Tesis sobre el tema "Polytropie"
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Moucheront, Nicolas. "Le Palais des doges de Venise à l'époque moderne (1595-1625) : la conclusion d’un grand chantier". Electronic Thesis or Diss., Paris, EHESS, 2024. http://www.theses.fr/2024EHES0014.
Texto completoThe gothic Venice Ducal Palace was realized for 1340 but all the last centuries of Middle Ages long and for whole Renaissance, works have gone ahead seamless. Around 1625, the building reach its actual design and till this moment, only restoration works have been realized. This PhD tesis in architecture history studies the conclusive moment of this building process in order to understand why and how for 1595 so big a building site achieves. Financing dynamics of public works in Venice are first of all inserted within a long term analysis from the amortization of public debt between Middle Ages and Modern times. Such a study consent to pass in review thanks to available publications the main steps of the Ducal Palace building and to advocate a financial study of some of the major public buildings in Venice late XVIth century such as Rialto bridge or Redentore church.This study on the institutional functions of the Salt Office is in a second moment addressed to a specific political moment for the Venice Republic, the Interdetto crisis. A series of biographic researches about public and private commissions of several doges on power from 1595 to 1625 is developed, focusing on the respective leaders from the pro papalist vecchi and their opponents, the giovani patricians, Marino Grimani and Leonardo Donà. Specific research on public records and family archives are also dedicated to the exceptional journey from Padua to Paris of Antonio Priuli. Indeed, as Surveyor from all the Ducal palace places, he is responsible for the transformation of this building between 1601 and 1614. Then, he relaunches the works when arriving on power from 1618 till his death in 1624. During all this time long, the carpenter Bartolomeo Manopola conducts the works as Salt office proto. A detailed study is realized on his family building firm associating stone carvers, carpenters and masons. The relationships between public building and important figures from the time such as the stone carver Giovanni Grapiglia, the architect Vincenzo Scamozzi and the art seller Daniel Nijs are also developed associating a study on the commissioners network, architecture details and building site accounts. Such a micro-historic approach from the productive structure of the building site is the base for an analysis from the superstructure, ie for a survey on the Ducal palace architecture transformations from 1595 to 1625.Internal conflicts enable an interpretation of the functional program for the room gradually arranged on the ground floor on the building and inside the lodges. The powers representations shaped on on the clock facade and inside the new banqueting room are then analyzed through a political length, considering the difficult situation resulting from the Gradisca war and the hot moment of the Bedmar plot in 1618, just when Antonio Priuli finally became doge. An opening chapter concludes the tesis putting the Ducal palace transformations within the current transformation cycles of the other headquarters of the Venitian power in Main Land and Sea Land main towns. The aim is to catch the political function from architecture design process in a Republic. Public palaces are sophisticated representations from power. Theirs material transformations are as a consequence the tools from complex negotiations in grade of overall political crisis moments
Hadley, Kathryn Z. 1955. "Linear stability analysis of nonaxisymmetric instabilities in self-gravitating polytropic disks". Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11253.
Texto completoAn important problem in astrophysics involves understanding the formation of planetary systems. When a star-forming cloud collapses under gravity its rotation causes it to flatten into a disk. Only a small percentage of the matter near the rotation axis falls inward to create the central object, yet our Sun contains over 99% of the matter of our Solar System. We examine how global hydrodynamic instabilities transport angular momentum through the disk causing material to accrete onto the central star. We analyze the stability of polytropic disks in the linear regime. A power law angular velocity of power q is imposed, and the equilibrium disk structure is found through solution of the time-independent hydrodynamic equations via the Hachisu self-consistent field method. The disk is perturbed, and the time-dependent linearized hydrodynamic equations are used to evolve it. If the system is unstable, the characteristic growth rate and frequency of the perturbation are calculated. We consider modes with azimuthal e im[varphi] dependence, where m is an integer and [varphi] is the azimuthal angle. We map trends across a wide parameter space by varying m , q and the ratios of the star-to-disk mass M * /M d and inner-to-outer disk radius r - /r + . We find that low m modes dominate for small r - /r + , increasing to higher r - /r + as M * /M d increases, independent of q . Three main realms of behavior are identified, for M * << M d , M * [approximate] M d and M * >> M d , and analyzed with respect to the I, J and P mode types as discussed in the literature. Analysis shows that for M * << M d , small r - /r + disks are dominated by low m I modes, which give way to high m J modes at high r - /r + . Low m J modes dominate M * [approximate] M d disks for small r - /r + , while higher m I modes dominate for high r - /r + . Behavior diverges with q for M * >> M d systems with high q models approximating M * [approximate] M d characteristics, while low q models exhibit m = 2 I modes dominating where r - /r + < 0.60.
