Mechanical Energy Changes Research Articles

From light powered by knocking on the door to the investigation on three types of collision

Abstract Can you imagine that when you knock hard on a door with your hands, 1350 LED lights can be lit up! Science and technologies are all constantly being developed and improved in practice. Any scientific theory is not ultimate and absolutely precise. In this paper, we studied the traditional macroscopic collision theory based on the latest research findings: electromagnetic field is generated when two objects collide with each other owing to the contact-electrification between the two. Three types of collision phenomena: elastic collision, inelastic collision, and ideal inelastic collision were investigated in detail. We found that electromagnetic field was produced during all three types of collisions, which means mechanical energy is converted into electromagnetic energy during any collision process of two objects. Under the same condition, the quantity of electric energy produced by elastic collision is greater than that of inelastic collision, and greater than that of ideal inelastic collision. Different from the conversion of mechanical energy into internal energy in the process of collision, the change of mechanical energy into electromagnetic energy in the process of collision will directly affect the law of conservation of energy and momentum in the whole collision system. The electric power generated in collision can not only be used for lighting, but also it can be used for positioning and tracking. This is completely new discoveries, which will provide new explanations and new ideas and will have a profound and an inestimable impact on some related scientific research fields, including physics and new energy.

Influence of Line Strategy Between Two Turns on Performance in Giant Slalom.

In alpine ski racing, different line choices can drastically affect turn or sectional performance. The straight-line transition between two turns is the main phase where skiers can gain speed in a race, open their trajectory, or reduce their path length. Between two turns, a skier can foster speed increase by spending more time in a straight line, inducing sharper turning phases (Z strategy). Inversely, speed can be conserved during the entire turn cycle by performing long curved turns separated by a short straight line (S strategy). This research aimed to evaluate the kinetic and kinematic specificities associated with the line strategy and to explore interactions of selected strategy with skier performance and energy dissipation. A mixed-level population of male alpine skiers (n = 17) skied a timed giant-slalom course while equipped with specialized force plates and a positional device collecting synchronized normal ground reaction force and position-time data, respectively. Time of edge switch was computed from the force signal as the period with the lowest force application on the outside ski. From positional data, turn cycles were separated into turning and straight-line phases (radius bellow and above 30 m, respectively). Time length, path length in the straight line, speed amplitude, and change in specific mechanical energy were computed for each turn and averaged for each skier. The path length during straight line was used to continuously characterize the line strategy within the spectrum between the Z (long straight line) and S (short straight line) strategy. Path length in the straight line was correlated with the amplitude of speed over a straight line (r = 0.672, p = 0.003) and relative and absolute time spent in the straight line (r = 0.967, p < 0.001). However, path length in straight line was not correlated with decrease of speed in the following turn (r = −0.418, p = 0.390) or time without force application on the outside ski (r = 0.195, p = 0.453). While higher-performing athletes on the course performed turns during which they dissipated less energy when normalized to entry speed (r = −0.620, p = 0.008), it appears they did so with variable turn strategies approaches.

THE IMPACT OF NATURAL MICROGEODYNAMIC PROCESSES AND TECHNOGENIC VIBRATIONS ON THE GEOLOGICAL ENVIRONMENT

The influence of geodynamic fields on the changes of the stress-strain state of soils is analyzed. Potential decrease of deformation and strength properties of soils is related to the geodynamic activity of the territory and, in particular, microgeodynamic processes within the boundaries of separate block structures. Technogenic vibrational effects, which can be compared with natural processes of excitation of oscillations of soil particles, are highlighted. Examples of destructive negative influence of periodic compression processes - stretching in the upper part of the soil layer on the state of engineering objects are given. According to the results of experimental research in-situ, the influence of electric currents generated by the atmosphere and the lithosphere on the processes of leaching and transportation of a number of chemical elements in the soils of the aeration zone was established. For reliable operation of engineering objects during designing it is proposed to take into account not only faults in their density within the unit of area but also within the block structures to allocate zones with microgeodynamic processes, where there are sharp changes in humidity, mechanical, thermal and electrical energy.

