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  • 19601.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hedman, Henry
    Energy Technology Centre, Piteå, Sweden.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Slagging tendencies of wood pellet ash during combustion in residential pellet burners2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 585-596Article in journal (Refereed)
    Abstract [en]

    Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were to; (i) evaluate how different raw materials for pellets affect the accessibility of the existing burner equipment, (ii) determine which of the ash forming element(s) that could be responsible for the deposit/slagg formation and, (iii) estimate the critical slagging temperature for the different raw materials. Stored and fresh materials from sawdust, logging residues and bark were used as raw material in three different pellet burners. The results showed that the slagging properties were relatively sensitive to the variations in total ash content and ash forming elements of the fuel. It is therefore recommended that ash rich fuels like bark and logging residues should not be used in the existing residential pellet burners. Both fuel and burner type affected the amounts of ash deposit produced. The degree of sintering (i.e. the strength of the deposits) was mostly affected by the fuel composition. Subsequent controlled sintering test of the produced deposits/slags showed critical slagging temperatures of about 850–900 °C for stored bark and about 1000 °C for fresh bark and stored and fresh materials from sawdust and logging residues. The results further indicated that the Si-content in the fuel correlated (relatively) well to the sintering tendencies in the burners. Chemical equilibrium models were used to interpret the experimental findings, and good quantitative agreements between modelling and experimental results were generally obtained.

  • 19602.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hedman, Henry
    Energy Technology Centre, Piteå, Sweden.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Slagging tendencies of wood pellet ash during combustion in residential pellet burners2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 585-596Article in journal (Refereed)
    Abstract [en]

    Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were to; (i) evaluate how different raw materials for pellets affect the accessibility of the existing burner equipment, (ii) determine which of the ash forming element(s) that could be responsible for the deposit/slagg formation and, (iii) estimate the critical slagging temperature for the different raw materials. Stored and fresh materials from sawdust, logging residues and bark were used as raw material in three different pellet burners. The results showed that the slagging properties were relatively sensitive to the variations in total ash content and ash forming elements of the fuel. It is therefore recommended that ash rich fuels like bark and logging residues should not be used in the existing residential pellet burners. Both fuel and burner type affected the amounts of ash deposit produced. The degree of sintering (i.e. the strength of the deposits) was mostly affected by the fuel composition. Subsequent controlled sintering test of the produced deposits/slags showed critical slagging temperatures of about 850–900 °C for stored bark and about 1000 °C for fresh bark and stored and fresh materials from sawdust and logging residues. The results further indicated that the Si-content in the fuel correlated (relatively) well to the sintering tendencies in the burners. Chemical equilibrium models were used to interpret the experimental findings, and good quantitative agreements between modelling and experimental results were generally obtained.

  • 19603.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    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, Henry
    Energy Technology Centre, Piteå, Sweden.
    Effect of kaolin and limestone addition on slag formation during combustion of wood fuels2004In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 18, no 5, p. 1370-1376Article in journal (Refereed)
    Abstract [en]

    Ash-related problems have more than occasionally been observed in wood-fuel-fired boilers and also recently in wood-pellet burners. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were, therefore, to determine the effects of kaolin and limestone addition on the slagging propensities of problematic and problem-free wood fuels during combustion in residential pellet appliances (burners), thus contributing to the understanding of the role of kaolin and limestone in preventing slagging on furnace grates. Pellets with additive-to-fuel ratios between 0 and 0.7 wt %d.s. were combusted in three different types of burner constructions (10 kW): over-, horizontal-, and under-feeding of the fuel. The collected slag deposits from the under-fed burner as well as the corresponding deposited fly ash in the boiler were characterized with X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The initial sintering temperatures of the formed slags were also determined. By adding limestone with an additive-to-fuel ratio of 0.5 wt %d.s. to the problematic stemwood raw material (Si-enriched probably because of contamination of sand/soil), the severe slagging of the fuel could totally be eliminated. Adding kaolin to the problematic raw material gave a minor decrease in slagging tendency of the problematic raw material and a major increase in slagging tendency of the problem-free stemwood raw material. When adding limestone to the problematic raw material, the composition of the formed slag was changed from relatively low temperature melting silicates to high temperature melting silicates and oxides. On the other hand, kaolin addition to the problematic raw material changed the content of the slag from mainly Ca-Mg silicates to be dominated by K-Al silicates which have relatively low melting points. When introducing kaolin to the problem-free raw material, the high temperature melting Ca-Mg oxides react to form lower temperature melting Ca-Al-K silicates. Chemical equilibrium model calculations were used to interpret the experimental findings, and generally good qualitative agreements between modeling and experimental results were obtained.

