1,520 research outputs found
The XII century towers, a benchmark of the Rome countryside almost cancelled. The safeguard plan by low cost uav and terrestrial DSM photogrammetry surveying and 3D Web GIS applications
“Giving a bird-fly look at the Rome countryside, throughout the Middle Age central period, it would show as if the multiple city
towers has been widely spread around the territory” on a radial range of maximum thirty kilometers far from the Capitol Hill center
(Carocci and Vendittelli, 2004).
This is the consequence of the phenomenon identified with the “Incasalamento” neologism, described in depth in the following
paper, intended as the general process of expansion of the urban society interests outside the downtown limits, started from the half
of the XII and developed through all the XIII century, slowing down and ending in the following years. From the XIX century till
today the architectural finds of this reality have raised the interest of many national and international scientists, which aimed to study
and catalog them all to create a complete framework that, cause of its extension, didn’t allow yet attempting any element by element
detailed analysis. From the described situation has started our plan of intervention, we will apply integrated survey methods and
technologies of terrestrial and UAV near stereo-photogrammetry, by the use of low cost drones, more than action cameras and reflex
on extensible rods, integrated and referenced with GPS and topographic survey. In the final project we intend to produce some 3D
scaled and textured surface models of any artifact (almost two hundreds were firstly observed still standing), to singularly study the
dimensions and structure, to analyze the building materials and details and to formulate an hypothesis about any function, based even
on the position along the territory. These models, successively georeferenced, will be imported into a 2D and 3D WebGIS and
organized in layers made visible on basemaps of reference, as much as on historical maps
Minimum Distance Distribution of Irregular Generalized LDPC Code Ensembles
In this paper, the minimum distance distribution of irregular generalized
LDPC (GLDPC) code ensembles is investigated. Two classes of GLDPC code
ensembles are analyzed; in one case, the Tanner graph is regular from the
variable node perspective, and in the other case the Tanner graph is completely
unstructured and irregular. In particular, for the former ensemble class we
determine exactly which ensembles have minimum distance growing linearly with
the block length with probability approaching unity with increasing block
length. This work extends previous results concerning LDPC and regular GLDPC
codes to the case where a hybrid mixture of check node types is used.Comment: 5 pages, 1 figure. Submitted to the IEEE International Symposium on
Information Theory (ISIT) 201
Spectral Shape of Check-Hybrid GLDPC Codes
This paper analyzes the asymptotic exponent of both the weight spectrum and
the stopping set size spectrum for a class of generalized low-density
parity-check (GLDPC) codes. Specifically, all variable nodes (VNs) are assumed
to have the same degree (regular VN set), while the check node (CN) set is
assumed to be composed of a mixture of different linear block codes (hybrid CN
set). A simple expression for the exponent (which is also referred to as the
growth rate or the spectral shape) is developed. This expression is consistent
with previous results, including the case where the normalized weight or
stopping set size tends to zero. Furthermore, it is shown how certain symmetry
properties of the local weight distribution at the CNs induce a symmetry in the
overall weight spectral shape function.Comment: 6 pages, 3 figures. Presented at the IEEE ICC 2010, Cape Town, South
Africa. A minor typo in equation (9) has been correcte
Growth Rate of the Weight Distribution of Doubly-Generalized LDPC Codes: General Case and Efficient Evaluation
The growth rate of the weight distribution of irregular doubly-generalized
LDPC (D-GLDPC) codes is developed and in the process, a new efficient numerical
technique for its evaluation is presented. The solution involves simultaneous
solution of a 4 x 4 system of polynomial equations. This represents the first
efficient numerical technique for exact evaluation of the growth rate, even for
LDPC codes. The technique is applied to two example D-GLDPC code ensembles.Comment: 6 pages, 1 figure. Proc. IEEE Globecom 2009, Hawaii, USA, November 30
- December 4, 200
Stability of Iterative Decoding of Multi-Edge Type Doubly-Generalized LDPC Codes Over the BEC
Using the EXIT chart approach, a necessary and sufficient condition is
developed for the local stability of iterative decoding of multi-edge type
(MET) doubly-generalized low-density parity-check (D-GLDPC) code ensembles. In
such code ensembles, the use of arbitrary linear block codes as component codes
is combined with the further design of local Tanner graph connectivity through
the use of multiple edge types. The stability condition for these code
ensembles is shown to be succinctly described in terms of the value of the
spectral radius of an appropriately defined polynomial matrix.Comment: 6 pages, 3 figures. Presented at Globecom 2011, Houston, T
Spectral Shape of Doubly-Generalized LDPC Codes: Efficient and Exact Evaluation
This paper analyzes the asymptotic exponent of the weight spectrum for
irregular doubly-generalized LDPC (D-GLDPC) codes. In the process, an efficient
numerical technique for its evaluation is presented, involving the solution of
a 4 x 4 system of polynomial equations. The expression is consistent with
previous results, including the case where the normalized weight or stopping
set size tends to zero. The spectral shape is shown to admit a particularly
simple form in the special case where all variable nodes are repetition codes
of the same degree, a case which includes Tanner codes; for this case it is
also shown how certain symmetry properties of the local weight distribution at
the CNs induce a symmetry in the overall weight spectral shape function.
Finally, using these new results, weight and stopping set size spectral shapes
are evaluated for some example generalized and doubly-generalized LDPC code
ensembles.Comment: 17 pages, 6 figures. To appear in IEEE Transactions on Information
Theor
Factors Influencing Chat-Based Cultural Discussions for Learning History in a 3D Virtual World
In a fast-changing world, there is an increasingly felt need to bring
what we teach and how we teach it intothe 21st Century. Learning@Europe is an attempt in this direction: a shared online virtual world where students from different European countries meet to play and learn about European history.
Chat-based discussions of study material, research homework to prepare in col-laboration with remote peers on online forums, team games and a cultural com-petition are the main ingredients of this innovative experience, already tested by over 6000 high-school students and teachers from 18 European countries. This paper focuses on a particular Learning@Europe activity – chat-based cultural discussions about history – and analyzes the elements that are essential to its success. Basing on evaluation data and our 3-years experience, we describe strategies deal with the different elements to be taken into account: Technology; Content; Interaction Design; and – mostimportant of all – Social Behavior
Reviewing Technological Solutions of Source Address Validation
It is essential to know the source IP address of a packet to prevent the IP spoofing attack which masquerades the sender\u27s true identity. If there is a way to trace back the origin of the massive DDoS attacks, we could find the responsible parties of the incidents and prevent future attacks by blocking them. Unfortunately, the original TCP/IP stacks don\u27t require the real source IP address to forward the packets to the destination. Malicious attackers can modify the source IP address to hide its true identity and able to send the fraudulent packets to the victim. One of the critical features of the next generation Internet is having a secure Internet which provides trust between participants and protects the privacy of the individuals. In this paper, we review the various approach to provide the source address validation (SAV) schemes. There are many new methods have been proposed, no single way is providing the comprehensive solution to this issue. Privacy is a critical issue to consider when the true identity is available on the network as well
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