Riders Use Their Body Mass to Amplify Crank Power during Nonseated Ergometer Cycling

To date, neither the CoM movement strategies during nonseated cycling nor the limb mechanics that allow this phenomenon to occur have been quantified. Here we estimate how much power can be contributed by a rider's CoM at each instant during the crank cycle by combining a kinematic and kinetic approach to measure CoM movement and joint powers of 15 participants riding in a nonseated posture at three individualized power outputs (10%, 30%, and 50% of peak maximal power) and two different cadences (70 and 120 rpm). The peak-to-peak amplitude of vertical CoM displacement increased significantly with power output and with decreasing cadence. Accordingly, the greatest peak-to-peak amplitude of CoM displacement (0.06 ± 0.01 m) and change in total mechanical energy (0.54 ± 0.12 J·kg) occurred under the combination of high-power output and low cadence. At the same combination of high-power output and low cadence, we found that the peak rate of CoM energy loss (3.87 ± 0.93 W·kg) was equal to 18% of the peak crank power. Consequently, it appears that for a given power output, changes in CoM energy contribute to peak instantaneous power output at the crank, thus reducing the required muscular contribution. These findings suggest that the rise and fall of a rider's CoM acts as a mechanical amplifier during nonseated cycling, which has important implications for both rider and bicycle performance.

ЕКСПЕРИМЕНТАЛЬНЕ ВИЗНАЧЕННЯ ЕНЕРГІЇ НЕОБХІДНОЇ ДЛЯ ВІДДІЛЕННЯ МЕТАЛЕВИХ ДЕТАЛЕЙ ВІД ЛИВНИКІВ

Experimental determination of the energy and the number of impact interactions with the solid supporting surface of the castings of the «zipper» lock necessary to separate parts from the gate. Getting the corresponding calculated dependencies. Experimental modeling of impact interaction of metal parts of the “zipper” lock with the surface of the working capacity by falling castings of parts from different heights with their further collision with the supporting surface. Based on the conducted experimental study, mathematical dependences are obtained that allow one to evaluate the effect of changes in mechanical energy on the intensity of separation of metal parts of the lightning lock from the gate. In particular, it was found that with an increase in mechanical energy during the fall of castings, the intensity of separation of metal parts from gates increases significantly. The relationship between the kinetic energy needed to separate the parts of the castings of the “zipper” lock at the moment of collision with a solid surface and the total cross-sectional area of the gating system is established. The relationship between the number of shock interactions of castings of the “zipper” lock with a solid surface, necessary for separating parts, the interaction energy and the casting parameters, is determined. The obtained mathematical dependences for calculating the number of shock interactions of castings of the “zipper” lock necessary to separate all parts from the gate system of the corresponding type when falling from any chosen height. These dependencies can be used to carry out further research, in particular, to rationally determine the time spent on performing these technological operations.

Development of The Conception of Mechanical Energy Conservation with Interactive Lecture Demonstration Method using Simple Experiments for Grade 7 Students

The purpose of this research is to develop a student's conception of mechanical energy conservation with the Interactive Lecture Demonstration method. The participants consisted of 19 students of class 7E SMP Muhammadiyah 1 Mlati in 2018/2019 academic year. The analysis of the student's sheet prediction showed that most students do not understand the conception of mechanical energy conservation. After learning applied, it is known that all students have understood the influence of the height of the object on potential energy, 18 of them have understood the influence of the mass of the object on potential energy. While students' understanding of changes in mechanical energy when objects fall and the influence of mass on kinetic energy has increased slightly. Through the Wilcoxon signed-rank test, it was concluded that there was an effect of the use of interactive demonstration methods on student learning outcomes in the matter of mechanical energy conservation conceptions.

Mechanical and Surface-Chemical Properties of Polymer Derived Ceramic Replica Foams.

