• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.275-280
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• 2002

The peculiarities of using Self-propagating High-temperature Synthesis (SHS) and solid-stave chase synthesis for production of high temperature superconductor materials were discussed. Oxide superconductors with general formula of $ReBa_2Cu_3O_{7-x}$ (Re=Y, Sm) haute been made by using barium oxide initial powder instead of traditional barium carbonate. Phenomena observed during the grinding of the reactants mixture are presented. Mechano-chemical activation - as a pre-treatment of the reactants mixture - strongly influences the kinetic parameters, the reaction mechanism, and the composition and structure of the final product.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.164-169
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• 1986

Walsh analysis is applied to the numerical specification of the volume distribution which is the key parameter in the formulation of the constitutive equations of heterogeneous media, indicating the geometrical state of the mixture. An example of two-dimensional volume distribution, its approximation, and the Walsh correlation coefficients are presented and the change of the information distribution in the operations is investigated. The phenomena of information concentration upon the large-scale Walsh coefficients are applied to the volumetric response of porous slids, clarifying the validity of the spherical-model calculation.

• Journal of Korea Foundry Society
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• v.5 no.3
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• pp.13-18
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• 1985

Decarburization phenomena were investigated at $800^{\circ}C$ by the $PH_2O/PH_2$ + Ar gas mixture in the case iron range which contains Si, Mn and Cr as an alloying elements. Dissociation of cementite in a matrix which contains graphitizer as Si begins at the carbon rich cementite dendrite arms. Several primary austenite $({\gamma})$ skeletons are surrounded by those nucleated graphite nodules, and that forms a limited area of nucleation region. Decarburization reactions at $800^{\circ}C$ in Fe-C, Fe-Mn-C and Fe-Cr-C alloy are followed by parabolic rate law under the gas mixture of $PH_2O/PH_2=0.01$ and the modified rate const. ${\kappa}$ were in the range of $1{\sim}6{\times}10^{-10}cm^2/s$.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.168-174
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• 2000

This paper illustrates the validity of reciprocating type superadiabatic combustor as a industrial applicable dryer. After the investigations of inner and surface temperature distributions of combustor various with air-fuel(methane) ratio, mixture flow rate and reciprocating time, this combustor can be applied in industrial dryer at certain operating conditions. The results are as follows. 1) Higher equilivalence ratio emits more radiation heat flux at the censer chamber 2) Higher mixture flow rate makes more uniform temperature distribution. however, due to the heat transfer from censer chamber to porous media, the radiation beat flux is worse. 3) Longer reciprocating time emit more radiation heat flux. however, this case also makes temperature distribution wide

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.783-788
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• 1989

The reason of abnormal expansion in BaTiO3 synthesized in the equimolecular mixture and synthesized in Ba-rich region were investigated at the point of crystal and microstructure. The shrinkage and the expansion of the mixtures in BaCO3-TiO2 system were determined by the mass of BaCO3 added to the equimolecular BaCO3 and TiO2, Ba2TiO4 which was much formed and BaTi2O3 were important crystal in the reaction of Ba-rich region. Sintering phenomena of unreacted BaCO3 activity and the secondary phase caused to generate microcracks in the specimens.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.34-35
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• 1995

The unique feature of pervaporation is the mass transfer from a liquid phase to a vapor phase through a non-porous polymeric membrane. When a liquid mixture is brought into contact with a membrane at one side, it is sorbed into the membrane. Due to a driving force applied across the membrane, the sotbed liquid molecules permeate through the membrane and evaporate at the downstream side of the membrane. In pervaporation the permeated species are usually removed from the downstream side under a relatively low vapor pressure, for example by evacuation with a vacuum pump. As far as this condition is fulfilled, the evaporation step can be considered to be much faster than sorption or diffusion. Hence evaporation does not contribute to permselectivity. Therefore the separation by pervaporation results from the differences in the preferential sorption of the individual components of a mixture into the membrane together with the diffusion rates through the membrane. This postulation implies that both sorption and diffusion phenomena have to be accounted for to understand the physico-chemical nature of the pervaporation separation process.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.76-85
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• 1999

GDI(Gasoline Direct Injection( engine technology is well known as a new technology since it can improve fuel consumption and meet future emission regulations. But the GDI has many difficulties to be solved, such as complexity of injection control mode, unburned hydrocarbon, and restricted power. A 2-D shape combustion chamber was adopted to investigate mixture formation and combustion characteristics of GDI engine. Spray and combustion experiments were performed by changing the injection timing. injection pressure an din-cylinder flow in Rapid Compression and Expansion Machine(RCEM).Through the experiments, the detailed characteristics of fuel spray and combustion was analyzed by visualizing the in-cylinder phenomena according to the change of injection condition, and the optimal fuel injection timing and fuel injection pressure were obtained.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.41-43
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• 2013

In order to simulate and visually observe combustion phenomena in cylindrical radial-flow porous inert media, a radial multi-channel burner, made of transparent quartz plates, was fabricated. Flame stabilization characteristics and its pulsating instability in the burner were experimentally investigated with respect to various mixture flow rates and equivalence ratio. As a result, five different flame behaviors, such as stable flame, pulsating instability, sudden extinction, blowout and unstable extinction, were observed. Mean radial position of circularly arranged multi-flame and its averaged burning velocity were measured and then compared to the freely propagating flame. The multi-flame pulsation frequency is about several tens of Hz and it is supposed to be generated by the heat diffusion enhancement to cold pre-mixture by the intensive gas-solid interaction.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.34-34
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• 1993

The gelation phenomena of N-methylolated PAAm (M-PAAm) in aqueous media was studied. The critical gelation concentration (CGC) was very close to the calculated $C^*$ of the scaling theory. But the CGC of lower MW M-PAAm deviated from $C^*$ due to contamination of small molecules. We propose that the CGC is the close packing configuration of polymer molecules in solution. The experimental results of the gelation of M-PAAm/PAAm mixture proved that the close packing configuration is essential to make a gel. We calculated the minimum quantity of M-PAAm to make M-PAAm/PAAm mixture a gel by using the close packing configuration. We used a lattice model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.282-287
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• 2004

Unielement combustion tests were conducted using coaxial bi-swirl injectors. Major experimental parameters were a recess length and a fuel-side swirl chamber. Combustion efficiency mainly depends on a mixing mechanism for the present coaxial swirl injectors. Low-frequency pressure excitations around 200Hz were observed for all injectors. However, dynamic behaviors considerably differ for an external and an internal mixing case controlled by a recess length. The internal mixing induces mixture to be biased at a specific frequency in a mass flow rate, which results in a relatively high amplitude of pressure fluctuations but results for the external mixing case show that fuel and oxidizer mixture flow carries more complicated, multiple wave characteristics due to broad mixing region as well as disintegration and merging phenomena of propellant films.