• Progress in Medical Physics
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• v.23 no.1
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• pp.48-53
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• 2012

The pencil beam convolution (PBC) algorithms in radiation treatment planning system have been widely used to calculate the radiation dose. A new photon dose calculation algorithm, referred to as the anisotropic analytical algorithm (AAA), was released for use by the Varian medical system. The aim of this paper was to investigate the difference in dose calculation between the AAA and PBC algorithm using the intensity modulated radiation therapy (IMRT) plan for lung cancer cases that were inhomogeneous in the low density. We quantitatively analyzed the differences in dose using the eclipse planning system (Varian Medical System, Palo Alto, CA) and I'mRT matirxx (IBA, Schwarzenbruck, Germany) equipment to compare the gamma evaluation. 11 patients with lung cancer at various sites were used in this study. We also used the TLD-100 (LiF) to measure the differences in dose between the calculated dose and measured dose in the Alderson Rando phantom. The maximum, mean, minimum dose for the normal tissue did not change significantly. But the volume of the PTV covered by the 95% isodose curve was decreased by 6% in the lung due to the difference in the algorithms. The difference dose between the calculated dose by the PBC algorithms and AAA algorithms and the measured dose with TLD-100 (LiF) in the Alderson Rando phantom was -4.6% and -2.7% respectively. Based on the results of this study, the treatment plan calculated using the AAA algorithms is more accurate in lung sites with a low density when compared to the treatment plan calculated using the PBC algorithms.

• Journal of Science Education
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• v.38 no.3
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• pp.670-690
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• 2014

The purpose of this study was to analyze paper and pencil test items of life science I in high school to diagnose problems of the test items developed by teachers, and to provide some implication for better assessment. 690 selection-type items and 162 supply-type items in life science I were collected from 10 general high schools. In the analysis of test items, the ratio of the selection-type item and the supply-type item was 81:19 in the number of items based on item type, while the ratio was 74.4:25.6 in the distribution of marks, indicating that the distribution of marks compared to the number of items was higher in the supply-type items. In the analysis by the Bloom's revised taxonomy of educational objectives, the items of 'conceptual knowledge' in the knowledge and those of 'understanding' in the cognition process were shown most in both the selection-type item and the supply-type item. In the analysis by the science assessment frameworks of NAEA, the items of 'knowledge' were shown 9 times more than those of 'inquiry'. When compared to the level of difficulty presented in the two-way specification table and the percentage of correct answers in the selection-type item, the concurrence was 41.5%. When compared to the ratio of number of items based on the item type of the supply-type items, the short-answer items were 34.0%, the descriptive items were 61.1%, and the drawing items were 4.9%. The drawing items were mainly developed in the unit of 'Cells and Continuity of Life'. When the descriptive items were classified by the acceptance of response, all the items were 'response restricted' type, and the items of 'restricted in content range' type among them were highest. When the items were classified by presentation of data, the items of 'presentation of data' type were highest(65.4%), and when classified by type of question, the items of 'knowledge description' type were highest(80.4%). In conclusion, it is needed to develop items belonging to 'inquiry' area more in the school, and to increase the ratio of the descriptive items, presenting various types of items.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.586-592
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• 2017

In this study, acrylic resins with solids content of 75% were prepared by addition polymerization of n-butyl acrylate (BA), methyl methacrylate (MMA), 2-hydroxypropyl methacrylate (HPMA) and acetoacetoxyethyl methacrylate (AAEM) monomers. At this time, the glass transition temperature ($T_g$) of the acrylic resin was changed to 20, 30 and $40^{\circ}C$, and the hydroxyl value (OH value) was changed to 60, 90 and 120. As a result, the viscosity of acrylic resin increased with increasing $T_g$ and hydroxyl (OH) value. The synthesized acrylic resin was designed to have a high cross-link density to maintain high elasticity and high durability. The crosslinked acrylic resin was used to prepare an acrylic urethane clear coating by curing reaction with a block isocyanate (Desmodur BL-3175). The physical properties of the clear paints were analyzed by measuring viscosity, adhesion, pencil hardness and $60^{\circ}$ specular gloss. Acrylic urethane clear coatings were prepared as specimens and evaluated for various properties to be applied as top coatings for coil coating. The prepared coatings were excellent in adhesion, excellent in $60^{\circ}$ specular gloss and pencil hardness, and eco-friendly.

