• 한국응용과학기술학회지
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• 제16권4호
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• pp.317-322
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• 1999

Transparent films were prepared using the sol-gel process by mixing TEOS with PVA solution that was solved in EtOH and distilled water homogeneously. HCl, $CH_3COOH$ and $NH_4OH$ were used as catalysts of the sol-gel process, and for improving the flexibility of films glycerol was used as plasticizer. In case of each catalyst, transparency and tensile strength were increased, and glass transition temperature (Tg) was shifted to higher temperature with increasing TEOS ratio. Also, in case of adding the plasticizer, the flexibility of films was increased. On the contrary, transparency, thermal stability and tensile strength were decreased with increasing HCl and $NH_4OH$ ratio. Also, the range of being made of film type was expanded when $CH_3COOH$ was used than HCl and $NH_4OH$.

• Advances in Computational Design
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• 제5권1호
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• pp.35-54
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• 2020

One of the prevailing structural systems in high-rise buildings is the core-wall system. On the other hand, the existence of one or more underground stories causes the perimeter below-grade walls with the diaphragm of grade level to constitute of a very stiff box. In this case or a similar situation, during the lateral response of a tall building, underground perimeter walls and diaphragms that provide an increased lateral resistance relative to the core wall may introduce a prying action in the core that is called backstay effect. In this case, a rather great force is generated at the diaphragm of the grade-level, acting in a reverse direction to the lateral force on the core-wall system, and thus typically causes a reverse internal shear. In this research, in addition to review of the results of the preceding studies, an improved relationship is proposed for prediction of backstay force. The new proposed relationship takes into account the effect of foundation flexibility and is presented in a non-dimensional form. Furthermore, a specific range of the backstay force to lateral load ratio has been determined. And finally, it is shown that although all suggested formulas are valid in the elastic domain, yet with some changes in the initial considerations, they can be applied to some certain non-linear problems as well.

• 한국의류산업학회지
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• 제25권1호
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• pp.62-71
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• 2023

Recently, interest in natural fabric materials that are not harmful has increased, and hemp is being studied as a new eco-friendly product. This study produced hemp fabric with improved flexibility and increased antibacterial properties by blending it with Hanji yarn. Various weaving methods were proposed to overcome the rough physical properties of hemp, and the functions of the developed products were evaluated through antibacterial tests. The mixing ratios of hemp and Hanji yarns was 50% hemp: 50% Hanji weft, 70% hemp: 30% Hanji weft, 30% hemp: 70% Hanji weft, and 100% hemp. Overall, the higher the ratio of Hanji yarn, the higher the fastness property, and the higher the ratio of hemp yarn, the higher the flexibility of the fabric, which was evaluated to be comfortable to wear. The 99.9% antibacterial properties of hemp products were considered to contribute to maintaining the health of modern people. Owing to its high intensity and high air permeability, it is considered highly usable in the production of children's clothing with a lot of activity. It was evaluated as an advantage that the disadvantage of hemp, which was limited as a material for summer clothing, was broadened to use for all seasons due to the fusion of Hanji. Otherwise, low consumer satisfaction as an outdoor wear is a disadvantage because hemp products had low elasticity and wrinkles.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1340-1346
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• 2005

In this study, based on shaking table test results on a seismically isolated bridge model, an inelastic numerical model is refined by using Bouc-Wen model representing the hysteretic behavior of isolators. Seismic responses of isolated bridges are numerically investigated varying with relative stiffness ratio(RSR), which is a ratio of the effective stiffness of isolator to the lateral stiffness of bridge pier, From the results, it is found that an adequate range of relative stiffness ratio could be defined for seismic design of isolated bridges without considering the flexibility of piers.

• Structural Engineering and Mechanics
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• 제38권3호
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• pp.361-384
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• 2011

Earlier studies on hollow-circular rubber bearings, all of which are conducted for steel-reinforced bearings, indicate that the hole presence not only decreases the compression modulus of the bearing but also increases the maximum shear strain developing in the bearing due to compression, both of which are basic design parameters also for fiber-reinforced rubber bearings. This paper presents analytical solutions to the compression problem of hollow-circular fiber-reinforced rubber bearings. The problem is handled using the most-recent formulation of the "pressure method". The analytical solutions are, then, used to investigate the effects of reinforcement flexibility and hole presence on bearing's compression modulus and maximum shear strain in the bearing in view of four key parameters: (i) reinforcement extensibility, (ii) hole size, (iii) bearing's shape factor and (iv) rubber compressibility. It is shown that the compression stiffness of a hollow-circular fiber-reinforced bearing may decrease considerably as reinforcement flexibility and/or hole size increases particularly if the shape factor of the bearing is high and rubber compressibility is not negligible. Numerical studies also show that the existence of even a very small hole can increase the maximum shear strain in the bearing significantly, which has to be considered in the design of such annular bearings.

