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  • 201.
    Ahlström, Johan M.
    et al.
    Chalmers University of Technology, Sweden.
    Pettersson, Karin
    RISE - Research Institutes of Sweden, Built Environment, Energy and Circular Economy. Chalmers University of Technology, Sweden.
    Wetterlund, Elisabeth
    Luleå University of Technology, Sweden.
    Harvey, Simon
    Chalmers University of Technology, Sweden.
    Value chains for integrated production of liquefied bio-SNG at sawmill sites – Techno-economic and carbon footprint evaluation2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 206, p. 1590-1608Article in journal (Refereed)
    Abstract [en]

    Industry's increasing demand for liquefied natural gas could be met in the future by liquefied methane produced from biomass feedstock (LBG - liquefied biogas). This study presents results from an investigation of value chains for integrated production of LBG at a generic sawmill site, based on gasification of sawmill waste streams and forest residues. The objective was to investigate the cost for, as well as the carbon footprint reduction associated with, production and use of LBG as a fuel. Five different LBG plant sizes were investigated in combination with three different sawmill sizes. The resulting cases differ regarding biomass feedstock composition, biomass transportation distances, LBG plant sizes, how efficiently the excess heat from the LBG plant is used, and LBG distribution distances. Pinch technology was used to quantify the heat integration opportunities and to design the process steam network. The results show that efficient use of energy within the integrated process has the largest impact on the performance of the value chain in terms of carbon footprint. The fuel production cost are mainly determined by the investment cost of the plant, as well as feedstock transportation costs, which mainly affects larger plants. Production costs are shown to range from 68 to 156 EUR/MW hfuel and the carbon footprint ranges from 175 to 250 kg GHG-eq/MW hnet biomass assuming that the product is used to substitute fossil LNG fuel. The results indicate that process integration of an indirect biomass gasifier for LBG production is an effective way for a sawmill to utilize its by-products. Integration of this type of biorefinery can be done in such a way that the plant can still cover its heating needs whilst expanding its product portfolio in a competitive way, both from a carbon footprint and cost perspective. The results also indicate that the gains associated with efficient heat integration are important to achieve an efficient value chain.

  • 202.
    Ahlström, Johan
    et al.
    RISE, Swerea, Swerea KIMAB.
    Tidblad, Johan
    RISE, Swerea, Swerea KIMAB.
    Sandberg, Bertil
    RISE, Swerea, Swerea KIMAB.
    Wadsö, L.
    Lund University.
    Galvanic corrosion properties of steel in water saturated concrete2015In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 66, no 1, p. 67-75Article in journal (Refereed)
    Abstract [en]

    Aluminum-based sacrificial anodes were installed to reinforced concrete to stop ongoing corrosion in cooling water tunnels in a Swedish nuclear power plant. The steel rebars were also unintentionally connected to stainless steel water pumps. Therefore, the consumption rate of the sacrificial anodes was higher than predicted. An experimental and a field study were performed to assess if the steel rebar suffer from galvanic corrosion and if the stainless steel pumps are responsible alone for the high consumption rate. It was found from the experimental study that there is an increased risk of galvanic corrosion for steel rebar when the corrosion potential is raised to -200mV (SCE) for samples with 1% CL- by mass of cement and -500mV (SCE) for samples with 2% Cl- by mass of cement. The experimental results were compared with the corrosion potential measured in the cooling water tunnel where sacri ficial anodes were in use and not mounted at all. The cooling water tunnel without sacrificial anodes had generally more anodic corrosion potentials compared to the tunnel with anodes. The tunnel with anodes had also more anodic potentials closer to the stainless steel pumps than further away which means that the rebar is affected by the stainless steel pumps. However, the measured corrosion potentials in the tunnels were not as anodic as the potentials needed for high galvanic current measured in the experimental study. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA.

  • 203.
    Ahlström, Johan
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB. Chalmers University of Technology, Sweden.
    Tidblad, Johan
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Tang, Luping
    Chalmers University of Technology, Sweden.
    Sederholm, Bror
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Leijonmarck, Simon
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Electrochemical properties of oxide scale on steel exposed in saturated calcium hydroxide solutions with or without chlorides2018In: International Journal of Corrosion, ISSN 1687-9325, E-ISSN 1687-9333, Vol. 2018, article id 5623504Article in journal (Refereed)
    Abstract [en]

    The electrochemical properties of various iron oxide scales on steel exposed in saturated calcium hydroxide solutions were investigated. The iron oxide scales were manufactured by different heat treatments and grinding processes and characterized using X-ray diffraction and scanning electron microscope. The electrochemical properties of the scales were assessed by measuring the corrosion potential and using electrochemical impedance spectroscopy and potentiodynamic polarization curves. It was found that wustite and magnetite are less noble compared to hematite but are more effective as cathodic surfaces. The results show that the electrochemical properties of the mill scale can be an important contributing factor in the corrosion of steel in concrete.

  • 204.
    Ahlsén, Ulf
    et al.
    CBI - Cement- och betonginstitutet.
    Bellander, Ulf
    Uppskattning av armerings läge och diameter i färdig konstruktion1979Report (Refereed)
  • 205.
    Ahlsén, Ulf
    et al.
    CBI - Cement- och betonginstitutet.
    Klevbo, Göran
    Provningsmetod för plattsättningsbruk1979Report (Refereed)
  • 206.
    Ahlsén, Ulf
    et al.
    CBI - Cement- och betonginstitutet.
    Montin, Stefan
    Metoder för bestämning av komprimeringsgrad hos färsk betong1979Report (Refereed)
  • 207. Ahmad, SI
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Catalysis in micellar and liquid crystalline phases1973In: Chemie, Physikalische Chemie und Anwendungstechnik der Grenzflächenaktiven Stoffe, Munchen: Carl Hanser Verlag GmbH, 1973, p. 917-924Conference paper (Refereed)
  • 208. Ahmad, SI
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Catalysis in micellar and liquid-crystalline phases : I. the system water-hexadecyltrimethylammonium bromide-hexanol1972In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 94, p. 5196-5199Article in journal (Refereed)
  • 209. Ahmad, SI
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Phase equilibria and foam stability in solutions of cationic surfactants1971In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 102, p. 3-14Article in journal (Refereed)
  • 210. Ahmad, SI
    et al.
    Shinoda, K
    Friberg, S
    YKI – Ytkemiska institutet.
    Microemulsions and phase equilibria1974In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 47, p. 32-37Article in journal (Refereed)
  • 211.
    Ahmadkhaniha, D.
    et al.
    Jönköping University, Sweden.
    Eriksson, F.
    Linköping University, Sweden.
    Leisner, Peter
    RISE - Research Institutes of Sweden, Safety and Transport, Electronics. Jönköping University, Sweden.
    Zanella, C.
    Jönköping University, Sweden.
    Effect of SiC particle size and heat-treatment on microhardness and corrosion resistance of NiP electrodeposited coatings2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 769, p. 1080-1087Article in journal (Refereed)
    Abstract [en]

