• Progress in Medical Physics
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• v.27 no.4
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• pp.196-202
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• 2016

We aim to develop the breast bolus by using a 3D printer to minimize the air-gap, and compare it to commercial bolus used for patients undergoing reconstruction in breast cancer. The bolus-shaped region of interests (ROIs) were contoured at the surface of the intensity-modulated radiation therapy (IMRT) thorax phantom with 5 mm thickness, after which the digital imaging and communications in mdicine (DICOM)-RT structure file was acquired. The intensity-modulated radiation therapy (Tomo-IMRT) and direct mode (Tomo-Direct) using the Tomotherapy were established. The 13 point doses were measured by optically stimulated luminescence (OSLD) dosimetry. The measurement data was analyzed to quantitatively evaluate the applicability of 3D bolus. The percentage change of mean measured dose between the commercial bolus and 3D-bolus was 2.3% and 0.7% for the Tomo-direct and Tomo-IMRT, respectively. For air-gap, range of the commercial bolus was from 0.8 cm to 1.5 cm at the periphery of the right breast. In contrast, the 3D-bolus have occurred the air-gap (i.e., 0 cm). The 3D-bolus for radiation therapy reduces the air-gap on irregular body surface that believed to help in accurate and precise radiation therapy due to better property of adhesion.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.272-277
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• 2001

NiO-doped $WO_3$ thick films were prepared by a screen printing technique. The electrical Property and microstructure of the films were investigated with the partial pressure of oxygen and the amount of NiO. The grain size of NiO-doped $WO_3$ was smaller than that of undoped $WO_3$ but the grain sixte of 0.1, 1, 10 mol% NiO-doped$ WO_3$ were nearly the same. The electrical conductance of the $WO_3$ thick films decreased with the oxygen partial pressure, and increased with the amount of NiO to the limit of solid solution. The variation of the electrical conductance with temperature is not so large in the extrinsic region, but it changed rapidly in the intrinsic region. The conductance decreased with adsorption of oxygen in the intermediate range between the extrinsic and intrinsic region.

• Journal of the Korea Institute of Building Construction
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• v.20 no.2
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• pp.199-212
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• 2020

In evaluating the competitiveness of construction companies and their development strategies, patents are a useful and objective source of technical information. In this study, the cutting-edge technologies of construction industries of China, Japan, and South Korea were investigated based on the data of patent applications filed by a total of 15 construction companies (five companies from each country). The related technologies were classified into six core technology groups based on their keywords. After that, we used four patent analysis methods: time series analysis, IP (Intellectual Property) emergence level analysis, spiral module analysis, and OS (Object-Solution) Matrix analysis, to identify the promising technologies/vacant technologies for global construction companies in China, Japan, and South Korea, and to analyze the technical competitiveness of the three countries. The findings of this study showed that each country can claim a relative technological advantage over the others. Overall, 3D printing and offsite construction technology, data acquisition technology, AR and VR technology are expected to be promising in the Asian region. The present study contributes to the body of knowledge by expanding our understanding of technological innovation for the competitiveness of companies and the technology development strategies pursued by the construction industries of China, Japan, and South Korea.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.4
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• pp.1-8
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• 2013

High loading of printing and writing grades with fillers has many advantageous aspects in papermaking because it allows decreasing fiber use and reducing manufacturing cost. High loading technology, however, has some disadvantageous aspects as well. It decreases physical properties of papers, especially strength properties. The problem associated with high loading can be reduced by applying surface sizing starch solution onto paper surface. It is important to control the penetration of the surface sizing starch solution into paper web to obtain the desired property improvement. In this study, the effect of the addition of two polymers into starch solution on paper properties has been examined. PVOH and polyDADMAC were used as polymeric additives for surface sizing with oxidized starch. Viscosity of starch solutions and surface roughness of dried starch films on glass slides showed that some interactions between polymeric additives and oxidized starch have been occurred and the most extensive interaction with starch solution was obtained with high molecular weight polyDADMAC. Low molecular weight PVOH was most effective in improving folding endurance and internal bond strength. On the other hand, polymer addition showed no effect on surface strength of paper. This indicates that not the level of starch holdout but the bonding strength of starch itself has predominant influence on surface strength of paper.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.607-612
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• 2017

Recently, additive manufacturing (AM) technology, also known as 3D printing technology, has attracted attention as an innovative production method to fabricate functional components having complex shapes with saving materials. In particular, a fabrication of poly lactic acid (PLA) parts through a fused deposition modeling (FDM) technique has attracted much attention in the medical field. In this paper, an experimental study on the identification of dominant process parameters influencing mechanical properties of PLA parts fabricated by the FDM process is conducted, and their optimal values for maximizing the mechanical properties are obtained. Three process parameters are considered in this research, namely, layer thickness, a part orientation and in-fill. It is known that thin layer thickness, part orientation diagonal to the tension direction, and full in-fill are optimal conditions to maximize the mechanical properties.

