Perga M.-E.,French National Institute for Agricultural Research |
Desmet M.,National School of Public Works |
Desmet M.,University of Tours |
Enters D.,University of Bremen |
And 2 more authors.
Limnology and Oceanography | Year: 2010
We reconstructed the changes in the planktonic food web of an oligotrophic subalpine lake over the past century, combining paleoecological methods and historical monitoring data. Analyses of organic matter δ 15N from sediment cores show that nutrient enrichment started in the 1910s and intensified from the 1930s. Subsequent changes in sediment organic carbon content and accumulation rates, carotenoid pigment concentrations, organic matter δ 13C, and cladoceran subfossil remains show that excess nutrient inputs triggered bottom-up-driven increases in lake primary production, as well as in Daphnia abundance. Daphnia size, however, started to decrease in the late 1930s, indicating an increasing size-selective predation from zooplanktivorous whitefish populations (Coregonus lavaretus) that had been fostered by stocking and increased food availability. Whitefish predation is likely to have indirectly facilitated the establishment of Bosmina longirostris. With decreasing nutrient concentrations, Daphnia abundance decreased, but their size declined, presumably due to an ongoing size-selective predation. At this same time, Bosmina abundance doubled as a likely result of released interspecific competition from smaller Daphnia. δ 15N analyses on subfossil cladoceran remains revealed that these changes in cladoceran community structure were accompanied by major changes in the food web. In spite of successful measures to reduce nutrient inputs from the late 1960s and reduced primary production, anoxia still occurs every summer at the lake bottom. These patterns are the consequence of a still relatively high export of phytoplankton-derived organic matter to the sediment as a result of strong top-down effects on the planktonic food chain. © 2010, by the American Society of Limnology and Oceanography, Inc.
Agency: Cordis | Branch: H2020 | Program: CSA | Phase: MG-3.6-2016 | Award Amount: 3.00M | Year: 2016
SaferAfrica project aims at establishing a Dialogue Platform between Africa and Europe focused on road safety and traffic management issues. It will represent a high-level body with the main objective of providing recommendations to update the African Road Safety Action Plan and the African Road Safety Charter, as well as fostering the adoption of specific initiatives, properly funded. The involvement of Development Banks will ensure the identification of available resources and the definition of suitable schemes of funding. The activity of the Platform will also focus on the reinforcement of the endogenous African capabilities through the dissemination of the EU know-how. Twinning Programs will be set up, besides the conduction of different training activities. Local contexts will be duly taken into account and studies on specific risk factors as well as transferability analysis of measures already tested elsewhere will be conducted. The project activities will be oriented to the Safe System approach and grouped in four pillars: Road Safety Knowledge and Data; Road Safety and Traffic management Capacity Review; Capacity Building and Training; Sharing of Good Practices. The platform will work at two levels. A decision making level, run by a Management Board basing its actions on information provided and activities carried out by a technical level, with established Working Groups addressing specific topics. The Management Board will be constituted by prominent institutions like EC, the African Union Commission, Financial Institutions, Regional Economic Communities (UN). The technical level will involve government and research institutions, international and stakeholders organizations (e.g. NGOs), with a fair balance between African and EU partners, even for what concerns responsibilities (e.g. Euro-African work package co-leadership). The Dialogue Platform is intended to constitute a stable body, able to orient road safety policies beyond the project end.
