Study on the isolation and characterization of rhizobia strains as biofertilizer tools for growth improvement of four grain legumes in Ngaoundéré-Cameroon

Increasing the yield and economical efficiency of grain legumes in the Guinea-Savannah zone of Cameroon is a high researcher priority to assist growers in the rural areas. We report here a two-years study inthe production process of fertilizer containing rhizobia for a sustainable production of grain legumes in the region. To address the issue, nodulation and rhizobia strains characterization were assessed at Dang and Wakwa, two soils different in trapping rhizobia partners for groundnut, bambara groundnut, cowpea and soybean. This was a prerequisite step in the determination of the most efficient rhizobia strains for biofertilizer production. Results indicate that all the four grain legumes differently formed nodules in their roots system in the two experimental soils. Cowpea and soybean demonstrated a highly significant (p ≤ 0.001) potential in fixing atmospheric nitrogen through their nodules than groundnut and bambara groundnut. The dry weight of nodules in groundnut and bambara groundnut was significantly lower (0.0001 < p ≤ 0.038) than that of cowpea and soybean in the two soils. When rhizobia were isolated from root nodules of plant species, the number of isolates ranged from 2 to 4 per grain legumes. All the isolates were convex in elevation, smooth/humid on the surface, with regular edges, except one groundnut colony from wakwa soil. The colonies were either whitish for soybean, whitish/yellowish for cowpea, groundnut and bambara groundnut. The rhizobia biofertilizer produced for each grain legumes were stored in the refrigerator for field tests. This is a step forward for further molecular characterization of isolates to enable production of elite inoculum in the region.© 2009 International Formulae Group. All rights reserved.Key words: Grain legumes, nodulation, Rhizobium characterization, Rhizobium biofertilizer

Les plans d'expérience appliqués à l'optimisation des patchs composites

Les patchs en matériaux composite sont reconnus comme étant un des moyens les plus judicieux et efficaces pour la réparation des fissures et défauts. Leur utilisation se traduit par une réduction du facteur d'intensité des contraintes. Ce dernier dépend de plusieurs paramètres, tels que les dimensions et les propriétés intrinsèques du patch, de l'adhésif et du matériau. Dans ce travail, nous appliquons la méthode des plans d'expériences pour étudier les effets de ces paramètres pour aboutir à une optimisation du patch. Le calcul du facteur d'intensité de contrainte se fait par la méthode des éléments finis

Analysis of parameters effects on crack breathing and propagation in shaft of rotor dynamic systems

In this paper the design of experiment method is used to investigate and explain the effects of the rotor parameters on crack breathing and propagation in the shaft. Three factors are considered which have an influence on the behavior and the propagation of the crack: the rotational speed, the length of the rotor and the diameter of the shaft. The elaborated mathematical model allows determining the effects and interaction of speed, diameter and length on crack breathing mechanism.The model also determines the optimal values of the parameters to achieve high performance

Modeling of Cracked Beams by the Experimental Design Method

Abstract The understanding of phenomena, no matter their nature is based on the experimental results found. In the most cases, this requires an important number of tests in order to put a reliable and useful observation served into solving the technical problems subsequently. This paper is based on independent and variables combination resulting from experimentation in a mathematical formulation. Indeed, mathematical modeling gives us the advantage to optimize and predict the right choices without passing each case by the experiment. In this work we plan to apply the experimental design method on the experimental results found by (Deokar, A, 2011), concerning the effect of the size and position of a crack on the measured frequency of a beam console, and validating the mathematical model to predict other frequencie