Unsteady two dimensional airloads acting on oscillating thin airfoils in subsonic ventilated wind tunnels

The numerical calculation of unsteady two dimensional airloads which act upon thin airfoils in subsonic ventilated wind tunnels was studied. Neglecting certain quadrature errors, Bland's collocation method is rigorously proved to converge to the mathematically exact solution of Bland's integral equation, and a three way equivalence was established between collocation, Galerkin's method and least squares whenever the collocation points are chosen to be the nodes of the quadrature rule used for Galerkin's method. A computer program displayed convergence with respect to the number of pressure basis functions employed, and agreement with known special cases was demonstrated. Results are obtained for the combined effects of wind tunnel wall ventilation and wind tunnel depth to airfoil chord ratio, and for acoustic resonance between the airfoil and wind tunnel walls. A boundary condition is proposed for permeable walls through which mass flow rate is proportional to pressure jump

Numerical equation of state and other scaling functions from an improved three-dimensional Ising model

We study an improved three-dimensional Ising model with external magnetic field near the critical point by Monte Carlo simulations. From our data we determine numerically the universal scaling functions of the magnetization, that is the equation of state, of the susceptibility and of the correlation length. In order to normalize the scaling functions we calculate the critical amplitudes of the three observables on the critical line, the phase boundary and the critical isochore. These amplitudes lead to the universal ratios C^+/C^-=4.756(28), R_{chi}=1.723(13), Q_c=0.326(3) and Q_2=1.201(10). We find excellent agreement of the data with the parametric representation of the asymptotic equation of state as found by field theory methods. The comparison of the susceptibility data to the corresponding scaling function shows a marginal difference in the symmetric phase, which can be explained by the slightly different value for R_{chi} used in the parametrization. The shape of the correlation-length-scaling function is similar to the one of the susceptibility, as expected from earlier parametrizations. The peak positions of the two scaling functions are coinciding within the error bars.Comment: 27 pages, 14 Ps-figures, Latex2e, 10 pages added, including the scaling function of the correlation length, to appear in Nucl. Phys.

Top transport in electroweak baryogenesis

In non-supersymmetric models of electroweak baryogenesis the top quark plays a crucial role. Its CP-violating source term can be calculated in the WKB approximation. We point out how to resolve certain discrepancies between computations starting from the Dirac equation and the Schwinger--Keldysh formalism. We also improve on the transport equations, keeping the W-scatterings at finite rate. We apply these results to a model with one Higgs doublet, augmented by dimension-6 operators, where our refinements lead to an increase in the baryon asymmetry by a factor of up to about 5.Comment: 17 pages, 3 figures, references adde

Two dimensional aerodynamic interference effects on oscillating airfoils with flaps in ventilated subsonic wind tunnels

The numerical computation of unsteady airloads acting upon thin airfoils with multiple leading and trailing-edge controls in two-dimensional ventilated subsonic wind tunnels is studied. The foundation of the computational method is strengthened with a new and more powerful mathematical existence and convergence theory for solving Cauchy singular integral equations of the first kind, and the method of convergence acceleration by extrapolation to the limit is introduced to analyze airfoils with flaps. New results are presented for steady and unsteady flow, including the effect of acoustic resonance between ventilated wind-tunnel walls and airfoils with oscillating flaps. The computer program TWODI is available for general use and a complete set of instructions is provided

Socialisation in the Age of New Media

Media education is a comparatively young specialisation within educational science. It acts on the assumption that in modern (or postmodern) societies human's relation to the world is largely mediated by technical media. To act pedagogically therefore has to be conceived and understood as acting in a world shaped by information and communication technologies. Based on this media education addresses three different problems. First it tries to analyse and critically reflect on socio-cultural forms and practices of media usage in order to assess the social as well as individual relevance of technically mediated perception and communication. Second it tries do develop scientifically founded concepts for the practice of media education in order to foster people's media skills and media literacy. Third it tries to develop concepts for media didactics, that is for a methodical application of technical media in order to support teaching and learning processes

Lamb Wave (A(0) Mode) Scattering Directionality at Defects

Localized and distributed guided ultrasonic waves array systems offer an efficient way for the structural health monitoring of large structures. The detection sensitivity for fatigue cracks depends on the orientation of the crack relative to the location of the sensor elements. Crack-like defects have a directionality pattern of the scattered field depending on the angle of the incident wave relative to the defect orientation and on the ratio of the defect depth and length to the wavelength. From FE simulations it has been shown that for cracks and notches almost no energy is scattered in certain directions from the defect, i.e., the data processing algorithm must take into account that for some transducer combinations no change in the signal even for a significant defect will be detected. The scattered wave field directionality pattern for an incident low frequency A0 Lamb wave mode was predicted from 3D Finite Element simulations and verified from experimental measurements at machined part-through and through-thickness notches using a laser interferometer. Good agreement was found and the directionality pattern can be predicted accurately. The amplitude of the scattered wave was quantified for a systematic variation of the angle of the incident wave relative to the defect orientation, the defect depth, and the ratio of the characteristic defect size to the wavelength. Based on these results the detection sensitivity for crack-like defects in plate structures using guided wave sensor arrays can be quantified

