• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.205-214
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• 2010

Masonry structures have been used throughout the world for the construction of residential buildings. However, from a structural point of view, the masonry material is characterized by a very low tensile strength. Moreover, the bearing and shear capacity of masonry walls have been found to be vulnerable to earthquakes. In this study, to improve the seismic performance of masonry walls, hexagonal blocks were developed and six masonry walls made with hexagonal block were tested to failure under reversed cyclic lateral loading. This paper focuses on an experimental investigation of different types of wall with hexagonal blocks, i.e. walls with different hexagonal blocks and with different reinforcing bar arrangements, subjected to applied cyclic loads. The cracking, damage patterns and hysteretic feature were evaluated. Results from the hexagonal masonry wall were shown more damage reduction and less brittle failure in comparison to the existing rectangular masonry walls.

• Journal of the Korean Geotechnical Society
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• v.32 no.10
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• pp.31-40
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• 2016

In order to investigate the change in soil arch structure developed within the soil subjected to trapdoor movement, various responses in the deformed particle assembly were observed via photoelastic measurement technique. The particle assembly was composed of the regularly stacked model particles coated by thin photoelastic material. Variation of the internal structure transmitting contact forces were observed by taking images showing the photoelastic responses and compared with the change in slip lines and pressures measured by load cells placed beneath the assembly. Initial soil arch structure established immediately after the trapdoor movement collapsed progressively and meanwhile a new extended structure was developed against further movement of the trapdoor. For the sufficient movement of the trapdoor, initially identical regions bounded by the soil arch structure and slip lines were separated and the region enclosed by slip lines became a part of the region loosing the transmitting contact forces identified by photoelastic measurement.

• Journal of the Korean Chemical Society
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• v.43 no.3
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• pp.315-320
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• 1999

Novel electroluminescent materials, polymer material, PU-BCN and low molar mass material, D-BCN with the same chromophores were designed and synthesized. A molecular structure of chromophore was composed of bisstyrylbenzene derivative with cyano groups as electron injection and transport and phenylamine groups as hole injection and transport. Device structures with PU-BCN and D-BCN as an emission layer were fa-bricated, which were a single-layer device(SL), Indium-tin oxide(ITO)/emission layer/MgAg, and two kinds of double-layer devices which were composed of ITO/emission layer/oxadiazole derivative/MgAg as a DL-E device and ITO/triphenylamine derivative/emission layer/MgAg as a DL-H device. The two emission materials, PU-BCN and D-BCN with the same emission-chromophore were evaluated as having excellent performance of charge injection and transport and revealed almost the same emission characteristics in high current density. EL emission maximum peaks of two material were detected at about 640 nm wavelength of red emission region.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.445-452
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• 2017

The wing leading edge skin in this research is an essential structural factor for improving wings' aeromechanical functions, protecting the interior elements of the wings from external damage including birds, and navigating planes safely. The study compared and reviewed models manufactured for optimal light-weight wings of composite UAVs. It compared and investigated displacement forms of torsion loads through finite element analysis using MSC. Patran/Nastran. By confirming the improvement of light-weighting performance according to lamination type, thickness change and shape through torsion strength tests of each model, the research suggested the optimal light-weight wing leading edge skin for small composite UAVs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.5
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• pp.63-70
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• 2020

In this paper, the transmit-receive module for military seekers has been designed and fabricated in 35 GHz. To increase the performance of substrates and high integration of circuits in millimeter-wave band, a 4-layer LCP(Liquid Crystal Polymer) substrate was developed. This substrate was implemented with three FCCL substrates and two adhesive layers, and a process using the difference in melting point between the substrates was used for lamination. Using a strip line and a microstrip line was confirmed by the transmission loss along the length of the substrate, and the performance of LCP substrates was validated with a power divider in 35 GHz. After confirming the performance of individual blocks such as power amplifier and low noise amplifier, a single channel Ka-band transmission/reception module was developed using a 4-layer liquid crystal polymer substrate. The transmit power of this module has above 1.1W in pulse duty 10% and has an output power of 1.1W and it has receive noise figure less than 8.5 dB and receive gain more than 17.6 dB.

