Change search
Refine search result
123 101 - 139 of 139
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 101. Valduga, Samuel Tumelero
    et al.
    Alves, Dimas Irion
    Machado, Renato
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Legg, Andrei Piccinini
    Loiola, Murilo Bellezoni
    Low-complexity codebook-based beamforming with four transmit antennas and quantized feedback channel2014In: 2014 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC), Istanbul: IEEE , 2014Conference paper (Refereed)
    Abstract [en]

    In this paper we propose a low-complexity codebook-based beamforming with four transmit antennas and quantized feedback channel. The codebook design aggregates the effect of power allocation and phase rotation through a simple quantized transmit scheme. The codebook-based beamforming uses the feedback information in order to maximize the instantaneous signal-to-noise ratio (SNR) at the receiver. As a result, the proposed scheme presents an array gain. An SNR analysis is performed and it is used to find the optimal feedback information in the sense of maximizing the instantaneous SNR. A bit error rate (BER) analysis for a quantized feedback channel is also derived and it is used to compare to the results obtained for the proposed scheme under different levels of quantization. Simulations are performed over quasi-static flat Rayleigh fading channels for different closed-loop codebook-based schemes with four transmit antennas and unitary transmission rate. Results illustrate that the proposed scheme achieves full diversity order and outperforms other good schemes in terms of array gain.

  • 102.
    Viet Thuy, Vu
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Wavelength-resolution SAR Incoherent ChangeDetection Based on Image Stack2017In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 14, no 7, p. 1012-1016Article in journal (Refereed)
    Abstract [en]

    This letter presents a wavelength-resolution syn-thetic aperture radar incoherentchange detection method basedon image stack, i.e., there are more than one reference or/andsurveillance image. Considering image stack in statistical hypoth-esis test for change detection is expected to result into a simplemathematical expression for implementation and provide betterchange detection results. As presented in this letter, a statisticalhypothesis test is developed on bivariate Gaussian distributionfor an image stack of two reference images and one surveillanceimage. The requirement for the image stack is three imagesassociated with three measurements with no change between twoof them. A detection method with simple processing scheme isproposed. The method is experimented with 24 CARABAS datasets. The results indicate that high average detection probability,e.g., 96%, with very low false alarm rate, e.g., only 0.19/km2,is obtained with the proposal.

  • 103.
    Viet Thuy, Vu
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Mats, Pettersson
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Thomas, Sjögren
    Swedish Defence Research Agency.
    Monostatic pursuit mode for SAR GMTI based on change detection methods2016Conference paper (Refereed)
  • 104.
    Vu, Viet T.
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Machado, Renato
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Pettersson, Mats I.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Dammert, Patrik
    Saab Elect Defense Syst, S-41289 Gothenburg, Sweden..
    Hellsten, Hans
    Saab Elect Defense Syst, S-41289 Gothenburg, Sweden..
    SAR image statistics and adaptive signal processing for change detection2015In: ALGORITHMS FOR SYNTHETIC APERTURE RADAR IMAGERY XXII, 2015, article id 947509Conference paper (Refereed)
    Abstract [en]

    The paper presents investigations on SAR image statistics and adaptive signal processing for change detection. The investigations show that the amplitude distributions of SAR images with possibly detected changes, that is retrieved with a linear subtraction operator, can approximately be represented by the probability density function of the Gaussian or normal distribution. This allows emerging the idea to use the available adaptive signal processing techniques for change detection. The experiments indicate the promising change detection results obtained with an adaptive line enhancer, one of the adaptive signal processing technique. The experiments are conducted on the data collected by CARABAS, a UWB low frequency SAR system.

  • 105.
    Vu, Viet Thuy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Local Detection of Moving Targets in SAR Image Based on NRS Hypotheses2018In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 56, no 10, p. 6101-6110Article in journal (Refereed)
    Abstract [en]

    Ground moving target indication (GMTI) is one of the important applications of synthetic aperture radar (SAR). This paper introduces a GMTI method for local detection of the ground moving targets in SAR image based on normalized relative speed (NRS) hypotheses. The input of the GMTI method is a complex SAR image where areas of interest for GMTI are locally selected. The output of the method includes the detected targets, the NRSs with respect to the SAR platform, the locations where the detected targets are focused, and the SAR images of the detected targets. The mathematical background of the GMTI method is presented in detail. The method is validated with the data delivered by the Coherent All-Radio Band Sensor, an airborne ultrawideband-ultrawidebeam low-frequency SAR system. The shortcomings of the introduced method are investigated and followed with the solutions. IEEE

