80 research outputs found
MATHEMATICAL MODELING AND MULTI-OBJECTIVE OPTIMIZATION OF TECHNOLOGICAL PARAMETERS IN HARD TURNING OPERATION USING RSM AND GENETIC ALGORITHMIC APPROACH
In the present research work, the effects of machining parameters such as cutting radius, cutting speed, feed rate and depth of cut on the surface roughness, cutting force, and material removal rate in finish hard turning of hardened hot work steel X38CrMoV5-1 [AISI H11] treated at 50 HRC using coated mixed ceramic tools CC6050 were experimentally investigated. The factorial experiment design was based on Taguchi's L36 orthogonal array. The response surface methodology (RSM) and analysis of variance (ANOVA) were used to check the validity of multiple linear regression models and to determine the significant parameter affecting the responses factors. A multi-objective optimization technique based on the RSM method and the genetic algorithmic approach (GA) was then applied to find optimal combinations of the cutting conditions to minimize the surface quality, cutting force and maximum the productivity. The experimental results reveal that the most significant machining parameter for surface roughness is the feed followed by cutting radius. However, the cutting speed affects considerably the metal removal rate. The (GA) allowed the optimization of the cutting conditions for minimal surface roughness, cutting force and maximal material removal rate
Choosing the âright momentâ to retire : an analysis of end of career decisions for the 1945-1950 birth cohort
Cette thĂšse propose dâexpliquer le faible taux dâemploi enregistrĂ© en France aprĂšs 55 ans par les risques de fragilitĂ© Ă©conomique, professionnelle, sociale et familiale que rĂ©vĂšle le passage Ă la retraite. Elle repose sur le postulat de la libertĂ© de choix dans la dĂ©cision de retraite.En 2005, une Ă©tude quantitative sur les intentions de dĂ©part Ă la retraite a Ă©tĂ© menĂ©e auprĂšs de 1004 individus en emploi, ĂągĂ©s de 54 Ă 59 ans. Les trajectoires personnelles comportant leur part dâincertitude et de changements, 31 entretiens semi-directifs ont Ă©tĂ© rĂ©alisĂ©s auprĂšs de membres de lâĂ©chantillon initial, cinq ans plus tard, afin de permettre un suivi longitudinal. Lâarticulation des reprĂ©sentations de la retraite, du parcours professionnel et de la trajectoire familiale vise Ă cerner les Ă©carts entre les projets et les choix adoptĂ©s et Ă dĂ©terminer les facteurs-clĂ©s impliquĂ©s dans la dĂ©cision.Cette thĂšse souligne tout dâabord que la majoritĂ© des projets initiaux ne sont pas concrĂ©tisĂ©s. Le dĂ©terminisme du contexte professionnel sur la dĂ©cision de retraite explique en partie ces rĂ©ajustements : dĂ©gradation des conditions de travail, dĂ©classement en fin de carriĂšre, stigmatisation sont autant dâarguments susceptibles dâinciter les individus Ă partir Ă la retraite plus tĂŽt que prĂ©vu. Mais les itinĂ©raires familiaux pĂšsent Ă©galement sur ces choix : « pivots gĂ©nĂ©rationnels » entre des parents ĂągĂ©s et des descendants Ă soutenir, les jeunes retraitĂ©s doivent faire face Ă des charges familiales qui influent sur leur dĂ©cision. Enfin, cette recherche met en Ă©vidence la maniĂšre dont les jeunes retraitĂ©s issus du baby-boom, trĂšs attachĂ©s Ă leur libertĂ© individuelle tout au long de leur parcours, dĂ©fendent la prĂ©servation dâespaces personnels (individualisation des pratiques), adoptant ainsi des modĂšles familiaux et une maniĂšre de vivre la retraite inĂ©dits.This thesis seeks to explain the low employment rate in France for people aged 55 years and above in terms of the increasing risk of economic, professional, social and family fragility observed in the transition to retirement. The research is based on the postulate of âfree choiceâ in retirement decisions.In 2005, a quantitative study on the intentions of retirement was conducted among 1,004 employed individuals aged 54-59 years. As personal life courses are marked by change and uncertainties, a longitudinal analysis comprising 31 semi-structured interviews was conducted five years later with participants of the initial sample. The combined study of representations of retirement, end of career and family context allows differences to be identified between plans and the final