• Journal of Welding and Joining
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• 제29권6호
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• pp.65-70
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• 2011

The effect of flip chip bonding parameters on formation of intermetallic compounds (IMCs) between Au stud bumps and Sn-3.5Ag solder was investigated. In this study, flip chip bonding temperature was performed at $260^{\circ}C$ and $300^{\circ}C$ with various bonding times of 5, 10, and 20 sec. AuSn, $AuSn_2$ and $AuSn_4$ IMCs were formed at the interface of joints and (Au, Cu)$_6Sn_5$ IMC was observed near Cu pad side in the joint. At bonding temperature of $260^{\circ}C$, $AuSn_4$ IMC was dominant in the joint compared to other Au-Sn IMCs as bonding time increased. At bonding temperature of $300^{\circ}C$, $AuSn_2$ IMC clusters, which were surrounded by $AuSn_4$ IMC, were observed in the solder joint due to fast diffusivity of Au to molten solder with increased bonding temperature. Bond strength of Au stud bump joined with Sn-3.5Ag solder was about 23 gf/bump and fracture mode of the joint was intergranular fracture between $AuSn_2$ and $AuSn_4$ IMCs regardless bonding conditions.

• Restorative Dentistry and Endodontics
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• 제39권4호
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• pp.310-318
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• 2014

Objectives: This study examined the influence of the resin thickness on the polymerization of silorane- and methacrylate-based composites. Materials and Methods: One silorane-based (Filtek P90, 3M ESPE) and two methacrylate-based (Filtek Z250 and Z350, 3M ESPE) composite resins were used. The number of photons were detected using a photodiode detector at the different thicknesses (thickness, 1, 2 and 3 mm) specimens. The microhardness of the top and bottom surfaces was measured (n = 15) using a Vickers hardness with 200 gf load and 15 sec dwell time conditions. The degree of conversion (DC) of the specimens was determined using Fourier transform infrared spectroscopy (FTIR). Scratched powder of each top and bottom surface of the specimen dissolved in ethanol for transmission FTIR spectroscopy. The refractive index was measured using a Abbe-type refractometer. To measure the polymerization shrinkage, a linometer was used. The results were analyzed using two-way ANOVA and Tukey's test at p < 0.05 level. Results: The silorane-based resin composite showed the lowest filler content and light attenuation among the specimens. P90 showed the highest values in the DC and the lowest microhardness at all depth. In the polymerization shrinkage, P90 showed a significantly lower shrinkage than the rest two resin products (p < 0.05). P90 showed a significantly lower refractive index than the remaining two resin products (p < 0.05). Conclusions: DC, microhardness, polymerization rate and refractive index linearly decreased as specimen thickness linearly increased. P90 showed much less polymerization shrinkage compared to other specimens. P90, even though achieved the highest DC, showed the lowest microhardness and refractive index.

• 한국정보통신학회논문지
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• 제12권11호
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• pp.2031-2038
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• 2008

무선 USB 시스템의 호스트-디바이스 간에 4-way handshake 상호 인증을 위한 PRF(Pseudo Random Function)-256, PRF-64 및 데이터 암/복호 기능을 수행하는 저면적 고속 인증/보안 프로세서 (WUSB_Sec) IP를 설계하였다. PRF-256과 PRF-64는 CCM(Counter mode with CBC-MAC) 연산을 기반으로 구현되며, CCM은 AES(Advanced Encryption Standard) 암호 코어 2개를 사용하여 CBC 모드와 CTR 모드가 병렬로 처리되도록 설계되었다. WUSB_Sec 프로세서의 핵심 블록인 AES 암호 코어는 합성체 GF$(((2^2)^2)^2)$ 연산 기반의 S-Box로 설계되었으며, SubByte 블록과 키 스케줄러가 S-Box를 공유하도록 설계하여 약 10%의 면적을 감소시켰다. 설계된 WUSB_Sec IP는 약 25,000 게이트로 구현되었으며, 120MHz에 서 동작하여 480Mbps의 성능을 갖는다.

