침탄 두께에 따른 피로강도 영향 특성 평가

최현민,박용하,신용택,김명현,Choi, Hyun Min,Park, Yong Ha,Shin, Yong Taek,Kim, Myung Hyun 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.4

Carburizing treatments are the important way to developing fatigue strength and wear resistance. It is well known that the case depth is one of the most significant parameters determining fatigue strength. In this study, 3-point bending fatigue test was conducted to evaluate fatigue strength for the carburized depth with 18CrNiMo7-6 steel. As a result, fatigue strength increased with effective case depth decreased. It is shown that hardness in case hardened layer played principal role in the fatigue strength.

담배 조직배양에서 6 - Phosphogluconater Dehydrogenase 의 정제와 성질에 관한 연구

최현민,김승수 ( Hyun Min Choi,Soung Soo Kim ) 생화학분자생물학회 1984 BMB Reports Vol.17 No.4

One 6-phosphogluconate dehydrogenase isoenzyme, designated 6PG DH II, was purified from tobacco callus culture line (Nicotiana tobacum L., var. Virginia 115) utilizing ammonium sulfate precipitation, DEAE-cellulose chromatography, Red Sepharose CL-6 B affinity chromatography followed by Sephadex G-100 gel filtration. The purified enzyme was homogeneous according to the criteria of polyacrylamide gel electrophoresis. 6 PG DH II appears to have a dimeric structure with subunit molecular weight of 44,000 and native molecular weight of approximately 83,000. Double reciprocal plot of reaction velocity vs. 6-phosphogluconate concentrations indicated Km values of 17 μM with a marked inhibition of initial velocity at high 6-phosphogluconate concentrations.The NADP^+ double reciprocal plot showed an abrupt increase in the apparent Km and Vmax with increasing NADP^+. The two Km`s for low and high NADP^+ concentrations were 6.5 μM and 70 μM, respectively. The pH optimum of the enzyme was 8.5 in Tris-HCl and 8.0 in phosphate buffer. MgCl₂ was not required for the enzymatic activity. Furthermore, MgCl₂ inhibited the activity at high concentration.

감마선 조사된 남양진주의 검지

최현민,이보현,김영출,Choi, Hyun-Min,Lee, Bo-Hyun,Kim, Young-Chool 한국결정성장학회 2012 韓國結晶成長學會誌 Vol.22 No.1

남양진주에 $Co^{60}$을 이용하여 0.1~100 kGy까지 선량의 범위에서 방사선 조사 실험을 행하였다. 더불어 방사선 조사된 남양진주의 검지를 위해 전자상자성공명(EPR)과 아미노산분석(AAA)을 행하였다. EPR 분석에서 방사선 조사후, 방사선 조사전에는 없었던 free radical이 생성되었으며 $CO_2^-$ radical의 g-factor는 $2.001{\pm}0.002$이었다. 진주층의 아미노산 분석 결과 방사선 조사후의 glutamic acid는 11.43 %, alanine은 3.11 %, histidine은 43.75 %의 감소량을 보였으며, 이는 일부 아미노산이 파괴되었음을 보여준다. 본 연구의 결과로 EPR 분석은 방사선 조사된 남양진주의 검지에 적합하였다. We have been performed on $Co^{60}$ ${\gamma}$-ray irradiation of South Sea cultured pearls, with the absorbed dose of 0.1~100 kGy at room temperature. In addition, it was investigated electron paramagnetic resonance (EPR) and amino acid analysis (AAA) for detection of Gamma irradiated South Sea cultured pearls. It was observed that the irradiated South Sea cultured pearls revealed additional free radical peak such as $CO_2^-$, at a g-factor of $2.001{\pm}0.002$ in EPR spectra. From the amino acid analysis (AAA), it was shown that some of amino acid in the protein of the nacre destroyed after ${\gamma}$-ray; glutamic acid residue by 11.43 %, alanine by 3.11 %, and histidine by 43.75 %. It was useful to detect the irradiated South Sea cultured pearls by EPR measurement in our study.

