空气开关等离子体干涉条纹图像的处理

利用Mach-Zehnder干涉仪测量了空气开关中等离子体电子密度分布,使用高速分幅相机拍摄记录不同时延下的干涉条纹图像。针对实验获得的干涉条纹图像的特点,提出了一种首先进行频域FFT滤波去噪,然后进行空域二值化、细化的处理方法。该方法能够很好的消除图像噪声的影响,提取出单像素的亮条纹中心线,从而能够准确读取条纹坐标信息,再通过对干涉条纹偏移量进行Abel逆变换,得到等离子体电子密度分布。     

On parallel solution of linear elasticity problems. Part III: higher order finite elements

This is the third part of a trilogy on parallel solution of the linear elasticity problem. We consider the separate displacement ordering for a plain isotropic problem with full Dirichlet boundary conditions. The parallel solution methods presented in the first two parts of the trilogy are here generalised to higher order by using hierarchical finite elements. We discuss node numberings on regular grids for high degree of parallelism and even processor load as well as the problem of stability of the modified incomplete Cholesky factorisations used. Several preconditioning techniques for the conjugate gradient method are studied and compared for quadratic finite elements. Bounds for the condition numbers of the corresponding preconditioning methods are derived, and computer experiments are performed in order to confirm the theory and give recommendations on the choice of method. The parallel implementation is performed by message passing interface. Copyright © 2012 John Wiley & Sons, Ltd.     

Decomposition of small diagonals and Chow rings of hypersurfaces and Calabi–Yau complete intersections

On the one hand, for a general Calabi–Yau complete intersection X$X$, we establish a decomposition, up to rational equivalence, of the small diagonal in X×X×X$X\times X\times X$, from which we deduce that any decomposable 0-cycle of degree 0 is in fact rationally equivalent to 0, up to torsion. On the other hand, we find a similar decomposition of the smallest diagonal in a higher power of a hypersurface, which provides us an analogous result on the multiplicative structure of its Chow ring.     

Selective Carbanion–Pyridine Coordination of a Reactive P,N Ligand to RhI

Ligands with reactive carbon sites in the periphery of a metal center have emerged as a powerful approach for metal–ligand bond activation. These reactive carbon sites are commonly generated by deprotonation strategies. Carbon–silicon bond cleavage is a potential alternative to access such constructs. Herein, the monodesilylation of bis-silyl-substituted P,N scaffold PN^Si2 in the coordination sphere of [Rh^I(Cl)(CO)( PN^Si2 )] ( 1 ) with sodium azide is disclosed. This affords a unique dinucleating anionic κ²-C,N-κ¹-P ligand with a carbanionic methine carbon atom directly bound to rhodium as part of a four-membered Rh-N-C-C rhodacycle. This dimer undergoes meta-pyridine C−H activation facilitated by weak bases, which leads to a desymmetrization of the system and provides a σ,π-bridging 3-pyridyl fragment bound to Rh^I. The facile Si−C cleavage strategy may pave the way to studying the reactivity and functionalization of a variety of κ²-C,N-coordinated pyridine scaffolds for selective transformations.     

表面增强红外吸收光谱——表面敏感的原位免标记光谱电化学技术

表面增强红外吸收光谱（尤其衰减全反射表面增强红外吸收光谱）是一种超灵敏的红外光谱技术,能够实现亚单层膜水平的表面选择性探测. 由于增强基底可同时作为工作电极实现电化学调制,衰减全反射表面增强红外吸收光谱是一种表面敏感的原位免标记光谱电化学技术. 本文首先简要介绍了表面增强红外吸收光谱的基本原理和技术特点,之后通过代表性研究工作着重介绍近年衰减全反射表面增强红外吸收光谱电化学的应用和发展,最后展望了表面增强红外光谱所面临的挑战和潜在的研究方向.     

TM01-TE11三弯曲圆波导模式转换器

 从理论推导、理论设计和数值模拟3个方面对三弯曲圆波导模式转换器进行分析,得到了TM₀₁-TE₁₁模的功率转换效率解析公式和转换效率达到最高时的取值条件。以中心工作频率为4.25 GHz、波导半径分别为3.0 cm和3.5 cm的两个转换器为例进行了理论计算和数值模拟,模拟结果表明：它们的转换效率分别达到了99.64%和98.62%,高于90%的相对带宽分别达到了9.88%和12.71%。     

How to Build Stable Relationships Between People Who Lie and Cheat

This is a talk delivered at the conference “Mathematics in a Complex World”, on the occasion of the 150th anniversary of the Politecnico di Milano. Asymmetry of information, i.e. the possibility for human beings to hide their information, or not to keep their promises, is a fundamental fact of social life, and must be taken into account. I will show how this creates complexity, even in the very simple situation of a contract between two parties, one of whom commits to work for the other, but cannot be monitored.     

In Situ Photocatalytically Heterostructured ZnOAg Nanoparticle Composites as Effective Cathode‐Modifying Layers for Air‐Processed Polymer Solar Cells

A heterostructured semiconductor–metal ZnO?Ag nanoparticle (NP) composite was constructed through a straightforward photocatalytic strategy by using UV irradiation of ZnO NPs and an aqueous solution of Ag precursor. The ZnO?Ag NP composites serve as an effective cathode‐modifying layer in polymer solar cells (PSCs) with increased short‐circuit current density owing to the light‐trapping effect, and improved optical and electrical conductivity properties compared with pure ZnO NPs. The Ag NPs, which are photodeposited in situ on ZnO NPs, can act as effective antennas for incident light to maximize light harvesting and minimize radiative decay or nonradiative losses, consequently resulting in the enhanced photogeneration of excitons in PSCs. Systematic photoelectron and ‐physical investigations confirm that heterostructured ZnO?Ag NPs can significantly improve charge separation, transport, and collection, as well as lower charge recombination at the cathode interface, leading to a 14.0 % improvement in air‐processed device power conversion efficiency. In addition, this processable, cost‐effective, and scalable approach is compatible with roll‐to‐roll manufacturing of large‐scale PSCs.     

Single-slit diffraction of the arbitrary vector beams

We present the single-slit diffraction of the arbitrary vector fields with different parameters m, n, and φ0theoretically and experimentally. The single slit covers the polarization singularity in the center and therefore the influence of the polarization singularity on the diffraction fringes is analyzed. The experimental results which agree well with the simulation results show that the total intensity of the diffraction field is related only to the topological charge m, but the polarization distribution of the diffraction field is related to all the parameters m, n, and φ0. Therefore, the diffraction patterns allow to determine all the parameters of the arbitrary vector fields.