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Measurement of the impulsive force generated by colapsing bubble close to a solid boundary
Müller, M. ; Unger, J. ; Holata, J. ; Zima, Patrik
The article presents experimental results of the acoustical and optical study of cavitation bubble collapse close to a solid boundary in water. The bubble was generated by discharge of low-voltage capacitor into a couple of wires closing a simple circuit. Different distances from the solid wall and different maximum bubble radii were studied. The bubble radius was studied using time-resolved photography and by PVDF film sensor glued on the solid boundary. The illumination was provided by high-power led diode. Synchronization of the system was provided by pulse generator connected to an oscilloscope. The impact power of the bubble to the wall was estimated from the time-resolved photography of the bubble and from the PVDF film sensor signal. The PVDF film sensor calibration was performed by a pendulum test to estimate the impact force.
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New trends in internet marketing.
Vaľková, Alexandra ; Štědroň, Bohumír (advisor) ; Kocour, Vladimír (referee)
This Master's Thesis describes the evolution of the Internet, its importance in marketing and new trends and tools used in internet marketing. It also deals with question of potential Internet collapse in future, describes variants of how it could happen and gives the suggestions to solve this problem, too. The Master's Thesis also includes forecasts of evolution of the Internet till 2030 and forecasts of major global agencies concerning the evolution of information technologies and technological news, which can significantly influence the entrepreneurial activity of many companies all over the world.
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PERTURBANCE ANALYSIS AND FISSION MODEL OF COLLAPSING BUBBLE
Petrík, P. ; Zima, Patrik ; Ridha, A.
A new criterion for the assessment of the reliability of the Rayleigh-Plesset equation is proposed. An analysis of the shape stability of the spherical surface of the bubble during the collapse is used to develop a physical model, which incorporates the loss of shape stability, surface energy dissipation and fission process. The model also estimates the number of bubble fragments as well as conditions for the fission to occur. Finally, some aspects of the numerical code, especially error estimation and propagation of rounding error, are discussed.
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COLLAPSE OF A CAVITATION BUBBLE GENERATED BY LOW VOLTAGE DISCHARGE IN WATER
Müller, M. ; Unger, J. ; Buďárek, T. ; Zima, Patrik
The article presents experimental results of the optical study of cavitation bubble collapse close to a solid boundary in water. The bubble was generated by discharge of two low-voltage capacitors. High-speed CCD camera was used to record the time evolution of the bubble size. High-power halogen lamp was used for illumination. The system was synchronized by pulse generator connected to an oscilloscope. The velocity of the re-entrant jet was estimated from the time resolved photography for three different maximum bubble sizes.
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Kavitační bublina v blízkosti pevné stěny
Müller, M. ; Zima, Patrik
The article presents the results of the calculation of the cavitation bubble collapse near a solid boundary. The solution is obtained using the FLUENT CFD software. The VOF (Volume Of Fluid) model is applied to study the behavior of the interphase between the liquid and the bubble content. The calculations were performed for three different distances of the bubble from the solid wall. The evolution of the bubble radius is obtained from the phase interface contours. The bubble jet velocity and its thickness are determined for all bubble positions.
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Stock Price Bubbles
Li, Xiaokun ; Musílek, Petr (advisor) ; Veselý, Marek (referee)
Economic bubbles are playing an increasingly significant role in the current global economy. We believe these bubbles are to a certain extent dominating the real economy, and, therefore, research based on this specific economic phenomenon is becoming increasingly popular and important. The focus of this master's thesis is based upon analysis of stock price bubbles. This thesis contains author analyzed historical cases representative of stock price bubbles; summarizations of their traditional features; common factors causing their formation; and reasons leading to their bursting. Solutions to the dilemma of stock price bubbles are discussed in depth, and emphasis is placed upon clearly deciphering different theoretical approaches regarding this phenomenon-not only from the efficient market hypothesis viewpoint but also from the perspective of behavioral finance. The research contains testing and measuring methodologies of stock price bubbles, and the author's view concerning them is strongly supported by the results within the empirical data-testing chapter. Upon reading, one can expect to achieve a basic overview of this forefront science.
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