감마선 조사된 남양진주의 검지 II

최현민,이보현,김영출,Choi, Hyun-Min,Lee, Bo-Hyun,Kim, Young-Chool 한국결정성장학회 2012 韓國結晶成長學會誌 Vol.22 No.4

방사선 조사된 남양진주는 광투과 검사, 확대 검사, 형광반응 검사 등의 보석학적 검사방법으로는 감별이 어렵지만, ESR 분석을 통해 조사된 남양진주와 조사되지 않은 남양진주의 감별이 가능하였다. 본 연구에서는 조사선량이 증가함에 따른 $CO^-_2$ radical의 변화와 관련된 정보를 제공할 목적으로 진주층과 핵을 분리하여 분석하였으며, 핵보다는 진주층에서 $CO^-_2$ radical이 더 명료하게 나타남을 발견하였다. It is very difficult to detect irradiated South Sea cultured pearls (SSCPs) at a low dose by gemological methods (e.g. optical transmission method, microscopic examination, UV fluorescence reaction, and so on). In this study, however, it was possible to distinguish between irradiated SSCPs from un-irradiated SSCPs by ESR analysis. We have analyzed the pearl nacre and nucleus by separating them for the purposed of providing information about the change of $CO^-_2$ radical as growing absorbed doses. And it was found out that the signal of $CO^-_2$ radical of the nacre is more distinct than the nucleus.

단기간의 금연과 일회성 유산소 운동이 흡연자의 심혈관 반응에 미치는 영향

송준경(Jun Kyung·choi),최현민(Hyun Min Choi),김종경(Jong Kyung Kim),노호성(Ho Sung Nho) 한국사회체육학회 2012 한국사회체육학회지 Vol.0 No.48

The purpose of this study was to investigate cardiovascular responses to a bout of aerobic exercise and acute smoking cessation in smoker. nine collegiate male smoker who have been smoking(duration of smoking: 7.5 ± 0.9yrs; number of cigarettes per day: 15.5 ± 1.5) participated in this study. All subjects performed PEI to stimulate Group IV metaboreceptor at immediately after smoking, 24hours after smoking cessation and smoking after a bout of aerobic exercise. they were measured SBP, DBP, HR, SV, CO, TVC using by finometer(FMS co, Netherland). As a result, compared to immediately after smoking, SBP, DBP, and MAP were significantly decreased 24-hours after smoking cessation at rest and PEI(p<0.05). In addition, smoking after a bout of aerobic exercise caused by post-exercise hypotension indicated that SBP was significantly decreased compared to immediately after smoking(p<0.05). also, the changes in DBP and MAP at rest and handgrip exercise were significantly smaller compared to immediately after smoking(p<0.05). Thus, the results showed that smoking cessation during 24-hours and a bout of aerobic exercise relieve excess blood pressure response and enhanced arterial baroreflex in collegiate male smoker. It is concluded that caused exercise pressor reflex by stimulated Group IV may be effective to improve excess blood pressure responses.

유압식 저항운동이 허약한 고령자들의 기능적 체력과 삶의 질에 미치는 효과

이성철(Sung-Chul Lee),최현민(Hyun-Min Choi),타케시마 노부오(Nobuo Takeshima) 한국생활환경학회 2014 한국생활환경학회지 Vol.21 No.3

This study was to evaluate the effectiveness of hydraulic resistance exercise (HDRE) for frail elderly. Forty five participants were divided into exercise group (79±7.6 yr, 11 men, 14 women), and control group (76±7.9 yr, 11 men, 9 women). An exercise group was trained by 6 types of exercise: Knee extension (KE), knee flexion (KF), chest press (CPr), chest pull (CPu), low back flexion (LF), and low back extension (LE) 2 days/week. HDRE was consisted of 12-week supervised program, 50 min/day, and one set with an appropriate loading for 15 repetitions to fatigue. As a results, muscle strength and power were significantly increased between 16.6~27.1% and 18.9~81.2% in the KE, KF, CPr, CPu, and LF (p < .05). The functional fitness were also increased about 19~43% except for sit & reach test, and health related quality of life were improved about 15~24% in the sf-36v2 test (p<.05). However, there were no significant changes in the control group, and the HDRE is an effective form of resistance training that provides benefits using low and moderate intensity of training for frail elderly.

