Numerical simulation of a Trombe wall to predict the energy storage rate and time duration of room heating during the non-sunny periods

In this paper, 2D numerical simulation of the Trombe wall performance and indoor air environment under unsteady state condition for a room located in Yazd, Iran are studied. The governing equations involve mass, momentum and energy conservation, which are discretized by the finite volume method after non-dimensionalization. The SIMPLER algorithm is used for coupling the velocity and pressure. The average absorbed solar radiation on the Trombe wall has been defined for different hours of the coldest period of the year (21 January–19 February) in Yazd. All equations have been solved together using a FORTAN code. The main aim of this research is to investigate the time duration of room heating during the non-sunny periods. The stored energy of the wall being delivered to the inside room was defined for different materials of the Trombe wall. The results show that the Trombe wall made of paraffin wax can keep the room warmer in comparison with other materials for about 9 h.     

Dynamics of Isotropic Homogeneous Turbulence with Linear Forcing Using a Lattice Boltzmann Method

The Lattice Boltzmann Method (LBM) has proved to be a promising approach to solve the Navier–Stokes equations, especially for incompressible and isothermal cases. For turbulent flows, the quality of the predictions has been previously studied considering standard spectral forced (ten Cate et al., Comput Fluids 35:1239–1251, 2006) statistically homogeneous isotropic turbulence. In the present contribution, a recently proposed linear forcing scheme working in physical space (Lundgren 2003; Rosales and Meneveau, Phys Fluids 17(9):095106–1,8, 2005) has been integrated in a three-dimensional fifteen-velocity LBM formulation. Results have been analyzed, with special attention to the dynamics of the flow through the invariants of the velocity tensor. This topic had not been studied yet for the linear forcing, regardless of the nature (spectral or LBM) of the numerical method. Results fully agree with standard pseudo-spectral direct numerical simulations, results proving the validity of the LBM with linear forcing in real space to study this kind of turbulent flows.     

Effect of Rashba spin–orbit coupling on the spin polarized transport in diluted magnetic semiconductor barrier structures

We investigate theoretically the effects of Rashba spin–orbit coupling on the spin dependent transport through diluted magnetic semiconductor single and double barrier structures in the presence of a magnetic field. We find that the Rashba spin–orbit coupling gives rise to an enhancement of the negative tunnelling magnetoresistance of the diluted magnetic semiconductor single barrier structure and a pronounced beating pattern in the tunnelling magnetoresistance and spin polarization of the diluted magnetic semiconductor double barrier structure.     

Lattice dynamics of cubic SrZrO3

Using density functional perturbation theory, the optical dielectric constant, Born effective charges and phonon dispersion curves of cubic SrZrO₃ have been calculated. The obtained dispersion curves show a soft phonon branch spreading from R to M points of the cubic Brillouin zone. An analysis based on the symmetry relationships indicates that the experimentally observed low-symmetry phases of SrZrO₃ can be considered as results of the soft mode condensation at R and M points.     

Measurement of an aeroacoustic dipole using a linear microphone array

It is shown that the standard beamformer technique is inadequate for both the source location and the measurement of a simple dipole and that this is due to the assumption of monopole propagation in the calculation of the phase weights used to steer the focus of the array. A numerical simulation is used to illustrate the problem and to develop a correction to the signal processing algorithm to account for the dipole propagation characteristic. This is then applied to array measurements for an aeroacoustic dipole produced by a cylinder in a cross flow. The resulting source map and the beamformed spectrum are shown to give a true representation of the source energy and frequency content. A secondary effect of this correction is that the array becomes insensitive to other source types so that in addition to acting as a spatial filter, the array can perform as a source filter. This work also demonstrates how an array measurement can be misinterpreted if applied without consideration of the source mechanism.     

A Simple, Rapid and Reagentless Turbidimetric Method for Determination of Light Stabilizer Tinuvin 622 in Polyethylene

This study presents an inexpensive and reagentless turbidimetric technique for the determination of Tinuvin 622 in polyethylene matrix. Tinuvin is dissolved in acetone, and water is added to it. The solubility of the analyte is reduced in the water/acetone mixture and it precipitates in the form of small particles. Different parameters affecting the analysis were studied, and it was found that in a 50:50 mixture of water and acetone high turbidity was obtained. Turbidity increases to 30min and remains constant for at least 1h. Stirring speed and ionic strength are no effective factors in this method. The linear dynamic range is relatively large (10–250mgL^–1) with a limit of detection of 3mgL^–1. The repeatability of the method is good, and the relative standard deviation for six repeated experiments performed on solutions containing 100mgL^–1 is 1.5%. To analyze real samples (polyethylene polymer), the matter is dissolved in hot xylenes, and methanol is added while the solution is being stirred. The precipitated polymer is filtered and the solution evaporated into the rotary. The remaining solids are dissolved in acetone and analyzed as standards. The obtained results were compared with those obtained by gas chromatography (after saponification) and no significant differences were observed.     

Bis-[3]Ferrocenophanes with Central >E−E’< Bonds (E,E’=P,SiH): Preparation,Properties, and Thermal Activation

A series of bis-[3]ferrocenophanes of the general type Fe(C₅H₄E’)₂E−E(E'C₅H₄)₂Fe (E=P, SiH and E’=PtBu, NneoPentyl, NSi(CH₃)₃) with an isolobal molecular framework have been prepared and characterized by heteronuclear NMR spectroscopy and X-ray crystallography. The thermal dissociation behavior with respect to homolytic fission of the central bond generating phosphorus centered radicals was investigated using EPR spectroscopy and quantum chemical calculations.