Le processus de décision dans le choix modal : importance des déterminants individuels, symboliques et cognitifs

This thesis considers the problem of modal shift in terms of the limitations that exist in the classical model designed for understand transport mode choices. Three major dimensions that address individual behaviour are studied by means of three studies with residents of the Paris region in France. The naives explanations of modal choices for 307 participants are used in the first study to consider the determinants of their various transport preferences. The results show that from the point of view of these users, choices are primarily based on the instrumental characteristics of the transport modes. Additionally, analyses of the determinants of different transport mode choices show that the individual preference for minimising commute time does not distinguish car users from users of public urban rail transport. Study 2 considers the relative importance of symbolic parameters by manipulation of two hypothetical decision-making contexts for 200 participants. The results show that an instrumental parameter (commute time) and a symbolic parameter (social mix) have a similar impact on modal choices. Study 3 addresses the need to consider the cognitive dimensions of the transport mode decision, by manipulation of the attention given by 438 individuals to the evaluation of their freedom of choice. The results show that the feeling of freedom of choice tends to be less dominant in central processing than in peripheral processing. Together these studies show some effects of socio-demographic variables. The whole thesis emphasizes the need to take into consideration the behaviour of the individuals in order to increase the efficiency of strategies promoting the modal shift.Cette thèse envisage le problème du report modal sous l'angle des lacunes existant dans le modèle classique de compréhension des choix de mobilité. Trois grandes dimensions, propres au comportement individuel, sont étudiées au moyen de trois études sur les résidents de la région de Paris, en France. L'approche des explications naïves (étude 1), permet d'abord d'envisager les raisons des déterminants du choix modal pour 307 personnes aux pratiques modales diverses. Les résultats montrent qu'au point de vue des usagers, les choix modaux sont principalement fondés par les caractéristiques instrumentales des modes, la préférence individuelle pour le bénéfice temporel ne distingue cependant pas les usagers de la voiture des usagers des modes collectifs ferrés. L'importance relative des paramètres symboliques est envisagée par une manipulation de deux contextes hypothétiques auprès de 200 participants (étude 2). Les résultats montrent qu'un paramètre instrumental (le temps de trajet) et un paramètre symbolique (la mixité sociale) ont des impacts du même ordre sur les choix. La nécessité de considérer les dimensions cognitives de la décision est abordée au moyen d'une manipulation de l'attention portée par 438 individus à l'évaluation de leur liberté de choix (étude 3). Les résultats montrent que le sentiment de liberté de choix tend à être moins extrême en traitement central qu'en traitement périphérique. Cette thèse montre en outre, dans une visée critique, certains effets des variables sociodémographiques. Ces travaux soulignent dans l'ensemble la nécessité de prendre en compte les comportements individuels pour pouvoir espérer réaliser une promotion du report modal efficace

Le processus de décision dans le choix modal : importance des déterminants individuels, symboliques et cognitifs

This thesis considers the problem of modal shift in terms of the limitations that exist in the classical model designed for understand transport mode choices. Three major dimensions that address individual behaviour are studied by means of three studies with residents of the Paris region in France. The naives explanations of modal choices for 307 participants are used in the first study to consider the determinants of their various transport preferences. The results show that from the point of view of these users, choices are primarily based on the instrumental characteristics of the transport modes. Additionally, analyses of the determinants of different transport mode choices show that the individual preference for minimising commute time does not distinguish car users from users of public urban rail transport. Study 2 considers the relative importance of symbolic parameters by manipulation of two hypothetical decision-making contexts for 200 participants. The results show that an instrumental parameter (commute time) and a symbolic parameter (social mix) have a similar impact on modal choices. Study 3 addresses the need to consider the cognitive dimensions of the transport mode decision, by manipulation of the attention given by 438 individuals to the evaluation of their freedom of choice. The results show that the feeling of freedom of choice tends to be less dominant in central processing than in peripheral processing. Together these studies show some effects of socio-demographic variables. The whole thesis emphasizes the need to take into consideration the behaviour of the individuals in order to increase the efficiency of strategies promoting the modal shift.Cette thèse envisage le problème du report modal sous l'angle des lacunes existant dans le modèle classique de compréhension des choix de mobilité. Trois grandes dimensions, propres au comportement individuel, sont étudiées au moyen de trois études sur les résidents de la région de Paris, en France. L'approche des explications naïves (étude 1), permet d'abord d'envisager les raisons des déterminants du choix modal pour 307 personnes aux pratiques modales diverses. Les résultats montrent qu'au point de vue des usagers, les choix modaux sont principalement fondés par les caractéristiques instrumentales des modes, la préférence individuelle pour le bénéfice temporel ne distingue cependant pas les usagers de la voiture des usagers des modes collectifs ferrés. L'importance relative des paramètres symboliques est envisagée par une manipulation de deux contextes hypothétiques auprès de 200 participants (étude 2). Les résultats montrent qu'un paramètre instrumental (le temps de trajet) et un paramètre symbolique (la mixité sociale) ont des impacts du même ordre sur les choix. La nécessité de considérer les dimensions cognitives de la décision est abordée au moyen d'une manipulation de l'attention portée par 438 individus à l'évaluation de leur liberté de choix (étude 3). Les résultats montrent que le sentiment de liberté de choix tend à être moins extrême en traitement central qu'en traitement périphérique. Cette thèse montre en outre, dans une visée critique, certains effets des variables sociodémographiques. Ces travaux soulignent dans l'ensemble la nécessité de prendre en compte les comportements individuels pour pouvoir espérer réaliser une promotion du report modal efficace

