65 research outputs found
Etude de lâimpact des procĂ©dĂ©s de rafraĂźchissement passif de type « Cool Roof » sur la performance Ă©nergĂ©tique des bĂątiments dans les rĂ©gions chaudes et arides
Algeria, like many emerging countries, improving energy performance, while ensuring
the thermal and environmental quality of buildings has become an essential theme in the
current situation of sustainable development. Currently, the high rate of growth of urban areas
and the unsuitability of construction techniques result in a building stock that is perfectly
indifferent to its context, uncomfortable and energy-consuming, which continues to grow
unceasingly.
As such, the residential building sector is particularly is not only a substantial energy
consumer but also a contributor to greenhouse gas emissions, particularly in the in southern
regions of Algeria where desert conditions prevail. Moreover, in a hot and dry climate, the
continuous exposure of the roof to intense solar radiation mainly contributes to significant
internal overheating and extreme thermal discomfort; making space cooling a basic
requirement of occupants for most of the year. This total dependence on air conditioning
systems leads to considerable energy consumption. However, the roofs of buildings offer
significant opportunities to anticipate climate change and meet contemporary energy
challenges. This requires improving the thermal behaviour of roofs by incorporating passive
cooling processes. In this regard, the objective of this study is to assess the ability of "Cool
Roof" to achieve energy savings and to ensure an acceptable level of thermal comfort in
contemporary homes in Biskra.
As part of our contribution to this problem, a rigorous methodology based on three
complementary approaches has been adopted. As a start, an empirical study was carried out
on a sample of 12 houses representing the most commonly used roofing types in the city of
Biskra. Subsequently, through in-situ measurements and a questionnaire survey, the real
impact of flat, reinforced concrete roofs on the conditions of indoor thermal comfort was
assessed. Additionally, an experimental study was carried out by constructing four small-scale
models, where six passive cooling techniques were evaluated over two consecutive periods,
under real summer conditions. This experiment aimed to compare the thermal feasibility,
economic accessibility and social acceptance of the different solutions, thereby identifying the
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most suitable options for the local context. Finally, a numerical simulation using the
âTRNSYSâ software was carried out to study the influence of the most promising passive
alternatives identified in the experimental study on the energy, thermal, and environmental
efficiency of buildings. The overarching goal was to offer a roof adapted to the local context,
simple, cost-effective and easy to implement on existing surfaces or under construction, while
meeting modern lifestyle requirements.
The study's findings clearly demonstrated that by ensuring adequate protection of roofs,
particularly by optimizing its thermal properties and selecting appropriate roofing materials, it
is possible to improve significantly energy performance of buildings while ensuring a
favourable level of thermal comfort at the same time, reducing carbon footprint
ETUDE GEOCHIMIQUE DES METAUX TRACES DANS LES MILIEUX MARINS ET LACUSTRES
Cette Ă©tude a pour objectif dâĂ©valuer le degrĂ© de contamination inorganique par les mĂ©taux traces dans les sĂ©diments dans le cadre dâune Ă©tude comparative entre quatre Ă©cosystĂšmes aquatiques diffĂ©rents en AlgĂ©rie : Chott Melghir, Barrage Fontaine des gazelles, lac El Mellah et Baie dâAlger. LâĂ©tude de ce dernier site entre dans le cadre du projet de coopĂ©ration COMETALG-Mermex, entre le Centre EuropĂ©en de recherche et d'Enseignement de GĂ©osciences de lâEnvironnement (CEREGE), Aix-Marseille UniversitĂ© et Ecole National SupĂ©rieur des Sciences de la Mer et de lâAmĂ©nagement du Littoral (ENSSMAL). Six carottes sĂ©dimentaires ont Ă©tĂ© prĂ©levĂ©es dans les quatre sites avec un nombre dâĂ©chantillons Ă©gal Ă 130.
