IMPACT OF CREEP ON FLANGE CLAMPING FORCE

The study presents a numerical analysis of the impact of creep in thermoplastic stub ends on the flange clamping force of a thermoplastic pipe flange connection. The analysis uses available creep modulus values that depend on the stress level, temperature and time. A method that takes the creep modulus into account is proposed and applied to four different detailed variants with the aid of the finite element method. The calculations were performed for selected times at a constant temperature and with static load. The obtained results show that the influence of creep in thermoplastic stub ends causes a substantial reduction in flange clamping force in less than one year

Numerical Patterns for Evaluation of the Stability Slope

V diplomové práci se řeší numerické modely pro posuzování stability zemních těles. Výpočty byly provedeny metodou konečných prvků pro různé návrhové situace s využitím programového systému ANSYS. Výsledky byly porovnány s klasickými přístupy určování stupňů stability zemních svahů.The master’s thesis deals with numerical patterns for evaluation of the stability slopes. Solutions have been made with finite element method for different design situations with using programme system ANSYS. The results were compared with conventional approaches determining of the slope safety factor.

Analysis of Thermoplastic Pipes in a Soil Environment

Disertační práce je zaměřena na analýzu chování termoplastových potrubí v zemním prostředí, a to zejména pro potrubí prováděná pomocí bezvýkopových technologií. V rámci disertační práce byly provedeny experimenty, jejichž cílem bylo stanovit chování a únosnost polyethylenových potrubí při zatížení vnějším hydrostatickým tlakem. Pro experimenty byla navržena a vyrobena ocelová tlaková komora, která umožňovala zatížit a sledovat potrubí při jeho ztrátě stability. Mechanické vlastnosti materiálu trubek byly určovány pomocí tahových a ohybových zkoušek. Byla provedena řada podrobných numerických analýz experimentů potrubí, kde byly použity různé materiálové modely, geometrické imperfekce či metody řešení. Byly použity materiálové modely zohledňující pružné, plastické a viskózní chování termoplastů. Dále byla provedena řada normových výpočtů polyethylenových potrubí instalovaných bezvýkopovými technologiemi. Cílem bylo vytvořit nové návrhové diagramy pro praktické posuzování těchto potrubí umístěných ve stávajícím nosném potrubí. V případě nenosného stávajícího potrubí byl vytvořen numerický model pro stanovení návrhových součinitelů, které byly ověřeny s normovými hodnotami. Výsledky z tohoto modelu byly dále porovnány s výsledky komplexnějšího numerického modelu zohledňujícího lépe interakci potrubí a zemního prostředí pro různé třídy zemin.The doctoral thesis deals with an analysis of thermoplastics pipes in a soil environment, in particularly, pipes performed by using trenchless technologies. In the doctoral thesis, experiments of polyethylene pipes loaded by external hydrostatic pressure were performed. The aim of the experiments was to determine a behaviour and load-bearing capacity of the polyethylene pipes loaded by external hydrostatic pressure. For the experiments, a steel pressure chamber was designed and produced which allowed loading and observing a pipe during its loss of the stability. Mechanical properties of the pipe material were determined based on the tensile and bending tests. The series of detailed numerical analyses of the pipe experiments were performed. Various material models which take into account elastic, plastic and viscous behaviour of thermoplastic materials were used. In addition, series of standardized calculations of polyethylene pipes installed using trenchless technologies were performed. The aim was to create new design diagrams for practical assessment of these pipes placed in the partially deteriorated old pipes. In the case of the deteriorated old pipe, a numerical model for determination of design coefficients was created. These design coefficients were verified with standard values. Then, the results of the numerical model were compared with the results of the more complex numerical model which better take into account pipe-soil interaction of various soil types.

