Modelling Emotion Based Reward Valuation with Computational Reinforcement Learning

We show that computational reinforcement learning can model human decision making in the Iowa Gambling Task (IGT). The IGT is a card game, which tests decision making under uncertainty. In our experiments, we found that modulating learning rate decay in Q-learning, enables the approximation of both the behaviour of normal subjects and those who are emotionally impaired by ventromedial prefrontal lesions. Outcomes observed in impaired subjects are modeled by high learning rate decay, while low learning rate decay replicates healthy subjects under otherwise identical conditions. The ventromedial prefrontal cortex has been associated with emotion based reward valuation, and, the value function in reinforcement learning provides an analogous assessment mechanism. Thus reinforcement learning can provide a good model for the role of emotional reward as a modulator of the learning rate

Robust active heave compensated winch-driven overhead crane system for load transfer in marine operation

Active heave compensation (AHC) is important for load transfer in marine operation using the overhead crane system (OCS). The control of marine OCS aims to continuously regulate the displacement of the cart and the payload sway angle, whilst at the same time, maintaining the gap between the payload and the vessel main deck at a desirable and safe distance. As the marine OHC system is to be operated in a continuously changing environment, with plenty inevitable disturbances and undesirable loads, a robust controller, i.e., active force control (AFC) is thus greatly needed to promote accuracy and robustness features into the controllability of OCS in rough working environment. This paper highlights a novel method for controlling the payload in an OCS based on the combination of both AFC and AHC. Results from the simulation study clearly indicate that the performance of OCS can be greatly improved by the proposed robust AFC controller, as compared with the classical PID controller scheme

Quantum kinetic theory of trapped atomic gases

We present a general framework in which we can accurately describe the non-equilibrium dynamics of trapped atomic gases. This is achieved by deriving a single Fokker-Planck equation for the gas. In this way we are able to discuss not only the dynamics of an interacting gas above and below the critical temperature at which the gas becomes superfluid, but also during the phase transition itself. The last topic cannot be studied on the basis of the usual mean-field theory and was the main motivation for our work. To show, however, that the Fokker-Planck equation is not only of interest for recent experiments on the dynamics of Bose-Einstein condensation, we also indicate how it can, for instance, be applied to the study of the collective modes of a condensed Bose gas.Comment: 12 pages of LaTeX and two postscript figures. Contribution to NATO-ASI Dynamics: Models and Kinetic Methods for Non-Equilibrium Many-Body Systems edited by John Karkhec

Coherent versus Incoherent Dynamics during Bose-Einstein Condensation in Atomic Gases

We review and extend the theory of the dynamics of Bose-Einstein condensation in weakly interacting atomic gases. We present in a unified way both the semiclassical theory as well as the full quantum theory. This is achieved by deriving a Fokker-Planck equation that incorporates both the coherent and incoherent effects of the interactions in a dilute Bose gas. In first instance we focus our attention on the nonequilibrium dynamics of a homogeneous Bose gas with a positive interatomic scattering length. After that we discuss how our results can be generalized to the inhomogeneous situation that exists in the present experiments with magnetically trapped alkali gases, and how we can deal with a negative interatomic scattering length in that case as well. We also show how to arrive at a discription of the collective modes of the gas that obeys the Kohn theorem at all temperatures. The theory is based on the many-body T-matrix approximation throughout, since this approximation has the correct physical behavior near the critical temperature and also treats the coherent and incoherent processes taking place in the gas on an equal footing.Comment: In response to referee report I have rewritten the introduction. I have also added new results for the decay rate of a condensate with negative scattering length and for the collisionless collective modes of a Bose condensed atomic gas at nonzero temperature

Squeeze-film gas bearing technology

Squeeze-film bearing is studied to develop a low-friction suspension for the output-axis gimbal of a single-degree-of-freedom gyroscope. Included are a review of pertinent literature, the theory of squeeze-film lubrication, and design elements

Vibration damping system Patent

Vibration damping system operating in low vacuum environment for spacecraft mechanism

Tadpole renormalization and relativistic corrections in lattice NRQCD

We make a comparison of two tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Improved gauge-field and NRQCD actions are analyzed using the mean-link $u_{0,L}$ in Landau gauge, and using the fourth root of the average plaquette $u_{0,P}$. Simulations are done for $c\bar c$, $b\bar c$, and $b\bar b$ systems. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at lattice spacings in the range of about 0.14~fm to 0.38~fm. A number of features emerge, all of which favor tadpole renormalization using $u_{0,L}$. This includes much better scaling behavior of the hyperfine splittings in the three quarkonium systems when $u_{0,L}$ is used. We also find that relativistic corrections to the spin splittings are smaller when $u_{0,L}$ is used, particularly for the $c\bar c$ and $b\bar c$ systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units. Simulations with $u_{0,L}$ also appear to be better behaved in this context: the bare quark masses turn out to be larger when $u_{0,L}$ is used, compared to when $u_{0,P}$ is used on lattices with comparable spacings. These results also demonstrate the need to go beyond tree-level tadpole improvement for precision simulations.Comment: 14 pages, 7 figures (minor changes to some phraseology and references