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In this paper we show that the director profile of a low pre-tilt surface stabilized ferroelectric liquid crystal passes through quasi-static stressed states during domain switching under direct drive conditions. Using polarized stroboscopic microscopy, we have observed two quasi-static transmission levels during a domain switching transition from dark to light. This is a result of the directors reorienting into stressed profiles both before and after the chevron interface has switched. By modelling the interaction between the elastic forces and the torque from the applied field, we have determined these voltage dependent director profiles and, by calculating their corresponding transmissivities, have shown very good agreement with the experimentally observed values. 相似文献
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L. A. Parry‐Jones S. M. Beldon P. D. Brimicombe D. Rodriguez‐Martin S. J. Elston 《Liquid crystals》2013,40(7):767-773
X‐ray diffraction studies are carried out in order to probe the smectic layer structure in liquid crystal devices filled with FLC mixture SCE8 and AFLC mixture CS4001, at a temperature just above the SmA?–SmC? phase transtion. The data gathered are time‐resolved in synchronization with a bipolar voltage pulse applied across the device. The layers are observed to move dynamically and reversibly with voltage application and removal, giving evidence for temporary vertical chevron formation due to the electroclinic effect on a timescale consistent with this phenomenon. 相似文献
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The switching process in ferroelectric liquid crystal devices takes place through the formation and evolution of domains, which is modelled here using a three-variable approach. This approach includes variation of the director profile in one dimension, through the thickness of the cell. Here we discuss details of the model which are necessary in order to reproduce the domain nucleation and switching times as a function of applied voltage for both monopolar and bipolar pulses. We show that the three-variable modelling of SSFLC switching in one dimension produces excellent comparisons with experimental data for both bipolar and monopolar pulses. 相似文献
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An investigation into the transmission spectrum of a ferroelectric liquid crystal device is undertaken. This is done both for an initial static state and during a switching process. Comparisons are made between experimental data and theoretical predictions. The dynamic internal director configurations in the device is shown to be consistent with a simple model during both monopolar and bipolar addressing pulses. 相似文献
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W. A. Drushel und C. M. Elston 《Fresenius' Journal of Analytical Chemistry》1918,57(4):199-201
Ohne Zusammenfassung 相似文献
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The conoscopic images of twisted nematic liquid crystal devices filled with E7 are analysed under the application of in-plane electric fields. The differences observed between the images for positive and negative applied fields are attributed to the flexoelectric effect. By comparison of the conoscopic images with theoretical predictions made using an extended Jones technique, the sign and magnitude of the difference between the splay and bend flexoelectric coefficients is determined for E7. 相似文献
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S. J. Elston 《Liquid crystals》1994,16(1):151-157
Liquid crystal alignment is studied using propagating optical mode techniques for a cell with a high surface tilt SiO alignment. The director configuration is determined for both the nematic and smectic A phases. In the nematic phase a uniform splay across the cell is demonstrated, as predicted by continuum theory. In the smectic A phase the structure is seen to be nearly uniform in the central region of the cell with large splay in boundary layers of about 0.5 μm thickness. The reason for this appears to be competition between the tilted surface alignment forces and internal forces within the bulk of the smectic A layer which would induce a homogeneous configuration. 相似文献
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Macroscopic systems (e.g., hydrodynamics, chemical reactions, electrical circuits, etc.) manifest intrinsic fluctuations of molecular and thermal origin. When the macroscopic dynamics is deterministically chaotic, the intrinsic fluctuations may become amplified by several orders of magnitude. Numerical studies of this phenomenon are presented in detail for the Lorenz model. Amplification to macroscopic scales is exhibited, and quantitative methods (binning and a difference-norm) are presented for measuring macroscopically subliminal amplification effects. In order to test the quality of the numerical results, noise induced chaos is studied around a deterministically nonchaotic state, where the scaling law relating the Lyapunov exponent to noise strength obtained for maps is confirmed for the Lorenz model, a system of ordinary differential equations. 相似文献