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  • 13151.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lövgren, Lars
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hedlund, Tomas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The ionic strength dependency of mineral solubility and chemical speciation in solution2006In: Surface Complexation Modelling, Elsevier, 2006, p. 1-34Chapter in book (Other academic)
  • 13152.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution: 1. The Formation of Ternary Mononuclear and Polynuclear Complexes in the System Al(3+)--Gallic Acid--OH-. A Potentiometric Study in 0.6 M Na(Cl)1981In: Acta Chemica Scandinavica, ISSN 0302-4377, Vol. A 35, p. 201-212Article in journal (Refereed)
  • 13153.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution: 4. A Potentiometric Study of Polynuclear Aluminium(III) Hydroxo Complexes with Gallic Acid in Hydrolyzed Aluminium(III) Solutions.1982In: Acta Chemica Scandinavica, ISSN 0302-4377, Vol. A 36, p. 47-53Article in journal (Refereed)
  • 13154.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution: 8. A potentiometric study of aluminium(III) Salicylates and Aluminium(III) Hydroxo Salicylates in 0.6 M Na(C1)1983In: Acta Chemica Scandinavica. Series A., ISSN 0302-4377, Vol. 37, p. 875-880Article in journal (Refereed)
  • 13155.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution: Part 9. A Potentiometric Study of Mono- and Polynuclear Aluminium(III)-Citrates1983In: Journal of the Chemical Society. Dalton Transactions, ISSN 1472-7773, E-ISSN 1364-5447, no 11, p. 2513-2517Article in journal (Refereed)
  • 13156.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution—10: A potentiometric study of aluminium(III) pyrocatecholates and aluminium(III) hydroxo pyrocatecholates in 0.6 M Na(Cl)1983In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 2, no 12, p. 1329-1335Article in journal (Refereed)
  • 13157.
    Öhman, Lars-Olof
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ingri, Nils
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution: 7. Redox, Hydrolysis and Complexation Equilibria in the System Al(3+)-1,2-Naphthoquinone-4-sulfonate/1,2-Dihydroxy-naphthalene-4-sulfonate-OH(-). A Potentiometric Study in 0.6 M Na(Cl)1983In: Acta Chemica Scandinavica, ISSN 0302-4377, Vol. A 37, p. 561-568Article in journal (Refereed)
  • 13158. Öhman, Marcus
    et al.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Kofod-Hansen, Marie
    Minskade askrelaterade driftsproblem genom inblandning av torv i åkerbränslen2010Report (Other academic)
    Abstract [sv]

    Resultaten visar att inblandning av typisk starrbaserad bränntorv i salix och rörflen med låg askhalt ger positiva effekter vad avser bäddagglomerering och beläggningsbildning/(korrosion) i pannors konvektionsdelar redan vid relativt låga inblandningsgrader (15 vikts-% på TS basis). En starrbaserad bränntorv med relativt högt Ca/Si förhållande bör väljas för sameldning med salix i rosteranläggningar för att inte öka slaggningsrisken. Samma torvtyp kan också i rosteranläggningar nyttjas i sameldning med rörflen med låg askhalt (relativt låga inblandningsgrader räcker) och vetehalm (höga inblandningsgrader krävs) för att reducera slaggningsrisken. Vid val av torvslag för att maximera de ovanstående positiva effekterna vid förbränning kan därför en allmän rekommendation göras att torvar med hög askhalt (starrinnehållande torv), och gärna med högt inslag av svavel, ger de bästa sameldningsegenskaperna med det tilläget att vid rostereldning bör en torv med relativt högt Ca/Si förhållande väljas (gärna upp mot 1 på vikts-% basis).

  • 13159.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hedman, H
    Jirjis, R
    Reasons for slagging during stemwood pellet combustion and some measures for prevention2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 597-605Article in journal (Refereed)
    Abstract [en]

    Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems lead to reduced accessibility of the appliances and also bad publicity for the pellet market. The objectives of the present work were therefore to: (i) determine the critical levels of the problematic ash components in stemwood pellets regarding slagging, (ii) document the variations of these problematic elements in the outgoing pellets from two pellet-mills during one operational season, (iii) determine how frequently these elements exceed the critical levels, (iv) determine how different sub-processes in the pelletising process (especially the dryer) effect the slagging properties of the pellet, and if possible (v) suggest some measures for prevention. A significant number of wood pellets reported to be problematic and problem-free, regarding slagging in ordinary residential pellet burners, were collected from the Swedish market. The ash compositions of these fuels were analysed and the results compiled in a database. Partial Least-Squares Discriminant Analysis (PLS-DA) and F-tests were used to statistically identify both the critical ash components and the critical levels of these components that separated the two reported classes. In addition, chemical equilibrium model calculations were used to interpret the findings. The variations of these elements in the in-going raw material and in the produced pellets were determined during one season in two pellet mills equipped with exhaust gas dryers. The results showed that the problematic wood-pellets had a significantly higher amount of Si, but also Al and Fe, in the fuel ash. The critical level of Si (given as SiO2) was about 20-25 wt% of the fuel ash, i.e. pellets with levels in or over this range resulted in slagging problems in residential burners. This critical Si content was exceeded once and twice for the analysed samples in the two studied pellet mills. In one of the studied mills, this was because of contamination by sand of the raw material during storage and handling, and in the other mill the reason was found to be contamination of the raw material by elutriated particles from the dryer fuel. The major conclusion of the work is that both raw materials and drying fuels/processes should be carefully treated to avoid mineral contamination, and an additional cyclone separator could potentially also be used to improve the pellet quality.

