Dissertations / Theses on the topic 'Semi-isolation'
To see the other types of publications on this topic, follow the link: Semi-isolation.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 37 dissertations / theses for your research on the topic 'Semi-isolation.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Nguyen, The Minh. "A Novel Semi-Active Magnetorheological Mount for Vibration Isolation." University of Toledo / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1250008519.
Full text
2
Liu, Yuyou. "Semi-active damping control for vibration isolation of base disturbances." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/66164/.
Full textAbstract:
This thesis is concerned with semi-active damping control for vibration isolation of base disturbances. The aim is to investigate the effectiveness and suitability of semi-active damping control strategies for improving steady-state vibration isolation. A single-degree-of-freedom (SDOF) system, comprising a semi-active damper with a linear passive spring in parallel, is used to study the vibration isolation of base excitation. The semi-active control strategies investigated include on-off skyhook control, continuous skyhook control, on-off balance control and continuous balance control. Chatter and jerk problems are investigated, which can arise in numerical simulations and possibly in practice when using semi-active control strategies. Anti-chatter and anti-jerk control strategies are proposed. These control strategies are implemented numerically in Matlab/Simulink. Harmonic, periodic and random disturbances are considered in this thesis. The vibration isolation performance is evaluated in terms of Root-Mean-Square (RMS) acceleration transmissibility. The performance of these control strategies for the isolation of harmonic disturbances is firstly studied. The performance is compared with those of an adaptive-passive control strategy, a conventional and a skyhook passive damper. Results show that the semi-active control strategies can provide a better isolation than a conventional passive system with an equivalent damping level. The semi-active damper can provide isolation over the whole frequency range if the on-state damping of the semi-active damper is big enough. The fraction of time when the damper is turned on or off is found to be frequency dependent. The effects of secondary frequency, which is a harmonic or subharmonic of the fundamental frequency on switching time of the semi-active damper for isolation of the primary harmonic are examined. Upper bounds are derived for fraction of time when the switching time for the fundamental frequency may be affected by the presence of a secondary frequency. The performance of the semi-active isolation system for periodic and random disturbances, where there is more than one harmonic in the disturbance spectrum is investigated. The results for square wave and triangular wave disturbances suggest that semi-active control strategies are promising for periodic disturbance. Three special cases are considered for random disturbances when the acceleration, velocity and displacement inputs have flat spectra. The semi-active control strategies can provide some advantage in performance for random velocity and displacement disturbances with medium to high damping ratios. Only continuous skyhook control strategy can provide some benefit in isolation performance for random acceleration disturbances. Following on from the numerical simulations, experimental work is carried out to validate the simulation results. The experimental set-up incorporates an electromagnetic device as a semi-active damper. The on-off skyhook control algorithm is chosen to be implemented using an analogue circuit. The damping of the electromagnetic semi-active damper is achieved by opening and closing the magnet-coil circuit. Numerical predictions are confirmed by experimental observation. The performance of the electromagnetic damper is limited by the achievable damping level.
3
St-Amand, Olivier. "Modélisation semi-analytique dynamique d'un actionneur THUNDER utilisé en isolation vibratoire." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/28744/28744.pdf.
Full text
4
Hammond, Nicholas L. "Isolation, semi-synthesis and synthesis of agents for cancer, HIV, and malaria /." Full text available from ProQuest UM Digital Dissertations, 2008. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1850432521&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1279646503&clientId=22256.
Full textAbstract:
Thesis (Ph.D.)--University of Mississippi, 2008.Typescript. Vita. "January 2008." Major professor: Mitchell A. Avery Includes bibliographical references (leaves 200-226). Also available online via ProQuest to authorized users.
5
Liu, Yanqing. "Variable damping and stiffness semi-active vibration isolation control using magnetorheological fluid dampers." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144553.
Full text
6
Jean, Pierrick. "Isolation vibratoire par contrôle semi-actif d'amortisseurs magnéto-rhéologiques pour l'interface lanceur/charge utile." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2006. http://tel.archives-ouvertes.fr/tel-00352710.
Full textAbstract:
Le travail présenté dans cette thèse a pour objet l'isolation vibratoire entre 5 et 100 Hz d'une charge utile durant les 150 premières secondes de son lancement, par contrôle semi-actif d'amortisseurs magnéto-rhéologiques. L'isolateur envisagé est une interface souple dont les modes, compris entre 2 et 7 Hz, sont amortis par le dispositif à amortissement contrôlable. Dans un premier temps, afin de réaliser des simulations de contrôle semi-actif réalistes, un modèle de l'amortisseur magnéto-rhéologique utilisé est identifié à partir des mesures de l'effort et de la vitesse du piston. Puis on étudie l'isolateur semi-actif à 1 degré de liberté, à la fois par simulations et expérimentalement. On s'intéresse en particulier au contrôleur skyhook damper et à ses performances d'isolation haute fréquence et d'amortissement basse fréquence pour différents types d'excitations large bande, performances qui sont systématiquement comparées à celles de l'isolateur passif optimal. On présente ensuite une étude originale qui concerne un isolateur semi-actif à 6 degrés de liberté, basé sur la plateforme de Stewart, dont un démonstrateur expérimental a été développé et testé. On détaille en particulier les résultats du contrôle par Integral Force Feedback semi-actif pour les excitations lanceur reproduites expérimentalement. Enfin, l'étude est étendue à la configuration échelle 1 pour laquelle on envisage les performances de confort et de sécurité de l'isolateur. On considère en particulier un cas d'excitation transitoire latérale, la rafale de vent, pour laquelle on développe un contrôleur on-off à seuil de déclenchement, lequel semble également efficace pour l'isolation vibratoire. L'isolateur semi-actif ainsi obtenu semble présenter de meilleures performances qu'un isolateur passif stationnaire, tout en étant conforme aux contraintes propres à l'environnement lanceur.
7
Hiemenz, Gregory J. "Semi-active magnetorheological seat suspensions for enhanced crashworthiness and vibration isolation of rotorcraft seats." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7602.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
8
Tanner, Edward Troy. "Combined Shock and Vibration Isolation Through the Self-Powered, Semi-Active Control of a Magnetorheological Damper in Parallel with an Air Spring." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/29541.
Full textAbstract:
Combining shock and vibration isolation into a single isolation system package is explored through the use of an air spring in parallel with a controlled magnetorheological fluid damper. The benefits of combining shock and vibration isolation into a single package is discussed. Modeling and control issues are investigated and test and simulation results are discussed. It is shown that this hybrid isolation system provides significantly increased performance over current state-of-the-art passive systems. Also explored is the feasibility of scavenging and storing ambient shipboard vibration energy for use in powering the isolation system.
To date the literature has not adequately explored the direct design of a combined shock and vibration isolation system. As shock and vibration isolation are typically conflicting goals, the traditional approach has been to design separate shock and vibration isolation systems and operate them in parallel. This approach invariably leads to compromises in terms of the performance of both systems. Additionally, while considerable research has been performed on magnetorheological fluids and devices based on these fluids, there has been little research performed on the use of these fluids in devices that are subjected to high velocities such as the velocity seen by a ship exposed to underwater near-miss explosive events. Also missing from the literature is any research involving the scavenging and storage of ambient shipboard vibration energy. While the focus of this work is on the use of this scavenged energy to power the subject isolation system, many other uses for this energy can be envisioned.
Experimental and analytical results from this research clearly show the advantages of this hybrid isolation system. Drop tests show that inputs as great as 167 g's were reduced to 3.42 g's above mount at 1.11 inches of deflection using a Velocity Feedback controller suggested by the author. When contrasted with typical test results with similar inputs, the subject isolation system achieved reductions in above mount accelerations of 300% and reductions in mount deflections of 200% over current state-of-the-art passive shipboard isolation systems. Furthermore, simulations using a validated model of the isolation system suggest that this performance improvement can be achieved in multi-degree-of-freedom isolation systems as well. It was shown that above mount accelerations in the vertical and athwartship directions could be effectively limited to a predefined value, while achieving the absolute minimum mount defections, using an Acceleration Limiting Bang-Bang controller suggested by the author. Further experimentation suggests that the subject isolation system could be entirely self-powered from scavenged ambient shipboard vibration energy. An experiment using an energy scavenging and storage system consisting of a Piezoelectric Stack Generator and a bank of ultracapacitors showed that enough energy could be harvested to power the isolation system though several shock events.Ph. D.
