41 research outputs found
Magnetohydrodynamic Simulation of Electromagnetic Pump in TC-1
The pilot molten lead-bismuth target circuit (TC-1) in university of Nevada Las Vegas (UNLV) was designed for beam power of 1 MW accelerator driven system (ADS). The TC-1 is a liquid lead-bismuth eutectic (LBE) circulation loop. Circulation of the liquid alloy is driven by an annular linear induction pump (ALIP). Experimental measurements of system parameters have yielded a surprisingly low pump efficiency of less than 1%. A numerical study of the pump efficiency is being conducted to determine which operational parameters are responsible for this low efficiency and to give insight into future EM pump design. The numerical study will first entail calculating the EM phenomena such as the induced current distribution, magnetic field and electromagnetic body forces using both analytic and numerical methods. These calculated EM forces will be incorporated into fluid flow calculations using a commercial code such as FEMLab and/or Fluent. Parametric studies of the EM and fluid flow phenomena in the pump will be carried out
Which Echo Chamber? Regions of Attraction in Learning with Decision-Dependent Distributions
As data-driven methods are deployed in real-world settings, the processes
that generate the observed data will often react to the decisions of the
learner. For example, a data source may have some incentive for the algorithm
to provide a particular label (e.g. approve a bank loan), and manipulate their
features accordingly. Work in strategic classification and decision-dependent
distributions seeks to characterize the closed-loop behavior of deploying
learning algorithms by explicitly considering the effect of the classifier on
the underlying data distribution. More recently, works in performative
prediction seek to classify the closed-loop behavior by considering general
properties of the mapping from classifier to data distribution, rather than an
explicit form. Building on this notion, we analyze repeated risk minimization
as the perturbed trajectories of the gradient flows of performative risk
minimization. We consider the case where there may be multiple local minimizers
of performative risk, motivated by real world situations where the initial
conditions may have significant impact on the long-term behavior of the system.
As a motivating example, we consider a company whose current employee
demographics affect the applicant pool they interview: the initial demographics
of the company can affect the long-term hiring policies of the company. We
provide sufficient conditions to characterize the region of attraction for the
various equilibria in this settings. Additionally, we introduce the notion of
performative alignment, which provides a geometric condition on the convergence
of repeated risk minimization to performative risk minimizers
Energy Disaggregation via Adaptive Filtering
The energy disaggregation problem is recovering device level power
consumption signals from the aggregate power consumption signal for a building.
We show in this paper how the disaggregation problem can be reformulated as an
adaptive filtering problem. This gives both a novel disaggregation algorithm
and a better theoretical understanding for disaggregation. In particular, we
show how the disaggregation problem can be solved online using a filter bank
and discuss its optimality.Comment: Submitted to 51st Annual Allerton Conference on Communication,
Control, and Computin
Blind Identification via Lifting
Blind system identification is known to be an ill-posed problem and without
further assumptions, no unique solution is at hand. In this contribution, we
are concerned with the task of identifying an ARX model from only output
measurements. We phrase this as a constrained rank minimization problem and
present a relaxed convex formulation to approximate its solution. To make the
problem well posed we assume that the sought input lies in some known linear
subspace.Comment: Submitted to the IFAC World Congress 2014. arXiv admin note: text
overlap with arXiv:1303.671