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정명준,이경구,이도재,Jung, Myoung-Joon,Lee, Kyung-Ku,Lee, Doh-Jae 한국재료학회 1999 한국재료학회지 Vol.9 No.7
The interfacial reaction and joint properties of Sn-3.5Ag/Cu and Sn-3.5Ag-1Zn/Cu joint were studied. Modified double lap shear solder joints of Sn-3.5Ag and Sn-3.5Ag- lZn solder were aged for 60days at $100^{\circ}C$ and $150^{\circ}C$ and then loaded to failure in shear. The Sn-3.5Ag/Cu had a fast growth rate of the reaction layer in comparison with the Sn-3.5Ag-lZn at the aging temperature of $150^{\circ}C$ Through the SEM/EDS analysis of solder joint, it was proved that intermatallic layer was $Cu_{6}Sn_5$ phase and aged specimens showed that intermatallic layer grew in proportion to $t_{1/2}$, and the precipitate of $Ag_3Sn$ occur to both inner layer and interface of layer and solder. In case of Zn-containing composite solder, $Cu_{6}Sn_{5}$ phase formed at the side of substrate and $Cu_{5}Zn_{8}$ phase formed at the other side in double layer. The shear strength of the Sn-3.5Ag/Cu joint improved by addition of IZn. The strength of the joint increases with strain rate and decreases with aging temperature Sn-3.5Ag, Sn-3.5Ag-lZn Eoa납과 Cu기판과의 계면반응 및 접합특성에 관하여 검토하였다. Eoa납과 Cu기판이 접합된 시편은 $100^{\circ}C$와 $160^{\circ}C$에서 60일간 열처리하였으며, 전단하중을 가하여 강도를 측정하였다. $150^{\circ}C$에서 열처리에 따른 계면반응층의 두게는 Sn-3.5Ag/Cu계면이 Sn-3.5A9-IZn/Cu계면보다 빠르게 성장하였으며, 반응생성물 성장은$ t_{1/2}$에 비례하여 체적 확산 경향을 나타냈다. 계면 반응생성물은 Sn-3.5Ag/Cu계면의 경우 $Cu_{6}Sn_{5}$상이 형성되었고, $Ag_3Sn$상은 반응층 내부 및 반응층과 땜납의 계면에 석출하였으며, Zn을 첨가한 경우에는 계면에 $Cu_{6}Sn_{5}$ 상과 함께 $Cu_{5}Zn_{8}$상이 형성되었다. 땜납/기판의 전단강도는 Sn-3.5Ag합금에 Zn을 1% 첨가하면 증가하였으며, 열처리를 한 경우에는 감소하였다.
Improvement in the Superhydrophobicity of Cellulose Aerogels Using Cationic Polymers
정명준,양봉숙,강규영 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.2
In this study, a cross-linked cellulose aerogel was rst prepared using a cellulose wet-gel treated with a mixture of cationic poly (aminoamide)-epichlorohydrin and vinyl acetate ethylene copoly- mer. Following this, a cross-linked superhydrophobic cellulose aerogel was successfully fabricated using a simplied silanization process. The silane-coated cellulose aerogel exhibited an excellent oil absorption capacity (18 to 65 times the dry weight of the cellulose aerogel) without water absorp- tion, and the recovered dimensions of the cellulose aerogel after compression were improved via the cationic polymer treatment. This material, thus, exhibits great potential as an oil absorbent.
Changes in the Structure of Cellulose Aerogels with Depolymerization
정명준,이신아,강규영,Antje Potthast 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.4
To compare the cellulose aerogels from hydrolyzed and unhydrolyzed cotton linter, we prepared cellulose wet gels from cellulose solution dissolved in hydrated calcium thiocyanate at 110 C and dried them by using the freeze-drying method. The initial root-mean-square (RMS) radius and the weight average molar mass of cotton linter decreased from 71 nm and 405 kg·mol−1, respectively, to 13 nm and 35 kg·mol−1 upon acid hydrolysis. The density of cellulose aerogels increased from 39 to 87 kg/m3 as the cellulose starting material was depolymerized. The microstructure of the cellulose aerogel was viewed with a scanning electron microscope (SEM), and the microstructure and the micro-sized pores were found to be destroyed by cellulose degradation. The degree of polymerization (DP) of the cellulose was found to affect the aerogel’s density and network structure.
탄소나노튜브(CNT)를 혼입한 초고성능 콘크리트(UHPC)의 고고도 전자기파(HEMP) 방호성능 평가
정명준,홍성걸 한국군사과학기술학회 2019 한국군사과학기술학회지 Vol.22 No.2
In this study, to evaluate the High Altitude Electromagnetic Pulse(HEMP) protection performance of UHPC/CNT composites by the content of Carbon nanotubes(CNTs), Electromagnetic Shielding Effectiveness(SE) test was performed based on MIL-STD-188-125-1. And the results were verified by applying the Antenna theory. In the case of UHPC with a thickness of 200 mm mixed with 1 % CNT of cement weight, the SE was 28.98 dB at 10 kHz and 45.94 dB at 1 GHz. Then the Scabbing limit thickness for bullet proof was computed based on the result of compressive strength test which was 170 MPa, and it was examined whether it satisfied the HEMP protection criteria. As a result, the required HEMP shielding criteria were satisfied in all frequency ranges as well as the scabbing limit thickness was reduced by up to 43 % compared with that of ordinary concrete.
불연속적인 다중 주파수 측정치에 강인한 표적기동분석 알고리즘
정명준,Cheong, Myoung-Jun 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.3
Estimating underwater target state variables(position, velocity, course, etc) is necessary to counteract threatening targets. In passive sonar systems, conventional target motion analysis(TMA) techniques using bearing and frequency measurements of an underwater target are widely introduced. However, it is not clear how conventional TMA techniques can be used if some of frequency measurements are unavailable during parts of the scenario, partially unavailable frequency measurements are common in the ocean with complicated acoustic conditions where frequency measurements often come and go. This paper proposes a new TMA algorithm, which is robust to partially unavailable frequency measurements, using the frequency measurements fusion method.