• Journal of the Korean Applied Science and Technology
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• v.35 no.1
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• pp.163-172
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• 2018

In this study, selective catalytic reductions (SCR) of NO commercial catalysts were used to investigate the effect of ammonia gasification from urea solution. The effects of catalytic chemical composition on the reaction temperature and space velocity were studied. $V_2O_5/TiO_2$ catalysts, which are widely used as SCR catalysts for removal of nitrogen oxides, have better ammonia formation compare to $TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalysts. The $TiO_2$ catalyst not supporting the active metal was not affected by the space velocity as compared with the catalyst supporting $V_2O_5$ or $WO_3-V_2O_5$. The active metal supported catalysts decreased in the ammonia formation as the space velocity increased.

• Journal of Dental Rehabilitation and Applied Science
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• v.20 no.1
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• pp.51-56
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• 2004

이번 연구의 목적은 순수 타이타늄의 표면을 양극산화법으로 표면처리하여 표면의 특성변화를 연구하고, 이에 따른 세포부착 특성의 차이를 연구하는 것이다. 원반 모양의 타이타늄을 전해질용액에서 300V - 550V의 전압을 주어 양극산화 하고 표면특성을 관찰한 결과, 전압이 높아짐에 따라 표면의 분화구 크기가 커지는 양상을 보였으며 아울러 표면 거칠기도 증가되었다. 세포 부착 실험결과 전압이 증가함에 따라 세포부착 및 증식세포수는 감소하였다. 300V 이상의 양극산화 전압은 표면의 거칠기는 증가시키지만 세포증식은 오히려 억제되는 것이 관찰되었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.769-776
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• 2002

In this paper, we propose uniform slot width bow-tie-shaped meander slot antenna for 5 GHz application. The conventional bow-tie slot antenna has broadband characteristic, however, its size is large. Meanwhile, the meander slot antenna has small size, but it has quite narrow bandwidth. The proposed antenna geometry is a variation of the meander slot antenna incorporating bow-tie shape to realize miniaturized antenna having relatively large bandwidth. Simulated results show that with the same slot width and total slot length, the bandwidth of the proposed antenna is 3 times wider than that of meander slot antenna, and its resonant frequency is 3.01 GHz lower than that of the equal size(H x V) bow-tie slot antenna, and measured results show that the bandwidth of proposed antenna is 218 MHz(5.142 GHz ~ 5.360 GHz) which satisfy the required bandwidth from 5.15 GHz to 5.35 GHz.

• Journal of Periodontal and Implant Science
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• v.36 no.4
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• pp.849-861
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• 2006

타이타늄은 기계적 특성이 우수하고 생체적합성이 뛰어나 의료용 장비의 주 재료로 사용되고 있으며 타이타늄 보다 기계적 특성이 더 우수한 타이타늄 합금들(주로 Ti-6Al-4V와 Ti-6Al-7Nb 합금)도 개발되어 치과와 의료용 임플란트로 사용되고 있다. 그러나 타이타늄 합금 성분들 중 알루미늄 (aluminum)과 바나디움(vanadium)은 인체에 노출되면 세포손상과 신경계에 문제를 일으킬 수 있다. 따라서 인체에 독성이 없으면서 기계적 성질과 생체적합성이 우수한 타이타늄 합금의 개발이 필요하다. 최근 인체에 독성이 없는 성분들이 함유된 새로운 ${\beta}$ - 형태의 타이타늄 합금들이 개발되고 있는데, ${\beta}$ - 타이타늄 합금은 그 기계적 성질이 기존의 ${\alpha}+{\beta}$ 타이타늄 합금에 비해 우수하다고 알려져 있다. 최근 새로운 ${\beta}$ - 타이타늄 합금이 전남대학교 부설 타이타늄 연구소에서 개발되었다. 이 연구는 새로 개발된 ${\beta}$ - 타이타늄 합금의 생채 적합성을 세포 증식도, 알카리 인산 분해 효소 활성과 유전자 증폭을 통해 알아보고자 하였다. 그 결과는 다음과 같다; 1. Titanium-6aluminum-4vanadium (Ti-6Al-4V) 합금 표면애서의 세포 증식율은 Titanium-Titanium8Tantalum-3Niobium (Ti-8Ta-3Nb) 합금과 순수 타이타늄 표면에 비해 유의하게 낮았다(p<0.00l). Ti-8Ta-3Nb 합금 표면에서의 증식도는 순수 타이타늄 표면과 유사하였다. 2. Ti-8Ta-3Nb 합금과 순수 타이타늄에서 배양된 세포이 알카리 인산 분해 효소의 활성도는 Ti-6Al-4V 합금에서의 것보다 유의하게 높았다 (p<0.001). 3. 유전자 증폭 분석 결과, Ti-8Ta-3Nb 합금과 순수 타이타늄에서 collagen type I과 bone sialoprotein mRNA 가 유사한 수준으로 발현되었다. 이상의 결과는 생체 적합성 측면에서 Ti-8Ta-3Nb 합금과 순수 타이타늄의 차이가 없음을 보여주며 따라서 Ti-8Ta-3Nb 합금이 의학 및 치의학 영역에서 새로운 임프란트 재료로 사용될 수 있음을 의미한다.

