1,062 research outputs found
Perturbation Analysis of the Kuramoto Phase Diffusion Equation Subject to Quenched Frequency Disorder
The Kuramoto phase diffusion equation is a nonlinear partial differential
equation which describes the spatio-temporal evolution of a phase variable in
an oscillatory reaction diffusion system. Synchronization manifests itself in a
stationary phase gradient where all phases throughout a system evolve with the
same velocity, the synchronization frequency. The formation of concentric waves
can be explained by local impurities of higher frequency which can entrain
their surroundings. Concentric waves in synchronization also occur in
heterogeneous systems, where the local frequencies are distributed randomly. We
present a perturbation analysis of the synchronization frequency where the
perturbation is given by the heterogeneity of natural frequencies in the
system. The nonlinearity in form of dispersion, leads to an overall
acceleration of the oscillation for which the expected value can be calculated
from the second order perturbation terms. We apply the theory to simple
topologies, like a line or the sphere, and deduce the dependence of the
synchronization frequency on the size and the dimension of the oscillatory
medium. We show that our theory can be extended to include rotating waves in a
medium with periodic boundary conditions. By changing a system parameter the
synchronized state may become quasi degenerate. We demonstrate how perturbation
theory fails at such a critical point.Comment: 22 pages, 5 figure
Geology orbiter comparison study
Instrument requirements of planetary geology orbiters were examined with the objective of determining the feasibility of applying standard instrument designs to a host of terrestrial targets. Within the basic discipline area of geochemistry, gamma-ray, X-ray fluorescence, and atomic spectroscopy remote sensing techniques were considered. Within the discipline area of geophysics, the complementary techniques of gravimetry and radar were studied. Experiments using these techniques were analyzed for comparison at the Moon, Mercury, Mars and the Galilean satellites. On the basis of these comparative assessments, the adaptability of each sensing technique was judged as a basic technique for many targets, as a single instrument applied to many targets, as a single instrument used in different mission modes, and as an instrument capability for nongeoscience objectives
Recommended from our members
Altered chemomechanical coupling causes impaired motility of the kinesin-4 motors KIF27 and KIF7.
Kinesin-4 motors play important roles in cell division, microtubule organization, and signaling. Understanding how motors perform their functions requires an understanding of their mechanochemical and motility properties. We demonstrate that KIF27 can influence microtubule dynamics, suggesting a conserved function in microtubule organization across the kinesin-4 family. However, kinesin-4 motors display dramatically different motility characteristics: KIF4 and KIF21 motors are fast and processive, KIF7 and its Drosophila melanogaster homologue Costal2 (Cos2) are immotile, and KIF27 is slow and processive. Neither KIF7 nor KIF27 can cooperate for fast processive transport when working in teams. The mechanistic basis of immotile KIF7 behavior arises from an inability to release adenosine diphosphate in response to microtubule binding, whereas slow processive KIF27 behavior arises from a slow adenosine triphosphatase rate and a high affinity for both adenosine triphosphate and microtubules. We suggest that evolutionarily selected sequence differences enable immotile KIF7 and Cos2 motors to function not as transporters but as microtubule-based tethers of signaling complexes
Epidemic Dynamics on an Adaptive Network
Many real world networks are characterized by adaptive changes in their
topology depending on the dynamic state of their nodes. Here we study epidemic
dynamics in an adaptive network, where susceptibles are able to avoid contact
with infected by rewiring their network connections. We demonstrate that
adaptive rewiring has profound consequences for the emerging network structure,
giving rise to assortative degree correlation and a separation into two loosely
connected sub-compartments. This leads to dynamics such as oscillations,
hysteresis and 1st order transitions. We describe the system in terms of a
simple model using a pair-approximation and present a full local bifurcation
analysis. Our results indicate that the interplay between dynamics and topology
can have important consequences for the spreading of infectious diseases and
related applications.Comment: 4 pages, 4 figures, final versio
Network synchronization of groups
In this paper we study synchronized motions in complex networks in which
there are distinct groups of nodes where the dynamical systems on each node
within a group are the same but are different for nodes in different groups.
Both continuous time and discrete time systems are considered. We initially
focus on the case where two groups are present and the network has bipartite
topology (i.e., links exist between nodes in different groups but not between
nodes in the same group). We also show that group synchronous motions are
compatible with more general network topologies, where there are also
connections within the groups
Coexistence of ferromagnetism and superconductivity in the hybrid ruthenate-cuprate compound RuSr_2GdCu_2O_8 studied by muon spin rotation (\mu SR) and DC-magnetization
We have investigated the magnetic and the superconducting properties of the
hybrid ruthenate-cuprate compound RuSr_{2}GdCu_{2}O_{8} by means of zero-field
muon spin rotation- (ZF-SR) and DC magnetization measurements. The
DC-magnetisation data establish that this material exhibits ferromagnetic order
of the Ru-moments () below T_{Curie} = 133 K and
becomes superconducting at a much lower temperature T_c = 16 K. The ZF-SR
experiments indicate that the ferromagnetic phase is homogeneous on a
microscopic scale and accounts for most of the sample volume. They also suggest
that the magnetic order is not significantly modified at the onset of
superconductivity.Comment: improved version submitted to Phys. Rev.
The friction factor of two-dimensional rough-boundary turbulent soap film flows
We use momentum transfer arguments to predict the friction factor in
two-dimensional turbulent soap-film flows with rough boundaries (an analogue of
three-dimensional pipe flow) as a function of Reynolds number Re and roughness
, considering separately the inverse energy cascade and the forward
enstrophy cascade. At intermediate Re, we predict a Blasius-like friction
factor scaling of in flows dominated by the
enstrophy cascade, distinct from the energy cascade scaling of
. For large Re, in the enstrophy-dominated case.
We use conformal map techniques to perform direct numerical simulations that
are in satisfactory agreement with theory, and exhibit data collapse scaling of
roughness-induced criticality, previously shown to arise in the 3D pipe data of
Nikuradse.Comment: 4 pages, 3 figure
The complex network of global cargo ship movements
Transportation networks play a crucial role in human mobility, the exchange
of goods, and the spread of invasive species. With 90% of world trade carried
by sea, the global network of merchant ships provides one of the most important
modes of transportation. Here we use information about the itineraries of
16,363 cargo ships during the year 2007 to construct a network of links between
ports. We show that the network has several features which set it apart from
other transportation networks. In particular, most ships can be classified in
three categories: bulk dry carriers, container ships and oil tankers. These
three categories do not only differ in the ships' physical characteristics, but
also in their mobility patterns and networks. Container ships follow regularly
repeating paths whereas bulk dry carriers and oil tankers move less predictably
between ports. The network of all ship movements possesses a heavy-tailed
distribution for the connectivity of ports and for the loads transported on the
links with systematic differences between ship types. The data analyzed in this
paper improve current assumptions based on gravity models of ship movements, an
important step towards understanding patterns of global trade and bioinvasion.Comment: 7 figures Accepted for publication by Journal of the Royal Society
Interface (2010) For supplementary information, see
http://www.icbm.de/~blasius/publications.htm
Momentum and Heat Transfer in a Laminar Boundary Layer with Slip Flow
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77059/1/AIAA-22968-756.pd
Multimodality in Aerodynamic Wing Design Optimization
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143093/1/6.2017-3753.pd
- …