Preparation,characterization and application of a novel thermal stable composite nanofiltration membrane

A thermal stable composite membrane was prepared by interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on poly(phthalazinone ether amide) (PPEA) ultrafiltration membrane. The effect of reaction parameters on the performance of composite membranes was studied and optimized. The surface morphologies of the composite membrane and the substrate were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The rejection of optimized composite membrane for dyes Congo red (CGR) and Acid chrome blue K (ACBK), the molecular weight (MW) of which is over 400, was over 99.2%, with a flux at about 180 L m⁻² h⁻¹. While the rejection for NaCl was only 18.2% with a flux over 270 L m⁻² h⁻¹, when tested at 1.0 MPa 60 °C. The composite membrane was applied in the desalination-purification experiment of dye ACBK and NaCl mixed solution. The flux of the membrane increased obviously as the operation pressure and/or temperature increased, while the rejection for dye was constant and kept over 99.3%. The purification experiments were accomplished effectively at 1.0 MPa, 80 °C. Only after five rounds of desalination-concentration experiment, about 160 min, the salt mixed in dye solution was fully removed. The initial flux of the eighth cycle was about 254 L m⁻² h⁻¹, which was only 20 L m⁻² h⁻¹ lower than that of the first round. The rejection of the membrane was constant and kept over 99.3% through out the eight cycles of purification experiment.     

One-step fabrication of uniform Si-core/CdSe-sheath nanocables

A simple one-step thermal evaporation of CdSe powder using Si substrate at controlled conditions results in ultrauniform Si-core/CdSe-sheath nanocables. These nanocables are approximately 80 nm in diameter and several tens of micrometers in length. Detailed microstructure and chemical composition analysis of the nanocables indicates that they are composed of a single crystalline Si (cubic) core and CdSe (hexagonal) sheath. The experimental evidence suggested that the Si nanowires can be directly grown from the Si substrate via an oxide-assisted growth mechanism and further served as templates for CdSe, resulting in nanocable heterostructures.     

Synthesis of single-crystal magnesium-doped spinel lithium manganate and its applications for lithium-ion batteries

Single-crystal magnesium-doped spinel lithium manganate cathode materials are prepared by the hydrothermal method followed by the heat treatment. XRD patterns reveal that Mg²⁺ions have already diffused into the Li_1.088Mn_1.912O₄ crystal structure and not affect the Fd3m space group. SEM images demonstrate that the magnesium-doped spinel lithium manganates show uniform polyhedral single crystals with 2–4 μm. Electrochemical performance demonstrates that the optimized composition of Li_1.088Mg_0.070Mn_1.842O₄ electrode exhibits the best electrochemical properties. It delivers 92.0 mAh g^?1 at 8C rates and corresponds to 90.8% capacity retention (vs. 1C), far higher than those of the pristine electrode (70.4 mAh g^?1 and 69.2%). In addition, the Li_1.088Mg_0.070Mn_1.842O₄ electrode also shows 95.5% capacity retention after 100 cycles at 1C, while the pristine electrode only shows 91.0% capacity retention. The excellent electrochemical performances of Li_1.088Mg_0.070Mn_1.842O₄ electrode are ascribed to the suppressed polarization, more stable crystal structure, and better kinetic characteristics.     

一维双极量子能量输运稳态模型弱解的存在性

在一维有界区域上研究一个半导体双极量子能量输运稳态模型.将此模型变形为由2个四阶椭圆方程和1个二阶退化椭圆方程组成的耦合方程组.利用截断方法和Leray-Schauder不动点定理证明了其变形后方程组弱解的存在性.     

Investigating the Turing Conditions for Diffusion-driven Instability in Predator-prey System with Hunting Cooperation Functional Response

In this paper, we focus on stability analysis of steady-state solutions of a predator-prey system with hunting cooperation functional response. The results show that the Turing instability can be affected not only the existence of hunting cooperation, but also the diffusion coefficients: (1) in the absence of predator diffusion, diffusion-driven instability can be induced by hunting cooperation, but no stable patterns appear; (2) the system can occur diffusion-driven instability and Turing patterns, when both predator and prey have diffusion, and the diffusion coefficient of prey is greater than that of the predator. The numerical simulations of two cases are presented to verify the validity of our theoretical results.