Occupational fields of media educators: Results of a quantitative empirical study of career entries and careers of «Medienbildung» graduates

Die akademische Medienpädagogik weiss relativ wenig darüber, wo die Absolventen/-innen ihrer Studienprogramme beruflich tätig sind. Zwar wurden schon Ende der 1980er Jahre erste Diskussionen über den neuen Beruf «Medienpädagoge» geführt (z. B. GMK 1988; Schorb 1989), aber bis heute dominieren in den Veröffentlichungen zu diesem Thema theoretisch-konzeptionelle Überlegungen und Berichte einzelner Medienpädagogen/-innen über ihre Aufgaben und Tätigkeiten in ausgewählten Handlungsfeldern. Die bisherige Bilanz im Bereich empirischer Studien ist dagegen bescheiden. Es liegen einzelne Berufsfeldstudien vor (Aufenanger 2003; Bauer et al. 2012), die einen Überblick über Tätigkeiten und Qualifikationen von Medienpädagogen/-innen in als medienpädagogisch eingestuften Einrichtungen vermitteln. Aber es finden sich keine Verbleibstudien, die Absolventen/-innen medienpädagogischer Hochschulprogramme fokussieren und Auskunft darüber geben, in welche Arbeits- und Berufsfelder diese tatsächlich einmünden. In diesem Beitrag werden Befunde aus einer quantitativ-empirischen Verbleibstudie vorgestellt, die 2014 an der Otto-von-Guericke-Universität Magdeburg durchgeführt wurde. Das Sample bestand aus Absolventen/-innen des Magdeburger BA- und MA-Studiengangs «Medienbildung». Es zeigt sich, dass die Mehrheit von ihnen zwar mit Medien arbeitet, aber überwiegend nicht in Erziehungs- und Bildungseinrichtungen tätig ist. Diese und weitere Befunde deuten darauf hin, dass die Absolventen/-innen zumeist in Einrichtungen tätig sind, die mit Hugger den Randbereichen des medienpädagogischen Arbeitsmarktes zuzuordnen wären und nicht dem sog. Kernbereich (2008, 569). Daher wird am Ende des Beitrags die Frage aufgeworfen, ob die Absolventen/-innen in fachfremde Berufe einmünden. Vielleicht bedürfen aber auch die Vorstellungen der Medienpädagogik über den Arbeitsmarkt ihrer Absolventen/-innen einer Revision?Knowledge about their alumni is comparatively small in the academic community of media education. Indeed the new vocation «media educator» has been lively debated already in the late 1980ies (e. g. GMK 1988; Schorb 1989), but to date in publications on this topic there is a predominance of either theoretical concepts or practical descriptions of occupations and tasks that media educators are responsible for in selected fields. The sum of empirical studies, on the other hand, is quite unobtrusive. At least there are a few individual studies about the occupational field of media education (Aufenanger 2003; Bauer et al. 2012) which impart insights into tasks and qualifications of media educators in institutions which are concerned with media education. But we do not find studies which focus on the careers of media education students after their graduation and provide well-grounded information on the actual occupational fields they have been lead into. This article presents findings from a quantitative empirical study of career entries and careers that has been conducted at the University of Magdeburg in 2014. The sample consists of alumni of the bachelor and the master program «Medienbildung». We found that the majority of the respondents are working with media, but predominantly not in educational institutions. So there is evidence that our former students mostly work in institutions which, according to Hugger (2008, 569), would be attributed to the border areas of the occupational field of media education rather than to the so-called core area. From there the article finally raises the question whether or not the alumni are being discharged into professions outside of their subject area. Or may the picture that media education has of the occupational fields of their students need a revision

Corrosion monitoring using high-frequency guided waves

Corrosion can develop due to adverse environmental conditions during the service life of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the reduction of the strength and thus degradation of the structural health. The monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic transducers with single sided access to the structure, guided wave modes were selectively generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted and the wall thickness reduced by consecutive milling of the steel structure. Further measurements were conducted using accelerated corrosion in a salt water bath and the damage severity monitored. From the measured signal change due to the wave mode interference the wall thickness reduction was monitored. Good agreement with theoretical predictions was achieved. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance

Guided Wave Propagation and Scattering in Aerospace Composite Panels

Carbon fiber laminate composites, consisting of layers of polymer matrix reinforced with high strength carbon fibers, are increasingly employed for aerospace structures. They offer advantages for aerospace applications, e.g., good strength to weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Depending on the severity of the impact, delaminations can occur, reducing the load carrying capacity of the structure. Efficient structural health monitoring of composite panels can be achieved using guided ultrasonic waves propagating along the structure. The guided ultrasonic wave (A0 Lamb wave mode) propagation and scattering at delaminations was modelled using full three-dimensional Finite Element (FE) simulations. Impact damage was induced in the composite panels using standard drop weight procedures. Ultrasonic immersion C-scans were performed to quantify the extent and shape of delamination due to the impact. The guided wave scattering at the impact damage was measured using a noncontact laser interferometer, quantified, and compared to baseline measurements on an undamaged part of the composite panel. Good agreement between experiments and FE predictions was found. The sensitivity of guided waves for the detection of barely visible impact damage in composite panels has been verified