Now showing items 1-10 of 4057
Formability of aluminium alloy subjected to prestrain by rolling
(Doctoral thesis at NTNU;2014:363, Doctoral thesis, 2014)
The purpose of this thesis was to improve the understanding and the accuracy of the description of metal sheet formability following the needs of the automotive industry. In particular, the effects of plastic anisotropy ...
An immersed interface method for two-dimensional modelling of stratified flow in pipes
(Doktoravhandlinger ved NTNU, 1503-8181; 2004:139, Doctoral thesis, 2004)
<p>This thesis deals with the construction of a numerical method for solving two-dimensional elliptic interface problems, such as fully developed stratified flow in pipes. Interface problems are characterized by its ...
The impact of oncogenic signaling on the metabolomics of melanoma and prostate cancer
(Doctoral thesis at NTNU;2016:15, Doctoral thesis, 2016)
Thoracoabdominal aortic aneurysm repair: Operative technique, pathophysiology and results of treatment
(Doktoravhandlinger ved NTNU, 1503-8181; 2006:98, Doctoral thesis, 2006)
On the Design and Optimization of OFDM Systems
(Doktoravhandlinger ved NTNU, 1503-8181; 2006:196, Doctoral thesis, 2006)
<p>In this thesis, some selected aspects of OFDM systems have been investigated. We focus on the modulation and demodulation techniques, such as efficient equalization, robustness to carrier frequency offset (CFO) and CFO ...
Two Weight Discrete Hilbert Transforms and Systems of Reproducing Kernels
(Doktoravhandlinger ved NTNU, 1503-8181; 2011:124, Doctoral thesis, 2011)
<p>The Hilbert transform has become increasingly popular over the years due to its wide ranging applications not only in mathematics, but also in many other applied areas. In a quest for more applications, studying various aspects of its two weight forms has been a subject of high interest as early as the 1970’s. Of special interest is the interface of the Hilbert transform with the notions of Carleson measures and the system of reproducing kernels in spaces of analytic functions. Though these notions have proved to be of fundamental importance and ubiquitous in the development of function theoretic spaces, their properties for many significant spaces, including the model subspace of the Hardy spaces H<sup>2</sup> ;have not yet been well understood. The present thesis focuses on this interface and provides answers to several problems encompassing them.</p><p>The thesis consists of five chapters. The first chapter provides an up-to-date review of the relevant background literature. The remaining chapters contain results that have been published by, or intended for, international journals.</p><p>The work in chapter two covers the problems of unitarity, invertibility, boundedness, and surjective mapping properties of the two weight discrete Hilbert transforms, and a complete solution is obtained for the first one. Our solutions for the remaining problems are complete under a sparsity priori growth condition. Under such a condition, we describe bounded two weight Hilbert transforms in terms of a relatively simple A<sub>2</sub> conditions. As a consequence, computable geometric criteria have been established for invertibility of such maps. Chapter two also provides all the basic underpinnings for the materials presented in Chapter three and Chapter four, where links have been established to interpolate all our results on the weighted transforms into statements about Carleson measures and systems of reproducing kernels in certain Hilbert spaces, of which de Branges spaces and model subspaces of H<sup>2</sup>; are prime examples. As an application, a connection to the Feichtinger conjecture, which is known to be equivalent to dozens of other conjectures including the famous Kadison–Singer problem, is pointed out and verified for certain classes of spaces.</p><p>Chapter five deals again with normalized reproducing kernel Riesz bases in model subspaces of H<sup>2</sup> generated by the class of meromorphic inner functions. In this chapter, the approach to studying such bases digresses somewhat from the methods used in the preceding chapters. Here, we study the normalized kernel bases from an equality of spaces perspective. It is known that such bases can be described in terms of equality of spaces whenever the kernels are associated with points all from the real line. When the points are from the upper half-plane, it is now proved that the analogous conditions may still be sufficient while failing to be necessary.</p>...
