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Design and construction of advanced LED lighting system for aquarium
Novák, Pavel ; Škoda, Jan (referee) ; Pavelka, Tomáš (advisor)
The first part of this thesis is devoted to the presentation of light and the basic quantities describing the light and its properties. These quantities are then used to describe the light sources, which is the thesis engaged in in the following section. The light sources are divided into thermal and luminescent. Then, there are described the basic parameters that are monitored when choosing the light source, such as luminous flux, color rendering index, correlated color temperature, mean lifetime, beam angle. Next, the thesis engages in solar radiation, spectrum of radiation, process and the color temperature of daylight and turns to the requirements for the aquarium lighting. According to the requirements for the aquarium lighting, the lighting design is done and it is sought an ideal solution for the aquarium lighting using LEDs. In conclusion of this thesis, there is designed an effective cooling for the LEDs in order to maintain their lifetime and luminous flux as long as possible. Then, it is designed and realized control of the LEDs by the pulse width modulation, prepared software for controlling the lighting depending on the daytime to meet the demands on the aquarium lighting while monitoring the process of the daylight and to look natural.
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Production of electricity from the vibration of the bicycle
Novák, Pavel ; Sobotka, Jiří (referee) ; Koutný, Martin (advisor)
The work is focused on methods of obtaining energy from the environment. In the project, there are summarized and generally described some methods of energy conversion. A more detailed description is aimed at a method on the principal of the Faraday's effect. The work involves a calculation of the electromagnetic generator with specific parameters, a simulation of the calculated generator and builds a real product on the basis of the previous theoretical calculation. The aim is to create a product that accumulates the energy obtained in the attached battery.
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In-situ Synthesised Intermetallic Compounds in Powder Materials
Hanusová, Petra ; Novák, Pavel (referee) ; Skotnicová, Kateřina (referee) ; Dlouhý, Ivo (advisor)
The mechanical treatment of solids is one of the most common and widely used operations. The volume of solids subjected to chemical treatment is very large too. Therefore, combining these two ways into one seems to be a logical solution. This method is called the mechanochemical processing of materials. Processing materials in this way has many advantages. On the one hand, this processing is economically as well as technologically feasible. Even the materials that not react together in conventional way can be prepare in this way. The mechanochemistry/mechanochemical synthesis utilizes the mechanical energy to activate chemical reactions and structural changes. The aluminothermic reduction reactions induced by the high – energy ball milling are gaining importance because of the potential applications like the synthesis of microcrystalline and nanocrystalline in – situ metal matrix composites. The mechanical activation of the chemical reactions by high energy ball milling often changes the reaction mechanism and produces metastable materials. Changes of reaction mechanisms during mechanical alloying on four different systems were studied. The system was based on this composition: Al - B2O3 - X (X = C, Ti, Nb, Cr). The possibility of another in – situ reactions during spark plasma sintering process (SPS) was also investigated. All systems were mechanically alloyed under the same conditions. After alloying, on each system scanning electron microscopy was performed and qualitative and quantitative analysis was performed using X-ray diffraction. The indentation hardness and the indentation modulus of elasticity were evaluated using nanoindentation. All analyzes were performed after mechanical alloying as well as SPS and the results were compared to each other. Based on the results, a change of reaction mechanisms was proposed for all systems. It has been found that metal matrix composites are formed and, when chromium is used, hybrid composite material reinforced with intermetallic phase and aluminum borate has been developed.
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Narrowband PLC modem
Novák, Pavel ; Koton, Jaroslav (referee) ; Mlýnek, Petr (advisor)
The theses is focused on the use of PLC technology. The aim of the thesis is creating device which communicates in a narrowband transmission frequency band. Transmission of communication between plc elements runs through the low voltage distribution network. The frequency and phase modulations are used in order to change the character of data signal. Transmitter and receiver parameters are subjects to the CENELEC standard. The theses gives more attention to the area of hardware build communication element rather than the area of programming.
