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  • 1.
    Adbo, Karina
    et al.
    Malmö University.
    Åkesson Nilsson, Gunilla
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Moving beyond the language–Visualizing chemical concepts through one’s own creative expression2022In: Frontiers in Education, E-ISSN 2504-284X, Vol. 7, article id 1034140Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to explore university students’ interpretations of chemical content in the form of physical constructions of atomic nuclei. Playdough was chosen as the means for expression, since it provided the students with the task of choosing the number, form, size, shape, and distance of particles. Data was collected in the form of photographs, written explanations as well as ad hoc notes. Data from 64 students was analyzed using the three levels of analysis as presented by Hedegaard and framed within the theories of models. Results show that students’ choices gave rise to 34 variations of the atomic nuclei. The analysis provided two different categories: models with close resemblance to the teaching model and models with less resemblance to the teaching model. Results show the limitations of verbal and written communication and add to the discussion concerning students’ interpretations of the multitude of atomic models used in teaching. The method was indeed a beneficial tool both for students, who could explore the composition of atomic nuclei and isotopes, and for teachers, who could connect their teaching to students’ interpretations of scientific content since the method brings a new level of detail to discussions. Copyright © 2022 Adbo and AAkesson-Nilsson.

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  • 2.
    Aeddula, Omsri
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Gertsovich, Irina
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Image-Based Localization System2020In: Proceedings of the 8th ICIECE 2019, Springer , 2020, Vol. 107, p. 535-541Conference paper (Refereed)
    Abstract [en]

    The position of a vehicle is essential for navigation of the vehicle along the desired path without a human interference. A good positioning system should have both good positioning accuracy and reliability. Global Positioning System (GPS) employed for navigation in a vehicle may lose significant power due to signal attenuation caused by construction buildings or other obstacles. In this paper, a novel real-time indoor positioning system using a static camera is presented. The proposed positioning system exploits gradient information evaluated on the camera video stream to recognize the contours of the vehicle. Subsequently, the mass center of the vehicle contour is used for simultaneous localization of the vehicle. This solution minimizes the design and computational complexity of the positioning system. The experimental evaluation of the proposed approach has demonstrated the positioned accuracy of 92.26%. © Springer Nature Singapore Pte Ltd. 2020.

  • 3.
    Ahmed, Soban
    et al.
    Natl Univ Comp & Emerging Sci, PAK.
    Bhatti, Muhammad Tahir
    Natl Univ Comp & Emerging Sci, PAK.
    Khan, Muhammad Gufran
    Natl Univ Comp & Emerging Sci, PAK.
    Lövström, Benny
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Shahid, Muhammad
    Natl Univ Comp & Emerging Sci, PAK.
    Development and Optimization of Deep Learning Models for Weapon Detection in Surveillance Videos2022In: Applied Sciences, E-ISSN 2076-3417, Vol. 12, no 12, article id 5772Article in journal (Refereed)
    Abstract [en]

    Featured Application This work has applied computer vision and deep learning technology to develop a real-time weapon detector system and tested it on different computing devices for large-scale deployment. Weapon detection in CCTV camera surveillance videos is a challenging task and its importance is increasing because of the availability and easy access of weapons in the market. This becomes a big problem when weapons go into the wrong hands and are often misused. Advances in computer vision and object detection are enabling us to detect weapons in live videos without human intervention and, in turn, intelligent decisions can be made to protect people from dangerous situations. In this article, we have developed and presented an improved real-time weapon detection system that shows a higher mean average precision (mAP) score and better inference time performance compared to the previously proposed approaches in the literature. Using a custom weapons dataset, we implemented a state-of-the-art Scaled-YOLOv4 model that resulted in a 92.1 mAP score and frames per second (FPS) of 85.7 on a high-performance GPU (RTX 2080TI). Furthermore, to achieve the benefits of lower latency, higher throughput, and improved privacy, we optimized our model for implementation on a popular edge-computing device (Jetson Nano GPU) with the TensorRT network optimizer. We have also performed a comparative analysis of the previous weapon detector with our presented model using different CPU and GPU machines that fulfill the purpose of this work, making the selection of model and computing device easier for the users for deployment in a real-time scenario. The analysis shows that our presented models result in improved mAP scores on high-performance GPUs (such as RTX 2080TI), as well as on low-cost edge computing GPUs (such as Jetson Nano) for weapon detection in live CCTV camera surveillance videos.

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  • 4. Alaves, Dimas
    et al.
    Machado, Renato
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    da Costa, Daniel Benevides
    Legg, Andrei Piccinini
    Uchoa-Filho, Bartolomeu F.
    A dynamic hybrid antenna/relay selection scheme for the multiple-access relay channel2014In: 2014 11TH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS (ISWCS), IEEE , 2014, p. 594-599Conference paper (Refereed)
    Abstract [en]

    We propose a dynamic hybrid antenna/relay selection scheme for multiple-access relay systems. The proposed scheme aims to boost the system throughput while keeping a good error performance. By using the channel state information, the destination node performs a dynamic selection between the signals provided by the multi-antenna relay, located in the inter-cell region, and the relay nodes geographically distributed over the cells. The multi-antenna relay and the single-antenna relay nodes employ the decode-remodulate-and-forward and amplify-and-forward protocols, respectively. Results reveal that the proposed scheme offers a good tradeoff between spectral efficiency and diversity gain, which is one of the main requirements for the next generation of wireless communications systems.

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  • 5. Alves, Dimas I.
    et al.
    Machado, Renato
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Legg, Andrei P.
    Uchoa-Filho, Bartolomeu F.
    Cooperative multiple-access scheme with antenna selection and incremental relaying2014In: 2014 INTERNATIONAL TELECOMMUNICATIONS SYMPOSIUM (ITS), São Paulo: IEEE , 2014Conference paper (Refereed)
    Abstract [en]

    A cooperative multiple-access scheme for wireless communications systems with antenna selection and incremental relaying is proposed. The scheme aims to improve the system throughput while preserving good performance in terms of bit error rate. The system consists of N nodes which send their information to both the destination node and the multiple-antenna relay station. Based on the channel state information, the destination node decides whether or not relaying will be performed. When the relaying is performed, the decode-remodulate-and-forward protocol is used with the best antenna. Results reveal that the proposed scheme achieves a good tradeoff between throughput and bit error rate, which makes suitable to be considered for multi-user networks.

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  • 6.
    Alves, Dimas I
    et al.
    Fed Univ Pampa UNIPAMPA, Brasil.
    Muller, Christian
    Fed Univ Pampa UNIPAMPA, Brasil.
    Palm, Bruna
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Vu, Viet Thuy
    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
    Aeronaut Inst Technol ITA, Brasil.
    Bartolomeu F, Uchôa-Filho
    Fed Univ Santa Catarina UFSC, Brasil.
    Statistical Analysis for Wavelength-Resolution SARImage Stacks: New Case Studies2020In: XXXVIII SIMPÓSIO BRASILEIRO DE TELECOMUNICAÇÕES E PROCESSAMENTO DE SINAIS, 2020Conference paper (Refereed)
    Abstract [en]

    This paper presents new case studies for thestatistical analysis for wavelength resolution SAR image stacks.The statistical analysis considers the Anderson-Darling goodnessof-fit test in a set of pixel samples from the same position obtainedfrom a SAR image stack. The test is applied in wavelengthresolution SAR image stacks. The present work consists of twocase studies based on the use of multiple-pass stacks and TypeI error using the False Discovery Rate controlling procedures.In addition, an application scenario is presented for the studiedscenarios.

