Thoughts on 3D Digital Subplane Recognition and Minimum-Maximum of a Bilinear Congruence Sequence

International audienceIn this paper we take first steps in addressing the 3D Digital Subplane Recognition Problem. Let us consider a digital plane P : 0 ≤ ax + by − cz + d < c (w.l.o.g. 0 ≤ a ≤ b ≤ c) and a finite subplane S of P dened as the points (x, y, z) of P such that (x, y) ∈ [x0, x1] × [y0, y1]. The Digital Subplane Recognition Problem consists in determining the characteristics of the subplane S in less than linear (in the number of voxels) complexity. We discuss approaches based on remainder values ax+by+d c , (x, y) ∈ [x0, x1] × [y0, y1] of the subplane. This corresponds to a bilinear congruence sequence. We show that one can determine if the sequence contains a value in logarithmic time. An algorithm to determine the minimum and maximum of such a bilinear congruence sequence is also proposed. This is linked to leaning points of the subplane with remainder order conservation properties. The proposed algorithm has a complexity in, if m = x1 −x0 < n = y1 −y0, O(m log (min(a, c − a)) or O(n log (min(b, c − b)) otherwise

Properties and Applications of the Simplified Generalized Perpendicular Bisector

International audienceThis paper deals with the Simplified Generalized Perpendicular Bisector (SGBP) presented in [15,1]. The SGPB has some interesting properties that we explore. We show in particular that the SGPB can be used for the recognition and exhaustive parameter estimation of noisy discrete circles. A second application we are considering is the error estimation for a class of rotation reconstruction algorithms

Intestinal parasitic infections in schoolchildren in different settings of Côte d'Ivoire : effect of diagnostic approach and implications for control

BACKGROUND: Social-ecological systems govern parasitic infections in humans. Within the frame of assessing the accuracy of a rapid diagnostic test for Schistosoma mansoni in Cote d'Ivoire, three different endemicity settings had to be identified and schoolchildren's intestinal parasitic infection profiles were characterized. METHODS: In September 2010, a rapid screening was conducted in 11 schools in the Azaguie district, south Cote d'Ivoire. In each school, 25 children were examined for S. mansoni and S. haematobium. Based on predefined schistosome endemicity levels, three settings were selected, where schoolchildren aged 8-12 years were asked to provide three stool and three urine samples for an in-depth appraisal of parasitic infections. Triplicate Kato-Katz thick smears were prepared from each stool sample for S. mansoni and soil-transmitted helminth diagnosis, whereas urine samples were subjected to a filtration method for S. haematobium diagnosis. Additionally, a formol-ether concentration method was employed on one stool sample for the diagnosis of helminths and intestinal protozoa. Multivariable logistic regression models were employed to analyse associations between schoolchildren's parasitic infections, age, sex and study setting. RESULTS: The prevalences of S. mansoni and S. haematobium infections in the initial screening ranged from nil to 88% and from nil to 56%, respectively. The rapid screening in the three selected areas revealed prevalences of S. mansoni of 16%, 33% and 78%. Based on a more rigorous diagnostic approach, the respective prevalences increased to 92%, 53% and 33%. S. haematobium prevalences were 0.8%, 4% and 65%. Prevalence and intensity of Schistosoma spp., soil-transmitted helminths and intestinal protozoan infections showed setting-specific patterns. Infections with two or more species concurrently were most common in the rural setting (84%), followed by the peri-urban (28.3%) and urban setting (18.2%). CONCLUSIONS: More sensitive diagnostic tools or rigorous sampling approaches are needed to select endemicity settings with high fidelity. The observed small-scale heterogeneity of helminths and intestinal protozoan infections has important implications for contro

Évaluation de la teneur en vitamine A et de l’indice de peroxyde des huiles végétales couramment vendues dans les marchés au Burkina Faso

