Defence R and D Canada Suffield

Medicine Hat, Canada

Defence R and D Canada Suffield

Medicine Hat, Canada
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Zhang F.,Defence R and D Canada Suffield
AIP Conference Proceedings | Year: 2012

Metalized heterogeneous detonation and subsequent dense reactive particle flow have become a rapidly growing research area. Selected recent developments are reviewed with an emphasis on particle aspects in three parts: detonation-particle interactions, particle reaction and instability of particle dynamics. This includes the breakdown of the CJ detonation, detonation shock interaction effects on wave velocity, critical failure diameter, post-combustion and particle morphology, shocked particle reaction mechanism, critical charge diameter for particle reaction, multiple heat release laws, aerodynamic fragmentation combustion, particle dynamic instability, which leads to clustering, agglomeration and coherent jet structure, and its mechanisms through the role of stochastic particle interactions with shock waves and fluid vorticity and turbulence. These advances have laid down the fundamentals for the next stage of developments. © 2012 American Institute of Physics.

Bouchette G.,Neptec Design Group | Church P.,Neptec Design Group | McFee J.E.,Defence R and D Canada Suffield | Adler A.,Carleton University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

A detailed study is undertaken to investigate the performance and phenomenology of electrical impedance tomography for underwater applications. Experiments are performed in an aquarium tank filled with water and a sediment layer. A 64-electrode square array, appropriately scaled down in size, and a previously developed data acquisition system are used. An evaluation is conducted of the ability to detect compact objects buried at various depths in the sediment, with different horizontal separations, and at various vertical separations between the electrode array and the sediment layer. The objects include metallic and nonmetallic mine-like objects and inert ammunition projectiles, all appropriately scaled down in size. The effects of a number of other physical factors are studied, including sediment type, water turbidity and salinity, and object coating integrity and rusting. © 1980-2012 IEEE.

Vincent I.,Defence R and D Canada Suffield | Sun Q.,University of Calgary
Robotics and Autonomous Systems | Year: 2012

Unmanned ground vehicles currently exhibit simple autonomous behaviours. This paper presents a control algorithm developed for a tracked vehicle to autonomously climb obstacles by varying its front and back track orientations. A reactive controller computes a desired geometric configuration based on terrain information. A reinforcement learning algorithm enhances vehicle mobility by finding effective exit strategies in deadlock situations. It is capable of incorporating complex information including terrain and vehicle dynamics through learned experiences. Experiments illustrate the effectiveness of the proposed approach for climbing various obstacles.

Postma J.V.,University of Alberta | Wilson J.D.,University of Alberta | Yee E.,Defence R and D Canada Suffield
Boundary-Layer Meteorology | Year: 2011

A Lagrangian stochastic (LS) micromixing model is used for estimating concentration fluctuations in plumes of a passive, non-reactive tracer dispersing from elevated and ground-level compact sources into a neutral wall shear-layer flow. SPMMM (for sequential particle micromixing model) implements the familiar IECM (interaction by exchange with the conditional mean) micromixing scheme. The parametrization of the scalar micromixing time scale is identical to that proposed in a previously reported LS-IECM model (Cassiani et al., Atmos Environ 39:1457-1469, 2005a). However, while SPMMM is mathematically equivalent to the previously reported model, it differs in its numerical implementation: SPMMM releases N independent particles sequentially, whereas the previously reported model releases N independent particles simultaneously. In both implementations, the trajectories of the N particles are governed by single-point velocity statistics. The sequential particle implementation is computationally efficient, but cannot be applied to the case of reacting species. Results from both implementations are compared to experimental wind-tunnel dispersion data and to each other. © 2011 Springer Science+Business Media B.V.

Postma J.V.,University of Alberta | Wilson J.D.,University of Alberta | Yee E.,Defence R and D Canada Suffield
Boundary-Layer Meteorology | Year: 2011

The sequential particle micromixing model (SPMMM) is used to estimate concentration fluctuations in plumes dispersing into a canopy flow. SPMMM uses the familiar single-particle Lagrangian stochastic (LS) trajectory framework to pre-calculate the required conditional mean concentrations, which are then used by an interaction by exchange with the conditional mean (IECM) micromixing model to predict the higher-order fluctuations of the scalar concentration field. The predictions are compared with experimental wind-tunnel dispersion data for a neutrally stratified canopy flow, and with a previously reported implementation using simultaneous particle trajectories. The two implementations of the LS-IECM model are shown to be largely consistent with one another and are able to simulate dispersion in a canopy flow with fair to good accuracy. © 2011 Springer Science+Business Media B.V.

Stratilo C.W.,Defence R and D Canada Suffield | Bader D.E.,Defence R and D Canada Suffield
Applied and Environmental Microbiology | Year: 2012

Environmental samples were collected from carcass sites during and after anthrax outbreaks in 2000 and 2001 in the bison (Bison bison) population within Wood Buffalo National Park and the Hook Lake Region north of Wood Buffalo National Park. Bacillus anthracis spores were isolated from these samples and confirmed using phenotypic characterization and real-time PCR. Confirmed B. anthracis isolates were typed using multiple-locus variable-number tandem repeat analysis (MLVA15) and singlenucleotide-repeat analysis (SNRA). B. anthracis isolates split into two clades based on MLVA15, while SNRA allowed some isolates between carcass sites to be distinguished from each other. SNRA polymorphisms were also present within a single carcass site. Some isolates from different carcass sites having the same SNRA type had divergent MLVA types; this finding leads to questions about hierarchical typing methods and the robustness of the fine-scale typing of Bacillus anthracis. © 2012, American Society for Microbiology. All Rights Reserved.

Yee E.,Defence R and D Canada Suffield | Flesch T.K.,University of Alberta
Journal of Environmental Monitoring | Year: 2010

The determination of atmospheric emission rates from multiple sources using inversion (regularized least-squares or best-fit technique) is known to be very susceptible to measurement and model errors in the problem, rendering the solution unusable. In this paper, a new perspective is offered for this problem: namely, it is argued that the problem should be addressed as one of inference rather than inversion. Towards this objective, Bayesian probability theory is used to estimate the emission rates from multiple sources. The posterior probability distribution for the emission rates is derived, accounting fully for the measurement errors in the concentration data and the model errors in the dispersion model used to interpret the data. The Bayesian inferential methodology for emission rate recovery is validated against real dispersion data, obtained from a field experiment involving various source-sensor geometries (scenarios) consisting of four synthetic area sources and eight concentration sensors. The recovery of discrete emission rates from three different scenarios obtained using Bayesian inference and singular value decomposition inversion are compared and contrasted. © The Royal Society of Chemistry 2010.

Yee E.,Defence R and D Canada Suffield
Pure and Applied Geophysics | Year: 2012

Probability theory as logic (or Bayesian probability theory) is a rational inferential methodology that provides a natural and logically consistent framework for source reconstruction. This methodology fully utilizes the information provided by a limited number of noisy concentration data obtained from a network of sensors and combines it in a consistent manner with the available prior knowledge (mathematical representation of relevant physical laws), hence providing a rigorous basis for the assimilation of this data into models of atmospheric dispersion for the purpose of contaminant source reconstruction. This paper addresses the application of this framework to the reconstruction of contaminant source distributions consisting of an unknown number of localized sources, using concentration measurements obtained from a sensor array. To this purpose, Bayesian probability theory is used to formulate the full joint posterior probability density function for the parameters of the unknown source distribution. A simulated annealing algorithm, applied in conjunction with a reversible-jump Markov chain Monte Carlo technique, is used to draw random samples of source distribution models from the posterior probability density function. The methodology is validated against a real (full-scale) atmospheric dispersion experiment involving a multiple point source release. © 2011 Her Majesty the Queen in Right of Canada.

Ji H.,Consulting Inc. | Lien F.-S.,University of Waterloo | Yee E.,Defence R and D Canada Suffield
Journal of Computational Physics | Year: 2010

A new Cell-based Structured Adaptive Mesh Refinement (CSAMR) data structure is developed. In our CSAMR data structure, Cartesian-like indices are used to identify each cell. With these stored indices, the information on the parent, children and neighbors of a given cell can be accessed simply and efficiently. Owing to the usage of these indices, the computer memory required for storage of the proposed AMR data structure is only 58 word per cell, in contrast to the conventional oct-tree [P. MacNeice, K.M. Olson, C. Mobary, R. deFainchtein, C. Packer, PARAMESH: a parallel adaptive mesh refinement community toolkit, Comput. Phys. Commun. 330 (2000) 126] and the fully threaded tree (FTT) [A.M. Khokhlov, Fully threaded tree algorithms for adaptive mesh fluid dynamics simulations, J. Comput. Phys. 143 (1998) 519] data structures which require, respectively, 19 and 238 words per cell for storage of the connectivity information. Because the connectivity information (e.g., parent, children and neighbors) of a cell in our proposed AMR data structure can be accessed using only the cell indices, a tree structure which was required in previous approaches for the organization of the AMR data is no longer needed for this new data structure. Instead, a much simpler hash table structure is used to maintain the AMR data, with the entry keys in the hash table obtained directly from the explicitly stored cell indices. The proposed AMR data structure simplifies the implementation and parallelization of an AMR code. Two three-dimensional test cases are used to illustrate and evaluate the computational performance of the new CSAMR data structure. © 2010 Elsevier Inc.

Skvortsov A.,Defence Science and Technology Organisation, Australia | Yee E.,Defence R and D Canada Suffield
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

The scaling laws governing the concentration moments of a passive scalar released from a ground-level localized source in a neutrally stratified wall-shear layer are investigated using a theoretical framework recently formulated by Lebedev and Turitsyn. For the current application, this theoretical framework is generalized from the smooth random velocity field applicable in the viscous sublayer to the nonsmooth random velocity field that applies to the bulk of the wall-shear layer. Theoretical relationships for the passive scalar concentration moments are compared to a water-channel simulation of turbulent diffusion from a ground-level source in a wall-shear layer. The diffusion measurements in the wall-shear layer are shown to be consistent with the theoretical description and also imply the robustness of the identified scaling laws for the scalar concentration moments. © 2011 American Physical Society.

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