• Journal of Radiation Protection and Research
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• v.21 no.2
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• pp.125-129
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• 1996

The energy response of HPGe detector for low energy Photons was determined by using three Monte Carlo codes. MCNP4A. EGS4, and CYLTRAN in ITS3. In this study. bare HPGe detector$(100 mm^2{\times}10mm)$ was used and a pencil beam was incident perpendicularly on the center of the detector surface. The photopeak efficiency, $K_{\alpha}$ and $K_{\beta}$ escape fractions were calculated as a function of incident X-ray energies ranging from 12 to 60 keV in 2-keV increments. Since the Compton. elastic. ana penetration fraction were negligible in this energy range. they were ignored in the calculation. Although MCNP. EGS, and CYLTRAN codes calculated slightly different energy response of HPGe detector for low energy Photons, it appears that the three Monte Carlo codes can Predict the low energy Photon scattering Processes accurately. The MCNP results, which are generally known as to be less accurate at low energy ranges than the EGS and ITS results. are comparable to the results of EGS and ITS and are applicable to the calculation of the low energy response data of a detector.

• The Journal of Korean Society for Radiation Therapy
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• v.14 no.1
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• pp.175-186
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• 2002

The purpose of this study is directly measure and evaluate about absorbed dose change according to nominal energy and electron cone or medical accelerator on isodose curve, percentage depth dose, contaminated X-ray, inhomogeneous tissue, oblique surface and irradiation on intracavitary that electron beam with high energy distributed in tissue, and it settled standard data of hish energy electron beam treatment, and offer to exactly data for new dote distribution modeling study based on experimental resuls and theory. Electron beam with hish energy of $6{\sim}20$ MeV is used that generated from medical linear accelerator (Clinac 2100C/D, Varian) for the experiment, andwater phantom and Farmer chamber md Markus chamber und for absorbe d dose measurement of electron beam, and standard absorbed dose is calculated by standard measurements of International Atomic Energy Agency(IAEA) TRS 277. Dose analyzer (700i dose distribution analyzer, Wellhofer), film (X-OmatV, Kodak), external cone, intracavitary cone, cork, animal compact bone and air were used for don distribution measurement. As the results of absorbed dose ratio increased while irradiation field was increased, it appeared maximum at some irradiation field size and decreased though irradiation field size was more increased, and it decreased greatly while energy of electron beam was increased, and scattered dose on wall of electron cone was the cause. In percentage depth dose curve of electron beam, Effective depth dose(R80) for nominal energy of 6, 9, 12, 16 and 20 MeV are 1.85, 2.93, 4.07, 5.37 and 6.53 cm respectively, which seems to be one third of electron beam energy (MeV). Contaminated X-ray was generated from interaction between electron beam with high energy and material, and it was about $0.3{\sim}2.3\%$ of maximum dose and increased with increasing energy. Change of depth dose ratio of electron beam was compared with theory by Monte Carlo simulation, and calculation and measured value by Pencil beam model reciprocally, and percentage depth dose and measured value by Pencil beam were agreed almost, however, there were a little lack on build up area and error increased in pendulum and multi treatment since there was no contaminated X-ray part. Percentage depth dose calculated by Monte Carlo simulation appeared to be less from all part except maximum dose area from the curve. The change of percentage depth dose by inhomogeneous tissue, maximum range after penetration the 1 cm bone was moved 1 cm toward to surface then polystyrene phantom. In case of 1 cm and 2 cm cork, it was moved 0.5 cm and 1 cm toward to depth, respectively. In case of air, practical range was extended toward depth without energy loss. Irradiation on intracavitary is using straight and beveled type cones of 2.5, 3.0, 3.5 $cm{\phi}$, and maximum and effective $80\%$ dose depth increases while electron beam energy and size of electron cone increase. In case of contaminated X-ray, as the energy increase, straight type cones were more highly appeared then beveled type. The output factor of intracavitary small field electron cone was $15{\sim}86\%$ of standard external electron cone($15{\times}15cm^2$) and straight type was slightly higher then beveled type.

