ABSTRACT
In an increasingly connected global market, news sentiment towards one company may not only indicate its own market performance, but can also be associated with a broader movement on the sentiment and performance of other companies from the same or even different sectors. In this paper, we apply NLP techniques to understand news sentiment of 87 companies among the most reported on Reuters for a period of 7 years. We investigate the propagation of such sentiment in company networks and evaluate the associated market movements in terms of stock price and volatility. Our results suggest that, in certain sectors, strong media sentiment towards one company may indicate a significant change in media sentiment towards related companies measured as neighbours in a financial network constructed from news co-occurrence. Furthermore, there exists a weak but statistically significant association between strong media sentiment and abnormal market return as well as volatility. Such an association is more significant at the level of individual companies, but nevertheless remains visible at the level of sectors or groups of companies.
ABSTRACT
For an active electrode material, the morphology, microstructure and the effective specific surface area derived from them, have a dominant effect for the high performance supercapacitors. In this study, 3D interconnected activated carbons with controlled and optimized morphologies and porous structures were prepared from accessible carbon source and graphene oxide by a hydrothermal carbonization and following an activation method. Through optimizing the ratios of the precursors and reaction conditions, an electrode material with excellent specific surface area of 2318 m2 g-1, meso-/macro-pore ratio of 63.2% (meso-/macro-pore volume reached to 0.83 cm3 g-1), as well as an outstanding electrical conductivity of 46.6 S m-1, was obtained. The materials exhibit superior double-layer capacitive performances on a symmetric supercapacitor, delivering superior specific capacitance of 157 F g-1 in organic electrolyte system at current density of 0.5 A g-1, excellent energy density of 37.6 W h kg-1 with a power density of 7.1 kW kg-1 and good cycling stability of capacitance retention of 94% over 7000 cycles. These results offer a practical method to prepare the desired carbon electrode materials with controlled morphology and structure for high efficiency electrochemical energy storage devices.
ABSTRACT
High dispersibility and rapid electron transfer are required for a highly efficient catalyst. In this work, such materials have been designed using a scalable hydrothermal method from graphene oxide and a metal-organic framework. A cross-linked three-dimensional graphene (3DGraphene) material loaded with mono-dispersed nitrogen-doped carbon-coated metallic Co (NC@Co) nanoparticles with uniform size of 12.2 nm (3DGraphene/NC@Co) has been obtained and exhibits excellent activity for catalytic reduction of 4-nitrophenol to 4-aminophenol. Such high catalytic activity can be assigned to the highly energetic hot/free electrons arising from 3DGraphene under light illumination and the synergistic effect between 3DGraphene and NC@Co nanoparticles. The catalytic reaction can be finished in 240 s with NaBH4 as the reducing agent, and the corresponding rate constant (k) is 1.5 × 10-2 s-1, comparable to that of reported noble metal catalysts. Furthermore, the magnetic 3DGraphene/NC@Co materials are beneficial for the separation from the mixture after reaction and exhibit excellent cycling stability.
