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  • 251.
    Lavén, Rasmus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Ultra-Thin Ag Films on the Sn/Si(111)-√3×√3 Surface Studied by STM2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The growth of atomically flat silver films on Si(111) usually requires a two-step growth, including deposition at low temperature (≈100 K) followed by slowly annealing to room temperature. In addition, flat silver films are usually only obtained on Si(111) for film thicknesses larger than the critical thickness of 6 monolayer. In this work, Ag thin film formation at ambient temperature on Sn/Si(111)-√3×√3 has been investigated experimentally using a combination of scanning tunneling microscopy, scanning tunneling spectroscopy and low-energy electron diffraction. The first buffer layer, probably consisting of both Ag and Sn, formed a partially ordered structure consisting of atomic rows which mainly followed the high-symmetry directions of the underlying Si(111) lattice. From 3 ML coverage, an atomically flat Ag film was formed. Low-energy electron diffraction confirmed that the films grew in the [111]-direction. This shows that atomically flat Ag films as thin as 3 ML can be grown on Sn/Si(111)-√3×√3 by conventional deposition at room temperature. The electronic structures of the films were studied for a range of different coverages by scanning tunneling spectroscopy. The normalized tunneling conductance showed quantum well states in the occupied electronic states, which moved towards the Fermi energy with increasing film thicknesses. 

    Fulltekst (pdf)
    Arkivfil
  • 252.
    Leguillon, Prune
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Using infrared cameras in education2019Rapport (Annet vitenskapelig)
    Abstract [en]

    Previous researches about the use of Infrared cameras in education are presented. The first part is more focused on Physic applications. Different approaches are discussed like letting the students discovering phenomena by following a protocol or letting them discover it by themselves in an open-ended lab. The question about at which grade are Infrared cameras useful is also discussed. Then the second part deals with applications of Infrared cameras in Biology. It talks about many fields like plants and medicine for both humans and animals. After that, infrared pictures which were taken during biological phenomena exploration are presented and analyzed. It deals with some everyday biological phenomena and some explanations are given. To conclude, a presentation of some basic phenomena which are made viewable by the Infrared camera is done and some advantages and drawbacks of this device are explained.

    Fulltekst (pdf)
    fulltext
  • 253.
    Lennartsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Förbättring av Barillas interna materialflöde: Huvudfokus mot produktionslinje 192014Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Som en del i Maskiningenjörsutbildningen vid Karlstads Universitet har detta examensarbete utförts under höstterminen 2013. Uppdragsgivaren är Barillagruppen som är världens största producent av pasta och pastasåser samt Europas ledande bagerikoncern. I Sverige känner vi främst igen varumärkena Barilla och Wasa, den senare är världens största producent av knäckebröd. Produkter med varumärket Wasa produceras idag vid fabrikerna i Filipstad och i Celle i Tyskland. Det är i fabriken i Filipstad som detta examensarbete är utfört.

    Arbetets utformning har skett till en början genom att undersöka och bekanta sig med fabriken och dess processer. En nulägesanalys skapades för att identifiera de områden som har stor förbättringspotential, vid nulägesanalysen analyserades främst transporter, lagerplatser och transporttider.

    Ett förbättringsarbete på produktionslinje 19 arbetades fram utifrån den data och informationsom nulägesanalysen gett. Utformningen av det befintliga mellanlager som idag används vid linjen, arbetades om till ett mer standardiserat lager. Materialet som går igenom lagret kommer att användas enligt metoden FIFO, ”First in first out” på ett mycket bättre sätt än tidigare. Transporttiden är reducerad med 9,54 timmar per vecka för de 2 främst använda förpackningsmaterialen till PL18-19, nämligen well och innerpapper.

    Det har även getts ett nytt layoutförslag som skulle förbättra materialflödet i paketeringen genom kortare transportsträckor, tydligare beläget lager och lättåtkomlighet för de transport och servicemän som ansvarar för transporten av förpackningsmaterial i fabriken.

    Fulltekst (pdf)
    fulltext
  • 254.
    Lestelius, Magnus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013), Paper Surface Centre.
    Nyflött, Åsa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Järnström, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013), Paper Surface Centre.
    Carlsson, Gunilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Bonnerup, Chris
    Govindarajan, Venkatesh
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Oxygen permeabilityand economic-environmental impact studies of some polyvinyl alcohol dispersionbarrier coatings for packaging applications2017Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Purposes of employing barrier coatings in packaging, and in particular food packaging, can be to increase the shelf life, preserve colour, odour, and taste, and to protect from a harmful environment in general. Barrier coatings can thus help to reduce food waste along the value chain until end use. Including both materials choice for packaging and the possible fates of the used package, even further steps to provide greater knowledge for decisions on choices of packaging solutions. To that end, we have conducted several experimental and transport modeling studies on oxygen barrier coatings performance. The coating system of choice    has been dispersion coatings of poly vinyl alcohol (PVOH), with additions of kaolin. Physical and chemical features of the coatings were characterized to obtain information on polymer crystallinity, free volume and filler orientation as these characteristics are influential to the oxygen mass transport performance. In turn, the oxygen mass transport was also measured, both in steady state and dynamically. In so doing, we obtained information    useful for developing a general model to describe the oxygen permeability taking into account the physical and chemical features, described above, of the coating layer. Attempts on describing the interdependence and impact, for instance between crystalline and amorphous polymer regions and moisture, was added to the model. The model showed agreement to experimental data for PVOH-kaolin coating in this particular case. However, the basic permeability model has been applied to  many different polymers.

    To further explore the potential of these types of coating, which are technically possible to    produce in paperboard production, an economic-environmental impact comparison to other existing material solutions was made. Four barrier material alternatives – starch, polyethylene, ethyl vinyl alcohol (chosen as an alternative for PVOH, where data was difficult to obtain) and kaolin, and latex and kaolin, were analyzed with respect to cost and global warming potential. Weighting and comparing cost to environmental aspect, weighting    factors based on interviews with experts in the packaging value chain, starch emerges as the most sustainable alternative. However, previous coating and mass transport studies also shows how these renewable materials require some further technical development to be competitive.

    The mass transport model can serve as a tool for customizing barrier coatings and to predict the barrier performance, as permeability is obtained and thus shelf-life estimation is    possible. The overall concept, the combination of assessment of structural performance and the environmental studies, can be employed to find sustainable food packaging solutions.

  • 255.
    Li, Felicia
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Study of Gear design Concept to Reduce Root Bending- & Contact Stresses for Automotive Transmission2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Advanced technologies for the automotive industry require improved designed precision in different areas. Research is needed in order to meet customer demand and satisfaction to increase durability, efficiency, and reliability. That is why continuous development in transmission system has been an exciting topic for many years. The gears in the transmission system demand high resistance against repeated loads acting on the teeth and the ability to engage without energy loss. The intention is to support that effort by investigating seven design cases of a parallel helical gear pair.

    This master thesis aims to study a gear design concept of adding a supporting ring to reduce the root bending- and contact stresses. To implement this study, seven different design cases were modelled to study the effect of changing the design. One or two support ring structures were added, or the thickness was increased of the gear considered exposed to high stresses. The purpose is to gain a comparative advantage in the automotive industry. M1 is a reference standard design, while the other models (M2-M5/P1-P3) are modified designs with additional rings or changed in thickness. Simulation is an effective and an useful tool to understand and visualize how the complex interaction of the transmission component appears to be. A finite element method (FEM) program was used to investigate these models. The gear pairs were imported into the pre-processor ANSA, the FEM program Abaqus 2017 was used as a solver, and the results were extracted from the post-processor META.

