Siste publikasjoner

• Kristiansen, Lars (2021). On subrecursive representation of irrational numbers: Contractors and Baire sequences. Lecture Notes in Computer Science (LNCS).  ISSN 0302-9743.
• Brualdi, Richard A. & Dahl, Geir (2021). Sign-restricted matrices of 0's, 1's, and −1's. Linear Algebra and its Applications.  ISSN 0024-3795.  615, s 77- 103 . doi: 10.1016/j.laa.2021.01.001
• Nilssen, Torstein; Hofmanova, Martina & Leahy, James-Michael (2021). On a rough perturbation of the Navier–Stokes system and its vorticity formulation. The Annals of Applied Probability.  ISSN 1050-5164. . doi: 10.1214/20-AAP1603
• Pedersen, Geir Kleivstul (2021). Asymptotic, Convergent, and Exact Truncating Series Solutions of the Linear Shallow Water Equations for Channels with Power Law Geometry. SIAM Journal on Applied Mathematics.  ISSN 0036-1399.  81(2), s 285- 303 . doi: 10.1137/19M1305860
• Hultgren, Jakob & Wold, Erlend Fornæss (2021). Unipotent factorization of vector bundle automorphisms. International Journal of Mathematics.  ISSN 0129-167X. . doi: 10.1142/S0129167X21500130
• Brualdi, R.A. & Dahl, Geir (2021). Convex (0,1)-Matrices and Their Epitopes,. Discrete Applied Mathematics.  ISSN 0166-218X.
• Helsø, Martin & Ranestad, Kristian (2021). Rational Quartic Spectrahedra. Mathematica Scandinavica.  ISSN 0025-5521. . doi: 10.7146/math.scand.a-121456
• Ottem, John Christian & Benoist, Olivier (2021). Two coniveau filtrations. Duke mathematical journal.  ISSN 0012-7094.
• Chan, Tak Shing; Lee, Carmen L.; Pedersen, Christian; Dalnoki-Veress, Kari & Carlson, Andreas (2021). Film coating by directional droplet spreading on fibers. Physical Review Fluids.  ISSN 2469-990X. . doi: 10.1103/PhysRevFluids.6.014004 Fulltekst i vitenarkiv.
• Erhardt, André Henrik (2021). Stability of weak solutions to parabolic problems with nonstandard growth and cross–diffusion. Axioms.  ISSN 2075-1680.  10(1), s 1- 7 . doi: 10.3390/axioms10010014 Fulltekst i vitenarkiv.
• Friedemann, Christopher; Mortensen, Mikael & Nossen, Jan (2021). Two-phase co-current flow simulations using periodic boundary conditions in horizontal, 4, 10 and 90° inclined eccentric annulus, flow prediction using a modified interFoam solver and comparison with experimental results. International Journal of Heat and Fluid Flow.  ISSN 0142-727X.  88, s 1- 20 . doi: 10.1016/j.ijheatfluidflow.2020.108754 Fulltekst i vitenarkiv.
• Brualdi, R.A. & Dahl, Geir (2021). Sign-restricted matrices of 0's, 1's, and -1's. Linear Algebra and its Applications.  ISSN 0024-3795.
• Normann, Dag & Sanders, Sam (2021). The Axiom of Choice in computability theory and Reverse Mathematics with a cameo for the Continuum Hypothesis. Journal of Logic and Computation.  ISSN 0955-792X. . doi: 10.1093/logcom/exaa080
• Støle-Hentschel, Susanne; Nieto Borge, Jose Carlos & Trulsen, Karsten (2021). The deconvolution as a method to deal with gaps in ocean wave measurements. Ocean Engineering.  ISSN 0029-8018.  219 . doi: 10.1016/j.oceaneng.2020.108373 Fulltekst i vitenarkiv. Vis sammendrag

  This work introduces the deconvolution as a technique to reconstruct missing information in data. While the method was originally developed for ocean waves, it will be useful in a wider range of applications where gaps in data may alter the statistics or spikes have to be eliminated without removing extreme values. For the application to ocean waves, it is estimated that gaps as long as half of the peak period may be reconstructed well. It is possible to reconstruct data of longer gaps, however, in total the amount of missing points should be less than 50% of all points and the missing data should not be clustered.

• Vanem, Erik; Aarsnes, Lars Holterud; Storhaug, Gaute & Astrup, Ole Christian (2021). Statistical Modelling and Comparison of Model-Based Fatigue Calculations and Hull Monitoring Data for Container Vessels, In  Practical Design of Ships and Other Floating Structures. Proceedings of the 14th International Symposium, PRADS 2019, September 22-26, 2019, Yokohama, Japan- Volume II.  Springer.  ISBN 978-981-15-4671-6.  paper.  s 517 - 536 Fulltekst i vitenarkiv.
• Forstnerič, Franc & Wold, Erlend Fornæss (2020). Holomorphic families of fatou-bieberbach domains and applications to oka manifolds. Mathematical Research Letters.  ISSN 1073-2780.  27(6), s 1697- 1706 . doi: 10.4310/MRL.2020.V27.N6.A5
• Benth, Fred Espen; Detering, Nils & Krühner, Paul (2020). Independent increment processes: a multilinearity preserving property. Stochastics: An International Journal of Probability and Stochastic Processes.  ISSN 1744-2508. . doi: 10.1080/17442508.2020.1802458
• Cifuentes, Diego; Ranestad, Kristian; Sturmfels, Bernd & Weinstein, Madeleine (2020). Voronoi cells of varieties. Journal of symbolic computation.  ISSN 0747-7171.  s 1- 16 . doi: 10.1016/j.jsc.2020.07.009
• Biagini, Francesca; Fouque, Jean-Pierre; Frittelli, Marco & Meyer-Brandis, Thilo (2020). On fairness of systemic risk measures. Finance and Stochastics.  ISSN 0949-2984.  24(2), s 513- 564 . doi: 10.1007/s00780-020-00417-4
• Agram, Nacira & Øksendal, Bernt (2020). A financial market with singular drift and no arbitrage. Mathematics and Financial Economics.  ISSN 1862-9679. . doi: 10.1007/s11579-020-00284-9
• Daversin-Catty, Cecile; Vinje, Vegard; Mardal, Kent-Andre & Rognes, Marie E. (2020). The mechanisms behind perivascular fluid flow. PLOS ONE.  ISSN 1932-6203.  15(12) . doi: 10.1371/journal.pone.0244442
• Schwarzl, Richard; Liese, Susanne; Brünig, Florian N.; Laudisio, Fabio & Netz, Roland R. (2020). Force Response of Polypeptide Chains from Water-Explicit MD Simulations. Macromolecules.  ISSN 0024-9297.  53(12), s 4618- 4629 . doi: 10.1021/acs.macromol.0c00138
• Rauter, Matthias; Hosse, Luisa; Mulligan, Ryan P.; Take, W. A. & Løvholt, Finn (2020). Numerical simulation of impulse wave generation by idealized landslides with OpenFOAM. Coastal Engineering.  ISSN 0378-3839.  165 . doi: 10.1016/j.coastaleng.2020.103815 Fulltekst i vitenarkiv. Vis sammendrag