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  • 7.
    Alves, Dimas, I
    et al.
    Fed Univ Pampa UNIPAMPA, BRA.
    Muller, Cristian
    Fed Univ Pampa UNIPAMPA, BRA.
    Vu, Viet Thuy
    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.
    de Jesus, Pablo Kunz
    Aeronaut Inst Technol ITA, BRA.
    Machado, Renato
    Aeronaut Inst Technol ITA, BRA.
    Uchoa-Filho, Bartolomeu E.
    Fed Univ Santa Catarina UFSC, BRA.
    Incoherent Change Detection Methods for Wavelength-Resolution SAR Image Stacks Based on Masking Techniques2020In: 2020 IEEE National Radar Conference - Proceedings, IEEE , 2020, article id 9266431Conference paper (Refereed)
    Abstract [en]

    This paper presents two incoherent change detection methods for wavelength-resolution synthetic aperture radars (SAR) image stacks based on masking techniques. The first technique proposed is the Simple Masking Detection (SMD). This method uses the statistical behavior of pixels-sets in the image stack to create a binary mask, which is used to remove pixels that are not related to changes in a surveillance image from the same interest region. The second technique is the Multiple Concatenated Masking Detection (MCMD), which produces a more selective mask than the SMD by concatenating multiple masks from different image stacks. The MCMD can be used in specific applications where multiple stacks share common patterns of target deployments. Both proposed techniques were evaluated using 24 incoherent SAR images obtained by the CARABAS II system. The experimental results revealed that the proposed detection methods have better performance in terms of probability of detection and false alarm rate when compared with other change detection techniques, especially for high detection probabilities scenarios.

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  • 8.
    Alves, Dimas I.
    et al.
    Federal University of PAMPA (UNIPAMPA), BRA.
    Muller, Crístian
    Federal University of PAMPA (UNIPAMPA), BRA.
    Palm, Bruna G.
    Aeronautics Institute of Technology (ITA), BRA.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Vu, Viet Thuy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Machado, Renato
    Aeronautics Institute of Technology (ITA), BRA.
    Uchoa-Filho, Bartolomeu F.
    Federal University of Santa Catarina (UFSC), BRA.
    Dammert, Patrik
    Saab Surveillance, Saab AB, SWE.
    Hellsten, Hans
    Saab Surveillance, Saab AB, SWE.
    Neyman-Pearson Criterion-Based Change Detection Methods for Wavelength-Resolution SAR Image Stacks2022In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 19Article in journal (Refereed)
    Abstract [en]

    This letter presents two new change detection (CD) methods for synthetic aperture radar (SAR) image stacks based on the Neyman-Pearson criterion. The first proposed method uses the data from wavelength-resolution images stack to obtain background statistics, which are used in a hypothesis test to detect changes in a surveillance image. The second method considers a priori information about the targets to obtain the target statistics, which are used together with the previously obtained background statistics, to perform a hypothesis test to detect changes in a surveillance image. A straightforward processing scheme is presented to test the proposed CD methods. To assess the performance of both proposed methods, we considered the coherent all radio band sensing (CARABAS)-II SAR images. In particular, to obtain the temporal background statistics required by the derived methods, we used stacks with six images. The experimental results show that the proposed techniques provide a competitive performance in terms of probability of detection and false alarm rate compared with other CD methods. CCBY

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  • 9.
    Alves, Dimas I
    et al.
    Fed Univ Pampa UNIPAMPA, BRA.
    Palm, Bruna
    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.
    Vu, Viet Thuy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Machado, Renato
    Aeronaut Inst Technol ITA, BRA.
    Uchoa-Filho, Bartolomeu F.
    Fed Univ Santa Catarina UFSC, BRA.
    Dammert, Patrik
    Saab Elect Def Syst, SWE.
    Hellsten, Hans
    Saab Elect Def Syst, SWE.
    A Statistical Analysis for Wavelength-Resolution SAR Image Stacks2020In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 17, no 2, p. 227-231Article in journal (Refereed)
    Abstract [en]

    This letter presents a clutter statistical analysis for stacks of wavelength-resolution synthetic aperture radar (SAR) images. Each image stack consists of SAR images generated by the same sensor, using the same flight track illuminating the same scene but with a time separation between the illuminations. We test three candidate statistical distributions for time changes in the stack, namely, Rician, Rayleigh, and log-normal. The tests results reveal that the Rician distribution is a very good candidate for modeling stack of wavelength-resolution SAR images, where 98.59 & x0025; of the tested samples passed the Anderson-Darling (AD) goodness-of-fit test. Also, it is observed that the presence of changes in the ground scene is related to the tested samples that have failed in the AD test for the Rician distribution hypothesis.

  • 10.
    Alves, Dimas Irion
    et al.
    Fed Univ Pampa, BRA.
    Palm, Bruna Gregory
    Aeronaut Inst Technol, BRA.
    Hellsten, Hans
    Saab AB, SWE.
    Vu, Viet Thuy
    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. Blekinge Inst Technol, Karlskrona 37179, Sweden..
    Machado, Renato
    Aeronaut Inst Technol, Sao Jose Dos Campos 12228900, SP, Brazil..
    Uchoa-Filho, Bartolomeu F.
    Univ Fed Santa Catarina, Florianopolis 88040900, SC, Brazil..
    Dammert, Patrik
    Saab AB, Saab Surveillance, Gothenburg 41289, Sweden..
    Wavelength-Resolution SAR Change Detection Using Bayes' Theorem2020In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, ISSN 1939-1404, E-ISSN 2151-1535, Vol. 13, p. 5560-5568Article in journal (Refereed)
    Abstract [en]

    This article presents Bayes' theorem for wavelength-resolution synthetic aperture radar (SAR) change detection method development. Different change detection methods can be derived using Bayes' theorem in combination with the target model, clutter-plus-noise model, iterative implementation, and noniterative implementation. As an example of the Bayes' theorem use for wavelength-resolution SAR change detection method development, we propose a simple change detection method with a clutter-plus-noise model and noniterative implementation. In spite of simplicity, the proposed method provides a very competitive performance in terms of probability of detection and false alarm rate. The best result was a probability of detection of $\text{98.7}\%$ versus a false alarm rate of one per square kilometer.

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  • 11.
    Alves, Dimas irion
    et al.
    Aeronautics Institute of Technology (ITA), Brazil.
    Palm, Bruna
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Hellsten, Hans
    Halmstad University.
    Machado, Renato
    Aeronautics Institute of Technology (ITA), Brazil.
    Vu, Viet Thuy
    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.
    Dammert, Patrik
    Saab Surveillance, Saab AB, Gothenburg.
    Change Detection Method for Wavelength-Resolution SAR Images Based on Bayes’ Theorem: An Iterative Approach2023In: IEEE Access, E-ISSN 2169-3536, Vol. 11, p. 84734-84743Article in journal (Refereed)
    Abstract [en]

    This paper presents an iterative change detection (CD) method based on Bayes’ theorem for very high-frequency (VHF) ultra-wideband (UWB) SAR images considering commonly used clutter-plus-noise statistical models. The proposed detection technique uses the information of the detected changes to iteratively update the data and distribution information, obtaining more accurate clutter-plus-noise statistics resulting in false alarm reduction. The Bivariate Rayleigh and Bivariate Gaussian distributions are investigated as candidates to model the clutter-plus-noise, and the Anderson-Darling goodness-of-fit test is used to investigate three scenarios of interest. Different aspects related to the distributions are discussed, the observed mismatches are analyzed, and the impact of the distribution chosen for the proposed iterative change detection method is analyzed. Finally, the proposed iterative method performance is assessed in terms of the probability of detection and false alarm rate and compared with other competitive solutions. The experimental evaluation uses data from real measurements obtained using the CARABAS II SAR system. Results show that the proposed iterative CD algorithm performs better than the other methods. Author

