Impact of the spatial coherence on self-interference digital holography

Owing to the unique feature that the signal and reference waves of self-interference digital holography (SIDH) contain the same spatial information from the same point of object, compared with conventional digital holography, the SIDH has the special spatial coherence properties. We present a statistical optics approach to analyzing the formation of cross-correlation image in SIDH. Our study reveals that the spatial coherence of illumination light can greatly influence the imaging characteristics of SIDH, and the impact extent of the spatial coherence depends substantially on the recording distance of hologram. The theoretical conclusions are supported well by numerical simulation and optical experiments.     

回流效应下电磁轨道炮膛口电弧运动的数值分析

在电磁轨道炮发射过程中,膛口外的高温气团以远高于声速的运动速度向内膛运动,这会使得膛口的电弧形态发生改变以及电弧位移。为了实现膛口电弧运动过程的数值计算,本文基于磁流体理论,引入了一种和电弧等离子体自身电导率密切相关的电位边界条件处理方法,建立了膛口位置电弧仿真模型。对回流效应下的电弧运动规律进行了分析,并且研究了运动过程中电弧对内膛流场的温度分布产生的影响。结果表明电弧的运动加剧了膛内温升。     

3,4,5,6-四氟邻苯二甲酸与含氮配体的过渡金属配合物的合成、晶体结构及对Fe3+的荧光传感

利用过渡金属盐与3,4,5,6-四氟邻苯二甲酸（TFPT）、1,3-二（4-吡啶基）-丙烷（DPP）和1,4-二（1,2,4-三氮唑）-1-丁烷（BTB）经水热法合成了3个新的配合物：{[M（TFPT）（DPP）]·H₂O}_n（M=Cd（1）,Ni（2））,{[Cd（TFPT）（BTB）_0.5]·2H₂O}_n（3）。通过X射线单晶衍射分析测定了它们的结构。配合物1和2具有相似的一维链结构。中心金属离子表现为扭曲的[MO₄N₂]八面体构型。配合物3具有二维结构。中心金属离子表现为扭曲的[CdO₅N]八面体构型。配合物1和3分别在424 nm、442 nm处出现来自于配体的荧光发射,对应于配体的π^*-π的跃迁,配合物2在356 nm处有非常弱的荧光发射。不同金属阳离子对配合物1和3的荧光强度有不同程度的影响,并且通过荧光的猝灭机理,它们都能选择性检测Fe³⁺离子。     

Microwave interrogation cavity for the rubidium space cold atom clock

The performance of space cold atom clocks(SCACs) should be improved thanks to the microgravity environment in space.The microwave interrogation cavity is a key element in a SCAC.In this paper,we develop a microwave interrogation cavity especially for the rubidium SCAC.The interrogation cavity has two microwave interaction zones with a single feedin source,which is located at the center of the cavity for symmetric coupling excitation and to ensure that the two interaction zones are in phase.The interrogation cavity has a measured resonance frequency of 6.835056471 GHz with a loaded quality factor of nearly 4200,which shows good agreement with simulation results.We measure the Rabi frequency of the clock transition of the rubidium atom in each microwave interaction zone,and subsequently demonstrate that the distributions of the magnetic field in the two interaction zones are the same and meet all requirements of the rubidium SCAC.     

Prediction of quantum anomalous Hall effect in CrI3/ScCl2 bilayer heterostructure

Based on first-principles calculations, a two-dimensional (2D) van der Waals (vdW) bilayer heterostructure consisting of two topologically trivial ferromagnetic (FM) monolayers CrI₃ and ScCl₂ is proposed to realize the quantum anomalous Hall effect (QAHE) with a sizable topologically nontrivial band gap of 4.5 meV. Its topological nature is attributed to an interlayer band inversion between the monolayers and critically depends on the symmetry of the stacking configuration. We further demonstrate that the topologically nontrivial band gap can be increased nearly linearly by the application of a perpendicular external pressure and reaches 8.1 meV at 2.7 GPa, and the application of an external out-of-plane electric field can also modulate the band gap and convert the system back to topologically trivial via eliminating the band inversion. An effective model is developed to describe the topological phase evolution in this bilayer heterostructure. This work provides a new candidate system based on 2D vdW materials for realization of potential high-temperature QAHE with considerable controllability.     

燃料对燃烧法制备Ni-Al_2O_3催化剂结构及浆态床甲烷化催化性能的影响

分别采用浸渍燃烧法和共燃烧法制备了一系列Ni-Al_2O_3催化剂,并对催化剂进行了表征,研究了燃料种类对不同方法制备的催化剂结构及浆态床CO甲烷化性能的影响.结果表明,以尿素、甘氨酸和乙二醇为燃料时,采用浸渍燃烧法制备的Ni-Al_2O_3催化剂织构性质均与载体相近,各催化剂金属Ni分散度和Ni晶粒相差不大,甲烷化性能接近,在260℃反应温度下CO转化率在80.1%~83.5%之间.而共燃烧法制备的Ni-Al_2O_3催化剂受燃烧过程影响明显,以甘氨酸和乙二醇为燃料时制得的催化剂比表面积较小,金属Ni分散度低且Ni晶粒较大,因而甲烷化活性较低;以尿素为燃料制备的催化剂比表面积大且Ni晶粒较小,CO转化率和CH_4选择性分别达到84.7%和91.1%.     

光子结构猜想的仿真验证

从龚祖同院士的类氢光子结构模型和北大学者的电磁场粒子模型出发,提出了等效作用和动态光子层的概念,并在此基础上,利用蒙特卡罗法和伽尔顿板法,对光的干涉、衍射现象进行了定量分析和仿真实验,验证了光子结构猜想的正确性.     

X射线衍射法快速筛选含氧化锆纤维的耐火材料

采用X射线衍射法快速筛选出含氧化锆纤维的耐火材料,并用偏光显微镜对其进行确认。探讨了扫描速度、发射狭缝和衍射角对结果的影响,优化的试验条件为:扫描速率为2°·min^-1,发射狭缝为2 mm时,衍射角为30°。方法能快速地用于含氧化锆纤维的耐火材料的定性分析。     

金表面不同链长烷基硫醇自组装单分子膜表面电势的变化规律

从Helmholtz模型出发,对生长在金表面不同链长烷基硫醇自组装单分子膜(SAM)表面电势的变化规律进行了理论研究.利用量子化学软件Gaussian03和MOPAC,讨论了分子偶极矩、相对介电常数以及分子的倾斜角对SAM表面电势的影响.研究表明,不同链长烷基硫醇SAM中分子的倾斜角随烷基链长度的规律性变化是引起SAM表面电势变化的主要原因.从SAM形成机制出发,对金表面不同链长烷基硫醇SAM表面电势的变化规律及其成因提出了新的解释.     

晶粒尺寸调控Er~(3+)掺杂微晶玻璃上转换发光颜色的研究

首先,使用高温熔融冷却技术,制备了不同掺入比例的NaF,YF_3玻璃样品。然后将退火后的玻璃样品切割加工成15mm×15mm×3mm,实施抛光处理。最后,通过差热分析确定玻璃转变温度Tg、第一析晶峰Tx和玻璃整体析晶峰Tc等特征温度。将样品在600℃下热处理2h后,在玻璃样品中成功的析出了不同晶粒尺寸的NaYF4微晶。对样品进行了XRD,TEM和EDX的分析,可以确定不同样品中晶粒的尺寸与分布。结合样品荧光光谱和吸收光谱的分析,探讨了Er~(3+)在不同晶粒尺寸样品中的上转换发光特征,当晶粒尺寸由大变小时,Er~(3+)逐渐由红光发射转向绿光发射。通过析晶活化能的分析,确定了NaF可以改善玻璃网络结构,当NaF含量降低时,可以提高玻璃网络结构的完整性,增加玻璃样品的析晶活化能,降低了微晶玻璃样品的析晶能力,进而对微晶玻璃样品内微晶尺寸起到调节作用。因此:当样品中NaF含量较高时,晶粒尺寸较大,晶粒中的Er~(3+)浓度较高,使得Er~(3+)-Er~(3+)之间的交叉驰豫作用增强,导致Er~(3+)红光发射较强;相对应地,NaF含量较低时,晶粒尺寸较小,晶粒中Er~(3+)浓度较低及交叉弛豫减弱,因此,Er~(3+)绿光发射增强。通过改变玻璃组分,调节微晶玻璃中晶粒尺寸,实现了对Er~(3+)在微晶玻璃中发光颜色的调控。