9
Shi, Yundong. "Enhancement of Functionality of Structures Using Isolation and Semi-Active Control in Consideration of Performance of Furniture and Appliances." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180496.
Full text
10
Arzanpour, Siamak. "Active and Semi-Active Bushing Design for Variable Displacement Engine." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2886.
Full textAbstract:
The Variable Displacement Engine (VDE) is a new generation of engines that are designed to decrease the fuel consumption at the cruise speed of a vehicle. The isolation of the VDE's new vibration pattern is beyond the capabilities of conventional mounts and bushings. Consequently, in this thesis, novel active and semi-active solutions are proposed to develop various semi-active and active hydraulic bushing proof-of-concept systems that may solve the isolation problem in a VDE system. The dynamic stiffness response, which is the transfer function that relates the engine displacement to the transmitted force, is normally used as the key design criterion for engine mounts and bushings. In this thesis, a linear mathematical model of a conventional hydraulic bushing is purposed. The validity of the mathematical model is confirmed by an experimental analysis, and the various parameters in the dynamic stiffness equation are evaluated. The experimental results indicate that the dynamic stiffness frequency response of the conventional hydraulic bushing has both soft and stiff regions. The soft region is limited to low frequencies. For the VDE isolation, the goal is to provide a soft bushing for a wider range of frequencies than a conventional bushing can accommodate. Addition of a short inertia track, similar to a decoupler used in conventional hydraulic engine mounts, may be used to extend the soft region of a conventional hydraulic bushing, and the experimental results validate it.
Since the short inertia track provides no additional damping, a supplementary Magnetorheological (MR) valve is also devised. The MR valve has the advantage to minimize the amount of MR fluid used, which significantly reduces the cost of the overall system. The novel valve allows the damping coefficient of the bushing assembly to be controlled by varying the electrical current input to a solenoid coil. A mathematical model is derived for the MR bushing, and is validated experimentally.
In addition, an active bushing to solve the VDE isolation problem is purposed in this thesis. In this bushing, a magnetic actuator, composed of a permanent magnet and a solenoid coil, is included in the active bushing. This active chamber affects the dynamic stiffness response of the bushing by altering the bushing's internal pressure. The nonlinear equation of motion of the permanent magnet is linearized and is incorporated into the new mathematical model of the system. The new purposed model for the active bushing is in good agreement with the experimental results. This active chamber is also proved capable of producing complex dynamic stiffness frequency response.
The conclusion is that the proposals in this thesis can contribute to the isolation of the vibration pattern, imposed by the application of a VDE system.
11
Jaitlee, Rajneesh, and jaitlee@gmail com. "Mean and Fluctuating Pressures on an Automotive External Rear View Mirror." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070112.125531.
Full textAbstract:
The primary function of an automobile rear View Mirror is to provide the driver with a clear vision interpretation of all objects to the rear and side of the vehicle. The rear View Mirror is a bluff body and there are several problems associated with the rear View Mirror. These include buffeting, image distortion (due to aerodynamically induced and structural vibration), aerodynamically induced noise (due to cavities and gaps) and water and dirt accumulation on Mirror glass Surface. Due to excessive glass vibration, the rear View Mirror may not provide a clear image. Thus, vibrations of Mirror can severely impair the driver's vision and safety of the vehicle and its occupants. The rear View Mirrors are generally located close to the A-pillar region on the side window. A conical vortex forms on the side window close to A-pillar due to A-pillar geometry and the presence of side rear View Mirror and flow separation from it makes the airflow even more complex. The primary objective of this work is to study the aerodynamic pressures on Mirror Surface at Various speeds to determine the effects of aerodynamics on to Mirror vibration. Additionally, the Mirror was modified by Shrouding around the external periphery to determine the possibility of minimisation of aerodynamic pressure fluctuations and thereby vibration. The Shrouding length used for the analysis was of 24mm, 34mm and 44mm length. The mean and fluctuating pressures were measured using a production rear side View Mirror fitted to a ¼ quarter production passenger car in RMIT Industrial Wind Tunnel. The tests were also conducted in semi-isolation condition to understand influence of the A-pillar geometry. The mean and fluctuating pressures were converted into non-dimensional pressure coefficients (Cp and Cprms) and the frequency content of the fluctuating pressure was analysed. The results show that the fluctuating aerodynamic pressures are not uniformly distributed over an automobile Mirror Surface. The highest magnitude of fluctuating pressure for the standard Mirror was found at the central bottom part of the Mirror Surface. The highest magnitude of fluctuating pressure for the modified Mirror was found at the central top part of the Mirror Surface. As expected, the modification has significant effect on the magnitude of fluctuating pressure. The results show that an increase of Shrouding length reduces the magnitude of the fluctuating pressure. The frequency-based analysis was done to understand the energy characteristics of the flow, particularly to its phase, since it is the out of phase components that usually cause Mirror rotational vibration. The spectral analysis showed that the magnitude of the energy distribution reduces with increase of shrouding length throughout the frequency range. Flow visualisation was also used to supplement the pressure data. The effects of yaw angles were not included in this study, however, are thought to be worthy of further investigation. On road testing and the variation of mirror locations might have some effects on the fluctuating pressures. These need to be investigated in the future work. The quarter model used in this study was a car specific. However, for more generic results, a simplified model with variable geometry can be used in future study.
12
Vissouvanadin, Soubaretty Bertrand. "Matériaux de câble à isolation synthétique pour des applications au transport d'énergie HVDC." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1271/.
Full textAbstract:
Ce travail concerne le développement des câbles haute tension à courant continu (HVDC) à base de polyéthylène réticulé chimiquement (XLPE). Le développement de ce type de câble est confronté au problème d'accumulation de charges d'espace, lié à la nature des électrodes semi-conductrices et de l'isolant. Dans le cadre de cette thèse, la méthode électroacoustique pulsée (PEA) est utilisée pour étudier l'accumulation de charges d'espace dans les matériaux sur plaques modèles et sur câbles. Le rôle joué par les sous-produits de réticulation sur la formation d'hétérocharges est clairement mis en évidence par l'étude du conditionnement du XLPE. Un modèle basé sur une polarisation hétérogène est proposé pour expliquer la formation d'hétérocharges. Les résultats obtenus sur différentes formulations d'isolants montrent une implication certaine des additifs dans la formation de charges d'espace. L'étude réalisée sur les couches semi-conductrices a permis, par ailleurs, d'identifier l'impact des différents constituants (noir de carbone, matrice etc. . ) sur la formation de charges. Pour l'étude des câbles maquettes, une méthode de déconvolution des profils PEA tenant compte de la géométrie cylindrique, de l'atténuation et de la dispersion d'onde acoustique est d'abord mise au point. Les mesures sur des câbles maquettes non traités ont permis de mettre en évidence un déplacement du point de champ maximum depuis l'âme du câble vers le semi-conducteur extérieur du câble due à une accumulation massive d'hétérocharges au niveau de l'électrode externe. L'influence du gradient thermique sur l'accumulation de charges est également abordée dans ce travailThis work deals with the development of High Voltage Direct Current cables based Cross-linked polyethylene (XLPE). The development of such a cable is confronted to the problem of space charge build-up which is linked to the nature of the semiconducting electrodes and the insulating material. In the framework of this thesis, the pulsed electro-acoustic (PEA) method has been used to study space charge build-up in both plaque and model cables. The impact of cross-linking by-products on the heterocharges accumulation has been highlighted by investigations on XLPE conditioning. A model based on heterogeneous polarization has been established to describe heterocharges build-up. Results obtained on different insulating formulations have shown a clear impact of additives regarding space charge build-up. Furthermore, study of semi-conducting layers has enabled identifying the effect of the different compounds such as carbon black, polymer matrix on charges build-up. For model cables, a deconvolution method of raw PEA signal which takes into account the cylindrical geometry, the attenuation and the dispersion of acoustic waves has been developed. Measurements on non-treated model cables have shown a displacement of the point where the field is at maximum from the inner to the outer semi-conducting electrode. This is due to a massive heterocharges build-up adjacent to the external electrode. The impact of thermal gradient on space charge build-up has also been addressed in this work
13
Toledo, Thierry. "Modélisation des isolations axisymétriques basées sur l'utilisation des matériaux semi-conducteurs par couplage des éléments finis et des éléments de frontière." Phd thesis, Ecole Centrale de Lyon, 2004. http://tel.archives-ouvertes.fr/tel-00139534.
