Hayet Mebirouk
email: @yahoo.fr

Keywords: Amélioration urbaine, qualité de vie, espace public, ensemble collectif, Annaba

L'amélioration urbaine, une action plurielle pour rechercher la qualité de vie. Quels effets sur la population et le cadre de vie dans les ensembles collectifs d'Annaba

(Nord-Est Algérien).

Introduction

La notion de qualité de vie en milieu urbain « fut évoquée pour la première fois dans le traité sur l'architecture et le bien-être de Léon Bastita Alberti, De re aedificatoria connu dès 1452 » (El- Kadi, 1997 : 35). Aujourd'hui, cette notion multidimensionnelle se trouve, au coeur des projets d'aménagement et de développement, et s'impose en tant que revendication collective du bien-être portée par la société et en tant que promesse politique engageant à la fois l'État et les collectivités territoriales (Barbarino, 2005). Demeurant un enjeu de taille, la qualité de vie fait référence à plusieurs notions dont celle de l'amélioration des conditions et du cadre de vie reconnue par [START_REF] Lamri | portant loi d'orientation de la ville. Loi n° 90-09 du 07 Avril 1990 relative à la Wilaya Mebirouk, H[END_REF] comme déterminante de l'équilibre physique et psychologique des citadins. En Algérie, cette question a été initialement décrétée par l'instruction ministérielle n°89 du 24 juin 1995 relative à la décentralisation de la gestion des opérations d'études et d'aménagement urbain. L'objectif de cette opération étatique est de réhabiliter les zones d'habitat précaire en prenant essentiellement la forme de régularisation de la propriété foncière et l'investissement par l'État dans les infrastructures de viabilité. Il s'agit, en fait, d'une amélioration des conditions de viabilité des quartiers sous-équipés notamment ceux résultant d'un développement urbain spontané dont l'intégration aux tissus urbains planifié est devenu nécessaire (Mebirouk, 2018). Il est à rappeler que la recherche d'un cadre de vie agréable au sein des ensembles d'habitat collectif a émergé en 2001 avec le redressement des prix de pétrole. A partir de cette date, l'Algérie a connu le début d'une embellie financière qui a suscité le lancement des opérations publiques d'amélioration urbaine s'articulant autour de plusieurs thèmes: la reconquête spatiale, l'aménagement urbain, la valorisation des espaces publics, la redynamisation économique du quartier et notamment l'intégration sociale des habitants à la ville. La prédisposition des autorités publiques pour la réussite de ce programme s'est traduite par l'adoption de nouvelles lois: la loi n°06-06 du 20 février 2006 portant loi d'orientation de la ville promulguée dans un souci majeur celui d'une politique cohérente permettant d'améliorer le cadre de vie du citoyen ; la loi n°07-06 du 13 Mai 2007 relative à la gestion, à la protection et au développement des espaces verts; ainsi que par la mise en place de l'Observatoire national de la ville ayant pour mission le suivi de la mise en oeuvre de la politique de la ville.

L'amélioration urbaine est ainsi, un programme national ambitieux s'inscrivant dans le plan de soutien à la relance économique. Ce plan d'action multisectoriel a tenté d'assurer la requalification des zones périphériques par la mise en oeuvre d'opérations de réhabilitation et de reconquête spatiale. Du fait, l'objectif de ce travail est d'examiner ce programme qui semble avoir contribué à l'évolution du cadre de vie de plusieurs quartiers et l'amélioration de leur image. Cet objectif se réalise par l'analyse du produit fini dans certains quartiers de la ville d'Annaba en se référant d'une part au guide de mise en oeuvre des travaux d'amélioration urbaine, de requalification du cadre bâti et de réhabilitation des espaces libres élaboré (en 2007) par le Centre National des Etudes et Recherches Intégrées du Bâtiment (CNERIB); et d'autre part à l'enquête de terrain en interrogeant quelques habitants sur un projet qui se veut social par l'intégration et l'implication de la population résidente à sa concrétisation.

Méthodologie d'approche

Pour atteindre notre objectif, nous ciblons les ensembles de logements collectifs d'Annaba qui semblent constituer un excellent terrain d'investigation de la question car ils font partie des principaux quartiers sur lesquels ont été lancées les premières opérations d'amélioration urbaine. Cette typologie est le fruit de la procédure des ZHUN (Zones d'Habitat Urbain Nouvelles) engagée dans les années 1970, une procédure équivalente à celle des Zones à Urbanisation Prioritaire (ZUP) mises en place en France au cours des années 1960. Ce dispositif constitue une réponse adaptée aux besoins en logement d'une population de plus en plus nombreuse. L'approche adoptée étant qualitative, ses instruments sont :

l'observation visuelle du projet réalisé (espaces et aménagements), cet instrument est important pour évaluer les comportements des citadins vis-à-vis de l'espace produit et la qualité de mise en oeuvre des opérations d'aménagement; -le recueil de données auprès des services concernés: Direction de l'Urbanisme et de la Construction (DUC); -et l'enquête par entretien de type directif pour que l'enquêté puisse répondre avec plus de liberté. Les soixante-deux opérations inscrites au titre de l'année 2010 concernent les tissus urbains de l'époque coloniale (14 opérations) et postcoloniale. En cette date, l'attention des pouvoirs publics s'est tournée vers l'habitat collectif en lui consacrant 27 opérations (environ 44% du total) contre 35 destinées au reste des typologies (Figure 1). Les premiers sites dévolus aux programmes de logements collectifs à Annaba sont situés à l'Ouest de la ville: La « Plaine-Ouest »(1) et « Oued-Edheb» (2) (Voir Carte) ayant bénéficié de dix opérations d'aménagement en plus de celles achevées avant 2007. Réalisées au début des années 1980 dans le cadre des extensions urbaines de type habitat collectif, ces cités tirent leur nom soit de l'opération réalisée (cités 687 logements, 1172 logements, 1028 logements, etc.) soit de l'entreprise de réalisation (Sonatiba, OPGI, Géni-Sider, etc.). Le plus remarquable, tel que précisés par [START_REF] Mebirouk | Appropriation de l'espace public dans les ensembles de logements collectifs, forme d'adaptabilité ou contournement de normes ? Cas des ZHUN d'Annaba[END_REF], est que ces cités furent reconnues par des espaces extérieurs souvent imprécis tant dans leur délimitation physique que dans leur usage où se superposaient et coexistaient des pratiques urbaines et rurales (vente des articles à même le sol, pratiques ménagères, jardinages, jeux, etc.). Les espaces verts, s'ils y existaient, se résumaient à une verdure spontanée ou à quelques massifs mal-entretenus : les équipements d'agréments qui les accompagnent systématiquement (bancs de repos, aires de jeux pour enfants, éclairages, etc.) étaient absents ou détériorés.

Carte : Localisation des cités d'habitat collectif : Plaine-ouest et Oued-Edheb [START_REF] Mebirouk | Les espaces publics dans les grands ensembles : rapport entre espaces conçus et espaces vécus[END_REF] Par ailleurs, il convient de préciser que la problématique des espaces publics a été largement condamnée par les travaux de recherche [START_REF] Mebirouk | Les espaces publics dans les grands ensembles : rapport entre espaces conçus et espaces vécus[END_REF][START_REF] Zahi | Les retombées de l'amélioration urbaine sur le cadre de vie par la réhabilitation des quartiers de la plaine-ouest de la ville d'Annaba[END_REF], Bahri, 2014) lesquels ont tenté de mettre en scène la négligence de ces espaces et de leur entretien par les autorités publiques. Compte tenu de la situation financière favorable de l'Algérie ( 2001), une volonté de repenser les espaces vécus s'affiche dans les ensembles de logements collectifs par la réhabilitation et l'amélioration du cadre et des conditions de vie des habitants. Or la question qui se pose est de savoir si le produit fini dans le cadre de ce programme d'absorption des déficits d'aménagement urbain est acceptable d'autant qu'à travers ce programme l'État a tenté de rechercher une réponse durable en combinant trois aspects social, économique et environnemental -L'aspect social par la création des associations activant notamment dans le cadre de vie, l'environnement et les conditions de vie, à la fois matériel et immatériel de la population. -L'aspect économique par l'animation de l'activité économique et la création d'emplois à travers les opérations lancées, [START_REF] Sidi | La gouvernance urbaine Une démarche incontournable pour un habiter durable[END_REF]. Il est à noter que l'Office de Promotion et de Gestion Immobilière « OPGI » comme opérateur public a pris en charge les travaux de réhabilitations et de requalifications dans les quartiers ainsi que la réhabilitation du bâti (les vides sanitaires la reprise de l'étanchéité et le lot peinture).

