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The droop control strategy has different forms for inverters with different types of output impedance. Unlike a synchronous machine, of which the impedance is inductive, the impedance of an inverter around the fundamental frequency can be inductive (L‐inverters), resistive (R‐inverters), capacitive (C‐inverters), resistive‐inductive or resistive‐capacitive, etc. This chapter shows that there exists a universal droop control principle for impedance having a phase angle between ‐π/2 rad and π/2 rad. It reviews the widely adopted droop control strategy, with many new insights provided. The chapter presents real‐time simulation results and experimental results from a test rig consisting of an R‐inverter, an L‐inverter, and a C‐inverter operated in parallel. The results have demonstrated the effectiveness of the universal droop controller for the parallel operation of inverters with different types of output impedance, achieving accurate proportional power sharing, tight voltage and frequency regulation.

A retractable larynx and adaptations of the vocal folds in the males of several polygynous ruminants serve for the production of rutting calls that acoustically announce larger than actual body size to both rival males and potential female mates. Here, such features of the vocal tract and of the sound source are documented in another species. We investigated the vocal anatomy and laryngeal mobility including its acoustical effects during the rutting vocal display of free‐ranging male impala (Aepyceros melampus melampus) in Namibia. Male impala produced bouts of rutting calls (consisting of oral roars and interspersed explosive nasal snorts) in a low‐stretch posture while guarding a rutting territory or harem. For the duration of the roars, male impala retracted the larynx from its high resting position to a low mid‐neck position involving an extensible pharynx and a resilient connection between the hyoid apparatus and the larynx. Maximal larynx retraction was 108 mm based on estimates in video single frames. This was in good concordance with 91‐mm vocal tract elongation calculated on the basis of differences in formant dispersion between roar portions produced with the larynx still ascended and those produced with maximally retracted larynx. Judged by their morphological traits, the larynx‐retracting muscles of male impala are homologous to those of other larynx‐retracting ruminants. In contrast, the large and massive vocal keels are evolutionary novelties arising by fusion and linear arrangement of the arytenoid cartilage and the canonical vocal fold. These bulky and histologically complex vocal keels produced a low fundamental frequency of 50 Hz. Impala is another ruminant species in which the males are capable of larynx retraction. In addition, male impala vocal folds are spectacularly specialized compared with domestic bovids, allowing the production of impressive, low‐frequency roaring vocalizations as a significant part of their rutting behaviour. Our study expands knowledge on the evolutionary variation of vocal fold morphology in mammals, suggesting that the structure of the mammalian sound source is not always human‐like and should be considered in acoustic analysis and modelling., Male impala retract the larynx while producing their impressive rutting roars. The low fundamental frequency of these roars is produced by a highly modified vocal fold, a ‘vocal keel’. The anatomical and acoustical correlates of male impala's mobile larynx are discussed.

OBJECTIVE The stiffness of the vocal folds is an important factor in voice production, yet clinically applicable measurements are still lacking. It has been demonstrated in an in vivo canine model that fundamental frequency (F0 ) increased linearly as subglottic pressure (Ps ) increased, but with a lesser slope for higher levels of vocal fold tension. In this study, the relationship between F0 and Ps was investigated using the airflow interruption method in awake patients non-invasively. DESIGN Healthy volunteers enrolled for evaluation. SETTING Single-centre. PARTICIPANTS Thirty-three healthy volunteers aged 20 and older were recruited, with one excluded for a recent asthma attack. MAIN OUTCOME MEASURES The relationships between F0 and Ps , described as the slope (Hz/kPa), were investigated when the participants sustained voicing the vowel/o/at 3 incremental frequencies 4 semitones apart in the modal register (F1, F2 and F3). RESULTS Thirty-two healthy volunteers (20 females, 12 males) aged 20-47 years were enrolled for final analyses. There was a statistically significant difference in the slopes of the linear regression lines of F0 -Ps , depending on the frequency with which the vowel/o/ was produced (P

Communication among birds constitutes the foundation of social interactions, and acoustic signals should evolve based on their efficiency to convey information. We examined the acoustic signals of an Amazonian bird assemblage by testing whether vocal allometry was the main driver in song evolution. We expected the acoustic parameters of the songs to follow general allometric rules, as the size of the vocal apparatus limits the vibration capacity of the syrinx. We tested whether smaller species use lower than expected frequencies due to environmental filtering by examining deviations from allometric relationships. Alternatively, small species could use higher than expected frequencies as a consequence of competitive processes that promote the use of vacant portions of the acoustic spectrum. We recorded birdsongs between 2013 and 2018 and measured three spectral parameters: the dominant frequency (FDOM), the minimum fundamental frequency (FFMIN) and the maximum fundamental frequency (FFMAX). We created an allometric model based on the acoustic pattern of the larger species and used it to predict the frequencies of the smaller species. We compared the frequency values expected by allometry with the observed parameters of the avian assemblage. We found that FDOM and FFMIN were higher than expected by allometry alone, supporting competition structuring in the acoustic ecology of the assemblage. The successful insertion of many species into the acoustic space is the result of long processes of natural selection, with our data highlighting the importance of competition in the vocal structuring of the community.

