• YAKHAK HOEJI
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• v.48 no.3
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• pp.189-196
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• 2004

Matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) playa key role in tumor invasion and metastasis. As an inhibitor of MMP-2, TIMP-2 is known to block both the invasive and metastatic behavior of cancer cells, and decrease tumor growth activity. We performed this study to investigate the effects of TIMP-2 over-expression induced by retroviral mediated gene transfer in vitro and in vivo. The human colon cancer cell line SW480 was transfected with the retroviral vector encoding TIMP-2. The effects of TIMP-2 over-expression were analyzed by invasion assay and gelatinase activity test in colon cancer cells and tumorigencity in nude mice. In evaluation of the transfection efficiency of the retroviral vector encoding TIMP-2 in colon cancer cells, we confirmed up-regulation of TIMP-2 expression dependent on the time of cell culture. In addition, inhibition of MMP-2 expression in SW480/TIMP-2 was shown by gelatin zymography. In the in vitro invasion assay SW480/TIMP-2 inhibited the invasiveness on matrigel coated with collagen. To determine whether TIMP-2 can modulate in vivo tumorigenicity and metastasis, SW480/TIMP-2 cells were injected subcutaneously in nude mice. The tumor mass formation of SW480/TIMP-2 cells in nude mice was markedly decreased compared to nontransfected cancer cells. These results showed that colon cancer cells transfected with the retroviral vector encoding TIMP-2 inhibits the invasiveness in vitro and tumorigenicity in vivo.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2256-2268
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• 2018

Hydrophilic and hydrophobic polyethersulfone (PES)-zinc oxide (ZnO) sublayers were prepared by loading of ZnO nanoparticles into PES matrix. Both porosity and hydrophilicity of the hydrophilic sublayer were increased upon addition of hydrophilic ZnO, while these were decreased for the hydrophobic sublayer. In addition, the results demonstrated that the hydrophilic membrane exhibited smaller structural parameter (S value or S parameter or S), which is beneficial for improving pure water permeability and decreasing mass transfer resistance. In contrast, a higher S parameter was obtained for the hydrophobic membrane. With a 2 M NaCl as DS and DI water as FS, the pure water flux of hydrophilic TFN0.5 membrane was increased from $21.02L/m^2h$ to $30.06L/m^2h$ and decreased for hydrophobic TFN0.5 membrane to $14.98L/m^2h$, while the salt flux of hydrophilic membrane increased from $10.12g/m^2h$ to $17.31g/m^2h$ and decreased for hydrophobic TFN0.5 membrane to $3.12g/m^2h$. The increment in pure water permeability can be ascribed to reduction in S parameter, which resulted in reduced internal concentration polarization (ICP). The current study provides a feasible and low cost procedure to decrease the ICP in FO processes.

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.508-514
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• 2022

Piezoelectric composite films which are enabled by inorganic piezoelectric nanomaterials-embedded polymer, have attracted enormous attention as a sustainable power source for low powered electronics, because of their ease of fabrication and flexible nature. However, the absorption of applied stress by the soft polymeric matrices is a major issue that must be solved to expand the fields of piezoelectric composite applications. Herein, a flexible and porous piezoelectric composite (piezoelectric sponge) comprised of BaTiO₃ nanoparticles and polydimethylsiloxane was developed using template method to enhance the energy conversion efficiency by minimizing the stress that vanishes into the polymer matrix. In the porous structure, effective stress transfer can occur between the piezoelectric active materials in compression mode due to direct contact between the ceramic particles embedded in the pore-polymer interface. The piezoelectric sponge with 30 wt% of BaTiO₃ particles generated an open-circuit voltage of ~12 V and a short-circuit current of ~150 nA. A finite element method-based simulation was conducted to theoretically back up that the piezoelectric output performance was effectively improved by introducing the sponge structure. Furthermore, to demonstrate the feasibility of pressure detecting applications using the BaTiO₃ particles-embedded piezoelectric sponge, the composite was arranged in a 3 × 3 array and integrated into a single pressure sensor. The fabricated sensor array successfully detected the shape of the applied pressure. This work can provide a cost-effective, biocompatible, and structural strategy for realizing piezoelectric composite-based energy harvesters and self-powered sensors with improved energy conversion efficiency.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.961-965
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• 1998

