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Partager le résultat de cette recherche Interroger des sources externesEtude de la variation spatiotemporelle des précipitations dans le Nord-Est algérien. / Noureddine Merniz
Titre : Etude de la variation spatiotemporelle des précipitations dans le Nord-Est algérien. Type de document : texte imprimé Auteurs : Noureddine Merniz, Auteur ; Ali Tahar, Directeur de thèse Mention d'édition : 02/03/2021 Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2021 Importance : 147 f. Format : 30 cm. Note générale : 1 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
BiologieTags : Biologie et Ecologie Végétale:Ecologie végétale Nord-Est algérien variabilité climatique précipitation tendance régionalisation test de Mann-Kendall Northeastern Algeria climate variability precipitation trend regionalization Mann-Kendall test شمال شرق الجزائر تغيرات المناخية هطول الامطار الاتجاه الأقلمة إختبار مان-كيندال Index. décimale : 570 Sciences de la vie. Biologie Résumé :
Precipitation variability is one of the most important elements for climate and hydrometeorological studies. North African countries, and specifically Algeria, have an increased sensitivity to climate variability, particularly the precipitation, due to its effect on economic, social and demographic structure. In the present study, the main objective is to contribute to a better understanding of the spatial and temporal variability of rainfall for 22 meteorological stations distributed in Northeastern Algeria for the period1978-2010. The results showed that, spatially, precipitation decreases from North to South and from
East to West. The application of the Mann–Kendall test to the time series data showed that for annual precipitation, no station showed statistically significant trends, unlike the number of rainy days, where there was a significant negative trend in four stations (Jijel, Constantine, Oum El Bouaghi and Tébessa). For the monthly time series, significant positive trends were observed during the months of September in the coastal stations and July for the plateaus and southern Saharan Atlas stations, while significant negative trends were recorded during the months of February and March for the stations of the extreme
East in the study area. The regionalization of stations in northeastern Algeria based on inter-annual variability through Principal Component Analysis (PCA) and Hierarchical Ascending Classification
(HAC) has identified five distinct groups of stations for the period 1978-2010. These results revealed that for the period analyzed, there was no significant climate change in northeastern Algeria but there is a seasonal delay.
Note de contenu : Annexes. Diplôme : Doctorat en sciences En ligne : ../theses/biologie/MER7721.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=11555 Etude de la variation spatiotemporelle des précipitations dans le Nord-Est algérien. [texte imprimé] / Noureddine Merniz, Auteur ; Ali Tahar, Directeur de thèse . - 02/03/2021 . - جامعة الإخوة منتوري قسنطينة, 2021 . - 147 f. ; 30 cm.
1 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
BiologieTags : Biologie et Ecologie Végétale:Ecologie végétale Nord-Est algérien variabilité climatique précipitation tendance régionalisation test de Mann-Kendall Northeastern Algeria climate variability precipitation trend regionalization Mann-Kendall test شمال شرق الجزائر تغيرات المناخية هطول الامطار الاتجاه الأقلمة إختبار مان-كيندال Index. décimale : 570 Sciences de la vie. Biologie Résumé :
Precipitation variability is one of the most important elements for climate and hydrometeorological studies. North African countries, and specifically Algeria, have an increased sensitivity to climate variability, particularly the precipitation, due to its effect on economic, social and demographic structure. In the present study, the main objective is to contribute to a better understanding of the spatial and temporal variability of rainfall for 22 meteorological stations distributed in Northeastern Algeria for the period1978-2010. The results showed that, spatially, precipitation decreases from North to South and from
East to West. The application of the Mann–Kendall test to the time series data showed that for annual precipitation, no station showed statistically significant trends, unlike the number of rainy days, where there was a significant negative trend in four stations (Jijel, Constantine, Oum El Bouaghi and Tébessa). For the monthly time series, significant positive trends were observed during the months of September in the coastal stations and July for the plateaus and southern Saharan Atlas stations, while significant negative trends were recorded during the months of February and March for the stations of the extreme
East in the study area. The regionalization of stations in northeastern Algeria based on inter-annual variability through Principal Component Analysis (PCA) and Hierarchical Ascending Classification
(HAC) has identified five distinct groups of stations for the period 1978-2010. These results revealed that for the period analyzed, there was no significant climate change in northeastern Algeria but there is a seasonal delay.
