• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.116-116
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• 2004

편마비 환자의 보행운동 개선을 위한 보조기구로 족부보장구(Ankle Foot Orthosis, A.F.O.)가 활용되고 있다 족부보장구는 Fig. 1에 제시한 바와 같이 보행특성상 무수히 반복되는 충격과 굽힘하중을 받는다. 따라서 족부보장구용 재료는 피로특성이 우수한 탄소섬유 강화재(Carbon Fiber Reinforced Plastic, 이하 CFRP)를 주로 사용한다. 그러나 CFRP의 상용재인 프리프레그(prepreg)는 강한 이방성의 단방향 섬유이므로 섬유방향과 하중작용방향의 관계에 매우 민감하다.(중략)

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.86.2-86.2
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• 2012

산화금속은 높은 결정성, quantum size effect, 높은 투과도, 대기중의 안정도 등과 같은 탁월한 성질들로 인하여 오늘날 실리콘의 대체물로서 많은 연구가 보고되고 있다. 이러한 금속산화물의 크기와 모양을 조절하며 대량 생산하기 위한 합성방법으로 가수분해, 금속양이온 응축법과 같은 다양한 수용액상 방법이 연구되고 있다. 하지만 2차원 단일 층에 나노물질을 정렬하고 전기적 접합을 형성하는 것이 매우 어렵다는 점 때문에 나노물질을 기판 위에 자유롭게 성장시키는 방법에 대해서는 아직 많이 보고 되어있지 않다. 본 연구에서 저온의 수용액에서 1차원의 나노막대가 2차원의 스피넬 구조 위에 heteroepotaxial 접합을 이루며 성장시키는 방법을 이용하였다. P-n접합 형성을 위하여 (0001)방향으로 배향된 n-type ZnO 나노막대를 (111)방향의 p-type Co3O4 나노플레이트 위에 성장시킨 구조를 제작하였으며 이를 바탕으로 다이오드소자를 제작하여 ideal factor, turn-on voltage, rectifying ratio등의 전기적 특성을 평가하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.4
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• pp.6-14
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• 1982

Both the power increasing of a television broadcasting channel for the purpose of minimiaing weak signal areas and depressing of radiation pattern to prevent some interference in known quadrants may be needed in TV broadcasting. This study shows that, the two needs mentioned above are solvable by adjusting the phases of feeding points, or redesigning the lengths of feeder lines between transmitter outend and feeder inputs in super gain antenna. A theoretical study on lengths of coaxial cables and a practical procedure of designing cable lengths, which is simple and inexpensive to apply, is presented.

• Polymer(Korea)
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• v.27 no.4
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• pp.313-322
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• 2003

The morphology of poly(ethylene terephthalate) (PET)/poly(m-xylene adipamide) (MXD-6) blends, which was prepared by adding compatibilizer and interchange reaction agent, was investigated. The morphological change in the stretched blend films was also studied. The stretched film showed a dispersed MXD-6 fibril. This fibril became finer with increasing draw ratio (DR). The addition of compatibilizer and interchange reaction agent had no effect on the improvement of interfacial adhesion but caused a defect between the continuous phase and the dispersed phase, leading to the formation of irregular fibril. The change in the superstructure of blends with composition and draw ratio was examined with light scattering (LS). The H$\sub$v/ LS patterns showed a double-cross type pattern consisting of a broad rod-like pattern and a sharp cross streak. On the basis of the model calculation of the H$\sub$v/ pattern, it was found that the appearance of the double-cross type pattern was attributed to the stacking of crystals oriented along the draw direction. The crystals were gradually oriented to the stretching direction with draw ratio. As a result, the high level of orientation was obtained fur the sample of draw ratio is 6.0.

