We propose a thermodynamic interpretation of transfer entropy near equilibrium, using a specialised Boltzmann's principle. The approach relates conditional probabilities to the probabilities of the corresponding state transitions. This in turn characterises transfer entropy as a difference of two entropy rates: the rate for a resultant transition and another rate for a possibly irreversible transition within the system affected by an additional source. We then show that this difference, the local transfer entropy, is proportional to the external entropy production, possibly due to irreversibility. Near equilibrium, transfer entropy is also interpreted as the difference in equilibrium stabilities with respect to two scenarios: a default case and the case with an additional source. Finally, we demonstrated that such a thermodynamic treatment is not applicable to information flow, a measure of causal effect.

A heat exchanger, using mechanically compressed microporous matrices, is being developed for cooling high power electronics. The thermal efficiency of this new device depends on the hydraulic characteristics (porosity φ, permeability K, and Forchheimer coefficient cF) of the matrix inserted in it. These quantities have to be obtained experimentally as predictive models do not exist. Twenty-eight compressed matrices are initially chosen for experimental testing. Based on structural requirements, nine matrices are selected for full hydraulic characterization. The determination of permeability and inertia coefficient of each matrix is performed following a proposed direct methodology based on the curve fitting of the experimental results. This methodology is found to yield more consistent and accurate results than existing methods. The uncertainty of the experimental results is evaluated with a new and general procedure that can be applied to any curve fitting technique. Results indicate that the tested matrices have a unique characteristic, that of a relatively wide porosity range, from 0.3 to 0.7, within a relatively narrow permeability range, from 1.0 × 10−10 m2 to 12 × 10−10 m2. The inertia coefficient varies from 0.3 to 0.9. These hydraulic characteristics lead to a microporous heat exchanger performing within requirements.

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Special Issue: Special Issue on Space Robotics, Part II Mark Woods, Andy Shaw, Dave Barnes, Dave Price, Derek Long, Derek Pullan, Autonomous science for an ExoMars Rover-like mission, Journal of Field Robotics, Volume 26 Issue 4 (April 2009), pp 358-390. Sponsorship: STFCIn common with other Mars exploration missions, human supervision of Europe's ExoMars Rover will be mostly indirect via orbital relay spacecraft and thus far from immediate. The gap between issuing commands and witnessing the results of the consequent rover actions will typically be on the order of several hours or even sols. In addition, it will not be possible to observe the external environment at the time of action execution. This lengthens the time required to carry out scientific exploration and limits the mission's ability to respond quickly to favorable science events. To increase potential science return for such missions, it will be necessary to deploy autonomous systems that include science target selection and active data acquisition. In this work, we have developed and integrated technologies that we explored in previous studies and used the resulting test bed to demonstrate an autonomous, opportunistic science concept on a representative robotic platform. In addition to progressing the system design approach and individual autonomy components, we have introduced a methodology for autonomous science assessment based on terrestrial field science practice.Peer reviewe