• The monthly packaging world
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• s.156
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• pp.115-128
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• 2006

• 한국도로학회지:도로
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• v.3 no.3 s.9
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• pp.50-55
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• 2001

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.107-115
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• 2009

This study was conducted to investigate the effect of the slab thickness on the tensioning design and to determine the optimal slab thickness of the post-tensioned concrete pavement (PTCP). The tensile stresses due to the vehicle and environmental loads were obtained using a finite element analysis model and the tensioning stress was calculated employing an allowable flexural strength. The environmental loads of both the constant temperature gradient and the constant temperature difference between top and bottom of the slab were considered. The tensioning designs for various slab thicknesses were performed considering prestressing losses. The comparison results showed that generally as the thickness increased, the number of tendons became larger. Consequently, the design was not economical for a thicker slab thickness. Even though the number of tendons became smaller with an increase in the thickness under the small environmental load, a thicker PTCP slab was not economical because of a higher cost of concrete than that of steel. Therefore, the slab thickness should be kept in minimum within the construction available thicknesses.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.04a
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• pp.142.1-142
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• 2003

저장 중 단감은 과피 및 과육의 변색 발생으로 인한 품질저하가 심각하게 발생하고 있는데, 아직까지 이를 방지하기 위한 원인 규명은 매우 미흡한 실정이다. 이에 본 연구에서는 단감의 재배지, 수확시기, 크기, 예조기간, 저장온도, 저장기간, 포장재의 두께 등을 달리하여 저장하면서 처리조건에 따른 단감 과육의 갈변 발생 관련성을 조사하였다. 단감의 변색발생 증상은 저장 1개월 이후부터 일부 나타나기 시작하여 저장기간이 경과할수록 심하였다. 단감의 갈변 발생률 및 갈변 정도를 실험 처리구별로 살펴보면 과수원, 수확시기, 예조기간, 저장온도, 포장재의 두께, 포장 내 가스조성에 따라 차이를 보였는데 단감의 수확시기가 늦을수록, 수확후 예조기간이 짧을수록, 저장을 위해 사용한 포장필름의 두께가 얇을수록 갈변발생정도가 심하였다. 또한 단감의 과수원에 따라서도 갈변의 발생률이 차이를 보여 동일지역이더라도 재배조건에 의하여서도 영향을 받는 것으로 나타났다. 이와 같은 결과를 종합하여 보면 단감 과육의 갈변발생은 수확 전 및 수확 후 인자들의 단독적인 영향이기보다는 복합적인 영향에 의한 것으로 추정되었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.487-493
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• 2017

The main purpose of this study is to evaluate the main parameters involved in the asphalt pavement distresses, including IRI (International Rough Index), fatigue, and permanent deformation. The main parameters are the region (Seoul and Busan), traffic level, asphalt binder, maximum aggregate of surface course, thickness of the surface course and base. A total of 64 case studies were carried out under the auspices of the KPRP (Korea Pavement Research Program). From the analysis of the KPRP test results, the key factors for the asphalt pavement distress were determined. Considering the effect of one variable in the basic condition, asphalt binder was the major factor having an effect on the distresses for an AADT (Annual Average Daily Traffic) of 5000 in the Seoul area. Among the remaining factors, the results were found to be in the order of the base layer thickness (A), surface layer thickness (B), and aggregate particle size thickness (D). The same results were obtained for an AADT of 10000. In the case of Busan with an AADT of 5000, the same result was obtained as for Seoul. Among the remaining factors, the results were in the order of the base layer thickness (A), aggregate particle thickness (D), and surface layer thickness (B). Even though there was a slight difference in the effect of the traffic level and region, asphalt binder was the parameter having the greatest effect on the asphalt pavement distress. In the case where the effect of multiple parameters was analyzed, the combination of the asphalt binder and base thickness showed a relatively strong effect.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.133-141
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• 2017

Traffic volume increases according to highway expansion and industrial development which causes repetitive defect and durability degradation on pavement. The research of quality assurance system used abroad has introduced Korea. Korea Expressway Corporation (KEC) has developed a Quality Performance Index (QPI) that quantitatively assesses the level of quality of the final product, and practical applications. Assessment factor on concrete pavement consisted of pavement thickness, compressive strength, IRI and spacing factor. Assessment factor on concrete pavement is determined by empirical evaluation factor from abroad. In this study, analysis of evaluation factors of concrete pavement by using pavement life prediction simulation and measured data were evaluated with consideration of feasibility of the assessment factor. Pavement life, performance and durability are affected by pavement thickness, compressive strength, IRI and spacing factor in assessment factor on concrete pavement, QPI.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.13 no.2
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• pp.67-73
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• 2007

