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Path Planning in 3D Space
Němec, František ; Samek, Jan (referee) ; Rozman, Jaroslav (advisor)
This paper deals with the problem of object path planning in 3D space. The goal is to create program which allows users to create a scene used for path planning, perform the planning and finally visualize path in the scene. Work is focused on probabilistic algorithms that are described in the theoretical part. The practical part describes the design and implementation of application. Finally, several experiments are performed to compare the performance of different algorithms and demonstrate the functionality of the program.
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Public Transport Simulation in Brno
Němec, František ; Král, Jiří (referee) ; Rozman, Jaroslav (advisor)
The goal of this thesis is to design and implement public transport simulator in Brno. Information about the departure times and routes of each public transport lines are extracted from online traffic timetables. Data from which traffic network is generated are obtained from OpenStreetMap project. The thesis contains a description of the basic approaches to create traffic simulators, especially the description of the microscopic approach on which is this simulator based. The second part of thesis includes the design and implementation of simulator, whose main components are ways of traffic management, representation of transport networks and the generation of OpenStreetMap data.
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Využití laserového skenování k dokumentaci současného stavu dřevěné zvonice
Němec, František
This bachelor thesis deals with the use of laser scanning technology to document historical buildings. Its aim is to create a 3D model, floor plans and vertical sections for the needs of the National Heritage Institute and the township of Knínice. The thesis describes the procedure for using laser scanning, all the necessary tasks that must be performed before the actual scanning, as well as the method of subsequent processing of the scanned data and creating the model in the software chosen for this purpose. The result of the work is a digital 3D model of a wooden belfry, floor plans and vertical sections showing the position of individual elements in the structure and a technical description of the object. These results can be used for archiving this historical cultural monument, its possible future reconstruction or even restoration.
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Study of ionospheric variability
Mošna, Zbyšek ; Koucká Knížová, Petra (advisor) ; Truhlík, Vladimír (referee) ; Němec, František (referee)
High variability of the ionosphere is connected to geomagnetic, solar, and neutral atmosphere wave activity. Results of scaling analysis of solar data (F10.7, SSN), geomagnetic indices (Dst, Kp, AE), and ionospheric critical frequencies (foF2) show similar structure of Kp, AE and foF2 at periods in the range from 4 to 32 days. Data structure depends on the location of ionospheric stations. Correlation coefficients between foF2 and geomagnetic and solar indices depend on length of time scale. We show that vertical coupling exists between neutral atmosphere activity and sporadic E layer area. This connection is located predominantly on periods corresponding to internal modes of planetary waves. Interplanetary magnetic field discontinuities (Coronal mass ejections, Magnetic clouds, Hight speed solar streams) affect strongly the ionosphere. Analysed events lead to lowering of foF2, increase in heights of the layer F2 and oscillations of hmF2 and foF2 on periods in the order of hours. Powered by TCPDF (www.tcpdf.org)
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Multicomponent wave measurements performed by the DEMETER spacecraft
Kotková, Marie ; Němec, František (advisor) ; Chum, Jaroslav (referee)
We analyze data from wave measurements performed by the DEMETER spacecraft in the frequency range up to 1250 Hz. We investigate the dependence of wave parameters on daytime, geomagnetic latitude, geomagnetic activity, and season, both globally and in the geomagnetic longitude range corresponding to America, where there is a substantial seasonal variation in lightning occurrence. We show that, during the day, there is generally a prevalence of waves propagating from larger radial distances, i.e. generated by plasma instabilities; during the night, the situation is opposite, indicating a prevalence of waves generated by lightning activity. The difference in wave vector directions detected above America is the largest between winter days during elevated geomagnetic activity and summer nights during low geomagnetic activity. We use the typical wave vector directions to trace back the tentative source region of the waves detected during the daytime half-orbits.