  • 19604. 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).

  • 19605.
    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.

  • 19606.
    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.

  • 19607.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Chemistry.
    Skrifvars, Bengt-Johan
    Backman, Rainer
    Hupa, Mikko
    Bed Agglomeration Characteristics during Fluidized Bed Combustion of Biomass Fuels2000In: Energy Fuels, Vol. 14, no 1, p. 169-78Article in journal (Refereed)
    Abstract [en]

    The in-bed behavior of ash-forming elements in fluidized bed combustion (FBC) of different biomass fuels was examined by SEM/EDS analysis of samples collected during controlled agglomeration test runs. Eight fuels were chosen for the test. To cover the variations in biomass characteristics and to represent as many combinations of ash-forming elements in biomass fuels as possible, the selection was based on a principal-component analysis of some 300 biomass fuels, with respect to ash-forming elements. The fuels were then combusted in a bench-scale fluidized bed reactor (5 kW), and their specific agglomeration temperatures were determined. Bed samples were collected throughout the tests, and coatings and necks formed were characterized by SEM/EDS analyses. On the basis of their compositions, the corresponding melting behaviors were determined, using data extracted from phase diagrams. The bench-scale reactor bed samples were finally compared with bed samples collected from biomass-fired full-scale fluidized bed boilers. In all the analyzed samples, the bed particles were coated with a relatively homogeneous ash layer. The compositions of these coatings were most commonly constricted to the ternary system K2O-CaO-SiO2. Sulfur and chlorine were further found not to "participate" in the agglomeration mechanism. The estimated melting behavior of the bed coating generally correlated well with the measured agglomeration temperature, determined in the 5 kW bench-scale fluidized bed reactor. Thus, the results indicate that partial melting of the coating of the bed particles would be directly responsible for the agglomeration.

  • 19608.
    Öhman, Mikael
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    a Data-Warehouse Solution for OMS Data Management2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A database system for storing and querying data of a dynamic schema has been developed based on the kdb+ database management system and the q programming language for use in a financial setting of order and execution services. Some basic assumptions of mandatory fields of the data to be stored are made including that the data are time-series based.A dynamic schema enables an Order-Management System (OMS) to store information not suitable or usable when stored in log files or traditional databases. Log files are linear, cannot be queried effectively and are not suitable for the volumes produced by modern OMSs. Traditional databases are typically row-oriented which does not suit time-series based data and rely on the relational model which uses statically typed sets to store relations.The created system includes software that is capable of mining the actual schema stored in the database and visualize it. This enables ease of exploratory querying and production of applications which use the database. A feedhandler has been created optimized for handling high volumes of data. Volumes in finance are steadily growing as the industry continues to adopt computer automation of tasks. Feedhandler performance is important to reduce latency and for cost savings as a result of not having to scale horizontally. A study of the area of algorithmic trading has been performed with focus on transaction-cost analysis. Fundamental algorithms have been reviewed.A proof of concept application has been created that simulates an OMS storing logs on the execution of a Volume Weighted Average Price (VWAP) trading algorithm. The stored logs are then used in order to improve the performance of the trading algorithm through basic data mining and machine learning techniques. The actual learning algorithm focuses on predicting intraday volume patterns.

  • 19609.
    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.

  • 19610.
    Öhman, Samuel
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    A metagenomic approach to detect low abundance pathogens in complex samples2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 19611.
    Öhrling, Jenny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    En analys av EPC som modell för energieffektivisering: En djupdykning i energieffektiviseringsåtgärder i Umeå kommuns EPC-projekt för att närmare förstå EPC som projektform vid energieffektivisering2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta examensarbete har åtgärder i ett energieffektiviseringsarbete av typen EPC analyserats. Umeå kommuns fastighetsavdelning startade sitt EPC-projekt 2008 syftet att energieffektivisera mer än 130 byggnader. Detta projekt sades då vara det största av sitt slag i Sverige. Bakgrunden till behovet av att utföra detta grundades i att en stor del av de tekniska systemens livslängd i fastigheterna började vara uppnådd samtidigt som ett energieffektiviseringskrav ålades fastighetsavdelningen. Siemens anlitades som entreprenör. De villkor som styrde projektet kom från beslutsfattande politiker och handlade om den viktiga besparingsgarantin. Denna garanti var en förutsättning för att få ekonomiska medel att finansiera ett projekt av den här storleken. EPC som modell valdes för att möjliggöra dessa krav.

