Space-Time Shear-Slip Mesh Update Method for Fluid-Structure Interaction Problems

Presentation (2013)

Many practical problems in engineering consist of a structure surrounded by a fluid. These are all from the theoretical point of view fluid-structure interaction problems, in which the movement of the ... [more ▼]

Many practical problems in engineering consist of a structure surrounded by a fluid. These are all from the theoretical point of view fluid-structure interaction problems, in which the movement of the structure influences the flow field of the fluid and vice versa. In this contribution the structure is described in a total Lagrangian representation based on velocities and the 2nd Piola-Kirchhoff stress state as primal variables in a hybrid-mixed formulation, while the fluid is modelled via the incompressible Navier-Stokes equations with velocities and pressure as unknowns. The governing equations of fluid and structural dynamics are uniformly discretised using space-time finite elements [1]. The discretised model equations of the fluid are stabilised using a SUPG/PSPG approach. Shape and test functions are continuous within the space-time slabs, while across the space- time slabs the shape and test functions are continuous only in space, but discontinuous in time yielding a time-discontinuous Galerkin approach. The space-time discretisation of the coupled system with velocities and pressure as remaining unknowns lays the basis for a mathematically profound analysis due to its methodical uniformity. During the mesh generation of the fluid-structure problem a fitting mesh at the conjoint interface of fluid and structure is generated ensuring natively the geometric continuity. In the discretised flow domain, which model equations are formulated in the Eulerian framework, a mesh-moving scheme needs to be applied to avoid severe mesh distortions. In case of large but regular structural displacements a discontinuous mesh-moving scheme like the Shear-Slip Mesh Update Method (SSMUM) is applicable [2]. In order to increase robustness and conservation behaviour of the classical SSMUM a modification based on the space-time discretisation of the problem described above is investigated. In the Space- Time SSMUM (ST-SSMUM) the alteration of the spatial connectivity takes place continuously in the space-time domain. By avoiding sudden changes in the spatial connectivity between two adjacent space-time slabs any difficulty in evaluating the jump term is circumvented. The properties of the introduced ST-SSMUM is shown by a computation of the flow field of a rotating impeller, which can be interpreted as a simplified water turbine or blood pump. [less ▲]

Space-Time Triplet Loss Network for Dynamic 3D Face Verification

Scientific Conference (2020)

In this paper, we propose a new approach for 3D dynamic face verification exploiting 3D facial deformations. First, 3D faces are encoded into low-dimensional representations describing the local ... [more ▼]

In this paper, we propose a new approach for 3D dynamic face verification exploiting 3D facial deformations. First, 3D faces are encoded into low-dimensional representations describing the local deformations of the faces with respect to a mean face. Second, the encoded versions of the 3D faces along a sequence are stacked into 2D arrays for temporal modeling. The resulting 2D arrays are then fed to a triplet loss network for dynamic sequence embedding. Finally, the outputs of the triplet loss network are compared using cosine similarity measure for face verification. By projecting the feature maps of the triplet loss network into attention maps on the 3D face sequences, we are able to detect the space-time patterns that contribute most to the pairwise similarity between differ-ent 3D facial expressions of the same person. The evaluation is conducted on the publicly available BU4D dataset which contains dynamic 3D face sequences. Obtained results are promising with respect to baseline methods. [less ▲]

Spaceborne Gravimetric Satellite Constellations and Ocean Tides: aliasing effects

in Geophysical Journal International (2010), (181), 789-805

Ocean tides redistribute mass at high temporal frequencies. Satellite missions that aim to observe medium to low frequency mass variations need to take into account this rapidly varying mass signal ... [more ▼]

Ocean tides redistribute mass at high temporal frequencies. Satellite missions that aim to observe medium to low frequency mass variations need to take into account this rapidly varying mass signal. Correcting for the effects of ocean tides by means of imperfect models might hamper the observation of other temporal gravity field signals of interest. This paper explores different methods for mitigating aliasing errors for the specific example of observing mass variations due to land hydrology, including temporal filtering of time-series of gravity solutions, spatial smoothing and the use of satellite constellations. For this purpose, an Earth System Model (ESM) was constructed, which included state-of-the-art time varying components for ocean, atmosphere, solid Earth, hydrology, ice-sheets and ocean tides. Using the ESM, we simulated the retrieval of the hydrologically driven gravity field changes using a number of different satellite constellations. We find that (1) the ocean tide aliasing strongly depends on the satellite constellation, the choice of orbital parameters and the length of the data span; (2) the aliasing effect manifests itself differently for different geographical regions; (3) the aliasing causes a peculiar striping pattern along the ground track of the satellite orbits; (4) optimizing the choice of orbital parameters of a single GRACE-type tandem can be more effective at reducing the aliasing of ocean tide model errors than flying more tandems. Finally, we corroborate the experiences with GRACE data analysis that appropriate post-processing techniques can significantly improve the quality of the retrieved gravity changes. [less ▲]

