• International Journal of Highway Engineering
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• v.13 no.3
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• pp.39-49
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• 2011

The porous pavement system is widely considered very effective in urban street because of its various benefits on safety and environment, but the pavement thickness design system has not been established yet. In porous pavement system. rainwater penetrates to the subgrade through porous pavements layers. Porous pavements are expected to reduce or alleviate the problems caused by impermeable pavement layer such as flood damage due to heavy rain in the city, drainage load, disorder in ecosystem, and heat island. However, its structural design methods in traffic roads has not been made mainly because of not being able to consider adequately the effect of rainwater on subgrade strength. In this study, structural design method of porous pavements is suggested after considering the subgrade weakness due to rainwater and numerical mechanical analysis. It is noted that elastic modulus of subgrade is reduced by 20% as subgrade moisture content is increased by 2% at optimum moisture content in the literature review. As a result of both finite element analysis and strength loss of subgrade by the existing design method, it is necessary to increase subbase thickness about 30cm in porous pavements compared with the existing traffic road pavement system. It is similar to premium thickness of structural design of porous pavements in Japan.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.1
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• pp.78-84
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• 1993

This study was conducted to investigate the effect of various polyethylene (PE) film packaging on the quality of strawberry during storage at low temperature. Gas composition in film was changed rapidly at early stage of storage and then kept at the level of 5~10% $CO_2$and 1~3% $O_2$. Weight loss and decay rate were low at 0.08mm PE film packed strawberries. Titratable acidity, pH and soluble solids were changed slightly during storage but its large difference according to film thickness was not observed. Decrease of flesh firm-ness and a value was restrained by PE film packaging. Free sugar of strawberry was composed of glucose and fructose in similar content and it was decreased a little during storage but the difference according to film thickness was not observed. The organic acids in strawberry were citric acid, malic acid, succinic acid, ascorbir acid, oxalic acid, tartaric acid and pyruvic acid and the major organic acid was citric acid. The contents of citric acid, malic acid, succinir acid and ascorbic acid were decreased and oxalic acid and tartaric arid were not changed during storage but pyruvic acid was increased in early stage and then decreased. These changes of organic acid were slight in packaged with 0.08mm PE film strawberry.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.11 no.2
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• pp.81-85
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• 2005

The mature-red tomato fruits (cv. Pinky world) were packaged with functional modified atmosphere (MA) film (0.03, 0.06 mm) and stored at 0, 5, $15^{\circ}C$. The results showed that the concentrations of $CO_2$ and $O_2$ inside MA package were about $4.21{\sim}8.17%$ and $9.78{\sim}14.45%$ under steady state during storage 29 days at 0, $5^{\circ}C$, respectively. The MA packaging(MAP) suppressed the fruits softening and the color change. The minimum lycopene content and maximum firmness were separately observed in fruits packaged with MA film (0.03 mm) at $5^{\circ}C$ storage and film(0.06 mm) at $0^{\circ}C$, which the lycopene content 6.08 mg/100 g, and firmness was 0.49 Kgf at 29 th day storage. The optimal conditions to keep high quality of tomato fruits were obtained by MAP during storage at $0^{\circ}C$ for 29 days, independently of the film thickness, in which the adequate gas composition was $CO_2$ at $4.2%{\sim}5.6%$, $O_2$ at $14.3%{\sim}14.5%$, respectively.

• Journal of Bio-Environment Control
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• v.17 no.3
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• pp.226-230
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• 2008

A comparison was made of the effect of different packaging materials on storability of mixed sprout vegetables (alfalfa, broccoli, cabbage, radish, and red radish) stored at $8^{\circ}C$. They were packaged by several kinds of films that were 50 fm thickness low-density polyethylene film (PE 50), 50 fm thickness polypropylene film (PP 50), $50{\mu}m$ thickness ceramic film (CE 50), $25{\mu}m$ thickness ceramic film (CE 25), $10\sim13{\mu}m$ thickness polyethylene film (wrap), and polyethylene terephthalate box with ventilation hole (box). The fresh weight of mixed sprouts packaged with different materials decreased below to 2% except box packages that decreased around 7% compared with initial weight. The atmospheres that were developed inside the different materials during storage differed significantly. The carbon dioxide and oxygen concentration of packages were kept properly with 5% in CE 25, but the PE 50 and CE 50 treatments showed higher carbon dioxide and lower oxygen concentration. So the off-flavor of mixed sprouts was more severe in the PE 50 and CE 50 treatment. The ethylene concentration of packages showed lowest in box treatment, followed by PP 50, wrap and CE 25 treatment. The overall quality of mixed sprouts was lower in PE 50 and CE 50 than CE 25 treatment after 10 days storage, supposed to be resulted from highest ethylene concentration and lowest oxygen concentration. Conclusionally, the CE 25 film that showed below 1% fresh weight loss, 5% carbon dioxide, 5% oxygen and below 4 ppm ethylene concentration in package may be a proper packaging material for mixed sprout vegetables.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.120-127
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• 2016

