Search

An analytical solution for the fully coupled structural-acoustic response of a thin elastic plate mounted in a rectangular duct assuming linear dynamics is presented. The plate is subjected to harmonic planar acoustic waves at grazing incidence in the presence of a subsonic uniform mean flow in the duct. Both clamped and simply supported plates are considered. Regimes are identified in which the structural-acoustic coupling plays a significant role on the response of the plate. Four metrics characterizing the coupled response are considered: the deviation of the peak response frequency from the in vacuo natural frequency of plate, the amplitude of the peak response, the effective acoustic damping of the plate, and the plate intermodal coupling through the duct acoustic field. For a typical aerospace structure, the plate-fluid coupling does little to change the fundamental vibration frequencies from their in vacuo values but significantly alters the amplitudes of the plate vibration. This is a result of the acoustic radiation being a strong function of the in-duct flow Mach number M∞. Further, the intermodal coupling through the acoustic field is also a strong function of Mo∞. Therefore, reduced-order models relying on the panel's in vacuo modes require Mach-number-dependent coupling coefficients for accurate predictions. [ABSTRACT FROM AUTHOR]

ABSTRACT Tuned liquid dampers (TLDs) control the wind-induced vibrations of tall buildings using sloshing fluid. TLD tanks of complex geometry may be required in practice due to space limitations; however, their behaviour has not been considered in the literature. This study develops and experimentally validates a model to describe the structure-TLD interaction of a 2D system when the TLD tank geometry is complex. The equations of motion of the structure-TLD system are developed using Lagrange's equation. In general, the 2D structure-TLD interaction must be represented as a coupled four degree of freedom system. The model is validated using new structure-TLD system tests where the structure is subjected to 1D and 2D harmonic and random excitation. Two TLD tanks of complex geometry are considered; the first tank is anti-symmetric about both axes, whereas the second tank is symmetric about both axes. For the anti-symmetric tank, energy transfer between orthogonal structural sway modes and sloshing modes is significant; however, for the symmetric tank, this energy transfer is negligible. Experimental results indicate that the model adequately predicts the structural response; however, the nonlinear behaviour of the fluid response cannot be captured by the linearized model. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The notions of a N-subalgebra, a BCK-N-ideal, a (strong) BCC-N-ideal of BCC-algebras are introduced, and related properties are investigated. Characterizations of a coupled N-subalgebra, a coupled BCK-N-ideals, and a coupled (strong) BCC-N-ideals of BCC-algebras are given. Relations among a coupled N-subalgebra, a coupled BCK-N-ideal and a coupled (strong) BCC-N of BCC-algebras are discussed. [ABSTRACT FROM AUTHOR]

This paper deals with the existence results for solutions of coupled system of non-linear fractional differential equations with boundary value problems on an unbounded domain. Also, we give an illustrative example in order to indicate the validity of our assumptions. [ABSTRACT FROM AUTHOR]

Highlights: [•] We reduce a fully coupled structural–acoustic system, under aeroacoustic excitations. [•] An SEA-like approach is applied and the acoustic response inside the cavity is computed. [•] A dynamic scheme for the enhancement of the method’s calculation efficiency is proposed. [•] The results present an excellent conformity in a broadband frequency range. [•] The approach radically reduces the computation time needed. [ABSTRACT FROM AUTHOR]

This paper presents a CMOS wideband miniature balun operating over the full K- and Ka-bands. The balun is based on a single spiral coupled structure where two symmetric spiral lines are stacked vertically (i.e. broadside-coupled) in an antipodal manner. The proposed structure provides ultra-wideband balun performance while occupying a minimal chip area compared with conventional spiral baluns. In order to offset residual inductance of the spirals, a compensation capacitor is shunted at the end of an unbalanced input line, which further improves the bandwidth. The proposed balun is implemented in a bulk 0.13-μm CMOS process. The measured insertion loss is less than 6.5 dB from 14 to 40 GHz. The amplitude and phase imbalances are less than 1 dB and 10°, respectively, over the entire bandwidth. The balun occupies an area of only 0.0095 mm², which, to the authors' knowledge, is significantly smaller than any previously reported CMOS baluns at similar frequency bands. [ABSTRACT FROM AUTHOR]

