• Nuclear Engineering and Technology
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• 제51권4호
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• pp.977-986
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• 2019

In the thermal-hydraulic system codes, such as MARS and RELAP5/MOD3, the Savannah River Laboratory (SRL) model has been adopted as a subcooled boiling model. It, however, has been shown that the SRL model cannot take into account appropriately the effects of inlet liquid velocity and hydraulic diameter on axial void fraction development. To overcome the problems, Ha et al. (2018) proposed a modified SRL model, which is applicable to low-pressure and low-Pe conditions (P < 9.83 bar and $Pe{\leq}70,000$) only. In this work, the authors extended the modified SRL model by proposing a new net vapor generation (NVG) model and a wall evaporation model so that the new subcooled boiling model can cover a wide range of thermal-hydraulic conditions with pressures ranging from 1.1 to 69 bar, heat fluxes of $97-1186kW/m^2$, Pe of 3600 to 329,000, and hydraulic diameters of 5-25.5 mm. The new model was implemented in the MARS code and has been assessed using various subcooled boiling experimental data. The results of the new model showed better agreements with measured void fraction data, especially at low-pressure conditions.

• Korean Journal of Food Science and Technology
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• 제36권5호
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• pp.733-739
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• 2004

Model for optimally dimensioned PE film bag was developed according to fruit size to maintain best quality of 'Fuyu' persimmon in modified atmosphere packaging (MAP) storage based on relationship between quality and oxygen and carbon dioxide in PE film bag. Harvested persimmons were graded into five sizes, and average weights were LL:261, L:217, M:188, S:168, and SS:154 g. Five fruit units of each grade were optimized in five PE film bag sizes of $150{\times}376,\;140{\times}357,\;130{\times}344,\;130{\times}333,\;and\;120{\times}3l8\;mm$. To minimize quality deterioration such as softening and discoloration, optimal oxygen and carbon dioxide concentrations in PE film bag were 0.5-1.0 and 6.0-8.0%, respectively, and optimal thickness of PE film bag according to fruit size were LL:45, L:50, M:55, S:60, and $SS:65\;{\mu}m$. For all fruit sizes, model for PE film bag area $(mm^2)$ was good quadratic simple equation by fruit weight (g): $Y=-4055.707+627.993X_1-0.701{X_1}^2$. Model far optimal oxygen and carbon dioxide (Y) concentration in PE film bag was suited to linear multiple equation by fruit weight $(X_1,\;g)$ and PE film thickness $(X_2,\;{\mu}m)$. Equations for oxygen and carbon dioxide concentrations (%) were $Y=5.798-0.0109X_l-0.0491X_2\;and\;Y=-2.427+0.01927X_l +0.09646X_2$, respectively.

• Journal of Adhesion and Interface
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• 제1권1호
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• pp.23-29
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• 2000

Surface modification of hydrophobic polymeric materials to be hydrophilic or to have specific functional groups is of great importance for a diversity of applications of the materials. In this study, polyethylene (PE) film surfaces were modified by vapor phase photografting of hydrophilic vinyl monomers with different functional groups. The functional monomers were introduced on PE films by introducing the monomers in vapor phase using a vapor phase photografting apparatus designed by our laboratory. Functional monomers used were acrylic acid (negatively chargeable), acrylamide and allylalcohol (neutral), and allylamine and N,N-dimethyl aminopropyl acryamide (positively charged). The functional monomer-grafted PE film surfaces were characterized by the measurement of water contact angles and the attenuated total reflectance Fourier-transform infrared spectroscopy. The vapor phase photografting seems to be effective means for introduction of various functional groups onto polymeric substrates.

• Applied Chemistry for Engineering
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• 제28권6호
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• pp.670-678
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• 2017

Self-emulsifiable polyethylene (PE) wax was prepared using acrylic acid grafted PE wax with potassium hydroxide and various emulsifiers for the economic production of PE wax emulsion. Modification reaction completion was confirmed that the peak from carbonyl group of acrylic acid disappeared and the new peak from carboxylic acid salts appeared in the FT-IR (Fourier transform infrared) spectrum data. Self-emulsifiable properties of the modified PE wax were investigated by the emulsion size and the stability of wax emulsion without any additional emulsifiers. According to self-emulsifiable properties, the emulsion size and stability were varied on the concentration and structure of the emulsifier. The greater emulsion concentration and hydrophilic poly(ethylene oxide) (PEO) characteristics of the emulsifier resulted in the smaller emulsion size and better emulsion stability. In addition, the use of emulsifiers mixture was more effective to obtain smaller size and uniform distribution of emulsion than that of single emulsifier in PE wax modification reaction. Especially, modified PE wax with OAE-5 and LAE-15 emulsifiers mixture shows excellent performance in terms of the smallest emulsion size ($4.34{\mu}m$) and emulsion stability.