Background Voice analysis has a limited role in a day-to-day voice clinic. We developed objective measurements of vocal folds (VF) glottal closure insufficiency (GCI) during phonation. Methods We examined 18 subjects with no history of voice impairment and 20 patients with unilateral VF paralysis before and after injection medialization laryngoplasty. Voice analysis was extracted. We measured settling time, slope, and area under the fundamental frequency curve from the phonation onset to its settling-time. Results The measured parameters, settling time, slope, and area under the curve were in correlation with the traditional acoustic voice assessments and clinical findings before treatment and after injection medialization laryngoplasty. Conclusion We found that the fundamental frequency curve has several typical contours which correspond to different glottal closure conditions. We proposed a new set of parameters that captures the contour type, and showed that they could be used to quantitatively assess individuals with GCI.

Historical stone mosques with masonry dome are complex structures due to their different structural elements, material properties, boundary conditions, connections, etc. It is very difficult to develop the numerical models representing the real behaviour of these structures. Therefore, their numerical models should be checked with ambient vibration tests for the reliable safety evaluations before the restoration applications. However, it is known that the ambient vibration tests of historical mosques are very difficult and costly and need permissions from the owners and relevant government agencies. The paper aims to develop an empirical formulation for estimating the fundamental frequency of historical stone mosques with masonry dome to check the initial finite element models. Nine stone mosques with masonry dome in different dimensions in the eastern Black Sea Region of Turkey were selected as examples for this purpose. By performing ambient vibration tests of the selected mosques, experimental natural frequencies, mode shapes, and damping ratios have been determined and evaluated together. An empirical formulation for the fundamental frequency and coefficients for the second and third frequencies of stone mosques with masonry dome based on vibration data are obtained by using the statistical regression analysis and verified with the control data. The comparative results confirm that the proposed formulation has a reliable predictive performance.

To determine the effect of vocal fold anterior web formation on fundamental frequency with a cadaveric excised larynx model.Experimental study with excised human larynges.Academic tertiary care hospital.Sixteen freshly excised human larynges were evaluated with high-speed videoendoscopy and digital kymography during artificially produced vibration. Each larynx was assessed in 4 conditions: preoperative controls and after 25%, 33%, and 50% decreases in the vibratory portion of the vocal folds. The following parameters were evaluated: fundamental frequency, periodicity, vocal fold vibration amplitude, phase symmetry, and glottic closure.The mean fundamental frequencies were 208.87, 250.20, 292.37, and 342.67 Hz for preoperative controls and 25%, 33%, and 50% reductions in vibratory length of the vocal folds, respectively. Fundamental frequency increased with each increase in anterior glottic web extent, and the difference among the groups was statistically significant in absolute values in hertz and in semitone elevation. The mathematical models for estimating postoperative fundamental frequency had a statistically significant coefficient. The vibration of the vocal folds remained periodic in all larynges before and after the procedures.There was a significant and progressive increase in the fundamental frequency with each enlargement of anterior glottic web. Based on the control frequency, mathematical models could estimate the value of the fundamental frequency after the procedure.

The ambient noise measurements were performed at 200 sites in and around the upcoming urban centre of Kangra Valley to derive the predominant frequency of soil. The shear‐wave velocity of the soft soil cover is obtained by joint‐fit inversion modelling of the horizontal‐to‐vertical spectral ratio and the dispersion curves derived from multichannel simulation with one receiver survey. Simultaneously, shear‐wave velocity investigations were also performed employing an active 24‐channel engineering seismograph using multichannel analysis of surface waves. Finally, the derived one‐dimensional shear‐wave velocity profiles were compared between these two different approaches, which were found to be in good agreement. The shear‐wave velocity investigations of the study area have indicated that the majority of the sites either fall in soil class D (Vs=180−360 m/s, stiff soil) or class C (Vs=360−760 m/s, very stiff soil) as per NEHRP classification. The microtremor data also suggest high fundamental frequency (4 to >20 Hz) within and on the fringes of the basin, thus covering 80% of the study area, which is in agreement with the known shear‐wave velocity variation in the Kangra Valley. The large variation in high frequencies cannot be attributed to the presence of thick loose alluvial sediments (gravels and sand) but can be related to the presence of moraine deposits or bedrock (upper conglomerates) underneath the basin. However, a few isolated locations in the northern and southeastern parts of the basin are characterised by a low predominant frequency (2–3 Hz) or frequency less than even 2 Hz. The results further suggest that both multichannel analysis of surface waves and horizontal‐to‐vertical spectral ratio methods, in combination with multichannel simulation with one receiver, are complementary to each other and are suitable for estimating the shear‐wave velocity structure for hilly urban regions, where exploring a large area is a major challenge. The analysis further reveals that Kangra Valley can have a major devastation from a near‐source earthquake rather than from a far‐source event.

