Most current algorithms typically lack in robustness to noise or do not handle T-shaped curve joining properly. There is a challenge to not only detect features in the noisy 3D-data obtained from the digital scanners. Moreover, most of the algorithms even when they are robust to noise, they lose the feature information near the T-shaped junctions as the triplet of lines ``confuses'' the algorithm so it treats it as a plane. Powered by TCPDF (www.tcpdf.org)

The impact of rare disasters on equity premium and term premium in a New Keynesian DSGE model is explored in the thesis. Andreasen's (2012) model with Epstein-Zin preferences, bonds and a rare disaster shock in total factor productivity process is extended by a variable capital stock and an equity-type asset. We find that the variable capital significantly changes behavior of the model, capital depreciation must be substantially increased to counter the effect of variable capital and stochastic mean of inflation increases. The model calibrated to the US economy and a high risk aversion generates 10-year term premium of 90 basis points, rare disasters increase the premium only by 3 basis points. The equity premium is 163 basis points and rare disasters increase it also only by 3 basis points. The model with a low coefficient of relative risk aversion of 5.5 generates negative risk premia. Rare disasters increase the risk premia by mere 4 basis points in comparison to a model with i.i.d. shocks. Powered by TCPDF (www.tcpdf.org)

This thesis explores how to best choose data when curve fitting using power exponential functions. The power exponential functions used are μ(b; x)=(xe1-x)b and Φ(ρ; x)=((1-x)ex)ρ . We use a number of designs such as the equidistant design, the Chebyshev design and the the D-optimal design to compare which design gives the best fit. A few examples including the logistic and the heidler function are looked at during the comparison. The measurement of the errors were made based on the sum of least squares errors in the first part and the maximum error in the second part. MATLAB was used in this comparison.

Virtual work environments (VWEs) have been used in the private sector for more than a decade, but the United States Marine Corps (USMC), as a whole, has not yet taken advantage of associated benefits. The USMC construct parallels the bureaucratic organizational culture and uses an antiquated information technology (IT) infrastructure. During an effort to upgrade the Marine Corps Combat Development Command's infrastructure to a VWE, the change-agent noticed an immediate resistance towards the VWE and new work methodology. The problem identified for investigation was to discover why a bureaucratic organizational culture, matured through IT savvy and cognitively adept personnel, resists the VWE and new work methodology introduced by the evolution of IT. The explanatory, single case study documented the resistance towards the VWE and new work methodology and recommended a solution to the problem. Due to a noticeable resistance geared towards the adoption of the VWE, the case study and pre-trial preparation began in Fall, 2009 and the data-collection period occurred in the Spring of 2010. The preparation phase entailed developing extensive instruments that burrowed into the participants' technical expertise and willingness to accept change on an individual level. The instruments were validated by an expert panel from the following disciplines: knowledge management, information technology, and psychology, as part of the groundwork. Analysis of the data showed resistance towards the VWE, both collectively as a group and on the individual level. The final report articulates that the data proves the study successfully accomplished the goal. Resistance was found at the user level in the work environment. It stemmed from several key areas: lack of user input, lack of training, user ignorance, and absence of a vision statement. Leadership should review the implementation methodology and decide upon a new course of action. Training in the use of the VWE at entry and advanced levels should be offered to newcomers and be available on a continuous basis. Future change agents must examine the outcomes of similar, previous work in order to gain a better understanding of what makes an initiative fail or succeed.

