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Normal mode separation and information extraction are popular topics in marine acoustics. The extraction of modal wavenumbers and modal depth functions using the data of a vertical line array is beneficial to various applications. In this paper, we systematically introduce a normal mode separation method based on the consistency restraint of the horizontal wavenumber, obtain the modal depth functions using the singular value decomposition (SVD) method, determine the vertical distribution of the horizontal wavenumber, and determine the SVD accuracy by the consistency of modal wavenumbers on the vertical direction. Moreover, this method can be used to determine the SVD accuracy without true depth functions. When the degeneracy problem leads to a poor SVD effect, the linear relation between the degenerate and true modes is obtained, and the minimum standard deviation of the vertical distribution of the modal wavenumbers is taken as the loss function, thus optimizing the SVD result and improving the accuracy of modal wavenumber estimation. The proposed method is validated using simulated data. In addition, the modes are successfully extracted from ambient noise.

Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, imperfect knowledge of the actual propagation environment and sidelobes due to modal interference prevent accurate propagation modeling and source localization via MFP. To suppress the sidelobes and improve the method’s robustness, a linear frequency-difference matched field processing (LFDMFP) method for estimating the source range is proposed. A two-neighbor-frequency high-order cross-spectrum between the measurement and the replica of each hydrophone of the vertical line array is first computed. The cost function can then be derived from the dual summation or double integral of the high-order cross-spectrum with respect to the depth of the hydrophones and the candidate sources of the replicas, where the range that corresponds to the minimum is the optimal estimation. Because of the larger modal interference distances, LFDMFP can efficiently provide only one optimal range within the same range search interval rather than some conventional matched field processing. The efficiency of the presented method was verified using simulations and experiments. The LFDMFP unambiguously estimated the source range in two experimental datasets with average relative errors of 2.2 and 1.9%.

This work demonstrates deformation in hygrothermoelastic medium with an overlying non-viscous fluid of uniform thickness. A constant mechanical force is applied along the fluid-layer. The normal-mode analysis technique is applied to solve the governing equations of the medium. The analytical expressions of displacement, moisture concentration, temperature distribution, and stresses are obtained for the hygrothermoelastic medium and depicted graphically for different values of fluid-layer depth. The finding of this work is that the values of the aforementioned physical quantities decrease with an increase in the fluid-layer, which justifies the decaying nature of waves with depth. The novelty of the problem is that no research has been carried out so far for analyzing hygrothermoelastic medium subjected to thermoelastic deformation.

Malfunction of the CFTR protein results in cystic fibrosis, one of the most common hereditary diseases. CFTR functions as an anion channel, the gating of which is controlled by long-range allosteric communications. Allostery also has direct bearings on CF treatment: the most effective CFTR drugs modulate its activity allosterically. Herein, we integrated Gaussian network model, transfer entropy, and anisotropic normal mode-Langevin dynamics and investigated the allosteric communications network of CFTR. The results are in remarkable agreement with experimental observations and mutational analysis and provide extensive novel insight. We identified residues that serve as pivotal allosteric sources and transducers, many of which correspond to disease-causing mutations. We find that in the ATP-free form, dynamic fluctuations of the residues that comprise the ATP-binding sites facilitate the initial binding of the nucleotide. Subsequent binding of ATP then brings to the fore and focuses on dynamic fluctuations that were present in a latent and diffuse form in the absence of ATP. We demonstrate that drugs that potentiate CFTR’s conductance do so not by directly acting on the gating residues, but rather by mimicking the allosteric signal sent by the ATP-binding sites. We have also uncovered a previously undiscovered allosteric ‘hotspot’ located proximal to the docking site of the phosphorylated regulatory (R) domain, thereby establishing a molecular foundation for its phosphorylation-dependent excitatory role. This study unveils the molecular underpinnings of allosteric connectivity within CFTR and highlights a novel allosteric ‘hotspot’ that could serve as a promising target for the development of novel therapeutic interventions.