  Landslide tsunamis and impulse waves are hazardous events with severe socioeconomic impacts. A long standing problem with simulations of these events is the generation stage, where landslides and water interact. Depth-averaged models like the Saint-Venant or Boussinesq Equations lose their validity for such applications. Therefore, we have to rely on a full treatment of the hydrodynamics, for instance by applying the Navier-Stokes Equations and Computational Fluid Dynamics (CFD). However, applications of fully three-dimensional methods to landslide tsunamis are sparse, and have often been outperformed by depth averaged models when compared to experimental data. In this work, we evaluate the multiphase Navier-Stokes Equations as implemented in OpenFOAM® in terms of impulse wave generation. We focus on a simplified two-dimensional setup where the landslide consists of water, in order to circumvent additional complexities due to treatment of landslide rheologies. We conduct a thorough grid refinement study and compare results to experiments to investigate model convergence, stability, and accuracy. The simulations display good agreement with the experimental data if the Courant-Friedrichs-Lewy (CFL) condition is modified to account for the specific properties of the multiphase system. Further, we use the validated model for sensitivity studies and to review various scaling relations for landslide generated tsunamis. The application of numerical models allows us to perform broad parametric tests and dissect the underlying physics of these predictive equations systematically. We found that the first wave crest may be well estimated by solely the landslide mass in our setting. Including additional properties related to landslide momentum can improve the predictive skill, while other parameters lead to no substantial improvement.

• Benth, Fred Espen; Eikeset, Anne Maria; Levin, Simon A. & Ren, Wanjuan (2020). Analysis of the risk premium in the forward market for salmon. Journal of Commodity Markets.  ISSN 2405-8513.  s 1- 13 . doi: 10.1016/j.jcomm.2019.100122 Fulltekst i vitenarkiv.
• Arosio, Leandro; Fornæss, John Erik; Shcherbina, Nikolay & Wold, Erlend Fornæss (2020). Squeezing functions and Cantor sets. Annali della Scuola Normale Superiore di Pisa (Classe Scienze), Serie V.  ISSN 0391-173X.  s 1359- 1369 . doi: 10.2422/2036-2145.201807_003
• Forstneric, Franc & Wold, Erlend Fornæss (2020). Runge tubes in Stein manifolds with the density property. Proceedings of the American Mathematical Society.  ISSN 0002-9939.  148, s 569- 575 . doi: 10.1090/proc/14309
• Brownlowe, Nathan; Larsen, Nadia S.; Ramagge, Jacqui & Stammeier, Nicolai (2020). C*-algebras of right LCM monoids and their equilibrium states. Transactions of the American Mathematical Society.  ISSN 0002-9947.  373(7), s 5235- 5273 . doi: 10.1090/tran/8097 Fulltekst i vitenarkiv.
• Floater, Michael S. & Hu, Kaibo (2020). A characterization of supersmoothness of multivariate splines. Advances in Computational Mathematics.  ISSN 1019-7168. . doi: 10.1007/s10444-020-09813-y Fulltekst i vitenarkiv.
• Erik, Burman; Christiansen, Snorre H & Hansbo, Peter (2020). Application of a minimal compatible element to incompressible and nearly incompressible continuum mechanics. Computer Methods in Applied Mechanics and Engineering.  ISSN 0045-7825.  369 . doi: 10.1016/j.cma.2020.113224 Fulltekst i vitenarkiv.
• Chang, Qingjun; Deng, Chongyang & Floater, Michael S. (2020). An interpolatory view of polynomial least squares approximation. Journal of Approximation Theory.  ISSN 0021-9045.  252 . doi: 10.1016/j.jat.2019.105360 Fulltekst i vitenarkiv.
• Antollini, Giulia; Jensen, Atle; Grue, John; Riise, Bjørn & Brochini, Maurizio (2020). Wave-induced vortex generation around a slender vertical cylinder. Physics of Fluids.  ISSN 1070-6631.  32 . doi: 10.1063/1.5141131
• Hermansen, Gudmund Horn; Knutsen, Carl Henrik & Nygård, Håvard Mokleiv (2020). Characterizing and Assessing Temporal Heterogeneity: Introducing a Change Point Framework, with Applications on the Study of Democratization. Political Analysis.  ISSN 1047-1987. . doi: 10.1017/pan.2020.39 Fulltekst i vitenarkiv.
• Dabrowski, Ludwik; Hajac, Piotr M. & Neshveyev, Sergey (2020). Noncommutative Borsuk–Ulam-type conjectures revisited. Journal of Noncommutative Geometry.  ISSN 1661-6952.  14(4), s 1305- 1324 . doi: 10.4171/JNCG/352 Fulltekst i vitenarkiv.
• Ivarsson, Björn; Kutzschebauch, Frank & Løw, Erik (2020). Factorization of symplectic matrices into elementary factors. Proceedings of the American Mathematical Society.  ISSN 0002-9939.  148(5), s 1963- 1970 . doi: 10.1090/proc/14891
• Lauster, Daniel; Klenk, Simon; Ludwig, Kai; Nojoumi, Saba; Behren, Sandra; Adam, Lutz; Stadtmüller, Marlena; Saenger, Sandra; Zimmler, Stephanie; Hönzke, Katja; Yao, Ling; Hoffmann, Ute; Bardua, Markus; Hamann, Alf; Witzenrath, Martin; Sander, Leif E.; Wolff, Thorsten; Hocke, Andreas C.; Hippenstiel, Stefan; De Carlo, Sacha; Neudecker, Jens; Osterrieder, Nikolaus; Budisa, Nediljko; Netz, Roland R.; Böttcher, Christoph; Liese, Susanne; Herrmann, Andreas & Hackenberger, Christian P. R. (2020). Phage capsid nanoparticles with defined ligand arrangement block influenza virus entry. Nature Nanotechnology.  ISSN 1748-3387.  15(5), s 373- 379 . doi: 10.1038/s41565-020-0660-2
• Rossow, Ingeborg Margrete; Amundsen, Ellen Johanna & Samuelsen, Sven Ove (2020). Socio‐economic differences in all‐cause mortality in people with alcohol use disorder: a prospective cohort study. Addiction.  ISSN 0965-2140.  116(1), s 53- 59 . doi: 10.1111/add.15070 Fulltekst i vitenarkiv.
• Köksal, Elif; Liese, Susanne; Xue, Lin; Ryskulov, Ruslan; Viitala, Lauri; Carlson, Andreas & Gözen, Irep (2020). Rapid Growth and Fusion of Protocells in Surface‐Adhered Membrane Networks. Small.  ISSN 1613-6810.  16(38) . doi: 10.1002/smll.202002529 Vis sammendrag

