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Search Results: 1 - 10 of 206260 matches for " Matthias P. "
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Design of Wideband MIMO Car-to-Car Channel Models Based on the Geometrical Street Scattering Model
Nurilla Avazov,Matthias P?tzold
Modelling and Simulation in Engineering , 2012, DOI: 10.1155/2012/264213
Abstract: We propose a wideband multiple-input multiple-output (MIMO) car-to-car (C2C) channel model based on the geometrical street scattering model. Starting from the geometrical model, a MIMO reference channel model is derived under the assumption of single-bounce scattering in line-of-sight (LOS) and non-LOS (NLOS) propagation environments. The proposed channel model assumes an infinite number of scatterers, which are uniformly distributed in two rectangular areas located on both sides of the street. Analytical solutions are presented for the space-time-frequency cross-correlation function (STF-CCF), the two-dimensional (2D) space CCF, the time-frequency CCF (TF-CCF), the temporal autocorrelation function (ACF), and the frequency correlation function (FCF). An efficient sum-of-cisoids (SOCs) channel simulator is derived from the reference model. It is shown that the temporal ACF and the FCF of the SOC channel simulator fit very well to the corresponding correlation functions of the reference model. To validate the proposed channel model, the mean Doppler shift and the Doppler spread of the reference model have been matched to real-world measurement data. The comparison results demonstrate an excellent agreement between theory and measurements, which confirms the validity of the derived reference model. The proposed geometry-based channel simulator allows us to study the effect of nearby street scatterers on the performance of C2C communication systems. 1. Introduction C2C communications is an emerging technology, which receives considerable attention due to new traffic telematic applications that improve the efficiency of traffic flow and reduce the number of road accidents [1]. The development of C2C communication technologies is supported in Europe by respected organizations, such as the European Road Transport Telematics Implementation Coordinating Organization (ERTICO) [2] and the C2C Communication Consortium (C2C-CC) [3]. In this context, a large number of research projects focussing on C2C communications are currently being carried out throughout the world. In C2C communication systems, the underlying radio channel differs from traditional fixed-to-mobile and mobile-to-fixed channels in the way that both the transmitter and the receiver are in motion. In this connection, robust and reliable traffic telematic systems have to be developed and tested, which calls for new channel models for C2C communication systems. Furthermore, MIMO communication systems can also be of great interest for C2C communications due to their higher throughput [4]. In this
Pressure and Motion of Dry Sand -- Translation of Hagen's Paper from 1852
Brian P. Tighe,Matthias Sperl
Physics , 2006, DOI: 10.1007/s10035-006-0027-x
Abstract: In a remarkable paper from 1852, Gotthilf Heinrich Ludwig Hagen measured and explained two fundamental aspects of granular matter: The first effect is the saturation of pressure with depth in a static granular system confined by silo walls -- generally known as the Janssen effect. The second part of his paper describes the dynamics observed during the flow out of the container -- today often called the Beverloo law -- and forms the foundation of the hourglass theory. The following is a translation of the original German paper from 1852.
Transient stress evolution in repulsion and attraction dominated glasses
Christian P. Amann,Matthias Fuchs
Physics , 2014, DOI: 10.1122/1.4881256
Abstract: We present results from microscopic mode coupling theory generalized to colloidal dispersions under shear in an integration-through-transients formalism. Stress-strain curves in start-up shear, flow curves, and normal stresses are calculated with the equilibrium static structure factor as only input. Hard spheres close to their glass transition are considered, as are hard spheres with a short-ranged square-well attraction at their attraction dominated glass transition. The consequences of steric packing and physical bond formation on the linear elastic response, the stress release during yielding, and the steady plastic flow are discussed and compared to experimental data from concentrated model dispersions.
Overshoots in stress strain curves: Colloid experiments and schematic mode coupling theory
Christian P. Amann,Miriam Siebenbürger,Matthias Krüger,Fabian Weysser,Matthias Ballauff,Matthias Fuchs
Physics , 2012, DOI: 10.1122/1.4764000
Abstract: The stress versus strain curves in dense colloidal dispersions under start-up shear flow are investigated combining experiments on model core-shell microgels, computer simulations of hard disk mixtures, and mode coupling theory. In dense fluid and glassy states, the transient stresses exhibit first a linear increase with the accumulated strain, then a maximum ('stress overshoot') for strain values around 5%, before finally approaching the stationary value, which makes up the flow curve. These phenomena arise in well-equilibrated systems and for homogeneous flows, indicating that they are generic phenomena of the shear-driven transient structural relaxation. Microscopic mode coupling theory (generalized to flowing states by integration through the transients) derives them from the transient stress correlations, which first exhibit a plateau (corresponding to the solid-like elastic shear modulus) at intermediate times, and then negative stress correlations during the final decay. We introduce and validate a schematic model within mode coupling theory which captures all of these phenomena and handily can be used to jointly analyse linear and large-amplitude moduli, flow curves, and stress-strain curves. This is done by introducing a new strain- and time-dependent vertex into the relation between the the generalized shear modulus and the transient density correlator.
