1,067,150 research outputs found
Network Representation and Passivity of Delayed Teleoperation Systems
The paper proposes a general network based
analysis and design guidelines for teleoperation systems. The
electrical domain is appealing because it enjoys proficient analysis
and design tools and allows a one step higher abstraction
element, the network. Thus, in order to analyze the system by
means of network elements the mechanical system must be first
modeled as an electric circuit. Only then power ports become
apparent and networks can be defined. This kind of analysis
has been previously performed in systems with well defined
causalities, specially in the communication channel. Indeed,
a communication channel exchanging flow-like and effort-like
signals, as for instance velocity and computed force, has a
well defined causality and can thus be directly mapped as a
two-port electrical network. However, this is only one of the
many possible system architectures. This paper investigates how
other architectures, including those with ambiguous causalities,
can be modeled by means of networks, even in the lack of
flow or effort being transmitted, and how they can be made
passive for any communication channel characteristic (delay,
package-loss and jitter). The methods are exposed in the form
of design guidelines sustained with an example and validated
with experimental results
Multimode network representation of two dimensional steps in rectangular waveguides
In this paper a new Multimode Network representation for arbitrary rectangular waveguide junctions is presented. The energy coupling between the higher order modes excited in the junction is rigorously described via a multimode impedance matrix representation that can be used to build very efficient and accurate software tools for the analysis of complex structures. The elements of the impedance matrix are obtained from the solution of an integral equation. The main feature of the approach is that the kernel of the integral equation derived is essentially independent from frequency and therefore, the most time consuming task, namely the solution of the integral equation, need to be performed only once per each geometry. The formulation of the method is discussed and the form of the integral equation is given, showing explicitly the dependence with the frequency. A frequency extraction procedure that can lead to a considerable time saving for the analysis of complex structures is also discussed. Finally the design of a commercial communication satellite filter structure is presented, including comparisons between our analysis and measurements of the manufactured hardware
Who is the best player ever? A complex network analysis of the history of professional tennis
We consider all matches played by professional tennis players between 1968
and 2010, and, on the basis of this data set, construct a directed and weighted
network of contacts. The resulting graph shows complex features, typical of
many real networked systems studied in literature. We develop a diffusion
algorithm and apply it to the tennis contact network in order to rank
professional players. Jimmy Connors is identified as the best player of the
history of tennis according to our ranking procedure. We perform a complete
analysis by determining the best players on specific playing surfaces as well
as the best ones in each of the years covered by the data set. The results of
our technique are compared to those of two other well established methods. In
general, we observe that our ranking method performs better: it has a higher
predictive power and does not require the arbitrary introduction of external
criteria for the correct assessment of the quality of players. The present work
provides a novel evidence of the utility of tools and methods of network theory
in real applications.Comment: 10 pages, 4 figures, 4 table
Graph Theoretical Analysis of local ultraluminous infrared galaxies and quasars
We present a methodological framework for studying galaxy evolution by
utilizing Graph Theory and network analysis tools. We study the evolutionary
processes of local ultraluminous infrared galaxies (ULIRGs) and quasars and the
underlying physical processes, such as star formation and active galactic
nucleus (AGN) activity, through the application of Graph Theoretical analysis
tools. We extract, process and analyse mid-infrared spectra of local (z < 0.4)
ULIRGs and quasars between 5-38 microns through internally developed Python
routines, in order to generate similarity graphs, with the nodes representing
ULIRGs being grouped together based on the similarity of their spectra.
Additionally, we extract and compare physical features from the mid-IR spectra,
such as the polycyclic aromatic hydrocarbons (PAHs) emission and silicate depth
absorption features, as indicators of the presence of star-forming regions and
obscuring dust, in order to understand the underlying physical mechanisms of
each evolutionary stage of ULIRGs. Our analysis identifies five groups of local
ULIRGs based on their mid-IR spectra, which is quite consistent with the well
established fork classification diagram by providing a higher level
classification. We demonstrate how graph clustering algorithms and network
analysis tools can be utilized as unsupervised learning techniques for
revealing direct or indirect relations between various galaxy properties and
evolutionary stages, which provides an alternative methodology to previous
works for classification in galaxy evolution. Additionally, our methodology
compares the output of several graph clustering algorithms in order to
demonstrate the best-performing Graph Theoretical tools for studying galaxy
evolution.Comment: Accepted for publication in Astronomy and Computin
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