Oyebog S.A.,University of Buea |
Ako A.A.,Hydrological Research Center Yaounde |
Nkeng G.E.,National School of Public Works |
Suh E.C.,University of Buea
Journal of Geochemical Exploration | Year: 2012
In this study, 8 bottled water brands sold in Cameroon were analyzed for 76 elements/parameters by ICP-MS, IC, titration and mass spectrometric methods. This was to investigate the geochemical characteristics of the bottled waters in order to identify the main hydro geochemical processes controlling their chemical content. A comparison of the element concentrations and the legal limits for both bottled and tap water (Cameroon, EU, US EPA, WHO) shows that Aluminium concentration in three brands is above the lower guideline value set by EPA with very high lead concentration (6.4μg/l) in one brand. Various water quality classification systems were used in to characterize the different bottled water types. Piper diagram was used to establish that dominant chemical types of the bottled water brands are Ca-HCO 3, Ca-Mg-HCO 3, Ca-Na-Mg-HCO 3, Na-HCO 3 and Na-Mg-HCO 3. Application of R-Mode factor analysis to the data set allowed the determination of the possible relationship between the distribution of individual elements and lithology or other surface enrichment phenomena. In particular waters draining through volcanic rocks are enriched in elements such as As, B, Br -, Cl -, Cs, F, K, Li, Na, NO 3 -, PO 4 3-, Rb, Sc, SiO 2, Sr, Te, Ti, and V. One of the three R-Mode factor analysis associations, recognized as being representative of elements analyzed shows high nitrate and Pb loadings along with As, PO 4 3- and Zn. The latter association probably reflects a sign of anthropogenic contribution in the volcano-sedimentary aquifers of the study area. Q-Mode hierarchical cluster analysis established four major groups amongst the bottled water brands. Stable water isotopes (δD and δO 18) established that the recharge origin of the bottled waters and other groundwaters of the study area is meteoric. © 2011 Elsevier B.V.
Nguyen Q.T.,National School of Public Works |
Di Benedetto H.,National School of Public Works |
Sauzeat C.,National School of Public Works
Road Materials and Pavement Design | Year: 2012
This paper describes investigation into the change of temperature of asphalt mixtures during cyclic tests on cylindrical specimens. Tension-compression tests were performed at different strain amplitudes (from 55 μm/m to 133 μm/m). Temperature is measured at the surface and inside the specimen. From the analysis of the experimental results, the thermal conductivity (k) and the convection heat transfer coefficient (h) were determined during the steady temperature phase. The specific heat coefficient (C) of the material was determined during the transient temperature phase. This parameter is also indentified using a finite element simulation of the heat process. A thermal conductivity of 1.35 W/(m.°C) and a specific heat of 820 J/(kg.°C) were found for the asphalt mixtures used in this research. These values are quite realistic when compared to values proposed in the literature that are obtained using the traditional thermophysical measurements. Furthermore, the thermal parameters obtained from FP2C, a device used for the identification of thermal properties of materials, confirm the results. © 2012 Taylor & Francis.
Marquis-Favre C.,National School of Public Works |
Morel J.,National School of Public Works
International Journal of Environmental Research and Public Health | Year: 2015
Total annoyance due to combined noises is still difficult to predict adequately. This scientific gap is an obstacle for noise action planning, especially in urban areas where inhabitants are usually exposed to high noise levels from multiple sources. In this context, this work aims to highlight potential to enhance the prediction of total annoyance. The work is based on a simulated environment experiment where participants performed activities in a living room while exposed to combined road traffic and industrial noises. The first objective of the experiment presented in this paper was to gain further understanding of the effects on annoyance of some acoustical factors, non-acoustical factors and potential interactions between the combined noise sources. The second one was to assess total annoyance models constructed from the data collected during the experiment and tested using data gathered in situ. The results obtained in this work highlighted the superiority of perceptual models. In particular, perceptual models with an interaction term seemed to be the best predictors for the two combined noise sources under study, even with high differences in sound pressure level. Thus, these results reinforced the need to focus on perceptual models and to improve the prediction of partial annoyances. © 2015 by the authors; licensee MDPI, Basel, Switzerland.
Gueridi F.,National School of Public Works |
Derriche Z.,National School of Public Works
Geomechanics from Micro to Macro - Proceedings of the TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, IS-Cambridge 2014 | Year: 2015
The immediate reaction which occurs in lime-soil mixtures, is presented as being of physicochemical nature resulting from particle clay flocculation provoked by exchange of cations of the clay by calcium brought about by lime. Observations of the immediate effects of lime soil treatment refute somehow the hypotheses advanced so far to explain the mechanisms of soil-lime reactions. The long term reaction on the other hand, is defined as being of pozzolanic nature. Analyzing the immediate effects observed on a lime treated soil, we have underlined in a previous study, the possible presence of a chemical reaction responsible of the observed irreversible modifications. In order to gain a better understanding of this reaction, we present here some experimental results we use to try to analyze the lime-reaction. Results obtained indicate that lime consumption is far more important in the immediate reaction than that in the long term reaction. These results call naturally for more research work to achieve a better understanding of the nature of the phenomena constructing lime-soil reactions in order to ameliorate the outcome of this promising soil-stabilization technique. © 2015 Taylor & Francis Group.
