Electrochemical property of spinel LiMn_2O_4 prepared by sol-gel method

利用循环伏安法 (CV )、恒流充放电、电化学阻抗谱 (EIS)等电化学手段研究了溶胶凝胶法制备的尖晶石型LiMn2 O4 的电化学性质。结果表明用溶胶凝胶法制备的样品放电容量大 ,可逆性好 ,其中 5 5 0℃煅烧的样品电化学性能最好 ;XRD结果表明 ,样品经过充放电 ,尖晶石结构仍保留 ,但出现深度放电产物Li2 Mn2 O4 。The electrochemical properties of spinel LiMn 2O 4 electrodes prepared by a sol gel method were studied by cyclic voltammetry, constant current charge discharge and electrochemical impedance spectrum(EIS) techniques. The experimental results showed that the electrochemical performance of the samples prepared by sol gel method was better than that of the sample prepared by normal method. The electrochemical performance of the sample prepared by sol gel method at 550℃ showed the best electrochemical performance. After constant current charge discharge the spinel structures in all samples were reserved and deeply discharging product Li 2Mn 2O 4 was detected from XRD results.国家自然科学基金 ( 2 98330 90 );; “86 3”高技术发展计划 ( 715 -0 0 4-0 2 5 0

Investigation of lithium manganese oxides with large tunnel structure as electrode material in Li ion batteries

锂锰氧化物材料是一类重要的锂离子电池电极材料。文中报道一种新型大隧道结构镁锰复合氧化物〔结构类型：钡镁锰矿（TOdOrOkITE）型〕的合成方法及其电化学性能表征。X-光衍射（Xrd）谱证实了合成物具有所预想的（3x3）隧道结构。在慢速循环伏安图中可发现该类电极材料分别在3.35V及2.45V（VS.lI）出现一对锂离子的脱出-嵌入峰。充放电实验结果表明：该类大隧道结构复合氧化物可作为一种3V锂离子电池的电极材料，当充放电电流密度为0.1MA/CM2时，材料的初次容量可达158MAg/H，经过4次充放电循环后其容量仍可保持在约130MAH/g。Lithium manganese oxide is one kind of the important electrode material of Li ion batteries.In this paper, investigations of a novel Li Mn oxide electrode material with large tunnel structure such as todorokite type electode material For Li ion batteries are carried out in the lab.It is demonstrated that the material synthesized has a todo rokite structure (i.e.3×3 tunnel)using X ray diFFraction(XRD) method.It is also observed that a couple of deintercalation/intercalation peaks of lithium ion appear at 3.35V and 2.46V (vs.Li) respectively in the slow rate cyclic voltammograms.In addition,it is Found that the material shows quite good cyclic perFormance,the initial capacity of the material is 158mAh/g,and its discharge capacity is still kept at about 130mAh/g aFter Four cycles at charging/discharging current density of 0.1mA/cm 2.福建省自然科学基金;杰出青年基

MySQL密码认证算法的FPGA优化实现

My SQL数据库软件被广泛地应用于WEB项目中,因此它的安全性极为重要。本文针对My SQL密码认证算法的FPGA实现以及应用进行研究,利用并行化、流水线架构实现My SQL认证算法。提出一种基于BRAM的SHA-1算法流水线架构并对其流水线级数进行优化,从而实现高性能。同时利用多模块并行,多密码验证算法,以提高硬件运行速度和计算资源的利用效率。通过优化,高性能实现了基于FPGA硬件的My SQL认证算法,单块芯片的口令恢复速度为18亿个口令密码每秒,多个FPGA构成子板的认证速度为72亿/秒,比采用GPU GTX 690平台的速度提高了5倍。本研究项目获得集成电路设计与测试分析福建省高校重点实验室建设资金.厦门市科技局科技专项经费以及2017年厦门大学教学改革研究项目资金的支持

Novel cathode material for lithium ion batteries Investigation of the intercalation behavior of manganese dioxide nano fiber