Polymer derived ceramic foams were prepared with the replica method using filler free and filler loaded polysiloxane containing slurries for the impregnation of open celled polyurethane foams. A significant change in mechanical strength, porosity and surface energy, i.e., wettability after thermal treatment between 130 °C (crosslinking) and 1000 °C (pyrolysis) in argon atmosphere was observed. While low-temperature pyrolyzed foams are elastic and hydrophobic, foams pyrolyzed at high temperatures are brittle and hydrophilic, and they possess higher compression strength. Changes of these properties were correlated with the polymer-to-ceramic transformation.

Дослідження енергетичних співвідношень при аналізі автоколивальної системи

The terms of change mechanical energy are considered at determination of descriptions of autoswaying motion of the mechanical system. Power correlations are analyzed in the case of self-excited oscillations with soft and rigid self-excitation. Position of points of static and dynamic equilibrium of the autoswaying systems is found out on graphic dependences of change of mechanical energy of the system on amplitude of its fluctuating motion. Character of steady or&nbsp;unsteady static and dynamic equilibrium of the autoswaying systems is certain at necessary initial conditions. It is rotined that the mode of steady vibrations with eventual amplitude is possible only in the autoswaying systems with nonlinear properties. The task of prognostication of origin of steady autoswaying motions to decide in the linear raising is offered. Steady self-excited oscillations of the mechanical system are considered with a viscidlyresilient element in an environment with resistance, which can be presented as free vibrations of the nonlinear mechanical system.

External mechanical work done during the acceleration stage of maximal sprint running and its association with running performance

This study aimed to elucidate how external mechanical work done during maximal acceleration sprint running changes with increasing running velocity and is associated with running performance. In twelve young males, work done at each step over 50 m from the start was calculated from mechanical energy changes in horizontal anterior-posterior and vertical directions and was divided into braking (-W kap and - W v, respectively) and propulsive (+ W kap and + W v, respectively) phases. The maximal running velocity (V max) appeared at 35.87±7.76 m and the time required to run 50 m (T 50 m) was 7.11±0.54 s. At 80% V max or higher, +W kap largely decreased and -W kap abruptly increased. The change in the difference between +W kap and |-W kap| (ΔW kap) at every step was relatively small at 70% V max or lower. Total work done over 50 m was 82.4±7.5 J kg-1 for +W kap, 36.2±4.4 J kg-1 for |-W kap|, 14.3±1.9 J kg-1 for +W v, and 10.4±1.2 J kg-1 for |-W v|. The total ΔW kap over 50 m was more strongly correlated with T 50 m (r=-0.946, P<0.0001) than the corresponding associations for the other work variables. These results indicate that in maximal sprint running over 50 m, work done during the propulsive phase in the horizontal anterior-posterior direction accounts for the majority of the total external work done during the acceleration stage, and maximizing it while suppressing work done during the braking phase is essential to achieve a high running performance.

The role of path length- and speed-related factors for the enhancement of section performance in alpine giant slalom

Knowing how to enhance alpine skiing performance is essential for effective coaching. The purpose of this study was to explore the role of path length- and speed-related factors for performance enhancement, while skiing on a homogeneously set/constantly inclined giant slalom course section (average gate distance: 27 m; offset: 8 m; slope inclination: 26°). During a video-based three-dimensional kinematic field-experiment, the data of six athletes who skied a two-gate section on four different types of skis were collected. The performance parameter analysed was section time. The performance predictors analysed were centre of mass (CoM), path length and the change in specific mechanical energy per entrance speed along the analysed section. Furthermore, since the current study examined alpine skiing performance within short sections, the skier’s entrance speed was also considered. Classified as a high-performance and a low-performance group based on section time, slow and fast trials significantly differed in CoM path length, the change in specific mechanical energy per entrance speed and entrance speed. The entrance speed of all trials analysed ranged between 15.25 and 17.66 m/s. In trials with both high and low entrance speed, the change in specific mechanical energy per entrance speed was found to be more relevant for the prediction of section time than CoM path length. However, further studies should investigate whether such a prioritization can be unrestrictedly generalized to other situations, such as entrance speeds, course sets, slope inclinations and competition disciplines different to those assessed in the current study.

