Showing papers by "Helsinki University of Technology published in 1995"
TL;DR: In this article, neuromagnetic data provided evidence for distinct functional roles of these spectral components in the somatomotor cortex and showed that the sites of suppression during movement and the subsequent rebound of the 20-Hz rhythm followed, along the motor cortex, the representation of fingers, toes, and mouth, as opposed to the stable origin of the 10-Hz rhythms close to the hand somatosensory cortex.
527 citations
TL;DR: In this paper, a new electric equivalent circuit for the forces created by a squeezed gas film between vertically moving planar surfaces is presented. Butler et al. used the circuit model to calculate the effective viscosity in a narrow gap between the moving surfaces.
Abstract: We present a new electric equivalent circuit for the forces created by a squeezed gas film between vertically moving planar surfaces. The model is realized with frequency-dependent resistors and inductors. Circuit analysis tools are applied to calculate the response of a micromechanical silicon capacitive accelerometer in both the frequency and the time domains. The simulations are shown to match the measured frequency responses in an excellent way. We utilize the circuit model to calculate the effective viscosity in a narrow gap between the moving surfaces. The results are compared with different slip-flow equations discussed in the literature. We present a simple approximate equation of the pressure-dependent viscosity that is valid for both viscous and molecular damping regions, and has 5% accuracy.
483 citations
TL;DR: The significance of the Moran effect and dispersal in explaining the observed regional synchrony is explored using a metapopulation system and it is difficult to tell apart whether an observed negative correlation between the level of synchrony and distance among the compared populations is caused by dispersal alone, or both dispersal and Moran’s effect acting together.
Abstract: Our data are long-term population dynamics of a set of species in different localities in Finland. There is considerable level of species-specific synchrony in population fluctuations among the localities. The degree of synchrony levels off with increasing distance among the populations compared. Climatic perturbations and dispersal have been proposed as pace-making factors for synchrony. According to Moran's theorem, local populations sharing a common structure of density dependence should become synchronized under the influence of a spatially correlated density-independent factor. This predicts synchrony to decay slower with increasing distance between local populations than if the synchrony is caused by dispersal. To explore the significance of the Moran effect and dispersal in explaining the observed regional synchrony, we used a metapopulation system. The Moran effect and dispersal are both capable to synchronize alone local population fluctuations. However, with dispersal the level of synchrony decreases with distance among the populations. Adding Moran's effect does not greatly affect the level of synchrony, nor the negative correlation between synchrony and distance. This finding makes it difficult to tell apart whether an observed negative correlation between the level of synchrony and distance among the compared populations is caused by dispersal alone, or both dispersal and Moran's effect acting together.
393 citations
TL;DR: It is demonstrated that SSP is particularly useful for the description of multiple sources of distributed activity and for the comparison of the strengths of specific neuronal sources under a variety of different paradigms or subject conditions.
342 citations
TL;DR: In this article, the stabilization of finite element methods in which essential boundary conditions are approximated by Babuska's method of Lagrange multipliers is discussed and there is a close connection with this technique and a classical method by Nitsche.
310 citations
TL;DR: This framework study more closely generalizations of the problems of variance maximization and mean-square error minimization and derive gradient-type neural learning algorithms both for symmetric and hierarchic PCA-type networks.
295 citations
TL;DR: Tests in line detection with synthetic and real-world images demonstrate the high speed and low memory usage of the new extensions of the RHT, as compared both to the basic RHT and other versions of the Hough transform.
238 citations
TL;DR: In this article, the authors propose an interactive process of preference programming which allows the decision maker to enter ambiguous preference statements by indicating the relative importance of factors as intervals of values on a ratio scale, and synthesize the interval judgments into dominance relations on the alternatives by solving a series of linear programming problems.
233 citations
TL;DR: In this paper, the development in processing, properties and utilisation of light metal matrix composites is reviewed and other potential metal matrix composite materials, such as corrosion and wear resistant steel matrix composite composites are discussed.
184 citations
Journal Article•
178 citations
TL;DR: The results suggest that the visual cortex of blind humans can participate in auditory discrimination, and a whole-scalp magnetometer with 122 planar gradiometers is used to study this activity.
