Institution
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.
Papers published on a yearly basis
Papers
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TL;DR: In this article, Lanthanum oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 180-425°C on soda-lime glass and Si(1-0-0) substrates using a β-diketonate type precursor La(thd) 3 and ozone.
237 citations
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TL;DR: It has been verified experimentally that when nonlinear Principal Component Analysis (PCA) learning rules are used for the weights of a neural layer, the neurons have signal separation capabilities and can be used for image and speech signal separation.
237 citations
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TL;DR: The results show that in non-line-of-sight situations, the power distribution in elevation has a shape of a double-sided exponential function, with different slopes on the negative and positive sides of the peak.
Abstract: We measured the elevation angle distribution and cross-polarization power ratio of the incident power at a mobile station in different radio propagation environments at 2.15 GHz frequency. A novel measurement technique was utilized, based on a wideband channel sounder and a spherical dual-polarized antenna array at the receiver. Data were collected over 9 km of continuous measurement routes, both indoor and outdoor. Our results show that in non-line-of-sight situations, the power distribution in elevation has a shape of a double-sided exponential function, with different slopes on the negative and positive sides of the peak. The slopes and the peak elevation angle depend on the environment and base-station antenna height. The cross-polarization power ratio varied within 6.6 and 11.4 dB, being lowest for indoor and highest for urban microcell environments. We applied the experimental data for analysis of the mean effective gain (MEG) of several mobile handset antenna configurations, with and without the user's head. The obtained MEG values varied from approximately -5 dBi in free space to less than -11 dBi beside the head model. These values are considerably lower than what is typically used in system specifications. The result shows that considering only the maximum gain or total efficiency of the antenna is not enough to describe its performance in practical operating conditions. For most antennas, the environment type has little effect on the MEG, but clear differences exist between antennas. The effect of the user's head on the MEG depends on the antenna type and on which side of the head the user holds the handset.
236 citations
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TL;DR: In this paper, the effective permittivity of a heterogeneous medium with the properties of the constituent materials are considered and the results from different formulae are compared using dry and wet snow as paradigmatic examples.
Abstract: Dielectric mixing formulas that relate the effective permittivity of a heterogeneous medium with the properties of the constituent materials are considered. The restriction for this approach is that the sizes of the inclusions in the mixture have to be considerably smaller than the wavelength to avoid scattering effects. The mixing rules are presented for cases where the scatterers can be homogeneous or multilayer spheres. The formula contains a free parameter v, and for different choices of this parameter, many mixing formulae result as special cases of the given mixing rule. Mixing formulas presented in the literature are also reviewed and the results from different formulae are compared, using dry and wet snow as paradigmatic examples. >
234 citations
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TL;DR: The novel fabrication method of the polymer-free absorber and device parameters determined using nonlinear reflectivity measurement are described in detail and the observed operation bandwidth of approximately 1 microm is the broadest reported to date for a single carbon nanotube-based saturable absorber.
Abstract: Mode-locked sub-picosecond operation of Yb-, Er- and Tm:Hodoped fiber lasers operating at 1.05 microm, 1.56 microm and 1.99 microm, respectively, is demonstrated using the same sample carbon nanotube-based saturable absorber mirror. A mesh of single-walled carbon nanotubes was deposited on an Ag-mirror using a one-step dry-transfer contact press method to combine broadband saturable absorption and high reflectance properties. The novel fabrication method of the polymer-free absorber and device parameters determined using nonlinear reflectivity measurement are described in detail. To our knowledge the observed operation bandwidth of approximately 1 microm is the broadest reported to date for a single carbon nanotube-based saturable absorber.
234 citations
Authors
Showing all 8962 results
Name | H-index | Papers | Citations |
---|---|---|---|
Ashok Kumar | 151 | 5654 | 164086 |
Hannu Kurki-Suonio | 138 | 433 | 99607 |
Nicolas Gisin | 125 | 827 | 64298 |
Anne Lähteenmäki | 116 | 485 | 81977 |
Riitta Hari | 111 | 491 | 43873 |
Andreas Richter | 110 | 769 | 48262 |
Mika Sillanpää | 96 | 1019 | 44260 |
Markku Leskelä | 94 | 876 | 36881 |
Ullrich Scherf | 92 | 735 | 36972 |
Mikko Ritala | 91 | 584 | 29934 |
Axel H. E. Müller | 89 | 564 | 30283 |
Karl Henrik Johansson | 88 | 1089 | 33751 |
T. Poutanen | 86 | 120 | 33158 |
Elina Lindfors | 86 | 420 | 23846 |
Günter Breithardt | 85 | 554 | 33165 |