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The stability of viscoelastic pipes conveying fluid with the Zener fractional-order constitutive relationship is investigated in this paper. The pipe is subjected to the axial follower and directed forces with uniform distribution. The pipe’s beginning and end are restrained with lateral and rotational springs to satisfy a vast range of boundary conditions. The fluid flow effect is taken into account as a lateral distributed force. Based on the Euler-Bernoulli beam theory, the equation of motion is derived using the extended Hamilton’s principle. The Laplace transform and Galerkin method are used to obtain a set of algebraic equation. The pipe conveying fluid’s stability boundary will be obtained by calculating the roots of the determinant of the obtained equations coefficients. Effects of the fractional Zener viscoelastic model parameters are considered on the stability margin of pipes conveying fluid with different boundary conditions, and some conclusions are drawn.

Silicon carbide (SiC) MOSFET exhibits low channel resistance, low junction capacitances, and wider temperature range compared with silicon counterpart. However, the high dv=dt in a bridge-leg connected SiC MOSFETs induce the detrimental coupling noise, increasing device stress and EMI and restricting the converter operation at a high switching frequency. This paper presents two single-supply based variable gate voltage driving (SSVGVD) circuits for SiC MOSFETs to exploit the switching-speed capacity by mitigating the coupling noise during switching transients. Both driver circuits employ a simple auxiliary circuits comprising a transistor, zener diode, and resistor to control the gate voltage of power devices in a bridge-leg configuration. The proposed driver circuit can be easily realized with a driver IC using only positive driver supply, offering a compact, low-cost, and reliable solution. Experimental tests with SiC MOSFETs demonstrate the effectiveness of the SSVGVD gate driver.

Wide-bandgap and silicon power semiconductor devices require advanced pulsewidth gate-driver capability to successfully convert power for high-performance operation. In this article, a simplified forward isolated resonant converter structure with an integrated planar transformer is proposed, a cost-effective solution which eliminates the need of an output filter inductor while rearranging the clamp circuit for reduced component ratings and voltage stress. The first design option uses a simple back-to-back Zener diode voltage clamp circuit for low-power dc–dc isolated power supply applications. The second design employs a lossless voltage-clamped converter with auxiliary energy-recovering winding with an application example for an isolated gate-driver power supply. Through analysis of the converter, the switching frequency has been selected in relationship to the transformer inductance and the equivalent circuit capacitance for the benefit of soft-switching power device transitions. The proposed resonant converter structure features an integrated planar transformer designed with a specific layer disposition to ensure low interwinding capacitance. The converter offers isolated supplies for a gate-driver power devices pair, such as half-bridge SiC devices. The simulation and experimental results are obtained from a gate-driver application platform to demonstrate the validity of the proposed isolated dc–dc converter design and integrated planar transformer with a total conversion efficiency of 87.7%.

Accurate modeling of material behavior is very critical for the success of magnetorheological elastomer-based semi-active control device. The material property of magnetorheological elastomer is sensitive to the frequency, magnetic field and the input strain. Additionally, these properties are unique for a particular combination of matrix and the filler loading. An experimental-based characterization approach is costly and time consuming as it demands a large amount of experimental data. This process can be simplified by adopting material modeling approach. The material modeling of magnetorheological elastomer is an extension of conventional viscoelastic constitutive relations coupled with hysteresis and magnetic field sensitive attributes. In the present study, a mathematical relation to represent the frequency, magnetic field and strain dependent behavior of magnetorheological elastomer is presented. The viscoelastic behavior is represented by a fractional zener element and the magnetic field and strain dependent attributes incorporated in the model by a magnetic spring and linearized Bouc-–Wen element, respectively. The proposed model comprised of a total of eight parameters, which are identified by minimizing the least square error between the model predicted and the experimental response. The variations of each parameter with respect to the operating conditions are represented by a generalized expression. The parameters estimated from the generalized expression are used to assess the ability of the model in describing the dynamic response of magnetorheological elastomer. The proposed model effectively predicted the stiffness characteristics with an accuracy, more than 94.3% and the corresponding accuracy in predicting the damping properties is above 90.1%. This model is capable of fitting the experimental value with a fitness value of more than 93.22%.

Wireless network becoming an integral part of daily existence, and it is expected to become much more so in the future. The dual-band frequency-reconfigurable H-shaped microstrip antenna fed by two...

Compared with the thin plate production process, the behavior of NbC precipitating would be different in thicker plate from the rolling processing due to reduction ratio conditions. The mechanism of epitaxial growth of NbC precipitating along with TiN particles was observed. The distribution of TiN particles, which influenced by N content in steels, would determine the distribution of the combined TiN + NbC particles by transmission electron microscopy. TiN particle is a high-temperature precipitate. The TiN particle is precipitated completely before the NbC particle is precipitated. It is concluded that the distribution of TiN was most important factor to control austenite grain size by Zener drag force. When the N content was higher in the steel would result in the coarser TiN particles which are harmful to controlling the size in roughing. Increasing of N content did not lead to an increase in the Zener drag force to control austenite grain size.

In this work, the influence of varying mixing ratios of O-2 on positive streamer initiation in supercritical (SC) CO2 at different applied voltages was investigated using a 3-D particle model. Zener's model was included in the 3-D particle model to calculate the field ionization rate during streamer formation and propagation. The evolution of positive streamer was classified into three main stages namely inception cloud, primary streamer channels, and successive streamer branching. The effect of O-2 with different mixing ratios (2%, 10%, and 20%) on the morphology, average electron density, electric field distribution, streamer length, and electron energy distribution function (EEDF) for positive streamer in SC-CO2 at four different voltages (12, 12.5, 13, and 13.5 kV) is then investigated. The 2-D cross sections of the initial stage of the streamer and the electric field distribution are presented in detail. At the same applied voltage, the size of inception cloud, average electron density, electric field, and streamer length with the maximum electric field decreased with increasing oxygen concentration in SC-CO2. With increasing applied voltage, the apparent size of inception cloud, primary streamer channels, successive streamer branching, average electron density, electric field, and streamer length increased. The simulation results showed that adding O-2 to SC-CO2 can significantly affect the streamer initiation and propagation.

