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Resistive switching, a phenomenon in which the resistance of a device can be modified by applying an electric field.sup.1-5, is at the core of emerging technologies such as neuromorphic computing and resistive memories.sup.6-9. Among the different types of resistive switching, threshold firing.sup.10-14 is one of the most promising, as it may enable the implementation of artificial spiking neurons.sup.7,13,14. Threshold firing is observed in Mott insulators featuring an insulator-to-metal transition.sup.15,16, which can be triggered by applying an external voltage: the material becomes conducting ('fires') if a threshold voltage is exceeded.sup.7,10-12. The dynamics of this induced transition have been thoroughly studied, and its underlying mechanism and characteristic time are well documented.sup.10,12,17,18. By contrast, there is little knowledge regarding the opposite transition: the process by which the system returns to the insulating state after the voltage is removed. Here we show that Mott nanodevices retain a memory of previous resistive switching events long after the insulating resistance has recovered. We demonstrate that, although the device returns to its insulating state within 50 to 150 nanoseconds, it is possible to re-trigger the insulator-to-metal transition by using subthreshold voltages for a much longer time (up to several milliseconds). We find that the intrinsic metastability of first-order phase transitions is the origin of this phenomenon, and so it is potentially present in all Mott systems. This effect constitutes a new type of volatile memory in Mott-based devices, with potential applications in resistive memories, solid-state frequency discriminators and neuromorphic circuits. Mott materials feature scale-less relaxation dynamics after the insulator-to-metal transition that make its electric triggering dependent on recent switching events., Author(s): Javier del Valle [sup.1] , Pavel Salev [sup.1] , Federico Tesler [sup.2] [sup.3] , Nicolás M. Vargas [sup.1] , Yoav Kalcheim [sup.1] , Paul Wang [sup.1] , Juan Trastoy [...]

The experience gained during the growth of a chemical manufacturing facility from a 65 to 170-MW load in multiple stages is presented. Large filter banks are required to control harmonic current and provide reactive power compensation for the rectifiers that energize the chemical process. As the load grows and the filters become larger and more numerous, utility-generated harmonics are drawn into the filters, resulting in difficulties to comply with IEEE 519. The large size of the filters creates voltage rise issues for local equipment and the transmission system on load upset. Filter stress due to utility capacitor switching and in-plant filter element switching is compared for the initial load stages and the final load stage. Filter stress is reduced as the number and size of the filters are increased. Index Terms--Chemical rectifiers, harmonic filters, IEEE 519, reactive compensation, switching transient.

This paper presents a novel initial value compensation (IVC) using an additional input for semi-closed control systems. The authors have already proposed the IVC approach using the additional input for residual vibration suppression in the fast and precise positioning control. In the approach, however, an essential subject has remained, i.e., the positioning control in the load side could not satisfy the required performance because the systems have been constructed under the assumption of a semi-closed control system. An improvement of the control performance in load position, therefore, is discussed in this paper, where the appropriate assignments of poles and zeros in IVC are ensured, considering the transfer functions of position in both sensor and load for the control initial values. The effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype. Index Terms--Fast-response and high-precision positioning, high-order vibration modes, initial value compensation (IVC), residual vibration suppression, semi-closed control system.

The studies of the endurance properties of an integrated phase-change line cell are presented. The results obtained revealed that the endurance lifetime could be extended by timely adjustment of the reset-pulse polarity by using short reset pulses.

The static states and reversal processes of write head are studied and compared by two micromagnetic models with sawtooth edges or smooth edges, respectively. In the calculation of magnetostatic interaction with smooth edges, the analytical expression of demagnetization matrix for right-angle triangular prism clusters at hypotenuse has been found. The static domain structures in the main pole tip of both models have a slight difference and differ a little more with higher exchange constant. The switching processes in the two models also have similar behavior, except when the down-track film thickness is less than the pole tip width. Both the exchange field and film thickness affect the ultimate magnetization perpendicular to media and the speed of reversal. Index Terms--Hard disk drive (HDD), micromagnetic, regular mesh, sawtooth edge, write head.

