Revisit to frozen-in property of vorticity

Considering some simple topological properties of vorticity vector, the frozen-in property of vorticity herein is revisited. A vortex line, as is analogous to velocity vector along a streamline, is defined as such a coincident material(curve) line that connects many material fluid elements, on which the local vorticity vector for each fluid element is also tangent to the vortex line. The vortex line evolves in the same manner as the material line that it is initially associated with. The vortex line and the material line are both oriented to the same directions, and evolve with the proportional magnitude, just like being ‘frozen' or ‘glued' to the material elements of the fluid under the barotropic assumption. To relax the limits of incompressible and barotropic atmosphere, the frozen-in property is further derived and proved in the baroclinic case. Then two effective usages are given as examples. One is the derivation of potential vorticity conservation from the frozen-in property in both barotropic and baroclinic atmospheres, as a theory application, and the other is used to illuminate the vorticity generation and growth in ideal cases and real severe weather process, e.g., in squall line, tornado, and other severe convection weather with vortex. There is no necessity to derive vorticity equation, and this method is very intuitive to explain vorticity development qualitatively, especially for fast analysis for forecasters. Certainly, by investigating the evolution of vortex line, it is possible to locate the associated line element vector and its development on the basis of the frozen-in property of vorticity. Because it is simple and visualized, it manifests broad application prospects.     

Sn类钙钛矿太阳电池薄膜的掺杂改性研究

采用一步法分别制备了Sn类CH3NH3Sn I3和Pb类CH3NH3Pb I3钙钛矿太阳电池薄膜材料,并对其表面形貌、微观结构、吸收光谱和电池器件性能进行了表征和测试。研究结果表明:Sn类钙钛矿材料的吸收光谱相对于Pb类钙钛矿材料发生了明显的红移,吸收截止波长从800 nm上升到950 nm左右,光学带隙由1.45 e V降低至1.21 e V左右;Sn类钙钛矿材料的光谱吸收范围明显扩大,但吸收强度有所降低,相应太阳电池器件的光电转换效率也明显低于Pb类钙钛矿太阳电池,分别为2.05%和6.71%。而Br的掺杂可使Sn类钙钛矿材料带隙变宽,吸收光子能量增大,电池器件的开路电压也相应提高。当Br含量由0增加至完全替代I时,Sn类钙钛矿材料逐渐由黑褐色转变为黄色,光学带隙增大至1.95 e V,但吸收截止波长由950 nm降低至650nm。值得提及的是当Br含量为0.5时,电池器件的光电转换效率可由最初的2.05%提升至2.94%。     

Hard Superconducting Gap in Pb Te Nanowires

<正>Semiconductor nanowires coupled to a superconductor provide a powerful testbed for quantum device physics such as Majorana zero modes and gate-tunable hybrid qubits. The performance of these quantum devices heavily relies on the quality of the induced superconducting gap. A hard gap,     

五维自动调整差动共焦间隙测量方法

为精确、快速测量镜组内各透镜间的轴向间隙,提出一种基于五维自动调整的差动共焦间隙测量方法。该方法根据CCD探测器实时获取的光斑信号检测被测镜组光轴的平移偏差与倾斜偏差,依据偏差信息、通过五维自动调整技术实现镜组高精度调整,再利用差动共焦高精度层析定焦和镜组内部光线追迹实现轴向间隙高精度测量。分析和实验表明,本方法可以有效提高姿态调整效率3.4倍,透镜间隙重复测量精度可达到0.53μm。该方法为实现镜组间隙的快速高精度测量提供了有效途径,同时还为透镜的中心厚度、焦距、半径等多种参数快速高精度测量提供了有效方法。     

光催化剂SnC2O4的合成及其可见光催化活性

以(NH4)2C2O4为沉淀剂,采用直接沉淀法合成了新型光催化剂SnC2O4粉末.通过X射线粉末衍射、扫描电镜、紫外-可见分光光度计及荧光分光光度计等手段对样品的物相结构、微观形貌以及光吸收性能等进行了分析表征.结果表明:所制备的样品为单斜白钨矿型SnC2O4,空间群为C2/C(15).样品的微观形貌为不规则多面体,其禁带宽度为3.44 eV.光致发光光谱表明样品内部可能有大量的氧空位和其它缺陷.以甲基橙为模拟染料废水对SnC2 O4样品的光催化活性进行了评价.当甲基橙染料的浓度为40 mg/L,SnC2 O4光催化剂的投加量为40 mg/50 mL时,在模拟可见光照射下,甲基橙降解率可达99.1;,且光催化降解反应符合一级动力学方程.此外,通过引入活性物种捕获剂证明·O2-在光催化降解甲基橙反应中起重要作用.     

基于亲电/亲核反应描述符的气体介质绝缘强度预测

研究分子微观参数与气体介质绝缘强度的关联,可为SF₆替代气体筛选提供方向.本文基于密度泛函理论,采用M06-2X泛函与def2系列基组,计算了73种气体分子的亲电/亲核反应描述符,包括轨道能量参数、概念密度泛函理论的参数、不同电子概率密度等值面的静电势参数等;分析了各描述符与气体介质绝缘强度的相关性,以及描述符的独立性,最终提出了绝缘强度预测模型.最低空轨道能量、正负静电势表面积、静电势平均偏差、简缩局部亲电指数最小值与绝缘强度相关性较强,且彼此间相关性较低.预测模型在电子概率密度0.0002 a.u.时精度最优,其可决系数R²为0.809,均方误差MSE为0.096.     

Another look at the moist baroclinic Ertel–Rossby invariant with mass forcing

Due to the importance of the mass forcing induced by precipitation and condensation in moist processes, the Lagrangian continuity equation without a source/sink term utilized to prove the Ertel–Rossby invariant(ERI) and its conservation property is re-derived considering the mass forcing. By introducing moist enthalpy and moisture entropy, the baroclinic ERI could be adapted to moist flow. After another look at the moist ERI, it is deployed as the dot product between the generalized velocity and the generalized vorticity in moist flow, which constitutes a kind of generalized helicity.Thus, the baroclinic ERI is further extended to the moist case. Moreover, the derived moist ERI forumla remains formally consistent with the dry version, no matter whether mass forcing is present. By using the Weber transformation and the Lagrangian continuity equation with a source/sink effect, the conservation property of the baroclinic ERI in moist flow is revisited. The presence or absence of mass forcing in the Lagrangian continuity equation determines whether or not the baroclinic ERI in moist flow is materially conserved. In other words, it would be qualified as a quasi-invariant but only being dependent on the circumstances. By another look at the moist baroclinic ERI, it is surely a neat formalism with a simple physical explanation, and the usefulness of its anomaly in diagnosing atmospheric flow is demonstrated by case study.     

浅谈大学物理实验教学改革

首先对大学物理实验教学的重要性以及教学实践中出现的问题作了阐述,然后从三个方面提出了对大学物理实验教学的改革思路：一方面在实验内容的安排以及实验时间上作适当的词整,另一方面通过加强网络资源建设提高预习效果,最后是定期开展大学物理实验操作技能大赛。     

FTIR研究快中子辐照直拉硅中的VO2

快中子辐照直拉硅(CZ-Si)经400-450℃热处理后，空位-双氧复合体(VO2)是其主要的缺陷．在300-500℃热处理快中子辐照的CZ-Si后，IR光谱中有919．6cm^-1和1006cm^-1两个吸收峰伴随VO2(889cm^-1)出现，这两个IR吸收峰是VO2的一种亚稳态缺陷(O-V-O)引起的，此缺陷态是由一个VO(A中心)与次临近的一个间隙氧原子(Oi)相互作用所形成的．在300℃延长退火时间或升高退火温度，都会使(O-V-O)转变为稳态VO2．辐照剂量在10^19数量级，经400-450℃热处理所形成的缺陷主要为多空位型，而VO2被抑制．     

FTIR研究快中子辐照直拉硅中的VO2

快中子辐照直拉硅(CZ-Si)经400—450℃热处理后，空位_双氧复合体(VO₂)是其 主要 的缺陷.在300—500℃热处理快中子辐照的CZ_Si后，IR光谱中有919．6cm^-1和 1006cm^-1两个吸收峰伴随VO₂(889cm^-1)出现，这两个IR吸收 峰是VO₂的一种亚稳态缺陷(O-V-O)引起的，此缺陷态是由一个VO(A中心)与次临近的一个 间隙氧原子(O_i)相互作用所形成的.在300℃延长退火时间或升高退火温度，都 会使(O -V-O)转变为稳态VO₂.辐照剂量在10¹⁹数量级，经400—450℃热处 理所形成的缺陷主要为多空位型，而VO₂被抑制.