Umeå University's logo

umu.sePublications
Change search
Refine search result
12 1 - 50 of 100
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ahlgren, Per
    et al.
    Department of Statistics, Uppsala University, Uppsala (Sweden).
    Chen, Yunwei
    Scientometrics & Evaluation Research Center (SERC), Chengdu Library and Information Center of Chinese Academy of Sciences, Chengdu, 610041 (China).
    Colliander, Cristian
    Umeå University, Faculty of Social Sciences, Department of Sociology. Umeå University, Umeå University Library.
    Jan van Eck, Nees
    Centre for Science and Technology Studies, Leiden University (The Netherlands).
    Enhancing Direct Citations: A Comparison of Relatedness Measures for Community Detection in a Large Set of PubMed Publications2020In: Quantitative Science Studies, E-ISSN 2641-3337, Vol. 1, no 2, p. 1-20Article in journal (Refereed)
    Abstract [en]

    In this contribution, the effects of enhancing direct citations, with respect to publication-publication relatedness measurement, by indirect citation relations (bibliographic coupling, co-citation, and extended direct citations) and text relations on clustering solution accuracy are analyzed. We include in the study, for comparison reasons, each approach that is involved in the enhancement of direct citations. In total, we investigate the relative performance of seven approaches. For the evaluation of the approaches, we use a methodology proposed by earlier research. However, the used evaluation criterion is based on MeSH, one of the most sophisticated publication-level classification schemes available. We also introduce an approach, based on interpolated accuracy values, by which overall relative clustering solution accuracy can be studied. The results show that the co-citation approach has the worst performance, and that the direct citations approach is outperformed by the other five investigated approaches. The extended direct citations approach has the best performance, followed by an approach in which direct citations are enhanced by the BM25 textual relatedness measure. An approach that combines direct citations with bibliographic coupling and co-citation performs slightly better than the bibliographic coupling approach, which in turn has a better performance than the BM25 approach.

    Download full text (pdf)
    fulltext
  • 2.
    Ahlgren, Per
    et al.
    Department of e-Resources, University Library, Stockholm University.
    Colliander, Cristian
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Persson, Olle
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Field normalized citation rates, field normalized journal impact and Norwegian weights for allocation of university research funds2012In: Scientometrics, ISSN 0138-9130, E-ISSN 1588-2861, Vol. 92, no 2, p. 767-780Article in journal (Refereed)
    Abstract [en]

    We compared three different bibliometric evaluation approaches: two citationbased approaches and one based on manual classification of publishing channels into quality levels. Publication data for two universities was used, and we worked with two levels of analysis: article and department. For the article level, we investigated the predictive power of field normalized citation rates and field normalized journal impact with respect to journal level. The results for the article level show that evaluation of journals based on citation impact correlate rather well with manual classification of journals into quality levels. However, the prediction from field normalized citation rates to journal level was only marginally better than random guessing. At the department level, we studied three different indicators in the context of research fund allocation within universities and the extent to which the three indicators produce different distributions of research funds. It turned out that the three distributions of relative indicator values were very similar, which in turn yields that the corresponding distributions of hypothetical research funds would be very similar.

  • 3.
    Almeida, Teresa
    et al.
    ITI/LARSyS, Instituto Superior Técnico, Lisbon, Portugal.
    Shipp, Laura
    Newcastle University, UK.
    Mehrnezhad, Maryam
    Newcastle University, UK.
    Toreini, Ehsan
    Durham University, UK.
    Bodies like yours: enquiring data privacy in FemTech2022Conference paper (Refereed)
    Abstract [en]

    The digitalisation of the reproductive body has seen a myriad of cutting-edge technologies to prioritise neglected intimate health and care topics, such as fertility and contraception. The impact of these intimate data on livelihood and society is pervasive including that privacy is critical to safeguarding security as this increasing digitalisation also produces increasingly large datasets. In this paper, we enquire the collective nature of privacy in female-oriented technologies (FemTech) to show how this ever-extending collection of data implicates many beyond the individual. We introduce a pilot study on the data collection practices of a subset of FemTech devices with fertility tracking service. We demonstrate that data is collected about the user and others, such as their immediate relationships and user groups as a whole. We suggest that it is critical we ask who is vulnerable and discuss approaches to mitigate collective harm.

  • 4.
    Anani, Adi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    M-learning in review: Technology, standard and evaluation2008In: Journal of Communication and Computer, ISSN 1548-7709, Vol. 5, no 11, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Nowadays E-learning as a form of learning depending on networks and computer devices has been expanding by leaps and bounds. As a special kind of E-learning, M-learning (mobile learning) aims at the use of mobile devices anywhere at anytime by anybody. In this paper, the technologies to develop a M-learning system is deeply analyzed according to the layer model at first. Secondly, from the view of application, the standardization in M-learning is researched in order to accelerate the development and popularization of M-learning. Finally, quality estimation of M-learning system is discussed from the view of QoE (quality of experiences). The experience form end-user is the sole effective norm to judge the result of M-learning technology. It is no doubt that technologies, standardization and evaluation will play very important parts in the course of M-learning development.

    Download full text (pdf)
    FULLTEXT01
  • 5.
    Bala, Paulo
    et al.
    Iti / LARSyS, Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Sanches, Pedro
    Umeå University, Faculty of Social Sciences, Department of Informatics. Iti / LARSyS, Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Cesário, Vanessa
    Iti / LARSyS, Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Leão, Sarah
    Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Rodrigues, Catarina
    Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Nunes, Nuno Jardim
    Iti / LARSyS, Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Nisi, Valentina
    Iti / LARSyS, Instituto Superior Técnico, U. Lisbon, Lisbon, Portugal.
    Towards critical heritage in the wild: analysing discomfort through collaborative autoethnography2023In: CHI '23: proceedings of the 2023 CHI conference on human factors in computing systems / [ed] Albrecht Schmidt; Kaisa Väänänen; Tesh Goyal; Per Ola Kristensson; Anicia Peters; Stefanie Mueller; Julie R. Williamson; Max L. Wilson, New York: Association for Computing Machinery (ACM), 2023, article id 771Conference paper (Refereed)
    Abstract [en]

    As we engaged in designing digital interventions for intercultural dialogues around public cultural heritage sites, we saw an opportunity to surface multiple interpretations and points of view of history and shine a critical lens on current societal issues. To do so, we present the results of a collaborative auto-ethnography of alternative tours accompanied by intercultural guides, to explore sensory and embodied engagements with cultural heritage sites in a southern European capital. By focusing on the differences in how we experienced the heritage sites, we analyse the duality of discomfort, a common concept in HCI, in that it can both be deployed as a resource for designing systems that can transform people's understanding of history or it can be a hindrance for engagement, having an unequal effect on individuals.

  • 6.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Freund, Rudolf
    Hirvensalo, Mika
    Otto, Friedrich
    Non-Classical Models of Automata and Applications VI Preface2016In: Fundamenta Informaticae, ISSN 0169-2968, E-ISSN 1875-8681, Vol. 148, no 3-4, p. I-IIArticle in journal (Other academic)
  • 7.
    Bermell, Måns
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Identification of Problem Gambling via Recurrent Neural Networks: Predicting self-exclusion due to problem gambling within the remote gambling sector by means of recurrent neural networks2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Under recent years the gambling industry has been moving towards providing their customer the possibility to gamble online instead of visiting a physical location. Aggressive marketing, fast growth and a multitude of actors within the market have resulted in a spike of customers who have developed a gambling problem. Decision makers are trying to fight back by regulating markets in order to make the companies take responsibility and work towards preventing these problems. One method of working proactively in this regards is to identify vulnerable customers before they develop a destructive habit.

