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  • 1.
    Wimo, Anders
    et al.
    Aging Research Centre, Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet .
    Jönsson, Linus
    Aging Research Centre, Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet.
    Fratiglioni, Laura
    Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet, Huddinge .
    Sandman, Per-Olof
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Gustavsson, Andres
    Aging Research Centre, Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet.
    Sköldunger, Anders
    Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet, Huddinge.
    Johansson, Lennarth
    Stockholm Gerontology Research Centre.
    Erratum to: The societal costs of dementia in Sweden 2012: relevance and methodological challenges in valuing informal care2019In: Alzheimer's Research & Therapy, ISSN 0065-6755, E-ISSN 1758-9193, Vol. 9, no 1, 12Article in journal (Refereed)
    Abstract [en]

    During production of the original article [1], the line referring to “Informal Care” was omitted from Table 3. It should have been mentioned between “Total social care sector” and “Indirect costs”.

  • 2.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Stephen, James D
    Queen’s University.
    Mabee, Warren E
    Queen’s University.
    Avramidis, Stavros
    University of British Columbia.
    Bull, Gary Q
    University of British Columbia.
    An Integrated Forest Products Cluster for Off-Grid Lumber Production Using Biomass CHP in Remote Indigenous Communities2017Conference paper (Refereed)
  • 3.
    D'Orazio, Christian Javier
    et al.
    School of Information Technology and Mathematical Sciences, University of South Australia, Australia.
    Rongxing, Lu
    Faculty of Computer Science, University of New Brunswick, Fredericton, NB, Canada.
    Choo, Kim Kwang Raymond
    School of Information Technology and Mathematical Sciences, University of South Australia, Australia.
    Vasilakos, Athanasios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    A Markov adversary model to detect vulnerable iOS devices and vulnerabilities in iOS apps2017In: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 293, 523-544 p.Article in journal (Refereed)
    Abstract [en]

    With the increased convergence of technologies whereby a user can access, store and transmit data across different devices in real-time, risks will arise from factors such as lack of appropriate security measures in place and users not having requisite levels of security awareness and not fully understanding how security measures can be used to their advantage. In this paper, we adapt our previously published adversary model for digital rights management (DRM) apps and demonstrate how it can be used to detect vulnerable iOS devices and to analyse (non-DRM) apps for vulnerabilities that can potentially be exploited. Using our adversary model, we investigate several (jailbroken and non-jailbroken) iOS devices, Australian Government Medicare Expert Plus (MEP) app, Commonwealth Bank of Australia app, Western Union app, PayPal app, PocketCloud Remote Desktop app and Simple Transfer Pro app, and reveal previously unknown vulnerabilities. We then demonstrate how the identified vulnerabilities can be exploited to expose the user's sensitive data and personally identifiable information stored on or transmitted from the device. We conclude with several recommendations to enhance the security and privacy of user data stored on or transmitted from these devices.

  • 4.
    Yolal, Medet
    et al.
    Anadolu Üniversitesi.
    Chi, Christina Geng-Qing
    Washinton State University.
    Pesämaa, Ossi
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Examine destination loyalty of first-time and repeat visitors at all-inclusive resorts2017In: International Journal of Contemporary Hospitality Management, ISSN 0959-6119, E-ISSN 1757-1049, ISSN 0959-6119, Vol. 29, no 7Article in journal (Refereed)
  • 5.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cool, Julie
    University of British Columbia.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in computed tomography images of partially dried Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs2017In: nternational Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored in the log yard they dry to a certain extent, and this drying affects the density variation in the log, and therefore the X-ray images. For this reason, it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. The objective of this research was to investigate the effect of drying on knot detection in Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual measurements for this purpose, and the results show that knot detection was clearly affected by partial drying. Because dried heartwood and sapwood have similar densities, the algorithm had difficulties detecting the heartwood-sapwood border. Based on how well the heartwood-sapwood border was detected, it was statistically possible to sort logs into two groups: 1) Low knot detection rate, and 2) High knot detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. Therefore, logs that are partially dried out and fall in the low knot detection rate should be handled cautiously because the optimization results based on CT knot detection cannot be fully trusted. Sawing of these logs could be optimized using only their outer shape, ignoring internal quality. Similarly, only logs having a regular heartwood shape should be used when scanning logs for research purposes or in databases of CT scanned logs. Finally, a larger knot detection rate was obtained for Jack pine. This could have been facilitated by the fact that pine trees usually have larger but less numerous knots than spruce trees.

  • 6.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Using a Gaussian filter to reduce the effect of positioning errors when optimizing sawing of CT scanned Scots pine and Norway spruce logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    Computed tomography (CT) scanning of logs is being introduced in sawmills, so there is reason to study how log positioning can be controlled using information from CT. However, positioning errors affect this positioning optimization in a negative way. To reduce this effect, a method was developed using sawing simulation, where logs were sawn in a large number of positions, varying rotation and centering. This resulted in three-dimensional surfaces, with the sawn timber value, rotation and centering on the axes. The surfaces were filtered with a Gaussian filter using a distribution corresponding to that of the positioning error. The filtered values were used for optimization, choosing the global maximum. This resulted in a value recovery that was about two percent higher compared to a simpler optimization without filtering, for a normally distributed rotational error of 5 – 15° standard deviation and a ditto centering error of 3.5 – 10.5 mm standard deviation. This was tested using sawing simulation, using the optimal log position for the two methods, with an added positioning error. Furthermore, the robust method has been tested on a smaller number of rotational positions, starting from horns down, to reduce the number of necessary calculations. The result of this was that at least ± 60 ° in the rotational direction should be evaluated for the robust method to result in a higher recovery than the simpler optimization. The robust method was better than sawing horns down and centered, no matter the positioning error, using only 65 evaluated positions per log.

  • 7.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in coarse resolution CT images of logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    The use of X-ray computed tomography (CT) scanning of logs in sawmill is becoming a reality in the last few years, usually with rather costly and complex machines resembling medical scanners. However, a scanning solution has been developed that is less costly and more robust, and therefore more suited for sawmill needs. The rather coarse data from this machine has not been fully evaluated regarding possibilities to detect internal features such as knots. In this study, a knot detection algorithm developed for medical scanners was applied to images from a coarse resolution scanner, from four different logs of various species, and with different image resolution. The objective was to see if it was possible to detect knots automatically in the images. If so, the aim was to calculate the knot detection rate and the accuracy of detected knot size and position. These numbers were calculated compared to manually measured reference knots. This resulted in a knot detection rate of about 53 % overall, and a well detected knot position, but poorly detected knot size. It is possible to observe a certain difference between species and reconstruction resolution, however the material is too small to draw any definite conclusions. As a preliminary study, it provides input for further investigation on knot detection in coarse resolution X-ray CT images. Future work involves scanning more logs to get more data, and to pinpoint the resolution needed for accurate knot detection using the current algorithm.

  • 8.
    Guo, Xiaolei
    et al.
    Nanjing Forestry University, College of Material Science and Engineering.
    Lin, Yubin
    Nanjing Forestry University, College of Material Science and Engineering.
    Na, Bin
    Nanjing Forestry University, College of Material Science and Engineering.
    Liang, Xingyu
    Nanjing Forestry University, College of Material Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ji, Futang
    Nanjing Forestry University, College of Material Science and Engineering.
    Huang, Lingling
    Nanjing Forestry University, College of Material Science and Engineering.
    Evaluation of physical and mechanical properties of fiber-reinforced poplar scrimber2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 1, 43-55 p.Article in journal (Refereed)
    Abstract [en]

    The mechanical properties of poplar scrimber reinforced with glass fiber mesh were investigated. The influence of the different structures and densities were studied with respect to the modulus of rupture (MOR), modulus of elasticity (MOE), and impact toughness (IT). The glass fiber improved the mechanical properties of poplar scrimber. The MOR, MOE, and IT of the scrimber had an obvious dependence on the number of glass fiber layers. When the layers of glass fiber meshes were increased, the MOR, MOE, and IT were increased compared to the control group (scrimber without glass fiber reinforcement). The MOR, MOE, and IT of single-layer glass fiber reinforced scrimber increased a lot compared to the control group. The MOR, MOE, and IT of double-layer glass fiber reinforced scrimber (DGRS) were increased, but the amplitude of the increase was smaller than that of SGRS. Compared to the MOR, MOE, and IT of DGRS, the MOR, MOE, and IT of triple-layer glass fiber reinforced scrimber (TGRS) decreased slightly. When the density was increased, the increasing rate of the MOR, MOE, and IT of the glass fiber reinforced scrimber showed a downward trend, and the glass fiber had better strengthen effects on the scrimber at low density (0.6 g/cm3 and 0.7 g/cm3).

