用能化电子效应考察二次离子的发射机理

用能化电子改变样品的表面势,测量多种二次离子产额的能谱,发现在通常条件下,特别当存在氧增强发射时,离子的存活几率不为共振电子隧道效应所影响。动力学参量的数据表明,决定离子产额的表面势是高度局域的。并可推论电子束照射对二次离子质谱的定量分析可起有益的效用。 关键词：     

以一组统一的高斯函数为基函数的双原子分子的Hartree-Fock-Roothaan波函数(Ⅱ)——H2和第一列元素的同核双原子体系A2,A2~±和A2

采用文献的一组统一的doublezeta收缩高斯型函数为基函数,从头计算H₂和第一列元素的同核双原子体系的电子波函数和轨道能量、总能量等物理量。电子态包括同核体系的基态A₂,一些低激发态A₂~*和正负离子态A₂~±,A表示周期表中Li到F的各种元素。计算限于闭壳层电子组态或只带一个未填满的开壳层电子组态。作为例子,报道了H₂和几种基态A₂的电子波函数表。 关键词：     

基于3×3平行排列耦合器的全光光开关的特性分析

提出了一种新型的基于3×3平行排列耦合器的全光光开关。此种光开关具有两个独立的输出端口且具有极好的偏振稳定性,消光比可达20dB。介绍了其工作原理,详细分析了信号光强度、控制光强度、光纤长度及耦合器分光比偏差等因素对各端口消光比的影响。比较了不同种类和长度光纤环的开关性能,首次得到了耦合器分光比偏差对消光比的影响曲线。     

轴流式水轮机三维非定常湍流计算及压力脉动预测

水轮机的稳定性研究是目前工程上大型水轮机组流动分析的重要课题,本文以某水电站的大型轴流转桨式水轮机原型为基础建立计算模型,完成了从蜗壳进口到尾水管出口整个流道的非定常湍流计算,预测了固定导叶进口、转轮后、尾水管进口等多个位置的压力脉动,并利用FFT变换进行分析得到了压力脉动的频率和幅值,探讨了水轮机全流道内压力脉动产生和传播的原理．     

塑料闪烁体的辐照特性

利用⁶⁰Co放射源分别对3种塑料闪烁体(BC-408, EJ-200, BC-404)进行辐照损伤研究, 比较辐照前后的透射谱、发射谱及光产额的变化, 发现3种闪烁体在低剂量具有较好的抗辐照性能; 当照射剂量超过1.44×10⁴Gy时,透射谱明显变坏, 光输出减少很严重, 但发射谱却保持不变.     

二色补血草不同部位总黄酮含量的测定

采用分光光度法测定了二色补血草花、根、茎、叶总黄酮的含量,分别为35.5869、23.5367、24.7081、30.5378mg/g.RSD为0.1016%-0.1410%,稳定性R＞97.5%,平均回收率96.38%-100.2%.     

基于光谱合束技术的透射光栅模拟设计

半导体激光器光谱合束技术能够实现近衍射极限的高功率激光输出,已成为当前研究热点。衍射光栅的性能直接决定光谱合束的激光输出效果。模拟设计了一种针对940 nm波长、熔融石英材料的亚波长透射光栅。基于严格耦合波理论对光栅结构进行初步设计,运用Rsoft软件依次对光栅占空比、脊高和周期等参数进行优化确定,同时分析了各个参数对光栅衍射效率的影响。所设计的透射式光栅实现第-1级衍射级次的波分复用功能,衍射效率达到91.2%(TE模式),同时压缩其他衍射级次,使其衍射效率降到1.2%以下。同时在光栅入射角度59°±3°范围内保持90%以上的衍射效率,实现高功率激光输出的同时具有较高的误差容错率,易于调节,满足光谱合束技术的要求。     

Spatial heterogeneity in liquid–liquid phase transition

Molecular dynamics simulations are performed to investigate the liquid–liquid phase transition(LLPT) and the spatial heterogeneity in Al–Pb monotectic alloys. The results reveal that homogeneous liquid Al–Pb alloy undergoes an LLPT,separating into Al-rich and Pb-rich domains, which is quite different from the isocompositional liquid water with a transition between low-density liquid(LDL) and high-density liquid(HDL). With spatial heterogeneity becoming large, LLPT takes place correspondingly. The relationship between the cooling rate, relaxation temperature and percentage of Al and the spatial heterogeneity is also reported. This study may throw light on the relationship between the structure heterogeneity and LLPT, which provides novel strategies to control the microstructures in the fabrication of the material with high performance.     

Band structure of silicon and germanium thin films based on first principles

In nanomaterials, optical anisotropies reveal a fundamental relationship between structural and optical properties, in which directional optical properties can be exploited to enhance the performance of optoelectronic devices. First principles calculation based on density functional theory(DFT) with the generalized gradient approximation(GGA) are carried out to investigate the energy band gap structure on silicon(Si) and germanium(Ge) nanofilms. Simulation results show that the band gaps in Si(100) and Ge(111) nanofilms become the direct-gap structure in the thickness range less than 7.64 nm and7.25 nm respectively, but the band gaps of Si(111) and Ge(110) nanofilms still keep in an indirect-gap structure and are independent on film thickness, and the band gaps of Si(110) and Ge(100) nanofilms could be transferred into the direct-gap structure in nanofilms with smaller thickness. It is amazing that the band gaps of Si~((1-x)/2)Ge~xSi~((1-x)/2)sandwich structure become the direct-gap structure in a certain area whether(111) or(100) surface. The band structure change of Si and Ge thin films in three orientations is not the same and the physical mechanism is very interesting, where the changes of the band gaps on the Si and Ge nanofilms follow the quantum confinement effects.     

根在指定区间内的二次方程参数范围的确定

下面的五道试题都是从日本各大学入学试题中选来的: 1.k是什么实数时,二次方程 7x~2-(k+13)x+k~2-k-2=0有两个实根,它们分别在区间(0,1)和(1,2)内?(1975年东京大学) 2.在△ABC中,tgA、tgB是二次方程 x~2+mx+m+1=0