• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.519-528
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• 1994

Degradation problem due to long term service in machine or structure is now one of important problems in whole industrial field. In this study, pressure vessel steel, Cr-Mo steel, which was used more than 60,000 hours, was surface-modified by laser beam radiation for the improvement of fatigue strength. To find out optimum radiation condition, hardness, residual stress measurement and fatigue tests were carried out with the specimen of different radiation conditions. Experimental results show that micro-hardness values on the surface of the radiated specimens were approximately 2.2 times higher than those of un-radiated ones. In the depth direction of the specimen, hardness on the surface showed maximum value and was decreased at the inside the specimen. Different hardness values are due to the energy density Q which was absorbed by the specimen. Fatigue tests show that fatigue life was improved by the compressive residual stress after laser beam radiation. However, some specimens with differednt conditions show the shorter fatigue life. It means that laser beam radiation with optimum parameter can improve thae fatigue strength.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.360-360
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• 2011

In this work, SUS310S used for valve plate assembly was electron beam (EB) welded to determine the influence of the parametric conditions on the characteristics of the weld and to minimize porosity and micro-fissures among others. The evolution in the weld geometry and microstructure was examined as a function of the process conditions such as beam current and focusing current under a constant welding speed and accelerating voltage. The integrity of the EB welds in SUS310S was examined for defects (e.g. cracking, porosity, etc.), adequate penetration depth, and tolerable weld width deviation for the various welding conditions. Optical microscopy (OM), x-ray photoelectron spectroscopy analysis (XPS), scanning electron microscopy (SEM) and 3D micro-computed tomography (Micro-CT) for the cross section analysis of the electron beam welded SUS310S were utilized. The tensile strength and hardness were analyzed for the mechanical properties of the EB weld. At the 6 kV accelerating voltage, it was determined that a satisfactory penetration depth and desirable weld width deviation requires a beam current of 30 mA and a focusing current of 0.687 A at the welding speed of 25 mm/sec.

• The Journal of Korean Society for Radiation Therapy
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• v.5 no.1
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• pp.115-119
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• 1992

The beam characteristics and dosimetric measurements of the 6MV X-ray and 6MeV electron beam from a ML-6M linear accelerator are examined. The Percent Depth Dose(PDD) table and the tissue Maximum Ratio(TMR) table are taken from measurement as a function of the field size and the depth. The calculated TMR table from PDD table is compared with those from measurement. Other beam characteristics such as output factor, beam profile(including flatness, symmetry and penumbra), wedge, and the variation of Dmax are presented. All of these dosimetric measurements sufficiently characterized the beam to permit safe clinical use.

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.1
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• pp.65-69
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• 2010

High energy electron beams were to concentrically dose inside a tumor and more energy is a shape decreased of dose. Therefore, it is useful to radiation therapy of a tumor. Also high energy electron beams ionized into collision with a atom in structure material of tissue and it has big changes to dose distribution by multiple scattering. The study had to establish characteristic of electron beams from interaction of electron beams and materials. Experiment method was to measure dependence of electron beam central axis for depth dose curve, field flatness and symmetry and field size dependence. The results were able to evaluate data for a datum pint of electron beam. Also radiotherapy has to be considered for not only energy pencil of lines but characteristic, electron guide and isodose curves distribution.

• The Journal of Korean Society for Radiation Therapy
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• v.2 no.1
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• pp.87-92
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• 1987

The authors have intended to measure intrinsic dose distribution by Farmer dosimeter in irregularly shaped fields such as L, M, T,-shape model in order to determine dose inhomogeneity in those models. We made 2 off-axis points in each model and measured the depth dose at 1.5,5, and 9cm below surface. The results showed $1-3\%$ dose discrepancy between 2 points. We also measured the depth dose by geometric approximation and computer calculation in those models, and came to the conclusion that computer calculation using Clarkson's principle is simpler and the measurements are to the ideal data obtained by the experiment in those three models of irregularly shaped fields than those of geometric approximation method.

