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  • 1.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Harrysson, Ralph
    Luleå tekniska universitet.
    Lindbäck, Ture
    Tegman, R.
    Luleå tekniska universitet.
    High-temperature graphite furnace for X-ray powder diffraction1993In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 4, no 8, p. 816-819Article in journal (Refereed)
    Abstract [en]

    A modified computer-controlled high-temperature x-ray diffractometer with good stability and an upper temperature limit of more than 2300 K is described. A critical test of the system, determining the thermal expansion of Pt, Ni and AlN, showed close agreement with dilatometric and literature data. Lattice thermal expansion data of CrB2 and TiB2 up to 2100 K were also determined

  • 2.
    Candefjord, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nyberg, Morgan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jalkanen, Ville
    Umeå University. Department of Applied Physics and Electronics.
    Ramser, Kerstin
    Lindahl, Olof
    Combining fibre optic Raman spectroscopy and tactile resonance measurement for tissue characterization2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 12Article in journal (Refereed)
    Abstract [en]

    Tissue characterization is fundamental for identification of pathological conditions. Raman spectroscopy (RS) and tactile resonance measurement (TRM) are two promising techniques that measure biochemical content and stiffness, respectively. They have potential to complement the golden standard-–histological analysis. By combining RS and TRM, complementary information about tissue content can be obtained and specific drawbacks can be avoided. The aim of this study was to develop a multivariate approach to compare RS and TRM information. The approach was evaluated on measurements at the same points on porcine abdominal tissue. The measurement points were divided into five groups by multivariate analysis of the RS data. A regression analysis was performed and receiver operating characteristic (ROC) curves were used to compare the RS and TRM data. TRM identified one group efficiently (area under ROC curve 0.99). The RS data showed that the proportion of saturated fat was high in this group. The regression analysis showed that stiffness was mainly determined by the amount of fat and its composition. We concluded that RS provided additional, important information for tissue identification that was not provided by TRM alone. The results are promising for development of a method combining RS and TRM for intraoperative tissue characterization.

  • 3.
    Delsing, Jerker
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Lindgren, Per
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Sensor communication technology towards ambient intelligence2005In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 16, no 4, p. R37-R46Article in journal (Refereed)
    Abstract [en]

    This paper is a review of the fascinating development of sensors and the communication of sensor data. A brief historical introduction is given, followed by a discussion on architectures for sensor networks. Further, realistic specifications on sensor devices suitable for ambient intelligence and ubiquitous computing are given. Based on these specifications, the status and current frontline development are discussed. In total, it is shown that future technology for ambient intelligence based on sensor and actuator devices using standardized Internet communication is within the range of possibilities within five years.

  • 4.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Kaplan, Alexander
    Signal overlap in the monitoring of laser welding2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 10Article in journal (Refereed)
    Abstract [en]

    Laser weld monitoring is usually based on the feedback from three photodiodes which are intended to provide independent information about the thermal condition of the melt (the T signal), the radiation from the plume of a heated gas above the melt (the P signal) and the amount of reflected laser light (the R signal). This work demonstrates that, in fact, the plume of the hot gas above the weld pool contributes a large part of the thermal signal, which has hitherto been assumed to come only from the melt itself. It is suggested that the correlation between the T and P signals is so strong that a T-P signal would be more useful than the raw T signal in identifying the fluctuations in infrared radiation from the melt pool

  • 5.
    Forsberg, Fredrik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Siviour, Clive R
    University of Oxford.
    3D deformation and strain analysis in compacted sugar using x-ray microtomography and digital volume correlation2009In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 20, no 9Article in journal (Refereed)
    Abstract [en]

    Understanding the displacement of granular beds under compaction is important for a range of industrial, geological and civil engineering applications. Such materials exhibit inhomogeneous internal displacements including strain localization, which mean that a method for the in situ evaluation of internal 3D displacement fields at high spatial resolutions would be a major development. This paper presents results from the compaction of a cylindrical bed of sugar, with diameter 7.0 mm and height 8.2 mm, using x-ray microtomography to evaluate the internal structure and digital volume correlation to calculate 3D displacement information from these data. In contrast to previous studies, which generally track a small number of marker particles, the research here uses the natural structure of the sugar to provide a random pattern for 3D image correlation, allowing full-field information to be captured. The results show good agreement when compared with a well-established 2D image correlation technique; moreover, they indicate structural features associated with deformation of granular materials that would not necessarily be observed in a 2D slice.