    In this work a novel method of predicting customers that have a higher risk in regards to gambling-related problems is explored. More concretely, a recurrent neural network with long short-term memory cells is created to process raw behaviour data that are aggregated on a daily basis to classify them as high-risk or not. Supervised training is used in order to learn from historical data, where the usage of permanent self-exclusions due to gambling related problems defines problem gamblers. The work consists of: obtain a local optimal configuration of the network which enhances the performance for identifying problem gam- blers who favour the casino section over sports section, and analyze the model to provide insights in the field.

    This project was carried out together with LeoVegas Mobile Gaming Group. The group offers both online casino games and sports booking in a number of countries in Europe. This collaboration made both data and expertise within the industry accessible to perform this work. The company currently have a model in production to perform these predictions, but want to explore other approaches.

    The model that has been developed showed a significant increase in performance compared to the one that is currently used at the company. Specifically, the precision and recall which are two metrics important for a two class classification model, increased by 37% and 21% respectively. Using raw time series data, instead of aggregated data increased the responsiveness regarding customers change in behaviour over time. The model also scaled better with more history compared to the current model, which could be a result of the nature of a recurrent network compared to the current model used.

    Download full text (pdf)
    fulltext
  • 8.
    Bernenko, Dolores
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lee, Sang Hoon
    Department of Physics and Research Institute of Natural Science, Gyeongsang National University, Jinju, Republic of Korea; Future Convergence Technology Research Institute, Gyeongsang National University, Jinju, Republic of Korea.
    Lizana, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Exploring 3D community inconsistency in human chromosome contact networks2023In: Journal of physics. Complexity, ISSN 2632-072X, Vol. 4, no 3, article id 035004Article in journal (Other academic)
    Abstract [en]

    Researchers developed chromosome capture methods such as Hi-C to better understand DNA's 3D folding in nuclei. The Hi-C method captures contact frequencies between DNA segment pairs across the genome. When analyzing Hi-C data sets, it is common to group these pairs using standard bioinformatics methods (e.g., PCA). Other approaches handle Hi-C data as weighted networks, where connected node represent DNA segments in 3D proximity. In this representation, one can leverage community detection techniques developed in complex network theory to group nodes into mesoscale communities containing similar connection patterns. While there are several successful attempts to analyze Hi-C data in this way, it is common to report and study the most typical community structure. But in reality, there are often several valid candidates. Therefore, depending on algorithm design, different community detection methods focusing on slightly different connectivity features may have differing views on the ideal node groupings. In fact, even the same community detection method may yield different results if using a stochastic algorithm. This ambiguity is fundamental to community detection and shared by most complex networks whenever interactions span all scales in the network. This is known as community inconsistency. This paper explores this inconsistency of 3D communities in Hi-C data for all human chromosomes. We base our analysis on two inconsistency metrics, one local and one global, and quantify the network scales where the community separation is most variable. For example, we find that TADs are less reliable than A/B compartments and that nodes with highly variable node-community memberships are associated with open chromatin. Overall, our study provides a helpful framework for data-driven researchers and increases awareness of some inherent challenges when clustering Hi-C data into 3D communities.

    Download full text (pdf)
    fulltext
  • 9.
    Bernenko, Dolores
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lee, Sang Hoon
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stenberg, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lizana, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mapping the semi-nested community structure of 3D chromosome contact networks2022Manuscript (preprint) (Other academic)
    Abstract [en]

    Mammalian DNA folds into 3D structures that facilitate and regulate genetic processes such as transcription, DNA repair, and epigenetics. Several insights derive from chromosome capture methods, such as Hi-C, which allow researchers to construct contact maps depicting 3D interactions among all DNA segment pairs. These maps show a complex cross-scale organization spanning megabase-pair compartments to short-ranged DNA loops. To better understand the organizing principles, several groups analyzed Hi-C data assuming a Russian-doll-like nested hierarchy where DNA regions of similar sizes merge into larger and larger structures. Apart from being a simple and appealing description, this model explains, e.g., the omnipresent chequerboard pattern seen in Hi-C maps, known as A/B compartments, and foreshadows the co-localization of some functionally similar DNA regions. However, while successful, this model is incompatible with the two competing mechanisms that seem to shape a significant part of the chromosomes’ 3D organization: loop extrusion and phase separation. This paper aims to map out the chromosome’s actual folding hierarchy from empirical data. To this end, we take advantage of Hi-C experiments and treat the measured DNA-DNA interactions as a weighted network. From such a network, we extract 3D communities using the generalized Louvain algorithm. This algorithm has a resolution parameter that allows us to scan seamlessly through the community size spectrum, from A/B compartments to topologically associated domains (TADs). By constructing a hierarchical tree connecting these communities, we find that chromosomes are more complex than a perfect hierarchy. Analyzing how communities nest relative to a simple folding model, we found that chromosomes exhibit a significant portion of nested and non-nested community pairs alongside considerable randomness. In addition, by examining nesting and chromatin types, we discovered that nested parts are often associated with active chromatin. These results highlight that crossscale relationships will be essential components in models aiming to reach a deep understanding of the causal mechanisms of chromosome folding.

  • 10.
    Blöcker, Christopher
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Through the coding-lens: community detection and beyond2022Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    We live in a highly-connected world and find networks wherever we look: social networks, public transport networks, telecommunication networks, financial networks, and more. These networks can be immensely complex, comprising potentially millions or even billions of inter-connected objects. Answering questions such as how to control disease spreading in contact networks, how to optimise public transport networks, or how to diversify investment portfolios requires understanding each network's function and working principles.

    Network scientists analyse the structure of networks in search of communities: groups of objects that form clusters and are more connected to each other than the rest. Communities form the building blocks of networks, corresponding to their sub-systems, and allow us to represent networks with coarse-grained models. Analysing communities and their interactions helps us unravel how networks function.

    In this thesis, we use the so-called map equation framework, an information-theoretic community-detection approach. The map equation follows the minimum description length principle and assumes complete data in networks with one node type. We challenge these assumptions and adapt the map equation for community detection in networks with two node types and incomplete networks where some data is missing. We move beyond detecting communities and derive approaches for how, based on communities, we can identify influential objects in networks, and predict links that do not (yet) exist.

    Download full text (pdf)
    fulltext
    Download (pdf)
    spikblad
    Download (png)
    preview image
  • 11.
    Blöcker, Christopher
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nieves, Juan Carlos
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rosvall, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Map equation centrality: community-aware centrality based on the map equation2022In: Applied Network Science, E-ISSN 2364-8228, Vol. 7, no 1, article id 56Article in journal (Refereed)
    Abstract [en]

    To measure node importance, network scientists employ centrality scores that typically take a microscopic or macroscopic perspective, relying on node features or global network structure. However, traditional centrality measures such as degree centrality, betweenness centrality, or PageRank neglect the community structure found in real-world networks. To study node importance based on network flows from a mesoscopic perspective, we analytically derive a community-aware information-theoretic centrality score based on network flow and the coding principles behind the map equation: map equation centrality. Map equation centrality measures how much further we can compress the network's modular description by not coding for random walker transitions to the respective node, using an adapted coding scheme and determining node importance from a network flow-based point of view. The information-theoretic centrality measure can be determined from a node's local network context alone because changes to the coding scheme only affect other nodes in the same module. Map equation centrality is agnostic to the chosen network flow model and allows researchers to select the model that best reflects the dynamics of the process under study. Applied to synthetic networks, we highlight how our approach enables a more fine-grained differentiation between nodes than node-local or network-global measures. Predicting influential nodes for two different dynamical processes on real-world networks with traditional and other community-aware centrality measures, we find that activating nodes based on map equation centrality scores tends to create the largest cascades in a linear threshold model.