  • 106.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Gomes, Natanael Rodrigues
    Universidade Federal de Santa Maria, BRA.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Dämmert, Patrik
    Saab Surveillance, SWE.
    Hellsten, Hans
    Saab Surveillance, SWE.
    Bivariate Gamma Distribution for Wavelength-Resolution SAR Change Detection2019In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 57, no 1, p. 473-481Article in journal (Refereed)
    Abstract [en]

    A gamma probability density function (pdf) is shown to be an alternative to model the distribution of the magnitudes of high-resolution, i.e., wavelength-resolution, synthetic aperture radar (SAR) images. As investigated in this paper, it is more appropriate and more realistic statistical in comparison with, e.g., Rayleigh. A bivariate gamma pdf is considered for developing a statistical hypothesis test for wavelength-resolution incoherent SAR change detection. The practical issues in implementation of statistical hypothesis test, such as assumptions on target magnitudes, estimations for scale and shape parameters, and implementation of modified Bessel function, are addressed. This paper also proposes a simple processing scheme for incoherent change detection to validate the proposed statistical hypothesis test. The proposal was experimented with 24 CARABAS data sets. With an average detection probability of 96%, the false alarm rate is only 0.47 per square kilometer. IEEE

  • 107.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Nehru, Dheeraj
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    SAR Resolution Enhancement with Circular Aperture in Theory and Empirical Scenario2014Conference paper (Refereed)
    Abstract [en]

    SAR systems synthesizing circular apertures have been shown to result in better spatial resolutions than the ones synthesizing linear apertures. The paper presents an investigation about the enhancement of SAR spatial resolutions with the use of circular aperture. A comparison between the spatial resolutions obtained with a SAR system synthesizing a circular aperture and with the same SAR system synthesizing a linear aperture is therefore carried out. The studying results are verified by the experimental SAR data set provided by the experimental ground-based SAR system of Blekinge Institute of Technology (BTH GB-SAR).

  • 108.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Derivation of Bistatic SAR Resolution Equations Based on Backprojection2018In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 15, no 5, p. 694-698Article in journal (Refereed)
    Abstract [en]

    This letter introduces ground-range and cross-range resolution equations for the side-looking bistatic synthetic aperture radar (SAR). The derivation is based on the backprojection integral and the method of stationary phase. The ground-range and cross-range resolution equations are provided in closed form, making them easy for calculation. They are, therefore, helpful for bistatic SAR system development. The derived ground-range and cross-range resolution equations are validated with the bistatic data simulated mainly using the parameters of the LORA system. IEEE

  • 109.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Doppler and Cross-range Resolutions in Bistatic Forward-looking SAR Imaging2015In: 2015 IEEE INTERNATIONAL RADAR CONFERENCE (RADARCON), IEEE Computer Society, 2015, p. 72-76Conference paper (Refereed)
    Abstract [en]

    Left/right ambiguity and low Doppler resolution are severe problems for monostatic forward-looking SAR imaging. Among approaches for the problems, using bistatic SAR is very promising. The left/right ambiguity in bistatic forwardlooking SAR has been investigated in detail recently whereas an appropriate study for enhancing bistatic forward-looking SAR Doppler resolution is still desired. A research on Doppler resolution and then cross-range resolution in bistatic forward-looking SAR is therefore presented in this paper. The research is based on the use of the gradient. Several recommendations which allow maximizing Doppler resolution and cross-range in bistatic forward-looking SAR imaging are provided.

  • 110.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Fast Backprojection Algorithms Based on Subapertures and Local Polar Coordinates for General Bistatic Airborne SAR Systems2016In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 54, no 5, p. 2706-2712Article in journal (Refereed)
    Abstract [en]

    This paper introduces a bistatic fast backprojection synthetic aperture radar (SAR) algorithm that is available for different bistatic geometries. The proposed algorithm is tested with the bistatic CARABAS-like data, and the results indicate that the algorithm is a good candidate for bistatic SAR data processing. The image quality measurements are quite similar to the referenced values obtained with the bistatic global backprojection algorithm. That is, the peak sidelobe ratio (PSLR) is -13.7 dB in comparison to the referenced PSLR of -13.8 dB. The half-power beamwidths (HPBWs) measured on the cuts in x and y and the direction where the peak sidelobes locate are 2.8, 3.7, and 3.5 m, respectively, which are approximate to the referenced HPBWs. The small differences in the measured results mainly come from the interpolation step of the algorithm.

