Embedding quasi laminar 1D flame profiles to model turbulent premixed combustion with a joint PDF method

A new model for turbulent premixed combustion is presented which is based on a joint velocity composition probability density function (JPDF) method. The key idea is a scale separation approach. The method combines the model by Bray, Moss and Libby [1] (BML) for premixed combustion with the flamelet approach for nonpremixed combustion. Here, a Lagrangian formulation of the BML model is considered. The progress variable used by the BML model becomes a computational particle property and its value is triggered by the arrival of the flame front at the particle's position. Similar as in the flamelet approach we assume that the smallest eddies are not small enough to disturb the reactive diffusive flame structure. To resolve the (embedded) quasi laminar flame structure, a flame residence time is introduced. With that residence time, the evolution of the particle composition, including enthalpy, can be determined from precomputed laminar 1D flames. The main challenge with this approach is to model the probability that an embedded flamefront arrives at the particle location, which is necessary to close the chemical source term. Numerical experiments of a turbulent premixed flame show good agreement with experimental data. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of viscosity and chemical relaxation on acoustic pulse propagation in seawater

This paper considers acoustic pulse distortion in seawater due to effects of viscosity and chemical relaxation. The acoustic medium is modelled as a linear, time-invariant, space-invariant filter. The deformation of initially Gaussian-shaped pulses is estimated. The combined effects of the dissipative processes are that as a pulse propagates through the medium, the maximum amplitude is decreased, the pulse is stretched in time and a delayed tail is developed. Input pulses with high-frequency energy contents can undergo a considerable deformation due to these phenomena.     

Trims and extensions of quadratic APN functions

Designs, Codes and Cryptography - In this work, we study functions that can be obtained by restricting a vectorial Boolean function $$F :\mathbb {F}_{2}^n \rightarrow \mathbb {F}_{2}^n$$ to an...     

Identification of potential cannalis containing substance metabolites: nuclear resonance and mass spectroscopic studies on side chain hydroxylation of cannabinoids

The 100-MHz-NMR-spectra of 11 side chain hydroxylated derivatives of cannabidiol ( 1 ), Δ⁶-tetrahydrocannabinol ( 2 ) and cannabinol ( 3 ) were analysed for signals specific for the position of hydroxyl groups. The mass spectra of these compounds and their trimethylsilyl ethers were investigated at ionisation voltages between 70 and 10 eV. The mass spectra of the non-silylated compounds showed no similarities independent on the basic type of cannabinoid but in the case of their trimethylsilyl ethers it was possible to derive fragmentations specific for the site of hydroxylation. These data are presented as a general method for the identification of small quantities of side chain hydroxylated in vitro and in vivo metabolites of cannabinoids.     

Theoretical simulation of backscattered electron images of Si/SixGe1-x structures with a scanning electron microscope

In this work, we report on a theoretical study of the contrast formation at Si/Si_xGe_1–x interfaces in backscattered electron images of a scanning electron microscope. The contrast at the heterointerface is calculated for different atomic concentrations (0 < × < 1) and energies (E₀ = 10 and 20 keV). The electron scattering phenomenon is simulated by employing a Monte Carlo method by using a single scattering approach. The signal intensity close to the interface shows a peak on the alloy side and a dip on the Si side. We explain this phenomenon by using the diffusion theory of the backscattered electrons. The spatial resolution increases by decreasing the Si concentration in the alloy side and by decreasing the beam energy.     

Xylochemical Synthesis and Biological Evaluation of Shancigusin C and Bletistrin G

The biological activities of shancigusin C (1) and bletistrin G (2), natural products isolated from orchids, are reported along with their first total syntheses. The total synthesis of shancigusin C (1) was conducted by employing the Perkin reaction to forge the central stilbene core, whereas the synthesis of bletistrin G (2) was achieved by the Wittig olefination followed by several regioselective aromatic substitution reactions. Both syntheses were completed by applying only renewable starting materials according to the principles of xylochemistry. The cytotoxic properties of shancigusin C (1) and bletistrin G (2) against tumor cells suggest suitability as a starting point for further structural variation.