• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1115-1119
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• 2013

A kinetic study is reported for nucleophilic substitution reactions of benzyl 2-pyridyl thionocarbonate (5b) and t-butyl 2-pyridyl thionocarbonate (6b) with a series of alicyclic secondary amines in $H_2O$ at $25.0^{\circ}C$. General-base catalysis, which has often been reported to occur for aminolysis of esters possessing a C=S electrophilic center, is absent for the reactions of 5b and 6b. The Br${\o}$nsted-type plots for the reactions of 5b and 6b are linear with ${\beta}_{nuc}$ = 0.29 and 0.43, respectively, indicating that the reactions of 5b proceed through a stepwise mechanism with formation of a zwitterionic tetrahedral intermediate ($T^{\pm}$) being the rate-determining step while those of 6b proceed through a concerted mechanism. The reactivity of 5b and 6b is similar to that of their oxygen analogues (i.e., benzyl 2-pyridyl carbonate 5a and t-butyl 2-pyridyl carbonate 6a, respectively), indicating that the effect of modification of the electrophilic center from C=O to C=S (i.e., from 5a to 5b and from 6a to 6b) on reactivity is insignificant. In contrast, 6b is much less reactive than 5b, indicating that the replacement of the $PhCH_2$ in 5b by the t-Bu in 6b results in a significant decrease in reactivity as well as a change in the reaction mechanism (i.e., from a stepwise mechanism to a concerted pathway). It has been concluded that the contrasting reactivity and reaction mechanism for the reactions of 5b and 6b are not due to the electronic effects of $PhCH_2$ and t-Bu but are caused by the large steric hindrance exerted by the bulky t-Bu in 6b.

• Journal of Powder Materials
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• v.18 no.6
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• pp.496-501
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• 2011

In this study, the effect of milling time on the microstructure and phase transformation behaviors of Ni-12 wt.%B powders was investigated using vibratory ball milling process. X-ray diffraction patterns showed that the phase transformation of mixed Ni-B elemental powder occurred after 50 hours of milling, with a formation of nickel boride phases. Through the study of microstructures in mechanical alloying process, it was considered that ball milling strongly accelerates solid-state diffusions of the Ni and B atoms during mechanical alloying process. The results of X-ray photoelectron spectroscopy showed that most of B atoms in the powder were linked to Ni with a formation of nickel boride phases after 200 hours of milling. It was finally concluded that mechanical alloying using ball milling process is feasible to synthesize fine and uniform nickel boride powders.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.510-516
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• 2005

In this paper, we discuss parameters of line code and simulate a same optical ethernet having minimum bandwidth(MB810) and non-minimum bandwidth line code(8B/10B) to present the possibility of improving of transmission performance using minimum bandwidth line code on the high speed optical ethernet. We design the high speed optical ethernet using Serial type LAN PHY 10GBASE-E(WDM type LAN PHY 10GBASE-LX4) for the single(multi) channel link. To compare the transmission performance of MB810, 8B/10B line code we measure the bit error rate(BER) according to the received optical power of single and multi channel link.

• Journal of Korea Foundry Society
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• v.36 no.5
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• pp.147-152
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• 2016

Aluminum has been used as an alternative material for copper, due to its good electrical and thermal conductivities. However, small quantities of transition elements such as Ti and V affect the conductivities of aluminum. Therefore, in this study, the influence of B addition to reduce the effects of Ti and V on the conductivities of aluminum was investigated. Both the electrical and thermal conductivities of aluminum were improved with addition of B up to 0.05 wt%, while the conductivities were gradually reduced with an excess amount of B. SEM-EDS and XRD results exhibited that B reacted with Ti and V element to form diborides, such as $TiB_2$ and $VB_2$ phase, and those diborides tended to settle down to the bottom of the crucible because their densities were higher than that of aluminum melt. As a result, B reduced the deleterious effects of Ti and V, and the electrical and thermal conductivities of aluminum were improved.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2004.05a
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• pp.322-325
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• 2004

