Minimum Switching Time Research Articles

Improved Switchable Heat Pipe Based on Adsorption: Against-Gravity Operation and Enhanced Dynamics

Controlling heat transfer through components with adjustable thermal resistance can be of great benefit in a wide range of applications such as the thermal management of spacecraft or electric vehicles. A novel concept for both thermal switching and thermal regulation is the use of a water-loaded adsorbent within a reservoir that a regular heat pipe is expanded with. By reversibly desorbing or adsorbing water, states of low and high thermal resistance can be achieved. This concept has been studied so far only in thermosiphons that rely on gravity support. To expand potential application fields, we successfully investigated the utilization of heat pipes with a capillary structure, achieving against-gravity operation. Adsorption-based heat pipe demonstrators were experimentally examined regarding their characteristic properties. Thermal resistances during the on and off state of 0.25 KW−1 and 6.5 KW−1, respectively, were measured, yielding switching ratios of up to 26. Furthermore, the role of the adsorbent reservoir heat exchanger was examined and found to have a significant potential to yield an improvement with regards to dynamic performance. With an improved demonstrator design, the dynamic performance was enhanced as the hysteresis behavior was reduced and a minimum switching time of 5 min was recorded.

Investigation of Peak-to-Valley Current Ratio of GaN/AlN Resonant Tunneling Diodes

Peak-to-valley current ratios (PVCRs) achie-ved in GaN/AlN resonant tunneling diodes (RTDs) are less than 2, significantly less than their counterparts, such as InGaAs/AlAs RTDs (e.g., PVCR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 12). This has hindered their high-speed applications because the maximum self-oscillation frequency and minimum switching time generally increase and decrease with PVCR. In this article, we investigate the problem of low PVCR in GaN/AlN RTDs with both modeling and experiments. Firstly, we developed a Schrödinger equation-based solver for RTD simulations. While the solver gives reasonable agreement with the experimental current–voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> ) characteristics, such as the positions of resonant peaks, it predicts a much higher PVCR. Then, we conducted temperature dependence studies on GaN/AlN RTDs and compared them with InGaAs/AlAs RTDs. The similarities observed suggest that sequential tunneling with phase randomization, resulting from scattering processes such as optical phonon and interface roughness scattering, is responsible for the large valley currents in GaN/AlN RTDs.

Studies on Three-phase Imbalance Treatment Based on Beidou communication and Commutation Switch

In this paper, genetic algorithm and commutation switch based three-phase imbalanced distribution network are studied. A genetic algorithm-based commutation switch three-phase imbalance management strategy was developed, and the three-phase current distribution station area was established. A mathematical model was developed for the multi-objective optimal commutation based on the minimum imbalance degree and the minimum switching times of the low-voltage load online automatic commutation device during the commutation process. Additionally, the real-time online governance control strategies were balanced. Finally, the effectiveness of the proposed method was verified using simulation studies.

A Desired Voltage Vector Based MPTC Strategy for PMSM With Optimized Switching Pattern

The main challenges for Finite Set-model Predictive Torque and Flux Control (MPTC) include huge calculation amount, large torque ripple, and the selection of weighting factor. To deal with these challenges and achieve the fastest torque response, a novel MPTC strategy with virtual voltage vector-based pattern is proposed in this paper. In each control period, a desired voltage vector is computed based on the maximum torque variation rate. The virtual desired voltage vector is combined by using basic voltage vectors with the minimum switching times. The switching pattern between two adjacent control periods is optimized by using a cost function in realtime. Compared with the traditional MPTC approach, the novel strategy has multifaceted improved performances: faster torque response, less calculation amount, lower switching frequency, reduced torque ripple, higher efficiency and no weighting factor. The proposed method is contrasted with traditional MPTC method and a well-known generalized multiple-vector-based MPC method via experiments.

Analysis of bistability at the coupling between waveguide and whispering gallery modes of a nonlinear hemicylinder

The optical bistability caused by the coupling between modes of the parallel-plate waveguide and a nonlinear hemicylindrical crystal is studied using theoretical and numerical analysis. In such a system a waveguide channel is parallelly coupled to whispering gallery modes (WGMs) of a hemicylindrical microresonator ensuring bistable behaviour at input intensities of the order of a few MW cm−2. The characteristic minimum switching time of the system (around 30 ps) can be controlled by varying the thickness of the metal layer which couples the waveguide and WGMs. This is conditioned by the change of the quality Q-factor, as well as the coupling coefficient of the resonator. The main advantages of the system are fabrication simplicity, small sizes of the order of 3 µm, integrability with other optical components and the possibility of adjusting the processes by making use of the electro-optical effect.

