• Journal of Environmental Science International
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• v.8 no.3
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• pp.349-354
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• 1999

The transfer function was introduced to establish the prediction method for the DO concentration at the intaking point of Kongju Water Works System. In the mose cases we analyze a single time series without explicitly using information contained in the related time series. In many forecasting situations, other events will systematically influence the series to be forecasted(the dependent variables), and therefore, there is need to go beyond a univariate forecasting model. Thus, we must bulid a forecasting model that incorporates more than one time series and introduces explicitly the dynamic characteristics of the system. Such a model is called a multiple time series model or transfer function model. The purpose of this study is to develop the stochastic stream water quality model for the intaking station of Kongju city waterworks in Keum river system. The performance of the multiplicative ARIMA model and the transfer function noise model were examined through comparisons between the historical and generated monthly dissolved oxygen series. The result reveal that the transfer function noise model lead to the improved accuracy.

• Water Engineering Research
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• v.5 no.4
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• pp.195-206
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• 2004

This paper deals with oxygen transfer by air entrainment and energy dissipations by flow characteristics at the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height. Dominant flow features included an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. Skimming flow occurred at larger flow rates with formation of recirculating vortices between the main flow and the step comers. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number. It was more related to the flow discharge than to the Froude number. Energy dissipations in both cases of nappe flow and skimming flow were proportional to the step height and were inversely proportional to the overflow depth, and were not proportional to the step slope. The stepped drop structure was found to be efficient for water treatment associated with substantial air entrainment and for energy dissipation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.937-944
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• 2004

An experimental study has been conducted to evaluate the effects of $CO_2$ on heat transfer from oxygen-enriched hydrogen flame. Experiments were performed on flames stabilized by a co-flow swirl burner, which was mounted on top of the furnace. Five different oxidizer compositions were prepared by replacing $N_2$ with $CO_2$. In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace have been measured using a heat flux meter. Temperature distribution in furnace also has been measured and compared. By increasing $CO_2$ proportion in the oxidizer, the convection played a more significant role rather than radiation. Overall temperature in the furnace was seen to be decreased, while the total heat flux has increased.

• Design & Manufacturing
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• v.7 no.1
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• pp.50-54
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• 2013

Sewage treatment plants are energy hogs. Among many, aeration systems account for 40-50 percent of the total energy use. To save energy, strengthening oxygen transfer characteristics is necessary. In order to do so, microscopic bubble-creating equipment is a prerequisite. This study focuses on microscopic bubble-producing air diffuser manufacture to save energy and enhance oxygen transfer.

• The KSFM Journal of Fluid Machinery
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• v.8 no.5 s.32
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• pp.7-12
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• 2005

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers, the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better break-up of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1332-1335
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• 2003

This paper presents the enhancement of oxygen transfer efficiency using the vibrating intravascular lung assist device (VIVLAD) in in-vitro experiments for patients having chronic respiratory problems. The test section was a cylinder duct with the inner diameter of 30 mm. The flow rate was controlled by the pump and monitored by a built-in flow meter. The vibration apparatus was composed of a piezo-vibrator, a function generator. and a power amplifier. The direction of vibration was radial to the fluid flow. Gas flow rates of up to 6 l/min through the 120-cm-Jong hollow fibers have been achieved by exciting a piezo-vibrator. The output of PVDF sensor were investigated by various frequencies in VIVLAD. The experimental results showed that VIVLAD would be enhance oxygen transfer efficiency.

• Microbiology and Biotechnology Letters
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• v.22 no.6
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• pp.659-664
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• 1994

In order to predict gas hold-up and oxygen transfer rate during sisomicin fermentation employing air lift fermentor, simulated media similar to fermentation broths in rheological proper- ties were prepared and used. Rheological properties of fermentation broths from 40 hours and 60 hours of cultivation were analyzed by applying to Power's Law equation. Regardless of addition and no addition of MgSO$_{4}$, the tendencies, that n value was decreased and K value was increased as aeration rate was increased, were shown. Simulated media of twelve different fermentation broths were formulated in a range of 0.7 to 2.1% CMC, and the values of gas hold-up and k$_{L}$a depending on superficial air velocity were measured using these simulated media. And the relation- ships, $\varepsilon$=$\alpha$U$_{Gr}$$\beta$, K$_{L}$a=$\gamma$U$_{Gr}$$\delta$ were obtained, and these equations are thought to be used to predict the values of gas hold-up and k$_{L}$a during fermentation.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.34-39
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• 2012

In the present study, oxygen transfer process across gas-liquid interface in a Y-shape micro-channel is quantitatively visualized using the micro laser induced fluorescence (${\mu}$-LIF) technique. Diffusion coefficient of Oxygen ($D_L$) is estimated based on the experimental results and compared to its theoretical value. Tris ruthenium (II) chloride hexahydrate was used as the oxygen quenchable fluorescent dye. A light-emitting diode (LED) with wavelength of 450 nm was used as the light source and phosphorescence images of fluorescent dye were captured by a CMOS high speed camera installed on the microscope system. Water having dissolved oxygen (DO) value of 0% and pure oxygen gas were injected into the Y-shaped microchannel by using a double loading syringe pump. In-situ pixel-by-pixel calibration was carried out to obtain Stern-Volmer plots over whole flow field. Instantaneous DO concentration fields were successfully mapped according to Stern-Volmer plots and DL was calculated as $2.0675{\times}10^{-9}\;m^2/s$.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.153-161
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• 1993

Cathodic oxygen reduction kinetics on $La_{0.9}Sr_{0.1}MnO_3$ electrode have been examined at $700-900^{\circ}C$ under various oxygen partial pressures. AC impedance and current interruption techniques were employed for the determination of charge transfer resistances for electrochemical oxygen reduction. The $R_{ct}$ values obtained from two different methods were very close each other for $La_{0.9}Sr_{0.1}MnO_3$ electrode. Activation energy for the electrochemical oxygen reduction was found to be 174kJ/mol under atmospheric oxygen pressure. $R_{ct}$ measurements as a function of oxygen partial pressure indicate that the rate-determining step for the electrochemical oxygen reduction on $La_{0.9}Sr_{0.1}MnO_3$ electrode is the charge transfer process.

• Microbiology and Biotechnology Letters
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• v.26 no.6
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• pp.529-536
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• 1998

In a 20 L fermentor experiments the level of dissolved oxygen (D.O.) strongly affected growth and PHBV production of Azotobacter vinelandii UWD. A higher D.O. (5%) increased specific cell growth rate two folds but PHBV production was 17 folds higher (62.3 wt%) at a lower D.O.(1%) level. D.O. level was not a good criterion to evaluate the effect of aeration on fermentation characteristics of A. vinelandii UWD. This strain maintained an equal D.O. (5%) by decreasing its oxygen consumption rate when oxygen transfer rate (OTR) was decreased by changing agitation speed at a fixed aeration rate. OTR rather than D.O. was a criterion to explain the effect of aeration on the cell growth and PHBV production. At 5% D.O. with a lower 0TR cell growth rate decreased but PHBV production (57.3 wt%) approached to that (62.3 wt%) of the lower (1%) D.O.