    Den data som legat till grund för analysen av de energieffektiviseringsåtgärder som utförts har funnits samlad i eRoom, Siemens plattform för EPC-projekt. Den information som varit mest essentiell har varit de projektutvecklingsrapporter som för varje objekt beskrivit läge, problembild, åtgärdsförslag samt de energikartläggningar som innehållit alla energiberäkningar för energiläget i respektive fastighet samt potentiellt energiläge efter utförande av föreslagna åtgärder. De åtgärder som ansågs relevanta för att på det mest tydliga vis beskriva resultatet av Umeå EPC-projekt beslutades få ligga till grund för att reda ut hur besparingsfördelningen såg ut.

    Resultatet av detta arbete visar att de åtgärder som levererade störst del av den totala besparingen i ren energi var åtgärder kopplade till fläktar samt övriga åtgärder där styråtgärder av motorvärmare, injusteringar och pumpar rymdes. Efter dessa poster var tilläggsisolering samt belysningsåtgärder stora. Vidare vad gäller den ekonomiska besparingen var det konverteringar av uppvärmning som var absolut störst, därefter fläktarbeten samt kategorin övriga poster.

    Den ekonomiska investeringen var svår att på ett rättvist sätt jämföra mot hur stora besparingarna varit per åtgärd. En jämförelse av besparing mot antal åtgärder inom varje kategori visar däremot att konvertering till fjärrvärme samt värmeåtervinning var de mest effektiva åtgärderna. 

  • 19612.
    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.

  • 19613.
    Öhrman, Rickard
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energieffektivisering av Forsbacka oljesystem2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Skellefteå Kraft owns and operates the district heating network in the town of Lycksele. For this they have two sites, Skogsbacka CHP plant and Forsbacka heating plant. Forsbacka is the smaller plant with four boilers, two wood chip boilers and two that are oil-fired. The Forsbacka plant is mainly used during summer and at peak loads. For storage and supply of oil to the oil-fired boilers there are two 100 m3 cisterns. The oil system is old and built for heavy oil, which means that the oil has to be kept at minimum temperature of 35°C

    The aim of this report is to examine possible measures to make the storage and handling of the oil more energy and cost efficient.

    The results show that it would be a good idea to change to light oil and thus be able to lower the oil temperature to at least 20°C. This would halve the cost for keeping the oil warm, whereas an increased insulation of the cisterns would not be cost efficient. Another recommended measure for energy saving would be to install frequency converter for speed regulation of the oil pumps, which would reduce the energy use to halve.

  • 19614.
    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.

  • 19615. 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.

  • 19616.
    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.

  • 19617.
    Ölund, Andreas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Informationslager för stora mängder SNMP-data2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    TeliaSoneras internet operations center has a great need to quickly collect statistical data of nodes and costumer connections, collected data is then used to troubleshoot and repair problems in the network. To secure a reliability and quality that is demanded, one of the systems need to be further developed. The application that has been developed is intended to improve the collection and storage of the statistical data to speed up the quality analysis of the xDSL network. Requirements of the application development are that the collection, conversion and storage are that all parts should be horizontally scalable. During development of the application, concepts like multithreading, message queues, messaging patterns, JSON/BSON and NoSQL has been acquired. Results of the project are a prototype written in PHP. Its function is from a messaging pattern where a Client reads an file containing connection data. The Client then serializes this data and sends a request to the Job server. The Job server then receives the request and sends the workload to a ready Worker. The Worker receives the workload and deserializes the connection data. The Worker connects to the node specified in the request from the client and collects the SNMP-data and makes error checks before the Worker returns the results to the Client. In the end of the report future work is discussed of how the prototype can be further developed to be implemented in a production level.

  • 19618.
    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!

