J-Class Weighted Shifts on the Space of Bounded Sequences of Complex Numbers

We provide a characterization of J-class and J ^mix-class unilateral weighted shifts on in terms of their weight sequences. In contrast to the previously mentioned result we show that a bilateral weighted shift on cannot be a J-class operator. During this research the second author was fully supported by SFB 701 “Spektrale Strukturen und Topologische Methoden in der Mathematik" at the University of Bielefeld, Germany. He would also like to express his gratitude to Professor H. Abels for his support.     

A theoretical approach to the interpretation of the transient data in scanning laser ablation inductively coupled plasma mass spectrometry: Consideration of the geometry of the scanning area

This paper represents a further development of the theoretical basis for the interpretation of transient data obtained by scanning laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to overcome the non-linear distortion of the transient signal as well as to improve spatial resolution. The reconstruction of the relative concentration profile from transient data is suggested in terms of simple models of analytical information gathering for extreme cases of depth distribution of the analyte. The main attention is focused on the geometry of the overlap between the laser spot and the concentration profile, the consideration of which allows defining explicitly the response function necessary for the deconvolution procedure. The profile of the transient signal simulated according the proposed model for a real system (copper conductor lines in polymer matrix) is in good agreement with the measured data. The feasibility of the deconvolution procedure to reconstruct the relative concentration profile for a model system is demonstrated. The suggested analytical framework is intended to overcome certain limitations of scanning LA-ICP-MS which are caused by the measuring process independently from the optimization of hardware and experimental conditions.     

Induced cosmology on a regularized brane in six-dimensional flux compactification

We consider a six-dimensional Einstein–Maxwell system compactified in an axisymmetric two-dimensional space with one capped regularized conical brane of codimension one. We study the cosmological evolution which is induced on the regularized brane as it moves in between known static   bulk and cap solutions. Looking at the resulting Friedmann equation, we see that the brane cosmology at high energies is dominated by a five-dimensional ρ²${\rho }^2$ energy density term. At low energies, we obtain a Friedmann equation with a term linear to the energy density with, however, negative coefficient in the small four-brane radius limit (i.e., with negative effective Newton's constant). We discuss ways out of this problem.     

Computational modeling of domain wall interactions with dislocations in ferroelectric crystals

This paper provides a theoretical and numerical framework to investigate the interactions between domain walls and arrays of dislocations in ferroelectric single crystals. A phase-field approach is implemented in a non-linear finite element method to determine equilibrium solutions for the coupled electromechanical interactions between a domain wall and a dislocation array. The numerical simulations demonstrate the effect of the relative size and orientation of dislocations on 180° and 90° domain wall configurations. In addition, results for the pinning strength of dislocations in the case that domain walls move due the application of external electric field and shear stress are computed. The presented numerical results are compared with the findings reported for charged defects and it is shown that non-charged defects, such as dislocations, can also interact strongly with domain walls, and therefore affect the ferroelectric material behavior.     

Dipolar gradient elasticity of cables

The increasing structural use of cables and cable-systems has given rise to a substantial technical literature concerning their static and dynamic response. However, the majority of these works is based on classical elasticity theory, according to which the rigidity of the cable is neglected. The present work re-examines in detail the behavior of steel cables under in-plane loading, taking into account the effect of the material microstructure on the overall stiffness, on the basis of the well-established simplified gradient elasticity theory. Accounting for two-dimensional deformations the generalized equilibrium equations under dipolar action are assessed and the corresponding boundary value problem is solved. Numerical results obtained for a characteristic cable segment indicate a much stiffer behavior than the one predicted by classical elasticity theory. This phenomenon is observed in the rod or cable-actuated braking mechanism of bicycles and can be used in novel structural applications.     

Implementation Issues of the Conditional Moment Closure Model in Large Eddy Simulations

Different ways of transferring information regarding the mixture fraction, its sub-grid scale variance and the scalar dissipation rate are examined in terms of a Large Eddy Simulation (LES)/Conditional Moment Closure (CMC) calculation. In such a simulation, information must be transferred from a fine LES grid to a usually coarser CMC grid. Different options of calculating conditional and unconditional quantities in the CMC resolution are assessed by filtering experimental mixture fraction and scalar dissipation rate data at various resolutions. It was found that when a presumed shape for the Filtered Density Function at the CMC resolution is used, special care must be given to the mixture fraction variance. It was also found that the Amplitude Mapping Closure model can be used for the conditional scalar dissipation rate. LES/CMC with detailed chemistry of a bluff-body stabilised burner was performed using two different ways of calculating the turbulent diffusivity. The structure of the flame is realistic, with little difference noticed when using the two diffusivities.     

All-optical modulation based on electromagnetically induced transparency

We numerically investigate the implementation of all-optical absorption modulation of electromagnetic pulses by a medium that exhibits electromagnetically induced transparency. The quantum system is modelled as a three-level Λ-type system that interacts with two electromagnetic pulses, a probe pulse and a coupling pulse. The dynamics of the system is described by the coupled Maxwell-density matrix equations, and we explore the dependence of the optical modulation efficiency on the parameters of the system.