Acousto-optic modulators/frequency shifters with single-mode optic fibers

Acousto-optic modulators/frequency shifters based on TeO2 crystals with single-mode optical fibers supporting and not supporting polarization for collimated and focused light beams at radiation wavelengths of 785, 1064, 1550 nm have been developed, produced and experimentally investigated. The mechanisms of formation and methods of expanding the working band of the modulator are determined. A double-crystal acousto-optic laser emission frequency shifter with an working bandwidth of ≈40 MHz has been created. Single-crystal modulators based on collimated beams with a frequency band of ≈10 MHz are considered. A single-crystal modulator with a focused light beam with a switching time of ≈ 18 ns and an extended reception band of ≈ 40 MHz is investigated. It is shown that a light beam focusing makes it possible to implement a modulator with a minimum switching time of ≈ (2-3) ns. This value is limited by electrical breakdown of the ultrasonic wave transmitter.

3-Bit Digital-to-Analog Converter with Mechanical Amplifier for Binary Encoded Large Displacements

We present the design, fabrication, and characterization of a MEMS-based 3-bit Digital-to-Analog Converter (DAC) that allows the generation of large displacements. The DAC consists of electrostatic bending-plate actuators that are connected to a mechanical amplifier (mechAMP), enabling the amplification of the DAC output displacement. Based on a parallel binary-encoded voltage signal, the output displacement of the system can be controlled in an arbitrary order. Considering the system design, we present a simplified analytic model, which was confirmed by FE simulation results. The fabricated systems showed a total stroke of approx. 149.5 ± 0.3 µm and a linear stepwise displacement of 3 bit correlated to 23 ≙ eight defined positions at a control voltage of 60 V. The minimum switching time between two input binary states is 0.1 ms. We present the experimental characterization of the system and the DAC and derive the influence of the mechAMP on the functionality of the DAC. Furthermore, the resonant behavior and the switching speed of the system are analyzed. By changing the electrode activation sequence, 27 defined positions are achieved upgrading the 3-bit systems into a 3-tri-state (33) system.

Акустооптические модуляторы с расширенной частотной полосой для волоконно-оптических линий

A modulator-frequency shifter with single-mode optical fibers for a radiation wavelength of 1064 nm has been developed and manufactured. The light beam was focused in the center of the sound column. Modulator switching time ≃ 18 ns. Operating mode: pulse, continuous. Total optical loss at center frequency: -3.2 dB. An expression for the frequency band of reception of the modulator is obtained. The estimates are in good agreement with the experimental data ≃ 40 MHz. It is shown that the use of a scheme with a focused beam makes it possible to implement a modulator with a minimum switching time ≃ (2-3) ns and a receiving frequency band ≃ (200-300) MHz.

Effect of Surface Recombination on Diffusion Length and Active Cavity Life time

This work presents an analytical study for simulating a Fabry-Perot Bi-stable etalon (F-P cavity) filled with a dispersive optimized nonlinear optical material (Kerr type) such as semiconductors Indium Antimonite (InSb). Depending on the obtained results and because of a trade-off between the optical path length of the sample and active cavity lifetime, an optimization procedure was applied on the InSb etalon/CO laser parameters; critical switching irradiance (Ic) was applied via simulation systems of optimization procedures of optical cavity (Matlap program was used to study the optical Bi-stability of a nonlinear Fabry-Perot cavity). In order to achieve minimum switching power and faster switching time, the optimization surface recombination on the diffusion length and effective cavity lifetime was studied.&#x0D; In addition, for a specific absorption value 400 cm-1, the lifetime coefficient values were 0.33 , 0.091 , 0.0172 ns for sample thickness (D) = 500 , 60 , 20 mm, respectively. Also, for a bulk recombination time (Tl) of 200 ns, specific absorption (α) of 50 cm1, and D of 20 mm, the surface recombination speed value was 2.845 x 105 cm/sec, whereas the active lifetime, which is defined as the thickness over the surface recombination speed (sυ) (D/2sυ), was equal to 3.5ns.

Characterizing microfluidic approaches for a fast and efficient reagent exchange in single-molecule studies

Single-molecule experiments usually take place in flow cells. This experimental approach is essential for experiments requiring a liquid environment, but is also useful to allow the exchange of reagents before or during measurements. This is crucial in experiments that need to be triggered by ligands or require a sequential addition of proteins. Home-fabricated flow cells using two glass coverslips and a gasket made of paraffin wax are a widespread approach. The volume of the flow cell can be controlled by modifying the dimensions of the channel while the reagents are introduced using a syringe pump. In this system, high flow rates disturb the biological system, whereas lower flow rates lead to the generation of a reagent gradient in the flow cell. For very precise measurements it is thus desirable to have a very fast exchange of reagents with minimal diffusion. We propose the implementation of multistream laminar microfluidic cells with two inlets and one outlet, which achieve a minimum fluid switching time of 0.25 s. We additionally define a phenomenological expression to predict the boundary switching time for a particular flow cell cross section. Finally, we study the potential applicability of the platform to study kinetics at the single molecule level.

