Switching Period Research Articles

The behavioral and physiological correlates of affective mood switching in premenstrual dysphoric disorder

Premenstrual dysphoric disorder (PMDD), a more severe manifestation of premenstrual syndrome (PMS), is characterized by emotional, behavioral, and physical symptoms that begin in the mid-to-late luteal phase of the menstrual cycle, when estradiol and progesterone levels precipitously decline, and remit after the onset of menses. Remotely monitoring physiologic variables associated with PMDD depression symptoms, such as heart rate variability (HRV), sleep, and physical activity, holds promise for developing an affective state prediction model. Switching into and out of depressive states is associated with an increased risk of suicide, and therefore, monitoring periods of affective switching may help mitigate risk. Management of other chronic health conditions, including cardiovascular disease and diabetes, has benefited from remote digital monitoring paradigms that enable patients and physicians to monitor symptoms in real-time and make behavioral and medication adjustments. PMDD is a chronic condition that may benefit from real-time, remote monitoring. However, clinical practice has not advanced to monitoring affective states in real-time. Identifying remote monitoring paradigms that can detect within-person affective state change may help facilitate later research on timely and efficacious interventions for individuals with PMDD. This narrative review synthesizes the current literature on behavioral and physiological correlates of PMDD suitable for remote monitoring during the menstrual cycle. The reliable measurement of heart rate variability (HRV), sleep, and physical activity, with existing wearable technology, suggests the potential of a remote monitoring paradigm in PMDD and other depressive disorders.

Synchronous DTC for torque sub-harmonic reduction in low switching frequency induction motor drives

A direct torque control (DTC) algorithm with synchronous modulation for high-power induction motors is presented in this paper. While maintaining the dynamic response and robustness of a PI-based DTC operating in the stationary reference frame, the proposed scheme is able to keep an integer PWM modulation ratio, adjusting the stator flux angle and the switching period at each control step so that the synchronicity condition is always satisfied. In this way, it is possible to achieve an improvement of the very low-frequency harmonic spectrum of the torque, in particular by reducing torque sub-harmonics. These represent one of the main problems associated with low-frequency modulation typical of high-power drives and their reduction allows to avoid drawbacks such as resonance and mechanical stresses. The performance of the proposed algorithm is evaluated with experimental tests on a small-scale test bench.

Integrated design and maintenance strategies for wind turbine gearboxes

PurposeThe purpose of this paper is to optimize the maintenance strategies for wind turbine (WT) gearboxes to minimize costs associated with PM actions, cooling, production loss and gearbox replacement. Two approaches, periodic imperfect maintenance and a novel design incorporating alternating gearboxes are compared to identify the most cost-effective solution.Design/methodology/approachThis study employs mathematical modeling to analyze the design, operation and maintenance of WT gearboxes. Two maintenance strategies are investigated, involving periodic imperfect maintenance actions and the incorporation of two similar gearboxes operating alternately. The models determine optimal preventive maintenance (PM) and switching periods to minimize total expected costs over the operating time span.FindingsThe research findings reveal, for the considered case of a moroccan wind farm, that the use of two similar gearboxes operating alternately is more cost-effective than relying on a single gearbox. The mathematical models developed enable the determination and comparison of optimal strategies for various WT gearbox scenarios and associated maintenance costs.Research limitations/implicationsLimitations may arise from simplifications in the mathematical models and assumptions about degradation, temperature monitoring and maintenance effectiveness. Future research could refine the models and incorporate additional factors for a more comprehensive analysis.Practical implicationsPractically, the study provides insights into optimizing WT gearbox maintenance strategies, considering the trade-offs between PM actions, cooling, production loss and gearbox replacement costs. The findings can inform decisions on maintenance planning and design modifications to enhance cost efficiency.Social implicationsWhile the primary focus is on cost optimization, the study indirectly contributes to the broader societal goal of sustainable energy production. Efficient maintenance strategies for WTs help ensure reliable and cost-effective renewable energy, potentially benefiting communities relying on wind power.Originality/valueThis paper introduces two distinct strategies for WT gearbox maintenance, extending beyond traditional periodic maintenance. The incorporation of alternating gearboxes presents a novel design approach. The developed mathematical models offer a valuable tool for determining and comparing optimal strategies tailored to specific WT scenarios and associated maintenance costs.

