57949 research outputs found
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\uc9tude de la fissuration des t\uf4les coul\ue9es en bande
No full textThe publication is stored in the NRC Archives.La publication est conserv\ue9e dans les Archives du CNRC.Peer reviewed: NoNRC publication: Ye
Quality assessment of bulk Boron nitride nanotubes for advancing research, commercial and industrial applications
No full textEvaluating the quality of nanomaterials is essential for both basic research and industrial applications. Here, we describe a methodology for assessment of relative quality of boron nitride nanotube (BNNT) materials by absorption spectroscopy of regionrandom poly(3-hexyl-thiophene) (rra-P3HT) aggregates on BNNTs dispersed in chloroform. The strong selective \uf070\u2013\uf070 interaction between rra-P3HT and nanotubes combined with distinctive visual and spectroscopic changes allows a practical procedure for relative evaluation of BNNT external surface area and surface quality. The method calls first for the identification of the sample-specific polymer loading saturation point, which corresponds to the maximum BNNT surface polymer coverage in the sample. The sample quality (defined as the combination of sample purity and BNNT wall defect density) is determined from the structure and intensity of the absorption spectrum, which depend on the morphology and the total amount of rra-P3HT adsorbed on BNNT samples. This methodology for quality assessment is critical for accelerating the development of new, efficient purification strategies for bulk BNNT materials and advancing the investigation of BNNT properties and industrial applications.Peer reviewed: YesNRC publication: Ye
Candidate list maintenance in high utility sequential pattern mining
No full textHigh utility sequential pattern mining (HUSPM) lends the aspect of item value or importance to sequential pattern mining by identifying patterns that comprise a significant level of utility in a database. This paper addresses the challenge of establishing upper bounds on future candidate pattern utilities in an effort to reduce the search space required to identify the full set of patterns, and proposes a new approach where a list of possible candidate concatenation items is maintained. This list specifies the only items that ever need to be considered as possible candidates for concatenation with a sequential pattern being considered, or any future sequential pattern appearing as a descendant in the search tree. As a result of the elimination of items that are known to have no possibility of appearing in future high utility sequential patterns, an approach is presented that exploits this knowledge and computes a significantly tighter upper bound on the utilities of the such patterns. Tests on a variety of publicly available datasets show a dramatic reduction in the number of candidates considered, and the time taken to identify the full set of high utility sequential patterns is significantly reduced accordingly.Peer reviewed: YesNRC publication: Ye
A fatigue crack nucleation model for anisotropic materials
No full textBased on Tanaka\u2010Mura's dislocation\u2010dipole pile\u2010up configuration, a formulation of mixed mode fatigue crack nucleation is derived using the Stroh formalism for generally anisotropic materials. The fatigue life is explicitly expressed as inversely proportional to the stored plastic energy, depending on the material's anisotropic elastic matrix F 121, surface energy, Burgers vector, and lattice resistance. The model has been shown to agree with experimental observation on critical slip planes in PWA 1493 single crystal Ni\u2010base superalloy.Peer reviewed: YesNRC publication: Ye
Book Review: The story of offshore Arctic engineering
No full textThe story of offshore Arctic engineering. Dan Masterson. Cambridge Scholars Publishing; Unabridged edition (112015). (Hard cover), 195 pp. CDN$204.07. ISBN 978-1527518162.
Dan Masterson enjoyed a 45-year career in which he was engaged in ice engineering aspects of a number of the major offshore petroleum exploration programs in the Canadian High Arctic Islands and the Canadian and Alaskan Beaufort Sea. This generously illustrated book recounts Dan\u2019s own personal experiences in many of these projects. He writes well and his narration captures the spirit, enthusiasm, and optimism of the times. The book contains high level background information on the political and economic factors that set the scene or provide context for some of the projects he was involved in. This background information is factual and well researched, and clearly separated from his personal observations and opinions. The various problems and technical solutions described in the book are interspersed with some of the colourful experiences and characters he encountered.Peer reviewed: NoNRC publication: Ye
An optical H2S biosensor based on the chemoselective Hb-I protein tethered to a transparent, high surface area nanocolumnar electrode
No full textSensitive and selective detection of analytes in complex biological fluids can be an extremely challenging issue. The constructive association of biomolecules and transparent mesoporous electrodes is of interest in this area, as it can lead to innovative biosensors combining optical and electrochemical detection modes. This concept, however, requires the development of appropriate surface functionalization methodologies that are robust enough for long-term operation in physiological environments. In the present work, the high-surface area of 3D transparent mesoporous indium-tin oxide (ITO) electrodes (prepared by glancing angle deposition or GLAD) has been chemically functionalized with recombinant hemoglobin I from Lucina pectinata according to a versatile 2-step process. First, 4-diazoniumbenzoic acid salt is covalently electrografted onto the ITO surface, followed by amide coupling of the protein. The resulting electrodes were quantitatively characterized by cyclic voltammetry and UV\u2013vis absorption spectroscopy, demonstrating high surface coverages (up to 45% of a closed-packed monolayer for Hemoglobin-I) and homogeneous distribution across the entire thickness of the GLAD mesoporous structure. Good stability is also observed when the modified electrodes are immersed for prolonged times in a high ionic strength saline buffer. We also show that the hemoglobin I-modified electrode can be used as an optical biosensor for the selective, reversible, and fast detection of H2S in aqueous solutions over a 3ctwo-decade concentration range (i.e. up to 10 \u3bcM) and with a limit of detection of 0.35 \u3bcM. Good analytical performance was also achieved in human plasma without significant interference from the biological matrix.Peer reviewed: YesNRC publication: Ye
Cloud droplet activation properties and scavenged fraction of black carbon in liquid-phase clouds at the high-alpine research station Jungfraujoch (3580 m a.s.l.)
No full textLiquid clouds form by condensation of water vapour on aerosol particles in the atmosphere. Even black carbon (BC) particles, which are known to be slightly hygroscopic, have been shown to readily form cloud droplets once they have acquired water-soluble coatings by atmospheric aging processes. Accurately simulating the life cycle of BC in the atmosphere, which strongly depends on the wet removal following droplet activation, has recently been identified as a key element for accurate prediction of the climate forcing of BC. Here, to assess BC activation in detail, we performed in situ measurements during cloud events at the Jungfraujoch high-altitude station in Switzerland in summer 2010 and 2016. Cloud droplet residual and interstitial (unactivated) particles as well as the total aerosol were selectively sampled using different inlets, followed by their physical characterization using scanning mobility particle sizers (SMPSs), multi-angle absorption photometers (MAAPs) and a single-particle soot photometer (SP2). By calculating cloud droplet activated fractions with these measurements, we determined the roles of various parameters on the droplet activation of BC. The half-rise threshold diameter for droplet activation (Dcloudhalf), i.e. the size above which aerosol particles formed cloud droplets, was inferred from the aerosol size distributions measured behind the different inlets. The effective peak supersaturation (SSpeak) of a cloud was derived from Dcloudhalf by comparing it to the supersaturation dependence of the threshold diameter for cloud condensation nuclei (CCN) activation measured by a CCN counter (CCNC). In this way, we showed that the mass-based scavenged fraction of BC strongly correlates with that of the entire aerosol population because SSpeak modulates the critical size for activation of either particle type. A total of 50\u2009% of the BC-containing particles with a BC mass equivalent core diameter of 90\u2009nm was activated in clouds with SSpeak 480.21\u2009%, increasing up to 3c80\u2009% activated fraction at SSpeak 480.50\u2009%. On a single-particle basis, BC activation at a certain SSpeak is controlled by the BC core size and internally mixed coating, which increases overall particle size and hygroscopicity. However, the resulting effect on the population averaged and on the size-integrated BC scavenged fraction by mass is small for two reasons: first, acquisition of coatings only matters for small cores in clouds with low SSpeak; and, second, variations in BC core size distribution and mean coating thickness are limited in the lower free troposphere in summer. Finally, we tested the ability of a simplified theoretical model, which combines the \u3ba-K\uf6hler theory with the Zdanovskii\u2013Stokes\u2013Robinson (ZSR) mixing rule under the assumptions of spherical core\u2013shell particle geometry and surface tension of pure water, to predict the droplet activation behaviour of BC-containing particles in real clouds. Predictions of BC activation constrained with SSpeak and measured BC-containing particle size and mixing state were compared with direct cloud observations. These predictions achieved closure with the measurements for the particle size ranges accessible to our instrumentation, that is, BC core diameters and total particle diameters of approximately 50 and 180\u2009nm, respectively. This clearly indicates that such simplified theoretical models provide a sufficient description of BC activation in clouds, as previously shown for activation occurring in fog at lower supersaturation and also shown in laboratory experiments under controlled conditions. This further justifies application of such simplified theoretical approaches in regional and global simulations of BC activation in clouds, which include aerosol modules that explicitly simulate BC-containing particle size and mixing state.Peer reviewed: YesNRC publication: Ye
Development and implementation of automated fault detection and diagnostics for building systems: a review
No full textThis article reviews the current research on the development and implementation of automated fault detection and diagnostics (AFDD) technology for building systems. This article first examines the fundamentals of AFDD and its special requirements on building systems to provide a theoretical formulation of the problem. Some infrastructural barriers for scalable AFDD implementation are discussed. Then it reviews various methods used by previous researchers and real-life products in a typical AFDD workflow. The article compares different methods for feature generation and fault detection and fault diagnostics, and proposes ways to improve their current limitations from other research disciplines. The authors also discuss potential research topics to inspire further developed of new AFDD methodologies and make them more applicable, including: 1) fault assessments and improved information delivery; 2) benchmarking AFDD performance; 3) better interoperability of AFDD methods; and 4) cases of fault propagation and simultaneous faults.Peer reviewed: YesNRC publication: Ye