  • 6.
    Forsberg, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Non-iterative calibration for accelerometers with three non-orthogonal axes, reliable measurement setups and simple supplementary equipment2013In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 24, no 3Article in journal (Refereed)
    Abstract [en]

    The input-output relationship of an accelerometer depends on parameters that are sensitive to temperature and air humidity. High accuracy field measurements therefore require simple in-field estimation of these parameters.We present an extension of a simple non-iterative six-parameter calibration method for triaxial accelerometers with orthogonal input axes to a nine-parameter method that also handles non-orthogonal axes and cross-axis interference.We derive necessary and sufficient conditions on the accelerometer output that guarantee that the nine parameters can be uniquely determined from the calibration measurements in an idealized scenario with no noise or quantization errors. The method is based on measurements of the Earth gravity with the accelerometer placed at rest in at least nine different orientations.The choice of orientations is important for measurement accuracy. We compare two different setups, one called A090-45, which is based on 90 and 45 degree rotations of the accelerometer and one called A0max sep that has maximized smallest angle between any two of the orientations. For the A090-45 setup we have constructed a simple test equipment for quick positionings of the accelerometer. For the A0max sep setup, a similar equipment is more complicated to construct, but equally simple to use.We have done Monte Carlo simulations with accelerometer orientations deviating at most D degrees from the desired A090-45 or A0max sep and with D ranging from 1◦ to 30◦. For real-world noisy environments and D up to 18◦, our simulations showed slightly smaller errors for the A0max sep than for the A090-45 setup. For noise standard deviation typical for our field measurements, the measurement errors after nine-parameter calibration were about 100 times smaller than those for six-parameter calibration both for the A0max sep setup and, as long as D ≤ 13◦ for the A090-45 setup. For the A090-45 setup, however, we found that combinations of large noise levels and/or large D can makesix-parameter calibration the better choice.

  • 7.
    Gren, Per
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Tatar, Kourosh
    Granström, Jan
    Molin, Nils-Erik
    Jansson, E.V.
    Department of Speech, Music and Hearing, Royal Institute of Technology (KTH).
    Laser vibrometry measurements of vibration and sound fields of a bowed violin2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 4, p. 635-644Article in journal (Refereed)
    Abstract [en]

    Laser vibrometry measurements on a bowed violin are performed. A rotating disc apparatus, acting as a violin bow, is developed. It produces a continuous, long, repeatable, multi-frequency sound from the instrument that imitates the real bow-string interaction for a 'very long bow'. What mainly differs is that the back and forward motion of the real bow is replaced by the rotating motion with constant velocity of the disc and constant bowing force (bowing pressure). This procedure is repeatable. It is long lasting and allows laser vibrometry techniques to be used, which measure forced vibrations by bowing at all excited frequencies simultaneously. A chain of interacting parts of the played violin is studied: the string, the bridge and the plates as well as the emitted sound field. A description of the mechanics and the sound production of the bowed violin is given, i.e. the production chain from the bowed string to the produced tone

  • 8.
    Grip, Niklas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simple non-iterative calibration for triaxial accelerometers2011In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 22, no 12Article in journal (Refereed)
    Abstract [en]