    Download full text (pdf)
    fulltext
  • 12.
    Blöcker, Christopher
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Smiljanic, Jelena
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Scholtes, Ingo
    Rosvall, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Similarity-based Link Prediction from Modular Compression of Network FlowsManuscript (preprint) (Other academic)
    Abstract [en]

    Node similarity scores constitute a foundation for machine learning in graphs. Besides clustering, node classification, and anomaly detection, they are a basis for link prediction with critical applications in biological systems, information networks, and recommender systems. Recent works on link prediction use vector space embeddings to calculate node similarities. While these methods can provide good performance in undirected networks, they have several disadvantages: limited interpretability, problem-specific hyperparameter tuning, manual model fitting through dimensionality reduction, and poor performance of symmetric similarities in directed link prediction. To address these issues, we propose MapSim, a novel information-theoretic approach to assess node similarities based on modular compression of network flows. Different from vector space embeddings, MapSim represents nodes in a discrete, non-metric space of communities and yields asymmetric similarities suitable to predict directed and undirected links in an unsupervised fashion. The resulting similarities can be explained based on a network's hierarchical modular organisation, facilitating interpretability. MapSim naturally accounts for Occam's razor, leading to parsimonious representations of clusters at multiple scales. Addressing unsupervised link prediction, we compare MapSim to popular embedding-based algorithms across 47 data sets of networks from a few hundred to hundreds of thousands of nodes and millions of links. Our analysis shows that MapSim's average performance across all networks is more than 7% higher than its closest competitor, outperforming all embedding methods in 14 of the 47 networks, and a more than 33% better worst-case performance. Our method demonstrates the potential of compression-based approaches in graph representation learning, with promising applications in other graph learning tasks.

  • 13.
    Bohlin, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Toward higher-order network models2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Complex systems play an essential role in our daily lives. These systems consist of many connected components that interact with each other. Consider, for example, society with billions of collaborating individuals, the stock market with numerous buyers and sellers that trade equities, or communication infrastructures with billions of phones, computers and satellites.

    The key to understanding complex systems is to understand the interaction patterns between their components - their networks. To create the network, we need data from the system and a model that organizes the given data in a network representation. Today's increasing availability of data and improved computational capacity for analyzing networks have created great opportunities for the network approach to further prosper. However, increasingly rich data also gives rise to new challenges that question the effectiveness of the conventional approach to modeling data as a network. In this thesis, we explore those challenges and provide methods for simplifying and highlighting important interaction patterns in network models that make use of richer data.

    Using data from real-world complex systems, we first show that conventional network modeling can provide valuable insights about the function of the underlying system. To explore the impact of using richer data in the network representation, we then expand the analysis for higher-order models of networks and show why we need to go beyond conventional models when there is data that allows us to do so. In addition, we also present a new framework for higher-order network modeling and analysis. We find that network models that capture richer data can provide more accurate representations of many real-world complex systems.

    Download full text (pdf)
    fulltext
    Download (pdf)
    spikblad
    Download (jpg)
    presentationsbild
  • 14. Boshuijzen-van Burken, Christine
    et al.
    Gore, Ross
    Dignum, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Royakkers, Lamber
    Wozny, Phillip
    Shults, F. Leron
    Agent-Based Modelling of Values: The Case of Value Sensitive Design for Refugee Logistics2020In: JASSS: Journal of Artificial Societies and Social Simulation, E-ISSN 1460-7425, Vol. 23, no 4, article id 6Article in journal (Refereed)
    Abstract [en]

    We have used value sensitive design as a method to develop an agent-based model of values in humanitarian logistics for refugees. Schwartz's theory of universal values is implemented in the model in such a way that agents can make value trade-offs, which are operationalized into a measure of refugee wellbeing and a measure of public opinion about how the refugee logistics is being handled. By trying out different 'value-scenarios', stakeholders who are responsible for, or involved in refugee logistics can have insights into the effects of various value choices. The model is visualized and made usable as a platform (interactive website) for decision-makers to understand the trade-offs in policies for government and non-government organizations.

    Download full text (pdf)
    fulltext
  • 15.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    Buckland, Paul C.
    BugsCEP, an entomological database twenty-five years on2014In: Antenna (Journal of the Royal Entomological Society), ISSN 0140-1890, Vol. 38, no 1, p. 21-28Article in journal (Refereed)
  • 16.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik J.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    SEAD - The Strategic Environmental Archaeology Database: Progress Report Spring 20142014Report (Other academic)
    Abstract [en]

    This report provides an overview of the progress and results of the VR:KFI infrastructure projects 2007-7494 and (825-)2010-5976. It should be considered as a status report in an on-going long-term research infrastructure development project.

    Download full text (pdf)
    SEAD - Progress Report Spring 2014
  • 17.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Sjölander, Mattias
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Blombocken avslöjar forntiden2017In: Populär arkeologi, ISSN 0281-014X, no 5, p. 28-31Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Databaser. Fossila insekter och förkolnade fröer kan ge mycket information om de miljöer som människor har levt i och kan liksom annan biologisk information tjäna arkeologin.

  • 18.
    Burwall, William
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Building High-performing Web Rendering of Large Data Sets2023Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Interactive visualization is an essential tool for data analysis. Cloud-based data analysis software must handle growing data sets without relying on powerful end-user hardware. This thesis explores and tests various methods to speed up primarily time series plots of large data sets on the web for the biotechnology research company Sartorius.

    To increase rendering speed, I focused on two main approaches: downsampling and hardware acceleration. To find which sampling algorithms suit Sartorius's needs, I implemented multiple alternatives and compared them quantitatively and qualitatively. The results show that downsampling increases or eliminates data set size limits and that test users favored algorithms maintaining local outliers. With hardware acceleration that substantially increased the amount of simultaneously rendered points for more detailed representations, these methods pave the way for efficient visualization of large data sets on the web.

    Download full text (pdf)
    fulltext
  • 19.
    Bökman, Georg
    et al.
    Chalmers University of Technology, Gothenburg, Sweden.
    Flinth, Axel
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Kahl, Fredrik
    Chalmers University of Technology.
    In search of projectively equivariant networks2023In: Transactions on Machine Learning Research, E-ISSN 2835-8856Article in journal (Refereed)
    Abstract [en]

    Equivariance of linear neural network layers is well studied. In this work, we relax the equivariance condition to only be true in a projective sense. Hereby, we introduce the topic of projective equivariance to the machine learning audience. We theoretically study the relation of projectively and linearly equivariant linear layers. We find that in some important cases, surprisingly, the two types of layers coincide. We also propose a way to construct a projectively equivariant neural network, which boils down to building a standard equivariant network where the linear group representations acting on each intermediate feature space are lifts of projective group representations. Projective equivariance is showcased in two simple experiments. Code for the experiments is provided in the supplementary material.

