pinecone/core-2020-05-10-deduplication huggingface dataset:
Does Adding More Agents Make a Difference? A Case Study of Cover Time for the Rotor-Router.

International audienceWe consider the problem of graph exploration by a team of $k$ agents, which follow the so-called rotor router mechanism. Agents move in synchronous rounds, and each node successively propagates agents which visit it along its outgoing arcs in round-robin fashion. It has recently been established by Dereniowski et al.\ (STACS 2014) that the rotor-router cover time of a graph $G$, i.e., the number of steps required by the team of agents to visit all of the nodes of $G$, satisfies a lower bound of $\Omega(mD/k)$ and an upper bound of $O(mD/\log k)$ for any graph with $m$ edges and diameter $D$. In this paper, we consider the question of how the cover time of the rotor-router depends on $k$ for many important graph classes. We determine the precise asymptotic value of the rotor-router cover time for all values of $k$ for degree-restricted expanders, random graphs, and constant-dimensional tori. For hypercubes, we also resolve the question precisely, except for values of $k$ much larger than $n$. Our results can be compared to those obtained by Elsässer and Sauerwald (ICALP 2009) in an analogous study of the cover time of $k$ independent parallel random walks in a graph; for the rotor-router, we obtain tight bounds in a slightly broader spectrum of cases. Our proofs take advantage of a relation which we develop, linking the cover time of the rotor-router to the mixing time of the random walk and the local divergence of a discrete diffusion process on the considered graph
Interactive data exploration using pattern mining

We live in the era of data and need tools to discover valuable
information in large amounts of data. The goal of exploratory data mining
is to provide as much insight in given data as possible. Within this
field, pattern set mining aims at revealing structure in the form of sets
of patterns. Although pattern set mining has shown to be an effective
solution to the infamous pattern explosion, important challenges remain.
One of the key challenges is to develop principled methods that allow
user- and task-specic information to be taken into account, by directly
involving the user in the discovery process. This way, the resulting patterns
will be more relevant and interesting to the user. To achieve this,
pattern mining algorithms will need to be combined with techniques from
both visualisation and human-computer interaction. Another challenge
is to establish techniques that perform well under constrained resources,
as existing methods are usually computationally intensive. Consequently,
they are only applied to relatively small datasets and on fast computers.
The ultimate goal is to make pattern mining practically more useful, by
enabling the user to interactively explore the data and identify interesting
structure. In this paper we describe the state-of-the-art, discuss open
problems, and outline promising future directions.status: publishe
Uncertainty in Crowd Data Sourcing under Structural Constraints

Applications extracting data from crowdsourcing platforms must deal with the
uncertainty of crowd answers in two different ways: first, by deriving
estimates of the correct value from the answers; second, by choosing crowd
questions whose answers are expected to minimize this uncertainty relative to
the overall data collection goal. Such problems are already challenging when we
assume that questions are unrelated and answers are independent, but they are
even more complicated when we assume that the unknown values follow hard
structural constraints (such as monotonicity).
  In this vision paper, we examine how to formally address this issue with an
approach inspired by [Amsterdamer et al., 2013]. We describe a generalized
setting where we model constraints as linear inequalities, and use them to
guide the choice of crowd questions and the processing of answers. We present
the main challenges arising in this setting, and propose directions to solve
them.Comment: 8 pages, vision paper. To appear at UnCrowd 201
Metal Bioavailability in the Sava River Water

Metals present one of the major contamination problems for freshwater systems, such as the Sava River, due to their high toxicity, persistence, and tendency to accumulate in sediment and living organisms. The comprehensive assessment of the metal bioavailability in the Sava River encompassed the analyses of dissolved and DGT-labile metal species of nine metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the river water, as well as the evaluation of the accumulation of five metals (Cd, Cu, Fe, Mn, and Zn) in three organs (liver, gills, and gastrointestinal tissue) of the bioindicator organism, fish species European chub (Squalius cephalus L.).This survey was conducted mainly during the year 2006, in two sampling campaigns, in April/May and September, as periods representative for chub spawning and post-spawning. Additionally, metal concentrations were determined in the intestinal parasites acanthocephalans, which are known for their high affinity for metal accumulation. Metallothionein concentrations were also determined in three chub organs, as a commonly applied biomarker of metal exposure. Based on the metal concentrations in the river water, the Sava River was defined as weakly contaminated and mainly comparable with unpolluted rivers, which enabled the analyses of physiological variability of metal and metallothionein concentrations in the chub organs, as well as the establishment of their constitutive levels
The Impact of Shape on the Perception of Euler Diagrams

