The non-Fickian diffusion of deterrents into a nitrocellulose-based propellant

The diffusion of solutions of ethyl centralite (EC), dibutylphthalate (DBP), and dinitrotoluene (DNT) into a nitrocellulose (NC) propellant is investigated. DBP and EC penetrate the propellant in a way consistent with Case II diffusion. The diffusion of DNT solutions is Fickian. The apparent activation energy for Case II diffusion is 62 kJ/mol for DBP and 66 kJ/mol for EC. Changes to coating solvent polarity have little effect on DNT and DBP penetration and merely alter the rate, not the mechanism, of EC diffusion into the propellant.     

Energieinformatik

Due to the increasing importance of producing and consuming energy more sustainably, Energy Informatics (EI) has evolved into a thriving research area within the CS/IS community. The article attempts to characterize this young and highly dynamic field of research by describing current EI research topics and methods and provides an outlook of how the field might evolve in the future. It is shown that two general research questions have received the most attention so far and are likely to dominate the EI research agenda in the coming years: How to leverage information and communication technology (ICT) to (1) improve energy efficiency, and (2) to integrate decentralized renewable energy sources into the power grid. Selected EI streams are reviewed, highlighting how the respective research questions are broken down into specific research projects and how EI researchers have made contributions based on their individual academic background.     

Infrared heated μ-blistering,a new fabrication technology for HARMST

Polymeric replication technologies such as injection moulding or hot-embossing have gained wide acceptance in the microtechnological community, microthermoforming of thin polymer foils, also called μ-blistering, still remains relatively unknown. Although the general potentials of the µ-blistering have already been pointed out, little work has been carried out addressing its capability for high aspect ratio microstructuring. In the scope of this work we therefore demonstrate the feasibility of μ-blistering to obtain aspect ratios for free standing structures of up to 7 within a process cycle time of <4 min. The presented processing technology uniquely combines manufacturing of macro-, micro- and even nanoscopic feature sizes in a single process.     

Time-of-flight studies on catalytic model reactions

Time-of-flight spectroscopy (TOF) and REMPI-TOF (resonance enhanced multi-photon ionization-TOF) were applied to measure the angular and translational energy distribution, as well as the internal state resolved energy distribution of desorption and reaction products on some model systems. Desorption of hydrogen and deuterium from clean and modified Pd(111) surfaces was studied, where the palladium sample was part of a permeation source. Water formation by reaction of oxygen with hydrogen on palladium was investigated by using different types of hydrogen supply: molecular H₂ exposure and atomic H exposure from the gas phase, as well as H exposure by permeating hydrogen. Vanadium oxide nanostructures on Pd(111) were prepared and the influence on D₂ desorption and D₂O production was investigated with the permeation technique. Additionally, deuterium desorption from sulfur and oxygen covered V(111) and V(100) surfaces was studied by TOF and REMPI-TOF spectroscopy. From the TOF spectra information concerning the reaction and desorption dynamics (activation barriers) could be gained.     

Hierarchical opacity optimization for sets of 3D line fields

The selection of meaningful lines for 3D line data visualization has been intensively researched in recent years. Most approaches focus on single line fields where one line passes through each domain point. This paper presents a selection approach for sets of line fields which is based on a global optimization of the opacity of candidate lines. For this, existing approaches for single line fields are modified such that significantly larger amounts of line representatives are handled. Furthermore, time coherence is addressed for animations, making this the first approach that solves the line selection problem for 3D time‐dependent flow. We apply our technique to visualize dense sets of pathlines, sets of magnetic field lines, and animated sets of pathlines, streaklines and masslines.     

Mullite Coatings on SiC and C/C–Si–SiC Substrates Characterized by Infrared Spectroscopy

Mullite (3Al₂O₃·2SiO₂) coatings on SiC substrates and SiC precoated carbon/carbon composite (C/C-Si-SiC) substrates were produced by pulsed laser deposition (PLD) using pressed mullite powder targets. The layers can be characterized efficiently by IR reflection spectroscopy in the spectral range between 650 and 5000 cm⁻¹. The deposited coatings turn into mullite upon oxidation in air at temperatures between 1400° and 1600°C. Fabry-Perot interferences indicate a high quality and homogeneity of the mullite coating/SiC substrate interface. Amorphous SiO₂ gradually forms during prolonged heating or at higher temperatures.     