Note de contenu : Annexes. Diplôme : Doctorat en sciences En ligne : ../theses/biologie/MER7721.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=11555 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité MER/7721 MER/7721 Thèse Bibliothèque principale Thèses Disponible
Titre : Influence réciproque des précipitations discontinues et continues dans les systèmes Cu-Sn et Al-Ag Type de document : texte imprimé Auteurs : Messaoud Fatmi ; Univ. de Constantine, Éditeur scientifique ; R. Halimi, Directeur de thèse Année de publication : 1996 Importance : 81 f. Note générale : 03 disponibles au magasin de la bibliothèque centrale Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : Précipitation Alliage Métal Index. décimale : 530 Physique Permalink : index.php?lvl=notice_display&id=3360 Influence réciproque des précipitations discontinues et continues dans les systèmes Cu-Sn et Al-Ag [texte imprimé] / Messaoud Fatmi ; Univ. de Constantine, Éditeur scientifique ; R. Halimi, Directeur de thèse . - 1996 . - 81 f.
03 disponibles au magasin de la bibliothèque centrale
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : Précipitation Alliage Métal Index. décimale : 530 Physique Permalink : index.php?lvl=notice_display&id=3360 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité FAT/2925 FAT/2925 Thèse Bibliothèque principale Thèses Disponible 
Titre : Etude de la Cinétique de Précipitation dans les Alliages Al-Mg-Si contenants différentes teneurs des éléments d’additions Type de document : texte imprimé Auteurs : Fares Serradj, Auteur ; Rebai Guemini, Directeur de thèse Editeur : constantine [Algérie] : Université Constantine 1 Année de publication : 2014 Importance : 128 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : Alliages Al-Mg-Si Précipitation Cinétique de transformation Excès de silicium DSC Energie d’activation Traitements thermiques Al-Mg-Si alloys Precipitation Transformation kinetics Excess silicon Activation energy Heat treatments سبائك الألمنيوم المنغزيوم السيلسيوم الترسبات حركية التحول فائص في السيلسيوم الماسح الحراري التفاضلي طاقة النشاط المعالجة الحرارية Index. décimale : 530 Physique Résumé :
The aluminium alloys; in particular the Al-Mg-Si alloys (6xxx series) have a great interest for their privileged uses in the automotive and aeronautical industries. The aims of this research is focused on the comprehension of the influence of the addition elements and more particularly copper and excess silicon on the microstructure, the precipitation kinetics and the mechanical properties in Al-Mg-Si alloys series. The use of the different experimental techniques such as transmission electronic microscopy (TEM), differential scanning calorimetry (DSC) and Hardness Vickers (Hv) allowed us to define the influence of the addition elements on the precipitation kinetics, and to characterize age-hardening behavior of the Al-Mg-Si alloys. The effect of artificial ageing, natural ageing and preaging heat treatments on the microstructural evolution and the mechanical properties was studied, too. The Al-Mg-Si alloys with excess silicon presents the largest density of precipitates. The alloys with an excess of silicon require larger activation energy for precipitation despite the acceleration of the precipitation by the excess of silicon. The precipitation sequence of the four Al-Mg-Si alloys depends on the concentration of the addition elements silicon and copper. It is obtained as: Formation of Guinier - Preston (G.P) zones precipitation of ’’ phase precipitation of ’ or Q’ phase precipitation of phase and/or the Si particles. The copper addition to the Al-Mg-Si alloys led to the mechanical properties improvement after the heat treatment of an artificial ageing at 185°C. The double effect of the addition copper (0,10%) and the excess silicon (0,50%) in Al-Mg-Si alloys is found to have a very significant effect on the improvement of the mechanical properties (Hardness), especially after a preaging heat treatment. Key words: Al-Mg-Si alloys, Precipitation, Transformation kinetics, Excess silicon, DSC, Activation energy,Diplôme : Doctorat en sciences En ligne : ../theses/physique/SER6457.