Mechanochemical Processing(MP)에 의한 Cement-fly Ash 계 Mortar의 제조

이형직,구자훈,유인상,송두규,정해경,권혁병,윤상옥,이형복,이홍림,Lee, Hyung-Jik,Koo, Ja-Hun,Yoo, In-Sang,Song, Doo-Gyoo,Joung, Hae-Kyoung,Kwon, Hyouk-Byoung,Yoon, Sang-Ok,Lee, Hyung-Bock,Lee, Hong-Lim 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.2

Mechanochemical Processing(MP)을 거친 Cement(MPC) 또는 Fly Ash(MPFA)를 사용하여 fly ash 다량 혼화 고강도 mortar의 제조를 위한 연구를 수행하였다. 단순 ball milling processing를 거친 cement(Ball-mill Processed Cement, BPC)와 채취 그대로의 처리하지 않은 fly ash(As Received Fly Ash, ARFA) 혼화시의 공시체와 비교하여 동일한 fly ash의 혼화량(10, 20, 30 wt%), 동일한 재령(7일 및 28일)의 압축강도 및 미세구조의 관점에서 고찰하였다. MPC와 ARFA 및 BPC와 MPFA를 사용한 mortar 공시체가 BPC와 ARFA를 사용한 것보다 각각 5-11% 및 10-20% 상승한 압축강도 값을 나타내었다. 더욱이 MPC와 MPFA의 동시 혼화 mortar 공시체의 압축강도가 fly ash 혼화량 20 wt% 공시체에서 강도 상승률 24%를 나타내었는데 이 값은 MPC 사용에 의한 강도 향상 비율(8%)과 MPFA 혼화에 의한 강도 향상 비율(12%)의 합을 상회하는 synergy 효과를 나다내는 강도 향상율을 나타냈다. 상기의 강도 증진은 MP에 있어서 fly ash와 cement 입자가 혼합되면서 기계적 에너지가 공급되므로 각 입자의 서로에 대한 친화성이 증대되며, 이로 인하여 수화물 생성시 cement와 fly ash 입자간의 결합력이 더욱 증가하게 되어 압축강도가 증가하는 것으로 고려된다. Fabrication of mortar containing fly ash for high strength structural material was investigated by using a Mechanochemically Processed Cement (MPC) and/or Fly Ash (MPFA), which was compared to the specimen (at the same fabrication condition of fly ash adding contents (10, 20 and 30 wt%) and curing time (7 and 28 days)) fabricated by using Ball-mill Processed Cement (BPC) and As Received Fly Ash (ARFA) in terms with compressive strength and microstructures. Mortar specimen fabricated by using MPC and ARFA showed 5-11% higher compressive strength than that in the case of using BPC and ARFA, and mortar specimen by using BPC and MPFA represented 10-20% higher compressive strength than that for the case of using BPC and ARFA. Furthermore, mortar specimen fabricated by simultaneously using MPC and MPFA exhibited about 24% higher value of compressive strength than that for the case of using BPC and ARFA, which was considered to be synergic efficiency in increasing compressive strength. Increased compressive strength as above mentioned is considered to be caused by mutually increased affinity between cement and fly ash induced during mechanochemical Processing(MP).

심장 MRI 영상에서 혈류 윤곽선의 자동 추출

이형직,조상현,최흥문,Lee, Hyeong-Jik,Jo, Sang-Hyeon,Choe, Heung-Mun 대한전자공학회 2000 電子工學會論文誌-SC (System and control) Vol.37 No.5