설문지를 이용한 신체활동량과 참여강도가 중년여성의 체력 및 관상동맥 위험인자에 미치는 영향

안영환(Young Hwan An),박세정(Saejong Park),최현민(Hyun Min Choi),김종경(Jong Kyung Kim),노호성(Hosung Nho) 한국발육발달학회 2015 한국발육발달학회지 Vol.23 No.1

The purpose of the study was to investigate the effects of the volume of physical activity on obesity, physical fitness and coronary risk factors among the middle-aged women. physical activity was assessed from International Physical Activity Questionnaire (IPAQ) and were categorized by health enhancing physical activity group (PG), minimum activity group (MG), and non-activity group (NG) according to the volume of physical activity. Apparently healthy middle-aged women (n=163; 52.1±8.6 yrs) participated and they were classified as PG (n=46; 5,878±3547 MET·min/week), MG (n=64; 1,678±886 MET·min/week), and NG (n=52; 456±389 MET·min/week). Also, method of the study was categorized by vigorous activity and moderate activity according to the study of WHO (2010) and Mikael Fogeholm (2006). Measurement variables were body composition, physical fitness (hand-grip, sit-up, pacer, sit & reach, shuttle run, and long jump), total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), high-density lipoprotein cholesterol (HDLC), and triglycerides (TG). One-way ANOVA was used with Tukey post-hoc (p<.05). In the result, PG had significantly low percent body fat comparing with MG or NG (p=.02). And, among physical fitness variables flexibility was higher in PG than in MG (p=.03). While HDLC (p=.007) was higher in the PG than MG or NG, LDLC (p=.024) was lower in the PG than MG. TG (p=.021) was lower in the PG than MG or NG. Vigorous activity group had significantly high pacer in classification as physical activity intensity. Glucose was lower in vigorous activity group than in moderate activity group (p=.02). In conclusion, it was generally low body fat rate and coronary risk factors for middle-aged women to increased volume of physical activity of daily life and participating vigorous activity indicated that was able to keep a high fitness standard.

Effect of Pressurization Training with Walking on Body Composition, Respiratory Function, and Cardiovascular Response in Middle-Aged Obese Women

Hyun-Min Choi(최현민),Dong-Jun Lee(이동준) 한국생명과학회 2012 생명과학회지 Vol.22 No.4

중년 비만여성들을 대상으로 다리 근육의 정맥 혈류를 제한한 가압 걷기 트레이닝 그룹 15명으로 연구대상자를 선정하여 3주간의 가압 걷기 트레이닝을 실시한 결과 다음과 같은 결론을 얻었다. 첫째, 가압 걷기 트레이닝을 통해 LBM에서 트레이닝 전보다 후에 1.2 kg이 증가, FM과 %fat에서는 각각 2.8 kg, 3.3% 감소하였으며, 통계적으로도 유의한 차이를 나타냈다(p<0.05). 둘째, 가압 걷기 트레이닝을 통해 VO2max와 VEmax에서 트레이닝 전보다 후에 각각 3.6 ml/kg/min, 6.0 l/min 증가하였고, HRmax에서는 7 beat/min으로 감소하였으며 통계적으로도 유의한 차이를 나타냈다(p<0.05). 셋째, 가압 걷기 트레이닝을 통해 심혈관 반응에서 트레이닝 전보다 후에서 운동 강도가 증가함에 따라 CO과 TVC가 증가하는 것으로 나타났으며, 통계적으로도 유의한 차이를 나타냈다(p<0.05). 이상의 결과로부터 가압 걷기 트레이닝을 통해서 호흡?순환계 및 심혈관 기능의 증가와 근육량 증가에 따른 체성분의 변화를 유발할 수 있다는 것을 제시하였다. 본 연구의 결과를 토대로 향후 연구에서는 연구대상자의 범위를 넓혀 노년층까지 효과를 검증하는 연구와 3주 이상의 운동을 적용시키면 보다 높은 임상학적 효과가 나타날 것으로 판단된다. Pressurization walk training (PWT) with blood flow occlusion has been investigated with regard to muscle hypertrophy and physical fitness function in athletes and healthy people. However, the cardiorespiratory and cardiovascular responses of obese people to PWT are unknown. Thus, we investigated the effects of PWT on body composition (Weight, FM, LBM, %fat, BMI), cardiovascular responses (HR, SV, CO, TVC), and cardiorespiratory responses (VO2max, VEmax, HRmax) in middle-aged obese women. They participated in walk training with (n=15) blood flow occlusion and cross-sectional areas of the quadriceps on both legs. Five sets of 3-min walking (5.5 km/h at 5% grade) and 1-min resting were performed twice a day, 5 days/week for 3 weeks. The results showed that the LBM was significantly increased, and decreased body weight of reducing FM, %bodyfat in PWT (p<0.05). For the cardiovascular response, SBP and TPR were significantly decreased (p<0.05), and CO increased (p<0.05). In addition, the VO2max and VEmax were improved through PWT. Therefore, this study suggests that the presence of obesity in middle-aged women may result in body composition, cardiorespiratory, and cardiovascular responses caused by PWT.

RPE 13에서의 12분 걷기테스트를 이용한 적정 운동강도의 타당성

정은혜(Jung Eun-Hye),최현민(Choi Hyun-Min),김종경(Kim Jong-Kyung),노호성(Nho Ho-Sung) 한국체육과학회 2008 한국체육과학회지 Vol.17 No.1

The purpose of this study was to examine if a 12-min submaximal treadmill walk test corresponding to a rating of perceived exertion 13 (RPE13) was appropriate to determine exercise intensity. Twenty-seven subjects participated this study, aged from 22 to 26. VO2max, VO2AT and total distance were obtained from a graded exercise test (GXT). Also, VO2 and total distance were obtained during a 12-min submaximal treadmill walk test corresponding to RPE13. The results were obtained as follows: 1) The correlation coefficients between VO2 obtained during a 12-min submaximal treadmill walk test and VO2AT obtained during GXT were statistically significant (r=0.382). 2) The correlation coefficients between VO2 obtained during a 12-min submaximal treadmill walk test and VO2max obtained during GXT were statistically significant (r=0.434). 3) The correlation coefficients between total distance obtained during a 12-min submaximal treadmill walk test and V O2max, VO2AT obtained during GXT were statistically significant (r=0.721, 0.688). 4) The correlation coefficients between VO2 obtained during a 12-min submaximal treadmill walk test and VO2 obtained during RPE13 in GXT were statistically significant (r=0.526). These results suggest that a 12-min submaximal treadmill walk test corresponding to RPE13 is a valid for determining exercise intensity at AT level. Therefore, the 12-min submaximal treadmill walk test corresponding to RPE13 could be a useful for prescribing exercise intensity in the collegiate-student men.

대학 보디빌딩 선수의 대사적 수용기 자극에 따른 심혈관 반응

김성민(Kim, Sung-Min),최현민(Choi, Hyun-Min),김종경(Kim, Jong-Kyung),노호성(Nho, Ho-Sung) 한국체육과학회 2012 한국체육과학회지 Vol.21 No.3

Previous studies have shown that resistive exercise training such as isometric handgrip exercise or weight lifting decreases arterial blood pressure. However, the mechanisms responsible for reduction in arterial blood pressure have not been investigated. One mechanism that may lower arterial blood pressure is a neural mechanism termed the muscle metaboreflex that is activated when oxygen delivery to active skeletal muscle falls below a critical level. The muscle metaboreflex, a component of exercise pressor reflex, increases the sympathetic activity to heart and vasculature and then increases arterial blood pressure, cardiac output, and ventilation during exercise. Therefore, the purpose of this study was to investigate the effect of the muscle metaboreflex on hemodynamics following fatiguing rhythmic handgrip exercise and circulatory arrest in 10 male collegiate body builders and 10 age-matched controls. All subjects performed 3 min rhythmic handgrip exercise at the exercise intensity of 60% maximal voluntary contraction and 2 min of postexercise circulatory occlusion while heart rate (HR), stroke volume (SV), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured followed by the calculation of cardiac output, mean arterial pressure (MAP), and total vascular conductance (TVC). From resting baseline values, the changes in SBP, DBP, and MAP in body builders during PEI were significantly smaller compared to contol group (SBP: ? 31.2 ㎜Hg vs. ? 36.2 ㎜Hg; DBP: ? 9.9 ㎜Hg vs. ? 18.2 ㎜Hg; MAP: ? 17.0 ㎜Hg vs. ? 24.2 ㎜Hg, respectively). However, there was no difference in CO between two groups (? 2.2 l/min vs. ? 2.2 l/min) and TVC tended to be higher in body builders compared to control group (? 9.0 ml/min/㎜Hg vs. ? 3.9 ml/min/㎜Hg). This study suggest that chronic resistance training may improve the muscle metaboreflex. The mechanism in which the pressor response mediated by the muscle metaboreflex with resistance training is attenuated is due to peripheral vasodilation.