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졸-겔법에 의한 여러 상의 고순도 Alumina 제조에 관한 연구
황규민,박승수,이희철,Kyu Min Hwang,Seung Soo Park,Hee Chul Lee 대한화학회 1989 대한화학회지 Vol.33 No.2
Aluminum alkoxide, $Al(OC_3H_7\^i)_3\;and\;Al(OC_4H_9^s)_3$, were synthesized using aluminum sheet and corresponding alcohols to prepare various phase alumina in high purity. Aluminum hydroxides were prepared by hydrolysis of synthesized Al-alkoxides and from reagent $AlCl_3$. The catalytic properties of ${\gamma}$ and ${\eta}-Al_2O_3$ prepared at various temperatures were investigated and the reaction kinetics of ${\alpha}-Al_2O_3$ formation from $Al(OH)_3$ was considered. 금속알루미늄 조각과 alcohols을 반응시켜 Al-alkoxides를 합성하였으며 이것을 가수분해하여 얻은 Al-hydroxides와 시약 AlCl3로부터 얻은 Al-hydroxides를 여러 온도에서 소성하여 여러 상의 고순도 $Al_2O_3$를 제조하였다. 제조한 ${\gamma}$와 ${\eta}$상 알루미나의 촉매적 특성을 알아보았고, $Al(OH)_3$로부터 ${\alpha}-Al_2O_3$의 생성과정을 속도론적으로 고찰하였다.
황규민,신규보,박상혁,김효일 한국통신학회 2016 Journal of communications and networks Vol.18 No.3
Super Wi-Fi is a Wi-Fi-like service exploiting TV whitespace (WS) which is expected to achieve larger coverage thantoday’s Wi-Fi thanks to its superior propagation characteristics. Super Wi-Fi has been materialized as an international standard,IEEE 802.11af, targeting indoor and outdoor applications, and isundergoing worldwide field tests. This paper demonstrates the truepotential of indoor Super Wi-Fi, by experimentally comparing thesignal propagation characteristics of SuperWi-Fi andWi-Fi in thesame indoor environment. Specifically, we measured the wall andfloor attenuation factors and the path-loss distribution at 770MHz,2.401 GHz, and 5.540 GHz, and predicted the downlink capacityof Wi-Fi and Super Wi-Fi. The experimental results have revealedthat TVWS signals can penetrate up to two floors above and below,whereasWi-Fi signals experience significant path loss even througha single floor. It has been also shown that Super Wi-Fi mitigatesshaded regions of Wi-Fi by providing almost-homogeneous datarates within its coverage, performs comparable to Wi-Fi utilizingless bandwidth, and always achieves better spectral efficiency thanWi-Fi. The observed phenomena imply that SuperWi-Fi is suitablefor indoor applications and has the potential of extending horizontaland vertical coverage of today’s Wi-Fi.
분말 용가재판을 사용한 광폭 오버레이용 트윈토치 GMAW 공정개발
황규민,김성덕,정병호,조상명,Hwang, Kyu-Min,Kim, Sung-Deok,Jung, Byung-Ho,Cho, Sang-Myung 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.4
Generally, wear plate is steel plate having improved surface contact strength and impact strength by surface hardening which is welded using materials with good corrosion resistance, wear resistance and thermal resistance property. CFP GMAW(Compound Filler Plate Gas Metal Arc Welding) is the cladding method using GMAW with the CFP, which is bound with waterglass, on the substrate. It has advantages of reducing compound powder loss, uniform penetration, and preventing hardness decrease. To develope mass production technique of CFP GMAW process for production of high quality wear plate, the method for controling shallow penetration and increasing productivity is required. In this study, twin torch method applied to CFP GMAW process for increasing productivity. And the method was developed by controling penetration control, CFP dry time, gas formation flux and water glass concentration. As a result, applying twin torch method to CFP GMAW process was possible and high quality wide bead could be made without overlap joint.