• Journal of Biosystems Engineering
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• v.20 no.4
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• pp.333-342
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• 1995

The resistance to air flow through fruits and vegetables in bulk was an important consideration in the design of the pressure cooling system. The amount of resistance to air flow through produce in bulk normally depended upon air flow rate, stacking depth, porosity, stacking patterns and shape and site of product. But, there was not enough information relating the effects of those factors on air flow resistance. The objectives of this study were to investigate the effect of stacking depth, stacking patterns, porosity and airflow rate on airflow resistance and to develop a statistical model to predict static pressure drop across the produce bed as a function of air flow rate, stacking depth, bed porosity, and product size. Mandarins and tomatoes were used in the experiment. The airflow rate were in the range of 0.1~1.0 ㎥/s.$m^2$, the porosity were in the range of 0.25~0.45, the depth were in the range of 0.3~0.9m and the equivalent diameters were 5.3cm and 6.3cm for mandarins, and 6.5cm and 8.5cm for tomatoes. Three methods of stacking arrangement were used i.e. cubic, square staggered, and staggered stacking arrangement. The results were summarized as follows. 1. The pressure drops across produce bed increased in proportion to stacking depth and superficial air velocity and decreased in proportion to porosity. 2. The increasing rates of pressure drop according to stacking patterns with the increase of superficial air velocity were different one another. The staggered stacking arrangement produced the highest increasing rate and the cubic stacking arrangement produced the lowest increasing rate. But it could be assumed that the stacking patterns had not influenced greatly on pressure drops if it was of equal porosity. 3. The statistical models to predict the pressure drop across produce bed as a function of superficial air velocity, stacking depth, porosity, and product diameter were developed from these experiments.

• Journal of Integrative Natural Science
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• v.3 no.4
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• pp.210-214
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• 2010

Relationship between etch current and morphology and porosity of porous silicon (PS) has been investigated. The gravimetric method is applied to measured the porosity of PS. As the current density increase, the silicon dissolution rate increases, resulting in a higher porosity and etching rate. The result shows that linear dependence of PS porosity and etching rate as a function of current density. The morphology of porous silicon was investigated by using cold field emission scanning electron micrograph (FE-SEM). The size of pores formed during anodization is predominantly controlled by the current density, with an increase in the pore size corresponding to an increase in the current density.

• Journal of Korea Foundry Society
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• v.37 no.6
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• pp.193-198
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• 2017

In this study, volumes of shrinkage and porosity of A356.2 alloys during casting were analyzed as a function of melt temperature, pouring diameter, mold temperature, and Sr content. The temperature of the melt barely affected the shrinkage and porosity formation. The pouring diameter determined the pouring rate, and it was proportional to the shrinkage, yet no relationships with the density of porosity were observed. When the mold was heated at $400^{\circ}C$, shrinkage and porosity in the alloy increased above the one in the mold without heating. However, the mold without heating experienced interior shrinkage and the porosity was mainly distributed near interior shrinkage. The addition of Sr to the melt resulted in more shrinkage and less porosity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.124-133
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• 2012

Compressive strength in concrete increases with time. Regression analysis with time is conventionally performed for strength evaluation and prediction. In this study, hydrate amount is assumed as a function of hydration rate and porosity, and modeling on compressive strength is carried out considering decreasing porosity with time, which does not need the regression analysis with time. For twenty one mix proportions of HPC (High Performance Concrete), DUCOM (FE program) which can simulate the behavior in early aged concrete is utilized, and porosity from each mix proportions is obtained with time. For HPC with OPC (Ordinary Portland Cement) concrete, modeling on compressive strength is performed considering hydration rate, unit content of cement, and porosity with time. For HPC with mineral admixtures, a long-term parameter which can handle long-term strength development is additionally considered. From the comparison with the previous test results, the applicability of the proposed model is verified.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.5
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• pp.1-17
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• 2002

The immobilization and consolidation of the model coatings based on the plastic pigment and latex binder of known particle sizes were theoretically Studied in terms of the dense random packing of binary spheres and varying extent of latex film shrinkage. The porosity of the model coatings was calculated based on three proposed latex shrinkage models: Maximum, Minimum, and Linearly Decreasing Latex Shrinkage. The increasing extent of latex shrinkage was calculated up to the critical pigment volume concentration(CPVC) as a function of plastic pigment volume fractions, and the maximum latex shrinkage was estimated from the CPVC. Also, the number of pores and the average equivalent spherical pore diameters were calculated based on those proposed models. The opacity and gloss of the model coatings on polyester films were measured and their porosity was also determined by a simple coat weight-thickness method. As expected, various coating structure-property-composition relationships, such as opacity, gloss, porosity, etc., were shown to exhibit sharp transitions near the CPVC. The CPVC values determined by the opacity, gloss, and porosity vs. PVC relationships, respectively, agreed very well with each other. Especially, the CPVC's determined by the opacity and porosity vs. PVC curves were identical. The comparison between the theoretically calculated and experimental porosity values showed that the intermediate value between the maximum and minimum latex shrinkage would best fit the experimental porosity data. The effect of plastic pigment particle size on the optical properties and porosity of model coatings was also studied and it was observed that the coating opacity and porosity increased with increasing plastic pigment particle size, but the gloss decreased. The ink gloss of the uncalendered model coatings applied onto commercial sheet offset coated papers was shown to be affected by both the coating gloss and porosity: the higher the coating gloss, the higher the ink gloss, but the higher the coating porosity, the lower the ink gloss. Their printability was also studied in terms of the number of passes-to-fail and the rate of ink setting as a function of both plastic pigment volume fractions and plastic pigment particle sizes. A minimum crack-free temperature(MCR) of latex-bound coatings was proposed to better predict the behaviors of latexes as coating binders. The wet state of model coating dispersions, the surfaces of consolidated model coatings, and their internal structure were examined by both electron and atomic force microscopy, and their micrographs were found to be consistent with our immobilization and consolidation models.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.2
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• pp.144-152
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• 2013