  Elevated temperatures might have promoted the nucleation, growth, and replication of protocells on the early Earth. Recent reports have shown evidence that moderately high temperatures not only permit protocell assembly at the origin of life, but can have actively supported it. Here, the fast nucleation and growth of vesicular compartments from autonomously formed lipid networks on solid surfaces, induced by a moderate increase in temperature, are shown. Branches of the networks, initially consisting of self‐assembled interconnected nanotubes, rapidly swell into microcompartments which can spontaneously encapsulate RNA fragments. The increase in temperature further causes fusion of adjacent network‐connected compartments, resulting in the redistribution of the RNA. The experimental observations and the mathematical model indicate that the presence of nanotubular interconnections between protocells facilitates the fusion process.

• Bratteli, Tone; Digernes, Trond; Elliott, George A.; Evans, David E.; Jorgensen, Palle E.T.; Kishimoto, Akitaka; Landstad, Magnus Brostrup; Robinson, Derek W & Størmer, Erling (2020). Ola Bratteli and His Diagrams. Notices of the American Mathematical Society.  ISSN 0002-9920.  67(5), s 665- 675 . doi: 10.1090/noti2085 Fulltekst i vitenarkiv.
• Huseby, Arne; Kalinowska, Martyna & Abrahamsen, Tobias (2020). Birnbaum criticality and importance measures for multistate systems with repairable components. Probability in the engineering and informational sciences (Print).  ISSN 0269-9648.  s 1- 21 . doi: 10.1017/S0269964820000340 Fulltekst i vitenarkiv. Vis sammendrag

  We suggest four new measures of importance for repairable multistate systems based on the classical Birnbaum measure. Periodic component life cycles and general semi-Markov processes are considered. Similar to the Birnbaum measure, the proposed measures are generic in the sense that they only depend on the probabilistic properties of the compo- nents and the system structure. The multistate system model encodes physical properties of the components and the system directly into the structure function. As a result, cal- culating importance is easy, especially in the asymptotic case. Moreover, the proposed measures are composite measures, combining importance for all component states into a unified quantity. This simplifies ranking of the components with respect to importance. The proposed measures can be characterized with respect to two features: forward-looking versus backward-looking and with respect to how criticality is measured. Forward-looking importance measures focus on the next component states, while backward-looking impor- tance measures focus on the previous component states. Two approaches to measuring criticality are considered: probability of criticality versus expected impact. Examples show that the different importance measures may result in unequal rankings.

• Viinikka, Jussi; Hyttinen, Antti; Pensar, Johan & Koivisto, Mikko (2020). Towards Scalable Bayesian Learning of Causal DAGs. Advances in Neural Information Processing Systems.  ISSN 1049-5258.
• Tadei, Alessandro; Haajanen, Juulia; Pensar, Johan; Santtila, Pekka & Antfolk, Jan (2020). Counteracting deceptive responding in the Finnish Investigative Instrument of Child Sexual Abuse (FICSA). Journal of Sexual Aggression.  ISSN 1355-2600. . doi: 10.1080/13552600.2020.1846802 Fulltekst i vitenarkiv.
• Barker, T.; Rauter, Matthias; Maguire, E. S. F.; Johnson, C. G. & Gray, J. M. N. T. (2020). Coupling rheology and segregation in granular flows. Journal of Fluid Mechanics.  ISSN 0022-1120.  909(A22) . doi: 10.1017/jfm.2020.973 Fulltekst i vitenarkiv. Vis sammendrag

  During the last fifteen years there has been a paradigm shift in the continuum modelling of granular materials; most notably with the development of rheological models, such as the μ(I) μ(I) -rheology (where μ μ is the friction and I is the inertial number), but also with significant advances in theories for particle segregation. This paper details theoretical and numerical frameworks (based on OpenFOAM) which unify these currently disconnected endeavours. Coupling the segregation with the flow, and vice versa, is not only vital for a complete theory of granular materials, but is also beneficial for developing numerical methods to handle evolving free surfaces. This general approach is based on the partially regularized incompressible μ(I) μ(I) -rheology, which is coupled to the gravity-driven segregation theory of Gray & Ancey (J. Fluid Mech., vol. 678, 2011, pp. 353–588). These advection–diffusion–segregation equations describe the evolving concentrations of the constituents, which then couple back to the variable viscosity in the incompressible Navier–Stokes equations. A novel feature of this approach is that any number of differently sized phases may be included, which may have disparate frictional properties. Further inclusion of an excess air phase, which segregates away from the granular material, then allows the complex evolution of the free surface to be captured simultaneously. Three primary coupling mechanisms are identified: (i) advection of the particle concentrations by the bulk velocity, (ii) feedback of the particle-size and/or frictional properties on the bulk flow field and (iii) influence of the shear rate, pressure, gravity, particle size and particle-size ratio on the locally evolving segregation and diffusion rates. The numerical method is extensively tested in one-way coupled computations, before the fully coupled model is compared with the discrete element method simulations of Tripathi & Khakhar (Phys. Fluids, vol. 23, 2011, 113302) and used to compute the petal-like segregation pattern that spontaneously develops in a square rotating drum.

