Power consumption: Base stations of telecommunication in Sahel zone of Cameroon: Typology based on the power consumption—model and energy savings

In this paper, the work consists of categorizing telecommunication base stations (BTS) for the Sahel area of Cameroon according to their power consumption per month. It consists also of proposing a model of a power consumption and finally proceeding to energy audits in each type of base station in order to outline the possibilities of realizing energy savings. Three types of telecommunication base stations (BTS) are found in the Sahel area of Cameroon. The energy model takes into account power consumption of all equipment located in base stations (BTS). The energy audits showed that mismanagement of lighting systems, and of air-conditioning systems, and the type of buildings increased the power consumption of the base station. By applying energy savings techniques proposed for base stations (BTS) in the Sahel zone, up to 17% of energy savings are realized in CRTV base stations, approximately 24.4% of energy are realized in the base station of Missinguileo, and approximately 14.5% of energy savings are realized in the base station of Maroua market

Consequences of anisotropy in electrical charge storage: application to the characterization by the mirror method of TiO2 rutile

This article is devoted first to anisotropic distributions of stored electric charges in isotropic materials, second to charge trapping and induced electrostatic potential in anisotropic dielectrics. On the one hand, we examine the case of anisotropic trapped charge distributions in linear homogeneous isotropic (LHI) insulators, obtained after an electron irradiation in a scanning electron microscope. This injection leads to the formation of a mirror image

Mouvement et piégeage des charges électriques dans un matériau non-conducteur anisotrope (Application au rutile (TiO2))

La caractérisation du piégeage des charges est faite par la physique des isolants chargés qui englobe plusieurs domaines tant du point de vue fondamental qu'appliqué. Elle décrit les mécanismes de conduction et de piégeage des charges électriques dans les isolants mais aborde aussi les conditions de stabilité et de relaxation de celles-ci. Nous nous sommes intéressés aux mécanismes de piégeage des charges dans un semi-conducteur à grand gap (ou isolant à faible gap) : le dioxyde de titane, rutile. La caractérisation de ces mécanismes est faite par la méthode SEMME (Scanning Electron Microscopy Mirror Effect). Les travaux réalisés ont permis de mettre en évidence une diffusion importante des charges et plus particulièrement une conduction en surface. La forte valeur de la constante diéliectrique entraîne d'un côté un effet d'écran et de l'autre une anisotropie de la distribution des charges piégées (miroirs elliptique ou circulaire). Dans ce but, un modèle analytique est proposé.Non-conductive materials and particularly solid insulators have a capacity to trap electric charges under certain conditions. The characterization of the trapping mechanisms achieved by the space charge physic, which describes not only trapping and conduction mechanisms of electric charges but also the condition of the stability and relaxation of the charges distribution. In this report, the trapping mechanisms of electric in a wide band gap semi-conductor material, are studied by the Scanning Electron Microscopy Mirror Effect. The studies have shown that electric charges diffuse, with a great leakage surface current. The high value and the anisotropy of the dielectric constant induces respectively a screening effect and an anisotropy of the distribution of trapped charges (elliptical or circular, mirors images). From the fundamental point of view, an appropiate analytical model is propose to take into account these new caracteristics.LYON-Ecole Centrale (690812301) / SudocSudocFranceF

ON A MATHEMATICAL INVESTIGATION OF A SEDIMENTATION MODEL OF LAKES

Abstract: The study of the influence of sediments brought on the sedimentary bottom formation and evolution of rivers or lakes presents a big scientific interest both by its interdisciplinary aspect and by its importance. In this work, we propose to associate the hydrodynamic and geological points with a view to establish a continuous model of the sedimentary bottom evolution processes based on conservation mass law. This model, general and progressive, make it possible to consider the flocculation phenomenon, geological activities of the bottom, and other. We establish later on the conditions of existence of admissible solutions where sedimentation is more important than the erosion process

Morphological, mineralogical and geochemical features of topomorphic vertisols used for sorghum production in North Cameroon

