A density functional theory study on size-dependent structures, stabilities, and electronic properties of the bimetallic MnAgm (M=Na, Li; n+m ≤ 7) clusters

The equilibrium geometries, relative stabilities, and electronic properties of M_nAg_m (M=Na, Li; n+m≤ 7) as well as pure Ag_n, Na_n, Li_n (n≤ 7) clusters are systematically investigated by means of density functional theory. The optimized geometries reveal that for 2≤ n ≤ 7, there are significant similarities in geometry among pure Ag_n, Na_n, and Li_n clusters, and the transitions from planar to three-dimensional configurations occur at n=7, 7, and 6, respectively. In contrast, the first three-dimensional (3D) structures are observed at n+m=5 for both Na_nAg_m and Li_nAg_m cluters. When n+m ≥ 5, a striking feature is that the trigonal bipyramid becomes the main subunit of Li_nAg_m. Furthermore, dramatic odd-even alternative behaviours are obtained in the fragmentation energies, second-order difference energies, highest occupied and lowest unoccupied molecular orbital energy gaps, and chemical hardness for both pure and doped clusters. The analytic results exhibit that clusters with even electronic configuration (2, 4, 6) possess weakest chemical reactivity and more enhanced stability.     

喷墨打印高精度图案研究进展

近年来, 功能材料的图案化及其在高性能光电器件的应用研究受到了广泛关注. 与传统图案化方法相比, 喷墨打印技术更容易实现大面积复杂图案的直接书写和复合功能材料的图案化, 且制备简便, 成本低廉, 使其成为最受关注的图案化方法之一. 综述了近年来喷墨打印制备高精度图案的研究进展. 包括通过优化墨滴的化学组成、调控基材的化学或物理结构以及改进喷墨设备等方法以提高喷墨打印分辨率; 以及通过控制液滴内部的毛细流动和三相接触线的移动抑制喷墨液滴的“咖啡环”效应, 以实现均质打印. 文章最后展望了喷墨打印制备高精度图案的研究发展方向. 这些工作对于实现高性能器件的制备具有重要意义.     

固体NMR在玻璃微结构研究中的应用

核磁共振(NMR)是探测物质微结构的有力手段,本文简要介绍了固体NMR技术在玻璃微结构研究中的应用,尤其是近年来的新进展,包括硅酸盐玻璃、硼酸盐玻璃、磷酸盐玻璃以及含铝的氧化物玻璃等玻璃体系。     

（2R,3S）—2甲基—3—羟基戊酸甲酯的手性合成

１引言烟草甲ＬａｊｓｔｏｄｅｒｍａｓｅｒｒｉｃｏｒｎｅＦａｂｒ。ｉｎｓ是一种主要危害烟草、香烟、干燥植物以及谷物、面粉的农业害虫。这种害虫在我国主要分布在淮河以南地区以及世界各地的温暖地带［‘］。（２,３Ｓ）－２一甲基一３一羟基成酸甲酯是我们设计的合成烟草甲性信息素的一个重要中间体。我们以丙快醇为基本原料合成了该化合物。丙炔醇参照文献ｌ’］方法制得２一戊炔一ｌ一醇２,催化还原条件下,炔键可被部分加氢得到（Ｑ－２一戊烯一卜醇３。在四异丙氧基钛、Ｄ－（）一酒石酸＄［Ｊ４Ａ分于筛催化条件下,顺式烯丙醇…     

芽胞杆菌全细胞热裂解气相色谱聚类分析

通过热裂解气相色谱对１４ 个芽胞杆菌模式菌株全细胞进行分析, 确定芽胞杆菌不同属间特征性谱峰;利用ＳＴＡＴＩＳＴＩＣＡ 系统对热裂解气相色谱图中３０ 个主要谱峰进行聚类分析, 绘制出的树状谱清楚地表明各菌株间的亲缘关系。     

Thermal stresses in box-type laser packages

The effect of Au coating on thermally induced stresses in box-type semiconductor laser packages was investigated by a finite-element method (FEM). The simulated results showed that Invar–Invar joints with Au coating have maximum stresses two times higher than joints without Au coating. This is due to the different coefficients of the thermal expansion (CTE) between dissimilar materials of Invar and Au, resulting in higher stresses. Maximum stresses were also found to be increased as the Au thickness increased. This effect is attributed to the increase in the thermal gradient in the welded region provided by the increased thermal conduction of the thicker Au coating layer. These results suggest that both the difference in CTE between dissimilar materials and higher thermal conduction of Au coating layer have an important impact on thermally induced stresses for optoelectronic packages having laser-welded Au coated materials.     

Two-mode excited entangled coherent states and their entanglement properties

This paper introduces two types of two-mode excited entangled coherent states (TMEECSs) |Ψ_±(α,m,n)>, studies their entanglement characteristics, and investigates the influence of photon excitations on quantum entanglement. It shows that for the state |Ψ₊(α,m,m)> the two-mode photon excitations affect seriously entanglement character while the state |Ψ_-(α,m,m)> is always a maximally entangled state, and shows how such states can be produced by using cavity quantum electrodynamics and quantum measurements. It finds that the entanglement amount of the TMEECSs is larger than that of the single-mode excited entangled coherent states with the same photon excitation number.     

Chaotic flexural oscillations of a spinning nanoresonator

The paper investigates the chaotic flexural oscillations of the spinning nanoresonator. The influence of cubic nonlinearity arising from the van der Waals interactions between two neighboring layers of carbon nanotubes on the structural oscillations of the system is considered. The integral–differential equations describing the flexural displacements of the nanoresonator are discretized into two coupled Duffing-type equations using the Galerkin–Ritz procedures. The linear stiffness can be either positive or negative, depending on the amplitudes of the linear trap rigidity arising from both the van der Waals interactions and the axial tensile loads. The chaotic flexural oscillations of the appropriately excited spinning nanoresonator are predicted theoretically. Using the Nayfeh–Mook multiscale perturbation algorithms, the coupled Duffing-type equations with linear positive stiffness may be transformed into autonomous equations of slowly modulated amplitudes whose equilibrium points and chaotic dynamics are investigated numerically. The potential chaotic oscillations of the elastic nanoresonator can be determined by the Melnikov–Holmes–Marsden (MHM) integral associated with the homoclinic/heteroclinic solutions of the disturbed Hamiltonian systems with linear negative stiffness. The findings are validated through the Poincare sections and Lyapunov exponents.     

Reflection and Transmission of Elastic Waves at the Interface Between Water and a Double Porosity Solid

The reflection and transmission of an incident plane wave at an interface between water and a fluid-saturated double porosity solid are investigated. The properties of the three compressional waves and one shear wave in double porosity media are discussed in detail. The effect of the viscosity, permeability, and porosity on the phase velocity and attenuation of four bulk waves is presented. Comparison between the double porosity theory and the Biot theory reveals that there exists obvious difference in the phase velocity, attenuation and the reflection and transmission coefficients. Two cases of boundary conditions, i.e., the sealed-pore and the open-pore boundaries, are introduced in the numerical calculation. At last, the effect of the fracture permeability and porosity on the reflection and transmission coefficients considered. It is revealed that the amplitudes of the reflected and transmitted waves strongly depend the boundary condition, fracture permeability, and porosity.