Reports de recerca
http://hdl.handle.net/2117/5506
Tue, 30 May 2017 03:55:23 GMT2017-05-30T03:55:23ZMultisided patches
http://hdl.handle.net/2117/97925
Multisided patches
Pla García, Núria; Vigo Anglada, Marc; Cotrina Navau, Josep
We present a method to construct a patch of parametric surface of degree k + 1 that lls a n-sided hole, with n bigger than 2, and whose boundary coincides with a B-Spline, thus, the resulting patch can be easily connected with given B-Spline surfaces with xed continuity conditions. The method is inspired on a generic approach to construct free form surfaces, which gives a family of practical schemes to design surfaces from an arbitrary given mesh, using the di erentiable manifold theory. The input is a star shaped mesh which describes a generic n-hole and a surface in a neighborhood of the hole. The main advantages of the method are the following: arbitrary order k continuity conditions can be imposed; the involved hole can have an arbitrary number of sides and arbitrary shape (convex or not); the simplicity of the construction process gives an easy and exible method; and nally, the surface near the boundary is a B-Spline with piecewise uniform knot sequences and whose control points are vertices of the given mesh; both knot sequences and control points are easily computed. Implementation details to evaluate a surface point are given, showing that the de Boor algorithm can be exploited for efficiency.
Fri, 09 Dec 2016 10:50:42 GMThttp://hdl.handle.net/2117/979252016-12-09T10:50:42ZPla García, NúriaVigo Anglada, MarcCotrina Navau, JosepWe present a method to construct a patch of parametric surface of degree k + 1 that lls a n-sided hole, with n bigger than 2, and whose boundary coincides with a B-Spline, thus, the resulting patch can be easily connected with given B-Spline surfaces with xed continuity conditions. The method is inspired on a generic approach to construct free form surfaces, which gives a family of practical schemes to design surfaces from an arbitrary given mesh, using the di erentiable manifold theory. The input is a star shaped mesh which describes a generic n-hole and a surface in a neighborhood of the hole. The main advantages of the method are the following: arbitrary order k continuity conditions can be imposed; the involved hole can have an arbitrary number of sides and arbitrary shape (convex or not); the simplicity of the construction process gives an easy and exible method; and nally, the surface near the boundary is a B-Spline with piecewise uniform knot sequences and whose control points are vertices of the given mesh; both knot sequences and control points are easily computed. Implementation details to evaluate a surface point are given, showing that the de Boor algorithm can be exploited for efficiency.N-sided patches with B-spline boundaries
http://hdl.handle.net/2117/97827
N-sided patches with B-spline boundaries
Cotrina Navau, Josep; Pla García, Núria; Vigo Anglada, Marc
We present a method to construct a patch of parametric surface of
degree k+1 that fills a n-sided hole, with bigger than 2, and whose
boundary coincides with a B-Spline, thus, the resulting patch can be
easily connected with given B-Spline surfaces with fixed continuity
conditions. The method is based on the generic approach by the same
authors to con-struct free form surfaces, which gives a family of
practical schemes to design surfaces from an arbitrary given mesh,
using the differentiable manifold the-ory. The proposal uses a star
shaped mesh which describes a generic n-hole and a surface in a
neighborhood of the hole. From this mesh, a set of charts is defined,
one associated to each vertex or face of the mesh, depending on the
parity of the input parameter k. A basis function and a control point
is defined from each chart, and the surface is obtained as a
baricentric combination of the control points using the defined basis
functions. The main advantages of the method are the following:
arbitrary order k continuity conditions can be imposed; the involved
hole can have an arbitrary number of sides and arbitrary shape (convex
or not) the simplicity of the construction process gives an easy and
flexible method; and finally, the surface near the boundary is a
B-Spline with piecewise uniform knot sequences and whose control
points are vertices of the given mesh. Implementation details to
evaluate a surface point are given, showing that the de Boor algorithm
can be exploited for efficiency.
