## PhD supervisors at the DP DOCC

**Univ.-Prof. Dr. Christoph Adam**Department of Basic Sciences in Engineering Sciences

Unit for Applied Mechanics

Reserach area(s): Computational Mechanics, Dynamics

Personal webpage

Collaborators: Franosch, Haltmeier, Hofstetter, Rauch

Christoph Adam is professor of Applied Mechanics and head of the Unit of Applied Mechanics at the University of Innsbruck. His research interests include seismic safety of structures, modeling of linear and non-linear structures subjected to dynamic loads, structural vibration control, vibration propagation in buildings and soil, and vibration measurement and data interpretation in the lab and on-site.

Thesis topic: Reliability analysis of high-speed railway brides (SEN-1) »

Co-supervisors: Haltmeier/Rauch

Reliability analysis of railway bridges subjected to high-speed trains by application of nonstandard stochastic methods such as subset simulation or line-sampling with small estimator variances; Novel elaborate numerical modeling of dynamic vehicle-bridge-track-subsoil interaction; Application of high-performance computing.

Co-supervisors: Hofstetter/Rauch

Recent numerical studies have shown that earthquake excited regular steel-moment-resisting frames do not behave rigid in vertical direction, but show a significant peak acceleration response amplification. However, simulations based on recorded vertical free-field ground motions may overestimate this amplification. Aims of this project are to evaluate the impact of soil-structure interaction on recorded ground motion, develop soil-structure interaction models for HPC simulations, and derive seismic response on the free-field surface and at the base of the structure.

**assoz. Prof. Dipl.-Ing. Lukas Einkemmer, BSc MSc PhD**Department of Mathematics

Numerical Analysis Group

Reserach area(s): Numerical Analysis, Scientific & High Performance Computing

Personal webpage

Collaborators: Kendl, Kissmann, Ostermann, Reimer

Lukas Einkemmer is an Associate Professor at the Department of Mathematics at the University of Innsbruck. He is a member of the Numerical Analysis Group with research interests in numerical analysis and scientific computing, focusing on: Time integration of partial differential equations, splitting methods, exponential integrators, parallelization and scalability, and applications in physics.

Thesis topic: Dynamic low-rank approximations for kinetic models in plasma physics (MAT-1) »

Solving kinetic problems directly is extremely expensive from a computational point of view. We consider the recently developed dynamic low-rank approximation, which has the potential to reduce the required effort by orders of magnitudes. We focus on developing algorithms and their implementation on HPC systems in the context of problems in plasma physics.

Thesis topic: Semi-Lagrangian plasma simulation on modern computer architectures (MAT-2) »

Co-supervisors: Kendl/Ostermann

Large scale simulations on supercomputers are usually required to solve the various models for the nonlinear dynamics of magnetized fusion plasmas. Most of the algorithms currently available, however, do not fit very well to modern computer architectures (for example, GPUs). One approach to overcome this limitation are semi-Lagrangian discontinuous Galerkin methods. We will, in particular, further develop these algorithms, implement them on HPC systems, and demonstrate their efficiency for plasma simulation.

**Univ.-Prof. Dr. Thomas Franosch**Institute for Theoretical Physics

Bio and Nano Physics Group

Reserach area(s): Bio and Nano Physics Simulations

Personal webpage

Collaborators: Adam, Kendl, Ostermann, Rauch

We will simulate the nonlinear dynamics of a colloidal suspension in response to an external perturbation in the form of a strong step-strain, and elucidate the evolution of shear stresses. New algorithms are needed to subtract thermal noises of the non-interacting systems for optimization of the signal-to-noise ratio.

Thesis topic: Disentangling the noise from the interactions in Brownian Dynamics (NBP-2) »

In a conventional Brownian Dynamics simulation interacting particles undergo an erratic motion due to thermal noise between collisions. A novel algorithm will be elaborated that allows to directly simulate only the difference between an interacting and freely evolving system thereby basically eliminating all noise and making the relevant physics accessible to simulation studies.

