Introduction: Surface electromyography has been a technique used to describe muscle activity during running. However, there is little literature that analyses the behaviour of muscle coactivation in ...runners, describing the effect between two techniques associated with the initial contact, such as the use of rearfoot (RF) and forefoot (FF). Material and method: The purpose of this study was to compare muscle coactivation levels developed in the lower limb during two running techniques, FF vs RF. Fourteen amateur runners were evaluated (eight men, six women; age= 23.21 ± 3.58 years, mass= 63.89 ± 8.13 kg, height= 1.68 ± 0.08m). Surface electromyography was used to measure muscle activity during both running techniques evaluated on a treadmill, considering the muscle pairs: Rectus femoris- Biceps femoris (RFe-BF), Lateral Gastrocnemius–Tibialis Anterior (LG-TA), and Medial Gastrocnemius - Tibialis Anterior (MG-TA). These were calculated in three windows considering ten running cycles (0-5%, 80-100%, and 0-100%). To compare FF vs RF t-student test for paired data was used. Results: It was observed significant differences in the MG-TA pair (FF= 18.42 ± 11.84% vs RF = 39.05 ± 13.28%, p = 0.0018 during 0-5%, and RFe-BF pair (FF = 42.38 ± 18.11% vs RF = 28.37 ± 17.2%, p = 0.0331) during 80-100% of the race. Conclusion: Our findings show that the behaviour of muscle coactivation is different between FF vs RF techniques if we analyze little windows in the running cycle. This could be associated with an increase in the joint stability between these short intervals, represented in the initial and final regions of the running cycle.
Body sensor networks with a central gateway node can control wireless transmission and optimize the network lifetime. The central node should be placed within communication reach of other nodes ...spread out around the human body, such as on the chest. This paper reports a novel energy-efficient time multiplexing transmission method based on the human rhythmic movement of running for on-body wireless communication. The running style of each individual allows the network to self-calibrate the communication scheme so that transmissions occur only when high link reliability is predicted. This technique takes advantage of the periodic running actions to implement a dynamic time division multiple access strategy for a five node body network with very little communication overhead, long sleep times for the sensor transceivers, and robustness to communication errors. The results showed all wireless communications were successful, except when two nodes attempt to use the transmission medium simultaneously. An aggregated network reliability of 90% was achieved compared to 63% when employing traditional time multiplexing algorithms.
In many research or technical expertise studies the maximum noise level of a boiler is associated with the maximum thermal load of the burner. However, this type of air injected burners presents a ...complex running cycle with different functioning periods, where different parts (engine, fan, flame) of the burner are running separately or in the same time. In this study we are focused on the analysis, by experimental measurements, of the entire functioning cycle of a boiler by pointing out the noise differences and their importance when doing an experimental acoustical investigation. The entire 1/3 octave spectrum of the sound pressure level (SPL) was recorded during a complete running cycle by means of logging software associated to the sound meter. The sound equivalent level was calculated for each period of the running cycle and compared to the norms and with two theoretical prediction models that take into account the heating power and the boiler room volume. It was found that the most accurate data are obtained when the measurements are done in one-third octave. The maximum noise level was established to be not for the maximum thermal load period, but for the ventilation period of the boiler (before gas injection) with 82.1dB at 125Hz. A shut down delay was detected at the end of the cycle with 13s for higher frequencies, due to the vibration of the boiler parts. Two 3D graphical representations point out the most important frequencies characterizing each running state of the burner. Compared to the noise curve (NC85) the minimum differences between the admissible values and the ones produced by the burner were found to be around 5.5dB and therefore no acoustical treatment was needed. The results of the SPL prediction models matched the experimental data only for some of the boiler cycle periods and for only some of the frequencies. This type of detailed experiment investigation of the burner noise highlights the periods of the running cycle and the frequencies where the noise level requires acoustical treatment.
Through the analysis of Running cycle of Changsha City, and according to the automobile running equation, the minimal energy of driving and braking under the sampling points of 0.1 second interval is ...analyzed and summed, the recycle of braking energy of motor is analyzed, two formulas for calculating the energy consumption of BEV are derived based on the running and braking cycle, the expression of energy consumption per unit distance is also derived. The optimization objective function for powertrain ratio are established with the energy consumption per unit distance and the dynamic factor under the Changsha loop running cycle and the main road running cycle. In order to assure the dynamic and economy performance of the designed car, the ratio boundary constraints is established with the effect of maximum speed and peak torque of the motor and the lower state of charge of the battery. And the powertrain ratio optimization is presented with a particle swarm optimization based on the simulated annealing, the weighting coefficient and the method of dealing with Constraints based on penalty function are introduced. And the results of optimization indicate that the dynamic factor is increased and the energy consumption per unit distance of the designed car is reduced under a group of weighting coefficient.
In this work, the surface integrity (surface morphology, microstructure, microhardness, residual stress) of contact fatigue (CF) samples with different numbers of running cycles was comprehensively ...studied. Based on typical working conditions, a fatigue life evaluation method was proposed based on the evolution law of surface integrity. The CF with different numbers of running cycles revealed that the average grain size decreased with the increase in the number of running cycles, and the surface microhardness, residual stress and surface roughness Ra increased first and then decreased. In addition, the relationships between different surface integrity parameters and fatigue life were plotted. Moreover, based on the fatigue life profiles, the running state and remaining life of gear samples can be evaluated.
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