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Purpose: This study investigates the effects of exercises on sand on the frequency content of the lower limb muscles in individuals with anterior cruciate ligament reconstruction and pronated feet during walking. Methods: This was a semi-experimental and laboratory-type study. The study samples included 28 male students with pronated feet and anterior cruciate ligament reconstruction aged 22 to 25 years. The participants were randomly allocated into the following two groups: The experimental and the control group. The electrical activity of the lower limb muscles was recorded using an electromyography system before and after performing the exercises. The statistical analysis was done using a two-way analysis of variance method with a significance level of 0.05. Results: The findings showed that the main effect of time for the frequency content of the tibialis anterior, medial gastrocnemius, vastus medialis muscles during loading and push-off phases, the vastus lateralis muscle during the mid-stance, the rectus femoris at the mid-stance and push-off phases, semitendinosus muscle during the loading, mid-stance and push-off phases, biceps femoris muscle during the mid-stance and push-off phases, and gluteus medius muscle during the push-off phase (P

Featured Application: The conclusions of this article can be used to predict the uplift of tunnels or underground structures induced by soil liquefaction considering vertical earthquake motion. The uplift of underground structures induced by soil liquefaction can damage underground structure systems. Numerical simulations have shown that uplift is positively correlated with the energy of horizontal input motion. However, the effects of vertical input motion on uplift have not been studied comprehensively in the past. Previous studies on the vertical motion concluded that the effects of vertical motion on uplift depend on the overall characteristics of earthquake motion. These motion characteristics have only been studied separately in previous studies. A comprehensive study to explore the interactions and overall effects of these characteristics on the uplift of underground structures is essential. In this study, the FLAC program with the PM4Sand model was used as a numerical tool to explore the effects of vertical input motion on the uplift of underground structures. The numerical model was calibrated using centrifuge test results, and 48 earthquake motions were selected as input motions to study the effects of the overall characteristics of earthquake motions on the uplift of underground structures. The simulation results show that the frequency content characteristics of horizontal and vertical motion are the major factors affecting the uplift magnitude and the responses of liquefiable soils. However, most simulation cases show that the inclusion of vertical motion causes a 10% difference in the tunnel uplift, compared to cases without vertical motion. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates the effects of exercises on sand on the frequency content of the lower limb muscles in individuals with anterior cruciate ligament reconstruction and pronated feet during walking. Methods: This was a semi-experimental and laboratory-type study. The study samples included 28 male students with pronated feet and anterior... [ABSTRACT FROM AUTHOR]

The Lombard effect is an unconscious reflex of speakers to increase vocal effort when disturbed by noise, aiming to enhance speech intelligibility. This study aims to evaluate the effect of noise with different energetic content and levels at various frequencies on the Lombard effect, communication disturbance, vocal comfort, and speech intelligibility. Twenty university students participated in the study, reading a six-sentence excerpt and performing an intelligibility test under 12 randomized noise conditions. These conditions included noises at low (20–500 Hz), medium (500–4000 Hz), and high frequencies (4000–20,000 Hz), at four levels (45 dB, 55 dB, 65 dB, 75 dB). After each condition, participants rated their perceived communication disturbance and vocal discomfort. The results indicated that noise with energetic content at medium frequencies produced the highest Lombard effect, produced the most detrimental effect on communication disturbance and vocal comfort, and caused the strongest decrease in speech intelligibility, whereas it was minimally affected by low- and high-frequency noise. In conclusion, this study highlights that medium-frequency noise has the greatest impact on vocal effort, communication disturbance, and vocal comfort, while low- and high-frequency noise has minimal effect on speech intelligibility.

The Lombard effect is an unconscious reflex of speakers to increase vocal effort when disturbed by noise, aiming to enhance speech intelligibility. This study aims to evaluate the effect of noise with different energetic content and levels at various frequencies on the Lombard effect, communication disturbance, vocal comfort, and speech intelligibility. Twenty university students participated in the study, reading a six-sentence excerpt and performing an intelligibility test under 12 randomized noise conditions. These conditions included noises at low (20–500 Hz), medium (500–4000 Hz), and high frequencies (4000–20,000 Hz), at four levels (45 dB, 55 dB, 65 dB, 75 dB). After each condition, participants rated their perceived communication disturbance and vocal discomfort. The results indicated that noise with energetic content at medium frequencies produced the highest Lombard effect, produced the most detrimental effect on communication disturbance and vocal comfort, and caused the strongest decrease in speech intelligibility, whereas it was minimally affected by low- and high-frequency noise. In conclusion, this study highlights that medium-frequency noise has the greatest impact on vocal effort, communication disturbance, and vocal comfort, while low- and high-frequency noise has minimal effect on speech intelligibility. [ABSTRACT FROM AUTHOR]

