Rozprawy doktorskie na temat „Linjen for teknisk fysikk”
Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Linjen for teknisk fysikk.
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 48 najlepszych rozpraw doktorskich naukowych na temat „Linjen for teknisk fysikk”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Sognnæs, Ida Andrea Braathen. "Maximum Entropy and Maximum Entropy Production in Macroecology". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12651.
Pełny tekst źródłaStreszczenie:
The Maximum Entropy Theory of Ecology (METE), developed by John Harte, presents an entirely new method of making inferences in ecology. The method is based on the established mathematical procedure of Maximum Information Entropy (MaxEnt), developed by Edwin T. Jaynes, and is used to derive a range of important relationships in macroecology. The Maximum Entropy Production (MEP) principle is a more recent theory. This principle was used by Paltridge to successfully predict the climate on Earth in 1975. It has been suggested that this principle can be used for predicting the evolution of ecosystems over time in the framework of METE. This idea is at the very frontier of Harte's theory. This thesis investigates the hypothesis that the information entropy defined in METE is described by the MEP principle.I show that the application of the MEP principle to the information entropy in METE leads to a range of conceptual and mathematical difficulties. I show that the initial hypothesis alone cannot predict the time rate of change, but that it does predict that the number of individual organisms and the total metabolic rate of an ecosystem will continue to grow indefinitely, whereas the number of species will approach one.I also conduct a thorough review of the MEP literature and discuss the possibility of an application of the MEP principle to METE based on analogies. I also study a proof of the MEP principle published by Dewar in 2003 and 2005 in order to investigate the possibility of an application based on first principles. I conclude that the MEP principle has a low probability of success if applied directly to the information entropy in METE.One of the most central relationships derived in METE is the expected number of species in a plot of area $A$. I conduct a numerical simulation in order to study the variance of the actual number of species in a collection of plots. I then suggest two methods to be used for comparison between predictions and observations in METE.I also conduct a numerical study of selectied stability properties of Paltridge's climate model and conclude that none of these can explain the observed MEP state in nature.
2
Cappelen, Beate Ulrikke Krefting. "Experimental Studies of Finger and Fracture Instabilities in Clays Throughout the Sol-Gel Transition". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13093.
Pełny tekst źródłaStreszczenie:
This report concerns preliminary studies of fingering and fracturing in gelling materials, with the aim of identifying how the phenomena of fingering transitions into fracturing as the breaking medium gradually becomes more solid-like.
3
Voigt, Andre. "Fracturing of Optimal Paths in a Random Lattice". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13125.
Pełny tekst źródłaStreszczenie:
The subject of this thesis is the study of the creation of fault lines in a random lattice, provoked by the successive failure of optimal paths. Using the recently developed Optimal Path Cracked model, we investigate how central characteristics of the successive optimal paths evolve as the lattice breaks down, and how this progression of characteristics depends on the magnitude of disorder imparted on the lattice. We then see how the OPC model, while originally proposed in the context of the shortest path problem, can be generalized to alternate optimal path problems, namely the minimax problem and the widest path problem. It is shown that for a given lattice, the minimax OPC is equal to the the backbone of the shortest OPC. The widest path OPC, although constituting a distinct object on any lattice, is shown to scale with lattice size in the same manner as the minimax OPC and the backbone of the shortest path OPC; with the fundamental process behind it being closely related to the minimax OPC process. Lastly, we explain the connection between the OPC process and a variety of other phenomena which have previously been shown to exhibit similar scaling behavior. We show how the OPC process for the widest path problem can be reduced to the shortest path problem on the dual lattice using the limit of very high disorder, the so-called ultrametric limit, and how an algorithm based on invasion percolation can be used as a quicker method of finding an OPC.
4
Knutsen, Hege. "Characterization of GaN:ZnO p-n junctions". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13262.
Pełny tekst źródłaStreszczenie:
In this master thesis, thin lms of ZnO doped with various cobalt concentra-tions have been grown using Pulsed Laser Deposition (PLD). This growthtechnique is preferred because it is able to grow thin lms from a targetmaterial without changing the elemental ratios from the target. The targetsusing during deposition are sintered pellets of ZnO doped with cobalt, withdoping concentrations of 10, 20 and 30 %.The material was chosen because of its potential for Intermediate BandSolar Cells (IBSC). IBSC is a new concept which aims to create solar cellswhich have higher eciencies than the solar cells available today. From de-tailed balance theory, the concept of intermediate band solar cells shows apotential of a 86 % eciency limit under perfect conditions, which is remark-able compared to the conventional silicon solar cell devices on the markettoday with a eciency limit of 41 %.A series of ZnO thin lms of 10, 20 and 30 % cobalt concentration weredeposited by PLD on a sapphire substrate. These lms were, together with asimilar series containing 1,2 and 5 % cobalt concentration deposited on bothsilicon and sapphire substrates, characterized using Scanning Electron Mi-croscopy (SEM), Energy Dispersive X-ray (EDX) Microanalysis, X-ray Pho-toelectron Spectroscopy (XPS), Hall measurements, X-ray diraction (XRD)and optical transmission spectroscopy.In addition, an attempt to make Schottky diodes of the cobalt dopedZnO thin lms and a p-IB-n junction using GaN:Mg and ZnO:Al as the p-and n- emitter was done. These intermediate band solar cell devices weregoing to be studied by recording dark and illuminated current-voltage (I-V)characteristics.The focus in the study has been to determine which cobalt doping con-centration gives the desired properties for use of ZnO:Co in an intermediateband solar cell device, and to study how a solar cell device with an inter-mediate band material can be realized. The experiments were carried outat NTNU NanoLab, NTNU Department of Physics, NTNU Department ofElectronics and Telecommunications and SINTEF Oslo.Optical transmission spectroscopy and XPS showed that the cobalt inthe ZnO:Co lms were Co2+. This indicates that cobalt is substituting forzink in the ZnO lattice. XRD showed the crystal structure to be c-orientedwith reasonable order. The carrier concentration in the ZnO:Co lms were inthe order of 1018- 1019, decreasing with increasing cobalt concentration. Theresistivity in the samples increased with increasing doping concentration.Investigation of the GaN:Mg wafer showed that it did not have the desiredproperties for device fabrication as it showed n-type conductivity insteadof p-type. The Schottky diodes made of Au-ZnO:Co and Pt-ZnO:Co did not show diode behavior because of surface states in ZnO:Co making ohmiccontacts.
5
Austad, Karianne. "Characterization of electrical activity and lifetime in compensated multicrystalline silicon". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13263.
Pełny tekst źródłaStreszczenie:
This master's thesis concerns the electrical activity and lifetime in compensated multicrystalline silicon wafers used for solar cell production.Resistivity profiles across grain boundaries have been obtained by a Four Point Probe (FPP). Profiles have been investigated in relation to minority carrier lifetime acquired by Microwave Photo Conductance Decay (uW-PCD).It has been found that a two-step process consisting of pre-annealing at either 600C or at 900C followed by phosphorus diffusion (P) gettering will increase the electrical activity of crystalline defects. It has been proposed that a P gettering step should follow directly after annealing for a better dissolution of metallic precipitates. Introduced defects in the material as a consequence of both pre-annealing at 900$^circ$C and of resistivity measurements before gettering, have possibly enhanced the phosphorus diffusion depth in the gettering process. The higher concentration of phosphorus has lead to an augmented lifetime in the material. Metallic impurity precipitation at defects, affecting the electrical activity and the minority carrier recombination rate, has been observed. A good correlation between grain structure, resistivity- and lifetime profiles has thus been established.
6
Fintland, Trygve Westlye. "Measurements of Young's Modulus on Rock Samples at Small Amplitude and Low Frequency : RockHard Deformations". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13580.
Pełny tekst źródłaStreszczenie:
This thesis describes a new instrumental approach designed to measure the complex Young’s modulus on cylindrical samples 1 inch in diameter 2 inch long and typically in the range of 1-70 GPa. Excitation frequencies are from 11 Hz to 167 Hz. The setup is based on the Forced Deformation Method (Batzle et al., 2006) and is capable of measuring phase and magnitude of the dynamic stress and strain. An actuator provides an oscillating force from one end of the plug. Strain is measured on the cylindrical side with three strain gages evenly spaced around the circumference. The lowest recordable magnitude of strain is in the order of 10E-8. Force is measured by a piezoelectric transducer. Values are < 10 N. Plug sample measurements of the Young’s modulus values for Berea sandstone, Castlegate sandstone, Pierre shale, PEEK, and aluminium alloys (ALU-7075 and ALU-6061) are included. Reference material results are in accordance with published values. Some of the instrumentation needed is also given in detail in the previous work (Fintland, 2010).
