Stabilitätsanalyse eines aufgelassenen Gipsbergbaus – von der geologisch-hydrogeologisch-geotechnischen Datenerfassung zur numerischen 3D-Simulation

The assessment of the stability of underground structures is an interdisciplinary task which consists of geology, hydrogeology, surveying and geotechnical engineering. This paper gives an example of how these disciplines, their methods and the acquisition of data work together to create a complex three-dimensional computer-model of underground structures. It demonstrates, that especially the complex layout of old and “grown” underground structures cannot be represented accurately in two-dimensional analyses or models and provide no realistic results for stability investigations. Related to the stability of underground structures, a non-negligible factor is the influence of water, whether surface, rain or groundwater. The occurring leaching process of gypsum leads to a weakening of the surrounding rock which causes a strength reduction. This softening of the material must be considered in long-term simulations. The presented comprehensive approach tries to provide a possibility to predict the time-dependent occurrence of vulnerabilities in the rock mass and thus gives the possibility to install support measures in an early stage.     

Real-time 3D thermal modeling of a magnetically levitated planar actuator

A transient thermal model used to monitor the temperature distribution in real-time in a long-stroke moving-magnet planar actuator is presented. The temperature distribution in the stator coils of the planar actuator depends on the trajectory of the levitated magnet plate as the set of active coils changes with the position of the translator. Using the presented real-time model, the transient thermal behavior can be investigated. Using this thermal model, the commutation algorithm of the planar actuator is adjusted to actively limit the temperature of the coils, and better spread the temperature over the stator coils.     

Limitations of rapid myelin water quantification using 3D bSSFP

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Imaging of the myelin water fraction (MWF) is conventionally performed using a multi-echo spin-echo sequence. This technique requires long acquisition times and therefore often suffers from a lack of volume coverage. In this work, the application of 3D balanced steady-state free precession (bSSFP) sequences to extract high-resolution myelin water maps is discussed.     

Oxalylhydrazinium Nitrate and Dinitrate—Efficiency Meets Performance

Oxalylhydrazinium nitrate (OHN) and dinitrate (OHDN) were synthesized by protonation of oxalyldihydrazide with nitric acid. The synthesis is extremely cost effective (～$40/kg at the lab scale) and can be carried out in large scales and very good yields. OHN and OHDN were intensively characterized by low-temperature X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and vibrational spectroscopy. These new organic nitrate salts could be used as powerful ingredients in energetic formulations due to their low sensitivities (measured by Bundesanstalt für Materialforschung und Pröfung methods). Their thermal stability was investigated by differential scanning calorimetry (DSC) measurements. Further thermal studies of OHN showed compatibility with TNT (2,4,6-trinitrotoluene), DNAN (2,4-dinitroanisole), and RDX (1,3,5-trinitro-1,3,5-triazinane). The theoretical detonation and propulsion parameters of OHN and OHDN were calculated with the EXPLO5.5 code and compared to well-known insensitive explosives. The aquatic toxicity of OHN was determined by the luminescent bacteria inhibition test, yielding a much lower toxicity than RDX.     

Structure and density of deposits formed on filter fibers by inertial particle deposition and bounce

The morphology and packing density of particle deposits formed by accumulation on thin steel fibers suspended in an aerosol stream were studied by confocal microscopy. Measurements were made with electrically neutral polystyrene spheres (d_P=1.3, 2.0, 2.6 and 5.2 μm) as a function of flow velocity (v=0.7–5 m/s) and fiber diameters (d_F=8 and 30 μm). Deposition under these conditions was dominated by inertia (Stokes number St=0.3–9), interception (interception parameter R=0.04–0.35) and particle bounce, with a negligible contribution from diffusion.The experiments show a systematic transition of deposit morphologies with a newly introduced particle bounce parameter β～St/R, where St and R are based on the diameter d_F of the bare fiber. Compact, forward facing deposit structures dominate in case of significant particle bounce (i.e. for β>β?, where β* represents the critical conditions for the onset of bounce on the bare fiber). Dendritic structures with pronounced sideways branching are formed at β<β*. R is of relatively little influence as an independent parameter, probably because interception occurs mostly on preexisting deposit structures with dimensions in the order of d_P.The mean porosity ε of the deposit structures was determined on the basis of contour measurements by confocal microscopy, in combination with data on the accumulated particle volume per unit fiber length (known accurately from a previous paper by Kasper, Schollmeier, Meyer, and Hoferer (2009). Once noticeable deposits had formed, ε was found to attain stable values between 0.80 at d_P=1.3 μm and 0.55 at d_p=5.2 μm.     

W-Hierarchies Defined by Symmetric Gates

The classes of the W-hierarchy are the most important classes of intractable problems in parameterized complexity. These classes were originally defined via the weighted satisfiability problem for Boolean circuits. Here, besides the Boolean connectives we consider connectives such as majority, not-all-equal, and unique. For example, a gate labelled by the majority connective outputs true if more than half of its inputs are true. For any finite set C\mathcal{C} of connectives we construct the corresponding W( C\mathcal{C} )-hierarchy. We derive some general conditions which guarantee that the W-hierarchy and the W( C\mathcal{C} )-hierarchy coincide levelwise. If C\mathcal{C} only contains the majority connective then the first levels of the hierarchies coincide. We use this to show that a variant of the parameterized vertex cover problem, the majority vertex cover problem, is W[1]-complete.     

Vaporization--Condensation Generation of Ultrafine Hydrocarbon Particulate Matter for Inhalation Toxicology Studies

An evaporation/condensation particle generator produced 30-50 nm count median diameter particles from both pure hydrocarbons and from a complex mixture--used motor oil--at a concentration above 1 2 10 6 /cm 3 . The objective was to generate ultrafine aerosols for inhalation toxicology studies using specified organic components as surrogates for the particulate emissions generated by diesel internal combustion engines. This nanoparticle generation system, assembled from commercially available components, produced smaller particle size and higher particle number concentration than has been previously documented using Sinclair-La Mer condensation generator technology. The paper describes both the experiments used to design and characterize the particle generator and the operating conditions used for a specific inhalation experiment as an example of the system capability.