Euler diagrams are often used for visualizing data collected into sets. However, there is a significant lack of guidance regarding graphical choices for Euler diagram layout. To address this deficiency, this paper asks the question ‘does the shape of a closed curve affect a user’s comprehension of an Euler diagram?’ By empirical study, we establish that curve shape does indeed impact on understandability. Our analysis of performance data indicates that circles perform best, followed by squares, with ellipses and rectangles jointly performing worst. We conclude that, where possible, circles should be used to draw effective Euler diagrams. Further, the ability to discriminate curves from zones and the symmetry of the curve shapes is argued to be important. We utilize perceptual theory to explain these results. As a consequence of this research, improved diagram layout decisions can be made for Euler diagrams whether they are manually or automatically draw
Visualizing Sets: An Empirical Comparison of Diagram Types

There are a range of diagram types that can be used to visualize sets. However, there is a significant lack of insight into which is the most effective visualization. To address this knowledge gap, this paper empirically evaluates four diagram types: Venn diagrams, Euler diagrams with shading, Euler diagrams without shading, and the less well-known linear diagrams. By collecting performance data (time to complete tasks and error rate), through crowdsourcing, we establish that linear diagrams outperform the other three diagram types in terms of both task completion time and number of errors. Venn diagrams perform worst from both perspectives. Thus, we provide evidence that linear diagrams are the most effective of these four diagram types for representing sets
How to kill epsilons with a dagger: a coalgebraic take on systems with algebraic label structure

We propose an abstract framework for modeling state-based systems with internal behavior as e.g. given by silent or ϵ-transitions. Our approach employs monads with a parametrized fixpoint operator † to give a semantics to those systems and implement a sound procedure of abstraction of the internal transitions, whose labels are seen as the unit of a free monoid. More broadly, our approach extends the standard coalgebraic framework for state-based systems by taking into account the algebraic structure of the labels of their transitions. This allows to consider a wide range of other examples, including Mazurkiewicz traces for concurrent systems.Funded by the ERDF through the Programme COMPETE and by the Portuguese Foundation for Science and Technology, project ref. FCOMP-01-0124-FEDER-020537 and SFRH/BPD/71956/2010. Acknowledge support by project ANR 12IS0 2001 PACE
Optimal exploration strategies in haptic search

In this study, we have investigated which strategies were optimal in different haptic search tasks, where items were held in the hand. Blindfolded participants had to detect the presence of a target among distractors while using predetermined strategies. The optimal strategy was determined by considering reaction time and error data. In the search for salient targets, a rough sphere among smooth or a cube among spheres, parallel strategies were optimal. With non-salient targets, the results were different. In the search for a sphere among cubes, a parallel strategy was effective, but only if the fingers could be used. In the search for a smooth sphere among rough, only a serial strategy was successful. Thus, the optimal strategy depended on the required perceptual information
The influence of material cues on early grasping force

The object of this study was to see whether differences in texture influence grip force in the very early phase of grasping an object. Subjects were asked to pick up objects with different textures either blindfolded or sighted, while grip force was measured. Maximum force was found to be adjusted to suit the differences in coefficient of friction, confirming earlier results. Surprisingly, statistically significant differences in grip force were already present as short as 10 ms after touch onset in the blindfolded condition, despite the fact that only haptic information about the texture was available. This suggests that the haptic system is very fast in identifying a texture’s friction
Subject-specific distortions in haptic perception of force direction

In a previous study, we found that the accuracy of human haptic perception of force direction is not very high. We also found an effect of physical force direction on the error subjects made, resulting in ‘error patterns’. In the current study, we assessed the between- and within-subject variation of these patterns. The within-subject variation was assessed by measuring the error patterns repeatedly over time for the same set of subjects. Many of these patterns were correlated, which indi- cates that they are fairly stable over time and thus subject-specific. The between-subject analysis, conversely, yielded hardly any significant correlations. We also measured general subject parameters that might explain this between-subject variation, but these parameters did not correlate with the error patterns. Concluding, we found that the error patterns of haptic perception of force direction are subject-specific and probably governed by an internal subject parameter that we did not yet discover
Illusory rotations in the haptic perception of moving spheres and planes

