LONG–TERM AUTONOMY OF MOBILE ROBOTS IN CHANGING ENVIRONMENTS
Krajník, Tomáš
2018 - English
This habilitation thesis presents research that aims to enable long-term deployment of
mobile robots in changing environments. The presented approaches encompass methods
that ensure robustness of autonomous visual navigation in outdoor environments for prolonged
time periods, spatio-temporal representations that explicitly model the environment
changes over time, and supporting software modules that enable robust and accurate robot
localisation.
The main contribution of the thesis is a novel approach that allows to incorporate
the notion of time into most stationary environment models used in mobile robotics.
This is achieved by representing the uncertainty of the environment states not by fixed
probabilities, but by probabilistic functions of time, represented in the frequency domain.
The method allows to integrate unlimited numbers of sparse and irregular observations
obtained during long-term deployments of mobile robots into memory-efficient models that
reflect the persistence and recurrence of environment variations. The frequency-enhanced
spatio-temporal models allow to predict the future environment states, which improves the
efficiency of mobile robot operation in changing environments. In this thesis, we present a
series of articles, which demonstrate that the proposed approach improves mobile robot
localization, path and task planning, activity recognition, human-robot interaction and
allows for life-long spatio-temporal exploration of perpetually-changing environments.
Available in digital repository of ČVUT.
LONG–TERM AUTONOMY OF MOBILE ROBOTS IN CHANGING ENVIRONMENTS
This habilitation thesis presents research that aims to enable long-term deployment of mobile robots in changing environments. The presented approaches encompass methods that ensure robustness of ...
Challenges and Open Questions of Machine Learning in Computer Security
Pevný, Tomáš
2018 - English
This habilitation thesis presents advancements in machine learning for computer security,
arising from problems in network intrusion detection and steganography.
The thesis put an emphasis on explanation of traits shared by steganalysis, network intrusion
detection, and other security domains, which makes these domains different from
computer vision, speech recognition, and other fields where machine learning is typically
studied. Then, the thesis presents methods developed to at least partially solve the identified
problems with an overall goal to make machine learning based intrusion detection
system viable. Most of them are general in the sense that they can be used outside intrusion
detection and steganalysis on problems with similar constraints.
A common feature of all methods is that they are generally simple, yet surprisingly
effective. According to large-scale experiments they almost always improve the prior art,
which is likely caused by being tailored to security problems and designed for large volumes
of data.
Specifically, the thesis addresses following problems:
anomaly detection with low computational and memory complexity such that efficient
processing of large data is possible;
multiple-instance anomaly detection improving signal-to-noise ration by classifying
larger group of samples;
supervised classification of tree-structured data simplifying their encoding in neural
networks;
clustering of structured data;
supervised training with the emphasis on the precision in top p% of returned data;
and finally explanation of anomalies to help humans understand the nature of anomaly
and speed-up their decision.
Many algorithms and method presented in this thesis are deployed in the real intrusion
detection system protecting millions of computers around the globe.
Available in digital repository of ČVUT.
Challenges and Open Questions of Machine Learning in Computer Security
This habilitation thesis presents advancements in machine learning for computer security, arising from problems in network intrusion detection and steganography. The thesis put an emphasis on ...
TEXTILE-BASED STRUCTURES IN ELECTRONIC AND COMMUNICATION ENGINEERING
Vojtěch, Lukáš
2017 - English
This thesis deals with the search for and formulation of a theoretical approach to modelling the electrical conductivity of woven textiles and the experimental validation of the approach by measurements performed on woven textile samples. Drawing on these results, the thesis goes on to determine the electromagnetic shielding efficiency of nonhomogeneous 3D structures using modified approaches and succeeds in finding a new analytical description of the electromagnetic shielding efficiency of electrically conductive woven textiles. The proposed description applies to selected types of conductive woven textiles. The author’s basic observation is that woven textiles are structurally similar to metallic grids. The proposed modelling method was analytically validated for the different conductivity values of the yarns used; experimental validation was performed as well. This led to the identification of a set of usable conductivity values for yarns, for which these approaches are valid within a given error. In view of the new approaches to modelling the electrical conductivity and electromagnetic shielding efficiency of conductive textiles presented in this thesis, it is believed that these findings will significantly contribute to the body of interdisciplinary research and applications at the boundary between electrical engineering and materials science. The thesis describes the experiments performed and the development of applications of the proposed materials that span various branches of electronics and communications technologies and demonstrate application potential. The example and experiments presented here will certainly help the reader appreciate the scope and application potential of these materials, especially in the context of interdisciplinary cooperation. The thesis is also meant to serve as learning material for students and to be used for teaching purposes and scientific education in general.Tato habilitační práce se věnuje nejprve nalezení a odvození teoretického postupu modelování elektrické vodivosti tkaných textilií. Tento návrh je následně experimentálně ověřen, pomocí měření na vyrobených vzorcích. S využitím těchto výsledků práce pokračuje využitím modifikovaných postupů odvození elektromagnetické stínící účinnosti nehomogenních 3D struktur, kdy se podařilo dospět k novému způsobu analytického popisu elektromagnetické stínící účinnosti elektricky vodivých tkaných textilií. Navržený popis platí pro vybrané typy elektricky vodivých textilií, realizovaných technologií tkaní. Základním využitým pozorováním, je podobnost struktur tkaných textilií a mřížkových struktur na bázi kovových prvků. Navržený postup modelování je analyticky ověřen pro různé hodnoty elektrické vodivosti použitých přízí, zároveň je provedeno i ověření v experimentu. Výsledkem je nalezení oboru hodnot použitelných elektrických vodivostí přízí, pro které tyto postupy platí s danou chybou.
Z pohledu v této práci publikovaných nových postupů modelování elektrické vodivosti i elektromagnetické stínící účinnosti elektricky vodivých tkaných textilií, se jedná o soubor nových poznatků, které významně přispívají k rozvoji mezioborových znalostí a aplikací na rozhraní elektrotechniky a materiálového inženýrství. V práci jsou uvedeny také realizované experimenty i výsledky výzkumu a vývoje aplikací navrhovaných typů materiálů, které pokrývají různé oblasti elektroniky a komunikační techniky, s potenciálem jejich užití v praxi. Publikované příklady a experimenty jistě pomohou čtenáři lépe pochopit rozsah a potenciál aplikací těchto materiálů, zejména v kontextu mezioborové spolupráce. Práce si zároveň klade za cíl působit i jako didaktická podpora a umožnit další využití textu pro výukové a vědecké účely.
Keywords:
Electrically conductive textile; Electrical conductivity; Electromagnetic shielding efficiency; Communication engineering; Interdisciplinary research and application; Elektricky vodivé textilní materiály; Elektrická vodivost; Elektromagnetická stínící účinnost; Komunikační technika; Mezioborový výzkum a aplikace
Available in digital repository of ČVUT.
TEXTILE-BASED STRUCTURES IN ELECTRONIC AND COMMUNICATION ENGINEERING
This thesis deals with the search for and formulation of a theoretical approach to modelling the electrical conductivity of woven textiles and the experimental validation of the approach by ...
Energy and Economic Efficiency
Bemš, Július
2017 - English
Available in digital repository of ČVUT.
Energy and Economic Efficiency
Spectroscopy of the optical absorption edge of solar cell materials
Holovský, Jakub
2017 - English
The focus of this thesis is relatively narrowly defined as spectroscopy of the optical absorption edge of the actual or potential photovoltaic materials. This includes the spectroscopy methods and interpretation of results, the photovoltaic materials and their technological parameters and also the potential of certain photovoltaic technologies as a renewable source of energy.
The materials presented here are either absorbers: amorphous silicon (a-Si:H), microcrystalline silicon, organo-metalhalide perovskites (CH3NH3PbI3) or materials for transparent electrodes: graphene, amorphous InZnO and amorphous ZnSnO. The physical effects studied are related to material preparation methods, ageing, exposure to light, and annealing.
The methods employed here for the absorption spectroscopy are photothermal deflection spectroscopy and photocurrent spectroscopy. The two methods are briefly explained and compared. Two main issues related to correct interpretation of these measurements are discussed: effect of surface states and the effects of light scattering.
The absorption spectrum in sub-bandgap region is measured to obtain mainly the slope of the absorption edge parametrized by Urbach energy. It is shown here, how theoretically and practically this parameter correlates with the maximum attainable efficiency of solar cell – if the material is used as absorber. If the material is used as transparent electrode, correlation with conductivity is found.
The effect of cost evolution in the photovoltaic industry is discussed with the consequence on the efficiency as a most critical parameter dictating the cost of energy. The competitiveness of the solar energy is reviewed for different levels of autonomy.
Keywords:
solar cells; photovoltaics; photocurrent spectroscopy; photothermal spectroscopy; Urbach energy; sub-bandgap absorption
Available in digital repository of ČVUT.
Spectroscopy of the optical absorption edge of solar cell materials
The focus of this thesis is relatively narrowly defined as spectroscopy of the optical absorption edge of the actual or potential photovoltaic materials. This includes the spectroscopy methods and ...
Analysis of Heterogeneous Biomedical Data
Novák, Daniel
2016 - English
Available in digital repository of ČVUT.
Analysis of Heterogeneous Biomedical Data
Integrace systémů osobní dopravy - technologie provozu přestupních uzlů
Bulíček, Josef
2015 - Czech
Soubor publikovaných vědeckých prací je zaměřen na vybraná témata z oblasti přestupních uzlů veřejné hromadné osobní dopravy. Předmětem řešení je vedení linek veřejné hromadné osobní dopravy v hvězdicovitém uspořádání, aspekty zastavování a projíždění spojů, problém sjíždění spojů na stanovištích v terminálech veřejné hromadné osobní dopravy, přípojové vazby v případě nemožnosti vytvoření uzlu ITJŘ z důvodu nedostatečně dlouhého pobytu spojů pro obousměrný přestup a simulační posouzení přestupních uzlů v kontextu spolehlivosti přestupních vazeb. Využity jsou metody dopravního modelování, včetně modelu v softwaru OmniTRANS a simulačního modelu vytvořeného autorem v prostředí Microsoft Excel. Návrhy řešení jsou zaměřeny jak na možnosti prohloubení vyhodnocovacích přístupů a nástrojů, tak na možnosti zlepšení v praxi. Stěžejním kritériem, zejména závěrečné části, je provozní spolehlivost.
Keywords:
jízdní řády; provozní spolehlivost; přestupní uzly; simulace; veřejná hromadná doprava; time schedules; operational reliability; interchanging nodes; simulation; public mass transport
Available in the UPCE Library.
Integrace systémů osobní dopravy - technologie provozu přestupních uzlů
Soubor publikovaných vědeckých prací je zaměřen na vybraná témata z oblasti přestupních uzlů veřejné hromadné osobní dopravy. Předmětem řešení je vedení linek veřejné hromadné osobní dopravy v ...
Flashover performance investigation of polluted and ice covered insulators exposed to the transient overvoltages
Prochazka, Radek
2015 - English
Available in digital repository of ČVUT.
Flashover performance investigation of polluted and ice covered insulators exposed to the transient overvoltages
Habilitační práce
Zimmermann, Karel
2015 - English
Available in digital repository of ČVUT.
Habilitační práce
Geometry of Perspective Cameras – An Algebraic Approach
Pajdla, Tomáš
2015 -
Available in digital repository of ČVUT.
Geometry of Perspective Cameras – An Algebraic Approach
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