Browsing Institutt for matematiske fag by Title
Now showing items 1371-1390 of 2364
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Non-uniform dependence on initial data for equations of Whitham type
(Journal article, 2019)We consider the Cauchy problem ∂tu + u∂xu + L(∂xu) = 0, u(0, x) = u0(x) for a class of Fourier multiplier operators L, and prove that the solution map u0 7→ u(t) is not uniformly continuous in Hs on the real line or on the ... -
Noncommutative Geometry in Wireless Communication Applications
(Master thesis, 2018)The theory of time-frequency analysis is introduced, and basic results on modulation spaces are proved. We describe Gabor frames and prove results which are relevant to application in wireless communication. We outline a ... -
Noncommutative Gröbner bases in Polly Cracker cryptosystems
(Master thesis, 2009)We present the noncommutative version of the Polly Cracker cryptosystem, which is more promising than the commutative version. This is partly because many of the ideals in a free (noncommutative) algebra have an infinite ... -
Nonhomogeneous Poisson process with nonparametric frailty and covariates
(Journal article; Peer reviewed, 2017)The nonhomogeneous Poisson process is commonly used in the modeling of failure times of complex repairable systems. In practice there may be a substantial heterogeneity in the failure behavior among apparently identical ... -
Nonlinear Acoustic Waves in Heterogeneous Materials
(Master thesis, 2015)This thesis concerns the partial differential equations governing acoustic wave propagation in heterogeneous materials. We start with an investigation of the standard Eulerian formulation of the equations, and point out ... -
Nonlinear anisotropic degenerate parabolic-hyperbolic equations with stochastic forcing
(Journal article; Peer reviewed, 2021) -
Nonlinear domain decomposition scheme for sequential fully implicit formulation of compositional multiphase flow
(Journal article; Peer reviewed, 2019)New sequential fully implicit (SFI) methods for compositional flow simulation have been recently investigated. These SFI schemes decouple the fully coupled problem into separate pressure and transport problems and have ... -
Nonlinear fractional convection-diffusion equations, with nonlocal and nonlinear fractional diffusion
(Master thesis, 2013)We study nonlinear fractional convection-diffusion equations with nonlocal and nonlinear fractional diffusion. By the idea of Kru\v{z}kov (1970), entropy sub- and supersolutions are defined in order to prove well-posedness ... -
Nonlinear Gauss-Seidel solvers with higher order for black-oil models
(Chapter, 2018)The fully implicit method is the most commonly used approach to solve black-oil problems in reservoir simulation. The method requires repeated linearization of large nonlinear systems and produces ill-conditioned linear ... -
Nonlinear integro-differential Equations: Numerical Solutions by using Spectral Methods
(Master thesis, 2013)This article deals with numerical solutions of nonlinear integro-differential convection-diffusion equations using spectral methods. More specifically, the spectral vanishing viscosity method is introduced and analyzed to ... -
Nonlinear phase unwinding
(Master thesis, 2018)We start of by studying Hardy spaces and Blaschke products. Then we look at a natural nonlinear analogue of Fourier series called the unwinding series. It is obtained through iterative Blaschke factorization and unwinds ... -
Nonlinear Two-Point Flux Approximation Schemes for Reservoir Simulation
(Master thesis, 2018)The main objective of this thesis has been to investigate some methods for simulating CO2 storage and hydrocarbon recovery on complex polyhedral grids, with main focus on the nonlinear two-point flux approximation method. ... -
Nonlocal and monotone techniques in dispersive equations and inverse problems
(Doctoral theses at NTNU;2022:151, Doctoral thesis, 2022) -
Nonlocal Dispersive Models for Water Waves Existence, Symmetry and Related A Priori Properties
(Doctoral theses at NTNU;2017:6, Doctoral thesis, 2016) -
Nonlocal nonlinear diffusion equations. Smoothing effects, Green functions, and functional inequalities
(Peer reviewed; Journal article, 2023)We establish boundedness estimates for solutions of generalized porous medium equations of the form where and is a linear, symmetric, and nonnegative operator. The wide class of operators we consider includes, but is not ... -
Nonparametric estimation in trend-renewal processes
(Master thesis, 2017)This thesis gives an introduction to stochastic modeling of repairable systems with failure and maintenance data, in particular the nonhomogeneous Poisson process and the trend-renewal process. It is studying kernel-based ... -
Normalizing flows and deep Q-networks for shape analysis
(Master thesis, 2022)Denne oppgaven tar for seg to forskjellige tilnærminger for å analysere kurver. I den første tilnærmingen anvender vi dype q-nettverk for å finne en optimal reparametrisering mellom to kurver. Denne reparametriseringen er ... -
Norms and Eigenvalues of Time-Frequency Localization Operators
(Master thesis, 2018)In this report we study and compare two types of time-frequency localization operators, the first is based on composition of projections in time and frequency, and the second is Daubechies' localization operator. We provide ... -
Norms of composition operators on the $H^2$ space of Dirichlet series
(Journal article; Peer reviewed, 2020), generated by Dirichlet series symbols φ. We prove two different subordination principles for such operators. One concerns affine symbols only, and is based on an arithmetical condition on the coefficients of φ. The other ... -
A note on Bohr’s theorem for Beurling integer systems
(Journal article; Peer reviewed, 2023)Given a sequence of frequencies , a corresponding generalized Dirichlet series is of the form . We are interested in multiplicatively generated systems, where each number arises as a finite product of some given ...