• Wind and Structures
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• 제31권3호
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• pp.185-196
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• 2020

A method to reduce the wind pressure at the leading edge of a noise barrier was investigated by gradually lowering the height of a member added to the end of the noise barrier. The shape of the lowered height of the added member was defined by its length and slope, and the optimal variable was determined in wind tunnel testing via the boundary-layer wind profile. The goal of the optimal shape was to reduce the wind pressure at the leading edge of the noise barrier to the level suggested in the Eurocode and to maintain the base-bending moment of the added member at the same level as the noise-barrier section. Using parametric wind tunnel investigation, an added member with a slope of 1:2 that protruded 1.2 times the height of the noise barrier was proposed. This added member is expected to simplify, or at least minimize, the types of column members required to equidistantly support both added members and noise barriers, which should thereby improve the safety and construction convenience of noise-barrier structures.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.524-524
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• 2012

Thermal Barrier Coating (TBC)은 미사일, 로켓발사체와 같이 고온에 노출되는 장비를 열로부터 보호하기 위한 코팅이다. 일반적인 Thermal Barrier Coating (TBC)은 모재와 코팅층간의 낮은 접합력과 높은 열충격으로 인한 박리가 많이 나타난다. 그래서 접합력을 높이고, 열충격을 줄이기 위해 모재와 코팅층 사이에 본드코팅층을 만든 Duplex - Thermal Barrier Coating (Duplex-TBC)이 개발되었다. 그러나 Duplex - Thermal Barrier Coating (Duplex-TBC)은 금속재료인 본드코팅층과 세라믹재료인 탑코팅층 사이에서 박리가 많이 발생한다. 이러한 문제점을 해결하기 위해 두 가지 분말을 동시에 코팅하여 본드코팅과 탑코팅의 경계가 없는 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)의 연구가 필요하다. 본 연구에서는 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)의 열충격 특성에 미치는 진공 플라즈마 용사 조건의 영향을 조사하였다. Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)는 진공 플라즈마 용사장치를 사용하여 Cu-Cr 합금위에 코팅하였다. 거리, Carrier gas flow, 그리고 챔버 내부의 압력을 달리하여 제조하였다. 사용한 분말은 본드코팅용으로 Amdry 962와 내열 세라믹코팅을 위해 204NS를 사용하였고, 각각 분말 공급조건을 조절하여 두 분말의 비율을 달리하였다. 제조한 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC) 코팅은 전기로에서 50분간 가열한 후, 수조에서 10분간 냉각하는 열충격 실험을 통해 열차폐 성능을 평가 하였다. 이러한 과정에서 진공 플라즈마 용사 조건 및 FGM 조성과 비율이 내열충격 특성에 미치는 영향을 미세조직학적 관점에서 고찰하였다.

• 한국건축시공학회지
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• 제11권6호
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• pp.634-644
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• 2011

Recently, As a part of urban forestation, the introductions of green roofs into public projects has been actively driven. Supported by this policy, the sizes of domestic green roof related markets have been rapidly expanding and many types of root barrier materials developed in Korea or abroad are being commercially distributed. In this study, root barrier tests were conducted over two years with nine types of sheet type waterproof materials that are the most commonly used as root barrier layers in green roof systems. The test conditions prepared considered the climates, natural features and vegetation in Korea and the results and related root barrier performance were verified. From the results of this study, the necessity to improve the joint part of root barrier sheets and forming methods has been identified and a measure to improve domestic root barrier testing methods was proposed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.183-189
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• 2009

In this study, the growth diagnosis of root is analyzed through plant's auxanology point of view, and the inductive root barrier ability of panel type waterproofing method which is designed to deal with it, is confirmed positively through long term(2 years) mock-up test. Moreover, basic ideas for inductive root barrier design in joint is presented through this study. The experiment result for the root barrier of sealed A-type during 24 months, there were no damages found on the waterproofing layer. -urethane sealing material was used to apply for waterproofing of joint- for roots. As the result, it was confirmed that it is possible to maintain the root barrier of method through applying inductive root barrier design such as the installation of decreasing space of bearing power which considers the growth diagnosis of root, even if the root barrier was not secured.

• Ocean Systems Engineering
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• 제11권1호
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• Composites Research
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• 제35권3호
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• pp.121-126
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• 2022

Owing to advantages of polymeric materials for hydrogen tank liner like light-weight property and high specific strength, polymer based composites have gained much attention. Despite of many benefits, polymeric materials for fuel cell tank cause problems which is critical to applications as low gas barrier property, and poor processability when adding fillers. For these reasons, improving gas barrier property of polymer composites is required to study for expanding application fields. This work presents impermeable polymer nanocomposites by introducing thin barrier coating using layer by layer (LBL) deposition method. Also, bi-layered and quad-layered nanocomposites were fabricated and compared for identifying relationship between deposition step and gas barrier property. Reduction in gas permeability was observed without interrupting mechanical property and processability. It is discussed that proper coating conditions were suggested when different coating materials and deposition steps were applied. We investigated morphology, gas barrier property and mechanical properties of fabricated nanocomposites by FE-SEM, Oxygen permeation analyzer, UTM, respectively. In addition, we revealed the mechanism of barrier performance of LBL coating using materials which have high aspect ratio.

