Infinite non-causality in active cancellation of random noise

Active cancellation of broadband random noise requires the detection of the incoming noise with some time advance. In an duct for example this advance must be larger than the delays in the secondary path from the control source to the error sensor. In this paper it is shown that, in some cases, the advance required for perfect noise cancellation is theoretically infinite because the inverse of the secondary path, which is required for control, can include an infinite non-causal response. This is shown to be the result of two mechanisms: in the single-channel case (one control source and one error sensor), this can arise because of strong echoes in the control path. In the multi-channel case this can arise even in free field simply because of an unfortunate placing of sensors and actuators. In the present paper optimal feedforward control is derived through analytical and numerical computations, in the time and frequency domains. It is shown that, in practice, the advance required for significant noise attenuation can be much larger than the secondary path delays. Practical rules are also suggested in order to prevent infinite non-causality from appearing

Mathematical modeling and numerical simulation of a bioreactor landfill using Feel++

In this paper, we propose a mathematical model to describe the functioning of a bioreactor landfill, that is a waste management facility in which biodegradable waste is used to generate methane. The simulation of a bioreactor landfill is a very complex multiphysics problem in which bacteria catalyze a chemical reaction that starting from organic carbon leads to the production of methane, carbon dioxide and water. The resulting model features a heat equation coupled with a non-linear reaction equation describing the chemical phenomena under analysis and several advection and advection-diffusion equations modeling multiphase flows inside a porous environment representing the biodegradable waste. A framework for the approximation of the model is implemented using Feel++, a C++ open-source library to solve Partial Differential Equations. Some heuristic considerations on the quantitative values of the parameters in the model are discussed and preliminary numerical simulations are presented

Schwinger terms in gravitation in two dimensions as a consequence of the gravitational anomaly

We compute the Schwinger term in the gravitational constraints in two dimensions, starting from the path integral in Hamiltonian form and the Einstein anomaly.Comment: 8 pages, Latex, additional reference

Left ventricular systolic function in sickle cell anaemia: an echocardiographic evaluation in adult Nigerian patients.

Background: Reliable diagnostic measures for the evaluation of left ventricular systolic performance in the setting of altered myocardial loading characteristics in sickle cell anaemia remains unresolved. Objective: The study was designed to assess left ventricular systolic function in adult sickle cell patients using non-invasive endsystolic stress \u2013 end-systolic volume index ratio. Methods: A descriptive cross sectional comparative study was done using 52 patients recruited at the adult sickle cell anaemia clinic of the University of Nigeria Teaching Hospital Enugu. An equal number of age and sex-matched healthy volunteers served as controls. All the participants had haematocrit estimation, haemoglobin electrophoresis, as well as echocardiographic evaluation. Result: The mean age of the patients and controls were 23.93 \ub1 5.28 (range 18-42) and 24.17 \ub1 4.39 (range 19 -42) years respectively, (t = 0.262; p= .794). No significant difference was seen in estimate of fractional shortening, and ejection fraction. The cardiac out-put, cardiac index and velocity of circumferential shortening were all significantly increased in the cases compared with the controls. The end systolic stress \u2013 end systolic volume index ratio (ESS/ESVI) was significantly lower in cases than controls. There were strong positive correlation between the ejection phase indices (ejection fraction and fractional shortening) and end systolic stress and ESS/ESVI. Conclusion: The study findings suggest the presence of left ventricular systolic dysfunction in adult sickle cell anaemia. This is best detected using the loading-pressures independent force-length relationship expressed in ESS/ESVI ratio

GIS interfaced OECD/PIARC QRA model for road transportation of hazardous goods

International audienceWithin the framework of a research project carried out for both the OECD and the PIARC, INERIS developed a Quantitative Risk Assessment Model (QRA model) for the transport of Hazardous Goods on roads including tunnel sections. This work was also carried out with the collaboration of WS-Atkins (UK) and the University of Waterloo (Canada). INERIS, which was the leading developer of this original model, launched a new research project in order to facilitate the generation of data necessary for a given risk study. A new version of the model is in development. These new developments have been funded by the French Ministry of Ecology and Sustainable Growth and the French Ministry of Equipment, Transport and Buildings, Tourism and the Sea. These new developments have been processed in order to enhance the user-interface performance of the original models (QRAM 3.20 and 3.60) and to extend the QRAM capacities to the study of longer routes. These objectives has been reached by the introduction of a linked Geographical Information System (GIS). In between the original model (QRA v3.20) has been used for the application of the French regulation (circular 2000-82, 30th november 2000). Up to now approximately twenty tunnel safety cases have been studied in order to choose the lowest risky route between the open air route and the tunnel one. Doing that the risk level for the road transportation of hazardous goods has been reduced. In order to have in one hand a global view of the various developments of the QRAM and in an other hand to linked these models to the European regulation framework the present paper deals with the following topics : The present regulation for the transport of dangerous goods by road in Europe, The methodology governing the QRAM, The lessons from the French application of the QRAM, The new developments for a GIS interfaced QRAM, The application of the QRAM at European and International level