Full textAbstract:
L'isolation haute tension à base de matériaux semi-conducteurs est devenue une technique très répandue pour la réduction des fortes contraintes en champ électrique. Elle fait partie intégrante des nouveaux systèmes d'isolation à base de matériaux polymères comme par exemple les câbles haute tension à isolation synthétique. Il existe une grande quantité de produits semi-conducteurs conçus pour l'isolation haute tension mais leur utilisation reste assez empirique du fait de leur double comportement conducteur/isolant, du caractère non linéaire de la conductivité et de la permittivité et de leur anisotropie. Ce travail de thèse répond à l'intérêt grandissant de ces matériaux dans le domaine industriel. Il porte sur la modélisation de leur comportement à l'aide de techniques numériques. La procédure retenue consiste à coupler la méthode des éléments de frontière (BEM) et la méthode des éléments finis (FEM). La première est bien adaptée à la modélisation des grands domaines à propriété isotrope et uniforme alors que la seconde permet de prendre en compte les non linéarités et l'anisotropie présentes dans les matériaux semi-conducteurs. Afin de modéliser les matériaux semi-conducteurs ayant une conductivité qui dépend du module du champ électrique, un schéma temporel basé sur la méthode des trapèzes pour l'intégration temporelle et sur la méthode du point fixe pour la résolution des non linéarités, ont été développés. Les validations numériques démontrent que les fortes non linéarités de type exponentiel, apparaissant lors des coups de foudre, peuvent désormais être prises en compte. De plus, la bonne estimation du champ normal aux frontières s'est avérée indispensable lorsque la conductivité est dépendante du module du champ électrique. Cette bonne prise en compte a été permise grâce à l'utilisation des équations intégrales de frontière dans les régions diélectriques. Enfin, l'emploi de la méthode des équations intégrales de frontière (BEM) a nécessité la prise en compte des singularités géométriques en présence d'une région semi-conductrice. Les équations pouvant traiter ces cas n'étant pas connues, des tests numériques basés sur les équations traitant les singularités dans le cas électrostatique ont été menées, ce qui a permis de prendre en compte certains cas de ces singularités.
14
Gavrilenko, Veronika. "Characterization of winding insulation of electrical machines fed by voltage waves with high dV/dt." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST027.
Full textAbstract:
L’isolation des bobinages des moteurs alimentés par des convertisseurs statiques basés sur la modulation de largeur d'impulsion est soumise à des contraintes électriques provenant de la forme d'onde de la tension d'alimentation. Les phénomènes de nuisances électromagnétiques sur l’ensemble de la chaîne de conversion, les ondes réfléchies dans le câble d’alimentation, ainsi que la non adaptation des impédances du câble et de l’enroulement de la machine peuvent conduire à l’apparition de surtensions aux bornes de la machine suffisamment élevées pour dépasser la tension d’apparition des décharges partielles. Il en résulte une dégradation de l’isolation entre les spires qui, à terme, peut engendrer la défaillance de la machine. La mise en œuvre de composants à semi-conducteurs grand gap, tel que le Carbure de Silicium, permet la réalisation de convertisseurs de forte densité de puissance pour les systèmes d’entraînement à vitesse variable des machines électriques. Les vitesses et les fréquence de commutation élevées de ces composants conduisent à des contraintes électriques en dV/dt plus sévères sur l'isolation des enroulements des moteurs alimentés par de tels convertisseurs. L’étude expérimentale et les simulations numériques réalisées dans le cadre de cette thèse se concentrent essentiellement sur les effets des ondes de tension à forts dV/dt et de la fréquence de commutation élevée sur la robustesse de l’isolation du bobinage des machines électriques alimentées par des onduleurs. Par conséquent, les travaux touchent un certain nombre de questions liées à l’entraînement à vitesse variable, à l’électronique de puissance, aux machines électriques, aux matériaux diélectriques et aux décharges partiellesThe insulation of electrical machines driven by power converters with pulse width modulation are subjected to repetitive surges due to fast changing voltage pulses and reflection phenomena in supply cable, as well as non-uniform voltage distribution in the stator winding. The overvoltage at motor terminals may lead to partial discharge inception accelerating winding insulation degradation and causing its premature failure. The implementation of wide bandgap power semiconductors as Silicon Carbide allows to create converters with high power density for variable frequency drive applications. The fast and high frequency switching of electronic devices based on wide bandgap semiconductors increase electrical stresses caused by steep voltage changing rates in controlled electrical machine. It may increase a risk of partial discharges and accelerate insulation aging and destruction. The experimental investigation and numerical simulation study performed in this work is essentially focused on the effects of impulse voltage with high dV/dt and high switching frequency on winding insulation robustness of inverter-fed electrical machines. Therefore, the work covers a number of issues related to electric drives, power electronics, electrical machines, dielectric materials and partial discharges
15
Sarrazin, Benoît. "Optimisation d'une chaîne de traction pour véhicule électrique." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENT117/document.
Full textAbstract:
Les éléments constituant la chaîne de traction sont le plus souvent dissocies et indépendants entre eux (pack de batteries, convertisseur de traction et moteur). L'utilisation des convertisseurs en cascade en tant que convertisseurs de traction a été le cœur de ces travaux de thèse. Les performances énergétiques des convertisseurs en cascade et de l'onduleur de tension classique ont été comparées sur un cycle de conduite normalisé pour différentes configurations sur les convertisseurs de puissance (niveau de tension mis en jeu dans la chaîne de traction, variation du nombre d'onduleurs connectés en série pour les convertisseurs en cascade et variation du nombre de semi-conducteurs en parallèle pour réaliser la fonction des interrupteurs de puissance dans les convertisseurs). D'autres convertisseurs d'électronique de puissance sont nécessaires pour le bon fonctionnement d'un véhicule électrique. L'un de ces convertisseurs est le chargeur de batteries qui puise l'énergie du réseau électrique pour venir recharger les batteries du véhicule. Un autre est le système de monitoring des batteries qui permet d'assurer un équilibrage et un état de charge uniforme entre les différentes cellules qui composent le pack de batteries du véhicule. Dans une optique de mutualisation de fonction du convertisseur de puissance, les convertisseurs en cascade ont été étudiés pour assurer la fonction de chargeur et d'équilibreur lorsque la traction du véhicule n'est pas utiliséeThe elements that can be found in traction chain are usually separate and independent between them (battery pack, traction converter and motor). The use of cascaded inverter in order to drive the vehicle has been the heart of this thesis. The energy performance of cascaded inverter and classical voltage source inverter were compared on a standardized driving cycle for different power converters configurations (voltage level for the traction chain, variation of the number serial inverter for cascaded H-bridge and different number of semiconductors in parallel to do the function of the power switches in converters). Other power electronic converters are necessary for the electrical vehicle. One of these converters is the battery charger which tranfer energy from the network to the vehicle's batteries. Another is the battery monitoring system that ensures a balance and uniform state between the different cells which make up the battery pack of the vehicle. With an objective of increasing the function of the power converter, cascaded H-bridge have been designed to provide the function of charger and balance the battery cell when the traction chain of the vehicle is not used
16
Bigot, Dimitri. "Contribution à l’étude du couplage énergétique enveloppe / système dans le cas de parois complexes photovoltaïques (PC - PV)." Thesis, La Réunion, 2011. http://www.theses.fr/2011LARE0024/document.
