RECALAGE RIGIDE DE RELEVÉS LASER PAR MISE EN CORRESPONDANCE ROBUSTE BASÉE SUR DES SEGMENTS

International audienceLe recalage de relevés laser se révèle indispensable pour assembler des données précises devant servir à l'analyse, à la documentation et à la reconstruction tridimensionnelle d'environnements. Ce problème apparaît lorsqu'une zone d'intérêt est numérisée, au fil de temps, deux ou plusieurs fois, ou quand sa complexité nécessite un accroissement du nombre de stations de scanner laser fixe. Aussi, en raison de la variété des techniques disponibles d'acquisition, l'intégration multi-données devient une question importante puisqu'elle permet de mettre en cohérence des données contenant souvent une information complémentaire. La vaste majorité des algorithmes existants s'appuient sur les éléments ponctuels. C'est pourquoi les approches basées sur l'ICP demeurent actuellement les plus répandues. Cet article propose l'utilisation des arêtes sous forme d'intersections entre les plans modelés, pour le recalage rigide des nuages de points mobiles avec d'autres données, qu'elles soient 2D ou 3D. Ces primitives peuvent être aisément extraites, même si les données laser sont peu denses. Quelques méthodes de recalage basées sur les entités linéaires ont été examinées afin de vérifier leur précision et robustesse au bruit. Définie en tant que distance modifiée de Hausdorff entre deux jeux de segments, le critère d'exactitude a été employé pour les besoins d'une analyse quantitative. Au vu de ces éléments, la transformation rigide décrivant le meilleur alignement peut être déterminée avec l'algorithme FMII. Étant donné que la mise en correspondance automatique d'entités linéaires est ardue et influence l'estimation des paramètres de passage, une méthode d'appariement étudiant la similitude relative a été suggérée. Tous ces composants ont été ensuite intégrés pour créer une approche combinée RANSAC-FMII. Enfin, la précision de cette méthode de recalage avec appariements explicites itérés basant sur les segments a été évaluée et discutée. Abstract In the processes of analyzing, documenting and modelling the surrounding environment, an accurate registration of point clouds is necessary in order to obtain high-quality data. This procedure arises whenever a particular area is scanned by a laser more than once or from several different positions. Due to the variety of surveying techniques available, fusing the multi-source, complementary information data into one model is a very important matter. The vast majority of existing registration algorithms operate on feature points, hence ICP-like methods are the prevalent approach. This article proposes the use of edges obtained from intersecting planes modelled within individual point clouds for the accurate registration of mobile laser scans with other data, whether 2D or 3D. This type of primitives can be easily extracted, even from low-density point clouds. Using simulated data, several existing line-based registration algorithms have been evaluated in terms of reliability and robustness to noise. For the purpose of quantitative assessment, an accuracy criterion taking advantage of a modified Hausdorff distance between two sets of lines has been employed. Having regard to these elements, the rigid body transformation that gives the best alignment can be calculated with FMII algorithm. Since the automatic pairing of line segments is a challenging task influencing the accuracy of the estimated transformation parameters, a method that considers the relative similarity is proposed. All these components are used to form an approach combining RANSAC-FMII algorithms. Finally, the accuracy of this line-based registration method with an explicit iterative matching is evaluated and discussed

Assessing the Accuracy of Land-Based Mobile Laser Scanning Data

Also available online at http://journals.bg.agh.edu.pl/GEOMATICS/2012.6.3/geom.2012.6.3.73.pdfInternational audienceIn this paper, we have described an accuracy analysis of MLS point clouds collected using the LARA3D prototype platform in an urban area. Accuracy of the MLS was achieved through comparison with other data sources more accurate that the studied system. The study has shown, that when compared with control points, collected by a Total Station, the prototype system LARA3D is able to produce data with an accuracy better then 0.3 m. However, taking into consideration the uncertainty in the identification of common points, this method is affected by man-made error and limited by point cloud resolutions. Meanwhile, the use of existing reference data, such as e.g. high resolution point clouds from static terrestrial laser scanning provides fast and reliable data evaluation. The subjective element of operator interpretation is also removed. Results achieved using ICP algorithm show, that our mobile mapping system suffers from limitations of the sensor quality and Kalman filter implementation. In the case of point clouds locally degraded, proper matching is impossible and the obtained result does not reflect the type and scale of deformation correctly. Meanwhile, another less time-consuming and more automated method for assessing data accuracy should be developed. That may be referred to using the existing spatial data as reference, such as e.g.: cadastre, ALS data, Topographic Data Base (TBD), Digital Terrain Model, orthophotos and so on