Several problems including respiratory and skin disorders due to the problems for sick house syndrome have occurred, there appears echo friendly materials to solve the problems. The research is lacking in quality management techniques ocher concrete using nondestructive tests. In this research, the experimental works were conducted to study the initial quality control for the compressive strength of Ocher concrete(21 MPa). The purpose of this study is the implementation platform for quality management of ocher concrete using nondestructive tests. It uses the relationship between the compressive strength and ultrasonic pulse velocity of the ocher concrete to estimate the compressive strength of the ocher concrete. And using the impact echo method to estimate the thickness of the ocher concrete. The platform is based on a Java script, so that the user can obtain the data through the platform.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.179-188
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• 2008

This study was performed as part of the development of the payment adjustment regulations for ensuring high performance of concrete pavements. The objectives of this study were to develop the reasonable quality measurement approaches for the implementation of the payment adjustment regulations and to propose the methods to determine the quality dependent pay factors. First, by using the statistics the slab thickness measurement data was analyzed and the methods to determine the allowable measurement errors, the proper measurement spacing, and the selection of the measurement location were proposed. In addition, to suggest the reasonable methods to determine the pay factors, by using the data of the slab thickness and concrete flexural strength, the pay factors based on the PWL(Percent Within Limits) method used in the USA were compared with those obtained considering the normal probability distribution and t distribution. Finally, the most appropriate method to determine the pay factors was proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.46-54
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• 2015

Base on Korean design code, previous design code had not considered the effect of pavement on the orthotropic steel deck, however recent design code (Limit State Design Method, 2012) allowed to consider the effect of pavement on the orthotropic steel deck, and efforts to apply the stiffness of pavement to the deck continue. Meanwhile, research on the effect of ultra thin bridge deck overlay on the orthotropic steel deck is inadequate, previous study was limited in about fatigue stress and performance between pavement layer and the orthotropic steel deck. In this study, according to changing of pavement layer stiffness application, pavement materials, pavement thickness and steel deck thickness, analysis of deflection. In addition to base on this result, consider effectiveness of ultra-thin pavement stiffness application on the orthotropic steel deck.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.951-960
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• 2006

Structural pavement analysis considering lateral loads of moving vehicle was carried out in order to simulate passing vehicle loads under various interface conditions. To verify of existing multi-layer elastic analysis of layer interface effect parameters, this study compared outputs by using ABAQUS, a three dimensional finite element program and KENLAYER, multi-layer elastic analysis as vertical load was applied to the surface of asphalt pavements. Pavement performance depending on interface conditions was quantitatively evaluated and fundamental study of layer interface effect parameters was performed in this study. As results of the study, if only vertical loads of moving vehicle is applied, subdivision of either fully bonded or fully unbonded is enough to indicate interface effect parameters. On the other hand, when lateral loads are applied with vertical loads, pavement behavior and performance are greatly changed with respect to layer interface conditions. The thinner thickness of the asphalt layer is and the smaller elastic moduli of the asphalt layer is, the more pavement behavior is influenced by interface conditions. In addition, regression analysis equation analytically computing tensile strain which was considered thicknesses and elastic moduli of the asphalt layer and layer interface effect parameters at the bottom of the asphalt layer was presented using database from numerical analyses on national pavement model sections.

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.138-140
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• 1994

Permeability and mechanical properties of degradable films prepared with zein and gluten were measured. Tensile strength of zein-based films was ranged from 30.1 MPa to 138.5 MPa and the strength of gluten-based films was $37.1{\sim}98.6\;MPa$. This strength was increased with increase of thickness in both films. Water solubility of zein-based films, 1.3%, was lower than those of the gluten-based films and the cellulose-based films. The range of water vapor permeability was $0.0711{\sim}0.1778\;g\;mm/m^{2}\;hr\;mmHg$ for zein-based films and $0.2134{\sim}0.2972\;g\;mm/m^{2}\;hr\;mmHg$ for gluten-based films. The permeabilty of the films was also increased with thickness.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3D
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• pp.223-229
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• 2012

Skid resistance is defined as the friction between pavement surfaces and vehicle tires. Lower skid resistances were observed as the vehicle speeds the water film thicknesses were increased according to the analysis results using computer modeling. The lift force is calculated from the analysis results and depends on vehicle speeds and the water film thickness. A modified IFI(international friction index) skid resistance prediction model was developed to reduce the differences between the IFI resistance prediction model and the actual skid resistance. The correlation analysis results between the IFI prediction model and the actual skid resistance revealed that the $R^2$ using the modified IFI prediction model was 0.64 whereas the $R^2$ using the conventional IFI prediction model was 0.49. This presents the modified prediction model is better than the conventional one. An improved precise prediction model is to be obtained if water film thicknesses are considered in the modified prediction model.