• Tribology and Lubricants
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• 제26권4호
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• pp.246-253
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• 2010

Friction characteristics of the brake friction materials without environmentally regulated ingredients were examined to find their role in the brake performance. Five friction materials were produced based on a nearcommercial formulation by changing the relative amount of potentially hazardous ingredients to health and environment, such as $Sb_2S_3$, potassium titanate, and brass fiber. Tribological properties of the friction materials were obtained using a scale dynamometer and Krauss type tribometer. Results showed that the excluded three ingredients played important synergetic effects on tribological properties in terms of fade resistance, wear resistance and friction effectiveness. In particular, brass fibers played important roles in the friction stability by providing excellent thermal diffusivity at the friction interface. Potassium titanate whiskers showed excellent fade resistance and wear resistance compared to the substituted barite. Antimony trisulfide, on the other hand, showed little effect on the high temperature fade resistance and wear resistance, while it increased friction effectiveness at moderate temperatures. The friction materials without the three ingredients showed severe fade, indicating antisynergy effects.

• Tribology and Lubricants
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• 제36권4호
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• pp.207-214
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• 2020

In this study, we investigated the effects of copper and copper-alloy on the frictional and wear properties of low-steel friction material. The proportions of copper and copper-alloy in the brake friction materials used in passenger cars are very high (approximately 5-20% weight), and these materials have significant effects on friction and wear characteristics. In this study, the effects of cupric ingredients, such as the copper fiber and brass fiber, are investigated using the friction materials based on commercial formulations. After the copper and brass fibers from the same formulation were removed, the frictional and wear characteristics were evaluated to determine the influence of the copper and copper-alloy. We evaluated the frictional and wear characteristics by simulating various braking conditions using a 1/5 scale dynamometer. The results show that the friction material containing copper and brass fibers have excellent frictional stability and a low wear rate compared to the friction material that does not contain copper and brass fibers. These results are attributed to the excellent ductility, moderate melting point, high strength, and excellent thermal conductivity of copper and copper-alloy. We analyzed the surfaces of the friction materials before and after the performing the friction tests using a scanning electron microscope-energy dispersive X-ray spectroscope, confocal microscope, and roughness tester to verify the frictional behavior of copper and copper-alloy. In future studies, it will be applied to the development of copper-free friction materials based on the results of this study.

• Computers and Concrete
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• 제23권6호
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• pp.399-408
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• 2019

Structural health monitoring is important for the safety of lives and asset management. In this study, numerical models were developed for the piezoresistive behavior of smart concrete based on finite element (FE) method. Finite element models were calibrated with experimental data collected from compression test. The compression test was performed on smart concrete cube specimens with 75 mm dimensions. Smart concrete was made of cement CEM II 42.5 R, silica fume, fine and coarse crushed limestone aggregates, brass fibers and plasticizer. During the compression test, electrical resistance change and compressive strain measurements were conducted simultaneously. Smart concrete had a strong linear relationship between strain and electrical resistance change due to its piezoresistive function. The piezoresistivity of the smart concrete was modeled by FE method. Twenty-noded solid brick elements were used to model the smart concrete specimens in the finite element platform of Ansys. The numerical results were determined for strain induced resistivity change. The electrical resistivity of simulated smart concrete decreased with applied strain, as found in experimental investigation. The numerical findings are in good agreement with the experimental results.

• Journal of the Optical Society of Korea
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• 제3권2호
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• pp.74-79
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• 1999

We present a simple design rule for a passive temperature-compensating optical package. We also present experimentally that a package fabricated by using the design rule compensates the temperature dependence of the resonant wavelength of an optical long period fiber grating by varying the strain inside the fiber, The package fabricated in this work consists of two pieced of brass tube, 10 mm long, and a piece of nylon rod, 45.4 mm long. It is shown that the package can compensate the temperature-induce wavelength shifts of the long period grating to a range of 6.8 pm/$^{\circ}C$, compared with 0..48 nm/$^{\circ}C$ for an uncompensated grating. The reduced strength of the fiber caused by exposure to ultraviolet limits the performance of the package to the range operating temperature form -3 $^{\circ}C$ to 7$0^{\circ}C$.

• 대한토목학회논문집
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• 제39권6호
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• pp.675-689
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• 2019

자가응력 및 자가손상 감지능력을 모두 가지는 스마트 콘크리트의 개발은 아직까지 손상 감지 능력에 대한 원인 규명이 명확하지 않아 어려운 현실이다. 따라서, 본 연구에서는 매트릭스 강도, 섬유 형식 및 보강량이 강섬유 보강 시멘트 복합재료의 인발시 전기저항에 미치는 영향을 평가하였다. 실험으로부터 섬유와 매트릭스 사이 계면에서의 탈착으로 전기저항률이 감소한다는 사실을 알 수 있었다. 섬유와 매트릭스 사이 계면 부착강도가 높을수록 더 큰 전기저항률의 감소를 유발하였다. 따라서, 고강도 매트릭스, 황동 도금된 강섬유 그리고 변형된 강섬유를 사용시 높은 계면부착강도를 유발하고 그 결과 더 큰 전기저항률 감소를 유발하였다.