  • 111.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Ground Moving Target Detection and Estimation By Using Dual Speed SAR Platform2014Conference paper (Refereed)
    Abstract [en]

    The paper proposes a ground moving target detection and estimation method aiming at Ultra Wide Band and -Beam (UWB) Synthetic Aperture Radar (SAR) systems. The method is developed on the moving target detection by focusing technique and requires a SAR system flying with two different speeds during the integration time. The method allows us to detect ground moving target, even hidden by clutter, and to estimate the target parameters, i.e. speed and direction of motion. The accuracy of the estimations depends strongly on the computational cost and can therefore be controlled. The proposal is tested with the simulated CARABAS data.

  • 112.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Nyquist Sampling Requirements for Polar Grids in Bistatic Time-Domain Algorithms2015In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, no 2, p. 457-465Article in journal (Refereed)
    Abstract [en]

    The paper presents a derivation of Nyquist sampling requirements for the polar grids in some bistatic time-domain algorithms. The derivation is based on an airborne bistatic system with general bistatic geometry. The Nyquist sampling requirements are shown to be the functions of operating radar frequency, transmitter and receiver subaperture lengths, and bistatic geometry. How to decide the Nyquist sampling requirements for different bistatic geometries and the relationship between the Nyquist sampling requirements in the monostatic and bistatic cases are also addressed in the paper. The derived Nyquist sampling requirements is examined with the bistatic CARABAS-II like data.

  • 113.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    On Bistatic Forward-looking SAR Imaging2014Conference paper (Refereed)
    Abstract [en]

    Left/right ambiguity and low angular (azimuth) resolution are severe problems for monostatic forward-looking SAR imaging. It is strongly believed that these technical issues can definitely be solved with bistatic forward-looking SAR. The analysis presented in this paper points out that the left/right ambiguity problem still exits. However, an appropriate selection of the position of bistatic base line and antenna beamwidth allows us to conceal it. The paper also gives some recommendations which can be considred for the forward-looking SAR imaging.

  • 114.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Range migration algorithm for bistatic SAR2018In: IEEE Radar Conference, (RadarConf 2018), Institute of Electrical and Electronics Engineers Inc. , 2018, p. 665-669Conference paper (Refereed)
    Abstract [en]

    The paper introduces a Range Migration algorithm for bistatic SAR data processing. The algorithm is developed on the available function representing the two-dimension Fourier transform of the bistatic SAR data and relationship between radar signal frequency and wave-numbers for bistatic SAR or the ω - k relationship. The algorithm is tested with the simulations using different SAR geometries for validation. Some inherit limits of the developed Range Migration algorithm and the possible solutions are also discussed in the paper. © 2018 IEEE.

  • 115.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Björklund, Svante
    A method to implement SAR slow-time stap in beamforming stage of fast backprojection algorithm2014Conference paper (Refereed)
    Abstract [en]

    This paper presents a method to implement SAR slow-time space time adaptive processing (STAP) in the beamforming stage of the fast backprojection algorithm. This method is different from the recently published method where the SAR fast-time STAP is implemented after the beamforming stage for detection and then imaging. As a common SAR STAP method, the method proposed in this paper can be used for ground moving target indication (GMTI) and reconstruction of the image of the detected moving targets. The paper also presents some simulation results in order to illustrate the proposed method.

  • 116.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Dämmert, Patrik
    SAAB Surveillance, SWE.
    Hellsten, Hans
    SAAB Surveillance, SWE.
    Two-Dimensional Data Conversion for One-Dimensional Adaptive Noise Canceler in Low Frequency SAR Change Detection2018In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 54, no 5, p. 2611-2618Article in journal (Refereed)
    Abstract [en]

    One-dimensional (1-D) adaptive noise canceler (ANC) has been used for false alarm reduction in low frequency SAR change detection. The paper presents possibilities to process two-dimensional (2-D) data by an 1-D ANC. Beside concatenating the rows of 2-D data in a matrix form to convert it to 1-D data in a vector form, two conversion approaches are considered: concatenating the columns of 2-D data and local concatenation, i.e., the conversion to 1-D is performed locally on each block of the 2-D data. A ground object can occupy more than one row and/or more than one column of 2-D data. In addition, the properties in cross-range and range of an image are not the same. Thus, different conversion approaches may lead to different performance of an 1-D ANC and hence different change detection results. Among the considered approaches, the local concatenating approach is shown to provide slightly better performance in terms of probability of detection and false alarm rate. IEEE

  • 117.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Gomes, Natanael
    Universidade Federal de Santa Maria, BRA.
    Dammert, Patrik
    Saab Electronic Defense Systems, SWE.
    Hellsten, Hans
    Saab Electronic Defense Systems, SWE.
    Wavelength-resolution SAR change detection with constant false alarm rate2017In: 2017 IEEE Radar Conference, RadarConf 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 1504-1508Conference paper (Refereed)
    Abstract [en]

