Switching Function Research Articles

Mode-independent thermo-optic switch based on the total-internal-reflection effect.

A broadband mode-independent thermo-optic (TO) switch using the total-internal-reflection (TIR) effect is proposed and experimentally demonstrated on a polymer waveguide platform. By optimizing geometric parameters of the TIR switch, a mode-independent TO switching function with a large bandwidth and extinction ratio can be realized for E11, E12, and E21 modes. The measurement results show an extinction ratio larger than 18.1 dB with a driving power of 160 mW for each mode over the wavelength range of 1500-1620 nm. The designed structure can also be cascaded to form a 1 × N switch network for mode-division multiplexing (MDM) systems, which greatly improves the network flexibility.

Adaptive NN control for nominal backstepping form with periodically time‐varying and nonlinearly parameterized switching functions

AbstractIn this paper, the prescribed tracking performance control problem is addressed for uncertain nonlinear systems with unknown periodically time‐varying parameters and arbitrary switching signal. By utilizing radial basis function neural network and fourier series expansion, an approximator is developed to overcome the difficulty of identifying unknown periodically time‐varying and nonlinearly parameterized functions. To achieve the ideal tracking control performance and eliminate the influence of filtering error, a novel command filter‐based adaptive neural network prescribed tracking performance controller is designed by introducing a filtering compensation mechanism. Differently from the standard Backstepping technique, the proposed control scheme eliminates the “explosion of complexity” problem and relaxes the constraint condition on the reference signal. And then, it is warranted that the closed‐loop system is semi‐globally ultimately uniformly bounded and the tracking error is always limited to the specified region bounded by the performance functions. Three simulation examples are used to demonstrate the feasibility of the developed technique in this paper.

Quasi‐1D Polymer Semiconductor–Diarylethene Blends: High Performance Optically Switchable Transistors

AbstractOptically switchable field‐effect transistors (OSFETs) are non‐volatile photonic memory devices holding a great potential for applications in optical information storage and telecommunications. Solution processing of blends of photochromic molecules and π‐conjugated polymers is a low‐cost protocol to integrate simultaneously optical switching and charge transport functions in large‐area devices. However, the limited reversibility of the isomerization of photochromic molecules due to steric hindrance when embedded in ordered polymeric matrices represents a severe limitation and it obliges to incorporate as much as 20% in weight of the photochromic component, thereby drastically diluting the electronic function, limiting the device performance. Herein, a comparative study of the photoresponsivity of a suitably designed diarylethene molecule is reported when embedded in the matrix of six different polymer semiconductors displaying diverse charge transport properties. In particular, this study focuses on three semi‐crystalline polymers and three quasi‐1D polymers. It is found that 1% w/w of 1,2‐bis(5‐(3,5‐di‐tert‐butylphenyl)‐2‐methylthiophen‐3‐yl)cyclopent‐1‐ene in a blend with poly(indacenodithiophene‐co‐benzothiadiazole) is sufficient to fabricate OSFETs combining photo‐modulation efficiencies of 45.5%, mobilities >1 cm2 V−1s−1, and photo‐recovered efficiencies of 98.1%. These findings demonstrate that quasi‐1D polymer semiconductors, because of their charge transport dominated by intra‐molecular processes, epitomize the molecular design principles required for the fabrication of high‐performance OSFETs.

Annealing and intensity dependent femtosecond nonlinear optical studies of sodium zinc borate oxide glasses incorporated with gold nanoparticles

Herein, we explored the annealing and intensity–dependent femtosecond (fs) nonlinear optical (NLO) studies on sodium zinc borate (NZB) glasses embedded with gold nanoparticles (NPs). The glasses were prepared by the melt–quench process and subjected for thermal treatment at 450 °C at different schedules in a normal atmosphere. It was identified that the glass annealed for 12 hr (i.e., the NZBAu12 glass) had the maximum saturation intensity and negative nonlinear refraction values. Therefore, the intensity–sensitive NLO investigations then conducted on that glass to understand the influence of intensity of laser radiation on NLO proeprties on gold NPs embedded glasses. The saturable absorption observed at lower intensity was switched to reverse saturable absorption (two–photon absorption) during the exposure with high fluence laser pulses. However, the nonlinear refraction sign was unchanged with increase of intensity of laser radiation. The strategy explored in this work might pave the way for achieving the strong nonlinear traits in borate–based glasses routed with gold NPs. The study outcomes endorse the benefits of NZBAu12 glass for optical switching functionalities under low–intensity pulse excitation, as well as for optical limiting applications under high–intensity pulse excitation.

