First principles study on the structural, electronic and optical properties of diluted magnetic semiconductors Zn1-xCoxX （X=S, Se, Te）

The electronic and optical properties of zincblende ZnX（X=S, Se, Te） and ZnX：Co are studied from density functional theory （DFT） based first principles calculations. The local crystal structure changes around the Co atoms in the lattice are studied after Co atoms are doped. It is shown that the Co-doped materials have smaller lattice constant （about 0.6%-0.9%）. This is mainly due to the shortened Co-X bond length. The （partial） density of states （DOS） is calculated and differences between the pure and doped materials are studied. Results show that for the Co-doped materials, the valence bands are moving upward due to the existence of Co 3d electron states while the conductance bands are moving downward due to the reduced lattice constants. This results in the narrowed band gap of the doped materials. The complex dielectric indices and the absorption coefficients are calculated to examine the influences of the Co atoms on the optical properties. Results show that for the Co-doped materials, the absorption peaks in the high wavelength region are not as sharp and distinct as the undoped materials, and the absorption ranges are extended to even higher wavelength region.     

激光对碳纤维增强复合材料的热烧蚀数值模拟

高能激光对复合材料的辐照效应研究,可以拓展激光技术的应用范围。为了预测激光辐照下碳纤维增强复合材料的瞬态热响应,提出了一个简化计算模型。采用隐式有限体积方法求解控制方程,边界条件包括激光辐照加热、对流换热、辐射换热以及材料表面烧蚀。考虑了激光辐照过程中基体热分解、质量迁移、比热容变化情况。基于该烧蚀模型,预测了激光辐照下碳纤维增强复合材料的瞬态温度场和表面烧蚀速率,计算结果与文献试验数据一致。最后,通过修正烧蚀模型分析了高速气流剥蚀对激光辐照复合材料热效应的影响。     

稀土元素(Ce,Pr)掺杂GaN的电子结构和光学性质的理论研究

采用基于密度泛函理论的第一性原理平面波赝势法计算了稀土元素Ce,Pr掺杂GaN的晶格参数、能带、电子态密度和光学性质,使用LSDA +U的方法处理具有强关联作用的稀土4f态,并分析比较计算结果.计算表明:掺入Ce和Pr后的体系相比未掺杂的GaN晶格常数增大,带隙变窄,并分别在禁带中和价带顶附近引入了局域的杂质能级,该能级主要由Ce和Pr的4f电子提供;掺杂后都发生了磁有序化并产生磁矩;最后定性分析了掺杂前后介电函数和光吸收系数的变化,掺Ce的体系在介电函数和吸收系数的低能区出现了峰值,该峰的出现和禁带中的杂质能级到导带底的跃迁有关,而掺Pr的体系由于带隙变窄使介电峰和吸收边发生红移.     

基于灰色关联度-云模型的群评价数据质量改进方法及应用研究

针对群评价中的数据质量问题, 从评价专家和评价值两个角度进行了异常数据处理, 提出了基于灰色关联度-云模型的群评价数据质量改进方法。基于改进的云距离模型测算被评价对象云和目标云之间的差距, 采用TOPSIS法进行评价排序。将数据质量改进方法和云距离模型用于区域物流竞争力群评价, 改进了群评价的数据质量, 提高了评价结果的稳定性和代表性。     

Giant low-field magnetocaloric effect in EuTi(1-x)NbxO3(x = 0.05, 0.1, 0.15, and 0.2) compounds

The magnetic properties and magnetocaloric effect(MCE)of EuTi(1-x)NbxO3(x=0.05,0.1,0.15,and 0.2)compounds are investigated.Owing to electronic doping,parts of Ti ions are replaced by Nb ions,the lattice constant increases and a small number of Ti⁴⁺(3d^0)ions change into Ti³⁺(3d^1).It is the ferromagnetism state that is dominant in the derivative balance.The values of the maximum magnetic entropy change(-?SM^max)are 10.3 J/kg·K,9.6 J/kg·K,13.1 J/kg·K,and 11.9 J/kg·K for EuTi(1-x)NbxO3(x=0.05,0.1,0.15,and 0.2)compounds and the values of refrigeration capacity are 36,33,86,and 80 J/kg as magnetic field changes in a range of 0 T–1 T.The EuTi(1-x)NbxO3(x=0.05,0.1,0.15,and 0.2)compounds with giant reversible MCE are considered as a good candidate for magnetic refrigerant working at lowtemperature and low-field.     

基于平场全息凹面光栅的舌诊用光谱仪的研制

由于传统的望舌诊断法过于依赖中医师的经验判断,导致误诊的概率相对较大,而基于图像处理的舌诊法受光源、图像采集设备影响较大,同时对于病理不同而颜色相近的舌象识别率不高。为了克服上述缺点,利用舌光谱的“指纹效应”,通过使用光谱法来对不同性状的舌象进行诊断,为了实现这一目标,研制了一款用于舌象诊断的光谱仪,同时为了克服传统分光器件的不足,分光系统中采用了平场全息凹面光栅作为分光器件,能保证系统小型化、光通量利用率提高的同时,改善光谱成像的质量和分辨率。通过系统实验测试,该光谱仪的光谱范围达到340～850 nm, 分辨率优于2 nm,同时通过模拟实验充分验证了该系统的有效性。     

一种基于差动调焦的激光共轭引导传感器

提出了一种新型基于差动调焦的激光共轭引导传感器(简称LCTS),采用共轭引导原理,避免了在调试过程中激光直接打到靶上的散射影响,提高了对不同靶型的适应性,并克服了物镜景深对监测范围的限制,能够对不同高度的靶进行定位。LCTS实现了对靶和光点的同时定位和引导,能有效地提高靶和激光的引导精度和效率。     

二芳烯材料在重复擦写体全息存储中的应用研究

二芳烯材料是一种性能优异的光致色变材料,具有很好的抗疲劳性能,一般能重复擦写上万次,而不损失其性能。通过体全息光栅记录实验、角度复用体全息存储实验、重复擦写及强光记弱光读等实验,对二芳烯材料在重复擦写体全息存储中的应用进行了系统研究。由于二芳烯材料具有很高的折射率调制度(Δn=1.15×10-3)、可多次重复擦写、强光记弱光读的准非易失等性能,在可重复擦写的体全息存储中具有广阔的应用前景。     

Sixth Harmonic of A Nd：YVO4 Laser Generation In KBBF for ARPES

We report that a deep ultraviolet （DUV） laser from the sixth harmonic of a 1064nm laser has been firstly used as light source in an ultrahigh energy-resolution angle-resolved photoemission spectroscopy （ARPES）. The wavelength is 177.3nm obtained by using the second harmonic KBe2BO3F2 crystal with a frequency tripled 1064nm Nd：YVO4 laser. The large flux （10^14 - 10^15 photons/s） and narrow line width （0.26 meV） are suitable for the ultrahigh-energy resolution ARPES. The laser-ARPES can be a powerful tool to study the electronic structure at and near the Fermi level of the superconductor and correlated materials. The laser-ARPES has worked more than 500 h already.