Ako A.A.,Kumamoto University |
Ako A.A.,Hydrological Research Center Yaounde Cameroon |
Eyong G.E.T.,Hydrological Research Center Yaounde Cameroon |
Nkeng G.E.,National School of Public Works
Water Resources Management | Year: 2010
Cameroon is blessed with abundant water resources. Rapid population increase, unplanned urbanisation, intensive industrial and socio-economic development have led to poor and unsustainable management of these resources. Integrated Water Resources Management (IWRM) is a promising approach in ensuring sustainable management of Cameroon's water resources. It entails management of water for various purposes and not for a single purpose which therefore involves different stake holders aiming at achieving sustainable water resources management. This paper seeks to evaluate recent efforts to implement in IWRM in Cameroon by examining the institutional framework for IWRM in Cameroon, conditions for the implementation of IWRM and proposes reforms for improving IWRM in Cameroon. The paper concludes that reforms such as public participation at local council levels, recognition of water as both an economic and a social good, putting IWRM within the larger context of Integrated Natural Resource Management (INRM) and the exploitation of mathematical models within hydrological basins will improve IWRM in Cameroon. © 2009 Springer Science+Business Media B.V.
Gress J.C.,National School of Public Works
5th Asia-Pacific Conference on Unsaturated Soils 2012 | Year: 2012
Using the simple filter paper test, controlling at the same time the variation of void index, we have a good assessment of the law of the variation of void index with suction or of the swelling pressure, if displacement is not possible. We also show how this test allows knowing of in situ variation of soil stiffness, with moisture content.
Belabdelouahab F.,National School of Public Works |
Trouzine H.,University Djilali Liabes
Physics Procedia | Year: 2014
Currently engineers seeking to improve the characteristics of soils used for the construction of earthworks, with innovations developed from ideas, products or processes of original construction, the land army is an early example particularly successful but there are many other processes as well as other Pneusol processes more or less known to sometimes use bulky industrial wastes, while fitting well into the existing environment. In this paper, we discuss a particular research work within the framework of environmental protection and sustainable development, led to the realization of the recovery and reuse of used tires in the construction of works civil engineering. The main objective of this paper is to present the results of studies in Algiers on ENSTP " Pneusol reducing the thrust" on a scale model on the study of a retaining wall reinforced by a simulation tablecloths tires, and the results of particular research enterprise at the University Djillali Liabes of Sidi Bel Abbes, on an experimental campaign on the Pneusol under expansive soil foundations. Topics will also present the projects carried out in Algeria, as the pilot of stability of a slope to Pneusol in Bousmail (2005), then another item of protection against landslides in Bejaia (2006), from the project of Africa in Mostaganem (2007), concerning the stability of an embankment on the RN11 road, and the conduct of a small dike protection technology Pneusol in Blida (2008), and in 2010 the stability of a landslide in Miliana. © 2014 Elsevier B.V.
Belabdelouhab F.,National School of Public Works |
Kebaili N.,University of Ouargla
Energy Procedia | Year: 2015
The importance of protecting and conserving the environment has led the research community to think seriously about the use of used tyres in the field of civil Engineering, as a mean to absorb the huge quantities spread all over the world. The research has found that used tyre could resolve some problems related to stability or bearing and also to protect certain structures. The problem of used tyre is a problem related to all countries; in fact millions of tonnes of waste are thrown away prompting a serious threat to the ozone layer. In this article, it will be discussed the construction of a backfill in a full scale. This backfill is set at the bottom of a big slope reaching 20m high, conducted during the construction of a highway in Sidi Lakhdar in the wilaya of Mostaganem West of Algiers. Layers of used tyres were spread on a orthorhombic pattern over a height of about 20m and a base length of 100m. The analysis and later the checks conducted were able to quantity the degree of success of this technique "Pneusol" for slope stability, as well as its effect on improving the soil against skidding, of course in addition to its environmental importance. This project which is the second one conducted in full scale in Algeria will have the benefit to improve slope stability for the adjacent road. In this project we absorbed about 6000 used tyres of trucks. © 2015 The Authors. Published by Elsevier Ltd.