• Steel and Composite Structures
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• 제26권6호
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• pp.663-672
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• 2018

This paper contains a consistent couple-stress theory to capture size effects in Euler-Bernoulli nano-beams made of three-directional functionally graded materials (TDFGMs). These models can degenerate into the classical models if the material length scale parameter is taken to be zero. In this theory, the couple-stress tensor is skew-symmetric and energy conjugate to the skew-symmetric part of the rotation gradients as the curvature tensor. The material properties except Poisson's ratio are assumed to be graded in all three axial, thickness and width directions, which it can vary according to an arbitrary function. The governing equations are obtained using the concept of minimum potential energy. Generalized differential quadrature method (GDQM) is used to solve the governing equations for various boundary conditions to obtain the natural frequencies of TDFG nano-beam. At the end, some numerical results are performed to investigate some effective parameter on buckling load. In this theory the couple-stress tensor is skew-symmetric and energy conjugate to the skew-symmetric part of the rotation gradients as the curvature tensor.

• 한국정보통신학회논문지
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• 제10권5호
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• pp.905-909
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• 2006

최근 시야각 개선을 위한 다양한 커브형 집적 영상 시스템이 연구되어 왔지만, 광학적 구현에 있어서 한축으로만 제한되었다. 본 논문에서는 기존의 집적 영상 시스템에서 큰 구경의 렌즈를 추가적으로 사용하여 구현되는 전방향 커브형 집적 영상 시스템을 제안하고, 제안하는 시스템에서의 요소영상을 제작하는 방법을 설명한다. 제안한 시스템은 모든 방향에 대해서 커브 효과를 제공할 수 있고, 단순한 시스템의 구조를 가지는 것을 특징으로 한다. 전방향 커브형 집적 영상 시스템에 대해서 John 행렬을 도입한 기하광학적 분석을 수행하고, 이를 이용하여 새로운 요소 영상을 제작하였다. 제작한 요소영상의 성능을 확인하기 위해서 기초적인 광학적 실험을 수행하고, 그 실험 결과를 보고한다.

• 한국재난정보학회 논문집
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• 제10권3호
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• pp.458-464
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• 2014

화재방호계통 스프링클러 시스템의 경우 지진 발생 시 그리고 지진 발생 후에 유도되는 화재로부터 건물과 인명을 보호하고 에너지를 공급을 위한 필수 요소라 할 수 있다. 본연구의 주목적은 양방향 (x, y) 그리고 3축(x, y, z)방향의 지진의 영향을 받는 저층 건물에 설치된 복층구조 스프링클러 파이프라인의 거동과 내진성능을 평가 하고자 함이다. 결과적으로 건물의 비구조 요소인 스프링클러 파이프라인의 경우 각 층별로 다른 거동을 보이고 있으며, 또한 수직 방향의 지진의 경우 수평방향의 지진보다 파이프라인에 미치는 영향은 미미하다고 볼 수 있다.

• 한국정밀공학회지
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• 제25권11호
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• pp.126-133
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• 2008

Rapid Prototyping (RP) has been widely used for rapid development of prototypes in various industrial fields. In recent years, a new requirement in RP industry has issued so as to directly manufacture a functional prototype which has enough mechanical properties to be used as a functional part. The RP prototype, however, has a limitation in mechanical properties due to its layer-by-layer manufacturing process. This manufacturing process results in anisotropy of the prototype, especially showing weakness in the building direction. In the present work, we performed tensile tests for RP prototypes in order to determine directional mechanical properties. The test specimens were made by using $Eden330^{TM}$ by Object Geometries Ltd. Finite element analyses considering material anisotropy were then carried out for RP prototypes with various building directions. Effect of the building direction on the mechanical strength was investigated through the analysis, and compared with experimental results.

• 한국재료학회지
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• 제12권4호
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• pp.254-258
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• 2002

To realize channel cross-connecting in optical communications systems, a high speed optical matrix switch was fabricated using z-cut $LiNbO_3$. For switch fabrication was design bending structure and coupling length and four $2{\times}2$ directional couplers were integrated on one substrate far construction of a $4{\times}4$ switch. Single-mode optical waveguides were formed by Ti-diffusion at a wet $O_2$ atmosphere. Ti-diffusion profile, refractive index variation and waveguide morphology were analyzed by Prism coupler and optical microscopy, respectively.

