Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
Search Results
Item Open Access Self-consistent modelling of pulsar magnetospheres(1989) Herold, Heinz; Ertl, Thomas; Finkbeiner, Bernd; Ruder, HannsThe magnetosphere of a rapidly rotating, strongly magnetized neutron star with aligned magnetic and rotational axes (parallel rotator) is modelled numerically. Including the radiation of the particles accelerated to relativistic energies as an efficient damping mechanism, we obtain a quasi-stationary selfconsistent solution to this classical problem. The numerical simulation, which was started from the well-known vacuum solution, yields a global magnetospheric structure that can be characterized by two regions of oppositely charged particles, which eventually produce a relativistic pulsar wind, separated by a vacuum gap of considerable extent.Item Open Access Mikro-Profilometrie zur Bestimmung der Topographie und Rauheit technischer Oberflächen mittels Heterodyn-Laserinterferometrie(1989) Leonhardt, Klaus; Rippert, Karl-Heinz; Tiziani, Hans J.Ein Heterodyn-Profilometer zur Messung der Rauheit polierter und feingeschliffener Oberflächen und zur Formmessung wird beschrieben. Die Vertikal- oder Höhenauflösung liegt bei 0,5 nm, der Meßbereich für Formmessungen an glatten Oberflächen bei 40 pm bei einer maximalen Abtastlänge von 300 mm. Die Lateralauflösung kann je nach Aperturausleuchtung bis zu 0,5 pm eingestellt werden. Anwendungen und Grenzen werden gezeigt, Formeln zur Lateralauflösung und zur Erfassung von Phasensprüngen sowie Profilhöhen-Übertragungsfunktionen werden diskutiert.Item Open Access Biological effects and physical characterization of shock waves by an XL-1 experimental lithotripter(1989) Brümmer, Franz; Staudenraus, Joachim; Nesper, Martina; Suhr, Dierk; Eisenmenger, Wolfgang; Hülser, Dieter F.Extracorporeal shock wave lithotripsy (ESWL) has become the clinical standard method for non-invasive disintegration not only of concrements in kidney and urinary tract but also of gallstones. Despite the widespread clinical use of ESWL, the mechanism of stone destruction is not yet really understood, but several possibilities (cavitation, shock wave reflection) are discussed. The final cause of various side effects is still under discussion. Nevertheless, during the last few years much effort was put into possible extensions of ESWL applications On the other hand , physical characterizations of shock waves are rarely reported and combined measurements of biological effects in vitro and physical characterization of the applied shock waves are not available. We, therefore, examined the influence of water temperature and gas content on the shock wave efficency in biological systems and determined several physical characteristics (pressure amplitudes, rise time etc.) of the shock waves under the same experimental conditions.Item Open Access Optical methods of measuring rough surfaces(1989) Leonhardt, Klaus; Rippert, Karl-Heinz; Tiziani, Hans J.The statistical parameters of surfaces to be measured for industrial applications vary over several orders of magnitude. Surfaces with large slopes or edges are particularly difficult to be recorded. Some measuring methods developed in our laboratory are compared and the range of applications are discussed. For polished and fine ground glass and metal surfaces a heterodyne profilometer with a vertical resolution of 0.5 nm, lateral resolution of 0.6 μm, and large scanning length is discussed. The interferometer can be changed from single- to double-pass operation by rotation of a quarter-wave-plate. For rougher surfaces a profilometer of the photometric-balance type with resolution Rq < 4 nm and dynamic range of 20 μm and an interference microscope with automated fringe evaluation is described. An integral white light roughness sensor covers the roughness range 0.04μm to 10μm and measures independently mean roughness and autocorrelation width.Item Open Access Meeting the optical talent needs of industry in Europe(1989) Tiziani, Hans J.The thematic "meeting the optical talent needs of industry in Europe" can be looked at from different points of view. In the present report the industrial activities and the education in optics are summarized. My colleagues of the "Institut d'Optique" in Paris and the Imperial College in London will report on the curriculum in optics in Paris and London. The emphasis is more on the model we use at the University of Stuttgart. It is a particular engineering curriculum forming engineers with a good optics background.Item Open Access Linear stark coupling to the ground state of effective mass acceptors(1989) Köpf, Andreas; Ambrosy, Anton; Lassmann, KurtIt is shown by dielectric resonance absorption at 24 GHz and by ultrasonic resonance spectroscopy between 5 and 10 GHz that linear coupling of the electric field to the ground state of effective mass acceptors in Si exists and has a distinct chemical shift from B to In.Item Open Access One-phonon ionization of neutral donors in germanium(1989) Gienger, Martin; Groß, Peter; Lassmann, KurtHere we show by phonon spectroscopy with superconducting tunnelling junctions that one-phonon excitations from the ground state to the conduction band (CB) are measurable as phonon induced conductivity (PIC) changes in the special case of donors in Ge. For the conductivity thresholds we find somewhat smaller binding energies than evaluated from optical measurements whereas for the 1s-singlet to 1s-triplet ground state splitting as seen by elastic phonon scattering we obtain the optical values.Item Open Access Modulation transfer function obtained from image structures(1989) Lei, Fang; Tiziani, Hans J.A new and relatively simple method for edge gradient analysis (EGA) has been developed to determine the modulation transfer function (MTF) of photogrammetrical systems. The MTF can be calculated as the ratio of the amplitude of those frequencies present in the original edge to the amplitude of the same frequency in the scanned edge image. Thus a differentiation of the edge scan - as usually implemented - is not necessary. In order to avoid a division by zero we multiplied the edge images by the so called Hanning function before performing the Fourier analysis. From the point of noise sensitivity the method using a Hanning window is advantageous in comparison to the edge differentiation method. The edge gradient analysis method and the grating pattern method are compared. Artificial edge, natural roof edge, and grating patterns were used to determine the quality of the photogrammetrical system. Good agreement of all MTF measurements was found. Furthermore, the resolution found from MTF curves agreed well with the resolution obtained from threebar targets. Generally, the MTF curves obtained from patterns in the flight direction were lower than the MTF's perpendicular to the flight direction due to airplane movement. The influence of linear image motion and its compensation was examined and is discussed. Furthermore, the longitudinal motion of the object as defect of focus is studied analytically and experimentally for a close range.Item Open Access Visualization in astrophysics(1989) Ertl, Thomas; Geyer, Florian; Herold, Heinz; Kraus, Ute; Niemeier, Roland; Nollert, Hans-Peter; Rebetzky, Andreas; Ruder, Hanns; Zeller, GudrunThis paper reports on progress we have made in modelling cosmic X·ray sources on supercomputers. The results we present are meant to serve as an example for the fact that sophisticated visualization techniques play a crucial role in scientific computing. Among the graphical methods we demonstrate, raytracing in curved space-time and a physically motivated 3D-volume rendering algorithm might be of interest to the graphics community in general.