    Download full text (pdf)
    fulltext
  • 20. Christie, N.
    et al.
    Mannapperuma, Chanaka
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ployet, R.
    Van der Merwe, K.
    Mähler, Niklas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Delhomme, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Naidoo, S.
    Mizrachi, E.
    Street, Nathaniel
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Myburg, A. A.
    The Eucalyptus Genome Integrative Explorer: an online resource for systems genetics in forest tree species2020In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313XArticle in journal (Other academic)
  • 21.
    Colliander, Cristian
    et al.
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Ahlgren, Per
    Department of e-Resources, University Library, Stockholm University.
    Experimental comparison of first and second-order similarities in a scientometric context2012In: Scientometrics, ISSN 0138-9130, E-ISSN 1588-2861, Vol. 90, no 2, p. 675-685Article in journal (Refereed)
    Abstract [en]

    The measurement of similarity between objects plays a role in several scientific areas. In this article, we deal with document–document similarity in a scientometric context. We compare experimentally, using a large dataset, first-order with second-order similarities with respect to the overall quality of partitions of the dataset, where the partitions are obtained on the basis of optimizing weighted modularity. The quality of a partition is defined in terms of textual coherence. The results show that the second-order approach consistently outperforms the first-order approach. Each difference between the two approaches in overall partition quality values is significant at the 0.01 level.

  • 22.
    Dahlbäck, Marcus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evaluation of models for process time delay estimation in a pulp bleaching plant2020Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The chemical processes used to manufacture pulp are always in development to cope with increasing environmental demands and competition. With a deeper understanding of the processes, the pulping industry can become both more profitable and effective at keeping an even and good quality of pulp, while reducing emissions. One step in this direction is to more accurately determine the time delay for a process, defined as the time it takes for a change in input to affect the process’s output. This information can then be used to control the process more efficiently. The methods used today to estimate the time delay use simple models and assumptions of the processes, for example that that the pulp behaves like a ”plug” that never changes its shape throughout the process. The problem with these assumptions is that they are only valid under ideal circumstances where there are no disturbances. This Master’s thesis aims to investigate if it is possible to measure the process time delay using only the input and output data from the process, and see if this estimation is more accurate than the existing model based methods. Another aim is to investigate if the process time delay can be monitored in real time. We investigated three methods: cross-correlation applied to the raw input and output data, cross-correlation applied to the derivative of the input and output data, and a convolutional neural network trained to identify the process time delay from the input and output data. The results show that it is possible to find the time delay, but with significant deviations from the models used today. Due to a lack of data where the time delay was measured, the reason for this deviation requires more research. The results also show that the three methods are unsuitable for real-time estimation. However, the models can likely monitor how the process time delay develops over long periods.

    Download full text (pdf)
    Evaluation of models for process time delay estimation in a pulp bleaching plant
  • 23. Ding, Linfang
    et al.
    Xiao, Guohui
    Calvanese, Diego
    Umeå University, Faculty of Science and Technology, Department of Computing Science. KRDB Research Centre, Faculty of Computer Science, Free University of Bozen-Bolzano, Bolzano, Italy; Ontopic S.r.L, Bolzano, Italy.
    Meng, Liqiu
    A Framework Uniting Ontology-Based Geodata Integration and Geovisual Analytics2020In: ISPRS International Journal of Geo-Information, ISSN 2220-9964, Vol. 9, no 8, article id 474Article in journal (Refereed)
    Abstract [en]

    In a variety of applications relying on geospatial data, getting insights into heterogeneous geodata sources is crucial for decision making, but often challenging. The reason is that it typically requires combining information coming from different sources via data integration techniques, and then making sense out of the combined data via sophisticated analysis methods. To address this challenge we rely on two well-established research areas: data integration and geovisual analytics, and propose to adopt an ontology-based approach to decouple the challenges of data access and analytics. Our framework consists of two modules centered around an ontology: (1) an ontology-based data integration (OBDI) module, in which mappings specify the relationship between the underlying data and a domain ontology; (2) a geovisual analytics (GeoVA) module, designed for the exploration of the integrated data, by explicitly making use of standard ontologies. In this framework, ontologies play a central role by providing a coherent view over the heterogeneous data, and by acting as a mediator for visual analysis tasks. We test our framework in a scenario for the investigation of the spatiotemporal patterns of meteorological and traffic data from several open data sources. Initial studies show that our approach is feasible for the exploration and understanding of heterogeneous geospatial data.

    Download full text (pdf)
    fulltext
  • 24.
    Djuphammar, Felix
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Efficient graph embeddings with community detection2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Networks are useful when modeling interactions in real-world systems based on relational data. Since networks often contain thousands or millions of nodes and links, analyzing and exploring them requires powerful visualizations. Presenting the network nodes in a map-like fashion provides a large scale overview of the data while also providing specific details. A suite of algorithms can compute an appropriate layout of all nodes for the visualization. However, these algorithms are computationally expensive when applied to large networks because they must repeatedly derive relations between every node and every other node, leading to quadratic scaling. Also, the available implementations compute the layout from the raw data instead of the network, making customization difficult. In this thesis, I introduce a modular algorithm that removes the need to consider all node pairs by approximating groups of pairwise relations. The groups are determined by clustering the network into densely connected groups of nodes with a community-detection algorithm. The implementation accepts a network as input and returns the layout coordinates, enabling modular and straightforward integration in a data analysis pipeline. The approximations improve the new algorithm's scaling to an order of 2N1.5 compared to the original N2. For a network with one million nodes, this scaling improvement gives a 500-fold performance boost such that a computation that previously took one week now completes in about 20 minutes.

    Download full text (pdf)
    fulltext
  • 25.
    Dubois, Mathieu
    et al.
    NeuroSpin, I2BM, CEA.
    Hadj-Selem, Fouad
    NeuroSpin, I2BM, CEA.
    Löfstedt, Tommy
    NeuroSpin, I2BM, CEA.
    Perrot, Matthieu
    Centre d'Acquisition et de Traitement des Images (CATI).
    Fischer, Clara
    Centre d'Acquisition et de Traitement des Images (CATI).
    Frouin, Vincent
    NeuroSpin, I2BM, CEA.
    Duchesnay, Edouard
    NeuroSpin, I2BM, CEA.
    Predictive support recovery with TV-Elastic Net penalty and logistic regression: An application to structural MRI2014Conference paper (Refereed)
    Abstract [en]

    The use of machine-learning in neuroimaging offers new perspectives in early diagnosis and prognosis of brain diseases. Although such multivariate methods can capture complex relationships in the data, traditional approaches provide irregular (l12 penalty) or scattered (l1 penalty) predictive pattern with a very limited relevance. A penalty like Total Variation (TV) that exploits the natural 3D structure of the images can increase the spatial coherence of the weight map. However, TV penalization leads to non-smooth optimization problems that are hard to minimize. We propose an optimization framework that minimizes any combination of l1, l2, and TV penalties while preserving the exact l1 penalty. This algorithm uses Nesterov's smoothing technique to approximate the TV penalty with a smooth function such that the loss and the penalties are minimized with an exact accelerated proximal gradient algorithm. We propose an original continuation algorithm that uses successively smaller values of the smoothing parameter to reach a prescribed precision while achieving the best possible convergence rate. This algorithm can be used with other losses or penalties. The algorithm is applied on a classification problem on the ADNI dataset. We observe that the TV penalty does not necessarily improve the prediction but provides a major breakthrough in terms of support recovery of the predictive brain regions.