7
Martinsen, Fredrik Aleksander. "Clustering during Natural Aging and its Effect on Precipitation Hardening in Al-Mg-Si Alloys". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13636.
Pełny tekst źródłaStreszczenie:
The effect of clustering during natural aging of three different Al-Mg-Sialloys with equal Mg/Si-ratios, but different Mg+Si contents have beenstudied through hardness measurements and transmission electron mi-croscopy (TEM). Hardness measurements were performed both duringnatural aging (NA) and after various NA times followed by subsequentartificial aging for all alloys, while TEM-investigations were performedon selected samples. The results from the experiments were comparedand the existence of three different clustering processes were discovered.The first process was established to be Si-Si clustering causing a slighthardness increase during natural aging and a strong hardness increaseafter subsequent artificial aging. The second process was found to beMg-Mg clustering causing a significant hardness increase during naturalaging, and a clear decrease in hardness after subsequent artificial aging.The third process was found to be Mg-Si clustering and simultaneoustransformation of mono-clusters into co-clusters. This combined processcauses a hardness increase both during natural aging and after subse-quent artificial aging. The hardness increase is caused by a refinementof alloy microstructure including a higher number of smaller ” needles.This precipitate type was observed for all alloys and conditions. Thenegative effect of Mg-Mg clusters on precipitation hardness is suggestedto be related to the repulsion of Si from these clusters. This hinders theco-clustering of Mg and Si in the areas surrounding these clusters.
8
Osnes, Christine Birgitte. "Planetary Wave Oscillations observed in Ozone and Temperature Data from Antarctica during 2009". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13648.
Pełny tekst źródłaStreszczenie:
Ozone and temperature data from Troll and Rothera research stations has been analyzed in order to trace planetary waves. Seasonal variations were removed and spectral analysis was performed in order to find dominating frequencies. Possible planetary wave oscillations were found in the 4, 5, 8.5, 10-11, 11-13, 14-15, 17-20, 21-24 and 26-45 day bands, some corresponding to the atmospheric normal modes. These were found consistently in both the ozone and temperature data, indicating that the millimeter wave spectroscopy used to measure the ozone is a viable technique for tracing planetary waves in a region of the atmosphere where other measurements are sparse.
9
Tveiterås, Vebjørn. "Numerical Study of the Interaction of Flow over Two Airfoils in Relative Motion". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13652.
Pełny tekst źródłaStreszczenie:
Computational fluid dynamics (CFD) was be used to investigate aspects of interaction of flow over two airfoils in relatie motion in detail.%Problem statement2D tandem airfoil setups were studied, where the leading airfoil was performing an oscillating motion in the vertical direction while the trailing airfoil was kept stationary. The NACA 0012 and the S809 airfoils were considered.%ApproachAnsys Fluent v13.0 was used as the CFD solver, and Gambit v2.4.6 was employed for grid generation. All simulations were transient at a Reynolds number of either 2*10^4 (laminar flow) or 3*10^6 (turbulent flow). The Transition SST turbulence model was chosen to model turbulence, and Fluent's sliding grid technique was used to achieve the relative motion between the airfoils.%ResultsThe tandem setup was found able to outperform a single airfoil for similar conditions. The presence of a trailing airfoil did not significantly affect the leading airfoil's performance, whereas it did affect the wake structures significanlty. The suction peak near the nose of the airfoil was found to be the most important factor determining the airfoil's propulsive efficiency. Therefore, leading edge vortex (LEV) shedding was found to be of higher importance than trailing edge vortex (TEV) shedding when airfoil performance was concidered.The asymmetric S809 airfoil provided similar results as the symmetric NACA 0012 airfoil. However, the NACA 0012 airfoil achieved slightly higher propulsive efficiencies for the cases investigated, indicating that a symmetric airfoil is desired for flapping airfoil setups. For the tandem setup the highest propulsive efficienies were 0.766 and 0.742 for the NACA 0012 airfoil and the S809 airfoil, respectively. Both peaks were found at k = 0.3 and h = 0.6 (Sr = 0.11) for the leading airfoil. A maximum thrust coefficient of 2.32 was found for the tandem S809 airfoil setup at k = 1.5 and h = 0.5 (Sr = 0.48).The Strouhal number was found to be an important describing parameter, but additional information about the reduced frequency or the oscillating amplitude was needed in order to fully describe the setup.
10
Nord, Magnus Kristofer. "Quantitative (S)TEM analysis of intermediate band solar cell materials". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13655.
Pełny tekst źródłaStreszczenie:
In this thesis the strain properties of two InAs/GaAs quantum dot intermediate band solar cell materials have been explored. Both samples were thin films grown on a (100) GaAs substrate. The quantum dot material was InAs, and the bulk material was GaAs. One sample had AlAs-cap, while the other had GaAs-cap. Geometrical phase analysis was used to study the strain. A higher degree of strain was found in the AlAs-capped sample. Negative strain was observed in directly above and below the quantum dots in both samples. A stacking fault in a quantum dot in the AlAs-capped sample was found to relax all the strain. Analysis of the chemical composition of the AlAs-capped sample was performed using HAADF-STEM and multislice analysis. This analysis found an average indium concentration inside the quantum dots of 25% +- 10%, with peaks up to 50%.
11
Hagen, Torbjørn Ruud. "Numerical Simulations of Flow Past a Truss Tower with an Evaluation of Tower Shadow Models for Wind Turbines". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13726.
Pełny tekst źródłaStreszczenie:
The performance of steady-state tower shadow models for a wind turbine truss tower have been evaluated. The Reynolds-Averaged-Navier-Stokes (RANS) approach, in conjunction with the $k-omega$ Shear-Stress-Transport (SST) model, was used to simulate transient flows past cross sections of a truss tower. The objective was to compare numerical results with Powles', Blevins' and Schlichting's tower shadow models and evaluate their performance on a multimember structure. Parameters for each model have been estimated. It will be shown that the RANS model was able to reproduce realistic results when used in transient simulations on high Reynolds number flows (supercritical regime). The importance of considering unsteady motion when calculating the turbulence intensity, using RANS with transient simulations, will be explained. The multimember extension used for the tower shadow models reproduces the mean velocity profiles quite well, and by using a suitable estimation method, global parameters were found for all models. Additionally, turbulent inflow has been implemented with a user-defined function in Fluent. The results have been evaluated, and show that such such sophisticated inflow modeling is not necessary to predict realistic mean velocity profiles.
12
Hegge, Torstein Storflor. "Scalar wave scattering from two-dimensional, randomly rough surfaces". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13847.
Pełny tekst źródłaStreszczenie:
We study scalar waves scattered from self-affine and Gaussian correlated surfaces. The simulations are performed using rigorous simulation of the integral equations derived from the Helmholtz equation, describing a scalar wave above a non-penetrable surface with a hard wall or free surface boundary condition.An incident, Gaussian shaped beam is scattered from the surface, and the full angular distribution of the scattered intensity is obtained. Self-affine and Gaussian correlated random surfaces are generated, and the resulting scattered intensity is averaged over a large number of surfaces (in the order $N_s=3000$), using the ergodicity of the surface.Compared with analytical calculation of the scattered intensity in the Kirchhoff approximation, our approach gives similar results for less rough surfaces. Compared with simulations of electromagnetic waves scattered from a perfect conductor, without recording the polarisation of the scattered light, our simulations give similar results when using a hard wall boundary condition.We observe phenomena such as specular scattering for less rough surfaces, diffuse forward scattering for more rough surfaces and enhanced backscattering for surfaces where waves scattered multiple times by the surface roughness gives a large contribution to the scattered intensity.
13
Rivedal, Nikolai Hydle. "Two-dimensional Simulations of Particle Deposition on a Cylinder in a Turbulent Cross Flow at Intermediate Reynolds Numbers". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13994.
