Blar i NTNU Open på forfatter "Hansen, Alex"

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. ...

Aging and Failure of a Polymer Chain under Tension

Charan, Harish; Hansen, Alex; Hentschel, H. George E.; Procaccia, Itamar (Peer reviewed; Journal article, 2021)

The rupture of a polymer chain maintained at temperature T under fixed tension is prototypical to a wide array of systems failing under constant external stress and random perturbations. Past research focused on analytic ...

Anomalous diffusion in systems with concentration-dependent diffusivity: exact solutions and particle simulations

Hansen, Alex; Flekkøy, Eirik Grude; Baldelli, Beatrice (Journal article; Peer reviewed, 2020)

We explore the anomalous diffusion that may arise as a result of a concentration dependent diffusivity. The diffusivity is taken to be a power law in the concentration, and from exact analytical solutions we show that the ...

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 ...

Crack localization and the interplay between stress enhancement and thermal noise

Sinha, Santanu; Roy, Subhadeep; Hansen, Alex (Peer reviewed; Journal article, 2021)

We study the competition between thermal fluctuations and stress enhancement in the failure process of a disordered system by using a local load sharing fiber bundle model. The thermal noise is introduced by defining a ...

Criterion for Imminent Failure During Loading—Discrete Element Method Analysis

Debski, Wojciech; Pradhan, Srutarshi; Hansen, Alex (Peer reviewed; Journal article, 2021)

It has recently been reported that the equal load sharing fiber bundle model predicts the rate of change of the elastic energy stored in the bundle reaches its maximum before catastrophic failure occurs, making it a possible ...

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. ...