Modelling, prediction and analysis of surface roughness in turning process with carbide tool when cutting steel C38 using artificial neural network

Surface roughness is a very important measurement in machining process and a determining factor describing the quality of machined surface. This research aims to analyse the effect of cutting parameters [cutting speed(v), feed rate (f) and depth of cut (d)] on the surface roughness in turning process. For that purpose, an artificial neural network (ANN) model was built to predict and simulate the surface roughness. The ANN model shows a good correlation between the predicted and the experimental surface roughness values, which indicates its validity and accuracy. A set of 27 experimental data on steel C38 using carbide P20 tool have been conducted in this study

A methodology to investigate heterogeneous oxidation of thermally aged cross-linked polyethylene by ToF-SIMS

Artificial ageing of polymeric insulation jackets is routinely performed in order to assess end-of-life material characteristics. Practical constraints including high temperatures/ short times ageing treatments lead to strong influence of diffusion-limited oxidation (DLO) resulting in unreliable life-time predictions. This study proposes a new experimental approach to the investigation of cable insulation ageing, exploiting analytical techniques capable of resolving chemistry at the length scale relevant for DLO (nano-microscale). When studying the potential effects of DLO using time of flight secondary ion mass spectrometry (ToF-SIMS) sample preparation becomes crucial. This paper presents the development of a methodology to generate suitable specimens to investigate the DLO effect using ToF-SIMS. A reference polymeric material has been thermally aged in various DLO conditions. Cross sections of aged samples were generated using three different methods. In order to assess the most suitable approach for this study, cross-section topography were scanned using a profilometer and the surface chemistry was investigated using ToF-SIMS together with multivariate analysis methods

Grey matter density changes of structures involved in Posttraumatic Stress Disorder (PTSD) after recovery following Eye Movement Desensitization and Reprocessing (EMDR) therapy

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Neural mechanisms involved in posttraumatic stress disorder and in its recovery

L’objectif de cette thèse a été de comprendre les mécanismes cérébraux associés aux symptômes du trouble de stress post-traumatique (TSPT), ainsi que les mécanismes cérébraux modulés par la disparition des symptômes, en utilisant la thérapie de désensibilisation et de retraitement de l’information par les mouvements oculaires (Thérapie EMDR). Cette thérapie associe rappel du traumatisme et stimulations bilatérales alternées (SBA). Premièrement, en utilisant l’IRM fonctionnelle (IRMf), nous avons mis en évidence une altération de l’activité fonctionnelle du système de récompense dans le TSPT, correspondant à une mobilisation déséquilibrée des processus motivationnels cognitifs et hédoniques (étude 1). Deuxièmement, par l’intermédiaire d’une étude en IRMf au repos, nous avons montré que les patients présentent des altérations de connectivité fonctionnelle entre un réseau neuronal impliqué dans les processus mnésiques et émotionnels, et un réseau neuronal impliqué dans les processus attentionnels (étude 2). Troisièmement, nous avons montré que les structures initialement altérées par la pathologie évoluent après rémission symptomatique, suggérant un rétablissement des altérations neuronales induites par le stress chronique (étude 3). Enfin, nous avons montré que les SBA employées dans la thérapie EMDR facilitent l’extinction de la peur ainsi que la récupération de cette extinction au sein d’un groupe de volontaires sains (étude 4). Ainsi, ces travaux offrent de nouvelles perspectives en termes de modélisation de la pathologie, et offre de nouvelles pistes de réflexion quant à la prise en charge thérapeutique de ce trouble.Posttraumatic Stress Disorder (PTSD) is a debilitating psychiatric disorder that arises in the aftermath of a traumatic event. To date, the Eye Movement Desensitization and Reprocessing therapy (EMDR) therapy has shown to be the most efficient therapy for the treatment of PTSD. The aim of this thesis was therefore to understand neural mechanisms underlying PTSD and its recovery. To do so, we conducted four studies. In a first study, we showed alterations in the reward circuit activity in PTSD patients, which may underlie an imbalance mobilization of cognitive and hedonic motivational processes, possibly contributing to emotional numbing in PTSD (study 1). Following this, an altered resting state functional connectivity between a network associated with attentional processes and another associated with emotional and memory processes was also found, suggesting an atypical emotional regulation and attention processing (study 2). A third study showed changes of grey matter density in regions involved in emotional regulation after symptoms remission by EMDR therapy. Finally, we were also able to replicate, in PTSD patients, the fear extinction and fear extinction recall facilitation by bilateral alternating stimulations (BAS) a major component of EMDR therapy, previously demonstrated in animal studies. Taken together, the present findings of these studies contribute to enlarge our knowledge, opening new ways of thinking the actual model of explaining the PTSD. More importantly, we believe that our findings may contribute to improve therapeutic strategies to significantly ameliorate the life of these patients

