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  • 151.
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Influence of tool microstructure and sheet mechanical properties on galling initiation2011Ingår i: / [ed] K.C. Ludema, S.J. Shaffer, 2011Konferensbidrag (Refereegranskat)
  • 152.
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Införandet av Computer Based Mathematics (CBM) i ingenjörsutbildningar2017Konferensbidrag (Refereegranskat)
  • 153.
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Tool microstructure and the relation to tool life in deep drawing2014Konferensbidrag (Refereegranskat)
  • 154.
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wear mechanisms in thread joints of rock drill, a case study2017Konferensbidrag (Refereegranskat)
  • 155.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Karlsson, Patrik
    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).
    Broitman, Esteban
    Linköpings universitet, Tunnfilmsfysik.
    Nano-scale friction of multi-phase powder metallurgy tool steels2015Ingår i: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1119, s. 70-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Friction is a fundamental phenomenon in tribology involving complex mechanisms between thecontacting surfaces. Measurements of friction are often made using devices with substantially largercontact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials,influence of particular microstructural constituents is not resolved. In the present work, a tribometerwith a contact area in the nano-scale range was used to map friction for different types of tool steelswith different chemical- and phase composition. Owing to the small tip radius, frictionalcharacteristics of primary carbides and the steel matrix were measured and compared. Dependingon chemical composition, a difference was observed where the coefficient of friction wasapproximately twice higher for the steel possessing highest coefficient of friction, including bothcarbides and the steel matrix.

  • 156.
    Haglund, Jesper
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Schönborn, Konrad J.
    Linköpings universitet.
    The Pedagogical Potential of Infrared Cameras in Biology Education2019Ingår i: The American Biology Teacher, ISSN 0002-7685, E-ISSN 1938-4211, Vol. 81, nr 7, s. 520-523Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal imagery provides new opportunities to study concepts and processes in biology. Examples include using infrared (IR) cameras in educational activities to explore energy transfer and transformation in human physiology, animal thermoregulation, and plant metabolism. The user-friendly and visually intuitive nature of IR technology is well suited to the study of rapidly changing temperatures on biological surfaces, due to such energy transfers. IR cameras are therefore potentially helpful pedagogical tools for approaching the Energy and Matter crosscutting concept in the Life Sciences discipline of the Next Generation Science Standards.

  • 157.
    Hallbäck, Nils
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Korin, Christer
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Barbier, Christophe
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Nygårds, Mikael
    KTH.
    Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board2014Ingår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 27, nr 9, s. 701-712Artikel i tidskrift (Refereegranskat)
  • 158.
    Hallbäck, Nils
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Tofique, Muhammad Waqas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Development of a distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half-plane2014Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, s. 2878-2892Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half plane has been developed. The dipole density distribution is represented with a weighted Jacobi polynomial expansion where the weight function captures the asymptotic behaviour at each end of the crack. To allow for opening and sliding at crack kinking and branching the dipole density representation contains conditional extra terms which fulfil the asymptotic behaviour at each endpoint. Several test cases involving straight, kinked and branched cracks have been analysed, and the results suggest that the accuracy of the method is within 1% provided that Jacobi polynomial expansions up to at least the sixth order are used. Adopting even higher order Jacobi polynomials yields improved accuracy. The method is compared to a simplified procedure suggested in the literature where stress singularities associated with corners at kinking or branching are neglected in the representation for the dipole density distribution. The comparison suggests that both procedures work, but that the current procedure is superior, in as much as the same accuracy is reached using substantially lower order polynomial expansions.

  • 159.
    Hansson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Materials and Device Engineering for Efficient and Stable Polymer Solar Cells2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Polymer solar cells form a promising technology for converting sunlight into electricity, and have reached record efficiencies over 10% and lifetimes of several years. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor materials in the active layer. To achieve longer lifetimes, degradation processes in the materials have to be understood. In this thesis, a set of complementary spectroscopy and microscopy techniques, among which soft X-ray techniques have been used to determine the morphology of polymer:fullerene based active layers. We have found that the morphology of TQ1:PC70BM films is strongly influenced by the processing solvent and the use of solvent additives. We have also found, by using soft X-ray techniques, that not only the light-absorbing polymer TQ1, but also the fullerene is susceptible to photo-degradation in air. Moreover, the fullerene degradation is accelerated in the presence of the polymer. Additionally, this thesis addresses the role of the interfacial layers for device performance and stability. The commonly used hole transport material PEDOT:PSS has the advantage of being solution processable at room temperature, but this layer is also known to contribute to the device degradation. We have found that low-temperature processed NiOx is a promising alternative to PEDOT:PSS, leading to improved device performance. Even for encapsulated polymer solar cells, some photo-induced degradation of the electrical performance is observed and is found to depend on the nature of the hole transport material. We found a better initial stability for solar cells with MoO3 hole transport layers than with PEDOT:PSS. In the pursuit of understanding the initial decrease in electrical performance of PEDOT:PSS-based devices, simulations were performed, from which a number of degradation sources could be excluded.

  • 160.
    Hansson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Morphology and material stability in polymer solar cells2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Polymer solar cells are promising in that they are inexpensive to produce, and due to their mechanical flexibility have the potential for use in applications not possible for more traditional types of solar cells. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor material in the active layer. Understanding the connection between morphology and performance as well as how to control the morphology, is therefore of great importance. Furthermore, improving the lifetime of polymer solar cells has become at least as important as improving the efficiency.

     

    In this thesis, the relation between morphology and solar cell performance is studied, and the material stability for blend films of the thiophene-quinoxaline copolymer TQ1 and the fullerene derivatives PCBM and PC70BM. Atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM) are used to investigate the lateral morphology, secondary ion mass spectrometry (SIMS) to measure the vertical morphology and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to determine the surface composition. Lateral phase-separated domains are observed whose size is correlated to the solar cell performance, while the observed TQ1 surface enrichment does not affect the performance. Changes to the unoccupied molecular orbitals as a result of illumination in ambient air are observed by NEXAFS spectroscopy for PCBM, but not for TQ1. The NEXAFS spectrum of PCBM in a blend with TQ1 changes more than that of pristine PCBM. Solar cells in which the active layer has been illuminated in air prior to the deposition of the top electrode exhibit greatly reduced electrical performance. The valence band and absorption spectrum of TQ1 is affected by illumination in air, but the effects are not large enough to account for losses in solar cell performance, which are mainly attributed to PCBM degradation at the active layer surface.