본 논문에서는 심장 MRI 영상에서 혈류 윤곽선을 자동으로 추출하는 방법을 제안하였다. 제안한 방법에서는 기존 snake 보다 포획 범위가 넓은 GVF(gradient vector flow) snake를 사용하고, 심장 MRI의 에지 영상에서 GVF 계(field)가 영인 영역의 외곽을 따라 초기점들을 자동 발생시킴으로써, 전문가의 수작업 초기화에 의존하던 기존 방법과는 달리, 유두근으로 인한 요면을 갖는 혈류 윤곽선까지도 자동으로 추출할 수 있도록 하였다. 유두근 돌출로 인한 요면을 가지거나 잡영이 섞여있는 실제 심장 MRI들에 대해 실험하여 혈류 윤곽선을 효과적으로 자동 추출할 수 있음을 확인하였다. In this paper, an automatic extraction of the blood flow contour from cardiac MRI is proposed. By using the GVF snake which has wider capture range than the conventional snake, and by automatically generating the initial points along the outside of the contour of the zero GVF field in the edge image of the cardiac MRI, the blood flow contour can be automatically extracted, even when the contours have boundary concavities due to the papillary muscles, without any manual initialization of the experts. Experiments are conducted on the various real cardiac MRIs including noise and papillary muscles, and the proposed method is proved to be efficient in automatic extraction of the blood contours even if they have the boundary concavities.

하이브리드 플라즈마 입자가속 충격퇴적(Hybrid Plasma - Particle Accelerating Impact Deposition, HP-PAID) 프로세스에 의한 Si 나노구조 코팅층의 제조 및 특성평가

이형직,권혁병,정해경,장성식,윤상옥,이형복,이홍림 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.12

최근 개발된 하이브리드플라즈마 가속입자충격 프로세스를 이용하여 기상의 TEOS(tetraethoxysilane, (C$_2$ $H_{5}$O)$_4$Si)를 Ar-hybrid plasma 환경 하에 분사하는 방법으로 나노구조(nanostructured) Si 코팅 합성에 대해서 연구하였다. 반응가스와 함께 플라즈마제트는 노즐을 통해서 챔버속으로 700 torr정도에서 10 torr정도로 압력 강하를 동반하며 확장되었다. 노즐의 초중단부에서 핵생성 및 입성장한 초미세입자는 노즐의 하단의 자유 제트에서 가속되어 온도조절 기판위에 관성 충격에 의해 퇴적되어 10nm 이하의 비정질 실리콘 코팅층이 형성되었다. 퇴적된 비정질 코팅은 Ar분위기의 tube로에서 열처리 되었는데 90$0^{\circ}C$에서 30분간 열처리하여 결정화가 시작되었고, 이때 시편의 입자크기는 TEM을 통하여 10nm 이하로 유지됨을 알 수 있었다. 또한 라만분광기로 분석한 결과 이동치는 2.39$cm^{-1}$ /이며 반감폭은 5.92$cm^{-1}$ /으로 피크 이동치로 도출한 평균입자크기 7nm값과 일치하였으며, 특히 PL 피크는 398nm에서 강한 피크를 나타내어 3∼4 nm의 극미세 나노입자도 포함하고 있음을 알 수 있었다. Using a recently developed Hybric Plasma-Particle Accelerating Impact Deposition (HP-PAID) process, synthesis of nanostructured silicon coatings has been investigated by injecting vapor-phase TEOS (tetraethosysilane, (C$_2$H$\_$5/O)$_4$Si) into an Ar hybrid plasma. The plasma jet with reactants was expanded through nozzle into a deposition chamber, with the pressure dropping from 700 to 10 torr. Ultrafine particles accelerated in the free jet downstream of the nozzle, deposited by an inertial impaction onto a temperature controlled substrate. By using this process, nanostructured amorphous silicon coatings with grain size smaller than 10 nm could be synthesized. These samples were annealed in an Ar and crystallized at 900$^{\circ}C$ for 30 min. TEM analysis showed that the annealed coatings were also composed of nanoparticles smaller than 10 nm, which showed a good consistency that the average grain size of 7 nm was also estimated from a peak shift of 2.39 cm$\^$-1/ and Full Width at Half Maximum (FWHM) 5.92 cm$\^$-1/ of Raman analysis. The noteworthy is that a strong PL peak at 398 nm was also obtained for this sample, which indicates that the deposited coatings also contained 3∼4 nm nanostructured grains.

