Influence of corrosion and creep on intergranular fatigue crack path in 2XXX aluminium alloys

In this paper, two examples of the influence of time-dependent processes on crack path in two 2XXX aluminium alloys are presented. The first example is concerned with corrosion–fatigue crack growth resistance of a 2024 T351 alloy cracked in the S–L direction in 3.5% NaCl solution at free corrosion potential. The second example deals with the elevated temperature crack growth resistance of a 2650 T6 alloy that might be used in future supersonic aircraft fuselage panels. The common idea is to correlate quantitative measurements of relevant fractographic features of crack path to the effects of time-dependent processes on crack growth rates

Amoebal pathogens as emerging causal agents of pneumonia

Despite using modern microbiological diagnostic approaches, the aetiological agents of pneumonia remain unidentified in about 50% of cases. Some bacteria that grow poorly or not at all in axenic media used in routine clinical bacteriology laboratory but which can develop inside amoebae may be the agents of these lower respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae-resisting bacteria, which coevolved with amoebae to resist their microbicidal machinery, may have developed virulence traits that help them survive within human macrophages, i.e. the first line of innate immune defence in the lung. We review here the current evidence for the emerging pathogenic role of various amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.

What can best explain the prevalence of bilateralism in the investment regime?

Most efforts to negotiate a multilateral agreement on the liberalization and protection of investment have failed despite the fact that there are more than 2,400 bilateral investment treaties in existence. We have coined this phenomenon the “lateralism paradox.” Within this article, we consider five hypotheses that focus respectively on power asymmetries, incentives for defection, strategic linkages, domestic constraints, and ongoing adaptation. We found that the first four explanations are not supported by empirical evidence from the post-NAFTA period. We conclude that bilateralism appears to be the only feasible approach for negotiating investment rules, as well as the most sensible process to ensure continuous and dynamic adaptation

A dedicated constrained optimization method for 3D reflexion tomography

International audienceSeismic reflection tomography is a method for the determination of a subsurface velocity model from the traveltimes of seismic waves reflecting on geological interfaces. From an optimization viewpoint, the problem consists in minimizing a nonlinear least-squares function measuring the mismatch between observed traveltimes and those calculated by raytracing in this model. The introduction of a priori information on the model is crucial to reduce the under-determination. The contribution of this paper is to introduce a technique able to take into account geological a priori information in the reflection tomography problem expressed as constraints in the optimization problem. This constrained optimization is based on a Gauss-Newton Sequential Quadratic Programming approach. At each Gauss-Newton step, a solution to a strictly convex quadratic optimization problem subject to linear constraints is computed thanks to an augmented Lagrangian relaxation method. Our choice for this optimization method is motivated and its original aspects are described. The efficiency of the method is shown on applications on a 2D OBC real data set and on a 3D real data set: the introduction of constraints coming both from well logs and from geological knowledge allows to reduce the under-determination of the 2 inverse problems. Introduction Reflection tomography allows to determine a velocity model from the traveltimes of seismic waves reflecting on geological interfaces. This inverse problem is formulated as a nonlinear least-squares function which measures the mismatch between observed traveltimes and traveltimes computed by ray tracing method. This method has been successfully applied to real data sets (Ehinger et al, 2001, Broto et al, 2003). Nevertheless, the under-determination of the inverse problem generally requires the introduction of additional information on the model to reduce the number of admissible models. Penalization terms modelling this information can be added to the seismic terms in the objective functions but the tuning of the penalization weights may be tricky. In this paper, we propose to handle the a priori information by the introduction of equality and inequality constraints in the optimization process. This approach allows to introduce lot of constraints of different types, provided we have at our disposal an adequate constrained optimization method. We developed an original method designed for the tomographic inverse problem which presents the following characteristics: it is a large scale problem (10000-50000 unknowns), the forward operator is nonlinear and its computation may be expensive (large number of source-receiver couples, up to 500000), the problem is ill-conditioned. In the first part of this paper, the chosen method is motivated and its original aspects are shortly described (for further details, refer to Delbos et al, 2004). Applications on a 2D PP/PS real data set and on a 3D PP real data set are presented in a second part