**Univ.-Prof. Dr. Markus Haltmeier**Department of Mathematics

Applied Mathematics Group

Reserach area(s): Inverse Problems, Parameter Identification and Object Recognition

Personal webpage

Collaborators: Adam, Hofstetter, Kendl, Liedl, Ostermann, Probst, Rotach

The Applied Mathematics Group of Markus Haltmeier at the Department of Mathematics performs interdisciplinary research in the fields of inverse problems, parameter estimation and signal and image processing. Thereby the group focuses on a balance between theoretical analysis and the development of algorithms, which can be applied to real-world applications.

Thesis topic: Dynamic tomography of complex continua (MAT-3) »

Co-supervisors: Hofstetter/Probst

Dynamic tomography allows real-time imaging of many physiological processes, ranging from cardiovascular imaging to non-invasive surgery monitoring. Standard recovery methods accounting for rapid movements are only suitable for simple rigid motion. We consider efficient image reconstruction for complex motions, using tools from regularization theory, inverse problems, deep learning and neural networks to integrate suitable a-priori information.

Thesis topic: NETT deep learning for time dependent inverse problems (MAT-4) »

Co-supervisors: Kendl/Ostermann

Inverse problems arise in various applications ranging from medical imaging to non-destructive testing and remote sensing. Their characteristic feature is the inherent ill-posedness, requiring special techniques for its solution. We recently proposed network Tikhonov regularization (NETT) for static inverse problems, which is based on generalized Tikhonov regularization using a neural network as learned regularizer. The aim of this project is to extend the NETT to dynamic inverse problems. In particular, appropriate networks and training strategies will be designed, a convergence analysis developed and an efficient numerical implementation established.

**Univ.-Prof. Dr. Matthias Harders**Department of Computer Science

Interactive Graphics and Simulation Group

Reserach area(s): Visualisation and Interaction

Personal webpage

Collaborators: Einkemmer, Lackner, Rauch

Matthias Harders is professor at the Department of Computer Science. In February 2014 he established the Interactive Graphics and Simulation (IGS) group at the University of Innsbruck. The scientific focus of the group is on methods and algorithms in the areas of physically-based simulation, computer haptics and virtual/augmented reality. Further research addresses human-computer interaction and multi-modal data visualisation. The main application area of the developments has so far been in the medical domain.

Thesis topic: Machine learning for tuning parallel computations in surgical simulation (MEC-1) »

Co-supervisors: Einkemmer/Lackner

Simulators for computer-based surgical training comprise heterogeneous, computationally expensive components, running at fast update rates. We focus on techniques capable of autotuning for time-critical complex biomechanical simulations on parallel systems. A key difficulty is the dynamically changing requirements of simulation components, e.g. due to cutting or interaction.

Co-supervisors: Rauch

Machine learning methods have proven to be very efficient for approximating nonlinear functions, if an accurate and large enough dataset is provided for training. We examine if physically-based simulations, such as deformation or fluid flow computations, can be accelerated via machine learning, specifically using convolutional neural networks. Special focus will be on error tracking, prediction, and correction in adaptive methods for particle-based solvers.

**Univ.-Prof. Dr. Günter Hofstetter**Department of Basic Sciences in Engineering Sciences

Unit of Strength of Materials and Structural Analysis

Reserach area(s): Computational Mechanics, Soils & Concrete

Personal webpage

Collaborators: Adam, Haltmeier, Lackner, Ostermann

Günter Hofstetter is dean of the Faculty of Engineering Sciences and head of the Unit of Strength of Materials and Structural Analysis at the Institute of Basic Sciences in Engineering Science at the University of Innsbruck. The focus of the scientific activities of Günter Hofstetter and his group is on basic and applied research in the fields of structural analysis and strength of materials, and of numerical methods related to these areas. Main emphasis is laid on the development and application of models for numerical simulation of the load-carrying behaviour of structures up to failure and on validation of these models by experimental methods.

In particular, the scientific contributions comprise

- numerical modelling of the nonlinear material behaviour of concrete and of concrete structures, complemented by experimental investigations for validating numerical models,
- experimental investigation and numerical simulation of rehabilitation and strengthening measures of existing concrete structures by adding concrete overlays,
- numerical modelling of the nonlinear material behaviour of intact rock and of rock mass aiming at numerical simulations of the excavation of deep tunnels,
- numerical modelling of partially saturated soils targeted on numerical simulations of geotechnical problems in the framework of multi-phase formulations and,
- technology transfer of research results for solving demanding problems in engineering practice.

