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Lien F.-S.,University of Waterloo | Xu T.,University of Waterloo | Zhang F.,DRDC Suffield
AIP Conference Proceedings

The mechanism of the instability in heterogeneous post-detonation flows, which contain dense solid particles, is yet to be determined due to its physical complexity. Since both strain rate and vorticity are found to play an important role in the particle agglomeration processes, a new criterion is established to represent the tendency of particle agglomeration, either based on divergence of particle velocity related to the difference between strain-rate and vorticity invariants or time derivative of particle volume fraction. The particle jetting phenomenon observed in a heterogeneous explosion is simulated and investigated at mesoscales based on the same numerical platform, which paves the way to investigate the role of vorticity, strain-rate and turbulence in the formation of macroscopic particle jetting. © 2012 American Institute of Physics. Source

Scherbatiuk K.,DRDC Suffield | Rattanawangcharoen N.,University of Manitoba
International Journal of Impact Engineering

This study is aimed to provide an efficient analytical model to calculate a time history of response for a free-standing soil-filled HESCO Bastion concertainer® wall subjected to air blast loading. The model is formulated based on the observations of the wall response to air blast loading in the experiments and on the deformation of a finite element model. This hybrid rigid body rotation model combines both a reverse Winkler foundation to model the distribution of pressure at the base of the wall and perfectly plastic shear resistance to model the shear deformation at the corner. The time histories of horizontal and vertical displacements calculated from the proposed analytical model are validated with displacements from both full-scale blast testing of free-standing simple straight walls and calculations using a finite element model. © 2009 Elsevier Ltd. Source

Diakowski P.M.,University of Western Ontario | Xiao Y.,University of Western Ontario | Petryk M.W.P.,DRDC Suffield | Kraatz H.-B.,University of Western Ontario
Analytical Chemistry

A recognition layer formed by multiwalled carbon nanotubes (MWCNTs) covalently modified with a ferrocene?lysine conjugate deposited on the indium tin oxide (ITO) was investigated as a sensor for chemical warfare agent (CWA) mimics. Electrochemical impedance spectroscopy measurements showed that upon addition of CWA mimic dramatic changes occurred in the electrical properties of the recognition layer. These changes allowed the detection of nerve agent analogues at the micromolar level, and a limited sensitivity was observed toward a sulfur mustard mimic. Experimental parameters were optimized so as to allow the detection of CWAs at single frequency, thereby significantly reducing acquisition time and simplifying data treatment. A proposed method of detection represents a significant step toward the design of an affordable and "fieldable" electrochemical CWA sensor. © 2010 American Chemical Society. Source

D'Agostino P.A.,DRDC Suffield
NATO Science for Peace and Security Series A: Chemistry and Biology

Solid phase microextraction (SPME) fibers were used to headspace-sample chemical warfare agents and their hydrolysis products from glass vials and glass vials containing spiked media, including Dacron swabs, office carpet, paper and fabric. The interface of the Z-spray source was modified to permit safe introduction of the SPME fibers for desorption electrospray ionization mass spectrometric (DESI-MS) analysis. A "dip and shoot" method was also developed for the rapid sampling and DESI-MS analysis of chemical warfare agents and their hydrolysis products in liquid samples. Sampling was performed by simply dipping fused silica, stainless steel or SPME tips into the organic or aqueous samples. Replicate analyses were completed within several minutes under ambient conditions with no sample pre-treatment, resulting in a significant increase in sample throughput. The developed sample handling and analysis method was applied to the determination of chemical warfare agent content in samples containing unknown chemical and/or biological warfare agents. Ottawa sand was spiked with sulfur mustard, extracted with water and autoclaved to ensure sterility. Sulfur mustard was completely hydrolysed during the extraction/autoclave step and thiodiglycol was identified by DESI-MS, with analyses generally being completed within 1 min using the "dip and shoot" method. © 2011 Springer Science+Business Media B.V. Source

Collier J.,DRDC Suffield | Se S.,MDA Systems Ltd | Kotamraju V.,MDA Systems Ltd
Proceedings - 2013 International Conference on Computer and Robot Vision, CRV 2013

This paper describes a multi-sensor appearance-based place recognition system suitable for robotic mapping. Unlike systems that extract features from visual imagery only, here we apply the well known Bag-of-Words approach to features extracted from both visual and range sensors. By applying this technique to both sensor streams simultaneously we can overcome the deficiencies of each individual sensor. We show that lidar-based place recognition using a generative model learnt from Variable Dimensional Local Shape Descriptors can be used to perform place recognition regardless of lighting conditions or large changes in orientation, including traversing loops backward. Likewise, we are still able to exploit the feature rich place recognition that visual systems provide. Using a pose verification system we are able to effectively discard false positive loop detections. We present experimental results that highlight the strength of our approach and investigate alternative techniques for combining the results from the individual sensor streams. The multi-sensor approach enables the two sensors to complement each other well in large urban and rural environments under variable lighting conditions. © 2013 IEEE. Source

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