• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.109-114
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• 2012

The cathode catalyst layer in polymer electrolyte membrane fuel cells (PEMFCs) was fabricated with anodic aluminum oxide (AAO) template and its structure was characterized with scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The SEM analysis showed that the catalyst layer was fabricated the Pt nanowire with uniform shape and size. The BET analysis showed that the volume of pores in range of 20-100 nm was enhanced by AAO template. The electrochemical properties with the membrane electrode assembly (MEA) were evaluated by current-voltage polarization measurements and electrochemical impedance spectroscopy. The results showed that the MEA with AAO template reduced the mass transfer resistance and improved the cell performance by approximately 25% through controlling the structure of catalyst layer.

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.713-719
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• 2000

This study was performed to investigate the cytotoxic effect of the Prunus mume extracts containing beverages on the growth of SNU-16 gastric cancer cell, SNU-C2A colon cancer cell, SNU-449 liver cancer cell and HeLa cervical cancer cell. The inhibitory effect on the growth of the cancer cell lines was examined by MTT(3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, cytotoxicity test and microscopy. Also this study aimed to compare the changes of blood electrolytes and osmolarity during submaximal exercise for the intake of the Prunus mume extracts containing beverages. 20% Prunus mume extracts containing beverage exhibited the greatest inhibitory effect on the growth of SNU-16 and significantly inhibited at the concentration of $1000\;{\mu}g/mL$ in the MTT assay. Morphological changes in SNU-16 which treated with the same beverage were observed under inverted microscope. The change of blood electrolytes and osmolarity during submaximal exercise showed no significant differences between before and after intake of the beverage in both groups.

• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.19-24
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• 2010

Alloying degree is an important structural factor of PtRu catalysts for direct methanol fuel cells (DMFC). In this work, carbon supported PtRu catalysts were synthesized by reduction method using anhydrous ethanol as a solvent and $NaBH_4$ as a reducing agent. Using anhydrous ethanol as a solvent resulted in high alloying degree and good dispersion. The morphological structure and crystallanity of synthesized catalysts were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM). CO stripping and methanol oxidation reaction were measured. Due to high alloying degree catalyst prepared in anhydrous ethanol, exhibited low onset potential for methanol oxidation and negative peak shift of CO oxidation than commercial sample. Consequently, samples, applying ethanol as a solvent, exhibited not only enhanced CO oxidation, but also increased methanol oxidation reaction (MOR) activity compared with commercial PtRu/C (40 wt%, E-tek) and 40 wt% PtRu/C prepared in water solution.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.2
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• pp.250-259
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• 2012

The need for position information in indoor environments has been growing lately. Several indoor navigation systems have been studied. Among them, pseudolite-based indoor positioning systems are one of the best systems to obtain precise position measurements. However, the installation of such systems is very difficult because the calibration of pseudolite antenna position is complicated. For precise calibration, the use of carrier phase measurements is necessary, and whenever carrier phase measurements are considered, problems with cycle ambiguity appear. In this paper, a new approach to calibrate the positions of pseudolite antennas is proposed. By using a multi-antenna, the ambiguity can be eliminated, epoch by epoch, for every single carrier phase measurement. Moreover, the number of calibration points can be reduced down to 3 by use of measurements collected at unknown positions. Using the proposed methods, the process of the collection of carrier phase measurements becomes considerably simple and convenient. Simulation results are presented to verify the proposed algorithms.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.1
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• pp.212-217
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• 2005

The purpose of this study was to examine the effects of Citrus Reticulata(CR) on the Cell Detachment and Apoptosis in Human Gastric Cancer SNU-668 Cells. The effect of CR on apoptosis was investigated through MTT assay, DAPI staining, and TUNEL assay. We also performed RT-PCR for apoptotic genes including BCL-2, BAX, and caspase-3, the caspase-3 activity assay, and western blotting for pro-CASP-3. Then, to detect that adhesion of cell to ECM was reduced by CR, we investigated mRNA expression of CDH1 and PTK2 using RT-PCR, and their protein expressions using western blotting, and immunocytochemistry in SNU-668 cells. In this study, the results showed that treatment of CR induced time and dose-dependent cell death in SNU-668 cells. Downregulated mRNA expression of BCL-2, and upregulated mRNA expressions of BAX and CASP-3 indicated that the cell death was due to apoptosis. Protein expression of inactivated CASP-3, and caspase-3 activity assay also showed that apoptosis was induced in CR-treated cells.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.816-821
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• 2005

