Principales problemas de las cooperativas de trabajo asociado en Colombia desde el punto de vista regulatorio, jurisprudencial y de control

El gran crecimiento en el número de Cooperativas de Trabajo Asociado (en adelante CTA) creadas y el aumento de las personas afiliadas a estas entidades en los últimos años, ha venido acompañado de un considerable número de quejas contra este tipo de entidades por las múltiples irregularidades que con ellas se cometen, básicamente como consecuencia de la distorsión del espíritu cooperativo y de sus principios rectores.87 p.Contenido parcial: Cooperativas de trabajo asociado consideraciones generales -- El caso colombiano -- Principales problemas de las CTA en Colombia -- Control de las CTA en Colombia

Vers une commande basée modèle des machines complexes : application aux machines-outils et machines d'essais mécaniques

Nowadays, the requirements in productivity and costs mastering have forced the industrial manufacturers to develop new kind of mechanisms. Thus, the complexity of the machine-tools structures and machining processes has increased and new challenges have emerged : flexible structure, vibration, non-negligible dynamic effects, etc ... However, their implementation still comes from methods used for conventional machines. These works are thus about defining overall strategies including consideration of the kind of structure used and the task to realise. Two illustrative contexts are used. In the context of machining, we propose a generic tuning method based on kinematic and dynamic model of machine-tools structure that requires only a few manual modifications, in order to save time for implementation. A new computed torque control law is proposed, it reduces vibration phenomena in dynamical demanding phases. In the context of the mechanical tests, the objective is to demonstrate the feasibility of using parallel machines with 6 degrees of freedom in the context of mechanical tests, whereas the boundary conditions are perfectly controlled. We propose an instrumentation and control scheme that is able to perform mechanical tests with a maximum error of about 0.40 mu m, even in the case of very rigid specimen (concrete for example).De nos jours, les exigences de productivité et de maîtrise des coûts ont incité les industriels à développer de nouvelles machines, et avec elles, de nouveaux enjeux sont apparus : souplesse de la structure, vibration, effets dynamiques non-négligeables, etc. Pourtant, leur mise en œuvre est toujours issue de méthodes employées pour les machines conventionnelles. Ces travaux s’intéressent donc à la définition de stratégies globales englobant la prise en compte de la structure utilisée et de la tâche à réaliser, appliquée à deux contextes d’illustration. Dans le contexte de l’usinage, nous proposons un réglage des machines basé sur le modèle comportemental de la structure qui ne nécessite que peu de modifications manuelles et permettant un gain de temps pour la mise en œuvre. Une nouvelle loi de commande en couple calculé est également proposé, elle permet de réduire les phénomènes vibratoires lors de phases dynamiquement exigeantes. Dans le contexte des essais mécaniques, l’objectif est de montrer la faisabilité de l’utilisation de machines parallèles à 6 degrés de liberté dans le cadre d’essais dont la gestion des conditions aux limites est critique. Nous proposons une instrumentation et un schéma de commande qui permettent de respecter les consignes avec une erreur maximale de l’ordre de 0.40μm, même dans le cas d’éprouvettes très rigide (en béton par exemple)

Deterioration of Graphene Nanocoated Optical Taper Saturable Absorber at High Power

We experimentally investigate the loss of nonlinear transmission of graphene nanocoated optical taper (GNOT) saturable absorber at high input average power. Above a certain threshold of incident average power, the component experiences an irreversible modification of its nonlinear properties. This leads to a permanent deterioration of saturable absorption characteristics of this component. Such behavior is discussed and analyzed

High power passively mode-locked fiber laser based on graphene nanocoated optical taper

We experimentally demonstrate a passively mode-locked Er:Yb doped double-clad fiber laser usinga graphene nanocoated optical taper. Averaging 20lm of clad diameter with a length of 6 mm,such a saturable absorber enables a strong light–graphene interaction owing to the evanescent fieldof the excited cladding mode. With the highest pump power of 5 W, the 326th harmonic mode lock-ing of soliton bunches with an average output power of 520 mW was obtained in a fiber ring cavitythat has a fundamental frequency of 1.67 MHz. This is the highest average output power yetreported in graphene-based passively mode-locked fiber lasers

Limitations of graphene nanocoated optical tapers for high-power nonlinear applications

In this letter, we investigate the limitations of graphene as a saturable absorber for high-power nonlinear optical applications. The response of graphene nanocoated optical tapers against the average optical power injected is tested. We point out that the power handled by such components is limited and their nonlinear properties are strongly and permanently modified when exposed to high optical power. The origin of the degradation of the components is discussed

Transmission RZ de 40x40 Gbit/s sur 3 pas de 40 dB de Fibre Standard avec 27.4 dB de Gain Raman contra-propagatif et un EDFA de 27 dBm

session V « Systèmes de télécommunication » [502]National audienceLes amplificateurs EDFA forte puissance semblent de bons candidats pour des liaisons festons DWDM. Nous démontrons expérimentalement la transmission de 40 canaux à 40 Gbit/s sur la bande C sur 3 pas de 40 dB de pertes avec une modulation RZ classique

Optical Spectroscopy of Active Galactic Nuclei in SA57

The cosmological evolution of X-ray-selected and optically selected Active Galactic Nuclei (AGNs) show different behaviours interpreted in terms of two different populations. The difference is evident mainly for low luminosity AGNs (LLAGNs), many of which are lost by optical photometric surveys. We are conducting a spectroscopical study of a composite sample of AGN candidates selected in SA57 following different searching techniques, to identify low luminosity AGNs and break down the sample into different classes of objects. AGN candidates were obtained through optical variability and/or X-ray emission. Of special interest are the extended variable objects, which are expected to be galaxies hosting LLAGNs. Among the 26 classified objects a fair number (9) show typical AGN spectra. 10 objects show Narrow Emission Line Galaxy spectra, and in most of them (8/10) optical variability suggests the presence of LLAGNs.Comment: 7 pages, 8 figures, to appear in A&