Alkene Isomerisation Catalysed by a Ruthenium PNN Pincer Complex

The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2‐di‐tert‐butylphosphinomethyl‐6‐diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable‐temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side‐arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal–hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru⁰ coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined.     

Nonlinear free vibrations of porous composite microplates incorporating various microstructural-dependent strain gradient tensors

The main objective of the present numerical analysis is to predict the nonlinear frequency ratios associated with the nonlinear free vibration response of porous composite plates at microscale in the presence of different microstructural gradient tensors. To achieve this end, by taking cubic-type elements into account, isogeometric models of porous composite microplates are obtained with and without a central cutout and relevant to various porosity patterns of distribution along the plate thickness. The established unconventional models have the capability to capture the effects of various unconventional gradient tensors continuity on the basis of a refined shear deformable plate formulation. For the simply supported microsized uniform porous functionally graded material (U-PFGM) plate having the oscillation amplitude equal to the plate thickness, it is revealed that the rotation gradient tensor causes to reduce the frequency ratio about 0.73%, the dilatation gradient tensor causes to reduce it about 1.93%, and the deviatoric stretch gradient tensor leads to a decrease of it about 5.19%. On the other hand, for the clamped microsized U-PFGM plate having the oscillation amplitude equal to the plate thickness, these percentages are equal to 0.62%, 1.64%, and 4.40%, respectively. Accordingly, it is found that by changing the boundary conditions from clamped to simply supported, the effect of microsize on the reduction of frequency ratio decreases a bit.

     

基于图像的二维剪纸自动生成方法

中国剪纸的设计极具挑战性, 要求画面简洁、直观, 还需要表达特定的文化内涵, 且整张剪纸须整体连通。提出了一种基于图像的二维剪纸自动生成方法, 能够将任意数码照片自动转化为剪纸图形。首先,利用图像分割方法建立区域连接图; 接着, 基于该连接图对颜色、边界对比度和区域连通性进行数学建模, 并获得优化目标函数; 最后, 通过模拟退火算法求解目标方程, 自动生成保持图像内容的剪纸图形。还开发了连通性后处理和区域指定等用户交互工具, 允许用户在自动生成的剪纸图形中方便地加入个人设计。实验表明, 所生成的剪纸图形画面简洁、整体连通。 本方法在降低剪纸设计难度的同时还可满足个性化的设计需求, 有助于传播和传承我国的民间剪纸艺术。     

Geometric phase of an open double-quantum-dot system detected by a quantum point contact

We study theoretically the geometric phase of a double-quantum-dot(DQD) system measured by a quantum point contact(QPC) in the pure dephasing and dissipative environments, respectively. The results show that in these two environments, the coupling strength between the quantum dots has an enhanced impact on the geometric phase during a quasiperiod. This is due to the fact that the expansion of the width of the tunneling channel connecting the two quantum dots accelerates the oscillations of the electron between the quantum dots and makes the length of the evolution path longer.In addition, there is a notable near-zero region in the geometric phase because the stronger coupling between the system and the QPC freezes the electron in one quantum dot and the solid angle enclosed by the evolution path is approximately zero,which is associated with the quantum Zeno effect. For the pure dephasing environment, the geometric phase is suppressed as the dephasing rate increases which is caused only by the phase damping of the system. In the dissipative environment,the geometric phase is reduced with the increase of the relaxation rate which results from both the energy dissipation and phase damping of the system. Our results are helpful for using the geometric phase to construct the fault-tolerant quantum devices based on quantum dot systems in quantum information.     

基于非线性梁理论的有限质点法

有限质点法是以向量式力学为基础,用有限数量的质点来模拟结构的变形行为,质点的运动由牛顿运动定律来计算。在有限质点法中,质点通过构件相连,构件约束着质点的运动,并且其内力由质点的运动变量来描述。基于向量式力学的基本思想和非线性梁理论,提出了一种新的有限质点法,该方法在共旋单元坐标系中描述梁的非线性变形。以空间梁系结构为例,推导了计算构件内力的非线性公式,并考虑了弯扭耦合变形。通过两个连续欧拉角的变换公式得到共旋坐标系的旋转矩阵。与传统的有限质点法相比,本文提出的方法避免了刚体虚转动分析。通过四个结构的数值求解,验证了本文方法在计算结构大变形响应时具有较高的精度。     

TiO2-SiO2复合氧化物结构和红外光谱的量子化学研究

 构建了TiO2-SiO2复合氧化物晶胞结构,采用HyperChem量子化学程序中的从头计算方法以3-21G*基组对其进行了全优化计算,并进行了振动分析,预测了TiO2-SiO2复合氧化物各化学键的红外特征吸收频率. 采用IR谱对TiO2-SiO2复合氧化物进行了表征,通过理论计算与实验数据相结合的方法确定了TiO2-SiO2复合氧化物的分子结构,对其平衡几何构型、IR谱、电子结构和Lewis酸性进行了讨论.     

