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Coming dissertations at TekNat

  • Structure and representations of certain classes of infinite-dimensional algebras

    Author: Brendan Frisk Dubsky
    Publication date: 2018-11-14 13:27

    We study several infinite-dimensional algebras and their representation theory. 

    In Paper I, we study the category O for the (centrally extended) Schrödinger Lie algebra, which is an analogue of the classical BGG category O. We decompose the category into a direct sum of "blocks", and describe Gabriel quivers of these blocks. For the case of non-zero central charge, we in addition find the relations of these quivers. Also for the finite-dimensional part of O do we find the Gabriel quiver with relations. These results are then used to determine the center of the universal enveloping algebra, the annihilators of Verma modules, and primitive ideals of the universal enveloping algebra which intersect the center of the Schrödinger algebra trivially. 

    In Paper II, we construct a family of path categories which may be viewed as locally quadratic dual to preprojective algebras. We prove that these path categories are Koszul. This is done by constructing resolutions of simple modules, that are projective and linear up to arbitrary position. This is done by using the mapping cone to piece together certain short exact sequences which are chosen so as to fall into three...

  • Control of Wave Energy Converters in arrays

    Author: Simon Thomas
    Publication date: 2018-11-13 13:08

    One way to lower the levelized cost of energy for wave power plants and paving so the way for commercial success, is to increase the power absorption by use of advanced control algorithms. This thesis investigates the influence of the generator inertia, the generator damping and the layout on power absorption and presents a new model free strategy of controlling wave energy converters.

    The evaluation of all control strategies was done in a numerical simulation and in experimental 1:10 model scale wave tank tests conducted in the COAST laboratory at the University of Plymouth. The WECs used are inspired by the wave energy concept developed at Uppsala University.

    The influence of the generator inertia on the power absorption was tested with an uncontrolled WEC. Compared to a conventional WEC the power output could be significantly increased for small waves and high wave periods.   

    As a simple and easy to implement control strategy, a WEC with sea state optimized generator damping was used to create a power matrix. The optimal damping factor depends on both, wave period and wave height. The power absorption increases with the wave height and when the wave period...

  • The dynamic emplacement of felsic magma in the upper crust

    Author: Tobias Mattsson
    Publication date: 2018-11-13 08:04

    Felsic magma intrudes earth’s upper crust through a variety of mechanisms. Magma intrusion growth and shape have mainly been explained in terms of host rock properties and intrusion depth, while considering the magma as an overpressurised fluid. However, volcanologists view a magma as a rheologically evolving fluid, which affects the magma flow in volcanic conduits. This thesis seeks to explore intrusion dynamics during magma emplacement by taking both the magma and the host rock into account. The first part of the thesis investigates the emplacement of the Sandfell laccolith/cryptodome, the Cerro Bayo cryptodome and the Mourne granite pluton. Both cryptodomes grew initially by inflation, which resulted in contact-parallel magma flow. Later during the emplacement, the rim of the intrusions viscously stalled as indicated by brecciation and fracturing in the intrusion rims, which then forced them to grow vertically. Our observations suggest that rheological changes in the magma during intrusion growth may control the shape of the cryptodomes/laccoliths. Previously proposed emplacement mechanisms of the Mourne Mountains granite pluton were tested by investigating host-rock...

  • Theoretical and Computational Studies of Strongly Correlated Electron Systems : Dynamical Mean Field Theory, X-ray Absorption Spectroscopy and Analytical Continuation

    Author: Johan Schött
    Publication date: 2018-11-09 13:41

    This thesis encompasses theoretical and computational studies of strongly correlated elec-tron systems. Understanding how electrons in solids interact with each other is of great im-portance for future technology and other applications. From a fundamental point of view, the Coulomb interaction in a solid leads to a very challenging many-body problem, encapsulating many physical phenomena, e.g. magnetism. Treating this interaction, with a focus on local contributions, is the subject of this thesis. Both models and materials have been investigated, to obtain insight on the mechanisms determining the macroscopic properties of matter. This thesis is divided in four parts, each corresponding to a different project or topic.

    In the first project a many body method called dynamical mean field theory (DMFT) is used to study the paramagnetic phase of the Hubbard model. A stochastic version of the exact di-agonalization technique is developed for solving the effective impurity model arising in DMFT and generating real frequency spectral functions. In the next project, by combining density functional theory (DFT) with a static solution of the DMFT equations (DFT+U), magnetic...

  • Interaction kinetic analysis in drug design, enzymology and protein research

    Author: Vladimir O Talibov
    Publication date: 2018-11-09 12:45

    The work presented here is focused on the phenomenon of molecular recognition – the mutual ability of biological molecules to recognize each other through their chemical signatures. Here, the kinetic aspects of recognition were evaluated, as interaction kinetics reveal valuable dimensions in the description of molecular events in biological systems. The primary objects studied in this thesis were human proteins and their interaction partners. Proteins serve a fundamental role in living organisms, supporting the biochemical machinery by means of catalysis, signalling and transport; additionally, proteins are the main targets for drugs.

    In the first study, carbonic anhydrase (CA) isozymes were employed as a model system to address the problem of drug selectivity. Kinetic signatures preferable for the design of selective sulphonamide-based inhibitors were identified. In a follow up study, the recognition between CA and sulphonamides was separated into two parts, uncovering intrinsic recognition features that genuinely reflect the interaction mechanism. For the first time, the concept of intrinsic interaction kinetics was applied to a drug-target system.

    Another model...