Co-supervisors: Lackner/Ostermann

Development of 3D time-dependent numerical models of deep tunnel advance with a focus on the challenging task of interactions between several tubes. For this purpose advanced constitutive models for rock mass and shotcrete and regularization techniques for material softening, beyond the capabilities of standard material models are required.

Co-supervisors: Lackner/Ostermann

Rock mass is composed of intact rock and discontinuities, e.g. bedding planes and joints. The latter are already present in the prevailing in-situ conditions. However, discontinuities may also emerge from the stress changes in the rock mass due to tunnel advance. The aim of the thesis is to evaluate different approaches of modeling existing and emerging discontinuities in rock mass with special emphasis on applications to numerical simulations of tunnel advance.

Thesis topic: Constitutive modeling of orthotropic rock (ENG-3) »

Co-supervisors: Lackner/Ostermann

The thesis project comprises the development of a constitutive model for describing the nonlinear mechanical behavior of orthotropic rock subjected to 3D stress states, the implementation of the model in a finite element code and the validation of the model by numerical simulations of laboratory experiments. In particular, the model must be able to represent irreversible deformations, associated with strain hardening and strain softening as well as degradation of stiffness.

**Assoz. Prof. Dr. Alexander Kendl** (Programme Coordinator)

Department of Applied Physics and Ionphysics

Complex Systems Group

Reserach area(s): Complex Systems

Personal webpage

Collaborators: Einkemmer, Franosch, Haltmeier, Kissmann, Ostermann, Rotach, Scheier

Alexander Kendl is Associate Professor at the Institute for Ion Physics and Applied Physics at the University of Innsbruck. His research interests are in nonlinear dynamics, turbulence and structure formation, plasma physics and fusion research, and computational physics.

Thesis topic: Structure formation and instabilities in highly-charged nano droplets (NPH-1) »

Co-supervisors: Einkemmer/Scheier

This thesis project accompanies planned laboratory experiments in the Scheier group on formation and properties of highly-charged Helium nano droplets by modelling and simulation of formation of Coulomb crystals, their (in-)stability, and interactions with quantised vortices and neutral dopants, combining methods from molecular, fluid and plasma dynamics.

**Assoz. Prof. Dr. Ralf Kissmann** Institute of Astro- and Particle Physics

Computational Astroparticle Physics Group

Reserach area(s): Computational Astro-, Astroparticle and Space Physics

Personal webpage

Collaborators: Einkemmer, Ostermann, Reimer

Associated Professor Ralf Kissmann leads the computational astroparticle phyics group at the Institute of Astrophysics. His research interests are in the modelling of different astrophysical systems relevant for the acceleration of high-energy cosmic rays. In particular he is working on:

- numerical simulations of cosmic ray transport
- numerical modelling of astrophysical fluids
- the combination of the above topics in a single simulation framework.

In this context there are two numerical codes currently developed in the group: the Picard code for the investigation of cosmic-ray transport and the Cronos code for simulation of (magneto-) hydrodynamical fluids.

Co-supervisors: Einkemmer/Ostermann

Development of a dynamical model for Galactic cosmic-ray transport. With convergence time scales in the order of 107 years and electron-loss time scales in the order of years, corresponding numerical models require development of efficient time-integration schemes, including implicit time integrators and possibly local time-stepping schemes.

Co-supervisors: Kendl/Reimer

Determination of the three-dimensional Galactic gas distribution using probabilistic information field theory algorithms. Application of resulting gas distribution, together with statistical confidence intervals, in numerical Galactic cosmic-ray transport models with application to gamma-ray emission.

**Univ.-Prof. Dr. Roman Lackner**Department of Structural Engineering and Material Sciences

Unit of Material Technology

Reserach area(s): Material Technology

Personal webpage

Collaborators: Harders, Hofstetter, Rauch

Roman Lackner is head of the Unit of Material Technology at the Institute for Construction and Material Science at the University of Innsbruck. The focus of the scientific activities of Roman Lackner and his group is on basic and applied research in the field of material mechanics, especially within the framework of multiscale modeling. In particular, the scientific contributions comprise,

- experimental characterization of the material's behavior at different length scales (Roman Lackner is head of the NanoLab at the University of Innsbruck)
- homogenization techniques for upscaling physical material properties involving both analytical and numerical methods
- material optimization both as regards the production process and the in-service performance
- durability analysis of materials when subjected to chemical/physical attack.

Thesis topic: Multiscale framework for hierarchically-organized protective materials (MSC-1) »

Co-supervisors: Hofstetter

Impact processes take place frequently in daily life with e.g. protective materials reducing the severity of the occurring impact. In this project, the performance of protective materials shall be related to their microstructure employing a multiscale framework, upscaling information from the finer scales towards the macroscale, and finally enabling simulation of the compaction behaviour of protective materials when subjected to impact loading.

Thesis topic: Pore-space specific modeling of injection processes (MSC-2)

The injection process of viscous, chemo-mechanical (i.e. hardening) fluids into porous materials shall be modelled and simulated employing the smoothed particle hydrodynamics method. The underlying approach accounts for the ongoing hardening reaction during the injection, resulting in a temperature rise and hence heat flow. By considering realistic pore-space geometries generated by computer tomography the realistic simulation of strength-increasing injections as e.g. performed in medical applications (injection of PMMA into porous bone) becomes possible.

**Univ.-Prof. DDr. Klaus Liedl**Faculty of Chemistry and Pharmacy

Institute of General, Inorganic and Theoretical Chemistry

Reserach area(s): Computational Life Sciences

Personal webpage

Collaborators: Haltmeier, Probst

Klaus Liedl and his research group focus on the development and application of computational methods to rationalize and predict chemical and biochemical phenomena at a molecular level. This comprises scientific areas such as molecular dynamics simulations, quantum mechanical calculations and chemo- and bioinformatics. The group both develops molecular force fields and data analysis methods and applies existing methods to explain experimental results and to guide future experiments.

Co-supervisors: Haltmeier/Probst

Biomolecular processes occur on time scales not yet accessible by conventional molecular dynamics simulations. Different algorithms have been developed that modify the energy landscape to access longer time scales. However, after modification of the energy landscape, probabilities of the conformations have to be reweighted to regain a realistic ensemble. Most existing algorithms for reweighting suffer from large errors resulting in distorted probability distributions. In this project we will develop an alternative and more reliable solution to this problem based on Tikhonov type functionals.

Thesis topic: Deep Learning in Analysis of Molecular Dynamics Simulations (BCH-2) »

Co-supervisors: Haltmeier

Molecular dynamics simulations result in large amounts of data. Thus, state of the art methods relying on information theory and stochastics need to be developed and optimized to describe properties like hydration and aggregation. Pattern recognition of electrostatic and hydrophobic properties on complex surfaces will be applied using cutting-edge machine learning techniques.

**Univ.-Prof. Dr. Alexander Ostermann** (Deputy Coordinator)

Department of Mathematics

Numerical Analysis Group

Reserach area(s): Numerical Analysis

Personal webpage

Collaborators: Einkemmer, Haltmeier, Hofstetter, Kendl, Kissmann, Franosch, Probst

Alexander Ostermann is head of the Department of Mathematics, chair of the Numerical Analysis Group and head of the Research Area Scientific Computing. His research interests include numerical analysis and scientific computing, in particular: time integration of partial differential equations, exponential integrators, splitting methods, engineering mathematics, sensitivity analysis, and geometry.

Thesis topic: Advanced time integration schemes (MAT-5) »

Co-supervisors: Franosch/Kendl, Kissmann

Modelling complex continua results in PDEs exhibiting high oscillations, loss of regularity and nontrivial boundary conditions. Standard integrators typically fail in such situations and give unreliable solutions. Based on our recently developed exponential integrators and splitting methods, the thesis project aims at constructing integrators that address this challenge. The new methods will be developed in close coordination with the other DOCC projects.

Thesis topic: Exponential integrators for nonlinear advection-diffusion problems (MAT-6)»

Co-supervisors: Franosch/Kendl, Kissmann

The goal of this project is to construct and analyze a new class of exponential-type integrators, particularly designed for the time integration of nonlinear advection-dominated problems. Their construction will be based on the nonlinear variation of constants formula. We will analyze stability and convergence, and study the effect of non-trivial boundary conditions on the rate of convergence. The implementation of the method requires the action of a nonlinear flow, which is typically provided with the help of a semi-Lagrangian approach.