Empirical Papers on Public Opinion, Party Competition, and Income Redistribution in Developed Democracies
(Doktoravhandlinger ved NTNU, 1503-8181; 2009:265, Doctoral thesis, 2009)
High-order optimization methods for large-scale 3D CSEM data inversion
(Doctoral thesis at NTNU;2015:273, Doctoral thesis, 2015)
Marine controlled-source electromagnetic (CSEM) method is a non-invasive offshore technique used, in association with magnetotelluric and seismic data, for the study of the oceanographic lithosphere and hydrocarbon ...
Stability Investigation of Power Electronics Systems; A Microgrid Case
(Doctoral thesis at NTNU;2015:2, Doctoral thesis, 2015)
This thesis is focused on the stability of systems containing high power electronic devices. The study mainly involves the exchanger device in a hybrid current microgrid. This microgrid has a topology with a DC bus and ...
Multi-component interfacial transport as described by the square gradient model: evaporation and condensation.
(Doktoravhandlinger ved NTNU, 1503-8181; 2009:176, Doctoral thesis, 2009)
<p>The aim of this thesis is to build a theoretical approach which allows to describe the behavior of fluid during evaporation and condensation in multicomponent systems. We consider isotropic non-polarizable mixtures. We have developed the description of the surface using continuous non-equilibrium thermodynamics and established the link to the macroscopic non-equilibrium thermodynamics of surfaces, which uses excess densities and fluxes. The present analysis for the mixture’s surface generalizes the equilibrium square gradient model and the non-equilibrium description of one-component systems.</p><p>The thesis is based on four articles. Within this work we have addressed three major issues. First, we have established an analytical continuous description of an interfacial region between two different phases of a mixture under nonequilibrium conditions. Next, we have verified numerically the possibility to describe the non-equilibrium surface as a separate phase. Finally, we have investigated the connection between transport properties of a mixture inside an interfacial region and those for the whole surface, both analytically and numerically.</p><p>Within the continuous approach we have gone through a number of steps. First, the equilibrium thermodynamic behavior in the interfacial region was established. We used the square gradient theory as a model which describes thermodynamic phenomena in the interfacial region. It has been widely used for one-component equilibrium systems and has been extended to mixture interfaces. Next, we extended the description to non-equilibrium. The nonequilibrium Gibbs relation has been postulated and we discussed how the gradient theory motivates the chosen form of this equation. The expression for the entropy production, which gives one information about the measure of the irreversibility everywhere in the interfacial region, has been obtained. We have discussed how the gradient description breaks the three-dimensional isotropy of a mixture inside the interface. The resulting linear laws relating the forces and the fluxes were given. Having this approach established we have gotten the complete continuous description of a two-phase mixture under nonequilibrium conditions. The theory was applied to and solved for a particular mixture of cyclohexane and were discussed and resulting profiles of various thermodynamic quantities were obtained.</p><p>Another focus of the thesis was to make a link to the macroscopic description of transport through a surface. Within this approach a surface in non-equilibrium is treated as a separate phase which has its own thermodynamic properties, such as the temperature or the excess density. This hypothesis is called local equilibrium of a Gibbs surface. This is a simplifying assumption about the behavior of real systems which is physically elegant. With the help of the continuous gradient description we have verified the hypothesis of local equilibrium of a surface for a binary mixture.</p><p>The macroscopic approach uses interfacial resistances to heat and mass transfer through the surface as parameters of the theory. The continuous description allowed us to obtain these coefficients directly and gave insight of the nature of these coefficients. With the help of the continuous description we obtained the excess entropy production of the whole surface and the resulting linear laws. The interfacial resistances have been evaluated both numerically and with the help of derived integral relations. By comparison with results from kinetic theory it was shown that the continuous resistivity profiles have a peak in the interfacial region. We have also shown that the interfacial resistances depend among other things on the enthalpy profile across the interface. The enthalpy of evaporation is one of the main differences between liquid and vapor phases and therefore the interface is important for the resistance to heat and mass transfer</p><p>n-hexane. The details of the numerical procedure</p>...