scholarly journals Numerical and Experimental Studies on Nonlinear Dynamics and Performance of a Bistable Piezoelectric Cantilever Generator

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Kangkang Guo ◽  
Shuqian Cao ◽  
Shiyu Wang
Keyword(s):  
Power Output ◽  
Chaotic Motion ◽  
Experimental Studies ◽  
Period Doubling ◽  
Bistable System ◽  
Distributed Parameter ◽  
Response Characteristics ◽  
Output Performance ◽  
Piezoelectric Cantilever ◽  
And Performance

A piezo-magneto-elastically coupled distributed-parameter model of a bistable piezoelectric cantilever generator is developed by using the generalized Hamilton principle. The influence of the spacing between two adjacent magnets on the static bifurcation characteristics of the system is studied and the range of magnet spacing corresponding to the bistable states is obtained. Numerical and experimental studies are carried out to analyze the bifurcation, response characteristics, and their impact on the electrical output performance under varying external excitations. Results indicate that interwell limit cycle motion of the beam around the two centers corresponds to optimum power output; interwell chaotic motion and multiperiodic motion including intrawell oscillations are less effective. At a given frequency, the phenomena of symmetric-breaking and amplitude-phase modulation are observed with increase of base excitation. Both period-doubling bifurcation and intermittency routes to chaotic motion in the bistable system are found. It can be observed that the power output is not proportional to the excitation level because of the bifurcation behaviours.

Performance of a multipurpose piezoelectric energy harvester

2017 ◽  
Vol 31 (07) ◽  
pp. 1741007 ◽  
Author(s):  
Kangqi Fan ◽  
Liansong Wang ◽  
Yingmin Zhu ◽  
Zhaohui Liu ◽  
Bo Yu
Keyword(s):  
Power Output ◽  
Mechanical Vibration ◽  
Experimental Studies ◽  
Rotation Frequency ◽  
Peak Voltage ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Piezoelectric Cantilever ◽  
Power Outputs ◽  
Rotation Motion

Harvesting energy from the surrounding environment through piezoelectric conversion is a promising method for implementing self-sustained low-power devices. To date, most piezoelectric energy harvesters (PEHs) developed can only scavenge energy from the unidirectional mechanical vibration. This deficiency severely limits the adaptability of PEHs because the real-world excitations may involve different mechanical motions and the mechanical vibration may come from various directions. To tackle this issue, we proposed a multipurpose PEH, which is composed of a ferromagnetic ball, a cylindrical track and four piezoelectric cantilever beams. In this paper, theoretical and experimental studies were carried out to examine the performance of the multipurpose PEH. The experimental results indicate that, under the vibrations that are perpendicular to the ground, the maximum peak voltage is increased by 3.2 V and the bandwidth of the voltage above 4 V is expanded by more than 4 Hz by the proposed PEH as compared to its linear counterpart; the maximum power output of 0.8 mW is attained when the PEH is excited at 39.5 Hz. Under the sway motion around different directions on the horizontal plane, significant power outputs, varying from 0.05 mW to 0.18 mW, are also generated by the multipurpose PEH when the sway angle is larger than 5[Formula: see text] and the sway frequency is smaller than 2.8 Hz. In addition, the multipurpose PEH demonstrates the capacity of collecting energy from the rotation motion, and approximately 0.14 mW power output is achieved when the rotation frequency is 1 Hz.

scholarly journals Design and Performance Evaluation of a Single-Phase Driven Ultrasonic Motor Using Bending-Bending Vibrations

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 853
Author(s):  
Dongmei Xu ◽  
Wenzhong Yang ◽  
Xuhui Zhang ◽  
Simiao Yu
Keyword(s):  
Single Phase ◽  
Oblique Line ◽  
Ultrasonic Motor ◽  
Vibration Modes ◽  
Bending Vibrations ◽  
Bending Vibration ◽  
Output Performance ◽  
Resonance Frequencies ◽  
And Performance ◽  
Line Trajectory

An ultrasonic motor as a kind of smart material drive actuator has potential in robots, aerocraft, medical operations, etc. The size of the ultrasonic motor and complex circuit limits the further application of ultrasonic motors. In this paper, a single-phase driven ultrasonic motor using Bending-Bending vibrations is proposed, which has advantages in structure miniaturization and circuit simplification. Hybrid bending vibration modes were used, which were excited by only single-phase voltage. The working principle based on an oblique line trajectory is illustrated. The working bending vibration modes and resonance frequencies of the bending vibration modes were calculated by the finite element method to verify the feasibility of the proposed ultrasonic motor. Additionally, the output performance was evaluated by experiment. This paper provides a single-phase driven ultrasonic motor using Bending-Bending vibrations, which has advantages in structure miniaturization and circuit simplification.

