Analysis of Internal Conical Refraction Using Ray Tracing Formulas for the Biaxial Crystal

Internal or external conical refractions are strange optical phenomena appearing in biaxial crystal. In this paper the analysis of internal conical refraction is derived using the ray tracing formulas for the biaxial crystals, after explaining the theory of the ray tracing for the biaxial or uniaxial crystals. The double rings of conical refraction are also investigated; these are affected by the polarization state or angular intensity distributions of the incident light beam causing conical refraction.     

Dehnviskosität von Kautschukmischungen

It is shown that the extensional viscosity measured by uniaxial stretch may give useful information as to the processability of rubber compounds. A simple apparatus was constructed to measure this rheological property at constant rate of strain. The influence of rubber type, filler, aging, mastication and degree of crosslinking on the reduced stress is represented by diagrams. No steady-state extensional viscosity was obtained for highly filled rubber compounds. It was found that the flow behaviour of rubber compounds can be better characterized with an extensional rheometer than with a high-pressure capillary rheometer.

     

Propagation of Airy Gaussian vortex beams in uniaxial crystals

The propagation dynamics of the Airy Gaussian vortex beams in uniaxial crystals orthogonal to the optical axis has been investigated analytically and numerically. The propagation expression of the beams has been obtained. The propagation features of the Airy Gaussian vortex beams are shown with changes of the distribution factor and the ratio of the extraordinary refractive index to the ordinary refractive index. The correlations between the ratio and the maximum intensity value during the propagation, and its appearing distance have been investigated.     

单轴应变条件下Fe从α到ε结构相变机制的第一性原理计算

采用基于密度泛函理论的平面波赝势方法,研究了沿［001］方向单轴应变条件下Fe从体心立方结构(bcc,α相)到六角密排结构(hcp,ε相)相变的临界压力、相变路径、相变势垒以及相变过程中原子磁性的变化.结果发现:单轴应变条件下Fe从α到ε结构的相变路径与以前理论计算模拟给出的静水压力条件下的相变路径明显不同;原子磁矩沿着相变路径突然降低,同时伴随着能量和体积的突然变化,是典型的一阶磁性相转变,表明原子磁性的丧失导致了bcc结构不稳定而向hcp结构转变.对单轴应变下吉布斯自由能的计算表明,相变势垒随着单轴应 关键词： 相变 单轴应变 第一性原理 铁     

Ferromagnetic Properties of Bond-Dilution and Random Positive or Negative Uniaxial Anisotropy Blume-Capel Model

We study the ferromagnetic properties of spin-1 system, which is considered in the frame of the bonddilution and random positive or negative anisotropy Blume-Capel model in the effective field theory and a cutting approximation. The investigation of phase diagrams displays some rich properties of the trajectory of tricritical point,reentrant phenomena at low temperatures. Under certain both bond concentrations and random negative anisotropy,there are new transition lines of double tricritical points. So special emphasis is placed on the influence of the bond dilution and random anisotropy on phase diagrams. The magnetizations of the system are also discussed. Some results have not been revealed in previous reports.     

用布儒斯特角法同时测定单轴晶体的折射率和光轴方向

在理论上分析了光轴任意方向的单轴晶体的折射率．根据布儒斯特角原理,当线偏振光的电场矢量平行于入射面时,通过测出对样品三个表面的布儒斯特角,就能同时确定单轴晶体的折射率和光轴方向．并利用分光计,在光轴不确定的情况下,测定了方解石的两个主折射率和光轴方向．     

数字散斑技术在混凝土单轴压缩试验中的应用

数字散斑技术作为一种新兴的测量方法,它具有非接触、全场量测、精度高、操作简单等特点,随着计算机技术的迅猛发展,数字散斑技术得到了广泛的应用与研究。针对混凝土在外荷载作用下具有明显的非均匀变化的特征,借助传统的测量方法很难得到混凝土表面的全场变形结果的问题,结合数字散斑相关方法测量技术,开展了混凝土单轴压缩试验,拍摄了混凝土表面在单轴压缩过程中的位移与应变矢量场,为分析混凝土试件的损伤区域奠定了基础;与电测法测量结果进行了对比,其测量结果表明,这两种测量方法误差相对较小,且数字散斑技术能更早的发现混凝土表面的破坏,验证了数字散斑相关方法的准确性和可靠性。借助数字散斑技术可以更加方便准确的得到材料表面的变形场,这也将在一定程度上促进土木工程领域的发展,具有广阔的应用前景。     

附加球面相位引致Airy光束在单轴晶体传输时的两次镜像演化

利用单轴晶体光束传输理论,求得了具有附加球面相位Airy光束在单轴晶体中的传输公式.数值模拟计算结果表明,线偏振附加球面相位Airy光束在晶体中传输时仍为线偏振,但不是传输不变的.粗略地讲,具有附加球面相位的Airy光束在晶体中传输时,近场是传输不变的;而在由晶体寻常与非寻常折射率和球面半径共同确定的两个特定传输距离处,传输光束转换成了取向不同的Gaussian-Airy光束,且高斯依赖的束宽度敏感地与截断因子相关;而当光束依次穿过此两位置时光斑花样先后相对于两横向轴平面做镜像演化,且镜像演化顺序也与晶体寻常和非寻常折射率相对大小密切相关,其总的效果是远场强度花样能恢复原样但花样取向产生了关于对过横平面二、四象限平分平面的镜像演化.这些结果表明,通过恰当选择晶体材料(即折射率)和附加球面相位的半径R,可以调控光束花样的形状、取向及表征各向异性材料的相关性质.