Scipedia: Documents published in 2007

Class based ospf traffic engineering inspired on evolutionary computation

Scipedia content — Wed, 14 Oct 2020 14:57:46 +0200

This paper proposes a novel traffic engineering framework able to automatically provide near-optimal OSPF routing configurations for QoS constrained scenarios. Within this purpose, this work defines a mathematical model able to measure the QoS compliance in a class-based networking domain. Based on such model, the NP-hard optimization problem of OSPF weight setting is faced resorting to Evolutionary Algorithms. The presented results show that, independently of other QoS aware mechanisms that might be in place, the proposed framework is able to improve the QoS level of a given domain only taking into account the direct influence of the routing component of the network. The devised optimization tool is able to optimize OSPF weight configurations in scenarios either considering a single level of link weights or using multiple levels of weights (one for each class) in multi-topology routing scenarios.

Document type: Part of book or chapter of book

Learning in cooperating agents environment as a method of solving transport problems and limiting the effects of crisis situations

Scipedia content — Wed, 14 Oct 2020 14:54:43 +0200

The realising of transport requests plays an important role for companies regarding cost. For this reason the construction of an optimal and effective transport planning and scheduling, offering the best use of transport means is hugely important. One of the researched transport problems at present is PDPTW. In this work, the PDPTW problem will be extended by adding changeable and uncertain travel times between given locations, which will then be examined and learnt by the dispatching company system. The changeable travel times are the results of traffic jams forming and propagating. The applied multi-agent approach allows us to consider the problem on the level of a whole company and on the local level analysed by a particular vehicle. The other aspects which are taken into consideration are traffic patterns, whose goal it is to facilitate the optimal routes for the given traffic patterns. These patterns contain the information about the dependencies between the traffic state on the particular routes.

Document type: Part of book or chapter of book

Topology aware internet traffic forecasting using neural networks

Scipedia content — Wed, 14 Oct 2020 14:54:31 +0200

Forecasting Internet traffic is receiving an increasing attention from the computer networks domain. Indeed, by improving this task efficient traffic engineering and anomaly detection tools can be developed, leading to economic gains due to better resource management. This paper presents a Neural Network (NN) approach to predict TCP/IP traffic for all links of a backbone network, using both univariate and multivariate strategies. The former uses only past values of the forecasted link, while the latter is based on the neighbor links of the backbone topology. Several experiments were held by considering real-world data from the UK education and research network. Also, different time scales (e.g. every ten minutes and hourly) were analyzed. Overall, the proposed NN approach outperformed other forecasting methods (e.g. Holt-Winters). R&D Algoritmi centre

Document type: Part of book or chapter of book

Providing qos in mpls atm integrated environment

Scipedia content — Wed, 14 Oct 2020 14:51:46 +0200

Multiprotocol Label Switching (MPLS) is an advanced forwarding scheme, which allows the network to achieve the benefits provided by Traffic Engineering (TE) techniques. The establishment of an end-to-end LSP between two IP/MPLS networks interconnected through an ATM backbone is still an open issue. This paper focuses in an MPLS-ATM environment, and addresses the problem of providing a fast LSP establishment, with certain QoS (Bandwidth guarantee), between two MPLS subnetworks interconnected through an ATM backbone. The Private Network to network Interface (PNNI) is used in ATM backbone as a routing and signaling protocol. In order to achieve the paper objectives, new PNNI elements are defined and evaluated.

Document type: Part of book or chapter of book

Stable and Robust Multipath Oblivious Routing for Traffic Engineering

Scipedia content — Wed, 14 Oct 2020 14:50:56 +0200

Intra-domain traffic engineering is essential for the operation of an Internet Service Provider. Demand-oblivious routing [2] promises excellent performance guarantee with changing and uncertain traffic demands. However, it is difficult to implement it. We investigate an efficient and deployable implementation of oblivious routing. We study its performance by both numerical experiments and simulation. The performance study shows that the multipath implementation achieves a close approximation to oblivious routing [2], especially when approximate knowledge of traffic is available. The study also shows its robustness under varying traffic demands, link failures and an adversary attack. Its performance is excellent even with a 100% error in traffic estimation.

Document type: Part of book or chapter of book

Propagation of the hydraulic head in an elastic pipeline

Scipedia content — Wed, 14 Oct 2020 14:49:36 +0200

This paper deals with the measurement and simulation of the dynamic processes on the systems with distributed parameters. As an example of such a system the elastic pipeline transporting the elastic fluid has been chosen. The effort was mainly aimed at the measurement and modeling of prime hydraulic head in the pipeline which arises after sudden closing the valve. The problem described here can be considered as signals and systems analysis because we actually look for an output signal of the system that transforms the input signal. Finally the measured and simulated data are compared and their correspondence was evaluted.

Document type: Part of book or chapter of book

Exposing uninitialized variables strengthening and extending run time checks in ada

Scipedia content — Wed, 14 Oct 2020 14:49:23 +0200

Since its inception, a main objective of the Ada language has been to assist in the development of large and robust applications. In addition to that, the language also provides support for building safety-critical applications, e.g. by facilitating validation and verification of such programs. The latest revision of the language has brought some additional improvements in the safety area, such as the Normalize_Scalars pragma, which ensures an automatic initialization of the nonexplicitly initialized scalars. This paper presents Initialize Scalars, an enrichment of the Normalize_Scalars concept, and an extended mode to verify at run-time the validity of scalars, both designed for easy use in existing large applications. Their implementation in GNAT Pro (the GNU Ada 95 compiler) is discussed. The practical results obtained on a large Air Traffic Flow Management application are presented.

Document type: Part of book or chapter of book

Performance analysis for real time grid systems on cots operating systems

Scipedia content — Wed, 14 Oct 2020 14:48:16 +0200

Computer technology for communication has become an integral aspect of daily operation. The exponential growth of internet services with dynamic inquiries in such areas as manufacturing, business, air traffic control and mission critical systems demands that there be quick, reliable and safe use of services. Each service must contain QoS metrics to assure security, performance and accuracy. A new paradigm of resource management middleware techniques is in this paper presented which can provide QoS for dynamic, distributed real-time systems on Common Off The Shelf (COTS) operating systems. Accommodation of dynamic environments enables the middleware to carefully consider an efficient design of resource profiling, resource needs estimation, resource unification, and performance analysis (or compliant with schedulability analysis) infrastructure providing significant benefits for QoS management on COTS operating systems. First, the use of low-cost COTS systems is extended to real-time computing without changing the operating system. Further, experiments for response time analysis confirm that the worst-case analysis poorly utilizes computational resources. Finally, it is shown that the new method of middleware design employing scalability of software and hardware system can be easily applied to legacy systems to manage resources efficiently for quick, reliable services and accurate QoS.

Document type: Part of book or chapter of book

Migrating large applications from ada83 to ada95

Scipedia content — Wed, 14 Oct 2020 14:43:27 +0200

The CFMU has developed mission critical applications for Europewide flight plan processing and air traffic management activities using Ada83. This paper presents the techniques and tools used for the migration from an Ada83 to an Ada95 compiler and run-time. It puts a particular emphasis on both the software management aspects and the technical aspects e.g. language aspects, run-time evolution, how to cater for incompatibilities between Ada83 and Ada95, elaboration order, etc...

Document type: Part of book or chapter of book

Evolutionary computation for quality of service internet routing optimization

Scipedia content — Wed, 14 Oct 2020 14:37:30 +0200

In this work, the main goal is to develop and evaluate a number of optimization algorithms in the task of improving Quality of Service levels in TCP/IP based networks, by configuring the routing weights of link-state protocols such as OSPF. Since this is a complex problem, some meta-heuristics from the Evolutionary Computation arena were considered, working over a mathematical model that allows for flexible cost functions, taking into account several measures of the network behavior such as network congestion and end-to-end delays. A number of experiments were performed, resorting to a large set of network topologies, where Evolutionary Algorithms (EAs), Differential Evolution and some common heuristic methods including local search were compared. EAs make the most promising alternative leading to solutions with an effective network performance even under unfavorable scenarios.

Document type: Part of book or chapter of book

Measuring the Congestion Responsiveness of Internet Traffic

Scipedia content — Wed, 14 Oct 2020 14:31:14 +0200

A TCP flow is congestion responsive because it reduces its send window upon the appearance of congestion. An aggregate of nonpersistent TCP flows, however, may not be congestion responsive, depending on whether the flow (or session) arrival process reacts to congestion or not. In this paper, we describe a methodology for the passive estimation of traffic congestion responsiveness. The methodology aims to classify every TCP session as either "open-loop" or "closed-loop". In the closed-loop model, the arrival of a session depends on the completion of the previous session from the same user. When the network is congested, the arrival of a new session from that user is delayed. On the other hand, in the openloop model, TCP sessions arrive independently of previous sessions from the same user. The aggregate traffic that the open-loop model generates is not congestion responsive, despite the fact that each individual flow in the aggregate is congestion responsive. Our measurements at a dozen of access and core links show that more than 60-80% of the traffic that we could analyze (mostly HTTP traffic) follows the closed-loop model.

