Non-equilibrium dissociating nitrogen flow over a wedge

Experimental results for dissociating nitrogen flow over a wedge, obtained in a free-piston shock tunnel, are described. Interferograms of the flow show clearly the curvature of the shock wave and the rise in fringe shift after the shock associated with the dissociation. It is shown that the shock curvature at the tip of the wedge can be used to calculate the initial dissociation rate and that it is a more sensitive indication of the rate than can be obtained from fringe shift measurements under the prevailing experimental conditions. Because the freestream dissociation fraction can be adjusted in the shock tunnel, the dependence on atomic nitrogen concentration of the dissociation rate can be determined by the shock curvature method. A detailed calculation of the flow field by an inverse method, starting from the measured shock shape, shows good agreement with experiments

Oblique shock reflection from an axis of symmetry: shock dynamics and relation to the Guderley singularity

Oblique shock reflection from an axis of symmetry is studied using Whitham's theory of geometrical shock dynamics, and the results are compared with previous numerical simulations of the phenomenon by Hornung (2000). The shock shapes (for strong and weak shocks), and the location of the shock-shock (for strong shocks), are in good agreement with the numerical results, though the detail of the shock reflection structure is, of course, not resolved by shock dynamics. A guess at a mathematical form of the shock shape based on an analogy with the Guderley singularity in cylindrical shock implosion, in the form of a generalized hyperbola, fits the shock shape very well. The smooth variation of the exponent in this equation with initial shock angle from the Guderley value at zero to 0.5 at 90° supports the analogy. Finally, steady-flow shock reflection from a symmetry axis is related to the self-similar flow

3D Particle Tracking Velocimetry Method: Advances and Error Analysis

A full three-dimensional particle tracking system was developed and tested. By using three separate CCDs placed at the vertices of an equilateral triangle, the threedimensional location of particles can be determined. Particle locations measured at two different times can then be used to create a three-component, three-dimensional velocity field. Key developments are: the ability to accurately process overlapping particle images, offset CCDs to significantly improve effective resolution, allowance for dim particle images, and a hybrid particle tracking technique ideal for three-dimensional flows when only two sets of images exist. An in-depth theoretical error analysis was performed which gives the important sources of error and their effect on the overall system. This error analysis was verified through a series of experiments, which utilized a test target with 100 small dots per square inch. For displacements of 2.54mm the mean errors were less than 2% and the 90% confidence limits were less than 5.2 μm in the plane perpendicular to the camera axis, and 66 μm in the direction of the camera axis. The system was used for flow measurements around a delta wing at an angle of attack. These measurements show the successful implementation of the system for three-dimensional flow velocimetry

Experiments on Passive Hypervelocity Boundary-Layer Control Using an Ultrasonically Absorptive Surface

Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface to damp the second mode (Mack mode). Boundary-layer transition experiments were performed on a sharp 5.06-deg half-angle round cone at zero angle of attack in the T5 Hypervelocity Shock Tunnel to test this concept. The cone was constructed with a smooth surface around half the cone circumference (to serve as a control) and an acoustically absorptive porous surface on the other half. Test gases investigated included nitrogen and carbon dioxide at M∞ ≃ 5 with specific reservoir enthalpy ranging from 1.3 to 13.0 MJ/kg and reservoir pressure ranging from 9.0 to 50.0 MPa. Comparisons were performed to ensure that previous results obtained in similar experiments (on a regular smooth surface) were reproduced, and the results were extended to examine the effects of the porous surface. These experiments indicated that the porous surface was highly effective in delaying transition provided that the pore size was significantly smaller than the viscous length scale

Tabakkonsum bei Erwachsenen mit ADHS

Zusammenfassung: Hintergrund: Untersuchungen aus den USA wiesen Zusammenhänge zwischen der Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung (ADHS) und dem Rauchen nach. Bis heute wurden in der Schweiz keine vergleichbaren Studien durchgeführt. Ziel der vorliegenden Arbeit war es, neue Erkenntnisse über die Beziehung der ADHS und dem Tabakkonsum bei erwachsenen ADHS-Patienten aus der Schweiz zu gewinnen. Material und Methoden: Eine schriftliche Befragung zum Tabakkonsum erfolgte bei allen erwachsenen Patienten mit einer ADHS-Diagnose gemäß DSM-IV, die von September 2000 bis Januar 2006 ambulant im Rahmen der Spezialsprechstunde für ADHS der Psychiatrischen Universitätsklinik Zürich behandelt wurden. 100 der 134Patienten konnten in die Studie eingeschlossen werden. Ergebnisse: Der Raucheranteil in der ADHS-Stichprobe lag mit 55% signifikant über dem Raucheranteil in der Schweizer Wohnbevölkerung (31%). Zudem wiesen täglich rauchende ADHS-Patienten eine höhere Konsummenge und stärkere Nikotinabhängigkeit auf und haben früher begonnen, regelmäßig zu rauchen. Ihre Aufhörbereitschaft war hoch und vergleichbar mit Rauchenden aus der Schweizer Wohnbevölkerung. Schlussfolgerungen: Die Resultate dieser Schweizer Studie sind konsistent mit Befunden aus den USA. Viele ADHS-Patienten sind zum Rauchstopp motiviert und sollten in Abhängigkeit ihrer Aufhörmotivation eine Beratung zum Rauchstopp erhalte

Data management for heterogeneous research environments with CaosDB -- Experiences from an MPDL Open Source development project

Experimental and theoretical scientists in the turbulence department at the MPI-DS in Göttingen produce a large variety of heterogeneous data and analyze it in a number of different environments. In an MPDL project, the open source research data management software CaosDB was enhanced to meet these needs and hopefully those of other research groups as well. We will show the results of this process: automated integration of data from metadata-rich raw HDF 5 files and a new API with language bindings for Octave, C++ and Julia. Additionally, the user documentation was overhauled, programming tutorials published and perfomance bottlenecks identified. We will also share insights about "soft" measures to increase the overall utility of semantic data management: practical guidelines for scientists to produce truly FAIR data and workshops to empower scientists to work with CaosDB

Report on a collecting trip of the British Myriapod Group to Hungary in 1994

During a collecting trip participated jointly by the members of the British Myriapod Group and by Hungarian experts in 1994, 34 species of millipedes, 14 of centipedes, 8 of woodlice and 73 of spiders were recorded from Hungary. Two records of the millipede species Boreoiulus tenuis (Bigler, 1913) and Styrioiulus styricus (Verhoeff, 1896) were new to the fauna of Hungary

Influence of RANEY nickel on the formation of intermediates in the degradation of lignin

Lignin forms an important part of lignocellulosic biomass and is an abundantly available residue. It is a potential renewable source of phenol. Liquefaction of enzymatic hydrolysis lignin as well as catalytical hydrodeoxygenation of the main intermediates in the degradation of lignin, that is, catechol and guaiacol, was studied. The cleavage of the ether bonds, which are abundant in the molecular structure of lignin, can be realised in near-critical water (573 to 673 K, 20 to 30MPa). Hydrothermal treatment in this context provides high selectivity in respect to hydroxybenzenes, especially catechol. RANEY Nickel was found to be an adequate catalyst for hydrodeoxygenation. Although it does not influence the cleavage of ether bonds, RANEY Nickel favours the production of phenol from both lignin and catechol. The main product from hydrodeoxygenation of guaiacol with RANEY Nickel was cyclohexanol. Reaction mechanism and kinetics of the degradation of guaiacol were explored