Les rĂ©sultats de notre Ă©tude montrent que la composition chimique et minĂ©ralogique des sĂ©diments des Ă©chantillons par XRF et DRX est caractĂ©risĂ©e par la dominance des silicates et des carbonates avec des valeurs proches. Les plus fortes valeurs de la matiĂšre organique sont enregistrĂ©es dans les carottes sĂ©dimentaires du Lac El Mellah, qui est connu par une forte activitĂ© aquacole. MalgrĂ© la diffĂ©rence des quatre sites dâĂ©tude de point de vue du taux dâurbanisation, importance dâagglomĂ©ration et dâactivitĂ© industrielle et agricole, on enregistre une contamination de modĂ©rĂ©e Ă significative pour les mĂ©taux traces Ă©tudiĂ©s avec un enrichissement de naturel Ă significatif qui est dĂ» Ă la nature du sĂ©diment et Ă lâapport continu par les diffĂ©rents oueds des bassins versants des zones dâĂ©tudes. De bonnes corrĂ©lations positives sont observĂ©es pour la majoritĂ© des couples de mĂ©taux, ce qui signifie que ces Ă©lĂ©ments Ă©voluent dans le mĂȘme sens des variations des concentrations dans les carottes sĂ©dimentaires des trois sites (Lac El Mellah, Barrage Fontaine des Gazelles et Chott Melghir), pour la Baie dâAlger, les trois carottes sont constituĂ©es de deux couches de sĂ©diments, avec celle de la surface trĂšs mĂ©langĂ©e, ce qui a rendu trĂšs difficile le calcul des corrĂ©lation inter- mĂ©taux et la datation par le Pb210
Behavior of the dispersed phase in a biphasic liquid-liquid Comportement de la phase dispersé dans un contacteur diphasique liquide-liquide
In this work two major hydrodynamic parameters: the holdup of the dispersed phase
and the Sauter diameter are considered. In the first part, this is done for describing
the hydrodynamics of interacting liquidâliquid dispersions with using different drop
breakup, coalescence and growth models in a droplet population balance model. Based
on the variational iteration method, different process cases have been performed and, it
is possible to find the exact solution or a closed approximate solution of a problem. For
the simultaneous growth and the coalescence terms a comparison between the present
method and projection method which include discontinuous Galerkin and collocation
techniques are made respectively. The results are encouraging and the new method has
proven to be suitable to predict holdup and Sauter diameter profiles.
In the second part, we extended the dual quadrature method of generalized moments
(DuQMoGeM) to solve the population balance model for the hydrodynamics of liquidliquid
extraction columns using a multi-compartment model. The DuQMoGeM results
were compared to analytical solutions for batch and continuous well-mixed vessels and
extraction columns, showing that it is accurate for predicting the evolution of the low
order moments and the drop number distribution along with the column height. We
also modeled a Kš uhni column for which the simulation accurately predicted the steadystate
experimental holdup, encouraging the DuQMoGeM usage to solve the population
balance equation for heterogeneous systems and different columns
Effet des traitements de surfaces sur le comportement microstructural, mĂ©canique et rĂ©sistance Ă lâoxydation des aciers
In this work, the influence of vanadium addition to TiSiN/CrVxN multilayer coatings, deposited by D.C. reactive magnetron sputtering, on the microstructure, mechanical properties, thermal stability and oxidation resistance, was investigated. The results showed that all coatings exhibited a face-centered cubic (fcc) structure; the incorporation of vanadium has no effect on the adhesion and residual stresses values. However, the hardness and Youngâs modulus of the coatings increased with increasing vanadium content in the films, reaching the maximum value of 30 and 347 GPa, respectively, for the highest vanadium concentration, due to solid solution hardening. Annealing has a beneficial effect on the hardness and elastic modulus of the coatings due to the changes on the structure. Inversely, vanadium degrades the oxidation resistance of the films and lowered the onset point of oxidation. Three oxide-layers were formed in the case of the reference TiSiN/CrN film, i.e. TiO2 layer on the top followed by a continuous layer Cr2O3 and, underneath, a continuous Si-O layer. The diffusion kinetics of V rules the oxidation behavior of V containing films, i.e. the higher the V concentration is, the easier the disruption of the formation of the protective continuous oxide layers. However, the friction coefficient is constant independently on the chemical composition of the coatings, and the wear of the coating is driven by polishing wear in case of V-containing coatings