• Journal of the Semiconductor & Display Technology
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• v.19 no.1
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• pp.79-84
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• 2020

Unlike a printing process, it is difficult to pattern organic thin films in the longitudinal (coating) direction using a coating process. In this paper, we have investigated the feasibility of patterning organic thin films using needles. To this end, we have slot-coated an aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution in the form of a fine stripe or large area and then applied the dual needle; one for discharging the main solvent of the underlying thin film and the other for sucking the dissolved thin film. We have found that the pattern width and depth increase as the moving speed of the plate decreases. However, it is observed that the sidewall slope is very gentle (the length of the slope is of the order of 200 ㎛) due to the fact that the discharged main solvent is widely spread and then isotropic etching occurs. With this scheme, we have also demonstrated that a fine stripe can be obtained by scanning the dual needle closely. To demonstrate its applicability to solution-processable organic light-emitting diodes (OLEDs), we have also fabricated OLED with the patterned PEDOT:PSS stripe and observed the insulation property in the strong light-emitting stripe.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.465-470
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• 2020

Heterolayered K(Ta,Nb)O₃/Pb(Zr,Ti)O₃ thin films on Pt/Ti/SiO₂/Si substrates were prepared by a sol-gel process and spin-coating method. The structural and electrical properties were measured to investigate the possibility of application as an electrocaloric effect device. All specimens exhibited dense and uniform cross-sectional structures without pores, and the average thickness of the specimen coated six times was approximately 394 nm. Curie temperatures were observed at 5℃ or less in type-I and 10℃ in type-II specimens, respectively. Type-II specimens coated 6 times showed a relative dielectric constant of 758 and remanent polarization of 9.71 μC/㎠ at room temperature. The maximum electrocaloric effect occurred between 20 and 25℃, slightly higher than their Curie temperature, and the electrocaloric property (ΔT) of the type-II specimens coated 6 times was approximately 1.2℃ at room temperature.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.3
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• pp.74-83
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• 1998

The phenomenon of decrease in sizing efficiency when the stock temperature is increased is well recognized as summer sizing, and this is believed to be caused by uneven distribution of sizing agents on paper surface most often incurred by coagulation of sizing agents. When unevenly sized paper is used as coating base stock, nonuniform consolidation of the coating layer may result, which, in turn, causes uneven distribution of binder on coating surface. This causes nonuniform ink absorption to produce print mottle. In this study the effects of simple or polymeric electrolytes, storage temperature and time on the coagulation of cationic dispersed rosin size were investigated using a turbidity measurement method which was verified to correlate well with the particle size of rosin emulsion or its coagulates. Handsheets sized with rosin dispersions coagulated under various conditions were prepared and their sizing degree and coated paper properties including gloss and ink density were examined. The relationship between the sizing nonuniformity of coated papers and its ink absorption property was evaluated. Turbidity of rosin emulsion increased as the storage temperature and time were increased. Addition of simple or polymeric electrolytes caused reduction in $zeta$ -potential of the rosin dispersion and accelerated the coagulation tendency substantially. Reversion of the $zeta$ -potential of rosin dispersion, however, did not occur when coagulation was induced with simple electrolytes. On the other hand, addition of an anionic polyelectrolyte reversed the $zeta$ -potential of the flocculated rosin dispersion. This indicated that electrical double layer compaction and bridging flocculation were coagulation mechanisms for simple and polymeric electrolytes, respectively. Sizing degree decreased as coagulation of rosin was increased. Paper gloss, ink gloss and ink density were increased when sizing degree of base stock was increased most probably due to prevention of base paper swelling and increased binder migration to coating surface. This suggested that uneven printing ink density occurred when uneven sizing development was induced by coagulation of rosin particles.

• Progress in Medical Physics
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• v.30 no.1
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• pp.32-38
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• 2019

Purpose: The objective of this study is to evaluate the geometrical accuracy of a patient-specific bolus based on a three-dimensional (3D) printed mold and casting method. Materials and Methods: Three breast cancer patients undergoing treatment for a superficial region were scanned using computed tomography (CT) and a designed bolus structure through a treatment planning system (TPS). For the fabrication of patient-specific bolus, we cast harmless certified silicone into 3D printed molds. The produced bolus was also imaged using CT under the same conditions as the patient CT to acquire its geometrical shape. We compared the shapes of the produced bolus with the planned bolus structure from the TPS by measuring the average distance between two structures after a surface registration. Results and Conclusions: The result of the average difference in distance was within 1 mm and, as the worst case, the absolute difference did not exceed ${\pm}2mm$. The result of the geometric difference in the cross-section profile of each bolus was approximately 1 mm, which is a similar property of the average difference in distance. This discrepancy was negligible in affecting the dose reduction. The proposed fabrication of patient-specific bolus is useful for radiation therapy in the treatment of superficial regions, particularly those with an irregular shape.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.25-31
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• 2018

Selective Laser Melting is one of the representative 3D printing techniques for handling metal materials. The main factors influencing the characteristics of structures fabricated by the SLM method include the build-up angle of structures, laser power, laser scan speed, and scan spacing. In this study, the tensile properties of AlSi10Mg alloys were investigated by considering the build-up angle of tensile test specimens, laser scanning speed and scan spacing as variables. The yield stress, tensile strength, and elongation were considered as tensile properties. From the test results, it was confirmed that the yield stress values were lowered in the order of 0, 45, and 90 based on the manufacturing direction of the tensile specimen. The maximum yield stress value was obtained at 1870 mm / min based on the laser scan speed. The yield stress size decreased with decreasing scan speed. Based on the laser scan spacing, as the value increases, the yield stress increases, but the variation is smaller than the other test criteria. The tendency of the tensile strength and elongation variation depending on the test conditions was difficult to understand.