  • 9.
    Gawel, Erik
    et al.
    Helmholtz-Centre for Environmental Research – UFZ, Leipzig.
    Lehmann, Paul
    Helmholtz-Centre for Environmental Research – UFZ, Leipzig.
    Purkus, Alexandra
    Helmholtz-Centre for Environmental Research – UFZ, Leipzig.
    Söderholm, Patrik
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Witte, Katherina
    Leipzig University, Institute for Infrastructure and Resources Management.
    Rationales for technology-specific RES support and their relevance for German policy2017In: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, Vol. 102, 22 p.16-26 p.Article in journal (Refereed)
    Abstract [en]

    In order to achieve cost-effective RES-E deployment it is often argued that technology-neutral support schemes for renewables are indispensable. Against this background, RES-E support policies making widely use of technology differentiation in remuneration settings, e.g. across the EU, are frequently criticized from a theoretical point of view. However, in this paper we provide a systematic critique of the technology neutrality concept as a foundation for designing policy support schemes in the RES-E technology field. Specifically, the main objective of the paper is to scrutinize the arguments for technology-neutrality, and discuss three conceptual arguments for why technology-specific support schemes could in fact help minimize the societal costs of reaching future RES-E targets. We also briefly address different political economy concerns, which could constrain the choice of cost-effective policy support schemes, and that have to be taken into account for economic policy advice. For empirical illustration of the key arguments we refer to the case of German RES-E policy-making. The central conclusion from this paper is that technology-specific RES-E support schemes may generate significant economic benefits, particularly if technology markets work imperfectly and in second-best policy settings with additional non-internalized market failures.

  • 10.
    Martín-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    What ChemCam’s first shots tell us about martian dust?2017Conference paper (Other academic)
  • 11.
    Van Dal, Victor H.P.
    et al.
    Edge Hill University.
    Wass, Malin
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    First- and Second-Language Learnability Explained by Orthographic Depth and Orthographic Learning: A 'Natural' Scandinavian Experiment2017In: Scientific Studies of Reading, ISSN 1088-8438, E-ISSN 1532-799X, Vol. 21, no 1, 46-59 p.Article in journal (Refereed)
    Abstract [en]

    Effects of orthographic depth on orthographic learning ability were examined in 10- to 13-year-old children who learnt to read in similar orthographies differing in orthographic depth, defined as consistency of grapheme-to-phoneme correspondences. Danish children who learnt to read a deep orthography underperformed their Swedish counterparts who acquired a shallow orthography on vocabulary, phonological working memory, orthographic learning ability, and a range of first-language (L1: Danish/Swedish) and second-language (L2: English as a foreign language) measures. Orthographic learning ability explained over and above vocabulary and phonological working memory the better performance of Swedish children in comparison with Danish children on L1 reading accuracy and fluency, spelling, and visual word familiarity. With respect to L2 learning, orthographic learning ability determined spelling and visual word familiarity over and above L2 vocabulary and phonological working memory. It is concluded that shallow orthographies promote orthographic learning ability more efficiently than deep orthographies.

  • 12.
    Alvarez Perez, Manuel Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Stochastic Planning of Smart Electricity Distribution Networks2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The penetration of intermittent Distributed Generation (DG) brought additional uncertainty to the system operation and planning. To cope with uncertainties the Distribution System Operator (DSO) could implement several strategies. These strategies range from the inclusion of smart technologies which will increment system’s flexibility and resiliency, to improvements in forecasting, modeling, and regulatory pledge that will facilitate the planning activity. Regardless of the nature of the solutions, they could be collected in a sort of toolbox. The planner will access the toolbox to conform cost effective plans, better able to deal with any uncertainty. The present work will address the problem of distribution system planning under uncertainties, considering smart solutions along with traditional reinforcements, in the short-term lead time up to 3 years ahead. The work will be focused on three aspects that are the cornerstones of this work:

     • A planning facilitating strategy: Distribution Capacity Contracts (DCCs).

     • A flexibility enabler technology: Energy Storage.

     • A binding methodology: Multistage Stochastic Programming. Stochastic dual dynamic programming (SDDP). 

    Under the present directive of the European Parliament concerning common rules for the internal market in electricity, distribution companies are not allowed to own DG but entitled to include it as a planning option to differ investment in traditional grid reinforcements. An evaluation of the regulatory context will lead this work to consider DCCs as a planning alternative available in the toolbox. The impact of this type of contract on the remuneration of the DG owner will be assessed in order to provide insight on its willingness to participate. The DCCs might aid the DSO to defer grid i ii investments during planning stages and to control the network flows during operation. 

    Given that storage solutions help to match in time production from intermittent sources with load consumption, they will play a major role in dealing with uncertainties. A generic storage model (GSM) based on a future cost piecewise approximation will be developed. This model inspired by hydro-reservoirs will help assessing the impact of storage in planning decisions. This model will be tested by implementing it in short-term hydro scheduling and unit commitment studies. 

    To trace a path towards the future of this research work, a discussion on the planning problem formulation, under consideration of the lead time, the expansion options, the smart strategies, and the regulatory framework will be presented. Special focus will be given to multistage stochastic programming methods and in particular to the SDDP approach.

  • 13.
    Grzenda, Maciej (Editor)
    Faculty of Mathematics and Information Science, Warsaw University of Technology,, Research and Development Center.
    Awad, Ali Ismail (Editor)
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Furtak, Janusz (Editor)
    Military University of Technology, Warszawa.
    Legierski, Jarosław (Editor)
    Faculty of Mathematics and Information Science, Warsaw University of Technology, Warszawa.
    Advances in Network Systems: Architectures, Security, and Applications2017Book (Refereed)
  • 14.
    Martín-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    The EChO science case2017In: EChO - Exoplanet Characterisation Observatory / [ed] Giovanna Tinetti, Springer Netherlands: Springer Netherlands, 2017Chapter in book (Other (popular science, discussion, etc.))
    Abstract [en]

    The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population.We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and newpopulations of planets with masses between that of the Earth and Neptune – all unknown in the SolarSystem. Observations to date have shown that our Solar System is certainly not representative of the generalpopulation of planets in our Milky Way. The key science questions that urgently need addressing aretherefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work andwhat causes the exceptional diversity observed as compared to the Solar System? The EChO (ExoplanetCharacterisation Observatory) space mission was conceived to take up the challenge to explain this diversityin terms of formation, evolution, internal structure and planet and atmospheric composition. This requires indepthspectroscopic knowledge of the atmospheres of a large and well-defined planet sample for whichprecise physical, chemical and dynamical information can be obtained.In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission fortransit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample withinits four-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the starand planet are differentiated using knowledge of the planetary ephemerides, allows us to measureatmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved inconjunction with a carefully designed stable payload and satellite platform. It is also necessary to providebroad instantaneous wavelength coverage to detect as many molecular species as possible, to probe thethermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellarphotosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4to 16 μm. Only modest spectral resolving power is needed, with R~300 for wavelengths less than 5 μm andR~30 for wavelengths greater than this.The transit spectroscopy technique means that no spatial resolution is required. A telescope collecting area ofabout 1 m2 is sufficiently large to achieve the necessary spectro-photometric precision: for the Phase A studya 1.13 m2 telescope, diffraction limited at 3 μm has been adopted. Placing the satellite at L2 provides a coldand stable thermal environment as well as a large field of regard to allow efficient time-critical observationof targets randomly distributed over the sky. EChO has been conceived to achieve a single goal: exoplanetspectroscopy. The spectral coverage and signal-to-noise to be achieved by EChO, thanks to its high stabilityand dedicated design, would be a game changer by allowing atmospheric composition to be measured withunparalleled exactness: at least a factor 10 more precise and a factor 10 to 1000 more accurate than currentobservations. This would enable the detection of molecular abundances three orders of magnitude lower thancurrently possible and a fourfold increase from the handful of molecules detected to date. Combining thesedata with estimates of planetary bulk compositions from accurate measurements of their radii and masseswould allow degeneracies associated with planetary interior modelling to be broken, giving unique insightinto the interior structure and elemental abundances of these alien worlds.EChO would allow scientists to study exoplanets both as a population and as individuals. The mission cantarget super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planettemperatures of 300 K - 3000 K) of F to M-type host stars. The EChO core science would be delivered by athree-tier survey. The EChO Chemical Census: This is a broad survey of a few-hundred exoplanets, whichallows us to explore the spectroscopic and chemical diversity of the exoplanet population as a whole. TheEChO Origin: This is a deep survey of a subsample of tens of exoplanets for which significantly highersignal to noise and spectral resolution spectra can be obtained to explain the origin of the exoplanet diversity(such as formation mechanisms, chemical processes, atmospheric escape). The EChO Rosetta Stones: Thisis an ultra-high accuracy survey targeting a subsample of select exoplanets. These will be the bright"benchmark" cases for which a large number of measurements would be taken to explore temporalvariations, and to obtain two and three dimensional spatial information on the atmospheric conditionsthrough eclipse-mapping techniques.If EChO were launched today, the exoplanets currently observed are sufficient to provide a large and diversesample. The Chemical Census survey would consist of > 160 exoplanets with a range of planetary sizes,temperatures, orbital parameters and stellar host properties. Additionally, over the next ten years, severalnew ground- and space-based transit photometric surveys and missions will come on-line (e.g. NGTS,CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current5rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO’s launch and enable the atmospheric characterisation of hundreds of planets.