Recently, we have shown that a translating bar on which blindfolded participants position their hand is perceived as also rotating. Here, we investigated whether such an illusory rotation would also be found if a sphere or a plane (i.e. a stimulus without a clear orientation) was used as translating stimulus. We indeed found similar rotation biases: on average a stimulus that translates over a distance of 60cm has to rotate 25 degrees to be perceived as non-rotating. An additional research question was whether the biases were caused by the same underlying biasing egocentric reference frame. To our surprise, the correlations between the sizes of the biases of the individual participants in the various conditions were not high and mostly not even significant. This was possibly due to day-to-day variations, but clearly, more research is needed to answer this second research question
Making Gestural Interaction Accessible to Visually Impaired People

International audienceAs touch screens become widely spread, making them more accessible to visually impaired people is an important task. Touch displays possess a poor accessibility for visually impaired people. One possibility to make them more accessible without sight is through gestural interaction. Yet, there are still few studies on using gestural interaction for visually impaired people. In this paper we present a comprehensive summary of existing projects investigating accessible gestural interaction. We also highlight the limits of current approaches and propose future working directions. Then, we present the design of an interactive map prototype that includes both a raised-line map overlay and gestural interaction for accessing different types of information (e.g., opening hours, distances). Preliminary results of our project show that basic gestural interaction techniques can be successfully used in interactive maps for visually impaired people
A Parametric Framework for Cooperative Parallel Local Search

International audienceIn this paper we address the problem of parallelizing local search. We propose a general framework where different local search en-gines cooperate (through communication) in the quest for a solution. Several parameters allow the user to instantiate and customize the frame-work, like the degree of intensification and diversification. We imple-mented a prototype in the X10 programming language based on the adaptive search method. We decided to use X10 in order to benefit from its ease of use and the architectural independence from parallel resources which it offers. Initial experiments prove the approach to be successful, as it outperforms previous systems as the number of processes increases
A complexity approach for identifying aesthetic composite landscapes

Third European Conference, EvoMUSART 2014, Granada, Spain, April 23-25, 2014, Revised Selected Papers[Abstract] The present paper describes a series of features related to complexity which may allow to estimate the complexity of an image as a whole, of all the elements integrating it and of those which are its focus of attention. Using a neural network to create a classifier based on those features an accuracy over 85% in an aesthetic composition binary classification task is achieved. The obtained network seems to be useful for the purpose of assessing the Aesthetic Composition of landscapes. It could be used as part of a media device for facilitating the creation of images or videos with a more professional aesthetic composition.Xunta de Galicia, project XUGA-PGIDIT 10TIC105008PRPortuguese Foundation for Science and Technology, project PTDC/EIA-EIA/115667/200
Authorship ans aesthetics experiments: comparision of results between human and computational systems

[Abstract] This paper presents the results of two experiments comparing the functioning of a computational system and a group of humans when performing tasks related to art and aesthetics. The first experiment consists of the identification of a painting, while the second one uses the Maitland Graves’s aesthetic appreciation test. The proposed system employs a series of metrics based on complexity estimators and low level features. These metrics feed a learning system using neural networks. The computational approach achieves similar results to those achieved by humans, thus suggesting that the system captures some of the artistic style and aesthetics features which are relevant to the experiments performed
(Hierarchical) Identity-Based Encryption from Affine Message Authentication

International audienceWe provide a generic transformation from any affine message authentication code (MAC) to an identity-based encryption (IBE) scheme over pairing groups of prime order. If the MAC satisfies a security notion related to unforgeability against chosen-message attacks and, for example, the k-Linear assumption holds, then the resulting IBE scheme is adaptively secure. Our security reduction is tightness preserving, i.e., if the MAC has a tight security reduction so has the IBE scheme. Furthermore , the transformation also extends to hierarchical identity-based encryption (HIBE). We also show how to construct affine MACs with a tight security reduction to standard assumptions. This, among other things, provides the first tightly secure HIBE in the standard model
Optimal non-perfect uniform secret sharing schemes

