4 research outputs found
An Online Optimization-Based Decision Support Tool for Small Farmers in India: Learning in Non-stationary Environments
Crop management decision support systems are specialized tools for farmers
that reduce the riskiness of revenue streams, especially valuable for use under
the current climate changes that impact agricultural productivity.
Unfortunately, small farmers in India, who could greatly benefit from these
tools, do not have access to them. In this paper, we model an individual
greenhouse as a Markov Decision Process (MDP) and adapt Li and Li (2019)'s
Follow the Weighted Leader (FWL) online learning algorithm to offer crop
planning advice. We successfully produce utility-preserving cropping pattern
suggestions in simulations. When we compare against an offline planning
algorithm, we achieve the same cumulative revenue with greatly reduced runtime
Planning to Fairly Allocate: Probabilistic Fairness in the Restless Bandit Setting
Restless and collapsing bandits are commonly used to model constrained
resource allocation in settings featuring arms with action-dependent transition
probabilities, such as allocating health interventions among patients [Whittle,
1988; Mate et al., 2020]. However, state-of-the-art Whittle-index-based
approaches to this planning problem either do not consider fairness among arms,
or incentivize fairness without guaranteeing it [Mate et al., 2021].
Additionally, their optimality guarantees only apply when arms are indexable
and threshold-optimal. We demonstrate that the incorporation of hard fairness
constraints necessitates the coupling of arms, which undermines the
tractability, and by extension, indexability of the problem. We then introduce
ProbFair, a probabilistically fair stationary policy that maximizes total
expected reward and satisfies the budget constraint, while ensuring a strictly
positive lower bound on the probability of being pulled at each timestep. We
evaluate our algorithm on a real-world application, where interventions support
continuous positive airway pressure (CPAP) therapy adherence among obstructive
sleep apnea (OSA) patients, as well as simulations on a broader class of
synthetic transition matrices.Comment: 27 pages, 19 figure
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Investigation of Constant Volume and Constant Flux Initial Conditions on Bidensity Particle-Laden Slurries on an Incline
Particle-laden slurries are pervasive in both natural and industrial settings, whenever particles are suspended or transported in a fluid. Previous literature has investigated the case of a single species of negatively buoyant particles suspended in a viscous fluid. On an incline, three distinct regimes emerge depending on the particle concentration and inclination angle: settled (where particles settle and there is a pure fluid front), well-mixed (where particle concentration is constant throughout), and ridged (where a particle-rich ridge leads the flow). Recently, the same three regimes were also found for constant volume two species bidensity slurries. We extend the literature on bidensity slurries by presenting results on constant volume and a new type of initial condition: constant flux, where slurry is pumped onto the incline at a constant rate. We present front positions of the slurries and compare them to theoretical predictions. In addition, height profiles (film thicknesses) are also presented for the constant flux case, showing the distinct behavior of the ridged regime. We find that for constant flux conditions the settled regime forms for small particle volume fractions and inclination angles while the ridged regime forms for large corresponding values. Intermediate values of these two parameters are shown to produce a well-mixed regime.
KEYWORDS: Thin Films; Particle-Laden Flow; Multiphase Fluids; Interfacial Flows; Particle Segregatio
Recommended from our members
Investigation of Constant Volume and Constant Flux Initial Conditions on Bidensity Particle-Laden Slurries on an Incline
Particle-laden slurries are pervasive in both natural and industrial settings, whenever particles are suspended or transported in a fluid. Previous literature has investigated the case of a single species of negatively buoyant particles suspended in a viscous fluid. On an incline, three distinct regimes emerge depending on the particle concentration and inclination angle: settled (where particles settle and there is a pure fluid front), well-mixed (where particle concentration is constant throughout), and ridged (where a particle-rich ridge leads the flow). Recently, the same three regimes were also found for constant volume two species bidensity slurries. We extend the literature on bidensity slurries by presenting results on constant volume and a new type of initial condition: constant flux, where slurry is pumped onto the incline at a constant rate. We present front positions of the slurries and compare them to theoretical predictions. In addition, height profiles (film thicknesses) are also presented for the constant flux case, showing the distinct behavior of the ridged regime. We find that for constant flux conditions the settled regime forms for small particle volume fractions and inclination angles while the ridged regime forms for large corresponding values. Intermediate values of these two parameters are shown to produce a well-mixed regime.
KEYWORDS: Thin Films; Particle-Laden Flow; Multiphase Fluids; Interfacial Flows; Particle Segregatio