People (new)

The inverse problems group at the University of Helsinki has members and contributors ranging from professors to undergraduate students. The people of the inverse problems group come from a broad range of backgrounds which is reflected by the diverse research done here. Below you can find a list of our people along with their contact information and research interests.

2016-08-16 Inverse Problems Group

INVERSE PROBLEMS GROUP, AUGUST 2016

 

 

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: A410 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Telephone: +358-40 594 3560
Email: samuli.siltanen 'at' helsinki.fi
Office hours: please send me email

Research Interests

The goal of my scientific work is to design efficient numerical methods that have a sound mathematical basis and solve real-world problems. I have published research articles mostly about the following topics: Electrical Impedance Tomography (EIT), low-dose three-dimensional X-ray imaging, dynamic X-ray tomography, discretization-invariant Bayesian inversion, and the Novikov-Veselov equation.

Contact Information

Finland Distinguished Professor in Inverse Problems.

Research Interests

Gunther Uhlmann was named a Finland Distinguished Professor starting in 2013.  More information on the Finland Distinguished Professor programme can be found here.  Prof. Uhlmann's research includes topics from geometric inverse problems, partial data problems, and invisibility. Recent developments of hybrid inverse problems, such as thermo- and photoacoustic tomography, are also being studied.

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: D329 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Telephone: +358-9-191 51455
Email: Petri.Ola 'at' Helsinki.FI
Office hours: Mon 10-11

Research Interests

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: C312 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Telephone: +358-2-941 51424
Email: petteri.piiroinen 'at' helsinki.fi
Office hours: Tue 12-13

Research Interests

Contact Information

Room:
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Email: etunimi.sukunimi 'at' helsinki.fi

Research Interests

TUHAT profile

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: A422 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Telephone: +358 2 941 51494 
Email: tapio.helin 'at' helsinki.fi

Research Interests

My research interests include inverse problems related to Bayesian inference and stochastic partial differential equations. In particular, I work with an inverse problem appearing in next-generation telescope imaging called atmospheric tomography.

Read more about my research on my homepage.

 

Contact Information

E-mail: tony.liimatainen (at) helsinki.fi

Research Interests

 

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: D312 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Email: minh.mach@helsinki.fi 

Research Interests

I am interested in imaging reconstruction algorithms in electrical impedance tomography, such as the D-bar method or the monotonicity-based method. At this moment, I work with Matti Lassas and Samuli Siltanen on the stability analysis of the D-bar method and the stroke EIT imaging.

For more information about my research, please visit my webpage on ResearchGate:

ResearchGate profile

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: B408 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Email: esa.niemi (at) helsinki.fi

Research Interests 

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: A421 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Email: tatiana.bubba 'at' helsinki.fi

Research Interests

My research interests include inverse problems, regularization, numerical optimization and signal processing. In particular, I work on (limited data) tomographic reconstructions with multiresolution techniques (mainly, shearlets).

ResearchGate profile

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: B421 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Email: andreas.hauptmann@helsinki.fi  

Research Interests

As an applied mathematician with a focus on computational mathematics I am interested in inverse problems with real measurement data, in particular applications to medical imaging.

In my PhD thesis I investigate the problem of partial boundary data in electrical impedance tomography, a highly non-linear inverse problem that needs careful analysis of the underlying mathematics. My study is motivated by a computational point of view and seeks to recover the unknown conductivity from this incomplete data.

Furthermore, I am interested in dynamic imaging and regularization strategies. That is given a set of measurements at several time instances, we seek to compute a reconstruction that uses all time dependent information. These problems arise for instance in X-ray computed tomography of a moving object.

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: B424 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Telephone: +358-9-191

Research Interests

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: B407 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Telephone:
Email: zenith.purisha 'at' helsinki.fi

Research Interests

Sparse X-ray tomography problem is the main focus of my research. A new algorithm and some new implementations to get good reconstruction from the data has been implemented. Real data produced by CT/μCT machine are tested. B-spline and Markov Chain Monte Carlo (NURBS-MCMC) strategy is implemented successfully and the result is in a CAD-format. 

Another project that I am now also working is in applying the state-or-arts and modern methods, e.g Barzilai Borwein, Chambolle Pock, & Shearlet for studying bone analysis whether the bone is healthy or osteoarthritis.

Contact Information

 

Research Interests

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: A414 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
Email: teemu.saksala(at)helsinki.fi 

Research Interests

I'm interested in inverse problems on manifolds. In my Phd Thesis I study certain geometric inverse problems related to geophysical prospecting. The rough idea is that earthquakes produce seismic waves that propagate through the Earth and can be measured on different locations on the surface of Earht with instruments called geophones. Therefore it possible to measure travel time differences of seismic waves. Doing this kind of measurements, we can find indirect information about the inner structure of Earth. 

Mathematically speaking we study an inverse problem of a wave equation on Riemannian manifold with Dirichlet or Neumann boundary values. The goal is to reconstruct the unknown wave speed in the interior of the manifold or equivalently the Riemannian metric tensor. That is a mathematical consept that corresponds to the material parameters of the soil and in this way tells us about the structure of Earth.

At the moment I work with my advisor Matti Lassas, Hangming Zhou, Tapio Helin and Lauri Oksanen. I'm planing to defend my thesis at the fall of 2017.

Tuhat research database page

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: B414, Exactum
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
E-mail: jonatan.lehtonen@helsinki.fi

Research Interests

My primary interest is in applying mathematics to real-world problems, which naturally led me to the field of inverse problems. My PhD thesis focuses on atmospheric tomography, an inverse problem related to next-generation telescopes.

A well-known issue with ground-based telescope imaging is that atmospheric turbulence (fluctuations of the refractive index) perturbs the phase of incoming light waves, resulting in degraded resolution and blurred images. In atmospheric tomography, the basic idea is to reconstruct the turbulence profile in real time based on measurements of aberrations in the phase of incoming light waves from known light sources, e.g. natural stars or artificial laser stars.  The turbulence profile can then be used to correct for the effect of turbulence on images in real time

Contact Information

Department of Mathematics and Statistics, University of Helsinki
Room: A422 (Exactum)
Address: P.O. Box 68 (Gustaf Hällströmin katu 2b)
FI-00014 University of Helsinki
E-mail: antti.kujanpaa@helsinki.fi

Research Interests

My research centers around inverse problems for the wave equation on Riemannian manifolds. The focus is on models of physical systems with moving medium such as a layer of gas or water. The main objective is to develop effective techniques for indirect determination of turbulence and flow of the fluid from scattering data of waves. Motivation for my research arises naturally from atmospheric imaging and radar technology.