Persuader, engager, ou les deux ? Promouvoir la volonté d'agir pour l'environnement

International audienc

Being a hypocrite or committed while I am shopping? A comparison of the impact of two interventions on environmentally friendly behavior

International audienc

Healing Effect of Controlled Anti-Electromigration on Conventional and High-Tc Superconducting Nanowires

The electromigration process has the potential capability to move atoms one by one when properly controlled. It is therefore an appealing tool to tune the cross section of monoatomic compounds with ultimate resolution or, in the case of polyatomic compounds, to change the stoichiometry with the same atomic precision. As demonstrated here, a combination of electromigration and anti-electromigration can be used to reversibly displace atoms with a high degree of control. This enables a fine adjustment of the superconducting properties of Al weak links, whereas in Nb the diffusion of atoms leads to a more irreversible process. In a superconductor with a complex unit cell (La 2−x Ce x CuO 4 ), the electromigration process acts selectively on the oxygen atoms with no apparent modification of the structure. This allows to adjust the doping of this compound and switch from a superconducting to an insulating state in a nearly reversible fashion. In addition, the conditions needed to replace feedback controlled electromigration by a simpler technique of electropulsing are discussed. These findings have a direct practical application as a method to explore the dependence of the characteristic parameters on the exact oxygen content and pave the way for a reversible control of local properties of nanowires

Statistics of localized phase slips in tunable width planar point contacts

The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads. Profiting from the high current crowding at this spot, we are able to shrink in-situ the nanoconstriction. This procedure allows us to investigate, in the very same sample, thermally activated phase slips and the probability density function of the switching current I sw needed to trigger an avalanche of events. Furthermore, for an applied current larger than I sw , we unveil the existence of two distinct thermal regimes. One corresponding to efficient heat removal where the constriction and bath temperatures remain close to each other, and another one in which the constriction temperature can be substantially larger than the bath temperature leading to the formation of a hot spot. Considering that the switching current distribution depends on the exact thermal properties of the sample, the identification of different thermal regimes is of utmost importance for properly interpreting the dissipation mechanisms in narrow point contacts

Effet de guérison par anti-électromigration controlée dans des nanofils supraconducteurs conventionels et à haute température critique.

At the present time, electron beam lithography (EBL) is considered as the reference technique for nanoscale patterning. However, making nanostructures below the sub-10 nm scale is still challenging due to broadening effects (forward electron scattering, backscattering, electrostatic charging…), and requires strong investment in terms of cost for state-of-the-art EBL systems. In this sense, alternative methods are continuously explored in order to make such nanofabrication easily reachable. A promising approach consists of inducing atomic diffusion by a large current density. This phenomenon, called electromigration (EM), and well known since the 60’s as a failure mechanism in metallic interconnections [1], still attracts interests from scientists and engineers for its great potential for fabrication of microstructures and for its reversibility character [2, 3]. In this work, we show that the combination of electromigration and anti-electromigration allows the precise tuning of superconducting properties of Al nanoconstrictions and we also observe the reversibility of electromigration failure for this material (see Fig. 1). The same process has been applied on Nb, leading to a more irreversible process, and La2 xCexCuO4. For the latter material, we show that selective migration of oxygen atoms and the consequent doping modification induces a transition from a superconducting state to an insulating state in a reversible way [4]. We also discussed the possibility to enhance the electromigration technique by replacing the complex feedback control by a technique of electropulsing. These researches have direct practical impact as a method to explore the dependence of the characteristic parameters on the exact oxygen content and pave the way for a reversible control of local properties of nanowires

Healing Effect of Controlled Anti-Electromigration on Conventional and High-T-c Superconducting Nanowires

The electromigration process has the potential capability to move atoms one by one when properly controlled. It is therefore an appealing tool to tune the cross section of monoatomic compounds with ultimate resolution or, in the case of polyatomic compounds, to change the stoichiometry with the same atomic precision. As demonstrated here, a combination of electromigration and anti‐electromigration can be used to reversibly displace atoms with a high degree of control. This enables a fine adjustment of the superconducting properties of Al weak links, whereas in Nb the diffusion of atoms leads to a more irreversible process. In a superconductor with a complex unit cell (La2−xCexCuO4), the electromigration process acts selectively on the oxygen atoms with no apparent modification of the structure. This allows to adjust the doping of this compound and switch from a superconducting to an insulating state in a nearly reversible fashion. In addition, the conditions needed to replace feedback controlled electromigration by a simpler technique of electropulsing are discussed. These findings have a direct practical application as a method to explore the dependence of the characteristic parameters on the exact oxygen content and pave the way for a reversible control of local properties of nanowires.status: publishe

Statistics of localized phase slips in tunable width planar point contacts

The main dissipation mechanism in superconducting nanowires arises from phase slips. Thus far, most of the studies focus on long nanowires where coexisting events appear randomly along the nanowire. In the present work we investigate highly confined phase slips at the contact point of two superconducting leads. Profiting from the high current crowding at this spot, we are able to shrink insitu the nanoconstriction. This procedure allows us to investigate, in the very same sample, thermally activated phase slips and the probability density function of the switching current Isw needed to trigger an avalanche of events. Furthermore, for an applied current larger than Isw, we unveil the existence of two distinct thermal regimes. One corresponding to efficient heat removal where the constriction and bath temperatures remain close to each other, and another one in which the constriction temperature can be substantially larger than the bath temperature leading to the formation of a hot spot. Considering that the switching current distribution depends on the exact thermal properties of the sample, the identification of different thermal regimes is of utmost importance for properly interpreting the dissipation mechanisms in narrow point contacts.status: publishe