Nonlinear Switching Research Articles

A Holling Type II Discrete Switching Host-Parasitoid System with a Nonlinear Threshold Policy for Integrated Pest Management

A nonlinear discrete switching host-parasitoid model with Holling type II functional response function, in which the switch is guided by an economic threshold (ET), is proposed. Thus, if the weighted density of two generations of the host population increases and exceeds the ET, then integrated pest management (IPM) measures are enacted, i.e., biological and chemical measures are implemented together, assuming that the chemical immediately precedes the biological inputs to avoid pesticide-induced deaths of the natural enemies. First, the existence and local stability of the equilibria of two subsystems were studied, and the existence and coexistence of several types of equilibria of a nonlinear switching system were analysed. Next, the nonlinear switching system was investigated by numerical simulation, showing that the system exhibits quite complex dynamic behaviour. A two-dimensional bifurcation diagram revealed the existence and coexistence regions of different types of equilibria including regular and virtual equilibria. Moreover, period-adding bifurcations in two-dimensional parameter spaces were found. One-dimensional bifurcation diagrams revealed that the system has periodic, quasiperiodic, and chaotic solutions, Neimark–Sacker bifurcation, multiple coexisting attractors, period-doubling bifurcations, period-halving bifurcations, and so on. Finally, the initial densities of hosts and parasitoids associated with host outbreaks and their biological implications are discussed.

Molecule-based nonlinear optical switch with highly tunable on-off temperature using a dual solid solution approach

Nonlinear optical switches that reversibly convert between on/off states by thermal stimuli are promising for applications in the fields of photoelectronics and photonics. Currently one main drawback for practical application lies in the control of their switch temperature, especially for the temperature range near room temperature. By mixed melting treatment, here we describe an alloy-like nonlinear optical switch with tunable switch temperature via a dual solid solution approach within the coordination polymer system. We initially prepare a coordination polymer (i-PrNHMe2)[Cd(SCN)3], which functions as a high-contrast thermoresponsive nonlinear optical switch originating from a phase transition at around 328 K. Furthermore, by taking advantage of a synergistic dual solid solution effect, the melt mixing of it with its analogue (MeNHEt2)[Cd(SCN)3], which features an unequal anionic chain templated by an isomeric ammonium, can afford coordination polymer solid solutions with switch temperatures that are tunable in a range of 273–328 K merely by varying the component ratio.

Enhancement of shock-capturing methods via machine learning

In recent years, machine learning has been used to create data-driven solutions to problems for which an algorithmic solution is intractable, as well as fine-tuning existing algorithms. This research applies machine learning to the development of an improved finite-volume method for simulating PDEs with discontinuous solutions. Shock-capturing methods make use of nonlinear switching functions that are not guaranteed to be optimal. Because data can be used to learn nonlinear relationships, we train a neural network to improve the results of a fifth-order WENO method. We post-process the outputs of the neural network to guarantee that the method is consistent. The training data consist of the exact mapping between cell averages and interpolated values for a set of integrable functions that represent waveforms we would expect to see while simulating a PDE. We demonstrate our method on linear advection of a discontinuous function, the inviscid Burgers’ equation, and the 1-D Euler equations. For the latter, we examine the Shu–Osher model problem for turbulence–shock wave interactions. We find that our method outperforms WENO in simulations where the numerical solution becomes overly diffused due to numerical viscosity.

In Quest of Nonfilamentary Switching: A Synergistic Approach of Dual Nanostructure Engineering to Improve the Variability and Reliability of Resistive Random‐Access‐Memory Devices

AbstractThis study demonstrates a synergistic approach of dual nanostructure engineering to improve the performance of AlOx‐based resistive random access memory (RRAM) devices. More precisely, a novel material stack engineering of RRAM with nonlinear area scalable low current switching and extensive improvement of reliability and variability issues is reported. Dual nanostructures (nanodome bottom electrode and nanocrystals in switching layer) in RRAM is an effective way to change the switching from filamentary to a nonfilamentary one, resulting in forming‐free highly stable device. Several methods such as transmission electron microscopy, energy dispersive spectroscopy, and atomic force microscopy have been employed to investigate the morphology of the RRAM devices. Enhanced electric field within the enclave of switching layer is controlling the intrinsic distribution of oxygen vacancy profile with extrinsic operation. As compare to filamentary RRAM, nonfilamentary devices can effectively control dc switching for >103 cycles, ac switching for >106 cycles without any severe fluctuation of resistance states for different levels. Area and temperature‐dependent semiconducting behavior along with time‐dependent high resistance states are certainly confirming the nonfilamentary switching process. In addition, the device yield improvement ≈98% using nonfilamentary switching, is making dual nanostructure devices a very promising candidate for high‐density memory application, is highlighted.

