Learning Graphical Models
Modeling Ecological Integrity with Bayesian Belief Networks
Barrios, Juan M. (National Commission for Knowledge and Use of Biodiversity) | Sierra-Alcocer, Raúl (National Commission for Knowledge and Use of Biodiversity) | González-Salazar, Constantino (National Commission for Knowledge and Use of Biodiversity) | Mora, Franz E. (National Commission for Knowledge and Use of Biodiversity) | Munguía, Mariana (National Commission for Knowledge and Use of Biodiversity) | Pérez-Maqueo, Octavio M. (National Commission for Knowledge and Use of Biodiversity) | Trejo, Isabel (National Commission for Knowledge and Use of Biodiversity)
Although the concept of ecological integrity is referred in many country legislations there is no consensus on how to formalize and implement it. One possible definition is as the capacity of an ecosystem to support and maintain a balanced, integrated, and adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of a natural habitat of the region. Our objective is to model this interpretation of ecological integrity from a set of ecological measures that can be estimated from ecological inventory data.
RAPID: A Belief Convergence Strategy for Collaborating with Inconsistent Agents
Sarratt, Trevor (University of California Santa Cruz) | Jhala, Arnav (University of California Santa Cruz)
Maintaining an accurate set of beliefs in a partially observable scenario, particularly with respect to other agents operating in the same space, is a vital aspect of multiagent planning. We analyze how the beliefs of an agent can be updated for fast adaptivity to changes in the behavior of an unknown teammate. The main contribution of this paper is the empirical evaluation of an agent cooperating with a teammate whose goals change periodically. We test our approach in a collaborative multiagent domain where identification of goals is necessary for successful completion. The belief revision technique we propose outperforms the traditional approach in a majority of test cases. Additionally, our results suggest the ability to approximate a higher level model by utilizing a belief distribution over a set of lower level behaviors, particularly when the belief update strategy identifies changes in the behavior in a responsive manner.
Coarse Models for Bird Migrations Using Clustering and Non-Stationary Markov Chains
Jain, Nitin (Georgia Institute of Technology) | Dilkina, Bistra (Georgia Institute of Technology)
While great strides have been made in collecting presence data and developing accurate species distribution models, much less is known about the migratory process that guides the spatio-temporal changes in distributions for migrating species, especially birds. In this work, we address a challenging inference task, where given only aggregate and noisy data of the volume of birds for each spatial pixel and time window, we predict the likely transition links with their associated probabilities. We propose a framework to build such migration networks for different bird species and present a real world example of constructing a network using our approach.
Preventing HIV Spread in Homeless Populations Using PSINET
Yadav, Amulya (University of Southern California) | Marcolino, Leandro Soriano (University of Southern California) | Rice, Eric (University of Southern California) | Petering, Robin (University of Southern California) | Winetrobe, Hailey (University of Southern California) | Rhoades, Harmony (University of Southern California) | Tambe, Milind (University of Southern California) | Carmichael, Heather (University of Southern California)
Homeless youth are prone to Human Immunodeficiency Virus (HIV) due to their engagement in high risk behavior such as unprotected sex, sex under influence of drugs, etc. Many non-profit agencies conduct interventions to educate and train a select group of homeless youth about HIV prevention and treatment practices and rely on word-of-mouth spread of information through their social network. Previous work in strategic selection of intervention participants does not handle uncertainties in the social network's structure and evolving network state, potentially causing significant shortcomings in spread of information. Thus, we developed PSINET, a decision support system to aid the agencies in this task. PSINET includes the following key novelties: (i) it handles uncertainties in network structure and evolving network state; (ii) it addresses these uncertainties by using POMDPs in influence maximization; and (iii) it provides algorithmic advances to allow high quality approximate solutions for such POMDPs. Simulations show that PSINET achieves around 60% more information spread over the current state-of-the-art. PSINET was developed in collaboration with My Friend's Place (a drop-in agency serving homeless youth in Los Angeles) and is currently being reviewed by their officials.
Modeling Spatial-Temporal Dynamics of Human Movements for Predicting Future Trajectories
Wang, Zhan (KTH Royal Institute of Technology) | Jensfelt, Patric (KTH Royal Institute of Technology) | Folkesson, John (KTH Royal Institute of Technology)
This paper presents a novel approach to modeling the dynamics of human movements with a grid-based representation.For each grid cell, we formulate the local dynamics using a variant of the left-to-right HMM, and thus explicitly model the exiting direction from the current cell. The dependency of this process on the entry direction is captured by employing the Input-Output HMM (IOHMM). On a higher level, we introduce the place where the whole trajectory originated into the IOHMM framework forming a hierarchical input structure. Therefore, we manage to capture both local spatial-temporal correlations and the long-term dependency on faraway initiating events, thus enabling the developed model to incorporate more information and to generate more informative predictions of future trajectories.The experimental results in an office corridor environment verify the capabilities of our method.