    To support the aim of this thesis, two of the seven FEM models were validated against a specialized gear calculated program, WindowsLDP, in order to determine the robustness of the simulation models. The transmission error (TE) measurements, root bending- and contact stresses were observed for the validation.

    Introducing the different models M3-M5 and P1-P3, the root and contact stresses were reduced by 1.2-4.4 and 0.07-4.3 %, respectively, compared to M1. The transmission error TE could differ as much as 85% in M2-M3 as compared to M1. Systematic errors were generated in model M2, therefore the low root stresses obtained in M2 should be considered carefully. Implementing the so-called misalignment measurement, tilting parameter, microgeometry, and profile modification related to crowning and tip relief is discussed and believed to reduce TE measurements, root- and contact stresses. These modifications have not been studied in this thesis. The LDP results showed a trend of higher values compared to the FEM results, which was suggested to be further investigated in the future.

    Fulltekst (pdf)
    fulltext
    Fulltekst (pdf)
    Arkivfil
  • 256.
    Li, Kaiyuan
    et al.
    Aalto university Finland.
    Mousavi, Mahmoud
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hostikka, Simo
    Aalto university Finland.
    Char cracking of medium density fibreboard due to thermal shock effect induced pyrolysis shrinkage2017Inngår i: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 91, s. 165-173, artikkel-id SIArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pyrolysis experiments were conducted on medium density fibreboard (MDF) in inert atmosphere and different ambient pressures, to investigate the char shrinkage and cracking. It is found that the char cracking under uniform heat flux is a typical thermal shock process induced by unbalance shrinkage along the sample thickness during pyrolysis. To predict the number of char fissures, the critical stress criterion and energy conservation theory are used to develop mathematical models under plane constitutive stress state, which reveal that under the same surface degradation the number of char fissures (blisters) strongly relates to the pyrolysis depth at cracking time. Increasing external heat flux decreases the pyrolysis depth and increases the number of char fissures. Both experiments and numerical modelling are used to validate the models. The experimental results show that the horizontal shrinkage is 11% of original length and the micro-structure of char fissures of MDF is less uniform compared to the one of natural wood with a cellular pattern. The surface stresses after cracking are found similarly close to the tensile strength under different heat fluxes, while the surface stresses are very different assuming no crack, which indicates the cracking process reduces the surface stress to lower than the tensile strength. The modelled cracking times are different from the observed cracking time as the fissures are hard to identify at its initial stage and only when they have expanded to certain size the fissures are visually observed. Using the modelled cracking time, the number of char blisters can be well correlated with the pyrolysis depth.

  • 257.
    Lidström, Wilhelm
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Konceptframtagning av bas-högtalare för utbyggnadsbart ljudsystem: Produktutveckling med ett styrt formspråk och användaren i fokus2017Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Sound Dimension ämnar att starta upp utvecklingen av nästa produkt till deras varumärke aiFi. Idag är aiFi en smart högtalare som när flera placeras tillsammans skapar ett utbyggnadsbart ljudsystem. Sound Dimension söker nu nästa produkt till aiFi familjen och vill ha hjälp att ta fram ett koncept för denna. I kombination med utveckling av det nya konceptet vill de även ha hjälp med att identifiera problem kring användandet av dagens produkt och få förslag på hur dessa kan förbättras.

     

    I rapporten behandlas produktutvecklingsprocessen av ett nytt koncept i kombination med användarstudier och implementering av förändringar i ett redan styrt formspråk. Projektet är ett examensarbete vid Karlstads universitet för högskoleingenjörsprogrammet i innovationsteknik och design, MSGC12. Projektet motsvarar 22.5hp och utförs vid fakulteten hälsa, natur- och teknikvetenskap. Rapporten är skriven av Wilhelm Lidström, handledare industridesigner Kristina Gullander och examinator professor Leo De Vin.

     

    Under processen har skiss och modellarbete använts flitigt för att dokumentera processen och för att testa och visualisera olika idéer. Modeller har byggts både för att verifiera former och proportioner samt testa funktioner. Det slutliga konceptet presenteras i skiss, 3D-format med renderade bilder samt i form av en enkel fysisk prototyp.

     

    Det slutliga konceptet utgår från att uppfylla den kravspecifikation som framkommit under projektet. Kravspecifikationen har skapats utifrån de krav och önskemål uppdragsgivaren hade på projektet, samt en gedigen förstudie innehållande en litteraturstudie kring intressanta områden projektet berör. Ett stort antal intervjuer genomförs med fokus på hur dagens produkt uppfattas och användarvänligheten, både utifrån befintliga användare och personer som aldrig tidigare varit i kontakt med produkten för att få en så bred bild som möjligt av uppfattningen om dagens produkt.

     

    Resultatet är ett koncept med en form och storlek som gör den kompatibel med dagens produkt. Manöverpanelen har fått en ny position och ett förenklat gränssnitt vilket gör produkten tydligare både ur ett semantisktpersketiv och användarsynpunkt.

    Fulltekst (pdf)
    fulltext
  • 258.
    Lind, Sebastian
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Recombination losses in organic solar cells: Study of recombination losses in organic solar cells by light intensity-dependent measurements2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Easy manufacturing, light weight and inexpensive materials are the key qualities of organic solar cells that makes them a highly researched area. To make organic solar cells adequate for the market, the efficiency of power conversion has to increase further, and the lifetime of organic solar cells has to improve. Avoiding recombination losses is a piece in the puzzle that can make organic solar cells more efficient. Organic solar cells with two different hole transport layers were therefore examined by I-V measurements. It was found that the organic solar cell with MoO3 as the HTL possesses a higher current density in both the reverse region and forward region. The higher current density in both regions points towards a less successful blocking of electrons travelling to the anode (reverse region) and a better ability to transport holes from the active layer to the anode. Insight to different state of recombination was also found from the slope values in the Voc and Jsc as a function of light intensity plots. It was concluded that both solar cells experience a dominant monomolecular recombination under short circuit condition and evolved into bimolecular recombination under open circuit condition. However, the cell with CuSCN showed a more dominant bimolecular recombination, which was shown from a slope closer to one unity kT/q in the Voc as a function of light intensity plot.

    Fulltekst (pdf)
    Solar cells
  • 259.
    Lind, Sofia
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Zinklegering i åldrat och kylt tillstånd: Identifiering av parametrar som förändrar materialegenskaperna i Zamak52015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Bilsäkerhet är en viktig fråga i dagens samhälle. Det enklaste sättet att skydda sig vid en bilfärd är genom att använda säkerhetsbälte. En säkerhetsbältesrulle är uppbyggd av flera olika komponenter, en av dessa kallas torque tube som tar energi när kroppen fångas upp av bältet vid en eventuell kollison. Säkerhetsbältet ska skydda passagerarna i bilen i många år och vid olika temperaturer. Torque tuben är i detta fall gjuten i en zinklegering som heter Zamak5 som förändrar sina materialegenskaper i åldrat och kylt tillstånd. Målet med arbetet är att hitta de parametrar som förändrar materialegenskaperna i Zamak5.

    Olika metoder användes för att få fram ett resultat på en torque tube som är specialtillverkad med försvagad geometri. Provobjekten som testades var både åldrade och oåldade. Ett pendelprov kan motsvara en kollision mellan ett säkerhetsbälte och en tyngd. För att hitta den kritiska temperatur då Zamak5 förändrar materialegenskaperna gjordes det pendelprov vid olika temperaturer för att se vilka provobjekt som gav brott. Brottytorna studerades sedan i mikroskop för att se vilka parametrar som orsakat egenskapsförändringarna.