    For high precision measurements, accelerometers need recalibration between different measurement occasions. In this paper we derive a simple calibration method for triaxial accelerometers with orthogonal axes. Just like previously proposed iterative methods, we compute the calibration parameters (biases and gains) from measurements of the Earth gravity for six different unknown orientations of the accelerometer. However, our method is non-iterative, so there are no complicated convergence issues depending on input parameters, round-off errors etc.The main advantages of our method are that only from the accelerometer output voltages it gives a complete knowledge of whether it is possible, with any method, to recover the accelerometer biases and gains from the output voltages, and when this is possible, we have a simple explicit formula for computing them with a smaller number of arithmetic operations than previous iterative approaches. Moreover, we show that such successful recovery is guaranteed if the six calibration measurements deviate with angles smaller than some upper bound from a natural setup with two horizontal axes. We provide an estimate from below of this upper bound that, for instance, allows 5 degree deviations in arbitrary directions for the Colibrys SF3000L accelerometers in our lab.

  • 9.
    Huntley, J.M.
    et al.
    Loughborough University.
    Saldner, Henrik O.
    Luleå tekniska universitet.
    Shape measurement by temporal phase unwrapping: comparison of unwrapping algorithms1997In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 8, p. 986-992Article in journal (Refereed)
    Abstract [en]

    Projected fringes can be used to measure surface profiles unambiguously, even in the presence of surface discontinuities, if the fringe pitch is changed over time. We investigate by numerical, analytical and experimental means the reliability of two recently proposed algorithms for unwrapping the resulting phase histories. The first, which unwraps through a sequence of phase maps produced with a linear change in spatial frequency with time, is found to be superior to the second, which uses only the first and last maps in the sequence. A new method is proposed in which the spatial frequency is changed exponentially with time. It is shown to be significantly more robust than either of the other algorithms under most conditions...

  • 10. Hägglund, Fredrik
    et al.
    Carlson, Johan E.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Andersson, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ultrasonic classification of thin layers within multi-layered structures2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 1Article in journal (Refereed)
    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.

  • 11.
    Martinsson, Jesper
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Compensating distortion effects in repeated measurements under non-stationary conditions2009In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 20, no 2Article in journal (Refereed)
    Abstract [en]

    In this paper a compensation technique is presented for applications using repeated measurements under moderate non-stationary measurement conditions. The assumption is that the measurement conditions are stationary during a single repeated measurement but non-stationary over the entire measurement time. The objective with repeated measurements is often to retrieve an estimate of the (noise reduced) signal and its uncertainties. In order to obtain accurate estimates of these two quantities, stationary measurement conditions must be guaranteed under the measurement time. A condition that in many situations is difficult to achieve, e.g., during long measurement times or in a rapidly changing environment. The proposed method compensates for linear dynamic changes during the measurement time, where the dynamical changes, the underlying signal waveform and the noise covariance are considered unknown. The theoretical effect of moderate non-stationary conditions on repeated measurements is analyzed and experimentally validated. Estimation results using the proposed technique are presented for repeated ultrasonic measurements under non-stationary temperature conditions. The results show accurate signal estimation and noise characterization with uncorrelated normally distributed residuals, in contrast to standard synchronization techniques

  • 12.
    Martinsson, Jesper
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Estimating the underlying signal waveform, noise covariance and synchronization jitter from unsynchronized measurements2008In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 19, no 2Article in journal (Refereed)
    Abstract [en]

    In this paper a new synchronization technique is presented for applications using repeated measurements or experiments with periodically excited signals. The objective with repeated or periodic measurements is often to retrieve an estimate of the (noise reduced) signal and its uncertainties. However, these measurements need to be synchronized to obtain accurate estimates. Existing synchronization techniques are limited to specific signal and noise conditions, such as white Gaussian noise or narrowband signals, to achieve good performance. The proposed method, not limited by these conditions, extracts statistical information regarding the underlying signal and the noise contained 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 measurement noise, both considered unknown. The method, which is shown to be the maximum-likelihood estimator (MLE) in both white and colored Gaussian noise, is compared with the CRLB along with standard sub-sample estimation and aligning techniques using Monte Carlo simulations. The results show significant mean square error (MSE) improvements compared to standard synchronization techniques. Synchronization results using the proposed technique are presented for repeated ultrasonic measurements, to validate the method in a real measurement situation, and to experimentally support theoretical results.