    Electrodeposition of NiP composite coatings with nano and sub-micron sized SiC has been carried out to investigate the possibility of replacing hard chromium coatings. The composition and structure of the coatings were evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis, respectively. Microhardness was measured by Vickers indentation and polarization measurements were carried out to study the corrosion behavior of the coatings. The results showed that submicron particles can be codeposited with a higher content as compared to nano sized ones. However, even if a smaller amount of the nano-sized SiC particles are incorporated in the coating, the contribution to an increasing microhardness was comparable with the submicron sized particles, which can be related to the higher density of codeposited particles. SiC particles did not change the anodic polarization behavior of NiP coatings in a 3.5% NaCl solution. Finally, the effect of heat-treatment on the coatings properties at 400 °C for 1 h was studied to investigate the contribution of particles and heat-treatment on hardness and corrosion properties. It was found that the heat-treatment doubled the microhardness and changed the anodic polarization behavior of the coatings from passive to active with respect to the as-plated conditions.

  • 212.
    Ahmadkhaniha, Donya
    et al.
    Jönköping University, Sweden.
    Leisner, Peter
    RISE - Research Institutes of Sweden, Safety and Transport, Electronics. Jönköping University, Sweden.
    Zanella, Caterina
    Jönköping University, Sweden.
    Pinate, Santiago
    Jönköping University, Sweden.
    Electrodeposition of Ni high P composite coatings containing nano and submicron ceramic particles2017Conference paper (Refereed)
  • 213.
    Ahmadkhaniha, Donya
    et al.
    Jönköping University, Sweden.
    Pinate, S.
    Jönköping University, Sweden.
    Leisner, Peter
    RISE - Research Institutes of Sweden, Safety and Transport, Electronics. Jönköping University, Sweden.
    Zanella, C.
    Jönköping University, Sweden.
    Electrodeposition of Ni high P composite coatings containing nano and submicro ceramic particles2017In: EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017, Czech Association of Corrosion Engineers , 2017Conference paper (Refereed)
    Abstract [en]

    In this study, electrodeposition of Ni-P composite coatings has been carried out to investigate the possibility of replacing hard chromium coatings. Therefore, electrodeposition of Ni-P based composite coating with different SiC particle size (50 nm, 100 nm and 500 nm) or B4C (500 nm) was performed. The coating's composition was evaluated by energy dispersive spectroscopy (EDS), microhardness of the coatings was measured by Vickers indentor and polarization measurements were carried out to study the corrosion behavior of the coatings. The results showed that B4C particles can codeposit in higher percent respect to SiC ones. Ceramic particles increased microhardness of Ni-P coatings to 700HV0.01. The polarization behavior of all the coatings in 3.5% NaCl was similar in as plated state proving that particles did not hindered the passive behaviour. Finally, the effect of heat-treatment (at 400 ºC for 1 hour) on the coating's properties was studied to compare the contribution of particles and heat-treatment on mechanical and corrosion properties of the coatings. Heat-treatment increased the coating's microhardness and changed the anodic polarization behavior of the coatings respect to the as plated conditions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. All rights reserved.

  • 214.
    Ahmed, Jawwad
    et al.
    Ericsson Research, Sweden.
    Johnsson, Andreas
    Ericsson Research, Sweden.
    Moradi, Farnaz
    Ericsson Research, Sweden.
    Pasquini, Rafael
    KTH Royal Institute of Technology, Sweden; Federal University of Uberlandia, Brazil.
    Flinta, Christofer
    Ericsson Research, Sweden.
    Stadler, Rolf
    RISE - Research Institutes of Sweden, ICT, SICS. KTH Royal Institute of Technology, Sweden.
    Online approach to performance fault localization for cloud and datacenter services2017In: Proceedings of the IM 2017 - 2017 IFIP/IEEE International Symposium on Integrated Network and Service Management, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 873-874Conference paper (Refereed)
    Abstract [en]

    Automated detection and diagnosis of the performance faults in cloud and datacenter environments is a crucial task to maintain smooth operation of different services and minimize downtime. We demonstrate an effective machine learning approach based on detecting metric correlation stability violations (CSV) for automated localization of performance faults for datacenter services running under dynamic load conditions.

  • 215.
    Ahmed, Mobyen Uddin
    et al.
    Mälardalen University, Sweden.
    Fotouhi, Hossein
    Mälardalen University, Sweden.
    Köckemann, Uew
    Örebro University, Sweden.
    Lindén, Maria
    Mälardalen University, Sweden.
    Tomasic, Ivan
    Mälardalen University, Sweden.
    Tsiftes, Nicolas
    RISE - Research Institutes of Sweden, ICT, SICS.
    Voigt, Thiemo
    RISE - Research Institutes of Sweden, ICT, SICS.
    Run-Time Assurance for the E-care@home System2018In: Part of the Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering book series (LNICST, volume 225), 2018, p. 107-110Conference paper (Refereed)
    Abstract [en]

    This paper presents the design and implementation of the software for a run-time assurance infrastructure in the E-care@home system. An experimental evaluation is conducted to verify that the run-time assurance infrastructure is functioning correctly, and to enable detecting performance degradation in experimental IoT network deployments within the context of E-care@home. © 2018, ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering.

