Development of a 1-D Catalyzed Diesel Particulate Filter Model for Simulation of the Performance and the Oxidation of Particulate Matter and Nitrogen Oxides Using Passive Oxidation and Active Regeneration Engine Experimental Data

Back-pressure on a diesel engine equipped with an aftertreatment system is a function of the pressure drop across the individual components of the aftertreatment system, typically, a diesel oxidation catalyst (DOC), catalyzed particulate filter (CPF) and selective catalytic reduction (SCR) catalyst. Pressure drop across the CPF is a function of the mass flow rate and the temperature of the exhaust flowing through it as well as the mass of particulate matter (PM) retained in the substrate wall and the cake layer that forms on the substrate wall. Therefore, in order to control the back-pressure on the engine at low levels and to minimize the fuel consumption, it is important to control the PM mass retained in the CPF. Chemical reactions involving the oxidation of PM under passive oxidation and active regeneration conditions can be utilized with computer numerical models in the engine control unit (ECU) to control the pressure drop across the CPF. Hence, understanding and predicting the filtration and oxidation of PM in the CPF and the effect of these processes on the pressure drop across the CPF are necessary for developing control strategies for the aftertreatment system to reduce back-pressure on the engine and in turn fuel consumption particularly from active regeneration. Numerical modeling of CPF's has been proven to reduce development time and the cost of aftertreatment systems used in production as well as to facilitate understanding of the internal processes occurring during different operating conditions that the particulate filter is subjected to. A numerical model of the CPF was developed in this research work which was calibrated to data from passive oxidation and active regeneration experiments in order to determine the kinetic parameters for oxidation of PM and nitrogen oxides along with the model filtration parameters. The research results include the comparison between the model and the experimental data for pressure drop, PM mass retained, filtration efficiencies, CPF outlet gas temperatures and species (NO2) concentrations out of the CPF. Comparisons of PM oxidation reaction rates obtained from the model calibration to the data from the experiments for ULSD, 10 and 20% biodiesel-blended fuels are presented.

AN EXPERIMENTAL INVESTIGATION INTO THE EFFECTS OF BIODIESEL BLENDS ON PARTICULATE MATTER OXIDATION IN A CATALYZED PARTICULATE FILTER DURING ACTIVE REGENERATION

Active regeneration experiments were carried out on a production 2007 Cummins 8.9L ISL engine and associated DOC and CPF aftertreatment system. The effects of SME biodiesel blends were investigated in this study in order to determine the PM oxidation kinetics associated with active regeneration, and to determine the effect of biodiesel on them. The experimental data from this study will also be used to calibrate the MTU-1D CPF model. Accurately predicting the PM mass retained in the CPF and the oxidation characteristics will provide the basis for computation in the ECU that will minimize the fuel penalty associated with active regeneration. An active regeneration test procedure was developed based on previous experimentation at MTU. During each experiment, the PM mass in the CPF is determined by weighing the filter at various phases. In addition, DOC and CPF pressure drop, particle size distribution, gaseous emissions, temperature, and PM concentration data are collected and recorded throughout each experiment. The experiments covered a range of CPF inlet temperatures using ULSD, B10, and B20 blends of biodiesel. The majority of the tests were performed at CPF PM loading of 2.2 g/L with in-cylinder dosing, although 4.1 g/L and a post-turbo dosing injector were also used. The PM oxidation characteristics at different test conditions were studied in order to determine the effects of biodiesel on PM oxidation during active regeneration. A PM reaction rate calculation method was developed to determine the global activation energy and the corresponding pre-exponential factor for all test fuels. The changing sum of the total flow resistance of the wall, cake, and channels was also determined as part of the data analysis process in order to check on the integrity of the data and to correct input data to be consistent with the expected trends of the resistance based on the engine conditions used in the test procedure. It was determined that increasing the percent biodiesel content in the test fuel tends to increase the PM reaction rate and the regeneration efficiency of fuel dosing, i.e., at a constant CPF inlet temperature, B20 test fuel resulted in the highest PM reaction rate and regeneration efficiency of fuel dosing. Increasing the CPF inlet temperature also increases PM reaction rate and regeneration efficiency of fuel dosing. Performing active regeneration with B20 as opposed to ULSD allows for a lower CPF temperature to be used to reach the same level of regeneration efficiency, or it allows for a shorter regeneration time at a constant CPF temperature, resulting in decreased fuel consumption for the engine during active regeneration in either scenario.

Studio e realizzazione dell’emulatore μARM e del progetto JaeOS per la didattica dei Sistemi Operativi

La maggior parte degli strumenti per la didattica dei sistemi operativi sono basati sull'architettura MIPS, che è ampiamente superata. Questo lavoro introduce μARM, un emulatore, basato su architettura ARM7TDMI adeguato all'insegnamento a livello universitario. Inoltre viene presentato JaeOS, un manuale di specifiche per un sistema operativo multi-strato che supporti esecuzione multi-processo, memoria virtuale, sincronizzazione dei thread, gestione di dispositivi esterni ed un file system. I progetti tradizionali, come OSP2 o OS/161, forniscono un buon quantitativo di codice già sviluppato agli studenti, i quali devono modificare i moduli del sistema già implementati ed aggiungerne di nuovi. Con μARM/JaeOS gli studenti sono sottoposti ad un'esperienza pedagogicamente differente, partendo dal solo emulatore hardware e finendo con un sistema operativo, interamente sviluppato da loro, in grado di eseguire programmi sviluppati dagli studenti stessi.

Fitness cost and interference of Arm/Rmt aminoglycoside resistance with the RsmF housekeeping methyltransferases

Arm/Rmt methyltransferases have emerged recently in pathogenic bacteria as enzymes that confer high-level resistance to 4,6-disubstituted aminoglycosides through methylation of the G1405 residue in the 16S rRNA (like ArmA and RmtA to -E). In prokaryotes, nucleotide methylations are the most common type of rRNA modification, and they are introduced posttranscriptionally by a variety of site-specific housekeeping enzymes to optimize ribosomal function. Here we show that while the aminoglycoside resistance methyltransferase RmtC methylates G1405, it impedes methylation of the housekeeping methyltransferase RsmF at position C1407, a nucleotide that, like G1405, forms part of the aminoglycoside binding pocket of the 16S rRNA. To understand the origin and consequences of this phenomenon, we constructed a series of in-frame knockout and knock-in mutants of Escherichia coli, corresponding to the genotypes rsmF(+), ΔrsmF, rsmF(+) rmtC(+), and ΔrsmF rmtC(+). When analyzed for the antimicrobial resistance pattern, the ΔrsmF bacteria had a decreased susceptibility to aminoglycosides, including 4,6- and 4,5-deoxystreptamine aminoglycosides, showing that the housekeeping methylation at C1407 is involved in intrinsic aminoglycoside susceptibility in E. coli. Competition experiments between the isogenic E. coli strains showed that, contrary to expectation, acquisition of rmtC does not entail a fitness cost for the bacterium. Finally, matrix-assisted laser desorption ionization (MALDI) mass spectrometry allowed us to determine that RmtC methylates the G1405 residue not only in presence but also in the absence of aminoglycoside antibiotics. Thus, the coupling between housekeeping and acquired methyltransferases subverts the methylation architecture of the 16S rRNA but elicits Arm/Rmt methyltransferases to be selected and retained, posing an important threat to the usefulness of aminoglycosides worldwide.

Coiled armrings: an Hiberno-Viking silver arm-ring type

The purpose of this paper is to isolate and discuss a distinctive type of Hiberno-Viking silver armring. Here termed the 'coiled armring', it is dated to the late ninth/early tenth centuries. The methods of manufacture, ornamentation, date and origins of the type are discussed and the objects are assessed against the background of hoard-associated material and related types of silver armrings. A descriptive catalogue of the material is provided.

Évaluation de l’état des dalles en béton armé enterrées

Dans le souci d’améliorer le réseau de distribution de l'énergie électrique, tout en maintenant l'intégrité de certains sites urbains protégés, plusieurs municipalités du Québec ont choisi d’enfouir leurs fils électriques. Ce type d’installation requiert des chambres de raccordement souterraines afin de réaliser l’entretien du réseau et le câblage. Ces chambres sont typiquement placées à tous les 300 mètres du réseau et sont généralement recouvertes d’épaisseurs de remblai allant de 0,6 m à 1m. L’un des principaux problèmes affectant l’état structural de ces chambres est la dégradation du béton de la surface externe de celles-ci. Dans certains cas, la dégradation peut atteindre une portion non négligeable de l’épaisseur de la dalle, jusqu’à en causer l’effondrement. En plus de présenter un danger pour la population, ces effondrements entraînent des coûts d’entretien élevés pour les propriétaires d’ouvrages. En outre, ces chambres sont difficiles à inspecter par l’intérieur. Cette problématique est d’autant plus importante étant donné la grande quantité de chambres de raccordement souterraines construites par le passé. Dans ce contexte, Hydro-Québec a lancé un programme de recherche visant à faire l'évaluation par des techniques de contrôle non destructif de l’état du béton du toit des chambres de raccordement souterraines. C'est dans ce cadre que s'inscrit cette étude. Le but de notre projet est d'évaluer les capacités de la technique du Géoradar à détecter l’endommagement du béton et, si possible, déterminer l’étendue en profondeur des dégradations dans le béton de ces dalles en béton armé enterrées. Ce mémoire de maîtrise présente la méthode proposée pour atteindre cet objectif. Des simulations numériques ont été réalisées, dans un premier temps, pour établir les limites de l'application Géoradar dans le cadre de notre problématique. Les résultats obtenus ont ensuite été confrontés à des essais réalisés sur des dalles réelles enterrées. Les travaux ont permis de montrer sans équivoque qu'avec le Géoradar, il est possible de déceler la dégradation au niveau des dalles enterrées, lorsque celles-ci se situaient à une profondeur maximale de 75 cm sous un sol de type sableux. Mais, il est encore difficile de pouvoir estimer l’étendue en profondeur de la dégradation, sans connaître l'état initial des dalles.