• 한국초전도ㆍ저온공학회논문지
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• 제8권1호
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• pp.45-48
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• 2006

In the response to the demand for electrical energy , much effort was given to develop and commercialize high temperature superconducting (HTS) power equipments has been made around the world. Especially, HTS transformer is one of the most promising devices . but the cryogenic insulation technology should be established during development Hence many types of dielectric tests should be carried out to understand the dielectric phenomena at cryogenic temperature and to gather various dielectric data. Among the many types dielectric tests . the characteristic of barrier effect were conducted using simulated electrode after analysing the insulating configuration of HTS transformer main winding. The influence of a barrier on the dielectric strength was measured according to the position of the harriet the number of the barrier and thickness or the barrier. It was shown that the effectiveness . namely the ratio of the breakdown voltage in presence of barrier to the voltage without barrier, is highest when the barrier is placed at the needle electrode side. On the contrary, in the case of having the barrier between the electrodes, the harrier was placed between the electrodes the characteristic was even improved slightly.

• 한국의류산업학회지
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• 제14권5호
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• pp.803-810
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• 2012

This study investigates the effect of nonverbal communication on trust, switching barrier, and repurchase intention. Sample subjects used in this study were customers of a fashion shop in Sunchon. The questionnaires were conveniently sampled from July 2010 to August 2010. Questionnaire data from 335 customers of a national brand were analyzed through a reliability analysis, factor analysis, and multiple regression analysis. The results of this study are as follows. First, nonverbal communication by the service provider was divided into 3 types, physical appearance and paralanguage, postures and proxemics, and facial expressions. Second, it was found that physical appearance and paralanguage, postures and proxemics, facial expression of nonverbal communication had a significant impact on customer trust. Third, given the relationship between nonverbal communication and switching barrier, it was represented that the postures and proxemics and facial expressions (except physical appearance and paralanguage) had a significantly positive influence on the switching barrier. Forth, physical appearance/paralanguage, postures/proxemics, and facial expressions (nonverbal communication) had a positive influence on repurchase intention. Fifth, given the relationship between trust and repurchase intention as well as switching barrier and repurchase intention, it was represented that trust and switching barrier have a significantly positive influence upon repurchase intention. According to the results of this study, the more positive nonverbal communication by the service provider then the higher the customer repurchase intention as well as trust and switching barrier. Fifth, given the relationship between trust and repurchase intention as well as switching barrier and repurchase intention, it was represented that trust and switching barrier have a significantly positive influence upon repurchase intentions.

• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.193-207
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• 1999

The purpose of this study was to compare the clinical results of guided tissue regeneration(GTR) using a resorbable barrier manufactured from an copolymer of polylactic acid (PLA) and polylaetic-glycolic acid(PLGA) with those of nonresorbable ePTFE barrier. Thirty two patients(25 to 59 years old) with one radiographically evident intrabony lesion of probing depth ${\geq}$6mm participated in a 6-month controlled clinical trial. The subjects were randomly divided into three independent groups. The first group(n=8) received a ePTFE barrier. The second group (n=12) received a resorbable PLA/PLGA barrier. The third group (n=12) received a resorbable PLA/PLGA barrier combined with an alloplastic bone graft. Plaque index (PI), gingival index(GI), probing depth(PD), gingival recession, clinical attachment level(CAL), and tooth mobility were recorded prior to surgery and at 3, 6 months postsurgery, Statistical tests used to analyze these data included independent t-test, paired t-test, one-way ANOVA. The results were as follows : 1. Probing depth was significantly reduced in all groups at 3, 6 months postsurgery and there were not significant differences between groups. 2. Clinical attachment level was significantly increased in all groups at 3, 6 months postsurgery and there were not significant differences between groups. 3. There were not significant differences in probing depth, clinical attachment level, gingival recession, tooth mobility between second group (PLA/PLGA barrier) and third group (PLA/PLGA barrier combined with alloplastic bone graft) 4. Tooth mobility was not significantly increased in all groups at 3, 6 months postsurgery and there were not significant differences between groups. In conclusion, PLA/PLGA resorbable barrier has similar clinical potential to eP'IFE barrier in GTR procedure of intrabony pockets under the present protocol.

• 동의생리병리학회지
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• 제27권6호
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• pp.710-716
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• 2013

The purpose of this study is to observe the movements of Five Mimic-Animal Boxing(FAB) by the "three barrier in the back" of Donguibogam. The subject of this study is observation of the movements of FAB according to practice. The term of training FAB is two years and six months. By the theory of "three barrier in the back" in Donguibogam, we analyzed the movements of FAB. The standard of judgement was the union of the basic point in the arm and leg & the action point in three barrier in the back. The study results were as follows. The movements of FAB operated on the three barrier in the back. The preliminary exercise operated on one, two, trree barrier in the back. And moreover the remainder exercise operated on one, two, trree barrier in the back. The movements of FAB operated on the three barrier in the back for the circulation of vital essence and energy. FAB is the very important Gigong exercise on opening the three barrier in the back.