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  • 12.
    Alves, Gustavo R.
    et al.
    Polytechnic of Porto, Portugal.
    Fidalgo, André V.
    Polytechnic of Porto, Portugal.
    Marques, Maria A.
    Polytechnic of Porto, Portugal.
    Viegas, Maria C.
    Polytechnic of Porto, Portugal.
    Felgueiras, Manuel C.
    Polytechnic of Porto, Portugal.
    Costa, Ricardo J.
    Polytechnic of Porto, Portugal.
    Lima, Natércia
    Polytechnic of Porto, Portugal.
    Castro, Manuel
    National Distance Education University, Spain.
    Díaz-Orueta, Gabriel
    National Distance Education University, Spain.
    SanCristóbal-Ruiz, Elio
    National Distance Education University, Spain.
    García-Loro, Felix
    National Distance Education University, Spain.
    García-Zubía, Javier
    University of Deusto, Spain.
    Hernández-Jayo, Unai
    University of Deusto, Spain.
    Kulesza, Wlodek
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Nilsson, Kristian
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Zackrisson, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Pester, Andreas
    Carinthia University of Applied Sciences, Austria.
    Zutin, Danilo G.
    Carinthia University of Applied Sciences, Austria.
    Schlichting, Luis C.
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    Ferreira, Golberi
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    de Bona, Daniel D.
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    Pacheco, Fernando S.
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    da Silva, Juarez B.
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    Alves, João B.
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    Biléssimo, Simone
    Federal Institute of Education, Science and Technology of Santa Catarina, Brazil.
    Pavani, Ana M.
    Pontifical Catholic University of Rio de Janeiro, Brazil.
    Lima, Delberis A.
    Pontifical Catholic University of Rio de Janeiro, Brazil.
    Temporão, Guilherme
    Pontifical Catholic University of Rio de Janeiro, Brazil.
    Marchisio, Susana
    National University of Rosario, Argentina.
    Concari, Sonia B.
    National University of Rosario, Argentina.
    Lerro, Federico
    National University of Rosario, Argentina.
    de Arregui, Gaston S.
    National University of Rosario, Argentina.
    Merendino, Claudio
    National University of Rosario, Argentina.
    Plano, Miguel
    National University of Rosario, Argentina.
    Fernández, Rubén A.
    National University of Santiago del Estero, Argentina.
    Paz, Héctor R.
    National University of Santiago del Estero, Argentina.
    Soria, Mario F.
    National University of Santiago del Estero, Argentina.
    Gómez, Mario J.
    National University of Santiago del Estero, Argentina.
    de Almeida, Nival N.
    Brazilian Association of Engineering Education, Brazil.
    de Oliveira, Vanderli F.
    Brazilian Association of Engineering Education, Brazil.
    Pozzo, María I.
    Research Institute of Rosario in Educational Sciences, Argentina.
    Dobboletta, Elsa
    Research Institute of Rosario in Educational Sciences, Argentina.
    Bertramo, Brenda
    Research Institute of Rosario in Educational Sciences, Argentina.
    International Cooperation for Remote Laboratory Use2018In: Contributions to Higher Engineering Education / [ed] Maria M. Nascimento, Gustavo R. Alves, Eva Virgínia Araújo Morais, Springer, 2018, p. 1-31Chapter in book (Refereed)
    Abstract [en]

    Experimenting is fundamental to the training process of all scientists and engineers. While experiments have been traditionally done inside laboratories, the emergence of Information and Communication Technologies added two alternatives accessible anytime, anywhere. These two alternatives are known as virtual and remote laboratories and are sometimes indistinguishably referred as online laboratories. Similarly to other instructional technologies, virtual and remote laboratories require some effort from teachers in integrating them into curricula, taking into consideration several factors that affect their adoption (i.e., cost) and their educational effectiveness (i.e., benefit). This chapter analyzes these two dimensions and sustains the case where only through international cooperation it is possible to serve the large number of teachers and students involved in engineering education. It presents an example in the area of electrical and electronics engineering, based on a remote laboratory named Virtual Instruments System in Reality, and it then describes how a number of European and Latin American institutions have been cooperating under the scope of an Erasmus+ project, for spreading its use in Brazil and Argentina.

  • 13.
    Anco, S.
    et al.
    Brock Univ, Dept Math & Stat, St Catharines, ON L2S 3A1, Canada..
    Avdonina, E. D.
    Ufa State Aviat Tech Univ, Lab Grp Anal Math Models Nat & Engn Sci, Ufa 450000, Russia..
    Gainetdinova, A.
    Ufa State Aviat Tech Univ, Lab Grp Anal Math Models Nat & Engn Sci, Ufa 450000, Russia..
    Galiakberova, L. R.
    Ufa State Aviat Tech Univ, Lab Grp Anal Math Models Nat & Engn Sci, Ufa 450000, Russia..
    Ibragimov, Nail
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Wolf, T.
    Brock Univ, Dept Math & Stat, St Catharines, ON L2S 3A1, Canada..
    Symmetries and conservation laws of the generalized Krichever-Novikov equation2016In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 49, no 10, article id 105201Article in journal (Refereed)
    Abstract [en]

    A computational classification of contact symmetries and higher-order local symmetries that do not commute with t, x, as well as local conserved densities that are not invariant under t, x is carried out for a generalized version of the Krichever-Novikov (KN) equation. Several new results are obtained. First, the KN equation is explicitly shown to have a local conserved density that contains t, x. Second, apart from the dilational point symmetries known for special cases of the KN equation and its generalized version, no other local symmetries with low differential order are found to contain t, x. Third, the basic Hamiltonian structure of the KN equation is used to map the local conserved density containing t, x into a nonlocal symmetry that contains t, x. Fourth, a recursion operator is applied to this nonlocal symmetry to produce a hierarchy of nonlocal symmetries that have explicit dependence on t, x. When the inverse of the Hamiltonian map is applied to this hierarchy, only trivial conserved densities are obtained.

  • 14. Anco, S.
    et al.
    Ibragimov, Nail
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Imamutdinova, K.V.
    Karimova, E.N.
    Solutions of gasdynamic equations associated with classical and new conservation laws2015In: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 268, p. 52-58Article in journal (Refereed)
    Abstract [en]

    Exact solutions of the one-dimensional gasdynamic equations are constructed by applying the method of conservation laws to all point-wise conserved vectors of the equations under consideration. © 2015 Elsevier Inc.

  • 15.
    ANUPOJU, MEHER VIJAY
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    PONNADA, PRUDHVI
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    VALLU, HARI VEERA MANI KUMAR
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Platform Tilt Detection: For Drone Landing2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report describes a project aimed at determining the angle of the landing platform to the drones using a tilted platform, IMU, and image processing algorithms. The goal of this project is to determine the safe landing of drones and drone landings by optimizing the landing location via platform tilt adjustment and angle computation. A robotic arm was used to tilt the rectangular platform, and a web camera was used to get images from the top view. Image processing methods built-in MATLAB allow for approximate landing angle determination and angle determination is also done with IMU. The findings confirm the system’s efficiency, with reasonable angle estimates and successful drone landings.

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    Platform Tilt Detection - For Drone Landing
  • 16.
    Araujo, Gustavo F.
    et al.
    Aeronautics Institute of Technology, Brazil.
    MacHado, Renato
    Aeronautics Institute of Technology, Brazil.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    A Tailored cGAN SAR Synthetic Data Augmentation Method for ATR Application2023In: Proceedings of the IEEE Radar Conference, Institute of Electrical and Electronics Engineers (IEEE), 2023, Vol. 2023Conference paper (Refereed)
    Abstract [en]

    This article proposes a method to simulate Synthetic Aperture Radar (SAR) targets for specific incidence and azimuth angles. Images synthesized by Electromagnetic Computing (EMC) are used to train a Conditional Generative Adversarial Network (cGAN). Two synthetic image chips of the same class and incidence angle, separated by two degrees in azimuth, are used as input to the cGAN. The cGAN predicts the image of the same class and incidence angle whose azimuth angle corresponds to the bisector of the two input chips. An evaluation using the SAMPLE dataset was performed to verify the quality of the image prediction. Running through a total of 100 training epochs, the cGAN converges, reaching the best Mean Squared Error (MSE) after 77 epochs. The results demonstrate that the proposed method is promising for Automatic Target Recognition (ATR) applications. © 2023 IEEE.