The abstract is available here: https://uscholar.univie.ac.at/o:1005828

Traditional task‐evoked brain activations are based on detection and estimation of signal change from the mean signal. By contrast, the low‐frequency steady‐state brain response (lfSSBR) reflects frequency‐tagging activity at the fundamental frequency of the task presentation and its harmonics. Compared to the activity at these resonant frequencies, brain responses at nonresonant frequencies are largely unknown. Additionally, because the lfSSBR is defined by power change, we hypothesize using Parseval's theorem that the power change reflects brain signal variability rather than the change of mean signal. Using a face recognition task, we observed power increase at the fundamental frequency (0.05 Hz) and two harmonics (0.1 and 0.15 Hz) and power decrease within the infra‐slow frequency band ( .955) of their spatial distribution and brain–behavior relationship at all frequency bands. Additionally, the reallocation of finite energy was observed across various brain regions and frequency bands, forming a particular spatiotemporal pattern. Overall, results from this study strongly suggest that frequency‐specific power and variability may measure the same underlying brain activity and that these results may shed light on different mechanisms between lfSSBR and brain activation, and spatiotemporal characteristics of energy reallocation induced by cognitive tasks.

Voices can be characterized by their fundamental frequency as well as by speech timbre characteristics, such as formant frequencies. While infants' responses to fundamental frequency characteristics are well established, very little is known about how infants respond to changes in formant frequencies. This study tested whether 6-month-old infants prefer listening to speech with raised formant frequencies over speech with lowered formant frequencies. Naturally spoken utterances were acoustically manipulated to render raised-formant and lowered-formant stimuli that only differed in the formant frequencies, while keeping fundamental frequency and other acoustic characteristics constant. Infants in an infant-controlled listening procedure listened longer to the raised-formant than to the lowered-formant stimuli. These results provide the first evidence that infants distinguish and show preferences for variations in formant frequencies in adult speech.

Purpose To develop a purpose-built quiet echo planar imaging capability for fetal functional and diffusion scans, for which acoustic considerations often compromise efficiency and resolution as well as angular/temporal coverage. Methods The gradient waveforms in multiband-accelerated single-shot echo planar imaging sequences have been redesigned to minimize spectral content. This includes a sinusoidal read-out with a single fundamental frequency, a constant phase encoding gradient, overlapping smoothed CAIPIRINHA blips, and a novel strategy to merge the crushers in diffusion MRI. These changes are then tuned in conjunction with the gradient system frequency response function. Results Maintained image quality, SNR, and quantitative diffusion values while reducing acoustic noise up to 12 dB (A) is illustrated in two adult experiments. Fetal experiments in 10 subjects covering a range of parameters depict the adaptability and increased efficiency of quiet echo planar imaging. Conclusion Purpose-built for highly efficient multiband fetal echo planar imaging studies, the presented framework reduces acoustic noise for all echo planar imaging-based sequences. Full optimization by tuning to the gradient frequency response functions allows for a maximally time-efficient scan within safe limits. This allows ambitious in-utero studies such as functional brain imaging with high spatial/temporal resolution and diffusion scans with high angular/spatial resolution to be run in a highly efficient manner at acceptable sound levels. Magn Reson Med 79:1447-1459, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Objectives Subharmonic imaging (SHI) is a technique that uses the nonlinear oscillations of microbubbles when exposed to ultrasound at high pressures transmitting at the fundamental frequency ie, fo and receiving at half the transmit frequency (ie, fo/2). Subharmonic aided pressure estimation (SHAPE) is based on the inverse relationship between the subharmonic amplitude of the microbubbles and the ambient pressure change. Methods Eight waveforms with different envelopes were optimized with respect to acoustic power at which the SHAPE study is most sensitive. The study was run with four input transmit cycles, first in vitro and then in vivo in three canines to select the waveform that achieved the best sensitivity for detecting changes in portal pressures using SHAPE. A Logiq 9 scanner with a 4C curvi-linear array was used to acquire 2.5 MHz radio-frequency data. Scanning was performed in dual imaging mode with B-mode imaging at 4 MHz and a SHI contrast mode transmitting at 2.5 MHz and receiving at 1.25 MHz. Sonazoid, which is a lipid stabilized gas filled bubble of perfluorobutane, was used as the contrast agent in this study. Results A linear decrease in subharmonic amplitude with increased pressure was observed for all waveforms (r from −0.77 to −0.93; P

Large rock slope failures play a pivotal role in long‐term landscape evolution and are a major concern in land use planning and hazard aspects. While the failure phase and the time immediately prior to failure are increasingly well studied, the nature of the preparation phase remains enigmatic. This knowledge gap is due, to a large degree, to difficulties associated with instrumenting high mountain terrain and the local nature of classic monitoring methods, which does not allow integral observation of large rock volumes. Here, we analyse data from a small network of up to seven seismic sensors installed during July–October 2018 (with 43 days of data loss) at the summit of the Hochvogel, a 2592 m high Alpine peak. We develop proxy time series indicative of cyclic and progressive changes of the summit. Modal analysis, horizontal‐to‐vertical spectral ratio data and end‐member modelling analysis reveal diurnal cycles of increasing and decreasing coupling stiffness of a 260,000 m3 large, instable rock volume, due to thermal forcing. Relative seismic wave velocity changes also indicate diurnal accumulation and release of stress within the rock mass. At longer time scales, there is a systematic superimposed pattern of stress increased over multiple days and episodic stress release within a few days, expressed in an increased emission of short seismic pulses indicative of rock cracking. Our data provide essential first order information on the development of large‐scale slope instabilities towards catastrophic failure. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd., We use a small seismic networks on the summit of the Hochvogel to record continuous and discrete failure preparation signals of a large‐scale slope instability. Reversible and irreversible mechanisms at the diurnal, multi‐day and seasonal scale are quantified. We infer an early stage of stick slip motion and thermally forced diurnal stress release and rock mass stiffness changes.