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Control Unit for Church Bell Electric Drive
Bureš, Petr ; Novák, Pavel (referee) ; Šebesta, Jiří (advisor)
This work deals with analysis induction motors. There are described their principle and methods of starting, the engine controls and the stop braking. In terms of this study it was determined the engine controls type for control unit for church bell electric drive design. In next part there is complete hardware and software design of control unit.
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Powder Metallurgy of Hybrid Materials for Advanced Applications
Kozlík, Jiří ; Stráský, Josef (advisor) ; Kim, Hyoung Seop (referee) ; Novák, Pavel (referee)
Powder Metallurgy of Hybrid Materials for Advanced Applications The field-assisted sintering technology (FAST) is a versatile powder consolidation method, which uses electrical current for rapid heating of the sintered material. It is routinely used for sintering of various metallic materials, but mostly with preal- loyed powders as a feedstock. The aim of the thesis is to explore the capabilities of FAST for sintering of composite materials and for using blended elemental powders as a raw material in following areas: 1. Manufacturing of architectured composites 2. Consolidation and ageing in a single processing run (in-situ ageing) 3. Rapid alloy prototyping using blended elemental powders 4. High-throughput experimental investigations of multicomponent phase dia- grams Al6061 + Ti-6Al-4V architectured composite was produced, but issues with the pow- der penetration into the lattice have arisen due to the small lattice dimensions. Me- chanical properties could have been assessed by a three-point bending only. The composite has shown improved strength over the plain, unannealed Al6061 matrix, but a premature fracture when the Al matrix was aged properly. Using FAST was found to be inconvenient for architectured composite manufacturing. A long, fully dense rod was manufactured from the Ti-5Al-5V-5Mo-3Cr...
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GRAIL and LOLA Satellite Data Resolve the Long-Lasting Convergence/Divergence Problem for the Analytical Downward Continuation of the External Spherical Harmonic Expansions
Šprlák, Michal ; Han, Shin-Chan ; Pitoňák, Martin ; Novák, Pavel
Spherical harmonic expansions are routinely used to represent the gravitational potential and its higherorder spatial derivatives in global geodetic, geophysical, and planetary science applications. The convergence domain of external spherical harmonic expansions is the space outside the minimum Brillouin sphere (the smallest sphere containing all masses of the planetary body). Nevertheless, these expansions are commonly employed inside this bounding surface without any corrections. Justification of this procedure has been debated for several decades, but conclusions among scholars are indefinite and even contradictory. In this contribution, we examine the use of external spherical harmonic expansions for the gravitational field modelling inside the minimum Brillouin sphere. We employ the most recent lunar topographic LOLA (Lunar Orbiter Laser Altimeter) products and the measurements of the lunar gravitational field by the GRAIL (Gravity Recovery and Interior Laboratory) satellite mission. We analyse selected 39 http://dx.doi.org/10.13164/seminargnss.2023.38 quantities calculated from the most recent GRAIL-derived gravitational field models and forwardmodelled (topography-inferred) quantities synthesised by internal/external spherical harmonic expansions. The comparison is performed in the spectral domain (in terms of degree variances depending on the spherical harmonic degree) and in the spatial domain (in terms of spatial maps). To our knowledge, GRAIL is the first gravitational sensor ever, which helped to resolve the long-lasting convergence/divergence problem for the analytical downward continuation of the external spherical harmonic expansions, see [1].
