• Journal of the Microelectronics and Packaging Society
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• v.24 no.3
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• pp.63-69
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• 2017

This paper presents a highly efficient power management system for UAV-drones. For free from the battery cell-balancing issue, the proposed system allows the drone to utilize a single-cell Li-Po battery. To realize low-voltage input of 3.7V, the switch-mode step-up DC-DC converter is optimally designed with high power efficiency. The prototype DC-DC converter was implemented with an output voltage of 5V, which will be provided to digital parts of the drone. The power efficiency was measured to be max. 91.3% with low surface temperature. The measured line and load regulations were 0.02V/V and 0.15V/A, respectively. Thanks to the proposed power management system, the available time-to-fly of the drone is expected to be significantly extended in virtue of the enhanced power efficiency.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.2
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• pp.27-31
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• 2015

Thermal management becomes a key technology as the power density of high performance and high density devices increases. Conventional heat sink or TIM methods will be limited to resolve thermal problems of next-generation IC devices. Recently, to increase heat flux through high powered IC devices liquid cooling system has been actively studied. In this study a chip-level liquid cooling system with TSV and microchannel was fabricated on Si wafer using DRIE process and analyzed the cooling characteristics. Three different TSV shapes were fabricated and the effect of TSV shapes was analyzed. The shape of liquid flowing through microchannel was observed by fluorescence microscope. The temperature differential of liquid cooling system was measured by IR microscope from RT to $300^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.1-7
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• 2008

We studied a growth behavior of Intermetallic compounds(IMCs) during solder bumping with two reflow methods. Ti(50 nm), Cu($1{\mu}m$), Au(50 nm) and Ti(50 nm) thin films were deposited on $SiO_2$/Si wafer using the DC magnetron sputtering system as the under bump metallization(UBM). And the $5{\mu}m$ thick Cu bumps and $20{\mu}m$ thick Sn bumps were fabricated on UBM by electroplating. Sn bumps were reflowed in RTA(Rapid Thermal Annealing) system and convection reflow oven. When RTA system was used, reflow was possible without using flux and IMC thickness formed in the solder interface was thinner than that of a convectional method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.763-768
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• 2005

Bare-chip packaging becomes more popular along with the miniaturization of IT components. In this paper, we have studied flip-chip process, and developed automated bonding system. Among the several bonding method, NCP bonding is chosen and batch-type equipment is manufactured. The dual optics and vision system aligns the chip with the substrate. The bonding head equipped with temperature and force controllers bonds the chip. The system can be easily modified for other bonding methods such as ACF In bonding process, the bonding forte and temperature are known as the most dominant bonding parameters. A parametric study is performed for these two parameters. For the test sample, we used standard flip-chip test kit which consists of FR4 boards and dummy flip-chips. The bonding test was performed fur two types of flip-chips with different chip size and lead pitch. The bonding temperatures are chosen between $25^{\circ}C\;to\;300^{\circ}C$. The bonding forces are chosen between 5N and 300N. The bonding strength is checked using bonding force tester. After the bonding force test, the samples are examined by microscope to determine the failure mode. The relations between the bonding strength and the bonding parameters are analyzed and compared with bonding models. Finally, the most suitable bonding condition is suggested in terms of temperature and force.

• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.404-410
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• 2017

An analytical method for determination of propylene glycol alginate (PGA) in food products was developed by HPLC-size-exclusion chromatography. The GF-7M HQ column and LT-ELSD detector were determined by considering the instrumental analysis conditions for PGA analysis. The pretreatment method for the analysis of PGA was suitable for 3 hr extraction at $20^{\circ}C$ and 150 rpm according to the extraction temperature. Linearity ($R^2$) for the analysis of PGA was 0.9873 at calibration curve range of 300, 500, 700, 1,000, and 1,500 mg/kg (5 points). The limit of detection and limit of quantification of PGA on HPLC system was 171.43 and 519.50 mg/kg, respectively. The accuracy and coefficient of variation obtained by size-exclusion chromatography were 86.1~110.4% and 4.1~13.5%, respectively. By applying the HPLC-size-exclusion chromatography system, it was possible to analyze the contents of PGA in 134 different types of food products.

• Food Science and Preservation
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• v.19 no.1
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• pp.1-6
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• 2012

The effect of the packing methods for enhancing the shelf life and improving the postharvest quality of the $tah$ $tasai$ Chinese cabbage baby leaf vegetable was studied during storage. Fresh baby leaf vegetables were packed in four commercial packaging types: (1) a non-perforated bag with a 0.03-mm oriented polypropylene (OPP) film; (2) a perforated bag with 1.0-mm-diameter holes on an OPP film; (3) a 0.40-mm polyethylene terephthalate (PET) container with a hinged lid; and (4) an expanded polystyrene (EPS) tray wrapped with a 0.02-mm polyvinyl chloride (PVC) film. The quality parameters, such as the weight loss, moisture content change, color difference, and appearance of the baby leaf vegetables were investigated. The baby leaf vegetables in the PET container and in the non-perforated OPP film bag showed relatively low weight loss, high moisture content, and good external appearance compared to those in the EPS tray and in the perforated OPP film bag during limited storage periods, at $16^{\circ}C$. The PET container also protected the baby leaf vegetables from physical damage. The study results will enable the selection of a better packaging system for extending the freshness and increasing the market ability of baby leaf vegetables.

• Conservation Science in Museum
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• v.16
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• pp.96-113
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• 2015

High-barrier films are used to store cultural heritage objects in a safe environment sealed from oxygen and moisture. One of the high-barrier films use populary E manufactured by Japanese company M from the 1990's. However, this product has stayed in wide use, due to dearth of research on related subjects - including studies comparing it with other similar products-, in spite of the fact that high price information about its characteristics and environmental conditions is largely lacking. This study examines the characteristics of a number of high-barrier films with the goal to establish environmental standards for safer conservation of cultural heritage objects. E by the Japanese manufacturer M is compared with four other films; an electronics packaging films by a Korean firm, a film specially produced for the purposes of experiment in this study and a zipper bag-type film. Experiments were performed to compare the properties and gas blocking ability of the films by looking at their cross-section and measuring the thickness, tensile strength, elongation, absorbance of UV and visible light, yellowing and the permeability for oxygen and vapor. Based on these experiments, there are observed changes under different environmental conditions and depending on the length of use through temparature and humidification reproucing test. The results showed that while the high-barrier film by the Korean manufacturer was suitable for use as a packaging material for cultural heritage objects, the zipper bag-type film (P) was ill-adapted for this purpose. Based on the experiments reproducing the real-world environment, the length of useful life was also determined for each.

• Food Science and Preservation
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• v.11 no.2
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• pp.135-141
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• 2004

To examine the quality changes of tomato and plum fruits during storage under various storage conditions, the rate of weight loss, pH change, titratable acidity, Hunter a value, firmness, and anthocyanin content were determined during storage. Tomato and plum fruits were stored at 4$^{\circ}C$ and 25$^{\circ}C$. Tomato fruits were packaged with high density polyethylene film (HDPE) and polyvinylidene chloride film (PVDC), and plum fruits were packaged with HDPE. Tomato fruits packaged with PVDC and plum fruits packaged with HDPE at 4$^{\circ}C$ were the most desirable in terms of weight loss. Titratable acidity of tomato fruits decreased with increasing storage time regardless of temperature and packaging method. Hunter a value of tomato fruits stored at 25$^{\circ}C$ increased regardless of packaging method, while it was not changed for tomato fruits stored at 4$^{\circ}C$. Firmness of plum fruits stored at 25$^{\circ}C$ significantly decreased during storage and anthocyanin content increased. Microbial numbers of tomato fruits increased during storage, but its rate was retarded during storage when tomato fruits were packaged with HDPE and stored at 4$^{\circ}C$. These results suggest that cold chain system and appropriate packaging could maintain the quality and prolong the shelf life of fresh produce.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.610-616
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• 2011

A series of polyurethane acrylate/ZnO (PUA/ZnO) nanocomposite films with different ZnO contents were successfully prepared via a UV-curing system. The synthesis and physical properties including morphological structure, thermal properties, barrier properties and optical properties, and antimicrobial properties were investigated as a function of ZnO concentration. FTIR and SEM results showed that these PUA/ZnO nanocomposite films did not have a strong interaction between PUA and ZnO, which may lead to no increase in thermal stability. By incorporating ZnO nanoparticles, the UV blocking and antibacterial properties increased as the content of ZnO increased. Specially, the oxygen permeability in composite films changed from $2005cc/m^2/day$ to $150cc/m^2/day$ by adding the ZnO nanoparticle, which indicates that the PUA/ZnO nanocomposite films can be applied as good barrier packaging materials. Physical properties of the UV-cured PUA/ZnO nanocomposite film are strongly dependent upon the dispersion state of ZnO nanoparticles and their morphology in the films.

• Journal of the Korea Convergence Society
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• v.13 no.1
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• pp.149-160
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• 2022

In this study, the physical quality and microbial changes of ginseng sprout according to the pretreatment process and packaging container were evaluated to improve the storage properties of ginseng sprout produced in smart farm. Quality change during storage (10 days) according to pretreatment method (ascorbic acid, citric acid, peroxyacetic acid) and packaging container (expanded polystyrene (EP), polypropylene (PP), polyethylene (PE), polypropylene + polyethylene + cast polypropylene (PP+PE+CPP)) was evaluated in terms of texture, viable cell count, water content, and color. As a result of comparison according to the type of pretreatment, the citric acid treatment group showed the lowest texture change and the effect on inhibition of bacterial growth. On the other hand, citric acid, which was most effective among pretreatments, was treated in all samples and then stored in 4 types of containers. Specially, the ginseng sprout in PP packaging container was not observed significant softening or color changes after 10 days storage, and the lowest changes in viable cell number. Therefore, this study was shown that citric acid treatment and use of PP packaging container are effective in increasing the shelf life of ginseng sprout.