An AC-DC LED Integrated Streetlight Driver with Power Factor Correction and Soft-Switching Functions

The use of light-emitting diodes (LEDs) in street lighting applications has been greatly welcomed with the current trends of energy saving, environmental protection, carbon reduction, and sustainable development. This paper presents a novel AC-DC LED integrated streetlight driver that combines an interleaved buck converter with a coupled inductor and a half-bridge series resonant converter with a full-bridge rectifier into a single-stage power conversion topology with power factor correction (PFC) and soft switching capabilities. The PFC is achieved by designing the coupling inductor in the interleaved buck converter sub-circuit in discontinuous conduction mode. In addition, the resonant tank in the half-bridge series resonant converter sub-circuit is designed to be similar to an inductive load, thus giving the power switch a zero-voltage switching (ZVS) function, decreasing switching losses and increasing the overall efficiency of the proposed circuit. A prototype circuit of the proposed LED integrated streetlight driver with a power rating of 165 W (235 V/0.7 A) and 110 V input utility voltage has been developed and tested. According to the measurement results, a power factor greater than 0.98, a total harmonic distortion coefficient of the input current less than 3%, and an efficiency greater than 89% were obtained in the AC-DC LED integrated streetlight driver. Therefore, the experimental results are satisfactory and demonstrate the functionality of the proposed AC-DC LED integrated streetlight driver.

A Power Quality Assessment of Electric Submersible Pumps Fed by Variable Frequency Drives under Normal and Failure Modes

This paper proposed a simplified modeling approach for a power quality (PQ) assessment of Electric Submersible Pumps (ESP) systems supplied by the two-level, the neutral-point-clamped three-level, and the cascaded H-bridge (CHB) multilevel inverter VFD topologies. The VFD switching function models and their analytical expressions are proposed to understand how they can create high-frequency components that might excite the resonance mode in a transmission cable or a rotating shaft system. Voltage, current, and motor airgap torque harmonics induced by each VFD topology in a balanced operation mode are derived and correlated to the PWM carrier and motor operating frequencies. The motor airgap harmonics are calculated based on Concordia’s transformation of voltages and currents in αβ-plan. These harmonic components are represented in the form of Campbell diagrams. An analysis of harmonics under unbalanced conditions was also conducted in a CHB VFD topology-powered ESP system with failed and bypassed cells. The investigated modulation technique is a neutral-shift PWM method that enables the system to operate balanced line-line voltages even if the line-neutral voltages are unbalanced. The effects of modifying the electrical spectrum using the neutral-shift PWM method on electrical and mechanical spectra are analyzed. The results of the Matlab/Simulink-based simulation show that the proposed full ESP system model is highly accurate in both normal and failure modes. The results are consistent with theoretical predictions and are graphically shown in the time and frequency domains for easy analysis. Hybrid experimental–numerical results on a reduced-scale laboratory setup are also discussed to confirm the correctness of the suggested developments.

Robust Deadbeat Predictive Direct Speed Control for PMSM With Dual Second-Order Sliding-Mode Disturbance Observers and Sensitivity Analysis

A novel robust deadbeat predictive direct speed control (RDP-DSC) method for permanent magnet synchronous motor (PMSM) is proposed to improve the speed control bandwidth and eliminate the conventional cascaded speed control structure. Firstly, the basic DP-DSC method with one-step ahead time delay compensation is introduced briefly. Then, the control sensitivity analysis issue on the electrical and mechanical parameter mismatches, external disturbance, and inverter nonlinearity are inspirationally discussed. Further, based on the analysis above, a novel dual second-order sliding-mode disturbance observer (SOSMDO) structure is proposed for both current and speed disturbance suppression. The proposed RDP-DSC equipped with SOSMDO is presented with full control errors completely compensated. Meanwhile, the undesired chattering phenomenon caused by the switching function in the existing popular sliding-mode observers is eliminated by the proposed SOSMDO. Rich experiments are then performed, showing that the proposed method has strong enough robustness to various parameter mismatches and external disturbances while the system still holds the direct speed control methods' advantages, such as high response speed and satisfying bandwidth.

