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  • 801.
    Winter, Stephan
    et al.
    Department of Infrastructure Engineering, University of Melbourne.
    Tomko, Martin
    Department of Infrastructure Engineering, University of Melbourne.
    Vasardani, Maria
    Department of Infrastructure Engineering, University of Melbourne.
    Richter, Kai-Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Koshelham, Kourosh
    Department of Infrastructure Engineering, University of Melbourne.
    Indoor localization and navigation independent of sensor based technologies2017Rapport (Annet vitenskapelig)
    Abstract [en]

    In this short article we present concepts of indoor localization and navigation that are independent of sensors embedded in the environment, and thus, standing against the tide of technology-based indoor localization. The motivation for doing so is clear: We seek solutions that are independent of particular environments, and thus globally applicable.

  • 802.
    Wu, Naomi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A long-distance relationship: Reconnecting hotels with their guests via intuitive design2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Currently for travel planning, guests will research via hotel websites while still preferring to book through third-party sites, which leads to a disconnect between hotels and their guests. A chat widget artifact that is added onto the hotel’s website and linked through messaging applications was created by a start-up company, Bookboost, to bridge this gap. The current intuitiveness of the artifact and future improvements that may increase intuitiveness was investigated through a case study of user and expert analysis. 10 participants – 5 hotel staff users and 5 guest users – were sampled at hotel lobbies via systematic sampling and non-random sampling. Participants ranged in age from 18 to 65 years old, with 30% being millennials. Task analysis, an interview, and a questionnaire were used for user analysis. The researcher acted as an evaluator and examined the artifact for flaws and possible improvements using activity theory’s human-artifact model (HAM). Analyses suggest that current intuitiveness is fairly high, but there is room for improvement. There seems to be a difference between millennials and non-millennials, especially regarding the amount of time taken and preference for the artifact (versus more familiar methods for communicating with others). Interest and comfort in technology usage was a factor in intuitiveness. Generally, those more comfortable with technology had higher zone of proximal development (ZPD) scores. Improvements have been suggested that may increase artifact intuitiveness, although this was not tested due to the scope of the study. Future research can continue to examine if the suggested improvements have indeed increased intuitiveness in the artifact for users of all ages.

  • 803.
    Xie, Yingfu
    et al.
    SLU, Centre of Biostochastics.
    Yu, Jun
    SLU, Centre of Biostochastics.
    Ranneby, Bo
    SLU, Centre of Biostochastics.
    Forecasting using locally stationary wavelet processes2009Inngår i: Journal of Statistical Computation and Simulation, ISSN 0094-9655, E-ISSN 1563-5163, Vol. 79, nr 9, s. 1067-1082Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Locally stationary wavelet (LSW) processes, built on non-decimated wavelets, can be used to analyse and forecast non-stationary time series. They have been proved useful in the analysis of financial data. In this paper, we first carry out a sensitivity analysis, then propose some practical guidelines for choosing the wavelet bases for these processes. The existing forecasting algorithm is found to be vulnerable to outliers, and a new algorithm is proposed to overcome the weakness. The new algorithm is shown to be stable and outperforms the existing algorithm when applied to real financial data. The volatility forecasting ability of LSW modelling based on our new algorithm is then discussed and shown to be competitive with traditional GARCH models.

  • 804.
    Xu, Lei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A time interval-based credit reservation approach for prepaid composite services in cloud environments2011Inngår i: Web Services (ECOWS), 2011 Ninth IEEE European Conference on, 2011, s. 158-165Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A typical business model in cloud environments for service providers is the provision of composite services built from resources and services offered by other providers. Customers of these composite services can make an advance payment before consumption. In this scenario, accounting systems will supervise each service comprising given composite services individually. As the number of constituent services and requests submitted by customers increase dramatically, scalability issues arise. To tackle this problem, we present an approach that estimates the highest cost of a given composite service composed of multiple pre-paid services, and then calculates the duration of a time interval based on which accounting systems access and update target customers' account. It is intended to reduce overhead imposed by supervising services individually in real-time. Commercial agreements between involved business partners and potential economic compensations due to the violation of Service Level Agreement (SLA) are mirrored in the cost estimation.

