• Bulletin of the Korean Chemical Society
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• 제30권8호
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• pp.1805-1810
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• 2009

The adsorptions of trimethygallium (TMG) and arsine (As$H_3$) on H/Si(100)-2x1 surface were theoretically investigated. In the case of TMG adsorption, methane loss reaction, surface methylation, hydrogen loss reaction and ring closing reaction channels were found. The mechanism of As$H_3$ adsorption on the surface was also identified. Among these, the methane loss reaction depositing –Ga(C$H_3)_2$ was found to be the major channel due to its low barrier height and the large exothermicity. The surface methylation reaction is the second most favorable channel. In contrast, arsine turned out to be less reactive on the surface, implying that Arsine surface reaction would be the rate limiting step in the overall ALD process.

• Environmental Analysis Health and Toxicology
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• 제24권2호
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• pp.159-167
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• 2009

To investigate the alleviative effects of Peonia japonica water extract(PJWE) on inflammation and skin barrier damage, both the irradiation of UVB and the application of squalene monohydroperoxide (Sq-OOH) to the backs of hairless mice were performed for 4 weeks. And at the same time experimental materials were applied topically. The skin erythema indices for the positive control (PC, 0.01% retinoic acid) and experimental (E, PJWE) groups were lower than that of the control (C) group. Whereas both the lipid and water capacities for the PC and E groups were higher than those of the C group. Epidermis and dermis of the C group were remarkably thickened in comparison with the PC and E groups. Relatively much less number of inflammatory cells, including lymphocytes, neutrophils and macrophages were found in dermis of the PC and E groups compared with the C group. Lipid lamellae of the C group were broken severely showing an irregular arrangement and lipid content was much reduced. Whereas those of the PC and E groups were almost intact with a regular arrangement, which were similar to that of the N group. Taken the results all together, it was confirmed that PJWE could be effective natural herbal material for the alleviation of inflammation and skin barrier damage in hairless mice skin which were induced by UVB and Sq-OOH.

• Ocean and Polar Research
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• 제28권3호
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• pp.339-352
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• 2006

Seasonal and tidal variations of density stratification in the Saemangeum waters are investigated based on synoptic CTD observations between July 2003 and September 2005. CTD data used in this study are those obtained after closing the dike No. 4 and before closing the two final gaps, the Sinsi and the Garyeok, on the Saemangeum tidal harrier. A total of 19 field campaigns comprehend a wide temporal spectrum, that is, few seasons, spring and neap tides, and high and low waters. In addition, ADCPs were anchored and CTDs were cast at three stations for 25 h in July 2005. Water columns are vertically homogeneous in autumn and winter. The vertical homogeneity persists in spring but with an occasional weak stratification in i:he northern part of the Gogunsan Islands. Increased reshwater runoff tends to stabilize the water columns and strong density stratification is established in summer. The mean potential energy anomaly (PEA) in summer used as a stratification parameter is the largest $(27.7\;J\;m^{-3})$ in the northern part of the Gogunsan Islands where the Geum River discharge dominates, the smallest $(16.9\;J\;m^{-3})$ is in the inner area of the barrier, in between the two $(21.6\;J\;m^{-3})$ in the southern part of the Gogunsan Islands. Whereas the stratification is generally strengthened in summer, strong winds or large tidal currents over the shallow depths frequently destratify the water column near the mouth of river runoff inside the tidal barrier. Periodic stratification, the development of stratification on the ebb and its breakdown on the flood, occurs in the mid-area inside the barrier induced by the tidal straining, which can also be found in the results of 25 h observation.