Committee in charge: Raymond Frey, Chairperson; James Imamura, Advisor; Robert Zimmerman, Member; Paul Csonka, Member; Alan Rempel, Outside Member
Loiler, Scott A. "In Vitro and in vivo Studies of Murine Polytropic Retrovirus Infections: a Dissertation". eScholarship@UMMS, 2000. https://escholarship.umassmed.edu/gsbs_diss/119.
Texto completoKroschel, Joris Dominik [Verfasser]. "Einfluss von Empathie auf Gewalt – und polytrope Delinquenz bei Jugendlichen / Joris Dominik Kroschel". Ulm : Universität Ulm, 2017. http://d-nb.info/1136660496/34.
Texto completoBenjeddou, Saïd. "Simulation numérique directe des gaz fortement chauffés et approximation polytropique". Aix-Marseille 2, 2003. http://www.theses.fr/2003AIX22088.
Texto completoMarsh, Gordon E. "Conceptualizing Musical Texts: Polytropy and the Aesthetics of Recent Music". Bärenreiter Verlag, 1998. https://slub.qucosa.de/id/qucosa%3A37170.
Texto completoJabbar, J. R. "The effect of axial rotation on internal structure of the polytropic models of the stars". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355909.
Texto completoCassino, Valeria. "Un canto polytropo Geografie dell'Assenza e musiche d'Altrove in Vinicio Capossela". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7132/.
Texto completoRydén, Gustav y Fredrik Anarp. "Beräkningsmodell för slagtider av pneumatiska manöverdon : En experimentell och teoretisk studie av beteendet för pneumatiska cylindrar samt manöverdon". Thesis, Linköpings universitet, Fluida och mekatroniska system, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166356.
Texto completoThis thesis work describes the development of a calculation model for stroke times of pneumatic cylinders and actuators. The stroke time of an actuator can be determined by experimental tests. To facilitate and reduce the time required in connection with the tests, a calculation model is created which presents theoretical values of the stroke time. This calculation model is qualitatively consistent with the experimental tests carried out in this work. The tests are first carried out on a simple pneumatic cylinder, which contributes to knowledge of stroke characteristics and stroke times. This knowledge is helpful for the development of the calculation model. During the tests the stroke time, chamber pressure and piston movement are measured in a variety of operating conditions. The tests show that one of the most critical parameters for the calculation model is the C value, a parameter that describes the flow characteristics of pneumatic components. To make the calculation model reliable, a reasonable C value need to be used. The calculation method consists largely of equations for filling and emptying of pneumatic volumes as well as pressure changes in the cylinder chambers during compression and expansion. With a combination of these equations it is possible to calculate the stroke time. Since the calculation model wants to be kept relatively simple, several assumptions are made about parameters in the system. These assumptions are evaluated according to their potential and impact on the stroke time. Validation experiments show that the calculation model generally works better at high supply pressures and critical flows. When the supply pressure is low and subcritical flow are obtained, the stroke time is affected by many more parameters, which lower the precision of the calculation model. This result is not entirely unexpected since the critical flow equations are relatively simple.
Gräf, Ingo [Verfasser] y B. [Akademischer Betreuer] Kraushaar-Czarnetzki. "Experimentelle Untersuchung und Modellierung des Wärmetransports in katalytischen Schwammpackungen unter polytropen Reaktionsbedingungen / Ingo Gräf. Betreuer: B. Kraushaar-Czarnetzki". Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1088553451/34.