Document type: Part of book or chapter of book

G networks multiple classes of positive customers signals and product form results

Scipedia content — Wed, 14 Oct 2020 14:25:58 +0200

The purpose of this tutorial presentation is to introduce G-Networks, or Gelenbe Networks, which are product form queueing networks which include normal or positive customers, as well as negative customers which destroy other customers, and triggers which displace other customers from one queue to another. We derive the balance equations for these models in the context of multiple customer classes, show the product form results, and exhibit the traffic equations which - in this case, contrary to BCMP and Jackson networks - are non-linear. This leads to interesting issues of existence and uniqueness of the steady-state solution. Gelenbe Network can be used to model large scale computer systems and networks in which signaling functions represented by negative customers and triggers are used to achieve flow and congestion control.

Document type: Part of book or chapter of book

Building MPLS VPNs with QoS Routing Capability

Scipedia content — Wed, 14 Oct 2020 14:25:32 +0200

Recently MPLS is used for building up VPNs in IP backbone, called MPLS VPNs. In this paper, we discuss issues on finding routes with QoS requirements (i.e., QoS routing) in MPLS VPNs. We first present background on MPLS VPNs as well as QoS routing. Then we discuss both the benefits and problems resulted from introducing QoS routing into MPLS VPNs. We particularly present an architecture of MPLS VPNs with QoS routing capability, on which we discuss some important issues on running QoS routing in MPLS VPNs.

Document type: Part of book or chapter of book

Optimizing content management system pipelines separation and merging of concerns

Scipedia content — Wed, 14 Oct 2020 14:15:05 +0200

Content management systems support the dissemination and maintenance of documents. In software engineering terms, they separate the concerns of content, application logic and visual styling. Current systems largely maintain this separation of concerns after document deployment. Their runtime processing pipeline is a composition of generators, or document transformations. We exploit commutativity to enable new static evaluations of the composite during document deployment. Unlike traditional caching, we arrive at closed-form composites even for styled, database-driven documents. This eliminates the runtime penalties of a separation of concerns while preserving their software engineering benefits.

Document type: Part of book or chapter of book

Formal verification of an optimal air traffic conflict resolution and recovery algorithm

Scipedia content — Wed, 14 Oct 2020 14:14:21 +0200

Highly accurate positioning systems and new broadcasting technology have enabled air traffic management concepts where the responsibility for aircraft separation resides on pilots rather than on air traffic controllers. The Formal Methods Group at the National Institute of Aerospace and NASA Langley Research Center has proposed and formally verified an algorithm, called KB3D, for distributed three dimensional conflict resolution. KB3D computes resolution maneuvers where only one component of the velocity vector, i.e., ground speed, vertical speed, or heading, is modified. Although these maneuvers are simple to implement by a pilot, they are not necessarily optimal from a geometrical point of view. In general, optimal resolutions require the combination of all the components of the velocity vector. In this paper, we propose a two dimensional version of KB3D, which we call KB2D, that computes resolution maneuvers that are optimal with respect to ground speed and heading changes. The algorithm has been mechanically verified in the Prototype Verification System (PVS). The verification relies on algebraic proof techniques for the manipulation of the geometrical concepts relevant to the algorithm as well as standard deductive techniques available in PVS.

Document type: Part of book or chapter of book

Fault Tolerant Scalable Support for Network Portability and Traffic Engineering

Scipedia content — Wed, 14 Oct 2020 14:07:22 +0200

The P-SHIM6 architecture provides ISP independence to IPv6 sites without compromising scalability. This architecture is based on a middle-box, the P-SHIM6, which manages the SHIM6 protocol exchange on behalf of the nodes of a site, which are configured with provider independent addresses. Incoming and outgoing packets are processed by the P-SHIM6 box, which can assign different locators to a given communication, either when it is started, or dynamically after the communication has been established. As a consequence, changes required for provider portability are minimized, and fine-grained Traffic Engineering can be enforced at the P-SHIM6 box, in addition to the fault tolerance support provided by SHIM6. This project has been supported by the RiNG project IST-2005-035167 and by the IMPROVISA project TSI2005-07384-C03-02. Publicado

Document type: Part of book or chapter of book

Models for the Logical Topology Design Problem

Scipedia content — Wed, 14 Oct 2020 13:58:52 +0200

We address the logical topology design problem (LTD) in WDM transport networks under static traffic assumptions. We start with one of the standard MILP formulations of the LTD problem that aims at optimizing the network congestion. We propose an improvement to this model that additionally optimizes the average hop count. We then derive a new MILP model that compels the traffic to be atomically routed. This last model enables fair comparisons of solutions obtained with MILP formulations and with metaheuristic algorithms. The latter allow us to deal with large size networks whereas the former are limited by their computational complexity. In this paper Tabu Search is used to tackle the LTD problem. We compare and discuss the logical topologies computed by the various methods described in the paper.

Document type: Part of book or chapter of book

Optimal Traffic Partitioning in MPLS Networks

Scipedia content — Wed, 14 Oct 2020 13:56:07 +0200

Multiprotocol Label Switching (MPLS) is an emerging Internet technology that facilitates traffic engineering in service provider networks. This paper considers a network performance optimization problem related to traffic engineering over MPLS. We investigate the issue of dynamic partitioning of MPLS ingress traffic into several parallel Label Switched Paths (LSP). Specifically, we present a stochastic framework for the traffic partitioning problem. Within this framework, a set of parallel edge disjoint LSPs is modeled by parallel queues and a partitioning algorithm is devised for different service classes that is adaptive to the prevailing state of the network. The performance of this approach is illustrated by numerical examples.

Document type: Part of book or chapter of book

Formal verification of complex out of order pipelines by combining model checking and theorem proving

Scipedia content — Wed, 14 Oct 2020 13:07:58 +0200

We describe a methodology for the formal verification of complex out-of-order pipelines as they may be used as execution units in out-of-order processors. The pipelines may process multiple instructions simultaneously, may have branches and cycles in the pipeline structure, may have variable latency, and may reorder instructions internally. The methodology combines model-checking for the verification of the pipeline control, and theorem proving for the verification of the pipeline functionality. In order to combine both techniques, we formally verify that the FairCTL operators defined in ?-calculus match their intended semantics expressed in a form where computation traces are explicit, since this form is better suited for theorem proving. This allows the formally safe translation of model-checked properties of the pipeline control into a theorem-proving friendly form, which is used for the verification of the overall correctness, including the functionality. As an example we prove the correctness of the pipeline of a multiplication/division floating point unit with all the features mentioned above.

Document type: Part of book or chapter of book

A policy based resource reservation service for maritime tactical networks

Scipedia content — Wed, 14 Oct 2020 13:04:13 +0200

Naval at sea (maritime tactical) networks are characterised by a dynamic, heterogeneous, and low-bandwidth environment. There is a critical need for Traffic Engineering (TE) mechanisms to support traffic prioritisation and resource optimisation in this environment. A desirable management service in this environment is end-to-end guaranteed bandwidth for critical application flows. Solutions such as RSVP are not appropriate for the maritime environment where links are error prone and easily overloaded. This paper describes the Resource Reservation Service (RRS), a policy-enabled flow-based TE management service developed specifically for the low-bandwidth, high-error rate, and mobility of the maritime environment. This service includes several novel features including multi-path probing, bi-directional reservations, and full policy control. The value of multi-path probing is demonstrated by simulation.

Document type: Part of book or chapter of book

Mathematical programming techniques for designing minimum cost pipeline networks for co2 sequestration

Scipedia content — Wed, 14 Oct 2020 13:02:27 +0200

Publisher Summary This chapter describes a mathematical model for a pipeline infrastructure for CO2 sequestration and utilizes various mathematical programming techniques to find minimum cost strategies for building and operating this pipeline network. The greenhouse gas emissions from direct combustion of fuels can be greatly reduced if they are replaced with hydrogen produced from fossil sources, and if hydrogen production is coupled with capture and secure sequestration of the resulting CO2 at storage sites such as aquifers and depleted hydrocarbon reservoirs. The transportation of CO2 from fossil hydrogen plants to sequestration sites can be accomplished via a pipeline network. The design of this pipeline is an important aspect of the overall energy network. It has been proposed that the CO2 produced at sources such as fossil energy conversion facilities and industrial process plants could be captured, compressed to supercritical pressures, transported via pipelines, and stored in underground geologic formations such as depleted oil and natural gas reservoirs and deep saline aquifers. A nonlinear model of the CO2 pipeline system is described, with appropriate constraints, and the lowest cost system is found using a state-of-the-art nonlinear optimization software called LOQO. The chapter also presents ways to model the behavior of the system over time, and to model the impact of uncertainties.

Document type: Part of book or chapter of book

Distributed dynamic capacity contracting a congestion pricing framework for diff serv

Scipedia content — Wed, 14 Oct 2020 12:57:54 +0200

In order to provide better Quality-of-Service (QoS) in large networks, several congestion pricing proposals have been made in the last decade. Usually, however, those proposals studied optimal strategies and did not focus on implementation issues. Our main contribution in this paper is to address implementation issues for congestion-sensitive pricing over a single domain of the differentiated-services (diff-serv) architecture of the Internet. We propose a new congestion-sensitive pricing framework Distributed Dynamic Capacity Contracting (Distributed-DCC), which is able to provide a range of fairness (e.g. max-min, proportional) in rate allocation by using pricing as a tool. Within the Distributed-DCC framework, we develop an Edge-to-Edge Pricing Scheme (EEP) and present simulation experiments of it.

