• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.192.2-192.2
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• 2012

위성시스템 소형화, 탑재체 수용증대, 발사비용절감, 탐사임무 효율화 등의 요구로 인하여, 위성 설계에 있어 경량화는 오랜 기간 진행되어온 연구 주제였다. 이러한 연구결과로서, 위성 구조체를 복합재료로 대신하기 위한 구조 경량화 연구와 적용이 성과를 거두었으며, 현재 위성체 프레임이나 전개형 안테나, 광학구조물 등에 경량 탄소섬유 강화 복합재료의 적용은 보편화되어 있다. 한편, 위성시스템에서 전력, 통신, 명령/데이터처리, 자세제어 및 관측기기의 각종 전자장비를 보호하는 하우징 구조물에는 여전히 금속재료가 광범하게 적용되고 있다. 특히, 알루미늄 합금은 하우징 재료로 널리 사용되는데, 강도, 강성, 열전달, 우주방사, 전기전도도 및 EMI 차폐특성과 더불어 가공성이 우수하다는 장점을 지닌 반면에, 금속재료로서 중량이 상당하여 위성 경량화 관점에서는 한계를 갖게 하는 단점이 있다. 전자장비에 부여된 전자기능 측면에서 보면, 하우징은 기생 구조물로서, 경량으로 제공될수록 전자장비 전체 무게에서 전자유닛만의 무게가 차지하는 전기전자기능비가 향상되고 위성 경량화에 크게 기여할 수 있다. 구조 경량화를 위하여 전자장비 하우징을 경량 복합재로 대체하여 설계 및 제작하였으며, 복합재 하우징의 강도, 강성, 열전달, 우주방사, 전기전도도 및 EMI 차폐를 검증할 수 있는 방법에 대하여 검토하였다.

• 건축구조
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• v.8 no.3
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• pp.40-41
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• 2001

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.9-17
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• 2005

The aeroelastic stability enhancement of composite hingeless rotor system through the structural damping increase has been investigated. In order to increase structural damping of the rotor system, constrained layer damping (CLD) treatment is applied to the composite flexures. Modal analysis of composite flexures with attached viscoelastic and constraining layers are performed using MSC/NASTRAN, and the effectiveness of CLD treatments are validated through modal test. The composite flexures with CLD are applied to a hingeless rotor system. The rotor system is tested in hovering condition and it is shown that in-plane damping is increased by means of CLD treatments.

• 한국정보통신설비학회:학술대회논문집
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• 2002.08a
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• pp.137-139
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• 2002

본 논문은 FTTC용 공유급전시스템을 구성하기 위한 광동복합케이블 연구에 관련한 것이다. 광섬유 및 구리 도체를 하나의 케이블에 포함한 복합케이블은 공유급전 시스템에서 포설 비용 절감 및 서비스의 운용 및 유지 보수의 효율 향상을 가능하게 한다. KT 운용시스템연구소의 공유급전 시스템 구성에 따라서 세 가지 type의 광동복합 케이블을 설계하였다. 구리 도체로는 200Vdc 출력 전력을 최대 500m까지 급전을 지원하는 0.65mm 직경의 구리 도체가 선정되었으며 KT 규격을 만족하는 일반 단일모드 광섬유가 적용되었다. 케이블 구조는 다심화에 유리하고 중간분기가 용이한 loose tube형 구조를 채택하였으며, 다심 케이블에서는 stranding된 3층의 집합 코아를 가지도록 설계하였다. 다심의 광동복합케이블은 32심 광섬유와 18페어(pair)의 동선을 실장하여, 두 조의 케이블로 32개의 ONU의 광신호전송 및 전력 공급이 가능하도록 하였다. 또한 포설 및 중간 분기 작업시 광섬유로의 접근이 용이하게 하기 위해 광섬유 튜브를 최외층에 배치하였다. 복합케이블은 상용 loose tube형 광케이블과 동일한 공정으로 제작되었으며, 기계적 및 환경적 특성에서 KT 규격을 만족하는 것을 확인하였다.

