Transportation and access to urban services in Dar es Salaam

Transportation in Dar es Salaam is particularly difficult. Statistical data drawn from the 1993 Human Resources Development Survey confirm that in unplanned settlements, transportation conditions and access to urban services are less favourable than in the rest of the city. The poverty of a majority of city inhabitants, the low quality of urban passenger transport and poor accessibility result in daily mobility reduced to the immediate neighbourhood, while in turn tends to perpetuate poverty.Access to urban services ; daily mobility ; Statistical data (HRDS 1993) ; poverty ; Dar es Salaam

Collection of passenger travel data in Sub-Saharan African cities: Towards improving survey instruments and procedures

This paper compares experiences in the application of different approaches to passenger travel data collection in francophone and anglophone cities of West, Central and Southern Africa. Its aim is to identify possible improvements through which common problems might be addressed. The paper draws from the available French and English literature on survey methods applied in Sub-Saharan Africa, as well as from the authors' experiences in designing and administering surveys in this context. Problems are discussed in terms of survey design and administration. Recommendations to address these problems relate to survey preparation, comparative instrument and cognitive testing, hierarchical multi-modal methods, interviewer selection and training methods, and survey administration and monitoring.African cities ; Passenger travel surveys ; Household surveys ; Methods

D comme Dar es Salam ou les dangers du désengagement public

Plus grande ville tanzanienne, Dar es Salam est emblématique de la complexité des problèmes de transport auxquels une grande métropole africaine peut être confrontée. Le système de transport darien a connu depuis le milieu des années 80 des évolutions rapides et relativement incontrôlées. Les auteurs chercheront à présenter ici trois d'entre elles : les pratiques nouvelles en matière d'investissement et d'entretien du réseau de voirie, le glissement du public vers le privé au sein du réseau de transport collectif, la mutation de l'organisation du stationnement des voitures particulières.politique des transports ; financement du transport ; financement des infrastructures ; évolution ; Afrique subsaharienne

Developing a service-oriented component framework for a landscape modeling language

With modeling and simulation, it is possible to study how a system works before trying to predict how it would behave in a variety of situations. However, when modeling landscape processes, issues related to space, time and multiple scales need to be addressed. In order to investigate these issues, a modeling platform based on a Domain Specific Language (DSL) has been developed. One of the main technical challenges of this platform is the ability to build applications with the capacity to themselves dynamically adapt to their environment. In this paper, we present the arguments and motivations behind the choice of the Service- Oriented Computing (SOC) approach when implementing the execution framework of the DSL. The modeling platform is composed of a development environment based on Eclipse IDE, a code generator, and an execution framework. The execution framework, which is the focus of this paper, must meet the constraints set by dynamic landscapes modeling, while capitalizing on the possibilities offered by the SOC approach. (Résumé d'auteur

Sedimentary processes in the Thau Lagoon (France): From seasonal to century time scales

As a part of the MICROBENT programme, an investigation of the sedimentation framework was carried out at the water-sediment interface in the Thau Lagoon (French Mediterranean coast). Two main sites, C4 in the middle of the lagoon and C5 near oyster farms, were visited six times between December 2001 and May 2003. Interface sediments were studied using classical sedimentology parameters (radiography RX, grain size distribution) and analysis of selected radionuclides (234Th, 7Be, 210Pb, 226Ra). On a century time scale, excess 210Pb (210Pbxs) presents classical profiles with an upper mixed layer, followed by an exponential decrease of activities to undetectable levels below 20 – 30 cm. At the central site, C4, cores seem to register episodic changes in mean grain size, presenting recurrently peaks. The upper 10 cm of 210Pbxs profiles at site C5 exhibit a mixed layer associated with coarser sediments: this could be related to biological activity. Sedimentation rates derived from 210Pbxs varied from 0.15 cm y−1 at the edge of the basin, to 0.25 cm y−1 at the central site. On a seasonal time scale, 234Th and 7Be both show significant variations in activities and in penetration within the sediment. Bioturbation rates derived from both radionuclides agree well and range between 1–10 cm2 y−1 at site C4 and 1–31 cm2 y−1 at site C5. 234Th and 7Be fluxes at the water-sediment interface show too seasonal variations, more pronounced for site C5. This latter site presents especially a higher variability that is well marked with season, probably in relation with its position near oyster farms

How Geometry Controls the Tearing of Adhesive Thin Films on Curved Surfaces

Flaps can be detached from a thin film glued on a solid substrate by tearing and peeling. For flat substrates, it has been shown that these flaps spontaneously narrow and collapse in pointy triangular shapes. Here we show that various shapes, triangular, elliptic, acuminate or spatulate, can be observed for the tears by adjusting the curvature of the substrate. From combined experiments and theoretical models, we show that the flap morphology is governed by simple geometric rules.Comment: 6 pages, 5 figure

Comparison of three algorithms for solving the convergent demand responsive transportation problem

International audienceLed by computer science and geography laboratories, this paper presents three algorithms for solving the Convergent Demand Responsive Transport Problem (CDRTP). Two of them are exact: the first one is based on a dynamic programming algorithm to enumerate exhaustively the sprawling spanning trees and the second one is based on a depth first search algorithm. The third one is stochastic and uses a steady state genetic algorithm. These approaches address the problems of scalability and flexibility, are compared and discussed

Marche à pied et pauvreté en Afrique Subsaharienne

Que sait-on sur la marche à pied et sur les citadins africains qui la pratiquent quotidiennement, parfois sur de longues distances ? Finalement, assez peu de choses, tant les enquêtes classiques se concentrent sur les modes motorisés. Partant de ce constat, nous montrons, à l'aide d'enquête mobilité réalisées auprès de ménages de villes sahéliennes, que la marche constitue le mode le plus utilisé. Puis, sur l'exemple de Niamey, nous nous intéressons à mieux connaître la mobilité quotidienne des citadins ne se déplaçant qu'à pied pour la totalité de leurs déplacements. Population globalement défavorisée, les espaces urbains qu'elle fréquente se réduise le plus souvent à la proximité du domicile. En considérant le contexte de rareté de moyens existant dans ces villes, nous apportons quelques pistes pour une meilleure reconnaissance, par les politiques mises en œuvre, de la marche à pied comme mode essentiel dans l'organisation du système de transport et plus globalement dans le fonctionnement des villes au quotidien.Marche à pied ; pauvreté ; Afrique subsaharienne ; Niamey