• Polymer(Korea)
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• v.24 no.6
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• pp.860-868
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• 2000

In this work, the electro-magnetic interference (EMI) characteristics of PAN-based carbon fibers-reinforced composites are investigated with difference to manufactural parameters, i.e., fiber grade, fiber orientation angle, and laminating method. As a result, EMI shielding effectiveness (SE) of the composites greatly depends on a fiber orientation in composite angle. Especially, the fiber grade affects SE of composites in case of orientation angle of 0$^{\circ}$. Then the SE become greater as the change of electric character according to the arrangement directions, i.e., electrical anisotropy in the same constituent materials. This is due to the skin effect which is represented in the surface of electro-magnetic wave in high-frequency range. In all cases according to lamination methods, the composites represents SE of 83~98% over. Whereas, in symmetric and unsymmetric laminate structures, the SE decreases slightly as the laminate angles of composites increases. On the contrary. the repeating laminates structure shows the opposite tendency. Especially, 90$^{\circ}$ repeating laminate structure shows the SE more than 90% over the measuring frequency.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.119-120
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• 2011

Kawazoe는 1997년 p-type TOS를 만들기 위해서는 3가지가 충족되어야 한다고 언급한바 있다. 첫 번째, 가시광영역에서 투명하기 위해서 cation의 d10s0이 가득 차야 한다. 가득 차지 않은 d10 shell은 광 흡수가 가능하여 투과도를 떨어뜨린다. N-type을 예로 들어 ZnO, TiO, In2O3가 각각 Zn2+, Ti4+, In3+가 되어 d shell을 가득 차게 만드는 것을 볼 수 있다. 두 번째, cation d10s0 shell은 산소의 2p shell과 overlap 되어야 한다. 이 valence band는 홀 전도를 더욱 좋게 한다. 예를 들어 Cu1+(3d), Ag1+(4d)가 해당한다. 세 번째로, 양이온과 산소간의 공유결합을 강하게 하기 위해서 결정학적 구조는 매우 중요하다. Delafossite 구조는 산소가 pseudo-tetrahedral 구조로서 공유결합에 유리하다. 이러한 환경은 O2- (2p6)을 형성하고 홀의 이동도를 증가시킨다. 예를 들어 Cu2O의 경우 앞의 2가지를 만족시키지만 광학적 특성에서 좋지 않다. 그 이유가 3번째 언급한 결정학적인 요인에 있다. 결정 계의 환경은 Cu2O를 따라가면서 3차원적인 연결을 2차원적으로 변형된 delafossite 구조에서는 quantum well이 형성되어 band gap이 커진다. 본 연구에서는 전기적 이방성을 가지고 있는 delafossite CuCrO2 상에서 우선배향을 일으키는 인자 중 기판을 변화시켜 실험을 진행하였다. 결과적으로 기판변화를 통해 우선배향조절이 가능하였으며 CuCrO2 박막을 시켰으며, 결정방향에 따른 전기적 물성의 이방성에 관한 연구는 계속 진행 중에 있다. c-plane sapphire 기판위에는 [00l]로 성장하는 반면, c-plane STO 기판 위에는 [015] 방향으로 성장하는 것을 확인하였다. 이러한 원인은 기판과 증착되는 박막간의 mismatch를 최소화 하여 strain을 줄이고, 계면에서의 Broken boning 수를 줄여 계면에너지를 낮추는 방법이기 때문일 것으로 예상된다. C-plane sapphire 기판위에 증착될 경우 증착온도가 증가함에 따라 c-축으로의 성장이 온전해지며 이에 따라 캐리어농도의 감소와 모빌리티의 증가가 급격하게 변하는 것을 확인할 수 있다. 반면 c-plane STO 기판에서는 증착온도에 따른 박막의 배향변화가 없으며 전기적 물성 변화 또한 비교적 작은 것을 간접적으로 확인하였다.

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.81-86
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• 2011

The aqueous solution of Sunset Yellow-FCF (SY-FCF) began to show schlieren texture at room temperature when its concentration reaches 25 wt%. A further increase of the concentration of SY-FCF to 28 wt% resulted in a perfect nematic liquid crystal phase. However, more than 30 wt% of SY-FCF in aqueous solution was required to make an optically anisotropic film simply by shear coating. In our study, concentration of SY-FCF solution, coating speed, drying temperature, and relative humidity were considered as coating parameters affecting the preparation of optically anisotropic thin films. From analysis of variance analysis (ANOVA), the solution concentration was revealed as a main factor affecting the film thickness. The drying temperature and solution concentration were main factors affecting the transmittance of parallel direction ($T_o$). Especially, SY-FCF aqueous solution with high concentration induced a better alignment of LC columns and produced highly oriented anisotropic films. In this study, optically anisotropic films prepared by 33 wt% of SY-FCF in aqueous solution showed 89.7~98.7% of degree of polarization.