  • 13160.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lundholm, Karin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hedman, Hedman
    Energy Technology Centre, Piteå.
    Lundberg, Margareta
    Kvaerner Pulping AB, Power Division, Göteborg.
    Ash Transformations during Combustion of Meat-, Bonemeal, and RDF in a (bench-scale) Fluidized Bed Combustor2003In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 17, no 5, p. 1153-1159Article in journal (Refereed)
    Abstract [en]

    Following the recent Bovine spongiform encephalopathy (BSE) experiences, thermal treatment of meat- and bonemeal (MBM) in existing fluidized bed combustion (FBC) plants for refuse-derived fuels (RDFs) has evolved as an interesting disposal and disintegration method. However, only a limited number of studies have previously been performed for combustion of MBM in fluidized beds. The objectives of the present work were, therefore, to determine the bed agglomeration tendencies of these materials during combustion in fluidized beds and to evaluate the effects of dolomite and kaolin addition to the fuel mix, as well as to elucidate the overall ash transformation mechanisms governing the potential bed agglomeration and fouling processes. By controlled agglomeration experiments in a 5 kW bench-scale fluidized bed reactor, the fuel-specific critical agglomeration temperatures in normal quartz bed material were determined for the different fuel/additive mixtures. All collected samples of bed materials, final bed agglomerates, and cyclone ashes were analyzed using SEM/EDS and XRD. The results indicated that the MBM fuels could be expected to be problematic concerning bed agglomeration in normal quartz beds, while kaolin and possibly dolomite addition could be used to reduce this risk to moderate levels. A significant elemental fractionation between the bed material and the cyclone ash was obtained. Apatite (Ca5(PO4)3(OH) or potentially some other calcium phosphates are elutriated from the bed and enriched in the fly ash, while sodium and potassium are enriched in the bed material. The characteristics and the corresponding melting behavior estimations of the necks formed between agglomerated bed particles suggest that silicate melts are responsible for the bed agglomeration. Results from XRD analysis of the fly ash formed from the fuels used in the present study indicated that the risk for melt-related fly ash problems seem relatively small.

  • 13161.
    Öhman, Marie-Louise
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    A Monte Carlo study of some censored data Wilcoxon rank tests1990In: Biometrical Journal, ISSN 0323-3847, E-ISSN 1521-4036, Vol. 32, no 6, p. 721-735Article in journal (Refereed)
    Abstract [en]

    The variance estimators usually applied for the generalized censored data Wilcoxon rank tests by Gehan and Peto & Prentice, are heavily biased in unbalanced problems. This paper reports the results of a Monte Carlo simulation study, where jackknifing is used to construct estimators of variance. Size, power and variance properties are compared for five variance estimators, when using different combinations of group sizes, failure and censoring patterns. The variance estimators are the permutational, the conditional permutational and the jackknife variance estimators for the statistic of Gehan and the asymptotic and the jackknife variance estimators for the statistic of Peto & Prentice. It appears that observed size, power and variance properties may be improved by using the jackknife variance estimator, when comparing to the variance estimators usually applied.

  • 13162.
    Öhman, Marie-Louise
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Aspects of analysis of small-sample right censored data using generalized Wilcoxon rank tests1994Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The estimated bias and variance of commonly applied and jackknife variance estimators and observed significance level and power of standardised generalized Wilcoxon linear rank sum test statistics and tests, respectively, of Gehan and Prentice are compared in a Monte Carlo simulation study. The variance estimators are the permutational-, the conditional permutational- and the jackknife variance estimators of the test statistic of Gehan, and the asymptotic- and the jackknife variance estimators of the test statistic of Prentice. In unbalanced small sample size problems with right censoring, the commonly applied variance estimators for the generalized Wilcoxon rank test statistics of Gehan and Prentice may be biased. In the simulation study it appears that variance properties and observed level and power may be improved by using the jackknife variance estimator.

    To establish the sensitivity to gross errors and misclassifications for standardised generalized Wilcoxon linear rank sum statistics in small samples with right censoring, the sensitivity curves of Tukey are used. For a certain combined sample, which might contain gross errors, a relatively simple method is needed to establish the applicability of the inference drawn from the selected rank test. One way is to use the change of decision point, which in this thesis is defined as the smallest proportion of altered positions resulting in an opposite decision.

    When little is known about the shape of a distribution function, non-parametric estimates for the location parameter are found by making use of censored one-sample- and two-sample rank statistics. Methods for constructing censored small sample confidence intervals and asymptotic confidence intervals for a location parameter are also considered. Generalisations of the solutions from uncensored one-sample and two-sample rank tests are utilised. A Monte-Carlo simulation study indicates that rank estimators may have smaller absolute estimated bias and smaller estimated mean squared error than a location estimator derived from the Product-Limit estimator of the survival distribution function.

    The ideas described and discussed are illustrated with data from a clinical trial of Head and Neck cancer.

  • 13163.
    Öhman, Marie-Louise
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Contributions to generalized Wilcoxon rank tests1992Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In unbalanced small sample size problems with right censorings, the variance estmators of linear rank statistics, may be biased. This is the case with the commonly applied variance estimators for the generalized Wilcoxon rank test statistics of Gehan and Prentice. The bias and variance of different variance estimators and observed significance level and power for standardized tests are compared in a Monte Carlo simulation study. The variance estimators are the permutational-, the conditional permutational- and the jackknife variance estimators for the statistic Gehan, and the asymptotic- and the jackknife variance estimators for the statistic of Prentice. It appears that observed level and power and variance properties may be improved by using the jackknife variance estimator.

