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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Experimental and analytical studies of conventional (gasketed) and unconventional (non-gasketed) flanged pipe joints

Abid, Muhammad January 2001 (has links)
No description available.
2

Active/Passive control of fluid-borne and structure-borne disturbances in fluid-filled piping systems

Kiyar, Mustafa Baris 01 June 2004 (has links)
Energy due to fluid-borne and structure-borne disturbances propagating in a fluid-filled pipe will be carried by the structure and the fluid. Energy transfer may occur between these two media due to the coupling between the structure and the fluid. It's not clear when the excitation is fluid-borne or structure-borne, due to the complexity in piping installation designs and the strong coupling between the fluid and shell walls. It is necessary to devise control approaches that tackle both components of the excitation simultaneously. This study will demonstrate new approaches in active and passive control techniques and show their advantages over classical control approaches. It is necessary to understand the physical behavior of fluid-filled pipes, in order to develop a viable control methodology. The equations of motion for the shell and the fluid are needed to characterize the system. These combined with the dispersion equations can then be used to derive analytical expressions for energy flow in the system. The research is limited to lower order wave types. Hence, the expressions for energy flow are derived only for the n=0 and n=1 shell waves and n=0 fluid wave. Higher order waves have cut-on frequencies and were not analyzed. Current sensing methodologies are limited to the analysis of wave types separately. A new approach of wave decomposition using multiple sensors is developed and used to characterize discontinuities along the pipe. The effect of discontinuities and correct control methodologies are investigated. A new control methodology is developed and implemented. The natural distribution of energy into different wave types as it encounters discontinuities is used to devise control solutions with non-intrusive inertial actuators. Improvements of 16 dB in shell waves and 12 dB in fluid waves over the correct control approach are experimentally demonstrated. / Master of Science
3

International Purchasing in Two Iranian Polymer Piping Firms

Mousavi, Reza January 2013 (has links)
Many researchers have contributed to the field of international purchasing; but there are no consistent findings to illustrate particular connections within the field. This particular research studies the ways that two Iranian producers of polymer piping systems handle international purchasing in current complex Iranian economic circumstances. By going beyond macroeconomic theories of international trade and using three-factor model of international industrial purchasing this particular study aims to reveal how international industrial purchasing is handled by Iranian producers of polymer piping systems under current Iranian economic and politic circumstances. A case study approach employing face-to-face semi-structured interview method is designed. A set of interview questionnaires was designed to gather empirical qualitative and quantitative data. A narrative analysis was then conducted to lead the discussions and to draw conclusions. The results of the study show that international purchasing in both firms is influenced by internal factors including attitudes and competence as well as external factors including market conditions and regulations. The levels to which the first three mentioned factors influence international purchasing varies between the studied firms; but regulations have similar effects on the ways the studied firms handle international purchasing. Also, the modified three-factor model is perfectly applicable to the studied cases under current circumstances of Iranian economy.
4

Stanovení metodiky analýzy seismické odezvy potrubních soustav s viskózními tlumiči / Formulation the Methodology for Analysis the Seismic Response of the Piping Systems with Viscose Dampers

Chlud, Michal January 2015 (has links)
Viscous dampers are widely used to ensure seismic resistance of pipelines and equipment in nuclear power plants. Damping characteristics of these dampers are nonlinearly frequency dependent and thus causing complications in computational modelling of seismic response. Engineers commonly use two ways to deal with this nonlinearity: The first option is to consider damper by means of “snubber”. This is essentially linear spring element that is active for dynamic load and does not resist static loads. Snubber behaviour during seismic event is described by a equivalent stiffness (sometimes called pseudostiffness). The equivalent stiffness could be defined by the iterative calculations of piping natural frequencies and mode shapes taking into account seismic excitation. However, in complicated structures such as the main circulation loop of nuclear power plant the iterative calculation is difficult and could bring significant inaccuracies. On the other hand, the benefit of such modelling is a possibility to apply the commonly used linear response spectrum method for a solution. The second option is to describe damping characteristics using suitable rheological model. The seismic response is than determined by direct integration of the equations of motion. The behaviour of dampers is described exactly enough but the calculation and post-processing, especially nodal stresses time-histories, are time consuming. The goal of this work was to find a methodology for determining the seismic response of complex pipe systems with viscous dampers. Methodology allows a sufficiently accurate determination of the seismic response of piping systems and also allows obtaining of the results in effective time. The procedure is as follows. Firstly, specialized piping program (AutoPIPE) is used for the development of computational model. Next step is to determine a static response of structure and its verification with experimental measurements, if possible. Using script in Python language a computational model is converted from AutoPIPE into general finite element model in ANSYS system. Four-parameter Maxwell rheological model is used to describe behaviour of viscous dampers. Seismic load is represented by synthetic accelerograms. Newmark algorithm of direct integration of the equation of motion is used to obtain seismic response (only reactions and displacements in nodes of interest are necessary). Than is the equivalent stiffness is than gained from displacements and reactions as median value of their ratios. Received stiffness are subsequently transferred to AutoPIPE program where the seismic solution is performed using response spectra method. Finally, the dynamic response is combined with the static response and stress assessment according standards is done. The created methodology was applied in the seismic resistance calculation of the main circulation piping and piping of pressurizer in nuclear power plants type VVER 440 and type VVER 1000.
5