    The paper introduces an incoherent change detection algorithm with constant false alarm rate (CFAR). The algorithm is based on a CFAR detector that preceded with an adaptive noise smoothing filter while the input of the filter is preliminary changes retrieved from a subtraction of surveillance SAR image to reference SAR image. The algorithm is tested with 24 data sets provided by CARABAS. The average probability of detection calculated for 1200 deployed vehicles is up to 96% while the false alarm rate calculated for an area of 288 square kilometers is only 0.15 per square kilometer. In our test, the algorithm did not require a longer processing time than other wavelength-resolution SAR change detection algorithms. Based on these evaluations, the introduced algorithm is seen to be effective. © 2017 IEEE.

  • 118.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Machado, Renato
    Federal University of Santa Maria, BRA.
    Dammert, Patrik
    Saab Electronic Defense Systems, SWE.
    Hellsten, Hans
    Saab Electronic Defense Systems, SWE.
    False Alarm Reduction in Wavelength-Resolution SAR Change Detection Using Adaptive Noise Canceler2017In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 55, no 1, p. 591-599Article in journal (Refereed)
    Abstract [en]

    This paper introduces a method to reduce false alarms in wavelength-resolution synthetic aperture radar (SAR) change detection and aims at very high frequency-band systems like the Coherent All Radio Band System (CARABAS). The false alarms are usually caused by the elongated structures, such as power lines and fences, which stand out from the background. The responses of elongated structures are sensitive to flight path. The introduced method aims at minimizing the false alarms caused by the elongated structures and is based on the well-known adaptive processing mechanism, i.e., the so-called adaptive noise canceler (ANC) where a separate reference signal is required. The changes between measurements are considered by the input signal of ANC while the separate reference signal comes from the measurements without change. Hence, the method requires three SAR images associated with three measurements, with no changes between two of them. The reference data for the study are provided by CARABAS. The experimental results indicate that the method can reduce false alarms significantly and provide high probability of detection (≥98%). The experimental results also show that the method still works well even in the case where the flight tracks of the SAR system in the change detection measurements are slightly different.

  • 119.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    Swedish Defence Research Agency, Linköping, Sweden.
    Experimental results on focusing moving targets in TerraSAR-X and TanDEM-X images2016In: IEEE Radar Conference, IEEE Press, 2016, p. 874-878Conference paper (Refereed)
    Abstract [en]

    Moving targets appear in TerraSAR-X and TanDEM-X images in the form of elliptic or hyperbolic curves but they can be approximated to be lines. We present here the experimental results on refocusing moving targets directly in TerraSAR-X and TanDEM-X images. The refocusing method is developed from the Range Migration algorithm and the concept of normalized relative speed. The experimental results show that the target in TerraSAR-X and TanDEM-X images is well focused to the original shape. Motion parameters of the moving target can be further estimated thank to the pursuit mode of TerraSAR-X and TanDEM-X.

  • 120.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    Totalforsvarets forskningsinstitut, Stockholm, Sweden .
    Local detection of moving target by focusing in SAR images2016In: IEEE Radar Conference, IEEE Press, 2016, p. 827-832Conference paper (Refereed)
    Abstract [en]

    We present here a moving target detection method so-called local detection of moving target by focusing. The term local implies that the method only works with areas of interest but not whole SAR scene whereas the term focusing indicates that the method is based on the concept of relative movement. The mathematical background of the method is presented in details. The introduced method is then examined with simulated and experimental SAR data to evaluate the method as well as to show the practicality of the method. The reference SAR system for this study is CARABAS, an airborne UWB low frequency SAR system. The method shows a number of advantages in comparison to the original version.

  • 121.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    Two-Dimensional Spectrum for BiSAR Derivation Based on Lagrange Inversion Theorem2014In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 11, no 7, p. 1210-1214Article in journal (Refereed)
    Abstract [en]

    A 2-D spectrum for bistatic synthetic aperture radar is derived in this letter. The derivation is based on the commonly used mathematic principles such as themethod of stationary phase and the Fourier transform and the Lagrange inversion theorem in order to find the point of stationary phase in the method of stationary phase. Using the Lagrange inversion theorem allows minimizing the initial assumptions or the initial approximations. The derived 2-D spectrum is compared with the commonly

