Analogue of Aharonov-Bohm effect in spin gauge theory

We predict the possibility of observing analogue of the Aharonov-Bohm effect due to long range interaction between spins originating in the framework of spin gauge theory developed earlier. The effect is predicted for both electrons (fermions) and photons. Appropriate experimental set-ups are suggested.     

Stationary velocity distribution in an external field: A one-dimensional model

The velocity distribution of a charged hard rod coupled to an external field and moving in a neutral equilibrium hard rod gas is studied on the basis of Boltzmann's equation. The exact stationary solution is found. Above a threshold value the field becomes effective in the high-velocity region slowing down the decay of the velocity distribution. The drift velocity and the mean kinetic energy are discussed as functions of the field.     

Fast vectorized algorithm for the Monte Carlo simulation of the random field Ising model

An algorithm for the simulation of the 3-dimensional random field Ising model with a binary distribution of the random fields is presented. It uses multi-spin coding and simulates 64 physically different systems simultaneously. On one processor of a Cray YMP it reaches a speed of 184 million spin updates per second. For smaller field strength we present a version of the algorithm that can perform 242 million spin updates per second on the same machine.     

Ising model in a quasiperiodic transverse field,percolation, and contact processes in quasiperiodic environments

Quantum Ising models in a transverse field are related to continuous-time percolation processes whose oriented percolation versions are contact processes. We study such models in the presence of quasiperiodic disorder and prove localization in the ground state, no percolation, and extinction, respectively, for sufficiently large disorder.     

Three dimensional active sound field cancellation

In this paper, a novel method for Three dimensional active sound field cancellation is proposed. The optimum sound cancellations in different situations may be obtained. An array whose elements lie on a set of rings placed on the surface of a scattering object is considered as the device. It is quite possible to cancel the scattered sound field to any arbitrary level over either the whole space or a partial area of interest, as long as the number of the array elements is sufficient.     

高频地波雷达天线阵方向图的近场聚焦技术

详细分析了“聚集法”测量天线阵列方向图的理论依据和测量原理,提出利用“聚焦法”测量OSMAR2000天线阵列方向图的技术方案。理论计算和实测结果表明文中设计方案是可行性的。     

高频地波雷达的东海试验

“高频地波雷达海洋环境监测技术”是由武汉大学主持的国家“863”计划海洋领域的重大课题,本课题组研制了两套高频地波雷达OSMAR2000,并于1999年底,在浙江省舟山市朱家尖和宁波市象山分别建立了两个雷达实验站,进行了一年的现场自检试验和与传统海洋测量仪器的对比验证试验.试验结果表明,雷达探测海流和海风的距离达到200km,探测浪高的距离达到120km,系统整体性能达到国外同类雷达20世纪90年代后期先进水平.     

光场显微镜实现裸眼三维实时显示

提出了一种将光场显微镜与裸眼三维显示技术相结合的方法,实现了利用光场显微镜对微观样品进行三维裸眼实时观察的技术。该技术将光场显微镜得到的子图像阵列直接投影在微透镜阵列的焦平面上,在空间一定区域内双眼可分别观看到两幅不同视角图像,使观察者产生立体视觉。该系统具有结构简单,无需相干光源,无需佩戴特殊眼镜,可多人同时观看等优点,应用前景广泛。     

Donor impurity states in zinc-blende GaN/AlGaN quantum well: Quantum confinement and laser-dressed effects

Within the framework of effective-mass approximation, the effects of a laser field on the ground-state donor binding energy in zinc-blende (ZB) GaN/AlGaN quantum well (QW) have been investigated variationally. Numerical results show that the donor binding energy is highly dependent on QW structure parameters and Al composition in ZB GaN/AlGaN QW. The laser field effects are more noticeable on the donor binding energy of an impurity localized inside the QW with small well width and low Al composition. However, for the impurity located in the vicinity of the well edge of the QW, the donor binding energy is insensible to the variation of Al composition, well width and laser field intensity in ZB GaN/AlGaN QW. In particular, the competition effects between laser field and quantum confinement on impurity states have also been investigated in this paper.     

核磁共振成像一维空间编码教学实验

利用梯度磁场实现检测信号的空间编码,是核磁共振成像(MRI)的关键技术.本文采用ccc系列样品将二维问题简化为一维,使用超小型教学用核磁共振成像仪进行了一维空间编码实验研究,并对实验过程及实验结果进行了计算模拟和分析.