400GeV/c pp碰撞赝快度空间带电粒子数密度的研究

利用CERNNA27合作组提供的LEBC泡室照片,测量了400GeV/cpp碰撞产生的带电粒子多重数为4—24的赝快度分布.观察到在选择的赝快度窗口(Δη=0.5和0.1)内平均最大带电粒子数密度随带电粒子多重数线性增加的规律.最大带电粒子数密度的几率分布在n大时有加宽和变平坦的趋势.没有观察到最大粒子数密度反常高的事例.     

激光治疗近视眼中角膜曲率修正量的理论计算

本文从示意眼模型出发,利用自治的单透镜近似模型,根据矩阵光学原理,用计算机算出不同近视眼度数焦点的前移量以及在三种不同原因引起的近视眼的情况下角膜需要切除的数量。计算告诉我们即使1000°近视眼,角膜最大切除量也仅50μ,不到角膜总厚度的1/10。 理论上探讨了根据激光束的高斯分布经过光学系统改变光强分布来实现近视眼需要校正的曲率。     

基于人工神经网络的商业银行信用风险模型

在对人工神经网络的基本原理进行简要介绍的基础上 ,着重对构建商业银行信用风险的人工神经网络模型进行了研究 ,实证结果表明 ,人工神经网模型具有很高的预测精度     

具有吸收-反射边界的Boltzmann-Poisson输运模型的整体弱解

本文研究具有吸收-反射边界的Boltzmann-Poisson输运模型的初这值问题,并利用速度平均的稳定性和L~1空间紧致性理论,在较弱的初边值条件下,证明了其整体弱解的存在性。     

Hardy's inequality and the boundary size

We establish a self-improving property of the Hardy inequality and an estimate on the size of the boundary of a domain supporting a Hardy inequality.

     

过渡金属化合物OsB2与OsO2低压缩性的第一性原理计算研究

利用基于密度泛函理论平面波赝势法的第一性原理计算,研究了过渡金属化合物OsB2和OsO2的金红石相、黄铁矿相与萤石相三种结构在高压下的状态方程和结构特性以及OsO2可能的高压相变.理论计算结果支持OsB2与OsO2的萤石相是潜在超低可压缩性的硬性材料.同时,也分析了它们的电子结构,力求理解大体变模量和高硬度的微观机制.结果表明,可以利用过渡金属高的价电子浓度,掺入硼、氧、碳、氮等轻的元素形成强的方向键,这可能提供了一种合成超硬材料的新途径.     

Influence of the stress on magnetoelectric effect in magnetostrictive-PZT bilayers

In this letter, we investigate the influence of the stress on magnetoelectric (ME) effect in a magnetostrictive-PZT bilayer. ME voltage coefficient α*_E = δE / δH, where δE is the induced electric field for an applied alternating current (ac) magnetic field δH, is obtained by solving the stress-related piezoelectric constitutive equation and the conventional magnetostrictive equation with appropriate boundary condition. Based on the free-energy density function of the PZT film in stress state, we get the stress-related piezoelectric charge coefficient ^p d*₃₁ and dielectric permittivity ^pε*₃₃. After taking the cobalt ferrite (CFO) as magnetostrictive phase, it is found that α*_E increases with decreasing 2-d compressive stress for CFO-PZT, which not only is qualitatively consistent with previous experimental measurements, but also provides a possible route to improve the ME effect.      

The effect of toroidal field on the rotating magnetic field current drive in rotamak plasmas

A rotamak is one kind of compact spherically shaped magnetic-confinement device. In a rotamak the plasma current is driven by means of rotating magnetic field （RMF）. The driven current can reverse the original equilibrium field and generate a field-reversed-configuration. In a conventional rotamak, a toroidal field （TF） is not necessary for the RMF to drive plasma current, but it was found that the present of an additional TF can influence the RMF current drive. In this paper the effect of TF on the RMF current drive in a rotamak are investigated in some detail. The experimental results show that addition of TF increases the RMF driven current greatly and enhances the RMF penetration dramatically. Without TF, the RMF can only penetrate into plasma in the edge region. When a TF is added, the RMF can reach almost the whole plasma region. This is an optimal strength of toroidal magnetic field for getting maximum plasma current when Bv and radio frequency generator power are fixed. Besides driving current, the RMF generates high harmonic fields in rotamak plasma. The effect of TF on the harmonic field spectra are also reported.[第一段]     

CSRm束流径向和轴向振荡的耦合

介绍了由于磁铁的安装误差和螺线管的存在而造成的束流径向和轴向的耦合，以及耦合对束流稳定的影响。结合CSRm结构的典型参数分析得出:二极磁铁和四极磁铁在纵向角安装偏差为-0.5~0.5 mrad；有螺线管存在的情况下，工作点落在和共振线时，将导致束流不稳定而大量损失，落在差共振线时，束流稳定。通过模拟计算发现:螺线管产生的耦合远大于磁铁的纵向角安装偏差产生的耦合。