The presented work concerns the kinematically excited transient vibrations of a cantilever beam with a mass element fixed to its free end. The Euler–Bernoulli beam theory and the fractional Zener model of the beam material are assumed. A fractional Caputo derivative is used to formulate a viscoelastic material law. A characteristic equation, modal frequencies, eigenfunction and orthogonality conditions are achieved for the beam considered. The equations of motion of the system are solved numerically. A numerical solution of a multi-term fractional differential equation is obtained by means of a conversion to a mixed system of ordinary and fractional differential equations, each of the order of $$0 < \gamma \le 1$$ 0 < γ ≤ 1 . The transient time histories of the beam vibrations during the passage through resonance are calculated. A comparison between the beam responses obtained with a fractional and an integer viscoelastic material model is presented. The calculations performed reveal that use of the fractional damping affects on the time histories of the system. The calculated beam responses show that for some values of the order of the fractional derivative $$\gamma$$ γ , the amplitudes occurring in the area of the second resonance are greater than those obtained in the area of the first resonance, which does not occur in the case of the integer order of the fractional derivative. Moreover, an evaluation is made of the difference between the results obtained for the calculations using the fractional Zener model and the fractional Kelvin model. It is shown that for some physical beam parameters, the calculation results obtained using both models are virtually the same for both models, which means that the the simpler, fractional Kelvin–Voigt material can be used instead of the fractional Zener material model. This simplifies the solution and decreases the time needed to make the numerical calculations.

The quantum ballistic transmission properties of an electrically-doped guanine-nanosheet-based bio-Zener diode are investigated using density functional theory and nonequilibrium Green’s function-based first-principles calculations. The bio-Zener diode is gate-bias modulated, and its various quantum-electronic properties, for example, the V–I characteristic, the transmission spectra, and the device density of states, depend on both the electrical doping concentration and on the applied gate bias voltage. The junctionless highly doped bio-Zener diode shows high levels of reverse-bias current which is dominated by majority charge carriers. It is also found that, due to the presence of a wide bandgap and the backscattering effect, the forward-bias current is highly suppressed. The quantum simulation results confirm a strong reverse gate-bias-modulated biased current–voltage response as well as a charge transport phenomenon through the effective device region. The bio-Zener diode exhibits a specific reverse breakdown that can be varied from −0.78 to −3.2 V without affecting the forward current–voltage characteristic. The current findings are obtained by including the coherent tunneling and incoherent hopping processes with a minimal Hamiltonian model approach.

Previously reported experiments suggest that aspects of the physical environment, in particular measures of negentropy (i.e., order) associated with the statistical outputs of truly random number generators, may be affected during periods of focused mental attention. The present study was designed to conceptually replicate those reports during energy medicine sessions.A custom-built "quantum noise generator" (QNG) was used to continuously record and digitize (at 1 KHz) 16 independent channels of random samples (i.e., noise) produced by electron tunneling and avalanche effects in Zener diodes. One metric was developed to quantify temporal dependencies in the noise samples aggregated across the 16 channels, and a second metric was formed that measured spatial dependencies among the 16 channels. The two metrics were combined into a single "spacetime" variable used to measure fluctuations in entropy during 110 half-hour energy medicine sessions. As a control, the same measure was examined in data recorded eight hours after each energy medicine session took place, when no one was in the laboratory.QNG data recorded during the half-hour sessions showed significant deviations from chance expectation, with a peak deviation observed at 24 minutes into the half-hour (z = 4.24, p 0.00003, two-tail), and with deviations associated with p 0.05 from 20 to 29 min, after correction for multiple comparisons. By comparison, data recorded eight hours after each session showed uniformly null results. This outcome is consistent with previously reported studies, suggesting that during periods of focused attention negentropic deviations emerge in random physical systems. Counterarguments to this interpretation are discussed, as well as recommendations for future studies.

This study implemented a 30 kW, 750 Vdc, silicon-carbide (SiC)-based uninterruptible power supply(UPS) applied it on a three-phase four-leg inverter. For component selection, LC filter and DC-link capacitor were designed based on the PSIM simulation. SiC MOSFET was used to achieve higher efficiency and better reliability than the conventional Si IGBT-based UPS applications. Furthermore, desaturation (DeSat) protection method was applied to protect the overcurrent during the short-circuit condition of SiC MOSFET. Thus, the DeSat protection method was applied to SiC MOSFET, thereby enabling a 1 μs protection by complementally switching and zener diode voltage optimization. Accordingly, the transient time of the DeSat protection can be disregarded, thereby enabling fast protection. Meanwhile, several topologies have been studied for unbalanced loads compensation. The current research used a three-phase four-leg inverter topology for compactness and neutral current control. In addition, voltage compensation became possible even in unbalanced load condition by introducing a dual-loop controller for the three-phase four-leg inverter. A dual-loop controller comprises PR and PI controllers to the stationary αβo and synchronous dqo reference frames, respectively. Thermal and efficiency tests were also performed in the rated power test. Under a 30 kW load condition, the surface epoxy molding compound temperature of SiC MOSFET was approximately 72 °C, and the highest efficiency was approximately 99.1% under 10 kW load condition. Finally, the effectiveness of the implementation was demonstrated through the experiment results.