Ändra sökning
Avgränsa sökresultatet
123 51 - 100 av 120
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    IT som stöd för optimering och energimätning i fjärrvärme- och gasnät2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [sv]

    Vid EISLAB (Embedded Internet Systems Laboratory), Luleå tekniska universitet, pågår sedan några år tillbaka ett antal projekt kopplade till energimätning. Ett projekt behandlar noggrannhet, diagnostisering och optimering av energimätningar i fjärrvärmenät. Ett annat projekt syftar till att utveckla metoder baserade på ultraljud för mätning av energiflöde och sammansättning av bio- och naturgas. Föredraget ger en sammafattning av det arbete som hittills utförts inom dessa områden samt en framåtblick över de möjligheter och fördelar resultaten från dessa projekt ger i framtiden. Inom fjärrvärmeanvändningen finns ett behov av en förbättrad mätning av energianvändningen, dels för att kunna reglera processerna och dels för att kunder och leverantörer ska betala för rätt saker. Snabb och noggrann mätning är idag inte möjligt. Ur underhållssynpunkt är det även av intresse att på distans kunna diagnosticera systemen, både på leverantörs- och kundsidan. Samma teknik kommer även att kunna användas för optimering av processen. Bio- och naturgas har utpekats som möjliga alternativ till bensin och diesel som drivmedel. De mätmetoder som finns idag för att säkerställa kvaliteten och bestämma energivärdena lämpar sig inte för användning långt ut i distributionskedjan. Målet med forskningsprojektet vid EISLAB är att utveckla en ultraljudsmetod som kan mäta sammansättning, energivärde och flöde av dessa gaser. Fokus ligger på utveckling av statistiska metoder samt fysikaliska modeller för vågutbredning i gaser. Förutom tillämpningar inom bio- och naturgas, kan tekniken även användas inom petrokemisk- och processindustri.

  • 52.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Micella, M
    Luleå tekniska universitet.
    Accurate temperature estimation in ultrasonic pulse-echo systems2003Ingår i: 5th world congress on ultrasonics WCU 2003, Paris: Institut Biomedical des Cordeliers, Université Pierre et Marie Curie , 2003, s. 1565-1568Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ultrasonic pulse-echo systems are widely used to estimate properties of liquids and gases. A common principle is to use a buffer material (buffer-rod) fixed to the ultrasound transducer. Assuming the acoustic properties of the buffer-rod are known, it is then possible to calculate the acoustic impedance of the unknown material. A problem occurs if the temperature of the buffer-rod changes during the measurements, since the properties of the buffer-rod, such as the acoustic attenuation depends on temperature. If, however, the temperature is recognized, it is possible to compensate for this. In this paper we present a method based on speed of sound changes in the buffer-rod to estimate the temperature. With the resulting model we are able to estimate temperatures in PMMA for the interval 5°C to 60°C with a 0.1 °C accuracy (at a 95% confidence level).

  • 53.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Scolan, A
    Luleå tekniska universitet.
    Carlander, Carl
    Frequency and temperature dependence of acoustic properties of polymers used in pulse-echo systems2003Ingår i: Proceedings, 2003 IEEE Ultrasonics Symposium: October 5 - 8, 2003, Hilton Hawaiian Village, Honolulu, Hawaii ; an international symposium / / [ed] Donald E. Yuhas, Piscataway, NJ: IEEE Communications Society, 2003, s. 885-888Konferensbidrag (Refereegranskat)
    Abstract [en]

    In ultrasonic pulse-echo systems, polymers like PMMA (polymethylmethacrylate) and PEEK (polyetheretherketone) are often used as buffer-rods, placed between the ultrasound transducer and the unknown material (liquid, gas, or solid material). Provided the acoustic properties of the buffer-rods are known, it is possible to calculate these also for the unknown material, based on reflections between the buffer-rod and the unknown medium. However, temperature changes also affect these properties. In this paper we present a method for measuring acoustic attenuation, speed of sound and density, for buffer-rod materials. We also give experimental values for PMMA and PEEK, for temperatures between 5/spl deg/C and 37/spl deg/C, and for 5 MHz and 10 MHz ultrasound frequency.

  • 54.
    Carlson, Rolf
    et al.
    Tromsø University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Canonical analysis of response surfaces: a valuable tool for process development2005Ingår i: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 9, nr 3, s. 321-330Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The principles of response surface modelling are briefly described. The computations involved in the canonical analysis of response surface models are given in detail. Three examples of canonical analysis in the context of organic synthesis development are discussed. These examples treat enamine synthesis by a modified titanium tetrachloride procedure, kinetic modelling, and the synthesis of the trimethylsilyl enol ether from methyl vinyl ketone.

  • 55.
    Carlson, Rolf
    et al.
    Tromsø University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Design and optimization in organic synthesis2005 (uppl. 2. rev. and enl. ed.)Bok (Övrigt vetenskapligt)
    Abstract [en]

    Revised, and updated Design and Optimization in Organic Synthesis presents strategies to explore experimental conditions and methodologies for systematic studies of entire reaction systems (substrates, reagent(s), catalyst(s), and solvents). Chemical phenomena are not usually the result of a single factor and this book describes how statistically designed methods can be used to analyse and evaluate synthetic procedures. The methodology is based on multivariate statistical techniques. The accompanying CD contains data tables and programmes. This book is essential reading for anyone working in process design and development in fine chemicals or the pharmaceutical industry, and is suitable for those with no experience in the field.