La carence en vitamine A constitue un problème de santé publique dans les pays en développement et affecte en particulier les jeunes enfants et les femmes en âge de procréer. Le but de cette étude était d'évaluer l’application de la politique nationale en matière de production et d’importation, des huiles végétales raffinées, d’enrichissement obligatoire en vitamine A au Burkina Faso, à travers la détermination de la teneur en vitamine A et de l'indice de peroxyde des huiles végétales vendues sur le marché. Cette étude transversale a été menée dans cinq villes sélectionnées selon la densité de la population. Cinquante-neuf échantillons d’huile ont été achetés dans ces villes pour évaluer la teneur en vitamine A, l'indice de peroxyde et leur conformité aux normes nationales et internationales. Dans l'ensemble, 76,27% des huiles n'étaient pas suffisamment enrichies en vitamine A. Pour l'indice de peroxyde, 3,39% des huiles n'étaient pas conformes. Globalement, 77,97% des huiles n'étaient pas conformes pour ces deux paramètres. Au regard de ces résultats il est nécessaire d’intensifier la lutte contre la mise à la consommation des huiles non enrichies en vitamine A au Burkina Faso. English title: valuation of the vitamin A content and the peroxide value of vegetable oils commonly sold in markets in Burkina Faso Vitamin A deficiency is a public health problem in developing countries and particularly affects young children and women of childbearing age. The aim of this study was to assess the implementation of the national policy on the production and importation of refined vegetable oils and mandatory vitamin A fortification in Burkina Faso, through the determination of the vitamin A content and peroxide value of vegetable oils sold on the market. A cross-sectional study was conducted in five cities selected according to population density. Fifty-nine oil samples were purchased in these cities to assess vitamin A content, peroxide value and compliance with national and Codex standards. Overall, 76.17% of the oils were not adequately fortified with vitamin A. For the peroxide value, 3.39% of the oils did not comply. Overall, 77.97% of the oils did not comply for these two parameters. In view of these results, it is necessary to intensify the fight against the consumption of oils not enriched in vitamin A in Burkina Faso

Water efficiency and productivity concepts. A review.

Water efficiency and productivity indicators are used in many scientific disciplines, usually to account for water losses that occur during its use, or products generated per unit of water consumed. The interpretation of these indicators is very diverse in the literature. However, the majority of definitions consider water efficiency as a measure of the effectiveness of irrigation, and view water productivity as a measure of the effectiveness of the physiological processes of both biomass production and crop yield formation, linked to the actual consumption of water by the crops. Thus, the consensus seems to be for water application efficiency (Ea) to be considered as the ratio of actual evapotranspiration to the water applied and productivity as the ratio of yield to actual evapotranspiration. The point of divergence relates fundamentally to the understanding of the constituent expressions of productivity (PE, product/“water consumed”) and efficiency of water application (Ea, “water consumed”/“applied water”). Indeed, the term “water consumed” is referred to variously by several authors as “actual evapotranspiration”, “gross irrigation plus rainfall”, “evapotranspiration plus water lost at the plot but beneficial to other users”, etc. Furthermore, while providing more details on the concepts of efficiency and water productivity, this review shows that the factors affecting these indicators have not yet been sufficiently elucidated. Thus, one of the axes of investigation could be to model the application efficiency of water firstly, according to water management practices and secondly, in terms of productivity levels in relation to the crop establishment period