Abstract Despite being widely recognized, the importance of deep layers thermohaline and mixing processes in the ocean circulation and variability is still poorly investigated, especially in the Mediterranean Sea. This limits understanding and parametrizing deep dynamics, which result in evident biases in the global circulation representation by observations and numerical ocean simulations. Having access to hydrological datasets, collected on a whole water column, we investigated the abyssal stratification and its variability of the Ionian Sea (Central Mediterranean). Applying multiple analyses, we found a tidal‐period oscillation and the resulting activation of mixing, pointing out that the combined effect of stratification, morphology, and tides has a key role in enhancing local diapycnal diffusivity in the deepest layers, being a mechanism that connects the whole water column with a compelling impact on the vertical transport of heat and tracers.

This paper aims to modify the generalized thermoelasticity theory of Lord–Shulman. Higher-order time-derivative terms are incorporated to get accurate field variables. The refined theory is employed to examine the inclusion of a magnetic field, a two-temperature parameter, and the viscoelastic effects on a thermoelastic medium with two temperatures. The problem has been solved analytically and numerical data have been obtained by utilizing the normal mode technique. The analytic expressions of the displacements, stresses, dilatation, thermodynamic and conductive temperatures are outlined and investigated. The outcomes are reported for future comparison, and some are presented graphically in 2D and 3D plots. Comparisons with the existing literature due to the classical coupled and simple Lord–Shulman thermoviscoelasticity theories are made. The effects of many parameters are discussed.

This paper discovers a new finding regarding Christiaan Huygens’ coupled pendulums. The reason Christiaan Huygens’ coupled pendulums obtain synchrony is that the coupled pendulums are subject to a harmonic forcing. As the coupled pendulums swing back and forth, they generate a harmonic force, which, in turn drives the coupled pendulums, such that the two pendulums swing in synchrony once the angular frequency of the generated harmonic forcing satisfies a certain condition. The factor that determines the angular frequency of the generated harmonic forcing is the effective length of the pendulum, as its angular frequency solely depends on the length of the pendulum that swings about a fixed point. In other words, it is the effective length of the coupled pendulum that determines whether the coupled pendulum achieves synchrony or not. The novelty of this article is that the author explains and analyzes the synchronization behaviour of Christiaan Huygens’ coupled pendulums from the frequency and harmonic-forcing perspectives.

The direction-of-arrival (DOA) estimation of an underwater bottom-mounted horizontal linear array (HLA) based on weighted phase velocity has been proposed in this paper. The directional response is mainly affected by differences in the modal phase velocities and the sound speed of the water column. Based on the mode theory, the acoustic intensity distribution characteristics and beam deviation were analyzed. The beamforming result obtained provides a distinguishing feature of bearing deviation when the measured sound speed was used. By applying the modal weighted phase velocity instead, source bearing can be well estimated. Particularly, in the presence of a thermocline, the propagating modes can be selected on the basis of the mode trapping theory. Both surface and submerged sources were taken into account based on the experimental data, and the deviation was well explained and reduced. For a source near the end-fire direction, the bearing estimation error was reduced from several degrees to tenths of degrees.

Algorithms working in mode space instead of directly matching the received complex sound pressure were developed to improve computational efficiency and robustness, but these algorithms may be inconvenient to apply in practice because manual operations are often inevitable when performing modal filtering. Based on a phase-matched filter, an imperfect matching scheme named the modal phase based matched impulse response (MP-MIR) is proposed to estimate the source range rapidly and conveniently with a single hydrophone. The field to be matched is still the received complex sound pressure. The replica field is a sum of several “phase” modes, which can be efficiently and conveniently synthesized merely with the horizontal wavenumbers of normal modes and the source–receiver range. The effectiveness of the proposed MP-MIR was demonstrated in localizing 84 emissions along a weakly range-dependent track at ranges of 2.54–20 km in the South China Sea. Although it was found, from cross-correlation coefficients, that the received signals showed strong variation even between adjacent emissions, MP-MIR outperformed the classical matched impulse response (MIR) with a lower standard deviation in most cases, demonstrating good robustness and potential for practical applications.

The influence of hydrostatic initial stress in the context of the time-fractional heat order equation is investigated. The strong electromagnetic field is applied at the external surface of semiconductor elastic medium during the photothermal transport process. The Thomson influence appears due to the strong magnetic field. The behavior of wave propagations of the elastic medium is obtained in context of the thermoelectricity theory with initial stress. The governing main equations are taken in two dimensions to describe the interaction between elastic-thermal-plasma and electromagnetic waves for fractional cases. The density of charge is studied as a function of time only when the electric current is induced. The separation of variables is used as a mathematical technique to obtain the exact solutions of the distributions of physical quantities under investigation. Some mechanical, thermal, plasma and magnetic conditions are applied at the free surface elastic medium. A numerical simulation is used to obtain physical quantities distributions graphically and discussed theoretically in various fractional cases.

Based on horizontal velocity data recorded by a moored acoustic Doppler current profiler (ADCP) deployed on the southwestern continental slope of the East China Sea (ECS), this study investigates the characteristics of near-inertial waves (NIWs) induced by typhoon Mitag in October 2019. The results indicated that Mitag-induced near-inertial kinetic energy (NIKE) was mainly concentrated above 290 m and was subsurface-intensified; both the maximum velocity and kinetic energy of the NIWs occurred at a depth of 100 m and were 0.21 m/s and 23.01 J/m3, respectively. The rotary vertical wavenumber spectra suggested that both downward and upward energy propagation existed. However, upward energy propagation was much smaller than downward energy propagation, mainly in the 0.007–0.014 cpm wavenumber band. The NIWs had an e-folding timescale of 9.5 days and were red-shifted as a result of the Doppler shift of the Kuroshio. Normal mode analysis suggested that the NIWs were dominated by the first and fourth baroclinic modes, which together accounted for 76.7% of the total NIKE. Spectral analysis showed that although the spectral density of the semidiurnal internal tide (M2) peak overwhelmed that of the NIWs by a factor of approximately 30, the shear strength generated by the NIWs was comparable to that of the semidiurnal internal tide (M2), which plays an important role in upper ocean mixing on the southwestern continental slope of the ECS. In addition, the bicoherence analysis suggested that a harmonic wave (M2–f) was generated via the nonlinear interaction between the NIWs and semidiurnal internal tide (M2), which reflects the energy dissipation mechanism of semidiurnal tides and NIWs on the southwestern continental slope of the ECS.

Characterizing acoustic waveguide channels is becoming important for the development of communication and signal processing applications across diverse fields ranging from urban water supply systems to oil and gas distribution pipeline networks. These applications include sonar and transmission systems in support of leak detection, blockage location, sensing, monitoring, and signaling for example. In this paper, we provide experimental results and models for the wideband channel characterization of acoustic waveguides formed from gas and water pipelines over the 1-50 kHz frequency band. Experimental results are provided for two straight pipe systems comprising an acrylic pipe filled with air and a steel pipe filled with water. A mode-based analytical model for predicting acoustic wave propagation in rigid and elastic pipes is proposed with deterministic and stochastic characteristics both considered. Good matching is demonstrated between the model predictions and experimental results in terms of dispersion curves, channel spectrograms, and delay spread. A key finding is that acoustic waveguides filled with water should be treated as elastic pipes, and they have significantly different characteristics from those filled with gas, which can usually be treated as rigid pipes. Furthermore for the steel-water waveguide pipeline, link budget calculations and noise power spectral density measurements reveal that a communication range of more than 50 m can be obtained.

A mesoscale eddy is detected and tracked in the western North Pacific region. Within the life cycle of the cyclonic eddies, the intensities of eddies make a difference. Satellite images indicate the oceanic eddy keeps westward-moving until it disappears. Oceanographic and acoustic characteristics of the eddy are studied. The acoustic energy distribution results from the different intensity of both modelled eddy and measured eddy are calculated. With sound propagation through the cyclonic eddy and anticyclonic eddy, the position of convergence zone moves away from and towards the acoustic source compared with the sound propagation through background hydrography. The coupling coefficient of different orders of normal modes changes significantly. The closer to the centre of the eddy, the stronger the coupling coefficient.