The resistive leakage current in surge protectors is an important indicator to characterise its aging degree. It is of great significance to accurately extract the resistive components from the total leakage current for online monitoring of the surge protectors. An improved phase-shift current method is proposed to extract the weak resistive components. The fundamental frequency and phase-shift angle of the total leakage current are determined by the measures of zero-crossing detection, low-pass filtering, and phase measurement on the leakage current. The resistive components extracted from simulation and experimental data by this improved method are analysed with FFT. The results show that the improved method can significantly improve the extraction accuracy of the fundamental and harmonic resistive components.

Widefield frequency-domain fluorescence lifetime imaging microscopy (FD-FLIM) measures the fluorescence lifetime of entire images in a fast and efficient manner. We report a widefield FD-FLIM system based on a complementary metal-oxide semiconductor camera equipped with two-tap true correlated double sampling lock-in pixels and lateral electric field charge modulators. Owing to the fast intrinsic response and modulation of the camera, our system allows parallel multifrequency FLIM in one measurement via fast Fourier transform. We demonstrate that at a fundamental frequency of 20 MHz, 31-harmonics can be measured with 64 phase images per laser repetition period. As a proof of principle, we analyzed cells transfected with Cerulean and with a construct of Cerulean-Venus that shows Förster Resonance Energy Transfer at different modulation frequencies. We also tracked the temperature change of living cells via the fluorescence lifetime of Rhodamine B at different frequencies. These results indicate that our widefield multifrequency FD-FLIM system is a valuable tool in the biomedical field.

DC–DC modular multilevel converter (DC–DC MMC) is an attractive candidate for high-voltage DC (HVDC) interconnections since it can provide the required voltage matching, galvanic isolation and flexible power control abilities. The semiconductor loss of such a DC–DC MMC is a major concern for both system evaluation and parameter design. However, it cannot be measured directly since it is out of the precision range of the high-voltage measuring equipment, and thus, mathematical analysis is considered as a feasible alternative. This paper proposes an accurate off-line loss calculation method for DC–DC MMC modulated by fundamental frequency modulation. Based on the characteristics of the modulation, the switching moments along with the instantaneous voltage and current can be calculated exactly, and the conduction loss and switching loss of each submodule can be expressed in a mathematical way. The calculation results are compared with the simulation results from a comprehensive switched model and show good accuracy performance within a relative error of ± 2% under different operating conditions.

Static Synchronous Compensator (STATCOM), sometimes denoted as an 'Advanced Static VAr Compensator', is a Flexible Alternating Current Transmission System (FACTS) device connected in parallel with a power system that is capable to exchange reactive power with the system in both directions. The terms 'compensator' and 'synchronous' indicate that the device is equivalent to an ideal synchronous generator, which produces a set of three‐phase fundamental frequency sinusoidal voltages. The STATCOM device is mainly used for dynamic compensation in power systems, it can provide fast (dynamic) voltage support and might also be used for transient stability margin enhancement or oscillation damping improvement. The STATCOM consists of a voltage‐sourced converter (VSC), a magnetic circuit (MC), a shunt coupling transformer, a shunt breaker, and a control and protection unit. In a VSC, a number of square wave voltages are generated at fundamental frequency by operating the controllable semiconductor switches once per cycle of the fundamental frequency.

Harmonic suppression is an important study for microstrip patch antenna that radiates harmonic frequencies. In an active microstrip patch antenna, severe surface waves perturb the impedance parameters of the patch element, which cause pattern anomalies associated with the higher harmonics. In this study, the higher order modes including 1st harmonic and a subharmonic (which exist in between fundamental and 1st harmonic) have been removed by using open ended stubs. The subharmonic and the 1st harmonic have been suppressed by using a pair of quarter wave length stubs placed on either sides of the feed line. The introduction of stubs on the feed line does not affect antenna characteristics associated with the fundamental frequency. Simulated and measured results show that the harmonic components existing at 7.9 GHz (subharmonic) and 10.0 GHz (1st harmonic) of the fundamental frequency of 5.20 GHz have been successfully suppressed. The harmonic properties of microstrip antenna with and without stubs have been studied and the result indicates that the 1st and the subharmonic of the patch antenna have been well eliminated because of the effect of the tuning stubs. A parametric study has been done to optimize the stub dimensions. Finally, the influence of other antenna parameters at the presence of stubs in the antenna structure has been studied. Prototype antennas of different combination of stubs have been fabricated, measured and the idea has been verified. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1340–1345, 2016

