Modal domain analysis has gained special attention over the years due to its immense value both in fiber-optic sensor technology and communication systems. This presentation is aimed at reviewing the research done in that area so far and at describing a data acquisition system that can be used extensively for such analysis. This work primarily concentrates on the capabilities of the PN-2304 OPTOMATION II system in the study of mode coupling and transient distance analysis in graded-index optical fibers, as well as microbending loss measurements and phase modulation effects in a fiber guiding four modes. While the results of these measurements have been useful in themselves, the performance of the data acquisition system has been exploited to a great extent thus rendering a sophisticated tool for modal distribution studies. The system has been found useful in fiberdyne measurements and speckle pattern analysis thus leading to information on the propagating modes. Chapters I and 2 give a brief introduction to fiber optic systems and mode theory while Chapter 3 reviews the work already done in that area. Chapter 4 describes the PN-2304 OPTOMATION II and its capabilities in modal analysis and Chapter 5 reports the various measurements made using the system and their results. / M.S.

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The aim of this doctoral research is to understand domain evolution processes in ferroelectrics using piezoresponse force microscopy (PFM) and Monte Carlo simulation. The results provide improved knowledge of domain evolution processes, and systematic experimental methods for research on domain evolution. There has been extensive previous research on domain evolution in ferroelectrics, but the research was mainly constrained to simple domain patterns. However, ferroelectric domains tend to form complex patterns that generate low-energy domain configurations. In this research, several methods such as statistical analysis of PFM data, ex situ/in situ PFM observation under electrical/mechanical loading and combining PFM with electron backscatter diffraction are employed to study domain evolution processes in complex domain patterns. The results show that domain switching almost always takes place by the evolution of pre-existing domain patterns, rather than direct flipping of polarization. Also the net effect of domain evolution processes follows a primary principle that positive work is done by external loads. But this principle is not always followed for microscopic switching processes. Multiple types of domain switching occur simultaneously, and occasionally an overwriting process involves unfavourable as well as favourable domain switching. Domain switching is significantly constrained by the pre-existing domain patterns. Meanwhile, angle-resolved PFM is developed for the systematic interpretation of PFM signal. Using lateral PFM images taken from multiple sample orientations, angle-resolved PFM maps are generated based on the angle of phase reversal in the PFM signal. The resulting maps reliably show complex domain patterns which may not appear in vertical and lateral PFM images. A model of domain evolution is developed using Monte Carlo simulation. Polarization switching by electric field and mechanical stress in the model is shown to take place via the motion of domain walls between pre-existing domains. Typical domain broadening processes are reproduced through this simulation.

This thesis describes Monte-Carlo computer simulations of binary alloys, with comparisons between small angle neutron scattering (SANS) data, and numerically integrated solutions to the Cahn-Hilliard-Cook (CHC) equation. Elementary theories for droplet growth are also compared with computer simulated data. Monte-Carlo dynamical algorithms are investigated in detail, with special regard for universal dynamical times. The computer simulated systems are Fourier transformed to yield partial structure functions which are compared with SANS data for the binary Iron-Chromium system. A relation between real time and simulation time is found. Cluster statistics are measured in the simulated systems, and compared to droplet formation in the Copper-Cobalt system. Some scattering data for the complex steel PE16 is also discussed. The characterisation of domain size and its growth with time are investigated, and scaling laws fitted to real and simulated data. The simple scaling law of Lifshitz and Slyozov is found to be inadequate, and corrections such as those suggested by Huse, are necessary. Scaling behaviour is studied for the low-concentration nucleation regime and the high-concentration spinodal-decomposition regime. The need for multi-scaling is also considered. The effect of noise and fluctuations in the simulations is considered in the MonteCarlo model, a cellular-automaton (CA) model and in the Cahn-Billiard-Cook equation. The Cook noise term in the CHC equation is found to be important for correct growth scaling properties.