Texto completoVansnick, Michel P. D. G. "Optimization of reciprocating compressor maintenance based on performance deterioration study". Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210800.
Texto completoWhen we are analyzing the reliability of such equipment, as a result, there are few opportunities to crash a few pieces of equipment to actually verify component life.
Reliability is the probability that an item can perform its intended function for a specified interval of time under stated conditions and achieve low long-term cost of ownership for the system considering cost alternatives. From the economical standpoint, the overriding reliability issue is cost, particularly the cost of unreliability of existing equipment caused by failures.
Classical questions about reliability are:
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Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Samaké, Oumar. "Analyse thermo-économique d'un système de dessalement par thermocompression de vapeur et conception de l'éjecteur". Thèse, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8782.
Texto completoKong, Dali. "Analytical and numerical studies of several fluid mechanical problems". Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3651.
Texto completoVENTO, OSCAR. "Research on the fluid dynamics of diesel injection systems, design of innovative closed-loop control strategies, assessment of a new flowmeter for high-pressure fluids and 1D modelling of liquid and gaseous flows". Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2927462.
Texto completoLi, Ruijie. "Applications of Stirling engine in sustainable development : context-experimental and numerical study". Thesis, Paris 10, 2017. http://www.theses.fr/2017PA100066/document.
Texto completoIn this work a solar powered low temperature difference Gamma type Stirling engine has been studied experimentally and numerically using an isothermal model coupled with various losses and using an objective optimization. A new model named Polytropic Stirling Model with Losses (PSML) has been proposed which was applied to the Beta type GPU-3 Stirling engine. An Alpha type integral Stirling cryocooler has been studied numerically using an isothermal model with losses. To study a Gamma type Stirling engine of our laboratory, an isothermal model coupled with finite speed method has been developed, including mass and energy balances through different spaces of the engine. The engine is divided into 3 volumes: compression volume, regeneration volume, and expansion volume. Different kind of thermal and mechanical losses have been considered in the model, in order to analyze thermodynamic processes and losses in the Stirling Engine. In addition, parameter effects on the performance of the solar powered gamma type Stirling engine have also been studied experimentally and numerically. The comparison between the experimental results and the simulation results at different phase shift between the displacer and the piston, and at different piston stroke shows that the model is convincing to predict the Stirling engine performance. Based on the Finite Physical Dimensional Thermodynamic method, a multi-objective genetic method considering output power, thermal efficiency and entropy generating rate as objective functions simultaneously, has been used to multi-objective optimize the Gamma type Stirling engine. Comparing with the ecological optimization method, the multi-objective method can better balance the three objective goals. The new model (PSML) proposed in the thesis for predicting performance of Beta or Gamma type of Stirling engine divides the working space into 5 parts (compression volume, cooler, regenerator, heater, and expansion volume). A bypass linking compression volume and expansion volume has been added in the classic adiabatic model of Stirling engine. Thus, polytropic processes have been considered in the compression and expansion volumes of the Stirling engine. The GPU-3 Stirling engine has been used to validate the new model. It was shown that the new model (PSML) predict well the output power and the thermal efficiency of the engine well. An isothermal model considering various losses was developed and presented in the last part of this thesis to study an Alpha type Stirling cryocooler, whose geometrical dimensions were measured in our laboratory. The compression and expansion volumes are supposed to be isothermal, the variation of the regenerator temperature is supposed to be linear. Energy and exergy balances of the cryocooler were developed. The effect of various parameters on the cryocooler performance (cooling power and input power) are investigated. The simulation results for PPG-102 Stirling cryocooler were compared with two other simulation results of the literature and with experimental results which indicated that this model is convincing to predict the performance of the Stirling cyocooler
Khennich, Mohammed. "Optimisation thermodynamique d’un procédé solaire utilisant un système de réfrigération à éjecto-compression pour la production du froid". Thèse, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/9756.
Texto completoZHANG, TANTAN. "Design of innovative solutions for high-pressure fuel injection systems, optimization of measuring techniques for injected flow-rate and modeling of 1D flows". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2843978.