• Composites Research
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• v.14 no.1
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• pp.47-56
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• 2001

In order to enhance high speed stability the composite air spindle system composed of a high modulus carbon fiber composite shaft, powder contained epoxy composite squirrel cage rotor and aluminum tool holder was designed and manufactured. For the optimal design of the composite air spindle system, the stacking sequence and thickness of the composite shaft were selected by considering the fundamental natural frequency and deformation of the system. The analysis gave results that the composite air spindle system had 36% higher natural frequency relative to a conventional air spindle system. The dynamic characteristics of the composite spindle system were compared with those of a conventional steel air spindle system. From the calculated and test results, it was concluded that the composite shaft and the power contained composite rotor were able to enhance the dynamic characteristics of the spindle system effectively due to the low inertia and high speific stiffness of the composite materials.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.3
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• pp.304-309
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• 2014

In this paper, we design a hybrid wheeled and legged mobile robot with a waist joint. The proposed hybrid mobile robot is designed to have a hybrid structure with leg and wheel for the efficient movement in flat and uneven surfaces. The proposed robot have a waist joint that is used to stably transform from wheeled driving to legged walking of the robot and to overcome non-flat surface. In order to recognize various environments we use LRF sensor, PSD sensor, CCD camera. Also, a motion planning method for hybrid mobile robot with a waist joint is proposed to select wheeled driving motion and legged walking motion of the robot based the environment types. We verify the efficient mobility of the developed hybrid mobile robot through navigation experiments using the proposed motion planning method in various environments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.4
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• pp.201-208
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• 2003

The Hybrid Wall System(HWS) building composed of center core reinforced concrete walls and exterior steel frame has open space around the center core walls. It is necessary to develop design methodologies for the HWS building that the coupled shear walls withstand the most of lateral load and expect the most energy dissipation at the coupling beams and at wall foots. Major factors considered in this paper are connection type of coupling beams and scale of story. The studies of the system are investigated in terms of shear force, overturning moment, maximum lateral displacement, story drift ratio, and dynamical characteristics under the action of vertical and lateral forces such as wind and seismic loads.

• Composites Research
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• v.24 no.4
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• pp.41-47
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• 2011

This paper deals with anisotropic property and structural analysis for short fiber reinforced plastic composites manufactured by the injection molding process. The common approach for modeling this type of material is the consideration of the material as homogenous and isotropic. However, the common isotropy approach often results in unexpected failure. To overcome this, new structure analysis methodology was developed in order to consider fiber orientation effect using injection mold flow analysis and Halpin-Tsai equations for unidirectional composites and taking an orientation average. The numerical predictions are compared to experimental data for tensile specimen. The predicted mechanical properties agree well with experimental data for fiber orientation and weld line effect. The analysis system was also applied to an automobile part. The proposed anisotropic model predicted different mechanical properties by position of the part and different mechanical performance of the part was changed according to injection gate position.

• Composites Research
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• v.31 no.3
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• pp.104-110
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• 2018

This study is to propose the structural design and analysis procedure about composite blade and tower of vertical axis wind turbine technology. In this study, structural design of tower for vertical axis wind turbine was performed after vertical blade design and manufacturing. The structural design requirement and specification of blade and tower was investigated. After tower of structural design, the structural analysis of the tower was conducted by the finite element method. It was performed that the stress, deformation and natural frequency analysis at the applied loading. The design modification of tower configuration was proposed by structural analysis. It was confirmed that the final designed tower structure is safety through the structural analysis.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.106-111
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• 2018

Hydrodynamic ram phenomenon could be generated by external threats such as impact and blast in the aircraft. High strain rate deformation caused by the hydrodynamic ram phenomenon is one of the main factors to influence structural survivability. Mechanical properties of composite structure change rapidly under conditions of high strain rate. Therefore, it is necessary to experimentally investigate the influence of strain rates for aircraft structural survivability. In this paper, tensile tests of composite material were conducted for low and high strain rates to investigate the influence of the various strain rates. Tensile modulus increases more compared to tensile strength at high strain rate under hydrodynamic ram condition. Regression analysis was conducted to predict tensile modulus at various strain rates because it is one of the main damaging factors for composite structures under high strain rate conditions. Also, the mechanical properties of composite materials were acquired and analyzed under high strain rate conditions. It is hypothesized that the results from this study would be used for designing aircraft composite structures and evaluation considering structural survivability.