jump frequency
Recently Published Documents


TOTAL DOCUMENTS

56
(FIVE YEARS 7)

H-INDEX

10
(FIVE YEARS 1)

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8194
Author(s):  
Tomasz Binkowski

This paper proposes a method for synchronizing a grid inverter with the voltage of an on-board high-frequency power grid. The described synchronization method belongs to the adaptive methods, which use fuzzy logic in the process of estimating the fundamental component of the voltage. The synchronization system has been tuned to achieve the primary goal of achieving synchronization in the shortest possible time. This is to allow for the efficient energy fed from photovoltaic sources into the on-board grid at 400 Hz. The proposed method was implemented in the field programmable gate array (FPGA) based power converter controller and static and dynamic tests for harmonic, interharmonic and subharmonic voltage disturbances were performed. Dynamic tests for phase jump, frequency jump and sag of the on-board voltage were also performed. To evaluate the effectiveness of synchronization with high-frequency voltage, the grid current control system in the grid tied inverter was elaborated. Proper current waveforms at the perturbed voltage were recorded while identifying the effectiveness of power ripple suppression. The results obtained were compared with the enhanced phase locked loop (EPLL) synchronization method. Satisfactory test results confirmed the suitability of the proposed method in systems coupling the photovoltaic source to the on-board high-frequency power grid.


Author(s):  
Dong Yujian ◽  
Cao Lilin

To investigate the vibration response of a steel-wood composite floor system under walking and jump excitation. The ABAQUS subroutine Vdload is used to simulate the human walking and jumping process on the structure, while the human-induced excitation is equated to a combination of a Fourier-scale load model and a biomechanical model of mass, stiffness, and damping (MSD) to study the human-induced vibration response under human-structure interaction (HSI). The effects of walking and jumping excitation on the peak acceleration of the structure are also considered. The results show that the peak acceleration of the structure considering the human-structure interaction is significantly smaller than that without the human-structure interaction, and the results obtained from the numerical simulation analysis are more consistent with the experimental situation. In addition, the acceleration response of the steel-wood composite floor system under jump excitation is larger than that of walking excitation, and the peak acceleration increases with the increase of jump frequency. Then: any floor, no matter its structural configuration and material, is prone to vibrate under walking and jumpimg excitation if the excitation frequency is in resonance with one of its main frequencies. The induced vibrations affect the floor serviceability, when the induced peak acceleration exceeds the comfort requirements. The magnitude of the induced peak acceleration is the larger, the larger the acting force and the lower the vibrating floor mass and its damping.


2021 ◽  
Vol 8 ◽  
Author(s):  
Kayvan Khoramipour ◽  
Abbas Ali Gaeini ◽  
Elham Shirzad ◽  
Kambiz Gilany ◽  
Karim Chamari ◽  
...  

Purpose: The current study compared metabolic profiles and movement patterns between different player positions and explored relationships between indicators of internal and external loads during elite male basketball games.Methods: Five main players from 14 basketball teams (n = 70) were selected as subjects and defined as backcourt (positions 1–3) or frontcourt (positions 4–5) players. Video-based time motion analysis (VBTMA) was performed based on players’ individual maximal speeds. Movements were classified into high and low intensity running with and without ball, high and low intensity shuffling, static effort and jumps. Saliva samples were collected before and after 40-min basketball games with metabolomics data being analyzed by multivariate statistics. Independent t-tests were used to compare VBTMA.Results: Frequency, duration, and distance of high and low intensity running and -shuffling were higher in backcourt players, whereas static effort duration and frequency as well as jump frequency were higher in frontcourt players (all p ≤ 0.05). The levels of taurine, succinic acid, citric acid, pyruvate, glycerol, acetoacetic acid, acetone, and hypoxanthine were higher in backcourt players, while lactate, alanine, 3-methylhistidine were higher and methionine was lower in frontcourt players (all p < 0.05). High intensity running with ball was significantly associated by acetylecholine, hopoxanthine, histidine, lactic acid and leucine in backcourt players (p < 0.05).Conclusion: We demonstrate different metabolic profiles of backcourt and frontcourt players during elite male basketball games; while aerobic metabolic changes are more present in backcourt players, frontcourt players showed lager changes in anaerobic metabolic pathways due to more static movements.


AIP Advances ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 109905
Author(s):  
Tsang-Tse Fang ◽  
Ming-I. Chen ◽  
Wen-Dung Hsu

AIP Advances ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 065132 ◽  
Author(s):  
Tsang-Tse Fang ◽  
Ming-I Chen ◽  
Wen-Dung Hsu

Author(s):  
Tomasz Skowronek ◽  
Grzegorz Juras ◽  
Kajetan J. Słomka

Purpose: To estimate the influence of global anaerobic fatigue on rhythm performance. Methods: Fifteen young males participated in the experiment. Anaerobic fatigue was induced with 2 consecutive running-based anaerobic sprint tests (RAST). The level of lactate was controlled before the first RAST and 3 minutes after each RAST. The rhythm performance was assessed by using Optojump Next (Microgate, Bolzano, Italy). The rhythm test was conducted 3 times, before fatigue and immediately after each RAST. Eight variables of the rhythm test were analyzed: the mean frequency of jumps for the assisted and unassisted phase (XfAP and XfUAP), SD of jump frequency for the assisted and unassisted phase (SDfAP and SDfUAP), and mean absolute error for the assisted and unassisted phases of the test (XERAP and XERUAP, respectively). Results: One-way repeated-measures analysis of variance showed a significant main effect of anaerobic effort on rhythm variables only in the unassisted phase of the test. Statistically significant differences were observed in XfUAP between the first and third rhythm measurements (F2,28 = 4.98, P < .014, ), SD of jump frequency for the unassisted phase (SDfUAP; F2,28 = 3.48, P = .05, ), and mean absolute error for the unassisted phase (XERUAP; F2,28 = 3.36, P = .006, ). Conclusions: The results show that rhythm of movement may be negatively influenced after intensive anaerobic fatigue. The exact mechanism of this phenomenon is not precisely defined, but both central and peripheral fatigue are suspected to be involved.


Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2081
Author(s):  
Wenxiu Zheng ◽  
Chengzhen Sun ◽  
Boyao Wen ◽  
Bofeng Bai ◽  
Eric Lichtfouse

The movement of the contact line in liquid-liquid-solid systems is a major phenomenon in natural and industrial processes. In particular, n-alkanes are widely occurring in the oil, soil pollution, and chemical industries, yet there is little knowledge on the effects of molecular chain length on the contact line movement. Here, we studied the effects of molecular chain length on the contact line movement in water/n-alkane/solid systems with different surface wettabilities. We used n-heptane (C7), n-decane (C10), and n-hexadecane (C16) as alkanes and α-quartz as the solid surface. We calculated the time-variation contact line moving velocity and also analyzed the jump frequency and the mean distance of the molecular displacement occurring within the contact line zone by molecular-kinetic theory. Molecular dynamics simulation results show that the contact line velocity decreases with increasing the chain length, originally caused by the decreasing the jump frequency and mean distance. These variations with the molecular chain length are related to the more torsions and deformations of the molecules with a longer chain length. In addition, the moving mechanism of the contact line on the same solid surface does not change at different molecular chain lengths, implying that the moving mechanism mainly depends on the three-phase wettability.


Author(s):  
Hieu Nguyen ◽  
Hamzeh Bardaweel

The work presented here investigates a unique design platform for multi-stable energy harvesting using only interaction between magnets. A solid cylindrical magnet is levitated between two stationary magnets. Peripheral magnets are positioned around the casing of the energy harvester to create multiple stable positions. Upon external vibration, kinetic energy is converted into electric energy that is extracted using a coil wrapped around the casing of the harvester. A prototype of the multi-stable energy harvester is fabricated. Monostable and bistable configurations are demonstrated and fully characterized in static and dynamic modes. Compared to traditional multi-stable designs the harvester introduced in this work is compact, occupies less volume, and does not require complex circuitry normally needed for multi-stable harvesters involving piezoelectric elements. At 2.5g [m/s2], results from experiment show that the bistable harvester does not outperform the monostable harvester. At this level of acceleration, the bistable harvester exhibits intrawell motion away from jump frequency. Chaotic motion is observed in the bistable harvester when excited close to jump frequency. Interwell motion that yields high displacement amplitudes and velocities is absent at this acceleration.


2018 ◽  
Vol 19 ◽  
pp. 35-60
Author(s):  
Fabian Hergemöller ◽  
Nicolaas A. Stolwijk

In this paper some recent progress in the area of Monte Carlo simulation of diffusion via the interstitialcy mechanism in a randomly ordered binary alloy is reviewed. Topics discussed include the calculation of tracer correlation factorsfA and fBas a function of composition and jump frequency ratiowA/wBand interstitialcy correlation factors fI; which play a crucial role in the interpretation of ion-conductivity data. The percolation behavior of fI when wA ≪ wB is analysed in detail and limits of the tracer diffusivity ratios bD A/bD B for alloy compositions below thepercolation threshold are presented. Allowance for non-collinear jumps (partly) replacing concurrent collinear site exchanges leads to a reduction of diffusion correlation effects.This goes along with a shift of the diffusion percolation threshold to lower concentrations of the (more) mobile component B. Even stronger changes of mass and charge transport compared to an exclusively collinear interstitialcy scheme are observed for additional contributions of direct interstitial jumps. It is remarkable that for both extensions of interstitialcy-mediated diffusion the Haven ratio appears to be greater than unity in certain compositionranges poor in B.


2018 ◽  
Vol 19 ◽  
pp. 61-79 ◽  
Author(s):  
Gary S. Collins

Using the method of perturbed angular correlation of gamma rays, diffusional jump-frequencies of probe atoms can be measured through relaxation of the nuclear quadrupole interaction. This was first shown in 2004 for jumps of tracer atoms that lead to reorientation of the local electric field-gradient, such as jumps on the connected a-sublattice in the L12 crystal structure. Studies on many such phases using the 111In/Cd PAC probe are reviewed in this paper. A major finding from a 2009 study of indides of rare-earth elements, In3R, was the apparent observation of two diffusional regimes: one dominant for heavy-lanthanide phases, R= Lu, Tm, Er, Dy, Tb, Gd, that was consistent with a simple model of vacancy diffusion on the In a-sublattice, and another for light-lanthanides, R= La, Ce, Pr, Nd, that had no obvious explanation but for which several alternative diffusion mechanisms were suggested. It is herein proposed that the latter regime arises not from a diffusion mechanism but from transfer of Cd-probes from In-sites where they originate to R-sites as a consequence of a change in site-preference of 111Cd-daughter atoms from In-sites to R-sites following transmutation of 111In. Support for this transfer mechanism comes from a study of site-preferences and jump-frequencies of 111In/Cd probes in Pd3R phases. Possible mechanisms for transfer are described, with the most likely mechanism identified as one in which Cd-probes on a-sites transfer to interstitial sites, diffuse interstitially, and then react with vacancies on b-sites. Implications of this proposal are discussed. For indides of heavy-lanthanide elements, the Cd-tracer remains on the In-sublattice and relaxation gives the diffusional jump-frequency.


Sign in / Sign up

Export Citation Format

Share Document