Simulation and Data Analysis Algorithm for Broadband Sum Frequency Generation Spectroscopy

宽带和频光谱(Broadbandsumfrequencygeneration，BB-SFG)是二阶非线性光谱，BB-SFG具有很好的表面选择性和时间分辨能力，是研究界面结构和界面动力学的理想工具。在BB-SFG中，宽带飞秒(10-15秒)红外脉冲光(IR，ωIR)在介质中产生一阶极化P(1)，P(1)再与窄带的皮秒(10-12秒)可见光脉冲光(VIS，ωVIS)相互作用，得到频率为ωSFG=ωIR+ωVIS的信号光。由于VIS、非共振信号、IR与VIS之间延迟时间和界面动力学过程对BB-SFG的线型具有显著的影响，BB-SFG线型比线性光谱更为复杂。然而BB-SFG的复杂线型中包括着丰富的表/...Broadband sum frequency generation (BB-SFG) spectroscopy is a second order non-linear technique. The natural surface selectivity and high time resolution make BB-SFG an outstanding tool to explore the components and dynamics on interface. In BB-SFG, a broadband fs (10-15 s) infrared pulse (IR, IR) creates first order polarization, P(1), in the medium, then further interacts with a narrowba...学位：理学博士院系专业：化学化工学院_分析化学学号：2052012015348

CdS量子点表面巯基酸分子排列方式的宽带和频光谱研究

巯基酸是一种常用的量子点表面配体，对量子点的光电属性和催化活性具有重要影响。用宽带和频光谱（BB-SFG）研究巯基酸分子(HS-(CH2)n-COOH，n = 2，5，10)在金膜和硫化镉（CdS）量子点表面的排列方式。结果表明：在金表面上3种自组装巯基酸单分子膜，都可以检测到与巯基和羧基相连的两个亚甲基的C-H振动和频谱峰。而在CdS量子点表面，短链的HS-(CH2)2-COOH和HS-(CH2)5-COOH处于较无序的混乱包覆状态，检测不到C-H振动和频谱峰；但长链的HS-(CH2)10-COOH在CdS量子点表面是较有序的类似反胶束状的排列，可以检测到与羧基相连的亚甲基的C-H振动谱峰。国家重点研发计划项目(2017YFA0206500,2016YFA0200702)国家自然科学基金(21327901)

Probing nanoscale spatial distribution of plasmonically excited hot carriers

表面等离激元（SP）效应可产生远高于热平衡下费米能级能量的热电子-空穴对（热载流子），从而能够引发和促进相关的光电或者化学过程，为在纳米尺度上高效利用光能实现物质和能量转化提供了极为有效的手段，化学化工学院任斌教授课题组利用前期自主发展的电化学针尖增强拉曼光谱技术，通过调控电位开关SP热载流子催化的反应，实现了有效热载流子催化反应区域的纳米分辨成像，使反应区域在实空间的分布可视化。实验上获得了有效热载流子的输运距离，从而证明了能量越高的热载流子越需要在更短的输运距离范围内收集捕获。 该工作在任斌教授和王翔副教授的共同指导下完成。实验主要由化学化工学院已毕业博士生黄声超完成。理论计算主要由电子科学与技术学院的朱锦峰副教授和已毕业硕士生李察微完成。此外，化学化工学院已毕业硕士生赵庆庆、博后何玉韩和胡树等人也参与了部分研究与课题讨论。【Abstract】Surface plasmons (SPs) of metals enable the tight focusing and strong absorption of light to realize an efficient utilization of photons at nanoscale. In particular, the SP-generated hot carriers have emerged as a promising way to efficiently drive photochemical and photoelectric processes under moderate conditions. In situ measuring of the transport process and spatial distribution of hot carriers in real space is crucial to efficiently capture the hot carriers.Here, we use electrochemical tip-enhanced Raman spectroscopy (EC-TERS) to in situmonitor an SP-driven decarboxylation and resolve the spatial distribution of hot carriers with a nanometer spatial resolution. The transport distance of about 20 nm for the reactive hot carriers is obtained from the TERS imaging result. The hot carriers with a higher energy have a shorter transport distance. These conclusions can be guides for the design and arrangement of reactants and devices to efficiently make use of plasmonic hot carriers.The authors acknowledge the financial supports from MOST of China (2016YFA0200601), NSFC (21633005, 21790354, 21503181, 21711530704, U1830116), Natural Science Foundation of Fujian Province (2016J05046), China Postdoctoral Science Foundation (2017M622062) and the Fundamental Research Funds for the Central Universities (20720190010).本研究工作得到了国家自然科学基金委和科技部等的资助和支持