This paper focuses on guided wave propagation in elastic random structures. A numerical tool, referred to as the ’stochastic wave finite element method’ (SWFE) describing uncertain spectral parameters in periodic structures is presented. This approach represents an extension of the wave finite element for homogenous randomness media. The statistics of the kinematic diffusion matrix for two semi-infinite waveguides connected through an uncertain coupling element is offered. The diffusion relationships presented evaluate the statistics of reflection and transmission coefficients for semi-infinite connected waveguides subject to structural and geometrical variabilities on a coupling element. Finally, the effects of the uncertainties on kinematic and energetic parameters are investigated for two finite coupled structures based on the stochastic spectral approach. Numerical experiments show the effectiveness of the proposed formulation to predict the dynamics of periodic systems in mid- and high-frequency ranges with low CPU consumption. [ABSTRACT FROM AUTHOR]

Highlights: [•] Multilayer morphodynamics in shallow water. [•] Fully coupled Roe solvers in a discontinuous Galerkin framework. [•] Generalized sediment discharge implementations. [•] Numerical convergence and analysis. [•] Convergent channel validation, hydrothermal vent robustness tests. [ABSTRACT FROM AUTHOR]

Abstract: Friction Stir Welding (FSW) is a complex thermal-mechanical process. Numerical models have been used to calculate the thermal field, distortion and residual stress in welded components but some modeling parameters such as film coefficient and thermal radiation of the work pieces may be technically difficult and/or expensive to measure experimentally. Therefore, it is important to establish a systematic procedure to identify FSW process parameters. In this paper, a simplified finite element model for analysis of a FSW thermal progress is proposed in which two parameters, tool heat input rate and heat loss through the backing plate, are identified as parameters for optimization through application of a generic algorithm. A genetic algorithm is used to evaluate the two thermal parameters. By comparing the FEM numerical results with experimental results, the FSW process thermal parameters have been successfully identified. This automatic parameters characterization procedure could be used for the FSW process optimization. [Copyright &y& Elsevier]

Copyright of Revista Fuentes, El Reventón Energético is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Spatially coupled codes have been of interest recently owing to their superior performance over memoryless binary-input channels. The performance is good both asymptotically, since the belief propagation thresholds approach the Shannon limit, as well as for finite lengths, since degree-2 variable nodes that result in high error floors can be completely avoided. However, to realize the promised good performance, one needs large blocklengths. This in turn implies a large latency and decoding complexity. For the memoryless binary erasure channel, we consider the decoding of spatially coupled codes through a windowed decoder that aims to retain many of the attractive features of belief propagation, while trying to reduce complexity further. We characterize the performance of this scheme by defining thresholds on channel erasure rates that guarantee a target erasure rate. We give analytical lower bounds on these thresholds and show that the performance approaches that of belief propagation exponentially fast in the window size. We give numerical results including the thresholds computed using density evolution and the erasure rate curves for finite-length spatially coupled codes. [ABSTRACT FROM PUBLISHER]

Abstract: An inter-system iteration method is proposed for dynamic analysis of coupled vehicle–bridge system. In this method, the dynamic responses of vehicle subsystem and bridge subsystem are solved separately, the iteration within time-step is avoided, the computation memory is saved, the programming difficulty is reduced, and it is easy to adopt the commercial structural analysis software for bridge subsystem. The calculation efficiency of the method is discussed by case study and an updated iteration strategy is suggested to improve the convergence characteristics for the proposed method. [Copyright &y& Elsevier]

