丁磺酸内酯对锂离子电池性能及负极界面的影响

用循环伏安(CV)、电化学阻抗谱(EIS)、扫描电镜(SEM)、能谱分析(EDS)及理论计算等方法研究了添加剂丁磺酸内酯(BS)对锂离子电池负极界面性质的影响. 研究表明, 在初次循环过程中, BS具有较低的最低空轨道能量, 优先于溶剂在石墨电极上还原分解, 并形成固体电解质相界面膜(SEI膜). 在含BS的电解液中形成的SEI膜的热稳定性高, 在70 ℃下储存24 h后, 膜电阻和电荷迁移电阻大小基本保持不变, 而在不含BS的电解液中形成的SEI膜的热稳定性较差, 在70 ℃下储存24 h后, 膜电阻和电荷迁移电阻大小有明显的增加. 从BS对锂离子电池电化学性能影响的研究表明, 加入少量的BS能够显著提高锂离子电池的室温放电容量、低温及高温储存放电性能.     

Clean Aerobic Liquid Oxidation of Aldehydes with Solid Catalyst

Clean liquid oxidation of aldehydes can be accomplished using solid catalyst in the presence of molecular oxygen at room temperature, which is a valuable alternative to traditional counterparts.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.     

林火中的阴燃现象:研究前沿与展望

森林中的植物腐殖质和有机泥炭土的阴燃是地球上尺度最大的燃烧与火灾现象,造成了巨大的经济损失及跨国界的雾霾,并严重破坏了生态系统.本文综述了阴燃林火的基础燃烧理论和化学反应机理,总结了其点火、火蔓延和熄火的行为特性.同时,归纳了近年来泥炭阴燃火的研究动态,包括如何通过小尺度的阴燃实验理解大尺度的阴燃林火,如何构建阴燃的数...     

PARALLEL FINITE ELEMENT ANALYSIS OF HIGH FREQUENCY VIBRATIONS OF QUARTZ CRYSTAL RESONATORS ON LINUX CLUSTER

Quartz crystal resonators are typical piezoelectric acoustic wave devices for frequency control applications with mechanical vibration frequency at the radio-frequency （RF） range. Precise analyses of the vibration and deformation are generally required in the resonator design and improvement process. The considerations include the presence of electrodes, mountings, bias fields such as temperature, initial stresses, and acceleration. Naturally, the finite element method is the only effective tool for such a coupled problem with multi-physics nature. The main challenge is the extremely large size of resulted linear equations. For this reason, we have been employing the Mindlin plate equations to reduce the computational difficulty. In addition, we have to utilize the parallel computing techniques on Linux clusters, which are widely available for academic and industrial applications nowadays, to improve the computing efficiency. The general principle of our research is to use open source software components and public domain technology to reduce cost for developers and users on a Linux cluster. We start with a mesh generator specifically for quartz crystal resonators of rectangular and circular types, and the Mindlin plate equations are implemented for the finite element analysis. Computing techniques like parallel processing, sparse matrix handling, and the latest eigenvalue extraction package are integrated into the program. It is clear from our computation that the combination of these algorithms and methods on a cluster can meet the memory requirement and reduce computing time significantly.     

TRANSIENT TORSIONAL WAVE IN FINITE HOLLOW CYLINDER WITH INITIAL AXIAL STRESS

An analytical solution is obtained for transient torsional vibration of a finite hollow cylinder with initial axial stress. The cylinder is subjected to dynamic shearing stress at the internal surface and is fixed at the external surface. The basic equations are presented and the solution is obtained by means of Fourier series expansion technique and the separation of variables method. The effects of the initial stress on the natural frequencies and transient torsional responses are presented and discussed.     

ELECTRICALLY FORCED THICKNESS-SHEAR VIBRATIONS OF QUARTZ PLATE WITH NONLINEAR COUPLING TO EXTENSION

We study electrically forced nonlinear thickness-shear vibrations of a quartz plate resonator with relatively large amplitude. It is shown that thickness-shear is nonlinearly coupled to extension due to the well-known Poynting effect in nonlinear elasticity. This coupling is relatively strong when the resonant frequency of the extensional mode is about twice the resonant frequency of the thickness-shear mode. This happens when the plate length/thickness ratio assumes certain values. With this nonlinear coupling, the thickness-shear motion is no longer sinusoidal. Coupling to extension also affects energy trapping which is related to device mounting. When damping is 0.01, nonlinear coupling causes a frequency shift of the order of 10^-6 which is not insignificant,and an amplitude change of the order of 10^-8. The effects are expected to be stronger under real damping of 10^-5 or larger. To avoid nonlinear coupling to extension, certain values of the aspect ratio of the plate should be avoided.     

多目标多光谱辐射高速高温计的研制

固体火箭羽焰是一种特殊的火焰,固体火箭发动机喷管羽流沿径向和轴向的温度是研究固体推进剂燃烧状况和发动机燃烧流场的基本参数。针对固体火箭发动机尾喷焰温度及其空间分布测量的需要,继1999年采用多光谱辐射测温方法和技术实现航天某型号固体火箭发动机测量后,研制了新型的多目标多光谱辐射高速高温计用于固体火箭发动机地面搭载试验。仪器使用组合棱镜和光电二极管阵列实现目标0.4~1.1μm光谱的热辐射测量,在主光路设计中首次使用光纤技术,实现一台仪器同时测量空间分布6个目标点的温度和发射率,每个点的空间位置由光阑上的通光孔精确确定,且每个目标测点均有8个工作光谱,研制的同步高速数据采集系统完成48个测量通道的数据同步时间小于10 ns。     

同步扫描－固体基质室温磷光法同时测定痕量对位三联苯和间位三联苯的研究

本文提出了一种新的测定间三联苯和对三联苯的同步扫描－ＳＳ－ＲＴＰ法。固体基质选用慢速定量滤纸，重原子盐为Ｔｌ２ＳＯ４。以激发单色器和发射单色器的波长差△λ＝１８０ｎｍ进行同步扫描，其同步特征峰间三联苯为４５０ｎｍ，对三联苯为４９０ｎｍ（均指发射波长）。间三联苯可直接由该特征峰的高度进行定量测定。对三联苯在４９０ｎｍ处的特征峰略受间三联苯同步拖尾的影响，其峰值信号需加校正。间三联苯和对三联苯的线性范围分别为０．４６～９２ｎｇ／斑点和０．４６～４６ｎｇ／斑点     

10MW串级脉冲发电机的理论、设计、实验及应用研究

 脉冲发电机具有小型、机动、灵活、可靠、寿命长等特点, 作为高功率固体激光器和加速器电源是一新的技术路线。比较了各种类型脉冲电源的性能指标,解释了旋转磁通压缩和串级原理,提出串级脉冲发电机的自激、偏极与双机同壳概念,给出电机的设计公式,10MW串级脉冲发电机的设计、实验及在强激光与粒子束领域中的潜在应用。