Identifying the Winner's Curse in the First Spectrum Auction in the Republic of Korea Using an Event Study Approach

이형직,설성호,권수천 한국전자통신연구원 2013 ETRI Journal Vol.35 No.6

The first spectrum auction in the Republic of Korea is attention-worthy owing to the fierce competition for the only 1.8-GHz spectrum license, the winning bidder of which was suspected of overpaying for its acquisition. This study empirically investigates the existence of a “winner’s curse” in the first Korean spectrum auction by using a standard event study methodology. The results show that both the winner and loser experienced significant positive returns on the completion day of the auction. The results imply that there was no winner’s curse in the auction and that the losing firm might increase its competitive advantage by acquiring other spectrum licenses despite failing to achieve its initial target spectrum. Therefore, these results suggest that regulators may need to consider bringing about positive short-term wealth benefits to all bidders by appropriately designing a spectrum auction, such as by performing multiband auctions.

급속가열 이력 제어에 의한 $Si_3-N_4-SiC$계 미분말 시편의 치밀화

이형직 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.7

The densifying behavior of ultrafine amorphous Si3N4 (about 20 nm)-$\beta$-SiC (about 40~80 nm) powders (O2 : 1.3~15wt%, 0<C<8 : wt%) was investigated with a particular attention to the microstructural changes. The specimens were heated to 1$700^{\circ}C$ within 15 sec and then immediately cooled and held at 135$0^{\circ}C$ for 10 min in N2 atmosphere without resorting to additives using a Xe image heating apparatus. Using an ultrafine pure Si3N4 powder with particle size less than 30nm, further more, mixed with an appropriate amount of $\beta$-SiC, was found to be advantageous to obtain uniform and homogeneous microstructure. In addition, ultrafine Si3N4 powders were also proved to be effective as sintering additive on densifying large sized Si3N4 powder compacts.

NOM의 오존처리에 따른 분자크기분포변화가 활성탄 흡착에 미치는 영향

이형직,홍성호 대한상하수도학회 2013 상하수도학회지 Vol.27 No.6

In this study, molecular size distribution of natural organic matter (NOM) after ozonation was measured and its effect on adsorption capacity of activated carbon was investigated. According to the results, the molecular size of NOM was limitedly changed. Specifically, the molecular size of NOM between 5,000 to 10,000 Da were slightly decreased with increasing ozone doses. The adsorption capacity after ozonation was evaluated using Freundlich isotherm with ideal adsorbed solution theory (IAST) which simulated the multi components adsorption. Further, mini-column test was conducted. The Freundlich constant, K was reduced after ozonation and the non-adsorbable fraction was increased with ozonation. However, no correlation between K and ozone doses was found. The present study also agreed with the correlation between adsorption capacity and pore size characteristics of activated carbon.

가열이력 제어에 의한 $Si_3N_4$ 미분말 시편의 급속가열

이형직 한국세라믹학회 1993 한국세라믹학회지 Vol.30 No.3

The sintering and renitridation behaviors of ultrafine Si3N4 powder compacts, which were heavily oxidized and/or free-Si rich, were investigated with particular attentiion to microstructures. The specimens were heated without restoring to additives and pressure by controlling heating process attained a Xe image apparatus. The effect of particle size, free-Si contents, decomposition and renitridation, were investigated. When fired to 1$650^{\circ}C$ within 15 sec and then immediately held at 135$0^{\circ}C$ for 10min N2 atmosphere, significant densification took place in the limited region, in addition to decreasing oxygen contents to less than 0.3wt%. On the other hand, specimens decomposed due to overheating at the initial stage were rapidly renitridated at the relatively lower temperature of the holding stage. And, then, the activation energy for the renitridation was calculated to be 49kcal/mole.