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=9493 Etude de la Cinétique de Précipitation dans les Alliages Al-Mg-Si contenants différentes teneurs des éléments d’additions [texte imprimé] / Fares Serradj, Auteur ; Rebai Guemini, Directeur de thèse . - constantine [Algérie] : Université Constantine 1, 2014 . - 128 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : Alliages Al-Mg-Si Précipitation Cinétique de transformation Excès de silicium DSC Energie d’activation Traitements thermiques Al-Mg-Si alloys Precipitation Transformation kinetics Excess silicon Activation energy Heat treatments سبائك الألمنيوم المنغزيوم السيلسيوم الترسبات حركية التحول فائص في السيلسيوم الماسح الحراري التفاضلي طاقة النشاط المعالجة الحرارية Index. décimale : 530 Physique Résumé :
The aluminium alloys; in particular the Al-Mg-Si alloys (6xxx series) have a great interest for their privileged uses in the automotive and aeronautical industries. The aims of this research is focused on the comprehension of the influence of the addition elements and more particularly copper and excess silicon on the microstructure, the precipitation kinetics and the mechanical properties in Al-Mg-Si alloys series. The use of the different experimental techniques such as transmission electronic microscopy (TEM), differential scanning calorimetry (DSC) and Hardness Vickers (Hv) allowed us to define the influence of the addition elements on the precipitation kinetics, and to characterize age-hardening behavior of the Al-Mg-Si alloys. The effect of artificial ageing, natural ageing and preaging heat treatments on the microstructural evolution and the mechanical properties was studied, too. The Al-Mg-Si alloys with excess silicon presents the largest density of precipitates. The alloys with an excess of silicon require larger activation energy for precipitation despite the acceleration of the precipitation by the excess of silicon. The precipitation sequence of the four Al-Mg-Si alloys depends on the concentration of the addition elements silicon and copper. It is obtained as: Formation of Guinier - Preston (G.P) zones precipitation of ’’ phase precipitation of ’ or Q’ phase precipitation of phase and/or the Si particles. The copper addition to the Al-Mg-Si alloys led to the mechanical properties improvement after the heat treatment of an artificial ageing at 185°C. The double effect of the addition copper (0,10%) and the excess silicon (0,50%) in Al-Mg-Si alloys is found to have a very significant effect on the improvement of the mechanical properties (Hardness), especially after a preaging heat treatment. Key words: Al-Mg-Si alloys, Precipitation, Transformation kinetics, Excess silicon, DSC, Activation energy,Diplôme : Doctorat en sciences En ligne : ../theses/physique/SER6457.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=9493 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité SER/6457 SER/6457 Thèse Bibliothèque principale Thèses Disponible Documents numériques
texte intégraleAdobe Acrobat PDF
Titre : Etude de la precipitation des phases S'/S etT1 dans un alliage quaternaire a base d’aluminium vieilli a differentes temperatures. identification par diffraction electronique a transmission.. Type de document : texte imprimé Auteurs : Halima Djaaboube, Auteur ; Djamila Thabet-Khireddine, Directeur de thèse Editeur : constantine [Algérie] : Université Constantine 1 Année de publication : 2014 Importance : 215 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : 8090 alloy precipitation S’/S T1 DSC XRD Hv TEM diffraction Alliage 8090 précipitation DRX, Hv, diffraction par MET.
