Extraction de connaissances pour la description de l'environnement maritime côtier à partir de textes d'aide à la navigation
Publisher : RNTI
Les référentiels de données géoréférencées sont de plus en plus utilisés pour permettre l'annotation spatiale de documents textuels et ainsi faciliter l'accès à leur contenu, voire son analyse spatiale. En revanche, peu de travaux se sont intéressés à l'extraction d'information géographique à partir de textes pour alimenter de tels référentiels. Le travail présenté dans cet article explore les potentialités de l'extraction d'information spatiale indirecte (noms de lieux, relations spatiales, etc.) dans les textes des Instructions Nautiques produites par le Service Hydrographique et Océanographique de la Marine (SHOM). La méthode proposée combine une approche lexicale et une approche à base de patrons linguistiques puis est comparée aux principales approches d'extraction d'information géographique en français. L'objectif est de construire et peupler une ontologie assurant le lien entre les connaissances textuelles sur l'environnement côtier et les référentiels cartographiques associés afin de développer des services d'aide à la navigation à base de raisonnement.
Tunable electromagnetic resonant shunt using pulse-width modulation
Publisher : Elsevier BV
This article proposes a novel mean for tuning the natural frequency of an electromagnetic resonant shunt, using a pulse-width modulation (PWM) circuit. It is used to modulate the value of the capacitance of the shunt, and the electrical frequency is shown to be proportional to the command parameter of the PWM, the duty cycle. An easy and efficient strategy to tune the resonant shunt in real time is then proposed, thus obtaining a low powered and always stable vibration control device. The article proposes the theory of PWM, giving a robust method to predict the dynamics of the system. Then, an accurate multi-mode theoretical model of the tunable resonant shunt coupled to an elastic structure is proposed and experimentally validated on an elastic multi-mode structure, in the case of two different control strategies. The first one is a standard resonant shunt with both the electrical frequency and damping optimized to reduce a given resonance peak. The second one is based on a resonant shunt with the electrical damping as low as possible, which creates an antiresonance and a “notch” type mechanical response at the driving frequency. Both strategies are experimentally validated with real time variation and adaptation of the electrical frequency, obtaining an efficient vibration control device, able to reduce by a factor 40 the vibration level.
New Perspectives for LVL Manufacturing from Wood of Heterogeneous Quality—Part 2: Modeling and Manufacturing of Variable Stiffness Beams
Publisher : MDPI AG
This paper presents a new strategy in the use of wood of heterogeneous quality for composing LVL products. The idea is to consider veneers representative of the resource variability and retain local stiffness information to control panel manufacturing fully. The placement of veneers is also no longer random as in the first part of this group of papers but optimized for the quality of veneers according to the requirement of bending stresses along the beam. In a four-point bending test arrangement, this means the high-quality veneer is concentrated in the center of the beam in the area between the loading points where the bending moments are the most important, and the low quality is located at the extremities. This initiates the creation of variable stiffness beams. This is driven by an algorithm developed and tested on representative veneer samples from the resource. Four LVL panels were manufactured by positioning the veneers in the same positions as in an analytical calculation model, which allowed the calculation of beam mechanical properties in four-point bending. The proposed optimization of LVL manufacturing from variable quality veneers should help for more efficient usage of forest resources. This optimization strategy showed notable gains for modeled and experimental mechanical properties, whether in terms of stiffness or strength. The analytical calculation of the local modulus of elasticity from modelized beams was satisfactory compared to the tests of the manufactured beams test results, allowing the reliability of the model for this property to be confirmed.