A study of magnetization dynamics experiments in nanostructured materials using the rf susceptibility tunnel diode oscillator (TDO) method is presented along with a extensive theoretical analysis. An original, computer controlled experimental setup that measures the change in susceptibility with the variation in external magnetic field and sample temperature was constructed. The TDO-based experiment design and construction is explained in detail, showing all the elements of originality. This experimental technique has proven reliable for characterizing samples with uncoupled magnetic structure and various magnetic anisotropies like: CrO2 , FeCo/IrMn and Co/SiO2 thin films. The TDO was subsequently used to explore the magnetization switching in coupled magnetic systems, like synthetic antiferromagnet (SAF) structures. Magnetoresistive random access memory (MRAM) is an important example of devices where the use of SAF structure is essential. To support the understanding of the SAF magnetic behavior, its configuration and application are reviewed and more details are provided in an appendix. Current problems in increasing the scalability and decreasing the error rate of MRAM devices are closely connected to the switching properties of the SAF structures. Several theoretical studies that were devoted to the understanding of the concepts of SAF critical curve are reviewed. As one can notice, there was no experimental determination of SAF critical curve, due to the difficulties in characterizing a magnetic coupled structure. Depending of the coupling strength between the two ferromagnetic layers, on the SAF critical curve one distinguishes several new features, inexistent in the case of uncoupled systems. Knowing the configuration of the SAF critical curve is of great importance in order to control its switching characteristics. For the first time a method of experimentally recording the critical curve for SAF is proposed in this work. In order to overcome technological limitations, a new way of recording the critical curve by using an additional magnetic bias field was explored.

Understanding magnetization reversal is very important in designing high density and high data transfer rate recording media. This research has been motivated by interest in developing new nonvolatile data storage solutions as magnetic random access memories - MRAMs. This dissertation is intended to provide a theoretical analysis of static and dynamic magnetization switching of magnetic systems within the framework of critical curve (CC). Based on the time scale involved, a quasi-static or dynamic CC approach is used. The static magnetization switching can be elegantly described using the concept of critical curves. The critical curves of simple uncoupled films used in MRAM are discussed. We propose a new sensitive method for CC determination of 2D magnetic systems. This method is validated experimentally by measuring experimental critical curves of a series of Co/SiO2 multilayers systems. The dynamics switching is studied using the Landau-Lifshitz-Gilbert (LLG) equation of motion. The switching diagram so-called dynamic critical curve of Stonerlike particles subject to short magnetic field pulses is presented, giving useful information for optimizing field pulse parameters in order to make ultrafast and stable switching possible. For the first time, the dynamic critical curves (dCCs) for synthetic antiferromagnet (SAF) structures are introduced in this work. Comparing with CC, which are currently used for studying the switching in toggle MRAM, dCCs show the consistent switching and bring more useful information on the speed of magnetization reversal. Based on dCCs, better understanding of the switching diagram of toggle MRAM following toggle writing scheme can be achieved. The dynamic switching triggered by spin torque transfer in spin-torque MRAM cell has been also derived in this dissertation. We have studied the magnetization's dynamics properties as a function of applied current pulse amplitude, shape, and also as a function of the Gilbert damping constant. The great important result has been obtained is that, the boundary between switching/non-switching regions is not smooth but having a seashell spiral fringes. The influence of thermal fluctuation on the switching behavior is also discussed in this work.

The Interactions and magnetization reversal of Ni nanowire arrays and synthetic anit-ferromagnetic coupled thin film trilayers have been investigated through first order reversal curve (FORC) method. By using a quantitative analysis of the local interaction field profile distributions obtained from FORC, it has proven to be a powerful characterization tool that can reveal subtle features of magnetic interactions.

M.Comm. / The aim of this dissertation is to undertake an empirical study of the determinants of the Phillips curve for South Africa (SA). The work will be concentrated on the relationship between inflation (or wage inflation) and unemployment in SA from 1980 to 1998 with a particular focus on the behaviour of the Non Accelerating Inflation Rate of Unemployment (NAIRU). Given the importance of the NAIRU in formulating monetary policy, it will be therfore be appropriate to analysed this parameter. The NAIRU tends to perform differently in the face of price and wage inflation and therefore it has been found wise to divide the model into two categories. Price/unemployment model. Wage/unemployment model. The first model will be referred to as the Price-Phillips curve where as the second will usually be referred to as the Wage-Phillips curve. Models of Price-Phillips curve and Wage-Phillips curve are valuable tools for policy makers for a number of different purposes. In its original form the wage (or price) — unemployment relationship presents politicians with a list of different trade — offs to choose between inflation and unemployment. The trade-off seems to suggest that policy makers could choose a specific inflation-unemployment combination by controlling aggregate demand. This clearly points out that the trade-off postulated in the Phillips curve can be an usefull tool for monetary policy.