• Journal of Korean Association for Spatial Structures
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• v.20 no.2
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• pp.11-18
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• 2020

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.6
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• pp.791-797
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• 1999

The activity of domestic pigment titania$(TiO_2)$ impregnated with vanadia$(V_2O_5)$ was investigated in the laboratory microreactor. The meta-titanic acid$(TiO(OH)_2)$ which was produced at Hankook Titanium was selected as the precursor for support. The domestic pigment $TiO_2$ showed higher activity in the reduction of NO with $NH_3$ than the foreign commercial $TiO_2$. $WO_3$ were added to domestic $V_2O_5/TiO_2$ catalytic system to improve the catalytic activity at higher reaction temperature between 400~50$0^{\circ}C$ Also, the deactivation of domestic $V_2O_5/TiO_2$ and $WO_3-V_2O_5/TiO_2$ catalyst by $SO_2$ and $H_2O$ was investigated.

• Resources Recycling
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• v.24 no.1
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• pp.21-27
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• 2015

The present study describes the process of producing low oxygen content alloy powder from Ti-6Al-4V and Ti-8Al-1Mo-1V (AMS 4972) alloy scraps using hydrogenation-dehydrogenation (HDH) and deoxidation in solid state (DOSS) processes. Each prepared powder was deoxidized with Ca contact and non-contact method to compare the deoxidation capability. It is known that the non-contact deoxidation method, using Ca vapor above the melting temperature $T_m$ of Ca, has greater deoxidation capability. However, Oxygen contents in Ti-6Al-4V and Ti-8Al-1Mo-1V powder after non-contact deoxidation method were higher than those after contact deoxidation method. Therefore, we investigate the effect of Al - the richest alloy element in theses Ti based metals - on the deoxidation processes.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.2
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• pp.8-14
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• 2013

Deep beam shall be designed either by taking into account nonlinear distribution of strain or by Appendix A of Strut-and-Tie Models (STM) according to ACI 318(M) from version of 2002. Although STM is accepted as tool in design Discontinuity region (D-region) which mostly exist in Deep beam, Corbels, Dapped ends etc., it has been modified by many researchers. In this study we design deep beam by STMs which use simple truss for load distribution and the model of complex truss for load distribution compare with the ACI traditional which is designed by flexure design method and shear provided by concrete($V_c$) as provided in special provisions section of 11.8 in ACI 318-99 [1]. This study aims to find the different and efficiency of deep beam design based on variation of parameter compiled from many samples selected from ACI traditional and two model of STMs, simple and complex load distribution.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.571-578
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• 2003

An effective seismic retrofit scheme for inverted V braced (or chevron type) steel frames was proposed by studying the redistribution of forces in the post-buckling range. The steel frames with chevron bracing are highly prone to soft story response once the compression brace buckles under earthquake loading. This paper shows that the seismic performance of such frames could be significantly improved by supplying tie bars to redistribute the inelastic deformation demand over the height of the building. A practical design method of the retrofit tie bars was also proposed by considering the sequence of buckling occurrence.

• Korean Journal of Metals and Materials
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• v.46 no.8
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• pp.477-481
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• 2008

The secondary hardening and fracture behavior in P/M high speed steels bearing V content of 9 to 10 wt% have been investigated in terms of austenitizing temperature and precipitation behavior. Austenitizing was conducted at 1,100 and $1,175^{\circ}C$ of relatively low and high temperatures. Coarse primary carbides retained after austenitization were mainly V-rich MC type. They give a significant influence on hardeness and toughness, as well as wear resistance. Tempering was performed in the range of $500{\sim}600^{\circ}C$. The peak hardness resulting from the precipitation of the fine MC secondary carbides was observed near 520, irrespective of austenitizing temperature. Aging acceleration(or deceleration) did not occur with increasing austenitizing temperature because it mainly influences contents of V and C of matrix through the dissloution of coarse primary MC containing lots of V and C. The precipitation of secondary MC carbides, which also contain V and C, did not change the aging kinetics itself. In the 10V alloy containing much higher C content, the impact toughness was lower than 9V alloy, because of the larger amount of primary carbide and high hardness.