The application of the thermodynamics of irreversible processes to welding arcs

The self-regulation of an inert gas shielded metal welding arc is dealt with briefly. A thermodynamic equation is derived for the self-regulation of such an arc.

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Die Integralbeziehungen bei der stationären laminaren Strömung mit geschlossenen Stromlinien in annähernd kreisförmigen Gebieten

Zusammenfassung Für die statioäre lineare ebene Strömung mit geschlossenen Stromlinien bei einer großen Reynoldsschen Zahl in annähernd kreisförmigen Gebieten werden zwei Integralbeziehungen (5) und (9) abgeleitet. Nach der ersten von diesen ist das Integral der Reibungskraft entlang der Grenze des Strömungsgebiets direkt proportional der Länge dieser Grenze und der Größe der Rotation der Geschwindigkeit im Kern der Strömung. Aus der zweiten Beziehung geht hervor: Das Volumen der in der Zeiteinheit den Schnitt der Rezirkulationsgrenzschicht durchfließenden Flüssigkeit ist direkt proportional dem Integral entlang der Gebietsgrenze aus der Differenz der Quadrate der Strömungsgeschwindigkeit an der Grenze des Kerns und der Geschwindigkeit an der Gebietsgrenze und umgekehrt proportional der Größe der Geschwindigkeitsrotation im Kern und der Länge der Gebietsgrenze.

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(5) (9). . : , , .

     

Some applications of the discrete fourier transform to problems of crystal lattice deformation II

The method elaborated in [1] is applied to the solution of some problems for a plane lattice and the linear chain. The method can be used to investigate deformations around crystal lattice defects.

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, [1] . .

     

Elektronenemission aus frisch gespaltetem Glimmer

Ohne Zusammenfassung

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Some applications of the discrete fourier transform to problems of crystal lattice deformation I

The theory of the discrete Fourier transform [1], [2] is applied in solving a system of difference equations describing the positions of atoms in a deformed crystal lattice. The crystal lattice is approximated by the Born-Kármán model modified to include the internal energy of the undeformed crystal.

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, , , [1] [2]. - , , .

     

Electron microscope study of dislocations in slip bands of bent Fe-3·2% Si alloy single crystals

Dislocations in Fe-3·2% Si alloy single crystals deformed by bending are studied in this paper. The specimens were cut parallel to the slip plane into platelets, polished, and studied in places at various distances from the neutral plane with an electron microscope. A large number of jogs of various sizes was found on screw dislocations. Many loops are formed by the motion of dislocations with jogs and by the stopping of moving dislocations by obstacles. Some of them grow as a result of stress. The activity of sources on large jogs is stopped at an early stage by a cross slip. The formation and growth of loops increases the dislocation density and causes the growth of slip bands.

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Fe-3,2% Si

Fe-3,2% Si, , , . . , . . . .

     

Die Wirkung von Flüssigkeitsdämpfen auf den Geigerschen Spitzenzähler

Ohne Zusammenfassung

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Double cascade transitions of gamma rays from radiative capture on Co59

Pairs of gamma quanta, giving a sum equal to the binding energy of the last neutron in a Co⁶⁰ isotope, were studied during radiation capture on a Co⁵⁹ nucleus. The energies of the gamma quanta giving such cascades were determined and an attempt was made to determine the relative intensities of the different cascades.

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- Co⁵⁹

Co⁵⁹ -, Co⁶⁰. -, , .

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In conclusion the authors thank J. Vávra for cooperation in the measurements.     

A remark on the third law of thermodynamics

It is shown that Falk's formulation of the third law of thermodynamics (when the energy has minimum value the entropy is also minimum) can be replaced by an equivalent assertion: the absolute minimum energy is unattainable with a finite number of processes.

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,

( , ) : .

     

The effect of the orientation of zinc single crystals and of the rate of growth on the direction of cell substructure

The effect of the orientation of zinc single crystals and the rate of growth on the direction of the formation of cellular substructure is observed. A model accounting for the observed dependences is proposed.

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Anwendung der Hochfrequenzmessmethode für die Elektronenkonzentration zur Messung in der geschichteten positiven säule der Gleichstromglimmentladung

Zusammenfassung In der vorliegenden Arbeit werden Beziehungen abgeleitet, mit deren Hilfe es möglich ist, die Hochfrequenzresonanzmethode der Diagnostik des Plasmas zur Messung der Änderungen der Elektronenkonzentration in den laufenden Schichten in der positiven Säule der Glimmentladung zu verwenden. Ferner wird die Anwendung dieser Methode diskutiert, und zwar für den Fall, daß die Zusammenstoßfrequenz der Elektronen nicht von der Elektronengeschwindigkeit abhängt, und für den Fall, in dem die Zusammenstoßfrequenz der Elektronen eine Funktion der Elektronengeschwindigkeit ist.

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. , , , , .

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Abschließend dankt der Verfasser den Herren Prof. V. Kunzl und R. Bakule für ihre wertvollen Hinweise zu dieser Arbeit.     

Experimental verification of the theory of the successive production of striations in a glow discharge

The properties of the wave of stratification in the plasma of the positive column in a glow discharge in neon are measured. The measurements are compared with the results of the theory of the successive production of striations and good agreement is found.

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In conclusion the author thanks M. Novák for help in measuring and evaluating the experimental results, and F. Kroupa and V. Krejí for carefully reading this paper and for valuable remarks.     

Der Exzitonenzerfall im elektrostatischen Felde der Störstellen von Ionenkristallen

Zusammenfassung Es wird theoretisch der Prozeß des Exzitonenzerfalls mit Hilfe der Ionisation durch das elektrostatische Feld der Störstelle untersucht. Die Wirkungsquerschnitte werden in zwei Grenzfällen bestimmt: bei einer kleinen und einer großen mittleren freien Bahn des Exzitons, die durch dessen Wechselwirkung mit den Phononen bedingt ist. Die Ergebnisse werden zum Studium des Exzitonenzerfalls an einer Vakanz nach einem Kupferion in Cu₂O-Kristallen mit einem stöchiometrischen Sauerstoffüberschuß verwendet.

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. : , . Cu₂0 .

     

The crystal structure of meta-zeunerite Cu(UO2)2(AsO4)2⋅8 H2O

The structure of the mineral zeunerite (deposits at Rotava near Kraslice, Ore Mountains) was determined. The tetragonal unit cell, having the dimensionsa=7.10₅Å andc=17.70₄Å, contains two structure units of Cu(UO₂)₂(AsO₄)₂8H₂O. The space group isP4₂/nmc. The distribution of the atoms in the unit cell was determined from the Patterson projectionP(vw) and by means of (F ₀-F _c) synthesis. Meta-Zeunerite has a layer type structure. The sheets [(UO₂)(AsO₄)] are separated by layers containing the cations (Cu(H₂O)₄)²⁺ and molecules of water. The uranium is coordinated octahedrally with six oxygen atoms at distances: U-O₁ 1.94 Å, U-O₂ 1.78 Å, U-O₃₍₄₎ 2.18 Å (4×). The uranyl radical O₁-U-O₂ is linear. In the tetrahedron AsO₄ the interatomic distances are As-O 1.77 Å and the bond angles 102°, 102°, 113° and 113°. Each oxygen atom of the tetrahedron AsO₄ is simultaneously bonded to the uranium atom. The bond angle As-O-U is 137°. The layers [(UO₂)₂(AsO₄)] are bonded together by the cations (Cu(H₂O)₄)²⁺. The distances Cu-O₁ and Cu-O₂ are 2.55 and 2.58Å respectively. The structural changes during hydration and dehydration are explaned.

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- Cu(UO₂)₂(AsO₄)₂8 H₂O

( , ). =7,10₅ Å,=17,70₄ Å Cu(UO₂)₂(AsO₄)₂8 ₂O. P4₂/nmc. P(v w) (F ₀-F _c) . . , [(UO₂)(AsO₄)], , [u(₂)₄]²⁺ . : U-O₁ 1,94 Å, U-O₂ 1,78 Å, U-O₃₍₄₎ 2,18 Å ( ). ₁-U-₂. AsO₄ As- 1,77 Å -102°, 102°, 113° 113°. AsO₄ . As--U 137°. [(UO₂)₂(AsO₄)] [u(₂O)₄]²⁺. u-O₁ 2,55 Å, u-O₂ 2,58 Å. .

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In conclusion the author thanks T. Veselská for assistance in the calculations and workers of the National Museum in Prague, and primarily Dr. ípek, for supplying the sample. The experimental work was carried out at the Department of Physics of the Natural Science Faculty of Komenský University.     

Elastic stress around linear dislocation in anisotropic medium

Relations are derived for the elastic stress field around a linear dislocation in an infinite medium with general anisotropy. The strongly deformed material around the core of the dislocation is cut out in the shape of an elliptic cylinder. The conditions of a free surface are used on the boundary thus formed. The calculation of the field around a crack in a crystal, the model of which was proposed by Fujita in [9], is given as an example.

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. , , , . , [9] .

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The author thanks Dr. F. Kroupa for valuable discussions and all-round help in solving the problem and Z. Hemanová for performing the numerical calculations.     

СПЕКТРАЛЬНЫЙ СОСТАВ И ИНТЕНСИВНОСТЬ ЛЮМИНЕСЦЕНТНОГО СВЕ ЧЕНИЯ ФОТОГРАФИЧЕСК ОЙ ЭМУЛЬСИИ

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The influence of successive asymmetrical magnetization reversal on the magnetic state of open samples

A study is made of the influence of successive asymmetrical magnetization reversal on the magnetic state of open samples, where the macroscopic demagnetization field has a significant effect during magnetization reversal and leads to a sort of rotation of the asymmetrical loops performed one after another. This effect is similar to reptation, which was studied experimentally by Nguyen van Dang [1–4] and theoretically explained by Néel [5, 6]. The quantitative expression of the rotation of asymmetrical loops in open samples as a function of the number of loops and amplitude of the disymmetry is similar to that with the reptation effect.

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, , . , . .

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In conclusion the authors thank Dr. L. Valenta, C. Sc., and Z. Málek, C. Sc., for valuable discussions.     

Der Einfluss der Plastischen Verformung durch Kaltwalzen auf die Koerzitivkraft

Zusammenfassung Es werden die Ergebnisse der Messungen der Koerzitivkraft von Eisen, Nickel und einiger Fe-Ni-Legierungen in Abhängigkeit von der plastischen Verformung durch Kaltwalzen angegeben. Gemessen wurde in Richtung parallel und senkrecht zur Walzrichtung. Die Ergebnisse werden insbesondere vom Gesichtspunkt des Einflusses der Versetzungen und der einachsigen induzierten Anisotropie diskutiert.

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Für die wertvollen Diskussionen und das Durchlesen der Arbeit danken wir den Kollegen J. Kaczér und V. Janovec, für die wirkungsvolle Hilfe bei den Messungen Koll. J. Grolmus.     

Change in primary extinction during decomposition of supersaturated solid solution II. Al-Cu 4% alloy-formation of G.P. zones

The change in integrated intensity of the (200) reflections of a solid solution during the formation of G.P. zones was measured and compared with the change in the character of the diffuse streaks corresponding to them. It was found that the. formation of G.P. zones does not lead to a decrease in primary extinction despite the great changes in the distribution of the copper atoms. It was shown that the formation of a precipitate accompanied by the formation of crystallographically incoherent boundaries greatly decreases the primary extinction.

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. II. 1-u 4%: [. . ]

(200) . . , . , . . , . , , , .

     

Релятивистские волн овые уравнения ддя ча стиц со спином 3/2

3/2.