  • 161.
    Hansson, Rickard
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ericsson, Leif
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Holmes, Natalie P.
    Blazinic, Vanja
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Dastoor, Paul
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Opportunities and challenges in probing local composition of organic material blends for photovoltaics2017Ingår i: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 32, nr 10, s. 1982-1992Artikel i tidskrift (Refereegranskat)
  • 162.
    Hansson, Rickard
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ericsson, Leif K.E.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Holmes, Natalie P.
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Opitz, Andreas
    Department of Physics, Humboldt-Universit¨at zu Berlin, 12489 Berlin, Germany.
    Campoy-Quiles, Mariano
    Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193, Spain.
    Wang, Ergang
    Chalmers University of Technology, 41296 Göteborg, Sweden.
    Barr, Matthew G.
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Kilcoyne, A. L. David
    Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
    Zhou, Xiaojing
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Dastoor, Paul
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Vertical and lateral morphology effects on solar cell performance for a thiophene–quinoxaline copolymer:PC70BM blend2015Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, s. 6970-6979Artikel i tidskrift (Refereegranskat)
  • 163.
    Hansson, Rickard
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Lindqvist, Camilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ericsson, Leif
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Opitz, Andreas
    Humboldt univ. .
    Wang, Ergang
    Chalmers.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Photodegradation in air of the active layer components in a thiophene-quinoxaline copolymer:fullerene solar cell2016Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 16, s. 11132-11138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied the photo-degradation in air of a blend of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), and how the photo-degradation affects the solar cell performance. Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, changes to the electronic structure of TQ1 and PCBM caused by illumination in ambient air are investigated and compared between the pristine materials and the blend. The NEXAFS spectra show that the unoccupied molecular orbitals of TQ1 are not significantly changed by the exposure of pristine TQ1 to light in air, whereas those of PCBM are severely affected as a result of photo-induced degradation of PCBM. Furthermore, the photo-degradation of PCBM is accelerated by blending it with TQ1. While the NEXAFS spectrum of TQ1 remains unchanged upon illumination in air, its valence band spectrum shows that the occupied molecular orbitals are weakly affected. Yet, UV-Vis absorption spectra demonstrate photo-bleaching of TQ1, which is attenuated in the presence of PCBM in blend films. Illumination of the active layer of TQ1: PCBM solar cells prior to cathode deposition causes severe losses in electrical performance.

  • 164.
    Heidkamp, William
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Predicting the concentration of residual methanol in industrial formalin using machine learning2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis, a machine learning approach was used to develop a predictive model for residual methanol concentration in industrial formalin produced at the Akzo Nobel factory in Kristinehamn, Sweden. The MATLABTM computational environment supplemented with the Statistics and Machine LearningTM toolbox from the MathWorks were used to test various machine learning algorithms on the formalin production data from Akzo Nobel. As a result, the Gaussian Process Regression algorithm was found to provide the best results and was used to create the predictive model. The model was compiled to a stand-alone application with a graphical user interface using the MATLAB CompilerTM.

  • 165.
    Heinzle, Mark
    et al.
    University of Vienna, Austria.
    Uggla, Claes
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Spike Statistics2013Ingår i: General Relativity and Gravitation, ISSN 0001-7701, E-ISSN 1572-9532, Vol. 45, nr 5, s. 939-957Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we explore stochastical and statistical properties of so-called recurring spike induced Kasner sequences. Such sequences arise in recurring spike formation, which is needed together with the more familiar BKL scenario to yield a complete description of generic spacelike singularities. In particular we derive a probability distribution for recurring spike induced Kasner sequences, complementing similar available BKL results, which makes comparisons possible. As examples of applications, we derive results for so-called large and small curvature phases and the Hubble-normalized Weyl scalar.

  • 166.
    Hernvall Jonsson, Erik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Konceptuell modell för ljusförsörjning i skyddsrum vid strömbortfall2019Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In a parallel with the potential reestablishment of new production of swedish shelters, an awareness of a great potential of modernisation on swedish shelters has occurred. Sweden is in the process of a new potential production of modern swedish shelters, but there is a long process before all the technical details has been updated. This is a bachelor thesis for a degree in mechanical engineering at Karlstad university. The object of this report is to show how a shelter can be best supplied with light during a period when normal power fail.

    The recommendation of the report is to use wall mounted LED units that are supplied from an electric generator, operated manually by hand. This model has been developed based on swedish regulations for shelters and includes recommendations from these regulations. The concept could also be considered as a necessity for protectetive cautions during realistic crise circumstances.

    This project was initially a construction developing-oriented project for a specific product that aimed for higher security and functionality in shelters, but resulted in a koncept for light. The method has therefore followed processes for product developing.

  • 167.
    Hidén Rudander, Petter
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Case hardened steel plates for ballistic armour: A study of ballistic and mechanical properties of case hardened ARMOX® steel2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Protective materials are a necessity to ensure the safety of personnel or property subjected to impacts by bullets, fragments and/or explosions. To shatter an inbound projectile, the surface of the target needs to exhibit a very high hardness but also the ability to prevent crack growth and plastically deform to avoid brittle fracture. The need for a combination of hardness and toughness led to the invention of dual hard steel which can be achieved within a homogeneous plate by modification of the surface through single-sided case hardening. In this work ARMOX® 440T and ARMOX® 500T was case hardened with a case depth of 2 and 2.3 mm and shoot upon with armour piercing rounds P80 to determine the ballistic limit of the material and to compare with the reference ARMOX®. Metallographic investigation was performed together with grain size measurement and mechanical properties were tested including hardness, impact toughness, dimensional deviation and tensile strength.

    A considerable increase of the ballistic performance with 40-70 % was reached by single-sided case hardening even though an irregular failure of the diffusion barrier had led to double-sided cases in various areas. Mass efficiency also increased considerably. Especially ARMOX® 440T was suitable for the treatment since it increased by the largest relative amount despite the fact that it had a thinner case then ARMOX® 500T plates.

    The complete penetrations were caused by formation of adiabatic shear bands and lead to punching of the plates except for hits at areas with double-sided case where back spall also occurred. The backside-case also resulted in a sharp reduction in impact toughness. Crack formation in close proximity to the impact site was found in all case hardened plates perpendicular to the front surface originating from inter-granular oxides near the surface.

    All the conventionally case hardened plates deviated from the reference plate flatness. Most likely because of placement in the furnace.

    Collectively the material is not recommended to be implemented in structural components until further investigations have been made concerning multi-hit threat, heat treat optimisation to minimize dimensional changes and bending because of the formation of perpendicular cracks under tensile load.

