二阶Volterra系统对平稳正态激励的统计响应的表示定理的数学证明

1974年,Neal根据Kac和Siegert的思想,给出了一个在电子工程、海洋工程、建筑工程、航空工程、自动控制的随机振动中有重要应用的二阶Volterra非线性系统对平稳正态输入的统计响应的表示定理.1984年,Naess对此定理又给出了一个数学证明.经过研究后发现,他们对定理条件的叙述都是模糊的,而且其数学证明都是有问题的.本文重新讨论了这个表示定理,给出了明确的定理条件及严格的数学证明,为它的广泛应用奠定了理论基础.     

Ca+-Pyridine络合物的光解反应

使用反射式飞行时间质谱仪,得到 Ca~ -pyridine 络合物在412～ 690nm 的光解谱.从谱图可见,反应有两个通道,一个是 Ca~ 与 pyridine 分子解离开的非反应淬灭过程,这个通道在所有波段都有,且占优势；生成产物 Ca~ NH_2的通道不仅所占比例小,且在530～590nm 波段关闭. 作为激光波长函数的 Action spectrum 显示出明显的峰,对应于络合物的跃迁.反应的分支比也支持了光解谱图的结论.     

The properties and structures of the mono- and the di- vacancy in Cu crystal

The structures and energies of formation and migration of the mono- and di-vacancy in Cu crystal have been described and calculated with modified analytical embedded atom method (MAEAM). The lattice relaxation is considered with molecular dynamics (MD) method at T=0 K. The results show the FN di-vacancy is the most stable and likely occurs in practice from the energy minimization. Compared with the mono-vacancy, the formation energy of the FN di-vacancy is higher than that of a mono-vacancy, but lower than that of two isolated mono-vacancy. The preferred migration mechanism of the FN di-vacancy is multi-jump of either vacancy (rotating the di-vacancy). The calculated migration energy of the FN di-vacancy is lower than that of a mono-vacancy, so the FN di-vacancy is easier to migrate. All of the calculated results are in good agreement with the experimental values.     

接枝羧基的有限长碳纳米管电子结构的第一性原理研究

基于局域密度泛函理论，采用第一性原理方法，建立了对(5,5)型和(9,0)型有限长碳纳米管接枝羧基官能团的原子模型，通过计算其电子分布和态密度的变化，讨论羧基官能团对碳纳米管电子结构和电子输运特性的影响. 计算表明，接枝羧基的碳纳米管,其电子结构明显改变，其费米能级上的电子态密度下降；最高占据轨道上的非定域程度减弱,致使电子输运性能呈下降趋势. 关键词： 碳纳米管 密度泛函理论 电子结构     

Bipyridinophane‐containing conjugated polymers modulated with an intramolecular aromatic C?H/π interaction

Bipyridinophane–fluorene conjugated copolymers have been synthesized via Suzuki and Heck coupling reactions from 5,8‐dibromo‐2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane and suitable fluorene precursors. Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P7 ) exhibits large absorption and emission redshifts of 20 and 34 nm, respectively, with respect to its planar reference polymer Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐1,4‐(2,5‐dimethylbenzene)] ( P11 ), which bears the same polymer backbone as P7 . These spectral shifts originate from intramolecular aromatic C? H/π interactions, which are evidenced by ultraviolet–visible and ¹H NMR spectra as well as X‐ray single‐crystal structural analysis. However, the effect of the intramolecular aromatic C? H/π interactions on the spectral shift in poly[9,9‐dihexylfluorene‐2,7‐yleneethynylene‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P10 ) is much weaker. Most interestingly, the quenching behaviors of these two conjugated polymers are largely dependent on the polymer backbone. For example, the fluorescence of P7 is efficiently quenched by Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mn²⁺, and Ag⁺ ions. In contrast, only Cu²⁺, Co²⁺, and Ni²⁺ ions can partially quench the fluorescence of P10 , but much less efficiently than the fluorescence of P7 . The static Stern–Volmer quenching constants of Cu²⁺, Co²⁺, and Ni²⁺ ions toward P7 are of the order of 10⁶ M^?1, being 1300, 2500, and 37,300 times larger than those of P10 , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4154–4164, 2006     

VUV-UV excited luminescent properties of LnCa4O(BO3)3:RE (Ln=Y, La, Gd; Re=Eu, Tb, Dy, Ce)

Calcium lanthanide oxyborate doped with rare-earth ions LnCa₄O(BO₃)₃:RE³⁺ (LnCOB:RE, Ln=Y, La, Gd, RE=Eu, Tb, Dy, Ce) was synthesized by the method of solid-state reaction at high temperature. Their fluorescent spectra were measured from vacuum ultraviolet (VUV) to visible region at room temperature. Their excitation spectra all have a broadband center at about 188 nm, which is ascribed to host absorption. Using Dorenbos’ and Jφrgensen's work [P. Dorenbos, J. Lumin. 91 (2000) 91, R. Resfeld, C.K. Jφrgensen, Lasers and Excite States of Rare Earth [M], Springer, Berlin, 1977, p. 45], the position of the lowest 5d levels E(Ln,A) and charge transfer band E_ct were calculated and compared with their excitation spectra.Eu³⁺ and Tb³⁺ ions doped into LnCOB show efficient luminescence under VUV and UV irradiation. In this system, Ce³⁺ ions do not show efficient luminescence and quench the luminescence of Tb³⁺ ions when Tb³⁺ and Ce³⁺ ions are co-doped into LnCOB. GdCOB doped with Dy³⁺ shows yellowish white light under irradiation of 254 nm light for the reason that Gd³⁺ ions transfer the energy from itself to Dy³⁺. Because of the existence of Gd³⁺, the samples of GdCOB:RE³⁺ show higher excitation efficiency than LaCOB:RE³⁺ and YCOB:RE³⁺, around 188 nm, which indicates that the Gd³⁺ ions have an effect on the host absorption and can transfer the excitation energy to the luminescent center such as Tb³⁺, Dy³⁺ and Eu³⁺.     

表面活性剂对均相沉淀法制备单晶Ce2O(CO3)2￠H2O微粉形貌及 形成机理的影响

在尿素及硝酸铈的混合溶液中分别加入表面活性剂CTAB、 PEG19000、OP-10,利用均相沉淀法合成了不同形貌的CeO2超细前驱体Ce2O(COa)2·H2O,采用X射线衍射及透射电子显微镜等测试手段,对产品的物相和形貌进行了表征．实验结果表明,所得产品均为斜方晶系的单晶Ce2O(CO3)2·H2O,且表面活性剂的加入使晶体的晶化程度明显提高;添加不同的表面活性剂得到不同形貌尺寸的产物: 阳离子型表面活性剂CTAB对Ce2O(CO3)2·H2O晶体的形貌影响不大,所得产物尺寸变小,且分散性得到一定的改善;非离子型表面活性剂对所得产物的形貌影响显著．加入PEG19000和OP-10分别得到了形状排列有序的、尺寸较均匀的、较规则无团聚的微米棒及具有紧密结合中心的发散状的花样微粒．不同形貌前驱体的形成与晶粒形成生长机理的改变有关．     

不同方法制备的CO2-3替换磷灰石固溶体晶体化学的FTIR研究

采用不同方法制备了CO2-3替换的磷灰石固溶体,利用FTIR结合XRD对其进行了晶体化学研究,结果表明均相沉淀法制备的碳羟磷灰石(CHAP)属B型替换且替换方式是[CO3·OH]四面体替换[PO4]四面体;固相离子交换法制备的CHAP属A型替换且替换方式是[CO3]三角形配位体替换通道位置的OH-;固相反应法制备的碳氟磷灰石(CFAP)属B型替换,其替换方式是[CO3·F]四面体替换[PO4]四面体;sol-gel法制备的CHAP属AB混合型替换,其Ψ3分裂为Ψ3-1,Ψ3F,Ψ3-4.高斯函数法拟合表明Ψ3F峰是A型替换的Ψ3-2与B型替换的Ψ3-3的叠合.当WCO2-3＜3.34%时,随CO2-3含量增加,A型替换量增大,且当WCO2-3=3.34%时达最大值,当3.34%＜WCO2-3＜7.52%时,随CO2-3含量增加,B型替换量增大,且当WCO2-3= 7.52%时亦到饱和.     

准二维无序系统的电子结构

对形如N_t×N_l型准二维无序系统，只考虑格点之间的最近邻跳跃积分，采用特殊的格点编号方案，在单电子近似下，系统的哈密顿量可表示为简明对称矩阵，借助豪斯荷尔德变换将其约化为对称三对角矩阵，再利用负本征值理论及传输矩阵等方法,对系统态密度、局域长度及电导等电子结构特性进行数值计算. 重点研究了准一维四平行链和五平行链无序系统， 将结果与一维单链、准一维双链及三链系统进行对比，发现随维度的增加，系统的能带有所展宽，能态密度分布发生很大的变化，其峰值数量呈偶数规律增加. 并且在能带中心处存在有局域长度大于系统大小的扩展态，处于这些态下的系统具有较大电导. 从单链到多链，相当于扩大了系统的关联范围，使系统出现了类似非对角长程关联的行为. 关键词： 准二维无序系统 态密度 局域长度 电导     

金刚石窗口冷却Yb3+∶YAG DPSSL设计

针对高功率二极管重复率抽运的V型非稳腔Yb3+∶YAG激光头，提出了利用金刚石窗口冷却和直接水冷相结合的复合冷却设计.在YAG片的抽运面进行直接水冷，同时在激光提取面利用金刚石窗口冷却介质.金刚石优异的导热性能不仅能够有效地冷却激光介质，还能消除横向的温度梯度，解决了高功率激光器冷却和高功率抽运的矛盾.模拟结果表明对掺杂10 at %厚度为1.6 mm的Yb3+∶YAG片在抽运功率密度为20 kW/cm2，重复频率为10 Hz的条件下，要将最高温度控制在可接受的范围内（比如320 K），周围冷却水的对流换热系数约为4000 W/m2K.