• 대한금속재료학회지
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• 제50권7호
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• pp.487-493
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• 2012

To analyze the factors on stretch-flangeability for 980 MPa-grade hot-rolled steels, two types of steels (Fe-Cr and Fe-Mo) were manufactured by hot-rolling. Manufactured steels at the low coiling temperature, such as 400 and $500^{\circ}C$, had poor stretch-flangeability due to un-uniformly distributed carbides and a large deviation of interphase hardness. However, when the coiling temperature was set at $650^{\circ}C$ with Fe-Cr steel, 998 MPa of ultimate tensile strength, 19% of total elongation and 65% of the hole expanding ratio were achieved by microstructural constituents of polygonal ferrite (PF) and granular ferrite (GF) dispersed with fine carbides (<50 nm). Therefore, the material to attain 980 MPa with superior formability was the Fe-Cr steel that was precipitation-hardened in polygonal ferrite and granular ferrite at the coiling temperature $650^{\circ}C$.

• 대한예방한의학회지
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• 제22권3호
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• pp.21-29
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• 2018

Objectives : The purpose of this study was to examine the lifestyle of korean medicine students based on their drinking patterns and eating attitudes. Methods : The survey was conducted on 101 korean medicine students to investigate their psychological characteristics. They were asked to complete Self-Administered Alcoholism Screening Test, Eating Attitude Test, and Minnesota Multiphasic Personality Inventory-2. Results : A total of 101 Korean medical students participated in the study. Non-drinker 19, drinker were 82. Unlikely to, possible and potential alcoholism 79(78.2%), 17(16.8%) and 5(5%) respectively. The mean and standard deviation of SAAST in the subjects were $3.88{\pm}3.33$ and the EAT score was $8.09{\pm}8.693$. There was a significant difference in the MMPI-2 items between non-drinker and drinker. The SAAST had an effect on the EAT score(${\beta}=0.319$). Conclusions : As a result of MMPI-2 test, in the potential alcoholism group, scale D, Mf, Si, INTR, TPA, SOD, Mt and GF were shown higher, and AAS and GM were shown lower than the normal group. In the bad eating attitude group, scale Hy, RC4, DISC and AA were shown higher than the good eating attitude group.

• 대한본초학회지
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• 제36권5호
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• pp.93-99
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• 2021

Objective : Caryophylli Flos has been used in Korean medicine to relieve vomiting and pains caused by chills that make fluid circulation difficult. This study was designed to investigate the protective effect of ethanol extract of Caryophylli Flos (CF) in hydrogen peroxide (H₂O₂)-induced apoptotic cell death in human keratinocyte HaCaT cells. Methods : CF was prepared by extracting 200 g of Caryophylli Flos in 2 L of ethanol for 48 h. Cell viability was measured by MTT assay, and the protein expression was monitored by Western blot analysis. Apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Reactive oxygen species (ROS) was measured using fluorescent dye, and reduced glutathione (GSH) was determined with a colorimetric commercial kit. Results : CF protected HaCaT cells from cell death caused by oxidative stress after H₂O₂ treatment. H₂O₂ amplified generation of ROS and induced depletion of GSH, whereas these changes in ROS and GSH were inhibited by GF treatment. In addition, H₂O₂ resulted in apoptosis as assessed by TUNEL assay and the expression of apoptosis regulator proteins. However, cells treated with CF showed a decrease in TUNEL-positive cells and restored the reduced expression of procaspase-9, -3 and PARP. Conclusion : This study showed cytoprotective effects of CF by anti-apoptotic activity while exerting antioxidative activity in H₂O₂-treated HaCaT cells. These results suggest that CF could be beneficial in skin damage caused by oxidative stress.

• 한국인터넷방송통신학회논문지
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• 제21권1호
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• pp.1-6
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• 2021

본 논문은 하드웨어 자원이 제한되는 사물인터넷 시스템의 보안을 위하여 AES 기반의 효율적인 암호화칩 설계를 제안한다. ROM 기반의 S-Box는 메모리를 액세스하는데 많은 메모리 공간이 필요함과 동시에 지연문제가 발생하게 된다. 제안한 방법에서는 저면적/고성능의 암호화 칩 설계를 위해 합성체 기반의 고속 S-Box를 설계하여 보다 빠른 연산결과를 얻도록 한다. 또한, 각 라운드 변환과정 및 키 스케쥴링 과정에서 사용되는 S-Box를 공유하도록 설계하여 보다 높은 처리율 및 적은 지연을 갖도록 한다. 설계된 AES 암호프로세서는 Verilog-HDL를 사용하여 회로동작을 기술하였으며, Xilinx ISE 14.7 툴을 이용하여 논리 합성을 수행하였다. 또한, 설계 검증은 Modelsim 10.3 툴을 이용하였으며, Xilinx XC6VLX75T FPGA 소자를 사용하여 하드웨어 동작을 검증하였다.

