Cooperative localization for mobile agents: a recursive decentralized algorithm based on Kalman filter decoupling

We consider cooperative localization technique for mobile agents with communication and computation capabilities. We start by provide and overview of different decentralization strategies in the literature, with special focus on how these algorithms maintain an account of intrinsic correlations between state estimate of team members. Then, we present a novel decentralized cooperative localization algorithm that is a decentralized implementation of a centralized Extended Kalman Filter for cooperative localization. In this algorithm, instead of propagating cross-covariance terms, each agent propagates new intermediate local variables that can be used in an update stage to create the required propagated cross-covariance terms. Whenever there is a relative measurement in the network, the algorithm declares the agent making this measurement as the interim master. By acquiring information from the interim landmark, the agent the relative measurement is taken from, the interim master can calculate and broadcast a set of intermediate variables which each robot can then use to update its estimates to match that of a centralized Extended Kalman Filter for cooperative localization. Once an update is done, no further communication is needed until the next relative measurement

Testing the effectiveness of two natural selection simulations in the context of a large‑enrollment undergraduate laboratory class

Background: Simulations can be an active and engaging way for students to learn about natural selection, and many have been developed, including both physical and virtual simulations. In this study we assessed the student experience of, and learning from, two natural selection simulations, one physical and one virtual, in a large enrollment introductory biology lab course. We assigned students to treatments (the physical or virtual simulation activity) by section and assessed their understanding of natural selection using a multiple-choice pre-/post-test and short-answer responses on a post-lab assignment. We assessed student experience of the activities through structured observations and an affective survey. Results: Students in both treatments showed increased understanding of natural selection after completing the simulation activity, but there were no differences between treatments in learning gains on the pre-/post-test, or in the prevalence of concepts and misconceptions in written answers. On a survey of self-reported enjoyment they rated the physical activity significantly higher than the virtual activity. In classroom observations of student behavior, we found significant differences in the distribution of behaviors between treatments, including a higher frequency of off task behavior during the physical activity. Conclusions: Our results suggest that both simulations are valuable active learning tools to aid students’ understanding of natural selection, so decisions about which simulation to use in a given class, and how to best implement it, can be motivated by contextual factors

A computational group theoretic symmetry reduction package for the SPIN model checker

Symmetry reduced model checking is hindered by two problems: how to identify state space symmetry when systems are not fully symmetric, and how to determine equivalence of states during search. We present TopSpin, a fully automatic symmetry reduction package for the Spin model checker. TopSpin uses the Gap computational algebra system to effectively detect state space symmetry from the associated Promela specification, and to choose an efficient symmetry reduction strategy by classifying automorphism groups as a disjoint/wreath product of subgroups. We present encouraging experimental results for a variety of Promela examples

Laser photosensitization and metabolic inhibition of tissue culture cells treated with quinacrine hydrochloride

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32698/1/0000065.pd

Aeronautic Instruments. Section IV : Direction Instruments

Part one points out the adequacy of a consideration of the steady state gyroscopic motion as a basis for the discussion of displacements of the gyroscope mounted on an airplane, and develops a simple theory on this basis. Principal types of gyroscopic inclinometers are described and requirements stated. Part two describes a new type of stabilizing gyro mounted on top of a spindle by means of a universal joint, the spindle being kept in a vertical position by supporting it as a pendulum of which the bob is the driving motor. Methods of tests and the difficulties in designing a satisfactory and reliable compass for aircraft use in considered in part three. Part four contains a brief general treatment of the important features of construction of aircraft compasses and description of the principal types used

Non-O157 Shiga Toxin–producing Escherichia coli Associated with Venison

News reports of “E. coli outbreaks” usually refer to Shiga toxin–producing E. coli O157. But there are other types of Shiga toxin–producing E. coli, often called STEC,about which less is known. For these other types of STEC, what is the source? What are the risk factors? An outbreak among 29 high school students in Minnesota provided some answers. The source of this outbreak was a white-tailed deer that had been butchered and eaten at the school. The risk factors for infection were handling raw or eating undercooked venison. To prevent this type of STECinfection, people should handle and cook venison with the same caution recommended for other meats

A physically-based model of global freshwater surface temperature

Temperature determines a range of physical properties of water and exerts a strong control on surface water biogeochemistry. Thus, in freshwater ecosystems the thermal regime directly affects the geographical distribution of aquatic species through their growth and metabolism and indirectly through their tolerance to parasites and diseases. Models used to predict surface water temperature range between physically based deterministic models and statistical approaches. Here we present the initial results of a physically based deterministic model of global freshwater surface temperature. The model adds a surface water energy balance to river discharge modeled by the global hydrological model PCR-GLOBWB. In addition to advection of energy from direct precipitation, runoff, and lateral exchange along the drainage network, energy is exchanged between the water body and the atmosphere by shortwave and longwave radiation and sensible and latent heat fluxes. Also included are ice formation and its effect on heat storage and river hydraulics. We use the coupled surface water and energy balance model to simulate global freshwater surface temperature at daily time steps with a spatial resolution of 0.5 degrees on a regular grid for the period 1976-2000. We opt to parameterize the model with globally available data and apply it without calibration in order to preserve its physical basis with the outlook of evaluating the effects of atmospheric warming on freshwater surface temperature. We validate our simulation results with daily temperature data from rivers and lakes (U.S. Geological Survey (USGS), limited to the USA) and compare mean monthly temperatures with those recorded in the Global Environment Monitoring System (GEMS) data set. Results show that the model is able to capture the mean monthly surface temperature for the majority of the GEMS stations, while the interannual variability as derived from the USGS and NOAA data was captured reasonably well. Results are poorest for the Arctic rivers because the timing of ice breakup is predicted too late in the year due to the lack of including a mechanical breakup mechanism. Moreover, surface water temperatures for tropical rivers were overestimated, most likely due to an overestimation of rainfall temperature and incoming shortwave radiation. The spatiotemporal variation of water temperature reveals large temperature differences between water and atmosphere for the higher latitudes, while considerable lateral transport of heat can be observed for rivers crossing hydroclimatic zones, such as the Nile, the Mississippi, and the large rivers flowing to the Arctic. Overall, our model results show promise for future projection of global surface freshwater temperature under global change