• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.348-351
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• 2006

Bipolar plate, which forms about 50% of the stack cost, is an important core part with polymer electrolyte membrane in PEMFC. Bipolar plates have been commonly fabricated from graphite meterial having high electrical conductivity and corrosion resistance. Lately, many researchers have concentrated their efforts on the development of metallic bipolar plate and stainless steel has been considered as a potential material for metallic bipolar plate because of its high strength, chemical stability, low gas permeability and applicability to mass production. However, it has been reported that its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions and an increase in contact resistance by the growth of passive film therefore, its corrosion resistance as well as contact resistance must be improved for bipolar plate application. In this work, several types of coating were applied to 316L and their electrical conductivity and corrosion resistance were evaluated In the simulated PEMFC environment. Application of coating gave rise to low interfacial contact resistances below $19m{\Omega}cm^2$ under the compress force of $150N/cm^2$. It also made the corrosion potential to shift in the posit ive direct ion by 0.3V or above and decreased the corrosion current from ca. $9{\mu}A/cm^2$ to ca. $0.5{\mu}A/cm^2$ in the mixed solution of $0.1N\;N_2SO_4$ and 2ppm HF A coat ing layer under potentiostatic control of 0.6V and $0.75V_{SCE}$ for 500 hours or longer showed some instabilities, however, no significant change in coat Ing layer were observed from Impedance data. In addition, the corrosion current maintained less than $1{\mu}A/cm^2$ for most of time for potentiostatic tests. It indicates that high electrical conductivity and corrosion resistance can be obtained by application of coatings in the present work.

• Analytical Science and Technology
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• v.15 no.1
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• pp.80-86
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• 2002

The simultaneous analysis of the odorous compounds designated by law in Korea and Japan was examined with the thermal desorber gas chromatography-mass spectrometry using one column. The approximate concentrations of trimethyl amine, acetaldehyde, methyl mercaptan and dimethyl sulfide were estimated. Styrene, dimethyl disulfide, propionaldehyde, n-butyl aldehyde, i-butyl aldehyde, n-valeraldehyde, i-valeraldehyde, ethyl acetate, toluene, xylene, methyl i-butyl ketone and i-butanol were detected at concentrations of the detection limits of their threshold values. As a typical example of simultaneous analysis of the odorous compounds, the volatile organic compounds emitted from compost procedure of food waste were concentrated and analyzed with thermal desorber/GC/MSD, and major malodorous compounds were estimated from the concentrations and threshold values of the detected components. From the result of analysis, 34 compounds were confirmed and among them, trimethyl amine, i-valeraldehyde, methyl mercaptan, methyl allyl sulfide, dimethyl sulfide, acetaldehyde, ethanol, n-butyaldehyde were expected to attribute to the odor in order of strength.

• Journal of the Korean Society of Food Culture
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• v.8 no.4
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• pp.337-348
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• 1993

This study was carried out to investigate the succession patterns of dietary culture and to find out all the educational problems with female college students in both countries as the central figure. The results are as follows. The degree of knowledge acquisition about food of annual custom is 58% in Korea and 72% in Japan. What the rate of knowledge acquisition is high among both countries’ similar food of annual custom are ${\ulcorner}Seolnal(Gantan){\lrcorner}$, ${\ulcorner}Sambok(Doyonohi){\lrcorner}$, and ${\ulcorner}Chuseok(Tsukimi){\lrcorner}$. Cooking experience of festive food is 45% in Korea and 58% in Japan. Among both countries' common festive food what cooking experience is high in Korea are ${\ulcorner}Seolnal{\lrcorner}$ and ${\ulcorner}Chuseok{\lrcorner}$, which are over 97%. In Japan those are ${\ulcorner}Gantan{\lrcorner}$ and ${\ulcorner}Tsukimi{\lrcorner}$, which are over 80%. Regarding learning experience of festive food ${\ulcorner}Seolnal{\lrcorner}$ and ${\ulcorner}Gantan{\lrcorner}$ are beyond 80% and ${\ulcorner}Chuseok{\lrcorner}$ is 88%. In Japan ${\ulcorner}Tsukimi{\lrcorner}$ is 71% and ${\ulcorner}Omisoka{\lrcorner}$ is 85%. The learning sources of food of annual custom are parents and schools in common, and Korea has another learning sources, mass communication. Festive food that is cooked shows much similarity between two countries, but each country has originality. As common food of annual custom ${\ulcorner}Seolnal{\lrcorner}$ has nine kinds of food, ${\ulcorner}Sambok{\lrcorner}$ has three kinds, and ${\ulcorner}Chuseok{\lrcorner}$ has five kinds in Korea In Japan ${\ulcorner}Gantan{\lrcorner}$ has fourteen kinds of food, ${\ulcorner}Doyonohi{\lrcorner}$ has three kinds, and ${\ulcorner}Tsukimi{\lrcorner}$ has five kinds. The successive consciousness about food of annual custom is concentrated on a specific food in Korea. And Japanese consciousness is shown as an expansion-type on diverse food. Korean successive consciousness is 69.4% and Japanese consciousness is 82%. The higher the rate of knowledge acquisition, cooking experience, and learning experience are in both countries, the higher successive consciousness is. So we must note for the importance of home and school’s education.