Les acteurs de la sphère sociale : Les habitants L'objectif du programme d'amélioration urbaine est la reconquête des territoires périphériques. Ce projet se concrétise en prenant en compte la dimension sociale comme objectif principal. Il est également fondé sur le partenariat entre l'État et la population locale, et vise à conforter plusieurs options notamment celle de l'implication responsable des populations locales par leur participation [START_REF] Zahi | Les retombées de l'amélioration urbaine sur le cadre de vie par la réhabilitation des quartiers de la plaine-ouest de la ville d'Annaba[END_REF]. L'on conclut que l'opération d'amélioration urbaine, selon le discours des pouvoirs publics, doit émaner d'un effort collectif et à tous les niveaux et les citoyens se doivent d'être associés au plus près d'une action plurielle de redéploiement qui engage le sort urbanistique du citoyen. L'implication du citoyen se traduit non seulement par ses conseils lors du suivi et de la phase de réalisation des aménagements mais également par l'entretien de ces espaces (Mebirouk, 2018). En réalité et en se référant à l'enquête de terrain, les acteurs de l'opération d'amélioration se réduisent aux sphères politique et économique. L'habitant étant considéré comme un acteur « invisible » puisqu'il était exclu de la proposition d'aménagement et du processus de mise en oeuvre de ces opérations. En dépit de son exclusion, l'habitant a accueilli ce projet avec satisfaction, les personnes interrogées (sexes et statuts socioprofessionnels confondus) attestent toutes que le programme a amélioré l'image de leur quartier.

Quels effets du projet sur l'habitant et le cadre de vie?

Toute politique urbaine peut prêter le flanc à la critique par la communauté scientifique, les acteurs publics et aussi la société civile. Le programme d'amélioration urbaine a dégagé une série d'actions urgentes privilégiant un compromis entre besoins, objectifs et moyens disponibles selon un calendrier allant du court au long termes. Etant achevées dans la plupart des cités d'habitat collectif, les actions inscrites dans le court terme: sécurité, confort sanitaire, hygiène urbaine, aménagement des espaces communs, création des espaces de détente, etc. semblent parvenir à redorer l'image des quartiers réhabilités. L'analyse du projet fini a permis d'identifier des succès autant que des échecs déclinées selon trois dimensions : environnementale et paysagère, socio-urbaine et technique.

1-Dimension environnementale et paysagère 1-1-Rénovation du réseau d'assainissement et d'eau potable

Le lancement de l'opération urbaine a été conditionné par la rénovation du réseau d'assainissement et d'eau potable. L'intervention sur ce réseau a atténué les risques d'inondation qu'a connue la ville depuis 1982 et ses dégâts matériels et humains importants. Un vaste programme d'aménagement hydraulique a été mis en oeuvre et a permis de réduire la menace d'inondation qui pesait sur la ville. Pourtant, les intempéries de 2002 ont dévoilé certaines carences rectifiées en 2010 suite à une étude élaborée par une entreprise étrangère à l'effet d'évacuer les eaux de crues, malheureusement, cette expérience s'est soldée par un échec cuisant (Mebirouk, 2018: 55). La succession d'averses frappant la ville en période hivernale a toujours provoqué la submersion de ses espaces extérieurs. Ce phénomène dont les effets sont préjudiciables à l'environnement et la santé publique est lié d'une part à la topographie de la ville : extension de la ville vers l'ouest et le sud, dans une plaine de faible altitude sujette aux effets nuisibles des cours d'eau dévalant le massif de l'Edough( 3

1-2 Création des espaces verts et réalisation du mobilier urbain

La présence de la nature en milieu urbain représente une composante très importante pour la qualité du cadre de vie grâce à la diversité de ses fonctions: sociale, psychologique, paysagère et politique [START_REF] Lamri | portant loi d'orientation de la ville. Loi n° 90-09 du 07 Avril 1990 relative à la Wilaya Mebirouk, H[END_REF].

2-1 Un pas vers l'intégration sociale

Parmi les quartiers marginaux d'Annaba, nous pouvons mentionner l'exemple de la Cité 600 logements (située à la Plaine Ouest) dont les habitants sont des sinistrés provenant du bidonville de Oued-D'heb suite aux inondations de 1982. Le processus de relogement a poursuivi les habitants comme attribut stigmatisant car il s'agit d'une population « bidonvilloise » vivant dans des conditions de vie pénibles et provenant (à l'origine) des villes limitrophes dans le cadre de l'exode rural. Ce quartier, préalablement destiné aux militaires de la région de Annaba [START_REF]Selon l'enquête menée avec les habitants relogés[END_REF] a été disqualifié en portant un toponyme dévalorisant « Bengladesh » pour justifier et légitimer les comportements et attitudes d'une population dite du deuxième rang : non-citadine et rurale. L'isolement et le rejet vécus par les habitants pourraient faire naitre de l'hostilité pour un quartier dégradé où l'on ne peut échapper à l'insécurité, pourtant la population reste très attachée à sa cité. Les jeunes interrogés nous disent « nous aimons notre quartier, et nous y restons », mais ils déclinent un toponyme synonyme d'incivisme et de décadence.

Les travaux d'exécution de l'opération urbaine prévus en 2004 par l'Office de Promotion et de Gestion Immobilière « OPGI » (peinture des immeubles, étanchéité et infiltration d'eau) ainsi que les opérations d'aménagement des espaces extérieurs n'ont pas vu le jour. C'est seulement au mois de mars que la réhabilitation urbaine s'amorce par l'intervention sur deux équipements de proximité: l'un socioculturel (Mosquée) et l'autre sportif (terrain de proximité) (Photos 7 et 8); et par la création ou la rénovation des voies piétonnes (Photo 9). La requalification de ces équipements est perçue comme un pas vers le désenclavement du quartier qui développe une certaine attractivité en captivant une population venant de tous les quartiers limitrophes pour pratiquer du sport ou faire de la prière. Au vu de cette amélioration, le président du comité de quartier conteste le rythme relativement faible de l'exécution des travaux en remettant en cause les compétences de l'entreprise désignée à cet effet. Obstinée par l'insertion totale de son quartier et l'amélioration de son image, la population résidente a cotisé une somme d'argent conséquente(6) pour réaliser des travaux de salubrité indispensables pour la qualité de vie des habitants. Initiée sans l'appui des pouvoirs publics, cette action respectueuse de l'environnement a porté sur la collecte des déchets et la désobstruction des égouts occasionnant des inondations menaçantes(7). Par ces actions volontaristes, les jeunes essayent d'affirmer le mérite d'un nouveau toponyme "quartier Suisse" à la place de "Bangladesh" que les pouvoirs locaux leur ont promis il y a environ 15 ans (2004) (8).

Figure 1 :

 1 Figure 1 : Opérations d'amélioration urbaine au titre de l'année 2010 (DUC, 2010) 0

  Photos 1 et 2 : La cité 1276 logements (en 2004) submergée par les eaux de pluies et actuellement (2018) après la rénovation du réseau d'assainissement (Source,Mebirouk, 2004Mebirouk, et auteur 2018)).

  Photo 3: Introduction de l'espace vert Photo 4 : Création des aires de jeux clôturées dans la cité 400 logements (cité 08 mai 1945) (Auteur, 2018)

  Photos 7 et 8 : Vers une intégration urbaine par la réhabilitation de la mosquée et le terrain de proximité(Auteur, 2018)

  Bien que l'échantillon de personnes soit réduit (environ 100 personnes) nous le considérons comme significatif car composé de personnes d'âge, de sexes et de niveau socio-économique différents (femmes, enfants, commerçants, retraités, fonctionnaires, enseignants universitaires et visiteurs). Les questions retenues sont centrées sur la qualité de l'espace public, une question suffisamment développée au cours des années 1980 par des travaux de recherche notamment ceux qui ont abordé la problématique du renouvellement urbain dans les grands ensembles.

	Tableau 1: Opérations d'amélioration urbaine des cités périphériques d'Annaba
	Sites	Intervenant	Types d'intervention
	El-Fakharine El-Moukawama Seybous 08 Mai 1945 Cité 687 logements Cité 1028 logements DUC & Privé Direction d'Urbanisme de Construction (DUC) et Cité 1172 Plaine-Ouest logements	Assainissement, espace vert, aires de jeux, mobilier urbain Assainissement, trottoirs, éclairages publics, espaces verts, mobilier urbain Assainissement, éclairage public, espaces verts, aires de jeux, mobilier urbain Assainissement, éclairage public, espaces verts, aires de jeux, mobilier urbain Voirie, aire de stationnement, assainissement, éclairage public, espaces verts. Contenu non identifié
	Source: DUC, 2007
	De ce tableau nous constatons que les interventions sont centrées sur trois principales
	actions :
	-Première action: aménagement des espaces extérieurs (aires de jeux, aires de
	stationnement, espaces verts);
	-Deuxième action: renforcement de la desserte et des réseaux divers. Il s'agit d'une
	solution technique pour résoudre essentiellement les problèmes d'alimentation en eau
	potable, de raccordement en énergie électrique, d'assainissement des eaux usées et
	ménagères, et des eaux pluviales, les trottoirs et allées piétonnes et la réhabilitation de
	la voirie urbaine.
	-Troisième action: embellissement par le mobilier urbain (bancs, éclairage publics).
			jeu
	des opposés: tout ce qui est libre et tout ce qui n'est pas privé constituent l'espace public.
	Pourtant, cette question reste extrêmement féconde si on se réfère à l'aménagement, à l'usage
	et à l'appropriation de ces espaces (Navez-Bouchanine, 1992).
	Si cette question est posée, c'est pour affirmer que jusqu'aux années 2005, les espaces publics
	caractérisant les ensembles collectif d'Annaba étaient dépourvus du moindre aménagement et
	ne répondaient pas aux aspirations des usagers (Mebirouk et al., 2005, Semmoud 2009). Ces
	espaces se contentaient le plus souvent des miettes d'un espace figé par la voirie et les
	volumes bâtis. Leur définition résiduelle et leur traitement à posteriori ont suscité chez
	l'individu un sentiment d'insécurité et de désagrément. Laissés à l'abandon plus de trois
	décennies (1974-2007), ces espaces deviennent à partir de l'année 2001 l'enjeu des pouvoirs
	publics en se reconnaissant comme un élément fondamental dans le processus de
	revitalisation urbaine. Et c'est à partir de là que l'espace public n'est plus perçu comme
	espace de «vide» entre deux entités construites, son aménagement devient un véritable enjeu
	social méritant toute l'attention. A cet effet, un programme de mise à niveau du tissu urbain a
	touché environ 3693 quartiers à travers le territoire national dont 762 constructions de type
	tissu spontané; 1092 lotissements; 938 grands ensembles. Ce programme a été mené sur
	l'ensemble du parc national du logement pour une durée s'étalant sur quatre ans.
	La wilaya d'Annaba située au Nord-Est Algérien a bénéficié en 2007 de deux opérations
	d'amélioration urbaine (Tableau 1) pour une autorisation de programme de 235 millions de
	dinars (environ 1370000 Dollars) (El-Annabi, 2007).

