• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.25-31
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• 2021

Boundary conditions for thermal-hydraulic problems of soils play an essential role in the numerical accuracy. This study presents a boundary condition considering the thermo-hydraulic interaction between the ground and the atmosphere. Ground surface energy balance consists of solar radiation, ground radiation, wind convection, latent heat from water evaporation, and heat conduction to the ground. Equations for each heat flux are presented, and numerical analyses are performed in conjunction with the FEM program for the thermal-hydraulic phenomenon of unsaturated soils. Numerical results using the weather data at the Ulsan Meteorological Observatory are similar to the measured surface temperature. Latent heat caused by water evaporation during the daytime lowers the surface temperature of the bare soil, and a thermal equilibrium is reached at nighttime when the effect of the ground condition is significantly reduced. The temperature change of the surface ground is diminished at the deeper ground due to its thermal diffusion. Numerical analysis where the surface ground temperature is the primary concern requires considering the thermo-hydraulic interaction between the ground and the atmosphere.

• Composites Research
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• v.36 no.2
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• pp.101-107
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• 2023

In this study, aluminum nitride (AlN) reinforced aluminum (Al) matrix composites are fabricated via plasma arc melting under a nitrogen atmosphere. Within a minute of the chemical reaction between Al and N, dispersed AlN with the shape of transient and lamellar layers is in situ formed in the Al matrix. The composite contains 10 vol.% AlN reinforcements with low thermal resistance and strong bonding at the interfaces, which leads to the unique combination of thermal expansivity and conductivity in the resulting composites. The coefficient of thermal expansion of the composite can be further reduced when Si was alloyed into the Al matrix, which proposes the potential of the in situ Al matrix composites for thermal management applications.

• Horticultural Science & Technology
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• v.32 no.2
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• pp.184-192
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• 2014

Various types of unit packaging methods were applied for 'Fuji' apples during short-term cold storage and export simulation. Gas tightness of the package was controlled stepwise in the successive two-year experiments using different perforation treatments (none, punch hole, or pinhole) and sealing methods (tie v s. heat seal). Risk of tight packaging and effectiveness of macroperforation on weight loss and quality maintenance were analyzed as related to changes in gas concentration inside the packages. Immediately after harvest, each 5 apple units were packaged in $40{\mu}m$ polypropylene (PP) film bags, stored 4 weeks at $0^{\circ}C$, and then put on the shelf for one week at ambient temperature in the preliminary experiment, In the main experiment, export process was imposed after storage simulating 2 week refrigerated container shipment at $0^{\circ}C$ plus one week local marketing at ambient temperature. Non-perforated film packaging with relatively high gas tightness induced flesh browning caused by carbon dioxide accumulation regardless of the sealing methods. Among perforated film packaging, in contrast, atmospheric modification was partly established only in the pinhole treatment and flesh browning symptom was not observed in all the treatments. Even the punch hole perforated film packaging without gas tightness effectively reduced the weight loss, whereas had slight benefits for quality maintenance. Reduced perforation using pinhole treatment seemed to improve sensory texture, while effects on physicochemical quality were insignificant. Overall results suggest the need of more minute perforation treatments on the packaging film to ensure modified atmosphere effects on quality maintenance.

• Food Science and Preservation
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• v.15 no.6
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• pp.804-809
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• 2008

Modified atmosphere packaging (MAP) was assessed in terms of extending the shelf life of Solidago virgaurea spp. gigantea. In June 2005 Solidago virgaurea spp. gigantea were harvested from Ulleung Island, packaged in $30\;{\mu}m$ PP, $30\;{\mu}m$ Antifogging-OPP, $30\;{\mu}m$ LDPE, $18\;{\mu}m$ Macroperforated-HDPE, $60\;{\mu}m$ nylon/PE, or $85\;{\mu}m$ PVC/PE film, then stored at 4, 10 or $20^{\circ}C$ for up to 14 days. The $O_2$ concentration decreased to $9{\sim}10%$ in the PP and A-OPP packaging, to $12{\sim}16%$ in LDPE packaging, and to 2% in nylon/PE and PVC/PE packaging at $10^{\circ}C$. The $CO_2$ concentration increased to 5% at $10^{\circ}C$ in PP, A-OPP and LDPE packaging, but increased consistently in the nylon/PE and PVC/PE packaging. Weight loss was markedly reduced by all MAP films except M-HDPE, and which was enhanced with decreasing storage temperature. The soluble solids and pH were not affected by the packaging material at $4^{\circ}C$ and $10^{\circ}C$, but were affected at $20^{\circ}C$. The highest score for sensory qualities (appearance, color and overall acceptability) was obtained for vegetables stored at $4^{\circ}C$ in PP films. Our results show that MAP using PP films and $4^{\circ}C$ storage can effectively maintain the quality of Solidago virgaurea spp. gigantea.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.347-356
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• 1992

