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  • 1.
    Eppanapelli, Lavan Kumar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    3D analysis of deformation and porosity of dry natural snow during compaction2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 6, artikel-id 850Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present study focuses on three-dimensional (3D) microstructure analysis of dry natural snow during compaction. An X-ray computed microtomography (micro-CT) system was used to record a total of 1601 projections of a snow volume. Experiments were performed in-situ at four load states as 0 MPa, 0.3 MPa, 0.6 MPa and 0.8 MPa, to investigate the effect of compaction on structural features of snow grains. The micro-CT system produces high resolution images (4.3 μm voxel) in 6 hours of scanning time. The micro-CT images of the investigated snow volume illustrate that grain shapes are mostly dominated by needles, capped columns and dendrites. It was found that a significant number of grains appeared to have a deep hollow core irrespective of the grain shape. Digital volume correlation (DVC) was applied to investigate displacement and strain fields in the snow volume due to the compaction. Results from the DVC analysis show that grains close to the moving punch experience most of the displacement. The reconstructed snow volume is segmented into several cylinders via horizontal cross-sectioning, to evaluate the vertical heterogeneity of porosity distribution of the snow volume. It was observed that the porosity (for the whole volume) in principle decreases as the level of compaction increases. A distinct vertical heterogeneity is observed in porosity distribution in response to compaction. The observations from this initial study may be useful to understand the snow microstructure under applied stress.

  • 2.
    Khodadad, Davood
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Department of Mechanical Engineering, Örebro University, Örebro, Sweden.
    Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement2019Ingår i: International Journal of Optics, ISSN 1687-9384, E-ISSN 1687-9392, Vol. 2019, artikel-id 4906109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a digital holographic method to increase height range measurement with a reduced phase ambiguity using a dual-directional illumination. Small changes in the angle of incident illumination introduce phase differences between the recorded complex fields. We decrease relative phase difference between the recorded complex fields 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈300 μm  . Further, numerical refocusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

  • 3.
    Rajput, Moeen S
    et al.
    KTH Royal Institute of Technology, Stockholm.
    Burman, Magnus
    KTH Royal Institute of Technology, Stockholm.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hallström, Stefan
    KTH Royal Institute of Technology, Stockholm.
    Experimental and numerical study of the response to various impact energy levels for composite sandwich plates with different face thicknesses2019Ingår i: Journal of Sandwich Structures and Materials, ISSN 1099-6362, E-ISSN 1530-7972Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Composite sandwich structures find wide application in the aerospace sector thanks to their lightweight characteristics. However, composite structures are highly susceptible to low-velocity impact damage and therefore thorough characterization of the impact response and damage process for the used material configurations is necessary. The present study investigates the effect of face-sheet thickness on the impact response and damage mechanisms, experimentally and numerically. A uni-directional, non-crimp fabric is used as reinforcement in the face-sheets, and a closed cell Rohacell 200 Hero polymer foam is used as core material. Low-velocity impact tests are performed in a novel instrumented drop-weight rig that is able to capture the true impact response. A range of impact energies are initially utilized in order to identify when low level damage (LLD), barely visible impact damage (BVID) and visible impact damage (VID) occur. A thorough fractography investigation is performed to characterize the impact damage using both destructive and non-destructive testing. The damage from the impacts in terms of dent depth, peak contact force, deflection and absorbed energy is measured. The results show bilinear responses in dent depth vs. impact energy and absorbed energy vs. impact energy. It is found than the BVID energy works well as an indication for the onset of excessive damage. Fractography reveals that there is a failure mode shift between the LLD and the VID energy levels, and that delaminations predominantly grow along the fiber direction and rotate in a spiral pattern through the thickness, following the laminate ply orientations. Finally, a progressive damage finite element model is developed to simulate both the impact response and the delamination extent, incorporating both intra-laminar and inter-laminar damage modes. The simulation shows good agreement with the experiments.

  • 4.
    Malinovskis, Uldis
    et al.
    Institute of Chemical Physics, University of Latvia, Riga, Latvia.
    Poplausks, Raimonds
    Institute of Chemical Physics, University of Latvia, Riga, Latvia.
    Erts, Donats
    Institute of Chemical Physics, University of Latvia, Riga, Latvia.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Tamulevičius, Sigitas
    Institute of Materials Science, Kaunas University of Technology, Kaunas, Lithuania.
    Tamulevičienė, Asta
    Institute of Materials Science, Kaunas University of Technology, Kaunas, Lithuania.
    Gu, Yesong
    Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan.
    Prikulis, Juris
    Institute of Chemical Physics, University of Latvia, Riga, Latvia.
    High-Density Plasmonic Nanoparticle Arrays Deposited on Nanoporous Anodic Alumina Templates for Optical Sensor Applications2019Ingår i: Nanomaterials, E-ISSN 2079-4991, Vol. 9, nr 4, artikel-id 531Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study demonstrates a new, robust, and accessible deposition technique of metal nanoparticle arrays (NPAs), which uses nanoporous anodic alumina (NAA) as a template for capillary force-assisted convective colloid (40, 60, and 80 nm diameter Au) assembly. The NPA density and nanoparticle size can be independently tuned by the anodization conditions and colloid synthesis protocols. This enables production of non-touching variable-density NPAs with controllable gaps in the 20–60 nm range. The NPA nearest neighbor center distance in the present study was fixed to 100 nm by the choice of anodization protocol. The obtained Au NPAs have the resonant scattering maxima in the visible spectral range, with a refractometric sensitivity, which can be tuned by the variation of the array density. The thickness of the NAA layer in an Aluminum-NAA-NPA multilayer system enables further tuning of the resonance frequency and optimization for use with specific molecules, e.g., to avoid absorption bands. Applicability of the mentioned multilayers for colorimetric refractive index (RI) sensing is demonstrated. Their use as Surface-Enhanced Raman Scattering (SERS) substrates is tested using hemoglobin as a biological probe molecule

  • 5.
    Krige, Adolf
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    On-line Raman spectroscopic study of cytochromes’ redox state of biofilms in microbial fuel cells2019Ingår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 24, nr 3, artikel-id 646Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bio-electrochemical systems such as microbial fuel cells and microbial electrosynthesis cells depend on efficient electron transfer between the microorganisms and the electrodes. Understanding the mechanisms and dynamics of the electron transfer is important in order to design more efficient reactors, as well as modifying microorganisms for enhanced electricity production. Geobacter are well known for their ability to form thick biofilms and transfer electrons to the surfaces of electrodes. Currently, there are not many “on-line” systems for monitoring the activity of the biofilm and the electron transfer process without harming the biofilm. Raman microscopy was shown to be capable of providing biochemical information, i.e., the redox state of C-type cytochromes, which is integral to external electron transfer, without harming the biofilm. In the current study, a custom 3D printed flow-through cuvette was used in order to analyze the oxidation state of the C-type cytochromes of suspended cultures of three Geobacter sulfurreducens strains (PCA, KN400 and ∆pilA). It was found that the oxidation state is a good indicator of the metabolic state of the cells. Furthermore, an anaerobic fluidic system enabling in situ Raman measurements was designed and applied successfully to monitor and characterize G. sulfurreducens biofilms during electricity generation, for both a wild strain, PCA, and a mutant, ∆S. The cytochrome redox state, monitored by the Raman peak areas, could be modulated by applying different poise voltages to the electrodes. This also correlated with the modulation of current transferred from the cytochromes to the electrode. The Raman peak area changed in a predictable and reversible manner, indicating that the system could be used for analyzing the oxidation state of the proteins responsible for the electron transfer process and the kinetics thereof in-situ. 

  • 6.
    Tóth, Pál
    et al.
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå. Institute of Thermal Energy, University of Miskolc, Miskolc, Hungary.
    Ögren, Yngve
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Sepma, Alexey
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Vikström, Therese
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Wiinikka, Henrik
    RISE Bioekonomi/RISE Energy Technology Center AB, Piteå, Sweden.
    Spray combustion of biomass fast pyrolysis oil: Experiments and modeling2019Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 237, s. 580-591Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we are the first to report a detailed comparison between the predictions of a current Computational Fluid Dynamics (CFD) model for describing Fast Pyrolysis Oil (FPO) spray combustion and results from a laboratory-scale experiment. The objectives were to assess the predictive power of the CFD model, evaluate its usefulness in a numerical optimization scenario and characterize the spray flame. The spray flame was produced by using an air-assist atomizer piloted by a CH4" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 14.4px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">CH4/air flat-flame. Pyrolysis oil from a cyclone fast pyrolysis plant was combusted. The flame was characterized by using two-color pyrometry, Tunable Diode Laser Absorption Spectroscopy and high-magnification shadowgraphy. Overall, the assessed model correctly predicted flame structure and seemed appropriate for engineering applications, but lacked predictive power in estimating droplet size distributions. Numerical results were the most sensitive to variations in the initial droplet size distribution; however, seemed robust to changes in the multicomponent fuel formulation. Several conclusions were drawn regarding FPO spray combustion itself; e.g., the amount of produced soot in the flames was very low and droplets exhibited microexplosion behavior in a characteristic size-shape regime.

