Statistical Aspects of Tensile Fracture of Isotactic Polypropylene

The fracture behavior of isotactic polypropylene (iPP) specimen with double-notched shape under a fixed elongation speed at room temperature is described. Over 100 tensile tests were performed, and the statistic fracture data were obtained for the tensile condition. The statistical data of fracture were obtained by examining the time to fracture, the ultimate stress, and the tensile toughness (determined from the area under the nominal stress–strain curve from the origin to the fracture point). The probability density distributions for time to fracture, the ultimate stress, and the tensile toughness approximately followed the normal Gaussian statistics. Using a linear relationship between stress and elongation time near the fracture point, we can apply a static Kalman filter system to the present fracture data to determine a conditional probability density function. As a consequence, this application makes it possible to predict the probability of fracture of iPP under any static condition.     

Fast current-induced motion of a transverse domain wall induced by interfacial Dzyaloshinskii–Moriya interaction

Based on a theoretical study, we show that the interfacial Dzyaloshinskii–Moriya interaction results in very efficient current-induced manipulation of a transverse domain wall in magnetic nanowires. The efficient domain wall motion is caused by combined effects of the domain wall distortion induced by the interfacial Dzyaloshinskii–Moriya interaction and the damping-like spin–orbit spin transfer torque. We find that with reasonable parameters, the domain wall velocity reaches a few hundreds m/s at the current density of 10⁷ A/cm², which has never been achieved before. Our result will be beneficial for low-power operation of domain wall devices.     

Mechanical behaviour of MWCNTs reinforced electrospun nanofibres

Abstract

The nanoscale dimension of electrospun polymeric nanofibres produced by electrospinning are highly captivating, yet facing limitation of resisting external forces due to the weak tensile properties. Carbon nanotubes providing tremendous toughness due to extraordinary strong sp² bonding network of carbon atoms in honeycomb lattice structure, augmented the physical resistant strength and is easily recover to its original state after load is removed. This study reports the performance of multi-walled carbon nanotubes (MWCNTs) as filler in the electrospinning of poly (_L-lactide)-co-ε-caprolactone) (PLCL) composite nanofibres. Voltage of 10?kV is applied to the spinning solution mixture of 11?wt% (w/v) PLCL and MWCNTs, yielded nanofibres having diameters less than 400?nm. Results obtained showed the formation of composite nanofibres with tailored tensile behavior by modifying the content of MWCNTs. The addition of MWCNTs improved the tensile properties of resultant composite nanofibres, signified by tensile strength of 5.82 to 15.95?MPa, which were obtained using 0.1 to 1.0?wt% of MWCNTs. The structural integrity of nanofibres mats were retained in phosphate buffer saline (PBS) medium. Scanning Electron Microscopy (SEM) micrographs revealed the minimal of fiber deformation over 30?days of incubation and are closely identical to the initial diameter of as-spun fiber.     

均匀球扭矩德拜级数分析

基于会聚光束所产生的扭矩来实现对小粒子的操纵已在物理学、生物学等领域得到了广泛的应用。为了分离出单个散射过程对扭矩的贡献,给出扭矩物理机理的解释,本文引入德拜级数分析了高斯波束对均匀球粒子所产生的扭矩。计算表明,当德拜项P从1取到一个足够大的值后,德拜级数计算结果与广义米氏理论结果吻合。文中重点分析了单阶P散射过程对横向扭矩的贡献,结果表明：当线极化光束入射时,P=1～5散射过程都可以产生横向扭矩,但扭矩的方向不同;当圆极化光束入射时,P=一1和0对应的扭矩远大于P=1～4对应的扭矩,且P=0过程产生与其他P过程相反方向的扭矩。     

From microelectronics to spintronics and magnonics

In this review, the recent developments in microelectronics, spintronics, and magnonics have been summarized and compared. Firstly, the history of the spintronics has been briefly reviewed. Moreover, the recent development of magnonics such as magnon-mediated current drag effect (MCDE), magnon valve effect (MVE), magnon junction effect (MJE), magnon blocking effect (MBE), magnon-mediated nonlocal spin Hall magnetoresistance (MNSMR), magnon-transfer torque (MTT) effect, and magnon resonant tunneling (MRT) effect, magnon skin effect (MSE), etc., existing in magnon junctions or magnon heterojunctions, have been summarized and their potential applications in memory and logic devices, etc., are prospected, from which we can see a promising future for spintronics and magnonics beyond micro-electronics.     

