• 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.

• Research in Community and Public Health Nursing
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• v.13 no.1
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• pp.68-78
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• 2002

This study intended to analyze the health promoting behaviors by comparing various factors according to the residence areas(Korea or Japan) of Korean Elderly. and to present basic data in planning systematic and effective programs of health promotion for each residence area. The subjects of this study were 164 Korean elders in Daegu, South Korea, and 164 elders in Aichi prefecture, Japan. Data was collected by interviews and self-administered questionnaires from the 1st to the 20th of April in 2000. The tool for this study was based on Walker et al.(1987)'s Health Promotion lifestyle Profiles (HPLP). The analysis was performed with Cronbach's $x^2-test$, t-test. ANCOVA, Kendal tau, Pearson correlation, and Stepwise Multiple Regression test using SPSS program. The results are as follows: 1. There was a significant difference in occupation($x^2$=41.3. p=0.000), the source of the pocket money($x^2$=114.36. p=0.000) by the residence areas in terms of socio-demographic characteristics. 2. There was a significant difference between the two groups on the health promoting behaviors(t=-8.19. p=0.000). The score of elders group in the South Korean group on health promoting behaviors was 2.32. showing 0.33 lower than that of the elders group in Japan(2.65). 3. ANCOVA involving occupation and the source of pocket money as co-variables. showed significant differences (F=15.37. p=0.000) regarding health promoting behaviors according to the residence areas. 4. In consideration of variables that have an influence on health promoting behavior by residence areas, pocket money occupied 11.5% of health promoting behavior in the elders group in South Korea. In the elders group in Japan, pocket money occupied 18.1% of health promoting behavior and 20.6% including education. The suggestions based on the results of this study are as follows.: 1. It is necessary to develop health promoting programs considering the residence areas of Korean elders. 2. It is necessary to develop social programs for improving the education level and solving pocket money problems, which are the significant factors for the health promoting behavior of Korean elders.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1074-1081
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• 2021

Nitrous oxide (N₂O) is one of the six major greenhouse gases and is known to produce a greenhouse ef ect by absorbing infrared radiation in the atmosphere. In particular, its global warming potential (GWP) is 310 times higher than that of CO₂, making N₂O a global concern. Accordingly, strong environmental regulations are being proposed. N₂O reduction technology can be classified into concentration recovery, catalytic decomposition, and pyrolysis according to physical methods. This study intends to provide information on temperature conditions and reaction time required to reduce nitrogen oxides with cost. The high-temperature ranges selected for pyrolysis conditions were calculated at intervals of 100 K from 1073 K to 1373 K. Under temperatures of 1073 K and 1173 K, the N₂O reduction rate and nitrogen monoxide concentration were observed to be proportional to the residence time, and for 1273 K, the N₂O reduction rate decreased due to generation of the reverse reaction as the residence time increased. Particularly for 1373 K, the positive and reverse reactions for all residence times reached chemical equilibrium, resulting in a rather reduced reaction progression to N₂O reduction.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.183-190
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• 2002

In order to reduce NOx emissions in the 20kw class microturbines under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and pressure. Air from a compressor with the temperature of 500K to 650K and the pressure of 0.3bar gauge to 0.7bar gauge, was supplied to the combustor through an air preheat-treatment. Sampling exhaust gases were measured at the immediate exit of the combustor. for the effect of temperature on NO and CO emissions. though NOx was increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx and CO were increased also. NOx was decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratios of 0.10 to 0.25 in a lean region. NOx was increased with increasing equivalent ratios, but CO was decreased as an influence of flame temperature. In the very lean region of the equivalent ratio below 0.12, CO was increased suddenly, due to instability. As the results of this study, NOx and CO are found to be reduced to the similar level at the same time when operated at optimal conditions.

