The overall goals of the present PhD research are to explore the giant magnetoimpedance (GMI) and giant magnetocaloric (GMC) effects in functional magnetic materials and provide guidance on the optimization of the material properties for use in advanced magnetic sensor and refrigeration applications. GMI has attracted growing interest due to its promising applications in high-performance magnetic sensors. Research in this field is focused on the development of new materials with properties appropriate for practical GMI sensor applications. In this project, we have successfully set up a new magneto-impedance measurement system in the Functional Materials Laboratory at USF. We have established, for the first time, the correlation between sample surface, magnetic softness, critical length, and GMI in Co-based amorphous ribbon materials, which provide a good handle on selecting the suitable operating frequency range of magnetic materials for GMI-based field sensor applications. The impact of field-induced magnetic anisotropy on the GMI effect in Co-based nanocrystalline ribbon materials has also been investigated, providing an important understanding of the correlation between the microstructure, magnetic anisotropy, and GMI in these materials. We have shown that coating a thin layer of magnetic metal on the surface of a magnetic ribbon can reduce stray fields due to surface irregularities and enhance the magnetic flux paths closure of the bilayer structure, both of which, in effect, increase the GMI and its field sensitivity. This finding provides a new way for tailoring GMI in surface-modified soft ferromagnetic ribbons for use in highly sensitive magnetic sensors. We have also introduced the new concepts of incorporating GMI technology with superparamagnetic nanopthesiss for biosensing applications and with carbon nanotubes for gas and chemical sensing applications. GMC forms the basis for developing advanced magnetic refrigeration technology and research in this field is of topical interest. In this project, we have systematically studied the ferromagnetism and magnetocaloric effect in Eu8Ga16Ge30 clathrate materials, which are better known for their thermoelectric applications. We have discovered the GMC effect in the type-VIII clathrate and enhanced refrigerant capacity in the type-I clathrate. We have successfully used the clathrates as excellent host matrices to produce novel Eu8Ga16Ge30-EuO composite materials with desirable properties for active magnetic refrigeration technologies. A large refrigerant capacity of 794 J/kg for a field change of 5 T over a temperature interval of 70 K has been achieved in the Eu8Ga16Ge30-EuO composite with a 40%-60% weight ratio. This is the largest value ever achieved among existing magnetocaloric materials for magnetic refrigeration in the temperature range 10 K - 100 K. The excellent magnetocaloric properties of the Eu8Ga16Ge30-EuO composites make them attractive for active magnetic refrigeration in the liquid nitrogen temperature range.

This study explores how racial differences may influence achievement and persistence in physics by using data provided by the Persistence Research in Science and Engineering (PRiSE) project, which surveyed college students throughout the United States about their backgrounds, high school science experiences, and science attitudes. This study draws upon previous studies to first determine the factors that predict achievement and persistence in physics by using hierarchal linear multiple regression analysis. Once statistically significant factors of persistence and achievement were determined, the study determines whether those variables are significantly different among students of determine races. The study found that race was ultimately not a good predictor of both achievement and persistence in physics; however, this does not necessarily mean that race was an insignificant component. Due to the nature of hierarchal regression analysis, the component of race may have been accounted for in other predictors. However, the analyzed predictors for could not fully account for the variance in either achievement or persistence. This may be due to the limited scope of the PRiSE survey, which did not include socioeconomic factors. The study concludes with a proposal for future research.

The space simulation chambers at Arnold Engineering Development Complex (AEDC) allow for the testing and calibration of seeker sensors in cryogenic, high vacuum environments. During operation of these chambers, contaminant films can form on the components in the chamber and disrupt operation. Although these contaminant films can be composed of many molecular species, depending on the species outgassed by warm chamber components and any leaks or virtual leaks (pockets of gas trapped within a vacuum chamber) that may be present, water vapor is most common, and it will be the focus of this dissertation. In this dissertation, some properties of the water molecule and low pressure ice are reviewed with a focus on the optical properties. The method of angular coefficients is utilized to calculate flux distributions for general three dimensional situations and the program written is applied to a model of the AEDC 10V space simulation chamber. The optical effects of varying amounts of contamination on a generic germanium window and gold mirror, along with the effects on two components specific to the space chambers, is determined. Also, an experiment to measure the thickness and other properties of contaminant films is discussed, and initial results are given for the first two tests of the experimental setup.