The welds of thick plates are, preferable, performed by submerged arc welding procedure (SAW) with multiple arcs in order to increase the productivity and to achieve better mechanical properties of the welded joints. This research focuses on theoretical investigations of temperatures field in the welded joints achieved by double SAW process on ordinary steel. The authors developed a 3D model for the coupled finite element analysis of butt-joint using double SAW procedure, in distinct melted pools. Finally, numerical results on the temperature field are analysed and discussed and important conclusions are drawn. [ABSTRACT FROM AUTHOR]

Abstract: The trends of solar radiation are not easy to capture and become especially hard to predict when weather conditions change dramatically, such as with clouds blocking the sun. At present, the better performing methods to forecast solar radiation are time series methods, artificial neural networks and stochastic models. This paper will describe a new and efficient method capable of forecasting 1-h ahead solar radiation during cloudy days. The method combines an autoregressive (AR) model with a dynamical system model. In addition, the difference of solar radiation values at present and lag one time step is used as a correction to a predicted value, improving the forecasting accuracy by 30% compared to models without this correction. [Copyright &y& Elsevier]

This paper proposes methods for designing bidirectionally coupled systems via generalized synchronization technique. Starting from a chaotic system we are constructing synchronized bidirectionally coupled driving and response systems. Numerical simulation results are presented to prove the effectiveness of the scheme. [ABSTRACT FROM AUTHOR]

We investigate the initialisation of North- ern Hemisphere sea ice in the global climate model ECHAM5/MPI-OM by assimilating sea-ice concentration data. The analysis updates for concentration are given by Newtonian relaxation, and we discuss different ways of specifying the analysis updates for mean thickness. Because the conservation of mean ice thickness or actual ice thickness in the analysis updates leads to poor assimilation performance, we introduce a proportional dependence between concentration and mean thickness analysis updates. Assimilation with these proportional mean-thickness analysis up- dates leads to good assimilation performance for sea-ice concentration and thickness, both in identical-twin experiments and when assimilating sea-ice observations. The simulation of other Arctic surface fields in the coupled model is, however, not significantly improved by the assimilation. To understand the physical aspects of assimilation errors, we construct a simple prognostic model of the sea-ice thermodynamics, and analyze its response to the assimilation. We find that an adjustment of mean ice thickness in the analysis update is essential to arrive at plausible state estimates. To understand the statistical aspects of assimilation errors, we study the model background error covariance between ice concentration and ice thickness. We find that the spatial structure of covariances is best represented by the proportional mean-thickness analysis updates. Both physical and statistical evidence supports the experimental finding that assimilation with proportional mean-thickness updates outperforms the other two methods considered. The method described here is very simple to implement, and gives results that are sufficiently good to be used for initialising sea ice in a global climate model for seasonal to decadal predictions. [ABSTRACT FROM AUTHOR]

Abstract: We present a numerical study of the magnetic structure of nanostructured iron fluoride, using the Monte Carlo Metropolis simulated annealing technique and a classical Heisenberg Hamiltonian with superexchange angle dependent interactions. The parameters are adjusted on experimental results, and the atomic structure and topology taken from a previous atomistic model of grain boundaries in the same system. We find perfect antiferromagnetic crystalline grains and a disordered magnetic configuration (speromagnetic) at the grain boundary, in agreement with experimental features. Both the lowest magnetic energy and the rate of magnetic frustration are found to be dependent on the relative disorientation of crystalline grains, i.e. on the cationic topology. We conclude on possible extensions of the model. [Copyright &y& Elsevier]

We measure the transport properties of mechanically strained single crystals of BaFe2(As1-xPx)2 over a wide range of x. The Néel transition is extremely sensitive to stress and this sensitivity increases as optimal doping is approached (doping with the highest superconducting Tc), even though the magnetic transition itself is strongly suppressed. Furthermore, we observe significant changes in the superconducting transition temperature with applied strain, which mirror changes in the composition x. These experiments are a direct illustration of the intimate coupling between different degrees of freedom in iron-based superconductors, revealing the importance of magnetoelastic coupling to the magnetic and superconducting transition temperatures. [ABSTRACT FROM AUTHOR]