Thermodynamic characteristics of a novel solar single and double effect absorption refrigeration cycle

Solar absorption refrigeration systems provide one of the economical options for air conditioning. In order to reduce the complexity and economic cost, a more advanced solar single-double-effect switching system is proposed. The innovation of this system is that it replaces the single-effect and high-pressure generators in previously developed single-double-effect switching system with a specific generator. The optimal heat source switching temperature of the new system was determined by the genetic algorithm to be 125.5 °C. Compared with the original single-double-effect switching system, the average coefficient of performance of the system is increased by 8.6 %, and the fluctuation of refrigeration capacity during the switching period is reduced by 48 %. The new solar single-double-effect switching system is investigated based on thermodynamic characteristics, energy, exergy, and economy aspects. The results showed that heat exchangers of the system have strong coupling. The cooling water temperature has a greater impact on the performance of the dual-effect mode. In the single-effect mode, the special-pressure generator has the largest exergy destruction (39 %), while in the double-effect mode, the absorber has the largest exergy destruction (41 %). Besides, the economic analysis demonstrated that the new system is economically viable with a payback period of 9.33 years.

Design and implementation of an innovative single-phase direct AC-AC bipolar voltage buck converter with enhanced control topology

Direct AC–AC converters are strong candidates in the power converting system to regulate grid voltage against the perturbation in the line voltage and to acquire frequency regulation at discrete step levels in variable speed drivers for industrial systems. All such applications require the inverted and non-inverted form of the input voltage across the output with voltage-regulating capabilities. The required value of the output frequency is gained with the proper arrangement of the number of positive and negative pulses of the input voltage across the output terminals. The period of each such pulse for low-frequency operation is almost the same as the half period of the input grid or utility voltage. These output pulses are generated by converting the positive and negative input half cycles in noninverting and inverting forms as per requirement. There is no control complication to generate control signals used to adjust the load frequency as the operating period of the switching devices is normally greater than the period of the source voltage. However, high-frequency pulse width modulated (PWM) control signals are used to regulate the output voltage. The size of the inductor and capacitor is inversely related to the value of the switching frequency. Similarly, the ripple contents of voltage and currents in these filtering components are also inversely linked with PWM frequency. These constraints motivate the circuit designer to select high PWM frequency. However, the alignment of the high-frequency control input with the variation in the input source voltage is a big challenge for a design engineer as the switching period of a high-frequency signal normally lies in the microsecond. It is also required to operate some high-frequency devices for various half cycles of the source voltage, creating control complications as the polarities of the half cycles are continuously changing. This requires at least the generation of two high-frequency signals for different intervals. The interruption of the filtering inductor current is a big source of high voltage surges in circuits where the high-frequency transistors operate in a complementary way. This may be due to internal defects in the switching transistors or some unnecessary inherent delay in their control signals. In this research work, a simplified AC–AC converter is developed that does not need alignment of high-frequency control with the polarity of the source voltage. With this approach, high-frequency signals can be generated with the help of any analog or digital control system. By applying this technique, only one high-frequency control signal is generated and applied in AC circuits, as in a DC converter, without applying a highly sensitive polarity sensing circuit. So, controlling complications is drastically simplified. The circuit and configuration always avoid the current interruption problem of filtering the inductor. The proposed control and circuit topology are tested both in computer-based simulation and practically developed circuits. The results obtained from these platforms endorse the effectiveness and validation of the proposed work.

Switching from cigarettes to IQOS: the relative importance of IQOS-associated reward, reinforcement and abstinence relief

IntroductionThis study investigated whether IQOS, a heated tobacco product, can fully substitute for combustible cigarettes and the factors that promote substitution.MethodsAdults who smoked cigarettes daily (N=90; 21–65 years) completed a...

