• Wind and Structures
• /
• 제18권5호
• /
• pp.511-528
• /
• 2014

The characteristics of wake galloping phenomenon for two parallel/unparallel circular cylinders were investigated via wind tunnel tests. The two cylinders were initially deployed in parallel and wake galloping phenomena were observed by varying the center-to-center distance. The effect of an unparallel arrangement of two cylinders was next investigated by fixing the spacing ratio of one side of the cylinders at 5.0D and the other side at 3.0D, in which D represents the diameter of the cylinder. For the unparallel disposition, the 5.0D side showed a small, limited vibration while the 3.0D side produced much larger amplitude of vibration, resulting in a rolling motion. However, the overall amplitude appeared to decrease in unparallel disposition when compared with the amplitude of the 3.0D - 3.0D parallel case. This represents the mitigation effect of wake galloping due to the unparallel disposition between two cylinders. Flow visualization tests with particle image velocimetry were conducted to identify flow fields between two cylinders. The test results demonstrate the existence of a complex interaction of the downstream cylinder with the shear layer generated by the upstream cylinder. When the spacing ratio was large enough, the shear layer was not observed and the downstream cylinder showed only limited random vibration.

• Structural Engineering and Mechanics
• /
• 제60권3호
• /
• pp.387-404
• /
• 2016

In this paper, the response and failure of sharp-notched 6061-T6 aluminum alloy circular tubes with five different notch depths of 0.4, 0.8, 1.2, 1.6 and 2.0 mm subjected to cyclic bending were experimentally and theoretically investigated. The experimental moment-curvature relationship exhibits an almost steady loop from the beginning of the first cycle. And, the notch depth has almost no influence on its relationship. However, the ovalization-curvature relationship exhibits a symmetrical, increasing, and ratcheting behavior as the number of cycles increases. In addition, a higher notch depth of a tube leads to a more severe unsymmetrical trend of the ovalization-curvature relationship. Focusing on the aforementioned relationships, the finite element software ANSYS was used to continue the related theoretical simulation. Furthermore, the five groups of tubes tested have different notch depths, from which five unparallel straight lines can be observed from the relationship between the controlled curvature and the number of cycles required to produce failure in the log-log scale. Finally, a failure model was proposed to simulate the aforementioned relationship. Through comparison with the experimental data, the proposed model can properly simulate the experimental data.

• 산업기술연구
• /
• 제25권B호
• /
• pp.81-87
• /
• 2005

This project addresses the product identification and design application of corrugated products for kinetic architectural applications. Initially, an architectural approach to product identification was carried out with the end goal of demonstrating application design principles of numerous novel architectural examples from the forest products industry. A design and prototyping stage followed demonstrating such application design principles and functional analysis on various novel architectural examples. The results of coupling product identification with proven application advantages will be of potential value not only to architecture but also to other designers in the arts and sciences. The general motivation for the research arises out of a growing interest corrugated and paper products to be ideally suited for various architectural applications for their unparallel environmental benefits. Applications in architecture that use fewer resources and that adapt efficiently to complex and changing conditions are particularly relevant for an industry (architecture) that is increasingly aware of its environmental responsibilities. Corrugated and paper products are highly under-utilized by the building industry as design choice material for both interior and exterior applications. An increased awareness of the benefits of corrugated and paper products coupled with a process of designing for the total use and reuse will prove to be a valuable means by which issues of energy efficiency and environmental quality of buildings could be enhanced to be more efficient, affordable, and therefore reach a broader audience of users.

• 대한치과보철학회지
• /
• 제54권4호
• /
• pp.401-406
• /
• 2016

임플란트 피개의치는 전통적인 총의치에 비해 높은 유지력 및 저작능력, 환자의 만족도를 보인다. 특히 골흡수가 심한 하악 무치악 환자의 치료에서는 우선되는 치료방법으로 고려된다. 임플란트 피개의치를 위한 attachment에는 임플란트간 연결된 bar type과 연결되어있지 않은 solitary type으로 구분할 수 있다. 최근 임상에서 많이 사용하는 solitary type의 경우 임플란트간의 평행관계가 중요하며, 임플란트간의 평행관계가 불량한 경우 attachment의 마모 및 유지력 감소로 유지관리를 내원횟수가 증가할 수 있다. 본 증례는 평행하지 못한 두 개의 하악 임플란트 식립 환자에서 milled bar를 이용하여 제작한 임플란트 피개의치로 만족할 만한 결과를 얻었기에 이를 보고하고자 한다.

• 대한치과보철학회지
• /
• 제47권2호
• /
• pp.222-231
• /
• 2009

연구목적: 임플란트 피개의치에서 연결고정형과 비연결고정형 보철물 지대주와 골의 변형률을 비교하고 임플란트 식립 경사에 따른 변형률을 비교 분석하고자 하였다. 연구 재료 및 방법: 2개의 아크릴릭 레진 모형의 좌측과 우측 견치 부위에 2개의 외부연결형 임플란트를 각각의 모형에 식립하였다. 한 모형에는 두 개의 임플란트를 평행하게 식립하였고, 다른 모형에는 순측과 설측으로 10도의 이개도(divergence)를 가지게 임플란트를 식립하였다. 모형에서 바를 이용한 연결고정형 지대주와 볼을 이용한 비연결고정형 지대주를 고정체에 번갈아 연결하고, 각각의 경우 대응하는 유지장치가 부착된 피개의치를 제작하여 지대주 상에 안착시켰다. 전기저항 스트레인 게이지(strain gauge)를 이용하여 피개의치에 100 N에서 200 N의 부하를 가하였을 때 지대주와 가상골 표면의 변형률(strain)을 측정하였다. 결과 및 결론: 측정된 값들을 통계분석하여 얻은 결과는 다음과 같다. 바를 이용한 연결고정형 보철물은 비연결형 보철물 보다 높은 변형률 값을 보였다. 그러나 방향은 주로 압축력이었으며 부하는 분산되었다(P<.05). 볼을 이용한 비연결고정형 보철물은 연결고정형보다 낮은 변형률 값을 보였다(P<.05). 순측경사된 임플란트에서는 비연결고정형 보철물이 연결고정형 보철물보다 더 높은 변형률 값을 보였다. 설측경사된 임플란트는 순측경사된 임플란트보다 낮은 변형률을 보였다(P<.05). 임플란트가 평행하게 식립된 경우보다 평행하지 않게 식립된 경우 지대주와 가상골의 변형률 값이 더 높았다(P<.05).