A general symplectic method for the random response analysis of infinitely periodic structures subjected to stationary/non-stationary random excitations is developed using symplectic mathematics in conjunction with variable separation and the pseudo-excitation method (PEM). Starting from the equation of motion for a single loaded substructure, symplectic analysis is firstly used to eliminate the dependent degrees of the freedom through condensation. A Fourier expansion of the condensed equation of motion is then applied to separate the variables of time and wave number, thus enabling the necessary recurrence scheme to be developed. The random response is finally determined by implementing PEM. The proposed method is justified by comparison with results available in the literature and is then applied to a more complicated time-dependent coupled system. [ABSTRACT FROM AUTHOR]

A compact and tunable low-pass filter utilising a coupled structure is presented. A closed-form design method is used to estimate the required design parameters so that the filter can have a tunable cutoff frequency across wide range of values. The filter also has an extremely wide stopband, sharp cutoff response and compact size. The theory of operation for the proposed filter is explained, and its design procedure and equivalent circuit are derived. The tuning capability of the filter is enabled by using two varactor diodes connected between the coupled lines to change their π-mode impedance. The simulated and measured results of a prototype with dimensions 15 mm×20 mm designed to have a cutoff frequency tuning range from 1.5 to 2.5 GHz and a stopband that extends to 25 GHz prove the validity of the presented design method. [ABSTRACT FROM AUTHOR]

In this study, the relationship between the limit of predictability and initial error was investigated using two simple chaotic systems: the Lorenz model, which possesses a single characteristic time scale, and the coupled Lorenz model, which possesses two different characteristic time scales. The limit of predictability is defined here as the time at which the error reaches 95% of its saturation level; nonlinear behaviors of the error growth are therefore involved in the definition of the limit of predictability. Our results show that the logarithmic function performs well in describing the relationship between the limit of predictability and initial error in both models, although the coefficients in the logarithmic function were not constant across the examined range of initial errors. Compared with the Lorenz model, in the coupled Lorenz model-in which the slow dynamics and the fast dynamics interact with each other-there is a more complex relationship between the limit of predictability and initial error. The limit of predictability of the Lorenz model is unbounded as the initial error becomes infinitesimally small; therefore, the limit of predictability of the Lorenz model may be extended by reducing the amplitude of the initial error. In contrast, if there exists a fixed initial error in the fast dynamics of the coupled Lorenz model, the slow dynamics has an intrinsic finite limit of predictability that cannot be extended by reducing the amplitude of the initial error in the slow dynamics, and vice versa. The findings reported here reveal the possible existence of an intrinsic finite limit of predictability in a coupled system that possesses many scales of time or motion. [ABSTRACT FROM AUTHOR]

Standard coupling approaches for simulating coupled MBS/FEM systems may entail enormous CPU times in order to achieve a stable and accurate solution. To stabilize and speed up the solution process, semi-implicit coupling approaches can be applied successfully. In literature, semi-implicit coupling approaches have been introduced, where Jacobian information is exchanged between the subsystems using partial derivatives with respect to the state vectors of the subsystems. The drawback of these methods is that the numerical calculation of the Jacobians with respect to the whole state vector of the subsystems is very time-consuming. The key idea of the semi-implicit coupling technique presented here is to reduce the computational effort by using Jacobian information only with respect to the coupling variables. The semi-implicit coupling technique introduced here is exemplarily applied for coupling a commercial MBS code with a commercial FEM code. As a practical example, we consider a hybrid nonlinear rotor/bearing model of a high-speed turbine. The rotor is modeled as a flexible multibody system. For calculating the bearing reactions, a finite element discretization of Reynolds fluid film equation is applied which yields the pressure distribution in the fluid films of the hydrodynamic bearings. Both codes are coupled via interprocess communication (IPC). A very time-efficient implementation of the semi-implicit coupling approach can be accomplished by a parallelization on multiple CPUs. [ABSTRACT FROM AUTHOR]