• The Journal of the Petrological Society of Korea
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• v.16 no.1 s.47
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• pp.12-26
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• 2007

We have studied orientational characteristics of vertical rift and grain planes developing in 108 quarries for Mesozoic granites. Orientations of these planes vary in different localities. In general, orientations of these planes are predominantly NNE in South Korea. From the regional distribution chart, orientations of these planes show three dominant sets in terms of frequency orders: (1) $N2{\sim}10^{\circ}E(1st-order),\;(2)\;N15{\sim}25^{\circ}E(2nd-order),\;(3)\;N45{\sim}70^{\circ}E,\;N10{\sim}30^{\circ}W\;and\;N70{\sim}80^{\circ}W(3rd-order)$. These granite quarries are classified by the relative difference in the easiness of rock splitting between horizontal and vertical quarrying planes into: R-type, G-type, and H-type. The results showed that quarries for Triassic granites belong to R and G-types;those for Jurassic granites belong to R, G and H-types. In addition, quarries for Cretaceous granites belong mainly to R-type. Among these quarry types, the most diverse type was identified in the quarries for Jurassic granites. R-type (77.8%) shows a higher distribution ratio compared with G and H-types (22.2%). In general, anisotropy of physical properties is found in granitic rocks and there exists close correlation between orientations of granitic rock splitting planes and those of the open microcracks. Meanwhile, it has been reported that preferred orientations of open microcracks suggest maxinum principal stress orientations.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.115-135
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• 2009

We have studied general orientational characteristics of microcracks distributed in Tertiary crystalline tuff from the northeastern part of the Gyeongsang Basin. 108 sets of microcracks on horizontal surfaces of 6 rock samples from Heunghae-eup and Cheongha-myeon, Pohang-si areas were distinguished by image processing. Those microcrack sets show a distinct linear array in 38 images. Whole domain of the directional angle(${\theta}$)-frequency(N) chart for crystalline tuff can be divided into 20 domains in terms of the phases of the distribution of microcracks. From the related chart, microcrack sets show preferred orientation which are coincident with the direction of vertical common joints. Consequently, the potential for macroscopic vertical joints in a rock body can be inferred from the directional angle showing high frequency in each domain of the related chart. This joint pattern is nearly the same in Mesozoic granites from Seokmo-do, Gwanghwa-gun. From the rose diagram for orientations of microcrack in crystalline tuff, orientations of dominant sets of microcracks in terms of frequency orders reflect representative orientations of maximum principal stress acted on crystalline tuff. Meanwhile, orientations of microcracks in crystalline tuff were compared with those of open microcracks in Bulgugsa granites from the southwestern part of the Gyeongsang Basin, and vertical rift/grain planes from Mesozoic granite quarries in Korea. In regional distribution chart, the agreement of distribution pattern between above two types of microcrack sets and vertical planes suggests that microcrack systems developed in crystalline tuff probably occur regionally in Mesozoic granites in Korea.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.107-107
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• 2014

p형 자원 친화형 산화물 기반 능동형 층 성장에 대한 연구는 아직 개발 초기 단계이다. $Cu_2O$는 이러한 자원 친화형 저가 p형 산화물 중 하나로서 다양한 광학 응용분야에 있어 적용되고 있으며 특히 저가형 증착법인 전기증착법을 통해 형성시킨다면 가격 절감을 극대화 시킬 수 있다. 하지만 낮은 전도성으로 인해 전자소자에는 적용시키기 어렵다는 단점이 있기 때문에 본 연구팀은 5족 물질인 Antimony 를 $Cu_2O$의 p형 도펀트로 적용시켜 전기적 구조적 특성을 개선시키고자 하였다. 결과적으로 [111] 방향으로 높은 우선배향성을 갖고 전도성이 향상된 Sb-Cu2O 박막을 확인하였다.