Inspirées de la grille de lecture

[START_REF] Sablet | Des espaces urbains agréables à vivre Place, Rues, Squares et jardins[END_REF]

, les principales questions portent sur l'attractivité urbaine, le besoin des habitants en matière d'espaces, le paysage végétal, le mobilier urbain et les matériaux de mise en oeuvre, le sentiment de sécurité, l'implication de l'usager dans le processus d'aménagement des espaces extérieurs, la satisfaction apparente des usagers. Il est vrai que la grille de lecture remonte aux années 1990 mais la situation actuelle des espaces publics dans les ensembles collectifs algériens et le besoin en espace sont, pour ainsi dire comparables à ceux des pays développés des années 1960-1970.

Les espaces publics des ensembles collectifs d'Annaba, de l'abandon au regain d'intérêt

Les zones périphériques d'Annaba disposent-elles d'espaces publics? La question peut paraître banale si on se base sur une définition physique de l'espace ou si on se livre au

Quels acteurs pour la mise en oeuvre des opérations urbaines?

  L'amélioration urbaine ne fait référence à aucune loi. C'est une opération régie par des correspondances ministérielles et des directives du wali appliquées par les directions déconcentrées. Cette opération est exécutée sur la base d'un document établi par le Centre National des Etudes et Recherches Intégrées du Bâtiment (CNERIB) sous la Tutelle du Ministère de l'Habitat et de l'Urbanisme. Le document prescrit toutes les dispositions visant à assurer la sécurité, la stabilité, l'hygiène et le niveau de confort conformément aux exigences normatives, environnementales et sociales. Le programme d'amélioration urbaine est une action Étatique décidée à l'échelle centrale et mise en oeuvre à l'échelle locale par la wilaya et ses organes déconcentrés. Théoriquement, le programme est conduit par trois sphères (Figure2).

	Les	Oued-Dheb

-L'aspect environnemental par la rénovation des réseaux d'assainissement existants et aussi par l'aménagement et la création des espaces verts.

acteurs de la sphère politique 1-Les collectivités locales : La wilaya La

Wilaya (Préfecture) est une collectivité publique territoriale dotée de deux organes: l'Assemblée Populaire de Wilaya « APW», et le Wali (Préfet). Représentant de l'Etat et délégué du Gouvernement au niveau de la wilaya, le Wali est chargé d'exécuter les décisions et les instructions reçues de chacun des ministres. Il anime, coordonne et contrôle l'activité des services de l'Etat chargés des différents secteurs d'activités dans la wilaya (Loi n° 90-09 de 1990).

2-

Les Directions déconcentrées : Direction de l'Urbanisme et de la Construction (DUC)

	La Direction de l'Urbanisme et de la Construction (DUC) est une direction déconcentrée
	assurant multiples missions dont les principales consistent à rassembler et analyser les
	données concernant l'urbanisme et l'architecture, à centraliser les éléments permettant
	l'établissement du programme d'études d'urbanisme à retenir sur le territoire de wilaya
	(Décret n°90-327 de 1990). Elle entreprend toute action en vue de l'amélioration du cadre bâti
	et du développement d'un habitat conforme aux exigences socio-géo-climatiques et
	d'aménagement foncier; et encourage des actions d'intégration des tissus spontanés en
	matière d'urbanisme et d'architecture. Les interventions directes sur le tissu urbain se

traduisent actuellement par les opérations d'amélioration urbaine dont les travaux de réalisation et de suivi sont assurés par le service de la construction.

Les acteurs de la sphère économique : Le professionnel et l'

entreprise de réalisation Amélioration urbaine

  Ce sont les agences ou bureaux d'études ainsi que les entreprises de réalisation désignés par la DUC et la Wilaya pour la conception puis la réalisation du projet. Les critères de choix des bureaux d'études et des entreprises s'élaborent en fonction du critère du moins disant. En effet les projets d'architecture et d'urbanisme sont toujours considérés comme produits financiers et que le moins disant, en étude ou en réalisation aura les meilleures chances d'être retenu

	Sphère
	politique
	Sphère	Sphère
	sociale	économique
	Figure 2 : Les sphères de l'opération d'amélioration urbaine

  à une simple information sans que leurs avis ne soient pris en compte dans le processus de conception. L'implication du citoyen se limite-t-elle à une simple procédure d'information si l'on sache que l'amélioration urbaine vise à réintégrer les habitants dans le processus de production de leur cadre de vie? La réponse est forcément négative, l'implication est un processus de construction collective qui se poursuit jusqu'à la réalisation du projet et même au-delà si nécessaire. Ceci renvoie à la notion de concertation qui constitue une démarche par laquelle est organisée la participation des citoyens, directement ou à travers des instances représentatives, au processus de décision. La finalité de cet outil est d'améliorer réellement la participation du public à la conception des projets, y compris lorsque celle-ci est déjà exigée par des dispositions tant législatives que réglementaires. Il faut rappeler que la démarche concertée comme cadre général d'orientation rejoint les nouveaux objectifs de l'État Algérien afin d'inciter le citoyen à réfléchir son quotidien social et urbain et à agir davantage en ce sens.ConclusionLes opérations d'amélioration urbaine ont réellement traduit la volonté de l'État de réhabiliter l'image des quartiers dégradés et d'y rechercher la qualité de vie synonyme du bien-être social. Seulement, pour que ces actions (parfois conjoncturelles) aboutissent, il faut d'une part, mobiliser les compétences en alliant l'ensemble des forces intellectuelles intervenant dans le processus de l'amélioration urbaine, et d'autre part se rapprocher de la population qui doit se motiver par le projet pour réussir son cadre de vie. L'opération d'amélioration urbaine n'est pas uniquement affaire de règles mais aussi de savoir-faire. Pour une amélioration « palpable » du tissu urbain, les autorités publiques ainsi que les citoyens sont interpellés chacun en ce qui le concerne à assumer pleinement leurs responsabilités en la matière. A cet effet, de lourds engagements sont à prendre de la part des autorités politiques, des élus, des professionnels et également de la communauté citoyenne. L'État algérien est conscient qu'aucun résultat probant en matière de développement, s'il se veut durable, ne peut se concrétiser qu'à travers la participation de toutes les parties prenantes. En l'absence de négociation, les études ne peuvent révéler les attentes et aspiration des habitants et citoyens. La concertation et le débat public sont aujourd'hui les instruments de réflexion collective, et de construction des politiques et actions durables. La démarche concertée est plus qu'un paradigme, c'est un instrument à mettre en oeuvre dans toute opération urbaine afin de garantir sa réussite.BibliographieAgence Régionale de l'Environnement et des Nouvelles Energies (ARENE) 2003, La concertation: outils et pratique dans les projets de territoire, Compte rendu synthétique, journées techniques de l'ARENE, Territoire Agenda 21 Locale, 9 Octobre, Ile de France. Barbarino, N 2005, De la qualité de vie au diagnostic urbain, vers une nouvelle méthode d'évaluation. Le cas de la ville de Lyon, Thèse de Doctorat en Géographie. Université Lumière Lyon 02. Bahri, R 2014, Intervention sur les espaces extérieurs dans les grands ensembles. Cas d'El-Bouni, Mémoire de Master, Département d'Architecture. Université Badji Mokhtar Annaba. Benachour, K 2011, Constantine : Plan d'amélioration urbaine Fini l'amateurisme, Horizon quotidien national d'information du 23 Mai. Centre National d'Etudes et Recherches Intégrées du Bâtiment (CNERIB) 2007, Guide de mise en oeuvre des travaux d'amélioration urbaine, Ministère de l'Habitat et de l'Urbanisme. Alger. Décret exécutif n°90-327 du 27 Octobre 1990 fixant les règles d'organisation et de fonctionnement des services de l'équipement de wilaya.