A chipless light switch for smart‐homes

AbstractThe limited and inconvenient functionality of conventional light switches is out of pace with current advancements in wireless sensors. A chipless RFID light switch (CLS) that is passive, battery‐free and relocatable and maintains the convenience of having physical buttons for controlling lightbulbs or other electrical devices is introduced. These characteristics have been achieved by attaching single‐pole‐single‐through toggle switches to the edges of radio frequency spiral resonators. The status of the switches activates or deactivates the resonators, allowing the CLS tag to passively communicate the status of the switches. A CLS tag with two ID resonators (used for tag identifications), and two measurement resonators [MRs] (connected with switches and used to communicate the status of the switches) was designed and fabricated using a 1‐mm‐thick FR4 substrate. Measurement results showed resonant frequencies at 1115 and 1220 MHz corresponding to the ID resonators and frequencies at 848 and 971 MHz corresponding to the MRs. Turning the switches OFF and ON successfully activated and deactivated the MRs.

Spin Transport Properties of MnBi2Te4-Based Magnetic Tunnel Junctions

The van der Waals heterojunctions, stacking of different two-dimensional materials, have opened unprecedented opportunities to explore new physics and device concepts. Here, combining the density functional theory with non-equilibrium Green's function technique, we systematically investigate the spin-polarized transport properties of van der Waals magnetic tunnel junctions (MTJs), Cu/MnBi2Te4/MnBi2Te4/Cu and Cu/MnBi2Te4/h-BN/n⋅MnBi2Te4/Cu (n = 1, 2, 3). It is found that the maximum tunnel magnetoresistance of Cu/MnBi2Te4/h-BN/3⋅MnBi2Te4/Cu MTJs can reach 162.6%, exceeding the system with only a single layer MnBi2Te4. More interestingly, our results indicate that Cu/MnBi2Te4/h-BN/n⋅MnBi2Te4/Cu (n = 2, 3) MTJs can realize the switching function, while Cu/MnBi2Te4/h-BN/3⋅MnBi2Te4/Cu MTJs exhibit the negative differential resistance. The Cu/MnBi2Te4/h-BN/3⋅MnBi2Te4/Cu in the parallel state shows a spin injection efficiency of more than 83.3%. Our theoretical findings of the transport properties will shed light on the possible experimental studies of MnBi2Te4-based van der Waals magnetic tunneling junctions.

Accelerating Unruh-DeWitt detectors coupled with a spinor field

The behavior of accelerating Unruh-DeWitt detectors coupled with a spinor field in (3+1)-dimensional spacetime is investigated. For a single point-like detector with Gaussian switching function, the transition probability increases with the acceleration and thus the antiUnruh effect effect cannot occur. Due to the spinor structure of the Dirac field, UV divergences are encountered in the calculation of the entanglement between the detectors. After introducing some UV cutoff Λ, the negativity of detectors is shown to behave nonmonotonically with respect to the acceleration. Besides, the negativity increases with the cutoff Λ and decreases with the distance between the detectors. The mutual information between the two detectors is also discussed.

Terahertz Metamaterial Absorber Based on Ni–Mn–Sn Ferromagnetic Shape Memory Alloy Films

Terahertz absorbers have been extensively investigated by researchers due to their applications in thermophotovoltaic energy conversion and sensors, but a key factor limiting their development is the lack of vital and versatile materials. Ferromagnetic shape memory alloys (FSMAs) offer a novel remedy for tunable metamaterials due to their brilliant recovery of deformation, remote control, and transient response. In this study, we propose a tunable absorber based on magnetic field tuning, consisting of Ni–Mn–Sn ferro-magnetic shape memory alloy films in fractal geometry and optically excited Si plates. Numerical analysis shows that the proposed absorber has an absorbance bandwidth of 1.129 THz above 90% between 1.950 THz and 3.079 THz. The absorber geometry can be regulated by an external magnetic field, allowing dynamic switching between broadband and narrowband absorption modes, the latter showing an ultra-narrow bandwidth and a high-quality factor Q of ~25.8. The proposed terahertz absorber has several advantages over current state-of-the-art bifunctional absorbers, including its ultra-thin structure of 10.39 μm and an additional switching function. The absorption can be continuously tuned from 90% to 5% when the light-excited silicon plate is transferred from the insulator state to the metal state. This study presents a promising alternative strategy for developing actively regulated and versatile terahertz-integrated devices.

STUDY OF PARALLEL COMPUTING STRUCTURE AND CIRCUIT ANALYSIS FOR INTERCONNECTION NETWORK

Parallel computing has become a crucial topic in the concern of computer science and also it is revealed to be critical when researching in high performance. The evolution of computer architectures towards an improved number of nodes, where parallelism could be the approach to option for speeding up an algorithm within the last few decades. The combination of processing units build a model of computation (circuits) has gained an essential place in the area of high performance computing (HPC) due to its configuration and considerable processing supremacy that is parallel, series, etc…. In this paper, we study the idea of parallel computing, and its programming models and also explore some theoretical and technical concepts which can be often needed to understand the Interconnection network. In particular, we show how this technology is new in assisting the field of computational physics, especially when the issue is data parallel. In this paper firstly we convert the graphical model of perfect difference network into circuit diagram then convert circuit diagram into switching function, then simplify it and redraw the equivalent network.

THE USE OF CODE SWITCHING AND CODE MIXING BY INDOFOOD AND UNILEVER FOOD ADVERTISEMENTS ON TELEVISION

<p class="Default">The aims of the research are to find out the type, function and reason of code switching and code mixing mostly used by Indofood and Unilever Food Advertisements on Television. The research design of this research is descriptive qualitative because the result of the data analyzed is in descriptive phenomenon such as words, sentence and utterance while the research method used in this research is library research. The result findings are: 1). The type of code switching mostly used here is intra sentential switching which occurs 36 times. While the type of code mixing mostly used here is intra sentential mixing which occurs 38 times. 2). The function of code switching and code mixing mostly used here is metalinguistic function which occurs 60 times. 3). The reason of code switching and code mixing mostly used here is talking about particular topic which occurs 48 times.</p>

Out-of-plane uniaxial loading of paperboard: experimental procedure and evaluation

Abstract Development of three-dimensional continuum models for paperboard is an active field and the need for reliable measurements to calibrate and validate such models is evident. An experimental device and protocol for cyclic out-of-plane loading is developed. This loading sequence is present during converting operations of paperboard. The experimental tests reveals that the commonly observed soft initial non-linear response during out-of-plane compression is a structural effect that stems from the surface roughness rather than being an inherent material behavior. A gluing procedure, used to perform cyclic out-of-plane loading, is mitigating the effect of the surface roughness. Several novel cyclic loading experiments are performed, alternating between compression and tension which indicates that fiber bonds are not recovered in compression after they have been broken through delamination. Measurements also show that the transition in compression and tension is continuous, hence the use of a switch function present in a number of constitutive continuum models for paperboard is deemed questionable.

Event-Triggered Distributed Sliding Mode Control of Fractional-Order Nonlinear Multi-Agent Systems

In this study, the state consensus problem is investigated for a class of nonlinear fractional-order multi-agent systems (FOMASs) by using a dynamics event-triggered sliding mode control approach. The main objective is to steer all agents to some bounded position based on their own information and the information of neighbor agent. Different from the existing results, both asymptotic consensus problem and Zeno-free behavior are ensured simultaneously. To reach this objective, a novel event-triggered sliding mode control approach is proposed, composed of distributed dynamic event-triggered schemes, event-triggered sliding mode controllers, and auxiliary switching functions. Moreover, to implement the distributed control scheme, the fractional-order adaptive law is also developed to tuning the coupling weight, which is addressed in distributed protocol. With the improved distributed control scheme, all signals in the fractional-order closed-loop systems are guaranteed to be consensus and bounded, and a novel approach is developed to avoid the Zeno behavior. Finally, the availability and the effectiveness of the above-mentioned approach are demonstrated by means of a numerical example.

Switching-Algebraic Calculation of Banzhaf Voting Indices

This paper employs switching-algebraic techniques for the calculation of a fundamental index of voting powers, namely, the total Banzhaf power. This calculation involves two distinct operations: (a) Boolean differencing or differentiation, and (b) computation of the weight (the number of true vectors or minterms) of a switching function. Both operations can be considerably simplified and facilitated if the pertinent switching function is symmetric or it is expressed in a disjoint sum-of-products form. We provide a tutorial exposition on how to implement these two operations, with a stress on situations in which partial symmetry is observed among certain subsets of a set of arguments. We introduce novel Boolean-based symmetry-aware techniques for computing the Banzhaf index by way of two prominent voting systems. These are scalar systems involving six variables and nine variables, respectively. The paper is a part of our on- going effort for transforming the methodologies and concepts of voting systems to the switching-algebraic domain, and subsequently utilizing switching-algebraic tools in the calculation of pertinent quantities in voting theory.

A high-performance thermal transistor based on interfacial negative differential thermal resistance

A thermal transistor, which can achieve the smart, flexible, and precisely controlled thermal management, proves to be a promising thermal device. Recently, thermal transistors based on the negative differential thermal resistance (NDTR) have been regarded as the most feasible configuration considering their simple structures. Among the several methods to implement NDTR, the method of reducing the contact pressure between mated surfaces by using the negative thermal expansion material, thus generating a negative temperature dependent interface thermal conductance and accompanied NDTR, is the most likely to be observed experimentally. In this paper, a thermal transistor based on NDTR is designed by engineering the interfacial thermal resistance. Moreover, we optimize the switching function and the amplification function of the transistor by only adjusting the temperature and the length of the source terminal. As an example, a silicon thermal transistor with a high switching ratio as well as an accurately controlled thermal flux amplification function is discussed at low temperature. The design and optimization of macroscopic thermal transistor will promote the rapid development of thermal functional devices and help to control thermal flux in a more flexible and effective way.

Antiunwinding Sliding Mode Control for Rigid Spacecraft Based on Modified Rodrigues Parameters

In this paper, attitude maneuver control without unwinding phenomenon is investigated for rigid spacecraft via modified Rodrigues parameters. A novel switching function is constructed by a hyperbolic sine function to guarantee that the sliding surface contains two stable equilibria. A sliding mode controller is developed to ensure that the sliding surface is reachable. Moreover, a dynamic parameter is designed to guarantee unwinding-free performance of the closed-loop system when the system states outside the sliding surface. In addition, a boundary layer is introduced to deal with the chattering problem. Further, the unwinding-free performance within the boundary layer is guaranteed by imposing some conditions on the parameters of the switching function. Finally, comparison simulations are performed to verify the effectiveness and superiority of the presented control law.

Terahertz wideband modulator devices using phase change material switchable frequency selective surfaces

Phase change materials (PCMs) such as temperature sensitive materials have received considerable attention in the optics and THz regime because of the reversable switching of their electromagnetic properties. In this paper, wideband switchable absorbers based on vanadium dioxide (VO2) have been designed and simulated at the terahertz (THz) regime. The switching functionality is enabled by the phase change of the VO2 layer from a metal state to an insulator through the temperature transition. The phase change temperature is 68 °C. The first designed absorber shows a wideband absorption spectrum (fractional bandwidth of 92.3%) with absorptivity above 90% in the metal state, where conductivity of the VO2 layer is 200000 S m−1, whereas the absorptivity is less than 3% in the insulator state, when the conductivity of the VO2 reaches 200 S m−1. An equivalent circuit model-based analysis is presented for metal state. Based on the results, the extinction ration is less than –11 dB with 0.9 modulation depth for a wide frequency range from 2.2 to 5.87 THz. This makes the proposed structure a suitable candidate for broadband modulation at THz frequencies. An ultra-broadband absorption spectrum is achieved in the second design utilizing the stacked structure of two VO2 layers in metal state, where each layer acts as a resonator. This absorber prototype offers more than 90% absorptivity within 1.2–6.1 THz corresponding to a relative bandwidth of 135%.

An Input-Series-Output-Parallel Cascaded Converter System Applied to DC Microgrids

Direct current transformer (DCT) is a key piece of equipment in direct current (DC) microgrids, and the mainstream topologies mainly include LLC resonant converter (LLC) and dual active bridge (DAB). In this paper, a novel bi-directional buck/boost + CLLLC cascade topology is proposed for the input-series-output-parallel cascade converter system of a DC microgrid. To solve the problem that frequency variation causes the converter to deviate from the optimal operating point, resulting in low efficiency, and the inability to achieve a soft switching function. The CLLLC converter operates near the resonant frequency point as a DCT, only providing electrical isolation and voltage matching, while the buck/boost converter controls the output voltage and the voltage and current sharing of each module. Compared to other cascaded converter systems, the cascaded converter proposed in this paper has high efficiency, simplifies the parameter design, and is suitable for wide input and wide output operating conditions. The system adopts a three-loop control strategy, establishes the small-signal modeling of the system, and its stability is verified by theoretical analysis and simulation. The simulation and experimental results verify the correctness of the proposed cascaded converter based on buck/boost + CLLLC and the effectiveness of the control strategy.