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  • 1.
    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. 

  • 2.
    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, Signaler och system. 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 2228-6179Artikel 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.

  • 3.
    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.

  • 4.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ranefjärd, Simon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Trulsson, Felix
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A Subspace Based Method for Near Transducer Interference Suppression2018Ingår i: 2018 IEEE International Ultrasonics Symposium, IEEE, 2018, artikel-id 8579817Konferensbidrag (Refereegranskat)
    Abstract [en]

    In applications of direct -contact ultrasound, operating in pulse -echo mode, the transient resulting from the excitation of the transducer will mask any reflections from scatterers near the transducer surface. This results in a so called dead zone, preventing any defects to be detected. This is normally solved by introducing a delay line between the transducer and the specimen. There are drawbacks with this approach, and therefore we propose an alternative technique, which instead suppresses the transient from the excitation by a statistical modeling technique. This paper describes an algorithm for reduction of the dead zone and shows with experiments using both a single -element transducer and a 128 element linear array, that the transient from the transducer excitation can be suppressed sufficiently well to reveal side -drilled holes in a test block, which were previously masked.

  • 5.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Measurement systems engineering: design, modeling, and computational methods2018Bok (Övrigt vetenskapligt)
  • 6.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Andren, Erik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mohamad, Medhat
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Beek, Jaap van de
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Monitoring Changes in Mechanical Properties of Rock Bolts Using a Low-Power Coded-Excitation Scheme2018Ingår i: 2018 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), IEEE, 2018, artikel-id 8580038Konferensbidrag (Refereegranskat)
    Abstract [en]

    In-situ inspection and quality assessment of rock bolts and other load-bearing structural elements, has received significant attention over the years, but there are still no techniques available capable of monitoring changes over time in mechanical properties of already installed bolts. Since mechanical changes will also affect the propagation of mechanical waves, ultrasound is a strong candidate. In this paper we propose a technique based on Orthogonal Frequency Division Multiplexing (OFDM) for coding the transmitted ultrasound pulse in such a way that the propagation channel (transducer and rock bolt combined) can be estimated. We show that a transmit voltage of 1.1 V r.m.s. is sufficient to obtain reliable channel estimates even in bolts as long as one meter. The channel estimates are then used to predict changes in tensile stress on the bolt, from experiments conducted in a laboratory environment.

  • 7.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ovacikli, Aziz Kubilay
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Rubico Vibration Analysis AB.
    Pääjärvi, Patrik
    Rubico Vibration Analysis AB.
    Material Impulse Response Estimation from Overlapping Ultrasound Echoes Using a Compressed Sensing Technique2017Ingår i: IEEE International Ultrasonics Symposium, IUS, IEEE Computer Society, 2017, artikel-id 8091788Konferensbidrag (Refereegranskat)
    Abstract [en]

    When investigating thin materials with pulse echo ultrasound, multiple reflections (reverberations) from the layer(s) will overlap. It is therefore difficult to deduce information about speed of sound, thickness, density, etc. from the raw data. In order to extract this information, the overlapping pulses must be either decoupled or we must find some model of the material sample describing the wave propagation. It is, however, often reasonable to assume that the the number of reflections is small relative to the number of samples in the record signal of interest. In other words, the system describing the reverberations is sparse. In this paper we investigate, with simulations and with experiments on a 4.8 and 2.2 mm thick glass plate, respectively, how the framework of compressed sensing can be adopted in order to retrieve the impulse response of the material specimen

  • 8.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ovacikli, Aziz Kubilay
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Rubico Vibration Analysis AB.
    Pääjärvi, Patrik
    Rubico Vibration Analysis AB.
    Material Impulse Response Estimation from Overlapping Ultrasound Echoes Using a Compressed Sensing Technique2017Ingår i: IEEE International Ultrasonics Symposium, IUS, IEEE Computer Society, 2017, artikel-id 8092248Konferensbidrag (Refereegranskat)
    Abstract [en]

    In ultrasound examination of thin multi-layered materials, the received signal is, in both through-transmission and pulse-echo configurations, a superposition of multiple reflections from inside the sample. If the layer thicknesses are small compared to the duration of the emitted ultrasound pulse, the received signal will be a sum of overlapping ultrasound pulses. In such scenarios, estimation of the layer thicknesses is challenging. Previous work has adopted model-based decomposition of the overlapping echoes, or various pulse compression or deconvolution schemes, in order to better reveal the arrival times of each individual echo.

