Publications (15)
An early warning system for multivariate time series with sparse and non-uniform sampling
Andrew Roberts, Sasanka Are
In this paper we propose a new early warning test statistic, the ratio of deviations (RoD), which is defined to be the root mean squared of successive differences divided by the st…
Code review and cooperative pair programming best practice
Qiang Fu, Francis Grady, Bjoern Flemming Broberg +4
We need ways to improve the code quality. Programmers have different level of tenure and experience. Standard and programming languages change and we are forced to re-use legacy co…
Mixed mode oscillations in a conceptual climate model
Andrew Roberts, Esther Widiasih, Chris K. R. T. Jones +1
Much work has been done on relaxation oscillations and other simple oscillators in conceptual climate models. However, the oscillatory patterns in climate data are often more compl…
Relaxation oscillations in an idealized ocean circulation model
Andrew Roberts, Raj Saha
This work is motivated by a desire to understand transitions between stable equilibria observed in Stommel's 1961 thermohaline circulation model. We adapt the model, including a fo…
A New Position Control Strategy for VTOL UAVs using IMU and GPS measurements
Andrew Roberts, Abdelhamid Tayebi
We propose a new position control strategy for VTOL-UAVs using IMU and GPS measurements. Since there is no sensor that measures the attitude, our approach does not rely on the know…
Intrinsic unpredictability of strong El Niño events
John Guckenheimer, Andrew Roberts, Axel Timmermann +1
The El Niño-Southern Oscillation (ENSO) is a mode of interannual variability in the coupled equatorial ocean/atmosphere Pacific. El Niño describes a state in which sea surface te…
Mixed mode oscillations of the El Niño-Southern Oscillation
Andrew Roberts, Esther Widiasih, Axel Timmermann +2
Very strong El Niño events occur sporadically every 10-20 years. The origin of this bursting behavior still remains elusive. Using a simplified 3-dimensional dynamical model of th…
(Un)predictability of strong El Niño events
John Guckenheimer, Axel Timmermann, Henk Dijkstra +1
The El Niño-Southern Oscillation (ENSO) is a mode of interannual variability in the coupled equatorial Pacific coupled atmosphere/ocean system. El Niño describes a state in which…
FuzzSense: Towards A Modular Fuzzing Framework for Autonomous Driving Software
Andrew Roberts, Lorenz Teply, Mert D. Pese +3
Fuzz testing to find semantic control vulnerabilities is an essential activity to evaluate the robustness of autonomous driving (AD) software. Whilst there is a preponderance of di…
Canard explosion and relaxation oscillation in planar, piecewise-smooth, continuous systems
Andrew Roberts
Classical canard explosion results in smooth systems require the vector field to be at least , since canard cycles are created as the result of a Hopf bifurcation. The work on…
Canard-like phenomena in piecewise-smooth Van der Pol systems
Andrew Roberts, Paul Glendinning
We show that a nonlinear, piecewise-smooth, planar dynamical system can exhibit canard phenomena. Canard solutions and explosion in nonlinear, piecewise-smooth systems can be quali…
Stochastic Emulation of a Fully Coupled Preindustrial E3SMv3 Simulation
Elynn Wu, James P. C. Duncan, Troy Arcomano +11
We present a stochastic coupled emulator of E3SM version 3, built on the SamudrACE framework, which couples an atmosphere emulator (ACE2) with a full-depth ocean emulator (Samudra)…
Persistence of Saddle Behavior in the Nonsmooth Limit of Smooth Dynamical Systems
Julie Leifeld, Kaitlin Hill, Andrew Roberts
Models such as those involving abrupt changes in the Earth's reflectivity due to ice melt and formation often use nonlinear terms (e.g., hyperbolic tangent) to model the transition…
REACT: Autonomous Intrusion Response System for Intelligent Vehicles
Mohammad Hamad, Andreas Finkenzeller, Michael Kühr +4
Autonomous and connected vehicles are rapidly evolving, integrating numerous technologies and software. This progress, however, has made them appealing targets for cybersecurity at…
Detecting transient rate-tipping using Steklov averages and Lyapunov vectors
Alanna Hoyer-Leitzel, Alice Nadeau, Andrew Roberts +1
A wide variety of physical systems ranging from the firing of neurons to eutrophication of lakes to the presence of Arctic summer sea ice exhibit a phenomenon known as tipping. In…