Influence of Fuzzy Parameters on the Modeling Quality of XLPE Insulation Properties under Thermal Aging

In this work, we have used the fuzzy logic approach to predict mechanical properties (hot set test) of cross-linked polyethylene (XLPE) used as insulation in high voltage cables. The studied property presents non linear variations according to the aging time under high temperatures. So it is very difficult to find a theoretical or experimental model of the properties evolution under thermal aging. For that reason, several factors have been considered such as aging time and applied temperature. The obtained results are very encouraging and pointed out that the fuzzy logic is a powerful tool to predict the insulation proprieties. In other words, the obtained results are in good accordance with the experimental results with an acceptable error margin

Detection of faults in the asynchronous machine by the use of smartmaterials

This paper aimed with diagnosis of defects in asynchronous machine. The used method is based on the exploitation of the behavioural laws of magnetostrictive and piezoelectric materials, under harmonic regime, used in the construction of the asynchronous machine. Piezoelectric sensors are used both in the stator and in the rotor. The used one in the stator serves to detect the rupture at the stator windings and the one used in the rotor helps us to detect the rupture of the rotor bars. The produced electric potential in the terminals of piezoelectric sensor is due to the deformation generated by magnetic induction under the effect of magnetostriction. A finite element method (FEM) is selected to be the resolution numerical method. This method is used for modelling the asynchronous machine under anomaly conditions and non-load

Cracking the EMDR code: Recruitment of sensory, memory and emotional networks during bilateral alternating auditory stimulation

International audienceIntroduction: The inability to extinguish a conditioned fear is thought to be at the core of post-traumatic stress disorder. Eye movement desensitization and reprocessing therapy has been efficacious for post-traumatic stress disorder, but the brain mechanisms underlying the effect are still unknown. The core effect of eye movement desensitization and reprocessing therapy seems to rely on the simultaneous association of bilateral alternating stimulation and the recall of the traumatic memory. To shed light on how eye movement desensitization and reprocessing therapy functions, we aimed to highlight the structures activated by bilateral alternating stimulation during fear extinction and its recall. Methods: We included 38 healthy participants in this study. Participants were examined twice in functional magnetic resonance imaging, over 2 consecutive days. On the first day, they performed two fear conditioning and extinction procedures, one with and one without the bilateral alternating stimulation during the fear extinction learning phase in a counterbalanced order across the participants. On the second day, participants completed the fear extinction recall procedure, in the same order as the previous day. Statistical significance of maps was set at p < 0.05 after correction for family-wise error at the cluster level. Results: The analysis revealed significant activation with versus without bilateral alternating stimulation at the early extinction in the bilateral auditory areas, the right precuneus, and the left medial frontal gyrus. The same pattern was found in the early recall on the second day. The connectivity analysis found a significant increase in connectivity during bilateral alternating stimulation versus without bilateral alternating stimulation in the early extinction and recall between the two superior temporal gyri, the precuneus, the middle frontal gyrus and a set of structures involved in multisensory integration, executive control, emotional processing, salience and memory. Conclusion: We show for the first time that in the eye movement desensitization and reprocessing therapy the bilateral alternating stimulation is not a simple sensory signal and can activate large emotional neural networks