    Further, The sensitivity curves of Turkey are used to establish the sensitivity to gross errors and misclassifications for standardized generalized Wilcoxon rank sum statistics in small samples with right censorings. For a certain combined sample, which might contain gross errors, a relatively fast method is needed to establish the applicability of the inference drawn from the selected ranktest. Ome way is to use the "change of decision point" (cdp), which in this thesis is defined as the smallest proportion of altered positions resulting in an opposite decision.

  • 13164.
    Öhman, Marie-Louise
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Estimating location parameters using censored rank statistics1995In: Biometrical Journal, ISSN 0323-3847, E-ISSN 1521-4036, Vol. 37, no 7, p. 767-782Article in journal (Refereed)
    Abstract [en]

    In this paper censored data rank location estimators are obtained by using censored one-sample rank test statistics of the location parameter and censored two-sample rank test statistics of the shift of location parameter. Also, methods for constructing censored small sample confidence intervals and asymptotic confidence intervals for the location are considered. Generalizations of the solutions from uncensored one-sample and two-sample rank tests are utilized.

  • 13165.
    Öhman, Marie-Louise
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Generalized Wilcoxon rank tests and sensitivity curves1991In: Biometrical Journal, ISSN 0323-3847, E-ISSN 1521-4036, Vol. 33, no 7, p. 789-806Article in journal (Refereed)
    Abstract [en]

    In this paper we use the sensitivity curves of TUKEY (1977) and the change of decision point (cdp) (a modified version of the breakdown point of YLVISAKER, 1977), supplemented by simulation studies to acquire knowledge about sensitivity in generalized Wilcoxon rank test statistics. Sensitivity depends on balanced or unbalanced sample size cases, censoring, combinations of failure distributions and sources of errors in the data. It is important to consider the quality of the data, and the results show that cdp and some properties of the sensitivity curves may serve as a hint when selecting a test statistic and when making a decision for a given test statistic.

  • 13166.
    Öhman, Nikanor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Simulation of LiDAR data for forestry applications2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In forestry it is important to have accurate information about the forest. LiDAR (laser scanning) can be used to scan vast areas of forest and from the data extract information about the trees. The purpose of this thesis is to develop a simulator for LiDAR data. The simulator will be tested on a method for tree localization (Holmgren and Lindberg 2013) to see how parameters like tree density and laser frequency effects the accuracy of the localization. First a simulator which uses simple shaped trees (in the shape of cones) is written. Later on a tree model based on real laser data is created by the use of histogram density estimation. Ray-tracing is used to simulate the LiDAR data which the trees give rise to. This is done by following each ray of laser and see where it is reflected. The tree localization method is tested on the data and we report the following findings: 1: The percentage of correctly located trees decreases with increasing tree density. 2: Larger trees yields an increase in false trees found by the localization method. 3: Higher laser pulse density decreases the number of false trees. 4: The minimum radius at which the localization method start fitting ellipsoids greatly effects the number of false trees. Smaller radius yield more false trees.

  • 13167.
    Öhman, Oscar
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Rating corrumption within insurance companies using Bayesian network classifiers2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Bayesian Network (BN) classifiers are a type of probabilistic models. The learning process consists of two steps, structure learning and parameter learning. Four BN classifiers will be learned. These are two different Naive Bayes classifiers (NB), one Tree Augmented Naive Bayes classifier (TAN) and one Forest Naive Bayes classifier (FAN). The NB classifiers will utililize two different parameter learning techniques, which are generative learning and discriminative learning. Generative learning uses maximum likelihood estimation (MLE) to optimize the parameters, while discriminative learning uses conditional likelihood estimation (CLE). The latter is more appropriate given the target at hand, while the former is less complicated. These four models are created in order to find the model best suited for predicting/rating the corruption levels of different insurance companies, given their features. Multi-class Area under the receiver operating characteristic (ROC) curve (AUC), as well as accuracy, is used in order to compare the predictive performances of the models. We observe that the classifiers learnt by generative parameter learning performed remarkably well, even outperforming the NB classifier with discriminative parameter learning. But unfortunately, this might imply an optimization issue when learning the parameters discriminately. Another unexpected result was that the CL-TAN classifier had the highest multi-class AUC, even though FAN is supposed to be an upgrade of CL-TAN. Further, the generatively learned NB performed about as good as the other two generative classifiers, which was also unexpected.

  • 13168.
    Öhman, Oscar
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Boman, Alexander
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Statistics.
    Effekter av svält, krig och epidemi: En studie i överlevnadsanalys2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Finska kriget mellan 1808 och 1809, nödåren under den senare delen av 1860-talet, samt spanska sjukan mellan 1918 och 1919 var händelser som fick katastrofala konsekvenser för befolkningen i Umeå- samt Skellefteåtrakterna. Denna studie har som syfte att undersöka vilken av dessa händelser som hade störst effekt på dödligheten bland invånarna i dessa områden. Individer delades in i fyra olika grupper efter kön och ålder. För respektive grupp genomfördes lämpliga regressionsmetoder inom överlevnadsanalys. Resultatet visade på att finska kriget hade störst effekt på samtliga fyra grupper.

  • 13169.
    Öhrman, Jakob
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evaluation of a CFD method for estimating aerodynamic loads on external stores on JAS 39 Gripen2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Loads determination for external stores on fighter aircraft is an important task for manufacturers in ensuring the safe operation of their aircraft. Due to the large number of possible store combinations, wind tunnel tests – the primary approach to obtaining loads data – cannot be performed for all configurations. Instead, supplementary techniques to estimating loads are necessary. One approach is to use information from another store and adapt it, using so-called scaling methods, to the non-tested store.

