On the composition of ISO 25964 hierarchical relations (BTG,BTP, BTI)

Knowledge organization systems (KOS) can use different types of hierarchical relations: broader generic (BTG), broader partitive (BTP), and broader instantial (BTI). The latest ISO standard on thesauri (ISO 25964) has formalized these relations in a corresponding OWL ontology (De Smedt et al., ISO 25964 part 1: thesauri for information retrieval: RDF/OWL vocabulary, extension of SKOS and SKOS-XL. http://purl.org/iso25964/skos-thes, 2013) and expressed them as properties: broaderGeneric, broaderPartitive, and broaderInstantial, respectively. These relations are used in actual thesaurus data. The compositionality of these types of hierarchical relations has not been investigated systematically yet. They all contribute to the general broader (BT) thesaurus relation and its transitive generalization broader transitive defined in the SKOS model for representing KOS. But specialized relationship types cannot be arbitrarily combined to produce new statements that have the same semantic precision, leading to cases where inference of broader transitive relationships may be misleading. We define Extended properties (BTGE, BTPE, BTIE) and analyze which compositions of the original “one-step” properties and the Extended properties are appropriate. This enables providing the new properties with valuable semantics usable, e.g., for fine-grained information retrieval purposes. In addition, we relax some of the constraints assigned to the ISO properties, namely the fact that hierarchical relationships apply to SKOS concepts only. This allows us to apply them to the Getty Art and Architecture Thesaurus (AAT), where they are also used for non-concepts (facets, hierarchy names, guide terms). In this paper, we present extensive examples derived from the recent publication of AAT as linked open data.     

Behaviour based on decision matrices for a coordination between agents in a urban traffic simulation

This paper describes a multi-agent coordination mechanism applied to intersection simulation situations. In a goal of urban traffic simulation, we must consider the dynamic interactions between autonomous vehicles. The field of multi-agent systems provides us some studies for such systems, in particular on the coordination mechanisms. Conflicts between vehicles (i.e. agents) are very frequent in such applications, and they may cause deadlocks, particularly at intersections such as crossroads. Our approach is based on the solving of two player games/decision matrices which characterize three basic situations. An aggregation method generalizes to n-player games for complex crossroads. The objective of this approach consists in searching basic two-player matrices for solving n-agent problems. To explain the principle, we describe our approach for a particular case of crossroad with three agents. Finally, the obtained results have been examined via a tool of road traffic simulation, ARCHISIM. We assume also that the global traffic replicates the behavior of agents in different situations.     

A framework for dynamic implicit curve approximation by an irregular discrete approach

The approximation of implicit planar curves by line segments is a very classical problem. Many algorithms use interval analysis to approximate this curve, and to handle the topology of the final reconstruction. In this article, we use discrete geometry tools to build an original geometrical and topological representation of the implicit curve. The polygonal approximation contains few segments, and the Reeb graph permits to sum up efficiently the shape and the topology of the curve. Furthermore, we propose two algorithms to process local cells refinement and local cells grouping schemes. We illustrate these schemes with a global system that efficiently handles manual or automatic fast updates on the global reconstruction, by considering topological or geometrical constraints. We also compare the speed and the quality of our approach with two classical methods.     

Workload assignment for global real-time scheduling on unrelated clustered platforms

Real-Time Systems - Heterogeneous MPSoCs are being used more and more, from cellphones to critical embedded systems. Most of those systems offer heterogeneous sets of identical cores. In this...     

Impact of arteriovenous fistula cannulation on the quality of dialysis

Introduction: Adequate hemodialysis directly improves health. Puncturing an arteriovenous fistula (AVF) and the amount of blood recirculation greatly affect the quality of dialysis. Few studies have assessed the method to cannulate a fistula and its influence on efficiency of hemodialysis. Methods: This prospective pilot study included 14 patients with end‐stage renal failure receiving regular intermittent hemodialysis. Patients received three consecutive treatments with both needles directed upstream then three consecutive treatments with the venous needle directed upstream and the arterial needle directed downstream. With both techniques, the distance between the needles was kept constant at 2.5 cm. Recirculation rate and Kt/V ratio were measured during each treatment using thermodilution and a diascan Fresenius generator. Findings: The 14 patients received 84 hemodialysis sessions: i.e., 8 (57.1%) males and 6 (42.8%) females, mean age 62.3 ± 15.57 years. Results showed that mean recirculation rates and Kt/V did not significantly differ between the two techniques. Discussion: Because no significant difference was found between the two techniques, the direction of insertion of needles should be decided upon on a case‐by‐case basis depending on the anatomy of the AVF and the feasibility of the puncture.     

