Aalto University

About: Aalto University is a education organization based out in Espoo, Finland. It is known for research contribution in the topics: Population & Carbon nanotube. The organization has 9969 authors who have published 32648 publications receiving 829626 citations. The organization is also known as: TKK & Aalto-korkeakoulu.

Kalman filtering and smoothing solutions to temporal Gaussian process regression models

Abstract: In this paper, we show how temporal (i.e., time-series) Gaussian process regression models in machine learning can be reformulated as linear-Gaussian state space models, which can be solved exactly with classical Kalman filtering theory. The result is an efficient non-parametric learning algorithm, whose computational complexity grows linearly with respect to number of observations. We show how the reformulation can be done for Matern family of covariance functions analytically and for squared exponential covariance function by applying spectral Taylor series approximation. Advantages of the proposed approach are illustrated with two numerical experiments.

Ion-exchanged glass waveguide technology: a review

Abstract: We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applica- tions are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, in- tegrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active wave- guide components. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Binding energies of exciton complexes in transition metal dichalcogenide monolayers and effect of dielectric environment

Abstract: Excitons, trions, biexcitons, and exciton-trion complexes in two-dimensional transition metal dichalcogenide sheets of ${\mathrm{MoS}}_{2}, {\mathrm{MoSe}}_{2}, {\mathrm{MoTe}}_{2}, {\mathrm{WS}}_{2}$, and ${\mathrm{WSe}}_{2}$ are studied by means of density functional theory and path-integral Monte Carlo method in order to accurately account for the particle-particle correlations. In addition, the effect of dielectric environment on the properties of these exciton complexes is studied by modifying the effective interaction potential between particles. Calculated exciton and trion binding energies are consistent with previous experimental and computational studies, and larger systems such as biexciton and exciton-trion complex are found highly stable. Binding energies of biexcitons are similar to or higher than those of trions, but the binding energy of the trion depends significantly stronger on the dielectric environment than that of biexciton. Therefore, as a function of an increasing dielectric constant of the environment the exciton-trion complex ``dissociates'' to a biexciton rather than to an exciton and a trion.