  • 13.
    Mohan, N. Krishna
    et al.
    Indian Institute of Technology, Madras.
    Saldner, Henrik O.
    Luleå tekniska universitet.
    Molin, Nils-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Combined phase stepping and sinusoidal phase modulation applied to de-sensitized TV holography1996In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 7, p. 712-715Article in journal (Refereed)
    Abstract [en]

    Many TV holography techniques use phase stepping between frames. In vibration studies, sinusoidal phase modulation extends the use of these techniques. A simple technique is presented to combine phase stepping and phase modulation (bias vibration) on a single mirror. It is applied to a de-sensitized TV holographic (DTV) configuration for quantitative evaluation of the large vibration amplitudes.

  • 14.
    Niemi, Jan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Wood pulp characterization by a novel photoacoustic sensor2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 8Article in journal (Refereed)
    Abstract [en]

    In this paper we introduce a novel photoacoustic sensing technique that captures a photoacoustic signal excited by a laser light pulse after the light has propagated through a turbid medium. Simultaneously, the ultrasonic sound wave is captured after it has propagated through the same turbid medium. By combining the two signals, more information on the investigated medium can be obtained. Applications can be found in the pulp and paper industry where monitoring wood pulp compositions is of interest. Depending on its origin, pulp suspension contains different compositions of fibres and fibre fragments (fines). Poor control of the pulp composition leads to an unstable process that compromises the production, quality and energy efficiency in the pulp mill. The result shows the feasibility of the photoacoustic sensor in monitoring the mass fractions of fibres and fines in a pulp suspension. The first received echo, corresponding to the light interaction with the sample, showed a stronger correlation to the fines mass fraction compared to fibre mass fraction. The second echo, corresponding to the sound wave interaction with the sample, showed a much stronger correlation to fibre mass fraction than to fines mass fraction. Hence, it is proposed that by combining these two echoes, more information about the pulp suspension could be extracted than from any other sensor built on a single sensing principle.

  • 15.
    Norman, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Bäckström, Mikael
    Luleå tekniska universitet.
    Rantatalo, Matti
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    A sophisticated platform for characterization, monitoring and control of machining2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 4, p. 847-854Article in journal (Refereed)
    Abstract [en]

    The potential for improving the performance of machine tools is considerable. However, for this to be achieved without tool failure or product damage, the process must be sufficiently well understood to enable real-time monitoring and control to be applied. A unique sophisticated measurement platform has been developed and applied to two different machining centres, particularly for high-speed machining up to 24 000 rpm. Characterization and on-line monitoring of the dynamic behaviour of the machining processes has been carried out using both contact-based methods (accelerometer, force sensor) and non-contact methods (laser Doppler vibrometry and magnetic shaker) and numerical simulation (finite element based modal analysis). The platform was applied both pre-process and on-line for studying an aluminium testpiece based on a thin-walled aerospace component. Stability lobe diagrams for this specific machine/component combination were generated allowing selection of optimal process parameters giving stable cutting and metal removal rates some 8-10 times higher than those possible in unstable machining. Based on dynamic characterization and monitoring, a concept for an adaptive control with constraints based machine tool controller has been developed. The developed platform can be applied in manifold machining situations. It offers a reliable way of achieving significant process improvement

  • 16.
    Norman, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander
    Rantatalo, Matti
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Svenningsson, Inge
    AB Sandvik Coromant, Sandviken.
    Study of a sensor platform for monitoring machining of aluminium and steel2007In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 18, no 5, p. 1155-1166Article in journal (Refereed)
    Abstract [en]