  • 9.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mohamad, Medhat
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mbit/second Communication through a Rock Bolt Using Ultrasound2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In most industrial processes transfer of data and software from or to sensors is an essential part of the monitoring and control systems. Many of the older, wired communication systems have been or are being replaced with wireless alternatives. A number of challenges are associated with this replacement: Radio receivers are subject to interference from other radio sources. Similarly, radio transmitters may cause undesired interference into other equipment and environments. Compared to wired solutions, security becomes an issue as radio communication links are more vulnerable to eavesdropping than wired schemes. Radio communication with sensors and sensor platforms embedded deep inside large metal structures or fluid tanks may be difficult or even impossible. The objective of this work is to develop and evaluate a high data-rate communications scheme based on ultrasound, which can be used to transmit wirelessly through solid structures. An example will be given using a one-meter segment of a rock bolt.

  • 10.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mohamad, Medhat
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Mbit/second Communication through a Rock Bolt Using Ultrasound2017Ingår i: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, artikel-id 8092474Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a digital communication system based on Orthogonal Frequency Division Multiplexing (OFDM) and MHz-range ultrasound, for transmission of data through solid materials and liquids. The system is tested on experiments using a off-the-shelf ultrasound transducers with a center frequency of 3.5 MHz as transmitter and receiver, respectively. The propagation medium in the experiment was a 1 m long section of an epoxy coated steel rock bolt. The results show that data rates in excess of 1 Mbit/second is attainable, using readily available hardware and software.

  • 11.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    A Stokesian Dynamics Approach for Simulation of Magnetic Particle Suspensions2016Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 90, nr SI , s. 70-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamic behaviour of μm-scale ferromagnetic particles in suspension is of interest for various mineral beneficiation processes. It is, however, difficult to experimentally study such processes at the particle-level. In these instances it can be advantageous to resort to suitable particle simulation methods.Stokesian dynamics is a mesh-free numerical technique developed for suspensions of nm to mm size particles. The method inherently considers hydrodynamic interactions, but additional interaction models can be included depending on the system under investigation. We here present a Stokesian dynamics (SD) implementation, which allows for simulation of the motion of suspended magnetic particles in presence of an external magnetic field. The magnetic interaction model includes particle-field interactions as well as pairwise interactions between magnetised particles.Simulations are compared with experiments using a laboratory-scale flow cell. The method is shown to be realistic for studying ferromagnetic suspensions in mineral processing applications, and can be useful in understanding and predicting the efficiency of mineral separation processes.

  • 12.
    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.

  • 13.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Direct measurement of internal material flow in a bench scale wet Low-Intensity Magnetic Separator2016Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 91, s. 55-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work an ultrasound-based measurement method is used formonitoring suspension velocity and build-up of magnetic material inside awet Low-Intensity Magnetic Separator, a process used e.g. inbeneficiation of magnetite ores. Today the only available option is tomonitor material transport between unit operations; i.e. flow rate,solids concentration, and particle size distribution of suspension flowin pipes are measured online using standard equipment.An Acoustic Backscatter System is fitted to the tank of a separator, andused to monitor the internal flow. A method called Ultrasonic VelocityProfiling is used to capture internal velocity profiles. Simultaneously,the backscatter signal intensity is used to get indications about localsolids concentration of the flow, and build-up of magnetic material. Themethods are evaluated in realistic conditions, where the effect ofvarying factors relevant to machine performance is investigated. Theincluded factors are; the slurry feed rate, the slurry solidsconcentration, the magnet assembly angle, and the drum rotational speed.The presented method gives useful information about the internal materialflow inside the separator. The velocity measurements capture the,sometimes complex, internal flow patterns, for example the presence andvelocity of a recirculating flow in the dewatering zone. Additionally,keeping a balanced material loading in the concentrate dewatering zone isimportant to separator performance. Using the signal backscatterintensity it is possible to qualitatively monitor this material loading.Generally these direct measurements can aid in improvements to machinedesign, process optimization, and process control.

