• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 동계학술발표회 논문집
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• pp.151-152
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• 2007

In this study, the optical porosity of $TiO_2$ films with helical structure deposited by glancing angle deposition (GLAD) were investigated. Helical films are of interest due to their ability to differentiate states of circularly polarized light. We designed and fabricated normal-incidence circular-polarization separator deposited by GLAD (Helical structure). The optical porosity of $TiO_2$ film deposited by helical method can be applied many optical coatings.

• Smart Structures and Systems
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• 제25권3호
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• pp.311-322
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• 2020

This paper studies the influence of parameters of a novel SMA helical spring energy dissipation brace on the seismic resistance of a frame structure. The force-displacement relationship of the SMA springs is established mathematically based on a multilinear constitutive model of the SMA material. Four SMA helical springs are fabricated, and the force-displacement relationship curves of the SMA springs are obtained via tension tests. A numerical dynamic model of a two-floor frame with spring energy dissipation braces is constructed and evaluated via vibration table tests. Then, two spring parameters, namely, the ratio of the helical spring diameter to the wire diameter and the pre-stretch length, are selected to investigate their influences on the seismic responses of the frame structure. The simulation results demonstrate that the optimal ratio of the helical spring diameter to the wire diameter can be found to minimize the absolute acceleration and the relative displacement of the frame structure. Meanwhile, if the pre-stretch length is assigned a suitable value, excellent vibration reduction performance can be realized. Compared with the frame structure without braces, the frames with spring braces exhibit highly satisfactory seismic resistance performance under various earthquake waves. However, it is necessary to select an SMA spring with optimal parameters for realizing optimal vibration reduction performance.

• Structural Monitoring and Maintenance
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• 제1권4호
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• pp.393-409
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• 2014

Across-wind response is often the cause of significant structural vibrations that in turn cause fatigue damage to welded and other connections. The efficacy of low-cost helical strakes to mitigate such adverse response is presented for a traffic signal structure. Field observations are made on a prototype structure in a natural wind environment without and with helical strakes installed on the cantilevered arm. Through continuous monitoring, the strakes were found to be effective in reducing across-wind response at wind speeds less than 10 m/s. Estimates of fatigue life are made for four different geographical locations and wind environments. Results for the class of traffic signal structure show that helical arm strakes are most effective in locations with benign wind environments where the average annual wind speed is not more than the vortex shedding wind speed, which for this investigation is 5 m/s. It is concluded that while strakes may be effective, it is not the panacea to mitigating connection fatigue at all locations.

• 한국광학회지
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• 제25권6호
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• pp.311-314
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• 2014

본 논문에서는 LED 모듈의 방열성능을 개선하기 위하여 히트싱크의 새로운 핀 구조를 설계하고 열 특성을 분석하였다. 대부분의 히트싱크는 판상형이나 침상형의 핀으로 구성되는 것이 일반적이나, 스프링 모양의 헬리컬 핀 구조를 설계변수와 함께 도입하여 제한된 부피 대비 넓은 표면적을 갖는 히트싱크를 설계하였다. 약 14% 넓어진 표면적을 통해 방열 효율을 개선하였고, 그에 따라 LED 칩의 온도를 약 12% 정도 저감하는 효과를 가져 올 수 있었다. 또한, 기존의 히트싱크 보다 넓은 표면적을 가지는데 비해 형성 부피는 약 15% 감소하게 되어 재료비 절감은 물론 공정상의 이점에 따른 공정 생산비의 절감을 기대할 수 있는 새로운 고성능 LED 조명용 히트싱크를 설계하였다.