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Significant boundaries around Mars: magnetic pileup boundary and bow shock
Linzmayer, Václav ; Němec, František (advisor) ; Pitňa, Alexander (referee)
The main objective of this thesis is to use the data measured by the MAVEN spacecraft and machine learning methods to develop models of the locations of bow shock and magnetic pileup boundary. Characteristic values of density, flow speed, and magnetic field magnitude in solar wind, magne- tosheath, and magnetosphere allows an automatic classification of measured data into respective regions using the SVM method, as well as the identi- fication of the boundary crossings. Models of the two boundaries based on multilayer neural networks are then developed. Two different approaches are used: i) model based directly on the classification of individual regions, and ii) model using only the identified boundary crossings. The accuracy of the developed models is validated both by using individual boundary crossings and by a comparison with former empirical models. 1
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Solar wind variability close to the Lagrange L1 point
Drastichová, Kristýna ; Němec, František (advisor) ; Gončarov, Oleksandr (referee)
In the near future, the European space agency (ESA) is planning a space mission with objective to detect gravitational waves in the frequency range 10-4 Hz - 10-1 Hz (LISA mission). The detection of the gravitational waves is going to be carried by three spacecraft acting like a large interferometer. Omnipresent solar wind plasma could have a negative impact on the measurements. In this thesis, we analyze the temporal and spatial varibility od the solar wind near the Lagrange point L1. Both single-point and two-point measurements provided by several different spacecraft (Wind, ACE, STEREO) are used to determine the appropriate spatial and temporal scales.
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Fine structure of quasiperiodic emissions observed in the Earth's magnetosphere
Partík, Vojtěch ; Němec, František (advisor) ; Bezděková, Barbora (referee)
Title: Fine structure of quasiperiodic emissions observed in the Earth's magne- tosphere Author: Vojtěch Partík Supervisor: doc. RNDr. František Němec, Ph.D. Abstract: Quasiperiodic emissions are a type of electromagnetic waves detected in the Earth's inner magnetosphere which are not yet fully understood. In this thesis, we use high resolution electric field data obtained by the DEMETER satellite, at an altitude of about 700 km, to analyze their fine inner structure. Overall, we analyzed 251 events, which were classified into three categories (with fine inner structure, without fine inner structure, and borderline cases). Additionally, we determined the periods of the fine inner structure and studied their dependance on relevant parameters. We show that the periods of the fine inner structure (on the order of seconds) do not significantly change during individual events and they are typically larger for events with longer modulation periods. We also show that the modulation periods of events without the fine inner structure are longer than the modulation periods of events with the fine inner structure, indicating their possibly different generation mechanisms. Keywords: DEMETER, quasiperiodic emissions, spectral analysis
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Lightning activity accompanying tropical cyclones
Rosická, Kateřina ; Kolmašová, Ivana (advisor) ; Němec, František (referee)
This thesis is focused on study of properties of the lightning strokes accompanying tropical cyclones. We investigated lightning densities, median energies of lightning strokes, their multiplicity, radial distribution of lightning and a correlation of lightning activity with the development of the cyclone wind speed. We used 429 cyclones occuring all over the world in the period 2012-2017 and lightning data provided by WWLLN (World Wide Lightning Location Network). We found substantial differences in the lightning densities and energies when comparing cyclones of different intensities appearing in both hemispheres and individual basins. Radial distribution of lightning in the cyclones shows a strong maximum of the stroke density and a minimum of the median stroke energy near the center of the cyclone. The increase in the lightning density often preceded the increase of wind, but the time interval between them varied substantially when considering the cyclone intensity and the hemisphere of cyclone occurrence. The analysis of properties of lightning accompanying nearly five hundred tropical cyclones (the largest data set so far) revealed that there isn't a fix delay between the time of the maximum lightning activity and the time of the maximum wind speed which can be globally used for predictions of the...
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Empirical modeling of the location of the Earth's magnetopause
Machková, Anna ; Němec, František (advisor) ; Grygorov, Kostiantyn (referee)
This bachelor thesis focuses on suggesting possible improvements of the existing models of the magnetopause stand-off distance, i.e., on identification of the parameters which are not properly (or not at all) included. Magnetopause is a border between the terrestrial and interplanetary magnetic fields, where the pressure of the Earth's magnetic field balances the solar wind dynamic pressure. In order to analyze the parameters, which have an influence on the magnetopause radial distance, we perform a systematic study of an existing database of 16800 magnetopause crossings registered by 8 different satellites. We focus on the effect of the topology of the terrestrial magnetic field, which is not perfectly dipolar, and whose values close to the subsolar point exhibit significant diurnal and annual variations. Another analyzed phenomenon is the magnetospheric ring current and its influence on the magnetic field strength near the magnetopause. Possible changes of this magnetic field have a direct influence on the magnetopause distance from the Earth. Attention is also devoted to the potentially different positions of the magnetopause at the times of fast and slow solar wind. Finally, we discuss complications related to the satellite orbits and the resulting uneven spatial distribution of the used data set.
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