• 한국세라믹학회지
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• 제21권4호
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• pp.361-365
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• 1984

This study has been carried out to sinter silicon nitride with additives and to show the effect of surface finishments on its strength and Weibull modulus which are two most important factors for its applications into structural ceramics. Silicon nitride was sintered with the additions of $Al_2O_3$ and $Y_2O_3$ under pressureless cond-ition. The optimum properties were obtained by sintering at 1, 75$0^{\circ}C$ for 3hrs under $N_2$ atmosphere and the strength showed 6, 500kg/$cm^2$ at room temperature and 3, 300kg/$cm^2$ at 120$0^{\circ}C$. The effects of surface treatment on the strength of sintered $Si_3N_4$ were studied and the results showed that fine surface treatment increased the strength by up to 50% The Weibull analysis showed that its modulus was increased with increasing fineness of surface finishments. It was concluded that the mechanical properties of sintered silicon nitride could be improved by fine surface grinding which implied the brittle-fracture nature of sintered silicon nitride.

• 한국표면공학회지
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• 제34권3호
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• pp.187-194
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• 2001

Galvalume sheet steel was developed recently, and is used widely in several fields. It has and had a good corrosion resistance in open atmosphere, but it has week corrosion resistance in the ambient surroundings of an airtight packing. Therefore, black patina was synthesized on the surface of Galvalume sheet steel. Corrosion by moisture on a Galvalume surface begins from edge of a droplet and proceeds to the center of droplet. It begins mainly on the interdendritic structure instead of dendritic structure. This suggests that corrosion by moisture occurs on the Zn shrinkage hole from rapid air cooling. In addition, the initial corrosion occurs by the local cell and continues by the oxygen concentration cell.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.12-15
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• 1994

To establish the sea surface temperature estimation scheme for the upcoming advanced remote sensor, the quasi-analytical solution of the approximated radiative transfer equation which express the radiative transfer process of the radiant energy radiated from the sea surface to the satellite is approximated into the non-linear equation. To solve the simultaneous approximated radiative transfer equation which express the radiative transfer process of the radiant energy radiated from the sea surface to the satellite is approximated into the nonlinear equation. To solve the simultaneous approximated radiative transfer equation at each channel, the constrained non-linear optimization technique is adopted. To define the coefficients of the approximated radiative transfer equation and the constraints, the satellite detected radiance and the total transmittance are computed from the 1350 kinds of simulated atmosphere / surface models via radiative transfer code. The verification from the simulated data show the sufficient result.

• 대기
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• 제16권4호
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• pp.371-378
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• 2006

The surface observation probability system (SOPS) of the Korea Multi-Purpose Satellite (KOMPSAT) has been developed based on the climatological distribution of cloud coverage and the expected passage of satellite orbit. While the optical camera loaded on KOMPSAT series has been operated with the purpose of observing earth's surface, it cannot see the surface when an obstacle (i.e., cloud) exists between them. In the present study, cloud information of International Satellite Cloud Climatology Project incorporates into high resolution grid of the KOMPSAT-3 orbit. The characteristics of the KOMPSAT SOPS are discussed.

• 한국환경과학회지
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• 제7권2호
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• pp.195-202
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• 1998

The low level atmospheric obsewation carried out to Investigate magnitude, formation and dissipation of nocturnal surface Inversion layer, also to survey relation to each meterological parameter In Inversion layer at Pusan power plant for Oct. 13, 1996. As coastal area, the surface Inversion layer height was relatively high(186m), and after sunset unstable layer formated firom surface to around 40m, and the Inversion layer was left still in the upper layer. The surface Inversion layer dissipated at 0920LST perfectly. The layer that strong Inversion layer was formated, showed steep variation of potential temperature and wand speed and relative humidity.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.254-254
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• 2012

The purposed of this work was to determine surface charateristics of anodized Ti-30Nb-xTa alloys with Ta content. Samples were prepared by arc melting, followed by followed by homogenization for 12 hr at $1000^{\circ}C$ in argon atmosphere. The electrolyte for anodization treatment was prepared by mixing 465ml $H_2O$ with 35M $H_3PO_4$ and anodized at 180V to 220V. The microstructures of the alloys were examined by X-ray diffractometer (XRD) and optical microscopy (OM). Surface characteristics of anodized Ti-30Nb-xTa alloys was investigated by potentiodynamic test and potentiostatic in 0.9% Nacl solution at $36.5{\pm}1^{\circ}C$. It was observed that the changed ${\alpha}$ phase to ${\beta}$ phase with Ta content.