Nonlinear phenomena in vibro-impact dynamics: central collisions and energy jumps between two rolling bodies

Central collisions and energy jumps between two rolling bodies as singular nonlinear phenomena are investigated in vibro-impact system dynamics. For that purpose, an extension of theory of collision of two rigid bodies, in rolling dynamics, is presented. Under the authors’ use of the Petroviċ’s elements of mathematical phenomenology, especially mathematical analogy between kinetic parameters of central collision of two bodies in translator motions and central collision of two rolling different axial symmetrically bodies, new original expressions of two post-collision outgoing angular velocities for each of rolling bodies after collision are defined. Presented results are the generalization of author’s previous published results. Using this new and original result for collisions, the vibro-impact dynamics of two rolling heavy thin disks with different radiuses on the rotating circle trace in vertical plane in the period of series of collisions is investigated. Using the series of the elliptic integrals, new nonlinear equations for obtaining the angles, which defined the disks positions of successive collisions, are defined. Phase trajectories of the disks in vibro-impact dynamics are analytically and graphically presented. Two cases of vibro-impact dynamics when phase portraits contain trigger of coupled singularities and homoclinic phase trajectory in the form of number “eight,” as well as in the case without that trigger of coupled singularities, are discussed. Phase trajectory branches of dynamics of both of the rolling disks in the period from initial positions to first collision between them are presented. By using the pre-collisions impact (arrival) angular velocities and post-collision (outgoing) angular velocities of the rolling bodies, the rates of the total mechanical energy change for each disk in comparison under kinetic state that corresponds to pre- and post-collision are expressed, and also of both of the rolling bodies as system pre-collision and post-collision kinetic states. From the energy analysis, some conclusions are formulated. Full theory and new methodology for the investigation of the vibro-impact system dynamics with rolling bodies is found.

Motor functions assessment method based on energy changes in gait cycle.

The aim of the research was to determine the energy changes during the gait cycle for a group of healthy children and a group of patients with cerebral palsy, and to compare the value of energy expenditure (EE) with the determined values of the Gillette Gait Index (GGI) and the Gait Deviation Index (GDI). The study group consisted of 56 children with regular gait and 56 patients with diagnosed cerebral palsy (CP). The gait kinematics was determined by BTS Smart System. Based on the identified position of the body mass, the following parameters were determined: the potential energy, kinetic energy, and total energy. The values were standardized to 100% of the gait cycle. The values of the Gillette Gait Index (GGI) and the Gait Deviation Index (GDI) were calculated using the authors' own software. Values of potential, kinematic and mechanical energy changes and mean values of total energy (energy expenditure - EE) were calculated for a reference group and for patients with CP. The obtained results were standardized in relation to the body mass and stride length. Furthermore, the values of the Gillette Gait Index (GGI) and the Gait Deviation Index (GDI) were calculated. Statistical analysis of the obtained results was performed. The Spearman rank correlation coefficient was defined between the calculated GGI and GDI values and energy expenditure EE. Values of energy expenditure changes can be used as an objective comparative tool for gait results concerning children with various neurological and orthopaedic dysfunctions.

Mechanical Energy Change in Inertial Reference Frames

The mechanical energy change of a system in an inertial frame of reference equals work done by the total nonconservative force in the same frame. This relation is covariant under the Galilean transformations from inertial frame S to S′, where S′ moves with constant velocity relative to S. In the presence of nonconservative forces, such as normal and tension forces, the mechanical energy of a system can be conserved in S and not be conserved in S′. In this paper we find useful relations between the mechanical energy changes in two inertial frames of reference.

Body Segment Kinematics and Energy Expenditure in Active Videogames.

