Sökning: "dipolar polarization"

Visar resultat 1 - 5 av 10 avhandlingar innehållade orden dipolar polarization.

1. 1. Electrical Characterization of Partial Discharge Resistant Enamel Insulation

   Författare :Tuan Anh Hoang; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Enamel wire insulation; dipolar polarization; charge injection; charge transport; chromium oxide; dc conductivity; partial discharge; twisted pair.; dielectric permittivity;

   Sammanfattning : Adjustable speed drives for rotating machines have become increasingly popular as they provide possibilities of smooth and accurate process control as well as for energy savings. In such systems, due to the fact that the voltage applied at terminals of motor windings is no longer purely sinusoidal but characterized by a high content of harmonics, the appearing electrical and thermal stresses yield premature failures of the winding insulation, mainly because of an increased partial discharge (PD) activity. LÄS MER

3. 2. Dipolar recoupling sequences in 13C and 31P nuclear magnetic resonance studies of mineral surfaces

   Författare :Dan Sandström; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Chemistry of Interfaces; Gränsytors kemi;

   Sammanfattning : Solid state magic angle spinning (MAS) 31P nuclear magnetic resonance (NMR) experiments, both cross polarization (CP) and dipole-dipole recoupling, were used as tools in the investigation of the reaction products at the surface of synthetic galena (PbS) mineral and O,O'-dialkyldithiophosphate potassium salts. Various dipole-dipole recoupling sequences have been tested on powder glycine-13C2 NMR and a polycrystalline powder sample of O,O'-diethyldithiophosphate2-Ni(II) to find one or several sequences suitable for the surface experiments. LÄS MER

4. 3. Switching Kinetics and Charge Transport in Organic Ferroelectrics

   Författare :Tim Cornelissen; Martijn Kemerink; Mats Fahlman; Kamal Asadi; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Organic Electronics; Ferroelectrics; Organic Ferroelectrics;

   Sammanfattning : The continued digitalization of our society means that more and more things are getting connected electronically. Since currently used inorganic electronics are not well suited for these new applications because of costs and environmental issues, organic electronics can play an important role here. LÄS MER

5. 4. Magnetic fields and chemical maps of Ap stars from four Stokes parameter observations

   Författare :Naum Rusomarov; Oleg Kochukhov; Nikolai Piskunov; Werner Weiss; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; chemically peculiar stars; magnetic fields; spectropolarimetry; Doppler imaging; stellar atmospheres; Astronomy with specialization in Astrophysics; Astronomi med intiktning mot astrofysik; Astronomy; Astronomi;

   Sammanfattning : Our knowledge of stellar magnetic fields relies almost entirely on circular polarization observations, which has historically limited our understanding of the stellar magnetic field topologies. Recently, it has become possible to obtain phase-resolved high-resolution spectropolarimetric observations in all four Stokes parameters for early-type magnetic stars. LÄS MER

7. 5. Simulations of directionality effects and optical forces in plasmonic nanostructures

   Författare :Vladimir Miljkovic; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Comsol multiphysics; optical forces; nanoparticles; nanowires; DDA; surface plasmons; Green’s function; Mie theory;

   Sammanfattning : With the rapid development of nanoscience and nanotechnology, surface plasmonics based on metal nanoparticles and nanostructures gain increasing interest, not only for fundamental scientific studies, but also for optical and sensor applications. At the nanoscale, the physical and chemical properties of metal particles, especially their optical properties, strongly depend on size and shape, as well as on the surrounding media and structures. LÄS MER