• Polymer(Korea)
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• v.24 no.6
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• pp.845-853
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• 2000

The optimum cure cycle and carbonization condition were selected by the DSC and TGA analysis and green bodies were prepared by the method of hot press molding and then carbonized up to 140$0^{\circ}C$. Additives such as graphite powder, carbon black, milled carbon fiber and carbon fiber mat, which were considered to be effective in improving the interlaminar shear strength, were also added to check their effects on the density and porosity of products. Then, their relations with mechanical properties such as ILSS and flexural strength were investigated. The composites added 9 vol% of graphite powder showed the greatest values of ILSS and flexural strength. Otherwise, in case of adding carbon black, the composites showed the slight improvement of ILSS at its contents of 3 vol% but the flexural strength was decreased. When milled carbon fiber and carbon fiber mat were added, the lack of resin and the heat shrinkage during the carbonization caused the delamination, resulting in decreasing the density, ILSS and flexural strength.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.107-115
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• 2002

A parametric study has been conducted to evaluate the effects of finite element modeling methods on the internal loads, sizing and the weight of the multi-spar aircraft wing structures. The wing is idealized into total 18finite element models and subjected to 4typical external load conditions. An automatic sizing algorithm based on MSC/NASTRAN and MSC/PATRAN is developed. The results show that the critical part affection the internal loads and weight of the structure is wing skin. Effect of modeling of the spar and rib on the structural behavior is not manifest. On the contrast to the general expectation, the models using the bending-resistant elements show the heavier weight than ones by the elements without bending stiffness. From this results, designers of multi-spar wing are recommended to construct the finite element model considering the bending stiffness, or to check the characteristics of the structure before modeling.

• Proceedings of the KIEE Conference
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• 2006.07e
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• pp.9-10
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• 2006

가공배전선로는 태풍 내습시 전주 및 전선에 작용하는 풍압에 대하여 견딜 수 있도록 설계되어져야 한다. 따라서 본 연구에서는 가공배전선로의 설계시 사용되는 전주에 가해지는 풍압에 의한 굽힘모멘트 및 굴곡개소의 합성모멘트 계산시 사용하는 기존 계산식의 문제점을 분석하고 현장에서 쉽게 적용 가능한 새로운 계산식을 유도하였다. 새로운 계산식을 이용하여 설계자들이 가공배전선로의 지지물 및 지선강도를 검토할 수 있게 됨으로써 태풍과 같은 재해시에도 안전한 설비를 시설할 수 있게 되었다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.12
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• pp.1310-1316
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• 2008

Bi-layer and tri-layer structures of electro-active paper(EAPap) using conductive polyaniline(PANI) coating were investigated to improve bending displacement of cellulose EAPap. Two different counter ions, perchlorate($CIO_4^-$) and tetrafluoroborate($BF_4^-$), are used as dopant ions in the PANI processing. The actuation performances of hi-layer and tri-layer structure are evaluated in terms of tip displacement, blocked force, strain energy density and power output density. The actuation performance of the tri-layer actuator was better than the hi-layer structure, and the maximum displacement and blocked force of tri-layer $CIO_4^-$ doped-PANI-EAPap were 13.2 mm and 0.15 mN, respectively. Also the power output of the actuator is similar to the required power of biological muscle application.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.89-94
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• 2021

The mechanical reliability of flexible devices has become a major concern on their commercialization, where the importance of reliable bonding is highlighted. In terms of component materials' properties, it is important to consider thermal damage of polymer substrates that occupy large area of the flexible device. Therefore, room temperature bonding process is highly advantageous for implementing flexible device assemblies with mechanical reliability. Conventional epoxy resins for the bonding still require curing at high temperatures. Even after the curing procedure, the bonding joint loses flexibility and exhibits poor fatigue durability. To solve this problems, low-temperature and adhesive-free bonding are required. In this work, we develop a room temperature bonding process for polymer substrates using carbon nanotube heated by microwave irradiations. After depositing multiple-wall carbon nanotubes (MWNTs) on PET polymer substrates, they are heated locally with by microwave while the entire bonding specimen maintains room temperature and the heating induces mechanical entanglement of CNT-PET. The room temperature bonding was conducted for a PET/CNT/PET specimen at 600 watt of microwave power for 10 seconds. Thickness of the CNT bonding joint was very thin that it obtains flexibility as well. In order to evaluate the mechanical reliability of the joint specimen, we performed lap shear test, three-point bending test, and dynamic bending test, and confirmed excellent joint strength, flexibility, and bending durability from each test.

