Effects Of Nonlinear Response Research Articles

Unveiling Gating Behavior in Piezoionic Effect: toward Neuromimetic Tactile Sensing.

The human perception system's information processing is intricately linked to the nonlinear response and gating effect of neurons. While piezoionics holds potential in emulating the pressure sensing capability of biological skin, the incorporation of information processing functions seems neglected. Here, ionic gating behavior in piezoionic hydrogels is uncovered as a notable extension beyond the previously observed linear responses. The hydrogel can generate remarkably high voltages (700mV) and currents (7mA) when indentation forces surpass the threshold. Through a comprehensive analysis involving simulations and experimental investigations, it is proposed that the gating behavior emerges due to significant diffusion differences between cations and anions. To showcase the practical implications of this breakthrough, the piezoionic hydrogels are successfully integrated with prostheses and robot hands, demonstrating that the gating effect enables accurate discrimination between gentle and harsh touch. The advancement in neuromimetic tactile sensing has significant potential for emerging applications such as humanoid robotics and biomedical engineering, offering valuable opportunities for further development of embodied neuromorphic intelligence.

The Effect of Nonlinear Sloshing Response of Water on Seismic Behavior of Reinforced Concrete Elevated Water Tanks

In this study, the fluid-structure interactive behavior by using the Westergaard approach and the Smoothed Particle Hydrodynamics (SPH) method of a 1000 m3 reinforced concrete (RC) elevated water tank under different seismic activities i.e., Kocaeli, Van, Kahramanmaraş and Kobe earthquakes was investigated. In the SPH method, the resulting hydrodynamic pressures were applied to the interior of the wall of the structure as an external force which is made as mass additions to the tank walls in Westergaard approach. With the help of software developed, the load carrying system of the elevated water tank was modeled using the MATLAB Partial Differential Equation Toolbox (PDE) software, based on the finite element method, and its verification was made by comparing with ANSYS software model. Dynamic condensation method was used to perform time history analyses for the cited earthquakes. The time-dependent solutions of partial differential equations are solved with the help of ODE45 functions based on Runge-Kutta method, by arranging the equation of motion in state-space format. The cited tank was analyzed linearly under different seismic activities for empty, half-filled (50%) and full-filled (100%) cases and the obtained results were compared with each other. It has been concluded that considering nonlinear behavior of the fluid during the earthquake with the SPH method provided consistency with the real behavior of RC elevated water tanks and gave more realistic results than the traditional Westergaard approach.

Universal Enhancement Effect of Nonlinear Optical Response from Band Hybridization

AbstractBulk photovoltaic effect, i.e. shift current, is a nonlinear second‐order optical response that can rectify an alternating current (AC) electric field into a direct current (DC). Depending on the wavelength of the incident light, shift current finds applications in various fields, including solar energy conversion and radiation detection. Its promising application in energy conversion and information processing has inspired investigations to uncover the relationship between shift current and electronic structures of materials. Despite numerous efforts dedicated to designing principles for strong bulk photovoltaic effect materials, the only widely accepted crucial parameter is the joint density of states (JDOS). In this study, employing effective model analysis and first‐principles calculations, an enhancement effect of bulk photovoltaic effect is found to arise from band hybridization that is typically along with anti‐crossing‐like electronic band structures, similar to the Berry curvature effects in intrinsic anomalous Hall conductivity. While this mechanism does not offer a comprehensive understanding of the relationship between electronic structure and the magnitude of bulk photovoltaic effect, it represents practical progress in the design of materials with strong bulk photovoltaic effect.

Effects of site response on ground motion directionality based on KiK-net records and numerical analysis

The orientation variability of earthquake ground motions (i.e., GM directionality) is an important engineering characteristic in the seismic design of structures. The GM directionality is believed to be mainly related to source and site contributions. This paper investigated the effect of site response on the change of GM directionality from the borehole depth to the ground surface. Distribution of the range for orientation variability level at both borehole and surface was presented for different intensity measures of 3006 records from downhole arrays in the KiK-net database. It was observed that both the maximum direction orientation of intensity measures and the ratio at various orientations may change significantly from depth to surface, and it is dependent on the specific intensity measures and site class. The numerical analysis of soil column considering bi-directional shaking was demonstrated to have a good ability to capture the influence of site response on the GM directionality. Thereafter, some preliminary insights into the linear and nonlinear site response effects on the GM directionality were provided. The azimuthal variation associated with the predominant period of the input borehole motion is an important factor that results in the change of GM directionality at the surface.

A Gaussian field approach to the planar electric double layer structures in electrolyte solutions.