    In this thesis, a scaling method combining the results of computational fluid dynamics (CFD) simulations, for both a non-tested and a reference store, with existing wind tunnel data for the reference store, is thoroughly examined for a number of different stores, angles of attack, sideslip angles and Mach numbers. The performance of the proposed scaling method is assessed in relation to currently used scaling methods, using non-parametric and multivariate statistics.

    The results show no definitive improvement in performance for the proposed scaling method over the current methods. Although the proposed method is slightly more conservative, considerable variability in the estimates and an increased time consumption for scaling leads the author to advise against using the proposed method for scaling aerodynamic loads on external stores.

  • 13170.
    Öhrvall, Malin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Matavfallssortering för restauranger: En studie av restaurangers möjligheter och inställning till matavfallssortering2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to examine attitudes and potential for sorting of food waste at restaurants in the central part of Umeå. The information was gathered through a questionnaire survey and by exploring different sorting methods. The questionnaire was sent to 55 restaurants and 24 of them responded. A majority of the respondents wanted to sort out food waste. 72.8 % believe they have a good or moderate potential to sort out food waste in the future and none of the respondents answered that they believed that they had no means of sorting out food waste. Overall, the restaurants are considered to have good attitudes about sorting food waste. However, this may be because the respondents have a better attitude than those who chose not to respond. The sorting methods were evaluated by reviewing reports written by government agencies and industry associations. Mill systems connected to a tank had the most pros and least cons of the sorting methods, but were expensive to install and required a lot of space. Sorting in individual containers was less expensive and required less space but was considered worse from a working environment standpoint. It seems that a combination of individual containers and a mill system connected to a tank suit most restaurants.

  • 13171. Öhrvik, Helena
    et al.
    Wittung-Stafshede, Pernilla
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Identification of New Potential Interaction Partners for Human Cytoplasmic Copper Chaperone Atox1: Roles in Gene Regulation?2015In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 16, no 8, p. 16728-16739Article in journal (Refereed)
    Abstract [en]

    The human copper (Cu) chaperone Atox1 delivers Cu to P-1B type ATPases in the Golgi network, for incorporation into essential Cu-dependent enzymes. Atox1 homologs are found in most organisms; it is a 68-residue ferredoxin-fold protein that binds Cu in a conserved surface-exposed Cys-X-X-Cys (CXXC) motif. In addition to its well-documented cytoplasmic chaperone function, in 2008 Atox1 was suggested to have functionality in the nucleus. To identify new interactions partners of Atox1, we performed a yeast two-hybrid screen with a large human placenta library of cDNA fragments using Atox1 as bait. Among 98 million fragments investigated, 25 proteins were found to be confident interaction partners. Nine of these were uncharacterized proteins, and the remaining 16 proteins were analyzed by bioinformatics with respect to cell localization, tissue distribution, function, sequence motifs, three-dimensional structures and interaction networks. Several of the hits were eukaryotic-specific proteins interacting with DNA or RNA implying that Atox1 may act as a modulator of gene regulation. Notably, because many of the identified proteins contain CXXC motifs, similarly to the Cu transport reactions, interactions between these and Atox1 may be mediated by Cu.

  • 13172. Öjerskog,
    Utformning av miljömässiga nyckeltal och en bedömningsmall för miljöaspekter på Umeå Energi AB2006Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 13173.
    Ölund, Anders
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Jämförelse av olika metoder att generera Bernoullifördelade slumptal givet deras summa2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master’s thesis the problem of simulating conditional Bernoulli distributed stochastic variables, given the sum, is considered. Three simulation methods are considered, namely the acceptance/rejection technique, Bondesson’s method and the Markov chain Monte Carlo method.

    To compare the three methods the bias and the standard deviations of the simulated variables are evaluated. The results of the simulation study shows that the Markov chain Monte Carlo method is not the best method for this type of simulation. Both the other methods were quite suitable for the task. The acceptance/rejection technique is a little bit more time consuming than Bondesson’s method, but on the other hand the acceptance/rejection technique is easier to implement.

  • 13174.
    Ölund, Marie
    Umeå University, Faculty of Science and Technology, Department of Science and Mathematics Education.
    Att utveckla lärandet i matematik: En studie i hur lärare genom sin undervisning utvecklar elevers lärande i grundskolans tidigare år2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The most important influencing factor in student learning is the teacher. It is not so much what the teacher does, but what the teacher makes his students to do that is important. That is what this study investigates. Which workingmethods are used and how are they varied? It also investigates how formative assessment is used in practice. Which formative elements can be found in the teachers practice and what methods are used? As data collection methods interviews, classroom observations and a student questionare have been used. The results shows that teachers who vary their working methods and who use interactive methods have more positive pupils. The result also shows that the teachers use formative assessment but in varied extent. No teaching method can safely be said to be the best but one thing is certain - varied teaching promotes pupils learning!

