Browsing by Author "Manninen, Matti"

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  • A 24-hour population distribution dataset based on mobile phone data from Helsinki Metropolitan Area, Finland
    (2022-02-04) Bergroth, Claudia; Järv, Olle; Tenkanen, Henrikki; Manninen, Matti; Toivonen, Tuuli
     Data Article
    In this article, we present temporally dynamic population distribution data from the Helsinki Metropolitan Area, Finland, at the level of 250 m by 250 m statistical grid cells. An hourly population distribution dataset is provided for regular workdays (Mon - Thu), Saturdays and Sundays. The data are based on aggregated mobile phone data collected by the biggest mobile network operator in Finland. Mobile phone data are assigned to statistical grid cells using an advanced dasymetric interpolation method based on ancillary data about land cover, buildings and a time use survey. The dataset is validated by comparing population register data from Statistics Finland for night hours and a daytime workplace registry. The resulting 24-hour population data can be used to reveal the temporal dynamics of the city, and examine population variations relevant to spatial accessibility analyses, crisis management, planning and beyond.
  • Automated lock-in amplifier measurements using a matrix switch
    (2021-09-30) Räty, Topi
     Perustieteiden korkeakoulu | Bachelor's thesis
  • Comment on binding of hydrogen molecules by a transition-metal ion
    (1993) Manninen, Matti; Nieminen, Risto
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    A Comment on the Letter by Niu, Rao, and Jena Phys. Rev. Lett. 68, 2277 (1992).
  • Comment on the positron surface-state lifetime
    (1984-09-24) Nieminen, R. M.; Puska, M. J.; Manninen, Matti
     Comment/debate
  • Electronically induced trapping of hydrogen by impurities in niobium
    (1984-07-15) Manninen, Matti; Puska, M. J.; Nieminen, R. M.; Jena, P.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The binding energies of hydrogen and its isotopes to substitutional impurities Ti, Cr, and V in niobium have been calculated. The hydrogen-metal interaction is based on the effective-medium theory. The wave mechanics of the hydrogenic interstitials are explicity dealt with, and the lattice distortion created by the hydrogen is incorporated through the method of lattice statics. The difference in the electronic structure between impurity and host atoms is shown to be largely responsible for the binding of hydrogen to the impurities. The results are in agreement with recent inelastic neutron scattering experiments.
  • Elektronitiheys metallin vakanssissa
    (1974) Manninen, Matti
     Helsinki University of Technology | Master's thesis
  • Kapton compression cell for the studies of 3He crystals
    (2009) Kaikkonen, Jukka-Pekka
     Informaatio- ja luonnontieteiden tiedekunta | Bachelor's thesis
  • Muon states in uniaxially strained iron
    (1984-04-01) Jena, P.; Manninen, Matti; Nieminen, R. M.; Puska, M. J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Effects of lattice relaxation, quantum motion, and uniaxial strain on the internal field at a positive-muon site in iron have been calculated. The uniaxial strain gives rise to a statistical shift of the muon population at interstitial sites. The effect of the population shift is found to be primarily responsible for the observed changes in the muon-precession frequency. The theory also predicts a 1T temperature dependence of the frequency shifts.
  • Preparation of an interdigital capacitor for high voltage and ultra-low temperature experiments
    (2011) Peri, Ville
     Perustieteiden korkeakoulu | Bachelor's thesis
  • Quantum motion of chemisorbed hydrogen on Ni surfaces
    (1983-09-19) Puska, M. J.; Nieminen, R. M.; Manninen, Matti; Chakraborty, Bulbul; Holloway, S.; Nørskov, J. K.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Quantum mechanical energy levels and wave functions have been calculated for the motion of chemisorbed hydrogen atoms on Ni surfaces. The results show considerable quantum effects for the adatom in both the ground and the excited states. The description of the adparticles as being delocalized along the surface offers a novel interpretation of several phenomena, in particular the vibrational excitations.
