• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.3
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• pp.88-93
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• 2009

Lubricant oil is needed in air conditioning and refrigeration system because the compressor requires oil to prevent surface to surface contact between its moving parts, to remove heat, to provide sealing, to keep out contaminants, to prevent corrosion, and to dispose of debris created by wear. Thus, the oil separation in an oil separator is one of the most important characteristics for proper compressor operation. In this study, a gravity type of oil separator is used. Oil separation characteristics have been investigated for $CO_2$/PAG mixture in the range of oil concentration 0 to 5 weight-percent and the mixture temperature range of $0^{\circ}C$ to $15^{\circ}C$ at 50 bar and $70^{\circ}C$ to $90^{\circ}C$ at 80 bar. The results obtained indicate that the oil separation is increased with an increase in the oil concentration. It is also found that the oil separation in liquid state is increased with an increase in the mixture temperature while the oil separation in gas state is decreased.

• Journal of the Korean Society of Safety
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• v.36 no.3
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• pp.1-6
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• 2021

Hydrogen is considered a cleaner energy source than fossil fuels. As a result, the use of hydrogen in daily life and economic industries is expected to increase. However, the use of hydrogen energy is currently limited because of safety issues. The rate of combustion of the hydrogen mixture is about seven times higher than that of hydrocarbon fuels. The hydrogen mixture is highly flammable and has a low minimum ignition energy. Therefore, it presents considerable risks for fire and explosions in all areas of hydrogen manufacturing, transportation, storage, and use. In this study, the auto-ignition characteristics of hydrogen were investigated numerically for diluted hydrogen mixtures. Auto-ignition temperature, a critical property predicting the fire and explosion risk in hydrogen combustion, was determined in well-stirred reactors. When N₂ and CO₂ were used to dilute the hydrogen/air mixture, the ignition delay time increased with increasing dilution ratios in both cases. The CO₂-diluted mixtures exhibited a longer ignition delay than the N₂-diluted mixtures. We also confirmed that lower initial ignition temperatures increased the ignition delay times at 950 K and above. Overall, the auto-ignition characteristics, such as the concentrations of participating species and ignition delay times, were primarily affected by the initial temperature of the mixture.

• Korean Journal of Organic Agriculture
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• v.21 no.4
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• pp.701-710
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• 2013

This experiment was carried out to determine the forage production and soil characteristics in mixtures of barley and annual legumes at riverbed. The dry matter (DM) and total digestible nutrients (TDN) in barley and hairy vetch mixture were higher compared to other mixtures. Barley, single cropping was the highest in DM content. Comparing different mixtures, barley and crimson clover mixture was higher than other mixtures in DM contest. The crude protein (CP) content of barely and hairy vetch mixture was highest, but ether extract (EE) and TDN contents were lower than other mixtures. Barely and hairy vetch mixture significantly removed organic matter and phosphorus from riverbed through forage production (P<0.05). The total nitrogen (TN) of barley and hairy vetch mixture was highest because of high nitrogen fixation in riverbed soil. Single barley was highest in organic matter (OM) of soil. Comparing different mixtures, barley and crimson clover mixture was higher than other mixtures in OM contest. The available P2O5 of soil in barley and crimson clover mixture and barley and rape mixture were higher than others, and that of barley and hairy vetch was lower than other mixtures. The barely and hairy vetch mixture was highest in cation exchange capacity (CEC) content. Therefore barley and hairy vetch mixture is more suitable in forage mixtures because of high forage production and protein, and reduction of soil phosphorus in riverbed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2374-2382
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• 2002

Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It'as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.1-9
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Because this concept reduced NOx and smoke emissions simultaneously. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and intake air temperature affect the mixture formation. The purpose of this study is to investigate characteristics of combustion and mixture formation according to injection timing and intake air temperature in a common rail direct injection type HCCI engine using an early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel injection timing and intake air temperature affect the mixture formation and in turn affects combustion in the PCCI engine.

• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.15-21
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• 2011

An experimental study was conducted to investigate the flame stability of the synthetic gas (syngas) using an impinging premixed jet burner. Since the syngas mainly consisted of $H_2$ and CO, the $H_2$/CO mixture was simulated as the syngas. $H_2$/CO mixture ratios, fuel/air mixture velocities and equivalence ratios were used as major parameters on the flame stabilitym The role of the impinging plate on the flame stability was also examined. In addition, laminar burning velocities of the $H_2$/CO mixture were predicted numerically to understand the characteristics of the flame stability for the syngas. The increase in the H2 concentration into the syngas brings about the extension of the blowout limit and the reduction in the flashback limit in terms of the stable flame region. The impinging jet plate broadened the blowout limit but does not play important role in changing of the flashback limit. Finally, it was found that the stability region of the flame using the syngas, which is expressed in terms of the mixture velocity and the equivalence ratio in this study, significantly differed from that of $CH_4$.

• Fashion & Textile Research Journal
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• v.10 no.5
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• pp.589-600
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• 2008

The purpose of the study was to segment home-shoppers by the Mixture model and to examine the characteristics of the segmented markets. Total 700 copies of questionnaires were distributed to home-shoppers more than 19 years old in Seoul and Busan and analyzed 638 copies with the Mixture model using LatentGold Program. The results of the study were as follows: In the segmented market 1, women in forties and housewives with a lowly educated person purchased for the most part from 10 A.M. to 5 P.M and the study named them as the average home shopping purchaser group. In the segmented market 2, men in twenties and students with a highly educated person often purchased with a small amount of money at 6, 7, 12 P.M and the study named them as the high-satisfaction frequent group purchasing a few goods. In the segmented market 3, professional men in forties with a highly educated person rarely purchased with a lot of amount of money from 8 P.M to 11 P.M and the study named them as low-satisfaction rare group purchasing not a few goods. Marketing strategies and discussion were suggested in detail.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.121-134
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• 1994

Shock tube investigation of ethylene oxide-$0_{2}-N_{2}$ mixture have been performed to reveal detonation characteristics of the mixture in terms of detonation pressure and speed. Theoretical calculation of thermodynamic parameters at the Chapmann-Jouguet detonation of the mixture has been also performed. A comparision of the observed results with the calculated ones can lead us to predict the detonation parameters of ethylene oxide in an artificial air. In addition, we have observed ignition delay times of ethylene oxide mixtures. The best fit of the observed delay times to Arrhenius gas kinetic relation gives : ${\tau}=10^{-144}{e{xp}}(E_a/RT)[C_{2}H_{4}O]^{-4.8}[O_{2}]^{-12.4}[N_{2}]^{-14.1}$ $E_a=3.67kcal/mole$ The observed activation energy is markedly reduced, compared with the case of ethylene oxide diluted in Ar. It could be due to the factor that $N_2$ play a role as detonation promoter yielding very reactive NOx radicals.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.844-851
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• 2009

A soil mixture with low permeability and bentonite as an additive has been highly utilized as a cutoff material in landfills, banks, and dams. Even though it is anticipated that the water can seep through shear failures in the filter layer due to external loads and embankment loads during construction, usually only the coefficient of permeability of the soil mixture is considered rather than the changes of strength from the different amounts of additives. Therefore, the amount of bentonite was changed between 0%~4% in the soil mixture of the bed material to conduct a series of unconfined compressive strength, tensile strength, and shear strength tests on a specimen in order to study the characteristics of the strength. In the result, the unconfined compressive and tensile strength were increased along with the increased amount of bentonite in the low water content; however, the tensile strength in the consolidated-drained shear test generally showed similar values without significant changes.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.12
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• pp.1440-1453
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• 2011

Proper consumer segmentation is receiving more attention from industry professionals as markets become more diverse and consumer-centered. Researchers have recognized the limitations of the traditional cluster analysis technique and this research study analyzes market segmentation using Mixture-model or latent-class segmentation. This study used a questionnaire to determine the characteristics of clothing shoppers using a new technique that proved its superiority over traditional techniques. Questions included items measuring fashion shopping behavior, store choice criteria, apparel consumption styles, price perception by product type, and demographic characteristics. Data were collected from 1074 males and females in their 20s and 30s through an online survey. SPSS 16.0 and Latent GOLD 4.0 were used to analyze the data. The ideal typology of clothing shoppers using the Mixture-model were: 'brand loyalty orientated group', 'group of conservative late 30s', 'group of pleasure-emotion early 20s', 'value oriented consumer product with high-income group', 'group of eco/symbol oriented consumer', and 'group of utility/goal oriented male consumer'. This study showed differences in fashion product purchasing behavior by conducting market segmentation for clothing shoppers using the Mixture-model.