• Elastomers and Composites
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• 제46권1호
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• pp.2-9
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• 2011

Permeability to gases and vapors is an important function in tires, rubber tubes and diaphragms. It mainly depends on the rubber material. Generally, permeability increases in the following order: silicone rubber > NR > EPDM > SBR > NBR > FPM > ECO > IIR. And, for an elastomer permeability is also very much dependent on compounding. Many research works are reported in the area of gas permeability for formed rubber,$^{1-7}$ however, few studies are found for unformed elastomer products. Incorporation of nano-particles, use of thermoplastic elastomers and applying high barrier multilayer coatings are the main approaches to obtain a high barrier elastomeric product. In this paper, barrier article for vehicle is introduced.

• Journal of the Korean Home Economics Association
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• 제40권5호
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• pp.15-24
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• 2002

The following research conclusions were made, relative to the experiments of the textiles of fire fighters Protective Clothing. 1. When the body protection efficiency such as the thickness, the strength and heat resistance are considered, Nomex(N) is tuned out the best outer shelf, Gore-tex(KG) the best moisture barrier, and Wool-felt(WC) the best thermal barrier. 2. In the hygienic and sanitary efficiency also, N is turned out the best outer shelf, KG the best moisture barrier, and WC the best thermal barrier in its degree of water resistance, water vapour permeability, and air permeability. 3. In the washing and maintenance efficiency, too. N is turned out the best outer shell, KG the best moisture barrier, and WC the best thermal barrier, being considered the material's rate of contraction, the changing rate of frame resistance, water resistance, and water vapour permeability. 4. When considered the frame resistance against the reflection tape and reflection efficiency, O is the best material for it marks the highest score in the frame resistance and reflective effect.

• Journal of the Korean Society of Radiology
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• 제81권3호
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• pp.488-500
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• 2020

Accumulating evidence suggests that Alzheimer's disease (AD) is not only caused by accumulation of abnormal proteins, including amyloid and tau, but is also closely associated with abnormalities in the microvascular environment including the blood-brain barrier (BBB), both of which lead to neuroinflammation and neurodegeneration. Application of in vivo magnetic resonance imaging (MRI) has recently increased to assess BBB permeability in AD and related diseases. Here, we provide a narrative review of BBB permeability-related pathology in Alzheimer dementia and recent MRI research on BBB permeability changes in AD and related diseases. Furthermore, we briefly introduce the measurement of BBB permeability using MRI and its methodological issues.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.189-196
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• 2003

Soil-cement column is often used as a contaminant barrier. This study presents the results of experimental study performed to investigate the changes of properties of soil-cement column under the attack of acids. Sulfuric nitric, and ascetic acid were used as contaminants. Specimen were made of clayey and sandy soils with addition of cement and water Permeability of soil-cement decreased with time during permeability test. When significant amount of acid percolated the specimen, permeability increased and compressive strength decreased due to the dissolution and leaching of cement and its chemical reaction compounds. Sulfuric and nitric acid were more effective than ascetic acid in deteriorating soil-cement column. Amount of acid required to lower the pH of soil cement below 12 was calculated from the results of permeability tests. This leads to a conclusion that, under the conditions employed in this study, the chemical stability of soil-cement column could be maintained against acid attack for longer than generally accepted lifetime of contaminant barriers.

• Journal of the Semiconductor & Display Technology
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• 제5권3호
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• pp.17-21
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• 2006

The oxygen barrier films were formed on poly(ethylene terephthalate) (PET) substrate by a sol-gel process using aminoalkoxysilanes. The coating layers were characterized by FT-IR and SEM. The oxygen permeability coefficients of coating films were measured by variable volume method, and then the influences of solvent ratio in sol and film drying temperature on the oxygen barrier properties were investigated. The aminoalkoxysilane coating films exhibited much higher oxygen barrier properties than PET film. The oxygen permeability coefficient of the film coated with each of APTEOS and APTMOS was measured to be $2.96{\times}10^{-6}$ and $3.05{\times}10^{-5}\;GPU$, respectively, while that of PET film was $1.16{\times}10^{-4}\;GPU$.

• Proceedings of the SCSK Conference
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
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• pp.765-779
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• 2003

