• 대한방사선치료학회지
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• 제29권1호
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• pp.19-26
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• 2017

목 적: 양성자 치료계획에서 metal 재질의 fiducial marker에 의한 선량 계산오차를 최소화하려면 density override의 적용은 매우 중요하다. 하지만 실제 metal 재질로 density override을 할 경우 정확한 contouring 및 range compensator 제작에 어려움이 있기에 본 연구에서는 fiducial marker의 주변 재질로 density override를 시행하고 fiducial marker의 위치, 재질, beam의 개수에 따른 선량분포를 비교, 분석하여 평가하고자 한다. 대상 및 방법: Water phantom을 이용하여 fiducial marker의 위치를 proton beam의 최대 비정 끝에서부터 1.5, 2.5, 4.0, 6.0 cm로 설정하고 재질로는 gold, steel, titanium으로 설정하여 실제 metal 재질 및 주변 재질로 density override를 적용한 치료계획을 세웠다. 또한 본원에서 양성자치료를 받은 간암 환자 1명을 선정하여 proton beam의 최대 비정 끝에서부터 0, 1.5, 3.5 cm로 설정하고 재질로는 gold, steel, titanium으로 설정하여 치료계획을 세웠다. Fiducial marker의 재질, 위치 및 beam의 개수에 따른 PTV 내에 Homogeneity Index(HI), Conformity Index(CI), 종양에 가장 근접한 Organ At Risk(OAR)인 Esophagus의 maximum dose을 평가 지표로 설정하고 비교 분석하였다. 결 과: Water phantom 및 간암 환자를 대상으로 한 치료계획에서 fiducial marker의 위치에 따른 Homogeneity Index를 분석한 결과 실제 metal 재질로 density override 했을 때보다 주변 재질로 density override했을 때 Homogeneity Index가 감소했으며 주변 재질의 density override에서 하나의 beam에 대해서는 최대 비정 끝에서 멀리 위치할수록, 두 개 이상의 beam에서는 isocenter에 가까이 위치할수록 Homogeneity Index가 증가하였다. Fiducial marker의 위치에 따른 Conformity Index 및 종양 주위 OAR의 maximum dose를 분석한 결과 주변 재질로 density override 했을 때 Conformity Index는 1에 가까웠으며 OAR의 maximum dose는 크게 감소했다. 결 론: 일반적으로 임상에서 사용하는 작은 fiducial marker에 대해서 실제 metal 재질이 아닌 주변 재질로 density override 했을 때 선량 균등도 및 target coverage를 높이는 동시에 주변 정상조직에 대한 선량을 줄일 수 있었다. 따라서 fiducial marker을 최대한 피해서 치료계획을 세우는 것이 바람직하지만 beam path 상에 fiducial marker가 있는 경우 주변 재질의 density override 시행함으로써 보다 정밀한 양성자 치료 효과를 기대할 수 있을 것으로 사료된다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4685-4694
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• 2023

The ability to calculate the material density sensitivity coefficients of power with respect to the material density has broad application prospects for accelerating Monte Carlo-Thermal Hydraulics iterations. The second-order material density sensitivity coefficients for the general Monte Carlo score have been derived based on the differential operator sampling method in this paper, and the calculation of the sensitivity coefficients of cell power scores with respect to the material density has been realized in continuous-energy Monte Carlo code RMC. Based on the power-density sensitivity coefficients, the sensitivity coefficients of power scores to some other physical quantities, such as power-boron concentration coefficients and power-temperature coefficients considering only the thermal expansion, were subsequently calculated. The effectiveness of the proposed method is demonstrated in the power-density coefficients problems of the pressurized water reactor (PWR) moderator and the heat pipe reactor (HPR) reflectors. The calculations were carried out using RMC and the ENDF/B-VII.1 neutron nuclear data. It is shown that the calculated sensitivity coefficients can be used to predict the power scores accurately over a wide range of boron concentration of the PWR moderator and a wide range of temperature of HPR reflectors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.489-492
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• 1997

Partial discharge characteristics of normal butyl acrylate grafted low density polyethylenes were investigated by an ultrasonic sensor made of ceramic piezoelectric material. It was found that the partial discharging activities in normal butyl acrylate grafted low density polyethylenes were considerably suppressed compared to those in plain low density polyethylene. It was found that acrylic acid grafted polyethylene was more effective than normal butyl acrylate grafted low density polyethylene.

