Obstacle avoidance based-visual navigation for micro aerial vehicles

This paper describes an obstacle avoidance system for low-cost Unmanned Aerial Vehicles (UAVs) using vision as the principal source of information through the monocular onboard camera. For detecting obstacles, the proposed system compares the image obtained in real time from the UAV with a database of obstacles that must be avoided. In our proposal, we include the feature point detector Speeded Up Robust Features (SURF) for fast obstacle detection and a control law to avoid them. Furthermore, our research includes a path recovery algorithm. Our method is attractive for compact MAVs in which other sensors will not be implemented. The system was tested in real time on a Micro Aerial Vehicle (MAV), to detect and avoid obstacles in an unknown controlled environment; we compared our approach with related works.Peer ReviewedPostprint (published version

Condensed tannins in the gastrointestinal tract of cattle after sainfoin (Onobrychis viciifolia) intake and their possible relationship with anthelmintic effects

The fate of condensed tannins (CTs) along the digestive tract of ruminants is not well known and may account for the variable efficacy of CTs against gastrointestinal nematodes in different locations. Here, we analyzed sainfoin CTs in the digesta of cattle from two separate experiments. When using the acetone-butanol-HCl assay, the total CTs concentrations in the digestive tract were close to those in the diets (6.3 and 1.5% of DM in Expt. 1 and 2, resp.) indicating that CTs remained largely undegraded and unabsorbed. Yet with the thiolysis assay in Expt. 1, CTs concentration was much higher in the abomasum (2.3 ± 0.4 % of DM) compared with the rumen, small and large intestines, along with increases of mean size and percentage of prodelphinidins within CTs. This corroborates the anthelmintic efficacy reported only against Ostertagia ostertagi in the abomasum. In Expt. 2, no anthelmintic effect was observed against the larval exsheathment in the rumen, probably because the dietary level of CTs was too low. Overall, the level of CTs accessible to thiolysis in the gut appears to be critical for anthelmintic activity, which is favored under the acidic conditions of the abomasum

Optical polarization of neutron-rich sodium isotopes and β\beta-NMR measurements of quadrupole moments

The nuclear quadrupole moments of neutron-rich sodium isotopes are being investigated with the help of in-beam polarization by optical pumping in combination with $\beta$-NMR techniques. First measurements have yielded the quadrupole splittings of NMR signals in the lattice of LiNbO$_{3}$ for the isotopes $^{26}$Na, $^{27}$Na and $^{28}$Na. Interaction constants and ratios of the electric quadrupole moments are derived. In view of future experiments, $\beta$-decay asymmetries for the sequence of isotopes up to the $N$=20 neutron shell closure, $^{26-31}$Na, have been measured

Measurement of the magnetic moment of the one-neutron halo nucleus 11^{11}Be

The magnetic moment of $^{11}$Be was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a $^{11}$Be$^+$ ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal and observation of rf resonances in the asymmetric angular distribution of the $\beta$-decay ($\beta$-NMR). The nuclear magnetic moment $\mu(^{11}{\rm Be}) = -1.6816(8)\,\mu_N$ provides a stringent test for theoretical models describing the structure of the 1/2$^+$ neutron halo state

Data compression for the First G-APD Cherenkov Telescope

The First Geiger-mode Avalanche photodiode (G-APD) Cherenkov Telescope (FACT) has been operating on the Canary island of La Palma since October 2011. Operations were automated so that the system can be operated remotely. Manual interaction is required only when the observation schedule is modified due to weather conditions or in case of unexpected events such as a mechanical failure. Automatic operations enabled high data taking efficiency, which resulted in up to two terabytes of FITS files being recorded nightly and transferred from La Palma to the FACT archive at ISDC in Switzerland. Since long term storage of hundreds of terabytes of observations data is costly, data compression is mandatory. This paper discusses the design choices that were made to increase the compression ratio and speed of writing of the data with respect to existing compression algorithms. Following a more detailed motivation, the FACT compression algorithm along with the associated I/O layer is discussed. Eventually, the performances of the algorithm is compared to other approaches.Comment: 17 pages, accepted to Astronomy and Computing special issue on astronomical file format

Case Conferencing Decreases Occupational Stress for VRS Interpreters: A Qualitative Study

Many sign language interpreters working within Video Relay Services (VRS) experience more occupational stress than interpreters working in community settings (Dean, Pollard, & Samar, 2010). There exists a lack of research to guide the field of sign language interpreting in coping strategies that can be used to decrease the stress and burnout that is endemic to working in VRS. This qualitative research case study explores how case conferencing can be strategic in mitigating stress and increasing retention in the field. Case conferencing combined with Dean and Pollard’s Demand Control Schema is a relatively recent approach for critical thinking and ethical decision making in the field of sign language interpreting. This researcher found that case conferencing can be a useful vehicle for ameliorating the stressful effects of working in VRS. Focus groups were conducted with VRS interpreters who participated in case conferencing workshops that were facilitated by the researcher between 2013 and 2017. Themes of effectively reducing stress, application of skills, integration of practice, increased retention and a more positive professional community were derived from the participants in the focus groups. The elements of validation and empathy combined with a group format for case conferencing could be used to increase VRS’ interpreters’ self-efficacy. Case conferencing, in turn, may result in improved access for consumers who are deaf and hard of hearing who utilize telecommunication services