Optimization of polypropylene cellular films for piezoelectric applications

Cette thèse comporte deux objectifs principaux: la production en continu de films de polypropylène (PP) moussés ayant une structure cellulaire de forme oculaire, suivie par la préparation de films PP ferroélectrets par décharge corona pour des applications piézoélectriques. Dans la première partie de ce travail, une production en continu par extrusion-calandrage a été développée pour produire des films de PP moussés pour des applications piézoélectriques. Le système est basé sur un moussage physique en utilisant de l'azote supercritique (SC-N2) et le carbonate de calcium (CaCO3) comme agent de nucléation. Les paramètres de mise en œuvre (conception de vis, profil de température, agent gonflant et de nucléation ainsi que leur contenu, et la vitesse d'étirement) ont été optimisés pour obtenir une forme spécifique (oculaire) comme structure cellulaire avec une distribution uniforme de la taille des cellules. Les résultats ont montré qu'une structure cellulaire avec un plus grand rapport d'aspect (AR) des cellules possède un plus faible module de Young, ce qui est approprié pour les films cellulaires piézoélectriques. Dans la deuxième partie, des films PP ferroélectrets ont été produits. Suite à l'optimisation du procédé de décharge corona (tension de charge, distance de l'aiguille, temps de charge), les propriétés piézoélectriques des films obtenus ont été caractérisées et le coefficient piézoélectrique quasi-statique d33 a produit une valeur de 550 pC/N. Afin de mieux caractériser le comportement du film, l’analyse mécanique dynamique (DMA) a été proposée comme une méthode simple pour relier les propriétés piézoélectriques des films PP cellulaires à leur morphologie (taille, géométrie et densité des cellules). Finalement, grâce à un post-traitement basé sur la saturation du film PP moussé avec le SC-N2, une procédure en température et pression a été développée afin d’améliorer la structure cellulaire (cellules plus allongées). Ce traitement a permis d’augmenter de 45% le coefficient d33 (800 pC/N).This thesis is composed of two main objectives: the continuous production of thin foamed polypropylene (PP) films having an eye-like cellular structure, followed by the preparation of ferroelectret PP films through corona discharge for piezoelectric applications. In the first part of this work, a continuous extrusion-calendaring setup was developed to produce PP foamed films for piezoelectric applications. The setup is based on physical foaming using supercritical nitrogen (SC-N2) and calcium carbonate (CaCO3) as nucleating agent. The processing parameters (screw design, temperature profile, blowing agent and nucleating agent content, and stretching speed) were optimized to achieve a specific stretched eye-like cellular structure with a uniform cell size distribution. The results showed that a cellular structure with higher cell aspect ratio (AR) has lower Young’s modulus, which is appropriate for piezoelectric cellular films. In the second part, ferroelectret PP films were produced. After optimization of the corona discharge process (charging voltage, needle distance, charging time), the piezoelectric properties of the resulting films were characterized and the optimum quasi-static piezoelectric d33 coefficient value was 550 pC/N. To better characterize the film behavior, dynamic mechanical analysis (DMA) was proposed as a simple method to relate the piezoelectric properties of the cellular PP films to their morphology (cell size, geometry and density). Finally, through a post-processing treatment based on the saturation of the foamed PP film with SC-N2, a temperature-pressure procedure was developed to improve the cellular structure (more stretched eye-like cells). This treatment was shown to increase by 45% the d33 coefficient (800 pC/N)

Real-Time Stereo Visual Servoing of a 6-DOF Robot for Tracking and Grasping Moving Objects

Robotic systems have been increasingly employed in various industrial, urban, mili-tary and exploratory applications during last decades. To enhance the robot control per-formance, vision data are integrated into the robot control systems. Using visual feedback has a great potential for increasing the flexibility of conventional robotic and mechatronic systems to deal with changing and less-structured environments. How to use visual in-formation in control systems has always been a major research area in robotics and mechatronics. Visual servoing methods which utilize direct feedback from image features to motion control have been proposed to handle many stability and reliability issues in vision-based control systems. This thesis introduces a stereo Image-based Visual Servoing (IBVS) (to the contrary Position-based Visual Servoing (PBVS)) with eye‐in‐hand configuration that is able to track and grasp a moving object in real time. The robustness of the control system is in-creased by the means of accurate 3-D information extracted from binocular images. At first, an image-based visual servoing (IBVS) approach based on stereo vision is proposed for 6 DOF robots. A classical proportional control strategy has been designed and the ste-reo image interaction matrix which relates the image feature velocity to the cameras’ ve-locity screw has been developed for two cases of parallel and non-parallel cameras in-stalled on the end-effector of the robot. Then, the properties of tracking a moving target and corresponding variant feature points on visual servoing system has been investigated. Second, a method for position prediction and trajectory estimation of the moving tar-get in order to use in the proposed image-based stereo visual servoing for a real-time grasping task has been proposed and developed through the linear and nonlinear model-ing of the system dynamics. Three trajectory estimation algorithms, “Kalman Filter”, “Recursive Least Square (RLS)” and “Extended Kalman Filter (EKF)” have been applied to predict the position of moving object in image planes. Finally, computer simulations and real implementation have been carried out to verify the effectiveness of the proposed method for the task of tracking and grasping a moving object using a 6-DOF manipulator

