具有三阶精度的数值微分紧致格式及其应用

本文从微分代数精度概念出发 ,引入了数值微分的紧致性概念 ,并且构造了在一般意义下的具有三点三阶精度的数值微分格式 ,以及在等距节点这种特殊情况下的计算格式 .最后 ,通过数值实验证实了格式的精度 .     

Al-Mg合金中析出强化相对Portevin-Le Chatelier效应的影响

Portevin-Le Chatelier(PLC)效应作为广泛存在于各种合金材料中的重要塑性失稳现象一直受到研究者的广泛关注。本文对镁原子质量百分含量分别为2.5%和5%的两种铝合金-国标LF2和LF5铝合金进行宏观拉伸实验和透射电子显微镜观察实验。通过宏观和微观实验结果的对比分析表明,由于LF5合金中作为溶质的Mg原子的含量相对于LF2合金成倍增加导致析出相颗粒数量也成倍增加,进而引起PLC效应在强度和加工硬化时间的倍增,这些对应关系表明Al-Mg合金中析出相颗粒是产生并影响PLC效应的重要因素。实验结果显示虽然析出相颗粒数量在多方面影响PLC效应,但是对其飞行时间的影响却微乎其微。     

158Tm核中的带结构及电磁跃迁性质

通过融合蒸发反应¹⁴⁴Nd(¹⁹F,5n)E=108, 112MeV对双奇核¹⁵⁸Tm的高自旋态进行了研究. 扩展了原已建立的带结构, 并建立了2条新转动带. 获得了γ射线的相对强度和耦合带的B(M1)/B(E2)比值.观测到了πh_11/2⊙νi_13/2组态带的旋称反转点. 对新建立的转动带进行了自旋-宇称以及组态的讨论.     

Characterization of Al2O3 Thin Films on GaAs Substrate Grown by Atomic Layer Deposition

Al2O3 thin films are grown by atomic layer deposition on GaAs substrates at 300℃. The structural properties of the Al2O3 thin film and the Al2O3/GaAs interface are characterized using x-ray diffraction （XRD）, high- resolution transmission electron microscopy （HRTEM）, and x-ray photoelectron spectroscopy （XPS）. The XRD results show that the as-deposited Al2O3 film is amorphous. For 30 atomic layer deposition growth cycles, the thicknesses of the Al2O3 thin film and the interface layer from the HRTEM are 3.3 nm and 0.Snm, respectively. XPS analyses reveal that the Al2O3/GaAs interface is almost free from As2O3.     

稀土区奇奇核πh1／2×vi13／2带B（M1）／B（E2）比值增强特性

在稀土区奇奇核πh1／2×vi13／2转动带中，系统地观测到随转动频率或角动量增加，B(M1)／B(E2)曲线表现出所谓parabola-1ike形状，即在增加到某一转动频率或自旋后，B(M1)／B(E2)比值快速增强。基于推转模型和粒子转子模型关于奇奇核二准粒子转动带磁偶极约化跃迁几率的描述，对稀土区双奇核的这一行为进行了讨论。指出该现象的发生与vi13/2准中子转动顺排特性密切相关。B(M1)／B(E2)比值在接近第二带交叉(即BC准中子对顺排)的较高频率处的增强效果，可以理解为主要来源于带交叉引起的波函数中混合四准粒子成分的结果。通过对B(M1)/B(E2)比值的增强效果发生在较低频率处的分析，对稀土区奇奇核πh1／2×vi13／2带角动量耦合图像有了进一步认识。It is systematically observed that the B(M1)/B(E2) plots with the increasing of rotational frequency, behaves as a so called parabola like shape in the π h11/2 νi13/2 bands of rare earth doubly odd nuclei (i.e., the B(M1)/B(E2) ratios increase rapidly after a certain rotational frequency). Such a phenomenon is discussed based on the formula of magnetic dipole reduced transition probability deduced from the Cranking Shell Model and Particle Rotor Model respectively. It is pointed out that, the occurrence of this behavior is closely related to the alignment nature of the νi 13/2 quasineutron. The increasing of B(M1)/B(E2) occurring at large frequency approaching the second BC crossing can be understood as mainly resulted from the mixing of wave function with the 4 quasiparticle band caused by the band crossing. Insight into the angular momentum coupling scheme between the quasiparticles and collective core in the πh11/2 νi 13/2 structures of rare earth doubly odd nuclei is gained by analyzing the increasing behavior of B(M1)/B(E2) ratios occurring at low rotational frequency.     