  • 17.
    Araujo, Gustavo F.
    et al.
    Aeronautics Institute of Technology, BRA.
    Machado, Renato
    Aeronautics Institute of Technology, BRA.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Assessment of preprocessing techniques in a model-based automatic target recognition algorithm for the SAMPLE dataset2022In: Image and Signal Processing for Remote Sensing XXVIII 2022 / [ed] Bruzzone L., Bovolo F., Pierdicca N., SPIE - International Society for Optical Engineering, 2022, article id 1226705Conference paper (Refereed)
    Abstract [en]

    This article investigates basic preprocessing techniques to improve classification accuracy in the context of Automatic Target Recognition (ATR) of non-cooperative targets in Synthetic Aperture Radar (SAR) images. Preprocessing techniques are considered in synthetic data providing different inputs to a model-based classification algorithm. Experiments with preprocessing techniques such as area reduction, morphological transformations, and speckle filtering were run using ten target classes of the SAMPLE dataset. The classification is performed in measure data using scattering centers as features. The results reveal that the original image without any preprocessing techniques reached the best classification performance. However, investigations with other classifiers that use different features may benefit from such preprocessing techniques. © 2022 SPIE.

  • 18.
    Araujo, Gustavo F.
    et al.
    Aeronautics Institute of Technology, BRA.
    Machado, Renato
    Aeronautics Institute of Technology, BRA.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Non-Cooperative SAR Automatic Target Recognition Based on Scattering Centers Models2022In: Sensors, E-ISSN 1424-8220, Vol. 22, no 3, article id 1293Article in journal (Refereed)
    Abstract [en]

    This article proposes an Automatic Target Recognition (ATR) algorithm to classify non-cooperative targets in Synthetic Aperture Radar (SAR) images. The scarcity or nonexistence of measured SAR data demands that classification algorithms rely only on synthetic data for training purposes. Based on a model represented by the set of scattering centers extracted from purely synthetic data, the proposed algorithm generates hypotheses for the set of scattering centers extracted from the target under test belonging to each class. A Goodness of Fit test is considered to verify each hypothesis, where the Likelihood Ratio Test is modified by a scattering center-weighting function common to both the model and target. Some algorithm variations are assessed for scattering center extraction and hypothesis generation and verification. The proposed solution is the first model-based classification algorithm to address the recently released Synthetic and Measured Paired Labeled Experiment (SAMPLE) dataset on a 100% synthetic training data basis. As a result, an accuracy of 91.30% in a 10-target test within a class experiment under Standard Operating Conditions (SOCs) was obtained. The algorithm was also pioneered in testing the SAMPLE dataset in Extend Operating Conditions (EOCs), assuming noise contamination and different target configurations. The proposed algorithm was shown to be robust for SNRs greater than −5 dB. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

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  • 19.
    Araujo, Gustavo F.
    et al.
    Aeronaut Inst Technol ITA, Brazil.
    Machado, Renato
    Aeronaut Inst Technol ITA, Brazil.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Synthetic SAR Data Generator Using Pix2pix cGAN Architecture for Automatic Target Recognition2023In: IEEE Access, E-ISSN 2169-3536, Vol. 11, p. 143369-143386Article in journal (Refereed)
    Abstract [en]

    Synthetic Aperture Radar (SAR) technology has unique advantages but faces challenges in obtaining enough data for noncooperative target classes. We propose a method to generate synthetic SAR data using a modified pix2pix Conditional Generative Adversarial Networks (cGAN) architecture. The cGAN is trained to create synthetic SAR images with specific azimuth and elevation angles, demonstrating its capability to closely mimic authentic SAR imagery through convergence and collapsing analyses. The study uses a model-based algorithm to assess the practicality of the generated synthetic data for Automatic Target Recognition (ATR). The results reveal that the classification accuracy achieved with synthetic data is comparable to that attained with original data, highlighting the effectiveness of the proposed method in mitigating the limitations imposed by noncooperative SAR data scarcity for ATR. This innovative approach offers a promising solution to craft customized synthetic SAR data, ultimately enhancing ATR performance in remote sensing.

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  • 20.
    Back, Per
    et al.
    Mälardalens universitet, SWE.
    Richter, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    The hom-associative Weyl algebras in prime characteristic2022In: International Electronic Journal of Algebra, E-ISSN 1306-6048, Vol. 31, no 31, p. 203-229Article in journal (Refereed)
    Abstract [en]

    We introduce the first hom-associative Weyl algebras over a field of prime characteristic as a generalization of the first associative Weyl algebra in prime characteristic. First, we study properties of hom-associative algebras constructed from associative algebras by a general twisting'' procedure. Then, with the help of these results, we determine the commuter, center, nuclei, and set of derivations of the first hom-associative Weyl algebras. We also classify them up to isomorphism, and show, among other things, that all nonzero endomorphisms on them are injective, but not surjective. Last, we show that they can be described as a multi-parameter formal hom-associative deformation of the first associative Weyl algebra, and that this deformation induces a multi-parameter formal hom-Lie deformation of the corresponding Lie algebra, when using the commutator as bracket. © 2022, Hacettepe University. All rights reserved.

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  • 21.
    Baghdari, Samaneh
    et al.
    Isfahan University of Technology, Iran.
    Öinert, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pure semisimple and Kothe group rings2023In: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 51, no 7, p. 2779-2790Article in journal (Refereed)
    Abstract [en]

    In this article, we provide a complete characterization of abelian group rings which are Kothe rings. We also provide characterizations of (possibly non-abelian) group rings over division rings which are Kothe rings, both in characteristic zero and in prime characteristic, and prove a Maschke type result for pure semisimplicity of group rings. Furthermore, we illustrate our results by several examples.Communicated by Eric Jespers

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  • 22.
    Bagio, Dirceu
    et al.
    Universidade Federal de Santa Catarina, Brazil.
    Gonçalves, Daniel
    Universidade Federal de Santa Catarina, Brazil.
    Moreira, Paula Savana Estácio
    Universidade Federal de Santa Catarina, Brazil.
    Öinert, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    The ideal structure of partial skew groupoid rings with applications to topological dynamics and ultragraph algebras2024In: Forum mathematicum, ISSN 0933-7741, E-ISSN 1435-5337Article in journal (Refereed)
    Abstract [en]

    Given a partial action α of a groupoid G on a ring R, we study the associated partial skew groupoid ring R ⋊ α G {R\rtimes_{\alpha}G}, which carries a natural G-grading. We show that there is a one-to-one correspondence between the G-invariant ideals of R and the graded ideals of the G-graded ring R ⋊ α G {R\rtimes_{\alpha}G}. We provide sufficient conditions for primeness, and necessary and sufficient conditions for simplicity of R ⋊ α G {R\rtimes_{\alpha}G}. We show that every ideal of R ⋊ α G {R\rtimes_{\alpha}G} is graded if and only if α has the residual intersection property. Furthermore, if α is induced by a topological partial action θ, then we prove that minimality of θ is equivalent to G-simplicity of R, topological transitivity of θ is equivalent to G-primeness of R, and topological freeness of θ on every closed invariant subset of the underlying topological space is equivalent to α having the residual intersection property. As an application, we characterize condition (K) for an ultragraph in terms of topological properties of the associated partial action and in terms of algebraic properties of the associated ultragraph algebra. © 2024 Walter de Gruyter GmbH, Berlin/Boston 2024.

  • 23. Barbosa, V.L.
    et al.
    E.R., Schlosser
    Machado, Renato
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    F. G., Ferreira
    S. M., Tolfo
    M. V. T., Heckler
    Linear Array Design with Switched Beams for Wireless Communications Systems2015In: International Journal of Antennas and Propagation, ISSN 1687-5869, E-ISSN 1687-5877, Vol. 2015, article id 278160Article in journal (Refereed)
    Abstract [en]

    This paper presents an analysis for optimal design of switched beamforming applied to a linear array for wireless communication systems. The beam switching scheme provides coverage of a given sector in azimuth and controls the sidelobe level simultaneously. The analysis was developed considering arrays composed of Quasi-Yagi elements. The model assumes a user moving in the azimuthal direction under a constant velocity and with an estimation of the signal-to-noise ratio (SNR) at the mobile user (MU). The radio base station applies the beam that yields the best performance during transmission. The decision is based on the feedback information received from the MU. The goal of the analysis is to determine the best trade-off between the array size and number of feedback bits necessary to maximize the SNR at the receiver. The results show that a compromise between the number of beam-pointing directions and the array size should be taken into consideration for a wireless communication system design.

