• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.86-88
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• 2004

본 연구에서는 고주파 이동통신 기기용 칩형 세라믹 안테나의 사용을 위한 저유전율 및 저온동시소성이 가능한 CaO-B2O3-SiO2계 유리를 제조하고자 하였다. 제조된 CaO-B2O3-SiO2계 유리는 열분석을 통하여 낮은 연화온도를 갖는 안정한 유리조성을 선정하였다. 유리분말을 이용하여 성형된 샘플은 소결온도에 따른 특성을 조사하였다. 소결온도변화에 따라 유전율(${\epsilon}_r$)은 4-4.5값을 나타냈으며, 유전손실(tan$\delta$)은 <$0.1\%$ 보였으나, 품질계수(Q$\times$f)는 큰 변화폭을 보였다.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2531-2536
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• 2010

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the molecular structures and absorption spectra of two dyes containing diphenylaniline and 4-diphenylamino-diphenylaniline as donor moiety (TPA1 and TPA3). The geometries indicate that the strong conjugation is formed in the dyes. The electronic structures suggest that the intramolecular charge transfer from the donor to the acceptor occurs, and the electron-donating capability of 4-diphenylamino-diphenylaniline is stronger than that of diphenylaniline. The computed highest occupied molecular orbital (HOMO) energy levels are -5.31 and -4.90 eV, while the lowest unoccupied molecular orbital (LUMO) energies are -2.29 and -2.26 eV for TPA1 and TPA3, respectively, revealing that the interfacial charge transfer between the dyes and the semiconductor electrode are electron injection processes from the photon-excited dyes to the semiconductor conduction band. Furthermore, all the experimental absorption bands of TPA1 and TPA3 have been assigned according to the TDDFT calculations.

• The Plant Pathology Journal
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• v.16 no.3
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• pp.151-155
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• 2000

A cDNA (Oslls1) encoding Lls1-homologue of maize was isolated from cDNA library of rice (Oryza sativa cv. Ilpum). The 2,138 bp of full length Oslls1 clone contains an open reading frame of 1,623 nucleotides encoding 575 amino acid residues. The deduced amino acid sequence of Oslls1 has a high level of homology with chlorophyll a oxygenases of Arabidopsis thaliana (67%) and Marchantia polymorpha (65%). Southern blot analysis of genomic DNA indicates the existence of a small gene family for Oslls1 in the rice genome. The expression of Oslls1 mRNA was induced in leaves and germinating seeds. Treatment of $H_2O$$_2$significantly down-regulated Oslls1 expression. The expression of Oslls1 mRNA was consititutively down-regulated in the blm, a rice mutant exhibiting spontaneous necrotic lesions. These results suggest that this Oslls1 gene may be involved incell death mechanisms in the blm mutant of rice.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.963-965
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• 2003

We have synthesized new hole transport materials(HTMs). Then we have fabricated structures of ITO/new HTM/$Alq_{3}$/EIL/Al. New HTM based devices have higher current density and lower turn-on voltage than TPD based devices. New HTMs have higher HOMO level than TPD. The new HTM based OLEDs have shown better current injection than the TPD based OLEDs, due to the lower injection barrier between ITO surface and HTM.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.96-99
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• 2004

A new proton conductive inorganic-organic hybrid membrane doped with $H_3PO_4$ was fabricated via sol-gel process wit 3- glycidoxypropyltrimethoxysilane(GPTMS), 3-aminopropyltriethoxysilane(APTES) and tetraethoxysilane(TEOS) asprecursors. Theproto conductivity of about 3.0$\times10^{-3}S/cm$ was obtained at $120^{\circ}C$ under $50\%$ relative humidity (R.H). DTA curves showed that the thermal stability of the membrane is significantly enhanced by the presence of $SiO_2$ framework up to $250^{\circ}C$. SEM and XRD revealed that the gel is microporou and amorphous. The addition of APTES improved the conductivity of the membranes and the effect of the APTES on the conductivity was also discussed in this paper.

• Korean Journal of Materials Research
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• v.10 no.7
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• pp.459-463
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• 2000

Direct use of negative ions for modification of materials has opened new research such as charging-free ion implantation and new materials syntheses by pure kinetic bonding reactions. For these purposes, a new solid-state ce-sium ion source has been developed in the laboratory scale. In this paper, diamond like carbon(DLC) films were prepared on silicon wafer by a negative cesium ion gun. This system does not need any gas in the chamber; deposition occurs under high vacuum. The ion source has good control of the C- beam energy(from 80 to 150eV). The result of Raman spectrophotometer shows that the degree of diamond-like character in the films, $sp^3$ fraction, increased as ion beam energy increases. The nanoindentation hardness of the films also increases from 7 to 14 GPa as a function of beam energy. DLC films showed ultra-smooth surface(Ra~1$\AA$)and an impurity-free quality.

• Journal of Korea Foundry Society
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• v.25 no.5
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• pp.195-202
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• 2005

In this study, we investigated the effect of Sb/RE on the microstructure and mechanical properties of as-cast heavy sectioned, over 250mm thickness, ferritic ductile cast iron. Exothermic and thermal insulation material were equipped on the wall of sand cast mold having the dimensions of $250{\times}250{\times}250$ mm. The nominal composition of the molten metal was controlled to be on the eutectic composition and Sb was added about 0, 0.005 and 0.02% respectively. In the center of as-cast ingot without Sb addition, the solidification of chunky graphite was induced by the eutectic reaction that took long time, which caused the decrease of elongation and impact energy. In case that the value of Sb/RE is 0.8, the solidification of chunky graphite could be suppressed and the improvement of nodularity was observed. On the other hand, the excessive addition of Sb suppressed the solidification of chunky graphite but gave rise to the solidification of flake graphite and the increase of pearlite contents. This results in poor elongation and impact energy which is lower than those in the case of no Sb addition.

• Journal of Korea Foundry Society
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• v.26 no.1
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• pp.17-26
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• 2006

The substitution of cooling method from water quenching to air cooling after solution heat treatment was aimed for the development of a convenient and economical heat treatment process of duplex stainless steels without deterioration of mechanical and corrosion resistant properties for the industry. In order to achieve this goal, the mechanical properties and corrosion properties of a ASTM A890-4A duplex stainless steel were systematically investigated as functions of casting condition and cooling method after solution heat treatment. A 3-stepped sand mold and a permanent Y-block mold were used to check the effects of solidification structure and cooling rate after solution heat treatment. The microstructural characteristics such as the ferrite/austenite phase ratio and the precipitation behavior of ${\sigma}$ phase and carbides were investigated by combined analysis of OM and SEM-EDX with an aid of TTT diagram. Hardness and tension test were performed to evaluate the mechanical properties. Impact property at $-40^{\circ}C$ and corrosion resistance were also examined to check the possibility of the industrial application of this basic study. Throughout this investigation, air-cooling method was proved to effectively substitute for water-quenching process after the solution heat treatment, when the duplex stainless steel was sand mold cast with a thickness below 15 mm or permanent mold cast with a thickness below 20 mm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.1-10
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• 1994

It is well known that crystal growth is an essential area of research for optoelectronic materials. In the present paper the growth techniques and the advanced progress in development of crystal materials important for optoelectronic applications are described. New growth techniques, developed in the authors' laboratory, enabling the introduction of expanded applications of new materials are presented. After a review of recent developments of new techniques for optoelectronic materials, own experimental studies will be discussed.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.142.2-142
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• 2000