Spaceflight-associated changes in immunoglobulin VH gene expression in the amphibian Pleurodeles waltl

in FASEB Journal (2009), 23(5), 1607-1615

Understanding why the immune system is depressed during spaceflight is of obvious importance for future human deep-space missions, such as the foreseen missions to Mars. However, little is known about the ... [more ▼]

Understanding why the immune system is depressed during spaceflight is of obvious importance for future human deep-space missions, such as the foreseen missions to Mars. However, little is known about the effects of these flights on humoral immunity. We previously immunized adult Pleurodeles waltl (urodele amphibian) onboard the Mir space station and showed that heavy-chain variable (VH) domains of specific IgM antibodies are encoded by genes belonging to the VHII and VHVI families. We have now determined how these animals use their individual VHII and VHVI genes by screening IgM heavy-chain cDNA libraries and by quantifying IgM heavy-chain transcripts encoded by these genes. Results were compared with those obtained using control animals immunized on Earth under the same conditions as onboard Mir. Our experiments revealed an increase in the expression of IgM heavy-chain mRNAs encoded by the VHII and VHVI.C genes and a strong decrease in the expression of IgM heavy-chain mRNAs encoded by the VHVI.A and VHVI.B genes in spaceflight animals. Consequently, different heavy-chain mRNAs are expressed by spaceflight animals, demonstrating that this environment affects the humoral response. These observations may be due to a change in B-cell selection under spaceflight conditions. [less ▲]

Spaces and Identities

in IPSE (Ed.) Doing Identity. Subjektive Appropriations – Institutional Attributions – Socio-cultural Milieus (2011)

Spaces of the Border - a Practice-theoretical Cultural Studies Perspective in Border Studies

in Europa Regional (2015), 21(1-2), 60-71

This paper examines how practice-theoretical considerations can be linked with those of a spatial-theoretical nature and translated into a heuristic of spatial analysis from a cultural studies perspective ... [more ▼]

This paper examines how practice-theoretical considerations can be linked with those of a spatial-theoretical nature and translated into a heuristic of spatial analysis from a cultural studies perspective. This question focus results from the understanding that space should be regarded as an emergent aspect of the social and that it is still largely insufficiently defined in Border Studies. Drawing on a number of different spatial concepts, the paper first presents an action-theoretical notion of space and reformulates it in a practice-theoretical framework. It constitutes the point of departure for the development of the spaces of the border model with its analytical categories of social practices, practical knowledge as well as physical-material and social-structural aspects. The diversity of connections between these analytical categories have proven to be heuristically particularly useful. [less ▲]

Spaces: Approaches and Perspectives of Investigation

in Wille, Christian; Reckinger, Rachel; Kmec, Sonja (Eds.) et al Spaces and Identities in Border Regions. Politics – Media – Subjects (2016)

Ein spannendes Mosaik. Bevölkerungs- und Raumentwicklung in den USA.

in Kommune (2001), 19(7), 19-23

Spannungsfeld Berufsdomäne - Wirkt sich die Tätigkeit in einer Männer- oder Frauendomäne negativ auf das Karriereverhalten von Frauen und Männern aus?

in Zeitschrift für Sozialmanagement (2005), 3

Anhand von drei empirischen Studien wurde überprüft, welchen Einfluss die Tätigkeit in einer geschlechtsspezifischen Berufsdomäne (z. B. in einer Männer oder Frauendomäne) auf die Wahrnehmung und das ... [more ▼]

Anhand von drei empirischen Studien wurde überprüft, welchen Einfluss die Tätigkeit in einer geschlechtsspezifischen Berufsdomäne (z. B. in einer Männer oder Frauendomäne) auf die Wahrnehmung und das Erleben erwerbstätiger Männer und Frauen ausübt. Mittelpunkt der Untersuchung waren Erwerbstätige, die in einer Berufsdomäne tätig sind, die nicht mit ihrer Geschlechtsrolle übereinstimmt. [less ▲]

Spannungskopfschmerzen in der pädiatrischen Versorgung

in Pädiatrische praxis (2013)