  • 15.
    Lindström, John
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Källström, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kyösti, Petter
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems. Luleå University of Technology, Department of Applied Physics and Mechanical Engineering, Fastelaboratoriet.
    Development and Operation of Functional Products: Improving knowledge on availability through use of monitoring and service related data2017In: Through-life Engineering Services, Springer International Publishing , 2017Chapter in book (Refereed)
  • 16.
    Grip, Niklas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    School of Civil Engineering, Southeast University, Nanjing.
    Sensitivity-based model updating for structural damage identification using total variation regularization2017In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 84, no A, 365-383 p.Article in journal (Refereed)
    Abstract [en]

    Sensitivity-based Finite Element Model Updating (FEMU) is one of the widely accepted techniques used for damage identification in structures. FEMU can be formulated as a numerical optimization problem and solved iteratively making automatic updating of the unknown model parameters by minimizing the difference between measured and analytical structural properties. However, in the presence of noise in the measurements, the updating results are usually prone to errors. This is mathematically described as instability of the damage identification as an inverse problem. One way to resolve this problem is by using regularization. In this paper, we compare a well established interpolation-based regularization method against methods based on the minimization of the total variation of the unknown model parameters. These are new regularization methods for structural damage identification. We investigate how using Huber and pseudo Huber functions in the definition of total variation affects important properties of the methods. For instance, for well-localized damages the results show a clear advantage of the total variation based regularization in terms of the identified location and severity of damage compared with the interpolation-based solution.For a practical test of the proposed method we use a reinforced concrete plate. Measurements and analysis were performed first on an undamaged plate, and then repeated after applying four different degrees of damage.

  • 17.
    Pocorni, Jetro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Deichsel, Eckard
    Bystronic Laser AG, Industriestrasse 21, CH-3362 Niederönz.
    Frostevarg, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Fibre laser cutting stainless steel: Fluid dynamics and cut front morphology2017In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 87, 87-93 p.Article in journal (Refereed)
    Abstract [en]

    In this paper the morphology of the laser cut front generated by fibre lasers was investigated by observation of the ‘frozen’ cut front, additionally high speed imaging (HSI) was employed to study the fluid dynamics on the cut front while cutting. During laser cutting the morphology and flow properties of the melt film on the cut front affect cut quality parameters such as cut edge roughness and dross (residual melt attached to the bottom of the cut edge). HSI observation of melt flow down a laser cutting front using standard cutting parameters is experimentally problematic because the cut front is narrow and surrounded by the kerf walls. To compensate for this, artificial parameters are usually chosen to obtain wide cut fronts which are unrepresentative of the actual industrial process. This paper presents a new experimental cutting geometry which permits HSI of the laser cut front using standard, commercial parameters. These results suggest that the cut front produced when cutting medium section (10 mm thick) stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered by a thin layer of liquid. HSI observation and theoretical analysis reveal that under these conditions the humps move down the cut front at an average speed of approximately 0.4 m/s while the covering liquid flows at an average speed of approximately 1.1 m/s, with an average melt depth at the bottom of the cut zone of approximately 0.17 mm.

  • 18.
    Samarjy, R.S.M.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. University of Mosul, College of Engineering, Department of Mechanical Engineering.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Transient interaction of a boiling melt with a pulsed Nd:YAG-laser2017In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 88, 28-36 p.Article in journal (Refereed)
    Abstract [en]

    The boiling front induced by a pulsed Nd:YAG-laser at very slow translation speed was studied. The purpose is to understand fundamental melt movement mechanisms. The melt was observed by high speed imaging, with and without illumination. When switching on the laser beam a hole is drilled through a bulk of melt. The hole expands and the boiling pressure gradually opens the melt bridge, instead developing an interaction front similar to cutting. These conditions remain in quasi-steady state during the pulse. The ablation pressure from boiling shears waves down the front and keeps the melt downwards in a stable position. When switching off, the waves smoothen and in absence of boiling the surface tension drags the melt back upwards, to semi-torus-like Catenoid shape. Evidence on the large melt pool and its shape was achieved by three-dimensional reconstruction from cross section macrographs. The basic findings how melt can move with and without ablation pressure can enable controlled melt dynamics for various laser processing techniques, like remote cutting, ablation, keyhole welding or drilling.

  • 19.
    Jafri, Yawer
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kirtania, Kawnish
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Granberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    A study of black liquor and pyrolysis oil co-gasification in pilot scale2017In: Biomass Conversion and Biorefinery, ISSN 2190-6815Article in journal (Refereed)
    Abstract [en]

    The effect of the blend ratio and reactor temperature on the gasification characteristics of pyrolysis oil (PO) and black liquor (BL) blends with up to 20 wt% PO was studied in a pilot-scale entrained-flow gasifier. In addition to unblended BL, three blends with PO/BL ratios of 10/90, 15/85, and 20/80 wt% were gasified at a constant load of 2.75 MWth. The 15/85 PO/BL blend was used to investigate the effect of temperature in the range 1000–1100 °C. The decrease in fuel inorganic content with increasing PO fraction resulted in more dilute green liquor (GL), and a greater portion of the feedstock carbon ended up in syngas as CO. As a consequence, the cold gas efficiency increased by about 5%-units. Carbon conversion was in the range 98.8–99.5% and did not vary systematically with either fuel composition or temperature. Although the measured reactor temperatures increased slightly with increasing PO fraction, both unblended BL and the 15% PO blend exhibited largely similar behavior in response to temperature variations. The results from this study show that blending BL with the more energy-rich PO can increase the cold gas efficiency and improve the process carbon distribution without adversely affecting either carbon conversion or the general process performance.

  • 20.
    Strandkvist, Ida
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Effect of FeO/MgO Ratio on Dissolution and Leaching of Magnesiowüstite2017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed)
    Abstract [en]

    If slag is to be used as construction material, the leaching of some elements, such as chromium must be limited. The leaching of slag depends on the leaching properties of the minerals in the slag. However, the leaching/dissolution properties of individual slag minerals are usually not studied. One common slag mineral that can contribute to the leaching of chromium is magnesiowüstite. The object of this study is to determine whether magnesiowüstite can be modified to avoid chromium leaching. Magnesiowüstite samples with different FeO/MgO ratios with and without chromium content are manufactured. The dissolution is evaluated at pH 7 and 10 using the magnesiowüstite samples without chromium, at size fraction 20–38 μm, by measuring the acid consumption required to maintain constant pH level. The magnesiowüstite samples with chromium content are leached at pH 10; the leachate is analyzed for chromium. The results are unanimous, with increasing FeO content the dissolution of magnesiowüstite and leaching of chromium decrease. At pH 10 the magnesiowüstite, with ≥60 wt% FeO show no sign of dissolution and no chromium leaching could be detected with ≥70 wt% FeO. The results prove that the FeO content can stabilize magnesiowüstite and, thereby, prevent chromium leaching

  • 21.
    Saintilan, Nicholas J.
    et al.
    Section of Earth and Environmental Sciences, University of Geneva.
    Stephens, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Spikings, Richard A.
    Section of Earth and Environmental Sciences, University of Geneva.
    Schneider, Jens C.
    Department of Mineralogy, Technische Universität Bergakademie Freiberg.
    Chiaradia, Massimo
    Section of Earth and Environmental Sciences, University of Geneva.
    Spangenberg, Jorge E.
    Institute of Earth Surface Dynamics, University of Lausanne.
    Ulianov, Alexey
    Institute of Earth Sciences, University of Lausanne.
    Fontboté, Lluis
    Section of Earth and Environmental Sciences, University of Geneva.
    Polyphase vein mineralization in the Fennoscandian Shield at Åkerlandet, Järvsand, and Laisvall along the erosional front of the Caledonian orogen, Sweden2017In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866Article in journal (Refereed)
    Abstract [en]

