5,512 research outputs found
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
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