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Identification and structure elucidation of janthitrems A and D from Penicillium janthinellum and determination of the tremorgenic and anti-insect activity of janthitrems A and B
No full textNew compounds, 11,12-epoxyjanthitrem B (1) and 11,12-epoxyjanthitrem C (4), were isolated from Penicillium janthinellum and given the trivial names janthitrem A and janthitrem D, respectively. The known compounds janthitrem B (2) and janthitrem C (3) were also isolated, and NMR assignments were made for all four compounds. This showed that the previously published NMR assignments for 3 needed considerable revision. 1 and 2 were used as model compounds for the more complex, and highly unstable, epoxyjanthitrems that have been isolated from perennial ryegrass infected with the AR37 endophyte and which contain an epoxide group analogous to that of 1. Both 1 and 2 induced tremors in mice and reduced weight gain and food consumption of porina (Wiseana cervinata) larvae, although 1 showed greater potency. This shows the importance of the epoxy group and suggests that epoxyjanthitrems are likely to be involved in the observed effects of the AR37 endophyte on livestock and insects.Peer reviewed: YesNRC publication: Ye
In situ synchrotron X-ray diffraction analysis of phase transformation in epitaxial metastable hcp nickel thin films, prepared via plasma-enhanced atomic layer deposition
No full textUltrathin metal films have a wide variety of applications, especially in microelectronics. A key method to deposit these films is plasma\u2010enhanced atomic layer deposition (PEALD), which is known for its ability to deposit thin films conformally and at relatively low temperatures. Building on the recent work, an improved recipe is reported on for the development of nickel PEALD technology, through which fully epitaxial nickel thin films are deposited. The effect of continuous heating on the phase structure and agglomeration in the metastable thin films is investigated in this paper. The variations of the phase structure are monitored via in situ synchrotron X\u2010ray diffraction, as well as optical roughness analysis. The temperature windows for phase transformation and particle formation are determined. It is noted that, after the hcp\u2010to\u2010fcc transformation and particle coalescence processes are complete, the particles reshape to acquire the thermodynamically stable shapes dictated by the Wulff theorem. Additionally, a crystallographic orientation relationship between the fcc particles and the sapphire substrate is observed, i.e., Ni (111)||Sapphire(002).Peer reviewed: YesNRC publication: Ye
Linking MRO to prognosis based health management through physics-of-failures understanding
No full textTraditional engine maintenance, repair and overhaul (MRO) are geared toward fixed schedules. However, with online condition monitoring, assessments and prognosis, it is required that MRO be adaptive to the life consumption with respect to the actual usage of the engine to realize the benefit of prognosis. Shifting to this new paradigm, there are several challenges: 1. How exactly the life is consumed in components under complex usage profiles that may involve a combination of low and high cycle fatigue, thermomechanical fatigue and creep, for regular usage (aside from incidents)? 2. What are the physical failure mechanism(s) in components under the above conditions, the understanding of which may help to select the most appropriate detection, repair and replacement (including material insertion) strategy, for life renewal/extension and cost reduction? 3. Understanding the limitations of repairs for the particular failure mechanism. To overcome these challenges, one needs physics-based material failure models that can reflect the true failure mechanisms on the component level under actual (complex) usage profiles. Conventional, empirical test-data correlations for isolated conditions fall short of this requirement because pure fatigue and pure creep are not experienced by real components in service. In addition, to ensure the repaired component\u2019s structural integrity, the material database would have to be comprehensive enough to cover the effect of intrinsic repair defects and microstructures that are not present in the original component material. While models and data are integral parts of digital twins, it is proposed that physics-based models are needed to cover the entire application domain continuously. This paper will introduce a physics-based method of life consumption evaluation and discussion through past experience in line with the development of Digital Twin concepts for sustainment.Peer reviewed: YesNRC publication: Ye
Performance of pre-1970s squat reinforced concrete shear walls
No full textThe seismic performance of pre-1970s squat reinforced concrete shear walls is assessed with the capacity spectrum method to expose structural deficiencies that arise due to current estimates of seismic demands. The walls are 1/3 scale models of a prototype building, designed and detailed in accordance with the 1965 edition of the National Building Code of Canada (NBCC-1965) for four locations, two in high seismic zones in western Canada and two in moderate seismic zones in eastern Canada. Seismic demands for different drifts are evaluated against the spectral capacities of the walls to determine the performance. The seismic demands are based on uniform hazard spectra specified by the NBCC-2015. The calculated effective damping and the spectral capacity of the walls are determined from the force\u2013displacement envelopes of the reverse cyclic responses of the shear walls. In addition, spectral capacities based on experimental and numerical results are used to study the effect of axial load and low-strength reinforcing steel on the performance of the shear walls.La performance parasismique des murs de contreventement trapus en b\ue9ton arm\ue9 des ann\ue9es pr\ue9 1970 est \ue9valu\ue9e au moyen de la m\ue9thode de spectre de capacit\ue9 afin d\u2019exposer les imperfections structurelles qui surgissent \ue0 cause des \ue9valuations actuelles de demandes sismiques. Les murs sont des mod\ue8les \ue0 une \ue9chelle d\u2019un tiers d\u2019un b\ue2timent prototype, con\ue7us et d\ue9taill\ue9s conform\ue9ment \ue0 l\u2019\ue9dition 1965 du Code national du b\ue2timent du Canada (CNB-1965) pour quatre emplacements, deux dans des zones \ue0 risque sismique \ue9lev\ue9 dans l\u2019Ouest canadien et deux dans des zones sismiques \ue0 risque mod\ue9r\ue9 dans l\u2019est du Canada. Les demandes sismiques pour diff\ue9rents mouvements sont \ue9valu\ue9es par rapport aux capacit\ue9s spectrales des murs afin de d\ue9terminer leur performance. Les demandes sismiques reposent sur des spectres de risque uniforme selon les prescriptions du CNB-2015. L\u2019amortissement efficace et la capacit\ue9 spectrale des murs sont d\ue9termin\ue9s \ue0 partir des enveloppes de force-d\ue9placement des r\ue9ponses cycliques inverses des murs de contreventement. De plus, les capacit\ue9s spectrales bas\ue9es sur les r\ue9sultats exp\ue9rimentaux et num\ue9riques sont utilis\ue9es pour \ue9tudier l\u2019effet qu\u2019ont la charge axiale et l\u2019acier d\u2019armature de faible r\ue9sistance sur la performance des murs de contreventement.Peer reviewed: YesNRC publication: Ye
Single channel continuous wave doppler radar for differentiating types of human activity
No full textIn real life applications, it is crucial to monitor the different kinds of human activity without interfering with their regular occupations. Contactless physiological monitoring using radars is a valuable tool, but typically it is performed when the human subjects are immobile. This paper analyzes single channel Continuous Wave (CW) Doppler radar signals in relation to three levels of human activity: i) Sedentary and still, ii) Sedentary and moving and iii) Walking. A combination of computational intelligence techniques (GammaTest, neural networks, random forest and genetic algorithms) was used for assessing the predictive ability of 43 features derived from the radar return signal, as well as of subsets of them, which were composed of highly predictive attributes. It is shown that with about one half the number of attributes it is possible to achieve high levels of classification accuracy, in some cases improving false negative ratios. While several attributes were completely irrelevant and noisy, others were required by discriminating each of the classes. There are attributes required by certain classes in particular and there are others associated to the distinction of classes with subtle differences.Peer reviewed: YesNRC publication: Ye
Review of bridge design practice for water loads, scour, and ice action: opportunities for climate resilience
No full textAn appraisal of historical and recent damage to bridges in Canada and internationally underlines the risks posed by water loads, scour and ice effects. More than 50% of bridge failures in North America are attributed to floods and hydraulic factors, including scour, debris impacts and ice effects. River ice is a unique challenge for bridges in northern climates, with estimates of annual average damages in Canada due to ice jams exceeding $100 million. The rising costs and damages associated with extreme weather events highlight the vulnerabilities of Canadian infrastructure to climate change. Potential changes in exposure to ice and flood hazards (from riverine, pluvial, and coastal sources) pose a threat to the integrity and sustainability of transportation infrastructure, including bridges and overpasses. The Canadian Highway Bridge Design Code contains provisions for evaluating water loads, scour and ice action for new bridges, and refers to the Transportation Association of Canada\u2019s (TAC) Guide to Bridge Hydraulics for additional guidance. However, there are no provisions for evaluating potential climate change impacts on these loads and actions. A review of the current state of bridge design practice for evaluating, mitigating and adapting to water loads, scour, ice action and related climate change impacts was conducted. This included an appraisal of bridge design codes, standards and guidelines in Canada and other countries. The review identified current gaps, emerging best practices, and possible steps towards improving design guidance and the resilience of Canadian bridges and overpasses to water loads, scour, ice action and climate change.Peer reviewed: YesNRC publication: Ye
The Canadian winter road infrastructure and climate change adaptation: prospective solutions through R&D
No full textPeer reviewed: NoNRC publication: Ye
Arctic and offshore patrol ship: site selection for full scale trials
No full textPeer reviewed: NoNRC publication: Ye
Effects of oxidation-resistant coating on creep behavior of modified 9Cr-1Mo steels
No full textOxidation is a life-limiting factor for material durability. In this study, constant-load creep tests are conducted on modified 9Cr-1Mo steel (F91) with an oxidation-resistant coating, MCrAlY, to evaluate the coating effect on the creep behavior. The creep strain vs. time curves are compared with that of the uncoated material under constant-load conditions. The previously developed deformation-mechanism based true-stress (DMTS) model and the composite stress rule are applied to analyze the creep data for the coated material coupons. This way, the effect of coating and the contributions from material-intrinsic deformation mechanisms, i.e., intragranular dislocation glide and climb, as well as grain boundary sliding, are all delineated quantitatively. The model is shown to describe well the entire creep deformation process consisting of primary, steady-state, and tertiary creep of the F91 with MCrAlY coating.Peer reviewed: YesNRC publication: Ye
A generic modeling and power-flow analysis approach for isochronous and droop-controlled microgrids
No full textThis paper proposes a generic steady-state modeling and power-flow analysis approach for droop- and isochronously-controlled microgrids. The proposed framework adopts symmetrical sequence component models, rather than phase-coordinate models, of microgrid components. Such approach immensely reduces the power-flow execution time, as it breaks down the system model into independent equation sets with considerably reduced sizes. To render the proposed approach practical and generic, it incorporates unbalanced loads and feeders, transformer connections, different load characteristics and configurations, as well as microgrid droop features. Furthermore, it models and integrates different types and control schemes of distributed generation (DG), including synchronous generator-based DG (SGDG) and electronically-interfaced DG (EIDG) units. A novel power-flow algorithm based on a modified Newton-Raphson (NR) method is proposed to solve for the microgrid steady-state voltage magnitudes, angles, and frequency. The accuracy of the models and algorithm is verified through comparison with detailed time-domain simulations in MATALB/Simulink. Additionally, the proposed algorithm is shown to outperform the reported Newton-Trust Region (NTR) approach in accuracy and computational cost. Two case studies, incorporating IEEE 123-node test microgrid, are further performed to examine the effectiveness of the proposed approach in solving complicated droop-controlled microgrids, and to investigate the behavior of droop-controlled DGs in isochronous microgrids.Peer reviewed: YesNRC publication: Ye