Benoit Ozell

École Polytechnique de Montréal, Computer Engineering and Software Engineering, Faculty Member

École Polytechnique de Montréal, Cmputer and Software Engineering, Faculty Member

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Address: Montréal, Québec, Canada

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Papers by Benoit Ozell

A Geometrie Modeller for Turbomachinery Applications

This paper deseribes a software paekage modelling of turbines, as weIl as for body-fitted eoordin... more This paper deseribes a software paekage modelling of turbines, as weIl as for body-fitted eoordinate grid. The paekage used respeetively for: tailored for the geometrie the automatie generation of a eonsists of four programs 1. The ereation and the modi fi cation of a model;" the designer ean "edit" the model by means of commands whose basic entities are points, profiles, blades,the hub and the shroud. 2. The refinement of the model by the distribution of points over each profile defining the blade, and then by the interpolation of new intermediate profiles between the hub and the shroud. 3. The construetion of surfaces delimiting the blade-to-blade ehannel boundaries (the eomputational domain). 4. The calculation of a body-fitted coordinate system, inside the channel, by the solution of a system of differential equations. A set of modeled turbines is shown to illustrate the results of eaeh st.ep.

Hydraulic Turbine Performance Prediction by Supercomputing

Virtual reality simulator for scoliosis surgery training: Transatlantic collaborative tests

Scoliosis is a complex deformation of the spine requiring, in severe cases, a highly delicate and... more Scoliosis is a complex deformation of the spine requiring, in severe cases, a highly delicate and invasive surgical instrumentation operation to correct the spinal deformities. Available traditional tools for surgical training have major drawbacks for which virtual reality (VR) technologies and computer simulation can offer solutions. In this paper, we introduce a surgical simulator integrating a complex patient-specific biomechanical model

A configurable visualization environment

The different steps in developing a simulation program, as well as the multiple application domai... more The different steps in developing a simulation program, as well as the multiple application domains, imply many expectations from visualization and the visualization environment greatly influences the perception of the information contained in the solution. The methodology presented is centered around the concept of configurability, i.e. the possibility for a user to specialize the visualizator for current needs and therefore create a working environment tailored for specific domains and situations. Configurability allows for the sharing of generic elements and algorithms of visualization, and also for a natural environment of communication. It provides functions for a linear thinking context (repetitive creation of same representations, systematic use of a set of images for comparison or validation), but also for exploration of the characteristics of the solution. This communication uses the paradigm and the syntagm of a language, the language of visualization. This work presents the results of an analysis of visualization from the point of view of linguistics. The goal is not to present new methods for displaying results, but it is rather an attempt to define its structure. We present visualization as an activity of communication of information. Visualization Environments Historically, in the visualization world, applications have generally preceded the structuration of ideas. Existing visualizators individually present new concepts and ideas, but without integrating them into a structured approach appropriate to a model of visualization. Early visualization tools were iri-house efforts carried out at the level of specific routines, custom made for a given problem, and written by the end°Copyright ©1995 by Ozell and Camarero. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. user himself. These evidently lacked generality, both from the functionality and the portability perspectives. The first step to improve this, was to isolate the display functions. Hidden line removal, shading, interactive manipulations were given to a graphic language or even to specialized hardware. It was then possible to support a greater variety of equipment and to orient their development to conform with the emerging standards. The next step was to apply the same standardization to the dialogue functions using commercial libraries like OSF/Motif. The result is a modularization of the visualization process with the emergence of a well-defined core, consisting in data extraction and virtual image creation (Fig. 1). This evolution has been characterized by a shift from a situation where the end-user is also the author, to one where the development is carried out by professional computer scientists. The next phase in this evolutionary process, is the ability to service the diversity of needs ranging from debugging a grid generation or a simulation program, to the production phase of a project. This requires a configurable software package that allows to share the most generic elements of visualization: dialogue, graphics, basic extraction algorithms. Configurable is not to be confused with programmable. It is rather the ability to assemble, from a given tool set a combination of functions within a visual and communication environment, i.e. a non-programming environment. The current visualization environments can be grouped in three categories with varying flexibility. Programs [1, 2] offer a turnkey architecture with a fixed functionality that the user cannot modify. Libraries [3, 4] lend themselves to a better flexibility providing access to visualization "functions, but require programming knowledge. The interaction with the end-user is then the responsibility of the programmer. Visual programming environments [5, 6, 7, 8, 9] based on data flow diagrams are more recent. They are excellent for prototyping, but not u s E R Extraction + calculations

