Enumerating kk-arc-connected orientations

12 pagesWe study the problem of enumerating the $k$-arc-connected orientations of a graph $G$, i.e., generating each exactly once. A first algorithm using submodular flow optimization is easy to state, but intricate to implement. In a second approach we present a simple algorithm with delay $O(knm^2)$ and amortized time $O(m^2)$, which improves over the analysis of the submodular flow algorithm. As ingredients, we obtain enumeration algorithms for the $\alpha$-orientations of a graph $G$ in delay $O(m^2)$ and for the outdegree sequences attained by $k$-arc-connected orientations of $G$ in delay $O(knm^2)$

Electroplated Ni mask for plasma etching of submicron-sized features in LiNbO3

International audienceWe here report on the fabrication of electroplated nickel (Ni) masks for dry etching of sub-micron patterns in lithium niobate (LiNbO3). This process allows obtaining 350-nm thick Ni masks defining high air filling fraction holey arrays (e.g. openings of 1800 nm in diameter with inter-hole spacing of 300 nm, or 330 nm diameter holes spaced by 440 nm). The mask profile is perfectly vertical (angle ≈ 90°). The obtained metallic masks are used to realise photonic and phononic crystals. High aspect ratio and dense arrays of holey patterns were defined and transferred into LiNbO3 through RIE (Reactive Ionic Etching) in sulphur hexafluoride (SF6) chemistry. Nanometric holes exhibiting sidewall slope angles of the order of 60° have in this way been etched in LiNbO3. The LiNbO3/Ni selectivity is close to 6 and the etch rate around 6 nm/min

Generalized Quantifiers and Dynamicity — preliminary results —

International audienceWe classify determiners according to the dynamic properties of the generalized quantifiers they denote. We then show how these dynamic generalized quantifiers can be defined in a continuation-based dynamic logic

Algorithmes "output-sensitifs" pour les problèmes d’énumération dans les graphes

This thesis is a study, from an algorithmic point of view, of the complexity of solving some enumeration problems in graphs. Algorithms for enumeration problems are meant to produce all solutions of a combinatorial problem, without repetition. Because there is a potentially exponential number of solutions to be generated, different approaches to analyse the performance of those algorithms have been developed: the input-sensitive approach and the output-sensitive approach. The first is a measure of the complexity that is based on the size of the input, and which consists in analysing the total time needed to enumerate the objects. The second is a measure based on the size of the input and the output. Here we will be interested in an output-sensitive approach and we will pay special attention to the notion of delay, i.e., the time needed between the production of two consecutive solutions. The thesis is divided into two independent parts. In the first one we propose a general framework that allows for the study of enumeration of vertex set properties in graphs. We prove that when such a property is locally definable with respect to some order on the set of vertices, then it can be enumerated with linear delay. Our method is a reduction of the considered enumeration problem to the enumeration of paths in directed acyclic graphs. We apply this general method to enumerate with linear delay minimal connected dominating sets and maximal irredundant sets in interval graphs and in permutation graphs, as well as maximal irredundant sets in circular-arc graphs and in circular-permutation graphs. The second part of the thesis is dedicated to the study of k-arc-connected orientations. These are orientations for which at least k arcs have to be removed in order to destroy the strong connectivity. We first give a simple algorithm to enumerate the k-arc-connected orientations respecting some fix outdegree sequence. We then give a simple algorithm to enumerate the outdegree sequences attained by k-arc-connected orientations. Combining both yields an algorithm that enumerates all k-arc-connected orientations of a graph in delay O(knm²) and amortized time O(m²).Cette thèse est une étude, d’un point de vue algorithmique, de la complexité de la résolution de certains problèmes d’énumération dans les graphes. Les algorithmes pour les problèmes d’énumération ont pour but la production de toutes les solutions d’un problème combinatoire, et ce sans répétition. Comme il existe un nombre potentiellement exponentiel de solutions à générer, différentes approches pour analyser la performance de ces algorithmes ont été développées: l’approche "input-sensitive" et l’approche "output-sensitive". La première est une mesure de la complexité basée sur la taille de l’entrée, elle consiste en l’analyse du temps total nécessaire à l’énumération des objets. La seconde est une mesure basée sur la taille de l’entrée et de la sortie. Nous nous intéresserons ici à l’approche output-sensitive et nous accorderons une attention particulière à la notion de délai, i.e., le temps nécessaire entre la production de deux solutions consécutives. La thèse est divisée en deux parties indépendantes. Dans la première, nous proposons un cadre général qui permet d’étudier l’énumération d’ensembles de sommets d’un graphe respectant une certaine propriété. Nous prouvons que lorsqu’une telle propriété peut être définie localement par rapport à un certain ordre sur l’ensemble des sommets du graphe, alors les ensembles de sommets respectant cette propriété peuvent être énumérés avec un délai linéaire. Notre méthode consiste à réduire le problème d’énumération considéré à l’énumération de chemins dans les graphes acycliques dirigés. Nous appliquons cette méthode générale pour énumérer avec un délai linéaire les ensembles dominants connexes minimaux et les ensembles irredondants maximaux dans les graphes d’intervalles et dans les graphes de permutation, ainsi que les ensembles irredondants maximaux dans les graphes arc-circulaires et dans les graphes permutation-circulaires. La deuxième partie de la thèse est consacrée à l’étude des orientations k-arc-connexes. Il s’agit d’orientations pour lesquelles il est nécessaire de supprimer au moins k arcs pour détruire la forte connexité. Nous présentons d’abord un algorithme simple pour énumérer les orientations k-arc-connexes respectant une séquence de degrés sortants. Ensuite nous présentons un algorithme simple pour énumérer les séquences de degrés sortants pour lesquelles il existe une orientation k-arc-connexe. En combinant ces deux algorithmes, nous obtenons un algorithme qui énumère toutes les orientations k-arc-connexes d’un graphe avec un délai de O(knm²) et un temps amorti de O(m²)

Locally definable vertex set properties are efficiently enumerable

International audienceWe propose a general framework that allows for the study of enumeration of vertex set properties ingraphs. We prove that when such a property is locally definable with respect to some order on the setof vertices, then it can be enumerated with linear delay. Our method consists in reducing the consideredenumeration problem to the enumeration of paths in directed acyclic graphs. We then apply this generalmethod to enumerate minimal connected dominating sets and maximal irredundant sets in interval graphsand in permutation graphs, as well as maximal irredundant sets in circular-arc graphs and in circularpermutation graphs, with linear dela

Enumerating kk-arc-connected orientations

13 pagesInternational audienceWe study the problem of enumerating the $k$-arc-connected orientations of a graph $G$, i.e., generating each exactly once. A first algorithm using submodular flow optimization is easy to state, but intricate to implement. In a second approach we present a simple algorithm with $O(knm^2)$ time delay and amortized time $O(m^2)$, which improves over the analysis of the submodular flow algorithm. As ingredients, we obtain enumeration algorithms for the $\alpha$-orientations of a graph $G$ in $O(m^2)$ time delay and for the outdegree sequences attained by $k$-arc-connected orientations of $G$ in $O(knm^2)$ time delay

A systematic review on visual scanning behaviour in hemianopia considering task specificity, performance improvement, spontaneous and training-induced adaptations

People with homonymous hemianopia (HH) benefit from applying compensatory scanning behaviour that limits the consequences of HH in a specific task. The aim of the study is to (i) review the current literature on task-specific scanning behaviour that improves performance and (ii) identify differences between this performance-enhancing scanning behaviour and scanning behaviour that is spontaneously adopted or acquired through training. The databases PsycInfo, Medline, and Web of Science were searched for articles on scanning behaviour in people with HH. The final sample contained 60 articles, reporting on three main tasks, i.e., search (N = 17), reading (N = 16) and mobility (N = 14), and other tasks (N = 18). Five articles reported on two different tasks. Specific scanning behaviour related to task performance in search, reading, and mobility tasks. In search and reading tasks, spontaneous adaptations differed from this performance-enhancing scanning behaviour. Training could induce adaptations in scanning behaviour, enhancing performance in these two tasks. For mobility tasks, limited to no information was found on spontaneous and training-induced adaptations to scanning behaviour. Performance-enhancing scanning behaviour is mainly task-specific. Spontaneous development of such scanning behaviour is rare. Luckily, current compensatory scanning training programs can induce such scanning behaviour, which confirms that providing scanning training is important.IMPLICATIONS FOR REHABILITATIONScanning behaviour that improves performance in people with homonymous hemianopia (HH) is task-specific.Most people with HH do not spontaneously adopt scanning behaviour that improves performance.Compensatory scanning training can induce performance-enhancing scanning behaviour. Scanning behaviour that improves performance in people with homonymous hemianopia (HH) is task-specific. Most people with HH do not spontaneously adopt scanning behaviour that improves performance. Compensatory scanning training can induce performance-enhancing scanning behaviour