Contributions to the Characterization of Chlorinated Polyisoprene Surfaces

Summary: The present work is focused on the characterization of the surface properties and the mechanical properties of chlorinated polyisoprene films. Cross-linked polyisoprene films were treated with acidified hypochlorite solution and the influence of the chlorination time on the surface properties was determined by spectroscopic techniques including FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface morphology was investigated by scanning electron microscopy (SEM), optical microscopy and contact angle measurements. In addition, the effect of the chlorination time on the tensile strength and ageing stability of natural rubber latex gloves was investigated.     

Continuous in situ measurements of alkali species in the gasification of biomass

This work describes the first on-line, in situ measurement of alkali species in biomass gasification using excimer laser induced fragmentation fluorescence (ELIF). Three pelletised biomass fuels were gasified under different operating conditions in a bubbling fluidized-bed reactor, using steam as the gasifying medium. Concentrations of potassium and sodium were measured in real time for several hours per measurement. Average concentrations obtained for potassium ranged from 140 to 350 ppb, and those for sodium ranged from 1.7 to 60 ppb. Also observed was a slow release of alkali after shutting off the fuel feed, which suggests that alkali species had been taken up in the bed material (olivine); this was confirmed by analysing the bed material before and after use. Consideration of the olivine structure/composition and possible interactions with alkali and other elements during gasification suggests that alkali-containing layers could have formed on the bed particles but appear not to form crystalline phases. This may allow for re-release of alkali while the bed is still hot.     

Monotone difference schemes stabilized by discrete mollification for strongly degenerate parabolic equations

The discrete mollification method is a convolution‐based filtering procedure suitable for the regularization of ill‐posed problems and for the stabilization of explicit schemes for the solution of PDEs. This method is applied to the discretization of the diffusive terms of a known first‐order monotone finite difference scheme [Evje and Karlsen, SIAM J Numer Anal 37 (2000) 1838–1860] for initial value problems of strongly degenerate parabolic equations in one space dimension. It is proved that the mollified scheme is monotone and converges to the unique entropy solution of the initial value problem, under a CFL stability condition which permits to use time steps that are larger than with the unmollified (basic) scheme. Several numerical experiments illustrate the performance and gains in CPU time for the mollified scheme. Applications to initial‐boundary value problems are included. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 28: 38–62, 2012     

A finite volume element method for simulating secondary settling tanks

This contribution summarizes a new finite volume element (FVE) method as a unified scheme for coupled sedimentation-flow problems in secondary settling tanks in wastewater treatment. The model is two-dimensional in an axisymmetric setting. A new numerical example is presented. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

In‐band pumped Ti:Tm:LiNbO3 waveguide amplifier and low threshold laser

The fabrication by diffusion doping and a detailed optical investigation of a Ti:Tm:LiNbO₃ waveguide amplifier and of a Fabry‐Pérot type Ti:Tm:LiNbO₃ laser are reported. Both devices are in‐band pumped by a laser diode at 1650 nm. The wave‐guide amplifier shows broad‐band optical gain in the wavelength range 1750 nm < λ < 1900 nm. The laser emits at 1890 nm, the longest emission wavelength of a Tm:LiNbO₃ laser reported so far; also 1850 nm emission could be demonstrated. Laser threshold (1890 nm) is at 4 mW coupled pump power; the slope efficiency is ∼13.3%. Properties and potential of both devices are analyzed by extensive modeling.     

Conditional detection of pure quantum states of light after storage in a Tm-doped waveguide

We demonstrate the conditional detection of time-bin qubits after storage in and retrieval from a photon-echo-based waveguide quantum memory. Each qubit is encoded into one member of a photon pair produced via spontaneous parametric down-conversion, and the conditioning is achieved by the detection of the other member of the pair. By performing projection measurements with the stored and retrieved photons onto different bases, we obtain an average storage fidelity of 0.885±0.020, which exceeds the relevant classical bounds and shows the suitability of our integrated light-matter interface for future applications of quantum information processing.     

Stochastische Theorie der magnetischen Relaxation

Let a single magnetic dipole be in a constant magnetic field ?₀ and a fluctuating field ?′(t). For this problem the equation of motion is solved exactly. Averaging the magnetic moment over a convenient ensemble relations of relaxation of a macroscopic system of many spins are obtained. In this way a relaxation tensorΦ for magnetisation is derived from the stochastic properties of the fluctuating field which is a generalization ofKubo's oscillator model. For small timesΦ approaches a Gaußian for large times an exponential function. There are two relaxation times which may be expressed by two correlation times of the fluctuating field. The results give a classification of the absorption line shape in Gaußian and Lorentzian type.