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Québec, Canada

Potvin G.,Valcartier Research Center
Journal of the Optical Society of America A: Optics and Image Science, and Vision

We examine how the Rytov approximation describing log-amplitude and phase fluctuations of a wave propagating through weak uniform turbulence can be generalized to the case of turbulence with a large-scale nonuniform component. We show how the large-scale refractive index field creates Fermat rays using the path integral formulation for paraxial propagation. We then show how the second-order derivatives of the Fermat ray action affect the Rytov approximation, and we discuss how a numerical algorithm would model the general Rytov approximation. © 2015 Optical Society of America. Source

Despeyroux A.,Royal Military College of Canada | Hickey J.-P.,Royal Military College of Canada | Desaulnier R.,Royal Military College of Canada | Luciano R.,Royal Military College of Canada | And 2 more authors.
Journal of Spacecraft and Rockets

Grid fins provide good maneuverability to missiles in supersonic flow because they can maintain lift at a higher angle of attack. Although static aerodynamic data exist, very little quantitative dynamic performance information is available for grid fin controlled missiles. The high drag associated with grid fins is also a concern. Dynamic simulations are carried out using computational fluid dynamics to investigate the dynamic stability of a generic missile, controlled by grid fins or planar fins, in supersonic and transonic regimes at angles of attack up to 30 deg. In supersonic flow, the pitch-damping derivative is found to be insensitive to the control fin type; however, in transonic flow, grid fins provide a lower damping in pitch than planar fins due to the blockage effect induced by its choked cells. The reduction of the high drag associated with grid fins is also investigated by comparing the performances of two isolated grid fin geometries with and without the use of a Busemann biplane configuration. The application of this concept to grid fins reduces its drag in the supersonic regime while maintaining its beneficial lift characteristics. Furthermore, the drag of grid fins in transonic flow can be reduced by using an optimized profile with a higher inletto- Throat area ratio. Copyright © 2015 by Her Majesty the Queen in Right of Canada. Source

Rabbath C.A.,Valcartier Research Center | Lechevin N.,Valcartier Research Center
Journal of Intelligent and Robotic Systems: Theory and Applications

This article presents a control system enabling coverage of a prescribed ground area by a team of wheeled mobile robots. The control system relies on equal balancing of the costs among the wheeled robots. Cost balancing leverages the intuition that a healthy neighbor could help a degraded robot to carry out its monitoring task simply by moving slightly towards the degraded robot. This feature allows the control system to support situations where vehicles have varying sensor characteristics. The article focuses on the design of the system and the results of experiments obtained with a small number of networked ground robots. The coverage control system is decentralized. Hence, no element of the system is a single point of failure, and the computations can be distributed. The experiments show (1) the satisfactory, yet suboptimal, performance of the coverage control system under healthy conditions, and the adaptation of the vehicles in case a team member is subject to a degraded condition of operation, and (2) the feasibility of the integration of the coverage control system with low-cost commercial wheeled mobile robot systems. © 2014, Her Majesty the Queen in Right of Canada. Source

Espinola R.L.,U.S. Army | Leonard K.R.,U.S. Army | Byrd K.A.,U.S. Army | Potvin G.,Valcartier Research Center
Proceedings of SPIE - The International Society for Optical Engineering

Biometric technologies composed of electro-optical/infrared (EO/IR) sensor systems and advanced matching algorithms are being used in various force protection/security and tactical surveillance applications. To date, most of these sensor systems have been widely used in controlled conditions with varying success (e.g., short range, uniform illumination, cooperative subjects). However the limiting conditions of such systems have yet to be fully studied for long range applications and degraded imaging environments. Biometric technologies used for long range applications will invariably suffer from the effects of atmospheric turbulence degradation. Atmospheric turbulence causes blur, distortion and intensity fluctuations that can severely degrade image quality of electro-optic and thermal imaging systems and, for the case of biometrics technology, translate to poor matching algorithm performance. In this paper, we evaluate the effects of atmospheric turbulence and sensor resolution on biometric matching algorithm performance. We use a subset of the Facial Recognition Technology (FERET) database and a commercial algorithm to analyze facial recognition performance on turbulence degraded facial images. The goal of this work is to understand the feasibility of long-range facial recognition in degraded imaging conditions, and the utility of camera parameter trade studies to enable the design of the next generation biometrics sensor systems. © 2015 SPIE. Source

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