Leibniz University of Hanover

About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.

Roll vortices in the planetary boundary layer: A review

Abstract: Roll vortices may be loosely defined as quasi two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL). Their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures. Although this phenomenon has been known for more than twenty years and has been treated in a review by one of us (R.A.Brown) in 1980, there has been a recent resurgence in interest and information. The interest in ocena/land-atmosphere interactions in the context of climate modeling has led to detailed observational and modeling efforts on this problem. The presence of rolls can have a large impact on flux modelling in the PBL. Hence, we shall review recent advances in our understanding of organized large eddies in the PBL and on their role in vertical transport of momentum, heat, moisture and chemical trace substances within the lowest part of the atmosphere.

Intrinsic defects of Ti O 2 (110): Interaction with chemisorbed O 2 , H 2 , CO, and C O 2

Abstract: The interaction of Ti${\mathrm{O}}_{2}$(110) with ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, and C${\mathrm{O}}_{2}$ was studied by means of low-energy electron diffraction, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, thermal desorption, electron paramagnetic resonance, and measurements of changes in surface conductivities, $\ensuremath{\Delta}\ensuremath{\sigma}$, and work functions, $\ensuremath{\Delta}\ensuremath{\phi}$, for $300\ensuremath{\le}T\ensuremath{\le}1000$ K with particular emphasis on surface reactions involving intrinsic surface defects $2{\mathrm{Ti}}^{3+}\ifmmode\cdot\else\textperiodcentered\fi{}V_{O}^{}{}_{}{}^{(+)}$. The defects are thermodynamically stable at high temperatures and act as donors and specific adsorption sites for ${\mathrm{H}}_{2}$ and CO. Surface and subsurface reactions involving ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, and C${\mathrm{O}}_{2}$ can be separated from each other by analyzing the $\ensuremath{\Delta}\ensuremath{\sigma}$ and $\ensuremath{\Delta}\ensuremath{\phi}$ effects in a charge-transfer model, which takes into account surface and bulk electronic states in the band gap attributed to the different defects formed during the interaction.

Particle trajectories in solitary water waves

Abstract: Analyzing a free boundary problem for harmonic functions in an infinite planar domain, we prove that in a solitary water wave each particle is transported in the wave direction but slower than the wave speed. As the solitary wave propagates, all particles located ahead of the wave crest are lifted, while those behind it experience a downward motion, with the particle trajectory having asymptotically the same height above the flat bed.