Nonlinear elastic switch based on solid–solid phononic crystals

Mass density nonlinearity in a solid–solid phononic crystal and its effect on phononic band gap tunability are investigated. Also, a phononic On–Off switch is designed based on nonlinear phononic crystals. The proposed switch is formed of tungsten scatterers with a square arrangement, embedded in a poly methyl methacrylate background. Also, this structure contains a linear channel that creates a defect mode in the phononic band gap. Increment of input intensity causes the wave propagation medium to be dynamic. This effect allows phononic band gap to be tuned, and the defect mode frequency of the linear channel to be shifted to higher frequencies. Due to these features, the On–Off switch is designed and controlled by the excitation wave intensity. In the linear regime the switch is On, and by increasing the intensity of applied wave, it becomes Off. To the best of our knowledge, this is the first time a nonlinear phononic crystal switch is proposed. The calculated extinction ratio for the proposed structure is equal to − 19.96 dB, which seems to be suitable for switching applications.

Three-Dimensional Perovskite Methylhydrazinium Lead Chloride with Two Polar Phases and Unusual Second-Harmonic Generation Bistability above Room Temperature

Formation of noncentrosymmetric three-dimensional (3D) lead halide perovskites has been a widely sought after goal because the polar structure opens up new vistas to properties of these materials, e.g., improved charge separation for photovoltaics arising from ferroelectric order. Here, we report growth and unique properties of a new highly distorted 3D perovskite, methylhydrazinium lead chloride (CH3NH2NH2PbCl3, MHyPbCl3). This perovskite crystallizes in polar P21 structure at room temperature, which consists of two types of PbCl6 octahedra: one weakly and another strongly deformed. The unusual deformation of every second perovskite layer is forced by the large size of methylhydrazinium cations and the ability of NH2+ terminal groups of methylhydrazinium cations to form coordination bonds with Pb2+ metal centers. On heating, MHyPbCl3 undergoes a phase transition at 342 K into another polar Pb21m phase with ordered organic cations. Temperature-resolved second-harmonic generation (TR-SHG) measurements confirm acentricity of both phases and show that second-harmonic response is enhanced for the high-temperature Pb21m phase. This intriguing property of MHyPbCl3 has been employed to demonstrate an unprecedented kind of quadratic nonlinear optical switching in which a second-harmonic response is switched between a room-temperature, low-SHG state and a high-temperature, high-SHG state. X-ray diffraction shows that enhancement of polar properties is due to rearrangement of the perovskite’s organic substructure. There is a clear pyrocurrent peak, but switching of the electric polarization could not be observed. Optical studies showed that MHyPbCl3 is a wide-bandgap material with a bandgap of 3.4 eV (365 nm). At low temperatures, it exhibits weak UV emissions at 362 and 369 nm as well as a strong broadband white emission.

Discrimination of Internal Faults and Other Transients in an Interconnected System With Power Transformers and Phase Angle Regulators

This study solves the problem of accurate detection of internal faults and classification of transients in a 5-bus interconnected system for Phase Angle Regulators (PAR) and Power Transformers. The analysis prevents mal-operation of differential relays in case of transients other than faults which include magnetizing inrush, sympathetic inrush, external faults with CT saturation, capacitor switching, non-linear load switching, and ferroresonance. A gradient boosting classifier (GBC) is used to distinguish the internal faults from the transient disturbances based on 1.5 cycles of 3-phase differential currents registered by a change detector. After the detection of an internal fault, GBCs are used to locate the faulty unit (Power Transformer, PAR series, or exciting unit) and identify the type of fault. In case a transient disturbance is detected, another GBC classifies them into the six transient disturbances. Five most relevant frequency and time domain features obtained using Information Gain are used to train and test the classifiers. The proposed algorithm distinguishes the internal faults from the other transients with a balanced accuracy of 99.95%. The faulty transformer unit is located with a balanced accuracy of 99.5% and the different transient disturbances are identified with a balanced accuracy of 99.3%. Moreover, the reliability of the scheme is verified for different rating and connection of the transformers involved, CT saturation, and noise levels in the signals. These GBC classifiers can work together with a conventional differential relay and offer a supervisory control over its operation. PSCAD/EMTDC software is used for simulation of the transients and to develop the two and three-winding transformer models for creating the internal faults including inter-turn and inter-winding faults.