Voltage regulation in an interleaved circular chain sliding mode controlled multiphase converter

In this article a multiphase synchronous buck converter controlled by a sliding mode control (SMC) in a circular chain control (CCC) configuration is presented. The proposed switching functions with the CCC architecture ensure a robust output voltage regulation when facing changes in the load or the input voltage, while providing current equalization among the phases. The novelty of the work is the simple control structure based on a first order SMC implemented by means of hysteresis-band comparators, requiring no external signals or additional hardware to lead the system to an interleaving operation, obtaining a harmonic cancellation that allows the size reduction not only of the output capacitor but also of the inductors. It is proved that, in the steady state, the switching function exhibits a periodic solution with a period equal to the switching period. Besides, the steady-state switching frequency expression as a function of the hysteresis bandwidth is derived. The work includes the analytical analysis of the proposed solution, a set of numerical simulations and, finally, an experimental validation. The numerical and experimental results confirm the predicted good performance of the proposed control.

Non-Equilibrium Assembly of Atomically-Precise Copper Nanoclusters.

Accurate structure control in dissipative assemblies (DSAs) is vital for precise biological functions. However, accuracy and functionality of artificial DSAs are far from this objective. Herein, a novel approach is introduced by harnessing complex chemical reaction networks rooted in coordination chemistry to create atomically-precise copper nanoclusters (CuNCs), specifically Cu11(µ9-Cl)(µ3-Cl)3L6Cl (L = 4-methyl-piperazine-1-carbodithioate). Cu(I)-ligand ratio change and dynamic Cu(I)-Cu(I) metallophilic/coordination interactions enable the reorganization of CuNCs into metastable CuL2, finally converting into equilibrium [CuL·Y]Cl (Y = MeCN/H2O) via Cu(I) oxidation/reorganization and ligand exchange process. Upon adding ascorbic acid (AA), the system goes further dissipative cycles. It is observed that the encapsulated/bridging halide ions exert subtle influence on the optical properties of CuNCs and topological changes of polymeric networks when integrating CuNCs as crosslink sites. CuNCs duration/switch period could be controlled by varying the ions, AA concentration, O2 pressure and pH. Cu(I)-Cu(I) metallophilic and coordination interactions provide a versatile toolbox for designing delicate life-like materials, paving the way for DSAs with precise structures and functionalities. Furthermore, CuNCs can be employed as modular units within polymers for materials mechanics or functionalization studies.

Analysis and design of an efficient three‐phase voltage source inverter with performance optimization

SummaryThe paper designs a novel efficient three‐phase voltage source inverter with performance optimization. When auxiliary circuits connected in parallel with every bridge arm are involved in working process of the designed inverter, main switches will realize zero‐voltage switching in the wide load range, which is beneficial for further decline of the loss of main switches. Furthermore, the optimized duty cycle of the gate drive signal of auxiliary switches is used to restrict circuiting current loss. Besides, when the designed inverter works in a dead zone, the resonance will occur in the auxiliary circuits to cause the output phase voltage to vary from zero or the DC supply voltage to the DC supply voltage or zero as soon as possible, which is beneficial for further decline of the output phase voltage error and the suppression of dead effect. The paper provides relevant analysis on each working status within a switching period along with design requirements. By analyzing test waveforms, it affirms that main switches realize zero‐voltage switching. The efficiency of the designed inverter reaches 98.8% at rating condition. The experiment affirms that the designed inverter has an edge over another two inverters for comparison in performance optimization.

