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.

Implementation of simplified chemical kinetics based on intrinsic low-dimensional manifolds

Abstract: A general procedure for simplifying chemical kinetics and its use in reacting flow models is developed, which is based on the dynamical systems approach. In contrast to conventional reduced mechanisms no information is required concerning which reactions are to be assumed to be in partial equilibrium nor which species are assumed to be in steady state. Based on a local eigenvector analysis, the method identifies the fast time scales of the chemical reaction systems, which differ typically by orders of magnitude. Assuming that the fastest relaxation processes in chemical reactions proceed infinitely fast (i.e., are in local equilibrium), it is then possible to reduce the state space globally, such that it can be described by means of only a small number of reaction progress variables. The only “inputs” to the procedure are the detailed kinetics mechanism and the number of degrees of freedom required in the simplified scheme. Then the state properties given by the simplified scheme are automatically determined as functions of the coordinates associated with the degrees of freedom. A tabulation procedure allows an efficient use of the results in CFD codes. Furthermore a general procedure for coupling the reduced mechanism with other than chemical processes like flow and molecular transport is discussed. Results are presented for the CO/H2/air system both for a simple homogeneous closed system and a flow reactor.

Implantation of labelled single nitrogen vacancy centers in diamond using N15

Abstract: Nitrogen-vacancy (NV−) color centers in diamond were created by implantation of 7 keV N15(I=1∕2) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of single NV− centers. The hyperfine spectrum from NV−15 arising from implanted N15 can be distinguished from NV−14 centers created by native N14(I=1) sites. Analysis indicates 1 in 40 implanted N15 atoms give rise to an optically observable NV−15 center. This report ultimately demonstrates a mechanism by which the yield of NV− center formation by nitrogen implantation can be measured.

The Meaning Structure of Social Networks

Abstract: This essay proposes to view networks as sociocultural structures. Following authors from Leopold von Wiese and Norbert Elias to Gary Alan Fine and Harrison White, networks are configurations of social relationships interwoven with meaning. Social relationships as the basic building blocks of networks are conceived of as dynamic structures of reciprocal (but not necessarily symmetric) expectations between alter and ego. Through their transactions, alter and ego construct an idiosyncratic “relationship culture” comprising symbols, narratives, and relational identities. The coupling of social relationships to networks, too, is heavily laden with meaning. The symbolic construction of persons is one instance of this coupling. Another instance is the application of social categories (like race or gender), which both map and structure social networks. The conclusion offers an agenda for research on this “meaning structure of social networks.”