Helsinki University of Technology

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

Planck pre-launch status: the Planck-LFI programme

Abstract: This paper provides an overview of the Low Frequency Instrument (LFI) programme within the ESA Planck mission. The LFI instrument has been developed to produce high precision maps of the microwave sky at frequencies in the range 27−77 GHz, below the peak of the cosmic microwave background (CMB) radiation spectrum. The scientific goals are described, ranging from fundamental cosmology to Galactic and extragalactic astrophysics. The instrument design and development are outlined, together with the model philosophy and testing strategy. The instrument is presented in the context of the Planck mission. The LFI approach to ground and inflight calibration is described. We also describe the LFI ground segment. We present the results of a number of tests demonstrating the capability of the LFI data processing centre (DPC) to properly reduce and analyse LFI flight data, from telemetry information to calibrated and cleaned time ordered data, sky maps at each frequency (in temperature and polarization), component emission maps (CMB and diffuse foregrounds), catalogs for various classes of sources (the Early Release Compact Source Catalogue and the Final Compact Source Catalogue). The organization of the LFI consortium is briefly presented as well as the role of the core team in data analysis and scientific exploitation. All tests carried out on the LFI flight model demonstrate the excellent performance of the instrument and its various subunits. The data analysis pipeline has been tested and its main steps verified. In the first three months after launch, the commissioning, calibration, performance, and verification phases will be completed, after which Planck will begin its operational life, in which LFI will have an integral part.

Selective listening modifies activity of the human auditory cortex.

Abstract: We have studied the effect of selective listening on the neuromagnetic evoked activity of the human auditory cortex In the word categorization experiment the stimuli were 5-letter words, each beginning with /k/ Half of them were targets, ie, names of animals or plants, and half other meaningful Finnish words In the duration discrimination experiment equiprobable tones of 425 ms (targets) or 600 ms duration were presented In both experiments the interstimulus interval (ISI) was 23 s and the stimuli of the two classes were presented randomly Subjects either ignored the stimuli (reading condition) or counted the number of targets (listening condition) The magnetic field over the head was measured with a 7-channel 1st-order SQUID-gradiometer The stimuli evoked a transient response followed by a sustained field The transient response did not differ between the two conditions but the sustained field was significantly larger in the listening than reading condition; the increase began 120–200 ms after stimulus onset and continued for several hundred milliseconds The equivalent source locations of both transient and sustained responses agreed with activation of the supratemporal auditory cortex In the dichotic listening experiment 25-ms square-wave stimuli were presented randomly and equiprobably either to the left or to the right ear at an ISI of 08–1 s, either alone or in presence of a speech masker Counting the stimuli of either ear resulted in differences between responses to relevant and irrelevant sounds The difference began 140–150 ms after stimulus onset and peaked at 200–240 ms During monaural speech masking, N100m was larger for attended than ignored stimuli The results suggest that neural mechanisms underlying direction of attention include modification of the activity of the auditory cortex and that the mechanisms are similar for words and tones

Backscattering properties of boreal forests at the C- and X-bands

Abstract: The backscattering properties of boreal forests are studied using empirical airborne and spaceborne radar data from Finland. Airborne measurements were carried out in the summer of 1992 by the HUTSCAT scatterometer at the Teijo test area in southern Finland. The HUTSCAT scatterometer is an eight-channel helicopter-borne profiling radar operating at the C- and X-bands. The ranging capability of the HUTSCAT scatterometer was employed in the semiempirical modeling of forest backscatter. The backscatter profile information was used in the analysis of the canopy transmissivity and the canopy backscattering coefficient by distinguishing backscattering contributions from the canopy and the ground. Additionally, ERS-1 C-band satellite SAR measurements were obtained for the Teijo test area and for the reference test area in Sodankyla in northern Finland. The radar results were compared with operational ground-based forest assessment data on forest compartments (stands) of the area. The key parameter investigated was the stem (bole) volume per hectare. The results obtained show the behavior of the canopy transmissivity and the canopy backscatter as a function of stem volume (directly related to the forest biomass). The influence of seasonal and diurnal changes on, and the effects of the changes in soil moisture to the backscattering coefficient were also investigated. >