The understanding of how different parts of a landscape contribute to streamflow by storing and releasing water has long been a central issue in hydrology. Knowledge about what controls streamflow dynamics across landscapes can further our understanding of how catchments store and release water, facilitate predictions for ungauged catchments, and improve the management of water quality and resources. This thesis makes use of data from the Krycklan catchment in northern Sweden. Streamflow data from 14 catchments (0.12 - 68 km2) with variable landscape characteristics such as topography, vegetation, wetland cover, glacial till soils and deeper sediment soils were used to investigate spatial patterns and controls on runoff. The differences in specific discharge (discharge per unit catchment area) between nearby catchments were large at the annual scale, and have the same magnitude as predicted effects of a century of climate change or the observed effects of major forestry operations. This variability is important to consider when studying the effects of climate change and land use changes on streamflow, as well as for our understanding of geochemical mass balances. Streamflow from different catchments was strongly related to landscape characteristics. The distribution of wetland areas had a particularly strong influence, with an annual specific discharge 40-80% higher than catchments with high tree volume on till soils. During drier periods, catchments with deeper sediment soils at the lower elevations of Krycklan had a higher base flow compared to both forested till and wetland catchments. This pattern was reversed at high flows. The storages releasing water to streams in downstream sediment areas were able to maintain base flow for longer periods and were less influenced by evapotranspiration compared to the more superficial till and wetland systems. The results of this thesis have led to a better understanding of the landscape wide patterns of streamflow during different seasons and time scales. The strong associations to landscape characteristics and variable spatial patterns with season and antecedent conditions form the basis for a conceptual understanding of the processes and spatial patterns that shape the heterogeneity of streamflow responses in boreal catchments. / Hur olika delar av landskapet påverkar vattenbalansen och bidrar till avrinning har länge varit en central fråga inom hydrologin. Kunskap om vad som styr avrinningsdynamiken i ett landskap kan öka vår förståelse av hur olika delar av landskapet bidrar till avrinning, hur avrinningsområden lagrar vatten och bildar avrinning, underlätta prognoser för avrinningsområden utan vattenföringsmätningar och förbättra hanteringen av vattenkvaliteten och vattenresurser. Denna avhandling använder data från Krycklans avrinningsområde i norra Sverige. Vattenföringsdata från 14 delavrinningsområden (0.12 - 68 km2) med olika landskapskarakteristik såsom topografi, vegetation och jordarter, användes för att undersöka rumsliga mönster hos avrinningen över olika tidsperioder samt hur landskapet påverkar variabiliteten. Skillnaderna i specifik avrinning (avrinning per areaenhet) mellan närliggande avrinningsområden var stor för årliga värden, och är i samma storleksordning som effekterna av stora skogsavverkningar samt av förutspådda effekter av det kommande seklets förväntade klimatförändringar. Denna variation är viktig att ta hänsyn till när man studerar hur klimatförändringar och ändrad markanvändning påverkar avrinningen, liksom för vår förståelse av geokemiska massbalanser. Avrinning från olika områden var starkt relaterad till deras landskapsegenskaper. Förekomsten av våtmarker hade ett särskilt starkt inflytande. Områden med en stor andel våtmarker hade 40-80% högre årlig specifik avrinning än områden med hög trädvolym på moränjordar. Under torrare perioder hade områden med djupare sedimentjordar hög avrinning jämfört med både områden med skog på morän och med våtmarker. Under höga flöden var detta mönster omvänt. De vattenlager som bidrar till avrinning i sedimentområden kan upprätthålla basflöde under längre tidsperioder och påverkas mindre av evapotranspirationen än de ytligare flödessystemen i morän och våtmarker. Avhandlingen har givit en bättre förståelse av avrinningens rumsliga variation under olika årstider och i olika tidsskalor. Det starka sambandet mellan landskapskarakteristik och avrinningens varierande mönster under olika årstider och lagringsförhållanden utgör en grund för en begreppsmässig förståelse av de processer och rumsliga mönster som skapar heterogeniteten i flödesrespons i boreala områden.

