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Wideband Ge-Rich SiGe polarization-insensitive waveguides for mid-infrared free-space communications
No full textThe recent development of quantum cascade lasers, with room-temperature emission in the mid-infrared range, opened new opportunities for the implementation of ultra-wideband communication systems. Specifically, the mid-infrared atmospheric transparency windows, comprising wavelengths between 3\u20135 \ub5m and 8\u201314 \ub5m, have great potential for free-space communications, as they provide a wide unregulated spectrum with low Mie and Rayleigh scattering and reduced background noise. Despite the great efforts devoted to the development of mid-infrared sources and detectors, little attention is dedicated to the management of polarization for signal processing. In this work, we used Ge-rich SiGe alloys to build a wideband and polarization-insensitive mid-infrared photonic platform. We showed that the gradual index change in the SiGe alloys enabled the design of waveguides with remarkably low birefringence, below 2
7 10 124, over ultra-wide wavelength ranges within both atmospheric transparency windows, near wavelengths of 3.5 \ub5m and 9 \ub5m. We also report on the design of a polarization-independent multimode interference device achieving efficient power splitting in an unprecedented 4.5-\ub5m bandwidth at around 10-\ub5m wavelength. The ultra-wideband polarization-insensitive building blocks presented here pave the way for the development of high-performance on-chip photonic circuits for next-generation mid-infrared free-space communication systems.Peer reviewed: YesNRC publication: Ye
A specific demetalation of Fe\u2013N4 catalytic sites in the micropores of NC_Ar + NH3 is at the origin of the initial activity loss of the highly active Fe/N/C catalyst used for the reduction of oxygen in PEM fuel cells
No full textIn this study, we explored the behavior of NC_Ar + NH3, an initially highly active catalyst for oxygen electroreduction, in H2/air fuel cells from 0.8 to 0.2 V at 80 \ub0C and 25 \ub0C, in order to find the causes of its instability. We discovered that the decay of the current density always involves the superposition of fast and slow first order kinetics, for which half-lives were obtained. The half-life of the fast decay was practically the same at all potentials and temperatures with a value of around 138 \ub1 55 min, while the half-life of the slow decay greatly varied from a minimum of 482400 min (40 h) to infinity. From the adsorption\u2013desorption isotherm of NC_Ar + NH3, it was deduced that the Fe/N/C carbonaceous catalyst is characterized by interconnected open-end slit-shaped micropores, in which water (with dissolved H+ and O2) quickly flows in the fuel cells if their width is 650.7 nm as it has no interaction with the hydrophobic walls of the micropores. The driving force of this quick water flow is the humidified air streaming through the working cathode. Fe\u2013N4-like active sites are thermodynamically stable in stagnant acidic conditions, but according to the Le Chatelier principle, they demetalate in the flux of water running into the micropores. This specific demetalation is the cause of the initial loss of ORR activity of NC_Ar + NH3 catalysts assigned to the fast current decay in fuel cells.Peer reviewed: YesNRC publication: Ye
High density genetic mapping of Fusarium head blight resistance QTL in tetraploid wheat
No full textBreeding for Fusarium head blight (FHB) resistance in durum wheat is complicated by the quantitative trait expression and narrow genetic diversity of available resources. High-density mapping of the FHB resistance quantitative trait loci (QTL), evaluation of their co-localization with plant height and maturity QTL and the interaction among the identified QTL are the objectives of this study. Two doubled haploid (DH) populations, one developed from crosses between Triticum turgidum ssp. durum lines DT707 and DT696 and the other between T. turgidum ssp. durum cv. Strongfield and T. turgidum ssp. carthlicum cv. Blackbird were genotyped using the 90K Infinium iSelect chip and evaluated phenotypically at multiple field FHB nurseries over years. A moderate broad-sense heritability indicated a genotype-by-environment interaction for the expression of FHB resistance in both populations. Resistance QTL were identified for the DT707
7 DT696 population on chromosomes 1B, 2B, 5A (two loci) and 7A and for the Strongfield
7 Blackbird population on chromosomes 1A, 2A, 2B, 3A, 6A, 6B and 7B with the QTL on chromosome 1A and those on chromosome 5A being more consistently expressed over environments. FHB resistance co-located with plant height and maturity QTL on chromosome 5A and with a maturity QTL on chromosome 7A for the DT707
7 DT696 population. Resistance also co-located with plant height QTL on chromosomes 2A and 3A and with maturity QTL on chromosomes 1A and 7B for the Strongfield
7 Blackbird population. Additive
7 additive interactions were identified, for example between the two FHB resistance QTL on chromosome 5A for the DT707
7 DT696 population and the FHB resistance QTL on chromosomes 1A and 7B for the Strongfield
7 Blackbird population. Application of the Single Nucleotide Polymorphic (SNP) markers associated with FHB resistance QTL identified in this study will accelerate combining genes from the two populations.Peer reviewed: YesNRC publication: Ye
Numerical simulation of shrinkage and warpage deformation of an intermittent-extrusion blow molded part: validation case study
No full textIntermittent extrusion blow molding is increasingly being used in polymer forming processes for the production of complex thermoplastic industrial parts with short cycle times. During this process residual stresses caused by inhomogeneous cooling and relaxation of polymer chains, often result in shrinkage and warpage of the final part. One challenging quality requirement of industrial blow molded parts is geometric tolerances. Therefore part deformation, due to cooling and solidification, needs to be controlled and optimized according to specific design criteria. In particular, the complex design shapes of plastic fuel tank (PFT) shells exacerbate these challenges which need to be resolved upfront, in the early stages of product development and tool design. Consequently, the development of an accurate simulation tool, well suited for industrial applications, to predict thermoplastic part deformations due to cooling and solidification, has become essential for part designers to help achieve an efficient production with minimum manufacturing cost. The aim of this work is to present the latest advancements in predicting the shrinkage and warpage deformation of a curved PFT, designed for agricultural machinery, using NRC\u2019s BlowView software. This case study validation considers the entire blow molding stages (i.e., polymer flow in the die, parison formation, inflation, and finally in and out of mold cooling during part solidification). The simulation results, in terms of thickness distribution and displacements, are compared to an actual scanned part using the best fit technique in order to exemplify the accuracy and reliability of the modelling approach.Peer reviewed: YesNRC publication: Ye
Fire testing of rooms with exposed wood surfaces in encapsulated mass timber construction
No full textIn early 2018, with funding support from Natural Resources Canada and the Province of Ontario, the National Research Council Canada conducted a series of room scale fire tests of Encapsulated Mass Timber Construction (EMTC). The goal of this test series is to further quantify the contribution of mass timber elements to fires and provide additional data for forming the technical basis for exposed mass timber elements in EMTC buildings without significantly increasing fire risks to life and property. The goal includes studying the fire performance of the 2nd generation cross-laminated timber (CLT) in resisting char layer fall-off, which could cause fire regrowth in the cooling phase of fully developed fires. The issues of char layer fall-off for the 1st generation CLT panels resulting in fire regrowth during the cooling phase of the fire were clearly revealed in the previous large scale CLT compartment fire tests under the auspices of the Fire Protection Research Foundation.Peer reviewed: NoNRC publication: Ye
Cold spraying of mixed Sn-Al powders onto carbon fibre reinforced polymers
No full textPure metal coatings have successfully been cold sprayed on Carbon Fibre Reinforced Polymers (CFRPs) in previous studies at McGill University. As a means to improve coating conductivity for lightning-strike protection (LSP) purposes, coatings with mixed elements were tested. The studied coatings were based on a mix of tin powder and aluminum, a metal commonly used in the aerospace industry for its lightweight properties. The different coatings were characterized and compared to results on pure tin coatings. The deposition efficiency (DE) and the conductivity were measured for different conditions and compared to those of pure tin coatings. Based on the results, mixing tin and aluminium powders is discussed and various mechanisms related to cold spraying mixed powders on polymers are explored.Peer reviewed: YesNRC publication: Ye
Effect of precipitation hardening on the properties of 17-4ph stainless steel foams
No full textThis paper presents the results of a study on the impact of precipitation hardening on the mechanical properties of 17-4PH stainless steel open-cell foams produced using a powder-metallurgy-based process patented by the National Research Council Canada (NRC). Pre-alloyed powder was used to manufacture stainless steel (SS) foams with either medium or high porosity by changing the nature of the organic binder used to process the porous materials. Some of these were kept in the as-sintered state, while others were submitted to the H900 precipitation hardening treatment frequently prescribed for 17-4PH stainless steels. Metallurgical and physical characterization was carried out on the resulting materials, along with mechanical testing at the micro (nano-indentation) and macro (compressive testing) scales. It was found that the Medium-Porosity (MP) and High-Porosity (HP) foams had very different morphologies, the HP foams having a delicate porous structure featuring thin sintered walls with many openings (a.k.a. windows) between the main cells, while the MP foams exhibited much thicker walls with few windows connecting the larger pores. As expected from these foam morphologies, the mechanical properties of MP foams were much higher than those of the more porous and delicate HP materials. For both foam types, the average mechanical properties were improved by the H900 treatment. However, a large scatter was observed on compressive properties versus relative porosity of individual specimens for both HP and MP foams, whose origin should be further investigated.NRC publication: Ye
Bioinformatics identification of drug gene modules: application to clear cell carcinoma of the ovary
No full textTargeted therapy is a treatment that targets the cancer's specific genes, proteins, or the tissue environment that contributes to cancer growth and survival. Identification of therapeutics targets is a very challenging problem in bioinformatics. An integrative and iterative approach for the identification of drug-gene modules (i.e., groups of genes and drugs such that genes in the same module may regulate each other and are targets of some of the drugs in the same module) is developed. Application to clear cell carcinoma of the ovary data reveals several drug-gene modules and a target network that may play important roles in treating this disease.Peer reviewed: YesNRC publication: Ye
