Variable Structure Controller for Surface Ship Steering

A Lyapunov approach to constructing switching surfaces for variable structure systems is investigated in this paper. The method guarantees sliding mode for any initial condition of the state vector and asymptotic stability is always achieved during sliding motion. An application for  the design of  a variable structure ship steering controller is carried out and  simulation results are presented. The designed controller exhibits robustness as applied to a linear time-invariant ship model and a time varying non-linear  ship model operating in  an uncertain and  time-varying environment

Thermogravimetric analysis of anningre tannin resin

Three formulations of aningre tannin resins containing in order the paraformaldehyde powder, hexamethylenetetramine and aqueous glyoxal as hardeners were developed. Their thermogravimetric analysis have shown that they begin to decompose respectively from 135°C, 145°C and 140°C. About 24%, 40% and 39 % solid residues of their initial masses exist at the end of the analysis. Thermomechanical analysis has shown that the formulation containing paraformaldehyde powder as hardener has the best rigidity and the worst contains the hexamethylenetetramine. All formulations have different thermal degradation, differences were more significant between 400 and 900°C.The decomposition of hardeners become more significant from 400°C

Etude en Laboratoire des Caracteristques Geotechniques de Compressibilite et de Cisaillement de l\'Argile-Sableuse Jaunatre de Ndogbong dans la Region de Douala au Cameroun

The knowledge on the behaviour of soil is one of aspects in the research programme of the department of civil engineering of ENSET of University of Douala. In this aspect, studies have been carried out on soils with the aim of determining the different parameters of the soil on campus II, which is the proposed site on which future infrastructure of the university of Douala have to be built. Also the collection of samples intact had been effected on the site.These samples collected have permitted the execution of the different types of tests in the laboratory.The aim of this tests was to obtain the characteristics of the state, compressibility and shearing of the soil. The obtained results have permitted us to understand the nature of soil, its behaviour under the effect of loading by an odometer and its short term behaviour when subjected to shearing by a triaxial test in non-drained conditions. The results of the present study forms a geotecnical bank of data base usable in dimensioning the underground or buried buildings. A brief recall of the pedology of the region and a bibliographical review relative to the geotechnical parameters of the sandy-clays in the region permitted us to frame the results obtained in this study. This study was carried out with the collaboration of the tests laboratory “LABOGENIE” of Douala. KEY-WORDS: Pedology, samples, shearing, compressibility, identification, sandy-clays, stress of preconsolidation stress, void indices, specific weight, water content, frictional angle. Résumé La connaissance du comportement des sols est l\'un des aspects du programme de recherche du département de génie civil de l\'Ecole Normale Supérieure de l\'Enseignement Technique de l\'Université de Douala. Dans cette optique des études de sols ont été conduites dans le but de déterminer les différents paramètres du sol du campus II, qui est le domaine pressenti pour recevoir les infrastructures futures de cette Université. Aussi, des prélèvements d\'échantillons intacts ont-ils été exécutés sur le site. Ces prélèvements ont permis l\'exécution en laboratoire des différents types d\'essais. Le but de ces essais était d\'obtenir les caractéristiques d\'état, de compressibilité et de cisaillement. Les résultats obtenus ont permis de comprendre la nature du sol, son comportement sous l\'effet des chargements à l\'œdomètre d\'une part et, sous l\'action de cisaillement au triaxial de l\'autre. Les résultats de la présente étude constituent une base de données géotechniques utilisables dans le dimensionnement des ouvrages enterrés. Un bref aperçu de la pédologie de la région faisant état d\'un vaste bassin sédimentaire constitué des sols en formation a permis de mieux comprendre les résultats obtenus dans cette étude. En outre, une revue bibliographique relative aux parameters géotechniques des sols argileux sableux dans la région a permis de cadrer les résultats obtenus. Cette étude a été menée avec la collaboration du laboratoire d\'essais « LABOGENIE-AGENCE DE DOUALA ». MOTS CLES : Pédologie, échantillons, cisaillement, compressibilité, identification, argile sableuse, contrainte de préconsolidation, indice des vides, poids spécifique, teneur en eau, angle de frottement. (Af. J. of Science and Technology: 2002 3(2): 84-95