A High Efficiency and Fast Transient Digital Low-Dropout Regulator With the Burst Mode Corresponding to the Power-Saving Modes of DC–DC Switching Converters

The proposed digital low-dropout regulator uses nonlinear switching control (NLSC) technique to suppress voltage ripple to less than 6 mV when the switching noise voltage of a switching regulator operating in a power-saving mode is greater than 50 mV. In addition, the NLSC technique improves the current efficiency by reducing the quiescent current to less than 10 μ A and reduces the switching power loss through variable switching frequency control. With a load step of 1–20 mA, the transient response time is 1.3 μ s and the peak current efficiency is 99.8% at heavy loads.

Nonlinear spin wave switches in layered structure based on magnonic crystals

The features of spin wave processes in a layered structure based on two magnonic crystals (MC-1 and MC-2) separated by a dielectric layer have been studied theoretically and experimentally at different levels of input power. The theoretical model has been developed for the cases of magnetic field oriented in-plane and out-of-plane to MC surfaces in order to identify the mechanisms of nonlinear interactions. Two types of nonlinear switching are implemented in the structure MC-1/MC-2 with increasing input power. Depending on parameters of the structure the input signal can exit from three (“double nonlinear switching”) or two (“single nonlinear switching”) outputs. This feature allows to consider MC-1/MC-2 structure as a basic element in a multifunctional device for the spatial separation of signals with different power levels.

Lyapunov–Krasovskii Characterizations of Stability Notions for Switching Retarded Systems

In this article, we characterize the global asymptotic and exponential stability of nonlinear switching retarded systems through direct and converse Lyapunov-Krasovskii theorems. Thanks to these theorems, a link between the exponential stability of an unforced switching retarded system and the input-to-state stability property is obtained. An example illustrating the applicability of our results is given.

Solid-State Nonlinear Optical Switch with the Widest Switching Temperature Range Owing to Its Continuously Tunable Tc.

Interest on the nonlinear optical (NLO) switches that turn on/off the second-harmonic generation (SHG) triggered by the external stimulus (such as heat) have continuously grown, especially on the solid-state NLO switches showing superior stability, reversibility, and reproducibility. Herein, we discover (NH4)2PO3F, as an entirely new solid-state NLO switch showing outstanding switch contrast and reversibility as well as strong SHG intensity (1.1 × KH2PO4 (KDP)) and high laser-induced damage threshold (2.0 × KDP), undergoes a unique first-order phase transition that originates from a reversible hydrogen-bond rearrangement and needs to overcome an energy barrier. Accordingly, we put forward a strategy to continuously modify such an energy barrier by reducing the number of hydrogen bonds per unit cell via an isoelectronic replacement of NH4+ by K+ with a similar size yet incapability of providing any hydrogen bond. Consequently, Kx(NH4)2-xPO3F (x = 0-0.3) exhibiting excellent switching performance are obtained. Remarkably, Kx(NH4)2-xPO3F not only realizes a continuously tunable Tc spanning from 270 to 150 K, representing the widest NLO switching temperature range ever known but also indicates the first solid-state NLO switch example with continuous Tc. Intrinsically, such a Tc decline depends on the weakening degree of the hydrogen-bonding interactions in the unit cell. These new insights will shed useful light on the future material design and open new application possibilities.

Boundary Control With Corrected Second-Order Switching Surface for Buck Converters Connected to Capacitive Loads

Boundary control (BC) with second-order switching surface is exploited for achieving faster response time and robust operation of switching power converters. However, the system performance of the boundary-controlled converters is significantly affected when it is connected to a second-stage converter with a large input capacitor. This article studies the shortcomings in second-order BC schemes of buck converter with capacitive loads and nonlinear switching loads. Second, this article proposes a BC scheme with corrected second-order switching surface to drive buck converters cascaded to boost converters. The switching criteria of the corrected control law account for the effect of unknown load capacitance as well as the variation in filter parameters. Therefore, an outer voltage ripple feedback loop is introduced to determine the corresponding switching criteria gain factor that adjusts the overall gain, while maintaining the output voltage ripple at a specified voltage band. The proposed method is verified by both simulation and hardware experiments. A 250-W buck converter prototype has been built to validate the control scheme under different load types, including a resistive-capacitive load, a boost converter, and a commercial dc electronic load. A comparison is drawn between conventional BC and the proposed method in both simulation and experimental environment, in order to highlight the advantages of the proposed method. With this approach, the converter operates at designed BC parameters independent of load capacitance and system parameter variations.