• Analytical Science and Technology
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• v.26 no.4
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• pp.221-227
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• 2013

A sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the investigation of the ginsenoside Rg1 in human plasma. After addition of internal standard (digoxin), plasma was diluted with acetone and methanol (80:20), the supernatant was concentrated and analyzed by LC-MS/MS. The optimal chromatographic separation was achieved on an Agilent Eclipse XDB-C18 column ($4.6{\times}150mm$, $5{\mu}m$) with a mobile phase of 0.1% formic acid in water and 0.1% formic acid in methanol at a flow rate of 0.9 mL/min gradient mode. The standard calibration curve for ginsenoside Rg1 was linear ($r^2=0.9995$) over the concentration range 1~500 ng/mL in human plasma. The intra- and inter-day precision over the concentration range of ginsenoside Rg1 was lower than 7.53% (correlation of variance, CV), and accuracy exceeded 98.28%. This LC-MS/MS assay of ginsenoside Rg1 in human plasma is applicable for quantifying in the pharmacokinetic study.

• Journal of Applied Biological Chemistry
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• v.54 no.1
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• pp.63-66
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• 2011

The bark of Machilus thunbergii was extracted with 80% aqueous methanol (MeOH), and the concentrated extract was partitioned using ethyl acetate (EtOAc), butanol (n-BuOH), and $H_2O$, successively. From the EtOAc fraction, five lignans were isolated through the repeated silica gel, octadecyl silica gel (ODS) and, Sephadex LH-20 column chromatography. Based on nuclear magnetic resonance (NMR), mass spectroscopy (MS), and infrared spectroscopy (IR) spectroscopic data, the chemical structures of the compounds were determined to be machilin A (1), machilin F (2), licarin A (3), nectandrin A (4), and nectandrin B, (5). This study presents comparative account of five lignans from M. thunbergii bark contributing inhibition of low density lipoprotein (LDL), ACAT-1, and ACAT-2. Compounds 2-5 showed varied degree of antioxidant activity on LDL with $IC_{50}$ values of 2.1, 11.8, 15.3, and $4.1{\mu}M$. Compounds 1, 2, and 3 showed inhibition activity on ACAT-1 with values $63.4{\pm}6.9%$ ($IC_{50}=66.8{\mu}M$), $53.7{\pm}0.9%$ ($IC_{50}=109.2{\mu}M$), and $78.7{\pm}0.2%$ ($IC_{50}=40.6{\mu}M$), respectively, at a concentration of 50 mg/mL, and on ACAT-2 with values $47.3{\pm}1.5%$ ($IC_{50}=149.7{\mu}M$), $39.2{\pm}0.2%$ ($IC_{50}=165.2{\mu}M$), and $52.1{\pm}1.0%$ ($IC_{50}=131.0{\mu}M$, respectively, at a concentration of 50 mg/mL.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.147-154
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• 2006

The certificate status validation mechanism is a critical component of a public key infrastructure based on certificate system. The most generally mechanisms used these days are the use of the certificate revocation list and the real-time certificate status protocol. But the certificate revocation list can not give the real-time certificate status because the certificate is being delivered periodically, and the real-time certificate status protocol method will generate a concentrated load to the server because the protocol in the central server will be accessed whenever a certification is necessary. It will also take a long time to validate the certificate because each trade has to send mass information through the network. This paper will present that real-time validation is guaranteed as the real-time certificate status protocol method and the traffic congestion in the network Is reduced in a way that the certification would be requested using the user information hash value and would be validated using the user information kept in the certification authorities and the service providers. Based on the this study, we suggest a real-time certificate status validation mechanism which can reduce the certificate status validation time using the signed user information hash value. And we confirm speed of certificate status verification faster than existing CRL(Certificate Revocation List) and OCSP(Online Certificate Status Protocol) method by test.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.125-133
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• 1979

The characteristics of landslides occurred in August 5, 1979 in pyeongchangkun were surveyed and indentified as follows. 1. Deep limestone regions. Distinct differences in soil texture between A1 and B horizon could be observed on soil profile, which is attributed to the clay illuviation. The clay illuvial horizon is supposed to be an important cause of large scale mudflows on middle slopes by the lubricant action of ground water flowing between top soil and subsoil. 2. Shallow limestone regions. Very shallow top soils (less than 50cm) laid on tilted bedrock stratification provide a proper condition of mass soil movement if the top soil is saturated and ground water flows between top soil and bedrock when concentrated heavy rainfalls shower. 3. Granite regions. Weathering granitic bedrock produces very coarse textured top soils which are very cohesionless and have many pores. Therefore, the soil has high infiltration ratio and is easy to be saturated by water and to be detached from the bedrock. The landslides abrase very severely both sides of gully with high potential energy when they flow down. The following methods for landslide prevention can be recommended. 1. The original parts of landslides on top of the gully must be treated by intensive planting of deep rooting species and check dams. 2. Clear-cutting and crop planting on steep slope (more than 25 degrees) should be controlled and prohibited. 3. Establishment of landslide prevention forest should be practised on proper site.

