Online Observer-Based Inverse Reinforcement Learning

In this paper, a novel approach to the output-feedback inverse reinforcement learning (IRL) problem is developed by casting the IRL problem, for linear systems with quadratic cost functions, as a state estimation problem. Two observer-based techniques for IRL are developed, including a novel observer method that re-uses previous state estimates via history stacks. Theoretical guarantees for convergence and robustness are established under appropriate excitation conditions. Simulations demonstrate the performance of the developed observers and filters under noisy and noise-free measurements.Comment: 7 pages, 3 figure

Space-Based Ionosonde Receiver and Visible Limb-Viewing Airglow Sensor (SIRVLAS): A CubeSat Instrument Suite for Enhanced Ionospheric Charge Density Measurements

Spatially and temporally varying plasma in the ionosphere refracts passing electromagnetic waves, affecting services including over-the-horizon radar, global positioning systems, and long-distance amateur radio communication. The reliability of these services requires accurate measurements of the charge density of ionospheric plasma. Current methods for estimating ionospheric charge density include ground-based radar soundings in the high frequency (HF) band and airglow limb sensing, typically in the extreme ultraviolet (EUV) spectrum. SIRVLAS is a low-cost, compact instrument suite for these measurements designed by blair3sat, a high school satellite team based in Montgomery County, Maryland. It takes electron density measurements below the F peak of the ionosphere by receiving ionosonde soundings with an onboard VHF antenna and measuring airglow with a limb-view scanner. The payload will take measurements from many locations along its orbital path, enabling high-accuracy electron density mappings in previously unmapped regions. In addition, data correlation between the radar receiver and the airglow detector allows for verification of the instruments’ operation and increased accuracy of local mappings. blair3sat plans to launch a 1U CubeSat in 2022 to demonstrate the feasibility of SIRVLAS. SIRVLAS’ novel method of ionospheric electron density data collection can be utilized on future missions to extend and enhance global ionospheric databases, essential for many radio services and applications. The presence of VHF antenna systems on existing satellites similar to the antenna system on SIRVLAS may allow SIRVLAS RF measurements to be implemented on many satellites using a software modification, allowing existing fleets to contribute towards ionospheric datasets

Personal Information Interfaces

poster abstractAs the ubiquitous computing vision of “computation everywhere” has become increasingly mainstream, people make use of electronic information across multiple form factors, in more places, as part of more activities, and in more social contexts than ever before. This is the crux of the information overload problem: with a vast increase in exposure to information, there is a corresponding increase in the amount of work that people need to invest to keep up with the demands of perceiving, sense-making, organizing, utilizing, and managing that information. Dr. Stephen Voida and his student researchers in the Personal Information Interfaces (PII) laboratory explore ways that the interfaces, interaction techniques, and context-aware infrastructure employed in the next generation of information systems might better respond to the critical, real-world challenges associated with information overload. A new generation of sensor-enabled computing devices stands to magnify the information overload effect by adding streams of data about our environment, our working contexts, and traces of our activities—both online and in the real world—into the mix. A popular example is the growing number of fitness tracking devices that have appeared on the market in the last few years, for example, Fitbits, Nike+ Fuelbands, and the Jawbone Up (just to name a few). Proponents of the “quantified self” movement suggest one way to use the data streams provided by these devices: as a means for self-reflection. However, effective self-reflection requires that a vast amount of information—often highly personal in nature—be captured by our devices, and it introduces new work for end-users, such as finding patterns in the data and translating sensed trends into effective actions. We are currently launching a study of commercial fitness trackers to understand when different representations of self-reflective data streams are effective in helping to facilitate behavior change…and when those representations contribute instead to a sense of information overload. We are also exploring similar questions related to other technologies that collect and present self-reflective data about daily life—time management tools, mood-tracking apps, and the like. In general, we aim to understand how infrastructure and interface design can prevent people’s experiences of sensed data streams from contributing to information overload while still allowing us to capitalize on the positive behavior change and self-reflection potential of this information

Energy Consumption Reduction Strategies for Plug-in Hybrid Electric Vehicles with Connected Vehicle Technology in an Urban Environment

Automobile manufacturers have introduced plug-in hybrid electric vehicles (PHEVs) to reduce fossil fuel consumption. This paper details three optimization strategies that can be utilized to further minimize energy consumption of PHEVs through an information exchange between PHEVs and infrastructure agents supported by the connected vehicle technology (CVT). While an earlier research by the authors focused on a freeway scenario, this study developed strategies for an urban scenario in which frequent ‘stop-and-go’ conditions exist. Three strategies were considered in this study based on different types of information availability using CVT; only signal timing information was available in Strategy One, only headway information was available in Strategy Two, and both signal timing and headway information were available in Strategy Three. The performance of PHEVs that received no real-time information was used as the base case for Strategies One, Two or Three to evaluate each strategy. The optimization strategies resulted in energy consumption savings ranging from 60% to 76%. An analysis with various levels of penetration of CVT-supported PHEVs in the traffic was conducted to demonstrate the impact of these optimization strategies with their increased market share. For a case study network, the authors found a linear trend between energy savings and penetration rate of CVT supported PHEVs. The Strategy Three in which signal timing and headway data were provided to CVT supported PHEVs, resulted in about 31% to 35% energy savings with 30% penetration of CVT supported PHEVs at the peak hour volume

Intragranular Nanocomposite Powders As Building Blocks For Ceramic Nanocomposites

A powder-based bottom-up processing scheme is introduced for the production of ceramic nanocomposites. Internal displacement reactions between solid solution powders and metallic reactants proceeding via gaseous intermediates are utilized to generate nanostructured building blocks for the synthesis of ceramic nanocomposites. Subsequent rapid sintering results in ceramic nanocomposites, whose microstructures are inherited from the building blocks. This processing scheme is demonstrated for the production of titanium carbide nanocomposites featuring up to 28 wt.% intragranular tungsten inclusions derived from titanium-tungsten mixed carbide powders. Heat treatment of mixed carbide powders in evacuated ampoules containing titanium sponge and iodine at 1000°C for 24 h resulted in nanocomposite powders featuring tungsten precipitates within titanium carbide grains that were subsequently consolidated via spark plasma sintering at 1300°C for 10 min to produce titanium carbide/metallic tungsten nanocomposites. Transformation of mixed titanium–tungsten carbide powders to titanium carbide/metallic tungsten nanocomposite powders was analyzed via X-ray diffraction. Electron microscopy observations of microstructures pre- and post- sintering showed that the intragranular character of nanocomposite powders can be retained in sintered ceramic nanocomposites. The building block approach demonstrated in this work represents an improved method to make ceramic nanocomposites with majority intragranular character