pinecone/core-2020-05-10-deduplication huggingface dataset:
3D Viscoelastic Anisotropic Seismic Modeling with High-Order Mimetic Finite Differences

We present a scheme to solve three-dimensional viscoelastic anisotropic wave propagation on structured staggered grids. The scheme uses a fully-staggered grid (FSG) or Lebedev grid (Lebedev, J Sov Comput Math Math Phys 4:449–465, 1964; Rubio et al. Comput Geosci 70:181–189, 2014), which allows for arbitrary anisotropy as well as grid deformation. This is useful when attempting to incorporate a bathymetry or topography in the model. The correct representation of surface waves is achieved by means of using high-order mimetic operators (Castillo and Grone, SIAM J Matrix Anal Appl 25:128–142, 2003; Castillo and Miranda, Mimetic discretization methods. CRC Press, Boca Raton, 2013), which allow for an accurate, compact and spatially high-order solution at the physical boundary condition. Furthermore, viscoelastic attenuation is represented with a generalized Maxwell body approximation, which requires of auxiliary variables to model the convolutional behavior of the stresses in lossy media. We present the scheme’s accuracy with a series of tests against analytical and numerical solutions. Similarly we show the scheme’s performance in high-performance computing platforms. Due to its accuracy and simple pre- and post-processing, the scheme is attractive for carrying out thousands of simulations in quick succession, as is necessary in many geophysical forward and inverse problems both for the industry and academia.The authors want to thank Repsol for the permission to publish the present research, carried out at the Repsol-BSC Research Center as a part of the Kaleidoscope Project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 644602.Peer ReviewedPostprint (published version
A low-overhead secure communication framework for an inter-cloud environment

Most of the current cloud computing platforms offer Infrastructure as a Service (IaaS) model, which aims to provision basic virtualized computing resources as on-demand and dynamic services. Nevertheless, a single cloud provider may not have limitless resources to offer to its users, hence the notion of an Inter-Cloud environment where a cloud can use the infrastructure resources of other clouds. However, there is no common framework in existence that allows the service owners to seamlessly provision even some basic services across multiple cloud service providers, albeit not due to any inherent incompatibility or proprietary nature of the foundation technologies on which these cloud platforms are built. In this paper we present a novel solution which aims to cover a gap in a subsection of this problem domain. Our solution offers a security architecture that enables service owners to provision a dynamic and service-oriented secure virtual private network on top of multiple cloud IaaS providers. It does this by leveraging the scalability, robustness and flexibility of peer-to-peer overlay techniques to eliminate the manual configuration, key management and peer churn problems encountered in setting up the secure communication channels dynamically, between different components of a typical service that is deployed on multiple clouds. We present the implementation details of our solution as well as experimental results detailing the overheads of our solution carried out on two commercial clouds
GEFCOM 2014 - Probabilistic Electricity Price Forecasting

Energy price forecasting is a relevant yet hard task in the field of
multi-step time series forecasting. In this paper we compare a well-known and
established method, ARMA with exogenous variables with a relatively new
technique Gradient Boosting Regression. The method was tested on data from
Global Energy Forecasting Competition 2014 with a year long rolling window
forecast. The results from the experiment reveal that a multi-model approach is
significantly better performing in terms of error metrics. Gradient Boosting
can deal with seasonality and auto-correlation out-of-the box and achieve lower
rate of normalized mean absolute error on real-world data.Comment: 10 pages, 5 figures, KES-IDT 2015 conference. The final publication
  is available at Springer via http://dx.doi.org/10.1007/978-3-319-19857-6_
The Development and Validation of a Roadmap for Traceability.

Organisations who operate in the safety critical domains such as the medical device, avaition, and automotive domains must ensure their software is safe and provide objective evidence to this effect. One way of achieving this is by adhering to domain specific regulations and guidelines which specify a comprehensive implementation of traceability. However there is a gap between regulatory traceability requirements and what is implemented in practice. This lack of compliance means that organisations find it difficult to assess the safety of their software and thus ensure its safety. One reason for non-compliance with regards to traceability is a lack of guidance on what traceability to implement or how to implement it. In this paper we present the development and validation of a roadmap for the implementation of traceability in the medical device domain. The roadmap will provide medical device organisations with a pathway for effective traceability implementation
Evaluation of Software Mediated Process Assessments for IT Service Management