  • 19619.
    Ölund, Viktor
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mobilapplikation för driftinformation och analysverktyg2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    TeliaSonera has many subsystems to analyze the quality of TeliaSonera's network. Some of the main subsystems is ADSL-analys and Mibview.

    An ADSL analysis shows the current status of sync, broadband speeds, bit error, signal-to-noise ratio, attenuation and retrains on customers in TeliaSonera's network.

    Mibview is a measurement which lasts for three days and demonstrating graphs in different categories, the graphs show data minute by minute during the day the measurement is made. Some of the most commonly used graphs of the analysis is

    IfOperStatus -Displays the status of the sync

    CurrBrAtuc -Sync speed

    Curr24CvAtuc -Incoming bit error

     

    Today TeliaSonera's technicians have a great need to use these subsystems to take quicker decisions when technicians are working on customer assignments.

    Currently the subsystems exists in the form of technical support in computer systems.

     

    The requirement of the project is therefore to develop an application that receive these subsystems to TeliaSonera technicians.

    The conclusion of the project is a mobile application developed in android operating system with the subsystems ADSL analys and Mibview, where technicians voluntarily can utilise the subsystems.

    The mobile app is designed to execute requests against scripts in servers to retrieve stored data from databases.

    In the end of the report there are mentioned suggestions for improvements of the app to be deployed in production.

  • 19620.
    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.

  • 19621.
    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)
  • 19622.
    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.

  • 19623.
    Önnerlöv, Jonathan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Montageplattform: För inredning av två vertikala ventilationsschakt i Garpenbergs gruva2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The company Bergteamet, Boliden, Sweden, is installing ventilation shafts of the Garpenberg mine. For such work a platform is needed which you can stand on and work from. The Shaft Reinforcement Team at Bergteamet performs the installation work and is the sponsor of the platform. The project described in this report is performed at the department MEC, Mining Equipment Construction, which has been given the task to design and construct the platform, customized for the current shaft. After this the platform is manufactured and inspected at the workshop at Bergteamet.

    The design work was carried out as follows:

    - After an initial meeting a requirement specification was worked out, describing the problem and previous experiences of platforms and requirements for the design and equipment.

    - A concept sketch was developed with consideration of surrounding factors.

    - A constructed 3D model was presented along with the choice of materials. Improvements were made after feedback from Bergteamet.

    - Development of production drawings. The drawings were reviewed and handed over to the preparer for manufacturing.

     

    The result was a platform designed with different square tubes where the floor follows the geometrical shape of the shaft. The platform is suspended from a rectangular center tube with dimensions 100x100x8, which is centered in the shaft. The purpose of a center tube is that it facilitates the final stage of the work in the shaft, namely the installation of a fall protection. The platform has a roof to protect from stone rain and dripping water. Under the floor is an air tank places to run the air-powered outriggers. Around the workplace there is a guardrail with a door for access and egress. The design work was done using the drawing program SolidWorks. Calculations were made by hand.

    The platform fulfills the requirements defined by the trade organization for mine elevators in Sweden, (BRAGS), as well as Bolidens for the design and Bergteamets internal design requirements. The platform has been manufactured, inspected and soon filled its purpose for the shaft installation in the Garpenberg mine.

  • 19624.
    Önnerlöv, Lisa
    Umeå University, Faculty of Science and Technology, Umeå Institute of Design.
    Användarorienterad förarsituation för bergavläsning vid fjärrstyrt skrotningsarbete2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Mechanical scaling is one of the most complex operations of all in the mining process. The operators are using both hearing, sight and feel to read the rock and to know where to scale and where to leave. They say they go on gut feeling in great extent, something that comes with experience. The scaling machine is placed into the edge of unsecured and newly blasted rock to hammer off the blocks that has become loose after the blast, but not enough to fall down. It goes without sayingthat it is a risky job. Boliden Mineral has a desire to remotely control this operation from above ground and thus became this challenge a degree project in industrial design. With a focus on ease of use and the sensory feedback, the project aims to develop a proposal on the driver situation that allows the operator to do an as equally good job above as below ground.

  • 19625.
    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.

  • 19626.
    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.

  • 19627.
    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.

  • 19628.
    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.

  • 19629.
    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.

  • 19630.
    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.