Energy expenditure (EE) in active videogames (AVGs) is a component for assessing its benefit for cardiovascular health. Existing evidence suggests that AVGs are able to increase EE above rest and when compared with playing passive videogames. However, the association between body movement and EE remains unclear. Furthermore, for goal-directed game design, it is important to know the contribution of body segments to EE. This knowledge will help to acquire a certain level of exercise intensity during active gaming. Therefore, the purpose of this study was to determine the best predictors of EE from body segment energies, acceleration, and heart rate during different game situations. EE and body segment movement of 17 subjects, aged 22.1 ± 2.5 years, were measured in two different AVGs. In randomized order, the subjects played a handheld-controlled Nintendo(®) Wii™ tennis (NWT) game and a whole body-controlled Sony EyeToy(®) waterfall (ETW) game. Body segment movement was analyzed using a three-dimensional motion capture system. From the video data, mean values of mechanical energy change and acceleration of 10 body segments were analyzed. Measured EE was significantly higher in ETW (7.8 ± 1.4 metabolic equivalents [METs]) than in NWT (3.4 ± 1.0 METs). The best prediction parameter for the more intense ETW game was the energy change of the right thigh and for the less intense hand-controlled NWT game was the energy change of the upper torso. Segment acceleration was less accurate in predicting EE. The best predictors of metabolic EE were the thighs and the upper torso in whole body and handheld-controlled games, respectively. Increasing movement of these body segments would lead to higher physical activity intensity during gaming, reducing sedentary behavior.

Fuzzy Prioritization Approach for Risks of Wind Turbine Life Cycle

Recently, wind force which is renewable energy resource has been used widely throughout the world. Wind turbines are system which firstly, converts the kinetic energy of the wind into mechanical energy secondly mechanical energy change into electrical energy. Starting from the design and development phase of wind turbines till the establishment of and operate this system, this process includes too many risks in terms of occupational health and safety. For this study, the life cycle phase used is taken from1: design, development, manufacture, transport, construction, operation associated infrastructure, maintenance, repowering/life extension, decommissioning and waste treatment and recycling. Design and development phase relates to measures to be taken, rather than contain risk. Also related to waste treatment and recycling phase we have a few information about that contains risk. For these reason in this study these two phase is neglect. In this study we aimed at gain a prioritization of risks which exist during the life cycle of wind turbine. Prioritization of risk is very important in terms of to determine which steps should be taken further measures. For prioritization of risk is employed fuzzy AHP α-cut analysis method.

Dispersive Pressure, Boundary Jerk and Configurational Changes in Debris Flows

The granular rock material within a debris flow experiences jerk (change in acceleration) as it runs over a rough basal bed or collides with sidewalls. This creates a pressure – the so-called dispersive pressure – which acts to change the configuration of the granular mass and therefore the frictional relationship of the debris flow with the basal boundary. Normal pressures are no longer hydrostatic and pressure fluctuations are created in the fluid phase. In this paper we formulate relationships between internal shear work, free mechanical energy, dispersive pressure and configurational changes within a debris flow. We associate the potential energy of the debris flow configuration with dilatant kinematic motions and show why it is necessary to integrate the shear work over time to calculate boundary jerks which cannot be represented by closed-form, analytical pressure functions. The effect of the dispersive pressure is mediated by the presence of the viscous muddy fluid which consists of two types: a) the free fluid and b) the bonded fluid attached to the solid granular phase.

Mechanical work makes important contributions to surface chemistry at steps.

The effect of mechanical strain on the binding energy of adsorbates to late transition metals is believed to be entirely controlled by electronic factors, with tensile stress inducing stronger binding. Here we show, via computation, that mechanical strain of late transition metals can modify binding at stepped surfaces opposite to well-established trends on flat surfaces. The mechanism driving the trend is mechanical, arising from the relaxation of stored mechanical energy. The mechanical energy change can be larger than, and of opposite sign than, the energy changes due to electronic effects and leads to a violation of trends predicted by the widely accepted electronic ‘d-band’ model. This trend has a direct impact on catalytic activity, which is demonstrated here for methanation, where biaxial tension is predicted to shift the activity of nickel significantly, reaching the peak of the volcano plot and comparable to cobalt and ruthenium.