具有生物活性的紫檀芪和3’-甲氧基紫檀芪及其糖苷类化合物的合成

以3,5-二羟基苯甲酸、对羟基苯甲醛或香草醛为原料,以Wittig-Horner反应为关键步骤,合成了天然产物紫檀芪(1)和3’-甲氧基紫檀芪(2).以稀碱NaOH水溶液作缩合剂,四丁基溴化铵(TBAB)为相转移催化剂,使1和2在氯仿-水体系中分别与糖基供体α-溴代乙酰葡萄糖、乳糖和麦芽糖进行糖苷化反应,合成了一系列未见文献报道的紫檀芪和3’-甲氧基紫檀芪的糖苷类化合物3～10.所合成化合物的结构已由核磁共振谱、红外光谱和质谱所证实.并用MTT蛋白染色法对紫檀芪(1)和3’-甲氧基紫檀芪(2)进行了体外抗肿瘤细胞生物活性测试,发现其对HL-60(白血病细胞)、SMMC-7721(肝癌细胞)和SK-BR-3(乳腺癌细胞)三种肿瘤细胞均具有较好的细胞毒活性.     

Energy transfer relation of a novel Ce~(3+)/Pr~(3+)/Eu~(3+) co-doped Sr_(2.975-x)La_xAlO_(4+x)F_(1-x) solid solution phosphor

The photoluminescence properties and energy transfer of a new Ce3+/ Pr3+/ Eu3+co-doped solid-solution composition of Sr2.975-xLaxAlO4+xF1-x(LSAF) phosphor are investigated. Upon doping Pr3+into lattices of LSAF:Ce host,a shoulder emission peak is observed at about 620 nm, owing to the transition of1D2→3H4. Addition of Eu3+to LSAF:Ce3+, Pr3+phosphor results in a sharp emission peaked at 675 nm for the5D0→7F3transition and an increase of the intensity of red emission for Pr3+with increasing Eu3+concentration. The pathways of energy transfer among Ce3+, Pr3+, and Eu3+are proposed to be responsible for color addition of a red component to the primary yellow emission,enabling a potential adjustable color for blue excitable warm white.     

(E)-1,5-二苯基-2-烯-1-戊酮的合成及生物活性研究

(E)-1,5-二苯基-2-戊烯-1-酮(I)是从瑞香狼毒(Stellera chamaejasme L.)中分离得到的天然产物,能有效防治重要农业害虫蚜虫.以价廉易得的苯乙酮为起始原料,经过4步反应合成化合物I,所得目标产物结构经过1HNMR,IR和元素分析确证.并探讨了反应温度和溶剂对产物顺反比例的影响.生物活性测试结果表明,化合物I对桃蚜(Myzus persicae)具有较强的杀蚜活性,其LC50为178.96μg/mL.     

Level scheme in 160Tm towards complete high-spin structure

High-spin states of ¹⁶⁰Tm have been studied through the ¹⁴⁶Nd(¹⁹F, 5n) reaction at a beam energy of 102 MeV. The previously known πh_11/2⊙νi_13/2 yrast band and πh_11/2⊙νh_9/2 side band are confirmed, and several low-lying levels are observed. A 4-quasiparticle band feeding into the yrast band based on the πg_7/2⊙νh_9/2⊙νi_13/2² is suggested. Other two bands are observed and assigned to be based on the πd_3/2⊙νi_13/2 and πg_7/2⊙νi_13/2 configurations, respectively.     

Essence of Inviscid Shear Instability: a Point View of Vortex Dynamics

The essence of shear instability is reviewed both mathematically and physically, which extends the instability theory of a sheet vortex from the viewpoint of vortex dynamics. For this, the Kelvin-Arnol＇d theorem is retrieved in linear context, i.e., the stable flow minimizes the kinetic energy associated with vorticity. Then the mechanism of shear instability is explored by combining the mechanisms of both Kelvin Helmholtz instability （K-H instability） and resonance of waves. The waves, which have the same phase speed with the concentrated vortex, have interactions with the vortex to trigger the instability. The physical explanation of shear instability is also sketched by extending Batchelor＇s theory. These results should lead to a more comprehensive understanding on shear instabilities.