Impact of passive cooling techniques on the thermal behavior of residential buildings in hot and arid regions -An experimental study-
The thermal performance of the roof is one of the most important factors for a comfortable environment. As 50% of the thermal loads received by a building come from the roof, this research seeks to find the roofing system that opposes the transmission of heat during the hottest days and promotes indoor thermal comfort. In this regard, this paper presents an experimental study carried out on four (04) testing cells constructed on a reduced scale and submitted to climatic external conditions. Three (03) cells were used to test passive cooling strategies through the roof, namely: the cool roof, ventilated roof and a roof with inverted earth pots. The fourth cell that served as cell-reference, for its part, a conventional roof. The experimentation concerned the types of roofs most used in residential buildings in Biskra, Algeria. The measurements process was effectuated in an exposed field during the month of July, prevailing the metrological data of the hot and arid climate. The obtained results show that the use of the cool-roof technique makes it possible to record the lowest internal temperatures in comparison with the other systems. Thus, the reflective coating technique is capable of reducing the internal temperature from 3.33 °C to 4.80 °C, also the internal and external surface temperature of the roofs from 5.31 °C to 10.18 °C, respectively. These experimental results confirm the effectiveness of the "cool roof" technique as an innovative and efficient solution that contributes to the achievement of the comfort conditions in a hot and arid climate by eliminating heat gains through the roof
Mobilização de Ăguas Superficiais: ComentĂĄrios Gerais sobre Barragens na ArgĂ©lia no Passado, Presente e Futuro
Algeria is located in a region with an arid climate, which requires rational management of water resources. According to the current state of knowledge, the mobilisation of water through dams started with diversion works before the colonial period. During the colonial period (1830-1962), sixteen dams with a total capacity of one billion m3 were built. It was only after independence that large dams were erected to reach a capacity of about nine billion m3 in 2020. The preservation of these structures is one of the current and future priorities. The phenomenon of silting risks compromising development in terms of water mobilisation. Currently, the storage capacity lost through silting is 11 %. To remedy this phenomenon, studies have been carried out at the University of Biskra (Algeria) with Hydrocoop-France which have made it possible to define new techniques for increasing storage capacity.Argelia se encuentra en una regiĂłn de clima ĂĄrido, que exige una gestiĂłn racional de los recursos hĂdricos. SegĂșn los conocimientos actuales, la movilizaciĂłn del agua con presas comenzĂł con las obras de desviaciĂłn antes del periodo colonial. Durante este periodo (1830-1962) se construyeron diecisĂ©is presas con una capacidad total de mil millones de m3. DespuĂ©s de la independencia, se construyeron grandes presas para alcanzar una capacidad de unos nueve mil millones m3 en 2020. La conservaciĂłn de estas estructuras es una de las prioridades actuales y futuras. El fenĂłmeno del encenagamiento corre el riesgo de comprometer el desarrollo en tĂ©rminos de movilizaciĂłn del agua. Actualmente, la capacidad de almacenamiento que se pierde por sedimentaciĂłn es del 11 %. Para remediarlo, se han realizado estudios en la Universidad de Biskra (Argelia) con Hydrocoop-Francia, que han permitido definir nuevas tĂ©cnicas para aumentar la capacidad de almacenamientoLâAlgĂ©rie est dans une rĂ©gion Ă climat aride, ceci nĂ©cessite une gestion