Zur Bildung von Adsorptionsmischkristallen

By investigating the systems KCl-H₂O-impurity and NH₄Cl-H₂O-impurity the knowledge of the formation of Adsorptionsmischkristallen could be extended. Some specific properties of complex mixed systems are stated.     

Principles of the Design of Straining Stages

The paper describes the elastic properties of tensile stages for the HVEM. The quality of the force control depends on the accuracy of the drives related to the maximum elongation as well as on the elastic compliance of the stage. The best accuracy of the load is obtained in soft stages. The fundamental operation of a soft and a hard stage is reviewed. These stages use a special thermal drive.     

HVEM In-situ Deformation Investigations on Cyclically Deformed Nickel Single Crystal

In-situ deformation investigations were carried out on thin foils of a nickel single crystal which was cyclically pre-deformed. The motion of dislocations does not start in the whole specimen simultaneously but begins at localized places in the dislocation-poor regions. The plastic deformation may be characterized by a collective movement of dislocations. Measurements of the effective stress show its characteristic dependence on the position in the direction of the Burgers vector. There are clear indications of structural changes in the dense regions of dislocations at strains exceeding the cyclic total strain amplitude.     

Massless Fields as Unitary Representations of the Poincaré Group

Relativistic zero-mass fields are described as manifestly covariant unitary irreducible representations of the Poincaré group. The wave-equations, which are a necessary condition for unitarity, are constructed for spinor fields of arbitrary spin and for tensor fields of integer spin. Poincaré covariance together with causality and positive energy are used to determine the commutators of quantized fields up to a positive multiple and to prove the spin-statistics theorem. The use of potentials for boson fields is discussed and it is shown that, at the expense of manifest covariance, potentials may be introduced as zero-mass limits of the massive Wigner representations.     

Photoinduced optical activity of C<Subscript>70</Subscript> fullerene in organic solvents

We have experimentally studied for the first time the effect of photoinduced rotation of the plane of polarization for pulsed laser radiation in solutions of C₇₀ fullerene in organic solvents and their mixtures. We have shown that the effect is observed for elliptical polarization of the laser radiation and is absent for linear polarization. We present the results of a study of the nonlinear optical characteristics of the C₇₀ solutions. We discuss the physical mechanisms by which nonlinear gyrotropy is induced in solutions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 93–99, January–February, 2009.     

Zur Berechnung von Geometriefaktoren bei der Kernstrahlungsmessung

Der Geometriefaktor von radioaktiven umschlossenen oder offenen Strahlenquellen hängt bei der Messung mittels einer Kernstrahlungsmeßsonde von der räumlichen Anordnung der Strahlenquelle zu der strahlenexponierten wirksamen Fläche des Detektors und von der Geometrie der Strahlenquelle selbst ab. Fūr punktförmige Strahler in verschiedenen Positionen, Geraden, Kreisflächen und Zylinder wurde in möglichst einheitlicher Vorgehensweise die Berechnung der Geometriefaktoren bezüglich kreisförmiger ebener Detektionsflächen vorgenommen und rechentechnisch in Form von BESM 6-Algolprogrammen realisiert. Die Berechnungsergebnisse sind untereinander konsistent und wurden möglichst durch unabhängige Verfahren oder experimentelle Werte kontrolliert. Die Rechengenauigkeit kann gemäß den vorliegenden Anforderungen frei gewählt werden.     

Self-starting 6.5-fs pulses from a Ti:sapphire laser

We demonstrate self-starting 6.5-fs pulses from a Kerr-lens mode-locked Ti:sapphire laser with 200-mW average output power at a pulse repetition rate of ~86 M Hz. This is to our knowledge the shortest pulse ever generated directly from a laser. For dispersion compensation we used a prism pair in combination with double-chirped mirrors, which balances the higher-order dispersion of the prism pair and therefore flattens the average total group-delay dispersion in the laser cavity. For self-starting mode locking we used a broadband semiconductor saturable-absorber mirror.     

A surrogate fuel for kerosene

Experimental and numerical studies are carried out to develop a surrogate that can reproduce selected aspects of combustion of kerosene. Jet fuels, in particular Jet-A1, Jet-A, and JP-8 are kerosene type fuels. Surrogate fuels are defined as mixtures of few hydrocarbon compounds with combustion characteristics similar to those of commercial fuels. A mixture of n-decane 80% and 1,2,4-trimethylbenzene 20% by weight, called the Aachen surrogate, is selected for consideration as a possible surrogate of kerosene. Experiments are carried out employing the counterflow configuration. The fuels tested are kerosene and the Aachen surrogate. Critical conditions of extinction, autoignition, and volume fraction of soot measured in laminar non premixed flows burning the Aachen surrogate are found to be similar to those in flames burning kerosene.A chemical-kinetic mechanism is developed to describe the combustion of the Aachen surrogate. This mechanism is assembled using previously developed chemical-kinetic mechanisms for the components: n-decane and 1,2,4-trimethylbenzene. Improvements are made to the previously developed chemical-kinetic mechanism for n-decane. The combined mechanisms are validated using experimental data obtained from shock tubes, rapid compression machines, jet stirred reactor, burner stabilized premixed flames, and a freely propagating premixed flame. Numerical calculations are performed using the chemical-kinetic mechanism for the Aachen surrogate. The calculated values of the critical conditions of autoignition and soot volume fraction agree well with experimental data. The present study shows that the chemical-kinetic mechanism for the Aachen surrogate can be employed to predict non premixed combustion of kerosene.