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Optimal control of the exhaust aftertreatment components is an important aspect for minimizing pollutants. Nitrogen oxides are therefore monitored using amperometric gas sensors. However, they show marked cross-sensitivities to ammonia, which can be disadvantageous, e.g., if they are applied in NH3 selective catalytic reduction systems. In this study, a model that simulates the operation of a NOx sensor is developed. The three oxygen pumping cells and the upstream diffusion barriers were implemented in a 1D geometry, with the relevant electrode reactions taking place over its length. The diffusion barriers were calculated quasi-stationary. The dynamics of incoming gas components as a function of the exhaust mass flow were integrated with a first order linear time invariant system. The problem was calculated using the convection-diffusion equation. The reaction kinetics were determined based on stationary measurements in laboratory atmosphere, whereby initially only the reaction with respect to NO and NO2 was considered. Then, the cross-sensitivities to oxygen, water and ammonia were examined. The developed data set could then be used for transient boundary conditions. The simulated and the measured sensor signals in the case of engine test bench conditions with real driving cycles agree very well. [ABSTRACT FROM AUTHOR]

A 36-year-old woman with anorexia nervosa and resulting malnutrition decided to change her life and eat properly. One day after the refeeding start, instead of feeling better she felt much worse: fatigue, nausea and leg swelling occurred. She consulted our emergency department. A «refeeding syndrome» has been diagnosed. In this case report we discuss causes, clinical presentation and treatment of this illness. The aim is to make practitians aware about the existing of this disease even with oral refeeding. Warning signs have to be interpreted correctly in order to avoid dramatic consequences. [ABSTRACT FROM AUTHOR]

With the introduction of stringent emission standards in the US in 2007 (Tier II Bin8, 5) an exhaust aftertreatment for NO x reduction is required for compliance with the emission regulations. A new approach consists in the synergetic combination of existing technologies NSC (NO x Storage Catalyst) and SCR (Selective Catalytic Reduction) with onboard generation of ammonia as the reducing agent for the SCR. It is shown in this work that the performance of the combined system exceeds those of each one considered separately, especially after ageing. The generation of ammonia is correlated to the ammonia selectivity during the regeneration of the NSC. The selectivity is primarily dependent on the temperature, A/F ratio (Air/Fuel) and the rich time. It is shown that the development of a suitable control strategy leads to a high level of NO x reduction under transient conditions in an FTP driving cycle. Due to the complexity and high development costs of current exhaust aftertreatment systems, modelling and simulation were identified as an important aspect in the development process. A system simulation tool named ExACT ( Exhaust Gas Aftertreatment Components Toolbox) developed at Daimler is presented. By using the simulation already at an early stage, specific development work can be carried out prior to the experimental work on an engine test bench. [ABSTRACT FROM AUTHOR]