Showing papers by "Hydro-Québec published in 2003"

Diagnostics of dielectric barrier discharges in noble gases: atmospheric pressure glow and pseudoglow discharges and spatio-temporal patterns

Abstract: We present experimental results of atmospheric pressure glow discharges (APGD) in a dielectric barrier discharge reactor. These are examined in different noble gases and in the N/sub 2//O/sub 2/ system (air and pure N/sub 2/), under varying experimental conditions (frequency f; gap length d; and electric field intensity E). Discharge diagnostics have been carried out using ultrahigh speed imaging, and synchronous dual-detection of light emission and current-voltage measurements, the former using a photomultiplier . The time evolutions of the discharges and of columnar patterns in regular geometric arrangements at atmospheric pressure under different experimental conditions are reported for all of the noble gases studied here. We present evidence that columnar patterns and APGD are manifestations of the same discharge physics, which is discussed with reference to recent work reported by others.

Scaling laws for edge plasma parameters in ITER from two-dimensional edge modelling

Abstract: Results of a detailed study of the parameter space of the ITER divertor with the B2-Eirene code are presented. Relations between plasma parameters at the separatrix, the interface between the core and edge plasma, are parametrized to provide a set of boundary conditions for the core models. The reference ITER divertor geometry is compared with the straight target option, and the possibility of controlling the edge density by shifting the plasma equilibrium in ITER is explored.

Assessment of the impact of meteorological network density on the estimation of basin precipitation and runoff: a case study

Abstract: In recent years in North America, a number of government agencies and industries have begun to reinvest in meteorological networks. This investment must be based on sound scientific advice. Increased meteorological station network density can be beneficial for a number of purposes, including flood forecasting. This study aimed at investigating the impact of network density at two temporal scales, i.e. for the estimation of total annual precipitation and for the estimation of daily precipitation during specific rain events. This was done using kriging as a means to estimate the spatial distribution and variance of rainfall. Kriged precipitation from two network scenarios (sparse and dense) were used as input into the HSAMI hydrological model and simulations were compared on five drainage basins in the Mauricie area (Qu´ ebec, Canada). A comparison of the distribution of total annual precipitation interpolated from the two network scenarios showed that adding stations changed the distribution and magnitude of rainfall in the study area. High precipitation cells were better defined with the denser network, and decreases in the relative spatial variance were observed. Similarly, kriged daily precipitation provided a more defined spatial distribution of rainfall during important rain events of 1999, and variance was also reduced when the denser network was used. Finally, simulations performed with the HSAMI model were generally improved when the precipitation inputs were estimated using a denser station network for most drainage basins studied, as expressed by increased Nash coefficients and a decreased root-mean-square error. Peak flows during important summer flood events were generally better simulated when a denser network was used to calculate the mean daily precipitation used as input. Total cumulated volume estimations during the rain events were also generally improved with a denser network. This study showed that the estimation of variance remains an important tool for rain gauge network design. Moreover, network density was shown to have an important impact on the quality of flow simulations, even when a lumped model is used. Copyright  2003 John Wiley & Sons, Ltd.

Dynamic modeling of DC arc discharge on ice surfaces

Abstract: A dynamic model for predicting DC arc behavior and critical flashover voltage of ice-covered insulating surfaces is presented. The model takes into consideration insulating geometry, pre-contamination level, and characteristics of ice layers. Assuming arc behavior as a time dependant impedance, it is possible to determine various arc characteristics such as time histories of leakage currents, potential gradient, channel radius, trajectory, propagation velocity and the energy injected into the zones free of ice (also called air gaps). The simulated results provided by the model are in agreement with those obtained experimentally using a simplified ice-covered cylinder as well as a short string of five IEEE standard porcelain suspension units covered with artificial ice.

Assessment of health economics in Alzheimer's disease (AHEAD): treatment with galantamine in the UK.