In this letter, a novel differential transmission-line (TL) loaded with circular substrate integrated waveguide (SIW) cavity is presented for realizing K-band push-push oscillator. The SIW cavity is working at TM110 mode to enforce the 180° phase difference between two sub-oscillators, and the tuning metal vias perturbation is introduced in the SIW resonator to maximize the distance between desired odd TM110 mode and adjacent even modes to stabilize the oscillation mode. Unlike the conventional SIW resonator structure, this differential TL possesses a reflective-type property at the resonance frequency. A 19.76 GHz push–push oscillator based on this differential TL is designed and implemented. The measured suppression of fundamental frequency component is −25.62 dBc, and the phase noise is −118.1 dBc Hz−1 at 1 MHz offset frequency, which corresponds to a figure-of-merit (FOM) of −191 dBc Hz−1. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1217–1221, 2016

Objectives/Hypothesis Fundamental frequency (F0) and intensity sound pressure level (SPL) of voice are controlled by intrinsic laryngeal muscle (ILM) activation and subglottal pressure (Psub). Their interactions were investigated. Methods In an in vivo canine model, the thyroarytenoid (TA), lateral cricoarytenoid/interarytenoid (LCA/IA), and cricothyroid (CT) muscles were independently activated from threshold to maximal contraction by neuromuscular stimulation in various combinations, whereas airflow was increased to phonation onset pressure and beyond. The resultant acoustic output was analyzed for effects of Psub on vibratory stability, F0, and SPL. Muscle activation plots and vocal range profiles by individual ILM activation states were analyzed. Results Cricothyroid activation increased phonation onset F0, but vibration was less stable in high CT conditions and displayed vibratory mode change. In addition, a decrease in F0 with increased Psub was observed in high CT conditions. Intensity increased with Psub in all conditions, but the slope was greater at high CT, low TA/LCA/IA activations. Lateral cricoarytenoid/interarytenoid activation improved vocal efficiency. To maintain same F0 with increasing SPL (messa di voce), TA activation was decreased and LCA/IA activation was increased. The same F0 and SPL could be achieved with a variety of ILM activation combinations. Conclusion Cricothyroid is primarily required for increasing F0, whereas TA can increase or decrease F0 and SPL. Lateral cricoarytenoid/interarytenoid activation likely maintains vocal fold adduction during increased Psub and improves vocal efficiency. This study also demonstrates laryngeal motor equivalence, the ability of the larynx to achieve the same target F0 and SPL with multiple combinations of ILM activation. Level of Evidence N/A. Laryngoscope, 2015

Rectangular arrays of pyramidal recesses coated by silver film are investigated by means of polarization-resolved nonlinear microscopy at 900 nm fundamental wavelength, demonstrating strong dependence of the dipole-allowed SHG upon the lattice parameters. The plasmonic band gap causes nearly complete SHG suppression in arrays of 650 nm periodicity, whereas a sharp resonance at 550 nm periodicity is observed due to excitation of band edge Bloch states at fundamental frequency, accompanied by symmetry-constrained interactions with similar modes at the second-harmonic frequency. Additionally, coupling with modes at the bottom side of the silver film may lead to extraordinary optical transmission, opening a channel for SHG from the highly nonlinear GaAs substrate. Changing the lattice geometry enables SHG intensity modulation over three orders of magnitude, while the effective nonlinear anisotropy can be continuously switched between the two lattice directions, reaching values as high as +/- 0.96.

We present an explicit numerical analysis on GaN-based multi-quantum-well planar Gunn diodes. The simulation demonstrates that Gunn oscillations generated in the multi-channel can be self-synchronized to each other, which significantly improves the output characteristics of planar Gunn diode due to the superposition of the dipole domain in each channel. The optimized output characteristics are obtained in the triple-channel Gunn diode, where the RF output power is about 6.45 mW and the DC-to-RF conversion efficiency is about 2.39% at the fundamental frequency of 216.05 GHz, more than three times larger than that of the single-channel AlGaN/GaN Gunn diode. The proposed GaN HEMT-like multi-channel planar Gunn diode with higher level of output characteristics shows great potential as a solid-state radiation source of millimeter-wave and sub-terahertz.

PURPOSE To combine vocal tract measurements with dynamic MRI of the lungs to provide fundamental insights into the lung physiology during singing. METHODS To analyze vocal fold oscillatory patterns during dynamic lung MRI, an electroglottography (EGG) system was modified to allow for simultaneous EGG measurements during MR image acquisitions. A low-pass filter was introduced to suppress residual radiofrequency (RF) coupling into the EGG signal. RF heating was tested in a gel phantom to ensure MR safety, and functionality of the EGG device was assessed in a volunteer experiment at singing frequencies from A5 to A3. In the recorded EGG signals, remaining RF interferences were removed by independent component analysis post processing, and standard EGG parameters such as fundamental frequency, contact quotient and jitter were calculated. In a second volunteer experiment, EGG recordings were compared with lung diameter measurements from 2D time-resolved trueFISP acquisitions. RESULTS RF heating measurements resulted in less than 1.2°C temperature increase in the gel phantom. EGG parameters measured during MR imaging are within the range of ideal values. In the lung measurement, both the lung diameter and the EGG recordings could be successfully performed with only minimal interference. CONCLUSION EGG recording is pos sible during dynamic lung MRI, and glottal activity can be studied safely at 1.5T. Magn Reson Med 76:1629-1635, 2016. © 2015 International Society for Magnetic Resonance in Medicine.