**Univ.-Prof. Dr. Michael Probst**Institute for Ion Physics and Applied Physics

Numerical Chemistry Group

Reserach area(s): Computational Chemistry

Curriculum vitae

Collaborators: Haltmeier, Liedl, Ostermann, Scheier

Michael Probst is professor at the Institute for Ion Physics and Applied Physics at the University of Innsbruck. His Computational Chemistry and Molecular Physics group investigates properties and reactions of neutral and charged clusters and molecules. His fields of research are: elucidation of reaction mechanisms by combined quantum-(thermo)chemical and molecular dynamical calculations and simulations, visualisation methods, metastable anions, electro- and physical chemistry of electrolytes.

Thesis topic: Machine learning methods for advanced material simulations (MCH-1) »

Co-supervisors: Haltmeier/Liedl

Modern materials science makes heavy use of atomistic simulations to predict and optimize compounds. Dynamical properties, for example degradation, self-diffusion, atom migration at surfaces and reconstruction are, however, not directly accessible on this level. We want to find out how information gained by atomistic simulations can be extracted so that also slow processes or new features can be modelled. Besides established methods like kinetic Monte Carlo, it shall be explored at which level machine learning algorithms might be best applied to this aim.

Thesis topic: Dynamics of molecules in the plasma / surface region (MCH-2) »

Co-supervisors: Haltmeier/Ostermann

We want to predict the dynamic interactions of plasma components with respect to each other and to the material and energy exchange near a surface. Important interactions of the first type are electron-impact excitation, ionization and photoemission from excited states, which are simulated by empirical and quantum chemical modelling. The second types are governed by sputtering and diffusion. They can be studied by molecular dynamics, also on an empirical level or by direct dynamics. This project shall improve our numerical models for plasma-surface interactions.

**Univ.-Prof. Dr. Wolfgang Rauch**Department of Infrastructure Engineering

Unit of Environmental Engineering

Reserach area(s): Smoothed Particle Hydrodynamics in Urban Water Systems

Personal webpage

Collaborators: Adam, Franosch, Harders, Lackner, Rotach

Wolfgang Rauch is professor at the Institute of Infrastructure Engineering. His research focus lies on smoothed particle hydrodynamics, which is an applied and established computational fluid dynamics (CFD) technology in other disciplines (e.g. astrophysics), whereas the technology has currently not been applied in urban water engineering. Problematic issues are the large computational burden of the method and the numerical stability of the code in connection with multiphase problems.

Thesis topic: Lagrangian microscopic biokinetic model (CEN-1) »

Co-supervisors: Franosch/Rotach

Application of Lagrangian based CFD methods in urban water management (such as smoothed particle hydrodynamics) is a relatively recent method which allows for a novel treatment of biochemical processes in the water phase. The thesis aims to couple the flow simulation with a microscopic description of biokinetic conversion, based on a stochastic distribution of particles representing microbial flocs. This will allow to decouple fluid and particle phase in the numerical description of biokinetic processes in urban water systems.

Thesis topic: Lagrangian sewer solids transport model (CEN-2) »

Co-supervisors: Franosch/Rauch

The transport of solids in sewers is usually simulated by one-dimensional Navier-Stokes equations coupled with simplified transport models. Despite significant research efforts these models show limited predictive capabilities for special problems like clogging by textile materials or FOG (fat, oil and grease). Contrarily, this thesis should apply a Lagrangian computational fluid dynamics method, i.e. smoothed particle hydrodynamics (SPH), for establishing a multiphase (water, gas and particles) model of the sewer. The multiphase SPH model will be coupled with transport models for special objects like textiles and buildup / erosion of FOG deposits.

**assoz. Prof. Dr. Anita Reimer**Department of Theoretical Physics

Theoretical High Energy Astrophysics

Reserach area(s): Theoretical High Energy Astrophysics and Astroparticle Physics

Personal webpage

Collaborators: Einkemmer, Kissmann

The research group of Anita Reimer studies the physics of cosmic high energy sources and phenomena with particular focus on solving the quest for the origin of the ultrahigh energy cosmic rays. Here the multi-messenger approach (leading to gamma-ray, neutrino and cosmic-ray astrophysics), and a detailed understanding of hadronic interactions, particle and photon propagation and radiation processes from non-thermal particle distributions is central.