    Being able to measure and monitor the forces applied and the resulting vibrations is important to be able to understand and control the process of milling, which is a highly interrupted process based on many variables. The present work concerns analysis of signals gathered during shoulder milling of toughened steel 2541-3 and aluminium alloy 7010. The signals acquired are force in three dimensions and accelerometer in the two horizontal dimensions. Moreover, a laser Doppler vibrometer is applied. The correlations of the analysed signals of the different sensors with the surface roughness were studied. While the signal stability and correlation were unsatisfactory for several sensors, the three sensors measuring along the feed direction were most suitable to monitor the increase of the machined surface roughness with increasing feed rate

  • 17.
    Nyberg, Morgan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Candefjord, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jalkanen, Ville
    Umeå University. Department of Applied Physics and Electronics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A combined tactile and Raman probe for tissue characterization: design considerations2012In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 23, no 6Article in journal (Refereed)
    Abstract [en]

    Histopathology is the golden standard for cancer diagnosis and involves the characterization of tissue components. It is labour intensive and time consuming. We have earlier proposed a combined fibre-optic near-infrared Raman spectroscopy (NIR-RS) and tactile resonance method (TRM) probe for detecting positive surgical margins as a complement to interoperative histopathology. The aims of this study were to investigate the effects of attaching an RS probe inside a cylindrical TRM sensor and to investigate how laser-induced heating of the fibre-optic NIR-RS affected the temperature of the RS probe tip and an encasing TRM sensor. In addition, the possibility to perform fibre-optic NIR-RS in a well-lit environment was investigated. A small amount of rubber latex was preferable for attaching the thin RS probe inside the TRM sensor. The temperature rise of the TRM sensor due to a fibre-optic NIR-RS at 270 mW during 20 s was less than 2 °C. Fibre-optic NIR-RS was feasible in a dimmed bright environment using a small light shield and automatic subtraction of a pre-recorded contaminant spectrum. The results are promising for a combined probe for tissue characterization.

  • 18.
    Olsson, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Tatar, Kourosh
    Sound field determination and projection effects using laser vibrometry2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 10, p. 2843-2851Article in journal (Refereed)
    Abstract [en]

    Sound measurements using laser vibrometry have the advantage that field measurement can be obtained through scanning. It is a non-contact method that provides both qualitative and quantitative information. However, it must be noted that the measurement is an integral along the path of the probing beam. Some effects of this projection are investigated both through measurements and calculations. The sound field calculations are made from measured surface vibrations and they are in good agreement with the measured sound field. The calculations show that the projections very much depend on parameters such as integral depth, or probing depth, and the orientation of the sources. In addition to this, the calculated, or measured, amplitude experiences an enhancement which depends on the wavelength and the distance from the sound source. This enhancement can even result in increasing amplitude with distance. Even though this makes the quantitative data obtained not trustworthy, it is a benefit for the qualitative results which become clearer.

  • 19.
    Törmänen, Matti
    et al.
    Department of Electrical Engineering, 90014 University of Oulu.
    Niemi, Jan
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Myllylä, Risto
    Department of Electrical Engineering, 90014 University of Oulu.
    Pulp consistency determined by a combination of optical and acoustical measurement techniques2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 4, p. 695-702Article in journal (Refereed)
    Abstract [en]

    In this study, methods based on ultrasonic attenuation and optical time-of-flight measurements are used simultaneously in determining both the fibres and fines mass fractions, respectively, of a cellulose pulp fibre suspension. The optical measurements are done by a laser radar and the acoustical measurements are based on ultrasonic attenuation measurements in a pulse-echo set-up. Two kinds of long-fibre fractions are studied, thermo-mechanical pulp and chemical softwood pulp. Fibre and fines mass fraction ranges are 0.25–1.0% and 0–0.75%, respectively. The results show that the fibres are the predominant source for absorption and scattering of ultrasonic waves and are thus mainly contributing to the attenuation of ultrasound in the pulp. It is also found that the fines are the predominant source for optical scattering and fines are thus mainly contributing to the propagation delay of the light pulse in the laser radar set-up. By combining the ultrasonic attenuation and the optical time-of-flight measurements, it is shown that the mass fraction of fines and the mass fraction of fibres in a pulp sample could be determined, respectively.

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