Full textAbstract:
Cette thèse présente un modèle thermique et électrique de paroi photovoltaïque (PV) intégrée ou semi-intégrée au bâtiment. La particularité du modèle est le transfert de chaleur entre le panneau et le bâtiment, décrit de telle manière que leurs modèles respectifs soient totalement couplés. Ceci a l'avantage de permettre la prédiction de l'impact de l'installation PV sur le champ de température du bâtiment et donc sur le confort thermique associé. Le but de l'étude est de mettre en évidence l'impact des panneaux PV en termes d'isolation thermique ou de protection solaire pour le bâtiment et la résultante en termes de gain énergétique. De plus, une séquence expérimentale a été menée à l'île de La Réunion, où le climat est tropical et humide, avec un rayonnement solaire important. Dans de telles conditions, il est important de minimiser la sollicitation thermique à travers l'enveloppe du bâtiment, en particulier la toiture. Le modèle est intégré à un code de simulation thermique du bâtiment (ISOLAB) et peut prédire l'impact des panneaux PV installés selon différentes configurations, mais aussi le productible photovoltaïque de l'installation. Finalement, l'étude expérimentale est utilisée pour fournir des éléments de validation du modèle numérique et une analyse de sensibilité est lancée pour mettre en évidence les paramètres les plus influents du modèle. Il a été démontré que les paramètres radiatifs du panneau PV ont un impact important sur le champ de température du bâtiment et que leur détermination doit être faite correctement. Les résultats de cette analyse sont ensuite utilisés pour optimiser le modèle thermique à l'aide du logiciel d'optimisation GenOptThis thesis presents a thermal and electrical modelling of PV walls integrated to buildings. The particularity of this model is that the heat transfer that occurs through the panel to the building is described so that both building and PV thermal modelling are fully coupled. This has the advantage of allowing the prediction of the impact of PV installation on the building temperature field and also the comfort inside it. The aim of this study is to show the impact of the PV panels in terms of level of insulation or solar protection for the building. Moreover, the study has been conducted in La Reunion Island, where the climate is tropical and humid, with a strong solar radiation. In such conditions, it is important to minimise the thermal load through the roof of the building. The thermal model is integrated in a building simulation code and is able to predict the thermal impact of PV panels installed on buildings in several configurations and also their production of electricity. Finally, the experimental study is used to give elements of validation for the numerical model and a sensitivity analysis has been run to put in evidence the governing parameters. It has been shown that the radiative properties of the PV panel have a great impact on the temperature field of the tested building and the determination of these parameters has to be taken with care. Results of sensitivity analysis are used to optimize the PV thermal model using the GenOpt optimization program
17
Van, Halder Inge. "Conservation des communautés de papillons de jour dans les paysages forestiers hétérogènes : effets de la qualité, de la diversité et de la fragmentation des habitats." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0001/document.
Full textAbstract:
Alors que la superficie des forêts de plantation continue d'augmenter dans le monde, leurcontribution à la conservation de la biodiversité reste controversée. L’objectif de cette thèse estd'identifier les facteurs clés, à la fois au niveau de l'habitat local et à celui du paysage, qui influent surla diversité des papillons de jour dans les paysages en mosaïque dominés par des plantations de pins.Les communautés de papillons ont été échantillonnées en lisière et à l’intérieur de plantations de pinmaritime, pare-feux, ripisylves et fragments de forêts de feuillus variant par la taille et le degréd’isolement spatial. Les traits biologiques et écologiques des papillons ont été liés auxcaractéristiques de l’habitat et aux variables paysagères.Les éléments les plus importants pour la conservation des papillons dans les paysages dominés parles plantations de pins sont les habitats semi-naturels: forêts de feuillus, pare-feux et lisières. Lesripisylves se révèlent être les plus riches en papillons forestiers, abritant des espèces spécialisées. Lespare-feux hébergent deux fois plus d'espèces que les autres types d'habitats et sont importants pourla conservation de plusieurs espèces menacées. Toutefois les plantations de pin ne sont pas vide depapillons. La qualité de l'habitat, notamment la présence de plantes hôtes, est le facteur le plusdéterminant de la composition des communautés de rhopalocères. La composition et laconfiguration du paysage ont également une influence importante sur la diversité des papillons. Denombreuses espèces de papillons ont été observées dans plusieurs types d'habitat suggérant que lacomplémentation et supplémentation des ressources soient des processus clés pour maintenir ladiversité des papillons dans les paysages forestiers hétérogènesWhile the area of plantation forests continues to increase worldwide, their contribution to theconservation of biodiversity is still controversial. The aim of this thesis is to identify key habitat andlandscape factors that drive butterfly diversity in mosaic landscapes dominated by pine plantations.Butterfly communities were sampled at edges and interiors of five successional stages of pine stands,in firebreaks, riparian forests and in deciduous woodlands varying in fragment size and isolation.Biological and ecological traits of butterflies were related to habitat patch attributes and tolandscape composition and configuration.The results highlighted the critical importance of semi-natural habitats for butterfly conservation inpine plantation mosaics, i.e. deciduous woodlands, firebreaks and edges. Riparian forests wereespecially rich in forest butterfly species, harboring specialized species with both narrow habitat andthermal ranges. Firebreaks had twice as many species as other habitat types and were ofconservation value for several threatened butterfly species. Our results also showed that pine standswere not ‘free of butterflies'. Habitat quality, particularly the presence of host plants, was the mostimportant driver of butterfly community composition. Landscape composition and configuration alsoinfluenced butterfly diversity. Many species used more than one distinct habitat type, suggestingthat resource complementation and supplementation are important mechanisms of butterflydiversity persistence in pine plantation mosaics
18
Boufridi, Asmaa. "De l’étude d’éponges du genre Dactylospongia aux particularités chimiques des ilimaquinones." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA114848/document.
Full textAbstract:
Notre équipe est l’un des partenaires du projet international PoMaRé (« Invertébrésbenthiques de Polynésie, Martinique et de la Réunion »). Nous travaillons encollaboration directe avec le Dr Cécile Debitus de l’IRD en Polynésie française, sonéquipe étant notamment en charge de collecter des échantillons d’éponges marinesdans différents atolls du Pacifique.Au laboratoire, nous nous sommes intéressés particulièrement à deux espècesabondantes en Polynésie : Dactylospongia metachromia et Dactylospongia elegans.Notre travail a consisté à isoler leurs métabolites spécialisés majoritaires : lesilimaquinones, puis à réaliser diverses études autour de ces deux sesquiterpènesquinoniques épimériques. Le travail s’est organisé de la façon suivante :- Extraction des ilimaquinones : les ilimaquinones ont été isolées de l’éponge Dactylospongia metachromia avec un rendement > 3 %. Une étude de la variation de leur pourcentage respectif par rapport à la géographie de collecte de l’éponge a été entreprise. Impliquant plus d’une centaine d’échantillons, c’est la première fois qu’une étude d’une telle ampleur est réalisée. L’éponge D. elegans a également été étudiée, nos études ont révélé la présence de l’ilimaquinone mais aussi d’une structure proche : l’isospongiaquinone.- Modifications structurales autour des ilimaquinones : Par voie chimique : des modifications ont été étudiées sur les ilimaquinones afin de cerner leur réactivité, divers analogues ont ainsi été obtenus. Entre autres, les substances naturelles isospongiaquinone, 5-epi-isospongiaquinone et néomamanuthaquinone ont pu être hémisynthétisées. Lors de ces études, une nouvelle réaction a été découverte modifiant la quinone de façon surprenante dans des conditions oxydantes. Par voie enzymatique : des micro-organismes ont été utilisés pour réaliser des biotransformations sur le squelette de l’ilimaquinone, trois composés ont été obtenus. Ces modifications ont touché à la fois la décaline et la quinone de notre substrat. Une réaction de fonctionnalisation originale a d’ailleurs pu être observée pour la première fois.- Modélisation moléculaire et électrochimie : une étude de modélisation moléculaire nous a permis de calculer l’énergie de formation des ilimaquinones en nous basant sur les hypothèses de biosynthèse que nous pouvons maintenant mieux appréhender. Finalement une étude d’électrochimie nous a permis d’évaluer les propriétés oxydo-réductrices de ces molécules naturelles à fortes potentialités en termes d’activités biologiquesOur team is one of the partners of the international project PoMaRe ("Benthic Invertebrates of Polynesia, Martinique and Reunion"). We worked directly with Dr. Cécile Debitus from the IRD in French Polynesia, her team was in charge of collecting samples of marine sponges in different atolls of the Pacific.In the laboratory, we focused particularly on two abundant species in Polynesia: Dactylospongia metachromia and Dactylospongia elegans. Our job was to isolate their major metabolites: the ilimaquinones and perform various studies around these two epimeric sesquiterpene quinones.The work was organized as follows:- Extraction of ilimaquinones: ilimaquinones were isolated from the sponge Dactylospongia metachromia with a yield > 3%. A study of the variation of their respective percentage in relation with the geography of collection was undertaken, involving more than one hundred samples. This is the first study of this scale to be achieved. The sponge D. elegans was also studied, our results revealed the presence of ilimaquinone but also a nearby structure: isospongiaquinone.- Structural modifications of ilimaquinones:* Chemical modifications: structural changes were studied on ilimaquinones to delimit their reactivity: various analogues have been obtained. Among others, natural substances isospongiaquinone, 5-epi-isospongiaquinone and neomamanuthaquinone have been obtained. In these studies, a new reaction was discovered modifying the quinone surprisingly under oxidizing conditions.* Enzymatic modifications: micro-organisms were used to carry out biotransformations on the skeleton of ilimaquinone, three compounds were obtained. These changes have affected both the decalin and the quinone of our substrate. An original reaction has also been observed for the first time.- Molecular modeling and electrochemistry: a molecular modeling study has allowed us to calculate the energy of formation of ilimaquinones based on biosynthesis assumptions that we can now better understand. Finally an electrochemistry study evaluated the redox properties of these natural molecules with high potential in terms of biological activity
19
Gutierrez, Soto Mariantonieta. "MULTI-AGENT REPLICATOR CONTROL METHODOLOGIES FOR SUSTAINABLE VIBRATION CONTROL OF SMART BUILDING AND BRIDGE STRUCTURES." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1494249419696286.