Analysis and design of an efficient soft‐switching inverter with asymmetric auxiliary circuits

SummaryThe paper designs an efficient three‐phase soft‐switching inverter with asymmetric auxiliary circuits, which is beneficial for further miniaturization and efficiency optimization. Only two auxiliary switches, one resonant inductor, and three resonant capacitors make up simple asymmetric auxiliary circuits of each phase, contributing to the reduction of power loss and hardware cost. As soon as the simple auxiliary circuits get involved in the operation of the designed inverter, main switches can realize zero‐voltage switching within the entire load range. The reduction of power loss of auxiliary circuits and main switches is conducive to further efficiency optimization. The paper expounds every operating status during one switching period. The relevant experimental waveforms make known that switching devices can realize soft‐switching. The efficiency reaches 99% at rated operation status of the designed inverter, confirming that the designed inverter has superiority over comparison objects in the experiment with regard to the efficiency. Thus, the structural simplification of auxiliary circuits is an effective method for further miniaturization and efficiency optimization.

Multi-Constraint and Multi-Policy Path Hopping Active Defense Method Based on SDN

Path hopping serves as an active defense mechanism in network security, yet it encounters challenges like a restricted path switching space, the recurrent use of similar paths and vital nodes, a singular triggering mechanism for path switching, and fixed hopping intervals. This paper introduces an active defense method employing multiple constraints and strategies for path hopping. A depth-first search (DFS) traversal is utilized to compute all possible paths between nodes, thereby broadening the path switching space while simplifying path generation complexity. Subsequently, constraints are imposed on residual bandwidth, selection periods, path similitude, and critical nodes to reduce the likelihood of reusing similar paths and crucial nodes. Moreover, two path switching strategies are formulated based on the weights of residual bandwidth and critical nodes, along with the calculation of path switching periods. This facilitates adaptive switching of path hopping paths and intervals, contingent on the network’s residual bandwidth threshold, in response to diverse attack scenarios. Simulation outcomes illustrate that this method, while maintaining normal communication performance, expands the path switching space effectively, safeguards against eavesdropping and link-flooding attacks, enhances path switching diversity and unpredictability, and fortifies the network’s resilience against malicious attacks.

Improving Low-Frequency Digital Control in the Voltage Source Inverter for the UPS System

Today voltage source inverters (VSIs) operate with high switching frequencies (let us assume higher than 50 kHz) owing to the fast Si (Silicon) or SiC (Silicon Carbide) switching transistors. However, there are some applications, e.g., with slower switches (e.g., IGBT—Isolated Gate Bipolar Transistor) or when lower dynamic power losses are required when the switching frequency is low (let us assume about 10 kHz). The resonant frequency of the output filter is usually below 1 kHz. The measurements of Bode plots of the measurement traces of various microprocessor-controlled VSIs show that in this frequency range, the characteristics of these channels can be simply approximated through two or three switching periods delay. For the high switching frequency, it is not noticeable, but for the low frequency it can cause some oscillations in the output voltage. One of the solutions can be to use the predictor of the measured state variables based on the full-state Luenberger observer or the linear Kalman filter. Both solutions will be simulated in MATLAB/Simulink and the chosen one will be tested in the experimental VSI. The research aims to omit delays in the measurement channels for the low switching frequency by using the predictions for the measured state variables and finally increasing the gains of the controller to decrease the output voltage distortions.

Real-Time Digital Mapped Method for Sensorless Multitimescale Operation Condition Monitoring of Power Electronics Systems

Operation condition monitoring of power electronics systems can improve analysis visibility for device administrators and researchers. However, the current sensor-based monitoring methods have limitations in accurately monitoring variables at multi-timescales. This article presents a real-time digital mapped (RTDM) method for the sensorless multi-timescale operation condition monitoring in power electronics systems using FPGA simulators. The mathematic models of power converters are deployed in the simulator considering multi-timescale characteristics. Both the digital simulator and the physical power converter are controlled by the same control signals, allowing the simulator to map the accurate operation conditions of the power converters without additional physical sensors. The RTDM method can monitor variables on the switching period timescale to the system transient timescale due to the consideration for the ideal switch modeling of the semiconductor switch. The effectiveness of the proposed method is demonstrated using a 30kW DAB converter as an example, through the integration of an experimental prototype and a simulator to create an RTDM platform. This method offers an easy and sensorless way to monitor multi-timescale variables in power electronics systems, providing a more comprehensive and visual analysis of their operation.

