• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.56-62
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• 2014

The present study investigated numerically heat and mass transfer characteristics of a fixed bed reactor by using a computational fluid dynamics (CFD) code of Fluent (ver. 13.0). The temperature and species fraction were estimated for different porosities. For modeling of the catalyst in a fixed bed tube, catalysts were regarded as the porous material, and the empirical correlation of pressure drop based on the modified Eugun equation was used for simulation. In addition, the averaged porosities were taken as 0.545, 0.409, and 0.443 and compared with non-porous state. The predicted results showed that the temperature at the tube wall became higher than that estimated along the center line of tube, leading to higher hydrogen generation by the endothermic reaction and heat transfer. As the mean porosity increases, the hydrogen yield and the outlet temperature decreased because of the pressure drop inside the reformer tube.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.84-93
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• 2018

Three-dimensional (3D) numerical simulations have been carried out to study how coolant injection conditions influence the cooling efficiency and projectile ejection performance in a mixture-gas ejection system (or gas-steam launch system). The 3D single-phase computational model was verified using a 1D model constructed with reference to the previous research and then a two-phase flow computation simulating coolant injection on to hot gas was performed using a DPM (Discrete Phase Model). As a result of varying the coolant flow rate and number of injection holes, cooling efficiency was improved when the number of injection holes were increased. In addition, the change of the coalescence frequency and spatial distribution of coolant droplets caused by the injection condition variation resulted in a change of the droplet diameter, affecting the evaporation rate of coolant. The evaporation was found to be a critical factor in the design optimization of the ejection system by suppressing the pressure drop while the temperature decreases inside the breech.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.336-344
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• 2019

The Ministry of Education (2015) announced the "2015 Revised Curriculum for Elementary and Secondary Schools" and announced that SW (Software) training for elementary and junior high school students to develop Computational Thinking will be gradually introduced from 2018. In addition, 'problem solving' and 'programming' have become important areas. Furthermore, the ability to analyze and utilize big data is becoming more emphasized. We developed and applied the statistical - Python programming convergence curriculum based on the idea that convergence education combining information and mathematics, programming and statistical literacy is needed according to current trends. Before and after the experiment, problem solving ability test and programming / mathematical interest test were conducted and compared with the corresponding sample t-test. According to the analysis results, there were significant differences in the pre- and post-test on problem solving ability, programming interest and mathematical interest at the significance level of 0.05.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.328-335
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• 2019

Nb-doped $TiO_2$(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ${\sim}25.3^{\circ}$, corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.1-7
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• 2024

In this study, in order to analyze physical changes that occur in real space in a survival game set in space and effectively apply this to the game, we investigated changes in the body exposed to a weightless environment based on literature on physical changes that occur in space. In addition, survival elements were derived by analyzing the system of survival games registered on the global platform STEAM. Based on the results obtained, a survival system was constructed so that it could be practically applied to a survival game set in space, and a method was designed to apply survival elements related to actual physical changes. Therefore, this study is expected to be used as a way to apply scientific facts as a survival factor for player characters when producing survival games set in space.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.345-349
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• 2006

Conversion of DME (dimethyl ether) or methanol to light olefins (ethylene, propylene, butenes) over SAPO-34 were systematically studied, where it was observed that DME was dehydrated to light olefins and partially converted to by-products such as CO and $CO_2$ at various reaction temperatures on the time-on-stream. SAPO-34 catalyst during the DTO (dimetyl ether-to-olefins) reaction was significantly deactivated compared with MTO (methanol-toolefins) reaction. By addition of water to the reaction feed, the yield to light olefins was not only increased, but the life time of the catalyst was also prolonged by the suppression of the coke formation by steam.

• Food Science and Biotechnology
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• v.14 no.4
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• pp.529-532
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• 2005

Volatile compounds, isolated from Chopi (Zanthoxylum piperitum A.P. DC.) using steam distillation, were analyzed by gas chromatography/mass spectrometry-olfactometry (GC-MS-O). Forty-six volatile compounds, consisting of 12 hydrocarbons, 8 aldehydes, 5 esters, 12 alcohols, 4 ketones, 4 oxides and 1 acid, were tentatively identified from the essential oil of Chopi. Unidentified compounds constituted 7.2% of the total peak area. Limonene was the most abundant compound, followed by geranyl acetate, citronellal, cryptone and ${\beta}$-myrcene. In addition, aroma-active compounds, in particular citronellal and limonene, which are related to the citrus and Chopi flavors of Chopi essential oil, were detected. The aroma of Chopi essential oil had a score of 4.8 on the preference test (neither like nor dislike) and a score of 5.97 on the intensity test (slightly strong) using the 9-point hedonic scale.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1602-1604
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• 1999

Crosslinked polyethylene/silane crosslinked polyethylene (XLPE/SXLPE) blends were prepared by a twin screw extruder and their water tree and crosslinking characteristics were investigated. The water tree characteristics of XLPE were improved by the addition of SXLPE, when samples were cross- linked only by the thermorolysis of DCP (dicumyl peroxide). However, steam curing process was not good for water tree characteristics. It was also found that the degree of crosslinking of XLPE/SXLPE blends were higher than that of XLPE.

• Korean journal of food and cookery science
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• v.8 no.4
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• pp.411-419
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• 1992

Retention of ascorbic acid in vegetables as influenced by various blanching methods was measured and the effects of blanching time, amount of water added, and with or without lid on the retention were compared. It was found that blanching with small amount of water and without lid generally retained the higher activity of ascorbic acid. Although steam blanching showed the highest retention of the vitamin, the longer heating time was needed to blanch the vegetables. Blanching by microwave oven has revealed that addition of small amount of water did not affect the retention. From the scoring difference test for texture of blanched spinach, the samples which were indicated as best in texture by the 8-panel members have retained 73~96% of ascorbic acid and samples blanched by microwave oven for 60 seconds showed highest retention.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.27-32
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• 2002

In this research influences of type and concentration of alkali activator and curing condition on the hydration, and properties of alkali activated blast furnace slag(AAS) concrete were investigated. Sodium carbonate and sulfate were used as alkali activators and their concentration were 4~10 weight percent with Na$_2$O equivalent to binder. The curing conditions were standard curing using 23$^{\circ}C$ water and activated curing chamber at $65^{\circ}C$. Results show that in case of sodium carbonate addition high early strengths were gained by activation of early hydration, but later strength gained was slight. On the other side sodium sulfate strengths were continuously increased with adding amount and ages. Steam curing activated early hydration so that early strengths were improved but later strengths were similar to standard curing. The strength reduction of AAS mortar with sodium sulfate was less than OPC mortar in 5% sulfuric acid solution so that AAS concrete can be useful for acid-resistance concrete.