• 한국재료학회지
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• 제23권1호
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• pp.31-34
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• 2013

Trivalent cerium-ion-doped $Y_3(Al,\;Ga)_5O_{12}$ nanoparticle phosphor nanoparticles were synthesized using the reverse micelle process. The Ce doped $Y_3(Al,\;Ga)_5O_{12}$ particles were obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase and poly(oxyethylene) nonylphenyl ether (Igepal CO-520) as the non-ionic surfactant. The crystallinity, morphology, and thermal properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy. The crystallinity, morphology, and chemical states of the ions were characterized; the photo-physical properties were studied by taking absorption, excitation, and emission spectra for various concentrations of cerium. The photo physical properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were studied by taking the excitation and emission spectra for various concentrations of cerium. The average particle size of the synthesized YAG powders was below $1{\mu}m$. Excitation spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ samples were 485 nm and 475 nm, respectively. The emission spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ were around 560 nm and 545 nm, respectively. $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ is a red-emitting phosphor; it has a high efficiency for operation under near UV excitation, and may be a promising candidate for photonic applications.

• 폴리머
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• 제32권1호
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• pp.56-62
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• 2008

Diol과 diacid 단량체들의 다양한 조합으로 2단계 축합중합으로 가교구조를 가지는 세 종류의 신규 폴리에스테르를 새롭게 합성하였다. 이들 고분자 필름은 $240^{\circ}C$에서 수 시간 고온 열처리하면, 주사슬에 의한 금지 전이에도 불구하고, 가시영역에서 흡수를 나타내었으며 330 nm 이상의 파장에서 여기시키면 청색에서 근적외선에 이르는 넓은 범위에서 발광을 나타내었다. 신규 폴리에스테르의 발광 현상은 주사슬에 포함된 말로네이트기가 고온 열처리를 통해 자기축합 형태의 Knoevenagel 반응을 일으켜 분자 내 공역구조를 형성하기 때문이다. 또한 이들 고분자의 열적 특성은 가지화도 차이에 의한 화학적 가교정도에 따라 현저한 차이를 보였을 뿐 아니라 광분해 현상도 관찰되었다. 필름 상태에서 강한 자외선을 조사하여 말로네이트기의 분해반응을 유도하고, 이를 이용한 형광 이미지 패터닝을 수행한 결과, 고해상도의 이미지 패턴을 얻을 수 있었다.

• 한국생활과학회지
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• 제21권4호
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• pp.791-803
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• 2012

This study intends to identify applicability of natural dye extracted from Aplysia kurodai, aiming to standardization of Aplysia kurodai natural dyeing through scientific validation by analyzing characteristics of pigment elements to review dyeability, colorfastness and antibacterial activity. Such material as silk fabrics that is animal fiber were used for this purpose, and derived following summarized results. UV/VIS spectrum analysis on the pigment of Aplysia kurodai that was extracted from purple gland showed that maximum absorbtion was near 540 nm. The silk fabric optimal dyeing can be achieved at a temperature of $55^{\circ}C$ with a colorant concentration of 5%. Dyed at $55^{\circ}C$ with interval of 10~90 minutes for identifying dye uptake over time to observed slow increase of dye uptake over time, and equilibrium occurred at 50 minutes. For dye uptake according to pH, while dye uptake was superior in acidity, it decreased rapidly in a base after pH 7. For color changes according to pH variation, it was reddish purple in acidity and was purplish red in a base. For color changes according to mordanting method, more clear color change had been obtained when process with aluminium pre-mordanting than non-mordanting and post-mordanting. The colorfastness to light, perspiration and washing was 1, 4~5, and 3~4 ratings respectively. The silk fabric dyed with Aplysia kurodai demonstrated excellent antimicrobial activity to Staphylococcus aureus and Klebsiella pneumoniae. The Aplysia kurodai can be used as a new colorant for the natural dyeing of silk.

