Performance analysis of a planted roof as a passive cooling technique in hot-humid tropics

Planted roofs are passive cooling techniques that reduce the thermal load of buildings. In this paper, the authors have developed a model for evaluating the cooling potential of green roofs. Transfer equations are solved using a finite difference scheme and Thomas algorithm. The study was conducted taking into account the Togolese climate conditions. The effect of Leaf Area Index (LAI) and Biot (Bi) number on diurnal variation of the Solar Heat gain Factor (SHF) is presented and analysed. A correlation for the estimation of the Solar Heat gain Factor as a function of LAI and Bi has been established. The results presented in terms of evapotranspiration (ET) and Solar Heat gains Factor (SHF) show notably that the foliage density and hence the vegetable canopy type selection influence the thermal efficiency of the bioclimatic insulation screen greatly. It was found that a larger LAI reduces the solar flux penetration, stabilizes the fluctuating values, and reduces the indoor air temperature.     

Modelling and simulation of a wood solar dryer in a Moroccan climate

We present a numerical simulation of the functioning of a wood solar dryer in atmospheric conditions of Moroccan climate. A comparison of our numerical results with experimental measurements carried out on a wood solar dryer shows a good agreement. Results show that drying period is closely linked to glass partitions and timber thickness. The type of ventilation has no effect on the drying period (initial timber humidity lower than 40%). The substitution of east and west glass faces by concrete walls has practically no effect on drying period.     

Étude de l'évaporation par convection forcée au‐dessus de corps tournants à symétrie de révolution dans un fluide au repos

This paper presents a theoretical and experimental study of the vaporization over rotating bodies of revolution, which are subjected to a constant wall heat flux. The laminar boundary‐layer approach and the first stage of drying conditions are considered when writing the governing equations. Numerical results are presented for the disc and sphere geometries. The experimental procedure is based upon infrared thermography and pyrometry techniques which help to obtain some quantitative comparisons with the theoretical results for the case of the rotating disc.     

Improvement in DTC-SVM of AC drives using a new robust adaptive control algorithm

In this paper a new robust adaptive speed controller algorithm for AC motor drives is presented. The main feature of this algorithm is that minimum synthesis is required to implement the strategy. MCS algorithm is a significant development of MRAC. The stability of the proposed system is achieved through Popov’s Hyperstability criteria. The new algorithm appeared to be robust in the face of totally unknown plant dynamics, external disturbances and parameter variations with the plant. Finally, a new approach has been successfully implemented on DTC-SVM. Extensive simulation results are presented to validate the proposed technique. The system is tested at different speeds and a very satisfactory performance has been achieved.     

Improvement of photoelectrochemical and optical characteristics of MEH-PPV using titanium dioxide nanoparticles

The use of bulk heterojunctions can increase the efficiency of exciton dissociation in polymer-based photovoltaics. We prepared and characterized bulk heterojunctions of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and titanium dioxide nanoparticles deposited by spin coating on indium tin oxide substrates. The surface morphology of the MEH-PPV+TiO₂ composite films revealed that addition of TiO₂ nanoparticles increased the film roughness. The effect of TiO₂ nanoparticles on the photoelectrochemical and optical characteristics of MEH-PPV polymer heterojunctions was studied. Addition of TiO₂ nanoparticles improved the absorbance of MEH-PPV composite films. Moreover, the photocurrent of the composite devices increased with the TiO₂ nanoparticle concentration. These observations provide an insight into new approaches to improve the light collection efficiency in photoconductive polymers.     

Model based real time monitoring for collision detection of an industrial robot

This paper deals with a model based real-time virtual simulator of industrial robot in order to detect eventual external collision. The implemented method concerns a model based Fault Detection and Isolation used to determine any lock of motion from an actuated robot joint after contact with static obstacles. Online implementation has been done in order to validate the proposed approach.     

Service level agreement in optical networks

This article proposes a Service Level Agreement applied to the optical domain (O-sla), which is expected to be the near and long term network technology thanks, among other things, to the great bandwidth capacity offered by optical devices. After an exposition of the rationale behind an optical sla, parameters which could enter in thisO-sla, as well as their values for four classes of services, are proposed. Different client (wavelength or sub-wavelength) and services types (from leased wavelength to bandwidth on demand) are distinguished when necessary.     

Numerical Study of Boundary-Layer Transition in Flowing Film Evaporation on Horizontal Elliptical Cylinder

ABSTRACT

A numerical study of the onset of transverse and longitudinal transitions between turbulent and laminar regimes during the evaporation of a water film is presented. The water film streams, without interfacial shear stress, along a horizontal elliptical tube under the simultaneous effects of gravity, pressure gradients, and viscous forces. Outside the boundary layer, the vapor-phase velocity is obtained from potential flow. In the analysis, a turbulence model taking into account various pressure gradients is proposed, and the inertia and convection terms are retained. Transfer equations are discretized by using the implicit Keller method. The effects of different turbulence models and the main parameters, such as the initial liquid flow rate per unit of length, the Froude number, the temperature difference between the wall and the liquid–vapor interface, and the ellipticity, on the transition position are evaluated. The transition criterion is given in term of the critical film Reynolds number.