  • 26.
    Eklöf, Johannes
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Efficient use of resources when implementing machine learning in an embedded environment2023Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Machine learning and in particular deep-learning models have been in the spotlight for the last year. Particularly the release of ChatGPT caught the attention of the public. But many of the most popular models are large with millions or billions of parameters. Parallel with this, the number of smart products constituting the Internet of Things is rapidly increasing. The need for small resource-efficient machine-learning models can therefore be expected to increase in the coming years. This work investigates the implementation of two different models in embedded environments. The investigated models are, random forests, that are straight-forward and relatively easy to implement, and transformer models, that are more complex and challenging to implement. The process of training the models in a high-level language and implementing and running inference in a low-level language has been studied. It is shown that it is possible to train a transformer in Python and export it by hand to C, but that it comes with several challenges that should be taken into consideration before this approach is chosen. It is also shown that a transformer model can be successfully used for signal extraction, a new area of application. Different possible ways of optimizing the model, such as pruning and quantization, have been studied. Finally, it has been shown that a transformer model with an initial noise-filter performs better than the existing hand-written code on self-generated messages, but worse on real-world data. This indicates that the training data should be improved.

    Download full text (pdf)
    Slutrapport
  • 27.
    Eriksson, Anton
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Interactive visualization of community structure in complex networks2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Several applied sciences model system dynamics with networks. Since networks often contain thousands or millions of nodes and links, researchers have developed methods that reveal and high- light their essential structures. One such method developed by researchers in IceLab uses information theory to compress descrip- tions of network flows with memory based on paths rather than links and identify hierarchically nested modules with long flow persistence times. However, current visualization tools for navigat- ing and exploring nested modules build on obsolete software that requires plugins and cannot handle such memory networks.

    Drawing from ideas in cartography, this thesis presents a pow- erful visualization method that enables researchers to analyze and explore modular decompositions of any network. The resulting application uses an efficient graph layout algorithm adapted with a simulation based on information flow. Like in a topographic map, zooming into the map successively reveals more detailed commu- nity structures and network features in a continuous fashion.

    Download full text (pdf)
    fulltext
  • 28.
    Eriksson, John
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Inloggning på trådlöst nätverk vid Umeå Stadsbibliotek2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The goal of this project is to present a solution for the wireless network at the city library in Umeå. The new system will allow users to log on to the wireless network using their library card along with a password of some kind. There must also be a way for guests without library cards to be allowed access to the network in some way. The result of this project was based on hardware that Umeå already had access to, and certain functions in that hardware that hasn’t been explored earlier and offered a lot of potential. This solution was tested to some extent and could be implemented in a near future.

    Download full text (pdf)
    Inloggning på trådlöst nätverk vid Umeå Stadsbibliotek
  • 29.
    Eriksson Krutrök, Moa
    et al.
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Lindgren, Simon
    Umeå University, Faculty of Social Sciences, Department of Sociology.
    Continued contexts of terror: analyzing temporal patterns of hashtag co-occurrence as discursive articulations2018In: Social Media + Society, E-ISSN 2056-3051, Vol. 4, no 4, article id 2056305118813649Article in journal (Refereed)
    Abstract [en]

    This study looks at how terror attacks are rendered discursively meaningful on social media through the concurrent use and reiteration of terror hashtags, which were created following previous incidents of terror. The article focuses on 12 terror attacks in Europe in 2015-2017 and their relating hashtags on Twitter, to see how various combinations of these were reused and co-articulated in tweets posted in relation to subsequent attacks. Through social network analysis of co-occurring hashtags in about 3 million tweets, in combination with close readings of a smaller sample, this study aims to analyze both the networks of hashtags in relation to terror attacks as well as the discursive process of hashtag co-articulation. The study shows that the patterns by which attack hashtags are reused and co-articulated depend on both temporal and contextual differences.

    Download full text (pdf)
    fulltext
  • 30.
    Eriksson, Maria
    Umeå University, Faculty of Arts, Department of culture and media studies.
    Close Reading Big Data: The Echo Nest and the Production of (Rotten) Music Metadata2016In: First Monday, E-ISSN 1396-0466, Vol. 21, no 7Article in journal (Refereed)
    Abstract [en]

    Digital music distribution is increasingly powered by automated mechanisms that continuously capture, sort and analyze large amounts of Web-based data. This paper traces the historical development of music metadata management and its ties to the growing of the field of ‘big data’ knowledge production. In particular, it explores the data catching mechanisms enabled by the Spotify-owned company The Echo Nest, and provides a close reading of parts of the company’s collection and analysis of data regarding musicians. Doing so, it reveals evidence of the ways in which trivial, random, and unintentional data enters into the data steams that power today’s digital music distribution. The presence of such curious data needs to be understood as a central part of contemporary algorithmic knowledge production, and calls for a need to re-conceptualize both (digital) musical artifacts and (digital) musical expertize.

    Download full text (pdf)
    fulltext
  • 31.
    Forsman, Mona
    et al.
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holmgren, Johan
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Estimation of tree stem attributes using terrestrial photogrammetry2012In: International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Copernicus Gesellschaft , 2012, p. B5-261-B5-265Conference paper (Other academic)
    Abstract [en]

    The objective of this work was to create a method to measure stem attributes of standing trees on field plots in the forest using terrestrial photogrammetry. The primary attributes of interest are the position and the diameter at breast height (DBH).

    The developed method creates point clouds from image from three or more calibrated cameras attached to a calibrated rig. SIFT features in multiple images in combination with epipolar line filtering are used to make high quality matching in images with large amounts of similar features and many occlusions. After projection of the point cloud to a simulated ground plane, RANSAC filtering is applied, followed by circle fitting to the remaining points.

    To evaluate the algorithm, a camera rig of five Canon digital system cameras with a baseline of 123 cm and up to 40 cm offset in height was constructed. The rig was used in a field campaign at the Remningstorp forest test area in southern Sweden. Ground truth was collected manually by surveying and manual measurements.

    Initial results show estimated tree stem diameters within 10% of the ground truth. This suggest that terrestrial photogrammetry is a viable method to measure tree stem diameters on circular field plots.

    Download full text (pdf)
    fulltext
  • 32.
    Främling, Kary
    Umeå University, Faculty of Science and Technology, Department of Computing Science. School of Science and Technology, Aalto University, Espoo, Finland.
    Decision Theory Meets Explainable AI2020In: Explainable, Transparent Autonomous Agents and Multi-Agent Systems: Second International Workshop, EXTRAAMAS 2020, Auckland, New Zealand, May 9–13, 2020, Revised Selected Papers / [ed] Davide Calvaresi, Amro Najjar, Michael Winikoff, Kary Främling, Cham: Springer, 2020, p. 57-74Conference paper (Refereed)
    Abstract [en]

    Explainability has been a core research topic in AI for decades and therefore it is surprising that the current concept of Explain- able AI (XAI) seems to have been launched as late as 2016. This is a problem with current XAI research because it tends to ignore existing knowledge and wisdom gathered over decades or even centuries by other relevant domains. This paper presents the notion of Contextual Impor- tance and Utility (CIU), which is based on known notions and methods of Decision Theory. CIU extends the notions of importance and utility for the non-linear models of AI systems and notably those produced by Machine Learning methods. CIU provides a universal and model-agnostic foundation for XAI.

