• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1470-1476
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• 2020

This paper describes a design of a lightweight security system-on-chip (SoC) suitable for the implementation of security protocols for IoT and mobile devices. The security SoC using Cortex-M0 as a CPU integrates hardware crypto engines including an elliptic curve cryptography (ECC) core, a SHA3 hash core, an ARIA-AES block cipher core and a true random number generator (TRNG) core. The ECC core was designed to support twenty elliptic curves over both prime field and binary field defined in the SEC2, and was based on a word-based Montgomery multiplier in which the partial product generations/additions and modular reductions are processed in a sub-pipelining manner. The H/W-S/W co-operation for elliptic curve digital signature algorithm (EC-DSA) protocol was demonstrated by implementing the security SoC on a Cyclone-5 FPGA device. The security SoC, synthesized with a 65-nm CMOS cell library, occupies 193,312 gate equivalents (GEs) and 84 kbytes of RAM.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.945-951
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• 1994

In order to elucidate the extrusion characteristics of $SiC_{p}$/6061 Al composite, defomation resistance, $K_{w}$ was determined using the empirical formula suggested by Watanabe et al, and also extrusion pressure was measured using the extrusion press with a capacity of 350 ton. The $K_{w}$ which are propotional to extrudability, was increased with increasing volume fraction of reinforcement, $SiC_{p}$, but decreased with increasing the particle size. The peaks of maximum extrusion pressure in curves of extrusion force vs ram stroke were changed sharply with decreasing the particle size. The elevated extrustion temperature resulted in the decreased $K_{w}$ and extrusion pressure, but caused the surface tearing of extrusion composite bars. The results showed that extrudability of the composite billets is depend on the extrusion conditions as well as the characteristics of reinforcement, $SiC_{p}$.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.175-178
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• 2004

This paper describes a new IP address lookup algorithm using a binary search on multiple balanced trees stored in one memory. The proposed scheme has 3 different tables; a range table, a main table, and multiple sub-tables. The range table includes $2^8$ entries of 22 bits wide. Each of the main table and sub-table entries is composed of fields for a prefix, a prefix length, the number of sub-table entries, a sub-table pointer, and a forwarding RAM pointer. Binary searches are performed in the main table and the multiple sub-tables in sequence. Address lookups in our proposed scheme are achieved by memory access times of 11 in average, 1 in minimum, and 24 in maximum using 267 Kbytes of memory for 38.000 prefixes. Hence the forwarding table of the proposed scheme is stored into L2 cache, and the address lookup algorithm is implemented in software running on general purpose processor. Since the proposed scheme only depends on the number of prefixes not the length of prefixes, it is easily scaled to IPv6.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.285-288
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• 2001

Hypereutectic Al-25Si-X alloys, expected to be applied to the cylinder-liner-part of the engine-block of an automobile due to the excellent wear resistance, low density and low thermal expansion coefficient has been fabricated through a spray forming process. The obtained microstructure of the hypereutectic Al-25Si-X alloy appeared to consist of Al matrix and equiaxed Si particles of average diameter of $5-7{\mu}m$. To characterize the deformation behavior of this alloy, a series of load relaxation and compression tests have been conducted at temperatures ranging from RT to $500^{\circ}C$. The strain rate sensitivity parameter (m) of this alloy has been found to be very low (0.1) below foot and reached 0.2 at $500^{\circ}C$. During the deformation above 300'c in compression, strain softening has been observed. The diagram of extrusion pressure vs. ram-speed has been constructed, providing the extrusion condition of Al-25Si-X alloys.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.594-599
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• 2014

The heat dissipation conditions of high-power 5 watt LEDs-based searchlight modules were optimized with varying LED bar'shape, materials, and ambient temperature. The LED junction temperature was estimated by using Computational Fluid Dynamics simulation. The optimal heat dissipation conditions were found as follows; LED bar' shape: L=80 mm, W=4 mm, t=10 mm, copper material, LED junction temperature of $116.6^{\circ}C$, ambient temperature of $50^{\circ}C$, total mass of 184 g, and shadowing area of $320mm^2$. The difference between the junction temperatures of our fabricated and simulated LEDs-based searchlight modules is about $3^{\circ}C$, which confirms the validity of our thermal simulation results.