• 화약ㆍ발파
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• 제34권3호
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• pp.1-9
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• 2016

성형폭약의 조절발파 효과를 확인하기 위하여 정밀폭약에 금속라이너의 재질과 두께를 달리하여 상대적으로 폭속이 작은 암석 절단용 성형폭약을 제작하였다. 성형폭약이 암반 내부에서 기폭될 때 방향성 절단을 유도하기 위하여 폭약 양쪽으로 금속라이너를 부착하였다. 또한 콘크리트 부재 실험을 통하여 성형폭약의 성능을 확인하였고 성형폭약과 공벽과의 적정 이격거리를 유지하기 위한 센터 가이더를 제작하였다. 실험결과 0.8mm 두께의 Fe 라이너가 장착된 성형폭약을 사용할 때 가장 깊은 노치가 형성되었고, 콘크리트 부재의 방향성 절단을 확인할 수 있었다.

• 상하수도학회지
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• 제29권3호
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• pp.371-380
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• 2015

Particulate matters in a water distribution system are main causes of turbidity and discoloration of tap water. They could be removed by conventional or uni-directional flushing in a water distribution system. The behaviors and required flow velocity of particles are not well known for their flushing. A model water main and hydrant were made from transparent acrylic pipe of 30mm and 16mm in diameter, respectively. We analyzed the effect of flushing velocity, particle density, and particle diameter. We found that the existence of break-though velocities at which particles begin to be removed, and which are affected by their physical properties. The removal efficiencies seemed to be influenced by resuspension capabilities related to their upward movement from the bottom. Heavy particles like scale were hard to remove through upflow hydrant because the falling velocity, calculated using Stokes' law, was higher. Particle removal efficiencies of upward hydrant and downward drain showed minor differences. Additionally, the length between hydrant and control valve affected flushing efficiency because the particulate matters were trapped in this space by inertia and recirculating flow.

• 전자공학회논문지B
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• 제28B권11호
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• pp.852-858
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• 1991

An adaptive hierarchical classifier(AHCL) for Korean character recognition using a neural net is designed. This classifier has two neural nets: USACL (Unsupervised Adaptive Classifier) and SACL (Supervised Adaptive Classifier). USACL has the input layer and the output layer. The input layer and the output layer are fully connected. The nodes in the output layer are generated by the unsupervised and nearest neighbor learning rule during learning. SACL has the input layer, the hidden layer and the output layer. The input layer and the hidden layer arefully connected, and the hidden layer and the output layer are partially connected. The nodes in the SACL are generated by the supervised and nearest neighbor learning rule during learning. USACL has pre-attentive effect, which perform partial search instead of full search during SACL classification to enhance processing speed. The input of USACL and SACL is a directional edge feature with a directional receptive field. In order to test the performance of the AHCL, various multi-font printed Hangul characters are used in learning and testing, and its processing its speed and and classification rate are compared with the conventional LVQ(Learning Vector Quantizer) which has the nearest neighbor learning rule.

• 복식
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• 제65권2호
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• pp.144-156
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• 2015

This research aims to develop textile patterns using mythical motives based on Buldoje in the Jeju myth. this textile design is not only decoration effect by filling the space, but also plays the original role of a pattern by expressing its symbolic meaning. The research methods are as follows: 1) Using integral analysis on materials related to the myth of Jeju and Gime used in Buldoje Gut, where Halmangbonpuli story is performed to set formative elements for textile design and their meanings; 2) Designing motive by composing formative elements; 3) Coloring properly; and 4) Layout motives. Adobe CS5 (Photoshop, Illustrator) and TexPro, a design CAD program, were used for textile design. Motives were combined in a various ways. Two-directional, four-directional, set, rotating, toss layout techniques, which are frequently used in apparel design and able to reduce cloth use, were used in developing patterns. Coloring methods including tone-in-tone and Faux camaieu were used to deliver coherence and soft effects. Developed textile design symbolizes the desire for the conception of a child, birth, and health, so it is made on baby clothes. In doing so, the plan for development of a fashion-cultural product applying Jeju myth symbol is suggested.

• 조명전기설비학회논문지
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• 제29권2호
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• pp.82-90
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• 2015

This paper proposes an efficient bi-directional DC/DC converter topology using multi-phase interleaved method for power storage system. The proposed converter topology is used for a power storage system using a vanadium redox flow battery(VRFB) and is configured to enable bidirectional power flow for charging and discharging of VRFB. Proposed DC/DC converter of the 4 leg method is reduced to 1/4 times the rating of the reactor and the power semiconductor device so can be reduce the system size. Also, proposed topology is obtained the effect of four times the switching frequency as compared to the conventional converter in each leg with a 90 degree phase shift 4 leg method. This can suppress the reduction of the life of the secondary battery because it is possible to reduce the current ripple in accordance with the charging and discharging of VRFB and may increase the efficiency of the entire system. In this paper, it proposed bidirectional high-efficiency DC/DC converter topology Using multi-phase interleaved method and proved the validity through simulations and experiments.