A new method for characterizing the interphase regions of carbon nanotube composites

The elastic properties of a carbon nanotube (CNT) reinforced composite are affected by many factors such as the CNT–matrix interphase. As such, mechanical analysis without sufficient consideration of these factors can give rise to incorrect predictions. Using single-walled carbon nanotube (SWCNT) reinforced Polyvinylchloride (PVC) as an example, this paper presents a new technique to characterize interphase regions. The representative volume element (RVE) of the SWCNT–PVC system is modeled as an assemblage of three phases, the equivalent solid fiber (ESF) mimicking the SWCNT under the van der Waals (vdW) forces, the dense interphase PVC of appropriate thickness and density, and the bulk PVC matrix. Two methods are proposed to extract the elastic properties of the ESF from the atomistic RVE and the CNT-cluster. Using atomistic simulations, the thickness and the average density of interphase matrix are determined and the elastic properties of amorphous interphase matrix are characterized as a function of density. The method is examined in a continuum-based three-phase model developed with the aid of molecular mechanics (MM) and the finite element (FE) method. The predictions of the continuum-based model show a good agreement with the atomistic results verifies that the interphase properties of amorphous matrix in CNT-composites could be approximated as a function of density. The results show that ignoring either the vdW interaction region or the interphase matrix layer can bring about misleading results, and that the effect of internal walls of multi-walled carbon nanotubes (MWCNTs) on the density and thickness of the dense interphase is negligible.     

Boundedness of Singular Integrals in Journé’s Class on Weighted Multiparameter Hardy Spaces

In this paper, we obtain the boundedness of singular integral operators T in Journé’s class on weighted multiparameter Hardy spaces \(H^{p}_{w}\) of arbitrary k number of parameters (k≥3) under the assumption that \(T^{\ast}_{i}(1)=0\) , i=1,…,k, and the kernel of T has a regularity of order ?>0, where \(w \in A_{r}(\Bbb{R}^{n_{1}}\times \cdots \times \Bbb{R}^{n_{k}}), r \geq 1\) and \(\max\{ \frac{r n_{1} }{n_{1}+\varepsilon}, \ldots, \frac{r n_{k} }{n_{k}+\varepsilon}\} .     

The Perspective and Challenge of Nanomaterials in Oil and Gas Wastewater Treatment

Oil and gas wastewater refers to the waste stream produced in special production activities such as drilling and fracturing. This kind of wastewater has the following characteristics: high salinity, high chromaticity, toxic and harmful substances, poor biodegradability, and a difficulty to treat. Interestingly, nanomaterials show great potential in water treatment technology because of their small size, large surface area, and high surface energy. When nanotechnology is combined with membrane treatment materials, nanofiber membranes with a controllable pore size and high porosity can be prepared, which provides more possibilities for oil–water separation. In this review, the important applications of nanomaterials in wastewater treatment, including membrane separation technology and photocatalysis technology, are summarized. Membrane separation technology is mainly manifested in ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). It also focuses on the application of semiconductor photocatalysis technology induced by TiO₂ in the degradation of oil and gas wastewater. Finally, the development trends of nanomaterials in oil and gas wastewater treatment are prospected.     

二极管泵浦高能激光研究进展和展望

高能激光广泛应用于材料加工、科学研究、空间碎片清除、军事应用等领域。二极管泵浦高能激光具有结构紧凑,系统简单、全电驱无限弹仓的特点,近年来,各类二极管泵浦高能激光围绕着同时实现高功率、高效率、高光束质量这一总目标发展迅速。详细综述了国内外高平均功率块状固体激光、高功率可见光波段激光、高峰值功率激光、高功率光纤激光、碱金属蒸气激光等二极管泵浦高能激光的研究进展,并对其发展趋势进行了展望。     

Infrared spectroscopy of goethite dehydroxylation. II. Effect of aluminium substitution on the behaviour of hydroxyl units

Dehydroxylation of goethite as affected by aluminium substitution was investigated using Fourier transform infrared spectroscopy (FT-IR) in conjunction with X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA). The band intensities of hydroxyl vibrations were indicative of the degree of dehydroxylation and the changes in band parameters due to aluminium substitution were observed. The effect of aluminium substitution on band parameters of FT-IR spectra of goethite and its partially and fully dehydroxylated products, the mixture of goethite/hematite and hematite, were interpreted. The results of this study have confirmed that aluminium substituted goethite is thermally more stable than non-substituted goethite and is in harmony with the results of XRD and DTGA. A larger amount of non-stoichiometric hydroxyl units is associated with a higher aluminium substitution. A shift to a higher wavenumber of bending and hydroxyl stretching vibrations is attributed to the effects of aluminium substitution associated with non-stoichiometric hydroxyl units on the a-b plane relative to the b-c plane of goethite. The results provide information for the characterisation of activated bauxite containing hematite and goethite.     

Relativistic Heavy-Ion Collider (RHIC) physics overview

The results from data taken during the last several years at the Relativistic Heavy-Ion Collider (RHIC) will be reviewed in the paper. Several selected topics that further our understanding of constituent quark scaling, jet quenching and color screening effect of heavy quarkonia in the hot dense medium will be presented. Detector upgrades will further probe the properties of Quark Gluon Plasma. Future measurements with upgraded detectors will be presented. The discovery perspectives from future measurements will also be discussed.     

A new hopane triterpenoid from Saxiglossum angustissimum

A new hopane triterpenoid, hopane 22, 29-diol-29-formate （1）, has been isolated from the whole herbs of Saxiglossum angustissimum （Cries.） Ching and its structure has been successfully determined on the basis of spectroscopic evidences.     

在同步辐射装置中配置电流扭摆器的建议

提出了第三代同步辐射光源中的低温超导电流扭摆器和室温水冷电流扭摆器的物理设计方案。文中还讨论了电流扭摆器内腔中的磁场的分布特性，测量方法和电流扭摆器的制造技术的可行性。     

光纤小位移传感器实验

本文介绍了光纤小位移测量原理，并利用微机作了光纤小位移传感器的标定和校验。     

Stability of some nonlinear systems with delay including populations systems

We establish sufficient conditions for asymptotical stability of some nonlinear systems with delay which include populations systems by using Lyapunov functional. Furthermore, we get the results of global stability of these systems when the delays are less than the critical values.