  • 168.
    Holmes, Natalie P.
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). University of Newcastle, Australia.
    Marks, Melissa
    University of Newcastle, Australia.
    Cave, James M.
    University of Bath, United Kingdom.
    Feron, Krishna
    University of Newcastle, Australia.
    Barr, Matthew G.
    University of Newcastle, Australia.
    Fahy, Adam
    University of Newcastle, Australia.
    Sharma, Anirudh
    Flinders University, Australia; University of Bordeaux, France.
    Pan, Xun
    Flinders University, Australia.
    Kilcoyne, David A. L.
    Lawrence Berkeley National Laboratory, United States.
    Zhou, Xiaojing
    University of Newcastle, Australia.
    Lewis, David A.
    Flinders University, Australia.
    Andersson, Mats R.
    Flinders University, Australia.
    van Stam, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Walker, Alison B.
    University of Bath, United Kingdom.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Belcher, Warwick J.
    University of Newcastle, Australia.
    Dastoor, Paul C.
    University of Newcastle, Australia.
    Engineering Two-Phase and Three-Phase Microstructures from Water-Based Dispersions of Nanoparticles for Eco-Friendly Polymer Solar Cell Applications2018Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 18, s. 6521-6531Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanoparticle organic photovoltaics, a subfield of organic photovoltaics (OPV), has attracted increasing interest in recent years due to the eco-friendly fabrication of solar modules afforded by colloidal ink technology. Importantly, using this approach it is now possible to engineer the microstructure of the light absorbing/charge generating layer of organic photovoltaics; decoupling film morphology from film deposition. In this study, single-component nanoparticles of poly(3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PC61BM) were synthesized and used to generate a two-phase microstructure with control over domain size prior to film deposition. Scanning transmission X-ray microscopy (STXM) and electron microscopy were used to characterize the thin film morphology. Uniquely, the measured microstructure was a direct input for a nanoscopic kinetic Monte Carlo (KMC) model allowing us to assess exciton transport properties that are experimentally inaccessible in these single-component particles. Photoluminescence, UV-vis spectroscopy measurements, and KMC results of the nanoparticle thin films enabled the calculation of an experimental exciton dissociation efficiency (ηED) of 37% for the two-phase microstructure. The glass transition temperature (Tg) of the materials was characterized with dynamic mechanical thermal analysis (DMTA) and thermal annealing led to an increase in ηED to 64% due to an increase in donor-acceptor interfaces in the thin film from both sintering of neighboring opposite-type particles in addition to the generation of a third mixed phase from diffusion of PC61BM into amorphous P3HT domains. As such, this study demonstrates the higher level of control over donor-acceptor film morphology enabled by customizing nanoparticulate colloidal inks, where the optimal three-phase film morphology for an OPV photoactive layer can be designed and engineered.

  • 169.
    Holmes, Natalie P.
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). University of Newcastle, Australia.
    Munday, Holly
    University of Newcastle, Australia.
    Barr, Matthew G.
    University of Newcastle, Australia.
    Thomsen, Lars
    Australian Synchrotron, Australia.
    Marcus, Matthew A.
    Lawrence Berkeley National Laboratory, USA.
    Kilcoyne, A. L. David
    Lawrence Berkeley National Laboratory, USA.
    Fahy, Adam
    University of Newcastle, Australia.
    van Stam, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Dastoor, Paul C.
    University of Newcastle, Australia.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Unravelling donor–acceptor film morphologyformation for environmentally-friendly OPV inkformulations2019Ingår i: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The challenge of coating organic photovoltaics (OPV) from green solvents is to achieve the requirednanostructured interpenetrating network of donor and acceptor domains based on a rational choice ofsolvent approach as opposed to the usual trial-and-error methods. We demonstrate here that we canachieve a bicontinuous interpenetrating network with nanoscale phase separation for the chosen donor–acceptor material system poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl]:phenyl-C61 butyric acid methyl ester (TQ1:PC61BM) when processing from green solvent ink formulations.This structure is achieved by first calculating the Hansen solubility parameters (HSP) of the donor andacceptor materials, followed by careful choice of solvents with selective relative solubilities for the twomaterials based on the desired order of precipitation necessary for forming a nanostructured interdigitatednetwork morphology. We found that the relative distances in Hansen space (Ra) between TQ1 andthe primary solvent, on the one hand, and PC61BM and the primary solvent, on the other hand, could becorrelated to the donor–acceptor morphology for the formulations based on the solvents d-limonene,anisole, and 2-methyl anisole, as well as the halogenated reference solvent o-dichlorobenzene. Thisnanostructured blend film morphology was characterised with scanning transmission X-ray microscopy(STXM) and transmission electron microscopy (TEM), and the film surface composition was analysed bynear edge X-ray absorption fine structure (NEXAFS) spectroscopy. Hansen solubility theory, based onsolution thermodynamics, has been used and we propose an HSP-based method that is a general platformfor the rational design of ink formulations for solution-based organic electronics, in particular facilitatingthe green solvent transition of organic photovoltaics. Our results show that the bulk heterojunctionmorphology for a donor–acceptor system processed from customised solvent mixtures can be predictedby the HSP-based method with good reliability.

  • 170.
    Häggström, Per-Martin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Omkonstruktion av treaxlig plockrobot och dess plockverktyg2014Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis has treated a three-axis robot which task is to serve a larger test machine tomove the modules to be tested, from the storage to the test site. The robot is composed ofthree linear actuators; two standard components of ball screw type and a custom-builtactuator of trapezoidal type. The work has mainly focused on the custom-built device to seeif it could be replaced with a standard component. Part of the work has been to look into thepicking tool and to see if there are any possibilities to improve its function.The report presents two different proposals which I decided to call Robot 1 and Robot 2 andthey aim to address the problems arising in the purpose-built linear unit and the X-axislinearity problems. Robot 1 focuses on eliminating the problems that arise around therobot's X-axis, with such simple means as possible and without making excessive materialchanges. The idea behind the solution of Robot 1 is also to be able to apply it onto existingmachinery without too much interference. Robot 2 is significantly more advanced and alsoimplies considerable material changes. The advantage of Robot 2 is that it takes into accountboth the problems with the X-axis and Y-axis, and should absolutely be considered on newmachines, but also for existing machines. For the picking tool the thesis presents the solutionin the form of both a modified existing vacuum tool and a brand new pneumatic gripper forRobot 2 which differ from the vacuum system. I think that the vacuum tool presented shouldbe considered to be implemented even if no other modifications are made on the robotbecause of its simple construction.The thesis presents the functions and problems with the current robot and its picking tool.For the described problems the different solutions have been presented, partly by findingcompletely new market components but also through new self-designed components.During this time, choices of materials and material dimensions have been based onoverestimates and previous material selections, which later were controlled by using FEManalysisin CAD-environment.The work is considered to have gone well and the goals that have been set have beenachieved in a satisfactory manner.

  • 171.
    Hämäläinen, Pyry
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Hallbäck, Nils
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    On the determination of transverse shear properties of paper using the short span compression test2017Ingår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 107, s. 22-30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko-Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young's modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko-Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose.