Morphofunctional changes of phytoplankton community during pluvial anomaly in a tropical reservoir

AbstractThe present study focuses on the structure and function of phytoplankton community during periods of marked changes in hydrological traits, influenced by an atypical climatic event (La Niña) and its impact on Armando Ribeiro Gonçalves Reservoir of Rio Grande do Norte, situated in the Caatinga biome of northeastern Brazil. The main questions addressed were: What are the effects of environmental factors on the temporal variation of Morphologically Based Functional Group (MBFG) of phytoplankton community? How does the composition of cyanobacterial species shift in relation to high and low trends of phytoplankton diversity? The samples were collected monthly during 2008-2009 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen content and the nutrients, such as, nitrate-nitrogen, ammoniacal nitrogen, total nitrogen and orthophosphate. Phytoplankton samples were collected for both qualitative and quantitative analyses to evaluate species richness index and species diversity index. The data was divided into two distinct hydrodynamic periods of instability and stability. The results demonstrate considerable changes in dissolved oxygen content, water transparency and nitrogen nutrients, which directly influenced the MBFG of phytoplankton community in space and time. The instability of reservoir water was caused by heavy rainfall, which exerts atypical external disturbances. The seasonal variation of MBFG demonstrates a change in cyanobacterial composition and their diversity during instability and stability periods. MBFG VII, composed by colonial cyanobacteria with mucilage, was associated with reduced values of electrical conductance and alterations in pH. The predominance of filamentous species with heterocyst (MBFG III) occurs only during the hydrodynamic stability period and did not show significant association with analyzed parameters. The co-dominance of MBGFs III, V and VII along with high species diversity of phytoplankton community occurred during the second hydrodynamic instability period which was associated with the reduction in water temperature. It is concluded that the decrease in cyanobacterial species dominance and the general increase in the diversity of phytoplankton community are influenced by pluvial anomaly. The higher water level during the period of pluvial anomaly resulted in nutrient pulse and the mixing of water column in the reservoir, which determined the MBPG phytoplankton community distribution

Electrical separators diagnostics using fractional separability

Import 26/06/2013Diplomová práce se zabývá odlučovači tuhých znečišťujících látek. V druhé části jsou popsány možnosti zpřesnění diagnostiky elektrických odlučovačů. Třetí část je věnována praktickému využití frakčních odlučivostí pro diagnostiku elektrických odlučovačů.This thesis deals with the separators of solid pollutants. The second part describes the options for more precise diagnosis of electrical precipitators. The third part is devoted to practical use fractional separating capacity for diagnosing electrical precipitators.635 - Katedra tepelné technikyvýborn

Morphofunctional changes of phytoplankton community during pluvial anomaly in a tropical reservoir

AbstractThe present study focuses on the structure and function of phytoplankton community during periods of marked changes in hydrological traits, influenced by an atypical climatic event (La Niña) and its impact on Armando Ribeiro Gonçalves Reservoir of Rio Grande do Norte, situated in the Caatinga biome of northeastern Brazil. The main questions addressed were: What are the effects of environmental factors on the temporal variation of Morphologically Based Functional Group (MBFG) of phytoplankton community? How does the composition of cyanobacterial species shift in relation to high and low trends of phytoplankton diversity? The samples were collected monthly during 2008-2009 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen content and the nutrients, such as, nitrate-nitrogen, ammoniacal nitrogen, total nitrogen and orthophosphate. Phytoplankton samples were collected for both qualitative and quantitative analyses to evaluate species richness index and species diversity index. The data was divided into two distinct hydrodynamic periods of instability and stability. The results demonstrate considerable changes in dissolved oxygen content, water transparency and nitrogen nutrients, which directly influenced the MBFG of phytoplankton community in space and time. The instability of reservoir water was caused by heavy rainfall, which exerts atypical external disturbances. The seasonal variation of MBFG demonstrates a change in cyanobacterial composition and their diversity during instability and stability periods. MBFG VII, composed by colonial cyanobacteria with mucilage, was associated with reduced values of electrical conductance and alterations in pH. The predominance of filamentous species with heterocyst (MBFG III) occurs only during the hydrodynamic stability period and did not show significant association with analyzed parameters. The co-dominance of MBGFs III, V and VII along with high species diversity of phytoplankton community occurred during the second hydrodynamic instability period which was associated with the reduction in water temperature. It is concluded that the decrease in cyanobacterial species dominance and the general increase in the diversity of phytoplankton community are influenced by pluvial anomaly. The higher water level during the period of pluvial anomaly resulted in nutrient pulse and the mixing of water column in the reservoir, which determined the MBPG phytoplankton community distribution