    The Åkerlandet, Järvsand, and Laisvall deposits in Sweden are calcite-fluorite-sulfide vein deposits and occurrences located close to the current erosional front of the Caledonian orogen and hosted by crystalline basement rocks in the Fennoscandian Shield. At Laisvall, basement-hosted veinlets occur beneath Ediacaran to Cambrian sandstones that host a strata-bound Pb-Zn deposit. The mineralized fractures at Åkerlandet and Järvsand occur along fault systems oriented N–S to NNW–SSE. Veins or veinlets strike NNW–SSE and NW–SE at Åkerlandet, NNE–SSW at Järvsand, and NNW–SSE and NNE–SSW to NE–SW at Laisvall. At Åkerlandet and Järvsand, fractures acted as conduits for hydrothermal fluids of variable composition and formed during separate tectonic events. At Åkerlandet, the fault zone with NNW–SSE strike shows kinematic indicators consistent with ~NE–SW bulk horizontal extension. At Järvsand, the calcite-fluorite-galena veins formed along R-Riedel shears related to the host N–S to NNW–SSE fault system. The kinematic indicators are consistent with ~NW–SE bulk horizontal extension, similar to the extensional deformation during the later part of the Caledonian orogeny (Silurian to Devonian). At Åkerlandet, adularia-quartz deposition was followed by sphalerite ± galena and finally by precipitation of fluorite and calcite. 40Ar-39Ar thermochronology of a single adularia sample did not yield a well-defined plateau age but the gas released at higher temperatures suggests an early Tonian (980 to 950 Ma) crystallization age, i.e., during the later part of the Sveconorwegian orogeny, although the data do not exclude other less likely interpretations. Previous fluid inclusion microthermometry and geochronological studies and new petrographic and geochemical results suggest that sphalerite ± galena mineralization formed from saline, relatively oxidizing, moderate-temperature, and slightly acidic hydrothermal fluids, either during the Ediacaran or the Middle Ordovician. Metals and H2S were derived from local basement rocks. Based on petrographic evidence, rare earth element composition, and S, C, and O isotope data, fluorite and calcite precipitated under near neutral and relatively reducing conditions. Occurrence of solid bitumen in veins at Åkerlandet and C and O isotope data of calcite at Åkerlandet and in the Laisvall basement veinlets suggest that the precipitation of calcite and fluorite was triggered by interaction of hot and evolved hydrothermal fluids (87Sr/86Sr = 0.718–0.732) with organic matter. Structural, petrographic, and geochemical data at Laisvall suggest that the basement structures hosting calcite-fluorite ± pyrite veinlets were utilized in the Middle Ordovician as the plumbing system for the oxidizing, slightly acidic, metal-bearing brines that caused the economic Pb-Zn mineralization in the overlying sandstones

  • 22.
    Bergmark, Ulrika
    et al.
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    Kostenius, Catrine
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Students’ Experiences of Meaningful Situations in School2017In: Scandinavian Journal of Educational Research, ISSN 0031-3831, E-ISSN 1470-1170Article in journal (Refereed)
    Abstract [en]

    This paper focuses on school situations students experienced as meaningful and how these experiences can guide educational improvement. Participants included 15 students in grade 3 from a Swedish school. In this qualitative study, the data consisted of drawings, multimodal productions, interviews, and field notes. The analysis resulted in four themes: Having the opportunity to learn in different spaces; Being free and able to participate; Experiencing caring and sharing, and Recognizing one’s own growth and achievement. The findings suggest that situations students find meaningful involve aspects of both learning and wellbeing. The practical implication for these results is that student-generated qualitative data can help indicate needs for educational improvement.

  • 23.
    Wijk, Olle
    et al.
    Systecon.
    Andersson, Patric
    Systecon.
    Block, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Righard, Thord
    Systecon.
    Phase-Out Maintenance Optimization for an Aircraft Fleet2017In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel approach for cost-effective optimization of stop-maintenance strategies for a set of repairable items (rotables). The optimization method has two steps. First, the novel concept of matrix simulations is introduced to locate the solution space of the optimization problem in question. Second, a genetic algorithm is applied to find the minimum cost solution. The combination of matrix simulations and genetic algorithm is shown to constitute a powerful method for solving the optimization problem in a fast manner. To demonstrate the efficacy of the proposed method, it is compared with a crude search, and a steepest descent algorithm. Our proposed method is faster than the crude search and also locates the optimum more often than the steepest descent search. The method is illustrated by applying it to a phase-out scenario of an aircraft fleet, where the optimal stop-maintenance strategy is determined for a set of rotables.

  • 24.
    Pelcastre, Leonardo
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Hardell, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Prakash, Braham
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of Zn coated UHSS sliding against hot-work tool steel at high temperatures2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577Article in journal (Refereed)
    Abstract [en]

    The increasing demands for light-weight components in vehicles contribute to the global expansion of hot sheet metal forming technologies. Structural components are typically produced using hot stamping of ultra-high strength steel (UHSS). This process allows forming of complex shapes whilst enabling control of the mechanical properties of the end product. Interest in zinc coated UHSS has increased in recent years in view of the corrosion protection it provides to the final components. There is a need for increased understanding of its tribological behaviour during the interaction with tool steel at elevated temperatures. In this work, tribological studies have been carried out in a novel hot strip tribometer. The aim was to study the effect of different operating conditions on the tribological behaviour of zinc coated UHSS sliding against a hot-work tool steel under un-lubricated conditions. The parameters studied in this work were; temperature, ranging from 400˚C to 700˚C; and contact pressure, from 5 to 30 MPa. The UHSS was initially heated up to austenitising temperature (840˚C) and then cooled down to the testing temperature. Upon stabilisation of temperature, the load was applied and sliding was carried out for a total of 1500 mm at 100 mm/s. The results showed a trend towards decreasing average coefficient of friction as temperature and contact pressure increased. Unstable friction behaviour was observed at low temperature (400˚C) and high contact pressure (30 MPa) whilst higher temperatures (600˚C) facilitated the development of a low and stable friction behaviour. It is proposed that the friction behaviour is controlled by the properties of the zinc phases in the coating developed during heating of the UHSS. The combination of high temperature and sliding conditions result in the removal of the uppermost oxide layer and the phases beneath control the friction behaviour.

  • 25.
    Källström, Elisabeth
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Volvo Construction Equipment, Eskilstuna, Sweden.
    Olsson, Tomas
    SICS Swedish ICT, Kista, Sweden.
    Lindström, John
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Håkansson, Lars
    Linnaeus University, Växjö, Sweden.
    Larsson, Jonas
    Volvo Construction Equipment, Eskilstuna, Sweden.
    On-board Clutch Slippage Detection and Diagnosis in Heavy Duty Machine2017In: International Journal of Prognostics and Health Management, ISSN ISSN2153-2648Article in journal (Refereed)
    Abstract [en]

    In order to reduce unnecessary stops and expensive downtime originating from clutch failure of construction equipment machines; adequate real time sensor data measured on the machinein combination with feature extraction and classification methods may be utilized.This paper, based on a study at Volvo Construction Equipment,presents a framework with feature extraction methods and an anomaly detection module combined with Case-Based Reasoning (CBR) for on-board clutch slippage detection and diagnosis in a heavy duty equipment. The feature extraction methods used are Moving Average Square Value Filtering (MASVF) and a measure of the fourth order statistical properties of the signals implemented as continuous queries over data streams. The anomaly detection module has two components,the Gaussian Mixture Model (GMM) and the Logistics Regression classifier. CBR is a learning approach that classifies faults by creating a new solution for a new fault case from the solution of the previous fault cases. Through use of a data stream management system and continuous queries (CQs), the anomaly detection module continuously waits for a clutch slippage event detected by the feature extraction methods, the query returns a set of features which activates the anomaly detection module. The first component of the anomaly detection module trains a GMM to extracted features while the second component uses a Logistic Regression classifier for classifying normal and anomalous data. When an anomalyis detected, the Case-Based diagnosis module is activated for fault severity estimation.

  • 26.
    Kim, Kyounghak
    et al.
    Department of Welding and Joining Science Engineering, Graduate School, Chosun University.
    Bang, Heeseon
    Department of Welding and Joining Science Engineering, Chosun University.
    Bang, Hansur
    Department of Welding and Joining Science Engineering, Chosun University.
    Kaplan, Alexander F.H.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Joint properties of ultra thin 430M2 ferritic stainless steel sheets by friction stir welding using pinless tool2017In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 243, 381-386 p.Article in journal (Refereed)
    Abstract [en]

    In this study, friction stir butt welding of ultra thin 430M2 ferritic stainless steel sheets with satisfactory joint properties has been achieved using a pinless WC-Co tool. Friction stir welding was carried out at a tool rotational speed of 900 rpm and a travel speed of 96 mm/min. FSW joints were welded completely without any unwelded zone resulting from smooth material flow, despite of being adopted pinless tool. It was revealed that the maximum tensile strength of FSW welds was 468 MPa, equivalent to the tensile strength of base metal. Notably, it was found that sigma phase formation in FSW welds is suppressed compared with that of arc welds, resulting in improving joint strength. These results suggest that the low input process of FSW is an effective substitute for the conventional fusion welding GTAW in ultra thin ferritic stainless steel plate.