In this work, the planar, electric, double-layer structures of non-polarizable electrodes in electrolyte solutions are studied with Gaussian field theory. A response function with two Yukawa functions is used to capture the electrostatic response of the electrolyte solution, from which the modified response function in the planar symmetry is derived analytically. The modified response function is further used to evaluate the induced charge density and the electrostatic potential near an electrode. The Gaussian field theory, combined with a two-Yukawa response function, can reproduce the oscillatory decay behavior of the electric potentials in concentrated electrolyte solutions. When the exact sum rules for the bulk electrolyte solutions and the electric double layers are used as constraints to determine the parameters of the response function, the Gaussian field theory could at least partly capture the nonlinear response effect of the surface charge density. Comparison with results for a planar electrode with fixed surface charge densities from molecular simulations demonstrates the validity of Gaussian field theory.

Non-linear dose response effect of cathodal transcranial direct current stimulation on muscle strength in young healthy adults: a randomized controlled study

BackgroundTranscranial direct current stimulation (tDCS) is a technique that modulates brain excitability in humans. Increasing the stimulation intensity or duration within certain limits could enhance tDCS efficacy with a polarity-dependent effect; anodal stimulation increases cortical excitability, whereas cathodal stimulation decreases excitability. However, recent studies have reported a non-linear effect of cathodal tDCS on neuronal excitability in humans, and there is no conclusive result regarding the effect of cathodal tDCS on muscle performance.MethodsOur study aimed to investigate the immediate effects of different intensities (i.e., 1, 1.5, and 2 mA and sham tDCS) of cathodal tDCS on muscle strength in healthy participants. All participants [mean age 23.17 (3.90) years] were recruited and randomly allocated into four groups (1, 1.5, and 2 mA cathodal tDCS and sham tDCS). Muscle strength in bilateral upper and lower extremities was measured before and immediately after tDCS using a handheld dynamometer.ResultsOur results showed that cathodal tDCS at 1 and 1.5 mA reduced muscle strength bilaterally in upper and lower extremity muscles, whereas stimulation at 2 mA tended to increase muscle strength on the dominant limb.ConclusionThese findings support the non-linear effects of cathodal tDCS on muscle strength, which should be considered for the clinical use of tDCS in motor rehabilitation.Trial registration: NCT04672122, date of first registration 17/12/2020.

Phase properties of several nonlinear optical waves described by rational solutions

Phase plays an essential role in both classical and quantum wave dynamics, which has motivated many scientists to study the phases of many different nonlinear waves. Among those nonlinear waves, the ones described by rational solutions have been given much attention, partly because some of them can describe rogue wave dynamics. We revisit the phase of several well-known one-dimensional rational solutions and clarify that sudden phase inversion processes indeed exist for rogue waves, in contrast to the ones reported before. Moreover, we investigate the phase properties of rogue waves and rational W-shaped solitons in the Hirota and Sasa-Satsuma model, for which some high-order physical effects are considered, i.e., the third-order dispersion delayed nonlinear response and self-steeping effects. The quite distinctive phases are uncovered for the rational W-shaped solitons with similar density profiles in the two models, by limitation analysis on the underlying topological vector potentials of other related nonlinear waves. These results indicate that the underlying topological vector potentials can be used to identify the phases of nonlinear waves, especially for localized waves with abrupt phase jumps.

The Influence of Input Motion Scaling Strategies on Nonlinear Ground Response Analyses of Soft Soil Deposits

A key issue for the estimation of ground shaking is the proper selection of input motions at the seismic bedrock. At the same time, the effect of the input motion scaling strategy on structural response is typically studied disregarding the presence of the soil deposit. In this work, different soft soil deposits are selected by varying the shear wave velocity profiles and the depth to the seismic bedrock, modelling the soil behaviour through a nonlinear constitutive model implemented into a fully coupled FE code. Seven input motions are retrieved for several selection strategies in conjunction with two seismic intensity levels. Hence, more than 300 one-dimensional ground response analyses are performed. The results of the analysed cases, which are presented in terms of spectral response at ground surface and amplification factors, indicate that: (i) the use of an advanced elasto-plastic soil constitutive model accounts for nonlinear ground response effects, including higher site amplification in the mid-period range and deamplification of the peak ground accelerations; (ii) the different scaling strategies lead to comparable mean values of the amplification factors, and (iii) the variability of the amplification factors is significantly reduced when the scaling strategy seeks the compatibility with the target spectrum over a specified period range. The research will aid the prediction of local seismic site response over large areas, particularly in the absence of the fundamental period of a structure and facilitate its use in general recommendation for quantifying and reducing uncertainty.

Efficient Low-Complexity Optimized Channel Estimating Methods for OFDM-Based Low-Voltage Broadband Power Line Communication Systems

Broadband Power Line Communication (BB-PLC) technology enables data transmission for smart grid applications. Nevertheless, channel equalizers are required in the receiver to estimate and compensate for the nonlinear time-variant impulse response and noise interference effects introduced by the BB-PLC channel. In this paper, we append the Particle Swarm Optimization (PSO) algorithm and its proposed improved version to the commonly used Least-Square (LS) and Linear Minimum Mean Square Error (LMMSE) algorithms to advance four new blocktype pilot-aided hybrid channel estimation algorithms for low-voltage Orthogonal Frequency Division Multiplexing (OFDM)-based BB-PLC systems. Extensive numerical simulation results for four different M-QAM formats (M = 8, 16, 32, 64) show that the proposed algorithms significantly improve the performance of the traditional LS and LMMSE estimators, at least for the parameters of the BB-PLC system studied in this work. In addition, the computational load complexity of the PSO-inspired LMMSE algorithm is lower compared to the conventional LMMSE estimator.

Complex unloading behavior of titanium alloy in cold and thermal-mechanical working

Unloading behavior is of crucial importance in metal forming, which particularly creates challenges for springback analysis and control of shape and dimensional accuracies of the manufactured components. For the working with hard-to-form materials at elevated temperatures, the thermal-mechanical coupling effect makes the unloading process more complicated and thus more difficult to model and control. Establishing an insight into the thermal-mechanical unloading behavior is crucial for ultimately improving the shape and dimensional accuracy of formed components. In this research, by using a near-alpha high-strength titanium alloy as a case study material, a series of continuous loading-unloading-reloading experiments within cold and warm forming domains were designed and conducted. Through the experiments, the complex unloading behavior, specially for the temperature-dependent degradation effect of elastic modulus and nonlinear stress-strain response, was investigated. A physically-based model was developed to reproduce the temperature-dependent nonlinear reduction effect of elastic modulus. In this model, the reversible mobile dislocation density is particularly included and represented to describe the evolving nonlinear elastic strain component upon unloading affected by both plastic strain and deformation temperature. Based on the model-based analysis, the mechanism accounting for the complex unloading nonlinearity in thermal-mechanical working was discussed and revealed from different evolutions of dislocation behaviors depending on plastic deformation and temperature.

Nonlinear seismic response and amplification effect of 3D sedimentary basin based on bounding surface constitutive model

Sedimentary basins can have significant amplification effects on seismic ground motion. It is very necessary to use appropriate nonlinear soil constitutive model to quantitatively analyze the seismic response of three-dimensional (3D) sedimentary basins subjected to strong ground motion. This paper employs a bounding surface constitutive model to simulate the soil nonlinearity, which is successfully incorporated into ABAQUS software. A finite element model is then established to investigate the nonlinear seismic response of 3D sedimentary employing the constitutive model along with viscoelastic artificial boundary and equivalent nodal force method. The nonlinear amplification effect of a typical 3D layered sedimentary basin is extensively evaluated. The influence of a soft interlayer in the sedimentary basin on the seismic amplification is further analyzed. The results demonstrate that the maximum surface peak acceleration usually occurs in specific areas; as the input ground motion intensity increases, the focusing and amplification effects become more significant in deeper soil layers. A soft interlayer will significantly increase the short period component of the surface response spectrum, and shorten the predominant period of sedimentary basin. These results can provide a reference basis for seismic risk analysis and determination of ground motion parameters in a sedimentary basin.

Development of three-dimensional co-rotational beam model for nonlinear dynamic analysis of highly flexible slender composite blades

The main purpose of this work is to introduce a novel method analyzing the dynamic response of a highly flexible slender composite beam having anisotropic property and variable cross-section. A three-dimensional co-rotational model is developed. The beam deformation in dynamic conditions is obtained by applying HHT-α method as dynamic analysis tool. Validation studies with various boundary conditions, multiple external loads and pre-curved structures are performed. Furthermore, dynamic analysis with a large, flexible, and slender composite blade is performed with and without structural couplings. It is shown the developed beam model accurately predicts nonlinear three-dimensional response and anisotropic structural coupling effects.

