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101.
介绍了倾斜镜在恒星光干涉仪中的作用及倾斜镜系统的组成和工作原理,对倾斜镜系统中的AT89C51控制单元、高压驱动电源、压电陶瓷微位移装置(PZT)以及倾斜镜的机械结构设计进行了详细的讨论并给出了倾余镜系统闭环实验调试平台。 相似文献
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对主动抛光盘在加工、测量状态下盘面的变形及提升的数学分析* 总被引:1,自引:2,他引:1
用主动抛光盘磨制非球面是一个动态的过程,必须保证在计算机控制下,主轴的移动、旋转。和抛光盘的旋转、倾斜、变形及升降,以及主镜的旋转都步调一致。推导出在模式中诸要点的位置、速度、加速度和时间的关系,并根据所加工的口径φ910mm,焦比为F/2的抛物面主镜参量和所用主动抛光盘的参量分析:1)主动抛光盘基板的变形特性。即它的变形量、变形的速度和加速度。以及近似公式与精确公式之间的差异;2)主动抛光盘背面的三个提升点运动规律。即它的升降量、升降的速度和加速度;3)主动抛光盘的变形量和它在差分变压器式线性微位移传感器(LVDT)测试架上所测得的测量量之间的关系;4)分析主动抛光盘的变形与提升的速度与加速度和抛光盘沿横梁的运动速度V1以及抛光盘自身的转速V2之间的关系和特性。此分析是主动抛光盘的数学基础,它为主动抛光盘的机械和电控设计提供了技术依据,为实现计算机控制下的6轴联动提供了保证。 相似文献
104.
Using interatomic potentials derived from the second moment approximation of the tight-binding scheme, we study the relative stabilities for the different structures of the = 5 (210) [001] tilt boundary in Cu and Ag. Relatively to the numerous previous studies, we obtain two new structures characterised by a larger periodicity along the tilt axis. Depending on the metal and on subtle features of the potentials, we show a very significant evolution of the relative stabilities. Using a local analysis on the different sites of the grain boundary, we link the stability of a given structure to peculiar features of the interatomic potential and to physical properties of the metal. 相似文献
105.
William N. Thurmes Kundalika M. More Michael R. Meadows Matthew B. O'Neill Rohini T. Vohra Michael D. Wand 《Liquid crystals》2013,40(5):461-477
Liquid-crystalline compounds containing germanium atoms were synthesised and assessed for liquid-crystalline properties. These new compounds generally possess smectic C phases, and many also possess nematic, smectic A and higher order smectic phases. The germanium-containing liquid crystals were incorporated into smectic C mixtures. These mixtures tend to exhibit little change in smectic C*?layer thickness over temperature. This characteristic is associated with de Vries smectic A materials, but measurements show that, although they have high smectic C stability, the materials' smectic cone angles are small. Measurement of smectic cone angle versus temperature of an exemplar material and its analogues containing carbon and silicon in place of the germanium, all show small cone angles which fall smoothly and extrapolate to zero as the smectic C*?to smectic A transition is approached. These measurements largely explain the observed small layer changes and establish that the materials are not first-order de Vries materials. They must be located elsewhere along the de Vries-orthogonal continuum of smectic A phases. 相似文献
106.
A new method for measuring a polar anchoring energy of nematic liquid crystals (LCs) is proposed. A variation of LC tilt angle on the surface with an applied electrical field was determined by a reflective method. The twisted LC cell configuration was selected to compensate a contribution of the induced birefringence in the reflective spectra. The electrical field controlled reflectance was used to analyse the potential form of the polar anchoring energy and to define the anchoring strength. The proposed method is applicable for 2–5 μm thick LC cells. 相似文献
107.
An external electric field applied across a planar-aligned cell in Smectic A* phase of de Vries smectic liquid crystal induces director redistribution over a cone, resulting in a substantial increase in the birefringence and the apparent optical tilt angle. Such an electro-optic response is modelled by Shen et al. [Y. Shen et al., Phys. Rev. E 88, 062504 (2013)], who modified their previous hollow cone with a diffuse cone model by introducing the molecular distribution function limited over a range of tilt angles, that lie in between θmin and θmax. The limits in these two tilt angles are assumed to be temperature independent though the tilt angle in between the two values can be temperature dependent. However, the high resolution measurements of birefringence and the layer thickness indicate the presence of temperature dependent diffuse cone angle in SmA* phase.. In the proposed model, we replace θmin by θT, a temperature dependent fitting parameter and the change shows that a better fit of the experimental data to the model is obtained. We determine the temperature dependence of θmin and show that this angle increases as SmA* to SmC* phase transition temperature is approached. 相似文献
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对倾斜角为20°、24°、28°和32°的单头以及32°的双头周向重叠三分螺旋折流板换热器和弓形折流板换热器的传热和压降性能进行了测试,换热器采用公共壳体和可更换管芯结构。采用壳侧轴向雷诺数和轴向欧拉数分别作为反映壳侧流量和阻力系数的无因次参数。试验结果显示在试验范围内周向重叠三分螺旋折流板换热器壳侧换热系数、壳侧压降和综合性能指标都随着倾斜角增大而减小;倾斜角20°方案的性能指标最佳,其平均壳侧努塞尔数和轴向欧拉数与弓形折流板方案的数值之比分别为1.123和0.45;双头螺旋折流板方案的换热系数和压降都大于同样倾斜角的单头螺旋折流板方案,但两者的综合性能较接近。 相似文献