Integration of control loops in coupled field circuit model to study magnetic devices supplied by power electronic converter and their control

In this paper, we present a method to take into account the feedback control in software developed from coupled field circuit models. The implementation of control loops is done in a software which is able to simulate electromagnetic devices associated with power electronic circuits having a time dependent topology. The control strategy is implemented in a discrete‐time version and can manage all controllable electronic switches by means of different electric or magnetic quantities calculated during the simulation (flux, currents, voltages, …). Electrical systems involving magnetic devices, power electronic converters and their control devices can be simulated in presence of phenomena such as eddy currents or saturation of the magnetic materials

L’influence de la gouvernance sur la capacité de changement du système de soins : l’exemple de l’implantation des groupes de médecine de famille

Cette thèse s’intéresse à la gouvernance de changements en contextes pluralistes. Nous souhaitons mieux comprendre l’exercice de gouvernance déployé pour développer et implanter un changement par le biais d’une politique publique visant la transformation d’organisations pluralistes. Pour ce faire, nous étudions l’émergence et l’implantation de la politique encadrant la création de groupes de médecine de famille (GMF) à l’aide d’études de cas correspondant à cinq GMF. Les cas sont informés par plus de cents entrevues réalisées en deux vagues ainsi que par une analyse documentaire et des questionnaires portant sur l’organisation du GMF. Trois articles constituent le cœur de la thèse. Dans le premier article, nous proposons une analyse de l’émergence et de l’implantation de la politique GMF à l’aide d’une perspective processuelle et contextuelle développée à partir du champ du changement organisationnel, tel qu’étudié en théorie des organisations. Les résultats démontrent que la gestion du changement en contexte pluraliste est liée à de multiples processus prescrits et construits. Nous avons qualifié ce phénomène de régulation de l’action social (regulation of collective action). La conceptualisation développée et les résultats de l’analyse permettent de mieux comprendre les interactions entre les processus, le contexte et la nature du changement. Le deuxième article propose une conceptualisation de la gouvernance permettant l’étude de la gouvernance en contextes pluralistes. La conceptualisation de la gouvernance proposée tire profit de plusieurs courants des sciences politiques et de l’administration publique. Elle considère la gouvernance comme un ensemble de processus auxquels participent plusieurs acteurs détenant des capacités variables de gouvernance. Ces processus émergent des actions des acteurs et des instruments qu’ils mobilisent. Ils permettent la réalisation des fonctions de la gouvernance (la prospective, la prise de décisions ainsi que la régulation) assurant la coordination de l’action collective. Le troisième article propose, comme le premier, une analyse de l’émergence et de l’implantation de la politique mais cette fois à l’aide de la conceptualisation de la gouvernance développée dans l’article précédent. Nos résultats permettent des apprentissages particuliers concernant les différentes fonctions de la gouvernance et les processus permettant leur réalisation. Ils révèlent l’influence du pluralisme sur les différentes fonctions de gouvernance. Dans un tel contexte, la fonction de régulation s’exerce de façon indirecte et est étroitement liée aux fonctions de prospective et de prise de décisions. Ces fonctions rendent possibles les apprentissages et le développement de consensus nécessaires à l’action collective. L’analyse des actions et des instruments a permis de mieux comprendre les multiples formes qu’ils prennent, en lien avec les contextes dans lesquels ils sont mobilisés. Les instruments indirects permettent les interactions (p. ex. commission d’étude, comité ou réunion) et la formalisation d’ententes entre acteurs (p. ex. des contrats ou des protocoles de soins). Ils se sont révélés fondamentaux pour coordonner les différents acteurs participant à la gouvernance, et ce tant aux niveaux organisationnel qu’inter organisationnel. Les résultats démontrent que les deux conceptualisations contribuent à l’étude de la gouvernance du changement. Nous avons développé deux perspectives inspirées par les sciences politiques, l’administration publique et la théorie des organisations et les analyses qu’elles ont permises ont révélé leur complémentarité. Les résultats permettent de mieux comprendre les processus impliqués dans un tel changement ainsi que leur lien avec les efforts déployés aux différents niveaux par les acteurs mobilisant leurs capacités de gouvernance pour influencer et construire la politique GMF.This thesis is concerned with the governance of change in pluralistic contexts. We wanted to gain a better understanding of the governance processes utilised to develop and implement a public policy aimed at transforming pluralistic organisations. To this end, we conducted a multiple-case study of the emergence and implementation of a policy supporting the creation of family medicine groups (FMG) as it unfolded in five FMGs. The case studies were informed by over 100 interviews conducted in two periods in time as well as from an analysis of documents and questionnaires relating to the organisation of the FMGs. This thesis is essentially composed of three articles. In the first article, we propose an analysis of the emergence and implementation of the FMG policy based on a combined processual-contextual perspective, which has its roots in the field of organisational change, as studied in organisational theory. The results demonstrated that the management of change in a pluralistic context is associated with multiple prescribed and constructed processes. We termed this phenomenon a regulation of collective action. The conceptual framework we developed enabled an analysis which in turn fostered a more enlightened understanding of the interactions that take place between processes, the context and the nature of change. The second article proposes a conceptualisation of governance that enables it to be studied in pluralistic contexts. This framework draws from several branches of political science and public administration. It considers governance as the set of processes involving the participation of many actors, who possess varying degrees of governance capacities. These governance processes are manifested in actors’ actions and the instruments they mobilise. Furthermore, the governance processes consist of three types of functions—avenue-prospecting, decision-making and regulation—which together serve to coordinate collective action. Like the first article, the third proposes an analysis of the emergence and implementation of a policy; however this article incorporates the framework of governance developed in the preceding article. Our analyses yielded some novel findings about the various functions of governance and the processes that lead to their realisation. Specifically, they revealed how the pluralistic context influences and shapes governance functions. In such contexts, the regulation function was found to be carried out in an indirect manner and to be closely tied to the functions of avenue-prospectings and decision making. These functions fostered the knowledge gathering and the consensus building needed to mobilise collective action and were manifested in the use of governance instruments. An analysis of actors’ actions and the instruments they used gave us insight into the many forms that such actions and instruments can take as well as the contexts in which they may be mobilised. Indirect instruments allowed for interactions (e.g. task force, committee or meeting) and the formalisation of agreements between actors (e.g. contracts, care protocols). These instruments proved to be fundamental to the coordination of the various actors participating in governance, both within organisations and between them. Our results demonstrate that the two frameworks contribute significantly to the study of change governance. We developed two conceptualisations inspired from political science, public administration and organisational theory, and the analyses they enabled revealed how the two frameworks complement each other. These results have given us a more clarified understanding of the processes involved in such a systemic change as well as the relationship between these processes and the efforts deployed at various levels of governance by actors exercising their capacity to influence or shape a far-reaching public policy