• Progress in Medical Physics
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• v.18 no.4
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• pp.226-232
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• 2007

We studied a Monte Carlo simulation of the proton beam delivery system at the National Cancer Center (NCC) using the Geant4 Monte Carlo toolkit and tested its feasibility as a dose verification framework. The Monte Carlo technique for dose calculation methodology has been recognized as the most accurate way for understanding the dose distribution in given materials. In order to take advantage of this methodology for application to external-beam radiotherapy, a precise modeling of the nozzle elements along with the beam delivery path and correct initial beam characteristics are mandatory. Among three different treatment modes, double/single-scattering, uniform scanning and pencil beam scanning, we have modeled and simulated the double-scattering mode for the nozzle elements, including all components and varying the time and space with the Geant4.8.2 Monte Carlo code. We have obtained simulation data that showed an excellent correlation to the measured dose distributions at a specific treatment depth. We successfully set up the Monte Carlo simulation platform for the NCC proton therapy facility. It can be adapted to the precise dosimetry for therapeutic proton beam use at the NCC. Additional Monte Carlo work for the full proton beam energy range can be performed.

• Journal of Gifted/Talented Education
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• v.24 no.3
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• pp.445-462
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• 2014

The purpose of the present study is to compare paper and pencil test utilized to identify gifted students so far to the recently introduced teacher observation-recommendation system. More specifically, this study compared intelligence, career patterns, and self- regulated learning abilities of gifted students who were identified through those two different identification system to explore the possibility of the newly introduced teacher observation-recommendation system. The results show that there was no significant difference in the aspect of overall IQ score. However, students who were identified through the observation-recommendation system showed significantly higher scores at some subscores of intelligence test, such as vocabulary application, comprehension, and schematization. In the aspects of career patterns, about 72% of gifted students who were identified through the previous paper and pencil test belonged to the 'investigative' category of Holland. But more diverse career patterns such as enterprising, social, realistic, conventional including investigative categories were found in those students who were identified by the observation-recommendation system. There were also significant differences in the self-regulated learning abilities between two groups of students. Practical implications of the study were discussed in depth.

• Journal of Gifted/Talented Education
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• v.20 no.1
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• pp.107-130
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• 2010

The purpose of this study is to investigate the characteristics that indicate scientifically gifted students by analyzing the verbal interactions in developmental biology inquiry-experimental classes. The subjects were 20 first-grade middle school students who were participating in SNU Science Gifted Education Center. In these experimental classes which were developed based on the CPS Model, we conducted a total of four experimental sessions of small group discussions, and the students' verbal interactions were both taped and video recorded, and observed. From the transcriptions, the patterns of question-answer and the characteristics of scientifically gifted students were analyzed. In the case of question-answer patterns, thinking questions appeared 3~6 times more frequently than the standard information questions. Especially, the case of experimental class I showed 40% more thinking questions as well as standard information questions that the other 3 classes. Through the results of analysing verbal interactions, we were able to find more detailed aspects to creativity that were not identifiable in paper-pencil examinations, as well as affective characteristics such as task commitment and leadership. We believe our findings upon inquiry will be of substantial significance in substituting for the paper-pencil examination in distinguishing and selecting scientifically gifted students.