  • 805.
    Xu, Lei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Jennings, Brendan
    Automating the generation, deployment and application of charging schemes for composed communications services2012Inngår i: 2012 IEEE Network operations and management symposium (NOMS), 2012, s. 853-859Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Creating composed services dynamically to meet the demand of every individual customer can be an inexpensive way for a service provider to differentiate itself from its competitors. Charging and billing systems are one of the key components supporting this business model. However, many existing charging and billing systems suffer from their time-consuming scheme 1 configuration process. This limits the flexibility of service providers to offer composed services. This paper proposes a framework named Accounting Logic Generator (ALG) that automates the generation and deployment of charging schemes for composed services. It processes a two-part charging scheme which contains rules that can be used to govern how the usage of a service is charged for when it is executed standalone, used in the context of a composed service, invoked within specific time intervals of interest or completed successfully in the context of composed service invocations where one or more other services fail. Furthermore, an approach that estimates service cost for the selection process of service composition is presented.

  • 806.
    Yan, Chunli
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Diagnostic Reasoning Guided by a Decision-Support System: a Case Study2017Inngår i: Proceedings of the European Conference on Cognitive Ergonomics 2017: Transforming the everyday, New York, NY, USA: ACM Digital Library, 2017, s. 25-30Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A clinical decision-support system for dementia investigation was used in clinical practice. User information was collected based on interactions with the application. The aim of this study is to identify features in logged data that can be used for detecting learning and reasoning patterns in the user. A case of a physician who is novice to both the application and the dementia domain was studied and compared to the case of an expert physician using the system. Diferences between them were found, and a clear pattern that indicates that learning takes place, both how to use the system and about dementia, was observed in the novice user. Further studies need to be conducted, focusing on whether patterns become stable over time, and with complementary methods that can detect reasons for observed behaviors. Software for automatic detection will be developed based on the results of this study.

  • 807.
    Yan, Chunli
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hypothesis-Driven Agent Dialogues for Dementia Assessment2013Inngår i: VIII Workshop on Agents Applied in Health Care (A2HC), 2013, s. 13-24Konferansepaper (Fagfellevurdert)
  • 808.
    Yan, Chunli
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nieves, Juan Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A Multi-agent System for Nested Inquiry Dialogues2014Inngår i: Advances in Practical Applications of Heterogeneous Multi-Agent Systems: The PAAMS Collection : 12th International Conference, PAAMS 2014, Salamanca, Spain, June 4-6, 2014. Proceedings / [ed] Demazeau, Yves; Zambonelli, Franco; Corchado, JuanM.; Bajo, Javier, Springer, 2014, Vol. 8473, s. 303-314Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Generating and evaluating arguments are two important aspects in argumentation-based dialogue systems. In current research, however, generating and evaluating arguments are normally treated separately. Also, there are rarely implementations of the approaches in real applications. In this paper, we generate inquiry dialogues and evaluate arguments during the dialogue procedure simultaneously. Furthermore, we have implemented this approach in a real medical domain and demonstrated a practical example extracted from this application.

  • 809.
    Yedeg, Esubalewe Lakie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Analysis, Control, and Design Optimization of Engineering Mechanics Systems2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis considers applications of gradient-based optimization algorithms to the design and control of some mechanics systems. The material distribution approach to topology optimization is applied to design two different acoustic devices, a reactive muffler and an acoustic horn, and optimization is used to control a ball pitching robot.

    Reactive mufflers are widely used to attenuate the exhaust noise of internal combustion engines by reflecting the acoustic energy back to the source. A material distribution optimization method is developed to design the layout of sound-hard material inside the expansion chamber of a reactive muffler. The objective is to minimize the acoustic energy at the muffler outlet. The presence or absence of material is represented by design variables that are mapped to varying coefficients in the governing equation. An anisotropic design filter is used to control the minimum thickness of materials separately in different directions. Numerical results demonstrate that the approach can produce mufflers with high transmission loss for a broad range of frequencies.

    For acoustic devices, it is possible to improve their performance, without adding extended volumes of materials, by an appropriate placement of thin structures with suitable material properties. We apply layout optimization of thin sound-hard material in the interior of an acoustic horn to improve its far-field directivity properties. Absence or presence of thin sound-hard material is modeled by a surface transmission impedance, and the optimization determines the distribution of materials along a “ground structure” in the form of a grid inside the horn. Horns provided with the optimized scatterers show a much improved angular coverage, compared to the initial configuration.

    The surface impedance is handled by a new finite element method developed for Helmholtz equation in the situation where an interface is embedded in the computational domain. A Nitschetype method, different from the standard one, weakly enforces the impedance conditions for transmission through the interface. As opposed to a standard finite-element discretization of the problem, our method seamlessly handles both vanishing and non-vanishing interface conditions. We show the stability of the method for a quite general class of surface impedance functions, provided that possible surface waves are sufficiently resolved by the mesh.

