A carbon–LiFePO<Subscript>4</Subscript> nanocomposite as high-performance cathode material for lithium-ion batteries

A cathode material of an electrically conducting carbon–LiFePO₄ nanocomposite is synthesized by wet ball milling and spray drying of precursor powders prior to a solid-state reaction. The structural characterization shows that the composite is composed of LiFePO₄ crystals and 4.8 wt.% amorphous carbon. Galvanostatic charge/discharge measurements indicate that the composite exhibits a superior high energy and high cycling stability. This composite delivers a discharge capacity of 159.1 mAh g⁻¹ at 0.1 C, 150.8 mAh g⁻¹ at 1 C, and 140.1 mAh g⁻¹ at 2 C rate. The capacity retention of 99% is achieved after 200 cycles at 2 C. The 18,650 cylindrical batteries are assembled using the composite as cathode materials and demonstrate the capacity of 1,400 mAh and the capacity retention of 97% after 100 cycles at 1 C. These results reveal that the as-prepared LiFePO₄–carbon composite is one of the promising cathode materials for high-performance, advanced lithium-ion batteries directed to the hybrid electric vehicle and pure electric vehicle markets.     

连续变量1.34 μm量子纠缠态光场的实验制备

设计研制了连续单频671 nm/1342 nm双波长激光器,并通过模式清洁器降低了激光器额外噪声.利用该低噪声连续单频激光器抽运由Ⅱ类准相位匹配晶体构成的双共振非简并光学参量放大器,实验制备出纠缠度达3 dB的光通信波段1.34μm连续变量量子纠缠态光场.该波段量子纠缠态光场在光纤中传输损耗低且相散效应小,与现有的光纤通信系统相兼容,可用于实现基于光纤的实用化连续变量量子通信.     

混有协同自适应巡航控制车辆的异质交通流稳定性解析与基本图模型

针对传统车辆和协同自适应巡航控制(cooperative adaptive cruise control,CACC)车辆构成的异质交通流,研究其稳定性与基本图模型.应用实车测试验证的CACC模型和智能驾驶员模型(intelligent driver model)分别作为CACC车辆和传统车辆的跟驰模型,建立异质流稳定性解析框架,研究不同平衡态速度、不同CACC车辆比例时的异质流稳定性.推导异质流基本图模型,并进行数值仿真实验.研究结果表明,在传统车辆稳定的速度范围,异质流处于稳定状态.在传统车辆不稳定的速度范围,CACC车辆比例增加以及平衡态速度远离9.6—18.6 m/s速度范围,均能够改善异质流的不稳定性.通行能力随着CACC车辆比例的增加而提高.此外,CACC模型的期望车间时距越大,异质流稳定域越大,但通行能力降低.因此,恒定车间时距CACC控制策略下的期望车间时距取值应权衡异质流稳定域和通行能力两个方面的影响.     

基于PXI总线的阵列探测器数据获取系统

描述了一种适用于阵列探测器的数据获取系统。系统基于PXI总线, 采用标准NIM插件作为前端电子学。系统软件采用C/C++语言编写, 在线分析通过调用ROOT类库实现, 系统运行在Linux操作系统下。多次测试结果表明, 系统稳定可靠, 单个ADC通道可以处理的最大事例率为40 kHz。A data acquisition system for array detectors is described. The system is based on PXI bus with standard NIM modules used as front\|end electronics. The system software is written in C/C++ language with its online analysis modules realized by ROOT class library. Several runs of the system under Linux show that it is reliable and is capable of handling event rates up to 40 k events/s for 1 ADC channel.     

用于实时溅射深度测量的新型Grimm辉光放电光源的设计

采用辉光放电光谱仪进行物质表面深度分析时,样品溅射深度是重要的分析信息.本文设计了一种新型Grimm辉光放电光源,此光源与激光位移测距传感器构成的测昔系统可对样品溅射深度进行实时测量,并保证了良好的辉光溅射效果和分辨多层结构及界面的能力.采用激光三角测量技术,在辉光光谱分析的同时对溅射深度进行实时测量,能够有效地解决传统深度分析方法中步骤繁琐以及对深度估算不准确等问题.本光源采用光纤将辉光光谱信号从光源传至多道分光光电检测系统,在结构上首次实现了元素光谱信号和溅射深度信号的实时采集及基于时间的同步分析,对标准样品得到了理想的实时溅射深度测量曲线.本文详细介绍了此新型辉光放电光源的设计思路和工作原理.本辉光放电光源具有良好的深度分辨率,在30 mA,900 V,20 min的溅射条件下,对铁基和铜基样品的溅射速率分别约为10和55 nm·s-1,文中给出了样品的溅射坑表面形貌图和溅射坑显微照片.对中低合金钢标准样品进行了分析精密度实验,分析精度良好,其中C,Cu,Al,Ni,Mo,Mn,V元素相对标准偏差(RSD)均小于1.7%.Cr和Si元素RSD小于2.6%,给出了实测数据.     

Hydrothermal synthesis of graphene oxide/multiwalled carbon nanotube/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> ternary nanocomposite for removal of Cu (II) and methylene blue

In this work, highly activated graphene oxide/multiwalled carbon nanotube/Fe₃O₄ ternary nanocomposite adsorbent was prepared from a simple hydrothermal route by using ferrous sulfate as precursor. For this purpose, the graphene oxide/multiwalled carbon nanotube architectures were formed through the π-π attractions between them, followed by attaching Fe₃O₄ nanoparticles onto their surface. The structure and composition of as-prepared ternary nanocomposite were characterized by XRD, FTIR, XPS, SEM, TEM, Raman, TGA, and BET. It was found that the resultant porous graphene oxide/multiwalled carbon nanotube/Fe₃O₄ ternary nanocomposite with large surface area could effectively prevent the π-π stacking interactions between graphene oxide nanosheets and greatly improve sorption sites on the surfaces. Thus, owing to the unique ternary nanocomposite architecture and synergistic effect among various components, as-prepared ternary nanocomposite exhibited high separation efficiency when they were used to remove the Cu (II) and methylene blue from aqueous solutions. Furthermore, the adsorption isotherms of ternary nanocomposite structures for Cu (II) and methylene blue removal fitted the Langmuir isotherm model. This work demonstrated that the graphene oxide/multiwalled carbon nanotube/Fe₃O₄ ternary nanocomposite was promising as an efficient adsorbent for heavy metal ions and organic dye removal from wastewater in low concentration.     

Novel Fluorometric Turn On Detection of Aluminum by Chalcone-Based Chemosensor in Aqueous Phase

A novel, 100% water-soluble chalcone based chemosensing receptor {1-[3-(2-Hydroxy-phenyl)-3-oxo-propenyl]-naphthalen-2-yloxy}-acetic acid, L was synthesized and characterized. The receptor L is designed based on the chelation enhanced fluorescence (CHEF) mechanism. The chemosensing properties of L were evaluated by UV–vis and fluorescence spectrometric methods. It exhibits highly selective recognition ability towards aluminum ions in water over other metal ions. The binding stoichiometry of L? Al³⁺ complex is 2:1 by means of Job’s plot and the detection limit is 5.66?×?10^??8 M.     

High-Power Diode-End-Pumped Slab Composite Tm:YLF Compact Laser

We design a continuous-wave Tm:YLF laser with a composite slab crystal end-pumped by two fiber-coupled laser diodes at room temperature. We achieve a maximum continuous wave output power of 105 W for the bonded slab Tm:YLF laser; the corresponding slope efficiency is 47.7% and the optical-to-optical conversion efficiency is 42.0% with respect to the incident pump power. The laser operated at 1,907.5 nm with a beam quality factor of M² ～3.2 at the highest output power.     

基于双核模型对超重元素合成机制的研究

在双核模型基础上，考虑了熔合与准裂变的竞争，通过数值法求解主方程，计算了⁵⁰Ti，⁵⁸Fe+²⁰⁸Pb，²⁰⁹Bi这4个反应系统通过冷熔合反应合成超重元素的激发函数，得到了与实验比较符合的结果.计算了不同入射能量时各角动量分波对熔合概率和超重核存活概率的影响以及对蒸发剩余截面的贡献.这些结果对进一步理解超重核的合成机制有重要意义. 关键词： 超重元素 双核模型 熔合反应 蒸发剩余截面     

介质阻挡放电中的能量转换过程研究

研究了介质阻挡放电过程中的电流强度、电场强度以及电荷分布的演变规律，并对能量转换性质进行了分析.研究结果表明，在一个放电脉冲过程中，外加驱动电源所作的功、电场能量的增量均与起始时刻的壁电荷密度有关，而气体中放电电流所作的功即沉积于气体中的能量与起始时刻的壁电荷密度、放电电流的具体波形无关. 关键词： 介质阻挡放电 壁电荷 动力学过程 能量转换