7,235 research outputs found
An effective line search for the subgradient method
One of the main drawbacks of the subgradient method is
the tuning process to determine the sequence of steplengths. In this
paper, the radar subgradient method, a heuristic method designed
to compute a tuning-free subgradient steplength, is geometrically
motivated and algebraically deduced. The unit commitment problem,
which arises in the electrical engineering field, is used to compare the
performance of the subgradient method with the new radar subgradient
method.Peer ReviewedPostprint (published version
Fault-tolerant formation driving mechanism designed for heterogeneous MAVs-UGVs groups
A fault-tolerant method for stabilization and navigation of 3D heterogeneous formations is proposed in this paper. The presented Model Predictive Control (MPC) based approach enables to deploy compact formations of closely cooperating autonomous aerial and ground robots in surveillance scenarios without the necessity of a precise external localization. Instead, the proposed method relies on a top-view visual relative localization provided by the micro aerial vehicles flying above the ground robots and on a simple yet stable visual based navigation using images from an onboard monocular camera. The MPC based schema together with a fault detection and recovery mechanism provide a robust solution applicable in complex environments with static and dynamic obstacles. The core of the proposed leader-follower based formation driving method consists in a representation of the entire 3D formation as a convex hull projected along a desired path that has to be followed by the group. Such an approach provides non-collision solution and respects requirements of the direct visibility between the team members. The uninterrupted visibility is crucial for the employed top-view localization and therefore for the stabilization of the group. The proposed formation driving method and the fault recovery mechanisms are verified by simulations and hardware experiments presented in the paper
ï»żA new stream treefrog of the genus Hyloscirtus (Amphibia, Hylidae) from the RĂo Negro-Sopladora National Park, Ecuador
Recent surveys in the RĂo Negro-Sopladora National Park revealed a striking new species of Hyloscirtus. The new species is easily diagnosed from all other congeners by its large body size (64.9 mm SVL in adult female); broad dermal fringes in fingers and toes; prepollex not projected into a prepollical spine and hidden under thenar tubercle; dorsum greyish-green, with paler-hued reticulum, yellow spots and black speckles; throat, venter, flanks and hidden surfaces of limbs golden-yellow with large black blotches and spots; fingers, toes and webbing yellow with black bars and spots; iris pale pink with black periphery. It is currently known only from its type locality, in the high montane forest on the southern slopes of the Cordillera Oriental of the Andes, southeastern Ecuador. The new species might be related to the H. larinopygion species group based on its morphology
Use of Native Grassland in Small-Scale Dairy Systems in the Highlands of Central Mexico. A Case Study
Small-scale dairy systems in Mexico comprise 78% of specialized dairy farms and provide 37% of national production. They are small farms with herds 3-35 cows plus replacements, and rely on family labour (Posadas-DomĂnguez et al., 2014).
In the highlands, many farms have native grasslands, grazed during the rainy season, and supplemented with other feeds as maize straw, maize grain and maize ears. Native grasslands have not been studied in this context. This is a case study on the use of native grassland in a small-scale dairy farm. The objective was to determine how native grasslands are integrated in feeding milking dairy cows, and the feeding costs involved
On Optimal Coverage of a Tree with Multiple Robots
We study the algorithmic problem of optimally covering a tree with mobile
robots. The tree is known to all robots, and our goal is to assign a walk to
each robot in such a way that the union of these walks covers the whole tree.
We assume that the edges have the same length, and that traveling along an edge
takes a unit of time. Two objective functions are considered: the cover time
and the cover length. The cover time is the maximum time a robot needs to
finish its assigned walk and the cover length is the sum of the lengths of all
the walks. We also consider a variant in which the robots must rendezvous
periodically at the same vertex in at most a certain number of moves. We show
that the problem is different for the two cost functions. For the cover time
minimization problem, we prove that the problem is NP-hard when is part of
the input, regardless of whether periodic rendezvous are required or not. For
the cover length minimization problem, we show that it can be solved in
polynomial time when periodic rendezvous are not required, and it is NP-hard
otherwise
Education for innovation and entrepreneurship in the food system: the Erasmus+ BoostEdu approach and results
Innovation and entrepreneurship are key factors to provide added value for food systems. Based on the findings of the Erasmus+ Strategic Partnership BoostEdu, the objective of this paper is to provide answers to three knowledge gaps: 1) identify the needs for innovation and entrepreneurship (I&E) in the food sector; 2) understand the best way to organize learning; 3) provide flexibility in turbulent times. BoostEdu aimed to provide a platform for continuing education within I&E for food professionals and was carried out through co-creation workshops and the development of an e-learning course. The results of the project in particular during the Covid-19 pandemics, highlighted the need for flexible access to modules that are complementary to other sources and based on a mix of theoretical concepts and practical experiences. The main lessons learned concern the need of co-creation and co-learning processes to identify suitable practices for the use of innovative digital technologies
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