Linear Active Disturbance Rejection Control for DC Bus Voltage Under Low-Voltage Ride-Through at the Grid-Side of Energy Storage System

The energy storage inverter system has the characteristics of nonlinearity, strong coupling, variable parameters, and flexible mode switching between parallel and off grid. In order to improve the control performance of the grid-side inverter of the energy storage system, an improved Linear Active Disturbance Rejection Control (LADRC) based on proportional differentiation is proposed to replace the traditional LADRC in the voltage outer loop control. In this paper, the observation gain coefficient of the sum of the disturbances of the traditional Linear Extended State Observer (LESO) is improved to a proportional differentiation link, which effectively reduces the degree of the disturbance observation amplitude drop and the phase lag, and increases the observation bandwidth of LESO. Compared with traditional LADRC, it not only improves the observation accuracy of LESO for disturbance, but also improves the anti-interference performance of LADRC. Finally, the control effects of improved LADRC and traditional LADRC on low-voltage ride-through at different degrees are analyzed and compared through simulation, which proves the rationality of the controller designed in this paper.

Photostimulated nonlinear optical switching materials based on CdBr0·95Cl0.1 nanocrystalline layers

Abstract New types of crystalline materials based on CdBr0·95Cl0.1 nanolayers have been fabricated. Due to the layered structure, it is possible to achieve nanolayers by cleaving layers of CdBr2 single crystals. These layers anisotropy opens a principal opportunity for fabricating thin CdBr0·95Cl0.1 nanocrystals with a thickness up to several nanometers without additional treatment. We have prepared the samples within a 3–30 nm thickness range. The phototreatment has been performed by bicolor coherent Nd: YAG laser with wavelengths 1540 nm/770 nm. The third-harmonic generation (THG) was detected for a fundamental 20 ns Er-glass laser beam at wavelength 1540 nm with a frequency reception of ∼10 Hz. The phototreatment was done for 2–3 min and was controlled by cw He–Ne laser-induced diffraction patterns. The maximal photoinduced changes have been found for the thinnest film possessing thickness about 3 nm. The THG effect at 1540 nm was maximal at ambient temperature. The effect is explained within a framework of the phenomenological consideration. The principal role of the space electron charge density anisotropy is discussed.

Equilibrium stability of a nonlinear structural switching system with actuator delay

In this paper, a Lyapunov–Krasovskii functional is used to obtain sufficient conditions of asymptotic stability for the equilibrium of a nonlinear feedback system with state-dependent uncontrolled switching, herein called structural switching, and with actuator delay. The solution of the problem is addressed in two steps. First, a predictive feedback method is used to compensate the actuator delay of the associated linearized system. Thus, the time-delayed control is replaced with a state delay, and the effect of the control appears in a non-homogeneous term in the linearized system. Second, a theorem of asymptotic stability of equilibrium is obtained for the nonlinear switched system, whose linearized components were considered separately in the first step. The result is also valid for certain problems of state-dependent controlled switching. The numerical application, done on a consecrated real world system, the electrohydraulic servomechanism, highlights real difficulties, which are usually avoided by academic constructs in which the results are sometimes illustrated on insignificant models, represented, for example, by 2 × 2 didactic matrices.

Nonlinear optical absorption switching behavior of BaTiO3 in asymmetric microcavity

In this paper, an asymmetric 1-D photonic microcavity with BaTiO3 as defect has been fabricated using RF magnetron sputtering technique. Open aperture Z-scan shows enhancement in nonlinear absorption of BaTiO3 due to strong field confinement around the defect layer. We further report the switching behavior in nonlinear absorption from reverse saturable absorption to saturable absorption in response to the angle tuning of the sample. The transfer matrix simulation results further support the cavity defect in asymmetric photonic crystal confine the photon and thereby enhancing nonlinear optical phenomena.