Wed, 07 Dec 2016 10:03:03 GMThttp://hdl.handle.net/2117/978272016-12-07T10:03:03ZCotrina Navau, JosepPla García, NúriaVigo Anglada, MarcWe present a method to construct a patch of parametric surface of
degree k+1 that fills a n-sided hole, with bigger than 2, and whose
boundary coincides with a B-Spline, thus, the resulting patch can be
easily connected with given B-Spline surfaces with fixed continuity
conditions. The method is based on the generic approach by the same
authors to con-struct free form surfaces, which gives a family of
practical schemes to design surfaces from an arbitrary given mesh,
using the differentiable manifold the-ory. The proposal uses a star
shaped mesh which describes a generic n-hole and a surface in a
neighborhood of the hole. From this mesh, a set of charts is defined,
one associated to each vertex or face of the mesh, depending on the
parity of the input parameter k. A basis function and a control point
is defined from each chart, and the surface is obtained as a
baricentric combination of the control points using the defined basis
functions. The main advantages of the method are the following:
arbitrary order k continuity conditions can be imposed; the involved
hole can have an arbitrary number of sides and arbitrary shape (convex
or not) the simplicity of the construction process gives an easy and
flexible method; and finally, the surface near the boundary is a
B-Spline with piecewise uniform knot sequences and whose control
points are vertices of the given mesh. Implementation details to
evaluate a surface point are given, showing that the de Boor algorithm
can be exploited for efficiency.Towards free form surfaces
http://hdl.handle.net/2117/97654
Towards free form surfaces
Cotrina Navau, Josep; Pla García, Núria; Vigo Anglada, Marc
A theoretical approach to construct free form surfaces is presented. We
develop the conceps that arise when a free form surface is generated by
tracing a mesh, using differentiable manifold theory, and generalizing
the B-spline scheme. This approach allows to define a family of
practical schemes.
Thu, 01 Dec 2016 18:18:08 GMThttp://hdl.handle.net/2117/976542016-12-01T18:18:08ZCotrina Navau, JosepPla García, NúriaVigo Anglada, MarcA theoretical approach to construct free form surfaces is presented. We
develop the conceps that arise when a free form surface is generated by
tracing a mesh, using differentiable manifold theory, and generalizing
the B-spline scheme. This approach allows to define a family of
practical schemes.MALLBA: a library of skeletons for combinatorial optimisation
http://hdl.handle.net/2117/97560
MALLBA: a library of skeletons for combinatorial optimisation
Alba, E; Almeida, F; Blesa Aguilera, Maria Josep; Cabeza, J; Cotta, C; Díaz, M; Dorta, I; Gabarró Vallès, Joaquim; León, C; Luna Garcia, Jesus; Moreno Boronat, Lidia Ana; Pablos, C; Petit Silvestre, Jordi; Rojas Espinosa, Alfonso; Xhafa Xhafa, Fatos
The MALLBA project tackles the resolution of combinatorial
optimization
problems using algorithmic skeletons implemented in C++.
MALLBA offers three
families of generic resolution methods: exact, heuristic and
hybrid. Moreover,
for each resolution method, MALLBA provides three different
implementations:
sequential, parallel for local area networks, and parallel
for wide area
networks (currently under development). This paper shows
the architecture of
the MALLBA library, presents some of its skeletons and
offers several
computational results to show the viability of the approach.
Wed, 30 Nov 2016 16:50:04 GMThttp://hdl.handle.net/2117/975602016-11-30T16:50:04ZAlba, EAlmeida, FBlesa Aguilera, Maria JosepCabeza, JCotta, CDíaz, MDorta, IGabarró Vallès, JoaquimLeón, CLuna Garcia, JesusMoreno Boronat, Lidia AnaPablos, CPetit Silvestre, JordiRojas Espinosa, AlfonsoXhafa Xhafa, FatosThe MALLBA project tackles the resolution of combinatorial
optimization
problems using algorithmic skeletons implemented in C++.
MALLBA offers three
families of generic resolution methods: exact, heuristic and
hybrid. Moreover,
for each resolution method, MALLBA provides three different
implementations:
sequential, parallel for local area networks, and parallel
for wide area
networks (currently under development). This paper shows
the architecture of
the MALLBA library, presents some of its skeletons and
offers several
computational results to show the viability of the approach.Free form surfaces
http://hdl.handle.net/2117/95949
Free form surfaces
Cotrina Navau, Josep; Pla García, Núria
A method to construct continuous order k surfaces of arbitrary
topological type by tracing a mesh that represents a 2-manifold is
presented. The presented approach constructs the surface from a
collection of pieces which overlap, using the known technology of
manifolds. The surface is built from the given mesh and two arbitrary
input parameters, k and n. The value of k gives the continuity of the
resulting surface and n controls the local influence of the vertices
of the mesh. The presented scheme generalizes the B-spline approach
in terms of manifolds. The surface that arises from regular zones of
the mesh is a tensorial product B-spline surface. For the rest, that
is, the irregular zones, the surface has the following good
properties: it is k continuous, affine invariant, the convex hull
property is guaranteed, and it has local control. The algorithm is
simple and efficient in time and space.
