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  • 1. Aitomäki, Yvonne
    et al.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Material property estimates from ultrasound attenuation in fibre suspensions2009In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 49, no 4-5, p. 432-437Article in journal (Refereed)
    Abstract [en]

    An investigation of a new method for measuring fibre material properties from ultrasonic attenuation in a dilute suspension of synthetic fibres of uniform geometry is presented. The method is based on inversely solving an ultrasound scattering and absorption model of suspended fibres in water for the material properties of the fibres. Experimental results were obtained from three suspensions of nylon 66 fibres each with different fibre diameters. A forward solution to the model with reference material values is compared to experimental data to verify the model's behaviour. Estimates of the shear and Young's modulus, the compressional wave velocity, Poisson's ratio and loss tangent from nylon 66 fibres are compared to data available from other sources. Experimental data confirms that the model successfully predicts that the resonance features in the frequency response of the attenuation are a function of diameter. Consistent estimated values for the compressional wave velocity and the Poisson's ratio were found to be difficult to obtain but in combination gave values of shear modulus within previously reported values and with low sensitivity to noise. Young's modulus was underestimated by 54% but was consistent and had low sensitivity to noise. The underestimation is believed to be caused by the assumption of isotropic material used in the model. Additional tests on isotropic fibre would confirm this. Further analysis of the model sensitivity and the reasons for the resonance features are required.

  • 2.
    Carlson, Johan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Martinsson, Pär-Erik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A simple scattering model for measuring particle mass fractions in multiphase flows2002In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 39, no 8, p. 585-590Article in journal (Refereed)
    Abstract [en]

    In this paper we present a simple theoretical model of how pulsed ultrasound is attenuated by the particles in a solid/liquid flow. The theoretical model is then used to predict the attenuation of sound, given the mass fraction, the density, and the size distribution of the solid particles. The model is verified experimentally for suspensions of 0–10% (by mass) Dolomite ((Ca,Mg)CO3) particles and water. The experimental results show that the attenuation of sound due to particles varies linearly with mass fraction, and that the proposed theoretical model can be used to predict this attenuation. In all experiments the transmitter and receiver array were clamped onto the pipe wall, thus providing a completely non-invasive and non-intrusive measurement technique.

  • 3.
    Delsing, Jerker
    Department of Electrical Measurements, Lund Institute of Technology.
    Ultrasonic gas flow meter with corrections for large dynamic metering range1989In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 27, no 6, p. 349-356Article in journal (Refereed)
    Abstract [en]

    Extreme accuracy is required in sing-around type gas flow meters in the sing-around period measurement. Thus the detection of the ultrasound is critical. Accurate detection of an ultrasound pulse transmitted through gas is not straightforward. Normally a zero crossing technique is applied, where a level trigger determines when to enable the zero crossing triggering. In a flowing gas, the ultrasound amplitude is modulated due to turbulence, humidity and changes in dynamic gas pressure. This introduces uncertainty as to the cycle in which the ultrasound pulse is detected. This in turn results in large errors in sing-around type gas flow meters. This paper discusses a new correction algorithm which will eliminate such trigger errors. To accomplish the verification of the new correction algorithm, a microprocessor-based sing-around gas flow meter, using 500 kHz ultrasound has been designed. The correction algorithm significantly increases the repeatability of this meter. Repeatability better than 0.5% over a dynamic meter range of 1 to 35 has been measured. Limitations of the sing-around method imposed by the new correction algorithm have been derived theoretically.

  • 4.
    Johansson, Jonny
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Delsing, Jerker
    Microelectronics mounted on a piezoelectric transducer: method, simulations, and measurements2006In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 44, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    This paper describes the design of a highly integrated ultrasound sensor where the piezoelectric ceramic transducer is used as the carrier for the driver electronics. Intended as one part in a complete portable, battery operated ultrasound sensor system, focus has been to achieve small size and low power consumption. An optimized ASIC driver stage is mounted directly on the piezoelectric transducer and connected using wire bond technology. The absence of wiring between driver and transducer provides excellent pulse control possibilities and eliminates the need for broad band matching networks. Estimates of the sensor power consumption are made based on the capacitive behavior of the piezoelectric transducer. System behavior and power consumption are simulated using SPICE models of the ultrasound transducer together with transistor level modelling of the driver stage. Measurements and simulations are presented of system power consumption and echo energy in a pulse echo setup. It is shown that the power consumption varies with the excitation pulse width, which also affects the received ultrasound energy in a pulse echo setup. The measured power consumption for a 16 mm diameter 4.4 MHz piezoelectric transducer varies between 95 μW and 130 μW at a repetition frequency of 1 kHz. As a lower repetition frequency gives a linearly lower power consumption, very long battery operating times can be achieved. The measured results come very close to simulations as well as estimated ideal minimum power consumption.

  • 5. Martinsson, Jesper
    et al.
    Carlson, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Parametric estimation of ultrasonic phase velocity and attenuation in dispersive media2006In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 44, no Supplement 1, p. e991-e994Article in journal (Refereed)
    Abstract [en]

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

  • 6. Martinsson, Jesper
    et al.
    Hägglund, Fredrik
    Carlson, Johan E.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Complete post-separation of overlapping ultrasonic signals by combining hard and soft modeling2008In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 48, no 5, p. 427-443Article in journal (Refereed)
    Abstract [en]

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

  • 7.
    Schäfer, Robert
    et al.
    Otto-von-Guerricke University Magdeburg.
    Carlson, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hauptmann, Peter
    Otto-von-Guerricke University Magdeburg.
    Ultrasonic concentration measurement of aqueous solutions using PLS regression2006In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 44, no Supplement 1, p. e947-e950Article in journal (Refereed)
    Abstract [en]

    This work demonstrates the use of a multivariate statistical technique called partial least squares (PLS) to extract material related data by analyzing spectra of ultrasonic pulses. We show how PLS can be used to estimate the concentration of sodium chloride in an aqueous solution. The paper describes the use of PLS and discusses pre-processing of ultrasonic data, the PLS algorithm as well as model validation. The measured concentrations are compared to reference values. The influence of disturbances and parameter changes is highlighted. The proposed method is easily adaptable to similar applications and permits a cost-saving implementation using existing and approved hardware

  • 8.
    Svanström, Erika
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Linder, Tomas
    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.
    Analytical one-dimensional model for laser-induced ultrasound in planar optically absorbing layer2014In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 54, no 3, p. 888-893Article in journal (Refereed)
    Abstract [en]

    Ultrasound generated by means of laser-based photoacoustic principles are in common use today and applications can be found both in biomedical diagnostics, non-destructive testing and materials characterisation. For certain measurement applications it could be beneficial to shape the generated ultrasound regarding spectral properties and temporal profile. To address this, we studied the generation and propagation of laser-induced ultrasound in a planar, layered structure. We derived an analytical expression for the induced pressure wave, including different physical and optical properties of each layer. A Laplace transform approach was employed in analytically solving the resulting set of photoacoustic wave equations. The results correspond to simulations and were compared to experimental results. To enable the comparison between recorded voltage from the experiments and the calculated pressure we employed a system identification procedure based on physical properties of the ultrasonic transducer to convert the calculated acoustic pressure to voltages. We found reasonable agreement between experimentally obtained voltages and the voltages determined from the calculated acoustic pressure, for the samples studied. The system identification procedure was found to be unstable, however, possibly from violations of material isotropy assumptions by film adhesives and coatings in the experiment. The presented analytical model can serve as a basis when addressing the inverse problem of shaping an acoustic pulse from absorption of a laser pulse in a planar layered structure of elastic materials.

  • 9.
    van Deventer, Jan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    One dimensional modeling of a step-down ultrasonic densitometer for liquids2004In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 42, no 1-9, p. 309-314Article in journal (Refereed)
    Abstract [en]

    This article studies the possibilities and limitations of modeling a step-down ultrasonic densitometer using its electrical analogous representation. The purpose of the model is to simulate the system in order to optimize its performance. The advantage of an analogous electrical is the complete simulation of both the electrical and mechanical parts of the system. The ultrasonic densitometer and the need for the step down are presented. The analogy to the electrical representation is briefly introduced along with the step down notion. Experimental results of probes equipped with piezoceramic disk of 10 and 16 mm in diameter are shown to consider diffraction. Simulated signals from modeled probes are judged against the real signals. The limitations of the simulations are discussed. They are beam spreading, reference echo to different media and superfluous multiple reflections.

  • 10.
    van Deventer, Jan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Delsing, Jerker
    Apparent transducer non-reciprocity in an ultrasonic flow meter2002In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 40, no 1-8, p. 403-405Article in journal (Refereed)
    Abstract [en]

    This paper investigates the effects of non-identical ultrasonic transducers on reciprocity and zero-flow calibration in transit time flow meters. According to the theorem of reciprocity, there should not be any difference between the up- and downstream acoustic times of flight in a zero-flow situation. This would thus eliminate zero-flow estimation drifts. The flow meter is modeled as a one dimensional system with equivalent electrical circuits and simulated with simulation program with integrated circuits emphasis. The work shows that variations between the two transducers cause false estimates of flow and indicate which parameters have the largest influence. It indicates that reciprocity holds only for identical transducers.

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