  • 19631.
    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)
  • 19632.
    Öquist, Gunnar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Benner, M.
    Why are some nations more successful than others in research impact?: a comparison between Denmark and Sweden2015In: Incentives and Performance: Governance of Research Organizations / [ed] Isabell M. Welpe, Jutta Wollersheim, Stefanie Ringelhan, Margit Osterloh, Springer, 2015, p. 241-257Chapter in book (Other academic)
    Abstract [en]

    Bibliometric impact analyses show that Swedish research has less international visibility than Danish research. When taking a global view on all subject fields and selecting publications cited higher than the 90th percentile, i.e., the Top 10 %—publications, the Swedish Research Council shows that although Sweden ranks 15 % above world average, Denmark, the Netherlands and Switzerland rank 35–40 % above. To explain these different performances, The Royal Swedish Academy of Sciences asked us to compare the national research systems on three levels: priority setting at national level, governance of universities and direction and funding of research. There are of course many similarities between the Danish and Swedish research systems but there are still subtle differences that have developed over time, which may explain the different international visibility. First of all, it does not depend on different levels of public spending on research and development. However, the core funding of universities relative external funding is higher in Denmark than in Sweden. The academic leadership of Danish universities in terms of board, vice-chancellor, faculty dean and department chair is also more coherent and focused on priority setting, recruitment, organization and deployment of resources to establish research environments that operate at the forefront of international research. On all these points we see a weaker leadership in Sweden. Furthermore, over the last 20 years, public funding of research in Sweden has become more and more unpredictable and program oriented with many new actors, while the Danish funding system, although it also has developed over time, shows more consistency with strong actors to fund individuals with novel ideas. The research policy in Sweden has also developed multiple, sometimes even conflicting goals, which have undermined conditions for high-impact research, while in Denmark a policy to support excellence in research has been more coherent.

  • 19633.
    Öquist, Gunnar
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Huner, Norman P.A.
    Department of Plant Sciences, University of Western Ontario, London, Canada.
    Photosynthesis of overwintering evergreen plants2003In: Annual Review of Plant Physiology and Plant Molecular Biology, ISSN 1040-2519, E-ISSN 2331-0960, Vol. 54, p. 329-355Article, review/survey (Refereed)
    Abstract [en]

    In this review we focus on photosynthetic behavior of overwintering evergreens with an emphasis on both the acclimative responses of photosynthesis to cold and the winter behavior of photosynthesis in conifers. Photosynthetic acclimation is discussed in terms of the requirement for a balance between the energy absorbed through largely temperature-insensitive photochemical processes and the energy used for temperature-sensitive biochemical processes and growth. Cold acclimation transforms the xanthophyll-mediated nonphotochemical antenna quenching of absorbed light from a short-term dynamic response to a long-term sustained quenching for the whole winter period. This acclimative response helps protect the evergreen foliage from photooxidative damage during the winter when photosynthesis is restricted or prevented by low temperatures. Although the molecular mechanisms behind the sustained winter excitation quenching are largely unknown, it does involve major alterations in the organization and composition of the photosystem II antenna. In addition, photosystem I may play an important role in overwintering evergreens not only by quenching absorbed light photochemically via its support of cyclic electron transport at low temperatures, but also by nonphotochemical quenching of absorbed light irrespective of temperature. The possible role of photosystem II reaction centers in nonphotochemical quenching of absorbed energy in overwintering evergreens is also discussed. Processes like chlororespiration and cyclic electron transport may also be important for maintaining the functional integrity of the photosynthetic apparatus of overwintering evergreens both during periods of thawing in winter and during recovery from winter stress in spring. We suggest that the photosynthetic acclimation responses of overwintering evergreens represent specific evolutionary adaptations for plant species that invest in the long-term maintenance of leaf structure in cold climatic zones as exemplified by the boreal forests of the Northern Hemisphere.

  • 19634. Öquist, Mats G.
    et al.
    Erhagen, Björn
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Forest Ecology & Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
    Haei, Mahsa
    Sparrman, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ilstedt, Ulrik
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Mats B.
    The effect of temperature and substrate quality on the carbon use efficiency of saprotrophic decomposition2017In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 414, no 1, p. 113-125Article in journal (Refereed)
    Abstract [en]

    Background and aims: Mineralization of soil organic matter (SOM) constitutes a major carbon flux to the atmosphere. The carbon use efficiency (CUE) of the saprotrophic microorganisms mineralizing SOM is integral for soil carbon dynamics. Here we investigate how the CUE is affected by temperature, metabolic conditions, and the molecular complexity of the substrate.

