密封容器中后处理制备Tl2Ba2CaCu2Oy高温超导薄膜及其性能研究

以铝酸镧（001）单晶为基片，采用两步法制备Tl2Ba2CaCu2Oy（Tl 2212）高 温超导薄膜.首先，利用脉冲激光沉积（PLD）工艺沉积Ba2CaCu2Ox非晶前驱体薄膜；然后，前驱体薄膜在高温（720—850℃）下密封钢容器里铊化结晶形成Tl 2212薄膜.XRD结果表明Tl2212 薄膜是沿c轴方向生长的，其相组成为Tl 2212，摇摆曲线（0012）的半高宽为0.72° ，SEM图像显示其表面光滑平整，其零电阻温度为106.2K. 关键词： Tl 2212超导薄膜 脉冲激光沉积     

超声速等离子体射流的数值模拟

基于可压缩的全Naiver-Stokes方程，利用PHOENICS程序对由会聚 辐射阳极形状等离子体炬产生的超声速等离子体射流进行了数值模拟.考虑了等离子体的黏性、可压缩性以及变物性对等离子体射流特性影响.研究了超声速等离子体射流的流场结构特性以及不同环境压力对等离子体射流产生激波结构的影响.结果表明，超声速等离子体射流在喷口附近形成的周期性激波结构是其和环境气体相互作用的结果. 关键词： 等离子体炬 超声速等离子体射流 PHOENICS     

三维光晶格中玻色凝聚气体基态波函数及干涉演化

基于Gross-Pitaevskii方程，运用有效化学势概念，研究了囚禁在组合势(由磁阱和三维光 晶格组成)中玻色凝聚气体在三维光晶格中的分布规律，并由此得到玻色凝聚气体的归 一化基态波函数.在取消组合势和仅取消光晶格而保留磁阱的两种情况下，运用传播子方 法求解出玻色凝聚气体密度分布的解析表达式.取消组合势后，理论计算所得到的玻色凝聚 气体聚随时间的演化规律与Greiner等的实验结果相一致.仅取消光晶格而保留磁阱时，研 究表明玻色凝聚气体的干涉模式呈现周期性的振荡行为.此外，在磁阱为各向异性的情况下 ， 关键词： 玻色凝聚气体 磁阱 光晶格 干涉模式     

聚乙烯基咔唑与Alq3混合薄膜的发光性能与能量传递过程

研究了Alq3与聚乙烯基咔唑(PVK)按不同比例的混合体系制备的薄膜的发光特性.通过对混合薄膜的吸收光谱、激发光谱和发射光谱的分析，研究了PVK与Alq3之间的 能量传递规律.当Alq3与PVK的质量比为1∶7时，能量传递效率最高.用一个由单链模 型扩展到包括杂质的哈密顿量对实验进行模拟，发现该模型能够较好地解释有关的实验结果. 关键词： 吸收光谱 激发光谱 发射光谱 能量传递     

Yb3+掺杂铝氟磷酸盐玻璃的光谱和激光性能

研究了Yb3 掺杂铝氟磷酸盐 (AFP)玻璃的吸收光谱、荧光光谱 ,测量了Yb3 离子的荧光有效线宽 (Δλeff>5 5nm)以及2 F5 2 能级的荧光寿命 (τmax=2ms)及随掺杂浓度的变化 .应用倒易法计算了Yb3 的发射截面 ,其发射截面可达 0 6 6 82 3pm2 ,且激光增益系数τfσemi达 1 2 89ms.pm2 .评估了Yb3 在AFP玻璃中的激光性能 ,发现其具有较理想的激发态最小粒子数 (0 15 )、饱和抽运强度 (8 3kW cm2 )和最小抽运强度 (1 2 4 5kW cm2 )值及良好的热稳定性 .研究结果表明掺Yb3 氟磷酸盐玻璃是实现高功率超短可调谐激光器的理想增益介质 .     

超短脉冲超强激光与固体靶相互作用中高能离子的产生

 用2D3V PIC粒子模拟方法得到了超短脉冲超强激光与固体靶相互作用中高能离子产生的图像，并对其机理进行了研究。在靶前后表面都观察到了高能离子的产生，并诊断了离子能谱。模拟结果表明，在靶前表面所产生的高能离子，角分布较大，在向靶内输运过程中会损失能量；在靶后表面产生的高能离子，定向性很好，能获得很高的能量。模拟得到的离子能量和实验观测结果在量级上相符。     

Study on the covalence of Cu and chemical bonding in an inorganic fullerene-like molecule, [CuCl]20[Cp*FeP5]12 [Cu-(CH3CN)+2Cl-]5, by a density functional approach

The electronic structure and chemical bonding in a recently synthesized inorganic fullerene-like molecule, [CuCl]₂₀[Cp*FeP₅]₁₂[Cu-(CH₃CN) ⁺ ₂Cl⁻]₅ has been studied by a density functional approach. Geometrical optimization of the three basic structural units of the molecule is performed with Amsterdam Density Functional Program. The results are in agreement with the experiment. Localized MO’s obtained by Boys-Foster method give a clear picture of the chemical bonding in this molecule. The reason why CuCl can react with Cp*FeP₅ in solvent CH₃CN to form the fullerene-like molecule is explained in terms of the soft-hard Lewis acid base theory and a new concept of covalence.     

On division rings with algebraic commutators of bounded degree

We shall answer several questions concerning additive or multiplicative commutators in a division ring which are algebraic of bounded degree over its center.     

Seizure warning algorithm based on optimization and nonlinear dynamics

There is growing evidence that temporal lobe seizures are preceded by a preictal transition, characterized by a gradual dynamical change from asymptomatic interictal state to seizure. We herein report the first prospective analysis of the online automated algorithm for detecting the preictal transition in ongoing EEG signals. Such, the algorithm constitutes a seizure warning system. The algorithm estimates STL_max, a measure of the order or disorder of the signal, of EEG signals recorded from individual electrode sites. The optimization techniques were employed to select critical brain electrode sites that exhibit the preictal transition for the warning of epileptic seizures. Specifically, a quadratically constrained quadratic 0-1 programming problem is formulated to identify critical electrode sites. The automated seizure warning algorithm was tested in continuous, long-term EEG recordings obtained from 5 patients with temporal lobe epilepsy. For individual patient, we use the first half of seizures to train the parameter settings, which is evaluated by ROC (Receiver Operating Characteristic) curve analysis. With the best parameter setting, the algorithm applied to all cases predicted an average of 91.7% of seizures with an average false prediction rate of 0.196 per hour. These results indicate that it may be possible to develop automated seizure warning devices for diagnostic and therapeutic purposes.Mathematics Subject Classification (1991):20E28, 20G40, 20C20     

On Einstein four-manifolds with <Emphasis Type="Italic">S</Emphasis><Superscript>1</Superscript>-actions

We study closed Einstein 4-manifolds which admit S¹ actions of a certain type, i.e., warped products. In particular, we classify them up to isometry when the fixed point of the S¹ action satisfies certain natural geometric conditions. The proof uses the Bochner-Weitzenböck formula for 1-forms and the theory of minimal surfaces in 3-manifolds.in final form: 22 January 2003