• Journal of Environmental Science International
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• v.25 no.6
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• pp.897-904
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• 2016

We investigated the local climatological characteristics of the mountain adjacent the Dongyeong herb garden in Chilgok. We established one set of automatic weather system (AWS) on a hill where development of herb garden is in progress. The observations were continued for 2 years(2013. 07-2015.06). In this study, we analyzed the observed data comparing the data of Gumi meteorological observatory (GMO). The results showed that the air temperature(relative humidity) of Dongyeong herb garden were lower(higher) than those of GMO. Especially the differences are more during warm climate season. It means that the gaps of thermal environment between two points are mainly caused by the evaporation effects of forest. In addition, we analyzed the warmth indices(warmth index and coldness index) with the observed air temperature. The warmth and coldness indices indicate about 107 and -12, respectively. The values correspond to warm temperature climate.

• The Journal of Advanced Prosthodontics
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• v.9 no.5
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• pp.364-370
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• 2017

PURPOSE. To explore the influence of different surface conditionings on surface changes and the influence of surface treatments and aging on the bond strengths of composites to non-aged and aged resin nanoceramics. MATERIALS AND METHODS. Rectangular-shaped non-aged and aged (5000 thermocycles) resin nanoceramic specimens (Lava Ultimate) (n=63, each) were divided into 3 groups according to surface treatments (untreated, air abrasion, or silica coating) (n=21). The surface roughness was measured and scanning electron microscopy was used to examine one specimen from each group. Afterwards, the specimens were repaired with a composite resin (Filtek Z550) and half were sent for aging (5000 thermocycles, n=10, each). Shear bond strengths and failure types were evaluated. Roughness and bond strength were investigated by two- and three-way analysis of variance, respectively. The correlation between the roughness and bond strength was investigated by Pearson's correlation test. RESULTS. Surface-treated samples had higher roughness compared with the untreated specimens (P=.000). For the non-aged resin nanoceramic groups, aging was a significant factor for bond strength; for the aged resin nanoceramic groups, surface treatment and aging were significant factors. The failures were mostly adhesive after thermal cycling, except in the non-aged untreated group and the aged air-abraded group, which had mostly mixed failures. Roughness and bond strength were positively correlated (P=.003). CONCLUSION. Surface treatment is not required for the repair of non-aged resin nanoceramic; for the repair of aged resin nanoceramic restorations, air abrasion is recommended.

• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.272-277
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• 2017

Organic-inorganic hybrid thermoelectric materials have obtained increasing attention because it opens the possibility of enhancing thermoelectric performance by utilizing the low thermal conductivity of organic thermoelectric materials and the high Seebeck coefficient of inorganic thermoelectric materials. Moreover, the organic-inorganic hybrid thermoelectric materials possess numerous advantages, including functional aspects such as flexibility or transparency, low cost raw materials, and simplified fabrication processes, thus, allowing for a wide range of potential applications. In this study, the types and synthesis methods of organic-inorganic thermoelectric hybrid materials were discussed along with the methods used to enhance their thermoelectric properties. As a key factor to maximize the thermoelectric performances of hybrid thermoelectric materials, the nanoengineering to control the nanostructure of the inorganic materials as well as the modification of the organic material structure and doping level are considered, respectively. Meanwhile, the interface between the inorganic and organic phase is also important to develop the hybrid thermoelectric module with excellent reliability and high thermoelectric efficiency in addition to its performance in various electronic devices.

• Preventive Nutrition and Food Science
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• v.7 no.4
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• pp.378-385
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• 2002

Oxidant radicals are implicated as a causal factor in the pathogenesis of neurobiological disorders and neuro-degenerative diseases. The objective of this study was to investigate the antioxidant activity of edible plants against oxidative stress in bovine brain tissue. Fifty five kinds of edible plants grown in Korea were dried either by freeze-drying or hot-air drying (7$0^{\circ}C$), and evaluated for their antioxidant activity by measuring TBARS (thiobarbituric acid-reactive substances) in brain homogenates subjected to Fe$^{+2}$_mediated lipid peroxidation with or without the addition of botanical extracts. Heat-drying decreased the antioxidant activity of most plant extracts by 10~81%, compared with freeze-drying. However, Aruncus americanus, Ligularia stenocephala, Artemisia princceps var. orientalis, Petasites japonicus and Aster scaber showed very strong antioxidant activities regardless of processing, with or without heat treatment. The $IC_{50}$/ values of the methanol extracts from these edible plants were in the range of 0.093~0.379 mg/$m\ell$, which was lower than that of ascorbic acid (0.79 mg/$m\ell$). Thermal processing of some edible plants enhanced their antioxidant activity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.211-212
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• 2011

It was very important to evaluate concrete experimentally at elevated temperature because concrete was filled with aggregate of concrete volume about 70 percent. Concrete exposure to high temperatures produces changes in its internal structure, for instance loss of its strength and deformation capacity, in extreme cases risking the service life of the structure. The work of this paper is performed to evaluate the thermal behavior of ultra-high strength concrete having different water to cement ratio (strength), fine aggregate to aggregate ratio and maximum size of coarse aggregate. For exposure to 500℃ during 1 hour, residual mechanical properties of the ultra-high strength concrete decreased as the s/a ratio decreases and the maximum size of coarse aggregate increases.