This correspondence is concerned with the robust stability for a class of impulsive switched systems under the LQ guaranteed cost control. Some results on robust stability for this class of impulsive switched systems are obtained. Sufficient conditions for the existence of a guaranteed cost control law are also given. Subject to these sufficient conditions, the closed-loop uncertain impulsive switched system under the guaranteed cost control law is robustly stable with a guaranteed cost value. Index Terms--Impulsive switched system, linear quadratic (LQ) guaranteed cost control, robust stability.

The influence of switching conditions and a dynamic avalanche on the extraction of the charge-carrier plasma during the reverse-recovery period of [p.sup.+]-[n.sup.-]-[n.sup.+] diodes is examined. The results have shown that a low ON-state current density, a high circuit inductance and the appearance of a dynamic avalanche has modified the reverse-recovery behavior.

The switching, locking and stability properties of a bistable semiconductor ring laser (SRL) are examined subject to an external optical injection. The smallest of the minimum switching settling time (MSST) for both direction of SRL at certain detuning frequencies is found in the negative detuning frequency side.

A novel zero-voltage-switching (ZVS) combined three-level (TL) converter is proposed in this paper. It is essentially a hybrid combination of a half-bridge TL section and a full-bridge section. The main advantages of the proposed converter are given as follows: the voltage stress of all the switches is ensured to be only half of the input voltage; the secondary rectified voltage is very close to the output voltage, so the high-frequency content is very low, leading to a reduced output filter requirement; the voltage stress of the rectifier diodes is also reduced; and the switches can achieve ZVS with the use of the leakage inductances of the transformers and the intrinsic capacitors of the switches. This paper describes the operating principles and design procedures for the proposed converter. Experimental results from a 1080 W prototype converter operating at 100 kHz are presented to validate the theoretical analysis and demonstrate the performance of the proposed converter. Index Terms--Combined three-level converter, high input voltage, phase-shifted, wide range, zero-voltage-switching (ZVS).

The idea of dynamic programming is general and very simple, but the "curse of dimensionality" is often prohibitive and restricts the fields of application. This paper introduces a method to reduce the complexity by relaxing the demand for optimality. The distance from optimality is kept within prespecified bounds and the size of the bounds determines the computational complexity. Several computational examples are considered. The first is optimal switching between linear systems, with application to design of a dc/dc voltage converter. The second is optimal control of a linear system with piecewise linear cost with application to stock order control. Finally, the method is applied to a partially observable Markov decision problem (POMDP). Index Terms--Dynamic programming, nonlinear synthesis, optimal control, switching systems.

We analyze stability for switched systems which are composed of both continuous-time and discrete-time subsystems. By considering a Lie algebra generated by all subsystem matrices, we show that if all continuous-time subsystems are Hurwitz stable, all discrete-time subsystems are Schur stable, and furthermore the obtained Lie algebra is solvable, then there is a common quadratic Lyapunov function for all subsystems and thus the switched system is exponentially stable under arbitrary switching. A numerical example is provided to demonstrate the result. Index Terms--Arbitrary switching, common quadratic Lyapunov functions, continuous-time, discrete-time, exponential stability, Lie algebra, switched systems.

A new family of zero-voltage-switching (ZVS) pulse-width-modulated (PWM) converters that uses a new ZVS-PWM switch cell is presented in this paper. Except for the auxiliary switch, all active and passive semiconductor devices in the ZVS-PWM converters operate at ZVS turn ON and turn OFF. The auxiliary switch operates at zero-current-switching (ZCS) turns ON and OFF. Besides operating at constant frequency, these new converters have no overvoltage across the switches and no additional current stress on the main switch in comparison to the hard-switching converter counterpart. Auxiliary components rated at very small current are used. The principle of operation, theoretical analysis, and experimental results of the new ZVS-PWM boost converter, rated 1 kW, and operating at 80 kHz, are provided in this paper to verify the performance of this new family of converters. Index Terms--DC-DC converter, zero-voltage-switching (ZVS).

A Persistent-Current Switch (PCS) for high temperature superconducting magnets is fabricated. The experimental results of rated current operation, switching operation and persistent-current operation are described.

