Implementation of the Semi Empirical Kinetic Soot Model within Chemistry Tabulation Framework for Efficient Emissions Predictions in Diesel Engines

Soot prediction for diesel engines is a very important aspect of internal combustion engine emissions research, especially nowadays with very strict emission norms. Computational Fluid Dynamics (CFD) is often used in this research and optimisation of CFD models in terms of a trade-off between accuracy and computational efficiency is essential. This is especially true in the industrial environment where good predictivity is necessary for engine optimisation, but computational power is limited. To investigate soot emissions for Diesel engines, in this work CFD is coupled with chemistry tabulation framework and semi-empirical soot model. The Flamelet Generated Manifold (FGM) combustion model precomputes chemistry using detailed calculations of the 0D homogeneous reactor and then stores the species mass fractions in the table, based on six look-up variables: pressure, temperature, mixture fraction, mixture fraction variance, progress variable and progress variable variance. Data is then retrieved during online CFD simulation, enabling fast execution times while keeping the accuracy of the direct chemistry calculation. In this work, the theory behind the model is discussed as well as implementation in commercial CFD code. Also, soot modelling in the framework of tabulated chemistry is investigated: mathematical model and implementation of the kinetic soot model on the tabulation side is described, and 0D simulation results are used for verification. Then, the model is validated using real-life engine geometry under different operating conditions, where better agreement with experimental measurements is achieved, compared to the standard implementation of the kinetic soot model on the CFD side

Première mention du Marssonina salicicola sur des saules pleureurs au Québec

Au cours des printemps 1996 et 1997, des prélèvements ont été réalisés sur cinq sites à Montréal (Québec) pour établir l'étiologie de l'anthracnose des saules pleureurs (Salix alba Tristis' et S. babylonica). Sur les 25 arbres examinés, 21 étaient affectés par une maladie fongique due au Marssonina salicicola qui constitue le stade conidien du Drepanopeziza sphaeroides. Cette détection est la première mention de la présence du champignon au Canada, à l’est des Rocheuses.During spring 1996 and 1997, five sites on the Island of Montreal, Quebec, were examined to study the occurrence of anthracnose on weeping willows (Salix alba Tristis' and S. babylonica). On 21 trees of 25 surveyed, the pathogenic fungus Marssonina salicicola, the conidial state of Drepanopeziza sphaeroides, was found. This report is the first mention of the presence of this fungus in Canada, east of the Rocky Mountains

Properties of the phi meson at high temperatures and densities

We calculate the spectral density of the phi meson in a hot bath of nucleons and pions using a general formalism relating self-energy to the forward scattering amplitude (FSA). In order to describe the low energy FSA, we use experimental data along with a background term. For the high energy FSA, a Regge parameterization is employed. We verify the resulting FSA using dispersion techniques. We find that the position of the peak of the spectral density is slightly shifted from its vacuum position and that its width is considerably increased. The width of the spectral density at a temperature of 150 MeV and at normal nuclear density is more than 90 MeV.Comment: 4 pages, 5 figures, Poster presented at Quark Matter 200

CFD modelling of a spark ignition internal combustion engine fuelled with syngas for a mCHP system

Micro Combined Heat and Power (mCHP) powered with biomass is nowadays a technology attracting increasing interest to develop a local supply chain to produce, process and valorise the available material in territorial areas as much as possible circumscribed, with a considerable reduction also of the CO2 related to transportation. Application for biomass powered mCHP produces environmental benefits by reducing primary energy consumption and associated greenhouse gas emissions and complies with the need for increased decentralization of energy supply. Of particular relevance is mCHP based on biomass gasification due to the negligible particulate matter release with respect to combustion. The present work describes a 3D CFD model of the spark ignition (SI) internal combustion engine (ICE) fuelled with syngas installed in the mCHP pilot system ECO20 manufactured by the Italian company Costruzioni Motori Diesel S.p.A. (CMD). The considered system is made of a gasifier combined with proper syngas cleaning devices, an ICE and a generator to deliver a maximum electrical and thermal power of 20 kW and 40 kW, respectively. For the proper initialisation of the 3D CFD model, the syngas composition is experimentally characterised using a gas-chromatograph on samples collected under real operation. The calculated pressure cycle is verified by comparison with the one calculated through a properly developed 1D ICE model. Main goals of the performed numerical analysis are to study into detail the combustion process and to assess the engine performance characteristics related to the use of syngas

Is it possible to formulate least action principle for dissipative systems?

