• Computational Structural Engineering
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• v.11 no.1
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• pp.38-45
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• 1998

최근 국내외에서 활발히 개발되고 있는 지진격리 시스템은 원자력 발전소, 교량, 중요한 공공건물 등의 지진피해를 최소화하기 이하여 널리 적용되고 있다. 그리고 다른 방법에 비하여 경제성 및 효율성이 우수하기 때문에 관련 연구 및 응용이 활발히 진행되고 있다. 이에 따라 국내외에서 격리시스템의 비선형성과 구조물의 불연속성을 고려한 지진격리 구조물의 해석을 통한 거동을 규명하는 연구가 과거 수년간 활발히 진행되어 왔다. 당사(금호건설)는 상부하중 지지능력과 감쇠능력이 우수한 지진격리장치를 개발하였으며 지진격리장치를 설치한 교량의 지진해석을 수행하여 본 지진격리 시스템의 이론적 성능을 파악하였다. 본 수치해석은 CrayC94에 탑재된 비선형 해석에 뛰어난 것으로 알려진 ABAQU를 이용하였다. 본 지진격리 시스템은 적층고무받침(Laminated Rubber Bearing)과 PTFE 미끄럼받침으로 구성되어 있으며, 적층고무받침은 주로 복원력을 제공하며 PTFE 미끄럼받침은 상부하중을 지지하며 마찰감쇠를 제공하여 에너지를 소산하는 역할을 한다. 본 수치해석에서는 선형스프링과 마찰요소를 이용하여 각각을 모형화하였다. 개발된 지진격리 시스템이 주로 사용될 상판자중이 무거운 다경간 연속 PC Box Girder교를 모델교량으로 선택하여 해석을 수행하였으며 수치해석에 사용된 격리시스템의 사전에 수행된 동특성 실험결과를 활용하였다. 이러한 해석을 통하여 이론적 효율성을 파악할 수 있었다.

• Composites Research
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• v.13 no.6
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• pp.30-38
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• 2000

In this paper, a system of falling weight impact tester was built up to evaluate the impact energy absorbing characteristics and impact strength of CFRP laminate plates in consideration of stress wave propagation theory. Delamination area of impacted specimens for the different ply orientation was measured with ultrasonic C-scanner to find correlation between impact energy and delamination area. Absorbed energy of quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the more absorbed energy. Hybrid specimen containing GFRP layer was higher than that of normal specimens.

• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.33-41
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• 2022

This paper describes a planar microstrip patch antenna designed on dielectric substrate. Two types of planar microstrip patch antennas are studied for the 5G wireless applications, one type is conventional microstrip structure, the other type is stacked microstrip structure fed by coaxial probe. Using electromagnetically coupling method, stacked microstrip patch antenna employing a multi-layer substrate structure was designed. The results indicate that the proposed stacked microstrip patch antenna performs well at 5G wireless service bandwith a broadband from 3.42GHz to 3.70GHz. The impedance bandwidth(VSWR≤2) is 360MHz(10.28%) from 3.42GHz to 3.78GHz. In this paper, through the designing of a stacked microstrip patch antenna, we have presented the availability for 5G wireless repeater system.

• Journal of Korean Society of Steel Construction
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• v.29 no.6
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• pp.435-442
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• 2017

A lateral load resisting system is a necessary structural element for the mid- to high-rise modular buildings and concrete cores are known as the most typical lateral load resisting systems in 10- to 20-story modular buildings. It is difficult to construct a concrete core simultaneously with the installation and finishing work of modular units because concrete placed using wet methods might contaminate or destroy the modular unit. Therefore, we have developed a hybrid PC (precast concrete) panel construction method that can construct a concrete core together with the installation of modular units. The hybrid PC panel is a load-bearing element in which a pair of C-shaped beams are combined at the top and bottom of a concrete wall. Concrete cores can be constructed by dry method to connect the hybrid PC panels with bolts. In this study, the details and connection of hybrid PC panels are improved to have the lateral performance comparable to reinforced concrete structural walls and are verified through FE analysis.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.31-35
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• 2006

This paper is studied on a protective control system for electrical fire used electrical characteristics of SCR and multilayer-type PTC thermistor. The PTC thermistor has characteristic or positive resistivity temperature coefficient according to the temperature variation, which is construction of a regular square and cube demarcation with $BaTiO_{3_}$Ceramics of positive temperature coefficient. Also PTC shows the phenomenon which is rapidly increased in the resistivity if the temperature is increased over Curie temperature point. This paper is proposed on a protective control system used multilayer-type PTC which is protected from electrical fire due to electric short circuit faults or overload faults. Some experimental results of the proposed apparatus is confirmed to the validity of the analytical results.