adopted choices, and the key factors involved in the final decision to be determined.First of all, this thesis demonstrates that most of the initial plans are not realised. The determinism of the professional context on the retirement decision partly explains the observed adjustments: a degradation of working conditions, the assignation of under-qualified tasks at the end of a career, and stigmatisation are all factors that encourage people to retire earlier than expected. But the family environment also influences choices: as "generational pivots" between elderly parents and children to support, young retired people have to face family responsibilities that affect their decisions. Finally, this research highlights how young retirees from the baby boom, for whom individual freedom played a central role in their past life course, adopt new family models and a new way of living (the preservation of âindividual spacesâ and individualised behaviours) during retirement
Ancrage et mobilité de familles d'origine africaine : regards croisés de deux générations
L'article propose dâĂ©tudier lâĂ©volution des relations au sein de familles d'origine subsaharienne vivant en France, Ă partir de l'interrogation de deux gĂ©nĂ©rations adultes (parents et enfants jeunes adultes). La double rĂ©fĂ©rence des pays d'attache en matiĂšre de pratiques, de valeurs, de normes ou de principes Ă©ducatifs est permanente. Enfants et parents apportent leurs regards croisĂ©s sur le parcours, l'histoire et le destin de chacun. La construction dâidentitĂ©s individuelles marquĂ©es par des rĂ©fĂ©rences multiples diffĂšre selon la gĂ©nĂ©ration dâappartenance. Les parents migrants restent attachĂ©s Ă leur identitĂ© africaine (ethnique, nationale, panafricaine, voire transnationale) tout en reconnaissant que leur identitĂ© a intĂ©grĂ© une « part » française. Les jeunes en revanche dĂ©clarent se sentir citoyens français et souhaiteraient ĂȘtre reconnus comme tels. Les deux gĂ©nĂ©rations affirment se sentir Ă lâaise en France. Si les jeunes expriment un intĂ©rĂȘt pour lâAfrique, preuve de leur attachement pour les terres dâorigine, ils ne sont pas pour autant tentĂ©s dây vivre. Quant aux parents, ils hĂ©sitent sur le lieu de leur « derniĂšre demeure », entre reposer dans la terre des ancĂȘtres ou ĂȘtre inhumĂ©s en France pour rester proches de la lignĂ©e quâils y ont fondĂ©e. La rĂ©flexion sâappuie sur une soixantaine dâentretiens rĂ©alisĂ©s auprĂšs de parents migrants (socialisĂ©s en Afrique) et de leurs enfants (nĂ©s ou arrivĂ©s jeunes en France).This article aims at studying the development of relationships in families of Sub-Saharan origin now living in France, and is based on interviews with two generations of adults (parents and young adult children). The duality of references to the home countries as regards practices, values, standards or educational principles is constant. Children and parents provide a dual focus on the journey, the background and the destiny of each person. The building up of individual identities, impacted by a wide range of references, varies according to the generation to which the individual belongs. Migrant parents remain attached to their African identities (ethnic, national, pan African, even transnational), whilst acknowledging that their identity has acquired a French "segment." The young people, on the other hand, declare that they feel themselves to be French citizens and would like to be recognized as such. Both generations affirm that they are comfortable in France. Where children express an interest for Africa, proof of their attachment to their countries of origin, this does not mean they are therefore tempted to live in them. As for the parents, they hesitate when it comes to determining their "final resting place," between deciding whether to be laid to rest in their ancestral mainland, or to be buried in France and thus remain close to those of their immediate lineage. The above considerations are drawn from some sixty interviews carried out amongst immigrant parents (whose social upbringing took place in Africa) and the children (born in France or brought there at an early age)
Entre transmission et construction de l'identité : le cas des enfants de vieux immigrés africains