Vamzdyno trūkio vietos nustatymo algoritmo sukūrimas pagal fizikine elgsena grįstą slėgio bangos sklidimo modelį / Algorithm for identification of pipeline rupture location based on finite element model of pressure wave propagation

Kriščiūnas, Andrius 04 November 2013 (has links)
Darbo metu apžvelgiami metodai pereinamiesiems procesams vamzdyne realizuoti. Aprašyta vamzdyno tėkmės pereinamųjų procesų dinamika matematinės lygtys ir sudarytas baigtinių elementų modelis skaitiniam vamzdynų pereinamųjų procesų modeliavimui. Panaudojant atgalinį slėgio bangos modeliavimą esant idealizuotam slėgio bangos sklidimo modeliui, sudaromas slėgio impulso vietos nustatymo algoritmas ir įvertinamos atsirandančios paklaidos. Realizuota programine įranga patikrinamas sudarytų modelių ir algoritmo teisingumas, bei pateikiami pasiūlymai, atsiradusioms paklaidoms mažinti. / During this research, the methods to realize the transient processes in piping systems are overviewed, also finite element method and idealized wave propagation of pressure mathematical models are set up. Using the backward pressure wave modelling at idealized pressure wave propagation model, piping system rupture location algorithm and the assessment of estimated errors are set up. With released software, the developed models and correctness of the algorithm are verified, and suggestions to reduce the resulting errors are presented.
6

Využití zobecněných funkcí v mechanice kontinua / Using generalized functions in continuum mechanics

Procházka, Petr January 2018 (has links)
Tato práce se zabývá využitím distribucí neboli zobecněných funkcí k řešení nestacionárních okrajových problémů v mechanice kontinua. Nejprve je zavedena teorie distribucí a jejich definice jako spojitých lineárních funkcionálů na prostoru testovacích funkcí. Druhá část teoretické kapitoly představuje Laplaceovu integrální transformaci. Následující kapitola se věnuje řešení průhybu nosníků pod vlivem nespojitého časově proměnlivého zatížení. Jejím výsledkem je vytvoření obecného modelu řešení průhybových čar nosníků vužitím distribucí. Poslední kapitola se zabývá řešením nestacionárního proudění v trubicích spojených hydraulickými prvky.
7

Simulation, Analysis and Design of Systems with Multiple Seismic Support Motion

Nizamiev, Kamil 13 September 2016 (has links)
No description available.
8

Vliv vzduchotechnických zařízení na akustické mikroklima čistých prostorů / The impact of HVAC systems on the acoustic microclimate of clean rooms

Jelínek, Ondřej January 2016 (has links)
The work description is to create a system of measures to prevent the spread and the consequent attenuation of sound in air handling systems serving the cleanrooms. The thesis presents a solution to noise attenuation in the investigated area, and in HVAC duct, which uses a commercially available material in the form of sound insulation hoses. In the systém solution is part of the work focuses on the optimal design of terminal elements to distribute air in a clean room. Processing methods utilize theoretical and experimental approach. The experiment comprises a unique analysis of the sound insulation properties of selected products under specific conditions. The data obtained are analyzed and incorporated into the framework of this work created program module for determining the attenuation and noise propagation in an enclosed space. Math and physical dependence are programmed into their own DLL by programming language DELPHI.

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