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Lleida, Spain

Garcia A.L.,University of Lleida | Recasens J.,University of Lleida | Forcella F.,U.S. Department of Agriculture | Torra J.,Fundacio Center | Royo-Esnal A.,University of Lleida
Weed Science | Year: 2013

A model that describes the emergence of ripgut brome was developed using a two-season data set from a no-tilled field in northeastern Spain. The relationship between cumulative emergence and hydrothermal time (HTT) was described by a sigmoid growth function (Chapman). HTT was calculated with a set of water potentials and temperatures, iteratively used, to determine the base water potential and base temperature. Emergence of ripgut brome was well described with a Chapman function. The newly-developed function was validated with four sets of data, two of them belonging to a third season in the same field and the other two coming from independent data from Southern Spain. The model also successfully described the emergence in different field management and tillage systems. This model may be useful for predicting ripgut brome emergence in winter cereal fields of semiarid Mediterranean regions. © Weed Science Society of America. Source

Westerman P.R.,University of Rostock | Atanackovic V.,University of Lleida | Royo-Esnal A.,University of Lleida | Torra J.,University of Lleida | Torra J.,Fundacio Center
Arthropod-Plant Interactions | Year: 2012

Weeds persist in rain-fed cereal fields in NE Spain, despite intense herbicide use and high seed removal rates by granivorous harvester ants. Herbicide resistance is involved, but certain weed species also appear to escape seed removal by granivores. To identify the mechanisms involved, we measured seed removal rates (three fields in 2010) and the timing of seed shed (one field in 2009 and three fields in 2010) and used an existing model, which integrates short-term rates of seed shed, burial and removal, to estimate long-term seed removal rates. Averaged over years, fields and weed species, the long-term seed removal rate was estimated at 72 % (range 46-100 %). Fifteen to 25 % of the seeds of Bromusdiandrus avoided removal by being less attractive (low removal rates), and another 0-29 % escaped through crop harvest, which made seeds inaccessible to granivores. Similarly, 20-32 % of the Papaverrhoeas seeds escaped through crop harvest, while another 13-17 % escaped by burial into the soil (small seed size). Other species, such as Galiumspurium or Diplotaxiserucoides, had no means of avoiding seed removal by harvester ants. In particular, the more troublesome weeds, such as B. diandrus, P. rhoeas and L. rigidum, combined herbicide resistance or tolerance with avoidance mechanisms against granivory. © 2012 Springer Science+Business Media B.V. Source

Gom Ayats J.R.,Polytechnic University of Catalonia | Diego-Ayala U.,Electronic Variable Technologies SL | Artes F.F.,Polytechnic University of Catalonia | Artes F.F.,Fundacio Center
Journal of Power Sources | Year: 2012

The singular point transition concept relates a novel type of continuously variable transmission. This transmission comprises a pair of planetary gear trains and a couple of electric motors, used to control the overall speed ratio. Its singularity lies in the topology of operation, with less than 10% of nominal power circulating through the electric path. This low power level is achieved by segmenting the range of operation of the transmission. To validate this technology, a test bed was built. The transmission presented here is able to provide any output/input speed ratio within the interval of 0:1.55, meaning that it also offers the function of an infinite variable transmission. Description of the system and results of experimental tests are presented. The results showed that the transmission is able to function in the whole range of operation. They also showed that under load conditions the fraction of power transmitted through the electric path is maintained around the design value. © 2011 Published by Elsevier B.V. Source

Baino F.,Polytechnic University of Turin | Tallia F.,Imperial College London | Novajra G.,Fundacio Center | Minguella J.,Technology Center | And 2 more authors.
Key Engineering Materials | Year: 2015

Over the last two decades, the philosophy behind an optimal fixation of orthopaedic implants progressively evolved towards "bone-conservative" solutions and, accordingly, the researchers' attention moved from simple mechanical fixation of the prosthesis to host bone by using screws or acrylic cement to new strategies based on a physico-chemical bond (surface modification) in order to minimize bone resection/loss and maximize tissue-implant integration. This research work explores the feasibility of a novel bioceramic single-piece acetabular cup for hip joint prosthesis that can be anchored to the patient's pelvic bone by means of a bone-like trabecular coating (scaffold) able to promote implant osteointegration. © (2015) Trans Tech Publications, Switzerland. Source

Goma Ayats J.R.,Polytechnic University of Catalonia | Diego-Ayala U.,Electronic Variable Technologies SL | Minguella Canela J.,Polytechnic University of Catalonia | Minguella Canela J.,Fundacio Center | And 3 more authors.
Mechanism and Machine Theory | Year: 2012

This article presents a methodology for the kinematic analysis of complex gear trains comprised of planetary gear trains. It is based on the utilisation of hypergraphs, which provides a novel view into the analysis of this type of power trains. The hypergraphs are used to aid in the understanding of the inter-relation between the various branches of the mechanism and to develop the kinematic equations. The method presented here provides a way to define the kinematic relations existing between all the branches of a mechanism, including branches with a variable speed ratio. The time required to determine the equations for the speeds of different branches can be dramatically reduced if this method is followed. © 2011 Elsevier Ltd. All rights reserved. Source

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