  • 172.
    Hörling, Daniel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Parameter identification of GISSMO damage model for DOCOL 1200M: A study on crash simulation for high strength steel sheet components2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I bilindustrin finns en konflikt mellan viljan att minska vikten för att ge ett lägre CO2-utsläpp och kravet på god krocksäkerhet, detta har lett till att höghållfasta stål används istället för de traditionella lättviktsmaterialen. Användningen av höghållfasta stål i kombination med att utvecklingstiden i bilindustrin har minskat måste krocksimuleringarna förutsäga krockbeteendet bra då ett fullskaligt krocktest både är dyrt och tidskrävande.Skademodellen GISSMO har undersökts för att användas med DOCOL 1200M, GISSMO skademodell har ett antal parametrar och kurvor som definierar när instabilitet och brott uppstår, dessa måste fastställas. GISSMO är en fenomenbaserad skademodell som är baserad på experiment och tar därför inte hänsyn till inneslutningar eller sprickor och är därför bara pålitlig för liknande spänningsfall som de som analyserades i experimenten. De olika spänningsfallen är representerade av triaxialiteten som är kvoten mellan medelspänningen och von Mises spänningen.För att hitta parametrarna tillverkades och testadess ett antal provstavar i enaxligt dragprov sen skapades en FEM-modell och kraft-förskjutningskurvan som erhålls från simuleringen mappas för att matcha kraft-förskjutningskurvan som erhållits från dragprovet. Parametrarna ändrades av mjukvaran LS-OPT® för att öka matchningen. En metamodel-baserad optimering utfördes för att hitta kurvorna och parametrarna med en feedforward neural-network och punkter jämnt fördelade över parameterrummet.Resultatet visar att GISSMO har potential att förutsäga brottbeteendet bra, när de olika provstavarna optimerades individuellt så är passningen god och när simuleringen undersöks ses tydligt midjebildning och lokalisering av deformationen. När provstavarna är optimerade tillsammans är passningen inte lika god som de individuella passningarna.För att förbättra resultaten skulle mer exakta kraft-förskjutningskurvor vara av värde, t.ex. lastceller och optisk mätning/trådtöjningsgivare kunde ha använts för att se den lokala förskjutningen och den lokala spänningen och spänningstillståndet. För att göra modellen mer pålitlig kan skjuvtester och kompressionstester användas i framtiden. Att låta optimeringen pågå i fler iterationer kan också förbättra resultatet.

  • 173.
    Hörmann, Ulrich
    et al.
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Lorch, Christopher
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Hinderhofer, Alexander
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Gerlach, Alexander
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Gruber, Mark
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Kraus, Julia
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Sykora, Benedikt
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Grob, Stefan
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Linderl, Theresa
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Wilke, Andreas
    Department of Physics, Humboldt University of Berlin, Brook-Taylor-Straße 15, 12489 Berlin, Germany.
    Opitz, Andreas
    Department of Physics, Humboldt-Universität zu Berlin, 12489 Berlin, Germany.
    Hansson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Anselmo, Ana Sofia
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ozawa, Yusuke
    Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Nakayama, Yasuo
    Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Ishii, Hisao
    Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan and Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Koch, Norbert
    Department of Physics, Humboldt University of Berlin, Brook-Taylor-Straße 15, 12489 Berlin, Germany and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH - BESSY II, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Schreiber, Frank
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Brütting, Wolfgang
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Voc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells2014Ingår i: Journal of physical chemistry C, ISSN 1932-7455, Vol. 118, nr 46, s. 26462-26470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The film morphology and device performance of planar heterojunction

    solar cells based on the molecular donor material α-sexithiophene (6T) are investigated.

    Planar heterojunctions of 6T with two different acceptor molecules, the C60 fullerene and

    diindenoperylene (DIP), have been prepared. The growth temperature of the 6T bottom

    layer has been varied between room temperature and 100 °C for each acceptor. By means

    of X-ray diffraction and X-ray absorption, we show that the crystallinity and the molecular

    orientation of 6T is influenced by the preparation conditions and that the 6T film

    templates the growth of the subsequent acceptor layer. These structural changes are

    accompanied by changes in the characteristic parameters of the corresponding

    photovoltaic cells. This is most prominently observed as a shift of the open circuit

    voltage (Voc): In the case of 6T/C60 heterojunctions, Voc decreases from 0.4 to 0.3 V,

    approximately, if the growth temperature of 6T is increased from room temperature to 100

    °C. By contrast, Voc increases from about 1.2 V to almost 1.4 V in the case of 6T/DIP solar

    cells under the same conditions. We attribute these changes upon substrate heating to

    increased recombination in the C60 case while an orientation dependent intermolecular coupling seems to change the origin of the photovoltaic gap in the DIP case.

  • 174.
    Inglese, Alessandro
    et al.
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Focareta, Alessia
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Schindler, Florian
    Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg im Breisgau, Germany.
    Schön, Jonas
    Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg im Breisgau, Germany.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Schubert, Martin C.
    Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg im Breisgau, Germany.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Light-induced degradation in multicrystalline silicon: the role of copper2016Ingår i: PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON CRYSTALLINE SILICON PHOTOVOLTAICS (SILICONPV 2016) / [ed] Ribeyron, PJ; Cuevas, A; Weeber, A; Ballif, C; Glunz, S; Poortmans, J; Brendel, R; Aberle, A; Sinton, R; Verlinden, P; Hahn, G, Elsevier, 2016, Vol. 92, s. 808-814Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this contribution, we provide an insight into the light-induced degradation of multicrystalline (mc-) silicon caused by copper contamination. Particularly we analyze the degradation kinetics of intentionally contaminated B- and Ga-doped mc-Si through spatially resolved photoluminescence (PL) imaging. Our results show that even small copper concentrations are capable of causing a strong LID effect in both B- and Ga-doped samples. Furthermore, the light intensity, the dopant and the grain quality were found to strongly impact the degradation kinetics, since faster LID was observed with stronger illumination intensity, B-doping and in the grains featuring low initial lifetime. Interestingly after degradation we also observe the formation of bright denuded zones near the edges of the B-doped grains, which might indicate the possible accumulation of copper impurities at the grain boundaries.

  • 175.
    Inglese, Alessandro
    et al.
    Aalto University.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Aalto University.
    Savin, Hele
    Aalto University.
    Accelerated light-induced degradation for detecting copper contamination in p-type silicon2015Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, nr 5, artikel-id 052101Artikel i tidskrift (Refereegranskat)
  • 176.
    Inglese, Alessandro
    et al.
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Vahlman, Henri
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Recombination activity of light-activated copper defects in p-type siliconstudied by injection- and temperature-dependent lifetime spectroscopy2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, nr 12, artikel-id 125703Artikel i tidskrift (Refereegranskat)
  • 177.
    Irshad, Yasir
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    On some continuous-time modeling and estimation problems for control and communication2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The scope of the thesis is to estimate the parameters of continuous-time models used within control and communication from sampled data with high accuracy and in a computationally efficient way.In the thesis, continuous-time models of systems controlled in a networked environment, errors-in-variables systems, stochastic closed-loop systems, and wireless channels are considered. The parameters of a transfer function based model for the process in a networked control system are estimated by a covariance function based approach relying upon the second order statistical properties of input and output signals. Some other approaches for estimating the parameters of continuous-time models for processes in networked environments are also considered. The multiple input multiple output errors-in-variables problem is solved by means of a covariance matching algorithm. An analysis of a covariance matching method for single input single output errors-in-variables system identification is also presented. The parameters of continuous-time autoregressive exogenous models are estimated from closed-loop filtered data, where the controllers in the closed-loop are of proportional and proportional integral type, and where the closed-loop also contains a time-delay. A stochastic differential equation is derived for Jakes's wireless channel model, describing the dynamics of a scattered electric field with the moving receiver incorporating a Doppler shift.