Real-Time Optimal Selection of Multirobot Coalition Formation Algorithms Using Conceptual Clustering
Sen, Sayan Dev (Vanderbilt University) | Adams, Julie Ann (Vanderbilt University)
The presented framework is the The multirobot coalition formation problem seeks to intelligently first to leverage a conceptual clustering technique to partition partition a team of heterogeneous robots into any set of coalition formation algorithms in order to derive coalitions for a set of real-world tasks. Besides being N Pan optimal hierarchy classification tree, given any classification complete (Sandholm et al. 1999), the problem is also hard taxonomy. The results contribute to the state-ofthe-art to approximate (Service and Adams 2011a). Traditional approaches in multiagent systems by demonstrating the existence to solving the problem include a number of greedy of crucial patterns and intricate relationships among existing algorithms (Shehory and Kraus 1998; Vig and Adams coalition algorithms.
Encoding Time Series as Images for Visual Inspection and Classification Using Tiled Convolutional Neural Networks
Wang, Zhiguang (University of Maryland Baltimore County) | Oates, Tim (University of Maryland Baltimore County)
Inspired by recent successes of deep learning in computer vision and speech recognition, we propose a novel framework to encode time series data as different types of images, namely, Gramian Angular Fields (GAF) and Markov Transition Fields (MTF). This enables the use of techniques from computer vision for classification. Using a polar coordinate system, GAF images are represented as a Gramian matrix where each element is the trigonometric sum (i.e., superposition of directions) between different time intervals. MTF images represent the first order Markov transition probability along one dimension and temporal dependency along the other. We used Tiled Convolutional Neural Networks (tiled CNNs) on 12 standard datasets to learn high-level features from individual GAF, MTF, and GAF-MTF images that resulted from combining GAF and MTF representations into a single image. The classification results of our approach are competitive with five stateof-the-art approaches. An analysis of the features and weights learned via tiled CNNs explains why the approach works.
An Additive Autoregressive Hidden Markov Model for Energy Disaggregation
Early, Kirstin (Carnegie Mellon University) | Kolter, J. Zico (Carnegie Mellon University)
We motivate and develop an additive autoregressive hidden Markov model specifically designed to work on the task of energy disaggregation; that is, separating a whole-building electricity signal into its component device signals whose sum is the aggregate signal observed by a smart meter. This model assumes each device in the building operates as an individual autoregressive HMM, where hidden states represent the underlying power mode of the device and Gaussian emissions correspond to that device's power consumption. The additive property models the observed output (whole-building power signal) as the sum of the emissions of multiple hidden states (i.e., as the sum of individual consumptions of multiple devices in the building). The autoregressive property realistically models how many appliances consume energy and is a new extension to previous work using factorial HMMs for energy disaggregation. Finally, our model also includes a robust mixture component, via an L1-regularized noise term, that can absorb outliers arising in this setting from unknown or rarely-used devices. We extract the power signals and underlying state sequences of single devices in a stagewise fashion and illustrate the results of this process on the Reference Energy Disaggregation Dataset (REDD).
Adaptive Advice in Automobile Climate Control Systems
Rosenfeld, Ariel (Bar-Ilan University) | Azaria, Amos (Carnegie Mellon University) | Kraus, Sarit ( Bar-Ilan University ) | Goldman, Claudia V. (General Motors Advanced Technical Center) | Tsimhoni, Omer (General Motors Advanced Technical Center)
Reducing an automobile's energy consumption will lower its dependency on fossil fuel and extend the travel range of electric vehicles. Automobile Climate Control Systems (CCS) are known to be heavy energy consumers. To help reduce CCS energy consumption, this paper presents an adaptive automated agent, MDP Agent for Climate control Systems -- MACS, which provides drivers advice as to how to set their CCS. First, we present a model which has 78% accuracy in predicting drivers' reactions to different advice in different situations. Using the prediction model, we designed a Markov Decision Process which solution provided the advising policy for MACS. Through empirical evaluation using an electric car, with 83 human subjects, we show that MACS successfully reduced the energy consumption of the subjects by 33% compared to subjects who were not equipped with MACS. MACS also outperformed the state-of-the-art Social agent for Advice Provision (SAP).
Generative Modeling of Hidden Functional Brain Networks
Nandy, Shaurabh, Golden, Richard M.
Functional connectivity refers to the temporal statistical relationship between spatially distinct brain regions and is usually inferred from the time series coherence/correlation in brain activity between regions of interest. In human functional brain networks, the network structure is often inferred from functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) signal. Since the BOLD signal is a proxy for neuronal activity, it is of interest to learn the latent functional network structure. Additionally, despite a core set of observations about functional networks such as small-worldness, modularity, exponentially truncated degree distributions, and presence of various types of hubs, very little is known about the computational principles which can give rise to these observations. This paper introduces a Hidden Markov Random Field framework for the purpose of representing, estimating, and evaluating latent neuronal functional relationships between different brain regions using fMRI data.