Experimental and numerical study of a conical turbulent partially premixed flame

The structure and dynamics of a turbulent partially premixed methane/air flame in a conical burner were investigated using laser diagnostics and large-eddy simulations (LES). The flame structure inside the cone was characterized in detail using LES based on a two-scalar flamelet model, with the mixture fraction for the mixing field and level-set G-function for the partially premixed flame front propagation. In addition, planar laser induced florescence (PLIF) of CH and chemiluminescence imaging with high speed video were performed through a glass cone. CH and CH₂O PLIF were also used to examine the flame structures above the cone. It is shown that in the entire flame the CH layer remains very thin, whereas the CH₂O layer is rather thick. The flame is stabilized inside the cone a short distance above the nozzle. The stabilization of the flame can be simulated by the triple-flame model but not the flamelet-quenching model. The results show that flame stabilization in the cone is a result of premixed flame front propagation and flow reversal near the wall of the cone which is deemed to be dependent on the cone angle. Flamelet based LES is shown to capture the measured CH structures whereas the predicted CH₂O structure is somewhat thinner than the experiments.     

外应力对铁磁/反铁磁体系交换偏置的影响及阶跃现象

采用能量极小原理及S-W模型研究了外应力对铁磁/反铁磁（FM/AFM）双层薄膜体系交换偏置的影响.不施加外磁场时,根据能量与铁磁层磁化强度方向之间的关系,指出体系存在单稳态和双稳态两种不同的状态,是由交换各向异性与单轴各向异性之间的竞争控制的.体系处于单稳态还是双稳态直接决定着交换偏置的角度依赖关系.分析磁化过程发现,外磁场沿内禀易轴及内禀难轴方向施加时,磁滞回线的一支转换场发生突变,而另一支转换场则保持不变,最终导致交换偏置场和矫顽场出现阶跃行为.数值计算表明,交换偏置场和矫顽场在阶跃点均具有较大的数值 关键词： 单稳态 双稳态 外应力     

SiC缓冲层对Si表面生长的 ZnO薄膜结构和光电性能的改善

用脉冲激光沉积(PLD)技术制备了ZnO/SiC/Si和 ZnO/Si薄膜并制成了紫外探测器。利用X射线衍射(XRD),光致发光(PL)谱,I-V曲线和光电响应谱对薄膜的结构和光电性能进行了研究。实验结果表明:SiC缓冲层改善了ZnO薄膜的结晶质量和光电性能,其原因可能是SiC作为柔性衬底能够减少ZnO与Si 之间大的晶格失配和热失配导致的界面缺陷和界面态。     

可膨胀过热水系统多气核演化过程与临界过热度分析

使用分子动力学方法,研究过热水系统均质沸腾核化过程.采用Langevin 动力学方法控制体积可变系统的温度与压力,更好地模拟了沸腾实际物理过程.得到了液相系统体积连续膨胀、分子间距逐渐增大,最终稳定在汽相的现象学规律.当过热温度较高时,亚稳态液相系统可能在局部形成不同大小的近球形区域：气核,这些气核是不稳定的,处于不断演化之中.通过分析分子所受引力与斥力的共同作用,得到了气核形成与消亡以及多个气核融合的机理.比较了模拟结果与经典沸腾理论的差异,提出了气核生长是比气泡生长更为微观过程的认识.通过研究不同过热 关键词： 过热水系统 分子动力学 气核 临界过热度     

低反轰多腔热阴极微波电子枪物理设计

 为了开展基于自由电子激光的紧凑型太赫兹源技术研究,获得高品质（强流、低能散、低发射度）电子束,提出了一个低反轰双路微波馈入多腔热阴极微波电子枪的设计方案。用两路独立微波馈入激励微波电子枪,一路由首腔馈入激励首腔和实现阴极表面建场引出电子,另一路由后续腔馈入并通过腔间耦合激励各腔。两路微波互不耦合,通过移相器实现首腔和第2腔之间的相移连续可调。理论模拟结果表明:在一个射频周期内,热阴极微波电子枪的电子反轰功率约8 kW,平均反轰功率仅为1.2 W（重复频率25 Hz和脉宽6 μs）。     

EAST装置内置低温冷凝泵低温分配阀箱的研制

在全超导磁约束核聚变试验装置EAST中,为了防止杂质从偏虑器靶板附近进入等离子体核心,为EAST长脉冲放电试验提供持续的排灰能力以及装置长冲放电等,低温冷凝泵是必不可少的部件之一,在装置真空室上下安装了内置低温凝泵以提高装置运行参数,为满足低温泵的低温条件,增加一低温分配阀箱给内置低温冷凝泵提供低温条件。文中介绍应用于EAST装置系统中的内置低温冷凝泵分配阀箱研制的技术要求、冷却流程、结构特征。     

Influence of interface roughness on reflectivity of tungsten/boron-carbide multilayers with variable hi-layer number by X-ray reflection and diffuse scattering

from layer to layer during multilayer growing. The variation of the reflectivity and interface roughness with bi-layer number is accurately explained by the presented real-structure model.     

The static and hyper-frequency magnetic properties of a ferromagnetic-ferroelectric composite

This paper reports the static and hyper-frequency magnetic properties, as well as their relationship with microstructure, of the ferromagnetic-ferroelectric co-fired composite ceramic, (1−x)Ba₂Zn_1.2Cu_0.8Fe₁₂O₂₂-xPb(Ni_1/3Nb_2/3)_0.8Ti_0.2O₃. The X-ray diffraction results did not detect any other phase in the co-fired ceramics, but found a crystal structural distortion of ferrite phase. Scanning electron microscopy photos showed that two phases’ grains matched well and stacked compactly and the hexagonal ferrite changed its grain morphology. The saturation magnetization increased with the reduction of magnetic phase in the range of 0<x<0.65 because of the stress-induced structural distortion. The permeability decreases monotonically with the reduction of magnetic phase in the whole composition range.     

Talbot effect under illumination of double femtosecond laser pulses

The Talbot effect under illumination of double femtosecond laser pulses has been reported. Spectrums of double femtosecond laser pulses with phase differences are quite different from that of one single femtosecond laser pulse. Therefore, the Talbot images of the double femtosecond laser pulses with phase differences are different from that of one single femtosecond laser pulse. Specifically, for the phase difference corresponding to π, the Talbot image shows the largest difference from that of one single pulse. Experimental results are in good agreement with the theoretical analysis. The behaviors of Talbot images under double femtosecond laser pulses illumination cannot be obtained under one femtosecond laser pulse, monochromatic or polychromatic light illumination. Therefore, it is a new interesting optical phenomenon for the Talbot effect which should have potential applications.     

Fibrinogen adsorption onto 316L stainless steel, Nitinol and titanium

Fibrinogen adsorption onto mechanically polished biomedical grade 316L stainless steel (316LSS), nickel titanium alloy (Nitinol) and commercially pure titanium (CpTi) surfaces were studied by measurements of adsorption isotherms and adsorption kinetics using an ex-situ wavelength dispersive spectroscopy technique (WDS). Surface composition, roughness and wettability of these materials were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle (WCA) measurements. Adsorption isotherm results showed that surface protein concentration on these materials increased with increasing concentration of fibrinogen in phosphate buffer solution. The fibrinogen adsorption isotherms were modeled by both the monolayer Langmuir isotherm and the multilayer Brunauer-Emmett-Teller (BET) isotherm. The results strongly suggest that fibrinogen forms multilayer structures on these materials when the concentration in solution is high. Complementary measurements on the absorbed fibrinogen films by spectroscopic ellipsometry (SE) support this view.