We engage in the development of models for high energy cosmic sources such as black hole sources (e.g., jetted Active Galactic Nuclei), stellar binary systems involving massive stars, etc., including particle acceleration processes. We also study the source content of diffuse radiation fields and the impact of low energy diffuse radiation fields on high energy photon and particle propagation.

Thesis topic: Multimessenger astrophysics of high-energy sources (APP-1) »

Co-supervisors: Einkemmer/Kissmann

This project develops emission models of candidate cosmic-ray sources to predict the spectral evolution of cosmic rays, photons and neutrinos following in-source acceleration of nuclei. Including extensive nuclear reaction networks into the system of transport equations to be solved requires development of elaborate methods.

Co-supervisors: Einkemmer/Kissmann

Colliding wind massive binary (CWMB) systems have recently entered the gamma-ray regime, but their role as a contributor to the galactic cosmic-ray flux is an open question. This project develops emission models of CWMB systems with emphasis on the in-source nuclear cosmic ray flux evolution and escape. The photon output will be used with corresponding observations to constrain model parameters, by solving the transport equation considering all relevant interactions related to relativistic nuclei (including relevant nuclear reaction networks) and electron injection.

**Univ.-Prof. Dr. Mathias Rotach**Department of Atmospheric and Cryospheric Sciences

Dynamic Meteorology group

Reserach area(s): Atmospheric Modelling

Personal webpage

Collaborators: Haltmeier, Kendl, Rauch

Mathias Rotach is professor at the Institute of Atmospheric and Cryospheric Sciences. One of the major research areas at this is atmospheric numerical modelling. Themes are in both short-term (weather) and long-term (climate) modelling. As an overarching goal the members of the institute aim at a better understanding of atmospheric exchange processes over mountainous terrain. For the statistical downscaling of coarse-resolution climate information (what the global centres presently can provide) for point applications the team presently plans to develop a so-called ‘weather generator’ for which in many instances spatial correlations of meteorological parameters are required.

Thesis topic: Atmospheric turbulence modelling (ATS-1) »

Weather and climate models rely on a closure for sub-grid scale turbulence, which is often based on Turbulence Kinetic Energy (TKE). Recent results on TKE dissipation from non-ideal (i.e. real) terrain suggest that revisions in model parameterizations are needed. This will be investigated using Large-Eddy (and/or Direct Numerical) Simulation.

Co-supervisors: Haltmeier/Kendl

The atmosphere is characterized by deterministic chaos, which is in numerical weather prediction and climate modeling exploited by using so-called Ensemble Prediction Systems (EPSs): many simulations with slightly perturbed initial conditions are run in order to not only obtain the most likely future state but also its uncertainty. Essentially, all the established ‘perturbation schemes’ are for the synoptic (weather) scale, so that for the present project a small-scale (boundary layer) perturbation scheme shall be explored.

**Univ.-Prof. Dr. Paul Scheier**Department of Applied Physics and Ionphysics

Nano-Bio-Physics workgroup

Reserach area(s): Nano-bio physics

Personal webpage

Professor Paul Scheier is head of the working group Nano-Bio-Physics at the Institute for Applied Physics and Ionphysics. His research focuses on experimental cluster and nano physics, mass spectrometry and ion spectroscopy, helium nano droplets and laboratory astro chemistry. Recent work addresses the multicenter growth of dopant cluster ions in highly-charged helium nanodroplets.

Multicenter growth processes of nano-clusters in suprafluid Helium (NPH-2) »

Pickup of individual atoms or molecules into superfluid He nanodroplets leads to formation of clusters, nanoparticles and wires. When initially ionized, charge centers will act as seeds for cluster growth. In large droplets containing many charge centers, Coulomb repulsion keeps them apart at maximum distances, resulting in a uniform distribution of highly attractive nucleation seeds. Thus homogeneous cluster growth is expected around each charge, and confirmed by first experiments. In this project we plan to simulate such multicenter growth processes via classical and quantum molecular dynamics simulation with the aim to understand the basic molecular processes. This can be utilized to optimize particular structures, such as core-shell or Janus particles. Predictions derived from these models will be compared with experimental studies.

##### Funding

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 847476.