Cristin

2023
1.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. Weighted sparsity regularization for source identification for elliptic PDEs. Journal of Inverse and Ill-Posed Problems 2023 ;Volum 31.(5) s. 687-709 NMBU Untitled
2022
2.	Gergelits, Tomáš; Nielsen, Bjørn Fredrik; Strakoš, Zdeněk. Numerical approximation of the spectrum of self-adjoint operators in operator preconditioning. Numerical Algorithms 2022 ;Volum 91.(1) s. 301-325 NMBU Untitled
2021
3.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. A regularization operator for source identification for elliptic PDEs. Inverse Problems and Imaging 2021 ;Volum 15.(4) s. 599-618 NMBU Untitled

4.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. Modified Tikhonov Regularization for Identifying Several Sources. International Journal of Numerical Analysis & Modeling 2021 ;Volum 18.(6) s. 740-757 NMBU Untitled
2020
5.	Gergelits, Tomas; Nielsen, Bjørn Fredrik; Strakos, Zdenek. Generalized spectrum of second order differential operators. SIAM Journal on Numerical Analysis 2020 ;Volum 58.(4) s. 2193-2211 NMBU Untitled
2019
6.	Gergelits, Tomas; Mardal, Kent-Andre; Nielsen, Bjørn Fredrik; Strakos, Zdenek. Laplacian preconditioning of elliptic PDEs: Localization of the eigenvalues of the discretized operator. SIAM Journal on Numerical Analysis 2019 ;Volum 57.(3) s. 1369-1394 UiO NMBU Untitled
2017
7.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. Preconditioners for PDE-constrained optimization problems with box constraints: Towards high resolution inverse ECG images. International Journal of Numerical Analysis & Modeling 2017 ;Volum 14.(6) s. 935-962 NMBU Untitled

8.	Nielsen, Bjørn Fredrik. Regularization of Ill-Posed Point Neuron Models. The Journal of Mathematical Neuroscience 2017 ;Volum 7.(1) NMBU Untitled
2016
9.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. PDE-constrained optimization with local control and boundary observations: Robust preconditioners. SIAM Journal on Scientific Computing 2016 ;Volum 38.(6) s. A3461-A3491 NMBU Untitled

10.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. The split Bregman algorithm applied to PDE-constrained optimization problems with total variation regularization. Computational optimization and applications 2016 ;Volum 64.(3) s. 699-724 NMBU Untitled

11.	Mardal, Kent-Andre; Nielsen, Bjørn Fredrik; Nordaas, Magne. Robust preconditioners for PDE-constrained optimization with limited observations. BIT Numerical Mathematics 2016 ;Volum 57.(2) s. 405-431 NMBU UiO Untitled

12.	Nielsen, Bjørn Fredrik; Wyller, John Andreas. Ill-posed Point Neuron Models. The Journal of Mathematical Neuroscience 2016 ;Volum 6.(1) NMBU Untitled
2014
13.	Lysaker, Ola Marius; Nielsen, Bjørn Fredrik; Wall, Samuel T. Bidomain Simulations of Subendocardial Ischemia: The Forward and Inverse Problems. Computing in cardiology 2014 ;Volum 41.(January) s. 1149-1152 USN OUS NMBU Untitled
2013
14.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. A general and effective solution method for PDE-constrained optimization problems with box constraints. International Conference on Preconditioning Techniques for Scientific and Industrial Applications; 2013-06-19 - 2013-06-21 NMBU Untitled

15.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik. PDE-constrained optimization problems with box constraints; Effective solutions and real world applications. Applied Inverse Problems; 2013-07-01 - 2013-07-05 NMBU Untitled

16.	Lines, Glenn Terje; Lysaker, Ola Marius; Nielsen, Bjørn Fredrik. Observability of Ischemia and the Need for Patient Specific Geometrical Models in Inverse ECG. Computers in cardiology 2013 ;Volum 40. s. 679-682 USN OUS NMBU UiO Untitled

17.	Lysaker, Ola Marius; Nielsen, Bjørn Fredrik; Wall, Samuel Thomas. Computing Ischemic regions in the heart: on the use of internal electrodes. Computers in cardiology 2013 ;Volum 40. s. 675-678 USN NMBU OUS Untitled

18.	Nielsen, Bjørn Fredrik; Lysaker, Ola Marius; Grøttum, Per. Computing Ischemic Regions in the Heart With the Bidomain Model—First Steps Towards Validation. IEEE Transactions on Medical Imaging 2013 ;Volum 32.(6) s. 1085-1096 UiO OUS NMBU USN Untitled

19.	Nielsen, Bjørn Fredrik; Mardal, Kent-Andre. Analysis of the Minimal Residual Method Applied to Ill Posed Optimality Systems. SIAM Journal on Scientific Computing 2013 ;Volum 35.(2) s. A785-A814 OUS NMBU UiO Untitled
2012
20.	Burger, Martin; Nielsen, Bjørn Fredrik. Funding: Deutscher Akademischer Austauschdienst Programme des Projektbezogenen Personenaustauschs DAADppp Mobility Programme Germany–Norway. Circulation 2012 ;Volum 125.(18) s. f107-f108 NMBU Untitled