  • 27.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Ass. Ltd.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Karshon, Yael
    Department of Mathematics, University of Toronto.
    Reduction of Hamiltonian Mechanical Systems With Affine Constraints: A Geometric Unification2017In: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423, Vol. 12, no 2Article in journal (Refereed)
    Abstract [en]

    This paper presents a geometrical approach to the dynamical reduction of a class of constrained mechanical systems. The mechanical systems considered are with affine nonholonomic constraints plus a symmetry group. The dynamical equations are formulated in a Hamiltonian formalism using the Hamilton-d'Alembert equation, and constraint forces determine an affine distribution on the configuration manifold. The proposed reduction approach consists of three main steps: (1) restricting to the constrained submanifold of the phase space, (2) quotienting the constrained submanifold, and (3) identifying the quotient manifold with a cotangent bundle. Finally, as a case study, the dynamical reduction of a two-wheeled rover on a rotating disk is detailed. The symmetry group for this example is the relative configuration manifold of the rover with respect to the inertial space. The proposed approach in this paper unifies the existing reduction procedures for symmetric Hamiltonian systems with conserved momentum, and for Chaplygin systems, which are normally treated separately in the literature. Another characteristic of this approach is that although it tracks the structure of the equations in each reduction step, it does not insist on preserving the properties of the system. For example, the resulting dynamical equations may no longer correspond to a Hamiltonian system. As a result, the invariance condition of the Hamiltonian under a group action that lies at the heart of almost every reduction procedure is relaxed

  • 28.
    Samuelsson, Lina N.
    et al.
    Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Babler, Mattheus U.
    Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Mass loss rates for wood chips at isothermal pyrolysis conditions: A comparison with low heating rate powder data2017In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 158, 26-34 p.Article in journal (Refereed)
    Abstract [en]

    Spruce chips of three different thicknesses were pyrolyzed isothermally in a vertical furnace macro-TGA at 574 to 676K, which is the temperature range relevant for char production. The measured mass loss data was analyzed in terms of mass loss rate, thermal lag and char yield as a function of chip size and pyrolysis temperature. The char yield decreased with increasing temperature and there was no significant difference in char yield as a function of sample thickness, ranging from 1mm to 7mm. Thermal lag was present for all chip sizes above 600K. At 574K the data suggests that chips below 1mm in thickness are decomposing at rates governed by reaction kinetics. An isoconversional kinetic model based on low heating rate data of spruce powder was adopted to analyze the data. The model predicted lower mass loss rates than those measured for the chips, suggesting that the pyrolysis process of wood proceeds through a network of parallel reactions. Despite this, the model could predict the final char yield of the wood chips with an accuracy above 80%. The predictive capability of the isoconversional reaction rate expression is promising since the procedure to derive such a rate expression is straight-forward, compared to the conventional model-fitting methods. The data and modeling approach presented in this work is important to the field of biomass pyrolysis as it covers the temperature range and chip sizes relevant for pyrolysis in multi-staged gasification plants which has been given little attention.

  • 29.
    Sandström, Linda
    et al.
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Nilsson, Carina
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Juuso, Päivi
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Engström, Åsa
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    CCNs experiences of nursing trauma patients2017Conference paper (Refereed)
  • 30.
    Sandström, Linda
    et al.
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Juuso, Päivi
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Engström, Åsa
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    The helicopter as a caring context: trauma patients’ experiences2017Conference paper (Refereed)
  • 31.
    Engström, Åsa
    et al.
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    Jansson, Anna
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Critical Care Nurses Experiences of Temporary Staffing in ICU2017Conference paper (Refereed)
  • 32.
    Strömbäck, Ulrica
    et al.
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Vikman, Irene
    Luleå University of Technology, Department of Health Sciences, Health and Rehab.
    Lundblad, Dan
    Sunderby Research Unit, Department of Public Health and Clinical Medicine, Umeå University.
    Lundqvist, Robert
    Department of Research, Norrbotten County Council, Luleå.
    Engström, Åsa
    Luleå University of Technology, Department of Health Sciences, Nursing Care.
    The second myocardial infarction: Higher risk factor burden and earlier second myocardial infarction in women compared to men : The Northern Sweden MONICA study2017In: European Journal of Cardiovascular Nursing, ISSN 1474-5151, E-ISSN 1873-1953Article in journal (Refereed)
    Abstract [en]

    BACKGROUND:

    Several studies have examined various parameters and experiences when patients suffer their first myocardial infarction (MI), but knowledge about when they suffer their second MI is limited.

    AIM:

    To compare risk factors for MI, that is, diabetes, hypertension and smoking, for the first and second MI events in men and women affected by two MIs and to analyse the time intervals between the first and second MIs.

    METHODS:

    A retrospective cohort study of 1017 patients aged 25-74 years with first and second MIs from 1990 through 2009 registered in the Northern Sweden MONICA registry.

    RESULTS:

    More women than men have diabetes and hypertension and are smokers at the first MI. Similar differences between the genders remain at the time of the second MI for diabetes and hypertension, although both risk factors have increased. Smoking decreased at the second MI without any remaining difference between genders. Women suffer their second MI within a shorter time interval than men do. Within 16 months of their first MI, 50% of women had a second MI. The corresponding time interval for men was 33 months.

    CONCLUSION:

    Patients affected by an MI should be made aware of their risk of recurrent MI and that the risk of recurrence is highest during the first few years after an MI. In patients affected by two MIs, women have a higher risk factor burden and suffer their second MI earlier than men do and thus may need more aggressive and more prompt secondary prevention.

  • 33.
    Nygren Zotterman, Anna
    Luleå University of Technology, Department of Health Sciences.
    Encounters in primary healthcare from the perspectives of people with long-term illness, their close relatives and district nurses2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    People with a long-term illness and their close relatives regard encounters as the foundation of their relationshipwith the district nurses within the primary healthcare setting. The overall aim of this doctoral thesis was todescribe and elucidate the experiences of encounters for people with long-term illness, their close relatives anddistrict nurses within a primary healthcare setting. From the overall aim, specific aims were formulated asfollows: to describe district nurses’ views on quality of healthcare encounters in primary healthcare (I), toelucidate meanings of encounters for patients with long-term illness within the primary healthcare setting (II), toelucidate meanings of encounters for close relatives of people with a long-term illness within a primaryhealthcare setting (III) and to describe the experiences of dignity encounters from the perspective of people withlong-term illness and their close relatives within a primary healthcare setting (IV). Data were collected fromfocus group interviews (I), narrative interviews (II, III), and semi-structured interviews (IV). The interviewswere analysed using thematic content analysis (I, IV) and phenomenological hermeneutics (II, III). The findingsshow that encounters are given great importance among people who have a long-term illness, their closerelatives, and district nurses in the setting of primary healthcare. The manner in which the encounter wasexperienced in the relationship with healthcare personnel was, at many times, crucial for the whole careexperience to be viewed as beneficial or not. The findings show that district nurses described that the encountersformed the basis of their work as an important aspect and that many times they were difficult because of stressand lack of time. The first meeting with the patient was important since it was unique and unrepeatable. Districtnurses considered themselves as being the patients ‘advocate’ who helped them and protected their interests.They indicated the importance of confirming the patient as a person deserving of respect, and if a meeting turnedout poorly, it was their duty to give the patient an apology (I). The findings also show that patients with a longtermillness experienced that good encounters had health-promoting effects on their health and recovery. Patientsfelt well when they were welcomed as a person with respect, interest, and attention by the healthcare personnel.They wanted to participate in their own care by receiving regular information and follow-up dialogues abouttheir status with the healthcare personnel. Continuity with the healthcare personnel laid the foundation for apersonal and a trustful relationship (II). Close relatives of people with a long-term illness wanted to beencountered as part of the ill person’s family as they accompanied him or her to the healthcare centre. To beconfirmed as a family was important, as it gave meaning to their lives and strengthened their well-being. A goodencounter was characterised by aspects of being involved in the care of the ill person and being respected as avaluable person (III). The findings show that people with a long-term illness and their close relatives experienceddignity in the encounter when they had access to care. They experienced that it was important to be encounteredwith dignity, as it meant receiving help with their needs from the healthcare personnel. To be confirmed by beingseen and listened to was important. When the couples experienced dignity in the encounter, they felt satisfiedwith the care they received. To be encountered with dignity made they feel valuable; this facilitated their healthand well-being, and it contributed to a good impression of the healthcare personnel within primary healthcare(IV). In conclusion, the findings of this thesis show that healthcare encounters are more than just meetings; theyalso mean being confirmed as a human being by being treated with respect, engagement and dignity. Healthcarepersonnel should promote encounters for people with long-term illness and their close relatives in order tosupport their feelings of being regarded as persons and to feel that they are welcomed to primary healthcare withtheir needs, which can empower their health and well-being.

