Search results for "simulointi"

Fast Green’s Function Method for Ultrafast Electron-Boson Dynamics

2020

The interaction of electrons with quantized phonons and photons underlies the ultrafast dynamics of systems ranging from molecules to solids, and it gives rise to a plethora of physical phenomena experimentally accessible using time-resolved techniques. Green's function methods offer an invaluable interpretation tool since scattering mechanisms of growing complexity can be selectively incorporated in the theory. Currently, however, real-time Green's function simulations are either prohibitively expensive due to the cubic scaling with the propagation time or do neglect the feedback of electrons on the bosons, thus violating energy conservation. We put forward a computationally efficient Gree…

Time-linear scaling nonequilibrium Green's function methods for real-time simulations of interacting electrons and bosons. I : Formalism

2022

Simulations of interacting electrons and bosons out of equilibrium, starting from first principles and aiming at realistic multiscale scenarios, is a grand theoretical challenge. Here, using the formalism of nonequilibrium Green's functions and relying in a crucial way on the recently discovered time-linear formulation of the Kadanoff-Baym equations, we present a versatile toolbox for the simulation of correlated electron-boson dynamics. A large class of methods are available, from the Ehrenfest to the dressed GD for the treatment of electron-boson interactions in combination with perturbative, i.e., Hartree-Fock and second-Born, or nonperturbative, i.e., GW and T matrices either without or…

The joint evolution of learning and dispersal maintains intraspecific diversity in metapopulations

2021

The evolution of dispersal tendencies and of cognitive abilities have both been intensely studied. Yet little attention has been given to the question of how these two aspects may relate to each other, as a result of their joint evolution. On the one hand, learning abilities may help dispersers to cope with their new habitat. On the other hand, dispersal may sometimes reduce the need for learning, because local environments may differ in how much there is to learn. To get a better understanding of this relationship, we built an individual‐based simulation in which both learning speed and dispersal tendency were free to evolve. We found that both positive and negative correlations could evol…

Density functional/molecular dynamics simulations of phase-change materials

2013

Interactions and patterns between species diversity and genetic diversity

2015

Global warming, forest biodiversity and conservation strategies in boreal landscapes

2014

Communication-Efficient Federated Learning in Channel Constrained Internet of Things

2022

Federated learning (FL) is able to utilize the computing capability and maintain the privacy of the end devices by collecting and aggregating the locally trained learning model parameters while keeping the local personal data. As the most widely-used FL framework,Jederated averaging (FedAvg) suffers an expensive communication cost especially when there are large amounts of devices involving the FL process. Moreover, when considering asynchronous FL, the slowest device becomes the bottleneck for the cask effect and determines the overall latency. In this work, we propose a communication-efficient federated learning framework with partial model aggregation (CE-FedPA) algorithm to utilize comp…

Dye molecules on titatium dioxide surface: cluster and periodic surface models

2008

Evolution of anticipatory effects mediated by epigenetic changes.

2022

Abstract Anticipatory effects mediated by epigenetic changes occur when parents modify the phenotype of their offspring by making epigenetic changes in their gametes guided by information from an environmental cue. To investigate when do anticipatory effects mediated by epigenetic changes evolve in a fluctuating environment, I use an individual based simulation model with explicit genetic architecture. The model allows for the population to respond to environmental changes by evolving within generation plasticity, bet-hedging, or track the environment with genetic adaptation, in addition to the evolution of anticipatory effects. The results show that anticipatory effects evolve when the env…

Tietokoneohjelma epälineaaristen elektroniikkapiirien simulointiin

2014

Tässä työssä esitetään kuinka lineaarisissa ja epälineaarisissa elektroniikkapiireissä toimiva piirisimulaattoriohjelma voidaan toteuttaa oliokielellä. Työ aloitettiin itse kehitetyn TICER-yksinkertaistusalgoritmin pohjalta ja yhtenä työn motivaationa olikin tutkia kuinka kyseistä algoritmia voi käyttää muiden analysointimenetelmien apuna. Työn edetessä osoittautuikin, että TICER-yksinkertaistusta kannattaa käyttää muiden analysointimenetelmien apuna, sillä se voi nopeuttaa huomattavasti RC-piirien analysointia. TICER ei kuitenkaan nopeuttanut ohjelman toimintaa poikkeuksetta, mutta se ei hidastanutkaan analysointia koskaan niin paljon, etteikö sitä olisi kannattanut käyttää. Ohjelman pääas…