共查询到20条相似文献,搜索用时 218 毫秒
1.
本文采用第一性原理方法, 计算了CaF2的理想晶体和含钙、氟空位点缺陷晶体在100 GPa压力范围内的光吸收谱和折射率. 吸收谱数据表明, 压力因素诱导的两个结构相变对 CaF2的吸收谱均有影响: 第一个相变将导致其吸收边蓝移, 而第二个相变却引起其吸收边红移. 钙空位点缺陷会使得CaF2的吸收边微弱蓝移, 但氟空位点缺陷却导致其吸收边有显著的红移. 然而, 这些红移的行为并未使得CaF2晶体在250-1000 nm的波段范围内出现光吸收的现象(是透明的). 532 nm处的折射率数据显示, 在 CaF2的三个结构相区(Fm3m、Pnma、P63/mmc相区), 其折射率均随压力增大而增加; 同时, 高压结构相变以及氟空位点缺陷也使得CaF2的折射率增大, 但钙空位点缺陷却导致其折射率减小. 数据分析表明, CaF2晶体有成为冲击窗口材料的可能, 本文所获得的信息对未来的实验研究有参考价值. 相似文献
2.
本文采用第一性原理方法, 计算了SrF2的理想晶体和含锶、氟空位点缺陷晶体在100 GPa压力范围内的光学性质. 吸收谱数据表明, 压力因素引起的两个结构相变对SrF2的吸收谱均有影响: 第一个相变将导致其吸收边蓝移, 第二个相变将导致其吸收边红移. 空位点缺陷的存在将使得SrF2的吸收边红移, 其中氟空位点缺陷引起的红移行为更显著. 尽管如此, 这些红移并未使得SrF2晶体在可见光区出现光吸收的现象(是透明的). 波长在532 nm处的折射率数据指明, 在SrF2的三个结构相区, 其折射率均随压力的增加而增大, 且SrF2的高压结构相变也使得其折射率增大. 锶空位点缺陷将导致SrF2的折射率降低, 但氟空位点缺陷的存在对其基本没有影响. 分析表明, SrF2晶体有成为冲击窗口材料的可能. 相似文献
3.
光胶垫板技术条件的给定,直接影响到光胶垫板的使用性能和加工效率。通过对其目前所应用规范的分析,指出对其修正的必要性,提出了较合理并经实践验证的有关技术条件,不但确保了使用性能,而且降低了加工和检测的难度,提高了加工效率。 相似文献
5.
Javier Catalán 《Journal of Physical Organic Chemistry》2013,26(11):948-952
The solvatochromism of β‐carotene confirms its high sensitivity not only to the polarizability of the medium, but is also contaminated by additional solute/solvent interactions due to its dipolarity and acidity, as well as to changes in its molecular structure in some solvents. A thermochromic analysis of β‐carotene dissolved in 2‐methylbutane and 1‐chlorobutane (ClB) revealed the influence of the solvent dipolarity on its UV/Vis‐spectroscopy behavior in these solvents. Applying Abe's method to the solvent‐induced shift of the first Vis absorption band of β‐carotene in ClB revealed that the electronic excitation substantially increases its polarizability and its dipole moment. Other experimental evidence also confirms that β‐carotene is not a suitable polarizability probe of the medium. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
6.
7.
8.
An-Ge Wang Wen-Shu Yang Sheng-Fang Lv Xiao-Fei Yue Song-Lin Wu Jie Liu 《International Journal of Theoretical Physics》2017,56(2):339-350
The stationary state entanglement in a chain with three spins is reported. Each of spins couples to its own separate bosonic reservoir. The master equation for such spins’ system is derived under the Born-Markovian approximation. The result presents that the coupling between the middle spin and its bosonic bath in some special temperature region reinforce the entanglement between the spins. By analyzing the heat current between the middle spin and its bosonic bath, we find a tight relationship between the direction of heat current from the middle spin to its bosonic bath and the reinforcement of the entanglement. The entanglement increases with the heat current between the middle spin and its bosonic bath almost linearly. 相似文献
9.
It is proven that the relativistic charged ball with its charge less than its mass (in natural units) cannot have a nonsingular static configuration while its radius approaches its external horizon size. This conclusion does not depend on the details of charge distribution and the equation of state. The involved assumptions are (i) the ball is made of perfect fluid;(ii) the energy density is everywhere non-negative. 相似文献
10.
Giacomo Grasso Carlo Oppici Federico Rocchi Marco Sumini 《Physics in Perspective (PIP)》2009,11(3):318-335
We present a neutronics study of the German B-VIII nuclear reactor, which was built in Haigerloch, Germany, between February
and April 1945. We used the Monte Carlo code MCNP5 to estimate its effective nuclear-multiplication constant keff and its corresponding neutron-multiplication factor M, its neutron energy-distribution spectrum, and its neutron-flux distribution in its central horizontal and veritical planes
for both thermal and fast neutrons. Our calculations agree well with the known measurements the German scientists made, who
determined M to be 6.7. We also found that the effect on keff of impurities in the graphite of its neutron reflector could have been only on the order of few hundredths of a percent. 相似文献
11.
12.
Meng Chen Heng Jiang Yafei Feng Yuren Wang 《Applied Physics A: Materials Science & Processing》2014,117(4):2067-2072
We experimentally and theoretically investigated the mechanisms of acoustic absorption in phononic glass to optimize its properties. First, we experimentally studied its locally resonant absorption mechanism. From these results, we attributed its strong sound attenuation to its locally resonant units and its broadband absorption to its networked structure. These experiments also indicated that the porosity and thickness of the phononic glass must be tuned to achieve the best sound absorption at given frequencies. Then, using lumped-mass methods, we studied how the absorption bandgaps of the phononic glass were affected by various factors, including the porosity and the properties of the coating materials. These calculations gave optimal ranges for selecting the porosity, modulus of the coating material, and ratio of the compliant coating to the stiff matrix to achieve absorption bandgaps in the range of 6–30 kHz. This paper provides guidelines for designing phononic glasses with proper structures and component materials to work in specific frequency ranges. 相似文献
13.
The distribution of wealth in human populations displays a Log–Gauss–Pareto composite statistical structure: its density is Log–Gauss in its central body, and follows power-law decay in its tails. This composite statistical structure is further observed in other complex systems, and on a logarithmic scale it displays a Gauss-Exponential structure: its density is Gauss in its central body, and follows exponential decay in its tails. In this paper we establish an equilibrium Langevin explanation for this statistical phenomenon, and show that: (i) the stationary distributions of Langevin dynamics with sigmoidal force functions display a Gauss-Exponential composite statistical structure; (ii) the stationary distributions of geometric Langevin dynamics with sigmoidal force functions display a Log–Gauss–Pareto composite statistical structure. This equilibrium Langevin explanation is universal — as it is invariant with respect to the specific details of the sigmoidal force functions applied, and as it is invariant with respect to the specific statistics of the underlying noise. 相似文献
14.
Chryssomalis Chryssomalakos Ralf A. Engeldinger Branislav Jurčo Michael Schlieker Bruno Zumino 《Letters in Mathematical Physics》1994,32(4):275-281
We introduce a *-structure on the quantum double and its dual in order to make contact with various approaches to the enveloping algebras of complex quantum groups. Furthermore, we introduce a canonical basis in the quantum double, its universalR-matrices and give its relation to subgroups in the dual Hopf algebra. 相似文献
15.
The ISOLDE on-line isotope separator started its operation in an external beam from the CERN SC in 1967. Since then there
has been a steady development of its technical performance and its physics programme so that ISOLDE today is a major facility
at CERN.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Larry S. Liebovitch Vincent Naudot Andrzej Nowak Lan Bui-Wrzosinska Peter Coleman 《Physica A》2008,387(25):6360-6378
We present a nonlinear ordinary differential equation model of the conflict between two actors, who could be individuals, groups, or nations. The state of each actor depends on its own state in isolation, its previous state in time, its inertia to change, and the positive feedback (cooperation) or negative feedback (competition) from the other actor. We analytically determined the stability of the critical points of the model and explored its dynamical behavior through numerical integrations and analytical proofs. Some results of the model are consistent with previously observed characteristics of conflicts, and other results make new testable predictions on how the dynamics of a conflict and its outcome depend on the strategies chosen by the actors. 相似文献
17.
Graphene is an emergent research topic that has attracted a huge amount of research interest ever since its experimental demonstration as a two-dimensional realization of Dirac fermions in 2005. In subsequent years, the research on graphene has rapidly expanded its field not only due to the new paradigm to study relativistic high energy physics in a condensed matter, but also due to its potential in the application for next generation devices. Most of the novel phenomena observed so far in graphene are attributed to its low-energy excitations, which is described by those of relativistic Dirac fermions. This article reviews recent progress in angle-resolved photoemission spectroscopy studies of electron-electron interactions in graphene. 相似文献
18.
19.
简述三类光子晶体光纤(Photonic crystal fibers,PCF)的结构、导光机制及特性,介绍了PCF的研究现状和在光通信中的应用,并探讨了PCF的应用前景。 相似文献
20.
测角系统的精度及其可靠性直接影响光电经纬仪的测量精度。GJ-341小型遥控光电经纬仪的测角系统采用19位增量式编码器,理论上达到了要求。但由于测角系统及其可靠性存在诸多问题,使其在实际使用中无法满足GJ-341小型遥控光电经纬仪测角精度的要求。本文分析测角系统及其可靠性对GJ-341小型遥控光电经纬仪测量精度的影响。 相似文献