• 천문학회보
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• 제41권1호
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• pp.70.3-70.3
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• 2016

Active galactic nuclei (AGNs) typically show a non-thermal continuum locally represented by a power-law and many prominent emission lines in the UV and optical regions. AGNs are classified by two types, where Type I AGNs exhibit both broad and narrow lines and only narrow lines are observed in Type 2 AGNs. The unification models of AGNs invoke the existence of a molecular torus just outside of the broad line region. In the presence of a high column HI region associated with the molecular torus, we propose that significant fraction of broad line photons near Lyman series can be scattered by atomic hydrogen in the torus. In particular, $Ly{\alpha}$ being the strongest emission line, strong linear polarization may develop around $Ly{\alpha}$ through Rayleigh scattering. We adopt a Monte Carlo technique to investigate the polarized transfer of $Ly{\alpha}$ in a thick HI region with the shape of a torus. We consider the range of HI column density N_HI = 1020-23 with fixed geometric parameters of the torus such as the inner and outer radii and the height. We present the polarized spectra and angular distribution of Rayleigh scattered radiation around $Ly{\alpha}$. We find that the $Ly{\alpha}$ core part is polarized in the direction perpendicular to the symmetry axis whereas in the far wing part it is polarized in the parallel direction. It is concluded that the unification of AGNs implies that $Ly{\alpha}$ can be uniquely polarized through Rayleigh scattering.

• 한국재료학회지
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• 제24권7호
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• pp.351-356
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• 2014

A spherical $Sr_4Al_{14}O_{25}:Eu^{2+}$ phosphor for use in white-light-emitting diodes was synthesized using a liquid-state reaction with two precipitation stages. For the formation of phosphor from a precursor, the calcination temperature was $1,100^{\circ}C$. The particle morphology of the phosphor was changed by controlling the processing conditions. The synthesized phosphor particles were spherical with a narrow size-distribution and had mono-dispersity. Upon excitation at 395 nm, the phosphor exhibited an emission band centered at 497 nm, corresponding to the $4f^65d{\rightarrow}4f^7$ electronic transitions of $Eu^{2+}$. The critical quenching-concentration of $Eu^{2+}$ in the synthesized $Sr_4Al_{14}O_{25}:Eu^{2+}$ phosphor was 5 mol%. A phosphor-converted LED was fabricated by the combination of the optimized spherical phosphor and a near-UV 390 nm LED chip. When this pc-LED was operated under various forward-bias currents at room temperature, the pc-LED exhibited a bright blue-green emission band, and high color-stability against changes in input power. Accordingly, the prepared spherical phosphor appears to be an excellent candidate for white LED applications.

• 한국재료학회지
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• 제8권8호
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• pp.733-736
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• 1998

분자들이 용액 내에서의 cluster나 박막 내에서의 cluster와 같이 다른 cluster로 뭉쳐졌을 때, 가시광선과 자외선부근의 영역에서 fullerene $C_{60}$의 전자흡수 스펙트럼 변화가 관찰되었다. 2.73eV에서 흡수 피크들이 관찰되었는데, 이러한 피크들은 독립된 분자들로부터 온 것이 아니라 분자들의 직접적인 상호작용으로부터 온 것으로 생각된다. Grained fullerene 박막에서는 흡수피크들이 3.35eV에서도 관찰되었는데 이러한 피크들은 grain의 계면에서 분자들의 상호작용으로부터 온 것으로 생각된다. 이러한 흡수의 Dichroism은 비등방성 macrostructure를 갖는 시료에서도 관찰되었다.

• 한국환경과학회지
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• 제2권1호
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• pp.57-68
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• 1993

Polycyclic aromatic hydrocarbons (PAMs) are ubiquitous contaminants in marine environments. PAHs enter estuarine and nearshore marine environment via several routes such as combustion of fossil fuels, domestic and industrial effluents and oil spills PAHs have been the focus of numerous studies in the world because they owe potentially carcinogenic, mutagenic, and teratogenic to aquatic organisms and humans from consuming contaminated food. However, one can hardly find any available data on PAM content in marine organisms in Korea. The present study was carried out in order to determine PAH content in oysters from the intertidal and subtidal zones of Chinhae Bay, which is located in near urban communities and an industrial complex, and the bay is considered to be a major repositories of PAHs. 16 PAHs were analyzed by High Performance Liquid Chromatography (HPLC) with uv/vis and fluorescence detectors in oysters: they are naphthalene (NPTHL), acenaphthylene (ANCPL), acenaphthene (ACNPN), fluorene (FLURN), phenanthrene (PKEN), anthracene (ANTHR), fluoranthene (FLRTH), pyrene (PYRf), benzo(a)anthracene (BaA), chrysene (CHRY), benzo(b)- fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), dibenz(a, h)anthracene (DhA), benzo(g, h, i)peryne (Bghip) and indeno(1, 2, 3, -cd)pyrene (I123cdP). The PAH contents in oysters from the intertidal and subtidal zones of Chinhae Bay ranged from < 0.1 to 992.0 $\mu\textrm{g}$/kg (mean 69.8 $\pm$ 9.8 $\mu\textrm{g}$/kg). Key words . polycyclic aromatic hydrocarbon, high performance liquid chromatography, oyster, Chinhae Bay.