Summary A spherical tuned liquid damper (TLD) is proposed as a cost-effective method to reduce the earthquake-induced vibration of wind turbines. A 1/20-scale test model was designed to investigate its performance of controlling the structural vibration. A series of free and forced vibration experiments with different water depths in hemispherical containers were performed on the shaking table. Three measured ground acceleration-time histories, including El Centro NS, El Centro EW and Tianjin EW, were selected to verify the effectiveness of spherical TLD in suppressing the earthquake-induced vibration. The experimental results showed that the spherical TLD could effectively improve the damping capacity of the test model. The standard deviation of the dynamic response could be effectively reduced when the excitation frequency was approximately equal to its fundamental frequency. The liquid sloshing motion in containers was characterized by a highly nonlinear and complex nature. The effectiveness of spherical TLDs does not increase linearly as the mass of water in containers and is influenced greatly by the frequency components of earthquake excitations. For El Centro EW excitation, the standard deviations of the dynamic responses could be reduced more than 40% when the liquid mass was about 2% of the generalized mass. Copyright © 2015 John Wiley & Sons, Ltd.

Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (

A compact equal power divider (PD) with filtering function and improved out-of-band performance is proposed in this article. The proposed PD is based on the conventional Wilkinson PD and two filtering cells. The filtering cell is composed of four λ/4 stepped-impedance resonators (SIRs). Using the edge and quasi-lumped coupling topology, a compact PD with improving passband selectivity can be achieved. Meanwhile, by appropriately adjusting the impedance and electric length ratios of SIRs, the stopband can be extended to 39.2 GHz with a rejection level of 20 dB, which is 25 times of the fundamental frequency. The predicted results on S-parameters are compared with the measured ones and good agreement is achieved. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2274–2277, 2015

59.8 andtand50.0022 at 10 GHz. Microwave IC is packaged in Alumin-ium test box. Upper cover height is considered to be at 11 mmand it is electromagnetically modeled and simulated. Carrierplate was made from Kovar and was plated with Gold. Metalli-zation process is Cr-Cu-Au with 17.5 lm accuracy. Measuredspectrum output is presented in Figure 5 when varactors arebiased at 8 V. Measured fundamental tone is at 14.98 GHz with6.87 dBm output power. Figure 6 shows the measured VCOoscillation frequency and output power as a function of varactortuning voltage. VCO can be tuned for 180 MHz in 14.89 to15.06 GHz range by varying resonators’ varactors from 0 to 22V. Measured output power remains in between 4.20 and 8.06dBm for the entire tuning range. The device draws 8.5 mA cur-rent at 3 V resulting into very low 25.5 mW dc power consump-tion. Measured phase noise is 260 dBc/Hz at 1 KHz offset and2145 dBc/Hz at 1 MHz offset from the carrier 14.98 GHz. Nor-malized phase noise figure of merit (PNFOM) for VCO can becalculated using [7],PNFOM ¼ LðÞDf 220log

A low phase noise push–push oscillator using compact spiral resonator (SR) array is presented in this letter. The proposed SR array can provide high frequency selectivity in compact size due to its intrinsic source-load coupling structure. In addition, the SR array acts as a phase coupling network to ensure the out of phase operation mode in two suboscillators. The proposed SR array has a very compact size of 0.17λg×0.17λg. A 14.2 GHz push–push oscillator based on this SR array has been designed and implemented. The measured phase noise is −108.35 dBc/Hz at 100 kHz offset frequency, and the suppression of fundamental frequency and the third harmonic are −23.16 dBc and −37.21 dBc, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1683–1686, 2015

A fluid‐saturated flat channel between solids, such as a fracture, is known to support guided waves—sometimes called Krauklis waves. At low frequencies, Krauklis waves can have very low velocity and large attenuation and are very dispersive. Because they propagate primarily within the fluid channel formed by a fracture, Krauklis waves can potentially be used for geological fracture characterization in the field. Using an analogue fracture consisting of a pair of flat slender plates with a mediating fluid layer—a trilayer model—we conducted laboratory measurements of the velocity and attenuation of Krauklis waves. Unlike previous experiments using ultrasonic waves, these experiments used frequencies well below 1 kHz, resulting in extremely low velocity and large attenuation of the waves. The mechanical compliance of the fracture was varied by modifying the stiffness of the fluid seal of the physical fracture model, and proppant (fracture‐filling high‐permeability sand) was also introduced into the fracture to examine its impact on wave propagation. A theoretical frequency equation for the trilayer model was derived using the poroelastic linear‐slip interface model, and its solutions were compared to the experimental results.