The uplift of underground structures induced by soil liquefaction can damage underground structure systems. Numerical simulations have shown that uplift is positively correlated with the energy of horizontal input motion. However, the effects of vertical input motion on uplift have not been studied comprehensively in the past. Previous studies on the vertical motion concluded that the effects of vertical motion on uplift depend on the overall characteristics of earthquake motion. These motion characteristics have only been studied separately in previous studies. A comprehensive study to explore the interactions and overall effects of these characteristics on the uplift of underground structures is essential. In this study, the FLAC program with the PM4Sand model was used as a numerical tool to explore the effects of vertical input motion on the uplift of underground structures. The numerical model was calibrated using centrifuge test results, and 48 earthquake motions were selected as input motions to study the effects of the overall characteristics of earthquake motions on the uplift of underground structures. The simulation results show that the frequency content characteristics of horizontal and vertical motion are the major factors affecting the uplift magnitude and the responses of liquefiable soils. However, most simulation cases show that the inclusion of vertical motion causes a 10% difference in the tunnel uplift, compared to cases without vertical motion.

Numerous bridges in the mountainous areas of southwest China are constructed with tall reinforced-concrete (RC) piers. This paper presents the influence of higher-mode effects of pier columns on seismic performance in a quantitative manner for, to our knowledge, the first time, while the impact of excitation intensity and the frequency content of input motion, which do not appear to be considered in any previous study, are incorporated as well. Numerical models are developed for three bridges with different pier heights, considering higher-mode effects by comparing the seismic responses computed from multi-degree-of-freedom and single-degree-of-freedom systems. An incremental dynamic analysis method is used to investigate the influence of input intensity, and motions matching different target spectra are employed, showing the effects of frequency components. The analytical results show that when the tall piers remain elastic or experience substantial nonlinearity approaching the ultimate state, the higher-order modes contribute more significantly to the seismic responses, while input excitations with more low-frequency components could generally suppress the effects of higher-order modes. Based on the analysis, seismic design strategies for tall piers are discussed and a novel design scheme using preset plastic region length is proposed, which is demonstrated to be able to limit the range of damage with a negligible increase in maximum curvature demand. [ABSTRACT FROM AUTHOR]

The ground vibrations observed in Taiwan during three teleseismic earthquakes in 2011 by broadband seismometers near major science parks were investigated. Their frequency content was exhibited via spectral analysis, and their effect on structures was examined by response spectra. To assess their possible impact on vibration-sensitive facilities, three vibration criteria in terms of velocity or displacement were utilized. Their predominant frequencies were between 0.04– and 0.16 Hz and somewhat dependent on focal depth and site geology, and they were therefore only influential to very long-period structures. However, the vibration levels exceeded the adopted criteria to some extent, especially at the softer site. [ABSTRACT FROM AUTHOR]

A new non-parametric procedure is presented for extracting seismic fragility curves by considering frequency content of real ground motion records. The implemented non-parametric method is based on parametric methods averaging and clustering the input data based on an intensity measure (IM) using K-means clustering method. As an advantage, it can considerably decrease the number of analyses via an optimization process and using Monte Carlo procedure. The proposed method's accuracy is evaluated for real ground motion records. Results show that although the random selection of records among different clusters can be effective for synthetic records, but it's not suitable for selecting the real ones and can lead to large errors in estimations. Therefore, a classification procedure based on frequency content of the records is used in this study to select an appropriate set of real ground motion records for providing the required IM observations in the method. Then, a set of 472 real ground motion records corresponding to 60 earthquakes is chosen as input data for extracting the fragility curves of the case study structure for evaluating the accuracy and applicability of the non-parametric method. Mean period ( T m ) of the ground motions is considered as a suitable frequency content measure to classify the real ground motion records while this classification can lead to better and more accurate results rather than the Monte Carlo procedure. According to the results, with using the classification procedure, the optimized non-parametric method may require less than 70 nonlinear analyses to extract the fragility curves. [ABSTRACT FROM AUTHOR]

Wavelet transform is one of the mathematical concepts for studying the frequency content of waves. It can be divided into two groups, continuous and discrete. In general, the continuous wavelet transform is used to examine the time-frequency relationship, whereas the discrete wavelet transform is used for filtering and noise reduction in waves. In this paper, for the first time, the combination of these two concepts is used for the earthquake acceleration wave. For this purpose, eight earthquakes from four different locations in the world have been selected. Initially, each earthquake is filtered up to 5 stages using a discrete wavelet transform. At each stage of the filter, two waves of approximations and details are obtained. Due to the close approximation of the frequency content of the wave to the original earthquake, the approximate wave is used for subsequent calculations. The Fourier spectrum and the diagram of five of the dominant frequency of the earthquake are plotted in the next step. Also, using the continuous wavelet transform, the time-frequency curves of the main earthquakes and the time-frequency curves of the wave obtained from the discrete wavelet transform are investigated. The goal was to find the best stage of a discrete wavelet filter based on frequency content to reduce computations by more than 80%. The time of the strong ground motion, the structural response of a single degree of freedom, and the dynamical response of the timing of the structure of a degree of freedom are all investigated in the following step. By examining the above parameters, the best-performing wavelet transformation step is inferred. © 2022 Sharif University of Technology. All rights reserved. Abstract. Wavelet transform is one of the mathematical concepts for studying the frequency content of waves. It can be divided into two groups, continuous and discrete. In general, the continuous wavelet transform is used to examine the time-frequency relationship, whereas the discrete wavelet transform is used for filtering and noise reduction in waves. In this paper, for the first time, the combination of these two concepts is used for the earthquake acceleration wave. For this purpose, eight earthquakes from four different locations in the world have been selected. Initially, each earthquake is filtered up to 5 stages using a discrete wavelet transform. At each stage of the filter, two waves of approximations and details are obtained. Due to the close approximation of the frequency content of the wave to the original earthquake, the approximate wave is used for subsequent calculations. The Fourier spectrum and the diagram of five of the dominant frequency of the earthquake are plotted in the next step. Also, using the continuous wavelet transform, the time-frequency curves of the main earthquakes and the time-frequency curves of the wave obtained from the discrete wavelet transform are investigated. The goal was to find the best stage of a discrete wavelet filter based on frequency content to reduce computations by more than 80%. The time of the strong ground motion, the structural response of a single degree of freedom, and the dynamical response of the timing of the structure of a degree of freedom are all investigated in the following step. By examining the above parameters, the best-performing wavelet transformation step is inferred. [ABSTRACT FROM AUTHOR]

• Mode frequency of pipeline system without soil-pipeline interaction is obtained using two FEMs and one analytic solution • Fundamental mode frequencies of soil-pipeline interaction system are compared with those of the soil stratum. • Soil-pipeline interaction on the dynamic behaviors of the pipeline system are evaluated. • Effects of soil-pipeline interaction on the dynamic behaviors of the pipeline system are evaluated. • Effects of mainshock-aftershock sequences on the dynamic behaviors of the pipeline are evaluated. • Soil-pipeline interaction and mainshock-aftershock sequences may significantly affect the dynamic behaviors of the pipeline. Pipelines are important structural elements that are frequently used today to meet many infrastructures needs such as drainage, natural gas or water transmission. In this context, the usability of such structures, which are important elements of infrastructure systems, especially after disasters such as earthquakes, is of great importance. For this reason, within the scope of this study, a parametric investigation of the seismic behaviors of a natural gas pipeline system under mainshock-aftershock sequences have been carried out, specifically taking into account the soil-natural gas pipeline interaction (SNGPI) in the help of finite element model (FEM) proposed. Before developing the model of SNGPI system proposed using solid element, the fundamental mode frequencies of the pipeline system modeled using the solid element for the verification have been compared with those of obtained from the pipeline system modeled using the beam element and the analytical solutions. After verification of proposed model is demonstrated, SNGPI system has been modeled and its fundamental modes have been compared with mode frequencies of soil stratum obtained from well-known simple analytic solutions. After this stage, the dynamic analyses of natural gas pipeline (NGP) system in the time domain have been carried out using four different soil systems and four different mainshock-aftershock sequences. The results of the nonlinear time-history analyses have been investigated in terms of the stress and the displacement responses. Parametric evaluations show that the greatest displacements and the stresses occurring at the considered nodes of NGP system may be importantly affected from mainshock-aftershock sequences and soil stiffness changes. As the soil stiffness decreases, both the peak stresses and displacements increased significantly. On the other hand, the same responses obtained under mainshock loadings, which have relatively lower peak ground acceleration (PGA)/peak ground velocity (PGV) ratio compared to aftershock loadings, are generally larger than those obtained under aftershock loadings. [ABSTRACT FROM AUTHOR]

Seismic sequence as a result of occurrence of strong and moderate earthquake ground motion in a short time strongly affects the seismic response of structures. This kind of excitation causes, in many cases, more deteriorated effects compared to the corresponding single ground motion. The aim of this paper is to investigate the effect of seismic sequence of earthquake ground motion on the seismic responses of steel moment frame structures considering soil-structure interaction (SSI). To this end, four steel moment frames with 8 and 16 stories are considered each of which have three and six bays. Soil-structure-interaction is considered by employing dampers and springs having specified damping and stiffness through cone method. For modelling SSI effects, three types of soil based on standard 2800 are considered. The time history of responses show that the relative displacement of structure is increased when the structure is subjected to the seismic sequence. As a result, the damage induced to the structure. It is noteworthy to say that the effect of seismic sequence is more in soft soil. The obtained responses show that a special attention should be paid for designing of steel structures in high seismic zone when they are subjected to seismic sequence excitation. Furthermore, soil-structure-interaction is an important parameter that should be considered for such conditions.Therefore, it is recommended that the effects of seismic sequence and soil-structure-interaction should be accounted for better estimation and evaluate accurate responses of steel shear frame.