Biplanar Low-Dose Radiograph Is Suitable for Cephalometric Analysis in Patients Requiring 3D Evaluation of the Whole Skeleton
Publisher : MDPI AG
Background: The biplanar 2D/3D X-ray technology (BPXR) is a 2D/3D imaging system allowing simultaneous stereo-corresponding posteroanterior (PA) and lateral 2D views of the whole body. The aim of our study was to assess the feasibility of cephalometric analysis based on the BPXR lateral skull view to accurately characterize facial morphology. Method: A total of 17 landmarks and 11 angles were placed and/or calculated on lateral BPXR and lateral cephalograms of 13 patients by three investigators. Five methods of angle identification were performed: the direct construction of straight lines on lateral cephalograms (LC-A) and on BPXR (BPXR-A), as well as the calculation of angles based on landmark identification on lateral cephalograms (LA-L) and on BPXR with the PA image (BPXR-LPA) or without (BPXR-L). Intra- and interoperator reliability of landmark identification and angle measurement of each method were calculated. To determine the most reliable method among the BPXR-based methods, their concordance with the reference method, LC-A, was evaluated. Results: Both imaging techniques had excellent intra- and interoperator reliability for landmark identification. On lateral BPXR, BPXR-A presented the best concordance with the reference method and a good intra- and interoperator reliability. Conclusion: BPXR provides a lateral view of the skull suitable for cephalometric analysis with good reliability.
A calibration procedure for the assessment of work hardening part I: Effects of the microstructure and load type
Publisher : Elsevier BV
This paper presents a methodology to define and quantify the level of work hardening locally in a material. The methodology is proposed after a thorough experimental study based on three complementary experimental techniques for microstructural characterizations: microhardness, X-ray diffraction (XRD) and Electron Backscatter Diffraction (EBSD) applied on Inconel 718 samples. In our analysis, several loading histories including single tension, single compression, high strain rates and low cycle fatigue have been investigated. The effects of the microstructure have been further investigated by modifying the size of the grains and the size of the strengthening precipitates. Experimental tests have also been simulated to choose a model variable able to represent work hardening. A reciprocal link between work hardening and experimental characterizations has then been established. Correlation curves have been proposed that enable to quantify the level of work hardening from the knowledge of the experimental data. Accuracy and complementarity of the three experimental approaches are discussed as well as the impact of the microstructure of the material on the measured quantities.
Multiscale Modeling Approaches for Composites
Publisher : Elsevier
Multiscale Modeling Approaches for Composites outlines the fundamentals of common multiscale modeling techniques and provides detailed guidance for putting them into practice. Various homogenization methods are presented in a simple, didactic manner, with an array of numerical examples. The book starts by covering the theoretical underpinnings of tensors and continuum mechanics concepts, then progresses to actual micromechanic techniques for composite media and laminate plates. In the last chapters the book covers advanced topics in homogenization, including Green’s tensor, Hashin-Shtrikman bounds, and special types of problems. All chapters feature comprehensive analytical and numerical examples (Python and ABAQUS scripts) to better illustrate the theory.
Breathing through a spirometer perturbs balance
Publisher : Informa UK Limited
Natural breathing is known to induce at each inspiration/expiration, minimal perturbations of body balance that are compensated by movement of trunk and lower limb (Hodges et al. 2002). This phenomenon called posturo ventilatory synchronization may be impaired (Manor et al. 2012). Its evaluation requires simultaneous assessments of ventilation profile and postural control, using the less disruptive methods. Spirometry is the reference method to assess the ventilatory parameters. It requires however to connect the subject to the spirometer, using a mouthpiece, that is known to modify significantly the respiratory frequency (Gilbert et al. 1972) and may influence the postural control. The Optoelectronic Plethysmography (OEP) was validated as an alternative non-disruptive method to assess ventilation as it allows subjects to breathe naturally. Evidently, non-contact measure of ventilation by camera is supposed to induce no perturbation of postural control, and may be more appropriate than spirometer to assess the posturo ventilator synchronization. The objective of this study was to evaluate the postural perturbations due to the use of the spirometer, by comparing it to the OEP method, on postural control.
