Na_2Ge_2Se_5电子结构和光学性质的第一性原理研究

Na_2Ge_2Se_5是一种优异的红外非线性晶体材料.采用基于第一性原理的密度泛函理论赝势平面波方法对Na_2Ge_2Se_5进行结构优化,并以此为基础计算研究了Na_2Ge_2Se_5的电子结构和光学性质.结果表明:Na2Ge2Se5是宽禁带间接带隙半导体,价带至导带的电子跃迁主要来自于Ge和Se的48,4p态;Na对光学性质的贡献较小,Ge和Se之间的相互耦合作用决定了Na_2Ge_2Se_5的光学性质;该晶体在紫外区有强烈的反射和吸收,静态折射率为2.133,双折射率值适中,为0.145.理论计算结果表明,Na_2Ge_2Se_5是一种性能优良的红外非线性光学晶体材料.     

L_p-新几何体极的几个不等式

通过分析Lp-类质心体TpK和类新几何体T-pK的概念,研究它们之间的性质及关系,建立了关于Lp-类质心体和类新几何体极体的几个有趣的不等式,同时探讨了Lp-类质心体TpK和类新几何体T-pK的单调性问题.     

铅卤钙钛矿法布里-帕罗谐振腔激光器

随着后摩尔时代的到来,对大容量、高速度信息处理的需求使得半导体器件应用由电子集成转向光子集成,高性能微纳激光器是实现光子集成的重要环节.种类丰富的半导体材料促进了半导体微纳激光器的快速发展,近年来,随着大量新型半导体材料(如二维半导体、铅卤钙钛矿等)的涌现,有望实现半导体微纳激光器性能的进一步提升.由于钙钛矿材料具有高光吸收、缺陷高容忍、激子结合能大等优异光学性质,使其成为高增益、低阈值半导体微纳激光器的优秀候选材料.法布里-珀罗(F-P)谐振腔激光器是钙钛矿激光器中研究广泛、结构简单、应用价值较高的一类激光器.本文以铅卤钙钛矿F-P谐振腔激光器为例,对其工作机理以及近年来的研究成果进行综述,从激子与光子弱耦合的光子激光和强耦合的极化子激光两个方面出发,详细介绍了钙钛矿材料既作为增益介质又作为谐振腔的F-P结构激光器以及仅作为增益介质的F-P腔激光器的激光的产生原理和影响因素,最后总结了钙钛矿F-P谐振腔激光器当前面临的挑战,展望了其进一步发展可能具备的前景.     

Coulomb expansion of deuterated methane clusters irradiated by an ultrashort intense laser pulse

The simulations of three-dimensional particle dynamics show that when irradiated by an ultrashort intense laser pulse, the deuterated methane cluster expands and the majority of deuterons overrun the more slowly expanding carbon ions, resulting in the creation of two separated subelusters. The enhanced deuteron kinetic energy and a narrow peak around the energy maximum in the deuteron energy distribution make a considerable contribution to the efficiency of nuclear fusion compared with the ease of homonuelear deuterium clusters. With the intense laser irradiation, the nuclear fusion yield increases with the increase of the cluster size, so that deuterated heteronuelear clusters with larger sizes are required to achieve a greater neutron yield.     

Core loss analysis of Finemet type nanocrystalline alloy ribbon with different thickness

Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability,magnetization and low core loss.In this paper,Fe_(73.5)Cu_1Nb_3Si_(15.5)B_7(at%)nanocrystalline alloy ribbons,with ultra-thin thickness of 14μm,and also 18 and 22μm,were prepared by a planar flow casting method with a single roller device.Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing.The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10–100 kHz,at induction amplitudes of 100–500 m T,at room temperature.It was found that the excess eddy current loss P_(ex)was the dominant factor in the overall core loss above 10 k Hz.The toroidal samples made of the 14μm thickness ribbon exhibit very low total core loss of 48 W/kg at a frequency of100 kHz and magnetic flux density of 300 mT.The ratio of the P_(ex)was up to 89%at 100 kHz.The ribbon with lower thickness exhibits lower P_(ex)and therefore lower total core loss.The domain structure evidences were found.It indicates that the ribbons with small thickness are preferable for application in high frequency condition.     

