The supervised and semi-supervised machine learning paradigms hinge on the idea that the training data is labeled. The label quality is often brought into question, and problems related to noisy, inaccurate, or missing labels are studied. One of these is an interesting and prevalent problem in the semi-supervised classification area where only some positive labels are known. At the same time, the remaining and often the majority of the available data is unlabeled, i.e., there are no negative examples. Known as Positive-Unlabeled (PU) learning, this problem has been identified with increasing frequency across many disciplines, including but not limited to health science, biology, bioinformatics, geoscience, physics, business, and politics. Also, there are several closely related machine learning problems, such as cost-sensitive learning and mixture proportion estimation. This dissertation explores the PU learning problem from the perspective of density estimation and proposes a new modular method compatible with the relabeling framework that is common in PU learning literature. This approach is compared with two existing algorithms throughout the manuscript, one from a seminal work by Elkan and Noto and a current state-of-the-art algorithm by Ivanov. Furthermore, this thesis identifies two machine learning application domains that can benefit from PU learning approaches, which were not previously seen that way: predicting length of stay in hospitals and automatic music tagging. Experimental results with multiple synthetic and real-world datasets from different application domains validate the proposed approach. Accurately predicting the in-hospital length of stay (LOS) at the time of admission can positively impact healthcare metrics, particularly in novel response scenarios such as the Covid-19 pandemic. During the regular steady-state operation, traditional classification algorithms can be used for this purpose to inform planning and resource management. However, when there are sudden changes to the admission and patient statistics, such as during the onset of a pandemic, these approaches break down because reliable training data becomes available only gradually over time. This thesis demonstrates the effectiveness of PU learning approaches in such situations through experiments by simulating the positive-unlabeled scenario using two fully-labeled publicly available LOS datasets. Music auto-tagging systems are typically trained using tag labels provided by human listeners. In many cases, this labeling is weak, which means that the provided tags are valid for the associated tracks, but there can be tracks for which a tag would be valid but not present. This situation is analogous to PU learning with the additional complication of being a multi-label scenario. Experimental results on publicly available music datasets with tags representing three different labeling paradigms demonstrate the effectiveness of PU learning techniques in recovering the missing labels and improving auto-tagger performance. / Graduate

We tackle the task of semi-supervised video object segmentation, i.e, pixel-level object classification of the images in video sequences using very limited ground truth training data of its corresponding video. Recently introduced online adaptation of convolutional neural networks for video object segmentation (OnAVOS) has achieved good results by pretraining the network, fine-tuning on the first frame and training the network at test time using its approximate prediction as newly obtained ground truth. We propose Flow Adaptive Video Object Segmentation (FAVOS) that refines the generated adaptive ground truth for online updates and utilizes temporal consistency between video frames with the help of optical flow. We validate our approach on the DAVIS Challenge and achieve rank 1 results on the DAVIS 2016 Challenge (single-object segmentation) and competitive scores on both DAVIS 2018 Semi-supervised Challenge and Interactive Challenge (multi-object segmentation). While most models tend to have increasing complexity for the challenging task of video object segmentation, FAVOS provides a simple and efficient pipeline that produces accurate predictions.

Lorsqu'un enseignant veut évaluer le savoir-faire des apprenants à l'aide d'un logiciel, il utilise souvent les systèmes Tutoriels Intelligents (STI). Or, les STI sont difficiles à développer et destinés à un domaine pédagogique très ciblé. Depuis plusieurs années, l'utilisation d'algorithmes de classification par apprentissage supervisé a été proposée pour évaluer le savoir des apprenants. Notre hypothèse est que ces mêmes algorithmes vont aussi nous permettre d'évaluer leur savoir-faire. Notre domaine d'application étant l'électronique numérique, nous proposons une mesure de similarité entre schémas électroniques et une bas d'apprentissage générée automatiquement. cette base d'apprentissage est composées de schémas électroniques pédagogiquement étiquetés "bons" ou "mauvais" avec des informations concernant le degré de simplification des erreurs commises. Finalement, l'utilisation d'un algorithme de classification simple (les k plus proches voisins) nous a permis de faire une évaluation des schémas électroniques dans la majorité des cas. / When a teacher wants to evaluate the know-how of the learners using a software, he often uses Intelligent Tutorial Systems (ITS). However, those systems are difficult to develop and intended for a very targeted educational domain. For several years, the used of supervised classification algorithms was proposed to estimate the learners' knowledge. From this fact, we assume that the same kinf of algorithms can help to adress the learners' know-how evaluation. Our application field being digital system design, we propose a similarity measure between digital circuits and instances issued from an automatically generated database. This database consists of electronic circuits pedagogically labelled "good" or "bad" with information concerning the simplification degrees or made mistakes. Finally, the use of a simple classification algorithm (namely k-nearest neighbours classifier) allowed us to achieve a circuit's evaluation in most cases.

