• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.47-52
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• 2008

As the packing density of IC devices gets ever higher, the thickness of the gate $SiO_2$ layer of the MOS devices is now required to be reduced down to 1 nm. For such a thin $SiO_2$ layer, the MOS device cannot operate properly because of tunneling current and threshold voltage shift. Hence there has been much effort to develop new dielectric materials which have higher dielectric constants than $SiO_2$ and is free from such undesirable effects. In this work, the physical and electrical characteristics of ALD $ZrO_2$ film have been studied. After deposition of a thin ALD $ZrO_2$ film, it went through thermal treatment in the presence of argon gas at $800^{\circ}C$ for 1 hr. The characteristics of morphology, crystallization kinetics, and interfacial layer of $Pt/ZrO_2/Si$ samples have been investigated by using the analyzing instruments like XRD, TEM and C-V plots. It has been found that the characteristics of the $Pt/ZrO_2/Si$ device was enhanced by the thermal treatment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.2
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• pp.146-151
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• 2014

Objectives: Chrysotile is mineralogically distinct from amphiboles, displaying a notably different chemical structure. The thin sheets that form chrysotile fiber lead to the ability of the lung/macrophage system to decompose the chrysotile fibers. This study was performed in order to compare the physicochemical characteristics of Korean asbestos with those of Canadian amphiboles. Materials: An acid solubility test for each test substance was done to compare pH 4.5 and pH 1.2 distilled water. Asbestos fibers which had been placed in acid solutions for five days, five weeks and weeks were analyzed with a transmission electron microscope equipped with an energy dispersive X-ray spectrometer (TEM-EDS). Results: The composition element (Mg) of Korean chrysotile, Korean anthophyllite and Canadian amosite significantly decreased from 5 days and also decreased significantly after 5 weeks and 10 weeks. Only the composition (Mg) of Canadian crocidolite did not change under any conditions. From 5 days, the Mg of Korean chrysotile, Korean anthophyllite and Canadian amosite were significantly lower than before the acid treatment, but there were no changes over time or by the pH of the acid solutions. Particularly after 10 weeks, the composition (Mg) of Korean chrysotile in the pH 1.2 acid solution showed a rapid reduction of 15.86%. Conclusions: Korean chrysotile was very weak in an acid environment, beginning to show significant changes after 5 days. The Mg component rapidly decreased after 10 weeks in the pH 1.2 acid solution.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.290-296
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• 1999

We have studied the phase separation and ordering phenomeon of InAlAs epilayers grown on InP substrate by LP-MOCVD with DCXRD, PL, and TEM. From the intensity and FWHM of DCXRD and PL, we observed that the structural and optical quality of InAlAs epilayers were improved as growth temperature increased. The band-gap reduction due to phase separation and ordering is 291, 246, and 28 meV in the InAlAs epilayers grown at $565^{\circ}C$, $615^{\circ}C$, and $700^{\circ}C$, respectively, and shows the same from the InAlAs epilayer town at 5$65^{\circ}C$ in which the HRTEM micrograph showed the lattice fringe between InAs-rich and AlAs-rich regions was tilted by $2^{\circ}$ due to composition difference. However the maximum degree of ordering by intensity of extra spots was obtained at medium growth temperature. The annealing experiment by RTA of sample grown at $565^{\circ}$ shows a maximum band-gap shift of 78eV at $880^{\circ}$ for 3 min, and TEM shows that the origin of the blue shift of band-gap is the complete disappearance of ordering. Through annealing we can conclude that short time annealing affects only ordering and that most of the total band-gap reduction (~3/4) occurs by phase separation.

• Korean Journal of Clinical Laboratory Science
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• v.47 no.1
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• pp.6-10
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• 2015

Photodynamic therapy (PDT) apply photosensitizers and light. The purpose of this study was to evaluate the in vitro efficacy of PDT using blue LED (light emitting diode) with photofrin and radachlorin for Propionibacterium acnes. The colony forming units method was used to assess the antibacterial activity. Suspension (1 mL) containing P. acnes at $1{\times}10^5CFU/mL$ were prepared and then 2 fold serial diluted to $12.5{\mu}g/mL$ from $50{\mu}g/mL$ concentration of photofrin and radachlorin. After 60 minutes incubation, light was irradiated for 10 to 30 minutes using the following light source of wavelength 460 nm, each energy density 36, 72 and $108J/cm^2$. Bacterial growth was evaluated after 72 hours incubation in a Phenylethanol Blood Agar (PEBA) culture. In addition, flow cytometric analysis were performed to measure the live cell after PDT. Also transmission electron microscopy (TEM) was employed to evaluate the effect of pathogens by PDT. The PDT Group was perfectly killed to all kind of photosensitizers dose of $12.5{\mu}g/mL$ with irradiation of 10 minutes. Also other Groups were killed to all kind of photosensitizers dose of $6.25{\mu}g/mL$ with irradiation time of 20 and 30 minutes. The flow cytometry showed a lower number of viable bacteria in the PDT group compared to the control group. The images of the TEM results were showed in cytoplasmic membrane damage and partially deformed to cell morphologies. These results suggest that radachlorin and photofrin combine blue LED PDT can be effectively treated when was proved treatment for acnes therapy.

