The master thesis deals with the possibility of using dynamic damper in hydrodynamics. Specifically, the assessment of the impact of dynamic damper on the dynamic stability of the fluid system when the system exhibited unstable behaviour prior to damper installation due to self-excited vibration. In the thesis is presented the algorithm for the calculation of pressure and flow pulsations based on the transfer matrix method, the transition matrices for different damper designs variants are derived. Using the algorithm, the effect of a damper placed in a stable and unstable fluid system is solved. The output of this work is software for solution of pressure and flow pulsations in the system with serially arranged hydrodynamic elements created in the MATLAB program.

This thesis deals with propagation of pressure and flow pulsations, which are strongly affected by the tube flexibility. There are two mathematic models introduced, which are derived from basic physical relations. First model assumes velocity only in the axis direction. Second one assumes also non-zero radial velocity. Kelvin-Voigt model for viscoelasticity was used. Furthermore, experimental measurement was designed and evaluated. Measured data was used to calculate material properties. In addition, dynamic transfer was determined.

The diploma thesis deals with the mathematical modeling of high-frequency pressure pulsations in water turbines. Pulsations are caused by the interaction between stator a rotor blades. These high-frequency pressure pulsations then cause high cycle fatigue of the head cover, spiral casing, runner and distributor. The mathematical model is solved by transfer matrix method. Data are processed in F-A char and MS Excel programs. Final results are demonstrated by frequency amplitude characteristics and by pressure mode shapes, where comparison of the mathematical model with the measurement is shown.

High speed water jets have un-substitutable place in unconventional technologies in the machining of materials. Indeed its larger spreading is limited above all by its really high purchase price and also high costs of the operation. Certain possibility is represented by high-speed pulsating jets, which don’t put such a high pretension on arrangement of generating the pressure during the comparable operation. Probably the most effective method of the generating of pulsating water jets is ultrasonic modulation. This work could benefit to understanding spreading of pressure impulses between ultrasonic generator and output nozzle. Pulsating is solved by the numerical calculation using transfer matrix method.

The thesis discusses the fiber Bragg gratings simulations, analysis and design. In the present time, there are several methods to simulate fiber gratings response based on the stated parameters that define their dimensions and material features. However, this work deals with a different issue, that is the synthesis of the input parameters for demanded spectral responses. The main aim of the work is to achieve a synthesis method that would help to discover parameters describing advanced grating structure, based on the required spectral reflectivity. The basic demand for the parameter synthesis is an achievement of the real values in terms of the consequent production of the suggested structure. The described synthesis method considers advanced fiber grating structure as a structure of several uniform grating sections. The input parameters are estimated in steps, using the well-known direct methods in order to obtain grating responses and feedback to establish the parameters changes. The principle methods involve establishment of initial input parameter values and necessary subsequent algorithm leading to optimize the required spectral response. The initial values are calculated by a simplified model based on the coupled theory equations that are handled for the periodic disturbances in cylindrical waveguide. The following optimization uses the multiple thin film stack and transfer matrix methods. The properties of grating structure spectral reflectivity are step by step calculated while using these direct methods. Input parameters are established in the next several steps. Establishment of input parameters is done subsequently, based on the demanded and calculated output spectral reflectivity properties. Optimizing process is limited by possibilities of the grating manufacture technology. It is possible to assemble arbitrary fiber grating structure taking in term the demanded spectral response. Nevertheless, the calculated input parameters are real for the following manufacture. This method could be used to design optical band stop filter, high-pass and low-pass filters or filters for special applications.

Cette thèse développe un cadre rigoureux qui permet de démontrer des représentations exactes associées à divers observables de la chaîne XXZ de Heisenberg de spin 1/2 à température finie. Il a était argumenté dans la littérature que l’énergie libre par site ou les longueurs de corrélations admettent des représentations intégrales où les intégrandes sont exprimées en termes de solutions d’équations intégrales non-linéaires. Les dérivations de ces représentations reposaient sur divers conjectures telles que l’existence d’une valeur propre de la matrice de transfert quantique, real, non-dégénérée, de module maximale, de l’échangeabilitée de la limite du volume infinie et du nombre de Trotter à l’infinie, de l’existence et de l’unicité des solutions des equation intégrales non-linéaires auxiliaires et finalement de l’identification des valeurs propers de la matrice de transfert quantiques avec les solutions de l’équations intégrales non-linéaires. Nous démontrons toutes ces conjectures dans le regime de haute température. Nôtre analyse nous permet aussi de démontrer que pour ces température suffisamment élevées, il est possible d’avoir une description d’un certain sous-ensemble de valeurs propres sous-dominante de la matrice de transfert quantique décrite en terme de solutions d’une chaîne de spin-1 de taille finie. / This thesis develops a rigorous framework allowing one to prove the exact representations for various observables in the XXZ Heisenberg spin-1/2 chain at finite temperature. Previously it has been argued in the literature that the per-site free energy or the correlation lengths admit integral representations whose integrands are expressed in terms of solutions of non-linear integral equations. The derivations of such representations relied on various conjectures such as the existence of a real, non-degenerate, maximal in modulus Eigenvalue of the quantum transfer matrix, the exchangeability of the infinite volume limit and the Trotter number limits, the existence and uniqueness of the solutions to the auxiliary non-linear integral equations and finally the identification of the quantum transfer matrix’s Eigenvalues with solutions to the non-linear integral equation. We rigorously prove all these conjectures in the high temperature regime. Our analysis also allows us to prove that for temperatures high enough, one may describe a certain subset of sub-dominant Eigenvalues of the quantum transfer matrix described in terms of solutions to a spin-1 chain of finite length.

