University of Stuttgart

About: University of Stuttgart is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Laser & Finite element method. The organization has 27715 authors who have published 56370 publications receiving 1363382 citations. The organization is also known as: Universität Stuttgart.

Resolving the nanoscale adhesion of individual gecko spatulae by atomic force microscopy

Abstract: Animals that cling to walls and walk on ceilings owe this ability to micrometre and nanoscale attachment elements. The highest adhesion forces are encountered in geckoes, which have developed intricate hierarchical structures consisting of toes (millimetre dimensions), lamella (400-600microm size), setae (micrometre dimensions) and spatulae ( approximately 200nm size). Adhesion forces of setae on different substrates have previously been measured by a micro-electromechanical system technique. Here we report the first successful experiments in which the force-displacement curves were determined for individual spatulae by atomic force microscopy. The adhesion force for these smallest elements of the gecko's attachment system is reproducibly found to be about 10nN. This method sheds new light on the nanomechanisms of attachment and will help in the rational design of artificial attachment systems.

Cavity-enhanced localized plasmon resonance sensing

Abstract: We present a method to enhance the sensing properties of a localized plasmon sensor. The concept is based on the combination of localized plasmons in nanostructures and a photonic microcavity. Metal nanorods that are placed at Bragg distance above a metal mirror form a Fabry–Perot microcavity and constitute a coupled photonic-plasmonic system. The localized plasmon resonances of the nanorods and the phase shifts upon plasmon excitation are extremely sensitive to changes in the refractive index of the material surrounding the nanorods. Compared to the plasmonic nanorods alone, the coupled photonic-plasmonic system allows for a much more sensitive detection of small refractive index changes.

Failure mechanisms of additively manufactured porous biomaterials: Effects of porosity and type of unit cell

Abstract: Since the advent of additive manufacturing techniques, regular porous biomaterials have emerged as promising candidates for tissue engineering scaffolds owing to their controllable pore architecture and feasibility in producing scaffolds from a variety of biomaterials. The architecture of scaffolds could be designed to achieve similar mechanical properties as in the host bone tissue, thereby avoiding issues such as stress shielding in bone replacement procedure. In this paper, the deformation and failure mechanisms of porous titanium (Ti6Al4V) biomaterials manufactured by selective laser melting from two different types of repeating unit cells, namely cubic and diamond lattice structures, with four different porosities are studied. The mechanical behavior of the above-mentioned porous biomaterials was studied using finite element models. The computational results were compared with the experimental findings from a previous study of ours. The Johnson–Cook plasticity and damage model was implemented in the finite element models to simulate the failure of the additively manufactured scaffolds under compression. The computationally predicted stress–strain curves were compared with the experimental ones. The computational models incorporating the Johnson–Cook damage model could predict the plateau stress and maximum stress at the first peak with less than 18% error. Moreover, the computationally predicted deformation modes were in good agreement with the results of scaling law analysis. A layer-by-layer failure mechanism was found for the stretch-dominated structures, i.e. structures made from the cubic unit cell, while the failure of the bending-dominated structures, i.e. structures made from the diamond unit cells, was accompanied by the shearing bands of 45°.

Dynamics of Droplets

Abstract: 1. Theory.- 2. Droplet Generation.- 3. Droplet Systems.- 4. Experimental and Measurement Techniques.- 5. Experiments to Study Mechanical Interactions.- 6. Experiments to Study Phase Transition Processes.- 7. Miscellaneous Applications.- References.

Priority management in ATM switching nodes

Abstract: Various space priority mechanisms and their detailed performance evaluation are described. A comparative performance study is given, indicating the excellent performance characteristics of a simple buffer management scheme called partial buffer sharing. The introduction of a second bearer capability provides a 10/sup -6/ cell loss rate instead of 10/sup -10/. >