• Polymer(Korea)
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• v.29 no.1
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• pp.8-13
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• 2005

Polystyrene (PS) particles containing the phase change material (PCM) were synthesized by miniemulsion polymerization. The polymer particles prepared with different parameters were investigated in terms of average particle size, particle distribution, and latent heat storage of encapsulated paraffin wax (PW) as PCM. The morphology and particle features of PS particles were analyzed by scanning electron microscope and particle size analyzer, respectively. As a result, the diameters of PS particles were adjusted with manufacturing conditions. The stable and spherical PS particles of nanosize were obtained by miniemulsion polymerization, which could be attributed to the prevention of Ostwald ripening by cosurfactant. Thermal properties of PS particle containing PCM were studied by differential scanning calorimetry. From DSC freeze-thaw cycle, PCM coated with PS exhibited the thermal energy storage and release behaviors, and the latent heat was found to be a maximum 145 J/g. It was noted that PS particles containing PCM showed a good potential as a thermal energy storage medium.

• Journal of Powder Materials
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• v.19 no.6
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• pp.446-450
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• 2012

In order to fabricate the porous Mo with controlled pore characteristics, unique processing by using $MoO_3$ powder as the source and camphene as the sublimable material is introduced. Camphene-based 15 vol% $MoO_3$ slurries, prepared by milling at $50^{\circ}C$ with a small amount of dispersant, were frozen at $-25^{\circ}C$. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green body was hydrogen-reduced at $750^{\circ}C$, and sintered at $1000-1100^{\circ}C$ for 1 h. After heat treatment in hydrogen atmosphere, $MoO_3$ powders were completely converted to metallic W without any reaction phases. The sintered samples showed large pores with the size of about $150{\mu}m$ which were aligned parallel to the camphene growth direction. Also, the internal wall of large pores and near bottom part of specimen had relatively small pores due to the difference in the camphene growth rate during freezing process. The size of small pores was decreased with increase in sintering temperature, while that of large pores was unchanged. The results are strongly suggested that the porous metal with required pore characteristics can be successfully fabricated by freeze-drying process using metal oxide powders.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.602-606
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• 2015

Porous W with spherical and directionally aligned pores was fabricated by the combination of sacrificial fugitives and a freeze-drying process. Camphene slurries with powder mixtures of $WO_3$ and spherical PMMA of 20 vol% were frozen at $-25^{\circ}C$ and dried for the sublimation of the camphene. The green bodies were heat-treated at $400^{\circ}C$ for 2 h to decompose the PMMA; then, sintering was carried out at $1200^{\circ}C$ in a hydrogen atmosphere for 2 h. TGA and XRD analysis showed that the PMMA decomposed at about $400^{\circ}C$, and $WO_3$ was reduced to metallic W at $800^{\circ}C$ without any reaction phases. The sintered bodies with $WO_3$-PMMA contents of 15 and 20 vol% showed large pores with aligned direction and small pores in the internal walls of the large pores. The pore formation was discussed in terms of the solidication behavior of liquid camphene with solid particles. Spherical pores, formed by decomposition of PMMA, were observed in the sintered specimens. Also, microstructural observation revealed that struts between the small pores consisted of very fine particles with size of about 300 nm.

• Korean Journal of Food Science and Technology
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• v.16 no.3
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• pp.279-284
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• 1984

Microstructure of milk powder and cheese made from milk powder were observed by electron microscope. Freeze dried milk powder showed apple-like appearance. The cheese made from freeze dried milk powder had relatively flat surface and homogenous deposit in compare with classical processed cheese. Imported milk powder also indicated similar surface as well as freeze dried milk powder, however, the cheese made from imported milk powder had somewhat coarse surface structures with the spaces between casein matrix and deposit. Commericial milk powder showed irregular shape in size and coagulum which were possibly denatured in the course of drying. The cheese made from commercial powder indicted irregular and small deposit and porous structure. The porousity of the cheese seemed to be influenced by the degree of heat treatment. Denatured protein would be less dispersive than native in presence of polyphosphates. Fat globule and protein micelle of cheese made from skim milk powder get very adjacent to each other and showed compactness of micelles. It is thought that melting mechanism of skim milk powder was different from the melting of typical processed cheese.

• Food Science of Animal Resources
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• v.42 no.5
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• pp.861-873
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• 2022

The drying of duck blood provides safety and commercial benefits, but each drying method has its own characteristics. Moreover, information on the effects of diverse drying methods on the quality of duck blood is limited. This study aimed to investigate the effects of various drying methods on the chemical and functional properties of duck blood. The physicochemical characteristics and functional properties of duck blood subjected to spray drying (SD), freeze drying (FD), vacuum drying (VD), and hot air drying (HD) were examined. The carbonyl content of FD duck blood powder was the lowest and the thermal stability was higher than that of the other treatments (p<0.05). The gel obtained from spray-dried blood displayed the lowest malondialdehyde content. The hardness, gumminess, and chewiness were the highest in the heat-induced gel prepared from FD duck blood powder (p<0.05). The gel obtained from FD duck blood displayed a denser structure than the other gel samples. Taken together, the FD duck blood exhibited excellent chemical properties and processing suitability.