• 한국콘텐츠학회논문지
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• 제18권12호
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• pp.229-237
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• 2018

본 논문에서는 대학교에서 시간표 작성 시 사용자의 다양한 요구사항들을 쉽게 충족시킬 수 있는 효과적인 시간표 모듈에 대하여 논의한다. 시간표 모듈에 따라서 시간블록의 할당방법도 달라진다는 점에 주목하고 먼저 4 블록 단위로 구성된 대칭적 시간표 모듈 6종을 제시하고 3블록 단위로 구성된 것에 비하여, 수요자 관점에서는 아무 손실 없이 그리고 공급자 관점에서는 공간사용율 상한선 감소를 감안하면, 더 많은 장점을 가진다는 점을 보인다. 제시된 모델들에 잠재적으로만 결정된 잠재블록 개념을 도입 적응시키고 운용 전략을 제시함으로써, 최종적으로 대학시간표 작성 시 유연성과 제어성을 동시에 얻는 방법을 완성한다.

• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.11-17
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• 2020

In this study, a new method for fabricating flexible transparent electrodes based on silver nanowire-polymer (AgNW-PEDOT:PSS) composite materials having a mesh pattern formed by a solution-based process without lithography was proposed. By optimizing conditions such as the amount of ultraviolet (UV) photosensitizer injected into the suspension of AgNW and PEDOT:PSS, UV exposure time, and deionized (DI) washing time, a clear and uniform mesh pattern was obtained. For the fabricated AgNW-PEDOT:PSS-based mesh-type electrodes, characteristics such as electrical sheet resistance, light transmittance, haze, and bending flexibility were analyzed according to the mixing ratio of AgNW and PEDOT:PSS included in the suspension. The fabricated mesh electrodes typically exhibited a low electrical sheet resistance of less than 20 Ω/sq while maintaining a high transmittance of 80% or more. In addition, it was confirmed from the results of analyzing the effect of PEDOT:PSS on the characteristics of the mesh-type AgNW-PEDOT electrode that the optical visibility was greatly enhanced by reducing the surface roughness and haze, and the bending flexibility was remarkably improved.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1775-1780
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• 2003

A hybrid finite element analysis was used to analyze the influence of ring gear rim thickness and spline number on the static properties of an epicyclic gear system with manufacturing errors. Both of these parameters affected the bearing force and critical stress. The effect of changes in the rim thickness on the load sharing between the gears depended on the type of manufacturing error. Ring flexibility improved the load sharing between planetary gears only in systems with planet tooth thickness or planet tangential errors; for other types of error, ring flexibility worsened the load sharing. To improve load sharing, rim thickness and spline number should be controlled within a specific range. The effect of the ring gear boundary condition was more apparent in a system with errors than in a normal system.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1161-1169
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• 2007

In this paper, the dynamic stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influence of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating cantilever pipe are derived by using extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the rotating angular velocity of a pipe. Also, the critical flow velocity and stability maps of the rotating pipe system for the variation each parameter are obtained.

• STI Policy Review
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• 제2권3호
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• pp.35-44
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• 2011

Korea has rapidly increased R&D investment over the last few decades and the intensity of R&D investment is among the highest in the world; however, there are serious concerns about R&D performance and R&D efficiency. This study is to improve the economic assessment methodology regarding a feasibility study for national R&D programs that are thought to be one of the most prominent ways to enhance R&D efficiency. In order to improve the methodology of economic assessment, a few of important factors such as technical or market uncertainty, spillover effect, and R&D contribution ratio should be covered in the model. The focus of this article is technological and market uncertainty that has a close relation with strategic flexibility and utilization potential to increase the value of R&D programs. To improve the current linear and definitive R&D process, a new framework with strategic flexibility is suggested, in which the result of economic assessment that considers technological and market uncertainty is reflected in planning. That kind of feedback process is expected to enhance the value of the program/project as well as R&D efficiency.