s); ST (8s); OV (1 min); PS (preshade)), to evaluate biaxial flexural strength and Vickers hardness. After fracture, X-ray diffraction analysis was performed using fractured specimens. Results were analyzed with one-way ANOVA test. Results. There was no significant difference between groups in the biaxial flexural strength test. However, in the Vickers hardness test, the group with standard dipping time (ST) showed significantly higher value than the group without dipping in coloring liquid (PU)(P=.038). Also, there was no significant difference in the rest of the groups (P>.05). As a result of X-ray diffraction analysis, specific peaks of tetragonal phase were shown and the volume of monoclinic phase fraction was lower than 25%. Conclusion. Although this study has several limitations, coloring liquids had no significant effect on biaxial flexural strength. Vickers hardness was significantly different between the group to which the coloring liquid was applied and the group to which the coloring solution was not applied, but there was no significant difference between the other groups. Also, the flexural strength of monolithic zirconia corresponds to Class 5 of the minimal flexural strength standard according to the use of dental ceramics.

• Journal of the Korean Chemical Society
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• v.37 no.6
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• pp.599-603
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• 1993

Crystal structure of bis(1,2-diaminopropane)palladium(II) bis(oxalato)palladate(II) has been determined by X-ray crystallography. Crystal data: $Pd_2C_{10}H_{10}N_{4}O_{8}$, $M_W$ = 573.09, orthorhombic, space group $P_{ccn}$ (No = 56), a = 16.178(5), b = 16.381(6), c = 6.685(2)$\{AA}$, V = 1771.6 $\{AA}^3$, $M_W$W = 573.09, $D_c$ = 2.014 g${\cdot}c\;m^{-3}$, Z = 4, T = 294K, F(000) = 1056.0 and $\mu$ = 20.466 c$m^{-1}$. The intensity data were collected with $Mo-K\alpha$ radiation (${\lambda}$ = 0.7107 $\AA)$ on an automatic four-circle diffractometer with a graphite monochromater. The structure was solved by Patterson method and refined by full matrix least-squares methods using Pivot weights. The final R and S values were R = 0.065, $R_W = 0.059, R_{all}$ = 0.065 and S = 4.315 for 605 observed reflections. Both cation and anion complexes are essentially planar and have dihedral angle of $18(l)^{\circ}$ between thier planes. In the crystal structure, they do not have the Magnus's salt type mixed stacks; instead, the complex anions form regular stacks along the c-axis with the M-M bond length of $3.343(5)\AA$ and their stacks are surrounded by the complex cations through hydrogen bonds with the nitrogen-oxygen distances of 2.94(3) and $3.31(4)\AA.$