Effect of cobalt on the magnetoresistance characteristics of rare-earth doped manganites

The effect of cobalt-doping on the magnetic, transport and magnetoresistance characteristics of La_1-xSr_xMnO₃ was investigated. The results show that the magnetoelectric property of rare-earth doped manganites is greatly affected by substitution of Co for Mn sites. The Curie temperature as well as the magnetic moment decreases with the increase of doping concentration, and the samples exhibit obvious characteristics of the spin glass state. Moreover, the magnetoresistance is evidently modulated by doping concentration, and the relevant temperature dependence is also suppressed. In addition, low-temperature magnetoresistance is significantly promoted as doping concentration increases, which renders a value of approximately 50% in the temperature range of 5--200~K and varies within 12.5%. It can be attributed to the effect of spin scattering, induced by cobalt doping, on the itinerant electrons of Mn ions, thus introducing a spin-disorder region into the ferromagnetic region of double-exchange interaction between neighbouring Mn³⁺ and Mn ³⁺ ions.     

绿色杜氏藻GGR基因生物信息学分析及表达研究

采用Illumina HiSeqTM 2000高通量测序方法获得绿色杜氏藻GGR基因(GenBank序号: KX100480) cDNA全长序列, 研究了甲基茉莉酸(MeJA)对绿色杜氏藻GGR基因表达的影响. 测序结果表明, 绿色杜氏藻GGR基因cDNA全长2356bp, 开放阅读框1539bp, 编码512个氨基酸, 分子量为52.2961kDa, 理论等电点为6.54. 序列分析结果表明, 该蛋白具有保守的ChlP结构域, 为可溶性蛋白, 具有跨膜区域, 无信号肽. TargetP 1.1 Server预测结果表明, 该蛋白可能定位于线粒体. 系统进化树结果表明, 绿色杜氏藻GGR蛋白较其他植物的GGR蛋白亲缘关系较 远. RT-PCR结果表明, 100?mol·L-1 MeJA可显著地提升绿色杜氏藻GGR基因的表达(P<0.01). 同时, 绿色杜氏藻叶绿素和类胡萝卜素含量达到最高, 说明GGR基因与绿色杜氏藻叶绿素和类胡萝卜素的合成存在一定关系     

不同价态稀土元素Eu掺杂锐钛矿相TiO2的电子结构及光学性质

基于密度泛函理论(DFT)的第一性原理的平面波超软赝势法对锐钛矿TiO2晶体和Eu3+,Eu2分别掺杂的锐钛矿TiO2晶体的晶格参数、能带结构、态密度、差分电荷密度以及吸收光谱进行了计算.结果表明:不同价态Eu掺杂后锐钛矿TiO2晶胞膨胀,晶格都发生畸变;同时引入了杂质能级,减小了锐钛矿相TiO2的禁带宽度,TiO2的光吸收带边发生明显红移,在紫外区和可见光区的吸收系数增大.     

直流磁场下销盘摩擦过程中的电磁感应力矩分析

为了研究磁场对材料摩擦磨损性能的影响,本文分析了直流磁场下销盘摩擦过程中的涡流和电磁感应力,并通过积分得到感应力矩的计算公式.在销盘0.1 mm间隙时检测了磁吸力和在不同试验条件下盘试样所受的感应力矩,利用试验数据对感应力矩公式中的修正系数进行了最小二乘法拟合,所得感应力矩公式的计算结果与不同电流和转速下的试验数据很好地吻合.在摩擦磨损过程中,可利用感应力矩公式计算出相应试验条件下盘所受的感应力矩,分析其对摩擦系数的影响.     

