钙钛矿结构ZrBeO3稳定性的第一性原理研究

基于密度泛函理论构建了钙钛矿结构ZrBeO3晶体模型,计算了该晶体模型结合能,表明了该构型热力学稳定性;计算出该结构在不同压力下的弹性常数,并据此计算了ZrBeO3的体积模量、剪切模量、杨氏模量、泊松比、BH/GH(体模量/剪切模量)等参数,结果表明该材料具有机械稳定性,随着等静压力增加,材料由脆性向韧性转变;计算了零压下ZrBeO3的硬度,为34.5 GPa,表明该结构晶体应为超硬材料;计算了ZrBeO3的声子能谱,结果表明ZrBeO3在低温零压下热动力学不稳定,为此分析比较了不同压力下的声子能谱、不同原子轨道及化学键布居值,研究表明随着压力增加,Be原子sp杂化后形成的Be-O共价键成分增强、Zr-O键离子键成分增强,晶格动力学趋于稳定。     

Aberration improvement of the floating 3D display system based on Tessar array and directional diffuser screen

The floating 3D display system based on Tessar array and directional diffuser screen is proposed. The directional diffuser screen can smoothen the gap of lens array and make the 3D image’s brightness continuous. The optical structure and aberration characteristics of the floating three-dimensional (3D) display system are analyzed. The simulation and experiment are carried out, which show that the 3D image quality becomes more and more deteriorative with the further distance of the image plane and the increasing viewing angle. To suppress the aberrations, the Tessar array is proposed according to the aberration characteristics of the floating 3D display system. A 3840?×?2160 liquid crystal display panel (LCD) with the size of 23.6 inches, a directional diffuser screen and a Tessar array are used to display the final 3D images. The aberrations are reduced and the definition is improved compared with that of the display with a single-lens array. The display depth of more than 20 cm and the viewing angle of more than 45° can be achieved.     

Tunable dual-wavelength fiber laser based on an opto-VLSI processor and four-wave mixing in a photonic crystal fiber

A stable wavelength and wavelength spacing tunable dual-wavelength fiber laser based on an Opto-very-large-scale-integration (Opto-VLSI) processor and four-wave mixing (FWM) in a high-nonlinear photonic crystal fiber is experimentally demonstrated. The results show that the line width of the tunable dual-wavelength fiber laser is 0.02 nm, and the wavelength spacing can be tuned from 0.8 nm to 4 nm with a 0.15 nm step. Under the influence of the FWM, the uniformity is below 0.6 dB and the measured side mode suppression ratio (SMSR) is above 45 dB.     

带有环境反馈的不对称劳动分工博弈模型

带有环境反馈的两策略博弈被广泛研究,本文研究带有环境反馈的三策略博弈模型.环境被分为富裕斑块和贫穷斑块,富裕的斑块可以为玩家提供额外的环境收益,而贫穷斑块不为玩家提供任何收益.首先,建立模仿者动力学模型,推导模型平衡点稳定性的充分条件.该模型平衡点的稳定性取决于各策略的成本、富裕环境的收益、策略C对策略A和策略B的干扰以及策略A和策略B的合作效益.此外,通过对模型进行数值模拟,可以发现与初始期望结果一致,并且得到了在异质环境下各策略的频率.     

Dynamic analysis of Michaelis–Menten chemostat-type competition models with time delay and pulse in a polluted environment

In this paper, a new Michaelis–Menten type chemostat model with time delay and pulsed input nutrient concentration in a polluted environment is considered. We obtain a ‘microorganism-extinction’ semi-trivial periodic solution and establish the sufficient conditions for the global attractivity of the semi-trivial periodic solution. By use of new computational techniques for impulsive differential equations with delay, we prove and support with numerical calculations that the system is permanent. Our results show that time delays and the polluted environment can lead the microorganism species to be extinct.     

Pressure–volume–temperature equations of state of Au and Pt up to 300 GPa and 3000 K: internally consistent pressure scales

By using a Mie–Grüneisen-type analysis method, the pressure–volume–temperature equations of state (P–V–T EOSs) of Au and Pt have been determined up to 300?GPa and 3000?K based on the experimental shock Hugoniot and thermodynamic data. The calculated results of Au and Pt show an excellent agreement with available experimental volume compression data over a wide range of pressures and temperatures. A comparison of our results with previous theoretical investigations has also been done. In addition, we have further examined the consistency of our results and the P–V–T EOS of MgO [K. Jin, X.Z. Li, Q. Wu, H.Y. Geng, L.C. Cai, X.M. Zhou, and F.Q. Jing, The pressure–volume–temperature equation of state of MgO derived from shock Hugoniot data and its application as a pressure scale, J. Appl. Phys. 107 (2010), pp. 113518] using simultaneous volume measurements of Au, Pt, and MgO at various temperatures. The good agreement among the P–V–T EOSs of Au, Pt, and MgO implies that these EOSs can be used as the reliable pressure scales in high pressure–temperature diamond anvil cell experiments.     

Applications of Nonlinear Effects in Highly Nonlinear Photonic Crystal Fiber to Optical Communications

Unique dispersion characteristics and enhanced nonlinearity make the small-core photonic crystal fiber (PCF) an ideal candidate for nonlinear optical devices to telecommunication applications. Some technical reasons behind great research interest of highly nonlinear PCFs in optical communication components are reviewed. Nonlinear effects in highly nonlinear PCFs and their research progress are presented. Several typical applications including WDM sources, optical amplification, optical switching, wavelength conversion, optical regeneration and all-optical demultiplexing etc are introduced, together with state-of-the art performances. Some new possible applications and future prospects are discussed.     

Periodic solution of a pest management Gompertz model with impulsive state feedback control

In this paper, a new model with two state impulses is proposed for pest management. According to different thresholds, an integrated strategy of pest management is considered, that is to say if the density of the pest population reaches the lower threshold \(h_1\) at which pests cause slight damage to the forest, biological control (releasing natural enemy) will be taken to control pests; while if the density of the pest population reaches the higher threshold \(h_2\) at which pests cause serious damage to the forest, both chemical control (spraying pesticide) and biological control (releasing natural enemy) will be taken at the same time. For the model, firstly, we qualitatively analyse its singularity. Then, we investigate the existence of periodic solution by successor functions and Poincaré-Bendixson theorem and the stability of periodic solution by the stability theorem for periodic solutions of impulsive differential equations. Lastly, we use numerical simulations to illustrate our theoretical results.     

Configuration of virtual cameras for ground based 360° three-dimensional display

Most technologies provide three-dimensional (3D) display in the front of screens which are in parallel with the walls, and the sense of immersion is decreased. To get the right ground based 3D imaging, cameras’ imaging planes should be parallel to the public focus plane, and the cameras’ optical axes should be shifted to the center of the public focus plane in both vertical and horizontal directions. Virtual cameras are used to display 3D model in computer system. Two virtually capturing methods for ground based 3D display are presented. The position of virtual camera is determined by the observer's eye positions in the real world. When the observer stands in the displayed circumcircle on the ground, off-axis perspective projection virtual cameras are used. If the observer stands out the circumcircle, offset perspective projection virtual cameras and the orthogonal projection virtual cameras are adopted. An experimental system for ground based 360° 3D display is demonstrated for viewing horizontally, which provides high-immersion 3D visualization. The displayed heights are compared with the measured results.