본 연구의 목적은 고정저항과 가변저항을 적용한 백 스쿼트 시 단축성 구간을 전반부와 후반부 로 나누어 신체중심의 속도와 근전도 분석을 통하여 스티킹 포인트에 미치는 영향을 분석하는 것이다. 본 연구의 대상자로 19세 이상의 성인 15명이 연구에 참여하였다(연령: .25.8±2.6 yr, 신장: 181.4±2.2 cm, 체중: 79.7±3.9 kg). 2가지 부하 방법(고정부하, 고정부하+가변부하)를 통하여 백 스쿼트 시 3차원 동작분 석과 하지 근전도를 통하여 자료를 수집하였다. 이에 따른 결론은 다음과 같다. 신체중심의 속도는 VRT가 CRT보다 빠른 속도가 나타났고, 후반부가 전반부보다 빠른 속도가 나타났다. 근전도 분석에서 대퇴직근은 CRT가 VRT보다 근활성도가 크게 나타났고, 전경골근은 CRT의 전반부가 후반부보다 근활성도가 크게 나타났지만, VRT는 차이가 없었다. 이러한 결과를 통하여 고정부하의 약점을 가변부하를 통하여 효율적인 운동을 기대할 수 있다.

A black nickel oxide powder, one of the commercial nickel oxide ores, was reduced by hydrogen gas in a batchtype fluidized-bed reactor in a temperature range of 350 to 500 oC and in a residence time range of 5 to 120 min. The hydrogen reduction behavior of the black nickel oxide was found to be somewhat different from that of green nickel oxide ore. For the black nickel oxide, the maximum temperature (below which nickel oxide particles can be reduced without any agglomeration) was significantly lower than that observed for the green nickel oxide. In addition, the best curve fittings of the Avrami model were obtained at higher values of the overall rate constant “k” and at lower values of the exponent “m”, compared to those values for the green nickel oxide. It may be inferred from these results that the hydrogen reduction rate of the black nickel oxide is faster than that of the green nickel oxide in the early stages, but the situation reverses in the later stages. For the black nickel oxide ore, in spite of the low temperature sintering, it was possible to achieve a high degree fluidized-bed reduction at lower temperatures and at lower gas consumption rates than was possible for the green nickel oxide. In this regard, the use of black nickel oxide is expected to yield a benefit if its ore price is sufficiently lower than that of the green nickel oxide.

A commercial NiO (green nickel oxide, 86 wt% Ni) powder was reduced using a batch-type fluidized-bed reactor in a temperature range of 500 to 600 oC and in a residence time range of 5 to 90 min. The reduction rate increased with increases in temperature; however, agglomeration and sintering (sticking) of Ni particles noticeably took place at high temperatures above 600 oC. An increasing tendency toward sticking was also observed at long residence times. In order to reduce the oxygen content in the powder to a level below 1 % without any sticking problems, which can lead to defluidization, proper temperature and residence time for a stable fluidized-bed operation should be established. In this study, these values were found to be 550 oC and 60 min, respectively. Another important condition is the specific gas consumption rate, i.e. the volume amount (Nm3) of hydrogen gas used to reduce 1 ton of Green NiO ore. The optimum gas consumption rate was found to be 5,000 Nm3/ton-NiO for the complete reduction. The Avrami model was applied to this study; experimental data are most closely fitted with an exponent (m) of 0.6 ± 0.01 and with an overall rate constant (k) in the range of 0.35~0.45, depending on the temperature.