• Environmental Engineering Research
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• 제17권4호
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• pp.179-184
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• 2012

The light absorbance of photocatalysts and reaction kinetics of environmental pollutants at the liquid-solid and gas-solid interfaces differ from each other. Nevertheless, many previous photocatalytic studies have applied the science to aqueopus applications without due consideration of the environment. As such, this work reports the surface and morphological characteristics and photocatalytic activities of carbon-embedded (C-$TiO_2$) photocatalysts for control of gas-phase methyl tertiary-butyl ether (MTBE) under a range of different operational conditions. The C-$TiO_2$ photocatalysts were prepared by oxidizing titanium carbide powders at $350^{\circ}C$. The characteristics of the C-$TiO_2$ photocatalysts, along with pure TiC and the reference pure $TiO_2$, were then determined by X-ray diffraction, scanning emission microscope, diffuse reflectance ultraviolet-visible-near infrared (UV-VIS-NIR), and Fourier transform infrared spectroscopy. The C-$TiO_2$ powders showed a clear shift in the absorbance spectrum towards the visible region, which indicated that the C-$TiO_2$ photocatalyst could be activated effectively by visible-light irradiation. The MTBE decomposition efficiency depended on operational parameters, including the air flow rate (AFR), input concentration (IC), and relative humidity (RH). As the AFRs decreased from 1.5 to 0.1 L/min, the average efficiencies for MTBE increased from 11% to 77%. The average decomposition efficiencies for the ICs of 0.1, 0.5, 1.0, and 2.0 ppm were 77%, 77%, 54%, and 38%, respectively. In addition, the decomposition efficiencies for RHs of 20%, 45%, 70%, and 95% were 92%, 76%, 50%, and 32%, respectively. These findings indicate that the prepared photocatalysts could be effectively applied to control airborne MTBE if their operational conditions were optimized.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.521-522
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• 2006

In this paper, hybrid air-water discharges were used to develop an optimal condition for providing a high level of water decomposition for hydrogen yield. Electrical and optical phenomena accompanying the discharges were investigated along with feeding gases, flow rates, and point-to-plane electrode gap distance. The primary focus of this experiment was put on the optical emission of the near UV range, with the energy threshold sufficient for water dissociation and excitation. The $OH(A^{2+},'=0\;X^2,"=0$) band's optical emission intensity indicated the presence of plasma chemical reactions involving hydrogen formation. In the gaseous atmosphere saturated with water vapor the OH(A-X) band intensity was relatively high compared to the liquid and transient phases although the optical emission strongly depended on the flow rate and type of feeding gas. In the gaseous phase discharge phenomenon for Ar carrier gas transformed into a gliding arc via the flow rate growth. OH(A-X) band's intensity increased according to the flow rate or residence time of He feeding gas. Reciprocal tendency was acquired for $N_2$ and Ar carrier gases. The peak value of OH(A-X) intensity was observed in the proximity of the water surface, however in the cases of Ar and $N_2$ with 0.5 SLM flow rate peaks shifted to the region below the water surface. Rotational temperature ($T_{rot}$) was estimated to be in the range of 900-3600 K, according to the carrier gas and flow rate, which corresponds to the arc-like-streamer discharge.

• 한국전기전자재료학회논문지
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• 제27권12호
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• pp.831-836
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• 2014

One-dimensional (1D) photonic crystals (PCs) were prepared by $TeO_x(2&lt;x&lt;3)/SiO_2$ with the difference refractive index, and fabricated by sputtering technique from a $TeO_2$ and $SiO_2$ target. The $TeO_x$(2$Ar:O_2=40:10$). A 10-pair $TeO_x(2&lt;x&lt;3)/SiO_2$ 1D PCs were fabricated with the structure parameters of filling factor=0.5185, and period=410 nm. The properties of 1D PCs with and without a defect layer were evaluated by UV-VIS-NIR. A normal mode 1D PC have a photonic band gap (PBG) in the near infrared (NIR) region from 1,203 to 1,421 nm. In the case of 1D PC containing a defect layer, a defect level appears at 1,291 nm. The measured transmittance (T) spectra are nearly corresponding to calculated results. After He-Cd laser exposure, the defect level is shifted from 1,291 nm to 1,304 nm.