The physicomechanical and thermal properties of Algerian Aleppo pine (Pinus halepensis) wood as a component of sandwich panels

Research ArticleAleppo pine (Pinus halepensis Mill.) is the main forest species of Algeria occupying more than 35% of the total forest area of the country. However, the physicomechanical and thermal characteristics of Algerian P. halepensis wood are not well-known. This research investigates the physical (moisture, density, swelling, and shrinkage), mechanical (bending strength and modulus of elasticity), and thermal (mass loss under combustion and pyrolysis as well as thermal conductivity) properties of P. halepensis wood from the Darguina (Bejaia) forest in Algeria. The results showed that Algerian P. halepensis wood with a mean density of 540 kg m-3 has good dimensional stability in swelling and shrinkage, with 116.43 MPa bending strength and a modulus of elasticity of 17,520 MPa. The wood shows a good thermal resistance under low-temperature range and has a thermal conductivity of 0.21 W m-1 K-1. The overall results indicate that Algerian P. halepensis wood may be commercially exploited for construction and insulation applications, namely in the production of sandwich compositesinfo:eu-repo/semantics/publishedVersio

Air Pollution from Diesel Particles and Chronic Obstruction Pulmonary Disease - CT Scan Study

Health problems have been observed in rabbits at low DEP concentration. The subject (animal) showed signs of chronic obstruction pulmonary disease (COPD). CT scan of the biopsy reveals significant emphysematous lesions. DEP grain causes inflammation of lung tissues around sites of deposition. Observations of tissue after formalin fixation reveal brown spots around the points of impact. It also reveals the double organic and inorganic aspect of DEPs. The organic compounds dissolve through slow diffusion in the lung physiological fluid while the inorganic part is partly handled by macrophages (phagocytosis)

Local thermal non-equilibrium effects in the Horton-Rogers-Lapwood problem with a free surface

The onset of thermoconvective instability in a modified Horton-Rogers-Lapwood problem is here investigated. Since the local thermal non equilibrium model is employed, two temperatures, one for the solid phase and one for the fluid phase, are considered. The porous layer is saturated by a Newtonian fluid and the lower plate is impermeable. A horizontal free surface is assumed as top boundary. The free surface is subject to a uniform pressure condition and a third kind boundary condition rules the heat transfer with the external environment. The lower boundary is subject to a uniform heat flux modelled by means of Model A proposed by Amiri et\ua0al. [1]. The linear stability of the basic state is investigated by means of normal modes method. An eigenvalue problem characterised by ordinary differential equations is obtained. This eigenvalue problem is governed by a number of parameters. This feature gives the chance of investigating different limiting cases. Some of these cases are solved analytically. These analytical solutions are employed as benchmark and as guess values for the numerical solver employed to solve the general case: a fourth order Runge-Kutta method coupled with the shooting method. The critical values of the stability parameter for the onset of convective instability are obtained for a number of cases

Forward chaining and change operators

En conjonction avec l'International Logic Programming Symposium (ILPS-97)International audienc

The fatigue flexural behavior of fiber reinforced concrete : effect of the parameters of coarse aggregates

The effect of the coarse aggregate type on the fatigue flexural behavior of concrete was investigated in this work. Three types of the coarse aggregates were selected from three different careers (CA1, CA2 and CA3). The mechanical parameters of these aggregates were determined (Los Anglos and Micro Deval). Prismatic specimens (70×70×280 mm) for each concrete mixture were made with aggregates of each source. The flexural fatigue tests were conducted on these concrete samples with varying levels of loading of 55 to 80% and the ultimate flexural strength. The test frequency is around 80 Hz and it is automatically determined by pulsing the fatigue machine for a resonance situation (the phase shift is δ=0) between the mass-spring-specimen system. The obtained results show that the aggregates which have the similar parameters (Micro Deval and LA), provide better adhesion with cement paste, and therefore a greater bending strength. The strength evolution at short-term age is typical for specimens based on aggregates with low wear resistance by triturate (a high Micro Deval coefficient). Regarding the fatigue flexural behavior, the concrete specimens based on CA1, which have similar coefficients of Los Angeles and Micro Deval (respectively 18 and 16) present the behavior (load/cycle numbers) close to that of the model prototype of the Wöhler curve. This can be explained by a high homogeneity of the charge distribution during fatigue test compared to other concrete mixtures. Also, it was noted that the relationship between the endurance limit and the coefficient of Los Angeles is inversely proportional: The aggregates which have good strength to fragmentation (low coefficient of LA), as aggregates CA2 case give an endurance limit at around 70% max bending loa

Solvothermal Synthesis and Electrochemical Characterization of Nanocrystalline ZnO

International audienc

The quantitative/qualitative watershed for rules of uncertain inference

We chart the ways in which closure properties of consequence relations for uncertain inference take on different forms according to whether the relations are generated in a quantitative or a qualitative manner. Among the main themes are: the identification of watershed conditions between probabilistically and qualitatively sound rules; failsafe and classicality transforms of qualitatively sound rules; non-Horn conditions satisfied by probabilistic consequence; representation and completeness problems; and threshold-sensitive conditions such as `preface' and `lottery' rules