The rapid development of small-scale (1-10 MJ) Superconducting Magnetic Energy Storage Systems (SMES) can be explained by real perspective of practical implementation of these devices in electro power nets. However the serious problem of all high mechanically stressed superconducting coils-problem of training and degradation (decreasing) of operating current still exists. Moreover for SMES systems this problems is more dangerous because of pulsed origin of mechanical stresses-one of the major sources of local heat disturbances in superconducting coils. We investigated acoustic emission (AE) phenomenon on model and 0.5 MJ SMES coils taking into account close correlation of AE and local heat disturbances. Two-coils 0.5 MJ SMES system was developed, manufactured and tested at Russian Research Center in the frames of cooperation with Korean Electrical Engineering Company (KEPCO) [1]. The two-coil SMES operates with the stored energy transmitted between coils in the course of a single cycle with 2 seconds energy transfer time. Maximum operating current 1.55 kA corresponds to 0.5 MF in each coil. The Nb-Ti-based conductor was designed and used for SMES manufacturing. It represents transposed cable made of Nb-Ti strands in copper matrix, several cooper strands and several stainless steel strands. The coils are wound onto fiberglass cylindrical bobbins. To make AE event information more useful a real time instrumentation system was used. Two main measured and computer processed AE parameters were considered: the energy of AE events (E) and the accumulated energy of AE events (E ). Influence of current value in 0.5 MJ coils on E and E was studied. The sensors were installed onto the bobbin and the external surface of magnets. Three levels of initial current were examined: 600A, 1000A, 2450 A. An extraordinary strong dependence of the current level on E and E was observed. The specific features of AE from model coils, operated in sinusoidal vibration current changing mode were investigated. Three current frequency modes were examined: 0.012 Hz, 0.03 Hz and 0.12 Hz. In all modes maximum amplitude 1200 A was realized.

• Animal Bioscience
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• v.36 no.9
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• pp.1327-1335
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• 2023

Objective: When evaluating individuals with the same parent and no phenotype by pedigree best linear unbiased prediction (BLUP), it is difficult to explain carcass grade difference and select individuals because they have the same value in pedigree BLUP (PBLUP). However, single step GBLUP (ssGBLUP), which can estimate the breeding value suitable for the individual by adding genotype, is more accurate than the existing method. Methods: The breeding value and accuracy were estimated with pedigree BLUP and ssGBLUP using pedigree and genotype of 408 Hanwoo cattle from 16 families with the same parent among siblings produced by fertilized egg transplantation. A total of 14,225 Hanwoo cattle with pedigree, genotype and phenotype were used as the reference population. PBLUP obtained estimated breeding value (EBV) using the pedigree of the test and reference populations, and ssGBLUP obtained genomic EBV (GEBV) after constructing and H-matrix by integrating the pedigree and genotype of the test and reference populations. Results: For all traits, the accuracy of GEBV using ssGBLUP is 0.18 to 0.20 higher than the accuracy of EBV obtained with PBLUP. Comparison of EBV and GEBV of individuals without phenotype, since the value of EBV is estimated based on expected values of alleles passed down from common ancestors. It does not take Mendelian sampling into consideration, so the EBV of all individuals within the same family is estimated to be the same value. However, GEBV makes estimating true kinship coefficient based on different genotypes of individuals possible, so GEBV that corresponds to each individual is estimated rather than a uniform GEBV for each individual. Conclusion: Since Hanwoo cows bred through embryo transfer have a high possibility of having the same parent, if ssGBLUP after adding genotype is used, estimating true kinship coefficient corresponding to each individual becomes possible, allowing for more accurate estimation of breeding value.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1297-1303
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• 2023

Research on enhancing the mechanical strength, lightweight properties, electrical conductivity, and thermal conductivity of composite materials by incorporating nano-materials is actively underway. Thermoplastic resins can change their form under heat, making them highly processable and recyclable. In this study, Polyamide-Nylon 6 (PA6), a thermoplastic resin, was utilized, and as reinforcing agents, fused carbon nano-materials (FCN) formed by structurally combining Carbon Nanotube(CNT) and Graphene were employed. Nano-materials often face challenges related to cohesion and dispersion. To address this issue, Silane functional groups were introduced to enhance the dispersion of FCN in PA6. The manufacturing conditions for the composite materials involved determining the use of a dispersant and varying FCN content at 0.05 wt%, 0.1 wt%, and 0.2 wt%. Tensile strength measurements were conducted, and FE-SEM analysis was performed on fracture surfaces. As a result of the tensile strength test, it was confirmed that compared to pure PA6, the strength of the polymer composite with a content of 0.05 wt% was improved by about 60%, for 0.1 wt%, about 65%, and for 0.2 wt%, the strength was improved by 50%. Also, when compared according to the content of FCN, the best strength value was shown when 0.1 wt% was added. The elastic modulus also showed an improvement of about 15% in the case of surface treatment compared to the case without surface treatment, and an improvement of about 70% compared to pure PA6. Through FE-SEM, it was confirmed that the matrix material and silane-modified nanomaterial improved the dispersibility and bonding strength of the interface, helping to support the load evenly and enabling effective stress transfer.