  • Repulsive interaction of the helium atom with a metal surface
    (1984-02-15) Manninen, Matti; Nørskov, J. K.; Puska, M. J.; Umrigar, Cyrus
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The repulsive part of the helium scattering potential at a surface is approximately proportional to the surface electron density. The proportionality coefficient is shown to be a well-defined quantity, which can be related to the electron-helium scattering length. The spread in the values of the proportionality constant suggested in the literature is shown to be due to different definitions of the coefficient or due to inadequate calculational methods. The value calculated using the local density approximation with a self-interaction correction is in very good agreement with the electron-scattering-length measurements.
  • Risk analysis of base station subsystem
    (1999) Manninen, Matti
     School of Business | Master's thesis
  • Role of elastic and electronic interactions in trapping of hydrogen by impurities in transition metals
    (1985-06-15) Jena, P.; Nieminen, R. M.; Puska, M. J.; Manninen, Matti
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The interplay between the lattice distortion and the electronic contributions to the trapping of migrating hydrogen isotopes by substitutional impurities is investigated. We use a comprehensive calculational scheme incorporating (i) the effective-medium theory for the electronic interaction, (ii) the lattice Greens function for elastic coupling, and (iii) the hydrogen quantum motion. The calculations for Ti and Cr impurities in V host show that lattice strain effects dominate. Cr, which otherwise provides an electronic trap site, does not induce trapping when elastic effects are incorporated. The situation in the case of Ti is just the reverse. We find no isotope dependence of the binding energy of hydrogen.
  • Screening of positrons in semiconductors and insulators
    (1989-04-15) Puska, M. J.; Mäkinen, S.; Manninen, Matti; Nieminen, Risto
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Theoretical models are presented for the enhancement of the electron density at a positron in a semiconductor or insulator host. The model better suited for typical semiconductors is based on the many-body theory for the screening of a positron in electron gas. The starting point of the model for insulators is the atomic polarizability. The common parameter in both models is the high-frequency dielectric constant. Moreover, the enhancement depends on the ambient electron density in the semiconductor model and on the unit-cell volume in the insulator model. With use of the models developed, positron lifetimes in perfect semiconductor and insulator crystals have been calculated. In the calculations, three-dimensional electron densities and electrostatic potentials are obtained by atomic superposition and the fully three-dimensional positron wave functions are solved by a relaxation method. The calculated positron lifetimes agree with the experimental ones within a few picoseconds. Moreover, we have used the model to predict lifetimes of positrons trapped by lattice defects such as vacancies and vacancy clusters.
  • Using common XML Schemas for interoperability in Spatial Systems
    (2010) Manninen, Matti
     Informaatio- ja luonnontieteiden tiedekunta | Master's thesis
    Tässä työssä selvitetään kuinka tietoa voidaan muuntaa toimittajakohtaisesta muodosta standardoituun XML-muotoon ja tämän jälkeen jakaa WFS- tai WMS-rajapintojen kautta käyttäjille. Työn XML-tiedostot perustuvat KuntaGML-skeemaan. Tiedon muokkaamisesta ja luomisesta lähtien tarvitaan kolme asiaa: XML-tiedosto, muokkausohjelma ja WMS/WFS -julkaisuohjelma. Työssä selvitetään näiden vaiheiden tarpeellisuus sekä mitä vaiheita näiden lisäksi tarvitaan. Tärkeässä osassa on myös tutkimus siitä millainen tietokanta kannattaa määritellä tilanteessa, jossa muokkausohjelma ja XML-skeema sisältävät kukin osittain sellaista tietoa, jota toinen ei sisällä. Tavoitteena on löytää tehokas ratkaisu, jossa tietoa ei häviä talletettaessa sitä tietokantaan. Tutkimuksen pohjalta työssä implementoidaan tiedonsiirtojärjestelmä, jolla voidaan varmistaa oletuksia.
  • Samakanavahäiriötason vaihtelu radioyhteydellä matkapuhelimesta tukiasemalle CDMA -solukkoradioverkossa
    (1995) Manninen, Matti
     Helsinki University of Technology | Master's thesis