• 대한금속재료학회지
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• 제50권9호
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• pp.697-702
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• 2012

In this study, unidirectional and plain woven carbon fiber reinforced magnesium matrix composite laminates were fabricated by the liquid pressing infiltration process, and evolutions of the microstructure and compressive strength of the composite laminates under corrosion were investigated by static immersion tests. In the case of the unidirectional composite laminate, the main microstructural damage during immersion appeared as a form of corrosion induced cracks, which were formed at both CF/Mg interfaces and the interfaces between layers. On the otherhand, wrap/fill interface cracks were mainly formed in the plain woven composite laminate, without any cracks at the CF/Mg interface. The formation of these cracks was considered to be associated with internal thermal residual stress, which was generated during cooling after the fabrication process of these materials. As a consequence of the corrosion induced cracks, the thickness of both laminates increased in directions vertical to the fibers with increasing immersion time. With increasing immersion time, the compressive strengths of both composite laminates also decreased continuously. It was found that the plain woven composite laminates have superior corrosion resistance and stability under a corrosive condition than unidirectional laminates.

• Advances in concrete construction
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• 제13권1호
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• pp.35-43
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• 2022

The experimental investigations into hooked-end round steel fibers (HSF) effect on the age-dependent strengths of high volume fly ash (HVFA) concrete is studied. The concrete was prepared with class F fly ash used as partial cement replacement varied from 0% to 70% on an equal weight basis. Two percentages of HSF (i.e., 0.5% and 1.5% by volume fraction) of 50 mm length were added in plain, and 50% fly ash concrete mixes. The compressive and flexural tensile strength was determined at 7, 28, 56, and 90 days. The strength results of fly ash concrete mixes with and without steel fibers were compared with the plain concrete strength. The test results indicated that the strength of fly ash concrete is comparable with the plain concrete strength and further increases with an increase in the percentage of steel fibers. The maximum flexure strength of HVFA concrete is found with 0.5% steel fibers. It is concluded that the HVFA concrete with steel fibers of 50 mm length can effectively be used in concrete construction. The analytical models are proposed to predict the age-dependent compressive and flexural tensile strength of HVFA concrete with and without HSF. The compressive and tensile strength of HVFA concrete with HSF can be predicted using these models when the 28-day compressive strength of plain concrete is known. The present study will be helpful in the design and construction of reinforced and pre-stressed concrete structures made with HVFA and HSF.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.21-30
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• 2023

This work presents a correlation between the behavior of formic acid oxidation (FAO) on various Bi-modified Pt(poly) disk electrodes and their morphologies observed on Bi-modified Pt(111) disk electrodes using electrochemical scanning tunneling microscopy (EC-STM) to understand the effects of Bi on Pt. To distinguish the FAO activities of Bi on Pt and plain Pt around Bi, additional Pt was intentionally deposited using two different routes: direct route and iodine route. In direct route, Pt was directly deposited on Bi islands and plain Pt sites around Bi islands, while in iodine route, Pt was exclusively deposited on Bi islands by protecting plain Pt sites with adsorbed iodine. Thus, a comparison of FAO performances on the two Bi-modified Pt electrodes with additional Pt (deposited in the different ways) disclosed a difference in FAO performances on plain Pt sites and Bi islands. When Bi coverage was ~0.04, the Bi deposits were scattered Bi islands enhancing FAO on Pt(poly). The additional Pt deposits using direct route increased FAO efficiency, while the ones using iodine route slightly decreased FAO current. The EC-STM observations indicated that Pt deposits around Bi islands, not on Bi islands, were responsible for the FAO current increase on Bi-modified Pt(poly). The FAO efficiency on Bi-modified Pt(poly) with a Bi coverage of ~0.25 increased by a factor of 2. However, the additional Pt deposits using the two Pt deposition routes notably decreased the FAO current. The dependency of FAO on Bi coverage was discussed in terms of electronic effect and ensemble effect.