• Journal of the Korean Society of Combustion
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• v.13 no.1
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• pp.1-9
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• 2008

Emission characteristics of NOx and CO with heat loss under high efficiency combustion conditions of $CH_4$/Air prmixed flame were examined numerically using detailed-kinetic chemistry. The one-dimensional combustor length was fixed 5cm, and the equivalence ratio was varied from 0.75 to 0.95. To consider the effects of heat loss on NOx and CO formation, the radiative heat loss rate and combined heat loss rate of conductive and convective heat transfer are included. The following conclusions were drawn. In order to reduce the NOx and CO emission level simultaneously, the temperature of product gases must be reduced under 1,800K as soon as possible but kept over 1,300K during the residence time which is needed to converge CO to $CO_2$.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.1
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• pp.83-92
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• 2012

Syngas combustion characteristics of mass produced oxygen carrier particle (OCN706-1100) were investigated in a pressurized fluidized bed reactor using simulated syngas and air as reactants for reduction and oxidation, respectively. The oxygen carrier showed high fuel conversion, high $CO_2$ selectivity, and low CO concentration at reduction conditions and no NO emission at oxidation conditions. Moreover, OCN706-1100 particle showed good regeneration ability during successive reduction-oxidation cyclic tests up to the 10th cycle. Fuel conversion and $CO_2$ selectivity decreased and CO emission increased as temperature increased. These results can be explained by trend of calculated equilibrium CO concentration with temperature. However, fuel conversion and $CO_2$ selectivity increased and CO emission decreased as pressure and gas residence time increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4656-4663
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• 2010

In this study, the 3D computational fluid dynamics (CFD) was performed in relation to the internal fluid characteristics, flow distribution, air mean ages, and residence time for the development of the most optimal model in the complex post-disposal device. As it is expected that a channeling (drift) would be made by the semi-dry reactor due to the large difference in the flow distribution by the compartment in the bag filter, a structural improvement should be urgently made for more uniformed flow distribution in the bag filter. In addition, it showed the possibility that the velocity field and distribution characteristics of the residence time could be improved through a modification to inlet structure of the spray dryer reactor. The complex post-disposal device, modified and supplemented with this analysis, integrated the semi-dry reactor and the bag filter in a single body, so it follows that the improvement can make the device compact, the installation area, the operation fee, and management more convenient.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.66-71
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• 2010

This study was the effect of CO tube insert for NOx and CO emission characteristics in a compact combustion chamber. In detail, NOx and CO emission characteristics with changing of distance due to inserting the CO tube between the burner and the main heat exchanger were investigated. For this study, the commercial program, FLUENT, and the GRI 2.11 detail reaction mechanism were used for the numerical study and a simple model heat exchanger was tested for the experimental study. As results, when the CO tube was inserted between the burner and the main heat exchanger, it was verified the simultaneous NOx and CO reduction method because of increasing the residence time and decreasing the flame temperature.

• Korean Journal of Human Ecology
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• v.20 no.1
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• pp.91-100
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• 2011

This study was conducted in order to understand grandmothers' intent of caring for working mothers' children and the influence of related variables with regard to living arrangements. The data was collected from 245 grandmothers who have been caring for their grandchildren for more than 6 months. The data was analyzed by mean, t-test, x2-test, and logistic regression analysis. The results were as follows: first, as to whether the grandmothers were willing to take care of their grandchildren again, 56.5% answered "yes", while 43.5% were not willing to do so. Those who were not living together with their grandchildren were more likely to answer positively. Second, it was found upon analysis that the significant variables of the experience differed according to grandmothers' residential status. In the case of co-residing grandmothers, the significant variables were the number and age of the grandchildren, their relationship, satisfaction, and feeling of burden, while only satisfaction was significant in non-co-residing grandmothers' cases. This implies that the more satisfaction the non-co-residing grandmothers experience, the more likely they are willing to take care of their grandchildren again. As for the co-residing grandmothers, it implies that the characteristics of the grandchildren, satisfaction, and feeling of burden, all influence their caregiving intent for the next time.

• Particle and aerosol research
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• v.11 no.2
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• pp.29-36
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• 2015

The purpose of this research is to find out the collection property of nanoparticle in diffusion filter to know particle size dispersion of nanomaterial using inertial force and principle of Brownian diffusion motion. We used inertial filters which are two different type and diffusion filters made by various kinds of Wiremesh and the different pieces of filter to compare with particle size distribution using NaCl particles. Finally, We made a conclusion as follows : (1) the bigger available charging volume is and the larger specific surface area of inertial filter is, the better collection efficiency is. (2) The higher wire-mesh number of filter is, the more collection efficiency of small particle is increasing because the wire of the higher Wiremesh number filter is thinner and denser. (3) The more pieces of wire-mesh filter, the more collection efficiency is increasing because it makes the residence time longer.