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  1. Dignum, F. ; Lomuscio, A. (Ed.)
  2. We consider the problem of finding the lowest order stable rational transfer function that interpolates a set of given noisy time and frequency domain data points. Our main result shows that exploiting results from rational interpolation theory allows for recasting this problem as minimizing the rank of a matrix constructed from the frequency domain data (the Loewner matrix) along with the Hankel matrix of time domain data, subject to a semidefinite constraint that enforces stability and consistency between the time and frequency domain data. These results are applied to a practical problem: identifying a system from noisy measurements of its time and frequency responses. The proposed method is able to obtain stable low order models using substantially smaller matrices than those reported earlier and consequently in a fraction of the computation time.
  3. This paper is concerned about improving the resilience of power grids against extreme events which may lead to the line and generator outages and subsequent voltage stability problems and blackouts. The reported study investigates ways of eliminating or substantially reducing the chances of having such voltage stability problems during expected extreme events, by strategically placing a few distributed generators in the system. The problem is addressed in two stages, where a reasonably inclusive list of credible contingencies are individually considered first. A minimum number of distributed generators are selected and placed in order to maintain voltage stability under each considered contingency. In the second stage, the number of generators is minimized by the strategic selection of locations to reach a solution that ensures voltage stability under all considered contingencies in the system. Effectiveness and computational performance of the developed strategy are illustrated by simulating several outage scenarios using the IEEE 118-bus system.
  4. Recent advances in convolutional neural network (CNN) model interpretability have led to impressive progress in vi- sualizing and understanding model predictions. In partic- ular, gradient-based visual attention methods have driven much recent effort in using visual attention maps as a means for visual explanations. A key problem, however, is these methods are designed for classification and categorization tasks, and their extension to explaining generative models, e.g., variational autoencoders (VAE) is not trivial. In this work, we take a step towards bridging this crucial gap, proposing the first technique to visually explain VAEs by means of gradient-based attention. We present methods to generate visual attention from the learned latent space, and also demonstrate such attention explanations serve more than just explaining VAE predictions. We show how these attention maps can be used to localize anomalies in images, demonstrating state-of-the-art performance on the MVTec- AD dataset. We also show how they can be infused into model training, helping bootstrap the VAE into learning im- proved latent space disentanglement, demonstrated on the Dsprites dataset.
  5. Hurricanes are devastating natural disasters. In deciding how to respond to a hurricane, in particular whether and when to evacuate, a decision-maker must weigh often highly uncertain and contradic- tory information about the future path and intensity of the storm. To effectively plan to help people during a hurricane, it is crucial to be able to predict and understand this evacuation decision. To this end, we propose a computational model of human sequential decision-making in response to a hurricane based on a Partial Ob- servable Markov Decision Process (POMDP) that models concerns, uncertain beliefs about the hurricane, and future information. We evaluate the model in two ways. First, hurricane data from 2018 was used to evaluate the model’s predictive ability on real data. Second, a simulation study was conducted to qualitatively evaluate the sequential aspect of the model to illustrate the role that the acquisition of future, more accurate information can play on cur- rent decision-making. The evaluation with 2018 hurricane season data shows that our proposed features are significant predictors and the model can predict the data well, within and across distinct hurricane datasets. The simulation results show that, across dif- ferent setups, our model generates predictions on themore »sequential decisions making aspect that align with expectations qualitatively and suggests the importance of modeling information.« less