Lâarticle Ă©tudie les transmissions et les relations au sein de familles dâorigine subsaharienne vivant en France, Ă partir de lâinterrogation de deux gĂ©nĂ©rations adultes (parents et enfants adultes). La double rĂ©fĂ©rence des pays dâattache en matiĂšre de pratiques, de valeurs, de normes ou de principes Ă©ducatifs est permanente. La construction des identitĂ©s marquĂ©e par des rĂ©fĂ©rences multiples diffĂšre selon la gĂ©nĂ©ration dâappartenance. Si les parents restent attachĂ©s avant tout Ă leur identitĂ© africaine (ethnique ou nationale), ils se reconnaissent une «âpartâ» française. Les jeunes dĂ©clarent se sentir citoyens français et souhaiteraient ĂȘtre reconnus comme tels. Si les jeunes expriment un intĂ©rĂȘt pour lâAfrique, preuve de leur attachement pour les terres dâorigine, ils ne sont pas pour autant tentĂ©s dây vivre
DĂ©mĂ©nager Ă la retraite : mieux cerner les enjeux de relations et de soutiens Ă lâaide de la recherche qualitative. Lâexemple de lâenquĂȘte AMARE en France
Pendant la retraite, la mobilitĂ© rĂ©sidentielle ne rĂ©pond plus aux exigences du travail, mais Ă une diversitĂ© de motifs Ă©voluant avec lâavancĂ©e en Ăąge. Lâobjectif de cet article est de comprendre ce qui se joue et se renĂ©gocie en matiĂšre de sociabilitĂ© et de soutien chez les retraitĂ©s qui dĂ©mĂ©nagent, sachant que cette action pourrait ĂȘtre un moyen dâanticiper les consĂ©quences du vieillissement. AprĂšs avoir dressĂ© un panorama des grands motifs de la mobilitĂ© rĂ©sidentielle Ă la retraite en France, notre approche qualitative permet de mettre en Ă©vidence une plus grande complexitĂ© des logiques de lâaction. En sâappuyant sur les donnĂ©es de gestion de la Caisse nationale dâassurance vieillesse (CNAV) pour la sĂ©lection des enquĂȘtĂ©s, notre dispositif dâenquĂȘte a permis de rĂ©aliser en 2015 et 2016, sur trois terrains dâĂ©tudes trĂšs diffĂ©rents, 72 entretiens semi-directifs auprĂšs de retraitĂ©s du rĂ©gime gĂ©nĂ©ral ayant rĂ©alisĂ© un dĂ©mĂ©nagement dans les 18 derniers mois. Que les mobilitĂ©s rĂ©sidentielles soient de courte ou de longue distance, on rĂ©alise alors quâelles posent constamment la question des relations aux proches et celle des soutiens. Si dans les sociĂ©tĂ©s vieillissantes les retraitĂ©s sâinscrivent plus que jamais dans des relations intergĂ©nĂ©rationnelles, le renforcement de lâautonomie entre les gĂ©nĂ©rations conduit Ă les faire Ă©voluer. En dĂ©mĂ©nageant, les retraitĂ©s cherchent majoritairement la « bonne distance » Ă lâĂ©gard de leurs enfants pour poser les principes de la solidaritĂ© entre gĂ©nĂ©rations, et cela mĂȘme sâils maintiennent un soutien renforcĂ© Ă lâĂ©gard de leurs parents ĂągĂ©s (quand ces derniers sont encore en vie).During retirement, residential mobility is no longer associated with the demands of work but instead with a variety of reasons related to ageing. The objective of this article is to focus on what is being played out and renegotiated in terms of the sociability and support of retirees who move, knowing that this action could be a way to anticipate the consequences of ageing. After having drawn up a panorama of the main reasons for residential mobility during retirement in France, our qualitative approach highlights the complexity of the reasons for moving. Based on administrative data of the French pension fund (Caisse nationale dâassurance vieillesse) for the selection of respondents, 72 semi-directive interviews were conducted in 2015 and 2016, in three contrasting regions, with retirees from the general scheme who had moved within the last 18 months. Whether residential mobility is a short or a long distance move, the analysis shows that it constantly involves relationships and support with/from relatives. Although in ageing societies retirees increasingly take part in intergenerational relationships, more autonomy between generations leads to changes in these relationships. Through their residential mobility, most retirees seek the âright distanceâ to live from their children and to reset the principles of solidarity between generations, even though the support for their elderly parents (while they are still alive) remains strong
Déménager à la retraite : enjeux de relations et de soutiens.
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