171 research outputs found
Apports des formations e-learning dans le cadre du travail : la perspective des salariés.
Une nouvelle modalitĂ© de formation se dĂ©veloppe dans les entreprises : le e-learning. Elle vise Ă favoriser lâapprentissage en vue dâamĂ©liorer la performance des salariĂ©s au travail. Cette communication, rĂ©sultat dâune recherche exploratoire, sâintĂ©resse Ă lâapprentissage perçu par les salariĂ©s. 29 entretiens semi-directifs ont au total Ă©tĂ© conduits avec les collaborateurs dâune entreprise industrielle française. Ils ont suivi lâune des 3 formations e-learning prĂ©sentĂ©es dans ce travail : formation aux processus achats de lâentreprise, formation au rĂ©fĂ©rencement dâune piĂšce dans lâentreprise, et formation en efficacitĂ© personnelle. La question de lâapport des formations e-learning au travail a Ă©tĂ© abordĂ©e directement avec eux lors de ces entretiens. Il rĂ©sulte de cette Ă©tude que les formations e-learning permettent une acquisition des connaissances (factuelles, notionnelles et sur les procĂ©dures) liĂ©es au cadre de travail ainsi quâune meilleure comprĂ©hension par les salariĂ©s de leur environnement de travail.Travail; Apprentissage; Formation; E-learning;
A DTN routing scheme for quasi-deterministic networks with application to LEO satellites topology
We propose a novel DTN routing algorithm, called DQN, specifically designed for quasi-deterministic networks with an application to satellite constellations. We demonstrate that our proposal efficiently forwards the information over a satellite network derived from the Orbcomm topology while keeping a low replication overhead. We compare our algorithm against other well-known DTN routing schemes and show that we obtain the lowest replication ratio without the knowledge of the topology and with a delivery ratio of the same order of magnitude than a reference theoretical optimal routing
DTN routing for quasi-deterministic networks with application to LEO constellations
We propose a novel DTN routing algorithm, called DQN, specifically designed for quasi-deterministic networks with an application to satellite constellations. We demonstrate that our proposal efficiently forwards the information over a satellite network derived from the Orbcomm topology while keeping a low replication overhead. We compare our algorithm against other well-known DTN routing schemes and show that we obtain the lowest replication ratio with a delivery ratio of the same order of magnitude than a reference theoretical optimal routing. We also analyze the impact of terrestrial gateways density and analyze DQN performances in heterogeneous cases
FLOWER - Fuzzy lower than-best effort transport protocol
We present a new delay-based transport protocol named FLOWER, that aims at providing a Lower-than-Best-Effort (LBE) service. The objective is to propose an alternative to the Low Extra Delay Background Transport (LEDBAT) widely deployed within the official BitTorrent client. Indeed, besides its intra-fairness problem, known as latecomer unfairness, LEDBAT can be too aggressive against TCP, making it ill suited for providing LBE services over certain networks such as constrained wireless networks. By using a fuzzy controller to modulate the sending rate, FLOWER aims to solve LEDBAT issues while fulfilling the role of a LBE protocol. Our simulation results show that FLOWER can carry LBE traffic in network scenarios where LEDBAT cannot while solving the latecomer unfairness problem. Finally, the presented algorithm is simple to implement and does not require complex computation that would prevent its deployment
On The Existence Of Optimal LEDBAT Parameters
The Low Extra Delay Background Transport (LEDBAT) protocol is a recently standardized protocol that aims to offer a scavenger service (i.e. the goal is to exploit the remaining and unused capacity of a link). LEDBAT is a delay-based protocol mainly defined by two parameters: a target queuing delay and a gain. The RFC 6817 provides guidelines to configure both parameters that strongly impact on the LEDBAT behavior in terms of fairness with other protocols. However, these guidelines are questioned by several studies as they might lead to the generation of a non-LBE (Less-than-Best-Effort) traffic. This paper explores the set of optimal parameters allowing LEDBAT protocol to effectively perform as an LBE traffic. We conclude that the optimal couple of target and decrease gain is (5ms; 10). However, we observe that the aggregated use of optimized LEDBAT sources still disturb the overall traffic performance and that the exponential backoff is not an answer to this issue. As a result, we believe that additional strategies to limit the number of LEDBAT flows are required for integrating this protocol at a large scale
Randomized rounding algorithms for large scale unsplittable flow problems
Unsplittable flow problems cover a wide range of telecommunication and
transportation problems and their efficient resolution is key to a number of
applications. In this work, we study algorithms that can scale up to large
graphs and important numbers of commodities. We present and analyze in detail a
heuristic based on the linear relaxation of the problem and randomized
rounding. We provide empirical evidence that this approach is competitive with
state-of-the-art resolution methods either by its scaling performance or by the
quality of its solutions. We provide a variation of the heuristic which has the
same approximation factor as the state-of-the-art approximation algorithm. We
also derive a tighter analysis for the approximation factor of both the
variation and the state-of-the-art algorithm. We introduce a new objective
function for the unsplittable flow problem and discuss its differences with the
classical congestion objective function. Finally, we discuss the gap in
practical performance and theoretical guarantees between all the aforementioned
algorithms
Dynamic unsplittable flows with path-change penalties: new formulations and solution schemes for large instances
In this work, we consider the dynamic unsplittable flow problem. This
variation of the unsplittable flow problem has received little attention so
far. The unsplittable flow problem is an NP-hard extension of the