TL;DR: N1 m amplitude suppression at short ISIs was stronger in children than in adults and may reflect a longer refractory period of the N1 generator neurons during early childhood than later in life.
Abstract: Neuromagnetic responses to tones and pseudowords were measured with a 24-channel magnetometer in nine adults and in 23 children, the latter aged 0.3-15 years. Both stimulus types elicited substantially similar responses in all subjects. At 0.9-s interstimulus interval (ISI), the adult response was a stable P1m-N1m-P2m-N2m sequence peaking at 50, 100, 200, and 250 ms, respectively. A biphasic P1m-N1,2m response with peaks at 100 and 260 ms occurred in children up to 12 years of age. At longer ISIs (1.2-2.4 s), an adult-type N1m response appeared in most children. N1m amplitude suppression at short ISIs was stronger in children than in adults and may reflect a longer refractory period of the N1 generator neurons during early childhood than later in life. Peak latencies of P1m, N1m, and N2m decreased with age, most rapidly < 7 years of age. All deflections originated in nearby cortical areas within the posterior sylvian fissure, and may serve as functional landmarks for that anatomic area.
TL;DR: HMBC and NOESY experiments showed that hexenuronic acid is attached beta-elimination product of 4-O-methylglucuronic Acid and is formed during kraft pulping, and NoESY data further indicated that Hexenuonic acid protrudes from the main xylan chain.
TL;DR: The results for several metals and semiconductors show that the GGA systematically improves the predictive power of positron lifetime calculations over those based on the LDA.
Abstract: First-principles calculations of positron-annihilation characteristics in solids are usually based on the local-density approximation (LDA) for positron-electron correlation. The LDA systematically overestimates the annihilation rate. As a remedy we introduce a generalized gradient approximation (GGA). Our results for several metals and semiconductors show that the GGA systematically improves the predictive power of positron lifetime calculations over those based on the LDA. We compare also the resulting positron energy levels in solids with data from slow-positron experiments.
TL;DR: The contra- vs. ipsilateral MEF amplitude ratio C/I decreased from 4.0 during index finger movements to 0.6 during rapid finger flexions, reflecting the enhanced activation of the ipsilaterally primary somatomotor cortex with increasing complexity of movement.
TL;DR: In this article, an electrochemical model for a microbial fuel cell process was proposed, which was set up on the basis of the experimental results and analysis of biochemical and electrochemical processes.
Abstract: An electrochemical model for a microbial fuel cell process is proposed here. The model was set up on the basis of the experimental results and analysis of biochemical and electrochemical processes. Simulation of the process shows that the model describes the process reasonably well. The analysis of model simulation illustrates how the current output depends on the substrate concentration, mediator concentration and other main variables. The relationship between the current output and over-voltage is revealed from the modelling study.
TL;DR: This is the accepted version of the following article: Korhonen, T.J. & Puska, M. J. 1995.
Abstract: Rights: © 1995 American Physical Society (APS). This is the accepted version of the following article: Korhonen, T. & Puska, M. J. & Nieminen, Risto M. 1995. Vacancy-formation energies for fcc and bcc transition metals. Physical Review B. Volume 51, Issue 15. 9526-9532. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.51.9526, which has been published in final form at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.51.9526.
TL;DR: The observed redshift and peak separation are in agreement with simple calculations using a finite-element method and two-dimensional parabolic potential model and offers a great potential for the optical study of relaxation and recombination phenomena.
Abstract: We have fabricated quantum dots by locally straining ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum wells with self-organized growth of nanometer-scale InP stressors on the sample surface. The structure is completed in a single growth run using metalorganic vapor-phase epitaxy. Photoluminescence from the dots is redshifted by up to 105 meV from the quantum-well peak due to the lateral confinement of excitons. Clearly resolved luminescence peaks from three excited states separated by 16--20 meV are observed when the quantum well is placed at the depth of 1--10 nm from the surface of the sample. The observed redshift and peak separation are in agreement with simple calculations using a finite-element method and two-dimensional parabolic potential model. This structure is easily fabricated and offers a great potential for the optical study of relaxation and recombination phenomena.
TL;DR: The functional consequences of changes in scale of the middle ear when going from the smallest mammals to the largest are analyzed and it is shown that if the high frequency hearing limit of isometric ears is limited by ossicle inertia, it should be inversely proportional to the cubic root of the ossicular mass.
TL;DR: It is proved that decision analysis interviews can well be used in assessing the importance of environment impacts and is a useful way of improving stakeholders' participation in environmental decision making and it provides a systematic way of dealing with conflicting opinions.
TL;DR: The authors' data provide evidence in humans for the access of cutaneous information from the hands to ipsilateral SI, probably via excitatory transcallosal pathways, and may represent a neurophysiological substrate of somatosensory fusion between the hands.
TL;DR: In this article, the authors have studied the whole solution phase in the system tetraethyl orthosilicate-ethanol-aqueous ammonia and have mapped the region for monodisperse particles.
TL;DR: In this article, a triangular element for nearly incompressible elasticity and fluid flow is introduced, which consists of conforming linear elements for one of the displacement (or velocity for flows) component and linear non-conforming elements for the other component.
TL;DR: The strong nonlinear dependence of the operating lifetime and the conversion efficiency of material tested on the pump-pulse-repetition rate was observed and possible mechanisms responsible for the conversionefficiency drop and the useful lifetime of the material are discussed.
Abstract: Laser generation with modified poly(methyl methacrylate) (MPMMA)-doped matrices with several different types of Rhodamine-based dyes was obtained. Pumping with a frequency-doubled Q-switched Nd:YAG laser was used. During the experiments, high conversion efficiency was achieved. The strong nonlinear dependence of the operating lifetime and the conversion efficiency of material tested on the pump-pulse-repetition rate was observed. Possible mechanisms responsible for the conversion-efficiency drop and the useful lifetime of the material are discussed.
TL;DR: A generic, modular, neural network-based feature extraction and pattern classification system is proposed for finding essentially two-dimensional objects or object parts from digital images in a distortion tolerant manner, and the feature space has sufficient resolution power for a moderate number of classes with rather strong distortions.
Abstract: A generic, modular, neural network-based feature extraction and pattern classification system is proposed for finding essentially two-dimensional objects or object parts from digital images in a distortion tolerant manner, The distortion tolerance is built up gradually by successive blocks in a pipeline architecture. The system consists of only feedforward neural networks, allowing efficient parallel implementation. The most time and data-consuming stage, learning the relevant features, is wholly unsupervised and can be made off-line. The consequent supervised stage where the object classes are learned is simple and fast. The feature extraction is based on distortion tolerant Gabor transformations, followed by minimum distortion clustering by multilayer self-organizing maps. Due to the unsupervised learning strategy, there is no need for preclassified training samples or other explicit selection for training patterns during the training, which allows a large amount of training material to be used at the early stages, A supervised, one-layer subspace network classifier on top of the feature extractor is used for object labeling. The system has been trained with natural images giving the relevant features, and human faces and their parts have been used as the object classes for testing. The current experiments indicate that the feature space has sufficient resolution power for a moderate number of classes with rather strong distortions. >
TL;DR: In this article, various two-dimensional charts for illustrating the DEA efficiency results have been drawn using an experimental DEA software tool, AskDEA, developed by the authors, using a set of decision-making units.
01 Jul 1995
TL;DR: In this article, a polyester of 46,400 g mol−1 (degree of polymerization = 184) was obtained when 0.51 m (46 g l−1) 1,4-butanediol in diphenyl ether for 168 h (7 days) with 36.5% M. miehei lipase powder.
TL;DR: This paper presents Electron-positron Car-Parrinello methods: Self-consistent treatment of charge densities and ionic relaxations, which have been published in final form at Physical Review B.
Abstract: Rights: © 1995 American Physical Society (APS). This is the accepted version of the following article: Puska, M. J. & Seitsonen, Ari P. & Nieminen, Risto M. 1995. Electron-positron Car-Parrinello methods: Self-consistent treatment of charge densities and ionic relaxations. Physical Review B. Volume 52, Issue 15. 10947-10961. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.52.10947, which has been published in final form at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.52.10947.
TL;DR: Spontaneous MEG signals were recorded during visual imagery from 13 healthy adults with a whole-scalp neuromagnetometer while subjects visualized and evaluated letters and found sources for the alpha activity clustered in the parietal and occipital lobes.