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  • 51.
    Wittsten, Jens
    et al.
    Lunds universitet.
    Andersson, F.
    Institute of Geophysics, ETH-Zurich.
    Robertsson, J.
    Institute of Geophysics, ETH-Zurich.
    van Manen, D.
    Institute of Geophysics, ETH-Zurich.
    Amundsen, L.
    Norwegian university of science and technology.
    Stability of signal apparition2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The recently introduced method of ‘signal apparition’ offers a fundamentally different approach to separation of multiple interfering sources, by using a periodic sequence of source signatures along one source line. This leads to exact separation of signals in diamond-shaped regions of the frequency-wavenumber domain which are twice as large compared to those recovered by other methods. In this paper we investigate the method’s sensitivity to the appearance of white noise in the periodic sequence, and show that signal apparition is stable by using a probabilistic model. We also demonstrate the stability by numerical simulations on a finite-difference synthetic data set generated over a complex salt model.

  • 52.
    Wittsten, Jens
    et al.
    Lunds universitet.
    Andersson, Fredrik
    Institute of Geophysics, ETH-Zurich.
    Robertsson, Johan
    Institute of Geophysics, ETH-Zurich.
    Amundsen, Lasse
    Norwegian university of science and technology.
    Perfect partial reconstructions for multiple simultaneous sources2019Ingår i: Geophysical Prospecting, Vol. 67, nr 6, s. 1486-1497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major focus of research in the seismic industry of the past two decades has been the acquisition and subsequent separation of seismic data using multiple sources fired simultaneously. The recently introduced method of signal apparition provides a new take on the problem by replacing the random time-shifts usually employed to encode the different sources by fully deterministic periodic time-shifts. In this paper, we give a mathematical proof showing that the signal apparition method results in optimally large regions in the frequency–wavenumber space where exact separation of sources is achieved. These regions are diamond shaped and we prove that using any other method of source encoding results in strictly smaller regions of exact separation. The results are valid for arbitrary number of sources. Numerical examples for different number of sources (three, respectively, four sources) demonstrate the exact recovery of these diamond-shaped regions. The implementation of the theoretical proofs in the field is illustrated by the results of a conducted field test.

  • 53.
    Wittsten, Jens
    et al.
    Lunds universitet.
    Andersson, Fredrik
    Institute of Geophysics, ETH-Zurich.
    Robertsson, Johan
    Institute of Geophysics, ETH-Zurich.
    Van Manen, Dirk-Jan
    Institute of Geophysics, ETH-Zurich.
    Amundsen, Lasse
    Norwegian university of science and technology.
    Perturbations of time shifts in signal apparition2018Ingår i: SIAM Journal on Applied Mathematics, ISSN 0036-1399, E-ISSN 1095-712X, SIAM Journal on Applied Mathematics, ISSN 0036-1399, Vol. 78, nr 5, s. 2840-2864Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the field of exploration geophysics, the method known as "signal apparition" offers a different perspective on how to separate signals acquired from simultaneously fired seismic sources. The method uses a periodic sequence of small time shift variations to encode the different sources, and this choice leads to exact separation of signals in diamond-shaped regions of the frequency-wavenumber domain which are twice as large compared to those recovered by other methods. In this paper we investigate the signal apparition method's sensitivity to perturbations of the periodic time shift sequence. We model (measured or unknown) perturbations in a stochastic fashion and prove that the resulting inverse problem of separating the data is still well-posed, and we demonstrate the stability by numerical simulations on a finite-difference synthetic data set generated over a complex salt model.

  • 54.
    Zhou, Yuwen
    et al.
    College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China.
    Qin, Shiyi
    College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China.
    Verma, Shivpal
    College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China.
    Sar, Taner
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Sarsaiya, Surendra
    Key Laboratory of Basic Pharmacology and Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China.
    Ravindran, Balasubramani
    Department of Environmental Energy and Engineering, Kyonggi University, Youngtong – Gu, Suwon 16227, South Korea.
    Liu, Tao
    College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China.
    Sindhu, Raveendran
    Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Thiruvananthapuram, Kerala, 695019, India.
    Kumar Patel, Anil
    Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan.
    Binod, Parameswaran
    Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Thiruvananthapuram, Kerala, 695019, India.
    Varjani, Sunita
    Gujarat Pollution Control Board, Gandhinagar, Gujarat 382010, India.
    Rani Singhnia, Reeta
    Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City, Taiwan.
    Zhang, Zengqiang
    College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China.
    Mukesh Kumar, Awasthi
    Högskolan i Borås, Akademin för textil, teknik och ekonomi. College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, PR China.
    Production and beneficial impact of biochar for environmental application: A comprehensive review2021Ingår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, artikel-id 125451Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    This review focuses on a holistic view of biochar, production from feedstock’s, engineering production strategies, its applications and future prospects. This article reveals a systematic emphasis on the continuation and development of biochar and its production methods such as Physical engineering, chemical and bio-engineering techniques. In addition, biochar alternatives such as nutrient formations and surface area made it a promising cheap source of carbon-based products such as anaerobic digestion, gasification, and pyrolysis, commercially available wastewater treatment, carbons, energy storage, microbial fuel cell electrodes, and super-capacitors repair have been reviewed. This paper also covers the knowledge blanks of strategies and ideas for the future in the field of engineering biochar production techniques and application as well as expand the technology used in the circular bio-economy.

  • 55.
    Keune, Svenja (Forskare)
    Högskolan i Borås, Akademin för textil, teknik och ekonomi. Centre for Inforation Technology and Architecture (CITA) at the Royal Danish Academy.
    Ståhl, Åsa (Forskare)
    Cerna, Katerina Katka (Forskare)
    Ludwig, Colleen (Konstnär)
    Nystrup Lund, Lotte (Forskare)
    USK – A UIA Side Event2023Konstnärlig output (Granskad)
    Ladda ner (zip)
    image
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