Remote measurement of electric field generated by lightning has played a major role in understanding the lightning phenomenon. Even though other measurements such as photographic and channel base current have contributed to this research field, due to practical reasons remote measurements of electric field is considered as the most useful tool in lightning research. This thesis discusses the remotely measured radiation field component of electric field generated by cloud flashes (ICs) and narrow bipolar pulses (NBPs). The associated HF radiation of these events at 3 MHz and 30 MHz are also discussed. To understand the initiation process of these discharges, a comparative study of the initial pulse of cloud flashes against the initial pulse of cloud to ground flashes was conducted. The result suggests that both discharges might have been initiated by similar physical processes inside the thunderclouds. Comparing the features of initial pulse of cloud and ground flashes with that of pulses that appeared in the later stages of cloud flashes suggests that the initiation process involved in both flashes are not very much different from the initiation of cloud flashes at the later stage. The average spectral amplitudes of electric field of full duration cloud flashes (180 ms) showed f  -1 frequency dependence within the interval of 10 kHz to approximately 10 MHz. This is in contrast to the standard f  -2 decrement (or even steeper ) at high frequency region for other lightning processes such as return strokes. It was suggested that small pulses which repeatedly appeared at the later stage of cloud flashes might have contributed to enhance the spectral amplitude at higher frequencies. Electric fields generated by Narrow Bipolar Pulses (NBPs), which are considered as one of the strongest sources of HF radiation, were measured in the tropics of Malaysia and Sri Lanka.  Their features were also studied and show a good agreement with previously published observations of NBPs from other geographical regions. Thorough analyses and observations of these pulses found previously unreported sharp, fine peaks embedded in the rising and decaying edge of the electric field change of NBPs. Therefore it was suggested that these fine peaks are mostly responsible for the intense HF radiation at 30 MHz.

I detta projekt analyseras utmattningsbrott orsakade av ytdefekter i höghållfast stål som utsätts för fler än tio miljoner cykliska belastningar. Vanligen orsakas utmattningsbrott i denna region av interna materialdefekter där brottytan ofta innehåller ett område med grövre morfologi - fine granular area (FGA). FGA är en ackumulerad skada som bildas under sprickinitieringsstadiet och utgör cirka 99 % av den totala utmattningslivslängden. Resterande 1 % utgörs av spricktillväxt. På grund av detta är mekanismen som initierar sprickor i detta skede essentiell. Om FGA kan observeras vid ytinitierade utmattningsbrott för material som utsätts för fler än tio miljoner cykliska belastningar, är ännu inte fastställt. . Det här projektet syftar till att undersöka om FGA kan observeras i ytinitierat utmattningsbrott gällande material med väldigt långa livslängder, samt till att utreda hur ytinitieringar påverkar utmattningslivslängden. För att söka svar på dessa frågor utförs utmattningsprovning med ultraljudsutrustning, följt av karaktärisering av brottytorna i svepelektronmikroskop för att studera de morfologiska förändringarna. Vidare utförs finita element analyser med mjukvaran ABAQUS för att jämföra den maximala huvudspänningen mellan prov med, respektive utan ytdefekter. Resultatet från ABAQUS visar att proven med hårdhetsintryck utsätts för en större maximal huvudspänning än proven utan hårdhetsintryck, därigenom kan skillnaden i livslängder förklaras. . Testresultaten från utmattningsprovningen presenteras i ett S-N diagram som visar spänningsamplituden i förhållande till materialets livslängd. De analyserade bilderna från svepelektronmikroskopet av ytinitierat utmattningsbrott visar en antydan till FGA i två av 20 prov. Däremot tycks sprickorna, i samtliga fall, initiera på grund av ackumulering av plastisk deformation i ytan. Interna materialdefekter orsakade inte utmattningsbrott i något av de 20 testade proverna med ytdefekter. Två prover utan ytdefekter genomgick samma process och för båda dessa introducerades en spricka på grund av interna materialdefekter, båda innehöll ett tydligt FGA. Sammanfattningsvis indikerar resultaten från denna studie att FGA inte är lika uppenbara och eventuellt lika vanligt förekommande vid ytinitierat utmattningsbrott av höghållfasta stål med mycket långa livslängder. Även att ytdefekter introducerar en högre maximal huvudspänning i provets centrum, vilket resulterar i en kortare utmattningslivslängd.

