基于离子液体的绿色催化过程

离子液体为构建绿色催化反应过程提供了新途径.本文简要评述了离子液体在几个代表性催化反应中的研究进展,如CO2羰基化、烷基化、酯交换、氧化、CO2加氢、共聚以及PET降解等;分析讨论了离子液体的特点和优势,如提高反应活性、降低废物排放以及简化分离等,并对离子液体催化反应的未来发展方向进行了展望.     

Light-shift induced by two unbalanced spontaneous decay rates in EIT (CPT) spectroscopies under Ramsey pulse excitation

Light shift is important and inevitably affects the long-term stability of an atomic clock. In this work, considering two unbalanced branches of the spontaneous decay rate in a three-level system, we studied the frequency shifts of electromagnetically induced transparency (EIT) and coherent population trapping (CPT) clocks operating under the pulse sequence regime by numerically solving the Liouville density matrix equations. The results show that the frequency shifts are larger when the two branches of spontaneous emission rate are not equal compared to the equal case. In addition, in EIT-Ramsey, the effect of the unbalanced branches of the spontaneous decay rate and relaxations of low-energy states on the frequency shift is greater than that of Rabi frequency. In CPT-Ramsey, the relaxations of low-energy states play a dominant role in frequency shift.     

Temperature independent 80 Gb/s transmission system using spectral phase modulation-based TDC

A temperature independent 80-Gb/s 100-km transmission system is demonstrated with the use of spectral phase modulation-based tunable dispersion compensator (TDC). The principle of dispersion compensation based on spectral phase modulation as well as the relationship between spectral phase modulation function and group velocity dispersion (GVD) are theoretically studied. TDC based on spectral phase modulation is implemented. The performance of 80-Gb/s transmission system is experimentally evaluated. The nonlinear relationship between temperature and temperature-induced dispersion fluctuations is demonstrated through the asymmetric temperature-induced power penalty without dispersion compensation. With respect to the low temperature area, the temperature-induced dispersion fluctuations are smaller than those in the high temperature area. By using the proposed TDC, temperature independent 80-Gb/s transmission is successfully demonstrated under a temperature range of -20 - 60 ?C with a power penalty of less than 0.8 dB.     

地球与太阳、脉冲双星相撞的半定量讨论

当代最伟大的天体物理学家之一,霍金在其科普名著《时间史之谜》中有一段饶有兴趣地叙述:“地球在绕太阳的轨道上运行产生引力波。能量丧失的效应将改变地球的轨道,以致它离太阳越来越近,最终与太阳相撞,并保持在一种静止状态上。就地球与太阳来说,     

Si掺杂TiO2纤维的溶胶-凝胶法制备及其光催化活性

采用溶胶-凝胶法并结合水蒸气活化制备了Si掺杂TiO₂纤维, 通过TG-DSC, XRD, FT-IR, UV-Vis-DRS, N₂吸附-脱附, SEM等手段对纤维样品的结构参数及其表面形貌进行了表征, 并以活性艳红X-3B模拟废水体系评价了其光催化活性．结果表明, 与纯TiO₂产物相比, 适量Si掺杂制得的产物是具有丰富介孔结构的TiO₂长纤维, 不仅热稳定性和晶型稳定性俱佳, 而且光催化活性得以显著提高, 经900 ℃热处理后仍能保持结晶完好的锐钛矿相; 在Si/Ti摩尔比为0.15时, 其比表面积和孔容最大, 光催化活性最佳, 该纤维作为光催化剂反应75 min, 水中X-3B的降解率可达99.6%.     

Transport dynamics of an interacting binary Bose Einstein condensate in an incommensurate optical lattice

We investigate the transport dynamics of an interacting binary Bose-Einstein condensate in an incommensurate optical lattice and predict a novel splitting of a matter wavepacket induced by disorder potential and inter-species interaction. The effect of atomic interaction on the dynamics of the mobile and localized atoms are also studied in detail. We also discuss the behavior of the balanced and inbalanced mixtures in the incommensurate optical lattice.     

无溶剂路线制备分子筛封装的钴基催化剂及其在费托合成制汽油反应中的应用（英文）

自2012年浙江大学肖丰收教授(J.Am.Chem.Soc.,2012,134,15173-15176)首次提出无溶剂法合成分子筛以来,该路线已备受关注.无溶剂合成分子筛方法具有废液少、产率高、安全系数高等优点.本文针对合成气经费托路线(FTS)一步法制备富含异构烷烃汽油馏分的研究,通过无溶剂研磨法制备了分子筛封装金属催化剂.一般来说,烷烃异构化催化剂的性能主要取决于分子筛的孔道结构及其酸性,其次是分子筛晶粒大小、结晶度和表面性质等因素.本文对比了三种具有相同拓扑结构的MFI分子筛(Silicalite-1,HZSM-5和NaZSM-5)对汽油和异构烷烃选择性的影响规律.结果显示,在CO转化率(~30%)近似相同的情况下,具有最弱酸性的Silicalite-1封装的Co颗粒表现出最高的汽油选择性(~70%)和异构烷烃选择性(~30.7%).这意味着正构烷烃异构化反应只需要弱酸即可实现,较强的酸性则会使其发生过度裂解反应.Py-IR谱图显示,Silicalite-1在1445 cm-1附近的L酸是区别于NaZSM-5和HZSM-5的一个重要酸性位,可作为FTS路线制备富含异构烷烃汽油的一个关键参数.另外,与封装型(Co@MFI)催化剂相比,浸渍型催化剂(Co/MFI)的汽油选择性明显偏低,可能与金属活性位与分子筛酸性位之间的距离有直接关系.因此,无溶剂合成分子筛是一条具有前景和适宜放大的催化剂合成路线.对于合成气经费托路线制取富含异构烷烃汽油反应,正构烷烃在分子筛催化剂上的裂解和异构化之间的竞争反应是核心问题.未来有待突破的研究方向包括:(1)多支链异构烷烃的合成,目前对于有效调控多支链烷烃的生成关注较少;(2)反应路线的设计,合成气经甲醇路线,联合甲醇制汽油(MTG)反应获得异构烷烃;(3)裂解反应的抑制;(4)分子筛孔道/笼对异构烷烃选择性的调控机制.     

吸附—光催化联用去除室内挥发性有机物*

多孔吸附剂吸附和纳米TiO₂光催化是目前室内挥发性有机物（VOCs）去除所采用的主要手段。但存在吸附剂容量有限、饱和失效、TiO₂光催化剂活性低、失活和负载困难等问题。多孔吸附剂与纳米TiO₂联用,通过TiO₂光催化作用可实现吸附剂的原位再生,增加吸附剂的吸附容量;通过多孔吸附剂的吸附作用可为TiO₂光催化提供高浓度污染环境,提高催化剂活性,抑制催化剂失活,消除水蒸气分子对TiO₂表面活性吸附位的竞争吸附,解决催化剂分离难题;从而实现对室内VOCs污染的高效深度净化。本文对近年来多孔吸附剂与纳米TiO₂光催化联用去除室内VOCs进行了综合评述。介绍了吸附—光催化联用去除室内VOCs的多孔吸附剂类型,吸附/光催化复合材料的制备方法及常用反应器,分析了吸附—光催化联用去除室内VOCs过程中水蒸气、催化剂失活对光催化的影响等问题。     

高稳定性星载多普勒差分干涉仪支撑结构设计

为了保证星载测风多普勒差分干涉仪的力学稳定性和热稳定性,设计了一种低热传导微应力装夹支撑结构,采用胶合与弹性压紧相结合的方法对干涉仪进行安装.首先,结合多普勒差分干涉仪的结构特点和稳定性要求,采用四点环形凸台的粘接形式对底座粘接面进行了优化设计,并与已有的网格化多点凸台粘接面形式进行对比.然后,针对随机振动条件下干涉仪与底座粘接面响应应力过大的问题,设计了施加预紧力的压盖结构来提高粘接可靠性.最后,对干涉仪组件进行了有限元仿真和环境振动试验,分析和验证了干涉仪组件的低热传导性和力学可靠性.结果表明,所设计的四点环形凸台粘接形式相较于已有粘接形式在相同条件下由底座导入光学组件的热量减少了63.54%,随机振动时粘接面最大响应应力为2MPa,干涉仪组件的模态频率均在1 900Hz以上;有限元仿真与试验结果的相对误差均在8.6%以内.基于四点环形凸台面粘接并施加预紧力的干涉仪组件具有低热传导、高力学可靠性的特点,结构设计合理,性能可靠.     

Effects of transverse trapping on the ground state of a cigar-shaped two-component Bose-Einstein condensate

We derive the coupled nonpolynomial nonlinear Schro¨dinger equations for a two-component Bose-Einstein condensate in a quasi-one-dimension geometry and investigate the effects of a tightly transverse trapping on the ground state and the miscibility-immiscibility threshold. We find that the density profile of the matter wavepacket is remarkably dependent on the transverse width and the effective one-dimension nonlinear coupling strengths in miscible and immiscible regimes.