• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.65-65
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• 2015

In this talk, I will introduce two topics. The first topic is the polymer light emitting diodes (PLEDs) using graphene oxide quantum dots as emissive center. More specifically, the energy transfer mechanism as well as the origin of white electroluminescence in the PLED were investigated. The second topic is the facile synthesis of eco-friendly III-V colloidal quantum dots and their application to light emitting diodes. Polymer (organic) light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nanomaterial without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence (EL) from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. (Sci Rep., 5, 11032, 2015). New III-V colloidal quantum dots (CQDs) were synthesized using the hot-injection method and the QD-light emitting diodes (QLEDs) using these CQDs as emissive layer were demonstrated for the first time. The band gaps of the III-V CQDs were varied by varying the metal fraction and by particle size control. The X-ray absorption fine structure (XAFS) results show that the crystal states of the III-V CQDs consist of multi-phase states; multi-peak photoluminescence (PL) resulted from these multi-phase states. Inverted structured QLED shows green EL emission and a maximum luminance of ~45 cd/m2. This result shows that III-V CQDs can be a good substitute for conventional cadmium-containing CQDs in various opto-electronic applications, e.g., eco-friendly displays. (Un-published results).

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.47-56
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• 2006

The repeated loading responses of four shear-critical reinforced concrete beams with two different shear span-to-depth ratios, were studied. One series of beams was reinforced using pairs of bundled stirrups with $90^{\circ}$ standard hooks, haying free end extensions of $6d_b$. The companion beams contained shear reinforcement made with larger diameter headed bars anchored with 50mm diameter circular heads. A single headed bar had the same area as a pair of bundled stirrups and hence the two series were comparable. The test results indicate that beams containing headed bar stirrups have a superior performance to companion beams containing bundled standard stirrups with improved ductility, larger energy absorption and enhanced post-peak load carrying capability. Due to splitting of the concrete cover and local crushing, the hooks of the standard stirrups opened resulting in loss of anchorage. In contrast, the headed bar stirrups did not lose their anchorage and hence were able to develop strain hardening and also served to delay buckling of the flexural compression steel. Excellent load-deflection predictions were obtained by reducing the tension stiffening to account for repeated load effects.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.683-692
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• 2011

In piloti-type low-rise RC residential buildings, severe damages have been usually concentrated at piloti stories under the earthquake. In this study, a piloti story was retrofitted by installation of buckling-restrained braces (BRB's) to increase strength and stiffness of piloti story and by application of fiber reinforced polymer (FRP) sheet on columns to avoid the brittle shear and axial failure of columns. To verify this retrofit performance, reversed cyclic lateral load tests were performed on 1:5 scale bare and retrofitted frames. The test results showed that yield strength (43.2 kN) appeared to be significantly larger than design value (30 kN) due to the increase of strength in the compression side, but the stiffness value (11.6 kN/mm) turned out to be approximately one-half of the design value (24.2 kN/mm). The reasons for this difference in stiffness were due to slippage at joint between the frame and the BRB's, displacement and rotation at footing. The energy absorption capacity of the retrofitted frame was 7.5 times larger than that of the bare frame. The change of the number of load cells under the footing from 2 to 1 reduced lateral stiffness from 11.6 kN/mm to 6 kN/mm, which was only three times larger than that of the bare frame (2.1 kN/mm).

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.4
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• pp.524-532
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• 2016

This study was performed to compare the antioxidative activities of methanol extracts from Asparagus cochinchinensis with whole root (W-AC), flesh (F-AC), and root bark (B-AC). To evaluate the antioxidative properties of their methanol extracts, 1,1-diphenyl-2-picrylhydrazyl radical, nitrite, hydroxyl radical, 2,2'-azino-bis(3-ethylbenz thiazoline-6-sulfonate) radical scavenging activities, and contents of total flavonoid and polyphenol contents were measured. B-AC extract showed the highest antioxidative activity, whereas F-AC extract showed the lowest. For B-AC extract, caffeic acid was isolated by preparative high-performance liquid chromatography and confirmed by liquid chromatography-mass spectrometry and absorption spectroscopy, which showed 1.6% of total polyphenol contents among all methanol extracts.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.7 no.1
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• pp.165-175
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• 2012