• Composites Research
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• v.14 no.3
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• pp.77-89
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• 2001

Since the critical whirling vibration frequency of high speed built-in type motor spindle systems is dependent on the rotor mass of the built-in motor and the spindle specific bending modulus, the rotor and the shaft were designed using magnetic powder containing epoxy and high modulus carbon fiber epoxy composite, respectively. In order to increase the amount of the magnetic flux of the composite squirrel cage rotor of an AC induction motor, a steel core was inserted into the composite rotor. From the magnetic analysis, the optimal configurations of steel core and conductor bars for the dynamic characteristics of the rotor system were determined and proposed. The temperature dependence of composite squirrel cage rotor materials was investigated by various experiments such as TMA, DMA and VSM.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.143-153
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• 2009

Using a discrete wavenumber method, we examine the effects on Logging-While-Drilling (LWD) logs when a mismatch exists between the amplitudes or generating times of the signals from individual monopoles in a LWD multipole source. An amplitude-mismatched LWD dipole/quadrupole source produces non-dipole/non-quadrupole modes as well as flexural and screw modes. The strongest of non-dipole/non-quadrupole modes is the Stoneley mode, whose amplitude increases with increasing mismatch. However, we can recover the flexural mode signals by A-C processing, and the screw mode by A-B+C-D processing, respectively. The Stoneley mode, which has the same amplitude at the same radial distance from the borehole axis, is cancelled out by A-C and A-B+C-D processing as long as the tool is placed at the centre of the borehole. The responses from a time-mismatched LWD multipole source look like the summation of responses by two or four monopole sources off the borehole axis. However, we can avoid the misinterpretation of the formation velocities by referring to the computed dispersion curves, which are independent of the arrival times of the modes, on the frequency semblance plot.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.409-412
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• 2001

현재의 섬유산업의 동향은 소비자의 욕구가 다양화되고 있다는 점과 고급화가 되고 있다는 점에 초점을 맞춘 의복과 고기능 및 특수기능을 가진 생활관련제품 및 첨단제품으로서 발전되고 있다는 특징을 가지고 있다. 본 연구에 사용된 water-jet loom은 air-jet loom의 제직 폭의 한계를 해결하기 위해 연구하던 체코의 기술자 V. Svaty에 의해 개발되어 졌으며, 그 이후 Murata사가 기술도입을 통하여 1960년에 일본에서 처음 제작되었고, 그 후 다수의 직기 메이커들이 개발 및 개선을 거듭하여 상업적인 생산을 본격화한 것이다. (중략)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.137-142
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• 2017

Recently, the reduction of vehicle weight has been increasingly studied, in order to enhance the fuel efficiency of passenger cars. In particular, the seat frame is being studied actively, owing to considerations of driver safety from external impact damage. Therefore, this study focuses on high strength steel sheet (SPFC980)/polymer heterojunction hybrid materials, and their performance in regards to impact energy absorption. The ratio of impact energy absorption was observed to be relatively higher in the SPFC980/polymer hybrid materials under the impact load. This was found by calculating the equivalent flexural rigidity, which is the bending effect, according to the Castigliano theorem. An efficient wire-web structure was investigated through the simulation of different wire-web designs such as triangular, rectangular, octagonal, and hexagonal structures. The hexagonal wire-web structure was shown to have the least impact damage, according to the simulations. This study can be utilized for seat frame design for passengers' safety, owing to efficient impact absorption.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2009.11a
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• pp.251-253
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• 2009

본 연구에서는 팔의 굽힘(flexion)과 폄(extension)운동 시 물체의 무게에 따른 저크의 변화를 통해 부드러움을 정량화하고, 물체무게와 움직임의 형태(type)에 따른 동작의 부드러움을 비교하고자 한다. 10 명의 오른손잡이 남자 대학생(평균 $24.8{\pm}1.1$ 세)을 실험 참여자로 선정하였다. 물체무게(0g, 1000g)와 움직임의 형태(손등 위/아래)를 달리하여 팔의 굽힘과 폄 운동을 실시하였다. 또한 3 축 가속도 센서를 이용하여 x 와 z 축의 가속도를 측정하였고, 측정된 신호로 부터 저크값을 추출 하였다. 실험은 총 8 분으로 4 개의 block 으로 구성되며 각 block 은 resting 구간 1 분과 lifting 구간 1 분으로 구성된다. 실험 결과 물체무게 0g 에 비해 1000g 에서 가속도와 정규저크 값이 유의미하게 감소하였다.