Search

A2/O is a common domestic sewage treatment process.The aeration method of aerobic section is usually the traditional bottom aeration, which has low oxygen dissolution efficiency. In order to achieve high quality and efficient treatment of sewage, a static spiral cutter without power drive was developed based on gas-liquid mass transfer enhancement and fluid mechanics theory. Large bubbles in gas-liquid mixture could be cut into micro-nanometer scale small bubbles, which can improve dissolved oxygen in a short time, and control gas flow to achieve the adjustment of dissolved oxygen. Experiments with no aeration, traditional bottom aeration, and static spiral cutting were carried out. The results showed that compared with the traditional bottom aeration process, with the static spiral cutting, the removal rate of solid suspended solids(SS) increased by 12.3%,the removal rate of COD by 5.6%, the removal rates of ammonia nitrogen (NH3-N) and total phosphorus (TP) were increased by 8.1% and 8.5% respectively, and the concentration of saturated dissolved oxygen (DO) was increased by 48.2%. Overall,static spiral cutter has advantages of simple structure and good economy, it has a promising application for the optimization of sewage treatment aeration.

In recent years, 2D materials have been widely used in optical and photonic applications such as mode lockers, optical switches, polarizers, and optical modulators. As is known, many 2D optical materials are parabolic semiconductors. The electronic states determines the material's optical characteristics. The energy band structure with a bandgap dominates the electron dynamics process associated with intrinsic light absorption. Particularly, the Dirac cone and flat band (FB) are special nonparabolic energy band structures in materials. Dirac materials are characterized by a zero bandgap, and FB materials have a completely flat dispersionless band in the Brillouin zone. These materials are used as emergent and promising 2D materials for saturable absorbers (SAs) due to their excellent nonlinear optical response, and they become potential candidates for ultrafast photonics applications. Herein, the focus is on the characteristics of the energy band structure; the carrier dynamics are reviewed, and application in ultrafast photonics are summarized. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile (PAN)‐based composite nanofibers incorporated with high‐percentage inexpensive pitch were successfully prepared by a simple electrospinning technique. Low‐softening‐point naphthalene pitch (NP) has the merit of high solubility but inevitably brings about preoxidation problem. Thus the influence of different preoxidation strategies on the morphology, composition, and structure of composite nanofibers was systematically investigated. The results show that there exists a ternary phase diagram consisting of PAN‐pitch‐solvent and a suitable apparent viscosity of homogeneous solution, which favors the smooth electrospinning and good adjustment for the diameter of carbon nanofibers (100–500 nm). The crystallinity, crystalline order, and electrical conduction of composite nanofibers are enhanced by incorporating graphitizable NP, for example, the electrical resistance of 50% NP‐PAN composite nanofiber films after 800°C carbonization decreases about 30%. Both increasing the oxidation temperature and extending the oxidation time are beneficial to the oxidative stabilization of composite nanofibers with a suitable NP percentage below 50%. Gradient heating (240–340°C) and pressurized (0.08 MPa) preoxidations could accelerate the oxidative stabilization of composite nanofibers with a high NP percentage up to 110% and significantly shorten the oxidation time by half. Therefore, this study paves the road for facile preparation of cost‐competitive carbon nanofibers with controllable morphology, structure, and properties. [ABSTRACT FROM AUTHOR]