  • 216.
    Ahmed, Mobyen Uddin
    et al.
    Mälardalen University, Sweden.
    Fotouhi, Hossein
    Mälardalen University, Sweden.
    Köckemann, Uwe
    Örebro University, Sweden.
    Lindén, Maria
    Mälardalen University, Sweden.
    Tomasic, Ivan
    Mälardalen University, Sweden.
    Tsiftes, Nicolas
    RISE - Research Institutes of Sweden, ICT, SICS.
    Voigt, Thiemo
    RISE - Research Institutes of Sweden, ICT, SICS.
    Run-Time Assurance for the E-care@home System2017In: Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST, 2017, Vol. 225, p. 107-110Conference paper (Refereed)
  • 217.
    Ahmed, Jawwad Imtiaz
    et al.
    Ericsson Research, Sweden.
    Josefsson, Tim
    Uppsala University, Sweden.
    Johnsson, Andreas
    Ericsson Research, Sweden.
    Flinta, Christofer
    Ericsson Research, Sweden.
    Moradi, Farnaz
    Ericsson Research, Sweden.
    Pasquini, Rafael
    UFU Federal University of Uberlandia, Brazil.
    Stadler, Rolf
    RISE - Research Institutes of Sweden, ICT, SICS. KTH Royal Institute of Technology, Sweden.
    Automated diagnostic of virtualized service performance degradation2018In: IEEE/IFIP Network Operations and Management Symposium: Cognitive Management in a Cyber World, NOMS 2018, 2018Conference paper (Refereed)
    Abstract [en]

    Service assurance for cloud applications is a challenging task and is an active area of research for academia and industry. One promising approach is to utilize machine learning for service quality prediction and fault detection so that suitable mitigation actions can be executed. In our previous work, we have shown how to predict service-level metrics in real-time just from operational data gathered at the server side. This gives the service provider early indications on whether the platform can support the current load demand. This paper provides the logical next step where we extend our work by proposing an automated detection and diagnostic capability for the performance faults manifesting themselves in cloud and datacenter environments. This is a crucial task to maintain the smooth operation of running services and minimizing downtime. We demonstrate the effectiveness of our approach which exploits the interpretative capabilities of Self- Organizing Maps (SOMs) to automatically detect and localize different performance faults for cloud services.

  • 218.
    Ahmed, Mobyen
    et al.
    Mälardalen University, Sweden.
    Andersson, Peter
    Mälardalen University, Sweden.
    Andersson, Tim
    Mälardalen University, Sweden.
    Aparicio, Elena
    Mälardalen University, Sweden; Mälarenergi AB, Sweden.
    Baaz, Hampus
    Mälardalen University, Sweden.
    Barua, Shaibal
    RISE - Research Institutes of Sweden, ICT, SICS. Mälardalen University, Sweden.
    Bergström, Albert
    Mälardalen University, Sweden.
    Bengtsson, Daniel
    Mälardalen University, Sweden.
    Orisio, Daniele
    State Institute of Higher Education "Guglielmo Marconi", Italy.
    Skvaril, Jan
    Mälardalen University, Sweden.
    Zambrano, Jesus
    Mälardalen University, Sweden.
    A machine learning approach for biomass characterization2019In: Energy Procedia, Elsevier Ltd , 2019, p. 1279-1287Conference paper (Refereed)
    Abstract [en]

    The aim of this work is to apply and evaluate different chemometric approaches employing several machine learning techniques in order to characterize the moisture content in biomass from data obtained by Near Infrared (NIR) spectroscopy. The approaches include three main parts: a) data pre-processing, b) wavelength selection and c) development of a regression model enabling moisture content measurement. Standard Normal Variate (SNV), Multiplicative Scatter Correction and Savitzky-Golay first (SG1) and second (SG2) derivatives and its combinations were applied for data pre-processing. Genetic algorithm (GA) and iterative PLS (iPLS) were used for wavelength selection. Artificial Neural Network (ANN), Gaussian Process Regression (GPR), Support Vector Regression (SVR) and traditional Partial Least Squares (PLS) regression, were employed as machine learning regression methods. Results shows that SNV combined with SG1 first derivative performs the best in data pre-processing. The GA is the most effective methods for variable selection and GPR achieved a high accuracy in regression modeling while having low demands on computation time. Overall, the machine learning techniques demonstrate a great potential to be used in future NIR spectroscopy applications. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.

  • 219. Ahniyaz, A
    et al.
    Seisenbaeva, GA
    Häggström, L
    Kamali, S
    Kessler, G
    Nordblad, P
    Johansson, C
    RISE, Swedish ICT, Acreo.
    Bergström, L
    Preparation of iron oxide nanocrystals by surfactant-free or oleic acid-assisted thermal decomposition of a Fe(III) alkoxide2008In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 320, p. 781-87Article in journal (Refereed)
  • 220. Ahniyaz, Anwar
    Electrochemical investigation of the inhibition effect of CeO2 nanoparticles on the corrosion of mild steel2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 131, no Jun, p. 71-78Article in journal (Refereed)
  • 221. Ahniyaz, Anwar
    Influence of polyaniline and cerium oxide nanoparticles on the corrosion protection properties of alkyd coating (AETOC 2013: "Workshop on the Application of Electrochemical Techniques to Organic Coatings")2014In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 77, no 12, p. 2031-2038Article in journal (Refereed)
  • 222.
    Ahniyaz, Anwar
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Precise control over shape and size of iron oxide nanocrystals suitable for assembly into ordered particle arrays2014In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 15, no 5, p. 55010-Article in journal (Refereed)
  • 223.
    Ahrentorp, F
    et al.
    RISE, Swedish ICT, Acreo.
    Astalan, A
    Blomgren, J
    RISE, Swedish ICT, Acreo.
    Jonasson, C
    Wetterskog, E
    Svedlindh, P
    Lak, A
    Ludwig, F
    van Ijzendoorn, LJ
    Westphal, F
    Gruttner, C
    Gehrke, N
    Gustafsson, S
    Olsson, E
    Johansson, C
    RISE, Swedish ICT, Acreo.
    Effective particle magnetic moment of multi-core particles2015In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 380, p. 221-6Article in journal (Refereed)
  • 224.
    Ahrentorp, F
    et al.
    RISE, Swedish ICT, Acreo.
    Astalan, AP
    Jonasson, C
    Blomgren, J
    RISE, Swedish ICT, Acreo.
    Qi, B
    Thompson Mefford, O
    Yan, M
    Courtois, J
    Berret, JF
    Fresnais, J
    Sandre, O
    Dutz, S
    Muller, R
    Johansson, C
    RISE, Swedish ICT, Acreo.
    Sensitive High Frequency AC Suceptometry in Magnetic Nanoparticle Applications2010In: AIP Conference Proceedings, Vol. 1311, p. 213-23Article in journal (Refereed)
  • 225.
    Ahrentorp, Fredrik
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Blomgren, Jacob
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jonasson, Christian
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sarwe, Anna
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sepehri, Sobhan
    Chalmers University of Technology, Sweden.
    Eriksson, Emil
    Chalmers University of Technology, Sweden.
    Kalaboukhov, Alexei
    Chalmers University of Technology, Sweden.
    Jesorka, Aldo
    Chalmers University of Technology, Sweden.
    Winkler, Dag
    Chalmers University of Technology, Sweden.
    Schneiderman, Justin F.
    University of Gothenburg, Sweden.
    Nilsson, Mats
    Stockholm University, Sweden.
    Albert, Jan
    Karolinska University Hospital, Sweden; Karolinska Institute, Sweden.
    de la Torre, Theresa Z. G.
    Uppsala University, Sweden.
    Strømme, Maria
    Uppsala University, Sweden.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils2017In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 427, p. 14-18Article in journal (Refereed)
    Abstract [en]

    We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 µm. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 µL) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.