• Molecules and Cells
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• 제42권10호
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• pp.729-738
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• 2019

Autophagy is an important process for protein recycling. Oligomerization of p62/SQSTM1 is an essential step in this process and is achieved in two steps. Phox and Bem1p (PB1) domains can oligomerize through both basic and acidic surfaces in each molecule. The ZZ-type zinc finger (ZZ) domain binds to target proteins and promotes higher-oligomerization of p62. This mechanism is an important step in routing target proteins to the autophagosome. Here, we determined the crystal structure of the PB1 homo-dimer and modeled the p62 PB1 oligomers. These oligomer models were represented by a cylindrical helix and were compared with the previously determined electron microscopic map of a PB1 oligomer. To accurately compare, we mathematically calculated the lead length and radius of the helical oligomers. Our PB1 oligomer model fits the electron microscopy map and is both bendable and stretchable as a flexible helical filament.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2534-2546
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• 2023

Gas-cooled space reactor, which adopts He-Xe gas mixture as working fluid, is a better choice for megawatt power generation. In this paper, thermal-hydraulic characteristics of He-Xe gas mixture in 2×2 rod bundle wrapped with helical wires is numerically investigated. The velocity, pressure and temperature distribution of the coolant are obtained and analyzed. The results show that the existence of helical wires forms the vortexes and changes the velocity and temperature distribution. Hot spots are found at the contact corners between helical wires and fuel rods. The highest temperature of the hot spots reach 1600K, while the mainstream temperature is less than 400K. The helical wire structure increases the friction pressure drop by 20%-50%. The effect extent varies with the pitch and the number of helical wires. The helical wire structure leads to the reduction of Nusselt number. Comparing thermal-hydraulic performance ratios (THPR) of different structures, the THPR values are all less than 1. It means that gas-cooled space reactor adopting helical wires could not strengthen the core heat removal performance. This work provides the thermal-hydraulic design basis for He-Xe gas cooled space nuclear reactor.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.248-248
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• 2006

The notable feature of the Cu(II) coordination polymer investigated here is its ability to self-assemble into a double-stranded helical structure with regular grooves along the helical axis, through the combination of metal-chloride dimeric interactions and repulsive interactions, as an organizing force. It is also remarkable that the double-stranded helices self-organize into a 2-D columnar structure in both the bulk state and aqueous solution. These results represent a unique example that weak metal-ligand bridging interactions can provide a useful strategy to construct stable double-stranded helical nanotubes.

• Journal of Advanced Marine Engineering and Technology
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• 제37권1호
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• pp.59-65
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• 2013

본 논문은 헬리컬 풍력터빈을 이용한 풍력터빈 나무의 구조적 안정성을 검토하는데 목적이 있다. 복합재료를 적용하여 헬리컬 로터 블레이드를 설계하였으며, 유한요소 해석을 통하여 안정성을 검토하였다. 또한 4개의 헬리컬 로터를 지지하고 있는 풍력터빈 나무에 대하여 풍압, 로터의 회전 그리고 자중을 고려한 구조해석을 수행하여 설계 타당성을 검토 하였다.

• 한국기계가공학회지
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• 제13권3호
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• pp.103-110
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• 2014

In this study, spur and helical box models of an existing machine tool are investigated using structural and fatigue analyses. As the helical box model is shown to have less stress and deformation than those characteristics of the spur box model, the helical box has more strength and more transmission efficiency on the structure. In terms of fatigue analysis, the helical box model has more repeated fatigue strength than that of the spur box model. These study results can be effectively utilized in the design of real gear boxes of machine tools by anticipating and investigating prevention and durability against damage.

• BMB Reports
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• 제30권6호
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• pp.426-430
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• 1997

The helical periodicity of the triple-stranded $(dT)_n{\cdot}(dA)_n{\cdot}(dT)_n$ sequence was determined by measuring gel-mobilities of bent DNA fragments containing the sequence. In the bent DNA fragments, a $GA_{22}G$ $CT_{22}C$ sequence was located between two bent DNA loci composed of six $A_{6}{\cdot}T_{6}$ repeats. and the DNA length between the bent DNA loci was varied by 1 base pair over a full helical turn. The gel mobility of each bent DNA fragment reflected the overall extent of DNA bending and varied with the DNA length between the two bent loci. Mobilities of the bent DNA fragments in 5% polyacrylamide gel were measured after preincubating the DNA fragments both in the presence and absence of $CT_{22}C$ oligonucleotide. By comparing the bent DNA fragments containing an intermolecular triplex structure with those of a genuine duplex structure in the gel mobilities, the helical periodicity of the $T_n{\cdot}A_n{\cdot}T_n$ triplex DNA was determined to be $11.5({\pm}0.3)bp/turn$.