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Passive and active safety features in passenger cars
Jahoda, Patrik ; Kučera, Pavel (referee) ; Píštěk, Václav (advisor)
This bachelor thesis deals with safety elements of all kinds in personal vehicles and their general introduction. This elements are divided and broadened and roughly described. My work contains short summary of history of safety elements. Conclusion contains evaluation of individual elements. Video with crash test is inserted in this graduate work.
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Better Chaperone Bounds Using 3D Sensors
Tinka, Jan ; Beran, Vítězslav (referee) ; Najman, Pavel (advisor)
Room-scale tracking encourages users to move more freely and even walk. Even though there has been much research on making the limited physical workspace feel larger in the VR, these approaches have their limitations and require certain conditions to be met. This thesis proposes an alternative approach to the conventional play-area boundaries of high-end VR products such as the HTC Vive and Oculus Rift which are set by the user in a 2-D fashion as a means of enhance workspace utilization. A 3-D scanner is used to make a 3-D point-cloud model of the play area's surroundings. This model is then used to detect collisions and provide feedback to the user. Evaluation based on user tests showed that this approach can be useful, is well accepted by users and might be worth further research.
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Hash functions - characteristics, implementation and collisions
Karásek, Jan ; Sobotka, Jiří (referee) ; Lambertová, Petra (advisor)
Hash functions belong to elements of modern cryptography. Their task is to transfer the data expected on the entry into a unique bite sequence. Hash functions are used in many application areas, such as message integrity verification, information authentication, and are used in cryptographic protocols, to compare data and other applications. The goal of the master’s thesis is to characterize hash functions to describe their basic characteristics and use. Next task was to focus on one hash function, in particular MD5, and describe it properly. That means, to describe its construction, safety and possible attacks on this function. The last task was to implement this function and collisions. The introductory chapters describe the basic definition of hash function, the properties of the function. The chapters mention the methods preventing collisions and the areas were the hash functions are used. Further chapters are focused on the characteristics of various types of hash functions. These types include basic hash functions built on basic bit operations, perfect hash functions and cryptographic hash functions. After concluding the characteristics of hash functions, I devoted to practical matters. The thesis describes the basic appearance and control of the program and its individual functions which are explained theoretically. The following text describes the function MD5, its construction, safety risks and implementation. The last chapter refers to attacks on hash functions and describes the hash function tunneling method, brute force attack and dictionary attack.
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Species-specific and individual predictors of birds' collisions with glass obstacles in the Czech Republic
Semeráková, Anna ; Sedláček, Ondřej (advisor) ; Viktora, Lukáš (referee)
Recent landscape transformation is associated with the emergence of various artificial obstacles that change the natural form of habitats and biocorridors of free-ranging animals. Glass obstacles represent a particular problem due to their transparency and reflectivity. Collisions with glass represent one of the most significant causes of bird mortality worldwide, accounting for over hundreds of millions bird deaths annually. Many authors consider this source of mortality to be completely non-selective. In that case, total collisions mortality would represent a function of population size. However, here I assume that the relationship between collision mortality and population size is more complex and that certain avian ecological groups may be differently susceptible to glass collisions based on their specific ecological characteristics. Long-term records of bird-glass collisions in the Czech Republic were provided by the Czech faunistic databases. These records were compared with the population size of analysed species and with selected ecological and morphological species characteristics. Consistently with the premise, I found out that the greatest amount of collision mortality is explained by the species' population size. However, other species characteristics, such as higher body weight,...
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Properties of near-horizon geometry of spacetimes
Daněk, Jiří ; Žofka, Martin (advisor) ; Svítek, Otakar (referee)
Nowadays, the near-horizon regions of black holes have enjoyed great attention thanks to their role in the popular AdS/CFT correspondence and their specific geometry suitable for formulations of uniqueness theorems in higher dimensions. A strictly general-relativistic point of view reveals also many interesting phenomena taking place near black-hole horizons. Our aim was to investigate how horizon multiplicity affects near-horizon geometry, geodesical distance, radial motion of photons and massive, charged particles, and also the possibility of collision processes leading to unbound collision energies near the horizon. We chose the Reissner-Nordström-de Sitter metric, which, on the one hand, is simple thanks to being static and spherically symmetric but which, on the other hand, is rich enough to enable the existence of up to a doubly degenerate ultra-extreme horizon. After discussing the physical feasibility of the near-horizon limit, we applied it to single, double, and triple horizons, their near-horizon geometries, and local collision processes. We found continuous coordinate systems covering all types of horizons and analytic solutions for motion of radial photons and special or critical, massive, charged particles in their vicinity. We addressed particle collisions in the immediate vicinity of horizons...
