Abdelillah Hakam

Solar drying of pine lumber: Verification of a mathematical model

This work presents verification of a mathematical model for drying of a wood stack in a greenhouse type solar dryer. A simplified heat and mass transfer numerical model has been developed with input parameters based on the actual metrological data of a Moroccan climate. For its validation, a comparative study is performed in this work; the present model is solved to simulate the solar drying of pine wood using experimental data of previous wood drying experiments. The average relative discrepancies between the model predicted and experimental data are 1,2% for wood moisture content, 1% for drying air temperature and 5% for the air relative humidity. The close agreement between the predicted and experimental results shows the ability of the model to reproduce experimental drying data for wood.

Searching for material symmetries in the burr wood of Thuja by a direct contact ultrasonic method on spherical samples

This work is part of a program that aims at studying the burr wood of thuja (Tetraclinis articulata). The goal of this work is to identify material symmetries of burr wood to improve its machining. To have a sufficient number of data and to limit the variability between samples, an ultrasonic experimental device, in direct contact on spherical samples, has been developed and improved. Until now, the geometry used in direct contact ultrasonic methods was either cubic or polyhedral allowing to obtain, on the same sample, 3 (cube) to 13 (polyhedron) measurements or usable data. By choosing a reasonable angular gap, the spherical geometry allows the ultrasonic velocity to be measured in 133 different directions on the same specimen. We present here the adaptation and development of the ultrasonic experimental device and results obtained on (i) aluminum chosen as a reference material, (ii) beech wood and (iii) burr wood of thuja.

Effects of deposition rate on the optical and electrical properties of reactively evaporated thin films of indium oxide.

Summary Thin films of indium oxide were prepared by thermal reactive evaporation of a mixture of indium oxide and metallic indium followed by thermal treatment in a vacuum chamber containing a low pressure of oxygen just after deposition. This investigation optimizes the deposition rate to obtain high electrical conductivity and a good optical transparency. The films prepared with an optimum deposition rate Ve = 2 A.s −1 are nearly stoichiometric and have a good cristallinity. These films showed a transmittance of more than 80% in the visible region and a conductivity >10 3 (Ω.cm) −1 .

Effects of annealing on the structural, electrical and optical properties of reactively evaporated thin fdlms of indium oxide

Abstract Thin films of indium oxide were prepared by thermal reactive evaporation of a mixture of indium oxide and metallic indium. This work is an experimental study of the modifications induced by an annealing treatment, on the structural, electrical and optical properties of indium oxide (In 2 O 3 ). The results show important changes of different parameters determined after annealing. The films obtained after annealing at 350 °C for 3 hours under oxygen atmosphere have a good cristallinity. These films showed a transmittance of more than 80% in the visible region and a conductivity >10 3 (Ω.cm) −1 .

Wood-cement inhibition revisited and development of new wood-cement inhibitory and compatibility indices based on twelve wood species

Abstract A new approach is presented in terms of the analysis of wood-cement (WC) compatibility, which is based on a similarity coefficient (CS) that reflects the degree of resemblance between the curves of the “WC hydration temperature vs. time (24 h)” based on 15 g WC mixture and that of neat cement (C). This approach classifies clearly the compatibilities of different wood species on a scale of 0–100%, on which the most incompatible species have CS-values <5% and the upper compatibility class CS data around 95%, which is close to that of C, and which cannot be exceeded. The CS-value is well suited for modelling the inhibitory behaviour of all woods. In the discussion, the CS-approach is compared with other inhibitory indices proposed in the literature.

Study of structural and electrical properties of germanium-doped indium oxide ceramics

Abstract This work is an experimental study of the effects of germanium doping on the structural and electrical properties of indium oxide ceramics. The samples were prepared using the solid state reaction between appropriate mixtures of indium oxide (In 2 O 3 ) and germanium oxide (GeO 2 ). The chemical nature of the compounds was investigated by X-ray diffraction. Electrical measurements showed that the electrical conductivity increases appreciably with the addition of germanium. Varying the composition of the ceramics allows to show that an increase by a factor of about 1.5 of the conductivity of germanium- doped indium oxide ceramics can be obtained.