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  • 1.
    Abedan Kondori, Farid
    et al.
    Umeå universitet.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology.
    Li, Haibo
    KTH Royal Institute of Technology.
    Direct three-dimensional head pose estimation from Kinect-type sensors2014In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 50, no 4, p. 268-270Article in journal (Refereed)
    Abstract [en]

    A direct method for recovering three-dimensional (3D) head motion parameters from a sequence of range images acquired by Kinect sensors is presented. Based on the range images, a new version of the optical flow constraint equation is derived, which can be used to directly estimate 3D motion parameters without any need of imposing other constraints. Since all calculations with the new constraint equation are based on the range images, Z(xyt), the existing techniques and experiences developed and accumulated on the topic of motion from optical flow can be directly applied simply by treating the range images as normal intensity images I(xyt). In this reported work, it is demonstrated how to employ the new optical flow constraint equation to recover the 3D motion of a moving head from the sequences of range images, and furthermore, how to use an old trick to handle the case when the optical flow is large. It is shown, in the end, that the performance of the proposed approach is comparable with that of some of the state-of-the-art approaches that use range data to recover 3D motion parameters.

  • 2.
    Ahmad, Aftab
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Performance of MLSE over Fading Channels2013Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    This work examines the performance of a wireless transceiver system. The environment is indoor channelsimulated by Rayleigh and Rician fading channels. The modulation scheme implemented is GMSK inthe transmitter. In the receiver the Viterbi MLSE is implemented to cancel noise and interference dueto the ltering and the channel. The BER against the SNR is analyzed in this thesis. The waterfallcurves are compared for two data rates of 1 M bps and 2 Mbps over both the Rayleigh and Rician fadingchannels.

  • 3.
    Alhasan, Raghda
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Software defined radio2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Software Defined Radio (SDR) technology is used to receive and transmit radio signals. Radio signals can be received using the SDR_sharp software that can be downloaded to a personal computer and combined with the RTL-SDR dongle hardware that is connected to the computer. This report gives a brief explanation of the SDR receiver, the supported software, and some applications that can be implemented with SDR. Moreover, it is shown how to install the SDR_sharp software and the hardware Zadig. After installation, wideband FM (WFM) reception and adjustment of RF gain and frequency error is illustrated. The reception of some national, regional and community/commercial stations that can be received in Växjö Sweden is presented.

    Keyword: Software defined radio, FM radio.

  • 4.
    Andersson, Anders
    et al.
    Jönköping University.
    Nilsson, Börje
    Linnaeus University, Faculty of Technology, Department of Mathematics.
    Biro, Thomas
    Jönköping University.
    Fourier Methods for harmonic scalar waves in general waveguides2016In: Journal of Engineering Mathematics, ISSN 0022-0833, E-ISSN 1573-2703, Vol. 98, no 1, p. 21-38Article in journal (Refereed)
    Abstract [en]

    A set of semi-analytic techniques based on Fourier analysis is used to solve wave-scattering problems in variously shaped waveguides with varying normal admittance boundary conditions. Key components are the newly developed conformal mapping methods, wave splitting, Fourier series expansions in eigenfunctions to non-normal operators, the building block method or the cascade technique, Dirichlet-to-Neumann operators, and reformulation in terms of stable differential equations for reflection and transmission matrices. For an example, the results show good correspondence with a finite element method solution to the same problem in the low- and medium-frequency domains. The Fourier method complements finite element analysis as a waveguide simulation tool. For inverse engineering involving tuning of straight waveguide parts joining complicated waveguide elements, the Fourier method is an attractive alternative including time aspects. The prime motivation for the Fourier method is its added physical understanding primarily at low frequencies.

  • 5.
    Baglee, David
    et al.
    University of Sunderland, UK.
    Gorostegui, Unai
    Mondragon University, Spain.
    Jantunen, Erkki
    VTT Technical Research Centre of Finland, Finland.
    Sharma, Pankaj
    Indian Institute of Technology Dehli, India.
    Campos, Jaime
    Linnaeus University, Faculty of Technology, Department of Informatics.
    How can SMEs adopt a new method to advanced maintenance strategies: A Case study approach2017In: 30th International Congress & Exhibition on Condition Monitoring and Diagnostic Engineering Management COMADEM, July 10th-13th 2017, University of Central Lancashire, 2017Conference paper (Refereed)
  • 6.
    Berggren, Magnus
    et al.
    Blekinge Institute of Technology.
    Nilsson, Kristian
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Agnesson, Helen
    Hedsten, Stefan
    Noise Measurements in Incubators at Neonatal Intensive Care Unit2012In: 19th International Congress on Sound and Vibration 2012 (ICSV 19), Curran Associates, Inc., 2012Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to investigate the noise properties and levels of common noise sources in a neonatal intensive care unit (NICU) and in particular inside and around an incubator. Many previous studies have been made on noise levels in NICU, frequently focusing on A-weighted sound levels. In this study it was not assumed that infant's hearing follows the same equal loudness curve as adults and hence instead of A-weighting, short time averaged sound spectra in the frequency range 20 Hz to 20 kHz was logged to identify the frequency distribution of specific noise generating events. It was seen that alarms and CPAP air-flow increased the noise level by up to 8 dB outside but was barely noticed inside when considering the un-weighted noise level. However, by analyzing individual frequencies, most events were noticeable inside the incubator. For instance, frequencies above 1 kHz were increased by 10 dB inside and 11 dB outside the incubator when CPAP was turned on. Opening and closing the incubator increased the un-weighted noise level by 8 dB inside and 7 dB outside.

  • 7.
    Berrevoets, Robbe
    et al.
    Katholieke Univ Leuven, Belgium.
    Weyns, Danny
    Linnaeus University, Faculty of Technology, Department of computer science and media technology (CM). Katholieke Univ Leuven, Belgium.
    A QoS-aware Adaptive Mobility Handling Approach for LoRa-based IoT Systems2018In: 2018 12TH IEEE International Conference on Self-Adaptive and Self-Organizing Systems (SASO 2018), IEEE, 2018, p. 130-139Conference paper (Refereed)
    Abstract [en]

    Internet-of-Things (IoT) is an emergent paradigm that is increasingly applied in smart cities. A popular technology used in IoT is LoRa that supports long-range wireless communication. In this research, we study LoRa-based IoT systems with battery-powered end nodes that collect and communicate data to a gateway for further processing. Existing approaches in such IoT systems usually only consider stationary end nodes. We focus on systems with mobile end nodes, paving the way to new applications such as target tracking. Key Quality of Service (QoS) requirements for these settings are the reliability of the communication and energy consumption. With mobile end nodes, ensuring these QoS is challenging as the system is subject to continuous changes. In this paper, we investigate how the settings of a mobile end node impact key performance indicators for reliability and energy consumption. Based on insights obtained from extensive field experiments, we devise an algorithm that automatically adapts the settings of a mobile end node to ensure its QoS requirements for a setup with a single gateway. We then extend the algorithm to a setup with multiple gateways. We demonstrate how the algorithms achieve the QoS requirements of a mobile end node in a concrete IoT deployment.

  • 8.
    Cijvat, Ellie
    et al.
    Lund University.
    Sjöland, Henrik
    Lund University.
    A Fully Integrated 2.45 GHz 0.25 um CMOS Power Amplifier2003In: Proceedings of the 2003 10th IEEE International Conference on Electronics, Circuits and Systems, 2003. ICECS 2003, IEEE Press, 2003, p. 1094-1097Conference paper (Refereed)
    Abstract [en]

    A fully integrated differential class-AB power amplifier has been designed in a 0.25um CMOS technology. It is intended for medium output power ranges such as Bluetooth class I, and has an operating frequency of 2.45GHz. By using two parallel output stages that can be switched on or off, a high efficiency can be achieved for both high and low output power levels. The simulated maximum output power is 22.7 dBm, while the maximum power- added efficiency is 22%.

  • 9.
    Cijvat, Ellie
    et al.
    University of California, USA.
    Tadjpour, Shahrzad
    University of California, USA.
    Abidi, A.A.
    University of California, USA.
    Spurious mixing of off-channel signals in a wireless receiver and the choice of IF2002In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 49, no 8, p. 539-544Article in journal (Refereed)
    Abstract [en]

    Circuit nonlinearity and LO harmonics can cause large interferers to translate on to the same intermediate frequency as the desired channel. The mechanisms responsible for spurious mixing, which are distinct from intermodulation distortion, are analyzed and catalogued. The analysis leads to an optimal choice of IF for a fully integrated 900 MHz GSM receiver that resists all blockers.

  • 10.
    Cijvat, Ellie
    et al.
    Lund University.
    Tom, Kevin
    Victoria University, Australia.
    Faulkner, Mike
    Victoria University, Australia.
    Sjöland, Henrik
    Lund University.
    A GaN HEMT Power Amplifier with Variable Gate Bias for Envelope and Phase Signals2007In: Proceedings of Norchip 2007, Aalborg, Denmark, 2007, Aalborg, Denmark: Institute of Electrical and Electronics Engineers (IEEE), 2007Conference paper (Refereed)
    Abstract [en]

    This paper describes the design, simulation and measurement of a GaN power amplifier suitable for envelope and phase signal combination. The low-frequency envelope signal is used to vary the gate (bias) voltage of the device, resulting in a pulse width modulated drain voltage, while modulation of supply voltage or current is avoided. The test circuit is implemented using a discrete GaN HEMT power amplifier and discrete surface-mount passive components assembled on a PCB. Measurements showed a maximum drain efficiency of 59% at 360 MHz, at an output power of 29 dBm. The output power as a function of the gate bias voltage varied between 3 and 29 dBm, with the drain efficiency varying between 6 and 59%.

  • 11.
    Cijvat, Ellie
    et al.
    Lund University.
    Tom, Kevon
    Victoria University, Australia.
    Faulkner, Mike
    Victoria University, Australia.
    Sjöland, Henrik
    Lund University.
    Comparing polar transmitter architectures using a GaN HEMT power amplifier2008In: Abstracts book of The Gigahertz Symposium 2008: 5-6 March, 2008, Chalmers University of Technology, Göteborg, Sweden / [ed] Jan Grahn, Gothenburg: Chalmers University of Technology , 2008, p. 21-21Conference paper (Other academic)
    Abstract [en]

    A power amplifier (PA) with variable gate bias is compared to an Envelope Elimination and Restoration (EER) configuration. Each use the lowfrequency envelope and high-frequency phase component of the signal. The test circuit is implemented using a discrete GaN HEMT power device. Measurements show that the EER architecture maintains a relatively high drain efficiency for a wide output power range, while the PA with variable gate bias shows a significant drop in efficiency for lower output powers.

  • 12.
    Cijvat, Ellie
    et al.
    Lund University.
    Troedsson, Niclas
    Lund University.
    Sjöland, Henrik
    Lund University.
    A 2.4GHz CMOS Power Amplifier Using Internal Frequency Doubling2005In: IEEE International Symposium on Circuits and Systems, 2005. ISCAS 2005, Kobe, Japan: IEEE Press, 2005, p. 2683-2686Conference paper (Refereed)
    Abstract [en]

    A fully integrated 0.18 /spl mu/m 1P6M CMOS power amplifier using internal frequency doubling is presented. Two chips were measured, one stand-alone PA and one PA with a VCO on the same chip. Since the PA and VCO operate at different frequencies, this configuration is suitable for direct-upconversion or low-IF upconversion since oscillator pulling is reduced. The maximum output power is 15 dBm, and the maximum drain efficiency is 10.7% at an output operating frequency of 2.4 GHz.

  • 13.
    Cinar, Gökhan
    et al.
    Eskisehir Osmangazi University, Turkey.
    Aksimsek, Sinan
    Istanbul KÄultÄur University, Turkey.
    Nilsson, Börje
    Linnaeus University, Faculty of Technology, Department of Mathematics.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Cinar, Özge
    Eskisehir Osmangazi University, Turkey.
    Wiener-Hopf analysis of TM wave reflection by a step discontinuity on the junction of two coaxial waveguides with perfectly conducting and impedance walls2015In: Progress In Electromagnetics Research Symposium Abstracts, Prague, Czech Republic, July 6-9, 2015, Electromagnetics Academy , 2015, p. 1062-Conference paper (Other academic)
  • 14.
    Dautbegovic, Dino
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Convex Optimization Methods for System Identification2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The extensive use of a least-squares problem formulation in many fields is partly motivated by the existence of an analytic solution formula which makes the theory comprehensible and readily applicable, but also easily embedded in computer-aided design or analysis tools. While the mathematics behind convex optimization has been studied for about a century, several recent researches have stimulated a new interest in the topic. Convex optimization, being a special class of mathematical optimization problems, can be considered as generalization of both least-squares and linear programming. As in the case of a linear programming problem there is in general no simple analytical formula that can be used to find the solution of a convex optimization problem. There exists however efficient methods or software implementations for solving a large class of convex problems. The challenge and the state of the art in using convex optimization comes from the difficulty in recognizing and formulating the problem. The main goal of this thesis is to investigate the potential advantages and benefits of convex optimization techniques in the field of system identification. The primary work focuses on parametric discrete-time system identification models in which we assume or choose a specific model structure and try to estimate the model parameters for best fit using experimental input-output (IO) data. By developing a working knowledge of convex optimization and treating the system identification problem as a convex optimization problem will allow us to reduce the uncertainties in the parameter estimation. This is achieved by reecting prior knowledge about the system in terms of constraint functions in the least-squares formulation.

  • 15.
    Dorosh, Anastasiia
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Direction-of-Arrival Estimation in Spherically Isotropic Noise2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today the multisensor array signal processing of noisy measurements has received much attention. The classical problem in array signal processing is determining the location of an energy-radiating source relative to the location of the array, in other words, direction-of-arrival (DOA) estimation. One is considering the signal estimation problem when together with the signal(s) of interest some noise and interfering signals are present.

    In this report a direction-of-arrival estimation system is described based on an antenna array for detecting arrival angles in azimuth plane of signals pitched by the antenna array. For this, the Multiple Signal Classication (MUSIC) algorithmis first of all considered. Studies show that in spite of its good reputation and popularity among researches, it has a certain limit of its performance. In this subspace-based method for DOA estimation of signal wavefronts, the term corresponding to additive noise is initially assumed spatially white. In our paper, we address the problem of DOA estimation of multiple target signals in a particular noise situation - in correlated spherically isotropic noise, which, in many practical cases, models a more real context than under the white noise assumption.

    The purpose of this work is to analyze the behaviour of the MUSIC algorithm and compare its performance with some other algorithms (such as the Capon and the Classical algorithms) and, uppermost, to explore the quality of the detected angles in terms of precision depending on different parameters, e.g. number of samples, noise variance, number of incoming signals. Some modifications of the algorithms are also done is order to increase their performance.

    Program MATLAB is used to conduct the studies. The simulation results on the considered antenna array system indicate that in complex conditions the algorithms in question (and first of all, the MUSIC algorithm) are unable to automatically detect and localize the DOA signals with high accuracy. Other algorithms andways for simplification the problem (for example, procedure of denoising) exist and may provide more precision but require more computation time.

  • 16.
    Ek, Christoffer
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Singular Value Decomposition2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Digital information transmission is a growing field. Emails, videos and so on are transmitting around the world on a daily basis. Along the growth of using digital devises there is in some cases a great interest of keeping this information secure.

    In the field of signal processing a general concept is antenna transmission. Free space between an antenna transmitter and a receiver is an example of a system. In a rough environment such as a room with reflections and independent electrical devices there will be a lot of distortion in the system and the signal that is transmitted might, due to the system characteristics and noise be distorted.

    System identification is another well-known concept in signal processing. This thesis will focus on system identification in a rough environment and unknown systems. It will introduce mathematical tools from the field of linear algebra and applying them in signal processing. Mainly this thesis focus on a specific matrix factorization called Singular Value Decomposition (SVD). This is used to solve complicated inverses and identifying systems.

    This thesis is formed and accomplished in collaboration with Combitech AB. Their expertise in the field of signal processing was of great help when putting the algorithm in practice. Using a well-known programming script called LabView the mathematical tools were synchronized with the instruments that were used to generate the systems and signals.

  • 17.
    Georgiadis, Abraham
    et al.
    Linnaeus University, Faculty of Technology, Department of computer science and media technology (CM), Department of Media Technology.
    Yousefi, Shahrouz
    Linnaeus University, Faculty of Technology, Department of computer science and media technology (CM), Department of Media Technology.
    Analysis of the user experience in a 3D gesture-based supported mobile VR game2017In: VRST '17 Proceedings of the 23rd ACM Symposium on Virtual Reality Software and Technology, ACM Publications, 2017, article id 47Conference paper (Refereed)
    Abstract [en]

    The work presented in this paper, explored the enhancement of User Experience (UX) by introducing a novel gesture-based controller in a mobile multiplayer Virtual Reality (VR) game. Using only the smartphone's RGB camera, the image input was used for both gesture analysis, capable of understanding user actions, as well as segmenting the real hand that was illustrated in the Virtual Environment (VE). Users were also able to share the VR space by cooperating in a survival-strategy scenario. The results from the user studies indicated that both the bare hand controller and the addition of another player in the VR scene, affected the experience for the participants. Users had a stronger feeling of presence in the VE when participated with an other user, and the visual representation of their hand in the VR world made the interactions seem more natural. Even though, there is still a number of limitations, this project nodes this approach capable of offering a natural and engaging solution of VR interaction, capable of rich UX while maintaining a low entry level for the end users.

  • 18.
    Gertsovich, Irina
    et al.
    Blekinge Institute of Technology.
    Ström Bartunek, Josef
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Nilsson, Mikael
    Lund University.
    A Novel Methodology for the Interoperability Evaluation of An Iris Segmentation Algorithm2013In: 2013 IEEE Sixth International Conference on Biometrics: Theory, Applications and Systems (BTAS), IEEE, 2013Conference paper (Refereed)
    Abstract [en]

    The performance of an iris recognition system depends greatly on how well the iris segmentation part of the system performs its task. The performance of an iris segmentation algorithm can be evaluated using different criteria and methods. Some of the methods evaluate the performance of the segmentation algorithm based on the performance of the whole iris recognition system. Other methods evaluate the performance of an iris segmentation subsystem independent of the performance of the system's other subsystems. To our knowledge there do not exist a generally accepted method or criteria for the evaluation of the standalone iris segmentation subsystem. This paper proposes a novel methodology to compare the performance of different iris segmentation algorithms, applied to different image datasets in a consistent way. The methodology employs the F1 score and an empirical cumulative distribution function. The implementation of the F1 score estimation, adapted to the iris segmentation task is described. Finally the application of the proposed methodology is demonstrated and discussed.

  • 19.
    Gustafsson, Mats
    et al.
    Lund University.
    Cismasu, Marius
    Lund University.
    Nordebo, Sven
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Absorption Efficiency and Physical Bounds on Antennas2010In: International Journal of Antennas and Propagation, ISSN 1687-5869, E-ISSN 1687-5877, Vol. 2010, article id 946746Article in journal (Refereed)
    Abstract [en]

    The all spectrum absorption efficiency appears in the physical bounds on antennas expressed in the polarizability dyadics. Here, it is shown that this generalized absorption efficiency is close to 1/2 for small idealized dipole antennas and for antennas with a dominant resonance in their absorption. Also, the usefulness of this parameter is analyzed for estimation of antenna performance. The results are illustrated with numerical data for several antennas.

  • 20. Gustafsson, Mats
    et al.
    Nordebo, Sven
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Bandwidth, Q factor, and resonance models of antennas2006In: Progress in Electromagnetics Research PIER, Vol. 62, p. 1-20Article in journal (Refereed)
    Abstract [en]

    In this paper, we introduce a first order accurate resonance model based on a second order Pade approximation of the reflection coefficient of a narrowband antenna. The resonance model is characterized by its Q factor, given by the frequency derivative of the reflection coefficient. The Bode-Fano matching theory is used to determine the bandwidth of the resonance model and it is shown that it also determines the bandwidth of the antenna for sufficiently narrow bandwidths. The bandwidth is expressed in the Q factor of the resonance model and the threshold limit on the reflection coefficient. Spherical vector modes are used to illustrate the results. Finally, we demonstrate the fundamental difficulty of finding a simple relation between the Q of the resonance model, and the classical Q defined as the quotient between the stored and radiated energies, even though there is usually a close resemblance between these entities for many real antennas.

  • 21. Gustafsson, Mats
    et al.
    Nordebo, Sven
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    Cramer-Rao Lower Bounds for Inverse Scattering Problems of Multilayer Structures2006In: Inverse Problems, Vol. 22, p. 1359-1380Article in journal (Refereed)
    Abstract [en]

    In this paper, the inverse scattering problem of amultilayer structure is analysed with the Fisher information matrix and the Cramer–Rao lower bound (CRLB). The CRLB quantifies the ill-posedness of the inverse scattering problem in terms of resolution versus estimation accuracy based on the observation of noisy data. The limit for feasible inversion is identified by an asymptotic eigenvalue analysis of the Toeplitz Fisher information matrix and an application of the sampling theorem. It is shown that the resolution is inversely proportional to the bandwidth of the reflection data and that the CRLB increases linearly with the number of slabs. The transmission data give a rank-1 Fisher information matrix which can approximately reduce the CRLB by a factor of 4. Moreover, the effect of dispersive material parameters and simultaneous estimation of two material parameters are analysed. The results are illustrated with numerical examples.

  • 22.
    Gustafsson, Stefan
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Biro, Thomas
    Jönköping University.
    Cinar, Gökhan
    Gebze Institute of Technology, Gebze, Kocaeli, Turkey.
    Gustafsson, Mats
    Lund University.
    Karlsson, Anders
    Lund University.
    Nilsson, Börje
    Linnaeus University, Faculty of Technology, Department of Mathematics.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Sjöberg, Mats
    ABB AB, Karlskrona.
    Electromagnetic dispersion modeling and measurements for HVDC power cables2014In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 29, no 6, p. 2439-2447Article in journal (Refereed)
    Abstract [en]

    This paper provides a general framework for electromagnetic (EM) modeling, sensitivity analysis, computation, and measurements regarding the wave propagation characteristics of high-voltage direct-current (HVDC) power cables. The modeling is motivated by the potential use with transient analysis, partial-discharge measurements, fault localization and monitoring, and is focused on very long (10 km or more) HVDC power cables with transients propagating in the low-frequency regime of about 0-100 kHz. An exact dispersion relation is formulated together with a discussion on practical aspects regarding the computation of the propagation constant. Experimental time-domain measurement data from an 80-km-long HVDC power cable are used to validate the electromagnetic model, and a mismatch calibration procedure is devised to account for the connection between the measurement equipment and the cable. Quantitative sensitivity analysis is devised to study the impact of parameter uncertainty on wave propagation characteristics. The sensitivity analysis can be used to study how material choices affect the propagation characteristics, and to indicate which material parameters need to be identified accurately in order to achieve accurate fault localization. The analysis shows that the sensitivity of the propagation constant due to a change in the conductivity in the three metallic layers (the inner conductor, the intermediate lead shield, and the outer steel armor) is comparable to the sensitivity with respect to the permittivity of the insulating layer. Hence, proper modeling of the EM fields inside the metallic layers is crucial in the low-frequency regime of 0-100 kHz.

  • 23. Hashemzadeh, Parham
    et al.
    Kantaritzis, Panagiotis
    Liatsis, Panos
    Bayford, Richard
    Nordebo, Sven
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    A Cramer-Rao Bound Approach for Evaluating the Quality of Experimental Setups in Electrical Impedance Tomography2011In: Proceeding (723) Biomedical Engineering, 2011Conference paper (Refereed)
    Abstract [en]

    In this report, we propose the application of the Cramer Rao Lower Bound (CRLB) as a performance measure for optimal design of experimental setups in electrical impedance tomography. In particular, we focus on the optimum positioning of electrodes. Cramer Rao Bound is bounded from below by the inverse of the Fisher information matrix (FIM). FIM incorporates all aspects of the forward problem, statistical properties of the measurement noise, and multi-frequency data. We consider the application of CRB in both the deterministic as well as the Bayesian setting. We first present the CRB for the case of the unbiased estimator and then the Bayesian Cramer Rao Bound (BCRB) for the case of the biased estimator. All CRB computations are performed using a measured noise model from a clinical experiment.

  • 24.
    Haydar Lazem Al-Saadi, Adel
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Approximation of antenna patterns by means of a combination of Gaussian beams2012Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Modeling of electromagnetic wave propagation in terms of Gaussian beams (GBs) has been considered in recent years. The incident radiation is expanded in terms of GBs by means of the point matching method. The simultaneous equations can be solved directly to produce excitation coefficients that generate the approximate pattern of a known antenna. Two different types of antenna patterns have been approximated in terms of GBs: a truncated antenna pattern and a hyperbolic antenna pattern. The influence of the Gaussian beam parameters on the approximation process is clarified.

  • 25.
    Huang, Gang
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. university.
    Distance measurement by means of phase radar2019Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    A distance measurement by means of phase is used in a scheme to locate a transmitter. The system consists of three antennas. There is a transmitter, that in a sense acts as a target, in terms of radar concepts. Two receivers are used to determine the distance needed to find the position of the transmitter in the 2D plane. The software LabVIEW is used in this study. The cable lengths are adapted to the measurement.

  • 26.
    Håkansson, Lars
    IIAV, United States.
    The Fourier Transform in Sound and Vibration2015In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 20, no 4, p. 190-190Article in journal (Refereed)
  • 27.
    Håkansson, Lars
    et al.
    Blekinge Institute of Technology.
    Johansson, Sven
    Blekinge Institute of Technology.
    Claesson, Ingvar
    Blekinge Institute of Technology.
    Chapter 81– Machine Tool Noise, Vibration and Chatter Prediction and Control2007In: Handbook of Noise and Vibration Control / [ed] Malcolm J. Crocker, John Wiley & Sons, 2007Chapter in book (Refereed)
  • 28. Håkansson, Lars
    et al.
    Johansson, Sven
    Dahl, Mattias
    Sjösten, Per
    Claesson, Ingvar
    Chapter 12 – Noise Canceling Headsets for Speech Communication2002In: Noise Reduction in Speech Applications / [ed] Gillian M. Davis, CRC Press, 2002, p. 305-328Chapter in book (Refereed)
  • 29. Håkansson, Lars
    et al.
    Khan, Imran
    Sharafi, Amir
    Zackrisson, Johan
    Development and Implementation of an Advanced Remotely Controlled Vibration Laboratory2014In: 2014 11th International Conference on Remote Engineering and Virtual Instrumentation (REV), IEEE, 2014, p. 382-385Conference paper (Refereed)
    Abstract [en]

    Currently an advanced remotely controlled vibration laboratory is developed and implemented at Blekinge Institute of Technology, Karlskrona, Sweden. The new developments in the laboratory setup will provide users to carry out vibration measurements on a cantilever beam system with remotely adjustable dynamic properties and to estimate dynamic characteristics of it. The dynamic properties of the cantilever beam are remotely modified by attaching structural parts such as a block of mass, a spring mass system and a non-linear spring. In the development of this remote-lab, a number of different approaches were adopted for the production of well-defined experiments. Also, the new prototype laboratory is designed based on finite elements modeling (FEM) and LABVIEW. The test object, attachment mechanism for sub structures, relevant experiments, and proper interface for managing the lab via Internet and many other things have been considered.

  • 30.
    Ishaq, Muhammad Irfan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Khan, Yasir Ali
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Gul, Muhammad Talha
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Precoding in MIMO, OFDM to reduce PAPR (Peak to Average Power Ratio)2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    One of the critical issues of systems utilizing Orthogonal Frequency Division Multiplexing (OFDM) is the high peak to the average power ratio of OFDM signals. We have used Precoding as a way to mitigate the PAPR problem. Furthermore the performance of Precoded OFDM in fading multi-path channels has been studied. This thesis is based on an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is data-independent and thus, does not require new processing and optimization for each transmitted OFDM block. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a Precoding scheme that distributes the power of each modulated symbol over the OFDM block. The obtained results show that this Precoding scheme is an attractive solution to the PAPR problem of OFDM signals.

  • 31.
    Ivanenko, Yevhen
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Estimation of complex valued permeability of cable armour steel2016In: 2016 URSI International Symposium on Electromagnetic Theory (EMTS), IEEE Press, 2016Conference paper (Refereed)
    Abstract [en]

    This paper presents a model based technique to estimate the complex valued permeability of cable armour steel. An efficient analytical model is derived for the linearized mutual impedance of a transformer coil built on a core of magnetic armour steel. A numerical residue calculation is used to solve the related inverse problem based on impedance data. The analytical model is validated using commercial finite element (FEM) software to establish that edge effects can be neglected. The numerical residue calculation is investigated by studying its convergence based on a simple rectangular quadrature rule in comparison to the composite Simpson's rule. When there are no measurement errors, both methods converge with an unexpected high order (superconvergence). However, in practice the estimation performance will be governed by measurement and model errors. Assuming that there are Gaussian measurement errors, the present performance of the estimation technique is quantified and investigated by means of the Cramér-Rao lower bound. In future, the proposed method will be useful as an input to general calculations of power losses in three-phase power cables.

  • 32.
    Jantunen, Erkki
    et al.
    Technical Research Centre of Finland Ltd., Finland.
    Campos, Jaime
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Sharma, Pankaj
    Indian Institute of Technology, India.
    Baglee, David
    University of Sunderland, UK.
    Digitalisation of Maintenance2017In: 2nd International Conference on System Reliability and Safety, ICSRS 2017, 20 - 22 December 2017, Milan, Italy, IEEE, 2017, p. 343-347Conference paper (Refereed)
    Abstract [en]

    The digitalisation of industry and the Industry 4.0 concept with its connected ICTs are important developments for the industry to acquire and implement to be able to keep ahead in competition. In connection to Industry 4.0, the predictive maintenance systems and approach are getting more popular in maintenance. This is because these systems enable a change in the maintenance mind-set where the break-fix mentality is substituted by a predictive maintenance system, such as Condition Based Maintenance (CBM), where the equipment is monitored with the support of ICTs to detect failures before they occur. The Industry 4.0 seems more attainable even for small and medium sized companies because of the drop in the prices of the components of these systems, both in the sensing elements and in the data processing part. The manufacturing methods used in the Integrated Circuit (IC) industry create the possibility to reduce significantly the price tag of sensors and processors. Therefore, the authors go through the CBM approach and technologies, such as Microelectromechanical System (MEMS) sensors as well as such emerging ICTs as the Cloud and Big data. These could offer a turning point in traditional maintenance by widening the amount of monitored assets, allowing multiple parameters to be measured and analysed and enabling wireless and immediate data access across the globe.

  • 33.
    Jayaraman, Vinoth
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Sivalingam, Sivakumaran
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Munian, Sangeetha
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Analysis of Real Time EEG Signals2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The recent evolution in multidisciplinary fields of Engineering, neuroscience, microelectronics,

    bioengineering and neurophysiology have reduced the gap between human and

    machine intelligence. Many methods and algorithms have been developed for analysis

    and classification of bio signals, 1 or 2-dimensional, in time or frequency distribution.

    The integration of signal processing with the electronic devices serves as a major root for

    the development of various biomedical applications. There are many ongoing research

    in this area to constantly improvise and build an efficient human- robotic system.

    Electroencephalography (EEG) technology is an efficient way of recording electrical activity

    of the brain. The advancement of EEG technology in biomedical application helps

    in diagnosing various brain disorders as tumors, seizures, Alzheimer’s disease, epilepsy

    and other malfunctions in human brain.

    The main objective of our thesis deals with acquiring and pre-processing of real time

    EEG signals using a single dry electrode placed on the forehead. The raw EEG signals

    are transmitted in a wireless mode (Bluetooth) to the local acquisition server and stored

    in the computer. Various machine learning techniques are preferred to classify EEG

    signals precisely. Different algorithms are built for analysing various signal processing

    techniques to process the signals. These results can be further used for the development

    of better Brain-computer interface systems.

  • 34.
    Juhlin, Tobias
    et al.
    Linnaeus University, Faculty of Technology, Department of Computer Science.
    Wangberg, Dan
    Linnaeus University, Faculty of Technology, Department of Computer Science.
    Bristfällig säkerhet inom trådlösa routrar med fokus på WPS2014Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    In this report the WPS-function is evaluated due to the vulnerabilty of the protocol. Interviews, tests and observations have been conducted to evaluate the problems with WPS. The tests and interviews conducted indicates that the vulnerability of the WPS-function has been secured with extra functions. 

  • 35.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Gertsovich, Irina
    Blekinge Institute of Technology.
    Claesson, Ingvar
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Johansson, Per-Erik
    Blekinge County Hospital.
    Wirenstedt, Maria
    Blekinge County Hospital.
    Bona, Oscar
    Blekinge County Hospital.
    Petersson, Stefan
    GE Healthcare, UK, MR Division, Hertfordshire, United Kingdom .
    MRI scanner vibration path analysis2013In: 20th International Congress on Sound and Vibration 2013 (ICSV 20), Curran Associates, Inc., 2013, Vol. 4, p. 3560-3567Conference paper (Other academic)
    Abstract [en]

    Magnetic Resonance Imaging (MRI) scanner is one of the most important tools in clinical diagnostics. MRI scanners are associated by strong vibration which results in unpleasant and disturbing acoustic noise. The primary source of this vibration is the Lorentz force produced by fast switching of the currents inside the gradient coils of MRI scanners under a strong static magnetic field. During an MR-imaging scan the switching is controlled in order to spatially code the hydrogen nuclei that will generate the signal, which is reconstructed into anatomical images. Faster switching of the currents allows for shorter scan times and/or higher image resolutions. Consequently, the clinical quality has motivated the drive for shorter switching time and higher currents. This development, however, has also caused an undesired increase of MRI vibrations. The overall vibration phenomenon of an installed fully functional MRI scanner system becomes unique because of the installed location and ambiance. This vibration can potentially degrade the image quality and hence the diagnosis. Apart from the vibration produced, the associated annoying acoustic noise may not only affect the patients under examination and the clinical staff, but may also be transmitted to other parts of the building and causing discomfort for the personnel working there. In order to devise an effective isolation plan or improve an existing one both for vibration and acoustic noise it is important to study the noise and vibration transfer paths. This paper concerns an investigation of vibration transfer paths for vibration excited by an installed functional MRI scanner at a medical facility. The vibration transfer paths have been investigated experimentally. The obtained results are presented and discussed.

  • 36.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Moazzam, Muhammad
    Rabbani, Shoaib
    Blekinge Institute of Technology.
    Johansson, Sven
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Performance  Evaluation of Control Algorithms Implemented on a Remotely Controlled Active Noise Control Laboratory2013In: 20th International Congress on Sound and Vibration 2013 (ICSV 20), Curran Associates, Inc., 2013Conference paper (Other academic)
    Abstract [en]

    The remotely controlled laboratory setup for Active Noise Control (ANC) developed by Blekin-ge Institute of Technology, Sweden provides an efficient learning platform for the students to implement and learn ANC algorithms with real world physical system, hardware and signals. The initial laboratory prototype based on a Digital Signal Processor (DSP) TMS320C6713 from Texas Instruments (TI) was successfully tested with Filtered-x Least Mean Square (F-XLMS) algorithm applied to control noise in a ventilation duct. The resources of the DSP platform used in the remote laboratory setup enable testing and investigating substantially more challenging and computationally demanding algorithms. In this paper, we expand the horizon of the laboratory setup by testing more advanced and complicated single channel feed forward ANC algorithms. Filtered-x versions of algorithms such as the normalized least mean square (N-LMS), leaky least mean square (L-LMS), Filtered-U recursive least mean square (FURLMS) and recursive least square (RLS) algorithm etc. have been implemented utilizing the remote web based client provided in the remote laboratory. A comprehensive performance comparison of the aforementioned algorithms for the remote laboratory setup is presented to demonstrate the viability of the remote laboratory.

  • 37.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Muthusamy, Dinesh
    Blekinge Institute of Technology.
    Ahmad, Waqas
    Blekinge Institute of Technology.
    Gustavsson, Ingvar
    Blekinge Institute of Technology.
    Zackrisson, Johan
    Blekinge Institute of Technology.
    Nilsson, Kristian
    Blekinge Institute of Technology.
    Johansson, Sven
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Remotely Controlled Active Noise Contol Laboratiories2012In: The Nineteenth International Congress on Sound and Vivration, Curran Associates, Inc., 2012Conference paper (Other academic)
    Abstract [en]

    Remotely controlled laboratories in educational institutions are gaining popularity at an exponential rate due to the multidimensional benefits they provide. The Virtual Instrument Systems in Reality (VISIR) project by Blekinge Institute of Technology (BTH) Sweden has successfully implemented remotely controlled laboratories, with remotely controlled real instruments and experimental setups. Currently these laboratories provide students the opportunity to conduct experiments in the field of electronics, antenna theory and mechanical vibration measurements. In this paper a prototype system of a remotely controlled laboratory for active noise control (ANC) is introduced. The proposed lab will focus on addressing the problem of a ventilation duct noise. The laboratory is informative and to a great extent introduces a student to the general steps in ANC when it is suggested as a plausible solution for a noise problem. The student can perform an investigation concerning feasibility of active control, design, configuration and implementation of an active control system. The laboratory is based on a modern and relevant DSP platform with the corresponding software development environment controlled remotely. In addition, it may be utilized remotely both for lab assignments in acoustics courses and digital signal processing courses.

  • 38.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Muthusamy, Dinesh
    Blekinge Institute of Technology.
    Ahmad, Waqas
    Sällberg, Benny
    Blekinge Institute of Technology.
    Nilsson, Kristian
    Blekinge Institute of Technology.
    Zackrisson, Johan
    Blekinge Institute of Technology.
    Gustavsson, Ingvar
    Blekinge Institute of Technology.
    Håkansson, Lars
    Performing Active Noise Control and Acoustic Experiments Remotely2012In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 8, no Special Issue, p. 65-74Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel and advanced remotely controlled laboratory for conducting Active Noise Control (ANC), acoustic and Digital Signal Processing (DSP) experiments. The laboratory facility, recently developed by Blekinge Institute of Technology (BTH) Sweden, supports remote learning through internet covering beginners level such as simple experimental measurements to advanced users and even researchers such as algorithm development and their performance evaluation on DSP. The required software development for ANC algorithms and equipment control are carried out anywhere in the world remotely from an internet-connected client PC using a standard web browser. The paper describes in detail how ANC, acoustic and DSP experiments can be performed remotely The necessary steps involved in an ANC experiment such as validity of ANC, forward path estimation and active control applied to a broad band random noise [0-200Hz] in a ventilation duct will be described in detail. The limitations and challenges such as the forward path and nonlinearities pertinent to the remote laboratory setup will be described for the guidance of the user. Based on the acoustic properties of the ventilation duct some of the possible acoustic experiments such as mode shapes analysis and standing waves analysis etc. will also be discussed in the paper.

  • 39.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Nygren, Åse
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Challenges in Fulfilling the Intended Learning Outcomes of Remote of Laboratories: A Case Study of Active Noise Control and Acoustic Remote Laboratory2015In: 22nd International Congress on Sound and Vibration 2015 (ICSV 22), Curran Associates, Inc., 2015Conference paper (Other academic)
  • 40.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Żmuda, Maciej
    Blekinge Institute of Technology.
    Konopka, Piotr
    Blekinge Institute of Technology.
    Gustavsson, Ingvar
    Blekinge Institute of Technology.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Enhancement of Remotely Controlled Laboratory for Active Noise Control and Acoustic Experiments2014In: 2014 11th International Conference on Remote Engineering and Virtual Instrumentation (REV), IEEE, 2014, p. 285-290Conference paper (Refereed)
    Abstract [en]

    The latest important developments in the remotely controlled Active Noise Control (ANC) and Acoustics laboratory at Blekinge Institute of Technology (BTH), Sweden, are introduced. The remotely controlled laboratory is based on the Virtual Instruments Systems in Reality (VISIR) concept, and concerns multi-channel measurement and control of the sound field in a heating ventilation and air conditioning (HVAC) duct. Originally the ventilation duct was equipped with a fixed number of microphones at fixed spatial locations in the duct. A microphone positioning system has been designed and implemented. It enables control of the spatial positions of a number of microphones inside the HVAC duct using a suitable web interface for controlling stepper motors via a National Instruments (NI) PXI system. With the new developments, the spatial number of selectable positions for the microphones have been extended substantially. The new microphone positioning control system is presented and to enhance the user interaction with the laboratory equipment, an audio and visual system is also proposed.

  • 41.
    Khan, Imran
    et al.
    Blekinge Institute of Technology.
    Żmuda, Maciej
    Konopka, Piotr
    Håkansson, Lars
    Blekinge Institute of Technology.
    Remote Control of Active Noise Control and Acoustics Experiment Setup via the Internet2014In: 21st International Congress on Sound and Vibration 2014 (ICSV 21) / [ed] Crocker, M.J., Curran Associates, Inc., 2014Conference paper (Other academic)
  • 42.
    Khodadad, Davood
    Luleå University of Technology.
    Multiplexed Digital Holography incorporating Speckle Correlation2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In manufacturing industry there is a high demand for on line quality control to minimize therisk of incorrectly produced objects. Conventional contact measurement methods are usuallyslow and invasive, meaning that they cannot be used for soft materials and for complexshapes without influencing the controlled parts. In contrast, interferometry and digitalholography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digitalholography, access to the complex wave field and the possibility to numerically reconstructholograms in different planes introduce a new degree of flexibility to optical metrology. Withdigital holography high resolution and precise three dimensional (3D) images of themanufactured parts can be generated. This technique can also be used to capture data in asingle exposure, which is important when doing measurements in a disturbed environment.

    The aim of this thesis is devoted to the theoretical and experimental development of shapeand deformation measurements. To perform online process control of free-formmanufactured objects, the measured shape is compared with the CAD-model to obtaindeviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckledisplacements is demonstrated. Based on an analytical relation between phase gradients andspeckle displacements it is shown that an object is retrieved uniquely to shape, position anddeformation without the unwrapping problems that usually appear in dual-wavelengthholography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual corediode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm isused. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformationmeasurements.

    One significant problem when using the dual-wavelength single-shot approach is that phaseambiguities are built in to the system that needs to be corrected. An automatic calibrationscheme is therefore required. The intrinsic flexibility of digital holography gives a possibilityto compensate these aberrations and to remove errors, fully numerically without mechanicalmovements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps andspeckle displacements can be recovered free of chromatic aberrations. This is the first time that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria tomake an automatic procedure.

    Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3Ddeformations. In order to do 3D deformation measurement, usually multi-cameras andintricate set-up are required. In this thesis I demonstrate the use of only one single camera torecord four sets of speckle patterns recorded by illuminating the object from four differentdirections. In this manner, meanwhile 3D speckle displacement is calculated and used for themeasurement of the 3D deformations, wrapping problems are also avoided. Further, the samescale of speckle images of the surface for all four images is guaranteed. Furthermore, a needfor calibration of the 3D deformation measurement that occurs in the multi-camera methods,is removed.

    By the results of the presented work, it is experimentally verified that the multiplexed singleshotdual wavelength digital holography and numerically generated speckle images can beused together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. Theproposed method is robust to large phase gradients and large movements within the intensitypatterns. The advantage of the approach is that, using speckle displacements, shape anddeformation measurements can be performed even though the synthetic wavelength is out ofthe dynamic range of the object deformation and/or height variation.

  • 43.
    Khodadad, Davood
    Luleå University of Technology.
    Phase-derivative-based estimation of a digital reference wave from a single off-axis digital hologram2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 7, p. 1663-1669Article in journal (Refereed)
    Abstract [en]

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

  • 44.
    Khodadad, Davood
    et al.
    Luleå University of Technology.
    Ahmadian, Alireza
    Tehran University of Medical Science, Iran.
    Yousefi Banaem, Hossein
    Isfahan University of Medical Sciences, Iran.
    Ay, Mohammad Reza
    Tehran University of Medical Science, Iran.
    Fard-Esfahani, Armaghan
    Tehran University of Medical Science, Iran.
    CT and PET Image Registration: Application to Thorax Area2013In: International Journal of Image and Graphics, ISSN 0219-4678, Vol. 1, no 4, p. 171-175Article in journal (Refereed)
    Abstract [en]

    Accurate attenuation correction of emission data is mandatory for quantitative analysis of PET images. One of the main concerns in CT-based attenuation correction (CTAC) of PET data in multimodality PET/CT imaging is misalignment occurred due to respiratory artifact between PET and CT images. In this paper a combined method which is simple and fast is proposed for registration of PET and CT data to correct the effect of this artifact. The algorithm is composed of two step: First step is meant to reduce the noise by applying an adaptive gradient anistropic diffusion filter then using Iterative closest point (ICP) registration method in order to obtain initial estimation to ensure fast and accurate convergence of the algorithm. At the second step, the respiratory related artifact of PET images is greatly reduced by employing Free Form Deformation algorithm based on B-spline which provides more accurate adaptive transformation to align the images

  • 45.
    Khodadad, Davood
    et al.
    Luleå University of Technology.
    Amer, Eynas
    Luleå University of Technology.
    Gren, Per
    Luleå University of Technology.
    Melander, Emil
    Uppsala University.
    Hällstig, Emil
    Fotonic.
    Sjödahl, Mikael
    Luleå University of Technology.
    Single-shot dual-polarization holography: measurement of the polarization state of a magnetic sample2015In: SPECKLE 2015: VI International Conference on Speckle Metrology / [ed] Fernando Mendoza Santoyo, Eugenio R. Méndez, 2015, article id 96601EConference paper (Refereed)
    Abstract [en]

    In this paper a single-shot digital holographic set-up with two orthogonally polarized reference beams is proposed to achieve rapid acquisition of Magneto-Optical Kerr Effect images. Principles of the method and the background theory for dynamic state of polarization measurement by use of digital holography are presented. This system has no mechanically moving elements or active elements for polarization control and modulation. An object beam is combined with two reference beams at different off-axis angles and is guided to a detector. Then two complex fields (interference terms) representing two orthogonal polarizations are recorded in a single frame simultaneously. Thereafter the complex fields are numerically reconstructed and carrier frequency calibration is done to remove aberrations introduced in multiplexed digital holographic recordings. From the numerical values of amplitude and phase, a real time quantitative analysis of the polarization state is possible by use of Jones vectors. The technique is demonstrated on a magnetic sample that is a lithographically patterned magnetic microstructure consisting of thin permalloy parallel stripes.

  • 46.
    Khodadad, Davood
    et al.
    Luleå University of Technology.
    Bergström, Per
    Luleå University of Technology.
    Hällstig, Emil
    Optronic Partner dp AB.
    Sjödahl, Mikael
    Luleå University of Technology.
    Single shot dual-wavelength digital holography: calibration based on speckle displacements2014In: International Journal of Optomechatronics, ISSN 1559-9612, Vol. 8, no 4, p. 326-339Article in journal (Refereed)
    Abstract [en]

    We present a calibration method which allows single shot dual wavelength online shape measurement in a disturbed environment. Effects of uncontrolled carrier frequency filtering are discussed as well. We demonstrate that phase maps and speckle displacements can be recovered free of chromatic aberrations. To our knowledge, this is the first time that a single shot dual wavelength calibration is reported by defining a criteria to make the spatial filtering automatic avoiding the problems of manual methods. The procedure is shown to give shape accuracy of 35 µm with negligible systematic errors using a synthetic wavelength of 1.1 mm.

  • 47.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco, SWE.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Comparison of Spectral Properties of the Vibration Signal and Line Pressure Signal of DTH Drill2016In: 23rd International Congress on Sound and Vibration 2016 (ICSV 23): From Ancient to Modern Acoustics, Publisher: Curran Associates, Inc., Curran Associates, Inc., 2016Conference paper (Other academic)
    Abstract [en]

    Quantifying and Monitoring of drilling performance are becoming exceedingly important in the case of Down the Hole drilling. Various economic, environmental and safety constraints are driving the drilling process to become more efficient. To make a robust system that would enable the performance/condition monitoring of the drilling, we must understand how different properties like different line pressure etc. respond to various drilling conditions and what information can they provide regarding the Drilling Performance. A comparison of different properties like spectral properties, of the vibration signals and Pressure signals under known conditions would enable better understanding of the drilling system and the physics behind the process. A comparison is made between the Spectral properties of the vibrational signals obtained from remote locations on the drill rig and pressure signals that provide the feed and holdback forces to the drill string and a correlation between their characteristics and patterns under good and bad drilling conditions have been made. A simplified model of the system is simulated and results are compared with the patterns obtained from analyzing the Vibration signals.

  • 48.
    Kodakadath Premachandran, Rammohan
    et al.
    Atlas Copco.
    Håkansson, Lars
    Blekinge Institute of Technology.
    Signal Analysis for Performance Monitoring of Drilling with Down the Hole (DTH) Rock Drills2015In: 22nd International Congress on Sound and Vibration 2015 (ICSV 22), Curran Associates, Inc., 2015Conference paper (Other academic)
  • 49.
    Kondori, Abedan Farid
    et al.
    Umeå University.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology.
    Kouma, Jean-Paul
    Liu, Li
    Umeå University.
    Li, Haibo
    Umeå University.
    Direct hand pose estimation for immersive gestural interactionManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    This paper presents a novel approach for performing intuitive gesture-based interactionusing depth data acquired by Kinect. The main challenge to enableimmersive gestural interaction is dynamic gesture recognition. This problemcan be formulated as a combination of two tasks; gesture recognition and gesturepose estimation. Incorporation of fast and robust pose estimation methodwould lessen the burden to a great extent. In this paper we propose a directmethod for real-time hand pose estimation. Based on the range images, a newversion of optical flow constraint equation is derived, which can be utilizedto directly estimate 3D hand motion without any need of imposing other constraints.Extensive experiments illustrate that the proposed approach performsproperly in real-time with high accuracy. As a proof of concept, we demonstratethe system performance in 3D object manipulation on two dierent setups;desktop computing, and mobile platform. This reveals the system capabilityto accommodate dierent interaction procedures. In addition, user studyis conducted to evaluate learnability, user experience and interaction quality in3D gestural interaction in comparison to 2D touch-screen interaction.

  • 50. Kondori, Farid Abedan
    et al.
    Yousefi, Shahrouz
    KTH, Medieteknik och interaktionsdesign, MID.
    Li, Haibo
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Real 3D interaction behind mobile phones for augmented environments2011In: Multimedia and Expo (ICME), 2011 IEEE International Conference on, IEEE Press, 2011, p. 1-6Conference paper (Refereed)
123 1 - 50 of 101
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