Ab initio quantum-chemical calculations of interactions of ions and hydrides of alkali metals with C3H6 and C4H8 molecules

Calculations of the C₃H₆ · LiH, C₄H₈ · M⁺, and C₄H₈ · MH systems and of C₂H₂ · MH complexes (M = Li or Na) were carried out by the unrestricted Hartree-Fock-Roothaan (UHF) method with partial optimization of the geometry using fixed geometric parameters of the C₃H₆ and C₄H₈ molecules. The standard 3-21G and 6-31G* basis sets were used. Unlike the C₃H₆ · LiH structure, the C₄H₈ · M⁺ and C₄H₈ · MH systems are typical complexes. It was found that the C₄H₈ · M⁺, C₄H₈ · MH, and C₂H₂ · MH complexes are similar in coordination of M⁺ ions and MH molecules by carbon atoms in spite of considerable differences in the interatomic distances (–1 A) between these atoms in the C₄H₈ and C₂H₂ molecules. The heats of formation (Q), which were calculated in the UHF/6-31G* approximation and using second- and fourth-order Möller-Plesset perturbation theory taking into account the electron correlation energy in the MP2/6-31G*. MP4(SDQ)/6-31G*, and MP4(SDTQ)/6-31G* approximations, satisfy the following relationships: Q(C₂H₃ · MH) < Q(C₄H₈ · MH) < Q(C₄H₈ · M⁺). It was observed that in going from Li to Na the corresponding values of Q tend to decrease.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 7, pp. 1636–1640, July, 1996.     

2-溴-4-[1-(E)-亚乙基-2-对甲氧基苯基-丁基]-1-甲氧基苯脱甲基及双键转位反应的研究

2-溴-4-[1-(E)-亚乙基-2-对甲氧基苯基-丁基]-1-甲氧基苯(3)是在合成3’-甲氧基己烯雌酚(2)过程中获得的意外羟基消除产物. 报道了2-溴-4-[1-(E)-亚乙基-2-对甲氧基苯基-丁基]-1-甲氧基苯在不同条件下的脱甲基反应产物以及双键转位反应的情况. 部分重要中间体的人脐静脉内皮细胞(HUVEC)抑制活性结果显示, 己烯雌酚骨架上的基团对该类化合物的抑制新生血管生成活性具有显著的影响, 甲氧基为活性有利基团, 而酚羟基全部游离时化合物没有活性.     

非线性粘弹性大挠度梁的动力学模型及其简化

本文建立了描述几何非线性均匀梁动力学行为的偏微分－－积分方程,梁的材料满足Ｌｅａｄｅｍａｎ非线性本构关系,对于两端简支的情形用Ｇａｌｅｒｋｉｎ方法进行了截断简化为常微分－－积分方程,然后引进附加变量的方法进一步简化为常微分方程组。     

横向磁场激励下铁磁梁式板的混沌运动分析

在磁体力分布的磁弹性理论模型和磁场准静态假定模式基础上，对于处在周期时变磁场 中的不可移简支铁磁梁式板非线性磁弹性动力特性进行定性与定量分析．首先利用磁场的摄 动技术和结构变形的模态法，导出了关于模态坐标的非线性动力方程；然后利用Ｍｅｌｎｉｋｏｖ方 法，从理论上给出这一磁弹性动力系统可能出现混沌运动的必要条件及参数范围；最后采用变 步长Ｒｕｎｇｅ－Ｋｕｔｔａ数值积分方法对其磁弹性相互作用的混沌现象进行了定量搜索与模拟，并 利用其轨迹的Ｐｏｉｎｃａｒｅ截面图与Ｌｉａｐｕｎｏｖ指数加以判断．结果表明磁弹性简支梁式板在横 向周期时变磁场中存在混沌吸引子，且在机械阻尼很小时其混沌吸引子表现出稠的特性．