  • 56.
    Carlson, Rolf
    et al.
    Department of Chemistry, University of Tromsoe.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Principal properties and designs for discrete variations2005Ingår i: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 9, nr 5, s. 680-689Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A problem that is often encountered when a new synthetic reaction is developed is to determine suitable combinations of reagents, co-reagents, catalysts, solvents, etc. This contribution presents general strategies for designing experiments when the objective is to explore the discrete variations defined by different reagents, different catalysts, different solvents, etc. The concept of principal properties is introduced, and it is shown how the principal properties of the constituents of the reaction system can be used for the selection of suitable test systems. Chemical examples are provided by the following: the selection of test solvents in the reduction of an enamine; the selection of combinations of Lewis acids and amines in the synthesis of benzamides; the selection of ketone substrates, amines, and solvents in the Willgerodt-Kindler reaction; and the selection of ketone substrates, Lewis acid catalysts, and solvents for analysing the regioselectivity in the Fischer indole synthesis with dissymmetric ketones.

  • 57.
    Carlson, Rolf
    et al.
    Department of Chemistry, University of Tromsoe.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Strategy for screening variations in organic synthesis1997Konferensbidrag (Övrigt vetenskapligt)
  • 58.
    Carlson, Rolf
    et al.
    Tromsø University.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    The study of experimental factors2009Ingår i: Comprehensice Chemometrics: Chemical and Biochemical Data Analysis, Amsterdam: Elsevier, 2009, 1, s. 301-344Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 59.
    Carlson, Rolf
    et al.
    Tromsø University.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Simonsen, Geir
    Tromsø University.
    Improvement of kilolab processes when the time constraints are severe2008Konferensbidrag (Övrigt vetenskapligt)
  • 60.
    Carlson, Rolf
    et al.
    Tromsø University.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Simonsen, Geir
    Tromsø University.
    Improvement of kilolab processes when the time constraints are severe2007Ingår i: Proceedings of Optimising Organic Reactions, 2007Konferensbidrag (Övrigt vetenskapligt)
  • 61.
    Carlson, Rolf
    et al.
    Department of Chemistry, University of Tromsoe.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Grennberg, Anders
    A novel approach for screening discrete variations in organic synthesis2001Ingår i: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 15, nr 5, s. 455-474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we present a general strategy for screening discrete variations in organic synthesis. The strategy is based upon principal properties, i.e. principal component characterization of the constituents defining the reaction system. The first step is to select subsets of test items from each class of constituents defining the reaction space, i.e. substrates, reagents, solvents, catalysts, etc., so that the selected items from each class cover the properties considered. The second step is to construct a candidate matrix which contains all possible combinations of the items in the subsets. This matrix is a full multilevel factorial design. The third step is to assign a tentative model for the screening experiment and to construct the corresponding candidate model matrix. The fourth step is to select experiments to yield an experimental design that spans the variable space efficiently and that also gives good estimates of the model parameters. We present an algorithm that uses singular value decomposition to select experiments. The proposed strategy is then illustrated with an example of the Fischer indole synthesis.

  • 62.
    Carlson, Rolf
    et al.
    Tromsø University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Grennberg, Anders
    Novel and optimal strategy for screening discrete variations in organic synthesis1999Konferensbidrag (Refereegranskat)
  • 63.
    Carlson, Rolf
    et al.
    Department of Chemistry, University of Tromsoe.
    SImonsen, Geir
    Department of Chemistry, University of Tromsoe.
    Descomps, Alexandre
    Department of Chemistry, University of Tromsoe.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Identification of important experimental variables in organic synthetic procedures by near-orthogonal experiments2012Ingår i: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 16, nr 8, s. 1371-1377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new strategy is presented for the design of screening experiments in synthetic chemistry when the objective is to identify the important experimental variables from a limited number of experimental runs. The methodology is based on Taylor expansion (response surface) models The experimental design is constructed in such a way that the vector of the variables in the Taylor model in each run are near-orthogonal to each other. This is achieved by laying out a grid of possible experiments in the experimental space, expanding this candidate experimental design matrix to the corresponding model matrix, i.e. the matrix containing columns for all variables in the Taylor expansion. This model matrix is then factorised by singular value decomposition, SVD. The row in the model matrix that is most parallel to the first singular vectors is selected as the first experiment. .The variation displaced by this first experiment is removed from the elements of the model matrix by projections. The resulting matrix is the orthogonal complement to the first selected row. The procedure is repeated until all dimensions of the model space have been spanned by the selected experiments The singular vectors are mutually orthogonal, and selected experiments will be nearly orthogonal and span the dimensions of the model space. The experiments can be run in sequence and thus allow for a systematic search, one experiment at a time. It is shown that subset selections from such designs in combination with PLS modelling can be used to identify the important variables. The principles are illustrated with two examples: (a) a dibromination of an acetyl with four experimental variables and (b) a synthesis of an enamine by condensing a ketone and morpholine in the presence of molecular sieves in which seven experimental variables are involved. In the acetal bromination, it was found that 5 experiments out of 12 were sufficient for identifying the most important variables. In the enamine example, 8 experiments out of 30 were sufficient.