Various kaolin samples with different alumina content were prepared from calcined admixture of kaolin and ammonium sulfate by varying the treatment time in sulfuric acid. Samples were nitridated under N2 or N2-H2 atmosphere with changing the amount of added carbon, the reaction time and temperature. As the alumina content lowered, the size of kaolin particles decreased and the specific surface area increased. XRD analysis indicated that ${\alpha}$-quartz remained by decomposition of halloysite and meta-halloysite. Experimental results of nitridation behavior are summerized as follows; 1) Nitridation under N2 atmosphere. With the increase of C/SiO2 ratio and with the decrease of Al2O3 content, disappearance of XRD pattern peaks of mullite, ${\alpha}$-quartz and ${\alpha}$-Al2O3 were accelerated at 1300$^{\circ}C$. SiC was the main phase in the reaction product of acid-treated kaolin samples nitridated at 1300$^{\circ}C$ for 10 hours regardless of C/SiO2 ratio. But the XRD peak intensities of ${\beta}$-Si3N4, ${\beta}$-sialon and SiC did not show much difference when untreated raw kaolin was fired at the same condition. When the ratio of C/SiO2 was 3.5, ${\beta}$-sialon and ${\beta}$-Si3N4 existed in the reaction product of about 22% alumina containing kaolin sample fired at 1350$^{\circ}C$ for 7 hours. Only ${\beta}$-sialon existed in the same sample fired at 1400$^{\circ}C$ for 10 hours. ${\beta}$-sialon was obtained from all of the acid-treated kaolin samples fired at 1400$^{\circ}C$ for 40 hours, but AlN and SiC remained in the untreated kaolin sample. Z value of the ${\beta}$-sialon obtained from the 22% alumina containing kaolin sample fired at 1400$^{\circ}C$ for 40 hours was about 1.3(XRD) and 1.5(EDS). 2) Nitridation under 80N2+2OH2 mixed gas atmosphere with the C/SiO2 ratio of 1 Mullite was not found, but ${\alpha}$-Si3N4, and ${\beta}$-sialon were present in the reaction product of about 22% alumina containing kaolin sample fired at 1300$^{\circ}C$ for 10 hours. When untreated kaolin sample was nitridated at the same condition, mullite remained. AlN and SiC were not found in the reaction product of about 22% alumina containing kaolin sample fired at 1350$^{\circ}C$ for 5 hours. On the other hand, AlN and SiC remained in the product of untreated kaolin fired at the same condition.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.130-136
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• 1986

'Shingo' pears were seal-packaged in polyethylene (PE) film with different thickness of 0.04. 0.06, 0.07, and 0.08mm and stored for five months in an experimental storehouse with the temperature varyine 0 to $7^{\circ}C$ and relative humidity varying 86 to 89%. The atmosphere in PE film bags was modified to 5-l4% oxygen with 3-5% carbon dioxide depending on the film thickness and the storage period. Packaging of pears with PE film effectively reduced the weight loss, which resulted in good appearance after 5 months' storage, while non-packaged pears showed a slight wilt. Decay occurrence was not significantly different among the treatments. but role browning occurred a little more in packaged lots than in non-packaged lot. The sensory panel rated the pears front 0.07mm-thick bag highest in flavor, texture, and juiciness, which might be due to the high sugar content and low titratable acidity. The firmness of pear flesh decreased with the stogare time and its change was found to be highly correlated with that of cellulase activity (correlation coefficient= -0.946). Thisresult indicated that cellulase might be one of the enzymes responsible for the softening of pear fruit during storage.