    The thesis also presents a method for optimal control of a two-link ball pitching robot with the aim of throwing a ball as far as possible. The pitching robot is connected to a motor via a non-linear torsional spring at the shoulder joint. Constraints on the motor torque, power, and angular velocity of the motor shaft are included in the model. The control problem is solved by an interior point method to determine the optimal motor torque profile and release position. Numerical experiments show the effectiveness of the method and the effect of the constraints on the performance.

  • 810.
    Yedeg, Esubalewe Lakie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Control and design of engineering mechanics systems2013Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 811.
    Yedeg, Esubalewe Lakie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Wadbro, Eddie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Optimal ball pitchingArtikkel i tidsskrift (Annet vitenskapelig)
  • 812.
    Yedeg, Esubalewe Lakie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Wadbro, Eddie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Berggren, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Anisotropic Topology Optimization of a Reactive Muffler with a Perforated PipeArtikkel i tidsskrift (Annet vitenskapelig)
  • 813.
    Zander, Carol
    et al.
    University of Washinton, Bothell, Bothell, WA, USA .
    Boustedt, Jonas
    Högskolan i Gävle, Gävle, Sweden.
    McCartney, Robert
    University of Connecticut, Storrs, CT, USA.
    Moström, Jan Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Sanders, Kate
    Rhode Island College, Providence, RI, USA.
    Thomas, Lynda
    Aberystwyth University, Aberystwyth, Wales Uk.
    Student transformations: are they computer scientists yet?2009Inngår i: Proceedings of the fifth international workshop on Computing education research workshop, New York, NY, USA: ACM, Association for Computing Machinery , 2009, s. 129-140Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We examine the changes in the ways computing students view their field as they learn, as reported by the students themselves in short written biographies. In many ways, these changes result in students thinking and acting more like computer scientists and identifying more with the computing community. Most of the changes are associated with programming and software engineering, rather than theoretical computer science, however.

  • 814.
    Zechner, Niklas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A novel approach to text classification2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis explores the foundations of text classification, using both empirical and deductive methods, with a focus on author identification and syntactic methods. We strive for a thorough theoretical understanding of what affects the effectiveness of classification in general. 

    To begin with, we systematically investigate the effects of some parameters on the accuracy of author identification. How is the accuracy affected by the number of candidate authors, and the amount of data per candidate? Are there differences in how methods react to the changes in parameters? Using the same techniques, we see indications that methods previously thought to be topic-independent might not be so, but that syntactic methods may be the best option for avoiding topic dependence. This means that previous studies may have overestimated the power of lexical methods. We also briefly look for ways of spotting which particular features might be the most effective for classification. Apart from author identification, we apply similar methods to identifying properties of the author, including age and gender, and attempt to estimate the number of distinct authors in a text sample. In all cases, the techniques are proven viable if not overwhelmingly accurate, and we see that lexical and syntactic methods give very similar results. 

    In the final parts, we see some results of automata theory that can be of use for syntactic analysis and classification. First, we generalise a known algorithm for finding a list of the best-ranked strings according to a weighted automaton, to doing the same with trees and a tree automaton. This result can be of use for speeding up parsing, which often runs in several steps, where each step needs several trees from the previous as input. Second, we use a compressed version of deterministic finite automata, known as failure automata, and prove that finding the optimal compression is NP-complete, but that there are efficient algorithms for finding good approximations. Third, we find and prove the derivatives of regular expressions with cuts. Derivatives are an operation on expressions to calculate the remaining expression after reading a given symbol, and cuts are an extension to regular expressions found in many programming languages. Together, these findings may be able to improve on the syntactic analysis which we have seen is a valuable tool for text classification.

  • 815.
    Zhang, Hong
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Jiangsu Univ, Dept Math, Zhenjiang 212013, Jiangsu, Peoples R China.
    Georgescu, Paul
    The global properties of an age-dependent SI model involving pathogenic virus release and defence mechanisms for pests2010Inngår i: Mathematical and computer modelling, ISSN 0895-7177, E-ISSN 1872-9479, Vol. 52, nr 1-2, s. 37-54Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Insect pests are common but undesirable elements in ecosystems and represent thorny problems for most developing countries. To prevent pest outbreaks, growers often resort to insect-pathogenic viruses rather than to pesticides which affect human health and the environment. The purpose of this paper is to investigate a new age-structured pest management model which describes the interaction between susceptible insect pests, infected insect pests, pathogenic viruses and defence immunity mechanisms. A feature of this model is that it accounts for the dependence of the amount of pathogenic viruses released and of the efficiency of the defence mechanisms upon the so-called age of infection. First, the asymptotic behavior of the system is established via a monotonicity argument which makes use of several integral inequalities, being shown that the infection ultimately dies out, while under certain circumstances the susceptible pests also become extinct. By means of the Michailov criterion, one then analyzes the linearized stability of the trivial equilibrium and of the semi-trivial infected pest-free equilibrium. In this regard, it is observed that the defence mechanisms and maximal length of the infective period play important roles in the dynamics of the system. Several pest controls strategies are further investigated by means of numerical simulations, which show that when the dose of pathogenic viruses released initially is larger than a certain amount the profile of the response of defence mechanisms can be modified by changing this dose. Finally, the paper is concluded with a discussion on the biological significance of the mathematical results and framework.

