95 research outputs found

    Probabilistic Graphical Models for Credibility Analysis in Evolving Online Communities

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    One of the major hurdles preventing the full exploitation of information from online communities is the widespread concern regarding the quality and credibility of user-contributed content. Prior works in this domain operate on a static snapshot of the community, making strong assumptions about the structure of the data (e.g., relational tables), or consider only shallow features for text classification. To address the above limitations, we propose probabilistic graphical models that can leverage the joint interplay between multiple factors in online communities --- like user interactions, community dynamics, and textual content --- to automatically assess the credibility of user-contributed online content, and the expertise of users and their evolution with user-interpretable explanation. To this end, we devise new models based on Conditional Random Fields for different settings like incorporating partial expert knowledge for semi-supervised learning, and handling discrete labels as well as numeric ratings for fine-grained analysis. This enables applications such as extracting reliable side-effects of drugs from user-contributed posts in healthforums, and identifying credible content in news communities. Online communities are dynamic, as users join and leave, adapt to evolving trends, and mature over time. To capture this dynamics, we propose generative models based on Hidden Markov Model, Latent Dirichlet Allocation, and Brownian Motion to trace the continuous evolution of user expertise and their language model over time. This allows us to identify expert users and credible content jointly over time, improving state-of-the-art recommender systems by explicitly considering the maturity of users. This also enables applications such as identifying helpful product reviews, and detecting fake and anomalous reviews with limited information.Comment: PhD thesis, Mar 201

    Improving Demand Forecasting: The Challenge of Forecasting Studies Comparability and a Novel Approach to Hierarchical Time Series Forecasting

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    Bedarfsprognosen sind in der Wirtschaft unerlässlich. Anhand des erwarteten Kundenbe-darfs bestimmen Firmen beispielsweise welche Produkte sie entwickeln, wie viele Fabri-ken sie bauen, wie viel Personal eingestellt wird oder wie viel Rohmaterial geordert wer-den muss. Fehleinschätzungen bei Bedarfsprognosen können schwerwiegende Auswir-kungen haben, zu Fehlentscheidungen führen, und im schlimmsten Fall den Bankrott einer Firma herbeiführen. Doch in vielen Fällen ist es komplex, den tatsächlichen Bedarf in der Zukunft zu antizipie-ren. Die Einflussfaktoren können vielfältig sein, beispielsweise makroökonomische Ent-wicklung, das Verhalten von Wettbewerbern oder technologische Entwicklungen. Selbst wenn alle Einflussfaktoren bekannt sind, sind die Zusammenhänge und Wechselwirkun-gen häufig nur schwer zu quantifizieren. Diese Dissertation trägt dazu bei, die Genauigkeit von Bedarfsprognosen zu verbessern. Im ersten Teil der Arbeit wird im Rahmen einer überfassenden Übersicht über das gesamte Spektrum der Anwendungsfelder von Bedarfsprognosen ein neuartiger Ansatz eingeführt, wie Studien zu Bedarfsprognosen systematisch verglichen werden können und am Bei-spiel von 116 aktuellen Studien angewandt. Die Vergleichbarkeit von Studien zu verbes-sern ist ein wesentlicher Beitrag zur aktuellen Forschung. Denn anders als bspw. in der Medizinforschung, gibt es für Bedarfsprognosen keine wesentlichen vergleichenden quan-titativen Meta-Studien. Der Grund dafür ist, dass empirische Studien für Bedarfsprognosen keine vereinheitlichte Beschreibung nutzen, um ihre Daten, Verfahren und Ergebnisse zu beschreiben. Wenn Studien hingegen durch systematische Beschreibung direkt miteinan-der verglichen werden können, ermöglicht das anderen Forschern besser zu analysieren, wie sich Variationen in Ansätzen auf die Prognosegüte auswirken – ohne die aufwändige Notwendigkeit, empirische Experimente erneut durchzuführen, die bereits in Studien beschrieben wurden. Diese Arbeit führt erstmals eine solche Systematik zur Beschreibung ein. Der weitere Teil dieser Arbeit behandelt Prognoseverfahren für intermittierende Zeitreihen, also Zeitreihen mit wesentlichem Anteil von Bedarfen gleich Null. Diese Art der Zeitreihen erfüllen die Anforderungen an Stetigkeit der meisten Prognoseverfahren nicht, weshalb gängige Verfahren häufig ungenügende Prognosegüte erreichen. Gleichwohl ist die Rele-vanz intermittierender Zeitreihen hoch – insbesondere Ersatzteile weisen dieses Bedarfs-muster typischerweise auf. Zunächst zeigt diese Arbeit in drei Studien auf, dass auch die getesteten Stand-der-Technik Machine Learning Ansätze bei einigen bekannten Datensät-zen keine generelle Verbesserung herbeiführen. Als wesentlichen Beitrag zur Forschung zeigt diese Arbeit im Weiteren ein neuartiges Verfahren auf: Der Similarity-based Time Series Forecasting (STSF) Ansatz nutzt ein Aggregation-Disaggregationsverfahren basie-rend auf einer selbst erzeugten Hierarchie statistischer Eigenschaften der Zeitreihen. In Zusammenhang mit dem STSF Ansatz können alle verfügbaren Prognosealgorithmen eingesetzt werden – durch die Aggregation wird die Stetigkeitsbedingung erfüllt. In Expe-rimenten an insgesamt sieben öffentlich bekannten Datensätzen und einem proprietären Datensatz zeigt die Arbeit auf, dass die Prognosegüte (gemessen anhand des Root Mean Square Error RMSE) statistisch signifikant um 1-5% im Schnitt gegenüber dem gleichen Verfahren ohne Einsatz von STSF verbessert werden kann. Somit führt das Verfahren eine wesentliche Verbesserung der Prognosegüte herbei. Zusammengefasst trägt diese Dissertation zum aktuellen Stand der Forschung durch die zuvor genannten Verfahren wesentlich bei. Das vorgeschlagene Verfahren zur Standardi-sierung empirischer Studien beschleunigt den Fortschritt der Forschung, da sie verglei-chende Studien ermöglicht. Und mit dem STSF Verfahren steht ein Ansatz bereit, der zuverlässig die Prognosegüte verbessert, und dabei flexibel mit verschiedenen Arten von Prognosealgorithmen einsetzbar ist. Nach dem Erkenntnisstand der umfassenden Literatur-recherche sind keine vergleichbaren Ansätze bislang beschrieben worden

    Learning Context-sensitive Human Emotions in Categorical and Dimensional Domains

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    Still image emotion recognition (ER) has been receiving increasing attention in recent years due to the tremendous amount of social media content on the Web. Many works offer both categorical and dimensional methods to detect image sentiments, while others focus on extracting the true social signals, such as happiness and anger. Deep learning architectures have delivered great suc- cess, however, their dependency on large-scale datasets labeled with (1) emotion, and (2) valence, arousal and dominance, in categorical and dimensional domains respectively, introduce challenges the community tries to tackle. Emotions offer dissimilar semantics when aroused in different con- texts, however context-sensitive ER has been by and large discarded in the literature so far. Moreover, while dimensional methods deliver higher accuracy, they have been less attended due to (1) lack of reliable large-scale labeled datasets, and (2) challenges involved in architecting un- supervised solutions to the problem. Owing to the success offered by multi-modal ER, still image ER in the single-modal domain; i.e. using only still images, remains less resorted to. In this work, (1) we first architect a novel fully automated dataset collection pipeline, equipped with a built-in semantic sanitizer, (2) we then build UCF-ER with 50K images, and LUCFER, the largest labeled ER dataset in the literature with more than 3.6M images, both datasets labeled with emotion and context, (3) next, we build a single-modal context-sensitive ER CNN model, fine-tuned on UCF-ER and LUCFER, (4) we then claim and show empirically that infusing context to the unified training process helps achieve a more balanced precision and recall, while boosting performance, yielding an overall classification accuracy of 73.12% compared to the state of the art 58.3%, (5) next, we propose an unsupervised approach for ranking of continuous emotions in images using canonical polyadic (CP) decomposition, providing theoretical proof that rank-1 CP decomposition can be used as a ranking machine, (6) finally, we provide empirical proof that our method generates a Pearson Correlation Coefficient, outperforming the state of the art by a large margin; i.e. 65.13% (difference) in one experiment and 104.08% (difference) in another, when applied to valence rank estimation

    Visual analytics and artificial intelligence for marketing

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    In today’s online environments, such as social media platforms and e-commerce websites, consumers are overloaded with information and firms are competing for their attention. Most of the data on these platforms comes in the form of text, images, or other unstructured data sources. It is important to understand which information on company websites and social media platforms are enticing and/or likeable by consumers. The impact of online visual content, in particular, remains largely unknown. Finding the drivers behind likes and clicks can help (1) understand how consumers interact with the information that is presented to them and (2) leverage this knowledge to improve marketing content. The main goal of this dissertation is to learn more about why consumers like and click on visual content online. To reach this goal visual analytics are used for automatic extraction of relevant information from visual content. This information can then be related, at scale, to consumer and their decisions

    Fairness-Aware Data-Driven Building Models (DDBMs) and Their Application in Model Predictive Controller (MPC)

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    In recent years, the massive data collection in buildings has paved the way for the development of accurate data-driven building models (DDBMs) for various applications. However, due to the variation in data volume of different conditions, existing DDBMs may present distinct accuracy for different users/occupants or periods/conditions. Accuracy variation among users or periods may creates unfairness problems (i.e., algorithmic biases created by data-driven models). This thesis explores and tackles this research problem called fairness-aware prediction of DDBMs. This thesis first presents a comprehensive review of the entire process involved in developing a DDBM and emphasizes the research gap on achieving fairness in DDBMs. As the first research that introduces fairness concepts into the building engineering domain, this thesis summarizes three types of commonly used fairness definitions. Among these concepts, achieving Type I and Type II fairness in DDBMs shows the beneficial for enabling users to do authority management, achieving uniform predictive performance under different periods or situations, and preserving fairness for different users. In addition, this thesis reviews the commonly used fairness improvement methods for data-driven models. Then, with the aim of improving fairness for DDBMs to have uniform predictive performance under different conditions and letting MPCs in buildings get optimal control signals based on fair prediction, this research proposes fairness improvement methods for both classification problems and regression problems in the building engineering domain and integrates fairness-aware DDBMs into model predictive controllers (MPCs). This work is separated into three tasks: 1) Task A: For classification problems, four kinds of pre-processing methods are proposed to balance the training dataset. 2) Task B: For regression problems, four in-processing methods, which incorporate fairness-related constraints or penalties into the optimization objective function during the training process of data-driven models, are studied. 3) Task C: The fairness improvement methods proposed in Task A and Task B will be integrated into MPCs. Case studies are conducted to implement the proposed fairness improvement methods to DDBMs for apartments, develop and integrate the fairness-aware DDBMs into MPCs to get the optimal set-point temperature for controlling the electrically heated floor system (EHF, a heating system with energy storage ability) in a bungalow building. The results show that 1) The proposed pre-processing methods could improve the predictive accuracy of minority conditions and increase fairness in terms of the accuracy rate between different conditions. 2) The proposed in-processing methods could achieve user-defined trade-off between accuracy and fairness. The Type II fairness is achieved by increasing the predictive performance similarity between different conditions. 3) Although improving predictive fairness would decrease the overall predictive accuracy, fairness-aware data-driven based MPCs would not decrease the cost saving and peak shifting ability, compared to the traditional MPC without considering fairness

    Advances in knowledge discovery and data mining Part II

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    19th Pacific-Asia Conference, PAKDD 2015, Ho Chi Minh City, Vietnam, May 19-22, 2015, Proceedings, Part II</p

    Ubiquitous Technologies for Emotion Recognition

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    Emotions play a very important role in how we think and behave. As such, the emotions we feel every day can compel us to act and influence the decisions and plans we make about our lives. Being able to measure, analyze, and better comprehend how or why our emotions may change is thus of much relevance to understand human behavior and its consequences. Despite the great efforts made in the past in the study of human emotions, it is only now, with the advent of wearable, mobile, and ubiquitous technologies, that we can aim to sense and recognize emotions, continuously and in real time. This book brings together the latest experiences, findings, and developments regarding ubiquitous sensing, modeling, and the recognition of human emotions
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