• Composites Research
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• v.17 no.3
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• pp.29-37
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• 2004

The aeroelastic stability analysis of composite bearingless rotors is investigated using a large deflection beam theory in hover. The bearingless rotor configuration consists of a single flexbeam with a wrap-around type torque tube and the pitch links located at the leading edge and trailing edge of the torque tube. The outboard main blade, flexbeam and torque tube are all assumed to be an elastic beam undergoing flap bending, lead-lag bending, elastic twist and axial deflections, which are discretized into beam finite elements. For the analysis of composite bearingless rotors, flexbeam is assumed to be a rectangular section made of laminate. Two-dimensional quasi-steady strip theory is used for aerodynamic computation. The finite element equations of motion for beams are obtained from Hamilton's principle. The p-k method is used to determine aeroelastic stability boundary. Numerical results are presented for selected bearingless rotor configurations based on the lay-up of laminae in the flexbeam and pitch links location. A systematic study is made to identify the importance of the stiffness coupling terms on aeroelastic stability for various fiber orientation and for different configuration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.143-150
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• 2015

At present, the actual condition is that Korean modular structures are limited to a low rise detached house and military barracks. And there is no standardized structural design method of stacked modular structure. Accordingly, in general, they don't review impact force in the stage of stacking and installing a module, the effect which wind load has on a structure in the stage of lifting, and inertial force occurring in the stage of lifting or transporting a module in the process of constructing a structure. Therefore, this study investigated the construction method of modular system to be studied in stages, and decided on the position to which load was applied and boundary condition in structural analysis at each construction stage. Besides, inertial force according to each speed was calculated in the lifting and wheeled transport of module. And we calculated impact load according to lifting speed in module stacking and installation work and wind load due to instantaneous wind speed in the installation work by lifting. On the basis of the suggested method, in the modular system to be studied, it carried out review of structure by changing determining conditions of load being applied by construction stage, such as in the stage of lifting, in the stage of transport, and in the stage of installation, and drew construction conditions securing stability structurally.

• Journal of Korea Ship Safrty Technology Authority
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• s.37
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• pp.2-11
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• 2014

본 연구에서는 최근, 전기자동차 및 소형 레저용 선박을 중심으로 연구가 진행 중인, 대용량 이차전지의 용량 증대를 위하여 필요한 내부 전극 접합 기술에 관하여 연구하였다. 종래의 초음파 용접으로 적층할 수 있는 적층량의 한계를 극복하기 위한 방안으로 전극 소재에 직접 가열을 통한 용접 방법이 아닌 용가제 금속을 적용하여 전극을 접합시켜, 통전성과 인장강도를 증대시킴과 동시에 열적요인으로 인한 전극표면에 화학적 활성물질의 변성을 최소화할 수 있는 저온 접합 방법에 대하여 연구하였다. 부연하여 용접을 위하여 무리하게 출력을 상승시킬 경우 용접열의 영향으로 전극의 변형 및 활성물질의 변성을 야기함과 동시에 최종 페키징 이후 출력저하, 발열 등, 배터리의 안정성을 저하시키는 요인으로 작용한다. 따라서 본 연구에서는 고주파 유도가열을 통한 유도 가열 방식의 접합 방법과 용융 도금을 통한 용가제 금속의 전처리를 통한 종래와는 차별화된 전극접합 방법을 소개한다.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.686-692
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• 2012

Solid free-form fabrication (SFF) technology was developed to fabricate three-dimensional (3D) scaffolds for tissue engineering (TE) applications. In this study, we developed a polymer deposition system (PDS) and created 3D microstructures using a bioresorbable polycaprolactone (PCL) polymer. Fabrication of 3D scaffolds by PDS requires a combination of several devices, including a heating system, dispenser, and motion controller. The system can process a polymer with extremely high precision by using a 200 ${\mu}m$ nozzle. Based on scanning electron microscope (SEM) images, both the line width and the piled line height were fine and uniform. Several 3D micro-structures, including the ANU pattern (a pattern named after Andong National University), $45^{\circ}$ pattern square, frame, cylindrical, triangular, cross-shaped, and hexagon, have been fabricated using the polymer deposition system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.260-261
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• 2007

본 논문에서는 800MHz와 1.9GHz 대역의 시스템에 적용할 수 있는 20dB 방향성 결합기를 8층 PCB 기판에 내장하여 소형화 및 저가화 할 수 있도록 설계하였다. 방향성 결합기는 4층과 6층에 coupled line으로 적층함으로써, 다층 PCB기판을 최대한 활용하여 공간을 최소화하였다. 또한, 고유전율을 가진 필름을 이용하여, coupled line의 끝에 내장형 고용량 커패시터를 연결하여 설계하였다. 6 $\times$ 6 $\times$ 0.7 (height)$mm^3$ 크기로 설계된 방향성 800MHz 결합기의 경우 -20dB의 coupling 특성, -0.6dB의 transmission 특성, -25dB의 isolation 특성을 나타내었다. 패키징 기판에 내장된 방향성 결합기는 단말기 및 통신시스템의 소형화에 크게 기여할 수 있을 것이다.