  • 816.
    Zhang, Jin
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mucs, Daniel
    Norinder, Ulf
    Svensson, Fredrik
    LightGBM: An Effective and Scalable Algorithm for Prediction of Chemical Toxicity-Application to the Tox21 and Mutagenicity Data Sets2019Inngår i: Journal of Chemical Information and Modeling, ISSN 1549-9596, E-ISSN 1549-960X, Vol. 59, nr 10, s. 4150-4158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Machine learning algorithms have attained widespread use in assessing the potential toxicities of pharmaceuticals and industrial chemicals because of their faster speed and lower cost compared to experimental bioassays. Gradient boosting is an effective algorithm that often achieves high predictivity, but historically the relative long computational time limited its applications in predicting large compound libraries or developing in silico predictive models that require frequent retraining. LightGBM, a recent improvement of the gradient boosting algorithm, inherited its high predictivity but resolved its scalability and long computational time by adopting a leaf-wise tree growth strategy and introducing novel techniques. In this study, we compared the predictive performance and the computational time of LightGBM to deep neural networks, random forests, support vector machines, and XGBoost. All algorithms were rigorously evaluated on publicly available Tox21 and mutagenicity data sets using a Bayesian optimization integrated nested 10-fold cross-validation scheme that performs hyperparameter optimization while examining model generalizability and transferability to new data. The evaluation results demonstrated that LightGBM is an effective and highly scalable algorithm offering the best predictive performance while consuming significantly shorter computational time than the other investigated algorithms across all Tox21 and mutagenicity data sets. We recommend LightGBM for applications of in silico safety assessment and also other areas of cheminformatics to fulfill the ever-growing demand for accurate and rapid prediction of various toxicity or activity related end points of large compound libraries present in the pharmaceutical and chemical industry.

  • 817.
    Zhou, Jun
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Eklund, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Parameter sensitivity in tuning fuzzy controllers1996Inngår i: IEEE International Conference on Systems, Man and Cybernetics,: Information, Intelligence and Systems (Volume 1), 1996, s. 390-393Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The purpose of this paper is to study the effect of training parameter subclasses in sequences as opposed to simultaneous learning. Parameter classes for rule bases reside mainly in membership functions but also in connectives and defuzzifications. In particular update rules also learning rates and epoch sizes needs to be considered.

  • 818.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    AlgExt: an Algorithm Extractor for C Programs2001Rapport (Annet vitenskapelig)
    Abstract [en]

    ALGEXT is a program that extracts strategic/block comments from C source files to improve maintainability and to keep documentation consistent with source code. This is done by writing the comments in the source code in what we call extractable algorithms, describing the algorithm used in the functions.

    ALGEXT recognizes different kinds of comments:

    • Strategic comments are comments that proceed a block of code, with only whitespace preceding it on the line,
    • Tactical comments are comments that describes the code that precedes it on the same line,
    • Function comments are comments immediately preceding a function definition, describing the function,
    • File comments are comments at the head of the file, before any declarations of functions and variables, and finally
    • Global comments are comments within the global scope, but not associated with a function.

    Only strategic comment are used as basis for algorithm extraction in ALGEXT.

    The paper discusses the rationale for ALGEXT and describes its implementation and usage. Examples are presented for clarification of what can be done with ALGEXT.

    Our experience shows that students who use ALGEXT for preparing theirassignments tend to write about 66% more comments than non-ALGEXT users.

  • 819.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Assessment of WWW-Based Ranking Systems for Smaller Web Sites2006Inngår i: INFOCOMP Journal of Computer Science, ISSN 1807-4545, Vol. 5, nr 2, s. 45-55Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A comparison between a number of search engines from three different families (HITS, PageRank, and Propagation of Trust) is presented for a small web server with respect to perceived relevance. A total of 307 individual tests have been done and the results from these were disseminated to the algorithms, and then handled using confidence intervals, Kolmogorov-Smirnov and ANOVA. We show that the results can be grouped according to algorithm family, and also that the algorithms (or at least families) can be partially ordered in order of relevance.