In the present study, two topomorphic vertisols profiles used for sorghum production were described and characterized. After macroscopic characterization, physicochemical, mineralogical and geochemical analyses were made. Physicochemical analyses were made by standard methods while mineralogy was determined on clay fraction (˂2µm) by X-ray diffraction coupled to Fourier transform infrared spectroscopy. Geochemical analysis was determined on 180µm fraction by inductively coupled plasma- Atomic Emission Spectroscopy (ICP-AES) and mass spectrometry (ICP-MS). Results revealed that studied vertisols were average deep, less differentiated with desiccations cracks and gilgai micro relief. The angular blocky structure and clayey texture were observed. They were alkaline (7.3 ≤ pHwater ≤ 8.4) and recorded a low to moderate organic matter and nitrogen contents. Cation exchange capacity was high reaching 52.24 meq 100g-1 and exchangeable cations were moderates with Ca2+ (3.69- 29.6 meq 100g-1) the most represented cation. Vertisols were made of smectites associated to kaolinite and a lesser content of quartz. Illites and calcite were also identified in some horizons. On the geochemical point of view, Si02 (55.87- 83.64%), Al2O3 (6.08-20.25%), Fe2O3 (2.09-6.39%) and K2O (1.43-2.24 %) were the dominant oxides. Traces elements were represented essentially by Ba (518-1202 mg kg-1), Zr (334-685 mg kg-1) and Sr (71-190 mg kg-1). The overall features are suitable to dry season sorghum production. The amount of smectites seemed to be an important factor affecting their water holding capacity on which dry season sorghum production depends. Improved cropping systems have to be developed to sustain productivity in vertisols with low smectites and where annual rainfall is lesser

Valorisation of crude earth as sustainable building material: a case of international cooperation in the Logone Valley (Chad-Cameroon)

Deforestation is one of the most dramatic threats to environmental equilibrium and food safety in many regions of the world, and particularly in sub-Saharan Africa. It is enhanced by many kinds of human activities, among which is the earth brick-firing process that needs large amounts of wood for attaining and maintaining temperatures required during this process. In order to reduce deforestation, the present study investigated from different points of view the potential of crude earth to be used as building material, taking as a case study the Logone Valley located at the border between Chad and Cameroon. First, an on-site investigation was made to verify the state-of-the-art of brick production technologies and to evaluate their impact on the environment. Subsequently, morphological and geotechnical analyses on soil samples collected from different sites of the Logone Valley were carried out, to evaluate their suitability to brick production. Finally, a pilot plant for crude earthen brick production was set, particularly based on a new press designed for this purpose

INTERNATIONAL UNIVERSITY COOPERATION FOR VALORIZING CRUDE EARTH AS BUILDING MATERIAL IN CHAD AND CAMEROON

Deforestation is one of the most dramatic threats to environmental equilibrium and food safety in many regions of the world, and particularly in sub-Saharan Africa. It is enhanced by many kinds of human activities, among which is the earth brick firing process, that needs large amounts of wood for attaining and maintaining temperatures required during this process. Crude earthen bricks can be used as an alternative for buildings, with environmental benefits; however, the economical and social sustainability of this building technique is linked to the improvement of the brick production technology, based on a deeper knowledge of the local resources. For this reason, a partnership was developed between an Italian University and a Cameroonian one for valorizing crude earth as building material in the Logone valley, located at the border between Chad and Cameroon: this way, the knowledge of the local context owned by the Cameroonian university was an added value to the technical skills of both universities, driving the choices made during the project. The Cameroonian university carried out mainly morphological and geotechnical analyses on soils, in order to choose the best site for brick production in the region; the Italian university designed and followed the realization of a machine for improving brick production. As a result, a pilot plant for crude earth brick production was installed

Land use impact on clay dispersion/flocculation in irrigated and flooded vertisols from Northern Cameroon

Clay dispersion by water is important for soil and water conservation as well as for irrigation scheduling. In the present study, clay dispersion/flocculation of irrigated and flooded vertisols in North Cameroon was investigated using clay dispersion/stability indices. Nine vertisols topsoils (0–20 cm) samples were collected on different land use and their clay dispersion indices were assessed. Vertisols were acidic to slightly basic, with smectites as dominant clay mineral. The water dispersible clay (160–340 g kg−1), the dispersion ratio (0.55–0.79) and the clay dispersion ratio (0.48–0.83) were high in the studied vertisols while the clay flocculation index (0.17–0.54) and the clay aggregation (70–230 g kg−1) were low to moderate, indicating their high dispersion. Cropped vertisols displayed the higher amount of water dispersible clay while not cropped recorded the smaller amount. Concerning the cropped soils, irrigated vertisols displayed the highest clay dispersion indices suggesting that agricultural practices (irrigation) enhance clay dispersion. Globally, the clay dispersibility trend was: irrigated paddy ˃ rainy sorghum ˃ rainfed paddy ˃ dry-season sorghum ˃ not cropped. Statistical analyses revealed that amorphous Al, Na+ and electrical conductivity enhance clay dispersion while organic matter, nitrogen and Ca++ promote clay flocculation/aggregation. The overall findings emphasized that practices such as heavy tillage and irrigation induce clay dispersion. Minimum tillage, electrolytes concentration monitoring in irrigation water, irrigation scheduling based on soil moisture control, organic matter inputs and implementation of adapted dams are measures susceptible to limit their degradation through clay dispersion. Keywords: Vertisols, Clay dispersion, Irrigation, Land use, North Cameroo