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Validation of Satellite Gravitational Gradients Grids by Spectral Combination Method and GNSS/Levelling Data Over Norway, Czechia and Slovakia
Pitoňák, Martin ; Šprlák, Michal ; Ophaugh, Vegard ; Omang, Ove C. D. ; Novák, Pavel
The launch of gravity-dedicated satellite missions at the beginning of the new millennium led to an accuracy improvement of global Earth gravity field models (GGMs). One of these missions was the Gravity field and steady-state Ocean Circulation Explorer (GOCE) launched in 2009. As the first ESA's Earth Explorer Mission, the satellite carried a novel instrument, a 3-D gradiometer, which allowed to measure of second-order directional derivatives of the gravitational potential (gravitational gradients) 37 http://dx.doi.org/10.13164/seminargnss.2023.36 with uniform quality and near-global coverage. The main mission goal was to determine the static Earth's gravity field with the ambitious precision of 1-2 cm in terms of geoid heights and 1 mGal in terms of gravity anomalies for a spatial resolution of 100 km (half wavelength at the equator). More than three years of outstanding measurements resulted in three levels of data products (Level 0, Level 1b and Level 2), six releases of GGMs, and several global grids of gravitational gradients. The grids, which represent a step between gravitational gradients measured directly along the GOCE orbit and those represented by GGMs, were used mainly in geophysical applications. In this contribution, we validate the official Level 2 product GRD SPW 2 using height anomalies over two test areas in central and northern Europe (Czechia/Slovakia and Norway). A mathematical model based on the least-squares spectral weighting is employed with corresponding spectral weights estimated to validate gravitational gradient grids. This model continues gravitational gradients from the mean orbital altitude of GOCE down to the irregular Earth's surface (not to a sphere) and transforms them to height anomalies in one computational step. Analytical downward continuation errors of the model are estimated using a closed-loop test. Before comparing, height anomalies estimated from gravitational gradients with their reference values derived from GNSS/levelling over the two test areas, the gravitational gradients and reference data are corrected for all systematic effects, such as the tide system conversion. Moreover, the high-frequency part of the gravitational signal is estimated and subtracted from reference data as it is attenuated in the gravitational gradients measured by GOCE. A relative improvement between the release 6 and release 2 gradient grids reaches 48% in terms of height anomalies in Czechia/Slovakia. The relative improvement in Norway is even more significant and reaches 55%. Release 6 of the official Level 2 product GRD SPW 2 gained absolute accuracy with the standard deviation of 9.1 cm over Czechia/Slovakia and 9.6 cm over Norway.
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Far Zone Effects for Integral Transformations: Theory and Implementation
Trnka, Petr ; Belinger, Jiří ; Šprlák, Michal ; Pitoňák, Martin ; Novák, Pavel
Integral transformations are a useful mathematical apparatus for modelling the gravitational field and require the formulation of integral estimates including error propagation. For classical integral transformations, this issue has already been studied, but the formulation for all available gravitational observables has not been studied yet. The assumption of integral transformations is global data coverage. In practice, however, data availability is limited, so we divide the global integration into the effects of the near and far zones. The computation of distant zones is a non-negligible systematic effect requiring an accurate calculation. The theory is implemented in the form of a precise software. In this paper, we present the basic theory for the evaluation of the far zones. We also investigate properties of integral kernels and truncation error coefficients. In the numerical experiments, we compare calculation of the far zones by numerical integration with truncated spherical harmonic series. One of the outputs of this contribution is a software library for computation of the far zones for integral transformations mutually relating all quantities up to the third derivatives of the gravitational potential.
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The private Business in Czechoslovakia in the second half of the eighties
Novák, Pavel ; Štemberk, Jan (advisor) ; Šalanda, Bohuslav (referee)
The diploma thesis "Private business in Czechoslovakia in the second half of the eighties" focuses on the period of "perestrojka" in the conditions of socialist Czechoslovakia in the second half of the eighties. The aim of the thesis is to describe and especially evaluate the beginnings of private business in socialist Czechoslovakia at the end of the eighties. The research question then is whether this economic form of production and trade had any hope of greater development given the given political order. Derived questions are to what extent private business was successful, what and how big a response it evoked among the population and especially how it was accepted and evaluated by the ruling elite. The thesis traces the change in the attitude of the Communist Party of Czechoslovakia towards private business after Mikhail Gorbachev took over as General Secretary of the Central Committee of the Communist Party of the Soviet Union and the reconstruction of the economic mechanism announced by him both in the Soviet Union and in its satellites. The primary method will be work with archival materials from the National Archives of the Czech Republic, the Archive of the Security Forces and other state organizations, as well as work with information from the contemporary press. The secondary source...
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