  • 122.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    Gustavsson, Anders
    Swedish Def Res Agcy, SWE.
    A hybrid GMTI method for reliable detec ion results in SAR images2018In: PROCEEDINGS OF 2018 2ND INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN SIGNAL PROCESSING, TELECOMMUNICATIONS & COMPUTING (SIGTELCOM 2018) / [ed] Bao, VNQ Duy, TT, IEEE , 2018, p. 73-78Conference paper (Refereed)
    Abstract [en]

    Stand-alone synthetic aperture radar (SAR) ground moving target indication (GNITI) methods have both advantages and disadvantages. This paper introduces a hybrid SAR GMTI method that is based on two well-known methods: space time adaptive processing (STAP) and moving target detection by focusing (MTDF). The input of the proposed hybrid method is two time separated complex radar images. The output is detected ground moving targets, the target normalized relative speeds (NRS), and focused images of the detected targets. In the paper, we provide the mathematical background behind the hybrid SAR GMTI method in details. We also provide some experimental results for validating the proposed method. The data for the experiments was acquired in early 2015 by TanDEMX and TerraSAR-X operating in monostatic pursuit mode. The ground scene where the measurements were conducted is around Mantorp, west of Linkoping, Sweden.

  • 123.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    Gustavsson, Anders
    Totalförsvarets forskningsinstitut, SWE.
    A hybrid GMTI method for reliable detection results in SAR images2018In: Proceedings - 2018 2nd International Conference on Recent Advances in Signal Processing, Telecommunications and Computing, SIGTELCOM 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 73-78Conference paper (Refereed)
    Abstract [en]

    Stand-alone synthetic aperture radar (SAR) ground moving target indication (GMTI) methods have both advantages and disadvantages. This paper introduces a hybrid SAR GMTI method that is based on two well-known methods: space time adaptive processing (STAP) and moving target detection by focusing (MTDF). The input of the proposed hybrid method is two time separated complex radar images. The output is detected ground moving targets, the target normalized relative speeds (NRS), and focused images of the detected targets. In the paper, we provide the mathematical background behind the hybrid SAR GMTI method in details. We also provide some experimental results for validating the proposed method. The data for the experiments was acquired in early 2015 by TanDEM-X and TerraSAR-X operating in monostatic pursuit mode. The ground scene where the measurements were conducted is around Mantorp, west of Linköping, Sweden. © 2018 IEEE.

  • 124.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Institute of Technology, School of Engineering, Department of Signal Processing. Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences. Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    thomas, Sjögren
    Swedish Defence Research Agency, SWE.
    Moving Target Focusing in SAR Image with Known Normalized Relative Speed2017In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 53, no 2, p. 854-861Article in journal (Refereed)
    Abstract [en]

    This paper presents the moving target focusing method, whichallows focusing moving targets in complex synthetic aperture radar(SAR) images without raw data. The method is developed on the rangemigration algorithm, where focusing moving target is an interpolationstep in the wave domain. The simulated results are provided in thepaper to illustrate the proposed method whereas the experimentalresults show its practicality. The method can be flexibly applied fromsmall area to the whole SAR scene.

  • 125.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sjögren, Thomas
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Dahl, Mattias
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Measurement of traffic flows with SAR: Field test on the swedish road network2017In: International Geoscience and Remote Sensing Symposium (IGARSS), Institute of Electrical and Electronics Engineers Inc. , 2017, p. 3321-3324Conference paper (Refereed)
    Abstract [en]

    This paper reports the measurement campaign Blekingetraffic that was performed by Blekinge Institute of Technology with collaboration with the partners. The measurements are part of a case study to evaluate the feasibility of spaceborne SAR for measuring traffic flow change before and after toll charge introduced in Sweden. The radar measurements were conducted around Pukavik, western of Karlshamn, Sweden in the end of 2015 and in the beginning of 2016. In this paper, the results of one of the controlled measurements performed in the first week of February 2016 is presented. In the ground scene, some trucks tracked with GPS were deployed in European route E22 and local roads. The trucks have either cabinets or food tankers resulting in different radar cross sections. The data acquisition is with TanDEM-X using two satellites giving up to 6 data channels. Since the measurements were performed at 5:00 pm there were unknown traffic i.e. trucks and cars that were not controlled. Therefore, the traffic on the roads was recorded by cameras next to the road and on a drone. The initial analysis of the measured data shows the possibilities to apply available processing techniques such as ground moving target indication and change detection to obtain the knowledge of traffic flow change. © 2017 IEEE.