Abstract: Objective To assess the long-term health and economic impact of treating mild to moderate Alzheimer's disease (AD) with galantamine (16 mg or 24 mg per day) compared to no cholinesterase therapy in the UK. Methods The long-term costs and outcomes were assessed using a model developed from longitudinal data on a cohort of AD patients. The model predicts the time until patients require full-time care, defined as the consistent requirement for a significant amount of care and supervision each day. Efficacy data were obtained from three clinical trials comparing galantamine with placebo, forecasts were made for ten years. Costs were determined in 2001 British pounds (£) and discounted at 6% per annum, while outcomes such as time to full-time care were discounted at 1.5%. Results Without pharmacological treatment, patients are expected to incur costs of £28,134 over ten years, 70% of costs accrue from providing full-time care. Galantamine (16 mg per day) is predicted to reduce the duration of the full-time care state by 12%; approximately five patients need to be treated to avoid one year of full-time care. The ten-year incremental costs per month of full-time care avoided average £192 per patient and £8,693 per QALY. Savings (£1380) are predicted for patients who continue treatment beyond six months and whose cognitive function is maintained or improved. Comparable results were estimated for the 24 mg dose. Conclusion In addition to the clinical benefits associated with galantamine treatment, the savings predicted from delaying when full-time care is needed may offset the treatment costs. Copyright © 2003 John Wiley & Sons, Ltd.

Voltage and lamp flicker issues: should the IEEE adopt the IEC approach?

Abstract: This paper is intended to provide an overview of the IEC flicker measurement and assessment procedures. The IEC procedures are correlated with existing IEEE flicker standards to show the benefits of the IEC methodology. Application issues, such as customer impact assessment, are also discussed. Three case studies, two field tests, and one EMTP analysis are provided to show the correlation of IEC flickermeter output values with documented customer complaints. The case studies also provide areas where modifications to the IEC flicker standards may be necessary when developing a new IEEE flicker standard.

Modeling and closed-loop validation of a new PSS concept, the multi-band PSS

Abstract: This paper describes the characteristics of a new power system stabilizer, the multi-band PSS. Its model, IEEE PSS4B, is presented to explain its basic principles and functions. This Delta-Omega PSS makes use of three distinct working bands to process the whole spectrum of oscillating modes present in power systems. To illustrate the PSS performance, a simple setting technique, specially developed for this PSS, is presented and used to validate the closed-loop performance of the MB-PSS either in stability simulation or field testing conditions. Presented results are for Hydro-Quebec LG2 power plant.

Electrode coated with a film obtained from an aqueous solution comprising a water-soluble binder, production method thereof and uses of same

Abstract: The invention relates to a method of preparing an electrochemical electrode which is partially or totally covered with a film that is obtained by spreading an aqueous solution comprising a water-soluble binder over the electrode and subsequently drying same The production cost of the electrodes thus obtained is reduced and the surface porosity thereof is associated with desirable resistance values

Dielectric barrier discharges in helium at atmospheric pressure: experiments and model in the needle-plane geometry

Abstract: We present an experimental and numerical modelling study of dielectric barrier discharges in pure, flowing helium at atmospheric pressure, in a 3.0 mm length needle-plane gap. Ultra-high speed imaging and synchronous, real-time dual detection (optical–electrical) diagnostics have been carried out. The high-voltage electrode was a hyperboloidal steel needle with a sharp point of 40 μm radius, while the grounded electrode was covered with 1.6 mm of Al2O3. The surface of the latter was either bare (case 1) or coated with ~20 nm of semiconducting graphite (case 2) or metallic aluminium (case 3), all at floating potential. Axial [z(t)] and radial [r(t)] time-evolutions (≤2 μs) of discharge propagation across the gap were found to depend very strongly upon surface charging or conduction (cases 1–3). A two-dimensional model of the needle-plane discharge, based on coupled solution of the continuity equations for electrons, ions and excited neutral particles and of Poisson's equation, was found to agree very well with the observed [r,z](t) behaviour.