  • 226.
    Ahrentorp, Fredrik
    et al.
    RISE, Swedish ICT, Acreo, Sensor Systems.
    Blomgrten, Jakob
    Coil comprising a winding comprising a multi-axial cable2011Patent (Other (popular science, discussion, etc.))
  • 227.
    Ahrné, Lilia
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Effect of Infrared Blanching on Enzyme Activity and Retention of β-Carotene and Vitamin C in Dried Mango2015In: Journal of Food Science, ISSN 0022-1147, E-ISSN 1750-3841, Vol. 80, no 6, p. E1235-E1242Article in journal (Refereed)
  • 228.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Andersson, C.-G.
    Floberg, P.
    Rosen, J.
    Lingnert, Hans
    SIK – Institutet för livsmedel och bioteknik.
    Effect of crust temperature and water content on acrylamide formation during baking of white bread: Steam and falling temperature baking2007In: Lebensmittel-Wissenschaft + Technologie, ISSN 0023-6438, E-ISSN 1096-1127, Vol. 40, no 10, p. 1708-1715Article in journal (Refereed)
    Abstract [en]

    The effect of crust temperature and water content on acrylamide formation was studied during the baking of white bread. To assess the effect of over-baking, we used a full factorial experimental design in which the baking time was increased by 5 and 10 min at each baking temperature. Additional experiments were performed with steam baking and falling temperature baking. Immediately after baking, the crust was divided into the outer and inner crust fractions, and the water content and acrylamide concentration of each fraction was measured. The outer crust had a significantly lower water content and higher acrylamide concentration than the inner crust did. Crust temperature in combination with water content had a significant effect on acrylamide formation, higher temperatures resulting in higher acrylamide concentrations. However, at very high temperatures and lower water contents, acrylamide concentration was observed to decrease, though the bread colour was then unacceptable for consumption. Steam and falling temperature baking, on the other hand, decreased the acrylamide content while producing bread crust with an acceptable colour. The lowest acrylamide values and an acceptable crust colour were produced by steam baking. © 2007 Swiss Society of Food Science and Technology.

  • 229.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Chamayou, A.
    Dewettinck, K.
    Depypere, F.
    Dumoulin, E.
    Fitzpatrick, J.
    Processing of food powders2008In: Food Materials Science: Principles and Practice, p. 341-368Article in journal (Refereed)
    Abstract [en]

    The development of formulation engineering concepts in food manufacturing and the demand for diversity in food products has driven a substantial market increase for food ingredients. Most ingredients are supplied in powder form and therefore a better understanding of dispersed solid food systems is important both for food ingredient manufactures and food producers. © 2008 Springer Science+Business Media, LLC.

  • 230.
    Ahrné, Lilia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Eliasson, Lovisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Isaksson, Sven
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Erdogdu, Ferruh
    Experimental determination of penetration depths of various spice commodities (black pepper seeds, paprika powder and oregano leaves) under infrared radiation2015In: Journal of Food Engineering, Vol. 161, p. 75-81Article in journal (Refereed)
    Abstract [en]

    During infrared processing, transmitted energy is attenuated exponentially with penetration distance, and its intensity is gradually lost while passing through absorbing or scattering media. Penetration depth is a complex function of chemical composition of a food product, its physico-chemical state and physical properties and wavelength spectrum of energy source. Knowing penetration depth leads to better designing commercial sterilization processes for food products like spices. Therefore, the objective of this study was to determine penetration depth of various spices (paprika powder, black pepper and oregano) as a function of water activity under infrared processing conditions. For this purpose, spice samples were prepared at various water activity (aw) levels, and heat flux measurements were carried out to determine the penetration depth. Penetration depth was determined to increase with increasing aw for black pepper seeds and paprika powder while there was no significant change for oregano leaves as a function of aw. Knowing penetration depth is important to design an effective infra-red processing system and an important issue for surface pasteurization processes since infrared radiation effects on microbial inactivation decrease with sample thickness

  • 231.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Frias, J.
    Oliveira, F.A.R.
    Singh, R.P.
    Modelling textural changes of vegetables during acidification under isothermal and non-isothermal conditions2001In: Acta Horticulturae, ISSN 0567-7572, Vol. 566, p. 323-328Article in journal (Refereed)
    Abstract [en]

    Acidification can be used to improve the quality of canned vegetables because it can decrease thermal processing requirements. Moreover, there is some evidence that acidified vegetables retain a better texture than non-acidified ones. Optimisation of the acidification processes requires the knowledge of the relationship between texture and thermal process at low/moderate temperature. The main objective of this work was the modelling of textural changes of vegetables during acidification under isothermal conditions, and the application of the model to predict textural changes in non-isothermal processes. Turnip was the vegetable used in the experiments. The effect of pre-treatments (blanching, freezing/thawing, calcium addition and vacuum infusion of water before acidification) on the kinetics of textural changes during acidification was also studied. Turnips were acidified in acetic acid under isothermal (20, 50, 70, 80, 90 and 100°C) and non-isothermal conditions (20 to 90°C). Texture was modelled by a two subtract first order kinetic model, assuming an Arrhenius-type dependence of the rate constants on temperature. The model parameters were estimated by nonlinear regression. At temperatures lower then 70°C no significant changes in texture were detected. At higher temperatures the model showed a good fit to the data for all the conditions tested. Acidification decreased the percentage of heat labile substrate from 96% to 62%, thus improving firmness retention. The parameters of the kinetic model estimated under isothermal conditions provided an adequate prediction of texture changes under non-isothermal conditions. The methodology developed in this work can be further applied to model the textural changes of vegetables during other thermal processes, such as drying, blanching, and frying.