• 한국환경과학회지
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• 제19권12호
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• pp.1343-1354
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• 2010

The purpose of the study was to analyze the persistence of HCH in atmosphere, soil, sediment and water of the western and southern regions of Korea. The samples from the western region were collected from Anmyeon Island, and the samples from the southern region were collected from Kimhae and Busan. The concentration of HCH isomers in atmosphere showed the pattern of $\alpha$-HCH>$\gamma$-HCH>$\beta$-HCH. The regions with high HCH concentration in the atmosphere are the regions that have been highly exposed to HCH used in the past, and the areas that have been influenced by the long range transport. The HCH that persists in the soil, water and sediment evaporates into the atmosphere, showing the characteristics of Air-Surface exchange. When the regional concentration distributions are compared, the concentration of HCH was higher in the atmosphere of a plain and the cities near the plain, than the urban areas. In this study, the ratio of $\alpha/\beta$-HCH was used as an indicator for estimating the source of Technical HCH and Lindane. According to the result, the contribution of Lindane was high in Kimhae plain and Kimhae urban areas. However, in Busan, the contribution of Technical HCH was higher than Lindane. In case of Anmyeon Island, the western region of Korea had high contribution from Tehcnical HCH. In soil and sediment, $\beta$-HCH was dominant. In water, $\gamma$-HCH was dominant among other isomers. Such results are due to $\gamma$-HCH inLindane. Furthermore, the source of $\gamma$-HCH in urban areas is assumed to be the use of medicine, medical supplies and other living supplies. Based on the results of this study, the management of HCH, a newly list up emerging POPs, should be strengthened by further research on sources, fate, persistency, accumulation and exposures and etc. to the risk assessments.

• 한국환경과학회지
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• 제23권3호
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• pp.399-407
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• 2014

In this study, before and after sunset carbon dioxide concentration and air temperature were observed in two points of atmosphere (lower observation point of the GL + 0.1 m, the upper observation point of GL + 1.0 m) on the foreshore at located in Suncheon Bay and their variations were analyzed. Observation was performed on the foreshore on 2~4 August 2010. Instrument (VAISALA, GMP343) was set two hours before sunset and then observation was made continuously for six hours. In three days, observed carbon dioxide concentration was 375~419 ppm, and the air temperature was in the range of $28.7{\sim}32.5^{\circ}C$. The average concentration of carbon dioxide was 388~399 ppm in the upper observation point and 386~396 ppm in the lower observation point. It was higher in the upper observation point and its fluctuations were similar in two observation points. Correlation coefficients between carbon dioxide concentration and air temperature in the upper observation point were in the range of -0.64~-0.88, and were calculated -0.65 to -0.90 in the lower observation point. For the carbon dioxide concentration, correlation coefficients between the upper part and the lower part were very high as 0.98 in three times. For the air temperature, correlation coefficients between the upper part and the lower part were very high as 0.97 and 0.99. In the same observation time, the slope of the linear regression function as carbon dioxide concentration in the lower observation point for the upper observation point was in the range of 0.97~1.01. Carbon dioxide concentration was slightly higher in the upper observation point. Because carbon dioxide in the lower observation point was closer on the surface of the foreshore and absorbed from atmosphere to the foreshore. In this study, it was showed that the vertical variation of carbon dioxide concentration was insignificant in the several meter scale of atmosphere on the surface of the foreshore.

• Ocean and Polar Research
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• 제27권3호
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• pp.237-250
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• 2005

To investigate the air mass modification related with Yeongdong Heavy snowfall events, we examined sensible and latent heat fluxes on the East Sea, the energy exchange between atmosphere and ocean in this study. Sensible and latent heats were calculated by a bulk aerodynamic method, in which NCEP/NCAR reanalysis data and NOAA/AVHRR weekly SST data with high resolution were used. Among winter precipitation events in the Yeongdong region, 19 heavy precipitation events $(1995{\sim}2001)$ were selected and classified into three types (mountain, cold-coastal, and warm types). Mountain-type precipitation shows highly positive anomalies of sensible and latent heats over the southwestern part of the East Set When separating them into the two components due to variability of wind and temperature/ specific Humidity, it is shown that the wind components are dominant. Cold-coastal-type precipitation also shows strong positive anomalies of sensible and latent heats over the northern part and over the central-northern part of the East Sea, respectively. It is shown that the sensible heat anomalies are caused mostly by the decrease of surface air temperature. So it can be explained that cold-coastal-type precipitation is closely related with the air mass modification due to cold air advection over warm ocean surface. But in warm-type precipitation, negative anomalies are found in the sensible and latent heat distributions. From this result, it may be postulated that warm-type precipitation is affected by the internal process of the atmosphere rather than the atmosphere-ocean interaction.

• Asian Journal of Atmospheric Environment
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• 제6권1호
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• pp.33-40
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• 2012

In this study, we characterized the physical form of allergenic Cry j 1 in the urban atmosphere. Through an immunofluorescence antibody method, we showed that allergenic Cry j 1 exists as fine particles (${\leq}1.1{\mu}m$). To determine Cry j 1 concentrations and its particle size distribution, we used the ELISA method to confirm that most Cry j 1 exists as fine particles in the urban atmosphere and is found at high concentrations on fine day next to rainy day. Furthermore, we evaluated Cry j 1 denaturation by using the Biacore J system based on the surface plasmon resonence (SPR) principle and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). We showed that the dissociation constant ($K_D$) of Cry j 1 that has been exposed to urban polluted air is lower ($1.76{\times}10^{-14}$ M) than that of Cry j 1 ($1.32{\times}10^{-9}-3.37{\times}10^{-9}$ M) of original pollen grains that has not been exposed to air pollutants. Cry j 1 turns into low molecular weight proteins by reacting with various acidic solutions. In sum, we showed that allergenic Cry j 1 exists as fine particles that can deposit in the lower respiratory tract. This finding clarifies the relationship between Japanese cedar pollinosis and air pollutants.