Concurrent, Integrated and Multicriteria Design Support for Mechatronic Systems

RÉSUMÉ Les systèmes mécatroniques sont une combinaison coopérative de composantes mécaniques, électroniques, de contrôle et logiciels. Dans les dernières décennies, Ils ont trouvé diverses applications dans l'industrie et la vie quotidienne. En raison de leur aspect multi-physique, du nombre élevé de leurs composantes et des interconnexions dynamiques entre les différents domaines impliqués dans leur fonctionnement, les dispositifs mécatroniques sont souvent considérés comme hautement complexes ce qui rend la tâche de les concevoir très difficile pour les ingénieurs. Cette complexité inhérente a attiré l’attention de la communauté de recherche en conception, en particulier dans le but d’atteindre une conception optimale des systèmes multi-domaines. Ainsi, cette thèse, représente une recherche originale sur le développement d'un paradigme de conception systématique, intégrée et multi-objectifs pour remplacer l'approche de conception séquentielle traditionnelle qui tend à traiter les différents domaines de la mécatronique séparément. Dans le but d'augmenter l'efficacité, la fiabilité, la facilité de contrôle et sa flexibilité, tout en réduisant la complexité et le coût effectif, ainsi que l'intégration systèmes, cette thèse présente de nouvelles approches pour la conception concurrente et optimale des systèmes mécatroniques aux stades de design conceptuel et détaillé. Les modèles mathématiques et les fondements qui soutiennent cette pensée sont présentés dans cette thèse. Les contributions des travaux de recherche de ce doctorat ont commencé par l'introduction d'un vecteur d'indices appelé le profile mécatronique multicritère (PMM) utilisé pour l'évaluation des concepts lors de la conception des systèmes mécatroniques. Les intégrales floues non linéaires de la théorie de décisions multicritères sont utilisées pour agréger les critères de conception et pour gérer les interactions possibles entre elles. Ensuite, une méthodologie de conception conceptuelle systématique est proposée et formulée. Le soutien à l'intégration d'outils d’aide à la décision multicritère dans le processus de conception est un autre objectif de cette thèse où un certain nombre de cadres de travail sont proposés pour aider les ingénieurs concepteurs à évaluer l’importance de certains critères et des paramètres d'interaction. Ces cadres de travail ne s'appliquent pas uniquement l'évaluation de la conception et de la conception optimales, mais aussi à la détermination des possibles façons d'améliorer les concepts développés. Des méthodes basées sur l’exploitation de données ainsi que des algorithmes d'optimisation sémantique sont utilisées pour identifier les paramètres flous avec le peu d’information disponibles sur les différents choix de concepts et les préférences des concepteurs.----------ABSTRACT Mechatronic systems are a combination of cooperative mechanical, electronics, control and software components. They have found vast applications in industry and everyday life during past decades. Due to their multi-physical aspect, the high number of their components, and the dynamic inter-connections between the different domains involved, mechatronic devices are often considered to be highly complex which makes the design task very tedious and non-trivial. This inherent complexity, has attracted a great deal of attention in the research community, particularly in the context of optimal design of multi-domain systems. To this end, the present thesis represents an original investigation into the development of a systematic, integrated and multi-objective design paradigm to replace the traditional sequential design approach that tends to deal with the different domains separately. With the aim of increasing efficiency, reliability, controllability and flexibility, while reducing complexity and effective cost, and finally facilitating system integration, this thesis presents new approaches towards concurrent and optimal design of mechatronic systems in conceptual and detailed design stages. The mathematical models and foundations which support this thinking are presented in the thesis. The contributions of our research work start with introducing an index vector called Mechatronic Multi-criteria Profile (MMP) used for concept evaluation in design of mechatronic systems. Nonlinear fuzzy integrals from multicriteria decision theory are utilized to aggregate design criteria and for handling possible interactions among them. Then, a systematic conceptual design methodology is proposed and formulated. Supporting the incorporation of multicriteria decision making tools into the design process, is another focus of this work where a number of frameworks are proposed to help the designers with assessment of criteria importance and interaction parameters. These frameworks are not only applicable in optimal design and design evaluation procedures, but also for determining possible ways for design improvements. Both data-driven methods as well as semantic-based optimization algorithms are used to identify the fuzzy parameters with limited available information about the design alternatives and designer preferences. Moreover, a fuzzy-based multi-objective approach has been undertaken for proposing and formulating a detailed design methodology. A unified performance evaluation index is introduced by the means of Choquet integrals and then optimized using a constrained particle swarm optimization (PSO) algorithm