Full text
20
Teodorescu, Catalin Stefan. "Commande de systèmes d'isolation antisismique mixte." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00904280.
Full textAbstract:
Nous nous intéressons aux méthodes de contrôle de vibrations de modèles réduits de structures à n degrés de liberté, sismiquement isolées au niveau de la base par des systèmes d'isolation mixte.Le mouvement provoqué par une sollicitation sismique horizontale a lieu dans le plan vertical.Nous avons construit un problème de contrôle semi-actif de systèmes incertains soumis à des perturbations inconnues, mais bornées. Dans le langage de l'automatique, il s'agit d'un problème d'atténuation de perturbations.Le résultat principal de cette thèse porte sur la construction d'une version modifiée des résultats de Leitmann et de ses collaborateurs sur la stabilisation de systèmes non linéaires incertains. Le théorème proposé repose sur une loi de commande par retour d'état qui assure en boucle fermée les propriétés de "uniform boundedness" et "uniform ultimate boundedness".En particulier, il peut être appliqué à la résolution de problèmes de contrôle semi-actif, qui sont actuellement traités en génie parasismique.L'objectif du contrôle est d'améliorer le comportement (i.e. la réponse) de structures isolées pour faire face aux perturbations externes, c'est-à-dire les séismes. Plusieurs points différencient notre problème de la majorité que l'on trouve dans la littérature: (i) on ne s'intéresse pas seulement à la protection de la structure isolée, mais aussi aux équipements situés à l'intérieur de la structure, et (ii) au lieu d'utiliser des indicateurs de performance habituels exprimés en termes de déplacement relatif de la base versus des accélérations absolues des planchers, nous utilisons uniquement le spectre de plancher en pseudo-accélération, comme il a été proposé dans des travaux précédents par Politopoulos et Pham. Ce travail est une tentative d'utiliser explicitement les spectres de plancher comme critère de performance.Concernant la procédure d'application, plusieurs étapes intermédiaires ont été détaillées:(i) modélisation de signaux sismiques;(ii) réglage des paramètres de la loi de commande utilisant la théorie des vibrations;(iii) validation et test du comportement en boucle fermée à travers des simulations numériques: pour des raisons de simplicité, on se limite au cas n=2.Cette procédure peut être utilisée sur des structures en industrie nucléaire, mais aussi en génie civil.D'autres sujets traités incluent une tentative d'utiliser les outils temps-fréquence, et en particulier la distribution de Wigner-Ville, pour la synthèse de lois de commande, en espérant pouvoir mieux contrôler les composants transitoires des signaux de perturbation (les entrées) et des variables d'état (les sorties).
21
Mantzaflaris, Angelos. "Méthodes algébriques robustes pour le calcul géométrique." Phd thesis, Université de Nice Sophia-Antipolis, 2011. http://tel.archives-ouvertes.fr/tel-00651672.
Full textAbstract:
Le calcul géométrique en modélisation et en CAO nécessite la résolution approchée, et néanmoins certifiée, de systèmes polynomiaux. Nous introduisons de nouveaux algorithmes de sous-division afin de résoudre ce problème fondamental, calculant des développements en fractions continues des coordonnées des solutions. Au delà des exemples concrets, nous fournissons des estimations de la complexité en bits et des bornes dans le modèle de RAM réelle. La difficulté principale de toute méthode de résolution consiste en les points singuliers isolés. Nous utilisons les systèmes locaux inverses et des calculs numériques certifiés afin d'obtenir un critère de certification pour traiter les solutions singulières. Ce faisant, nous sommes en mesure de vérifier l'existence et l'unicité des singularités d'une structure de multiplicité donnée. Nous traitons deux principales applications géométriques. La première: l'approximation des ensembles semi-algébriques plans, apparaît fréquemment dans la résolution de contraintes géométriques. Nous présentons un algorithme efficace pour identifier les composants connexes et pour calculer des approximations polygonales et isotopiques à l'ensemble exact. Dans un deuxième temps, nous présentons un cadre algébrique afin de calculer des diagrammes de Voronoi. Celui-ci sera applicable à tout type de diagramme dans lequel la distance à partir d'un site peut être exprimé par une fonction polynomiale à deux variables (anisotrope, diagramme de puissance etc). Si cela n'est pas possible (par exemple diagramme de Apollonius, VD des ellipses etc), nous étendons la théorie aux distances implicitement données.
22
Moura, Luis Mauro. "Identification des propriétés radiatives des matériaux semi-transparents diffusants en situation de non-symétrie azimutale du champ radiatif." Lyon, INSA, 1998. http://theses.insa-lyon.fr/publication/1998ISAL0059/these.pdf.
Full textAbstract:
Ce mémoire de thèse présente une formulation d'un problème radiatif en situation de non-symétrie azimutale du champ radiatif appliquée à l'identification des propriétés radiatives (épaisseur optique, albédo et fonction de phase) des matériaux fibreux et des mousses. Une géométrie monodimensionnelle a été considérée. La solution numérique de l'équation du transfert radiatif est basée sur la méthode des ordonnées discrètes appliquée à un volume de contrôle. Une nouvelle quadrature spatiale est proposée. La quadrature est adaptée aux conditions expérimentales, en permettant d'avoir un nombre maximal de points selon les directions susceptibles d'être explorées par le dispositif expérimental. Le programme développé permet de considérer différentes situations expérimentales. De ce fait, cinq stratégies expérimentales sont analysés de manière à déterminer la plus performante pour l'identification des propriétés radiatives des matériaux considérés. L'identification des propriétés radiatives est réalisé à partir des. .This work is focused on identification methodology for thermal radiation properties of dispersed media with non-azimuthal symmetry of the radiation field. The properties identified are the optical thickness, the albedo and three parameters of the phase function. The radiative transfer equation is solved numerically by a finite volume discrete ordinate method. A new non-azimuthally quadrature is proposed. The ad hoc quadrature allows the experimental directional measurement considerations. The experimental device is the combination of Fourier transform infrared spectrometer and a goniometer device which allows the bidirectional transmittance and reflectance measurements. The radiative properties have been determined by the minimisation of the quadratic error between the measured and calculated bidirectional transmittances and reflectances. Measurements are performed for oblique incident beam in the range from 0 and 40 degrees. Results are presented to fiber glass and foam insulation in the 1,5 µm to 15 µm wave
23
Addepalli, T., A. Desai, Issa T. Elfergani, N. Anveshkumar, J. Kulkarni, C. Zebiri, J. Rodriguez, and Raed A. Abd-Alhameed. "8-Port Semi-Circular Arc MIMO Antenna with an Inverted L-Strip Loaded Connected Ground for UWB Applications." MDPI, 2021. http://hdl.handle.net/10454/18536.
Full textAbstract:
yesMultiple-input multiple-output (MIMO) antennas with four and eight elements having connected grounds are designed for ultra-wideband applications. Careful optimization of the lines connecting the grounds leads to reduced mutual coupling amongst the radiating patches. The proposed antenna has a modified substrate geometry and comprises a circular arc-shaped conductive element on the top with the modified ground plane geometry. Polarization diversity and isolation are achieved by replicating the elements orthogonally forming a plus shape antenna structure. The modified ground plane consists of an inverted L strip and semi ellipse slot over the partial ground that helps the antenna in achieving effective wide bandwidth spanning from (117.91%) 2.84–11 GHz. Both 4/8-port antenna achieves a size of 0.61 λ × 0.61 λ mm2 (lowest frequency) where 4-port antenna is printed on FR4 substrate. The 4-port UWB MIMO antenna attains wide impedance bandwidth, Omni-directional pattern, isolation >15 dB, ECC 4.5 dB making the MIMO antenna suitable for portable UWB applications. Four element antenna structure is further extended to 8-element configuration with the connected ground where the decent value of IBW, isolation, and ECC is achieved.