Teja Rebernik

Jidde Jacobi

Roel Jonkers

Aude Noiray

Sanne Oud

Aliene Reinders

Martijn Wieling

Investigating feedback and feedforward control during vowel production by Dutch adult speakers: insights from auditory feedback perturbation tasks

Introduction

In this study, we investigated how Dutch adult speakers respond to changes in their auditory feedback. Specifically, participants produced speech while their formants were shifted upwards or downwards in either an unexpected or a sustained manner: an unexpected perturbation taps into a speaker's reflexive responses and the functioning of their feedback system, while a sustained perturbation assesses a speaker's adaptive responses and the ability of their feedforward system to learn new motor commands.

Some studies have previously investigated adaptive responses in Dutch speakers (e.g., van Brenk & Terband, 2020) but to our knowledge none have tested Dutch speakers' reflexive responses nor used the target word combinations of this study. In line with prior studies on other languages (predominantly English), we expected participants to respond to the formant perturbation by shifting their own formant production in the opposite direction (e.g., [START_REF] Houde | Sensorimotor Adaptation of Speech I: Compensation and Adaptation[END_REF].

Methods

In total 60 speakers (34 female; age range 22 to 59) completed a sustained perturbations task, an unexpected perturbations task, or both. Speakers were instructed to read several high-frequency monosyllabic Dutch words containing the vowel /ɛ/ while wearing headphones. During production, vowel formants were shifted using Audapter software [START_REF] Cai | A system for online dynamic perturbation of formant frequencies and results from perturbation of the Mandarin triphthong /iau[END_REF].

During the sustained perturbations task, formants were gradually shifted with each successive production, until reaching the maximum perturbation of 20% decrease in F1 and 15% increase in F2 (resulting in a vowel closer to /ɪ/). There were altogether 114 trials, of which 48 were produced at the maximum perturbation (i.e., the STAY phase). During the unexpected perturbations task, the perturbation was smaller than in the sustained perturbations task, namely a 10% decrease in F1 and 5% increase in F2 for an upward trial (resulting in /ɪ/), and a 10% increase in F1 and 5% decrease in F2 for a downward trial (resulting in /ɑ/). There were altogether 120 trials: two thirds of the trials were randomly perturbed either upwards or downwards, the rest were control catch trials.

Most shifts in both experimental tasks resulted in a real Dutch word being produced. For example, the target word /bɛt/ ('bed') could be shifted towards /bɪt/ ('bridle bit') or /bɑt/ ('bath'). After completing the experiment, the participants filled out a questionnaire, asking them whether they had noticed the perturbation.

Results and discussion

We used generalized additive mixed models to analyse participants' reflexive and adaptive responses. For both tasks, participants showed expected responses: when vowels were perturbed upwards, the speakers shifted their productions downwards and vice versa (see Figure 1 for plotted response to the sustained perturbations task). This adaptation occurred even though, according to their questionnaire responses, few speakers consciously noticed the perturbation.

Figure 1 :

 1 Figure 1: Change in F1 (left) and F2 (right) in response to a sustained perturbation. Dotted vertical lines denote the four phases of the experiment (START, RAMP, STAY, END).


Fleur Nadine Ndjock
email: fleur_nadinendjock@yahoo.fr

Academic success of first year university students and mastery of documentary research: applicability of the predictive model in the digital age

In the first year of university, those who have the best results are those who have mastered or the skills in documentary research». These are the conclusions of several studies and predictive models of the academic success of newcomers to the university. In an era where digital technology is the rhythm of daily life, where access to information is facilitated, today's students have developed capacities for autonomy in information research. Is academic success enhanced? Using surveys, interviews and direct observation, this paper aims to study the validity of the predictive model presented above. This, with the final aim of identifying the gaps faced by students entering university today and thus rethinking the training offer, particularly in the use and access to sources of information in order to allow them a better adaptation and ensure their academic success.

Introduction

Academic success according to Leclercq and Parmentier is synonymous with the successful completion of a course (achievement of learning objectives and mastery of knowledge); results and obtaining recognition of prior learning (diploma, certificate, attestation of studies, etc.) are indicators of this success [START_REF] Leclercq | Qu'est-ce que la réussite à l'université d'un étudiant primant[END_REF]. It is the result of a process of affiliation (Coulon, 1997) or integration (Dubet, 1994). Researchers distinguish two types of academic success; quantitative success and qualitative success. If the first refers to the pass rate, the second refers to the skills learned. Whatever the type of academic success, it is equated with accomplishment, the achievement of goals. In the first year of university, however, it is almost always and exclusively a question of authorization to move on to the following year. With or without repetition. Above all, we must not forget that the first academic year is considered a year of transition between two education systems. Secondary school students who reach higher education are not always equipped to face the new environment surrounded by «pedagogical vagueness» [START_REF] Oberti | Les étudiants et leurs études[END_REF] as to the work practices to be implemented in order to succeed. Newly arrived students at university do not know what work techniques to use. However, according to [START_REF] Perret | Pratiques de recherche documentaire et réussite universitaire des étudiants de première année[END_REF], university success is partly based on learning new standards and forms of work that are largely implicit when entering university, and the ability to self-document is essential to succeed (Coulon, 1997 and1999).

Several research results [Alain Coulon (1996), Boyer and Coridian (2002), [START_REF] Mittermeyer | Étude sur les connaissances en recherche documentaire des étudiants entrant au premier cycle dans les universités québécoises[END_REF], Sylvie Gervais and Clément Arsenault (2005), [START_REF] Thirion | Enquête sur les compétences documentaires et informationnelles des étudiants qui accèdent à l'enseignement supérieur en Communauté français de Belgique[END_REF], Cathy Perret (2017)] make the link between the capacity for documentary research and the academic success of first-year university students. This predictive model would suggest that students who have developed independent skills in documentary research do best in their first year of university. For example, according to the studies of Alain [START_REF] Coulon | Penser, classer et catégoriser : l'efficacité de l'enseignement de méthodologie documentaire à l'université[END_REF] on the importance and effectiveness of documentary learning in intellectual work and the success of undergraduate students: from 1986 to 1989, the researcher followed 8171 students. Its aim was to find out if there was a correlation between the academic success of students with a mastery of documentary methodology. The results are striking. Indeed, students with an aptitude for documentary research succeed more easily and validate their university year. A new study carried out between 1995 and 1996 showed the same effects. Let us specify here that by «capacity for documentary research»: Coulon assimilates it to the capacity to seek and appropriate information with the objective of «knowing how to use the available resources, to master reading, to improve memory and organize their work "and documentary research proper" is a working method offered to students to enable them to build knowledge, to evolve in line with the society in which they live ". (Coulon,1996). However, if this predictive model is verified until 1996, what about now when digital is law and where access to information is facilitated by the Internet modifying the report of the student and information? Indeed, with the advent of Information and Communication Technologies (ICT), student practices have changed. According to an American study in the dawn of the 2000s, it showed the predispositions of students to use the Internet in studies [START_REF] Jones | The Internet goes to colleges : how students are living in the future with to day's technology[END_REF]. Increasingly, students are autonomous on the question of information research, and most of the time, most of the time, they carry out their information research at home and in any place, without the help of an intermediary.

However, in the information age where students have relatively easy access to information, where information abounds, where new skills are developed, can it be said that students have developed the skills necessary for mastery of this new information environment to the point of successfully completing their university studies? In other words, under what conditions is the predictive model according to which students with a mastery of documentary research methodology are the most successful still valid today when students seem to change their relationship to l information? With regard to the context (accessibility of information, autonomy in research, and more recently with the constraints linked to the pandemic), can we say that the autonomy in the search for information developed by the students is mastered and sufficient to ensure their success? Is academic success improved quantitatively and qualitatively? This article aims on the one hand, to study the predictive validity of the model in its current environment in order to help in the orientation of the decision-making aiming at the integration or not in the programs, of a support module in documentary research. At least, extend this module to other sectors that do not relate to documentary information or info-com. On the other hand, the exploratory analysis of this predictive model could make it possible to identify the gaps faced by students entering university and thus rethink the training offer, particularly in the use and access to sources of information in order to allow them a better adaptation and ensure their academic success. To carry out our work, the chosen methodology includes a qualitative approach by direct observation and a quantitative approach by questionnaire.

Related Work

Three major elements of the information search process have been studied in surveys of university students in recent years: the use of information sources, research strategy and academic success in the first year of university. This over two distinct periods: before and after the arrival of the Internet.

Before Internet

A year of transition between two systems (secondary and higher), the first year at university is decisive and validating it is a major challenge for any student entering higher education. [START_REF] Leclercq | Qu'est-ce que la réussite à l'université d'un étudiant primant[END_REF] estimates that «when statistics tell us about success at the end of the first year of university education, it is almost always exclusively the authorization to move on to the following year. With or without repeating a year" [START_REF] Leclercq | Qu'est-ce que la réussite à l'université d'un étudiant primant[END_REF]. However, students entering high school have no mastery of research methodology. Also, a researcher carried out a study within the framework of the reform of higher education, provided for in the orientation law, the University of Paris 8 introduced in 1984 the teaching of documentary methodology, in the first university cycles. «It was about training the students in a method of intellectual work based on observable activities in the processes of research and appropriation of information. The objectives of documentary methodology were then to know how to use available resources, to master reading, to improve memory and to organize work " [START_REF] Coulon | Penser, classer et catégoriser : l'efficacité de l'enseignement de méthodologie documentaire à l'université[END_REF]. Of the 8,171 students followed for three years, from 1986 to 1989, some of whom were studying documentary methodology and some not, the study showed a noticeable difference between the two groups. Alain Coulon affirms by this study that the performances of these students lead to a faster course.