IT service organisations are cognisant that continual service improvement can be achieved by conducting regular process assessments. However, such assessments are expensive and so we have developed a Decision Support System (DSS) tool which uses the international standard for process assessment ISO/IEC 15504 to offer a transparent and efficient approach. This paper provides evidence of evaluation of this software-mediated process assessment (SMPA) approach which was based on ISO/IEC 15504, ISO/IEC 20000 and the IT Infrastructure Library (ITIL®). In a usability evaluation of the online tool, participants reported largely positive experiences finding the online survey easy to use trustworthy, comfortable, generally effective, and more transparent and less costly to implement than a manual assessment. However, to engage in process improvement, human judgment, and possibly expert assessment facilitators are necessary for assessment validation and improvement, that is, a fully automated online survey that is strictly standard-based is not very useful. Further clarification of the survey questions with relevant examples, clearer answer options and having more visible goal statements on every question page were suggested.Full Tex
User Interface Adaptation Using Web Augmentation Techniques: Towards a Negotiated Approach

The use of Web augmentation techniques has an impact on tasks of owners of Web sites, developers of scripts and end-users. Because the Web sites can be modified by external scripts, their owners might lose control about how Web site contents are delivered. To prevent this, they might be tempted to modify the structure of Web pages thus making harder to execute external scripts. However, communities of Web augmentation scripters are increasing since end-users still have needs not yet covered by Web sites. In this paper we analyze the trade-offs of the introduction of Web augmentation scripts. In order to mitigate some negative effects, such as the loss of control, we propose an approach based on negotiation and coordination between actors involved in the process. We present a set of tools to facilitate the integration of scripts and to foster their dissemination for the benefit of all actors involved
Live, Personal Data Integration Through UI-Oriented Computing

This paper proposes a new perspective on the problem of data integration on the Web: the one of the Surface Web. It introduces the concept of UI-oriented computing as a computing paradigm whose core ingredient are the user interfaces that build up the SurfaceWeb, and shows how a sensible mapping of data integration tasks to user interface elements and user interactions is able to cope with data integration scenarios that so far have only be conceived for the Deep Web with its APIs and Web services. The described approach provides a novel conceptual and technological framework for practices, such as the integration of data APIs/services and the extraction of content from Web pages, that are common practice but still not adequately supported. The approach targets both programmers and users alike and comes as an extensible, open-source browser extension
On Maximal Unbordered Factors

International audienceGiven a string S of length n, its maximal unbordered factor is the longest factor which does not have a border. In this work we investigate the relationship between n and the length of the maximal unbordered factor of S. We prove that for the alphabet of size σ ≥ 5 the expected length of the maximal unbordered factor of a string of length n is at least 0.99n (for sufficiently large values of n). As an application of this result, we propose a new algorithm for computing the maximal unbordered factor of a string
Encoding Nearest Larger Values

In nearest larger value (NLV) problems, we are given an array A[1..n] of numbers, and need to preprocess A to answer queries of the following form: given any index i ∈ [1, n], return a “nearest” index j such that A[j] > A[i]. We consider the variant where the values in A are distinct, and we wish to return an index j such that A[j] > A[i] and |j − i| is minimized, the nondirectional NLV (NNLV) problem. We consider NNLV in the encoding model, where the array A is delete after preprocessing, and note that NNLV encoding problem has an unexpectedly rich structure: the effective entropy (optimal space usage) of the problem depends crucially on details in the definition of the problem. Using a new path-compressed representation of binary trees, that may have other applications, we encode NNLV in 1.9n + o(n) bits, and answer queries in O(1) time.Peer-reviewedPost-print26th Annual Symposium on Combinatorial Pattern Matching, Ischia Island, Ital
Modelling ciphersuite and version negotiation in the TLS protocol

Real-world cryptographic protocols such as the widely used Transport Layer Security (TLS) protocol support many different combinations of cryptographic algorithms (called ciphersuites) and simultaneously support different versions. Recent advances in provable security have shown that most modern TLS ciphersuites are secure authenticated and confidential channel establishment (ACCE) protocols, but these analyses generally focus on single ciphersuites in isolation. In this paper we extend the ACCE model to cover protocols with many different sub-protocols, capturing both multiple ciphersuites and multiple versions, and define a security notion for secure negotiation of the optimal sub-protocol. We give a generic theorem that shows how secure negotiation follows, with some additional conditions, from the authentication property of secure ACCE protocols. Using this framework, we analyse the security of ciphersuite and three variants of version negotiation in TLS, including a recently proposed mechanism for detecting fallback attacks
BP-XACML: An authorisation policy language for business processes