Operational experience with the new ATLAS HLT framework for LHC Run 3

Athena is the software framework used in the ATLAS experiment throughout the data processing path, from the software trigger system through offline event reconstruction to physics analysis. For Run 3 data taking (which started in 2022) the framework has been reimplemented into a multi-threaded framework. The ATLAS High Level Trigger (HLT) system has also been updated to rely to a greater extent than in Run 2 (data taking between 2015-2018) on common solutions between online and offline software. We present the now operational new HLT system, report on how the system was tested, commissioned and optimised. In addition, we show developments that have been made in tools that are used to monitor and configure the HLT, some of which are designed from scratch for Run 3

Modification of the Cu-ETP copper surface layer with chromium by physical vapor deposition (PvD) and diffusion annealing

In the study, an attempt was made to increase durability of copper by creating a surface layer saturated or supersaturated with chromium only in the area of the highest thermo-mechanical loads during the welding process. There was developed a two-stage technological process, consisting of: application of chrome coating of the thickness approx. 1 µm on the Cu-ETP copper surface using the PVD method, and then performing the process of its diffusion by annealing at a temperature of 950°C in the vacuum. As a result, a diffusion CuCr layer with a thickness of approx. 20 µm was obtained, with hardness of approx. 120 HV0,01

Structure and thickness of Y2O3 coatings deposited by plasma spray physical vapour deposition (PS-PvD) method on graphite

Graphite is one of materials used in metallurgical applications; however, it is characterized by low oxidation resistance. In the article, an yttrium oxide coating was deposited using Plasma Spray Physical Vapour deposition method (PS-PVD) on graphite. Next, the influence of selected process parameters (power current, powder feed rate, or plasma gasses composition) on coating thickness and structure were discussed. The obtained coatings were characterized by hybrid structure with partially formed columns. The linear relationship between power current and coating thickness was observed. There was no significant influence of other analyses’ process parameters on coating thickness or microstructure

Structure and thickness of Y2O3 coatings deposited by plasma spray physical vapour deposition (PS-PvD) method on graphite

Graphite is one of materials used in metallurgical applications; however, it is characterized by low oxidation resistance. In the article, an yttrium oxide coating was deposited using Plasma Spray Physical Vapour deposition method (PS-PVD) on graphite. Next, the influence of selected process parameters (power current, powder feed rate, or plasma gasses composition) on coating thickness and structure were discussed. The obtained coatings were characterized by hybrid structure with partially formed columns. The linear relationship between power current and coating thickness was observed. There was no significant influence of other analyses’ process parameters on coating thickness or microstructure

Modification of the Cu-ETP copper surface layer with chromium by physical vapor deposition (PvD) and diffusion annealing

In the study, an attempt was made to increase durability of copper by creating a surface layer saturated or supersaturated with chromium only in the area of the highest thermo-mechanical loads during the welding process. There was developed a two-stage technological process, consisting of: application of chrome coating of the thickness approx. 1 µm on the Cu-ETP copper surface using the PVD method, and then performing the process of its diffusion by annealing at a temperature of 950°C in the vacuum. As a result, a diffusion CuCr layer with a thickness of approx. 20 µm was obtained, with hardness of approx. 120 HV0,01

Surface and thermomechanical characterization of polyurethane networks based on poly(dimethylsiloxane) and hyperbranched polyester

Two series of polyurethane (PU) networks based on Boltorn® hyperbranched polyester (HBP) and hydroxyethoxy propyl terminated poly(dimethylsiloxane) (EO-PDMS) or hydroxy propyl terminated poly(dimethylsiloxane) (HPPDMS), were synthesized. The effect of the type of soft PDMS segment on the properties of PUs was investigated by Fourier transform infrared spectroscopy (FTIR), contact angle measurements, surface free energy determination, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). The surface characterization of PUs showed existence of slightly amphiphilic character and it revealed that PUs based on HP-PDMS have lower surface free energy, more hydrophobic surface and better waterproof performances than PUs based on EO-PDMS. PUs based on HPPDMS had higher crosslinking density than PUs based on EO-PDMS. DSC and DMTA results revealed that these newlysynthesized PUs exhibit the glass transition temperatures of the soft and hard segments. DMTA, SEM and AFM results confirmed existence of microphase separated morphology. The results obtained in this work indicate that PU networks based on HBP and PDMS have improved surface and thermomechanical properties

Оптимизация условий для контроля качества наполнителя в металлических трубках

Проанализирована возможность с помощью цифровой радиографии контролировать качество наполнителя в детонирующем шнуре с целью обнаружения разноплотных включений, разрывов и других технологических нарушений. Проанализированы закономерности изменений интенсивности прошедшего потока квантов в геометрии узкого пучка. Определена энергия рентгеновского излучения, обеспечивающая максимальный перепад интенсивности прошедшего потока при изменении плотности наполнителя на +-30 %