煤粒均相着火规律的研究

煤粒均相着火规律的研究张军，傅维标（清华大学工程力学系北京１０００８４）关键词均相着火，简化模型，预报１前言煤粉颗粒既能发生均相着火，又能发生非均相着火山。对非均相着火，许多学者进行了研究，取得了很多有价值的成果。均相着火由于比较复杂，一直发展缓慢。...     

A neuron as a quantum-optical device: A model

Inversion in the structure of polyaminoacids and proteins is discussed, and the electrodynamic quantum-optical model of a neuron is constructed. The feasibility of the quantum-logical summation of exciting pulses by a nanomembrane is considered. The model is consistent with the physiology foundations and assumes implementation by means of techniques used in microelectronics, integrated optics, and nanooptics.     

A positron buncher-cooler

The positron buncher-cooler is a concept for a new compact device, which serves to produce a high quality pulsed positron beam for use in atomic physics experiments. It is predicted that pulses of at least 8000 positrons (from a 50 mCi source) with an energy spread of 25 meV and a bunch length of <50 ns may be produced at a repetition rate of 10 Hz with a duty cycle of 90%.     

A Mille-feuille Universe

Motivated by seeking kinetic origins for seedsof the large-scale structure formation in the universe,we investigate the properties of a generalizedaxisymmetric Bianchi IX type model. Such a model, which is supposed to describe non-interactingradiation of dust-like matter posterior to decoupling,has the advantage ofbehaving asymptotically as a closefrw model with a cosmological constant. It shows avanishing vorticity, a decreasing shear of matter withtime and a frw chronology, which are properties thatmake it likely when compared to observationalconstraints. The formula which provides us with theredshifts of sources is derived.     

充分发展槽道湍流的小波数值分析

数值计算了高斯子波变换Navier Stokes(N-S)方程后得到的积分方程.在利用高斯子波得到的以弯曲度为基本量的无穷域中N-S方程的基础上,得到了有界区域内的以弯曲度为基本量的N-S方程.将此N-S方程看作一个特殊的扩散方程,将压力项与对流项看作是源项,得到一个积分方程.利用特征线法对该方程求解,得到通解.并将所得结果运用于对称槽道湍流和非对称槽道湍流的研究中.将计算与实验所得的平均量与实验结果进行了对比.     

长椭圆旋转介质球中的半波振子天线

本文从麦克斯韦方程出发,求出有损耗的长椭圆旋转介质球中一个同焦点的小的长椭圆旋转形半波振子发射天线上的电流分布和其输入阻抗,以及它在有损耗的介质球中和外部自由空间中所产生的场。     

A noncommutative catenoid

A noncommutative algebra corresponding to the classical catenoid is introduced together with a differential calculus of derivations. We prove that there exists a unique metric and torsion-free connection that is compatible with the complex structure, and the curvature is explicitly calculated. A noncommutative analogue of the fact that the catenoid is a minimal surface is studied by constructing a Laplace operator from the connection and showing that the embedding coordinates are harmonic. Furthermore, an integral is defined and the total curvature is computed. Finally, classes of left and right modules are introduced together with constant curvature connections, and bimodule compatibility conditions are discussed in detail.     

RESONANT INTERACTION BETWEEN A PAUL-TRAPPED ION AND A STANDING WAVE LASER

An ultracold two-level ion experiencing the standing wave of a resonant laser in a Paul trap is investigated in the Lamb-Dicke limit and weak excitation regime, with full consideration of the time-dependence of the trapping potential. The analytical forms of the wave functions of the system can be described with our approach, and the time evolution of the pseudo-energy of the system as well as the squeezing property of the quadrature components is studied in comparison with the treatment of harmonic oscillator model.     

HL-2A装置等离子体可见光成像系统

在HL-2A装置上研制了等离子体可见光成像系统,用于孔栏、偏滤器位形放电的诊断。该成像系统由彩色摄像机、观察窗和转向镜、广角收集和准直透镜组、采集卡和计算机组成。本文描述了系统的布局和各部件参数的匹配,报道了观测到的实验结果。等离子体成像系统能监视放电的整个过程,实时显示可见光辐射图形,特别在识别孔栏与偏滤器位形放电的诊断中发挥了重要作用,成为HL-2A装置放电的重要诊断手段。     

高强度均匀静磁场中氢原子能级的计算

采用一种简便的变分法，计算了在均匀高强度静磁场下氢原子的１１个低能态能级和平均半径，讨论了高强度磁场对能级和半径的影响。     

SOLUTION OF COUPLED ACOUSTIC PROBLEMS: A PARTIALLY OPENED CAVITY COUPLED WITH A MEMBRANE AND A SEMI-INFINITE EXTERIOR FIELD

