26,608 research outputs found
UAV as a Reliable Wingman: A Flight Demonstration
In this brief, we present the results from a flight experiment demonstrating two significant advances in software enabled control: optimization-based control using real-time trajectory generation and logical programming environments for formal analysis of control software. Our demonstration platform consisted of a human-piloted F-15 jet flying together with an autonomous T-33 jet. We describe the behavior of the system in two scenarios. In the first, nominal state communications were present and the autonomous aircraft maintained formation as the human pilot flew maneuvers. In the second, we imposed the loss of high-rate communications and demonstrated an autonomous safe “lost wingman” procedure to increase separation and reacquire contact. The flight demonstration included both a nominal formation flight component and an execution of the lost wingman scenario
Implementation of a Direct-Imaging and FX Correlator for the BEST-2 Array
A new digital backend has been developed for the BEST-2 array at
Radiotelescopi di Medicina, INAF-IRA, Italy which allows concurrent operation
of an FX correlator, and a direct-imaging correlator and beamformer. This
backend serves as a platform for testing some of the spatial Fourier transform
concepts which have been proposed for use in computing correlations on
regularly gridded arrays. While spatial Fourier transform-based beamformers
have been implemented previously, this is to our knowledge, the first time a
direct-imaging correlator has been deployed on a radio astronomy array.
Concurrent observations with the FX and direct-imaging correlator allows for
direct comparison between the two architectures. Additionally, we show the
potential of the direct-imaging correlator for time-domain astronomy, by
passing a subset of beams though a pulsar and transient detection pipeline.
These results provide a timely verification for spatial Fourier transform-based
instruments that are currently in commissioning. These instruments aim to
detect highly-redshifted hydrogen from the Epoch of Reionization and/or to
perform widefield surveys for time-domain studies of the radio sky. We
experimentally show the direct-imaging correlator architecture to be a viable
solution for correlation and beamforming.Comment: 12 pages, 17 figures, 2 tables, Accepted to MNRAS January 24, 2014,
includes appendix diagram
Measuring and explaining cross-country immigration policies
The intensified international migration pressures of the recent decades prompted many developed countries to revise their immigration regulations and increase border controls. However, the development of these reforms as well as their effectiveness in actually managing new immigration flows remains poorly understood. The main reason is that migration regulations are hard to quantify, which has prevented the construction of a universal measure of migration policy. To fill this gap in the literature, we construct an indicator of the restrictiveness of immigration entry policy across countries as well as a more comprehensive indicator of migration policy that also accounts for staying requirements and regulations to foster integration. These indexes are then used to disentangle the factors determining the toughness of migration regulations. Our empirical framework combines elements from the median voter and interest group approach and accounts for cross-country correlation in migration policies. We find strong evidence of spatial correlation in particular in entry restrictiveness, while the impact of economic determinants of migration policy remains much more modest
LTLf/LDLf Non-Markovian Rewards
In Markov Decision Processes (MDPs), the reward obtained in a state is Markovian, i.e., depends on the last state and action. This dependency makes it difficult to reward more interesting long-term behaviors, such as always closing a door after it has been opened, or providing coffee only following a request. Extending MDPs to handle non-Markovian reward functions was the subject of two previous lines of work. Both use LTL variants to specify the reward function and then compile the new model back into a Markovian model. Building on recent progress in temporal logics over finite traces, we adopt LDLf for specifying non-Markovian rewards and provide an elegant automata construction for building a Markovian model, which extends that of previous work and offers strong minimality and compositionality guarantees
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