• Johansen, Rune; Sørensen, Adam Peder Wie & Szymanski, Wojciech (2020). The polynomial endomorphisms of graph algebras. Groups, Geometry, and Dynamics.  ISSN 1661-7207.  14(3), s 1043- 1075 . doi: 10.4171/GGD/574
• Sørensen, Øystein; Crispino, Marta; Liu, Qinghua & Vitelli, Valeria (2020). BayesMallows: An R Package for the Bayesian Mallows Model. The R Journal.  ISSN 2073-4859.  12(1), s 324- 342 . doi: 10.32614/RJ-2020-026 Fulltekst i vitenarkiv.
• Catral, Minerva; Ciardo, Lorenzo; Hogben, Leslie & Reinhart, Carolyn (2020). Spectra of products of digraphs. The Electronic Journal of Linear Algebra.  ISSN 1537-9582.  36(1), s 744- 763 . doi: 10.13001/ELA.2020.5243 Fulltekst i vitenarkiv.
• Viquerat, Jonathan; Rabault, Jean; Kuhnle, Alexander; Ghraieb, Hassan; Larcher, Aurelien & Hachem, Elie (2020). DIRECT SHAPE OPTIMIZATION THROUGH DEEP REINFORCEMENT LEARNING. Journal of Computational Physics.  ISSN 0021-9991.  428(1) . doi: 10.1016/j.jcp.2020.110080 Fulltekst i vitenarkiv.
• Truong, Tuyen Trung (2020). Strong submeasures and applications to non-compact dynamical systems. Ergodic Theory and Dynamical Systems.  ISSN 0143-3857. . doi: 10.1017/etds.2020.132 Fulltekst i vitenarkiv.
• Chan, Tak Shing; Pedersen, Christian; Koplik, Joel & Carlson, Andreas (2020). Film deposition and dynamics of a self-propelled wetting droplet on a conical fibre. Journal of Fluid Mechanics.  ISSN 0022-1120.  907, A29, s 907 A29-1- 907 A29-22 . doi: 10.1017/jfm.2020.834 Fulltekst i vitenarkiv.
• Ren, Shuai; Pedersen, Christian; Carlson, Andreas; Salez, Thomas & Wang, Yuliang (2020). Capillary deformation of ultrathin glassy polymer films by air nanobubbles. Physical Review Research (PRResearch).  ISSN 2643-1564.  2(4) . doi: 10.1103/PhysRevResearch.2.043166 Fulltekst i vitenarkiv.
• Rojas Molina, Rossana Virginia; Liese, Susanne & Carlson, Andreas (2020). Diffusion on membrane domes, tubes and pearling structures. Biophysical Journal.  ISSN 0006-3495.  120(3), s 424- 431 . doi: 10.1016/j.bpj.2020.12.014 Fulltekst i vitenarkiv.
• Antun, Vegard; Renna, Francesco; Poon, Clarice; Adcock, Ben & Hansen, Anders Christian (2020). On instabilities of deep learning in image reconstruction and the potential costs of AI. Proceedings of the National Academy of Sciences of the United States of America.  ISSN 0027-8424.  117(48), s 30088- 30095 . doi: 10.1073/pnas.1907377117 Fulltekst i vitenarkiv. Vis sammendrag

  Deep learning, due to its unprecedented success in tasks such as image classification, has emerged as a new tool in image reconstruction with potential to change the field. In this paper we demonstrate a crucial phenomenon: deep learning typically yields unstable methods for image reconstruction. The instabilities usually occur in several forms: (1) certain tiny, almost undetectable perturbations, both in the image and sampling domain, may result in severe artefacts in the reconstruction, (2) a small structural change, for example a tumour, may not be captured in the reconstructed image and (3) (a counterintuitive type of instability) more samples may yield poorer performance. Our new stability test with algorithms and easy to use software detects the instability phenomena. The test is aimed at researchers to test their networks for instabilities and for government agencies, such as the Food and Drug Administration (FDA), to secure safe use of deep learning methods.

• Arumugam, Gurusamy & Erhardt, André Henrik (2020). Existence and uniqueness of weak solutions to parabolic problems with nonstandard growth and cross diffusion. Electronic Journal of Differential Equations.  ISSN 1550-6150.  123 Fulltekst i vitenarkiv.
• Lavagnini, Silvia (2020). CARMA Approximations and Estimation. Frontiers in Applied Mathematics and Statistics.  ISSN 2297-4687.  6 . doi: 10.3389/fams.2020.00037 Fulltekst i vitenarkiv.
• Aiken, John Mark; De Bin, Riccardo; Hjorth-Jensen, Morten & Caballero, Marcos Daniel (2020). Predicting time to graduation at a large enrollment American university. PLOS ONE.  ISSN 1932-6203. . doi: 10.1371/journal.pone.0242334 Fulltekst i vitenarkiv.
• Grytten, Ivar; Rand, Knut Dagestad; Nederbragt, Alexander Johan & Sandve, Geir Kjetil (2020). Assessing graph-based read mappers against a baseline approach highlights strengths and weaknesses of current methods. BMC Genomics.  ISSN 1471-2164.  21 . doi: 10.1186/s12864-020-6685-y Fulltekst i vitenarkiv.
• Binde, Caroline Ditlev; Tvete, Ingunn Fride; Gåsemyr, Jørund Inge; Natvig, Bent & Klemp, Marianne (2020). Comparative effectiveness of dopamine agonists and monoamine oxidase type-B inhibitors for Parkinson’s disease: a multiple treatment comparison meta-analysis. European Journal of Clinical Pharmacology.  ISSN 0031-6970.  76(12), s 1731- 1743 . doi: 10.1007/s00228-020-02961-6 Fulltekst i vitenarkiv. Vis sammendrag

