Daphne Skipper
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Daphne Skipper has a total of 17 co-authors. Here are the top co-authors by number of shared publications:
- Jon Lee
University of Michigan
6 shared publications - Luze Xu
Department of Mathematics, UC Davis, Davis, USA
4 shared publications - Emily Speakman
Department of Mathematical and Statistical Sciences, University of Colorado Denver, Denver, Colorado 80204
3 shared publications - Christopher Lourenco
Department of Mathematics, US Naval Academy, Annapolis, USA
2 shared publications - Geonhee Kim
Department of Mathematics, US Naval Academy, Annapolis, USA
2 shared publications - Tom McLeod Logan
Civil and Natural Resources Engineering University of Canterbury Christchurch New Zealand
2 shared publications
Latest Publications
- Open Access
- 23 May 2026
- Published by Elsevier in Reliability Engineering & System Safety
- Vol. 276
Estimating whole-of-event consequences in interdependent infrastructure systems
- 23 May 2026
- Published by Elsevier in Reliability Engineering & System Safety
- Vol. 276
Open AccessEstimating whole-of-event consequences in interdependent infrastructure systems
- Open Access
- 30 September 2025
- Published by Elsevier in Transportation Research Part B: Methodological
- Vol. 201
A scalable optimization approach for equitable facility location: Methodology and transportation applications
- 30 September 2025
- Published by Elsevier in Transportation Research Part B: Methodological
- Vol. 201
Open AccessA scalable optimization approach for equitable facility location: Methodology and transportation applications
- 5 June 2025
- Published by Springer Nature in Optimization and Engineering
- Vol. 26 (4) , 2731-2758
Improved mixing and pressure loss formulations for gas network optimization
- 5 June 2025
- Published by Springer Nature in Optimization and Engineering
- Vol. 26 (4) , 2731-2758
Improved mixing and pressure loss formulations for gas network optimization
- Open Access
Improved Mixing and Pressure Loss Formulations for Gas Network Optimization
Non-convex, nonlinear gas network optimization models are used to determine the feasibility of flows on existing networks given constraints on network flows, gas mixing, and pressure loss along pipes. This work improves two existing gas network models: a discrete mixed-integer nonlinear program (MINLP) that uses binary variables to model positive and negative flows, and a continuous nonlinear program (NLP) that implements complementarity constraints with continuous variables. We introduce cuts to expedite the MINLP and we formulate two new pressure loss models that leverage the flow-splitting variables: one that is highly accurate and another that is simpler but less accurate. In computational tests using the global solver BARON our cuts and accurate pressure loss improves: (1) the average run time of the MINLP by a factor of 35, (2) the stability of the MINLP by solving every tested instance within 2.5 minutes (the baseline model timed out on 25% of instances), (3) the stability of the NLP by solving more instances than the baseline. Our simpler pressure loss model further improved run times in the MINLP (by a factor of 48 versus the baseline MINLP), but was unstable in the context of the NLP.
Open AccessImproved Mixing and Pressure Loss Formulations for Gas Network Optimization
Non-convex, nonlinear gas network optimization models are used to determine the feasibility of flows on existing networks given constraints on network flows, gas mixing, and pressure loss along pipes. This work improves two existing gas network models: a discrete mixed-integer nonlinear program (MINLP) that uses binary variables to model positive and negative flows, and a continuous nonlinear program (NLP) that implements complementarity constraints with continuous variables. We introduce cuts to expedite the MINLP and we formulate two new pressure loss models that leverage the flow-splitting variables: one that is highly accurate and another that is simpler but less accurate. In computational tests using the global solver BARON our cuts and accurate pressure loss improves: (1) the average run time of the MINLP by a factor of 35, (2) the stability of the MINLP by solving every tested instance within 2.5 minutes (the baseline model timed out on 25% of instances), (3) the stability of the NLP by solving more instances than the baseline. Our simpler pressure loss model further improved run times in the MINLP (by a factor of 48 versus the baseline MINLP), but was unstable in the context of the NLP.