  • 14.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Internal flow measurements in pilot scale wet low-intensity magnetic separation2016Ingår i: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 155, s. 55-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the mining industry, ferromagnetic particles (e.g. magnetite) are concentrated using wet low-intensity magnetic separation (LIMS). The performance is to a large extent controlled by the internal flow conditions in the separator. In previous work, it was shown how an ultrasound pulse-echo setup can be used to simultaneously measure particle velocity profiles and local solids concentration variations in laboratory conditions. In this paper, a real-world case is demonstrated where the system is installed on one of the wet LIMS at the LKAB R&D facilities in Malmberget, Sweden. For the pilot scale experiments a setup with two ultrasound transducers, mounted at the bottom of the separator tank, is used. The design of experiments method is used to study the effects of the feed solids concentration, drum rotational speed, position of the concentrate weir, and the magnet assembly angle on the measured flow patterns. The results show that it is possible to detect changes in the flow velocity patterns and the local solids concentration, as the operational conditions of the separator are varied. Of the factors studied, the drum rotational speed has the strongest influence on the overall flow velocity in the dewatering zone. Also, the presence of a recirculating flow transporting gangue particles away from the concentrate is confirmed. The factor with the strongest influence on this recirculating flow is also the drum rotational speed, together with the magnet assembly angle. Using this method it is possible to make high quality measurements of internal flow velocity profiles. It is also possible to monitor material build-up on the separator drum, and e.g. detect overload of magnetic material. The insights gained, and the methods developed, have generated new possibilities to control, optimise, and develop the wet LIMS process.

  • 15.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Monitoring Mineral Slurry Flow using Pulse-Echo Ultrasound2016Ingår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 50, s. 135-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultrasound based flow measurement methods have a large potential for the mining industry and its processing plants. Ultrasound travel through dense suspensions and is not affected by the magnetic fields sometimes present in this type of equipment.A cross-correlation based method is used for localized particle velocity measurements in one and two dimensions. Simultaneously, using the same data, information about local particle concentration is extracted from the power spectral density of the backscattered signal. Experiments are carried out both in simplified geometry and in full scale equipment in an iron ore pilot benefication plant.In the simple geometry it is possible to assess the precision of the methods by comparing the measurements to theory and numerical simulations. The results from the pilot plant experiments show that these methods can be applied to real world processes

  • 16.
    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

  • 17.
    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.

  • 18.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    A Stokesian Dynamics Approach for Simulation of Magnetic Particle Suspensions2015Ingår i: Proceedings of Computational Modelling 2015: Minerals Engineering International, 2015Konferensbidrag (Refereegranskat)
  • 19.
    Stenström, Christer
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Condition monitoring of cracks and wear in mining mills using water squirter ultrasonics2015Ingår i: International Journal of Condition Monitoring, ISSN 0019-6398, E-ISSN 2047-6426, Vol. 5, nr 1, s. 2-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mining mills are continuously exposed to loads that give rise to wear of the liners, as well as fatigue and crack development in the steel shell. The feasibility of using water squirter ultrasonics for condition monitoring of the shell and the lining of mining mills during operation has been studied in this paper. This method will make it possible to monitor cracks in mining mills without stopping them, which can result in significant monetary savings due to less downtime and increased product quality. The practical requirements of such a system were first analysed, which shows that it is possible to achieve the spatial resolution of 1 × 1 mm, using a pulse-echo set-up with a pulse repetition frequency of approximately 6 kHz. Experiments were then performed on a lab-scale prototype, where typical defects were introduced. The results show that it is possible to detect and image internal defects down to a size of around 1 × 0.4 mm.

  • 20.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Direct measurement of internal material flow in bench scale wet Low-Intensity Magnetic Separator2015Ingår i: Proceedings of Physical Separation '15, Minerals Engineering International , 2015Konferensbidrag (Övrigt vetenskapligt)
  • 21.
    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.

  • 22.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    In-Situ Monitoring of Particle Velocities and Solids Concentration Variations in wet Low-Intensity Magnetic Separators2015Ingår i: 2015 IEEE International Ultrasonics Symposium, IUS 2015: Taipei, 21-24 Oct. 2015, Piscataway, NJ: IEEE Communications Society, 2015, artikel-id 7329339Konferensbidrag (Refereegranskat)
    Abstract [en]

    In previous work, we have shown how an ultrasound pulse-echo setup can be used to simultaneously measure particle velocity profiles and local solids concentration variations in solid/liquid particle suspensions. In this paper, we demonstrate a real-world case where the system is installed in a wet low-intensity magnetic separator, a process in which magnetic material is separated from gangue. The method was evaluated at LKAB's R&D facilities in Malmberget, Sweden, on one of their pilot scale separators. The results show that it is possible to detect changes in the flow velocity patterns and the local solids concentration, as the operational conditions of the separator are varied.