由太阳引力矩引起的地-月系统角动量的变化

导出了地-月系统受到的太阳引力对其质心的引力矩,讨论了由引力矩引起的地-月系统角动量的变化,提出了对理论所预期的变化的观测验证方法。     

Spin-pumping-enhanced magnetic damping in ultrathin Cu(0 0 1)/Co/Cu and Cu(0 0 1)/Ni/Cu films

The influence of the Cu capping layer thickness on the spin pumping effect in ultrathin epitaxial Co and Ni films on Cu(0 0 1) was investigated by in situ ultrahigh vacuum ferromagnetic resonance. A pronounced increase in the linewidth is observed at the onset of spin pumping for capping layer thicknesses d_Cu larger than 5 ML, saturating at d_Cu = 20 ML for both systems. The spin mixing conductance for Co/Cu and Ni/Cu interfaces was evaluated.     

Interparticle force and torque on rigid spheroidal particles in acoustophoresis

The movement of the particles in acoustophoresis is driven by the acoustic radiation force acting on the particles. Particles with positive contrast factor tend to agglomerate once they are pushed by the primary force to the vicinity of the pressure node. The main driving force of this agglomeration is the interparticle force. In this study, the boundary element method is used to calculate the interparticle force and torque acting on a pair of spheroidal particles. The numerical results show that the interparticle force is dominant over the primary force when the spheroids are near the pressure nodal plane, similar to the case of two spheres. On contrary, the interparticle torque is insignificant compared to the primary torque, even when the spheroids are close to each other. The results also provide a preliminary study about how biological cells, which are mostly not spherical in shape, agglomerate and orient themselves in the vicinity of the pressure node.     

U形切口的有限断裂准则

有限断裂力学准则综合了应力和能量参数,假设裂纹或切口端部有限裂纹长度的增长．特别地,该有限裂纹的长度不是材料的基本常数,而是与构件的结构有关．基于U形切口两种形式：点方式和线方式有限断裂准则,对文献中的铝合金U形切口三点弯曲断裂实验进行了分析验证．一方面基于材料的断裂韧度和抗拉强度,预测切口件断裂载荷;另一方面根据几组不同的切口根部半径及其对应的临界切口应力强度因子,同时估算材料的断裂参数：断裂韧度和抗拉强度．将点方式和线方式两种不同形式有限断裂准则的预测结果,与平均周向应力准则、最大周向应力准则以及文献中相关结果进行了比较得出：无论是预测断裂载荷还是估算材料断裂参数,线方式有限断裂准则,与文献中相关结果比较吻合,尤其是估算的断裂韧度精度较高．     

薄膜异质结中磁性斯格明子的相关研究

磁性斯格明子由于具有拓扑保护、尺寸小、驱动电流密度低等优异的属性,有望作为未来超高密度磁存储和逻辑功能器件的信息载体.为了满足器件中信息写入和读取的基本要求,需要在室温下实现斯格明子的精确产生、操控和探测.该综述简要介绍最近我们针对上述问题取得的一系列研究进展,包括:1)证明可以通过控制磁性薄膜材料的垂直磁各向异性在室温下产生斯格明子,并进一步在基于反铁磁的薄膜异质结中发现了室温、零磁场下稳定存在的斯格明子;2)证明能够利用电流产生的自旋轨道力矩操控斯格明子,并进一步制备出一种基于斯格明子的原理型器件,实现了利用电学方式产生和操控数量可控的斯格明子.