The experimental observations of the current-induced polarization switching, in vertical-activity surface-emitting lasers, accompanied by a decrease of the total output power at the switching point, are reported. It is concluded that the experimentally observed polarization switching, is from the mode with higher unsaturated net gain to the mode with lower unsaturated net gain.

AlGaN-GaN power high-electron mobility transistors (HEMT) with 600-V breakdown voltage are fabricated and demonstrated as switching power devices for motor drive and power supply applications. The findings present AlGaN-GaN power-HEMTs as switching power devices for motor drive and power supply applications.

A concept of paired Haar transform (PHT) for representation and efficient optimization of systems of incompletely Boolean functions has recently been introduced. In this article a method to calculate PHT for incompletely specified switching functions through shared binary decision diagrams (SBDDs) is presented. The algorithm converts switching functions in the form of SBDDs into their paired Haar spectra and can operate on functions with many variables. Keywords: Discrete transform; Haar transform; Paired transform; Decision diagrams; Switching functions

This paper explores the natural balancing mechanisms of the three-level neutral-point-clamped (NPC) multilevel inverter. An equivalent circuit of the three-level NPC inverter is derived that facilitates an understanding of the balancing mechanisms. This is followed by a detailed analysis of the balancing mechanisms. The theory is applied to a three-level NPC inverter under vector control. It is shown that this inverter possesses natural balancing mechanisms in which the load impedance and spectra of the switching functions play an important role. Finally, it is illustrated how the natural balancing can be enhanced by using a passive balancing circuit which provides a low impedance at the sampling frequency. Index Terms--Natural balancing, neutral-point voltage, three-level inverter, vector modulation.

In this paper, the relationship between common-mode voltage and switching states in a neutral-point-clamped (NPC) inverter is clarified, and a new pulsewidth-modulation (PWM) strategy for reducing the common-mode voltage in an NPC inverter-fed ac motor drives is proposed. Among a total of 27 switching states in the NPC inverter, the proposed PWM uses only 19 switching states that generate common-mode voltage of which the magnitude is the same or less than one-sixth of dc-bus voltage. Moreover, the proposed PWM strategy satisfied the constraint that the output voltage vector should be changed by only one switching action. Not requiring extra hardware, the NPC inverter with the proposed PWM results in a remarkable reduction in peak-to-peak of common-mode voltage, compared to a two-level inverter and an NPC inverter controlled by conventional PWM. The proposed PWM strategy can be easily implemented in software without degradation of control performance in ac motor drives, Index Terms--Common-mode voltage, neutral-point-clamped inverter, pulsewidth modulation, switching states.

One of the important considerations in designing waveguide-based photonic switching networks is to avoid crosstalk. Two approaches have been proposed which dilate a network in the space and time domains, respectively, to establish crosstalk-free connections. The space-domain dilation uses more hardware, representing cost in space, while the time-domain dilation uses more rounds (or time slots), representing cost in time. In order to evaluate the space-time tradeoffs involved in these two approaches, an analytical model is developed. We describe a recursive procedure which calculates the probability that a new connection can be established without crosstalk in a Banyan (or dilated Banyan) network by taking into consideration the dependency between traffic distributions at different stages. A Markov process based on such probabilities is then used to determine the average number of rounds needed for a set of one-to-one random connections. The model is applicable to both Banyan and dilated Banyan networks, with either stage or individual control. Simulation results are also obtained and compared to the analytic results. We show that the time-domain approach can achieve better space-time tradeoffs than the space-domain approach. One of the practical implications of this result is that a multiplane Banyan network may be more cost-effective than a dilated Banyan in avoiding crosstalk. Index Terms-Banyan, blocking probability, crosstalk, photonic switching, scheduling, space-time tradeoff.

The switch topologies, are discussed in terms of graph theory. It is shown that non-blocking circuit switches can handle any requested data flow if the switch-controller is intelligent enough. It is also shown that most event builders do not need non-blocking switches to get high performance.