The Drosophila Cytosine-5 Methyltransferase Dnmt2 Is Associated with the Nuclear Matrix and Can Access DNA during Mitosis
Matthias Schaefer, Julia P. Steringer, Frank Lyko
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0001414
Abstract: Cytosine-5 methyltransferases of the Dnmt2 family are highly conserved in evolution and their biological function is being studied in several organisms. Although all structural DNA methyltransferase motifs are present in Dnmt2, these enzymes show a strong tRNA methyltransferase activity. In line with an enzymatic activity towards substrates other than DNA, Dnmt2 has been described to localize to the cytoplasm. Using molecular and biochemical approaches we show here that Dnmt2 is both a cytoplasmic and a nuclear protein. Sub-cellular fractionation shows that a significant amount of Dnmt2 is bound to the nuclear matrix. Sub-cellular localization analysis reveals that Dnmt2 proteins are enriched in actively dividing cells. Dnmt2 localization is highly dynamic during the cell cycle. Using live imaging we observed that Dnmt2-EGFP enters prophase nuclei and shows a spindle-like localization pattern during mitotic divisions. Additional experiments suggest that this localization is microtubule dependent and that Dnmt2 can access DNA during mitotic cell divisions. Our results represent the first comprehensive characterization of Dnmt2 proteins on the cellular level and have important implications for our understanding of the molecular activities of Dnmt2.
A Geometrical Three-Ring-Based Model for MIMO Mobile-to-Mobile Fading Channels in Cooperative Networks
Batool Talha,Matthias Pätzold
EURASIP Journal on Advances in Signal Processing , 2011, DOI: 10.1155/2011/892871
Abstract:
Two parity violating asymmetries from $n p \to d γ$ in pionless effective field theories
Matthias R. Schindler,Roxanne P. Springer
Physics , 2009, DOI: 10.1016/j.nuclphysa.2010.06.002
Abstract: We consider parity-violating observables from the processes $\vec n p\to d \gamma$ and $ np \to d \overset {\circlearrowleft}{\gamma}$. We perform calculations using pionless effective field theory both with and without explicit dibaryon fields. After combining these results with ones we have already obtained on parity-violating asymmetries in $\vec NN$ scattering, experimental input would in principle allow the extraction of all five parameters occurring at leading order in the parity-violating Lagrangian.
A Generic Random Number Generator Test Suite
Mario Ruetti,Matthias Troyer,Wesley P. Petersen
Physics , 2004,
Abstract: The heart of every Monte Carlo simulation is a source of high quality random numbers and the generator has to be picked carefully. Since the ``Ferrenberg affair'' it is known to a broad community that statistical tests alone do not suffice to determine the quality of a generator, but also application-based tests are needed. With the inclusion of an extensible random number library and the definition of a generic interface into the revised C++ standard it will be important to have access to an extensive C++ random number test suite. Most currently available test suites are limited to a subset of tests are written in Fortran or C and cannot easily be used with the C++ random number generator library.
Classification of Gauge Orbit Types for SU(n)-Gauge Theories
Gerd Rudolph,Matthias Schmidt,Igor P. Volobuev
Physics , 2000,
Abstract: A method for determining the orbit types of the action of the group of gauge transformations on the space of connections for gauge theories with gauge group SU(n) in space-time dimension d<=4 is presented. The method is based on the 1:1-correspondence between orbit types and holonomy-induced Howe subbundles of the underlying principal SU(n)-bundle. It is shown that the orbit types are labelled by certain cohomology elements of space-time satisfying two relations. Thus, for every principal SU(n)-bundle the corresponding stratification of the gauge orbit space can be determined explicitly. As an application, a criterion characterizing kinematical nodes for physical states in 2+1-dimensional Chern-Simons theory proposed by Asorey et al. is discussed.
Primary tunnel junction thermometry
Jukka P. Pekola,Tommy Holmqvist,Matthias Meschke
Physics , 2008, DOI: 10.1103/PhysRevLett.101.206801
Abstract: We describe the concept and experimental demonstration of primary thermometry based on a four probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future.
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