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기계적 합금화법에 의한 Nanocomposite의 합성 및 자기적 성질
홍대석,이성희,이충효,김지순,권영순 한국분말야금학회 2002 한국분말야금학회 학술대회논문집 Vol.2002 No.1
현재 기계적 합금화법에서는 주로 합금을 구성하는 성분원소 분말을 불활성분위기에서 볼밀처리 함으로써 함금화를 시키거나 모합금에 산화물을 분산시켜 복합화시키는 공정을 통하여 각종 화합물, 비정질상 및 과포화고용체등의 준안정상의 합성 뿐만이 아니라 초미세조직의 생성에 관한 폭 넓은 분야의 연구가 행하여지고 있다. 한편 MA에서는 볼멀처리중 기계적 에너지의 투여에 의하여 실제 반응온도보다 낮은 온도에서 발생하는 특이한 화학반응 즉 Mechanochemical
트레드밀에서의 노르딕워킹과 일반걷기 운동을 통한 심박수, 산소섭취, 에너지소비 및 젖산농도의 비교
홍대석,남혜주 대한체육학회 2023 대한스포츠융합학회지 (jcses) Vol.21 No.3
The purpose of this study was to characterize responses in energy expenditure(EE), heart rate(HR), lactic acid, and oxygen uptake(VO2) during nordic walking(NW) and general walking(GW) on a treadmill. Fourteen healthy females students(NW=7, GW=7) volunteered to participate. Nordic walking and General walking for 30 minutes at a speed of 6 km/h on a treadmill were performed to measure energy expenditure(EE), heart rate(HR), and lactate concentration befor and after exercise. HR and EE was statistically higher(p<.05) during NW than during GW. The lactate concentration did not show any significant difference between the two groups, but the lactate concentration showed a statistically significant(p<.05) difference before and after exercise in the two group. The VO2 was higher(p<.05) in NW than GW in 10 minutes of exercise, and there was no statistically significant difference in the subsequent time period. In conclusion, it was found that Nordic Walking recommended as an exercise for maintaining and improving health in busy daily life. In particular, it is thought to be a positive walking exercise for the elderly who unstable in walking.
마그네타이트와 금속(Ti, Al)의 기계적 합금화에 의한 복합분말의 합성
홍대석,이성희,이충효,김지순,권영순 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.3
Recently, it has been found that mechanical alloying (MA) facilitates the nanocomposites formation of metal-metal oxide systems through solid-state reduction during ball milling. In this work, we studied the MA effect of Fe$_{3}$O$_{4}$-M (M = Al, Ti) systems, where pure metals are used as reducing agents. It is found that composite powders in which $Al_{2}$O$_{3}$ and TiO$_{2}$ are dispersed in $\alpha$-Fe matrix with nano-sized grains are obtained by mechanical alloying of Fe$_{3}$O$_{4}$ with Al and Ti for 25 and 75 hours, respectively. It is suggested that the large negative heat associated with the chemical reduction of magnetite by aluminum is responsible for the shorter MA time for composite powder formation in Fe$_{3}$O$_{4}$-Al system. X-ray diffraction results show that the reduction of magnetite by Al and Ti if a relatively simple reaction, involving one intermediate phase of FeAl$_{2}$O$_{4}$ or Fe$_{3}$Ti$_{3}$O$_{10}$. The average grain size of $\alpha$-Fe in Fe-TiO$_{2}$ composite powders is in the range of 30 nm. From magnetic measurement, we can also obtain indirect information about the details of the solid-state reduction process during MA.