• Journal of The Korean Association For Science Education
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• v.25 no.2
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• pp.173-183
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• 2005

In this study, we questioned what assessment types and scoring methods of science performance assessment(SPA) were being used in middle and high school, and how much these SPA scores were reliable(generalizable). To answer these questions, SPA data obtained from the seven schools were classified according to assessment type and scoring method. Based upon this classification, we analyzed the reliability by applying generalizability theory. The result, from the classification of assessment type and scoring method, showed that SPA types of the seven schools were divided into two types: paper-pencil type and task type. Paper-pencil type included answer(content)-restricted essay-type test solely. Task type has two parts: process and outcome assessment. As the results of analyzing scoring methods of the seven schools, there were two cases in the way of scoring methods: one case is scoring all essay-type items and performance tasks by one teacher, the other is scoring assigned performance tasks by two teachers. But the case of scoring assigned essay-type items or the case of cross scoring by two or more teachers were not found. The findings of the reliability analysis are as follows: (1) Effect of essay-type item to SPA score was larger than that of performance task. (2) There was remarkable difference among the seven schools' interaction effect of person and rater in scoring performance tasks. (3) Most of generalizability(reliability) coefficients of SPA for the seven schools were smaller than the acceptable generalizability coefficient(0.80). Therefore, the population of statistical parameters such as number of item, task and rater, should be increased for approaching the acceptable generalizability level.

• Restorative Dentistry and Endodontics
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• v.26 no.5
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• pp.418-435
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• 2001

Root canal preparation process is of utmost importance in successful treatment of root canal. Also, one of the most important purpose of the root canal preparation is to enlarge the root canal three dimensionally without changing the curvature of the root canal However as the curvature of the root canal increases, there are many difficulties involved in formation of optimum root canal. Therefore in order to solve the above mentioned problems, new developments in methods of root canal preparation and equipments for such purposes were made. Recently, vigorous studies about newly introduced engine-driven nickel-ti-tanium rotary file are conducted. As shown in research results to dates, it is well established that the use of nickel-titanium file is better suited for curved root canal than stainless steel file in maintaining the curvature or root canal and reducing the deformation of root canal. However it is also acknowledged that there are a few discrepancies in research results according to protocol, due to failure to remove variables in experiments. In addition, although it is recommended by the manufacturer that the GT rotary file should maintain a low rotational speed of 150~350rpm and 'light pressure' as light as not to break the lead of a pencil, academic studies about the vertical force which is not yet standardized are not sufficiently explored. Therefore, this research devised and utilized a special research equipment to standardize the appropriate range of vertical force for GT rotary file through experiments by breaking of the lead of a pencil as expressed by the manufacturer and to accurately measure factors involved through repeating and recreating the environment of root canal preparation. Forming nine experimental groups by varying the vertical forces (150g. 220g, 300g) and rpm (150rpm, 250rpm, 350rpm), the effects of changing vertical forces and rpm on working efficiency were measured in terms of time expended in root canal preparation by crown-down method using a transparent resin block with 35 degree curvature and GT rotary file (z-test). The following research using this special research equipment that involved nine experimental groups and varying the vertical force for root canal preparation from 300g which is within the normal vertical force range to 700g and 1000g which fall outside the normal rpm range. The results were as follows : 1. Analysis of the experiment results revealed that the time spent in root canal preparation decreased as the vertical forces and rpm increased (p<0.05). Also, the effects of rpm were greater than those of the vertical forces within the normal vertical force range ($\beta$-weight test). 2. Observation of the deformation of GT rotary file revealed that deformation increases in a direct correlation with the vertical force increase and in a reverse correlation with the rpm decrease. In the case of the vertical forces close to the normal range, the probability of GT rotary file deformation were quite different depending on the rpm changes. In the case of greater vertical forces, the occurrences of deformation of the file were more frequent regardless of the rpm changes. 3. Deformation and breakage of file were also commonly observed in the expended time measurement experiments and GT rotary file deformation experiments in which low speed rpm (150rpm) was used and at the curved portion of the resin block.