时间相关穆斯堡尔谱与GaAs的119mTe离子注入

本文提出并实现了一种新的穆斯堡尔谱——时间相关穆斯堡尔谱。这是利用两步衰变^119mTe→¹¹⁹Sb→¹¹⁹Sn而获得的。测量了110keV ^119mTe加10¹⁵稳定Te/cm²注入并经600℃退火的样品在不同测量时间内的穆斯堡尔谱,分析了各谱线随ξ的变化。这里ξ是我们定义的参量,它等于Φ_Te/Φ_总,由退火时刻t_{a关键词：}     

Large-N c quantum chromodynamics and harmonic sums

In the large-N _c limit of QCD, two-point functions of local operators become harmonic sums. I review some properties which follow from this fact and which are relevant for phenomenological applications. This has led us to consider a class of analytic number theory functions as toy models of large-N _c QCD which also is discussed.     

BC_2N薄膜的柱状生长及生长机理

应用热丝辅助等离子体化学气相沉积法 (CVD)合成了表面呈柱状的BC2 N薄膜 ,X射线、红外及X射线电子能谱分析表明 ,薄膜的化学组分主要为BC2 N ,B ,C和N原子间互相结合成键 .扫描电镜观察到 ,薄膜表面形貌呈排列整齐、取向一致的柱体 ,并且发现这种生长方式与沉积参数密切相关 .最后从结合能方面讨论了柱状BC2 N的生长机理 .     

液氦温区两级4K脉冲管制冷机数值模拟

为模拟和动态显示工作在液氦温区的两级4K脉冲管制冷机内部工作过程和参数变化规律,发展了一种新的欧拉法-拉格朗日法数值计算模型。采用拉格朗日方法,直接跟踪脉冲管中气体微元随周期性压力波动的具体运行轨迹;采用欧拉法,直接模拟蓄冷器内部的动态参数变化。本文简单介绍该模型,并模拟了一典型两级4 K脉冲管制冷机各参数的变化情况,分析了多层磁性蓄冷材料对制冷机性能的影响情况。     

S.I.S.向量随机测度在弱拓扑及相容拓扑下的收敛性

本文主要研究ｓ．ｉ．ｓ．向量随机测度在弱拓扑及相容拓扑下的收敛性,给出了ｓ．ｉ．ｓ．向量随机测度在弱拓扑 容拓扑下的Ｖｉｔａｌｉ－Ｈａｌｍ－Ｓａｋｓ定理,作为应用,我们建立了Ｒ＾１－值有界可测函数关于Ｂａｎａｃｈ空间值ｓ．ｉ．ｓ．向量随机测度的随机积分的收敛定理,并得到了具ｔｙｐｅｐ的Ｂａｎａｃｈ空间中ｓ．ｉ．ｓ．向量随机测度的大数定律及中心极限定理。     

EFFICIENT COMPUTATIONS USING UPWIND BIASED SCHEMES

A new multiblock unfactored implicit upwind scheme for inviscid two-dimensional flow calculations is presented. Spatial discretization is carried out by means of an upwind first-order method; an original extension to higher accuracy is also presented. The integration algorithm is constructed in a ‘δ’ form that provides a direct derivation of the scheme and leads to an efficient computational method. Fast solutions of the linear systems arising at each time step are obtained by means of the bi-conjugate gradient stabilized technique. The computational results for super/hypersonic steady state flows illustrate the efficiency and accuracy of the algorithm.     

球形BaZnF_4∶Yb,Er纳米颗粒的热分解法合成及其上转换发光性质

采用热分解法制备了Ba Zn F4∶Yb,Er纳米颗粒。通过荧光分光光度计、X射线粉末衍射仪(XRD)和透射电子显微镜(TEM)对样品进行了表征。合成样品的形貌为球形,晶相为四方相,平均粒径为8 nm。当敏化剂Yb3+和激活剂Er3+的掺杂摩尔分数分别为20%和4%时,样品的发光性能较好。绿光和红光发射对应的辐射跃迁分别为Er3+离子的2H11/2→4I15/2(绿光)和4S3/2→4I15/2(绿光),以及Er3+离子的4F9/2→4I15/2(红光)。     

Homogeneous tandem catalysis of the bis‐(diphenylphosphino)‐amine/chromium tetramerization catalyst with metallocene catalysts

Homogeneous tandem catalysis of the bis(diphenylphoshino)amine‐chromium oligomerization catalyst with the metallocenes Ph₂C(Cp)(9‐Flu)ZrCl₂ and rac‐EtIn₂ZrCl₂, is discussed. GC, CRYSTAF, and ¹³C NMR analysis of the products obtained from reactions at constant temperatures show that during tandem catalysis, α‐olefins, mainly 1‐hexene and 1‐octene, are produced from ethylene by the oligomerization catalyst and subsequently built into the polyethylene chain. At 40 °C the Cr/PNP catalyst acts as a tetramerization catalyst while the polymerization catalyst activity is low. Copolymerization of ethylene and the in situ produced α‐olefins have also been carried out by increasing the temperature from 40 °C, where primarily oligomerization takes place, to above 100 °C, where polymerization becomes dominant. The melting temperature of the polymer is dependent on the catalyst and cocatalyst ratios as well as on the temperature gradient followed during the reaction, while the presence of the oligomerization catalyst reduces the activity of the polymerization catalyst. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6847–6856, 2006     

稳态实验考察经模拟道路老化的全配方稀燃Nox捕集催化剂上的Nox还原

Fully formulated lean NOx trap(LNT)catalysts of the type Pt/Rh/BaO/Al2O3 were prepared with and without incorporation of CeO2-ZrO2 in the washcoat,and their NOx reduction behavior was evaluated in steady-state,continuous flow experiments.In the fresh state, the CeO2-ZrO2 addition was found to exert little effect on NOx reduction activity using H2,CO,and NH3 as the reductants.However,after simulated road aging,NOx reduction activity was significantly impaired for the CeO2-ZrO2-free catalyst,whereas the perfo...