强阿秒XUV激走脉冲下H2^＋分子光电子能谱角分布非对称性

利用2D平面模型,求解了描述定向H2^＋分子和阿秒XUV脉冲相互作用的薛定谔方程,并求得光电子的角度分布．在计算模型中,采用基态1sσg和第一激发态2pσu的等比例混合态作为初始态,而激光脉冲的光子能量大于电离势,强度为10^14 W/cm^2． 计算结果表明,光电子角分布的非对称性和脉冲的宽度密切相关．这种非对称性实际上是由于初始态的基态和激发态的相干振荡而导致的．当使用长脉冲时,这种相干振荡的周期效应就会被平均而消失,从而产生的光电子能谱会呈对称角分布．     

High-Pressure and High-Temperature Behaviour of Gallium Oxide

High-temperature and high-pressure behaviours of β-Ga2O3 powder are studied by energy-dispersive x-ray diffrac- tion in a diamond anvil cell （DAC）. It is found that the phase transition from the monoclinic β-Ga2O3 to the trigonal α-Ga2O3 occurs at around 19.2 GPa under cold compression. By heating the powder to 2000 K at 30 GPa, we confirm that α-Ga2O3 is the most stable structure at the high pressure. Furthermore, the structural transition from β-Ga2O3 to α-Ga2O3 is irreversible. After laser heating, the recrystallized Ga2O3 has a preferable （012） orientation. This interesting behaviour is also discussed.     

基于FOA-FSVM的RF模式台风期阵风精细化预报

For the sake of improving the accuracy of forecasting wind speed during typhoon strike in WRF model forecast, a new method for precision forecasting of typhoon wind speed is proposed by combining the data collected from the WRF model forecast and an automatic observation station. The method incorporates many factors influencing the typhoon wind speed. The wind speed which is obtained using the traditional human prediction produces large error when compared with actual wind speed. To address this issue, a fuzzy support vector regression model for wind forecasting is built. Considering the fact that the fuzzy support vector regression model is not adequately efficient in determining the punishment factor and kernel parameter, the fly optimization algorithm is introduced into optimizing the parameters of the fuzzy support vector machine. According to the characteristics of the wind speed regression, the fruit fly optimization algorithm is developed in three dimensional space, combining with the enhancement factor γ for improving the global optimization ability of traditional fruit fly optimization algorithm. The results show that the forecasting wind speed and the actual one is in good agreement with each other, and the correlation is as high as 99％. The presented method of wind speed prediction provides higher accuracy than that of traditional FOA-FSVM model and FOA-SVM model.     

宽激发带稀土激活碱土金属硅酸盐发光材料特性研究

采用高温固相法合成了系列新的宽激发带发光材料M2MgSi₂O₇∶Eu, Dy(M=Ca, Sr);表征了各基质化合物的晶体结构;考察了碱土金属离子相互部分替代对晶体结构、光谱及发光特性的影响。荧光光谱和发光特性研究结果表明,该系列硅酸盐基质发光材料具有很宽的激发光谱,激发带均延伸到了可见区,紫外或可见光照射后可分别产生黄、绿、蓝不同颜色长余辉光发射。在450～480 nm区域间可以非常有效地激发Ca₂MgSi₂O₇∶Eu, Dy,于536 nm处产生强光发射,与InGaN芯片的蓝光复合可产生白光,表明该体系可用作白光LED的黄光发射发光材料。     

Effect of the liquid temperature on the interaction behavior for single water droplet impacting on the immiscible liquid

The interaction of single water droplet impacting on immiscible liquid surface was focused with the temperature varying from 50 ℃ to 210 ℃. The impact behavior is recorded with a high-speed camera running at 2000 frames per second. It is found that droplet diameter, oil temperature, and Weber number have important influences on impact behaviors. Three typical phenomena, including penetration, crater-jet, and crater-jet-secondary jet, were observed. Penetration only occurs when the Weber number is below 105. With Weber number increasing to 302, the jet begins to appear. Moreover, to gain deeper physical insight into the crater formation and jet formation, the energy of droplet impingement onto the liquid pool surface was estimated. The oil temperature has a significant effect on the energy conversion efficiency. High temperature is beneficial to improve energy conversion efficiency.     

关于极大外平面图的度偏差的极值

设G是一个由n个顶点,m条边构成的简单连通图.如果图G所有顶点的度相同,则我们称图G是正则图,反之,称图G是不规则图.对于一个不规则图G,由其不变量定义的度偏差为s(G)=∑_(i=1)^(n)|d_(i)-2m/n|,其中d_(i)表示G的第i个顶点的度.本文给出极大外平面图的度偏差的极大值和极小值,并刻画其对应的极值图.