سبیكة 8090 ترسب الحیود بواسطةMETIndex. décimale : 530 Physique Résumé :
Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), microhardness and Transmission Electron Microscopy (TEM) are used to study the precipitation of Al2CuMg (S’/S) and Al2LiCu (T1) phases which lead to structural strengthening of Al-2,7Li-1,4Cu- 1Mg-0,11Zr (wt%) alloy (8090).
DSC results for aged samples for various times at 160, 190 and 210°C, show that threshold-times for (S’+T1) precipitation are 2h, 30mn and 15 mn respectively. These results are confirmed by XRD.
DSC analysis, for the water quenching state, carried out with various scanning rates, permits to evaluate the activation energy of (GPBS’+δ’) formation, activation energy of their dissolution and activation energy of (T1 + S’/S) precipitation.
TEM diffraction revealed extra-reflexions from the orthorhombic S’/S and hexagonal T1 phases in addition to those of α matrix and L12 structure δ’ and β’ phases.
Theoretical study, based on orientation relationships precipitate/matrix, shows that 12 different systems S’/S and 12 variants T1 can simultaneously diffract with α matrix. Two diagrams
100 and 112
are plotted on which the S’/S and T1 reflexions are indexed. The obtained results for the theoretical patterns are in good agreement with those observed experimentally.Diplôme : Doctorat en sciences En ligne : ../theses/physique/DJA6440.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=9472 Etude de la precipitation des phases S'/S etT1 dans un alliage quaternaire a base d’aluminium vieilli a differentes temperatures. identification par diffraction electronique a transmission.. [texte imprimé] / Halima Djaaboube, Auteur ; Djamila Thabet-Khireddine, Directeur de thèse . - constantine [Algérie] : Université Constantine 1, 2014 . - 215 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : 8090 alloy precipitation S’/S T1 DSC XRD Hv TEM diffraction Alliage 8090 précipitation DRX, Hv, diffraction par MET.
سبیكة 8090 ترسب الحیود بواسطةMETIndex. décimale : 530 Physique Résumé :
Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), microhardness and Transmission Electron Microscopy (TEM) are used to study the precipitation of Al2CuMg (S’/S) and Al2LiCu (T1) phases which lead to structural strengthening of Al-2,7Li-1,4Cu- 1Mg-0,11Zr (wt%) alloy (8090).
DSC results for aged samples for various times at 160, 190 and 210°C, show that threshold-times for (S’+T1) precipitation are 2h, 30mn and 15 mn respectively. These results are confirmed by XRD.
DSC analysis, for the water quenching state, carried out with various scanning rates, permits to evaluate the activation energy of (GPBS’+δ’) formation, activation energy of their dissolution and activation energy of (T1 + S’/S) precipitation.
TEM diffraction revealed extra-reflexions from the orthorhombic S’/S and hexagonal T1 phases in addition to those of α matrix and L12 structure δ’ and β’ phases.
