Determination of Abrasiveness in Copper-Gold Sulfide Ores: A Contribution to the Geometallurgical Model of the Sossego Deposit

The geological context of this study is established in the iron oxide-copper-gold (IOCG) deposit of Sossego (Canaã dos Carajás, Brazil), where hydrothermal alterations in shear zones concentrated the metals of interest and added new characteristics to the metavolcanic-sedimentary and granite rocks. The mineral transformation of rocks by hypersaline fluids enriched in metals and silica also modifies some metallurgical properties, such as abrasiveness. Special bench tests on rock drill cores are used in mapping the abrasiveness of rocks, with the Bond abrasion test being more commonly used in the mining industry, but it has a restrictive sampling protocol and mass requirement for geometallurgical studies. As a counterpoint, the test of the Laboratoire Central des Ponts et Chaussées/Central Laboratory of Bridges and Roads (LCPC) requires a smaller amount of fine material and a finer granulometric range. The study on the use of LCPC was implemented in 40 samples, using Bond Ai as a reference. The results showed a strong correlation between both methodologies (R2 = 95%), validating the use of LCPC to quantify abrasiveness in the Sossego mine. It was also possible to classify the most abrasive lithologies.

Rage au Mali, analyse des données de surveillance de la rage animale de 2009 à 2018

Introduction : La rage est une maladie infectieuse, inoculable, provoquée par un virus du genre Lyssavirus. La contamination à l'homme se fait par morsure ou griffure par un chien enragé. Les laboratoires sont un élément essentiel de la surveillance de cette maladie. L'objectif de cette étude était d'analyser les données de la base de données de la rage au Mali de 2009 à 2018. Méthodes : Il s'agissait d'une étude descriptive du 6 au 30 juin 2019. Nous avons réalisé une revue documentaire et exploité des données de la Base Access des résultats envoyées au Laboratoire Central Vétérinaire (LCV) par la Direction Nationale des Services Vétérinaires (DNSV). Les données de 10 ans, du 1er janvier 2009 au 31 décembre 2018, ont été exportées sur Excel 2013 et analysées sur EpiInfo7. Le Khi2 de Pearson ou le test Exact de Fisher ont été utilisés pour tester la liaison entre les variables. Résultats : La moyenne d'âge des chiens mordeurs était de 2,78 ans. Les mâles étaient plus fréquents avec 81,86%. Les chiens étaient surtout du milieu urbain (72,55%). L'incidence de la rage était de 39,92%. Les chiens mordaient plus en saison sèche (61,27%). L'agressivité (74,02%) était le signe le dominant, suivi par la fureur avec 57,35%. La fréquence de la vaccination chez les chiens de notre étude était 4,41%. Conclusion : L'incidence de la rage était de 39,92%. Les mâles étaient beaucoup plus impliqués dans la contamination, qui se faisait plus saison sèche. La fréquence de la vaccination était très faible. L'étude suggère l'intensification des mesures de vaccination des chiens.

THE CONDITION OF TANGIER BAY

During recent years, the spectacular growth of the sand deposit has made a great beach located at the base of the town of Tangier, and created a problem for local authorities. They are afraid that this deposition may endanger the harbor accessibility. Before beginning correcting or protecting works, the International Zone Administration of Tangier has asked the Laboratoire Central d'Hydraulique de France to study the conditions of Tangier Bay, and to determine the mechanism of sand deposition; and also to define on a reduced scale model the best arrangements to be taken in the near future for an extension of the harbor. This paper aims to present the results of field observations on the prototype.

Investigations into Phase Multipath Mitigation Techniques for High Precision Positioning in Difficult Environments

The modelling of most Global Navigation Satellite System (GNSS) errors/biases and developments of data processing techniques have been improved substantially since the birth of Global Positioning System (GPS), however, there has been much less progress in the improvement of phase multipath mitigation techniques. Multipath therefore remains one of the most important error sources in high precision GNSS positioning. This is because multipath is site-dependent and therefore cannot be eliminated by differencing techniques. Also multipath is highly dependent on satellite-reflector-antenna geometry, which usually causes rapid changes in phase multipath errors especially in Real-Time Kinematic (RTK) applications. Multipath mitigation for static antennas such as those at reference stations can be carried out by site calibration, averaging over long observation times, and through the estimation of the error using filtering based on signal-to-noise ratio (SNR) data. However, multipath mitigation for kinematic antennas is still very difficult today.Nevertheless, much research has been carried out on a particular class of phase multipath mitigation techniques: ones that can be applied within positioning algorithms (rather than incorporated into the receiver tracking loops or antennas). This paper investigates and further develops a number of state-of-the-art techniques in this category. They include phase multipath estimation using SNR data, phase multipath estimation through the use of closely spaced antennas, multipath mitigation stochastic models such as the satellite elevation angle model and SNR-based models (SIGMA-∊ model and our modified SNR-based model), and our own novel ray-tracing method. The techniques are tested with both real and simulated data, the real test datasets have been collected on the Laboratoire Central des Ponts et Chaussées (LCPC) testbed near Nantes in France, and on the campus of the University of Nottingham during SPACE data collection experiments.

Thermal Aspect of Frost-Thaw Pavement Dimensioning: In Situ Measurement and Numerical Modeling

The thermal behavior of pavements in winter has a major influence on their dimensioning. The Paris-based Laboratoire Central des Ponts et Chaussées and the Ministère des Transports du Quebec have models to forecast the propagation of frost, frost heave, and thaw events. They have developed a collaborative project to validate these models on an experimental pavement. This pavement was constructed in Quebec in 1998, and its thermal behavior was monitored for 3 years. Two pavements, one with a cement-treated base and one with a hot-mix asphalt pavement, were selected. Two test beds were constructed on each pavement. One test bed was thermally insulated by a layer of extruded polystyrene, and the second was not. The SSR, GEL1D, and CESAR–GELS thermal models; the site and the temperature conditions of the three winters; the pavement structures and their physical properties; the instrumentation setup; and the analysis and comparison of the results of the models among themselves and in relation to the observations conducted on the pavements were assessed. The models provided a satisfactory estimate of frost penetrations, with less than 10% deviation observed between the measured and calculated depths. The deviations between the results of the different models are explained by the differences between the modeling principles. The size and quality of the database constituted will make it possible to improve the thermal forecasting models through more in-depth studies.