Nonlinear Element Research Articles

Experimental and numerical investigation of a fluid inerter for structural control

In the study presented here, the dynamic properties of a fluid inerter, including nonlinear effects, are characterized and the degree of its effectiveness in structural control is assessed. A fluid inerter is a mechanical device that models an element with unit of mass whose mass property (called inertance) greatly exceeds its physical mass. To this end, a small-scale prototype is realized and experimentally investigated. Linear and nonlinear parameters are identified to obtain a mechanical model suitable for more accurate parametric studies. Numerical simulations based on a finite element model are performed to evaluate the effects of the air unavoidably trapped in the system. In order to apply the device to engineering problems in more general configurations, a linearization procedure is performed for the nonlinear system elements and a comparison is made between the real and the linearized system.

The impacting vibration absorbers

Impacting vibration absorbers (IVA) and impacting inertial amplifier vibration absorbers (IIAVA) are established in this study to control the vibrations of the single and multiple degrees of freedom systems, i.e. SDOF and MDOF. Further, by incorporating the IVA and IIAVA with the base isolator, two hybrid passive vibration absorbers, namely base-isolated impacting vibration absorbers (BI-IVA) and base-isolated impacting inertial amplifier vibration absorbers, are developed and applied to SDOF and MDOF systems. In order to derive the equations of the motion for controlled dynamic systems, Newton's second law has been employed. The impact between the absorber mass and barrier has been modelled using the “signum” function. The standard linearization method has been used to linearise each nonlinear element of the equations of motion. H2 and H∞ optimization techniques are implemented to determine optimal design parameters analytically. The frequency response function is developed to obtain the dynamic system's responses. Accordingly, each proposed absorber's vibration reduction capacity is determined. For SDOF systems, the optimum IIAVA and BI-IVA have 59.44% and 96.63% more vibration reduction capacities than the optimum IVA. In contrast, the optimum IIAVA and BI-IVA have 46.83% and 96.74% more vibration reduction capacities than the optimum IVA when applied to the MDOF systems. In this paper, each one of the results is mathematically accurate.

Dynamic Analysis of A Three Dimension Chaotic System

Memristor is a newly realized physical element, and it is a non-linear circuit element with memory function. We constructed a new three-dimensional chaotic system is constructed which contains four parameters and five non-linear terms. The system is analyzed by nonlinear dynamic analysis methods such as theoretical deduction analysis, numerical simulation, lyapunov exponent spectrum, and bifurcation diagram. The dynamic behavior of the system. This paper proposes a new three-dimensional chaotic system. The system contains four parameters, and each equation contains a non-linear product term. Based on theoretical derivation, numerical simulation, Lyapunov exponential spectrum, bifurcation diagram, the basic dynamic characteristics of the chaotic system are analyzed.

Diffraction-based nonlinear model for the design of broadband adiabatic up-conversion imaging.

In recent years, mid-infrared parametric upconversion imaging, a nonlinear optical method that involves converting mid-infrared light into visible images, has significantly advanced and has shown considerable potential for various applications, including biomedical imaging and remote sensing. While diffraction-based parametric upconversion imaging modeling in standard thin birefringence crystals have been addressed, the numerical framework developed so far fails to address long aperiodic poled crystals. Specifically, diffraction-based analysis of the recent broadband adiabatic frequency upconversion imaging, which allows simultaneous image upconversion of extremely broadband signals is still lacking. Here, we introduce a diffraction-based numerical simulation framework for predicting the evolution of the nonlinear image/signal generation in upconversion imaging systems. This generalized framework can handle both periodically and aperiodically poled crystal designs. Specifically, the model captures faithfully and addresses the varying image magnification arising from upconversion at a Fourier plane of a multiwavelength object. The numerical simulations are validated by experimental measurements of broadband upconversion 3-5 µm mid-IR images to the visible-NIR, showing a good agreement. Moreover, the model allows the exploration of the trade-offs in the spectral span when moving to the full visible range. Our numerical framework will be useful for the interpretation of experimental results obtained in an imaging setting with nonlinear optical elements.

