Search results for "simulations"

GPU accelerated Monte Carlo simulations of lattice spin models

2011

We consider Monte Carlo simulations of classical spin models of statistical mechanics using the massively parallel architecture provided by graphics processing units (GPUs). We discuss simulations of models with discrete and continuous variables, and using an array of algorithms ranging from single-spin flip Metropolis updates over cluster algorithms to multicanonical and Wang-Landau techniques to judge the scope and limitations of GPU accelerated computation in this field. For most simulations discussed, we find significant speed-ups by two to three orders of magnitude as compared to single-threaded CPU implementations.

Mechanical properties of carbon nanotube reinforced nanocomposites

2013

One way to take advantage of the marvelous properties of the carbon nanotubes consists in incorporating them into a matrix to build composite materials. The best candidates for this task are undoubtedly polymers thanks to their strength, toughness, low weight, and easy processing. A mixed model, numerical-analytical, is presented that allows one to predict the elastic properties of carbon nanotube (CNT)/polymer composites containing a random distribution of CNTs, while taking account of the curvature that they show when immersed in the polymer. A three-dimensional model, using a single CNT immersed in an infinite matrix, allows us to numerically evaluate the concentration tensor by evaluati…

Density functional/molecular dynamics simulations of phase-change materials

2013

Estimating QCD uncertainties in Monte Carlo event generators for gamma-ray dark matter searches

2018

Motivated by the recent galactic center gamma-ray excess identified in the Fermi-LAT data, we perform a detailed study of QCD fragmentation uncertainties in the modeling of the energy spectra of gamma-rays from Dark-Matter (DM) annihilation. When Dark-Matter particles annihilate to coloured final states, either directly or via decays such as $W^{(*)}\to q\bar{q}'$, photons are produced from a complex sequence of shower, hadronisation and hadron decays. In phenomenological studies, their energy spectra are typically computed using Monte Carlo event generators. These results have however intrinsic uncertainties due to the specific model used and the choice of model parameters, which are diffi…

Physics reach of the XENON1T dark matter experiment.

2016

The XENON1T experiment is currently in the commissioning phase at the Laboratori Nazionali del Gran Sasso, Italy. In this article we study the experiment's expected sensitivity to the spin-independent WIMP-nucleon interaction cross section, based on Monte Carlo predictions of the electronic and nuclear recoil backgrounds. The total electronic recoil background in $1$ tonne fiducial volume and ($1$, $12$) keV electronic recoil equivalent energy region, before applying any selection to discriminate between electronic and nuclear recoils, is $(1.80 \pm 0.15) \cdot 10^{-4}$ ($\rm{kg} \cdot day \cdot keV)^{-1}$, mainly due to the decay of $^{222}\rm{Rn}$ daughters inside the xenon target. The nu…

Training machine learning models with synthetic data improves the prediction of ventricular origin in outflow tract ventricular arrhythmias

2022

In order to determine the site of origin (SOO) in outflow tract ventricular arrhythmias (OTVAs) before an ablation procedure, several algorithms based on manual identification of electrocardiogram (ECG) features, have been developed. However, the reported accuracy decreases when tested with different datasets. Machine learning algorithms can automatize the process and improve generalization, but their performance is hampered by the lack of large enough OTVA databases. We propose the use of detailed electrophysiological simulations of OTVAs to train a machine learning classification model to predict the ventricular origin of the SOO of ectopic beats. We generated a synthetic database of 12-l…

Opiskelijan huomion kiinnittyminen simulaation aikana fysiikan oppitunnilla : silmänliiketutkimus autenttisessa ympäristössä

2017

Tässä pro gradu -tutkielmassa tutkittiin opiskelijan huomion kohdetta lukion fysiikan tunnilla. Tutkimuksessa selvitettiin, vastaako opiskelijan visuaalinen huomio opettajan antamia vihjeitä, kun opettaja opettaa luokassa yhteisesti simulaation avulla. Aineiston kerääminen toteutettiin Tobii Pro Glasses 2 -katseenseurantalaseilla ja SRI-haastattelun avulla ja datan analysointiin käytettiin Microsoft Excel -ohjelmistoa. Luotettavuuden arviointiin käytettiin vertauskoodausta. Tutkimustuloksena oli, että opiskelija seuraa opettajan antamia vihjeitä suurimman osan simulaatio-opetuksen ajasta. Opiskelija katsoi 60 % ajasta sinne, minne opettaja haluaa opiskelijoiden katsovan ja 41 % ajasta opete…

Influence of bed roughness on flow and turbulence structure around a partially-buried, isolated freshwater mussel

2023

The present study uses eddy-resolving numerical simulations to investigate how bed roughness affects flow and turbulence structure around an isolated, partially-buried mussel (Unio elongatulus) aligned with the incoming flow. The rough-bed simulations resolve the flow past the exposed part of a gravel bed, whose surface is obtained from a laboratory experiment that also provides some additional data for validation of the numerical model. Results are also discussed for the limiting case of a horizontal smooth bed. Additionally, the effects of varying the level of burial of the mussel inside the substrate and the discharge through the two mussel siphons are investigated via a set of simulatio…

B–T phase diagram of Pd/Fe/Ir(111) computed with parallel tempering Monte Carlo

2017

We use an atomistic spin model derived from density functional theory calculations for the ultra-thin film Pd/Fe/Ir(111) to show that temperature induces coexisting non-zero skyrmion and antiskyrmion densities. We apply the parallel tempering Monte Carlo method in order to reliably compute thermodynamical quantities and the B-T phase diagram in the presence of frustrated exchange interactions. We evaluate the critical temperatures using the topological susceptibility. We show that the critical temperatures depend on the magnetic field in contrast to previous work. In total, we identify five phases: spin spiral, skyrmion lattice, ferromagnetic phase, intermediate region with finite topologic…

Bayesian estimation of partial population continuity using ancient DNA and spatially explicit simulations.

2017

Abstract The retrieval of ancient DNA from osteological material provides direct evidence of human genetic diversity in the past. Ancient DNA samples are often used to investigate whether there was population continuity in the settlement history of an area. Methods based on the serial coalescent algorithm have been developed to test whether the population continuity hypothesis can be statistically rejected by analysing DNA samples from the same region but of different ages. Rejection of this hypothesis is indicative of a large genetic shift, possibly due to immigration occurring between two sampling times. However, this approach is only able to reject a model of full continuity model (a tot…