Document type: Part of book or chapter of book

Can Forwarding Loops Appear When Activating iBGP Multipath Load Sharing?

Scipedia content — Wed, 14 Oct 2020 12:55:54 +0200

We analyse the possible consequences of activating iBGP multipath load sharing in a given domain (or AS), which allows for load balancing over multiple exit routers. It has been stated that interdomain routing loops may appear in this case. We show that under reasonable assumptions (which reflect commercial relationships between ASes) such routing loops cannot appear. Furthermore we show that even if theses assumptions are not met, routing loops can only be transient.

Document type: Part of book or chapter of book

Low weight congestion control for multi sender applications

Scipedia content — Wed, 14 Oct 2020 12:55:12 +0200

This paper presents a prototype for single-rate reliable multicast congestion control, which has been built into an existing commercial whiteboard. The prototype was developed using a novel scheme that was engineered around conflicting industry provided requirements for collaborative workspaces. This required the scheme to be both low-weight when used with many senders and compatible with NAT, firewalls and reflectors. The key to overcome this conflict was to combine congestion control and recovery feedback. This differs from many current solutions in that they are often designed for use with a wide variety of protocols and thus operate independent of the recovery mechanism. This paper does not go into the detail required to specify a protocol but instead discusses a few important design requirements for multi-sender applications, which are generally not considered by current research, and describes an approach towards meeting these requirements.

Document type: Part of book or chapter of book

In-pipe Robot with Active Steering Capability for Moving Inside of Pipelines

Scipedia content — Wed, 14 Oct 2020 12:52:06 +0200

In this chapter we presented the robotic systems MRINSPECT series for a long-distance inspection of pipelines. The systems show outstanding mobility and several characteristic features, which make it possible to apply the proposed systems in pipelines with complicate geometries regardless of the effect of gravity, its postures, and the direction of moving. Though the algorithms were described based on MRINSPECT series, the ideas can be generalized to the other robots. However, according to our experiences on this work, the mechanism of the in-pipe robot should be adaptable to the characteristic condition of the pipelines and it is the preliminary requirement for the successful movement. The use of a general- purpose robot may not be possible in in-pipe applications. For that means, MRINSPECT series has the possibility of being used in practical applications, although it is still under improvement through testing in the field conditions. In the near future, field tests will be conducted with the system and the system is to be modified according to the results of field evaluation.

Document type: Part of book or chapter of book

Distributed scheduling via pricing in a communication network

Scipedia content — Tue, 29 Sep 2020 09:55:54 +0200

This paper addresses the issue of pricing-based distributed resource allocation via scheduling in a communication network. Introducing the temporal aspect in the resource allocation problem presents new challenges e.g. in accounting for the durations and deadlines of the resource requests. Dynamic real-time pricing concepts are discussed for the decentralized sharing of network resources. A numerical example illustrates the benefit of congestion based pricing in a dynamic communication network. The quality of service that results from decentralized resource allocation is studied from the point of view of a power-controlled wireless network. The model is based on a dynamic noncooperative game and is related to recent work on centrally optimal (Pareto-optimal) distributed dynamic resource allocation.

Document type: Part of book or chapter of book

Current Debates On Infrastructure Policy

Scipedia content — Tue, 29 Sep 2020 09:54:58 +0200

This paper provides an overview of the major current debates on infrastructure policy. It reviews the evidence on the macroeconomic significance of the sector in terms of growth and poverty alleviation. It also discusses the major institutional debates, including the relative comparative advantage of the public and the private sector in the various stages of infrastructure service delivery as well as the main options for changes in the role of government (i.e. regulation and decentralization).

Document type: Book

Processor pipelines and their properties for static wcet analysis

Scipedia content — Tue, 29 Sep 2020 09:51:53 +0200

When developing real-time systems, the worst-case execution time (WCET) is a commonly used measure for predicting and analyzing program and system timing behavior. Such estimates should preferrably be provided by static WCET analysis tools. Their analysis is made difficult by features of common processors, such as pipelines and caches.This paper examines the properties of single-issue in-order pipelines, based on a mathematical model of temporal constraints. The key problem addressed is to determine the distance (measured in number of subsequent instructions) over which an instruction can affect the timing behavior of other instructions, and when this effect must be considered in static WCET analysis. We characterize classes of pipelines for which static analysis can safely ignore effects longer than some arbitrary threshold. For other classes of pipelines, pipeline effects can propagate across arbitrary numbers of instructions, making it harder to design safe and precise analysis methods.Based on our results, we discuss how to construct safe WCET analysis methods. We also prove when it is correct to use localworst-case approximations to construct an overall WCET estimate.

Document type: Part of book or chapter of book

Traffic Engineering with AIMD in MPLS Networks

Scipedia content — Tue, 29 Sep 2020 09:47:14 +0200

We consider the problem of allocating bandwidth to competing flows in an MPLS network, subject to constraints on fairness, efficiency, and administrative complexity. The aggregate traffic between a source and a destination, called a flow, is mapped to label switched paths (LSPs) across the network. Each flow is assigned a preferred ('primary') LSP, but traffic may be sent to other ('secondary') LSPs. Within this context, we define objectives for traffic engineering, such as fairness, efficiency, and preferred flow assignment to the primary LSP of a flow ('Primary Path First', PPF). We propose a distributed, feedback-based multipath routing algorithm that attempts to apply additive-increase and multiplicative-decrease (AIMD) to implement our traffic engineering objectives. The new algorithm is referred to as multipath-AIMD. We use ns-2 simulations to illustrate the fairness criteria and PPF property of our multipath-AIMD scheme in an MPLS network.

Document type: Part of book or chapter of book

Real time cell arrival sequence estimation and simulator for ip atm networks

Scipedia content — Tue, 29 Sep 2020 09:12:26 +0200

We have developed a new traffic measuring tool and applied it to the real-time simulation of a network. It monitors IP traffic on an ATM link and continuously transfers the length and timestamp of each IP packet to a post-processing system. The post-processing system receives the data, estimates the cell's arrival epoch at the transmission queue of the ATM link, and simulates the queueing behavior on-line if conditions differ from those of the actual system. The measuring tool and real-time simulation rep resent a new approach to traffic engineering. A new estimation problem, the arrival sequence estimation, is shown and some algorithms are proposed and evaluated.

Document type: Part of book or chapter of book

Posibilidades de los métodos numéricos en obras subterráneas

María Jesús Samper — Mon, 25 Nov 2019 15:28:37 +0100

Se presenta un resumen de las posibilidades de diversos métodos numéricos basados en la combinación de técnicas de elementos finitos y de partículas para la simulación de problemas típicos de obras subterráneas, tales como la excavación de túneles y la inundación de cavidades.

Numerical modelling of tectonic plates subduction using X-FEM

María Jesús Samper — Mon, 28 Oct 2019 14:23:22 +0100

The numerical modelling of plate subduction requires solving a coupled thermo-mechanical highly-nonlinear transient problem. The mechanical description of the phenomenon results in a multiphase quasi-static Stokes ﬂow, where the inertia terms are neglected. The transient thermal problem is dominated by the advection term. Here, the representation and evolution of the different phases are described using level sets. The phase tracking is carried out transporting the level set along with the material, using a pure advective model. The gradient discontinuities induced by the viscosity jump across the interface are resolved numerically by enriching the solution using a partition of unity method in a eXtended Finite Element Method (X-FEM) context. These numerical tools are used to simulate plate subduction with different parameters and to derive useful correlations between relevant geophysical factors.

Equilibrated Patch Recovery error estimates: simple and accurate upper bounds of the error

María Jesús Samper — Mon, 28 Oct 2019 14:15:00 +0100

This paper introduces a new recovery‐type error estimator ensuring local equilibrium and yielding a guaranteed upper bound of the error. The upper bound property requires the recovered solution to be both statically equilibrated and continuous. The equilibrium is obtained locally (patch‐by‐patch) and the continuity is enforced by a postprocessing based on the partition of the unity concept. This postprocess is expected to preserve the features of the locally equilibrated stress field. Nevertheless, the postprocess phase modifies the equilibrium, which is no longer exactly fulfilled. A new methodology is introduced that yields upper bound estimates by taking into account this lack of equilibrium. This requires computing the ℒ︁2 norm of the error or relating it with the energy norm.

The guaranteed upper bounds are obtained by using a pessimistic bound of the error ℒ︁2 norm, derived from an eigenvalue problem. Nevertheless, these bounds are not sharp. An additional strategy based on a more accurate assessment of the error ℒ︁2 norm is introduced, providing sharp estimates, which are practical upper bounds as it is demonstrated in the numerical tests.