In an effort to find the optimum porous of Taewoo through the mathematical model 2 - dimensional tank water experiment among the approached to a problem related to ocean engineering, this study analyzed the porosity by dividing it into 9 cases. As the wave penetrates through the longitudinal porous of the Taewoo model, it was found that there is a wave energy loss because of the phenomenon of the separation of the porous due to the eddy. Looking into the general tendency based on the wave-height meter (probe) data, it was found that the shorter wavelength and higher frequency area, the more reflection coefficients increased, but in contrast, the longer wavelength and lower frequency area, the transmission coefficients showed the increasing trend and energy dissipation was in a similar way with reflection coefficients. In addition, it was found that the bigger the porosity was, the narrower distribution range of reflection coefficients was, and the more its average value decreased. On the other hand the transmission coefficients in direct opposition to reflection was found to show the wider range and the more gradual increase in the average value as porosity was the bigger around the average value. In contrast, energy dissipation rate was found to increase linearly as porosity increased the more around the porosity of 0.2518 but it decreased gradually around the peak point. Through the above results, it is judged that the porous of optimum in the longitudinal direction of the Taewoo model perforated plate was about 2.6cm because it was found that the porosity which produced the lowest reflection and transmission coefficient and the highest energy dissipation. As a result of comparing this to the case where there was no porosity at all, it showed the function of wave absorbing about 31.60%.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1547-1549
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• 1999

As a preliminary experiment for the development of anode-supported tubular cell with proper porosity, we have investigated the anode substrate and the electrolyte-coated anode tube. The anode substrate was manufactured as a function of carbon content in the range of 20 to 50 vol.%. As the caron content increased, the porosity of the anode substrate increased slightly and the carbon content with proper porosity was obtained at 30 vol.%. The anode tube was fabricated by extrusion process and the electrolyte layer was coated on the anode tube by slurry dipping process. The anode-supported tube was cofired successfully. Their sintered property and microstructure were examined and the porosity of the anode tube was 35%. From the gas permeation test, the anode tube was found to be porous enough for gas supply. On the other hand, the anode-supported tube with electrolyte layer indicated a very low gas permeation rate. This means that the coated electrolyte was dense. Based upon these experimental results. we will fabricate and test the anode-supported tubular cell.

• Transactions of Materials Processing
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• v.22 no.6
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• pp.334-339
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• 2013

Direct Laser Melting is a prototyping process whereby a 3-D part is built layer wise by melting the metal powder with laser scanning. This process is strongly influenced by the shielding gas and the laser operating parameters such as laser power, scan rate, layering thickness, and rescanning. The shielding gas is especially important in affecting the microstructure and mechanical properties. In the current study, fabrication experiments were conducted in order to analyze the effect of shielding gas on the forming characteristics of direct laser melting. Cylindrical parts were produced from a Fe-Ni-Cr powder with a 200W fiber laser. Surface quality, porosity and hardness as a function of the layering thickness and shield gas were evaluated. By decreasing the layering thickness, the surface quality improved and porosity decreased. The selection of which shield gas, Ar or $N_2$, to obtain better surface quality, lower porosity, and higher hardness was examined. The formability and mechanical properties with a $N_2$ atmosphere are better than those parts formed under an Ar atmosphere.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.185-188
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• 2006

During the carbonation process in concrete, the rate of carbonation depends on porosity and moisture content of the concrete. For underground reinforced concrete structures, the interior concrete surface may be exposed to carbonation and the exterior concrete surface exposed to moisture due to wet soil or underground water. In this study, the permeability coefficients in mortar partially carbonated is derived as a function of carbonation depth and porosity of mortar by applying the so-called micro pore structure formation model (MPSFM) which was developed for the modeling of early-aged concrete. The permeability coefficient obtained from the micro-level modeling of carbonated mortar is verified with the results of accelerated carbonation test and water penetration test in cement mortar.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.261-265
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• 2014

As the need for miniaturization in water purification filter increases, the development of filter media for single filtration with multiple function was strongly required. In this study, the molded activated carbon composed of single unit was manufactured by extrusion-sintering process, and then the flow rate, density and porosity were investigated using the molded activated carbon manufactured at various extrusion temperature. We confirmed that it was possible to manufacture the single unit-molded activated carbon when the extrusion temperature was $140{\sim}230^{\circ}C$ more than $133^{\circ}C$ being of polymer binder melting point, and the optimal extrusion temperature for the molded activated carbon with maximum flow rate was $170^{\circ}C$ since the molded activated carbon had low density and high through porosity. Also we confirmed that the flow rate through the molded activated carbon was strongly dependent upon through pore porosity compared to total porosity for the molded activated carbon.