Electric vehicle braking system

Abstract: A braking system for electric vehicles that gives a driver the feel of a conventional hydraulic braking system while maximizing the recuperation of electrical power is described herein. A single brake pedal is used to control both electric and hydraulic braking assemblies. A feedback force generator is provided to give the driver the impression that a completely hydraulic braking system is used. Therefore, the driver is not inclined to further depress the pedal, thereby preventing the premature activation of the hydraulic braking system.

Electrical heating reactor for gas phase reforming

Abstract: The invention concerns an electrical reactor for reforming, in the presence of an oxidant gas, a gas comprising at least one hydrocarbon, and/or at least one organic compound, including carbon and hydrogen atoms as well as at least one heteroatom. Said reactor comprises: an enclosure, a reaction chamber provided with at least two electrodes comprising at least one conductive lining material electrically isolated from the metal wall of the enclosure, at least one supply of gas to be reformed, at least one oxidant gas supply, at least one outlet for the gases from the reforming and one electrical source for powering the electrodes and resulting in generation of an electronic flux in the conductive lining between the electrodes and in heating said lining.

Highly-stable polymeric electrolyte and use thereof in electrochemical systems

Abstract: The invention relates to a polymeric electrolyte for an electrochemical generator, comprising at least one four-branched polymer, at least one poly(vinylidene fluoride), a co-polymer of poly(vinylidene fluoride-co-hexafluoropropene), a polytetrafluoroethylene, a poly(ethylene-co-propylene-co-5-methylene-2-norbornene) or a copolymer of ethylene propylene diene, a polyol, a polymethylmethacrylate, a polyacrylonitrile, SiO2-Al2O3, or nano TiO2 coated or not with an organic material. Said electrolyte permits the preparation of electrolytic compositions which find application in high-performance electrochemical devices.

Particles comprising a non-conducting or semi-conducting core, which are coated with a hybrid conducting layer, production methods thereof and uses of same in electrical devices

Abstract: Particle mixture (I) comprises particles having a nonconducting or semiconducting core and a hybrid conductor coating, the particles being interconnected with hybrid conductor chains to form a network of electrical conductivity. Independent claims are also included for the following: (1) production of (I) by preparing a mixture of a nonconducting or semiconducting material with a conductive material and adding a second conductive material, preparing a mixture of a nonconducting or semiconducting material with at least two conductive materials, or preparing a mixture of conductive material and mixing it with a nonconducting or semiconducting material; (2) battery cathode and anode comprising (I); (3) lithium battery comprising a metallic lithium anode and a cathode comprising (I); (4) hybrid supercapacitor comprising an electrolyte, an anode comprising (I), and a high surface area carbon or graphite cathode.

Implementation of a ROV navigation system using acoustic/Doppler sensors and Kalman filtering

Abstract: Hydro-Que/spl acute/bec developed a new underwater ROV which is use to inspect its dams. Since 2000, the ROV has allowed Hydro-Que/spl acute/bec to save 5M$ in inspection costs. This paper presents the study of a Kalman filter and its performances. Kalman filtering is used to merge data from fiber gyros, DVL, accelerometers and global positioning system in order to have a better estimation of the position and orientation of the ROV. In real systems, sensors do not send data at the same rate and data acquisition is often intermittent. One innovative aspect of this approach is that it accepts asynchronous information and delay from the sensors. Experimental results in a real environment are presented.

Design of an undervoltage load shedding scheme for the Hydro-Quebec system

Abstract: This paper deals with the control logic of an undervoltage, closed-loop load shedding scheme aimed at protecting the Hydro-Quebec system against long-term voltage instability. This scheme relies on a set of "if-then" rules whose parameters are determined through combinatorial optimisation, relying on the system dynamic response over a set of scenarios. Preliminary results of the above optimisation technique are given, besides a brief description of the foreseen implementation.

Triggering and guiding of an upward positive leader from a ground rod with an ultrashort laser pulse. II. Modeling

Abstract: We have used the Bondio-Gallimberti model of positive leader propagation to simulate laboratory experiments of laser triggering and guiding of upward leaders initiated from a ground rod. The model proves to be capable of reproducing all the important features of laser-guided leader propagation that have been observed experimentally. The leader guiding effect of the laser-created plasma channel is taken into account in the model by adjusting the value of the charge per unit length of the leader, which has been measured in the laboratory to be lower for a laser-guided leader than for an ordinary one. The charge per unit length of the leader is related in the model to the critical temperature at which the air in the transition region at the leader tip must be heated to be conductive enough to become a new leader portion. For an ordinary leader, this critical temperature is 1500 K, at which the electrons all detach from the negative ions in the leader corona, increasing the air conductivity. We give the interpretation that in the case of the laser-guided leaders, because of the relatively high density of negative ions per unit length in the laser-ionized channel, the right conditions of conductivity can be met in the transition region without the electrons being all detached from the ions, allowing a reduction of the critical temperature and of the charge per unit length.

Characterization of CFx films plasma chemically deposited from C3F8/C2H2 precursors

Abstract: The properties of a variety of plasma produced fluorocarbon (CFx) thin films are described The project objectives were: (i) to explore the widest range of process parameters and properties, with an emphasis on comparative characterizations of wetting and mechanical properties (ii) To develop effective interfacial bonding layers for films of 1 μm and more (iii) To utilize safe, non-toxic, environmentally acceptable and relatively inexpensive precursor gases Wetting and surface energy were studied by the dynamic advancing and receding contact angle method These properties are interpreted in terms of the surface chemistry revealed by X-ray photoelectron spectroscopy and the morphology characterized by optical and atomic force microscopy The mechanical properties were determined by micro- and nano-indentation and scratch testing Finally, simple tests of resistance to pollution, handling and aging were carried out The process–structure–properties relationships are discussed Process parameters giving films displaying attractive combinations of wetting and mechanical properties are identified

Core plasma operation consistent with SOL parameters in ITER

Abstract: The constraints of divertor operation have been applied to ITER core plasma simulations by imposing boundary conditions on the calculation, implemented as a set of scaling relations derived from B2-Eirene modelling which describe the effect of the divertor. The core plasma simulations use the integrated core pedestal sol (ICPS) model, based on ITG transport for ions and RLW-like transport for electrons, which includes an increase of transport when the ballooning limit is attained in order to simulate the effect of ELMs in a time-averaged fashion. At the nominal average core density for ITER with the ICPS transport model stationary operation with a fusion power multiplier Q of 12–16 is obtained and a reasonable operating range exists for realistic pumping speeds and particle throughput at a peak divertor power load controlled to remain below 10 MW m−2. Fuelling of the plasma must be predominantly direct core fuelling, and the resulting required core-fuelling rates are realistic. Increased pumping speed and particle throughput are beneficial for maximizing Q. The relaxation to these stationary conditions is very slow, and transient values of fusion multiplier are appreciably higher.

Electrocatalytic hydrogenation of cyclohexanone: Simple dynamic cell design

Abstract: The electrocatalytic hydrogenation of cyclohexanone has been investigated with catalytic powder particles made of metal nanoaggregates deposited on a nonconductive material such as activated carbon and alumina. The catalytic powder particles were suspended in the solution under vigorous stirring conditions. The brief contact of the powder particles with a porous carbon cathode was sufficient to form adsorbed hydrogen on the metallic nanoaggregates through water electrolysis and initiate the electrohydrogenation process. It is demonstrated that the key parameters of the electrohydrogenation process are both the nature of the metallic nanoaggregates and the nature of the non-conductive material. The hydrodynamics of the solution under vigorous stirring conditions have also been studied for the particular cell used in the present study.