Estimating pulmonary function after surgery for adolescent idiopathic scoliosis using biplanar radiographs of the chest with 3D reconstruction
Publisher : The British Editorial Society of Bone & Joint Surgery
Aims This study addressed two questions: first, does surgical correction of an idiopathic scoliosis increase the volume of the rib cage, and second, is it possible to evaluate the change in lung function after corrective surgery for adolescent idiopathic scoliosis (AIS) using biplanar radiographs of the ribcage with 3D reconstruction? Methods A total of 45 patients with a thoracic AIS which needed surgical correction and fusion were included in a prospective study. All patients underwent pulmonary function testing (PFT) and low-dose biplanar radiographs both preoperatively and one year after surgery. The following measurements were recorded: forced vital capacity (FVC), slow vital capacity (SVC), and total lung capacity (TLC). Rib cage volume (RCV), maximum rib hump, main thoracic curve Cobb angle (MCCA), medial-lateral and anteroposterior diameter, and T4-T12 kyphosis were calculated from 3D reconstructions of the biplanar radiographs. Results All spinal and thoracic measurements improved significantly after surgery (p < 0.001). RCV increased from 4.9 l (SD 1) preoperatively to 5.3 l (SD 0.9) (p < 0.001) while TLC increased from 4.1 l (SD 0.9) preoperatively to 4.3 l (SD 0.8) (p < 0.001). RCV was correlated with all functional indexes before and after correction of the deformity. Improvement in RCV was weakly correlated with correction of the mean thoracic Cobb angle (p = 0.006). The difference in TLC was significantly correlated with changes in RCV (p = 0.041). It was possible to predict postoperative TLC from the postoperative RCV. Conclusion 3D rib cage assessment from biplanar radiographs could be a minimally invasive method of estimating pulmonary function before and after spinal fusion in patients with an AIS. The 3D RCV reflects virtual chest capacity and hence pulmonary function in this group of patients.
Verification and validation for the cavitating flow around a NACA0015 hydrofoil
When cavitation occurs around hydrofoils it is the cause of noise radiation, vibration and erosion. Consequently numerical cavitation models have been developped and tested over the last decades (Schnerr and Sauer ). However, recent works show that numerical predictions for cavitating flow might be very sensitive to the spatial resolution of the mesh and require dicretization errors estimations (Negrato et al. , Asnaghi et al. ). The experimental and numerical approches joined in this work are the first step of the validation of the ISIS-CFD code for cavitating flows with fluid-structure interaction. Although, only results for a rigid profile in cavitating conditions are presented in this work. The test case is a NACA0015 profile in the cavitation tunnel located at the french Naval Academy Research Institute. On the numerical side, the ISIS-CFD code is used to solve the unsteady Reynolds Averaged Navier Stokes Equations (uRANSE). The two phases mixture dynamics are solved thanks to an interface capturing method and the Sauer cavitation model. The test case is first adressed using a two-dimensional computational domain. A set of unstructured grids is generated using Hexpress to perform a grids and time steps convergence study and obtain uncertainty estimations for both wetted and cavitating flow conditions. Then, the same study is done for an extended three-dimensional geometry taking into account the lateral walls of the tunnel and the convergent section located upstream of the test section. Influences of the turbulence quantities at the inflow and the cavitation model parameters are also assessed. The numerical results are compared with experimental effort measurements, high-speed camera signals and PIV acquisitions provided by Lelong . From the verification and validation analysis a three dimensional grid and a set of computational parameters are chosen for future calculations with fluid-structure interaction and cavitation.
Knowledge-Based Recommendation for On-Demand Mapping: Application to Nautical Charts
Publisher : MDPI AG
Maps have long been seen as a single cartographic product for different uses, with the user having to adapt their interpretation to his or her own needs. On-demand mapping reverses this paradigm in that it is the map that adapts to the user’s needs and context of use. Still often manual and reserved for professionals, on-demand mapping is evolving toward an automation of its processes and a democratization of its use. An on-demand mapping service is a chain of several consecutive steps leading to a target map that precisely meets the needs and requirements of a user. This article addresses the issue of selecting relevant thematic layers with a specific context of use. We propose a knowledge-based recommendation approach that aims to guide a cartographer through the process of map-making. Our system is based on high- and low-level ontologies, the latter modeling the concepts specific to different types of maps targeted. By focusing on maritime maps, we address the representation of knowledge in this context of use, where recommendations rely on axiomatic and rule-based reasoning. For this purpose, we choose description logics as a formalism for knowledge representation in order to make cartographic knowledge machine readable.