Subsurface characterization has always been an interesting issue in Geotechnical and geological engineering, especially when there is a potential risk of subsurface anomalies such as cavities and sinkholes. Due to the low resolution and accuracy of seismic recorded data at higher depths, anomalies identification has become more difficult. In this paper, the effect of various types of seismic source loads such as hammer impact, short-time impact, sinusoidal source and Ricker wavelet with a peak frequency of 100, 50 and 20 Hz is evaluated to identify the subsurface cavities by using the Finite Element Method in Abaqus 6.14 software. In addition, The ability of R and P waves are compared after the filtering the waves to detect cavities at different depths of 2, 6, 10 and 20 m. The results show that the frequency content and peak frequency of source load have a significant effect on the penetration depth and wave field resolution. Furthermore, filtering methods and separating R and P waves could be more helpful to identify the shallow and high depths cavities. Also, Ricker seismic source with a central frequency of 100 Hz, hammer impact and short-time impact indicate suitable results for cavities located at depths of 2, 6 and 10 meters. Whereas, it is difficult to identify the backscattered R waves from the cavity at the depth of 20 meters. However, low-frequency seismic load, such as 20 Hz Ricker source load, provides backscattered R and P waves from the cavity at the depth of 20 m. In general, the acceptable results can be obtained by using a combination of P and R waves and applying seismic load proportional to the depth of identification.

Liquefaction poses a potential threat to the safety, serviceability and stability of shield tunnels during seismic events. This study investigates the seismic response of shield tunnels in liquefiable soils employing a fully coupled dynamic effective stress analysis model. The model accounts for the nonlinear mechanical behavior of the shield tunnel structure and incorporates the advanced bounding surface elastoplastic PM4Sand and PM4Silt models integrated with Biot u - p formulation to simulate the constitutive behavior of liquefiable and non-liquefiable soil layers. The seismic performance of shield tunnel-liquefiable soil system is evaluated considering ground motions with different characteristics in the transverse direction. The numerical results reveal the significant effects of ground motion frequency content and seismic intensity on the liquefaction triggering, the tunnel deformation and the internal forces of segmental joints. The soil-structure dynamic interaction and the soil shear dilatancy characteristics greatly influence the generation of the earthquake-induced excess pore water pressure and post-liquefaction shear strains. It is observed that the soil contact pressures on the left and right springlines of the tunnel experience larger increase compared to the contact pressure on the tunnel crown and invert. This observation suggests that the soil could cause racking deformation on both sides of the tunnel structure towards the center. Besides, the deformations and mechanical behaviors of the segmental joints around the tunnel left and right feet and the right springline are notably higher than at other joints in the saturated deposits. Furthermore, it is found that ground motion characterized by low-frequency contents, amplifies the seismic response of the soil and the tunnel when compared to the ground motions with high or moderate-frequency contents. • A two-dimensional fully coupled nonlinear effective stress numerical model of soil-shield tunnel systems is performed. • The nonlinear mechanical behaviors of the shield tunnel are considered in the study. • The seismic response of the shield tunnel in potential-liquefiable soil deposit as well as the interaction mechanism between the tunnel and the liquefiable soil layer are investigated. • Ground motion characterized by low-frequency contents, amplifies the seismic response of the soil deposit and the segmental tunnel when compared to the ground motions with high or moderate-frequency contents. [ABSTRACT FROM AUTHOR]

Recently, a class of fractional multi-frequency oscillators, constructed based on using n integrators and n half-order ones, has been introduced, whose steady-state responses contain sinusoidal components with 0.5 (3 n - 1) number of selectable frequencies. In this paper, the structure of the introduced multi-frequency oscillator is modified such that, notwithstanding the frequency content preservation, the number of its involved integrators is reduced. With no effect on the frequency content of the generated oscillations, this modification causes that the circuitry implementation of the considered class of multi-frequency oscillators can be done with a less number of energy storage elements. [ABSTRACT FROM AUTHOR]

