2,241 research outputs found
Evaluation of laser range-finder mapping for agricultural spraying vehicles
In this paper, we present a new application of laser range-finder sensing to agricultural spraying vehicles. The current generation of spraying vehicles use automatic controllers to maintain the height of the sprayer booms above the crop.
However, these control systems are typically based on ultrasonic sensors mounted on the booms, which limits the accuracy of the measurements and the response of the controller to changes in the terrain, resulting in a sub-optimal spraying process. To overcome these limitations, we propose to use a laser scanner, attached to the front of the sprayer's cabin, to scan the ground surface in front of the vehicle and to build a scrolling 3d map of the terrain. We evaluate the proposed solution in a series of field tests, demonstrating that the approach provides a more detailed and accurate representation of the environment than the current sonar-based solution, and which can lead to the development of more efficient boom control systems
Exchange coupling inversion in a high-spin organic triradical molecule
The magnetic properties of a nanoscale system are inextricably linked to its
local environment. In ad-atoms on surfaces and inorganic layered structures the
exchange interactions result from the relative lattice positions, layer
thicknesses and other environmental parameters. Here, we report on a
sample-dependent sign inversion of the magnetic exchange coupling between the
three unpaired spins of an organic triradical molecule embedded in a
three-terminal device. This ferro-to-antiferromagnetic transition is due to
structural distortions and results in a high-to-low spin ground state change in
a molecule traditionally considered to be a robust high-spin quartet. Moreover,
the flexibility of the molecule yields an in-situ electric tunability of the
exchange coupling via the gate electrode. These findings open a route to the
controlled reversal of the magnetic states in organic molecule-based
nanodevices by mechanical means, electrical gating or chemical tailoring
144 Hadron minibeam radiation therapy: feasibility study at the Heidelberg Ion-Beam Therapy Center (HIT)
Autonomous Guidance of a Corn Harvester using Stereo Vision
Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 9 (2007): Autonomous Guidance of a Corn Harvester using Stereo Vision. Manuscript ATOE 07 013. Vol. IX. July, 2007
Fitting in a complex chi^2 landscape using an optimized hypersurface sampling
Fitting a data set with a parametrized model can be seen geometrically as
finding the global minimum of the chi^2 hypersurface, depending on a set of
parameters {P_i}. This is usually done using the Levenberg-Marquardt algorithm.
The main drawback of this algorithm is that despite of its fast convergence, it
can get stuck if the parameters are not initialized close to the final
solution. We propose a modification of the Metropolis algorithm introducing a
parameter step tuning that optimizes the sampling of parameter space. The
ability of the parameter tuning algorithm together with simulated annealing to
find the global chi^2 hypersurface minimum, jumping across chi^2{P_i} barriers
when necessary, is demonstrated with synthetic functions and with real data
Guidance and surroundings awareness in outdoor handheld augmented reality
Handheld and wearable devices are becoming ubiquitous in our lives and augmented reality technology is stepping out of the laboratory environment and becoming ready to be used by anyone with portable devices. The success of augmented reality applications for pedestrians depends on different factors including a reliable guidance system and preventing risks. We show that different guidance systems can be supplementary to provide directions to a point of interest and offer clues that help the user find the augmented data when they get close to the location they have to visit. We tested the helpfulness of a map with the points of interest, an image preview of the next point of interest to visit, and an arrow showing the direction to it. The results show that the effectiveness of these guidance systems depend on the distance to the point of interest and the accuracy of the data obtained from the Global Positioning System. We also measured the total time that participants spent looking at the screen, as well as the perceived elapsed time as a measurement of real world dissociation. Finally, we discuss preliminary results to minimize the risk of accidents when using augmented reality applications in an outdoor urban environment
Infrared Investigation of the Charge Ordering Pattern in the Organic Spin Ladder Candidate (DTTTF)2Cu(mnt)2
We measured the variable temperature infrared response of the spin ladder
candidate (DTTTF)2Cu(mnt)2 in order to distinguish between two competing ladder
models, rectangular versus zigzag, proposed for this family of materials. The
distortion along the stack direction below 235 K is consistent with a doubling
along b through the metal-insulator transition. While this would agree with
either of the ladder models, the concomitant transverse distortion rules out
the rectangular ladder model and supports the zigzag scenario. Intramolecular
distortions within the DTTTF building block molecule also give rise to on-site
charge asymmetry.Comment: 4 pages, 4 figures, submitted to Solid State Science
- …