    Download full text (pdf)
    fulltext
  • 33.
    Hale, Oliver
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vehicle Breakdown using Pattern Recognition and Machine Learning2022Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today in Sweden there are thousands of sensors used to check the state of train vehicles to detect faults. Almost all these sensors get separate measurements for every axle on a train so if an error is detected its location is defined by an axle number within a train. This axle number needs to be matched with a certain vehicle to be able to easily locate it and remove or at least check the vehicle. It is, therefore, necessary to be able to break down trains into vehicles from timestamps readings. This project explores the possibilities of using machine learning to classify the train vehicles based on timestamp readings made by RFID detector setups.Throughout the project, several algorithms were attempted with different structures and different ways of using the timestamp data. In the end, the MLP-neural network structure was most promising and a model that could predict 91% of the trains correctly was created. This model showed that machinelearning was a promising way to classify vehicles from axle timestamp readings. The model also worked for some of the faulting sensors. It worked since it did not require the entire RFID detector setup to be fully functional, which was an unexpected extra positive outcome of the project

    Download full text (pdf)
    fulltext
  • 34. Harrie, Lars
    et al.
    Oucheikh, Rachid
    Nilsson, Åsa
    Oxenstierna, Andreas
    Cederholm, Pontus
    Wei, Lai
    Richter, Kai-Florian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Olsson, Perola
    Label Placement Challenges in City Wayfinding Map Production - Identification and Possible Solutions2022In: Journal of Geovisualization and Spatial Analysis, ISSN 2509-8810, E-ISSN 2509-8829, Vol. 6, no 1, article id 16Article in journal (Refereed)
    Abstract [en]

    Map label placement is an important task in map production, which needs to be automated since it is tedious and requires a significant amount of manual work. In this paper, we identify five cartographic labeling situations that present challenges by causing intensive manual work in map production of city wayfinding maps, e.g., label placement in high density areas, utilizing true label geometries in automated methods, and creating a good relationship between text labels and icons. We evaluate these challenges in an open source map labeling tool (QGIS), provide results from a preliminary study, and discuss if there are other techniques that could be applicable to solving these challenges. These techniques are based on quantified cartographic rules or on machine learning. We focus on deep learning for which we provide several examples of techniques from other application domains that might have a potential in map label placement. The aim of the paper is to explore those techniques and to recommend future practical studies for each of the identified five challenges in map production. We believe that targeting the revealed challenges using the proposed solutions will significantly raise the automation level for producing city wayfinding maps, thus, having a real, measurable impact on production time and costs.

    Download full text (pdf)
    fulltext
  • 35.
    Hegner, Stephen
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A model of independence and overlap for transactions on database schemata2010In: Advances in Databases and Information Systems, 14th East European Conference, Proceedings / [ed] Barbara Catania, Mirjana Ivanovic, and Bernhard Thalheim, Springer Berlin/Heidelberg, 2010, p. 204-218Conference paper (Refereed)
    Abstract [en]

    Traditional models of support for concurrent transactions invariably rely upon a notion of serializability, which involves not only complex scheduling, but also primitives (such as locks) for requiring transactions to wait, as well for aborting a transaction and forcing it to re-run. For batch transactions, this approach is often the most reasonable. On the other hand, for interactive transactions, only a very limited amount of waiting and aborting is tolerable, and so minimizing their occurrence, even at the cost of increased analysis of the transactions themselves, is warranted. In this work, a systematic study of independence for transactions, without any explicit serialization, is initiated. Each transaction operates on a view of the main schema, and each such view is partitioned into a write region and a read-only region. For a set of transactions to run concurrently, their views may overlap only on their read-only regions. These regions need not be specified explicitly; rather, they are defined naturally using a component-based model of the main schema. Furthermore, when two transactions do conflict, because their views overlap on write regions, the precise point of conflict is immediately identified. To illustrate the utility of the framework, the case of relational schemata governed by the most common types of constraints in practice -- functional and foreign-key dependencies -- is developed in detail.

  • 36.
    Helgesson, Emil
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Evaluating User Experiences of Mockup Data created through Regex2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study is to evaluate the possibility of having a library function capable of creating SQL inserts. The values for the inserts were created through regex. The study is conducted through a user study where the test participants tested three methods to create inserts for SQL, including the library function. The results show that the test participants performed on average the worst in terms of time while using the library function. When analysing the results manual insertion was preferred for a few inserts and the web-client was the preferred method for many inserts. This study indicated that the library function does not simplify the creation of SQL inserts under the circumstances of this study.

    Download full text (pdf)
    fulltext
  • 37.
    Holme, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Temporal networks2014In: Encyclopedia of Social Network Analysis and Mining / [ed] Reda Alhajj, Jon Rokne, Springer-Verlag New York, 2014, p. 2119-2128Chapter in book (Refereed)
  • 38.
    Holme, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Liljeros, Fredrik
    Birth and death of links control disease spreading in empirical contact networks2014In: Scientific Reports, E-ISSN 2045-2322, Vol. 4, p. 4999-Article in journal (Refereed)
    Abstract [en]

    We investigate what structural aspects of a collection of twelve empirical temporal networks of human contacts are important to disease spreading. We scan the entire parameter spaces of the two canonical models of infectious disease epidemiology-the Susceptible-Infectious-Susceptible (SIS) and Susceptible-Infectious-Removed (SIR) models. The results from these simulations are compared to reference data where we eliminate structures in the interevent intervals, the time to the first contact in the data, or the time from the last contact to the end of the sampling. The picture we find is that the birth and death of links, and the total number of contacts over a link, are essential to predict outbreaks. On the other hand, the exact times of contacts between the beginning and end, or the interevent interval distribution, do not matter much. In other words, a simplified picture of these empirical data sets that suffices for epidemiological purposes is that links are born, is active with some intensity, and die.

    Download full text (pdf)
    fulltext
  • 39.
    Holme, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Energy Science, Sungkyunkwan University, Suwon, Korea; Department of Sociology, Stockholm University.
    Takaguchi, Taro
    Time evolution of predictability of epidemics on networks2015In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 91, no 4, article id 042811Article in journal (Refereed)
    Abstract [en]

    Epidemic outbreaks of new pathogens, or known pathogens in new populations, cause a great deal of fear because they are hard to predict. For theoretical models of disease spreading, on the other hand, quantities characterizing the outbreak converge to deterministic functions of time. Our goal in this paper is to shed some light on this apparent discrepancy. We measure the diversity of (and, thus, the predictability of) outbreak sizes and extinction times as functions of time given different scenarios of the amount of information available. Under the assumption of perfect information-i.e., knowing the state of each individual with respect to the disease-the predictability decreases exponentially, or faster, with time. The decay is slowest for intermediate values of the per-contact transmission probability. With a weaker assumption on the information available, assuming that we know only the fraction of currently infectious, recovered, or susceptible individuals, the predictability also decreases exponentially most of the time. There are, however, some peculiar regions in this scenario where the predictability decreases. In other words, to predict its final size with a given accuracy, we would need increasingly more information about the outbreak.

