Mechanical Alloying에 의한 비정질 Ti₄₀Cu₄₀Ni₁₀Al₁₀ 합금의 형성 및 열적특성

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.

풍력발전기 풍상부 지면설치 구조물에 의한 풍속전단 개선효과의 전산유동해석

김현구(Kim, Hyun-Goo),우상우(Woo, Sang-Woo),장문석(Jang, Moon-Seok),신형기(Shin, Hyuong-Ki) 한국신재생에너지학회 2008 한국신재생에너지학회 학술대회논문집 Vol.2008 No.05

This study demonstrates the advantages of a shear-free structure designed to modify vertical profiles of wind speed in the atmospheric surface layer. Computational fluid dynamics(CFD) software, FLUENT is used to interpret the velocity field modification around the structure and wind turbine. The shapes of shear-free structure, installed at upstream toward prevailing wind direction, would be fences, buildings and trees, etc. According to the simulation results, it is obvious that wind shear between heights of wind turbine's blades is decreased together with a speed-up advantage. This would lead decrease of periodic wind loading caused by wind shear and power-out increase by flow uniformity and wind speed-up.

풍력자원 잠재량 산출을 위한 저해상도 바람지도 구축

김현구(Kim, Hyun-Goo),장문석(Jang, Moon-Seok),경남호(Kyong, Nam-Ho) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11

The national goal of wind energy dissemination has to be determined rationally based on technically available wind resource potential. For a reliable and scientific estimation or wind resource potential, a wind map is requisite. This paper presents the national wind map of Korea established by numerical wind simulation. Prediction accuracy of the low-resolution wind map is Improved by nudging QuikSCAT data and is validated by comparing with marine buoy beacon and met-mast measurements. Therefore, quantification of national wind resource potential is now possible and is anticipating to be utilized as a core index for policy and strategy building of wind energy dissemination and technology development.

주성분분석에 의한 표준기상년(TMY)의 체계성 검증

김현구(Hyun-Goo Kim),김보영(Bo-Young Kim),강용혁(Yong-Heack Kang) 한국태양에너지학회 2021 한국태양에너지학회 학술대회논문집 Vol.2021 No.11

환경규제를 고려한 남한 육상풍력 잠재량 산정

김현구(Kim Hyun-Goo),황효정(Hwang Hyo-Jung),강용혁(Kang Yong-Heack),윤창열(Yun Chang-Yeol) 한국태양에너지학회 2014 한국태양에너지학회 학술대회논문집 Vol.2014 No.3

풍력발전 예보를 위한 풍력단지 발전량 현장적응

김현구(Hyun-Goo Kim),김진영(Jin-Young Kim),김창기(Chang Ki Kim),황수진(Soo-Jin Hwang) 한국태양에너지학회 2022 한국태양에너지학회 학술대회논문집 Vol.2022 No.10

제주도 김녕 풍황마스트 측정자료를 적용한 해상풍/육상풍 난류특성 분석

김현구(Kim Hyun-Goo),정태윤(Jeong Tae-Yoon),장문석(Jang Moon-Seok) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.11

Analysis on turbulence intensity profile depending on wind speed is an important process to set up design condition of wind turbine in terms of fatigue load. This paper tests goodness of fit of turbulence intensity empirical equations suggested by the IEC 61400 Standards with Jejudo Gimnyeong met-tower measurement, which is erected at a seashore. Therefore sea breeze and land breeze coexist. Sea breeze case showed apparent increasing trend of turbulence intensity in a high wind speed regime due to increase of sea surface roughness. However, neither inland wind turbine standard IEC 61400-1 nor offshore wind turbine standard IEC 61400-3 fit such a trend adequately. Whereas modified empirical equation of turbulence intensity of IEC 61400-3 derived from Germany FINO1 application study by considering turbulence intensity behavior in a high wind speed regime showed good agreement with the measurement. Therefore, we can reconfirm and conclude that IEC 61400-3 Ed.1 legislated in 2009 needs to be modified.

수치바람모의에 의한 한반도 바람지도 구축

김현구(Hyun-Goo Kim),장문석(Moon-Seok Jang),이화운(Hwa-Woon Lee),최현정(Hyun-Jeong Choi) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

In this paper, the research background and objectives of the wind mapping project of the Korean Peninsula, which has been carrying out as a part of “Investigation of new-renewable energy resources and establishment of comprehensive management system” funded by Korea Ministry of Commerce, Industry and Energy, are introduced together with the intermediate result of the project so far. The Korean wind map is to be established by numerical wind simulation based on terrain model ME-DEM and land-use model ME-LUM with the spatial resolution of 10㎞.

국가바람지도 데이터베이스화 및 가시화를 위한 IDL 활용

김현구(Kim, Hyun-Goo),이순환(Lee, Soon-Hwan),이상우(Lee, Sang-Woo),이종혁(Lee, Jong-Hyuk) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

한반도 국가바람지도(김현구, 2009)는 한국에너지기술연구원에서 지식경제부의 부처임무사업으로 구축되었으며 현재 웹서비스(http://www.kier-wind.org)를 통하여 정보를 제공하고 있다. 국가바람지도는 수치기상예측(NWP; Numerical Weather Prediction) 모델을 이용하여 영토, 영해에 대해 1km{times}1km의 고해상도로 작성한 뒤(이순환 등, 2009) 풍력자원 정보로 재가공되었다. 한반도 국가바람지도는 5년의 장기간에 대한 시계열 수치기상예측에 의하여 구축되었기 때문에 데이터베이스(DB; database)의 효율적 관리가 필연적으로 요구된다. MM5 또는 WRF 모델의 고유 출력포맷의 자료구조는 풍력자원분석에 필요한 기상요소 외에도 대기과학자에게 필요한 수많은 기상인자를 종합적으로 포함하고 있다. 따라서 2차원 층(layer) 또는 3차원 공간분포 분석 및 계산격자인 셀(cell)에서의 1차원 시계열 분석 등 다양한 자료축출에는 비효율적인 자료구조가 된다. 이러한 자료구조의 불편을 해소하기 위해서는 기상요소별로 독립적이고 빈번한 시계열 자료 추출에 효율성을 가지며 어떤 프로그래밍 언어를 사용하든지 직관적으로 쉽게 사용할 수 있는 바람지도 데이터베이스의 재구성이 요구된다. 이에 대용량 수치자료의 처리 측면에서 장점을 가지는 과학기술 프로그래밍 언어인 IDL을 기반으로 국가바람지도의 자료구조를 효율화하여 데이터베이스화 하였으며 IDL에 내재된 그래픽 기능을 활용하여 가시화를 구현함으로써 연구개발자의 입장에서 국가바람지도의 활용성 및 효율성을 향상시키고자 하였다.