• Food Science of Animal Resources
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• v.30 no.4
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• pp.685-694
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• 2010

The present study investigated the combined effects of modified atmosphere packaging (MAP) and organic acid salts on the quality and shelf-life of Hanwoo ground beef patties. The ground beef containing 500 ppm of ascorbic acid was prepared with air-packaging (Air-P), high oxygen-MAP (70% $O_2$+30% $CO_2$/OxyMAP), and nitrogen-MAP (100% $N_2$/NitroMAP), in combination with organic acid salts (1500 ppm of sodium acetate and 500 ppm of calcium lactate). The samples were stored for 11 d at $5^{\circ}C$. The pH value of ground beef patties decreased during storage in all the treatments. The ground beef patties with organic acid salts showed relatively higher level of pH during storage compared with non-added patties (p<0.05). Lipid oxidation was accelerated in OxyMAP while it was delayed in NitroMAP treated with organic acid salts. Nitro-MAP treated with organic acid salts was effective in stabilizing the color characteristics of lightness (CIE $L^*$) and redness (CIE $a^*$) during storage. Oxygen content in MAP was shown to be a more important factor affecting color stability and lipid oxidation of ground beef than organic acid salts. The aerobic and anaerobic bacterial counts were reduced both in OxyMAP and NitroMAP (p<0.05), and the lactic acid bacteria was inhibited by Oxy-MAP (p<0.05). Coliform bacteria decreased during storage as pH value was decreased in all treatments. According to the sensory evaluation, the ground beef patties in NitroMAP showed the best quality among all treatments during storage. Therefore, Hanwoo ground beef patties added with sodium acetate and calcium lactate and packed with NitroMAP showed better quality characteristics than other treatments. This packaging method is recommended and could be utilized for packaging hanwoo ground beef patties for improving quality and extending shelf-life.

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.668-673
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• 2000

The influence of storage atmosphere on ethylene production, quality attributes and storage injury of 'Tsugaru' apples was investigated. Apples were stored in 1% $O_2+1%\;CO_2,\;1%\;O_2+3%\;CO_2,\;3%\;O_2+1%\;CO_2,\;3%\;O_2+3%\;CO_2$ and air at $0^{\circ}C$ for 5 months. Ethylene production was more suppressed by 1% $O_2$ than 3% $O_2$ atmospheres regardless $CO_2$ levels. The loss of flesh firmness and the decrease of titratable acidity were not significantly different among the storage atmospheres until 3 months of storage but more retarded by 1% $O_2$ than 3% $O_2$ atmospheres thereafter. Soluble solid content was unaffected by the storage atmosphere, but the content tended to be increased until 2 months of storage and then not varied. Ethanol content increased up to a peak level followed by a gradual loss during storage in CA but increased continuously in air. In the sensory evaluation after storage for 5 months, hardness, tartness and overall acceptability of apples stored in 1% $O_2$ atmospheres were significantly higher than those stored in the others. There was no fruit injury or off-flavor production resulting from the 1% $O_2$ atmospheres. The incidence of bitter pit was reduced as storage $O_2$ level decreased. The results show that the optimum conditions of CA storage for 'Tsugaru' apples are $0^{\circ}C$ and 1% $O_2+1{\sim}3%\;CO_2$.

• Korean Journal of Food Science and Technology
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• v.37 no.1
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• pp.11-14
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• 2005

White radish was minimally processed, packed with air, $CO_{2}$ (100%), and $CO_{2}/N_{2}$ (25/75%), and irradiated at 0, 1, and 2 kGy, and its microbiological quality and pH were investigated during storage for 2 weeks at $4^{\circ}C$. Irradiation significantly reduced total aerobic, coli-form, and lactic acid bacteria counts. Modified atmosphere packaging (MAP) enhanced microorganism control during storage. Acidity decreased by MAP but was restored during storage, Irradiation did not affect sample pH. Results show irradiation at 2 kGy combined with MAP can enhance microbiological safety and quality of minimally processed radish.

• Korean Journal of Agricultural Science
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• v.6 no.1
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• pp.15-20
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• 1979

In order to determine the effects of different degrees of moisture stress on germination of various plant species, hundred seeds of six vegetables and six turfgrasses were germinated in petri dishes on filter papers moistened with water-mannitol solutions of 0, 2, 4, 8, 10, and 12 atmosphere osmotic concentration (degrees of moisture stress). The percentages and rates of germination of all species tested were generally decreased with: increase in moisture stress. Chinese cabbage and cucumber were quite resistant to physiological drought as the germination was not appreciably affected until moisture stress exceeded 10 atmosphere. However, increase in moisture stress decreased germination affecting most seriously tomato, carrot and squash. Weeping lovegrass, Italian ryegrass and perennial ryegrass germinated well at 10 atmosphere but the germination of Kentucky bluegrass, meadow fescue and orchardgrass was greatly reduced by increasing osmotic pressure. The result indicates that it may be possible to select drought resistant species and varieties by their ability to germinate in osmotic solutions.