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The purpose of this paper is to present an analytical model and simulation for cylindrical gate all around MOSFTEs including quantum effects.

To incorporating the impact of quantum effects, the authors have used variational method for solving the Poisson and Schrodinger equations. The accuracy of the results obtained using this model is verified by comparing them with simulation results.

This model is developed to provide an analytical expression for inversion charge distribution function for all regions of device operation. This expression is used to calculate the other important parameters like inversion charge centroid, threshold voltage, inversion charge, gate capacitance and drain current. The calculated expressions for the above parameters are simple and accurate. The validity of this model was checked for the devices with different dimensions and bias voltages.

Simulation based on the compact physical models reduces the cost of developing a sophisticated fabrication technology and shortens the time-to-market. They may also be utilized to explore innovative device structures.

This paper presents, for the first time, a compact quantum analytical model for cylindrical surrounding gate MOSFETs which predicts the device characteristics reasonably well over the entire range of device operation (above threshold as well as sub-threshold region).

A numerical study is reported of natural convection melting of ice within a vertical cylinder. A stream function‐vorticity‐temperature formulation is employed in conjunction with body‐fitted coordinates for tracking the irregular shape of the timewise varying solid‐liquid interface. A parabolic density profile versus temperature is assumed for water. Numerical experiments are carried out for a temperature of the cylinder wall ranging from 4°C to 10°C. Results show that natural convection heat transfer involving density anomaly leads to complex flow patterns and strongly affects the time evolution of the phase front. The maximum Nusselt number at the heated cylinder wall is obtained for Tw = 4°C while the minimum is observed for Tw = 8°C.

The purpose of this paper is to analyse the buoyancy flow, mass and heat transfer in coaxial duct under Soret and Dufour effect. The combined effects of the thermal-diffusion and diffusion-thermo coefficients, as well as the Schmidt number, on natural convection in a heated lower coaxial curve were explored using the proposed physical model. The Dufour and Soret effects are taken into consideration in the energy and concentration equations, respectively.

The dominating mathematical models are converted into a set of non-linear coupled partial differential equations, which are solved using a numerical approach. The controlling non-linear boundary value problem is numerically solved using the penalty finite element method with Galerkin’s weighted residual scheme over the entire variety of essential parameters.

It was observed that different parameters were tested such as heat generation or absorption coefficient, buoyancy ratio, Soret coefficient, Dufour coefficient, Lewis number and Rayleigh number. Effect of Rayleigh number, absorption/generation and Dufour coefficient on isotherm are significantly reported. For greater values of Lewis number, maximum mass transfer in duct in the form of molecular particles is produced. Buoyancy ratio parameter decreases the average rate of heat flow and increases its mass transfer.

The main originality of this work is to make an application of Soret and Dufour effects in a coaxial duct in the presence of source sink.

The stability of two‐dimensional natural convection of water near its density maximum (cold water) inside a vertical rectangular enclosure with an aspect ratio of eight is investigated via a series of direct numerical simulations. The simulations aim to clarify, under the influence of density inversion, the physical nature of the instability mechanism responsible for the laminar buoyancy‐driven flow transition from a steady state to an oscillatory state in the enclosure filled with cold water. Two values of the density inversion parameter, _m= 0.4 and 0.5, where the density inversion of cold water may exert strong influence on the flow, are considered in the present study. The results show that the transition from steady state to periodically oscillatory convection arises in the cold‐water‐filled enclosure through a Hopf bifurcation. The oscillatory convection in the water‐filled enclosure for both values of _m is found to feature an oscillatory multicellular structure within the contra‐rotating bicellular flow regions. A traveling wave motion accordingly results along the maximum density contour, which demarcates the contra‐rotating bicellular flows in the enclosure. For both cases the nature of transition into unsteadiness is found to be buoyancy‐driven. The critical Rayleigh number for the bifurcation at _m = 0.4 is found to be markedly higher than that at _m = 0.5.

The aim of the present study is to analyze the natural convection flow and heat transfer of cold water around °C in a square porous cavity. The horizontal walls of cavity are adiabatic, and the vertical walls are maintained at different temperatures. The right side wall is maintained at temperature θ_c, and the left side wall is maintained at sinusoidal temperature distribution.

The Brinkman–Forchheimer-extended Darcy model for porous medium is used to study the effects of density inversion parameter, Rayleigh number and impact of Darcy number and porosity. The finite volume method is used to solve the governing equations.

The heat transfer rate is increased on increasing the Darcy number and porosity. Also, the convective heat transfer rate is decreased first and then increased on increasing the density inversion parameter.

The numerical computations have been carried out for the Darcy number ranging of 10⁽⁻⁴⁾ ≤ Da ≤ 10⁽⁻¹⁾, the porosity ranging of 0.4 ≤ ε ≤ 0.8 and the density inversion parameter ranging of 0 ≤ T_m ≤ 1 and keeping Ra = 10⁶.