It has been stated that an unbalanced data flow cannot be handled by blocking switches such as a barrel shifter. It is not true for a square switch, which has the same number of destination nodes as source nodes. However, if the switch is not square, a simple barrel shifter is not adequate. We have studied the minimal switch configuration for the event builder system in a BELLE experiment in KEK. The performance in the actual experiment was measured.

A passive lossless snubber cell is proposed to improve the turn-on and turnoff transients of the MOSFET's in nonisolated pulsewidth modulated (PWM) dc/dc converters. Switching losses and EMI noise are reduced by restricting di/dt of the reverse-recovery current and dv/dt of the drain-source voltage. The MOSFET operates at zero-voltage-switching (ZVS) turnoff and near zero-current-switching (ZCS) turn-on. The freewheeling diode is also commutated under ZVS. As an example, operation principles, theoretical analysis, relevant equations, and experimental results of a boost converter equipped with the proposed snubber cell are presented in detail. Efficiency of 96% has also been measured in the experimental results reported for a 1-kW 100-kHz prototype in the laboratory. Six basic nonisolated PWM dc/dc converters (buck, boost, buck-boost, Cuk, Sepic, and Zeta) equipped with the proposed general snubber cells are also shown in this paper. Index Terms - Converters, pulsewidth modulation, switching circuits.

Thermal switching has been recognized as a possible limit to archival storage in advanced high density recording media . Thinner films with more isolated grains suffer from large magnetic viscosities [approximately]10%/decade. Previous work has shown that the observed remanent coercivity [H.sub.CR]([Tau]) in high viscosity tapes can be predicted from Sharrock's Law down to [10.sup.-9]s. Here we report high speed switching results on thin film media which show that the remanent coercivity at [10.sup.-8]s is increased [approximately]40 % relative to the VSM value in these films. A quantitative relationship between the viscosity, irreversible susceptibility, and the increase in [H.sub.CR)([Tau]) is demonstrated.

Signal delay's performance is measured through individual field effect transistors. This measurement apparatus has proven that conventional electric equipment can accurately measure delays of full logic swing, thus be an alternative to small ac signals for performance characterization. In addition, it has the capacity to determine device switching delays on the order of 10 ps.

This paper treats the autonomous induction generator as a two-phase oscillator and compares it with another one, the very simple and well-known LC resonant circuit. As a result, an original explanation of the excitation process of the induction generator is presented. Furthermore, it is shown that the autonomous induction generator could be excited without capacitors by switching, in a suitable way, its resistive load in and out in the stator circuit. Index Terms - Autonomous excitation, induction generators, oscillators.

Class E circuits have usually been analyzed for particular values of the switch duty ratio. This paper presents a systematic analysis of the effects of the switch duty ratio on the design values and performance of Class E amplifiers and frequency multipliers, for various values of the output network Q. Some new and promising design possibilities are pointed out, especially for Class E frequency multipliers operating at low Q values. Index Terms - Frequency conversion, inverters, power amplifiers, Q factor, switching circuits.

A hybrid time-domain simulation technique for pulse-width-modulated (PWM) switching regulators is presented. The methodology integrates the advantages of the simulation concepts for switched and nonswitched networks. A regulator is decoupled into dual-analysis components, namely, the power conversion stage (PCS) and feedback network (FN). The former component is simulated by a time-domain digital integration technique with stepwise analysis of the switches' state and automatic determination of correct topological configuration in the PCS operation while the latter one is analyzed by formulating a modified system difference equation and defining at each switching period with second-order extrapolations and corrections of the PCS and error amplifier outputs. Other superior features of this approach include: 1) elegant numerical method of determining the gate signals from the PWM modulator; 2) simple manipulations of numeric and algebraic equations; and 3) applicability to simulate regulators with multiple parameters feedback from PCS. The proposed methodology is illustrated with several examples. The simulated steady-state and large-signal transient waveforms are favorably verified with experimental measurements and available literature. Index Terms - Circuit simulation, switching regulators.