"In fact, 59% of the students who have followed the documentation course reach the license two years later, against only 33% for the sub-group who did not follow this course. In addition, the exits by failure are much less numerous" [START_REF] Coulon | Penser, classer et catégoriser : l'efficacité de l'enseignement de méthodologie documentaire à l'université[END_REF]. Through this study, the researcher believes that the teaching of documentary methodology contributes to «the intellectual affiliation of first-year students». By «affiliation» he means the development of new working methods, the acquisition of knowledge, the management of time, the use of documentation.

After Internet

Since the arrival of the Internet and connected objects, Information and Communication Technologies (ICT) have become the centerpiece in info-communication practices and information research. Indeed, [START_REF] Hatim | Pratiques info-communicationnelles des usagers des dispositifs numériques. Théorie de l'acteur-réseau[END_REF] states that «the development of digital devices has led to the emergence of a new information-communication environment.

Ergonomics, accessibility and ease of communication and access to information make them attractive means of benefiting from personalized digital services, in particular obtaining the desired information and communicating it with the desired person " [START_REF] Hatim | Pratiques info-communicationnelles des usagers des dispositifs numériques. Théorie de l'acteur-réseau[END_REF]. [START_REF] Sylvie | Habiletés en recherche d'information des étudiants de première année universitaire en sciences de l'éducation[END_REF] studied 24 students in a situation of information research autonomy. They note that "in addition, a large number of students access information outside the walls of the library, therefore in a situation of autonomy. Autonomous practices make training in the search for information difficult and they prevent us from knowing their real needs" [START_REF] Sylvie | Habiletés en recherche d'information des étudiants de première année universitaire en sciences de l'éducation[END_REF].

Indeed, the arrival of the Internet and its computerized catalogs as well as online resources have transformed the way people find and use information sources. [START_REF] Mittermeyer | Étude sur les connaissances en recherche documentaire des étudiants entrant au premier cycle dans les universités québécoises[END_REF] go further in their observation by noting that «a good number of students seem to know little or not at all, the basic elements of documentary research» [START_REF] Mittermeyer | Étude sur les connaissances en recherche documentaire des étudiants entrant au premier cycle dans les universités québécoises[END_REF] in particular the use of information sources. This is shown by [START_REF] Loiselle | La recherche d'information et les habiletés de recherche et de traitement de l'information chez les étudiants de niveau post-secondaire utilisant des environnements d'apprentissage informatisés[END_REF]. The autonomy observed among students in mastering and manipulating the Internet is only apparent. According to the study, students on the Internet use regular search engines more than databases. "89% of students learn to search on their own, few (35%) have received training and 63% of them consider that they do not need training. It seems that students, especially in the first year of university, have a minimal understanding of effective use of information " [START_REF] Loiselle | La recherche d'information et les habiletés de recherche et de traitement de l'information chez les étudiants de niveau post-secondaire utilisant des environnements d'apprentissage informatisés[END_REF].

Regarding the search strategy, it is about the ability for the one who seeks information to is the ability to «define his subject well, to find the adequate concepts and to combine them with the search operators» [START_REF] Sylvie | Habiletés en recherche d'information des étudiants de première année universitaire en sciences de l'éducation[END_REF]. The problem for information seekers and especially students is to be able to transform the problem into an information seeking problem.

On this subject, Amos [START_REF] David | L'intelligence économique et les systèmes d'informations : problématiques et approches de solutions[END_REF] believes that it is the problem to be solved that must trigger the search for information in his approach to economic intelligence.

He thinks that to make the right decision and conduct good research, you have to define your problem. Of the 07 steps resulting from the economic intelligence process, he defines the first 03 as crucial: Identification of a decision-making problem; Translation of the decision problem into an information search problem and Identification of relevant sources of information [START_REF] David | L'intelligence économique et les systèmes d'informations : problématiques et approches de solutions[END_REF]. Along the same lines, other researchers say that it is the ability to translate their need for information into a query that allows students to pick up more useful references. The development of an adequate search strategy is at the heart of information retrieval concerns [START_REF] Pennanen | Students' conceptual structure, search process, and outcome while preparing a research proposal: A longitudinal case study[END_REF].

The Internet environment is more complex than it looks and students struggle to master the right approach for effective documentary research. Knowledge of specialized databases is limited without prior training. Learners learn on their own and discover tricks at random. Observing the methodological practices of students allows them to understand their difficulties in terms of seeking information and to provide them with adequate assistance.

Research Methodology

It should be recalled here that this article aims to validate the predictive model of success in the first year of university and its strong correlation with the ability to search for documents. Indeed, researchers show that the most successful first year university students are those who are autonomous and master the methodology of documentary research. However, given the globalization of the Internet and the democratization of research tools; given that our young people live in a completely digital environment and have developed autonomy in its use; in this article, we would like to know if this new environment impacts on the results of the students and if so, in what way? In other words, are first-year college results improving in the digital age?

It is preferable here to clarify the terms "uses" and "practices" which are sometimes confused because, having a common semantic field. To summarize the definitions proposed by various researchers Jouet (1993), [START_REF] Millerand | Usages des NTIC : les approches de la diffusion, de l'innovation et de l'appropriation (1e partie)[END_REF], Jauréguiberry and Proulx (2011), [START_REF] Vidal | La sociologie des usages : Continuités et transformations[END_REF], and [START_REF] Badillo | Usages et usagers de l'information numérique[END_REF], we will say that we speak of use by putting emphasis on the object studied. Here, it is about the Internet, the digital environment and we are talking about practice by centering the study on the man who manipulates the object. [START_REF] Hatim | Pratiques info-communicationnelles des usagers des dispositifs numériques. Théorie de l'acteur-réseau[END_REF] worked on the differentiation of the two terms. It emerges several works before him which come back to the two difinitions. This is how in Information and Communication Science (CIS), Jeanneret et al. (2003) specify that the practices take into account «the social depth of the practice under construction» by taking into account the question of the context.

For them, "the context is a major and indispensable element which determines the meaning and dynamism of practices and which allows them to grasp their latter as" phenomena of signification in specific social places " (Davallon et al., 2003) . They are the result of actions by individuals who «take on both styles, individual issues and social and professional commitments that link them to standardized systems» (Davallon et al., 2003) « [START_REF] Hatim | Pratiques info-communicationnelles des usagers des dispositifs numériques. Théorie de l'acteur-réseau[END_REF] Latour suggests studying the practice as combining «places, bodies, groups, tools, devices, laboratories, procedures, texts, documents, instruments, hierarchies allowing any activity to take place» [START_REF] Latour | Sur la pratique des théoriciens[END_REF]; That is to say, «practice is a term without opposite which designates the totality of human activities» [START_REF] Latour | Sur la pratique des théoriciens[END_REF]. In a synthetic way, «the use is [...] more restrictive and refers to the simple use while the practice is a more elaborate concept which covers not only the use of the techniques (the use) but the behaviors, the attitudes and representations of individuals that relate directly or indirectly to the tool " (Jouet, 1993).

For [START_REF] Jeanneret | La relation entre médiation et usage dans les recherches en informationcommunication en France[END_REF], the term "use" "does not replace that of" practice "but dialogues with it". According to him, use is a component of cultural practice, an element relating to situations where individuals («social subjects») are confronted with devices designed by others. So, we will say that studying the uses and practices of documentary research allows us not only to understand how students seek information but also how they seek it, in what environment and what are the motivations. To carry out this study, we thus observed the uses and practices of documentary research of the first year students of the Advanced School of Mass Communication (ASMAC) of the University of Yaoundé 2 and the first year students of the Faculty of Sciences of the University of Yaoundé 1 in Cameroon. Our approach is rather qualitative by direct observation and quantitative by questionnaire. The quantitative approach by question is administered to approximately 340 first year students from ASMAC and 300 from the Faculty of Science for a total of approximately 640 respondents. The relatively low representability of the Faculty of Sciences lies in the fact that the questionnaire was optional and random. We were supported by some colleagues from the Faculty who encouraged the students to fill out the questionnaire. Being a professional school of communication, our survey was easily carried out because we had the full collaboration of teachers and students.

Evaluating the correlation between mastery of research methodology and academic success, our study extended over one semester, in particular the first semester of the 2020/2021 academic year, from October 2020 to April 2021. The semester 1 was ideal as the results of the various competitions were available and the new students had just obtained their baccalaureate and were thus taking their first steps in the world of higher education, with their heads full of dreams and prejudices. The exams to mark the end of the first semester take place around the end of February or early March and the results are posted as soon as the corrections are completed. The qualitative survey by direct observation was extended to a larger population at the Faculty of Sciences (around 1000 students) because it did not engage anyone other than us. We had freedom in our actions. Direct observation focused on specific dimensions based on the directto-reference model of ACRL's documentary skills model. This presents the performance indicators as well as the expected results for the five principles that a university student in Quebec but also in most countries of the world [START_REF] Mokhtar | Information literacy standards, guidelines and their implementation : An analysis[END_REF] should master (ACRL, 2000):

• determine the extent of information he needs;

• access the information he needs effectively and efficiently;

• critically appraise information and its sources, and integrate the information into its knowledge network;

• use the information effectively to achieve a specific objective;

• understand the economic, legal and social issues surrounding the use of information, access and use information ethically and in accordance with the law.