• Journal of Powder Materials
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• v.10 no.1
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• pp.26-33
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• 2003

Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders rapidly solidified by the gas atomization method were subjected to mechanical milling(MM). The morphology, microstructure and hardness of the powders were investigated as a function of milling time using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Vickers microhardness tester. Microstructural evolution in gas-atomized Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders was studied during mechanical milling. It was noted that the as-solidified particle size of $200\mutextrm{m}$ decreases during the first 48 hours and then increases up to 72 hours of milling due to cold bonding and subsequently there was continuous refinement to $20\mutextrm{m}$ on milling to 200 hours. Two microstructurally different zones, Zone A, which is fine microstructure area and Zone B, which has the structure of the as-solidified powder, were observed. The average thickness of the Zone A layer increased from about 10 to $15\mutextrm{m}$ in the powder milled for 24 hours. Increasing the milling time to 72 hours resulted in the formation of a thicker and more uniform Zone A layer, whose thickness increased to about $30~50\mutextrm{m}$. The TEM micrograph of ball milled powder for 200 hours shows formation of nano-particles, less than 20 nm in size, embedded in an Al matrix.

• Journal of Powder Materials
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• v.18 no.2
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• pp.112-121
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• 2011

This study investigated the effect of solvent on the fabrication of Ni-free Fe-based alloy nano powders by employing the PWE (pulsed wire evaporation) in liquid and compared the alloy particles fabricated by three different methods (PWE in liquid, PWE in Ar, plasma arc discharge), for high temperature oxidation-resistant metallic porous body for high temperature soot filter system. Three different solvents (ethanol, acetone, distilled water) of liquid were adapted in PWE in liquid process, while X-ray diffraction (XRD), field emission scanning microscope (FE-SEM), and transmission electron microscope (TEM) were used to investigate the characteristics of the Fe-Cr-Al nano powders. The alloy powder synthesized by PWE in ethanol has good particle size and no surface oxidation compared to that of distilled water. Since the Fe-based alloy powders, which were fabricated by PWE in Ar and PAD process, showed surface oxidation by TEM analysis, the PWE in ethanol is the best way to fabricate Fe-based alloy nano powder.

• Journal of Powder Materials
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• v.20 no.4
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• pp.275-279
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• 2013

Fe-based oxide dispersion strengthened (ODS) powders were produced by high energy ball milling, followed by spark plasma sintering (SPS) for consolidation. The mixed powders of 84Fe-14Cr-$2Y_2O_3$ (wt%) were mechanically milled for 10 and 90 mins, and then consolidated at different temperatures ($900{\sim}1100^{\circ}C$). Mechanically-Alloyed (MAed) particles were examined by means of cross-sectional images using scanning electron microscopy (SEM). Both mechanical alloying and sintering behavior was investigated by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). To confirm the thermal behavior of $Y_2O_3$, a replica method was applied after the SPS process. From the SEM observation, MAed powders milled for 10 min showed a lamella structure consisting of rich regions of Fe and Cr, while both regions were fully alloyed after 90 min. The results of sintering behavior clearly indicate that as the SPS temperature increased, micro-sized defects decreased and the density of consolidated ODS alloys increased. TEM images revealed that precipitates smaller than 50 nm consisted of $YCrO_3$.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.1019-1024
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• 2009

Visible-light-active $TiO_2-_xN_x$ nanoparticles with a homogeneous anatase crystalline structure were successfully prepared through a hydrolysis of $TiCl_4$ with ammonia solution. The samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), $N_2$-sorption, and UV-vis diffuse reflectance spectra (DRS) techniques. The light absorption onset shifted from 390 nm on pure $TiO_2$ to the visible region at 530 nm on nitrogen-doped $TiO_2$. A clear decrease in the band gap was deduced from the DRS results. The photocatalytic activity was evaluated from the photodegradation of congo red solution under visible light irradiation. The photocatalyst showed the highest photocatalytic activity at an optimal value of nitrogen doping concentration. This was suggested that the nitrogen doping should have an important effects on the improvement of photocatalytic activity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2260-2266
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• 2009

In this paper, the problem of electromagnetic coupling between a slit fed by a flanged parallel-plate waveguide (FPPW) and a nearby conducting strip parallel to the slit is studied as a simplified problem for a near-field scanning microscopy (NSM). The characteristics of the FPPW are investigated from the results for the variations of the equivalent slit admittance, the reactive powers near the slit inside and outside the FPPW, the magnitude and phase of the voltage reflection coefficient of the TEM wave. The performance of the proposed apparatus as an NSM is tested by examining the effects of various geometrical parameters such as guide height, slit width, strip width, distance between slit and strip, and the ratio of slit width to guide height on the magnitude and phase of the voltage reflection coefficient of the TEM wave. From the results for the voltage reflection coefficient against the strip offset from the slit, it is found that a slit in the FPPW with smaller guide height gives higher scanning resolution and the phase variation is more sensitive than the magnitude variation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.814-821
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• 2005

When there are many tags using the same frequency around the reader in RFID system, they disturb each other and in the end their response cannot be received by the reader. To solve this disturbance and fast identify the tags, the anti-collision algorithm, which is the core technology in RFID system, is needed. We propose two ALOHA-type Dynamic Framed Slotted ALOHA(DFS-ALOHA) algorithms using Dynamic Slot Allocation(DSA), which dynamically allocates the frame size in accordance with the number of tags and Tag Estimation Method(TEM), which estimates the number of tags around the reader. We also compare the performance of the proposed DFS-ALOHA algorithms with that of the conventional Framed Slotted ALOHA (FS-ALOHA) algorithms and the algorithms proposed by Vogt using OPNET simulation. According to the analysis, the two proposed DFS-ALOHA algorithms(DFS-ALOHA I and DFS-ALOHA II) show better performance than the conventional ALOHA-based algorithms regardless of the number of tags. Although the two proposed DFS-ALOHA algorithms show the similar performance, BFS-ALOHA ll is better because it is easier to be implemented in the system and the complexity is lower.