Development of in situ characterization techniques in molecular beam epitaxy

Ex situ characterization techniques in molecular beam epitaxy(MBE)have inherent limitations,such as being prone to sample contamination and unstable surfaces during sample transfer from the MBE chamber.In recent years,the need for improved accuracy and reliability in measurement has driven the increasing adoption of in situ characterization techniques.These techniques,such as reflection high-energy electron diffraction,scanning tunneling microscopy,and X-ray photoelectron spectroscopy,allow direct observation of film growth processes in real time without exposing the sample to air,hence offering insights into the growth mechanisms of epitaxial films with controlled properties.By combining multiple in situ characterization techniques with MBE,researchers can better understand film growth processes,realizing novel materials with customized properties and extensive applications.This review aims to overview the benefits and achievements of in situ characterization techniques in MBE and their applications for material science research.In addition,through further analysis of these techniques regarding their challenges and potential solutions,particularly highlighting the assistance of machine learning to correlate in situ characterization with other material information,we hope to provide a guideline for future efforts in the development of novel monitoring and control schemes for MBE growth processes with improved material properties.

大尺度类周期阵列结构快速电磁仿真方法

类周期结构具有独特的电磁波调控特性,在天线、雷达探测、目标隐身等领域具有重要研究价值,而针对大尺度类周期阵列的高效精确电磁仿真一直是电磁计算领域的重难点问题.本文从类周期阵列几何相似性出发,提出了一种具有函数复用机制的并行综合函数法(parallel synthetic basis functions method, p-SBFM),首次实现并验证了p-SBFM在多构型类周期阵列分析中的有效性.相比传统电磁数值算法, p-SBFM在大尺度类周期阵列分析中,能够在一定程度上克服精度、效率、内存消耗三方面指标难以兼顾的难题,为类周期结构的工程应用提供理论分析和仿真手段.

Synthesis of covalent organic framework materials and their application in the field of sensing

Covalent organic frameworks(COFs)are an emerging type of porous crystalline polymers formed by combining strong covalent bonds with organic building blocks.Due to their large surface area,high intrinsic pore space,good crystallization properties,high stability,and designability of the resultant units,COFs are widely studied and used in the fields of gas adsorption,drug transport,energy storage,photoelectric catalysis,electrochemistry,and sensors.In recent years,the rapid development of the Internet of Things and people’s yearning for a better life have put forward higher and more requirements for sensors,which are the core components of the Internet of Things.Therefore,this paper reviews the recent progress of COFs in synthesis methods and sensing applications,especially in the last five years.This paper first introduces structure,properties,and synthesis methods of COFs and discusses advantages and disadvantages of different synthesis methods.Then,the research progress of COFs in different sensing fields,such as metal ion sensors,gas sensors,biomedical sensors,humidity sensors,and pH sensors,is introduced systematically.Conclusions and prospects are also presented in order to provide a reference for researchers concerned with COFs and sensors.

基于碳纳米管的光伏电池

碳纳米管具有独特的一维结构和优异的光电特性,是构建光伏电池的理想材料。本文主要综述了近年来碳纳米管基光伏电池的结构设计、制备方法以及碳纳米管在器件中的不同功能应用。首先概述了碳纳米管的结构和光电特性,重点讨论了碳纳米管作为光电转换材料、导电电极和载流子传输层等功能层时器件的原理、制作方法及优缺点,介绍了碳纳米管在微型光伏电池、碳纳米管/硅异质结光伏电池、染料敏化光伏电池、钙钛矿光伏电池、有机光伏电池以及柔性光伏电池中的应用,最后总结了碳纳米管基光伏电池的优势和挑战,以期为新型碳基光伏电池的设计和制作提供思路和参考。

Construction of a Noncentrosymmetric Luminescent Coordination Polymer from [BaL3] Unit (L = Pyridine-2,6-dicarboxylate Acid) and Li(l) Ion

Summary of main observation and conclusion This work presents the synthesis, crystal structure and properties of a novel noncentrosymmetric (NCS) coordination polymer (CP), namely,(Me2NH2)3[BaLi(2,6-PyDC)3(H2O)](1)(2,6-PyDC = pyridine-2,6-dicarboxylate acid), which represents the first example of BaLi-CPs with 2,6-PyDC ligand. Single-crystal X-ray structural analysis reveals that the compound features a two-dimensional (2D) layered structure. The simplified structure of each layer belongs to the hcb topology. The second harmonic generation (SHG) response of 1 is about 0.5 times that of KH2PO4 (KDP) marker. What is more, 1 emits bright blue light upon the excitation of 365 nm UV light with the quantum yield (QX Ф) of 1.63%. The successful con struction of this compound convinces the feasibility of constructing NCS CPs via the combi nation of [BaL3] unit and Li(l) ion.

A Comparative Study on the Luminescence of the Cd2＋ and Mn2＋ Coordination Polymers Based on the Same Mixed Ligands

Presented here is the solvothermal preparation of two luminescent coordination polymers （L-CPs） based on the same mixed ligands, namely [Cd2（1,4-NDC）2（dppe）] （1） and [Mn3（OH）2（1,4-NDC）2（dppe）（H2O）] （2） （1,4-NDCH2 = 1,4-naphthalene dicarboxylic acid, dppe---- 1,3-di（4-pyridyl）propane）. Both the title compounds feature a neutral three-dimensional （3D） network. Photoluminescence （PL） studies indicated that the compound 1 based on d10 Cd2＋ exhibited dual emissions with tunable intensities that could result in direct white-light emission based on the in- traligand charge transfer （LLCT）; while the compound 2 showed a single band of yellow emission based on the charge transfer between the ligands and the metal ion （LMCT）, due to the partially filled d-orbital of Mn2＋ ion. The temperature-dependent powder X-ray diffraction patterns （PXRD） and PL spectra were further measured to identify their thermal stabilities. This work may provide a certain guiding significance for exploiting L-CPs based on different metal ions.

Fast counting the cardinality of flows for big traffic over sliding windows

Counting the cardinality of flows for massive high-speed traffic over sliding windows is still a challenging work under time and space constrains, but plays a key role in many network applications, such as traffic management and routing optimization in software defined network. In this pa- per, we propose a novel data structure （called LRU-Sketch） to address the problem. The significant contributions are as follows. 1） The proposed data structure adapts a well-known probabilistic sketch to sliding window model; 2） By using the least-recently used （LRU） replacement policy, we design a highly time-efficient algorithm for timely forgetting stale information, which takes constant （O（1）） time per time slot; 3） Moreover, a further memory-reducing schema is given at a cost of very little loss of accuracy; 4） Comprehensive ex- periments, performed on two real IP trace files, confirm that the proposed schema attains high accuracy and high time efficiency.ferences including IEEE TPDS, ACM ToS, JCST, MIDDLEWARE, CLUSTER, NAS, etc. Currently, his research interests include big data management, cloud storage, and distributed file systems.