• 보존과학연구
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• 통권32호
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• pp.75-87
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• 2011

유물을 처리하기 전에 제작 시기, 기법, 재질 등의 정보를 수집하는 것은 보존처리 방법 결정에 중요하다. 대상유물인 팔사품도는 이순신 장군이 명나라 신종황제로부터 하사받은 팔사품을 그림으로 그린 것으로 바탕재료인 직물에 안료를 이용하여 채색되어 있었으며, 뒷면에는 1장의 종이로 배접이 되어있는 상태였다. 제작연대나 작가 등 유물에 대한 정보가 남아있지 않았기 때문에 유물의 재질 분석을 통해서 제작 연대를 추정해보고, 처리 및 보관 방향을 결정하고자 하였다. 팔사품도의 바탕재료로 사용된 직물의 분석 결과 리본 꼬임과 강낭콩 모양의 단면이 관찰되어 면으로 확인되었다. 배접지에 사용된 종이를 분석한 결과 C 염색액에 의해 오렌지색으로 염색되었으며, 섬유장이 짧고 섬유 측면에 가도관이 관찰되어 침엽수 펄프로 제조된 종이로 추정된다. 또한 채색안료를 분석한 결과 자황(Orpiment, $As_2S_3$), 연단(Minium, $Pb_3O_4$), 석간주(Hematite, $Fe_2O_3$), 화록청[Emerald green, $C_2H_3As_3Cu_2O_8$], 군청(Ultramarine, [$2(Na_2O{\cdot}Al_2O_3{\cdot}2SiO_2){\cdot}Na_2S_2$]), 활석[Talc, $Mg_3Si_4O_{10}\;(OH)_2$] 및 황산바륨($BaSO_4$), 황동(Brass)을 사용한 것으로 추정된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.194-197
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• 1997

The texture of a 0.25mm dia high-carbon(0.73%) steel wire made by drawing the patented and brass coated 1.4mm wire through 22 dies with a die-angle of 12$^{\circ}$has been measured. The ideal fiber texture was obtained in the center layer, while the circular texture and the near fiber texture having {111}<110> and weak {112}<110> components were obtained in the intermediate and surface layers, respectively. The circular texture was approximated by {110}<110> plus {110}<114>. The texture could be predicted by the Taylor-Bishop-Hill theory coupled with FEM for deformation.

• 보존과학회지
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• 제38권2호
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• pp.133-143
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• 2022

본 연구에서는 대구근대역사관 소장 인력거의 재질별 분석을 통해 다양한 재질이 복합적으로 사용되는 근·현대문화재의 재료를 확인하고, 보존 및 관리의 기초 자료를 구축하고자 하였다. 금속, 목재, 섬유, 도료를 대상으로 P-XRF, 수종분석, 섬유동정, 도막층 분석(층상 구조, SEM-EDS, FTIR)을 실시한 결과, 금속은 구리(Cu), 아연(Zn), 황동(Brass)과 철(Fe)로 확인되었다. 목재는 상수리나무류, 삼나무, 대나무아과, 비자나무속이 식별되었으며, 이 중 삼나무는 일본 자생종으로 인력거 제작 당시 일본에서 목재를 수입하여 제작하고, 근대 일본 인력거의 제작 양식에 영향을 받은 것으로 추정되었다. 섬유는 면(Cotton)을 주로 사용하였으며, 일부는 가죽(Leather)도 확인되었다, 도막층은 캐슈(Cashew)를 사용하여 1회 이상 도포한 것으로 관찰되었으며, 특히 인력거 몸체부는 섬유층, 토회층, 도료층, 채색층이 중복되어 관찰되고, 성분이 다른 적색 안료(산화철 및 진사)층이 관찰된 점을 보아, 과거 일부 보수 및 보존처리가 진행된 것으로 판단된다.

• Advances in concrete construction
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• 제9권4호
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• pp.387-395
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• 2020

This study has been carried out in two-phases to develop Fiber Reinforced Self-Compacting Concrete (FRSCC) performance. In the first phase, the composition of the quaternary composite binder compromised CEM I 42.5N (58-70%), Rice Husk Ash (25-37%), quartz sand (2.5-7.5%) and limestone crushing waste (2.5-7.5%) were optimized. And in the second phase, the effect of two fiber types (steel brass-plated and basalt) was investigated on the SCC optimized with the optimum CB as disperse reinforcement at 6 different ratios of 1, 1.2, 1.4, 1.6, 1.8, and 2.0% by weight of mix for each type. In this study, the theoretical principles of the synthesis of self-compacting dispersion-reinforced concrete have been developed which consists of optimizing structure-formation processes through the use of a mineral modifier, together with ground crushed cement in a vario-planetary mill to a specific surface area of 550 m2 / kg. The amorphous silica in the modifier composition intensifies the binding of calcium hydroxide formed during the hydration of C3S, helps reduce the basicity of the cement-composite, while reducing the growth of portlandite crystals. Limestone particles contribute to the formation of calcium hydrocarbonate and, together with fine ground quartz sand; act as microfiller, clogging the pores of the cement. Furthermore, the results revealed that the effect of fiber addition improves the mechanical properties of FRSCC. It was found that the steel fiber performed better than basalt fiber on tensile strength and modulus of elasticity; however, both fibers have the same performance on the first crack strength and sample destruction of FRSCC. It also illustrates that there will be an optimum percentage of fiber addition.

• 센서학회지
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• 제25권5호
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• pp.344-348
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• 2016

We developed a 2-channel fiber-optic temperature sensor (FOTS) using a temperature sensing probe, a fiber-optic coupler, transmitting optical fiber, and an optical time domain reflectometer (OTDR). The temperature sensing probe is divided into a sensing probe and a reference probe for accurate thermometry. A sensing probe is composed of a silicon oil, a FC terminator, a brass pipe, and a singlemode optical fiber and the structure of a reference probe is identical with that of the sensing probe excluding a silicon oil. In this study, we measured the modified optical powers of the light signals reflected from the temperature sensing probe placed inside of the water with a thermal variation from 5 to $70^{\circ}C$. Although the optical power of the reference probe was constant regardless of the temperature change, the optical power of the sensing probe decreased linearly as the temperature increased. As experimental results, the FOTS using a subtraction method showed a small difference (i.e., hysteresis) in its response due to heating and cooling. The reversibility and reproducibility of the FOTS were also evaluated.