La faune ichtyologique des bassins du Mono et du lac Togo (Togo)

D'une façon générale le climat du Togo peut se diviser en deux régimes principaux : un régime subéquatorial au Sud et un régime tropical au Nord. Le Mono qui coule du Nord au Sud subit l'influence combinée de ces deux climats. Son régime hydrologique est du type tropical de transition, c'est-à-dire qu'il n'y a qu'une crue mais plus durable que celle des rivières de la région sahélo-soudanienne. Au total, 50 espèces ont été recensées dans le Mono grâce à divers moyens d'échantillonnage. Cela est assez loin de la capacité théorique qui est estimée à 60-61 si l'on considère l'ensemble du bassin versant mais se situe près de la capacité théorique calculée (52-53) sur une base ne prenant en compte que la partie du Mono toujours en eau, le cours supérieur étant asséché environ six mois de l'année. Le régime alimentaire de 20 espèces a été étudié, il ne diffère pas de ce qui est habituellement observé dans les autres rivières d'Afrique de l'Ouest. Certaines espèces ont une période de reproduction limitée durant la saison des hautes eaux, d'autres n'ont pas de saison de frai particulière. La fécondité observée sur neuf espèces est de l'ordre de celle constatée chez les mêmes espèces d'Afrique occidentale. (Résumé d'auteur

Straightness of rectilinear vs. radio-concentric networks: modeling simulation and comparison

International audienceThis paper proposes a comparison between rectilinear and radio-concentric networks. Indeed, those networks are often observed in urban areas, in several cities all over the world. One of the interesting properties of such networks is described by the \textit{straightness} measure from graph theory, which assesses how much moving from one node to another along the network links departs from the network-independent straightforward path. We study this property in both rectilinear and radio-concentric networks, first by analyzing mathematically routes from the center to peripheral locations in a theoretical framework with perfect topology, then using simulations for multiple origin-destination paths. We show that in most of the cases, radio-concentric networks have a better straightness than rectilinear ones. How may this property be used in the future for urban networks

Warm mix asphalt: mechanical performance assessment and coating quality evaluation

Asphalt mix manufacturing requires heating and the drying of aggregates. The induced energy cost has opened the way to develop alternatives processes with low energy/ carbon materials such as Warm Mix (WMA). Their manufacturing requires specifics techniques to achieve similar performances to those of Hot Mix (HMA). However, the manufacturing temperature reduction can locally lead to imperfect bonding between bitumen and aggregates, although bonding quality measurement remains a challenge. This paper deals with mechanical performance of some mixes manufactured according to WMA processes in comparison to HMA. In addition, bitumen was extracted from the mixes and its rheological properties were studied. In a second step, the bonding quality was assessed by studying the heat fluxes exchanged between hot bitumen and warm aggregate in asphalt mix manufacturing conditions. This approach is based on the Thermal Contact Resistance (TCR) assessment at the binder / aggregate interface. The TCR reflects the contact imperfection at the microscopic scale when two materials are put into contact. This TCR was proposed as bonding quality indicator. Our studies showed that bonding quality depends on bitumen and aggregate temperatures during the contact. The higher the component’s temperatures, the lower the TCR values and better the bonding quality

Warm mix asphalt : Mechanical performances assessment and bonding quality measurement by thermal contact resistance

The classical asphalt mix manufacturing commonly requires the heating and the complete drying of aggregates. The induced energy cost has opened the way to develop alternatives processes with low energy/ carbon materials such as Warm Mix Asphalt (WMA). Their manufacturing requires specifics techniques to achieve similar performances than Hot Mix Asphalt (HMA). However, manufacturing temperature reduction can locally lead to incomplete aggregate coating by bitumen, although the coating quality measurement remains a challenge. This paper deals with modulus and fatigue performances of some bituminous mixtures manufactured at warm temperatures according to WMA processes in comparison with HMA. In addition, the binder has been extracted from asphalt and complex modulus has been studied. In a second step, an innovative thermal approach based on experimental and numerical method was studied. This approach is based on the Thermal Contact Resistance (TCR) assessment at the interface between the binder and the warm aggregate at the manufacturing step. This TCR is proposed as a coating quality indicator measurement. Our studies have shown that bonding quality depends on bitumen and aggregate temperatures during the contact. The higher the temperature, the lower the TCR and the better the bonding quality. Moreover, we found that TCR value is influenced by additives to modified bitumen properties