  • 40.
    Holmgren, Anton
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bernenko, Dolores
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lizana, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mapping robust multiscale communities in chromosome contact networks2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 12979Article in journal (Refereed)
    Abstract [en]

    To better understand DNA’s 3D folding in cell nuclei, researchers developed chromosome capture methods such as Hi-C that measure the contact frequencies between all DNA segment pairs across the genome. As Hi-C data sets often are massive, it is common to use bioinformatics methods to group DNA segments into 3D regions with correlated contact patterns, such as Topologically associated domains and A/B compartments. Recently, another research direction emerged that treats the Hi-C data as a network of 3D contacts. In this representation, one can use community detection algorithms from complex network theory that group nodes into tightly connected mesoscale communities. However, because Hi-C networks are so densely connected, several node partitions may represent feasible solutions to the community detection problem but are indistinguishable unless including other data. Because this limitation is a fundamental property of the network, this problem persists regardless of the community-finding or data-clustering method. To help remedy this problem, we developed a method that charts the solution landscape of network partitions in Hi-C data from human cells. Our approach allows us to scan seamlessly through the scales of the network and determine regimes where we can expect reliable community structures. We find that some scales are more robust than others and that strong clusters may differ significantly. Our work highlights that finding a robust community structure hinges on thoughtful algorithm design or method cross-evaluation.

    Download full text (pdf)
    fulltext
  • 41. Huang, Xiao-Yu
    et al.
    Xiang, Xian-Hong
    Li, Wubin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Chen, Kang
    Cai, Wen-Xue
    Li, Lei
    Matrix Factorization for Evolution Data2014In: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, p. 525398-Article in journal (Refereed)
    Abstract [en]

    We study a matrix factorization problem, that is, to find two factor matrices U and V such that R approximate to U-T x V, where R is a matrix composed of the values of the objects O-1, O-2, ... , O-n at consecutive time points T-1, T-2, ... , T-t. We first present MAFED, a constrained optimization model for this problem, which straightforwardly performs factorization on R. Then based on the interplay of the data in U,V, and R, a probabilistic graphical model using the same optimization objects is constructed, in which structural dependencies of the data in these matrices are revealed. Finally, we present a fitting algorithm to solve the proposed MAFED model, which produces the desired factorization. Empirical studies on real-world datasets demonstrate that our approach outperforms the state-of-the-art comparison algorithms.

    Download full text (pdf)
    fulltext
  • 42.
    Huotari, Matti
    et al.
    Department of Computer Science, Aalto University, Espoo, Finland.
    Arora, Shashank
    Department of Mechanical Engineering, Aalto University, Espoo, Finland.
    Malhi, Avleen
    Department of Computer Science, Aalto University, Espoo, Finland; Department of Computing and Informatics, Bournemouth University, Bournemouth, UK.
    Främling, Kary
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of Computer Science, Aalto University, Espoo, Finland.
    Comparing seven methods for state-of-health time series prediction for the lithium-ion battery packs of forklifts2021In: Applied Soft Computing, ISSN 1568-4946, E-ISSN 1872-9681, Vol. 111, article id 107670Article in journal (Refereed)
    Abstract [en]

    A key aspect for the forklifts is the state-of-health (SoH) assessment to ensure the safety and the reliability of uninterrupted power source. Forecasting the battery SoH well is imperative to enable preventive maintenance and hence to reduce the costs. This paper demonstrates the capabilities of gradient boosting regression for predicting the SoH timeseries under circumstances when there is little prior information available about the batteries. We compared the gradient boosting method with light gradient boosting, extra trees, extreme gradient boosting, random forests, long short-term memory networks and with combined convolutional neural network and long short-term memory networks methods. We used multiple predictors and lagged target signal decomposition results as additional predictors and compared the yielded prediction results with different sets of predictors for each method. For this work, we are in possession of a unique data set of 45 lithium-ion battery packs with large variation in the data. The best model that we derived was validated by a novel walk-forward algorithm that also calculates point-wise confidence intervals for the predictions; we yielded reasonable predictions and confidence intervals for the predictions. Furthermore, we verified this model against five other lithium-ion battery packs; the best model generalised to greater extent to this set of battery packs. The results about the final model suggest that we were able to enhance the results in respect to previously developed models. Moreover, we further validated the model for extracting cycle counts presented in our previous work with data from new forklifts; their battery packs completed around 3000 cycles in a 10-year service period, which corresponds to the cycle life for commercial Nickel–Cobalt–Manganese (NMC) cells.

    Download full text (pdf)
    fulltext
  • 43.
    Huotari, Matti
    et al.
    School of Science, Aalto University, Espoo, Finland; Metropolia University of Applied Sciences, Helsinki, Finland.
    Malhi, Avleen
    School of Science, Aalto University, Espoo, Finland; Warwick University, Coventry, UK.
    Främling, Kary
    Umeå University, Faculty of Science and Technology, Department of Computing Science. School of Science, Aalto University, Espoo, Finland.
    Machine learning applications for smart building energy utilization: a survey2024In: Archives of Computational Methods in Engineering, ISSN 1134-3060, E-ISSN 1886-1784Article in journal (Refereed)
    Abstract [en]

    The United Nations launched sustainable development goals in 2015 that include goals for sustainable energy. From global energy consumption, households consume 20–30% of energy in Europe, North America and Asia; furthermore, the overall global energy consumption has steadily increased in the recent decades. Consequently, to meet the increased energy demand and to promote efficient energy consumption, there is a persistent need to develop applications enhancing utilization of energy in buildings. However, despite the potential significance of AI in this area, few surveys have systematically categorized these applications. Therefore, this paper presents a systematic review of the literature, and then creates a novel taxonomy for applications of smart building energy utilization. The contributions of this paper are (a) a systematic review of applications and machine learning methods for smart building energy utilization, (b) a novel taxonomy for the applications, (c) detailed analysis of these solutions and techniques used for the applications (electric grid, smart building energy management and control, maintenance and security, and personalization), and, finally, (d) a discussion on open issues and developments in the field.

    Download full text (pdf)
    fulltext
  • 44.
    Jaunsen, Andreas O.
    et al.
    NeIC.
    Alaterä, Tuomas J.
    FSD/TUNI.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Holmstrand, Katrine F.
    DTU, Denmark.
    Lahti, Kari
    University of Helsinki, Finland.
    Parland-von Essen, Jessica
    CSC, Finland.
    Pfeil, Benjamin
    BCCR, Norway.
    Nordic FAIR Data Collaboration Opportunities2021Report (Refereed)
    Abstract [en]

    Executive summary

    In September 2020 the NeIC Director and board initiated a working group on FAIR collaborationopportunities in the Nordics. This came in the wake of the data tsunami era and the realisationthat machine learning and connected data will become of crucial importance to society andscience. Furthermore, the findings of the EOSC-Nordic project show that the FAIR uptake in theregion is slow and a majority of data repositories are not FAIR, while only a small fractionmeasures up to the available FAIR metrics. Sharing publicly-funded data in a meaningful,reusable way must become part of the normative behaviour in order to nurture data-drivensciences. By enabling data capabilities we are facilitating interdisciplinary data reuse, along withinformation and knowledge exchange. A key objective is data integration, where concepts andproperties, and the relationships between them are linked, forming knowledge graphs andproviding an opportunity to provide insight (new knowledge) from the multitude of relations andpatterns.

