Modélisation et observation du flux hydrique vers la surface du sol depuis une nappe peu profonde

Il n'est guère besoin de rappeler l'importance des transferts d'eau à travers la zone non saturée depuis une nappe peu profonde vers la surface du sol. Si l'eau est de qualité ou le lessivage naturel suffisant, ces transferts peuvent contribuer notablement à l'alimentation en eau des horizons superficiels, alors que dans le cas contraire, on peut assister à une salinisation progressive du sol. Lorsqu'il y a risque de salinisation, on peut être amené à abaisser la nappe pour limiter les vitesses d'ascension capillaire et l'accumulation de sels en surface. Dans ce cas, la connaissance du flux d'eau que le sol est capable de transmettre depuis la nappe jusqu'à la surface est un élément important d'appréciation de la profondeur à donner à la nappe. En régime permanent, les études conduites sur ce sujet sont en général inspirées de celles de GARDNER (1958) qui propose des solutions applicables à certains cas particuliers. Par la suite, RIPPLE et al. (1972) ont élargi la théorie de GARDNER à des situations de portée beaucoup plus générale. Le présent article propose des relations simples pour estimer, dans le cas du régime permanent et pour des relations caractéristiques du type Brooks et Corey, d'une part, le profil de pression capillaire correspondant à une valeur donnée d'évaporation et, d'autre part, le flux ascendant maximal que peut soutenir une nappe située à une profondeur déterminée. Les résultats obtenus sont comparés avec ceux fournis par les équations de GARDNER généralisées et ceux relevés sur deux sites d'observation installés in situ. (Résumé d'auteur

Baerveldt tube implantation following failed deep sclerectomy versus repeat deep sclerectomy.

PURPOSE: To compare the surgical outcomes of repeat deep sclerectomy (DS) and the Baerveldt glaucoma implant (BGI) in eyes with failed primary deep sclerectomy. DESIGN: A retrospective comparative case-control study. METHODS: Fifty-eight eyes of 56 glaucoma patients with previously failed DS underwent BGI (group BGI) and 58 eyes of 55 patients underwent repeat DS (group DS) at a tertiary referral centre. Visual acuity, intraocular pressure (IOP), number of glaucoma medications, surgical failure rates and complication rates were compared between groups. Surgical failure was defined as loss of IOP control, loss of light perception, or need for further glaucoma surgery. RESULTS: Baseline demographics were similar between groups. Preoperatively, median IOP was lower in the DS than the BGI group (19 mmHg versus 21 mmHg, p = 0.10). Postoperatively at year 1, median IOP was significantly higher in the DS than BGI group (14 mmHg versus 11 mmHg, p = 0.02). There were no differences between the DS and BGI groups in mean number of medications preoperatively (2.3 versus 2.6) or postoperatively (1.3 versus 1.1). Complication rates were significantly higher in the DS group [41 % (n = 24) versus 14 % (n = 8); p = 0.01]. The failure rate at 1 year was higher in eyes with repeat DS than in eyes with BGI (30 vs. 21 %, respectively; p = 0.07). CONCLUSIONS: Baerveldt implants were more effective in lowering IOP and resulted in significantly fewer complications than repeat deep sclerectomy in eyes with previously failed deep sclerectomy

In vivo testing of a novel adjustable glaucoma drainage device.

PURPOSE: We report on the in vivo testing of a novel noninvasively adjustable glaucoma drainage device (AGDD), which features an adjustable outflow resistance, and assess the safety and efficiency of this implant. METHODS: Under general anesthesia, the AGDD was implanted on seven white New Zealand rabbits for a duration of 4 months under a scleral flap in a way analogous to the Ex-PRESS device and set in an operationally closed position. The IOP was measured on a regular basis on the operated and control eyes using a rebound tonometer. Once a month the AGDD was adjusted noninvasively from its fully closed to its fully open position and the resulting pressure drop was measured. The contralateral eye was not operated and served as control. After euthanization, the eyes were collected for histology evaluation. RESULTS: The mean preoperative IOP was 11.1 ± 2.4 mm Hg. The IOP was significantly lower for the operated eye (6.8 ± 2 mm Hg) compared to the nonoperated eye (13.1 ± 1.6 mm Hg) during the first 8 days after surgery. When opening the AGDD from its fully closed to fully open position, the IOP dropped significantly from 11.2 ± 2.9 to 4.8 ± 0.9 mm Hg (P < 0.05). CONCLUSIONS: Implanting the AGDD is a safe and uncomplicated surgical procedure. The fluidic resistance was noninvasively adjustable during the postoperative period with the AGDD between its fully closed and fully open positions

Passivity based stabilization of non-minimum phase nonlinear systems

summary:A cascade scheme for passivity-based stabilization of a wide class of nonlinear systems is proposed in this paper. Starting from the definitions and basic concepts of passivity-based stabilization via feedback (which are applicable to minimum phase nonlinear systems expressed in their normal forms) a cascade stabilization scheme is proposed for minimum and non-minimum phase nonlinear systems where the constraint of stable zero dynamics imposed by previous stabilization approaches is abandoned. Simulation results of the proposed algorithm are presented to demonstrate its performance

Biocompatibility of an x-shaped zirconium implant in deep sclerectomy in rabbits.

BACKGROUND: The aim of this study was to evaluate the mid-term biocompatibility of a new x-shaped implant made of zirconium in an animal model of glaucoma surgery. METHODS: Preoperatively, ultrasound biomicroscopy (UBM), intraocular pressure (IOP) and outflow facility (OF) data were acquired. Upon surgery, one eye was chosen randomly to receive an implant, while the other received none. Ten rabbits went through a 1-, 2-, 3-, 4- and 6-month follow-up. IOP was measured regularly, UBM performed at 1, 3 and 6 months after surgery. At the end of the follow-up, OF was again measured. Histology sections were analyzed. RESULTS: For both groups IOP control was satisfactory, while OF initially increased at month 1 to resume preoperative values thereafter. Eyes with implants had larger filtration blebs which decreased faster than in eyes without the implant. Drainage vessel density, inflammatory cell number and fibrosis were higher in tissues near the implant. CONCLUSIONS: The zirconium implant initially promoted the positive effects of the surgery (IOP control, OF increase). Nevertheless, after several months, foreign body reactions and fibrosis had occurred on some implants that restrained the early benefit of such a procedure. Modifications of the zirconium implant geometry could enhance the overall success rate

Attractiveness and stability for Riemann-Liouville fractional systems

We propose a novel approach to study the asymptotic behavior of solutions to Riemann–Liouville (RL) fractional equations. It is shown that the standard Lyapunov approach is not suited and an extension employing two (pseudo) state spaces is needed. Theorems of Lyapunov and LaSalle type for general multi-order (commensurate or non-commensurate) nonlinear RL systems are stated. It is shown that stability and passivity concepts are thus well defined and can be employed in L 2 -control. Main applications provide convergence conditions for linear time-varying and nonlinear RL systems having the latter a linear part plus a Lipschitz term. Finally, computational realizations of RL systems, as well as relationships with Caputo fractional systems, are proposed

Power System Stabilizer based on Model Predictive Control

[EN] A model predictive power system stabilizer is proposed in this paper to damp power oscillations in an electric power system (EPS). The design of the stabilizer is optimal in the sense that its parameters are determined by using off-line particle swarm optimization (PSO) technique. The proposed methodology is applied to an EPS composed by a single machine connected to an infinite bus (SMIB). The analysis is performed through a small signal stability analysis, deriving incremental equations linearized around an operating point. The results obtained by the proposed method are compared with a conventional power system stabilizer, also optimized by PSO. Through numerous computer simulations under different operating conditions andperturbations on the SMIB, it was possible to establish some advantages of the proposed technique as compared with the conventional technique.[ES] Se propone un estabilizador de potencia predictivo para amortiguar oscilaciones de potencia en un sistema eléctrico de potencia(SEP) formado por una sola máquina conectada a una barra infinita (Single Machine Infinite Bus, SMIB). Este enfoque considera un análisis de estabilidad de pequeña señal, usando un modelo incremental alrededor de un punto de operación. El estabilizador proporciona señales de control óptimas, debido a que además de utilizar el controlador predictivo basado en modelo (Model Predictive Controller, MPC) sus parámetros se optimizan fuera de línea empleando un algoritmo de optimización por enjambre de partículas (Particle Swarm Optimization, PSO). Su comportamiento se compara con un estabilizador del sistema potencia convencional, con parámetros también optimizados con PSO fuera de línea. Para validar la metodología propuesta, se presentan numerosas simulaciones de respuestas dinámicas del SMIB, para diferentes condiciones de operación y perturbaciones.Este trabajo ha contado con el apoyo de CONICYT-Chile, a través del proyecto FB0809 “Centro Avanzado de Tecnología para la Minería” (AMTC)”. El segundo autor agradece el apoyo de CONICYT / FONDECYT / (N ° 3140604).Duarte-Mermoud, MA.; Milla, F. (2018). Estabilizador de Sistemas de Potencia usando Control Predictivo basado en Modelo. Revista Iberoamericana de Automática e Informática industrial. 15(3):286-296. https://doi.org/10.4995/riai.2018.10056OJS286296153Abido. M.A., 2002. 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Reuse of domestic wastewater treated in macrophyte ponds to irrigate tomato and eggplant in semi-arid West-Africa: benefits and risks

The scarcity of freshwater resources is a critical problem in semi-arid zones and marginal quality water is increasingly being used in agriculture. This paper aimed at evaluating the physico-chemical and biological risks on irrigated soils and fruits of macrophyte treated wastewater (TWW), the nutrients supply, and the effect on tomato and eggplant production in semi-arid Burkina Faso. During three years of experiments, treated wastewater was used, with fresh water as control, in combination with or without mineral fertilizer application at recommended rate (140 kg N/ha + 180 kg P2O5/ha + 180 kg K2O/ha). The study revealed that the treated wastewater provided variable nutrients supply depending on year and element. The treated wastewater without mineral fertilizer improved eggplant yield (40% in average) compared to the freshwater. Both crops responded better to mineral fertilizer (52% for tomato and 82% for eggplant) and the effects of the treated wastewater and fertilizer were additive. As the N supply of TWW was very unsteady (8-227% of crop need), and P2O5 supply did not satisfy in whole crop need (3-58%) during any of the three years of experiment, we recommended that moderate N and P2O5 fertilizers be applied when irrigating with TWW in semi-arid West-Africa. On the contrary, the K2O supply was more steady and close to crop requirement (78-126%) over the three years of experiment and no addition of K fertilizer may be needed when irrigated with TWW. Faecal coliforms and helminth eggs were observed in treated wastewater and irrigated soils at rate over the FAO and WHO recommended limits for vegetable to be eaten uncooked. Tomato fruits were observed to be faecal coliform contaminated with the direct on-foliage irrigation with treated wastewater. Our results indicate that treated wastewater can effectively be used as both nutrients source and crop water supply in market gardening in the semi-arid Sub-Saharan West Africa (SSWA) where freshwater and farm income are limiting. Yet consumers should properly cook or disinfect treated-wastewater irrigated vegetables before eating, and market gardeners should also be careful manipulating treated wastewater to avoid direct health contamination in this environment. (c) 2010 Elsevier B.V. All rights reserved