  • Dynamic Modelling of Physical Processes in Magmatic Systems: Dyke Emplacement and Flow-Induced Crystal Rotations

    Author: Rémi Vachon
    Publication date: 2018-11-09 12:11

    The main motivation for this thesis is to develop and improve numerical tools and methods that help further our comprehension of the volcanic plumbing system and its dynamics.

    The commonly used standard elastic model predicts solutions of dyke shape, thickness, over-pressure and fracturing criteria that do not always fit natural observations. In the first part of the thesis, we want to test whether other host-rock rheologies leads to more realistic dykes. We examine three different rheologies: 1) elasticity with pressure dependent elastic moduli, 2) elastoplasticity with plastic failure in regions of high shear stresses and 3) viscoelasticity to describe ductile flow of rocks by creeping mechanisms in regions of high temperature. Solu-tions from the three tested models give dykes with more rectangular shapes relative to solutions computed from the model of linear elasticity. In addition, the calculated magma pressure for an intrusion of a given thickness is reduced for all tested rheologies. Greatest differences with the linear elastic solution are given by the elastoplastic model, in which computed magma over-pressures are lower than elastic solutions by a factor of 2 to 10...

  • Ion-Crosslinked Nanocellulose Hydrogels for Advanced Wound Care Applications

    Author: Alex Basu
    Publication date: 2018-11-09 09:39

    A current trend in the field of wound care is the development of wound healing materials that are designed to address specific types of wounds or underlying pathologies to achieve improved healing. At the same time, there is a societal drive to replace synthetic materials with renewable alternatives. The work presented in this thesis was therefore carried out to investigate the use of wood nanocellulose, produced from the world’s most abundant biopolymer, cellulose, in advanced wound care applications.

    Wood-based nanofibrillated cellulose (NFC) was chemically functionalized and crosslinked using calcium to obtain a self-standing hydrogel. The NFC hydrogel was evaluated in terms of its physicochemical properties, biocompatibility, blood interactions, bacterial interactions, in vivo wound healing ability and, finally, as a protein carrier. Parallel with the assessment of the NFC hydrogel, modified versions of the material were tested to investigate the tunability of the above-mentioned characteristics.

    The ability of the hydrogel to maintain a moist wound bed was demonstrated. Evaluation of the biocompatibility showed that the material was cytocompatible and...

  • Carboligation using the aldol reaction : A comparison of stereoselectivity and methods

    Author: Derar Al-Smadi
    Publication date: 2018-11-07 07:55

    The research summarized in this thesis focuses on synthesizing aldehyde and aldol compounds as substrates and products for the enzyme D-fructose-6-aldolase (FSA). Aldolases are important enzymes for the formation of carbon-carbon bonds in nature. In biological systems, aldol reactions, both cleavage and formation play central roles in sugar metabolism. Aldolases exhibit high degrees of stereoselectivity and can steer the product configurations to a given enantiomeric and diastereomeric form. To become truly useful synthetic tools, the substrate scope of these enzymes needs to become broadened.

    In the first project, phenylacetaldehyde derivatives were synthesized for the use as test substrates for E. coli FSA. Different methods were discussed to prepare phenylacetaldehyde derivatives, the addition of a one carbon unit to benzaldehyde derivatives using a homologation reaction was successful and was proven efficient and non-sensitive to the moisture. The analogues were prepared through two steps with 75-80 % yields for both meta- and para-substituted compounds.

    The second project focuses on synthesizing aldol compound using FSA enzymes, both...

  • Self-Consumption of Photovoltaic Electricity in Residential Buildings

    Author: Rasmus Luthander
    Publication date: 2018-11-06 07:59

    Worldwide installations of photovoltaics (PV) have increased rapidly due to national subsidies and decreasing prices. One important market segment is building-applied PV systems, for which the generated electricity can be self-consumed. Self-consumption is likely to become important both for the profitability and to facilitate integration of high shares of PV in the power system. The purpose of this doctoral thesis is to examine opportunities and challenges with distributed PV in the power system on four system levels: detached houses, communities, distribution systems and national level. This was done through literature studies and computer simulations. Previous research has shown a larger potential to increase the PV self-consumption in detached houses by using battery storage rather than shifting the household appliance loads. This thesis shows that, on the community level, the self-consumption increased more when sharing one large storage instead of individual storages in each house. On the distribution system level, PV power curtailment was identified as an effective solution to reduce the risk of overvoltage due to high PV penetration levels. However, the curtailment...

  • Application of Uncertainty Quantification Techniques to Studies of Wall-Bounded Turbulent Flows

    Author: Saleh Rezaeiravesh
    Publication date: 2018-11-01 10:22

    Wall-bounded turbulent flows occur in many engineering applications. The quantities of interest (QoIs) of these flows can be accurately obtained through experimental measurements and scale-resolving numerical approaches, such as large eddy simulation (LES). However, due to the prohibitive computational costs imposed by the turbulent boundary layers (TBL) involved in these flows, the use of a standard wall-resolving (WR)LES is limited to low Reynolds (Re-) numbers. As an alternative, wall-modeled (WM)LES can be employed, in which the near-wall region of the TBL is modeled.

    This thesis evaluates the uncertainties involved in the measured QoIs of a set of experiments on TBLs, and also, investigates the predictive accuracy and sensitivity of LES, both wall-resolving and wall-modeled. For these purposes, different uncertainty quantification (UQ) techniques are employed.

    In particular, such techniques are applied to the forward (uncertainty propagation) and inverse (parameter estimation) problems involved in the measurement of mean velocity and wall shear stress using hot-wire anemometry and oil-film interferometry, respectively. The possibility of reducing epistemic...