  • 232.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Frias, J
    Oliveira, F.A.R.
    Singh, R.P.
    Modelling textural changes of vegetables during acidification under isothermal and non-isothermal conditions2001In: Acta Horticulturae, ISSN 0567-7572, Vol. 566, p. 323-328Article in journal (Refereed)
    Abstract [en]

    Acidification can be used to improve the quality of canned vegetables because it can decrease thermal processing requirements. Moreover, there is some evidence that acidified vegetables retain a better texture than non-acidified ones. Optimisation of the acidification processes requires the knowledge of the relationship between texture and thermal process at low/moderate temperature. The main objective of this work was the modelling of textural changes of vegetables during acidification under isothermal conditions, and the application of the model to predict textural changes in non-isothermal processes. Turnip was the vegetable used in the experiments. The effect of pre-treatments (blanching, freezing/thawing, calcium addition and vacuum infusion of water before acidification) on the kinetics of textural changes during acidification was also studied. Turnips were acidified in acetic acid under isothermal (20, 50, 70, 80, 90 and 100°C) and non-isothermal conditions (20 to 90°C). Texture was modelled by a two subtract first order kinetic model, assuming an Arrhenius-type dependence of the rate constants on temperature. The model parameters were estimated by nonlinear regression. At temperatures lower then 70°C no significant changes in texture were detected. At higher temperatures the model showed a good fit to the data for all the conditions tested. Acidification decreased the percentage of heat labile substrate from 96% to 62%, thus improving firmness retention. The parameters of the kinetic model estimated under isothermal conditions provided an adequate prediction of texture changes under non-isothermal conditions. The methodology developed in this work can be further applied to model the textural changes of vegetables during other thermal processes, such as drying, blanching, and frying.

  • 233.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Gonzalez-Martinez, G.
    Sjoholm, I.
    Nilsson, Katarina
    SIK – Institutet för livsmedel och bioteknik.
    Improvement of texture by modifying processing conditions2003In: Acta Horticulturae, ISSN 0567-7572, Vol. 604, p. 277-283Article in journal (Refereed)
    Abstract [en]

    Fruit and vegetable processors, faced with the challenge of gaining and maintaining a healthy position in the competitive fruit and vegetable sector, are optimising traditional processes towards product quality. Using frozen potatoes as a case study, the aim of this study was to evaluate the potential of improving the texture of potatoes by modifying the processing conditions. The texture of processed frozen potatoes is the result of the integral effect of the unit operations applied through the production chain. Production of frozen potatoes includes a blanching, a freezing, thawing/cooking step before being served. In this study, blanching temperatures from 70 to 97 °C up to 10 minutes were tested and combined with freezing by two freezing methods, impingement and air-blast freezing. The texture was measured after cooking of frozen potatoes in boiling water. Besides texture, water holding capacity, microstructural evaluation and pectinmethylesterase (PME) activity were determined. Blanching of potatoes prior to freezing can both improve water holding capacity and texture of potatoes, but this effect depends on the freezing rate and blanching temperature. Potatoes frozen with fastest freezing method are firmer and hold more water than the ones frozen by air-blast freezing. Blanching at 70 °C can lead to potatoes that after cooking retain a firmer texture, compared with blanching at 90 °C. The duration of the blanching treatment has also an important effect on texture changes. The studies of PME activity showed a good correlation between texture and PME for blanching at 90 °C, but for blanching at 70°C and longer times, the development of texture does not seem to be solely related to PME activity. Microstructural studies showed that the differences in texture are due to differences in the degree of starch gelatinisation and integrity of the cellular structure.

  • 234.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Gonzalez-Martinez, G
    Sjoholm, I
    Nilsson, Katarina
    SIK – Institutet för livsmedel och bioteknik.
    Improvement of texture by modifying processing conditions2003In: Acta Horticulturae, ISSN 0567-7572, Vol. 604, p. 277-283Article in journal (Refereed)
    Abstract [en]

    Fruit and vegetable processors, faced with the challenge of gaining and maintaining a healthy position in the competitive fruit and vegetable sector, are optimising traditional processes towards product quality. Using frozen potatoes as a case study, the aim of this study was to evaluate the potential of improving the texture of potatoes by modifying the processing conditions. The texture of processed frozen potatoes is the result of the integral effect of the unit operations applied through the production chain. Production of frozen potatoes includes a blanching, a freezing, thawing/cooking step before being served. In this study, blanching temperatures from 70 to 97 °C up to 10 minutes were tested and combined with freezing by two freezing methods, impingement and air-blast freezing. The texture was measured after cooking of frozen potatoes in boiling water. Besides texture, water holding capacity, microstructural evaluation and pectinmethylesterase (PME) activity were determined. Blanching of potatoes prior to freezing can both improve water holding capacity and texture of potatoes, but this effect depends on the freezing rate and blanching temperature. Potatoes frozen with fastest freezing method are firmer and hold more water than the ones frozen by air-blast freezing. Blanching at 70 °C can lead to potatoes that after cooking retain a firmer texture, compared with blanching at 90 °C. The duration of the blanching treatment has also an important effect on texture changes. The studies of PME activity showed a good correlation between texture and PME for blanching at 90 °C, but for blanching at 70°C and longer times, the development of texture does not seem to be solely related to PME activity. Microstructural studies showed that the differences in texture are due to differences in the degree of starch gelatinisation and integrity of the cellular structure.

  • 235.
    Ahrné, Lilia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Malafronte, Loredana
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Kaunisto, Erik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Innings, F.
    Rasmuson, Anders
    Estimation of the effective diffusion coefficient of water in skim milk during single-drop drying2015In: Journal of Food Engineering, ISSN 0260-8774, E-ISSN 1873-5770, Vol. 147, p. 111-119Article in journal (Refereed)
    Abstract [en]

    This paper presents a new approach combining experimental methodology and modelling, developed to evaluate the effective diffusivity of water in skim milk during drying over a full range of water contents and temperatures. This parameter is important to support modelling of spray-drying processes and designing of equipment. The effective diffusion coefficient is evaluated using a combination of nuclear magnetic resonance (NMR) and parameter estimation. NMR is used to determine the temperature dependence and parameter estimation is used to estimate the water concentration dependence of the effective diffusivity of water in skim milk (0.90 on total weight basis) during drying by comparing the experimental data obtained using a suspended-drop method, which allows the recording of weight and temperature changes during drying, with the results of a distributed heat and mass transport model. The results indicate that the free-volume theory best predicts the dependence of the effective diffusion coefficient of water in skim milk. A mathematical correlation of effective diffusivity over a full range of water contents and temperatures (from 50 to 90°C) was obtained and experimentally successfully validated for concentrated skim milk (0.70 on total weight basis).

  • 236.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Pereira, N.R.
    Staack, N.
    Floberg, P.
    Microwave convective drying of plant foods at constant and variable microwave power2007In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 25, no 42193, p. 1149-1153Article in journal (Refereed)
    Abstract [en]

    Microwave convective drying of plant foods is a promising process due to the shorter drying time and better product quality. High microwave power decreases the drying time but causes charring of the product. In this work, microwave drying under constant and variable microwave power were compared. Temperature-sensitive products, such as plant foods, are especially affected by microwave power during the final drying period. Therefore, drying at variable microwave power was found to be a more suitable drying process. Air (temperature and velocity) has an important role during microwave drying, not only as carrier of evaporated moisture but also as it contributes to a more homogeneous and faster drying.

  • 237.
    Ahrné, Lilia
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Prothon, F.
    Funebo, Tomas
    SIK – Institutet för livsmedel och bioteknik.
    Comparison of drying kinetics and texture effects of two calcium pretreatments before microwave-assisted dehydration of apple and potato2003In: International journal of food science & technology, ISSN 0950-5423, E-ISSN 1365-2621, Vol. 38, no 4, p. 411-420Article in journal (Refereed)
    Abstract [en]

    The effects on drying rate and texture of treating two plant tissues with calcium, before drying in air with microwave assistance, were studied in this work. The two tissues, potato and apple cubes, which have different structures and composition, were pretreated by immersion in CaCl2 solutions at 20 or at 70 °C before microwave-assisted air dehydration at 50, 60 and 70 °C. The pretreatments with calcium influenced the strength of the plant tissue cell wall, producing products of varying hardness after rehydration. The effect of the two calcium pretreatments was quite different for apples and potatoes. For apples, calcium pretreatment at 20 °C increased the hardness of rehydrated apples compared with untreated apples, but calcium pretreatment at 70 °C had no effect on texture. For potatoes, both calcium pretreatments at 20 and at 70 °C significantly increased the hardness of rehydrated potatoes. The water diffusivity during drying varied mainly because of the type of plant tissue, with secondary effects caused by the drying temperature and the type of calcium pretreatment.

  • 238.
    Ahrné, Lilia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Shenoy, Pooja
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Innings, F.
    Fitzpatrick, J.
    Tanmmel, K
    Evaluation of a digital colour imaging system for assessing the mixture quality of spice powder mixes by comparison with a salt conductivity method2015In: Powder Technology, Vol. 286, p. 48-54Article in journal (Refereed)
    Abstract [en]

    Mixture quality or homogeneity analysis is a crucial step in powder industries to evaluate if the final product meets the requisite standards and therefore industries prefer a method that is reliable and easy to use. In this study the mixture quality of food powder mixtures that differ in mixability and number of components is studied by using digital colour imaging method (DCI) and comparing it with a salt conductivity method. Two binary food and two quaternary food powder mixtures with different coloured particles were studied. Salt was one of the key ingredients commonly used in all the mixtures. Samples were taken at specific times during mixing. The digital colour imaging method was used to measure colour of each sample and salt conductivity analysis measured the corresponding concentration of salt in each sample. Coefficient of variation (CoV) was used to determine the homogeneity of the mixture. Results showed that both methods gave similar results for the well mixing paprika-salt mixture however the DCI method did not work for the oregano-salt mixture which was highly segregating in nature. When the colour difference between the powders was high the DCI method showed a good trend with the salt concentration method. When quaternary mixture consisting of similar coloured particles and segregating particles was used this trend was weaker as compared to the mixture that consisted of cohesive powders that mixed well with each other although they had some particles that were similarly coloured. Overall it showed that DCI method has potential for use by industries that can analyse powder mixtures with components that have differences in colour and that are not strongly segregating in nature

  • 239.
    Ahrné, Lilia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    Xanthakis, Epameinondas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Processing.
    van Ommen, Ruud
    Flowability characterization of nanopowders2015In: Powder Technology, Vol. 286, p. 156-163Article in journal (Refereed)
    Abstract [en]

    The applications of nanopowders are increasing significantly over the last years. In most of these applications, the flow behavior of the nanopowders seems to be a complicated, multiparametric but critical issue for the proper design of the processes. We have investigated, classified and compared several different metal oxide nanoparticles with respect to their flow properties. The flow properties of titania, silica and alumina hydrophilic nanopowders as well as their corresponding hydrophobic counterparts were determined by means of an annular shear cell powder flow tester (PFT). All the tested powders showed difficulties in flow while the titania nanopowders showed the highest difficulty among them. The results acquired regarding the compressibility, the flow functions and the effective angle of internal friction revealed that in all the cases the hydrophobic nanopowder seemed to be more cohesive than its hydrophilic counterpart. Moreover, the nanoparticles, no matter their polarity, showed negligible hygroscopicity while in the case of the alumina nanopowders the flow properties can be significantly influenced by ca. 1% (w/w) of moisture content.

  • 240.
    Aicher, Simon mfl
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Bygg och Mekanik.
    Determination of fracture energy of wood in Mode II. RILEM TC 133 Report.1997Report (Refereed)
  • 241.
    Ail, Ujwala
    et al.
    Linköpings Universitet, Sweden.
    Khan, Zia Ullah
    Linköpings Universitet, Sweden.
    Granberg, Hjalmar
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Berthold, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Parasuraman, Rajasekar
    Indian Institute of Science, India.
    Umarji, Arun M.
    Indian Institute of Science, India.
    Slettengren, Kerstin
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Pettersson, Henrik
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Crispin, Xavier
    Linköpings Universitet, Sweden.
    Room temperature synthesis of transition metal silicide-conducting polymer micro-composites for thermoelectric applications2017In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 225, p. 55-63Article in journal (Refereed)
    Abstract [en]

    Organic polymer thermoelectrics (TE) as well as transition metal (TM) silicides are two thermoelectric class of materials of interest because they are composed of atomic elements of high abundance; which is a prerequisite for mass implementation of thermoelectric (TE) solutions for solar and waste heat recovery. But both materials have drawbacks when it comes to finding low-cost manufacturing. The metal silicide needs high temperature (>1000 °C) for creating TE legs in a device from solid powder, but it is easy to achieve long TE legs in this case. On the contrary, organic TEs are synthesized at low temperature from solution. However, it is difficult to form long legs or thick films because of their low solubility. In this work, we propose a novel method for the room temperature synthesis of TE composite containing the microparticles of chromium disilicide; CrSi2 (inorganic filler) in an organic matrix of nanofibrillated cellulose- poly(3,4-ethyelenedioxythiophene)-polystyrene sulfonate (NFC-PEDOT:PSS). With this method, it is easy to create long TE legs in a room temperature process. The originality of the approach is the use of conducting polymer aerogel microparticles mixed with CrSi2 microparticles to obtain a composite solid at room temperature under pressure. We foresee that the method can be scaled up to fabricate and pattern TE modules. The composite has an electrical conductivity (σ) of 5.4 ± 0.5 S/cm and the Seebeck coefficient (α) of 88 ± 9 ΌV/K, power factor (α2σ) of 4 ± 1 ΌWm−1K−2 at room temperature. At a temperature difference of 32 °C, the output power/unit area drawn across the load, with the resistance same as the internal resistance of the device is 0.6 ± 0.1 ΌW/cm2.

