Equations de la physique mathématique appliquées

406 p. : ill. ; 28 c

Physique de la terre

389 p. : ill. ; 30 cmCe livre s'adresse aux étudiants, chercheurs et les enseignants physiciens, mathématiciens, géophysiciens et aux spécialistes des sciences de la terr

Tomographic velocity images by artificial neural networks

The present study deals with the use of Elman artificial neural network (feedback connexion) to reconstruct the velocity image from a traveltime in the seismic tomography experiment. This recurrent connection provides the advantage to store values from the previous time step, which can be used in the actual time step. The backpropagation algorithm has been used to learn the suggested neural network. Efficiency of these networks has been tested in training and generalization phases. A comparative reconstruction with two classical methods was performed using backprojection and Algebraic Reconstruction Techniques (ART). The obtained results clearly show improvements of the quality of the reconstruction obtained by artificial neural network

Complex-valued forecasting of the global solar irradiation

In this paper, a forecasting of the global solar irradiation in the complex-valued domain is proposed. A method to transform the meteorological data into complex values is developed and the Complex Valued Neural Network (CVNN) is used to model and forecast the daily and the hourly solar irradiation. The measured data of Tamanrasset city, Algeria (altitude: 1362 m; latitude: 22°48 N; longitude: 05°26 E) is used to validate the developed model. In the hourly solar irradiation case, the 24 h ahead will be forecasted using the combination of the past daily meteorological dataset. Several models are presented to test the feasibility and the performance of the CVNN for forecasting either daily or hourly solar irradiation for both multi input single output and multi input multi output strategies. Results obtained throughout this paper show that the CVNN technique is suitable for modeling and forecasting daily and hourly solar irradiatio

A fuzzy logic-based filter for the removal of spike noise from 2D electrical resistivity data

In this paper, a filter based on fuzzy logic is proposed to remove spike noise from 2 dimensional electrical resistivity data. The noise detection used in this paper is based on differentiating noisy samples from the central sample inside a moving window. These fuzzy derivatives are used by the fuzzy inference system to detect corrupted samples. To assess the performance of the proposed filter for the removal of spike noise, the root-mean squared error as well as the signal-to-noise ratio were used as an objective criterion. It has been demonstrated by synthetic and real examples that the proposed filter achieves quite good results compared to the standard median filter as well as to the very effective SD-ROM filte

Application of signal dependent rank-order mean filter to the removal of noise spikes from 2D electrical resistivity imaging data

It is well-known that when inverting two-dimensional (2D) electrical resistivity data, a major source of errors is the presence of noise and in particular noise spikes. The popular median filter is often applied to the removal of single spikes. However, when the signal is highly corrupted with successive spikes, the median filter performance is poor. This paper deals with the use of the signal dependent rank-order mean filter for the detection and removal of noise spikes from highly corrupted 2D electrical resistivity imaging data. In addition to its computational simplicity, this filter is shown to be extremely robust, even in the presence of very strong noise, especially when it is applied recursively. The signal dependent rank-order mean filter was tested on 2D synthetic resistivity data contaminated by near-surface inhomogeneities and the results confirmed efficient removal of the disturbances normally associated with near-surface inhomogeneities. The signal dependent rank-order mean filter was also applied to field data and demonstrated its ability to significantly improve the accuracy of the inversion process and to produce good visual results in the inverted electrical section

Apport de la géoélectricité et des diagraphies à la reconnaissance des minéralisations polymétalliques dans la région d'El Tarf - prospect de Zitouna

Les cibles courantes en méthodes électriques et en polarisation provoquée sont les gisements de minerais métalliques, qu’ils soient massifs ou disséminés. Ces cibles sont généralement conductrices et ont des propriétés physiques caractéristiques permettant de les détecter dans les conditions in situ à l’aide de mesures faites en surface. A ce propos, L’analyse et l’interprétation des documents graphiques élaborés à partir des données de base acquises par l’O.R.G.M au cours de la campagne de prospection géophysique de détail de 1999-2001 sur les secteurs limitrophes de Djebel Zitouna et Kef Zoukrane a permis de relever quelques anomalies de polarisation provoquée appréciables en extension et en amplitude. Ces anomalies semblent traduire l’effet des zones minéralisées en pyrite, galène et sphalérite. Les corps perturbateurs ayant généré les anomalies observées peuvent se définir de par leurs caractères géoélectriques comme des corps résistants chargeables. Les forages implantés à posteriori aux épicentres des anomalies PP ont recoupé des niveaux minéralisés dans les grès numidiens fissurés et bréchifiés, confortant ainsi les interprétations antérieure