  • 64.
    Carlson, Rolf
    et al.
    Department of Chemistry, University of Tromsoe.
    Simonsen, Geir
    Department of Chemistry, University of Tromsoe.
    Descomps, Alexandre
    Department of Chemistry, University of Tromsoe.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Near-orthogonal experiments in explorative synthetic organic chemistry2009Konferensbidrag (Övrigt vetenskapligt)
  • 65.
    Carlson, Rolf
    et al.
    Department of Chemistry, University of Tromsoe.
    Simonsen, Geir
    Department of Chemistry, University of Tromsoe.
    Descomps, Alexandre
    Department of Chemistry, University of Tromsoe.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Orthogonal experiments in the development of organic synthetic processes2009Ingår i: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 13, nr 4, s. 798-803Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new strategy is presented for the design of explorative experiments in synthetic chemistry when the objective is to identify the important experimental variables. The methodology is based on Taylor expansion (response surface) models, and the principles are: A grid of possible settings of the experimental variables is laid out in the experimental domain. These experiments define a candidate design matrix, DC. From DC, a candidate model matrix, XC is defined by appending columns for each variable in the Taylor model XC is then factored by singular value decomposition (SVD), and XC = USVT. The rows in XC that are most parallel to the singular column vectors in V are selected, and the corresponding experiments in DC are identified. This gives the experimental design. The selected experiments are nearly orthogonal, and they span the dimensions of the model space. The experiments can be run in sequence, and thus, they allow for a systematic search, one experiment at a time. The design principles are illustrated by an example of the dibromination of an acetal. Four variables were studied, and from 12 experiments, all the main effects and all two-factor interaction effects were estimated. From the response surface model, conditions for quantitative yield were predicted, and a mol-scale synthesis carried out under these conditions afforded 98% yield of the isolated pure, >97% product.

  • 66.
    Castaño, Miguel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Risberg, Robert
    Creo Dynamics AB.
    Weston, Miles
    TWI Technology Centre Wales.
    3D Synthetic Aperture Imaging Using a Water-Jet Coupled Large-Aperture Single Transducer2014Konferensbidrag (Övrigt vetenskapligt)
  • 67.
    Castaño, Miguel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Risberg, Robert
    Creo Dynamics AB.
    Weston, Miles
    TWI Technology Centre Wales.
    3D Synthetic Aperture Imaging Using a Water-Jet Coupled Large-Aperture Single Transducer2014Konferensbidrag (Övrigt vetenskapligt)
  • 68.
    Castaño, Miguel
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Weston, Miles
    TWI Technology Centre Wales.
    Risberg, Robert
    Creo Dynamics AB.
    3D Synthetic Aperture Imaging Using a Water-Jet Coupled Large Aperture Single Transducer2014Ingår i: 2014 IEEE International Ultrasonics Symposium (IUS 2014): Chicago, Ill. 3-6 September 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 1372-1375Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a technique for in-situ non-destructive testing of materials with applications in railway crossings. The novelty is in successfully applying the Virtual Source (VS) concept using water jet coupling for a large transducer. By focusing the sound field at the surface of the sample, the water jet probe can be built with a small nozzle opening, limiting the water consumption and making it viable for field applications. The annular geometry of the large transducer ensures the spherical wavefront assumed in the application of the SAFT algorithm, which usually limits the size of the transducer

  • 69.
    Gasson, J. R.
    et al.
    University of Bergen, Department of Chemistry.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Eide, I.
    Statoil Research Centre, Trondheim.
    Barth, T.
    University of Bergen, Department of Chemistry.
    Extracting homologous series from fingerprint mass spectrometry data of bio-oils: a complement to PCA2012Konferensbidrag (Refereegranskat)
  • 70.
    Gasson, James R.
    et al.
    Department of Chemistry, University of Bergen.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Eide, Ingvar
    Statoil Research Centre, Trondheim.
    Barth, Tanja
    Department of Chemistry, University of Bergen.
    Deciphering complex bio-oil mass spectra with the help of chemometrics2011Konferensbidrag (Refereegranskat)
  • 71.
    Gasson, James R.
    et al.
    Department of Chemistry, University of Bergen.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Eide, Ingvar
    Statoil Research Centre, Trondheim.
    Barth, Tanja
    Department of Chemistry, University of Bergen.
    Extracting homologous series from fingerprint bio-oil mass spectra: a complement to PCA2012Konferensbidrag (Refereegranskat)
  • 72. Hägglund, Fredrik
    et al.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Andersson, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ultrasonic classification of thin layers within multi-layered structures2010Ingår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methods for non-destructive inspection of layered materials are becoming more and more popular as a way of assuring product integrity and quality. In this paper, we present a model-based technique using ultrasonic measurements for classification of thin bonding layers within three-layered materials. This could be, for example, an adhesive bond between two thin plates, where the integrity of the bonding layer needs to be evaluated. The method is based on a model of the wave propagation of pulse-echo ultrasound that first reduces the measured data to a few parameters for each measured point. The model parameters are then fed into a statistical classifier that assigns the bonding layer to one of a set of predefined classes. In this paper, two glass plates are bonded together with construction silicone, and the classifiers are trained to determine if the bonding layer is intact or if it contains regions of air or water. Two different classification methods are evaluated: nominal logistic regression and discriminant analysis. The former is slightly more computationally demanding but, as the results show, it performs better when the model parameters cannot be assumed to belong to a multivariate Gaussian distribution. The performance of the classifiers is evaluated using both simulations and real measurements.

  • 73. Hägglund, Fredrik
    et al.
    Martinsson, Jesper
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Flaw detection in layered media based on parametric modeling of overlapping ultrasonic echoes2006Ingår i: Proceedings: 2006 IEEE Ultrasonics Symposium : Vancouver, Canada, 3 - 6 October 2006, Piscataway, NJ: IEEE Communications Society, 2006, s. 136-139Konferensbidrag (Refereegranskat)
    Abstract [en]

    In materials consisting of several thin layers, multiple reflections within the structure give rise to received ultrasonic signals composed of overlapping echoes. In this paper we present a parametric model that can be used to decompose such signals into the individual reflections. We derive a Maximum Likelihood Estimator for the the model parameters, which are then used in a Generalized Likelihood Ratio Test (GLRT) to detect flaws in multi-layered structures. We show with simulations how the presence of a thin bonding layer in a three-layer structure can be detected. The probability of detection is shown to be ≈ 96%, for a signal-to-noise ratio (SNR) of 15 dB and a probability of false alarm of 5%.