• 한국산업융합학회 논문집
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• 제6권4호
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• pp.367-371
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• 2003

In order to determine the effective way of measuring the Mode I stress intensity factor for a material containing a two-dimensional surface crack by means of the alternating current potential drop(ACPD) technique, the change in magnetic flux density between crack surfaces and above the specimen surface due to load was studied theoretically. The magnetic flux density in the air between crack surfaces is uniform and above the specimen surface is not changed by increasing the load in the material. Therefore, the change in potential drop due to load in a measuring system which was designed to induce a large amount of electro-motive force was caused by the change in internal inductance of material, the change in the mutual inductance between internal inductance of material and measuring system and the change in the mutual inductance between internal inductance of material and power supply line.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.132-137
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• 2004

In this work, effects of hyper-elastic rubber material properties on the indentation load-deflection curve and subindenter deformation are first examined via [mite element (FE) analyses. An optimal data acquisition spot is selected, which features maximum strain energy density and negligible frictional effect. We then contrive two normalized functions. which map an indentation load vs. deflection curve into a strain energy density vs. first invariant curve. From the strain energy density vs. first invariant curve, we can extract the rubber material properties. This new spherical indentation approach produces the rubber material properties in a manner more effective than the common uniaxial tensile/compression tests. The indentation approach successfully measures the rubber material properties and the corresponding nominal stress.strain curve with an average error less than 3%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.574-574
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• 2005

To found out the degradation characteristic of transformer insulation, insulation material was depisited into transformer oil and heated. Due to the thermal stress which added to insulation, the density of carbon dioxide which included in transformer oil was mesured by using the gas density detection equipment of gas sensor and air circulation method. As a result, it didn't match with the transformer supervision standard. But it was found that as thermal stress increased, the density of carbon dioxide propertionally increased.

• 한국농공학회지
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• 제36권4호
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• pp.103-116
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• 1994

The objective of this study was to determine the criteria for density and moisture content measurements made with a nuclear density meter on common materials in the construction field. The study also sought to test a full-type nuclear density meter in controlling the density of overlay layers( 2.5~5.0cm). In order to determine the accuracy and reliablility of nuclear guage measurements made on construction materials, laboratory and field tests were conducted. Wooden blocks( 65 x 45 ${\times}$ 50 cm) and a special steel compactor( 4.7kg) were constructed in order to carry out tests which were conducted on three different materials; coarse gramed soil, fine grained soil, and AC material. Throughout all laboratory and field tests, the nuclear density and moisture content were determined using Humboldt 5OOLP nuclear gauge. The tests on subgrade material entailed obtaining density measurements by means of both the sand replacement method and the nuclear density meter. The results of the sand replacement method were then compared to the readings recorded bu the meter. As in the subgrade material tests, density measurements made during AC pavement tests were also determined using the unclear meter in addition to a second means; through the core method. The meter readings and core densties were compared as was done in the tests on subgrade materials. The correlation between the results of the sand replacement test( also, the core method) and meter readings on subgrade material was then determined. Sirnilarly, the observed results were then analyzed through linear regression. The tests to determine thin-lift density by means of a full-type nuclear density meter also conducted on the overlay layers( about 4. 8cm thickness) above AC pavements at road construction sities in Korea.

• International Journal of Precision Engineering and Manufacturing
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• 제2권1호
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• pp.18-25
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• 2001

Electrolytic polishing is the anodic dissolution process in the transpassive state. It removes non-metallic inclusion and improves mechanical and corrosion resistance of stainless steel. If there is a Bailby layer, it will be removed and the true structure of the surface will be restored. Electrolytic polishing is normally used to remove a very thin layer of material from the surface of metal object. A new electrolyte composed of phosphoric, sulfuric and distilled water has been developed in this study. Two current density, high & low current density regions, have been applied in this study. In this study, In the region of high current density, there is no plateau region but excellent electrolytic polishing effect can be accomplished in short machining time because material removel process and leveling process occur simultaneously. In the low current density region, there can be found plateau region. The material removal process and leveling process occur successively. The aim of this work is to determine electrolytic polishing for stainless steel in terms of high & low current density and workpiece surface roughness.

• 대한기계학회논문집B
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• 제33권6호
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• pp.443-453
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• 2009

The Rayleigh-Taylor instability, the bubble rising in both partially and fully filled containers and the droplet splash are simulated by an in-house solution code(PowerCFD), which are typical benchmark problems among multiphase flows with material interface due to density difference. The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The present results are compared with other numerical solutions found in the literature. It is found that the present method simulates efficiently and accurately complex free surface flows such as multiphase flows with material interface due to both density difference and instability.

• 전기학회논문지
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• 제65권5호
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• pp.825-830
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• 2016

The purpose of this study optimizes the conditions of PLA printing material for 3D printer. Deltabot type 3D printer is used. The ranges of printing temperature, printing speed, and infill density are $195{\sim}215^{\circ}C$, 10~70mm/sec, and 10~100% respectively. From the results of printing temperature, printing quality is almost same every printing temperature. From the results of printing speed and infill density, printing quality is excellent under 40mm/sec, and over 50% respectively. Surface roughness is $2.28{\mu}mRa$ at $205^{\circ}C$, 10mm/sec, 100%, and is $5.93{\mu}mRa$ at $205^{\circ}C$, 70mm/sec. Surface roughness is directly proportional to the printing speed, and is inversely proportional to the infill density. Objects fabricated PLA printing material adhere bed at room temperature.