<p>The magnetic properties of transition metal compounds have been studied using SQUID-magnetometry, magnetic force microscopy and Lorentz transmission electron microscopy. New magnetic materials have been found and their magnetic properties have been determined. How the magnetic properties of a material can be changed through e.g. chemical substitution of magnetic and nonmagnetic atoms and shape and size effects have also been studied. Three different sets of samples have been investigated: three new Mn-compounds, two substitution series of layered magnetic structures and ferromagnetic micronsized thin film elements.</p><p>The three Mn-compounds, Mn₃IrSi, IrMnSi and Mn₈Pd₁₅Si₇, show different magnetic ordering. Mn₃IrSi orders 'antiferromagnetically' at 210 K. IrMnSi forms a double cycloidal spin spiral below 460 K. Mn₈Pd₁₅Si₇ only shows short-range magnetic ordering.</p><p>Substituting Se with S in TlCo₂Se_2-xS_x changes the magnetic order from a spin spiral to a colinear ferromagnet for a composition of <i>x</i>=1.75. An intermediate region exists where the compound is neither a pure ferromagnet, nor purely a spin spiral, as evidenced by the magnetization versus field measurements for the <i>x</i>=1.3 and 1.5 samples. This is also seen in the temperature dependent susceptibility measurements. For the TlCu_2-xFe_xSe₂ compounds it was found that the ordering temperature and saturation magnetic moment per Fe-atom changed with composition <i>x</i>.</p><p>Ferromagnetic micronsized thin film elements in permalloy, Fe₂₀Ni₈₀, and epitaxial Fe/Co multilayers were studied. For the Fe/Co multilayer thin film elements it was found that it is possible to change the magnetization reversal process, by aligning the easy shape anisotropy axis with either the easy or the hard magnetocrystalline anisotropy axis. In the permalloy elements the effect of inter-elemental distance was found to determine the interval of fields where multidomain states were stable, so that for shorter inter-elemental distances multidomain states were stable for a shorter interval of fields. The domain structure of permalloy elements in rotating magnetic fields was also studied. Higher applied fields led to a broader interval of angles in which saturated states were stable.</p>

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 145-151).

Husqvarna is a Swedish company producing products for forestry, park and gardens. Due to harder competition they wish to increase efficacy in production. This can be achieved by shorter lead-times in the complex process of making casting molds. Activities within this process have certain relations and dependencies between each other that can be analyzed by using a Dependence Structure Matrix. The Dependence Structure Matrix is a tool that can improve efficiency by rearranging activities according to how they are dependent of each other. The purpose is to make a Dependence Structure Matrix of activities that Husqvarna can use to analyze dependencies within the process of cast molding. The DSM Matrix will propose restructured activities of the process which can be evaluated to determine if greater efficacy can be reached. To determine the activities within the process of making cast molds a workshop at Husqvarna for the people involved was conducted. A matrix has been constructed based on the information of activities and their dependencies. This information has then been analyzed by the software Multiplan. The process of making casting molds could be analyzed by the DSM/DMM approach. A new order of how to carry out activities is the outcome of the analysis. The result can be analyzed by Husqvarna in order to determine if greater efficacy can be reached.

<p>Husqvarna is a Swedish company producing products for forestry, park and gardens. Due to harder competition they wish to increase efficacy in production. This can be achieved by shorter lead-times in the complex process of making casting molds. Activities within this process have certain relations and dependencies between each other that can be analyzed by using a Dependence Structure Matrix. The Dependence Structure Matrix is a tool that can improve efficiency by rearranging activities according to how they are dependent of each other.</p><p>The purpose is to make a Dependence Structure Matrix of activities that Husqvarna can use to analyze dependencies within the process of cast molding. The DSM Matrix will propose restructured activities of the process which can be evaluated to determine if greater efficacy can be reached.</p><p>To determine the activities within the process of making cast molds a workshop at Husqvarna for the people involved was conducted. A matrix has been constructed based on the information of activities and their dependencies. This information has then been analyzed by the software Multiplan.</p><p>The process of making casting molds could be analyzed by the DSM/DMM approach. A new order of how to carry out activities is the outcome of the analysis. The result can be analyzed by Husqvarna in order to determine if greater efficacy can be reached.</p>