• Wind and Structures
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• 제20권5호
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• pp.643-660
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• 2015

The wind tunnel test of large-scale sectional model and computational fluid dynamics (CFD) are employed for the purpose of studying the aerodynamic appendices and mechanism on suppression for the vortex-induced vibration (VIV). This paper takes the HongKong-Zhuhai-Macao Bridge as an example to conduct the wind tunnel test of large-scale sectional model. The results of wind tunnel test show that it is the crash barrier that induces the vertical VIV. CFD numerical simulation results show that the distance between the curb and crash barrier is not long enough to accelerate the flow velocity between them, resulting in an approximate stagnation region forming behind those two, where the continuous vortex-shedding occurs, giving rise to the vertical VIV in the end. According to the above, 3 types of wind fairing (trapezoidal, airfoil and smaller airfoil) are proposed to accelerate the flow velocity between the crash barrier and curb in order to avoid the continuous vortex-shedding. Both of the CFD numerical simulation and the velocity field measurement show that the flow velocity of all the measuring points in case of the section with airfoil wind fairing, can be increased greatly compared to the results of original section, and the energy is reduced considerably at the natural frequency, indicating that the wind fairing do accelerate the flow velocity behind the crash barrier. Wind tunnel tests in case of the sections with three different countermeasures mentioned above are conducted and the results compared with the original section show that all the three different countermeasures can be used to control VIV to varying degrees.

• 대한화장품학회지
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• 제24권3호
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• pp.6-16
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• 1998

Ceramides are currently emerging as the major skin care ingredients due to !heir barrier properties in the stratum corneum of the human skin. Thus, major cosmetic companies have developed synthetic ceramide analogs for their own use. In this study, several ceramide mimic compounds , new skin barrier lipids, were designed and synthesized, and their physical and biological properties were investigated to evaluate their skin care capability. Several structures were designed from the variation of hydrophobic alkyl chain and hydrophilic moiety by the use of molecular modeling software. The selected targets were synthesized, and their properties and activities were studied as the pure form, in the emulsion, or in the lamellar mixture containing cholesterol and fatty acid. Some compounds, such as 1,3-bis(N-(2-hydroxyethyl)-palmitoylamino)-2-hydroxypropane, enhanced the restoration of skin barrier damaged by SDS(sodium dodecyl sulfate), and by acetone treatment. The rate of restoration was comparable to that of natural ceramides. The synthesized compounds alleviated SDS induced skin irritation and facilitated lamellar phase liquid crystal formation. The treatment of 1,3-Dis(N-(2-hydroxyethyl)-palmitoylam ino)-2-hyd roxypropane on the acetone damaged skin revealed that the compound promoted the recovery of intercellular lipid lamellar structure of stratum corneum layer. The replacement of palmitoyl groups of the compound with shorter alkyl chain gave lower emulsion viscosity and liquid crystal density, suggesting easier formulation and poorer barrier activity. Most of the synthesized compounds were non-irritable in various toxicological tests proving that they can be safely introduced to the skin care formulations.

• 보건교육건강증진학회지
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• 제26권4호
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• pp.23-33
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• 2009

Objectives: This study was to examined the level of psychosocial factors, dietary habits and DMFT index and to examined the relationship among variables in 12-year-old adolescents. Methods: Participants were 1,831 total students from 14 middle school who lived Seosan with mean age of 12.46 years. Data was collected using a self administrated questionnaire from April 13 to May 24, 2009. Psychosocial factors and dietary habits were measured using the 5-items and 10-items. A trained investigator made an oral examination of them in natural light using a mirror and explorer to determine their DMFT index. Data were analyzed with t-test, one-way ANOVA, and Tukey test, pearson correlation coefficient using the SPSS WIN 15.0 program. Results: Regarding dietary self-efficacy, perceived benefit and perceived barrier degree, the subjects achieved a mean of $3.89{\pm}0.69$, $3.48{\pm}0.63$ and $3.82{\pm}0.63$ out of a maximum 5 points. And the dietary habit degree of subjects achieved a mean of $10.69{\pm}4.02$ out of a maximum 20 points and the DMFT index were $1.91{\pm}2.26$. Dietary habits was positively correlated with psychosocial factors and negatively correlated with DMFT index. And then perceived barrier score were negatively correlated with DMFT index. Conclusion: Based on the findings, dental caries experience is associated with perceived barrier and dietary habits. These results suggest that the implementation of health promotion should be considered for various psychosocial factors and dietary habits in adolescents.