Multi-scale discrete primitives recognition

Dans cette thèse, nous nous intéressons à la reconnaissance des primitives discrètes multi-échelles. Nous considérons qu'une primitive discrète multi-échelles est une superposition de primitives discrètes de différentes échelles ; et nous proposons des approches qui permettent de déterminer les caractéristiques d'une primitive discrète ou d'une partie d'une primitive discrète.Nous proposons une nouvelle approche de reconnaissance de sous-segment discret qui se base sur des propriétés portant sur l'ordre des restes arithmétiques de la droite discrète. Nous établissons des liens entre les points d'appuis du sous-segment discret et les points ayant des restes arithmétiques minimaux et maximaux sur la droite discrète. D'après les résultats de nos comparaisons, cette approche se relève être plus efficace que des approches existantes.Nous nous intéressons ensuite à des approches de reconnaissance d'arcs et de cercles discrets par le centre généralisé. Nous étudions le dual de la médiatrice généralisée et proposons de calculer le centre généralisé par des calculs de visibilité dans l'espace dual afin de réduire son temps de calcul. Cette approche est valide aussi bien dans une grille régulière que dans une grille irrégulière isothétique.Finalement, nous nous intéressons à des approches de reconnaissance de droite discrète par la préimage généralisée. Nous utilisons la notion de frontière afin de diminuer le nombre d'éléments rentrant dans le calcul de la préimage généralisée ; ce qui simplifie le calcul et réduit le temps de calcul. Cette approche s'applique aussi dans une grille régulière comme dans une grille irrégulière isothétique.This thesis is about discrete geometry and particularly recognition of multi-scale discrete primitives. We consider that a multiscale discrete primitive is a superimposition of many discrete primitives of different scales. Then we propose approaches of recognition of discrete primitives or parts of a discrete primitives.Firstly we propose a new approach for the recognition of digital subsegment that is based on properties of the sequence of arithmetic remainders of the digital straight line. We show there are sorne links between the leaning points of the digital subsegment and the points that have the minimal and maximal arithmetic remainders on the digital straight line. Based on the results of comparisons with others approaches, the approach seems more efficient. Secondly we present sorne work on improving digital rings and circles recognition by general circumcenter. We use the dual of the generalized bissector in order to simplify the computation of the intersections of generalized bissectors as a polygon stabbing problem. The dual of the generalized bissector is computed likely for pixels of a regular grid or paves of an irregular isothetic grid. Finaly we present some work on improving digital straight line recogrutlon by generalized preimage. To reduce the number of elements to take into account for the computation of the generalized preimage we introduce the concept of boundary. The approach based on boundary could be used in a regular grid or an irregular isothetic grid

Rayleigh wave group velocity dispersion tomography of West Africa using regional earthquakes and ambient seismic noise

International audienceWest Africa could teach us much about the early tectonic history of Earth, but current seismic models of the regional crustal and lithospheric structure lack the resolution required to answer all but the most basic research questions. We have improved the resolution of group velocity maps of the West African Craton by complementing the uneven path distribution of earthquake-generated surface waves with surface waves reconstructed from ambient noise cross-correlations. Our joint dataset provides good spatial coverage of group velocity measurements from 20- to 100-s period, enabling us to reduce artefacts in our group velocity maps and improve their resolution. Our maps correlate well with regional geological features. At short periods, they highlight differences in crustal thickness, recent tectonic activity, and thick sediments. At long periods, we found lower velocities due to hot, thin lithosphere under the Pan-African mobile belt and faster velocities due to cold, thick lithosphere under the Man-Leo and Reguibat shields. Our higher resolution maps advance us a step towards revealing the detailed lithospheric structure and tectonic processes of West Africa

Remainder approach for the computation of digital straight line subsegment characteristics

International audienc

Evaluation and Proposals for Improving Irrigation Performance Around Small Reservoirs in Burkina Faso

Irrigation of crops using water from the Savili and Mogtédo reservoirs in Burkina Faso provides an opportunity to increase rural incomes. In order to ensure the sustainability and improvement of the irrigation infrastructure, it is necessary to monitor and evaluate its technical performance. To this end, the authors evaluated crop water use efficiency, water application, and conveyance efficiencies; modeled theoretical irrigation schedules for comparison with actual irrigation schedules; and assessed overall water management. The results show that water application efficiencies were less than 20% at Savili, and between 41% and 55% at Mogtédo. Water use efficiencies ranged from 1.12 to 3.4 kg m-3 for Allium cepa (onion) in three networks, 0.31 kg m-3 for Zea mays (corn) at Mogtédo, and 0.34 kg m-3 for Phaseolus vulgaris (green beans) at Savili. Poor irrigation management resulted in significant water loss, estimated to be 2,999,923 m3/year for the Mogtédo and Savili sites. The main reason for this underperformance seems to be related to technical and organizational failures by producers. Strengthening local farmers' technical and organizational capacities could help improve network performance and achieve significant water savings. © 2019 American Society of Civil Engineers