  • 178.
    Irshad, Yasir
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Mossberg, Magnus
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Söderström, Torsten
    Division of Systems and Control, Department of Information Technology, Uppsala University.
    System identification in a networked environment using second order statistical properties2013Ingår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 49, nr 2, s. 652-659Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    System identification for networked control is considered. Due to the time-delays in the network, it can be difficult to work with a discrete-time model and a continuous-time model is therefore chosen. A covariance function based method that relies on the second order statistical properties of the output signal, where it is assumed that the input signal samples are from a discrete-time white noise sequence, is proposed for estimating the parameters. The method is easy to use since the actual time instants when new input signal levels are applied at the actuator do not have to be known. An analysis of the networked system and the effects of the time-delays is made, and the results of the analysis motivate and support the chosen approach. Numerical studies indicate that the method is robust to randomly distributed time-delays, packet drop-outs, and additive measurement noise.

  • 179.
    Jackman, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Mechanical behaviour of carbon nanostructures2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Abstract

    Carbon nanotubes (CNTs) have extraordinary mechanical and electrical properties. Together with their small dimensions and low density, they are attractive candidates for building blocks in future nanoelectromechanical systems and for many other applications. The extraordinary properties are however only attained by perfectly crystalline CNTs and quickly deteriorate when defects are introduced to the structure. The growth technique affects the crystallinity where in general CNTs grown by arc-discharge are close to perfectly crystalline, while CVD-grown CNTs have large defect densities. Mechanical deformation also affects these properties, even without introducing defects. When CNTs are bent they behave similarly to drinking straws, i.e. they buckle or ripple and their bending stiffness drops abruptly.

    In this thesis, the mechanical behaviour of individual CNTs and vertically aligned carbon nanofibers (VACNFs) has been studied by performing force measurements inside electron microscopes. Cantilevered CNTs, and VACNFs, were bent using a force sensor, yielding force-deflection curves while their structure was imaged simultaneously.

    We have found that CNTs grown by arc-discharge have a high enough crystallinity to possess a Young’s modulus close to the ideal value of 1 TPa. CVD-grown CNTs possess a Young’s modulus that is about one order of magnitude smaller, due to their large defect density. The VACNFs are yet another order of magnitude softer as a result of their cup-stacked internal structure.  We also found that a high defect density will increase the critical strain for the rippling onset and the relative post-rippling stiffness. Multi-walled CNTs with a small inner diameter are less prone to ripple and have a larger relative post-rippling stiffness. Our findings show large variations in the onset of rippling and the bending stiffness before and after rippling. These variations open up possibilities of tailoring the mechanical properties for specific applications.

  • 180.
    Jackman, Henrik
    et al.
    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.
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Mechanical behavior of carbon nanotubes in the rippled and buckled phase2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 8, s. 084318-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied the mechanical behavior of multi-walled carbon nanotubes for bending strains beyond the onset for rippling and buckling. We found a characteristic drop in the bending stiffness at the rippling and buckling onset and the relative retained stiffness was dependent on the nanotube dimensions and crystallinity. Thin tubes are more prone to buckle, where some lose all of their bending stiffness, while thicker tubes are more prone to ripple and on average retain about 20\% of their bending stiffness. In defect rich tubes the bending stiffness is very low prior to rippling but these tubes retain up to 70\% of their initial bending stiffness.

  • 181.
    Jackman, Henrik
    et al.
    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.
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Mechanical beviour of carbon nanotubes in the rippled phaseManuskript (preprint) (Övrigt vetenskapligt)
  • 182.
    Jacobsson, Lasse
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wickberg, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    De Vin, Leo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    A Realistic Lean Training Environment for the Manufacturing Industry: Karlstad Lean Factory2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Simulation for training lean manufacturing ranges from simple paper-based or LEGO®-based games to larger scale simulation environments, for instance push car assembly. Whilst such simulations may be suitable for educating students, they are often less suitable for training industry workers. The latter group is more diverse and is more used to intuitive learning than to formal instruction. Thus, it is important that a training environment for this group more realistically represents the work environment; otherwise training transfer will be limited. For this reason, a lean training environment that includes materials processing stations as well as assembly areas was created. The stations exhibit some realistic behaviour such as stochastic breakdowns. Based on a comparison between factory workers and university students, hypotheses for testing in future work are proposed.

  • 183.
    Jacobsson, Lasse
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wickberg, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    De Vin, Leo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Creating Industrially Relevant Environments for Teaching Lean Manufacturing at Karlstad University2016Ingår i: Advances in Manufacturing Technology XXX / [ed] Y.M. Goh and K. Case, IOS Press, 2016, Vol. 3, s. 514-519Konferensbidrag (Refereegranskat)
    Abstract [en]

    Simulation for training lean manufacturing ranges from simple paperbasedor LEGO®-based games to larger scale simulation environments, forinstance push car assembly. Whilst such simulations may be suitable for educatingstudents, they are often less suitable for training industry workers. The latter groupis more diverse and is more used to intuitive learning than to formal instruction.Thus, it is important that the training environment for this group more realisticallyrepresents the work environment; otherwise training transfer will be limited. Forthis reason, a lean training environment that includes materials processing stationsas well as assembly areas was created. The stations exhibit some realisticbehaviour such as stochastic breakdowns.

  • 184.
    Jansson, Adam
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Further development of Sand Bed Burner2014Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To determine whether a weapon system meets the requirements set for insensitivity, the system is getting exposed for special tests. One of these tests shows how the system reacts when it ends up in a fire. This test is called the "Fast Cook-Off (FCO) Test", called FCO-test, and performed with a Sand Bed Burner (SBB). According to primary testing provision, the fuel for this test is used of jet fuel such as Jet A-1. A project at Bofors Test Center (BTC) is in progress to use an alternative fuel of Liquefied Petroleum Gas (LPG). This fuel is very advantageous compared to jet fuel in terms of environmental impact, work environment and testing costs.

    The aim of this thesis is to improve the existing test equipment considering fire over the entire surface and solve the problems with dropped gas flow and freezing of gas bottles.

    SBB works in the sense that the new petrol LPG streams into the SBB and expands in the free space below the sand bed before the gas will diffuse through the bed of sand and the fire engulfs the object.

    LPG is a condensable gas that requires oxygen. LPG exceed from liquid to gas phase and needs a large lateral surface to take up more energy which results in better evaporationto the phase transfer. Reaction products from complete combustion of LPG are only water vapor and carbon dioxide, the same as in your exhaled air.

    To solve these problems it was needed to change P11 composite bottles to P45 steel bottles to get a longer evaporation and larger lateral surface. Four flow inlets instead were used of one into SBB for a better stream in the free space under the sand bed. Propane regulators used to get a lower and more constant flow to avoid freezing. Compressed airconnected tothe SBB to geta mix between oxygen and LPG.

    The result shows in higherheat radiation efficiency even though the flow was settled down to 1/3 with the new propane regulators. In test 2 the value was 37 kW/m2 and in test 7 it was around 57 kW/m2. Because of a smaller flow and bigger steel bottles the freezing disappeared. Smaller grain of sand together with four inlets and compressed air gave a more complete combustion.