  • 126.
    Wagner, Stefan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Extending characters of fixed point algebras2018In: Axioms, ISSN 2075-1680, Vol. 7, no 4, article id 79Article in journal (Refereed)
    Abstract [en]

    A dynamical system is a triple (A, G, α) consisting of a unital locally convex algebra A, a topological group G, and a group homomorphism α: G → Aut(A) that induces a continuous action of G on A. Furthermore, a unital locally convex algebra A is called a continuous inverse algebra, or CIA for short, if its group of units A× is open in A and the inversion map i: A× → A×, a → a-1 is continuous at 1A. Given a dynamical system (A, G, α) with a complete commutative CIA A and a compact group G, we show that each character of the corresponding fixed point algebra can be extended to a character of A. © 2018 by the authors.

  • 127.
    Wagner, Stefan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Secondary Characteristic Classes of Lie Algebra ExtensionsIn: Article in journal (Other academic)
    Abstract [en]

    We introduce a notion of secondary characteristic classes of Lie algebra extensions. As a spin-off of our construction we obtain a new proof of Lecomte’s generalization of the Chern–Weil homomorphism.

  • 128.
    Wagner, Stefan
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Schwieger, Kay
    iteratec GmbH, GER.
    Noncommutative Coverings of Quantum ToriIn: Mathematica Scandinavica, ISSN 0025-5521, E-ISSN 1903-1807Article in journal (Other academic)
    Abstract [en]

    We investigate a framework for coverings of noncommutative spaces. Furthermore, we study noncommutative coverings of irrational quantum tori and characterize all such coverings that are connected in a reasonable sense.

  • 129. Wiaderek, Krzysztof
    et al.
    Rutkowska, Danuta
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Color Digital Picture Recognition Based on Fuzzy Granulation Approach2014In: ARTIFICIAL INTELLIGENCE AND SOFT COMPUTING ICAISC 2014, PT I / [ed] Rutkowski, L; Korytkowski, M; Scherer, R; Tadeusiewicz, R; Zadeh, LA; Zurada, JM, Springer, 2014, Vol. 8467, p. 319-332Conference paper (Refereed)
    Abstract [en]

    The paper concerns specific problems of color digital picture recognition by use of the concept of fuzzy granulation, and in addition rough information granulation. This idea employs information granules that contain pieces of knowledge about digital pictures such as location of objects as well as their size and color. Each of those attributes is described by means of linguistic values of fuzzy sets, and the shape attribute is also considered with regard to the rough sets. The picture recognition approach is focused on retrieving a picture (or pictures) from a large collection of color digital pictures (images) - based on the linguistic description of a specific object included in the picture to be recognized.

  • 130.
    Wiaderek, Krzysztof
    et al.
    Institute of Computer and Information Sciences, POL.
    Rutkowska, Danuta
    Institute of Computer and Information Sciences, POL.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Image retrieval by use of linguistic description in databases2018In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer Verlag , 2018, Vol. 10842, p. 92-103Conference paper (Refereed)
    Abstract [en]

    In this paper, a new method of image retrieval is proposed. This concerns retrieving color digital images from a database that contains a specific linguistic description considered within the theory of fuzzy granulation and computing with words. The linguistic description is generated by use of the CIE chromaticity color model. The image retrieval is performed in different way depending on users’ knowledge about the color image. Specific database queries can be formulated for the image retrieval. © Springer International Publishing AG, part of Springer Nature 2018.

  • 131.
    Wiaderek, Krzysztof
    et al.
    Czestochowa University of Technology, POL.
    Rutkowska, Danuta
    Czestochowa University of Technology, POL.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Image Retrieval by Use of Linguistic Description in Databases2018In: Artificial Intelligence and Soft Computing, Part II / [ed] Rutkowski, L., Scherer, R., Korytkowski, M., Pedrycz, W., Tadeusiewicz, R., Zurada, J.M., Springer, 2018, Vol. 10842, p. 92-103Conference paper (Refereed)
    Abstract [en]

    In this paper, a new method of image retrieval is proposed. This concerns retrieving color digital images from a database that contains a specific linguistic description considered within the theory of fuzzy granulation and computing with words. The linguistic description is generated by use of the CIE chromaticity color model. The image retrieval is performed in different way depending on users' knowledge about the color image. Specific database queries can be formulated for the image retrieval.