XACML has become the defacto standard for enterprise- wide, policy-based access control. It is a structured, extensible language that can express and enforce complex access control policies. There have been several efforts to extend XACML to support specific authorisation models, such as the OASIS RBAC profile to support Role Based Access Control. A number of proposals for authorisation models that support business processes and workflow systems have also appeared in the literature. However, there is no published work describing an extension to allow XACML to be used as a policy language with these models. This paper analyses the specific requirements of a policy language to express and enforce business process authorisation policies. It then introduces BP-XACML, a new profile that extends the RBAC profile for XACML so it can support business process authorisation policies. In particular, BP-XACML supports the notion of tasks, and constraints at the level of a task instance, which are important requirements in enforcing business process authorisation policies
Joint Morphometry of Fiber Tracts and Gray Matter structures using Double Diffeomorphisms

International audienceThis work proposes an atlas construction method to jointly analyse the relative position and shape of fiber tracts and gray matter structures. It is based on a double diffeomorphism which is a composition of two diffeomorphisms. The first diffeomorphism acts only on the white matter keeping fixed the gray matter of the atlas. The resulting white matter , together with the gray matter , are then deformed by the second diffeomorphism. The two diffeomorphisms are related and jointly optimised. In this way , the first diffeomorphisms explain the variability in structural connectivity within the population , namely both changes in the connected areas of the gray matter and in the geometry of the pathway of the tracts. The second diffeomorphisms put into correspondence the homologous anatomical structures across subjects. Fiber bundles are approximated with weighted prototypes using the metric of weighted currents . The atlas , the covariance matrix of deformation parameters and the noise variance of each structure are automatically estimated using a Bayesian approach. This method is applied to patients with Tourette syndrome and controls showing a variability in the structural connectiv-ity of the left cortico-putamen circuit
Viscoelastic Interfaces Driven in Disordered Media and Applications to
  Friction

Many complex systems respond to a continuous input of energy by an
accumulation of stress over time, interrupted by sudden energy releases called
avalanches. Recently, it has been pointed out that several basic features of
avalanche dynamics are induced at the microscopic level by relaxation
processes, which are neglected by most models. During my thesis, I studied two
well-known models of avalanche dynamics, modified minimally by the inclusion of
some forms of relaxation.
  The first system is that of a viscoelastic interface driven in a disordered
medium. In mean-field, we prove that the interface has a periodic behaviour
(with a new, emerging time scale), with avalanche events that span the whole
system. We compute semi-analytically the friction force acting on this surface,
and find that it is compatible with classical friction experiments. In finite
dimensions (2D), the mean-field system-sized events become local, and numerical
simulations give qualitative and quantitative results in good agreement with
several important features of real earthquakes.
  The second system including a minimal form of relaxation consists in a toy
model of avalanches: the Directed Percolation process. In our study of a
non-Markovian variant of Directed Percolation, we observed that the
universality class was modified but not completely. In particular, in the
non-Markov case an exponent changes of value while several scaling relations
still hold. This picture of an extended universality class obtained by the
addition of a non-Markovian perturbation to the dynamics provides promising
prospects for our first system.Comment: Thesis defended in Sept. 2014. Minor additions in the introduction
  and minor corrections to the bibliographical references. Received the
  Springer Theses award (2015). Springer Theses (2015). eBook ISBN:
  978-3-319-20022-4. Hardcover ISBN: 978-3-319-20021-
Newton’s Forward Difference Equation for Functions from Words to Words

International audienceNewton's forward difference equation gives an expression of a function from ℕ to ℤ in terms of the initial value of the function and the powers of the forward difference operator. An extension of this formula to functions from A* to ℤ was given in 2008 by P. Silva and the author. In this paper, the formula is further extended to functions from A* into the free group over B.L'équation aux différences avant de Newton donne une expression d'une fonction de ℕ dans ℤ en termes de la valeur initiale de la fonction et des puissances de l'opérateur de difference avant. Une extension de cette formule aux fonctions de A* dans ℤ a été donnée en 2008 par P. Silva et l'auteur. Dans cet article, cette formule est à nouveau généralisée, cette fois aux fonctions de A* dans le groupe libre sur B
Schengen routing: a compliance analysis

Schengen Routing was proposed as a countermeasure to traffic monitoring activities practiced by intelligence agencies. This work here presents the results of a larger-scale measurement performed to quantify Schengen Routing compliance in today’s Internet. Based on 3388 TCP, UDP, and ICMP traceroute measurements executed from RIPE Atlas probes located in over 1100 different Autonomous Systems (AS) in the Schengen Area, it was found that 34.5% to 39.7% of these routes are Schengen-compliant, while compliance levels vary from 0% to 80% among countries. Finally, an approach was developed that allows end-users to determine whether a specific route to a host is Schengen-compliant or not
Thermodynamic of Distorted Reissner-Nordstr\"om Black Holes in
  Five-dimensions

