|
|
Design of adjustable fully-differential filters with current active elements
Polášek, Lubomír ; Koton, Jaroslav (referee) ; Jeřábek, Jan (advisor)
The master thesis deals with design of the fully differential frequency filters working in the current mode and is focused on possibilities of the natural frequency and the quality factor adjustment. At the beginning, there is a brief description of frequency filters and active elements (MO-CF, FD-CF and DACA), which are used in the thesis. Furthermore, simplified signal flow graphs design method and transformation of passive and active elements to the differential structures are described. The designs of four differential circuitries which provide possibility of tuning the natural frequency or quality factor by the gain of the DACA element are shown in the thesis. Simulation results made in OrCAD program with help of third-order models are included. The practical implementation of the differential frequency filter for tuning of the natural frequency by the DACA elements is shown in the last chapter.
|
|
| |
|
|
Modelling of dynamics systems with multi degrees of freedom
Světnický, Tomáš ; Lošák, Petr (referee) ; Dušek, Daniel (advisor)
The goal of this thesis is to create a mathematical model of multi-degree-of-freedom vibrating system based on motion equations. The introduction describes the theoretical distribution of dynamic vibrating systems and their main characteristics. The next part deals with the analysis of assigned system and the motion equations are constructed by using Lagrange equations of the second kind. The process of system solving is provided together with equations which were used for obtaining the natural frequencies, eigenmodes and amplitudes of objects in time. The actual solution is carried out in MAPLE software; graphs of amplitude characteristics, phase characteristics and objects amplitude in time are constructed. Influence of parameters entering the calculation is discussed. At the end is verified the accuracy of the analytical solution by the finite element method in ANSYS software.
|
|
| |
|
|
Modelling of vibration of dynamic systems with n-degrees of freedom
Luky, Robin ; Hadaš, Zdeněk (referee) ; Dušek, Daniel (advisor)
This Bachelor’s thesis deals with vibration of dynamic systems with luminous parameters with n-degrees of freedom. It features decision procedures of free-running undamped systems, exciting undamped systems, exciting damped systems and their natural shapes, natural frequency and gain-frequency characteristic. At the end of this Bachelor thesis there is an analysis of dynamic damper. The analysis is conducted in agreement with the theoretical procedures listed above.
|
|
|
Comparison of composite material degradation assesment methods using acoustic analysis and laser vibrometry
Urushadze, Shota ; Šperl, Martin ; Kytýř, D. ; Valach, J. ; Fíla, T.
Assessment of degradation rate of material can be carried out by many experimental techniques differing in complexity and sophistication. A relatively simple method based on acoustic analysis is described in this contribution. Degradation of material’s properties due to fatigue loading is detectable in decrease of their modulus of elasticity that can be derived from natural frequencies of specimens. These measurements utilize self-designed device capable of specimen excitation and acquisition of its vibration. The recorded signal is then processed by spectral analysis enabling determination of natural frequencies. Usefulness of the above mentioned acoustic method can be seen in the fact that the measured changes of material’s parameters are comparable to those obtained by laser vibrometry, which is by several orders more expensive technique.
|
|
|
Investigation of C/PPS Composites Degradation Process Using Acoustic Measurement
Fíla, Tomáš ; Valach, Jaroslav ; Kytýř, Daniel ; Šperl, Martin
The article deals with assessment of fatigue degradation of C/PPS composites using simple acoustic measurement technique. Changes in natural frequency and attenuation decrement were chosen as indicators of fatigue damage accumulation in the studied composite material. New testing device was developed for acoustic measurement. The experimental setup was designed to chime the specimen by repeatable force of stiff striker exciting a specific natural mode of vibration and to record the acoustic response of the specimen to the impact simultaneously. From the power spectral density of the signal the natural frequency was obtained. Using the same signal, the attenuation decrement was estimated from regression of the its envelope.
|
|
|
Dynamika impaktních proudů zkoumaná v příčných řezech proudem
Tesař, Václav ; Něnička, Václav
Authors investigated experimentally air jets impinging on a flat plate. The object of interest were vortical instability structures in the mixing layer of the jet. Their formation was triggered by azimuthal waves generated in the nozzle exit. The structures were visualised by planar laser-light sheet illuminating a jet cross section where it scattered on by water mist particles added into air. The cross section was, photographed by a high-frequency camera located behind transparent impingement plate.
|
|
|
Calculation of natural frequency of high-pressure system
Foldyna, Josef ; Říha, Zdeněk ; Sitek, Libor
The paper presents results of numerical simulation of 3D, unsteady, turbulent flow of compressible water in a high-pressure system equipped with acoustic generator of pressure pulsations and its response to a pressure impulse. Results of numerical simulation are compared to the laboratory measurement of response of high-pressure system to a pressure impulse using dynamic pressure sensor placed upstream to the nozzle exit.
|
|
| |
guest ::