A Fuzzy-based Framework to Support Multicriteria Design of Mechatronic Systems

Designing a mechatronic system is a complex task since it deals with a high number of system components with multi-disciplinary nature in the presence of interacting design objectives. Currently, the sequential design is widely used by designers in industries that deal with different domains and their corresponding design objectives separately leading to a functional but not necessarily an optimal result. Consequently, the need for a systematic and multi-objective design methodology arises. A new conceptual design approach based on a multi-criteria profile for mechatronic systems has been previously presented by the authors which uses a series of nonlinear fuzzy-based aggregation functions to facilitate decision-making for design evaluation in the presence of interacting criteria. Choquet fuzzy integrals are one of the most expressive and reliable preference models used in decision theory for multicriteria decision making. They perform a weighted aggregation by the means of fuzzy measures assigning a weight to any coalition of criteria. This enables the designers to model importance and also interactions among criteria thus covering an important range of possible decision outcomes. However, specification of the fuzzy measures involves many parameters and is very difficult when only relying on the designer's intuition. In this paper, we discuss three different methods of fuzzy measure identification tailored for a mechatronic design process and exemplified by a case study of designing a vision-guided quadrotor drone. The results obtained from each method are discussed in the end

The Analysis of Keyumarth Myth in Shahnameh from the Perspective of Levi Strauss’ Mythological Structuralism

The myth of Keyumarth is one of the most important myths of Iranian culture enjoying a high research capacity in various aspects and qualities. Therefore, it requires systematic and consistent theory-based research and literal criticism. In the present research, an attempt has been made to analyze Keyumarth myth based on the theory of structuralist mythology from Levi Strauss. Since enough and even more traditional literary criticism-related studies have been conducted on books such as Shahmnameh, and systematic and modern critiques have not received enough attention, a theory-based research considering literary criticisms approaches richly needs to be carried out in this area. The present study followed a qualitative design making use of a plenty of literary and documentary studies; i.e., first, the narratives related to Keyumarth myth were extracted from various books and then they were classified. Then, mythological units were extracted from among the narratives, arranged in a dichotomous manner and finally analyzed. The results of the present study revealed that the structure of Keyumarth myth is based on three dichotomies: holy/ unholy dichotomy, power/ power decline dichotomy, and nature/ culture dichotomy

Digoxin Inhibits Retinoblastoma through Suppressing a Non-canonical TGFβ Signaling Pathway.

Aims: Retinoblastoma is a childhood ocular tumor rapidly developing from the immature cells of the retina due to loss of functional retinoblastoma protein. Digoxin, a cardiac glycoside, has been reported to be effective in inducing apoptosis, cell cycle arrest, and cytotoxic effects on human cancers. In this regard, the present study aims to investigate whether digoxin could suppress retinoblastoma cancer through the regulation of transforming growth factor-β (TGF-β) signaling pathway. Methodology: The effects of digoxin on Y-79 cells, retinoblastoma cancer cell line, were investigated using MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazoli-umbromide) and BrdU (bromodeoxyuridine) assays to measure cellular cytotoxicity effects and cell apoptosis, respectively. Also, a qPCR assay was employed to analyze the mRNA expression levels of TGFβ signaling pathway including C-MYC, P21, P15, TGFβRI, TGFβRII, and SMAD2, 3, and 4 genes. Results: The results of the cell function assays revealed that digoxin inhibited the cell viability and proliferation of Y-79 cells. In addition, it was found that digoxin significantly suppressed C-MYC expression and enhanced the expression of P21, P15, SMAD2 and SMAD4 genes in a dose-and time-dependent manner. However, the obtained results could not detect any significant effect of digoxin on TGFβRI, TGFβRII and SMAD3 genes. Conclusion: Taken together, the findings of the present study suggest that digoxin could be a potential therapeutic agent in the treatment of retinoblastoma by regulating the cell cycle genes via a non-canonical TGF-β signaling pathway

Determinants of perivascular adipose tissue stranding as a novel imaging marker and its relation to inflammatory biomarker high-sensitivity C-reactive protein

Purpose: This study aimed to examine the relationship of perivascular adipose tissue (PVAT) stranding in coronary computed tomography angiography (CCTA) with high-sensitivity C-reactive protein (hsCRP) and the determinants of PVAT stranding in coronary artery disease (CAD) patients. Material and methods: This retrospective cross-sectional study was done by collecting data from CAD patients who were referred to Rajaie Cardiovascular Centre between January 2018 and September 2020, with CCTA and hsCRP test 72 hours apart from the CCTA. PVAT stranding was defined as irregular obscuration of PVAT adjacent to the coronary arteries. An attempt was made to find a correlation between included variables and PVAT stranding by comparing them between 2 groups: patients with and without PVAT stranding. Results: From 92 patients, 31 participants had PVAT stranding, and statistically significant higher levels of hsCRP were detected in them (p = 0.007). We demonstrated significantly higher prevalence of history of hyperlipidaemia (OR = 3.83, p = 0.029), high-risk plaque features (OR = 11.80, p = 0.015), and obstructive coronary luminal stenosis (OR = 3.25, p = 0.025) in patients with PVAT stranding. Also, significantly higher PVAT attenuation was detected in patients with PVAT stranding (p < 0.001) independently from mean attenuation of epicardial fat. Conclusion: PVAT stranding could be used as a novel non-invasive marker in CCTA of CAD patients. More studies focusing on patient outcomes are required to better evaluate the reliability and prognostic value of this marker