  • 74. Hägglund, Fredrik
    et al.
    Martinsson, Jesper
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlander, Carl
    D-Flow Technology AB.
    Model-based characterization of thin layers using pulse-echo ultrasound2008Ingår i: Proceedings of the International Congress on Ultrasonics: Vienna, April 9-13, 2007, Paper ID 1562, Session R17, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    Measurements performed on a thin multilayered structure will imply a received signal waveform consisting of reverberant overlapping echoes. In this paper the multi-layered structure is modeled by a physical model and the Maximum Likelihood Estimator (MLE) is derived for the model parameters. A general recursive expression for the model is given. The model is evaluated using measurements on a thin three-layered structure, where two glass layers are bonded together. We show that measured signal waveforms can be reconstructed using the estimated parameters, and that physical properties can be extracted from the estimated model parameters. Simulations also show that physical parameters can be estimated for thicknesses of the bonding layer down to 50 μm for a wavelength of 200 μm of the ultrasonic pulse.

  • 75. Hägglund, Fredrik
    et al.
    Martinsson, Jesper
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Model-based classification of thin layers in multi-layered materials using nondestructive ultrasonic testing2008Ingår i: Paper summaries CD-ROM, ASNT fall conference & quality testing show 2008: Charleston, SC, November 10 - 14, 2008, Columbus, Ohio: American Society for Nondestructive Testing , 2008, s. 213-220Konferensbidrag (Refereegranskat)
  • 76. Hägglund, Fredrik
    et al.
    Martinsson, Jesper
    LKAB, Research & Development, 983 81 Malmberget.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Model-based estimation of thin multi-layered media using ultrasonic measurements2009Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 56, nr 8, s. 1689-1702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In ultrasonic measurement situations, when dealing with media of multi-layered structures consisting of 1 or more thin layers, analysis of the measured ultrasonic waveform can be difficult because of overlapping and reverberant echoes. Information from the individual layers is then difficult to extract because the individual echoes cannot be detected. In this study, we use a parametric layer model to analyze the multi-layered material in a system identification approach. The parameters of the model are connected to physical properties of the investigated material, e.g., the reflection coefficients, the time-of-flight, and the attenuation. The main advantage using this model is that the complexity of the model is connected to the number of layers rather than the number of observable echoes in the received ultrasonic waveform. A system of linear equations is presented, giving the opportunity to find the model for both pulse-echo and through-transmission measurements. A thorough effort is made on the parameter estimation and optimization algorithm. The model is validated with practical measurements on a 3-layered structure using both pulse-echo and through-transmission techniques. The 3-layered material consists of a thin embedded middle layer with the time-of-flight in that layer shorter than the emitted signal¿s time support, giving rise to overlapping echoes. Finally the relation between the model parameters and physical properties of the material is established.

  • 77. Hägglund, Fredrik
    et al.
    Martinsson, Jesper
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ultrasonic imaging of thin layers within multi-layered structures2008Ingår i: 2008 IEEE International Ultrasonics Symposium: IUS ; Beijing, China, 2 - 5 November 2008, New York: IEEE Communications Society, 2008, s. 828-831Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the area of process control, non-destructive testing (NDT) using ultrasound is valuable due to its noninvasive properties. In process control, imaging of surface profiles is used to locate defects or problematic areas in order to quickly steer the manufacturing process on track again. This paper presents a method for imaging of parallel thin layers within multi-layered structures. Due to the application in process control a parametric model is used, and all subsequent analysis is performed on the model parameters rather than on the signal waveforms, resulting in a necessary data reduction. The parameters in the model are directly connected to physical properties, such as the reflection coefficients, time-of-flights, and attenuation coefficients. Experimental results shows that the estimated model parameters can be used in imaging of thin layer properties within the material structure. Images of embedded layers with a thickness about the wavelength is shown. Result also show that flaws can be detected in such structures. The results are verified by comparing the images to visual inspections of photographs.

  • 78.
    Håkansson, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Multivariate prediction of key kraft paper properties from designed experiments in a pilot plant2015Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 2, s. 258-264Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A two-level factorial design was set up where five factors in a kraft paper process were varied, from wood chip origin to paper machine roll pressure. Nine paper properties were selected for a more in-depth analysis. This paper shows how these 9 responses can be modeled as a function of the experimental factors. The model, a full interaction model, was estimated using Partial Least-Squares Regression. The resulting model shows that there is a strong correlation between the experimental factors and the measured paper properties. The paper also presents a careful analysis of how the uncertainties of the measured values propagate through the model and contribute to the final model uncertainty. Finally, the interpretations and application of the resulting model is discussed. Specifically, having access to a good model enables the plant operators to simulate the effect of changing the process variables, either for training purposes or to test new production scenarios

  • 79.
    Håkansson, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Factorial study of connections between process variables and kraft paper quality properties2014Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, nr 2, s. 286-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By investigating how properties of a finished paper product are related to different process variables as well as pulp characteristics throughout the fiber line, the understanding of the process will increase. In this paper we investigate the correlation between some key paper quality parameters and five tunable process variables, along the entire fiber production line. A full two-level factorial experiment has been conducted, where five factors were varied. The factor settings were based on a laboratory replica of a specific kraft mill’s paper product. The mill replicate was then used as a center point in the factorial design and appropriate levels of the factors were set based on these center points. Several experimental runs could be simulated via a Monte Carlo approach making it possible to get a reliable estimate of the significance of each factor effect. Analysis of the results shows that there are interaction effects present between variables, and that these interaction effects can be utilized to achieve similar paper properties using different variable settings.

