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Space Exploration of Mars
Válek, Jiří ; Sedláček, Pavel (referee) ; Froehling, Kenneth (advisor)
Tato bakalářská práce shrnuje minulé a současné mise k Marsu a uvádí objevy, úspěchy a technologie použité během jednotlivých misí. První kapitola se zaměřuje na první průzkumné mise Sovětského svazu a Spojených států během studené války a popisuje důležité úspěchy jednotlivých misí. Dále tato práce pojednává o roverech, jako jsou Opportunity, Spirit, Curiosity a také o Perseverance, které byly navrženy pro mobilní průzkum povrchu planety. Poslední část této práce se zabývá možností vyslání lidské posádky na tuto planetu, stavbou habitatů a samotnou cestou mezi Zemí a Marsem. V této kapitole jsou také nastíněna zdravotní rizika a různé problémy, kterým by posádka během takové mise musela čelit.
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Selection of mortars samples for radiocarbon dating
Válek, Jan ; Kozlovcev, Petr ; Fialová, Anna ; Kotková, Kristýna ; Frankeová, Dita ; Skružná, Olga ; Maříková-Kubková, Jana ; Tomanová, Pavla ; Herichová, Iva ; Světlík, Ivo ; Pachnerová Brabcová, Kateřina ; Šimek, Pavel
Radiocarbon dating of organic residues may not always correctly determine the age of analysed historic mortars. Therefore, it seems advantageous to use of carbon dating of the carbon contained in the structure of the lime mortar, which will provide representative data of the age of the investigated structure. The methodology presents basic instructions and rules for sample selection, processing, and evaluation. The aim of this methodology is the identification of cases where the radiocarbon dating of a binder is appropriate and to define the reasons why some binder systems fail to provide relevant results.
Plný tet:  PDF; PDF
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Influence of the stress field on weathering and erosion of sandstone landforms
Řihošek, Jaroslav ; Bruthans, Jiří (advisor) ; Mikuláš, Radek (referee) ; Válek, Jan (referee)
The influence of mechanical stress on weathering and erosion has been overlooked in works focused on sandstone landforms formation, although stress has been shown to be a key factor in the formation of a number of different sandstone landforms recently. The main goal of the doctoral thesis is to understand the relationship between mechanical stress and weathering or erosion in the formation and development of sandstone landforms. The influence of mechanical stress on the mode of weathering and the rate of disintegration of the material forming historical monuments in Petra, Jordan was investigated on the site and on samples in laboratory. A negative exponential dependence has been proven between the speed of salt weathering and the magnitude of uniaxial compression of Petra sandstone samples. The role of mechanical stress as a mechanism controlling the formation and development of the shape of sandstone forms was further studied in rock overhangs, sandstone arcades and rock gates in the Czech Republic and the USA. The doctoral thesis presents and verifies a method using Střeleč sandstone as a natural analogue in physical models simulating weathering and erosion of cemented sandstone. These physical models usually take the form of a reduced initial shape of a sandstone object created in situ from...
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Determination of reference parameters for evaluating the strengthening of degraded sandstone masonry of the Cathedral of St. Vit at Prague Castle
Válek, Jan ; Kozlovcev, Petr ; Fialová, Anna ; Slížková, Zuzana ; Kotková, Kristýna ; Svoboda, Milan ; Koudelková, Veronika
Sandstone materials exposed to weather conditions degrade naturally, consequently consolidation of these materials is often required. The aim of this research was to evaluate the impact of four commercials organosilicate consolidants on degraded sandstones, which were used during the neogothic rebuilding of st. Vithus Cathedral at the turn of the 19th to 20th century. The depth of penetration of consolidants into the sandstone porous system and the impact of consolidants on the physical properties of sandstones, namely on the hydrofobicity, water absorption and evaporation, were evaluated primarily. According to the test results, all four consolidants should be suitable for consolidation of sandstones mentioned above even though the results varied slightly between consolidants. For final chose of appropriate consolidant, it is necessary to consider the properties of the treated sandstoned and the technological conditions of the application given by the manufacturer.
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Magnetorheological fluid response time in shear mode
Válek, Josef ; Vimmr, Jan (referee) ; Kubík, Michal (advisor)
Magnetorheological fluids (MRF) are suspensions of (commonly) oils and carbonyl iron powder. Under magnetic field, apparent viscosity of suspension changes in short time. This so-called response time can’t be neglected in modern MR devices. Multiple response times are distinguished based on load mode. Rheological response time (MRF under shear rate) will be affected by load and composition of MRF. In this thesis, these influencing parameters are investigated, which was allowed by developing rheometer with minimal hardware response time and methodology. Gained data shows, that most affecting parameter is ratio of inner forces, described e.g., Mason number. Model of Mason number was verified for larger values, but in lower values, significant difference was observed (probably caused by different shear stress mechanism in MRF). After other investigation and clarification of model, precise prediction of MRF and MR devices behaviour will be possible, which can lead to improving their function and e.g., road safety.
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