• Radiation Oncology Journal
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• v.2 no.2
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• pp.281-285
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• 1984

The authors have intended to measure intrinsic dose distribution by Farmer dosimeter in irregularly shaped fields such as L.M and T shape models in order to determine dose inhomogeneity in those models. We made 2 off·axis points in each model and measured the depth dose at 1.5, 5 and 9cm below surface. The results showed $l\~3\%$ dose discrepancy between 2 points. We also measured the depth dose by geometric approximation and computer calculation in those models, and came to the conclusion that computer calculation using Clarkson's principle is simpler and the measurements are closer to the ideal data obtained by the experiment in three models of irregularly shaped fields than those of geometric approximation method.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.180-187
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• 1998

One of the major difficulties in the seismic analysis of a dam-reservoir system is the treatment of the energy radiation in the upstream direction of the reservoir. In this paper a new transmitting boundary is presented that can model properly the radiation of energy in the far field direction of a semi-infinite reservoir with constant depth. In the newly developed method, effects of surface wave motion are taken into account and the reservoir-foundation interaction is approximately accounted for with an absorbing boundary condition. If a dam has vertical upstream face and the infinitely long reservoir maintains constant depth, then the proposed transmitting boundary can be directly coupled with the model of dam body. In present study, the dam body is assumed to behave elastically and modeled by finite element method. Seismic responses of a dam model are investigated using the newly developed transmitting boundary.

• Journal of Ship and Ocean Technology
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• v.7 no.2
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• pp.1-19
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• 2003

This paper introduces a unified theory for the radiation problem of adjacent multiple floating bodies. The particular case of interest is the multiple slender bodies that their centerlines are parallel. The infinite-and finite-depth unified theories for the single-body problem are extended to solve each sub-problem of multiple bodies. The present method is valid for deep water and moderate water depth, and applicable for individually floating bodies as well as multimaran-type vehicles. For the validation of the present method, the heave and pitch hydrodynamic coefficients for two adjacent ships are compared with the results of a three-dimensional method, and an excellent agreement is shown. The application includes the hydrodynamic coefficients and motion RAOs of four trimarans which have different longitudinal and transverse arrangements for sidehulls.

• Journal of Biomedical Engineering Research
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• v.27 no.6
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• pp.332-336
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• 2006

In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator for high energy electron beam therapy. The intensities of scintillating light from a fiber-optic radiation sensor are measured with different field size, electron beam energy and monitor unit of a clinical linear accelerator. To obtain percent depth dose(PDD), the amount of scintillating light is measured at different depth of polymethylmethacrylate(PMMA) phantom. Also the intensity of Cerenkov light is measured and characterized as a function of incident angle of electron beam and a subtraction method is investigated using a background optical fiber to remove a Cerenkov light.

• Journal of radiological science and technology
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• v.43 no.1
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• pp.9-14
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• 2020

Commercial plate bolus is generally used for treatment of surface tumor and required surface dose. We fabricated 3D-printed bolus by using 3D printing technology and usability of 3D-printed bolus was evaluated. RT-structure of contoured plate bolus in the TPS was exported to DICOM files and converted to STL file by using converting program. The 3D-printed bolus was manufactured with rubber-like translucent materials using a 3D printer. The dose distribution calculated in the TPS and compared the characteristics of the plate bolus and the 3D printed bolus. The absolute dose was measured inserting an ion chamber to the depth of 5 cm and 10 cm from the surface of the blue water phantom. HU and ED were measured to compare the material characteristics. 100% dose was distributed at Dmax of 1.5 cm below the surface when was applied without bolus. When the plate bolus and 3D-plate bolus were applied, dose distributed at 0.9 cm and 0.8 cm below the surface of the bolus. After the comparative analysis of the radiation dose at the reference depth, differences in radiation dose of 0.1 ~ 0.3% were found, but there was no difference dose. The usability of the 3D-printed bolus was thus confirmed and it is considered that the 3D-printed bolus can be applied in radiation therapy.