• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.849-856
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• 2012

Chip on board type white light emitting diode on metal core printed circuit board with high thixotropy silicone is fabricated by vacuum printing encapsulation system. Encapsulant is chosen by taking into account experimental results from differential scanning calorimeter, shearing strength, and optical transmittance. We have observed that radiant flux and package efficacy are increased from 336 mW to 450 mW and from 11.9 lm/W to 36.2 lm/W as single dome diameter is varied from 2.2 mm to 2.8 mm, respectively. Double encapsulation structure with 2.8 mm of dome diameter shows further significant enhancement of radiant flux and package efficacy to 667 mW and 52.4 lm/W, which are 417 mW and 34.8 lm/W at single encapsulation structure, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.5
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• pp.294-302
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• 2021

In this study, the 3D printing technique called design for additive manufacturing (DfAM) that is widely used in various industries was applied to marine leisure ships of equipment. The DfAM for the stanchion for crew safety was applied to the equipment used in an actual recreational craft. As design constraints, the design alternatives were not to exceed the safety and weight of the existing stainless steel material, which were reviewed, and the production of a low-cost FFF-type 3D printing method that can be used even in small shipyards was considered. Until now, additive manufacturing has been used for manufacturing only prototypes owing to its limitations of high manufacturing cost and low strength; however, in this study, it was applied to the mass production process to replace existing products. Thus, a design was developed with low manufacturing cost, adequate performance maintenance, and increased design freedom, and the optimal design was derived via structural analysis comparisons for each design alternative. In addition, a life-cycle assessment based on the ISO 1404X was conducted to develop sustainable products. Through this study, the effectiveness of additive manufacturing was examined for future applications in the shipbuilding industry.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.1
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• pp.106-122
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• 2021

This study confirmed the mechanical properties of an auxetic re-entrant pattern prepared using 3D printing technology and its composite fabric with neoprene for the production of functional auxetic patterns/textiles for safety shoes. Samples were prepared by the tilt angle of a re-entrant pattern of 0°, 30°, 45°, 60° and 90°, and then analyzed using Poisson's ratio, bending, compression, and tensile properties. A 3D printed auxetic re-entrant pattern (3DP-RE) and its composite fabric (3DP-RE/NP) showed a negative Poisson's ratio in all tilting angles that indicated auxetic properties. The results of the bending property shown that strength of 3DP-RE/NP was 1.5 times lower than NP, but the strain improved 2.0 times. It was confirmed that the deformation of 3DP-RE/NP is possible with a low load. Each sample type of compression behavior indicated similar regardless of the tilting angles; in addition, the compression toughness of 3DP-RE/NP increased 1.2 times compared with NP. In the case of tensile properties, 3DP-RE and 3DP-RE/NP were affected by the tilting angle, samples with 90° (the opposite of load direction) showed best tensile property and toughness. 3DP-RE/NP indicated improved bending, compression, and tensile properties.

• Composites Research
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• v.36 no.3
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• pp.193-198
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• 2023

Currently, there are many discussions about composite materials and 3D printed composite material to weight reduction of ships. A test was conducted to confirm the applicability of the 3D printed composite material to ships and offshore structures by linking the 3D printing technology with excellent productivity and the composite material with corrosion resistance and lightweight characteristics in salt water environments. In order to apply the 3D printed composite material used in this paper to ships and offshore structures, the temperature environmental effects that can be exposed in the marine environment should be considered. Therefore, the tensile test was conducted with specimen of Carbon + Onyx, Carbon + Nylon, HSHT glass + Onyx, HSHT glass + Nylon material in low temperature (-50℃), room temperature (20℃), and high temperature (50℃) environments that can be exposed to the marine environment. As a result of the tensile test, the carbon + onyx specimen showed the highest tensile strength and the HSHT glass + onyx specimen showed the highest tensile strain. In addition, by analyzing the tested specimens, the failure mode of the 3D printed composite material specimens exposed to various temperature environments was analyzed.

• Analytical Science and Technology
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• v.19 no.5
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• pp.389-393
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• 2006

The detector consisted of ZnS(Ag) scintillator and photomultiplier tube (PMT) is widely used as contamination monitor in the nuclear facilities. Such detectors are mainly manufactured by adhering the ZnS(Ag) powder onto the transparent plastic. In this study the preparation condition for ZnS(Ag) scintillator sheet using a simple method was established. The scintillator sheet was composed with a support polymer sheet and ZnS(Ag) scintillator layer. The base sheet was prepared by casting the polymer solution after solving the polymer with solvent and the scintillator layer was manufactured by printing the mixture solution with ZnS(Ag) and paste. It was found that the polysulfone(PSf) as a polymer for the base sheet and a cyano resin as a paste for adhering the ZnS(Ag) scintillator was suitable. Also, the prepared thin scintillator sheet had a sufficient mechanical strength, a optical transparency and an alpha-ray detection performance.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.301-306
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• 2005

