arXiv subjects

Sarah M. Ryan

Publications and source records attributed to Sarah M. Ryan.

3 recordsLinked to original sources

arXiv2018

Optimizing Service Restoration in Distribution Systems with Uncertain Repair Time and Demand

This paper proposes a novel method to co-optimize distribution system operation and repair crew routing for outage restoration after extreme weather events. A two-stage stochastic mixed integer linear program is developed. The first stage is to dispatch the repair crews to the damaged components. The second stage is distribution system restoration using distributed generators, and reconfiguration. We consider demand uncertainty in terms of a truncated normal forecast error distribution, and model the uncertainty of the repair time using a lognormal distribution. A new decomposition approach, combined with the Progressive Hedging algorithm, is developed for solving large-scale outage management problems in an effective and timely manner. The proposed method is validated on modified IEEE 34- and 8500-bus distribution test systems.

math.OC↗

arXiv2018

An Exploration of Spatial Radiomic Features in Pulmonary Sarcoidosis

Sarcoidosis is a rare, multi-systemic, inflammatory disease, primarily affecting the lungs. High-resolution computed tomography (CT) scans are used to clinically characterize pulmonary sarcoidosis. In the medical imaging field, there is growing recognition to switch from visual examination of CT images to more rapid, objective assessments of the abnormalities. In this work, we explore the usefulness of various objective measures of spatial heterogeneity---fractal dimension, Moran's I, and Geary's C ---for distinguishing between abnormal sarcoidosis and normal lung parenchyma. CT data for N=58 sarcoidosis subjects enrolled at National Jewish Health were obtained from the GRADS study. CT data for N=101 control patients were obtained from the COPDGene study. Radiomic measures were computed for each two-dimensional slice of a given scan, in the axial, coronal, and sagittal planes. Functional regression was applied to identify lung regions where CT nodules tend to proliferate. Moran's I, Geary's C and fractal dimension significantly differentiate between subjects with and without sarcoidosis throughout the majority of the lung, with disease abnormalities most apparent in the top axial, middle coronal, and outer sagittal regions. A trend appeared across Scadding stages, with CT scans from patients with Scadding stages I and III appearing the healthiest, and Scadding stage IV appearing the least healthy. The radiomic measures and techniques presented herein successfully characterize CT images in sarcoidosis by objectively and efficiently approximating what we know about the pathology of sarcoidosis.

physics.med-ph↗

arXiv2007

Understanding Student Pathways in Context-rich Problems

In this paper we investigate the extent to which students' problem-solving behaviors change as a result of working on multi-faceted, context-rich problems. During the semester, groups of two to three students work on several problems that require more than one concept and hence cannot be readily solved with simple plug-and-chug strategies. The problems are presented to students in a data-rich, online problem-solving environment that tracks which information items are selected by students as they attempt to solve the problem. The students also complete a variety of tasks, such as entering their qualitative analysis into an online form. Students are not constrained to complete these tasks in any order. As they gain more experience in solving multifaceted physics problems, the student groups show some progression towards expert-like behavior: earlier qualitative analysis and more selective requests for information. However, there is room for more improvement as approximately half of the groups still complete the qualitative analysis task towards the end of the solution instead of earlier when it would be most useful to their work.

physics.ed-ph↗