Molecular Dynamics Simulations of Li Insertion in a Nanocrystalline V 2 O 5 Thin Film Cathode
The behavior of lithium ion diffusion from an electrolyte into a polycrystalline layered cathode has been studied using molecular dynamics computer simulations. Lithium silicate glass was the model solid electrolyte whilethe cathode was a nanocrystalline vanadia with amorphous V 2 O 5 intergranular films (IGF) between the crystals. Nanosized V 2 O 5 crystals were aligned with their (001) planes parallel to electrolyte/cathode interface, rotated 90° from each other around this interface's normal in order to present two different orientations between the crystal planes for lithium intercalation via the amorphous vanadia IGF. A series of nanocrystalline vanadia cathodes with different IGF thicknesses was simulated to examine the effects of the IGF thickness on lithium transport into the cathodes. Results showed preferential diffusion of Li from the electrolyte into the amorphous vanadia IGF, with some of those Li diffusing into the crystalline V 2 O 5 from the IGF. Results also showed easier lithium diffusion from the IGF into the V 2 O 5 crystal along the (010) direction than along the (100) direction. Additionally, an optimum IGF thickness of 2.5-3.0 nm is suggested as being neither too thick to decrease the capacity of the cathode nor too thin to impede the transport of lithium from glassy electrolyte into the cathode.
High-Specific-Capacitance Supercapacitor Based on Vanadium Oxide Nanoribbon
A variety of storage technologies for transmission grid and electric vehicle applications has been gaining importance in the last few years. The supercapacitor is one of the most viable energy storage devices. In this paper, a high-specific-capacitance supercapacitor with vanadium oxide nanoribbon electrode was fabricated. Vanadium oxide nanoribbon was synthesized by a facile and effective hydrothermal treatment with controlling the condensation speeds of precursors in the solution along the 〈010〉, 〈010〉, and 〈010〉 directions. The synthesis involved dissolution of V2O5 into H2O2, and investigation of the precursor weight ratio and the hydrothermal time. The product was characterized by using scanning electron microscopy, transmission electron microscope and X-ray. The electrochemical properties of the material as the electrode of electrochemical capacitor were evaluated by cyclic voltammetry in a three electrode system consisting of a saturated calomel electrode as reference electrode, platinum as a counter electrode and the active material as the working electrode. As far as we know, it is for the first time to report the fabrication of vanadium oxide nanoribbon by using the hydrothermal method. The prepared nanoribbon structure possesses relative short width and significant length. The narrow nanoribbon with ultra-length optimizes the ion diffusion path thereby enhancing the specific capacitance. A high capacitance of 453 F/g was obtained at the scan rate of 2 mV/s in 2 M NaCl electrolyte, and it still maintained a high capacitance of 201 F/g at a higher scan rate of 50 mV/s. And the nanoribbon exhibits faster ion propagation and better conductivity than the nanotube as revealed by the immediate current response to the potentials added on the electrode. The electrochemical performances of the vanadium oxide were found to strongly depend on the nanostructures and electrolytes.
Automatic classification of TV news articles based on telop character recognition
The purpose of this study is to develop a multimedia database system for TV news video data. TV news video data consist of speech, characters and images. In this study, telop characters are recognized and given to the news articles as indices for classification. At first, telop frames which include telop characters are detected and then the telop characters are extracted and recognized. Through morphological analysis of the recognized telop characters, keywords are extracted which consist of more than two characters. Their keywords are used as indices to classify the TV news articles. We carried out experiments for 30 days of NHK 5 minutes news and obtained 95.4% telop character extraction rate, 81.4% character recognition rate and 83.8% article classification rate. We improved the article classification rate by 43.4% through character recognition improvement from 44.1% to 81.4%.