• Macromolecular Research
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• v.11 no.6
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• pp.418-424
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• 2003

Exfoliated poly(methyl methacrylate-co-styrene) [P(MMA-co-ST)]/silicate nanocomposites were synthesized through a multistep emulsion polymerization. The methyl methacrylate monomers were polymerized first and then the styrene monomers were polymerized. The nanocomposites had core-shell structures consisting of PMMA (core) and PS (shell); these structures were confirmed by $^1$H NMR spectroscopy and TEM, respectively. P(MMA-co-ST) copolymers showed two molecular weight profiles and two glass transition temperatures (T$_{g}$) in GPC and DMA measurements. At 30 $^{\circ}C$, the nanocomposites exhibited 83 and 91 % increases in their storage moduli relative to the neat copolymer because the silicate layers were dispersed uniformly in the polymer matrix.x.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1454-1460
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• 2012

In order to develop an new electric insulation material for heavy electric equipments, epoxy/micro/nano composite (EMNC) was prepared by mixing micro-silica with nano layered silicate, where the nano layered silicate was synthesized by our electric field dispersion method, EMNSC was prepared by treating the EMNC with a silane coupling agent. Thermal properties such as glass transition temperature (Tg) and thermal expansion coefficient, and DMA characteristics were studied, and mechanicla properties such as tensile and flexural tests were performed. AC electrical insulation strength was also tested. All properties of EMNSC were modified by treating EMNC with silane coupling agent and it was confirmed that our new developed composites could be used in the heavy electric equipments.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.417-420
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• 2010

최근 UWB, IEEE802.11n과 같은 고속 무선 통신에서는 고속의 암호/복호 처리가 요구되고 있다. 본 논문은 UWB, Zigbee, IEEE802.11과 같은 최신 무선 통신 기술에서 보안 기능의 근간이 되는 CCM(CTR+CBC-MAC) 보안 모드 구현에 관한 것이다. AES와 같은 블록암호알고리즘과 결합된 CCM 기능을 하드웨어로 구현하는 방법을 제시한다. 특히, MAC, DMA모듈과 Hard-wired된 형태로 구현하여 통신속도 저하없이 무선 데이터 송/수신과 동시에 실시간으로 암호/복호 연산을 수행할 수 있으며, CCM 구동 clock을 최소화하여 고속 동작과 저전력 설계의 목적을 달성할 수 있다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.649-656
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• 2013

A conventional epoxy-microsilica composite (EMC) and an epoxy-microsilica-nanosilicate composite (EMNC) were prepared in order to apply them to mold-type transformers, current transformers (CT) and potential transformers (PT). Nanosilicate was exfoliated in a epoxy resin using our electric field dispersion process and AC insulation breakdown strength at $30{\sim}150^{\circ}C$, glass transition temperature and viscoelasticity were studied. AC insulation breakdown strength of EMNC was higher than that of EMC and that value of EMNC was far higher at high temperature. Glass transition temperature and viscoelasticity property of EMNC was higher than those of EMC at high temperature. These results was due to the even dispersion of nanosilicates among the nanosilicas, which could be observed using transmission electron microscopy (TEM). That is, the nanosilicates interrupt the electron transfer and restrict the mobility of the epoxy chains.

• Journal of information and communication convergence engineering
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• v.15 no.1
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• pp.37-42
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• 2017

The constrained application protocol (CoAP) can be used for remotely controlling various sensor devices in Internet of Things (IoT) networks. In CoAP, to support the handover of a mobile sensor device, service discovery and message transmission needs to be repeated, although doing so would increase the handover delay significantly. To address this limitation of CoAP, a centralized CoAP scheme has been proposed. However, it tends to result in performance degradation for an inter-domain handover case. In this letter, we propose a distributed CoAP handover scheme to support the inter-domain handover. In the proposed scheme, a distributed mobility agent (DMA) is used for managing the location of mobile sensors in a domain and performing handover control operations with its neighboring DMAs in a distributed manner. A performance comparison reveals that the proposed scheme offers a performance improvement of up to 29.5% in terms of the handover delay.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1449-1453
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• 1987