• Korean Journal of Food Science and Technology
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• v.28 no.5
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• pp.827-833
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• 1996

Along with the increased necessity for an efficient utilization of Korean wild edible plants growing in fields and mountains, attempts were made to investigate the patterns of flavor changes accompanied hy various conditions of dispersion medium. The effect of various pH values and concentration of sucrose or NaCl of dispersion medium on volatile flavor patterns was investigated to evaluate the applicability of flavor components extracted from Capsella bursa-pastoris for food industry. Essential oils from this wild plant were isolated by simultaneous steam distillation-extraction (SDE) method using diethyl ether as solvent. Concentrated samples were analyzed s chromatography (GC) and combined gas chromatography-mass spectrometry (GC-MS). Most volatile flavor components of Capsella bursa-pastoris showed good recovery when steam distilled at pH 7 by SDE method. Increasing concentration of sucrose and 15% by NaCl, resulted in greater numbers of identified flavor components from Capsella bursa-pastoris.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.73-83
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• 2001

The mass and stiffness of upper wall-lower frame system(mixed building structures) change sharply at transfer floor due to different structural system in upper and lower part. These mixed building structures generally show the stiffness, weight or geometric vertical irregularities. The purpose of this study is to investigate the response characteristics of these structures by push-over analysis and nonlinear time history analysis. For four types of analysed models, only the variation of upper wall stories was considered. The conclusions of this study are following; (1) In the push-over analysis, yielding hinges in beams and columns of lower frame occurred at the base shear of similar magnitude in all models. But as the number of stories of upper wall increases, yielding hinges at ends of coupling beams were observed in the small magnitude of base shear. (2) In the nonlinear time history analysis, yielding of lower frame occurred at beams with as small ground acceleration as 55gal, and in upper walls yielding was concentrated on coupling beams and shear walls near the transfer floor. (3) As the number of stories of upper walls decreases, the story stiffness of the lower frames decreased relatively and the occurrence of soft stories in the lower frame was observed.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.595-604
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• 2006

The growth characteristics of Commercially Developed Nitrifying Bacteria (CDNB) were studied in laboratoryscale. CDNB, a pure, artificially isolated bacterium, was cultivated to produce Cultivated Nitrifying Bacterium Group (CNBG). The average ammonia removal rate of CDNB was 0.0234g $NH_4^+-N/g$ MLSS/hr. CNBG was produced in the batch reactor and Specific Nitrification Rate (SNR) was determined at 0.0107g $NH_4^+-N/g$ MLSS/hr. The SNR of CNBG was lower than the SNR of CDNB because the diverse and multi-cultured microbial growth took place during cultivation. The effect of the temperatures and the mixing ratios of sewage and culture solution on the SNR of CNBG was studied. The SNR of CNBG, 0.0107g $NH_4^+-N/g$ MLSS/hr at $27^{\circ}C$, decreased to 0.0048g $NH_4^+-N/g$ MLSS/hr at $15^{\circ}C$, and temperature coefficient (${\Theta}$) was calculated to be 1.07. With the varied sewage mixing ratios, the SNR of CNBG remained unchanged. Activated sludge reactors maintaining an MLSS of 2,000mg/L at HRT of 4 h were operated under conditions in which dosage of Concentrated CNBG Solution (CCNBGS, 10,000mg MLSS/L) and application method of CNBG were varied. The reactor with 20mL of CCNBGS took shorter time to oxidize $NH_4^+-N$ reaching 1mg/L than the reactor with 5mL of CCNBGS showing that higher dosages were associated with greater mass removal of $NH_4^+-N$. However, the total removal was not great. In terms of different methods of CNBG application, reactor seeded with 20mL of CCNBGS took 3days to reach 1mg/L of effluent ammonia concentration while reactor dosed with 20% (v/v) CNBG implanted media took 2days. Both the control reactor and the reactor dosed with 20% (v/v) media only did not reach 1mg $NH_4^+-N/L$ after operating 18days. The reactor with CNBG implanted media had the highest $NH_4^+-N$ removal rate because of maintaining high concentration of Nitrifying Oxidizing Bacteria (NOM), and is regarded as an appropriate method for the activated sludge process.