Aging characteristics of newly developed Sn-1.8Bi-0.7Cu-0.6In solder was evaluated by shear strength and microstructure. Stencil printing was applied to form solder. The shear strength of Sn-1.8Bi-0.7Cu-0.6In at $150^{\circ}C$ showed the highest values through aging. Intermetallic compounds formed on the interface between solder and Au/Cu/Ni/Al UBM were $(Cu,\;Ni)_6Sn_5$ Furthermore, it was found that Spatting of Intermetallic compounds started before 500h aging at $150^{\circ}C$.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.129-135
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• 2021

Recently, additive manufacturing (AM) technology such as powder bed fusion (PBF) and directed energy deposition (DED) are actively attempted as consumers' needs for parts with complex shapes and expensive materials. In the present work, the effect of processing parameters on the mechanical properties of 316L stainless steel coupons fabricated by PBF and DED AM technology was investigated. Three major mechanical tests, including tension, impact, and fatigue, were performed on coupons extracted from the standard components at angles of 0, 45, 90 degrees for the build layers, and compared with those of investment casting and commercial wrought products. Austenitic 316L stainless steel additively manufactured have been well known to be generally stronger but highly vulnerable to impact and lack in elongation compared to casting and wrought materials. The process-induced pore density has been proved the most critical factor in determining the mechanical properties of AM-built metal parts. Therefore, it was strongly recommended to reduce those lack of fusion defects as much as possible by carefully control the energy density of the laser. For example, under the high energy density conditions, PBF-built parts showed 46% higher tensile strength but more than 75% lower impact strength than the wrought products. However, by optimizing the energy density of the laser of the metal AM system, it has been confirmed that it is possible to manufacture metal parts that can satisfy both strength and ductility, and thus it is expected to be actively applied in the field of electric power section soon.

• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.93-100
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• 2020

3D printing technology enables proper objects to be made through an additive manufacturing method, but resulting in dimension deviation of the product due to contraction phenomenon as cooling melted filament resin injected from high-temperature use environment. In this research, we studied on acrylic adhesives for 3D printer build sheet in order to fabricate high-quality products with a precise shape and to well-mount without distortion. The solvent-free UV-curable acrylic adhesive formulation was designed by adding 4-acryloylmorpholine (ACMO) with high adhesion, toughness, glass transition temperature so that adhesion properties are stable at high temperature and products are easily mounted/detached from the adhesives. The designed formulation was polymerized through two-steps using post-addition of monomers. Using this, the acrylic adhesive was coated to make a film and then analyzed using various experimental techniques. As a result, the fabricated adhesive exhibited high glass transition temperature and there was little gap in peel strength before and after thermal treatment. Moreover, it was confirmed by rheological analysis that this adhesive can provide great bonding/debonding ability without distortion. We demonstrated the fabrication of a rectangular product using a 3D printing method using our acrylic adhesive as a build sheet. Mounting ability and workability were satisfactory and dimension deviation of the product was tiny. Because the product is easily detachable from the acrylic adhesive developed here than conventional build sheets, it is expected that this will provide work convenience to users who use the 3D printer.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.233-240
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• 2022

Research on the presence or absence of radiation shielding for FDM-type filaments has recently begun to be studied, but filaments with shielding capabilities are not sold in Korea, and not studies yet. Therefore, in this research, we will use HDPE (High Density Polyethylene) as a base material, select bismuth as a reinforcing material to manufacture a composite filament, evaluate the shielding ability, and provide basic data for the development of a radiation shielding composite material using 3D printing.A filament is produced by mixing Bismuth with an effective atomic number 83 with HDPE of PE series and adjusting the content of Bismuth to 20% wt, 30% wt, 40% wt. Compounded filaments were evaluated for their physical properties and shielding capabilities by ASTM evaluation methods. As the bismuth content increases, the density, weight, and tensile strength increase, and the shielding capacity is confirmed to be excellent. As a result of the radiation shielding capacity evaluation, it was confirmed that HDPE (80%) + Bi (20%) showed a shielding rate of 82% at 60 kV and a shielding rate of up to 94% or more at 40% bismuth content. In this study, we confirmed that it was possible to produce a radiation shield that is lighter than the metal particle-containing filaments. Furthermore, that have been shield radiation by using HDPE + Bi filaments, and radiation in the medical and radiation industries. The possibility of using it as a shielding complex was confirmed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1665-1673
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• 2013

Recently, the interest and demand on free formed structure providing aesthetic value as well as functionality has been increasing. Formwork has numerous advantages such as high strength, convenience, accuracy and good quality of surface roughness. Nevertheless, it increases construction cost and period to build complex shapes. For these purpose, deposition construction systems such as Contour Crafting and Concrete Printing have been developed with active collaboration between university and industry by applying the rapid prototyping technology to the construction industry in USA and England. Since there has been no related research in Korea, the possibility of spin-off technology and its fusion cannot be expected. In this paper, design elements including mechanical system and control system related to automatic deposition construction system prototype for constructing a free curved structure without mold are described. As for an appropriate material for the system, fiber reinforced mortar was selected by experiments on compressive strength, fluidity, viscosity and setting time. By performing transfer and extrusion experiments, the possibility of the development of deposition construction system was demonstrated. Based on this research results, it is required to keep the automatic deposition construction system improve and extend it into the new application area in construction industry.