Sampled-data techniques are used to examine the dynamic characteristics and closed-loop performance of the quasi-square-wave boost converter. Direct duty-ratio control and current-mode control are considered. With direct duty-ratio control, the system poles remain well damped under all load conditions, and there is no zero in the control-to-output transfer function. Good closed-loop performance is therefore achieved. Under current-mode control, the requirement for a stabilizing ramp is seen to depend on load conditions, and the achievable voltage control-loop bandwidth is smaller than that using direct duty-ratio control, however, there is a significant reduction in the magnitude of the dc source to output-voltage frequency response. Index Terms - DC-DC converters, quasi-square-wave converters, zero-voltage switching, sampled-data modeling.

This paper is an improved version of a previous one that describes a boost pulse-width-modulated (PWM) soft-single-switched converter, which, having only a single active switch, is able to operate with soft switching in a PWM way without high voltage and current stresses. In addition, such a converter can work at high-switching frequencies for a wide load range. In order to illustrate the operating principles of this converter, a detailed study, including simulations and experimental tests, is carried out. The validity of this converter is guaranteed by the obtained results. Index Terms - Boost converter, nondissipative snubber, soft switching.

This paper presents a new fuzzy-set based algorithm for optimal switching. The algorithm deals with feeder contingencies and service restoration. Optimality will be pursued to get a preventive solution to avoid further contingencies. Issues of the inter-feeder load balance and inter-phase load balance will be emphasized. A fast algorithm has been developed by the fuzzy approach to avoid numerical computation. And the state-space of all the feasible solutions is confined by limited search instead of the time-consuming exhaustive search.

Existing zero-current transition (ZCT) converters do not solve main switch turn-on problems and require auxiliary switches to be turned off with high current and, therefore, are not suitable for high-power applications. Novel ZCT schemes proposed in this paper enable all main switches and auxiliary switches to be turned on and off under zero-current conditions. The zero-current switching at both turn-on and turnoff not only reduces switching losses significantly, but also eliminates the need for passive snubbers, due to the much reduced switch stress. The cost of the auxiliary switches can be reduced compared to the existing ZCT schemes, due to their zero-current turnoff. The proposed technology is well suited for dc-dc and three-phase converters with insulated gate bipolar transistors (IGBT's), MOS-controlled thyristors (MCT's), and gate-turnoff switches (GTO's). Theoretical analysis, computer simulation, and experimental results are presented to explain the proposed schemes. Index Terms - High-power applications, soft switching, zero-current transition.

The authors have worked in computer-aided design (CAD) and in simulation of switched networks over many years. In this brief, they consider all CAD aspects related to simulation of these networks and present practical suggestions and methods useful for analysis in time and frequency domain. Index Terms - Simulation, switched networks.

A comparison study was conducted to characterize the loss mechanisms, component stresses, and overall efficiencies of a group of voltage-mode soft-switching pulse width modulation (PWM) methods, including two methods developed by the authors. All soft-switching methods in the selected group allow zero voltage turn-on and turn-off of the main switch and utilize a single auxiliary switch with some resonant components. Advantages and disadvantages are identified for each method. Experimental verification for each soft-switching method is provided. It was found that only those methods that softly switch the auxiliary switch, minimize redirection current, and recover the auxiliary circuit energy improved efficiency over most of the load range. Index Terms - PWM, soft switching, switching converters, zero-voltage switching.

Two important problems in implementing multi-valued logic (MVL) as compared to binary logic (BL) are the lack of an efficient logic minimization technique and larger chip area and power consumption for realizing an MVL function. In this paper, a new theory for the implementation of MVL is proposed in an attempt to address these problems. In the proposed theory, an MVL function is decomposed into a set of subfunctions that can be efficiently realized using switches that are multivalued-in-nature. Each switch consists of a group of more elementary switches, called subswitches. A complete set of algebraic operators and relations are presented to facilitate the construction of the switches from a set of subswitches. The proposed algebra can be used to minimize the number of subswitches required for each switch in a function realization. Application of the proposed theory to implementing a ternary logic (TL) truth table is illustrated which is expected to encourage further investigation into exploring the possibility of using TL as a competitor to BL. The realization of subswitches is done using CMOS transistors that has potential for a VLSI implementation which can have a small chip area and consume low power.

