Dimethyl carbonate (DMC) electrolytes – the effect of solvent purity on Li–ion intercalation into graphite anodes

Graphite electrodes cycled in single solvent electrolytes based on dimethyl carbonate (DMC) exhibit surprising and unfamiliar behavior. The electrochemical performance of graphite anodes cycled vs. Li metal in DMC electrolytes, containing 1 M LiPF₆ is strongly dependent on the solvent purity. The behavior of the graphite anodes in electrolytes containing “pure” DMC is dependent mainly on the identity of the contamination present in the native solvent. It was found that methanol is causing deterioration in the electrochemical performance of the cycled graphite electrode, while carbon dioxide and mainly carbonochloridic acid methyl ester are enhancing the performance. It was established that it is essential to investigate and understand the processes and materials used during the production of battery grade solvents, in order to clarify the roll of traces of chemical compounds responsible for the variation and modification in the electrochemical behavior of the cycled electrodes.     

Rogue waves in nonlinear Schrödinger models with variable coefficients: Application to Bose–Einstein condensates

We explore the form of rogue wave solutions in a select set of case examples of nonlinear Schrödinger equations with variable coefficients. We focus on systems with constant dispersion, and present three different models that describe atomic Bose–Einstein condensates in different experimentally relevant settings. For these models, we identify exact rogue wave solutions. Our analytical findings are corroborated by direct numerical integration of the original equations, performed by two different schemes. Very good agreement between numerical results and analytical predictions for the emergence of the rogue waves is identified. Additionally, the nontrivial fate of small numerically induced perturbations to the exact rogue wave solutions is also discussed.     

Fabrication and characterization of Ge20Sb15S65 chalcogenide glass for photonic crystal fibers

Chalcogenide glasses are known for their high transparency in the mid-infrared (IR) range, which includes two atmospheric windows that lie from 3 to 5 μm and 8 to 12 μm, respectively. Chalcogenide photonic crystal fibers have numerous potential applications in the field of IR, such as spectroscopy, microscopy, astronomy, biology, and sensing. In this paper, Ge₂₀Sb₁₅S₆₅ chalcogenide glass was fabricated and systematically studied. Chalcogenide glass has high transmission property (>70 %), good thermal stability, and good mechanical stability. The glass transition temperature T _g is 296 °C, and no exothermic peak was associated with crystallization up to 500 °C, which indicates its suitability for fiber drawing. As a result of its excellent mechanical properties, preforms with a variety of geometrical patterns were fabricated by using mechanical drilling. The near-field intensity distribution image of the drawn fiber shows a strong light propagation confinement.     

Ge28Sb6S(66－x)Sex玻璃系统光学特性与结构

采用熔融-急冷法制备了系列Ge₂₈Sb₆S_(66－x)Se_xSe_x(x=0,10,20,30摩尔比)硫系玻璃样品.分别测试了样品的密度、折射率、可见-近红外透过光谱、红外透过光谱以及喇曼光谱,并分析了在Ge-Sb-S中引入Se对其物理、光学特性的影响.利用喇曼光谱讨论了玻璃的结构与特性之间的关系.结果表明：随着Se含量的增加,样品的密度和线性折射率都增大,可见和红外截止波长都发生红移,纯硫化物玻璃样品主要由GeS₄四面体和SbS₃三角锥组成,随着Se逐渐代替S,硫-硒混合样品中逐渐出现了GeS_4－xSe_x结构单元以及链状和环状的Se-Se键.     

抗混叠轮廓波域采用压缩感知的云图融合方法

提出一种采用压缩感知的云图融合方法.该方法针对传统轮廓波存在频谱混叠的缺点,结合抗混叠塔式滤波器组和方向滤波器组,构造出一种抗混叠的轮廓波变换,并将其引入压缩感知中的稀疏表示环节,将云图分解成稠密和稀疏两部分|对稠密成份采用传统方法进行融合,而对稀疏成份,则在压缩感知框架下,通过少数线性测量的融合,并采用二步迭代收缩的图像重构算法,在迭代时利用前面两个估计值更新当前值,得到融合结果.实验表明,该方法的融合结果无论在视觉质量及定量指标上都明显优于传统方法,有利于揭示全面的天气信息.     

Er3+掺杂Ge-Ga-S-KBr硫卤玻璃的中红外发光和多声子弛豫的研究

用熔融急冷法制备了系列不同Er3+离子掺杂浓度的Ge-Ga-S-KBr硫卤玻璃,测试了样品折射率、吸收光谱、中红外荧光光谱。通过吸收光谱计算了Er3+离子吸收谱线的振子强度,应用Judd-Ofelt理论计算分析了Er3+离子在Ge-Ga-S-KBr硫卤玻璃中的强度参数Ωi ( i = 2 , 4 , 6) 、自发辐射跃迁几率A、荧光分支比?和辐射寿命?rad等光谱参数。研究了808nm激光泵浦下样品中红外荧光特性与掺杂浓度之间变化关系,并用Futchbauer-Ladenburg公式分别计算了2.8?m处的受激发射截面。结果表明,在808nm 激光泵浦下观察到了2.8?m中红外荧光,分别对应于Er3+： 4I11/2?4I13/2跃迁,当Er3+离子掺杂浓度从0.4wt%增加到1.0wt%时,中红外荧光强度都随相应增加,计算的Er3+:4I11/2?4I13/2跃迁多声子驰豫速率分别为37 s-1。     

基于帧的多描述视频编码及其错误隐藏

为了解决视频流在不可靠网络上的错误传播问题,使用基于帧的多描述视频编码,提出采用预测的预处理和后处理过程方案,实现了描述间的冗余插入|实现了几种不同复杂度,不同性能的错误掩盖算法以适应多样化的网络传输环境.仿真实验结果表明,这种编码系统能有效控制视频流的错误传播,并且编码后的数据流更能适应各种网络传输状况.     

基于改进Mean Shift算法的实时视频目标跟踪

设计了一套嵌入式平台上实现的视频目标跟踪系统.该系统采用CMOS图像传感器获取视频信号,利用Z228多媒体芯片自带的ARM9处理器完成视频信号的控制,并通过MPEG-4硬件编码器实现视频信号的压缩.用Mean Shift算法跟踪运动目标,针对其收敛的局限性设置多个搜索点来提高其跟踪效果.通过减少采样点和标记已计算点来提高代码运行速度,增强了跟踪的实时性.实验结果表明,本系统能以27 fps速率连续稳定地实现视频目标的跟踪.     

RV减速器摆线轮组合修形及优化

为提高RV减速器的传动性能, 本文针对摆线轮齿廓的工作区域及组合修形方法等展开研究. 对应用广泛的“等距+移距”修形进行组合比较, 确定“正等距+负移距”的组合方式下初始间隙最小, 即啮合刚度最高; 分析针齿与摆线轮啮合的极限位置, 推导摆线轮的实际工作区域, 并对其采用遗传算法寻找最优修形量, 使组合修形逼近转角修形所得齿廓. 结果显示, 该方法得到的摆线轮齿廓在工作区域内更接近共轭齿廓, 且在齿顶与齿根处有合适的径向间隙, 可在提高摆线轮强度的同时有效补偿制造误差和安装误差, 对摆线轮的修形方式选择及修形量确定具有一定的借鉴意义.     

Characteristics of Wave Propagation in The Saturated Thermoelastic Porous Medium

Took into consideration the coupling effect of thermo, hydraulics and mechanics, a set of thermo–hydro-mechanical coupled wave equations for fluid–saturated soil are developed. In these wave equations, the $P_{3}$ -wave in solid phase and $P_{4}$ -wave in fluid phase are coupled into $T$ -wave in fluid–saturated soil by the assumption that the temperature of the solid phase is equal to the temperature of liquid phase at the same position. The dispersion equations for the thermo-elastic wave, which can be degraded to the equations for elastic wave in fluid–saturated soil, are derived from the above equations by introducing four potential functions. Then, these equations are solved numerically. The characteristics of wave phase velocity, attenuation and the effect of thermal expansion, initial temperature and porosity, etc., on phase velocities of $P_{1}$ -, $P_{2}$ -, and $T$ -wave are discussed. As a reference, the characteristics of the propagation of elastic waves in fluid–saturated soil are also studied. The computation results show that (1) the phase velocity of $P_{1}$ -wave obtained by the theory of thermoporoelascity (THM) is faster than that by the theory of poroelasticity (HM); (2) the attenuation of $P_{1}$ -wave obtained by either the theory of THM or HM are consistent; (3) the dissemination characteristics of $P_{2}$ -wave are almost consistent; (4) the phase velocity of $T$ -wave is the slowest among the three compressional waves; and (5) The attenuation versus frequency characteristic of $T$ -wave is similar to that of $P_{2}$ -wave.