scholarly journals Analysis of a Cantilevered Piezoelectric Energy Harvester in Different Orientations for Rotational Motion

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1206 ◽  
Author(s):  
Wei-Jiun Su ◽  
Jia-Han Lin ◽  
Wei-Chang Li
Keyword(s):  
Theoretical Model ◽  
Resonant Frequency ◽  
Rotational Motion ◽  
Axial Load ◽  
Energy Harvester ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Piezoelectric Energy ◽  
Piezoelectric Cantilever ◽  
Tip Mass

This paper investigates a piezoelectric energy harvester that consists of a piezoelectric cantilever and a tip mass for horizontal rotational motion. Rotational motion results in centrifugal force, which causes the axial load on the beam and alters the resonant frequency of the system. The piezoelectric energy harvester is installed on a rotational hub in three orientations—inward, outward, and tilted configurations—to examine their influence on the performance of the harvester. The theoretical model of the piezoelectric energy harvester is developed to explain the dynamics of the system and experiments are conducted to validate the model. Theoretical and experimental studies are presented with various tilt angles and distances between the harvester and the rotating center. The results show that the installation distance and the tilt angle can be used to adjust the resonant frequency of the system to match the excitation frequency.

Optimum Design and Performance Simulation of a Multi-device Integrated System Based on a Proton Exchange Membrane Fuel Cell

2022 ◽  
pp. 1-33
Author(s):  
Xiuqin Zhang ◽  
Wentao Cheng ◽  
Qiubao Lin ◽  
Longquan Wu ◽  
Junyi Wang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Power Density ◽  
Power Output ◽  
Proton Exchange Membrane ◽  
Waste Heat ◽  
Proton Exchange ◽  
Integrated System ◽  
Interior Space ◽  
And Performance ◽  
Exchange Membrane

Abstract Proton exchange membrane fuel cells (PEMFCs) based on syngas are a promising technology for electric vehicle applications. To increase the fuel conversion efficiency, the low-temperature waste heat from the PEMFC is absorbed by a refrigerator. The absorption refrigerator provides cool air for the interior space of the vehicle. Between finishing the steam reforming reaction and flowing into the fuel cell, the gases release heat continuously. A Brayton engine is introduced to absorb heat and provide a useful power output. A novel thermodynamic model of the integrated system of the PEMFC, refrigerator, and Brayton engine is established. Expressions for the power output and efficiency of the integrated system are derived. The effects of some key parameters are discussed in detail to attain optimum performance of the integrated system. The simulation results show that when the syngas consumption rate is 4.0 × 10−5 mol s−1cm−2, the integrated system operates in an optimum state, and the product of the efficiency and power density reaches a maximum. In this case, the efficiency and power density of the integrated system are 0.28 and 0.96 J s−1 cm−2, respectively, which are 46% higher than those of a PEMFC.

Physical Demands and Performance Indicators in Male Professional Cyclists During a Grand Tour: WorldTour Versus ProTeam Category

2021 ◽  
pp. 1-9
Author(s):  
Xabier Muriel ◽  
Pedro L. Valenzuela ◽  
Manuel Mateo-March ◽  
Jesús G. Pallarés ◽  
Alejandro Lucia ◽  
...  
Keyword(s):  
Power Output ◽  
Performance Indicators ◽  
Cycling Performance ◽  
Threshold Power ◽  
Grand Tour ◽  
Physical Demands ◽  
Physical Demand ◽  
Stress Score ◽  
And Performance ◽  
Training Stress

Purpose: To compare the physical demands and performance indicators of male professional cyclists of 2 different categories (Union Cycliste Internationale WorldTour [WT] and ProTeam [PT]) during a cycling grand tour. Methods: A WT team (n = 8, 31.4 [5.4] y) and a PT team (n = 7, 26.9 [3.3] y) that completed “La Vuelta 2020” volunteered to participate. Participants’ power output (PO) was registered, and measures of physical demand and physiological performance (kilojoules spent, training stress score, time spent at different PO bands/zones, and mean maximal PO [MMP] for different exertion durations) were computed. Results: WT achieved a higher final individual position than PT (31 [interquartile range = 33] vs 71 [59], P = .004). WT cyclists showed higher mean PO and kilojoule values than their PT peers and spent more time at high-intensity PO values (>5.25 W·kg−1) and zones (91%–120% of individualized functional threshold power) (Ps < .05). Although no differences were found for MMP values in the overall analysis (P > .05), subanalyses revealed that the between-groups gap increased through the race, with WT cyclists reaching higher MMP values for ≥5-minute efforts in the second and third weeks (Ps < .05). Conclusions: Despite the multifactorial nature of cycling performance, WT cyclists spend more time at high intensities and show higher kilojoules and mean PO than their PT referents during a grand tour. Although the highest MMP values attained during the whole race might not differentiate between WT and PT cyclists, the former achieve higher MMP values as the race progresses.

scholarly journals Influence of COVID-19 Restrictions on Training and Physiological Characteristics in U23 Elite Cyclists

2021 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Peter Leo ◽  
Iñigo Mujika ◽  
Justin Lawley
Keyword(s):  
Power Output ◽  
Ventilatory Threshold ◽  
Training Load ◽  
Peak Power Output ◽  
Physiological Performance ◽  
Performance Variables ◽  
Elite Level ◽  
And Performance ◽  
Power Outputs ◽  
Elite Cyclists

PURPOSE: The COVID-19 pandemic and its associated mobility restrictions caused many athletes to adjust or reduce their usual training load. The aim of this study was to investigate how the COVID-19 restrictions affected training and performance physiology measures in U23 elite cyclists. METHODS: Twelve U23 elite cyclists (n = 12) participated in this study (mean ± SD: Age 21.2 ± 1.2 years; height 182.9 ± 4.7 cm; body mass 71.4 ± 6.5 kg). Training characteristics were assessed between 30 days pre, during, and post COVID-19 restrictions, respectively. The physiological assessment in the laboratory was 30 days pre and post COVID-19 restrictions and included maximum oxygen uptake (V̇O2max), peak power output for sprint (SprintPmax), and ramp incremental graded exercise (GXTPmax), as well as power output at ventilatory threshold (VT) and respiratory compensation point (RCP). RESULTS: Training load characteristics before, during, and after the lockdown remained statistically unchanged (p > 0.05) despite large effects (>0.8) with mean reductions of 4.7 to 25.0% during COVID-19 restrictions. There were no significant differences in maximal and submaximal power outputs, as well as relative and absolute V̇O2max between pre and post COVID-19 restrictions (p > 0.05) with small to moderate effects. DISCUSSION: These results indicate that COVID-19 restrictions did not negatively affect training characteristics and physiological performance measures in U23 elite cyclists for a period of <30 days. In contrast with recent reports on professional cyclists and other elite level athletes, these findings reveal that as long as athletes are able to maintain and/or slightly adapt their training routine, physiological performance variables remain stable.

scholarly journals Impact of eating disorders on paid or unpaid work participation and performance: a systematic review and meta-analysis protocol

2022 ◽  
Vol 10 (1) ◽  
Author(s):  
Fatima Safi ◽  
Anna M. Aniserowicz ◽  
Heather Colquhoun ◽  
Jill Stier ◽  
Behdin Nowrouzi-Kia
Keyword(s):  
Systematic Review ◽  
Eating Disorders ◽  
Meta Analysis ◽  
Experimental Studies ◽  
Work Participation ◽  
Unpaid Work ◽  
Cochrane Library ◽  
And Performance ◽  
The Impact

Abstract Background Eating disorders (ED) can reduce quality of life by limiting participation and performance in social and occupational roles, including paid or unpaid work. The association between ED pathologies and work participation and performance must be well understood to strengthen vocational rehabilitation programmes and prevent occupational disruptions in the ED population. The aims of this study are: (1) to examine the degree of association between ED pathologies and work participation and performance in 15-year-olds and older; (2) to highlight the specific ED symptoms that are most correlated with changes in work performance and participation; (3) to compile the most common metrics and assessments used to measure work participation and performance with ED. Methods Medline, Embase, CINAHL, Web of Science, PsycINFO, and Cochrane Library will be searched for observational and experimental studies that meet the following criteria: (1) a clinical sample of typical or atypical ED; (2) paid or unpaid employment or training; (3) an association between ED pathologies and work participation or performance. Unpublished data will also be examined. Title and abstract, and full-text screening will be conducted in duplicate. Risk of bias and quality of evidence assessments will be completed. A random-effect meta-analysis will be performed. Discussion This synthesis can clarify knowledge and gaps around the impact of ED on work functioning, thereby allowing better evaluation, improvements and development of current workplace assessments, interventions, and policies. Trial registration The registration number for this systematic review on PROSPERO is CRD42021255055.

scholarly journals Watching television in a home environment: effect on children’s attention, comprehension and behavior

2019 ◽  
Author(s):  
Sarah E Rose ◽  
Alexandra Lamont ◽  
Nicholas Reyland
Keyword(s):  
Problem Solving ◽  
Ecological Validity ◽  
Experimental Studies ◽  
Tv Viewing ◽  
Facilitation Effect ◽  
Environment Effect ◽  
And Performance ◽  
And Behavior ◽  
Harmful Effects ◽  
Problem Solving Task

Correlational studies have suggested some harmful effects of television (TV) viewing in early childhood, especially for the viewing of fast-paced entertainment programs. However, this has not been consistently supported by experimental studies, many of which have lacked ecological validity. The current study explores the effects of pace of program on the attention, problem solving and comprehension of 41 3- and 4-year-olds using an ecologically valid experimental design. Children were visited twice at home; on each visit they were shown an episode of a popular animated entertainment program which differed in pace: one faster paced, one slower paced. Children’s behavior was coded for attention and arousal during viewing, attention, effort and performance after viewing during a problem-solving task, and comprehension of the program. The faster paced program was attended to more, but this had no impact on comprehension. Although 3-year-olds showed more attention and effort on the problem-solving task after watching the slower program, both 3- and 4-year-olds completed more problems successfully after watching the faster program. The results provide evidence to counter the ‘harm’ perceived in young children watching fast-paced entertainment programs as where differences were found it was the fast-paced program which appeared to have a cognitive facilitation effect.

scholarly journals Physiological Responses and Predictors of Performance in a Simulated Competitive Ski Mountaineering Race

2021 ◽  
pp. 250-257
Author(s):  
Michael Lasshofer ◽  
John Seifert ◽  
Anna-Maria Wörndle ◽  
Thomas Stöggl
Keyword(s):  
Laboratory Test ◽  
Power Output ◽  
Ventilatory Threshold ◽  
Elite Athletes ◽  
Physiological Responses ◽  
Performance Parameters ◽  
Ramp Test ◽  
The Past ◽  
Treadmill Speed ◽  
And Performance

Competitive ski mountaineering (SKIMO) has achieved great popularity within the past years. However, knowledge about the predictors of performance and physiological response to SKIMO racing is limited. Therefore, 21 male SKIMO athletes split into two performance groups (elite: VO2max 71.2 ± 6.8 ml· min-1· kg-1 vs. sub-elite: 62.5 ± 4.7 ml· min-1· kg-1) were tested and analysed during a vertical SKIMO race simulation (523 m elevation gain) and in a laboratory SKIMO specific ramp test. In both cases, oxygen consumption (VO2), heart rate (HR), blood lactate and cycle characteristics were measured. During the race simulation, the elite athletes were approximately 5 min faster compared with the sub-elite (27:15 ± 1:16 min; 32:31 ± 2:13 min; p < 0.001). VO2 was higher for elite athletes during the race simulation (p = 0.046) and in the laboratory test at ventilatory threshold 2 (p = 0.005) and at maximum VO2 (p = 0.003). Laboratory maximum power output is displayed as treadmill speed and was higher for elite than sub-elite athletes (7.4 ± 0.3 km h-1; 6.6 ± 0.3 km h-1; p < 0.001). Lactate values were higher in the laboratory maximum ramp test than in the race simulation (p < 0.001). Pearson’s correlation coefficient between race time and performance parameters was highest for velocity and VO2 related parameters during the laboratory test (r > 0.6). Elite athletes showed their superiority in the race simulation as well as during the maximum ramp test. While HR analysis revealed a similar strain to both cohorts in both tests, the superiority can be explainable by higher VO2 and power output. To further push the performance of SKIMO athletes, the development of named factors like power output at maximum and ventilatory threshold 2 seems crucial.

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