Apprentissage incrémental et synthèse de données pour la reconnaissance de caractères manuscrits en-ligne

International audienceDans ce papier, nous proposons une stratégie d'apprentissage incrémental d'un système de reconnaissance de caractères manuscrits. Cette stratégie est en-ligne et rapide, dans le sens où toute nouvelle classe de caractères peut être apprise par le système à partir de très peu d'exemples de caractères. La stratégie proposée vise à surmonter le problème du manque de données d'apprentissage lors de l'introduction d'une nouvelle classe de caractères. La synthèse de caractères manuscrits est utilisée à cette fin. Les résultats ont montré qu'un bon taux de reconnaissance (environ 90%) est atteint en utilisant seulement 3 exemples d'apprentissage. De plus, ce taux augmente rapidement pour atteindre 96% pour 10 exemples, et 97% pour 30. Une réduction d'erreur de 45% est obtenue en utilisant la synthèse de caractères par rapport à une stratégie sans synthèse

Experimental study of the reduction of field emission by gas injection in vacuum for accelerator applications

LGEP 2014 ID = 1590International audienceField emission current from surfaces under vacuum and at high field strengths can be reduced by the injection of gas into the evacuated volume. In this paper, the effects of H 2 , He, N 2 , and Ar on this "dark" current emitted from a tungsten carbide point cathode for 2 cm gap distance is studied. Exposure to any of these gases at pressures on the order of 10 −3 –10 −2 Pa was found to reduce the emission current by up to 90% with a time constant on the order of ∼1 minute as compared to the current at 10 −6 Pa. The effect was strongly dependent on the gas nature, with Ar and N 2 having larger effects at lower pressures than He and H 2 . The reduction was reversible, with the current increasing to near its original value with a time constant on the order of ∼1–10 minutes after pumping down. The effect of the gas remained in the absence of electric field, whatever the gas pressure. Mechanisms for these and related phenomena are discussed

Ability of lactobacilli isolated from traditional cereal-based fermented food to produce folate in culture media under different growth conditions

Folates are essential vitamins (B9). Lactic acid bacteria (LAB) can be used to increase the folate levels in foods during fermentation. Here, 151 LAB strains isolated from fermented food were screened for folate production. Folates were extracted by heat treatment coupled with enzymatic extraction. Total, extra and intracellular folate were quantified by microbiological assay. Most Lactobacillus plantarum and Lactobacillus fermentum strains synthesized folate, Pediococcus pentosaceus strains consumed folate, and Pediococcus acidilactici strains either consumed or produced. Seven strains were further examined for their ability to synthesize or consume folate during growth in rich folate medium (MRS) and folate-free medium (FACM). For most strains, the differences observed in MRS were attenuated in FACM. L. fermentum 8.2 and L. plantarum 6.2 produced the highest levels of folates in MRS (97 and 93 ng.mL(-1)) and FACM (29 and 44 ng.mL(-1)). In most cases, production reached a maximum from 9 or 11 h to 24 h. Incubations in FACM with mixed LAB cultures showed that folate production is not additive. We demonstrated how biosynthesis of folate by LAB depends on species, strains, and is highly influenced by time and medium composition. Characterized LAB strains can be further explored for novel folate bioenriched functional food

Development of a compact bushing for NBI

International audienceResearch into a novel type of compact bushing is being conducted through the HVIV (High Voltage holding In Vacuum) partnership between CEA-Cadarache 1 , GeePs-Centralesupélec 4 , LPGP 3 and LCAR 2. The bushing aims to concentrate the high electric field inside its interior, rather than in the vacuum tank. Hence the field emission current is also concentrated inside the bushing and it can be attempted to suppress this so-called dark current by conditioning the internal surfaces and by adding gas. LCAR have performed theoretical quantum mechanical studies of electron field emission and the role of adsorbates in changing the work function. LPGP studied the ionization of gas due to field emission current and the behavior of micro particles exposed to emissive electron current in the vacuum gap under high electric fields. Experiments at Geeps have clarified the role of surface conditioning in reducing the dark current. Geeps also found that adding low pressure nitrogen gas to the vacuum is much more effective than helium in reducing the field emission. An interesting observation is the growth of carbon structures after exposure of an electrode to the electric field. Finally, IRFM have performed experiments on a single stage test bushing that features a 36 cm high porcelain insulator and two cylindrical electrode surfaces in vacuum or low-pressure gas. Using 0.1 Pa N 2 gas, the voltage holding exceeded 185 kV over a 40 mm "vacuum" gap without dark current. Above this voltage, exterior breakdowns occurred over the insulator, which was in air. The project will finish with the fabrication of a 2-stage compact bushing, capable to withstand 400 kV