Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Thin film & Vortex. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

Analysis of research into the teaching and learning of programming

Abstract: This paper presents an analysis of research papers about programming education that were published in computing education conferences in the years 2005 to 2008. We employed Simon's classification scheme to identify the papers of interest from the ICER, SIGCSE, ITiCSE, ACE, Koli Calling and NACCQ conferences. Having identified the papers, we analyzed the type of data collected, whether the analysis was qualitative, quantitative, or mixed, and the aims and outcomes being reported. The greatest number of papers employed quantitative research methods, investigated the ability, aptitude, or understanding of students, and were based in single courses. The theme of the research and the type of study conducted vary across the conferences, indicating the different nature and role of each conference. Papers that investigated student learning of programming in terms of established theories or models of learning were not common, indicating an area of research that deserves more attention.

Total Flux Density Variations in Extragalactic Radio Sources. I. Decomposition of Variations into Exponential Flares

Abstract: We show that 22 and 37 GHz total flux density variations in compact extragalactic radio sources can to a good accuracy be modeled by superposition of a small number of flare components. Both the rise and the decay of these flares are exponential, with a characteristic decay timescale 1.3 times longer than the rise timescale. The properties of the individual model flares derived from these flux decompositions are in agreement with data obtained from VLBI observations of the corresponding new shock components. The total flux density decompositions can be used to search correlations between radio and other regimes, to calibrate and to interpret VLBI observations, and to derive physical parameters of the shocks. In particular, the associated brightness temperatures of the flares can be used to estimate the amount of Doppler boosting in each source and, using additional VLBI data, to derive the intrinsic brightness temperatures, the Lorentz factors and the viewing angles of the sources.

Clustering based on conditional distributions in an auxiliary space

Abstract: We study the problem of learning groups or categories that are local in the continuous primary space but homogeneous by the distributions of an associated auxiliary random variable over a discrete auxiliary space. Assuming that variation in the auxiliary space is meaningful, categories will emphasize similarly meaningful aspects of the primary space. From a data set consisting of pairs of primary and auxiliary items, the categories are learned by minimizing a Kullback-Leibler divergence-based distortion between (implicitly estimated) distributions of the auxiliary data, conditioned on the primary data. Still, the categories are defined in terms of the primary space. An online algorithm resembling the traditional Hebb-type competitive learning is introduced for learning the categories. Minimizing the distortion criterion turns out to be equivalent to maximizing the mutual information between the categories and the auxiliary data. In addition, connections to density estimation and to the distributional clustering paradigm are outlined. The method is demonstrated by clustering yeast gene expression data from DNA chips, with biological knowledge about the functional classes of the genes as the auxiliary data.

Empirical characterization of wideband indoor radio channel at 5.3 GHz

Abstract: Characteristics of wideband indoor radio channel at 5.3 GHz were defined based on an extensive measurement campaign using a wideband channel sounder with 19 ns delay resolution. Pathloss exponents were 1.3-1.5 in LOS and 2.9-4.8 in non-line of sight (NLOS). Large difference in NLOS exponents was due to different dominating propagation mechanisms in different types of building structures. The delay dispersion was characterized by cumulative distribution functions (CDF) of the RMS delay spreads, the values for CDF=0.9 varied from 20 to 180 ns in different setups in an office building and large hall environments. The correlation functions of the radio channel in spatial and frequency domains were extracted. Small scale models for five typical indoor scenarios were developed using tapped delay lines.