Particle simulation of vibrated gas-fluidized beds of cohesive fine powders

We use three-dimensional particle dynamics simulations, coupled with volume-averaged gas phase hydrodynamics, to study vertically vibrated gas-fluidized beds of fine, cohesive powders. The volume-averaged interstitial gas flow is restricted to be one-dimensional (1D). This simplified model captures the spontaneous development of 1D traveling waves, which corresponds to bubble formation in real fluidized beds. We use this model to probe the manner in which vibration and gas flow combine to influence the dynamics of cohesive particles. We find that as the gas flow rate increases, cyclic pressure pulsation produced by vibration becomes more and more significant than direct impact, and in a fully fluidized bed this pulsation is virtually the only relevant mechanism. We demonstrate that vibration assists fluidization by creating large tensile stresses during transient periods, which helps break up the cohesive assembly into agglomerates.Comment: to appear in I&EC Research, a special issue (Oct. 2006) in honor of Prof. William B. Russe

Non-equilibrium Transport in the Anderson model of a biased Quantum Dot: Scattering Bethe Ansatz Phenomenology

We derive the transport properties of a quantum dot subject to a source-drain bias voltage at zero temperature and magnetic field. Using the Scattering Bethe Anstaz, a generalization of the traditional Thermodynamic Bethe Ansatz to open systems out of equilibrium, we derive exact results for the quantum dot occupation out of equilibrium and, by introducing phenomenological spin- and charge-fluctuation distribution functions in the computation of the current, obtain the differential conductance for large U/\Gamma. The Hamiltonian to describe the quantum dot system is the Anderson impurity Hamiltonian and the current and dot occupation as a function of voltage are obtained numerically. We also vary the gate voltage and study the transition from the mixed valence to the Kondo regime in the presence of a non-equilibrium current. We conclude with the difficulty we encounter in this model and possible way to solve them without resorting to a phenomenological method.Comment: 20 pages, 20 figures, published versio

Susceptibility of a spinon Fermi surface coupled to a U(1) gauge field

We study the theory of a U(1) gauge field coupled to a spinon Fermi surface. Recently this model has been proposed as a possible description of the organic compound $\kappa-(BEDT-TTF)_2 Cu_2 (CN)_3$. We calculate the susceptibility of this system and in particular examine the effect of pairing of the underlying spin liquid. We show that this proposed theory is consistent with the observed susceptibility measurements.Comment: 5 pages, 4 figure

Type IIP supernova light curves affected by the acceleration of red supergiant winds

We introduce the first synthetic light-curve model set of Type IIP supernovae exploded within circumstellar media in which the acceleration of the red supergiant winds is taken into account. Because wind acceleration makes the wind velocities near the progenitors low, the density of the immediate vicinity of the red supergiant supernova progenitors can be higher than that extrapolated by using a constant terminal wind velocity. Therefore, even if the mass-loss rate of the progenitor is relatively low, it can have a dense circumstellar medium at the immediate stellar vicinity and the early light curves of Type IIP supernovae are significantly affected by it. We adopt a simple beta velocity law to formulate the wind acceleration. We provide bolometric and multicolor light curves of Type IIP supernovae exploding within such accelerated winds from the combinations of three progenitors, 12 - 16 Msun; five beta, 1-5; seven mass-loss rates, 1e-5 - 1e-2 Msun/yr; and four explosion energies, 0.5e51 - 2e51 erg. All the light curve models are available at https://goo.gl/o5phYb. When the circumstellar density is sufficiently high, our models do not show a classical shock breakout as a consequence of the interaction with the dense and optically-thick circumstellar media. Instead, they show a delayed 'wind breakout', substantially affecting early light curves of Type IIP supernovae. We find that the mass-loss rates of the progenitors need to be 1e-3 - 1e-2 Msun/yr to explain typical rise times of 5 - 10 days in Type IIP supernovae assuming a dense circumstellar radius of 1e15 cm.Comment: 12 pages, 9 figures, 2 tables, accepted by Monthly Notices of the Royal Astronomical Societ

A Supersymmetric U(1)' Model with Multiple Dark Matters

We consider a scenario where a supersymmetric model has multiple dark matter particles. Adding a U(1)' gauge symmetry is a well-motivated extension of the Minimal Supersymmetric Standard Model (MSSM). It can cure the problems of the MSSM such as the mu-problem or the proton decay problem with high-dimensional lepton number and baryon number violating operators which R-parity allows. An extra parity (U-parity) may arise as a residual discrete symmetry after U(1)' gauge symmetry is spontaneously broken. The Lightest U-parity Particle (LUP) is stable under the new parity becoming a new dark matter candidate. Up to three massive particles can be stable in the presence of the R-parity and the U-parity. We numerically illustrate that multiple stable particles in our model can satisfy both constraints from the relic density and the direct detection, thus providing a specific scenario where a supersymmetric model has well-motivated multiple dark matters consistent with experimental constraints. The scenario provides new possibilities in the present and upcoming dark matter searches in the direct detection and collider experiments.Comment: 25 pages, 5 figure

Editorial.

Welcome to the third issue of our journal . We are delighted to feature in this issue two peer-reviewed papers looking in detail at some of the outcomes of the ring-fenced money used for researcher development in the UK under the guise of Roberts funding. In her paper looking at impact of the training provided by this funding on late stage doctoral student researchers, Walsh and colleagues draw our attention to detailed analysis of impact via a variety of evaluation approaches. She also alerts us to the question of whether such development programmes should run alongside the traditional apprenticeship style training of such students. The second paper by Heading and colleagues provides a detailed example of a development programme event in information management and provides further evidence for impact of such training. Bai and Hudson move the focus to the research –teaching nexus and highlight the difficulty for TEFL staff in Chinese HEIs to develop a research strand in their careers. The importance in developing research capacity, providing support and mentoring to such staff is shown to be pivotal in their development. Finally conceptions of research from a variety of viewpoints are analyzed by Pitcher. Pitcher considers how the PhD itself, alongwith how the knowledge and outcomes of PhD research are perceived. In a preliminary survey of students on these matters, Pitcher highlights the importance of alignment with these concepts between student and supervisor thus avoiding difficulties between apprentice and supervisor as the research progresses which might inhibit development