• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.04a
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• pp.9-15
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• 2000

Flip chip assembly on organic substrates using ACAs have received much attentions due to many advantages such as easier processing, good electrical performance, lower cost, and low temperature processing compatible with organic substrates. ACAs are generally composed of epoxy polymer resin and small amount of conductive fillers (less than 10 wt. %). As a result, ACAs have almost the same CTE values as an epoxy material itself which are higher than conventional underfill materials which contains lots of fillers. Therefore, it is necessary to lower the CTE value of ACAs to obtain more reliable flip chip assembly on organic substrates using ACAs. To modify the ACA composite materials with some amount of conductive fillers, non-conductive fillers were incorporated into ACAs. In this paper, we investigated the effect of fillers on the thermo-mechanical properties of modified ACA composite materials and the reliability of flip chip assembly on organic substrates using modified ACA composite materials. For the characterization of modified ACAs composites with different content of non-conducting fillers, dynamic scanning calorimeter (DSC), and thermo-gravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), and thermo-mechanical analyzer (TMA) were utilized. As the non-conducting filler content increased, CTE values decreased and storage modulus at room temperature increased. In addition, the increase in tile content of filler brought about the increase of Tg$^{DSC}$ and Tg$^{TMA}$. However, the TGA behaviors stayed almost the same. Contact resistance changes were measured during reliability tests such as thermal cycling, high humidity and temperature, and high temperature at dry condition. It was observed that reliability results were significant affected by CTEs of ACA materials especially at the thermal cycling test. Results showed that flip chip assembly using modified ACA composites with lower CTEs and higher modulus by loading non-conducting fillers exhibited better contact resistance behavior than conventional ACAs without non-conducting fillers.ers.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.1
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• pp.41-49
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• 2000

Flip chip assembly on organic substrates using ACAs have received much attentions due to many advantages such as easier processing, good electrical performance, lower cost, and low temperature processing compatible with organic substrates. ACAs are generally composed of epoxy polymer resin and small amount of conductive fillers (less than 10 wt.%). As a result, ACAs have almost the same CTE values as an epoxy material itself which are higher than conventional underfill materials which contains lots of fillers. Therefore, it is necessary to lower the CTE value of ACAs to obtain more reliable flip chip assembly on organic substrates using ACAs. To modify the ACA composite materials with some amount of conductive fillers, non-conductive fillers were incorporated into ACAs. In this paper, we investigated the effect of fillers on the thermo-mechanical properties of modified ACA composite materials and the reliability of flip chip assembly on organic substrates using modified ACA composite materials. For the characterization of modified ACAs composites with different content of non-conducting fillers, dynamic scanning calorimeter (DSC), and thermo-gravimetric analyser (TGA), dynamic mechanical analyzer (DMA), and thermo-mechanical analyzer (TMA) were utilized. As the non-conducting filler content increased, CTE values decreased and storage modulus at room temperature increased. In addition, the increase in the content of filler brought about the increase of $Tg^{DSC}$ and $Tg^{TMA}$. However, the TGA behaviors stayed almost the same. Contact resistance changes were measured during reliability tests such as thermal cycling, high humidity and temperature, and high temperature at dry condition. It was observed that reliability results were significantly affected by CTEs of ACA materials especially at the thermal cycling test. Results showed that flip chip assembly using modified ACA composites with lower CTEs and higher modulus by loading non-conducting fillers exhibited better contact resistance behavior than conventional ACAs without non-conducting fillers.

• Journal of Electrochemical Science and Technology
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• v.9 no.3
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• pp.229-237
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• 2018

The electrochemical sensing performance of metal-graphene hybrid based sensor may be significantly decreased due to the dissolution and aggregation of metal catalyst during operation. For the first time, we developed a novel large-area high quality three dimensional graphene foam-incorporated gold nanoparticles (3D-GF@Au) via chemical vapor deposition method and employed as free-standing electrocatalysis for non-enzymatic electrochemical glucose detection. 3D-GF@Au based sensor is capable to detect glucose with a wide linear detection range of $2.5{\mu}M$ to 11.6 mM, remarkable low detection limit of $1{\mu}M$, high selectivity, and good stability. This was resulted from enhanced electrochemical active sites and charge transfer possibility due to the stable and uniform distribution of Au NPs along with the enhanced interactions between Au and GF. The obtained results indicated that 3D-GF@Au hybrid can be expected as a high quality candidate for non-enzymatic glucose sensor application.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1414-1417
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• 1996

The purpose of this study Is to research and develop $V_{6}O_{13}$ composite cathode for lithium thin film battery. $V_{6}O_{13}$ represents a class of cathode active material used in Li rechargeable batteries. In this study, we investigated cyclic voltammetry and charge/discharge characteristics of $V_6O_{13}$/SPE/Li cells. Cyclic voltammogram of $V_{6}O_{13}$/SPE/Li cell at scan rate 1mV/sec showed reduction peaks of 2.25V and 2.4V and oxidation peaks of 2.4V and 2.2V. The discharge curve of $V_{6}O_{13}$/SPE/Li cell showed 4 potential plateaus. The discharge capacity was decreased in the beginning of charge/discharge cycling. After 8th cycling, the discharge capacity was stable. The discharge capacity of 1st cycle and 15th cycle was 290mAh/g and 147mAh/g at $25^{\circ}C$, respectively.

• Composites Research
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• v.27 no.3
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• pp.103-108
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• 2014

Fiber reinforced polymer plastic (FRP) structural members are recently available in construction industries due to various material properties such as high specific strength and stiffness, light-weight, and corrosionresistance. The floating PV generation structure can also be an illustration for applying FRP in construction applications. The floating PV generation structure has been recently issued as a representative item for the low carbon and green growth campaign and many related studies have been conducted for the structural safety and commercial viability. Moreover, the floating PV generation structures for the commercial purpose have been constructed. In this paper, the investigation and development processes of elements for the floating PV generation structure are presented during commercialization.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.669-674
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• 2013

A three-dimensional hydrogel scaffold has been proposed for the effective production of biomimetic intestinal villi to reduce ethical and cost problems caused by animal testing in pharmaceutical development. This study explores an experimental approach to develop a new technique based on laser machining and microdrilling processes to produce a plastic mold for the fabrication of a three-dimensional hydrogel scaffold. For process optimization, both the laser machining and the microdrilling experiments are conducted by varying the experimental conditions, and structural characterization of the mold and intestinal villi were performed using SEM (scanning electron microscope) and OM (optical microscope) images. Polycarbonate (PC) was used as a candidate material. The experimental results show that intestinal villi can be fabricated by both laser and microdrilling machining processes.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.59-65
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• 2005

Poly-${\gamma}$-glutamic acid (PGA) is an unusual anionic polypeptide and has great potential as an environmentally and industrially significant biodegradable material. A new ${\gamma}$-PGA producer, Bacillus mesentericus MJM1, with high production capacity was isolated from Korean domestic Chungkuckjang bean paste. It produced ${\gamma}$-PGA at the level of 10 g/l in suitable media. The viscosities of 5% initially extracted mucin and purified ${\gamma}$-PGA solutions were 660 cps and 600 cps, respectively. The produced ${\gamma}$-PGA polymer consisted of 2,000 glutamic acid residues with even proportion of L and D types with molecular mass of about 200- 300 kDa. Bacillus mesentericus MJM1 displayed ${\gamma}$-glutamyltranspeptidase (${\gamma}$-GTP) activity that is known to play a key role in ${\gamma}$-PGA biosynthesis. The ${\gamma}$-GTP coding region was located on the plasmid of 5.8 kb. The plasmid, named pMMH1, is a rolling-circle replication (RCR) plasmid and additionally contained a replication origin and type I signal peptidase (sipP) coding region.

• The Korea Journal of Herbology
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• v.31 no.4
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• pp.71-77
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• 2016

Objectives : Adipogenesis was defined as a differentiation process of preadipocytes into the adipocytes. Thus, to control of this process can be one of the most important strategies to prevent obesity. Korean ginseng(Panax ginseng C.A. Meyer) is one of the most widely used medicinal herbs. Although multiple biological activities of Korean ginseng, particularly ginsenosides, have been known, the anti-adipogenic role and function of polysaccharides from Korean ginseng are still unclear. In this study, we examined anti-adipogenic activity of polysaccharides and its molecular basis mechanisms are further investigated.Methods : The cytotoxicity of KGP in 3T3-L1 was evaluated by MTT assay. Anti-adipogenic effect of KGP was examined by Oil Red O (ORO) staining and microscopy observation in 3T3-L1 mature adipocytes. The mRNA expression levels of adipogenic transcriptional factors were analyzed by reverse transcription-polymer chain reaction (RT-PCR). To elucidate the adipogenic molecular mechanism of KGT, SB431542 (TGF-β specific inhibitor) was used.Results : We found that polysaccharides showed no effect on the viability of 3T3-L1 preadipocytes. Dose dependent inhibitory effect of polysaccharides on 3T3-L1 adipogenesis was observed as judged by ORO staining and microscopic image analysis. To obtain further mechanistic insight into anti-adipogenic function of polysaccharides, we then tested the effect of polysaccharides treatment on the adipogenic marker genes. The mRNA expressions level of C/EBPα, PPARγ, C/EBPβ, and fatty acid synthase (FAS) were dose-dependently inhibited by KGP treatment in 3T3-L1 mature adipocytes.Conclusions : In conclusion, these findings suggest that the KGP could be used in treatment of obesity and overweight related diseases.

• Journal of Conservation Science
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• v.25 no.2
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• pp.171-178
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• 2009

When we considered the superior ability of the semi-water soluble urethane 1st transcription and final epoxy products, the stability for moving historic sites depend on physical properties and the peel off state of separation media. In this paper, we synthesised three type of water-borne epoxy solution without using a surfactant, and investigated the peel off state, physical properties, and the state between urethane surface and epoxy surface after exfoliation. The life time of water-borne separation media is over the 60 days. When it is used the 30% solution of water-borne separation media, it made good separation of urethane pre-products surface and epoxy final product surface and no color change. The separation tension pressure is about 15~50 kg/$cm^2$ and there is no surface whitewash phenomenon. We suggest that this water-borne epoxy will be best material as separation media of low viscosity type.

• Composites Research
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• v.33 no.1
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• pp.7-12
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• 2020

Over the past decade, liquid crystalline epoxy (LCER) has attracted much attention as a promising matrix for the development of efficient heat dissipation materials. This study presents a comprehensive study including synthesis, preparation and chacterization of polymer/inorganic composites using typical 4,4-diglycidyloxybiphenyl (DP) epoxy among LECR. To confirm the thermal conductivity of composite materials, we have prepared composite samples composed of epoxy resin and single-wall carbon nanotube (SWCNT) as a filler. In particular, DP composites exhibit higher thermal conductivity than commercial epoxy composites that use the same type of filler due to the highly ordered microstructure of the LCER. In addition, the thermal conductivity of the DP composite can be controlled by controlling the amount of filler. In particular, the DP composite containing a SWCNT content of 50 wt% has the highest thermal conductivity of 2.008 W/mK.