The cycloid reducer has very high efficiency, high ratios, high stiffness and small size, in comparison with a conventional gear mechanism, which makes it an attractive candidate for limited space and precision application such as industrial robot. There are several publications on analysis and design of the cycloid reducer, however, it was assumed that the contact stiffness of pin rollers and cycloid disk is constant regardless of their contact geometry. Moreover, the torsional stiffness of the cycloid reducer couldn't be calculated due to the assumption. In this paper, we present a new procedure of calculating torsional stiffness of the cycloid reducer using Hertz contact theory. First, conventional force analysis of the cycloid reducer is briefly reviewed. Then, iterative numerical calculation procedure of the contact stiffness is proposed based on the Hertz contact theory where the contact stiffness depends on the contact force. In addition, total torsional stiffness of the cycloid reducer is estimated considering its rolling element bearing stiffness. The torsional stiffness of the cycloid reducer is dominated by the rolling element bearing stiffness since the contact stiffness of the cycloid disk is too large.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1277-1280
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• 2005

A high-aspect-ratio and high-resolution stainless steel shadow mask for organic thin-film transistors (OTFTs) circuit has been fabricated by a new method which combines photochemical machining, micro-electrical discharge machining (micro-EDM), and electrochemical etching (ECE). First, connection lines and source-drain holes are roughly machined by photochemical etching, and then the part of source and drain holes is finished by the combination of micro-EDM and ECE processes. Using this method a $100\;\mu{m}$ thick stainless steel (AISI 304) shadow mask for inverter can be fabricated with the channel length of $30\;\mu{m}\;and\;10\;\mu{m}\;respectively.\;The\;width\;of\;connection line\;is\;150\;\mu{m}$. The aspect ratio of the wall is about 5 and 15, respectively. Metal lines and source-drain electrodes of OTFTs were successfully deposited through the fabricated shadow mask.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.1
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• pp.41-48
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• 1994

A monitoring system for atmospheric CFC-12 and CFC-11 has been established at Mt. Kwan-Ak, Seoul National University (SNU) since July, 1991. The concentrations showed quite a large variation ranging from 495 to 37600 pptv (pptv=part per trillion, 10$^{-12}$ , v/v) for CFC-12 and from 233 to 12100 pptv for CFC-11 due to many local sources. However, monthly medians show rather limited ranges ; 553~765 pptv for CFC-12 and 301~431 pptv for CFC-11. Furthermore minimum concentrations could be defined relatively well during the whole period of observation. The regional background concentrations in 1993 near SNU wer estimated as 533 pptv for CFC-12 and 293 pptv for CFC-11. These values are very comparable to global averages in Northern Hemisphere, 523 pptv for CFC-12 and 287 pptv for CFC-11, reflecting the fast atmospheric mixing processes within the hemisphere. Examinations with meteorological parameters such as wind speed and direction suggest the possible measurement-window at SNU, appropriate for regional monitoring. Studies for improving the monitoring capability of the SNU station such as automation of the analysis system along with correlation with other meteorological parameters, are in progress at the present time.

• Proceedings of the KOSOMBE Conference
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• v.1990 no.11
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• pp.11-14
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• 1990

The detection of pulmonary blood vessels is very difficult owing to their complex tree structures and different widths. In this paper, We propose a new detection algorithm. The motivation of this algorithm is that Han is the best detector. So, this algorithm is developed to imitate the human searching process. To realize it, the algorithm consist of two components. One is Pyramid Images whose one pixel is median value of four pixels of the previous low level. Searching gradually from high level to low level, We concentrate on global and main information of structure at the first. Then based on it, We search the detailed data in low level. The other is fuzzy logic which makes it easy to convert searching process expressed as human language into numeric multi_value. This algorithm showes speedy and robust results. But the more study on both human searching process and the detection of small part is needed.

• Korean Journal of Microbiology
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• v.31 no.3
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• pp.189-196
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• 1993

Nucleotide sequences of nodD and nodA from Bradyrhizobium sp. SNUOOI were determined. The open reading frame (ORF) of nodD was 942 bp in length and encoded 314 amino acids. while ORF of nodA, sequence of which is the first one among legume symbionts Bradyrhizobium, was 630 bp and encoded 210 amino acids. The nucleotide sequence of nodD showed 99.4% homology with nodDI of B. japonicum USDAllO. while that of nodA showed 81.5% with B. sp. (Parasponial. At the 5' of nodYAB operon and nodD, consensus nod box sequences composed of 9 bp unit repeated four times and two times respectively were found. Also an A.T-rich sequence was found at 5' of nodD.