multi-commodity flow problem where each commodity sends its flow on only one
path. In its dynamic version, this problem features several time steps and a
penalty is paid when a commodity changes its path from one time step to the
next. We present several mixed-integer linear programming formulations for this
problem and compare the strength of their linear relaxation. These formulations
are embedded in several solvers which are extensively compared on small to
large instances. One of these formulations must be solved through a column
generation process whose pricing problem is more difficult than those used in
classical flow problems. We present limitations of the pricing schemes proposed
in earlier works and describe two new schemes with a better worst-case
complexity. Overall, this work lays a strong algorithmic baseline for the
resolution of the dynamic unsplittable flow problem, proposes original
formulations, and discusses the compared advantages of each, thus hopefully
contributing a step towards a better understanding of this problem for both OR
researchers and practical applications
Randomized rounding algorithms for large scale unsplittable flow problems
Unsplittable flow problems cover a wide range of telecommunication and transporta-
tion problems and their efficient resolution is key to a number of applications. In
this work, we study algorithms that can scale up to large graphs and important num-
bers of commodities. We present and analyze in detail a heuristic based on the linear
relaxation of the problem and randomized rounding. We provide empirical evidence
that this approach is competitive with state-of-the-art resolution methods either by its
scaling performance or by the quality of its solutions. We provide a variation of the
heuristic which has the same approximation factor as the state-of-the-art approxima-
tion algorithm. We also derive a tighter analysis for the approximation factor of both
the variation and the state-of-the-art algorithm. We introduce a new objective function
for the unsplittable flow problem and discuss its differences with the classical con-
gestion objective function. Finally, we discuss the gap in practical performance and
theoretical guarantees between all the aforementioned algorithms
On the Impact of Intrinsic Delay Variation Sources on Iridium LEO Constellation
The recent decades have seen an increasing interest in Medium Earth Orbit and Low Earth Orbit satellite constellations. However, there is little information on the delay variation characteristics of these systems and the resulting impact on high layer protocols. To fill this gap, this paper simulates a constellation that exhibits the same delay characteristics as the already deployed Iridium but considers closer bandwidths to constellation projectsâ.
We identify five major sources of delay variation in polar satellite constellations with different occurrence rates: elevation, intra-orbital handover, inter-orbital handover, orbital seam handover and Inter-Satellite Link changes. We simulate file transfers of different sizes to assess the impact of each of these delay variations on the file transfer.
We conclude that the orbital seam is the less frequent source of delay and induces a larger impact on a small file transfers: the orbital seam, which occurs at most three times during 24 h, induces a 66%
increase of the time needed to transmit a small file. Inter-orbital and intra-orbital handovers occur less often and reduce the throughput by approximately ⌠8% for both low and high throughput configurations. The other sources of delay variations have a negligible impact on small file transfers, and long file transfers are not impacted much by the delay variations
European Position Paper on Rhinosinusitis and Nasal Polyps 2020
The European Position Paper on Rhinosinusitis and Nasal Polyps 2020 is the update of similar evidence based position papers published in 2005 and 2007 and 2012. The core objective of the EPOS2020 guideline is to provide revised, up-to-date and clear evidence-based recommendations and integrated care pathways in ARS and CRS. EPOS2020 provides an update on the literature published and studies undertaken in the eight years since the EPOS2012 position paper was published and addresses areas not extensively covered in EPOS2012 such as paediatric CRS and sinus surgery. EPOS2020 also involves new stakeholders, including pharmacists and patients, and addresses new target users who have become more involved in the management and treatment of rhinosinusitis since the publication of the last EPOS document, including pharmacists, nurses, specialised care givers and indeed patients themselves, who employ increasing self-management of their condition using over the counter treatments. The document provides suggestions for future research in this area and offers updated guidance for definitions and outcome measurements in research in different settings. EPOS2020 contains chapters on definitions and classification where we have defined a large number of terms and indicated preferred terms. A new classification of CRS into primary and secondary CRS and further division into localized and diffuse disease, based on anatomic distribution is proposed. There are extensive chapters on epidemiology and predisposing factors, inflammatory mechanisms, (differential) diagnosis of facial pain, allergic rhinitis, genetics, cystic fibrosis, aspirin exacerbated respiratory disease, immunodeficiencies, allergic fungal rhinosinusitis and the relationship between upper and lower airways. The chapters on paediatric acute and chronic rhinosinusitis are totally rewritten. All available evidence for the management of acute rhinosinusitis and chronic rhinosinusitis with or without nasal polyps in adults and children is systematically reviewed and integrated care pathways based on the evidence are proposed. Despite considerable increases in the amount of quality publications in recent years, a large number of practical clinical questions remain. It was agreed that the best way to address these was to conduct a Delphi exercise. The results have been integrated into the respective sections. Last but not least, advice for patients and pharmacists and a new list of research needs are included.Peer reviewe
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