  • 34.
    Chibba, Aron
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Supply Chain Quality Management - Exploring performance of manufacturing organizations2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis addresses the issue of quality performance in supply chains in the manufacturers’context. Research shows that the management and performance of supply chains play a major rolein gaining competitive advantage, especially in times of decreasing international trade barriers andquickly evolving information technology. Some researchers claim that it is the supply chain itselfthat competes on a market and not merely the organisations with their specific strategies andgoals. Supply chain performance has been widely discussed in the research literature in recentyears. However, this research points out that supply chain quality management (SCQM) and itsimpact on firm performance (both inter-organisational and intra-organisational) have not beensufficiently understood. Further studies are needed to identify the direct and indirect impact ofSCQM practices on firm performance at multiple levels.A problem that many organisations face is the lack of resources and knowledge on how to managesupply chain quality performance (i.e., which performance to measure, how to controlperformance, and how to improve performance). Studies show that often even large companiesmeasure effectiveness using key performance indicators (KPI) and that these indicators often donot depict key characteristics critical to organisational performance or customer behaviour.Therefore, such indicators might be inadequate for fully capturing the performance of supplychains. As quality management standards evolve, managers need to adapt to changingrequirements. To fulfil the new version of ISO 9001, organisations are required to determinecriteria and apply methods to ensure effective operation and control of their processes (both intraorganisationaland inter-organisational performance). This includes monitoring and measuringperformance indicators. The quality performance of a supply chain is dependent on its ability toimprove and thereby enable organisations to stay competitive over time. Good measurements ofsupply chain quality performance must reflect this ability. To do so, organisations need to knowwhich measures and metrics to use and how to analyse performance of their supply chains.From the seven studies presented in this thesis we are able to draw a number of more generalconclusions that bear on the main research question: What improves quality performance of supplychains that include manufacturing? At the process level, it has been found that manufacturersshould focus on the quality and delivery performance of each process within the organisation. Atthe internal, integrated supply chain level, a manufacturing organisation should focus on quality(conformance), delivery performance (on-time delivery), and cost cutting in the internal supplychain. Collaboration using cross-functional teams seems most appropriate when working withproduct development. The use of a process-oriented mapping tool was found to facilitatedescription of information flows and physical material flows and also to identify disturbances thatcould be improved and rationalized to generate a better flow in the total supply chain. At both theupstream and downstream sides of the supply chain, one-sided measures that depict performanceover organisational boundaries were found to be the most common. At the downstream side of asupply chain, suppliers could be chosen based on cost, conformance, speed, and flexibility. At theupstream side, procedures that handle changing requirements and information about delays orincorrectness of materials were found to influence flow. The results from these seven studies arethe basis for the development of a supply chain quality improvement model. In the literature,supply chain performance is often discussed on a strategic level with measures for quality,flexibility and delivery. Managers also need metrics that can be followed up on at a detailed level(e.g., capacity load, breakdown rates, claims, cost of poor quality, and lead-times). To bridge thisgap, a Key Performance Indicators Matrix of supply chain quality performance indicators formanufacturers is proposed.

  • 35.
    Schnabel, Stephan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Golling, Stefan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Absolute Measurement of Elastic Waves Excited by Hertzian Contacts in Boundary Restricted Systems2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 1, 7Article in journal (Refereed)
    Abstract [en]

    In most applied monitoring investigations using acoustic emission, measurements are carried out relatively, even though that limits the use of the extracted information. The authors believe acoustic emission monitoring can be improved by instead using absolute measurements. However, knowledge about absolute measurement in boundary restricted systems is limited. This article evaluates a method for absolute calibration of acoustic emission transducers and evaluates its performance in a boundary restricted system. Absolute measured signals of Hertzian contact excited elastic waves in boundary restricted systems were studied with respect to contact time and excitation energy. Good agreement is shown between measured and calculated signals. For contact times short enough to avoid interaction between elastic waves and initiating forces, the signals contain both resonances and zero frequencies, whereas for longer contact times the signals exclusively contained resonances. For both cases, a Green’s function model and measured signals showed good agreement.

  • 36.
    Schnabel, Stephan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Marklund, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Elastic Waves of a Single Elasto-Hydrodynamically Lubricated Contact2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 1, 5Article in journal (Refereed)
    Abstract [en]

    Elastic waves are widely used for condition monitoring of rolling element bearings through vibration or acoustic emission measurements . While vibration signals are understood to a high degree due to many scientific investigations as well as a long history of usage in the field, acoustic emission signals of rolling element bearings are poorly understood. Therefore, this investigation presents simulation studies and measurements of a single elasto-hydrodynamically lubricated (EHL) contact. In this investigation the EHL contact is a ball bouncing on a lubricated plate. The simulation based on Green’s function and the measurements based on a accelerometer to some extent agree. A shift of zero frequencies towards higher frequencies when compared to Hertzian reference measurements was determined for an infinite plate setup. Taking boundary restrictions into account, elastic waves of a Hertzian contact and an EHL contact only differ by a damping of higher resonances which is most likely caused by the EHL film.

  • 37.
    Stoklosa, Ryan J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    del Pilar Orjuela, Andrea
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    da Costa Sousa, Leonardo
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Uppugundla, Nirmal
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Williams, Daniel L.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Dale, Bruce E.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Hodge, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Balan, Venkatesh
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Techno-economic comparison of centralized versus decentralized biorefineries for two alkaline pretreatment processes2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 226, 9-17 p.Article in journal (Refereed)
    Abstract [en]

    In this work, corn stover subjected to ammonia fiber expansion (AFEX™) pretreatment or alkaline pre-extraction followed by hydrogen peroxide post-treatment (AHP pretreatment) were compared for their enzymatic hydrolysis yields over a range of solids loadings, enzymes loadings, and enzyme combinations. Process techno-economic models were compared for cellulosic ethanol production for a biorefinery that handles 2000 tons per day of corn stover employing a centralized biorefinery approach with AHP or a de-centralized AFEX pretreatment followed by biomass densification feeding a centralized biorefinery. A techno-economic analysis (TEA) of these scenarios shows that the AFEX process resulted in the highest capital investment but also has the lowest minimum ethanol selling price (MESP) at $2.09/gal, primarily due to good energy integration and an efficient ammonia recovery system. The economics of AHP could be made more competitive if oxidant loadings were reduced and the alkali and sugar losses were also decreased.

  • 38.
    Prpic, John
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Keitzmann, Jan H.
    Beedie School of Business, Simon Fraser University.
    Crowd Science: Research on IT-Mediated Crowds-Mini-Track Overview2017Conference paper (Refereed)
  • 39.
    Qarahasanlou, Ali Nouri
    et al.
    Faculty of Mining, Petroleum & Geophysics, Shahrood University of Technology, .
    Khalokakaie, Reza
    Faculty of Mining, Petroleum & Geophysics, Shahrood University of Technology, .
    Ataei, Mohammad
    Faculty of Mining, Petroleum & Geophysics, Shahrood University of Technology, .
    Ghodrati, Behzad
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Operating Environment-Based Availability Importance Measures for Mining Equipment: (Case Study: Sungun Copper Mine)2017In: Journal of Failure Analysis and Prevention, ISSN 1547-7029, E-ISSN 1864-1245, Vol. 17, no 1, 56-67 p.Article in journal (Refereed)
    Abstract [en]

    When a system’s performance is inadequate, the concept of availability importance can be used to improve it. The availability of an item depends on the combined aspects of its reliability and maintainability. In a system consisting of many subsystems, the availability of some subsystems is more important to system performance than others. The availability measure determines the priority of availability across subsystems. Most researchers only consider operation time and ignore the influence of the operating environment; therefore, their estimations are not accurate enough. In contrast to previous research, we focus on the influence of the operating environment on the system/subsystem’s characteristics with a view to prioritizing them based on the importance of availability. The paper considers part of the mining fleet system of Sungun copper mine, including the wagon drill, loader, bulldozer, and dump truck subsystems. We identify an ordered list of possibilities for availability improvement and suggest changes or remedial actions for each item to either reduce its failure rate or reduce the time required to repair it.

