• Journal of the Korean institute of surface engineering
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• v.40 no.4
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• pp.165-169
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• 2007

Compared to conventional Indium Tin Oxide (ITO) film deposition methods, cesium (Cs) assisted sputtering offers higher film characteristics in terms of electrical, mechanical and optical properties. However, it showed highly non-linear characteristics between process input factors and equipment responses. Therefore, to maximize film quality, optimization of manufacturing process is essential and process characterization is the first step for process optimization. For this, we designed 2 level design of experiment (DOE) to analyze ITO film characteristics including film thickness, resistivity and transmittance. DC power, pressure, carrier flow, Cs temperature and substrate temperature were selected for process input variables. Through statistical effect analysis methods, relation between three types of ITO film characteristics and five kinds of process inputs are successfully characterized and eventually, it can be used to optimize Cs assisted sputtering processes for various types of film deposition.

• Advances in aircraft and spacecraft science
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• v.6 no.4
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• pp.333-348
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• 2019

Low fuel regression rate is the main drawback of hybrid rocket which should be overcome. One of the improvement techniques to this problem is usage of a solid fuel grain with a complicated geometry port, which has been promoted owing to the recent development of additive manufacturing technologies. In the design of a hybrid rocket fuel grain with a complicated geometry port, the understanding of fuel regression behavior is very important. Numerical investigations of fuel regression behavior requires a capturing method of solid fuel surface, i.e. gas-solid interface. In this study, level set method is employed as such a method and the preliminary numerical tool for capturing a hybrid rocket solid fuel surface is developed. At first, to test the adequacy of the numerical modeling, the simulation results for circular port are compared to the experimental results in open literature. The regression rates and oxidizer to fuel ratios show good agreements between the simulations and the experiments, after passing enough time. However, during the early period of combustion, there are the discrepancies between the simulations and the experiments, owing to transient phenomena. Second, the simulations of complicated geometry ports are demonstrated. In this preliminary step, a star shape is employed as complicated geometry of port. The slot number effect in star port is investigated. The regression rate decreases with increasing the slot number, except for the star port with many slots (8 slots) in the latter half of combustion. The oxidizer to fuel ratio increases with increasing the slot number.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.267-271
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• 2019

A shingled PV module is manufactured by dividing and bonding. In this method, the solar cell is divided by lasers and bonded using electrically conductive adhesives (ECAs). Consequently, the manufacturing cost increases because a process step is added. Therefore, we aim to reduce the production cost by reducing the amount of Ag paste used in the solar cell front. Various electrode structures were designed and simulated. The number of fingers was optimized by designing thinner fingers, and the number of fingers with the maximum power conversion efficiency was confirmed. The simulation confirmed the maximum efficiency in the 4-divided electrode pattern. The amount of Ag paste used for each electrode pattern was calculated and analyzed. The number of fingers was optimized by decreasing the width of the finger; this will not only reduce the amount of Ag paste required but also the increase the efficiency.

• Korean Journal of Pharmacognosy
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• v.50 no.3
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• pp.198-204
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• 2019

A facile and convenient method was developed for the mass production of epigallocatechin gallate (EGCG) rich green tea extract (Er-GTE). The Er-GTE was successfully obtained from the crude water extract of green tea by the combination of two step purification, i.e., a simple adsorption process on the cation exchange resins (Trilite SCR-B) followed by the chromatography with Diaion HP-20 resins. The green tea extract produced by water extraction under $45^{\circ}C$ was subjected to adsorb on the strongly acidic cation exchange resin, Trilite SCR-B. The eluate passed through the resin was reabsorbed on Diaion HP-20 resin, which was subjected to elute with a mixture of water and alcohol by conventional chromatographical manner. The EGCG content in Er-GTE was estimated above 97% by HP-LC analysis and the newly developed method was regarded as the most suitable and appropriate process for the mass production of epigallocatechin gallate rich green tea extract (Er-GTE).

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.1
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• pp.1-5
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• 2019

$^{19}F$ NMR experiments were carried out to observe the change of the characteristics of the PVdF binder which is an auxiliary material of the lithium ion battery. PVdF has various crystalline or amorphous phases by thermal treatment. A mixture of cathode and auxiliary materials including PVdF was coated on aluminum foil as an electron collector and then subjected to thermal treatment at various temperatures. The overlapped $^{19}F$ NMR signals obtained from the various phases were separately convoluted into the respective phases, and it was found that there was a relative ratio change of these phases. In addition, the crystal and amorphous phase of PVdF was changed during the vacuum drying, which is the last step of the actual electrode manufacturing. It was observed that the relative amount of amorphous phase, which may affect the flexibility of the electrode or the wettability of the electrolyte, abruptly changes after a certain temperature.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.645-656
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• 2020

In this study (Part II), the empirical formulation of corrosion model of a ship's ballast tank was developed to predict nonlinear time-dependent corrosion wastage based on the advanced data processing technique proposed by Part I. The detail on how to propose generalised mathematical formulation of corrosion model was precisely documented in the previous paper (Part I). The statistical scatter of corrosion data at any exposure time was investigated by the refined method and formulated based on a 2-parameter Weibull distribution which selected the best fit PDF. Throughout the nine (9) steps, empirical formulation of the ship's seawater ballast tank was successfully proposed and four (4) key step results were also obtained. The proposed method in Part I was verified and confirmed by this application of seawater ballast tank, thus making it possible to predict accurate behaviours of nonlinear timedependent corrosion. Developed procedures and obtained corrosion damage model for ship's seawater ballast tank can be used for development of engineering software.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.947-956
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• 2018

This research has been conducted to design upright parts of hand-made vehicles with the purpose of reducing material and machining cost while ensuring structural safety. Aluminum knuckles were modelled with three parts in order to enhance design flexibility as well as to reduce CNC machining cost. A vehicle model was constructed in CAD program and simulated in ADAMS View in order to estimate joint forces developing during 20 degree step steering condition at 60km/h. The joint forces obtained in the vehicle dynamics simulation were used for the structural analysis in ANSYS and dimensions of knuckle parts were adjusted until the lowest safety factor reached 2.0. The weight of knuckle decreased by 50% compared to the previous version that was designed without the structural analysis. The overall manufacturing cost decreased by 33% due to the reduction in the material as well as the CNC machining effort.

• Membrane Journal
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• v.30 no.6
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• pp.373-384
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• 2020

Antibody-based therapeutics have been receiving great attention as a representative biopharmaceutical, in which many researches are also carried out for its commercialization. The downstream process is considered an important part of the manufacturing processes of antibody-based therapeutics since it directly affects the performance and stability of products. Ultrafiltration/diafiltration (UF/DF), mostly performed in final step during downstream process, are used for the final concentration and formulation of antibody-based therapeutics. This paper reviewed the major products of the UF membrane, process characteristics, and recent research trends in UF/DF.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.361-365
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• 2022

Advanced packaging demands are driven by the need for dense integration systems. Consequently, stacked packaging technology has been proposed instead of reducing the ultra-fine patterns to secure economic feasibility. This study proposed an effective packaging process technology for semiconductor devices using a 9-inch dicing die attach film (DDAF), wherein the die attach and dicing films were combined. The process involved three steps: tape lamination, dicing, and bonding. Following the grinding of a silicon wafer, the tape lamination process was conducted, and the DDAF was arranged. Subsequently, a silicon wafer attached to the DDAF was separated into dies employing a blade dicing process with a two-step cut. Thereafter, one separated die was bonded with the other die as a substrate at 130 ℃ for 2 s under a pressure of 2 kgf and the chip was hardened at 120 ℃ for 30 min under a pressure of 10 kPa to remove air bubbles within the DAF. Finally, a curing process was conducted at 175 ℃ for 2 h at atmospheric pressure. Upon completing the manufacturing processes, external inspections, cross-sectional analyses, and thermal stability evaluations were conducted to confirm the optimality of the proposed technology for application of the DDAF. In particular, the shear strength test was evaluated to obtain an average of 9,905 Pa from 17 samples. Consequently, a 3D integration packaging process using DDAF is expected to be utilized as an advanced packaging technology with high reliability.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.687-704
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• 2023

This study aims to examine the structural response of glass fibre-reinforced polymer (Glass-FRP) reinforced geopolymer electronic waste aggregate concrete (GEWC) compression elements under axial compression for sustainable development. The research includes the fabrication of nine GEWC circular compression elements with different reinforcement ratios and a 3-D nonlinear finite element model using ABAQUS. The study involves a detailed parametric analysis to examine the impact of various parameters on the behavior of GEWC compression elements. The results indicate that reducing the vertical distance of glass-FRP ties improves the ductility of GEWC compression elements, and those with eight longitudinal rebars have higher axial load-carrying capacities. The finite element predictions were in good agreement with the testing results, and the put forwarded empirical model shows higher accuracy than previous models by involving the confinement effect of lateral glass-FRP ties on the axial strength of GEWC compression elements. This research work contributes to minimizing the carbon footprint of cement manufacturing and electronic waste materials for sustainable development.