  • 80.
    Håkansson, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjölund, Torbjörn
    MoRe Research AB.
    Lambert, François
    MoRe Research AB.
    Experimental study of the kraft paper making process: compilation of reference tests performed at a paper mill and reproduced in a laboratory environment2012Konferensbidrag (Refereegranskat)
  • 81.
    Jacobson, Karin
    et al.
    Swerea KIMAB AB, Kista Sweden.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lindblad, Philip
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Non-Destructive Testing of Plastics and Composites in the Chemical Processing Industry2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Equipment and components made of plastics and composites are widely used in highly corrosive environments in the processing industry. Examples are the storage tanks, pumps and pipes for chemical transport and stacks in combustion plants. The demand for reliable nondestructive testing of plastic process equipment has increased significantly in recent years. Glass fiber reinforced plastics (GRP) is a common construction material for process equipment in the chemical industry. It can be used both as structural bearing in a dual laminate with a thermoplastic material as a corrosion barrier or as a solid GRP. In the latter case, the laminate is generally built up with a resin rich corrosion barrier (about 2.5 to 5 mm thick) with a low content of glass closest to the chemical. The glass fiber in this layer is usually a surface veil and chopped strand mats (CSM), i.e. it has no general fiber orientation. Outside this is the structural bearing layer with much higher glass content, usually wound fiber and / or woven fiber mats with a preferential fiber direction. The corrosion barrier is not load bearing and corrosion of this layer can be allowed. However, no corrosion can be permitted in the structural support layer. Because of this it is important to measure the thickness of the corrosion barrier for quality control but also to determine how far an attack has reached in the corrosion barrier. Today there is no non-destructive testing method that can answer this. Instead destructive sampling (often a drill core) must be made. This is difficult, expensive and sometimes impossible. There is thus a great interest in a method that, preferably at any time during operation, can provide answers to these questions. Due to the heterogeneity of the GRP material in terms of amount, type and direction of the fibers, conventional algorithm for ultrasound imaging will not work. One aim of our work is thus to develop new signal processing methods to handle this heterogeneity. In addition we are also looking at the possibility to use optical fibers and Fiber Bragg Grating (FBG) sensors for corrosion monitoring of GRP structures

  • 82.
    Jiang, Biao
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Castaño, Miguel
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lindblad, Philip
    Öhman, Johan
    Ultrasonic Imaging Through Thin Reverberating Materials2015Ingår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 70, s. 380-383Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Imaging through anisotropic or highly heterogeneous materials is challenging for the existence of strong boundary and volume reverberations. To image small cracks or flaws in a reverberating thin layers, high resolution techniques are needed in both temporal and spatial domain, so that the reverberation can be suppressed to some level. In this paper, the reverberation suppression performance of the total focusing beamforming method (TFM) was evaluated by simulation and real data processing. The results showed that the more the focusing point moves away from the array central line, the more multi-reflections can be suppressed. Furthermore, TFM combined with adaptive processing greatly improves the small flaw detection performance. Test results on real samples confirmed the robustness and reverberation suppression capability of the TFM imaging method.

  • 83. Johansson, Gustav
    et al.
    Hägglund, Fredrik
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Jonny
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Picosecond level error detection using PCA in the hardware timing systems for the EISCAT_3D LAAR2010Ingår i: Radio Science Bulletin, ISSN 1024-4530, nr 333, s. 45-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    While developing the timing system for the receiver arrays for the EISCAT_3D system, several approaches to detect and adjust for timing errors within the array have been explored. The demand on the timing error between all elements in the array is to have a standard deviation of less than 120 ps, thus requiring high quality error detection systems to guarantee radar operation. This paper investigates the qualities of a secondary error detection system based on statistical analysis of captured data. The measurements are assembled with a Signal-to-Noise Ratio (SNR) of -30 dB implying that the elements in a 2112 element array need to be grouped into sub-arrays of 48 elements each. The captured data is then evaluated by Principal Component Analysis (PCA) and averaged over 20,000 measurements, or about half a second. Timing errors between sub-arrays of down to ~120 ps and a percentage of faulty sub-arrays of up to 20% are detectable. As a secondary error detection system PCA is cheap to implement since the only need of the analysis is a small amount of computer time. It also provides a valuable detection system for hardware errors in the primary timing system that can otherwise be hard to find.

  • 84.
    Lemlikchi, Safia
    et al.
    Division milieu ionisés et lasers, Centre de Developpement des Technologies Avancees, Algiers, Algeria.
    Martinsson, Jesper
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hamrit, Ahmed
    ALGESCO, Blida, Algeria.
    Djelouah, Hakim
    Universite´ des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Asmani, Mohammed
    Université d’Alger 1, Algiers, Algeria.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Correction to: Ultrasonic Characterization of Thermally Sprayed Coatings2019Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, nr 3, s. 591-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The first name of author Ahmed Hamrit was misspelled as “Ahmet” in the original article. Please note that the correct spelling of his name is “Ahmed” as shown in this correction. 