A High Performance Interleaved Discontinuous PWM Strategy for Two Paralleled Three-Phase Inverter

This article aims to obtain the optimal combination of the switching loss, maximum zero-sequence circulating current (ZSCC), and line current ripple, which benefits most of the applications. The analysis shows that the interleaved discontinues pulsewidth modulation (IDPWM) maintains the minimum switching loss and line current ripples, but it introduces a larger ZSCC. Therefore, to obtain the optimal combination of the switching loss, maximum ZSCC peak, and line current ripple, it is essential to retain the minimum switching times and the optimal line current ripple of IDPWM but further reducing its overly large ZSCC. Further analysis reveals that IDPWM includes the vector combinations with medium ZSCC change rates, resulting in the larger ZSCC. Given the redundancies of the vector combinations, this article proposes a simple matrix to modify the original modulation signals of IDPWM, eliminating the medium ZSCC change rates. The proposed PWM scheme retains the minimum line current ripple and switching times as those of IDPWM while further reducing its overly large ZSCC, as validated by analytical results as well as experimental results. Since the proposed method obtains the optimal combination among switching loss, line current ripple, and maximum ZSCC peak, we name the proposed PWM scheme a high-performance DPWM.

Switching Dynamics Measurement of Ferroelectric Y-Doped HfO2 M-I-M Capacitor

Domain-switching kinetics of 5 mol% Y-doped HfO2 metal-insulator-metal (MIM) capacitor was characterized. The changes in polarization indicate the polarization reversal in HfO2. In this research, we show the polarization reversal of an 20-nm-thick Y-doped HfO2 deposited by atomic layer deposition (ALD) by switching the applied voltage (2.6 to 4.6V) and the pulse duration (1μs to 500μs). We use the measurements of Kolmogorov-Avrami-Ishibashi (KAI) model to extract the minimum switching time of the domains. Introduction Ferroelectric HfO2 layer has attracted attraction in CMOS and memory applications owing to its scaling ability and process compatibility. It has been demonstrated that doping of foreign elements, including Zr, Si, Al, Y, atoms under post-deposition annealing (PDA) or post-metallization annealing (PMA) induces the ferroelectricity in HfO2 [1]. The switching dynamics of ferroelectric Al- and Zr-doped HfO2 metal-insulator-metal (MIM) capacitors has been well-modeled by nucleation limited switching (NLS) model, where multigrain polarization takes place assuming a distribution in the switching time [2, 3]. In this study, we apply the KAI model to fit the switching dynamics of Y-doped HfO2 MIM capacitor using the following equation,, △P=Ps*(1-exp{-(t/τ)β })where △P, P s, τ and β are the partial, saturation polarization, switching time constant and a fitting parameter, respectively [4]. Experiments An MIM capacitor with a 20-nm-thick 5 mol% Y-doped HfO2 film was fabricated by atomic layer deposition (ALD). The top and bottom electrode were both W deposited by sputtering. PMA was then carried out at 500 oC for 1 minute. Typical polarization-voltage (P-V) hysteresis is shown in fig. 1, where a remanent polarization (P r) of 12 mC/cm2 was obtained. A voltage waveform shown in fig. 2 was applied to the electrode to measure the polarization reversal of the devices after certain polling process. Polarization reversal was extracted by applying pulses with various height ranging from 2.6 to 4.6 V and width from 1 ms to 500 ms followed by half P-V measurement. Results and discussions Fig 3 shows measured partial polarization with different pulse width and voltage. As the pulse width increases, △P increases, indicating that a certain time is required to fully switch the domains. Data fit using the KAI model has well reproduced the measured data, indicating the presence of multigrain switching. However, a β of 0.6 to 0.8, which is smaller than those of Zr-doped HfO2 (typically b=2.1), needs to be used to fit the data. This may imply the difference in the domain size among dopants incorporated in the HfO2 layer. Conclusion Switching dynamics of ferroelectric Y-doped HfO2 MIM capacitors has been measured. The device has shown to follow the multidomain switching based on KAI model as is explained for Zr-doped HfO2 ones, except for the difference in the fitting parameter.