  • 132.
    Wiaderek, Krzysztof
    et al.
    Czestochowa Uniwersity of Technology, Czestochowa, Poland.
    Rutkowska, Danuta
    Czestochowa University of Technology, Czestochowa, Poland.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Information Granules in Application to Image Recognition2015In: Artificial Intelligence and Soft Computing LNAI 9119: The 14th International Conference on Artificial Intelligence and Soft Computing - ICAISC 2015 / [ed] L. Rutkowski, M. Korytkowski, R. Scherer, R. Tadeusiewicz, L.A. Zadeh, J.M. Zurada, Cham Heidelberg New York Dortrecht London: Springer, 2015, Vol. I, p. 649-659Conference paper (Refereed)
    Abstract [en]

    The paper concerns specifc problems of color digital image recognition by use of the concept of fuzzy and rough granulation. This idea employs information granules that contain pieces of knowledge about digital pictures such as color, location, size, and shape of an object to be recognized. The object information granule (OIG) is introduced, and the Granular Pattern Recognition System (GPRS) proposed, in order to solve different tasks formulated with regard to the information granules.

  • 133.
    Wiaderek, Krzysztof
    et al.
    Politechnika Czestochowska, POL.
    Rutkowska, Danuta
    Politechnika Czestochowska, POL.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Linguistic description of color images generated by a granular recognition system2017In: ARTIFICIAL INTELLIGENCE AND SOFT COMPUTING, ICAISC 2017, PT I / [ed] Rutkowski, L., Korytkowski, M., Scherer, R., Tadeusiewicz, R., Zadeh, L.A., Zurada, J.M., Springer Verlag , 2017, Vol. 10245, p. 603-615Conference paper (Refereed)
    Abstract [en]

    The paper proposes a new method employed in an intelligent pattern recognition system that generates linguistic description of color digital images. The linguistic description is produced based on fuzzy rules and information granules concerning colors as most important among image attributes. With regard to the color, the CIE chromaticity color model is applied, with the concept of fuzzy color areas. The linguistic description uses information about location of color granules in input images. © Springer International Publishing AG 2017.

  • 134.
    Wiaderek, Krzysztof
    et al.
    Czestochowa University of Technology, POL.
    Rutkowska, Danuta
    Czestochowa University of Technology.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    New Algorithms for a Granular Image Recognition System2016In: Artificial Intelligence and Soft Computing LNAI 9693: Proceedings of the 15th International Conference, ICAISC 2016 / [ed] Leszek Rutkowski et al., Berlin Heidelberg: Springer, 2016, Vol. II, p. 755-766Conference paper (Refereed)
    Abstract [en]

    The paper describes new algorithms proposed for the granular pattern recognition system that retrieves an image from a collection of color digital pictures based on the knowledge contained in the object information granule (OIG). The algorithms use the granulation approach that employs fuzzy and rough granules. The information granules present knowledge concerning attributes of the object to be recognized. Different problems are considered depending on the full or partial knowledge where attributes are "color", "location", "size", and  "shape".

  • 135.
    Wiaderek, Krzysztof
    et al.
    Czestochowa University of Technology, POL.
    Rutkowska, Danuta
    University of Social Sciences, 90-113 Lodz, POL.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Parallel Processing of Color Digital Images for Linguistic Description of Their Content2018In: PARALLEL PROCESSING AND APPLIED MATHEMATICS (PPAM 2017), PT I: Proceedings of the 12th International Conference, PPAM 2017 / [ed] Roman Wyrzykowski, Jack J. Dongarra, Ewa Deelman, Konrad Karczewski, Springer, 2018, Vol. I, p. 544-554Conference paper (Refereed)
    Abstract [en]

    This paper presents different aspects of parallelization of a problem of processing color digital images in order to generate linguistic description of their content. A parallel architecture of an intelligent image recognition system is proposed. Fuzzy classifcation and inference is performed in parallel, based on the CIE chromaticity color model and granulation approach. In addition, the parallelization concerns, e.g., processing a large collection of images or parts of a single image.

  • 136.
    Zalasinski, Marcin
    et al.
    Czestochowa University of Technology, POL.
    Cpalka, Krzysztof
    Czestochowa University of Technology, POL.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    An Idea of the Dynamic Signature Verification Based on a Hybrid Approach2016In: Artificial Intelligence and Soft Computing LNAI 9693: Proceedings of the 15th International Conference, ICAISC 2016 / [ed] Leszek Rutkowski et al., Berlin Heidelberg: Springer, 2016, Vol. II, p. 232-246Conference paper (Refereed)
    Abstract [en]

    Dynamic signature verification is a very interesting biometric issue. It is difficult to realize because signatures of the user are characterized by relatively high intra-class and low inter-class variability. However, this method of an identity verification is commonly socially acceptable.

    It is a big advantage of the dynamic signature biometric attribute. In this paper, we propose a new hybrid algorithm for the dynamic signature verification based on global and regional approach. We present the simulation results of the proposed method for BioSecure DS2 database, distributed by the BioSecure Association.

