|
|
Bituminous mixture desing with the use of 30 % reclaimed asphalt and its functional evaluation
Horáček, Daniel ; Šperka, Pavel (referee) ; Kudrna, Jan (advisor)
The aim of my bachelor thesis is to design asphalt mixture with a higher lifetime (mixture of type VMT 16) and its subsequent assessment by selected functional tests. VMT blends are used for load and underlayer layers of roads with higher transport loads. The main idea of this bachelor thesis is the design of an asphalt mixture consisting of natural aggregates, recycled asphalt mixtures and crumb rubber modified bitumen, yet retaining good road-holding properties. The use of recyclable bituminous mixtures will allow the recycling of bent or milled asphalt layers, which is currently high in surplus, and will allow the overall cost of building new high-quality asphalt layers to be reduced. The bachelor thesis describes the empirical and functional tests performed, according to which the resulting asphalt mixture was designed, and the results compared with the TP151 Asphalt mixture with high modulus of stiffness (VMT).
|
|
|
Computational modeling of radial hydrodynamic bearings for water machines
Pokorný, Jan ; Šimek,, Jiří (referee) ; Návrat, Tomáš (advisor)
The aim of this thesis is to calculate the stiffness and damping coefficients for radial hydrodynamic bearings. Cylindrical and lemon hydrodynamic bearings are considered. The solution to this problem mainly depends on the hydrodynamic pressure in the bearing. The numerical solution of the Reynolds equation is used to calculate the pressure. The effect of variable viscosity and density of the lubricant due to temperature changes is considered. The static equilibrium position of the journal centre is also solved. The stiffness and damping coefficients are determined using small amplitude journal motions about the equilibrium position. Three methods for determining these coefficients are presented. The outcome of this thesis is an algorithm for the calculation of stiffness and damping coefficients for cylindrical and lemon bearings. Results for lemon bearings are presented and comparison with the commercial software DynRot BR is made. The benefit of this thesis is the creation of an algorithm for the calculation of journal centre equilibrium position, a new way of incorporating the temperature changes in the viscosity and the density of the lubricant, and the modification of a method for calculating stiffness and damping coefficients based on experimental analogy.
|
|
|
The effect of intensity of voluntary isometric contraction on rheological characteristics of skeletal muscle tissue in vivo, in situ
Kopecká, Barbora ; Bittner, Václav (advisor) ; Jelen, Karel (referee)
Title: The effect of intensity of voluntary isometric contraction on rheological characteristics of skeletal muscle tissue in vivo, in situ Objectives: The main aim of this study is to determine the effect of intensity of isometric voluntary contraction of skeletal muscle on its viscoelastic characteristics. The work also aims to contribute to the verification of myotonometer as an objective diagnostic instrument and compares it to known methods for evaluation of muscle tone, or its partial characteristics. Methods: We used myotonometer - utility model 29456 for evaluation of changes of stiffness and viscous behavior of skeletal muscle in vivo, in situ in 20 healthy volunteers. The values were compared during 0%, 20%, 35% and 50% of maximal strength of isometric contraction of finger flexors, controlled by hand-held dynamometer. Results: We concluded that both stiffness and viscous behavior of skeletal muscle increases with higher intensity of isometric voluntary contraction. Keywords: myotonometer, skeletal muscle, viscous behavior, stiffness, muscle tone
|
|
|
Influence of changed shape and dimensions of a helical spring on its compression characteristic
Melichar, Marek ; Majer, Zdeněk (referee) ; Burša, Jiří (advisor)
The bachelor thesis deals with a change of a shape of a spring in order to facilitate its assembly in a gas boiler controller assembly. The introductory part deals with familiarization with the given issue. Then, based on the algorithm created in the bachelor thesis "Assessment of characteristic of a helical conus-shaped spring under compression" of Libor Loveček, the calculation program is adapted for calculating the existing conical spring and is further modified for other spring shapes. Accuracy of the created algorithms is verified by comparing the results with commercial computing programs. Based on the calculations, new shapes are designed, manufactured and experimentally tested. At the end of the thesis the possibility of usage of created alternative shapes is evaluated.
|
|
|
Correlation analysis of optically trapped particle motion
Koudelníček, Karel ; Jákl,, Petr (referee) ; Harabiš, Vratislav (advisor)
This bachelor’s thesis deals with the description of random (Brownian) motion of microscopic particle trapped by optical trap. This thesis provides overview of possible usage in biology. The major part of the thesis is dedicated to description of methods that allow characterize optical trap with etc. stiffness thanks to the random motion. First, the estimation methods are tested on the simulated data. Before using these methods for real data, it was necessary to modify them, specifically to eliminate crosstalk and frequency noise. The differences in the estimation of the stiffness from the autocorrelation function and the power spectrum were described in the conclusion.