These are information skills, defined as «the set of skills that enable individuals to identify when they need information, and to find, assess and use that information" (ACRL, 2000). We retained certain elements of steps 1 and 2 of the competency model for our analysis. These elements correspond to the primary skills that students must develop in information research.

The questionnaire is made up of four parts:

• the first includes questions on the student: date of birth, gender, school of origin, course, attendance at the CDI (Documentation and Information Center) in high school, and access to a computer;

• the second part looks at Internet access: Frequency of use, applications used, terminal used to access the Internet (computer, tablet, phone, etc.), connection mode (wifi, modem, etc.);

• the third part is devoted to the methodology of information research, use of Boolean operators, the functioning of a search engine, knowledge of databases;

• the fourth part is mainly dedicated to the results of the end of the first semester, personal opinion on the documentary research methodology.

Results and Discussion

Our results will be presented in different tables representing the different parts. We will also make a distinction between the results of ASMAC and those of the Faculty of Sciences for a better comparison.

Part 1: student's identification (Questionnaire) Several elements emerge from the identification of the students questioned:

• The relatively high percentage of girls than boys in the two entities, whether at ASMAC (58.82%) and at the Faculty of Sciences (53.33%);

• The relative youth of the students who arrive at university. The 13 to 17 age group is fairly representative. ASMAC (20.58%); Faculty of Sciences (48.33%);

• We see that a good percentage of new students come from private schools before entering university. ASMAC (60.29%); Faculty of Sciences (40%). Which from our point of view calls out because of the big difference in the study environment. The lecture halls are crowded and it is easy to understand that these students are «lost» when you know that they come from private schools where enrollment is controlled;

• In the same sense, on the percentage of those who used the libraries of their school, more than the majority are those of private schools. ASMAC (66.66%); Faculty of Sciences (70%). The reason would be in the fact that most high schools do not have functioning libraries.

• More than half of the students have a laptop.

Part 2: Internet (Questionnaire)

When it comes to frequency of use and access to the Internet, all students report having access to it every day. We note that more than the majority of students have a computer at ASMAC unlike the Faculty of Sciences. The explanation may lie in the fact that at ASMAC, the computer is part of the material required of the student. On the other hand, all students, whether they are at ASMAC or the Faculty of Sciences, have a phone and access social networks every day. However, research does not occupy a very large place in the digital lives of students. Being a professional school of communication, it is quite normal that students develop aptitude for research, compared to the Faculty of Sciences. Failure is more pronounced in college than ASMAC. Probably due to the teacher / student ration. To the question of knowing what are the consequences of not validating your semester? The students concerned say they have to take the unvalidated teaching unit and that this affects their morale. They realize it's not that easy. Some are discouraged and we believe that failure may be the cause of dropping out of school. This is the reason why some students do not complete their course or change courses, thinking that it will be less difficult elsewhere. Of those who have not completed their semester at ASMAC, most are students who do not have the documentary methodology course.

Access the Internet Connetion mode Uses of Internet

This study clearly shows us that even though we are in the digital age, the uses and practices of information retrieval have not changed. While the information is readily available, first-year students do not have full access to it.

The autonomy they demonstrate is apparent. Most of the time, they are dangerously on social networks for which they have no control. They act out of mimicry without knowing or understanding the significance of what they are doing. The predictive model that «the most successful first year students are those who have mastered the literature search methodology» holds true. The digital environment in which we operate and which we thought would have a positive influence on the academic results of first year students is having no effect. On the contrary, the students seem to be lost in all this flood of information and they are floundering without benchmarks. The tracking, access and production of information has been greatly facilitated.

These changes have had multiple repercussions on our behavior, causing several notable transformations, but also causing certain problems that are reflected in academic results. However, mastery of information skills encourages students to pursue their studies and helps them develop self-confidence.

Conclusion and Future Work

In view of the gaps encountered and observed in the daily practice of students in documentary research and the link which is confirmed with academic success, it is more important than ever to train students in information skills. On the other hand, several universities too often limit themselves to more traditional models of these skills, such as that of the Association of College & Research Libraries (ACRL), which take too little into account the tools and possibilities of Web 2.0, with which are however so familiar to the students. "The integration of information skills into the student journey has not evolved as quickly as the dissemination of information. Individual initiatives abound, but programs aimed at standardizing and evaluating these initiatives are needed « [START_REF] D'amour | Cadre de référence pour un développement optimal des compétences informationnelles au premier cycle[END_REF]. In this regard, Karsenti et al. propose a model that seeks to «strike a fair balance between the traditional models of information retrieval presented above and the new technological reality which is transforming our habits of research, evaluation and sharing of information» [START_REF] Karsenti | Les compétences informationnelles des étudiants à l'heure du Web 2.0 : proposition d'un modèle pour baliser les formations[END_REF]. This is divided into five steps which are iterative:

• information research; • its treatment; • its use; • its transmission and;

• the evaluation of the process carried out.

«Each of these stages is characterized by a series of interrelated skills, the result of which would form, in our opinion, the notion of information skills in the era of Web 2.0» [START_REF] Karsenti | Les compétences informationnelles des étudiants à l'heure du Web 2.0 : proposition d'un modèle pour baliser les formations[END_REF]. On the one hand, this model has the advantage of better identifying the different skills that make up the set of current information skills. On the other hand, this model makes it possible to adapt the traditional model of information retrieval to new technological tools.

Finally, the model presented can also participate in an improvement of the training in information skills which are currently offered, for example at ASMAC, where all students can be introduced to the handling and mastery of tools such as databases or search engine. It would be beneficial to make students aware that their academic skills could better develop if they mastered research tools. Also, instead of offering training in research methodology only to students in the sector, it would be beneficial for everyone to extend it to all other fields. We can suggest some avenues for reflection: • integration of skills in a program approach, place of anchoring in targeted courses and alignment with the content, requirements / lesson plans and student learning methods;

• improvement in the quality of the work produced by students, mainly with regard to the presentation of citations and references in a bibliography [START_REF] Lebrun | Le développement des compétences informationnelles et sonintégration disciplinaire dans un programme EPEP à l'heure des TIC[END_REF].

  Association of College & Research Libraries (ACRL 2000) has set up a repository translated by the Conference of Rectors and Principals of Universities of Quebec (CREPUQ 2005).

  It is very clear in this section that first year college students do not have a great deal of knowledge of how search engines work. They have no ability to search using Boolean operators and very few know what a database is. With these statistics, it should nevertheless be noted that the relative difference which emerges from ASMAC, relates to the students of the «documentary information» sector who have courses in research methodology. They know what a database is and how to use it. They know how a search engine works. Most students do research blind. The only search engine they know of is «Google». They don't know how it works. Some people copy from their peers without knowing exactly what they are doing.

		Part 4 : First semester's results (2020/2021)
				Can the Research
		validation of all teaching units	Methodology Course Help You Improve Your	Do you have the documentary research methodology courses?
				Results?
		Yes	No	Yes	No	Yes
							No
	ASMAC	315	25	320	20	220	120
	Faculty of Sciences	200	800	758	242	0		1000
	Part 3 : Literature research (Questionnaire + Observation)
		knowledge of how a search engine works	knowledge of Boolean operators	knowledge of database
		Yes	No	Yes	No		Yes
								No
	ASMAC	75 (22,05)	265 (77,94%)	80 (23,52%)	260 (76,47%) 120 (35,29%) 220 (64,70%)
	Faculty of Sciences	85 (08,5%)	915 (91,15%)	50 (05%)	950 (95%)	75 (07,5%)	925 (92,5%)


Didier Bresch
email: didier.bresch@univ-savoie.fr

Benoît Desjardins
email: desjardins@mines.org

Emmanuel Grenier
email: egrenier@umpa.ens-lyon.fr

Singular ordinary differential equations homogeneous of degree 0 near a codimension 2 set

Keywords: Singular ODE's, co-dimension 2 singularity, global existence and uniqueness AMS subject classification : 47305, 37N10, 35A05, 74H35

This note deals with an example of class of ordinary differential equations which are singular near a codimension 2 set, with an homogeneous singularity, of degree 0. Under some structural assumptions, we prove that for almost all initial data there exists a unique global solution and study the evolution of the Lebesgue measure of a transported set of initial data.

Introduction

This note deals with a simple example of a class of ordinary differential equations which are singular on a manifold of codimension 2, the singularity being homogeneous of degree 0 near this singularity.

Let H be an Hilbert space. Let Π denotes the orthogonal projection on a given plane P . Let x h = Πx and let x v = x -Πx. Note that x = x h + x v . By a slight abuse of notation we shall say that x = (x h , x v ), x h and x v referring to the "horizontal" and "vertical" components of x. We then identify the plane P with C by choosing arbitrarily a basis on P . This allows to use polar coordinates on P and thus to define the modulus r and argument θ of x h , and to use the notation x h = r exp(iθ).