Metal-Insulator Transitions in β′-CuxV2O5 Mediated by Polaron Oscillation and Cation Shuttling

Summary Silicon circuitry has dominated the semiconductor industry for decades but is constrained in its power efficiency by the Fermi-Dirac distribution of electron energies. Electron-correlated transition metal oxides exhibiting metal-to-insulator transitions (MITs) are excellent candidates for energy-efficient computation, which can further emulate the spiking behavior of biological neural circuitry. We demonstrate that β′-CuxV2O5 exhibits a pronounced nonlinear response to applied temperature, voltage, and current, and the response can be modulated as a function of Cu stoichiometry. We show that polaron oscillation, coupled to the real-space shuttling of Cu ions across two adjacent sites, underpins the MIT of this material. These results reveal the interplay between crystal structure distortions and electron correlation in underpinning the metal-insulator transition of a strongly correlated system. The utilization of coupled cation diffusion and polaron oscillation further demonstrates a means of using ionic vectors to obtain highly nonlinear conductance switching as required for neuromorphic computing.

Electric spring average model development and dynamic analysis for demand‐side management

This study proposes a new averaged model for steady-state and dynamic response analysis of the electric spring (ES). The accuracy of steady-state and dynamic behaviour of the ES is demonstrated. Further, the dynamic behaviour of the proposed model is described as a function of the modulating signal. The developed model is used to design a controller for bus voltage regulation in a distribution system with an intermittent renewable energy source. The ES controller design problem is formulated as an optimization problem with a time domain-based objective function to reduce the time-weighted voltage deviations using particle swarm optimization method. Different disturbances have been applied to verify the developed ES model accuracy including sudden changes in renewable source current and load variations. An experimental analysis is also performed with the detailed non-linear switching model of the ES to verify its behaviour with that of the proposed averaged model. The characteristics and performance of ES are thoroughly investigated. The effectiveness of the developed model and the proposed controller design approach is demonstrated in terms of a significant improvement in the dynamic performance of the distribution system

Impact of Non-Linear Electronic Circuits and Switch of Chaotic Dynamics

Switch-mode power supply is an extremely non-linear system that can inevitably exhibit unpredictable behavior. These control laws may be insufficient for nonlinear systems because they are not robust when the requirements on the dynamic characteristics of the system are strict [10]. Control laws that are insensitive to parameter variations, disturbances, and nonlinearities must be used. In this paper, we have tested the method of the first harmonic, used to analyses servo controls with a nonlinear element, and to predict certain non-linear behaviors. It mainly allows predicting the limit cycles, but also the jump phenomena, the harmonics as well as the responses of non-linear systems to sinusoidal inputs. We apply this method for the prediction of limit cycles and the determination of their amplitude and frequency. We take as an example a Boost converter controlled by current [4]. This system is chaotic when the duty cycle is more significant than 0.5: we then eliminate the chaos by applying the slippery mode command (for the ripple of the output voltage, for the current ripple of the inductance and switching frequency) when the output is periodic (duty cycle less than or equal to 0.5). In this article, we assess that established approach provides the best outcomes: it appears that the preference between the classical mode and the sliding mode depends heavily on the variance domain of the parameters E, R, and Iref.

Impact of Non-Linear Electronic Circuits and Switch of Chaotic Dynamics

Switch-mode power supply is an extremely non-linear system that can inevitably exhibit unpredictable behavior. These control laws may be insufficient for nonlinear systems because they are not robust when the requirements on the dynamic characteristics of the system are strict [10]. Control laws that are insensitive to parameter variations, disturbances, and nonlinearities must be used. In this paper, we have tested the method of the first harmonic, used to analyses servo controls with a nonlinear element, and to predict certain non-linear behaviors. It mainly allows predicting the limit cycles, but also the jump phenomena, the harmonics as well as the responses of non-linear systems to sinusoidal inputs. We apply this method for the prediction of limit cycles and the determination of their amplitude and frequency. We take as an example a Boost converter controlled by current [4]. This system is chaotic when the duty cycle is more significant than 0.5: we then eliminate the chaos by applying the slippery mode command (for the ripple of the output voltage, for the current ripple of the inductance and switching frequency) when the output is periodic (duty cycle less than or equal to 0.5). In this article, we assess that established approach provides the best outcomes: it appears that the preference between the classical mode and the sliding mode depends heavily on the variance domain of the parameters E, R, and Iref.