Algebraic-differential equations of a nonlinear pass-through quadripole

A method of forming algebraic-differential equations of a nonlinear pass-through active quadripole, which connect its independent pole currents and independent polar voltages, is proposed. The difficulty of the analysis lies in the fact that some of both internal and external unknowns may be under the symbol of differentiation. The common differential equations of the system of internal and external currents and voltages act as starting information for this formation. The method is demonstrated on two cases of the formation of corresponding algebraic-differential equations of systems as formed by nonlinear two-port elements. The analysis is significantly simplified in the case of internal D-degeneracies of the system or purely resistive circuits.

Grain Crystallinity, Anisotropy, and Boundaries Govern Microscale Hydrodynamic Transport in Semicrystalline Porous Media.

Polycrystallinity is often an unintended consequence of real manufacturing processes used to produce designer porous media with deterministic and periodic architectures. Porous media are widely employed as high-surface conduits for fluid transport; unfortunately, even small concentrations of defects in the long-range order become the dominant impediment to hydrodynamic transport. In this study, we isolate the effects of these defects using a microfluidic analogy to energy transport in atomic polycrystals by directly tracking capillary transport through polycrystalline inverse opals. We reveal─using high-fidelity florescent microscopy─the boundary-limited nature of flow motions, along with nonlinear impedance elements introduced by the presence of "grain boundaries" that are separating the well-ordered "crystalline grains". Coupled crystallinity, anisotropy, and linear defect density contribute to direction-dominated flow characteristics in a discretized manner rather than traditional diffusive-like flow patterns. Separating individual crystal grains' transport properties from polycrystals along with new probabilistic data sets enables demonstrating statistical predictive models. These results provide fundamental insight into transport phenomena in (poly)crystalline porous media beyond the deterministic properties of an idealized unit cell and bridge the gap between engineering models and the ubiquitous imperfections found in manufactured porous materials.

Nonlinear macromodeling of multistory RC buildings with masonry infill walls

The structural behavior prediction of the multistory reinforced concrete (RC) buildings with masonry infill walls (MIWs) during earthquakes is challenging. This paper presents a nonlinear macromodeling strategy seeking a simple, reliable, and low-cost computational analysis of the multistory RC buildings that comprise MIWs, and that use frames or shear walls (SWs) for resisting the lateral load. The strategy employed four plastic hinge (PH) models for tracking the deformations (flexural, shear, and torsion) of the frame elements and joints, a multilinear plastic link for modeling the MIW, and a nonlinear multilayer shell element for modeling the SW. A flexural PH model characterized by discretization into fibers, a recommended position, and an iterative estimating for the PH length using a distinct formula for each loading level was proposed. This strategy was validated through eleven macromodels investigating four bare frames, four MIWs frames, and a SW where the average ultimate lateral load error was 9.2%, 3.6%, and 0.4%, respectively. Finally, the structural behavior of real ten-story buildings with/without MIWs was investigated. The results showed that the MIWs increased the shear capacity and the lateral stiffness with an average of 44.3% and 118.6%, respectively. Also, both the frames buildings with MIWs and the bare SWs buildings showed approximately equal lateral load capacities. Local damages in the RC vertical elements and yielding of the MIWs were recorded simultaneously. However, the MIWs yielding (and also failure) occurred earlier for the frames buildings compared with the SWs buildings in which the stress was relaxed in their MIWs.

Construction of small confusion component based on logarithmic permutation for hybrid information hiding scheme

The design and development of secure nonlinear cryptographic Boolean function plays an unavoidable measure for modern information confidentiality schemes. This ensure the importance and applicability of nonlinear cryptographic Boolean functions. The current communication is about to suggest an innovative and energy efficient lightweight nonlinear multivalued cryptographic Boolean function of modern block ciphers. The proposed nonlinear confusion element is used in image encryption of secret images and information hiding techniques. We have suggested a robust LSB steganography structure for the secret hiding in the cover image. The suggested approach provides an effective and efficient storage security mechanism for digital image protection. The technique is evaluated against various cryptographic analyses which authenticated our proposed mechanism.

Fluid-structure interaction behaviors of tension membrane roofs by fully-coupled numerical simulation

This study aims to investigate fluid-structure interaction (FSI) behaviors of an enclosed-type tension membrane flat roof. The roof with rectangular shape is chosen as the object because of its relatively idealized geometry for FSI analysis, which is a simplified shape compared to typical membrane roofs. Fully-coupled numerical simulations are performed to obtain the wind induced vibration, aerodynamic forces and surrounding flow field of the tension membrane roof structure, where large-eddy simulation (LES) is used for solving of the flow field, non-linear membrane elements are adopted for the structure field and partitioned algorithm is applied for the coupling between the flow and membrane vibration. The numerical simulations are validated by the aero-elastic experimental results. The characteristics of the wind-induced displacements and aerodynamic forces of the tension membrane roof are investigated in both time and frequency domains. The energy transfer characteristics between wind and the vibrating roof are investigated based on the phase analysis between the generalized forces and displacements of the membrane roof. The underlying mechanism of the modal-jump phenomena that the vibration mode of the membrane jumps from the first mode to the second mode with increasing wind velocity, as well as the instability mechanism of the tension membrane roof, are revealed by flow visualizations and unsteady aerodynamic forces identifications. It is found that the aero-elastic instability of the flat membrane roof is a kind of vortex-induced vibration (VIV), where the modal-jump phenomena and unstable vibration of the membrane roof occur with the occurrence of negative aerodynamic damping, induced by the interaction between the vortex transporting and the roof motion.

Analogue tachyons in SNAIL transmission lines

Tachyons are hypothetical particles with imaginary mass that travel faster than light. However, methods to experimentally verify whether tachyons exist are lacking. Here, we propose a novel scheme to create analogue tachyons using a transmission line composed of superconducting nonlinear asymmetric inductive elements and to detect them by controlling the wavenumber in order to extend their lifetime. In particular, we numerically demonstrate the exotic property of tachyons where their velocity increases with decreasing energy. Our proposal offers a promising approach to understanding tachyon condensation, which is crucial for elucidating the origins of the Universe, in a realizable laboratory system.

Результаты исследований высших гармоник при эксплуатации судовых частотно-регулируемых асинхронных электроприводов

One of the directions of scientific and technological progress at sea-based facilities is the use of electrical technologies based on nonlinear elements. It is revealed that the use of such technologies leads to a deterioration in the quality of electricity, mainly due to higher harmonic. The results of theoretical and experimental studies of the higher harmonic components of voltage and current occurring during the operation of ship frequency-controlled asynchronous electric drives are presented. During operation of a frequency-controlled electric drive high current harmonics of mainly 5, 7, 11, 13 orders are emitted into the power supply network, which is due to the presence of a six-phase rectifier. This leads to distortion of the sinusoid of the supply voltage, since the higher harmonic components of the current, propagating through the electrical network, create corresponding voltage drops on its elements. Along with the main harmonic of the voltage of a given frequency, the higher harmonic components of the voltage flow from the autonomous voltage inverter to the stator winding of the asynchronous electric motor, which causes the higher current harmonics and torques of the forward and reverse current sequences in the stator and rotor windings. As a result additional heating of the stator and rotor windings occurs and vibrations of the asynchronous motor shaft at frequencies of 300 and 600 Hz occur. A method for measuring the vibration of a frequency-controlled asynchronous electric drive from the interaction of the moments of the reverse and forward sequences has been developed and experimentally confirmed. A method for calculating the intrinsic frequency of oscillations of the asynchronous motor-load machine system is proposed, confirmed by the example of a laboratory installation. To accurately calculate the natural frequency of the oscillatory system, it is necessary to experimentally measure the moments of inertia of the rotor of an asynchronous motor and the armature of a DC motor.

Quasiperiodic circuit quantum electrodynamics

Superconducting circuits are an extremely versatile platform to realize quantum information hardware and to emulate topological materials. We here show how a simple arrangement of capacitors and conventional superconductor-insulator-superconductor junctions can realize an even broader class of systems, in the form of a nonlinear capacitive element which is quasiperiodic with respect to the quantized Cooper-pair charge. Our setup allows to create protected Dirac points defined in the transport degrees of freedom, whose presence leads to a suppression of the classical finite-frequency current noise. Furthermore, the quasiperiodicity can emulate Anderson localization in charge space, measurable via vanishing charge quantum fluctuations. The realization by means of the macroscopic transport degrees of freedom allows for a straightforward generalization to arbitrary dimensions and implements truly non-interacting versions of the considered models. As an outlook, we discuss potential ideas to simulate a transport version of the magic-angle effect known from twisted bilayer graphene.

Resolving Fock states near the Kerr-free point of a superconducting resonator

We have designed a tunable nonlinear resonator terminated by a SNAIL (Superconducting Nonlinear Asymmetric Inductive eLement). Such a device possesses a Kerr-free point in which the external magnetic flux allows to suppress the Kerr interaction. We have excited photons near this Kerr-free point and characterized the device using a transmon qubit. The excitation spectrum of the qubit allows to observe photon-number-dependent frequency shifts about nine times larger than the qubit linewidth. Our study demonstrates a compact integrated platform for continuous-variable quantum processing that combines large couplings, considerable relaxation times and excellent control over the photon mode structure in the microwave domain.

A general configuration for nonlinear circuit employing current-controlled nonlinearity: Application in Chua’s circuit

In this paper, a general configuration for nonlinear circuit employing current-controlled nonlinearity is proposed, which has a simple topology and only contains three linear energy storage components, one nonlinear element, and one multi-port network that can be made by linear resistor. Under this configuration, we design two new five-element chaotic circuits including the first third-order one employing a current-controlled anti-parallel connection diode pair and the second fourth-order one employing a current-controlled memristor emulator. The analyses show that the third-order chaotic circuit is dual to the canonical Chua’s circuit, and the extended fourth-order one can be regarded as a dual canonical memristive Chua’s circuit. The basic analyses including the model description, equilibrium point and stability are presented. Several rich dynamical properties of the two chaotic circuits are investigated using numerical simulations and certified by both Pspice circuit simulations and analog circuit measurements.

Investigation of a weathervaning FPSO based on a fully nonlinear boundary element method

Investigation of a weathervaning FPSO based on a fully nonlinear boundary element method

Characterising non-linear elements with free-free and fixed boundary conditions for dynamic substructuring

In the context of dynamic substructuring applied to the automotive field, a crucial aspect for determining the noise property of a vehicle is the evaluation of the transfer behaviour of the rubber elements connecting the different components of a car. The goal of this research is to extract the frequency dependent dynamic stiffness for different models of rubber bushings presenting a similar architecture. In particular we will compare two different methods for characterising the dynamic behaviour of non-linear elements using the virtual point transformation. Firstly, a free-free measurement with hammer impacts will be performed. Here, particular attention will be given to the weighting matrices of the virtual point transformation to explore how those terms could improve the method. Secondly, on the same bushings, we modify the experiment by clamping the rubber mounts to the ground and creating fixed boundary conditions. Here, the system is excited both with hammer impacts and shaker excitation and we will highlight comparable results with the previous experiment. The different approaches will be compared in terms of accuracy, experimental effort, and numerical stability.

Nonlinear data-driven zero-thickness joint element for concrete dam shear keys

Shear keys have been designed into the contraction joints of many concrete gravity dams to provide interlocking and shear transfer between adjacent monoliths. Their shear transferring capacity is usually estimated as the friction and cohesion that can be mobilized across a 2D plane located at the base of the keys. Once the shear stress in the contraction joint exceeds its estimated shear capacity, the shear keys are typically considered failed, and the joint may subsequently only transfer shear through concrete-concrete friction. This behaviour is often simulated in practice by placing tiebreak contact formulations along contraction joints. However, the nonlinear response and potential residual strength of the keys are usually ignored. In this paper, a novel nonlinear zero-thickness joint element named Macro Shear Key Joint Element (MSKJE) is proposed to simulate the response of a detailed shear key while capturing its nonlinear behaviour. A detailed geometrical numerical model of shear keys using a concrete Continuous Surface Cap Model (CSCM) is first validated against experimental data. Then, a parametric analysis of the number of keys in the joint, confinement pressure, initial opening and lateral boundary condition is performed using the validated detailed shear key numerical models. The stress-displacement responses obtained from the parametric analysis are used to calibrate the proposed MSKJE. At the local shear key scale, the MSKJE models present a very similar stress-displacement response compared to the detailed geometrical key models in terms of stiffness, maximum shear capacity, residual strength and nonlinear softening. At the global dam scale, the MSKJE presents a somewhat similar behaviour to the conventional tiebreak formulations. However, the advantages of the MSKJE over the tiebreak contact include its capability to simulate the nonlinear softening of shear keys, and residual sliding displacement, and, once calibrated, it is not necessary to estimate the shear keys capacity a priori.

Post-buckling shear capacity of steel plates with opening strengthened by fiber fabric

Shear capacity is one of the most important factors of steel plates and the steel plates with opening is widely adopted in engineering. This study investigates steel plates reinforced with fiber fabric. Opening shapes, positions, panel thicknesses, and material strengths, are considered to assess the effectiveness of fiber fabric in reinforcing steel plates. Two types of fibers, carbon fiber and basalt fiber, are employed. Specimens with various opening positions and shapes are meticulously designed. The study includes an analysis of how effectively fiber fabric improves shear capacity and examines the resulting failure modes. A comparison is made regarding the shear behavior of plates reinforced with different types of fiber fabrics. The study also explores how plate thickness influences the strengthening effect. The results indicate that the presence of fiber fabric does not enhance the shear capacity of steel plates without openings. Carbon fiber demonstrates a greater enhancement in shear capacity compared to basalt fiber. The use of fiber fabric and epoxy resin to reinforce thin steel plates shows limited improvement in shear capacity. A numerical model is proposed to simulate plates reinforced with fiber fabric, incorporating a nonlinear spring element to represent the behavior of epoxy resin.

An unsupervised machine learning approach to reduce nonlinear FE[formula omitted] multiscale calculations using macro clustering

Solving nonlinear multiscale methods with history-dependent behaviors and fine macroscopic meshes is a well-known challenge. In this work, an unsupervised machine learning-based clustering approach is developed to reduce nonlinear Multilevel Finite Element-FE2 calculations. In contrast with most available techniques which aim at developing Reduced Order Models (ROM) or AI-based surrogate models for the microscale nonlinear problems, the present technique reduces the problem from the macro scale by creating clusters of macro Gauss points which are assumed to be in close mechanical states. Then, a single micro nonlinear Representative Volume Element (RVE) calculation is performed for each cluster. A linear approximation of the macro stress is used in each cluster. Handling internal variables is carried out by using anelastic macro strains in the clustering vectors in addition to the macro strains components. Finally, some convergence issues related to the use of clusters at the macro scale are addressed through a cluster freezing algorithm. The technique is applied to nonlinear hyperelastic, viscoelastic and elastoplastic composites. In contrast to available ROM or machine-learning -based acceleration techniques, the present method does not require neither preliminary off-line calculations, nor training, nor data base, nor reduced basis at the macro scale, while maintaining typical speed-up factors about 20 as compared to classical FE2.

Investigation of memristive memory in the framework of low power consumption and improved Read/Write time

Memristor is a non-linear passive circuit element. It was visualized by Leon Chua in 1971. Memristor can form a non-linear relationship with electric charge and magnetic flux. Memristor has the capability to hold data even if it is not connected to any power source. This property makes it non-volatile in nature. Memristor is a non-volatile memory which can be used for data storage. International Technology Roadmap for Semiconductors acknowledges that it is difficult to scale the transistor beyond its current size and to overcome the existing memory issues, emerging memristor technology is being developed. The objective of this research is to realize the memristor based non-volatile memory which can consume less power with better Read/Write time. In this research, properties and construction of memristor is analyzed. In order to construct a memristor, various softwares like LTspice and MATLAB are used.