• Journal of Powder Materials
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• v.20 no.1
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• pp.53-59
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• 2013

Fe-TiC composite powder was fabricated via two steps. The first step was a high-energy milling of FeO and carbon powders followed by heat treatment for reduction to obtain a (Fe+C) powder mixture. The optimal condition for high-energy milling was 500 rpm for 1h, which had been determined by a series of preliminary experiment. Reduction heat-treatment was carried out at $900^{\circ}C$ for 1h in flowing argon gas atmosphere. Reduced powder mixture was investigated by X-ray Diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Laser Particle Size Analyser (LPSA). The second step was a high-energy milling of (Fe+C) powder mixture and additional $TiH_2$ powder, and subsequent in-situ synthesis of TiC particulate in Fe matrix through a reaction of carbon and Ti. High-energy milling was carried out at 500 rpm for 1 h. Heat treatment for reaction synthesis was carried out at $1000{\sim}1200^{\circ}C$ for 1 h in flowing argon gas atmosphere. X-ray diffraction (XRD) results of the fabricated Fe-TiC composite powder showed that only TiC and Fe phases exist. Results from FE-SEM observation and Energy-Dispersive X-ray Spectros-copy (EDS) revealed that TiC phase exists uniformly dispersed in the Fe matrix in a form of particulate with a size of submicron.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.407-408
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• 2011

Natural boron consists of two stable isotopes 10B and 11B with natural abundance of 18.8 atom percent of 10B and 81.2 atom percent of 11B. The thermal neutron absorption cross-section for 10B and 11B are 3837 barn and 0.005 barn respectively. 10B enriched specific compounds are used for control rods and as a reactor coolant additives. In this work 2 methods for boron enrichment were analysed: 1) Gas irradiation in static conditions. Dissociation occurs due to multiphoton absorption by specific isotopes in appropriately tuned laser field. IR shifted laser pulses are usually used in combination with increasing the laser intensity also improves selectivity up to some degree. In order to prevent recombination of dissociated molecules BCl3 is mixed with H2S 2) SILARC method. Advantages of this method: a) Gas cooling is helpful to split and shrink boron isotopes absorption bands. In order to achieve better selectivity BCl3 gas has to be substantially rarefied (~0.01%-5%) in mixture with carrier gas. b) Laser intensity is lower than in the first method. Some preliminary calculations of dissociation and recombination with carrier gas molecules energetics for both methods will be demonstrated Boron separation in SILARC method can be represented as multistage process: 1) Mixture of BCl3 with carrier gas is putted in reservoir 2) Gas overcooling due to expansion through Laval nozzle 3) IR multiphoton absorption by gas irradiated by specifically tuned laser field with subsequent gradual gas condensation in outlet chamber It is planned to develop software which includes these stages. This software will rely on the following available software based on quantum molecular dynamics in external quantized field: 1) WavePacket: Each particle is treated semiclassicaly based on Wigner transform method 2) Turbomole: It is based on local density methods like density of functional methods (DFT) and its improvement- coupled clusters approach (CC) to take into account quantum correlation. These models will be used to extract information concerning kinetic coefficients, and their dependence on applied external field. Information on radiative corrections to equation of state induced by laser field which take into account possible phase transition (or crossover?) can be also revealed. This mixed phase equation of state with quantum corrections will be further used in hydrodynamical simulations. Moreover results of these hydrodynamical simulations can be compared with results of CFD calculations. The first reasonable question to ask before starting the CFD simulations is whether turbulent effects are significant or not, and how to model turbulence? The questions of laser beam parameters and outlet chamber geometry which are most optimal to make all gas volume irradiated is also discussed. Relationship between enrichment factor and stagnation pressure and temperature based on experimental data is also reported.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.1
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• pp.35-40
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• 2021

Calcium hydroxide (CH) reacts with CO2 to produce moisture, and sodium carbonate (SC) reacts with CO2 in the presence of moisture. Using these different characteristics of these two reactants, a CH/SC mixture of CO2 absorber tuned for kimchi ripening to produce CO2 in a flexible package was selected. A ratio of CH:SC (1:2) in highly gas permeable microporous spunbonded film (Tyvek) sachet was found to be appropriate for delayed and consistent CO2 absorption useful for kimchi package. Addition of superabsorbent polymer (SAP) as moisture buffer was helpful for boosting the consistency of CO2 absorption. In a package of 0.5 kg kimchi at 10℃, the sachet consisting of 0.794 g of CH + 2.276 g of SC + 0.4 g of SAP suppressed its volume expansion and maintained a suitable range of CO2 partial pressure (PCO2) steadily inside. These optimal conditions may vary depending on the type and salinity of kimchi, storage and distribution temperature, and the material and area of the absorber sachet. This study showed a potential of mixture CO2 absorber to be tuned for CO2 producing packaged kimchi for the purpose of keeping consistent PCO2 at tolerable volume expansion.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2983-2988
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• 2007

In the present study, the numerical investigation on the effects of water-mist characteristics has been carried out for the fire suppression mechanism. The FDS are used to simulate the interaction of fire plume and water mists, and program describes the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The numerical model is consisted of a rectangular enclosure of $L{\times}W{\times}H=1.5{\times}1.5{\times}2.0m$ and a water mist nozzle that be installed 1.8m from fire pool. In the study, the parameters of nozzle for simulation are the droplet size and the spray velocity. Finally, the droplet size influences to fire flume on fire suppression than spray velocity because of the effect of terminal velocity, and the optimal condition for fire suppression is that the droplet size and the spray velocity are $100{\mu}m$ and 20m/s, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.8-20
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• 2006