Let φ be a smooth function defined on H × S 1 (S 1 being the unit circle). Then ẋ = φ x,

x h |x h | (1)
is a dynamical system, singular on P ⊥ , orthogonal of P , which is of codimension 2. Moreover, this system is homogeneous of degree 0 in any direction orthogonal to P ⊥ . Under some assumptions on φ, we show global existence and uniqueness of solution for almost every initial data. Note that we only take care of the behavior of t → x(t) near P ⊥ and by a slight abuse of language we shall say that a solution is global if it does not reach the singularity P ⊥ in finite time.

Motivation

The toy model (1) mimics phenomena occurring in the low Mach number limit problem for non-isentropic flows in a periodic box for instance. Such flows are described through a velocity field u, a density ρ implicitly given by a state law depending on the entropy S and the pressure p, see [START_REF] Métivier | Averaging theorems for conservative systems and the weakly compressible Euler equations[END_REF]). After some change of variables, namely introducing q defined by p = pe εq with p a prescribed constant and ε the low Mach number, the adimensionnalized system reads

a(∂ t q + u • ∇q) + 1 ε divu = 0, (2)
r(∂ t u + u • ∇u) + 1 ε ∇p = 0, (3)
∂ t S + u • ∇S = 0, (4)
where a and r are two smooth functions of S and ε q. The singular limit consists in letting the Mach number ε go to 0. In the ill prepared-data case, namely when the initial data do not satisfy the condition div u 0 = 0, ∇p 0 = 0.

(5)

an oscillatory limit with changing eigenvalues occurs. Indeed the eigenvalues and the spectrum of the singular operator A where

A = 0 a -1 div r -1 ∇ 0 . (6)
will depend on the solution itself. This leads to complex problem, since eigenvalues may cross. The wave equation, related to the operator A, may also be written in this case ε∂ tt ψ -div (S -1 ∇ψ) = 0 (7

)
where S is the entropy quantity, see [START_REF] Métivier | Averaging theorems for conservative systems and the weakly compressible Euler equations[END_REF] for more details.

In the very special case of only one spatial dimension, the limit can be both calculated completely and justified, see [START_REF] Métivier | Averaging theorems for conservative systems and the weakly compressible Euler equations[END_REF]. In the multi-dimensional case the formal calculation of the extra term in the limit, which once again involves the spectral decomposition of the fast operator, assumes that the spectrum of that fast operator is simple and non-resonant, see [START_REF] Bresch | Low Mach number limit of viscous polytropic flows : formal asymptotics in the periodic case[END_REF] for the viscous case and [START_REF] Métivier | Averaging theorems for conservative systems and the weakly compressible Euler equations[END_REF] for the inviscid one. For certain finite-dimension al truncations of the equations those assumptions can be shown to be generic and to ensure convergence to the limit equations. This has been done in the paper [START_REF] Métivier | Averaging theorems for conservative systems and the weakly compressible Euler equations[END_REF].

The main difficulty in the general study is to prove, after defining appropriate infinite dimension measures, that for almost all initial data, the limit flow does not meet double eigenvalues and crosses the resonance set transversally. Difficulties occur since the flow is singular across the resonant set which may be shown to define a codimension 2 set. This explain the necessity to study ODEs of the form [START_REF] Bianchini | Invariant manifolds for a singular ordinary differential equations[END_REF]. Our result will be used to treat oscillatory limits with changing eigenvalues and particularly the low Mach number limit in a forthcoming paper [START_REF] Bresch | Oscillatory Limits with Changing Eigenvalues[END_REF]. Note that another type of singular ordinary differential equation occuring in fluid mechanics has been studied recently, see for instance [START_REF] Bianchini | Invariant manifolds for a singular ordinary differential equations[END_REF].

3 Setup and main result 3.1 Notations.

Let us first introduce some notations. We define ψ(x h , x v , θ) as the argument of Πφ (x h , x v ), exp(iθ) , and ψ(x h , x v , θ) its modulus in such a way that

Πφ (x h , x v ), exp(iθ) = ψ(x h , x v , θ) exp iψ(x h , x v , θ) .
Structural properties. We will assume that there exists an integer N 0 > 0 and N 0 smooth functions of x v , Θ 1 (x h , x v ), . . ., Θ N0 (x h , x v ), satisfying the following properties :

(H1) For all x = (x h , x v ) ∈ H, the equation in θ ψ(x h , x v , θ) ∈ θ + πZ, has exactly N 0 solutions Θ 1 (x h , x v ) . . . Θ N0 (x h , x v ).
(H2) For every j, the following sign condition holds for all

x = (x h , x v ) ∈ H ∂ θ ψ(x h , x v , Θ j (x h , x v )) < 1.
Note that this implies that the solutions Θ j are all simple.

(H3) ψ does not vanish.

Note that (H1) implies that (τ exp(iΘ j (0,

x v )), x v ), τ > 0 is a trajectory for ẋh = Πφ (0, x v ), x h x h . ( 8
)
This trajectory goes to the singularity or leaves it, depending on its orientation.

In particular for some initial data we reach the singularity in finite time. The flow is not defined everywhere and we can only get almost everywhere results.

Main result and consequences

The main result of this paper is :

Theorem 3.

Stable and unstable manifolds.

Let us assume that (H1), (H2) and (H3) hold true. Let x 0 ∈ P ⊥ and let ρ > 0.

There exists a finite number of manifolds V k , of codimension 1, with boundary Σ, such that : -For any initial data x 1 in one of the manifolds V k , the corresponding solution of (9) reaches Σ in finite time (in the past or in the future). -For any initial data x 1 in B(x 0 , ρ) outside all these manifold V k , the corresponding solution of (9) reaches the boundary of B(x 0 , ρ) before Σ.

With this result one can define the flow Ψ(t) of this equation, flow which is defined everywhere except on the manifolds V k . Let A be some set of initial data. We now want to bound the measure of Ψ(t)A in terms of the measure of A. This of course depends on the measure of H, which is not canonical. In order to fix the ideas we will restrict ourselves to a finite dimensional space H, with the Lebesgue measure µ, in order to prove Theorem 3.2 Control of the divergence. Let x 0 ∈ P ⊥ . Let ρ > 0. There exists a constant C 0 (t) such that for any borelian set

A of H, µ Ψ(t)(A ∩ B(x 0 , ρ)) ≤ C 0 (t)µ(A ∩ B(x 0 , ρ)),
for any t > 0.

The outline of the paper is as follows. First we study the simplified equation

ẋ = φ x h |x h | (9)
and then extend it by perturbation arguments to equations of the general form (1). More precisely, in Section 4, we will study trajectories near the singular set. The last section concerns measure type estimate of a transported set by the flow which is defined everywhere except on the manifolds V k of codimension one.

4 Study of systems of the form (9)

We first prove Theorem 2.1 in the particular case of systems of the form (9). Note that (9) is a two dimensional dynamical system, which takes places in x h + P . Changing the notations, (9) is of the form ẏ = φ y y

where y ∈ C. First we turn to polar coordinates, define y = r exp(iθ) and make the change of time defined by dτ /dt = 1/r to get

dr dτ = r ψ(θ) cos(ψ(θ) -θ) (10)
dθ dτ = ψ(θ) sin(ψ(θ) -θ). (11)
Note that (11) does not involve r, which greatly simplifies the analysis of (9). Note also that ψ is always positive. Therefore the dynamics of (11) is given by Assumption (H1). There exists N 0 fixed points Θ j (x v ) which are stable provided (ψ (Θ j ) -1) cos(ψ(Θ j ) -Θ j ) < 0 and unstable if (ψ (Θ j ) -1) cos(ψ(Θ j ) -Θ j ) > 0 (the null case being ruled out by (H2)). Moreover the Θ j are the only fixed points of (11) and the dynamics of solutions t → θ(t) of ( 11) is very simple : t → θ(t) goes in a monotonic way from some Θ j (x v ) (unstable equilibrium, limit value as τ goes to -∞) to Θ j-1 (x v ) or Θ j+1 (x v ) as τ goes to +∞ (stable equilibria). All the solutions of (11) are global in the τ variable and go from an unstable Θ j to a close stable one.

It then remains to solve (10). The behavior depends on the sign of ψ(θ) cos(ψ(θ) -θ).

As ψ(θ) > 0 and as ψ (Θ j ) < 1, ψ(θ) cos(ψ(θ) -θ) is positive if Θ j is stable and negative if Θ j is unstable. Therefore solutions of (9) are global (except if θ constantly equals some of the Θ j where the solution goes to the singularity in finite time in the future or in the past), and are asymptotic in +∞ to some stable Θ j and in -∞ to some instable Θ j .

The phase portrait can be described as follows :

-There exists N 0 particular solutions which are straight lines, going to or coming from the origin in finite positive or negative times. -All the other trajectories are global in time and are asymptotic to two of the particular solutions as time goes to +∞ or -∞. Theorem 2.1 is then straightforward.

Note that Hypothesis (H2) is crucial. If we assume ψ (Θ ) > 1, then the conclusion is completely changed : all the trajectories come from the singularity and go back to the singularity in finite time, except for θ = Θ j . In this case, almost all the trajectories blow up in finite time.