Acoustic absorbing liners are efficient and commonly used measures to reduce sound levels in many fields of application. The sound reducingperformance of the liners is dependent on the acoustic state, defined by e.g. the flow and sound field interacting with the liner. To enable liner optimization the impact of these factors on the liner performance must be predictable. Studies of the impact of these factors were performed with existing experimental, analytical and numerical methods at low Mach number flows and material used in truck engine compartments. The study showed significant impact of both flow and sound field onthe liner performance. The size of the impact of the flow depends on which of the existing methods and models that was used, implying theneed of complementary methods. A new numerical method to model the boundary layer effect was for this reason developed in this work. The method was shown to predict the impact of flow correctly compared to the Pridmore-Brown solution and the method was computationally efficient. The sound reducing performance of a liner exposed to complex sound field and grazing flow can be predicted using existing methods together with the new proposed method. Extra care has to be taken when bulk reacting liners are considered since additional complications compared to locally reacting surfaces occur in presence the of grazing flow. / <p>QC 20130916</p>

The validity of transfer matrix method (TMM) employed in a nonlinear gear cam system is studied in this thesis. The nonlinear dynamic responses of each part in the nonlinear system are estimated by applying the 4th-order Runge-Kutta method. A high speed gear cam drive automatic die cutter was analyzed in this study. A 25 horsepower AC induction motor is designed to drive the system. To complete the cutting work, a sequential process of the harmonic motion and the intermittent motion are generated by the elbow mechanism and the gear cam mechanism, respectively. A simplified branched multi-rotor system is modeled to approximate the motion of the system. The variation of the dynamic parameters of the system in a loading cycle is estimated under a branched torsional system. The Holzer¡¦s transfer matrix method is used to study the variation of the system parameters during the intermittent movement. Moreover, the effect of time-varied speed introduced from the torque variation of the induction motor and gear cam mechanism on the nonlinear dynamic response of the system has also been investigated. To explore the dynamic effect of different cam designs, three different cam motion curves and seven operating rates have been analyzed in this work. The residual vibration of the last sprocket has also been discussed. Numerical results indicate that the proposed model is available to simulate the dynamic responses of a nonlinear gear cam drive system.

Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-03-20T12:36:39Z No. of bitstreams: 1 TeseDAN.pdf: 8462805 bytes, checksum: 612f3289bd6eedee49e627d6f99f7762 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-04-20T13:36:31Z (GMT) No. of bitstreams: 1 TeseDAN.pdf: 8462805 bytes, checksum: 612f3289bd6eedee49e627d6f99f7762 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-04-20T13:36:43Z (GMT) No. of bitstreams: 1 TeseDAN.pdf: 8462805 bytes, checksum: 612f3289bd6eedee49e627d6f99f7762 (MD5) / Made available in DSpace on 2017-04-20T13:54:43Z (GMT). No. of bitstreams: 1 TeseDAN.pdf: 8462805 bytes, checksum: 612f3289bd6eedee49e627d6f99f7762 (MD5) Previous issue date: 2016-10-31 / Não recebi financiamento / In this Thesis we propose to describe the thermodynamical properties of dimer chains in a one-dimensional lattice rstly considering q-states of chain orientation in the lattice and secondly by a three states model where the chain orientation is associated with a energy " > 0 or " = 0. For this reason we describe our system by a microcanonical ensemble to get the canonical partition function and through this function obtain the Helmholtz free energy, the entropy, internal energy and pressure. We solved also the problem by adopting the grand canonical ensemble using the transfer matrix method and we get in the thermodynamical limit the equivalence between both ensembles. However the analysis of the thermodynamic properties for systems with nite size is quite relevant since for these nite systems can be found a inequivalence of ensembles. Thereby we performed a detailed study of the Statistical Mechanics for nite particles systems verifying the equivalence o ensembles. / O presente trabalho tem por finalidade descrever as propriedades termodinâmicas de cadeias de dímeros em uma rede unidimensional, inicialmente considerando q-estados de orientações das cadeias na rede, e posteriormente um modelo de 3 estados, onde orientação da cadeia está associada a uma energia " > 0 ou " = 0. Para isso, consideramos o problema de um ponto de vista combinatório, no ensemble microcanônico, de maneira a obter sua função de partição canônica e através dela encontrarmos as grandezas termodinâmicas de interesse, tais como a energia livre de Helmholtz, entropia, energia interna, pressão, por exemplo. Posteriormente, resolvemos o problema no ensemble grande canôncio usando a técnica de matriz de transferência, obtendo assim, no limite termodinâmico a equivalência entre os ensembles. Entretanto, têm-se tornado cada vez mais importante e frequente, o estudo termodinâmico de sistemas “pequenos", onde nestes casos pode haver a inequivalência entre as grandezas físicas obtidas nos ensembles. Desse modo, realizamos um estudo detalhado do que acontece ao aplicarmos ferramentas da mecânica estatística a sistemas com poucas partículas, verificando se os diferentes ensembles estatísticos estudados neste trabalho ainda levam aos mesmos resultados.

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