• 폴리머
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• 제37권6호
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• pp.770-776
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• 2013

낮은 기체투과성을 보이는 epoxidized natural rubber 50(ENR 50)에 매우 낮은 기체투과성을 가지고 있고 마모 특성이 우수한 Nylon 6를 이축형 압출기를 사용해서 블렌드하였다. 혼합물의 기계적 물성과 기체차단성이 향상되는 효과를 얻었으나 ENR 50 매트릭스상에 Nylon 6의 분산성이 떨어져 큰 상승효과를 보이지는 않았다. 따라서 Nylon 6의 분산성을 개선하기 위해 ENR 50에 maleic anhydride(MAH)를 그래프트시켰다. MAH와 ENR 50간의 그래프트 반응은 FTIR 스펙트럼을 통해서 확인할 수 있었다. ENR 50-g-MAH/Nylon 6 배합물을 제조함으로 인해 기체차단성, 기계적 물성이 MAH를 사용하지 않았을 때보다 향상시킬 수 있었다. MAH의 그래프트 비율을 최대로 높인 5 phr을 첨가하였을 때 가교밀도가 높았으며 가장 좋은 물성을 보였다.

• 대한조선학회논문집
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• 제58권3호
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• pp.137-143
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• 2021

In this study, the fracture strength of Flexible Secondary Barrier (FSB) composites was standardized by conducting a distribution analysis of the fracture probability, considering that the fracture strength of FSB composites such as glass fiber reinforced composites is relatively large. As the mechanical performance of FSB composites varies with the fiber direction, 20 replicate uniaxial tensile tests were performed for different temperatures ranging from the ambient to cryogenic conditions, considering the actual operating environment of liquefied natural gas. For the probability statistical analysis, the Weibull distribution analysis derived from the weakest link theory was used, considering the large variance in the fracture strength and brittle fracture behavior. The results of the Weibull distribution analysis were used to calculate the standard fracture strength of the FSB composites for different fiber directions. The findings can help ensure the reliability of the FSB mechanical properties in different fiber directions in the design of the secondary barrier and structural analyses.

• 한국의류학회지
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• 제43권1호
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• pp.65-80
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• 2019

Mobile shopping has spread rapidly in the consumer's daily life, and numerous fashion companies have now launched a mobile shopping application. By focusing on mobile social commerce apps, this study was to: (a) segment consumers based on loyalty and switching intentions, (b) to test differences in perceived service quality and switching barrier factors among segments, and (c) examine the effects of perceived service quality and switching barriers on loyalty intention. A total of 550 responses were obtained from mobile users in their 20s to 40s who purchased fashion products through a social commerce app in the last six months. Consumers were classified into four clusters: split-loyals, latent loyals, habitual loyals, and switchers. The split-loyal group showed the highest level of mean scores on perceived service quality and switching barrier factors; however, the switcher group showed the lowest mean scores. Of service qualities, app design had a significant effect on loyalty intentions in both split-loyal and latent loyal groups; the factors of ease of use and privacy had significant effects on loyalty intentions in switchers. Of switching barrier factors, virtual relationship had the most strongly effect on loyalty intention for the four segments.

• 한국산업융합학회 논문집
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• 제26권3호
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• pp.499-507
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• 2023

The core of the liquefied natural gas (LNG) carrier cargo containment system (CCS) is to store and transport LNG safely under temperatures below -163 degrees Celsius. The secondary barrier of the LNG CCS is adopted to prevent LNG leakage from CCS to the ship's hull structure. Recently, as the size of the LNG CCS increases, various studies have been conducted on the applied temperature and load ranges. The present study investigates the working condition-dependent bonding strength of the PU15 adhesives of the secondary barrier. In addition, the mechanical performance is analyzed at a cryogenic temperature of -170 degrees Celsius, and the failure surface and failure mode are investigated depending on the working condition of the bonded process. Even though the RSB and FSB-based fracture mode was confirmed, the results showed that all the tested scenarios satisfied the minimum requirement of the regulation.