Granular materials, large collections of macroscopic particles, are something that is commonly found in both nature and industry. Examples of such can be sand, ore, grains, seeds or snow. Simulations of granular materials are important in many industrial cases. It gives an opportunity to study the behavior of the particles as they interact with machinery and gives an indication of how efficient new designs perform. In some areas, such as vehicle-terrain interaction, plastic deformation of the particles can be an important factor. The Ume˚a based company Algoryx Simulation can simulate granular materials in their physics engine AGX Dynamics using a nonsmooth discrete element approach (NDEM), but currently lack support for plastic deformation. The purpose of this thesis is to implement a plastic contact model in the source code of AGX Dynamics, such that plastic deformation can be observed. The implementation was first tested for single particle-particle compression where measured contact forces were compared to theoretical models. Uniaxial compression tests were performed for bulk testing, filling a cylinder with particles and compressing them while monitoring the axial stress and strain. The results from the single particle compression correspond well to theory, giving the correct plastic deformation for a given contact force and correctly illustrates the effects of changing different model parameters. Plastic deformation could also be observed in the results from bulk testing. Additionally, it was observed that the current version of the implementation is best suited for simulating either very cohesive materials, where particles stick to each other when colliding, or cohesionless materials, where colliding particles are separated after impact. Additional research is needed to study how the separation velocity for colliding particles should be updated in a way that is consistent with the plastic model parameters and experimental results.

The aim of the thesis is to study the AdS/CFT correspondence and the AdS2/SYK connection as a very special example of the duality. While the first part of the thesis contains a review of AdS/CFT correspondence in arbitrary dimensions, the later parts focus on an interesting and speculative connection between the gravitational physics in two dimensional nearly AdS2 spacetime and one dimensional SYK model. More specifically, the connection is realized in terms of certain features of the SYK model in strong coupling limit, which resembles those of nearly AdS2 Jackiw-Teitelboim theory.

SpinChem AB designs rotating bed reactors (RBR:s) that are used to conduct reactions between solid and liquid phase. In this work a model have been developed that predicts the performance of the S2 RBR. Coupled with simulations the model could be used to improve current and future RBR designs.  The model predicts the reaction rate inside the RBR during a de-colourization process where methylene blue was adsorped onto an adsorbent that was chosen during a screening study. The materials investigated were XAD1600N, MN102, activated carbon and IRN99 where the suitability of a material was judged upon the capacity and reproducibility of the process, and the reaction rate dependency on the mass transport. The DOE software MODDE Pro was used to design a parameter study that produced a function that describes the reaction rate of the process as a function of the RPM of the RBR and the temperature, pH and initial concentration of the methylene blue solution. Using simulations in ANSYS Fluent and modelling the function was then converted to the final model. It was then tested by comparing experimental results with simulations of the de-colourization process where the reaction rate inside the RBR was set using the model. IRN99 was chosen as the adsorbent of the process as its capacity was the highest of the four materials studied and its reaction rate displayed a sufficient mass transport dependence. The parameter study produced a function with a high R2, Q2 and reproducibility (>0.85) but displayed a low model validity (-0.2) as a result of the noise in the experimental data. The final model agrees well with the experimental results in the whole parameter space of experiments conducted. The model is meant to be a general model that could be applied to other RBR sizes. It could therefore be used to investigate the performance of new RBR models before they are built or improve current RBR:s. Other geometries has however not been tested during this work and therefore not much can be said about its accuracy when used in this way. / SpinChem AB designar roterande bäddreaktorer (RBR:s) som används för att genomföra reaktioner mellan fast och flytande fas. I detta arbete har en modell utvecklats som förutspår prestandan hos en S2 RBR. Tillsammans med simuleringar kan modellen användas för att förbättra nuvarande och framtida RBR-modeller. Modellen förutspår reaktionshastigheten inuti RBR:en under en avfärgningsprocess där metylenblått adsorberades på ett adsorbent som valdes under en screeningsstudie. Materialet som undersöktes var XAD1600N, MN102, aktiverat kol och IRN99 där lämpligheten av ett material bedömdes på processens kapacitet och reproducerbarhet och reaktionshastighetens beroende på masstransport. DOE-mjukvaran MODDE Pro användes för att utforma en parameterstudie som gav en funktion som beskriver processens reaktionshastighet som en funktion av RBR:ens RPM och temperaturen, pH och initialkoncentrationen av metylenblålösningen. Genom att använda simuleringar i ANSYS Fluent och modellering kunde funktionen omvandlas till en modell som beskriver reaktionens hastighet inne i RBR:en. Den testades sedan genom att jämföra experimentella resultat med simuleringar av avfärgningsprocessen där reaktionshastigheten inuti RBR:en sattes med hjälp av modellen. IRN99 valdes som adsorbent av processen eftersom dess kapacitet var den högsta av de fyra studerade materialen och dess reaktionshastighet visade ett tillräckligt masstransportberoende. Parameterstudien gav en funktion med hög R2, Q2 och reproducerbarhet (> 0,85) men visade på en låg modellgiltighet (-0.2) vilket beror på brus i experimentdata. Den slutliga modellen stämmer väl överens med experimentresultaten i hela parameterrummet för de utförda experimenten. Modellen är avsedd att vara en allmän modell som kan tillämpas på andra RBR-storlekar. Det kan därför användas för att undersöka prestandan hos nya RBR-modeller innan de byggs eller förbättra nuvarande RBR:er. Andra geometrier har dock inte testats under detta arbete och därför kan inte mycket sägas om dess noggrannhet när den används på detta sätt.