Theoretical study, based on orientation relationships precipitate/matrix, shows that 12 different systems S’/S and 12 variants T1 can simultaneously diffract with α matrix. Two diagrams
100 and 112
are plotted on which the S’/S and T1 reflexions are indexed. The obtained results for the theoretical patterns are in good agreement with those observed experimentally.Diplôme : Doctorat en sciences En ligne : ../theses/physique/DJA6440.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=9472 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité DJA/6440 DJA/6440 Thèse Bibliothèque principale Thèses Disponible Documents numériques
texte intégraleAdobe Acrobat PDF
Titre : Etude des réactions de précipitation continue et des propriétés mécaniques des alliages à base d’aluminium. Type de document : texte imprimé Auteurs : Chahira Amrane, Auteur ; Djamel Hamana, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2018 Importance : 135 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : Al-Mg vieillissement précipitation frottement intérieur microstructure propriétés mécaniques Al-Mg alloys ageing precipitation internal friction mechanical properties سبائك Al-Mgالتعتيق الترسيب الاحتكاك الداخلي البنية المجهرية الخصائص الميكانيكية Index. décimale : 530 Physique Résumé : The Al-Mg alloys are widely used in industry especially for marine applications since they
possess good properties such as general corrosion resistance, strength, weldability, weight
compared to other Al alloys and formability. These properties are related to the magnesium
content and to the applied heat treatments. These alloys undergo phase transitions by
precipitation which improves their mechanical properties following solution heat treatments
and suitable ageing ones. Although these alloys are already well studied, the questions
concerning the stability of the microstructure and the effect of the various heat treatments are
always asked. In this work, we present a study on the evolution of the precipitation
(continuous one) reactions after quenching, more precisely the evolution of the precipitated
phases (formation, coalescence, and dissolution), in Al-(12, 10 and 8)wt.% Mg alloys aged at
150 and 250 °C during different ageing times. The use of various experimental techniques as
differential dilatometry, differential scanning calorimetry, scanning and transmission electron
microscopy, X-ray diffraction, microhardness and internal friction measurements, shows their
importance and their complementarity in the study of ageing process in these alloys. The
obtained results clarified the parameters that govern the stage of β’and β particles appearance
and the mechanical responses to the applied heat treatments. The ageing effect of a
supersaturated solid solution on the Temperature Dependent Internal Friction (TDIF) spectra
has been studied. A detailed TDIF analysis revealed the sensibility of the internal friction
technique to the formation of semi-coherent and non-coherent phases (β' and β) but not
enough to the formation of coherent phases (GP zones). Several observations on the nature
and the shape of the precipitates are also discussed.
Diplôme : Doctorat En ligne : ../theses/physique/AMR7234.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=10804 Etude des réactions de précipitation continue et des propriétés mécaniques des alliages à base d’aluminium. [texte imprimé] / Chahira Amrane, Auteur ; Djamel Hamana, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2018 . - 135 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : Al-Mg vieillissement précipitation frottement intérieur microstructure propriétés mécaniques Al-Mg alloys ageing precipitation internal friction mechanical properties سبائك Al-Mgالتعتيق الترسيب الاحتكاك الداخلي البنية المجهرية الخصائص الميكانيكية Index. décimale : 530 Physique Résumé : The Al-Mg alloys are widely used in industry especially for marine applications since they
possess good properties such as general corrosion resistance, strength, weldability, weight
compared to other Al alloys and formability. These properties are related to the magnesium
content and to the applied heat treatments. These alloys undergo phase transitions by
precipitation which improves their mechanical properties following solution heat treatments
and suitable ageing ones. Although these alloys are already well studied, the questions
concerning the stability of the microstructure and the effect of the various heat treatments are
always asked. In this work, we present a study on the evolution of the precipitation
(continuous one) reactions after quenching, more precisely the evolution of the precipitated
phases (formation, coalescence, and dissolution), in Al-(12, 10 and 8)wt.% Mg alloys aged at
150 and 250 °C during different ageing times. The use of various experimental techniques as
differential dilatometry, differential scanning calorimetry, scanning and transmission electron
microscopy, X-ray diffraction, microhardness and internal friction measurements, shows their
importance and their complementarity in the study of ageing process in these alloys. The
obtained results clarified the parameters that govern the stage of β’and β particles appearance
and the mechanical responses to the applied heat treatments. The ageing effect of a
supersaturated solid solution on the Temperature Dependent Internal Friction (TDIF) spectra
has been studied. A detailed TDIF analysis revealed the sensibility of the internal friction
technique to the formation of semi-coherent and non-coherent phases (β' and β) but not
enough to the formation of coherent phases (GP zones). Several observations on the nature
and the shape of the precipitates are also discussed.
Diplôme : Doctorat En ligne : ../theses/physique/AMR7234.pdf Format de la ressource électronique : Permalink : index.php?lvl=notice_display&id=10804 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité AMR/7234 AMR/7234 Thèse Bibliothèque principale Thèses Disponible
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