454 research outputs found
A simple maximum power point tracking based control strategy applied to a variable speed squirrel cage induction generator
This paper presents a comprehensive modelling and control study of a variable speed wind energy conversion system based on a squirrel-cage induction generator (SCIG). The mathematical model of the SCIG is derived in Park frame along with the indirect field oriented control (IFOC) scheme based on a proportional and integral speed controller. A simple maximum power point tracking strategy is used to determine the optimal speed under variable wind speed conditions which is then used as the reference in the IFOC scheme. Power flow between the supply and the inverter is regulated via simultaneous control of the active and reactive currents of the grid and the DC link voltage. The simulation results show that the proposed control technique is able to maximise the energy extracted from the wind during the simulation scenarios considered. The results also demonstrate good transient response characteristics in the decoupled real and reactive powers.Peer reviewedFinal Accepted Versio
Control of the power quality for a DFIG powered by multilevel inverters
This paper treats the modeling, and the control of a wind power system based on a doubly fed induction generator DFIG, the stator is directly connected to the grid, while the rotor is powered by multilevel inverters. In order to get a decoupled system of controlfor an independently transits of active and reactive power, a vector control method based on stator flux orientation SFOC is considered: Direct vector control based on PI controllers. Cascaded H-bridge CHBI multilevel inverters are used in the rotor circuit to study its effect on supply power quality. All simulation models are built in MATLAB/Simulink software. Results and waveforms clearly show the effectiveness of vector control strategy. Finally, performances of the system will tested and compared for each levels of inverter
Don't forget primary progressive aphasia for anti-amyloid drugs: An estimation of eligible patients from the Lausanne Memory Center registry.
The study recently published on the clinical effect of lecanemab in early Alzheimer's disease (AD) only includes patients with amnestic presentation. However, a significant portion of AD patients presents a non-amnestic phenotype of AD, such as primary progressive aphasia (PPA) and could benefit of rather than on lecanemab. Therefore, we conducted a 10-year retrospective study at the Leenaards Memory Center in Lausanne (Switzerland) to identify how many PPA patients would be eligible for lecanemab. Among 54 patients with PPA, we identified 11 (20%) eligible patients. Furthermore, almost half of the 18 patients with logopenic variant would be eligible for lecanemab treatment
Application of Recurrent Neural Networks for Drought Projections in California
We use recurrent neural networks (RNNs) to investigate the complex interactions between the long-term trend in dryness and a projected, short but intense, period of wetness due to the 2015-2016 El Niño. Although it was forecasted that this El Niño season would bring significant rainfall to the region, our long-term projections of the Palmer Z Index (PZI) showed a continuing drought trend, contrasting with the 1998-1999 El Niño event. RNN training considered PZI data during 1896-2006 that was validated against the 2006-2015 period to evaluate the potential of extreme precipitation forecast. We achieved a statistically significant correlation of 0.610 between forecasted and observed PZI on the validation set for a lead time of 1 month. This gives strong confidence to the forecasted precipitation indicator. The 2015-2016 El Niño season proved to be relatively weak as compared with the 1997-1998, with a peak PZI anomaly of 0.242 standard deviations below historical averages, continuing drought conditions
The 6th international conference on envenomation by snakebites and scorpion stings in Africa : a crucial step for the management of envenomation
During the 6th International Conference on Envenomation by Snakebites and Scorpion Stings in Africa held in Abidjan, from 1 to 5 June 2015, the measures for the management of envenomation were discussed and new recommendations were adopted by the participants. The high incidence and severity of this affliction were confirmed by several studies conducted in African countries. The poor availability of antivenom, particularly because of the cost, was also highlighted. Some experiences have been reported, mainly those regarding the financial support of antivenom in Burkina Faso (more than 90 %) and Togo (up to 60 %) or the mandatory reporting of cases in Cameroon. Key recommendations concerned: improvement of epidemiological information based on case collection; training of health workers in the management of envenomation; policy to promote the use of effective and safe antivenom; and antivenom funding by sharing its costs with stakeholders in order to improve antivenom accessibility for low-income patients
Studies on Cu and TiO[2] Water-based Nanofluids: A Comparative Approach in Laminar Flow
In this paper, a numerical simulation has been performed to study the fluid fllow and heat transfer
around a circular cylinder utilizing Cu and TiO2 water-based nanofluids over low Reynolds numbers. Here,
the Reynolds number is varied within the range of 1 to 40 and the volume fraction of nanoparticles (ᔩ) is
varied within the range of 0 < ᔩ < 0.05. Two-dimensional and steady mass continuity, momentum, and
energy equations have been discretized using finite volume method. SIMPLE algorithm has been applied
for solving the pressure linked equations. The effect of volume fraction of nanoparticles on fluid flow and
heat transfer were investigated numerically. It was found that at a given Reynolds number, the Nusselt
number, drag coefficient, re-circulation length, and pressure coefficient increases by increasing the volume
fraction of nanoparticles
CONTRIBUTION AU DESIGN, STABILITĂ, PERFORMANCE ET OPTIMISATION DâUN UAV
Ce travail porte sur la simulation numĂ©rique, lâĂ©tude de performance, la stabilitĂ© et lâoptimisation dâun modĂšle de drone (PIPER CUB J3).Dans ce but plusieurs logiciels de conception et de dessin assistĂ© par ordinateur ont Ă©tĂ© utilisĂ©s : le modĂšle de lâUAV est conçu sous le logiciel « SolidWorks », les Ă©tapes de maillage et rĂ©solution des Ă©quations de Navier-Stokes dĂ©crivant lâĂ©coulement sous « Ansys 16.0 », lâĂ©tude de stabilitĂ© et performance de vol par « Advanced Anlysis Aircraft 2.5 ».Pour des fins dâoptimisation et dâamĂ©lioration en termes de finesse et dâendurance, trois types dâailette ont Ă©tĂ© Ă©tudiĂ©
Examen de lâaptitude Ă la reproduction chez le bĂ©lier et le bouc
Male breeding soundness examination (BSE) is an important component of sheep and goat farming. BSE is best performed 2 months before the breeding season and is based on clinical and physical examination as well as sperm abnormalities detection. Rams are classified based on physical examination and semen evaluation finding in one of 4 categories: Unsatisfactory, questionable, satisfactory, and excellent. The satisfactory rams will achieve good reproductive performance if joined to ewes at a ratio of 1:50 for 60 days. However exceptional rams are expected to achieve good reproductive performance at a ratio of 1 ram to 100 ewes. For Buck, scrotal circumference should be at least 25 cm for breeds weighing more than 40 kg. Buck is deemed satisfactory breeder if he passes the physical examination, and has an ejaculate with at least 50 % progressively motile spermatozoa and less than 30 % total sperm abnormalities. This paper reviews factors affecting fertility, sperm production and quality as well as libido and mating ability in the ram. Details of genital examination and semen evaluation and interpretation of results are discussed. Classification of rams according to their reproductive potential is presented. Specific recommendations, when available for the buck, are highlighted. The main genital diseases are presented. The most frequent culling reason for ram is epididymitis due to Brucella ovis. Systematic culling of rams with epididymitis improves flock lambing rates by 10 to 15 %. Overall, the examination of the reproductive capacity in the ram and the buck is an important tool for improvement of flocks/herds fertility and prevention of contagious or hereditary diseases.
Keywords: Genital diseases, fertility, sheep, goat.Lâexamen de lâaptitude Ă la reproduction (EAR) du mĂąle est une composante importante de lâĂ©levage des petits ruminants. LâEAR est mieux rĂ©alisĂ©e 2 mois avant la saison de reproduction. Il est basĂ© sur lâexamen clinique et physique ainsi que sur la dĂ©tection des anomalies des spermatozoĂŻdes. En considĂ©rant les rĂ©sultats de cet examen, les bĂ©liers sont classĂ©s en 4 catĂ©gories: Insatisfaisant, douteux, satisfaisant et excellent. Les bĂ©liers satisfaisants permettront dâobtenir de bonnes performances de reproduction sâils sont mis pendant 60 jours pour saillir des brebis au ratio de 1:50. Cependant, des bĂ©liers exceptionnels peuvent rĂ©aliser une bonne performance reproductive au ratio de 1 bĂ©lier pour 100 brebis. Chez le bouc, la circonfĂ©rence scrotale doit ĂȘtre dâau moins 25 cm pour les races pesant plus de 40 kg. Il est considĂ©rĂ© comme satisfaisant sâil passe lâexamen physique et produit un Ă©jaculat avec au moins 50 % de spermatozoĂŻdes progressivement mobiles et moins de 30 % dâanomalies totales des spermatozoĂŻdes. Cet article examine les facteurs affectant la fertilitĂ©, la production et la qualitĂ© du sperme ainsi que la libido et la capacitĂ© de saillie chez le bĂ©lier. Les dĂ©tails de lâexamen de lâappareil gĂ©nital et du sperme et lâinterprĂ©tation des rĂ©sultats sont traitĂ©s. La classification des bĂ©liers selon leur potentiel de reproduction est prĂ©sentĂ©e. Des recommandations spĂ©cifiques, lorsquâelles sont disponibles pour le bouc, sont mises en Ă©vidence. Les principales maladies gĂ©nitales sont traitĂ©es. La cause de rĂ©forme la plus frĂ©quente chez le bĂ©lier est lâĂ©pididymite Ă Brucella ovis. La rĂ©forme systĂ©matique des bĂ©liers Ă Ă©pididymite amĂ©liore les taux dâagnelage des troupeaux de 10 Ă 15 %. Globalement, lâexamen de lâaptitude de reproduction chez le bĂ©lier et le bouc est un outil important pour lâamĂ©lioration de la fertilitĂ© des troupeaux et la prĂ©vention des maladies contagieuses ou hĂ©rĂ©ditaires.
Mots-clés: Reproduction, maladies génitales, fertilité, bélier, bou
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