There have been many attempts to understand the coupling phenomena between a solid structure and the surrounding fluid. However, the studies were restricted to interaction only between a structure and a finite cavity or a structure and acoustic field of infinite size. The system that we have studied has a structure that faces both a cavity of finite size and an external field of semi-infinite size. We also allow a hole, which can directly interact with the cavity as well as the external field. This configuration, therefore, provides two different interactions, or communication means. One is the finite structure and the other is the hole of finite size. This paper studies as to how these two components interact with the other two systems: the finite cavity covered by the structure and the hole, and the semi-infinite fluid. For simplicity, a two-dimensional and partially opened cavity coupled with a membrane and an exterior field was selected. The solution has to be found by solving a boundary value problem, but this case has to do with the boundaries that have two different conditions: one is the membrane and the other is the hole. The solution has been found in terms of the modal functions that satisfy the boundary conditions of finite cavity, membrane and hole. Non-dimensional coupling coefficients are obtained from the solution. The results exhibit that the coupling effect gives additional peaks and troughs in the averaged pressure of the cavity. These peaks and troughs are symmetrically arranged with respect to Helmholtz frequency of the cavity. The strong coupling occurs at the trough frequencies where the membrane interacts actively with the cavity and the exterior field.     

A nonlinear granular medium with particle rotation: A one-dimensional model

Equations of nonlinear acoustics are derived from the micromechanical representation of a granular medium as a system of elastically interacting particles possessing translational and rotational degrees of freedom. The structure of the equations is invariant with respect to the shape and size of the particles. The changes in the latter affect only the coefficients in the equations. The inclusion of microrotations and moment interactions of particles leads to the formation of a new type of waves in the medium—microrotational waves. Their dispersion properties are similar to those of spin waves propagating in a magnetoelastic medium. In the low-frequency approximation, the microrotational waves disappear, and the equation describing the transverse waves acquires a term with quadratic nonlinearity. The latter provides an explanation for the generation of the second shear harmonic that is observed in real solids contrary to the predictions of the nonlinear theory of elasticity, which prohibits such phenomena.     

有限磁场中等离子体圆柱波导的传播特性

分析了有耗介质中等离子体圆柱波导在有限外加磁场中的传播特性.重点讨论了波导传播常数随等离子体参数、介质参数和外加磁场的变化.分析结果表明，有限强磁场中的等离子体波导的传播特性比无外磁场或外加磁场为无穷大时具有更强的控制能力. 关键词：     

A Spin Decomposition of the Verlinde Formulas for Type A Modular Categories

A modular category is a braided category with some additional algebraic features. The interest of this concept is that it provides a Topological Quantum Field Theory in dimension 3. The Verlinde formulas associated with a modular category are the dimensions of the TQFT modules. We discuss reductions and refinements of these formulas for modular categories related with SU(N). Our main result is a splitting of the Verlinde formula, corresponding to a brick decomposition of the TQFT modules whose summands are indexed by spin structures modulo an even integer. We introduce here the notion of a spin modular category, and give the proof of the decomposition theorem in this general context.     

在环形理想导体空腔中极向线电流产生的磁场

本文研究在环形理想导体空腔中极向线电流产生的磁场。在一级环形效应近似下得到的理论结果，基本上与实验数据一致，并且可以推广使用到具有一定类型极向电流分布的情况。     

A Lorentz-invariant clock

Relative distance and velocity magnitudes between two arbitrarily moving particles are independent of an observer's reference frame, and may be used to construct theoretically a clock whose rate is Lorentz-invariant. This result is in accord with the principle of relativity, using the interaction interpretation: Relativistic changes arise in association with momentum-energy transfer, rather than in consequence of velocity-induced changes in measuring clocks and rods.     

THE EXACT SOLUTION OF A TWO-LEVEL ATOM MOVING IN A QUANTIZED TRAVELLING LIGHT FIELD AND A GRAVITATIONAL FIELD

We adopt a dynamical algebraic approach to study the system of a two-level atom moving in a quantized travelling light field and a gravitational field with a multiphoton interaction. The exact solution of the system is obtained and used to discuss the influence of the gravitational field on the collapses and revivals of atomic population, sub-Poissonian statistics.     

A Definition of Time

We present a definition of time based on a particle’s interaction with the Higgs field. Just as a particle acquires mass by interacting with the Higgs field our model proposes that time is acquired via the energy of virtual particles participating in the quantum exchange interactions with Higgs particles. We show that, for macroscopic time, this definition accords with the Lorentz transformation of special relativity. The research of the authors was supported by NSERC grants.     

可变焦列阵柱面透镜均匀线聚焦系统

用两个列阵柱面透镜与非球面透镜组成变焦线聚焦系统，能将入射激光束会聚成辐照均匀、长度连续可调的焦线，它可用于Ｘ光激光实验研究．文中详细分析了焦线上光场分布的情况，给出了物理光学分析的结果，并与巳有技术作了比较．     

A possible polar smectic A—Non-polar smectic A transition line in a binary system?

We show the thermal evolution of the orientational order near nematic-smectic A or smectic A-smectic A transitions which we recently revealed in binary mixtures. We compare the experimental behavior to theoretical predictions of a possible smectic A phase with polarized layers.