2,399 research outputs found
Design, implementation and verification of the User Terminal Emulator for the Iris Verification TestBed
The present thesis results from an internship inside Thales Alenia Space Italia S.p.A. (TAS-I) located in Rome. Thales Alenia Space is an european leader for satellite systems and is a worldwide reference in telecoms, radar and optical Earth observation, defense and security, navigation and science.
TAS-I is the prime contractor of the Phase B of Iris Programme, the ESA project to develop a new satellite communication system for Air Traffic Management; in particular TAS-I is one of the contractors involved in the realization of the Verification TestBed (VTB) for the new Communication Standard (CS).
Our activities concerned the functional design of the logical component of the VTB and the software development of the User Terminal Emulator for the VTB itself. Precisely, we implemented a tool in C/C++ languages that emulates the UT resources assignment signalling protocol and the traffic flows management for several aircraft instances.
This application supplies TAS-I with a tool, as flexible as possible to adapt to the upcoming CS specifications and useful to resolve several trade-off by means of preliminary tests. Besides, it could be a comparison instrument to evaluate, in terms of software design and implementation, similar emulation frameworks which at the moment do not belong to TAS-I testbed heritage
Fast Hessenberg reduction of some rank structured matrices
We develop two fast algorithms for Hessenberg reduction of a structured
matrix where is a real or unitary diagonal
matrix and . The proposed algorithm for the
real case exploits a two--stage approach by first reducing the matrix to a
generalized Hessenberg form and then completing the reduction by annihilation
of the unwanted sub-diagonals. It is shown that the novel method requires
arithmetic operations and it is significantly faster than other
reduction algorithms for rank structured matrices. The method is then extended
to the unitary plus low rank case by using a block analogue of the CMV form of
unitary matrices. It is shown that a block Lanczos-type procedure for the block
tridiagonalization of induces a structured reduction on in a block
staircase CMV--type shape. Then, we present a numerically stable method for
performing this reduction using unitary transformations and we show how to
generalize the sub-diagonal elimination to this shape, while still being able
to provide a condensed representation for the reduced matrix. In this way the
complexity still remains linear in and, moreover, the resulting algorithm
can be adapted to deal efficiently with block companion matrices.Comment: 25 page
From approximating to interpolatory non-stationary subdivision schemes with the same generation properties
In this paper we describe a general, computationally feasible strategy to
deduce a family of interpolatory non-stationary subdivision schemes from a
symmetric non-stationary, non-interpolatory one satisfying quite mild
assumptions. To achieve this result we extend our previous work [C.Conti,
L.Gemignani, L.Romani, Linear Algebra Appl. 431 (2009), no. 10, 1971-1987] to
full generality by removing additional assumptions on the input symbols. For
the so obtained interpolatory schemes we prove that they are capable of
reproducing the same exponential polynomial space as the one generated by the
original approximating scheme. Moreover, we specialize the computational
methods for the case of symbols obtained by shifted non-stationary affine
combinations of exponential B-splines, that are at the basis of most
non-stationary subdivision schemes. In this case we find that the associated
family of interpolatory symbols can be determined to satisfy a suitable set of
generalized interpolating conditions at the set of the zeros (with reversed
signs) of the input symbol. Finally, we discuss some computational examples by
showing that the proposed approach can yield novel smooth non-stationary
interpolatory subdivision schemes possessing very interesting reproduction
properties
Language-based sensing descriptors for robot object grounding
In this work, we consider an autonomous robot that is required
to understand commands given by a human through natural language.
Specifically, we assume that this robot is provided with an internal
representation of the environment. However, such a representation is unknown
to the user. In this context, we address the problem of allowing a
human to understand the robot internal representation through dialog.
To this end, we introduce the concept of sensing descriptors. Such representations
are used by the robot to recognize unknown object properties
in the given commands and warn the user about them. Additionally, we
show how these properties can be learned over time by leveraging past
interactions in order to enhance the grounding capabilities of the robot
Exponential Splines and Pseudo-Splines: Generation versus reproduction of exponential polynomials
Subdivision schemes are iterative methods for the design of smooth curves and
surfaces. Any linear subdivision scheme can be identified by a sequence of
Laurent polynomials, also called subdivision symbols, which describe the linear
rules determining successive refinements of coarse initial meshes. One
important property of subdivision schemes is their capability of exactly
reproducing in the limit specific types of functions from which the data is
sampled. Indeed, this property is linked to the approximation order of the
scheme and to its regularity. When the capability of reproducing polynomials is
required, it is possible to define a family of subdivision schemes that allows
to meet various demands for balancing approximation order, regularity and
support size. The members of this family are known in the literature with the
name of pseudo-splines. In case reproduction of exponential polynomials instead
of polynomials is requested, the resulting family turns out to be the
non-stationary counterpart of the one of pseudo-splines, that we here call the
family of exponential pseudo-splines. The goal of this work is to derive the
explicit expressions of the subdivision symbols of exponential pseudo-splines
and to study their symmetry properties as well as their convergence and
regularity.Comment: 25 page
Teaching robots parametrized executable plans through spoken interaction
While operating in domestic environments, robots will necessarily
face difficulties not envisioned by their developers at programming
time. Moreover, the tasks to be performed by a robot will often
have to be specialized and/or adapted to the needs of specific users
and specific environments. Hence, learning how to operate by interacting
with the user seems a key enabling feature to support the
introduction of robots in everyday environments.
In this paper we contribute a novel approach for learning, through
the interaction with the user, task descriptions that are defined as a
combination of primitive actions. The proposed approach makes
a significant step forward by making task descriptions parametric
with respect to domain specific semantic categories. Moreover, by
mapping the task representation into a task representation language,
we are able to express complex execution paradigms and to revise
the learned tasks in a high-level fashion. The approach is evaluated
in multiple practical applications with a service robot
Block Tridiagonal Reduction of Perturbed Normal and Rank Structured Matrices
It is well known that if a matrix solves the
matrix equation , where is a linear bivariate polynomial,
then is normal; and can be simultaneously reduced in a finite
number of operations to tridiagonal form by a unitary congruence and, moreover,
the spectrum of is located on a straight line in the complex plane. In this
paper we present some generalizations of these properties for almost normal
matrices which satisfy certain quadratic matrix equations arising in the study
of structured eigenvalue problems for perturbed Hermitian and unitary matrices.Comment: 13 pages, 3 figure
A CMV--based eigensolver for companion matrices
In this paper we present a novel matrix method for polynomial rootfinding. By
exploiting the properties of the QR eigenvalue algorithm applied to a suitable
CMV-like form of a companion matrix we design a fast and computationally simple
structured QR iteration.Comment: 14 pages, 4 figure
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