Wed, 09 Nov 2016 12:52:04 GMThttp://hdl.handle.net/2117/959492016-11-09T12:52:04ZCotrina Navau, JosepPla García, NúriaA method to construct continuous order k surfaces of arbitrary
topological type by tracing a mesh that represents a 2-manifold is
presented. The presented approach constructs the surface from a
collection of pieces which overlap, using the known technology of
manifolds. The surface is built from the given mesh and two arbitrary
input parameters, k and n. The value of k gives the continuity of the
resulting surface and n controls the local influence of the vertices
of the mesh. The presented scheme generalizes the B-spline approach
in terms of manifolds. The surface that arises from regular zones of
the mesh is a tensorial product B-spline surface. For the rest, that
is, the irregular zones, the surface has the following good
properties: it is k continuous, affine invariant, the convex hull
property is guaranteed, and it has local control. The algorithm is
simple and efficient in time and space.Modelling surfaces from planar irregular meshes
http://hdl.handle.net/2117/84371
Modelling surfaces from planar irregular meshes
Cotrina Navau, Josep; Pla García, Núria
We present a method for constructing surfaces from irregular control
meshes that can be embedded in the plane. This method results from a
generalization of B-Splines using the known technology of
manifolds. The resulting surface can be built with {GC}^k
continuity.
The presented approach constructs the surface from a collection of
pieces which overlap. This method can be generalized to arbitrary
meshes to generate general closed surfaces or surfaces with handles by
application of an analogous reasoning locally in a general case.
Tue, 15 Mar 2016 12:17:37 GMThttp://hdl.handle.net/2117/843712016-03-15T12:17:37ZCotrina Navau, JosepPla García, NúriaWe present a method for constructing surfaces from irregular control
meshes that can be embedded in the plane. This method results from a
generalization of B-Splines using the known technology of
manifolds. The resulting surface can be built with {GC}^k
continuity.
The presented approach constructs the surface from a collection of
pieces which overlap. This method can be generalized to arbitrary
meshes to generate general closed surfaces or surfaces with handles by
application of an analogous reasoning locally in a general case.Current Trends of Topology Discovery in OpenFlow-based Software Defined Networks
http://hdl.handle.net/2117/77672
Current Trends of Topology Discovery in OpenFlow-based Software Defined Networks
Ochoa Aday, Leonardo; Cervelló Pastor, Cristina; Fernández Fernández, Adriana
The explosion of Internet services such as video on demand, big data, server virtualization and cloud services is among the trends driving the networking industry to change traditional network architectures to more flexible and dynamic schemes.
Software Defined Networking is an emerging network architecture that could address the needs of services providers and networks operator. This new technology consist in decoupling the control plane from the data plane, enabling to centralize control functions in a concentrated or distributed platform. It also creates an abstraction between the network infrastructure and network applications that allows to design more flexible and programmable networks. However, in order to both services and network applications can run properly, a global and updated view of the network is required at every moment.
This paper attempts to address the main protocols and approaches of the topology discovery service provided by the controller in a single administrative domain. Also the procedure of topology discovery in a network composed by non-OpenFlow and OpenFlow switches are presented. In addition, attention is focused on Layer 2 discovery protocols LLDP and BDDP and major limitations of these procedures are discussed.
Wed, 14 Oct 2015 10:06:26 GMThttp://hdl.handle.net/2117/776722015-10-14T10:06:26ZOchoa Aday, LeonardoCervelló Pastor, CristinaFernández Fernández, AdrianaThe explosion of Internet services such as video on demand, big data, server virtualization and cloud services is among the trends driving the networking industry to change traditional network architectures to more flexible and dynamic schemes.
Software Defined Networking is an emerging network architecture that could address the needs of services providers and networks operator. This new technology consist in decoupling the control plane from the data plane, enabling to centralize control functions in a concentrated or distributed platform. It also creates an abstraction between the network infrastructure and network applications that allows to design more flexible and programmable networks. However, in order to both services and network applications can run properly, a global and updated view of the network is required at every moment.
This paper attempts to address the main protocols and approaches of the topology discovery service provided by the controller in a single administrative domain. Also the procedure of topology discovery in a network composed by non-OpenFlow and OpenFlow switches are presented. In addition, attention is focused on Layer 2 discovery protocols LLDP and BDDP and major limitations of these procedures are discussed.Economía de la accesibilidad 20+20 : marco teórico
http://hdl.handle.net/2117/16429
Economía de la accesibilidad 20+20 : marco teórico
Guasch Murillo, Daniel; Berbegal Mirabent, Jasmina; Villalta, Marta
Wed, 05 Sep 2012 07:41:05 GMThttp://hdl.handle.net/2117/164292012-09-05T07:41:05ZGuasch Murillo, DanielBerbegal Mirabent, JasminaVillalta, MartaHierarchical categorisation of web tags for Delicious
http://hdl.handle.net/2117/13884
Hierarchical categorisation of web tags for Delicious
Parra Arnau, Javier; Perego, Andrea; Ferrari, Elena; Forné Muñoz, Jorge; Rebollo Monedero, David
In the scenario of social bookmarking, a user browsing the Web bookmarks web pages and assigns free-text labels (i.e., tags) to them according to their personal preferences. The benefits of social tagging are clear – tags enhance Web content browsing and search. However, since these tags may be publicly available to any Internet user, a privacy attacker may collect this information and extract an accurate snapshot of users’ interests or user profiles, containing sensitive information, such as health-related information, political preferences, salary or religion. In order to hinder attackers in their efforts to profile users, this report focuses on the practical aspects of capturing user interests from their tagging activity. More accurately, we study how to categorise a collection of tags posted by users in one of the most popular bookmarking services, Delicious (http://delicious.com).