  • 24.
    Batra, A.
    et al.
    Univ Duisburg Essen, Germany.
    Ivanenko, Yevhen
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Vu, Viet Thuy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Wiemeler, M.
    Univ Duisburg Essen, Germany.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Goehringer, D.
    Tech Univ Dresden, Germany.
    Kaiser, T.
    Univ Duisburg Essen, Germany.
    Analysis of Surface Roughness with 3D SAR Imaging at 1.5 THz2023In: 2023 48TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, IRMMW-THZ, Institute of Electrical and Electronics Engineers (IEEE), 2023Conference paper (Refereed)
    Abstract [en]

    The expansion of the synthetic aperture radar (SAR) to the emerging THz spectrum has enabled a new era of applications in the areas of automobile, security, non-destructive testing, and material characterization. Thanks to the sub-mm wavelength, extraction of material surface properties is possible and of significant interest for the THz SAR applications. The properties define the surface scattering behavior, which is relational to the applied frequency. This study focuses on surface classification. We evaluate the scattering behavior of a rough surface and a smooth surface at 1.5 THz based on a SAR processing sequence that is introduced in this paper. First, we form the 3D SAR images of the metallic objects and then evaluate the surface properties based on the variation in the energy reflected by the object's surface.

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  • 25.
    Batra, Aman
    et al.
    University of Duisburg-Essen, DEU.
    Vu, Viet Thuy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Zantah, Yamen
    University of Duisburg-Essen, DEU.
    Wiemeler, Michael
    University of Duisburg-Essen, DEU.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Goehringer, Diana
    Technische Universitaet Dresden, DEU.
    Kaiser, Thomas
    University of Duisburg-Essen, DEU.
    Sub-mm Resolution Indoor THz Range and SAR Imaging of Concealed Object2020In: 2020 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility, ICMIM 2020, Institute of Electrical and Electronics Engineers Inc. , 2020, article id 9299034Conference paper (Refereed)
    Abstract [en]

    In radar systems, the frequency range is being extended to high frequencies such as THz for sub-mm resolution. The spectrum offers high resolution but on the contrary, propagation distance and penetration depth are limited because of smaller wavelength. It suffers from higher atmospheric absorption in comparison to sub-GHz systems. In comparison to optical technology, the radar technique majorly benefits with respect to the penetration property such as cloud/smoke cover penetration and detection of concealed objects. However, the THz range and synthetic aperture radar (SAR) imaging of concealed objects are not very well established. Therefore, this paper examines this property at THz. A testbed has been set up with a bandwidth of 110 GHz at a carrier frequency of 275 GHz. The imaging is performed of a very small metal object. Firstly, the sub-mm resolution is validated with the experiment after that the range and SAR imaging are performed in which this object is covered with different types of materials. The backscattered data is processed with the image reconstruction algorithms and the results are presented in this paper with respect to sub-mm resolution and detection. © 2020 IEEE.

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  • 26.
    Batra, Aman
    et al.
    University of Duisburg-Essen, DEU.
    Zantah, Yamen
    University of Duisburg-Essen, DEU.
    Vu, Viet Thuy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Wiemeler, Michael
    University of Duisburg-Essen, DEU.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Goehringer, Diana
    Technische Universitaet Dresden, DEU.
    Kaiser, Thomas
    University of Duisburg-Essen, DEU.
    Experimental analysis of high resolution indoor THz SAR imaging2020In: WSA 2020 - 24th International ITG Workshop on Smart Antennas, VDE Verlag GmbH , 2020Conference paper (Refereed)
    Abstract [en]

    Synthetic Aperture Radar (SAR) technology is most commonly used in the frequency span of sub-30 GHz which provides the spatial resolution in the range of sub-cm. This technology is being extended to higher frequencies such as millimeter wave and THz region to achieve higher resolution in the range of sub-mm. This expands the SAR applications for material characterization, classification and sub-mm localization. However, the region is suitable for short propagation distance such as an indoor environment. Therefore, to investigate the achieved resolution and quality of the SAR images at THz, an indoor SAR testbed based on vector network analyzer has been setup for the measurements. This paper explains the indoor SAR geometry and describes the associated testbed along with the system parameters. The measurements are performed at a centre frequency of 275 GHz with a bandwidth of 110 GHz. The measurement results are analyzed for the theoretical resolution with the Backprojection Algorithm and the findings are presented in this paper. The sub-mm spatial resolution imaging of two small size metallic objects are performed. © WSA 2020.

  • 27.
    Bayford, Richard H.
    et al.
    Middlesex Univ Burroughs Hendon, GBR.
    Damaso, Rui
    Middlesex Univ, GBR.
    Neshatvar, Nazanin
    University College London, GBR.
    Ivanenko, Yevhen
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Rademacher, Thomas W.
    Emergex Vaccines Holding Ltd, GBR.
    Wu, Yu
    University College London, GBR.
    Seifnaraghi, Nima
    Middlesex Univ, GBR.
    Ghali, Lucy
    Middlesex Univ, GBR.
    Patel, Nakul
    Middlesex Univ, GBR.
    Roitt, Ivan
    Middlesex Univ, GBR.
    Nordebo, Sven
    Linnaeus Univ, SWE.
    Demosthenous, Andreas
    University College London, GBR.
    Locating Functionalized Gold Nanoparticles Using Electrical Impedance Tomography2022In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 69, no 1, p. 494-502Article in journal (Refereed)
    Abstract [en]

    Objective: An imaging device to locate functionalised nanoparticles, whereby therapeutic agents are transported from the site of administration specifically to diseased tissues, remains a challenge for pharmaceutical research. Here, we show a new method based on electrical impedance tomography (EIT) to provide images of the location of gold nanoparticles (GNPs) and the excitation of GNPs with radio frequencies (RF) to change impedance permitting an estimation of their location in cell models Methods: We have created an imaging system using quantum cluster GNPs as contrast agent, activated with RF fields to heat the functionalized GNPs, which causes a change in impedance in the surrounding region. This change is then identified with EIT. Results: Images of impedance changes of around 80 +/- 4% are obtained for a sample of citrate stabilized GNPs in a solution of phosphate-buffered saline. A second quantification was carried out using colorectal cancer cells incubated with culture media, and the internalization of GNPs into the colorectal cancer cells was undertaken to compare them with the EIT images. When the cells were incubated with functionalised GNPs, the change was more apparent, approximately 40 +/- 2%. This change was reflected in the EIT image as the cell area was more clearly identifiable from the rest of the area. Significance: EIT can be used as a new method to locate functionalized GNPs in human cells and help in the development of GNP-based drugs in humans to improve their efficacy in the future.

  • 28.
    Bechter, Jonathan
    et al.
    Ulm Univ, DEU.
    Rameez, Muhammad
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Waldschmidt, Christian
    Ulm Univ, DEU.
    Analytical and Experimental Investigations on Mitigation of Interference in a DBF MIMO Radar2017In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 5, p. 1727-1734Article in journal (Refereed)
    Abstract [en]

    As driver assistance systems and autonomous driving are on the rise, radar sensors become a common device for automobiles. The high sensor density leads to the occurrence of interference, which decreases the detection capabilities. Here, digital beamforming (DBF) is applied to mitigate such interference. A DBF system requires a calibration of the different receiving channels. It is shown how this calibration completely changes the DBF beam pattern required to cancel interferences, if the system has no IQ receiver. Afterward, the application of DBF on a multiple-input multiple-output (MIMO) radar is investigated. It is shown that only the real aperture and not the virtual one can be used for interference suppression, leading to wide notches in the pattern. However, for any target the large virtual aperture can be exploited, even if interferers are blinded out. Moreover, the wide notches for interference suppression of the real aperture appear narrow in the virtual aperture for target localization. The results are verified by measurements with time-multiplexing MIMO radar.