  • 185.
    Jansson, Anna
    et al.
    Chalmers University of Technology.
    Nafari, Alexandra
    Chalmers University of Technology.
    Hedfalk, Kristina
    Göteborgs Universiet.
    Olsson, Eva
    Chalmers University of Technology.
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Sanz-Velasco, Anke
    Chalmers Tekniska Högskola.
    Monitoring the osmotic response of single yeast cells through force measurements in the environmental scanning electron microscope2014Ingår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, artikel-id 025901Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a measurement system that combines an environmental scanning electron microscope (ESEM) and an atomic force microscope (AFM). This combination enables studies of static and dynamic mechanical properties of hydrated specimens, such as individual living cells. The integrated AFM sensor provides direct and continuous force measurement based on piezoresistive force transduction, allowing the recording of events in the millisecond range. The in situ ESEM-AFM setup was used to study Pichia pastoris wild-type yeast cells. For the first time, a quantified measure of the osmotic response of an individual yeast cell inside an ESEM is presented. With this technique, cell size changes due to humidity variations can be monitored with nanometre accuracy. In addition, mechanical properties were extracted from load–displacement curves. A Young's modulus of 13–15 MPa was obtained for the Ppastoris yeast cells. The developed method is highly interesting as a complementary tool for the screening of drugs directed towards cellular water transport activity and provides new possibilities of studying mechanosensitive regulation of aquaporins.

  • 186.
    Jansson, Anton
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Characterization of epitaxial graphene grown on silicon carbide2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis work several manufacturing methods for graphene is discussed followed by an indepth study of graphene grown by a high temperature sublimation method (sublimation of siliconcarbide). The graphene surfaces studied have been grown by Graphensic AB, both graphenegrown on the Si-face and the C-face of the silicon carbide were studied. Six graphene samplesgrown 4H-SiC substrates were examined for homogeneity and surface morphology as well assome surface roughness parameters using Atomic Force Microscopy (AFM). The graphene wasstudied to get a better understanding of the surfaces and the growth mechanisms to improvemanufacturing parameters while also being informative for graphene sample customers. Anadditional graphene sample grown on 6H-SiC epitaxial layer was also studied to get a betterunderstanding of the sublimation mechanism. If graphene could be manufactured in a cheaprepeatable way the applications are endless and a new era of technology could emerge muchlike the silicon era that began several decades ago. In this thesis work the results are presentedas topography images as well as tables and histograms in the results section. The growth onthe Si-face is found to be well ordered when compared to the C-face which shows signs of alargely complex growth. The graphene on the Si-face lies on top of silicon carbide steps like acarpet with a buer layer interface against the silicon carbide. On the C-face this buer layeris not present but the graphene is deformed by buckling which is suspected to originate fromdierences in thermal properties between the graphene and the C-face. The in uence of AFMsettings for characterization of graphene while using intermittent mode have been evaluated andrecommendations are given. Finally a method for evaluating the homogeneity of the graphenelm is proposed but is in need of further verication.

  • 187.
    Jeppsson, Fredrik
    et al.
    Linköpings universitet.
    Haglund, Jesper
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). SMEER.
    Sampublicering med studenter – ett sätt att stärka forskningsanknytningen i lärarutbildningen2019Ingår i: Högre Utbildning, ISSN 2000-7558, E-ISSN 2000-7558, Vol. 9, nr 1, s. 98-111Artikel i tidskrift (Refereegranskat)
    Abstract [sv]

    Lärarutbildningen uppmärksammas inte sällan för att dess studenter har svårt att uppnå den nivå av akademiskt skrivande som krävs, inte minst vid examensarbeten. Som kontrast till den beskrivningen vill vi lyfta fram motexempel, där lärarstudenters examensarbeten och andra skrivuppgifter har nått en sådan kvalitet att de genom samförfattande med handledare och andra medförfattare har kunnat omarbetas och publiceras som vetenskapliga artiklar eller i mer lärartillvända forum, i vårt fall inom fysikdidaktik. Samförfattande med lärarstudenter kan på så vis vara ett sätt att stärka forskningsförankringen i lärarutbildningen. Förutsättningarna för att kunna lyckas med detta diskuteras, bland annat utifrån att under lärarutbildningen gradvis låta studenterna inlemmas i en praktikgemenskap av ämnesdidaktisk forskning.

  • 188.
    Johansson, Adam
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Phased Array System toolbox: An implementation of Radar System: A qualitative study of plane geometry and bearing estimation2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 189.
    Johansson Lopez, Teresa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Utveckling av stödverktyg och kravspecifikationsmall: Mot en mer effektiv och kundcentrerad maskinkonstruktion2015Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Detta projekt har under våren 2015 genomförts som examensarbete för högskoleingenjörsprogrammet i innovationsteknik och design vid fakulteten för hälsa, natur- och teknikvetenskap på Karlstads universitet. Merparten av arbetet har utförts på Valmets konstruktionsavdelning för den våta änden av pappersmaskinen på Lamberget. Där har intervjuer och observationer gjorts för att kunna utveckla ett digitalt stödverktyg och en kravspecifikationsmall i Excel.

     

    För att kunna utveckla ett verkyg och en mall anpassat efter Valmets verksamhet har en kravspecifikation för en komponent i pappersmaskinen tagits fram. En omfattande förstudie har gjorts med kunden i fokus för att ta fram en fungerande kravspecfikation enligt teorin i projektets teoretiska referensram. I förstudien har bland annat intervjuer och observationer gjorts på Valmet och på tre olika pappersbruk i Sverige. Intervjuerna på pappersbruk har gjorts för att få förstahandsinformation från de verkliga användarna som är operatörerna.

     

    I förstudien ingår informationssökning, kartläggning av intressenter, intervjuer och observationer. All information från förstudien sammanställdes i en funktionsanalys och QFD-analys som slutligen mynnade ut i en kravspecifikation för komponenten. En produktspecifikation med komponentens faktiska egenskaper togs också fram. Utifrån detta material utvecklades ett digitalt stödverktyg i Excel som ska underlätta användningen av de metoder som valts. Stödverktyget översätter identifierade kundbehov från förstudien till mätbara kundkrav. De mätbara kundkraven kan sedan sammanställas i en kravspecifikationsmall i Excel som också utvecklats.

     

    Genom testning och förbättring tillsammans med personal på Valmet har verktyget och mallen anpassats efter företagets verksamhet. Användningen av detta material ska underlätta arbetet med att ta fram kravspecifikationer för en effektiv och mer kundcentrerad produktutveckling. 

  • 190.
    Jordansson, Hannah
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. 1988.
    Beräkningsprogram för transportbanor2016Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This project has been implemented as a degree of Bachelor of Science education in Mechanical Engineering at the University of Karlstad during the spring of 2016. The work has been carried out by Hannah Jordansson, a student at the Faculty of Health, Nature and Technology science. The main task of the project was to develop a calculation program in Excel for industrial conveyors for the company ÅF Industry. ÅF Industry requested a calculation program to use as a tool when building the conveyors. The conveyors consist of two different types, one rolling conveyor and one chain conveyor. The two types will be developed separately in the calculation program. The goal with the work was to build a program that will give the user the right outputs from certain inputs. The desired outputs from ÅF Industry for both conveyors was the deflection of the trolley tracks, if needed a cross beam and also information about the required drive. During the development of functional calculation program the work began with preparing all the equations needed. The equations were then put together and evaluated. When all of the equations were approved they were put in and performed in Excel. The calculation program is completed, tested and evaluated. The program has been formed to a layout that meet ÅF Industry’s requests.