• 동력기계공학회지
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• 제13권2호
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• pp.11-17
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• 2009

The heat transfer characteristics of flow through two inclined wire-mesh baffles in a rectangular channel were investigated experimentally with varying the mesh number of wire screens and inclination angle of the baffles. Two different types of wire meshes such as dutch and plain weaves, were used in this experiment. Three kinds of baffle plates with different mesh specifications in the dutch weave and four different kinds in the plain weave were manufactured. Baffles were mounted on bottom wall with varied angles of inclination. Reynolds number was varied from 23,000 to 57,000. It is found that the placement of inclined wire-mesh baffles in the channel affects the heat transfer characteristics by combining both jet impingement and flow disturbance. The wire screen modified the flow structure leading to a change in the heat transfer characteristics. The results show that the baffle plate with the most number of mesh (type SA) has the highest heat transfer rate.

• 한국의류산업학회지
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• 제7권4호
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• pp.433-438
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• 2005

Seven commercial lining fabrics normally used in a market were selected: plain-weave fabrics with polyester, nylon, rayon and acetate fiber, and polyester textured yarn, in addition, polyester fabrics with plain, twill and satin weave. Then seam strength, seam efficiency, resistance to slippage of yarns and type of seam destruction were examined related to endurance by textiles in sewing capability of the lining fabrics. In results, as tensile strength was greater, seam strength got greater, which shows tensile strength and seam strength have close relationship. Tensile and seam strength of acetate fabric were the least, but seam efficiency was the greatest. It presents that strong tensile and seam strengths do not show high seam efficiency at the same time. Various types of seam destruction have been shown. When tensile strength of the sewing thread was greater than tensile strength of fabric, fabric destruction was occurred before the sewing thread destruction. When tensile strength of the fabric was greater than seam strength, the sewing thread destruction was occurred. Resistance to slippage of yarns got greater as tensile strength of the fabric got greater. The plain-weave fabric, which tensile strength of fabric was smaller, showed the greater resistance to slippage of yarns than twill and satin weave fabrics. The stretch fabric revealed the optimal lining fabric with the greatest resistance to slippage of yarns.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.805-808
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• 2002

This study is designed to reduction of hydration heat of 4 layer division-placed mass concrete considering the difference of setting time of super retarding agent. According to the results, peak temperature of plain concrete by hydration heat show $63^{\circ}C$ around the age of 1 days. Hydration heat is lowest in the bottom layer, and highest in the middle of 3rd layer from the bottom. Hydration heat of mock up structure, which is division-placed at the same interval of 1 and 2 days by setting time difference of super retarding agent, is highest in the bottom layer because after peak temperature of 4th layer, hydration reaction progresses in order of 3rd, 2nd and 1st layer. But in mock up structure which is division-placed at the various interval. peak temperature by hydration heat is reduced by about $13^{\circ}C$, compared with plain concrete because after first peak hydration heat of 4th layer (plain concrete), hydration reaction progresses after the drop of hydration heat in order of 3rd, 2nd and 1st layer.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2006년도 학술대회 1부
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• pp.1137-1142
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• 2006

3D 가상공간을 협업에 효과적으로 이용하기 위해서는 3D 가상공간에서 빠르고 쉽게 의사를 표현할 수 있는 기술이 필요하다. 본 연구에서는 이런 효과적인 의사표현 방법으로 Sketch 기법을 제안한다. Sketch 기법은 간단한 2D 선들의 표현을 통해 매우 빠르게 아이디어를 표현 할 수 있으며, 의도에 따라 부분을 강조하거나 가감할 수 있기 때문에 좀 더 직관적으로 의도를 전달 할 수 있다. 그래서 이러한 Sketch 를 공간상에서 손쉽게 3D 모델의 표면이나 공간 위에 입력하고, 입력한 Sketch 를 3D 가상공간과 연동하여 보여 줌으로써 쉽게 3D 가상공간 안에 Sketch 로 의견을 표현 할 수 있게 하는 Sketch 기반 인터페이스를 연구 하였다. Sketch 기법을 3D 가상공간에 적용하기 위해서는 3D 가상공간 상에서 2D Sketch 를 입력하기 위한 방법과 입력 시 발생할 수 있는 위상차의 문제를 해결해야 한다. 이 연구에서는 2D Sketch 입력을 대상 3D 객체 중심에서 Sketch할 부분의 Sketch plain 을 선택 및 생성함으로써 입력하는 방법을 연구하였으며, 입력 시 발생하는 위상차는 View-point 및 View-Plain 의 이동 등을 통해 해결점을 찾고자 하였다. 그리고 추후 연구를 통해 Sketch 를 Annotation 으로 활용, 협업에서 필요로 하는 Sketch Annotation 으로 개발하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.181-188
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• 2001