Mon, 14 Nov 2011 18:59:20 GMThttp://hdl.handle.net/2117/138842011-11-14T18:59:20ZParra Arnau, JavierPerego, AndreaFerrari, ElenaForné Muñoz, JorgeRebollo Monedero, DavidIn the scenario of social bookmarking, a user browsing the Web bookmarks web pages and assigns free-text labels (i.e., tags) to them according to their personal preferences. The benefits of social tagging are clear – tags enhance Web content browsing and search. However, since these tags may be publicly available to any Internet user, a privacy attacker may collect this information and extract an accurate snapshot of users’ interests or user profiles, containing sensitive information, such as health-related information, political preferences, salary or religion. In order to hinder attackers in their efforts to profile users, this report focuses on the practical aspects of capturing user interests from their tagging activity. More accurately, we study how to categorise a collection of tags posted by users in one of the most popular bookmarking services, Delicious (http://delicious.com).Influence maximization in social Networks when negative opinions may emerge and propagate
http://hdl.handle.net/2117/11184
Influence maximization in social Networks when negative opinions may emerge and propagate
Yuan, Yifei; Wei, Wei; Chen, Wei; Collins, Alex; Cummings, Rachel; Ke, Te; Liu, Zhenming; Rincón Rivera, David; Sun, Xiaorui; Wang, Yajun
Influence maximization, defined by Kempe, Kleinberg, and
Tardos (2003), is the problem of finding a small set of seed
nodes in a social network that maximizes the spread of influence
under certain influence cascade models. In this paper,
we propose an extension to the independent cascade model
that incorporates the emergence and propagation of negative
opinions. The new model has an explicit parameter called
quality factor to model the natural behavior of people turning
negative to a product due to product defects. Our model
incorporates negativity bias (negative opinions usually dominate
over positive opinions) commonly acknowledged in
the social psychology literature. The model maintains some
nice properties such as submodularity, which allows a greedy
approximation algorithm for maximizing positive influence
within a ratio of 1 1=e. We define a quality sensitivity ratio
(qs-ratio) of influence graphs and show a tight bound of
(
p
n=k) on the qs-ratio, where n is the number of nodes
in the network and k is the number of seeds selected, which
indicates that seed selection is sensitive to the quality factor
for general graphs. We design an efficient algorithm to compute influence in tree structures, which is nontrivial due to
the negativity bias in the model. We use this algorithm as the
core to build a heuristic algorithm for influence maximization
for general graphs. Through simulations, we show that
our heuristic algorithm has matching influence with a standard
greedy approximation algorithm while being orders of
magnitude faster.
Tue, 25 Jan 2011 07:59:07 GMThttp://hdl.handle.net/2117/111842011-01-25T07:59:07ZYuan, YifeiWei, WeiChen, WeiCollins, AlexCummings, RachelKe, TeLiu, ZhenmingRincón Rivera, DavidSun, XiaoruiWang, YajunInfluence maximization, defined by Kempe, Kleinberg, and
Tardos (2003), is the problem of finding a small set of seed
nodes in a social network that maximizes the spread of influence
under certain influence cascade models. In this paper,
we propose an extension to the independent cascade model
that incorporates the emergence and propagation of negative
opinions. The new model has an explicit parameter called
quality factor to model the natural behavior of people turning
negative to a product due to product defects. Our model
incorporates negativity bias (negative opinions usually dominate
over positive opinions) commonly acknowledged in
the social psychology literature. The model maintains some
nice properties such as submodularity, which allows a greedy
approximation algorithm for maximizing positive influence
within a ratio of 1 1=e. We define a quality sensitivity ratio
(qs-ratio) of influence graphs and show a tight bound of
(
p
n=k) on the qs-ratio, where n is the number of nodes
in the network and k is the number of seeds selected, which
indicates that seed selection is sensitive to the quality factor
for general graphs. We design an efficient algorithm to compute influence in tree structures, which is nontrivial due to
the negativity bias in the model. We use this algorithm as the
core to build a heuristic algorithm for influence maximization
for general graphs. Through simulations, we show that
our heuristic algorithm has matching influence with a standard
greedy approximation algorithm while being orders of
magnitude faster.