Recently, accumulation of technology, transfer, absorption, and commercialization is being significantly recognized as a key factor for sustainable growth of the 21st century global economy. The government established "Technology Transfer and Commercialization Promotion Act" In order that the technology developed at public research institutions can be transferred to the private sector and commercialized; the technology developed in the private sector can be traded and commercialized. Also, the Article 14 of "Technology Transfer and Commercialization Promotion Act" is concerning technology transfer agents' registration, promotion, and support: it introduced the special status system of technology transfer agents and the government registers, manages, and supervises it. In most developed countries, the technology transfer agency is transferred to the private sector and it is referred as a technology transfer agent or technology broker. In the domestic market, despite the introduction of the above special status system and the building a various organization and transfer medium system for boosting the market's revitalization, some problems occurred; because the registration system of a technology transfer agent and legal basis and system about its following-up control fall short. For example, recently technology transfer-related performance exemption has brought the activation of technology transfer agent's registration, but there was the limit of selecting the expert above a certain level. Therefore, some countermeasures for this are urgent, In addition, through a compulsory training completion system before the technology trade agent registration is prepared, a short period of curriculum was not sufficient to provide applicants various specialized knowledge. In this research, it is considered about the reform of technology transfer agent through its comparative study in China and Korea. Some improvements are suggested for expanding the market of technology transfer commercialization, assuring the agents' service and strengthening the competitiveness.

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.12
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• pp.1662-1671
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• 2007

The change in physical properties of polypropylene nonwoven fabrics used as top sheet for disposable sanitary goods was carried out using chitosan that is a type of natural polymer and has excellent human affinity by varying the molecular weight and concentration of chitosan. Low molecular weight(LMW) chitosan treated fabrics were found to be evenly coated on fabrics and had better dyeability by apparent dye uptake and its deodorization rate increased over the time. On the other hand, high molecular weight(HMW) chitosan treated fabrics showed higher add-on ratio and its dynamic water absorption rate and represented an increase in water transport rate. With chitosan treatment, its air permeability was improved. Regardless of the type of bacteria and chitosan concentration, its antibacterial activity was excellent in the case of the HMW chitosan treatment. In this regard, chitosan treatments by using a relatively high molecular weight was found as an effective way in the functional improvement of moisture properties and antibacterial activity including their most important performance in sanitary nonwoven fabrics.

• Journal of Preventive Medicine and Public Health
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• v.31 no.3 s.62
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• pp.449-459
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• 1998

This study was started to find out if plasma malondialdehyde(MDA), $\alpha-tocopherol$ and erythrocyte superoxide dismutase(SOD) activity could be markers of biological activity resulting from exposed to lead in workers. Blood samples were randomly obtained from lead-exposed workers(n=29), $CO_2$, welders(n=60) and office workers(n=60). We used whole blood to analyse blood lead with atomic absorption spectrophotometer. Superoxide dismutase activity in erythrocyte was measured with spetrophotometer. MDA and $\alpha-tocopherol$ in plasma were measured with high performance liquid chromatography. Lead-exposed workers was significantly high in blood lead concentration$(29.37{\mu}g/d\ell)$ compared with welders$(6.42{\mu}g/d\ell)$ and office workers$(5.01{\mu}g/d\ell)$. The level of plasma MDA was significantly higher in the lead-exposed workers($1.87{\mu}mol/g$ cholesterol) than the welders($1.41{\mu}mol/g$ cholesterol) and office workers($1.41{\mu}mol/g$ cholesterol). Erythrocyte SOD activity in lead-exposed workers(56.80 U/g Hb) was significantly increased than those of welders(37.63 U/g Hb) and office workers(20.47 U/g Hb). The plasma $\alpha-tocopherol$ level of lead-exposed workers($4.93{\mu}g/g$ cholesterol) was statistically different from welders($4.25{\mu}g/g$ cholesterol) and office workers$4.28{\mu}g/g$ cholesterol). Neither age nor smoking was related to SOD or MDA level. Blood lead was significantly correlated with erythrocyte SOD activity(r=0.405), plasma MDA(r=0.296) and $\alpha-tocopherol$ (r=0.207). Plasma MDA was also significantly correlated with SOD (r=0.217). In multiple regression analysis, the change of MDA and SOD activity level related to the blood lead concentration. These results suggested that the increase of plasma MDA and erythrocyte SOD activity in lead-exposed workers had a close relationship with the oxidative stress induced by lead.

• Journal of radiological science and technology
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• v.26 no.3
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• pp.51-57
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• 2003

Mitigation of fast neutron irradiation damage on reactor vessel and improvement of mechanical integrity are desired for the successful plant life-time extension. In this study, the performance of metallic hydride for this application is reviewed and compared. First, selected prospective metallic hydrides are evaluated by MCNP code and put into the attenuation test using Cf-252 neutron source. Since for the reactor application high moderation and reflection with no absorption are favored, Z factor is introduced for the evaluation. According to the Z value estimation $ZrD_2$ and $TiD_2$ are turned out to be the most favorable fast neutron shielding materials. More thorough evaluation by computer simulation and experimentally, will be followed.

• Journal of Pharmaceutical Investigation
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• v.33 no.3
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• pp.215-221
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• 2003

A bioequivalence study of $Ambrect^{TM}$ tablets (Dong Wha Pharm. Ind. Co., Ltd.) to $Mucopect^{TM}$ tablets (Boehringer Ingelheim Korea, Ltd.) was conducted according to the guideline of Korea Food and Drug Administration (KFDA). Twenty four healthy male Korea volunteers received each medicine at the ambroxol hydrochloride dose of 30 mg in a $2{\times}2$ crossover study. There was a one-week wash out period between the doses. Plasma concentrations of ambroxol were monitored by a high-performance liquid chromatography for over a period of 24 hours after the administration. $AUC_t$ (the area under the plasma concentration-time curve from time zero to 24 hr) was calulated by the linear trapezoidal rule method. $C_{max}$ (maximum plasma drug concentration) and $T_{max}\;(time\;to\;reach\;C_{max})$ were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed $AUC_t\;and\;C_{max}$. No significant sequence effect was found for all of the bioavailability parameters indicating that the crossover design was properly performed. The 90% confidence intervals of the $AUC_t$ ratio and the $C_{max}$ ratio for $Ambrect^{TM}/Mucopect^{TM}$ were 0.89-1.01 and 0.89-1.02, respectively. These values were within the acceptable bioequivalence intervals of 0.80-1.25. Thus, our study demonstrated the bioequivalence of $Ambrect^{TM}\;and\;Mucopect^{TM}$ with respect to the rate and extent of absorption.

• Korean Journal of Environmental Agriculture
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• v.27 no.3
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• pp.231-238
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• 2008

This study proposed the method of phosphate recovery from municipal wastewater by using ferrous iron waste, generated from the mechanical process in the steel industry. In the analysis of XRD, ferrous iron waste was composed of $Fe_3O_4$ (magnetite), practically with $Fe^{2+}$ and $Fe^{3+}$. It had inverse spinel structure. In order to identify the adsorption characteristic of phosphate on ferrous iron waste, isotherm adsorption test was designed. Experimental results were well analyzed by Freundlich and Langmuir isotherm theories. Empirical constants of all isotherms applied increased with alkalinity in the samples, ranging from 1.2 to 235 $CaCO_3/L$. In the regeneration test, empirical constants of Langmuir isotherm, i.e., $q_{max}$ (maximum adsorption capacity) and b (energy of adsorption) decreased as the frequency of regeneration was increased. Experiment was further performed to evaluate the performance of the treatment scheme of chemical precipitation by ferrous iron waste followed by biological aerated filter (BAF). The overall removal efficiency in the system increased up to 80% and 90% for total phosphate (TP) and soluble phosphate (SP), respectively, and the corresponding effluent concentrations were detected below 2 mg/L and 1 mg/L for TP and SP, respectively. However, short-circuit problem was still unsolved operational consideration in this system. The practical concept applied in this study will give potential benefits in achieving environmentally sound wastewater treatment as well as environmentally compatible waste disposal in terms of closed substance cycle waste management.