This dissertation explores how students’ beliefs and attitudes interact with their identities as physics people, motivated by calls to increase participation in science, technology, engineering, and mathematics (STEM) careers. This work combines several theoretical frameworks, including Identity theory, Future Time Perspective theory, and other personality traits to investigate associations between these factors. An enriched understanding of how these attitudinal factors are associated with each other extends prior models of identity and link theoretical frameworks used in psychological and educational research. The research uses a series of quantitative and qualitative methodologies, including linear and logistic regression analysis, thematic interview analysis, and an innovative analytic technique adapted for use with student educational data for the first time: topological data analysis via the Mapper algorithm. Engineering students were surveyed in their introductory engineering courses. Several factors are found to be associated with physics identity, including student interest in particular engineering majors. The distributions of student scores on these affective constructs are simultaneously represented in a map of beliefs, from which the existence of a large “normative group” of students (according to their beliefs) is identified, defined by the data as a large concentration of similarly minded students. Significant differences exist in the demographic representation of this normative group compared to other students, which has implications for recruitment efforts that seek to increase diversity in STEM fields. Select students from both the normative group and outside the normative group were selected for subsequent interviews investigating their associations between physics and engineering, and how their physics identities evolve during their engineering careers. Further analyses suggest a more complex model of physics and engineering identity which is not necessarily uniform for all engineering students, including discipline-specific differences that should be further investigated. Further, the use of physics identity as a model to describe engineering student choices may be limited in applicability to early college. Interview analysis shows that physics recognition beliefs become contextualized in engineering as students begin to view physics as an increasingly distinct domain from engineering.

The purpose of this study was to observe in which way educator´s interactions with children stimulate the learning process, in this case of the study about friction. How does the interaction between preeschool teachers and children affect and stimulate their curiosity to learn? The study was conducted with a preschool teacher and 6 children between the ages 4-6 years. The preschool teacher planned an activity that involved separate ways to learn about friction and performed this with the children. The chosen method of the study was a qualitative non-participation observation and an open interview with the preschool teacher. The result shows that interaction play an important part in children's learning processes, that by confirming and sharing knowledge with others in a social context, it is also easier to ask questions and explore the phenomenon of friction. The study shows that when an educator is active and present, cooperation between children-children but also children-educator increases, and it gives the children an increased understanding of the learning object