• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.19-26
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• 2017

Purpose: The application of density override is very important to minimize dose calculation errors by fiducial markers of metal material in proton treatment plan. However, density override with actual material of the fiducial marker could make problem such as inaccurate target contouring and compensator fabrication. Therefore, we perform density override with surrounding material instead of actual material and we intend to evaluate the usefulness of density override with surrounding material of the fiducial marker by analyzing the dose distribution according to the position, material of the fiducial marker and number of beams. Materials and Method: We supposed that the fiducial marker of gold, steel, titanium is located in 1.5, 2.5, 4.0, 6.0 cm from the proton beam's end of range using water phantom. Treatment plans were created by applying density override with the surrounding material and actual material of the fiducial marker. Also, a liver cancer patient who received proton therapy was selected. We located the fiducial marker of gold, steel, titanium in 0, 1.5, 3.5 cm from the proton beam's end of range and the treatment plans were created by same method with water phantom. Homogeneity Index(HI), Conformity Index(CI) and maximum dose of Organ At Risk(OAR) in Planning Target Volume(PTV) as the evaluation index were compared according to the material, position of the fiducial marker and number of beam. Results: The HI value was more decreased when density override with surrounding material of the fiducial marker was performed comparing with density override with actual material. Especially the HI value was increased when the fiducial marker was located farther from the proton beam's end of the range for a single beam and the fiducial marker's position was closer to isocenter for two or more beams. The CI value was close to 1 and OAR maximum dose was greatly reduced when density override with surrounding material of the fiducial marker was performed comparing with density override with actual material. Conclusion: Density override with surrounding material can be expected to achieve more precise proton therapy than density override with actual material of the fiducial marker and could increase the dose uniformity and target coverage and reduce the dose to surrounding normal tissues for the small fiducial markers used in clinical practice. Most of all, it is desirable to plan the treatment by avoiding the fiducial marker of metal material as much as possible. However, if the fiducial marker have on the beam path, density override of the surrounding material can be expected to achieve more precise proton therapy.

• Nuclear Engineering and Technology
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• v.55 no.12
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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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.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.4
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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.

• Proceedings of the KSME Conference
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• 2004.04a
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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%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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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.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.4
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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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• v.2 no.1
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.6
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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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.