Kefir에서 유산균인 Lactobacillus acidophilus와 Lactococcus lactis 그리고 효모인 Candida kefir를 분리하였고, 이를 이용하여 FM(Fermented milk) A, B, C 제조${\cdot}$분석하였다. 유산균 수는 FM B가 $8.6{\times}\;10^9\;cfu/ml$로 가장 많았고, 효모수는 FM C가 $1.3{\times}\;10^7cfu/ml$로 가장 많았다. 알콜 함량은 FM C가 3.2%, FM A가 0.98%, FM B가 0.15% 였다. 아미노산은 FM A에서는 Glu, Pro, Leu, Lys, Asp 등이, FM B에서는 Glu, Leu, Pro, Lys 등이, FM C에서는 Glu, Leu, Pro, Lys 등이 주요 아미노산으로 나타났다. 지방산은 FM A, FM B, FM C 모두 palmitic acid(Cl6:0)와 oleic acid(Cl8:1)가 각각 33.5${\sim}$37.7%와 22.1${\sim}$22.4%의 수준으로 주요 지방산을 차지하였다. 관능검사 결과FM C가 가장 높은 점수를 받았으며, 다음은 FM A, FM B 순이었다.

• Archives of Pharmacal Research
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• v.27 no.10
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• pp.1073-1079
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• 2004

Interactions of the cell adhesion molecules are known to play important roles in mediating inflammation. The proinflammatory cytokine, tumor necrosis factor-${\alpha}$(TNF-${\alpha}$), activates the NF-kB signaling pathway, which induces the expression of various genes, such as intercellular adhesion molecule-1 (ICAM-1). In this study, the effect of vitamin C on the ICAM-1 expression induced by TNF-${\alpha}$ in a human neuroblastoma cell line, SK-N-SH was investigated. Treatment with vitamin C resulted in the downregulation of the TNF-${\alpha}$-induced surface expression and ICAM-1 mRNA levels in a concentration-dependent manner. Moreover, a gel shift analysis indicated that vitamin C dose-dependently inhibited the NF-kB activation and IkB${\alpha}$ degradation induced by TNF-${\alpha}$. Taken together, these results suggest that vitamin C downregulates TNF-${\alpha}$- induced ICAM-1 expression via the inhibition of NF-kB activation.

• Archives of Pharmacal Research
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• v.25 no.4
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• pp.475-479
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• 2002

Capsaicin, a major pungent constituent of red pepper (Capsicum annuum L.) possesses a vast variety of pharmacologic and physiologic activities. Despite its irritant properties, the compound exerts anti-inflammatory and anti-nociceptive effects. Previous studies from this laboratory revealed that capsaicin, when topically applied onto dorsal skin of female ICR mice, strongly attenuated activation of NF-kB and AP-1 induced by the typical tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), which may account for its anti-tumor promoting activity in mouse skin. In the present work, we have found that capsaicin suppresses TPA-stimulated activation of NF-kB through inhibition of $IkB{\alpha}$ degradation and blockade of subsequent nuclear translocation of p65 in human pro myelocytic leukemia HL-60 cells. Methylation of the phenolic hydroxyl group of capsaicin abolished its inhibitory effect on NF-kB DNA binding. Likewise, TPA-induced activation of AP-1 was mitigated by capsaicin treatment.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.2
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• pp.11-16
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• 2010

In this papar, we have proposed a small electronically steerable parasitic array radiator with 180 degree azimuth beam coverage and high gain characteristics. The proposed antenna is composed of a uniplanar Yagi dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna is tested by electronically changing the reactance loaded on the parasitic dipoles and the results show that it has 5.2dB~6.7dB gain in $-90^{\circ}{\sim}90^{\circ}$wide azimuth range and -10dB return loss characteristics within 5.725GHz~5.825GHz UNII band.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.326-329
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• 2009

This paper proposes a new video compression algorithm using an adaptive transform that is adjusted depending on the frequency contents of the input signals. The adaptive transform is based on the warped discrete cosine transform (WDCT) which is shown to provide better performance than the DCT at high bit rates, when applied to JPEG compression scheme [1, 2, 3]. The WDCT is applied to the video compression in this paper, as a new feature in the H.264/AVC. The proposed method shows the coding gain over the H.264/AVC at high bit rates. The coding gain is shown over the 35dB PSNR quality, and the gain increases as the bit rate increases. (about 1.0dB at 45dB PSNR quality at maximum)

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.119-124
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• 2004

In this study, a rotor blade of a Curtis turbine is investigated. Bezier curve is generally used to define the profile of turbine blades. However, this curve gives a feature of global control, which is not proper to a supersonic impulse turbine blade. Thus, a blade design method is developed by using B-spline curve so that local control is possible to obtain an optimized blade section. To design a Curtis turbine blade section systematically, the blade section has been changed by varying three design parameters using central composite design method. Flow analyses have been carried out for the blade sections, and the effects of design parameters are evaluated.