  Purpose To investigate the comparative effectiveness of dopamine agonists and monoamine oxidase type-B (MAO-B) inhibitors available for treatment of Parkinson’s disease. Methods We performed a systematic literature search identifying randomized controlled trials investigating 4 dopamine agonists (cabergoline, pramipexole, ropinirole, rotigotine) and 3 MAO-B inhibitors (selegiline, rasagiline, safinamide) for Parkinson’s disease. We extracted and pooled data from included clinical trials in a joint model allowing both direct and indirect comparison of the seven drugs. We considered dopamine agonists and MAO-B inhibitors given as monotherapy or in combination with levodopa. Selected endpoints were change in the Unified Parkinson’s Disease Rating Scale (UPDRS) score, serious adverse events and withdrawals. We estimated the relative effectiveness of each dopamine agonist and MAO-B inhibitor versus comparator drug. Results Altogether, 79 publications were included in the analysis. We found all the investigated drugs to be effective compared with placebo when given as monotherapy except safinamide. When considering combination treatment, the estimated relative effects of selegiline, pramipexole, ropinirole, rotigotine, cabergoline, rasagiline and safinamide were 2.316 (1.819, 2.951), 2.091 (1.889, 2.317), 2.037 (1.804, 2.294), 1.912 (1.716, 2.129), 1.664 (1.113, 2.418), 1.584 (1.379, 1.820) and 1.179 (1.031, 1.352), respectively, compared with joint placebo and levodopa treatment. Conclusions Dopamine agonists were found to be effective as treatment for Parkinson’s disease, both when given as monotherapy and in combination with levodopa. Selegiline and rasagiline were also found to be effective for treating Parkinson’s disease, and selegiline was the best option in combination with levodopa among all the drugs investigated.

• Huseby, Arne & Christensen, Daniel (2020). Optimal reinsurance contracts in the multivariate case, In Piero Baraldi; Francesco P. Di Maio & Enrico Zio (ed.),  e-proceedings of the 30th European Safety and Reliability Conference and 15th Probabilistic Safety Assessment and Management Conference (ESREL2020 PSAM15).  Research Publishing Services.  ISBN 9789811485930.  4280. Vis sammendrag

  An insurance contract implies that risk is ceded from ordinary policy holders to companies. Companies do the same thing between themselves as well. The rationale could be the same; i.e., that a financially weaker agent is passing risk to a stronger one. In reality even the largest companies do this to diversify risk, and financially the cedent may be as strong as the reinsurer. The problem of determining reinsurance contracts which are optimal with respect to some reasonable criterion has been studied extensively within actuarial science. Different contact types are considered such as stop-loss contracts where the reinsurance company covers risk above a certain level, and insurance layer contracts where the reinsurance company covers risk within an interval. The contracts are then optimized with respect to some risk measure, such as value-at-risk or conditional tail expectation. In the present paper we consider the problem of minimizing value-at-risk in the case of multiple insurance layer contracts. Such contracts are known to be optimal in the univariate case, and the optimal contract is easily determined. In the multivariate case, however, finding an optimal set of contracts is not easy. By considering solutions where the risk is balanced between the contracts, we show how to find a solution using an efficient iterative Monte Carlo method. We also consider more general unbalanced solutions for which a slightly more complex optimization method must be applied. The methods are illustrated by numerical examples.

• Zhang, Li-Chun (2020). Proxy expenditure weights for Consumer Price Index: Audit sampling inference for big-data statistics. Journal of the Royal Statistical Society: Series A (Statistics in Society).  ISSN 0964-1998. . doi: 10.1111/rssa.12632
• Grønneberg, Steffen; Moss, Jonas & Foldnes, Njål (2020). Partial identification of latent correlations with binary data. Psychometrika.  ISSN 0033-3123.  85, s 1028- 1051 . doi: 10.1007/s11336-020-09737-y Fulltekst i vitenarkiv. Vis sammendrag

  The tetrachoric correlation is a popular measure of association for binary data and estimates the correlation of an underlying normal latent vector. However, when the underlying vector is not normal, the tetrachoric correlation will be different from the underlying correlation. Since assuming underlying normality is often done on pragmatic and not substantial grounds, the estimated tetrachoric correlation may therefore be quite different from the true underlying correlation that is modeled in structural equation modeling. This motivates studying the range of latent correlations that are compatible with given binary data, when the distribution of the latent vector is partly or completely unknown. We show that nothing can be said about the latent correlations unless we know more than what can be derived from the data. We identify an interval constituting all latent correlations compatible with observed data when the marginals of the latent variables are known. Also, we quantify how partial knowledge of the dependence structure of the latent variables affect the range of compatible latent correlations. Implications for tests of underlying normality are briefly discussed.

• Løken, Trygve Kvåle; Rabault, Jean; Thomas, Erin E.; Müller, Malte; Christensen, Kai Håkon; Sutherland, Graig & Jensen, Atle (2020). A comparison of wave observations in the Arctic marginal ice zone with spectral models. Proceedings of the IAHR International Symposium on ice.  ISSN 2414-6331.  s 499- 508
• Løken, Trygve Kvåle; Rabault, Jean; Jensen, Atle; Sutherland, Graig; Christensen, Kai Håkon & Müller, Malte (2020). Wave measurements from ship mounted sensors in the Arctic marginal ice zone. Cold Regions Science and Technology.  ISSN 0165-232X.  182 . doi: 10.1016/j.coldregions.2020.103207 Fulltekst i vitenarkiv.
• Voermans, Joey; Rabault, Jean; Filchuk, Kirill V.; Ryzhov, Ivan; Heil, Petra; Marchenko, Aleksey; Collins, Clarence O.; Dabboor, Mohammed; Sutherland, Graig J. & Babanin, Alexander V. (2020). Experimental evidence for a universal threshold characterizing wave-induced sea ice break-up. The Cryosphere.  ISSN 1994-0416.  14, s 4265- 4278 . doi: 10.5194/tc-14-4265-2020 Fulltekst i vitenarkiv.
• Rabault, Jean; Voermans, Joey; Sutherland, Graig J.; Jensen, Atle; Babanin, Alexander V. & Filchuk, Kirill V. (2020). Development of Open Source instruments for in-situ measurements of waves in ice. Proceedings of the IAHR International Symposium on ice.  ISSN 2414-6331.  s 521
• ABDELMALEK, Samir; Dali, Ali; Bakdi, Azzeddine & Bettayeb, Maamar (2020). Design and experimental implementation of a new robust observer-based nonlinear controller for DC-DC buck converters. Energy.  ISSN 0360-5442.  213 . doi: 10.1016/j.energy.2020.118816 Fulltekst i vitenarkiv.
• Bakdi, Azzeddine; Bounoua, Wahiba; Guichi, Amar & Mekhilef, Saad (2020). Real-time fault detection in PV systems under MPPT using PMU and high-frequency multi-sensor data through online PCA-KDE-based multivariate KL divergence. International Journal of Electrical Power & Energy Systems.  ISSN 0142-0615. . doi: 10.1016/j.ijepes.2020.106457 Fulltekst i vitenarkiv.
• Bounoua, Wahiba & Bakdi, Azzeddine (2020). Fault detection and diagnosis of nonlinear dynamical processes through correlation dimension and fractal analysis based dynamic kernel PCA. Chemical Engineering Science (CES).  ISSN 0009-2509.  229 . doi: 10.1016/j.ces.2020.116099 Fulltekst i vitenarkiv.
• ABDELMALEK, Samir; Dali, Ali; Bettayeb, Maamar & Bakdi, Azzeddine (2020). A new effective robust nonlinear controller based on PSO for interleaved DC–DC boost converters for fuel cell voltage regulation. Soft Computing - A Fusion of Foundations, Methodologies and Applications.  ISSN 1432-7643.  24, s 17051- 17064 . doi: 10.1007/s00500-020-04996-4 Fulltekst i vitenarkiv.
• Manzaroli, Matilde (2020). Real algebraic curves on real del Pezzo surfaces. International mathematics research notices.  ISSN 1073-7928. . doi: 10.1093/imrn/rnaa169 Fulltekst i vitenarkiv. Vis sammendrag