21.	Elvetun, Ole Løseth; Nielsen, Bjørn Fredrik; Mardal, Kent-Andre. Early detection of heart attacks using PDE-constrained optimization. 4th National PhD Conference in Medical Imaging; 2012-11-28 - 2012-11-29 UiO NMBU Untitled

22.	Lysaker, Ola Marius; Nielsen, Bjørn Fredrik; Grøttum, Per. On the Use of the Bidomain Model for Computing the Position and Size of Ischemic Regions; a Validation Study. I: Computing in Cardiology 2012, Volume 39. : Computing in Cardiology 2012 ISBN 978-1-4673-2076-4. s. 449-452 USN OUS UiO NMBU Untitled

23.	Nielsen, Bjørn Fredrik; Mardal, Kent-Andre. The Minimal Residual Method applied to ill-posed optimality systems; eigenvalues and convergence properties. Numerical Methods for Optimal Control and Inverse Problems; 2012-03-12 - 2012-03-14 UiO NMBU Untitled
2011
24.	Mardal, Kent-Andre; Nielsen, Bjørn Fredrik. Efficient preconditioning of optimality systems. International Conference On Preconditioning Techniques For Scientific And Industrial Applications; 2011-05-16 - 2011-05-18 UiO NMBU Untitled
2010
25.	Burger, Martin; Mardal, Kent-Andre; Nielsen, Bjørn Fredrik. Stability analysis of the inverse transmembrane potential problem in electrocardiography. Inverse Problems 2010 ;Volum 26.(10) s. - UiO NMBU Untitled

26.	Nielsen, Bjørn Fredrik; Lysaker, O.M.; Grøttum, Per; Mardal, Kent-Andre; Tveito, Aslak; Tarrou, Christian; Haugaa, K.; Abildgaard, A.; Fjeld, J.G.. Can ECG recordings and mathematics tell the condition of your heart?. I: Simula Research Laboratory - by thinking constantly about it. Springer 2010 ISBN 978-3-642-01155-9. s. 287-319 UiO Untitled

27.	Nielsen, Bjørn Fredrik; Mardal, Kent-Andre. Efficient preconditioners for optimality systems arising in connection with inverse problems. SIAM Journal of Control and Optimization 2010 ;Volum 48.(8) s. 5143-5177 NMBU Untitled

28.	Tveito, Aslak; Langtangen, Hans Petter; Nielsen, Bjørn Fredrik; Cai, Xing. Elements of scientific computing. Springer 2010 (ISBN 9783642112980) 459 s. NMBU Untitled
2009
29.	Almendral-Vazquez, Ariel; Nielsen, Bjørn Fredrik. The multigrid algorithm applied to a degenerate equation: A convergence analysis. Journal of Computational and Applied Mathematics 2009 ;Volum 225.(1) s. 251-267 NR Untitled

30.	Haga, Joachim Berdal; Langtangen, Hans Petter; Nielsen, Bjørn Fredrik; Osnes, Harald. On the performance of an algebraic multigrid preconditioner for the pressure equation with highly discontinuous media. I: Proceedings of MekIT'09. Tapir Akademisk Forlag 2009 ISBN 978-82-519-2421-4. s. 191-204 UiO Untitled

31.	Lysaker, M.; Nielsen, Bjørn Fredrik; Nielsen, Bjørn Fredrik; Grøttum, P.; Haugaa, K.; Fjeld, J.G.; Abildgaard, A.. Mathematical Based Imaging of Regional Ischemia. I: World Congress on Medical Physics and Biomedical Engineering September 7 - 12, 2009 Munich, Germany. Germany: IFMBE Proceedings 2009 ISBN 978-3-642-03881-5. UiO Untitled

32.	Nielsen, Bjørn Fredrik; Cai, Xing; Sundnes, Joakim; Tveito, Aslak. Towards a computational method for imaging the extracellular potassium concentration during regional ischemia. Mathematical Biosciences 2009 ;Volum 220.(2) s. 118-130 UiO Untitled

33.	Nielsen, Bjørn Fredrik; Tveito, Aslak; Hackbusch, W. Preconditioning by inverting the Laplacian: an analysis of the eigenvalues. IMA Journal of Numerical Analysis 2009 ;Volum 29.(1) s. 24-42 UiO Untitled

34.	Ruud, Tomas Syrstad; Nielsen, Bjørn Fredrik; Lysaker, Marius; Sundnes, Joakim. A Computationally Efficient Method for Determining the Size and Location of Myocardial Ischemia. IEEE Transactions on Biomedical Engineering 2009 ;Volum 56.(2) s. 263-272 UiO Untitled
2008
35.	Nielsen, Bjørn Fredrik; Skavhaug, Ola; Tveito, Aslak. Penalty methods for the numerical solution of American multi-asset option problems. Journal of Computational and Applied Mathematics 2008 ;Volum 222.(1) s. 3-16 UiO Untitled
2007
36.	Cai, Xing; Nielsen, Bjørn Fredrik; Tveito, Aslak. A note on the efficiency of the conjugate gradient method for a class of time-dependent problems. Numerical Linear Algebra with Applications 2007 ;Volum 14.(5) s. 459-467 UiO Untitled

