Etude des facteurs de variation des prix d’intérêt des matières premières de substitution utilisées dans les aliments concentrés des animaux d’élevage

Ce travail vise à étudier les facteurs de variation du prix d’intérêt de quelques matières de substitution, notamment le blé fourrager, seigle, le sorgho, le triticale, l’avoine, le manioc, les grains de tournesol, les grains de colza, le tourteau de colza, le tourteau d’arachide, le tourteau de palmiste, la féverole, le pois, les drêches et distilleries du maïs (DDGS), le corn gluten feed (CGF), le lupin blanc, le lupin bleu, les coques de soja, le pois chiche et l’orge, afin de remplacer totalement ou partiellement le maïs et/ou le tourteau de soja dans les aliments composés des bovins, ovins, poules pondeuses, poulets de chair, dindes et lapins. Des modèles permettant la prédiction du prix d’intérêt de ces matières de substitution ont été établis en utilisant des régressions linéaires multiples et validés (R2>0,990). Les résultats de ce travail montrent que les matières de substitution peuvent être classées en matières énergétiques, protéiques ou mixtes. Ainsi, le prix d’intérêt d’une matière de substitution donnée varie suivant les fluctuations des prix de marché du maïs et/ou du tourteau de soja (p<0,0001). Le prix d’intérêt varie aussi en fonction de l’espèce animale à laquelle l’aliment concentré est destiné et de la composition de la formule du concentré (p<0,0001). Le taux protéique du tourteau de soja n’affecte pas significativement le prix d’intérêt des matières premières étudiées.Mots-clés: prix d’intérêt, matière de substitution, maïs, tourteau de soja, taux protéique. Study of the factors influencing the minimum prices of raw substituting materials used in livestock concentratesThis work aims to study the factors influencing the minimum price of some substituting raw materials, such as fodder wheat, rye, sorghum, triticale, oat, manioc, sunflower grains, colza grains, colza meal, peanut meal, palm meal, fababean, pea, corn distillers (DDGS), corn gluten feed (CGF), white and blue lupin, soya hulls, chickpea and barley, in poultry, rabbits, ovine and bovine concentrates. Predictive minimum price models of the studied substituting raw materials were developed using multiple linear regression models and validated (R2>0,990). Our results allow to classify substituting materials into 3 groups: materials source of energy, materials source of nitrogen, and materials source of energy and nitrogen at the same time. Hence, the minimum price depends on market prices of corn and/or soyabean meal (p<0,0001). Moreover, the minimum price varies according to the animal species and the composition of the concentrate (p<0,0001). The protein level of soyabean does not affect significantly the minimum price of the studied materials.Keywords: minimum price, substituting materials, corn, soyabean, protein leve

Weibel instability in Weakly Relativistic Laser Fusion Plasma

In this work, we used the MATLAB code to calculate the growth rate of the Weibel instability (WI) in weakly relativistic parameters of laser-plasma interaction in the inertial thermonuclear fusion. In this study, the basic equation is the relativistic Fokker-Planck equation (FPE). However in our paper, the distribution function is not supposed but it is calculated from FPE by considering the fusion plasma heating by the laser source and the collisions term which corresponds to the laser fusion experiments. The main obtained result is a decrease in the spectral range of Weibel unstable modes. This decreasing is accompanied by a reduction of two orders in the growth rate spectrum of instability, this spectrum presents a maximum, which can be in terpreted by the competition between the loss effects (collisions and Landau damping) and the inverse bremsstrahlung absorption (IBA) with parameters of laser-plasma interactions

BANKING SHORT- AND LONG-TERM STABILITY: A COMPARATIVE STUDY BETWEEN ISLAMIC AND CONVENTIONAL BANKS IN GCC COUNTRIES

This research empirically assesses the contribution of Islamic finance to the financial stability of banks. The empirical analysis is based on the annual data related to 103 banks (51 Islamic banks and 52 conventional banks) operating in six countries of the Gulf Cooperation Council (GCC) region during the period 2006–2015. The LADR ratio was computed and used to measure banks stability in the short term, and the Z -score was used to assess long-term stability.The results show that, overall, Islamic banks are financially more stable in the short-term but less stable in the long term than conventional banks. The comparative analysis of the financial stability determinants in the two systems shows that these determinants contribute differently to the short- and long-term financial stability of Islamic and conventional banks. This is due to the dissimilarities in the two operating principles

BANKING EFFICIENCY: A COMPARATIVE STUDY BETWEEN ISLAMIC AND CONVENTIONAL BANKS IN GCC COUNTRIES

This research aims at comparing the efficiency of Islamic and conventional banks operating in the GCC countries from 2006 to 2015 for a sample of 51 conventional and 48 Islamic banks using stochastic frontier analysis and the CIR ratio. The results show that Islamic banks are less efficient in terms of cost than conventional banks, and that this result remains valid even during the 2008 crisis period and even after controlling for bank-specific variables. Regarding the determinants of bank efficiency, empirical results show that capital adequacy and size positively affect bank efficiency as measured by the stochastic frontier analysis. Results also indicate that productive assets are negatively related to efficiency as measured by the CIR ratio. This study provides new insights in terms of financial efficiency of the banking system. Findings could help Islamic and conventional banks to increase their efficiency and their performance and improve the service provided to customers

Weibel instability in Weakly Relativistic Laser Fusion Plasma

In this work, the Weibel instability due to inverse bremsstrahlung (IB) absorption in laser fusion plasma has been investigated. The stabilization effect due to the coupling of the self-generated magnetic field by Weibel instability with the laser wave field is explicitly showed. In this study, the relativistic effects are taken into account; here the basic equation is the relativistic Fokker-Planck equation. The main obtained result is that the coupling of self-generated magnetic field with the laser wave causes a stabilizing effect of excited Weibel modes. We found a decrease in the spectral range of Weibel unstable modes. This decreasing is accompanied by a reduction of two orders in the growth rate spectrum of instability, or even stabilization of these modes. It has been shown that the previous analysis of the Weibel instability due to IB have overestimated the values of the generated magnetic fields

Étude expérimentale et numérique des joints simple recouvrement en alliage d’aluminium 5052-H36 soudés au laser

De nos jours, l’industrie du transport est à la recherche de structures de véhicules légères et performantes afin de réduire le poids et d’augmenter la durabilité. Pour répondre à ces exigences, l'aluminium devient un matériau de choix qui offre à l'industrie la possibilité d'alléger les structures portantes des véhicules. Toutefois, la problématique de la durabilité des assemblages des structures en aluminium soulève plusieurs obstacles technologiques, tel que le choix du procédé d’assemblage. Cette étude s’intéresse à l’utilisation de la technologie du soudage au laser autogène, en tenant compte de l'influence des paramètres opératoires de soudage sur des assemblages du type joint à simple recouvrement en alliage d’aluminium 5052-H36. Ce travail met l’accent sur la caractérisation mécanique de ces joints soudés afin de déterminer l’influence de la forme du cordon, la présence d’un jeu et une deuxième passe de soudage permettant de générer des courbes de fatigue en exploitant les résultats de la caractérisation expérimentale en fatigue. En se basant sur ces données expérimentales, des modèles analytiques et numériques ont été développés pour prédire la durée de vie en fatigue de ces joints soudés au laser. Après validation expérimentale, ces modèles de prédiction de comportement en fatigue sont appliqués à des composantes assemblées ayant des configurations complexes. Finalement, les modèles et les lois développés corroborent les résultats des essais de fatigue obtenus pour les échantillons soudés

Lactation Performance of Small Ruminants in the Maghreb Region

Maghreb areas are characterized by rainfall seasonality and scarcity resulting in a low fodder potential. In these arid and semiarid regions areas, small ruminant production is the main source of income of farmers living where sheep (Ovis aries) and goats (Capra hircus) are generally confronted with severe nutritional deficits during feed scarcity period which exacerbate disease and health troubles and consequently low performances. Interestingly and despite the importance of the milk performance to the dairy industry, very few works studied the potentialities of the mammary gland through the lactation period both in sheep and goats elevated in the Maghreb areas. Nevertheless, understanding the different mammary gland patterns throughout lactation is essential to improve dairy production and to reduce poverty and vulnerability in rural farming systems in these developing areas. The main objective of this review is to analyse the lactate processes as well as to underline the mammary gland morphological patterns, health and physiology traits and to evaluate milk potentialities of the main breeds of goats and sheep raised in Maghreb