A comparative study of nature inspired optimization algorithms on multilevel thresholding image segmentation

In this paper, five successful nature inspired algorithms; the artificial tree algorithm (AT), the particle swarm optimization (PSO), the genetic algorithm (GA), the cultural algorithm (CA), and the cuckoo search algorithm (CS) have been compared on multilevel image thresholding. The segmentation process is based on the Levine and Nazif intra class uniformity criterion which is seen as an optimization problem. The comparison performances are in terms of the value of the objectif function, the peak signal to noise ratio (PSNR) and the computation time. Empirical results over different benchmark images for different threshold numbers reveal the robustness, the reliability and the rapidity of the cultural algorithm (CA).

     

Large Eddy simulation for lean premixed combustion

In comparison to previous numerical studies interested in the ORACLES benchmark (One Rig for Accurate Comparisons with Large Eddy Simulations), the present study demonstrates the advantages of LES‐WALE model in both inert and reacting flows using the Fluent‐CFD. So, the confirmation is based on the experimental research effort that was involved in the European Union‐funded research program MOLECULES (Modelling of Low Emissions Combustors Using Large Eddy Simulations), for three parameters: longitudinal velocity, longitudinal velocity fluctuation, and length of recirculation zone. In line with what was observed by the experimental reference study, the dynamic model (LES‐WALE) predicts, respectively, as well as the asymmetry and the symmetry, for both inert and reacting flows. In addition, the simulation succeeds to predict the zones of recirculation and shows the differences between the two cases, inert and reacting flows. Moreover, results have been compared with those of the k–ε model performed by Kurenkov and Obserlack [Kurenkov and Obserlack, Flow Turbulence Combustion 74, 387–407 (2005)] study. © 2012 Canadian Society for Chemical Engineering     

Sinus node dysfunction after complete correction of tetralogy of Fallot. Report of a case

Atrioventricular conduction defects after complete correction of tetralogy of Fallot are well known and their prevalence is decreasing with improved operative techniques. On the other hand, sinus node dysfunction has not been described after this type of surgery. The authors report the case of a 24 year old patient operated at the age of 2 for a favourable form of tetralogy of Fallot. In the long-term, this patient had a minimal anatomical sequel (mild pulmonary insufficiency) and first degree AVB with complete right bundle branch block with sinus bradycardia on the surface ECG. A recent aggravation of the patient's functional status led to rhythmological investigation which showed chronotropic atrial incompetence with nodal atrioventricular delay. The patient was implanted with a permanent DDD cardiac pacemaker programmed in the DDDR mode with a good outcome. Atrial chronotropic incompetence is one of the modes of expression of sinus node dysfunction. This has not been previously described in this context. This form of sinus node dysfunction should be systematically excluded after surgical cure of tetralogy of Fallot by exercise stress testing and 24 hour Holter ECG. Symptomatic patients are greatly improved by permanent cardiac pacing with hysteresis.     

A new approach in tracking maximum power under partially shaded conditions with consideration of converter losses

The fact that photovoltaic panels are very sensitive to non-uniform insolation conditions, which can occur several times a day, causes a decrease of efficiency and so increases time for return on investment. This work presents a maximum power point tracking algorithm (MPPT) operating on the load characteristic in order to take the converters losses into account. In addition, the proposed MPPT deals with the problems of shadowing for which the power-load characteristic can present two or more local maximums close to each other. Considering the converters losses it can be shown that the maximum output power of the photovoltaic panels does not necessarily coincide with the maximum output power of the converters. The proposed MPPT algorithm tracks the maximum power with the intention of reducing the total losses including those of converters. Its performance is verified by simulation and confirmed by experimental results.     

The fate of furfurals and other volatile markers during the baking process of a model cookie

This work investigates the generation and the evolution of some neoformed compounds formed during the baking of a model biscuit. Thank to their physicochemical properties of volatility and hydrophobicity, furfurylic compounds were followed by a double approach: the analysis of the volatile fraction extracted from food matrix and from the vapours released during the thermal process. 5-Hydroxymethylfurfural (HMF) was the main furfurylic compound formed, it followed an exponential kinetic in both the matrix and the vapours of baking biscuits. However, at the very final stage of baking a drop in HMF was observed in the cookie matrix whereas increasing amounts of HMF were still found in the vapours of baking. Moreover, some degradation products of HMF such as furaldehyde (F) and 2-methylfurfural (MF) were also detected. These observations support the hypothesis of a concomitant volatilization and degradation of HMF during the baking of the model cookie, under our experimental conditions.     

A novel five-variable refined plate theory for vibration analysis of functionally graded sandwich plates

In this article, a new five-variable refined plate theory for the free vibration analysis of functionally graded sandwich plates is developed. By dividing the transverse displacement into bending, shear, and thickness stretching parts, the number of unknowns and governing equations of the present theory is reduced, and hence, makes it simple to use. Indeed, the number of unknown functions involved in the present theory is only five, as opposed to six or more in the case of other shear and normal deformation theories. The theory accounts for hyperbolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using a shear correction factor. Two common types of functionally graded material (FGM) sandwich plates, namely, the sandwich with FGM facesheet and homogeneous core and the sandwich with homogeneous facesheet and FGM core, are considered. The equations of motion are obtained using Hamilton's principle. Numerical results of the present theory are compared with three-dimensional elasticity solutions and other higher-order theories reported in the literature. It can be concluded that the proposed theory is accurate and efficient in predicting the free-vibration response of functionally graded sandwich plates.     

Synthesis of controllers for symmetric systems

This article deals with supervisory control problem for coloured Petri (CP) nets. Considering a CP-net, we build a condensed version of the ordinary state-space, namely the symbolic reachability graph (SRG). This latter graph allows to cope with state-space explosion problem for symmetric systems. The control specification can be expressed in terms of either forbidden states or forbidden sequences of transitions. According to these specifications, we derive the controller by applying the theory of regions on the basis of the SRG. Thanks to expressiveness power of CP-nets, the obtained controller to be connected to the plant model is reduced to one single place.     

Polynomial parametrization of nonsingular complete intersection curves

In this paper we give a new method to compute a polynomial parametrization, in case it exists, of an affine nonsingular complete intersection curve. Our method is based on the study of vector fields on nonsingular algebraic curves. In contrast to the existing methods, our algorithm does not use any projection, and no sample point on the curve is needed. It is also important to stress the fact that the algorithm produces a parametrization with coefficients in the ground field.     

Thermal Buckling of Functionally Graded Plates According to a Four-Variable Refined Plate Theory

In this article, a four-variable refined plate theory is presented for buckling analysis of functionally graded plates. The theory, which has strong similarity with classical plate theory in many aspects, accounts for a quadratic variation of the transverse shear strains across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. A power law distribution is used to describe the variation of volume fraction of material compositions. Equilibrium and stability equations are derived based on the present theory. The non-linear governing equations are solved for plates subjected to simply supported boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. The influences of many plate parameters on buckling temperature difference will be investigated. It is noticed that the present refined plate theory can predict accurately the critical temperatures of simply supported functionally graded plates.