    Methods: We incubated O-horizon soil samples (with either 13C–glucose or 13C–cellulose) from a boreal coniferous forest at 4, 9, 14, and 19 °C, and calculated CUEs based on the amount of 13C–CO2and 13C–labelled microbial biomass produced. The effects of substrate, temperature, and metabolic conditions (representing unlimited substrate supply and substrate limitation) on CUE were evaluated.

    Results: CUE from metabolizing glucose was higher as compared to cellulose. A slight decrease in CUE with increasing temperature was observed in glucose amended samples (but only in the range 9–19 °C), but not in cellulose amended samples. CUE differed significantly with metabolic conditions, i.e. CUE was higher during unlimited growth conditions as compared to conditions with substrate limitation.

    Conclusions: We conclude that it is integral to account for both differences in CUE during different metabolic phases, as well as complexity of substrate, when interpreting temperature dependence on CUE in incubation studies.

  • 19635. Öquist, Mats
    et al.
    Sparrman, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Klemedtsson, Leif
    Harrysson Drotz, Stina
    Grip, Harald
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Mats
    Water availability controls microbial temperature responses in frozen soil CO2 production2009In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 15, no 11, p. 2715-22Article in journal (Refereed)
    Abstract [en]

    Soil processes in high-latitude regions during winter are important contributors to global carbon circulation, but our understanding of the mechanisms controlling these processes is poor and observed temperature response coefficients of CO2 production in frozen soils deviate markedly from thermodynamically predicted responses (sometimes by several orders of magnitude). We investigated the temperature response of CO2 production in 23 unfrozen and frozen surface soil samples from various types of boreal forests and peatland ecosystems and also measured changes in water content in them after freezing. We demonstrate that deviations in temperature responses at subzero temperatures primarily emanates from water deficiency caused by freezing of the soil water, and that the amount of unfrozen water is mainly determined by the quality of the soil organic matter, which is linked to the vegetation cover. Factoring out the contribution of water limitation to the CO2 temperature responses yields response coefficients that agree well with expectations based on thermodynamic theory concerning biochemical temperature responses. This partitioning between a pure temperature response and the effect of water availability on the response of soil CO2 production at low temperatures is crucial for a thorough understanding of low-temperature soil processes and for accurate predictions of C-balances in northern terrestrial ecosystems.

  • 19636. Öquist, M.G.
    et al.
    Laudon, Hjalmar
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Winter soil frost conditions in boreal forests control growing season soil CO2 concentration and its atmospheric exchange2008In: Global Change Biology, Vol. 14, no 12, p. 2839-2847Article in journal (Refereed)
    Abstract [en]

    The impact of changes in winter soil frost regime on soil CO2 concentration and its atmospheric exchange in a boreal Norway spruce forest was investigated using a field-scale soil frost manipulation experiment. The experiment comprised three treatments: deep soil frost, shallow soil frost and control plots (n = 3). Winter soil temperatures and soil frost distribution were significantly altered by the different treatments. The average soil CO2 concentrations during the growing season were significantly lower in plots with deep soil frost than in plots with shallow soil frost. The average CO2 soil-atmosphere exchange rate exhibited the same pattern, and differences in soil respiration rates among the treatments were statistically significant. Both the variation in soil CO2 concentration and the CO2 soil-atmosphere exchange rate could statistically be explained by the differences in the maximum soil frost depth during the previous winter. A response model for growing season soil respiration rates suggests that every 1 cm change in winter soil frost depth will change the emission rates by ca. 0.01 g CO2 m(-2) day(-1), corresponding to 0.2-0.5% of the estimated net ecosystem productivity (NEP). This suggests that the soil frost regime has a significant influence on the C balance of the system, because interannual variations in soil frost up to 60 cm have been recorded at the site. We conclude that winter climate conditions can be important in controlling C balances in northern terrestrial ecosystems, and also that indirect effects of the winter season must be taken into account, because these can affect the prevailing conditions during the growing season.