  The study of the topology of real algebraic varieties dates back to the work of Harnack, Klein and Hilbert in the 19th century; in particular, the isotopy type classification of real algebraic curves in real toric surfaces is a classical subject that has undergone considerable evolution. On the other hand, not much is known for more general ambient surfaces. We take a step forward in the study of topological type classification of real algebraic curves on non-toric surfaces focusing on real del Pezzo surfaces of degree 1 and 2 with multi-components real part. We use degeneration methods and real enumerative geometry in combination with variations of classical methods to give obstructions to the existence of topological type classes realised by real algebraic curves and to give constructions of real algebraic curves with prescribed topology.

• Mannino, Carlo; Nakkerud, Andreas & Sartor, Giorgio (2020). Air Traffic Flow Management with Layered Workload Constraints. Computers & Operations Research.  ISSN 0305-0548.  127 . doi: 10.1016/j.cor.2020.105159 Fulltekst i vitenarkiv. Vis sammendrag

  Many regions of the world are currently struggling with congested airspace, and Europe is no exception. Motivated by our collaboration with relevant European authorities and companies in the Single European Sky ATM Research (SESAR) initiative, we investigate novel mathematical models and algorithms for supporting the Air Traffic Flow Management in Europe. In particular, we consider the problem of optimally choosing new (delayed) departure times for a set of scheduled flights to prevent en-route congestion and high workload for air traffic controllers while minimizing the total delay. This congestion is a function of the number of flights in a certain sector of the airspace, which in turn determines the workload of the air traffic controller(s) assigned to that sector. We present a MIP model that accurately captures the current definition of workload, and extend it to overcome some of the drawbacks of the current definition. The resulting scheduling problem makes use of a novel formulation, Path&Cycle, which is alternative to the classic big-M or time-indexed formulations. We describe a solution algorithm based on delayed variable and constraint generation to substantially speed up the computation. We conclude by showing the great potential of this approach on randomly generated, realistic instances.

• Dahl, Kristina Rognlien & Huseby, Arne (2020). Environmental contours and optimal design, In Piero Baraldi; Francesco P. Di Maio & Enrico Zio (ed.),  e-proceedings of the 30th European Safety and Reliability Conference and 15th Probabilistic Safety Assessment and Management Conference (ESREL2020 PSAM15).  Research Publishing Services.  ISBN 9789811485930.  3647.
• Belmans, Pieter; Oberdieck, Georg & Rennemo, Jørgen Vold (2020). Automorphisms of Hilbert schemes of points on surfaces. Transactions of the American Mathematical Society.  ISSN 0002-9947.  373(9), s 6139- 6156 . doi: 10.1090/tran/8106 Fulltekst i vitenarkiv.
• Zhang, Li-Chun & Tuoto, Tiziana (2020). Linkage‐data linear regression. Journal of the Royal Statistical Society: Series A (Statistics in Society).  ISSN 0964-1998. . doi: 10.1111/rssa.12630 Vis sammendrag

  Data linkage is increasingly being used to combine data from different sources with the aim of identifying and bringing together records from separate files, which correspond to the same entities. Usually, data linkage is not a trivial procedure and linkage errors, false and missed links, are unavoidable. In these cases, standard statistical techniques may produce misleading inference. In this paper, we propose a method for secondary linear regression analysis, where the linked data have to be prepared by someone else, and neither the match-key variables nor the unlinked records are available to the analyst. We develop also a diagnostic test for the assumption of non-informative linkage errors, which is required for all existing secondary analysis adjustment methods. Our approach provides important advantages: it relies on the realistic assumption that the probabilities of correct linkage vary across the records but it does not assume that one is able to estimate the probability of correct linkage for each individual record. Moreover, it accommodates in a simple manner the general situation where the files are of different sizes and none of them is a subset of another. The proposed methodology of adjustment and testing is studied by simulation and applied to real data.

• Cunen, Celine; Walløe, Lars & Hjort, Nils Lid (2020). Focused model selection for linear mixed models with an application to whale ecology. Annals of Applied Statistics.  ISSN 1932-6157.  14(2) . doi: 10.1214/20-AOAS1331 Fulltekst i vitenarkiv.
• Cunen, Celine; Hjort, Nils Lid & Schweder, Tore (2020). Confidence in confidence distributions!. Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences.  ISSN 1364-5021. . doi: 10.1098/rspa.2019.0781 Fulltekst i vitenarkiv.
• Cunen, Celine & Hjort, Nils Lid (2020). Confidence Distributions for FIC Scores. Econometrics.  ISSN 2225-1146.  8(27) . doi: 10.3390/econometrics8030027 Fulltekst i vitenarkiv.
• Bojarskaite, Laura; Bjørnstad, Daniel Marelius; Pettersen, Klas Henning; Cunen, Celine; Hermansen, Gudmund Horn; Åbjørsbråten, Knut Sindre; Chambers, Anna; Sprengel, Rolf; Vervaeke, Koen Gerard Alois; Tang, Wannan; Enger, Rune & Nagelhus, Erlend Arnulf (2020). Astrocytic Ca2+ signaling is reduced during sleep and is involved in the regulation of slow wave sleep. Nature Communications.  ISSN 2041-1723.  11 . doi: 10.1038/s41467-020-17062-2 Fulltekst i vitenarkiv.
• Liese, Susanne; Wenzel, Eva; Kjos, Ingrid; Rojas Molina, Rossana Virginia; Schultz, Sebastian; Brech, Andreas; Stenmark, Harald; Raiborg, Camilla & Carlson, Andreas (2020). Protein crowding mediates membrane remodeling in upstream ESCRT-induced formation of intraluminal vesicles. Proceedings of the National Academy of Sciences of the United States of America.  ISSN 0027-8424.  117(46), s 28614- 28624 . doi: 10.1073/pnas.2014228117 Vis sammendrag

