No description available.

This thesis presents the area under the ROC (Receiver Operating Characteristics) curve, or abbreviated AUC, as an alternate measure for evaluating the predictive performance of ANNs (Artificial Neural Networks) classifiers. Conventionally, neural networks are trained to have total error converge to zero which may give rise to over-fitting problems. To ensure that they do not over fit the training data and then fail to generalize well in new data, it appears effective to stop training as early as possible once getting AUC sufficiently large via integrating ROC/AUC analysis into the training process. In order to reduce learning costs involving the imbalanced data set of the uneven class distribution, random sampling and k-means clustering are implemented to draw a smaller subset of representatives from the original training data set. Finally, the confidence interval for the AUC is estimated in a non-parametric approach.

Trafiksäkerhet är något som är viktigt för trafikanten och den som arbetar på vägarna. Säkerheten längs vägar är något som har utvecklats, men inte flyttbara säkerhetsbarriär för vägarbeten. Den här rapporten följer ett produktutvecklingsprojekt där ett koncept för en ny trafikbuffert tas fram. Dagens trafikbuffertar är svåra att hantera, inte anpassade för stadsmiljöer och ger en lång stoppsträcka för fordonet vid kollision. Den ger även en hög kraftpåkänning för de inblandade vid kollision då det blir en hög impuls. Utgångspunkten för projektet har varit att minska stoppsträckan och minska de inblandas upplevda kraftpåkänning. Detta genomfördes genom att följa en beprövad produktutvecklingsprocess. Under förstudien upptäcktes att det fanns begränsat med information och forskning inom området, men det finns liknande lösningar som det togs inspiration från. Det togs sedan fram ett koncept som baserades på att använda en del av bilens vikt för att minska stoppsträckan, tillsammans med en deformationszon som ska minska rörelseenergin i bilen och kraftpåkänningen för de iblandade. Ett flertal iterationer gjordes på konceptet för att uppfylla så många krav som möjligt och bli ett realiserbart koncept. Simuleringar gjordes för att säkerställa hållfastheten på konstruktionen och beräkningar för att få en uppfattning om stoppsträckan.  Resultatet är ett koncept som har kortare stoppsträcka i teorin och en lägre kraftpåkänning än dagens använda trafikbuffert. Konceptet kräver vidare arbete för att definiera tillverkningsteknik och få ett godkännande av Trafikverket. Slutsatsen är att användningen av bilens vikt är ett bra sätt att minska stoppsträckan. Dock krävs krocksimuleringar och krocktester för att validera resultaten. / Traffic safety is something that is important for both drivers and road workers. Safety along roads has seen developments, but portable safety barriers for road work have not. This report follows a product development project where a concept for a new traffic buffer is being developed. Current traffic buffers are difficult to handle, not suitable for urban environments, and have a long stopping distance when a collision occurs. They also exert high force on those involved, resulting in a severe impact.  The goal of this project was to reduce the vehicle stopping distance and the perceived force on the passengers involved. A proven product development process was used to achieve this goal. During the preliminary study it was discovered that there was limited information and research in the field, but there are similar solutions that provided inspiration. A concept was then developed based on utilizing a portion of the vehicle's weight to reduce the stopping distance, along with a deformation zone that would reduce the vehicle's kinetic energy and the force on those involved. Several iterations were made on the concept to meet as many requirements as possible and make it a feasible concept. Simulations were conducted to ensure the structural strength and calculations were made to estimate the stopping distance. The result is a concept that requires further work to make it ready for production and approved by the Swedish Transport Administration. The concept has a theoretical stopping distance of 4.5 meters and lower force exertion. In conclusion, utilizing the vehicle's weight is a good way to reduce the stopping distance. However, crash simulations and tests are required to validate the results. / <p>Betygsdatum 2023-06-28</p>

The modern attention economy incentivizes the use of persuasive designs in software development. Scrolling is an interaction technique commonly associated with persuasive designs because of its lack of natural stopping cues and potential for habit promotion. A scroll-like interaction is used in gesture navigation, which is a method of navigating mobile operating systems. This paper investigates gesture navigation in mobile operating systems in the context of persuasive designs. The aim of this paper is to answer whether gesture navigation affects mobile usage and if there is a systematic preference for gesture navigation over traditional button navigation. In order to answer these questions a pre-post study was conducted. The participants were instructed to change system navigation controls for ten days; whereafter data regarding their mobile usage was collected. The collected data was analyzed in order to determine if there was a difference in mobile usage after changing system navigation controls and whether there was a systematic preference for gesture navigation. The results did not suggest that gesture navigation has an effect on mobile usage. The results did however point towards a systematic preference for gesture navigation over button navigation. The idéa of a systematic preference for gesture navigation motivates further research about the mechanisms behind it. / Den moderna uppmärksamhets-ekonomin motiverar implementering av persuasive design-tekniker inom mjukvaruutveckling. Scrolling är en interaktionsteknik som ofta förknippas med persuasive design på grund av dess brist på naturliga stoppsignaler och förmåga att forma användarvanor. En scrolling-liknande interaktion används i gestnavigering, vilket är en navigeringsmetod i mobila operativsystem. Denna uppsats undersöker gestnavigering i mobila operativsystem i anknytning till persuasive design. Syftet med uppsatsen är att besvara om gestnavigering påverkar mobilanvändning och om det finns en systematisk preferens för gestnavigering framför traditionell knappnavigering. För att besvara dessa frågor genomfördes en inventionsstudie. Deltagarna instruerades att ändra systemnavigering i tio dagar; varefter data om deras mobilanvändning samlades in. De insamlade uppgifterna analyserades för att avgöra om det förekom någon skillnad på mobilanvändandet efter bytet av systemnavigering och om det fanns en systematisk preferens för gestnavigering. Resultaten tydde inte på att gestnavigering påverkar mobilanvändning. Resultaten pekade däremot på en systematisk preferens för gestnavigering framför knappnavigering. Idén om en systematisk preferens för gestnavigering motiverar vidare forskning om preferensens bakomliggande mekanismer.

