Self-Reinforced High-Density Polyethylene Prepared by Low Frequency Vibration-Assisted Injection Molding. II: Microstructure Investigation

Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) were employed to study the microstructure of self-reinforced high-density polyethylene (HDPE) prepared by conventional injection molding (CIM) and a low frequency vibration-assisted injection molding (VAIM). SEM micrographs following permanganic etching showed the self-reinforcement of HDPE is mainly due to the existence of shish-kebab morphology within the core region for VAIM-processed HDPE samples. Pronounced molecular alignment was identified by the WAXD data. An approximate 9% increase in the crystallinity was confirmed by DSC. Both preferred molecular orientation and increased crystallinity serve to yield stronger VAIM-processed injection moldings.     

Essential Work of Fracture Parameters of Injection-Molded Polypropylene/Polyolefin Elastomer Blends

The influence of polyolefin elastomer (POE) content on the fracture behavior of injection-molded polypropylene (PP)/POE blends was evaluated by means of the essential work of fracture (EWF) method. The results indicated that the EWF approach worked well for the PP/POE blends when POE content was 0～7.5 wt% of the blends. The specific essential work of fracture (w _e) increased with increasing POE content, and the dominant factor that affected w _e was the necking and subsequent fracture process. The specific nonessential work of fracture (βw _p) slightly decreased with increasing POE content, while the specific plastic work (w _p) showed an increasing trend with the decrease of the shape factor (β) of the specimen. Finally, it was shown that w _e could be predicted reasonably well via the COD values.     

Dynamic mechanical and morphological studies of homopolymer/block copolymer blends

A triblock copolymer of styrene-butadiene-styrene (SBS) was blended with a high and a low molecular weight polybutadiene [designated as PB(H) and PB(L), respectively]. Electron micrographs of these blends show that PB(L) was solubilized into the butadiene domains of the SBS, while PB(H) was present in a separate phase. Dynamic mechanical data of the SBS&PB(L) blends indicate the presence of an intermediate loss peak between those of the glass transitions of the styrene and butadiene blocks in SBS, which can be attributed to the slippage of untrapped entanglements of PB(L) chains. Similar data for blends containing PB(H) also show an intermediate loss peak, which is, however, due to crystallization and melting of the polycisbutadiene chains. The peak due to the primary glass transition of the butadiene phase was shifted to lower temperatures upon incorporation of PB(L) as a result of plasticization effect of PB(L). The same transition for PB(H) blends is split into a doublet because of the presence of the homopolymer in a separate phase. Dynamic mechanical data for cross-linked blends were also taken for comparison.     

ZnO nanowire array ultraviolet photodetectors with self-powered properties

A ZnO nanowire (NW) array ultraviolet photodetector (PD) with Pt Schottky contacts has been fabricated on a glass substrate. Under UV light illumination, this PD showed a high photo-to-dark current ratio of 892 at 30 V bias. Interestingly, it was also found that this PD had a high sensitivity of 475 without external bias. This phenomenon could be explained by the asymmetric Schottky barrier height (SBH) at the two ends causing different separation efficiency of photogenerated electron–hole pairs, which resulted in the formation of photocurrent. It is anticipated to have potential applications in self-powered UV detection field.     

广义流体动力学守恒方程组的弱解的存在性和唯一性问题

本文讨论了非定常广义流体动力学方程组在大尺度情况下平均流动参数所应满足的条件,提出了相应的假设,证明了大尺度平均流动参数弱解的存在性和唯一性。     

On the Volume of Unit Tangent Spheres in a Pinsler Manifold

Motivated by some issues which enter into the Gauss-Bonnet-Chern theorem in Finsler geometry, this paper studies the unit tangent sphere (or indicatrix) I_x M at each point x of a Pinsler manifold M. We demonstrate that the volume of I_mM, calculated with respect to a Riemannian metric induced naturally by the Finsler structure, is in general a function of x. This contrasts sharply with the situation in Riemannian geometry. We also express the derivative of such volume function in terms of the second curvature tensor of the Chern connection. In particular, we find that this function is constant on Landsberg spaces (though that constant need not be equal to the value taken by Riemannian manifolds).     

快速发光二极管的性能与分析

本文叙述了用于光通信快速、高辐射度GaAs/GaAlAs双异质结发光管的性能.其电带宽大于60MHz,光带宽在100MHz以上.在200mA辐射度为1017W/cm2·sr.尾纤输出超过160μw(NA=0.2).分析和讨论了影响辐射输出和调制能力的诸因素,并选取了最佳折衷方案.     

CaPtAs: A new noncentrosymmetric superconductor

We report the discovery of a new noncentrosymmetric superconductor CaPtAs.It crystallizes in a tetragonal structure(space group I41md,No.109),featuring three dimensional honeycomb networks of Pt-As and a much elongated c-axis(a=b=4.18?,and c=43.70?).The superconductivity of CaPtAs with Tc=1.47 K was characterized by means of electrical resistivity,specific heat,and ac magnetic susceptibility.The electronic specific heat Ce(T)/T shows evidence for a deviation from the behavior of a conventional BCS superconductor,and can be reasonably fitted by a p-wave model.The upper critical fieldμ0Hc2 of CaPtAs exhibits a moderate anisotropy,with an in-plane value of around 204 mT and an out-of-plane value of 148 mT.Density functional theory calculations indicate that the Pt-5 d and As-4 p orbitals mainly contribute to the density of states near the Fermi level,showing that the Pt-As honeycomb networks may significantly influence the superconducting properties.     

质子治疗装置动态电源控制系统研发

针对质子治疗装置中主环动态电源多平台能量的引出需求,研制了基于开源平台的高速实时动态电源控制系统,该控制系统以开源平台Beaglebone作为顶层硬件接口,以现场可编程逻辑门阵列（FPGA）为核心的控制器作为底层硬件接口,采用分布式的实验物理及工业控制系统（EPICS）进行远程控制。该系统可实时传输任意动态电源的输出参考电流波形数据,并结合定时系统与联锁系统,控制动态电源按预设电流波形进行输出,并实现多平台能量的引出。实验结果显示该控制系统能实现每秒最高十万条指令传输,百万次数据传输零误码率。同时,该系统结构灵活、扩展性强,可作为通用控制平台。