U
Unto Tapper
Researcher at University of Helsinki
Publications - 47
Citations - 6099
Unto Tapper is an academic researcher from University of Helsinki. The author has contributed to research in topics: Nanoparticle & Particle. The author has an hindex of 15, co-authored 47 publications receiving 5315 citations.
Papers
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Journal ArticleDOI
Positive matrix factorization: A non-negative factor model with optimal utilization of error estimates of data values†
Pentti Paatero,Unto Tapper +1 more
TL;DR: In this paper, a new variant of Factor Analysis (PMF) is described, where the problem is solved in the weighted least squares sense: G and F are determined so that the Frobenius norm of E divided (element-by-element) by σ is minimized.
Journal ArticleDOI
Analysis of different modes of factor analysis as least squares fit problems
Pentti Paatero,Unto Tapper +1 more
TL;DR: It is shown that each mode of principal component analysis or ‘factor analysis’ is equivalent to solving a certain least squares problem where certain error estimators σ ij are assumed for the measured data matrix X ij and the best posssible scaling and a near-optimal scaling are introduced.
Journal ArticleDOI
Source identification of bulk wet deposition in Finland by positive matrix factorization
TL;DR: In this paper, a positive matrix factorization (PMF) was applied to a Finnish data set (18 years, 15 locations) of monthly bulk wet deposition concentrations of strong acids, SO4, NO3, NH4, total nitrogen (Ntot), total phosphorus (Ptot) and total organic carbon (TOC).
Journal ArticleDOI
Biogenic iodine emissions and identification of end-products in coastal ultrafine particles during nucleation bursts
Jyrki M. Mäkelä,Jyrki M. Mäkelä,Thorsten Hoffmann,C. Holzke,M. Väkevä,Tanja Suni,Timo Mattila,Pasi Aalto,Unto Tapper,Esko I. Kauppinen,Colin D. O'Dowd +10 more
TL;DR: In this paper, it was observed that both iodine and sulphur were present in the new particles with diameter below 10 mn, while the contribution of sulphate was significantly higher than iodine.
Journal Article
Biogenic iodine emissions and identification of end-products in coastal ultrafine particles during nucleation bursts : New Particle Formation and Fate in the Coastal Environment (PARFORCE)
Jarmo Mäkelä,Thorsten Hoffmann,C. Holzke,M. Väkevä,Tanja Suni,Timo Mattila,Pasi Aalto,Unto Tapper,Esko I. Kauppinen,Colin D. O'Dowd +9 more
TL;DR: In this paper, the authors used transmission electron microscopy (TEM) and elemental analysis using energy-dispersive X ray (EDX) to study low-tide particle formation bursts in the coastal zone.