Antiferromagnetic interactions in Er-doped SnO<Subscript>2</Subscript> DMS nanoparticles

Diluted magnetic semiconductor (DMS) nanoparticles of Sn_1−x Er _x O₂ (x = 0.0, 0.02, 0.04, and 0.1) were prepared by sol–gel method. The X-ray diffraction patterns showed SnO₂ rutile structure for all samples with no impurity peaks. The decrease in crystallite size with Er concentration was confirmed from TEM measurements (from 12 to 4 nm). The UV–Visible absorption spectra of Er-doped SnO₂ nanoparticles showed blue shift in band gap compared to undoped SnO₂. The electron spin resonance analysis of Er-doped SnO₂ nanoparticles indicate Er³⁺ in a rutile lattice and also decrease in intensity with Er concentration above x = 0.02. Temperature-dependent magnetization studies and the inverse susceptibility curves indicated increased antiferromagnetic interaction with Er concentration.     

Mechanical and corrosion resistance of hydrophilic sphene/titania composite coatings on titanium and deposition and release of cefazolin sodium/chitosan films

The mechanical and corrosion resistance of hydrophilic sphene/titania composite coatings on titanium formed by a hybid technique of microarc oxidation (MAO) and heat-treatment were investigated. The results indicated that the heat-treatment could improve the hardness, elastic modulus, elastic recovery and corrosion resistance of the MAO coatings, and reinforce the interface bonding between MAO coatings and titanium. A cefazolin sodium/chitosan drug film was prepared on the coating surfaces. The drug load procedures such as the addition of chitosan obviously increased the sustained-release ability of drug films. In addition, the increase of cefazolin sodium concentration could increase the accumulative release concentration of cefazolin sodium. The sustaining-release ability of drug films deposited on the MAO and heat-treated MAO coatings is similar. In the interior of drug film, the physical and chemical bonding reactions such as Coulombic interactions, van der Waals force and H-bonding etc. could be produced, through the chemical group interactions such as -OH and -NH₂ groups of chitosan with -CO of cefazolin sodium.     

A density functional theory study on parameters fitting of ultra long armchair （n, n） single walled boron nitride nanotubes

Armchair(n,n) single walled boron nitride nanotubes with n = 2-17 are studied by the density functional theory at the B3LYP/3-21G(d) level combined with the periodic boundary conditions for simulating the ultra long model.The results show that the structure parameters and the formation energies bear a strong relationship to n.The fitted analytical equations are developed with correlation coefficients larger than 0.999.The energy gaps of(2,2) and(3,3) tubes are indirect gaps,and the larger tubes(n = 4-17) have direct energy gaps.Results show that the armchair boron nitride nanotubes(n = 2-17) are insulators with wide energy gaps of between 5.93 eV and 6.23 eV.     

抗磁悬浮振动能量采集器动力学响应的仿真分析

分析了微型抗磁悬浮振动能量采集器中悬浮磁体的受力特性,发现了能量采集器的单稳态和双稳态现象,研究了能量采集器在不同工作状态下该两种稳态类型时的动力学响应特性.当能量采集器处于非工作的单稳态状态时,其动力学响应是在线性系统的基础上加入非线性扰动、幅频响应曲线向右偏转;热解石墨板间距越大,非线性扰动越强烈,右偏现象则越显著.当能量采集器处于非工作的双稳态状态时,其动力学响应比较复杂,出现倍周期、4倍周期以及混沌等非线性系统特有的现象.当能量采集器处于工作状态的双稳态状态时,其振动频率和外界激励频率保持一致,进行周期振动.该研究对抗磁悬浮振动能量采集器的结构设计具有重要的参考价值,为提高能量采集器的响应特性和输出性能提供了理论指导.     

傅里叶变换轮廓术中新的相位及高度算法分析

在传统傅里叶变换轮廓术三维面型测量中,为了准确得到被测物体的高度分布,必需保证投影仪出射光瞳和摄像机入射光瞳的连线与参考面平行并且在同一水平面,否则存在较大的误差。着眼于更普通的情况,讨论双瞳连线与参考面成某一夹角时的高度计算,推导出了非平行时的参考面光场及物面变形条纹光场的表达式,并给出了高度映射公式。因而,传统的傅里叶变换轮廓术测量成为角度α=0时的特例。该方法使傅里叶变换轮廓术的测量条件得到了放宽;易于通过移动投影装置或成像装置获取全场条纹;并为在难以实现双瞳与参考面平行的特殊环境下的测量提供了可行的方法。计算机模拟及实验均证实了该方法的有效性。     

Loop quantum gravity and black hole entropy quantization

Using the spin networks and the asymptotic quasinormal mode frequencies of black holes given by loop quantum gravity, the minimum horizon area gap is obtained. Then the quantum area spectrum of black holes is derived and the black hole entropy is a realized quantization. The results show that the black hole entropy given by loop quantum gravity is in full accord with the Bekenstein-Hawking entropy with a suitable Immirzi. Supported by the National Natural Science Foundation of China (Grant No. 10773002)     

Numerical study of optical properties of InGaN multi-quantum-well laser diodes with polarization-matched AlInGaN barrier layers

The optical properties of InGaN multi-quantum-well laser diodes with different polarization-matched AlInGaN barrier layers have been investigated numerically by employing an advanced device simulation program. The use of quaternary polarization-matched AlInGaN barrier layers enhances the electron–hole wave function overlap due to the compensation of polarization charges between InGaN quantum well and AlInGaN barrier layer. According to the simulation results, it is found that, among the polarization-matched quantum-well structures under study, lower threshold current and higher slope efficiency can be achieved simultaneously when the aluminum composition in AlInGaN barrier layers is about 10–15%. The optimal polarization-matched InGaN/AlInGaN laser diode shows lower threshold current and higher slope efficiency compared to conventional InGaN/InGaN laser diodes.     

Beam focusing from double subwavelength metallic slits filled with nonlinear material surrounded by dielectric surface gratings

Based on the radiation properties of surface plasmon polaritons (SPPs) can be controlled by adjusting the refractive indexes of dielectric materials in the metallic slits, a novel plasmonic focusing structure formed by two subwavelength metal apertures filled with Kerr nonlinear material surrounded by surface dielectric gratings is proposed and demonstrated numerically. Directions of radiation fields are determined by the phase difference of the surface waves at the exit interface and resonance property of each surface grating. Numerical simulations using two-dimensional (2D) Finite-Difference Time-Domain (FDTD) method verify that the deflection angle and focal length can be controlled easily by changing the intensity of incident light, dynamically tunable on-axis and off-axis focusing effects can be achieved.