    Resultatet visade att brottet var sprött. Det beror på att temperaturen understigit omslagstemperaturen. Det åldrade och kylda provobjektet visade på sämre hållfasthet och detta beror på att inkoherenta partiklar bildats och lagt sig i korngränser och i kritiska skjuvplan.

    Fulltekst (pdf)
    fulltext
  • 260.
    Lindberg, Therese
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Modelling and Evaluation of Distributed Airflow Control in Data Centers2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this work a suggested method to reduce the energy consumption of the cooling system in a data center is modelled and evaluated. Introduced is different approaches to distributed airflow control, in which different amounts of airflow can be supplied in different parts of the data center (instead of an even airflow distribution). Two different kinds of distributed airflow control are compared to a traditional approach without airflow control. The difference between the two control approaches being the type of server rack used, either traditional ones or a new kind of rack with vertically placed servers. A model capable of describing the power consumption of the data center cooling system for these different approaches to airflow control was constructed. Based on the model, MATLAB simulations of three different server work load scenarios were then carried out. It was found that introducing distributed airflow control reduced the power consumption for all scenarios and that the control approach with the new kind of rack had the largest reduction. For this case the power consumption of the cooling system could be reduced to 60% - 69% of the initial consumption, depending on the workload scenario. Also examined was the effect on the data center of different parameters and process variables (parameters held fixed with the help of feedback loops), as well as optimal set point values.

    Fulltekst (pdf)
    fulltext
  • 261.
    Lindgren, Alexander
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Implementeringsutmaningar vid införande av tillståndsbaserat underhåll på reglerventiler inom ett kartongbruk.: En fallstudie utförd på ett kartongbruk i Sverige.2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 262.
    Lindqvist, Camilla
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    van Stam, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Fullerene aggregation in thin films of polymer blends for solar cell applications2018Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, nr 11, artikkel-id 2068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the effects of the film morphology on the fluorescence spectra for a thin film including a quinoxaline-based co-polymer (TQ1) and a fullerene derivative ([6,6]-phenyl-C71-butyric acid methyl ester-PC70BM). The ratio between the polymer and the fullerene derivative, as well as the processing solvent, were varied. Besides the main emission peak at 700 nm in the fluorescence spectra of thin films of this phase-separated blend, a broad emission band is observed with a maximum at 520-550 nm. The intensity of this emission band decreases with an increasing degree of mixing in the film and becomes most prominent in thicker films, films with high PC70BM content, and films that were spin-coated from solvents with lower PC70BM solubility. We assign this emission band to aggregated PC70BM.

    Fulltekst (pdf)
    fulltext
  • 263.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Copper-related light-induced degradation in crystalline silicon2015Doktoravhandling, med artikler (Annet vitenskapelig)
  • 264.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Department of Micro- and Nanosciences, Aalto University.
    Boulfrad, Yacine
    Yli-Koski, Marko
    Savin, Hele
    Preventing light-induced degradation in multicrystalline silicon2014Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 15, artikkel-id 154902Artikkel i tidsskrift (Fagfellevurdert)
  • 265.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Petter, Kai
    Hanwha Q CELLS GmbH.
    Sporleder, Kai
    Fraunhofer Center for Silicon Photovoltaics CSP.
    Turek, Marko
    Fraunhofer Center for Silicon Photovoltaics CSP.
    Pacho, Paolo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Light beam induced current of light-induced degradation in high-performance multicrystalline Al-BSF cells.2017Inngår i: Proceedings of the 7th International Conference on Silicon Photovoltaics, SiliconPV 2017, 3-5 April 2017, Freiburg, Germany / [ed] Ralf Preu, Elsevier, 2017, Vol. 124, s. 99-106Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sponge-LID decreases the Al-BSF cell efficiency by up to 10 %rel. and is only partially recoverable at 200°C. This contributionshows that Sponge-LID occurs at and near most grain boundaries, but only in the centre of the affected cell.  Furthermore,Sponge-LID is not the only type of LID in the silicon bulk. High-resolution Light Beam Induced Current mapping reveals localinternal quantum efficiency losses of up to 8 %rel. at dislocation clusters and small angle grain boundaries, which recover(nearly) fully at 200°C. Nevertheless, this dislocation-related LID appears to reduce the Al-BSF efficiency by less than 1 %rel.

    Fulltekst (pdf)
    Fulltext
  • 266.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Finland.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Review of light-induced degradation in crystalline silicon solar cells2016Inngår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 147, s. 115-126Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Although several advances have been made in the characterization and the mitigation of light-induced degradation (LID), industrial silicon solar cells still suffer from different types of light-induced efficiency losses. This review compiles four decades of LID results in both electronic- and solar-grade crystalline silicon. The review focuses on the properties and the defect models of boron-oxygen LID and copper-related LID. Current techniques for LID mitigation are presented in order to reduce cell degradation and separate copper-related LID from boron-oxygen LID. Finally, the review summarizes recent observations of severe LID in modern multicrystalline silicon solar cells.

  • 267.
    Lindström, Björn
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Metodik för analys av batteriets laddningscykel i entreprenadmaskiner: Prototypbyggnad och teori2015Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Volvo Construction Equipment AB, Volvo CE, är en global tillverkare av entreprenadmaskiner. Detta exjobb fokuserar på batterierna i dessa entreprenadmaskiner som försörjer maskinens elsystem och startmotor vid start.

    Med dagens teknik ställs nya krav på strömförsörjning i entreprenadmaskiner. Den största skillnaden är att förbrukare är igång när motorn är avstängd och strömförsörjningen kommer enbart från batteriet. Ett startbatteri av bly-syra typ är inte konstruerad för detta användningsfall. Volvo CE jobbar därför med att ta fram kunskap om hur laddningen i batterierna används och cyklas under drift.

    Frågeställning om vilka parametrar och trender som är relevanta för att utvärdera batteriladdning har behandlats i detta arbete. Bakomliggande teori har undersökts, förklarats och vidareutvecklats i beskrivningen av den föreslagna metodiken för analys av batteriladdningsnivå i entreprenadmaskiner.

    En metod för hur identifierad relevant mätdata skall extraheras ur entreprenadmaskinerna har beskrivits i samband med beskrivningen av den utvecklade och framtagna prototyputrustningen.

    Den i detta arbete föreslagna analysmetodiken för dimensionering av batterikapacitet och tillämpad på mätdata från batteriladdningen under driftsmässiga förhållanden för entreprenadmaskiner kan också hjälpa till att ge svar på om de batterier som idag används av Volvo CE är lämpliga i den nya generationens entreprenadmaskiner.

    Arbetet innehåller ett nyhetsvärde för Volvo CE och andra då den föreslagna analysmetodiken inte beskrivits eller tillämpats tidigare på Volvo CE. Arbetet ger också förslag på hur man kan gå vidare i kunskapsuppbyggnaden och utvecklingsarbetet kring batterier inom Volvo CE.

