scholarly journals A Higher-Order Accurate Operator Splitting Spectral Method for The Wigner-Poisson System

2021 ◽  
Author(s):  
Zhenzhu Chen ◽  
Sihong Shao
Keyword(s):  
Phase Space ◽  
Spectral Method ◽  
Poisson Equation ◽  
Operator Splitting ◽  
Coupled System ◽  
Oxide Semiconductor ◽  
Wigner Equation ◽  
Current Voltage ◽  
Spectral Convergence ◽  
Long Time

Abstract An accurate description of 2-D quantum transport in a double-gate metal oxide semiconductor filed effect transistor (dgMOSFET) requires a high-resolution solver to a coupled system of the 4-D Wigner equation and 2-D Poisson equation. In this paper, we propose an operator splitting spectral method to evolve such Wigner-Poisson (WP) system in 4-D phase space with high accuracy. After an operator splitting of the Wigner equation, the resulting two sub-equations can be solved analytically with spectral approximation in phase space. Meanwhile, we adopt a Chebyshev spectral method to solve the Poisson equation. Spectral convergence in phase space and a fourth-order accuracy in time are both numerically verified. Finally, we apply the proposed solver into simulating dgMOSFET, develop the steady states from long-time simulations and obtain numerically converged current-voltage (I-V) curves.

Instability of 4H-SiC MOSFET Characteristics due to Interface Traps with Long Time Constants

2011 ◽  
Vol 679-680 ◽  
pp. 603-606 ◽  
Author(s):  
Hiroshi Yano ◽  
Yuki Oshiro ◽  
Dai Okamoto ◽  
Tomoaki Hatayama ◽  
Takashi Fuyuki
Keyword(s):  
Field Effect Transistor ◽  
Pulse Current ◽  
Oxide Semiconductor ◽  
Interface Traps ◽  
Gate Oxides ◽  
Time Constants ◽  
Large Hysteresis ◽  
Current Voltage ◽  
Long Time ◽  
Effect Transistor

Instability of metal-oxide-semiconductor field-effect transistor (MOSFET) characteristics was evaluated by DC and pulse current-voltage (I-V) measurements. MOSFETs with nirided gate oxides were fabricated on C-face 4H-SiC. Their interfaces have near interface traps (NITs) with long time constants, depending on the cooling down process after nitridation. Such devices exhibited a large hysteresis in DC I-V and a large transient current in pulse I-V measurements. These phenomena can be explained by the charge state of NITs due to capture/emission of electrons in the channel.

scholarly journals Quasi-stability and continuity of attractors for nonlinear system of wave equations

2021 ◽  
Vol 8 (1) ◽  
pp. 27-45
Author(s):  
M. M. Freitas ◽  
M. J. Dos Santos ◽  
A. J. A. Ramos ◽  
M. S. Vinhote ◽  
M. L. Santos
Keyword(s):  
Wave Equations ◽  
Coupled System ◽  
Global Attractors ◽  
Time Behavior ◽  
Exponential Attractors ◽  
Small Perturbations ◽  
Recent Approach ◽  
Nonlinear Coupled System ◽  
Long Time ◽  
External Forces

Abstract In this paper, we study the long-time behavior of a nonlinear coupled system of wave equations with damping terms and subjected to small perturbations of autonomous external forces. Using the recent approach by Chueshov and Lasiecka in [21], we prove that this dynamical system is quasi-stable by establishing a quasistability estimate, as consequence, the existence of global and exponential attractors is proved. Finally, we investigate the upper and lower semicontinuity of global attractors under autonomous perturbations.

scholarly journals Study and Assessment of Defect and Trap Effects on the Current Capabilities of a 4H-SiC-Based Power MOSFET

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 735
Author(s):  
Fortunato Pezzimenti ◽  
Hichem Bencherif ◽  
Giuseppe De Martino ◽  
Lakhdar Dehimi ◽  
Riccardo Carotenuto ◽  
...  
Keyword(s):  
Drain Current ◽  
Oxide Semiconductor ◽  
Temperature Dependent ◽  
Channel Mobility ◽  
Blocking Voltage ◽  
Current Voltage ◽  
Wide Range ◽  
Temperature Ranges ◽  
Joint Contribution ◽  
State Resistance

A numerical simulation study accounting for trap and defect effects on the current-voltage characteristics of a 4H-SiC-based power metal-oxide-semiconductor field effect transistor (MOSFET) is performed in a wide range of temperatures and bias conditions. In particular, the most penalizing native defects in the starting substrate (i.e., EH6/7 and Z1/2) as well as the fixed oxide trap concentration and the density of states (DoS) at the 4H-SiC/SiO2 interface are carefully taken into account. The temperature-dependent physics of the interface traps are considered in detail. Scattering phenomena related to the joint contribution of defects and traps shift the MOSFET threshold voltage, reduce the channel mobility, and penalize the device current capabilities. However, while the MOSFET on-state resistance (RON) tends to increase with scattering centers, the sensitivity of the drain current to the temperature decreases especially when the device is operating at a high gate voltage (VGS). Assuming the temperature ranges from 300 K to 573 K, RON is about 2.5 MΩ·µm2 for VGS > 16 V with a percentage variation ΔRON lower than 20%. The device is rated to perform a blocking voltage of 650 V.