In this article, two goals are followed. First, free vibrations of laminated beams reinforced by Single-Walled Carbon Nanotubes (SWCNTs) are studied based on various Higher order Shear Deformation Beam Theories (HSDBTs) and using an analytical method. The SWCNTs are assumed to be aligned and straight with a uniform layout. The extended rule of mixture is applied to describe the effective material properties of the structure. The natural frequencies of the nanocomposite beam are compared with the existing solutions to verify the validity of the theories. Results show the simplicity and accuracy of the method for free vibration analysis of nanocomposite beams. The effects of Carbon Nanotube (CNT) volume fractions in the layers and span-to-depth ratio on the fundamental frequency of the structure are also studied. As for the second goal of this study, optimization of nanocomposite-laminated beams is presented. The main objective of the optimization problem is maximizing the fundamental frequency of the structure. The total amount of CNT in the structure is considered as a constraint on the optimization problem. The primary optimization variables are the values of CNT volume fraction in layers of a 10-layer laminated nanocomposite beam. Since the search space of the optimization problem is large, the optimization processes becomes so complicated and time consuming. Thus, a novel meta–heuristic approach called Imperialist Competitive Algorithm (ICA), which is a socio-politically motivated global search strategy, is applied to find the optimal solution. Results show the success of ICA for the design of nanocomposite structures. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

We present Frequency Analyser, an AndroidTM application for measuring the fundamental frequency of a sound wave with very high precision in a frequency range between 100 Hz and 11 kHz. The application allows exporting the data of frequency as a function of time to an ASCII file. Several examples of application to Physics and Engineering teaching experiments are presented. © 2015 Wiley Periodicals, Inc. Comput Appl Eng Educ 23:471–476, 2015; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21618

An algorithm for time velocity analysis of building response is presented, which identifies the wave velocity of vertically propagating waves through the building and detects their changes. The algorithm is intended for use in SHM systems for rapid assessment of the structural health and integrity following an earthquake. The velocities are identified by an interferometric algorithm, which involves least squares fit of pulses in impulse response functions. An important feature of this method is that it is not sensitive to the effects of soil– structure interaction. The algorithm is applied to a 12-story RC building in Los Angeles, lightly damaged by the San Fernando 1971 earthquake. The results of the time velocity analysis are critically compared with results of analysis of input power, interstory drift, and instantaneous frequency. The identified average vertical wave velocity was initially ~140m/s for the NS and ~110m/s for the EW response and reduced by ~26% and 32%, respectively. The detected reduction of the fundamental frequency of vibration was larger (~44% for the NS and 48% for the EW response). The difference is interpreted to be due to softening of the soil–foundation system, to which the identified frequency of vibration is sensitive. The change was larger in the lower half of the building (~31% for the NS and ~37% for the EW response) as compared with the upper half (~24% for the NS and ~27% for the EW response), consistent with the observed damage. Copyright © 2014 John Wiley & Sons, Ltd.

A novel technique of beam shaping and beam steering at the central frequency using uniformly excited time-modulated linear array is proposed. Unlike conventional time-switched antenna array, the technique utilises a common complex time exponential signal with unit amplitude at the switching frequency, while each element is controlled by radio frequency switches with unique switching intervals that results on a relative amplitude weight and phase difference between the elements at the central frequency without phase shifters. Artificial bees colony based approach is applied to approximate the switching intervals that produce the desired pattern at the fundamental frequency and suppress the sideband radiation losses. The paper presents an analytical evaluation of the power radiated by the array at the central frequency and power wasted at the sidebands and thereby calculates the dynamic efficiency of the proposed array considering a mutual coupling effect. Representative examples are shown and simulated using commercial electromagnetic simulation software to justify the applicability of the derived expression. Copyright © 2014 John Wiley & Sons, Ltd.

The paper presents a study of propagation of shear wave (SH-wave) in an orthotropic elastic medium under initial stress sandwiched by a homogeneous semi-infinite medium and an inhomogeneous half-space. The technique of separation of variables has been adopted to get the analytical solutions for the dispersion relation in a closed form. The propagation of SH-waves is influenced by inhomogeneity parameters and initial stress parameter. Velocities of SH-waves are calculated numerically for different cases. As a special case when the intermediate layer and half-space are homogeneous, computed frequency equation coincides with general equation of Love wave. To study the effect of inhomogeneity parameters and initial stress parameter, we have plotted the velocity of SH-wave in several figures and observed that the velocity of wave decreases with the increases of non-dimensional wave number. It can be found that the phase velocity decreases with the increase of inhomogeneity parameters. We observed that the velocity of SH-wave decreases with the increases of initial stress parameter in both homogeneous and inhomogeneous media. GUI has been developed by using MATLAB to generalize the effect of the parameters discussed. Copyright © 2014 John Wiley & Sons, Ltd.