    Fulltekst (pdf)
    fulltext
  • 268.
    Lindvall, Fredrik W.
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Study of the influence of contact geometry and contact pressure on sliding distance to galling in the Slider-On-Flat-Surface wear tester2013Inngår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 56, nr 6, s. 1137-1145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the major causes of tool failure in sheet metal forming is wear in the form of galling. Galling is gradual buildup of adhered sheet material on the tool and leads to unacceptable scratches on the sheet surface and to components that fail to meet tolerances. Because it is difficult to reproduce operational and interactional conditions in laboratory test equipments it is hard to test, model, and predict galling initiation.Here the authors examine how changes from elliptical to line contact geometry influenced galling initiation under dry sliding by using a slider-on-flat surface (SOFS) wear tester. A micro clean tool steel was tested against ferritic low-strength and martensitic high-strength steel sheets.The sliding distance to galling initiation was extracted from friction data and verified by scanning electron microscopy (SEM) observations. The presence of adhesive wear on worn tools after completed tests was used as a criterion. Experimental results showed that the elliptical contact causes galling quicker than the line contact.Applicability of experimental results depends on the relevance of test conditions, so contact pressures calculated for the described tests were compared to calculated contact pressures in a semi-industrial U-bending test and to literature data relevant to industrial applications. Good agreement between values observed for SOFS and for most selected industrial applications was found, which assume that contact pressures typical for most common industrial applications can be successfully simulated by selection of tool geometry and normal load in the SOFS tester.

  • 269.
    Lundin, Lukas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Tip vortex cavitation and diffused vorticity of propeller profiles: a modelling approach: Investigation of an implemented TVI model, and  implementation and investigation of a DVH model2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    To predict fluid properties and interactions is an important task for the industry. It is plagued, however, by being close to impossible to predict analytically. Hence, it is customary to turn to numerical solutions. This in itself comes with many different methods and approaches suitable for different needs. This work focuses on two methods: Tip Vortex Index (TVI) and Diffused Vortex Hydrodynamics (DVH). TVI is a method to predict when a marine propeller will experience cavitation of tip vortices and is based on calculations from a Boundary Element Method (BEM). DVH is a particle method for simulating the circulation of a fluid in two dimensions and three dimensions. The aim is to investigate an implemented TVI model based on MPUF-3A for different marine propeller series, with different sub-designs for a total of 28 unique propellers, and implement the DVH method and test it for 3 different bodies. The results of this thesis show that the implemented TVI model is non-functional for the 28 different propellers, but the DVH method is successfully implemented and able to handle 2 different bodies.

    Fulltekst (pdf)
    KAU_LL_TVI_AND_DVH
  • 270.
    Lundskog, Måns
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Analysis of 3D design tools for tubing and piping design: Evaluating E3D and CATIA for on-machine tubing and piping design of paper machines using the analytic hierarchy process2019Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    This thesis covers a degree project for a Bachelor of Science in mechanical engineering degree and is written on behalf of Valmet AB. The purpose of the project is to evaluate and analyse the differences between CATIA and E3D and conclude which of the software is most suitable for on-machine tubing and piping design at Valmet. The tubing and piping modules in CATIA are currently used but is considered somewhat ineffective. E3D is also used at Valmet but in another branch of engineering design, namely field pipe engineering.

    The analysis is done using the analytic hierarchy process (AHP) which is a multi-criteria decision making (MCDM) methodology developed to aid in complex decision-making problems. The methodology follows a six-step process which results in a prioritized ranking or relative weight of both alternatives with respect to the established criteria and sub-criteria for selection. A total of four main criteria and 12 sub-criteria for the selection of the most suitable CAD system were identified and analysed with the help of relevant personnel in various departments such as engineering, purchasing and management

    The results of the project conclude that E3D is the preferred CAD system for on-machine tubing and piping at Valmet with regards to the given criteria and sub-criteria. The criteria that favoured E3D most were the availability of the systems, meaning the possibility that Valmet can outsource projects to consultants, as well as the more effective 3D modelling process. However, the results are not heavily one-sided which suggest that more research should be done before a final decision can be taken.

    The suggested further research includes looking at the in-direct implications of using a new CAD system such as computer updates and the usage of a new PLM system. Moreover, the actual performance of 3D modelling using the two systems is beyond the scope of this thesis and would have to be further researched in another thesis or a pilot case.

    Fulltekst (pdf)
    fulltext
  • 271.
    Malmborg, Petter
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Engine air filter requirements: How different running conditions affect service life2019Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    The internal combustion engine requires clean air in order to operate without problems the entire service life. The air filter acts as a barrier between the ambient air ridden with particulate matter, and the sensitive interior of the engine. Several factors affect the air filter performance, such as pressure drop, efficiency, and dust holding capacity. Many external factors affect the air filter too, such as driving style, engine type, if the car is equipped with hybrid propulsion et cetera.

    The scope for this thesis work aims to extend the knowledge of air filtration for the customer, in this case, Volvo Cars. A comprehensive literature study along with benchmarking of competitors acts as a foundational approach. Regarding air filter service life, three parameters are identified as the most significant: dust holding capacity, efficiency and pressure drop over the filter element.

    Reverse engineering shows some competitor design decisions. A model of estimating air consumption is developed using a data-driven approach with real-world driving data as a basis. The model shows how much the actual air consumption varies between different markets and various engines. As a result, the service lifetime of air filters in certain cars with certain engines may be extended or allow for a smaller filter size for the same service lifetime.

    Fulltekst (pdf)
    fulltext
  • 272.
    Maninnerby, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Simulering av ett elnät med hänsyn till förnybar energi: En studie av möjliga lösningar på problemet med fler elbilar i elnätet2018Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    The purpose of this thesis is to simulate different scenarios where all vehicles are replaced by electric vehicles in the future.

     

    An addition of electric vehicles to the electric grid is not easy to handle, especially not if the consumers choose to charge their vehicles with higher power. As can be seen in the results of this report, flexible demand through power management is a good option to reduce overall power consumption. Of course, customers will have to agree to that their consumption is controlled in this manner.

     

    Using solar cells during the summer works well, but it’s harder wintertime as the largest electric demands arise during the night, when there is close to no sunlight. However, in the case of batteries, they may be helpful. Possibly by letting the solar cells charge the battery during the day and then use it to help charge the electric vehicle during the night. Unfortunately, it was not possible to include this scenario as the used software was unable to handle batteries in that way.

     

    By completely replacing the heat source, in this case with district heating, and thus releasing available power in the transformer, turned out to be the best option. In this way, virtually all predicted amounts of electric cars could be charged with optional charging strength between 3.7 and 11 kW.

     

    As for the T422 transformer, there is no choice but to replace it if a larger number of electric vehicles wants to start charging there. At present, it can handle a maximum of 10-20 electric vehicles that charge at the lowest power as there is only about 50 kW available there winter time.

    District heating cannot be applied either as the connected customers do not use electric heating.

    Fulltekst (pdf)
    fulltext
  • 273.
    Michels, Jasper J.
    et al.
    Holst Centre/TNO, Eindhoven, The Netherlands.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Simulation of Surface-Directed Phase Separation in a Solution- Processed Polymer/PCBM Blend2013Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 46, nr 21, s. 8693-8701Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of the surface-induced stratified lamellar composition profile experimentally evidenced in spincoated layers of the photovoltaic donor–acceptor blend consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole]/phenyl-C61-butyric acid methyl ester (APFO-3/PCBM), as processed from chloroform, is simulated using square gradient theory extended with terms describing the interaction of the blend components with the air and substrate interfaces. The surface energy contributions have been formulated based on an enthalpic nearest-neighbor model which allows integration of common surface tension theory and experimentally accessible surface energies of the fluid phase constituents with a mean field description of a multicomponent blend confined by substrate and air interfaces. Using estimates for the quench depth and transport properties of the blend components as a function of polymer concentration, the time-resolved numerical simulations yield results that compare favorably with experimental observations, both in terms of the number of lamellae as a function of the blend layer thickness and their compositional order. The effect of blend ratio is reproduced as well, the lamellar pattern becoming more pronounced if the amount of PCBM increases relative to APFO-3.

