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Experimental life improvement quantification of shot peening and fastener modifications
No full textTwo coupon test programs were recently carried out at the National Research Council of Canada to certify shot peening and fastener modifications that aim at extending the lives of military aircraft components that are short of their revised usage goals. The life improvement associated with each modification was experimentally quantified by comparing the lives resulting from variants of each modification with that of pre-modification baseline configurations. This approach allowed determining the effects of several parameters, such as the applied stress level, geometric configuration, and modification specifications, on the life extension.Peer reviewed: YesNRC publication: Ye
Further investigation of surface velocity measurements for material characterization in laser shockwave experiments
No full textAs part of the U.S. High Performance Research Reactor program, a laser shock test system is being developed by the Idaho National Laboratory (INL) to characterize interface strength in innovative plate fuel for research reactors around the world. The INL has been working with National Research Council Canada (NRC) on this project for the last five years. One of the concerns is the difficulty of calibrating and standardizing the laser shock technique. A recent analytical study and testing support the use of the Hugoniot Elastic Limit (HEL) in materials as a robust and simple benchmark to compare stresses generated by different laser shock systems. Using a non-contact laser velocimeter based on a solid Fabry-Perot etalon, the systems at NRC and INL show that the back-surface velocity reached at the HEL is consistent, and independent of the laser power used. In this work, the laser velocimeter of the NRC system is tested against a fast rotating wheel to verify accuracy and determine best operating conditions. A round robin test between the two laser shock systems on plates of different aluminum alloys is presented that shows the consistent characterization of the aluminum alloys based on the HEL velocities as well as determines the bias between the systems. The effects of setup parameters on other characteristics of the back-surface velocity trace and corresponding stress wave are also discussed.Peer reviewed: YesNRC publication: Ye
Printed UHF RFID reader antennas for potential retail applications
No full textAutomation of retail industry is calling for the low cost solution due to its sheer size and varied needs. Printed electronics offers a great potential in addressing the needs in point-of-sales, inventory management and self-service, in particular the RFID systems consisting of the printed components. Screen printed UHF RFID reader antennas have been investigated in this work for their application potentials in retails for achieving easy-implementation and low cost. The results obtained clearly demonstrated that the screen printed UHF RFID reader antennas are closely matching the performance of their circularly polarized patch antenna counterparts fabricated using the conventional chemical etching method in most critical specifications. The screen printed antennas have been explored for the monitoring of items on metal shelves targeting potential inventory management and point-of-sales applications. It has been found that all tagged items can be identified using a home developed UHF RFID system consisting of the printed antennas. The findings pave the way for the use of low cost printed antennas in the potential retail automation applications.Peer reviewed: YesNRC publication: Ye
AC-DC difference of a thermal tansfer standard measured with a pulse-driven Josephson voltage standard
No full textAn upgraded pulse-driven AC Josephson voltage standard system at the National Research Council Canada allows the generation of quantum-accurate root-mean-square voltages up to 1 V at frequencies down to 10 Hz. The system is used to determine the AC-DC difference of a commercial thermal transfer standard, and an uncertainty budget is presented. Such quantum voltage systems could replace aging multi-junction thermal converters.Peer reviewed: YesNRC publication: Ye
Measuring sentence parallelism using Mahalanobis distances: the NRC unsupervised submissions to the WMT18 Parallel Corpus Filtering shared task
No full textThe WMT18 shared task on parallel corpus filtering (Koehn et al., 2018b) challenged teams to score sentence pairs from a large high recall, low-precision web-scraped parallel corpus (Koehn et al., 2018a). Participants could use existing sample corpora (e.g. past WMT data) as a supervisory signal to learn what a \u201cclean\u201d corpus looks like. However, in lower resource situations it often happens that the target corpus of the language is the only sample of parallel text in that language. We therefore made several unsupervised entries, setting ourselves an additional constraint that we not utilize the additional clean parallel corpora. One such entry fairly consistently scored in the top ten systems in the 100M-word conditions, and for one task\u2014translating the European Medicines Agency corpus (Tiedemann, 2009)\u2014scored among the best systems even in the 10M-word conditions.Peer reviewed: YesNRC publication: Ye