  As part of the lysosomal degradation pathway, the endosomal sorting complexes required for transport (ESCRT-0-III/VPS4) sequester receptors at the endosome and simultaneously deform the membrane to generate intraluminal vesicles (ILVs). Whereas ESCRT-III/VPS4 have an established function in ILV formation, the role of upstream ESCRTs (0-II) in membrane shape remodeling is not understood. Combining experimental measurements and electron microscopy analysis of ESCRT-III depleted cells with a mathematical model, we show that upstream ESCRT-induced alteration of the Gaussian bending rigidity and their crowding in concert with the transmembrane cargo on the membrane induces membrane deformation and facilitates ILV formation: upstream ESCRT-driven budding does not require ATP consumption as only a small energy barrier needs to be overcome. Our model predicts that ESCRTs do not become part of the ILV, but localize with a high density at the membrane neck, where the steep decline in the Gaussian curvature likely triggers ESCRT-III/VPS4 assembly to enable neck constriction and scission.

• Cazzador, Elisa & Skauli, Bjørn (2020). Towards the Degree of the PGL(4)-Orbit of a Cubic Surface. Le Mathematiche.  ISSN 2037-5298.  75(2), s 439- 456 . doi: 10.4418/2020.75.2.3 Fulltekst i vitenarkiv.
• Buccino, Alessio Paolo; Kuchta, Miroslav; Schreiner, Jakob Emil & Mardal, Kent-Andre (2020). Improving Neural Simulations with the EMI Model, In Aslak Tveito; Kent-Andre Mardal & Marie Rognes (ed.),  Modeling Excitable Tissue -- The EMI Framework.  Springer.  ISBN 978-3-030-61156-9.  Chapter 7.  s 87 - 98
• Kuchta, Miroslav & Mardal, Kent-Andre (2020). Iterative Solvers for EMI Models, In Aslak Tveito; Kent-Andre Mardal & Marie Rognes (ed.),  Modeling Excitable Tissue -- The EMI Framework.  Springer.  ISBN 978-3-030-61156-9.  Chapter 6.
• Kuchta, Miroslav; Mardal, Kent-Andre & Rognes, Marie Elisabeth (2020). Solving the EMI Equations using Finite Element Methods, In Aslak Tveito; Kent-Andre Mardal & Marie Rognes (ed.),  Modeling Excitable Tissue -- The EMI Framework.  Springer.  ISBN 978-3-030-61156-9.  Chapter 5.
• Feneuil, Blandine Fleur Prudence; Jensen, Atle & Carlson, Andreas (2020). Destabilization and phase separation of particle suspensions in emulsions. Soft Matter.  ISSN 1744-683X.  16(47), s 10697- 10706 . doi: 10.1039/d0sm01485k
• Riiser, Even Sannes; Haverkamp, Thomas Hendricus Augustus; Varadharajan, Srinidhi; Borgan, Ørnulf; Jakobsen, Kjetill Sigurd; Jentoft, Sissel & Star, Bastiaan (2020). Metagenomic Shotgun Analyses Reveal Complex Patterns of Intra- and Interspecific Variation in the Intestinal Microbiomes of Codfishes. Applied and Environmental Microbiology.  ISSN 0099-2240.  86(6), s 1- 16 . doi: 10.1128/AEM.02788-19
• Afsar, Zahra; Larsen, Nadia S. & Neshveyev, Sergey (2020). KMS States on Nica-Toeplitz C∗-algebras. Communications in Mathematical Physics.  ISSN 0010-3616.  378(3), s 1875- 1929 . doi: 10.1007/s00220-020-03711-6 Fulltekst i vitenarkiv.
• Truong, Tuyen Trung (2020). When will a sequence of points in a Riemannian submanifold converge?. Mathematics.  ISSN 2227-7390.  8(11) . doi: 10.3390/math8111934 Fulltekst i vitenarkiv.
• Mossige, Endre Joachim & Jensen, Atle (2020). Clog-free trilobite filtration: Tunable flow setup and velocity measurements. Micromachines.  ISSN 2072-666X.  11(10) . doi: 10.3390/mi11100904 Fulltekst i vitenarkiv.
• Young, Bruce A.; Adams, James; Beary, Jonathan M.; Mardal, Kent-Andre; Schneider, Robert & Kondrashova, Tatyana (2020). The myodural bridge of the American alligator (Alligator mississippiensis) alters CSF flow. Journal of Experimental Biology.  ISSN 0022-0949.  223(22) . doi: 10.1242/jeb.230896 Fulltekst i vitenarkiv.
• Midtfjord, Alise Danielle & Huseby, Arne (2020). Estimating Runway Friction Using Flight Data, In Piero Baraldi; Francesco P. Di Maio & Enrico Zio (ed.),  e-proceedings of the 30th European Safety and Reliability Conference and 15th Probabilistic Safety Assessment and Management Conference (ESREL2020 PSAM15).  Research Publishing Services.  ISBN 9789811485930.  Artikkel. Vis sammendrag

  During the winter season, contamination of runway surfaces with snow, ice, or slush causes potential economic and safety threats for the aviation industry. The presence of these materials reduces the available tire-pavement friction needed for retardation and directional control. Therefore, pilots operating on contaminated runways need accurate and timely information on the actual runway surface conditions. Avinor, the company that operates most civil airports in Norway, have developed an integrated runway information system, called IRIS, currently used on 16 Norwegian airports. The system uses a scenario approach to identify slippery conditions. In order to validate the scenario model, it is necessary to estimate runway friction. The present paper outlines how this can be done using flight data from the Quick Access Recorder (QAR) of Boeing 737-600/700/800 NG airplanes. Data such as longitudinal acceleration, airspeed, ground speed, flap settings, engine speed, brake pressures are sampled at least each second during landings. The paper discusses some of the challenges with this. In particular, issues related to calibration of data are considered, and two different regression methods are compared.