In this paper, we study mechanics and thermodynamics of distorted,
five-dimensional, electrically charged (non-extremal) black holes on the
example of a static and "axisymmetric" black hole distorted by external,
electrically neutral matter. Such a black hole is represented by the derived
here solution of the Einstein-Maxwell equations which admits an
$\mathbb{R}^1\times U(1)\times U(1)$ isometry group. We study the properties of
this distorted black hole.Comment: 7 pages, submitted for the proceedings of the First Karl
  Schwarzschild Meeting (Frankfurt, 2013
Quadratic Palatini gravity and stable black hole remnants

We present a four-dimensional Planck-scale corrected quadratic extension of
General Relativity (GR) where no a priori relation between metric and
connection is imposed (Palatini formalism). Static spherically symmetric
electrovacuum solutions are obtained in exact analytical form. The macroscopic
properties of these solutions are in excellent agreement with GR, though the
region around the central singularity is modified. In fact, the singularity is
generically replaced by a wormhole supported by the electric field, which
provides a non-trivial topology to the space-time. Moreover, for a certain
charge-to-mass ratio the geometry is completely regular everywhere. For such
regular solutions, the horizon disappears in the microscopic regime below a
critical number of charges ($N<17$), yielding a set of massive objects that
could be naturally identified as black hole remnants.Comment: To appear in the Proceedings of the 2013 Karl Schwarzschild Meeting
  on Gravitational Physics (KSM2013), held in FIAS, Frankfurt (Germany), 22-26
  July 2013, Springe
Boundary States of the Potts Model on Random Planar Maps

We revisit the 3-states Potts model on random planar triangulations as a
Hermitian matrix model. As a novelty, we obtain an algebraic curve which
encodes the partition function on the disc with both fixed and mixed spin
boundary conditions. We investigate the critical behaviour of this model and
find scaling exponents consistent with previous literature. We argue that the
conformal field theory that describes the double scaling limit is Liouville
quantum gravity coupled to the $(A_4,D_4)$ minimal model with extended
$\mathcal{W}_3$-symmetry.Comment: Based on talk given by B.N. at the First Karl Schwarzschild Meeting
  (Frankfurt, July 22-26, 2013
A physical derivation of the Kerr-Newman black hole solution

According to the no-hair theorem, the Kerr-Newman black hole solution
represents the most general asymptotically flat, stationary (electro-) vacuum
black hole solution in general relativity. The procedure described here shows
how this solution can indeed be constructed as the unique solution to the
corresponding boundary value problem of the axially symmetric Einstein-Maxwell
equations in a straightforward manner.Comment: 8 pages, contribution to the Proceedings of the Karl Schwarzschild
  Meeting (Frankfurt, July 22-26, 2013
Specifying artifact-centric business process models in UML

In recent years, the artifact-centric approach to process mod-\ud
eling has attracted a lot of attention. One of the research lines in this area\ud
is finding a suitable way to represent the dimensions in this approach.\ud
Bearing this in mind, this paper proposes a way to specify artifact-centric\ud
business process models by means of well-known UML diagrams, from a\ud
high-level of abstraction and with a technology-independent perspective.\ud
UML is a graphical language, widely used and with a precise semantics.Peer ReviewedPostprint (author's final draft
Tree Compression with Top Trees Revisited

We revisit tree compression with top trees (Bille et al. Information & Computation 2015), and present several improvements to the compressor and its analysis. By significantly reducing the amount of information stored and guiding the compression step using a RePair-inspired heuristic, we obtain a fast compressor achieving good compression ratios, addressing an open problem posed by Bille et al. We show how, with relatively small overhead, the compressed file can be converted into an in-memory representation that supports basic navigation operations in worst-case logarithmic time without decompression. We also show a much improved worst-case bound on the size of the output of top-tree compression (answering an open question posed in a talk on this algorithm by Weimann in 2012).Peer-reviewedPost-print14th International Symposium on Experimental Algorithms (SEA 2015)  SEA 2015, Paris, Franc
On the Quadratic Shortest Path Problem

International audienceFinding the shortest path in a directed graph is one of the most important combinatorial optimization problems, having applications in a wide range of fields. In its basic version, however, the problem fails to represent situations in which the value of the objective function is determined not only by the choice of each single arc, but also by the combined presence of pairs of arcs in the solution. In this paper we model these situations as a Quadratic Shortest Path Problem, which calls for the minimization of a quadratic objective function subject to shortest-path constraints. We prove strong NP-hardness of the problem and analyze polynomially solvable special cases, obtained by restricting the distance of arc pairs in the graph that appear jointly in a quadratic monomial of the objective function. Based on this special case and problem structure, we devise fast lower bounding procedures for the general problem and show computationally that they clearly outperform other approaches proposed in the literature in terms of its strength