Texto completoBurzler, Josef Maximilian. "Performance Optima for Endoreversible Systems". Doctoral thesis, Universitätsbibliothek Chemnitz, 2003. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200300012.
Texto completoTheoretische Grenzen für verschiedene Leistungsmerkmale von thermodynamischen Systemen werden unter der Bedingung endlicher Zeiten und Prozessraten im Rahmen endoreversibler Modelle untersucht. Diese Modelle bestehen aus reversiblen Subsystemen, welche über allgemein irreversible Wechselwirkungen Energie austauschen. Analytische und nummerische Berechnungen quantifizieren diese Grenzen und liefern optimale Prozess- und Konstruktionsparameter für vier Modellsysteme. Für eine auf maximale Ausgangsarbeit optimierte Wärmekraftmaschine, bei der die Wärme zwischen Arbeitsmedium und Wärmereservoirs während allgemeiner polytroper Zustandsänderungen des Arbeitsmediums übertragen wird, werden optimale Temperaturen und Zeiten für die Wärmeübertragungsprozesse sowie die thermischen Wirkungsgrade bestimmt. Für ein wirkungsgrad-optimiertes Modell eines verallgemeinerten thermischen Umwandlungssytems, das sowohl Wärmekraftmaschinen, Kühler und Wärmepumpen beschreibt, wird die optimale Verteilung von Investitionskosten auf die Wärmetauscher ermittelt und die Anwendung der allgemeingültigen Ergebnisse anhand mehrerer Beispiele demonstriert. Für eine Wärmekraftmaschine mit mehreren Wärmereservoirs wird bestimmt, welche der Wärmereservoirs wie lange kontaktiert werden müssen, um eine maximale Ausgangsarbeit zu erzielen. Für einen Dieselmotor wird die Kolbenbewegung so optimiert, dass bei gegebener Treibstoffmenge eine maximale Ausgangsarbeit erzielt wird. Das endoreversible Modell des Dieselmotors berücksichtigt die Temperaturabhängigkeit der Wärmekapazität, Wärmeleitfähigkeit und Viskosität des Arbeitsfluids, die Zeitabhängigkeit des Verbrennungsprozesses sowie Reibungs- und Wärmeverluste
Tavant, Antoine. "Study of the plasma/wall interaction and erosion on a plasma thruster of low power". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX085.
Texto completoElectric propulsion systems that accelerate plasma ions are important for the success of spatial missions (GPS, weather forecast, communication, etc.).The Hall effect thruster is one of the most used and efficient technology.However, its conception and optimization is slow and costly, as key processes are still poorly understood, in particular the electron transport and the plasma-wall interaction.In order to study both phenomena, we use a bi-dimensional kinetic simulation.We showed with 2D PIC simulation results that electrons are non-local, as they are absorbed more quickly at the wall compared to the collision frequency.Consequently, we derived a non-isothermal sheath model using a polytropic state law for the electrons that describes more accurately the plasma-wall interaction.The model can be used with and without secondary electron emission.With electron emission, the sheath model can present up to three solutions, explaining the oscillations observed in the simulations.The azimuthal instability observed, responsible for the electron transport, is compared to the dispersion relation of the ion acoustic wave and the electron cyclotron drift instability.We show that, while the first linear stage of the instability is well understood, the saturated quasi-steady-state is affected by particle-wave interactions and non-linear mechanisms that are not included in the dispersion relation
Kopečný, Lukáš. "McKibbenův pneumatický sval - modelování a použití v hmatovém rozhraní". Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233458.
Texto completoΦωτόπουλος, Αθανάσιος. "Μετανευτώνειες προσεγγίσεις στους αστέρες νετρονίων". Thesis, 2014. http://hdl.handle.net/10889/8381.
