• Progress in Medical Physics
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• v.10 no.3
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• pp.133-140
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• 1999

In this paper, as a preliminary study for developing a full 3D electron dose calculation algorithm, We developed 2.5D electron dose calculation algorithm by extending 2D pencil-beam model to consider three dimensional geometry such as air-gap and obliquity appropriately. The dose calculation algorithm was implemented using the IDL5.2(Research Systems Inc., USA), For calculation of the Hogstrom's pencil-beam algorithm, the measured data of the central-axis depth-dose for 12 MeV(Siemens M6740) and the linear stopping power and the linear scattering power of water and air from ICRU report 35 was used. To evaluate the accuracy of the implemented program, we compared the calculated dose distribution with the film measurements in the three situations; the normal incident beam, the 45$^{\circ}$ oblique incident beam, and the beam incident on the pit-shaped phantom. As results, about 120 seconds had been required on the PC (Pentium III 450MHz) to calculate dose distribution of a single beam. It needs some optimizing methods to speed up the dose calculation. For the accuracy of dose calculation, in the case of the normal incident beam of the regular and irregular shaped field, at the rapid dose gradient region of penumbra, the errors were within $\pm$3 mm and the dose profiles were agreed within 5%. However, the discrepancy between the calculation and the measurement were about 10% for the oblique incident beam and the beam incident on the pit-shaped phantom. In conclusions, we expended 2D pencil-beam algorithm to take into account the three dimensional geometry of the patient. And also, as well as the dose calculation of irregular field, the irregular shaped body contour and the air-gap could be considered appropriately in the implemented program. In the near future, the more accurate algorithm will be implemented considering inhomogeneity correction using CT, and at that time, the program can be used as a tool for educational and research purpose. This study was supported by a grant (＃HMP-98-G-1-016) of the HAN(Highly Advanced National) Project, Ministry of Health & Welfare, R.O.K.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.71-71
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• 2003

The study on magnetic field combined radiation therapy, as a new technique to modify the dose distributions using external magnetic field, has been investigated. The goal of the study is to develop the techniques for dose localization, as a particle beam, from the strong magnetic fields. In this study, in order to study the principle of dose deposition in external fields, as a basic approach, we have calculated approximately the paths of traveling electrons in water under external magnetic fields with numerical methods. The calculations are performed for a primary particle by cumulating the steps which are defined as small path lengths which energy loss can be ignored. In this calculation, the energy loss and direction change for a step was calculated by using total stopping power and Lorentz force equation respectively. We have examined the deflected paths of the electron through water as a function of external magnetic field and incident electron s energy. Since we did not take account of the multiple scattering effects for electrons through water, there are errors in this calculation. However, from the results we can explain the principle of dose variation and dose focusing for electron beams under strong magnetic fields in water.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.10-14
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• 2010

Biodiesel of 20% (BD20) and 100% (BD100), alterative fuels for tractor, were tested for its power and competitiveness in the various farm operations including plowing and rotary tilling in the paddy fields. No troubles such as engine ignition or abrupt stopping were monitored during the works of plowing, rotary tilling and travelling on the road. According to the tractor PTO test in accordance with OECD tractor PTO test codes, no significant PTO output difference was found between the three fuels. However, fuel consumption rates were different between the biodiesels and diesel fuel in the paddy works, where as biodiesel percentage increased more fuels were spent than the diesel fuel. The reason for this phenomenon seems came from density difference of the three fuels. Maximum fuel consumption difference occurred between BD100 and diesel fuel was about 10% in the plowing. More energy was spent on the rotary tilling operations than the plowing, where 35~40 % more fuel needed on rotary tilling than plowing. Of the exhaust gases, more $CO_2$ was discharged from diesel fuel than biodiesels, but more NOx from biodiesels and CO was hard to determine which fuel produce more amount.

• Progress in Medical Physics
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• v.30 no.4
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• pp.112-119
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• 2019

Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber. Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose. Results: The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively. Conclusions: An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.81-86
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• 2016

Background: For positron emission tomography (PET) application, cadmium zinc telluride (CZT) has been investigated by several institutes to replace detectors from a conventional system using photomultipliers or Silicon-photomultipliers (SiPMs). The spatial and energy resolution in using CZT can be superior to current scintillator-based state-of-the-art PET detectors. CZT has been under development for several years at the Korea Atomic Energy Research Institute (KAERI) to provide a high performance gamma ray detection, which needs a single crystallinity, a good uniformity, a high stopping power, and a wide band gap. Materials and Methods: Before applying our own grown CZT detectors in the prototype PET system, we investigated preliminary research with a developed discrete type data acquisition (DAQ) system for coincident events at 128 anode pixels and two common cathodes of two CZT detectors from Redlen. Each detector has a $19.4{\times}19.4{\times}6mm^3$ volume size with a 2.2 mm anode pixel pitch. Discrete amplifiers consist of a preamplifier with a gain of $8mV{\cdot}fC^{-1}$ and noise of 55 equivalent noise charge (ENC), a $CR-RC^4$ shaping amplifier with a $5{\mu}s$ peak time, and an analog-to-digital converter (ADC) driver. The DAQ system has 65 mega-sample per second flash ADC, a self and external trigger, and a USB 3.0 interface. Results and Discussion: Characteristics such as the current-to-voltage curve, energy resolution, and electron mobility life-time products for CZT detectors are investigated. In addition, preliminary results of gamma ray imaging using 511 keV of a $^{22}Na$ gamma ray source were obtained. Conclusion: In this study, the DAQ system with a CZT radiation sensor was successfully developed and a PET image was acquired by two sets of the developed DAQ system.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.156-164
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• 2003