SUMMARY This paper proposes a new estimation method to determine arbitrary circuit parameters for the harmonic analysis of a distribution network. Harmonic analysis is important in maintaining electric power quality. An interesting phenomenon, a temporary cut-down of the harmonic voltage level at dawn, even if demand is slightly increasing at this time, is often observed in actual power systems. This paper proposes to utilize observations of this phenomenon to estimate circuit parameters. In addition, it is claimed that a detailed equivalent circuit is preferable to a conventional simplified equivalent circuit for explaining the phenomenon. This paper also discusses the usefulness of the Harmonic Characteristics Curve, which is proposed in this paper as a new concept, at the secondary winding of the distribution transformer, and the correlation of PQ, the monitored values of the active and reactive power at the secondary winding of distribution transformer. This correlation should determine the equivalent fundamental frequency admittance of the shunt capacitors installed for distribution lines. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 16–23, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22451

In this article, a simple-to-design technique is presented to improve the out of band response as well as miniaturize the overall size of the waveguide filters. By appropriate coupling of capacitively loaded cavities resonating at the same fundamental frequency with different higher resonant modes, the out of band response of the filter is considerably improved. A third-order filter is designed, simulated, and fabricated. The response of the proposed filter is compared with one from conventional third-order inductive post filter. Good agreement between simulated and measured responses confirms the validity and accuracy of the design. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:512–515, 2014

Background The dominant atrial frequency is a key parameter for the analysis of atrial fibrillation (AF) from intracardiac recordings. The preprocessing approach employed by Botteron et al. in an early work is able to retrieve this frequency. The preprocessing steps are: (1) 40–250-Hz band-pass filtering, (2) rectification, and (3) 20 Hz low-pass filtering. Methods and results The theoretical aspects of this process are addressed. Moreover, its time-domain and frequency-domain properties are evaluated using both simulations and real electrogram (EGM) recordings. The fundamental frequency is emphasized, due to the rectification step. As the interval between consecutive activations becomes more irregular, fundamental frequency detection becomes less robust. In the case of fractionated EGM, this approach fails. In time-domain, the waveform of the atrial beats are dramatically modified, hence hindering any further analysis on the morphology of the activations. Conclusions Botteron preprocessing succeeds in estimating the dominant atrial rate in most EGMs during AF. However, this approach presents some limitations and improved methods are required.

SUMMARY There is no consensus at the present time regarding an appropriate approach to model viscous damping in nonlinear time-history analysis of base-isolated buildings because of uncertainties associated with quantification of energy dissipation. Therefore, in this study, the effects of modeling viscous damping on the response of base-isolated reinforced concrete buildings subjected to earthquake ground motions are investigated. The test results of a reduced-scale three-story building previously tested on a shaking table are compared with three-dimensional finite element simulation results. The study is primarily focused on nonlinear direct-integration time-history analysis, where many different approaches of modeling viscous damping, developed within the framework of Rayleigh damping are considered. Nonlinear direct-integration time-history analysis results reveal that the damping ratio as well as the approach used to model damping has significant effects on the response, and quite importantly, a damping ratio of 1% is more appropriate in simulating the response than a damping ratio of 5%. It is shown that stiffness-proportional damping, where the coefficient multiplying the stiffness matrix is calculated from the frequency of the base-isolated building with the post-elastic stiffness of the isolation system, provides reasonable estimates of the peak response indicators, in addition to being able to capture the frequency content of the response very well. Furthermore, nonlinear modal time-history analyses using constant as well as frequency-dependent modal damping are also performed for comparison purposes. It was found that for nonlinear modal time-history analysis, frequency-dependent damping, where zero damping is assigned to the frequencies below the fundamental frequency of the superstructure for a fixed-base condition and 5% damping is assigned to all other frequencies, is more appropriate, than 5% constant damping. Copyright © 2013 John Wiley & Sons, Ltd.

An inverse relationship between body size and advertisement call frequency has been found in several frog species. However, the generalizability of this relationship across different clades and across a large distribution of species remains underexplored. We investigated this relationship in a large sample of 136 species belonging to four clades of anurans (Bufo, Hylina, Leptodactylus and Rana) using semi-automatic, high-throughput analysis software. We employed two measures of call frequency: fundamental frequency (F0) and dominant frequency (DF). The slope of the relationship between male snout-vent length (SVL) and frequency did not differ significantly among the four clades. However, Rana call at a significantly lower frequency relative to size than the other clades, and Bufo call at a significantly higher frequency relative to size than Leptodactylus. Because the relationship between F0 and body size may be more straightforwardly explained by biomechanical constraints, we confirmed that a similar inverse relationship was observed between F0 and SVL. Finally, spectral flatness, an indicator of the tonality of the vocalizations, was found to be inversely correlated with SVL, contradicting an oft-cited prediction that larger animals should have rougher voices. Our results confirm a tight and widespread link between body size and call frequency in anurans, and suggest that laryngeal allometry and vocal fold dimensions in particular are responsible.

In this paper, on the basis of the D'Alembert's principle, approximate formulas for dynamic response of tubular tall building structures are presented. Using D'Alembert's principle and applying the compatibility conditions on deformation of the tubes, the governing dynamic equation of the tubular structure's motion is derived. Then, natural boundary conditions of the parallel cantilevered flexural–shear beams are derived, and by using Rayleigh–Ritz method, value problem is solved, and trivial and nontrivial solutions are derived, which can be used for calculating natural frequencies and mode shapes of tubular structures. By solving numerically the frequency equation, a design chart and graph are given for the first five nondimensional natural frequencies of tubular tall buildings. The proposed mathematical model gives dynamic characteristics and provides a simple, efficient and reasonably accurate algorithm for free vibration studies that are needed to be quick at the preliminary design stages of tall buildings with tubular systems. Copyright © 2012 John Wiley & Sons, Ltd.