24
Mogniotte, Jean-François. "Conception d'un circuit intégré en SiC appliqué aux convertisseur de moyenne puissance." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0004/document.
Full textAbstract:
L’émergence d’interrupteurs de puissance en SiC permet d’envisager des convertisseurs de puissance capables de fonctionner au sein des environnements sévères tels que la haute tension (> 10 kV ) et la haute température (> 300 °C). Aucune solution de commande spécifique à ces environnements n’existe pour le moment. Le développement de fonctions élémentaires en SiC (comparateur, oscillateur) est une étape préliminaire à la réalisation d’un premier démonstrateur. Plusieurs laboratoires ont développé des fonctions basées sur des transistors bipolaires, MOSFETs ou JFETs. Cependant les recherches ont principalement portées sur la conception de fonctions logiques et non sur l’intégration de drivers de puissance. Le laboratoire AMPERE (INSA de Lyon) et le Centre National de Microélectronique de Barcelone (Espagne) ont conçu un MESFET latéral double grille en SiC. Ce composant élémentaire sera à la base des différentes fonctions intégrées envisagées. L’objectif de ces recherches est la réalisation d’un convertisseur élévateur de tension "boost" monolithique et de sa commande en SiC. La démarche scientifique a consisté à définir dans un premier temps un modèle de simulation SPICE du MESFET SiC à partir de caractérisations électriques statique et dynamique. En se basant sur ce modèle, des circuits analogiques tels que des amplificateurs, oscillateurs, paires différentielles, trigger de Schmitt ont été conçus pour élaborer le circuit de commande (driver). La conception de ces fonctions s’avère complexe puisqu’il n’existe pas de MESFETs de type P et une polarisation négative de -15 V est nécessaire au blocage des MESFETs SiC. Une structure constituée d’un pont redresseur, d’un boost régulé avec sa commande basée sur ces différentes fonctions a été réalisée et simulée sous SPICE. L’ensemble de cette structure a été fabriqué au CNM de Barcelone sur un même substrat SiC semi-isolant. L’intégration des éléments passifs n’a pas été envisagée de façon monolithique (mais pourrait être considérée pour les inductances et capacités dans la mesure où les valeurs des composants intégrés sont compatibles avec les processus de réalisation). Le convertisseur a été dimensionné pour délivrer une de puissance de 2.2 W pour une surface de 0.27 cm2, soit 8.14 W/cm2. Les caractérisations électriques des différents composants latéraux (résistances, diodes, transistors) valident la conception, le dimensionnement et le procédé de fabrication de ces structures élémentaires, mais aussi de la majorité des fonctions analogiques. Les résultats obtenus permettent d’envisager la réalisation d’un driver monolithique de composants Grand Gap. La perspective des travaux porte désormais sur la réalisation complète du démonstrateur et sur l’étude de son comportement en environnement sévère notamment en haute température (> 300 °C). Des analyses des mécanismes de dégradation et de fiabilité des convertisseurs intégrés devront alors être envisagéesThe new SiC power switches is able to consider power converters, which could operate in harsh environments as in High Voltage (> 10kV) and High Temperature (> 300 °C). Currently, they are no specific solutions for controlling these devices in harsh environments. The development of elementary functions in SiC is a preliminary step toward the realization of a first demonstrator for these fields of applications. AMPERE laboratory (France) and the National Center of Microelectronic of Barcelona (Spain) have elaborated an elementary electrical compound, which is a lateral dual gate MESFET in Silicon Carbide (SiC). The purpose of this research is to conceive a monolithic power converter and its driver in SiC. The scientific approach has consisted of defining in a first time a SPICE model of the elementary MESFET from electric characterizations (fitting). Analog functions as : comparator, ring oscillator, Schmitt’s trigger . . . have been designed thanks to this SPICE’s model. A device based on a bridge rectifier, a regulated "boost" and its driver has been established and simulated with the SPICE Simulator. The converter has been sized for supplying 2.2 W for an area of 0.27 cm2. This device has been fabricated at CNM of Barcelona on semi-insulating SiC substrate. The electrical characterizations of the lateral compounds (resistors, diodes, MESFETs) checked the design, the "sizing" and the manufacturing process of these elementary devices and analog functions. The experimental results is able to considerer a monolithic driver in Wide Band Gap. The prospects of this research is now to realize a fully integrated power converter in SiC and study its behavior in harsh environments (especially in high temperature > 300 °C). Analysis of degradation mechanisms and reliability of the power converters would be so considerer in the future
25
Pham, Khac Hoan. "Vulnérabilité et spectres de plancher des structures sismiquement isolées." Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00530149.
Full textAbstract:
Cette thèse a été motivée par diverses questions qui se posent quant à l'utilisation de la méthode de l'isolation sismique dans l'industrie nucléaire. Malgré la recherche effectuée pendant les dernières décennies dans le domaine de l'isolation sismique, plusieurs questions restent ouvertes quant au comportement des structures isolées. Ces questions concernent d'une part la vulnérabilité de ces structures, due à une excursion (inattendue) dans le domaine post-linéaire et d'autre part, des phénomènes qui peuvent aboutir à une excitation significative des modes non isolés. Par ailleurs, à la différence des travaux antérieurs qui étudient le comportement sismique des bâtiments, une place importante est consacrée au comportement des équipements par le biais de l'étude des spectres de plancher. Dans un premier temps, la probabilité de défaillance, dans le cas de réponse non-linéaire de la superstructure, a été étudiée avec des modèles simples, pour différents lois de comportement non-linéaires et différents types d'appuis. Ensuite les effets de l'ajout d'un amortissement important ont été étudiés et le mécanisme d'amplification de la réponse des modes non-isolés a été expliqué. Afin de remédier au problème de l'amplification des modes non isolés, des systèmes d'isolation mixtes, combinant l'isolation passive avec des dispositifs semi-actifs, ont été considérés. Les analyses numériques confirment l'efficacité de cette approche. Enfin, une série d'essais, sur table vibrante, d'une maquette simple à deux degrés de liberté a été réalisée. La maquette est équipée d'un amortisseur magnéto-rhéologique qui est contrôlé comme un dispositif semi-actif. La comparaison des résultats expérimentaux avec ceux des simulations numériques montre que les modèles développés sont capables de représenter de façon satisfaisante les phénomènes physiques essentiels.
26
Dueñas, Cervantes Bruno, and Hinojosa Wilder Dimas Soto. "Propuesta de vivienda sostenible utilizando concreto con fibras PET en un sistema de albañilería confinada y trombe a fin de mejorar el confort térmico en la sierra semi urbana." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/655016.
Full textAbstract:
El calentamiento global es un tema que genera mucha preocupación en la población mundial. Siendo el cambio climático una de las consecuencias que se perciben en las diversas partes del mundo. La manifestación de este cambio ha ocasionado que se propongan diversas técnicas o métodos que permitan mitigar o controlar relativamente las temperaturas extremas, entre estos métodos ingenieriles se propone al plástico como componente del concreto para aislar las temperaturas externas. Ese estudio desarrolla una investigación experimental de la influencia del tereftalato de polietileno (PET), al ser incluido en la mezcla de concreto, en el logro del confort térmico que se pudiese llegar a obtener, al combinarlo con una innovadora adaptación del sistema trombe en la construcción de una vivienda. Para ello, se asumirán especificaciones de investigaciones realizadas, con respecto a la elaboración e inclusión del PET, que permiten concluir indirectamente la mejora del aislamiento térmico sin dejar de cumplir las restricciones estructurales. Asimismo, se explicó a detalle, la forma en la que se adoptó e innovo el sistema de muros trombe al construir el techo de un prototipo de la vivienda. Los resultados muestran que la técnica empleada en el presente estudio permitió mejorar considerablemente la eficiencia térmica en el prototipo de la vivienda.Global warming is a topic of great concern to the world population. Being climate change one of the consequences perceived in various parts of the world. The manifestation of this change has caused various techniques or methods to be proposed to mitigate or relatively control extreme temperatures. Among these engineering methods, plastic is proposed as a component of concrete to isolate external temperatures. This study develops an experimental investigation of the influence of polyethylene terephthalate (PET), when it is included in the concrete mix, in achieving the thermal comfort that could be obtained, when combined with an innovative adaptation of the trombe system in the construction of a house. For this, specifications of investigations carried out, with respect to the preparation and inclusion of PET, will be assumed, which allow indirectly to conclude the improvement of thermal insulation while still complying with structural restrictions. Likewise, the way in which the trombe system was adopted and innovated when building the roof of a prototype of the house was explained in detail. The results show that the technique used in the present study considerably improved the thermal efficiency of the prototype of the house.
Tesis
27
Lin, Ging-Long, and 林錦隆. "Semi-active isolation systems for seismic structures." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/91622685759917301180.
Full textAbstract:
博士國立高雄第一科技大學
工程科技研究所
96
Base isolation technology may be used for seismic protection of critical structures or equipments. However, recent studies have revealed that a conventional passive isolation system may induce an excessive base displacement when subjected to a near-fault earthquake with strong long-period components. In order to enhance the efficiency and safety of seismic isolation for structures in near-fault areas, a semi-active isolation system (SAIS) that consists of isolators and a variable damper is proposed in this study. Three kinds of variable dampers are discussed in this study. The first is the variable stiffness damper, the second is the variable friction damper, and the third is the variable viscous damper. The resistant force of a variable damper can be adjusted by its controllable parameter according to an on-line control law and the measured system response. The seismic response of the SAIS system equipped with each of the three types of variable dampers mentioned previously and subjected to near-fault earthquakes was simulated numerically in this study. In addition, its isolation performance was also evaluated and compared with the performance of a passive and an active isolation system. The results of these comparisons are discussed in this study. The simulation result demonstrates that the SAIS system is able to prevent the excessive displacement and acceleration response of structure induced by long-period pulse components of near-fault earthquakes.
28
Alanoly, James. "Vibration isolation characteristics of a class of semi-active suspensions." Thesis, 1985. http://spectrum.library.concordia.ca/5528/1/ML30652.pdf.
Full text
29
Fan, Yu-Cheng. "Performance and Reliability Analysis of Semi-Active Equipment Isolation System." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0107200822262400.
Full text
30
Fan, Yu-Cheng, and 范佑誠. "Performance and Reliability Analysis of Semi-Active Equipment Isolation System." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/71767453228143795516.
Full textAbstract:
碩士國立臺灣大學
土木工程學研究所
96
Critical non-structural equipment, including life-saving equipment in hospitals, circuit breakers, computers, high technology instrumentations, etc., are venerable to strong earthquakes, and the failure of these equipments may result in a heavy economic loss. In this connection, innovative control systems and strategies are needed for their seismic protections. The purpose of this thesis is to investigate performance evaluation of passive and semi-active control in the equipment isolation system for earthquake protection. Through shaking table tests of a 3-story steel frame with equipment on the first floor, a Magneto-Rheological (MR) damper together with a sliding rolling pendulum isolation system is placed between the equipment and floor to reduce the vibration of the equipment. Various control algorithms are used for these semi-active control studies, including the decentralized sliding mode control (DSMC) and LQR control. The passive-on and passive-off control of MR damper is used as a reference for the discussion on the control effectiveness. Finally, the reliability analysis for the development of probabilistic seismic demand curves is used to determine the probability of the equipment response measure.
31
Yang, Cho-Yen, and 楊卓諺. "Study on Structural Isolation by Eccentric Rolling Isolation System with Passive and Semi-Active Friction Damping Control Strategy." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/72261107938813171795.
Full textAbstract:
博士國立臺灣科技大學
營建工程系
100
Base isolation has been popular by implemented in civil engineering. However, conventional isolation system possessing linear restoring force may be invalid under a near-fault earthquake which possesses low-frequency content and may induce resonance. Therefore, the eccentric rolling isolation system (ERIS) possessing nonlinear restoring is proposed. The base, which can be mounted on a structure or equipment, is eccentrically pinned on a circular isolator; and friction damping, which can be tuned by bolts, is considered. In passive case, the ERIS performs as good as conventional linear isolation system under far-field earthquake. Subjected to near-fault earthquake, the ERIS shows better reduction in acceleration than the corresponding linear one. The ERIS also reduced the amplification under resonant sinusoidal excitation due to nonlinearity. However, the passive isolation case under non-design earthquake may not perform as well as itself subjected to design earthquake. Thus, semi-active control is considered to improve the performances of ERIS. Several switch control laws with low and high gain are investigated. The gain mode is switched by appropriate switch logic. When the system is subjected to a small earthquake, the low gain mode is taken to make sure that the system is effective. When the system is subjected to a large earthquake, the high gain mode is taken to reduce the base displacement and provide more energy dissipation. Moreover, the continuous type switch control law can mitigate the chatter and jerk which may occur for some discontinuous switch control law.
32
Kao, Chia-Hung, and 高嘉鴻. "The Isolation, Colony Growth and Semi-aseptic Mycorrhizal Synthesis of Tuber mesentericum Vitt." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/71967244269858388591.
Full textAbstract:
碩士國立臺灣大學
森林學研究所
93
The purposes of this study were: (1) to isolate Tuber mesentericum Vitt. from the ectomycorrhizae of Pinus taiwanensis Hay. associated with T. mesentericum; (2) approve the isolated pure hyphae could form ectomycorrhizae with P. taiwanensis. by semi-aseptic synthesis; and (3) find the best growth medium and optimum temperature to the colony growth of T. mesentericum. Pure hyphae of T. mesentericum were isolated successfully, when the ectomycorrhize of P. + T. mesentericum were sterilized with 0.25 % NaClO for about three minutes. After inoculating the agar mycelial inocula on the rootlets of semi-aseptic cultivated Pinus taiwanensis seedlings, ectomycorrhizae could be formed in 1~2 months. The characteristics of ectomycorrhizae observed under stereomicroscope were as followings: monopodial or dichotomous; yellow brown to light brown when young, dark brown when wilted; fungal mantle with dense yellowish-golden setae when young, smooth or surrounded by cottony yellowish hyphae when mature, shrinking when aged. The characteristics of ectomycorrhizae observed under light microscope were: extending hyphal and setal surface from mycorrhizae smooth, a little swollen at the setal base, both with septa; occasionally with vesicle at the setal top or with forked hyphae. The characteristics of ectomycorrhizae observed under scanning electron microscope were: fungus mantle 17~25μm thick, irregular synenchyma; setal hyphae smooth, without clamp connection, monopodial, diameter 1.5~2.5μm, a little swollen at the setal base, occasionally with vesicle at the top or with forked hyphae. Hartig nets extended to the second layer of cortex cells; starch grains seldom found, and tannins not observed. Lots of mulberry-like gathered vesicles were found around and at the top of the hyphae cultured on agar medium under light microscope; expanded vesicles were occasionally found on hyphae. To ascertain the best combination of two different agar media and four different temperature levels on the colony growth of T. mesentericum, the complete randomized design with factorial test was used. The results showed that YMT agar medium was better than that of MMN, and the best combination of agar medium and temperature was YMT and 25℃.
33
Rengarajan, Sampath. "An analytical and experimental investigation on the vibration isolation performance of semi-active suspensions." Thesis, 1991. http://spectrum.library.concordia.ca/4815/1/MM68777.pdf.
Full text
34
Azadi, Sohi Mojtaba. "Kinematically singular pre-stressed mechanisms as new semi-active variable stiffness springs for vibration isolation." Phd thesis, 2010. http://hdl.handle.net/10048/1490.
Full textAbstract:
Researchers have offered a variety of solutions for overcoming the old and challenging problem of undesired vibrations. The optimum vibration-control solution that can be a passive, semi-active or active solution, is chosen based on the desired level of vibration-control, the budget and the nature of the vibration source. Mechanical vibration-control systems, which work based on variable stiffness control, are categorized as semi-active solutions. They are advantageous for applications with multiple excitation frequencies, such as seismic applications. The available mechanical variable stiffness systems that are used for vibration-control, however, are slow and usually big, and their slowness and size have limited their application. A new semi-active variable stiffness solution is introduced and developed in this thesis to address these challenges by providing a faster vibration-control system with a feasible size.
The new solution proposed in this thesis is a semi-active variable stiffness mount/isolator called the antagonistic Variable Stiffness Mount (VSM), which uses a variable stiffness spring called the Antagonistic Variable stiffness Spring (AVS). The AVS is a kinematically singular prestressable mechanism. Its stiffness can be changed by controlling the prestress of the mechanisms links. The AVS provides additional stiffness for a VSM when such stiffness is needed and remains inactive when it is not needed. The damping of the VSM is constant and an additional constant stiffness in the VSM supports the deadweight. Two cable-mechanisms - kinematically singular cable-driven mechanisms and Prism Tensegrities - are developed as AVSs in this thesis. Their optimal configurations are identified and a general formulation for their prestress stiffness is provided by using the notion of infinitesimal mechanism.
The feasibility and practicality of the AVS and VSM are demonstrated through a case study of a typical engine mount by simulation of the mathematical models and by extensive experimental analysis. A VSM with an adjustable design, a piezo-actuation mechanism and a simple on-off controller is fabricated and tested for performance evaluation. The performance is measured based on four criteria: (1) how much the VSM controls the displacement near the resonance, (2) how well the VSM isolates the vibration at high frequencies, (3) how well the VSM controls the motion caused by shock, and (4) how fast the VSM reacts to control the vibration. For this evaluation, first the stiffness of the VSM was characterized through static and dynamic tests. Then performance of the VSM was evaluated and compared with an equivalent passive mount in two main areas of transmissibility and shock absorption. The response time of the VSM is also measured in a realistic scenario.
35
Su, Hong. "An investigation of vibration isolation systems using active, semi-active and tunable passive mechanisms, with applications to vehicle suspensions." Thesis, 1990. http://spectrum.library.concordia.ca/14/1/NL56068.pdf.
Full textAbstract:
In this dissertation, an analytical investigation on active, semi-active and passive vibration control mechanisms is presented in order to achieve improved shock and vibration isolation of mechanical systems, especially ground vehicle applications. A hybrid active vibration isolation system, incorporating an electro-magnetic force generator along with passive damping and spring elements, is mathematically modeled based on fundamental physical laws and taking into account the generator dynamics. Complete vibration isolation characteristics of the hybrid active control system are evaluated for various feedback variables and control schemes, using numerical simulations. Influence of the force generator dynamics on vibration isolation performance is illustrated through the simulation results. A concept of tunable pressure limiting modulation is proposed in hydraulic damper systems. A hydraulic orifice damper is modified by using the proposed tunable pressure limiting modulation to achieve variable damping in vibration isolation systems, without requiring any external energy source, sophisticated control devices and feedback instrumentation that are essential for active and semi-active isolators. The fluid flow equations are employed to develop the nonlinear mathematical model of the hydraulic damper, incorporating the fluid and mechanical compliance, and the dynamics of the pressure limiting mechanism. The computer simulation reveals that the shock and vibration isolation performance of the tunable pressure limited hydraulic damper systems is comparable to that of the semi-active 'on-off' vibration control systems. A generalized harmonic linearization technique, based on a principle of energy similarity of dynamic elements, is proposed to derive equivalent linear representations of both nonlinear damping and spring elements, in the frequency domain. An analysis of the nonlinear in-plane vehicle model, with air-springs, orifice damping and pressure limiting modulation due to tunable hydraulic shock absorbers, is carried out to establish the stochastic response to random road inputs in terms of power spectral density, and to illustrate the improved vehicle ride performance due to tunable shock absorbers. An interconnected hydro-pneumatic suspension with tunable pressure limiting mechanism is presented to achieve improved vehicle ride and handling performance. Analysis of a roll plane model of a vehicle employing the tunable interconnected suspension shows that the connections of fluid flow within the interconnected suspension provide an enhanced static roll stability; while the tunable pressure limiting modulation between the strut and the accumulator of each suspension unit offers an improved vehicle ride performance
36
Pasala, Dharma Theja. "Seismic response control of structures using novel adaptive passive and semi-active variable stiffness and negative stiffness devices." Thesis, 2013. http://hdl.handle.net/1911/72017.
Full textAbstract:
Current seismic design practice promotes inelastic response in order to reduce the design forces. By allowing the structure to yield while increasing the ductility of the structure, the global forces can be kept within the limited bounds dictated by the yield strength. However, during severe earthquakes, the structures undergo significant inelastic deformations leading to stiffness and strength degradation, increased interstory drifts, and damage with residual drift. The research presented in this thesis has three components that seek to address these challenges.
To prevent the inelastic effects observed in yielding systems, a new concept “apparent weakening” is proposed and verified through shake table studies in this thesis. “Apparent weakening” is introduced in the structural system using a complementary “adaptive negative stiffness device” (NSD) that mimics "yielding” of the global system thus attracting it away from the main structural system. Unlike the concept of weakening and damping, where the main structural system strength is reduced, the new system does not alter the original structural system, but produces effects compatible with an early yielding. Response reduction using NSD is achieved in a two step sequence. First the NSD, which is capable of exhibiting nonlinear elastic stiffness, is developed based on the properties of the structure. This NSD is added to the structure resulting in reduction of the stiffness of the structure and NSD assembly
or “apparent weakening”-thereby resulting in the reduction of the base shear of the assembly. Then a passive damper, designed for the assembly to reduce the displacements that are caused due to the “apparent weakening”, is added to the structure-thereby reducing the base shear, acceleration and displacement in a two step process.
The primary focus of this thesis is to analyze and experimentally verify the response reduction attributes of NSD in (a) elastic structural systems (b) yielding systems and (3) multistory structures. Experimental studies on 1:3 scale three-story frame structure have confirmed that consistent reductions in displacements, accelerations
and base shear can be achieved in an elastic structure and bilinear inelastic structure by adding the NSD and viscous fluid damper. It has also been demonstrated that the stiffening in NSD will prevent the structure from collapsing. Analogous to the inelastic design, the acceleration and base shear and deformation of the structure
and NSD assembly can be reduced by more than 20% for moderate ground motions and the collapse of structure can be prevented for severe ground motions.
Simulation studies have been carried on an inelastic multistoried shear building
to demonstrate the effectiveness of placing NSDs and dampers at multiple locations along the height of the building; referred to as “distributed isolation”. The results reported in this study have demonstrated that by placing a NSD in a particular story the superstructure above that story can be isolated from the effects of ground motion. Since the NSDs in the bottom floors will undergo large deformations, a generalized scheme to incorporate NSDs with different force deformation behavior in each storey is proposed. The properties of NSD are varied to minimize the localized inter-story deformation and distribute it evenly along the height of the building. Additionally, two semi-active approaches have also been proposed to improve the performance of NSD in yielding structures and also adapt to varying structure properties in real time.
The second component of this thesis deals with development of a novel device to control the response of structural system using adaptive length pendulum smart tuned mass damper (ALP-STMD). A mechanism to achieve the variable pendulum length is developed using shape memory alloy wire actuator. ALP-STMD acts as a
vibration absorber and since the length is tuned to match the instantaneous frequency, using a STFT algorithm, all the vibrations pertaining to the dominant frequency are absorbed. ALP-STMD is capable of absorbing all the energy pertaining to the tuned-frequency of the system; the performance is experimentally verified for forced vibration (stationary and non-stationary) and free vibration.
The third component of this thesis covers the development of an adaptive control algorithm to compensate hysteresis in hysteretic systems. Hysteretic system with variable stiffness hysteresis is represented as a quasi-linear parameter varying (LPV) system and a gain scheduled controller is designed for the quasi-LPV system using linear matrix inequalities approach. Designed controller is scheduled based on two parameters: linear time-varying stiffness (slow varying parameter) and the stiffness of friction hysteresis (fast varying parameter). The effectiveness of the proposed
controller is demonstrated through numerical studies by comparing the proposed controller with fixed robust H∞ controller. Superior tracking performance of the LPV-GS
over the robust H∞ controller in different displacement ranges and various stiffness switching cases is clearly evident from the results presented in this thesis. The LPV-GS controller is capable of adapting to the parameter changes and is effective over the entire range of parameter variations.
37
Du, Preez Frederika Elizabeth. "Ondersoek na die persoonlikheidsprofiel van slagoffers van afknouery." Diss., 2007. http://hdl.handle.net/10500/2083.
Full textAbstract:
Text in AfrikaansThe goal of the research is to explore the personality profile of aggressive victims of bullying in a special school. Qualitative, applied research of an explorative and descriptive nature was followed. In order to address the problem, namely that the personality profile of children can lead to aggressive victims, the researcher undertook a literature study to describe bullying in middle childhood with the focus on aggressive victims, the Five Factor Model of Personality, bullying in special schools and organismic selfregulation within Gestalt therapy. The researcher's knowledge of the Five Factor Model of Personality enabled her to compile the interview schedules for the semi-structured interviews. Purposeful sampling was conducted to identify respondents for the interviews. The interviews were conducted with four aggressive victims of bullying, their parents, as well as their class teachers. During the analysis of data, themes were identified. These themes were verified with literature and recommendations were made.
Social work
M.Diac.(Play therapy)