  • 820.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Automatic Generation of Concept Hierarchies for a Discrete Data Mining System2002Inngår i: International Conference on Information and Knowledge Engineering (IKE '02) / [ed] Hamid R. Arabnia, Youngsong Mun, Bhanu Prasad, CSREA Press, 2002, s. 287-293Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we propose an algorithm for automatic creation of concept hierarchies from discrete databases and datasets. The reason for doing this is to accommodate later data mining operations on the same set of data without having an expert create these hierachies by hand.

    We will go through the algorithm thoroughly and show the results from each step of the algorithm using a (small) example. We will also give actual execution times for our prototype for non-trivial example data sets and estimates of the complexity of the algorithm in terms of the number of records and the number of distinct data values in the data set.

  • 821.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    CHiC: A Fast Concept Hierarchy Constructor for Discrete or Mixed Mode Databases2003Inngår i: SEKE 2003: Proceedings of the Fifteenth International Conference on Software Engineering & Knowledge Engineering, Knowledge Systems Institute, 2003, s. 250-258Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we propose an algorithm that automatically creates concept hierarchies or lattices for discrete databases and datasets. The reason for doing this is to accommodate later data mining operations on the same sets of data without having an expert create these hierarchies by hand.

    Each step of the algorithm will be examined; We will show inputs and output for each step using a small example. The theoretical upper bound of the complexity for each part of the algorithm will be presented, as well as real time measurements for a number of databases. We will finally present a time model of the algorithm in terms of a number of attributes of the databases

  • 822.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Finding, extracting and exploiting structure in text and hypertext2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Data mining is a fast-developing field of study, using computations to either predict or describe large amounts of data. The increase in data produced each year goes hand in hand with this, requiring algorithms that are more and more efficient in order to find interesting information within a given time.

    In this thesis, we study methods for extracting information from semi-structured data, for finding structure within large sets of discrete data, and to efficiently rank web pages in a topic-sensitive way.

    The information extraction research focuses on support for keeping both documentation and source code up to date at the same time. Our approach to this problem is to embed parts of the documentation within strategic comments of the source code and then extracting them by using a specific tool.

    The structures that our structure mining algorithms are able to find among crisp data (such as keywords) is in the form of subsumptions, i.e. one keyword is a more general form of the other. We can use these subsumptions to build larger structures in the form of hierarchies or lattices, since subsumptions are transitive. Our tool has been used mainly as input to data mining systems and for visualisation of data-sets.

    The main part of the research has been on ranking web pages in a such a way that both the link structure between pages and also the content of each page matters. We have created a number of algorithms and compared them to other algorithms in use today. Our focus in these comparisons have been on convergence rate, algorithm stability and how relevant the answer sets from the algorithms are according to real-world users.

    The research has focused on the development of efficient algorithms for gathering and handling large data-sets of discrete and textual data. A proposed system of tools is described, all operating on a common database containing "fingerprints" and meta-data about items. This data could be searched by various algorithms to increase its usefulness or to find the real data more efficiently.

    All of the methods described handle data in a crisp manner, i.e. a word or a hyper-link either is or is not a part of a record or web page. This means that we can model their existence in a very efficient way. The methods and algorithms that we describe all make use of this fact.

  • 823.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Propagation of Meta Data over the World Wide Web2003Inngår i: Proceedings of the International Conference on Internet Computing (IC '03), Las Vegas, Nevada, USA: CSREA Press , 2003, s. 670-676Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we propose a distribution and propagation algorithm for meta data. The main purpose of this is to tentatively allocate or derive meta data for nodes (in our case sites and/or web pages) for which no meta data exists.

    We propose an algorithm that depends on 1) meta data given to a node, site and/or web page, 2) how pervasive we percieve this meta data, and 3) the trust that we give to this meta data. We will also show that PICS labels can be used to hold the meta data even for distant web pages and sites.

  • 824.
    Ågren, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    S²ProT: Rank Allocation by Superpositioned Propagation of Topic-Relevance2008Inngår i: International Journal of Web Information Systems, ISSN 1744-0084, Vol. 4, nr 4, s. 416-440Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose – The purpose of this paper is to assign topic-specific ratings to web pages.

    Design/methodology/approach – The paper uses power iteration to assign topic-specific rating values (called relevance) to web pages, creating a ranking or partial order among these pages for each topic. This approach depends on a set of pages that are initially assumed to be relevant for a specific topic; the spatial link structure of the web pages; and a net-specific decay factor designated ξ.

    Findings – The paper finds that this approach exhibits desirable properties such as fast convergence, stability and yields relevant answer sets. The first property will be shown using theoretical proofs, while the others are evaluated through stability experiments and assessments of real world data in comparison with already established algorithms.

    Research limitations/implications – In the assessment, all pages that a web spider was able to find in the Nordic countries were used. It is also important to note that entities that use domains outside the Nordic countries (e.g..com or.org) are not present in the paper's datasets even though they reside logically within one or more of the Nordic countries. This is quite a large dataset, but still small in comparison with the entire worldwide web. Moreover, the execution speed of some of the algorithms unfortunately prohibited the use of a large test dataset in the stability tests.

    Practical implications – It is not only possible, but also reasonable, to perform ranking of web pages without using Markov chain approaches. This means that the work of generating answer sets for complex questions could (at least in theory) be divided into smaller parts that are later summed up to give the final answer.

    Originality/value – This paper contributes to the research on internet search engines.

  • 825.
    Ågren, Ola M
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    The ProT Nordic Web Dataset2012Inngår i: Proceedings of the International Conference on Internet Computing: ICOMP 2012 / [ed] Hamid R. Arabnia, Victor A. Clincy, Leonidas Deligiannidis, Andy Marsh, Ashu M. G. Solo, Las Vegas, Nevada: CSREA Press, 2012, s. 125-128Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a free dataset, usable for testing web search engines.  The dataset corresponds to a snapshot of the Nordic part of the Internet in early 2007 and is highly abstracted, with numbers representing each web page.  The released dataset consists of three parts; a graph, 76 sets of pages containing each tested word combination, and some files to use when calculating relevance of the resulting sets of algorithms/search engines. We also present a new compound statistic as well as statistical results for some search engine and information retrieval algorithms.

  • 826.
    Ågren, Per-Olof
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för informatik.
    Is online democracy in the EU for professionals only?2001Inngår i: Communications of the ACM, ISSN 0001-0782, E-ISSN 1557-7317, Vol. 44, nr 1, s. 36-38Artikkel i tidsskrift (Annet vitenskapelig)
  • 827.
    Åhag, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Cegrell, Urban
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Hiep, Pham Hoang
    On the Guedj-Rashkovskii conjecture2019Inngår i: Annales Polonici Mathematici, ISSN 0066-2216, E-ISSN 1730-6272, Vol. 123, nr 1, s. 15-20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We prove some cases when the Guedj-Rashkovskii conjecture holds.

  • 828.
    Åhag, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Czyz, Rafal
    On a characterization of m-subharmonic functions with weak singularities2019Inngår i: Annales Polonici Mathematici, ISSN 0066-2216, E-ISSN 1730-6272, Vol. 123, nr 1, s. 21-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We provide a characterization of functions in Cegrell’s energy class Ep,m.

  • 829.
    Åström, Fredrik
    Umeå universitet, Samhällsvetenskapliga fakulteten, Sociologiska institutionen.
    Becoming a discipline: the institutionalization of Library and Information Science in the Nordic countries2008Inngår i: Journal of Documentation, ISSN 0022-0418, E-ISSN 1758-7379, Vol. 64, nr 5, s. 721-737Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose - The paper's objective is to analyze the social organization of library and information Science (LIS) using the Nordic countries as example, focusing on organizational setting, research work and relations between LIS and academia as well as the field of professional practice.

    Design/methodology/approach - Based on a framework for analyzing scientific fields, as well as its application on LIS, aspects relating to the impact of contextual factors on research was identified and discussed based on information front, e.g. LIS institution web sites. The results were discussed, not only in relation to the framework primarily utilized, but also from a less disciplinary view on research organization, for analytical contrast.

    Findings - A close connection between academic affiliation and research orientation was found, reflected in organizational issues, media for communicating research and access to resources. This relates to general issues of levels of independence front other disciplines and lay groups, to what extent research is evaluated by intra-disciplinary standards and to the level of consensus on terminology and research processes.

    Research limitations/implications - Limiting the study to institutions in one particular geographical area, where several institutions being at an early stage of formalization, the possibility of reaching generalizable conclusions is limited. The strength of the conclusions is also somewhat restrained Clue to the nature oft he empirical material, being based on web documents with varying levels of exhaustability in terms of data provision.

    Originality/vallue - The intellectual organization of LIS research is well-known, whereas social and imstitutional aspects have been analyzed to a lesser degree; and with the differences in age and size of Nordic LIS institutions, they provide an interesting case of contemporary institutionalization of LIS research.

  • 830.
    Östberg, Per-Olov
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A model for simulation of application and resource behavior in heterogeneous distributed computing environments2012Inngår i: Proceedings of the 2nd international conference on simulation and modeling methodologies, technologies and applications / [ed] Nuno Pina, Janusz Kacprzyk, Mohammad S. Obaidat, SciTePress, 2012, s. 144-151Konferansepaper (Fagfellevurdert)
  • 831.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Barry, McCollum
    Queens University of Belfast, United Kingdom.
    Heuristics and Algorithms for Data Center Optimization2015Inngår i: Proceedings of the 7th Multidisciplinary International Conference on Scheduling : Theory and Applications (MISTA 2015) / [ed] Zdenek Hanzálek, Graham Kendall, Barry McCollum, Premysl Šůcha, 2015, s. 921-927Konferansepaper (Annet vitenskapelig)
  • 832.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Byrne, James
    Casari, Paolo
    Eardley, Philip
    Fernandez Anta, Antonio
    Forsman, Johan
    Kennedy, John
    Le Duc, Thang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Noya Marino, Manuel
    Loomba, Radhika
    Lopez Pena, Miguel Angel
    Veiga, Jose Lopez
    Lynn, Theo
    Mancuso, Vincenzo
    Svorobej, Sergej
    Torneus, Anders
    Wesner, Stefan
    Willis, Peter
    Domaschka, Joerg
    Reliable Capacity Provisioning for Distributed Cloud/Edge/Fog Computing Applications2017Inngår i: 2017 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), IEEE , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The REliable CApacity Provisioning and enhanced remediation for distributed cloud applications (RECAP) project aims to advance cloud and edge computing technology, to develop mechanisms for reliable capacity provisioning, and to make application placement, infrastructure management, and capacity provisioning autonomous, predictable and optimized. This paper presents the RECAP vision for an integrated edge-cloud architecture, discusses the scientific foundation of the project, and outlines plans for toolsets for continuous data collection, application performance modeling, application and component auto-scaling and remediation, and deployment optimization. The paper also presents four use cases from complementing fields that will be used to showcase the advancements of RECAP.

  • 833.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A Performance Evaluation of the Grid Job Management Framework (GJMF)2011Konferansepaper (Fagfellevurdert)
  • 834.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Increasing flexibility and abstracting complexity in service-based Grid and cloud software2011Inngår i: Proceedings of the 1st International Conference on Cloud Computing and Services Science / [ed] F. Leyman, I. Ivanov, M. van Sinderen and B. Shishkov, SciTePress, 2011, s. 240-249Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work addresses service-based software development in Grid and Cloud computing environments, and proposes a methodology for Service-Oriented Architecture design. The approach consists of an architecture design methodology focused on facilitating system flexibility, a service model emphasizing component modularity and customization, and a development tool designed to abstract service development complexity. The approach is intended for use in computational eScience environments and is designed to increase flexibility in system design, development, and deployment, and reduce complexity in system development and administration. To illustrate the approach we present case studies from two recent Grid infrastructure software development projects, and evaluate impact of the development approach and the toolset on the projects.

  • 835.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Mediation of service overhead in service-oriented grid architectures2011Inngår i: 2011 IEEE/ACM 12th International Conference on Grid Computing, IEEE, 2011, s. 9-18Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Grid computing applications and infrastructures build heavily on Service-Oriented Computing development methodology and are often realized as Service-Oriented Architectures. The Grid Job Management Framework (GJMF) is a flexible Grid infrastructure and application support tool that offers a range of abstractive and platform independent interfaces for middleware-agnostic Grid job submission, monitoring, and control. In this paper we use the GJMF as a test bed for characterization of Grid Service-Oriented Architecture overhead, and evaluate the efficiency of a set of design patterns for overhead mediation mechanisms featured in the framework.

  • 836.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Espling, Daniel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Decentralized scalable fairshare scheduling2013Inngår i: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 29, nr 1, s. 130-143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work addresses Grid fairshare allocation policy enforcement and presents Aequus, a decentralized system for Grid-wide fairshare job prioritization. The main idea of fairshare scheduling is to prioritize users with regard to predefined resource allocation quotas. The presented system builds on three contributions: a flexible tree-based policy model that allows delegation of policy definition, a job prioritization algorithm based on local enforcement of distributed fairshare policies, and a decentralized architecture for non-intrusive integration with existing scheduling systems. The system supports organization of users in virtual organizations and divides usage policies into local and global policy components that are defined by resource owners and virtual organizations. The architecture realization is presented in detail along with an evaluation of the system behavior in an emulated environment. In the evaluation, convergence noise types (mechanisms counteracting policy allocation convergence) are characterized and quantified, and the system is demonstrated to meet scheduling objectives and perform scalably under realistic operating conditions.