The ubiquitous brain oscillations occur in bursts of oscillatory activity. The present report tries to define the statistical characteristics of electroencephalographical (EEG) bursts of oscillatory activity during resting state in humans to define (i) the statistical properties of amplitude and duration of oscillatory bursts, (ii) its possible correlation, (iii) its frequency content, and (iv) the presence or not of a fixed threshold to trigger an oscillatory burst. The open eyes EEG recordings of five subjects with no artifacts were selected from a sample of 40 subjects. The recordings were filtered in frequency ranges of 2 Hz wide from 1 to 99 Hz. The analytic Hilbert transform was computed to obtain the amplitude envelopes of oscillatory bursts. The criteria of thresholding and a minimum of three cycles to define an oscillatory burst were imposed. Amplitude and duration parameters were extracted and they showed durations between hundreds of milliseconds and a few seconds, and peak amplitudes showed a unimodal distribution. Both parameters were positively correlated and the oscillatory burst durations were explained by a linear model with the terms peak amplitude and peak amplitude of amplitude envelope time derivative. The frequency content of the amplitude envelope was contained in the 0–2 Hz range. The results suggest the presence of amplitude modulated continuous oscillations in the human EEG during the resting conditions in a broad frequency range, with durations in the range of few seconds and modulated positively by amplitude and negatively by the time derivative of the amplitude envelope suggesting activation-inhibition dynamics. This macroscopic oscillatory network behavior is less pronounced in the low-frequency range (1–3 Hz). [ABSTRACT FROM AUTHOR]

In this paper, the effect of earthquake frequency content on the tunnel permanent lining is studied. For this purpose, dynamic analysis of Gilavand tunnel was performed using 15 real accelerograms with different frequency contents by the finite difference method (FDM). Although accelerograms have the same maximum acceleration and duration, they are different in predominant frequency, peak particle velocity (PPV), peak particle displacement (PPD), and specific energy density (SED). The results showed that the closer the frequency of earthquakes to the ground natural frequency, the larger the forces and displacement in tunnel lining. [ABSTRACT FROM AUTHOR]

The present study proposes the use of base isolation for liquid containers and its effectiveness is investigated numerically. The seismic response of partially filled ground-supported rectangular tank with the submerged block is carried out under real earthquake ground motion. Six different earthquake ground excitations are considered, which are characterized as low-, intermediate-, and high-frequency-content earthquakes. The liquid domain is discretized as eight-noded isoparametric finite elements. The effect of variable height submerged block on sloshing response in the partially filled rectangular tank is investigated. Also, the effectiveness of base isolation in tank–submerged block systems is studied. The results of the parametric study imply that the laminated rubber bearings minimize the sloshing characteristics and thus improve the stability of the tank. [ABSTRACT FROM AUTHOR]

Abstract Background The aim of this study is to quantify the frequency content of the blood velocity waveform in different body regions by means of phase contrast (PC) cardiovascular magnetic resonance (CMR) and Doppler ultrasound. The highest frequency component of the spectrum is inversely proportional to the ideal temporal resolution to be used for the acquisition of flow-sensitive imaging (Shannon-Nyquist theorem). Methods Ten healthy subjects (median age 33y, range 24–40) were scanned with a high-temporal-resolution PC-CMR and with Doppler ultrasound on three body regions (carotid arteries, aorta and femoral arteries). Furthermore, 111 patients (median age 61y) with mild to moderate arterial hypertension and 58 patients with aortic aregurgitation, atrial septal defect, or repaired tetralogy of Fallot underwent aortic CMR scanning. The frequency power distribution was calculated for each location and the maximum frequency component, fmax, was extracted and expected limits for the general population were inferred. Results In the healthy subject cohort, significantly different fmax values were found across the different body locations, but they were nonsignificant across modalities. No significant correlation was found with heart rate. The measured fmax ranged from 7.7 ± 1.1 Hz in the ascending aorta, up to 12.3 ± 5.1 Hz in the femoral artery (considering PC-CMR data). The calculated upper boundary for the general population ranged from 11.0 Hz to 27.5 Hz, corresponding to optimal temporal resolutions of 45 ms and 18 ms, respectively. The patient cohort exhibited similar values for the frequencies in the aorta, with no correlation between blood pressure and frequency content. Conclusions The temporal resolution of PC-CMR acquisitions can be adapted based on the scanned body region and in the adult population, should approach approximately 20 ms in the peripheral arteries and 40 ms in the aorta. Trial registration This study presents results from a restrospective analysis of the clinical study NCT01870739 (ClinicalTrials.gov).