  • 274.
    Mikael, Olsson
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Framtagning och implementering av arbetssätt för utveckling av kostnadseffektiva reservdelar2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Detta examensarbete har utförts som en del av civilingenjörsprogrammet i maskinteknik vid Karlstads Universitet i samarbete med Valmet. För Valmet är försäljning av reservdelar är en vital del av deras totala affär. I avsikt att stärka konkurrenskraften mot kunder i framförallt lågkostnadsländer vill Valmet erbjuda mer kostnadseffektiva lösningar genom att utveckla konstruktionen på befintliga reservdelar. Målet med examensarbetet var därför att ta fram ett systematiskt arbetssätt för produktutveckling av kostnadseffektiva reservdelar och validera det genom implementering på en befintlig produkt i Valmets reservdelssortiment.

     

    Underlaget till det framtagna arbetssättet samlades in genom att utföra en litteraturstudie, en nulägesanalys på Valmet och en intervju på ett företag som är framgångsrikt inom eftermarknad. Arbetssättet syntetiserades som en process med stöttande riktlinjer genom att utgå från Valmets befintliga utvecklingsprocess och integrera teoretiska modeller, principer och verktyg ur vetenskaplig litteratur. Arbetssättet testades sedan på lutmunstycken för sodapannor.

     

    Grunden för det framtagna arbetssättet bestod av en kombination av Value Management och Design to Cost. Fokus i arbetssättet ligger vid att utveckla en reservdel som återställer systemet till sitt normala arbetstillstånd, för ett pris som kunden är beredd att betala, och som balanserar tillförlighet med tillgänglighet så att den totala kostnaden för kunden minimeras.

     

    Genom att implementera det framtagna arbetssättet på lutmunstycken för sodapannor kunde ett förslag på en lösning med 66 % lägre pris och med 50 % lägre total kostnad för kunden tas fram. Implementeringen visade att arbetssättet praktiskt kan användas på enklare reservdelar men att det behöver testas på komplexa produkter av ett tvärfunktionellt team innan det används av Valmet.  Arbetssättet stärker Valmets förutsättningar för att erbjuda ett mer kostnadseffektiv reservdelsortiment.

    Fulltekst (pdf)
    Arkivfil
  • 275.
    Milesson, Joel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Karlstad Universiy.
    Simulering av hydrodynamisk kraftverkan på vattenkolven i ett punktabsorberande vågkraftverk2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Vågenergi är en nära helt oanvänd förnybar energiresurs med enorm potential och många fördelar jämfört med andra förnybara energikällor. Men havsmiljön är hård och krafterna kan bli mycket stora vilket ställer höga krav på vågkraftverkets konstruktion. Detta har förhindrat ett kommersiellt genombrott för vågkraften.

    Waves4Power har utvecklat ett vågkraftverk, WaveEL, som består av en flytboj och en vertikal cylinder med vattenkolv. Vattenpelaren i cylindern oscillerar i takt med vågorna och driver vattenkolven. Ett hydraulsystem bromsar vattenkolvens rörelser och utvinner energi ur vågorna. Mellanrummet mellan vattenkolv och cylindervägg kallas läckspalt och varierar i storlek över kolvens slaglängd.

    Hur kraftverkan på kolven ser ut vid olika flöden i cylinder och läckspalt är mindre känt. Om läckspalten är för stor förlorar kraftverket i effektivitet medan kraftverkan på kolven minskar. Är läckspalten istället för liten medför detta att geometrisk orundhet kan leda till skador. Det är också möjligt att kavitation uppstår runt kolven vilket innebär påfrestningar för konstruktionen.

    Simulering av kraftverkan genomfördes i COMSOL Multiphysics för att kartlägga kraftverkan och finna ett samband mellan kraftverkan på vattenkolven och andra variabler samt undersöka kavitationsrisken.

    Ett linjärt, dimensionslöst samband mellan kraftverkan på vattenkolven och en funktion beroende av flödeshastighet, kolvradie, periodtid och läckspaltens storlek togs fram.

    De områden som under vissa givna förutsättningar kan utsättas för kaviterande ångblåsor har sammanställts och resultatet visar hög risk för kavitation då kolven befinner sig i övre bypass-sektionen.

    Fulltekst (pdf)
    fulltext
  • 276.
    Mogren, Anna
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Sund, Per
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013). Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    The work of higher education institutions to promote sustainable development2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In March 2016, the Swedish Higher Education Authority (UKÄ) was tasked by the Swedish government to conduct an evaluation of how universities and university colleges promote sustainable development, pursuant to the provisions of the Higher Education Act (1992:1434) introduced ten years earlier, 2006. The evaluation has resulted in a unique collection of empirical material that would have been difficult for an individual researcher to collect independently. The evaluation includes an analysis, but is related to background theory not a strict scientific study.  The empirical material could, however, form a basis for numerous interesting studies on, for example, the important factors for successfully working to integrate sustainable development into higher education. A comparison between nations is also possible to conduct based on the methodology of self-reporting by Higher Education institutions, HEI:s. 

     

    The evaluation defined sustainable development by the Bruntland detention, that the present and future generations are ensured a healthy and good environment, financial and social welfare, and justice. The evaluation was limited to the educational area of sustainable development, education for sustainable development ESD. 

     

    The purpose of the evaluation was to contribute with knowledge and a national comparison of HEIs, work with ESD,  and also to present the results that have been achieved so far. The evaluation was further conducted to give support to the HEIs development work on ESD.

     

    Success factors of a positive ESD implementation due to pre-defined criteria were identified in the  evaluation; the significance of management and control, building institutional support and providing support in implementation.  Apart from investigated criteria, factors that showed effects on a positive ESD implementation was also identified in the evaluation. An example is that several of the large and medium-sized HEIs referred their ESD work from teaching- and engineering programmes, which is the only two programmes where sustainable development is included in the national qualitative programme targets. Central bodies with specific responsibilities for sustainable development was also appointed an important structure in translating ESD policy document to the local context and practice. An interesting finding  was the link between HEIs rated high in this evaluation, to institutions with an environmental management system intended to improve the organisation’s environmental performance and contribute to national environmental goals and to the achievement of UN global goals for sustainable development. Such system takes a wider responsibility of sustainable development than education but seems influential and important in HEIs ESD work. A remaining challenge for a majority of HEIs in Sweden is the process of sustainable development in education where the ESD perspective is not only accounted for as a specific content in education but also a driving force to reach high quality education and society transformation.