The present research is an experimental study of subcooled flow boiling behavior using flat, microporousenhanced square heater surfaces in pure FC-72. Two $1-cm^{2}$ copper surfaces, one highly polished (plain) and one microporous coated, were flush-mounted into a 12.7 mm square, horizontal flow channel. Testing was performed for fluid velocities ranging from 0.5 to 4 m/s (Reynolds numbers from 18,700 to 174,500) and pure subcooling levels from 4 to 20 K. Results showed both surfaces' nucleate flow boiling curves collapsed to one line showing insensitivity to fluid velocity and subcooling. The log-log slope of the microporous surface nucleate boiling curves was lower than the plain surface due to the conductive thermal resistance of the microporous coating layer. Both, increased fluid velocity and subcooling, increase the CHF values for both surfaces, however, the already enhanced boiling characteristics of the microporous coating appear dominant and require higher fluid velocities to provide additional enhancement of CHF to the microporous surface.

• Tribology and Lubricants
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• 제25권5호
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• pp.324-329
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• 2009

In this study a complex design fitness analysis of journal bearings is carried out for the LPLi rotary-vane fuel pump application, as an external and horizontal installation, in LPG vehicles. Bearings considered in the analyses are plain and 3-axial groove journal bearings. Upon reflecting the fact that the primary failure mode of bearings in the application is a premature friction and wear failure of bearing metal due to a very low viscosity of liquid fuel LPG as a bearing lubricant, the performance factors of bearings used in an evaluation process of design fitness are a load carrying capacity and vibration suppression ability relative to a rated speed. At this time the design variables of bearings are a radial clearance and length. Results show that, in terms of both of the load carrying capacity and vibration suppression ability, the plain journal bearings are superior to the 3-axial groove journal bearings and among the plain bearings the smaller the bearing clearance (5>10>$15\;{\mu}m$) is and the longer the bearing length (6<8<10<12<14 mm) is, the better the bearing performance is.

• 설비공학논문집
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• 제16권6호
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• pp.522-529
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• 2004

In this study, external condensation heat transfer coefficients (HTCs) of flammable refrigerants of propylene, propane, isobutane, butane, DME, and HFC32 were measured on a horizontal plain tube, 26 fpi low fin tube, and Turbo-C tube. All data were taken at the temperature of 39$^{\circ}C$ with a wall subcooling of 3∼8$^{\circ}C$. Test results showed a typical trend that condensation HTCs of flammable refrigerants decrease with increasing wall subcooling. HFC32 had the highest HTCs among the tested refrigerants showing 44% higher HTCs than those of HCFC22 while DME showed 28% higher HTCs than those of HCFC22. HTCs of propylene and butane were similar to those of HCFC22 while those of propane and isobutane were similar to those of HFC134a. Based upon the tested data, Nusselt's equation is modified to predict the plain tube data within a deviation of 3%. For 26 fpi low fin tube, Beatty and Katz equation predicted the data within a deviation of 7.3% for all flammable refrigerants tested. The heat transfer enhancement factors for the 26 fpi low fin and Turbo-C tubes were 4.6∼5.7 and 4.7∼6.9 respectively for the refrigerants tested indicating that the performance of Turbo-C tube is the best among the tubes tested.