Goal-oriented error estimation for transient parabolic problems

María Jesús Samper — Mon, 28 Oct 2019 14:08:40 +0100

This work focuses on controlling the error and adapting the discretization in the context of parabolic problems. In order to obtain a sound mathematical framework, the time domain is discretized using a Discontinuous Galerkin (DG) approach. This
allows to formulate the time stepping procedure in a variational format. The error is measured in the basis of an output of interest of the solution, defined by a linear functional. A dual problem, associated with this linear output is introduced.
The dual problem has to be solved backward in time.
An error representation is introduced, based on the weak residual of the primal error applied to the dual solution. Two different alternatives are studied to estimate the error in the dual solution: 1) recovery based error estimators and 2) implicit
residual type estimators. Once the error assessment is performed implicitly in the dual problem, the obtained estimate is plugged into the primal residual to obtain the error in the quantity of interest. The implementation of the estimator
is drastically simplified by using the weak version of the residual instead of the strong version used in previous works.
Thus, the output error is assessed using a mixed technique, explicit for the primal problem and implicit for the dual. In the framework of adaptive computations of transient problems, this approach is very attractive because it allows using first
the implicit scheme for the dual problem and then integrating the primal problem, estimating the error explicitly and eventually adapting the space-time grid. Thus, at every time step of the time marching scheme, the estimate of the dual error is injected into the primal residual (explicit estimate for the primal problem).

Remeshing criteria and proper error representations for goal oriented h-adaptivity

María Jesús Samper — Mon, 28 Oct 2019 13:46:02 +0100

A key ingredient in h-adaptivity pertains to the transformation of output data from a given error estimator into input data, usually in the form of an element-size distribution, that needs to be supplied to a mesh generator.
This paper analyzes the different possibilities of de¯ning remeshing criteria in the framework of goal oriented adaptivity. In standard energy norm driven adaptivity, the optimal mesh is clearly obtained if the local error distribution is uniform.
The goal-oriented paradigm introduces new di±culties associated with the different possibilities for the spatial error representation and the signs of the local error contributions.
A nodal error representation is introduced in order to improve the communication with the automatic mesh generation tool, precluding the transfer of information from elements to nodes.
Numerical experiments demonstrate the ability of the introduced remeshing strategies to drive e±cient adaptive procedures and to control the error in quantities of interest. The results of the numerical tests fit the expected properties of the different remeshing strategies.

Vocational guidance, scope and role of the university in the twenty-first century

María Jesús Samper — Mon, 14 Oct 2019 15:07:21 +0200

The article refers to the role of the University, and particularly public universities, in the professional guidance of the public in the broadest sense of the term and, namely, its influence over higher education and the professional skills provided by the same. This is all considered within a setting of globalization and when taking into account the prevailing conditions defining the knowledge society and welfare.

On some fluid-structure iterative algorithms using pressure segregation methods. Applications to aeroelasticity

María Jesús Samper — Tue, 03 Sep 2019 12:01:39 +0200

In this paper we suggest some algorithms for the fluid-structure interaction problem stated using a domain decomposition framework. These methods involve stabilized pressure segregation methods for the solution of the fluid problem and fixed point iterative algorithms for the fluid-structure coupling. These coupling algorithms are applied to the aeroelastic simulation of suspension bridges. We assess flexural and torsional frequencies for a given inflow velocity. Increasing this velocity we reach the value for which the flutter phenomenon appears.

Convergence analysis of the FEM approximation of the first order projection method for incompressible flows with and without the inf-sup condition

María Jesús Samper — Tue, 03 Sep 2019 11:06:39 +0200

In this paper we obtain convergence results for the fully discrete projection method for the numerical approximation of the incompressible Navier–Stokes equations using a finite element approximation for the space discretization. We consider two situations. In the first one, the analysis relies on the satisfaction of the inf-sup condition for the velocity-pressure finite element spaces. After that, we study a fully discrete fractional step method using a Poisson equation for the pressure. In this case the velocity-pressure interpolations do not need to accomplish the inf-sup condition and in fact we consider the case in which equal velocity-pressure interpolation is used. Optimal convergence results in time and space have been obtained in both cases.

An algebraic subgrid scale finite element method for the convected Helmholtz equation in two dimensions with applications in aeroacoustics

María Jesús Samper — Tue, 03 Sep 2019 10:43:05 +0200

An algebraic subgrid scale finite element method formally equivalent to the Galerkin Least-Squares method is presented to improve the accuracy of the Galerkin finite element solution to the two-dimensional convected Helmholtz equation. A stabilizing term has been added to the discrete weak formulation containing a stabilization parameter whose value turns to be the key for the good performance of the method. An appropriate value for this parameter has been obtained by means of a dispersion analysis. As an application, we have considered the case of aerodynamic sound radiated by incompressible flow past a two-dimensional cylinder. Following Lighthill’s acoustic analogy, we have used the time Fourier transform of the double divergence of the Reynolds stress tensor as a source term for the Helmholtz and convected Helmholtz equations and showed the benefits of using the subgrid scale stabilization.

A finite element model for free surface flows on fixed meshes

María Jesús Samper — Tue, 03 Sep 2019 10:33:58 +0200

In this paper, we present a finite element model for free surface flows on fixed meshes. The main novelty of the approach, compared with typical fixed mesh finite element models for such flows, is that we take advantage of the particularities of free surface flow, instead of considering it a particular case of two‐phase flow. The fact that a given free surface implies a known boundary condition on the interface, allows us to solve the Navier–Stokes equations on the fluid domain uncoupled from the solution on the rest of the finite element mesh. This, together with the use of enhanced integration allows us to model low Froude number flows accurately, something that is not possible with typical two‐phase flow models applied to free surface flow.

Dynamic subscales in the finite element approximation of thermally coupled incompressible flows

María Jesús Samper — Tue, 03 Sep 2019 10:17:32 +0200

In this paper, we propose a variational multiscale finite‐element approximation for the incompressible Navier–Stokes equations using the Boussinesq approximation to model thermal coupling. The main feature of the formulation in contrast to other stabilized methods is that we consider the subscales as transient. They are solution of a differential equation in time that needs to be integrated. Likewise, we keep the effect of the subscales both in the nonlinear convective terms of the momentum and temperature equations and, if required, in the thermal coupling term of the momentum equation. Apart from presenting the main properties of the formulation, we also discuss some computational aspects such as the linearization strategy or the way to integrate in time the equation for the subscales.

Time dependent subscales in the stabilized finite element approximation of incompressible flow problems

María Jesús Samper — Tue, 03 Sep 2019 10:13:02 +0200

In this paper we analyze a stabilized finite element approximation for the incompressible Navier–Stokes equations based on the subgrid-scale concept. The essential point is that we explore the properties of the discrete formulation that results allowing the subgrid-scales to depend on time. This apparently “natural” idea avoids several inconsistencies of previous formulations and also opens the door to generalizations.

A finite element method for the solution of rotary pumps

María Jesús Samper — Tue, 03 Sep 2019 10:06:59 +0200

We present in this paper a numerical strategy for the simulation of rotary positive displacement pumps, taking as an example a gear pump. While the two gears of the pump are rotating, the intersection between them changes in time. Therefore, the computational domain should be recomputed in some way at each time step. The strategy used here consists in dividing a cycle into a certain number of time steps and obtaining different computational meshes for each of these time steps. The coupling between two consecutive time steps is achieved by interpolating the flow unknowns in a proper way. This geometrical decomposition enables one to have a plain control over the mesh, particularly in the zones of interest, which are the gap between the gears and the casing, and the engagement and disengagement zones of the gears.

Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE). Vint anys d'historia

María Jesús Samper — Wed, 19 Jun 2019 12:09:23 +0200

El CIMNE (www.cimne.com), un centre de recerca consorci entre la Universitat Politècnica de Catalunya i la Generalitat de Catalunya, fa vint anys. El CIMNE està especialitzat en el desenvolupament i l’aplicació de mètodes numèrics avançats per a la solució d’un ampli ventall de problemes en enginyeria, que van des de la mecánica de sòlids i estructures, fins als processos de fabricació, passant per les TIC i els sistemes de suport a la decisió per a la prevenció i el tractament de catàstrofes naturals, com poden ser les inundacions o els vessaments de productes tòxics. El CIMNE es posiciona com un centre clau en el paper del desenvolupament d’idees originades en entorns de recerca bàsica i la seva transferència al sector industrial, per a la seva posterior industrialització i comercialització.

A finite point method for three-dimensional compressible flow

María Jesús Samper — Wed, 19 Jun 2019 12:02:42 +0200

Analysis of ship hydrodynamics using the overlapping domain decomposition level set method

María Jesús Samper — Wed, 19 Jun 2019 11:56:39 +0200

This report investigates the free surface capture of the Overlapping Domain Decomposition Level Set Method (ODDLS). The CFD software Tdyn is used to carry out computations in unison with GiD a pre/post processor to prepare the model and to analysis data. The Arbitrary Lagrangian-Eulerian method is also applied to allow deformation of the model mesh to allow the hull to sink and trim and to optimise free surface capture.

The offshore patrol vessel NT-130 developed by Navtec in Chile is the focus of the computations. Experimental towing tank data for still water conditions was compared to Tdyn results to asses its performance. Also, data from tests in wave conditions is presented in this report.