Probing the edge-related properties of atomically thin MoS2 at nanoscale

层状二维材料具有独特的物理化学性质，使其在光电器件、传感、能源和催化等领域得到了高度关注和广泛应用。二维材料在制备过程中不可避免引入结构缺陷，虽然这些缺陷尺度仅为数纳米甚至单原子，但是会极大地改变材料的结构和电子性质，从而影响其应用。化学化工学院任斌教授课题组在层状二维材料缺陷表征方面取得进展。该工作表明了TERS在原位、高空间分辨表征缺陷位的结构和电子性质方面具有独特的优势，可以进一步推广到其他二维材料，从而有效地指导缺陷设计和材料应用。 该工作通过校内外课题组紧密合作，在任斌教授、谭平恒研究员（中科院半导体研究所）和王翔博士共同指导下完成。实验部分主要由黄腾翔博士（第一作者，已毕业化学系博士生）完成，电子能带结构与光谱理论计算由谭平恒研究员课题组从鑫博士生（共同第一作者）完成，吴思思、林楷强、姚旭、何玉韩、吴江滨、包一凡、黄声超等参与了实验与讨论。【Abstract】Defects can induce drastic changes of the electronic properties of two-dimensional transition metal dichalcogenides and influence their applications. It is still a great challenge to characterize small defects and correlate their structures with properties. Here, we show that tipenhanced Raman spectroscopy (TERS) can obtain distinctly different Raman features of edge defects in atomically thin MoS2, which allows us to probe their unique electronic properties and identify defect types (e.g., armchair and zigzag edges) in ambient. We observed an edgeinduced Raman peak (396 cm−1) activated by the double resonance Raman scattering (DRRS) process and revealed electron–phonon interaction in edges. We further visualize the edge-induced band bending region by using this DRRS peak and electronic transition region using the electron density-sensitive Raman peak at 406 cm−1. The power of TERS demonstrated in MoS2 can also be extended to other 2D materials, which may guide the defect engineering for desired properties.The authors acknowledge the final supports from MOST of China (2016YFA0200601 and 2016YFA0301204), NSFC (21633005, 21790354, 21503181, 21711530704, 21621091, 11874350, 11474277, and 11434010), Natural Science Foundation of Fujian Province (2016J05046), and China Postdoctoral Science Foundation (2017M622062). 研究工作得到科技部、国家自然科学基金委员会、福建省自然科学基金和中国博士后基金资助

Influence of substrate signals on molecular signals among sum frequency generation vibrational spectroscopy

和频振动光谱中基底信号和分子共振信号发生相干叠加,因此在分析和频振动光谱时需要考虑基底信号的影响。使用和频振动光谱分析金表面的正十八烷基硫醇自组装分子膜,结果表明,基底信号不仅使分子信号从正峰变为负峰,还能够使弱的分子信号在和频振动光谱中得到增强。Substrate signals can coherently interfere with molecular signals in sum frequency generation vibrational spectroscopy.Therefore,it is necessary to consider the influence of substrate signals when analyzing sum frequency generation vibrational spectra.The self-assembled monolayer 1-octadecanethiol on Au was investigated by summing frequency generation vibrational spectroscopy.The results show that the substrate signals not only make the shapes of molecular signals change from peaks to dips,but also enhance the weak molecular signals.高等学校博士学科点专项科研基金资助项目(20110121110015