An integrated study of physical precursors of failure in relation to earthquake prediction, using large scale rock blocks

This paper is multi-analysis approach to rock failure using metric size rock samples. The use of large-scale models permits simulation of the seismic process (including internal rupture on several scales) and utilization of a dense network for observation of the spatial variations of several physical parameters. The experiments were performed both on solid rock blocks and on concrete blocks with artificial defects, which enabled simulation of internal shear fracture. The number of various precursors appears to rise up to failure, all of them clearly manifest at the stage of a rapid drop in the applied stress (unstable deformation). The experiment suggests that rocks under strain and prior to failure must be characterized by a heterogeneous field of strains. This means that the strain is distributed mosaically, dilatancy does not generate uniformly and areas where it occurs are likely to be structurally mosaic themselves. To reinforce the prediction of micro- and macrofailure, we have realized simultaneous processing of the obtained data, using sophisticated multidimensional orthogonal functions to represent the different precursors. The possibility to identify the early stages of microfailures and to predict the macrofailure by means of statistical complex parameters derived from data on local deformations, acoustic emissions, elastic waves velocities, electric resistivity and self electric potentials is shown. Despite a considerable dissimilarity in mechanical properties of granite basalt and concrete, the complex parameter proves morphologically identical. Parameter S1 reveals exponential rise up to failure in all cases, and parameter S2 is bay-shaped in form, which makes it more promising in terms of prognosis

Impact of integrated clean energy on the future of the mediterranean: Exploitation of albian geothermal water in South Algeria

The Intercalary Continental aquifer generally called Albian aquifer constitutes the main geothermal resource in South Algeria. Additionally it represents the biggest water reserve in the word. Albian aquifer is used since centuries, especially in the areas where it levels like Tidikelt Touat and Gourara. But however in other areas where this aquifer is deep and whose water is hot, the exploitation of the aquifer is rather difficult. As the only geothermal resource in southern Algeria, the Albian aquifer has a lot of interest from geothermal point of view; therefore good knowledge of the different routes of its exploitations is necessary to facilitate future applications of geothermal in the Saharan regions. The present article gives an overview about various modes of exploitation of the Intercalary Continental aquifer and the major problems which have occurred during exploitation. Finally is added discussion about the main applications of geothermal energy in South Algeria based on projects completed or in progres

An integrated study of physical precursors of failure in relation to earthquake prediction, using large scale rock blocks

This paper is multi-analysis approach to rock failure using metric size rock samples. The use of large-scale models permits simulation of the seismic process (including internal rupture on several scales) and utilization of a dense network for observation of the spatial variations of several physical parameters. The experiments were performed both on solid rock blocks and on concrete blocks with artificial defects, which enabled simulation of internal shear fracture. The number of various precursors appears to rise up to failure, all of them clearly manifest at the stage of a rapid drop in the applied stress (unstable deformation). The experiment suggests that rocks under strain and prior to failure must be characterized by a heterogeneous field of strains. This means that the strain is distributed mosaically, dilatancy does not generate uniformly and areas where it occurs are likely to be structurally mosaic themselves. To reinforce the prediction of micro- and macrofailure, we have realized simultaneous processing of the obtained data, using sophisticated multidimensional orthogonal functions to represent the different precursors. The possibility to identify the early stages of microfailures and to predict the macrofailure by means of statistical complex parameters derived from data on local deformations, acoustic emissions, elastic waves velocities, electric resistivity and self electric potentials is shown. Despite a considerable dissimilarity in mechanical properties of granite basalt and concrete, the complex parameter proves morphologically identical. Parameter S1 reveals exponential rise up to failure in all cases, and parameter S2 is bay-shaped in form, which makes it more promising in terms of prognosis