  • 7.
    Öhman, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    3D localization in digital holography from scattered light from micrometer-sized particles2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    When a particle is illuminated by a beam of light it will scatter and redistribute the light in all directions. How it scatters depends on the size, shape and refractive index of the particle. Additionally, it depends on the wavelength and polarization of the illuminating beam. The direction and distance to the observer relative the particle also needs to be considered.  A digital holographic imaging system is used to collect parts of the scattered light from micrometer-sized particles. By utilizing digital holography a three-dimensional reconstruction of the imaged scene is possible. Traditionally, particles are localized based on the intensity in the holographic reconstructions. In this licentiate thesis, the phase response of the scattered light is investigated and utilized. An alternative method for locating spherical particles is presented. The method locate particles based on a simple feature of a propagating wave, namely the fact that the wavefront curvature changes from converging to diverging at the axial location of the particle. The wavefront curvature is estimated using two different methods. The first method estimates the lateral phase-gradients using a finite-difference method. The second method uses a three-dimensional parametric model based on a Chebyshev polynomial expansion. The methods are demonstrated using both simulations and experimental measurements. The simulations are based on the Lorenz-Mie scattering theory for spherical particles and are combined with an imaging system model. Experiments are performed using an off-axis polarization sensitive digital holographic system with a coherent Nd:YAG laser. Measurements of stationary particles are made to validate and evaluate the proposed method. It is found that these methods estimate the true axial position and does not have the offset that is associated with intensity-based methods. Additionally, it is possible to exclude noise that shows up as false particles since noise does not have the same phase response as a real particle. The second method, that uses a parametric model, also improves the standard deviation in the positioning.

  • 8.
    Wahl, Joel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Bergström, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lindbäck, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Magnusson, Malin
    GKN Aerospace Sweden AB.
    Domeij, Kristina
    GKN Aerospace Sweden AB.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Comparison between process simulation and deformation measured by defocused speckle photography2018Ingår i: Speckle 2018: VII International Conference On Speckle Metrology / [ed] M. Kujawińska ; L. R. Jaroszewicz, SPIE - International Society for Optical Engineering, 2018, Vol. 10834, artikel-id 108341KKonferensbidrag (Refereegranskat)
    Abstract [en]

    Defocused laser speckle photography is used as a tool to measure the heat responses in a titanium component during laser heating. The evolution of the response is compared with a set of preprocessed Finite Element Simulations of the corresponding process with the aim to verify the simulation model and to find the simulation settings that best resemble the experimental results. The titanium component consists of a 300 x 100 mm2 substrate of thickness 3.2 mm on which a 200 x 30 x 11 mm3 ridge is built up using the laser metal deposition by wire process. The component is heated on the top of the ridge by a 300 W laser for 10 s and the deformation of the subtrate is followed throughout the heating-cooling cycle. The simulated deformation gradient is shown to resemble the measured response, and the magnitude of the response indicates that about 70 % of the laser power transferres into heat in the metal.

  • 9.
    Neikter, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Pederson, Robert
    Department of Engineering Science, University West.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Åkerfeldt, Pia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Puyoo, Geraldine
    GKN-Aerospace Engine Systems.
    Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography2018Ingår i: Aeronautics and Aerospace Open Access Journal, ISSN 2576-4500, Vol. 2, nr 3, s. 139-145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron beam melting (EBM) is emerging as a promising manufacturing process where metallic components are manufactured from three-dimensional (3D) computer aided design models by melting layers onto layers. There are several advantages with this manufacturing process such as near net shaping, reduced lead times and the possibility to decrease weight by topology optimization, aspects that are of interest for the aerospace industry. In this work two alloys, Ti-6Al-4V and Alloy 718, widely used within the aerospace industry were investigated with X-ray microtomography (XMT), to characterize defects such as lack of fusion (LOF) and inclusions. It was furthermore possible to view the macrostructure with XMT, which was compared to macrostructure images obtained by light optical microscopy (LOM). XMT proved to be a useful tool for defect characterization and both LOF and un-melted powder could be found in the two investigated samples. In the EBM built Ti-6Al-4V sample high density inclusions, believed to be composed of tungsten, were found. One of the high-density inclusions was found to be hollow, which indicate that the inclusion stems from the powder manufacturing process and not related with the EBM process. By performing defect analyses with the XMT software it was also possible to quantify the amount of LOF and un-melted powder in vol%. From the XMT-data meshes were produced so that finite element method (FEM) simulations could be performed. From these FEM simulations the significant impact of defects on the material properties was evident, as the defects led to high stress concentrations. It could moreover, with FEM, be shown that the as-built surface roughness of EBM material is of importance as high surface roughness led to increased stress concentrations.

  • 10.
    Knoepp, F.
    et al.
    Excellence-Cluster Cardio-Pulmonary System (ECCPS), Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Justus-Liebig University Giessen, Giessen, Germany.
    Wahl, Joel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Anders G.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Borg, J.
    CMS, Imperial College, London, UK.
    Weissmann, N.
    Excellence-Cluster Cardio-Pulmonary System (ECCPS), Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Justus-Liebig University Giessen, D-35392 Giessen, Germany.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Development of a Gas-Tight Microfluidic System for Raman Sensing of Single Pulmonary Arterial Smooth Muscle Cells Under Normoxic/Hypoxic Conditions2018Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 10, artikel-id 3238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Acute hypoxia changes the redox-state of pulmonary arterial smooth muscle cells (PASMCs). This might influence the activity of redox-sensitive voltage-gated K⁺-channels (Kv-channels) whose inhibition initiates hypoxic pulmonary vasoconstriction (HPV). However, the molecular mechanism of how hypoxia-or the subsequent change in the cellular redox-state-inhibits Kv-channels remains elusive. For this purpose, a new multifunctional gas-tight microfluidic system was developed enabling simultaneous single-cell Raman spectroscopic studies (to sense the redox-state under normoxic/hypoxic conditions) and patch-clamp experiments (to study the Kv-channel activity). The performance of the system was tested by optically recording the O₂-content and taking Raman spectra on murine PASMCs under normoxic/hypoxic conditions or in the presence of H₂O₂. Oxygen sensing showed that hypoxic levels in the gas-tight microfluidic system were achieved faster, more stable and significantly lower compared to a conventional open system (1.6 ± 0.2%, respectively 6.7 ± 0.7%, n = 6, p < 0.001). Raman spectra revealed that the redistribution of biomarkers (cytochromes, FeS, myoglobin and NADH) under hypoxic/normoxic conditions were improved in the gas-tight microfluidic system (p-values from 0.00% to 16.30%) compared to the open system (p-value from 0.01% to 98.42%). In conclusion, the new redox sensor holds promise for future experiments that may elucidate the role of Kv-channels during HPV.

  • 11.
    Eppanapelli, Lavan Kumar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lintzen, Nina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Wåhlin, Johan
    Department of Civil and Transport Engineering, Norwegian University of Science and Technology.
    Estimation of Liquid Water Content of Snow Surface by Spectral Reflectance2018Ingår i: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 32, nr 1, artikel-id 05018001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study measures the spectral reflectance from snow with known liquid water content (LWC) in a climate chamber using two optical sensors, a near-infrared (NIR) spectrometer and a Road eye sensor. The spectrometer measures the backscattered radiation in the wavelength range of 920–1,650 nm. The Road eye sensor was developed to monitor and classify winter roads based on reflected intensity measurements at wavelengths of 980, 1,310, and 1,550 nm. Results of the study suggest that the spectral reflectance from snow is inversely proportional to the LWC in snow. Based on the effect of LWC on the spectral reflectance, three optimum wavelength bands are selected in which snow with different LWCs is clearly distinguishable. A widely used remote sensing index known as the normalized difference water index (NDWI) is used to develop a method to estimate the surface LWC for a given snow pack. The derived NDWI values with respect to the known LWC in snow show that the NDWI is sensitive to the LWC in snow and that the NDWI and LWC are directly proportional. Based on this information, the NDWI is used to estimate the surface LWC in snow from measurements on a ski track using the Road eye sensor. The findings suggest that the presented method can be applied to estimate the surface LWC in order to classify snow conditions potentially for ski track and piste applications.

  • 12.
    Li, Yiling
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Xi, Yinhu
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Shi, Yijun
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Estimation of rolling friction coefficients in a tribosystem using optical measurements2018Ingår i: Industrial Lubrication and Tribology, ISSN 0036-8792, E-ISSN 1758-5775, Vol. 70, nr 4, s. 680-686Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose

    This paper presents a method to measure the rolling friction coefficient in an easy and fast way. The aim is to measure the rolling friction coefficient between a small steel ball and a cylindrical aluminum surface.

    Design/methodology/approach

    An analytical model of the tribosystem of a freely rolling ball and a cylindrical surface is established. The rolling friction coefficient is evaluated from images recorded by a high-speed camera. The coefficient between a 1.58 mm diameter steel ball and a cylindrical aluminum surface is measured. A background subtraction algorithm is used to determine the position of the small steel ball.

    Findings

    The angular positions of the ball are predicted using the analytical model, and good agreement is found between the experimental and theoretical results.

    Originality/value

    An optical method for evaluating the rolling friction coefficient is presented, and the value of this coefficient between a small steel ball and a cylindrical aluminum surface is evaluated.

  • 13.
    Eppanapelli, Lavan Kumar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Experimental investigation of snow metamorphism at near-surface layers2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Snow metamorphism is a direct objective in many snow research areas, and its charac-terisation is a major challenge in areas including winter road maintenance, detection of icing on wind turbine blades, and snow quality mapping for skiing. A common effect of snow metamorphism is compaction, which can be investigated from the associated vari-ations in physical properties of snow. While the relation between snow metamorphism and physical properties of snow is fairly well-known, a method to quantify this relationis not extensively researched. This experimental based thesis focuses on the relationship between the physical properties of snow and its degree of metamorphism. The link isestablished and investigated by quantifying near-infrared (NIR) reflectance measure-ments and analysing the microtomographic data. Three experimental approaches are developed to record the NIR reflectance measurements and to understand the influence of compaction at near-surface layers of a snowpack. In addition, an X-ray microtomogra-phy (micro-CT) system is used to visualise the behaviour of snow microstructure during compaction. In this thesis, snow experienced compaction via aging, the melting-freezing process, uniaxial loading, settling and infiltration of liquid water.

    A numerical tool based on the well-established Discrete Ordinates Radiative Trans-fer (DISORT) method is used to solve the radiative transfer equation (RTE) for aplane-parallel and semi-infinite snowpack. The numerical solver takes the reflectance measurements as input and returns the coefficients of a first order Legendre phase function of an investigated snowpack at a given wavelength of light. The results from the solver show consistency and strong correlation between the Legendre coefficient sand the physical properties of snow. Furthermore, the physical properties of snow such as specific surface area (SSA) and liquid water content (LWC) were estimated via parameterisation where the reflectance data is used as input. The results suggest that the parameterisation of LWC can provide a qualitative estimate of the LWC in a snowpack, while the parameterisation of SSA provides a quantitative estimate of the snow SSA. As a next step, the influence of compaction on snow microstructure is investigated from three-dimensional (3D) images obtained using the micro-CT system. In this case, compaction is initiated by applying uniaxial load on a snow sample and the effect of compaction is analysed based on digital volume correlation (DVC) and porosity distribution. The micro-CT observations further emphasise that near-surface layers of a snowpack experience a higher degree of impact during compaction.

    In summary, this thesis presents experimental methods to quantify the link between snow compaction at near-surface layers, and the physical properties of snow. The mode observations show that the estimated Legendre coefficients can provide qualitative descriptions of snow grain distribution and surface texture. The parameterisation methods can provide the details about the LWC and the SSA of a snowpack. Further, the observations from the micro-CT study suggest that grains breakage and recrystallisation are the prevailing effects of snow compaction. All observations in this thesis are helpful in understanding the metamorphism in a snowpack for relevant research areas.

  • 14.
    Hu, Xianfeng
    et al.
    Process Metallurgy Department, Swerea MEFOS AB, Sweden.
    Sundqvist-Öqvist, Lena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi. Process Metallurgy Department, Swerea MEFOS AB, Sweden.
    Åström, Elin
    LKAB R&D.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. LKAB R&D.
    Checchia, Paolo
    INFN Sezione di Padova, Padova, Italy.
    Bonomi, Germano
    Universita degli Studi di Brescia, Brescia, Italy.
    Calliari, I.
    Universita degli Studi di Padova, Padua, Italy.
    Calvini, Piero
    Universita degli Studi di Genova, Genoa, Italy.
    Donzella, Antonietta
    Universita degli Studi di Brescia, Department of Mechanical and Industrial Engineering, Brescia, Italy.
    Faraci, Eros
    Centro Sviluppo Materiali S.p.A., Roma, Italy.
    Gonella, Franco
    Istituto Nazionale Di Fisica Nucleare, Frascati, Frascati, Italy.
    Klinger, Joel
    Istituto Nazionale Di Fisica Nucleare, Frascati, Frascati, Italy.
    Pagano, Davide
    Universita degli Studi di Brescia, Brescia, Italy.
    Rigoni, Andrea
    Consorzio Rfx, Padua, Italy.
    Zanuttigh, Pietro
    Universita degli Studi di Padova, Padua, Italy.
    Ronchese, Paolo
    Universita degli Studi di Padova, Padua, Italy.
    Urbani, Michele
    Universita degli Studi di Padova, Department of Physics and Astronomy, Padua, Italy.
    Vanini, Sara
    Universita degli Studi di Padova, Department of Physics and Astronomy, Padua, Italy.
    Zenoni, Aldo
    Universita degli Studi di Brescia, Department of Mechanical and Industrial Engineering, Brescia, Italy.
    Zumerle, Gianni
    Universita degli Studi di Padova, Department of Physics and Astronomy, Padua, Italy.
    Exploring the capability of muon scattering tomography for imaging the components in the blast furnace2018Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, nr 1, s. 35-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowing the distribution of the materials in the blast furnace (BF) is believed to be of great interest for BF operation and process optimization. In this paper calibration samples (ferrous pellets and coke) and samples from LKAB’s experimental blast furnace (probe samples, excavation samples and core-drilling samples) were measured by the muon scattering tomography detector to explore the capability of using the muon scattering tomography to image the components in the blast furnace. The experimental results show that it is possible to use this technique to discriminate the ferrous pellets from the coke and it is also shown that the measured linear scattering densities (LSD) linearly correlate with the bulk densities of the measured materials. By applying the Stovall’s model a correlation among the LSD values, the bulk densities and the components of the materials in the probe samples and excavation samples was established. The theoretical analysis indicates that it is potential to use the present muon scattering tomography technique to image the components in various zones of the blast furnace.

  • 15.
    Dagli, Deniz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zeinali, Amin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Laue, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Image analyses of frost heave mechanisms based on freezing tests with free access to water2018Ingår i: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 146, s. 187-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A freezing test apparatus was supplemented with a camera to allow for recording and monitoring one-dimensional freezing tests to analyze the development of ice lenses via particle image velocimetry (PIV) in the laboratory. Two tests on disturbed, partially saturated samples of silt loam were conducted. Image recording and correlation analyses provided detailed information about frost front penetration and ice lens formation(s) under varying temperature boundary conditions. Thawing has also been regarded in further studies.

    Results of the image analyses were compared to readings from conventional displacement measurements during the same test. Significant agreement between the results of image analyses and displacement measurements has been found. Test results were also used to establish a qualitative relationship between heat extraction and heave rates. Advantages and disadvantages of utilizing image analysis methods were discussed. Potential remedies for overcoming the drawbacks of using image analysis are suggested.

    Image analysis is shown to be a viable method in further understanding of frost heave mechanisms.

  • 16.
    Öhman, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Improved particle position accuracy from off-axis holograms using a Chebyshev model2018Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 57, nr 1, s. A157-A163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Side scattered light from micrometer-sized particles is recorded using an off-axis digital holographic setup. From holograms, a volume is reconstructed with information about both intensity and phase. Finding particle positions is non-trivial, since poor axial resolution elongates particles in the reconstruction. To overcome this problem, the reconstructed wavefront around a particle is used to find the axial position. The method is based on the change in the sign of the curvature around the true particle position plane. The wavefront curvature is directly linked to the phase response in the reconstruction. In this paper we propose a new method of estimating the curvature based on a parametric model. The model is based on Chebyshev polynomials and is fit to the phase anomaly and compared to a plane wave in the reconstructed volume. From the model coefficients, it is possible to find particle locations. Simulated results show increased performance in the presence of noise, compared to the use of finite difference methods. The standard deviation is decreased from 3–39 μm to 6–10 μm for varying noise levels. Experimental results show a corresponding improvement where the standard deviation is decreased from 18 μm to 13 μm.

  • 17.
    Rodiouchkina, Maria
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Berglund, Kim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shah, Faiz Ullah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rodushkin, Ilia
    ALS Laboratory Group, ALS Scandinavia AB.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Material Characterization and Influence of Sliding Speed and Pressure on Friction and Wear Behavior of Self-Lubricating Bearing Materials for Hydropower Applications2018Ingår i: Lubricants, ISSN 2075-4442, Vol. 6, nr 2, artikel-id 39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nowadays, hydropower plants are forced to have more frequent power control and the self-lubricated bearings used in the applications are one of the most critical components affected by the continuously changing operating conditions. In this study, microstructure and composition of two commercially available bearing materials (Orkot TXM Marine and Thordon ThorPlas) used in hydropower turbines were studied. In addition, the influence of sliding speed and applied pressure on the friction and wear behavior of the materials was investigated systematically for dry sliding conditions. The bearing materials were characterized using X-ray microtomography, Nuclear Magnetic Resonance (NMR) spectroscopy and Inductively Coupled Plasma–Sector Field Mass Spectrometry (ICP-SFMS) techniques. Friction and wear tests were carried out with a polymer pin sliding against a stainless steel (SS2333) plate with a linear reciprocating motion. Test conditions were: room temperature, 9–28 MPa pressure and 10–40 mm/s sliding speed ranges. Surface analysis of the polymer pins and the wear tracks were performed by optical profilometry, Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) techniques. Test results show that, for both materials, the coefficient of friction (COF) is decreasing at higher pressures. Surface analysis reveals higher concentrations of solid lubricants in the transfer layers formed at higher pressures, explaining the decrease in COF. Furthermore, the specific wear rate coefficients are increasing at higher sliding speeds, especially at lower pressures. Results of this study demonstrate that, under dry sliding conditions, changes in sliding speed and pressure have a significant influence on the tribological behavior of these bearing materials.

  • 18.
    Amer, Eynas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Measurement of selective species concentration using spectroscopic holography2018Ingår i: Speckle 2018: VII International Conference on Speckle Metrology / [ed] M. Kujawińska ; L. R. Jaroszewicz, SPIE - International Society for Optical Engineering, 2018, Vol. 10834, artikel-id 108340PKonferensbidrag (Refereegranskat)
    Abstract [en]

    Spectroscopic holography refers to techniques in which the detected hologram contains information about specific species in the medium under study. In general, at least two lasers are required with wavelengths chosen carefully to fit the interaction process utilized. In this process, energy from the shorter wavelength laser beam is transferred to the longer wavelength coherently through the process of stimulated emission. Two interaction mechanisms are considered; Stimulated Laser Induced Fluorescence (LIF) and Stimulated Raman Scattering (SRS), which both are species specific with the ability of coherent interaction. In this paper, the fundamental properties of spectroscopic holography is presented and demonstrated with a few idealized experiments. These validation experiments are performed in a gas chamber in which different gases may be blended and the gas pressure changed between 1-12 bars. In addition, two examples of applications are presented. In the first set of experiments, LIF holography is used to image light absorption and laser heating in a dye simultaneously. The second set of experiments is performed in a ow of methane gas. It is demonstrated that the combination of holographic phase measurements and SRS gain images may be used for calibration. This calibration may further be used to measure absolute concentration in a burning flame.

  • 19.
    Dittes, Nicholas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Pettersson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet M.
    SKF Engineering and Research Center, Nieuwegein.
    Optical Attenuation Characterization of Water Contaminated Lubricating Grease2018Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, nr 4, s. 726-732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Water-contaminated grease samples are investigated with attenuation spectra in the visible and near-infrared (NIR) regions in this article. The purpose of this investigation was to identify a model with optical attenuation spectra such that the water content of grease samples could be characterized with a simple measurement setup using common methodology from the field of instrumental chemistry. The ratio between two chosen wavelengths of light appears to approximate the water content of grease samples with an acceptable coefficient of determination using a methodology to show what can potentially be done to develop condition monitoring tools. To illustrate the outlined method, a prestudy of grease aging and oxidation levels is also investigated to show that other variables do not significantly change the measurement.

  • 20.
    Berglund, Linn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Jonoobi, Mehdi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Fibre and Particle Engineering, University of Oulu, Oulu, Finland.
    Promoted hydrogel formation of lignin-containing arabinoxylan aerogel using cellulose nanofibers as a functional biomaterial2018Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, nr 67, s. 38219-38228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, three-dimensional (3D) aerogels and hydrogels based on lignin-containing arabinoxylan (AX) and cellulose nanofibers (CNF) were prepared. The effects of the CNF and the crosslinking with citric acid (CA) of various contents (1, 3, 5 wt%) were evaluated. All the aerogels possessed highly porous (above 98%) and lightweight structures. The AX-CNF hydrogel with a CA content of 1 wt% revealed a favorable network structure with respect to the swelling ratio; nanofiber addition resulted in a five-fold increase in the degree of swelling (68 g of water per g). The compressive properties were improved when the higher CA content (5 wt%) was used; when combined with CNF, there was a seven-fold enhancement in the compressive strength. The AX-CNF hydrogels were prepared using a green and straightforward method that utilizes sustainable resources efficiently. Therefore, such natural hydrogels could find application potential, for example in the field of soft tissue engineering.

  • 21.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Michael, Fergusson
    Viospatia AB.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Virtual projective shape matching in targetless CAD-based close-range photogrammetry for efficient estimation of specific deviations2018Ingår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 57, nr 5, artikel-id 053110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A concept for targetless, computer-aided design (CAD)-based, close-range photogrammetry for online shape inspection is introduced. The shape of an object, which is arbitrarily located on a conveyor belt, is to be measured and compared with its nominal shape as defined by a CAD model. For most manufactured objects, deviations are only measured at a few given comparison points. These deviations can be estimated using local photogrammetry based on a priori geometrical information given by the CAD model and the comparison points. Our method results in faster output with higher precision, because we do not generate a shape representation of the entire measured object using typical photogrammetric methods. Images depicting the object from convergent angles are captured by an array of cameras in a precalibrated network, and the CAD model is matched and aligned, within the projective geometry of the camera network, to the depicted object in the images without the use of targets. An algorithm for solving this virtual projective targetless shape matching problem is presented.

  • 22.
    Öhman, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Axial Particle Positioning by Wavefront Parameterization using Chebyshev Polynomials and Off-axis Digital Holography2017Ingår i: Digital Holography and Three-Dimensional Imaging, Washington: The Optical Society , 2017, artikel-id M4A.3Konferensbidrag (Refereegranskat)
    Abstract [en]

    A particle can be axially positioned where its scattered light has a plane wavefront. The phase anomaly compared to a plane wave is fitted to 3D Chebyshev polynomial, where coefficients correspond to the axial position.

  • 23.
    Joffe, Roberts
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swerea SICOMP.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjögren, Anders
    Lund University.
    Characterization of defects in polymer composites used in medical devices by means of x-ray microtomography2017Ingår i: 3rd International Conference on Tomography of Materials and Structures (ICTMS2017), 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a study on micro-structural characterization of carbon fibre-reinforced plastics used inmedical devices. The focus of the investigation is on determination of void content in the materials, since voids act asdefects and will affect the service life of the composites/devices. The results show that x-ray microtomography is anaccurate and powerful technique to identify defects in composites, and it is of great value in quality control.