Shape optimization in aeronautical applications using neural networks

María Jesús Samper — Wed, 19 Jun 2019 11:49:52 +0200

An optimization methodology based on neural networks was developed for use in 2D optimal shape design problems. Neural networks were used as a parameterization scheme to represent the shape function, and an edge-based high-resolution scheme for the solution of the compressible Euler equations was used to model the flow around the shape. The global system incorporates neural networks and the Euler fluid solver into the C++ Flood optimization framework containing a library of optimization algorithms. The optimization scheme was applied to a minimal drag problem in an unconstrained optimization case and a constrained case in hypersonic flow using evolutionary training algorithms. The results indicate that the minimum drag problem is solved to a high degree of accuracy but at high computational cost. For more complex shapes, parallel computing methods are required to reduce computational time.

Drag prediction system based on neural networks

María Jesús Samper — Wed, 19 Jun 2019 11:44:54 +0200

In this work we will be based on two experimental-based statistical techniques, which allow us to determine approximately the residual resistance coefficient of the sailboat and the viscous coefficient and wave resistance coefficient in the case of merchants. For the calculation of the residual resistance in sailboats the most used method is the Delft series, and for the calculation of the residual resistance in merchants the most widespread method is that of Holtrop and Mennen. Both methods used experimental data to adjust a function, the results obtained with the functions are quite reliable, but it is difficult to improve the model since the statistical adjustment is complicated. For this reason, in this work we try to overcome that limitation and develop a tool that is capable of performing the same calculations, with the same or better reliability and also that allows to be constantly improved with experimental data. The tool used is the neural network.

Computation of turbulent flows using a finite element formulation

María Jesús Samper — Wed, 19 Jun 2019 11:38:05 +0200

We present a formulation for analysis of turbulent incompressible flows using a stabilized finite element method (FEM) based on the finite calculus (FIC) procedure. The stabilization terms introduced by the FIC approach allow to solve a wide range of fluid flow problems at different Reynolds numbers, including turbulent flows, without the need of a turbulence model. Examples of application of the FIC/FEM formulation to the analysis of 2D and 3D incompressible flows at large Reynolds numbers exhibiting turbulence features are presented.

Enhanced Rotation-Free Basic Shell Triangle. Applications to Sheet Metal Forming

María Jesús Samper — Wed, 19 Jun 2019 11:30:33 +0200

An enhanced rotation-free three node triangular shell element (termed EBST) is presented. The element formulation is based on a quadratic interpolation of the geometry in terms of the six nodes of a patch of four triangles associated to each triangular element. This allows to compute an assumed constant curvature field and an assumed linear membrane strain field which improves the in-plane behaviour of the element. A simple and economic version of the element using a single integration point is presented. The implementation of the element into an explicit dynamic scheme is described. The efficiency and accuracy of the EBST element and the explicit dynamic scheme are demonstrated in many examples of application including the analysis of a cylindrical panel under impulse loading and sheet metal stamping problems.

Membranes structures formed by low pressure inflatable tubes. New analysis methods and recent constructions

María Jesús Samper — Wed, 19 Jun 2019 11:01:32 +0200

This paper shows applications of a recently developed thin shell element adequate for the analysis of membrane and inflatable structures. The element is a three node triangle with only translational degrees of freedom that uses the configuration of the three adjacent elements to evaluate the strains in terms of the nodal displacements only. This allows to compute (constant) bending strains and (linear) membrane strains using a total Lagrangian formulation. Several examples, including inflation and deflation of membranes and some practical applications to the analysis, design and construction of membrane structures formed by low pressure inflatable tubes are presented.

NURBS-Enhanced finite element method for eular equations

María Jesús Samper — Wed, 19 Jun 2019 10:56:03 +0200

In this work the NURBS-Enhanced Finite Element Method (NEFEM) is combined with a Discontinuous Galerkin (DG) formulation for the numerical solution of the Euler equations of gas dynamics. With the NEFEM approach numerical fluxes along curved boundaries are computed much more accurately due to the exact geometric representation of the computational domain. The proper implementation of the wall boundary condition provides accurate results even with a linear interpolation of the solution. A detailed comparison of the NEFEM in front of isoparametric finite elements (FE) is presented, demonstrating the superiority of the NEFEM approach for both linear and higher order computations.

NURBS-Enhanced finite element methods (NEFEM)

María Jesús Samper — Wed, 19 Jun 2019 10:50:02 +0200

An improvement of the classical finite element method is proposed. It is able to exactly represent the geometry by means of the usual CAD description of the boundary with Non-Uniform Rational B-Splines (NURBS). Here, the two-dimensional case is presented. For elements not intersecting the boundary, a standard finite element interpolation and numerical integration is used. But elements intersecting the NURBS boundary need a specifically designed piecewise polynomial interpolation and numerical integration. A priori error estimates are also presented. Finally, some examples demonstrate the applicability and benefits of the proposed methodology. NEFEM is at least one order of magnitude more precise than the corresponding isoparametric finite element in every numerical example shown.

This is the case for both continuous and discontinuous Galerkin formulations. Moreover, for a desired precision NEFEM is also more computational efficient, as shown in the numerical examples. The use of NEFEM is strongly recommended in the presence of curved boundaries and/or when the boundary of the domain has complex geometric details. The possibility of computing accurate solution with coarse meshes and high order interpolations, makes NEFEM a more efficient strategy than classical isoparametric FE.

Posibilidades de los métodos numéricos en obras subterráneas

María Jesús Samper — Wed, 19 Jun 2019 10:37:59 +0200

Estado del arte sobre aplicación de métodos numéricos y la simulación de escenarios de riesgo y al cálculo de la seguridad estructural

María Jesús Samper — Tue, 18 Jun 2019 14:17:31 +0200

En este informe se estudian los métodos numéricos orientados hacia el cálculo de la seguridad de las estructuras, a la evaluación de su vulnerabilidad y riesgo, así como al desarrollo de escenarios de riesgo. Partiendo de una amplia revisión bibliográfica, se realiza una descripción del marco conceptual del riesgo, insistiéndose en las formulaciones que se han dado a los conceptos de amenaza, vulnerabilidad, fragilidad y daño involucrados en la definición del riesgo. A pesar de que los conceptos analizados son válidos para cualquier tipo de elemento en riesgo, para responder al principal objetivo de este estudio se pone énfasis en las estructuras de edificación y en las zonas urbanas. Dicho objetivo es el de estudiar los métodos de última generación orientados a la evaluación del daño esperado tanto en edificios individuales (lo que implica examinar su seguridad y vulnerabilidad) como en zonas urbanas (para las que se describirán procedimientos de simulación de escenarios de riesgo.) Después de incluir los principios relacionados con la evaluación de diferentes amenazas naturales (terremotos, tsunamis, erupciones volcánicas, huracanes, inundaciones, deslizamientos, avalanchas, etc.) para las que se introduce el concepto de escenario de amenaza, el presente estudio se centra más en la amenaza sísmica, al tener esta una mayor influencia en la seguridad de las estructuras que se hallan en zonas urbanas.

Se describe, primeramente, del método del índice de vulnerabilidad, desarrollado en el ámbito del riesgo sísmico, que permite caracterizar la vulnerabilidad de las estructuras. Unas funciones de vulnerabilidad semiempíricas permite estimar el daño estructural para diferentes intensidades de la acción y para diferentes índices de vulnerabilidad estructural. En el segundo lugar, se examina el método del espectro de capacidad que se fundamenta en modelos de análisis no lineal de las estructuras y de curvas de fragilidad estructural. La acción se define mediante el espectro de demanda. El método proporciona las probabilidades de ocurrencia para diferentes estados mencionados, utilizándose como ejemplo la ciudad de Barcelona para la se han desarrollado escenario de riesgo para la amenaza sísmica.

Bounds of functional outputs for parabolic problems. Part II: Bounds of the exact solution

María Jesús Samper — Tue, 18 Jun 2019 13:58:20 +0200

The paper introduces a methodology to compute upper and lower bounds for linear-functional outputs of the exact solutions of parabolic problems. In this second part, the bounds account for the error both in space and time. The assumption stating that the error introduced by the time marching scheme is negligible, used in the first part, is removed here. The bounds are computed starting from an approximation of the exact solution, associated with a spatial mesh and a time grid. Nevertheless, the bounds are guaranteed with respect to the exact solution, with no reference to any mesh or time discretization.

LES Turbulence models. Relation with stabilized numerical methods

María Jesús Samper — Thu, 13 Jun 2019 14:10:36 +0200

One of the aims of this text is to show some important results in LES modelling and to identify which are main mathematical problems for the development of a complete theory. A relevant aspect of LES theory, which we will consider in our work, is the close relationship between the mathematical properties of LES models and the numerical methods used for their implementation.