采用TEM、Xrd分析等方法对新型二氧化锰纳米纤维电极材料进行表征，TEM观测结果显示这种锰材料是由许多二氧化锰纳米纤维缠绕成巢状，其纤维直径约为1nM~10nM之间；从Xrd分析表明，它是一种复合结构的锰氧化物，以钡镁锰矿为主体结构，并含有其他钠水锰矿及水羟锰矿结构。从样品电极在1MOl/llIClO4的PC-dME（1∶1）溶剂中的循环伏安曲线，可以看出在扫描的电压范围内，在3.8V和2.8V附近出现一对可逆对称的氧化还原峰，它对应于二氧化锰纳米纤维电极中锂离子的脱出-嵌入反应。通过二氧化锰纳米纤维电极在不同电流密度下的放电，可以看出该电极采用小电流放电（0.24MA/CM2），其容量可达到约190MAH/g，而且具有3V的放电平台；而在较大的电流密度（0.96MA/CM2）放电仍具有约150MAH/g的放电容量。可见，该电极具有良好的负荷特性和较高的放电容量。A novel cathode material (MnO 2) has been characterized by using transmission electron microscope (TEM) and X ray diffraction (XRD). From the TEM examination, it was found that the MnO 2 has a distinct birds nest shaped nano fiber with the diameter in the range of 1nm～10 nm. XRD data shows that the MnO 2 has a complex structure that is in the form of todorokite (3×3 tunnel) birnessite, and vernadite structure. Cyclic voltammetry has been performed in 1 mol/L LiClO 4的PC DME(1∶1) electrolyte solution. It can be seen that a pair of reversible redox peaks, which mainly occurs in the potential ranged from 2.8 to 3.8 V vs.Li/Li +, it can be described by a lithium intercalation mechanism. The galvanostatic charge discharge experiments at various current density reveal that the MnO 2 nano fiber electrodes have a high electrochemical performance and stability. The reversible capacity can reach 190 mAh/g, 150 mAh/g at lower and higher current density respectively, i.e. 0.24mA/cm 2 and 0.96mA/cm 2.国家“863”高技术发展计划课题;中国大洋矿产资源研究开发课题;国家自然科学基

Method for generation of painting-like artistic effect

图像的绘画效果由平滑纹理,保持并加强边角获得。给出一种鲁棒的由真实图像自动生成相应绘画效果的算法。算法根据图像的局部结构,自适应地调节滤波器的带宽与形状,来模拟画笔宽度和绘画技法。实验结果表明,算法的处理结果在视觉效果上接近绘画,并且对低质量的输入图像同样有效。Painting-like artistic effects can be achieved from photographic images by filters that smooth out texture details,while preserving or enhancing edges and corners.A novel image filter is proposed in this paper to generate painting-like effects.By adaptively changing its bandwidth and shape to image features,this filter can simulate the size of brush and painting skills.A large variety of experimental results show that the output of the proposed operator is visually similar to a painting.The proposed operator is robust to degradations of the input image such as blurring and noise contamination.国家重点基础研究发展规划(973)No.2007CB311005;福建省自然科学基金No.A0710020---

In situ dynamic tracking of heterogeneous nanocatalytic processes by shell-isolated nanoparticle-enhanced Raman spectroscopy

原位监测纳米催化反应过程对深入认识反应机理、设计高效催化剂具有重要意义。作为一种具有超高灵敏度的表面分析技术，表面增强拉曼光谱（SERS）是可提供反应过程中催化剂表面吸附物种的丰富信息。然而，仅有Au、Ag、Cu等少数金属在形成特定纳米结构时才能提供较强的拉曼增强，且它们会对催化剂的性质及反应过程产生严重干扰。这就极大地限制了SERS在实际多相催化体系中的应用。鉴于此，该论文发展了一种利用壳层隔绝纳米粒子增强拉曼光谱原位监测纳米催化过程的方法。通过将纳米催化剂组装于壳层隔绝纳米粒子表面，形成SHIENRS卫星结构，利用内核Au纳米粒子增强催化剂表面的拉曼信号，SiO2壳层隔绝Au对催化剂及反应的影响，从而直接获得了纳米催化剂表面物种的真实信息。利用这种SHINERS卫星策略，他们实现了CO氧化反应的原位监测，直接观测到了反应条件下催化剂表面吸附物种。并结合DFT计算，对反应机理进行了阐述。该研究表明SHINERS卫星策略可作为原位跟踪催化反应过程的有效方法，为纳米催化的原位研究提供了一种新的思路。 同时，我校也将在今年12月5-9日举办表面增强拉曼光谱国际会议(International Conference on SERS)，讨论SERS领域的最新进展。会议期间，SERS领域的先驱与权威Richard P. Van Duyne、Martin Moskovits、Andreas Otto以及相关学科的顶级学者Peter G. Bruce、Stefan A. Maier等将作大会报告（会议官方网站http://sers2017.xmu.edu.cn/）。【Abstract】Surface molecular information acquired in situ from a catalytic process can greatly promote the rational design of highly efficient catalysts by revealing structure-activity relationships and reaction mechanisms. Raman spectroscopy can provide this rich structural information, but normal Raman is not sensitive enough to detect trace active species adsorbed on the surface of catalysts. Here we develop a general method for in situ monitoring of heterogeneous catalytic processes through shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) satellite nanocomposites (Au-core silica-shell nanocatalyst-satellite structures), which are stable and have extremely high surface Raman sensitivity. By combining operando SHINERS with density functional theory calculations, we identify the working mechanisms for CO oxidation over PtFe and Pd nanocatalysts, which are typical low- and high-temperature catalysts, respectively. Active species, such as surface oxides, superoxide/peroxide species and Pd–C/Pt–C bonds are directly observed during the reactions. We demonstrate that in situ SHINERS can provide a deep understanding of the fundamental concepts of catalysis.This work was supported by the NSFC (21522508, 21427813, 21373167, 21521004, 21573178 and 21673187), Natural Science Foundation of Guangdong Province (2016A030308012), the Fundamental Research Funds for the Central Universities (20720150039 and 20720160046), ‘111’Project (B16029), and the Thousand Youth Talents Plan of China。 研究工作得到国家自然科学基金优秀青年基金、谱学分析创新研究群体和青年千人计划等资助

表面等离激元“热点”的可控激发及近场增强光谱学

金属纳米结构中特定表面等离激元模式的光学激发及其相互作用是发展高分辨、高灵敏、高精度界面光谱学的物理基础.本文综述了我们研究组近期在表面等离激元共振的光学激发、分类识别、近场增强及在界面光谱学中的应用等方面的进展,主要内容包括:1)利用时域有限差分法,分析了金属粒子-基底体系中SPR\"热点\"产生的物理机制及影响因素,讨论了电模式和磁模式下界面\"热点\"的可控激发及\"热点\"转移的影响因素; 2)利用粒子-金膜体系,实现了可见光频率的表面等离激元磁共振,并利用其形成的\"热点\"进行了表面增强拉曼光谱实验,获得了比常规电模式更高的拉曼增强; 3)通过界面SPR\"热点\"增强二次谐波的实验和理论研究,提出并实现了空间分辨率达到1 nm的等离激元增强二次谐波纳米尺; 4)讨论了针尖增强拉曼光谱及针尖增强荧光体系中的空间分辨率、定向发射等关键共性问题的解决方案.相关研究成果可为界面SPR\"热点\"的可控激发及进一步发展表面增强拉曼、针尖增强拉曼、表面等离激元增强二次谐波等各类高灵敏度,高空间分辨率的界面光谱学方法提供新的思路.国家自然科学基金(批准号:21673192,91850119,11474239);;\n国家重点研发计划(批准号:2016YFA0200601,2017YFA0204902)资助的课题~

In situ probing electrified interfacial water structures at atomically flat surfaces using Raman spectroscopy

自然界中水无处不在，人们对水分子的研究已经长达一个多世纪。特别是在材料表面，从原子结构层面理解界面水所发生的各种物理和化学过程，将有利于指导能源和环境领域中开发更好的技术和器件。文献中采用振动光谱已经推知了水在金属界面的不同构型，如四配位水、三配位水、表面特性吸附水、自由水等。然而，仍然缺乏这些界面水在不同电位下清晰的构型图像。李剑锋教授课题组采用不受体相水干扰的表面增强拉曼光谱，首次在金（111）和（100）单晶电极表面上获得了界面水的拉曼信号，并且在析氢反应过程中原位观测到了界面水的两种构型转变。发现界面水随着电位的负移，由“平行”结构向“单端氢朝下”，再向“双端氢朝下”变化。程俊教授课题组采用从头算分子动力学理论方法，模拟出不同电位下，在双电层中界面水的三种构型以及相应的氢键数目，与实验数据很好地吻合，进一步揭示了双电层的原子级结构。该研究首次在实验和理论层面，将界面水的构型转变以及氢键断裂与精确的电极电势标尺进行关联，对探知双电层的三维结构具有指导性意义。 该研究工作通过厦门大学校内合作完成，化学化工学院李剑锋教授和程俊教授为通讯作者，田中群教授提供了重要指导。李超禹博士（现美国麻省理工学院博士后）和乐家波博士（现能源材料化学协同创新中心博士后）为共同第一作者，王耀辉博士生在实验上提供了帮助，物理系的陈舒博士和杨志林教授为本工作开展了电磁场增强计算【Abstract】Molecular structures of solid/liquid interfaces are of fundamental interest, and play significantly in the efficiencies of energy storage and conversion. To elucidate the structures of electric double layers at electrochemical interfaces under bias potentials, we have collaborated in situ Raman spectroscopy and ab initio molecular dynamics, and for the first time distinguished two structural transitions of interfacial water at electrified Au(111) and Au(100) single crystal electrode surfaces. Towards negative potentials, the interfacial water molecules evolve from structurally “parallel” to “one-H-down”, and further to “two-H-down”.Concurrently, the number of hydrogen bonds among the interfacial water shows an overall decrease along with the negative shift of the potential, and undergoes two transitions as well. Our findings shed light on fundamental understanding of electric double layers and electrochemical processes at the interfaces.National Natural Science Foundation of China (Grants No. 21373166, 21522508, 21775127, 21521004, 21321062 and 21621091). 该工作得到国家自然科学基金委的大力资助，也得到了固体表面物理化学国家重点实验室、谱学分析与仪器教育部重点实验室、能源材料化学协同创新中心的支持

Structure Object Tracking via Sparse Representation

运动目标跟踪技术在军事和民用等领域具有广泛的应用前景。但由于应用环境的复杂性，跟踪过程中目标容易受到部分或全部遮挡、外观变化、姿态变化、光照变化、平面内旋转等综合因素的影响，给跟踪技术的发展带来了极大的困难。 本文对基于稀疏表示的复杂场景下运动目标跟踪问题进行研究，将特征点检测、匹配等一系列算法与目前流行的图像稀疏表示理论相结合，提升了传统跟踪器的鲁棒性。本文完成的主要工作和贡献有： 1、 提出了两种关键点相关算法：基于稀疏表示的关键点误匹配去除算法以及基于在线字典学习的目标矩形区域背景特征点去除算法。利用带有上下文信息的关键点所在区域图像样本之间的稀疏性用以代替传统上基于统计的RANSA...Motion Target Tracking technology have broad application prospects in military and civilian areas. However, the target tracking system always work in clutter environment which includes partial or completely occlusion, appearance change, pose change, illumination change, rotation in/out plain, such factors leads a integrate trouble for tracking system. This paper analyses the motion target trackin...学位：工学硕士院系专业：信息科学与技术学院计算机科学系_计算机应用技术学号：2302009115275

Preparation of Spinel LiMn_2O_4 at Low Temperature

Nanosized spinel LiMn 2O 4 was prepared by a sol-gel method. The preparation process was monitored by XRD, BET, DTA, TGA and TEM observations. It is found that at temperature higher than 350 ℃ the spinel phase of the samples could be detected by XRD, which is lower than that temperature in common solid-state preparation. The diameters of the samples calculated by Sherrer equation were increased with the temperature of calcination.国家自然科学基金!(2 98330 90 );; “八六三”高技术发展计划!(715 - 0 0 4- 0 2 5 0 )资助课