Heart rate variability (HRV) is the time variation between adjacent heartbeats. This variation is regulated by the autonomic nervous system (ANS) and its two branches, the sympathetic and parasympathetic nervous system. HRV is considered as an essential clinical tool to estimate the imbalance between the two branches, hence as an indicator of age and cardiac-related events.This thesis focuses on the ECG recordings during nocturnal rest to estimate the influence of HRV in predicting the age decade of healthy individuals. Time and frequency domains, as well as non-linear methods, are explored to extract the HRV features. Three feature-based methods (support vector machine (SVM), random forest, and extreme gradient boosting (XGBoost)) were employed, and the overall test accuracy achieved in capturing the actual class was relatively low (lower than 30%). SVM classifier had the lowest performance, while random forests and XGBoost performed slightly better. Although the difference is negligible, the random forest had the highest test accuracy, approximately 29%, using a subset of ten optimal HRV features. Furthermore, to validate the findings, the original dataset was shuffled and used as a test set and compared the performance to other related research outputs.

Orientador: Jackson Gois da Silva / Resumo: A aprendizagem de alunos de licenciatura é de fundamental importância no processo formativo desses futuros profissionais e o estágio curricular supervisionado é parte central nessa aprendizagem. O estágio curricular supervisionado foi introduzido nas disciplinas das licenciaturas a fim de propiciar aos licenciandos a vivência do cotidiano escolar, com a intenção de prepará-los melhor para seu futuro profissional. Durante as atividades de estágio da Licenciatura em Química, os licenciandos utilizam conceitos químicos na elaboração e aplicação de seus projetos de estágio e o fazem juntamente com os saberes docentes. Assim, o estágio se constitui na elaboração de concepções acerca da docência, bem como na reelaboração do conhecimento químico direcionado para a prática docente, o que possibilita uma formação profissional mais concreta. Uma importante habilidade relacionada às áreas científicas é a argumentação científica, pois é através dela que o conhecimento científico é validado, seja em sala de aula e em todas as instâncias da sociedade. Em nosso trabalho, buscamos saber se as reflexões proporcionadas pelas atividades do estágio da Licenciatura em Química de uma universidade pública paulista influenciam na habilidade de argumentação científica dos alunos, através da aplicação de questionário e gravações em vídeos das reuniões de estágio, análise dos projetos e de relatórios dos licenciandos. A pesquisa é de caráter qualitativo, assim, utilizamos a análise textual discursiva p... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The learning of undergraduate students is of fundamental importance in the training process of these future professionals and the supervised curricular internship is a central part of this learning. The supervised internship was introduced in the disciplines of undergraduate courses in order to provide graduates with the experience of school daily, with the intention of preparing them better for their professional future. During the internship activities of the undergraduate degree in chemistry, undergraduates use chemical concepts in the elaboration and application of their internship projects, and do so together with the teaching knowledge. Thus, the internship is constituted in the elaboration of conceptions about teaching, as well as in the re-elaboration of the chemical knowledge directed to the teaching practice, what allows a more concrete professional formation. An important skill related to scientific areas is scientific argumentation, because it is through it that scientific knowledge is validated, whether in the classroom and in all instances of society. In our work, we seek to find out if the reflections provided by the activities of the degree in chemistry at a public university in São Paulo influence the ability of students to make scientific arguments, through the application of questionnaires and video recordings of internship meetings, project analysis and undergraduate reports. The research is of a qualitative character, therefore, we use discursive textual ... (Complete abstract click electronic access below) / Mestre

In dieser Arbeit wird ein Programm zur Sprachidentifikation von Web-Dokumenten vorgestellt. Das Verfahren nutzt Worthäufigkeitslisten als Trainingsdaten, um anhand dieser Dokumentenklassifikation in Sprachen vorzunehmen. Somit gehört dieses Werkzeug zu den supervised-learning-Systemen. Die zu klassifizierenden Web-Dokumente wurden mittels des von der Abteilung fur Automatische Sprachverarbeitung entwickelten Tools 'FindLinks' heruntergeladen. Das Programm ist somit in die Nachverarbeitung bestehender Rohdaten einzuordnen. / This BSc Thesis presents a program for automatic language identification of web-documents called LangSepa. The procedure uses training-data which is based on word-frequency-tables of over 350 natural languages. Thus this tool can be subsumed under supervised learning systems. The documents for the classification-task were crawled by an information-retrieval system called FindLinks, which is developed at the Natural Language Processing group at the University of Leipzig. Therefore the presented program will be employed for the postprocessing of existent raw data.

Fault detection for residential photovoltaic power systems is an often-ignored problem. This thesis introduces a novel method for detecting power losses due to faults in solar panel performance. Five years of data from a residential system in Dalarna, Sweden, was applied on a random forest regression to estimate power production. Estimated power was compared to true power to assess the performance of the power generating systems. By identifying trends in the difference and estimated power production, faults can be identified. The model is sufficiently competent to identify consistent energy losses of 10% or greater of the expected power output, while requiring only minimal modifications to existing power generating systems.

Understanding travel behavior and identifying the mode of transportation are essential for adequate urban devising and transportation planning. Global positioning systems (GPS) tracking data is mainly used to find human mobility patterns in cities. Some travel information, such as most visited location, temporal changes, and the trip speed, can be easily extracted from GPS raw tracking data. GPS trajectories can be used as a method to indicate the mobility modes of commuters. Most previous studies have applied traditional machine learning algorithms and manually computed data features, making the model error-prone. Thus, there is a demand for developing a new model to resolve these methods' weaknesses. The primary purpose of this study is to propose a semi-supervised model to identify transportation mode by using a contemporary machine learning algorithm and GPS tracking data. The model can accept GPS trajectory with adjustable length and extracts their latent information with LSTM Autoencoder. This study adopts a deep neural network architecture with three hidden layers to map the latent information to detect transportation mode. Moreover, different case studies are performed to evaluate the proposed model's efficiency. The model results in an accuracy of 93.6%, which significantly outperforms similar studies.

The technology developments of the last years allow measuring data in almost every field and area nowadays, especially increasing the potential for analytics in branches in which not much analytics have been done due to complicated data access before. The increased number of interest in sports analytics is highly connected to the better technology now available for visual and physical sensors on the one hand and sports as upcoming economic topic holding potentially large revenues and therefore investing interest on the other hand. With the underlying database, precise strategies and individual performance improvements within the field of professional sports are no longer a question of (coach)experience but can be derived from models with statistical accuracy. This thesis aims to evaluate if the available data together with complex and simple supervised machine learning models could generalize from the training data to unseen situations by evaluating performance metrics. Data from games of the ice hockey team of Linköping for the season 2017/2018 is processed with supervised learning algorithms such as binary logistic regression and neural networks. The result of this first step is to determine the strategies of passes by considering both, attempted but failed and successful shots on goals during the game. For that, the original, raw data set was aggregated to game-specific data. After having detected the distinct strategies, they are classified due to their rate of success.

In this work, we leverage the recent developments in computer science to address several of the challenges in current literature-based discovery (LBD) solutions. First, LBD solutions cannot use semantics or are too computational complex. To solve the problems we propose a generative model OverlapLDA based on topic modeling, which has been shown both effective and efficient in extracting semantics from a corpus. We also introduce an inference method of OverlapLDA. We conduct extensive experiments to show the effectiveness and efficiency of OverlapLDA in LBD. Second, we expand LBD to a more complex and realistic setting. The settings are that there can be more than one concept connecting the input concepts, and the connectivity pattern between concepts can also be more complex than a chain. Current LBD solutions can hardly complete the LBD task in the new setting. We simplify the hypotheses as concept sets and propose LBDSetNet based on graph neural networks to solve this problem. We also introduce different training schemes based on self-supervised learning to train LBDSetNet without relying on comprehensive labeled hypotheses that are extremely costly to get. Our comprehensive experiments show that LBDSetNet outperforms strong baselines on simple hypotheses and addresses complex hypotheses.