|
|
|
Simulation of Idiofonic System
Múčka, Martin ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The thesis deals with dynamic simulation of real bell behavior over time. The model is created according to principles of physical discretization as a spring in the FyDiK3D software. In order for the model to be declared as relevant, it is necessary to prove the behavior of the structures used in the elementary tasks of the mechanics. It shows the correlation between the stiffness of normal and diagonal springs. Describes how to use software import tools to create a model. The resulting model approaches its real bell behavior.
|
|
|
Influence of dispersed particles on utility properties od polyvinyl alcohol-based nanotextiles: macromechanical properties
Rácová, Z. ; Nežerka, V. ; Ryparová, Pavla ; Kromka, Alexander ; Tesárek, Pavel
The paper deals with the influence of different dispersed particles on utility properties of polyvinyl-alcohol (PVA) based nanofiber textiles. The purpose of the dispersed particles was to produce textiles of antibacterial character, and these were added into water-polymer solution, which was used for electrospinning in two various ways: in form of copper and silver ions, or in form of diamond nanoparticles. In order to assess the strength of textiles, macromechanical testing of modified PVA-based nanofiber textiles was carried out on samples with variable weight per area in range between 0.5 and 5 g/m(2). The obtained results were compared with the results of measurements on plain reference samples. The study revealed that the addition of silver ions causes the strength and stiffness reduction, the addition of copper ions has an opposite effect, while the diamond nanoparticles did not have any significant influence on the mechanical properties.\n
|
|
|
Asphalt mixtures with high resistance against cracks
Stromecký, Roman ; Šperka, Pavel (referee) ; Dašek, Ondřej (advisor)
In this bachelor's thesis were suggested two kinds of asphalt mixtures. The first one contains conventional asphalt binder and the second one Crumb Rubber modified Bitumen. The aim of this thesis is a comparison of stiffness and fatigue characteristics of these two mixtures by two-point bending test on truncated wedges. There will be also an evaluation of the impact of an asphalt addition of the Crumb Rubber modified Bitumen in one of these mixtures.
|
|
|
Influence of crank arm length on change of muscle tone of musculus triceps surae
Stránský, Vojtěch ; Šifta, Petr (advisor) ; Otáhal, Jakub (referee)
Title: Influence of crank arm length on change of muscle tone of musculus triceps surae Objectives: The aim of this thesis is to conclude the theoretical knowledge of this issue. The experiment is to uncover via the objective results, if the change of the crank arm length can influence the muscle tone of m.triceps surae and additionaly how much. Methods: The measurement for this thesis was processed at Charles University at the Faculty of Physical Activity and Sports, measuring 8 volunteers. Via myotonometry, the biomechanic properties (stiffness and viscosity) of m.triceps surae were measured before and after the workout on a bicycle ergometer. These steps were repeated twice within a week with different crank arm length (170mm and 175mm). On the basis of the reaction of soft tissues on deformation from the tip of the myotonometer, the graphs are depicted, containing the hysteresis curve. We evaluate there two phenomenons - steepness and the content of the curves. They indicate biomechanic properties of soft tissues, resp. also the muscle tissue. Results: The measurements from the 1st and 2nd week were compared. The results of 8 probands show that cycling as a physical activity changes stiffness and viscosity of m. triceps surae and has therefore an influence on the muscle tone. Considering larger...
|
|
|
Viscous and elastic properties of soft tissue "in situ"
Moravcová, Kamila ; Šifta, Petr (advisor) ; Bittner, Václav (referee)
Title: Viscousand elastic properties of soft tissue"in situ" Goals and methods: The aim of this thesis is to measure the viscoelastic properties of human soleus muscle and Achilles tendonin vivo and post mortem in situ. It is a pilot study that uses myotonometry as the method of measurement. Based on the response of connective tissues on deformation made by tip of myotonometer, resp. its viscoelastic properties, curves in graphsare created. Three main described parameters of thecurveare steepness, deflection and its surface area. Main goal of the experiment is to compare properties of different types of tissue and their potential differences while denervated or innervated. Results of this study may help with better understanding of the soft tissues behavior in response to manual therapeutic contact. The study also describes the differences between in vivo and post mortem tissue properties that may be help further studies which use post mortem tissues to predict in vivo behavior. Results: Soft tissues in vivo have higher viscosity. In comparison, post mortem tissues have significantly higher stiffness and energy dissipation than in vivo. Elasticproperties of denervated soft tissue manifest with approx. 7 secondsdelay. Viscoelastic properties of muscle tissueshow changes depending on deeper...
|
guest ::
