N2第二正带系发射光谱的理论计算及实验研究

本文利用分子光谱理论系统的计算和分析N₂第二正带系(C³∏_u→B³∏_g)的发射光谱, 以研究光谱强度的分布规律与不同温度条件和气体条件的关系. 基于N₂的三重态能级结构特性, 重点计算和讨论了发射光谱的概个重要参数: 通过求解高、低电子态的哈密顿矩阵得到了振转能级特性; 利用r质心近似法求取了能级间跃迁的电偶极矩函数和爱因斯坦跃迁概率; 进而计算了不同振动和转动温度条件下谱线的强度分布. 进行了N₂和Ar的混合放电实验, 利用实验光谱数据同理论结果进行拟合分析, 确定了N₂分子的振动温度和转动温度分别约为4300 K和800 K. 另外由于潘宁离化效应, N₂浓度减小时谱线强度呈现先增强后减弱的趋势. 实验结果很好的验证了N₂第二正带系光谱理论计算的正确性.     

水翼表面粗糙带对空化抑制效果的数值研究

为研究水翼表面粗糙带对空化的抑制效果,在修改的NACA16翼型吸力面施加一粗糙带,对在不同粗糙带条件下翼型的水动力学特性和周围流场进行了数值模拟研究,得到了升阻力系数、吸力面最小压力系数和近壁面湍动能随粗糙带变化的趋势,探讨了水翼表面粗糙带对抑制表面空化的效果。结果表明,随着粗糙带宽度和高度的增大,翼型周围流场的压强显著升高并使吸力面的最低压力高于饱和蒸汽压,从而延缓了初生空化的发生。该结果为认识粗糙带对水翼抗空蚀性能的影响提供了参考。     

Critical temperature oscillations and reentrant superconductivity due to the FFLO like state in F/S/F trilayers

Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers, in which the establishing of a Fulde‐Ferrell Larkin‐Ovchinnikov (FFLO) like state leads to interference effects of the superconducting pairing wave function, form the core of the superconducting spin valve. The realization of strong critical temperature oscillations in such trilayers, as a function of the ferromagnetic layer thicknesses or, even more efficient, reentrant superconductivity, are the key condition to obtain a large spin valve effect, i.e. a large shift in the critical temperature. Both phenomena have been realized experimentally in the Cu₄₁Ni₅₉/Nb/Cu₄₁Ni₅₉ trilayers investigated in the present work.     

Kinetic study of BH3 reduction of benzaldehydes: identification of effective reducing species

A kinetic study was carried out for the reaction of benzaldehyde and borane (BH₃) in tetrahydrofuran. The effect of BH₃ concentration on the rate constant showed that the reaction order with respect to BH₃ was 1.6. Substituent effects gave a linear Hammett plot with a ρ value of ?0.51. It was concluded that the reaction proceeds through a rate‐determining hydride‐transfer transition state with two BH₃ molecules, in which one molecule of BH₃ acts as a reducing agent and the other serves as a catalyst. Copyright © 2011 John Wiley & Sons, Ltd.     

Study on the Range of Particles Size Measured by Backscattering Method in Visual‐infrared Incident Spectrum

For the measurement of particles size with backscattering method, the suitable range of particles size measurement have been presented by independent algorithm in Visual‐infrared incident spectrum. We defined the range according to the retrieved results based on the analysis and comparison to many kinds of R‐R distribution function. The simulation computation results showed that the particles size measurement range is from 0.05 μm to 18 μm with incident spectrum from 0.4 μm to 2 μm and different refractive index. The results retrieved were satisfied even if 1 % noise was added into the backscattering intensity.     

Influence of polymer dielectric surface energy on thin‐film transistor performance of solution‐processed triethylsilylethynyl anthradithiophene (TES‐ADT)

This study investigates the correlation between surface energy of polymer dielectrics and the film morphology, microstructure, and thin‐film transistor performance of solution‐processed 5,11‐bis(triethylsilylethynyl) anthradithiophene (TES‐ADT) films. The low surface energy polyimide (PI) dielectric induced large grains with strong X‐ray reflections for spin‐cast TES‐ADT films in comparison to high surface en‐ ergy poly(4‐vinyl phenol) (PVP) dielectric. Furthermore, thin‐film transistors based on spin‐cast TES‐ADT films on PI dielectric exhibited enhanced electrical performance, small hysteresis, and high stability under bias stress with carrier mobility as high as 0.43 cm²/Vs and a current on/off ratio of 10⁷. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stability of symmetry breaking states in finite-size Dicke model with photon leakage

We investigate the finite-size Dicke model with photon leakage. It is shown that the symmetry breaking states, which are characterized by non-vanishing $〈\stackrel{?}{a}〉\ne 0$ and correspond to the ground states in the superradiant phase in the thermodynamic limit, are stable, while the eigenstates of the isolated finite-size Dicke Hamiltonian conserve parity symmetry. We introduce and analyze an effective master equation that describes the dynamics of a pair of the symmetry breaking states that are the degenerate lowest energy eigenstates in the superradiant region with photon leakage. It becomes clear that photon leakage is essential to stabilize the symmetry breaking states and to realize the superradiant phase without the thermodynamic limit. Our theoretical analysis provides an alternative interpretation using the finite-size model to explain results from cold atomic experiments showing superradiance with the symmetry breaking in an optical cavity.     

Pressure‐induced phase transitions in palmitic acid: C form

In this article, we report a high‐pressure Raman spectroscopy study of palmitic acid (PA, C form) from ambient pressure up to 21 GPa. The effects of hydrostatic pressure on the vibrational spectrum of PA are reported, and the data show that PA experiences a rich sequence of phase transformations. These changes in the crystal structure occur gradually as the pressure increases and they are related to the highly flexible crystalline structure. Copyright © 2011 John Wiley & Sons, Ltd.