  • 23.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lundin, Peter
    Swerea KIMAB AB.
    Measurement of the Clamping Force Applied by Load-Bearing Bolts Using a Combination of Compression and Shear Ultrasonic Waves2015Ingår i: 2015 IEEE International Ultrasonics Symposium (IUS 2015): Taipei, 21-24 Oct. 2015, Piscataway, NJ: IEEE Communications Society, 2015, artikel-id 7329418Konferensbidrag (Refereegranskat)
    Abstract [en]

    Quantitative measurement of the clamping or tightening force of rods and bolts is important when assessing the structural integrity of various constructions. This paper shows that by using a bi-wave ultrasonic pulse-echo technique, it is possible to determine this tightening force without the need of extensive calibration prior to installing the bolts. We show that the ratio of the time-of-flight (TOF) between the transversal and the longitudinal waves changes linearly with the clamping force and that we only need to know the TOF of the unstrained bolt prior to installment. This is then demonstrated experimentally on a 1.1 m rock bolt, using pulses that propagated 6.6 m. Two different methods for estimation of the TOF ratio are evaluated.

  • 24.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Monitoring local solids fraction variations in multiphase flow using pulse-echo ultrasound2015Ingår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 70, s. 376-379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an ultrasonic pulse-echo technique for on-line monitoring of variations in solids concentrations in particlesuspensions. The method is based on time-frequency analysis of the backscatter signals, exploring variations in spectral content ofthe backscatter as function of depth in the suspension. Experiments on a settling of magnetite particles in water, at varying solidsconcentrations, show that the settling process can be followed by studying the energy of backscattered ultrasound.

  • 25.
    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

  • 26.
    Sand, Anders
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Stener, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Toivakka, Martti
    Åbo Akademi University.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Simulation of Magnetic Particle Suspensions Using the Stokesian Dynamics Technique2015Ingår i: Proceedings of Conference in Minerals Engineering 2015, Luleå: Luleå tekniska universitet, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 27.
    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.

  • 28.
    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

  • 29.
    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)
  • 30.
    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)
  • 31.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Tomren, Andreas Linge
    Department of Chemistry, University of Bergen.
    Folgerø, Kjetil
    Michelsen Centre for Industrial Measurement Science & Technology, P.O.Box 6031, NO- 5892 Bergen, NORWAY, Christian Michelsen Research AS, Bergen.
    Barth, Tanja
    Department of Chemistry, University of Bergen.
    Estimation of dielectric properties of crude oils based on IR spectroscopy2014Ingår i: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 139, s. 1-5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dielectric properties of crude oils play an important role in characterization and quality control. Measuring permittivity accurately over a wide range of frequencies is, however, a time-consuming task and existing measurement methods are not easily adapted for real-time diagnostics. IR spectroscopy, on the other hand, provides rapid measurements of fundamental molecular properties.In this paper we show that by using multivariate calibration tools such as PLS regression, it is possible to extract dielectric properties of crude oils directly from IR spectra, in addition to conventional interpretation of the spectra, hence reducing the need for direct electrical measurements. Results on 16 different oil samples show that the dielectric parameters obtained with the proposed method agree well with those obtained using direct permittivity measurements. The PLS regression method has also been extended with Monte-Carlo simulation capabilities to account for uncertainties in the data

  • 32.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Svanström, Erika
    Onur, Tugba Özge
    Department of Electronics Engineering, Bulent Ecevit University.
    Estimation of the Flexural Stiffness of Thin Plates Using a Single Low-Cost Passive Sensor2014Ingår i: 2014 IEEE International Ultrasonics Symposium, IUS 2014: Chicago, Ill., 3-6 September 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 142-145Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a bending (flexural) wave mode in a thin plate is excited by tapping gently on the surface. The wave is recorded with single low-cost piezo-electric sensor. Due to the dispersive nature of this wave mode, the shape of the recorded signal depends on the flexural stiffness parameter of the plate. The recorded signal is also affected by the transfer function of the excitation and the sensor. In this paper we show, with simulations and measurements on a thin quartz glass plate, that the effect of the sensor and excitation can be decoupled from the bending wave, and that the flexural stiffness parameter can be estimated using a single sensor.