• Development and Reproduction
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• v.10 no.4
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• pp.263-269
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• 2006

To evaluate the potentiality of industrial use of cysteine proteinase inhibitor (cystatin) of tilapia egg and serum stability of the tilapia cystatin on low temperature storage and heat treatment was studied. When the eggs were stored at $4^{\circ}C$ for 3 days the cystatin activity was not changed much, while the supernatant of egg homogenate lost its cystatin activity significantly, remaining only about 65% of initial activity. When the eggs and serum were subjected to repeated freeze at $-20^{\circ}C$ and thaw at room temperature once a day, the egg cystatin was decreased after 5 cycles of freeze and thaw. However the serum cystatin was not changed by the 5 times repetition of freeze and thaw. More than 80% of egg cystatin activity was remained when the egg was heated at $35^{\circ}C$ for 30 min, but less than 10% was remained when heated at $50^{\circ}C$. On the other hand, the serum cystatin was very resistant to heat, remaining about 74% after heating at as high as $80^{\circ}C$ for 30 min. In summary, the egg cystatin was more stable when stored as intact form of egg rather than as supernatant of homogenate when stored at refrigeration. Egg cystatin was relatively stable against repeated freeze-thaw, and serum was found to be more stable in cysteine proteinase inhibitory activity than egg. Egg cystatin was not very resistant to heat treatment, while serum cystatin was quite resistant to high temperature heat treatment. These results suggest that tilapia egg and serum, especially the serum, would be a useful source for cysteine proteinase inhibitor in surimi production.

• Fire Science and Engineering
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• v.29 no.6
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• pp.33-39
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• 2015

In this paper, a numerical experiment was conducted to find out the optimal location of electrical heat trace for anti-freeze of water inside the CPVC pipe for fire protection. The unsteady incompressible Navier-Stokes equations coupled with energy equation were solved. Since the conduction equation of pipe was coupled with the natural convection of water, the analysis of conjugate heat transfer was conducted. A commercial code (ANSYS-FLUENT) based on SIMPLE-type algorithm was used for investigating the unsteady flows and temperature distributions in water region. From the present numerical experiment, it has been found that the vector field of water inside the PVC pipe is opposite to the case of steel because of the huge difference of material properties of the two pipes. Furthermore, it was found that the lowest part of the pipe was an optimal position for electrical heat trace since the minimum water temperature of the case was higher than those of the other cases.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.7
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• pp.21-29
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• 2018

This study aimed to find and suggest the purpose of future plans, critical items on designing and Related standards to amend construction standards for domestic energy saving and environmentally friendly housings. It would also activate and increase the supplies of passive house minimizing the problems on current apartment housings in winter and reducing heating energy which brings fine dust pollution. After defining the standard model of Korean apartment housings(reference model), this study calculated the amount of heating energy demand per unit area annually as applying the yearly changed standards from 2008 to 2017 to existing standard model. It turned out that applying 2017 construction standards of energy saving and eco-friendly housings to reference model has saved up to 75% of heating energy demand comparing to the one applied 2008's. However, it still could not solve the fundamental problems such as winter fungus, condensation, freezing, freeze and burst, and insulation weakness space, and could not be free from fine dust particles. To solve them, this study suggested improved standards adding critical items on design related to outside insulation, cut off the heat-bridge, enforce air-tightness and heat change efficiency on heat recovery ventilator. As a result, it has reduced more than 10% of heat demand from 2017. It would be more than 90% of savings from 2008 if we make the amount of heat loss be zero on heat bridge on designing stage in the future.

• Food Science and Preservation
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• v.12 no.5
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• pp.442-448
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• 2005

To develop efficient drying method, one of important process in manufacturing of Saengsik, uncooked food, the change of physicochemical characteristics and functional component contents of cereals dried by various drying methods was investigated. The proximate composition and dietary fiber content of rice, brown rice, glutinous rice and barley showed little changes during hot-air drying (50$\circC$, 55$\circC$, 60$\circC$) and freeze-drying. Yellowness(b) value of hot-air dried products was higher than one of freeze-dried products. The content of niacin was 0.77 mg% in milled rice, 1.84 mg% in brown rice, 0.68 mg% in glutinous rice, 1.00 mg% in barely dried by hot-air at 60$\circC$ and was lower than those of other samples. $\beta$-glucan content in barely was not changed by hot-air drying and freeze-drying method. In conclusion, hot-air drying would be recommended for barley having $\beta$-glucan, a kind of functional components and freeze-drying should be used for raw materials having heat-labile components such as niacin.

• Journal of Food Hygiene and Safety
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• v.26 no.1
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• pp.31-35
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• 2011

Arcobaeter butzleri is one of the aerotolerant Campylobaeter species which cause persistent diarrhea, abdominal pain, nausea and vomiting in human. The aim of this study was to determine the growth and survival of A. butzleri under the heat treatment or freezing storage condition. In heat treatment, two Korean isolates of A. butzleri were treated at 40 to $80^{\circ}C$ for various times. In freeze treatment, two Korean isolates of A. butzleri were kept at 4, -20 and $-70^{\circ}C$ from 1 to 15 d. The survivability of the A. butzleri Korean isolates significantly decreased at higher than $60^{\circ}C$ heating condition but it didn't show any significant difference in $40^{\circ}C$ treated group. Under the cold stress condition, survivability of A. butzleri were significantly decreased at $-20^{\circ}C$ storage. Like other foodborne pathogens, survivability of A. butzleri was controlled by heat and freezing treatment.