Enhancement-Mode Ambipolar Thin-Film Transistors and CMOS Logic Circuits using Bilayer Ga2O3/NiO Semiconductors.

Recent advancements in power electronics have been driven by Ga2O3-based ultrawide bandgap (UWBG) semiconductor devices, enabling efficient high-current switching. However, integrating Ga2O3 power devices with essential silicon CMOS logic circuits for advanced control poses fabrication challenges. Researchers have introduced Ga2O3-based NMOS and pseudo-CMOS circuits for integration, but these circuits may either consume more power or increase the design complexity. Hence, this article proposes Ga2O3-based CMOS realized using heterogeneous 3D-stacked bilayer ambipolar transistors. These ambipolar transistors consist of HfO2/NiO/Ga2O3/NiO/HfO2 heterostructures that are wrapped around by the Ti/Au gate electrode, resulting in record high electron and hole current on/off ratios of 109 and 107. The threshold voltage, subthreshold swing, and current density measured from 100 ambipolar devices (across 5 batches) are around -7.99 ± 0.92 V (p-channel) and 7.81 ± 0.81 V (n-channel), 0.59 ± 0.07 V/dec (p-channel) and 0.61 ± 0.06 V/dec (n-channel), and 0.99 ± 0.26 mA/mm (p-channel) and 58.23 ± 12.99 mA/mm (n-channel), respectively. All the 100 ambipolar devices showed decent long-term stability over a period of 200 days, exhibiting reliable electrical performance. The threshold voltage shift (ΔVTH) after negative bias stressing for a period of 3500 s is around 11.52 V (p-channel) and 10.21 V (n-channel), respectively. Notably, the n-channels exhibit ∼2 orders higher on/off ratio than the best Ga2O3 unipolar transistors at 300 °C. Moreover, the polarities of ambipolar transistors are reconfigurable into p- or n-MOS, which are integrated to demonstrate CMOS inverter, NOR, and NAND logic gates. The switching periods from "0" to "1" and from "1" to "0" of NOR are 0.12 and 0.17 μs, and those of NAND are 0.16 and 0.13 μs. This work lays the foundation of oxide-semiconductor-based CMOS for future integrated electronics.

Compensation of Discontinuous Conduction in Three Phase Voltage Source PWM Inverters

Nowadays the increasing utilization of alternative energy sources demand power converters capable of delivering high quality energy to the low voltage grid. Good dead time compensation and linear operation are essential to keep low order harmonics at acceptable levels. High-current operating conditions are well handled by traditional methods, but low current behaviour and waveforms with multiple zero crossings within a switching period are problematic, especially at low load conditions at or below 10% load. Such conditions often occur in the battery chargers of electric cars. Power quality is also essential for sensorless drives, as the accuracy of the output voltage is very important especially at low rotational speeds. This paper describes the identified cases of discontinuous conduction during dead time. Based on the voltage and current waveforms of the three phase inverter, an improved dead time compensation method is shown for symmetric PWM controlled inverters. The compensator uses already available measurement data, and compensates the resulting error voltage at duty cycle level. The described method can be used for any type of three phase modulation. A similar approach can also be used for two phase modulations.

Restrained Search Predictive Control of Dual Three-phase Induction Motor Drives

The interest in multiphase drives has re-emerged in the last decade, being the dual three-phase induction motor drive one of the most popular options. Predictive control techniques, already implemented in three-phase drives, have been recently adapted to the multiphase case. Schemes proposed so far have restricted the available number of voltage source inverter (VSI) switching vectors but do not impose any constraint on the allowable commutations of these vectors. This paper proposes not to select a subgroup of possible VSI switching vectors, but to constrain the commutations involved in the next sampling period. This procedure allows decreasing the switching period and improving the predictive control performance. The viability and effectiveness of the proposal is verified by simulation.

Frequency dependence of wake-up and fatigue characteristics in ferroelectric Al0.93B0.07N thin films

B-doped AlN ferroelectric thin films are promising candidates for non-volatile memory device applications, due to their relatively low deposition temperatures, large remanent polarizations (up to 120 μC/cm2), and outstanding polarization retention properties. In this research, the polarization switching fatigue characteristics in epitaxial B-doped AlN thin films were investigated. Films were deposited via reactive RF magnetron sputtering onto W-coated c-plane sapphire substrates. Polarization switching fatigue measurements were conducted with triangular waveforms for frequencies between 50 and 1000 Hz from room temperature to 200°C. On repeated cycling, the films undergo wake-up; the wake-up process was characterized by an activation energy of 0.15 ± 0.05 eV. After a period of normal switching, the film leakage current increased with additional cycling, and finally the films underwent dielectric breakdown. Unpatterned Al0.93B0.07N films with 100 nm thick Pt top electrodes survived ∼104 bipolar cycles, whereas films with 1000 nm W top electrodes survived ∼105 cycles before dielectric breakdown. Modeling was used to design a field plate, which improved the performance to ∼106 fatigue cycles. It was found that dielectric failure during fatigue was not due to surface flashover but was associated with hard breakdown events in the dielectric. Failure for 100 Hz cycling was not associated with device self-heating but was exacerbated by field concentrations; at higher frequencies, the instantaneous temperature rise during the switching becomes prominent. Based on the fatigue process under 100 Hz under various ambient temperatures, the activation energy of the polarization switching fatigue of B-doped AlN thin films was found to be Ea = 0.10 ± 0.03 eV.

Averaging for switched impulsive systems with pulse width modulation

Linear switched impulsive systems (SIS) are characterized by ordinary differential equations as modes dynamics and state jumps at the switching time instants. The presence of possible jumps in the state makes nontrivial the application of classical averaging techniques. In this paper we consider SIS with pulse width modulation (PWM) and we propose an averaged model whose solution approximates the moving average of the SIS solution with an error which decreases with the multiple of the switching period and by decreasing the PWM period. The averaging result requires milder assumptions on the system matrices with respect to those needed by the previous averaging techniques for SIS. The interest of the proposed model is strengthened by the fact that it reduces to the classical averaged model for PWM systems when there are no jumps in the state. The theoretical results are verified through simulations obtained by considering a switched capacitor electrical circuit.

Grid power control of direct matrix converter fed three-phase induction generator

The direct matrix converter (DMC) and the modulation technique were presented in this paper, moreover the power of the grid is controlled. Due to its high flexibility and low computation demands, the DMC's most widely used modulation technique is space vector modulation. The double-side modulation is used in this paper instead of the single-side modulation because less harmonics at the input and output side can be obtained, however this would increase slightly the number of branch-switch-overs (BSO) for each switching period. In addition to being able to create input and output sinusoidal currents with various frequencies, it would adjust the input power factor. Along with that, the simple power control loop would regulate the grid power and then generate controlled three-phase reference signals for pulses generation accordingly. Results from the simulations show that the topology is appropriate for machine drive applications.

Identifying the switching topology of dynamical networks based on adaptive synchronization.

This paper proposes an approach for identifying unknown switching topology in a complex dynamical network. The setup is divided into two components: a primary drive network and a specialized response network equipped with switched topology observers. Each class of observers is dedicated to tracking a specific topology structure. The updating law for these observers is dynamically adjusted based on the operational status of the corresponding topology in the drive network-active if engaged and dormant if not. The sufficient conditions for successful identification are obtained by employing adaptive synchronization control and the Lyapunov function method. In particular, this paper abandons the generally used assumption of linear independence and adopts an easily verifiable condition for accurate identification. The result shows that the proposed identification method is applicable for any finite switching periods. By employing the chaotic Lü system and the Lorenz system as the local dynamics of the networks, numerical examples demonstrate the effectiveness of the proposed topology identification method.