• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.110-110
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• 2018

여러 니켈합금 중 인코넬 600은 원전 가압경수로(PWR)의 튜브 재료로 널리 사용되는 재료이다. 스테인리스강과 비교하여 우수한 내식성과 기계적 특성으로 인해 화학설비, 발전설비, 그리고 해양설비 등과 같은 여러 산업분야에서도 널리 사용되고 있다. 그러나 가압경수로용 증기 발생기의 튜브 재료와 같은 특수 환경에서 예민화에 따른 입계부식 및 입계응력부식 등의 문제가 흔히 보고되고 있다. 이러한 내구성 문제는 설비 및 장비의 수명, 내구성 그리고 안정성 등의 치명적인 영향을 미친다. 따라서 용접, 열처리, 그리고 가공과정에서 발생하는 Inconel 600의 예민화 및 입계부식에 관한 연구가 활발히 진행되고 있다. 그러나 100시간 이상 장시간 열화된 시편에 대한 예민화 연구는 전무한 실정이다. 본 연구에서는 장시간 열화된 Inconel 600의 예민화를 평가하기 위해 최대 1,000시간까지 열화를 실시하였으며, 이에 대한 평가방법으로 Double-Loop Electrochemical Potentiokinetic Reactivation(DL-EPR) 시험법을 적용하였다. 본 실험에서 사용된 인코넬 600의 화학성분(wt, %)은 0.01 C, 0.05 Si, 0.14 Mn, 15.3 Cr, 0.5 Cu, 0.015 S, 그리고 나머지는 Ni 이다. 예민화 평가를 위한 등온 열화는 전기열처리로를 이용하여, $550^{\circ}C$와 $650^{\circ}C$에서 최대 1000시간까지 실시하였다. 열화에 따른 미세조직 변화는 scanning electron microscope와 energy dispersive x-ray spectroscopy를 이용하여 실시하였다. DL-EPR 실험은 $25^{\circ}C$의 0.1M $H_2SO_4$ + 0.001M KSCN(potasium thiocyanate) 수용액 하에서 실시하였으며, 분극은 OCP로부터 600 mV(SSE vs.)까지 1.67mV/s 주사속도로 forward scan을 실시 후, 동일한 속도로 OCP까지 reverse scan을 실시하였다. Degree Of Sensitization(DOS)값은 anodic scan peak($I_a$) 값과 reverse scan peak($I_r$) 값의 비로 산출하였다. $$i.e.\;DOS=I_r/I_a{\times}100$$. 그 결과, 온도 변수에 따른 Inconel 600강의 예민화 거동은 서로 상이한 경향을 나타내었다. $550^{\circ}C$의 경우, 열화가 진행됨에 따라 DOS값은 급격하게 증가하는 경향을 나타냈다. 반면, $650^{\circ}C$에서는 일정시간 이후부터 Cr 확산 현상에 의한 탈 예민화 현상이 관찰되었다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.189-194
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• 2014

In this study, from a new x-ray detector that combines a columnar CsI:Na scintillation layer with a photosensitive mercuric iodide layer was investigated. In this structure, X-rays are converted into visible light on a thick CsI:Na layer, which is then converted to electric charges in a thin $HgI_2$ bottom layer. The thin coplanar mercuric iodide films as a photosensitive converter requiring only a few tens of volts of bias, associated with a thick columnar coating of phosphor layer, were simulated and designed. The results of this research suggest that the new coplanar x-ray detector with a hybrid-type structure can resolve the following problems: high voltage from the a-Se, and low conversion efficiency from the indirect conversion method. The results of this research suggest that the new CsI:Na/$HgI_2$ x-ray detector with a double-layer type structure can resolve the following problems: high voltage from the direct conversion method, and low conversion efficiency from the indirect conversion method.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.499-505
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• 2012

The purpose of this study was to find out the difference of radiation dose value through energy, exposure number, fluoroscopy time, the number of days of exposed scatter X-ray when TLD and OSLD is used in diagnostic radiology. The difference of value were measured by relative ratio and interval. Energy makes high relative ratio of TLD($1.81{\pm}0.41$) than OSLD($1.40{\pm}0.26$), exposure number makes high of OSLD($1.40{\pm}0.26$) than TLD($2.10{\pm}0.10$). There are no significant differences between relative ratio of TLD and OSLD in fluoroscopy time and the number of days of exposed scatter X-ray. But interval of relative ratio in the number of days of exposed scatter X-ray was narrowed in less 0.2. That means, the measurement of scatter X-ray could more confident in TLD and OSLD than the measurement of direct ray. In conclusion, we have to recognize the relative ratio of TLD and OSLD could be vary depending on exposed condition of radiation. And in some cases, double test of TLD and OSLD get more creditable results of dose value.