Experimental demonstration of a phased-array antenna optically controlled with phase and time delays

The experimental demonstration and the far-field pattern characterization of an optically controlled phased-array antenna are described. It operates between 2.5 and 3.5 GHz and is made of 16 radiating elements. The optical control uses a two-dimensional architecture based on free-space propagation and on polarization switching by N spatial light modulators of p × p pixels. It provides 2(N-1) time-delay values and an analog control of the 0 to 2π phase for each of the p × p signals feeding the antenna (N = 5, p = 4).     

Cognitive control by brain-injured car drivers: an exploratory study

Cognitive control is a key tool for adaptation in dynamic situations. The aim of the study is to assess the relevance of a theoretical framework for cognitive control in dynamic situations, in order to understand brain-injured (BI) car drivers' cognitive impairment. The framework supports a cognitive control multimodality based on the crossing of two orthogonal dimensions: symbolic/subsymbolic; anticipative/reactive control. BI car drivers' behaviour was compared with that of a control group (CTRL) during driving simulator scenarios. Eye movement analysis, among other variables, revealed that BI car drivers made use of a more symbolic and reactive control than did CTRL drivers. CTRL drivers showed a more stable cognitive compromise than BI drivers. The latter became less symbolic and more reactive in the case of difficult scenarios. In addition, BI drivers focused on the main task of trajectory management, with fewer resources devoted to traffic interaction management. STATEMENT OF RELEVANCE: An explanation of differences between BI and CTRL drivers in terms of cognitive control requirements, attention and processing speed is put forward. From this, it is possible to derive some implications in terms of driver assistance (e.g. lane keeping or a warning assistance device) and rehabilitation.     

FAO’s AVHRR-based Agricultural Stress Index System (ASIS) for global drought monitoring

Agricultural production is highly dependent on climate variability in many parts of the world. In particular, drought may severely reduce crop yields, potentially affecting food availability at local, regional, and global scales. The Food and Agriculture Organization of the United Nations (FAO) operates the Global Early Warning System (GIEWS), which monitors global food supply and demand. One of the key challenges is to obtain synoptic information on a recurrent and timely basis about drought-affected agricultural zones. This is needed to quickly identify areas requiring immediate attention. The Agricultural Stress Index System (ASIS), based on imagery from the Advanced Very High Resolution Radiometer (AVHRR) sensors on board the National Oceanic and Atmospheric Administration (NOAA) and Meteorological Operational Satellite (METOP) satellites, was specifically developed to meet this need. The system is based on a methodology developed by Rojas, Vrieling, and Rembold over the African continent. This approach has been modified and adapted to the global scale to produce an agricultural stress index (ASI) representing, per administrative unit, the percentage of cropland (or pasture) areas affected by drought over the growing season. The vegetation health index (VHI), based on normalized difference vegetation index (NDVI) and temperature anomalies, is used as a drought indicator. A fused time series of AVHRR data from METOP and NOAA was used to produce a consistent time series of VHI at 1 km resolution. Global phenology maps, indicating the number of growing seasons and their start and end dates, were derived from a multi-annual image set of SPOT-Vegetation (1999–2011). The VHI time series and phenology maps were then combined to produce the ASI for the years 1984 to the present. This allowed evaluation of the suitability of the ASIS to identify drought using historical reports and ancillary data. As a result of this analysis, ASIS was positively evaluated to support the FAO early warning system.     

Fitting a Step Function to a Point Set

We consider the problem of fitting a step function to a set of points. More precisely, given an integer k and a set P of n points in the plane, our goal is to find a step function f with k steps that minimizes the maximum vertical distance between f and all the points in P. We first give an optimal Θ(nlog n) algorithm for the general case. In the special case where the points in P are given in sorted order according to their x-coordinates, we give an optimal Θ(n) time algorithm. Then, we show how to solve the weighted version of this problem in time O(nlog ⁴ n). Finally, we give an O(nh ²log n) algorithm for the case where h outliers are allowed. The running time of all our algorithms is independent of k.     

In-plane rigid-body vibration mode characterization with a nanometer resolution by stroboscopic imaging of a microstructured pattern

This article introduces an improved approach for the characterization of in-plane rigid-body vibration, based on digital processing of stroboscopic images of the moving part. The method involves a sample preparation step, in order to pattern a periodic microstructure on the vibrating device, for instance, by focused ion beam milling. An image processing method has then been developed to perform the optimum reconstruction of this a priori known object feature. In-plane displacement and rotation are deduced simultaneously with a high resolution (10-2 pixel and 0.5 x 10(-3) rad, respectively). The measurement principle combines phase measurements-that provide the high resolution-with correlation-that unwraps the phase with the proper phase constants. The vibration modes of a tuning fork are used for demonstrating the capabilities of the method. For applications allowing the sample preparation, the proposed methodology is more convenient than common interference methods or image processing techniques for the characterization of the vibration modes, even for amplitudes in the nanometer range.