This research addresses the influence of the load characteristics, that is, frequency content and maximum acceleration, on the wall stresses of an anchored water storage tank. A low‐density polyethylene tank with a range of six different aspect ratios (water height to tank radius) was tested using a shake table. Eight sine excitations that cover the lowest free vibration frequency of the tank‐water system were applied. Additionally, two sets of five Ricker wavelet excitations were utilized. Each set represents potential earthquakes with a bandwidth between a low and a high dominant frequency. The experimentally determined maximum stresses and those obtained from calculations using a common spring‐mass model employed for seismic analysis of tanks were compared. The results reveal that the relationship between the excitation frequency and the wall stresses strongly depends on the sloshing behavior, especially when the frequency of loading is in the vicinity of the lowest free–vibration frequency of the tank–water system. When the frequencies are dissimilar, there is a proportional relationship between stress and the maximum acceleration of the excitation. The spring‐mass model was found to underestimate both the maximum hoop stress (for aspect ratios greater than two) and axial stress (for aspect ratios equal to 0.5). This occurs because is the spring‐mass model cannot capture, in all cases, the contribution of chaotic sloshing to wall stress. [ABSTRACT FROM AUTHOR]

A different version of the classic proper orthogonal decomposition (POD) procedure introducing spatial and temporal weighting matrices is proposed. Furthermore, a newly defined non-Euclidean (NE) inner product that retain similarities with the POD is introduced in the paper. The aim is to emphasize fluctuation events localized in spatio-temporal regions with low kinetic energy magnitude, which are not highlighted by the classic POD. The different variants proposed in this work are applied to numerical and experimental data, highlighting analogies and differences with respect to the classic and other normalized variants of POD available in the literature. The numerical test case provides a noise-free environment of the strongly organized vortex shedding behind a cylinder. Conversely, experimental data describing transitional boundary layers are used to test the capability of the procedures in strongly not uniform flows. By-pass and separated flow transition processes developing with high free-stream disturbances have been considered. In both cases streaky structures are expected to interact with other vortical structures (i.e. free-stream vortices in the by-pass case and Kelvin–Helmholtz rolls in the separated type) that carry a significant different amount of energy. Modes obtained by the non-Euclidean POD (NE-POD) procedure (where weighted projections are considered) are shown to better extract low energy events sparse in time and space with respect to modes extracted by other variants. Moreover, NE-POD modes are further decomposed as a combination of Fourier transforms of the related temporal coefficients and the normalized data ensemble to isolate the frequency content of each mode. [ABSTRACT FROM AUTHOR]

Concrete ground tanks are widely used in storing water, sewage, oil, toxic chemicals and other liquids. Depending on their type of use, they are usually in the category of very important structures of lifelines; Therefore, the dynamic analysis of liquid storage tanks is one of the most important issues in earthquake engineering. On the other hand, the seismic behavior of the storage tanks and its interaction with liquid is very important. In this study, the water medium is modeled using smoothed particle hydrodynamics method and tank’s structure modeled by finite element method. The smooth particle hydrodynamics, which is a meshfree method, has many advantages over other traditional grid-based methods. For verification purposes, the modeling accuracy was compared with the available experimental and numerical results, the reasons and parameters that were effective on selecting the records were expressed, and then the time history analysis was performed on the modeled storage tank including records with different frequency content. The parameters of sloshing height, acceleration at the top of the tank’s wall, base shear, force per unit width and wall displacement were obtained for comparison. Finally, the effect of frequency content was studied considering the effect of water-structure interaction on the tank. The results showed that a record with low frequency content results higher sloshing height, while a record with moderate frequency content will cause larger responses on the tank’s structure despite of its lower sloshing height. The study also proved that the dominant frequencies of sloshing increases with decreasing frequency content of earthquake.

Background and Objective: The asymmetry index during walking can be used for clinical treatment. This study was done to determine the immediate and long-term effects of foot orthoses on asymmetry of ground reaction forces frequency spectrum in male children with flat foot during walking. Methods: This clinical trial study was done on fifteen children with flat foot. Subjects were randomly divided into without foot orthoses, immediate and long term usage of foot orthoses groups. The kinematic and kinetic data during three without foot orthoses, immediate and long term use of foot orthoses conditions were recorded by the motion analysis and force platform systems, respectively. Results: Asymmetry index of medio-lateral frequency spectrum component during walking without foot orthoses, immediate and long term use of orthoses in median frequency and band width were greater than 4 percent. There were not any significant differences in asymmetry index of ground reaction force frequency spectrum components, asymmetry index of essential harmony numbers, asymmetry index of essential harmony total powers, and asymmetry index of fundamental harmony number in vertical, anterior-posterior, and medio-lateral axes between without foot orthoses, immediate and long term use of foot orthoses conditions. However, asymmetry index of essential harmony total power in medio-lateral axis during immediate use of foot orthoses tend to be reduced than that walking without foot orthoses. However, this difference was not significant. Conclusion: Despite the high asymmetry index of the ground reaction force frequency spectrum in the medio-lateral component during walking without foot orthoses, immediate and long-term effects of foot orthoses in the median and bandwidth frequency variables, the acute or long term use of foot orthoses did not show any significant effect on improvement of asymmetry index of ground reaction force frequency spectrum components.