  • 29. Berggren, Magnus
    et al.
    Borgh, Markus
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Limes Audio AB, Umeå.
    Schüldt, Christian
    Lindström, Fredric
    Limes Audio AB, Umeå.
    Claesson, Ingvar
    Low-complexity network echo cancellation approach for systems equipped with external memory2011In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 19, no 8, p. 2506-2515Article in journal (Refereed)
    Abstract [en]

    Long delays and sparseness characterize impulse responses in telecommunication networks and a vast number of solutions for network echo cancellation have been proposed over the years. In this paper, an approach for detecting dispersive regions of a sparse impulse response and a proportionate normalized least mean square (PNLMS)-based selective updating approach are combined with an adaptive double-talk detector to form a complete solution for echo cancellation. The proposed solution has low computational complexity and is targeted for systems equipped with external memory.

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  • 30.
    Berner, Jessica
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Moraes, Ana Luiza Dallora
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Palm, Bruna
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Sanmartin Berglund, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Anderberg, Peter
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Five-factor model, technology enthusiasm and technology anxiety2023In: Digital Health, E-ISSN 2055-2076, Vol. 9Article in journal (Refereed)
    Abstract [en]

    Older adults need to participate in the digital society, as societal and personal changes and what they do with the remaining time that they have in their older years has an undeniable effect on motivation, cognition and emotion. Changes in personality traits were investigated in older adults over the period 2019–2021. Technology enthusiasm and technology anxiety are attitudes that affect the relationship to the technology used. The changes in the score of technology enthusiasm and technology anxiety were the dependent variables. They were investigated with personality traits, age, gender, education, whether someone lives alone, cognitive function, digital social participation (DSP) and health literacy as predictors of the outcome. The Edwards-Nunnally index and logistic regression were used. The results indicated that DSP, lower age, lower neuroticism and higher education were indicative of less technology anxiety. High DSP and high extraversion are indicative of technology enthusiasm. DSP and attitude towards technology seem to be key in getting older adults to stay active online. © The Author(s) 2023.

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  • 31.
    Berner, Jessica
    et al.
    Blekinge Institute of Technology, Faculty of Health Sciences, Department of Health.
    Rennemark, Mikael
    Blekinge Institute of Technology, Faculty of Health Sciences, Department of Health.
    Jogreus, Claes
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Anderberg, Peter
    Blekinge Institute of Technology, Faculty of Health Sciences, Department of Health.
    Sköldunger, Anders
    Wahlberg, Maria
    Elmståhl, Sölve
    Berglund, Johan
    Blekinge Institute of Technology, Faculty of Health Sciences, Department of Health.
    Factors influencing Internet usage in older adults (65 years and above) living in rural and urban Sweden2015In: Health Informatics Journal, ISSN 1460-4582, E-ISSN 1741-2811, Vol. 21, no 3, p. 237-249Article in journal (Refereed)
    Abstract [en]

    Older adults living in rural and urban areas have shown to distinguish themselves in technology adoption; a clearer profile of their Internet use is important in order to provide better technological and health-care solutions. Older adults' Internet use was investigated across large to midsize cities and rural Sweden. The sample consisted of 7181 older adults ranging from 59 to 100 years old. Internet use was investigated with age, education, gender, household economy, cognition, living alone/or with someone and rural/urban living. Logistic regression was used. Those living in rural areas used the Internet less than their urban counterparts. Being younger and higher educated influenced Internet use; for older urban adults, these factors as well as living with someone and having good cognitive functioning were influential. Solutions are needed to avoid the exclusion of some older adults by a society that is today being shaped by the Internet.

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  • 32.
    Beuter, Viviane
    et al.
    Universidade Federal de Santa Catarina, BRA.
    Gonçalves, Daniel
    Universidade Federal de Santa Catarina, BRA.
    Öinert, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Royer, Danilo
    Universidade Federal de Santa Catarina, BRA.
    Simplicity of skew inverse semigroup rings with applications to Steinberg algebras and topological dynamics2019In: Forum mathematicum, ISSN 0933-7741, E-ISSN 1435-5337, Vol. 31, no 3, p. 543-562Article in journal (Refereed)
    Abstract [en]

    Given a partial action π of an inverse semigroup S on a ring A {\mathcal{A}}, one may construct its associated skew inverse semigroup ring A π S {\mathcal{A}\rtimes-{\pi}S}. Our main result asserts that, when A {\mathcal{A}} is commutative, the ring A π S {\mathcal{A}\rtimes-{\pi}S} is simple if, and only if, A {\mathcal{A}} is a maximal commutative subring of A π S {\mathcal{A}\rtimes-{\pi}S} and A {\mathcal{A}} is S-simple. We apply this result in the context of topological inverse semigroup actions to connect simplicity of the associated skew inverse semigroup ring with topological properties of the action. Furthermore, we use our result to present a new proof of the simplicity criterion for a Steinberg algebra A R (g) {A-{R}(\mathcal{G})} associated with a Hausdorff and ample groupoid g {\mathcal{G}}. © 2018 Walter de Gruyter GmbH, Berlin/Boston.

  • 33.
    Bjorklund, Svante
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Johansson, Tommy
    Swedish Def Res Agcy FOI, SE-58111 Linkoping, Sweden..
    Petersson, Henrik
    Swedish Def Res Agcy FOI, SE-58111 Linkoping, Sweden..
    Target Classification in Perimeter Protection with a Micro-Doppler Radar2016In: 2016 17TH INTERNATIONAL RADAR SYMPOSIUM (IRS), 2016Conference paper (Refereed)
    Abstract [en]

    In security surveillance at the perimeter of critical infrastructure, such as airports and power plants, approaching objects have to be detected and classified. Especially important is to distinguish between humans, animals and vehicles. In this paper, micro-Doppler data (from movement of internal parts of the target) have been collected with a small radar of a low complexity and cost-effective type. From time-velocity diagrams of the data, some physical features have been extracted and used in a support vector machine classifier to distinguish between the classes "human", "animal" and "man-made object". Both the type of radar and the classes are suitable for perimeter protection. The classification result are rather good, 77% correct classification. Particularly interesting is the surprisingly good ability to distinguish between humans and animals. This also indicates that we can choose to have limitations in the radar and still solve the classification task.

  • 34.
    Bjorklund, Svante
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Petersson, Henrik
    Swedish Def Res Agcy FOI, SE-58111 Linkoping, Sweden..
    Hendeby, Gustaf
    Swedish Def Res Agcy FOI, SE-58111 Linkoping, Sweden.;Linkoping Univ, SE-58183 Linkoping, Sweden..
    Features for micro-Doppler based activity classification2015In: IET radar, sonar & navigation, ISSN 1751-8784, E-ISSN 1751-8792, Vol. 9, no 9, p. 1181-1187Article in journal (Refereed)
    Abstract [en]

    Safety and security applications benefit from better situational awareness. Radar micro-Doppler signatures from an observed target carry information about the target's activity, and have potential to improve situational awareness. This article describes, compares, and discusses two methods to classify human activity based on radar micro-Doppler data. The first method extracts physically interpretable features from the time-velocity domain such as the main cycle time and properties of the envelope of the micro-Doppler spectra and use these in the classification. The second method derives its features based on the components with the most energy in the cadence-velocity domain (obtained as the Fourier transform of the time-velocity domain). Measurements from a field trial show that the two methods have similar activity classification performance. It is suggested that target base velocity and main limb cadence frequency are indirect features of both methods, and that they do often alone suffice to discriminate between the studied activities. This is corroborated by experiments with a reduced feature set. This opens up for designing new more compact feature sets. Moreover, weaknesses of the methods and the impact of non-radial motion are discussed.

  • 35.
    Björklund, Svante
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Clutter Properties for a Side-Looking Radar with Planar Regular and Irregular Subarrays2015In: 2015 16TH INTERNATIONAL RADAR SYMPOSIUM (IRS), 2015, p. 730-735Conference paper (Refereed)
    Abstract [en]

    The effect of the subarray design in a side-looking moving radar with a planar antenna on some clutter properties which are important for suppressing the clutter with STAP (Space-Time Adaptive Processing) is investigated by simulations. These properties are interference DOA Doppler Spectrum (DDS) and clutter rank. The conclusions from the work is that irregular antennas give less clutter in the DDS and that larger subarrays give lower clutter rank.