In last years it is more and more common the idea in the scientific community, especially in the numerical community, that turbulence models and stabilization techniques play a very similar role. Methodologies used to simulate turbulent flows, RANS or LES approaches, are based on the same concept: unability to simulate a turbulent flow using a finite discretization in time and space. Turbulence models introduce additional information (impossible to be captured by the approximation technique used in the simulation) to obtain physically coherent solutions. On the other side, numerical methods used for the integration of partial differential equations (PDE) need to be modified in order to able to reproduce solutions that present very high localized gradients. These modifications, known as stabilization techniques, make possible to capture these sharp and localized changes of the solution. According with previous paragraphs, the following natural question appears: Is it possible to reinterpret stabilization methods as turbulence models? This question suggests a possible principle of duality between turbulence modelling and numerical stabilization. More than to share certain properties, actually, it is suggested that the numerical stabilization can be understood as turbulence. The opposite will occur if turbulence models are only necessary due to discretization limitations instead of a need for reproducing the physical behaviour of the flow. Finally: can turbulence models be understood as a component of a general stabilization method?

Stabilized solution of the multidimensional advection-diffusion-absorption equation using linear finite elements

María Jesús Samper — Fri, 07 Jun 2019 10:27:09 +0200

A stabilized finite element method (FEM) for the multidimensional steady state advection-diffusion-absorption equation is presented. The stabilized formulation is based on the modified governing differential equations derived via the Finite Calculus (FIC) method. For 1D problems the stabilization terms act as a nonlinear additional diffusion governed by a single stabilization parameter. It is shown that for multidimensional problems an orthotropic stabilizing diffusion must be added along the principal directions of curvature of the solution. A simple iterative algorithm yielding a stable and accurate solution for all the range of physical parameters and boundary conditions is described. Numerical results for 1D and 2D problems with sharp gradients are presented showing the effectiveness and accuracy of the new stabilized formulation.

A co-rotational 8-node assumed strain shell element for postbuckling analysis of laminated composite plates and shells

María Jesús Samper — Fri, 26 Apr 2019 10:44:47 +0200

A nonlinear resultant shell element is developed for the solution of problems of composite plates and shells undergoing nonlinear static and nonlinear dynamic behavior with progressive layer failure. The formulation of the tangent stiffness is defined on the mid-surface and is efficient for analyzing thick laminated plates and shells by incorporating bending moments and transverse shear resultant forces in the geometric stiffness. The composite element is free of both membrane and shear locking behavior by using the assumed natural strain method, such that the element also performs very well as thin laminate shells. An equilibrium approach is used to derive the improved transverse shear stiffness, instead of using a shear correction factor. The proposed formulation is computationally efficient and the test results show good agreement with references. The composite shell element is extended to determine ply failures in laminated composite structures undergoing nonlinear static or dynamic behavior. The failure analysis is done by first, computing for the inter-laminar stresses at each gauss point in an element. Having obtained the stresses in each layer, checking for failure is performed based on a chosen failure criterion. Four failure criteria are available to enable the user to adopt the appropriate criterion for the type of problem parameters present.

Multiscale analysis using a coupled discrete/finite element model

María Jesús Samper — Thu, 25 Apr 2019 10:38:11 +0200

The present paper presents multiscale modelling via coupling of the discrete and finite element methods. Theoretical formulation of the discrete element method using spherical or cylindrical particles has been briefly reviewed. Basic equations of the finite element method using the explicit time integration have been given. The micr-macro transition for the discrete element method has been discussed. Theoretical formulations for macroscopic stress and strain tensors have been given. Determination of macroscopic constitutive properties using dimensionless micro-macro relationships has been proposed. The formulation of the multiscale DEM/FEM model employing the DEM and FEM in different subdomains of the same body has been presented. The coupling allows the use of partially overlapping DEM and FEM subdomains. The overlap zone in the two coupling algorithms is introduced in order to provide a smooth transition from one discretization method to the other. Coupling between the DEM and FEM subdomains is provided by additional kinematic constraints imposed by means of either the Lagrange multipliers or penalty function method. The coupled DEM/FEM formulation has been implemented in the authors’ own numerical program. Good performance of the numerical algorithms has been demonstrated in a number of examples.

Simulation of flows with violent free surface motion and moving objects using unstructured grids

María Jesús Samper — Fri, 12 Apr 2019 11:21:22 +0200

A volume of fluid (VOF) technique has been developed and coupled with an incompressible Euler/Navier–Stokes solver operating on adaptive, unstructured grids to simulate the interactions of extreme waves and three‐dimensional structures. The present implementation follows the classic VOF implementation for the liquid–gas system, considering only the liquid phase. Extrapolation algorithms are used to obtain velocities and pressure in the gas region near the free surface. The VOF technique is validated against the classic dam‐break problem, as well as series of 2D sloshing experiments and results from SPH calculations. These and a series of other examples demonstrate that the ability of the present approach to simulate violent free surface flows with strong nonlinear behaviour.

Presentación de Medes (Medicina en español)

Scipedia content — Mon, 08 Apr 2019 12:16:14 +0200

EL 25 DE JUNIO DE 2007 la Fundación Lilly presentó la base de datos Medes, que recoge las referencias bibliográficas con resumen de 55 revistas médicas españolas. En acto presentación participó el catedrático Pedro García Barreno, miembro de la Real Academia Española y de la Real Academia de Ciencias.En el momento de escribir esta nota Medes contiene 22.000 registros, que pueden consultarse gratuitamente desde el URL:http://www.fundacionlilly.com/ medes/home.htm

Diseño de un sistema de información y evaluación científica (Doctoral Thesis by Daniel Torres-Salinas)

Scipedia content — Mon, 08 Apr 2019 12:16:06 +0200

QUANTITATIVE

31th ELAG Seminar sobre la biblioteca 2.0

Scipedia content — Mon, 08 Apr 2019 12:15:57 +0200

EL 31TH ELAG LIBRARY SYSTEMS SEMINAR tuvo lugar en Barcelona entre los días 9 y 11 de mayo, y reunió a 120 participantes vinculados al mundo de las bibliotecas y las tecnologías de la información y la comunicación (TIC) de más de 20 países europeos. Este evento anual fue organizado en esta ocasión por el Consorci de Biblioteques de les Universitats Catalanes (CBUC), la Universitat de Barcelona (UB), la Universitat Autònoma de Barcelona (UAB) y la Universitat Pompeu Fabra (UPF) y se desarrolló en el Edificio Histórico de la UB y en la recién inaugurada Biblioteca de Filosofía, Geografía e Historia de la misma universidad.

Personal managers of bibliographic reference data bases: Characteristics and comparative analysis

Scipedia content — Mon, 08 Apr 2019 12:15:49 +0200

Both the shared and unique characteristics of the most widely used personal managers of bibliographic reference data bases are analysed: Reference Manager, EndNote, ProCite, RefWorks and EndNote Web. The aspects considered include: data input, authority control, global editing commands, personal configuration of the data bases, reference exportation, visualization of records, insertion of bibliographic references and automatic generation of bibliographies.

SCImago journal & country rank: un nuevo portal, dos nuevos rankings

Scipedia content — Mon, 08 Apr 2019 12:15:40 +0200

EL PORTAL SCIMAGO JOURNAL & COUNTRY RANK nace de la alianza entre la empresa Elsevier B.V. y el grupo de investigación Scimago. Como resultado de esta sinergia se ha desarrollado una plataforma de indicadores científicos a partir de la información contenida en la base de datos Scopus. La plataforma toma su nombre del indicador Scimago journal rank (SJR), elaborado por el grupo a partir del algoritmo Page rank, que representa la visibilidad de las revistas contenidas en la base de datos desde 1999 hasta 2006.

Information standardization: the IraLIS contribution

Scipedia content — Mon, 08 Apr 2019 12:15:32 +0200

Standardization is essential for proper transfer, storage and recovery of information. Standardization affects all aspects of information usage, and not only for professionals in information processing. The most prominent aspects of professional practice in this field are adressed, including the IraLIS solution for citing Spanish authors with multiple surnames. There is a need for Spanish scientific authors to be aware that taking these actions will improve the visibility of their work in international citation resources.

Implementation of a new indexing system for a specialized resource collection in teacher preparation

Scipedia content — Mon, 08 Apr 2019 12:15:22 +0200

A collection of eight documents on primary education provides the example for presenting a new indexing system based on a structure of primary and secondary descriptors and illustrating its equivalence to Universal Decimal Classification. The article shows the advantages of this new system as an information retrieval system and describes its role in the indexing system and process. Another aim of this article is to describe an actual project using a postcoordinate indexing system based on nuclear ordering of the descriptors, as well as to define the system and software requirements for efficient operation of user search and information retrieval functions.

Evolution and use of controlled languages in news documentation

Scipedia content — Mon, 08 Apr 2019 12:15:14 +0200

News documentation lacks suitable instruments of classification and indexing, the only exception being the Subject Reference System of the International Press Telecommunications Council (IPTC), which is not yet fully developed. The most relevant contributions to classifying and indexing news in Spanish-language media, both in Spain and internationally, is reviewed. We also studied the development and use of controlled vocabularies for processing news information, primarily specialized thesauri. Finally, news documentation characteristics specific to indexing and information retrieval for print news media are described in detail.

