448 research outputs found
Robust Current Control of Doubly Fed Wind Turbine Generator under Unbalanced Grid Voltage Conditions
Micropumps for liquid transport inside biomimetic and microfabricated devices
The micropump is one of the most important parts of micro Total Analysis Systems. In this thesis, three types of pumps, (syringe pump, capillary pump and diffusion pump) are utilized for microfluidic transport inside biomimetic and microfabricated devices. Itâs confirmed that syringe pump can be efficient access in fluidic transport for wide range of microdevices, such as the 3D helical silicone tubing microreactor containing smooth channel surface, the Y-structured microchannel containing grooved-shaped sidewall, and PDMS/Polymer microchips microfabricated from photolithography, qualified for accurate flow rate control, microdroplet formation and multi-phage flow, anticorrosive assay and leakage test, etc. In addition, another two types of self-activated micropumps: the capillary micropump and the diffusion micropump are also applied for liquid transport through different microdevices in this thesis. Itâs found here that, the capillary micropump can be efficient approach for self-activated liquid transport inside 2.5D microchip for potential Point of Care applications, while the diffusion micropump can produce much more homogeneous flow than previously reported. The microfluidic transport properties of the diffusion micropump in biomimetic microdevice and 3D helix tubing microdevice is also characterized. Compared with the mainstream of traditional micropumps, I find diffusion micropump displays unique superiority in integrating a lot of advantages altogether, including much smaller size, dramatically simple structure, free of external power consumption, simple fabricating procedure, strong micro fluidic transportation ability, homogeneous flowing velocity over long distance, resistant to adverse external condition like high temperature, easiness of microdevice integration and much lower price.Die Mikropumpe ist eines der wichtigsten Komponenten eines miniaturisierten totalen Analysensystems. In dieser Arbeit werden drei Arten von Pumpen, Spritzenpumpe, KapillaritĂ€t und Diffusionspumpe beschrieben und angewandt fĂŒr mikrofluidischen Transport in biomimetischen und mikrofabrizierten Strukturen. Es wird gezeigt, dass Spritzenpumpen fĂŒr verschiedenartige mikrofluidische Chips eingesetzt werden können, zum Beispiel fĂŒr den 3-dimensionalen verschlungenen Reaktor aus Silikonschlauch, fĂŒr den Y-förmigen Reaktor mit steilen SeitenwĂ€nden, und photolithographischen Mikrochips aus PDMS-Polymer, mit kontrolliertem Durchfluss, fĂŒr die Formung von Tröpfchen und fĂŒr Mehrphasen-Fluss, fĂŒr Antikorrosions-Test und Leck-Test, etc. Ausserdem werden in dieser Dissertation zwei weitere Typen von autonomen Pumpen eingesetzt: die KapillaritĂ€t und die Diffusions-Mikropumpe. Es stellte sich heraus, dass Pumpen durch Kapillarkraft in 2.5- dimesnsionalen Mikrochips fĂŒr zukĂŒnftige klinische Anwendungen verwendet werden können, wĂ€hrend die Diffusionspumpe einen weit gleichmĂ€Ăigeren Fluss erzielt als bisher beschrieben. Mikrofluidische Transporteigenschaften der Diffusionspumpe in biomimetischen Strukturen und in 3-dimensionalen verschlungenen Strukturen werden beschrieben. Ich denke, im Vergleich zu den meisten herkömmlichen Mikropumpen zeigt die Diffusionspumpe klare Vorteile, sie ist klein, einfach gebaut, benötigt keine externe Stromversorgung, ist einfach herzustellen, funktioniert einwandfrei ĂŒber lĂ€ngere Strecken, ist pulsationsfrei, ist unabhĂ€ngig von Ă€uĂeren EinflĂŒssen wie hohe Temperatur, kann einfach integriert werden und zu niedrigerem Preis
Joint spectrum shrinking maps on projections
Let be a finite dimensional complex Hilbert space with dimension
and the set of projections on .
Let be a
surjective map. We show that shrinks the joint spectrum of any two
projections if and only if it is joint spectrum preserving for any two
projections and thus is induced by a ring automorphism on in a
particular way. In addition, for an arbitrary , shrinks the
joint spectrum of any projections if and only if it is induced by a unitary
or an anti-unitary. Assume that is a surjective map on the Grassmann
space of rank one projections. We show that is joint spectrum preserving
for any rank one projections if and only if it can be extended to a
surjective map on which is spectrum preserving for
any two projections. Moreover, for any , is joint spectrum
shrinking for any rank one projections if and only if it is induced by a
unitary or an anti-unitary.Comment: 14 page
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