  • 19637.
    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
  • 19638.
    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.

  • 19639.
    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.

  • 19640.
    Örestig, Johan
    et al.
    Umeå University, Faculty of Social Sciences, Department of Education.
    Bäckström, Hanna
    Umeå University, Faculty of Social Sciences, Umeå Centre for Gender Studies (UCGS).
    Persson, Erik
    Umeå University, Faculty of Science and Technology, Umeå School of Architecture.
    EU-migrantdebatten som ideologi2015In: Fronesis, ISSN 1404-2614, no 52-53, p. 240-252Article in journal (Other (popular science, discussion, etc.))
  • 19641.
    Örjansen, Beate
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kan probiotika forebygge utviklingen av eller behandle atopisk eksem hos barn?2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 19642.
    Örnberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fartygsanslutningar till landströmsnätet I Umeå hamn2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When ships are at dock they burn their fuel to generate electricity onboard, causing air and noise pollution in the port area. The pollution obtains negative effects on people, the environment and gives the community high costs. One solution to reduce these pollutions is to connect the ships to the on land electrical grid; this method is called cold ironing. To see if this is a solution the grid owner Umeå Energi has to investigate the condition of the grid for ship connection.The thesis is done with a background of six ships on three wharves with a power requirement of 3,755 MVA. The report suggests two potential solutions for engaging the shore, one with the wind power cable and the other with the nearest grid for the ports. The investigation showed a strong grid and an expansion of the grid for the cold ironing would need an investment for 800 thousand up to 1,7 million Swedish kronor, depending on the choice of solution. To find out the benefits for cold ironing in the area for environmental and social cost reduction. There is three wind power plants near Umeå harbor and they produced year 2014 13, 9 GWh, while the estimated energy consumption for the vessels is at 3, 95 GWh. Wind energy production is not continuous and other energy sources is needed. The cables in the harbor are connected to Holmsund distribution station which can supply the vessels at low wind power production. When connected to shore power the price of electricity for ships is less expensive when cold ironing instead of on board generation.Emissions at the shore could reduce to over 98% compared with fuel generated electricity. The reduction in emissions provides economic savings through lower social costs due to better health for people, the environment and nature. This proves that cold ironing can help to greatly reduce emissions in areas around the port and reduce costs.

  • 19643.
    Örnberg, Lina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effektivisering av byggservice, PEAB2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    All businesses in today’s society are constantly striving to develop their agency to keep up with the competition. For a company to be among the best in the industry, they must not only keep pace with the others, but also lead the development. This work has been about increasing Peab byggservice opportunities to be among the best, using only simple instruments. The focus has been on developing equipmentthat can simplify the documentation of materials, machines and hours worked, but also the management of trailers. It has also been on developing technical facilities and organizing the storage area that is connected to building service. Some parts work in the current situation quite well while others do not. In order to achieve better results within a business you have to both streamline what works good and bad. With the streamline new features was developed such as templates, forms and agreements, in order to simplify the work of supervisors in terms of summaries and compilations of the project. In addition there were also technical instruments in form of apps developed to digitize a large amount of project information that supervisors need access to. This proved to give a very positive effect in supervisors’ daily work, with better access to information and greater flexibility. In addition, a disposition-drawing plan was created to improve conditions so that in the future larger amount of materials can be bought and stored within their own premises. By buying larger bathes of materials it’s easier to keep expenses for material and transportations down, resulting in a more efficient use of resources and assets. These facilities will serve as basis for a more effective and progressive way of working in building services.

  • 19644.
    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
  • 19645. Örtenblad, Marcus
    et al.
    Parola, Stephane Chaput, Frédéric Desroches, Cédric Sigala, Catherine Létoffé, Jean Marie Miele, Philippe Baldeck, Patrice L. Eliasson, Bertil Umeå University, Faculty of Science and Technology, Chemistry.Eriksson, Anders Lopes, Cesar
      Hybrid Materials for Optical Limiting        2005Conference proceedings (editor) (Other academic)
    Abstract [en]

    Optical limiting materials based on alkynyl platinum derivatives and thiacalixarenes were produced using the sol-gel process. The molecular species were grafted to the matrix (class II hybrid) in order to maximise the concentration and the stability of the material. Broadband optical limiting performances in the visible wavelength region was observed in the prepared materials. Thermomechanical characterisation of the matrix will also be discussed.