rationnelle de la ressource en eau. Selon lâĂ©tat des connaissances actuelles, la mobilisation des eaux par le biais des barrages a commencĂ© par des ouvrages de dĂ©rivation avant lâĂ©poque coloniale. Pendant cette pĂ©riode (1830â1962), on compte lâĂ©dification de seize barrages dâune capacitĂ© totale dâun milliard de m3. AprĂšs lâindĂ©pendance, des grands barrages ont Ă©tĂ© Ă©rigĂ©s pour atteindre une capacitĂ© dâenviron neuf milliards de m3 en 2020. La prĂ©servation de ces ouvrages est lâune des prioritĂ©s actuelles et futur. Le phĂ©nomĂšne dâenvasement risque de compromettre le dĂ©veloppement en matiĂšre de mobilisation des eaux. Actuellement, la capacitĂ© de stockage perdue par envasement est de 11 %. Pour y remĂ©dier, des Ă©tudes ont Ă©tĂ© rĂ©alisĂ©es Ă lâuniversitĂ© de Biskra (AlgĂ©rie) avec Hydrocoop-France, qui ont permis de dĂ©finir de nouvelles techniques dâaccroissement de la capacitĂ© de stockage.L'Algeria si trova in una regione dal clima arido, che richiede una gestione razionale delle risorse idriche. Secondo lo stato attuale delle conoscenze, la mobilitazione dell'acqua attraverso le dighe Ăš iniziata con opere di deviazione prima del periodo coloniale. Durante il periodo coloniale (1830-1962), furono costruite sedici dighe con una capacitĂ totale di un miliardo di m3. Solo dopo l'indipendenza sono state erette grandi dighe per raggiungere una capacitĂ di circa nove miliardi di m3 nel 2020. La conservazione di queste strutture Ăš una delle prioritĂ attuali e future. Il fenomeno dell'insabbiamento rischia di compromettere lo sviluppo in termini di mobilitazione dell'acqua. Attualmente, la capacitĂ di stoccaggio persa a causa dell'insabbiamento Ăš dell'11 %. Per rimediare a questo fenomeno, sono stati condotti studi all'UniversitĂ di Biskra (Algeria) con Hydrocoop-France che hanno permesso di definire nuove tecniche per aumentare la capacitĂ di stoccaggio.A ArgĂ©lia estĂĄ situada numa regiĂŁo de clima ĂĄrido, o que requer uma gestĂŁo racional dos recursos hĂdricos. De acordo com o estado actual dos conhecimentos, a mobilização da ĂĄgua atravĂ©s de barragens começou com obras de desvio antes do perĂodo colonial. Durante este tempo (1830-1962), foram construĂdas dezasseis barragens com uma capacidade total de um biliĂŁo de m3. ApĂłs a independĂȘncia grandes barragens foram erguidas para atingir uma capacidade de cerca de nove mil milhĂ”es de m3 em 2020. A preservação destas estruturas Ă© uma das prioridades actuais e futuras. O fenĂłmeno do assoreamento corre o risco de comprometer o desenvolvimento em termos de mobilização de ĂĄgua. Actualmente, a capacidade de armazenamento perdida atravĂ©s do assoreamento Ă© de 11 %. Para remediar, foram realizados estudos na Universidade de Biskra (ArgĂ©lia) com Hydrocoop-France que permitiram definir novas tĂ©cnicas para aumentar a capacidade de armazenament
Suppression of crown and root rot of wheat by the rhizobacterium Paenibacillus polymyxa
A seedling bioassay was developed for screening a wheat root-associated rhizobacterial strain of Paenibacillus polymyxa for ability to suppress crown and root rot pathogens of wheat. The primary aim was to evaluate the ability of P. polymyxa to suppress Fusarium graminearum, F. culmorum, F. verticillioides and Microdochium nivale, the fungal pathogens responsible for Fusarium crown and root rot and head blight of wheat in Algeria. Bioassays conducted under controlled conditions indicated that seed treatments with P. polymyxa strain SGK2 significantly reduced disease symptoms caused by all four fungal pathogens. Plant growth promotion (increased shoot and root dry weights), however, depended on the pathogen tested. Our results indicate that seed treatments with a biocontrol agent could be an additional strategy for management of wheat crown and root rot pathogens
Optimisation de la forme du déversoir en touches de piano (PK-Weir) par voies numérique et expérimentale
Le dĂ©versoir en touche de piano (PK-Weir) permet un bon compromis entre le besoin dâune
grande capacitĂ© de dĂ©versement et la largeur limitĂ©e de lâemplacement disponible sur le site de
barrage. De plus, son faible coĂ»t par rapport aux dĂ©versoirs vannĂ©s, sa simplicitĂ© dâutilisation
en font une solution intéressante.
