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31.
从菲涅尔-基尔霍夫衍射积分公式出发,运用边界元法数值计算了平凹腔平面镜均匀反射率时倾斜和未倾斜情况下基模的场强分布、相位分布和本征值,同时与高斯反射率平面镜在腔镜倾斜时的情况做了比较。研究表明,腔镜倾斜使激光场模式分布沿发生倾斜的方向向镜边缘偏移,而且在腔镜倾斜较严重时模式分布发生畸变,不再是对称的高斯分布,基模本征值随倾斜角增大而变小,光束远场分布变差。同等条件下,高斯反射率平凹腔腔镜倾斜对谐振腔引起的模畸变小于均匀反射率平凹腔,且基模光场及本征值随镜倾斜的变化关系稍不同于均匀反射率平凹腔。 相似文献
32.
Measurements of the pressure and temperature dependence of the a-axis resistivity of (TMTSF) 2ReO4, are presented. The metal-insulator transition seen in this material at the remarkably high temperature of ~180 K at ambient pressure and which is associated with an ordering of the ReO4, anions is suppressed under pressure. For pressures above ~9.5 kbar we observe a superconducting transition near 1.3 K. There is a narrow intermediate pressure regime about 2.5 kbar in width in which both superconductivity and effects of anion ordering are observed. In this regime (i) a superconducting transition is seen near 1.3 K even though ρ just above the transition can be up to 10-100 times greater than ρ(300 K), and (ii) there is an extraordinarily large hysteresis in p below ~ 100 K with the possibility of varying the resistance of the low temperature state by several orders of magnitude by appropriate temperature cycling. These results establish the first order character of the transition. We suggest that at high pressures the anions remain frozen in a metastable disordered state to low temperatures. 相似文献
33.
That from us as X‐ray Rotation‐Tilt Technique (XRT Method) designated procedure principle represents a world innovation and overcomes essential disadvantages of comparable diffraction techniques known up to now. Starting from the origin and the informational content of the XRT interferences a realization of a special equipment and selected examples of some first applications are presented. 相似文献
34.
It is important to understand the mechanism to integrate visual and other information for the perception of gravitational
vertical under different conditions of gravity, although most of the experiments to investigate the topic reported so far
has been carried out under normal-gravity (1 G) and under micro-gravity produced in short duration of parabolic flight. The
purpose of this research is to investigate human perception of gravitational vertical under hyper-gravity (1.5G and 2G) to
compare that under normal-gravity (1 G). We measured perceived gravitational vertical using a visual probe presented at the
center while manipulating the orientation of visual stimuli (scenery picture) presented in the surround and the magnitude
of gravitational acceleration. The environment of hyper-gravity was produced by centrifugal force of a rotating flight simulator.
The results show that the accuracy of perceived gravitational vertical increased and the precision of it decreased under hyper-gravity
condition relative to those under the normal-gravity condition when no visual stimulus was presented. However, the effect
of the tilt of visual stimuli did not change under different gravity conditions. 相似文献
35.
Jakub Fitas Katarzyna Kurp Magdalena Żurowska Marzena Tykarska Alexej Bubnov 《Liquid crystals》2017,44(9):1468-1476
Several new binary liquid crystalline mixtures have been designed and their properties were studied by complementary methods. It has been shown that even both pure components used for the mixture design possess the ferroelectric behaviour; the induced antiferroelectric smectic phase has been detected for one of the prepared mixtures. The phase diagram has been constructed and the existence of the antiferroelectric phase was confirmed by switching time and dielectric spectroscopy measurements. Some of the resulted mixtures possess very high values of the tilt angle that reaches close below 45° degrees at saturation. Values of spontaneous polarisation were found within 50–200 nC/cm2 in dependence of the mixture’s composition. Due to specific properties, the obtained mixtures might be interesting for further design of multicomponent mixtures and formulation of the advanced nanocomposite systems. 相似文献
36.
Effects of Motion, Implied Direction and Displacement of a Large-Visual-Stimulus on Postural Control
Effects of motion, implied direction in a static stimulus and displacement on postural control were examined independently.
In Experiment 1, rotation of a random-dot stimulus was presented. In Experiments 2 and 3, photographic slides of natural scenes
were used; participants closed their eyes during stimulus rotation to eliminate motion information. In Experiment 2, the stimulus
was presented upright initially, then presented again with a tilt. In Experiment 3, the order was reversed to separate the
effects of implied direction and displacement. Results showed that all information of motion, implied direction, and displacement
had some effect on postural control, although visual information of motion has been presumed to have a principal effect on
postural control. Results suggested that the effects of implied direction might reflect an immediate processing of information.
The effects of displacement and motion might reflect a continuous processing of information. 相似文献
37.
There are world‐wide efforts to analyse micron regions of compact samples by means of X‐ray diffraction (“X‐ray Microdiffraction”). Two micro diffraction procedures, the KOSSEL technique excited by electron or synchrotron radiation beams and the new X‐ray Rotation‐Tilt Method (XRT), are compared to show their possibilities and limitations. Some selected examples of new applications are presented. 相似文献
38.
The effects of the hydrogen concentration, crystal orientation and grain size on the mechanical properties of an α-Fe bicrystal with symmetric tilt grain boundaries under tensile loading are investigated by molecular dynamics simulation. The results indicate that regardless of crystal orientation, the yield strength of bicrystal α-Fe decreases with the increase of hydrogen concentration. Hydrogen atoms have no influence on the primary dislocation (or twin) nucleation mechanism, but rather influence their multiplication process. The results also show that the degree of hydrogen embrittlement is obviously dependent on the misorientation angle, but it is almost independent of the grain size. 相似文献
39.
Compounds with the same chiral terminal chain but different structure of rigid core and non-chiral terminal chain were added to basic highly tilted ferroelectric compound in the aim of establishing whether the miscibility of phases, especially ferroelectric phase, exists in these compounds and what are the helical pitch and tilt angle temperature dependence in bicomponent systems. In certain systems, we obtained a mixture with very short helical pitch at broad temperature range of ferroelectric phase, which open opportunities for the formulation of multicomponent mixtures for fast switching ferroelectric liquid crystals modes. 相似文献
40.
ABSTRACTTwo partially fluorinated ferroelectric liquid crystals (2F3R, 3F3R) with biphenylyl benzoate core have been investigated by frequency domain dielectric spectroscopy and electro-optic method. Both the compounds exhibit SmC* phase over a wide range of temperature along with tilted hexatic phase SmF* and soft crystal phases SmJ* (in 2F3R) and SmG* (in 3F3R) and one coexistence phase of (SmF*+SmC*). Both BOO phason and tilt phason relaxations are observed in SmF* phase and cooperative relaxation behaviour is also observed in crystal-like smectic phases. Goldstone mode relaxation is observed in SmC* phase and Maxwell Wagner mode is observed in all the phases. In 2F3R soft mode is detected in both SmC* and SmA* phases but not in 3F3R which melts directly to isotropic phase from SmC* phase. Compounds possess moderate values of spontaneous polarisation and exhibit quite sharp electrical response especially in 2F3R. Rotational viscosities, pitch and elastic constant are also measured. Effect of chain length and fluorination on various physical parameters has been discussed. 相似文献