  • 36.
    Björklund, Svante
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Swedish Defence Research Agency (FOI ).
    Signal Processing for Radar with Array Antennas and for Radar with Micro-Doppler Measurements2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Radar (RAdio Detection And Ranging) uses radio waves to detect the presence of a target and measure its position and other properties. This sensor has found many civilian and military applications due to advantages such as possible large surveillance areas and operation day and night and in all weather. The contributions of this thesis are within applied signal processing for radar in two somewhat separate research areas: 1) radar with array antennas and 2) radar with micro-Doppler measurements.

    Radar with array antennas: An array antenna consists of several small antennas in the same space as a single large antenna. Compared to a traditional single-antenna radar, an array antenna radar gives higher flexibility, higher capacity, several radar functions simultaneously and increased reliability, and makes new types of signal processing possible which give new functions and higher performance.

    The contributions on array antenna radar in this thesis are in three different problem areas. The first is High Resolution DOA (Direction Of Arrival) Estimation (HRDE) as applied to radar and using real measurement data. HRDE is useful in several applications, including radar applications, to give new functions and improve the performance. The second problem area is suppression of interference (clutter, direct path jamming and scattered jamming) which often is necessary in order to detect and localize the target. The thesis presents various results on interference signal properties, antenna geometry and subarray design, and on interference suppression methods. The third problem area is measurement techniques for which the thesis suggests two measurement designs, one for radar-like measurements and one for scattered signal measurements.

    Radar with micro-Doppler measurements: There is an increasing interest and need for safety, security and military surveillance at short distances. Tasks include detecting targets, such as humans, animals, cars, boats, small aircraft and consumer drones; classifying the target type and target activity; distinguishing between target individuals; and also predicting target intention. An approach is to employ micro-Doppler radar to perform these tasks. Micro-Doppler is created by the movement of internal parts of the target, like arms and legs of humans and animals, wheels of cars and rotors of drones.

    Using micro-Doppler, this thesis presents results on feature extraction for classification; on classification of targets types (humans, animals and man-made objects) and human gaits; and on information in micro-Doppler signatures for re-identification of the same human individual. It also demonstrates the ability to use different kinds of radars for micro-Doppler measurements. The main conclusion about micro-Doppler radar is that it should be possible to use for safety, security and military surveillance applications.

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  • 37.
    Björklund, Svante
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Swedish Defence Research Agency (FOI ).
    Three-Dimensional DPCA with Rotating Antenna for Clutter Cancellation2015In: 2015 IEEE Radar Conference (RadarCon), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 1579-1583Conference paper (Refereed)
    Abstract [en]

    In moving radar, e.g. airborne radar, the clutter from land and sea needs to be suppressed in order to detect the target. One approach to total cancellation of the clutter is Displaced Phase Center Antenna (DPCA). DPCA assumes that the antenna elements are positioned on a line parallel to the velocity vector of the radar platform so that the elements can take each others positions at different points of times. In a previous paper we saw that it is possible with other antenna element positions, e.g. in three dimensions, for a total cancellation of the clutter. We arrived at a theoretical condition for this. In this new paper we extend the condition with rotating array antennas. We also formulate an optimization problem for, besides the clutter cancellation, also maximizing the target signal.

  • 38.
    Björklund, Svante
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Grahn, Per
    Nelander, Anders
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Measurement of Rank and Other Properties of Direct and Scattered Signals2016In: International Journal of Antennas and Propagation, ISSN 1687-5869, E-ISSN 1687-5877, Vol. 2016, article id 5483547Article in journal (Refereed)
    Abstract [en]

    We have designed an experiment for low-cost indoor measurements of rank and other properties of direct and scattered signals with radar interference suppression in mind. The signal rank is important also in many other applications, for example, DOA (Direction of Arrival) estimation, estimation of the number of and location of transmitters in electronic warfare, and increasing the capacity in wireless communications. In real radar applications, such measurements can be very expensive, for example, involving airborne radars with array antennas. We have performed the measurements in an anechoic chamber with several transmitters, a receiving array antenna, and a moving reflector. Our experiment takes several aspects into account: transmitted signals with different correlation, decorrelation of the signals during the acquisition interval, covariance matrix estimation, noise eigenvalue spread, calibration, near-field compensation, scattering in a rough surface, and good control of the influencing factors. With our measurements we have observed rank, DOA spectrum, and eigenpatterns of direct and scattered signals. The agreement of our measured properties with theoretic and simulated results in the literature shows that our experiment is realistic and sound. The detailed description of our experiment could serve as help for conducting other well-controlled experiments. © Copyright 2016 Svante Björklund et al.

  • 39.
    Björklund, Svante
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Nelander, Anders
    Swedish Def Res Agcy FOI, SWE.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Blekinge Inst Technol, Karlskrona, Sweden..
    Fast-Time and Slow-Time Space-Time Adaptive Processing for Bistatic Radar Interference Suppression2015In: 2015 IEEE INTERNATIONAL RADAR CONFERENCE (RADARCON), IEEE Communications Society, 2015, p. 674-678Conference paper (Refereed)
    Abstract [en]

    In bistatic radar with transmitter and receiver geographically separated the interference from ground clutter and the direct path signal transmitter-receiver will be strong and must be suppressed in order to detect the target. We apply FT-STAP (Fast-Time Space Time Adaptive Processing) to the suppression, which is unusual, and compare with conventional ST-STAP (Slow-Time STAP) by simulations in order to see whether FT-STAP is an alternative to ST-STAP. The performance of FT-STAP is much worse than of ST-STAP. We give an explanation for this, which also may be the basis for large improvements of FT-STAP. Moreover, we suggest two new performance measures.

  • 40. Björklund, Svante
    et al.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    A three-dimensional displaced phase center antenna condition for clutter cancellation2014In: Proceedings of the IEEE Sensor Array and Multichannel Signal Processing Workshop, IEEE , 2014, p. 305-308Conference paper (Refereed)
    Abstract [en]

    In moving radar, e.g. airborne radar, the clutter from land and sea needs to be suppressed in order to detect the target. One approach to total cancellation of the clutter is Displaced Phase Center Antenna (DPCA). DPCA assumes that the antenna elements are positioned on a line parallel to the velocity vector of the radar platform so that the elements can take each others positions at different points of times. This paper theoretically investigates if it is possible with other antenna element positions, e.g. in three dimensions, for a total cancellation of the clutter. We arrive at a condition which conforms to the principle that the elements should take each others positions at different times but allows other antennas than the single line parallel to the velocity vector. Our condition could be used as constraints in an optimization problem where the target signal performance is optimized. The multipulse DPCA condition is one solution to our condition.We also give two examples of non-linear antennas fulfilling our condition.

  • 41.
    Björklund, Svante
    et al.
    Swedish Defence Research Agency (FOI).
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Factors Affecting the Effective Clutter Rank for Planar and Conformal Antennas with Subarrays2023In: Proceedings of the IEEE Radar Conference 2023, Institute of Electrical and Electronics Engineers (IEEE), 2023Conference paper (Refereed)
    Abstract [en]

    The Effective Clutter Rank (ECR), the number of eigenvalues of the clutter covariance matrix larger than the white noise, has important consequences for the radar system when suppressing clutter with Space-Time Adaptive Processing (STAP), in terms of cost, complexity, usability and performance. In this paper some factors affecting the ECR are studied by simulations. The result is partly explained by theory from the literature. The main results are: 1) Factors affecting the ECR [subarray beam pointing direction, subarray design, antenna geometry, # radar pulses, PRF, radar velocity and target range]. 2) Differences between planar and conformal antennas. 3) A simulation-based rank calculation method for antennas with subarrays.

