Using Monte Carlo Search With Data Aggregation to Improve Robot Soccer Policies

RoboCup soccer competitions are considered among the most challenging multi-robot adversarial environments, due to their high dynamism and the partial observability of the environment. In this paper we introduce a method based on a combination of Monte Carlo search and data aggregation (MCSDA) to adapt discrete-action soccer policies for a defender robot to the strategy of the opponent team. By exploiting a simple representation of the domain, a supervised learning algorithm is trained over an initial collection of data consisting of several simulations of human expert policies. Monte Carlo policy rollouts are then generated and aggregated to previous data to improve the learned policy over multiple epochs and games. The proposed approach has been extensively tested both on a soccer-dedicated simulator and on real robots. Using this method, our learning robot soccer team achieves an improvement in ball interceptions, as well as a reduction in the number of opponents' goals. Together with a better performance, an overall more efficient positioning of the whole team within the field is achieved

A note on leapfrogging vortex rings

In this paper we provide examples, by numerical simulation using the Navier-Stokes equations for axisymmetric laminar flow, of the 'leapfrogging' motion of two, initially identical, vortex rings which share a common axis of symmetry. We show that the number of clear passes that each ring makes through the other increases with Reynolds number, and that as long as the configuration remains stable the two rings ultimately merge to form a single vortex ring

Simulator study of the effect of control-system time delays on the occurrence of pilot-induced oscillations and on pilot tracking performance with a space-shuttle-orbiter configuration

Using a six degree-of-freedom motion-base simulator, the effect of control-system time delays on the occurrence of pilot-induced oscillations (PIO's) on the vehicle handling qualities and on pilot tracking performance for a landing-approach configuration of the Space Shuttle orbiter was studied. A linearized math model was employed which represented a 300-knot orbiter with almost all time delays removed. Additional time delays were then inserted following the pilot's hand-controller signals. Only pitch and roll commands were used for vehicle control. The simulation employed an air to air tracking task as a means of emphasizing PIO tendencies. Two astronauts, two research pilots, and one simulation engineer served as test subjects. Results showed that PIO's occurred when the amount of added time delay approximated that existing for the orbiter configuration flown in the approach and landing tests. Increasing the amount of delay increased PIO occurrences and resulted in degraded tracking performance. Decreasing the amount of time delay eliminated the PIO's

Comparison of analytical predictions of longitudinal short period pilot-induced oscillations with results from a simulation study of the space shuttle orbiter

An analytical analysis of conditions producing pilot induced oscillations (PIO's) was made for the space shuttle orbiter in a landing approach configuration for the task of milling the elevation angle of the line of sight to a target vehicle. The analysis yielded a value of PIO frequency and a value for the amount of total system time delay (pilot + control system) that can be tolerated before instability results. Calculations were performed showing the effect of varying the range to the target and of varying the handling qualities of the orbiter vehicle. Analytical predictions were compared with simulation results obtained using a visual motion simulator

Simulator study of the effect of visual-motion time delays on pilot tracking performance with an audio side task

The effect of time delay was determined in the visual and motion cues in a flight simulator on pilot performance in tracking a target aircraft that was oscillating sinusoidally in altitude only. An audio side task was used to assure the subject was fully occupied at all times. The results indicate that, within the test grid employed, about the same acceptable time delay (250 msec) was obtained for a single aircraft (fighter type) by each of two subjects for both fixed-base and motion-base conditions. Acceptable time delay is defined as the largest amount of delay that can be inserted simultaneously into the visual and motion cues before performance degradation occurs. A statistical analysis of the data was made to establish this value of time delay. Audio side task provided quantitative data that documented the subject's work level

Preterm infants have deficient monocyte and lymphocyte cytokine responses to Group B Streptococcus

Group B streptococcus GBS) is an important cause of early-and late-onset sepsis in the newborn. Preterm infants have markedly increased susceptibility and worse outcomes, but their immunological responses to GBS are poorly defined. We compared mononuclear cell and whole-blood cytokine responses to heat-killed GBS HKGBS) of preterm infants gestational age [GA], 26 to 33 weeks), term infants, and healthy adults. We investigated the kinetics and cell source of induced cytokines and quantified HKGBS phagocytosis. HKGBS-induced tumor necrosis factor TNF) and interleukin 6 (IL-6) secretion was significantly impaired in preterm infants compared to that in term infants and adults. These cytokines were predominantly monocytic in origin, and production was intrinsically linked to HKGBS phagocytosis. Very preterm infants GA, < 30 weeks) had fewer cytokine-producing monocytes, but nonopsonic phagocytosis ability was comparable to that for term infants and adults. Exogenous complement supplementation increased phagocytosis in all groups, as well as the proportion of preterm monocytes producing IL-6, but for very preterm infants, responses were still deficient. Similar defective preterm monocyte responses were observed in fresh whole cord blood stimulated with live GBS. Lymphocyte-associated cytokines were significantly deficient for both preterm and term infants compared to levels for adults. These findings indicate that a subset of preterm monocytes do not respond to GBS, a defect compounded by generalized weaker lymphocyte responses in newborns. Together these deficient responses may increase the susceptibility of preterm infants to GBS infection

15 years of VLBI observations of two compact radio sources in Messier 82

We present the results of a second epoch of 18cm global Very Long-Baseline Interferometry (VLBI) observations, taken on 23 February 2001, of the central kiloparsec of the nearby starburst galaxy Messier 82. These observations further investigate the structural and flux evolution of the most compact radio sources in the central region of M82. The two most compact radio objects in M82 have been investigated (41.95+575 and 43.31+592). Using this recent epoch of data in comparison with our previous global VLBI observations and two earlier epochs of European VLBI Network observations we measure expansion velocities in the range of 1500-2000km/s for 41.95+575, and 9000-11000km/s for 43.31+592 using various independent methods. In each case the measured remnant expansion velocities are significantly larger than the canonical expansion velocity (500km/s) of supernova remnants within M82 predicted from theoretical models. In this paper we discuss the implications of these measured expansion velocities with respect to the high density environment that the SNR are expected to reside in within the centre of the M82 starburst.Comment: Accepted for publication in MNRAS, 9 pages, 8 figure

Second Epoch Global VLBI Observations of Compact Radio Sources in the M82 Starburst Galaxy

We have presented the results of a second epoch of global Very Long Baseline Interferometry observations, taken on 23 February 2001 at a wavelength of 18 cm, of the central kiloparsec of the nearby starburst galaxy Messier 82. These observations were aimed at studying the structural and flux evolution of some of the compact radio sources in the central region that have been identified as supernova remnants. The objects 41.95+575 and 43.31+592 have been studied, expansion velocities of 2500 +/- 1200 km/s and 7350 +/- 2100 km/s respectively have been derived. Flux densities of 31.1 +/- 0.3 mJy and 17.4 +/- 0.3 mJy have been measured for the two objects. These results are consistent with measurements and predictions from previous epochs.Comment: 5 pages, 3 figures. To be published on the accompanying CD of the Proceedings of IAU Colloquium 192: Supernova

The effect of seed origin and seed phosphorus on the growth of lupins

Trial: 89SC20 Location: South Carrabin Research Station, Hayden paddock. The effects of superphosphate and fertilizer on seeds planted over a 21 week period

Effects of seed phosphorus concentrations and the source of the seed on growth of lupins.

Trial 89EC31 Location: East Chapman Research Station. The effect of seed phosphorus concentration, source of seed and fertilizer P level on plant counts from six to 20 weeks