Anti-chiral edge states in an exciton polariton strip

We present a scheme to obtain anti-chiral edge states in an exciton-polariton honeycomb lattice with strip geometry, where the modes corresponding to both edges propagate in the same direction. Under resonant pumping the effect of a polariton condensate with nonzero velocity in one linear polarization is predicted to tilt the dispersion of polaritons in the other, which results in an energy shift between two Dirac cones and the otherwise flat edge states become tilted. Our simulations show that due to the spatial separation from the bulk modes the edge modes are robust against disorder.Comment: 6 pages, 5 figure

Characterisation of pressure-concentration-temperature profiles for metal hydride hydrogen storage alloys with model development

Metal hydride (MH) alloys have been applied to hydrogen storage and various energy conversion systems such as refrigeration, heat pump and heat transformer. However, to facilitate and efficiently investigate efficiently a particular application, an MH alloy must firstly be characterised with a purposely built test facility to measure profiles of pressure, MH hydrogen concentration and temperature (PCT). Obtaining detailed PCT profiles or curves could be an arduous and expensive task as each isothermal hydrogen absorption or desorption line requires hundreds of measurement points. It is thus desirable to develop an accurate correlative model for the PCT profiles with limited measurements of thermophysical property data for the purpose of characterisation of each MH alloy. This correlative model or characterisation process has been developed and is described in detail in this article. The correlative PCT MH alloy profiles can cover all applicable hydrogen storage phase regions of α, α + β and β as well as the phase transition dome curve and critical point such that a PCT phase diagram for a particular MH alloy can be depicted and characterised. As an application example, the correlative model is applied to predict an MH alloy's hydrogen storage capacity and hysteresis at a specific MH temperature. It has been discovered that each of these two parameters shows comparative trends in variation with reduced temperature. Correspondingly, for each parameter, a correlative function with reduced temperature has been produced. The MH alloy characterisation process is an essential step towards a detailed dynamic MH energy system modelling, simulation and optimisation as well as experimental investigation

Authorship Attribution Using a Neural Network Language Model

In practice, training language models for individual authors is often expensive because of limited data resources. In such cases, Neural Network Language Models (NNLMs), generally outperform the traditional non-parametric N-gram models. Here we investigate the performance of a feed-forward NNLM on an authorship attribution problem, with moderate author set size and relatively limited data. We also consider how the text topics impact performance. Compared with a well-constructed N-gram baseline method with Kneser-Ney smoothing, the proposed method achieves nearly 2:5% reduction in perplexity and increases author classification accuracy by 3:43% on average, given as few as 5 test sentences. The performance is very competitive with the state of the art in terms of accuracy and demand on test data. The source code, preprocessed datasets, a detailed description of the methodology and results are available at https://github.com/zge/authorship-attribution.Comment: Proceedings of the 30th AAAI Conference on Artificial Intelligence (AAAI'16

Density Dependence of Transport Coefficients from Holographic Hydrodynamics

We study the transport coefficients of Quark-Gluon-Plasma in finite temperature and finite baryon density. We use AdS/QCD of charged AdS black hole background with bulk-filling branes identifying the U(1) charge as the baryon number. We calculate the diffusion constant, the shear viscosity and the thermal conductivity to plot their density and temperature dependences. Hydrodynamic relations between those are shown to hold exactly. The diffusion constant and the shear viscosity are decreasing as a function of density for fixed total energy. For fixed temperature, the fluid becomes less diffusible and more viscous for larger baryon density.Comment: LaTeX, 1+33 pages, 6 figures, references adde

Performance analysis of a metal hydride refrigeration system

The varying applications of metal hydride refrigeration systems, such as cold storage and space air conditioning, grant them important advantages over conventional ones. These advantages include being a low-grade heat driven, more environmentally friendly and renewable working fluid with greater compactness and fewer moving parts. However, a metal hydride refrigeration system always operates under unsteady conditions due to the cyclic hydriding and dehydriding processes involved. To analyse and optimise the metal hydride refrigeration system’s design and performance, in this paper, a comprehensive transient system model has been developed with a new and revised intrinsic kinetic correlation inclusive of the essential operating controls and applicable process conditions of regeneration, cooling and transitions in between. In addition, the correlative model on the characterisation process of pressure, concentration and temperature (PCT) profiles for the metal hydride alloys employed in the system has been developed and is introduced briefly in this paper. It is integrated in the system model and ensures the accurate prediction of maximum capacities for the metal hydride isothermal desorption and absorption processes. The developed transient system model has been validated through comparison with experimental results from literature on the medium-temperature cooling process of a metal hydride refrigeration system. The model simulation is conducted for a specially designed low-temperature metal hydride refrigeration system at different operating conditions and controls. In quantity, when the high-grade heat source temperature increases from 90 ◦C to 120 ◦C, the low-grade heat source temperature increases from − 20 ◦C to 10 ◦C, the medium-grade heat sink temperature decreases from 30 ◦C to 15 ◦C, and the time period for regeneration or cooling process decreases from 10 min to 4 min, the cooling COP increases by 112.0%, 136.6%, 19.3% and 31.8% respectively. The optimisation strategies for the system operating conditions and controls are therefore recommended based on the detailed performance analyses of the system simulation results

The Design for a Nanoscale Single-Photon Spin Splitter

We propose using the effective spin-orbit interaction of light in Bragg-modulated cylindrical waveguides for the effcient separation of spin-up and spin-down photons emitted by a single photon emitter. Due to the spin and directional dependence of photonic stopbands in the waveguides, spin-up (down) photon propagation in the negative (positive) direction along the waveguide axis is blocked while the same photon freely propagates in the opposite direction.Comment: 5 pages, 3 figure