  • 191.
    Kadhim, Yasser
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Metalization of Micro Fibrillated Cellulose (MFC) films2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I denna avhandling karakteriserades två MFC-baserade filmer Carboxymethylated-MFC och   Enzymatic-MFC som metalliserades för att förbättra barriäregenskaperna vid hög relativ fuktighet. Flera metoder har används för karaktäriseringsprocessen, vilka var Atomic Force Microscopy (AFM), Contact Angle (CA), Energy Dispersive Spectra (EDS), Light Microscopy (LM), Scanning Electron Microscopy (SEM), och Oxygen Transmission Rate (OTR). Physical Vapor Deposition (PVD) systemet användes för metalliseringen av filmerna, där ett tunt skikt aluminium med en tjocklek av 200 nm deponerades. Resultaten visade att ENZ-MFC har högreråhet och lägre OTR-värden jämfört med CM-MFC. Kontaktvinkelvärdena påvisade att bådaicke-metalliserade MFC-filmer har en hydrofil yta med värden omkring 50 grader. SEM- och EDS-bilder visade att båda filmerna har ytdefekter i storleksordningen en mikrometer.

    Den bästa barriärförbättringen genom metallisering uppnåddes för den metalliserade CM-MFC, där OTR-värdena minskade med en storleksordning efter metallisering. För ENZ-MFCförbättrade dock metallisering inte OTR vid hög RH. Det skyddande skiktet skyddar effektivt MFC-filmen så länge som filmens ytråhet inte var för hög. Gränsen är intervallet mellan 40 och140 nm (Kvadratiskt medelvärde för ytråhet).

  • 192.
    Karlsson, Christian
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Regression Models of 3D Wakes for Propellers2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I det här arbetet, har regressionsmodeller för medströmsfältet in i en propeller vid viss axielloch nominell position utvecklats. Medströmsfältet är ojämn strömning efter en kropp nedsänkt i enviskös vätska. Vi har föreslagit modeller för axiell och tangentiell hastighetsfördelning som funktionerför fartygsskrov-och propeller-parametrar. Regressionsmodellerna modellerades med hjälpav Fourier-serier och parameterskattning baserade på skeva Gaussfördelningar och sinusfunktioner.Medströmsfältet är en viktig parameter i propeller design. Regressionsmodellerna är baserade påexperimentella data från Rolls-Royces Hydrodynamiska Forskningscenter i Kristinehamn. Vi harockså studerat flödet i axialhastighetsfördelningen i propellplanet med hjälp av den koherenta struktureringsfärgmetoden.Den koherenta struktureringsfärgmetoden används för att studera koherentamönster genom att titta på vätskepartikelkinematik. Med hjälp av denna typ av analys observeradevi att hastighetsfördelningen uppför sig kinematiskt lika i de olika regionerna i medströmsfältet,vilket enligt koherenta strukturfärgmetoden indikerar koherens.

  • 193.
    Karlsson, Christopher
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Thermal Analysis of Flatness Measuring System for Rolling Applications2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In rolling applications it is critical to be able to control the flatness of the metal strip. An uneven strip may in the most extreme cases lead to strip breaks. One of the systems used to measure the flatness consists of a measuring roll, which the strip is deflected over. During the contact time, heat is transferred from the hot strip to the roll. The roll is not allowed to get too hot due to risks of overheating the electronics. Previously the measuring roll have only been used in cold rolling applications, where this is usually not a problem. There is now an increased interested in using the roll in more extreme applications with higher strip temperatures. This requires knowledge about all the potential heat sources present in the system. The subject of this thesis work has been to investigate some of the contributions to the thermal balances of the measuring roll. A numerical model has been developed to describe conductive heat transfer between the metal strip and the measuring roll. Using the numerical model, the heat transfer was obtained as a function of the temperature, contact time and thickness of the strip. From these simulations a heat transfer coefficient associated with an external cooling demand was derived. The flatness measuring roll is equipped with pressure sensitive sensors used to measure the flatness of the strip. These sensors are located in internal channels and generate heat through resistive heating. The impact of this on the overall temperature of the roll was determined to be small. In the internal channels there is also a flow of air. In normal operation scenarios the flow is very low, leading to a small cooling capacity. From the thermal balance of the system it was concluded that the dominant heat source was the heat transfer between the strip and roll. This heat transfer is however heavily dependent on material properties and surface characteristics. The model used to describe the conductive heat transfer assumes no contact resistance between the strip and roll. This provides an upper-bound estimate of the heat transfer. If the contact resistance is included within the model the impact of the individual heat sources increases. Both the material properties and contact resistance requires further investigation. Combining the results of M. Gustafsson (Master of Science thesis, Karlstad University, 2018), a thermal balance for the measuring roll has successfully been developed. This balance clarifies the critical parameters which should be considered when designing the external cooling of the roll.

  • 194.
    Karlsson, Eilind
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Kitaev models for topologically ordered phases of matter2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Condensed matter physics is the study of the macroscopic and microscopic properties of condensed phases of matter. For quite some time, Landau’s symmetry breaking theory was believed to describe and explain the nature of any phase transition. However, since the late 1980s, it has become apparent that it is necessary to introduce some new kind of order, named topological order, that transcends the traditional symmetry description. In this thesis we will study the Kitaev model, which is a Hamiltonian lattice model that allows one to incorporate the concept of topological order, as well as the corresponding operators and algebras. First, we consider the model on an infinite lattice, and show how to relate local and global degrees of freedom of the anyons/quasi-particles living on sites to the ribbon operators. Afterwards, we introduce holes and an external boundary to the lattice, and examine the ramifications of this generalization in terms of the ground state degeneracy. Lastly, we verify that the algebra formed by boundary site operators has the structure of a quasi-Hopf algebra. 

  • 195.
    Karlsson, Joar
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Beri, Jacki
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Ett portabelt ramverk för modifiering av användargränssnitt: Applicerat på en smartspegel2019Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    On behalf of the consulting company Altran this project is to create a solution to modify a modular user interface, a user interface which is divided into areas where each area, module, contains some kind of information. For example a clock or today’s weather report. A cross- platform mobile application would be able to modify the modular user interface, in real-time over the same network. The project was to be implemented on a smart mirror, a product that had to be built and that displays information when turned on but when in an off mode looks like an ordinary mirror. The project was to be able to be reused on other similar modular user interfaces.

    A smartmirror was built with the single-board computer Raspberry Pi 3 B+ running the software MagicMirror2. To modify the smartmirror, a module for the smartmirror was developed to communicate with the other installed modules and the middleware. The developed module was also designed to enable easy modification of the user interface.

    A mobile application was developed to run on cellular phones running the operating systems iOS and Android. The application can modify the smartmirror thus changing the modules positions, installing new modules, replacing the existing modules with new ones and to hide or show the modules.

    A middleware was developed which had the function to create a connection between the mobile application and the modular user interface which is running the middleware thus working as a translation layer. With the middleware running, a modification of the user interface was able to happen, in real-time over the same network.

    This project can, in theory, be reused in other similar modular user interfaces other than the smartmirror if the messages sent through the middleware to the user interface are handled correctly.

  • 196.
    Karlsson, Marcus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    Implementering av LEAN i småskalig mejeriverksamhet2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Wermlands Mejeri AB startade under hösten 2015 som en ny leverantör av mjölk och grädde för de värmländska konsumenterna. Under det dryga året som mejeriet haft sin verksamhet igång har det skett flera investeringar och produktionskapaciteten har ökat. För att uppnå den nya kapaciteten ställs det krav på produktionsutrustningen. Den måste fungera utan avbrott för att få en jämn och kontinuerlig produktion samtidigt som kvaliteten i livsmedelsbranschen är högsta prioritet av hygieniska skäl.

    När mjölk tillverkas genomgår den ett antal processteg för att kunna säljas. Detta projekt är avgränsat till förpackningssteget och förpackningsavdelningen.

    Syftet med projektet är att kartlägga de åtta slöserierna som beskrivs i produktionssystemet Lean. Målet är att efter kartläggningen kunna ge konkreta förslag till förbättringar för att minska en eller två slöserier.

    Genom observationer, intervjuer och insamling av data har slöserierna analyserats och förbättringsåtgärder har föreslagits med hjälp av verktyget 5S. 5S är ett verktyg inom Lean som beskriver hur saker kan förbättras och hur det kan ske.

    Två av de åtta slöserierna valdes ut för att analyseras mer och ge förbättringsförslag. De två blev rörelser och defekter. Genom att använda sig av de två första S:en, sortera och strukturera så kan rörelser minskas för personalen i förpackningsavdelningen. Defekterna uppstår i de olika maskinerna och kan minskas genom att arbeta mer förebyggande. Genom att införa ett underhållssystem och kartlägga vart och varför defekterna uppstår så skapas en bild av hur defekterna uppstår. Att arbeta systematiskt med de delar som orsakar problem i maskinerna och föra statistik över dem kan antalet defekter minska. Ett avvikelserapporteringssystem bör införas för att se hur ofta och var defekterna uppstår.

    Projektet kan ses som ett första steg för att införa Lean i Wermlands mejeris verksamhet och kan användas för vidare studier inom området.

  • 197.
    Karlsson, Marcus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Kund- och användarinvolvering i utvärderingsprocessen: En utvärderingsmetod för gavelisolering till Yankee-cylindrar2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Uppsatsens syftet var:

    att ta fram – med tjänstelogik och ett hållbarhetsperspektiv - en holistisk insamlingsmetod för urvalskriterier och en utvärdeingsmetod samt undersöka om det finns skillnader mellan kund- och producentkriterier.

    Teorierna i uppsatsen är hämtade ifrån klassisk produktutveckling i kombination med tjänsteforsking och framförallt tjänsteinnovation. En fallstudie har genomförts för svara på de fyra forskningsfrågorna:

    1. Hur bör kriterierna tas fram för att uppnå ett holistiskt perspektiv?

    2. Vilka kriterier bör användas vid utvärdering av produkter?

    3. Hur bör kriterierna användas för att säkerställa att produkten uppfyller de krav som ställs?

    4. Hur förändras urvalskriterierna i utvecklingsprocessen på grund av kund- och användarinvolvering?

    Resulatet är en utvärderingsmetod för gavelisolering till Yankee-cylindrar som använder sig av en

    produktspecfikation, Phal och Beitz elimineringsmatris, Pughs relativa beslutsmatris och Kesselrings kriterieviktsmatris. En analys av processen och hur kund- och användarinvolvering påverkade kriterierna som används i utvärderingsmetoden utfördes när metoden var framtagen.

    Uppsatsen bidrar till ytterligare kunskaper om kund- och användarinvolvering i utvecklingsprocessen samt en metod för hur kunders och användares kunskap kan användas i utvärderingsprocessen.

  • 198.
    Karlsson, Patrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    The influence of tool steel microstructure on galling2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a sort of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, the overall aim was to gain knowledge of the influence of tool steel microstructure on galling initiation under sliding conditions. It was discovered that material transfer and tool steel damage caused by sheet material flow creating wear-induced galling initiation sites occurred in the early stage of galling. The galling resistance was higher for tool steels with higher matrix hardness due to better resistance to tool steel damage. Initial friction and critical contact pressure to galling was influenced by the strength of the sheet material. Material transfer happened at low pressures and the friction value was high in a case of sheet materials with lower proof strength, possibly due to the sheet contact against the tool steel matrix resulting in high adhesion and quicker tool damage. It was demonstrated that, in addition to hardness of the tool steel matrix and sheet material proof strength, tool steel microstructural features like size, shape, distribution and height of hard phases are important parameters influencing galling. Tool steels comprising homogeneously distributed, small and high hard phases better prevented the contact between sheet material and the tool steel matrix. Thus, a metal to metal contact with high friction was more efficiently avoided, which resulted in better tool performance.

     

  • 199.
    Karlsson, Patrik
    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.
    Influence of tool steel microstructure on friction and initial material transfer2014Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 319, nr 1-2, s. 12-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation was conducted to study the influence of tool steel microstructure on initial material transfer and friction. Two different powder metallurgy tool steels and an ingot cast tool material were tested in dry sliding against 1.4301, 1.4162, Domex 355 MC and Domex 700 MC sheet materials. It was found that tool steel hard phase heights influence initial material transfer and friction. The coefficient of friction increased with decreasing tool steel hard phase heights at 50 N normal load and initial material transfer occurred around protruding hard phases. At higher load of 500 N the sheet material adhered to both the tool steel matrix and hard phases. Coefficient of friction decreased with increasing proof strength of the sheet material at 500 N normal load.

  • 200.
    Katea, Billy
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    CFD Analysis of Air Flow Through a New Design For an Outlet Louver of a Cooling System: CFD Analys av luftflödet genom en ny design för utloppet i ett kylsystem2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In order to improve the performance of the outlet louver for the cooling system used in the Combat Vehicle CV90, the manufacturing company BAE System Hägglunds AB recently came out with a new design.

    This project deals with the possible modifications of the new design to achieve a higher performance in terms of air flow resistance without losing any protection capabilities.

    18 versions of BAE Systems Hägglunds AB new design were modeled using Creo Parametric 3.0 3D CAD-software. These versions were modeled with respect to the requirement of protection, when several possible threat scenarios  were carefully reviewed and studied.   

    The air flow through each one of these designs was CFD-simulated using ABAQUS/CAE 6.14 CFD-code, the pressure drop received in each CFD-model was compared to the pressure drop over the currently used design of the outlet louver. The concept called concept Arrows RD shows the lowest pressure drop, which is nearly 50 % lower than the pressure drop over the original design, showing that the new design could be a reasonable replacement to the currently used design.

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