• Journal of Environmental Science International
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• v.18 no.11
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• pp.1299-1307
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• 2009

In order to measure in-situ suspended particle size, volume concentration of suspended particulate matter and current speed, mooring observation was performed at the Gwangyang Bay by using of an optical instrument, 'LISST-100' and an acoustic instrument, 'ADV'(St. S1). And the sediment flux was obtained based on the concentration of suspended particulate matter and current speeds measured at three lines of Gwangyang Bay during ebb and flood tide of August 2006. To investigate the spatial variation of suspended particulate matter, profiling observations were measured difference echo intensity and beam attenuation coefficient by using of ADCP and Transmissometer (Line A, B, C). The suspended sediment flux rate at the mouth of Gwangyang Bay was observed to be higher during asymmetrical than symmetrical of current speeds. The flux of suspended particulate matter concentration and current speeds were transported to southeastern direction of surface layer and northwestern direction of bottom layer at the western area at line A of Gwangyang Bay. Small suspended particles have been found to increase attenuation and transmission more efficiently than similar large particles using acoustic intensity (ADV/ADCP) or optical transmit coefficient (LISST-100/Transmissometer). The application and problems as using optical or acoustic instruments will be detected for use in time varying calibrations to account for non-negligible changes in complex environments in situ particle dynamics are poorly understood.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.17-23
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• 2006

The influence of fuel spray characteristics on engine performance has been known as one of the major concerns to Improve fuel economy and to reduce exhaust emissions. In general, the UBHC(Unburned Hydrocarbon) emission could be reduced by decreasing the droplet size of the fuel sprays. In PFI (Port Fuel Injection) gasoline engines, the mixture of air and fuel would not be uniform under a certain condition, because the breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve sheat. In this study, were investigated the transient spray characteristics and dynamic behavior of droplets from 2holes-2sprays and 4holes-2sprays type injectors used in PFI gasoline engine. Mean droplet size and optical concentration were measured by LDPA (Laser Diffraction Particle size Analyzer). The variation of droplet mean diameter and optical concentration were measured for understanding the behavior of unsteady spray.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.967-974
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• 2012

Cultivation of Spirulina platensis using ammonium salts or wastewater containing ammonium as alternative nitrogen sources is considered as a commercial way to reduce the production cost. In this research, by analyzing the relationship between biomass production and ammonium-N consumption in the fed-batch culture of Spirulina platensis using ammonium bicarbonate as a nitrogen nutrient source, an online adaptive control strategy based on optical density (OD) measurements for controlling ammonium feeding was presented. The ammonium concentration was successfully controlled between the cell growth inhibitory and limiting concentrations using this OD-based feedback feeding method. As a result, the maximum biomass concentration (2.98 g/l), productivity (0.237 g/l d), nitrogen-to-cell conversion factor (7.32 gX/gN), and contents of protein (64.1%) and chlorophyll (13.4mg/g) obtained by using the OD-based feedback feeding method were higher than those using the constant and variable feeding methods. The OD-based feedback feeding method could be recognized as an applicable way to control ammonium feeding and a benefit for Spirulina platensis cultivations.

• Proceedings of the Korean Environmental Health Society Conference
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• 2002.04a
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• pp.44-46
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• 2002

This study was conducted to identify the proper analytical conditions regarding optical density for endotoxin analysis in the workplace using metalworking fludis. Our study found the "onset method" was more accurate than "time to Vmax" Reproducibility and accuracy analyzed by "onset method" was more greater than those by "time to Vmax""0.03"of optical density was the most appropriate analytical condition among onset method. Through this analytical condition, 0.998 of linearity was obtained and recovery rate ranged from 88％ to 105％ at endotoxin concentration below 5 EU/$m\ell$. No significant difference of endotoxins between "0.03"and "0.05" of optical density was observed from this study. Furthermore, correlation coefficients between them were statistically significant(p＜0.01). This study concluded that 0.03”or "0.05" of optical density is used to analyze endotoxin. Of these optical density value, value with higher linearity should be used to analyze endotoxin in environmental samples.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.374-377
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• 2009

The characteristics of the deposited thin films of the zinc oxide (ZnO) at different oxygen pressures will be elucidated in this work. The resistivity of ZnO thin films were dominated by the carrier concentration under high oxygen pressure conditions while controlled by the carrier mobility at low oxygen ambiences. In addition, we will show the characteristics of the transparent ZnO based thin film transistor (TFT) fabricated at a full room temperature process with gate dielectric of gadolinium oxide ($Gd_2O_3$) thin films.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.453-454
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• 2009

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.237-241
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• 1990

A detailed theoretical and experimental study of k-na exchange in soda lime silicate glasses by RTP is presented. Concentration profiles i.e. index profiles are given by complementary error function added Gaussian function. The estimated diffusion coefficient is 1.54${\mu}{\textrm}{m}$2/min.

• Proceedings of the Optical Society of Korea Conference
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• 2007.02a
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• pp.313-314
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.83-84
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.148-149
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• 2004