Trajectories near the singular set

In this section we will describe the behavior of solutions near the singular set. Let x 0 = (0, x 0 v ) be a point of P ⊥ . Locally the geometry of the flow is described by the angles Θ j (x 0 v ) which split the space into angular sectors

Ω j = {Θ j (x 0 v ) < θ < Θ j+1 (x 0 v )}.
If there were no x h dependence of the flow, the angles Ω j would be invariant under the flow as in the previous section. This is not the case here and we have to be more precise in the spatial description.

Domain decomposition.

Let α > 0 and η > 0 be small. Then by continuity there exists angles θ + j and θ - j such that

ψ(x h , x v , θ) sin(ψ(x h , x v , θ) -θ) ≥ α (12) when |x h | + |x v -x 0 v | < 2η and Θ j (x 0 v ) < θ + j < θ < θ - j+1 < Θ j+1 (x 0 v ).
Let us now introduce the following sets, for ε chosen later on with ε < η :

Ω j (ε, η) = (x h , x v , θ), | |x h | < ε, |x v -x 0 v | < η, θ - j < θ < θ + j , Σ j (ε, η) = (x h , x v , θ), | |x h | < ε, |x v -x 0 v | < η, θ + j < θ < θ - j+1 ,
and

Ω v (ε, η) = (x h , x v , θ), | |x h | < ε, |x v -x 0 v | < η .
Note that Ω v (ε, η) is the union of the Ω j (ε, η) and Σ j (ε, η) and of their boundaries. The Ω j (ε, η) will be the neighborhood of the stable and unstable manifolds.

Study of the trajectory.

Let us assume to fix the ideas that Θ j is unstable and Θ j+1 is stable (the discussion is similar if the stabilities are interchanged). Let x(t) be a trajectory with x(0) ∈ Σ j (ε, η/2). We claim Claim : If ε is small enough, the trajectory x(t) is contained in Ω j (η, η) for t < t -and is contained in Ω j+1 (η, η) for t > t + . Moreover, for |t| large enough, it exits Ω v (η).

Proof of the claim : Let x(t) be a solution of (1), such that x(0) = (x h (0), x v (0)) with x h (0) = r(0) exp(iθ(0)). Using polar coordinates and introducing again the change of time variable, we get

ẋv = r(1 -Π)φ (x h , x v ), x h x h , (13)
with ṙ = r ψ(x h , x v , θ) cos(ψ(x h , x v , θ) -θ) (14) θ = ψ(x h , x v , θ) sin(ψ(x h , x v , θ) -θ). (15)
Let ]a, b[ be the maximal time interval containing 0 such that x(t) ∈ Ω v (η) for t ∈]a, b[. By definition of θ j and θ j+1 , θ(t) is increasing as long as it be-

longs to Ω v (η, η) -Ω j (η, η) -Ω j+1 (η, η). Let ]a 1 , b 1 [ the maximum time interval containing 0 such that θ j < θ(t) < θ j+1 . Of course a ≤ a 1 < b 1 ≤ b. If a < a 1 then for t = a 1 , x(t) ∈ Ω j ∩ Ω v and therefore x(t) ∈ Ω j ∩ Ω v for any a < t < a 1 . Similarly, if b > b 1 then for any b 1 < t < b, x(t) ∈ Ω j+1 ∩ Ω v .
Note that, using (15) and (12), we can bound b 1 -a 1 , by

b 1 -a 1 ≤ θ 3 -θ 2 α . ( 16
)
This implies that b 1 and -a 1 are less than (θ 3 -θ 2 )/α Moreover

d dτ log r = ψ(x h , x v , θ) cos(ψ(x h , x v , θ) -θ) (17)
Note that on Ω v , ψ is bounded, by some constant C 0 . Hence for a 1 < τ < b 1 , integrating (17) with respect to τ and using (16), we get exp(-

C 0 α -1 (θ 3 -θ 2 )) ≤ r(τ ) R 0 (x) ≤ exp(C 0 α -1 (θ 3 -θ 2 )). ( 18
) Therefore if ε < η 1 + 2C 0 exp(-2C 0 α -1 (θ 3 -θ 2 )), (19)
r(τ ) remains smaller than η for a 1 < τ < b 1 . Hence the solution can not leave Ω v at τ = a 1 or τ = b 1 at the boundary |x h | = η. Now using (13), we see that as, using ( 18)-( 19), r(τ ) remains smaller than η/2C 0 , the trajectory can not leave Ω v at its horizontal boundary. Therefore the trajectory goes from Ω j (η) to Ω j+1 (η), which ends the proof of the claim.

Bounds on r(t) : Let us go back to the genuine time t. On Ω j (η) and Ω j+1 (η), provided α is small enough, | cos(ψ(x h , x v , θ) -θ)| is larger than 1/2. Therefore

d dt |x h (t)| 2 = 2r(t) ṙ(t)
is bounded away from 0 by r(t) min ψ/2. Therefore, as long as r(t) remains in Ω v , for t > b 1 we have

r(b 1 ) + γ 1 (t -b 1 ) ≤ r(t) ≤ r(b 1 ) + γ 2 (t -b 1 )
for some non negative constants γ 1 , γ 2 . A similar result is true for t < a 1 .

Dynamics on Ω j : As ṙ > 0 we change time to get

ẋv = r cos(ψ(x h , x v , θ) -θ) (1 -Π)φ (x h , x v ), x h x h , (20)
ṙ = r, (21) θ
= tan(ψ(x h , x v , θ) -θ). (22)
Note that (20,21,22) is a standard dynamical system, studied near the equilibrium set {(x v , 0, Θ j )|x v ∈ P ⊥ } which appears to be unstable. It therefore admits an unstable manifold, which is precisely the manifold V j .

Measure of a transported set

This section is divided in three parts. The first one concerns a control of the integral of the divergence along a trajectory x(t) passing through a point x 0 in terms of its minimum distance R 0 (x) to the singularity. The second part concerns the local intergrability of log(R -1 0 ) that will be used in the third part to prove Theorem 2.2 through the bound established in the first part.

Hence log(R -1 0 ) is locally integrable. Bound of the measure of a transported set. Let F (t 0 , t 1 ) denotes the resolvent of the flow, which is defined outside the manifolds V j , and thus defined almost everywhere. Let x 0 ∈ P ⊥ . Let ρ > 0, then for any measurable set A, µ F (t 0 , t 1 )(A ∩ B(x 0 , ρ) = µ(A) exp for some constant C since log(R -1 0 ) is locally integrable. This ends the proof of Theorem 2.2.

F 1 0

 1 (t0,τ )(A∩B(x0,ρ))D(τ, x)dτ dx = µ(A ∩ B(x 0 , ρ)) exp A∩B(x0,ρ) t1 t0 D(τ, F (t 0 , τ )x)dτ dx ≤ µ(A ∩ B(x 0 , ρ)) exp C -A∩B(x0,ρ) log(ηR -1 0 (x))dx ≤ Cµ(A ∩ B(x 0 , ρ))

Acknowledgments. The first author would like to thank the French ANR Project "MathOcean" (2008-2011) managed by D. Lannes.

Control of the divergence. Let us first bound the divergence of our vector field. This divergence D equals

where D 1 is a sum of terms which are bounded as r goes to 0. If α and η are small enough (see the domain decomposition part for their definitions), the sine is nearly 0 and much smaller than the cosine, hence D has the sign of cos(Θ j -θ) and, as ∂ θ ψ = 1 and ψ is bounded away from 0, D is bounded in modulus by

provided α is small enough.

Let us now evaluate the integral of the divergence along a trajectory. Let x(t) with t 1 < t < t 2 be a part of trajectory included in Ω j+1 . Note that r(t) is increasing and

for some constant C 0 depending only on ψ. Therefore,

since r(t 2 ) + C 0 (t 2 -t 1 ) ≤ η. A similar result is true for parts of trajectories included in Ω j . Note that the integral behaves like log(1/R 0 (x)).

Local integrability and minimum distance to the singularity set. It remains to provide a local integrability property related to log(R -1 0 ), where R -1 0 denotes the minimum distance between the singularity and a trajectory x(t) passing trough x 0 . Let us look at the formulation (13,14,15), and let us study a trajectory x(t). Up to a shift in time, we may assume that x(t) reaches R 0 at t = 0. Let us study x(t) when t becomes negative and large. First x(t) enters Ω j (ε, η) at some time t 1 < 0 with |t 1 | = O(1) as we consider sequences of trajectories with corresponding R 0 which go to 0.

For t < t 1 , when d(x(t), P ⊥ ) = δ (δ being fixed) then, using (14) and integrating from 0 to t, t is of order C 1 log(δ/R 0 ). Since the trajectory x(t) approaches V j with an exponential speed, we get that d(x(t), V j ) is of order C 2 (R 0 /δ) γ for some positive constants C 2 and γ.

Therefore the measure of {x 0 ∈ Ω j (ε, η)|d(x(t), P ⊥ ) = δ, the trajectory x(t) passes at a distance smaller than r 0 } is of order C 3 (r 0 /δ) γ for some positive constants C 3 and γ. Thus µ x : R 0 (x) ≤ r 0 and d(x, P ⊥ ) = δ ≤ C(r 0 /δ) γ .