933 research outputs found
Wetting of prototypical one- and two-dimensional systems: Thermodynamics and density functional theory.
Consider a two-dimensional capped capillary pore formed by capping two parallel planar walls with a third wall orthogonal to the two planar walls. This system reduces to a slit pore sufficiently far from the capping wall and to a single planar wall when the side walls are far apart. Not surprisingly, wetting of capped capillaries is related to wetting of slit pores and planar walls. For example, the wetting temperature of the capped capillary provides the boundary between first-order and continuous transitions to condensation. We present a numerical investigation of adsorption in capped capillaries of mesoscopic widths based on density functional theory. The fluid-fluid and fluid-substrate interactions are given by the pairwise Lennard-Jones potential. We also perform a parametric study of wetting in capped capillaries by a liquid phase by varying the applied chemical potential, temperature, and pore width. This allows us to construct surface phase diagrams and investigate the complicated interplay of wetting mechanisms specific to each system, in particular, the dependence of capillary wetting temperature on the pore width
On the moving contact line singularity: Asymptotics of a diffuse-interface model
The behaviour of a solid-liquid-gas system near the three-phase contact line
is considered using a diffuse-interface model with no-slip at the solid and
where the fluid phase is specified by a continuous density field. Relaxation of
the classical approach of a sharp liquid-gas interface and careful examination
of the asymptotic behaviour as the contact line is approached is shown to
resolve the stress and pressure singularities associated with the moving
contact line problem. Various features of the model are scrutinised, alongside
extensions to incorporate slip, finite-time relaxation of the chemical
potential, or a precursor film at the wall.Comment: 14 pages, 3 figure
A comparison of slip, disjoining pressure, and interface formation models for contact line motion through asymptotic analysis of thin two-dimensional droplet spreading
The motion of a contact line is examined, and comparisons drawn, for a
variety of models proposed in the literature. Pressure and stress behaviours at
the contact line are examined in the prototype system of quasistatic spreading
of a thin two-dimensional droplet on a planar substrate. The models analysed
include three disjoining pressure models based on van der Waals interactions, a
model introduced for polar fluids, and a liquid-gas diffuse-interface model;
Navier-slip and two non-linear slip models are investigated, with three
microscopic contact angle boundary conditions imposed (two of these contact
angle conditions having a contact line velocity dependence); and the interface
formation model is also considered. In certain parameter regimes it is shown
that all of the models predict the same quasistatic droplet spreading
behaviour.Comment: 29 pages, 3 figures, J. Eng. Math. 201
The contact line behaviour of solid-liquid-gas diffuse-interface models
A solid-liquid-gas moving contact line is considered through a
diffuse-interface model with the classical boundary condition of no-slip at the
solid surface. Examination of the asymptotic behaviour as the contact line is
approached shows that the relaxation of the classical model of a sharp
liquid-gas interface, whilst retaining the no-slip condition, resolves the
stress and pressure singularities associated with the moving contact line
problem while the fluid velocity is well defined (not multi-valued). The moving
contact line behaviour is analysed for a general problem relevant for any
density dependent dynamic viscosity and volume viscosity, and for general
microscopic contact angle and double well free-energy forms. Away from the
contact line, analysis of the diffuse-interface model shows that the
Navier--Stokes equations and classical interfacial boundary conditions are
obtained at leading order in the sharp-interface limit, justifying the creeping
flow problem imposed in an intermediate region in the seminal work of Seppecher
[Int. J. Eng. Sci. 34, 977--992 (1996)]. Corrections to Seppecher's work are
given, as an incorrect solution form was originally used.Comment: 33 pages, 3 figure
Dynamic Pricing in the Presence of Social Learning and Strategic Consumers
When a product of uncertain quality is first introduced, consumers may choose to strategically delay their purchasing decisions in anticipation of the product reviews of their peers. This paper investigates how the presence of social learning affects the strategic interaction between a dynamic-pricing monopolist and a forward-looking consumer population, within a simple two-period model. Our analysis yields three main insights. First, we find that the presence of social learning has significant structural implications for optimal pricing policies: In the absence of social learning, decreasing price plans are always preferred by the firm; by contrast, in the presence of social learning we find that (i) if the firm commits to a price path ex ante (preannounced pricing), an increasing price plan is typically announced, whereas (ii) if the firm adjusts price dynamically (responsive pricing), prices are initially low and may either rise or decline over time. Second, we establish that under both preannounced and responsive pricing, even though the social learning process exacerbates strategic consumer behavior (i.e., increases strategic purchasing delays), its presence results in an increase in expected firm profit. Third, we illustrate that, contrary to results reported in existing literature on strategic consumer behavior, in settings where social learning is significantly influential, preannounced pricing policies are generally not beneficial for the firm
A review of the healthcare-management (modeling) literature published at Manufacturing and Service Operations Management
Healthcare systems throughout the world are under pressure to widen access, improve efficiency and quality of care, and reduce inequity. Achieving these conflicting goals requires innovative approaches, utilizing new technologies, data analytics, and process improvements. The operations management community has taken on this challenge: more than 10% of articles published in M&SOM in the period from 2009 to 2018 has developed analytical models that aim to inform healthcare operational decisions and improve medical decision-making. This article presents a review of the research published in M&SOM on healthcare management since its inception 20 years ago and reflects on opportunities for further research
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Asymptotic analysis of evaporating droplets
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.We consider the evaporation dynamics of a two-dimensional, partially-wetting sessile droplet of a
volatile liquid in its pure vapour, which is supported on a smooth horizontal superheated substrate. Assuming
that the liquid properties remain unchanged, we utilise a one-sided lubrication-type model for the evolution of
the droplet thickness, which accounts for the effects of evaporation, capillarity, slip and the kinetic resistance
to evaporation. We follow an asymptotic approach, which yields a set of coupled evolution equations for
the droplet radius and area, estimating analytically the evaporation-modified apparent angle when evaporation
effects are weak. The validity of our matching procedure is verified by numerical experiments, obtaining also
an estimate for the evaporation time
Is IT enough? Evidence from a natural experiment in India's agriculture markets
Access to information and communication technologies (ICTs) such as mobile phone networks is widely known to improve market efficiency. In this paper, we examine whether access to timely and accurate information provided through ICT applications has any additional impact. Using a detailed data set from Reuters Market Light (RML), a text message service in India that provides daily price information to market participants, we find that this information reduces the geographic price dispersion of crops in rural communities by an average of 12%, over and above access to mobile phone technology and other means of communication. To identify the effect of information on price dispersion, we exploit a natural experiment where bulk text messages were banned unexpectedly across India for 12 days in 2010. We find that besides reducing geographic price dispersion, RML also increases the rate at which prices converge across India over time. We discuss the implications of this for development organizations and information providers
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