• Rojas Molina, Rossana Virginia; Liese, Susanne; Alimohamadi, Haleh; Rangamani, Padmini & Carlson, Andreas (2020). Diffuso-kinetic membrane budding dynamics. Soft Matter.  ISSN 1744-683X.  16(48), s 10889- 10899 . doi: 10.1039/d0sm01028f
• Lawrence, Christopher; Gramstad, Odin & Trulsen, Karsten (2020). Variational Boussinesq model for kinematics calculation of surface gravity waves over bathymetry. Wave motion.  ISSN 0165-2125.  100 . doi: 10.1016/j.wavemoti.2020.102665 Fulltekst i vitenarkiv. Vis sammendrag

  Many of the widely used models for description of nonlinear surface gravity waves, in deep or shallow water, such as High Order Spectral Method (HOSM) and Boussinesq-type equations, rely on the elimination of the vertical coordinate from the basic three-dimensional Euler equations. From a numerical point of view such models are often computationally efficient, which is one of the main reasons that many such models are frequently used in studies on nonlinear surface waves. While surface-based models provide the time-evolution of surface quantities, typically the surface elevation η and velocity potential at the surface φ , they do not directly provide the water particle kinematics in the fluid interior. However, in many practical applications information about the water-particle kinematics is crucial. The present paper presents a new method for the calculation of water-particle kinematics, from information about surface quantities. The presented methodology is a non-perturbative approach based on the fully nonlinear Variational Boussinesq model, and can be applied to wave propagation over both constant and variable water depth. The proposed method is validated on several cases, including Stokes waves, a solitary wave, and irregular waves over flat bottom. We have carried out new laboratory experiments of regular waves over a shoal with measurements of the horizontal velocity specifically taken for validation of the method. We also employ recent laboratory experiments for validation of statistical properties of wave kinematics of long crested irregular waves propagating over a shoal.

• Grue, John & Osyka, Bogdan (2020). Runup on a vertical column in strong water wave events. Coastal Engineering.  ISSN 0378-3839.  163 . doi: 10.1016/j.coastaleng.2020.103775
• Grue, John (2020). Mini-tsunami made by ship moving across a depth change. Journal of waterway, port, coastal, and ocean engineering.  ISSN 0733-950X.  146(5) . doi: 10.1061/(ASCE)WW.1943-5460.0000585
• Engebretsen, Solveig & Glad, Ingrid Kristine (2020). Partially linear monotone methods with automatic variable selection and monotonicity direction discovery. Statistics in Medicine.  ISSN 0277-6715.  39(25), s 3549- 3568 . doi: 10.1002/sim.8680 Vis sammendrag

  In many statistical regression and prediction problems, it is reasonable to assume monotone relationships between certain predictor variables and the outcome. Genomic effects on phenotypes are, for instance, often assumed to be monotone. However, in some settings, it may be reasonable to assume a partially linear model, where some of the covariates can be assumed to have a linear effect. One example is a prediction model using both high‐dimensional gene expression data, and low‐dimensional clinical data, or when combining continuous and categorical covariates. We study methods for fitting the partially linear monotone model, where some covariates are assumed to have a linear effect on the response, and some are assumed to have a monotone (potentially nonlinear) effect. Most existing methods in the literature for fitting such models are subject to the limitation that they have to be provided the monotonicity directions a priori for the different monotone effects. We here present methods for fitting partially linear monotone models which perform both automatic variable selection, and monotonicity direction discovery. The proposed methods perform comparably to, or better than, existing methods, in terms of estimation, prediction, and variable selection performance, in simulation experiments in both classical and high‐dimensional data settings.

• Bedos, Erik Christopher & Conti, Roberto (2020). The Fourier-Stieltjes algebra of a C*-dynamical system II. Studia Mathematica.  ISSN 0039-3223.  256, s 217- 239 . doi: 10.4064/sm190826-25-3 Fulltekst i vitenarkiv. Vis sammendrag

  We continue our study of the Fourier–Stieltjes algebra associated to a twisted (unital, discrete) C*-dynamical system and discuss how the various notions of equivalence of such systems are reflected at the algebra level. As an application, we show that the amenability of a system, as defined in our previous work, is preserved under Morita equivalence.

• Joki, Reidar Kvale; Grytten, Frode; Hayman, Brian & Sørensen, Bent Fruergaard (2020). A mixed mode cohesive model for FRP laminates incorporating large scale bridging behaviour. Engineering Fracture Mechanics.  ISSN 0013-7944.  239, s 1- 15 . doi: 10.1016/j.engfracmech.2020.107274 Fulltekst i vitenarkiv. Vis sammendrag

  A user defined cohesive material model is implemented in the LS-DYNA finite element code. The model is based on interface properties characterised from DCB specimens loaded with unequal bending moments. Different mode mixities are obtained by applying different ratios of moments to the two beams in the cracked part of the specimen. The mixed mode cohesive law is fitted for large scale bridging delamination through inverse modelling. In this way, the variations in stress and crack opening across the width of the specimen are taken into account. The J integral approach is used to find a starting point for the fitting procedure. Three properties from five moment configurations are evaluated to find a first estimate of the shape of the cohesive law: crack tip fracture energy, steady-state fracture resistance and crack end-opening at steady-state fracture resistance. The parameters of the cohesive law are then further adjusted using the optimisation tool LS-OPT. The implemented cohesive model is assessed by comparing numerical to experimental test results from the standardised ASTM double cantilever beam test and the ASTM mixed mode bending test.

Se alle arbeider i Cristin

• Tveito, Aslak; Mardal, Kent-Andre & Rognes, Marie (ed.) (2020). Modeling Excitable Tissue -- The EMI Framework. Springer.  ISBN 978-3-030-61156-9.  100 s.

Se alle arbeider i Cristin

• Lindstrøm, Tom Louis (2021). Nye eksamensformer i matematikk.
• Lindstrøm, Tom Louis (2021). Nye eksamensformer i matematikk.
• Lindstrøm, Tom Louis (2021). Overgangen fra ungdomsskole til videregående skole.
• Lindstrøm, Tom Louis (2021). Rollemodell, klassebesøk.

Se alle arbeider i Cristin