The results can be used in the cooling of electronic components, thermal storage system and in heat exchangers.

The choice of consideration of sinusoidal heating and density maximum effect produces good result in flow field and temperature distribution. The obtained results can be used in various fields.

By generalizing the equation of state of the conduction electron gas in a semiconductor to include a dependence not only on electron density but also on the density gradient we show that the standard diffusion‐drift description can be extended to describe much of the quantum mechanical behavior exhibited by strong inversion layers.

Numerical simulations have been performed for three‐dimensional natural convection of water near its maximum‐density (cold water) inside rectangular enclosures with differential heating at the vertical (left and right) walls. The horizontal (top and bottom) walls and the lateral (front and rear) walls are taken as insulated. Computations are performed for the buoyancy‐driven convection of cold water with density inversion parameter θ_m = 0.5 in the enclosures with aspect ratio (height/width) A_y = 8 and depth ratios (depth/width) A_z = 0.5, 1, and 2. The influence of the depth ratio on the onset of oscillatory convection in a cold‐water‐filled enclosure is investigated. The presence of the lateral walls tends to suppress the onset of unsteadiness in the convective flow. The main features of the oscillatory convection flow and temperature fields as well as the instability mechanism in the three‐dimensional enclosure were similar to those found in the two‐dimensional model. However, there exists a strong three‐dimensionality in the spatial distribution of the fluctuation amplitude. With the decrease of the depth ratio, the damping effect of the lateral walls becomes increasingly pronounced, leading to a reduced heat transfer rate.

A numerical study of the flow in and heat transfer across a vertical cavity containing pure water when the aspect ratio of the cavity is low, i.e. 1 or less, has been undertaken. One vertical wall of the cavity is kept at a temperature that is below the freezing point of water while the opposite wall is kept at a temperature that is above this freezing temperature. Ice therefore forms in part of the cavity, the conditions being such that there can be significant natural convection in the water. The upper surface of the cavity is open i.e. the water has a free surface, heat transfer from this surface being assumed negligible. The lower surface of the cavity is assumed to be adiabatic. Only the steady state has been considered here. It has been assumed that the flow is laminar and two‐dimensional and that liquid and solid properties are constant except for the water density change with temperature which gives rise to the buoyancy forces. The governing equations have been written in dimensionless form and these equations have been solved using a finite element‐based procedure in which the position of the solid‐liquid interface is obtained using an iterative approach. Solutions have been obtained for modified Rayleigh numbers of between 10³ and 10⁸ for various degrees of under‐cooling and for cavity aspect ratios of between 0.25 and 1. The density inversion that occurs with water has been shown to have a large effect on the steady state freezing of water in a cavity. The aspect ratio of the cavity has also been shown to have a significant influence on the results when the aspect ratio is less than 0.5.

The present experiments are intended to help characterize defects in very thin MOS oxide and at its Si/SiO₂ interface using a temperature‐dependent electrical characterization method, high low temperature capacitance voltage method and, especially, to investigate high temperature range. Oxide‐fixed traps are differentiated from slow‐state traps and from fast‐state traps by evaluating their electrical behaviour at different temperatures. The analysis points out the excess current after Fowler Nordheim electron injection based on hole generation, trapping, and hopping transport at high temperatures. The defect relaxation property versus temperature is investigated and defect relaxation activation energies are calculated. Creation mechanisms of interface states are especially identified by injection at different temperatures and these are compared with the other two kinds of defects. Fast‐state traps and all defect cross‐sections are calculated along and their creation activation energies are determined from Arrhenius plots.

To investigate the effect of viscous dissipation on unsteady, combined convective heat transfer to water near its density maximum in a rectangular cavity.

The upwind finite difference scheme along with successive over relaxation iteration technique is used to solve the governing equations for mixed convection flow of water with density maximum inversion in a rectangular cavity.

The effect of viscous dissipation was to increase the fluid temperature and resulted in the formation of vortex motion near the lower part of the cavity in an opposite direction to the central vortex. An increase in the Eckert number and Reynolds number of the flow resulted in augmented surface heat transfer rates from the top heated surface.

The analysis is valid for unsteady, two dimensional laminar flow. Isothermal conditions are assumed for the top and bottom walls. An extension to unsteady three dimensional flow case is left for future work.

The method is very useful to analyze nuclear reactor thermal/hydraulic loss of coolant transients, energy conservation, ventilation of rooms, solar energy collection, cooling of electronic equipment, dispersion of waste heat in estuaries and crystal growth in liquids.

The results of this study may be of interest to engineers interested in heat transfer augmentation of mixed convection in window cavities.