ZnO/WO_3纳米片薄膜的光电催化性能研究

采用水热法在不锈钢基底上制备WO3纳米片阵列,然后将其浸渍于不同浓度Zn(NO_3)_2溶液中以负载ZnO纳米颗粒,从而制备出ZnO/WO_3纳米片薄膜。采用场发射扫描电镜(FESEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见吸收光谱(UV-Vis)和电化学阻抗图谱(EIS)等方法对ZnO/WO_3复合薄膜的形貌、结构、物相组成和光电性能等进行分析,重点考察了薄膜电极对亚甲基蓝(MB)的光电催化降解性能。结果表明,WO_3纳米片均匀垂直于基底生长,Zn元素以ZnO颗粒的形式分布在WO_3表面;ZnO的引入促进了WO_3中产生的光生电子-空穴对的分离,从而使ZnO/WO_3复合薄膜表现出比纯WO_3薄膜更优异的光电性能和光电催化活性;在Zn(NO_3)_2浸渍液浓度为20mmol/L时,所制ZnO/WO_3复合薄膜具有最佳的光电催化性能,在MB溶液初始浓度为10mg/L、外加偏压为0.8V、光照1h的条件下,采用该样品对MB的降解率达96.5%,并且复合薄膜具有良好的循环稳定性,在重复使用5次后,对MB的光电催化降解效率没有明显降低,有望在实际污水处理中得到应用。     

磷化钴/碳纳米管纳米复合电极材料的电催化制氢性能研究

采用化学气相沉积法,在316L不锈钢基底上原位生长碳纳米管,然后在一定浓度的CoSO_4、NaH_2PO_2、NaOAc混合溶液中,用电化学沉积法在碳纳米管表面负载磷化钴纳米颗粒,得到磷化钴/碳纳米管复合结构。利用SEM、EDS和拉曼光谱,对CoP/CNTs复合材料的形貌、成分及物相组成进行分析;通过阴极极化曲线、交流阻抗等电化学测试,重点考察了复合电极在0.5mol/L H_2SO_4溶液中的电催化析氢性能。结果表明,所制CoP/CNTs复合结构中,CoP呈颗粒状均匀分布在CNTs表面;CoP的引入提高了碳纳米管材料的电催化性能,当沉积圈数为4圈时,所制CoP/CNTs复合电极具有最佳的电催化活性;极化曲线测试表明,该电极在电流密度为10mV·cm~(-2)时的过电位与沉积2圈和6圈的CoP/CNTs复合电极相比,正移了约140 mV和90mV,同时也呈现出良好的循环稳定性。     

Mechanism and simulation of droplet coalescence in molten steel

Droplet coalescence in liquid steel was carefully investigated through observations of the distribution pattern of inclusions in solidified steel samples. The process of droplet coalescence was slow, and the critical Weber number (We) was used to evaluate the coalescence or separation of droplets. The relationship between the collision parameter and the critical We indicated whether slow coalescence or bouncing of droplets occurred. The critical We was 5.5, which means that the droplets gradually coalesce when We ≤ 5.5, whereas they bounce when We > 5.5. For the carbonate wire feeding into liquid steel, a mathematical model implementing a combined computational fluid dynamics (CFD)-discrete element method (DEM) approach was developed to simulate the movement and coalescence of variably sized droplets in a bottom-argon-blowing ladle. In the CFD model, the flow field was solved on the premise that the fluid was a continuous medium. Meanwhile, the droplets were dispersed in the DEM model, and the coalescence criterion of the particles was added to simulate the collision-coalescence process of the particles. The numerical simulation results and observations of inclusion coalescence in steel samples are consistent.     

Spheroidization of silica powders by radio frequency inductively coupled plasma with Ar-H2 and Ar-N2 as the sheath gases at atmospheric pressu

Amorphous spherical silica powders were prepared by inductively coupled thermal plasma treatment at a radio frequency of 36.2 MHz. The effects of the added content of hydrogen and nitrogen into argon (serving as the sheath gas), as well as the carrier gas flow rate, on the spheroidization rate of silica powders, were investigated. The prepared silica powders before and after plasma treatment were examined by scanning electron microscopy, X-ray diffraction, and laser granulometric analysis. Results indicated that the average size of the silica particles increased, and the transformation of crystals into the amorphous state occurred after plasma treatment. Discharge image processing was employed to analyze the effect of the plasma temperature field on the spheroidization rate. The spheroidization rate of the silica powder increased with the increase of the hydrogen content in the sheath gas. On the other hand, the spheroidization rate of the silica power first increased and then decreased with the increase of the nitrogen content in the sheath gas. Moreover, the amorphous content increased with the increase of the spheroidization rate of the silica powder.     

Anti-Interference Low-Power Double-Edge Triggered Flip-Flop Based on C-Elements

When the input signal has been interfered and glitches occur,the power consumption of Double-Edge Triggered Flip-Flops (DETFFs) will significantly increase.To e...