Dissemination and characteristics of Spanish physical activity and sport sciences scientific and technical journals

Scipedia content — Mon, 08 Apr 2019 12:15:05 +0200

The aim is to present the current situation of Physical Activity and Sport Sciences (PASS) journals in Spain. The inventory of Spanish journals is updated and several basic editorial characteristics, such as longevity, periodicity, place of publication, editorial institution and support, and type of editorial format are analyzed. The journals’ circulation in national and international databases and internet dissemination (based on accessibility, content and added services) are also studied. We conclude that PASS is still a young field that has not yet consolidated its academic presence, as shown by the basic editorial characteristics of it scientific and technical journals. Nonetheless, these journals have seen a significant improvement in their database indexing and internet presence in recent years.

Methodology for knowledge structuring in a discipline: the PuertoTerm case

Scipedia content — Mon, 08 Apr 2019 12:14:55 +0200

The PuertoTerm research project reports the steps taken to formalize and structure the knowledge developed within the field of coastal and ports engineering. The process used to obtain the associated terminology is described and the way in which the terminology was structured and processed is analysed. Finally, development and implementation are described, with special attention to the design of a two-dimensional information visualization interface.

On the nature and typology of documentary classifications and their use in a networked environment

Scipedia content — Mon, 08 Apr 2019 12:14:46 +0200

Networked orientated standards for vocabulary publishing and exchange and proposals for terminological services and terminology registries will improve sharing and use of all knowledge organization systems in the networked information environment. This means that documentary classifications may also become more applicable for use outside their original domain of application. The paper summarises some characteristics common to documentary classifications and explains some terminological, functional and implementation aspects. The original purpose behind each classification scheme determines the functions that the vocabulary is designed to facilitate. These functions influence the structure, semantics and syntax, scheme coverage and format in which classification data are published and made available. The author suggests that attention should be paid to the differences between documentary classifications as these may determine their suitability for a certain purpose and may impose different requirements with respect to their use online. As we speak, many classifications are being created for knowledge organization and it may be important to promote expertise from the bibliographic domain with respect to building and using classification systems.

Semantic web and ontologies in document information processing

Scipedia content — Mon, 08 Apr 2019 12:14:38 +0200

The lack of a well defined model of information representation on the web has produced several problems related to processing information. In an effort to resolve these problems, the W3C has proposed the semantic web project. This new scenario offers both possibilities and difficulties for the future. Special attention is given to ontologies, fundamental tools for the representation of knowledge on the semantic web. Finally, the role of library and information professionals is considered in this new context.

And suddenly, everybody is talking about ontologies?

Scipedia content — Mon, 08 Apr 2019 12:14:28 +0200

The number of papers written on ontologies has increased considerably over the last twenty years. This trend can be easily observed by searching words like “ontology” or “thesaurus” in databases. Despite this fact, there hasn’t been a consensus about the significance of this concept. The graphical representation known as ontology spectrum must have generated a lot of confusion amongst readers. In this paper we argue that this confusion is due to the mix of the various types of knowledge organization systems with distinct objectives in the same graphical representation. Thus, constructing a formal ontology for a system does not always presume an improvement, frequently it is adequate with less complex representations.

Controlled indexing languages and ontologies

Scipedia content — Mon, 08 Apr 2019 12:14:19 +0200

The main points of convergence and divergence between controlled indexing languages and ontologies, tools for knowledge organization and information retrieval in the semantic web, are described. Fundamental aspects of ontologies are presented, as well as the basic semantic and structural characteristics of traditional controlled languages.

Onthologies and knowledge organization: challenges and opportunities for information professionals

Scipedia content — Mon, 08 Apr 2019 12:14:10 +0200

The emerging convergence in the field of ontologies between knowledge organization and knowledge engineering is examined in the context of the semantic web project. We describe the development of research on ontologies in library and information sciences and in other disciplines interested in ontological problems. The emergence of a research agenda on ontologies is discussed in the context of the development of the internet and, specifically, in relation to the semantic web project. Finally, some implications of this convergence for the information professional are discussed: the integration of knowledge organization into a broader transdisciplinary research arena with a very promising future, the need to clarify the role and potential contributions of the information professional, and the urgency of adequate education and training in the new standards and technologies.

La información especializada en internet: directorio de recursos de interés académico y profesional (Ángeles Maldonado y Luis Rodríguez-Yunta, coords.)

Scipedia content — Mon, 08 Apr 2019 12:09:52 +0200

LOS MÁS VIEJOS del lugar recordarán con nostalgia los repertorios clásicos de fuentes de información elaborados por Malclès y Sabor... A los no tan viejos les sonarán los nombres de Sheehy (o Balay) y Walfor.Maldonado- Martínez, Ángeles; Rodríguez-Yunta, Luis (coords.). La información especializada en Internet: directorio de recursos de interés académico y profesional. 2ª ed., correg. y aum. Madrid: Consejo Superior de Investigaciones Científicas, Centro de Información y Documentación Científica, 2006. 495 p., 1 CD. ISBN 84-00-08436-5. 28€ + IVA.

Pequeños y grandes desastres de la información (J. Cobarsí)

Scipedia content — Mon, 08 Apr 2019 12:09:44 +0200

LAS CAUSAS Y CONSECUENCIAS DE LA MALA GESTIÓN DE LA INFORMACIÓN han merecido, generalmente, menos atención que los éxitos. En este libro, recopilación de casos verídicos, se emprende una exploración del lado oscuro de la información.Cobarsí, Josep. Pequeños y grandes desastres de la información. Nº 21 de la colección “Los libros de Infonomia”. Barcelona: Zero Factory. 2006.

Information architecture & findability: Peter Morville interview

Scipedia content — Mon, 08 Apr 2019 12:09:36 +0200

Peter Morville es presidente y fundador de Semantic Studios, una consultora sobre arquitectura, experiencia de usuario, y encontrabilidad de la información. Se le reconoce como el padre de la arquitectura de la información, y aboga por analizar el papel crítico que juega la “encontrabilidad” para definir la “experiencia de los usuarios”. Su último libro, Ambient Findability, explora la búsqueda, formas de hallar, marketing, interacción con la información, alfabetización, la profesión de bibliotecario, autoridades, y la cultura en la encrucijada de la tan generalizada informatización y la internet. La fama la adquirió sobre todo como coautor (con Louis Rosenfeld) del best-seller Arquitectura de la información para la Web (del que se vendieron más de 100.000 copias), nombrado por Amazon el “mejor libro del internet de 1998” y “el libro más útil del mercado en diseño web” por el gurú de la usabilidad Jakob Nielsen. Se licenció en biblioteconomía y ciencia de la información por la School of Information de la University of Michigan, de la que ahora es profesor.http://semanticstudios.comhttp://findability.org

Web browsers and Web 2.0

Scipedia content — Mon, 08 Apr 2019 12:09:28 +0200

Web 2.0 and browsers are two very closely connected concepts. The reason is that browsers are the user agents that are needed to make navigating web 2.0 a reality. Within a very short span of time, new versions have been issued by the top three web browsers: Explorer, Firefox and Opera. In this article we examine and compare the new capabilities and functions of these three browsers in terms of the new web.

Ranking de instituciones de investigación iberoamericanas (RI3)

Scipedia content — Mon, 08 Apr 2019 12:09:19 +0200

A PESAR DEL TIEMPO TRANSCURRIDO, el ranking, sea cual fuere su naturaleza, sigue siendo la herramienta preferida para analizar comparativamente todo tipo de instituciones científicas. Producción, citación, recursos humanos, recursos financieros, páginas web, todo es susceptible de ser utilizado para crear estos listados ponderados que solemos identificar bajo este anglicismo tan extendido. En nuestro grupo de investigación, y con el fin de no desentonar de la tendencia general, hemos creado uno que hemos dado en llamar RI3 (léase “erre-i-cubo”), el Ranking de instituciones de investigación iberoamericanas.

Business information sources on Spanish enterprises

Scipedia content — Mon, 08 Apr 2019 12:09:10 +0200

Systematisation of information sources on Spanish companies in order to allow foreign companies to learn about the situation in Spain. The aim is to offer a panorama of what exists, to categorise the types of data provided, and to appraise their usefulness for capturing clients. To do this, the information sources have been searched systematically, structured into a model for evaluation, and finally classified and described in the most useful way for the expressed aims: to capture clients and to evaluate risks. As conclusions we suggest the most relevant acquisition formats, the most reliable collection methods, or the original data sources. The study’s contribution is its usefulness as a source of tertiary information for setting up businesses in Spain.

Digital newspapers in Spain: redesign and web 2.0

Scipedia content — Mon, 08 Apr 2019 12:09:00 +0200

Design changes in Spanish digital newspapers between May and December 2006 are described and analyzed. Principal changes include: substitution of the vertical navigation bar for a horizontal bar across the top of the page, design for a 1024-pixel resolution, and the uneven gains in reader services participation. A chronology of these changes is included.

EcSocial.com. Information service for the social economy

Scipedia content — Mon, 08 Apr 2019 12:08:51 +0200

The origins, planning, and implementation process for the Valencian Community Social Economy Information Portal (www.ecsocial.com) are described. Details are provided of the methodology used to encourage participation by companies in this business realm. Changes that have taken place during the life of the project are detailed, along with the budget that has made this initiative possible.

