Certainty grids for mobile robots

A numerical representation of uncertain and incomplete sensor knowledge called Certainty Grids has been used successfully in several mobile robot control programs, and has proven itself to be a powerful and efficient unifying solution for sensor fusion, motion planning, landmark identification, and many other central problems. Researchers propose to build a software framework running on processors onboard the new Uranus mobile robot that will maintain a probabilistic, geometric map of the robot's surroundings as it moves. The certainty grid representation will allow this map to be incrementally updated in a uniform way from various sources including sonar, stereo vision, proximity and contact sensors. The approach can correctly model the fuzziness of each reading, while at the same time combining multiple measurements to produce sharper map features, and it can deal correctly with uncertainties in the robot's motion. The map will be used by planning programs to choose clear paths, identify locations (by correlating maps), identify well-known and insufficiently sensed terrain, and perhaps identify objects by shape. The certainty grid representation can be extended in the same dimension and used to detect and track moving objects

A perspective on non-local electronic transport in metals : viscous, ballistic, and beyond

Funding: Open access funding enabled and organized by Projekt DEAL.Ohm's law for electrical conduction in metals is one of the first concepts taught in any physics curriculum. It is perfectly adequate in almost all practical circumstances, but breaks down in some special, interesting cases. To observe such breakdowns, one requires extremely pure materials, which are rare and often difficult to produce. Excitingly, forefront materials research is leading to the discovery of more and more examples in which one can break the ‘purity barrier’ and explore non-Ohmic transport. The rapid development of the field is seeing equally rapid developments in the understanding of exotic non-Ohmic regimes, but this is not always a smooth progression. New layers of insight often involve reversing what have previously been regarded as established facts. Indeed, the interpretations given of experimental data in many papers published less than a decade ago would (or should!) be different today. The goal of this article is to give an entry-level guide to some of the pertinent issues that have emerged from this intense decade of research, attempting to keep the style of the presentation as informal and non-mathematical as is practical. Although source literature will be cited, no attempt will be made at comprehensive citation, so the paper should not be regarded as a review. Rather, an effort will be made to identify and explain some issues that the authors believe are important but not sufficiently emphasized in the literature to date. In that sense the paper should be regarded as a kind of opinion piece, with, hopefully, some didactic value to a reader with a solid grounding in traditional condensed matter physics.Peer reviewe

Moon-tracking orbits using motorized tethers for continuous earth–moon payload exchanges

For human colonization of the moon to become reality, an efficient and regular means of exchanging resources between the Earth and the moon must be established. One possibility is to pass and receive payloads at regular intervals between a symmetrically laden motorized momentum-exchange tether orbiting about Earth and a second orbiting about the moon. There are significant challenges associated with this method, among the greatest of which is the development of a system that incorporates the complex motion of the moon into its operational architecture in addition to conducting these exchanges on a per-lunar-orbit basis. One way of achieving this is to use a motorized tether orbiting Earth and tracking the nodes of the moon’s orbit to allow payload exchanges to be undertaken periodically with the arrival of the moon at either of these nodes. Tracking these nodes is achieved by arranging the tether to orbit Earth with a critical inclination, thus rendering its argument of perigee stationary in addition to using the precession effects resulting from an oblate Earth. Using this in conjunction with pre-emptive adjustments to its angle of right ascension, the tether will periodically realign itself with these nodes simultaneously with the arrival of the moon

Electrical properties of CdTe near the melting point

A new experimental setup for the investigation of electrical conductivity (σ) in liquid and solid CdTe was built for a better understanding of the properties near the melting point (MP). The temperature dependence of σ was studied, within the interval 1,050-1,130°C, at defined Cd-partial pressures 1.3-1.6 atm, with special attention to the liquid-solid phase transition. We found that the degree of supercooling decreases with increasing Cd overpressure and reaches the lowest value at 1.6 atm without change of the melting temperature during heating

Conceptual spatial representations for indoor mobile robots

We present an approach for creating conceptual representations of human-made indoor environments using mobile robots. The concepts refer to spatial and functional properties of typical indoor environments. Following findings in cognitive psychology, our model is composed of layers representing maps at different levels of abstraction. The complete system is integrated in a mobile robot endowed with laser and vision sensors for place and object recognition. The system also incorporates a linguistic framework that actively supports the map acquisition process, and which is used for situated dialogue. Finally, we discuss the capabilities of the integrated system