Morphology of critical nuclei in solid-state phase transformations

Predicting the shape of a critical nucleus in solids has been a long-standing problem in solid-state phase transformations. We show that a diffuse-interface approach together with a minimax algorithm is able to predict the critical nucleus morphology in elastically anisotropic solids without a priori assumptions. We demonstrate the possibility of nonconvex surfaces for critical nuclei. It is found that strong elastic energy contributions may lead to critical nuclei whose point group symmetry is below the crystalline symmetries of both the new and the parent phases.     

Investigation of proton-proton short-range correlations via the 12C(e,e'pp) reaction

We investigated simultaneously the 12C(e,e'p) and 12C(e,e'pp) reactions at Q2=2 (GeV/c)2, xB=1.2, and in an (e, e'p) missing-momentum range from 300 to 600 MeV/c. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For (9.5+/-2)% of the 12C(e,e'p) events, a recoiling partner proton was observed back-to-back to the 12C(e,e'p) missing-momentum vector, an experimental signature of correlations.     

Sonochemical synthesis of polyaniline nanofibers

Conventionally, micro-sized irregular polyaniline (PANI) particles were synthesized by dropwise addition of the ammonium persulfate (APS) solution into the aniline (ANI) solution with mechanical stirring. By replacing the mechanical stirring with an ultrasonic irradiation, PANI nanofibers in diameters of approximately 50 nm and lengths of 200 nm to several micrometers were prepared. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that at the early stage of polymerization, the polymers formed in both the mechanical stirred and ultrasonicated systems are in the form of nanofiber. However, with continuing of the reaction, these primary nanofibers grow and agglomerate into irregular shaped PANI particles in the mechanical stirred system, while in the case of the ultrasonic irradiation, the growth and agglomeration are effectively prevented, preserving thus the PANI nanofibers in the final product. By increasing the APS/ANI molar ratio from 0.5 to 2.5, the aspect ratios of the PANI nanofibers decreased. The PANI nanofibers exhibit higher solubility than the irregular shaped PANI particles. Although the yield, as well as the conductivity of the ultrasonic synthesized PANI nanofibers, was slightly lower than the irregular shaped PANI particles, the ultrasonic synthesis approach is one of the facile and scalable approaches in synthesizing PANI nanofibers in comparison with other ones without use of templates (e.g., the interfacial polymerization and rapid mixing polymerization). UV-Vis and Fourier transformed infrared (FTIR) spectra indicated ultrasound had no significant effect on the chemical structure of the PANI.     

Global classical solutions to the compressible micropolar viscous fluids with large oscillations and vacuum

In this paper, we consider the three dimensional Cauchy problem of the compressible micropolar viscous flows. We prove the existence of unique global classical solution for smooth initial data with small initial energy but possibly large oscillations and the initial density may allowed to contain the interior and far field vacuum states. Furthermore, the large time behavior of the solution is obtained as well.     

Controlling the Trajectory of Swallowtail Gaussian Beams in Dynamic Parabolic Potentials

The propagation dynamics of finite-energy Swallowtail beams in a dynamic parabolic potential, including uniformly moving, accelerating, and oscillating potentials, are investigated. The strong influence of dynamic potentials on the propagation trajectory of Swallowtail beams is demonstrated and various effective manipulations of the beams, including trajectory control, are validated. The intensity and the focal position can also be affected. In addition, the extension to 2D scenarios is also presented. The results theoretically provide more diverse manipulation possibilities for Swallowtail beams, and thus may broaden their potential applications in trajectory and particle manipulation.     

双参考光全息—散斑干涉术的原理和实验

本文用统计光学方法对双参考光全息——散斑干涉术进行了详尽的理论分析,给出了全息和散斑干涉场区域平均光强分布与光学系统主要参数及三维变形场各分量之间关系的解析表达式,进而讨论了离面位移和面内位移测量的上、下限,最后还给出了有关的实验结果。     

一维快速拉伸下无氧铜的动态断裂与破碎

利用电磁膨胀环技术对无氧铜环进行了不同加载电压下的动态拉伸实验。对无氧铜在破碎前出现塑性失稳多重颈缩进行了初步分析,利用能量平衡的破碎理论给出了无氧铜环的破碎分布。三维数值模拟结果表明,颈缩区温升比非颈缩区高,且多重颈缩在环周上的分布服从泊松分布。     

非线性粘弹性拟静态问题与非线性弹性静力问题对应原理

本文应用多重单边拉氏变换导出了非线性粘弹性拟静态问题与非线性弹性静力问题的对应关系,从而把过去认为只有线性条件下存在的粘弹性——弹性对应原理拓展到了非线性范畴     

不同压实度下红层泥岩路堤沉降研究

压实系数是控制路堤填筑的关键性指标。本文通过分析不同压实系数下的强度特点以及通过离心试验和有限元对不同压实系数路堤沉降的模拟,得到粘聚力c值和摩擦角φ与不同压实系数的关系以及不同压实系数下路堤沉降的特点,为路堤填筑提供了重要的依据。     

床面固体颗粒圆柱绕流的试验现象观察

本文介绍了床面固体颗粒随水流绕过圆柱体时，将在圆柱周围的床面上形成一个无粒子运动区的试验现象。水槽试验结果表明，当固体颗粒的粒径减小时，无粒子区的范围将增大；无粒子区的范围随圆柱直径的增大而增大；水流条件的变化直接影响着床面固体颗粒的运动情况，同无粒子区的形成、消失及范围大小有密切的关系。根据试验资料，结合量纲分析，建立了无粒子区的无量纲经验关系式