Boundary-layer turbulence in experiments of quasi-Keplerian flows

Most flows in nature and engineering are turbulent because of their large velocities and spatial scales. Laboratory experiments of rotating quasi-Keplerian flows, for which the angular velocity decreases radially but the angular momentum increases, are however laminar at Reynolds numbers exceeding one million. This is in apparent contradiction to direct numerical simulations showing that in these experiments turbulence transition is triggered by the axial boundaries. We here show numerically that as the Reynolds number increases turbulence becomes progressively confined to the boundary layers and the flow in the bulk fully relaminarizes. Our findings support that turbulence is unlikely to occur in isothermal constant density quasi-Keplerian flows.Comment: 16 pages, 8 figures. Accepted for publication in Journal of Fluid Mechanic

Phase-field simulation of core-annular pipe flow

Phase-field methods have long been used to model the flow of immiscible fluids. Their ability to naturally capture interface topological changes is widely recognized, but their accuracy in simulating flows of real fluids in practical geometries is not established. We here quantitatively investigate the convergence of the phase-field method to the sharp-interface limit with simulations of two-phase pipe flow. We focus on core-annular flows, in which a highly viscous fluid is lubricated by a less viscous fluid, and validate our simulations with an analytic laminar solution, a formal linear stability analysis and also in the fully nonlinear regime. We demonstrate the ability of the phase-field method to accurately deal with non-rectangular geometry, strong advection, unsteady fluctuations and large viscosity contrast. We argue that phase-field methods are very promising for quantitatively studying moderately turbulent flows, especially at high concentrations of the disperse phase.Comment: Paper accepted for publication in International Journal of Multiphase Flo

How effective is lifeline banking in assisting the 'unbanked'?

Many consumers who lack checking accounts are paying relatively high costs to access the nation's payments system. Legislation aimed at opening the system to these unbanked individuals has centered on requiring commercial banks to offer low-cost "lifeline" accounts. But will cost savings alone motivate these consumers to access the payments system through banks?Checking accounts ; Banks and banking - Service charges ; Poverty

Automating decision making to help establish norm-based regulations

Norms have been extensively proposed as coordination mechanisms for both agent and human societies. Nevertheless, choosing the norms to regulate a society is by no means straightforward. The reasons are twofold. First, the norms to choose from may not be independent (i.e, they can be related to each other). Second, different preference criteria may be applied when choosing the norms to enact. This paper advances the state of the art by modeling a series of decision-making problems that regulation authorities confront when choosing the policies to establish. In order to do so, we first identify three different norm relationships -namely, generalisation, exclusivity, and substitutability- and we then consider norm representation power, cost, and associated moral values as alternative preference criteria. Thereafter, we show that the decision-making problems faced by policy makers can be encoded as linear programs, and hence solved with the aid of state-of-the-art solvers

Evaluation de la durabilité des systèmes de production agricoles : limites des démarches normatives et voies d'amélioration

International audienceThe concepts of sustainable development and multifunctional agriculture are at the origin of several efforts aiming at their clarification and the development of methods to make them operational. The main principles of agricultural sustainability stress the importance of economic viability, environmental protection and social equity. For farms and farmers, the concept of sustainability is commonly grounded by methods and tools to evaluate their contribution these principles. These methods and tools, abundantly developed in France (IDEA, DIALECTE, ARBRE ...) are commonly based on a fixed set of criteria and indicators chosen a priori, a series of preset measurement and monitoring methods to quantify indicators and aggregation and weighting methods aiming at a single note for the sustainability of the farm. The objective of this contribution is to critically review such types of methods and tools showing their unsuitability for common cases in the context of French agriculture such as (i) farms in transition phases or aiming at radical changes in the farming activities, (ii) multifunctional farms or farms strongly dependent upon off-farm activities and (iii) farms inserted in a territory where their sustainability depends on the spatial and organizational arrangements among different farms. The contribution concludes with some principle to develop evaluation approaches to overcome some of the limitations of existing methods

THE IMPACT OF TEACHING AND LEARNING METHODOLOGIES IN THE COLLEGE OF NURSING GRADUATES’ COMPETENCY: A TRACER STUDY FOR THE S.Y. 2019-2022

Nursing graduate competency is the ability to complete a task efficiently or successfully. However, it is a brief one that does not fully accommodate definitions. The vast majority would likely concur that competency is a positive trait to something an individual needs a more significant amount. In any case, an individual cannot make somebody more able just by giving them something like information. There is no supernatural competency pill. The term competency should be used and applied to the work setting in a broad scope of relevant circumstances and correct teaching and learning methodologies in any higher educational institution (Dede, 2010). With these concerns, it should be inculcated in most nursing graduates' capacity to apply competently the information, skills, and values that match the needs of their profession, satisfy the demands of the employer, and contribute to the overall attainment of institutional goals in their field of endeavor (Abas & Imam, 2016). Additionally, varied teaching and learning methodologies in the school play an important role in establishing these competencies that were not clearly emphasized and with no alignment as to the most suitable teaching and learning methodologies to enforce competent graduates. Thus, the present study tried to address this research gap to add more to a body of knowledge on employability, skills, and the graduates' contextual performance