This communication proposes a glass-integrated antenna using a coupled feed structure for military FM radio communications on aircraft. The proposed antenna consists of a feed strip and two radiators, printed on the left-side window of the cockpit. The proposed antenna structure is optimized with the genetic algorithm in conjunction with the FEKO EM simulator. The optimized antenna is built and installed on a 1/10-sized KUH-Surion mock-up and antenna performance, such as reflection coefficient and bore-sight gain, is measured in a semi-anechoic chamber. The optimized antenna shows a half-power matching bandwidth of 28% at the center frequency of the military FM radio band and an average bore-sight gain of about -2.60 dBi. The results show that the proposed antenna is suitable for use as a military FM antenna for aircraft applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents work on full-scale vibration testing of the 2nd and 3rd floor slabs of the Tin Shui Wai Indoor Recreation Center. The slabs are supported by one-way long span steel trusses, which are connected by diagonal members and vertical columns to form a mega-truss. On the 2nd floor are a large multi-function room and children play area, while the 3rd floor hosts two basketball courts. Based on their expected usage, significant cultural vibrations with possible rhythmic activities can be expected. To determine the dynamic characteristics of the constructed slab system, ambient and forced vibration tests were performed. Thirty-five setups were carried out in the ambient test to determine the mode shapes using six triaxial accelerometers. A recently developed Fast Bayesian FFT Method is used to identify the modal properties using the ambient data in individual setups. The mode shapes from the individual setups are assembled by a least square fitting procedure. Forced vibration tests were performed by loading the slabs at resonance with a long-stroke electromagnetic shaker, resulting in vibration amplitudes in the order of a few milli-g. A steady-state frequency sweep was carried out and the modal properties were identified by least square fitting of the measured steady-state amplitude spectra with a linear dynamic model. The dynamic properties identified from the ambient and forced vibration tests, as well as their posterior uncertainty and setup-to-setup variability, will be compared and discussed. The field tests provide an opportunity to apply the Fast Bayesian FFT Method in a practical context. [Copyright &y& Elsevier]

This article deals with some existence of weak solutions for a class of Caputo fractional q-difference inclusions and a coupled system of Caputo fractional q-difference inclusions by using the set-valued analysis, and Mönch's fixed point theorem associated with the technique of measure of weak noncompactness. Two illustrative examples are given in the end. [ABSTRACT FROM AUTHOR]

This letter presents the design of a micromechanical oscillator based on a vertically coupled (VC) CMOS-microelectromechanical systems (MEMS) resonator pair for phase noise reduction. The prototyped resonator pair consists of two vibrating plates coupled with each other, thus providing enhanced power handling while keeping compact footprint. The proof-of-concept oscillator based on a 6.5-MHz, VC mode resonator achieves a phase noise of −97 dBc/Hz at 1-kHz offset and −118 dBc/Hz at 1-MHz offset from carrier with a resonator size of 30\times 30\mu \textm^\mathrm \mathbf 2 . Compared with its nonresonance-coupled saddle mode counterpart, the VC-mode-based oscillator features 10-dB phase noise reduction using the same oscillator circuit setup. The design concept of this letter can be extended to three dimensional (3-D) mechanically coupled resonator designs in the future. [2015-0053] [ABSTRACT FROM AUTHOR]

ABSTRACT The design of a planar in-phase power divider for wideband applications is presented. The proposed divider uses a broadside coupled microstrip/slotline configuration with an improved isolation between the output ports using suitable isolation resistor. The proposed design is suitable for single layer integration as both the input and output ports are located at the same layer. Although the device can be used for any wideband application, the developed prototype is designed to operate within the band 2-5 GHz, which is used in microwave-based head imaging systems. The simulated and experimental results of the developed divider show equal power division with less than 0.5 dB of additional insertion loss, less than 2° of phase imbalance, more than 13 dB of isolation and more than 10 dB of return loss over the band 2.3-4.7 GHz. It has a compact size with an overall dimension of 30 × 30 mm2. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:789-791, 2015 [ABSTRACT FROM AUTHOR]