No description available.

This thesis is made up of two parts. Part A - describes the construction of a scintillation counter and its operation, as an instrument for use in medical research. Part B - is a study of the stopping of mesons in various absorbers as a preliminary to the investigation of the meson decay process. / Thesis / Master of Science (MS)

In an optimal visiting problem, we want to control a trajectory that has to pass as close as possible to a collection of target points or regions. We introduce a hybrid control-based approach for the classic problem where the trajectory can switch between a group of discrete states related to the targets of the problem. The model is subsequently adapted to a mean-field game framework, that is when a huge population of agents plays the optimal visiting problem with a controlled dynamics and with costs also depending on the distribution of the population. In particular, we investigate a single continuity equation with possible sinks and sources and the field possibly depending on the mass of the agents. The same problem is also studied on a network framework. More precisely, we study a mean-field game model by proving the existence of a suitable definition of an approximated mean-field equilibrium and then we address the passage to the limit.

In this thesis, we consider an optimal stopping problem interpreted as the task of valuating two so called real options written on an underlying asset following the dynamics of an observable geometric Brownian motion with non-observable drift; we have incomplete information. After exercising the first real option, however, the value of the underlying asset becomes observable with reduced noise; we obtain partial information. We then state some theoretical properties of the value function such as convexity and monotonicity. Furthermore, numerical solutions for the value functions are obtained by stating and solving a linear complementary problem. This is done in a Python implementation using the 2nd order backward differentiation formula and summation-by-parts operators for finite differences combined with an operator splitting method.