  • 242.
    Aitomäki, Y.
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Hagström, Bengt
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Långström, R.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Fernberg, P.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Novel reactive bicomponent fibres: Material in composite manufacturing2012In: Journal of Nanostructured Polymers and Nanocomposites, ISSN 17904439, Vol. 8, no 1, p. 11-majArticle in journal (Refereed)
    Abstract [en]

    The hypotheses that reactive uncured, thermoset bicomponent fibres can be prepared and mixed with reinforcing fibres and ultimately used in preparation of a composite was tested and is described. It is thought that such fibres have the two potential advantages: (1) to enable manufacturing with particle doped resins e.g. nanocomposites which add functionality to composites and (2) increased efficiency of structural composite manufacturing by increasing the level of automation. The structure of the thermoset fibres comprises of a sheath of thermoplastic and a core of uncured thermoset resin. Once manufactured, the fibres were wound with a reinforced fibre onto a plate, consolidated and cured. The resulting composite was examined and compared to other composites made with the same manufacturing method from commercially available materials. The results show that a laminate can be produced using these reactive bicomponent fibres. The resin system successfully impregnates the reinforcing carbon fibres and that the thermoplastic separates from the epoxy resin system during consolidation. In comparison to reference material, the bicomponent laminate shows promising characteristics. However, the processes developed are currently on a lab-scale and considerable improvement of various bicomponent fibre properties, such as the strength, are required before the technology can be used on a larger scale.

  • 243.
    Aitomäki, Yvonne
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Hagström, Bengt
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Långström, Runar
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Fernberg, Patrik
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Novel reactive bicomponent fibres: Material in composite manufacturing2012In: Journal of Nanostructured Polymers and Nanocomposites, ISSN 17904439, Vol. 8, no 1, p. s.5-11Article in journal (Refereed)
    Abstract [en]

    The hypotheses that reactive uncured, thermoset bicomponent fibres can be prepared and mixed with reinforcing fibres and ultimately used in preparation of a composite was tested and is described. It is thought that such fibres have the two potential advantages: (1) to enable manufacturing with particle doped resins e.g. nanocomposites which add functionality to composites and (2) increased efficiency of structural composite manufacturing by increasing the level of automation. The structure of the thermoset fibres comprises of a sheath of thermoplastic and a core of uncured thermoset resin. Once manufactured, the fibres were wound with a reinforced fibre onto a plate, consolidated and cured. The resulting composite was examined and compared to other composites made with the same manufacturing method from commercially available materials. The results show that a laminate can be produced using these reactive bicomponent fibres. The resin system successfully impregnates the reinforcing carbon fibres and that the thermoplastic separates from the epoxy resin system during consolidation. In comparison to reference material, the bicomponent laminate shows promising characteristics. However, the processes developed are currently on a lab-scale and considerable improvement of various bicomponent fibre properties, such as the strength, are required before the technology can be used on a larger scale.

  • 244.
    Akbari, Saaed
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lövberg, Andreas
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tegehall, Per-Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Brinkfeldt, Klas
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Andersson, Dag
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Effect of PCB cracks on thermal cycling reliability of passive microelectronic components with single-grained solder joints2019In: Microelectronics and reliability, ISSN 0026-2714, E-ISSN 1872-941X, Vol. 93, p. 61-71Article in journal (Refereed)
    Abstract [en]

    Lead-free tin-based solder joints often have a single-grained structure with random orientation and highly anisotropic properties. These alloys are typically stiffer than lead-based solders, hence transfer more stress to printed circuit boards (PCBs) during thermal cycling. This may lead to cracking of the PCB laminate close to the solder joints, which could increase the PCB flexibility, alleviate strain on the solder joints, and thereby enhance the solder fatigue life. If this happens during accelerated thermal cycling it may result in overestimating the lifetime of solder joints in field conditions. In this study, the grain structure of SAC305 solder joints connecting ceramic resistors to PCBs was studied using polarized light microscopy and was found to be mostly single-grained. After thermal cycling, cracks were observed in the PCB under the solder joints. These cracks were likely formed at the early stages of thermal cycling prior to damage initiation in the solder. A finite element model incorporating temperature-dependant anisotropic thermal and mechanical properties of single-grained solder joints is developed to study these observations in detail. The model is able to predict the location of damage initiation in the PCB and the solder joints of ceramic resistors with reasonable accuracy. It also shows that the PCB cracks of even very small lengths may significantly reduce accumulated creep strain and creep work in the solder joints. The proposed model is also able to evaluate the influence of solder anisotropy on damage evolution in the neighbouring (opposite) solder joints of a ceramic resistor.

  • 245.
    Akbari, Saeed
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Sakhaei, A. H.
    Singapore University of Technology and Design, Singapore; University of Exeter, UK.
    Panjwani, S.
    Singapore University of Technology and Design, Singapore.
    Kowsari, K.
    Singapore University of Technology and Design, Singapore.
    Serjourei, A.
    Singapore University of Technology and Design, Singapore.
    Ge, Q.
    Singapore University of Technology and Design, Singapore.
    Multimaterial 3D Printed Soft Actuators Powered by Shape Memory Alloy Wires2019In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 290, p. 177-189Article in journal (Refereed)
    Abstract [en]

    Shape memory alloys (SMAs) have been widely used to fabricate soft actuators by embedding SMA wires into various soft matrices manufactured by conventional moulding methods or novel three-dimensional (3D) printing techniques. However, soft matrices of SMA based actuators are typically fabricated from only one or two different materials. Here, we exploit the great manufacturing flexibility of multimaterial 3D printing to fabricate various bending, twisting and extensional actuators by precisely controlling the spatial arrangements of different printing materials with different stiffnesses. In order to achieve a broad range of deformations, ten different printing materials were characterized and used in the actuators design. In addition, we developed a finite element model to simulate complex deformations of the printed actuators and facilitate the design process. The model incorporates a user defined material subroutine that describes the nonlinear temperature dependant behavior of SMAs. The results show the efficiency and flexibility of multimaterial 3D printing in tailoring the deformed shape of the SMA based soft actuators, which cannot be accomplished using conventional manufacturing methods such as moulding.

