Plasma wave interactions in the microwave to THz range between carriers in a semiconductor 2DEG and interdigital slow waves

Traveling wave interactions between the plasma wave in a two-dimensional electron gas (2DEG) in the AlGaAs/GaAs high electron mobility transistor (HEMT) structure and the electromagnetic space harmonic slow waves produced by interdigital metal electrodes were investigated both theoretically and experimentally. By means of a TM mode analysis, a general expression for the ω- and k-dependent effective permittivity of the 2DEG plasma was derived. The two-terminal admittance was calculated by a Green’s function method from the microwave to the THz wave region. Occurrences of negative admittance were predicted, and its peak values increased with frequency to a very large value in the THz region due to the reduction in the number of collisions per cycle. Preliminary admittance measurements at microwave frequencies showed good agreement with calculations, confirming the existence of plasma wave interactions.     

A faster 2-approximation algorithm for the minmax p-traveling salesmen problem on a tree

Given an edge-weighted tree T and an integer p1, the minmax p-traveling salesmen problem on a tree T asks to find p tours such that the union of the p tours covers all the vertices. The objective is to minimize the maximum of length of the p tours. It is known that the problem is NP-hard and has a (2−2/(p+1))-approximation algorithm which runs in O(p^p−1n^p−1) time for a tree with n vertices. In this paper, we consider an extension of the problem in which the set of vertices to be covered now can be chosen as a subset S of vertices and weights to process vertices in S are also introduced in the tour length. For the problem, we give an approximation algorithm that has the same performance guarantee, but runs in O((p−1)!·n) time.     

同轴型行波热声热机的实验研究

自行设计搭建了国际首台同轴型行波热声热机的实验装置 ,以氮气为工质 ,获得频率为1 3 7Hz的谐振声波。回热器热端温度达到 2 0 0℃左右时 ,热声热机开始起振 ,平均振幅 0 .1 4bar     

The exact solutions to (2+1)-dimensional nonlinear Schrǒdinger equation

By using the extended F-expansion method, the exact solutions,including periodic wave solutions expressed by Jacobi elliptic functions, for (2+1)-dimensional nonlinear Schrǒdinger equation are derived. In the limit cases, the solitary wave solutions and the other type of traveling wave solutions for the system are obtained.     

Existence and global stability of traveling curved fronts in the Allen-Cahn equations

This paper is concerned with existence and stability of traveling curved fronts for the Allen-Cahn equation in the two-dimensional space. By using the supersolution and the subsolution, we construct a traveling curved front, and show that it is the unique traveling wave solution between them. Our supersolution can be taken arbitrarily large, which implies some global asymptotic stability for the traveling curved front.     

A type of bounded traveling wave solutions for the Fornberg-Whitham equation

In this paper, by using bifurcation method, we successfully find the Fornberg-Whitham equation

ut−uxxt+ux=uuxxx−uux+3uxuxx,     

The asymptotic critical wave speed in a family of scalar reaction-diffusion equations

We study traveling wave solutions for the class of scalar reaction-diffusion equations

     

Dynamics of neuronal waves

First of all, by studying the existence and stability of traveling wave fronts of the following nonlinear nonlocal model equation

On the generalized Kadomtsev-Petviashvili equation with generalized evolution and variable coefficients

In this Letter, the existence of the solitary wave solution of the Kadomtsev-Petviashvili equation with generalized evolution and time-dependent coefficients will be studied. We use the solitary wave ansätze-method to derive these solutions. A couple of conserved quantities are also computed. Moreover, some figures are plotted to see the effects of the coefficient functions on the propagation and asymptotic characteristics of the solitary waves.