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( Colin R. Carriker ),( Roger A. Vaughan ),( Trisha A. Vandusseldorp ),( Kelly E. Johnson ),( Nicholas M. Beltz ),( James J. Mccormick ),( Nathan H. Cole ),( Ann L. Gibson ) 한국운동영양학회 2016 Physical Activity and Nutrition (Phys Act Nutr) Vol.20 No.4
[Purpose] To examine the effect of a 4-day NO<sub>3</sub>- loading protocol on the submaximal oxygen cost of both low fit and high fit participants at five different exercise intensities. [Methods] Eleven (6 high fit, VO<sub>2max</sub> 60.1 ± 4.6ml/kg/min; 5 low fit, VO<sub>2max</sub> 42.4 ± 3.2ml/ kg/min) participants were initially assigned to a placebo (PL; negligible NO<sub>3</sub>-) or inorganic nitrate-rich (NR; 6.2 mmol nitrate/day) group using a double-blind, placebo-controlled, crossover design. Participants completed three trials (T1, T2 and T3). T1 included a maximal aerobic capacity (VO<sub>2max</sub>) treadmill test. A 6-day washout, minimizing nitrate consumption, preceded T2. Each of the four days prior to T2 and T3, participants consumed either PL or NR with the final dose 2.5 hours prior to exercise. A 14-day washout followed T2. T2 and T3 consisted of 5-minute submaximal treadmill bouts (45, 60, 70, 80 and 85% VO<sub>2max</sub>) determined during T1. [Results] Low fit nitrate-supplemented participants consumed less oxygen (p<0.05) at lower workloads (45% and 60% VO<sub>2max</sub>) compared to placebo trials; changes were not observed in high fit participants. The two lowest intensity workloads of 45 and 60% VO<sub>2max</sub> revealed the greatest correlation (r=0.54, p=0.09 and r=0.79, p<0.05; respectively) between VO<sub>2max</sub> and change in oxygen consumption. No differences were found between conditions for heart rate, respiratory exchange ratio or rating of perceived exertion for either fitness group. [Conclusion] Nitrate consumption promotes reduced oxygen consumption at lower exercise intensities in low fit, but not high fit males. Lesser fit individuals may receive greater benefit than higher fit participants exercising at intensities <60% VO<sub>2max</sub>.
On the Motion of the Structure Varying Multibody Systems with Two-Dimensional Dry Friction
Fujie Xia,Peter Wolfs,Colin Cole 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.4
In the present paper the dynamics of the structure varying multibody systems caused by stick-slip motion with two-dimensional dry friction are analyzed. The methods to determine friction force both in stick and slip states are described. The direct method of considering the wagon bogie system as a structure varying system was used to consider two dimensional friction at the wheelset-side frame connection. The concept of friction direction angle used to determine the friction force components of two-dimensional dry friction both in the stick and slip motion states was used. A speed depended friction coefficient was used and described approximately by hyperbolic secant function. All switch conditions were derived and friction forces both for stick and slip states. Some simulation results are provided.
On the Motion of the Structure Varying Multibody Systems with Two-Dimensional Dry Friction
Xie Fujie,Wolfs Peter,Cole Colin The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.4
In the present paper the dynamics of the structure varying multibody systems caused by stick-slip motion with two-dimensional dry friction are analyzed. The methods to determine friction force both in stick and slip states are described. The direct method of considering the wagon bogie system as a structure varying system was used to consider two dimensional friction at the wheelset-side frame connection. The concept of friction direction angle used to determine the friction force components of two-dimensional dry friction both in the stick and slip motion states was used. A speed depended friction coefficient was used and described approximately by hyperbolic secant function. All switch conditions were derived and friction forces both for stick and slip states. Some simulation results are provided.
Yan Quan Sun,Colin Cole,Maksym Spiryagin 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.3
A rail vehicle-track interaction dynamics model has been applied to determine the track vertical dynamic forces due to rail short-wavelength dip defects such as squat, dip joints and welds, etc., which are required in both rail vehicle acceptance procedure and track maintenance. The model is validated using the field measurement data of rail squat defects and accelerations on a vehicle axlebox. The simulated track dynamic forces – the P2 forces due to rail dipped joints have been compared with those calculated by using a well-known formula. The results are compared and the formula’s limitations have been discussed. The dependence of the track vertical dynamic forces on the rail dip defect size and vehicle speed has also been investigated.