  • 246.
    Akesson, D.
    et al.
    University of Borås.
    Skrifvars, M.
    University of Borås.
    Walkenström, Pernilla
    RISE, Swerea, Swerea IVF.
    Preparation of thermoset composites from natural fibres and acrylate modified soybean oil resins2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 114, no 4, p. 2502-2508Article in journal (Refereed)
    Abstract [en]

    Structural composites with a high content of renewable material were produced from natural fibres and an acrylated epoxidized soybean oil resin. Composites were prepared by spray impregnation followed by compression moulding at elevated temperature. The resulting composites had good mechanical properties in terms of tensile strength and flexural strength. Tensile testing as well as dynamical mechanical thermal analysis showed that increasing the fibre content, increased the mechanical properties. The resin can be reinforced with up to 70 wt % fibre without sacrifice in processability. The tensile modulus ranged between 5.8 and 9.7 GPa depending on the type of fibre mat. The study of the adhesion by low vacuum scanning electron microscopy shows that the fibres are well impregnated in the matrix. The aging properties were finally evaluated. This study shows that composites with a very high content of renewable constituents can be produced from soy bean oil resins and natural fibres. © 2009 Wiley Periodicals, Inc.

  • 247.
    Akesson, Karl Petter
    et al.
    RISE, Swedish ICT, SICS.
    Nilsson, Andreas
    RISE, Swedish ICT, Viktoria.
    Designing leisure applications for the mundane car-commute2002In: Personal and Ubiquitous Computing, ISSN 1617-4909, E-ISSN 1617-4917, Vol. 6, no 3, p. 176-187Article in journal (Refereed)
    Abstract [en]

    Commuting by car from home to work can be very time consuming. We have conducted a study to explore what people are doing, and want to do, while commuting. People use their time in the car on a wide variety of activities with great innovation. There was no unanimous activity that everyone wanted, rather a wide variety of activities were requested. Three different categories of activity were identified which we refer to as mundane, vocational and traffic related. To demonstrate a possible IT service supporting commuters, a prototype based on speech output and a simple input mechanism from a wheel was developed. This service moves sampling of music from the conventional shop into the car. The prototype was informally tested with users, which resulted in a number of improvements. Preliminary user results indicate good functionality, a comprehensive interaction interface.

  • 248. Aklint, T
    et al.
    Johansson, C
    RISE, Swedish ICT, Acreo.
    Hanson, M
    Olsson, E
    Gustavsson, F
    Wäppling, R
    A Rosen, A
    Magnetic Properties of deposited iron clusters produced in a high yield laser vaporization source1998In: Applied Organometallic Chemistry, Vol. 12, p. 479-Article in journal (Refereed)
  • 249.
    Al Nahas, Beshr
    RISE, Swedish ICT, SICS. Department of Information Technology.
    Multichannel Communication in Contiki's Low-power IPv6 Stack2013Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Vast majority of wireless appliances used in household, industry and medical field share the ISM frequency band. These devices need to coexist and thus are challenged to tolerate their mutual interference. One way of dealing with this is by using frequency hopping; where the device changes its radio channel periodically. Consequently, communications will not suffer from the same interference each time; instead, it should be fairer and more stable. This thesis investigates the aforementioned problem in the field of low power wireless sensor networks and Internet of Things where Contiki OS is used. We introduce a low-power pseudo-random frequency-hopping MAC protocol which is specifically characterized as a duty cycled asynchronous sender-initiated LPL style protocol. We illustrate two flavors of the protocol; one that does not use any dedicated channel and another which allows dedicated broadcast channels that can implement frequency-hopping as well. We implement the protocol in C for real hardware and extensively test and evaluate it in a simulated environment which runs Contiki. It proved to work with Contiki's IPv6 stack running RPL (the standardized routing protocol for low power and lossy wireless networks). We compare the performance of the implemented protocol to the singlechannel ContikiMAC with varying levels of interference. Results show a reduction down to 56% less radio-on time (1.50% vs. 3.4%) and 85% less latency (306 ms vs. 2050 ms) in the presence of noise, while keeping a good basecost in noise-free environments with 1.29% radio duty cycle when using 9 channels with no dedicated broadcast channels (vs. 0.80% for single channel) and 252 ms average latency(vs. 235 ms). Moreover, the results show that the multichannel protocol performance metrics converge to almost the same values regardless of the noise level. Therefore, it is recommended as a good alternative to single channel ContikiMAC in realworld deployments where noise presence is anticipated.

  • 250.
    Al Nahas, Beshr
    et al.
    RISE, Swedish ICT, SICS.
    Duquennoy, Simon
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Iyer, Venkatraman
    Voigt, Thiemo
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Low-Power Listening Goes Multi-Channel2014Conference paper (Refereed)
    Abstract [en]

    Exploiting multiple radio channels for communication has been long known as a practical way to mitigate interference in wireless settings. In Wireless Sensor Networks, however, multi-channel solutions have not reached their full potential: the MAC layers included in TinyOS or the Contiki OS for example are mostly single-channel. The literature offers a number of interesting solutions, but experimental results were often too few to build confidence. We propose a practical extension of low-power listening, MiCMAC, that performs channel hopping, operates in a distributed way, and is independent of upper layers of the protocol stack. The above properties make it easy to deploy in a variety of scenarios, without any extra configuration/scheduling/channel selection hassle. We implement our solution in Contiki and evaluate it in a 97-node testbed while running a complete, out-of-the-box low-power IPv6 communication stack (UDP/RPL/6LoWPAN). Our experimental results demonstrate increased resilience to emulated WiFi interference (e.g., data yield kept above 90% when ContikiMAC drops in the 40% range). In noiseless environments, MiCMAC keeps the overhead low in comparison to ContikiMAC, achieving performance as high as 99% data yield along with sub-percent duty cycle and sub-second latency for a 1-minute inter-packet interval data collection.

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