Mining the Relation between Sentiment Expression and Target Using Dependency of Words

PACLIC 20 / Wuhan, China / 1-3 November, 200

Electronic structure and bonding properties of cobalt oxide in the spinel structure

The spinel cobalt oxide Co3O4 is a magnetic semiconductor containing cobalt ions in Co2+ and Co3+ oxidation states. We have studied the electronic, magnetic and bonding properties of Co3O4 using density functional theory (DFT) at the Generalized Gradient Approximation (GGA), GGA+U, and PBE0 hybrid functional levels. The GGA correctly predicts Co3O4 to be a semiconductor, but severely underestimates the band gap. The GGA+U band gap (1.96 eV) agrees well with the available experimental value (~ 1.6 eV), whereas the band gap obtained using the PBE0 hybrid functional (3.42 eV) is strongly overestimated. All the employed exchange-correlation functionals predict 3 unpaired d electrons on the Co2+ ions, in agreement with crystal field theory, but the values of the magnetic moments given by GGA+U and PBE0 are in closer agreement with the experiment than the GGA value, indicating a better description of the cobalt localized d states. Bonding properties are studied by means of Maximally Localized Wannier Functions (MLWFs). We find d-type MLWFs on the cobalt ions, as well as Wannier functions with the character of sp3d bonds between cobalt and oxygen ions. Such hybridized bonding states indicate the presence of a small covalent component in the primarily ionic bonding mechanism of this compound.Comment: 24 pages, 8 figure

Versatile Cold Atom Source for Multi-Species Experiments

We present a dual-species oven and Zeeman slower setup capable of producing slow, high-flux atomic beams for loading magneto-optical traps. Our compact and versatile system is based on electronic switching between different magnetic field profiles and is applicable to a wide range of multi-species experiments. We give details of the vacuum setup, coils and simple electronic circuitry. In addition, we demonstrate the performance of our system by optimized, sequential loading of magneto-optical traps of lithium-6 and cesium-133.Comment: 7 pages, 10 figure

The TREC2001 video track: information retrieval on digital video information

The development of techniques to support content-based access to archives of digital video information has recently started to receive much attention from the research community. During 2001, the annual TREC activity, which has been benchmarking the performance of information retrieval techniques on a range of media for 10 years, included a ”track“ or activity which allowed investigation into approaches to support searching through a video library. This paper is not intended to provide a comprehensive picture of the different approaches taken by the TREC2001 video track participants but instead we give an overview of the TREC video search task and a thumbnail sketch of the approaches taken by different groups. The reason for writing this paper is to highlight the message from the TREC video track that there are now a variety of approaches available for searching and browsing through digital video archives, that these approaches do work, are scalable to larger archives and can yield useful retrieval performance for users. This has important implications in making digital libraries of video information attainable

Factors affecting particle collection by electro-osmosis in microfluidic systems

Alternating-current electro-osmosis, a phenomenon of fluid transport due to the interaction between an electrical double layer and a tangential electric field, has been used both for inducing fluid movement and for the concentration of particles suspended in the fluid. This offers many advantages over other phenomena used to trap particles, such as placing particles at an electrode centre rather than an edge; benefits of scale, where electrodes hundreds of micrometers across can trap particles from the molecules to cells at the same rate; and a trapping volume limited by the vortex height, a phenomenon thus far unstudied. In this paper, the collection of particles due to alternating-current electro-osmosis driven collection is examined for a range of particle concentrations, inter-electrode gap widths, chamber heights and media viscosity and density. A model of collection behaviour is described where particle collection over time is governed by two processes, one driven by the vortices and the other by sedimentation, allowing the determination of the maximum height of vortex-driven collection, but also indicates how trapping is limited by high particle concentrations and fluid velocities. The results also indicate that viscosity, rather than density, is a significant governing factor in determining the trapping behaviour of particles

Multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering

A multilayer passive radiative selective cooling coating based on Al/SiO2/SiNx/SiO2/TiO2/SiO2 prepared by dc magnetron sputtering is presented. The design was first theoretically optimized using the optical constants, refractive index and extinction coefficient, of thin single layers. The spectral optical constants in the wavelength range from 0.3 to 27 µm were calculated from the transmittance and reflectance data of thin single layers deposited on silicon and glass substrates. The samples were characterized by Scanning Electron Microscopy, X-ray diffraction, Fourier-transform Infrared Spectroscopy and UV–VIS–NIR spectroscopy. It is shown that the TiO2 layer presents a partially rutile phase polycrystalline structure and a higher refractive index than amorphous SiO2 and SiNx layers in the spectral range from 0.3 to 2.5 μm. The cooling device was deposited on copper substrates and a thin low-density polyethylene foil with high transmittance in the 8 to 13 µm spectral range was used as convection cover material. The device is characterized by both low reflectance (high emittance) in the sky atmospheric window (wavelength range from 8 to 13 µm) and high hemispherical reflectance elsewhere, allowing for temperature drops of average 7.4 °C at night-time in winter, which corresponds to a net cooling power of ~43 W m−2. Further, a temperature drop of 2.5 °C was obtained during winter daytime.FCT in the framework of the Strategic Funding UID/FIS/04650/2013 and the financial support of FCT, POCI and PORL operational programs through the project POCI-01-0145-FEDER-016907 (PTDC/CTM-ENE/2892/2014), co-financed by European community fund FEDE

Dual-barrel conductance micropipet as a new approach to the study of ionic crystal dissolution kinetics

A new approach to the study of ionic crystal dissolution kinetics is described, based on the use of a dual-barrel theta conductance micropipet. The solution in the pipet is undersaturated with respect to the crystal of interest, and when the meniscus at the end of the micropipet makes contact with a selected region of the crystal surface, dissolution occurs causing the solution composition to change. This is observed, with better than 1 ms time resolution, as a change in the ion conductance current, measured across a potential bias between an electrode in each barrel of the pipet. Key attributes of this new technique are: (i) dissolution can be targeted at a single crystal surface; (ii) multiple measurements can be made quickly and easily by moving the pipet to a new location on the surface; (iii) materials with a wide range of kinetics and solubilities are open to study because the duration of dissolution is controlled by the meniscus contact time; (iv) fast kinetics are readily amenable to study because of the intrinsically high mass transport rates within tapered micropipets; (v) the experimental geometry is well-defined, permitting finite element method modeling to allow quantitative analysis of experimental data. Herein, we study the dissolution of NaCl as an example system, with dissolution induced for just a few milliseconds, and estimate a first-order heterogeneous rate constant of 7.5 (±2.5) × 10–5 cm s–1 (equivalent surface dissolution flux ca. 0.5 μmol cm–2 s–1 into a completely undersaturated solution). Ionic crystals form a huge class of materials whose dissolution properties are of considerable interest, and we thus anticipate that this new localized microscale surface approach will have considerable applicability in the future

Co-doping Strategy for Developing Perovskite Oxides as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

A synergistic co-doping strategy is proposed to identify a series of BaCo0.9–xFexSn0.1O3–δ perovskites with tunable electrocatalytic activity for the oxygen evolution reaction (OER). Simply through tailoring the relative concentrations of less OER-active tin and iron dopants, a cubic perovskite structure (BaCo0.7Fe0.2Sn0.1O3–δ) is stabilized, showing intrinsic OER activity >1 order of magnitude larger than IrO2 and a Tafel slope of 69 mV dec−1