An efficient method for the transient simulation of diode switching circuits using the diode characteristic model, which takes into account the diode charge storage effect, is presented. The diode characteristic model is derived for a step-junction diode under the assumption of low-level injection. Unlike Linvill's multisection (physical) model that requires many lumped circuit elements for the analog transmission-line modeling of carrier diffusion and recombination processes, the diode characteristic model simulates such carrier redistribution phenomenon by using very few circuit elements and achieves the same simulation accuracy with two order reduction of computer simulation time. The diode characteristic model is derived from transforming the carrier continuity equation into an RCG transmission-line equation and is synthesized with lumped circuit elements derived from the Pade and Ritz optimization methods. For further reduction of computer simulation cost, the diode characteristic model is reduced into a time-varying characteristic model consisting of a depletion capacitor connected in parallel with a current source generated by recursive convolution integration. The current source has both forward and reverse current components for an accurate simulation of the storage charge recovery phenomenon. The diode recovery phenomenon and the transient response of a diode-terminated interconect are simulated for illustrations. The simulation accuracy has been verified by using a mixed-level circuit and device simulator.

The phase portrait technique is used to analyze transient and steady-state operation of switching regulators. The regulator model and analysis procedure are established. Treatment of circuit nonlinearities, its time varying nature and feedback configuration is included. The proposed technique is applied to the analysis of buck converter operation. The benefits of analysis are discussed in view of understanding the switching regulator operation.

Thyristor controlled reactors are high power switching circuits used for static VAR control and the emerging technology of flexible ac transmission. The static VAR control circuit considered in the paper is a nonlinear periodically operated RLC circuit with a sinusoidal source and ideal thyristors with equidistant firing pulses. This paper describes new instabilities in the circuit in which thyristor turn off times jump or bifurcate as a system parameter varies slowly. The new instabilities are called switching time bifurcations and are fold bifurcations of zeros of thyristor current. The bifurcation instabilities are explained and verified by simulation and an experiment. Switching time bifurcations are special to switching systems and, surprisingly, are not conventional bifurcations. In particular, switching time bifurcations cannot be predicted by observing the eigenvalues of the system Jacobian. We justify these claims by deriving a simple formula for the Jacobian of the Poincare map of the circuit and presenting theoretical and numerical evidence that conventional bifurcations do not occur.

An interval analysis-based method for the root-finding of nonmonotonic polynomials is presented in this paper. It has been developed for numerical time-domain analysis of switched nonlinear networks, where internally controlled switching instants must be calculated as zeros of strongly nonmonotonic nonlinear functions. The method in based on an interval extension of Newton's operator resulting from the application of the mean-value theorem (m.v.t.) at the highest order to the polynomials whose zeros are sought. It is demonstrated that such interval extension is the most efficient one with respect to not only all those derived from the application of m.v.t. at any order lower than the maximum one but also to that one obtained with the centered form of the first derivative of the polynomial. A recursive algorithm for roots finding is presented which uses this optimal interval Newton's contraction mapping. Some examples drawn from switching converters time-domain analysis are proposed to outline the robustness and the sharp convergence of the method and its improvements with respect to other interval operators.

Flash-lamp pumping at room temperature helps analyze tunable passive Q-switching of a Cr3:LiCaAlF6 (Cr:Li-CAF) laser with a Cr4+:Y2SiO5 (Cr4+:YSO) broad-band solid state saturable absorber. Bleaching experiments suggest ground state and excited state absorption cross sections of the Cr4+:YSO absorber to be (7.0 plus or minus 1.4) x 10(super -19) square cm and (2.3 plus or minus 0.5) x 10(super-19) square cm at 694 nm. The Cr:LiCAF passive Q-switching with the absorber is reproduced using numerical simulations.

Plasma opening switches (POS) are optimized on Gamble I in positive polarity into electron beam loads. The POS is widely used for inductive storage applications. The switch opening process is retarded by the positive polarity coaxial configuration. The optimization of the POS eliminates this configuration and enhances the wide applicability of the POS.