Universität Stuttgart
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Item Open Access Kinematics and dynamics for computer animation(1994) Ruder, Hanns; Ertl, Thomas; Gruber, Karin; Günther, Michael; Hospach, Frank; Ruder, Margret; Subke, Jörg; Widmayer, KarinThis tutorial will focus on the physical principles of kinematics and dynamics. After explaining the basic equations for point masses and rigid bodies a new approach for the dynamic simulation of multi-linked models with wobbling mass is presented, which has led to new insight in the field of biomechanics, but which has not been used in computer animation so far.Item Open Access Atomic beam splitters based on light(1993) Adams, Charles S.; Pfau, Tilman; Mlynek, JürgenIn this paper we review techniques to coherently split an atomic beam using the dipole force. We discuss the interaction of atoms with normal standing wave light field in the context of atomic beam splitters. The case where the atom enters the standing wave at a small angle such that Bragg diffraction and velocity selective resonances are observed is also considered. An alternative approach to realize a coherent beam splitter based on the optical Stem-Gerlach effect is discussed. Finally we consider the interaction of atoms with a magneto-optical potential formed by a polarization gradient light field and a static magnetic field. We show that the Stem-Gerlach effect and the magneto-optical potential produce a more effective beam splitting into states with high tranverse momentum than diffraction from a normal standing wave.Item Open Access Optical elements for atoms : a beamsplitter and a mirror(1993) Sigel, Martin; Pfau, Tilman; Adams, Charles S.; Kurtsiefer, Christian; Seifert, Werner; Heine, Claus; Mlynek, Jürgen; Kaiser, Robin; Aspect, AlainIn the first part of this article we attempt to provide a very brief introduction to atom optics. In the second and third part we report on recent experiments in our group on two specific atom-optical elements that may be useful in atom interferometers and atom cavities: the demonstration of a new beam splitter based on the diffraction of atomic matter waves from a "magneto-optical grating" and the investigation of a mirror based on the reflection of atoms from an evanescent light field.Item Open Access Diffraction of atoms from optical potentials(1994) Pfau, Tilman; Schnetz, Andreas; Adams, Charles S.; Kurtsiefer, Christian; Sigel, Martin; Mlynek, JürgenIn the first part of this article we attempt to provide a very brief introduction to atom optics. In the second part we report on a recent experiment in our group on an atom-optical element that may be useful in atom interferometers and atom cavities: the demonstration of a new beam splitter based on the diffraction of atomic matter waves from a "magneto-optical grating".Item Open Access Self-consistent numerical modelling of pulsar magnetospheres(1992) 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 self-consistent 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 Electric-field profiles in corona- or electron-beam-charged and thermally treated Teflon PTFE, FEP, and PFA films(1992) Gerhard-Multhaupt, Reimund; Eberle, Gernot; Xia, Zhongfou; Yang, Guomao; Eisenmenger, WolfgangCharge spreading in three different types of Teflon electrets was studied by means of piezoelectrically generated pressure steps, FEP and PFA samples corona-charged at room temperature usually exhibited only a surface charge layer. Uniform charge spreading throughout the bulk was found in FEP charged at or heated to high temperatures. Charge spreading was much less prominent in PFA because of a smaller retrapping efficiency. In PTFE (polytetrafluorethylene), charges from the surface and the rear electrode were injected into the bulk during charging at any temperature. Electron-beam-deposited charge layers broadened significantly upon heating.Item Open Access Fluid flow and heat transfer in an axially rotating pipe: the rotational entrance(1992) Weigand, Bernhard; Beer, HansThe complex interactions between turbulence and rotation in the rotational entrance region of a pipe, rotating about its axis, are examined. By assuming, a universal tangential velocity profile and with the use of a modified mixing length theory, the development of the axial velocIty profile and the heat transfer coefficient along the rotational entrance length are calculated. The theoretical results are compared with experimental flndings of Reich.Item Open Access Influence of magnetic order on optical properties of the heavy-electron antiferromagnets(1994) Degiorgi, Leonardo; Ott, Hans Rudolf; Grüner, George; Dressel, Martin; Fisk, ZacharyWe discuss the influence of antiferromagnetic order on optical properties of several heavy-electron systems. We find different electrodynamic responses of local magnetic moment and itinerant heavy-electron antiferromagnets.Item Open Access Atom interferometry with mechanical structures(1992) Sleator, Tycho; Carnal, Olivier; Pfau, Tilman; Faulstich, Andreas; Takuma, Hiroshi; Mlynek, JürgenWe present results on an interferometer for atoms based on Young's double-slit experiment. We also discuss proposed experiments in which the effect of spontaneous emission on the visibility of the atomic fringe pattern, as well as the effect of coherent atom-light interactions on the phase of the atomic wavefunction could be measured.Item Open Access Budding transition for bilayer fluid vesicles with area-difference elasticity(1992) Seifert, Udo; Miao, Ling; Döbereiner, Hans-Günther; Wortis, MichaelWe consider a curvature model for bilayer vesicles with an area-difference elasticity or non-local bending-energy term. Such a model interpolates between the bilayer-couple and spontaneous-curvature models. We report preliminary results for the budding transition. The shape transformation between the dumbbell and the pear phases can be continuous or discontinuous depending on the ratio of the non-local to the local bending rigidities.