• Archives of Pharmacal Research
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• v.18 no.6
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• pp.410-414
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• 1995

Adaptive response induced by low dese .gamma.-ray irradiation in human cervical carcinoma cells was examined. Cells were exposured to low dose of .gamma.-ray irradiation in human cervical carcinoma cells was examined. Cells were exposured to low dose of .gamma.-ray (1-cGy) followed by high doses of r-ray irradiation (0,1,2,3,5,7 and 9Gy for chlnogenic assay or 1.5Gy for micronucleus assay) with various time intervals. Survival fractions of cells in both low dose-irradiated and unirrated groups were analyzed by clonogenic assay. Surviva fractions of low dose-irradiated in cell survival was maximum when low and high dose irradiation time interval was 4 hr. Frequencies of micronuclei which is an indicative of chromosome aberration were also enutained from survival fractions analyzed by clonogenic assay, maximum when low and high dose irradiation time interval was 4hr. Frequencies of micronuclei which is an indicative of chromosome aberration were also enumerated in both low dose-irradiated and unirradiated groups. In consiststent with the result obtained from survival fractions analyzed by clonogenic assay, maximum reduction in frquencies of micronuclei was observed when low dose radiation was given 4 hr prior to high response to subsequent high dose .gamma.-ray irradiation in human cervical carcinomal cells. Our data suggest that one of the possible mechanisms of adaptive response induced by low dose rediation is the increase in repair of DNA double strand breaks in low dose radiation-adapted cells.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.340-348
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• 2016

Ray-based model for the calculation of the ocean surface-generated ambient noise coherence function has the form of double integral with respect to a range and a bearing angle. While the theoretical consideration about its numerical implementations was partly given in the past work of authors, the numerical results on the ocean environment have not been presented yet. In this paper, we perform numerical experiments for shallow and deep water environments. It is shown that the coherence function depends on the ocean sediment sound speed, and is more sensitive to the ocean sediment sound speed in the shallow water than in the deep water. Similar trend is also observed for varying the orientation of hydrophone pair. In addition, a post-processing technique is proposed in order to plot the noise intensity for the noise receiving angle. This procedure will supplement the weakness of the ray-based model about the output data type compared to the semi-analytic model of Harrison.

• Progress in Medical Physics
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• v.26 no.4
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• pp.223-228
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• 2015

Double-focused micro-Multileaf Collimator (${\mu}MLC$) is able to create radiation fields having sharper dose gradients at the field edges than common MLC. Therefore, ${\mu}MLC$ has been used for the stereotactic radiosurgery (SRS) and Stereotactic Radiotherapy (SRT). We evaluated the dosimetric characteristics of a doublefocused Dynamic-${\mu}MLC$ (DMLC) attached to the Elekta Synergy linear accelerator. For this study, the dosimetric parameters including, Percent Depth Dose (PDD), Leaf leakage and penumbra, have been measured by using of the radiochromic films (GafChromic EBT2), EDGE diode detector and three-dimensional water phantom. All datas were measured on 6 MV x-ray. As a result, The DMLC shows transmission below to 1% and because of double-focused construction of the DMLC, the penumbras of fields with DMLC are independent from the field sizes. In this paper, the resulting dosimetric evaluations proved the applicability of the DMLC attached to the Elekta Synergy linear accelerator.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.2
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• pp.58-61
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• 2016

Bulk GaN crystals were grown by the basic ammonothermal method. The c-plane GaN templates grown by hydride vapor phase epitaxy were used as seed crystals and sodium metal, amide, and azide were added as a mineralizer. The growth conditions are at temperatures from $500{\sim}600^{\circ}C$ and pressures from 2~3 kbar. The growth rate for the c-axis was increased with increasing the operating pressure. Average dislocation density was measured $1{\times}10^5/cm^2$ by the cathodoluminescence measurement. The full-width at half-maximum of the X-ray diffraction rocking curve for (002) reflection was approximately 270 arcsec for Ga face and 80 arcsec for N face.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.87-94
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• 2013

Purpose: Pineapple is now the third most important tropical fruit in world production after banana and citrus. Phytosanitary irradiation is recognized as a promising alternative treatment to chemical fumigation. However, most of the phytosanitary irradiation studies have dealt with physiochemical properties and its efficacy. Accurate dose calculation is crucial for ensuring proper process control in phytosanitary irradiation. The objective of this study was to optimize phytosanitary irradiation treatment of pineapple in various radiation sources using Monte Carlo simulation. Methods: 3-D geometry and component densities of the pineapple, extracted from CT scan data, were entered into a radiation transport Monte Carlo code (MCNP5) to obtain simulated dose distribution. Radiation energy used for simulation were 2 MeV (low-energy) and 10 MeV (high-energy) for electron beams, 1.25 MeV for gamma-rays, and 5 MeV for X-rays. Results: For low-energy electron beam simulation, electrons penetrated up to 0.75 cm from the pineapple skin, which is good for controlling insect eggs laid just below the fruit surface. For high-energy electron beam simulation, electrons penetrated up to 4.5 cm and the irradiation area occupied 60.2% of the whole area at single-side irradiation and 90.6% at double-side irradiation. For a single-side only gamma- and X-ray source simulation, the entire pineapple was irradiated and dose uniformity ratios (Dmax/Dmin) were 2.23 and 2.19, respectively. Even though both sources had all greater penetrating capability, the X-ray treatment is safer and the gamma-ray treatment is more widely used due to their availability. Conclusions: These results are invaluable for optimizing phytosanitary irradiation treatment planning of pineapple.

• Journal of the Korean institute of surface engineering
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• v.56 no.5
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• pp.299-308
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• 2023

In this study, phosphorus (P)-doped nickel cobaltite (P-NiCo₂O₄) and nickel-cobalt layered double hydroxide (P-NiCo-LDH) were synthesized on nickel (Ni) foam as a conductive support using hydrothermal synthesis. The thermal properties, crystal structure, microscopic surface morphology, chemical distribution, electronic state of the constituent elements on the sample surface, and electrical properties of the synthesized P-NiCo₂O₄ and P-NiCo-LDH samples were analyzed using thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The P-NiCo₂O₄ electrode exhibited a specific capacitance of 1,129 Fg^-1 at a current density of 1 Ag^-1, while the P-NiCo-LDH electrode displayed a specific capacitance of 1,012 Fg^-1 at a current density of 1 Ag-1. When assessing capacity changes for 3,000 cycles, the P-NiCo₂O₄ electrode exhibited a capacity retention rate of 54%, whereas the P-NiCo-LDH electrode showed a capacity retention rate of 57%.

• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.69-76
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• 2010

Prototype double-scattering Compton camera, which consists of three gamma-ray detectors, that is, two double-sided silicon strip detectors (DSSDs) as scatterer detectors and a NaI(Tl) scintillation detector as an absorber detector, could provide high imaging resolution with a compact system. In the present study, the energy resolution and the timing resolution of component detectors were measured, and the parameters affecting the energy resolution of the DSSD were examined in terms of equivalent noise charge (ENC). The energy resolutions of the DSSD-1 and DSSD-2 were, in average, $25.2keV{\pm}0.8keV$ FWHM and $31.8keV{\pm}4.6keV$ FWHM at the 59.5 keV peak of $^{241}Am$, respectively. The timing resolutions of the DSSD and NaI(Tl) scintillation detector were 57.25 ns FWHM and 7.98 ns FWHM, respectively. In addition, the Compton image was obtained for a point-like $^{137}Cs$ gamma source with double-scattering Compton camera. From the present experiment, the imaging resolution of 8.4 mm FWHM (angular resolution of $8.1^{\circ}$ FWHM), and the imaging sensitivity of $1.5{\times}10^{-7}$ (intrinsic efficiency of $1.9{\times}10^{-6}$) were obtained.