• Transactions on Electrical and Electronic Materials
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• v.3 no.2
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• pp.32-37
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• 2002

This paper gives the basic mechanical properties of indium-tin-oxide (ITO) films on polymer substrates which are exposed to externally and thermally induced bending force. By using modified Storney formula including triple layer structure and bulge test measuring the conductive changes of patterned ITO islands as a function of bending curvature, the mechanical stability of ITO films on polymer substrates was intensively investigated. The numerical analyses and experimental results show thermally and externally induced mechanical stresses in the films are responsible for the difference of thermal expansion between the ITO film and the substrate, and leer substrate material and its thickness, respectively. Therefore, a gradually ramped heating process and an organic buffer layer were employed to improve the mechanical stability, and then, the effects of the buffer layer were also quantified in terms of conductivity-strain variations. As a result, it is uncovered that a buffer layer is also a critical factor determining the magnitude of mechanical stress and the layer with the Young's modulus lower than a specific value can contribute to relieving the mechanical stress of the films.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.95-101
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• 1995

Crystallizable glasses with precipitation of celsian, anorthite, wollastonite and gahnite were prepared for the purpose of insulating dielectric layers in devices such as integrated circuit substrates. The starting glasses were prepared by melting the batches for 1 hour at 1450.deg. C and then Quenching to a distilled water. And crystallization behavior of these glasses were studied by DTA, TMA, XRD analysis and by the measurement of dielectric properties. The overall composition of the glass-ceramic consists in weight percent of 30-35% A1$_{2}$O$_{3}$, 13-26% BaO, 5-21% CaO, 10-24% ZnO, 4.5-9.0% TiO$_{2}$ and 4-8% B$_{2}$O$_{3}$. As a result, in barium-rich glasses only celsian phase was developed in the range of 850-900.deg. C. Also, the thermal expansion coefficient, dielectric constant and quality factor of these glass-ceramics were 68*10$^{-7}$ /.deg. C, about 9 and more than 1000, respectively.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1282-1284
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• 1998

ZnO Varistor is an electronic ceramic device for controlling the surge voltage from low level to high. In this study, the puncture mechanism occurring in ZnO varistor is investigated, and the simulation for restraining the puncture by formulating the relation between the applied voltage and the increase of the inside temperature of grain is applied. In order to simulate the cause of the current localization which is the primary factor causing the puncture, the localization phenomenon and the temperature distribution induced by the localized current, the Voronoi network is applied, which can realize the structure of the practical varistor better than the established simple network. Using the current through each grain and the voltage applied to the grain boundary obtained from that simulation, the Joule heating energy is calculated and the phenomenon that the puncture occurs can be analyzed quantitatively by simulating the electric and thermal characteristics according to the externally applied pulsed voltage.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1487-1489
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• 1998

In this paper, thin films of PI were fabricated VDPM of dry processes which are easy to control the film's thickness and hard to pollute due to volatile solvents. From FT-lR, PAA thin films fabricated by VDP were changed to PI thin films by thermal curing. From SEM, AFM and Ellipsometer experimental, as the higher curing temperatures the films thickness decreases and reflectance increases. Therefore, Pl could be fabricated stable by increasing curing temperature. The relative permitivity and dissipation loss factor were 3.7 and 0.008. Also, the resistivity was about $1.05{\times}10^{15}{\Omega}cm$ at $30^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.327-332
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• 2009

In the devices structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) /tris (8-hydroxyquinoline)aluminum$(Alq_3)$electron-transport-layer(ETL)(2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline(BCP))/Al, we have studied the efficiency improvement of organic light-emitting diodes depending on the thickness variation of BCP using electron transport layer. The thickness of TPD and $Alq_3$ was manufactured 40 nm, 60 nm under a base pressure of $5{\times}10^{-6}$ Torr using at thermal evaporation, respectively. The TPD and $Alq_3$ layer were evaporated to be deposition rate of $2.5{\AA}/s$. And the BCP was evaporated to be a4 a deposition of $1.0{\AA}/s$. As the experimental results, we found that the luminous efficiency and the external quantum efficiency of the device is superior to others when thickness of BCP is 5 nm. Also, operating voltage is lowest. Compared to the ones from the devices without BCP layer, the luminous efficiency and the external quantum efficiency were improved by a factor of four hundred ninty and five hundred, respectively. And operating voltage is reduced to about 2 V.