STS316L had been used as the structural material for energy environmental facilities, because austenite stainless steels like 316L have superior mechanical properties of which toughness, ductility, corrosion resistant and etc. However, those welded structures are receiving severe damage due to increasing of the aged degradation. Most studies until now have been carried out against fatigue behaviors of weldments, and were not well studied on nondestructive evaluation methods. In this study, the fatigue crack propagation behavior of STS316L weldment usually used for vessels of the nuclear power plant was investigated. Also, the degradation characteristics of 316L stainless steel weldments were evaluated by the ultrasonic parameter such as ultrasonic velocity, attenuation factor and time-frequency analysis. The results of this study can be used as a basic data for the prediction of the fatigue crack life of weldments structures without disjointing or stopping service of structures in service.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.816-822
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• 2003

In this paper, we propose an efficient iteration control method with low complexity for Turbo TCM(Turbo Trellis Coded Modulation) decoding which will be used fur power-limited environment. As the decoding approaches the performance limit of a given turbo code, any further iteration results in very little improvement. Therefore, it is important to devise an efficient criterion to stop the iteration process and prevent unnecessary computations and decoding delay. This paper presents an efficient algorithm for turbo TCM decoding that can greatly reduce the delay and iteration number. The proposed method use adaptive iteration number according to the criterion using the extrinsic information variance parameter in turbo TCM decoding process. The simulation results show that the proposed technique effectively can reduce the decoding delay and computation with very little performance degradation.

• Journal of Magnetics
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• v.21 no.2
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• pp.183-186
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• 2016

In this study, we report on an investigation of proton radiation resistance of 410 martensitic stainless steels under 3 MeV proton with the doses ranging from $1.0{\times}10^{15}$ to $1.0{\times}10^{17}p/cm^2$ at the temperature 623 K. Vibrating sample magnetometer (VSM) and X-ray diffractometer (XRD) were used to study the variation of magnetic properties and structural damages by virtue of proton irradiation, respectively. VSM and XRD analysis revealed that the 410 martensitic stainless steels showed proton radiation resistance up to $10^{17}p/cm^2$. Proton energy degradation and flux attenuations in 410 stainless steels as a function of penetration depth were calculated by using Stopping and Range of Ions in Matter (SRIM) code. It suggested that the 410 stainless steels have the radiation resistance up to $5.2{\times}10^{-3}$ dpa which corresponds to neutron irradiation of $3.5{\times}10^{18}n/cm^2$. These results could be used to predict the maintenance period of SUS410 stainless steels in fission power plants.

• Analytical Science and Technology
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• v.7 no.4
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• pp.471-476
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• 1994

The capability of PIXE (Proton Induced X-ray Emission) method for the precision measurement of coating thickness has been tested by measuring several gold coated copper plates. Two different experimental methods are applied and compared. The results are compared with those by the weight measurement and proton RBS (Rutherford Backscattering Spectrometry). The advantage of the method is that it can be also used for the nondestructive thickness measurement of this layers on large-scaled samples or archeological samples which cannot be placed in a vacuum chamber.

• The Journal of Korean Society for Radiation Therapy
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• v.10 no.1
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• pp.11-22
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• 1998

The absolute absorbed dose can be determined according to the measurement conditions ; measurement material, detector, energy and calibration protocols. The purpose of this study is to compare the absolute absorbed dose due to the differences of measurement condition and calibration protocols for photon beams. Dosimetric measurements were performed with a farmer type PTW and NEL ionization chambers in water, solid water, and polystyrene phantoms using 6MV photon beams from Siemens linear accelerator. Measurements were made along the central axis of $10{\times}10cm$ field size for constant target to surface distance of 100cm for water, solid water and polystyrene phantom. Theoretical absorbed dose intercomparisons between TG21 and IAEA protocol were performed for various measurement combinations on phantom, ion chamber, and electrometer. There were no significant differences of absorbed dose value between TG2l and IAEA protocol. The differences between two protocols are within $1\%\;while\;the\;average\;value\;of\;IAEA\;protocol\;was\;0.5\%$ smaller than TG2l protocol. For the purpose of comparison, all the relative absorbed dose were nomalized to NEL ion chamber with Keithley electrometer and water phantom, The average differences are within $1\%,\;but\;individual\;discrepancies\;are\;in\;the\;range\;of\;-2.5\%\;to\;1.2\%$ depending upon the choice of measurement combination. The largest discrepancy of $-25\%$ was observed when NEL ion chamber with Keithley electrometer is used in solid water phantom. The main cause for this discrepancy is due to the use of same parameters of stopping power, absorption coefficient, etc. as used in water phantom. It should be mentioned that the solid water phantom is not recommended for absolute dose calibration as the alternative of water, since absorbed dose show some dependency on phantom material other than water. In conclusion, the trend of variation was not much dependent on calibration protocol. However, It shows that absorbed dose could be affected by phantom material other than water.