Polynomial correction function for half-power bandwidth (HPB) method of damping of glulam beams reinforced with e-glass reinforced epoxy polymer (GRP)

2009 ◽  
Vol 36 (2) ◽  
pp. 241-252 ◽  
Author(s):  
M. Naghipour ◽  
M. Mehrzadi ◽  
F. Taheri ◽  
G. P. Zou
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Epoxy Polymer ◽  
Domain Analysis ◽  
Correction Function ◽  
Bottom Surface ◽  
New Approach ◽  
Half Power ◽  
High Level ◽  
The Impact

Analytical and experimental investigation into dynamic properties of glued–laminated (glulam) beams reinforced with various lay ups of e-glass reinforced epoxy polymer (GRP) composites are discussed. Three unreinforced glulam (control) beams and 11 glulam beams reinforced with GRP on their bottom surface were clamped in a cantilever condition and tested using an instrumental hammer. The natural frequencies of all beams determined by the impact dynamic (hammer) method using power spectral density (PSD) were used to estimate damping ratio of all the beams through both time domain and frequency domain methods. In the time domain analysis, the method of logarithmic decrement analysis (LDA) and the Hilbert transform analysis (HTA) were considered; in the frequency domain analysis, both moving block analysis (MBA) and half-power bandwidth (HPB) were applied to the data and a new approach HPB method with a polynomial correction function was numerically established. A comparison between the results obtained from all the methods of analysis and a new approach shows that this method may improve the accuracy of the HPB method in evaluation of vibration damping properties of glulam reinforced composite beams because glulam beams have high level damping ratios and that this method should be modified especially when used with materials having high level damping ratios.

scholarly journals Monitoring Individual Sleep and Nocturnal Heart Rate Variability Indices: The Impact of Training and Match Schedule and Load in High-Level Female Soccer Players

2021 ◽  
Vol 12 ◽  
Author(s):  
Júlio A. Costa ◽  
Pedro Figueiredo ◽  
Fábio Y. Nakamura ◽  
António Rebelo ◽  
João Brito
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Frequency Domain ◽  
Sleep Duration ◽  
Time Domain ◽  
Sleep Efficiency ◽  
Soccer Players ◽  
High Level ◽  
Training Impulse ◽  
The Impact

PurposeTo describe individual sleep habits and nocturnal heart rate variability (HRV) responses, and to explore intra-individual associations of workload with sleep and nocturnal HRV indices in high-level female soccer players throughout a 2-week competitive period.Materials and methodsThe study followed a descriptive, observational design. Thirty-four high-level female soccer players (aged 20.6 ± 2.3 years) wore wrist actigraph units and heart rate (HR) monitors during night-sleep to record objective sleep and HRV data throughout 14 days [six evening-time training sessions (ET), six rest-days (RD), and two match-days (MD)]. During each ET and MD, exercise HR (HRexe), %HRpeak, training impulse (TRIMP), session rating of perceived exertion (s-RPE) and perceived ratings of wellbeing were monitored.ResultsAfter ET, a higher number of players (17–22) slept less than 7 h/night, in contrast to the remaining days (i.e., MD and RD), but only 1–6 players had a sleep efficiency < 75%. The coefficient of variation (CV) for sleep duration and sleep efficiency ranged between 9–22% and 2–11%, respectively. A small negative within-subject correlation was found between TRIMP and sleep duration [r = −0.25 (−0.36; −0.12); P < 0.001] and sleep efficiency [r = −0.20 (−0.32; −0.08); P = 0.004]. A moderate and small negative within-subject correlation was found between s-RPE and sleep duration [r = −0.43 (−0.53; −0.32); P < 0.001] and sleep efficiency [r = −0.17 (−0.30; −0.05); P = 0.02]. Nocturnal HRV for the time-domain analyses ranged from 4.1 (3.9; 4.3) to 4.4 (4.1; 4.6) ln[ms], and for the frequency-domain analyses ranged from 6.3 (5.9; 6.7) to 7.5 (7.1; 7.9) ln[ms2]. CV for time-domain HRV ranged from 3 to 23%, and from 4 to 46% for the frequency-domain. Higher CV fluctuations in time- and frequency-domain HRV were particularly observed in four players.ConclusionOverall, this study highlights the individual variability of sleep and nocturnal HRV indices, indicating that sleep duration may be affected by training and match schedules and workloads. Training and matches workload were not associated with nocturnal HRV in high-level female soccer players.

scholarly journals Analysis of Three-Phase Wye-Delta Connected LLC

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3606
Author(s):  
Jing-Yuan Lin ◽  
Chuan-Ting Chen ◽  
Kuan-Hung Chen ◽  
Yi-Feng Lin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Operation Time ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Complete Analysis ◽  
Plane Analysis ◽  
Analysis Methods ◽  
Three Phase

Three-phase wye–delta LLC topology is suitable for voltage step down and high output current, and has been used in the industry for some time, e.g., for server power and EV charger. However, no comprehensive circuit analysis has been performed for three-phase wye–delta LLC. This paper provides complete analysis methods for three-phase wye–delta LLC. The analysis methods include circuit operation, time domain analysis, frequency domain analysis, and state–plane analysis. Circuit operation helps determine the circuit composition and operation sequence. Time domain analysis helps understand the detail operation, equivalent circuit model, and circuit equation. Frequency domain analysis helps obtain the curve of the transfer function and assists in circuit design. State–plane analysis is used for optimal trajectory control (OTC). These analyses not only can calculate the voltage/current stress, but can also help design three-phase wye-delta connected LLC and provide the OTC control reference. In addition, this paper uses PSIM simulation to verify the correctness of analysis. At the end, a 5-kW three-phase wye–delta LLC prototype is realized. The specification of the prototype is a DC input voltage of 380 V and output voltage/current of 48 V/105 A. The peak efficiency is 96.57%.

