Showing papers by "Helsinki University of Technology published in 1973"
TL;DR: In this paper, the functional counterpoise method was applied to the theoretical prediction of hydrogen bonding potential surfaces, using a minimal basis to represent the atomic orbitals (STO-3G).
Abstract: The “functional” counterpoise method, proposed by Boys and Bernardi [1], is applied to the theoretical prediction of hydrogen bonding potential surfaces, using a minimal basis to represent the atomic orbitals (STO-3G). Using this method, with a systematically chosen “correction factor”, one can compute potential surfaces with an STO-3G basis as accurately as with a much more flexible atomic basis.
167 citations
TL;DR: It is shown that associated pairs of vectoral items can be recorded by transforming them into a matrix operator M so that a particular stored vector X(r) can be reproduced by multiplying an associated cue vector Q( r) by M.
Abstract: It is shown that associated pairs of vectoral items (Q(r), X(r)) can be recorded by transforming them into a matrix operator M so that a particular stored vector X(r) can be reproduced by multiplying an associated cue vector Q(r) by M. If the number of pairs does not exceed the dimension of the cue and all cue vectors are linearly independent, then the recollections are perfect replicas of the recorded items and there will be no crosstalk from the other recorded items. If these conditions are not valid, the recollections are still linear least square approximations of the X(r). The relationship of these mappings to linear estimators is discussed. These transforms can be readily implemented by linear analog systems.
118 citations
TL;DR: In this article, it was shown that the existence of bounded solutions under weaker assumptions on the smoothness condition of a(t) and absolute continuity of f(i) was not required.
37 citations
TL;DR: In this article, the angular correlation curve caused by trapped positrons was constructed by subtracting the calculated momentum distribution of the ground state positrons in the crystal bulk from the total experimental curve.
Abstract: Positron lifetime spectra have been measured in several single crystals of KCI and KI. Angular correlation measurements of 2 γ annihilation radiation have been made in polycrystalline materials. The positron wave function calculated by the spherical symmetric Wigner-Seitz approximation in the neighbourhood of the anion is similar to that in metals and indicates that positrons are free in alkali halides. The experimental angular correlation curves are much narrower than those calculated with positrons in crystalline states, when Wigner-Seitz wave functions of the positron were used and only annihilations with anion shells were taken into account. The assumption that positrons are trapped by crystal defects explains the observed differences in lifetime measurements. The angular correlation curve caused by trapped positrons has been constructed by subtracting the calculated momentum distribution of the ground state positrons in the crystal bulk from the total experimental curve.
23 citations
TL;DR: In this article, the heat capacity of liquid 3He has been measured along the melting curve between 1.8 and 4.2 mK in an apparatus employing compressional cooling techniques.
15 citations
TL;DR: In this paper, the diffusion coefficient of ion implanted zinc in polycrystalline aluminium was measured using the backscattering method, which did not require any definite solution of the diffusion equation.
Abstract: The low-temperature diffusion of ion implanted zinc in polycrystalline aluminium was measured using the backscattering method. 1.5 MeV He+ ions were used as the probing particles. The zinc concentration profiles, which could be followed to a depth of 0.6 μm, were calculated from the energy spectra measured at different time values. Measurements were carried out at temperatures of 170 and 200°C. The diffusion coefficients were calculated from the depth distributions with a method, which did not require any definite solution of the diffusion equation. The hold-up phenomenon due to the Al2O3 layer on the specimen surface was demonstrated by performing the implantation and diffusion anneal with a sample preoxidized to a small depth.
Die Niedertemperaturdiffusion von ionenimplantiertem Zink in polykristallinem Aluminium wurde mit der Ruckstreuanalyse gemessen. Als Sondenpartikel wurden 1,5 MeV He+-Ionen angewended. Die Zinkkonzentrationsprofile, die bis zur Tiefe von 0,6 μm nachgewiesen werden konnten, wurden aus den bei verschiedenen Zeitwerten gemessenen Energiespektren berechnet. Die Messungen wurden bei den Temperaturen von 170 und 200°C ausgefuhrt. Die Diffusionskoeffizienten wurden aus der Tiefenverteilungen mit einer Methode berechnet, die keine definierte Losung der Diffusionsgleichung benotigt. Das „Aufhalten” der Zinkatome durch die Al2O3-Schicht auf der Oberflache der Probe wurde durch die Art der Implantierung und Diffusionswarmebehandlung mit einer bis zu geringer Tiefe anoxydierten Probe demonstriert.
11 citations
TL;DR: In this article, the redistribution of valence electrons at a vacancy in aluminium is calculated in the Thomas-Fermi approximation, which is then used in evaluating the annihilation characteristics of positrons trapped at vacancies.
11 citations
TL;DR: In this article, the phase velocity of generalized Lamb waves in cadmium and zinc platings was measured using the ultrasonic critical angle reflectivity method and a relatively good agreement was obtained between the theoretical computations and measured data.
Abstract: Ultrasonic critical angle reflectivity method is used to measure the phase velocity of generalized Lamb waves in cadmium and zinc platings. In addition to the free propagating modes, leaky-wave modes are also observed. Leaky waves are considered using principles familiar from the discussion of surface waves in anisotropic media and a relatively good agreement is obtained between the theoretical computations and measured data.
10 citations
TL;DR: In this paper, the wave function of the bound state of the positron and F-centre is determined in various approximations with and without the electron-positron correlation, and annihilation parameters are evaluated using this function.
Abstract: The trapping of positrons in F-colour centres in KCl is investigated in some model calculations. The wave function of the bound state of the positron and F-centre is determined in various approximations with and without the electron-positron correlation, and annihilation parameters are evaluated using this function. It is suggested that the screening of the electron-positron interaction in the bulk of the crystal has a strong influence on the trapping by promoting the localization of a neutral positronium-like state in the vacant anion site. In this case agreement with experiments is obtained.
10 citations
TL;DR: In this article, an ab initio molecular orbital calculation was carried out for three different conformations of 1,3 propanediol, one of which permits intramolecular H-bond studied by AB initio quantum mechanical methods.
9 citations
TL;DR: In this paper, three main forms of representations arc introduced: (causal) parameter mapping, state mapping, and state transition mapping, where the causality and state are defined independently on each other, but they turn out to be intimately connected via properties and interrelations of those forms.
Abstract: The subject is considered in n general set-theoretic formalism. A time system is hero a set of ordered pairs of functions on a common time domain ; extensions to more general forms are also noted. A representation of a system S is an ‘ aggregate ’ of sets and structures by the aid of which each pair of S can be generated. Leading principles of the work arc : (i) Just a representation is a primarily interesting description of S, and it is a starting-point in analysis in most practical eases, (ii) Tbo concepts, like causality and state, are primarily defined as properties of representations. Three main forms of representations arc introduced : (i) (causal) parameter mapping ; (ii) state mapping ; and (iii) state transition mapping. The causality and state are here defined independently on each other. However, they turn out to be intimately connected via properties and interrelations of those forms, presented by some propositions. The aim of the work is to present an alternative formalism which is m...
01 Mar 1973
TL;DR: In this paper, a real-valued random walk is defined on a Markov chain with countable state space I and a matrix Q (.) = ( q ij (.)) is given such that
Abstract: Consider a real-valued random walk which is defined on a Markov chain { X n : n ≥ 0} with countable state space I . We assume that a matrix Q (.) = ( q ij (.)) is given such that
TL;DR: In this paper, the results of Monte Carlo calculations of a cylindrical hydrogen cold neutron source in a tangential beam tube are discussed and the dependence of the cold neutron output on the relative ortho/para abundance was studied at the hydrogen boiling temperature 20.4 K. The maximum output was obtained with a mixture rich in parahydrogen.
TL;DR: In this paper, the electroreflectance and wavelength-modulated reflectance spectra of GaAs were measured before and after several reactor irradiation periods and the effect of possible internal stress produced by the fast neutron bombardment on the modulation spectra was also discussed.
01 Oct 1973
TL;DR: In this paper, conditions under which two thick plates, differing in dip, apparent susceptibility, and remanence, will produce similar magnetic anomalies are given, and from these conditions correction formulae are developed.
Abstract: Conditions are given under which two thick plates, differing in dip, apparent susceptibility, and remanence, will produce similar magnetic anomalies. From these conditions correction formulae are developed. Using these formulae the dip and susceptibility of a plate with remanent magnetization can be obtained from those of non-remanent plate. An interpretation procedure is suggested where the magnetic anomaly is first interpreted by means of a plate without remanence, dip and apparent susceptibility are then estimated by using the correction formulae developed. Thickness, position and depth of the plate are unaffected by the remanence correction procedure. The procedure is independent of the field component measured.
TL;DR: In this paper, the authors discuss the possibilities of reducing multiple scattering in neutron scattering experiments by using a sandwich structure of the sample with alternating slices of the scatterer and an absorbing material.
01 Oct 1973
TL;DR: By doping bismuth with tellurium to increase the charge carrier density and thus speed up the slow nuclear spin-lattice relaxation, the nuclear quadrupole heat capacity becomes measurable in contrast to pure Bismuth as discussed by the authors.
Abstract: By doping bismuth with tellurium to increase the charge carrier density and thus speed up the slow nuclear spin-lattice relaxation the nuclear quadrupole heat capacity becomes measurable in contrast to pure bismuth. The quadrupole heat capacity is greatly influenced by doping, increasing by 64% over the pure bismuth value on the addition of 0.23 at. % of tellurium. This results from a local asymmetric distortion of the valence electron states of the bismuth ions around the impurity site.
01 Oct 1973
TL;DR: In this paper, a superconducting stripline which is terminated at the edge of the Nb-oxide-Pb junction has been used for coupling to the thin-film Josephson tunneling junction.
Abstract: 2014 A certain way of coupling to the thin-film Josephson tunneling junction has been studied. The coupling structure comprises a superconducting stripline which is terminated to the edge of the Nb-oxide-Pb junction. A mismatch of 23 dB has been obtained so far between the signal source and the junction at X-band compared to the earlier estimates of 40 dB between conventional size outer circuits and the junction. Prospects for improving the coupling are good. Methods of estimating the voltage and power which are coupled to the junction are given. REVUE DE PHYSIQUE APPLIQUÉE TOME 9, JANVIER 1974, PAGE
01 Jan 1973
TL;DR: In this paper, the variations in varactor parameters which can be compensated by electrical re-tuning of two specific amplifiers have been studied using a digital computer, and the results show that considerable variations can also be compensated electrically.
Abstract: The variations in varactor parameters which can be compensated by the electrical re-tuning of two specific amplifiers have been studied using a digital computer. The designs of two different microstrip parametric amplifiers were at first optimized with respect to the bandwidth. Then after changing the varactor parameters, pumping and biasing conditions were optimized in order to attain maximum flat gain bandwidth within certain acceptable limits for gain and frequency. The results show that considerable variations can be compensated electrically.