Showing papers by "Helsinki University of Technology published in 1971"
TL;DR: In this article, a contactless plate wave excited in thin sheets (such as paper or cardboard) directly from air without touching the sample is described, which may prove to be useful in online testing of various other, non-woven materials like plastic sheets.
91 citations
TL;DR: In this article, a horizontal, high cooling power, dilution refrigerator has been built and tested for studying the feasibility of a spin-frozen, polarized proton target to be used at CERN in the Omega spectrometer.
26 citations
TL;DR: The role of Joule heating on the electrical characteristics of chalcogenide thin films has been analyzed both in the case of a static negative differential resistance (NDR) and switching as discussed by the authors.
Abstract: The role of Joule heating on the electrical characteristics of chalcogenide thin films has been analyzed both in the case of a static negative differential resistance (NDR) and switching. At electric fields above 104 V/cm the Poole-Frenkel effect causes an additional current component with a log I ∞ E12 dependency. In the presence of a disturbance in the sample the NDR characteristics will be replaced by switching due to a thermal runaway. Although a thermal runaway has a rather high speed in small samples a secondary switching mechanism can be expected to be present in the thermoformed filament.
21 citations
TL;DR: In this article, the authors measured the low temperature heat capacities of ordered FeRh alloys and found that a much higher density of states at the Fermi level is associated with the ferromagnetic structure than with the antiferromagnetic structures.
21 citations
TL;DR: In this article, the relative integrated intensities of five high-order reflections for V, Ni, Cu, Nb and Ag powders have been measured at 300 K and 4 K by MoKα radiation.
Abstract: The relative integrated intensities of five high-order reflections for V, Ni, Cu, Nb and Ag powders have been measured at 300 K and 4 K by MoKα radiation. The data were corrected for thermal diffuse scattering. At room temperatures the values 372 ± 6, 417 ± 12, 307 ± 3, 284 ± 6 and 200 ± 3 K were obtained for the Debye Temperatures. At absolute zero the Debye-Waller coefficients were found to be 0·152 ± 0·006, 0·117 ± 0·005, 0·147 ± 0·005, 0·109 ± 0·004 and 0·133 ± 0·004 A2, respectively.
18 citations
TL;DR: The gamma ray spectra associated with the decay of the136I isomers have been measured by means of a Ge(Li) detector as discussed by the authors, and the iodine samples were produced by using the technique of on-line isotope separation of the fission products of a235U target at the R2-O reactor in Studsvik, Sweden.
Abstract: The gamma ray spectra associated with the decay of the136I isomers have been measured by means of a Ge(Li) detector. The iodine samples were produced by using the technique of on-line isotope separation of the fission products of a235U target at the R2-O reactor in Studsvik, Sweden.
13 citations
TL;DR: In this article, it was shown that unit dislocations affected by a chemical force climb predominantly on distinct crystallographic planes of the type {110} and {111}, the most favoured being that {110] plane which is perpendicular to the Burgers vector of the climbing dislocation.
Abstract: On examining the discontinuous precipitation associated with the climb of the unit dislocation a/2〈110〉 in a precipitation-annealed copper–silver alloy it was shown that unit dislocations affected by a chemical force climb predominantly on distinct crystallographic planes of the types {110} and {111}, the most favoured being that {110} plane which is perpendicular to the Burgers vector of the climbing dislocation. The vacancy-emitting climb in question is not strictly bound to the planes of easy climb, however, but proceeds locally on non-crystallographic planes also.
11 citations
TL;DR: The specific heat of the semimetal arsenic has been measured in the temperature range 0.017-0.3 K as discussed by the authors, yielding a nuclear quadrupole coupling constant | e 2 qQ h | = (46.9±0.6) MHz.
10 citations
TL;DR: In this article, the influence of multiple scattering on an inelastic scattering experiment with liquid methane has been studied, and a correction for multiple scattering is found to improve the agreement between the theoretical scattering model and experimental results.
7 citations
6 citations
TL;DR: In this article, the relative energy and intensity of the potassium K β 5 line in KF, KCl and KBr have been measured in fluorescence, and the authors indicate that this line to be a cross transition between the K + 1 s state and the anion valence state with mixing of K + 3 p wave function.
TL;DR: In this paper, the authors measured the total neutron cross-section at the subthermal wavelength range from 7 A to 17 A varying the sample temperature from 20°C to 270°C.
TL;DR: The description of a partially specified quantum state by a density operator is shown to be equivalent to a description in terms of an ensemble of systems.
Abstract: It is emphasized that the use of statistical methods is a consequence of the incomplete isolation of physical systems. The description of a partially specified quantum state by a density operator is shown to be equivalent to a description in terms of an ensemble of systems. Several definitions of the statistical operator are shown to be identical.
01 Aug 1971
TL;DR: In this article, the effect of reactor irradiation on the electrical properties of thin films of amorphous germanium has been studied, and it was found that irradiation decreases the resistivity of heat treated germania thin films at the same time increasing the dielectric losses of thin film capacitors made of the same material.
Abstract: The effect of reactor irradiation on the electrical properties of thin films of amorphous germanium has been studied. The temperature during irradiation periods was 320 °K. The temperature dependence of dc resistivity was measured before and after heat treatment and irradiation periods. The resistivity measurements were supplemented by measuring the capacitance and the dielectric loss factor at 77 °K of thin film capacitors made of the same material. Irradiation was found to decrease the resistivity of heat treated germanium thin films at the same time increasing the dielectric losses of thin film capacitors made of the same material.
Die Auswirkung der Bestrahlung im Reaktor auf die elektrischen Eigenschaften dunner Schichten aus amorphem Germanium wurde untersucht. Die Bestrahlungstemperatur war 320 °K, und nach der Bestrahlung wurde die Anderung des spezifischen Widerstands gemessen. Die Widerstandsmessungen wurden durch Messungen der Kapazitat und des Verlustfaktors der Dunnschichtkondensatoren bei 77 °K erganzt. Bestrahlung verminderte den spezifischen Widerstand der bei hohen Temperaturen warmebehandelten Schichten. Gleichzeitig nahm der Verlustfaktor der Dunnschichtkondensatoren zu.
TL;DR: The atomic scattering factors for Cu and Al have been obtained from diffuse thermal scattering measurements as mentioned in this paper, and the results for Cu show a pronounced effect probably due to extinction, while Al shows a more moderate effect.
Abstract: The atomic scattering factors for Cu and Al have been obtained from diffuse thermal scattering measurements. The results for Cu show a pronounced effect probably due to extinction. A transmission method gives results for Al at low values of sin θ/λ for the first time. These seem to agree with the theoretical atomic scattering factors for neutral Al atoms.
TL;DR: It was decided to undertake the adaptation of the Elliott 803B computer at the Computer Centre of the University of Oulu for closed-loop control of physical process models.
Abstract: Introduction The number of professional engineers who come into contact with digital real-time control is rapidly increasing, and exercises with computer control systems are therefore required for education in control engineering. However, the prices of standard process control computers exceed the budgets of many university laboratories, and the computers available at the computer centres are not equipped for on-line control. On the other hand, the number of input and output channels need not be high for the above purpose, since otherwise the study of the control engineering and process dynamic aspects could be outweighed by the load of programming a complex system. For these reasons and, since it was also known that some general purpose computers could be used for on-line data acquisition\", it was decided to undertake the adaptation of the Elliott 803B computer at the Computer Centre of the University of Oulu for closed-loop control of physical process models.