The spin density and the optical spectrum of CoCl2- 4

The CoCl^2- ₄ ion has been studied using ab initio methods at various levels of approximation (RHF, UHF, CI and MC SCF). The calculations have been performed both with and without the Madelung field from crystalline surroundings. One of the main purposes has been to investigate the spin density, and determine its dependence on both correlation and external fields. The spin density is found to be fairly dependent on correlation but rather independent of the surrounding crystal. The lower excited quartet states have been calculated using CI expansions based upon ground state RHF and MC SCF wavefunctions. The experimental spectrum is very well reproduced on the MC SCF/CI level, both with and without the Madelung field.     

Berechnung reaktionskinetischer Isotopeeffekte für Wasserstoffübertragungs-reaktionen in Systemen mit Benzolderivaten in Abhängigkeit von Substituenten

Für die Wasserstoffübertragungsreaktionen zwischen Cumol und dem Cumolperoxyradikal sowie zwischen Toluol, Äthylbenzol, Cumol und Brom werden die Verhältnisse der Geschwindigkeitskonstanten k_H/k_D im Rahmen der Eyringschen Theorie unter Verwendung der Methode von Johnston (BEBO) berechnet, in Abhängigkeit von Substituenten am Benzolring. In der genannten Reihenfolge ergeben sich die Verhältnisse k_H/k_D zu: 4,76; 7,40; 6,75; 6,30 (T = 320 °K) und z. B. für die Übertragungsreaktionen zwischen p-Methyl-, p-Methoxy-, p-Nitro-Cumol und den entsprechenden Peroxyradikalen die Werte k_H/k_D; 4,71; 4,51; 4,83. Dabei werden modifizierungen der Methode von Johnston zur Festlegung der im Übergangskomplex realisierten Bindungsordnung vorgenommen, indem die Exponenten p und q (BEBO-Methode) auf eine neue Art bestimmt und die zu den beteiligten Bindungen gehörenden Überlappungsintegrale in die Ermittlung der Struktur des Übergangskomplexes einbezogen werden.     

Isotopieeffekte in Ladungsübertragungsreaktionen

Für Ladungsübertragungsreaktionen im. Bereich niedriger kinetischer Energien zwischen Edelgasionen (He⁺, Ar⁺) und zweiatomigen Molekülen (¹⁴N₂, ¹⁵N₂) werden Wirkungsquerschnitte und Isotopieeffekte im Rahmen der statistischen phasenraumtheorie berechnet. Bei niedrlgen kinetischen Energien zeigt das statistische Modell wesentliche Isotopieeffekte und inverse Isotopieeffekte in speziellen Reaktionskanälen.     

Microfabricated ion traps

Ion traps offer the opportunity to study fundamental quantum systems with a high level of accuracy highly decoupled from the environment. Individual atomic ions can be controlled and manipulated with electric fields, cooled to the ground state of motion with laser cooling and coherently manipulated using optical and microwave radiation. Microfabricated ion traps hold the advantage of allowing for smaller trap dimensions and better scalability towards large ion trap arrays also making them a vital ingredient for next generation quantum technologies. Here we provide an introduction into the principles and operation of microfabricated ion traps. We show an overview of material and electrical considerations which are vital for the design of such trap structures. We provide guidance on how to choose the appropriate fabrication design, consider different methods for the fabrication of microfabricated ion traps and discuss previously realised structures. We also discuss the phenomenon of anomalous heating of ions within ion traps, which becomes an important factor in the miniaturisation of ion traps.     

Modeling and Simulation of Rate-Dependent Magneto-Active Polymers

In the present work, the magneto-viscoelastic behavior of MAPs is studied by a thermodynamically consistent constitutive model. A finite deformation based framework of nonlinear magneto-viscoelastic coupling is introduced with a multiplicative decomposition of the deformation gradient. The viscosity is captured by evolution equations of the internal variables introduced. We propose energy functions for pure magnetic and magneto-mechanical coupling such that saturation behavior of the magnetostriction and magnetization is captured. After having established the general framework, the model is studied for homogeneous deformations for the purpose of a least-square-based parameter identification from experimental data. The model predictions of non-linear magneto-mechanical responses with strong rate and field dependency are presented. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transition in the propagation mechanism during flame acceleration in porous media

The combustion of stoichiometric hydrogen-air at various initial pressures was investigated in a 7.62 cm square cross-section channel filled with 1.27 cm diameter beads. The flame time-of-arrival and pressure time history along the channel were obtained by ionization probes and piezoelectric pressure transducers. Flame acceleration was found to be very rapid, e.g. at an initial pressure of 45 kPa the flame achieves a velocity of over 600 m/s in roughly 0.3 m. It was determined that at this high speed a well defined planar shock wave precedes a thick reaction zone. It was also shown that there is a transition in the flame propagation mechanism, similar to that observed in an obstacle laden channel [G. Ciccarelli and C. Johansen, The role of shock-flame interactions on flame acceleration in an obstacle laden channel, Proc. 22nd International Colloquium on the Dynamics of Explosions and Reactive Systems, Minsk, 2009]. By varying the initial pressure of the mixture, changes in the axial location of the transition between combustion propagation regimes was also observed. A soot foil technique was used to identify the transition in the propagation mechanism, as well as to provide information concerning the local flow field around the beads and the overall average flow direction.     

Diaphragm opening effects on shock wave formation and acceleration in a rectangular cross section channel

Shock wave formation and acceleration in a high-aspect ratio cross section shock tube were studied experimentally and numerically. The relative importance of geometric effects and diaphragm opening time on shock formation are assessed. The diaphragm opening time was controlled through the use of slit-type (fast opening time) and petal-type (slow opening time) diaphragms. A novel method of fabricating the petal-type diaphragms, which results in a consistent burst pressure and symmetric opening without fragmentation, is presented. High-speed schlieren photography was used to visualize the unsteady propagation of the lead shock wave and trailing gas dynamic structures. Surface-mounted pressure sensors were used to capture the spatial and temporal development of the pressure field. Unsteady Reynolds-Averaged Navier–Stokes simulation predictions using the shear-stress-transport turbulence model are compared to the experimental data. Simulation results are used to explain the presence of high-frequency pressure oscillations observed experimentally in the driver section as well as the cause of the initial acceleration and subsequent rapid decay of shock velocity measured along the top and bottom channel surfaces. A one-dimensional theoretical model predicting the effect of the finite opening time of the diaphragm on the rate of driver depressurization and shock acceleration is proposed. The model removes the large amount of empiricism that accompanies existing models published in the literature. Model accuracy is assessed through comparisons with experiments and simulations. Limitations of and potential improvements in the model are discussed.     

Construction and properties of quasi-linear functionals

Quasi-linear functionals are shown to be uniformly continuous and decomposable into a difference of two quasi-integrals. A predual space for the quasi-linear functionals inducing the weak*-topology is given. General constructions of quasi-linear functionals by solid set-functions and q-functions are given.

     

Convergence of the SMC Implementation of the PHD Filte

The probability hypothesis density (PHD) filter is a first moment approximation to the evolution of a dynamic point process which can be used to approximate the optimal filtering equations of the multiple-object tracking problem. We show that, under reasonable assumptions, a sequential Monte Carlo (SMC) approximation of the PHD filter converges in mean of order , and hence almost surely, to the true PHD filter. We also present a central limit theorem for the SMC approximation, show that the variance is finite under similar assumptions and establish a recursion for the asymptotic variance. This provides a theoretical justification for this implementation of a tractable multiple-object filtering methodology and generalises some results from sequential Monte Carlo theory.