  • 85.
    Lemlikchi, Safia
    et al.
    Division milieu ionisés et lasers, Centre de Developpement des Technologies Avancees, Algiers, Algeria.
    Martinsson, Jesper
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hamrit, Ahmet
    ALGESCO, Blida, Algeria.
    Djelouah, Hakim
    Universite´ des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Asmani, Mohammed
    Université d’Alger 1, Algiers, Algeria.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ultrasonic Characterization of Thermally Sprayed Coatings2019Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, nr 3, s. 391-404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes the simultaneous determination of the ultrasonic parameters in thermally sprayed coatings. The parameters of interest are the longitudinal wave velocity and the ultrasonic attenuation. The test materials are two cobalt-based coatings (FSX 414 and Diamalloy 4060), both deposited onto stainless steel (310SS) substrates. The ultrasonic measurements were carried out in the pulse-echo configuration using several transducers. The ultrasonic signals reflected from the coatings were successfully estimated using the combined model, together with the maximum likelihood estimation and the Levenberg–Marquardt approach. The best estimate was obtained for 20 MHz measurements. Once the model was validated, the ultrasonic parameters of the thermally sprayed coatings were extracted. Model validation is based on the analysis of the residual between measured and estimated signals. Results showed non-dispersive ultrasonic velocities with average values of (3940±50)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; 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; padding: 0px; margin: 0px; position: relative;">(3940±50)m/s(3940±50)m/s in Diamalloy 4060 and (4260±20)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; 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; padding: 0px; margin: 0px; position: relative;">(4260±20)m/s(4260±20)m/s in FSX 414. High ultrasonic attenuation with a quadratic frequency dependence was observed for both materials. Moreover, it was found that the ultrasonic parameters in thermally sprayed materials are microstructure dependent. For close densities, the harder the coating, the higher the ultrasonic wave velocity and attenuation.

  • 86. Martinsson, Jesper
    et al.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Parametric estimation of ultrasonic phase velocity and attenuation in dispersive media2006Ingår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 44, nr Supplement 1, s. e991-e994Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In ultrasonic characterization of liquids, gases, and solids, accurate estimation of frequency dependent attenuation and phase velocity is of great importance. Non-parametric methods, such as Fourier analysis, suffers from noise sensitivity, and the variance of the estimated quantities is limited by the signal-to-noise ratio. In this paper we present a parametric method for estimation of these properties. Pulse echo experiments in ethane, oxygen and mixtures of the two show that the proposed method can estimate phase velocity and attenuation with up to 50 times lower variance than standard non-parametric methods.

  • 87. Martinsson, Jesper
    et al.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Parametric modeling of wave propagation in gas mixtures: a system identification approach2005Ingår i: 2005 IEEE Ultrasonics Symposium: 18 - 21 September 2005, Rotterdam, the Netherlands, Piscataway, NJ: IEEE Communications Society, 2005, s. 2288-2292Konferensbidrag (Refereegranskat)
    Abstract [en]

    In ultrasonic pulse-echo systems, the observable properties are restricted to frequency dependent attenuation and phase velocity, which in turn are related to the material properties of the investigated media. In this paper we present a parametric model of the bulk modulus, composed of the basic physical building blocks of absorption (relaxation blocks). The parametric model is capable of handling the combined effect of the absorption mechanisms present in a gas or gas mixture and captures the experimental variation in the observation. The performance of the parametric model is demonstrated with pulse-echo experiments in oxygen, ethane and mixtures of the two. Compared to standard Fourier analysis techniques, the parametric model gives higher accuracy when estimating attenuation and phase velocity, and physical parameters such as relaxation strengths and relaxation frequencies can be extracted from it.

  • 88.
    Martinsson, Jesper
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Niemi, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Model-based phase velocity and attenuation estimation in wideband ultrasonic measurement systems2007Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 54, nr 1, s. 138-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A parametric method to estimate frequencydependent phase velocity and attenuation is presented in this paper. The parametric method is compared with standard nonparametric Fourier analysis techniques using numerical simulations as well as real pulse-echo experiments. Approximate standard deviations are derived for bothmethods and validated with numerical simulations. Compared to standard Fourier analysis, the parametric model gives considerably lower variance when estimating attenuation and phase velocity. In contrast to nonparametric techniques, the proposed estimator avoids the phase unwrapping problem because analytical expressions for thecontinuous phase velocity and attenuation can be derived.

  • 89. Martinsson, Jesper
    et al.
    Hägglund, Fredrik
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Estimating the underlying signal waveform and synchronization jitter from repeated measurements2006Ingår i: Proceedings: 2006 IEEE Ultrasonics Symposium : Vancouver, Canada, 3 - 6 October 2006, Piscataway, NJ: IEEE Communications Society, 2006, s. 440-443Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we present a synchronization technique, for applications using repeated or periodically excited measurements. The problem with existing techniques is their limitations to specific signal and noise conditions, such as white Gaussian noise or narrowband signals. The proposed method extracts statistical information about the underlying signal and noise in the measurements to obtain good synchronization (asymptotically optimal). The Cramér-Rao lower bound (CRLB) is derived for the synchronization problem, including bounds for the underlying signal waveform and the covariance of the noise. The method, which is the maximum-likelihood estimator for both white and colored Gaussian noise, is compared with standard sub-sample estimation and aligning techniques using Monte Carlo simulations. The results show significant improvements compared to standard synchronization techniques.

  • 90. Martinsson, Jesper
    et al.
    Hägglund, Fredrik
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Separation of dispersive coinciding signals by combining hard and soft modeling2008Ingår i: Proceedings of the International Congress on Ultrasonics: Vienna, April 9-13, 2007, Paper ID 1563, Session R17, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In some ultrasonic measurement situations, an adequate signal separation is difficult to achieve. A typical situation is material characterization of thin media, relative to the emitted signal's time support. In this paper a new method is proposed that enables accurate signal separation of measured coinciding signals in the postprocessing stage. The method is based on a combination of hard physical and soft empirical models, which allows for a description of both known and unknown dynamics making the separation possible. The proposed technique is verified using real measurements on thin dispersive samples and validated with residual analysis.

  • 91. Martinsson, Jesper
    et al.
    Hägglund, Fredrik
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Complete post-separation of overlapping ultrasonic signals by combining hard and soft modeling2008Ingår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 48, nr 5, s. 427-443Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In some ultrasonic measurement situations, an adequate signal separation is difficult to achieve. A typical situation is material characterization of thin media using pulse-echo or through-transmission techniques, when the time-of-flight in the media is shorter than the emitted signal's time support. Separated signals are necessary to obtain accurate estimates of material properties and transit times. In this paper a new method is proposed that enables complete post separation of measured coinciding signals. The method is based on a combination of hard physical and soft empirical models, which allows for a description of both known and unknown properties making a complete separation possible. The validity and limitations of the model and the separation results are thoroughly addressed. The proposed technique is verified using real measurements on thin dispersive samples and validated using residual analysis. The experimental results show a complete separation with uncorrelated and normally distributed residuals. The method enables characterization and/or flow analysis in difficult overlapping situations.

  • 92.
    Martinsson, Pär-Erik
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan
    Investigating the feasibility of using principal component analysis for ultrasonic classification of gas mixtures2003Ingår i: Proceedings, 2003 IEEE Ultrasonics Symposium: October 5 - 8, 2003, Hilton Hawaiian Village, Honolulu, Hawaii ; an international symposium / [ed] Donald E. Yuhas, Piscataway, NJ: IEEE Communications Society, 2003, s. 1396-1399Konferensbidrag (Refereegranskat)
    Abstract [en]

    On-line measurement of the energy content of natural gas is of interest for both industry and customers, since the energy content determines its monetary value. Experiments with pulsed ultrasound show that, in addition to changes in speed of sound and acoustic attenuation, there is also a change in the shape of the sound waveform. In this paper, we investigate the feasibility of using principal component analysis (PCA) to quantify this change in pulse shape. The principle is evaluated for pure oxygen, pure ethane, and mixtures of the two, for different pressures. The results show that by using PCA, it is possible to distinguish between pulses that have propagated through oxygen from pulses in ethane and mixtures of the two.

  • 93.
    Martinsson, Pär-Erik
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, R.E.
    Tromsø University.
    Ultrasonic classification of gases using principal component analysis2003Ingår i: 5th world congress on ultrasonics WCU 2003, Paris: Institut Biomedical des Cordeliers, Université Pierre et Marie Curie , 2003, s. 1129-1132Konferensbidrag (Refereegranskat)
    Abstract [en]

    On-line measurement of the energy content of natural gas is of interest for both industry and customers, since the energy content determines its monetary value. Experiments with pulsed ultrasound show that, in addition to changes in speed of sound and acoustic attenuation, there is also a change in the shape of the sound waveform. In this paper we investigate the feasibility of using Principal Component Analysis (PCA) to quantify this change in pulse shape. The principle is evaluated for Oxygen and Ethane, for different pressures and different temperatures. The results show that by using PCA, it is possible to distinguish between pulses that have propagated through Oxygen from pulses in Ethane.

  • 94. Niemi, Jan
    et al.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Löfqvist, Torbjörn
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Joint estimation of fibers and fines concentration in paper pulp suspensions using a combined optical and acoustic technique2010Ingår i: 2009 IEEE Ultrasonics Symposium: Rome, Italy, 20 - 23 September 2009, Piscataway, NJ: IEEE Communications Society, 2010, s. 1191-1194Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a method for joint estimation of fiber and fines mass fractions (i.e. pulp consistency) in paper pulp suspension. The technique is based on a combination of optical and ultrasonic measurements. The link between measured quantities and the mass fractions is established through Partial Least-Squares Regression (PLSR). The method is evaluated with experiments on unbleached softwood pulp for a total mass fraction of fibers and fines ranging from 0.6% to 0.54%. The results show that we are able to accurately predict both the fiber and fines mass fractions using the proposed technique. We also show that the performance is increased by combining the two techniques compared to using them by themselves.

  • 95.
    Onur, Tuğba Özge
    et al.
    Department of Electrical-Electronics Engineering, Bulent Ecevit University, Zonguldak, Turkey.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Svanström, Erika
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Estimation of the Propagation of Flexural Waves in Thin Plates Using a Single Low Cost Sensor2019Ingår i: Iranian Journal of Science and Technology, Transactions of Electrical Engineering, ISSN 2228-6179, Vol. 43, nr 3, s. 405-413Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper demonstrates how flexural wave propagation in a thin plate can be modeled by estimating the combined effect of the excitation source signal and the impulse response of the ultrasonic sensor. The wave propagation in the plate is modeled using the wave equation for the flexural wave mode. A theoretical model for flexural wave propagation in thin plates has been derived, and it has been compared with measurements excited by tapping gently on the surface. The combined effects of the excitation source signal and the impulse response of the low-cost piezoelectric sensor are modeled using finite-impulse response and/or infinite-impulse response filters. Thereafter, the performances of the selected filters are compared on estimating the wave propagation in a thin quartz glass plate. Results indicate that the most accurate estimation of wave propagation has been obtained using a linear phase filter which attributes all dispersions to the flexural wave.