  • 277.
    Moletsane, M G
    et al.
    Cent Univ Technol, Dept Mech & Mech Engn, Bloemfontein, Free State, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Kazantseva, N
    Urals Branch Acad Sci, Inst Met Phys, Ekaterinburg, Russia.
    du Plessis, Anton
    Univ Stellenbosch, CT Scanner Facil, Stellenbosch, South Africa.
    Yadroitsava, I
    Cent Univ Technol, Dept Mech & Mech Engn, Bloemfontein, Free State, South Africa.
    Yadroitsev, I
    Cent Univ Technol, Dept Mech & Mech Engn, Bloemfontein, Free State, South Africa.
    Tensile properties and microstructure of direct metal laser-sintered TI6AL4V (ELI) alloy2016Inngår i: South African Journal of Industrial Engineering, ISSN 1012-277X, E-ISSN 2224-7890, Vol. 27, nr 3, s. 110-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Direct metal laser sintering (DMLS) is an additive manufacturing technology used to melt metal powder by high laser power to produce customised parts, light-weight structures, or other complex objects. During DMLS, powder is melted and solidified track-by-track and layer-by-layer; thus, building direction can influence the mechanical properties of DMLS parts. The mechanical properties and microstructure of material produced by DMLS can depend on the powder properties, process parameters, scanning strategy, and building geometry. In this study, the microstructure, tensile properties, and porosity of DMLS Ti6Al4V (ELI) horizontal samples were analysed. Defect analysis by CT scans in pre-strained samples was used to detect the crack formation mechanism during tensile testing of as-built and heat-treated samples. The mechanical properties of the samples before and after stress relieving are discussed. 

  • 278.
    Mollaei, Yaghoub
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Shahmohammadi, Kaveh
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Design and Simulation of Nano-plasmonic Filter based on Nonlinear Nanocavity2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Fulltekst (pdf)
    MasterThesis_Yaghoub&Kaveh
  • 279.
    Mossberg, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    On the use of two sampling strategies for solving an errors-in-variables problem2015Inngår i: 2015 EUROPEAN CONTROL CONFERENCE (ECC), IEEE, 2015, s. 1778-1783Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two sampling strategies are used for solving an errors-in-variables problem where the system as well as the white measurement noises are of a continuous-time nature. The sampling strategies are integrated sampling, and lowpass filtering followed by instantaneous sampling. Covariance relations are derived and systems of equations are formed for the data obtained from the two sampling strategies, and parameter estimators based on these relations and equations are proposed.

  • 280.
    Mossberg, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Performance analysis and filter choice for an errors-in-variables method2016Inngår i: 2016 EUROPEAN CONTROL CONFERENCE (ECC), IEEE, 2016, s. 1371-1376Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An errors-in-variables problem where the system as well as the white measurement noises are in continuous-time is considered. Due to the intrinsic nature of the measurement noises, a strategy of lowpass filtering followed by instantaneous sampling is used for obtaining data from the system. A previously developed covariance function based parameter estimation method is first slightly improved. Thereafter, it is analyzed by evaluating the covariance matrix of the estimated parameter vector. Three different expressions for a generic element of an intermediate matrix in the expression for the covariance matrix are derived. One exact but computationally demanding, one approximate valid for small sampling intervals, and one exact for the case when the sampling interval tends to zero. The covariance matrix can be used for studying the influence of some user parameters, including the choice of the lowpass filter, on the quality of the estimated parameter vector.

  • 281.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Irshad, Yasir
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Closed-loop Identification of Stochastic Models from Filtered Data2008Konferansepaper (Fagfellevurdert)
  • 282.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Sinn, Mathieu
    Cross-correlations of zero crossings in jointly Gaussian and stationary processes with zero means2017Inngår i: 2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 5-9 March 2017, New Orleans, LA, IEEE, 2017, s. 4286-4290Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Zero crossing data contain information of a process in compact form and is therefore of interest in wireless sensor networks where only reduced amounts of data can be transmitted. When analyzing the properties of certain algorithms using zero crossing data, the cross-covariance between the zero crossing rates of two jointly Gaussian and stationary processes is needed. The evaluation of such a cross-covariance is considered in the paper and an exact numerical expression as well as an asymptotic expression are presented.

  • 283.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Söderström, Torsten
    Uppsala University.
    Covariance matching for continuous-time errors-in-variables problems2011Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 56, nr 6, s. 1478-1483Artikkel i tidsskrift (Fagfellevurdert)
  • 284.
    Mossberg, Magnus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Söderström, Torsten
    Uppsala University.
    On covariance matching for multiple input multiple output errors-in-variables systems2012Inngår i: IFAC Proceedings Volumes / [ed] Kinnaert, Michel, Elsevier, 2012, Vol. 45, s. 1371-1376Konferansepaper (Fagfellevurdert)
  • 285.
    Mousavi, Mahmoud
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Tehran Polytechnic, Iran.
    Fariborz, Shahriar
    Tehran Polytechnic, Iran.
    Anti-plane elastodynamic analysis of cracked graded orthotropic layers with viscous damping2012Inngår i: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 36, nr 4, s. 1626-1638Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stress analysis is carried out in a graded orthotropic layer containing a screw dislocation undergoing time-harmonic deformation. Energy dissipation in the layer is modeled by viscous damping. The stress fields are Cauchy singular at the location of dislocation. The dislocation solution is utilized to derive integral equations for multiple interacting cracks with any location and orientation in the layer. These equations are solved numerically thereby obtaining the dislocation density function on the crack surfaces and stress intensity factors of cracks. The dependencies of stress intensity factors of cracks on the excitation frequency of applied traction and material properties of the layer are investigated. The analysis allows the determination of natural frequencies of a cracked layer. Furthermore, the interactions of two cracks having various configurations are studied.

  • 286.
    Mussa, Abdulbaset
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    A study on wear characteristics of high strength steels under sliding contact2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In the last decades, significant improvements regarding the design, materials and technology of rock drills have been made. Likewise, in sheet metal forming, forming tools experience very high contact pressures when processing high strength steel sheets. In both applications components operate under extremely tough contact conditions that result in an accelerated component failure. Enhancements on mechanical properties of components material subjected to extreme contact conditions are highly required in order to withstand the application loads and prevent severe wear.

    The present thesis was focused on understanding of machinery component damage mechanisms under severe contact conditions. A case study of worn components used in rock drilling and sheet metal cold work was carried out. Thread joints from rock drilling and punches from sheet metal pressing were selected for the investigation. For these components, sliding contact under high contact pressure is a common load condition under the components usage. Then, to understand and quantify the influence of contact parameters, load and surface quality on material performance, laboratory simulations were performed. The results were used for a comparative analysis of the typical damage mechanisms observed in the tests and the case study of the components.

    The case study results showed that the threaded surfaces underwent severe plastic deformation due to the high-pressure sliding contact. The microstructure beneath the worn surface was altered and surface cracks and delamination were frequently observed at the worn surface. The dominant damage mechanism found on the investigated punches was adhesive wear. Material transfer adds friction stresses at the punch surface and ultimately, with repeated punch strokes, it leads to initiation and propagation of fatigue cracks.

    Wear process in thread joint and punch wear was simulated using the SOFS. The worn specimens tested experimentally showed similar wear mechanisms obtained in the case study. The thread joint wear simulation showed that the total damage at the worn surface was a result of adhesive wear, plastic deformation, and initiation and propagation of fatigue cracks. In addition, the results showed that the type of motion had a significant influence on the worn volume and crack initiation, and more severe wear was observed at reciprocal motion. The punch wear simulation showed that the friction quickly increased as work material from metal sheets transferred to the disc surface. The rate of the material transfer was strongly dependent on the combination of sheet material and tool steel. Further, the present experimental simulations were applicable to characterize and predict wear of components in the application.

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  • 287.
    Mussa, Abdulbaset
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Mapping of galling initiation and wear mechanisms at reciprocal sliding of PM tool steels against high performance steel sheetsManuskript (preprint) (Annet vitenskapelig)
  • 288.
    Mussa, Abdulbaset
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Wear characterization and wear mapping of a coated cutting tool: Development of cutting tool test fixture and wear testing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Wear mechanisms of the cutting tools are well investigated worldwide. Usually researchers use the cutting process itself, turning by single point cutting, as their investigation method, which includes turning a metal cylinder with a pre-selected work-material and predetermined cutting conditions. Thereafter the tool worn surface is examined by scanning electron microscopy in order to characterize the tool wear mechanisms and tool failure. However, this may be the most appropriate way to investigate the wear mechanisms which occur during machining since it simulates the real operation. Metal cutting involves extreme conditions such as high temperature and high-pressure and the different condition results in different wear modes on the insert’s surface. The wear modes are overlapping and the transition boarder between them are not sharp making it difficult to obtain a detailed information of wear mechanisms. Because of these reasons many researchers try to refine the machining to a single condition e.g; high pressure, at the laboratory level in order to characterize the wear mechanisms and to get a more detailed information.

    In this thesis the wear tests of the cutting tool are performed by using a slider-on-flat-surface (SOFS) wear tester. SOFS involves a normal load, which applies to the sample and a tangential force that enables the sliding of the sample against a counterface. To enable conducting the wear tests in SOFS a newly design of tool holder was prepared. The wear tests were performed at different contact conditions and the stainless steel EN 1.4310 was used as the counterface material. After the tools were tested, the worn surface of the tool was examined by optical light microscopy and scanning electron microscopy in order to identify the wear rate and wear mechanisms.

    At low load the dominating wear mechanism was adhesive wear. The adhesive wear was induced by material pick-up during sliding i.e. material from the counterface was transferred to the insert’s surface. Further sliding results in delamination of the insert surface and removal of a part of the coatings material.

    At high load the dominating wear mechanism was a combination of severe adhesive wear and fracture of the coating material. The fracture of the coating material occurred because of overloading. Coating defects promote crack formation under high load and these cracks propagate through the coating during sliding movement and result in microchipping of the coating material.

    This procedure does not simulate the metal cutting but it still gives an understanding of the behavior of the coating material when it is exposed to a high mechanical stress.

    Fulltekst (pdf)
    fulltext
  • 289.
    Mussa, Abdulbaset
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wear mechanisms in rock drilling and cold work tooling, a literature reviewManuskript (preprint) (Annet vitenskapelig)
  • 290.
    Mussa, Abdulbaset
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Failure analyses and wear mechanisms of rock drill rods: a case study2019Inngår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 102, s. 69-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rock drill rod failure is a big concern for the mining industry. The tough conditions required to break down rock material into small pieces subject rock drill components to high mechanical stresses and corrosion that lead to the failure of the drill rods. This paper describes a detailed examination of rock drill rods failed during field operations. The drill rods were manufactured from a high strength, hardened and tempered steel 22NiCrMo12-5F, carburized for better surface performance. The examination was carried out by means of light optical microscopy and scanning electron microscope. Microhardness profiles were performed for the studied rods. The focus of the present case study was to characterize the failure mechanisms and surface damages of the failed drill rods. The examined drill rods failed due to the initiation and propagation of fatigue microcracks at the outer surface of the thread. Surface cracks propagated to a certain crack length until the fracture toughness of the drill rod was exceeded and the final failure occurred. Multiple short cracks were observed on the fracture surface of the failed rods. The observed cracks propagated perpendicularly to the impacting direction towards the inner surface of the rods. Two different crack initiation mechanisms were observed in the present study, crack initiation from pits and crack initiation from severe plastic surface deformation. Sliding and abrasive wear damage, severe plastic deformation and pitting corrosion were observed on the threaded portion of the rods. Sliding wear was the most common wear damage mechanism observed in the thread joint. Pitting corrosion and severe plastic deformation, made the worn surface susceptible to crack initiation.

  • 291.
    Mussa, Abdulbaset
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Sliding wear and fatigue cracking damage mechanisms in reciprocal and unidirectional sliding of high-strength steels in dry contact2019Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 444, artikkel-id 203119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rock drill components operate under tough contact conditions during rock drilling. Reciprocal and unidirectional motion under high contact stresses are the common contact conditions between interconnected components. It will result in component damage and often the observed surface damage of rock drill tools is due to wear and fatigue cracks. Nevertheless, the effects of the properties and structure of the mating materials on tribological performance, is not fully understood. The present study is dedicated to simulation and investigation of the wear mechanisms observed in reciprocal and unidirectional sliding of high strength steels for rock drill components. A high strength martensitic steel, 22NiCrMo12–F, commonly used in rock drills was tested in self-mating contact. Wear mechanisms were investigated by means of electron microscopy and wear damage was quantified by a 3D optical interferometer. Total damage, as a result of adhesive wear, severe plastic deformation and nucleation and propagation of fatigue cracks, was discussed in relation to test conditions and material properties. It was observed that the coefficient of friction decreased with increasing normal load. Moreover, the results showed that the type of motion had a significant influence on the worn volume and crack nucleation of the specimens in sliding contact. In addition, the reciprocal motion resulted in higher wear than unidirectional motion under the same test conditions.

  • 292.
    Möllberg, Nadine
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Retractable Boarding Step to Scania Crew Cab: Product Development, Design, FEM Simulations and Verification2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis treats the development of a new solution for a retractable boarding step to Scania trucks, which is a part of the modular system.

    Some customers have the need to transport additional passengers. For such applications, Scania provides trucks featuring a Crew Cab, which is an extended cab with rear doors. Easy exit through the rear doors is important for many customers who use this type of cabin. Therefore, there is a possibility to get a retractable boarding step, equipped with an upper step and a lower foldable, that enables easy entry and exit. This function is especially important for fire fighters carrying heavy equipment and therefore has more difficulties exiting the truck. The robustness and dependability of the function is critical to ensure the safety. If it fails, the legal requirements are not met while driving or even worse, injury may occur. Pneumatics is used for the fold out of the step and a spring folds it in.

    The current boarding step needs improvement in order for it to be dependable and robust. If the boarding step have not been folded out, the entry and exit of the cab is not possible.

    This thesis covers the product development, simulations and verification of a new boarding step concept that shall improve the entry- and exit function, making it more robust and dependable. Through problem identification, a product specification and a thorough concept generation and development process a final concept has produced.

    Simulations were made in order to verify that the step could be stepped on when entering and exiting the cab.

    The result was a lower step, sliding on linear bearings in a linear motion. This enabled egress and ingress independent of the extraction or retraction of the step. This makes it more reliable than the current product. The sliding mechanism need to be tested in order to ensure the robustness. A prototype was made in order for the function to be tested. 

    Fulltekst (pdf)
    fulltext
  • 293.
    Neale, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Byggkonstruktion i förskolan.: En studie om 4-5 åringars intresse och förkunskaper till byggkonstruktion.2014Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna studie syftar till att se på hur barn tar sig an konstruktionsritningar i jämförelse med fritt byggande i en lekfull gruppmiljö. Tidigare forskning visar skillnad mellan mängden män och kvinnor i tekniska yrken och även män och kvinnors inställning till de tekniska ämnena. Vissa forskare visar också på åldersskillnader mellan hur barn lär sig tekniska ämnen. Tar fyra- och femåringar frivilligt sig an konstruktionsritningar, följer dem och färdigställer de konstruktionen? Studien har särskilt tittat på om det fanns skillnader mellan flickorna och pojkarna när de byggde? Hur påverkar barnens eget intresse hur de bygger? Om barn, fyra och fem år gamla kan följa bygginstruktioner?

    Resultatet av denna studie, i viss mån, stödjer tidigare forskning om att det finns en genus aspekt redan i förskoleåldern, pojkarna var mer försekomna och hade lättare för att följa lego instruktioner än flickorna, men frågan kvarstår; varför finns denna skillnad? Förutom genusaspekten fanns det också ett tydligt resultat som visade på skillnad i byggkunskap mellan fyraåringar och femåringar. Fyraåringarna utforskade främst byggmaterialet, medan många av femåringarna kunde följa en Legobygginstruktion näst intill perfekt.

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    fulltext
  • 294.
    Ng, Amos
    et al.
    Högskolan i Skövde.
    Adolfsson, Josef
    Sundberg, Martin
    De Vin, Leo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Virtual Manufacturing for Press Line Monitoring and Diagnostics2008Inngår i: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 35, s. 565-575Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    fulltext
  • 295.
    Nilsson, Frida
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Hole transport layers in organic solar cells: A study of work functions in nanofilms2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Organic solar cells have been showing promise as a way of producing renewableenergy with the help of light, flexible, and production effective materials.The efficiencies and lifetimes reached in organic solar cells have steadily beenincreasing over the years as more research in the field is being conducted.One way of increasing the efficiency in organic solar cell devices is introducingan interlayer between the photoactive material and the anode, referred toas the ’hole transport layer’. Most commonly used as a hole transport layer isthe material PEDOT:PSS, which offers desired properties such as transparency,simple processing and good ohmic contact between anode and photoactive material.PEDOT:PSS is also known to be a degradation site in organic solar cells,as it will corrode the electrode in the presence of water.This project has consisted of investigating PEDOT:PSS along with two othercandidates that may one day come to replace PEDOT:PSS as the most commonlyused material, molybdenum trioxide (MoO3) and phosphomolybdic acid(PMA). The aim was to investigate how the different materials energy bandstructure would be affected upon exposure to sunlight, air and annealing, byobserving the work function under different conditions.

    Fulltekst (pdf)
    fulltext
  • 296.
    Nordin, Adam
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Översyn av bältessträckning i ViscoNip-vals2018Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    The report was a finalization part of the thesis bachelor work in mechanical engineering at Karlstad University. A review of the ViscoNip roll belt stretch was made to Valmet. The background to the project was that the belts became resistant to wear, which meant that it was no longer necessary to adjust the machine direction. Previously the belt was moved in the machine direction to expose a new and fresh surface to even the wear. The increased quality of the belt has led to the possibility of applying a fixed side. The goal with the thesis work was to minimize the cost of the belt tension. 

    The project has gone thru a development process where project planning, product specification, concept generation, concept evaluation and layout design was included. Through a cost analysis and input from the relevant fitters and service staff, it was found that a trapezoidal screw was a highly rated solution for the head adjustment. Due to the requirement for continuous belt tension, the trapezoidal screw and a fixed end could not be combined.  As there were several advantages with the trapezoidal screw, a solution was created that was to combine a trapezoidal screw with a spring. These along with a fixed head became the winning concept.

    Before the thesis work, the cost of the ViscoNip roll belt stretch was 226 321 kr. In that price was installation, hydraulics, trapezoidal screw and displacement components.  Upon completion of the thesis, a fixed side was applied to the driving side together with a trapezoidal screw combined with a driver's spring. The estimated cost was instead 155 477 kr, a saving of 70 845 kr.

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    Fulltekst (pdf)
    fulltext
  • 297.
    Norstedt, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Verktyg för tillskärning av nätisoleringsmatta: Produktutvecklingsprojekt för en effektivare och mer användarcentrerad metod för tillskärning av nätisoleringsmattor2013Independent thesis Advanced level (professional degree), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    This report covers a product development project conducted as Bachelor of Science thesis forthe Innovation & design engineer program at Karlstad University.The assignment was supplied by MMB Consulting, Kristinehamn. The purpose of this projectwas to find an alternative way of shaping wire-net insulation mats. This insulation product isused for fire and thermal insulation of technical installations. The insulation consists of stoneor glass wool with a sewn on steel wire netting on the out facing side. This netting has thepurpose to enable fastening to e.g. ventilation ducts and to provide bounding of joints. Thiswire netting makes regular methods for fitting stone or glass wool non applicable. Theexisting method for shaping wire-net insulation has flaws due to not being designed for thisapplication. These flaws include poor ergonomics, efficiency and low result quality.The objectives with this project is to find a new method that makes fitting of wire-netinsulation more efficient and safer for the user regarding personal safety and ergonomics.The work has been conducted according to the methods of the industrial product developmentprocess and the design methodology.The project resulted in a motor driven tool for shaping wire-net insulation that according to atheoretical foundation has proven to be more user adapted through being designed for goodergonomics and by offering a simpler handling. This solution is also considered to be moreefficient and to give better results than the present solution. Some correlation betweenreductions in energy losses from technical installations and the new method is detectable.

    Fulltekst (pdf)
    Verktyg för tillskärning av nätisoleringsmatta
  • 298.
    Nyflött, Åsa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Meriçer, Çağlar
    Bologna University.
    Minelli, Matteo
    Bologna University.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Jarnstrom, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Giacinti Baschetti, Marco
    Bologna University.
    The influence of moisture content on the polymer structure of polyvinyl alcohol in dispersion barrier coatings and its effect on the mass transport of oxygen2017Inngår i: JCT Research, ISSN 1547-0091, E-ISSN 2168-8028, s. 1345-1355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a study of the effect of moisture on the gas permeability of polyvinyl alcohol (PVOH) and PVOH–kaolin dispersion barrier coatings. The oxygen permeability was measured at different humidity levels, and the material properties were characterized under the same conditions: polymer crystallinity, kaolin concentration, and kaolin orientation were all evaluated. The experimental results revealed that the water plasticizes the PVOH material of the coatings, and the presence of kaolin filler is unable to affect such behavior significantly. The PVOH crystallinity was affected drastically by the humidity, as water melts polymer crystallites, which is a reversible process under removal of water. The permeability data were analyzed using a thermodynamicbased model able to account for the water effect on both the solubility of the gas and the diffusivity coefficients in the polymer and composite. The results showed good agreement between the model’s predictions and the experimental data in terms of the overall permeability of the material.

    Fulltekst (pdf)
    Nyflött_et_al_2017
  • 299.
    Nyflött, Åsa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Petkova-Olsson, Yana
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bonnerup, Chris
    Stora Enso.
    Järnström, Lars
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Carlsson, Gunilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Minelli, Matteo
    Bologna University.
    Modelling of oxygen permeation through filled polymeric layers for barrier coatings2017Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 134, nr 20, artikkel-id 44834Artikkel i tidsskrift (Fagfellevurdert)
  • 300.
    Ogenvall, Mikael
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Solceller och elbilars påverkan på lokala elnätet2019Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Detta examensarbete har genomförts i samarbete med Arvika Teknik AB. Rapporten undersöker två bostadsområden i Arvika lokalnät, där syftet är att ge vägledning om framtidens energibehov för elbilar samt om solceller kan hjälpa till och minska effekttoppar. Rapporten visar på att lokalnät i vissa fall har stora effektutrymmen som kan användas till laddning av elbilar. Ytterligare visas att solceller endast kan ha en marginell inverkan på effekttoppar. Utmaningarna för nätbolagen innefattar många andra faktorer än de som berörs i denna rapport. Rapporten ger viss vägledning men mycket arbete återstår. Problem med elbilsladdning kommer inte komma de närmaste åren men på sikt kommer det vara viktigt att utveckla metoder att styra elbilsladdningen.

    Fulltekst (pdf)
    Examensarbete 2019
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