• Journal of Intelligence and Information Systems
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• v.19 no.2
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• pp.101-123
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• 2013

Recently due to the advancements of science and information technology, the socio-economic business areas are changing from the industrial economy to a knowledge economy. Furthermore, companies need to do creation of new value through continuous innovation, development of core competencies and technologies, and technological convergence. Therefore, the identification of major trends in technology research and the interdisciplinary knowledge-based prediction of integrated technologies and promising techniques are required for firms to gain and sustain competitive advantage and future growth engines. The aim of this paper is to understand the recent research trend in management of technology (MOT) and to foresee promising technologies with deep knowledge for both technology and business. Furthermore, this study intends to give a clear way to find new technical value for constant innovation and to capture core technology and technology convergence. Bibliometrics is a metrical analysis to understand literature's characteristics. Traditional bibliometrics has its limitation not to understand relationship between trend in technology management and technology itself, since it focuses on quantitative indices such as quotation frequency. To overcome this issue, the network focused bibliometrics has been used instead of traditional one. The network focused bibliometrics mainly uses "Co-citation" and "Co-word" analysis. In this study, a keywords network analysis, one of social network analysis, is performed to analyze recent research trend in MOT. For the analysis, we collected keywords from research papers published in international journals related MOT between 2002 and 2011, constructed a keyword network, and then conducted the keywords network analysis. Over the past 40 years, the studies in social network have attempted to understand the social interactions through the network structure represented by connection patterns. In other words, social network analysis has been used to explain the structures and behaviors of various social formations such as teams, organizations, and industries. In general, the social network analysis uses data as a form of matrix. In our context, the matrix depicts the relations between rows as papers and columns as keywords, where the relations are represented as binary. Even though there are no direct relations between papers who have been published, the relations between papers can be derived artificially as in the paper-keyword matrix, in which each cell has 1 for including or 0 for not including. For example, a keywords network can be configured in a way to connect the papers which have included one or more same keywords. After constructing a keywords network, we analyzed frequency of keywords, structural characteristics of keywords network, preferential attachment and growth of new keywords, component, and centrality. The results of this study are as follows. First, a paper has 4.574 keywords on the average. 90% of keywords were used three or less times for past 10 years and about 75% of keywords appeared only one time. Second, the keyword network in MOT is a small world network and a scale free network in which a small number of keywords have a tendency to become a monopoly. Third, the gap between the rich (with more edges) and the poor (with fewer edges) in the network is getting bigger as time goes on. Fourth, most of newly entering keywords become poor nodes within about 2~3 years. Finally, keywords with high degree centrality, betweenness centrality, and closeness centrality are "Innovation," "R&D," "Patent," "Forecast," "Technology transfer," "Technology," and "SME". The results of analysis will help researchers identify major trends in MOT research and then seek a new research topic. We hope that the result of the analysis will help researchers of MOT identify major trends in technology research, and utilize as useful reference information when they seek consilience with other fields of study and select a new research topic.

• Membrane Journal
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• v.27 no.3
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• pp.205-215
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• 2017

Polymer membranes are cheap and easy in fabrication, and show a high permeability and selectivity, thus play pivotal roles in gas separation as well as water purification. However, polymer membranes typically exhibit the trade-off relation between permeability and selectivity; i.e. when the permeability is high, the selectivity is low and vice versa. Facilitated transport has been considered one of the solutions to address this issue. Over the last decades, facilitated transport concept had played an important role in preparing the membranes and providing ideal and various models for the transport. Understanding the nature of carrier, the mobility of matrix and the physico-chemical properties of polymer composites are crucial for facilitated transport. Depending on the mobility of carrier, facilitated transport membrane is classified into three; mobile carrier membrane, semi-mobile carrier membrane, fixed-site carrier membrane. Also, there are four types of reversible reaction between the carrier and the specific target; proton transfer reaction, nucleophilic addition reaction, p-complexation reaction and electrochemical reaction. The facilitated transport membranes have been applied in the separation of CO2, O2 and olefin (propylene or ethylene). In this review, major challenges surrounding facilitated transport membranes and the strategies to tackle these challenges are given in detail.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.441-441
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• 2009

Dye-sensitized solar cells (DSSCs) have been widely investigated as a next-generation solar cell because of their simple fabrication process and low coats. The cells use a porous nanocrystalline TiO2 matrix coated with a sensitizer dye that acts as the light-harvesting element. The photo-exited dye injects electrons into the $TiO_2$ particles, and the oxide dye reacts with I- in the electrolyte in regenerative cycle that is completed by the reduction of $I_3^-$ at a platinum-coated counter electrode. Since $TiO_2$ porous film plays a key role in the enhancement of photoelectric conversion efficiency of DSSC, many scientists focus their researches on it. Especially, a high light-to-electricity conversion efficiency results from particle size and crystallographic phase, film porosity, surface structure, charge and surface area to volume ratio of porous $TiO_2$ electrodes, on which the dye can be sufficiently adsorbed. Effective treatment of the photoanode is important to improve DSSC performance. In this paper, to obtain properties of surface and dispersion as nitric acid treated $TiO_2$ photoelectrode was investigate. The photovoltaic characteristics of DSSCs based the electrode fabricated by nitric acid pre-treatment $TiO_2$ materials gave better performances on both of short circuit current density and open circuit voltage. We compare dispersion of $TiO_2$ nanoparticles before and after nitric acid treatment and measured Ti oxidized state from XPS. Low charge transfer resistance was obtained in nitric acid treated sample than that of untreated sample. The dye-sensitized solar cell based on the nitric acid treatment had open-circuit voltage of 0.71 V, a short-circuit current of 15.2 mAcm-2 and an energy conversion efficiency of 6.6 % under light intensity of $100\;mWcm^{-2}$. About 14 % increases in efficiency obtained when the $TiO_2$ electrode was treated by nitric acid.

• Korean Journal of Animal Reproduction
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• v.16 no.1
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• pp.21-38
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• 1992

The present study was carried out to investigate morphologic changes in the corpus luteum of the pregnant rat by electron microscope after administration of prostaglandin F2$\alpha$(PGF2$\alpha$). Pregnant rates were treated with PGF2$\alpha$(1,500$\mu\textrm{g}$/rat) and their corpura lutea were observed morphologically. The results obtained in this study were summarized as follows ; 1. The weight of the ovaries and corpura lutea were decreased slightly at 8~24 hours after PGF2$\alpha$ administratin but no significant differences were observed. 2. The number of corpora lutea and luteal cells decreased slightly at 12~48 hours and 18~24 hours after PGF2$\alpha$ tretment but there were no signifciant differences between control and treatment. 3. The weight of uterus and the unmber of embryo decreased slightly at 96 hours and at 18~96 hours after PGF2$\alpha$ administration but no significant differences were obtained. 4. In the electron microscopic observatons, lipid droplets which are electron dense and appear in the cytoplasm moderately increased in number after PGF2$\alpha$ treatment. The lipid droplets were surrounded by mitochodria and appeared in the autophagic vacuoles. 5. Moderated and high electron dense mitochondria which are round or elongated in shape showed pleomorphism from 3 hours after PGF2$\alpha$ treatment. Destruction of tubular of vesicular cristae was observed at 6 hours after the treatment. Dense body and myelin figures in matrix of mitochondria were also appeared. 6. Well-developed smooth endoplasmic reticulum(sER) showed tubular or vesicular cisternae. A number of whorl membranes containing ribosomes, mitochondria and lipid droplets were observed at 1.5 hour after treatment. sER was abundant in luteal cells at 12 hours were treatment. 7. Well-developed Golgi pparatus appeared obviously 6 hours and more prominently at 12 hours. Those Golgi vesicles were remarkably dilated. 8. Generally, a few rough endoplasmic reticulum (rER) were appeared after treatment and cisternae showed slight dilatation. No differences among the treatments were observed. However, slight dilation of cisternae was observed at 1.5 hours after treatment. 9. Ribosomes composed of free and polyribosomes were abundant before treatment but polyribosomes were appeared at 12 to 24 hours after treatment. 10. Intercellular space were slightly extended at 3 hours and markedly extended at 12 hours. Numerous microvillous protrusions were observed at these times. Membranous multivesicular structures and autophagic vacuoles were also appeared in the intercellular space. 11. At 3 hours after the treatment, autophagic vacuoles appeared in the cytoplasm of the cell. They increased in number with time and were observed to transfer to the intercellular space. Lysosomal dense body appeared in the cytoplasm and the inclusion body was also observed in nucleus at 12 to 24 hours after treatment.