  • 96.
    Ovacikli, Kubilay
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pääjärvi, Patrik
    Rubico Vibration Analysis AB.
    Blind pulse compression through skewness maximization on overlapping echoes from thin layers2016Ingår i: IEEE Ultrasonics Symposium 2016, Tours France, September 18-21, 2016, Piscataway, NJ: IEEE conference proceedings, 2016, artikel-id 7728571Konferensbidrag (Refereegranskat)
    Abstract [en]

    Pulse compression on overlapping echoes without knowledge of the pulse shape, transducer and propagation path impulse response is examined to provide valuable information about the sample structure in ultrasonic testing. A comparison against previous research is presented on two different levels of overlap severity with simulated signals. By exploiting the knowledge on the statistical characteristics of the signal of interest, an appropriate measure of merit, such as skewness, is maximized to promote impulsive occurrences to both extract the excitation signal and to enhance the impulse response of a material under test.

  • 97.
    Ovacikli, Kubilay
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik. Rubico Vibration Analysis AB.
    Castano, Miguel
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pääjärvi, Patrik
    Rubico AB, Luleå.
    Jiang, Biao
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lindblad, Philip
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Impulse Response Extraction and Parametric Modelling of Reverberating Ultrasonic Echoes from Thin Layers2015Ingår i: 2015 IEEE International Ultrasonics Symposium (IUS 2015): Taipei, 21-24 Oct. 2015, Piscataway, NJ: IEEE Communications Society, 2015, artikel-id 7329331Konferensbidrag (Refereegranskat)
    Abstract [en]

    Enhacement of material impulse response buried in reverberating ultrasonic echoes from thin layered materials can be exploited in order to be able to detect possible flaws. One of the methods presented in this study is to enhance the impulse response of a material by training an adaptive filter that promotes and appropriate statistical characteristic such as asymmetry. The other approach is to employ a parametric linear model of reverberations that utilizes Maximum Likelihood Estimation on its parameters, to later suppress the reverberations and reveal possible flaws. Both approaches are investigated and shown to succeeed under certain conditions and supported with experiments.

  • 98.
    Ovacikli, Kubilay
    et al.
    Rubico Vibration Analysis AB.
    Pääjärvi, Patrik
    Rubico Vibration Analysis AB.
    Leblanc, James
    Swedish Rifle AB.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Recovering Periodic Impulsive Signals Through Skewness Maximization2016Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 64, nr 6, s. 1586-1596Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Maximizing the skewness of a measured signal by adaptive filtering to reveal hidden periodic impulses is proposed as a pre-processing method. Periodic impulsive signals are modelled by harmonically related sinusoids to prove that amplitude and phase distortion from a transfer function, effects of sinusoidal interferences and noise can be compensated for by a linear filter. The convergence behaviour of the skewness maximization algorithm is analysed to show that it is possible to recover the original harmonic structure with an unknown fundamental frequency by achieving maximum skewness in the given signal. It is shown that maximizing the skewness always results in a sub-space containing only a single harmonic family. Defect detection in rolling element bearings is presented as an application example and as a comparative study against kurtosis maximization.

  • 99.
    Ovacikli, Kubilay
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik. Rubico Vibration Analysis AB.
    Pääjärvi, Patrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Uncovering harmonic content via skewness maximization: a Fourier analysis2014Ingår i: Proceedings of the 22nd European Signal Processing Conference (EUSIPCO 2014): Lisbon, Portugal, 1-5 Sept. 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 481-485, artikel-id 6952135Konferensbidrag (Refereegranskat)
    Abstract [en]

    Blind adaptation with appropriate objective function results in enhancement of signal of interest. Skewness is chosen as a measure of impulsiveness for blind adaptation to enhance impacting sources arising from defective rolling bearings. Such impacting sources can be modelled with harmonically related sinusoids which leads to discovery of harmonic content with unknown fundamental frequency by skewness maximization. Interfering components that do not possess harmonic relation are simultaneously suppressed with proposed method. An experimental example on rolling bearing fault detection is given to illustrate the ability of skewness maximization in uncovering harmonic content.

  • 100.
    Renbi, Abdelghani
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Impact of PCB manufacturing process variations on trace impedance2012Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 39, nr 1, s. 20-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper demonstrates statistically the impact of PCB manufacturing variations on the characteristic impedance. Moreover, it shows that the characteristics of the PCBs vary across different suppliers. These differences cannot be tolerated in some applications where the characteristic impedance is restricted to be within a specific range. We sampled 3 x 20 PCBs, each batch of twenty is ordered from a different manufacturer: The sampling consisted of measuring the phase shift between the reflected and the incident signals when injecting a ISO MHz sinewave into a PCB trace. The trace is selected to be the same for all samples. All the PCBs are ordered to be identical and designed for 50 devices. Our conclusion was drawn after running the T-tests to assess statistically the significance of the difference occurring between the PCBs. Based on the computed P-values all three batches are different from each other in the mean of the measured phase shift with 95 % confidence. The difference between the measured and the expected characteristic impedance is found as 3 %, 10 % and 20 %for these three manufacturers. We also witnessed board- to-board variations even within the same batch and from the same supplier due to the process instability by looking at the probability density of having the same phase shift that is equal to the mean. Some samples showed 2.6 % to 3.5 % difference above the mean.

123 51 - 100 av 120
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf