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利用静电探针阵列对HL-2A边缘等离子体径向和极向速度进行了测量,获得了最后闭合磁面附近湍流的雷诺协强〈(v)r(v)θ〉以及(v)r和(v)θ间相位差的剖面.实验表明,虽然(v)r、(v)θ的幅值对雷诺协强的大小会有影响,但雷诺协强的变化趋势主要取决于二者相位差的变化;另一方面,欧姆放电以及不同电子回旋加热功率L模放电条件下的实验结果显示,密度扰动引起的粒子输运所带来的极向动量输运的贡献与雷诺协强项对极向动量输运的贡献是可比的.这表明在分析湍流引起的动量输运时必须考虑粒子输运的贡献.     

湍流雷诺协强及密度扰动对极向动量输运影响的实验研究

利用静电探针阵列对HL-2A边缘等离子体径向和极向速度进行了测量,获得了最后闭合磁面附近湍流的雷诺协强 以及 和 间相位差的剖面。实验表明,虽然 、 的幅值对雷诺协强的大小会有影响,但雷诺协强的变化趋势主要取决于二者相位差的变化;另一方面,欧姆放电以及不同电子回旋加热功率L模放电条件下的实验结果显示,密度扰动引起的粒子输运所带来的极向动量输运的贡献与雷诺协强项对极向动量输运的贡献是可比的。这表明在分析湍流引起的动量输运时必须考虑粒子输运的贡献。     

强流相对论性电子束在真空漂移管中的传输

本文给出了40kA,880kV,脉冲宽度为100ns的强流相对论性电子束(IREB)在无外加磁场的真空金属漂移管中传输特性的研究结果。实验证实了束流在传输过程中净电流倍增现象的存在以及L.S.Bogdankevich等人对空间电荷极限电流的理论估计。理论上解释了净电流倍增及其明显滞后、上升时间缩短和脉宽变窄等现象。     

Flow characteristics in the downstream region of a conical diffuser

Using the Navier-Stokes equations in conjunction with the k-? model of turbulence, the characteristics of flow in the region downstream of a conical diffuser with 5° angle of inclination are calculated. Two representative stations 1D₂ and 10D₂ after the diffuser exit are selected for comparison against experimental results. The calculations indicate an underestimation of mean velocity and turbulence kinetic energy at the first station, while satisfactory agreement is obtained for the mean velocity at the second station. The use of a modified k-? model sensitive to adverse pressure conditions improves the predictions considerably. The effect of inlet properties and Reynolds number on the flow characteristics at the above stations is studied using various inlet profiles and a range of Reynolds numbers based on the inlet diameter from 50 000 to 280 000.     

四种磁绝缘传输线的横向空间电荷流

根据电磁场基本理论及电子运动守恒方程，导出平板、圆柱、圆锥和圆盘这4种常用传输线的横向空间电荷流的数值模型和磁绝缘临界条件。通过数值模拟得到:传输线的电压越高，无磁场的横向空间电荷流越大，但是磁缘性能却越显著；若分别增大圆柱、圆锥的几何结构因子，既有助于减小它们的无磁场横向空间电荷流又有助于增强它们的磁绝缘性能；对于圆锥，若电极夹角较大，内电极的极角较小，则对减小无磁场空间电荷流和增强磁绝缘性也有一定好处。     

基于分形博弈的动量和反转效应转换研究

动量和反转效应普遍存在于证券市场,且会相互转换,但两者间相互转换的特征却鲜有人知.在多数派和少数派博弈的基础上,首次引入分形市场理论对投资者决策特征进行描述,据此建立了分形博弈过程,以分析动量和反转效应转换的统计特征.研究结果表明:在三种博弈机制下,分形博弈机制下的仿真收益率序列的统计分形特征更为接近实际序列的对数收益率序列,且动量和反转效应的相互转换与真实情况也异常相似,这体现了采用分形博弈分析动量和反转效应转换的有效性,为投资者构建有效的动量或反转投资策略提供了决策参考.     

Bohmian mechanics in momentum representation and beyond

It is shown how to extend Bohmian mechanics to an arbitrary representation, based on the polar form of the wave function. The early criticism of Pauli and Heisenberg concerning the asymmetric role of the position variable in Bohm's approach can be removed by presenting the momentum space version of the theory. It is illustrated that for certain problems, like the motion in a linear position-dependent field, the momentum space representation can be advantageous. This analysis also allows to trace back the origin of the quantum potential to the squaring of complex quantities and the resulting mixing of phase and amplitude.     

Rollup region of a turbulent trailing vortex issued from a blade with flow separation

This paper presents the results of an experimental investigation on the near field of a tip vortex generated by a blade at moderate incidence. The experiments were conducted at Re=15 000 and the boundary layer over the blade separated around midchord on the upper surface. Laser-Doppler measurements of the turbulent flow (Tu=1.5%) were performed at various stations downstream of the blade. The three components of the mean velocity field and turbulent attributes were quantified at cross-planes, characterizing both the blade wake and the tip vortex structure. This allowed the analysis of the rollup and initial stages of decay of the tip vortex in the light of known theories and models. The axial velocity defect at the center of the vortex core evolved as x⁻¹ log x, without displaying any significant outgrowth imposed by the separated flow upstream. Momentum balances were also carried out at a station downstream to the conclusion of vortex rollup. The approximate axisymmetry of the flow field in the trailing vortex was used to formulate the balances in a cylindrical coordinate system. Among other observations, it was seen that an adverse axial pressure gradient developed in the vortex core, which reinforced the tenacity of the axial velocity defect. In contrast, an area influenced by a favorable pressure gradient was found outside the core.     

Axial momentum for the relativistic Majorana particle

The Hilbert space of states of the relativistic Majorana particle consists of normalizable bispinors with real components, hence the usual momentum operator $?i\mathrm{?}$ can not be defined in this space. For this reason, we introduce the axial momentum operator, $?i{\gamma }_5\mathrm{?}$ as a new observable for this particle. In the Heisenberg picture, the axial momentum contains a component which oscillates with the amplitude proportional to $m/E$, where E is the energy and m the mass of the particle. The presence of the oscillations discriminates between the massive and massless Majorana particle. Furthermore, we show how the eigenvectors of the axial momentum, called the axial plane waves, can be used as a basis for obtaining the general solution of the evolution equation, also in the case of free Majorana field. Here a novel feature is a coupling of modes with the opposite momenta, again present only in the case of massive particle or field.     

Spontaneous symmetry breaking of arbitrage

We introduce the concept of spontaneous symmetry breaking to arbitrage modeling. In the model, the arbitrage strategy is considered as being in the symmetry breaking phase and the phase transition between arbitrage mode and no-arbitrage mode is triggered by a control parameter. We estimate the control parameter for a momentum strategy with real historical data. The momentum strategy aided by symmetry breaking shows stronger performance and has a better risk measure than the naive momentum strategy in U.S. and South Korean markets.