Effects of gate underlap on electronic properties of conventional single-material-gate CNTFET (C-CNTFET) and heteromaterial-gate CNTFET (HMG-CNTFET) are investigated theoretically in a quantum kinetic model.The model is based on twodimensional non-equilibrium Green's functions (NEGF) solved self-consistently with Poisson's equations.It shows that intrinsic cutoff frequency of C-CNTFETs reaches a few THz.In addition,a comparison study was performed about C-and HMG-CNTFETs.Calculated results show that,C-CNTFETs with longer underlap have better switching speed but less on/off current ratios.For HMG-CNTFET,gate underlap improves sub-threshold performance and switching delay times,and decreases output conductance significantly.

Ballistic performance of single-material-gate and triple-material-gate graphene nanoribbon field effect transistors (GNRFETs) with various doping profiles is studied in a quantum kinetic model based on non-equilibrium Green's functions (NEGF) solved self-consistently with Poisson's equations.It shows that triple-material-gate GNRFET with linear doping (TL-GNRFET) exhibits significant advantage in reducing SCEs and DIBL effects,as well as achieving better subthreshold slope and better on/off current ratio.In addition,asymmetric gate underlap is also discussed.It is revealed that as top and bottom gates are both shifted towards source on/off state current performance is improved.

A linear difference scheme which is not coupled for a coupled nonlinear Schrodinger system is proposed. It is shown that the scheme reserves conservation of the original system. It is demonstrated with a discrete energy method that the scheme is unconditionally stable and convergent by second-order L₂ in norm on basis of some priori estimates. Collision of two solitary waves is simulated.

A two-level implicit scheme for Burgers equations is shown,whose truncation error is O(τ²+h²) (where τ is time step and h is space step).An alternating segment method is proposed and its unconditional linear stability is proved.The new method is free from nonphysical oscillations and suitable for parallel computers.A numerical example shows that the method has good applicability and high accuracy, in particular, it is more accurate when diffusion coefficient is small.

A new finite difference scheme is proposed for radial symmetric nonlinear Schrödinger equation. This is a scheme of three levels which needn't to iterate. Thus, the new scheme requires less CPU time. Convergence and stability of the new scheme are proved. By means of numerical computation, it is followed that the new scheme is efficient.

A new conservative difference scheme is proposed for nonlinear Schrödinger equation, and its convergence and stability are proved. By means of numerical computing, the discretization for nonlinear term of nonlinear Schrödinger equation is discussed, and it is followed that the new difference scheme is better than the scheme of paper[7] which is a special case of the new scheme in precision, when suitable parameter is adopted.

A finite difference of energy conservation is proposed for nonlinear Klein Gordon (NKG) equation.Its convergence and stability have been proved.Results of numerical computation are also analysed.

SCM finite difference method for solving inviscid subsonic, transonic and supersonic flow over spherical cone is presented. This method is based on the mathematical theory of characteristics.In the SCM approach these coefficients are split according to the sign of the chara-oteristic slopes. The split coefficients are multiplied by appropriate one-sided. F orwardiffe-rences are associated with negative characteristic stopes, while baokward diflerchces are associated with positive slope values.In the SCM technique the governing Euler equations are solved by a secondorder accurate finit difference elgori thm in a predictor-corrector sequence. To maintain Secondorder spatial accuracy for the one-sided derivatives associated with the split coefficients the discretization formulas alternate between two-point and three -point approximation.The numerical example of the blunt spherecones have been worked in this paper and compared with Conventional finite difference to demonstrate good accuracy of SCM in rate mesh.