Dans le diagnostic médical, la surface ROC est l'outil statistique utilisée pour évaluer la précision d'un test diagnostic dans la discrimination de trois états d'une maladie, et le volume sous la surface ROC est l'indice utilisé pour la quantification de la performance du test. Dans certaines situations, différents facteurs peuvent affecter les résultats du test et ainsi les mesures de précision. Dans le cas des études longitudinales, le statut du patient peut changer au cours du temps. Dans ce manuscrit, nous avons développé des méthodes statistiques permettant d'évaluer les capacités discriminatoires des outils diagnostics et pronostics. Nous avons d'abord proposé une méthode semi-paramétrique pour estimer la surface ROC sous des modèles de rapport de densité. La construction de la méthode proposée est basée sur le modèle logit à catégories adjacentes et l'approche de vraisemblance empirique. Nous avons décrit la méthode bootstrap pour l'inférence des estimateurs obtenus. Ensuite, nous avons présenté une méthode d'estimation des surfaces ROC appelée famille de Lehmann des surfaces ROC. Cette méthode est basée sur la famille d'alternatives de Lehmann ou modèle à hasards proportionnels. Elle a l'avantage de prendre en compte les covariables qui peuvent affecter la précision d'un test diagnostic. En outre, nous avons développé une surface ROC covariable-spécifique basée sur la règle de Bayes. Pour cela, nous avons proposé un estimateur semi-paramétrique pour les surfaces ROC covariable-spécifique via des procédures de régression logistique polytomique et un modèle semi-paramétrique de localisation. Enfin, dans le cas où le statut du patient peut évoluer à travers différents stades d'une maladie, une méthode des surfaces ROC dépendant du temps a été développée. L'estimateur obtenu utilise l'approche "Inverse Probability of Censoring Weighting" (IPCW). Des simulations et des exemples sont fournis afin d'illustrer la performance des estimateurs proposés. / In diagnostic medical, the receiver operating characteristic (ROC) surface is the statistical tool used to assess the accuracy of a diagnostic test in discriminating three disease states, and the volume under the ROC surface is the used index for the quantification of the performance of the test. In some situations, various factors can affect the test results and subsequently the accuracy measures. In the case of longitudinal studies, the patient's status may change over time. In this manuscript, we developed statistical methods to assess the discriminatory capabilities of diagnostic and pronostic tools. We first proposed a semiparametric method for estimating ROC surface under density ratio models. The construction of the proposed method is based on the adjacent-category logit model and the empirical likelihood approach. We described the bootstrap method for inference of the obtained estimators. Next, we presented a method for estimating ROC surfaces called Lehmann family ROC surfaces. This method is based on the family of Lehmann alternatives or proportional hazards model. It has the advantage of taking into account covariates that may affect the accuracy of a diagnostic test. Moreover, we have developed a covariate-specific ROC surface based on the Bayes rule. For that, we proposed semiparametric estimator for covariate-specific ROC surfaces via polytomous logistic regression procedures and a semiparametric location model. Finally, in the case where patient's status may evolve through different stages of disease a method of time-dependent ROC surfaces was developed. The proposed estimator uses the "Inverse Probability of Censoring Weighting" (IPCW) approach. Simulations and examples are provided to illustrate the performance of the proposed estimators.