We investigate the occurrence of collective dynamical states such as transient amplitude chimera, stable amplitude chimera, and imperfect breathing chimera states in a locally coupled network of Stuart-Landau oscillators. In an imperfect breathing chimera state, the synchronized group of oscillators exhibits oscillations with large amplitudes, while the desynchronized group of oscillators oscillates with small amplitudes, and this behavior of coexistence of synchronized and desynchronized oscillations fluctuates with time. Then, we analyze the stability of the amplitude chimera states under various circumstances, including variations in system parameters and coupling strength, and perturbations in the initial states of the oscillators. For an increase in the value of the system parameter, namely, the nonisochronicity parameter, the transient chimera state becomes a stable chimera state for a sufficiently large value of coupling strength. In addition, we also analyze the stability of these states by perturbing the initial states of the oscillators. We find that while a small perturbation allows one to perturb a large number of oscillators resulting in a stable amplitude chimera state, a large perturbation allows one to perturb a small number of oscillators to get a stable amplitude chimera state. We also find the stability of the transient and stable amplitude chimera states and traveling wave states for an appropriate number of oscillators using Floquet theory. In addition, we also find the stability of the incoherent oscillation death states. [ABSTRACT FROM AUTHOR]

We present a generalized analytical solution to the normalized state equations of a class of coupled simple second-order non-autonomous circuit systems. The analytical solutions thus obtained are used to study the synchronization dynamics of two different types of circuit systems, differing only by their constituting nonlinear element. The synchronization dynamics of the coupled systems is studied through two-parameter bifurcation diagrams, phase portraits, and time-series plots obtained from the explicit analytical solutions. Experimental figures are presented to substantiate the analytical results. The generalization of the analytical solution for other types of coupled simple chaotic systems is discussed. The synchronization dynamics of the coupled chaotic systems studied through two-parameter bifurcation diagrams obtained from the explicit analytical solutions is reported for the first time. [ABSTRACT FROM AUTHOR]

A compact in-phase power divider utilising a stepped-impedance three-line coupled structure and microstrip-to-slotline transitions is presented. The equivalent circuit of the structure is used to predict the required dimensions for ultra-wideband performance. The length of the structure, excluding the input/output ports needed for the measurements, is around a quarter guided wavelength. The simulated and measured results for the two developed devices indicate equal in-phase power division with less than 0.1 dB and 2° amplitude and phase imbalances, respectively. The return loss at the three ports is more than 15 dB in one prototype, whereas the isolation is more than 13 dB in the other across the band from 3.1 to 10.6 GHz. [ABSTRACT FROM AUTHOR]

Light-matter interaction is naturally described by coupled bosonic and fermionic subsystems. This suggests that a certain Bose-Fermi duality is naturally present in the fundamental quantum mechanical description of photons interacting with atoms. We reveal submanifolds in parameter space of a basic light-matter interacting system where this duality is promoted to a supersymmetry (SUSY) which remains unbroken. We show that SUSY is robust with respect to decoherence and dissipation. In particular, the stationary density matrix at the supersymmetric lines in parameter space has a degenerate subspace. The dimension of this subspace is given by the Witten index and thus is topologically protected. As a consequence, the dissipative dynamics is constrained by a robust additional conserved quantity which translates information about an initial state into the stationary state. In addition, we demonstrate that the same SUSY structures are present in condensed matter systems with spin-orbit couplings of Rashba and Dresselhaus types, and therefore spin-orbit coupled systems at the SUSY lines should be robust with respect to various types of disorder. Our findings suggest that optical and condensed matter systems at the SUSY points can be used for quantum information technology and can open an avenue for quantum simulation of SUSY field theories. [ABSTRACT FROM AUTHOR]