CaCoCu: a website for the dissemination of cultural multimedia content from public universities in Andalusia

Scipedia content — Mon, 08 Apr 2019 12:08:42 +0200

The Association of Public Andalusian Universities (AUPA) has introduced a portal that offers diverse multimedia content related to cultural events organised by these institutions, and whose objective is to disseminate this rich cultural heritage over the internet. The website, named CaCoCu, allows users to access audio-visual materials such as audio or video recordings, text documents and image galleries related to different themes. This paper describes the architecture of the web portal, taking into account both technological and documentary aspects, as well as the functionality and services that are provided.

Evolution of content management systems (CMS). From mainframe to open source

Scipedia content — Mon, 08 Apr 2019 12:08:32 +0200

Content management systems (CMS) let us automate the generation, management, and retrieval of digital information, giving us the ability to deliver the right content to the right people at the right time at the right cost. This article analyzes the concept of CMS, its evolution from the 1970s to the open source tools developed since 2000, and its relationship to other systems, such as document management, records management or enterprise content management. Finally, a set of basic functions is detailed, along with practical advice to help determine the best CMS to meet the specific needs of any particular information service.

The metamorphosis of portals: from hypertext to hypernet

Scipedia content — Mon, 08 Apr 2019 12:08:23 +0200

Perspective on some of the current trends in portal design, based on transformations in technology, information, and organization within the information society. Our purpose is to clarify the amalgamation of ideas that encompass the portal concept, with the goal of contributing or suggesting new scenarios for the future. In an effort to address the need for new models of electronic content management based on a network of interactive information and communication, the article proposes a model similar to social networks as a change agent in the portal paradigm.

Confidentiality and copyright in an intranet project

Scipedia content — Mon, 08 Apr 2019 12:08:12 +0200

This study addresses two questions in the legal realm that affect the planning, development, and use of intranets. Protection of the author’s rights and protection of the user’s personal information are two basic considerations that must be taken into account by those responsible for an organization’s intranet. Although intellectual property rights and confidentiality are totally different in nature, both are discussed in this article from the perspective of how they should be managed by information professionals. In recent years we have seen how technology can contribute to violation of copyright law and personal confidentiality. This conflict can occur in our intranets if proper measures are not taken to reconcile the interests of all users, of those whose personal information must be protected, and of copyright holders.

Distributed web editing for an institutional portal

Scipedia content — Mon, 08 Apr 2019 12:08:03 +0200

This article offers a case study about content administration and management support for institutional portals. It describes the structure and workings of a shared web editing system that has been implemented for the official portal of the Education and Culture Section of Murcia’s Regional Government. The article offers general instructions and advice for excellent system performance. It highlights the benefits of decentralized web editing as a method for supplying high quality content in civil service portals and recommends considering an institutional portal to be an added public service in public administration.

The portals meaning

Scipedia content — Mon, 08 Apr 2019 12:07:53 +0200

Review of the evolution of the websites since its beginning. Observation that at present it is being created a universal shared library, with contributions from many people. Each new piece of accessible information in the Network becomes eventually a small portal that contributes to enrich the knowledge of all the others.

10as Jornadas españolas de documentación

Scipedia content — Mon, 08 Apr 2019 11:49:55 +0200

CON LA PRESENCIA DE MÁS DE 800 PROFESIONALES desplazados desde toda la geografía española, los pasados 9, 10 y 11 de mayo de 2007 se celebraron en Santiago de Compostela las 10as Jornadas españolas de documentación, Fesabid 2007.

Situación actual de los estudios cuantitativos de la ciencia. Entrevista con Henk Moed

Scipedia content — Mon, 08 Apr 2019 11:49:45 +0200

EL PASADO MES DE JUNIO DE 2007, durante los días 25-27, el Campus Serrano del Consejo Superior de Investigaciones Científicas (CSIC) de Madrid acogió la celebración de la 11th International conference of the International Society for Scientometrics and Informetrics. Este evento, que tiene lugar cada 2 años, es la reunión científica más importante a nivel mundial en el campo de la informetría y la ciencimetría. Este año se celebró por primera vez en España, organizado por el Centro de Información y Documentación Científica (CSIC-Cindoc) con la colaboración como presidente científico de Henk Moed, investigador del Center for Science and Technology Studies (CWTS) de la Universidad de Leiden (Holanda). Precisamente para la coordinación científica de los diversos aspectos del congreso, especialmente para la elaboración y edición de sus actas, Henk Moed ha realizado una estancia en España durante los meses de abril y mayo en la Universidad de Granada como profesor invitado del Grupo de Evaluación de la Ciencia y la Comunicación Científica (EC3).

Virtual meetings: Adobe Connect and WebEx

Scipedia content — Mon, 08 Apr 2019 11:49:37 +0200

Videoconferencing and, in a broader sense, collaborative work platforms, have been in use for years, with more or less success. Recently, large companies such as Adobe in the software sector, Cisco Systems in hardware, and Google have begun to enter this niche in the technology market, which is still not standardised and has excellent prospects for the future. Two of these products are discussed: Adobe Connect and WebEx.

Obtaining, editing and managing images with free and open access resources

Scipedia content — Mon, 08 Apr 2019 11:49:29 +0200

The world of images is currently one of the privileged areas for cooperative systems and free use. A good selection of tools is available that address all or some of the following tasks: (1) search and selection, (2) editing and (3) management. This offers opportunities for cultural entities that do not have funding for multimedia. Three specific resources are described: YotoPhoto, Paint.NET and XnView.

Producción ISI y tramos de investigación: cómo combinarlos en un nuevo indicador (II)

Scipedia content — Mon, 08 Apr 2019 11:49:21 +0200

LA COMISIÓN NACIONAL EVALUADORA DE LA ACTIVIDAD INVESTIGADORA (CNEAI)1 fue creada en el año 1989 como organización dependiente del Ministerio de Educación y Ciencia. Lleva a cabo la evaluación de la actividad investigadora de los profesores universitarios y de las escalas científicas del CSIC. La solicitud de evaluación (por períodos de seis años) es voluntaria, al tratarse de conseguir un complemento de productividad incentivador, cuya finalidad es fomentar el trabajo investigador de los profesores universitarios y su mejor difusión tanto nacional como internacional.

Directory of Experts on Information Management (EXIT). Usage analysis

Scipedia content — Mon, 08 Apr 2019 11:49:13 +0200

The characteristics of the EXIT Directory (Experts in information management), officially launched in June of 2005, are described. After two years online (July of 2007), its use was evaluated and analyzed, taking into account its operations, impact, visibility, and acceptance on the part of the professional community it serves: librarians, information scientists, archivists and information specialists. Technically, EXIT is considered a stateof- the-art directory and a genuine product of web 2.0, since those involved submit and update their own records, under the supervision and filtering of EXIT creators-managers and an international Evaluation Committee.

Document engineering: potential academic applications

Scipedia content — Mon, 08 Apr 2019 11:49:04 +0200

Document design has long been a standard task for information professionals. Nonetheless, the use of XML to encode and transfer electronic documents across networks and the development of various methods to describe the characteristics of various document types (XML schemas, RelaxNG, etc.) and their metadata have made clear the need for a more formal, structured approach to the design of various document types and their implementation using XML standards. This insight, combined with the requirements of new technological approaches to integrating software applications – web services or service-oriented architecture (SOA) - that rely on XML for document exchange across platforms, results in a need for documents whose structure is precisely defined. The work of Robert J. Glushko, specifically document engineering, provides the primary theoretical approach to this problem. Document engineering includes the activities necessary for the design of document types and their use as interfaces between systems in SOA environments. His work offers a formal, academic approach to what is currently one of the most interesting opportunities for information professionals.

Chemical Abstracts celebrates one hundred years

Scipedia content — Mon, 08 Apr 2019 11:48:56 +0200

A review of the first hundred years of Chemical Abstracts Service (CAS) reviews its significance and role as: (i) a witness to the changes in international scientific leadership; (ii) a classical example of scientific documentation; (iii) a general catalogue of chemical molecules in our natural and artificial world; (iv) a close ally of chemical and pharmacological industries; and (v) a paradoxically unsettled agent at a crossroads of the digital world. The uncertain future of CAS also symbolizes the uncertainty that reigns in scientific communication nowadays.

Evaluation of the Library and Information Science degree of the Polytechnical University of Valencia

Scipedia content — Mon, 08 Apr 2019 11:48:47 +0200

The evaluation process of the Library and Information Science’s (LIS) Degree of the Polytechnic University of Valencia is described. The development of the Spanish LIS’s academic studies and the university education evaluation procedure according to the responsible Spanish agency (Aneca) are explained; and, finally, the most noticeable results of the evaluation of the UPV Documentation’s studies are exposed.

Moodle learning management system as a tool for information, documentation, and knowledge management by research groups

Scipedia content — Mon, 08 Apr 2019 11:48:38 +0200

Two research groups at the Inter-American School of Library Science, University of Antioquia (Medellín-Colombia), share their experience and lessons learned during the adaptation and use of the Moodle learning management system (LMS) platform as a useful means for information, documentation, and knowledge management in research projects. Moodle was developed as a tool for online course management. This ongoing adaptation has yielded important benefits to the researchers and become a model for the University. This type of technological platform, available to most universities for instructional purposes, has potential to become a key developmental tool for any research project or group.