• Progress in Superconductivity
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• v.13 no.3
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• pp.158-162
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• 2012

$Y(Pr)Ba_2Cu_4O_8$ system is one of the most studied high temperature superconductors. Substitution of Pr for Y in this system suppresses $T_c$ and superconductivity finally disappears at a high Pr doping. There are competing theories for the suppression of $T_c$ but systematic experimental results are very rare. In order to find the change in Fermi surface topology which can affect the superconductivity, we have performed angle-resolved photoemission studies on single crystal samples of $YBa_2Cu_4O_8$ and $PrBa_2Cu_4O_8$. While the Fermi surface of $YBa_2Cu_4O_8$ shows a similar topology to those of other cuprates, we observe only 1D like band structures in $PrBa_2Cu_4O_8$. We find no significant differences in the chain band for both samples.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.247-247
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• 2011

플라즈마 분자선 에피택시(plasma-assisted molecular beam epitaxy)법을 이용하여 다공질 실리콘(porous silicon)에 ZnO 박막을 성장하였다. 성장 후, 아르곤 분위기에서 10분 간 다양한 온도(500~700$^{\circ}C$)로 열처리하였다. 다공질 실리콘 및 열처리 온도가 ZnO 박막의 특성에 미치는 영향을 scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL)을 이용하여 분석하였다. 실리콘 기판에 성장된 ZnO 박막은 일반적은 섬구조(island structure)로 성장된 반면, 다공질 실리콘에 성장된 ZnO 박막은 산맥과 같은 구조(mountain range-like structure)로 성장되었다. 열처리 온도가 증가함에 따라 ZnO 박막의 grain size는 증가하였다. 실리콘 기판 위에 성장된 ZnO 박막은 wurtzite 구조를 나타내는 여러 개의 회절 피크가 관찰된 반면, 다공질 실리콘에 성장된 ZnO 박막은 c-축 배향성(c-axis preferred orientation)을 나타내는 ZnO (002) 회절 피크만이 나타났다. 다공질 실리콘에 성장된 ZnO 박막의 구조적 및 광학적 특성이 실리콘 기판에 성장된 ZnO 박막의 특성보다 우수하게 나타났다. 뿐만 아니라, 열처리 온도가 증가함에 따라 다공질 실리콘에 성장된 ZnO 박막의 PL 강도비(intensity ratio)가 실리콘 기판에 성장된 ZnO 박막의 강도비보다 월등하게 증가하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.246-246
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• 2011

졸-겔 스핀코팅(sol-gel spin-coating)법을 이용하여 실리콘 기판에 ZnO 박막을 증착하였다. 증착된 졸 용액을 전열처리(pre-heat treatment) 후, 다른 속도로 상온까지 냉각시켰다. ZnO 박막의 특성 분석을 위하여 atomic force microscopy (AFM), X-ray diffraction (XRD), Raman, photoluminescence (PL)을 이용하였다. 전열처리 후 5$^{\circ}C$/min의 속도로 천천히 냉각시킨 ZnO 박막은 산맥구조(mountain chain structure)로 표면이 매우 거친 반면, 빠르게 냉각시킨 ZnO 박막은 매우 매끄러운 표면을 나타내었다. 빠르게 냉각시킨 ZnO 박막의 c-축 배향성(c-axis preferred orientation)이 느리게 냉각시킨 ZnO 박막의 배향성보다 더 우세하게 나타났고, 결정성도 우수하였다. 뿐만 아니라, 빠르게 냉각시킨 ZnO 박막의 광학적 특성이 느리게 냉각시킨 ZnO 박막의 특성보다 우수하게 나타났다. 후열처리(post-heat treatment)에 의해 ZnO 박막의 구조적 및 광학적 특성이 더욱 향상되었다.

• Journal of Powder Materials
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• v.20 no.6
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• pp.425-431
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• 2013

Microstructural and mechanical properties of Ni-YSZ fabricated using SPS processing have been investigated at various sintering temperatures. Our study shows samples to be applied as a SOFC anode have the proper porosity of 40% and high hardness when processed at $1100^{\circ}C$. These results are comparable to the values obtained at $100-200^{\circ}C$ higher sintering temperature reported by others. This result is important because when the fabrication processes are performed above $1100^{\circ}C$, the mechanical property starts to decrease drastically. This is caused by the fast grain coarsening at the higher temperature, which initiates a mismatch between thermal expansion coefficients of Ni and YSZ and induces cracks as well.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.127-128
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• 2012

ZnO nanostructures were grown by the hydrothermal method on ZnO seed layers post-heated in the range $350-500^{\circ}C$. The effects of the post-heated ZnO seed layers on the structural and optical properties of the ZnO nanostructures were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and photoluminescence (PL) spectroscopy. The average grain sizes in the ZnO seed layers increased with increasing post-heating temperature, and nano-fibrous structures were observed on the surface of the ZnO seed layers post-heated at $450^{\circ}C$. The ZnO seed layers post-heated in the range $350-500^{\circ}C$ affected the residual stress, lattice distortion in the ZnO nanostructures and the intensity, positions, and full widths at half maximum of the 2-theta and PL peaks in the XRD and PL spectra for the ZnO nanostructures.