Characterization of dogfish gastric mucosa under hyperbaric conditions

1983 ◽  
Vol 245 (2) ◽  
pp. G236-G241
Author(s):  
G. W. Kidder
Keyword(s):  
Gastric Mucosa ◽  
Transient Response ◽  
Partial Pressure Of Oxygen ◽  
Urea Content ◽  
Current Voltage ◽  
Current Passage ◽  
Long Time ◽  
Voltage Clamping ◽  
Hyperbaric Conditions

Using hyperbaric conditions previously shown to give improved oxygen delivery to the chambered dogfish gastric mucosa, experiments were performed to further characterize this tissue under these conditions. Removal of Cl- depressed but did not abolish acid secretion, raised the transepithelial resistance, and caused the potential to become more negative with reference to the mucosal surface. Voltage clamping to -60 mV inhibited secretion significantly; voltage clamping to +60 mV sometimes gave a stimulation. There was no long time-constant transient response to current passage. Under hyperbaric conditions, addition of the normal 350 mM urea content of elasmobranch plasma stimulated secretion. A further increase in partial pressure of oxygen (PO2) above 1.9 atm had no effect on secretion. The current-voltage plot showed two breakpoints, one about -23 mV and a second (not always detectable) at +50 mV; the negative breakpoint was stable as PO2 changed from 0.9 to 1.9 atm. Many of these observations are different from those reported for normabaric tissue and closely resemble those in the isolated frog gastric mucosa.

scholarly journals Conditional Entropy: A Tool to Explore the Phase Space

1999 ◽  
Vol 172 ◽  
pp. 195-209
Author(s):  
P. Cincotta ◽  
C. Simó
Keyword(s):  
Phase Space ◽  
Chaotic Motion ◽  
Conditional Entropy ◽  
Characteristic Number ◽  
Random Variable ◽  
Arc Length ◽  
Unstable Periodic Orbits ◽  
Long Time ◽  
Stable Periodic ◽  
Lyapunov Characteristic Number

AbstractIn this paper we show that the Conditional Entropy of nearby orbits may be a useful tool to explore the phase space associated to a given Hamiltonian. The arc length parameter along the orbits, instead of the time, is used as a random variable to compute the entropy. In the first part of this work we summarise the main analytical results to support this tool while, in the second part, we present numerical evidence that this technique is able to localise (stable) periodic and quasiperiodic orbits, ‘aperiodic’ orbits (chaotic motion) and unstable periodic orbits (the ‘source’ of chaotic motion). Besides, we show that this technique provides a measure of chaos which is similar to that given by the largest Lyapunov Characteristic Number. It is important to remark that this method is very simple to compute and does not require long time integrations, just realistic physical times.

scholarly journals Phase Space Analysis of Pig Ear Skin Temperature during Air and Road Transport

2019 ◽  
Vol 9 (24) ◽  
pp. 5527
Author(s):  
Miguel Garrido-Izard ◽  
Eva-Cristina Correa ◽  
José-María Requejo ◽  
Morris Villarroel ◽  
Belén Diezma
Keyword(s):  
Time Series ◽  
Phase Space ◽  
Skin Temperature ◽  
Road Transport ◽  
Thermal Data ◽  
Intercontinental Transport ◽  
Long Time ◽  
65 H ◽  
Thermal Variability ◽  
Space Phase

High or variable ambient temperature can affect thermal regulation in livestock, but few studies have studied thermal variability during air and road transport, partly due to the lack of tools to compare thermal data from a long time series over periods of different duration. In this study, we recorded the ear skin temperature (EST) of 11 Duroc breeder pigs (7 females and 4 males) during commercial intercontinental transport from Canada to Spain, which included both road and aircraft travel and lasted 65 h. The EST was measured using a logger placed inside the left ear. Phase space diagrams EST, that is EST time series vs. itself delayed in time, were used to quantify the variability of the time-temperature series based on the areas that included all the points in the phase space. Phase space areas were significantly higher for all the animals during air travel, almost doubling that of road transport. Using the phase spaces, we identified an event during air transport that lasted 57 min, leading to a general decrease in EST by 8 °C, with respect to the average EST (34.1 °C). We also found that thermal variability was more stable in males (F = 20.81, p = 0.0014), which were also older and heavier.

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