A respiration rate analysed by enzyme kinetics-based respiration model and gas permeability data of LDPE film were applied to design the optical modified atmosphere (MA) packaging condition of persimmon (Diospyros kaki cv. Fuyu) fruits. The fruit quality rapidly decreases due to physiology disorder such as softening and peel blackening. $O_2$ permeance ($Q_{O2}$ in $ml{\cdot}hr^{-1}{\cdot}atm^{-1}{\cdot}m^{-2}$) and $CO_2$ performance ($Q_{CO2}$ in $ml{\cdot}hr^{-1}{\cdot}atm^{-1}{\cdot}m^{-2}$) of low density polyethylene (LDPE) film samples were measured at $0^{\circ}C$ and described as function of thickness (L in ${\mu}m$) as $Q_{O2}=(2540{\times}1/L)-16$, and $Q_{CO2}=(13742{\times}1/L)-70$, respectively. MA package containing single persimmon fruit of 225g was designed and tested experimentally at $0^{\circ}C$ by using LDPE films. Package atmospheres predicted from the relationship of $O_2$, $CO_2$ and $N_2$ balances on the packages was in good agreement with those obtained experimentally. Physiology disorder occurrence was the lowest at 52 ${\mu}m$ package that attained optimum gas condition ($O_2$ 2.8% and $CO_2$ 5.4%). The computer simulation was found to be effective to help to design the optimum MA packaging condition of individual persimmon fruit.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.13-24
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• 2006

The stresses in concrete pavement systems are larger when vehicle loads are applied at pavement edges, and these large stresses significantly affect the behavior and performance of pavements. Therefore, in this study, the stress distribution and the critical stresses in concrete pavements were investigated using a finite element model when dual-wheel single-, tandem-, and tridem-axle loads were applied at pavement edges. First, the stress distribution along the longitudinal and transverse directions was analyzed, and then the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were investigated. The effect of the tire contact pressure related to the tire print area was also studied. The location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to edge loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The effect of the tire contact pressure on the critical stress was clear as the slab thickness became smaller. The critical stress location in the transverse direction was independent of the concrete elastic modulus and the foundation stiffness; however, it moved into the interior as the slab thickness increased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.

• Korean Journal of Food Science and Technology
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• v.32 no.3
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• pp.481-490
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• 2000

Modified atmosphere packaging was applied to oriental melon(Cucumis melo L. var. makuwa Mak.) to extend its freshness during distribution. Gas composition and ethylene content in the film bags changed rapidly at the early stage of storage. Within 10 days, weight loss of the unpackaged increased upto 7.68% while those of the packaged remained less than 1.0% except LDPE film modified by addition of 5%(w/w) zeolite with $20\;{\mu}m$ thickness(20CK, 2.38%). Firmness was effectively maintained in the LDPE film modified by addition of 5%(w/w) zeolite with $40\;{\mu}m$ thickness(40CK) and the LDPE film with $40\;{\mu}m$ thickness containing ethylene absorber sachet(40LP). Peel color of the fruit changed rapidly in control and a little in 40CK. Oriental melon packages using 40CK provided better visual and sensory quality retention compared with others. Results suggested that packaging treatment such as 40CK could be used for extending freshness of oriental melon during transport period at ambient temperature.

• Korean Journal of Food Science and Technology
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• v.46 no.6
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• pp.739-742
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• 2014

This study investigated the effect of perforation by the Indian meal moth (Plodia interpunctella) larvae on various flexible food-packaging films, in relation to their thickness and type. Among the various flexible packaging films, polyethylene (PE), aluminum foil (AF), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were selected for this study due to their wide usage in food packaging. Based on their thickness, film penetration by P. interpunctella larvae was measured as in following order: PP, $20{\mu}m$; AF, $9{\mu}m$; PET, $12{\mu}m$; PP, $30{\mu}m$; PS, $30{\mu}m$; PE, $40{\mu}m$; PE, $35{\mu}m$; PS, $60{\mu}m$; and PET, $16{\mu}m$. P. interpunctella larvae rapidly penetrated through the packaging films regardless of their thickness and type. In particular, it was observed that PP of $20{\mu}m$ and PS of $30{\mu}m$ were completely penetrated by P. interpunctella larvae within 72 h, rendering thin PP and PS films less valuable as anti-insect packaging films. Our results show that the perforations by P. interpunctella larvae were observed in the thin films. These results imply that each packaging film has a marginal thickness against the perforations by P. interpunctella larvae.