Single-transverse-mode output from a fiber laser based on multimode interference

An alternative original approach to achieve single-transverse-mode laser emissions from multimode (MM) active fibers is demonstrated. The fiber cavity is constructed by simply splicing a conventional passive single-mode fiber (SMF-28) onto a few centimeters-long active MM fiber section whose length is precisely controlled. Owing to the self-imaging property of multimode interference (MMI) in the MM fiber, diffraction-limited laser output is obtained from the end of the SMF-28, and the MMI fiber laser is nearly as efficient as the corresponding MM fiber laser. Moreover, because of the spectral filtering effect during in-phase MMI, the bandwidth of the MMI fiber laser is below 0.5 nm.     

Sealed Sources. Some Aspects of Development and Production in the German Democratic Republic

Industrially advanced countries and inereasingly also agricultural countries today use radioisotopes as labelled compounds or scaled sources in order to solve their scientific and technological problems.     

Halbwertszeiten von 135 Radionukliden

Für 135 Radionuklide werden in der Literatur veröffentlichte Werte der Halbwertszeit mit Angabe von 200 Zitaten zusammengestellt. Dabei sind vorzugsweise die neuesten und zuverlässigsten Werte – maximal 4 je Nuklid – berücksichtigt. Für jades Nuklid wird ferner ein wahrscheinlichster Wert der Halbwertszeit angegeben. Die Anwendung dieses Wertes wird insbesondere auch bei der Umrechnung von Aktivitätsangaben der vom ASMW bereitgestellten Normallösungen radioaktiver Nuklide empfohlen.     

Broadband excitation pulses for high‐field solid‐state nuclear magnetic resonance spectroscopy

In nuclear magnetic resonance spectroscopy, experimental limits due to the radiofrequency transmitter and/or coil means that conventional radiofrequency pulses (“hard pulses”) are sometimes not sufficiently powerful to excite magnetization uniformly over a desired range of frequencies. Effects due to nonuniform excitation are most frequently encountered at high magnetic fields for nuclei with a large range of chemical shifts. Using optimal control theory, we have designed broadband excitation pulses that are suitable for solid‐state samples under magic‐angle‐spinning conditions. These pulses are easy to implement, robust to spinning frequency variations, and radiofrequency inhomogeneities, and only four times as long as a corresponding hard pulse. The utility of these pulses for uniformly exciting ¹³C nuclei is demonstrated on a 900 MHz (21.1 T) spectrometer. Copyright © 2012 John Wiley & Sons, Ltd.     

Port-Hamiltonian representation for pdes with second-order derivatives in the energy density

In this contribution we consider a port-Hamiltonian setting for partial differential equations. A crucial property of this system class is the property to be able to link a power balance relation to the structure of the equations. However, one has to take into account also the effects of energy flows via the boundary. This is straightforward when the Hamiltonian depends on derivative variables of first order, e.g. by using integration by parts. If second-order derivatives appear then integration by parts cannot be used without due care, thus we suggest an approach by using the so-called Cartan-form. We visualize the derivation of a power balance relation by using the Kirchhoff plate as an example. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the rotordynamic stability of two-pole synchronous electric machinery considering different load cases

This paper discusses stationary rotordynamics of synchronous electric machinery, considering different load cases. The model comprises the electrical operation in a rigid network and in an isolated condition. The mechanical part is modelled as a Laval Rotor (Jeffcott Rotor) with a noncircular shaft, accounting for both static- and dynamic rotor eccentricities. The results show, that the machine's electrical operation may influence the occurence of mechanical vibrations significantly and therefore demonstrate the importance of analysing the electromechanical interaction. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bifurcation behaviour and limit cycles of a compliant seal-rotor system

This contribution discusses the non-linear dynamic behaviour of a rotor system equipped with a compliant seal. The investigated model consists of a Laval-Rotor and a stiff seal ring which is visco-elastically supported. The fluid forces stemming from the turbulent incompressible lubricant film are accounted for by the non-linear Muszynska model. The added compliance leads to an improved stability behaviour of the steady state. Within the post-critical regime the additional compliance gives rise to bifurcations of the stationary vibration: Hopf bifurcations lead to limit cycles which can loose their stability via Neimark-Sacker bifurcations. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tetraphosphorus Hexoxide-Manufacture and Application

Abstract

Tetraphosphorus hexoxide, P₄O₆, is a starting material for the manufacture of inorganic and organic phosphorus compounds.