- 21 December 2022
- Published by Springer Nature in Journal of Optimization Theory and Applications
- Vol. 196 (1) , 1-35
Gaining or Losing Perspective for Piecewise-Linear Under-Estimators of Convex Univariate Functions
- 21 December 2022
- Published by Springer Nature in Journal of Optimization Theory and Applications
- Vol. 196 (1) , 1-35
Gaining or Losing Perspective for Piecewise-Linear Under-Estimators of Convex Univariate Functions
- 12 August 2021
- Published by Springer Nature in Journal of Global Optimization
- Vol. 82 (4) , 835-862
Gaining or losing perspective
- 12 August 2021
- Published by Springer Nature in Journal of Global Optimization
- Vol. 82 (4) , 835-862
Gaining or losing perspective
- 17 June 2020
- Published by Taylor & Francis in PRIMUS
- Vol. 31 (3-5) , 449-466
Activating Calculus to Command the Seas: Reflecting on Ten Years of Active and Inquiry-Based Learning at the US Naval Academy
Over the past ten years, the authors of this paper have implemented a series of project-based and inquiry-based learning initiatives in the calculus sequence at our institution. These initiatives took place in a department with an existing strong culture supporting teaching innovation and improvement. In this paper we describe three initiatives in detail. We describe how in one, a syllabus redesign allowed for more instructor autonomy. In another, we were able to significantly improve student buy-in. We describe key support we received from our department and institutional leadership at each stage, as well as from working in community with each other. Finally, by looking at the long arc of change in our department, we hope to encourage others who are encountering roadblocks. By working in community, we have created an environment where active learning can flourish.
- 17 June 2020
- Published by Taylor & Francis in PRIMUS
- Vol. 31 (3-5) , 449-466
Activating Calculus to Command the Seas: Reflecting on Ten Years of Active and Inquiry-Based Learning at the US Naval Academy
Over the past ten years, the authors of this paper have implemented a series of project-based and inquiry-based learning initiatives in the calculus sequence at our institution. These initiatives took place in a department with an existing strong culture supporting teaching innovation and improvement. In this paper we describe three initiatives in detail. We describe how in one, a syllabus redesign allowed for more instructor autonomy. In another, we were able to significantly improve student buy-in. We describe key support we received from our department and institutional leadership at each stage, as well as from working in community with each other. Finally, by looking at the long arc of change in our department, we hope to encourage others who are encountering roadblocks. By working in community, we have created an environment where active learning can flourish.
- Open Access
Gaining or losing perspective
We study MINLO (mixed-integer nonlinear optimization) formulations of the disjunction $x\in\{0\}\cup[l,u]$, where $z$ is a binary indicatorof $x\in[l,u]$ ($u> \ell > 0$), and $y$ "captures" $f(x)$, which is assumed to be convex on its domain $[l,u]$, but otherwise $y=0$ when $x=0$. This model is useful when activities have operating ranges, we pay a fixed cost for carrying out each activity, and costs on the levels of activities are convex. Using volume as a measure to compare convex bodies, we investigate a variety of continuous relaxations of this model, one of which is the convex-hull, achieved via the "perspective reformulation" inequality $y \geq zf(x/z)$. We compare this to various weaker relaxations, studying when they may be considered as viable alternatives. In the important special case when $f(x) := x^p$, for $p>1$, relaxations utilizing the inequality $yz^q \geq x^p$, for $q \in [0,p-1]$, are higher-dimensional power-cone representable, and hence tractable in theory. One well-known concrete application (with $f(x) := x^2$) is mean-variance optimization (in the style of Markowitz), and we carry out some experiments to illustrate our theory on this application.Open AccessGaining or losing perspective
We study MINLO (mixed-integer nonlinear optimization) formulations of the disjunction $x\in\{0\}\cup[l,u]$, where $z$ is a binary indicatorof $x\in[l,u]$ ($u> \ell > 0$), and $y$ "captures" $f(x)$, which is assumed to be convex on its domain $[l,u]$, but otherwise $y=0$ when $x=0$. This model is useful when activities have operating ranges, we pay a fixed cost for carrying out each activity, and costs on the levels of activities are convex. Using volume as a measure to compare convex bodies, we investigate a variety of continuous relaxations of this model, one of which is the convex-hull, achieved via the "perspective reformulation" inequality $y \geq zf(x/z)$. We compare this to various weaker relaxations, studying when they may be considered as viable alternatives. In the important special case when $f(x) := x^p$, for $p>1$, relaxations utilizing the inequality $yz^q \geq x^p$, for $q \in [0,p-1]$, are higher-dimensional power-cone representable, and hence tractable in theory. One well-known concrete application (with $f(x) := x^2$) is mean-variance optimization (in the style of Markowitz), and we carry out some experiments to illustrate our theory on this application. - 1 January 2020
- Published by Elsevier in Theoretical Computer Science
- Vol. 803, 160-177
Computing bounds on product graph pebbling numbers
- 1 January 2020
- Published by Elsevier in Theoretical Computer Science
- Vol. 803, 160-177
Computing bounds on product graph pebbling numbers
- 16 November 2018
- Published by Springer Nature
- p. 681-695
Integer-Programming Bounds on Pebbling Numbers of Cartesian-Product Graphs
- 16 November 2018
- Published by Springer Nature
- p. 681-695
Integer-Programming Bounds on Pebbling Numbers of Cartesian-Product Graphs