  • 40.
    Lidström Brock, Malin
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    Writing Feminist Lives: The Biographical Battles over Betty Friedan, Germaine Greer, Gloria Steinem, and Simone de Beauvoir2017Book (Refereed)
    Abstract [en]

    This book draws attention to the controversy that surrounds Betty Friedan, Germaine Greer, Gloria Steinem, and Simone de Beauvoir’s lives and the important role that their life stories have played in their feminist writing. Directly and indirectly, the four women have contributed to battles over feminism’s meaning through autobiographically informed political writing. Inevitably, therefore, their biographers are also participants in these battles, yet not always on the same side as their subjects. Writing Feminist Lives introduces a further fold of nuance into considerations of biography and feminism by showing that the biographers of the four women have made methodological choices that reflect their loyalty to, or their scepticism towards, competing ideological definitions of the exemplary feminist life. 

  • 41.
    Navarro-Pardo, F.
    et al.
    Centre for Energy, Materials and Telecommunications, Institut national de la recherche scientifique.
    Jin, L.
    Centre for Energy, Materials and Telecommunications, Institut national de la recherche scientifique.
    Adhikari, R.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique.
    Tong, X.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, School of Chemistry and Material Science, Guizhou Normal University.
    Benetti, D.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique.
    Basu, K.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique.
    Vanka, S.
    Department of Electrical and Computer Eng., McGill University.
    Zhao, H.G.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique.
    Mi, Z.T.
    Department of Electrical and Computer Eng., McGill University.
    Sun, S.H.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique.
    Castaño, V.M.
    Centre of Applied Physics and Advanced Technology, National Autonomous University of Mexico.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rosei, F.
    Centre for Energy, Materials and Telecommunications, Institut National de la Recherche Scientifique, Institute for Fundamental and Frontier Science, University of Electronic Science and Technology of China.
    Nanofiber-supported CuS nanoplatelets as high efficiency counter electrodes for quantum dot-based photoelectrochemical hydrogen production2017In: Materials Chemistry Frontiers, ISSN 2052-1537, Vol. 1, no 1, 65-72 p.Article in journal (Refereed)
    Abstract [en]

    We developed a hierarchically assembled hybrid counter electrode (CE) based on copper sulfide (CuS) nanoplatelets grown on polymer nanofibers. The resulting CE was used in a quantum dot (QD)-based photoelectrochemical (PEC) system for H2 generation in the presence of sacrificial agents (S2−/SO32−). The concept is to increase the specific surface area of the CE, aiming at maximizing charge exchange at the electrode, which boosts efficient generation of H2 and to obtain a stable structure for long-term operation of the device. Structural and morphological characterization indicated the presence of a covellite crystalline phase (CuS). PEC tests showed that the CuS nanoplatelets grown in the CEs could replace Pt CEs in either visible-active or near infrared (NIR)-active QD-based PEC systems. Specifically, saturation of the photocurrent density (∼7.5 mA cm−2) occurred at ∼0.6 V versus the RHE, when using a NIR QD-based TiO2 photoanode and a nanofiber-supported CuS as the CE. Stability tests of the nanofiber-supported CuS CE showed that 85% of the initial photocurrent density was maintained after ∼1 h, which is similar to that obtained with the Pt foil CE (86%). In contrast, CuS nanostructures directly deposited on FTO glass without nanofibers (CuS/FTO CE) exhibited poor stability. CuS/FTO CE degraded quickly, showing a 90% drop in the initial photocurrent within 200 s testing whereas a 14% drop in the initial photocurrent was observed for the CuxS on brass within 10 min of testing. Our new nanofiber supported-CuS CE stands out due to its higher performance compared to brass and its similar stability compared to Pt during long term PEC operation. Additionally, our hybrid CE showed a better catalytic performance than the Pt CE and good stability in cyclic voltammetry tests. These results demonstrate that the nanofiber-supported CuS is a promising cost effective alternative to Pt as a highly efficient CE for PEC H2 generation

  • 42.
    Bhardwaj, Anshuman
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Singh, Shaktiman
    Institut für Kartographie, Technische Universität Dresden.
    Sam, Lydia
    Institut für Kartographie, Technische Universität Dresden.
    Bhardwaj, Akanksha
    Banaras Hindu University, Varanasi.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Singh, Atar
    Department of Environmental Science, Sharda University.
    Kumar, Rajesh
    Department of Environmental Science, Sharda University.
    MODIS-based estimates of strong snow surface temperature anomaly related to high altitude earthquakes of 20152017In: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 188, 1-8 p.Article in journal (Refereed)
    Abstract [en]

    The high levels of uncertainty associated with earthquake prediction render earthquakes some of the worst natural calamities. Here, we present our observations of MODerate resolution Imaging Spectroradiometer (MODIS)-derived Land Surface Temperature (LST) anomaly for earthquakes in the largest tectonically active Himalayan and Andean mountain belts. We report the appearance of fairly detectable pre-earthquake Snow Surface Temperature (SST) anomalies. We use 16 years (2000–2015) of MODIS LST time-series data to robustly conclude our findings for three of the most destructive earthquakes that occurred in 2015 in the high mountains of Nepal, Chile, and Afghanistan. We propose the physical basis behind higher sensitivity of snow towards geothermal emissions. Although the preliminary appearance of SST anomalies and their amplitudes vary, we propose employing a global-scale monitoring system for detecting and studying such spatio-temporal geophysical signals. With the advent of improved remote sensors, we anticipate that such efforts can be another step towards improved earthquake predictions.

  • 43.
    Nguyen, Huong
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Diagnostic checks in multiple time series modelling2017In: Contributions to Statistics, Germany: Springer Berlin/Heidelberg, 2017Chapter in book (Refereed)
  • 44.
    Pusch, Roland
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Kasbohm, Jörn
    GeoENconLtd, Institute of Geography and Geology, Univ. of Greifswald, Germany.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Yang, Ting
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Two genuinely geological alternatives for disposal of highly radioactive waste (HLW)2017In: Communicacaoes Geologicas, ISSN 0873-948X; e-ISSN: 1647-581XArticle in journal (Refereed)
    Abstract [en]

    Disposal of highly radioactive waste (HLW) can be environmentally acceptable if radionuclides are kept isolated from the groundwater, which has inspired planners of repositories to work out multibarrier concepts that postulate defined functions of the host rock and engineered waste confinements. Assessment of the role of the host rock involves groundwater flow modelling and rock mechanical analysis, which are both highly speculative and ignore future changes in rock structure, stress conditions, and groundwater flow. Widening the perspective by considering the integrated physical performance of contacting geological strata respecting groundwater flow conditions can provide excellent isolation of HLW with a minimum of engineered barriers as illustrated by the principle of very deep boreholes (VDH) for which the very high salt content of deep water is the primary barrier by maintaining possibly contaminated groundwater at depth. Such isolation of groundwater regimes can also be obtained by constructing relatively shallow repositories in crystalline rock covered by clay-containing sedimentary rock in regions with no or very low hydraulic gradients. The paper describes a possible case of this type, showing that effective isolation of HLW in repositories of commonly discussed types, KBS-3H and VDH, can be achieved under present climatic conditions.

    The paper compares the short- and long-term functions of repositories located at the southern end of the Swedish island Gotland, being an example of desired geological conditions that are found also in other parts of Sweden and in Lithuania, Germany, Holland and the UK. Here, 500 m of sediment rock series cover gneiss bedrock in which a KBS-3H repository of SKB-type can be built under virtually “dry” conditions because of the tightness of the overlying sedimentary rock and lack of hydraulic gradients in the crystalline rock. Shafts leading down from the ground surface to the repository level are constructed by use of freezing technique and lined with low-pH concrete before installation of waste after which they have to be sealed with expanding clay. Use of initially largely water-saturated clay provides suitable physical properties of the embedment of waste containers. Alternatively, a VDH repository consisting of a number of steep 4 km deep boreholes with about 8oo mm diameter can be driven for installing waste below 2 km depth, leaving the upper 2 km for sealing with clay. The geological conditions, which are also believed to provide acceptable rock pressure conditions for construction of a KBS-3H repository at about 600 m depth, are believed to be suitable for the construction and short- and long-term performance of either repository type. 

  • 45.
    Ntuli, Herbert
    et al.
    School of Economics, University of Cape Town, Private Bag, Rondebosch .
    Muchapondwa, Edwin
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Effects of wildlife resources on community welfare in Southern Africa2017In: Ecological Economics, ISSN 0921-8009, E-ISSN 1873-6106, Vol. 131, 572-583 p.Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates the importance of wildlife in the portfolio of environmental income in the livelihoods of poor rural communities living adjacent to a national park. The results show that wealthier households use more wildlife resources in total than do relatively poor households. However, poorer households derive greater proportional benefit than wealthier households from the use of wildlife resources. Excluding wildlife understates the relative contribution of environmental resources while at the same time overstating the relative contribution of farm and wage income. Wildlife income alone accounts for about a 5.5% reduction in the proportion of people living below the poverty line. Furthermore, wildlife income has an equalizing effect, bringing about a 5.4% reduction in measured inequality. Regression analysis suggests that the likelihood of belonging to a wealthier category of income increases with an increase in environmental income. As expected, household wealth significantly and positively affects environmental income generated by households. This seems to suggest that wildlife-based land reform also needs to empower poor households in the area of capital accumulation while imposing restraints on the use of capital investments by well-off households to harvest wildlife.

  • 46.
    Rao Vuddanda, Parameswara
    et al.
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Montenegro-Nicolini, Miguel
    Department of Pharmaceutical Sciences and Technology, University of Chile, Santiago.
    Morales, Javier O.
    Department of Pharmaceutical Sciences and Technology, University of Chile, Santiago.
    Velaga, Sitaram
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Effect of plasticizers on the physico-mechanical properties of pullulan based pharmaceutical oral films2017In: European Journal of Pharmaceutical Sciences, ISSN 0928-0987, E-ISSN 1879-0720, Vol. 96, 290-298 p.Article in journal (Refereed)
    Abstract [en]

    The effect of different plasticizers (glycerol, vitamin E TPGS and triacetin) and their concentrations on the physico-mechanical properties of pullulan based oral films was studied. A full factorial (32) design of experiments was used. Elastic modulus, tensile strength, elongation at break and disintegration time were selected as response variables. Modulated differential scanning calorimeter (MDSC) was used for determining glass transition temperature (Tg) of pullulan films. The surface morphology of films was evaluated by SEM, while ATR-FTIR was used to obtain a molecular level understanding of polymer-plasticizer interactions. The DoE analysis allowed for the modelling of tensile strength and elongation at break. The highest elongations were observed in glycerol at 20% w/w. Majority of the films disintegrated within one minute without significant differences. ATR-FTIR spectra of pullulan alone and different plasticizer blend films show characteristic molecular interactions. The present study concluded that glycerol is suitable plasticizer compared to others for manufacturing pullulan based oral films.

  • 47.
    Khoshkhoo, Mohammad
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Dopson, Mark
    Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University.
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    New insights into the influence of redox potential on chalcopyrite leaching behaviour2017In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 100, 9-16 p.Article in journal (Refereed)
    Abstract [en]

    Chalcopyrite (CuFeS2) is the most economically important and most refractory copper mineral when treated in conventional sulphate media leaching systems. In this study, the effect of solution redox potential on leaching of a pure and a pyritic chalcopyrite concentrate was investigated using concentrates with fresh and aged surfaces. In experiments using concentrates with fresh surfaces, the response to redox potential depended on the presence of pyrite: fresh pyritic concentrate leached more effectively at low redox potential (in agreement with reductive leaching mechanisms), while the leaching efficiencies from fresh pure concentrate were similar at high and low redox potentials. The data suggested that the reductive leaching mechanism does not necessarily result in higher and faster recoveries in the absence of the galvanic interaction induced by the presence of pyrite. It was also found that exposure of chalcopyrite to atmospheric oxidation prior to leaching (ageing) had an effect on leaching behaviour in response to redox potential: copper recoveries in leaching of aged concentrates were higher at high redox potentials. This behaviour was attributed to the presence of iron–oxyhydroxides on the surface of aged concentrates. Based on the data from this investigation and previous surface studies, it is proposed that iron–oxyhydroxides play an important role in triggering the hindered dissolution of chalcopyrite.

  • 48.
    Zrida, Hana
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fernberg, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ayadi, Zoubir
    Institut Jean Lamour, Ecole Européenne d’Ingénieurs en Génie des Matériaux, Université de Lorraine.
    Varna, Janis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Microcracking in thermally cycled and aged Carbon fibre/polyimide laminates2017In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 94, no 1, 121-130 p.Article in journal (Refereed)
    Abstract [en]

    Carbon fibre T650 8-harness satin weave fabric composites with thermosetting polyimide resin designed for high service temperatures are solidified at 340 °C. High thermal stresses develop after cooling down to room temperature, which lead to multiple cracking in bundles of the studied quasi-isotropic composite. The composites are subjected to two thermal cycling ramps and the increase of crack density in each bundle is quantified. Comparison of two ramps with the same lowest temperature shows that the highest temperature in the cycle has a significant effect on thermal fatigue resistance. During thermal aging tests at 288 °C the mechanical properties are degrading with time and the crack density after certain aging time is measured. Aging and fatigue effects are separately analysed showing that part of the cracking in thermal cycling tests is related to material aging during the high temperature part of the cycle. Numerical edge stress analysis and fracture mechanics are used to explain observations. The 3-D finite element edge stress analysis reveals that there is large edge effect that induces a large difference in the damage state between the different layers on the edge. The linear elastic fracture mechanics explains the higher initiated and propagated crack density in the surface layers comparing to the inner layers.

  • 49.
    Ma, Chunyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. College of Chemical Engineering, Nanjing Tech University.
    Guo, Yanhua
    College of Chemical Engineering, Nanjing Tech University.
    Li, Dongxue
    College of Chemical Engineering, Nanjing Tech University.
    Zong, Jianpeng
    College of Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Liu, Chang
    College of Chemical Engineering, Nanjing Tech University.
    Molar enthalpy of mixing and refractive indices of choline chloride-based deep eutectic solvents with water2017In: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 105, 30-36 p.Article in journal (Refereed)
    Abstract [en]

    The molar enthalpies of mixing were measured for binary systems of choline chloride-based deep eutectic solvents (glycerol, ethylene glycol and malonic acid) with water at 298.15 K and 308.15 K, and atmospheric pressure with an isothermal calorimeter. Refractive indices were also measured at 303.15 K and atmospheric pressure. The binary mixtures of {chcl/glycerol (1:2) + water, chcl/ethylene glycol (1:2) + water} showed exothermic behaviour over the entire range of composition, while the binary mixture of {chcl/malonic acid (1:1) + water} showed endothermic behaviour at first and then changed to be exothermic with the increasing content of chcl/malonic acid (1:1). Experimental refractive indices were fitted with the Redlich–Kister equation, and experimental molar enthalpies of mixing were correlated with the Redlich–Kister equation and the non-random two-liquid (NRTL) model. The NRTL model with the fitted parameters was used to predict the vapour pressures of these three mixtures. For mixtures of {chcl/glycerol (1:2) + water} and {chcl/ethylene glycol (1:2) + water}, the predicted vapour pressures agreed well with the experimental reults from the literature. While for mixture of {chcl/malonic acid (1:1)+water}, the predicted vapour pressures showed deviation at the high concentration of chcl/malonic acid (1:1), and this was probably because of the complex molecular interaction between chcl/malonic acid (1:1) and water

  • 50.
    Sanda, Mohammed-Aminu
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Dynamics of National Culture and Employee Characteristics on Organizational Commitment in Retail Banks in Ghana2017In: Advances in Cross-Cultural Decision Making: Proceedings of the AHFE 2016 International Conference on Cross-Cultural Decision Making (CCDM), July 27-31,2016, Walt Disney World®, Florida, USA / [ed] Sae Schatz; Mark Hoffman, London: Encyclopedia of Global Archaeology/Springer Verlag, 2017, 71-83 p.Conference paper (Refereed)
    Abstract [en]

    Firms operating in high growth sectors are known to face the challenges of hiring and assimilating large numbers of new employees, providing new knowledge and skills to existing employees, and addressing the need for a rapid expansion of leadership capability. In the Ghanaian situation, such a challenge is known to prevail, since the country implemented major financial sector reforms starting in the late 1980s as part of its broad market reforms, key of which is the deregulation of the financial sub-sector. The banking sector in Ghana is therefore, faced with human resource management challenges, which includes the finding of the right caliber of employees to employ, and how to ensure that employees get committed to their organizations in order to reduce their desire to switch to competitor firms, due to apparent dissatisfaction with their jobs. This study therefore, examined a conceptual model that sought to hypothesize the impact of national culture and employee characteristics on employees’ organizational commitment in retail banks in Ghana. The purpose is to understand the extent to which Ghanaian national cultural values and employee characteristics impact on employee organizational commitment in Retail Banks operating in Ghana. Quantitative data was collected from 282 bank employee across nine different retail banks in Ghana, and analyzed stepwise, using the analysis of moment structures (AMOS) program. Firstly, path analysis was conducted to test the individual measurement models that constitute the various components of the conceptual structural model. In this analysis, the factor score weights and model fit estimates for the indicator variables in the various latent variables (i.e. national culture, employee characteristics, and organizational commitment,) were appraised. Results from the path analysis identified four measurable indicators for organizational commitment. The analysis showed that all the measurable indicators tested for national culture and employee characteristics did not have significant loads to serve as measurable indicators. It is concluded that employees’ organizational commitment in retail banks in Ghana is neither influenced by the Ghanaian national culture nor the employee’s characteristics.

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