Cette solution est également avantageusement utilisée dans des ouvrages de déversement ou de
protection pour les canaux et usines hydroĂ©lectriques au fil de lâeau. Ces avantages ont incitĂ©
plusieurs laboratoires de recherche et organismes du domaine des barrages à procéder à des
études et essais hydrauliques sur des modÚles physiques pour définir la forme optimale de PKWeir.
Cependant, la modélisation numérique de l'écoulement sur le PK-Weir qui peut aider au
prĂ©-dimensionnement du PK-Weir nâa fait l'objet que de quelques travaux rĂ©alisĂ©s
essentiellement par EDF-France.
La géométrie du déversoir en touches de piano se caractérise par un nombre important de
variables, ce qui ne permet pas la définition de la forme optimale par voie directe et nécessite
le recours Ă lâexpĂ©rimentation sur modĂšles rĂ©duits physiques, cependant, ceci nĂ©cessite la
rĂ©alisation dâun nombre de modĂšles physiques trĂšs important qui implique des dĂ©penses
onéreuses et beaucoup du temps. Actuellement on peut recenser plus de 300 modÚles physiques
qui ont été testés dans plusieurs laboratoires sans pour autant définir une forme optimale du
PK-Weir. La solution qui parait possible est de faire recours à la modélisation numérique pour
définir quelques formes optimales qui seront validés par quelques essais sur modÚles physiques.
Ceci permet de rĂ©aliser plusieurs tests sur modĂšles numĂ©riques dans un temps trĂšs court et Ă
coût faible
Ce travail s'inscrit dans le cadre d'une contribution Ă l'Ă©tude de l'optimisation de la forme du
PK-Weir par une modélisation numérique qui est réalisée essentiellement par le code Flow-3D.
Une confrontation avec les résultats expérimentaux a été effectuée et a montré une convergence
des résultats
Dégradation du Xyloglucane par les souches de Paenibacillus polymyxa isolées de la rhizosphÚre du blé dur sur des sols Algériens
Les espĂšces du genre Paenibacillus secrĂštent une variĂ©tĂ© dâenzymes extracellulaires parmi lesquelles figurent plusieurs types de ÎČ glucanases.
Nous avons rĂ©alisĂ© un test de dĂ©gradation du xyloglucane sur 29 souches isolĂ©es par immunopiĂ©geage et identifiĂ©es Ă P. polymyxa par le systĂšme API50CHB. Ces souches ont Ă©tĂ© groupĂ©es en sĂ©ries qui correspondent aux Ă©chantillons de sols Ă partir desquels elles avaient Ă©tĂ© isolĂ©es. Des souches de rĂ©fĂ©rences et des souches type E. coli ont Ă©tĂ© intĂ©grĂ©es lors de cette Ă©tude pour comparer leur activitĂ© Ă celles des souches isolĂ©es des sols dâAlgĂ©rie.
Les rĂ©sultats de cette recherche montrent que toutes les souches de P. polymyxa sont capables de dĂ©grader le xyloglucane, alors que les souches des espĂšces testĂ©es nâont pas cette activitĂ©. Ces rĂ©sultats semblent suggĂ©rer que cette propriĂ©tĂ© est partagĂ©e par tous les P. polymyxa et quâelle nâest pas liĂ©e au sol dâorigine de nos souches ni Ă lâanciennetĂ© de culture du blĂ© de ces sols. Nous avons Ă©galement montrĂ© que la xyloglucanase fait partie du pool dâenzymes inductibles qui ne sont normalement prĂ©sentes quâĂ lâĂ©tat de traces dans les bactĂ©ries, et dont la synthĂšse est amplifiĂ©e considĂ©rablement en prĂ©sence de leur substrat
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