Wolverine: A Distributed Scene-Graph Library

Presence: Teleoperators & Virtual Environments, Feb 1, 2005

In this paper we present Wolverine, a simple scene-graph library that incorporates advanced conce... more In this paper we present Wolverine, a simple scene-graph library that incorporates advanced concepts such as node and object differentiation, seamless serialization for distributed environments, and multimedia elements including dynamic textures and video sources. By examining the specifics of Wolverine, we will compare our approach to other scene-graph APIs and dwell on its use in a videoconferencing shared-reality collaborative application.

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PO-1017: Fast GPU-based Monte Carlo dose calculations for permanent prostate implants

Radiotherapy and Oncology, 2014

Poly-co: an unsupervised co-reference detection system

International Conference on Natural Language Generation, Jul 7, 2010

We describe our contribution to the Generation Challenge 2010 for the tasks of Named Entity Recog... more We describe our contribution to the Generation Challenge 2010 for the tasks of Named Entity Recognition and coreference detection (GREC-NER). To extract the NE and the referring expressions, we employ a combination of a Part of Speech Tagger and the Conditional Random Fields (CRF) learning technique. We finally experiment an original algorithm to detect co-references. We conclude with discussion about our system performances.

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Efficiency improvement in proton dose calculations with an equivalent restricted stopping power formalism

Physics in Medicine and Biology, Dec 19, 2017

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Analysis and visualization tools in CFD, part II: A case study in grid adaptivity

Finite Elements in Analysis and Design, May 1, 1995

... and visualization tools in CFD, Part II: A case study in grid adaptivity Francois Guibault&qu... more ... and visualization tools in CFD, Part II: A case study in grid adaptivity Francois Guibault"'b, Andr6 Garona'b, Benoit Ozella'b ... for elliptical equations The solver used for this study is based on a highly modular finite element environment coined as PIRATE (Programmable, Interactive ...

Improving Communication Using 3D Animation

Springer eBooks, 2010

A study of potential numerical pitfalls in GPU-based Monte Carlo dose calculation

Physics in Medicine and Biology, Jun 10, 2015

The purpose of this study was to evaluate the impact of numerical errors caused by the floating p... more The purpose of this study was to evaluate the impact of numerical errors caused by the floating point representation of real numbers in a GPU-based Monte Carlo code used for dose calculation in radiation oncology, and to identify situations where this type of error arises. The program used as a benchmark was bGPUMCD. Three tests were performed on the code, which was divided into three functional components: energy accumulation, particle tracking and physical interactions. First, the impact of single-precision calculations was assessed for each functional component. Second, a GPU-specific compilation option that reduces execution time as well as precision was examined. Third, a specific function used for tracking and potentially more sensitive to precision errors was tested by comparing it to a very high-precision implementation.Numerical errors were found in two components of the program. Because of the energy accumulation process, a few voxels surrounding a radiation source end up with a lower computed dose than they should. The tracking system contained a series of operations that abnormally amplify rounding errors in some situations. This resulted in some rare instances (less than 0.1%) of computed distances that are exceedingly far from what they should have been. Most errors detected had no significant effects on the result of a simulation due to its random nature, either because they cancel each other out or because they only affect a small fraction of particles. The results of this work can be extended to other types of GPU-based programs and be used as guidelines to avoid numerical errors on the GPU computing platform.