Optimization Procedures using Effect of Etalon Finesse and Driving Term on Optical Bistability

In this work, analytical study for simulating a Fabry-Perot bistable etalon (F-P cavity) filled with a dispersive optimized nonlinear optical material (Kerr type) such as semiconductors Indium Antimonide (InSb). Because of a trade off between the etalon finesse values and driving terms, an optimization procedures have been done on the InSb etalon/CO laser parameters, using critical switching irradiance (Ic) via simulation systems of optimization procedures of optical cavity. in order to achieve the minimum switching power and faster switching time, the optimization parameters of the finesse values and driving terms on optical bistability and switching dynamics must be studied.&#x0D; In addition, for different values of a cavity finesse (for example, F = 25 and 2.37) the switching intensity takes low values with a high finesse etalon compared to a high switching intensity with a low finesse etalon. So, the minimum switching power for a low finesse etalon is ⁓0.785mW, and is about 0.0785mW for a high finesse etalon. The driving term peak of a high finesse etalon becomes higher and the slowing down region becomes less, leading to a fast switching as compared with a slow switching in a low finesse etalon. So that, the minimum switching time was about 300ns for a low finesse etalon, and about 150ns for a high finesse etalon.

A Full Decentralized Multi-Agent Service Restoration for Distribution Network With DGs

The ever-growing requirement for reliability and quality of power supply suggests to enable self-healing features of smart distribution network using intelligent communication and control. In this article, a concept of fully decentralized multi-agent system (FDMAS) automation is proposed to build a unified restoration service framework for distribution network with distribution generators (DGs), where an FDMAS interaction mechanism is designed for establishing a reduced model which can significantly reduce the computational dimensions of service restoration. Furthermore, an FDMAS-based strategy is proposed for service restoration by combining network reconfiguration with intentional islanding; especially a network reconfiguration algorithm based on network flow model is presented, which, along with parameter justification, can mitigate the variations of loads and intermittence of DGs. The simulation studies are carried out on the 84-bus and 22-bus distribution system, respectively, using MATLAB and java agent development framework (JADE) simulation system and dynamic model test platform. The test results show that the proposed strategy can maximize restoration of out-of-service loads with minimum switching times and has an excellent performance on service restoration time.

Switching Dynamics of Ferroelectric Zr-Doped HfO2

Ferroelectric Zr-doped HfO2 (HZO) is a promising candidate for steep slope transistors and memory technology. For these applications, it is essential to understand and optimize the switching dynamics of the ferroelectric film. In this letter, we characterize the polarization reversal of an 8 nm-thick HZO film deposited by the atomic layer deposition with voltage pulses varying in amplitude (0.8–2 V) and duration (200 ns–7.6 ms). We show that the measurements are well described by a nucleation limited switching model, which enables extraction of the minimum switching time and the probability distribution of local electric field variations in the polycrystalline film. The close model fit spanning 5 orders of magnitude in pulse duration indicates the applicability of this model to HZO. This characterization framework can be used to quantify, compare, and optimize the switching dynamics of ferroelectric HZO.

Physical Insights on the Dynamic Response of SOI n- and p-Type Junc-tionless Nanowire Transistors

This work evaluates, for the first time, the roles of the intrinsic capacitances and the series resistance on the dynamic response of p- and n-type Junctionless Nanowire Transistors. The dynamic behavior evaluation will be carried out through the analysis of the limitation imposed by such parameters on the maximum oscillation frequency (fmax). In the sequence, it will be shown the impacts of fmax and the carriers’ transit time on the minimum switching time presented by JNTs. It has been observed that Junctionless devices present lower fmax than inversion mode transistors of similar dimensions due to higher resistance and lower transconductance. However, the intrinsic capacitances of such devices are smaller than the inversion mode ones, which compensates part of the degradation on fmax caused by the other parameters. Besides that, it is shown that transit time can be important on the dynamic behavior of long devices, but plays a negligible role in shorter ones.

A Fast-Switching (1.35-μs) Low-Control-Voltage (2.5-V) MEMS T/R Switch Monolithically Integrated With a Capacitive Micromachined Ultrasonic Transducer (CMUT).