For large scale separation hydrogen from different mixing ratio(60/40 and 80/20 vol.%) of hydrogen and methane $1Nm^3/hr$ and $4Nm^3/hr$ 2bed-6step pressure swing adsorption(PSA) process was used, respectively. The effects of the feed gas pressure, adsorption time, the feed flow rate and the P/F(purge to feed) ratio on the process performance were evaluated. In the $1Nm^3/hr$ PSA results, 11 atm adsorption pressure and 0.10 P/F ratio might be optimal values to obtain more than 75 % recovery and 99 % purity hydrogen in these processing. The optimum feed flowrate was 22 LPM and 17 LPM in the ratio 60/40 and 80/20, respectively. In the $4Nm^3/hr$ PSA results, 10 atm adsorption pressure might be simulated values to obtain more than 80 % recovery and 99 % purity hydrogen in these processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1074-1077
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• 2003

우리는 AC-PDP에서 휘도와 효율을 향상시키기 위하여 Ne-Xe(4%)와 He(7)-Ne(3)-Xe(3%)에 소량의 Ar 또는 Kr를 첨가하여 최적의 페닝 방전가스 혼합비를 연구하였다. 우리는 이것을 증명하기 위해 효율과 Q-V 방법을 이용하여 벽전하를 계산하였으며, 2차원 시뮬레이션에서의 결과값과 비교하였다. 200 Torr 압력에서 He-Ne-Xe 또는 Ne-Xe에 소량의 Ar(0.01-0.1%) 또는 Kr(0.01-0.1%)을 첨가시켰을 때, 우리는 20% 이상의 휘도의 증가와 25% 이상의 효율 증가를 발견하였고, 또한 벽전하도 25% 이상의 증가를 보였다. 400 Torr 압력에서 He-Ne-Xe-Kr(0.005%)에 소량의 Ar(0.005-0.1%)를 첨가시켰을 때는 8% 이상의 휘도의 증가와 18% 이상의 효율 증가, 12% 이상의 벽전하 증가를 확인하였다. 결론적으로 이 결과는 He, Ne, Ar, Kr 사이에 추가적인 페닝효과가 휘도와 효율을 향상시켰다는 것을 보여준다.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.175-184
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• 2017

The numerical investigation on the effects of water-mist characteristics has been carried out for the fire suppression mechanism. The FDS are used to simulate the interaction of fire plume and water mists, and program describes the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The numerical model is consisted of a rectangular enclosure of $L{\times}W{\times}H=1.5{\times}1.5{\times}2.0m^3$ and a water mist nozzle that be installed 1.8 m from fire pool. In the present study, the parameters of nozzle for simulation are the droplet size and the spray velocity. The droplet size influences to fire flume on fire suppression more than the spray velocity because of the effect of the terminal velocity. The optimal condition for fire suppression is that the droplet size and the spray velocity are $100{\mu}m$ and 20 m/s respectively.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.211-217
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• 2014

A new needle-based device for headspace wire coated in-needle microextraction (HS-WC-INME) was fabricated using a nichrome wire coated with poly(ethylene glycol) (PEG) and poly(dimethylsiloxane) (PDMS) mixture. The proposed needle device was applied for the determination of volatile compounds in lavender and lavandin essential oils by gas chromatography. Fundamental parameters such as needle design, conditions of extraction and desorption were optimized along with the validation of the extraction and desorption efficiency. The optimal conditions were 30 min extraction at $50^{\circ}C$ and 2 min desorption at $240^{\circ}C$. The calibration curves showed good linearity with the suitable values of the coefficients of determination ($r^2$) greater than 0.99. The limits of detection for linalyl acetate, ${\beta}$-caryophyllene, linalool and (+)-limonene were 7.15, 9.04, 10.79 and 22.26 ng, respectively. Analytical recoveries were acceptable in the test samples, varying from 86.7% to 108.0%. The values of relative standard deviations for run to run showed range less than 0.9% while 3.9% through 7.2% for needle to needle. The proposed PEG-PDMS coating could be more suitable than PDMS coating to extract particular polar groups such as alcohols.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1193-1202
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• 2000

The paper describes the use of genetic algorithms (GA's) to the minimum weight design of stiffened composite panels for buckling constraints. The proposed design problem is characterized by mixture of continuous and discrete design variables corresponding to panel elements and stacking sequence of laminates, respectively. Design space is multimodal and non-convex, thereby introducing the need for global search strategies. Advanced strategies in GA's such as directed crossover, multistage search and separated crossover are adopted to improve search ability and to save computational resource requirements. The paper explores the effectiveness of genetic algorithms and their advanced strategies in designing stiffened composite panels under various uniaxial compressive load conditions and the linrlit on stacking sequence of laminates.

• Korean Journal of Microbiology
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• v.21 no.1
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• pp.27-35
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• 1983

The stoichiometry between the consumption of CO and $O_2$ and the production of $CO_2(2CO+O_2{\rightarrow}2CO_2)$) showed that Pseudomonas carboxydohydrogena grows as a typical aerobic CO oxidizer with CO. The optimal concentration of CO for growth was found to be 30% in gas mixture with air. The initial buffer concentration of the culture medium did not affect the growth of this bacterium. P. carboxydohydrogena is an obligate aerobe and dose not use nitrate as a terminal electron acceptor. The CO dehydrogenase is an inducible and soluble enzyme. The reaction rate and stability were maximal at pH7.5, and the Arrhenius plot revealed an activation energy of 37.7kJ/mol (9.0 Kcal/mol). The crude enzyme used methylene blue, thionin, and toluylene blue as electron acceptors for the oxidation of CO to $Co_2$ under anaerobic conditions. It was found that water must be the source of the second oxygen atom for CO oxidation.