  • 33.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation2014Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 62, s. 2-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The internal material transport and selection processes of the wet low-intensity magnetic separators (LIMS) are poorly understood; this calls for improved measurement techniques. In this work an ultrasonic velocity profiling (UVP) technique for measuring how material flow velocity varies with penetration depth is presented. A measurement depth of just a couple of centimetres would greatly improve the understanding of the separation process in a LIMS.When applied to flows of mineral suspensions with high volumetric solids concentration, similar to those in the separators, UVP is unique in combining:•Non-intrusive measurements.•Operates using just one sensor element (transducer).•Relatively good spatial resolution.•Penetrates opaque suspensions.•Fast sampling rate.Here, flows are studied in a rectangular duct (50 × 75 mm). Using magnetite suspensions, measurement through the whole depth of 50 mm is made with good accuracy. Velocity profiles are presented for solids concentrations of 5% and 9% solids by volume (20% and 36% by weight). Even at 9 vol% solids it is possible to reach a penetration depth of more than 25 mm.

  • 34.
    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.

  • 35.
    Stenström, Christer
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Carlson, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Project: Squirter Ultrasonic Thickness Gauge for Monitoring of Mining Mill Lining During Operation (SV: Mätning av tjocklek på kvarninfodring med ultraljud under drift)2014Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 36.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Towards the measurement of local particle mass fractions in magnetite suspensions2014Ingår i: 2014 IEEE International Ultrasonics Symposium, IUS 2014: Chicago, Ill, 3-6 September 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 939-942Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the mining industry, magnetite particles are transported in suspensions with water through different stages of the process. In some of these stages, it is of interest to monitor both the concentration and particle velocity over a cross-section of the flow. High particle concentration makes development of flow measurement techniques challenging. An additional challenge is that the flow is often accessible from one side only, which further limits the selection of applicable techniques. Previous work by the authors focused on using pulse-echo ultrasound for flow velocity profile estimation. In this paper the same setup is used to simultaneously study local variations in solids concentration. Ultrasound pulses are transmitted into the suspension, and the resulting backscatter is recorded. The statistics of the backscatter depend on solids concentration, particle size distribution, particle density, etc. We demonstrate how a short-time (windowed) Power Spectral Density (PSD) estimate can be used to obtain qualitative information about local solids concentration variations. For demonstration, a magnetite suspension carrying up to 7.5 vol% particles (29 wt%, mean particle size 34 μm) is pumped through a closed rectangular channel. When the pump is stopped, pulse-echo ultrasound (with a center frequency of 2.25 or 3.5 MHz) is used to monitor the sedimentation process. Nine snapshots of the process are included. These show a time lapse of the sedimentation, with 5 s between each image. It is clear that the short-time PSD is a good indicator of local mass fraction variations.

  • 37.
    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.

  • 38.
    Svanström, Erika
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Linder, Tomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Combined physical and statistical modeling of laser induced ultrasound signals from thin light absorbing films2013Ingår i: 2013 IEEE International Ultrasonics Symposium: [IUS 2013, Prague, Czech Republic; 21 - 25 July 2013, Piscataway, NJ: IEEE Communications Society, 2013, s. 2167-2170Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a method for predicting the ultrasound pulses generated by thin semi-transparent polymer films, excited by a short laser pulse. The acoustic pressure is first modeled based on the physical properties of the polymer. Partial Least-Squares Regression is then used to link the model pressure to the ultrasound pulses measured by an ultrasound transducer. The uncertainty of the regression is also simulated, showing that the method is robust to noise in the measurements

  • 39.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation2013Ingår i: Proceedings of Physical Separation '13, Minerals Engineering International , 2013Konferensbidrag (Övrigt vetenskapligt)
  • 40.
    Stenström, Christer
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Mining mill condition monitoring using water jet ultrasonics2013Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS), Piscataway, NJ: IEEE Communications Society, 2013, s. 1913-1916Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we investigate the feasibility of using a water jet ultrasound scanning system for condition monitoring of the shell of a rotating mining mill. The practical requirements of such a system were first analyzed, which shows that it is possible to achieve the spatial resolution of 1±1 mm, using a pulse-echo setup with a pulse repetition frequency of approximately 6 kHz. Experiments were then performed on a lab-scale prototype, where typical defects were introduced. The results show that it is possible to detect and image internal defects down to a size of around than 1 ± 0.4 mm.

  • 41.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Robust estimation of particle velocity profiles in high concentration magnetite suspensions2013Ingår i: Proceedings of the 2013 International Congress on Ultrasonics / [ed] Gan Woon Siong; Lim Siak Piang; Khoo Boo Cheong, Singapore: Research Publishing Services, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the mining industry magnetite particles are transported in aqueous suspension through different stages of the process. In some stages it is of interest to monitor both the concentration and particle velocity profiles over a cross-section of the flow. In this paper an ultrasonic flow meter method based on cross-correlation of backscattered sound is presented. High solid particle content (e.g. 20-40 wt%) makes this challenging and therefore the emphasis lies on developing robust signal processing techniques for particle velocity estimation. The developed method is evaluated in laboratory experiments on flows in a rectangular duct. Transducers with centre frequency 1, 2, 4 and 5 MHz are evaluated in flows with a solid content of 20% by weight (4.7 vol% solids). Using the 2 MHz transducer a penetration depth of 50 mm is reached.