This paper describes the design and fabrication of an electrostatic MEMS switch that can be co-fabricated on the same substrate with a capacitive micromachined ultrasonic transducer (CMUT) as a transmit/receive (T/R) switch. The structure of the switch is modified from a single CMUT cell. An interrupted transmission line is defined across the center of the cell with control electrodes on both sides to pull a movable plate down. The plate has an insulation layer underneath and a metal bump is formed on the insulation layer and aligned to the transmission line gap, so that the switch could be turned on by pulling down the plate with electrostatic force and making the metal bump close the gap in the transmission line. The switch was designed using a finite-element model (FEM) and fabricated on a glass substrate using anodic bonding. A static characterization was first performed on a switch test structure, which shows the dc switching voltage was 68 V and the on-resistance was 50 Ω. The RF in and RF out isolation was measured as approximately 66 dB and insertion loss was approximately 4.5 dB for frequency range commonly used for medical ultrasound imaging. Then we performed the dynamic characterization in immersion. By setting the dc bias at 67 V, we found that the switch could be operated with a control-voltage as low as 2.5 V. The switching and release times are related to the rise time and the fall time of the control signal, respectively. The minimum switching time was measured as 1.34 μs with a control signal rise time of 300 ns, and the minimum release time was measured as 80 ns with a control signal fall time of 20 ns. We further demonstrated that a 1-kHz control signal with the optimized rise and fall times can be used to conduct and block a sinusoidal signal with 1-MHz frequency and 300-mV pp amplitude, as well as unipolar pulses with 5-V pp amplitude, 500-ns pulse width, and 2-kHz repetition rate. The presented MEMS switch could potentially eliminate the high-voltage process requirement for the on-chip front-end electronics of a CMUT-based ultrasound imaging system and thus improve the overall system efficiency.

All-Photonic Switching of (Fe, Mg) Co-Doped PbS/PVA Nanocomposite Films Under a Pump Laser Illumination

A new all-photonic switching of nonlinear optical materials with very low signal/noise background was presented. Fe and Mg were used to prepare doped and co-doped PbS/PVA freestanding nanocomposite; films were prepared by a simple chemical method with different doping concentrations. The X-ray diffraction patterns, scanning electron microscope images, and optical absorption spectrum of the prepared films were examined. The crystallinity and optical band gap of the prepared co-doped PbS/PVA were found to be affected by Fe and Mg, doping concentrations. The all prepared samples showed a blue shift in the absorption spectra and the optical band gap was increased when the doping concentration is increased. The all-optical switching effect performance of metal doped and (Fe, Mg) co-doped PbS/PVA with various Fe and Mg concentrations were investigated. The results showed that the (Fe, Mg) co-doped PbS/PVA at 1.2%M Fe and 0.8%M Mg doping concentration can demonstrate an active all-photonic switching device and lead to the realization with maximum modulation depth of 86.5% and switching contrast of 8.8 dB at minimum switching time of 47 ms.

Strain-mediated magnetoelectric effect for the electric-field control of magnetic states in nanomagnets

Electric-field control of magnetism without electric currents potentially revolutionizes spintronics toward ultralow power. Here, by using mechanically coupled phase field simulations, we computationally demonstrate the application of the strain-mediated magnetoelectric effect for the electric-field control of magnetic states in a heterostructure. In the model heterostructure constituted of the soft nanomagnet Co and the piezoelectric substrate PMN–PT, both the volatility of magnetic states and the magnetization switching dynamics excited by the electric field are explored. It is found that an electric field can drive the single-domain nanomagnet into an equilibrium vortex state. The nanomagnet remains in the vortex state even after removing the electric field or applying a reverse electric field, i.e., the vortex state is extremely stable and nonvolatile. Only by utilizing the precessional magnetization dynamics, the 180 $$^\circ $$ magnetization switching is possible in small-sized nanomagnets which are free of the stable vortex state. Electric-field pulses can realize the deterministic 180 $$^\circ $$ switching if the electric-field magnitude, pulse width, and ramp time are carefully designed. The minimum switching time is found to be less than 10 ns. These results provide useful information for the design of low-power, reliable, and fast electric-field-controlled spintronics.

All-photonic switching based on selective input pump polarization states in Fe-doped PbS/PVA freestanding nanocomposite films

A new optical pump–probe technique for all-optical switching is proposed based on three-selective input pump polarization states to pump material simultaneously. The new technique makes it possible to obtain efficient all-optical switching of nonlinear optical materials with very low signal background and increased stability of switching signals. Undoped and Fe-doped PbS/PVA freestanding nanocomposite films are prepared by a simple chemical method at different doping concentrations. The x-ray diffraction patterns and optical absorption spectra of the prepared films are examined. The crystallinity and optical band gap of the prepared Fe-PbS/PVA are found to be affected by Fe doping concentration. The all-optical switching effect of Fe-PbS/PVA freestanding nanocomposite films with various Fe concentrations was investigated. The proposed technique that demonstrates all-optical switching with three-input polarization states can lead to the realization of all-photonic switching at a threshold optical pump power of 19 mW with maximum modulation depth (ON/OFF) of 86% and switching contrast (ON/OFF) of 8.6 dB for a minimum switching time of 43 ms.