Stable error-free single channel 160-Gb/s OTDM 100-km transmission via high-precision dispersion management

<正>A single channel with a 160-Gb/s optical time-division-multiplexing(OTDM) transmission over 100 km is fabricated.With the help of 500-GHz optical sampling oscilloscopes,the fiber length is adjusted to the order of 10 m,which corresponds to the accuracy of 0.4 ps for the dispersion compensation.The dispersion map is optimized for the 100-km transmission link.A completely error-free transmission with the power penalty of 3.6 dB is achieved for 2 h without using forward error correction.     

Trends in the band-gap pressure coefficients and bulk moduli in different structures of ZnGa2S4, ZnGa2Se4 and ZnGa2Te4

We have performed a first-principles investigation for the family of compounds ZnGa2X4 (X = S, Se, Te). The properties of two possible structures, defect chalcopyrite and defect famatinite are both calculated. We reveal that ZnGa2S4 and ZnGa2Se4 have direct band gaps, while ZnGa2Te4 has an indirect band gap. The local density approximation band gaps are found to be very different in two structures, while the lattice parameters and bulk moduli are similar. We extend Cohen’s empirical formula for zinc-blende compounds to this family of compounds. The pressure coefficients are calculated and metallization pressures are discussed. We find that agi remains fairly constant when the group-Ⅵ element X is varied in ZnGa2X4 (Ⅱ-Ⅲ2 -Ⅵ4 ).     

PMN-PT晶体的生长、性质和应用进展

综述了驰豫型铁电单晶PMN—PT[（1-x）Pb（Mg1／3Nb2/3）O3-xPbTiO3]的研究现状，介绍了这种晶体的结构、生长和性质，讨论了其研究进展和发展趋势，并对其的可能应用做了简要分析。     

带非线性扩散项的脉冲时滞抛物方程的振动性与渐近性

研究一类带非线性扩散项的脉冲时滞抛物方程在Dirichlet边值条件下的振动性问题,借助脉冲时滞微分不等式,建立了该类方程一切解u(x,t)振动或者limt→+∞∫Ωu(x,t)dx=0的若干新的充分性判据.     

不同碳源合成Na2MnPO4F/C及其作为锂离子电池正极材料的性能

采用湿法球磨和原位热解碳包覆相结合的方法, 分别以硬脂酸、柠檬酸、聚乙二醇-6000 (PEG-6000)、β-环糊精为碳源, 制备了不同结构的Na₂MnPO₄F/C 复合材料, 并研究了它们作为锂离子电池正极材料的电化学行为. 通过X射线衍射(XRD)、扫描电镜(SEM)、BET比表面积测试、恒流充放电等表征手段, 比较和分析了产物的结构、形貌及电化学性能. 研究结果表明, 由不同碳源制备的材料在形貌和颗粒尺寸上有明显差异, 进而对它们的电化学性能造成很大影响. 影响电化学性能的关键因素在于材料一次颗粒的大小. 其中, 以柠檬酸为碳源制备的样品呈现出典型的微纳结构和最小的一次颗粒(10-40 nm). 并给出最佳的电化学性能: 在1.5-4.8 V电压范围内, 以5 mA·g^-1充放电电流获得的首次放电比容量约为80 mAh·g^-1, 且循环稳定性良好.     

微型自动光度滴定法测定铜矿中铜

建立了微波辅助消解-微型自动光度滴定法测量铜的方法。用4个有证标准物质验证方法的准确度,回收率为99.8%～99.9%。与经典方法相比,该法更加快速、准确,适合于铜矿石中Cu的测定。     

中空分级结构Fe3O4@C/rGO复合材料的合成及其储锂性能

以氧化石墨烯(GO)为基底,Fe(NO_3)_3·9H_2O、异丙醇、甘油为原料,通过溶剂热法和后续热处理过程2步合成了Fe_3O_4@C/rGO复合材料,实现了碳包覆的Fe_3O_4纳米粒子自组装形成的分级结构空心球在氧化石墨烯片上的原位生长。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和恒流充放电等手段分析了材料的物理化学性能与储锂性能。结果表明,该复合材料在5.0 A·g~(-1)的电流密度下,仍有437.7 mAh·g~(-1)的可逆容量,在1.0 A·g~(-1)下循环200圈后还有587.3 mAh·g~(-1)的放电比容量。这主要归因于还原态氧化石墨烯(rGO)对碳包覆Fe_3O_4分级空心球整体结构稳定性和导电性的提高。     

Ⅲ族元素掺杂对SnO2电子结构及电学性能的影响

采用密度泛函理论研究了Ⅲ族元素掺杂对SnO2电子结构及电学性能的影响.态密度分析结果表明,以替代位存在的Ⅲ族杂质均使SnO2的费米能级明显向低能态方向移动,使得价带顶不完全填满,因此在SnO2中均充当受主作用.部分态密度分析结果表明,相对于掺Al的SnO2,Ⅲ族元素中的Ga及In对费米能级附近态密度贡献较大,其主要贡献来自Ga3d态或In4d态,这预示着在SnO2中掺Ga或In能实现更好的p型掺杂效果.电离能计算结果进一步表明,在Al,Ga及In三种元素中,替位In有最小的电离能(0.06 eV),这说明其在SnO2中能形成最浅的受主能级,因而在同等掺杂情况下,可引入最高浓度的空穴,从而实现最佳的p型掺杂效果.     

Clifford分析中多个未知函数向量的非线性边值问题

设fi（x），1≤i≤p为取值在实2n－1维代数An（R）上的函数．我们称F（x）＝（f1，f2，...，fp）为函数向量，而fi，1≤i≤p为向量F的分量，本文借助于向量值分析的思想，利用积分方程方法、Shauder不动点原理和压缩映射原理研究多个未知函数的函数向量F带位移又带共轭值的四元素非线性过值问题解的存在性和相应线性边值问题解的存在唯一性．     

PHOTOLUMINESCENCE AND RAMAN SCATTERING OF PURE GERMANIUM/SILICON SHORT PERIOD SUPERLATTICE

Pure Ge/Si short period superlattice (SPS) samples grown by gas source molecular beam epitaxy (GS-MBE) were studied by photoluminescence and Raman scattering. For SPS samples with Germanium layer thickness (L_Ge) of 1.5 monolayer (ML), a new band of photoluminescence is observed for silicon layer thickness (L_Si) in an intermediate range of 1.9-2.9 nm. In contrast to pure Ge/Si quantum wells, the energy of the new band shows a red-shift with the increase of L_Si. Raman scattering results show that when the intensity of the photoluminescence of the new band reaches a maximum, the Raman shift relating the vibration of Si-Si reaches a minimum. It is therefore considered that the new band of the pure Ge/Si SPS is related with some kind of strain relaxation process.