The electrolyte flow states of all vanadium redox flow battery (VRB) have a direct effect on the battery performance and life. To reveal the electrolyte distribution in the battery, the computation fluid dynamics (CFD) method was used to simulate a parallel flow field. A hydraulics experiment and a battery performance experiment were carried out to confirm the simulated results. The results show that the predicted information agreed well with the experimental results. The electrolyte has a concentrated distribution in the central region of the parallel flow field and the disturbed flow and then vortex flow areas mainly appear in the inlet and outlet regions. The higher flux of electrolyte is helpful to uniform the distributions and to reduce the impact of flow irregularity on the battery performance. The battery with the flow field generates a power density of 15.9 mW∙cm-2, and the coulombic, voltage and energy efficiency is up to 90.5%, 74.0% and 67.2% at a current density of 20 mA·cm-2.
The platelike Co3O4/carbon nanofiber (CNF) composite materials were synthesized by the calcination of β-Co(OH)2/CNF precursor prepared by a surfactant-free hydrothermal method. As negative electrode materials for lithium-ion batteries, the platelike Co3O4/CNF composites can deliver a high reversible capacity of 900 mAh g-1 for a life extending over hundreds of cycles at a current density of 100 mA g-1. The high Li-storage capacity and excellent cycling performance for Co3O4/CNF composite materials may mainly attribute to the beneficial effect of the CNFs addition on enhancing structural stability and electrical conductivity of Co3O4 platelets.
Polyimide membrane pervaporation was introduced to separate the costly diene mixtures of cyclopentadiene/methylcyclopentadiene (CPD/MCPD) from cracking C5 fractions. Four kinds of membrane solutions were prepared and two kinds of polyimide homogenous membranes were fabricated by thermal imidizations using the dianhydrides (BPADAand PMDA) and the diamines (ODA and DDS). The effect of the casting solutions viscosity on the membrane formation was revealed, and the formation of functional groups and the synthesis mechanisms of the thermal imidizations were indicated by FT-IR. The adsorption behaviors and the pervaporation performances were studies for BPADA-ODA and PMDA-ODA membranes. The results show that the permeation fluxes are 164g∙m-2∙h-1 and 4.2g∙m-2∙h-1 for BPADA-ODA and PMDA-ODA membranes respectively, while the separation factor are 1.93 and 8.9 for these two membranes respectively. 88.5 wt% concentration of MCPD was achieved in the circulated feed side ultimately.
The relative adsorption coefficient, a novel parameter was introduced to describe the dominant adsorption ability of ions in cation membrane for all vanadium redox flow battery instead of traditional selectivity coefficient. The parameter as a function of membrane property and vanadium ions in membrane was derived from the relative potential differences in membrane between an isothermal adsorption and an ideal equivalent adsorption. The adsorption isotherms of three kinds of commercial membranes were measured for VO2+/H+ electrolyte system. The results show the reasonable rules that the relative adsorption coefficients increase as the VO2+ contents are increased whereas decrease as the H+ contents are increased in electrolyte.
Ming association rules have been proved as an important method to detect intrusions. To improve response speed and detecting precision in the current intrusion detection system, this papers proposes an intrusion detection system model of MMFIID-DS. Firstly, to improve response speed of the system by greatly reducing search space, various pruning strategies are proposed to mine the maximal frequent itemsets on trained normal data set, abnormal data set and current data streams to establish normal and abnormal behavior pattern as well as user behavior pattern of the system. Besides, to improve detection precision of the system, misuse detection and anomaly detection techniques are combined. Both theoretical and experimental results indicate that the MMFIID-DS intrusion detection system is fairly sound in performance.
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