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排序方式: 共有653条查询结果,搜索用时 31 毫秒
81.
In an anisotropic positive index media the tangential components of Poynting vector S and that of wavevector k can have the opposite signs under certain conditions. The phenomenon is called as the anomalous negative refraction. The negative refraction phenomenon at planar interfaces between isotropic medium-crystal and crystal-crystal media has been analyzed. The crystals can be both uniaxial axis and biaxial axis and the azimuth of optical axis can be arbitrary. The negative refraction phenomenon under various azimuth of optical axis is analyzed. The phenomena can be very evident if the optical axis angle is arranged appropriately. The optimal conditions are obtained. For strong anisotropy crystal, the maximum incident angle that yields the negative refraction and the bending angle could be very large. For the interface of biaxial crystal the anisotropy parameter of crystal u1 = nz/nx plays a dominant role in effect on negative refraction. 相似文献
82.
LUO Min-Jie LIU Qiu-Yu 《理论物理通讯》2008,50(8):451-458
We consider that the Higgs triplet Yukawa coupling takes the Friedberg-Lee texture, and the Higgs doublet Yukawa coupling simply identifies with the diagonal Yutawa coupling of charged lepton in the context of left-right symmetric model. In this scenario, the phenomenology, including effective neutrino masses, mixings, and thermal flavor-dependent leptogenesis and lepton flavor violation decays are studied. We investigate the combined constrain of the parameters in this scenario and test its consistency with present data. 相似文献
83.
84.
D. Tian S. Blacher Ph. Dubois J.P. Pirard R. Jérôme 《Journal of Sol-Gel Science and Technology》1998,13(1-3):415-419
Porous silicas have been successfully prepared from poly(-caprolactone) (PCL)-silica hybrid materials based on the template approach. The final texture of the porous silica can be tailored by the PCL template, i.e., molecular weight and molecular weight distribution, content, type and number of reactive end-groups per chain. Porosity has been investigated by nitrogen adsorption-desorption technique and small angle X-ray scattering (SAXS). 相似文献
85.
We have studied a polar, biaxial nematic liquid crystal formed from bent-core molecules using molecular field theory. The model includes a simple Heisenberg-form dipolar intermolecular interaction in addition to the usual quadrupolar nematic interaction, and mimics a system consisting of nematogenic bent-core molecules with a large transverse dipole along the bisector of the two molecular arms. Such systems are regarded as good candidates for biaxial nematic liquid crystals. In principle, the molecular dipoles can align, thus stabilising the ordering of the minor axes. Our calculations predict that, for suitable values of the bent-core interarm angle, the biaxial nematic phase can be stabilised at higher temperatures than in the absence of the transverse dipole. In general, the transverse macroscopic polar order stabilises the biaxial nematic phase. In particular, for a large enough dipolar interaction, the Landau point in the pure biaxial nematic develops into a line of first-order polar biaxial nematic-to-isotropic phase transitions. 相似文献
86.
Francesco Vita 《Liquid crystals》2016,43(13-15):2254-2276
ABSTRACTSince its theoretical prediction in 1970, the search for the biaxial nematic phase in thermotropic systems has challenged generations of liquid crystal scientists. Over the last 10 years, bent-core mesogens have drawn much interest as promising candidates for nematic biaxiality. However, despite a number of disputed claims, conclusive evidence of proper (spontaneous and macroscopic) biaxial order in these materials is still missing. By contrast, it is now widely recognised that biaxiality exists on a local scale, in the form of nano-sized clusters of molecules (cybotactic groups) possessing smectic-like positional order and biaxial orientational order. This article provides a review of X-ray diffraction studies on biaxiality and cybotaxis in bent-core nematics, discussing the most relevant issues related to this research field. 相似文献
87.
Frontispiece: Photon Energy Becomes the Third Dimension in Crystallographic Texture Analysis 下载免费PDF全文
88.
Alessandro Stroppa Paolo Barone Domenico Di Sante Mario Cuoco Silvia Picozzi Myung‐Hwan Whangbo 《International journal of quantum chemistry》2016,116(20):1442-1450
In developing physical theories, analogical reasoning has been found to be very powerful, as attested by a number of important historical examples. An analogy between two apparently different phenomena, once established, allows one to transfer information and bring new concepts from one phenomenon to the other. Here, we discuss an important analogy between two widely different physical problems, namely, the Jahn–Teller distortion in molecular physics and the Rashba spin splitting in condensed matter physics. By exploring their conceptual and mathematical features and by searching for the counterparts between them, we examine the orbital texture in Jahn–Teller systems, as the counterpart of the spin texture of the Rashba physics, and put forward a possible way of experimentally detecting the orbital texture. Finally, we discuss the analogy by comparing the coexistence of linear Rashba + Dresselhaus effects and Jahn–Teller problems for specific symmetries, which allow for nontrivial spin and orbital textures, respectively. 相似文献
89.
A new experimental technique has been developed to investigate the onset of fracture in metals at low and intermediate stress
triaxialities. The gage section of a flat specimen has been designed such that cracks are most likely to initiate within the
specimen center, remote from the specimen boundaries. Along with the specimen, a biaxial testing device has been built to
apply a well-defined displacement field to the specimen shoulders. The stress state within the specimen is adjusted by changing
the biaxial loading angle. Using this new experimental technique, the crack initiation in metals can be studied experimentally
for stress triaxialities ranging from 0.0 to 0.6. The stress and strain fields within the specimen gage section are determined
from finite element analysis. The reliability of the computational model of the test set-up has been verified by comparing
the simulation results with laser speckle-interferometric displacement measurements during testing. Sample experiments have
been performed on the Al-7Si-Mg gravity die casting alloy. A three-step hybrid experimental–numerical calibration procedure
has been proposed and applied to determine a phenomenological crack formation criterion for the Al-7Si-Mg alloy.
相似文献
D. MohrEmail: |
90.
董炎明 《高等学校化学学报》1995,16(6):981-983
用条带织构装饰技术研究液晶全芳共聚酯B—N的取向和非取向膜董炎明(厦门大学化学系,厦门,361005)关键词共聚芳酯,条带织构,退火,取向膜,微纤全芳共聚酯B—N在分子量较高时能出现黑白相间的条带织构[1~5],但分子量低时由于极易松驰,不能用普通剪... 相似文献