  • 24.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Engström, Niclas
    LKAB, SE-981-86 Kiruna, Sweden.
    Grönlund, Ulrika
    Autoliv Sverige AB, Active Saftey Tech Center, Linköping, Sweden.
    Evaluation of velocity and curvature dependence for roadgrip measured by low lateral slip2017Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 12, nr 1/2, s. 1-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Roadgrip is an important parameter for vehicle testing and road maintenance. Therefore, an evaluation of the velocity and curvature effects on roadgrip measurement was performed on asphalt roads and on two ice tracks using the continuous roadgrip apparatus RT3 Curve. The aim was to find suitable driving patterns for measurements on public roads and test tracks to ensure the repeatability of roadgrip measurements. During the evaluation, it was concluded that in order to achieve a reliable roadgrip value, regardless of road conditions, the radius of curvature should not be less than 20 m. The velocity dependency of the RT3 Curve is different for the two road conditions, with the measurements on ice being much more sensitive to velocity changes than the measurements on the dry asphalt.

  • 25.
    Knoepp, F.
    et al.
    Justus Liebig University Giessen.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Weissmann, N.
    Justus Liebig University Giessen.
    Hypoxia alters the redox state and inhibits K+-currents in mouse pulmonary arterial smooth muscle cells2017Ingår i: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 219, nr S711, s. 139-Artikel i tidskrift (Refereegranskat)
  • 26.
    Odelius, Johan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Famurewa, Stephen Mayowa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Forslöf, Lars
    Roadroid AB Ljusdal .
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Konttaniemi, Heikki
    Arctic Power RDI-team, Lapland University of Applied Sciences Rovaniemi .
    Industrial internet applications for efficient road winter maintenance2017Ingår i: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 23, nr 3, s. 355-367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: For the expected increase in the capacity of existing transportation systems and efficient energy utilisation, smart maintenance solutions that are supported by online and integrated condition monitoring systems are required. Industrial Internet is one of the smart maintenance solutions, which enables real-time acquisition and analysis of asset condition by linking intelligent devices with different stakeholdersᅵ applications and databases. This paper presents some aspects of Industrial Internet application as required for integrating weather information and floating road condition data from vehicle mounted sensors to enhance effective and efficient winter maintenance.

    Design/methodology/approach: The concept of real-time road condition assessment using in-vehicle sensors is demonstrated in a case study of a 3.5 km road section located in northern Sweden. The main floating data sources were acceleration and position sensors from a smartphone positioned on the dash board of a truck. Features extracted from the acceleration signal were two road roughness estimations. To extract targeted information and knowledge, the floating data were further processed to produce time series data of the road condition using Kalman filtering. The time series data were thereafter combined with weather data to assess the condition of the road.

    Findings: In the case study, examples of visualisation and analytics to support winter maintenance planning, execution, and resource allocation were presented. Reasonable correlation was shown between estimated road roughness and annual road survey data to validate and prove the presented results wider applicability.

    Originality/value: The paper describes a concept of floating data for an industrial internet application for efficient road maintenance. The resulting improvement in winter maintenance will promote dependable, safe and sustainable transportation of goods and people, especially in northern Nordic region with harsh and sometimes unpredictable weather conditions.

  • 27.
    Eppanapelli, Lavan Kumar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Wåhlin, Johan
    Norwegian University of Science and Technology.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Investigation of snow single scattering properties of snow based on first order Legendre phase function2017Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 91, s. 151-159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Angularly resolved bidirectional reflectance measurements were modelled by ap- proximating a first order Legendre expanded phase function to retrieve single scattering properties of snow. The measurements from 10 different snow types with known density and specific surface area (SSA) were investigated. A near infrared (NIR) spectrometer was used to measure reflected light above the snow surface over the hemisphere in the wavelength region 900 nm to 1650 nm. A solver based on discrete ordinate radiative transfer (DISORT) model was used to retrieve the estimated Legendre coefficients of the phase function and a cor- relation between the coefficients and physical properties of different snow types is investigated. Results of this study suggest that the first two coefficients of the first order Legendre phase function provide sufficient information about the physical properties of snow where the latter captures the anisotropic behaviour of snow and the former provides a relative estimate of the single scattering albedo of snow. The coefficients of the first order phase function were com- pared with the experimental data and observed that both the coefficients are in good agreement with the experimental data. These findings suggest that our approach can be applied as a qualitative tool to investigate physical properties of snow and also to classify different snow types.

  • 28.
    Lindahl, Olof A.
    et al.
    Department of Radiation Sciences, Biomedical Engineering, Umeå University.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Bäcklund, Tomas
    Department of Radiation Sciences, Biomedical Engineering, Umeå University.
    Ljungberg, Börje
    Department of Surgical and Perioperative sciences, Urology and Andrology, Umeå University.
    Bergh, Anders
    Department of Medical Bioscience, Pathology, Umeå University.
    Prostate cancer detection ex vivo combining Raman spectroscopy and tactile resonance technology2017Ingår i: EMBEC & NBC 2017: Joint Conference of the European Medical and Biological Engineering Conference (EMBEC) and the Nordic-Baltic Conference on Biomedical Engineering and Medical Physics (NBC), Tampere, Finland, June 2017 / [ed] Hannu Eskola, Outi Väisänen, Jari Viik, Jari Hyttinen, Singapore: Springer, 2017, s. 193-196Konferensbidrag (Refereegranskat)
    Abstract [en]

    Prostate cancer is the most common cancer for men in the western world. The most prevalent curative treatment is radical prostatectomy. However, prostate surgery can give unwanted side effects and there is a need for an instrument that can provide decision support to the surgeon during surgery on the presence of cancer cells in the surgical margin. A dual-modality probe, combining Raman spectroscopy and tactile resonance technology, has been used for detecting cancer in fresh human prostate tissue. The tactile resonance modality measures the tissue stiffness and Raman spectroscopy depicts the molecular content in tissue, both related to cancer. After ethical approval, the study investigated the potential of the dual-modality probe by testing its ability to differentiate between normal and cancerous prostate tissue ex vivo. It also investigated the minimal amount of measurement points needed to securely detect cancer on the surface of prostate tissue. Measurements on three prostate tissue slices show that the tactile resonance modality measuring stiffness was able to detect differences between normal and cancerous tissue on a significant level of 90%, but the sample size was too low to draw any firm conclusions. It was also suggested from the study results that the high wavenumber region in the Raman spectrum can give valuable information about cancer in prostate tissue. A number of 24 measurement points were enough for detecting cancer in prostate slices in this study. It can be suggested from this study that combining these two sensor modalities is promising for accurate detection of prostate cancer that is needed during prostate surgery, but more measurements including more prostates must be performed before the full value of the study result can be established.

  • 29.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Reusable road condition information system for traffic safety and targeted maintenance2017Ingår i: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 11, nr 4, s. 230-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Driver awareness of current winter road conditions (RCs) is known to affect the frequency of accidents due to sudden changes in these conditions. For example, partially icy roads that appear during autumn in northern areas typically result in collisions and ditch runs unless the drivers are generally aware of the situation. Availing motorists who drive under winter RCs of enhanced information is therefore highly desirable to increase their awareness of hazardous driving conditions. Such conditions need to be predicted ahead of time and presented to drivers before they attempt slippery road sections. Moreover, the identification of slippery RCs should quickly trigger targeted road maintenance to reduce the risk of accidents. This study presents a scalable and reusable collaborative intelligent transport system, herein referred to as an RC information system (RCIS). RCIS provides accurate RC predictions and forecasts based on RC measurements, road weather observations, and short-term weather forecasts. The prediction methods in the context of the distributed RCIS have been tested using a prototype implementation. These tests confirmed that these inputs could be combined into useful and accurate information about winter RCs that can be adapted for different types of users.

  • 30.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Edlund, Ove
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Robust registration of surfaces using a refined iterative closest point algorithm with a trust region approach2017Ingår i: Numerical Algorithms, ISSN 1017-1398, E-ISSN 1572-9265, Vol. 74, nr 3, s. 755-779Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of finding a rigid body transformation, which aligns a set of data points with a given surface, using a robust M-estimation technique is considered. A refined iterative closest point (ICP) algorithm is described where a minimization problem of point-to-plane distances with a proposed constraint is solved in each iteration to find an updating transformation. The constraint is derived from a sum of weighted squared point-to-point distances and forms a natural trust region, which ensures convergence. Only a minor number of additional computations are required to use it. Two alternative trust regions are introduced and analyzed. Finally, numerical results for some test problems are presented. It is obvious from these results that there is a significant advantage, with respect to convergence rate of accuracy, to use the proposed trust region approach in comparison with using point-to-point distance minimization as well as using point-to-plane distance minimization and a Newton- type update without any step size control.

  • 31.
    Murayama, Yoshinobu
    et al.
    Department of Electrical and Electronics Engineering, College of Engineering , Nihon University .
    Lindahl, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sensitivity improvements of a resonance-based tactile sensor2017Ingår i: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 41, nr 2, s. 131-140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Resonance-based contact-impedance measurement refers to the application of resonance sensors based on the measurement of the changes in the resonance curve of an ultrasonic resonator in contact with a surface. The advantage of the resonance sensor is that it is very sensitive to small changes in the contact impedance. A sensitive micro tactile sensor (MTS) was developed, which measured the elasticity of soft living tissues at the single-cell level. In the present paper, we studied the method of improving the touch and stiffness sensitivity of the MTS. First, the dependence of touch sensitivity in relation to the resonator length was studied by calculating the sensitivity coefficient at each length ranging from 9 to 40 mm. The highest touch sensitivity was obtained with a 30-mm-long glass needle driven at a resonance frequency of 100 kHz. Next, the numerical calculation of contact impedance showed that the highest stiffness sensitivity was achieved when the driving frequency was 100 kHz and the contact-tip diameter of the MTS was 10 μm. The theoretical model was then confirmed experimentally using a phase-locked-loop-based digital feedback oscillation circuit. It was found that the developed MTS, whose resonant frequency was 97.030 kHz, performed with the highest sensitivity of 53.2 × 106 Hz/N at the driving frequency of 97.986 kHz, i.e. the highest sensitivity was achieved at 956 Hz above the resonant frequency.

  • 32.
    Amer, Eynas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Single-shot polarization digital holography for recording stimulated Raman scattering signal for time-resolved measurement of gaseous species2017Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, nr 36, s. 10016-10023Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stimulated Raman scattering (SRS) process is sensitive to the relation between the polarization direction of the two laser beams (the pump and the Stokes) that generate it. In this paper, we made use of the polarization sensitivity of the SRS process and used polarization-resolved pulsed digital holography to record the signal from one single-shot hologram. The pump beam polarization was kept vertical, while the Stokes beam polarization was 45 deg. The two polarization components of the Stokes beam were recorded in a single hologram by blending the Stokes beam with two reference beams with orthogonal polarization on the detector. The two components of the Stokes beam were separated in the Fourier domain, and the corresponding intensity maps were calculated. The vertically polarized component of the Stokes beam was amplified due to the SRS process, while the horizontal component experienced no gain. The difference between the vertically and horizontally polarized intensity maps, respectively, was calculated and Fourier transformed to separate the gain signal in the spatial frequency domain. The method was demonstrated on methane (CH4) gas at a pressure of 12 bars. Results show that SRS polarization holography is a promising technique for recording the SRS signal from one single-shot hologram for time-resolved monitoring of specific species. 

  • 33.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Fergusson, Michael
    Xtura AB, Kungsbacka.
    Folkesson, Patrik
    Xtura AB, Kungsbacka.
    Runnemalm, Anna
    University West, Department of Engineering Sciences, Trollhättan.
    Ottosson, Mattias
    University West, Department of Engineering Sciences, Trollhättan.
    Andersson, Alf
    Chalmers University of Technology, Department of Product and Production Development.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Automatic in-line inspection of shape based on photogrammetry2016Ingår i: SPS16, Lund: SPS16 , 2016, , s. 9Konferensbidrag (Refereegranskat)
    Abstract [en]

    We are describing a fully automatic in-line shape inspection system for controlling the shape of moving objects on a conveyor belt. The shapes of the objects are measured using a full-field optical shape measurement method based on photogrammetry. The photogrammetry system consists of four cameras, a flash, and a triggering device. When an object to be measured arrives at a given position relative to the system, the flash and cameras are synchronously triggered to capture images of the moving object. From the captured images a point-cloud representing the measured shape is created. The point-cloud is then aligned to a CAD-model, which defines the nominal shape of the measured object, using a best-fit method and a feature-based alignment method. Deviations between the point-cloud and the CAD-model are computed giving the output of the inspection process. The computational time to create a point-cloud from the captured images is about 30 seconds and the computational time for the comparison with the CAD-model is about ten milliseconds. We report on recent progress with the shape inspection system.

  • 34.
    Eppanapelli, Lavan Kumar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Friberg, Benjamin
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Estimation of a low-order Legendre expanded phase function of snow2016Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 78, s. 174-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this paper is to estimate the scattering phase function of snow from angularly resolved measurements of light intensity in the plane of incidence. A solver is implemented that solves the scattering function for a semi-infinite geometry based on the radiative transfer equation (RTE). Two types of phase functions are considered. The first type is the general phase function based on a low-order series expansion of Legendre polynomials and the other type is the Henyey-Greenstein (HG) phase function. The measurements were performed at a wavelength of 1310 nm and six different snow samples were analysed. It was found that a first order expansion provides sufficient approximation to the measurements. The fit from the first order phase function outperforms that of the HG phase function in terms of accuracy, ease of implementation and computation time. Furthermore, a correlation between the magnitude of the first order component and the age of the snow was found. We believe that these findings may complement present non-contact detection techniques used to determine snow properties.

  • 35.
    Tatar, Kourosh
    et al.
    Division of Mechanical Engineering, University of Gävle.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Estimation of the in-plane vibrations of a rotating spindle, using out-of-plane laser vibrometry measurements2016Ingår i: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 72-73, s. 660-666Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for estimating the in-plane vibrations of a rotating spindle using out-of-plane laser vibrometry measurements is described. This method enables the possibility to obtain the two orthogonal radial vibration components of a rotating spindle. The method uses the fact that the laser vibrometer signal is a total surface velocity of the measurement point in the laser direction.Measurements are conducted on a rotating milling machine spindle. The spindle is excited in a controlled manner by an active magnetic bearing and the response is measured by laser vibrometer in one of the two orthogonal directions and inductive displacement sensors in two orthogonal directions simultaneously. The work shows how the laser vibrometry crosstalk can be used for resolving the in-plane vibration component, that is the vibrations in the laser vibrometer cross direction. The result is compared to independent measurement signals from the displacement sensors.The measurement method can be used for vibration measurements on rotating parts, for example, where there is lack of space for orthogonal measurements.

  • 36.
    Khodadad, Davood
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Multiplexed Digital Holography incorporating Speckle Correlation2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing the controlled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digital holography, access to the complex wave field and the possibility to numerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in asingle exposure, which is important when doing measurements in a disturbed environment. The aim of this thesis is devoted to the theoretical and experimental development of shape and deformation measurements. To perform online process control of free-form manufactured objects, the measured shape is compared with the CAD-model to obtain deviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape, position and deformation without the unwrapping problems that usually appear in dual-wavelength holography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformation measurements. One significant problem when using the dual-wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria tomake an automatic procedure. Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3D deformations. In order to do 3D deformation measurement, usually multi-cameras and intricate set-up are required. In this thesis I demonstrate the use of only one single camera torecord four sets of speckle patterns recorded by illuminating the object from four different directions. In this manner, meanwhile 3D speckle displacement is calculated and used for the measurement of the 3D deformations, wrapping problems are also avoided. Further, the same scale of speckle images of the surface for all four images is guaranteed. Furthermore, a need for calibration of the 3D deformation measurement that occurs in the multi-camera methods,is removed. By the results of the presented work, it is experimentally verified that the multiplexed singleshot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. The proposed method is robust to large phase gradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, shape and deformation measurements can be performed even though the synthetic wavelength is out of the dynamic range of the object deformation and/or height variation.

  • 37.
    Tjörhammar, Staffan
    et al.
    Department of Applied Physics, Royal Institute of Technology (KTH).
    Eklöf, Finn Klemming
    Department of Applied Physics, Royal Institute of Technology (KTH).
    Yu, Zhangwei
    Department of Applied Physics, Royal Institute of Technology (KTH).
    Khodadad, Davood
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hällstig, Emil
    Fotonic.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Laurell, Fredrik
    Department of Applied Physics, Royal Institute of Technology (KTH).
    Multiwavelength laser designed for single-frame digital holography2016Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 27, s. 7517-7521Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a tailored multiwavelength Yb-fiber laser source in the 1.03 μm spectral region for spatially multiplexed digital holographic acquisitions. The wavelengths with bandwidths below 0.1 nm were spectrally separated by approximately 1 nm by employing fiber Bragg gratings for spectral control. As a proof of concept, the shape of a cylindrically shaped object with a diameter of 48 mm was measured. The holographic acquisition was performed in single-shot dual-wavelength mode with a synthetic wavelength of 1.1 mm, and the accuracy was estimated to be 3% of the synthetic wavelength.

  • 38.
    Öhman, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Off-axis digital holographic particle positioning based on polarization-sensitive wavefront curvature estimation2016Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 27, s. 7503-7510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Poor axial resolution in holographic particle imaging applications makes particle positioning in 3D space morecomplex since the positions are not directly obtained. In this paper we estimate the axial position of micrometerparticles by finding the location where the wavefront curvature from the scattered light becomes zero. By record-ing scattered light at 90°using off-axis holography, the complex amplitude of the light is obtained. Byreconstruction of the imaged scene, a complex valued volume is produced. From this volume, phase gradientsare calculated for each particle and used to estimate the wavefront curvature. From simulations it is found that thewavefront curvature became zero at the true axial position of the particle. We applied this metric to track an axialtranslation experimentally using a telecentric off-axis holographic imaging system with a lateral magnification ofM1.33. A silicon cube with molded particles inside was used as sample. Holographic recordings are performedboth before and after a 100μm axial translation. From the estimated positions, it was found that the mean dis-placement of particles between recordings was 105.0μm with a standard deviation of 25.3μm.

  • 39.
    Khodadad, Davood
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Phase-derivative-based estimation of digital reference wave from single off-axis digital hologram2016Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 7, s. 1663-1669Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes a method to obtain an estimated digital reference wave from a single off-axis digital hologram that matches the actual experimental reference wave as closely as possible. The proposed method is independent of a reference flat plate and speckles. The digital reference wave parameters are estimated directly from the recorded phase information. The parameters include both the off-axis tilt angle and the curvature of the reference wave. Phase derivatives are used to extract the digital reference wave parameters without the need for a phase unwrapping process. Thus, problems associated with phase wrapping are avoided. Experimental results for the proposed method are provided. The simulated effect of the digital reference wave parameters on the reconstructed image phase distribution is shown. The pseudo phase gradient originating from incorrect estimation of the digital reference wave parameters and its effect on object reconstruction are discussed.

  • 40. Khayamyan, Shervin
    et al.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hellström, Gunnar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    PIV measurements within a randomly packed bed of spheres2016Konferensbidrag (Refereegranskat)
  • 41.
    Åström, E.
    et al.
    LKAB R&D, Luleå.
    Bonomi, Germano
    Department of Mechanical and Industrial Engineering, University of Brescia.
    Calliari, Irene
    Department of Industrial Engineering, University of Padova.
    Calvini, Piero
    Department of Physics, University of Genova and Sezione INFN di Genova.
    Checchia, Paolo
    INFN Sezione di Padova.
    Donzella, Antonietta
    Department of Mechanical and Industrial Engineering, University of Brescia.
    Faraci, E.
    Centro Sviluppo Materiali SPA, Rome.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gonella, F.
    INFN Sezione di Padova.
    Hu, X.
    Swerea MEFOS AB, Luleå.
    Klinger, Joel A.
    INFN Sezione di Padova.
    Sundqvist Ökvist, Lena
    Swerea MEFOS AB, Luleå.
    Pagano, Davide
    Department of Mechanical and Industrial Engineering, University of Brescia.
    Rigoni, Andrea
    Department of Physics and Astronomy, University of Padova.
    Ramous, Emilio
    Department of Industrial Engineering, University of Padova.
    Urbani, M.
    Department of Physics and Astronomy, University of Padova.
    Vanini, Sara
    Department of Physics and Astronomy, University of Padova.
    Zenoni, Aldo
    Department of Mechanical and Industrial Engineering, University of Brescia.
    Zumerle, Gianni
    Department of Physics and Astronomy, University of Padova.
    Precision measurements of linear scattering density using muon tomography2016Ingår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 11, nr P7010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate that muon tomography can be used to precisely measure the properties of various materials. The materials which have been considered have been extracted from an experimental blast furnace, including carbon (coke) and iron oxides, for which measurements of the linear scattering density relative to the mass density have been performed with an absolute precision of 10%. We report the procedures that are used in order to obtain such precision, and a discussion is presented to address the expected performance of the technique when applied to heavier materials. The results we obtain do not depend on the specific type of material considered and therefore they can be extended to any application

  • 42.
    Erjavec, Nika
    et al.
    CBZI, University of Nova Gorica, Vipava.
    Pinato, Giulietta
    CBZI, University of Nova Gorica, Vipava.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Raman spectroscopy as a tool for detecting mitochondrial fitness2016Ingår i: Journal of Raman Spectroscopy, ISSN 0377-0486, E-ISSN 1097-4555, Vol. 47, nr 8, s. 933-939Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Raman spectroscopy allows the molecular chemical analysis of whole living cells by comparing them to known Raman signatures of specific vibrational bonds. In this work we used Raman spectroscopy to differentiate between wild type yeast cells and mutants characterized by increased or reduced mitochondrial fragmentation. To associate mitochondrial fragmentation with biochemical markers, we performed Linear Discriminant Analysis (LDA) of whole cell Raman spectra (~50–100 cells/spectrum). We show that the long-lived, less fragmented mutants fall into a significantly distant cluster from the wild type and short-lived, more fragmented mutants. Clustering depends on respiratory growth and coincides with that of membrane phospholipids and some respiratory chain components. Spectral clustering is supported by enzymatic activity measurements of OXPHOS Complexes. In addition, we find that NAD(P)H autofluorescence also correlates with mitochondrial fragmentation, representing another likely aging biomarker, besides phospholipids and OXPHOS components. In summary, we demonstrate that Raman spectroscopy has the potential to become a powerful tool for differentiating healthy from unhealthy aged tissues, as well as for the prognostic evaluation of mitochondrial function and fitness.

  • 43.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Jonsson, Patrik
    Combitech AB, Mittuniversitetet, Department of Information Technology and Media, Mid-Sweden University.
    Road condition analysis using NIR illumination and compensating for surrounding light2016Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 77, s. 175-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation of a NIR camera system for road surface classification has been conducted for several road conditions. The surfaces were illuminated with three wavelengths, 980 nm, 1310 nm and 1550 nm and a halogen lamp, to simulate a real environment application with surrounding light. A measuring scheme to deal with surrounding light has been implemented enabling road condition classification from NIR images in a real environment. The retrieved camera images have been analyzed and an RGB representation of the different surfaces has been created to classify the different road conditions. The investigation shows that it is possible to distinguish between dry, moist, wet, frosty, icy and snowy road surfaces using a NIR camera system in a disturbed environment.

  • 44.
    Amer, Eynas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Edenharder, Stefan
    Institut für Technische Optik, Universität Stuttgart.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Stimulated Raman scattering detection for chemically specific time-resolved imaging of gases2016Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, nr 9, s. 9984-9993Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    stimulated Raman scattering (SRS) imaging technique based on spatial modulation of the pump beam has been used to study gases. The SRS gain signal was separated from the Stokes beam background in the spatial frequency domain. The SRS signal shows linear behaviour with the gas pressure at a range from 1.0 to 8.0 bars. The signal is linearly proportional to the pump beam intensity while it is enhanced with increasing the Stokes beam intensity to a certain limit than it saturates. Further, the chemical specificity of the technique has been investigated. Two sharp peaks with line width at half maximum of about 0.30 nm have been obtained at Stokes beam wavelengths of 629.93 nm and 634.05 nm corresponding to the methane and ethylene gases, respectively. The results show that SRS imaging is a promising technique to provide chemical specificity as well as spatial and temporal information of gaseous species

  • 45.
    Amer, Eynas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Edenharder, Stefan
    Institut für Technische Optik, Universität Stuttgart.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Stimulated Raman scattering holography for time-resolved imaging of methane gas2016Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 13, s. 3429-3434Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, pulsed digital holographic detection is coupled to the stimulated Raman scattering (SRS) process for imaging gases. A Q-switched Nd-YAG laser (532 nm) has been used to pump methane gas (CH4) at pressures up to 12 bars. The frequency-tripled (355 nm) beam from the same laser was used to pump an optical parametric oscillator (OPO). The Stokes beam (from the OPO) has been tuned to 629.93 nm so that the frequency difference between the pump (532 nm) and the Stokes beams fits a Raman active vibrational mode of the methane molecule (2922 cm(-1)). The pump beam has been spatially modulated with fringes produced in a Michelson interferometer. The pump and the Stokes beams were overlapped in time, space, and polarization on the gas molecules, resulting in a stimulated Raman gain of the Stokes beam and a corresponding loss of the pump beam through the SRS process. The resulting gain of the Stokes beam has been detected using pulsed digital holography by blending it with a reference beam on the detector. Two holograms of the Stokes beam, without and with the pump beam fringes present, were recorded. Intensity maps calculated from the recorded digital holograms showed amplification of the Stokes beam at the position of overlap with the pump beam fringes and the gas molecules. The gain of the Stokes beam has been separated from the background in the Fourier domain. A gain of about 4.5% at a pump beam average intensity of 4 MW/cm(2) and a Stokes beam intensity of 0.16 MW/cm(2) have been recorded at a gas pressure of 12 bars. The gain decreased linearly with decreasing gas pressure. The results show that SRS holography is a promising technique to pinpoint a specific species and record its spatial and temporal distribution

  • 46.
    Joffre, Thomas
    et al.
    Department of Engineering Sciences, Uppsala University.
    Girlanda, Orlando
    ABB Corporate Research, 721 78, Västerås.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sahlen, Fredrik
    ABB Corporate Research, 721 78, Västerås.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gamstedt, E. Kristofer
    Department of Fiber and Polymer Technology, Royal Institute of Technology - KTH, Luleå tekniska universitet, Risø National Laboratory, Roskilde, STFI-Packforsk AB, Department of Engineering Sciences, Division of Applied Mechanics, Uppsala University.
    A 3D in-situ investigation of the deformation in compressive loading in the thickness direction of cellulose fiber mats2015Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, nr 5, s. 2993-3001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fiber mat materials based on cellulose natural fibers combines a useful set of properties, including renewability, stiffness, strength and dielectric insulation, etc. The dominant in-plane fiber orientation ensures the in-plane performance, at the expense of reduced out-of-plane behavior, which has not been studied as extensively as the in-plane behavior. Quantitative use of X-ray micro-computed tomography and strain analyses under in-situ loading open up possibilities to identify key mechanisms responsible for deformation. In the present investigation, focus is placed on the out-of-plane deformation under compressive loading of thick, high density paper, known as pressboard. The samples were compressed in the chamber of a microtomographic scanner. 3D images were captured before and after the loading the sample. From sequential 3D images, the strain field inside the material was calculated using digital volume correlation. Two different test pieces were tested, namely unpolished and surface polished ones. The first principal strain component of the strain tensor showed a significant correlation with the density variation in the material, in particular on the top and bottom surfaces of unpolished samples. The manufacturing-induced grooves generate inhomogeneities in the microstructure of the surface, thus creating high strain concentration zones which give a sensible contribution to the overall compliance of the unpolished material. More generally, the results reveal that, on the micrometer scale, high density fiber pressboard behaves as a porous material rather than a low density fiber network.

  • 47. Alrifaiy, Ahmed
    et al.
    Borg, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Lindahl, Olof
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A lab-on-a-chip for hypoxic patch clamp measurements combined with optical tweezers and spectroscopy: first investigations of single biological cells2015Ingår i: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 14, artikel-id 36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The response and the reaction of the brain system to hypoxia is a vital research subject that requires special instrumentation. With this research subject in focus, a new multifunctional lab-on-a-chip (LOC) system with control over the oxygen content for studies on biological cells was developed. The chip was designed to incorporate the patch clamp technique, optical tweezers and absorption spectroscopy. The performance of the LOC was tested by a series of experiments. The oxygen content within the channels of the LOC was monitored by an oxygen sensor and verified by simultaneously studying the oxygenation state of chicken red blood cells (RBCs) with absorption spectra. The chicken RBCs were manipulated optically and steered in three dimensions towards a patch-clamp micropipette in a closed microfluidic channel. The oxygen level within the channels could be changed from a normoxic value of 18% O 2 to an anoxic value of 0.0-0.5% O 2. A time series of 3 experiments were performed, showing that the spectral transfer from the oxygenated to the deoxygenated state occurred after about 227 ± 1 s and a fully developed deoxygenated spectrum was observed after 298 ± 1 s, a mean value of 3 experiments. The tightness of the chamber to oxygen diffusion was verified by stopping the flow into the channel system while continuously recording absorption spectra showing an unchanged deoxygenated state during 5400 ± 2 s. A transfer of the oxygenated absorption spectra was achieved after 426 ± 1 s when exposing the cell to normoxic buffer. This showed the long time viability of the investigated cells. Successful patching and sealing were established on a trapped RBC and the whole-cell access (Ra) and membrane (Rm) resistances were measured to be 5.033 ± 0.412 M Ω and 889.7 ± 1.74 M Ω respectively.

  • 48.
    Girlanda, Orlando
    et al.
    ABB Corporate Research.
    Sahlen, Fredrik
    ABB Corporate Research.
    Joffre, Thomas
    Department of Engineering Sciences, Uppsala University.
    Gamstedt, E. Kristofer
    Department of Fiber and Polymer Technology, Royal Institute of Technology - KTH, Luleå tekniska universitet, Risø National Laboratory, Roskilde, STFI-Packforsk AB, Department of Engineering Sciences, Division of Applied Mechanics, Uppsala University.
    Schmidt, Lars E.
    ABB Figeholm.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Analysis of the Micromechanical Deformation in Pressboard performed by X-ray Microtomography2015Ingår i: IEEE Electrical Insulation Conference (EIC): Seattle, Jun 07-10, 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 89-92Konferensbidrag (Refereegranskat)
    Abstract [en]

    A large number of electrical insulation components are produced in paper-based materials. Paper combines good insulating properties with the necessary mechanical and chemical stability. Paper consists of a system of fibers binding to each other creating a strong network. The presence of large open pores allows for impregnability of the material but also causes mechanical weakness in particular in the out-of-plane direction of the material. This aspect is important for pressboard components, where the resistance to compression stress is relevant for e.g. transformer windings. It is therefore relevant to understand the mechanisms that underlay the out-of-plane deformation of pressboard. In order to get a clear picture of the deformation patterns within the material, X-ray micro-computed tomography was used. Pressboard test pieces were subjected to in-situ out-of-plane compressive loading. 3D images of the sample could be captured before, during and after the loading sequence. Image analysis allowed for the definition of strain fields. The results revealed a strong correlation between the density variation within the sample and the strain calculated from the 3D images.

  • 49. Nyberg, Morgan
    et al.
    Jalkanen, Ville
    Umeå University. Department of Applied Physics and Electronics, Umeå universitet.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Ljungberg, Börje
    Umeå University, Department of Surgical and Perioperative Science, Urology and Andrology.
    Bergh, Anders
    Umeå University, Department of Physiology, Umeå University, Department of Medical Biosciences, Pathology, Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    Dual-modality probe intended for prostate cancer detection combining Raman spectroscopy and tactile resonance technology—discrimination of normal human prostate tissues ex vivo2015Ingår i: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 39, nr 3, s. 198-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Prostate cancer is the most common cancer for men in the western world. For the first time, a dual-modality probe, combining Raman spectroscopy and tactile resonance technology, has been used for assessment of fresh human prostate tissue. The study investigates the potential of the dual-modality probe by testing its ability to differentiate prostate tissue types ex vivo. Measurements on four prostates show that the tactile resonance modality was able to discriminate soft epithelial tissue and stiff stroma (p < 0.05). The Raman spectra exhibited a strong fluorescent background at the current experimental settings. However, stroma could be discerned from epithelia by integrating the value of the spectral background. Combining both parameters by a stepwise analysis resulted in 100% sensitivity and 91% specificity. Although no cancer tissue was analysed, the results are promising for further development of the instrument and method for discriminating prostate tissues and cancer

  • 50.
    Khodadad, Davood
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Bergström, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hällstig, Emil
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Fast and robust automatic calibration for single-shot dual-wavelength digital holography based on speckle displacements2015Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, nr 16, s. 5003-5010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this paper is to describe a fast and robust automatic single-shot dual-wavelength holographic calibration method that can be used for online shape measurement applications. We present a model of the correction in two terms for each lobe, one to compensate the systematic errors caused by off-axis angles and the other for the curvature of the reference waves, respectively. Each hologram is calibrated independently without a need for an iterative procedure or information of the experimental set-up. The calibration parameters are extracted directly from speckle displacements between different reconstruction planes. The parameters can be defined as any fraction of a pixel to avoid the effect of quantization. Using the speckle displacements, problems associated with phase wrapping is avoided. The procedure is shown to give a shape accuracy of 34 μm using a synthetic wavelength of 1.1 mm for a measurement on a cylindrical test object with a trace over a field of view of 18  mm×18  mm.

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