[article-cris] Palvelut / Services

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Browsing [article-cris] Palvelut / Services by Department "BECS"

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  • Current injection to free-standing III-N nanowires by bipolar diffusion
    (2013) Kivisaari, Pyry; Oksanen, Jani; Tulkki, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Dynamic eye tracking based metrics for infant gaze patterns in the face-distractor competition paradigm
    (2014-05-20) Ahtola, Eero; Stjerna, Susanna; Yrttiaho, Santeri; Nelson, Charles A.; Leppänen, Jukka M.; Vanhatalo, Sampsa
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Objective: To develop new standardized eye tracking based measures and metrics for infants' gaze dynamics in the face-distractor competition paradigm. Method: Eye tracking data were collected from two samples of healthy 7-month-old (total n = 45), as well as one sample of 5-month-old infants (n = 22) in a paradigm with a picture of a face or a non-face pattern as a central stimulus, and a geometric shape as a lateral stimulus. The data were analyzed by using conventional measures of infants' initial disengagement from the central to the lateral stimulus (i.e., saccadic reaction time and probability) and, additionally, novel measures reflecting infants gaze dynamics after the initial disengagement (i.e., cumulative allocation of attention to the central vs. peripheral stimulus). Results: The results showed that the initial saccade away from the centrally presented stimulus is followed by a rapid re-engagement of attention with the central stimulus, leading to cumulative preference for the central stimulus over the lateral stimulus over time. This pattern tended to be stronger for salient facial expressions as compared to non-face patterns, was replicable across two independent samples of 7-month-old infants, and differentiated between 7 and 5 month-old infants. Conclusion: The results suggest that eye tracking based assessments of infants' cumulative preference for faces over time can be readily parameterized and standardized, and may provide valuable techniques for future studies examining normative developmental changes in preference for social signals. Significance: Standardized measures of early developing face preferences may have potential to become surrogate biomarkers of neurocognitive and social development.
  • Effects of lateral current injection in GaN multi-quantum well light-emitting diodes
    (2012) Kivisaari, P.; Oksanen, J.; Tulkki, J.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Polarization doping and the efficiency of III-nitride optoelectronic devices
    (2013) Kivisaari, Pyry; Oksanen, Jani; Tulkki, Jukka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Random matrix approach to the dynamics of stock inventory variations
    (2012-09) Zhou, Wei Xing; Mu, Guo Hua; Kertész, János
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    It is well accepted that investors can be classified into groups owing to distinct trading strategies, which forms the basic assumption of many agent-based models for financial markets when agents are not zero-intelligent. However, empirical tests of these assumptions are still very rare due to the lack of order flow data. Here we adopt the order flow data of Chinese stocks to tackle this problem by investigating the dynamics of inventory variations for individual and institutional investors that contain rich information about the trading behavior of investors and have a crucial influence on price fluctuations. We find that the distributions of cross-correlation coefficient C i j have power-law forms in the bulk that are followed by exponential tails, and there are more positive coefficients than negative ones. In addition, it is more likely that two individuals or two institutions have a stronger inventory variation correlation than one individual and one institution. We find that the largest and the second largest eigenvalues (λ 1 and λ 2) of the correlation matrix cannot be explained by random matrix theory and the projections of investors' inventory variations on the first eigenvector u(λ 1) are linearly correlated with stock returns, where individual investors play a dominating role. The investors are classified into three categories based on the cross-correlation coefficients C V R between inventory variations and stock returns. A strong Granger causality is unveiled from stock returns to inventory variations, which means that a large proportion of individuals hold the reversing trading strategy and a small part of individuals hold the trending strategy. Our empirical findings have scientific significance in the understanding of investors' trading behavior and in the construction of agent-based models for emerging stock markets.