A secret sharing scheme is non-perfect if some subsets of participants that cannot recover the secret value have partial information about it. The information ratio of a secret sharing scheme is the ratio between the maximum length of the shares and the length of the secret. This work is dedicated to the search of bounds on the information ratio of non-perfect secret sharing schemes. To this end, we extend the known connections between polymatroids and perfect secret sharing schemes to the non-perfect case. In order to study non-perfect secret sharing schemes in all generality, we describe their structure through their access function, a real function that measures the amount of information that every subset of participants obtains about the secret value. We prove that there exists a secret sharing scheme for every access function. Uniform access functions, that is, the ones whose values depend only on the number of participants, generalize the threshold access structures. Our main result is to determine the optimal information ratio of the uniform access functions. Moreover, we present a construction of linear secret sharing schemes with optimal information ratio for the rational uniform access functions.Peer ReviewedPostprint (author's final draft
Remove Noise in Video with 3D Topological Maps

International audienceIn this paper we present a new method for foreground masks denoising in videos. Our main idea is to consider videos as 3D images and to deal with regions in these images. Denoising is thus simply achieved by merging foreground regions corresponding to noise with background regions. In this framework, the main question is the definition of a cri-terion allowing to decide if a region corresponds to noise or not. Thanks to our complete cellular description of 3D images, we can propose an advanced criterion based on Betti numbers, a topological invariant. Our results show the interest of our approach which gives better results than previous methods
Tracking System with Re-identification Using a RGB String Kernel

International audiencePeople re-identification consists to identify a person which comes back in a scene where it has been previously detected. This key problem in visual surveillance applications may concern single or multi camera systems. Features encoding each person should be rich enough to provide an efficient re-identification while being sufficiently robust to remain significant through the different phenomena which may alter the appearance of a person in a video. We propose in this paper a method which encodes people's appearance through a string of salient points. The similarity between two such strings is encoded by a kernel. This last kernel is combined with a tracking algorithm in order to associate a set of strings to each person and to measure similarities between persons entering into the scene and persons who left it
Dialectics and contradictions in public procurement of information systems

Published version of a chapter from the book M. Janssen, H. Scholl, M. Wimmer & F. Bannister (Eds.), Electronic Government : Springer Berlin Heidelberg, 2014. Also available on SpringerLink: http://dx.doi.org/10.1007/978-3-662-44426-9_24Public procurement of Information Systems is a highly complex
process. Not surprisingly, systems often fail to meet the needs for which they
were procured. One of the main causes of this is the contradictions between
goals of different stakeholders. Identifying and understanding these conflicts
and contradictions are essential to develop strategies to improve the
procurement process. In this paper, we present a case study where we examined
the procurement process of a system carried out by a public entity in Norway.
Using dialectic theory and stakeholder theory as interpreting lenses, we
identified a number of conflicts and contradictions. Some of the contradictions
resulted from conflicting and divergent goals of the various stakeholders across
groups but also within groups, while others resulted from differing goals of
policies and regulations
Dynamical Processes in Globular Clusters

Globular clusters are among the most congested stellar systems in the
Universe. Internal dynamical evolution drives them toward states of high
central density, while simultaneously concentrating the most massive stars and
binary systems in their cores. As a result, these clusters are expected to be
sites of frequent close encounters and physical collisions between stars and
binaries, making them efficient factories for the production of interesting and
observable astrophysical exotica. I describe some elements of the competition
among stellar dynamics, stellar evolution, and other processes that control
globular cluster dynamics, with particular emphasis on pathways that may lead
to the formation of blue stragglers.Comment: Chapter 10, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
The Multiple Origin of Blue Straggler Stars: Theory vs. Observations

In this chapter we review the various suggested channels for the formation
and evolution of blue straggler stars (BSSs) in different environments and
their observational predictions. These include mass transfer during binary
stellar evolution - case A/B/C and D (wind Roche-lobe overflow) mass transfer,
stellar collisions during single and binary encounters in dense stellar
cluster, and coupled dynamical and stellar evolution of triple systems. We also
explore the importance of the BSS and binary dynamics in stellar clusters. We
review the various observed properties of BSSs in different environments (halo
and bulge BSSs, BSSs in globular clusters and BSSs in old open clusters), and
compare the current observations with the theoretical predictions for BSS
formation. We try to constrain the likely progenitors and processes that play a
role in the formation of BSSs and their evolution. We find that multiple
channels of BSS formation are likely to take part in producing the observed
BSSs, and we point out the strengths and weaknesses of each the formation
channel in respect to the observational constraints. Finally we point out
directions to further explore the origin of BSS, and highlight eclipsing binary
BSSs as important observational tool.Comment: Chapter 11, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe