Electrochemical behavior of Li intercalation processes into a Li[NixLi(1/3−2x/3)Mn(2/3−x/3)]O2 cathode

Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂ (X=0.17, 0.25, 0.33, 0.5) compounds are prepared by a simple combustion method. The Rietvelt analysis shows that these compounds could be classified as having the α-NaFeO₂ structure. The initial charge-discharge and irreversible capacity increases with the decrease of x in Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂. Indeed, Li[Ni_0.50Mn_0.50]O₂ compound shows relatively low initial discharge capacity of 200 mAh/g and large capacity loss during cycling, with Li[Ni_0.17Li_0.22Mn_0.61]O₂ and Li[Ni_0.25Li_0.17Mn₀.₅₈]O₂ compounds exhibit high initial discharge capacity over 245 mAh/g and stable cycle performance in the voltage range of 4.8 -2.0 V. On the other hand, XANES analysis shows that the oxidation state of Ni ion reversibly changes between Ni²⁺ and about Ni³⁺, while the oxidation state of Mn ion sustains Mn⁴⁺ during charge-discharge process. This result does not agree with the previously reported ‘electrochemistry model’ of Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂, in which Ni ion changes between Ni²⁺ and NI⁴⁺. Based on these results, we modified oxidation-state change of Mn and Ni ion during charge-discharge process.     

用于曲面精密检测的新型光纤三角传感器研究

基于光纤传感技术和三角测量方法，提出了一种用于曲面检测的新型光纤三角传感器。根据所设计的轮辐式接收光纤结构，可以在测量曲面与传感头间位移时，首先获取被测点处微面元的倾斜信息，以便对传感器测量值进行实时误差修正，从而解决了被测表面倾斜对坐标测量带来的影响。该传感器还能有效地消除环境光干扰、光源波动、表面反射率变化等对测量带来的影响。建立了传感器测量的数学模型。理论分析和初步的实验结果证明了系统的有效性和实用性。该传感器系统不稳定性好于0.3%，横向分辨率好于8μm，高度分辨率好于0.1μm。     

Memory Effect in Ceramic Superconductors

We measured the time decay of the magnetic moment of high T_c superconductors YBa₂Cu₃O_7-δ ceramic samples and found the memory effect which has hitherto been reported only in single crystals. The temperature and field ranges, especially the memory phenomenon in ceramic samples at liquid nitrogen temperature can only be understood in a combined picture of both flux creep and glass behaviour     

随机删失下乘积限过程和累积失效率过程振动模的局部渐近性

在随机删失下研究了乘积限过程和累积失效率过程的振动模的局部性质 .给出了这两个过程的振动模的重对数律 ,并应用这些结果得到了几种核密度估计和Bahadur-Kiefer过程的精确收敛速度     

Transfer matrix approach of vibration isolation analysis of periodic composite structure

The transmission properties of elastic waves propagating in a three-dimensional composite structure embedded periodically with spherical inclusions are analyzed by the transfer matrix method in this paper. Firstly, the periodic composite structures are divided into many layers, the transfer matrix of monolayer structure is deduced by the wave equations, and the transfer matrix of the entire structure is obtained in the case of boundary conditions of displacement and stress continuity between layers. Then, the effective impedance of the structure is analyzed to calculate its reflectivity and transmissivity of vibration isolation. Finally, numerical simulation is carried out; the experiment results validate the accuracy and feasibility of the method adopted in the paper and some useful conclusions are obtained. Project (No. 50075029) supported by the National Natural Science Foundation of China.     

In situ observation of NaBi(WO4)2 dendrite growth and the study on microstructure of solidification

The dendrite growth process of transparent NaBi(WO4)2 with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased in the diffusive-convective region. The growth rate of branch had the same change trends as the arm's. Based on the EPMA-EDS data of solidification structure of quenched NaBi(WO4)2 melt, it was found that there were component differences from stoichiometric concentration in the melt near the interface during the growth process.     

Synthesis and optoelectronic properties of silole‐containing polyfluorenes with binary structures

2,5‐Bis(2‐bromofluorene‐7‐yl)silole was prepared by a modified one‐pot synthesis with a reverse addition procedure, from which novel silole‐containing polyfluorenes with binary random and alternating structures (silole contents between 4.5 and 25% and high M_w up to 509 kDa were successfully synthesized. The well‐defined repeating unit of the alternating copolymer comprises a terfluorene and a silole ring. Optoelectronic properties including UV absorption, electrochemistry, photoluminescence (PL), and electroluminescence (EL) of the copolymers were examined. The different excitation energy transfers from fluorene to silole of the copolymers in solution and in the solid state were compared. The films of the copolymers showed silole‐dominant green emissions with high absolute PL quantum yields up to 83%. EL devices of the copolymers with a configuration of ITO/PEDOT/copolymer/Ba/Al displayed exclusive silole emissions peaked at around 543 nm and the highest EL efficiency was achieved with the alternating copolymer. Using the alternating copolymer and poly(9,9‐dioctylfluorene) as the blend‐type emissive layer, a maximum external quantum efficiency of 1.99% (four times to that of the neat film) was realized, which was a high efficiency so far reported for silole‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 756–767, 2007     

热等离子体裂解天然气制备C2烃

采用氮气热等离子体来裂解天然气制备乙炔乙烯,着重研究了天然气转化率和乙炔、乙烯收率随氮气流量和天然气流量的变化.结果表明,天然气流量与氮气流量之比为11时,可得到较好的结果.当等离子体功率为15kW、天然气流量为3Nm3*h-1、氮气流量为3Nm3*h-1时得到最好的结果.这时天然气转化率为57%,乙炔、乙烯的收率分别为34%和9%;乙炔在反应气中的体积浓度为7.5%,与部分氧化法相似;扣除不参加反应的氮气,乙炔在气相产品中的体积浓度为13.2%,与热力学平衡计算结果基本符合.