  • 19646.
    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)
  • 19647.
    Östberg, Per-Olov
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Architectures, design methodologies, and service composition techniques for Grid job and resource management2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The field of Grid computing has in recent years emerged and been established as an enabling technology for a range of computational eScience applications. The use of Grid technology allows researchers and industry experts to address problems too large to efficiently study using conventional computing technology, and enables new applications and collaboration models. Grid computing has today not only introduced new technologies, but also influenced new ways to utilize existing technologies.This work addresses technical aspects of the current methodology of Grid com- puting; to leverage highly functional, interconnected, and potentially under-utilized high-end systems to create virtual systems capable of processing problems too large to address using individual (supercomputing) systems. In particular, this thesis studies the job and resource management problem inherent to Grid environments, and aims to contribute to development of more mature job and resource management systems and software development processes. A number of aspects related to Grid job and resource management are here addressed, including software architectures for Grid job management, design methodologies for Grid software development, service composition (and refactorization) techniques for Service-Oriented Grid Architectures, Grid infrastructure and application integration issues, and middleware-independent and transparent techniques to leverage Grid resource capabilities.The software development model used in this work has been derived from the notion of an ecosystem of Grid components. In this model, a virtual ecosystem is defined by the set of available Grid infrastructure and application components, and ecosystem niches are defined by areas of component functionality. In the Grid ecosys- tem, applications are constructed through selection and composition of components, and individual components subject to evolution through meritocratic natural selection. Central to the idea of the Grid ecosystem is that mechanisms that promote traits beneficial to survival in the ecosystem, e.g., scalability, integrability, robustness, also influence Grid application and infrastructure adaptability and longevity. As Grid computing has evolved into a highly interdisciplinary field, current Grid applications are very diverse and utilize computational methodologies from a number of fields. Due to this, and the scale of the problems studied, Grid applications typically place great performance requirements on Grid infrastructures, making Grid infrastructure design and integration challenging tasks. In this work, a model of building on, and abstracting, Grid middlewares has been developed and is outlined in the papers. In addition to the contributions of this thesis, a number of software artefacts, e.g., the Grid Job Management Framework (GJMF), have resulted from this work.

  • 19648.
    Östberg, Per-Olov
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Virtual infrastructures for computational science: software and architectures for distributed job and resource management2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In computational science, the scale of problems addressed and the resolution of solu- tions achieved are often limited by the available computational capacity. The current methodology of scaling computational capacity to large scale (i.e. larger than individ- ual resource site capacity) includes aggregation and federation of distributed resource systems. Regardless of how this aggregation manifests, scaling of scientific compu- tational problems typically involves (re)formulation of computational structures and problems to exploit problem and resource parallelism. Efficient parallelization and scaling of scientific computations to large scale is difficult and further complicated by a number of factors introduced by resource aggregation, e.g., resource heterogene- ity and coupling of computational methodology. Scaling complexity severely impacts computation enactment and necessitates the use of mechanisms that provide higher abstractions for management of computations in distributed computing environments.This work addresses design and construction of virtual infrastructures for scientific computation that abstract computation enactment complexity, decouple computation specification from computation enactment, and facilitate large-scale use of compu- tational resource systems. In particular, this thesis discusses job and resource man- agement in distributed virtual scientific infrastructures intended for Grid and Cloud computing environments. The main area studied is Grid computing, which is ap- proached using Service-Oriented Computing and Architecture methodology. Thesis contributions discuss both methodology and mechanisms for construction of virtual infrastructures, and address individual problems such as job management, application integration, scheduling job prioritization, and service-based software development.I addition to scientific publications, this work also makes contributions in the form of software artifacts that demonstrate the concepts discussed. The Grid Job Manage- ment Framework (GJMF) abstracts job enactment complexity and provides a range of middleware-agnostic job submission, control, and monitoring interfaces. The FSGrid framework provides a generic model for specification and delegation of resource allo- cations in virtual organizations, and enacts allocations based on distributed fairshare job prioritization. Mechanisms such as these decouple job and resource management from computational infrastructure systems and facilitate the construction of scalable virtual infrastructures for computational science.

  • 19649.
    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)
  • 19650.
    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.

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