Electrothermal Monte Carlo simulation of submicron wurtzite GaN/AlGaN HEMTs

We present results from the simulation of the electrothermal behaviour of submicron wurtzite GaN/AlGaN High Electron Mobility Transistors (HEMTs). The simulator uses an iterative procedure which couples a Monte Carlo simulation with a fast Fourier series solution of the Heat Diffusion Equation (HDE). The results demonstrate the dependence of the extent of the thermal droop observed in the I_ds-V_ds characteristics and the device peak temperature on the device bias. The paper also investigates the effect of the inclusion of thermal self-consistency on the device microscopic properties and studies the dependence of the device electrothermal characteristics on the type of substrate material used.     

Thermo-hydrodynamic aspect analysis of flows in solar chimney power plants—A case study

The purpose of the work presented in this study is related to heat transfer and airflow modelling analysis in solar chimneys, according to some dominant parameters. A typical case of application is given in this study. It consists in analyzing a natural laminar convective heat transfer problem taking place in a chimney. Heat transfer and fluid dynamic aspects of the airflow, through an axis symmetric system in a dimensionless form, with well defined boundary conditions is thus examined. Results are related to the temperature distribution and the velocity field in the chimney and in the collector, determined by solving the energy equation, and the Navier–Stokes equations, using finite volume method. The numerical code based on this modelling is validated through the Vahl Davis benchmark solution for natural convection and to other authors for other cases.     

Chemometric Characterization of Eight Monovarietal Algerian Virgin Olive Oils

Differences in triacylglycerol, fatty acid, squalene, and tocopherol compositions were demonstrated between 8 varieties of virgin olive oils (Aberkane, Aguenaou, Aharoun, Aimel, Bouchouk Guergour, Bouichret, Chemlal, and Sigoise) from Petite Kabylie area, north eastern Algeria. Fatty acid and triacylglycerol morphotypes characterized each variety. A principal component analysis, based on triacylglycerol, fatty acid, and squalene compositions, differentiates between varieties. Minor fatty acids and squalene, usually not taken into account individually in authentication studies, are strongly involved in this differentiation, whereas the discriminant power of tocopherols is weak. Soft Independent Modeling of Class Analogy classification using chemical compositions as variables showed a high potential to authenticate the varietal origin of Algerian virgin olive oils.     

MHD mixed convection flow along a vertically heated sheet

Main objective of this frame work is to establish the modeling and simulation of mix convection flow along a vertically heated sheet filled with water. Two important mechanisms: magneto-hydrodynamics and porous medium are also considered within the restricted domain of the fluid flow. Temperature is controlled with the wall temperature and then mathematical model is constructed in the form of PDEs. To determine the similarity solution results are obtained via two different techniques. Numerically solutions are obtained with the help of shooting technique and then validate with the help of optimal homotopy analysis method (OHAM). Obtained analytical and numerical results are validated graphically. Effect of emerging parameters are plotted for velocity and temperature profiles. It is found that for mixed convection parameter $(\xi <0)\text{,}$ velocity profile depicts the increasing behavior for various values of power index m. However, for $\xi >0\text{,}$ velocity profile shows the decreasing behavior with respect the parameter m. Temperature distribution in the restricted domain depicts the decreasing behavior for both m and $\xi$.     

Thermal-Induced Wear Mechanisms of Sheet Nacre in Dry Friction

Sheet nacre is a natural biocomposite with a multiscale structure including a mineral phase of calcium carbonate (97 wt.%) and two organic matrices (3 wt.%). The mineral phase is constituted by an arrangement of CaCO₃ biocrystal nanograins (ca 40 nm in size) drowned in an “intracrystalline” organic matrix (4 nm thick) in order to form a microsized flat organomineral aragonite platelet. These platelets are themselves surrounded by an “intercrystalline” organic matrix (40 nm thick) building up a very tough materials. This microarchitecture referred to as “bricks and mortar” nacre structure, is mainly studied for the creation of new organic/inorganic hybrid materials. Currently, only little is known about the nacre mechanical behaviour under dynamical loading and more particularly under tribological conditions which involve shocks and thermal effects simultaneously. This paper brings out the thermal-induced damage mechanisms effect on the wear of sheet nacre by the assessment of the thermal component of the friction with a scanning thermal microscope. Results reveal that the mean contact pressure is the main driving force involved in the degradation of the organic constituents. For the lowest mean contact pressure (<0.4 MPa), wear is rather weak because the friction-induced thermal component is not sufficient for degrading the organic matrices. In contrast, beyond 0.4 MPa, the friction-induced contact temperature rises up over the melting point of the organic matrices, and may even reach the temperature of the aragonite–calcite phase transformation increasing dramatically the wear of sheet nacre.     

Analysis of the Dynamic Behavior of Magnetorheological Elastomer Composite: Elaboration and Identification of Rheological Properties

Silicon - The present work is devoted to experimental analysis of the magnetorheological elastomer composite behavior under dynamic loading. The elastomer is charged to 40% of ferromagnetic...     

Statistical study of the crushing of limestone grains under shearing

Bulletin of Engineering Geology and the Environment - The behavior of granular materials subjected to shear loading is often very complex to be correctly characterized. Loads on a discrete medium...     

Design optimization of a solar tower power plant heliostat field by considering different heliostat shapes

The present study focuses on the optimization of solar tower power plant heliostat field by considering different heliostat shapes including rectangular, square, pentagon, hexagon, heptagon, octagon, and circular heliostat shapes. The optimization is carried out using an in-house developed code-based MATLAB program. The developed in-house code is validated first on a well-known PS10 Solar Thermal Power plant having rectangular heliostats shape and the resulting yearly unweighted heliostat field efficiency of about 64.43% could be obtained. The optimized PS10 heliostat field using different heliostat shapes showed that the circular and octagon heliostat shapes provide better efficiency with minimum land area. The yearly efficiency is increased from 69.65% for the rectangular heliostat shape to 70.96% and 71% for the octagon and circular shapes, respectively. In addition, the calculated field area (land area) is reduced for the case of circular and octagon heliostat shapes with a gain of about 11.10% and 10.93% (about 42.0436 × 10³ and 41.4036 × 10³ m²), respectively, in comparison with the PS10 field area.