In this article, the effect of earthquake frequency content and noise effects on damage detection is inspected. For this purpose, the damage was defined as nonlinear behavior of beams and columns, and several ground motion records were scaled so that some elements yield under the applied excitation. Consequently, the acceleration response data of each floor obtained through the nonlinear dynamic analysis. Using the discrete wavelet analysis, the occurrence and time of damage in a frame can be detected based on the spikes appearing in the wavelet details plots acquired from discrete wavelet decomposition. The mean period (Tm) was utilized to compute the frequency content of earthquakes. The implications of this parameter for the analyses with dissimilar ground motion records were investigated and the results indicates that the records with low Tm are more suitable for structural damage detection. In order to examine the effect of noise or measurement errors on damage detection process, the discrete wavelet analysis was repeated with a noise introduced to the acceleration response data.

Power spectral density of horizontal ground displacement of large and recent events in earthquake-prone Latin America is analyzed. The results confirm -in a larger region of the worldthat strong motion horizontal displacement is a narrowband process, which was previously demonstrated solely on a very limited area: the State of California. Nonetheless, those limited and previous results proved to be important in seismic base isolation; particularly, in the solution of the problem of large displacements at the structure base. This is a current problem for which more expensive techniques than passive control are presently being implemented, as active or hybrid control; therefore, it is emphasized that a solution exists within simple base isolation, and it is based on ground displacement narrowbandness. [ABSTRACT FROM AUTHOR]

Background: The evaluation of balance measures can help identify postural control processes, but traditional data collection for the center of pressure (COP) may not reveal differences in postural control mechanisms. This study aimed to evaluate the reliability of the frequency component of postural sway using wavelet analysis of COP signals. Methods: Fifteen healthy male subjects (average age: 39.16±7.2 years, average weight: 72±11.06 kg, average height: 171±6.31 cm) participated in this project. They were requested to perform three trials of single-leg and tandem stance conditions for 20-second with and without vision on a force plate. The frequency content of COP signals, including the energy, root mean square (RMS), and velocity of the COP in four frequency bandwidths of postural sway, was evaluated. The test-retest reliability of COP parameters was tested using the intraclass correlation coefficient (ICC). Results: Among different COP parameters, the energy of the COP within a moderate (1.56–6.25 Hz) frequency band (.79≤ ICC ≤.97) with standard error measurement (SEM) ranged from .14 to .23, the RMS of COP within low (.39–1.56Hz) (.79≤ ICC ≤.93) and ultralow (< .10 Hz) (SEM ranged from .000 to .002) (.78≤ ICC ≤.94) in a tandem stance and the RMS of COP in a bandwidth of < .10 Hz (SEM=.00) in a single-leg stance (.70≤ ICC ≤.99) with the eyes closed and open showed good to excellent reliability. Conclusion: The results of this study showed moderate to excellent reliability of wavelet-based COP measures; therefore, these parameters can be used for the identification of postural control mechanisms.

Objective: The link between frequency content of gait ground reaction forces and hearing loss is not well understood. The objective of this study was to investigate the effects of hearing loss on gait ground reaction force frequency content. Methods: Thirty male children were equally divided into a healthy group and a group with hearing loss problems (Deaf group). Frequency content of ground reaction forces were analyzed during barefoot walking. Independent samples t-test was used for between group comparisons. The significance level was set at p0.05). Conclusion: The results reveal that gait ground reaction force frequency content in deaf children may have clinical values for rehabilitation of these subjects.

Seismic microzoning at a local scale of a given site or at a global scale of an urban center requires a fairly detailed knowledge of the lateral variations of the site effects, such as the amplification level, the fundamental soil frequency, and the site classification according to a given design seismic code. Over the last decade, the horizontal-to-vertical spectral ratio of background noise has become a widely used tool. However, it still has some shortcomings related to the windows selection as the microtremor contains many unknown and random sources other than the one related to the site effect. In this contribution, one proposes a new approach based on the frequency content to discriminate between the different sources. Site classification scheme recently proposed for seismic accelerations, which define target numerical and analytical horizontal over vertical spectral ratios for the 4 standard soil classes (Rock, soft rock, stiff soil and soft soil) defined in Eurocode-8, is adapted to background noise. In order to test the reliability of the proposed approach, microtremor measurements were performed on 67 sites with available shear-wave velocities down to a depth of at least 30 m. Free-field microtremor measurements are converted to accelerations instead to velocities, and split into 5 s non-overlapping windows. Automatic computation based statistical approach using a classification index which measures the similarity between the measured and target horizontal over vertical spectral ratios is performed for the 67 sites. The obtained results reveal a similar site classification, using the time-averaged shear-wave velocity to 30 m depth (Vs30) and the new approach, which can reach a success rate of about 84%. The automatic calculation provides the 67 sites with two fundamental parameters required for the preparation of a first-order microzonation map, the fundamental soil frequency, and the classification of the site according to Eurocode-8 guidelines. The proposed approach can be very useful for large-scale seismic micro-zoning of urban centers that may involve hundreds of measurement points, or supplement other geophysical measurements for a site specific seismic analysis. [ABSTRACT FROM AUTHOR]

