Showing papers by "Helsinki University of Technology published in 1976"
TL;DR: The system then acts as a filter, which optimally extracts the amount that is “new” in an input pattern with respect to all “old” patterns, and has features that are directly attributable to a distributed associative memory that is optimally selective.
Abstract: A demonstration is given that an orthogonalizing filter for patterns is formed adaptively and very rapidly in a network of neuron-like elements with internal feedback connections. It is here assumed that the feedback gain is variable, and proportional to the correlation matrix of the output pattern vectors. The time-dependent signal transfer properties of the complete system are described by a system matrix which satisfies a matrix Bernoulli differential equation; solutions of this equation are outlined. The asymptotic value of the system matrix is shown to correspond to the orthogonal projection operator on the space that is complementary to the space spanned by all of the earlier input pattern vectors. Such a system then acts as a filter, which optimally extracts the amount that is "new" in an input pattern with respect to all "old" patterns. It also has features that are directly attributable to a distributed associative memory that is optimally selective.
119 citations
TL;DR: In this article, transverse cw NMR measurements on the superfluid phases of 3He at temperatures between 3 and 0.7 mK were carried out in two NMR coil assemblies in which the liquid was confined between parallel Mylar foils with separations of 0.37 mm and 4 µm.
Abstract: We report transverse cw NMR measurements on the superfluid phases of3He at temperatures between 3 and 0.7 mK. Nuclear demagnetization of copper was used for refrigeration. For thermometry we employed pulsed NMR on platinum powder immersed in the liquid. The measurements on3He were carried out in two NMR coil assemblies in which the liquid was confined between parallel Mylar foils with separations of 0.37 mm and 4 µm. The transition temperatureT
c
was measured at pressures between 32 bars and the saturated vapor pressure; a pressure-independent increase of ∼11% was observed inT
c
with respect to earlier data obtained with the same apparatus. We found that our temperature scale is not proportional to that used in La Jolla. In the 4-µm stack we observe a reduction in the B → A transition temperature. In our measurements on the orientational anisotropy of the B phase we found qualitative agreement with the theory of Brinkman et al. We also measured the longitudinal resonance frequencies of the A and B phases between 32 bars and the polycritical point. In the 4-µm stack we found a negative NMR shift in the A phase when the field was oriented perpendicular to the Mylar plates, in agreement with the prediction of Takagi. The static susceptibility XB of the B phase was measured as a function of temperature at 18.7 and 29 bars; its low-temperature limiting value was observed to be (0.33±0.02)XN
, independent of pressure. We use our data to estimate the strong coupling corrections to the size of the energy gap. The initial slope of the reduced gap in the A phase, ΔA/T
c
, was found to increase by ∼25% when the pressure increased from 21.1 bars to the melting curve, whereas in the low-temperature limit ΔB(0)/T
c
was found to be independent of pressure and close to its weak coupling value.
94 citations
TL;DR: In this article, the sulphur 1s binding energies and KL2L3(1D2) Auger energies have been measured in gaseous H2S, SO2 and SF6.
50 citations
TL;DR: The release of coloured compounds from a dyed substrate is proportional to the solubilization, because the concentration ratio of cellobiose and glucose in the reaction mixture and thus on the β-glucosidase present.
34 citations
TL;DR: Orthogonal projection operations in a linear vector space are shown to have a close relation to the processes by which optimal associative recall of patterned information can be implemented.
Abstract: Orthogonal projection operations in a linear vector space are shown to have a close relation to the processes by which optimal associative recall of patterned information can be implemented. Two association schemes, the autoassociative mapping and the associative encoding, are introduced. The latter has a bearing on pattern recognition, especially in the recognition of an optical image from a small fragment of it. Analytical expressions for the quality of the recollections are derived, and computerized demonstrations of associative recall with 3024-element optical images are presented. Some preprocessing principles of the images are studied, whereby the two-dimensional Laplacian is found very effective. This finding may have some connection to lateral inhibition effects occurring in biological visual systems.
31 citations
TL;DR: The low-temperature magnetic susceptibility of normal and superfluid 3He confined between mylar foils spaced 4.0 mu m apart shows a large and field-dependent enhancement over the bulk Fermi liquid magnitude as mentioned in this paper.
Abstract: The low-temperature magnetic susceptibility of normal and superfluid 3He confined between mylar foils spaced 4.0 mu m apart shows a large and field-dependent enhancement over the bulk Fermi liquid magnitude. The excess susceptibility disappears when the liquid is doped with 0.5% 4He. The reason for the excess is unknown. The authors also studied the proton resonance of the mylar substrate and obtained spin polarizations large enough to permit the direct observation of double spin-flip RF absorption.
31 citations
30 citations
TL;DR: A nuclear demagnetization cryostat in which liquid He3 has been successfully cooled below 0.7 mK is described in this paper, where the essential parts of the apparatus and its operation and performance are explained.
29 citations
TL;DR: In this paper, the isochronal annealing of two plastically deformed irons of 99.998% and 99.86% purities is studied by positron lifetime and annihilation line shape measurements.
Abstract: The isochronal annealing of two plastically deformed irons of 99.998% and 99.86% purities is studied by positron lifetime and annihilation line shape measurements. The results show that trapping of positrons is caused by dislocations. At around 300° C a recovery process attributed to a rearrangement of dislocation structure is observed in the pure but not in the impure iron. The positron lifetime in deformed and recrystallized state is found to be 167 ps and 117 ps, respectively.
29 citations
TL;DR: In this paper, the strain-hardening parameters of steel, copper and brass were determined by uniaxial and balanced baoxial tensile tests and the results showed that the stress-strain relationship of steel was well described by the Hollomon equation while, the Voce equation was valid for copper and Brass.
Abstract: The strain-hardening parameters of steel, copper and brass were determined by uniaxial and balanced biaxial tensile tests. The stress-strain relationship of steel was well described by the Hollomon equation while, the Voce equation was valid for copper and brass. Thus the use of then-value as a measure of strain-hardening ability is justified for steel only and uniform strains have to be used for copper and brass. The uniaxial and biaxialn-values of steel were found to be equivalent. However, the stress-strain relationships of copper and especially brass were observed to be stress-state dependent. Forming limit diagrams of the materials were constructed using hydraulic bulging and tensile tests. The FLDs were also calculated using the plastic instability conditions and the strain-hardening parameters determined.
23 citations
TL;DR: In this article, the relative changes in the low-temperature susceptibility of a number of dilute mixtures of 3He in liquid 4He at various pressures are reported and analyzed, and no evidence of a BCS pairing transition was found in direct measurements of susceptibility and nuclear resonance frequency down to the temperature 1.5 mK in saturated solutions with a pressure of 21 bar.
Abstract: The relative changes in the low-temperature susceptibility of a number of dilute mixtures of3He in liquid4He at various pressures are reported and analyzed. Under elevated pressures, the solubility of3He in4He increases and the effects of the interaction between3He quasiparticles clearly become larger. However, no evidence of a BCS pairing transition was found in direct measurements of susceptibility and nuclear resonance frequency down to the temperature 1.5 mK in saturated solutions with a pressure of 21 bar.
TL;DR: Fetal magnetocardiography can be used for FHR processing from week 30 of gestation until term and a readable FHR curve was obtained in 21 cases with FMCG and in 12 cases with external FECG.
TL;DR: In this article, the solid solubility in the isostructural oxysulfide series is discussed in terms of the differences in ionic radii of the two rare-earth components.
01 Sep 1976
TL;DR: Sunflower seed husks were chosen as a typical lignocellulosic waste product of low value and a model substrate was hydrolyzed with sulphuric acid at 120°C as discussed by the authors.
Abstract: Sunflower seed husks were chosen as a typical lignocellulosic waste product of low value. This model substrate was hydrolyzed with sulphuric acid at 120°C. The hydrolysis was carried out in two steps: hydrolysis of the pentosan fraction and subsequent hydrolysis of the cellulose fraction. The pentosan fraction was nearly quantitatively hydrolyzed. For the cellulose hydrolysis the yield was 79% of the theoretical yield. The hydrolyzates were neutralized to pH 5 with solid calcium hydroxide and used for preparation of growth media forCandida yeasts andPaecilomyces variotii. For the pentosan hydrolyzates the yields of yeast biomass were 35–36 g per 100 g available reducing sugars (supplied to the medium). In cellulose hydrolyzates the corresponding yields were 45–48 g withCandida utilis andC. tropicalis and about 30 g withC. pseudotropicalis. P. variotii was noticeably superior to the yeasts. In pentosan hydrolyzates it produced 63 g dry mycelium from 100 g reducing sugars supplied; in cellulose hydrolyzates, 94 g. This suggests that it must be an effective utilizer of a wide range of compounds, for example, organic acids in the medium.
TL;DR: In this article, a special iterative method for a nonlinear TPBVP is proposed, where the stability properties of the above differential equations are taken into consideration in the method, so that the integration directions associated with these equations respectively are opposite to each other.
Abstract: The paper proposes a special iterative method for a nonlinear TPBVP of the form\(\dot x\)(t)=f(t, x(t),p(t)),\(\dot p\)(t)=g(t, x(t),p(t)), subject toh(x(0),p(0))=0,e(x(T),p(T))=0. Certain stability properties of the above differential equations are taken into consideration in the method, so that the integration directions associated with these equations respectively are opposite to each other, in contrast with the conventional shooting methods. Via an embedding and a Riccati-type transformation, the TPBVP is reduced to consecutive initial-value problems of ordinary differential equations. A preliminary numerical test is given by a simple example originating in an optimal control problem.
TL;DR: The present work deals with a new simple method of entrapping glucose isomerase or ~-galactosidase in cellulose fibre of highly hydrophilic nature and shows that the activity recovery of immobilized soluble 13-galactsidase could be markedly improved by recovering the fiber from 2.5% glutaraldehyde solution.
01 Feb 1976
TL;DR: In this article, the long time behavior and error bounds for discretized Volterra equations are discussed and a key property is positivity of the quadrature which is combined with monotonicity properties of the nonlinearities in the equations.
Abstract: The paper discusses long time behavior and error bounds for discretized Volterra equations. A key property is positivity of the quadrature which is combined with monotonicity properties of the nonlinearities in the equations. It is shown how the positivity of discretization quadrature is linked with \(A\)-stability property of linear multistep methods for ordinary differential equations. Some of the results are new when applied to differential equations with monotone nonlinearities and \(A\)-stable discretizations.
TL;DR: It is shown that the method must be implicit and e.g. that the repeated trapezoidal rule has this property, and how this property can be used in studying the asymptotic behaviour of the solutionsxn of the discretized equations, asn→∞ with a fixed steph.
Abstract: The present paper deals with discretizations to linear Volterra equations which preserve the possible positivity of the Volterra operator. It is shown that the method must be implicit and e.g. that the repeated trapezoidal rule has this property. It is then shown how this property can be used in studying the asymptotic behaviour of the solutionsx
n
of the discretized equations, asn→∞ with a fixed steph.
TL;DR: Error bounds for numerical solutions of the initial value problem are derived in this paper, where the methods (ϱ,σ) are assumed to be G-stable and satisfies for someμ teR and for some inner product.
Abstract: Error bounds for numerical solutions of the initial value problem
$$y' = f(y), y(0) = \bar y \in R^d ,$$
are derived. The methods (ϱ,σ) are assumed to beG-stable [2], andf satisfies for someμ teR and for some inner product 〈, 〉 the relation
$$\left\langle {u - v,f(u)} \right\rangle \leqq \mu \left\| {u - v} \right\|^2 ,u,v \in R^d $$
As corollaries of the bounds we get, forμ=0, the result that whenever the local errors {q
n
} ∈l
1 then the global errors {z
n
} ∈l
∞. Forμ<0, assuming in addition that the zeros ofσ(ζ) lie inside the unit circle, {q
n
} tel
p
implies {z
n
} tel
p
forp ≧ 2.
TL;DR: Isochronal annealing of plastically deformed Cu + 5 at.% Ge alloy is studied by positron lifetime and annihilation lineshape measurements in this article, where the continuous recovery of the annihilation characteristics below the recystallization is attributed to the formation of germanium atmospheres arounf dislocations.
TL;DR: In this paper, an equation of motion for a climbing, arbitrarily curved dislocation is derived, where the matter transport necessary for the climb movement is allowed to occur both by bulk diffusion by vacancy mechanism and by pipe diffusion along the dislocation core.
TL;DR: Theoretical calculations for the simple e.c. mechanism are presented in this paper using as current functions an arbitrary power of time function, and general relations are given which enable the calculations of the total current from the two partial currents and vice versa for any predetermined current-time function to be performed.
TL;DR: In this article, the theoretically predicted ac-response of the laser intensity to the excitation current modulation of an intracavity saturable absorber has been experimentally verified in a He-Ne laser with a Ne-absorber.
TL;DR: The radius and potential well-depth of the positronium bubble are estimated to vary from 14 A to 7 A and from 0.25 eV to 0.55 eV.
TL;DR: In this paper, the phase-separating Li 2 OSiO 2 glass system was studied as a function of molar composition and the longest lifetime was found to be proportional to the amount of the silica-rich phase.
01 Apr 1976
TL;DR: Explicit design procedures are given for maximally flat and equal ripple lowpass and highpass transfer functions of the form H(z) = (z ± 1)q/D n (z) , (q = 1, 2 ..... n - 1).
Abstract: Explicit design procedures are given for maximally flat and equal ripple lowpass and highpass transfer functions of the form H(z) = (z ± 1)q/D n (z) , (q = 1, 2 ..... n - 1). Efficient bandpass structures are obtained directly from the realization of H(z) using the Crochiere - Penfield method. The one-multiplier lattices of Gray and Markel realize the lowpass, highpass and bandpass transfer functions with n + 1 multipliers, if q = 1. If one-multiplier lattices with e = +1 are used in the realization, the coefficient sensitivity peaks down in the passband of the filter.
TL;DR: In this paper, a complicated low energy structure in the O K X-ray emission of MgO and CaO was reported and the main features of this structure were interpreted as KLL radiative Auger transitions.