37.	Nielsen, Bjørn Fredrik; Cai, Xing; Lysaker, Ola Marius. On the possibility for computing the transmembrane potential in the heart with a one shot method: An inverse problem. Mathematical Biosciences 2007 ;Volum 210.(2) s. 523-553 UiO Untitled

38.	Nielsen, Bjørn Fredrik; Ruud, Tomas Syrstad; Lines, Glenn Terje; Tveito, Aslak. Optimal monodomain approximations of the bidomain equations. Applied Mathematics and Computation 2007 ;Volum 184.(2) s. 276-290 UiO Untitled
2006
39.	Lysaker, Ola Marius; Tarrou, C; Abildgaard, A; Nielsen, Bjørn Fredrik. On the Use of Computers to Simulate Cardiac Functions. The 24th International EuroPACS Conference; 2006-06-14 - 2006-06-17 UiO Untitled

40.	MacLachlan, MC; Nielsen, Bjørn Fredrik; Lysaker, M; Tveito, Aslak. Computing the size and location of myocardial ischemia using measurements of ST-segment shift. IEEE Transactions on Biomedical Engineering 2006 ;Volum 53. s. 1024-1031 UiO Untitled

41.	Sundnes, Joakim; Lines, Glenn Terje; Cai, Xing; Nielsen, Bjørn Fredrik; Mardal, Kent-Andre; Tveito, Aslak. Computing the electrical activity in the heart. Springer 2006 (ISBN 978-3-540-33432-3) 311 s. UiO NMBU Untitled

42.	Sundnes, Joakim; Nielsen, Bjørn Fredrik; Mardal, Kent-Andre; Cai, Xing; Lines, Glenn Terje; Tveito, Aslak. On the computational complexity of the bidomain and the monodomain models of electrophysiology. Annals of Biomedical Engineering 2006 ;Volum 34.(7) s. 1088-1097 UiO Untitled
2005
43.	Lysaker, Ola Marius; Nielsen, Bjørn Fredrik; Tveito, Aslak; Lines, Glenn Terje; Sundnes, Joakim; Tarrou, C. Kan man simulere et hjerteslag?. LAMIS - SOMMERKURS "Matematikk ? med røtter og vinger"; 2005-08-07 - 2005-08-10 UiO Untitled

44.	Mardal, Kent-Andre; Nielsen, Bjørn Fredrik; Cai, Xing; Tveito, Aslak. An order optimal solver for the discretized Bidomain equations. Fornebu, Norway: Simula Research Laboratory 2005 14 s. UiO Untitled

45.	Mardal, Kent-Andre; Nielsen, Bjørn Fredrik; Cai, Xing; Tveito, Aslak. Optimal Preconditioners for Discrete Versions of the Bidomain Model. Lysaker: Simula Research Laboratory 2005 UiO Untitled

46.	Mardal, Kent-Andre; Nielsen, Bjørn Fredrik; Tveito, Aslak. Preconditioners for Elliptic Problems with Variable Coefficients. SIAM Conference on Mathematical and Computational Issues in the Geosciences; 2005-06-07 - 2005-06-10 UiO Untitled

47.	Nielsen, Bjørn Fredrik; Lysaker, Ola Marius; MacLachlan, Mary Catherine; Tveito, Aslak. On the use of level set techniques for identifying heart infarctions. Presented at the Level Set Methods for Direct and Inverse Problems workshop in Linz; 2005-09-14 - 2005-09-16 UiO Untitled

48.	Nielsen, Bjørn Fredrik; Lysaker, Ola Marius; Tarrou, C; Abildgaard, A; MacLachlan, Mary Catherine; Tveito, Aslak. On the Use of ST-Segment Shifts and Mathematical Models for Identifying Ischemic Heart Disease. I: Computers in Cardiology. IEEE 2005 ISBN 0-7803-9337-6. s. 1005-1008 UiO Untitled

49.	Nielsen, Bjørn Fredrik; Lysaker, Ola Marius; Tarrou, C; MacLachlan, Mary Catherine; Abildgaard, A; Tveito, Aslak. On the Use of ST-Segment Shifts and Mathematical Models for Identifying Ischemic Heart Disease. Computers in Cardiology conference; 2005-09-25 - 2005-09-28 UiO Untitled
2004
50.	MacLachlan, Mary Catherine; Nielsen, Bjørn Fredrik; Tveito, Aslak. On the use of ST shifts to identify ischemic heart disease: Towards a computational approach. : Simula Research Laboratory 2004 UiO Untitled

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