Comparative Numerical Study of Four Biodiesel Surrogates for Application on Diesel 0D Phenomenological Modeling

To meet more stringent norms and standards concerning engine performances and emissions, engine manufacturers need to develop new technologies enhancing the nonpolluting properties of the fuels. In that sense, the testing and development of alternative fuels such as biodiesel are of great importance. Fuel testing is nowadays a matter of experimental and numerical work. Researches on diesel engine’s fuel involve the use of surrogates, for which the combustion mechanisms are well known and relatively similar to the investigated fuel. Biodiesel, due to its complex molecular configuration, is still the subject of numerous investigations in that area. This study presents the comparison of four biodiesel surrogates, methyl-butanoate, ethyl-butyrate, methyl-decanoate, and methyl-9-decenoate, in a 0D phenomenological combustion model. They were investigated for in-cylinder pressure, thermal efficiency, and NOx emissions. Experiments were performed on a six-cylinder turbocharged DI diesel engine fuelled by methyl ester (MEB) and ethyl ester (EEB) biodiesel from wasted frying oil. Results showed that, among the four surrogates, methyl butanoate presented better results for all the studied parameters. In-cylinder pressure and thermal efficiency were predicted with good accuracy by the four surrogates. NOx emissions were well predicted for methyl butanoate but for the other three gave approximation errors over 50%

COMPARISON OF FIVE NUMERICAL METHODS FOR ESTIMATING WEIBULL PARAMETERS FOR WIND ENERGY APPLICATIONS IN THE DISTRICT OF KOUSSERI, CAMEROON

ABSTRAC

ANALYSIS OF SCALE EFFECTS ON THE BEHAVIOR OF COMPOSITE STRUCTURES: CASE OF AUTOMOTIVE BOD

For many years, composite materials include automotive industries to improve their performance. Manufacturers are constantly looking for a method of reducing scales presents various advantages. This work aims to show the influence of folds fittings techniques during the downscaling of a multilayer composite structure notched or un-notched, requested static. A numerical study is conducted on the plate-shaped structures. The results confirm the interest of the similarity. Similarities of meaningful relationships appear to be subject to the reproduction of the same modes of deformation and crushing. The results show that there is no difference between "ply level" technique and technology "sub laminate" and the technique of "reducing neutral report.

Thermogravimetric analysis of anningre tannin resin

Three formulations of aningre tannin resins containing in order the paraformaldehyde powder, hexamethylenetetramine and aqueous glyoxal as hardeners were developed. Their thermogravimetric analysis have shown that they begin to decompose respectively from 135°C, 145°C and 140°C. About 24%, 40% and 39 % solid residues of their initial masses exist at the end of the analysis. Thermomechanical analysis has shown that the formulation containing paraformaldehyde powder as hardener has the best rigidity and the worst contains the hexamethylenetetramine. All formulations have different thermal degradation, differences were more significant between 400 and 900°C.The decomposition of hardeners become more significant from 400°C

Mechanical properties of Aningeria superba (Aningre) and Austranella congolensis tannin adhesives

International audienc

Desorption Behavior and Thermogravimetric Analysis of Bio-Hardeners

In this work, the thermal degradation and drying of bio-hardeners are investigated. Four bio-hardeners based on exudates of Senegalia senegal, Vachellia nilotica, Vachellia seyal, and Acacia Siebteriana were analyzed by FTIR and thermogravimetric analysis, and a desorption study was also conducted. The analysis by infrared spectroscopy indicates the existence of oligomers of different types all giving 5-hydroxy-2-hydroxymethylfuran and 2, 5-dihydroxymethylfuran which are then the real hardening molecules. The pyrolysis of these extracts reveals three main regions of mass loss, a first region is located between 25 degrees C and 110 degrees C reflecting the loss of water from the adhesive and the formation of some traces of volatile organic compounds such as CO2 and CO, a second zone characterized by the release of CO, CO2 and CH4 gases with peaks between 110 degrees and 798.8 degrees C. At the end of the analysis, about 22% of the initial mass remains undecomposed, this mass corresponds to the rigid segments of the bio-hardener which are not completely decomposed