INTENSITY CONTROLLED, NONSPECULAR RESONANT BACK REFLECTION OF LIGHT

Subject and Purpose. Theoretical demonstration of controllable features of a non-conventional resonant back reflection of light, realizable with the aid of a structured silicon-on-metal covering. Methods and Methodology. The investigation has been performed through a full-wave numerical simulation in a finite-element technique. Results. The nonlinear optical properties of a planar structure, involving a set of silicon disks disposed periodically on a silver substrate, have been studied in the Littrow scenario of wave reflection. The structure manifests a bistable resonant reflectivity property. The magnitudes of both specular and back reflection ratios can be controlled by means of varying the incident light intensity. Conclusions. An array of identical silicon disks, placed in a periodic order on a silver substrate, can be employed as an efficiently excitable and tunable nonlinear resonant reflective structure implementing Littrow’s non-specular diffraction scenario. As has been found, the effect of nonlinear response from the silicon disks can be used for implementing a regimen of bistable back reflection, controllable by means of varying the incident wave’s intensity. The nonlinear tunability of the silicon-on-silver structure does promise extensions of the operation area of classical metamaterials of sub-wavelength scale sizes as it offers new

Effect of nonlinear flame response on the design of perforated liners in suppression of combustion instability

This paper aims at investigating how to suppress combustion instability using perforated liners under nonlinear flame response. A theoretical model is thus presented to describe the interaction between the unsteady heat release, acoustics, and fluid fields, which takes both perforated liner and flame nonlinearity into account. To establish an eigenvalue problem to evaluate combustion instability, appropriate matching and boundary conditions are set up by applying conservation laws across the interfaces, consequently deriving the dispersion relation equation in the form of a matrix. In view of the nonlinearity of flame response function, it is found that the control strategy of combustion instability should be devoted to the reduction of the limit cycle amplitude to an acceptable level rather than the complete elimination of its onset. Based on the present model, we have studied the first longitudinal mode of a Rijke tube equipped with perforated liners. It is noted that the change of combustion instability evolution is sensitive to the design parameters of perforated liners, including cavity depth, installation position, and bias flow velocity. On the one hand, it is indeed possible to suppress the onset of combustion instability with elaborately designed parameters of the perforated liners. On the other hand, the limit cycle amplitude can be reduced as small as possible under various design restrictions of perforated liners in practice. Therefore, this study presents an alternative design criteria of perforated liners for the control of combustion instability.

Reduction of peak ground velocity by nonlinear soil response – III: Excitation by an SV-wave pulse

We study how the peak velocity of an SV-wave pulse on the ground surface of a two-dimensional soil valley is reduced by loss of wave energy during large nonlinear response inside the valley. This is a follow-up on our previous studies in which we considered excitation by an SH-pulse and a P-wave pulse. We consider in-plane response for incident angle below critical and assume that the soil material does not support tension, but the normal stress at a point in the soil can be compression. A point in the soil with zero stress behaves as stress-free, does not transmit normal stress and appears as a crack. We study the interplay of two opposing effects. The first effect is a jump in impedance from a higher value (in the half-space) to a lower value (in the valley), which amplifies the linear motions at the free surface of the valley. The second effect is the occurrence of nonlinear zones in the valley, which reduce the motion at the valley surface. We show how, for small excitations, when the response is linear or almost linear, the valley amplifies the motion. As the excitation amplitudes increase, at low frequencies, at which the nonlinearities are weak, the effect of decrease in impedance is stronger than the effect of nonlinear zones and the valley amplifies the motion. At higher frequencies, the effect of nonlinearity becomes stronger and the amplitudes of motion are reduced. As the excitation further increases, the effect of nonlinear soil response prevails at all frequencies and the motion is reduced significantly.

Darboux-dressing transformation, semi-rational solutions, breathers and modulation instability for the cubic-quintic nonlinear Schrödinger system with variable coefficients in a non-Kerr medium, twin-core nonlinear optical fiber or waveguide

Twin-core optical fibers are applied in the fiber optic sensing technique and optical communication. Non-Kerr media are seen in plasma physics, nonlinear quantum mechanics and nonlinear optics. Propagation of an optical beam and superradiance for an atom in the waveguide are reported. This paper investigates the cubic-quintic nonlinear Schrödinger system with variable coefficients for the ultrashort optical pulse propagation in a non-Kerr medium, twin-core nonlinear optical fiber or waveguide. For the two components of the electromagnetic fields, Darboux-dressing transformation, semi-rational solutions and breather solutions are obtained. We acquire the Akhmediev breathers (ABs) and Kuznetsov-Ma (KM) solitons. Interaction between the rogue waves and KM/bright-dark solitons is presented. When b(z) is a linear/quadratic/cosine function, the ABs, rogue waves, KM and bright-dark solitons appear parabolic, cubic and wavy, respectively, where b(z) presents the delayed nonlinear response effects. We conduct the modulation instability for the plane wave solutions for a non-Kerr medium, twin-core nonlinear optical fiber or waveguide via the linear stability analysis: If χ < 0, the solutions are modulationally stable; otherwise, modulationally unstable, where χ is the growth rate of the instability.

Kappa (κ) in the 2011 Great East Japan Earthquake

Kappa ([Formula: see text]) describes the amplitude decay of acceleration Fourier spectrum at high frequencies. Using the records of K-NET and KiK-net stations during the mainshock of the 2011 Great East Japan Earthquake, we examine if the typical measurement method of [Formula: see text] can be extended to this size of event and how propagation path and site condition affect [Formula: see text]. The strength of the linear relationship between epicentral distance and [Formula: see text] is the most apparent in the KiK-net borehole data; for other data sets, the statistical significance of the best-fitting logarithmic model is more tenuous. Our study on site effects reveals that high-frequency amplitudes diminish about 20% at soft soil stations than they do at hard rock stations. The effect on high-frequency filters is around diminution in most cases. And, the effect of nonlinear site response on [Formula: see text] values can be observed.

Experimental study and numerical modeling of nonlinear dynamic response of SDOF system equipped with tuned mass damper inerter (TMDI) tested on shaking table under harmonic excitation

This paper considers a novel shaking table testing campaign to assess the tuned mass-damper-inerter (TMDI) vibrations suppression attributes in harmonically excited structures under the combined effect of nonlinear structural response and nonlinear inerter device behavior deviating from the ideal linear inerter element developing acceleration-dependent force proportional to the inertance constant. Physical specimens of TMDI-equipped single-degree-of-freedom (SDOF) structure are considered featuring a custom-built rack-and-pinion flywheel inerter device with nonlinear behavior due to friction and backlash effects to connect the TMDI secondary mass to the ground. Damping and elastic properties are endowed to the SDOF structure and to the TMDI via high damping rubber bearings (HDRBs) exhibiting softening nonlinear elastic behaviour. Comprehensive experimental data in time and frequency domains are presented for 9 specimens with different sets of secondary mass and inertance subject to sine-sweep excitations for three different amplitudes. The data demonstrate that the main practical advantage of the TMDI established in the literature for linear structures and ideal inerter elements (i.e., improved vibration suppression through increasing inertance without increasing secondary mass leading to lightweight vibration absorbers) is maintained for nonlinear structures and inerter devices. Moreover, a comparison of experimental data with data derived from two different nonlinear parametric numerical models capturing faithfully the HDRBs response, one using a nonlinear mechanical model to represent the inerter device and the other using an ideal linear inerter element instead, demonstrate that displacement, acceleration and base shear response of the SDOF structure is insignificantly influenced by the nonlinear attributes of the inerter device. This outcome paves the way for developing simplified, thus practically meritorious, optimal TMDI tuning approaches adopting the ideal inerter element assumption to model physical inerter devices.

Cyclic compressive deformation behavior of polymer matrix composites: Experiments and constitutive modeling

AbstractThis article presents integrated experiments and constitutive modeling of cyclic compressive deformation and Poisson behavior of unidirectional (UD) fiber‐reinforced polymer matrix composites (PMCs). Consecutive loading‐unloading tests with a gradually increasing peak stress are performed for five cycles and on UD laminates with different fiber orientations. Nonlinear accumulation of plastic strain with the peak stress is observed both in the axial and lateral directions for all fiber orientations and described by a nonassociative plasticity model. This model enables the collapsing of axial and lateral stress‐plastic strain curves from different fiber orientations into a single master curve in the effective stress‐effective plastic strain plane and allows accurate predictions of compressive plastic Poisson's ratio. Nonlinear unloading behavior appears in the cycles and is attributed to the recovery of nonlinear elastic strain. A linear relationship between plastic strain and nonlinear elastic strain is assumed regardless of the axial and lateral directions. By incorporating this linear dependence into the nonassociative plasticity model, the cyclic evolution of nonlinear elastic strain is simulated. Experimental results of UD laminates with different fiber orientations are used to validate the accuracy of the model in the cyclic compressive nonlinear response and Poisson effect of PMCs.

Suitability of Height Amplification Factors for Seismic Assessment of Existing Unreinforced Masonry Components

ABSTRACT The suitability of ‘design’ height amplification factors (HAF) for the purpose of seismic assessment of existing non-structural unreinforced masonry (URM) components with known strength was evaluated through a numerical study. Four building typologies were included that represented pre-1940 URM construction in Australia and New Zealand. Through pushover and incremental dynamic analyses, the effects of diaphragm flexibility and nonlinear building response on floor accelerations were studied. It was found that Australia/New Zealand code procedures include significant inelastic building behaviour that reduces HAF. An interpretation was made on the applicability of the assumptions in the context of assessing non-structural URM components.