Hybrid Force/Position Control of Aerial Manipulators in Contact Operation

针对飞行机械臂系统移动接触作业问题,使用了一个力/位置混合控制框架,用以控制飞行器系统持续可靠地接触外部环境同时保持一定大小的接触力,并实现在接触过程中的期望轨迹跟踪.首先将作业空间分成2个子空间&mdash;&mdash;约束空间和自由空间,并分别进行力控制和位置控制.对于力控制问题,证明闭环无人机系统是一个类弹簧-质量-阻尼系统,然后在约束子空间中设计逆动力学控制器来实现接触力控制.自由飞行空间中的运动控制依靠轨迹规划和位置控制器来实现.最后,开发了基于六旋翼飞行机器人的单自由度飞行机械臂系统,在飞行状态下进行接触墙面并跟踪倾斜直线轨迹的实验.结果显示本文所使用方法能够保证在平稳移动的同时控制期望的接触力.</p

Active LPV Yaw Keeping Control of an Unmanned Surface Vehicle

针对水面机器人(USV,unmanned surface vehicle)水动力学具有强非线性,并且容易受到风、浪与水流干扰的问题,提出一种主动增强LPV(linear parameter varying)建模与航向保持控制方法.LPV模型采用USV的速度作为线性变参,用来简化系统参数辨识与控制器设计.在LPV模型的基础上,将风、浪与水流等干扰看成是未建模误差,采用UKF在线估计,用来提高建模精度.然后,针对LPV模型采用线性矩阵不等式设计航向保持名义控制器,并在此基础上设计前馈控制器对未建模误差进行在线补偿.仿真结果表明,该方法可以有效减弱风、浪与水流等未建模误差对系统控制的影响.</p

Nonlinear model predictive control with regulable computational cost

Nonlinear model predictive control (NMPC) suffers from problems of closed loop instability and huge computational burden, which greatly limit its applications in real plants. In this paper, a new NMPC algorithm, whose stability is robust with respect to regulable computational cost, is presented. First, a new generalized pointwise min-norm (GPMN) control, as well as its analytic form considering a super-ball type input constraint, is given. Second, the GPMN controller is integrated into a normal NMPC algorithm as a structure of control input profile to be optimized, called GPMN enhanced NMPC (GPMN-ENMPC). Finally, a numerical example is presented and simulation results exhibit the advantage of the GPMN-ENMPC algorithm: computational cost can be regulated according to the computational resources with guaranteed stability

Real time Nonlinear Model Predictive Control Induced by Local Linear Controller

In this paper, a new nonlinear model predictive control (NMPC) algorithm guided by local linear controller is presented so that it is possible to be implemented in real time and obtain good performance. Firstly, in order to ensure the closed loop stability, a generalized pointwise min-norm (GPMN) controller formulation based on control Lyapunov functions (CLF) are given and parameterized. And then, the parameterized GPMN scheme is combined with the traditional NMPC algorithm. And the optimization variables in traditional NMPC are replaced by the parameters in GPMN, so that the computational burden of original NMPC algorithm can be reduced greatly. Finally, numerical simulations are conducted to verify the feasibility and validity of the new algorithms

Disturbance attenuation control of a class of unceractuated systems with acceleration measurement

In this paper, a new kind of disturbance attenuation controller design method, based on the acceleration measurement, is proposed for a class of underactuated systems by combining with the backstepping and H infinity technique. Comparing with the traditional high gain acceleration feedback control method, where the acceleration feedback loop is important but difficult to design, the acceleration measurement in the new controller is only used to obtain the disturbance signals. Simultaneously, in order to overcome the heavy noise accompanied with the acceleration measurement and the algebraic loop problem, a linear pre-filter is introduced. The designing process concerns both nonlinear H infinity controller and linear filter theory, which make the disturbance be attenuated from the concepts of both linear filter in frequency domain and input-output finite gain L-2 stability in time domain. In the end, simulations are conducted with respect to the tracking control of unmanned model helicopter. The results are compared with those obtained by the tracking control without acceleration measurement to verify the feasibility of it