## RESEARCHERS

#### DIRECTORS

**Director in charge of research:**

**Academy professor** ** Matti Lassas ** **, University of Helsinki.**

Matti Lassas is an expert in the field of mathematical theory of inverse problems, especially, in theory of inverse problems for partial differential equations. In the field of applications, Lassas has made significant contributions on medical imaging and invisibility cloaking which has a number of potential applications. Lassas has won several awards including the prestigious Vaisala price of the Finnish Academy of Science and Letters in 2004 and Calderon Prize awarded by the Inverse Problems International Association (IPIA).

**Vice director:**

**Professor** ** Mikko Kaasalainen ** **, Tampere University of Technology.**

Mikko Kaasalainen has long experience in finding comprehensive, practical, and computationally efficient mathematical solutions to interdisciplinary inverse problems. He has solved the long-open mathematical problem of determining the shape of an object from measurements of total brightness and the resulting mathematical methods have revolutionized the way we obtain information from small solar system bodies. Kaasalainen's research interests are planetary and space research, galactic dynamics, Hamiltonian systems in astrophysics, geophysics, signal processing, remote sensing and environmental studies.

#### TEAM LEADERS

**Research Professor Markku Lehtinen, University of Oulu.**

Lehtinen is an expert in the field of statistical inversion methods. His rigorous mathematical results include experiment comparison theory and discretization-independent prior models. The long-term way of work is to isolate and formalize problems in applications as formal mathematical questions. The main achievements are world-wide adapted new coding and analysis methods for ionospheric research radars and the latest breakthrough is rigorous characterization of radar experiment comparison and perfect pulse compression codes. The Council of the EISCAT Scientific Association awarded Lehtinen the Beynon Medal in 2008. Other research includes tomography, space debris detection, lunar imaging and fast numerical software for linear inverse problems. Lehtinen also leads the methodological planning of a the EISCAT3D radar - a new European infrastructure in the ESFRI roadmap and is the vice director of the Sodankylä Geophysical Observatory.

**Professor** ** ** ** Heikki Haario ** ** ** **, Lappeenranta University of Technology.**

Heikki Haario is internationally known by his contributions to Bayesian theory and algorithms. His works on efficient ergodic sampling methods have been forerunners on this increasingly topical field of Bayesian computational methods, and are now standard references on the area. Haario's research interests are strongly motivated by applications such as atmospheric remote sensing and climate research.

**Professor** ** Jari Kaipio ** **, University of Auckland and University of Eastern Finland.**

Professor Jari Kaipio is internationally regarded as one of the leading researcher in applied Bayesian inverse problems, with a co-authored book (with Erkki Somersalo), many related journal papers as well as plenary talks. Kaipio is a fellow of the Institute of Physics (GB), founder and representative of several international scientific societies,and member of the editorial board of three international journals. Kaipio's main contribution to this field has been the development of the Bayesian approximation error approach and nonstationary inversion framework. He leads the Inverse Problems Group of about 10 seniors and 10 graduate students in University of Eastern Finland. He is currently on leave in University of Auckland.

**Professor** ** Mikko Salo ** **, University of Jyväskylä.**

Mikko Salo works on fundamental theoretical aspects of inverse problems such as the Calderón problem in electrical imaging and travel time tomography in seismic imaging. His most important results are related to understanding electrical imaging in anisotropic media and the solution of the tensor tomography problem in two dimensions. Salo is the recipient of an Academy of Finland prize in 2011 and an ERC Starting Grant in 2012, and acts as Managing Editor of the journal Inverse Problems and Imaging.

**Professor** ** Valeriy Serov ** **, University of Oulu.**

Serov's main scientific interests are oriented toward the spectral theory of elliptic differential operators with singular coefficients and its applications to inverse scattering and inverse spectral problems for such operators as well as the nonlinear equations with applications in optics and electromagnetics. His most important results include the solution of inverse eigenvalue problems for Sturm-Liouville operator with singular coefficients in 1994 (with L. Zhornitskaya), the solution of backscattering problem in two dimensions in 2001 (together with P. Ola and L. Päivärinta), multi-dimensional Borg-Levinson theorem for singular potentials in 2002 (together with L. Päivärinta) and the uniqueness results and reconstruction of singularities in two-dimensional nonlinear Schrödinger operator with singular coefficients in 2007-2008.

**Professor** ** Samuli Siltanen ** **, University of Helsinki.**

Professor Samuli Siltanen is an expert in the field of applied inverse problems, in particular medical imaging techniques such as electrical impedance tomography and low-dose three-dimensional X-ray imaging. He has published many scientific articles and five patents, and given lots of invited talks at international conferences. He is the principal investigator of the research project *CSI Speech* developing computerized inversion methods for the research of spoken language; the EUR 1 200 000 funding is provided by the Academy of Finland for the period 2010-2014. Siltanen was a Postdoctoral Fellow of the Japan Society for the Promotion of Science in 2002-2004 and has worked for several years with GE Healthcare and other medical imaging technology companies. He has founded the Industrial Mathematics Laboratory of University of Helsinki.

**Professor** ** Aapo Hyvärinen ** **, University of Helsinki.**

Aapo Hyvärinen works on machine learning with applications in neuroscience, and is particularly known for his work on independent component analysis. In this CoE, his particular interest is in the combination of inverse problems with probabilistic models developed in machine learning.

#### PhD's 2005-2014

**Esa Vesalainen **(UH, 2014), *On Non-Scattering Energies.*

**Valter Pohjola **(UH, 2014), *Inverse boundary problems involving the magnetic Schrödinger operator.*

**Janne Tamminen **(UH, 2014), *Computational Studies on Direct Reconstruction Methods in Tomographic Imaging.*

**Martti Kalke **(UH, 2014), *Image processing methods for limited angle tomography and sparse angle tomography.*

**Jari Kourunen **(UEF, 2014), *Imaging of Mixing in Selected Industrial Processes Using Electrical Resistance Tomography.*

**Ossi Lehtikangas **(UEF, 2014), *Approximations and hybrid models for modeling light propagation in biological tissues.*

**Tuomas Koivumäki **(UEF, 2014), *The bioimpedance technique in respiratory- and dual-gated positron emission tomography imaging.*

**Antti Lipponen **(UEF, 2014), *Nonstationary flow fields, model reduction and approximation errors in process tomography.*

**Joonas Ilmavirta **(JYU, 2014), *On the broken ray transform.*

**Isambi Mbalawata **(LUT, 2014), *Adaptive Markov chain Monte Carlo and Bayesian filtering for state space models.*

**Gasper Godson Mwanga **(LUT, 2014), *Mathematical modeling and optimal control of malaria.*

**Eemeli Blåsten** (UH, 2013), *On the Gel'fand-Calderón inverse problem in two dimensions.*

**Kimmo Karhunen** (UEF, 2013), *Electrical Resistance Tomography Imaging of Concrete.*

**Kati Niinimäki** (UEF, 2013), *Computational optimization methods for large-scale inverse problems.*

**Anssi Lehikoinen** (UEF, 2012), *Modeling Uncertainties in Process Tomography and Hydrogeophysics.*

**Ville Rimpiläinen** (UEF, 2012), *Electrical tomography imaging in pharmaceutical processes.*

**Virpi Junttila** (LUT, 2011), *Automated, adaptive methods for forest inventory.*

**Hanna Kiili** (UO, 2011), *Transmission problem for the electromagnetic scattering by a chiral obstacle.*

**Teemu Laakso** (UH, 2011), *Embracing Integrability in Stellar and Planetary Dynamics.*

**Antti Nissinen **(UEF, 2011), *Modelling Errors in Electrical Impedance Tomography.*

**Lauri Oksanen** (2011, UH), *Inverse problem for the wave equation: partial data and novel boundary sources.*

**Antti Solonen** (2011, LUT), *Bayesian Methods for Estimation, Optimization and Experimental Design.*

**Markus Harju** (UO, 2010), *On the direct and inverse scattering problems for a nonlinear three-dimensional Schrödinger equation.*

**Tapio Helin** (TKK, 2010), *Discretization and Bayesian Modeling in Inverse Problems and Imaging.*

**Timo Lähivaara** (UEF, 2010), *Discontinuous Galerkin Method for Time-Domain Wave Problems.*

**Harri Auvinen** (LUT, 2009), *Inversion and Assimilation methods with applications in Geophysical Remote Sensing.*

**Ilkka Virtanen** (UO, 2009), *Multi-purpose methods for ionospheric radar measurements.*

**Janne Huttunen** (UEF, 2008), *Approximation and Modelling Errors in Nonstationary Inverse Problems.*

**Ruth Kaila** (TKK, 2008), *The integrated volatility implied by option prices, a Bayesian approach.*

**Marko Laine** (LUT, 2008), *Adaptive MCMC methods with applications in environmental and geophysical models.*

**Sampsa Pursiainen** (TKK, 2008), *Computational methods in electromagnetic biomedical inverse problems.*

**Tuomo Savolainen** (UEF, 2008), *Modular, adaptive electrical impedance tomography measurement system.*

**Eeva Boman** (UEF, 2007), *Radiotherapy forward and inverse problem applying Boltzmann transport equation.*

**Matias Dahl** (TKK, 2007), *Geometric Properties of Electromagnetic Waves.*

**Olga Shipilova** (LUT, 2007), *Particle Transport Method for Convection-Diffusion-Reaction Problems.*

**Olli-Pekka Tossavainen** (UEF, 2007), *Shape estimation in electrical impedance tomography.*

**Tanja Tarvainen** (UEF, 2006), *Computational Methods for Light Transport in Optical Tomography.*

**Simo-Pekka Vänskä** (UH, 2006), *Direct and Inverse Scattering for Beltrami Fields.*

**Kenrick Bingham** (TKK, 2005), *The Blagoveščenskiĭ Identity and the Inverse Scattering Problem.*

**Lasse Heikkinen** (UEF, 2005), *Statistical estimation methods for electrical impedance tomography.*

**Jenni Heino** (TKK, 2005), *Approaches for Modelling and Reconstruction in Optical Tomography in the Presence of Anisotropies.*

**Matti Malinen** (UEF, 2005), *Computational methods for optimal control in ultrasound therapy.*

**Petteri Piiroinen** (UH, 2005), *Statistical measurements, Experiments and Applications.*

**Hanna Pikkarainen** (TKK, 2005), *A Mathematical Model for Electrical Impedance Process Tomography.*

**Aku Seppänen** (UEF, 2005), *State estimation in process tomography.*

**Viktoria Sofieva** (TKK, 2005), *Inverse Problems in Stellar Occultation.*