Canadian seismic design provisions for CLT structures
No full textAlthough Cross-laminated timber (CLT) has been used as a product and a structural system for over 20 years around the world, the codification of CLT is lagging behind which presents a challenge for the design community. Driven by the popularity of CLT in residential and non-residential applications in Canada, design provisions for CLT have been implemented in the 2014 edition of CSA O86 Update No. 1 published in 2016, the Canadian Standard for Engineering Design in Wood. These design provisions for CLT are among the first such guidelines implemented in any code or design standard in the world. This paper summarizes the main aspects of the provisions that are related to seismic design of CLT structures in platform type application. As seismic design provisions for CLT structures are currently being developed in Europe, New Zealand, Japan and the US, the paper will be of great interest to researchers, designers and code officials in this field.Peer reviewed: YesNRC publication: Ye
Development of a material model for AA7075 aluminium hot stamping
No full textThis paper presents the development and validation of a material model for finite element analysis of aluminium hot stamping. It is based on Hill'48 yield function with a non-associated flow rule and isotropic, temperature and rate sensitive hardening. The model also includes phenomenological damage treatment which was developed for plastic instability and fracture prediction in non-isothermal conditions. A special attention was given to the calibration of thermal conductance. Validation was performed with a series of cross die hot stamping tests with in-situ temperature measurements.Peer reviewed: YesNRC publication: Ye
Mechanisms of the immune response cause by cationic and anionic surface functionalized cellulose nanocrystals using cell-based assays
No full textThe interest in functionalized cellulose nanocrystals (CNCs) for multiple biomedical application has been increasing in recent years. CNCs are suitable to functionalization with an array of polymers, generating chemically related nanomaterials with different morphologies, surface charges that can affect bioreactivity, including immune response. In this study, we sought to understand the mechanistic differences regarding immunological responses evoked by functionalized CNCs and whether surface charges play a role in this effect. We investigated the effect of a cationic, CNCs-poly(APMA), and an anionic, CNCs-poly(NIPAAm) derivatives on the secretion of inflammatory cytokines, mitochondria-derived ROS and mitochondrial function and antioxidant response as well as on endoplasmic reticulum (ER) stress, in human and murine inflammatory cells. The cationic CNCs-poly(APMA) evoked a more robust immunological response in murine cell line, while the anionic CNCs-poly(NIPAAm) showed a significant NLRP3 inflammasome-dependent and independent immunological response in human monocytes. Moreover, CNCs-poly(NIPAAm) induced greater formation of acidic vesicular organelles, mitochondrial ROS in non-stimulated cells while CNCs-poly(APMA) mainly affected mitochondrial function by decreasing the intracellular ATP. The differences on the biological responses may be related to the surface charges of CNCs, and their likely interactions with intra and extracellular biomolecules.Peer reviewed: YesNRC publication: Ye
High-speed and high-resolution interrogation of a strain and temperature random grating sensor
No full textHigh-speed and high-resolution interrogation of a random fiber grating sensor based on spectral shaping and wavelength-to-time (SS-WTT) mapping, and pulse compression for simultaneous measurement of strain and temperature is proposed and demonstrated. In the proposed system, an ultrashort pulse is spectrum shaped by a high-birefringence (Hi-Bi) random grating (HBRG) to generate two orthogonally polarized spectra with a wavelength difference determined by the birefringence of the HBRG, which are then fed to a dispersive optical loop in which a linearly chirped fiber Bragg grating (LCFBG) is incorporated, to perform linear WTT mapping, to generate two temporally separated optical pulses, which are converted to two random electrical waveforms at a photodetector). Random pulse compression is then performed to increase the interrogation resolution. By measuring the time shifts of the temporally compressed pulses, the strain and temperature information is retrieved. An experiment is performed. The experimental results show that the proposed random grating sensor and its interrogation system can provide a strain and temperature resolution of 7.1 \u3bc\u3b5 and 0.79 \ub0C at an ultrahigh speed of 20 MHz.Peer reviewed: YesNRC publication: Ye