A longstanding open question in classical mechanics is to formulate the least action principle for dissipative systems. In this work, we give a general formulation of this principle by considering a whole conservative system including the damped moving body and its environment receiving the dissipated energy. This composite system has the conservative Hamiltonian $H=K_1+V_1+H_2$ where $K_1$ is the kinetic energy of the moving body, $V_1$ its potential energy and $H_2$ the energy of the environment. The Lagrangian can be derived by using the usual Legendre transformation $L=2K_1+2K_2-H$ where $K_2$ is the total kinetic energy of the environment. An equivalent expression of this Lagrangian is $L=K_1-V_1-E_d$ where $E_d$ is the energy dissipated by the friction from the moving body into the environment from the beginning of the motion. The usual variation calculus of least action leads to the correct equation of the damped motion. We also show that this general formulation is a natural consequence of the virtual work principle.Comment: 11 pages, no figur

Distress Tolerance: Prospective Associations With Cognitive-Behavioral Therapy Outcomes in Adults With Posttraumatic Stress and Substance Use Disorders

Distress tolerance (DT; perceived or actual ability to tolerate aversive physical or emotional states) is related to both posttraumatic stress disorder (PTSD) symptoms and substance use disorders (SUD). This investigation evaluates self-report and behavioral measures of DT as potential predictors of PTSD and SUD cognitive-behavioral therapy outcomes. Participants included 41 treatment-seeking adults (53.7% women; 73.2% African American; Mage= 44.90, SD = 9.68) who met at least four symptoms of DSM-5 PTSD and DSM-IV substance dependence, assessed via structured interviews. At baseline (pre-treatment), participants completed the Distress Tolerance Scale (DTS), Mirror-Tracing Persistence Task (MTPT), Breath Holding task, and Paced Auditory Serial Addition Task. The Clinician-Administered PTSD Scale for DSM-5 severity scores and percent days of primary substance use, measured via Timeline Follow-back, were used as indicators of PTSD symptoms and substance use, respectively. Covariates included treatment condition, baseline PTSD symptom severity, and baseline substance use. Lower perceived DT at baseline (DTS total score) was associated with higher PTSD symptom severity at end-of-treatment. Lower behavioral DT at baseline (MTPT duration) was associated with higher substance use at the conclusion of treatment (i.e., proportion of number of use days to total number of days between two final treatment sessions)

Nonjudgmental Acceptance: Associations With Substance-Related Cue Reactivity in Adults With Substance Use Disorders and Posttraumatic Stress

The present investigation examined the predictive utility of nonjudgmental acceptance, a facet of mindfulness defined as the ability to remain aware and nonevaluative about internal experience, in terms of substance-related cue reactivity among adults with substance use disorders (SUD) and posttraumatic stress (PTS) symptomatology. We hypothesized that higher nonjudgmental acceptance, indexed via self-report, would predict higher levels of self-reported control over oneself and safety \u27in the moment\u27, broadly, and lower levels of substance-related craving in response to substance script cues. Effects were expected after subtracting reactivity to neutral script cues from each outcome rating. PTS severity was included as a covariate. The sample was comprised of 53 adults (48.1% women; 75.9% African American; 74.1% with past-month PTSD) with substance dependence per DSM-IV and at least four symptoms of PTSD per DSM-5. Higher baseline nonjudgmental acceptance predicted greater safety and control in response to substance cues; no effects were found for craving. These experimental laboratory results elucidate the potential clinical utility of mindfulness-based interventions in bolstering recovery from addiction among adults with SUD/PTS by fostering safety and control in response to substance cues

Posttraumatic Stress Symptom Clusters Differentially Predict Late Positive Potential to Cocaine Imagery Cues in Trauma-Exposed Adults With Cocaine Use Disorder

BACKGROUND: While studies have investigated the effects of posttraumatic stress disorder (PTSD) symptoms on substance use, information on these associations in the context of drug cue reactivity is lacking, which can provide meaningful information about risk for relapse. The current study assessed the associations between PTSD symptom clusters and reactivity to cues in trauma-exposed adults with cocaine use disorder. METHODS: We recorded electroencephalogram on 52 trauma-exposed participants (M RESULTS: Linear mixed modeling indicated that higher NACM symptomatology was associated with higher LPPs to cocaine cues and higher arousal/reactivity was associated with lower LPPs to cocaine cues. CONCLUSIONS: These results highlight the potential clinical utility of the LPP in assessing drug cue reactivity in trauma-exposed adults with substance use disorder