粗生物油催化裂解制取低碳轻烯烃

利用La/HZSM-5催化剂,研究了催化裂解粗生物油及其模型化合物(包括甲醇、乙醇、乙酸、丙酮和苯酚)制取轻烯烃的过程. 获得的最大轻烯烃产率为0.19 kg/kg粗生物油. 研究表明,温度、重时空速和镧对HZSM-5分子筛的改性等因素可用来调制烯烃产率和选择性. 分子筛中添加镧,可适当的调节催化剂酸度和强弱酸位比例,从而提高烯烃选择性、产率和催化剂稳定性. 生物油制备轻烯烃的效率与原料的化学成分和氢碳有效比(H/Ce? )密切相关. 此外,比较了粗生物油催化裂解和热裂解过程,同时利用模型化合物研究了生物油转化为轻烯烃的相关反应历程和机理.     

关于单缝衍射的疑点辨析

由惠更斯-菲涅尔原理可知衍射就是子波的干涉.虽然双缝干涉与单缝衍射同为干涉,但是它们的明暗条纹条件却存在很大差异.下面从物理角度对这一疑点给出清晰的定性解释,并且从数学角度给出单缝衍射明暗条纹产生条件的严格证明.     

基于改进小波阈值的微机械陀螺去噪方法

陀螺的噪声是影响组合导航系统精度的重要因素之一。以插秧机GPS/INS组合导航系统为研究背景,在分析常规硬阈值和软阈值小波去噪的基础上,提出了一种改进的小波阈值去噪方法。该方法构造了一种改进的阈值函数,改进的阈值函数具有较好的连续性,避免了将混叠在噪声中的有效信号完全消除,能够自动调节小波系数的收缩程度,具有一定的自适应性。利用插秧机组合导航系统中微机械陀螺的实际输出数据,分别采用硬阈值、软阈值和改进阈值小波去噪方法进行了对比试验。结果表明改进的小波阈值去噪方法处理后信号的信噪比提高了约3倍、均方差小,具有一定的实用价值。     

优化电激励光子晶体单缺陷激光腔结构

设计和制作电激励光子晶体微腔激光器的一个困难是电流的注入问题,而且电流的路径时常会导致微腔的Q值降低。将三维并行时域有限差分方法用于电激励光子晶体单缺陷激光腔研究,给出了微腔的本征模式分布。根据模式特点,选择单极子模式作为研究对象。数值模拟表明,在保持C_(6v)对称性条件前提下,微调最靠近微腔中心的6个空气孔的位置使得单极子模式的光场分布在腔边缘发生缓慢变化可以将单极子模的Q值和Purcell因子提高大约7倍。即激光器阈值可以降低7倍。     

对浸入水或甲醇中的石墨氧化物的理论研究 (cited: 3)

采用密度泛函理论优化了含水和不含水的石墨氧化物的多种结构. 当层间没有水分子时,优化的层间距在6 ?左右,小于6.5～7 ?的实验值. 反之,水石墨氧化物的层间距和实验值符合很好. 基于优化的石墨氧化物结构,用分子动力学方法模拟了水或甲醇中的石墨氧化物. 对于不含水的石墨氧化物,水和甲醇分子不进入其层间. 而对于含水的石墨氧化物,液体分子进入层间,增大了层间距,半定量地重复了实验现象.     

Molecular Dynamics Study of the Structural Modification of Porous Silica from Low-Energy Recoils

Molecular dynamics simulations are performed to investigate the effects of low-energy recoils on the microscopic structure of porous silica. Exhibiting a logistic growth with the recoil energy, the displacement probability of Si is shown to be smaller than that of O at the same primary knock-on level. Computations of pair distribution functions and bond angle distributions reveal that this material upon irradiation with energies around the displacement thresholds mainly undergoes structural changes in the medium-range order. In the porous network,while the formation of nonbridging oxygen defects tends to induce shorter Si–O bonds than those formed by bridging oxygen atoms, a remarkable increase of inter-tetrahedral bond angles created by multiple recoils can be observed and associated with the rearrangement of ring statistics.     

加强命题证明数列不等式

数列不等式是近年来高考和竞赛中的热点题型,其中一类形如     

熔石英亚表面修复形貌对光场的调制

基于标量衍射理论, 计算了熔石英亚表面高斯型修复形貌对于光场的调制，用Matlab对结果进行了仿真并与实验结果进行了比较。所得结果表明，二者有较好的一致性, 一定尺度的高斯面型修复形貌会对光场产生调制，且调制度随光场传输位置变化，通过适当选择后续光学元件位置，可降低光场调制造成光学元件损伤的风险。     

High-dispersive mirror for pulse stretcher in femtosecond fiber laser amplification system

We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system. The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provide a positive group delay dispersion (GDD) of 600 fs² and a high reflectance over 99.9% from 1010 to 1070 nm. The samples were prepared by dual ion beam sputtering. The measured transmittance matches well with the theoretical result. The GDD characteristics of samples were tested by home-made white light interferometer. The measured GDD is higher than the design results, an average GDD of +722 fs² from 1010 nm to 1070 nm. The mirrors were employed in a Yb-doped large-mode-area photonic crystal fiber amplification system. An input pulse compressed by the gratings with autocorrelation function of 83 fs is obtained with a stretched FWHM of 1.29 ps after 28 bounces between the dispersive mirrors. The results show that the multilayer dispersive mirror could be an effective and promising technique for pulse stretching in femtosecond amplification systems.