Doubly transitive 2‐factorizations

Let be a 2‐factorization of the complete graph K_v admitting an automorphism group G acting doubly transitively on the set of vertices. The vertex‐set V(K_v) can then be identified with the point‐set of AG(n, p) and each 2‐factor of is the union of p‐cycles which are obtained from a parallel class of lines of AG(n, p) in a suitable manner, the group G being a subgroup of A G L(n, p) in this case. The proof relies on the classification of 2‐(v, k, 1) designs admitting a doubly transitive automorphism group. The same conclusion holds even if G is only assumed to act doubly homogeneously. © 2006 Wiley Periodicals, Inc. J Combin Designs     

Simulation and experimental validation of the dynamic behavior of an electromechanically actuated multiple‐disk clutch

Automated multiple‐disk clutches in automotive drivelines are at present hydraulically or electrohydraulically actuated. The electromechanical clutch actuation represents an alternative. The subject of the investigation is a functional model of an electromechanical clutch actuator which consists of a servo motor, a reduction gear and a mechanism for the realization of the force acting on the disks. For the simulation of the dynamic behavior of the electromechanically actuated multiple‐disk clutch a detailed multibody model is developed which includes models of the electromechanical actuator and the wet multiple‐disk clutch. The multiple‐disk clutch is described by coupled partial models for the rotational and translational dynamics. The coupling parameters are the relative disk distances and the forces between the disks. The results of test bench measurements are compared to simulation results. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hadron masses and matrix elements from the QCD Schrödinger functional

We explain how masses and matrix elements can be computed in lattice QCD using Schrödinger functional boundary conditions. Numerical results in the quenched approximation demonstrate that good precision can be achieved. For a statistical sample of the same size, our hadron masses have a precision similar to what is achieved with standard methods, but for the computation of matrix elements such as the pseudoscalar decay constant the Schrödinger functional technique turns out to be much more efficient than the known alternatives.     

Degradation effects in polymer light emitting devices due to heat treatment

The characteristics of polymer light emitting diodes (PLEDs) (ITO/PPV/Ca) depend strongly on the conditions during preparation and operation. We studied the effects of heat treatment (during and after preparation) of PLEDs with OC₁C₁₀-PPV as active layer. PLEDs showed a reduction of both the current and the light output to 40 % after annealing for only 30 min at 65 °C. Effects on I-V characteristics were studied by measuring single carrier devices (hole- and electron-dominated devices). The current reduction after heat treatment can be ascribed to degradation of the ITO/PPV and the Ca/PPV interfaces.     

Methods for correlating T1ρ and FID components in wideline H NMR studies of motionally heterogeneous polymer systems

We address the problem of correlating the observed FID and T_1ρ components in wideline ¹H relaxation measurements of motionally heterogeneous polymers, and show that different methods of data treatment can highlight different aspects of the correlations present. For a sample of polypropylene we find that the T_1ρ relaxation behaviour is driven by relaxation associated with the intermediate FID component, which strongly suggests a motionally inhomogeneous amorphous region in the sample.