A microprogrammable Bit Slice Sinal Processor for image processing is implemented. Processing speed is increased by the parallelism in horizontal microprogram using 120bits microcode, pipelined architecture, 2 bank memory switching that interfaces with the Host through DMA, a variable clock control, overflow checking H/W,look-up table method and cache memory. With this processor, a DCT algorithm which uses 2-D FFT is performed. The execution time for $512{\times}512{\times}8$ image is 12 sec when 16 bit operation is runned, and the recovered image has acceptable quality with MSE 0.276%.

• Journal of Welding and Joining
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• v.24 no.2
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• pp.57-63
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• 2006

In this study, the curing kinetics and thermal degradation of underfill were investigated using differential scanning calorimetry (DSC) and thermo gravimetry analysis (TGA). The mechanical and thermal properties of underfill were characterized using dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA). Also, we presented on underfill dispensing process using Prostar tool. The non-isothermal DSC scans at various heating rates, the exothermic reaction peak became narrower with increasing the heating rate. The thermal degradation of underfill was composed of two processes, which involved chemical reactions between the degrading polymer and oxygen from the air atmosphere. The results of fluidity phenomena were simulated using Star CD program, the fluidity of the underfills with lower viscosity was faster.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.76-86
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• 2007

This study was conducted to investigate the effects of formaldehyde to urea (F/U) mole ratio on thermomechanical curing of UF resin adhesives with different F/U mole ratios. Thermomechanical curing of these UF resin adhesives was characterized using parameters of dynamic mechanical analysis (DMA) such as the gel temperature, maximum storage modulus, and peak temperatures of storage and loss modulus. As the F/U mole ratio decreased, the gel temperature of UF resin adhesives increased. The maximum storage modulus as an indicator of the rigidity of UF resin adhesives decreased with decreasing F/U mole ratio. The peak temperature of tan $\delta$ increased with decreasing F/U mole ratio, indicating that the vitrification occurred faster for high F/U mole ratio of UF resin adhesives than for the one of lower F/U mole ratio. These results partially explained the reason why UF resin adhesives with lower F/U mole ratio resulted in relatively poor adhesion performance when they were applied.

• Interaction and multiscale mechanics
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• v.4 no.3
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• pp.239-245
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• 2011

The dynamic mechanical behavior of silicone rubber reinforced with multi-walled carbon nanotubes (MWCNTs) has been investigated in this study. The MWCNT-reinforced nanocomposites are tested in compression mode through dynamic mechanical analysis (DMA). Multiple effects including MWCNT loading, testing frequency, dynamic strain amplitude, and pre-strain level are taken into consideration. Results show that, by adding 5 wt% of MWCNTs, the dynamic stiffness and damping coefficient of the silicone rubber are significantly enhanced. It is further observed that the dynamic mechanical properties of the nanocomposites are sensitive to dynamic strain amplitude but only slightly affected by pre-strains.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.835-838
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• 1998

본 연구에서는 칼라 CCD 센서를 제어하여, shading과 .gamma. correction 된 데이터를 읽어 들여, 이를 이진레벨 데이터로 바꾼후, 원래의 다치레벨 또는 이진레벨 데이터를 SCSI나 DMA I/F를 통해 전달하는 ASIC을 설계하였다. 본 ASIC에서는 이진화를 위하여 문자 모드에서는 simple threshold와 LAT(local adaptive threshold) 알고리즘을, 그림모드에서는 stucki error diffusion 알고리즘을 적용하였다. 그리고, 구성은 CCD센서 제어블락, 스텝 모타 제어제어블락, 이미지 축소블락, 데이터 이진화 블락, 그리고 DATA I/F 블락 등으로 이루어져 있다. 또한 사용된 technology는 삼성 0.5um CMOS standard cell이며, 크기는 45K gates(내부 메모리 제외)이고, 160QFP package로 구현되었다. ㅎㅁㅅㄷㄴ (soqn apa