Pełny tekst źródłaStreszczenie:
The behaviour of particles in turbulent flow, with emphasis on particle deposition on both the frontside and backside of a cylinder, was investigated by means of Direct Numerical Simulations. One-way coupling between the fluid and the particles was applied. Simulations of turbulence forced at small, intermediate and large scales were run on a three-dimensional domain. The turbulence was used as inlet on a two-dimensional flow domain, where a Lagrangian tracker was used to compute the particle motions. The Reynolds numbers used were Rec = 421 and Rec = 1685. For intermediate Stokes numbers, or particle sizes, the number of particles deposited increased when the Reynolds number was raised. The presence of turbulence lead to a further increase in the deposition for these Stokes numbers, compared to the deposition in laminar flow. The increase was at its highest for large scale forced turbulence. The increased deposition of intermediate Stokes numbers on the frontside of the cylinder in turbulent flow was found to be related to the variance of the effective Stokes number, resulting from the fluctuating nature of the turbulent velocity. The deposition of particles with small Stokes numbers was also altered by the presence of turbulence, but this could not be explained by the variance of Stokes number. The mechanism leading to deposition of these smallest particles is related to the turbulent eddies close to the boundary layer of the cylinder, and will need further study. At the backside of the cylinder, the increased deposition at raised Reynolds number and at the presence of turbulence was related to the magnitude of vorticity. Furthermore, preferential concentration of particles in turbulence was observed in the Rec = 1685 cases, demonstrating the effect of the vorticity magnitude being sustained throughout the domain.
14
Walter, Erik Løkken. "Time Series Analysis of Electricity Prices : A comparative study of power markets". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14046.
Pełny tekst źródłaStreszczenie:
During the past few decades, the power sectors of several countries have been substantially reorganized, and liberalized markets for trading of electricity have been established. In this report, evidence from six electricity markets are studied in order to identify characteristics of electricity prices. The market structures, statistical quantities, as well as long-term dependence, are investigated. Detrended fluctuation analysis and the average wavelet coefficient method are employed in order to estimate the Hurst exponent, which quantifies the presence of long-termed dependence. Since it is concluded that the price series are periodic on several time scales, all characteristics are investigated for both the original and deseasonalised versions of the time series. In particular, it is confirmed that the electricity prices are volatile, but that a considerable amount of the volatility is caused by the daily and weekly periodicities. Furthermore, the characteristic return distributions, volatility clustering and price spikes are analysed.
15
Vilpponen, Eirik Timo Bøe. "Analysis of Intermediate Band Solar Cell Performance". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14090.
Pełny tekst źródłaStreszczenie:
This is the Master’s Thesis of Eirik Timo Bøe Vilpponen, and was writtenat the Department of Physics at the Norwegian University of Science andTechnology (NTNU). The thesis is twofold, the first part being the comple-tion of a project undertaken during the fall of 2010. The project concernedthe setup of a solar cell current-voltage characterization lab [4] at the sameDept. of Physics.The second part is an analysis of the current-voltage characteristics ofNTNU-made quantum-dot intermediate band solar cells. A strong focus isput on exploring the possibility of utilizing the Two-Diode Model as a meansof analysis. The two-diode model has been found to have a good potential forthis use, but that it requires a specially made curve fitting computer programto fulfill this potential.
16
Jensen, Jens Tarjei. "Minimum Ignition Energy in a Hygrogen Combustible Mixture". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14095.
Pełny tekst źródłaStreszczenie:
In this thesis the Minimum Ignition Energy, in a hydrogen-air system, is studied by Direct Numerical Simulations (DNS) in a program called the Pencil Code. The heat source used to achieve ignition is modeled by a Gaussian temperature distribution. Three different geometries of the heat source are looked upon, one with spherical geometry in three dimensions, one with cylindrical geometry in two dimensions and the last in one dimension. The results show that the dimensionality of the heat source has a strong impact on ignition.In addition, a new simpler zero dimensional simulation method is proposed with the goal of replicating the results from the Pencil Code. This method needs less calculation power, and uses ignition delay time data together with the heat equation to simulate ignition. The model has proven itself useful since it reproduces the Pencil Code results very well.
17
Aanensen, Nina Sasaki. "Nonlinear Laser-induced Deformations and Forces at Liquid-Liquid Interfaces near the critical Point". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14264.
Pełny tekst źródłaStreszczenie:
The theory of laser-induced liquid-liquid interface deformation has been presented and used to derive a differential equation describing the shape of the deformation. The differential equation has been investigated and solved numerically, and the results have been compared to the experimental results of the Bordeaux group. A model describing the maximum depth of the deformation based on the theory of a sphere in an electric field has also been investigated.The deformations from the numerical solutions of the differential equation are too wide compared to the experimental results. The shoulder-shape that has been observed in the experiments is not present in the numerical solutions. There is reason to believe that the differential equation may be too simple in order to describe the liquid-liquid interface deformation for nonlinear cases. There may be thermal effects that changes the liquid properties due to local temperature variations induced by the laser, causing the liquid parameters to change along the deformation.The model used to estimate the deformation depth does not give reasonable results, as it leads to a deformation that is more than 100 times larger than what is observed in the corresponding experiments. The assumptions made for this model may not be valid, and a discussion on what should be done in order to improve the model is included in this text.
18
Theisen, Erik Bjørge. "Experimental Mueller Matrix Images of Liquid Crystalline Domains in Synthetic Clay Dispersions". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14329.
Pełny tekst źródłaStreszczenie:
This report is a study of how polarized light can improve our understandings of physical phenomena, such as local organization of anisometric nanoparticles dispersed in a liquid.The first part of the thesis considers the theoretical aspects of polarized light. The Maxwell's equations are considered together with the Stokes formalism and the Mueller matrix. The Mueller matrix is analyzed in depth by looking at different ways it can be decomposed into several matrices, each clearly representing the physical phenomena of depolarization, diattenuation and retardance. The physics behind the phenomena will then be shortly addressed.The second part of the thesis describes the Mueller Matrix Imaging (MMI) ellipsometer, developed in the Applied Optics Group at NTNU. The results of Mueller imaging of air will be presented and discussed in order to get more understanding of the ellipsometer.The third and main part of the thesis, focuses on applying the MMI ellipsometer in order to study complex phenomena in clay dispersion. By looking at the development of samples of aqueous clay dispersions, the creation of different phases will be recorded. Some of those phases have crystalline properties and a Mueller matrix imaging can reveal much about its structure. A decomposition of the Mueller matrix can tell even more about the properties of the phases.
19
Aursand, Peder Kristian. "Hyperbolic Conservation Laws with Relaxation Terms : A Theoretical and Numerical Study". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14540.
Pełny tekst źródłaStreszczenie:
Hyperbolic relaxation systems is an active field of research, with a largenumber of applications in physical modeling. Examples include modelsfor traffic flow, kinetic theory and fluid mechanics. This master’s thesis is a numerical and theoretical analysis of such systems, and consists of two main parts: The first is a new scheme for the stable numerical solution of hyperbolic relaxation systems using exponential integrators. First and second-order schemes of this type are derived and some desirable stability and accuracy properties are shown. The scheme is also used to solve a granular-gas model in order to demonstratethe practical use of the method. The second and largest part of this thesis is the analysis of the solutionsto 2 × 2 relaxation systems. In this work, the link between the the sub-characteristic condition and the stability of the solution of the relaxationsystem is discussed. In this context, the sub-characteristic condition andthe dissipativity of the Chapman–Enskog approximation are shown to beequivalent in both 1-D and 2-D. Also, the dispersive wave dynamics of hyperbolic relaxation systems isanalyzed in detail. For 2 × 2 systems, the wave-speeds of the individualFourier-components of the solution are shown to fulfill a transitional sub-characteristic condition. Moreover, the transition is monotonic in thevariable ξ = kε, where ε is the relaxation time of the system and k is thewave-number. A basic 2 × 2 model is used both as an example-model in the analyticaldiscussions, and as a model for numerical tests in order to demonstratethe implications of the analytical results.
20
Håkonseth, Gunnar. "Diffusjon av vann i sotfylte kappematerialer for polymere sjøkabler". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15008.