Background: Walking and running frequency domain analysis of ground reaction forces are associated with injuries. Comparison of frequency domain analysis of ground reaction forces could be useful in rehabilitation of low back patients. The objective of this study was to investigate frequency domain of ground reaction forces during running in patients with low back pain compared to healthy control ones. Methods: This study was a semi-experimental. The statistical sample of the present study include forty males that divided into a healthy control group (n=20) and a group of patients with low back pain (n=20). A foot scan system (sampling rate: 300 Hz) was used for measuring ground reaction forces in ten regions of the foot during running. Independent sample t-test was used for statistical analysis. Alpha level was set at p<0.05. Results: The frequency content with power 99.5% in the Toe 1 region in low back patients group was significantly greater that that healthy group by 50% (P=0.017). Also, the frequency content with power 99.5% in the Toe 1-5 region in low back patients group was significantly lower than that healthy group (P=0.007). Number of essential harmonics in forth metatarsal in low back patients group was greater than that healthy ones (P=0.049). Conclusion: Patients with low back pain had lower running speed than that healthy ones and therefore lower values of most of the components of the frequency may be due to the guarded gait mechanism in these patients. This altered running speed and lower frequency content is suggestive of a lower mechanical efficiency of running in patients with low back pain. [ABSTRACT FROM AUTHOR]

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The authors propose in this work to formulate multicomponent amplitude modulation (AM)–frequency modulation (FM) representations as a sparse approximation (SA) problem, which is solved using orthogonal matching pursuits (OMP) and least angle regression (LARS). The approach appears to be an efficient tool to separate the frequency content of linear and non‐linear signals and behaves in a better way like the well‐known data‐driven empirical mode decomposition (EMD). Contrary to related works where AM–FM models and/or EMD are used to improve sparsity or learned dictionaries, they propose instead a sparse approach framework in AM–FM modelling and EMD. Recasting EMD as a SA problem provides a new framework towards its comprehension, formulation, and convergence since OMP and LARS converge. Doing so presents an alternative to getting rid of the interpolation process that EMD terribly suffers from. Conducted experiments show noticeable improvements in terms of frequency separation of linear and non‐linear signals, tone separation capability and robustness in a noisy environment. [ABSTRACT FROM AUTHOR]

Dynamic testing of bridges has as target to establish their response on pulse forces between the wheels and unevenness of road surface. Generally, during the tests, real time accelerations or deformations are to be measured and which through successive processing methods lead to other data as velocities, displacements, dynamic impact factor, but also the damping ratio. In order to validate the bridge response following testing, the measured data are compared both with allowable limits existing in standards and with the results obtained using analytical or numerical models.

This study presents a newly developed modular system for control of power electronic amplifiers in high-power, high-frequency power hardware in the loop experiments. The proposed design comprises computational nodes connected via multi-gigabit fibre-optic links. Nodes are modular and reconfigurable, allowing interfacing with a range of sensors and actuators, typically voltage and current sensors, and switching converters. The system has been designed for scalability to permit arbitrarily high power ratings and fidelity to be achieved through paralleling and interleaving of multiple power converter modules, targeting an ultimate sample and control rate of 1 MHz. Experimental validation is presented using a two-node configuration to facilitate a power electronic experiment operating at 120 V(rms) and 10 A(rms), with a fundamental frequency of 50 Hz and frequency content up to the 11th harmonic.

This study presents a newly developed modular system for control of power electronic amplifiers in high-power, high-frequency power hardware in the loop experiments. The proposed design comprises computational nodes connected via multi-gigabit fibre-optic links. Nodes are modular and reconfigurable, allowing interfacing with a range of sensors and actuators, typically voltage and current sensors, and switching converters. The system has been designed for scalability to permit arbitrarily high power ratings and fidelity to be achieved through paralleling and interleaving of multiple power converter modules, targeting an ultimate sample and control rate of 1 MHz. Experimental validation is presented using a two-node configuration to facilitate a power electronic experiment operating at 120 Vrms and 10 Arms, with a fundamental frequency of 50 Hz and frequency content up to the 11th harmonic. [ABSTRACT FROM AUTHOR]