The hydrogen-disordered structure of ice, Ic, makes it difficult to analyze the vibrational normal modes in the far-infrared region (i.e., the molecular translation band). To clarify the origin of the energy-splitting of hydrogen bond vibrations in this area, a 64-molecule supercell was constructed and calculated using first-principles density functional theory. The results were in good agreement with inelastic neutron scattering experiments and our previous study of a hydrogen-ordered ice Ic model. Assisted by analytic equations, we concluded that the origin of the two hydrogen bond peaks in real ice Ic is consistent with that of hydrogen-ordered ice Ic: the peaks originate from two kinds of normal mode vibration. We categorize the four peaks in the far-infrared region recorded from inelastic neutron scattering experiments as the acoustic peak, the superposition peak, the two-hydrogen bond peak and the four-hydrogen bond peak. We conclude that the existence of two intrinsic hydrogen bond vibration modes represents a general rule among the ice family, except ice X.

The purpose of this paper is to study the two dimensional deformation in a thermoelastic micropolar solid with cubic symmetry. A mechanical force is applied along the interface of a thermoelastic micropolar solid with cubic symmetry (Medium I) and a thermoelastic solid with microtemperatures (Medium II). The normal mode analysis has been applied to obtain the exact expressions for components of normal displacement, temperature distribution, normal force stress and tangential coupled stress for a thermoelastic micropolar solid with cubic symmetry. The effects of anisotropy, micropolarity and thermoelasticity on the above components have been depicted graphically.

The main goal of this study is introducing a novel fault current limiter based on parallel resonance structure (PRFCL) for high voltage application. During normal mode, the PRFCL reactor is short-circuited via a rectifier bridge DC output voltage and LC resonance tank shows negligible impedance in the line. During a fault, the rectifier bridge switches are turned off, so that the parallel resonance LC tank connects to the line with high impedance. This impedance of the resonance structure can limit the fault current, successfully. It is shown that the suggested PRFCL can act as a breaker and opens the line during the fault period. In order to show the suggested PRFCL abilities, MATLAB software is used to simulate the normal and fault cases. In addition, a scale-down prototype is implemented to confirm the simulation results. The comparative study shows that PRFCL has acceptable performance in normal and current limiting operation modes.

In this study, we propose a simple linear least squares estimation method (LLS) based on a Fourier transform to estimate the complex frequency of a harmonic signal. We first use a synthetically-generated noisy time series to validate the accuracy and effectiveness of LLS by comparing it with the commonly used linear autoregressive method (AR). For an input frequency of 0.5 mHz, the calculated deviations from the theoretical value were 0.004‰ and 0.008‰ for the LLS and AR methods respectively; and for an input 5 × 10−6 attenuation, the calculated deviations for the LLS and AR methods were 2.4% and 1.6%. Though the theory of the AR method is more complex than that of LLS, the results show LLS is a useful alternative method. Finally, we use LLS to estimate the complex frequencies of the five singlets of the 0S2 mode of the Earth's free oscillation. Not only are the results consistent with previous studies, the method has high estimation precisions, which may prove helpful in determining constraints on the Earth's interior structures.

This paper presents a passive displacement sensor based on a normal mode helical antenna. The sensor consists of an external helical antenna and an inserting dielectric rod. First, the perturbation theory is adopted to demonstrate that both the electric intensity and magnetic intensity have a noticeable gradient change within the in-and-out entrance of the helical antenna, which will cause the sensor to experience a resonant frequency shift. This phenomenon was further verified by numerical simulation using the Ansoft high frequency structure simulator (HFSS), and results show the linear correlation between the retrieved resonant frequency and the displacement. Two sets of proposed sensors were fabricated. The experiments validated that the resonant frequency shifts are linearly proportional to the applied displacement, and the sensing range can be adjusted to accommodate the user’s needs.