• Composites Research
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• v.33 no.3
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• pp.140-146
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• 2020

The purpose of this paper is to examine the possibility of weight reduction by changing the partition panel of vehicle from an existing aluminum material to carbon fiber reinforced plastics. Three weaving methods (plain, twill and satin) were used in the manufacture of composite materials, and they were produced and tested to derive their material properties. The analysis model of composite partition panel for torsional conditions was developed and the structural stability and system stiffness were evaluated according to Tsai-Hill failure criteria. With design variables for fiber orientation angles and stacking sequence, evolutional optimal algorithm was performed and as the results, the optimal composite partition panel was designed. In addition, the structural analysis results for strength and specific stiffness were compared with aluminum partition panels and composite partition panels to verify the possibility of weight reduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.344-344
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• 2008

최근 들어, 압전 세라믹스 제조기술의 급속한 발전으로 기계, 전자뿐만 아니라 휴대용 전자기기의 초소형 적층형 압전모터 및 압전변압기 같은 고품질 압전소자의 개발에 있어 특히 소자의 소형화에 따라 나노크기의 분말제조가 연구의 주류를 이루고 있다. 현재 이러한 나노크기의 세라믹스 제조에 사용되는 방법으로는 화학적 공침법, 졸겔법, 수열반응, 그리고 고에너지 볼밀법등이 보고되고 있다. 볼밀링 공정은 세라믹제조 시 필수 불가결한 공정이나 일반적으로 미세화에 그 한계가 있어 $1{\mu}m$이하의 입자크기를 가지는 분말은 제조가 곤란한 것으로 인식되어 왔다. 그러나 고에너지 볼밀을 이용한 볼밀링은 원료의 변형, 파괴 등과 같은 원료의 물리적 변화 뿐만 아니라 원료를 구성하는 원자/분자 구조에 영향을 미쳐 원료의 화학적 특성의 변화를 유발한다. 이러한 화학적 특성의 변화는 이종 원료간의 화학 반응성을 향상시켜 밀링 중에 새로운 화학종의 생성을 유발하게 되는데 이러한 현상을 mechanochemical 효과라 한다. 이러한 mechanochemical 효과는 나노 분말 입자의 제조뿐만 아니라, 분자설계, 재료합성, 자원처리 및 리사이클링 등에도 그 적용이 시도되고 있다. 이러한 mechanochemical 효과를 이용하여 분말을 미세화 함으로써 저온 소결과 재료특성 향상을 기대해 볼 수 있다. 따라서, 이번 연구에서는 우수한 압전 특성을 가진 PMN-PNN-PZT조성을 가지고 시편을 제작하였으며, 고에너지 볼밀시간에 따라 그 압전 및 유전특성을 조사하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.95-102
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• 2004

For the simultaneous measurement of strain and damage signal, a fiber Bragg grating sensor system with a dual demodulator was proposed. One demodulator using a tunable Fabry-Perot filter can measure low-frequency signal such as strain and the other demodulator using a passive Mach-Zehnder interferometer can detect high-frequency signal such as damage signal or impact signal. Using a proposed fiber Bragg grating sensor system, both the strain and damage signal of a cross-ply laminated composite beam under tensile loading were simultaneously measured. Analysis of the strain and damage signals detected by single fiber Bragg grating sensor showed that sudden strain shifts were induced due to transverse crack propagation in the 90 degree layer of composite beam and vibration with a maximum frequency of several hundreds of kilohertz was generated.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.139-145
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• 2008

In this paper, a microstrip surface wave antenna(SWA) with a frequency selective surface structure(FSS) is designed and measured. A microstrip SWA has many advantages such as low profile, low weight, easy fabrication, and compatibility with monolithic microwave integrated circuits(MMIC). In addition, it has demonstrated monopole like beam patterns. The microstrip SWA consists of two parts : a center-fed modified microstrip patch to excite surface wave, and a periodic patches to support the propagation of the surface waves. To obtain wide bandwidth, the ring type parasitic element is inserted and the circular patch is selected for the unit element in FSS structure. Experimental results show that the microstrip SWA has monopole like beam patterns at 5.9GHz. Impedance bandwidth and gain is 12% and 5.6dBi.

• Membrane Journal
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• v.16 no.1
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• pp.1-8
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• 2006

Nanofiber is a broad phrase generally referring to a fiber with diameter less than 1 micron. Various polymers have been successfully electrospun into nanofibers in recent years. These nanofibers, due to their high surface area and porosity, have a great potential for use as filter medium, adsorption layers in protective clothing, etc. Nanofiber filters will enable new levels of filtration performance in the field of air filtration. In particular, nanofibers provide marked increases in filtration efficiency at relatively small pressure drop in permeability. Therefore, nanofiber filters could be substituted for conventional filter market due to the easy application of process and the possibility of coating to micron-sized non-woven sheets. This review is discussed on the trend of researche and development related to nanofiber filter including future marketability.