Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 458 for “"valves"”.
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Investigation of spring valves
This thesis presents a study of spring valves with the ultimate aim of using them as high pressure hydraulic flow-control valves for agricultural applications. A closed helical coil spring, when pressurized, will provide a controlled flow between the coils when extended or laterally deflected a …
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Polymeric Transcatheter Heart Valves
… currently available. Commercial bioprosthetic valves (surgical and transcatheter) suffer from calcification and decreased durability, especially when implanted into younger patients, while mechanical surgical valves require life-long anticoagulation. Polymeric transcatheter aortic valve …
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Silicon micromachined wafer-bonded valves
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1993.
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Paravalvular sealing pf percutaneous heart valves
… is still sought. Commercial transcatheter heart valves (THV's) rely on sealing skirts made from treated pericardium or polyethylene terephthalate (PET) fabrics. The current study was aimed at developing novel electrospun skirts for the minimization of PVR in THV's. Thermoplastic polyurethane …
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Bioprosthetic heart valves : ultrastructure and calcification
… widely used commercially produced tissue heart valves. Since stentless bioprostheses represent the latest promising trend in the development of biological heart valves, stentless models of the following makes were compared: Baxter, Medtronic, St. Jude and Biocor. Due to the fact that the aortic …
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Dynamic stability of hydraulic poppet valves
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1963.
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Computational Investigation of Lymphatic Valves and Vessels
… is regulated by unidirectional lymphatic valves, which allow lymphatic pumping against adverse pressure gradient. Despite the importance of the lymphatic system, understanding of lymphatic operation, especially the role of lymphatic valves, is still limited. By using a fully coupled …
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Fluid Dynamics Characterization of Transcatheter Aortic Valves
… compare to SAVR. Currently, transcatheter aortic valves (TAVs) have limited clinical data in term of fluid dynamics performance of TAVs, in contrast to surgical aortic valves (SAVs). Due to limitations associated with devices that are used to evaluate the performance of TAVs in patients such as …
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Spin transport through nanopillar superconducting spin valves
… spin currents with superconductivity using spin valves, where the difference in resistance between the antiparallel (AP) and parallel (P) alignments of the magnetic layers within the device [magnetoresistance, ∆R = RAP − RP ] has been used to quantify the spin decay occurring as the current …
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Mechanical aortic valves and the small aortic root
Includes bibliographical references.
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Gas forces during the rapid opening of disc valves
… additional understanding of the performance of "valves" under dynamic conditions and supplement existing steady state or continuous flow analysis as outlined by Wambsganss, MacLaren etc. The study describes tests carried out on disc valves in which the valve seat was withdrawn from the valve …
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Analysis of complex flows in safety valves using CFD
The aim of this thesis was to utilise Computational Fluid Dynamics (CFD) tools available to industry - primarily ANSYS FLUENT and ANSYS Workbench - to develop a modelling methodology which could allow CFD to be relied upon and be used as an analysis/design tool within the Pressure Relief Valve …
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Flow-Induced Forces Regulate the Development of Cardiac Valves
… the second most common surgery, and receive valves with limited strength and biocompatibility. In an effort to address these problematic issues, researchers have attempted to create tissue engineered replacement valves, and carry out investigations on valve mechanics. These efforts depend on …
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The interaction between rotary valves and pneumatic conveying pipelines
… to investigate the interaction between rotary valves and pneumatic conveying pipelines and the effect which this can have on overall system performance. A review of previous work and current industrial practice revealed that very little work has been published on this subject, although it was …
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The dynamic behaviour of check valves in pipeline systems
… to describe the dynamic behaviour of check valves in pipeline systems. The method is based on parameterized valve models and dimensionless valve characteristics, which may be obtained from experiments. The check valve is considered as a black box with certain input and output …
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Relative efficiencies and capacities obtained with a Warren duplex steam pump-equipped (a) with straight ported valves (b) with rotary inclined port valves
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1921
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Achieving Efficient Control of Hydraulic Systems Using On/Off Valves
… typical method of control, which uses throttling valves to place restrictions in the flow path to dissipate excess power as heat. Several approaches to reducing throttling losses have been studied, such as using pumps, motors, or transformers to control individual actuators, or creating circuits …
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A Computational Model for Design Optimization of Bioprosthetic Heart Valves
<p>Heart valves play an important role in directing blood flow and preventing back flow in the heart. Design and development of bioprosthetic heart valves has been a major focus of research in the field of cardiovascular engineering as they are a better replacement for natural diseased valves than …
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