빅데이터 지식처리 인공지능 기술동향

이형직,류법모,임수종,장명길,김현기,Lee, H.J.,Ryu, P.M.,Lim, S.J.,Jang, M.K.,Kim, H.K. 한국전자통신연구원 2014 전자통신동향분석 Vol.29 No.4

최근의 플랫폼 기술동향은 웹 기반 혹은 단순 의사소통이 가능한 모바일 플랫폼에서 빅데이터와 인공지능기술이 접목되면서 심층 질의응답이 가능한 차세대 지능형 지식처리 플랫폼으로의 진화가 진행 중이다. 선진국에서는 국가 차원 혹은 글로벌 기업의 주도하에 대형 장기 프로젝트가 진행 중이다. 국가 주도의 프로젝트로는 미국의 PAL, 유럽의 Human Brain, 일본의 Todai 프로젝트가 대표적인 예이며, 글로벌 기업의 경우는 IBM의 Watson, Google의 Knowledge Graph, Apple의 Sir가 대표적인 예이다. 본고에서는 차세대 지능형 플랫폼의 핵심기술인 인간과 기계의 지식소통을 위한 빅데이터 기반의 지식처리 인공지능 소프트웨어 기술의 개념과 국내외 기술 및 산업, 지식재산권 동향 등을 살펴보고 산업계 활용방안 및 발전방향에 대해 논하고자 한다.

유치에 대한 3-in-1 유동성 복합레진의 전단결합강도

이형직,신종현,김지연,정태성,김신 대한소아치과학회 2018 대한소아치과학회지 Vol.45 No.4

The purpose of this study was to compare the shear bond strengths of 3-in-1 flowable composite to the enamel and dentin of primary teeth to previous adhesive systems. 110 primary incisors were prepared and divided into two groups: Dentin group included 5 groups: 1) Scotch bond Multi-purpose plus(DSM), 2) Single-bond 2(DSB), 3) Clearfil SE bond(DSE), 4) All bond universal(DAB), 5) Constic(DC), and Enamel group included 6 groups: 1) Scotch bond Multipurpose plus(ESM), 2) Single bond 2(ESB), 3) Clearfil SE bond(ESE), 4) All bond universal(EAB), 5) Constic(EC), 6) Constic with additional etching(ECE). A cylinder of composite was bonded to the prepared surface, and the shear bond strength was measured. In the dentin groups, group DC had significantly lower shear bond strength than group DSE. No significant difference was found between group DC, group DSM, group DSB and group DAB. In the enamel groups, there was no significant difference between group EC, group ESE, and group EAB. This material showed lowest shear bond strength among all tested materials in both enamel and dentin groups, showing insignificant difference with some adhesive systems. Therefore, 3-in-1 flowable composite can be used for primary teeth restoration but further studies are needed. 이 연구의 목적은 최근 새로 소개된 3-in-1 자가부식, 자가접착 유동성 복합레진의 유치 법랑질과 상아질에 대한 결합력을 기존의접착 시스템들과 비교 평가하기 위함이다. 110개의 발치된 건전한 유전치를 상아질과 법랑질, 그리고 접착 시스템에 따라 11개의 군으로 나눴다. 연구재료로 Scotchbond Multi-Purpose Plus, Single bond 2, Clearfil SE Bond, All-Bond Universal, Constic을 사용하여 전단결합강도를 평가하였다. 3-in-1 자가부식, 자가접착 유동성 복합레진은 상아질과 법랑질 연구에서 모두 가장 낮은 전단결합강도를나타냈지만 몇몇 접착 시스템과는 유의한 차이를 나타내지 않아 유치 수복에서 사용될 수 있을 것으로 생각되나 추가적인 연구가 필요할 것으로 여겨진다.

국내외 모바일 인프라 공유 현황

이형직,조은진,정선구,이광희,Lee, H.J.,Cho, E.J.,Jeong, S.K.,Lee, K.H. 한국전자통신연구원 2021 전자통신동향분석 Vol.36 No.5

To reduce mobile network deployment costs and expand service coverage, mobile infrastructure sharing is becoming increasingly important. This paper introduces the concept and potential benefits of mobile infrastructure sharing as documented in the existing literature. Then, the current status of significant cases of mobile infrastructure sharing in major overseas countries is examined. Finally, sharing 5G infrastructure in rural areas in Korea is introduced. The Korean case is expected to complete national 5G coverage successfully without involving negative competition.