铁磁-绝缘层-铁磁-d波超导结中的量子干涉效应对微分电导与散粒噪声的影响

通过求解BogoliubovedeGennes(BdG)方程,利用推广的BlonderTinkhamKlapwijk(BTK)理论,计算铁磁绝缘层铁磁d波超导结中的微分电导、平均电流和散粒噪声功率.研究表明,系统的微分电导和散粒噪声与平均电流的比值都随中间铁磁层厚度作周期性振荡,振荡的幅度随绝缘层势垒增高而变大,随铁磁层中磁交换劈裂的增强而变小. 关键词： 微分电导 散粒噪声 磁交换劈裂     

Structural and electrical properties of lanthanum-substituted lead titanate ceramics

The effect of lanthanum substitution on the structural, dielectric and piezoelectric properties of lead calcium titanate (PCT) ceramics is studied. Samples with compositional formula Pb_{0.76? x} La _x Ca_0.24Ti_0.98Mn_0.02O₃ (PLCT) (x?=?0–0.08, in steps of 0.02) were prepared by the conventional dry ceramic technique. Phase and structural analysis was carried out using XRD and SEM respectively. X-ray analysis confirmed the formation of single-phase compound with tetragonal crystal structure. Dielectric properties were studied in detail as a function of frequency and temperature. The Curie temperature (T _C) and tetragonality (c/a) was found to decrease with increase in lanthanum content. The Curie temperature was also confirmed from the thermal-expansion behaviour of the sintered samples. Piezoelectric coefficients (d ₃₃, d ₃₁, g ₃₃, g ₃₁, g _h, d _h, k _t and k _p) were measured at room temperature. From this study it is found that La³⁺ substitution helps in the improvement of electro-mechanical anisotropy.     

射流式单重态氧发生器的气液两相耦合模型

 将气液两相耦合模型应用于射流式单重态氧发生器,通过数值模拟和实验的比较验证了该模型的可行性。分析了发生器工作参数对其动力学过程的影响,发现在保持其它参数不变的情况下,氯气和BHP溶液的相对浓度决定了发生器动力学过程的类型。给出了利用氯气吸收速率变化曲线判定发生器动力学过程类型的方法。在原有模型基础上考虑了热效应及其对模型参数的影响,计算了水蒸气的含量。模型改进后,模拟结果更接近于实验值。     

端面抽运四镜折叠腔Nd∶YVO4激光器的研究

基于传输矩阵理论,针对端面抽运的z型折叠腔Nd∶YVO4固体激光器的谐振腔设计进行了数值模拟,详细分析了腔内各参量对谐振腔稳定性的影响.由模拟结果推断,z型腔激光器具有两个稳区,并且稳区的范围可通过谐振腔各分臂的臂长来调节.利用相同的光学元件在不同的稳区范围设计了两种热稳腔,指出了长短腔型各自的利弊.实验考察了输出功率随腔长改变的变化情况,在不同腔长下的不同稳区分别获得了稳定的1 342 nm激光输出,谐振腔稳区范围的变化规律与理论计算基本符合.     

振动波包法模拟氢溴酸光解离动力学

研究了在零度和非零度时的双原子分子离子HBr⁺在不同包络函数的超快激光脉冲作用下的光解离动力学. 主要计算了HBr⁺电子基态时的参数. 利用从头算理论在CCSD/6-311++G(3df,2pd)水平计算了HBr+的势能值,用Morse参数模拟后,与非依时傅立叶格点哈密顿方法获得的束缚态振动能量本征值进行比较. 另外,探索了温度、脉冲包络函数和光强度对光解离过程的影响.     

利用BSO晶体的电控自聚焦效应实现的一种新型电光调制

BSO(硅酸铋)晶体除了具有热自聚焦效应外¹,还具有电控自聚焦效应²,基于电控自聚焦效应,又进一步对高斯光束经BSO晶体自聚焦后的远场光斑中心处的光强与加在晶体通光方向上的电压和入射光功率的关系进行了理论和实验研究,提出一种新的电光调制方法。理论与实验相符,进一步验证了文献1、2的结论.     

Characterization and chemical behavior of submonolayer coverages of titania on a Pt foil

The interaction between submonolayer titania coverages and Pt foil has been studied by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). The submonolayer titania can be fully oxidized to TiO₂ at 923 K under 10⁻⁸ Torr O₂, and partially oxidized to TiO_x at lower oxidation temperatures. The oxidized surface can be reduced by annealing to 1000 K or higher, or by heating in H₂ at 823 K, or by interacting with surface carbon formed from acetone decomposition. Under certain conditions (e.g., hydrogen reduction at 923 K), the surface titania can be fully reduced to metallic Ti which diffuses into bulk Pt readily. The reduced metallic Ti can resurface when the surface is oxidized at 923 K. Both XPS and HREELS data indicate the existence of subsurface oxygen, which plays an important role for the diffusion of Ti into and out of the Pt foil. Although no special interfacial active sites were revealed by HREELS studies of adsorbed acetone and CO, some TPD and XPS data suggest the presence of sites active for acetone decomposition.     

Cd(Ⅲ)、Co(Ⅲ)、Cu(Ⅲ)与异烟酸的配合物合成与性质

以异烟酸为配体合成了Cd(Ⅱ)、Co(Ⅱ)、Cu(Ⅱ)3种配合物,用X-射线单晶衍射研究了其结构,3种配合物具有类似的六配位结构,由于Jahn-Teller效应使Cu(Ⅱ)的配合物的结构为一伸长的八面体;3个配合物的配位原子均为4个水分子的氧原子和两个异烟酸根的氮原子,羧基仅参与形成氢键。对配合物的热稳定性进行了研究,并对Cd(Ⅱ)配合物非等温热分解动力学方程和动力学参数进行了拟合,结果表明动力学补偿效应方程与数据拟合方法无关。     

基于主成分回归的温度分布反演研究

多谱辐射测温是一种非接触温度测量方法,目前常用的多谱辐射测温只能反演出一个近似温度值,而无法给出实际的温度分布。针对此问题,基于普朗克定律,采用主成分回归算法,以强激光毁伤靶材温度测量为例,在脉冲能量为34.2 J的激光入射条件下,从热辐射谱中反演出近似温度值为2 700 K,拟合相对偏差为0.5%,当温度分布范围为2 600～2 800 K时,拟合相对偏差减小为0.13%,减小了温度反演偏差。首次给出了基于主成分回归方法的温度分布反演,提高了非接触式温度测量的表征精度。     

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介绍了为开展漏孔检测、氘-氦分辨性能及真空检漏技术等相关实验研究而进行的四极质谱计分析与测量系统的研制,描述了真空室结构、抽气设备的选型、测量仪器的选择及控制保护子系统工作方式。对系统进行了包括极限真空、残余气体质谱分析、漏放气率、质谱计性能等测试,结果表明本系统达到了设计要求。