The phenomenon of energy loss that occurs when an ion interacts with matter, also called stopping power, has been investigated for more than a century, and has provided findings of interest. However, reliable procedures for obtaining accurate experimental measurements and a fully theoretical comprehension of the process are tasks still in high demand by the scientific community. Moreover, stopping power data are prerequisites in several applications in modern science, such as engineering, ion implantation and modification of materials, damage to electronics devices (e.g. space radiation), medical physics (e.g. proton therapy), among others. In this thesis we i) develop a rigorous experimental protocol to measure stopping power with high precision, and ii) investigate the collapse of the free electron gas (FEG) model in energy loss of light ions (protons) at a low energy range in transition and rare-earth metals. In the first part, we present an approach to obtain, with high accuracy, the stopping cross sections in the pure materials Al and Mo for protons in the energy range of [0.9 - 3.6] MeV by means of the transmission method. The traceability of the sources of uncertainties are fully evaluated and the final accuracy of the results is 0.63% (0.32% rand. and 0.54% syst.) for Al, and 1.5 % (0.44 % rand. and 1.4% syst.) for Mo, with both results primarily limited by the quality and homogeneity of the stopping foils. For Al, this high accuracy represents an improvement compared to the results obtained in previous studies and serves as a benchmark for our procedure. The most important sources of uncertainties were random - the uncertainty in the peak positions and in the Gaussian fits; and systematic - the non-uniformity thickness of the foils (a special procedure was developed to correct this). Even though the final uncertainty for Mo is higher than for Al, our results improve on the amount of data currently available for the energy range considered. Both data sets are compared with the most commonly employed theoretical models and Monte Carlo codes in the literature. In the second part, electronic stopping cross sections of nontrivial solids, that is, transition and rare earth metals (Ta and Gd) for slow protons are experimentally investigated, and the data were compared with the results for Pt and Au, to understand how energy losses in these metals are correlated with electronic band structures, and to understand the failure of the FEG model predictions. The higher stopping powers found for Ta and Gd cannot be explained by means of the FEG model; however, these effects are successfully correlated with the high density of states (DOS) of both the occupied and unoccupied electronic levels in these metals. For the case of Gd, the experimental data are extended in the energy range until the Bragg\'s peak is reached. The two parts of this thesis were published in Physical Review A 93 022704 (2016), and in Physical Review Letters 18 103401 (2017), respectively. / O fenômeno de perda de energia quando um íon interage com a matéria, também conhecido como poder de freamento, vem sendo investigado por mais de um século, gerando grandes descobertas. Entretanto, conseguir obter medidas experimentais com alta precisão, ou elaborar um completo entendimento teórico dos processos de perda de energia são tarefas extremamente difíceis e ainda muito requeridas pela comunidade científica. Além disso, dados de perda de energia são pré-requisitos em várias aplicações e ramos da ciência moderna, tais como: engenharia, implantação e modificação de materiais, danos em dispositivos eletrônicos (radiação espacial), física médica (próton terapia), etc. Esta tese tem dois focos: i) desenvolver um rigoroso protocolo experimental para medir stopping power com alta precisão e ii) investigar a quebra de validade do modelo de Gás de Elétrons Livres (FEG) para a perda de energia de prótons lentos em metais de transição e terra raras. Na primeira parte apresentamos uma abordagem experimental para obter com alta precisão o poder de freamento em materiais puros (Al e Mo) para prótons no intervalo de energia de [0,9 - 3,6] MeV pelo método de transmissão. A rastreabilidade das fontes de incerteza foi determinada e as incertezas finais encontradas foram: 0,63 % (0,32 % aleat. e 0,54 % sist.) para Al e 1,5 % (0,44 % aleat. e 1,4 % sist.) para Mo, ambas devido a qualidade e homogeneidade das folhas freadoras. Para Al, esta acurácia representa um avanço comparado com publicações anteriores e, assim, serviu como uma referência de nosso procedimento. As mais importantes fontes de incerteza foram: aleatória incerteza das posições dos picos e dos ajustes Gaussianos e sistemática não-uniformidade das folhas-alvo (um procedimento foi desenvolvido para corrigir isso). Embora a incerteza final do Mo é um pouco maior do que do Al, nossos resultados ajudaram a complementar a baixa quantidade de dados disponíveis para o intervalo de energia considerado. Ambos conjuntos de dados foram comparados com os mais comuns modelos teóricos e códigos de Monte Carlo na literatura. Para a segunda parte, poder de freamento em metais não tão comuns tais como transição (Ta) e terras-raras (Gd) para prótons com baixas velocidades foram experimentalmente investigados, e os dados comparados com resultados de Pt e Au, a fim de entender como o stopping power destes metais está correlacionado com as estruturas de bandas eletrônicas, e assim tentar explicar a falha do modelo de FEG. Os altos valores das perdas de energias encontradas para Ta e Gd não puderam ser explicadas pelo modelo de FEG, e portanto foram correlacionados com a densidade de estados (DOS) em ambos os níveis ocupados e não ocupados destes metais. Para o caso do Gd, os dados experimentais foram estendidos em um intervalo de energia até alcançarem o pico de Bragg. A primeira parte desta tese foi publicada na Physical Review A 93 022704 (2016), e a segunda parte na Physical Review Letters 18 103401 (2017).

Es wird ein Ansatz und ein Algorithmus zur Lösung von stochastischen Stoppproblemen vorgestellt, der auf einer dualen Formulierung zum klassischen Lösungsansatz für Stoppprobleme mittels Variationsungleichungen basiert. Unter bestimmten Voraussetzungen kann man für diese duale Formulierung ein äquivalentes unendlichdimensionales lineares Programm aufstellen, das die Momente des Aufenthaltsmaßes des stochastischen Prozesses bis zum Stoppzeitpunkt und die Momente der Verteilung des Prozesses zum Zeitpunkt des Stoppens als Variablen enthält. Für dieses unendlichdimensionale Problem werden endlichdimensionale Approximationen formuliert und gelöst, wobei die Momente nur bis zu einer endlichen Ordnung berücksichtigt werden. Die Güte der numerischen Resultate hängt davon ab, wie genau der Träger des Maßes zum Stoppzeitpunkt identifiziert werden kann. Aus diesem Grund wird ein Verfeinerungsalgorithmus entwickelt, mit dem diese Identifizierung in einer Reihe von Fällen gelingt und sich sehr genaue Ergebnisse erzielen lassen. Der für Stoppprobleme entwickelte Algorithmus kann auch bei der Ermittlung von optimalen Steuerungen für stetige stochastische Prozesse angewandt werden. Für einzelne Beispiele wird gezeigt, welche Resultate dabei erzielt werden können. / We present an approach to, and an algorithm for solving optimal stopping problems. The approach is based on a dual formulation of the classical method for solving stopping problems using variational inequalities. Under suitable conditions it is possible to express the dual formulation as an infinite-dimensional linear program. This linear program uses the moments of the occupation measure and the moments of the stopping measure as variables. We formulate and solve finite-dimensional approximations to this infinite-dimensional program by restricting the number of moments. The accuracy of the numerical results depend on how well the support of the stopping measure can be identified. To this end we develop an iterative procedure which works very well in many cases. In the second part of the dissertation we show how the algorithm, developed for stopping problems, can be used for solving stochastic control problems.