• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.110-116
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• 2006

지금까지 대부분의 리던던시 할당문제(RAP: redundancy allocation problems) 관련 연구들에서는 최상위 수준에서의 시스템 리던던시보다는 최하위 수준인 부품의 리던던시를 고려하였다. 이는 최하위 수준에서의 리던던시가 최상위 수준의 리던던시보다 효과적이라고 알려진 일반적 원리 때문이었다. 최근 한 연구에서는 동일하지 않은 예비부품을 사용하여 리던던시를 실시하는 경우 직렬구조의 시스템에서도 일반적 원리와 다른 결과가 나타날 수 있음을 보이고, 시스템을 구성하는 모든 수준에서 리던던시가 가능한 다수준 리던던시 할당문제(MRAP: multi-level RAP)를 제시하였다. 그러나 MRAP는 모든 수준에서의 리던던시를 고려하지만 단지 한 수준을 선택하여 리던던시를 할 수 있다는 가정사항을 포함하고 있다. 본 연구에서는 MRAP의 이러한 가정사항을 완화하여 시스템을 구성하는 모든 수준에서 리던던시를 위한 수준을 복수로 선택 가능한 혼합 다수준 리던던시 할당문제(MMRAP: multiple MRAP)를 제시하고 모형화하며, 문제의 해법을 위한 유전자 알고리듬(GA: genetic algorithm)을 제시한다. 제시한 GA를 활용한 몇 가지 수치실험을 통해 모형이 기존의 RAP 경우보다 효과적임을 입증한다.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.58-59
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• 1995

기체 분리용 무기분리막은 고분자막과 비교하여 열 및 구조적 안정성이 우수하므로, 석탄가스화반응 혼합기체중의 기체분리 등 고온 또는 고압공정에 적합한 분리방법으로서 주목되고 있다. 기체의 분리를 위한 무기재료막은 크게 다공성막과 비다공성막으로 나눌 수 있으며, 이 중 비기공 성막의 경우 높은 선택도를 가지나 투과도가 낮아 경제성이 떨어지는 것으로 평가되고 있다. 한편, 기존의 다공성막의 경우 투과도는 높으나 기체의 분리가 혼합기체중 각 기체의 분자량의 차이에 의존하는 Knudsen 확산에 제한되는 낮은 선택도를 갖는 단점이 있다. 따라서 다공성막의 기공을 특정기체의 선택도가 우수한 촉매물질등으로 개선하여 비기공성막에 비해 우수한 투과도를 갖고, 기공성막에 비해 향상된 선택도를 보이는 복합막의 연구가 활발히 추진되고 이\ulcorner. 본 연구는 솔젤법에 의해 제조된 팔라듐 함침 알루미나 지지막의 기공을 침투$\cdot$증착(Soaking and Vapor-deposition)법에 의해 개선하여 기체의 투과도를 높게 유지하면서 수소의 선택성을 향상시키는 것을 목적으로 하였다.

• Composites Research
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• v.36 no.5
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• pp.349-354
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• 2023

Poly(3-hexylthiophene) (P3HT) is a conjugated polymer that is highly soluble in organic solvents and is readily available. However, its electrical properties as an active channel in electronic devices are not enough for practical applications, necessitating further improvement in the properties. In this study, we demonstrate that the blending of two P3HT polymers (i.e., regio-regular (RR) P3HT and regio-random (RRa) P3HT) with different regioregularities can significantly improve charge transport characteristics of the blend films. The morphological and electrical properties of the blend films were systematically investigated by varying the ratio between two P3HT polymers. Atomic force microscopy (AFM), X-ray diffraction (XRD), and UV-visible absorption spectroscopy (UV-vis) were employed to evaluate the morphological and optoelectronic properties of the blend films. The crystallinity of the blend films increased with increasing the content of RRa-P3HT to 20 wt% and gradually decreased as the content increased to 80%. Consistently, the highest charge carrier mobility was obtained from the blend films containing 20 wt% RRa-P3HT, which value was measured to be 0.029 cm²/V·s. The values gradually decreased to 0.0007 cm²/V·s with increasing the content of RRa-P3HT to 80 wt%.

• The Journal of the Acoustical Society of Korea
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• v.8 no.1
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• pp.23-30
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• 1989

Propagation phenomena of nonlinear pressure waves in a bubbly mixture are studied. The governing equations for a bubbly mixture are derived heuristically and energy equation is incorporated with other governing equations to take thermal effects into consideration inside the bubble. This non-isothermal condition of the bubble inside is especially important when high amplitude pressure waves are treated. Keller's equation is adapted for the bubble dynamics as practical problem. Some numerical simulations are carried out for the shock tube problem using a computer program based on the above model. A comparison with experimental results of Noordzij and van Wijngaarden shows that the structure of the wave in the shock tube experiment seems to be much more significantly affected 요 the complex heat transfer phenomena inside the bubbles than by the relative translational motion between bubbles and surrounding liquid.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.991-995
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• 2002

The engine booming noise heard inside a vehicle's cabin is due to the engine vibration that's transferred to the chassis in the form of structural vibration and it often causes discomfort to the passenger. In an effort to seek out the possible relation between the engine booming noise and the engine vibration of a vehicle, a position on the engine mount was selected and the vibration transmission through the position was attenuated to observe the corresponding change in the noise level inside the cabin. A system consisting of an actuator and a hybrid controller that has both the feed-forward and feed-back capabilities was developed in order to carry out the experiment.