  • 42.
    Björklund, Svante
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Rydell, Joakim
    Totalforsvarets forskningsinstitut, SWE.
    Micro-doppler classification with boosting in perimeter protection2017In: IET Conference Publications, Institution of Engineering and Technology , 2017, no CP728Conference paper (Refereed)
    Abstract [en]

    In security surveillance at the perimeter of critical infrastructure, such as airports and power plants, approaching objects have to be detected and classified. Especially important is to distinguish between humans, animals and vehicles. In this paper, micro-Doppler data (from movement of internal parts of the target) have been collected with a small radar. From time-velocity diagrams of the data, physical features have been extracted and used in a Boosting classifier to distinguish between the classes "human", "animal" and "man-made object". This type of classifier has received much attention lately, but not in radar micro-Doppler classification. The classification result on the current data reaches 90% correct classification with this classifier. The ability to distinguish between humans and animals is good on this data. This classifier type gives insight into the classifier and the utilized features, and is easy to use. A comparison with a SVM (Support Vector Machine) classifier, which is common for micro-Doppler, has also been performed. © 2017 Institution of Engineering and Technology. All rights reserved.

  • 43.
    Borgh, Markus
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Limes Audio AB, Umeå.
    Berggren, Magnus
    Schüldt, Christian
    Lindström, Fredric
    Limes Audio AB, Umeå.
    Claesson, Ingvar
    An improved adaptive gain equalizer for noise reduction with low speech distortion2011In: EURASIP Journal on Audio, Speech, and Music Processing, ISSN 1687-4714, E-ISSN 1687-4722, Vol. 7Article in journal (Refereed)
    Abstract [en]

    In high-quality conferencing systems, it is desired to perform noise reduction with as limited speech distortion as possible. Previous work, based on time varying amplification controlled by signal-to-noise ratio estimation in different frequency subbands, has shown promising results in this regard but can suffer from problems in situations with intense continuous speech. Further, the amount of noise reduction cannot exceed a certain level in order to avoid artifacts. This paper establishes the problems and proposes several improvements. The improved algorithm is evaluated with several different noise characteristics, and the results show that the algorithm provides even less speech distortion, better performance in a multi-speaker environment and improved noise suppression when speech is absent compared with previous work.

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  • 44.
    Borgh, Markus
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Johansson, Sven
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    From, Åsa
    Lindström, Fredric
    Limes Technology AB, Umeå.
    A Personal Voice Analyzer and Trainer2010Conference paper (Refereed)
    Abstract [en]

    This paper presents a personal voice analyzer and trainer that allow the user to perform four daily exercises to improve the voice capacity. The system grades how well the user is performing the exercises by analyzing the duration, the intensity and the pitch of the user’s voice.

    Download full text (pdf)
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  • 45.
    Borgh, Markus
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Lindström, Fredric
    Waye, Kerstin Persson
    Claesson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    The Effect of Own Voice on Noise Dosimeter Measurements: A Field Study in a Day-Care Environment, Including Adults and Children2008Conference paper (Refereed)
    Abstract [en]

    Noise dosimeters are valuable tools in assessing the individual noise dose in the workplace. At non-industrial work places with a high degree of communication, such measurements would include the wearer’s own voice which would be registered as noise. This may not always be desirable. The purpose of this investigation was to study the effect of the wearers own voice in noise dosimeter measurements, and especially the difference between children and adults as test subjects. The study took place at a day-care center and sixteen children and thirteen adult female preschool teachers participated. The participants wore a digital recorder during the day, which recorded the sound signal and vibrations originating from an accelerometer attached to the neck of the test subjects, for distinguishing of whether the subject was speaking or not. Thus, average A-weighted noise levels with and without the influence of the subjects own voice could be obtained. The Leq for the measurements with and without the own voice was 84.6 dBA and 72.2 dBA for the children, respectively, and 79.3 dBA and 70.0 dBA for adults. Student’s t-test showed a significant (p<0.01) difference of 12.4 dBA for children and 9.3 dBA for adults when comparing measurements including and excluding the own voice and also that the difference was significantly larger for children. Thus, the study conclude that the influence from the own voice implied an augmentation of the Leq value and that there is a significant difference between children and adults in how large this augmentation is.

  • 46.
    Borgh, Markus
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Schüldt, Christian
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Claesson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Efficient asynchronous re-sampling implementation on a low-power fixed-point DSP2013Conference paper (Refereed)
    Abstract [en]

    This paper presents an asynchronous resampling implementation on a low-power fixed-point DSP, which uses around 47% less computational resources compared to the solution provided by the DSP manufacturer, without compromising audio quality.

  • 47. Boszhkov, Yuri
    et al.
    Freire, Igor
    Ibragimov, Nail H.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Group analysis of the Novikov equation2014In: Computational and Applied Mathematics, ISSN 2238-3603, E-ISSN 1807-0302, Vol. 33, no 1, p. 193-202Article in journal (Refereed)
    Abstract [en]

    We find the Lie point symmetries of the Novikov equation and demonstrate that it is strictly self-adjoint. Using the self-adjointness and the recent technique for constructing conserved vectors associated with symmetries of differential equations, we find the conservation law corresponding to the dilation symmetry and show that other symmetries do not provide nontrivial conservation laws. Then we investigate the invariant solutions.

  • 48.
    Bäck, Per
    et al.
    Mälardalen University, SWE.
    Richter, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Hilbert’s Basis Theorem for Non-associative and Hom-associative Ore Extensions2023In: Algebras and Representation Theory, ISSN 1386-923X, E-ISSN 1572-9079, Vol. 26, no 4, p. 1051-1065Article in journal (Refereed)
    Abstract [en]

    We prove a hom-associative version of Hilbert’s basis theorem, which includes as special cases both a non-associative version and the classical Hilbert’s basis theorem for associative Ore extensions. Along the way, we develop hom-module theory. We conclude with some examples of both non-associative and hom-associative Ore extensions which are all noetherian by our theorem.

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  • 49.
    Bäck, Per
    et al.
    Mälardalen University, SWE.
    Richter, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    On the hom-associative Weyl algebras2020In: Journal of Pure and Applied Algebra, ISSN 0022-4049, E-ISSN 1873-1376, Vol. 224, no 9, article id 106368Article in journal (Refereed)
    Abstract [en]

    The first (associative) Weyl algebra is formally rigid in the classical sense. In this paper, we show that it can however be formally deformed in a nontrivial way when considered as a so-called hom-associative algebra, and that this deformation preserves properties such as the commuter, while deforming others, such as the center, power associativity, the set of derivations, and some commutation relations. We then show that this deformation induces a formal deformation of the corresponding Lie algebra into what is known as a hom-Lie algebra, when using the commutator as bracket. We also prove that all homomorphisms between any two purely hom-associative Weyl algebras are in fact isomorphisms. In particular, all endomorphisms are automorphisms in this case, hence proving a hom-associative analogue of the Dixmier conjecture to hold true. © 2020 Elsevier B.V.

  • 50.
    Campos, Alexandre B.
    et al.
    Microwaves and Radar Institute, German Aerospace Center (DLR), Germany.
    Molin, Ricardo D.
    Microwaves and Radar Institute, German Aerospace Center (DLR), Germany.
    Ramos, Lucas P.
    Aeronautics Institute of Technology (ITA), Brazil.
    MacHado, Renato
    Aeronautics Institute of Technology (ITA), Brazil.
    Vu, Viet Thuy
    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.
    Adaptive Target Enhancer: Bridging the Gap between Synthetic and Measured SAR Images for Automatic Target Recognition2023In: Proceedings of the IEEE Radar Conference, Institute of Electrical and Electronics Engineers (IEEE), 2023, Vol. 2023Conference paper (Refereed)
    Abstract [en]

    Automatic target recognition (ATR) algorithms have been successfully used for vehicle classification in synthetic aperture radar (SAR) images over the past few decades. For this application, however, the scarcity of labeled data is often a limiting factor for supervised approaches. While the advent of computer-simulated images may result in additional data for ATR, there is still a substantial gap between synthetic and measured images. In this paper, we propose the so-called adaptive target enhancer (ATE), a tool designed to automatically delimit and weight the region of an image that contains or is affected by the presence of a target. Results for the publicly released Synthetic and Measured Paired and Labeled Experiment (SAMPLE) dataset show that, by defining regions of interest and suppressing the background, we can increase the classification accuracy from 68% to 84% while only using artificially generated images for training. © 2023 IEEE.

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