  • 13175.
    Öman, Tommy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multivariate Analysis of 2D-NMR Spectroscopy: Applications in wood science and metabolomics2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood is our most important renewable resource. We need better quality and quantity both according to the wood itself and the processes that are using wood as a raw material. Hence, the understanding of the chemical composition of the wood is of high importance. Improved and new methods for analyzing wood are important to achieve better knowledge about both refining processes and raw material. The combination of NMR and multivariate analyses (MVA) is a powerful method for these analyses but so far it has been limited mainly to 1D NMR. In this project, we have developed methods for combining 2D NMR and MVA in both wood analysis and metabolomics. This combination was used to compare samples from normal wood and tension wood, and also trees with a down regulation of a pectin responsible gene. Dissolving pulp was also examined using the same combination of 2D-NMR and MVA, together with FT-IR and solid state 13C CP-MAS NMR. Here we focused on the difference between wood type (softwood and hardwood), process type (sulfite and sulfate) and viscosity. These methods confirmed and added knowledge about the dissolving pulp. Also reactivity was compared in relation to morphology of the cellulose and pulp composition. Based on the method and software used in the wood analysis projects, a new method called HSQC-STOCSY was developed. This method is especially suited for assignment of substances in complex mixtures. Peaks in 2D NMR spectra that correlate between different samples are plotted in correlation plots resembling regular NMR spectra. These correlation plots have great potential in identifying individual components in complex mixtures as shown here in a metabolic data set. This method could potentially also be used in other areas such as drug/target analyses, protein dynamics and assignment of wood spectra.

  • 13176.
    Öman, Tommy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Reactivity of dissolving pulp analyzed with multivariate data analysis of XRD and NMR data.Manuscript (preprint) (Other academic)
  • 13177.
    Öman, Tommy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tessem, Maj-Britt
    Bathen, Tone F
    Bertilsson, Helena
    Angelsen, Anders
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andreassen, Trygve
    Identification of metabolites from 2D 1H-13C HSQC NMR using peak correlation plots2014In: BMC Bioinformatics, ISSN 1471-2105, E-ISSN 1471-2105, Vol. 15, article id 413Article in journal (Refereed)
    Abstract [en]

    Background: Identification of individual components in complex mixtures is an important and sometimes daunting task in several research areas like metabolomics and natural product studies. NMR spectroscopy is an excellent technique for analysis of mixtures of organic compounds and gives a detailed chemical fingerprint of most individual components above the detection limit. For the identification of individual metabolites in metabolomics, correlation or covariance between peaks in 1H NMR spectra has previously been successfully employed. Similar correlation of 2D 1H-13C Heteronuclear Single Quantum Correlation spectra was recently applied to investigate the structure of heparine. In this paper, we demonstrate how a similar approach can be used to identify metabolites in human biofluids (post-prostatic palpation urine).

    Results: From 50 1H-13C Heteronuclear Single Quantum Correlation spectra, 23 correlation plots resembling pure metabolites were constructed. The identities of these metabolites were confirmed by comparing the correlation plots with reported NMR data, mostly from the Human Metabolome Database.

    Conclusions: Correlation plots prepared by statistically correlating 1H-13C Heteronuclear Single Quantum Correlation spectra from human biofluids provide unambiguous identification of metabolites. The correlation plots highlight cross-peaks belonging to each individual compound, not limited by long-range magnetization transfer as conventional NMR experiments.

  • 13178.
    Önskog, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Freyhult, Eva
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Landfors, Mattias
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Rydén, Patrik
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Hvidsten, Torgeir R
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Classification of microarrays: synergistic effects between normalization, gene selection and machine learning2011In: BMC Bioinformatics, ISSN 1471-2105, E-ISSN 1471-2105, Vol. 12, no 1, article id 390Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Machine learning is a powerful approach for describing and predicting classes in microarray data. Although several comparative studies have investigated the relative performance of various machine learning methods, these often do not account for the fact that performance (e.g. error rate) is a result of a series of analysis steps of which the most important are data normalization, gene selection and machine learning.

    RESULTS: In this study, we used seven previously published cancer-related microarray data sets to compare the effects on classification performance of five normalization methods, three gene selection methods with 21 different numbers of selected genes and eight machine learning methods. Performance in term of error rate was rigorously estimated by repeatedly employing a double cross validation approach. Since performance varies greatly between data sets, we devised an analysis method that first compares methods within individual data sets and then visualizes the comparisons across data sets. We discovered both well performing individual methods and synergies between different methods.

    CONCLUSION: Support Vector Machines with a radial basis kernel, linear kernel or polynomial kernel of degree 2 all performed consistently well across data sets. We show that there is a synergistic relationship between these methods and gene selection based on the T-test and the selection of a relatively high number of genes. Also, we find that these methods benefit significantly from using normalized data, although it is hard to draw general conclusions about the relative performance of different normalization procedures.

  • 13179.
    Önskog, Thomas
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Invariant Pseudodistances and Pseudometrics in Complex Analysis in Several Variables2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    At present time invariant pseudodistances and pseudometrics pose an important tool in complex analysis in several variables. This thesis is mainly devoted to giving a thorough definition of these objects and in particular to Schwarz-Pick systems such as the Carathéodory and Kobayashi pseudodistances.

    Most basic properties, such as continuity and boundary behaviour, of the Carathéodory and Kobayashi pseudo-distances and pseudometrics are investigated. As an application of the theory, the thesis is concluded with a proof of the biholomorphic inequivalence between the unit ball and unit polydisc in Cn.

  • 13180.
    Önskog, Thomas
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    The Skorohod problem and weak approximation of stochastic differential equations in time-dependent domains2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of a summary and four scientific articles. All four articles consider various aspects of stochastic differential equations and the purpose of the summary is to provide an introduction to this subject and to supply the notions required in order to fully understand the articles.

    In the first article we conduct a thorough study of the multi-dimensional Skorohod problem in time-dependent domains. In particular we prove the existence of cádlág solutions to the Skorohod problem with oblique reflection in time-independent domains with corners. We use this existence result to construct weak solutions to stochastic differential equations with oblique reflection in time-dependent domains. In the process of obtaining these results we also establish convergence results for sequences of solutions to the Skorohod problem and a number of estimates for solutions, with bounded jumps, to the Skorohod problem.

    The second article considers the problem of determining the sensitivities of a solution to a second order parabolic partial differential equation with respect to perturbations in the parameters of the equation. We derive an approximate representation of the sensitivities and an estimate of the discretization error arising in the sensitivity approximation. We apply these theoretical results to the problem of determining the sensitivities of the price of European swaptions in a LIBOR market model with respect to perturbations in the volatility structure (the so-called ‘Greeks’).

    The third article treats stopped diffusions in time-dependent graph domains with low regularity. We compare, numerically, the performance of one adaptive and three non-adaptive numerical methods with respect to order of convergence, efficiency and stability. In particular we investigate if the performance of the algorithms can be improved by a transformation which increases the regularity of the domain but, at the same time, reduces the regularity of the parameters of the diffusion.

    In the fourth article we use the existence results obtained in Article I to construct a projected Euler scheme for weak approximation of stochastic differential equations with oblique reflection in time-dependent domains. We prove theoretically that the order of convergence of the proposed algorithm is 1/2 and conduct numerical simulations which support this claim.

  • 13181.
    Önskog, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Nyström, Kaj
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Pricing and hedging of financial derivatives using a posteriori error estimates and adaptive methods for stochastic differential equations2010In: Journal of Computational and Applied Mathematics, ISSN 0377-0427, E-ISSN 1879-1778, Vol. 235, p. 563-592Article in journal (Refereed)
    Abstract [en]

    The efficient and accurate calculation of sensitivities of the price of financial derivatives with respect to perturbations of the parameters in the underlying model, the so-called `Greeks', remains a great practical challenge in the derivative industry. This is true regardless of whether methods for partial differential equations or stochastic differential equations (Monte Carlo techniques) are being used. The computation of the `Greeks' is essential to risk management and to the hedging of financial derivatives and typically requires substantially more computing time as compared to simply pricing the derivatives. Any numerical algorithm (Monte Carlo algorithm) for stochastic differential equations produces a time-discretization error and a statistical error in the process of pricing financial derivatives and calculating the associated `Greeks'. In this article we show how a posteriori error estimates and adaptive methods for stochastic differential equations can be used to control both these errors in the context of pricing and hedging of financial derivatives. In particular, we derive expansions, with leading order terms which are computable in a posteriori form, of the time-discretization errors for the price and the associated `Greeks'. These expansions allow the user to simultaneously first control the time-discretization errors in an adaptive fashion, when calculating the price, sensitivities and hedging parameters with respect to a large number of parameters, and then subsequently to ensure that the total errors are, with prescribed probability, within tolerance.

  • 13182.
    Önskog, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Nyström, Kaj
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    The Skorohod oblique reflection problem in time-dependent domains2010In: Annals of Probability, ISSN 0091-1798, E-ISSN 2168-894X, Vol. 38, no 6, p. 2170-2223Article in journal (Refereed)
    Abstract [en]

    The deterministic Skorohod problem plays an important role in the construction and analysis of diffusion processes with reflection. In the form studied here, the multidimensional Skorohod problem was introduced, in time-independent domains, by H. Tanaka and further investigated by P.-L. Lions and A.-S. Sznitman in their celebrated article. Subsequent results of several researchers have resulted in a large literature on the Skorohod problem in time-independent domains. In this article we conduct a thorough study of the multidimensional Skorohod problem in time-dependent domains. In particular, we prove the existence of càdlàg solutions (x, λ) to the Skorohod problem, with oblique reflection, for (D,,w) assuming, in particular, that D is a time-dependent domain (Theorem 1.2). In addition, we prove that if w is continuous, then x is continuous as well (Theorem 1.3). Subsequently, we use the established existence results to construct solutions to stochastic differential equations with oblique reflection (Theorem 1.9) in time-dependent domains. In the process of proving these results we establish a number of estimates for solutions to the Skorohod problem with bounded jumps and, in addition, several results concerning the convergence of sequences of solutions to Skorohod problems in the setting of time-dependent domains.

  • 13183.
    Önskog, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Nyström, Kaj
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Weak approximation of obliquely reflected diffusions in time-dependent domains2010In: Journal of Computational Mathematics, ISSN 0254-9409, E-ISSN 1991-7139, Vol. 28, no 5, p. 579-605Article in journal (Refereed)
    Abstract [en]

    In an earlier paper, we proved the existence of solutions to the Skorohod problem with oblique reflection in time-dependent domains and, subsequently, applied this result to the problem of constructing solutions, in time-dependent domains, to stochastic differential equations with oblique reflection. In this paper we use these results to construct weak approximations of solutions to stochastic differential equations with oblique reflection, in time-dependent domains in R^d, by means of a projected Euler scheme. We prove that the constructed method has, as is the case for normal reflection and time-independent domains, an order of convergence equal to 1/2 and we evaluate the method empirically by means of two numerical examples. Furthermore, using a well-known extension of the Feynman-Kac formula, to stochastic differential equations with reflection, our method gives, in addition, a Monte Carlo method for solving second order parabolic partial differential equations with Robin boundary conditions in time-dependent domains.

  • 13184.
    Öquist, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Effects of low temperature on photosynthesis1983In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 6, no 4, p. 281-300Article, review/survey (Refereed)
  • 13185.
    Öqvist, Annafia
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Hemkompost: en utvärdering av etapp 1 i UMEVA:s projekt för återvinning av matavfall i Umeå kommun2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 13186. Örberg, Håkan
    et al.
    Jansson, Stina
    Kalén, Gunnar
    Thyrel, Mikael
    Xiong, Shaojun
    Combustion and Slagging Behavior of Biomass Pellets Using a Burner Cup Developed for Ash-Rich Fuels2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 2, p. 1103-1110Article in journal (Refereed)
    Abstract [en]

    An innovative pellet burner cup (“BTC burner”) designed to enable the burning of ash-rich fuels in small-scale boilers (30–40 kW) was evaluated, with respect to slagging behavior, combustion performance, and flue gas composition. The BTC burner features an open, flat-bottomed channel with air supply tubes on top of its lateral sides. The pellets are fed in horizontally, pushing the formed ash forward until it drops down into the ash pan. Eight different pelletized biomass fuels were combusted in the BTC burner, and no unscheduled stops occurred during the combustion tests. Conversely, seven of the eight fuel assortments caused unscheduled stops, because of slagging and/or piling-up of ash when burned in a conventional underfeed burner. The level of slagging in the BTC burner was considerably lower than in the underfeed burner, and the slag and ash were transported out of the burner cup without any complications. Combustion in the BTC burner cup also produced lower CO concentrations in the flue gas for all significantly sintering wood fuels and reed canary grass, and reduced NO emissions for all but one of the studied fuels. However, the BTC burner produced higher NO2 and SO2 levels than the underfeed burner for most assortments, and higher CO concentrations when burning corn stover with or without added lime. Further optimization of the BTC design will be required, particularly in order to minimize particle emissions.

  • 13187.
    Örberg, Håkan
    et al.
    Sveriges Lantbruksuniversitet, Enheten för Biomassateknologi och Kemi.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Teknikutveckling för ökad etablering och nyttjande av rörflen: Demonstrationsförsök i fullskala2010Report (Other academic)
    Abstract [sv]

    Resultaten visar att energigräset rörflen kan utgöra ett kompletterande bränsle till det skogsbränsle och den torv som idag används i svenska värme- och kraftvärmeanläggningar. En inblandning av rörflen med ca 10 % på energibasis i en bränslemix som för övrigt består av 10-20 % carextorv och 70-80 % träbränsle har i demonstrationsförsök visat goda resultat. Denna bränslemix har vid fullskaliga förbränningsförsök i fluidiserande bädd (Hedensbyn,CFB 98 MW) under sammanlagt 4 dygn inte gett upphov till störningar eller negativa effekter på utrustning eller ökade utsläpp i rökgaserna i form av partiklar eller gasformiga emissioner. Vid simulerade påverkan på överhettare i form av kylda sonder har även konstaterats att beläggningstillväxten varit oförändrad och ej givit upphov till ökad korrosion.

    Inblandning i bränslemixen har skett med hackad rörflen (40-50 mm) i torvdelen för att en jämn inblandning kunde åstadkommas. Rörflensmaterialet har levererats i samband med skörden så att det hackats direkt på fältet med exakthack kopplad till vagn eller med containerhantering. Vid leverans under vår och försommar har rörflenen hållit mycket låg fukthalt med ett medel på 11,3 % fukt. Jämförande studier har gjorts med system där rörflen vid skörden under vår pressats till storbalar för vidare transport till terminal eller gårdscentrum. Detta system har visat sig mindre effektivt jämfört med direkthackning på fältet och transport av hackat material till värmeverk. En fördel med storbalssystemet är dock att det möjliggör mer kostnadseffektiv lagring utan att t.ex. fukthalten höjs under lagringstiden. Även vägtransport från terminal eller gårdscentrum till värmeverk har visat sig mer effektivt med storbalar jämfört med hackat material. Vid lastning av stora fyrkantsbalar (90x120x220 cm) på lastbil med släp uppnåddes i stort sett dubbla lastvikten jämfört med hackad rörflen (20,9 ton jmf. m. 11,0 ton).

    För de något mindre anläggningarna av typen rosterpannor som provats (0,6 och 4 MW) har den briketterade formen av rörflen använts för att uppnå en jämn och koncentrerad bränslematning. Även här har en blandning av rörflen och torv visat sig användbar och speciellt för rörflen med låg askhalt har torvinblandning på 15 vikts-% av gett minskad tendens till sintring av askan. Rörflen med hög askhalt (utan torvinblandning) har kunnat sameldas med träbränsle utan risk för sintrad aska i dessa anläggningar. Tillverkningen av briketter för försöken, sammanlagt ca 35 ton, varav hälften med inblandning av torv har genomförts utan störningar och med bra kvalité på briketterna.

  • 13188.
    Öredal, Therese
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Verksamhetsutövares egenkontroll av oljeavskiljare: Finns det brister, vilka krav kan tillsynsmyndigheten ställa samt vad kan verksamhetsutövare förbättra?2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this report was to investigate whether operators, in the municipality of Örnsköldsvik, comply to current regulations and guidelines regarding oil separator. In addition to this, the report also identify which standards the regulatory authority can demand of identified deficiencies, as well as an examination in how the status of oil separator are in other municipalities in Sweden. First a delimitation was made to only investigate environmentally hazardous activities such as haulage contractors. Inventories were made of a total of 12 haulage contractors, with questions from a previously made checklist. The results of the inventory indicated deficiencies in operators existing knowledge, regular self-inspection of oil separators, control frequency, record-keeping and documentation, lack of 5-year inspection and lack of oil- and sludge level alarm. This report also shows that regulatory authority can require the operators to rectify these deficiencies, in accordance with standards and established guidelines. The report also showed similar results when compared with similar surveys of operators' self-inspection of oil separator, in other municipalities in Sweden. The study suggests that regulatory authority should priority to oversight these environmentally hazardous activities with oil separators.

  • 13189.
    Örnmark, Jannice
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Utvärdering och optimering av en biologisk fosforavskiljningsprocess vid Duvbackens reningsverk.Mikrobiologiska, processtekniska och externa aspekter2007Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 13190.
    Östberg, Per-Olov
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A model for simulation of application and resource behavior in heterogeneous distributed computing environments2012In: Proceedings of the 2nd international conference on simulation and modeling methodologies, technologies and applications / [ed] Nuno Pina, Janusz Kacprzyk, Mohammad S. Obaidat, SciTePress, 2012, p. 144-151Conference paper (Refereed)
  • 13191.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Barry, McCollum
    Queens University of Belfast, United Kingdom.
    Heuristics and Algorithms for Data Center Optimization2015In: Proceedings of the 7th Multidisciplinary International Conference on Scheduling : Theory and Applications (MISTA 2015) / [ed] Zdenek Hanzálek, Graham Kendall, Barry McCollum, Premysl Šůcha, 2015, p. 921-927Conference paper (Other academic)
  • 13192.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Byrne, James
    Casari, Paolo
    Eardley, Philip
    Fernandez Anta, Antonio
    Forsman, Johan
    Kennedy, John
    Le Duc, Thang
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    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 Applications2017In: 2017 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), IEEE , 2017Conference paper (Refereed)
    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.

  • 13193.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A Performance Evaluation of the Grid Job Management Framework (GJMF)2011Conference paper (Refereed)
  • 13194.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Decentralized Prioritization-Based Management Systems for Distributed Computing2013In: 2013 IEEE 9th international conference on e-science (e-science), IEEE Computer Society, 2013, p. 228-237Conference paper (Refereed)
    Abstract [en]

    Fairshare scheduling is an established technique to provide user-level differentiation in management of capacity consumption in high-performance and grid computing scheduler systems. In this paper we extend on a state-of-the-art approach to decentralized grid fairshare and propose a generalized model for construction of decentralized prioritization-based management systems. The approach is based on (re) formulation of control problems as prioritization problems, and a proposed framework for computationally efficient decentralized priority calculation. The model is presented along with a discussion of application of decentralized management systems in distributed computing environments that outlines selected use cases and illustrates key trade-off behaviors of the proposed model.

  • 13195.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    GJMF - a composable service-oriented Grid job management framework2013In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 29, no 1, p. 144-157Article in journal (Refereed)
    Abstract [en]

    We investigate best practices for Grid software design and development, and propose a composable, loosely coupled Service-Oriented Architecture for Grid job management. The architecture focuses on providing a transparent Grid access model for concurrent use of multiple Grid middlewares and aims to decouple Grid applications from Grid middlewares and infrastructure. The notion of an ecosystem of Grid infrastructure components is extended, and Grid job management software design is discussed in this context. Non- intrusive integration models and abstraction of Grid middleware function- ality through hierarchical aggregation of autonomous Grid job management services are emphasized, and service composition techniques facilitating this process are explored. A proof-of-concept implementation of the architecture is presented along with a discussion of architecture implementation details and trade-offs introduced by the service composition techniques used.

  • 13196.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Increasing flexibility and abstracting complexity in service-based Grid and cloud software2011In: 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, p. 240-249Conference paper (Refereed)
    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.

  • 13197.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Mediation of service overhead in service-oriented grid architectures2011In: 2011 IEEE/ACM 12th International Conference on Grid Computing, IEEE, 2011, p. 9-18Conference paper (Refereed)
    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.

  • 13198.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Espling, Daniel
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Decentralized scalable fairshare scheduling2013In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 29, no 1, p. 130-143Article in journal (Refereed)
    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.

  • 13199.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Groenda, Henning
    Wesner, Stefan
    Byrne, James
    Nikolopoulos, Dimitris S.
    Sheridan, Craig
    Krzywda, Jakub
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ali-Eldin, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    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 Simulation2014In: 2014 IEEE 6th International Conference on Cloud Computing Technology and Science, 2014, p. 26-31Conference paper (Refereed)
    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.

  • 13200.
    Östberg, Per-Olov
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellander, Andreas
    Drawert, Brian
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Holmgren, Sverker
    Petzold, Linda
    Abstractions for scaling escience applications to distributed computing environments: a StratUm Integration Case Study in Molecular Systems Biology2012In: Bioinformatics: proceedings of the international conference on bioinformatics models, methods and algorithms / [ed] Correia, C; Fred, A; Gamboa, H; Schier, J, SETUBAL: SCITEPRESS , 2012, p. 290-294Conference paper (Other academic)
    Abstract [en]

    Management of eScience computations and resulting data in distributed computing environments is complicated and often introduces considerable overhead. In this work we address a lack of integration tools that provide the abstraction levels, performance, and usability required to facilitate migration of eScience applications to distributed computing environments, In particular, we explore an approach to raising abstraction levels based on separation of computation design computation management and present StratUm, a computation enactment tool for distributed computing environments. Results are illustrated in a case study of integration of a software from the systems biology community with a grid computation management system.

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