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Interactions of migrating giant planets and small solar-system bodies
Chrenko, Ondřej ; Brož, Miroslav (advisor)
Changes of semimajor axes of giant planets, which took place 4 billion years ago and evolved the Solar System towards its present state, affected various populations of minor Solar-System bodies. One of these populations was a group of dynamically stable asteroids in the 2:1 mean-motion resonance with Jupiter which reside in two islands of the phase space, denoted A and B, and exhibit lifetimes comparable to the age of the Solar System. The origin of stable asteroids has not been explained so far. Our main goal is to create a viable hypothesis of their origin. We update the resonant population and its physical properties on the basis of up-to-date observational data. Using an N-body model with seven giant planets and the Yarkovsky effect included, we demonstrate that the depletion of island A is faster compared to island B. We then investigate: (i) survivability of primordial resonant asteroids and (ii) capture of the population during planetary migration, using a recently described scenario with an escaping fifth giant planet and a jumping-Jupiter instability. We employ simulations with prescribed migration, smooth late migration and we statistically evaluate the results using dynamical maps. We also model collisions during the last 4 billion years. We conclude that the long-lived group was created by a...
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Better Chaperone Bounds Using 3D Sensors
Tinka, Jan ; Beran, Vítězslav (referee) ; Najman, Pavel (advisor)
Room-scale tracking encourages users to move more freely and even walk. Even though there has been much research on making the limited physical workspace feel larger in the VR, these approaches have their limitations and require certain conditions to be met. This thesis proposes an alternative approach to the conventional play-area boundaries of high-end VR products such as the HTC Vive and Oculus Rift which are set by the user in a 2-D fashion as a means of enhance workspace utilization. A 3-D scanner is used to make a 3-D point-cloud model of the play area's surroundings. This model is then used to detect collisions and provide feedback to the user. Evaluation based on user tests showed that this approach can be useful, is well accepted by users and might be worth further research.
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QCD factorization at forward rapidities
Nemchik, J. ; Šumbera, Michal
We analyze several reactions on nuclear targets at forward rapidities and different energies (at smallest experimentally accessible Bjorken x(2) in the target). Nuclear effects are then usually interpreted as a result of shadowing or the Color Glass Condensate. QCD factorization of soft and hard interactions requires the nucleus to be an universal filter for different Fock components of the projectile hadron. We demonstrate, however, that this is not the case in the vicinity of the kinematic limit, Feynman x(F) -> 1, where sharing of energy between the projectile constituents becomes an issue. The rise of suppression with x(F) is confirmed by the E772 and E886 data on the Drell-Yan and heavy quarkonium production. We show that this effect can be treated alternatively as an effective energy loss proportional to initial energy. This leads to a nuclear suppression at any energy, and predicts x(F) scaling of the suppression. We demonstrate also that the same kinematic limit can be approached in transverse momentum when the Cronin enhancement of particle production at medium-high p(T) switches to a suppression at larger p(T) violating thus QCD factorization. Such an unexpected effect seems to be confirmed by the RHIC data for pion production in d+A collisions, and even for direct photons in Au+Au collisions.
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Interactions of migrating giant planets and small solar-system bodies
Chrenko, Ondřej ; Brož, Miroslav (advisor)
Changes of semimajor axes of giant planets, which took place 4 billion years ago and evolved the Solar System towards its present state, affected various populations of minor Solar-System bodies. One of these populations was a group of dynamically stable asteroids in the 2:1 mean-motion resonance with Jupiter which reside in two islands of the phase space, denoted A and B, and exhibit lifetimes comparable to the age of the Solar System. The origin of stable asteroids has not been explained so far. Our main goal is to create a viable hypothesis of their origin. We update the resonant population and its physical properties on the basis of up-to-date observational data. Using an N-body model with seven giant planets and the Yarkovsky effect included, we demonstrate that the depletion of island A is faster compared to island B. We then investigate: (i) survivability of primordial resonant asteroids and (ii) capture of the population during planetary migration, using a recently described scenario with an escaping fifth giant planet and a jumping-Jupiter instability. We employ simulations with prescribed migration, smooth late migration and we statistically evaluate the results using dynamical maps. We also model collisions during the last 4 billion years. We conclude that the long-lived group was created by a...
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Hydrodynamic and N-particle simulations of asteroid collisions
Ševeček, Pavel ; Brož, Miroslav (advisor) ; Wünsch, Richard (referee)
We study asteroidal breakups, i.e. fragmentations of targets, subsequent gravitational reaccumulation and formation of small asteroid families. We fo- cused on parent bodies with diameters Dpb = 10 km. Simulations were per- formed with a smoothed-particle hydrodynamics (SPH) code combined with an efficient N-body integrator. We assumed various projectile sizes, impact veloci- ties and angles (125 runs in total). Resulting size-frequency distributions are sig- nificantly different from results of scaled-down simulations with Dpb = 100 km targets (Durda et al. 2007). We thus derive new parametric relations describing fragment distributions, suitable for Monte-Carlo collisional models. We also characterize velocity fields and angular distributions of fragments, which can be used in N-body simulations of asteroid families. Finally, we discuss several uncertainties related to SPH simulations.
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