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김현구,Kim, Hyun-Goo 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.5
The amorphization process and the thermal properties of amorphous Ti$_{40}$Cu$_{40}$Ni$_{10}$Al$_{10}$ powder during milling by mechanical alloying were examined by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The chemical composition of the samples was examined by an energy dispersive X-ray spectrometry (EDX) facility attached to the scanning electron microscope (SEM). The as-milled powders showed a broad peak (2$\theta$ = 42.4$^{\circ}$) with crystalline size of about 5.0 nm in the XRD patterns. The entire milling process could be divided into three different stages: agglomeration (0 < t$_m$ $\leq$ 3 h), disintegration (3 h < t$_m$ $\leq$ 20 h), and homogenization (20 h < t$_m$ $\leq$ 40 h) (t$_m$: milling time). In the DSC experiment, the peak temperature T$_p$ and crystallization temperature T$_x$ were 466.9$^{\circ}C$ and 444.3$^{\circ}C$, respectively, and the values of T$_p$, and T$_x$ increased with a heating rate (HR). The activation energies of crystallization for the as-milled powder was 291.5 kJ/mol for T$_p$.
Rod Milling과 Chemical Leaching에 의해 제작된 비평형 Al(Fe-Cu) 합금 분말의 결정화 및 자기적 특성
김현구,Kim Hyun-Goo 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.6
We report the crystallization and magnetic properties of non-equilibrium $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}(x=0.25, 0.50, 0.75)$ alloy powders produced by rod-milling as well as by new chemical leaching. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h or 500 h milling, only the broad peaks of nano bcc crystalline phases were detected in the XRD patterns. The crystallite size, the peak and the crystallization temperatures increased with increasing Fe. After being annealed at $600{^\circ}C$ for 1 h for as-milled alloy powders, the peaks of bcc $AlCu_{4}\;and\;Al_{13}Cu_{4}Fe_{3}\;for\;x=0.25,\;bcc\;AlCu_{4}\;and\;Al_{5}Fe_{2}\;for\;x=0.50,\;and\;Al_{5}Fe_{2},\;and\;Al_{0.5}Fe_{0.5}\;for\;x=0.75$ are observed. After being annealed at $500{^\circ}\;and\;600{^\circ}C$for 1 h for leached specimens, these non-equi-librium phases transformed into fcc Cu and $CuFe_{2}O_{4}$phases for the x=0.25 specimen, and into bcc ${\alpha}-Fe,\;fcc\;Cu,\;and\;CuFe_{2}O_{4}$ phases for both the x=0.50 and the x=0.75 specimens. The saturation magnetization decreased with increasing milling time for $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}$ alloy powders. On cooling the leached specimens from $800{\~}850^{\circ}C$,\;the magnetization first sharply increase at about $491.4{\circ}C,\;745{\circ}C,\;and\;750.0{\circ}C$ for x=0.25, x=0.50, and x=0.75 specimens, repectively.
국가바람지도 및 국가지리정보에 의한 해상풍력단지 개발계획의 적합성 검토
김현구(Kim, Hyun-Goo),황효정(Hwang, Hyo-Jung),송규봉(Song, Kyu-Bong),황선영(Hwang, Sun-Young),윤진호(Yun, Jin-Ho) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
The objective of this research aims preliminary assessments of the proposed plans of offshore wind farm development based on the recently established national offshore wind map and suitability assessment system of offshore wind farm. Incheon Mueodo, Busan Dadaepo-Gadukdo, Sinangun Haeodo have been assessed considering geographic constraints such as water depth, offshore distance, national park, grid connection, and meteorological constraint such as wind power density and wind direction. According to the assessment, Mueodo plan has a weak point in grid connection and several geographic limitations are involved in Haeodo plan while Dadaepo-Gadukdo seems the most possible plan among the review cases. Because of limited assessment in this research, more detail and further consideration are necessary to make a decision of a feasibility project at proposed sites.