• Korean Journal of Food Science and Technology
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• v.16 no.2
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• pp.185-191
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• 1984

The structure and textural properties of the traditional starch gel-form food Mook were investigated with the use of the Scanning Electron Microscope and Instron universal testing machine. Sensory evaluation was undertaken to evaluate the relationship between structure and textural properties of starch gel. When pure mungbean, potato, and sweet potato starches as well as 30% mungbean starches added to potato and to sweet potato starches were evaluated, it was found that mungbean starch gel had homogeneous and porous structure and showed the highest acceptability.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.699-708
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• 2007

Reinforced concrete deep beams are general structural members used as transfer-girder, pile cap, foundation wall and so on. They have a complex stess formation. Generally, failure mechanisms differ from either continuous deep beams or simple supported deep beams. In continuous deep beams, a negative moment is occurred over intermediate support and the location of maximum moment coincide with high shear force. Therefore, failure usually occurs at this region. While on the other hand, in simple supported deep beam, the region of high shear coincides with the region of low moment. The web opening of deep beams for accepting a facility makes shear behaviors of deep beams more complex and gives rise to an expansion of crack around the opening and a decline of shear capacity of deep beams. Therefore, Engineers must determine a delicate reinforcement method to control a crack and increase a shear capacity. The purpose of this report is a computation of an effective reinforcement method through non-linear finite element method by means of adopting various reinforcement method as variables and a computation of shear capacity formula taking an effectiveness of reinforcement into consideration.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.945-953
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• 1997

Aromatic polyetherimide membranes were prepared by dry/wet phase inversion method and investigated regarding the pervaporation characteristic of water-alcohol mixtures by using the permselective property of imide group and the structure modification of skin layer of the membrane. The membrane selectivity increased with the reaction time of surface-modification, to some extent, and the density of top layer tends to increases with increasing the reaction time. In the case of dense membrane, the separation factor was 160 and 2000 for 90wt% ethanol mixture and 90wt% isopropanol solution, respectively, which implies that aromatic polyetherimide has a high permselectivity. The temperature dependence of permeation flux seems to follow an Arrhenius type at the temperature range of ($40^{\circ}C-70^{\circ}C$).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.273-279
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• 1999

The home-made hot wall epitaxy (HWE) system was utilized for GaN epitaxial layer growth on the Si(001) substrate. It was appeared that GaN epilayer grow with mixed phase of Zinc blende and Wurtzite structure from photoluminescence (PL) and x-ray diffraction (XRD) analysis at the room temperature. We found that intial growth layer has Wurtzite structure from photoluminescence (PL) and x-ray diffractio (XRD) analyses at the room temperature. Wefound that initial growth layer has Wurtzite structure when initial deposition time, the temperature of substrate and source are 4 min, $720^{\circ}C$ and $860^{\circ}C$ respectively, and at the epi growth process GaN, epilayer was grown with relatively stable Wurtzite structure when the temperature of substrate and source are $1020^{\circ}C$ and $910^{\circ}C$ respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.104-104
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• 2016

음극아크증착과 스퍼터링을 동시에 사용한 하이브리드 공정으로 제조된 TiAlSiN 코팅층의 물성을 평가하였다. TiAlSiN 코팅층은 음극아크 소스에 Ti-Al 타겟을 장착하고 스퍼터링 소스에는 Si 타겟을 장착하여 아르곤과 질소 가스의 혼합가스 분위기에서 스테인리스(SUS304)와 초경(cemented carbide; WC-15wt.%Co) 기판 위에 제조되었다. 음극아크 소스에 인가되는 전류는 고정하고 스퍼터링 소스에 인가되는 전력을 조절하여 TiAlSiN 코팅층의 Si 함량을 제어하였다. TiAlSiN 코팅층의 Si 함량이 증가하면 코팅층의 구조가 주상정에서 비정질 구조로 변화한다. 이는 Si 함량이 증가하면 코팅층에 형성되는 알갱이 구조의 크기가 줄어들기 때문이다. X-선 회절 결과와 Scherrer's equation을 이용하여 Si 함량에 따른 알갱이 구조의 크기를 계산하면 Si이 없는 코팅층은 약 14 nm의 크기를 보이며 8 at.% 이상의 함량에서 약 2.5 nm로 포화된다. TiAlSiN 코팅층의 경도를 Si 함량에 따라 측정하면 Si 함량이 증가하면 경도도 증가하는 경향을 보이며 약 9 at.%의 Si 함량에서 3200 Hv로 최대가 되고 이후에는 감소한다. TiAlSiN이 코팅된 스테인리스 시편을 대기에서 열처리하고 시편 무게증가를 측정하여 코팅층의 내열성을 평가하였다. Si 함량이 증가하면 내열성도 향상되는데 14.4 at.%의 Si 함량에서 $700^{\circ}C$까지 무게 증가가 없으며 $900^{\circ}C$까지 0.43 mg의 증가를 보인다. 본 실험을 통해서 얻어진 TiAlSiN 코팅층은 비교적 높은 경도와 내열성을 확보하여 절상공구 보호막 코팅 소재 등으로 활용이 가능할 것으로 판단된다.