In the present study, modal analysis has been performed on modified Gazelle helicopter blade. The construction of the blade is fully composite with the honeycomb core. The approach to determining structure mode shapes and natural frequencies is presented. Modified blade consists of core material, 3D unidirectional composite spar and thin carbon composite facesheets as blade skin. To determine the stiffness of the honeycomb core, the equivalent mass approach was used. Several methods of eigenvalue extraction have been investigated in order to find optimal method which can be used in dynamic analysis of composite structures containing honeycomb cores. Among all extraction methods investigated, it was found that combined Lanczos method is most effective in terms of accuracy and CPU time for eigenvalue extraction in composite structures with honeycomb core having large number of degrees of freedom. Strain energies for first four mode shapes of modified helicopter blade have been calculated using numerical approach and results are presented.

The design strength of a greenhouse structure is generally determined by analyzing strength after applying wind load using the wind pressure coefficient according to a design guide. Until now, the stability analysis for wind load has been performed through static structural analysis. However, a greenhouse is subjected to dynamic wind loads of various amplitudes, and it is reasonable to judge stability through fatigue analysis. For fatigue analysis, a stress-normalized model was constructed based on the square of wind speed, and the value obtained by squaring wind speed was used as dynamic load time data. Life cycle was calculated under stress generated by self-weight by compensating fatigue estimation stress. Furthermore, the effect of self-weight was examined and errors of up to 21% were obtained depending on the configuration of the stress-normalized model. When self-weight and wind speed were applied simultaneously, the effect of self-weight reduced when the stress-normalized model was used at high wind speed. Therefore, it is appropriate that the fatigue analysis is based on the fatigue stress model normalized by the square of wind speed, fatigue estimation stress is corrected to the static stress due to self-weight, and the square of wind speed is used as the dynamic load.

Resonance, conventionally defined as the oscillation of a system when the temporal frequency of an external stimulus matches a natural frequency of the system, is important in both fundamental physics and applied disciplines. However, the spatial character of oscillation is not considered in this definition. We reveal the creation of spatial resonance when the stimulus matches the space pattern of a normal mode in an oscillating system. The complete resonance, which we call multidimensional resonance, should be a combination of both the temporal and the spatial resonance. We further elucidate that the spin wave produced by multidimensional resonance drives considerably faster reversal of the vortex core in a magnetic nanodisc. Multidimensional resonance provides insight into the nature of wave dynamics and opens the door to novel applications.

Second-harmonic generation in non-linear media is investigated. A normal mode analysis is proposed based on the Westervelt equation under the second-order approximation in nonlinear acoustics. This model takes into consideration attenuation, diffraction and nonlinear effects, together with dispersion. The fundamental and second harmonic is examined. The derived method is evaluated by 2-D analytical formulas which apply to tissue medium. doi:10.14456/WJST.2014.48

The article presents a synthesis technique for a symmetrically coupled multiconductor microstrip line operating in normal modes and looks at the examples of the synthesis of a ten-conductor symmetrically coupled multiconductor microstrip line operating in even- and odd normal modes. The paper investigates the dependences of the parameters of the introduced lines. Santrauka Straipsnyje išnagrinėtas simetrinių daugialaidžių mikrojuostelinių linijų, veikiančių normaliųjų bangų režimu, sintezės algoritmas. Kaip pavyzdys pateikti dešimties laidininkų simetrinės daugialaidės mikrojuostelinės linijos, veikiančios lyginės ir nelyginės bangų režimu, sintezės rezultatai, aprašyti linijos parametrai. Raktiniai žodžiai: daugialaidė mikrojuostelinė linija; momentų metodas; normalioji banga; daugialaidžių linijų sintezė; modalinė įtampa

In this work, an isolated DC/DC two-inductor boost converter is proposed. The topology is able to start up and operate in steady-state at any output level within 0V to 400V. The current and voltage characteristics make this topology suitable for applications where the relationship between input current and output voltage is too long, such as applications in hybrid electric vehicles (HEVs). In order for its operation to be possible at any output level, two auxiliary windings were added. These auxiliary windings were included to ensure that the startup current does not rise to a higher level, as opposed to other isolated boost converters where the start-up current level is high. The design of the converter and a detailed analysis are given; an experimental 200W prototype is presented to validate the converter operation and its design.