Blar i NTNU Open på forfatter "Hansen, Alex"
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A bridge between statistical learning and agent based modelling in stock market predictions
Hellenes, Arne Herman (Master thesis, 2016)The research related to agent based modelling and statistical learning has increased in the recent years, as alternatives to main stream econometrics. This project combines the three for constructing and evaluating a ... -
A Model for the Mixing of Black Carbon Aerosols and Mineral Dust Particles in the Atmosphere
Berntsen, Simen (Master thesis, 2016)The process when freshly emitted black carbon particles are forming clusters and the mixing of these black carbon clusters and mineral dust particles has been simulated for a two-dimensional system. This has been done by ... -
A Monte Carlo Algorithm for Immiscible Two-Phase Flow in Porous Media
Savani, Isha; Sinha, Santanu; Hansen, Alex; Bedeaux, Dick; Kjelstrup, Signe; Vassvik, Morten (Journal article; Peer reviewed, 2017)We present a Markov Chain Monte Carlo algorithm based on the Metropolis algorithm for simulation of the flow of two immiscible fluids in a porous medium under macroscopic steady-state conditions using a dynamical pore ... -
A Numerical Study of Transient Friction and Transient Friction Modelling in Ramp-up and Ramp-down Flow Conditions Similar to Pump Ramp-up and Valve Closure in Gas Transport Pipelines
Birkeland, Sigmund Andreas (Master thesis, 2014)When gas is transported in long pipelines, computational models are used as tools to plan and to optimize hydraulic capacities. Because of the length of the pipelines the models are mostly one-dimensional (1D) which in ... -
A Renormalization Group Procedure for Fiber Bundle Models
Pradhan, Srutarshi; Hansen, Alex; Ray, Purusattam (Journal article; Peer reviewed, 2018)We introduce two versions of a renormalization group scheme for the equal load sharing fiber bundle model. The renormalization group is based on formulating the fiber bundle model in the language of damage mechanics. A ... -
A Simulated Annealing Approach to Electrical Resistivity Tomography
Wiken, Håvard Eidal (Master thesis, 2018)In this study, a new approach to Electrical Resistivity Tomography (ERT) data inversion was investigated. ERT is a geophysical method for imaging the subsurface. An electrical current is injected into the surface, and the ... -
Accumulated Plastic Strain Program
Valnes, Lars Magnus (Master thesis, 2014)In this thesis we will look at the implementation and results of the APS program. The program computes the accumulated plastic strain in a umbilical tube for the deformations axial tension, bending and internal pressure. ... -
Can Local Stress Enhancement Induce Stability in Fracture Processes? Part I: Apparent Stability
Kjellstadli, Jonas Tøgersen; Bering, Eivind; Hendrick, Martin; Pradhan, Srutarshi; Hansen, Alex (Journal article; Peer reviewed, 2019)By comparing the evolution of the local and equal load sharing fiber bundle models, we point out the paradoxical result that stresses seem to make the local load sharing model stable when the equal load sharing model is ... -
Can Local Stress Enhancement Induce Stability in Fracture Processes? Part II: The Shielding Effect
Kjellstadli, Jonas Tøgersen; Bering, Eivind; Pradhan, Srutarshi; Hansen, Alex (Journal article; Peer reviewed, 2019)We use the local load sharing fiber bundle model to demonstrate a shielding effect where strong fibers protect weaker ones. This effect exists due to the local stress enhancement around broken fibers in the local load ... -
Critical Behaviour of the Local Load Sharing Fiber Bundle Model
Dahle, Magnus Holter-S (Master thesis, 2016)A generalised, history independent, Local Load Sharing Fiber Bundle Model, describing damage propagation in materials as failing fibers under under external load is studied. If the fibers' thresholds $t$ are drawn from an ... -
Detection and Localization of High-Frequency Interception Signals using Compressive Sensing
Breisjøberg, Torjus (Master thesis, 2013)We investigate detection and localization of high-frequency interception signals underwater using a fairly new framework known as Compressive Sensing. Within this framework we can sample at sub-Nyquist rate and still be ... -
Dynamic Wettability Alteration in Immiscible Two-phase Flow in Porous Media: Effect on Transport Properties and Critical Slowing Down
Flovik, Vegard; Sinha, Santanu; Hansen, Alex (Journal article; Peer reviewed, 2015)The change in contact angles due to the injection of low salinity water or any other wettability altering agent in an oil-rich porous medium is modeled by a network of disordered pores transporting two immiscible fluids. ... -
Effective rheology of two-phase flow in a capillary fiber bundle model
Roy, Subhadeep; Hansen, Alex; Sinha, Santanu (Journal article; Peer reviewed, 2019)We investigate the effective rheology of two-phase flow in a bundle of parallel capillary tubes carrying two immiscible fluids under an external pressure drop. The diameter of the tubes vary along the length which introduce ... -
Ensemble distribution for immiscible two-phase flow in porous media
Savani, Isha; Bedeaux, Dick; Kjelstrup, Signe; Vassvik, Morten; Sinha, Santanu; Hansen, Alex (Journal article, 2017)We construct an ensemble distribution to describe steady immiscible two-phase flow of two incompressible fluids in a porous medium. The system is found to be ergodic. The distribution is used to compute macroscopic flow ... -
Exploring Biopolymers by the Fibre Bundle Model
Indrehus, Sunniva (Master thesis, 2017)Bundles of polymeric chains in biological systems represent the analogue of macroscopic fibrous materials such as textile, wood or paper, scaled down to nanometric dimensions, and performing the same mechanical functions ... -
Film flow dominated simultaneous flow of two viscous incompressible fluids through a porous medium
Aursjø, Olav; Erpelding, Marion; Tallakstad, Ken Tore; Flekkøy, Eirik Grude; Hansen, Alex; Måløy, Knut Jørgen (Journal article; Peer reviewed, 2014-11-19)We present an experimental study of two-phase flow in a quasi-two-dimensional porous medium. The two phases, a water-glycerol solution and a commercial food grade rapeseed/canola oil, having an oil to water-glycerol viscosity ... -
Fracture networks in sea ice
Vevatne, Jonas Nesland; Rimstad, Eivind; Hope, Sigmund Mongstad; Korsnes, Reinert; Hansen, Alex (Journal article; Peer reviewed, 2014-04-16)Fracturing and refreezing of sea ice in the Kara sea are investigated using complex network analysis. By going to the dual network, where the fractures are nodes and their intersections links, we gain access to topological ... -
Fracturing of Optimal Paths in a Random Lattice
Voigt, Andre (Master thesis, 2011)The subject of this thesis is the study of the creation of fault lines in a random lattice, provoked by the successive failure of optimal paths. Using the recently developed Optimal Path Cracked model, we investigate how ... -
Implications of Realistic Fracture Criteria on Crack Morphology
Skjetne, Bjørn; Hansen, Alex (Journal article; Peer reviewed, 2019)We study the effects realistic fracture criteria have on crack morphology obtained in numerical simulations with a stochastic discrete element method. Results are obtained with two criteria which are consistent with the ... -
In-plane Fracture Front Propagation in the Thin Plate Fiber Bundle Model
Vågan, Jørgen (Master thesis, 2016)A new history independent thin plate Fiber Bundle Model is derived in or- der to model in-plane material fracture. The model provides an easy way of studying the not yet fully understood fracture processing zone. Only ...