自主协同系统的宏观稳定机理研究

为保证自主协同机群的内聚性, 实现多机的有效沟通和协作, 借鉴蜂王信息素机理, 抽象出跟踪型多无人机自主协同系统的宏观运动特征. 通过构造Lyapunov函数, 分析该系统的稳定性, 进而得到系统的稳定性判据. 仿真结果表明: 本文所提的稳定控制机理不仅能够保证自主协同系统的稳定性, 还能够通过调整相关控制参数有效地控制系统规模.     

熵在非晶材料合成中的作用

熵作为系统的状态函数,对于真实物质体系而言是一个极为重要的物理量.在非晶态合金的制备过程中最具代表性的指导原则有"混乱原理"和井上三原则,二者皆与熵有着紧密的联系.在过去很长一段时间内,这些经验准则指导了大量新型非晶体系的发现,但近些年的实验结果对这些理论提出了质疑.除组元数目之外,还有其他尚待研究的因素也影响着合金体系的玻璃形成能力.本文总结了玻璃转变过程中熵在热力学条件、动力学条件和结构条件中所扮演的角色,阐述了其对玻璃形成能力产生的或正或反的影响.特别是对近几年发展起来的高熵非晶体系的研究有助于开发出临界尺寸更大的非晶合金,也有助于进一步探索多组元合金和非晶形成能力之间的关系.     

Age determination for uranium standard samples by 231Pa/235U radiochronometer

Developing different model age determination methods of uranium sample could get more information on insight into source and suspected use in nuclear forensic investigation. A procedure for the determination of model age of uranium sample using ²³¹Pa/²³⁵U radiochronometer was reported. The ²³³Pa spike used in the procedure of ²³¹Pa–²³⁵U model age determination was separated from in-house ²³⁷Np stock solution by using two TRU resin columns and three silica gel columns and calibrated by CRM U100. Model ages of CRM U010 and IRMM-1000b were presented. The model age of IRMM-1000b using ²³¹Pa/²³⁵U radiochronometer were older than the literature reported results by ²³⁰Th/²³⁴U radiochronometer by amounts exceeded the expanded uncertainty.

     

Tandem synthesis of silver nanoparticles and nanorods in the presence of poly(oxyethylene)-amidoacid template

Sequential formation of silver nanoparticles (AgNPs) and nanorods from the reduction of AgNO₃ was affected by a poly(oxyethylene)-amidoacid (POE-amidoacid) in aqueous solution. The requisite POE-amidoacid, consisting of –(CH₂CH₂O)_n– segments with amide and carboxyl groups, was simply prepared via amidation with trimellitic anhydride of a poly(oxyethylene)-monoamine (POE-amine) of molecular weight (M_w) ∼2000 g/mol. The POE-amidoacid afforded AgNPs as small as 5 nm in diameter, which gradually (over a period of months) self-assembled into nanorods that were 10–15 nm in width and 30–50 nm in length. The hierarchical formation of Ag species occurred only at ambient temperature, but Ag aggregates formed above 50 °C. The process could be monitored by UV absorption at 420 and 380 nm for AgNPs and nanorods, respectively, and by transmission electron microscopy (TEM) for the nanorods. Fourier transform infrared (FTIR) and tapping-mode atomic force microscopy (TM-AFM) analyses revealed that the structurally tailored POE-amidoacid was indeed multifunctional: it reduced Ag⁺, stabilized the obtained Ag⁰ species, and served as a template for the tandem formation of AgNPs and nanorods.     

基于线性成像系统的光学超分辨显微术回顾

随着纳米科学技术的发展,如何打破光学衍射极限,将光学显微术的分辨本领推进到纳米尺度,已经成为光学领域的一个核心议题.在此背景下,过去的三十年间,发展了多种超分辨光学显微技术,并在生物、材料、化学领域取得了一系列令人瞩目的应用.本文以衍射理论为线索,回顾各类基于线性成像系统的超分辨光学显微技术;对以固浸物镜、结构光照明、扫描近场光学显微术、完美透镜以及超振荡透镜为代表的超分辨光学显微技术进行综述,讨论各种技术的原理,对其特点、应用与局限加以总结,并对该领域的未来发展予以展望.     

Simulation study on the emittance compensation of off-axis emitted beam in RF photoinjector

To make full use of the photocathode material and improve its quantum efficiency lifetime, it can be necessary to operate the laser away from the cathode center in photoinjectors. In RF guns, the off-axis emitted beam will see a time-dependent RF effect, which would generate a significant growth in transverse emittance. It has been demonstrated that such an emittance growth can be almost completely compensated by orienting the beam on a proper orbit in the downstream RF cavities along the injector [1]. In this paper we analyze in detail the simulation techniques used in reference [1] and the issues associated with them. The optimization of photoinjector systems involving off-axis beams is a challenging problem. To solve this problem, one needs advanced simulation tools including both genetic algorithms and an efficient algorithm for 3D space charge. In this paper, we report on simulation studies where the two codes ASTRA and IMPACT-T are used jointly to overcome these challenges, in order to optimize a system designed to compensate for the emittance growth in a beam emitted off axis.     

多无人机协同的稳定控制机理研究

多无人机协同系统的过度扩散会引起协同失效, 对系统进行规模控制是解决该问题的一种潜在方法. 首先抽象出多无人机协同搜索系统的宏观运动特征, 进而建立平台的运动方程, 然后通过构造合适的李雅普诺夫函数, 获得该系统的稳定控制规律及其控制参数. 仿真结果表明: 1)本文所提的稳定控制机制不仅能够使多无人机系统实现有效的协同, 还能确保系统的稳定性; 2)在系统稳定时, 通过调整相关控制参数可以有效地控制系统规模. 关键词： 无人机 协同系统 稳定控制     

共轭聚合物中受激吸收与受激辐射的量子动力学研究

基于扩展的一维SSH紧束缚模型结合非绝热的分子动力学方法,理论研究了共轭聚合物分子(PPV)在光脉冲作用下受激吸收和受激辐射的量子动力学过程.首先,设定分子初始处于基态,讨论了受激吸收过程中不同的电子受激跃迁模式与光激发脉冲的关系.通过对终态的分析,发现分子受激后只能产生电子-空穴的束缚态,包括:激子、双激子和高能激子.计算了各种激发态的产率,特别是,给出了各种激发态产率与光激发能量的定量关系.此外,基于实验,分别讨论了光激发强度对高能激子和双激子产率的影响,并与实验结果进行了比较.最后,设定分子初始分别处于激子和双激子态,研究了分子内定域能级之间的受激辐射过程,并简单讨论了激子和双激子受激辐射与光激发能量及强度的关系.