  • 137.
    Zettervall, Hang
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Fuzzy Set Theory Applied to Make Medical Prognoses for Cancer Patients2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    As we all know the classical set theory has a deep-rooted influence in the traditional mathematics. According to the two-valued logic, an element can belong to a set or cannot. In the former case, the element’s membership degree will be assigned to one, whereas in the latter case it takes the zero value. With other words, a feeling of imprecision or fuzziness in the two-valued logic does not exist. With the rapid development of science and technology, more and more scientists have gradually come to realize the vital importance of the multi-valued logic. Thus, in 1965, Professor Lotfi A. Zadeh from Berkeley University put forward the concept of a fuzzy set. In less than 60 years, people became more and more familiar with fuzzy set theory. The theory of fuzzy sets has been turned to be a favor applied to many fields. The study aims to apply some classical and extensional methods of fuzzy set theory in life expectancy and treatment prognoses for cancer patients. The research is based on real-life problems encountered in clinical works by physicians. From the introductory items of the fuzzy set theory to the medical applications, a collection of detailed analysis of fuzzy set theory and its extensions are presented in the thesis. Concretely speaking, the Mamdani fuzzy control systems and the Sugeno controller have been applied to predict the survival length of gastric cancer patients. In order to keep the gastric cancer patients, already examined, away from the unnecessary suffering from surgical operation, the fuzzy c-means clustering analysis has been adopted to investigate the possibilities for operation contra to nonoperation. Furthermore, the approach of point set approximation has been adopted to estimate the operation possibilities against to nonoperation for an arbitrary gastric cancer patient. In addition, in the domain of multi-expert decision-making, the probabilistic model, the model of 2-tuple linguistic representations and the hesitant fuzzy linguistic term sets (HFLTS) have been utilized to select the most consensual treatment scheme(s) for two separate prostate cancer patients. The obtained results have supplied the physicians with reliable and helpful information. Therefore, the research work can be seen as the mathematical complements to the physicians’ queries.

  • 138.
    Zettervall, Hang
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Rakus-Andersson, Elisabeth
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Frey, Janusz
    Making Medication Prognoses for Prostate Cancer Patients by the Application of Linguistic Approaches2013In: International Journal On Advances in Life Sciences, ISSN 1942-2660, E-ISSN 1942-2660, Vol. 5, no 3&4, p. 147-159Article in journal (Refereed)
    Abstract [en]

    Apart from the probabilistic model and the model of 2-tuple linguistic representations, a new extension of the fuzzy set, known as the hesitant fuzzy linguistic term set can be seen as the third representative of linguistic approaches. In this paper, we focus on multi-expert decision-making problems, in which a group of physicians are independently asked for assessing the effectiveness of a set of treatment therapies. Our goal is to rank the effectiveness of treatment modalities from the most recommended to the contraindicated. Two individual prostate cancer patients have been taken into account in the practical studies. For the first patient, the probabilistic model and the model of 2-tuple linguistic representations have been adopted to accomplish the medical application. Whereas, for the second patient, the approach of hesitant fuzzy linguistic term set has been used to make the medication prognoses. Moreover, the continuous fuzzy numbers in the Left-Right representations are used to mathematically express the experts’ judgments and s-parametric membership functions are designed to represent the fuzzy linguistic terms.

  • 139.
    Öinert, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Inst Technol, Dept Math & Nat Sci, S-37179 Karlskrona, Sweden..
    Bimodules in Group Graded Rings2017In: Algebras and Representation Theory, ISSN 1386-923X, E-ISSN 1572-9079, Vol. 20, no 6, p. 1483-1494Article in journal (Refereed)
    Abstract [en]

    In this article we introduce the notion of a controlled group graded ring. Let G be a group, with identity element e, and let R = aS center dot (gaG) R (g) be a unital G-graded ring. We say that R is G-controlled if there is a one-to-one correspondence between subsets of the group G and (mutually non-isomorphic) R (e) -sub-bimodules of R, given by G aSc Ha dagger broken vertical bar aS center dot (haH) R (h) . For strongly G-graded rings, the property of being G-controlled is stronger than that of being simple. We provide necessary and sufficient conditions for a general G-graded ring to be G-controlled. We also give a characterization of strongly G-graded rings which are G-controlled. As an application of our main results we give a description of all intermediate subrings T with R (e) aS dagger T aS dagger R of a G-controlled strongly G-graded ring R. Our results generalize results for artinian skew group rings which were shown by Azumaya 70 years ago. In the special case of skew group rings we obtain an algebraic analogue of a recent result by Cameron and Smith on bimodules in crossed products of von Neumann algebras.

123 101 - 139 of 139
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf