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Health monitoring of building structures: preliminary considerations on a case study
Bayer, Jan ; Urushadze, Shota ; Zíma, Pavel
Ageing, erosion, local damage or increase of the operating loads can decrease the reliability and load bearing capacity of building structures. Vibration monitoring may provide a promising solution of this problem, however robust health monitoring techniques are needed before wider practical applications. The presented analytical and experimental case study on a simple supported steel beam is an introductory practical investigation into this topic. It shows the sensitivity of chosen parameters to artificially induced damage and outlines possible directions or further research in conclusions. Special attention is paid to simultaneous monitoring of deformations and strains which can provide us with a useful information about the stress redistribution in monitored or tested structures.
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Stability analysis of the lateral oscillations of a flexibly supported viscoelastic Jeffcott rotor
Ferfecki, P. ; Zapoměl, Jaroslav ; Kozánek, Jan ; Dekýš, V.
Material damping has a significant influence on vibrations of flexible rotors and can induce their self excited oscillations. The squeeze film dampers inserted in the rotor supports are frequently used to suppress occurrence of these undesirable operating conditions. Modelling the shaft by means of a Kelvin- Voigt material can arrive at the overestimation of the effect of internal damping on the rotor movement. This was a motivation to develop a procedure based on utilization of the Zener material (standard solid theoretical material) to represent the shaft of a Jeffcott rotor supported by squeeze film dampers. The development and testing of this procedure, the experimental determination of the appropriate material constants, and learning more on the influence of material damping on the stability and vibration attenuation of flexible rotors are the principal contributions of the presented article.
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Průchod proudu vibrujícím molekulárním můstkem
Šmít, Daniel ; Čížek, Martin (advisor) ; Novotný, Tomáš (referee)
In the present work we study transmission of electron through vibrat- ing molecular junction interacting with leads using a method of nonequilibrium Green functions. Our Green functions use combination of first quantization to treat vibrational levels and second quantization to treat electron processes. We treat the change of vibrational potential of junction induced by charging of junc- tion, we find a spectral function and a magnitude of current through the junction. We confirm the effect of Fermi sea and Frack-Condon factors on sharpening of peaks. We study these processes on model motivated by biphenyl molecule, in- troducing double well potential and study an effect of quasidegenerate energy levels. We present the shift of peaks, resulting from an increase of moment of inertia, to positions determined by Franck-Condon factors.
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Study of oligonucleotide penetration through liposomal membrane
Nováková, Jana ; Kočišová, Eva (advisor) ; Holoubek, Aleš (referee)
Modified oligonucleotides, short pieces of nucleic acids, have become potential candidates for treatment of viral, malignant or genetic diseases. Efficient application of modified oligonucleotides requires their sufficient penetration inside the cell through the lipid membrane. Diploma thesis employs liposomes, synthetic vesicles formed by the lipid bilayer, as a model system for the study of interaction of lipid and complex of homooligonucleotides dT15 with cationic porphyrin CuTMPyP4 using Raman spectroscopy. Raman spectra were measured in solution on the slide and using special technique of drop coating deposition Raman spectroscopy (DCDR) on integrated Raman confocal microspectrophotometer. Processes of liposome formation and sample preparation were optimized. Experimental data were analysed using factor analysis based on singular value decomposition (SVD) algorithm. It was observed that interaction of oligonucleotide with porphyrin induces fluorescent background increase. Raman spectra of complex of oligonucleotide with porphyrin exhibit the domination of porphyrin vibrational bands. Stretching vibrations of lipid assigned to hydrogens of fatty acids are observed in the spectra of complex with liposomes. The observed spectral changes show the interaction of lipid with complex of oligonucleotide and...
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Analysis of the lateral vibration of a flexibly supported unbalanced viscoelastic Jeffcott rotor
Ferfecki, P. ; Zapoměl, Jaroslav ; Kozánek, Jan
The behaviour of flexible rotors is significantly influenced by elasticity and damping properties of the shaft. It implies a special attention has to be paid to appropriate choice of a theoretical material to represent the rotors in mathematical models of rotating machines. The procedure developed in this paper concentrates on the investigation of the steady state component of the Jeffcott rotor vibration induced by the disc unbalance and on magnitude of the forces transmitted to the rotor frame. The shaft material is represented by the Zener standard solid material model. The steady state response was determined by application of the trigonometric collocation method. The results of the simulations confirmed the influence of the input oil pressure on the shape of the rotor orbit and on the oscillation amplitude.
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Measurement of real-time gigacycle fatigue through real-time interferometry
Lazar, Josef ; Holá, Miroslava ; Hrabina, Jan ; Číp, Ondřej
We present an interferometric method for measurement of strain induced deformation of metal samples in experiments inducing high-cycle fatigue. The motivation is to get real-time information about the deformation of a metal sample under test, its elongation imposed by fast vibrating actuator. Fatigue of materials is a process of degradation of a material due to repeated application of forces which includes nucleation and propagation of cracks and leads to the failure of the component. It may appear in all parts of machines or structures which rotate, vibrate, are repeatedly loaded, are subjected to temperature gradients etc., so statistically, fatigue is implied in about 80% of all industrial failures.
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Polarization Imperfections of Light in Interferometry
Kučera, Petr ; Lazar, Josef (referee) ; Mohr, Fridemann (referee) ; Wilfert, Otakar (advisor)
Disertační práce pojednává o polarizačních nedokonalostech optických komponentů, které jsou využívány ke kontrole a k transformaci polarizačního stavu světla. Získané teoretické výsledky jsou pak využity ve vybraných aplikacích, jež ke své činnosti využívají právě polarizace světla. Konkrétně se jedná o zařízení měřící vibrace oscilujících objektů, dále o interferenční měření dvojlomu v transparentních materiálech a konečně, o vybraná témata z optické kvantové komunikace.
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