Proof Certification in Zenon Modulo: When Achilles Uses Deduction Modulo to Outrun the Tortoise with Shorter Steps

International audienceWe present the certifying part of the Zenon Modulo automated theorem prover, which is an extension of the Zenon tableau-based first order automated theorem prover to deduction modulo. The theory of deduction modulo is an extension of predicate calculus, which allows us to rewrite terms as well as propositions, and which is well suited for proof search in axiomatic theories, as it turns axioms into rewrite rules. In addition, deduction modulo allows Zenon Modulo to compress proofs by making computations implicit in proofs. To certify these proofs, we use Dedukti, an external proof checker for the λΠ-calculus modulo, which can deal natively with proofs in deduction modulo. To assess our approach, we rely on some experimental results obtained on the benchmarks provided by the TPTP library

A possible alternative method for collecting mosquito larvae in rice fields

BACKGROUND: Rice fields are efficient breeding places for malaria vectors in Madagascar. In order to establish as easily as possible if a rice field is an effective larval site for anophelines, we compared classical dipping versus a net as methods of collecting larvae. RESULTS: Using similar collecting procedures, we found that the total number of anopheline larvae collected with the net was exactly double (174/87) that collected by dipping. The number of anopheline species collected was also greater with a net. CONCLUSIONS: The net is an effective means of collecting anopheline larvae and can be used for qualitative ecological studies and to rapidly determine which rice fields are containing malaria vectors