Physiological lipid mixtures comprised of cholesterol, ceramide and free fatty acid better maintain epidermal homeostasis and have been recently used for dermatoses induced by skin barrier damage, for example for atopic dermatitis and xerotic skin. Itching and dry atopic dermatitis of the skin may be related to altered skin barrier function. In a previous study, the use of multi-lamellar emulsion (MLE), which is a lipid mixtures containing cholesterol, pseudoceramide and free fatty acid, has been shown to accelerate the recovery of the epidermal permeability barrier. In this study, we assessed the efficacy of MLE compared with a currently used anti-itch moisturizer (AIM), the active ingredients of which are menthol and camphor, on barrier recovery after barrier disruption. To clarify the effect of MLE and AIM after acute barrier perturbation, we measured the relation between transepidermal water loss (TEWL) and the barrier recovery rate at 3, 6, 24, and 48 hours after tape stripping hairless mice and then observed changes in the stratum corneum (SC), including the intercellular lipid structure and secretion of lamellar bodies, by electron microscopy. MLE treated skin recover skin barrier function more rapidly, and AIM treated skin delayed barrier repair. Morphological changes in the epidermis, of MLE treated skin revealed well-conserved lipid multi-lamellar structures at 24 h after tape stripping, whereas AIM treated skin showed altered lamellar bilayers within the SC interstices at 48 h. In addition, MLE treated skin showed an increase in the number of LBs and in their secretions and a decrease in the number of SC layers versus AIM treated skin. These results suggest that MLE may accelerate the production of an epidermal permeability barrier in hairless mice by increasing the number and secretion of LB and improve the dryness and itch associated with an altered epidermal permeability barrier.

• Journal of the Society of Cosmetic Scientists of Korea
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• 제34권1호
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• pp.1-8
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• 2008

Epidermis is one of the most dynamic organs in the human body. Multiple layers of keratinocytes in the epidermis continuously undergo proliferation, differentiation, and desquamation cycles, which is the bases of maintaining the epidermal homeostasis. Epidermal homeostasis eventually leads to establish and maintain permeability barrier homeostasis, the most important function of the epidermis. The permeability barrier is located in the stratum corneum. Tightly coordinated regulations are required for the sustained normal barrier function. Extensive studies have established that several nuclear hormone liposensors, including peroxisome proliferator-activated receptor a PPARa, PPARb/d, PPARg and LXRs are expressed in keratinocyte. Activation of PPARs and LXRs could provide a mechanism to coordinate the formation of the corneocytes and extracellular lipid membranes that constitute the stratum corneum. Topical application of PPAR/LXR ligands to murine skin results in the increased expression of keratinocyte differentiation-related proteins, such as involucrin, loricrin, profilaggrin, and trans-glutaminase 1, which would stimulate cornified envelope formation. In conclusion, topical application of ligands or activators of PPAR/LXR as an epidermotherapy would be a promising option to deal dry skin conditions such as atopy.

• Elastomers and Composites
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• 제54권3호
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• pp.175-181
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• 2019

The research and development of high-performance polymer materials with excellent gas barrier properties has gained considerable attention from the viewpoint of expanding their applications in various fields, including tire automobile parts and the polymer film industry. Natural rubber (NR) has been widely used as a rubber material in real-life, but its application is limited owing to its poor gas barrier properties. In this paper, we study the gas barrier properties of NR, epoxidized natural rubber (ENR), and their blend compositions by using molecular simulation. The results show that ENR-50 has superior oxygen barrier properties than those of NR. Moreover, the oxygen barrier properties of a blend of NR/ENR-50 improve with increasing volume fraction of ENR-50. The trend of improved oxygen barrier properties of NR, ENR-50, and their blend is in good agreement with experimental observations.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1283-1288
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• 2009

In general steel sheet piles are used in the containment system, which are vertical barrier systems for waste disposal and landfill purposes, and roads in excavation for temporary structure. This paper presents case study of the use of an interlocking sheet pile for water and containment. Cut-off Z-type sheet pile joints are investigated to determine their permeability from the field test. Four different joint sealing materials are used in field test. The results showed joint permeability is significant time-dependent and joint-dependent. These are explored and conclusions on permeability characteristics of different sealants are noted. A case study gives a design example as well as suggestion on permeability and water tightness can be implemented in using the sheet pile barrier in civil and environment works. From the test results, the effective sealing programs of sheet pile interlocks are suggested.

• Geomechanics and Engineering
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• 제31권3호
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• pp.305-318
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• 2022

Permeable reactive barriers used for groundwater treatment require proper estimation of the reactive material behavior regarding the emplacement method. This study evaluates the dry emplacement of zeolite (clinoptilolite) to be used as a reactive material in the barrier by carrying out several geotechnical laboratory tests. Dry zeolite samples, exhibited higher wetting-induced compression strains at the higher vertical stresses, up to 12% at 400 kN/m². The swelling potential was observed to be limited with a 3.5 swell index and less than 1% free swelling strain. Direct shear tests revealed that inundation reduces the shear strength of a dry zeolite column by a maximum of 10%. Falling head permeability tests indicate decreasing permeability values with increasing the vertical effective stress. Regarding self-loading and inundation, the porosity along the zeolite column was calculated using a proposed 1D numerical model to predict the permeability with depth considering the laboratory tests. The calculated discharge efficiency was significantly decreased with depth and less than 2% relative to the top for barrier depths deeper than 20 m. Finally, the importance of directional dependence in the permeability of the zeolite medium for calibrating 2D finite element flow analysis was highlighted by bench-scale tests performed under 2D flow conditions.