• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.610-617
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• 2020

In process installations, chemicals operate at high temperature and high pressure. Propylene is used as a basic raw material for manufacturing synthetic materials in the petrochemical industry; However, it is a flammable substance and explosive in the gaseous state. Thus, caution is needed when handling propylene. To prevent explosions, an inert gas, carbon dioxide, was used and the changes in the extent of explosion due to changes in pressure and oxygen concentration at 25 ℃, 100 ℃, and 200 ℃ were measured. At constant temperature, the increase in explosive pressure and the rates of the explosive pressure were observed to rise as the pressure was augmented. Moreover, as the oxygen concentration decreased, the maximum explosive pressure decreased. At 25 ℃ and oxygen concentration of 21%, as the pressure increased from 1.0 barg to 2.5 bar, the gas deflagration index (K_g) increased significantly from 4.71 barg·m/s to 18.83 barg·m/s.

• Journal of Preventive Medicine and Public Health
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• v.17 no.1
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• pp.217-221
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• 1984

In order to estimate interfering effects of mercury and lead on biochemical oxygen demand (BOD), BOD in 18 effluent samples were measured under three different concentrations of mercury and lead. The results obtained were as follows: 1. Biochemical oxygen demand(BOD) was decreased under the presence of mercury and lead, with parallel correlation of mercury concentration. 2. High correlations were noted between original BOD concentration and decreasing amount of BOD when concentrations of mercury or lead were increased. 3. When the lead concentration was high, the close correlation was observed between total organic carbon(TOC) and decreasing amount of BOD. 4. There was a negative correlation between TOC/BOD ratio and decreasing amount of BOD when the mercury concentrations were high.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.5
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• pp.54-60
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• 1988

This study is a theoretical analysis and experimental effect of oxygen concentration, exhaust velocity and trap inlet temperature on particulate ignition temperature with installation of ceramic filter trap in diesel engine. So the following results are obtained. 1, Based on the fundamental experiments of the regeneration process, the analytical model was developed and the results from the analytical model agreed with the experiments, then the validity of the model was proved. 2, The ignition temperature for accumulated particulate was proportional to the exhaust velocity and it was known that the optimum exhaust velocity was about 15m/sec. 3, The ignition temperature for accumulated particulate was inversely proportional to the oxygen concentration and the trap inlet temperature, and a minimum oxygen concentration of 5% was required to sustain regeneration. 4, This experimental filter trap(EX-66) is found about 30% of smoke reduction efficiency in comparison with existing muffler.

• KSBB Journal
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• v.9 no.5
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• pp.492-498
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• 1994

A hollow fiber device was utilized to perform a dialysis culture for E. coli. Acetic acid inhibition on the growth of E. coli was relieved by dialyzing the acid from broth into a dialysate reservoir. The rate of acetic acid formation was very sensitive to the concentration of glucose and dissolved oxygen. Therefore it was found that the glucose permeation rate should be balanced with the oxygen supply rate. Specific growth rate of E. coli was determined by the glucose permeation rate through membrane. Under a low permeation rate, acetic acid formation was depressed in accordance with high dissolved oxygen concentration as well as low glucose concentration.

• Journal of ILASS-Korea
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• v.8 no.4
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• pp.24-30
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• 2003

This paper presents the characteristics of lifted height and flame length from non-premixed jet flames in highly preheated air to investigate the detail combustion mechanism in the gas turbine or HCCI engine, etc. Special attention was paid to the effect of preheated air temperature, oxygen concentration and fuel injection flow rate on flame length and lifted hight. By using highly preheated air, stable flames were formed even in low oxygen concentration condition. The lifted height increased with decreasing preheated air temperature, where the flame length showed opposed phenomena. The flamelet model, which is thought to have very thin flamelet, is difficult to applicable to the present flame conditions which is formed In low oxygen concentration in highly preheated air.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.142-154
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• 1998

The effects of recirculated exhaust gas on the characteristic of soot emissions have been investigated by using an eight-cylinder, four-stroke, direct injection and water-cooled diesel engine operating at several loads and speeds. The experiments in this study are carried out at the fixed fuel injection timing of $38^{\circ}$ BTDC regardless of experimental conditions. The intake oxygen concentration and the mean equivalence ratio calculated by the intake air flow and fuel consumption rate are used to analyze and discuss the influences of EGR rate on soot emissions. Results of this study indicate that soot emissions increase owing to the drop of intake oxygen concentration and the rise of equivalence ratio as the EGR rate increases at a given engine load and speed, especially the high load.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2068-2076
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• 2005

The influence of oxygen concentration and CO$_{2}$ as diluent in oxidizer side on soot characteristics was studied by Laser Induced Incandescence, Time Resolved LII and Transmission Electron Microscopy photography in non-premixed co flowing flames. Through the comparison of TEM photographs and the decay rate of LII signal, suitable two delay times of TIRE-LII method and signal sensitivity ($\Delta$S$_{TIRE-LII/) were determined. The effects of O$_{2}$ and CO$_{2}$ as diluent in oxidizer side on soot formation are investigated with these calibrated techniques. The O$_{2}$+CO$_{2}$, N$_{2}$, and [Ar+CO$_{2}$] mixture in co-flow were used to isolate CO2 effects systematically. The number concentration of primary particle and soot volume fraction abruptly decrease by the addition of CO$_{2}$ to the co-flow. This suppression is resulted from the short residence time in inception region because of the late nucleation and the decrease of surface growth distance by the low flame temperature due to the higher thermal capacity and the chemical change of CO$_{2}$ including thermal dissociation. As the oxygen concentration increases, the number concentration of soot particles at the inception region increases and thus this increase of nucleation enhances the growth of soot particle.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.1
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• pp.11-16
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• 2016

The conduction behavior and electron concentration change in a-IGZO thin-films according to the RTA (rapid thermal annealing) were studied. The electrical characteristics of TFTs (thin-film-transistors) annealed by different temperatures were measured. The sheet resistance, electron concentration, and oxygen vacancy of a-IGZO film were measured by the four-point-probe-measurement, hall-effect-measurement, and XPS analysis. The RTA process increased the driving current of IGZO TFTs but the VTH shifted to the negative direction at the same time. When the RTA temperature is higher than $250^{\circ}C$, the leakage current at off-state increased significantly. This is attributed to the increase of oxygen vacancy resulting in the increase of electron concentration. We demonstrate that the RTA is a promising process to adjust the VTH of TFT because the RTA process can easily modify the electron concentration and control the conductivity of IGZO film with short process time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.238-245
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• 2021

In this study, we carried out case study to predict dissolved oxygen (DO) concentration of Nakdong river estuary with LSTM model. we aimed to figure out a optimal model condition and appropriate predictor for prediction in dissolved oxygen concentration with model parameter and predictor as cases. Model parameter case study results showed that Epoch = 300 and Sequence length = 1 showed higher accuracy than other conditions. In predictor case study, it was highest accuracy where DO and Temperature were used as a predictor, it was caused by high correlation between DO concentration and Temperature. From above results, we figured out an appropriate model condition and predictor for prediction in DO concentration of Nakdong river estuary.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.2
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• pp.59-66
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• 2007

The oxygen distribution at steady state is analyzed mathematically in a hexagonal cylinder. The domain is penetrated by parallel cylindrical capillaries of different oxygen squirt. Asymptotic solution is used to determine the effect of axial diffusion. Oxygen concentration profiles are displayed at some positions of capillary-beds. At the venous end some tissue areas suffer from a shortage of oxygen.