• 전기전자학회논문지
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• 제24권4호
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• pp.961-968
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• 2020

타원곡선 암호에 필수적으로 사용되는 모듈러 곱셈의 고성능 하드웨어 설계에 대해 기술한다. 본 논문의 모듈러 곱셈기는 NIST FIPS 186-2에 정의된 소수체 상의 5가지 체 크기(192, 224, 256, 384, 521 비트)의 모듈러 곱셈을 지원하며, 정수 곱셈과 축약의 두 단계 과정으로 모듈러 곱셈을 연산한다. 고속 정수 곱셈을 위해 카라추바-오프만 곱셈 알고리듬이 사용되었고, 축약 연산을 위해 Lazy 축약 알고리듬이 사용되었다. 또한, Lazy 축약에 포함된 나눗셈 연산을 위해 Nikhilam 나눗셈 알고리듬이 사용되었으며, 나눗셈 연산은 주어진 모듈러 값에 대해 처음 한 번만 연산되고, 모듈로 값이 고정된 상태로 연속적인 모듈러 곱셈이 수행되는 경우에는 나눗셈을 거치지 않도록 하였다. 설계된 모듈러 곱셈기는 32 MHz의 클록 주파수로 동작하는 경우에 초당 640만번의 모듈러 곱셈을 연산할 수 있는 것으로 평가되었으며, 180-nm CMOS 셀 라이브러리로 합성한 결과, 67 MHz의 클록 주파수로 동작이 가능하며, 456,400 등가 게이트로 구현되었다.

• 대한금속재료학회지
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• 제49권5호
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• pp.411-418
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• 2011

The current study investigates the electroplating characteristics of Sn-Cu eutectic micro-bumps electroplated on a Si chip for flip chip application. Under bump metallization (UBM) layers consisting of Cr, Cu, Ni and Au sequentially from bottom to top with the aim of achieving Sn-Cu bumps $10\times10\times6$ ${\mu}m$ in size, with 20${\mu}m$ pitch. In order to determine optimal plating parameters, the polarization curve, current density and plating time were analyzed. Experimental results showed the equilibrium potential from the Sn-Cu polarization curve is -0.465 V, which is attained when Sn-Cu electro-deposition occurred. The thickness of the electroplated bumps increased with rising current density and plating time up to 20 mA/$cm^2$ and 30 min respectively. The near eutectic composition of the Sn-0.72wt%Cu bump was obtained by plating at 10 mA/$cm^2$ for 20 min, and the bump size at these conditions was $10\times10\times6$ ${\mu}m$. The shear strength of the eutectic Sn-Cu bump was 9.0 gf when the shearing tip height was 50% of the bump height.

• 한국정보통신학회논문지
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• 제23권12호
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• pp.1609-1617
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• 2019

ECC (Elliptic Curve Cryptography)와 RSA를 기반으로 하는 다양한 공개키 암호 프로토콜 구현을 지원하는 하드웨어 가속기 설계에 관해 기술한다. NIST 표준으로 정의된 소수체 상의 5가지 타원곡선과 3가지 키길이의 RSA를 지원하며 또한, 4가지 타원곡선 점 연산과 6가지 모듈러 연산을 지원하도록 설계되어 ECC와 RSA 기반 다양한 공개키 암호 프로토콜의 하드웨어 구현에 응용될 수 있다. 저면적 구현을 위해 내부 유한체 연산회로는 32 비트의 데이터 패스로 설계되었으며, 워드 기반 몽고메리 곱셈 알고리듬, 타원곡선 점 연산을 위해서는 자코비안 좌표계, 그리고 모듈러 곱의 역원 연산을 위해서는 페르마 소정리를 적용하였다. 설계된 하드웨어 가속기를 FPGA 디바이스에 구현하여 EC-DH 키교환 프로토콜과 RSA 암호·복호 둥작을 구현하여 하드웨어 동작을 검증하였다. 180-nm CMOS 표준 셀 라이브러리로 합성한 결과, 50 MHz 클록 주파수에서 20,800 등가게이트와 28 kbit의 RAM으로 구현되었으며, Virtex-5 FPGA 디바이스에서 1,503 슬라이스와 2개의 BRAM으로 구현되었다.