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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.

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Positive matrix factorization: A non-negative factor model with optimal utilization of error estimates of data values†

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.
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Analysis of different modes of factor analysis as least squares fit problems

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.
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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).
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Biogenic iodine emissions and identification of end-products in coastal ultrafine particles during nucleation bursts

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)

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.