Texto completoThe main subject of my master thesis is the study of,the post-Newtonian approximations (PNA) in General Relativity (G-R), mainly those that concern the neutron stars. Owing to the study of neutron stars is on the hydrodynamic description of matter, our main interest lies uponthe way the PNA affects the hydrodynamic equations of G-R. In the first chapter there is presented the main theory around the physical attributes of compact stars. The second chapter reffers to the general features of the equations of state (EoS) of compact stars, giving emphasis to the polytropic EoS. In the yhird chapter, there is presented the theory of the PNA. There are also presented the the hydrodynamic equations in the PNA as the were introduced by Chandrasekhar. The fourth chapter is dedicated to the presentation of the method that was introduced by Fahlman and Anand, on the study of rotating polytropes in the PNA to G-R. The fifth chapter focuses on the second PNA as it formulated by Chandrasekhar and Nutku. During the sixth and final chapter there is presented a computer algebra package for post-Newtonian calculations in G-R, the PROCRUSTES. Whith the aid of thiw package, we calculated several quantities in the second PNA, as for example the E-M tensor 𝑇𝑖𝑗„ the Ricci tensor 𝑅𝑖𝑗 and the equations of motion (EoM) Τ𝑖𝑗 ;𝑗 = 0. PROCRUSTES is a very useful tool for the post-Newtonian study, as someone can produce the compicated equations of several quantities in no time and eliminating the possibility of making some mistake during the calculation. Moreover, using PROCRUSTES we calculated the expressions of the EoM’s in the second PNA. Under appropriate transformation of these expressions, we are able to apply the method of Fahlman and Anand onto these equations with a view to the study of rotating polytropes in the second PNA. At the end of this work there is quoted a supplement with the structure of the programm we used, along with some of the quantities that were calculated during this work.
Totten, Tracy L. "Determination of the polytropic index of the free-streaming solar wind". Thesis, 1994. http://hdl.handle.net/1911/13908.
Texto completoKita, David B. "A study of the vertical and radial structure of polytropic accretion disks". 1995. http://catalog.hathitrust.org/api/volumes/oclc/34266889.html.
Texto completoTypescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 201-202).
Totten, Tracy Lynn. "Application of an empirically-derived polytropic index for the solar wind to a solar wind shock propagation model". Thesis, 1994. http://hdl.handle.net/1911/16779.
Texto completoZhang, Yunchao. "Transport Properties of Charged Particles in Low Pressure Plasmas". Phd thesis, 2016. http://hdl.handle.net/1885/112124.
Texto completoΚλεφτόγιαννης, Γεώργιος. "Μελέτη των ταλαντώσεων των αστέρων νετρονίων με έμφαση στις ακτινικές ταλαντώσεις τους". Thesis, 2011. http://hdl.handle.net/10889/5724.
Texto completoIn the present Thesis we study the oscillations of neutron stars emphasizing on the radial oscillations. The Thesis is organized in four chapters. In the first chapter, we introduce the theoretical background of neutron stars and pulsars. We then discuss the importance of the role that the binary neutron stars play in modern Astrophysics. Next, we refer to the structure of these stars and introduce some of the equations of state (EOS) which try to describe the matter occupying the inner layers of neutron stars, emphasizing on the polytropic EOS which is adopted here. In the second chapter we, first introduce the Oppenheimer–Volkoff (OV) system of differential equations, describing the hydrostatic equilibrium of a non rotating, non pulsating neutron star, and considering the radial oscillations 1) as infinitesimal, baryon-number conserving, adiabatic oscillations 2) as the result of the slow rotation of the neutron star, we derive the second order differential equation governing the radial oscillations of a neutron star. We then rewrite this equation in the Sturm–Liouville form. The expression of the change of frequency of the radial oscillations due to slow rotation and the equations of state is obtained. Finally, we conclude this chapter with a mode analysis of oscillations of neutron stars in general. In the third chapter, we first solve the OV system of differential equations, implementing an original iterative algorithm, and thus calculate the physical parameters of the star. Next, some of the methods used for solving the equations describing the radial oscillations are discussed. Finally, we transform the Sturme–Liouville form to a set of two first order differential equations, which are computed by implementation of the shooting method. In the bibliography, the polytropic EOS is considered in two different ways, depending on which density (rest mass or total mass–energy) is involved in the polytropic EOS. In a similar manner, we have two different ways for considering the adiabatic exponent which enters the equation describing the radial oscillations (constant or variable). Considering these four different assumptions for the polytropic EOS and the adiabatic exponent, we construct four different models of pulsating neutron stars. In the final chapter, we compute and present the first three frequencies of each basic model concerning radial oscillations of neutron stars for three values of the polyropic index. We discuss the numerical methods implemented here and the involved subroutines, which can be found in the SLATEC Library. The main issues of the present Thesis are the development of an iterative algorithm for accurately computing the radius of the star and the computation of the frequencies for the four basic models describing th radial oscillations of neutron stars.
Σιδηράς, Μιχαήλ. "Συμβολή στο πρόβλημα του προσδιορισμού της δομής ενός πολυτροπικού αστέρα υπό την επίδραση διαφορικής περιστροφής, μαγνητικού πεδίου και ιξώδους". Thesis, 1995. http://nemertes.lis.upatras.gr/jspui/handle/10889/4522.
Texto completoIn the first part, it has primarily been described the "complex plane strategy"(cxps) and has also been explained the reason of implementing this method in the present investigation. With the cxps collaborates the "multiple partition technique" (MTP) which is involved in the corresponding computations. In particular, the model of a differentially rotating polytropic star is constructed, which is under the cooperating influence of a toroidal magnetic field. To this purpose, perturbation theory is used on the basis of the fundamental magnetic perturbation parameter h. the theory including terms up to the first order in both the perturbation parameters u (rotation) and h (magnetic field),is developed and the corresponding differential equations are set up. Our computation concerns mainly critical rotations. In the second part of the thesis, we consider models with differential rotation owing to the viscous material of the star, on the basis of the so called "coupling equation" that is consequence of the Navier-Stokes equation for viscous polytropic stars. Emphasis is given on the study of dissipative effects due to viscous friction, as they are determined by the combined action of rotation and magnetic field. The computations show that a toroidal magnetic field can play the role of an efficient "lubricant" injected into the material of the particular magnetic model, thus reducing drastically the energy dissipated due to viscous friction.
Καραγεωργόπουλος, Βασίλειος. "Μελέτη των περιστρεφομένων αστέρων νετρονίων με έμφαση στη μέθοδο των μετανευτωνείων προσεγγίσεων". Thesis, 2011. http://hdl.handle.net/10889/5154.
Texto completoIn the present Thesis, we study rotating neutron stars. Due to the fact that the classical perturbation methods implemented to compute the radius of a polytropic rotating model are restricted by the star's surface, we develop a method for continuing integrations beyond this limit. This general approach utilises the postnewtonian parameters in terms of disturbance. By the application of a code written in Fortran, we calculate extensive tables of quantities and constants. Furthermore, we compute the radius as well as the critical rotation parameter, which plays the role of a postnewtonian term. This Thesis is organized in five chapters. In the first chapter, the neutron star is presented as an astrophysical object. Its structure and physical characteristics are of a great importance. Moreover, the existence of neutron stars is linked to pulsars, which are "living" examples of rotating neutron stars. Therefore, the physical characteristics of these objects are discussed in this chapter. The second chapter refers to the equations that describe the structure of the neutron stars and to the concept of polytropes. First, due to the difficulty in implementing a study for these stars without the adoption of any equation of state as well as due to the most indicative one for their description which is that of the polytrope. Second, the equations that refer to the undistorted and those that describe the corresponding distorted configurations are analysed in this chapter, in accordance with Chandrasekhar's perturbation theory. In the third chapter, the General Theory of Relativity is used to the study of the polytropic model, focusing on how the classical theory is corrected, on how the basic model's quantities are transformed and on how the equations of the postnewtonian approach are derived. The equations to be solved result from the latter ones. Furthermore, a a discussion on the various numerical methods that have been developed for studying the relativistic rotating polytopric model is given in the fourth chapter. In the fifth chapter of this Thesis, a number of tables illustrating results as well as some interesting diagrams are included. Certain algorithmic details for our program are given. We also discuss the generalisation of the postnewtonian approach and its advantages.
Κατελούζος, Αναστάσιος. "Μαγνητοϋδροδυναμική μελέτη περιστρεφομένων αστέρων νετρονίων". Thesis, 2009. http://nemertes.lis.upatras.gr/jspui/handle/10889/2783.
Texto completoWe compute relativistic polytropic models as well as models obeying realistic equations of state, of rotating neutron stars. The purpose of this study is to calculate significant physical quantities of a neutron star, in the case of hydrostatic equilibrium, rigid and differential rotation, as well as in the case of a magnetic neutron star with both poloidal and toroidal components. A short description of the numerical treatment has as follows. First, we solve the Oppenheimer-Volkov system of differential equations. This system refers to hydrostatic equilibrium of non rotating polytropic models. Then, solid rotation is added as a perturbation, according to "Hartle’s perturbation method" and corrections to mass and radius are calculated, as also corrections due to spherical and quadrupole deformations. In addition a third order perturbation in angular velocity, Ω, is implemented. Angular momentum, J, moment of inertia, I, rotational kinetical energy, T, and gravitational potential energy, W, are quantites that are significally corrected by the third order approximation. Differential rotation is assumed that (i) obeys a specific law, or (ii) follows as a result of the solid rotation and radial oscillations combination; our purpose is the calculation of the main physical quantities that are altered by differential rotation. In the second part the effect of magnetic field is studied, which consists of a poloidal and a toroidal component. The "Ioka-Sasaki perturbation method" (IS) is implemented. This problem is described by the quantification of the flux function ψ, which comes as a solution of the "Grad-Shafranov" (GS) differential equation. Then the components of the magnetic field and the quadrupole deformation of the star are calculated. This method is also a perturbative method similar to "Hartle’s perturbation method". Having calculated models of rotating neutron stars, as also various models of magnetic fields, we can compose our results and determine models of neutron stars with zero deformation, the equalizers, these are neutron stars that are rotating and also have a magnetic field in a way that they, rotation and magnetic field, produce equal but opposite geometrical deformations in the shape of the star.
Burzler, Josef Maximilian. "Performance Optima for Endoreversible Systems". Doctoral thesis, 2001. https://monarch.qucosa.de/id/qucosa%3A17954.
Texto completoTheoretische Grenzen für verschiedene Leistungsmerkmale von thermodynamischen Systemen werden unter der Bedingung endlicher Zeiten und Prozessraten im Rahmen endoreversibler Modelle untersucht. Diese Modelle bestehen aus reversiblen Subsystemen, welche über allgemein irreversible Wechselwirkungen Energie austauschen. Analytische und nummerische Berechnungen quantifizieren diese Grenzen und liefern optimale Prozess- und Konstruktionsparameter für vier Modellsysteme. Für eine auf maximale Ausgangsarbeit optimierte Wärmekraftmaschine, bei der die Wärme zwischen Arbeitsmedium und Wärmereservoirs während allgemeiner polytroper Zustandsänderungen des Arbeitsmediums übertragen wird, werden optimale Temperaturen und Zeiten für die Wärmeübertragungsprozesse sowie die thermischen Wirkungsgrade bestimmt. Für ein wirkungsgrad-optimiertes Modell eines verallgemeinerten thermischen Umwandlungssytems, das sowohl Wärmekraftmaschinen, Kühler und Wärmepumpen beschreibt, wird die optimale Verteilung von Investitionskosten auf die Wärmetauscher ermittelt und die Anwendung der allgemeingültigen Ergebnisse anhand mehrerer Beispiele demonstriert. Für eine Wärmekraftmaschine mit mehreren Wärmereservoirs wird bestimmt, welche der Wärmereservoirs wie lange kontaktiert werden müssen, um eine maximale Ausgangsarbeit zu erzielen. Für einen Dieselmotor wird die Kolbenbewegung so optimiert, dass bei gegebener Treibstoffmenge eine maximale Ausgangsarbeit erzielt wird. Das endoreversible Modell des Dieselmotors berücksichtigt die Temperaturabhängigkeit der Wärmekapazität, Wärmeleitfähigkeit und Viskosität des Arbeitsfluids, die Zeitabhängigkeit des Verbrennungsprozesses sowie Reibungs- und Wärmeverluste.