A numerical study of particle wall-deposition in a turbulent square duct flow

The deposition of dense solid particles in a downward, fully developed turbulent square duct flow at Re_τ = 360, based on the mean friction velocity and the duct width, is studied using large eddy simulations of the fluid flow. The fluid and the particulate phases are treated using Eulerian and Lagrangian approaches, respectively. A finite-volume based, second-order accurate fractional step scheme is used to integrate the incompressible form of the unsteady, three-dimensional, filtered Navier-Stokes equations on an 80 × 80 × 128 grid. A dynamic subgrid kinetic energy model is used to account for the unresolved scales. The Lagrangian particle equation of motion includes the drag, lift, and gravity forces and is integrated using the fourth-order accurate Runge-Kutta scheme. Two values of particle to fluid density ratio (ρ_p/ρ_f = 1000 and 8900) and five values of dimensionless particle diameter (d_p/δ × 10⁶ = 100, 250, 500, 1000 and 2000, δ is the duct width) are studied. Two particle number densities, consisting of 10⁵ and 1.5 × 10⁶ particles initially in the domain, are examined.Variations in the probability distribution function (PDF) of the particle deposition location with dimensionless particle response time, i.e. Stokes number, are presented. The deposition is seen to occur with greater probability near the center of the duct walls, than at the corners. The average streamwise and wall-normal deposition velocities of the particles increase with Stokes number, with their maxima occurring near the center of the duct wall. The computed deposition rates are compared to previously reported results for a circular pipe flow. It is observed that the deposition rates in a square duct are greater than those in a pipe flow, especially for the low Stokes number particles. Also, wall-deposition of the low Stokes number particles increases significantly by including the subgrid velocity fluctuations in computing the fluid forces on the particles. Two-way coupling and, to a greater extent, four-way coupling are seen to increase the deposition rates.     

Compatibilisation of PPE/SAN blends by triblock terpolymers: Correlation between block terpolymer composition, morphology and properties

Immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN) with a weight composition of 60/40 were compatibilised by polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymers (SBM) using a two-stage melt-processing approach. In order to investigate the influence of the SBM composition on the compatibilisation efficiency, the block lengths of the triblock terpolymers were systematically varied. The resulting morphological features of the blend systems as function of SBM composition and processing parameters are correlated with the resulting thermal and thermo-mechanical properties. In the ideal case, SBM should be located at the interface as PS is miscible with PPE while PMMA is miscible with SAN. The elastomeric middle block as an immiscible component should remain at the interface. This particular morphological arrangement is known as the ‘raspberry morphology’. A detailed TEM analysis of the blend morphologies following initial extrusion-compounding revealed a high compatibilisation efficiency of the SBM types with equal lengths of the end blocks and, furthermore, the desired raspberry morphology was achieved. In contrast, high PS contents in comparison to the other blocks led to a pronounced micelle formation in the PPE phase. Further evaluation of the blend structures following injection-moulding indicated that the morphologies remain relatively stable during this second melt-processing step. A detailed thermal analysis of all blend systems supports the interpretation of the observed morphological features. The fundamental correlation between SBM composition and blend morphology established in this study opens the door for the controlled development of interfacial properties of such compatibilised PPE/SAN blends during melt-processing.     

Bridging the gap between formal semantics and implementation of triple graph grammars

The correctness of model transformations is a crucial element for model-driven engineering of high-quality software. A prerequisite to verify model transformations at the level of the model transformation specification is that an unambiguous formal semantics exists and that the implementation of the model transformation language adheres to this semantics. However, for existing relational model transformation approaches, it is usually not really clear under which constraints particular implementations really conform to the formal semantics. In this paper, we will bridge this gap for the formal semantics of triple graph grammars (TGG) and an existing efficient implementation. While the formal semantics assumes backtracking and ignores non-determinism, practical implementations do not support backtracking, require rule sets that ensure determinism, and include further optimizations. Therefore, we capture how the considered TGG implementation realizes the transformation by means of operational rules, define required criteria, and show conformance to the formal semantics if these criteria are fulfilled. We further outline how static and runtime checks can be employed to guarantee these criteria.