Carbon thin films through laser ablation

Thin carbon films were deposited on silicon substrates at room temperature using a 0.355 μm Nd:YAG laser wavelength at low irradiance in the presence of argon gas. Various techniques including scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to analyze the film quality. The influence of the argon gas pressure on the properties of the films is demonstrated and a correlation with the optical emission data is presented.     

Ion Beam Driven Ion Cyclotron Double Layers

We present here a self consistent theory of small amplitude double layers associated with electrostatic ion cyclotron waves in a plasma containing hot electrons, cold ions and traversed by an ion beam. It has been shown that compressive type of double layers solution exists when θ_b (beam temperature) < α_b (beam concentration) < 1.     

Experimental study of regions of reversed magnetization in an amorphous layer of Co70Fe5Si10B15

The characteristics of the distribution of magnetization and remagnetization of microsections of the surface in the amorphous alloy Co₇₀Fe₅Si₁₀B₁₅, prepared in the form of thin ribbons, were studied by the magnetooptical method. It was found that the magnetization I on the surface of the amorphous ribbon studied was strongly nonuniform. It was established that heat treatment (HT) of the sample leads to the appearance of regions of reversed magnetization in the surface layer of the ribbon, while thermomagnetic annealing reduces the nonuniformity of I. The conservation of the transverse component in the HT sample in fields where the magnitude of the component of magnetization parallel to the length of the ribbon remains virtually unchanged suggested that a domain structure of the magnetization ripple type, owing to the strong microdispersion of the magnetic anisotropy, is realized in this sample.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 89–94, March, 1988.     

Verdampfen und Kondensieren binärer Gemische als Strömungsproblem

Zusammenfassung Die Grenze zwischen gasförmiger und flüssiger Phase eines binären Gemisches stellt beim Verdampfen oder Kondensieren eine Wärme- und Stoffquelle dar. Phasenumwandlungen von Gemischen führen folglich im allgemeinen auf Strömungsvorgänge mit Wärme- und Stoffübertragung. Die Grundgleichungen dafür werden sowohl in Massen- wie in Moldarstellung hergeleitet. Bei Filmkondensation werden im Falle des Gleichstromes von Dampf und Flüssigkeit neue Erkenntnisse gewonnen, womit ältere Versuchsergebnisse erklärt werden.

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Evaporation and condensation of binary mixtures as a flow problem

The boundary between the gaseous and liquid phases of a binary mixture is a source of both heat and mass, if evaporation or condensation takes place. Thus phase transitions of binary mixtures are related to flow processes with combined heat and mass transfer. The basic equations for this type of processes are derived in terms of mass and mole fractions, respectively. New results, which allow an interpretation of previous experimental data, are obtained for film condensation under cocurrent flow conditions.

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Formelzeichen a Bewegungsgeschwindigkeit vonF in Normalenrichtung - b Spaltbreite des Ringrohres - B Integrationsbereich - C Massenanteil - c _p spez. Wärme bei konst. Druck - D Diffusionskoeffizient - e spez. innere Energie - E Molenergie - F Begrenzungsfläche - g Schwerebeschleunigung - i spez. Enthalpie - I Molenthalpie - j Diffusionsstromdichte - K _Hy hydraulische Kennzahl - L Rohrlänge - Massenstromdichte - M Masse - Massenstrom - n Moldichte - Molstromdichte - n Einheitsvektor der Flächennormalen - N Mohlzahl - Molstrom - p Druck - q Wärmestrom - R Rohrradius - T Temperatur - t Zeit - mittlere Geschwindigkeit - u, v, w Geschwindigkeitskomponenten - v Rücklaufverhältnis - V Volumen - W Geschwindigkeitsvektor - x, y, z Koordinaten - X Molanteil - Filmdicke - Verdampfungswärme bei konst. Druck - Molmasse - kinematische Zähigkeit - Dichte - Stromfunktion Indizes a Ausströmung - d Dampfphase - e Einströmung - f flüssige Phase - i Phasengrenze - i=1, 2 Komponente - n Normalenrichtung     

Untersuchung von Einzelblasen an ölbeschichteten Oberflächen mit künstlichen Keimstellen

Zusammenfassung An feinpolierten, ölbeschichteten V2A-Oberflächen mit jeweils einer gebohrten (d=140 µm) und einer geätzten (d=47 µm) Vertiefung als Keimstelle wurde für Wasserblasen das Wachstum, der Abreißdurchmesser und die Abreißfrequenz gemessen. Für die wärmetransportgesteuerte Blasenbildung liefert der Vergleich mit Beziehungen, die für reine Metallflächen gewonnen wurden, gute Übereinstimmung, so daß keine Einfluß der Ölschicht erkennbar wurde.

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Investigation of single vapor bubbles on surfaces covered with a thin oil film with artificial nuclei

For single vapor bubbles, the growth rates, the detachment diameter, and the frequency were measured on single artificial nuclei, either drilled (d=140 µm) or etched (d=47 µm) into a highly polished stainless steel plate which was covered with a thin oil film. For evaporation controlled by heat transport, good agreement was observed with relations from literature which were obtained for clean surfaces; thus, an effect of the oil film could not be discovered.

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Formelzeichen a Temperaturleitfähigkeit - D _a Blasenabreißdurchmesser - f Blasenfrequenz - Ja Jakob-Zahl - Pr Prandtl-Zahl /a - q Wärmestromdichte - R Blasenradius - T Temperatur - dynamische Zähigkeit - Wärmeleitfähigkeit - Dichte - Oberflächenspannung - Zeit Indizes g Gas, Dampf - l flüssig - s Sättigung - w Wand Herrn Prof. Dr.-Ing. Karl Stephan zum 60. Geburtstag gewidmet     

Taylor expansion of effective Hamiltonians by Monte Carlo simulations with fixed block spins

Monte Carlo simulations with fixed block spins allow the computation of Taylor expansion kernels for effective Hamiltonians. The expansion can be performed around arbitrary block spin configurations \(\bar \phi\) and does not suffer from truncation errors. Monte Carlo calculation of the Taylor kernels offers a ready possibility to check whether the effective Hamiltonian has good locality properties in the neighborhood of a given configuration \(\bar \phi\) . The method is applied in a renormalization group study of the 2-dimensional critical Ising model. The results show that one has to deal with a “large field problem”, as had been expected from rigorous renormalization group studies.     

Random fields and quantum effects in proton glasses

The effects of quantum fluctuations on the proton glass phase in mixed hydrogen-bonded ferro-antiferroelectric systems are considered. The system is described in terms of the infinite-ranged Ising pseudospin glass model in a transverse tunneling field in the presence of random parallel fields. The stability limit of the high-temperature proton glass phase is determined within the thermofield dynamic approach, and the behavior or linear and nonlinear susceptibility is evaluated.     

Disordered charge distributions and dielectric loss in extra dense flint glasses

The complex permittivities of some extra dense flint glasses (EDF glasses) have been studied. The dielectric features of the samples are dominated by their PbO content. Both refractive indices and dielectric losses exhibit a close relation to the concentration of Pb ions. The latter are located either at sites of the network atoms or filling the potential minima interstitially. They can be identified by their different relaxation mechanisms. The dispersion in the submillimeter wave and FIR area is characterized by a very broad distribution of comparably sharp resonant states. Thermal lens — or hysteresis effects can be excluded.     

On bundle shifts and cluster sets

An application of the Abrahamse-Douglas model of subnormal operators ([1], [7]) to the theory of analytic functions is presented. Section 1 shows a wide class of analytic Toeplitz operators covered by the model, i. e. equivalent to bundle shifts. In Section 2 their essential spectra are considered. As corollaries, we get the equality of essential spectra of certain quasisimilar Toeplitz operators and a nice property of global (boundary) cluster sets. Section 3, entitledApology points out two inexact claims made in the introductory part of [7]. Fortunately, none of the results was affected by these errors.