Transport and Coulomb drag for two interacting carbon nanotubes

We study nonlinear transport for two coupled one-dimensional quantum wires or carbon nanotubes described by Luttinger liquid theory. Transport properties are shown to crucially depend on the contact length L _c. For a special interaction strength, the problem can be solved analytically for arbitrary L _c. For point-like contacts and strong interactions, a qualitatively different picture compared to a Fermi liquid emerges, characterized by zero-bias anomalies and strong dependence on the applied cross voltage. In addition, pronounced Coulomb drag phenomena are important for extended contacts. Received 28 July 2000     

热原子核巨共振的微观研究——巨共振的衰变与热核的性质

运用微观多体理论,对热原子核巨四极共振进行了比较研究,发现两体关联密度矩阵理论能更好地描述热核的巨共振衰变和热核的其它性质.     

Calculation of pulsed NMR signal in I = 3/2 quadrupolar spin system

The rf pulse response of I=3/2 spin system experiencing first order quadrupolar splitting is studied using density matrix approach. A general expression is derived in terms of spin populations, quadrupole splitting and duration and amplitude of the rf pulse for calculating the NMR signal arising due to the centre line and satellite resonances for the situation where the impressed rf pulse excites the resonances selectively as well as non-selectively. The necessary 4×4 transformation matrix obtained analytically by diagonalyzing the Hamiltonian are used to get the expression for the centre line response. The satellite signals are obtained in the same way but by using the numerical values of the roots of the related quartics. The widths of the corresponding π/2-pulses are calculated for different initial spin populations. The variations of this pulse-width and the corresponding signal amplitude as a function of satellite splitting are studied.     

The Dilute Potts Model on Random Surfaces

We present a new solution of the asymmetric two-matrix model in the large-N limit which only involves a saddle point analysis. The model can be interpreted as Ising in the presence of a magnetic field, on random dynamical lattices with the topology of the sphere (resp. the disk) for closed (resp. open) surfaces; we elaborate on the resulting phase diagram. The method can be equally well applied to a more general (Q+1)-matrix model which represents the dilute Potts model on random dynamical lattices. We discuss in particular duality of boundary conditions for open random surfaces.     

线性分段折射率分布多量子阱波导色散关系的精确分析

本文从标量Helmholtz方程出发,采用转移矩阵技术,求出了线性分段折射率分布多量子阶波导TE模色散关系的精确解,数值计算结果显示出该波导的色散特性以及与波导结构的关系,为实际制作该量子阶波导进行参数选择提供了理论依据。     

Fermilab top mass and modified Fritzsch mass matrices

Fritzsch like mass matrices with non-zero 22-elements both in U sector and D sector have been investigated in the context of latest data regardingm _t ^phys , |V _ub|, |V _cb|, |V _td| and |V _ts|. Unlike several other phenomenological models, the present model not only accommodates the value ofm _t ^phys in the range 150–240 GeV, encompassing the CDF and D0 values, but is also able to reproduce |V _cb| ≊0.040 and |V _ub/V_cb| = 0.08±0.02 and |V _td| is predicted to lie in the range 0.005–0.014. Further, the angles of the unitarity triangle, related to the CP-violating asymmetries, are calculated to be in the ranges −1.0⩽sin2α⩽−0.1, 0.6 ⩽sin2α⩽1.0 and 0.48⩽sin2β⩽0.56, which are in agreement with other recent calculations.     

基于蒙卡和粒子示踪程序的电子成像模拟分析

借助理论分析和数值模拟,设计了基于高能电子束团的辐射成像系统,并通过Geant4和GPT软件对成像系统的相关参数进行了优化。模拟中分析了影响系统空间分辨率及物质厚度分辨率的因素,结果显示,模拟中设计的成像系统空间分辨率达到m量级,并且具有一定的厚度分辨能力。该设计指标满足对一定厚度及结构的样品进行成像的要求。     

A framework for classification with single feature kernel matrix

In this paper, we propose a novel classification framework using single feature kernel matrix. Different from the traditional kernel matrices which make use of the whole features of samples to build the kernel matrix, this research uses features of the same dimension of any two samples to build a sub-kernel matrix and sums up all the sub-kernel matrices to get the single feature kernel matrix. We also use single feature kernel matrix to build a new SVM classifier, and adapt SMO (Sequential Minimal Optimization) algorithm to solve the problem of SVM classifier. The results of the experiments on several artificial datasets and some challenging public cancer datasets display the classification performance of the algorithm. The comparisons between our algorithm and L₂-norm SVM on the cancer datasets demonstrate that the accuracy of our algorithm is higher, and the number of support vectors selected is fewer, indicating that our proposed framework is a more practical approach.     

Two matrix algorithms for eigenmodes of a Bessel-Gauss resonator

A Bessel-Gauss resonator (BGR) was proposed to produce the Bessel Gauss beams. In this paper transverse profiles and their corresponding losses of the BGR are computed by use of the entire matrix formalism and the transfer matrix method, and the computation results from two algorithms are compared. The computation results show that for the BGR there is no inconsistence in the mode fields yielded by two methods, and the transfer matrix methods are more accurate in the mode losses than the entire matrix formalism, which lead to a believable conclusion that the BGR with a convex-spherical mirror easily produces the fundamental Bessel-Gauss mode of good quality.     

Closed-form Analysis of Lossy Cosine-Squared Tapered Nonuniform Transmission Lines

The rigorous analytical solutions and the ABCD matrix of the lossy Cosine-Squared tapered nonuniform transmission lines (CSTNTL) are presented in this paper. According to different boundary conditions, the unique solution is obtained mathematically. Through the numerical calculations based on analytical solutions, the distributed voltages and currents in different terminated cases are shown to explain the transmission characteristics of CSTNTL. Especially in the lossy case the distributed power values are simulated to show the attenuation phenomenon.