• Journal of the Korean Society of Food Science and Nutrition
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• 제20권2호
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• pp.133-138
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• 1991

Several quality indices of Shiitake mushroom (Lentinus edodes) were measured during storage at modified atmosphere (MA) conditions made by plyethylene film bag with different thicknes. IN the mushrooms kept in the thicker film bag, larger amounts of ethyl alcohol and acetaldehyde were produced during storage. The lowest weight loss was marked by the mushrooms kept in 0.06mm thick film bag. Protein content of the mushrooms was increased with the storage period without any storage period without any significant trend depended on the storage treatments and electrophoresis pattern of protein was changed little in the mushrooms kept in 0.04mm thick P.E. film bag during storage.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.202-206
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• 2003

In this study, a modified bituminization technology has been developed, which needs no grinding of the granular resin waste, and enables the solid form to keep its shape stability as good as that of a cemented solid from Also, the study intended to apply the developed technology to the practical treatment of radioactive resin waste. In the experiment, the granular type resin was used and the straight-run distillation bitumen with penetration rate 60/70 was used as the solidifying agent. The PE was used as the additive. The shape stability increased remarkably with the additive of PE, which act as a binder in the solid form. The shape of the solid form was maintained without failure during the long-term exposure test when the additive content of spent PE is more than 10wt%. The proper ranges of bitumen content, PE content and operating temperature are 30-50wt%, 10-20wt% and $180^{\circ}C$ respectively. The bituminized solid form of radioactive resin waste by the technology of this study has the remarkably superior quality than the conventional solid forms, partially for the shape stability.

• Polymer(Korea)
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• 제36권2호
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• pp.137-144
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• 2012

The surface of polyethylene (PE) was modified through Ar atmospheric pressure plasma treatment and subsequent grafting of glycidyl methacrylate (GMA). Optimum plasma treatment conditions were determined through analyzing the surface free energies calculated from the contact angles between PE samples and three probe liquids, which were RF-power of 200 W, plasma treatment time of 600 sec, Ar flow rate of 5 LPM, and sample-holder moving speed of 20 mm/sec. To introduce the maximum amount of GMA on PE surface treated under the conditions, graft copolymerization conditions such as GMA concentration, temperature, and time were carefully controlled. Grafting degree (GD) was obtained through weight difference analysis of PE film before and after graft copolymerization. A maximum GD was achieved at the GMA concentration of 20 vol%, the temperature of $80^{\circ}C$, and the treatment time of 4 hr.

• Food Science and Preservation
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• 제6권4호
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• pp.351-356
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• 1999

To develop and extend the shelf-life of vitamin C enriched fresh-cut apples using CA stored Fuji apples, dipping in 10% L-ascorbic acid and packaging with 0.03 mm LDPE, 0.04 mm PP and 0.08 mm Nylon/PE film(N$_2$displacement) were carried out. The changes of gas concentrations in the packaging and quality attributes of fresh-cut apples were examined during storage at 10$^{\circ}C$. The concentrations of O$_2$was maintained lower in Nylon/PE film than the other film, the level of O$_2$was in the range of 1∼3%. The increase of C$_2$H$_4$ concentrations in Nylon/PE film bag was more suppressed than the others. The vitamin C content of fresh-cut apples was enriched by dipping in L-ascorbic acid solution up to 241 mg$.$100 g-1 f.w., and the loss or that content was retarded differently by the package conditions of lower O$_2$level during storage. Browning in fresh-cut apples was shown after 6 days of storage in LDPE and PP film. but it was not shown by 14 days of storage in Nylon/PE film. Spoilage and off odor in fresh-cut apples were not detected up to 14 days of storage in Nylon/PE film. The results indicated that the vitamin C enriched fresh-cut apples can be processed from the long-term CA stored apples, and maintaining high quality of the products ill be possible in cases of the application of sealing packaging after O$_2$removal with film having low O$_2$permeability.

• Korean Journal of Food Science and Technology
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• 제45권2호
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• pp.191-198
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• 2013

The storage quality of fresh Sulhyang strawberries packaged under modified atmospheres was investigated to examine the effect of high $O_2$ on the fruit. Fresh strawberries were packed into PP trays and top-sealed with PET/PP film. Initial gas compositions inside the packages were varied with air, 40% $O_2$/60% $N_2$, 60% $O_2$/40% $N_2$, and 80% $O_2$/20% $N_2$. Sealed packages in PE film bags with air and perforated PP trays were also used as another treatment and control, respectively. Quality attributes and viable cell counts of pathogenic bacteria were assessed during storage at $5^{\circ}C$ for 12 days. High $O_2$ concentration showed no significant effects on the physicochemical and microbial qualities of strawberries. Fruit packaged in PE film bags with 6-15% $O_2$ and 7-9% $CO_2$ during storage had the lowest viable cell counts of inherent microorganisms among the treatment samples. Growth of pathogenic bacteria was suppressed in perforated packages where molds occurred frequently. In an overall sensory aspect, the PE film packages exhibited higher scores than the others at the end of storage period. The experimental results suggested that gas-permeable film packaging with an appropriate combination of $O_2$ and $CO_2$ rather than gas-barrier tray packaging with an initially high $O_2$ concentration would be suitable for improving the storability of strawberries.

• Applied Biological Chemistry
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• 제35권2호
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• pp.126-131
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• 1992

For the development of kiwifruit storage method applicable to farm level, several quality indicator of kiwifruit(Actinidia chinensis Planch.) were measured during storage at modified atmosphere(MA) conditions(0.04, 0.06, 0.08 and 0.10 mm PE Film). The results obtained from the experiment were as follows. The highest firmness was marked by the kiwifruit kept in 0.06 mm thick film bag and the lowest weight loss was shown in 0.10 mm thick film bag. The largest production of respiratory rate was occured after storage for 30 days. The concentration of $O_2\;and\;CO_2$ in 0.06 mm thick film bag was 2.6% and 3.2% after storage for 60 days, respectively. It could be concluded that the optimum PE film thickness for MA storage of kiwifruit was 0.06 mm.