• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.277-284
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• 2001

One of the problems in a refrigerator operation is the frost formation on a cold surface of the evaporator. The frost layer is formed by the sublimation of water vapor when the surface temperature is below the freezing point. This frost layer is usually porous and formed on the cold surface of the evaporator. The frost layer on the surface of a evaporator will make side effect such as thermal resistance. However, these important factors have not been used in determining the defrosting period. Therefore, the proper defrosting operation period based on the new defrosting method is very important, and make a comparison between conventional method like electric defrost and new method in compression work, evaporation pressure, evaporation temperature.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.329-333
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• 2003

The high-temperature oxidation behavior of Ti39Al-10V alloy that consisted primarily of $\beta$-Ti, ${\gamma}$-TiAl, and $\alpha_2$ $-Ti_3$Al phases was studied. The relatively thick and porous oxide scales formed consisted primarily of an outermost, thin TiO$_2$ layer, and an outer, thin $Al_2$$O_3$-rich layer, and an inner, very thick (TiO$_2$, $Al_2$$O_3$) mixed layer. Vanadium was present uniformly throughout the oxide scale. The formation and subsequent evaporation of V-oxides such as VO, $VO_2$, and $V_2$O$_{5}$ deteriorated oxidation resistance and scale adherence of the TiAl alloy significantly.y.

• Journal of the Korean institute of surface engineering
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• v.52 no.3
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• pp.111-116
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• 2019

Chromium was coated on a steel substrate by the Cr(III) electroplating method, and corroded at $500-900^{\circ}C$ for 5 h in $N_2/0.1%H_2S-mixed$ gas to study the high-temperature corrosion behavior of the Cr(III) coating in the highly corrosive $H_2S-environment$. The coating consisted of (C, O)-supersaturated, nodular chromium grains with microcracks. Corrosion was dominated by oxidation owing to thermodynamic stability of oxides compared to sulfides and nitrides. Corrosion initially led to formation of the thin $Cr_2O_3$ layer, below which (S, O)-dissolved, thin, porous region developed. As corrosion progressed, a $Fe_2Cr_2O_4$ layer formed below the $Cr_2O_3$ layer. The coating displayed relatively good corrosion resistance due to formation of the $Cr_2O_3$ scale and progressive sealing of microcracks.

• Coupled systems mechanics
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• v.5 no.3
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• pp.203-221
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• 2016

The present study deals with the numerical modelling for the one dimensional contaminant transport through saturated homogeneous and stratified porous media using meshfree method. A numerical algorithm based on element free Galerkin method is developed. A one dimensional form of the advectivediffusive transport equation for homogeneous and stratified soil is considered for the analysis using irregular nodes. A Fortran program is developed to obtain numerical solution and the results are validated with the available results in the literature. A detailed parametric study is conducted to examine the effect of certain key parameters. Effect of change of dispersion, velocity, porosity, distribution coefficient and thickness of layer is studied on the concentration of the contaminant.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.273-279
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• 1998

Unite cell of soid oxide fuel cell (SOFC) that consists of a dense yttria-stabilized zirconia(YSZ) electrolyte a porous nickel-YSZ cermet anode and a porous strontium- doped lanthanum manganate(LSM) cathod was fabricated from using pore former through co-firing technique. Initial sintering shrinkage rates of each layer were identified for fabricating SOFC. Heterogenous sintering was very effective in tailoring shrinkage rate for three layers. The powder tailoring necessary for shrinkage rate matching are as follows ; electrolyte of 60% TZ8YS/ 40% TZ8Y mixture anode of 51wt% NiO/49 wt% (70wt% TZ8YS/30 wt% UT ZrO2) mixture and cathode of 80% LSM/20% UT ZrO2 mixture . The overall sintering shrinkage rate differences of three layers using these compositions were maintained in a few percent.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.59-62
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• 2007

The basic concept and preliminary performance results of a miniaturized electroosmotic (EO) pump with diaphragms were included in the present study. The separation of an electroosmotic pumping liquid from a drug using diaphragms is mainly to have a freedom in choosing an electroosmotic pumping liquid and to achieve the optimal drug delivery, and, preferably its precise control. We performed maximum flow rate, maximum pressure, and maximum current measurements with and without diaphragm designs. As a result, the effect of diaphragms on pump performance at the maximum condition is small. However, the presence of diaphragms does not allow indefinite continuous pumping.

• Textile Coloration and Finishing
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• v.15 no.2
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• pp.68-75
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• 2003

In this work, ultrafiltration(UF) membranes were prepared using polyethersulfone(PES). The polymer was dissolved in various solvent, such as N, N-dimethyl formamide(DMF), N,-dimethyl acetamide (DMAc), N,N-dimethyl sulfoxide(DMSO) and N-methyl-2- pynolidone(NMP). Each polymer solution was casted on the glass plate, and immersed into non-solvent bath. In this way finely porous UF membranes were prepared by phase inversion method. The cross sectional structure of PES membrane was asymmetric which was consist of sponge-like sublayer, finger-like toplayer, and active skin layer. From the solute rejection experiments, the molecular weight cut off of the prepared membrane in various solvent was evaluated 10,000 for DMF, 30,000 for DMAc, 50,000 for DMSO, and 10,000 for NMP respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.1016-1021
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• 2008

The development of the first wall whose major function is to withstand high neutron and heat fluxes is a critical path to fusion power. The materials database and the fabrication technology are being developed for design, construction and safety operation of the fusion reactor. The first wall was designed to consist of the plasma facing armor, the heat sink layer and the supporting plates. and Porous materials are of significant interest due to their wide applications in catalysis, separation, lightweight structural materials. In this study, the characteristics of the sintering process of SiC ceramic, $SiC_f$/SiC composite and porous $C_f$/SiC composite have been introduced order to study of the fusion blanket materials and heat-exchange pannel.

• Bulletin of the Korean Chemical Society
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• v.24 no.10
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• pp.1437-1443
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• 2003

Thermal decomposition of hydrated surface layer of $Mg(OH)_2$ at $500^{\circ}C$ in vacuum turned non-porous MgO into porous one with high surface area of around $270 m^2$/g. Most of its surface area, 74 %, was from micropores, and rest of it was from mesopores in wedge-shaped slits, exhibiting bimodal size distribution centered around 30 and 90${\AA}$. Rehydration followed by subsequent dehydration at $300 ^{\circ}C$ in dynamic vacuum further raised the surface area to 340 $m^2$/g. Fraction of microporous surface area was increased to 93%, and the shape of the mesopores was modified into parallel slits with a specific dimension of 32 ${\AA}$. Application of $Fe_2O_3$ over MgO via iron complex formation did not alter the pore characteristics of MgO core, except slightly increased pore dimension. Over the course of the modification, $Fe_2O_3$ stayed on the surface possibly via spill-over reaction.

• Coupled systems mechanics
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• v.9 no.3
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• pp.201-217
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• 2020

This paper employs differential quadrature method (DQM) and nonlocal strain gradient theory (NSGT) for studying free vibrational characteristics of porous functionally graded (FG) nanoplates coupled by visco-elastic foundation. A secant function based refined plate theory is used for mathematical modeling of the nano-size plate. Two scale factors are included in the formulation for describing size influences based on NSGT. The material properties for FG plate are porosity-dependent and defined employing a modified power-law form. Visco-elastic foundation is presented based on three factors including a viscous layer and two elastic layers.The governing equations achieved by Hamilton's principle are solved implementing DQM. The nanoplate vibration is shown to be affected by porosity, temperature rise,scale factors and viscous damping.