  • 42.
    Stener, Jan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sand, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ultrasonic velocity profiling of flows related to wet low intensity magnetic separation2013Ingår i: Conference in Minerals Engineering: Luleå 5-6 February 2013 / [ed] Jan Rosenkranz; Tommy Karlkvist, Luleå, 2013, s. 157-168Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The internal workings of wet Low Intensity Magnetic Separators (LIMS) are poorly understood. In this work an Ultrasonic Velocity Profiling (UVP) technique for measuring material flow speed at varying depth. A measurement depth of just a couple of centimetres will greatly improve our understanding of the separation process.When applied to flows of high density mineral suspensions, similar to those in wet LIMS, UVP is unique in combining:• Non-intrusive measurements.• A single transceiver element is sufficient.• Relatively good spatial resolution.• Penetrates opaque suspensions.• Fast sampling rate.Here, flows are studied in a simple rectangular geometry (50x75 mm), using dilute magnetite suspensions; measurement through the whole depth of 50 mm is made with good accuracy. Velocity profiles are presented for different sensors at solids concentrations of 5 vol% solids.

  • 43. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    A machine vision system for estimation of size distributions by weight of limestone particles during ship loading2012Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 25, nr 1, s. 38-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The size distribution as a function of weight of particles is an important measure of product quality in the mining and aggregates industries. When using manual sampling and sieving, the weight of particles is readily available. However, when using a machine vision system, the particle size distributions are determined as a function of the number of particles. In this paper we first show that there can be a significant weight-transformation error when transforming from one type of size distribution to another. We also show how the problem can be overcome by training a classifier and scaling the results according to calibrated average weights of rocks. The performance of the algorithm is demonstrated with results of measurements of limestone particles on conveyor belts.

  • 44.
    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)
  • 45.
    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)
  • 46.
    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)
  • 47.
    Carlson, Johan E.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gasson, J.R.
    University of Bergen.
    Barth, T.
    University of Bergen.
    Eide, I.
    Statoil Research Centre, Trondheim.
    Extracting homologous series from mass spectrometry data by projection on predefined vectors2012Ingår i: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 114, s. 36-43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multivariate statistical methods, such as Principal Component Analysis (PCA), have been used extensively over the past decades as tools for extracting significant information from complex data sets. As such they are very powerful and in combination with an understanding of underlying chemical principles, they have enabled researchers to develop useful models. A drawback with the methods is that they do not have the ability to incorporate any physical / chemical model of the system being studied during the statistical analysis. In this paper we present a method that can be used as a complement to traditional chemometric tools in finding patterns in mass spectrometry data. The method uses a pre-defined set of equally spaced sequences that are assumed to be present in the data. Allowing for some uncertainty in the peak locations due to the uncertainties for the measurement instrumentation, the measured spectra are then projected onto this set. It is shown that the resulting scores can be used to identify homologous series in measured mass spectra that differ significantly between different measured samples. As opposed to PCA, the loading vectors, in this case the pre-defined homologous series, are readily interpretable.

  • 48.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    High pressure characterization and modelling of CaCO3 powder mix in the Bridgman anvil apparatus2012Ingår i: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 32, nr 4, s. 490-508Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For investigating high pressure sintering processes, numerical models can be used. This will demand material models which give realistic mechanical response throughout the whole parameter space of the actual process. As the pressures become higher, the material density approaches its full theoretical value and the elastic part of the material properties becomes increasingly important. In this investigation, Poisson's ratio was determined using ultrasonic pulse-echo measurements. A new elastic model and an improved plasticity model were implemented into a user-defined material subroutine in a finite element (FE) code. To experimentally investigate the load displacement response and pressure distribution in powder compacts during pressing, a pressure instrumented Bridgman anvil apparatus was used. Validation of the FE model was conducted against experimental data from pressing experiments using two different start densities. The results show that the simulation model is indeed capable of reproducing load–thickness curves and pressure profiles reasonable close to the experimental curves.

  • 49.
    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.

  • 50.
    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.

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