Pełny tekst źródłaStreszczenie:
Vanntrevekst er den viktigste årsaken til aldring i polymerisk isolasjon i mellomspenningskabler. Sia vanntrær ikke dannes ved lav relativ fuktighet (R.H.), er det viktig å holde relativ fuktighet i isolasjonen lav så lenge som mulig. Dette kan gjøres ved å beskytte isolasjonen med ei kappe av to polymerer. For å beregne vanntransporten inn i isolasjonen, må kappematerialenes vanntransportegenskaper kjennes. For noen polymerer varierer vanntransportegenskapene med det hydrostatiske trykket og den relative fuktigheta (damptrykket). I denne oppgaven er det målt transportkoeffisienter for to kandidater til kappematerialer: én halvledende lineær lavdensitetspolyetylen (LLDPE) og én halvledende eterbasert termoplastisk polyuretan (TPU). Noen av prøvene har vært utsatt for strekking til 10 % statisk forlengelse og etterfølgende relaksasjon i forkant av forsøkene, for å finne ut om ei slik mekanisk påkjenning har noe å si for transportkoeffisientene. Det er gjort målinger av metningskonsentrasjoner ved 0,1 MPa og 30 MPa hydrostatisk trykk, og permeabilitetsmålinger ved forskjellige damptrykk. Konklusjonene om metningskonsentrasjonen i TPU ved 0,1 MPa og 30 MPa hydrostatisk trykk trekkes delvis på grunnlag av et tidligere arbeid. I tillegg har diffusjons- og løselighetskoeffisientene for ustrukket TPU blitt målt ved forskjellige damptrykk. Det er ikke funnet noen signifikant sammenheng mellom det hydrostatiske trykket og vannopptaket i noen av materialene, hverken med strukkede eller ustrukkede prøver. Det er heller ikke funnet at strekking har noen signifikant innvirkning på transportkoeffisientene, bortsett fra at strukket TPU viser en ca. 15 % større metningskonsentrasjon enn ustrukket TPU. Det er funnet at transportkoeffisientene i TPU varierer med damptrykket, men hverken diffusjons-, løselighets- eller permeabilitetskoeffisienten varierer mer enn med en faktor 3 mellom 20 % R.H. og 80 % R.H. For LLDPE er det ikke gjort like omfattende undersøkelser, men permeabilitetskoeffisienten i det materialet viser ingen damptrykkavhengighet.
21
Walle, Øystein. "Engineered Surfaces for Redirection of Light". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15402.
Pełny tekst źródłaStreszczenie:
It is of interest to construct windows that can spread the transmitted light in a specified manner. The Kirchhoff approximation in the geometrical optical limit in combination with a chosen general form of the window surfaces yields the profile for the window surfaces, letting us specify how the light should be spread.The probability distribution function for the slopes of a window surface consisting of joined line segments was implemented in the simulation software Maxwell1D. Simulations show the feasibility of such windows. However they do not respond well when subject to light incident with another angle of incidence than the angle in mind.By using Snell's law to compensate for using a simpler system, the time needed for the simulations can be greatly reduced while simultaneously obtaining a higher accuracy in the results.
22
Hansen, Christoffer Berge. "A random Matrix Approach to collective Trends of falling and rising Stock Markets". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16328.
Pełny tekst źródłaStreszczenie:
An inverse statistics analysis of one minute stock quotes from 492 large Europeancompanies has revealed the existence of a gain-loss asymmetry in thefollowing index. The gain-loss asymmetry differs from that observed for dailyclosure prices of the Dow Jones Industrial Average [38], as the probability ofthe optimal investment horizon for a gain is higher than that of a loss. Forindividual stocks, the gain-loss asymmetry was observed to only appear forsignificantly larger return-levels. To the best of our knowledge, this is thefirst time such an analysis has been performed on high-frequency data.A principal component analysis was done by performing an eigenvalue decompositionof the correlation matrix from a sliding time-window. The firstprincipal component was observed to describe the market excellently. Its correspondingeigenvalue was observed to be significantly larger than theoreticalpredictions from random matrix theory, implying that the eigenvalue carriesinformation common to all stocks. Using this eigenvalue as an index measuringthe collectivity in the market has revealed the existence of collectivetrends that appear to be stronger during falling than rising markets. Thishas been observed for two different datasets, the above described one minutestock quotes and daily closure prices from 29 stocks composing the DJIA lateFebruary 2008. The observation is in accordance with results of Balogh etal. [40], and provides further support to the speculation of Johansen et al.[37] that a difference in collective trends is the reason behind the gain-lossasymmetry observed in indexes and not for individual stocks for the samereturn-level.The key idea behind the fear factor model of Donangelo et al. [42] has beenstrongly supported by the observation that collective trends appear to bestronger during sharp index drops. As the collectivity increment has beenobserved to be dependent on the size of the index drop, it is suggested thatthe model should incorporate also individual fear factors for economic sectors,in addition to the global fear factor governing the market as a whole. Periodsexhibiting a rising index positively correlated to the strength of collectivityhas indicated the presence of an optimism factor that also should be incorporatedin the fear factor model [42], forcing stocks to rise synchronously.
23
Mersland, Mailinn Blandkjenn. "Asymmetriske Energivariasjoner i Turbulens : Invers statistikk metode for beskrivelse av asymmetrisk energivariasjon". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16332.
Pełny tekst źródłaStreszczenie:
Energivariasjon i fullt utviklet turbulens er studert. I en tidsserie for tur- bulens energi er det oppdaget en asymmetri mellom positive og negative energiendringer. Invers statistikk metode gir en mulighet til å studere denne asymmetrien nærmere.For analyse i denne oppgaven er turbulent strømning generert ved bruk av GOY skallmodell. Skallmodellen er en tilnærmingmodell til Navier-Stokes likninger for strømningens bevegelse. Modellen er tidligere vist å gi realistiske verdier for energi og hastighet for en turbulens strømning.Ved bruk av forward statistikk og invers statistikk på turbulens ener- gi er det funnet en asymmetri i energiendringen. Det er vist at en negativ energivariasjon høyst sannsynlig inntreffer før en positiv energivariasjon av samme størrelse. Tidsforskjellen er empirisk funnet til å følge sammenhen- gen δτδE ∼ δE0,749, hvor τδE er forventningstiden for en energivariasjon δE. I tillegg er det funnet en positiv trend i tidsserien for energi, som sier at ener- giendring etter korte tidsintervall høyst sannsynlig er positiv. Det er gjort et forsøk på å beskrive denne asymmetrien og opprinnelsen av dette fenomenet er drøftet.
24
Iden, Simon Riis. "Exploring possibilities in AFM studies of InAs/GaAs QDs". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16356.
Pełny tekst źródłaStreszczenie:
The main focus of this master thesis work has been to image InAs emph{quantum dots} (QDs) using emph{atomic force microscopy} (AFM), to identify and evaluate various image processing methods used to estimate the volume of the InAs QDs. The InAs QDs studied in this thesis work, had been deposited on GaAs substrates, using solid-source emph{molecular beam epitaxy} (MBE) before the thesis work started. The total QD volume was determined for all samples, using eight different estimation methods. The purpose of estimating the total QD volume, was to compare the total volume to the deposited volume.Previous studies on similar samples, have indicated that the total volume can be larger than the deposited volume during MBE growth. This discrepancy is explained by incorporation of Ga from the substrate during growth. This was not observed in this thesis work. One possible explanation is that the samples have oxidized; resulting in a lower measured height.In addition, the relationship between atomic steps, defects and the appearance of large QDs were studied. parTwo series of samples were studied: one in which the QD growth temperature was varied and one in which the amount of deposited InAs was varied. The total QD volumes were found to increase with the QD growth temperature and the deposited InAs thickness. Square-shaped defects and contours of 2D islands were observed in nearly all samples. Higher/multiple terraces seem to be related to regions of higher QD density.
25
Fyhn, Anna Maren Andersen. "Electrodeposition of Metal Oxides for Solar Cell Applications". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16361.
Pełny tekst źródłaStreszczenie:
This thesis investigates the electrodeposition process of zinc-, copper-, silver-, and silver copperoxides at cathodic and anodic voltages. Silver copper oxide has been successfully electrodepositedon a substrate of PtSi from a pH 12 dilute solution of copper nitrate, silver nitrate and sodiumhydroxide at 0.9V vs a silver metal cathode. This film was confirmed to be polycrystalline AgCuO2by EDS and XRD studies. Zinc oxide and copper oxide were deposited on gold substrates from their respective nitrates. The zinc oxide deposition was confirmed polycrystalline in XRD and had a band gap between 3.2eV and 3.5eV measured by optical reflectance. The copper oxide appeared polycrystalline in SEM but only amorphous signal was achieved in XRD, the material had a band gap of around 2eV. Despite many attempts, clean silver oxide was not successfully deposited. These materials may all be suitable for solar cells applications.
26
Aase, John Fjermestad. "Structure of Clean and Oxidized PdCu(100) Surfaces at the Atomic Scale". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16365.
Pełny tekst źródłaStreszczenie:
In this thesis, clean and oxidized Pd(57)Cu(43)(100) single crystal surfaces were studied by LEED, STM and XPS in UHV conditions. The clean sample annealed to 300 degrees C has been found to either consist of ordered domains of Pd or Cu atoms forming a c(2 × 2) structure, or by a more disordered alloy c(2 × 2) structure of p4g symmetry. Small areas of (1 × 1) structure as well as screw dislocations and island- like formations are present on this surface. Annealing the clean sample to 600 degrees C causes Cu segregation to the surface as well as a shift towards higher binding energy of Pd 3d(5/2) core levels, and an almost defect- free surface with p(2 × 2) structure is seen. Oxidation at 300 degrees C of the surface annealed to 300 degrees C shows that a c(2 × 2) covers the whole surface for all oxygen dosages at 68L or above, and XPS spectra do not vary with oxygen dosage, hence the c(2 × 2) is inert in this case. For dosages of 1350L or above, oxide islands and a large number of defects could appear, depending on the preparation history of the sample. Oxidation at 300 degrees C and 600 degrees C of the Cu rich surface annealed to 600 degrees C reveals up to seven structures, which are p(2 × 2), c(2 × 2), (4 × 4)- like, hexagonal, maze- like, (2root(2) ×root(2))R45degrees missing row type and one more structure that could not be characterized. There is evidence that copper oxide phases are formed for the Cu rich surfaces annealed to 600 degrees C, but no bulk oxide was formed in any experiments. A detailed understanding of clean and oxidized Pd(57)Cu(43)(100) has been obtained at the atomic scale.
27
Ingebretsen, Thomas. "System Identification of Unmanned Aerial Vehicles". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16776.
Pełny tekst źródłaStreszczenie:
The least squares method has been applied to estimate parameters inan aerodynamic model of a simulated aircraft, using data that can beexpected to available from sensors on an Unmanned Aerial Vehicle. Acombination of two non-linear state observers have been implemented toestimate wind data such as angle of attack, sideslip and dynamic pressure.Simulations have confirmed that the observers are able to estimete thewind data using noisy sensor measurements. Parameter estimation havebeen demonstrated with both measured and estimated wind data.
28
Kjerstad, Knut Brøndbo. "Clay-Oil Droplet Suspensions in Electric Field". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18354.
Pełny tekst źródłaStreszczenie:
Silicone oil droplets containing synthetic smectite clay submerged in another immiscible organic oil have been studied by observing clay particle movement, oil circulation and drop deformation when an electric field is applied. Results show how electric field strength, electrohydrodynamics, dielectric and conductive properties determines the fluid flow, clay particle formation and drop deformation.
29
Stige, Kristoffer. "Spin-Polarized Non-Local Transport in Hybrid Structures with Magnetic and Superconducting Correlations". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18396.
Pełny tekst źródłaStreszczenie:
In this thesis we theoretically examine spin-polarized non-local transport in two junctions built up by materials with superconducting and magnetic properties. The first consists of a Zeeman-split superconductor placed between two normal metals. We find that such systems can generate a spin-polarized non-local current even when the injected current is unpolarized. The effect is however mostly geometric and take place also when the superconductor is switched with a normal metal. The second system is built up by two ferromagnetic wires coupled by a superconductor via spin-active interfaces. We investigate the circumstances which allow for an inverse spin-valve effect. For certain parameter ranges we find that a crossover between positive and negative magnetoresistance is possible as a function of temperature.
30
Romijn, Elisabeth Inge. "Development of 3-D Quantitative Analysis of Multi-Photon Microscopy Images". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18425.
Pełny tekst źródłaStreszczenie:
Motivation: Cartilage is a robust but flexible connective tissue found in most joints of the body. The collagen fibres present in the extracellular matrix of cartilage contribute to its tensile strength and stiffness. The purpose of this study is to develop and implement methods to determine the orientation and anisotropy of collagen fibres in 3-D images gen- erated with multi-photon microscopy. The motivation behind developing these techniques is to improve the foundation for further studies on understanding the characteristics of the cartilage matrix. This in turn would give a better foundation for developing artificial matrices and mechanical models, as well as improve diagnostics.Material and methods: The two methods developed in this study are based on analysing the frequency domain. One is an expansion of a previous developed method by Chaudhuri et al. [1]. This method is based on evaluating the average intensity at different directions in the frequency domain. The direction with the least average intensity is equivalent to the direction of the fibres. The other method is based on thresholding the frequency domain according to intensity followed by fitting an ellipsoid to the remaining data set. The direction of the collagen fibres is equivalent to the direction of the shortest axis of the ellipsoid. These methods are called the sector and ellipsoid method, respectively. To determine how robust these methods are a series of tests were developed. The focus of these tests was to determine if the methods are rotational invariant and if the results are influences by different preprocessing techniques. These preprocessing techniques are: median filtering, deconvolution and skeletonization of the original image containing the collagen fibres. It is also important to determine the sensitivity of the ellipsoid method according to the chosen threshold value. In addition data generated fibres and frequency domains were made to determine the accuracy of the methods.Results and conclusion: The sector method was not very robust. For most cases there is not one specific direction that has the least average intensity in the frequency domain. Instead there is a quite large minimum area. The ellipsoid method shows promising results. It managed to find the correct direction both for the data generated data sets, but also for the real images. It seems like no preprocessing nor frequency filtering, except for thresholding, is needed to still find the correct direction and its anisotropy. The only remark is that the automatically chosen threshold value was to low for one of the samples. This can probably be improved by making a slight change in the process for choosing a threshold value.
31
Lutro, Henrik Fahre. "The Effect of Thermophoresis on the Particle Deposition on a Cylinder". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18489.
Pełny tekst źródłaStreszczenie:
The effect of thermophoresis on the particle deposition on a cooled cylinderin non-isothermal laminar gas ow has been studied using Direct NumericalSimulations (DNS). Simulations where thermophoresis have been taken intoaccount for different Stokes numbers and particle-to-gas thermal conductivityratios, Λ, have been performed at Reynolds number Re = 380. In additionreference cases, simulations where thermophoresis have not been taken intoaccount, have been performed both for isothermal and non-isothermal owfor Re = 20 and Re = 380.The ratio between the front side particle impaction efficiency in the non-isothermal reference case and the isothermal reference case for the smallestStokes numbers considered was expected to be proportional to the ratio ofthe free stream temperature and the cylinder temperature, according to an-analytical considerations. The simulations for Re = 20 was in good agreementwith this relation, but for Re = 380 the front side particle impaction efficiency for the smallest particles was lower in the non-isothermal referencecase compared to the isothermal reference case. This is believed to havebeen caused by inaccuracies in the numerical method for the non-isothermalsimulation at Re = 380.Thermophoresis was not found to affect the particle impaction for thelargest Stokes numbers. For intermediate and small Stokes numbers the effect of thermophoresis depended on Λ. The particle impaction efficiency wassignificantly higher, both for the front side and the back side, in the ther-mophoretic simulations compared to the non-isothermal reference case forparticles with Λ = 1 and Λ = 100. The particle impaction efficiency forparticles with Λ = 1000 was lower, both for the front side and the back side,in the thermophoretic case compared to the non-isothermal reference case.
32
Hansen, Eirik Schrøder. "Numerical modelling of marine icing on offshore structures and vessels". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18774.
Pełny tekst źródłaStreszczenie:
A numerical model for predicting icing on offshore structures and vessels has been developed and implemented. The model calculates the icing caused by freezing sea spray, and focuses on two distinct sources of spray - spray from droplets blowing off whitecaps on the sea surface, and spray from waves colliding with the vessel. The implementations of both wind-induced and wave-induced sea spray are based on existing theoretical models, and are combined with a thermodynamic model for the icing process. The model may be used to calculate icing on reference objects or structures on the vessel. In addition, algorithms have been developed so that the model can be applied to polygon-based vessel geometries, calculating the icing distribution over the entire vessel. The model has been applied to meteorological observations and hindcast data for locations in the Norwegian Sea and Barents Sea, in particular at the locations of the Norne field and the undeveloped Skrugard and Shtokman fields. The results indicate that the icing will be comparable at the locations of Skrugard and Shtokman, and that both the frequency and severity of icing events will be far greater for these two locations than for Norne. Although conditions at Shtokman are colder than at Skrugard, the higher winds and waves near Skrugard will increase the available sea spray in the model, thus making the number of severe icing events more similar for the two locations.
33
Øvland, Ragnhild. "Coherent Plane-Wave Compounding in Medical Ultrasound Imaging : Quality Investigation of 2D B-mode Images of Stationary and Moving Objects". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18834.
Pełny tekst źródłaStreszczenie:
Coherent plane-wave compounding is the coherent summation of several successive plane waves incident at different angles. This thesis presents results from simulations and in vitro and in vivo measurements of stationary and moving objects, with focus on loss of resolution and contrast due to object motion. Resolution and contrast results for several angle selections, angle sequences and object velocities with and without motion correction have been compared.It is shown that using a subset of plane-wave tilt angles by decimating the optimal selection introduces grating lobes which degrades the image contrast, while imaging with a lower maximum tilt angle degrades the lateral resolution. The contrast loss for decimation factor 2 was more significant for simulations than for in vitro measurements. While the contrast went from -40 to -30 dB for the simulations, a decimation factor of 4 was needed to degrade the contrast significantly for the measurements. Decimating the angle selection by a factor of 2 doubles the achievable frame rate. A reduction in maximum angle from 13.7 to 8.2 deg., which corresponds to an increase in transmit F-number from 2.1 to 3.5, gives less than 0.3 mm degradation of lateral resolution. The lateral resolution is of the order of 1 mm. This reduction in maximum angle increases the frame rate by a factor of 1.2.Axial point scatterer velocity leads to considerably worse image quality than for stationary scatterers, while the effect of lateral scatterer velocities is limited. The degree of contrast and resolution loss due to object motion is dependent on the selection of plane waves which constitute a frame, and the sequence in which the plane waves are transmitted. Using a subset of the optimal angle selection leads to improvement in image quality for an axial velocity of 10.0 cm/s for decimation factor 4, but not for decimation factor 2, even though the total scatterer movement per frame is reduced by the reduction of transmitted plane-waves. The loss of quality due to motion was less for fewer tilt angles, but the total image quality was still worse for many of these sets of angles due to grating lobes.The unwanted effects of motion for in vivo-measurements were not seen to the same extent as for simulated point scatterers, and working with the coherent plane-wave compound seems promising for moving objects.
34
Garberg, Øyvind Steensgaard. "Positive Partial Transpose States in Multipartite Quantum Systems". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18853.
Pełny tekst źródłaStreszczenie:
In this master thesis I study the extremal positive partial transpose (PPT) states of the three qubit $(2times2times2)$ system using numerical methods. Using two algorithms which locate PPT states of a specified rank and extremal PPT states respectively, I have located numerical examples of extremal PPT states with a variety of ranks. These numerical results confirm the analytical result that all PPT states of rank less than four are separable. I also derive an upper limit on the ranks of extremal PPT states. The extremal PPT states of lowest rank, the rank four states, were studied in more detail. These states were confirmed to be biseparable in accordance with both previous analytical and numerical results. The range and kernel of these states were examined for product vectors, but none were found. In an attempt to parametrize the SL$otimes$SL equivalence classes of these extremal rank four states I have studied an analytical method to construct such states based on unextendible product bases (UPBs). This method can be used to create PPT states from a single equivalence class where, by design, the kernel of all states contain a UPB and the range contains no product vectors. All states where the range is not spanned by a basis of product vectors are necessarily entangled. I also present a numerical method for creating extremal rank four states that are symmetric under various combinations of partial transposes. Numerical examination of these states reveal no product vectors in neither range nor kernel. The existence of rank four states with and without product vectors in their kernel implies the existence of at least two equivalence classes. To get a better impression of these equivalence classes I construct quantities that are invariant under SL$otimes$SL transformations and must therefore have the same value for all states in the same equivalence class. Calculating the values of these invariants for all the rank four extremal states I have generated gives a seemingly continuous range of values. This indicates that there is an infinite number of equivalence classes likely described by one or more continuous variables. The invariants also revealed an interesting set of states that may belong to a single equivalence class, where one invariant is zero and the others have identical values. This was the only equivalence class where more than one of my states were included. There is obviously something special about this class, but I do not know what it is.
35
Vandbakk, Martin. "Organic Contaminations in Sub-Marine AC and DC High-Voltage Cables". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18866.
Pełny tekst źródłaStreszczenie:
In dielectric insulating materials subjected to alternating electric fields there are energy losses associated with polarization mechanisms and resistivity. A typical dielectric material used for insulation of high voltage sub-marine cables is cross-linked polyethylene (XLPE) produced from polyethylene (PE). Under production, PE can stagnate in high temperature thermal zones and consequently be subjected to thermal oxidation that introduces polar carbonyl groups to the polyethylene chain, which leads to increased energy losses, inferior insulating properties and subsequent degradation and eventually breakdown and failure of the cable.The oxidized polyethylene can contaminate the insulating material in the form of microscopic particles embedded in the material, that are difficult to detect and separate from the polyethylene granulate. In this work the focus have been on documenting the fundamental properties of the oxidized XLPE contaminations, such as complex permittivity, associated energy losses and breakdown strengths, compared to that of un-oxidized XLPE.In this thesis the thermal oxidation process of XLPE and PE has been studied in order to determine the degree of oxidation and carbonyl contents, using Fourier transform infra red spectroscopy. Three real contaminations was found, investigated and categorized. The contaminations was replicated through thermal oxidation of XLPE samples in a ventilated heat cabin at 170˚C.The electrical properties of replicated contaminations has been investigated using dielectric spectroscopy and breakdown strength-tests. At 50Hz the real relative per- mittivities is measured to be ε' = 2.30 for un-oxidized XLPE, ε' = 2.57 for category 1 samples, ε' = 2.72 for category 2 samples and ε' = 4.19 for category 3 samples.The lossy polarization process is characterized by the imaginary part of the permittivity ε''. It is seen that the dielectric losses are indeed increasing with the presence of polar carbonyl group, as expected from theoretical considerations. It is also seen that ε'' in oxidized samples increases as the frequency decreases, which indicates that the conductive process dominates the low frequency domain, and that the DC conductivity is higher in contaminations than in un-oxidized XLPE. Break- down tests was preformed using the ASTM D149 standard for dielectric breakdown testing.It was observed a decrease in breakdown strength in oxidized XLPE. The breakdown strengths decreased from (55.31±31)kV/mm in un-oxidized XLPE to (24.07±12.88) kV/mm in the most oxidized category 3 XLPE sample.As a consequence of the theories and experimental results presented in this work, it can be said that there is a causal relation between dielectric losses and breakdown strengths in oxidized XLPE material which can be sumerized as follows: The intro- duction of polar carbonyl groups through thermal oxidation to polyethylene causes increased permittivities and dielectric losses. Subsequently there will be a decrease in electric breakdown strength of the XLPE insulation. Contaminations of oxidized material embedded in a solid insulation system may pose a reliability issue and may eventually be the cause of breakdown and failure of the cable.
36
Waage, Magnus Heskestad. "Radiative corrections to van der Waals interaction in fluids". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18872.
Pełny tekst źródłaStreszczenie:
The van der Waals interaction energy is derived for a homogenous fluid of polarizable particles. Low-temperature corrections to the van der Waals interaction energy are computed numerically for three cases: Dilute media with radiative interactions, arbitrarily dense media without radiative interactions, and arbitrarily dense media with radiative interactions. The validity of the model used to calculate the corrections at arbitrary densities is argued for, by comparison with the results for low densities.
37
Chapana, Randi Synnøve Hegdal. "The Relative Influence of Solar Radiative and Solar Geomagnetic Variation on the Dynamics of the Polar Upper Mesosphere". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18887.
Pełny tekst źródłaStreszczenie:
Resent research indicates that there might be a connection between perturbation of the Earth's geomagnetic field caused by solar wind, and the atmospheric circulation. In this project the mesospheric meridional and zonal wind, obtained from the SuperDARN radars Goose Bay, Hankasalmi, Kapuskasing, King Salmon, Kodiak, Pykkvibær, Saskatoon and Stokkseyri in the northern hemisphere was compared with the global Ap index along with the measure for solar radiance, the F10.7 index. Wind data from the SuperDARN radars were available for every hour and geomagnetic and irradiance data for every month. The solar atmospheric tides along with seasonal effects were removed from the wind data and the perturbation of the residual wind due to Ap and F10.7 was used to see if any connection between the mesospheric wind and Ap/F10.7 could be found, and if they influenced the wind in a similar manner. A tendency for more equatorwards and eastwards winds during periods of high geomagnetic activity was found. In addition, this effect was observed to increase with increasing geomagnetic latitude for the zonal wind. Ap and F10.7 often affected the wind in a similar manner, making it hard to distinguish the two. Using linear regression, the correlation between them was found to be high over the timescales of this study.
38
Hox, Kristian. "Experimental Studies of Instabilities Near the Sol-Gel Transition". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18888.
Pełny tekst źródłaStreszczenie:
This master thesis presents a new experimental way to dynamically determinerheological properties of a complex fluid. The fluid investigated is asuspension of the synthetic clay mineral laponite of 3 wt%. This is mixedtogether with distilled water or a NaCl solution with concentrations bellow10^2 M. Laponite gels are thixotropic and shear thinning with a yield stress.In the experiments done during this thesis the transition between liquid andsolid behavior is investigated using a Hele-Shaw cell and a rheometer. Threedifferent phases is observed with respect to waiting time and NaCl concentration.These are recognized as a liquid phase for small concentration ofNaCl and short waiting times and a solid phase for high concentration ofNaCl and long waiting time. In the intermediate range a viscoelastic phaseis observed.Some experiments were done with the sample placed between crossed polarizers,and birefringence was observed in all three phases. In the solid phaseit is observed only a small area around the fracture tip. In the liquid phasethis is observed in front of the finger, but this is not a stable phase. Inthe viscoelastic regime a stable nematic phase occur along the stress fieldaround the interface of the bubble. This nematic phase will align normal tothe glass surface. Fracture like patterns in the nematic phase are observed.This is an elastic behavior with the clay platelets aligning normal to thestress field to prepare for fractures to propagate there.Different NaCl concentrations will give different arrested states, respectivelya repulsive glass and a attractive gel. It is expected that glass and gels behavedifferently in this experiment, but this was not confirmed. A gel phasehave been observed in concentrations of NaCl above 5*10^3 for waitingtimes up to 605 hours. For smaller concentrations a even longer waitingtime is expected and experiments on this needs to be performed in futurestudies.In addition this experiment could investigate and give insight of flow incomplex fluid. To investigate this further, tracer particles have been usedin a few experiments. The results are promising for further studies.In this thesis work, a large range in waiting times and concentrations of NaClhave been investigated. In future studies it should be carried out experimentsin a smaller range of these parameters along with other parameters.Also a more quantitative analysis should be carried out. Especially thetransitions between fluid/viscoelastic and viscoelastic/solid is interesting toinvestigate further.
39
Rustenberg, Karin Hveding. "X-ray Studies of Capture, Storage and Release of CO2". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18889.
Pełny tekst źródłaStreszczenie:
We show experimentally that CO2 intercalates into the interlayer spaceof the synthetic smectite clay Li-fluorohectorite (LiFh). The intercalationoccurs for a range of conditions in terms of pressure (5 bar to 20 bar) andtemperature (-20'C to 5'C). The mean basal spacing of the clay layersin LiFh intercalated by CO2 is found to be approximately 12.0 Å.We observe that the dynamics depends on the pressure, with a higherintercalation rate at increased pressure. Even under pressure of 20 bar,intercalation of CO2 is slower than H2O intercalation in fluorohectoritesby orders of magnitude.In situ observations show that LiFh is able to retain CO2 in the interlayerspace at room temperature, and the CO2 only starts leaving the clay attemperatures exceeding 30'C. Hydrated and CO2-intercalated clays areindistinguishable by use of X-ray diffraction alone. The difference in behaviorat higher temperatures is used as an additional confirmation thatintercalation of residual water is not the cause of the observed swelling.Furthermore, we report a new intercalation state corresponding to intercalationof more than one layer of CO2 into the interlamellar space, andhave also observed changes in the intercalation state of a monohydratedLiFh sample under exposure to CO2.We believe that the findings, concerning both intercalation and deintercalation,could be relevant for application of clays related to capture, transportor storage of CO2.
40
Granholt, Jason Daniel David A. "Precipitate Structure Changes during Overaging in an Al-Mg-Si Alloy". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18908.
Pełny tekst źródłaStreszczenie:
Starting from a super saturated solid solution and two different conditions withβ′′ precipitates (T6) an Al-Mg-Si alloy was heat treated at 200◦C and investigated byhardness measurements. One of the T6 conditions was investigated with transmissionelectron microscopy (TEM). The phase transformation to post-β′′ was studiedwith TEM and there was found that post-β′′ phases nucleated on the β′′ particles.After longer overaging times the growths were larger. A simple model was proposed, and it suggested that the growth of post- β′′ phases was the first steps in thetransformation of β′′, and that the final result was a microstructure consisting onlyof post- β′′ particles
41
Gislesen, Halvor, i Hans Skarsvåg. "Renormalised Intrinsic and Extrinsic Impurity Induced Spin-orbit Scattering in Graphene". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19025.
Pełny tekst źródłaStreszczenie:
We study the effect of an impurity potential on spin-memory loss in graphene. Various general methods for finding the spin-orbit related effect of a slowly varying impurity potential on a semiconductor have been examined. We have also revisited problems concerning electronic properties and spin relaxation in graphene. To this end, the bandstructure for graphene has been calculated through analytical and computational methods. The following results have been reproduced: Low energy excitations behave like massless relativistic particles with an effective speed of light at roughly 10^6 m/s. Intrinsic spin-orbit coupling splits the bands at the Fermi level. The importance of the $d$ orbitals for this effect is also shown. Extrinsic spin-orbit coupling induced by a perpendicular electric field give rise to a Rashba type Hamiltonian. Our novel results are related to extrinsic effects from an impurity. We have calculated the renormalised impurity induced spin-orbit coupling due to mixing of the conduction bands and the other bands. This renormalisation is at most comparable to the vacuum term, and thus cannot explain the experimental results on spin relaxation.
42
Henriksen, Lisa Grav. "Pump-probe experiments of multicrystalline silicon for solar cell applications". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19207.
Pełny tekst źródłaStreszczenie:
In order to make cost effective solar cells from mc-Si materials, the negative contributions from defects and impurities should be reduced. The analysis of the photogenerated carrier properties is therefore of great importance for characterising carrier processes and hence, for improving the material performance.In this work, pump-probe measurement of a range of silicon wafers have been performed, using anultrafast laser of 800 nm wavelength and 85 fs pulses. The optical response in the samples were analysed by measuring the reflected probe beam initial transient.The purpose of this theses was to explore the use of pump-probe experiment to study carrier dynamics in mc-Si. Measurements of single c-Si samples were used as a basis for developing good experimental skills as well as achieving knowledge about carrier dynamics in c-Si. The initial Delta R/R was studied for a range of input parameters, aiming to characterise important contributions to the measurements.The effects of passivation has been studied, indicating a significant contribution to R~R. Etchingoff the passivated layer of an oxide (SiO2) wafer, showed a radically increased in pump beam reflectivity, from 9% to 32%, and a reduced DeltaR~R from 47×10-6 to 37×10-6 was be observed. Analysis has showed that incident angle may be chose such that the pump reflection loss is at a minimum for the given passivation thickness.The final results showed a R~R is in the range of (14-41)e-6 for bare c-Si, and (47-171)e-6 for passivated c-Si wafers.Ultrafast initial recovery has been observed for mc-Si samples, and attributed to trapping of carriers. Decay times in the range of 1-6 ps are deduced and trapping densities are found as (1:3 - 4:3) × 10^18 cm-3, which is in the same order as the excitation densities.A methodology for using pump-probe measurements to analyse mc-Si samples is established, and the technique is used in characterising the observed defect states, which is of great interest for improving solar cell materials.
43
Aas, Rune Øistein. "Electromagnetic Scattering : A Surface Integral Equation Formulation". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19240.
Pełny tekst źródłaStreszczenie:
A numerical approach to solving the problem of electromagnetic (EM) scattering on a single scatterer is studied. The problem involves calculating the total EM field in arbitrary observation points when a planar EM wave is scattered.The method considered is a surface integral equation (SIE) formulation involving the use of a dyadic Green's function. A theoretical derivation of the magnetic field integral equation (MFIE) and the electric field integral equation (EFIE) from Maxwell's equations are shown. The Method of Weighted Residuals (MWR) and Kirchoff's Approximation (KA) with their respective domains of application are studied as ways of estimating the surface current densities. A parallelized implementation of the SIE method including both the KA and the MWRis written using the FORTRAN language. The implementation is applied in three concrete versions of the scattering problem, all involving a spherical perfectly conducting scatterer, namely the cases of incoming wavelength much larger, much smaller and comparable with the radius of the scatterer. The problems are divided into two separate solution categories, separated by whether or not the KA is assumed valid. A recursive discretization algorithm was found to be superior to a Delaunay triangulationalgorithm due to less spread in element shape and area. The produced resultsfitted well considering the interference pattern and symmetry requirements with relative errors in the order of magnitude $10^{-5}$ and less. The case of having large wavelength compared to the radius was also compared with Rayleigh scattering theory considering the far field dependence on wavelenth, scattering angle and distance from the scatterer. This resulted in relative errors of 2.1 percent and less. The main advantage of the SIE method is only requiring the surface of the scatterer to be discretized thus saving computational time and memory compared to methods requiring discretization of volume. The method is also capable of producing accurate results for observation points arbitrary close to the scatterer surface. A brief discussion on how the program may be modified in order to extend its capabilities is also included.
44
Meyer, Karsten. "On the Design of Accurate Spatial and Temporal Temperature Measurements in Sea Ice". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19245.
Pełny tekst źródłaStreszczenie:
Studies on sea ice have become increasingly popular among researchers in the last decades, due to its effect on the global climate and the challenges it presents for arctic engineering. The research is in demand of reliable data acquisition on various properties, in this case the temperature gradient in forming sea ice.This project continues the development of a spatial temperature instrument, which intends to provide measurements with an accuracy of 0.01°C, making the researchers able to distinguish between fine variations in melting point due to salinity.The outcome of the project is a complete revision of the probe design, which according to simulations not until now provides an environment for the sensor array that satisfies the accuracy requirement. The design also combines the low thermal resistance between sensor and medium from an earlier steel probe with the low thermal interference of an insulating plastic probe.Manufacturing and assembly of the updated temperature instrument with a new probe is almost finished, and should after completion provide experimental data to back up the claims made by the simulations.
45
Kittang, Lars Oskar Osnes. "Development and testing of a Linnik Interference Microscope for Sub-surface Inspection of Silicon during moving Indentation". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19258.
Pełny tekst źródłaStreszczenie:
Fixed-abrasive diamond wire sawing is a promising technique for reduction of costs related to sawing of silicon wafers for solar cells. The microscopic mechanisms of material removal in the process are however not fully understood, and must be surveyed in order for costs to be further reduced.An interference microscope for sub-surface inspection of mono-crystalline silicon has been built based on the Linnik configuration, with specific application to in-situ monitoring of moving indentations. The working principles of the instrument are explained from a literature study on relevant theory, combining concepts of optical interference and coherence with imaging theory. The optical system has been experimentally tested in terms of its performance in conventional imaging as well as its interferometric capabilities. Tests on the imaging performance show that a large magnification is accompanied by a lateral resolution with a lower limit of $0.9mumathrm{m}$ and an adequately long depth of field. This provides improved conditions for imaging of internal reflections in silicon, compared to a previously used prototype.Using a light source of low temporal coherence, the capability of the system to measure depth profiles of silicon surfaces has been tested. The technique calculates depths from interferograms recorded by scanning of a reference field. Preliminary results from a flat test surface show that depths are not determined accurately enough for calculated profiles to be considered as reliable reconstructions. It is discussed that the inaccuracy is caused by a number of experimental factors including non-uniform illumination, undesired reflections and non-uniform sampling intervals in scanning.Two experiments with moving indentations on silicon surfaces have been performed, monitored by conventional imaging and calculation of interferometric phase maps, respectively. Results are seen in context with the theoretical understanding of material removal mechanisms in fixed-abrasive diamond wire sawing. The evolution of surface damage is observed as interconnection of chippings in both experiments. In addition, sub-surface lateral cracks are identified from interferometric phase maps. The phase maps of surface damage can, however, only to a limited extent be interpreted as topographic contour lines of surface depth. A deeper knowledge of removal mechanisms requires quantitative measurements of depths. This can be better achieved by calculating accurate depth profiles from interferograms. Future enhancement of the system is dependent on a reevaluation of the optical design as well as better control of sampling intervals in scanning.
46
Karlsen, Terje Kultom. "Gold and Platinum Surface Nanostructures on Highly Oriented Pyrolytic Graphite". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19411.
Pełny tekst źródłaStreszczenie:
Self-assembled platinum and gold nanostructures, which are formed by evaporation and subsequent diffusion limited aggregation of metal on highly oriented pyrolytic graphite, have been studied by photoemission spectroscopy and scanning electron microscopy. Dendritic gold nanostructures were observed on samples onto which gold was evaporated at room temperature. For samples onto which gold was evaporated at reduced temperatures, no such dendrites were found. For samples evaporated with platinum, small nano-spiders were seen at low evaporation time, and more complex fractal structures at higher evaporation time. Studying the oxidation of carbon monoxide over the platinum nanostructures yielded no clear corrolation between nanostructure size and oxidation rate.
47
Ervik, Åsmund. "The Local Level-Set Extraction Method for Robust Calculation of Geometric Quantities in the Level-Set Method". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19429.
Pełny tekst źródłaStreszczenie:
The level-set method is an implicit interface capturing method that can be used in two or more dimensions. The method is popular e.g. in computer graphics, and as here, in simulations of two-phase flow. The motivation for the simulations performed here is to obtain a better understanding of the complex two-phase flow phenomena ocurring in heat exchangers used for liquefaction of natural gas, including the study of droplet-film interactions and coalescence.One of the main advantages of the level-set method is that it handles changes in the interface topology in a natural way. In the present work, the calculation of the curvature and normal vectors of an interface represented by the level-set method is considered. The curvature and normal vectors are usually calculated using central-difference stencils, but this standard method fails when the interface undergoesa topological change, e.g. when two droplets collide and merge. Several methodshave previously been developed to handle this problem. In the present work,a new method is presented, which is a development on existing methods. The newmethod handles more general cases than previous methods. In contrast to someprevious methods, the present method retains the implicit formulation and can easily be extended to three-dimensional simulations, as demonstrated in this work.Briefly, the new method consists in extracting one or more local level sets forbodies close to the grid point considered, reinitializing these local level setsto remove kinks, and using these to calculate the curvature and normal vector atthe grid point considered. For the curvature, multiple values are averaged,while for the normal vector, the one corresponding to the closest interface isselected.With this new method, several two-phase flow simulations are performed that arerelevant for understanding the liquefaction of natural gas. The new methodenables simulations that are more general than previous ones. A two-dimensionalsimulation was performed of a 0.6 mm diameter methanol droplet falling through air and merging with a deep pool of methanol. The new method gave good results in this case, but unphysical oscillations in the pressure field rendered this result unsuitablefor comparison with experimental results.Several similar cases with significantly lower density differences between thetwo fluids were also considered; in these cases, the pressure field behavedphysically, but the results are less applicable to the understanding of naturalgas liquefication, and better suited for validation of the new method. Inparticular, an axisymmetric simulation of a 0.11 mm diameter water droplet in decanemerging with a deep pool of water has been considered. The results of thissimulation show a very close agreement with experimental data. Attempts werealso made to simulate a larger droplet, but in this case finer grids were neededthan what could be achieved here due to the computational time cost of gridrefinement. Purely geometrical results are also presented in order to validate the results of the new method, and three-dimensional results are given for a static interface configuration, demonstrating that the method is easily extended to higher dimensions.
48
Schønberg, Vegard, i Christian Dalheim Øien. "Simulations of impact using the modified Gurson model". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18779.
Pełny tekst źródłaStreszczenie:
We have performed modified Gurson model calibrations to the steel alloys Weldox 460E, Weldox 700E and Weldox 900E through finite element method (FEM) simulations of various tensile material tests performed, and used these material models to perform FEM simulations of impact of blunt tool steel projectiles on target plates made out of these steel alloys. The purpose of these FEM simulations was to study the dependence of target plate steel alloy on the ballistic limit velocity of the projectile resulting from the modified Gurson model. It was found that the modified Gurson model is able to reproduce the dependence seen in experiments, but that it is strongly dependent on a certain model parameter related to the shear stress dependence on material damage. We have also discovered potential problems, and possible solutions, regarding the calibration of these material models and the use of them in the FEM impact simulations carried out.