Fast GPU-based Monte Carlo simulations for LDR prostate brachytherapy

Physics in Medicine and Biology, Jun 10, 2015

Automatic Semantic Web Annotation of Named Entities

Springer eBooks, 2011

CFD and realistic visualization for the analysis of fire scenarios

129: Implementation of a GPU Monte Carlo protons transport code for dose calculations: methods and challenges

Radiotherapy and Oncology, Feb 1, 2014

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Design and Test of an adaptive augmented reality interface to manage systems to assist critical missions

arXiv (Cornell University), Mar 25, 2021

We present a user interface (UI) based on augmented reality (AR) with head-mounted display (HMD) ... more We present a user interface (UI) based on augmented reality (AR) with head-mounted display (HMD) for improving situational awareness during critical operation and improve human efficiency on operations. The UI displays contextual information as well as accepts orders given from the headset to control unmanned aerial vehicles (UAVs) for assisting the rescue team. We established experiments where people had been put in a stressful situation and are asked to resolve a complex mission using a headset and a computer. Comparing both technologies, our results show that augmented reality has the potential to be an important tool to help those involved in the emergency situation.

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Génération automatique de motifs de détection d’entités nommées en utilisant des contenus encyclopédiques (Automatic generation of named entity detection patterns using encyclopedic contents)

Les encyclopédies numériques contiennent aujourd'hui de vastes inventaires de formes d'écritures ... more Les encyclopédies numériques contiennent aujourd'hui de vastes inventaires de formes d'écritures pour des noms de personnes, de lieux, de produits ou d'organisation. Nous présentons un système hybride de détection d'entités nommées qui combine un classifieur à base de Champs Conditionnel Aléatoires avec un ensemble de motifs de détection extraits automatiquement d'un contenu encyclopédique. Nous proposons d'extraire depuis des éditions en plusieurs langues de l'encyclopédie Wikipédia de grandes quantités de formes d'écriture que nous utilisons en tant que motifs de détection des entités nommées. Nous décrivons une méthode qui nous assure de ne conserver dans cette ressources que des formes non ambiguës susceptibles de venir renforcer un système de détection d'entités nommées automatique. Nous procédons à un ensemble d'expériences qui nous permettent de comparer un système d'étiquetage à base de CRF avec un système utilisant exclusivement des motifs de détection. Puis nous fusionnons les résultats des deux systèmes et montrons qu'un gain de performances est obtenu grâce à cette proposition.

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A Configurable Framework for Multidisciplinary Analysis Integration and Management

This paper presents the data model developped in the context of the VADOR application framework p... more This paper presents the data model developped in the context of the VADOR application framework project. The purpose of the VADOR framework is to enable the seamless integration of commercial and in-house analysis applications in a heterogeneous, distributed computing environment, and to allow the management and sharing of the data in order to provide support to MDO. A multi-tiered client-server architecture has been devised, which comprises a client GUI for interactive data definition and execution launching, separate data and execution servers, and autonomous remotely executable application wrappers. The data model is at the core of the system and its contents and relations constitutes one of the main deliverables of the project.

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Extension d’un système d’étiquetage d’entités nommées en étiqueteur sémantique

<tt>pGPUMCD</tt>: an efficient GPU-based Monte Carlo code for accurate proton dose calculations

Physics in Medicine and Biology, Apr 12, 2019

In proton therapy, Monte Carlo simulations are desirable to accurately predict the delivered dose... more In proton therapy, Monte Carlo simulations are desirable to accurately predict the delivered dose. This paper introduces and benchmarks pGPUMCD, a GPU-based Monte Carlo code implementing the physical processes required for proton therapy applications. In pGPUMCD, the proton transport is carried out in a voxelized geometry with a class II condensed history scheme. For this purpose, the equivalent restricted stopping power formalism (L eq formalism), the Fermi-Eyges scattering theory and the discrete electromagnetic/nuclear interactions were considered. pGPUMCD was compared to Geant4 in a validation study where the physical processes were validated one after the other. Dose differences between pGPUMCD and Geant4 were smaller than 1% in the Bragg peak region and up to 3% in its distal fall-off. Moreover, a voxelwise dose difference below 1% was observed for 99.5% of calculation positions. The pGPUMCD 80% falloff positions matched with those of Geant4 within 0.1%. The pGPUMCD computation times were inversely proportional to the voxel size, with one million protons transported in less than 0.5 s with [Formula: see text] mm3 voxels. pGPUMCD, based on the L eq formalism variance reduction technique, is therefore an attractive candidate for integration in a clinical treatment planning system.

Benoit Ozell

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