The Generalized Theory of Thermo-Magnetoelectroelasticity

The governing equations for thermo-magnetoelectroelasticity are given for the heat-flux-dependent theory of Lebon. First, we establish a reciprocal relation using a new method of proof, which involves two thermoelastic processes at different instants. We show that this relation can be used to obtain reciprocity, uniqueness and continuous dependence theorems. The reciprocal theorem avoids both the use of the Laplace transform and the incorporation of initial conditions into the equations of motion. The uniqueness theorem is derived avoiding both the use of the definiteness assumption on the thermoelastic coefficients and the restriction that the conductivity tensor is positive definite. There are also no restrictions on the piezoelectric moduli, piezomagnetic moduli, and the thermal coupling coefficients other than symmetry conditions. We prove also that the reciprocal relation leads to a continuous dependence theorem studied on external body loads and heat supply, which ensures that the mathematical model for the generalized problem is well posed

Generalizations of Maysel’s Formula to Micropolar Thermoviscoelasticity with non-small Temperature Changes

Generalizations of Maysel’s formula to micropolar thermoviscoelasticity are given. The coupled term in generalized thermoelasticity formulation is modified with non-small temperature changes, where the absolute temperature is not replaced by the temperature of the body in its undeformed state, and is expressed as a linear function of time. The term including ((d/ds)¯ ui,i) in the Laplace transform domain is treated with an approximate method. The new reciprocity theorem and fundamental solutions of the linear micropolar thermoviscoelasticity with non-small temperature changes in the Laplace transform domain are also derived. To illustrate Maysel’s method, a mixed boundary value problem is considered as an example

Structural and Mechanical Properties of TaZrN Films: Experimental and ab initio Studies

This paper reports on the growth and characterization of the structural and mechanical properties of tantalum zirconium nitride films and the subsequent simulation of these properties using an ab initio calculation based on density functional theory (DFT) within the generalized gradient approximation. The films were deposited by reactive unbalanced magnetron sputtering and their physical and chemical properties were studied by means of x-ray diffraction (XRD), Rutherford backscattering (RBS), and nanoindentation. XRD revealed that these films formed a solid solution and that the lattice constant decreased linearly with Ta content. RBS provided the elemental composition of the films. Nanoindentation was used to evaluate the hardness and the elastic modulus. The hardness was found to have high values for a Ta/(Ta+Zr) of 30% and 100%. The elastic modulus was found to increase monotonically with Ta content. The intrinsic elastic constants were calculated using DFT and the results were compared to the experimental values. A correlation between the computational and the experimental Young’s modulus was established. However, the trends observed for the measured hardness and the calculated shear modulus were not in agreement. This disagreement was due to the prominent extrinsic component of the hardness for these materials. © 2006 American Institute of Physics

La relance du chêne-liège dans le Plan national de reboisement en Algérie -

En Algérie, la superficie forestière n'a cessé de régresser et, plus particulièrement, durant les deux dernières décennies. Aux causes multiples déjà connues, se sont rajoutés le terrorisme et les problèmes que risquent de poser les changements climatiques dont les effets ne sont pas encore bien cernés. Devant cette situation, les pouvoirs publics ont lancé un Plan national de reboisement (PNR), dont les réalisations à mi-parcours ne couvrent même pas la moitié de ce qui devrait être réalisé. Dans le même temps, les incendies ont brûlé plus que ce qui a été planté. S'agissant du chêne-liège, les techniques en usage sont loin de contribuer à la reconstitution de la subéraie. Sur la base des observations de terrain et l'analyse critique de ce qui s'est fait jusque-là, nous suggérons une nouvelle approche devant mener à une amélioration des résultat

Grain Boundary Sliding Mechanisms in ZrN-Ag, ZrN-Au, and ZrN-Pd Nanocomposite Films

Nanocomposite films of ZrN-Me (Me = Ag, Au, or Pd) were produced by reactive unbalanced magnetron sputtering and were found to form a dense and homogeneous microstructure whereby nanocrystals of Me are distributed evenly throughout the ZrN matrix. Interestingly, the Young’s modulus was found to decrease much more dramatically with the increase in metal content for the ZrN-Ag system. A systematic ab initio study was undertaken to understand the mechanism of grain boundary sliding in these nanostructures. The maximum energy variation during the sliding was found to be the largest and the smallest for ZrN-Pd and ZrN-Ag, respectively

Quantification of multiple adulterants in beef protein powder by FT-NIR

With its adverse effects on the health of consumers and the global economy, food adulteration is considered to be one of the pressing issues of our times. Beef Protein powders (BPP) are particularly among the most fraud-prone products mainly due to their ever-growing consumption. For the purpose of our study, FT-NIR spectroscopy was applied to quantify four commonly used adulterants: Melamine (M), Urea (U), Glycine (G) and Taurine (T) in BPP. Analysis with chemometric tools proved the efficiency of the aforementioned technique as a rapid nondestructive analytical tool for the detection of Beef protein powder adulteration

Correlation Between Interfacial Electronic Structure and Mechanical Properties of ZrN–Me (Me=Ag, Au, or Pd) Nanocomposite Films

Nanocomposite films of ZrN–Me (Me=Ag, Au, or Pd) were prepared using reactive unbalanced magnetron sputtering. The hardness and elastic modulus were measured by nanoindention and were found to vary differently with composition for the three nanocomposite structures. Young’s modulus was found to decrease much more dramatically with the increase in Me content for the ZrN–Ag system. These findings were attributed to the weaker bonding mechanism at the interface between the ceramic and the metallic phases, which is more prone to grain-boundary sliding as shown using first-principles calculations of the electronic structure at the interface for the three systems

Real-time Spectroscopic Ellipsometry Study of Ultrathin Diffusion Barriers for Integrated Circuits

The objective of this work is to monitor the growth process and the thermal stability of ultrathin tantalum nitride barrier nanostructures against copper diffusion in integrated circuits using real-time spectroscopic ellipsometry (RTSE). Single layers of copper and bilayer films of copper and tantalum nitride were produced on Si(111) substrates using unbalanced magnetron sputtering. The RTSE data was simulated using the Bruggeman effective medium approximation and a combined Drude-Lorentz model to obtain information about the growth process, film architecture, interface quality, and the conduction electron transport properties for these structures. The results deduced from the RTSE were verified by characterizing the structural and the chemical properties of the fabricated films using x-ray diffraction, Auger electron spectroscopy, and Rutherford backscattering. The effectiveness of the tantalum nitride barrier to stop the diffusion of copper into silicon was evaluated, monitoring their optical properties when annealed at 720 degreesC. The dielectric function of the films changed from a metallic to an insulating character when the diffusion proceeded. Also, the RTSE provided valuable information about the microstructure and the kinetics of the phase transformations that occur during heat treatment. (C) 2004 American Institute of Physics