Flying with the right principles at hand: An interactive lab to understand the physical origin of lift

A set of simple laboratory experiments aimed to understand the physical origin of lift is presented. The experiments are realized with simple materials and the use of multimedia reference sources (movies, computer simulations, flow visualizations) is extensively applied in order to put forward otherwise complex fluid dynamical concepts. Emphasis is put in the individuation and correction of commonly found misconceptions or wrong principles regarding, in particular, the concept of pressure, the role of viscosity, the flow behavior around an airfoil, the domain of applicability of fluid dynamical principles, the role of flow curvature in attaining lift and the dynamical mechanisms at the basis of flight

Esquistos bituminosos como materia prima alternative en la fabricación de clínker de cemento Portland. Reacciones de clinkerización y caracterización del clínker

For some time the cement industry has been seeking procedures to effectively lower the higher energy costs involved in cement manufacture. Timahdit oil shale and Jerada coal waste could potentially be used as alternative raw materials to produce clinker. This study explored the possibility of applying those materials to a greener use, based on the reactivity and burnability of raw mixes containing Moroccan oil shale and coal waste. The findings showed that, irrespective of particle size, oil shale mixes delivered higher reactivity than coal waste materials, although reactivity was highest in the oil shale clinker with a particle size 70 %).La industria cementerabusca desde hace algún tiempo procedimientos que reduzcan el alto consumo de energía de la producción de cemento. La pizarra bituminosa de Timahdit (BOS) y los desechos de carbón de Jerada (CW) se pueden utilizar potencialmente como materiales alternativos en la fabricación de clinker. Este estudio se enfoca en evaluar esta posibilidad, valorizar dichos materiales y considerar un uso más ecológico para ellos. Exploramos la reactividad y la aptitud a la cocción de mezclas crudas de clínker que contienen BOS o CW. La reactividad de los crudos que contienen BOS es mejor que la de los que contienen CW, independientemente de su tamaño de partícula, siendo el que contiene BOS con un tamaño de partícula 70%

Local-field correction to one- and two-atom van der Waals interactions

Based on macroscopic quantum electrodynamics in linearly and causally responding media, we study the local-field corrected van der Waals potentials and forces for unpolarized ground-state atoms placed within a magnetoelectric medium of arbitrary size and shape. We start from general expressions for the van der Waals potentials in terms of the (classical) Green tensor of the electromagnetic field and the atomic polarizability and incorporate the local-field correction by means of the real-cavity model. In this context, special emphasis is given to the decomposition of the Green tensor into a medium part multiplied by a global local-field correction factor and, in the single-atom case, a part that only depends on the cavity characteristics. The result is used to derive general formulas for the local-field corrected van der Waals potentials and forces. As an application, we calculate the van der Waals potential between two ground-state atoms placed within magnetoelectric bulk material.Comment: 9 pages, 2 figures, corrections according to erratu

Simple Applications of q-Bosons

A deformation of the harmonic oscillator algebra associated with the Morse potential and the SU(2) algebra is derived using the quantum analogue of the anharmonic oscillator. We use the quantum oscillator algebra or $q$-boson algebra which is a generalisation of the Heisenberg-Weyl algebra obtained by introducing a deformation parameter $q$. Further, we present a new algebraic realization of the $q$-bosons, for the case of $q$ being a root of unity, which corresponds to a periodic structure described by a finite-dimensional representation. We show that this structure represents the symmetry of a linear lattice with periodic boundary conditions.Comment: LATEX2e, 10 pages, v2: few misprints corrected, added Journal-re

Fermi resonance-algebraic model for molecular vibrational spectra

A Fermi resonance-algebraic model is proposed for molecular vibrations, where a U(2) algebra is used for describing the vibrations of each bond, and Fermi resonances between stretching and bending modes are taken into account. The model for a bent molecule XY_2 and a molecule XY_3 is successfully applied to fit the recently observed vibrational spectrum of the water molecule and arsine (AsH_3), respectively, and results are compared with those of other models. Calculations show that algebraic approaches can be used as an effective method for describing molecular vibrations with small standard deviations

Templeting of Thin Films Induced by Dewetting on Patterned Surfaces

The instability, dynamics and morphological transitions of patterns in thin liquid films on periodic striped surfaces (consisting of alternating less and more wettable stripes) are investigated based on 3-D nonlinear simulations that account for the inter-site hydrodynamic and surface-energetic interactions. The film breakup is suppressed on some potentially destabilizing nonwettable sites when their spacing is below a characteristic lengthscale of the instability, the upper bound for which is close to the spinodal lengthscale. The thin film pattern replicates the substrate surface energy pattern closely only when, (a) the periodicity of substrate pattern matches closely with the characteristic lengthscale, and (b) the stripe-width is within a range bounded by a lower critical length, below which no heterogeneous rupture occurs, and an upper transition length above which complex morphological features bearing little resemblance to the substrate pattern are formed.Comment: 5 pages TeX (REVTeX 4), other comments: submitted to Phys. Rev.Let