  • 837.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Groenda, Henning
    Wesner, Stefan
    Byrne, James
    Nikolopoulos, Dimitris S.
    Sheridan, Craig
    Krzywda, Jakub
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ali-Eldin, Ahmed
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Stier, Christian
    Krogmann, Klaus
    Domaschka, Jörg
    Hauser, Christopher B.
    Byrne, PJ
    Svorobej, Sergej
    McCollum, Barry
    Papazachos, Zafeiros
    Whigham, Darren
    Rüth, Stefan
    Paurevic, Dragana
    The CACTOS Vision of Context-Aware Cloud Topology Optimization and Simulation2014Inngår i: 2014 IEEE 6th International Conference on Cloud Computing Technology and Science, 2014, s. 26-31Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent advances in hardware development coupled with the rapid adoption and broad applicability of cloud computing have introduced widespread heterogeneity in data centers, significantly complicating the management of cloud applications and data center resources. This paper presents the CACTOS approach to cloud infrastructure automation and optimization, which addresses heterogeneity through a combination of in-depth analysis of application behavior with insights from commercial cloud providers. The aim of the approach is threefold: to model applications and data center resources, to simulate applications and resources for planning and operation, and to optimize application deployment and resource use in an autonomic manner. The approach is based on case studies from the areas of business analytics, enterprise applications, and scientific computing.

  • 838.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hellander, Andreas
    University of California, Santa Barbara, USA.
    Drawert, Brian
    University of California, Santa Barbara, USA.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Holmgren, Sverker
    Uppsala University, Sweden.
    Petzold, Linda
    University of California, Santa Barbara, USA.
    Reducing Complexity in Management of eScience Computation2012Inngår i: CCGrid 2012: Proceedings of the 12th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing / [ed] Balaji, P., Buyya, R., Majumdar, S., Pandey, S., IEEE, 2012, s. 845-852, artikkel-id 6217522Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we address reduction of complexity in management of scientific computations in distributed computing environments. We explore an approach based on separation of computation design (application development) and distributed execution of computations, and investigate best practices for construction of virtual infrastructures for computational science - software systems that abstract and virtualize the processes of managing scientific computations on heterogeneous distributed resource systems. As a result we present StratUm, a toolkit for management of eScience computations. To illustrate use of the toolkit, we present it in the context of a case study where we extend the capabilities of an existing kinetic Monte Carlo software framework to utilize distributed computational resources. The case study illustrates a viable design pattern for construction of virtual infrastructures for distributed scientific computing. The resulting infrastructure is evaluated using a computational experiment from molecular systems biology.

  • 839.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lockner, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Creo: reduced complexity service development2014Inngår i: Proceedings of CLOSER 2014 - 4th International Conference on Cloud Computing and Services Science / [ed] M. Helfert, F. Desprez, D. Ferguson, F. Leymann, V. Mendez Munoz, SciTePress, 2014, s. 230-241Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this work we address service-oriented software development in distributed computing environments, and investigate an approach to software development and integration based on code generation. The approach is illustrated in a toolkit for multi-language software generation built on three building blocks; a service description language, a serialization and transport protocol, and a set of code generation techniques. The approach is intended for use in the eScience domain and aims to reduce the complexity of development and integration of distributed software systems through a low-knowledge-requirements model for construction of network-accessible services. The toolkit is presented along with a discussion of use cases and a performance evaluation quantifying the performance of the toolkit against selected alternative techniques for code generation and service communication. In tests of communication overhead and response time, toolkit performance is found to be comparable to or improve upon the evaluated techniques.

  • 840.
    Östberg, Per-Olov
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lockner, Niclas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Reducing Complexity in Service Development and Integration2015Inngår i: Cloud computing and services sciences, CLOSER 2014, Springer Berlin/Heidelberg, 2015, s. 63-80Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The continuous growth and increasing complexity of distributed systems software has produced a need for software development tools and techniques that reduce the learning requirements and complexity of building distributed systems. In this work we address reduction of complexity in service-oriented software development and present an approach and a toolkit for multi-language service development based on three building blocks: a simplified service description language, an intuitive message serialization and transport protocol, and a set of code generation techniques that provide boilerplate environments for service implementations. The toolkit is intended for use in the eScience domain and is presented along with a performance evaluation that quantifies toolkit performance against that of selected alternative toolkits and technologies for service development. Toolkit performance is found to be comparable to or improve upon the performance of evaluated technologies.

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