Changes in energy cost and total external work of muscles in elite race walkers walking at different speeds.

The aim of the study was to assess energy cost and total external work (total energy) depending on the speed of race walking. Another objective was to determine the contribution of external work to total energy cost of walking at technical, threshold and racing speed in elite competitive race walkers.The study involved 12 competitive race walkers aged 24.9 4.10 years with 6 to 20 years of experience, who achieved a national or international sports level. Their aerobic endurance was determined by means of a direct method involving an incremental exercise test on the treadmill.The participants performed three tests walking each time with one of the three speeds according to the same protocol: an 8-minute walk with at steady speed was followed by a recovery phase until the oxygen debt was repaid. To measure exercise energy cost, an indirect method based on the volume of oxygen uptake was employed. The gait of the participants was recorded using the 3D Vicon opto-electronic motion capture system.Values of changes in potential energy and total kinetic energy in a gate cycle were determined based on vertical displacements of the centre of mass. Changes in mechanical energy amounted to the value of total external work of muscles needed to accelerate and lift the centre of mass during a normalised gait cycle.The values of average energy cost and of total external work standardised to body mass and distance covered calculated for technical speed, threshold and racing speeds turned out to be statistically significant (p 0.001).The total energy cost ranged from 51.2 kJ.m-1 during walking at technical speed to 78.3 kJ.m-1 during walking at a racing speed. Regardless of the type of speed, the total external work of muscles accounted for around 25% of total energy cost in race walking. Total external work mainly increased because of changes in the resultant kinetic energy of the centre of mass movement.

Effects of microtubule mechanics on hydrolysis and catastrophes

We introduce a model for microtubule (MT) mechanics containing lateral bonds between dimers in neighboring protofilaments, bending rigidity of dimers, and repulsive interactions between protofilaments modeling steric constraints to investigate the influence of mechanical forces on hydrolysis and catastrophes. We use the allosteric dimer model, where tubulin dimers are characterized by an equilibrium bending angle, which changes from to by hydrolysis of a dimer. This also affects the lateral interaction and bending energies and, thus, the mechanical equilibrium state of the MT. As hydrolysis gives rise to conformational changes in dimers, mechanical forces also influence the hydrolysis rates by mechanical energy changes modulating the hydrolysis rate. The interaction via the MT mechanics then gives rise to correlation effects in the hydrolysis dynamics, which have not been taken into account before. Assuming a dominant influence of mechanical energies on hydrolysis rates, we investigate the most probable hydrolysis pathways both for vectorial and random hydrolysis. Investigating the stability with respect to lateral bond rupture, we identify initiation configurations for catastrophes along the hydrolysis pathways and values for a lateral bond rupture force. If we allow for rupturing of lateral bonds between dimers in neighboring protofilaments above this threshold force, our model exhibits avalanche-like catastrophe events.

Atmospheric Density Reconstruction Using Satellite Orbit Tomography

Improved thermospheric neutral density models are required for the reduction of orbit prediction errors for satellites experiencing atmospheric drag. This research describes a new method for estimating density using a tomography-based approach, inspired by X-ray computed tomography from the medical imaging field. The change in specific mechanical energy of the orbit, which is related to the integrated drag acceleration over the orbit, is used as the measurement. Using several such measurements from a number of satellites, one can estimate a spatially resolved multiplicative correction to a reference density model. The problem considered here uses simulated measurements from 50 low-Earth-orbit satellites and solves for the correction factor discretized over 324 grid elements, spanning 300 to 500 km altitude. This ill-posed problem is solved using Tikhonov regularization, with the three-dimensional gradient as the regularization operator, resulting in a penalty on the spatial smoothness of the estimated density. Simulation results show that the true time-averaged density can be reconstructed to within approximately 10%, using only assumed ground-based tracking measurements separated over 12 h.