    Although FAIR awareness is growing and there is an appreciation of the Open Science visionamong researchers and support staff, a small survey conducted by the working group confirmssome challenges that are contradictory to the Open Science (OS) movement and contribute toconfusion and status quo when it comes to implementing FAIR. If we are serious aboutembracing OS and the implementation of the FAIR principles it is necessary to ensure that allelements pull in the same direction (this includes infrastructure, skills and services to policiesand incentives). Data stewardship is gradually becoming part of the researcher workflow insome organisations, institutions and departments. Professionalising this crucial support is key tosucceeding in a swift and effective transition to sharing discoverable, accessible and reusabledata. The working group finds that coordinating tasks such as raising awareness, training andskills development and developing common tools and services for research data management(RDM) can contribute to strengthen the momentum of FAIR uptake and better utilise resources,skills and tools across the Nordics. A Nordic coordination office may be one way to orchestratea common strategy on working towards the realisation of the Open Science vision. 

  • 45.
    Johansson, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Performance analysis of lattice based post-quantum secure cryptography with Java2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Efficient quantum computers will break most of today’s public-key cryptosystems. Therefore, the National Institute of Standards and Technology (NIST) calls for proposals to standardise one or more quantum-secure cryptographic schemes. Eventually, banks must adopt the standardised schemes, but little is known about how efficient such an implementation would be in Java, one of the standard programming languages for banks. In this thesis, we test and evaluate a post-quantum secure encryption scheme known as FrodoKEM, which is based on a hard lattice problem known as Learning With Errors (LWE). We found that a post-quantum secure encryption version of FrodoKEM provides strong theoretical security regarding the criteria given by NIST, and is also sufficiently fast for key generation, encryption and decryption. These results imply that it could be possible to implement these types of post-quantum secure algorithms in high-level programming languages such as Java, demonstrating that we no longer are limited to use low-level languages such as C. Consequently, we can easier and cheaper implement post-quantum secure cryptography.

    Download full text (pdf)
    fulltext
  • 46.
    Johansson, Kristoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utveckling av insticksprogram för DigiSign2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    DigiSign is a web application which is developed by a company called Omegapoint. The application is used tocontrol so called “Digital Signage” monitors and to administrate the content they show. The application islacking a function which lets the user create own templates. The goal with this project is to create a pluginthat integrates with DigiSign where the user can create their own templates and that facilitates the usage ofDigiSign by the customers.This project describes the development of the plugin and the integration with DigiSign. The plugin which isbeing developed is created with Microsoft ASP.NET Web forms and JavaScript.The work during the project has been divided into to three phases, pre-study, development of the userinterface and integration with the plugin in DigiSign. In the pre-study the technical options was explored,how competing products worked and a plan for the project was created. After deciding which technique touse and studying those techniques where knowledge was missing a meeting with the company was held.During the meeting, it was decided which requirements and features the plugin should have. Then the2development for the plugin started. The result of the work is a plugin which the customers can use to createown templates to use with their slideshows.

    Download full text (pdf)
    fulltext
  • 47.
    Jäger, Gerold
    Christian-Albrechts-Universität Kiel.
    The Theory of Tolerances with Applications to the Traveling Salesman Problem2011Other (Refereed)
  • 48.
    Jäger, Gerold
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An Optimal Strategy for Static Black-Peg Mastermind with Three Pegs2018In: SAGT: International Symposium on Algorithmic Game Theory: 11th International Symposium, SAGT 2018, Beijing, China, September 11-14, 2018, Proceedings / [ed] Xiaotie Deng, Springer, 2018, Vol. 11059, p. 261-266Conference paper (Refereed)
    Abstract [en]

    Mastermind is a famous game played by a codebreaker against a codemaker. We investigate its static (also called non-adaptive) black-peg variant. Given c colors and p pegs, the codemaker has to choose a secret, a p-tuple of c colors, and the codebreaker asks a set of questions all at once. Like the secret, a question is a p-tuple of c colors. The codemaker then tells the codebreaker how many pegs in each question are correct in position and color. Then the codebreaker has one final question to find the secret. His aim is to use as few of questions as possible. Our main result is an optimal strategy for the codebreaker for p=3 pegs and an arbitrary number c of colors using ⌊3c/2⌋+1questions.

    A reformulation of our result is that the metric dimension of ℤn×ℤn×ℤnis equal to ⌊3n/2⌋.

  • 49.
    Karlsson, Lars
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kjelgaard Mikkelsen, Carl Christian
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Negative stride in the column-major format makes sense and has useful applications2017Report (Other academic)
    Abstract [en]

    Two lower triangular or two upper triangular matrices of the same size can be stored with minimal memory footprint. If both positive and negative strides are used, then both matrices can be accessed as if they were stored in regular column-major format.

    Download full text (pdf)
    fulltext
  • 50.
    Kashian, Alireza
    et al.
    Dept. of Infrastructure Engineering, University of Melbourne, Parkville, Australia.
    Rajabifard, Abbas
    Dept. of Infrastructure Engineering, University of Melbourne, Parkville, Australia.
    Chen, Yiqun
    Dept. of Infrastructure Engineering, University of Melbourne, Parkville, Australia.
    Richter, Kai-Florian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    OSM POI Analyzer: A Platform for Assessing Position of POIs in OpenStreetMap2017In: ISPRS Geospatial Week 2017 / [ed] D. Li, J. Gong, B. Yang, H. Wu, L. Wu, Z. Gui, X. Cheng, H. Wu, S. Li, R. Lindenbergh, J. Boehm, M. Rutzinger, W. Yao, M. Weinmann, Z. Kang, K. Khoshelham, M. Peter, L. Díaz-Vilariño, W. Shi, B. Lu, H. Abdulmuttalib, M. R. Delavar, T. Balz, B. Osmanoglu, F. Rocca, U. Sörgel, J. Zhang, P. Li, S. Du, L. Zhao, X. Lin, K. Qin, C. Kang, X. Li, C. Chen, R. Li, G. Qiao, H. Wu, and C. Heipke, 2017, Vol. XLII-2/W7, p. 497-504Conference paper (Refereed)
    Abstract [en]

     In recent years, more and increased participation in Volunteered Geographical Information (VGI) projects provides enough data coverage for most places around the world for ordinary mapping and navigation purposes, however, the positional credibility of contributed data becomes more and more important to bring a long-term trust in VGI data. Today, it is hard to draw a definite traditional boundary between the authoritative map producers and the public map consumers and we observe that more and more volunteers are joining crowdsourcing activities for collecting geodata, which might result in higher rates of man-made mistakes in open map projects such as OpenStreetMap. While there are some methods for monitoring the accuracy and consistency of the created data, there is still a lack of advanced systems to automatically discover misplaced objects on the map. One feature type which is contributed daily to OSM is Point of Interest (POI). In order to understand how likely it is that a newly added POI represents a genuine real-world feature scientific means to calculate a probability of such a POI existing at that specific position is needed. This paper reports on a new analytic tool which dives into OSM data and finds co-existence patterns between one specific POI and its surrounding objects such as roads, parks and buildings. The platform uses a distance-based classification technique to find relationships among objects and tries to identify the high-frequency association patterns among each category of objects. Using such method, for each newly added POI, a probabilistic score would be generated, and the low scored POIs can be highlighted for editors for a manual check. The same scoring method can be used for existing registered POIs to check if they are located correctly. For a sample study, this paper reports on the evaluation of 800 pre-registered ATMs in Paris with associated scores to understand how outliers and fake entries could be detected automatically.

    Download full text (pdf)
    fulltext
12 1 - 50 of 100
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf