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Image Quality Assessment across Imaging Modalities: Metric Design and Performance Evaluation
(Czech Technical University in Prague. Faculty of Electrical Engineering. Department of Radioelectronics., 2026) Fliegel, K.
This habilitation thesis comprises ten works published over the past decade and a unifying commentary on objective image quality assessment across processing operations and imaging modalities. The research was collaborative, particularly with doctoral students supervised by the author. The thesis links the evaluation, design, adaptation, and application of quality measures. Receiver operating characteristic analysis assesses whether measures can detect statistically supported differences in perceived quality and identify the preferred image. Bootstrap resampling and Monte Carlo simulation propagate uncertainty in subjective scores and, optionally, dataset composition into distributions of correlation coefficients and metric rankings. Enhancement studies examine the transition from beneficial sharpening to over-sharpening and how content and reference conditions influence tone-mapping preferences. They contribute subjective datasets, adaptations of a sharpness measure, and an interpretable model combining complementary features to assess the quality of natural tone-mapped images. Fidelity to an unprocessed source alone cannot describe perceived quality after enhancement. Light-field studies show that measures predicting perceived quality need not predict disparity-map quality. High average view fidelity can coexist with non-uniform quality across views and changes in face-recognition performance and estimated disparity. An interpretable model combines complementary measures to predict the perceived quality of compressed omnidirectional images. Evaluation on two databases combines decision-oriented and uncertainty-aware analyses and distinguishes transfer of a fixed model from adaptation. Further contributions include a subjectively annotated dataset of distorted light fields and comparisons of measures for lossily compressed omnidirectional images. A key community contribution is QUALINET Databases, supporting resource discovery and reuse. Supporting studies in film digitisation, restoration, and projection relate perceived differences and their acceptability to colourimetric measurement, metric performance, and presentation conditions. They distinguish measurement-based comparison from historical and artistic judgement in defining a restoration target. Perceived quality, signal fidelity, and task performance are related but distinct assessment targets. The measure, reference evidence, and validation conditions must match the target property.
Planning and control for agile flight of unmanned aerial vehicles
(Czech Technical University in Prague. Faculty of Electrical Engineering. Department of Cybernetics., 2026) Pěnička, R.
This habilitation thesis presents the research contributions of the author in mission planning, path and trajectory planning, and control for agile flight of Unmanned Aerial Vehicles (UAVs). The studied problem is how to make a UAV carry out a useful mission, such as scanning a given area or searching a building, as quickly and as efficiently as possible. At the same time, the vehicle has to fly safely and autonomously through a real environment. The three studied topics form a large part of the autonomy pipeline that turns a mission specification into the actuator commands of a real quadrotor. The common goal of the presented contributions is to narrow the gap between the high-level mission planning and the low-level control. This allows planning a mission while considering the dynamics model of the vehicle, replanning a trajectory at the rate at which the control runs, and keeping the flight collision-free even when the reference trajectory cannot be tracked precisely. In mission planning, the proposed multi-tree planners find the cheapest order in which to visit a set of target locations among obstacles. They do so both for a geometric vehicle model and under its full dynamics. Further contributions address the energy-aware coverage of an area by a team of UAVs and the task allocation in a cooperative construction mission. In path planning, the proposed methods search for topologically distinct paths through an environment, i.e., paths that pass the obstacles in distinct ways. They find considerably more of such paths than the state-of-the- art methods. They also reduce the planning time for new, unseen robot shapes by reusing a library of previously found paths. In trajectory planning, the proposed minimum-time waypoint planners find trajectories that are only a few percent slower than the time-optimal solutions. While the proposed planners require an order of magnitude less computation time or even units of milliseconds, the time-optimal solutions take hours to compute. In control, the usual assumption that the planned reference stays collision-free is relaxed. The proposed sampling-based controller reaches the tracking accuracy of obstacle-blind control while avoiding obstacles online at high speed. A learned policy that drops the reference trajectory altogether then flies tracks cluttered with obstacles faster than the state-of-the-art methods and without a collision. The majority of the methods were validated in real-world flights, some of them reaching speeds over 100 km h−1 and accelerations of 3.5 g. Most of them were released as open-source software and are accompanied by videos of the experiments. The thesis also presents two open-source platforms that make the methods deployable in the real world.
Long-term monitoring of concrete structures (temperatures and volumetric changes)
Dlouhodobé sledování betonových konstrukcí (teploty a objemové změny)
(Czech Technical University in Prague) Němčic, Vít; Vítek, Jan; Kolísko, Jiří; Coufal, Robert; Klusáček, Ladislav
Increasing demands on load-bearing capacity, durability and other performance properties of structures, together with economic requirements and principles of sustainable construction, are leading to the use of new materials and new technologies. Concrete is one of the building materials that has a high potential for modifying its properties. Depending on the requirements on elements or structures, a variety of concrete properties can be achieved by choosing suitable raw materials and selecting an appropriate technology. The issue of massive concrete bridge structures and monitoring of their deformation is an important area. Optimum materials must be sought for such structures, as conflicting demands are often placed on these structures. On one hand, a reduction of temperatures from heat of hydration, requires a limited amount of cement and on the other hand, acceleration of the construction process, rapid increase of concrete strength and early demoulding are required. The aim of the PhD thesis was to summarize the research results in the area of monitoring the evolution of temperatures induced by heat of hydration and in the area of volume changes in massive concrete structures.
Validation of an edge turbulence code in the Compass tokamak
(Czech Technical University in Prague) Mácha, Petr; Seidl, Jakub; Stegmeir, Andreas; Tichý, Milan
The thesis validates and compares fluid models of turbulence in the edge plasma of the COMPASS tokamak. The three-dimensional GBS and GRILLIX codes and the reduced DIFFLOW ESEL-like model are compared with experimental measurements. The models reproduce plasma profiles and fluctuations well, with GRILLIX providing the best description of blob dynamics and DIFFLOW enabling rapid GPU calculations. The observed discrepancies highlight the importance of boundary conditions and plasma-wall interaction modeling. The thesis also describes the spontaneous formation of a transport barrier in helium plasma on the GOLEM tokamak.
Effect of Protective Coating on High Temperature Corrosion of Zr Alloys
Vliv ochranného pokrytí na vysokoteplotní korozi Zr slitin
(Czech Technical University in Prague) Celbová, Lucie; Kratochvílová, Irena; Lovecký, Martin; Novotný, Radek
This thesis investigates high-temperature steam oxidation of nuclear fuel cladding ZIRLO coated with polycrystalline diamond (PCD), magnetron-sputtered Cr (CrPVD), cold-sprayed Cr (CrCS), and double layers (ZIRLO/PCD/CrPVD, ZIRLO/PCD/CrCS) under LOCA-relevant conditions (900°C/30 min1000°C/30 min) and provides an explanation of the carbon protective effect in the ZIRLO/PCD system. The thesis structure includes an introduction to the motivation for accident tolerant fuel coatings, a literature review on Zr alloy corrosion, chromium and PCD coatings, experimental methods, results, discussion, and conclusions. At the explored conditions, PCD offers modest protection but suppresses breakaway oxidation. Absolute weight gains for ZIRLO/PCD/CrPVD and ZIRLO/PCD/CrCS exceed those of Cr-only coated counterparts. Carbon gasifies during the ramp to 1000°C, yet ZIRLO/PCD/CrPVD significantly softens the aggressive breakaway observed in ZIRLO/CrPVD. A comprehensive Raman study of ZrO2 scales formed on ZIRLO under steam oxidation at LOCArelevant transient conditions (900°C/30 min1000°C/30 min) is presented. The work spatially maps the quasielastic scattering (QES) tail in zirconia scales and reveals its two different sources, resolves the distributions of defective tetragonal-like (140 cm1) and classic tetragonal (260 cm1) modes, reports the 800 cm1 mode in steam-corroded ZrO2, and demonstrates widespread boson peak occurrence in an industry-relevant nuclear oxide system. The 140 cm1 peak is identified as a softened vibration of oxygen-deficient tetragonal-like Zr coordination. Secondary-phase particle is captured modulating the vacancy distribution and creating diffusion shadow with reduced defect signatures when in particular conditions. Analysis of previously published data reveals that in the case of PCD coated ZIRLO exposed to 400°C steam, carbon diffuses into ZrO2 grain boundaries under the vacancy flux present at the metal/oxide interface. Numerical modeling based on Fromholds theory and carbon-induced potential landscapes reproduces the weight gain experimental values under the assumption of anisotropic carbon transport. Two approaches for achieving sub-parabolic kinetics in the Fromholds framework are discussed.The PCD layer in the ZIRLO/PCD system strongly modulates hydrogen behavior. It retains excess hydrogen at lower temperatures while releasing it as hydrocarbons at high temperatures, resulting in significantly lower overall hydrogen concentration compared to bare ZIRLO at high temperatures (despite similar corrosion rates). However, ultimately, the corrosion rate reduction in the ZIRLO/PCD systems prior to transition is attributed to carbon diffused and bonded to ZrO2 grains, not the PCD layer itself. The absence of protection at high temperatures results from rapid ZrO2 growth limiting carbon transport into the oxide. An optimal balance between vacancy flux and carbon diffusion, dependent on temperature and surface sp2 carbon concentration, is expected. Carbon bonded in between layers of fine-grained ZrO2 (which are parallel to the direction of oxide growth) is expected to promote the protective behavior. Future work should identify conditions optimizing these structures that do not compromise the overall integrity of the resulting system and should be concerned with the behavior of such pre-oxidized PCD coated samples at high temperatures ( 1000°C) with the emphasis on carbon evolution in such environments.