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밀링 에너지 변화에 따른 TiC 분말의 미세화 거동에 관한 정량적 연구
홍성모,박은광,김경열,박진주,이민구,이창규,이진규,권영순,Hong, Sung-Mo,Park, Eun-Kwang,Kim, Kyeong-Yeol,Park, Jin-Ju,Lee, Min-Ku,Rhee, Chang-Kyu,Lee, Jin-Kyu,Kwon, Young-Soon 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.1
This study investigated refinement behaviors of TiC powders produced under different impact energy conditions using a mechanical milling process. The initial coarse TiC powders with an average diameter of 9.3 ${\mu}m$ were milled for 5, 20, 60 and 120 mins through the conventional low energy mechanical milling (LEMM, 22G) and specially designed high energy mechanical milling (HEMM, 65G). TiC powders with angular shape became spherical one and their sizes decreased as the milling time increased, irrespective of milling energy. Based upon the FE-SEM and BET results of milled powders, it was found initial coarse TiC powders readily became much finer near 100 nm within 60 min under HEMM, while their sizes were over 200 nm under LEMM, despite the long milling time of up to 120 min. Particularly, ultra-fine TiC powders with an average diameter of 77 nm were fabricated within 60 min in the presence of toluene under HEMM.
스테인리스 316강 및 8.8%알루미늄 청동 합금의 케비테이션 기포 충격 하중 및 침식 핏 손상 고찰
이민구 ( Min Ku Lee ),홍성모 ( Sung Mo Hong ),김광호 ( Gwang Ho Kim ),이창규 ( Chang Kyu Rhee ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.5
The impact loads of cavitation bubbles generated by ultrasonic vibratory device and their effects on the surface damage have been quantitatively evaluated for the 8.8Al-bronze, flame-quenched 8.8Al-bronze and SUS316 alloys. The cavitation impact loads were determined by calibrating the cavitation pulses through a steel ball drop test, and a linear relation between the cavitation pulse height and the impact load was established for each materials. The measured impact loads and frequency under the cavitation bubble collapse were correlated to the size and number of the pit formed on the surface by assuming that an individual pit is generated by a single collapse of bubble. The critical impact load Le required to form the pits (more than 5 μm) on the flame-quenched 8.8Al-bronze was 13.16N that is lower compared to those of the 8.8Al-bronze (13.33N) and SUS316 (13.9N) alloys. The very small amounts of cavitation bubbles were involved in the formation of pits, which were only 0.89~4.32%, 0.45~1.84% and 4.07~6.87% for the 8.8Al-bronze, flame quenched 8.8Al-bronze and SUS316 alloys, respectively.
압축 비트스트림 기반의 향상된 동영상 움직임 검출 방법
이민구(Min-Ku Lee),박유선(Yousun Park),장의선(Euee Seon Jang) 대한전자공학회 2018 대한전자공학회 학술대회 Vol.2018 No.11
In this paper, we propose an improved motion detection method from a compressed bitstream without decoding. In general, it is believed that a compressed video data is statistically uniform in that no meaningful data can be assessed solely from the bitstream without decoding. In this paper, we tackled this problem to classify an input video bitstream with or without motion activity. We extended our previous detection method to come up with higher accuracy in classification. Experimental results show that the proposed method improves the motion detection accuracy of the previous method.
이민구 ( Min Ku Lee ),신동일 ( Dong Ii Shin ),박희성 ( Hee Sung Park ) 한국균학회 2012 韓國菌學會誌 Vol.40 No.4
Trametes versicolor, a common inhabitant of dead hardwoods in temperate climates, belongs to one of the important medicinal mushrooms. In this study, spent coffee ground(SCG), instant coffee powder(ICP) and instant decaffeinated coffee powder(IDCP) were examined for their effect on the mycelial growth of T. versicolor. Adding SCG was proven to be significantly beneficial at the concentration as high as 10%. ICP and IDCP, both containing concentrated polyphenols, were also beneficial at low concentration less than 1%. 1% SCG culture resulted in ten-fold increased yield of dry cell mass compared to the control culture. Adding coffee substances was recommended as a useful tool for accelerating the growth and strengthening the physiological activity of the mycelium.
김광호(Gwang-Ho Kim),이민구(Min-Ku Lee),김경호(Kyeong-Ho Kim),김흥회(Whung-Whoe Kim),이창규(Chang-Kyu Rhee),김길무(Gil-Mu Kim) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.2
In this study, the movable flame hardening process of 12Cr steel for a uniform hardness and desirable residual stress have been investigated. For this, the temperature cycles have been controlled accurately as a function of the three processing variables, the flame intensity If, the scanning velocity Vs and the initial flame holding time th, where the standard surface temperature Ts, max was maintained at 960°C. The optimized conditions were Vs = 0.68 ㎜/s and th = 67 sec for the C₃H?:O₂ = 5:20 l/min, Vs = 0.80 ㎜/s and th= 56 sec for the C₃H?:O₂ = 6:24 l/min, Vs = 1.01 ㎜/s and th= 48 sec for the C₃H?:O₂= 7:28 l/min, and Vs = 1.15 ㎜/s and th= 39 sec for the C₃H?:O₂= 8:32 l/min. The optimally flame-hardened surface exhibited uniform distributions of the hardness and residual compressive stress over the treated area with moderate levels of 470~490HV0.2 in hardness and ?300~?450 MPa in residual stress, which were acceptable on the basis of the acceptance criteria of Siemens AG-KWU and GE Power Generation Engineering.
비스무스 나노분말 표지 전극의 카드뮴/납 검출특성에 관한 연구
이경자,김현진,이희민,이상훈,이민구,이창규,Lee, Gyeoung-Ja,Kim, Hyoun-Jin,Lee, Hi-Min,Lee, Sang-Hoon,Lee, Min-Ku,Lee, Chang-Kyu 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.5
Trace analysis of Cd and Pb at surface modified thick film graphite electrode with Bi nanopowder has been carried out using square-wave anodic stripping voltammetry (SWASV) technique. Bi nanopowder synthesized by gas condensation (GC) method showed the size of $50{\sim}100$ nm with BET surface area, $A_{BET}=6.8m^{2}g^{-l}$. For a strong adhesion of the Bi nanopowder onto the screen printed carbon paste electrode, nafion solution was added into Bi-containing suspension. From the SWASV, it was found that the Bi nanopowder electrode exhibited a well-defined responses relating to the oxidations of Cd and Pb. The current peak intensity increased with increasing concentration of Cd and Pb. From the linear relationship between Cd/Pb concentrations and peak current, the sensitivity of the Bi nanopowder electrode was quantitatively estimated. The detection limit of the electrode was estimated to be $0.15{\mu}g/l$ and $0.07{\mu}g/l$ for Cd and Pb, respectively, on the basis of the signal-to-noise characteristics (S/N=3) of the response for the $1.0{\mu}g/l$ solution under a 10 min accumulation.
이은희,이민구,이창규,Lee Eun-Hee,Lee Min-Ku,Rhee Chang-Kyu 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.2
In this study, the effects of the dispersants, i.e., Hypermer KD-2 and poly(l-vinyl-2-pyrrolidone) (PVP), and their concentration on the dispersion stability of Ni nanoparticles ($10nm{\sim}40nm$) in ethanol were investigated by using a visual inspection, a transmission profile (Turbiscan), and a zeta potential measurement. The transmission profiles measured by Turbiscan showed that the particle size increased over the entire height of the sample for suspensions with both the dispersants without showing any particle coalescence and sedimentation. The visual inspection also confirmed that the Ni suspensions with Hypermer KD-2 and PVP were very stable for more than a year. The zeta potential values varied from positive to negative with increasing the dispersant's concentration. The dispersion stability of the suspensions was not affected by both the dispersant's concentration and the zeta potential values. The observed suspension stability of Ni nanoparticles was attributed to the steric effect for the Hypermer KD-2 and to the bridging effect for the PVP.
김경호,이민구,이창규,위명용,김흥회,Kim, Kyeong-Ho,Lee, Min-Ku,Rhee, Chang-Kyu,Wey, Myeong-Yong,Kim, Whung-Whoe 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.12
In this research, fretting tests were conducted in air to investigate the wear characteristics of fuel cladding materials with the fretting parameters such as normal load, slip amplitude, frequency and the number of cycles. A high frequency fretting wear tester was designed for this experiment by KAERI. After the experiments, the wear volume and the shape of wear contour were measured by the surface roughness tester. Tribologically transformed structures(TTS) were analysed by means of optical and scanning electron microscopes to identify the main wear mechanisms. The results of this study showed that the wear volume were increased with increasing slip amplitude, and the shape of wear contour was transformed V-type to W-type. Also, it was found that the critical slip amplitude was 168${\mu}{\textrm}{m}$. These phenomena mean that wear mechanism transformed partial slip to gross slip to accelerate wear volume. The wear depth increased with an increase of friction coefficient due to increase of normal load and frequency. The fretting wear mechanisms were believed that, after adhesion and surface plastic deformation occurred by relative sliding motion on the contact between two specimens, TTS creation was induced by surface strain hardening and wear debris were detached from the contact surface which were produced by the micro crack propagation and creation.