Drilling Riser VIV Analysis Using Time Domain Code SimVIV

2013 ◽  
Author(s):  
Djoni E. Sidarta
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Ocean Currents

Drilling risers are often subjected to VIV from ocean currents, which may vary in directions over depth. VIV of drilling riser has commonly been analyzed using frequency domain code. This paper presents an alternative tool of analyzing VIV of drilling riser using time domain code SimVIV. With this tool it is possible to apply currents in varying directions over depth. Measured currents and VIV responses of a drilling riser available in the literature are used in this study. The results of time domain analysis using SimVIV are compared against measured responses. The effect of current directionality over depth on drilling riser VIV response is also analyzed.

scholarly journals Optimal implementation of frequency domain impedances in time domain simulations of building structures on embedded foundations

2020 ◽  
Author(s):  
Danilo S. Kusanovic ◽  
Elnaz E. Seylabi ◽  
Domniki Asimaki
Keyword(s):  
Finite Element ◽  
Frequency Domain ◽  
Time Domain ◽  
Response Spectrum ◽  
Free Field ◽  
Domain Analysis ◽  
Shallow Foundation ◽  
Rigid Base ◽  
Dimensionless Frequency ◽  
Building Structures

Soil-Structure Interaction (SSI) have been studied the last decades, and proper analysis for the linear elastic case in frequency domain has been established successfully. However, SSI is rarely considered in the seismic design of building structures. Regardless of its importance as a significant source of flexibility and energy dissipation, buildings are analyzed using a rigid base assumption, and the design is based on a response spectrum analysis, for which not only the soil, but also time are totally ignored. In a first attempt to improve and to incentivize time domain analyzes compatible with standard finite element packages for the engineering community, the state-of-practice introduces two major simplifications to transform the frequency domain analysis into a time domain analysis: (a) it assumes the frequency at which the impedance value should be read is the flexible-base frequency, and (b) it also assumes that the foundation input motion preserves the phase of the free field motion. Upon these simplifications, the following questions may arise: How does NIST recommendations perform in overall against a full finite element model? Are the embedment effects for shallow foundation not important so that the phase angle can be neglected? What is the best dimensionless frequency to estimate the soil impedance? Is it possible to make a better estimation of the dimensionless frequency to increase the NIST accuracy? In this study, we attempt to address these questions by using an inverse problem formulation.

scholarly journals Comparison of tibialis anterior and gastrocnemius muscles activation on balance training devices and hoverboard

2017 ◽  
Vol 13 (4-2) ◽  
pp. 495-500 ◽  
Author(s):  
Khairiyah Abdul Rahman ◽  
Aizreena Azaman ◽  
Hadafi Fitri Mohd Latip ◽  
Mohd Azuwan Mat Dzahir ◽  
Malarvili Balakrishnan
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Tibialis Anterior ◽  
Gastrocnemius Muscle ◽  
Balance Training ◽  
Domain Analysis ◽  
Median Frequency ◽  
Training Device ◽  
Emg Signal ◽  
Significant Difference

Balance training devices such as wobble board, basu ball and balance cushion are the tool use in balance training exercise programme in order to improve muscle strength and restore posture balance due degeneration of body function or injury. Recently, self-balancing scooter such as Segway and hover board showed a positive effects on rehabilitation. However, it is less known how these devices affect muscle physiological properties. This study aims to to measure ankle muscles activation on  difference balance training devices and hover board. Besides, a comparison between these device will be done in order to identify if hover board has a promising feature to be an alternative balance training device. In this research, surface EMG (sEMG) was used to record tibialis anterior and gastrocnemius muscle activities. Seventeen healthy subjects were required to stand on three different types of balance training device such as wobble board, balance cushion, bosu ball and a hover board. They were asked to maintain their standing position on each devices for two minutes. Both time domain and frequency domain analysis were used to identify the features of the EMG signal. Time domain analysis measurement involved average rectified value (ARV) and root mean square (RMS), meanwhile for frequency domain, median frequency (MDF) of the signal were measured. The results shows that, the RMS is differed significantly between the balance training devices (p<0.05) for tibialis anterior muscle but not gastrocnemius muscle. Meanwhile, no significant difference between the devices in the ARV and the MDF value (p>0.05). Besides, less stable devices increased muscle activity were observed. There is not much difference between hover board and the other devices in term of physiological effects of both tibialis anterior and gastrochemious muscle. It is also suggested that hover board offers a promising feature to be an alternative device for balance training device.

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