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  • Fabrication of electron beam generated, chirped, phase mask (1070 . 11 – 1070 . 66 nm) for fiber Bragg grating dispersion compensator

    Resource Type:
    Article
    Creator:
    Hill, K.O., Johnson, D.C., Mihailov, S.J., McClelland, A.W., Stryckman, D., Bilodeau, F., Albert, Jacques, Carr, D.W., Hugues, B.J., Tiberio, R.C., and Rooks, M.J.
    Abstract:
    We report on the fabrication of a chirped, phase mask that was used to create a fiber Bragg grating(FBG)device for the compensation of chromatic dispersion in longhaul optical transmission networks.Electron beamlithography was used to expose the grating onto a resist-coated quartz plate. After etching, this phase mask was used to holographically expose an index grating into the fiber core [K. O. Hill, F. Bilodeau, D. C. Johnson, and J. Albert, Appl. Phys. Lett.62, 1035 (1993)]. The linear increase in the grating period, “chirp,” is only 0.55 nm over the 10 cm grating. This is too small to be defined by computer aided design and a digital deflection system. Instead, the chirp was incorporated by repeatedly rescaling the analog electronics used for field size calibration. Special attention must be paid to minimize any field stitching and exposure artifacts. This was done by using overlapping fields in a “voting” method. As a result, each grating line is exposed by the accumulation of three overlapping exposures at 1/3 dose. This translates any abrupt stitching error into a small but uniform change in the line-to-space ratio of the grating. The phase mask was used with the double-exposure photoprinting technique [K. O. Hill, F. Bilodeau, B. Malo, T. Kitagawa, S. Thériault, D. C. Johnson, J. Albert, and K. Takiguchi, Opt. Lett. 19, 1314 (1994)]: a KrF excimer laser holographically imprints an apodized chirped Bragg grating in a hydrogen loaded SMF-28 optical fiber. Our experiments have demonstrated a spectral delay of −1311 ps/nm with a linearity of +/−10 ps over the 3 dB bandwidth of the resonant wavelength of the FBG. The reflectance, centered on 1550 nm, shows a side-lobe suppression of −25 dB. Fabrication processes and optical characterization will be discussed.
    Date Created:
    1998-09-16

  • A thin metal sheath lifts the EH to HE degeneracy in the cladding mode refractometric sensitivity of optical fiber sensors

    Resource Type:
    Article
    Creator:
    Albert, Jacques, Berini, P., Chen, Chengkun, Caucheteur, C., and Voisin, V.
    Abstract:
    The effective indices of the cladding modes of optical fibers depend on the refractive index of the medium surrounding the fiber. We show experimentally and theoretically that while cladding modes with similar effective indices normally have similar refractometric sensitivities, the addition of a 50 nm thick gold sheath enhances the sensitivity of some EH modes by more than one order of magnitude while nearly completely suppressing the sensitivity of neighbouring HE modes (by three orders of magnitude, down to insignificant levels). A differential sensitivity of ∼1000 nm/(refractive index unit) is experimentally reported between adjacent EH and HE grating resonances.
    Date Created:
    2011-07-25

  • Four-wave mixing in carbon nanotube-coated optical fiber gratings

    Resource Type:
    Article
    Creator:
    Shao, Li-Yang, Simard, Benoit, Albert, Jacques, Sun, Tingting, and Jakubinek, Michael B.
    Abstract:
    The observation of four-wave mixing (FWM) in single-walled carbon nanotubes (SWCNTs) deposited around a tilted fiber Bragg grating (TFBG) has been demonstrated. A thin, floating SWCNT film is manually wrapped around the outer cladding of the fiber and FWM occurs between two core-guided laser signals by TFBG-induced interaction of the core mode and cladding modes. The effective nonlinear coefficient is calculated to be 1.8 10 3W -1Km -1. The wavelength of generated idlers is tunable with a range of 7.8 nm.
    Date Created:
    2012-02-13

  • Bragg gratings fabricated in monomode photosensitive optical fiber by UV exposure through a phase mask

    Resource Type:
    Article
    Creator:
    Albert, Jacques, Bilodeau, F., Malo, B., Hill, K. O., and Johnson, D. C.
    Abstract:
    A photolithographic method is described for fabricating refractive index Bragg gratings in photosensitive optical fiber by using a special phase mask grating made of silica glass. A KrF excimer laser beam (249 nm) at normal incidence is modulated spatially by the phase mask grating. The diffracted light, which forms a periodic, high-contrast intensity pattern with half the phase mask grating pitch, photoimprints a refractive index modulation into the core of photosensitive fiber placed behind, in proximity, and parallel, to the mask; the phase mask grating striations are oriented normal to the fiber axis. This method of fabricating in-fiber Bragg gratings is flexible, simple to use, results in reduced mechanical sensitivity of the grating writing apparatus and is functional even with low spatial and temporal coherence laser sources.
    Date Created:
    1993-12-01

  • Simultaneous corona poling of multiple glass layers for enhanced effective second-order optical nonlinearities

    Resource Type:
    Article
    Creator:
    Blanchetiere, C., Jacob, S., Callender, C. L., Albert, Jacques, Yadav, Ksenia, and Smelser, Christopher W.
    Abstract:
    Silica-based thin-film multilayers are investigated as a means to enhance the effective second-order nonlinearity induced in silica glass structures by corona poling. Structures consisting of phosphorus-doped and undoped silica glass layers exhibit second harmonic generation (SHG) that is higher by an order of magnitude compared to the SHG in bulk silica glass poled under the same conditions. When the poled structure consists of two multilayered stacks separated in space, the stacks exhibit comparable poling-induced nonlinearities. This result suggests that the poling voltage is divided between the two stacks such that simultaneous poling of multiple regions within the sample is realized.
    Date Created:
    2011-07-18

  • Photosensitivity in phosphorus-doped silica glass and optical waveguides

    Resource Type:
    Article
    Creator:
    Hibino, Y., Hattori, K., Johnson, D. C., Hill, K. O., Kitagawa, T., Albert, Jacques, Bilodeau, F., Malo, B., and Gujrathi, S.
    Date Created:
    1994-12-01

  • 1 W tunable dual-wavelength emission from cascaded distributed feedback fiber lasers

    Resource Type:
    Article
    Creator:
    Zhu, X., Peyghambarian, N., Albert, Jacques, Li, L., Moloney, J. V., and Schülzgen, A.
    Date Created:
    2008-02-15

  • Difference in the behavior of oxygen deficient defects in Ge-doped silica optical fiber preforms under ArF and KrF excimer laser irradiation

    Resource Type:
    Article
    Creator:
    Essid, Mourad, Brebner, J.L., Awazu, K., and Albert, Jacques
    Abstract:
    Photobleaching of optical absorption bands in the 5 eV region and the creation of others at higher and lower energy have been examined in the case of ArF (6.4 eV) and KrF (5 eV) excimer laserirradiation of 3GeO2:97SiO2glasses. We report a difference in the transformation process of the neutral oxygen monovacancy and also of the germanium lone pair center (GLPC) into electron trap centers associated with fourfold coordinated Ge ions and Ge-E′ centers when we use one or the other laser. Correlations between absorption bands and electron spin resonance signals were made after different steps of laser irradiation. It was found that the KrF laser generates twice as many Ge-E′ centers as the ArF laser for the same dose of energy delivered. The main reason for this difference is found to be the more efficient bleaching of the GLPC (5.14 eV) by the KrF laser compared to that by the ArF laser.
    Date Created:
    1998-10-15

  • Si ion implantation-induced damage in fused silica probed by variable-energy positrons

    Resource Type:
    Article
    Creator:
    Simpson, P.J., Ilard, L.B., Brebner, J.L., Knights, A.P., and Albert, Jacques
    Abstract:
    Samples of synthetic fused silica have been implanted at room temperature with silicon ions of energy 1.5 MeV. Fluences ranged from 1011 to 1013 cm−2. Samples were probed using variable‐energy positron annihilation spectroscopy. The Doppler‐broadening S parameter corresponding to the implanted region decreased with increasing fluence and saturated at a fluence of 1013 cm−2. It is shown that the decrease in the S parameter is due to the suppression of positronium (Ps) which is formed in the preimplanted material, due to the competing process of implantation‐induced trapping of positrons. In order to satisfactorily model the positron data it was necessary to account for positron trapping due to defects created by both electronic and nuclear stopping of the implanted ions. Annealing of the 1013 cm−2 sample resulted in measurable recovery of the preimplanted S parameter spectrum at 350 °C and complete recovery to the preimplanted condition at 600 °C. Volume compaction was also observed afterimplantation. Upon annealing, the compaction was seen to decrease by 75%.
    Date Created:
    1996-06-16

  • Comparison of one-photon and two-photon effects in the photosensitivity of germanium-doped silica optical fibers exposed to intense ArF excimer laser pulses

    Resource Type:
    Article
    Creator:
    Johnson, D. C., Malo, B., Hill, K. O., Thériault, S., Bilodeau, F., and Albert, Jacques
    Date Created:
    1995-12-01

  • Route discovery with constant memory in oriented planar geometric networks

    Resource Type:
    Article
    Creator:
    Urrutia, J., Opatrny, J., Chávez, E., Dobrev, S., Stacho, L., and Kranakis, Evangelos
    Abstract:
    We address the problem of discovering routes in strongly connected planar geometric networks with directed links. Motivated by the necessity for establishing communication in wireless ad hoc networks in which the only information available to a vertex is its immediate neighborhood, we are considering routing algorithms that use the neighborhood information of a vertex for routing with constant memory only. We solve the problem for three types of directed planar geometric networks: Eulerian (in which every vertex has the same number of incoming and outgoing edges), Outerplanar (in which a single face contains all vertices of the network), and Strongly Face Connected, a new class of geometric networks that we define in the article, consisting of several faces, each face being a strongly connected outerplanar graph.
    Date Created:
    2006-08-01

  • An identification-robust test for time-varying parameters in the dynamics of energy prices

    Resource Type:
    Article
    Creator:
    Khalaf, Lynda A., Kichian, Maral, Bernard, Jean-Thomas, and Dufour, Jean-Marie
    Abstract:
    We test for the presence of time-varying parameters (TVP) in the long-run dynamics of energy prices for oil, natural gas and coal, within a standard class of mean-reverting models. We also propose residual-based diagnostic tests and examine out-of-sample forecasts. In-sample LR tests support the TVP model for coal and gas but not for oil, though companion diagnostics suggest that the model is too restrictive to conclusively fit the data. Out-of-sample analysis suggests a random-walk specification for oil price, and TVP models for both real-time forecasting in the case of gas and long-run forecasting in the case of coal.
    Date Created:
    2012-06-01

  • Age-at-arrival differences in home-ownership attainment among immigrants and their foreign-born offspring in Canada

    Resource Type:
    Article
    Creator:
    Mendez, Pablo
    Abstract:
    This paper asks whether age at arrival matters when it comes to home-ownership attainment among immigrants, paying particular attention to householders' self-identification as a visible minority. Combining methods that were developed separately in the immigrant housing and the immigrant offspring literatures, this study shows the importance of recognising generational groups based on age at arrival, while also accounting for the interacting effects of current age (or birth cohorts) and arrival cohorts. The paper advocates a (quasi-)longitudinal approach to studying home-ownership attainment among immigrants and their foreign-born offspring. Analysis of data from the Canadian Census reveals that foreign-born householders who immigrated as adults in the 1970s and the 1980s are more likely to be home-owners than their counterparts who immigrated at a younger age when they self-identify as South Asian or White, but not always so when they self-identify as Chinese or as ‘other visible minority’. The same bifurcated pattern recurs between householders who immigrated at secondary-school age and those who were younger upon arrival. Age at arrival therefore emerges as a variable of significance to help explain differences in immigrant housing outcomes, and should be taken into account in future studies of immigrant home-ownership attainment. Copyright © 2009 John Wiley & Sons, Ltd.
    Date Created:
    2009-01-01

  • Subterranean Commodification: Informal Housing and the Legalization of Basement Suites in Vancouver from 1928 to 2009

    Resource Type:
    Article
    Creator:
    Quastel, Noah and Mendez, Pablo
    Abstract:
    This article draws on Margaret Radin's theorization of 'contested commodities' to explore the process whereby informal housing becomes formalized while also being shaped by legal regulation. In seeking to move once-informal housing into the domain of official legality, cities can seldom rely on a simple legal framework of private-law principles of property and contract. Instead, they face complex trade-offs between providing basic needs and affordability and meeting public-law norms around living standards, traditional neighbourhood feel and the environment. This article highlights these issues through an examination of the uneven process of legal formalization of basement apartments in Vancouver, Canada. We chose a lengthy period-from 1928 to 2009-to explore how basement apartments became a vital source of housing often at odds with city planning that has long favoured a low-density residential built form. We suggest that Radin's theoretical account makes it possible to link legalization and official market construction with two questions: whether to permit commodification and how to permit commodification. Real-world commodification processes-including legal sanction-reflect hybridization, pragmatic decision making and regulatory compromise. The resolution of questions concerning how to legalize commodification are also intertwined with processes of market expansion.
    Date Created:
    2015-11-01

  • A geography-based critique of new US biofuels regulations

    Resource Type:
    Article
    Creator:
    Fast, Stewart, Saner, Marc, and Brklacich, Michael
    Abstract:
    The new renewable fuels standard (RFS 2) aims to distinguish corn-ethanol that achieves a 20% reduction in greenhouse gas (GHG) emissions compared with gasoline. Field data from Kim et al. (2009) and from our own study suggest that geographic variability in the GHG emissions arising from corn production casts considerable doubt on the approach used in the RFS 2 to measure compliance with the 20% target. If regulators wish to require compliance of fuels with specific GHG emission reduction thresholds, then data from growing biomass should be disaggregated to a level that captures the level of variability in grain corn production and the application of life cycle assessment to biofuels should be modified to capture this variability.
    Date Created:
    2012-05-01

  • Reframing the history of new religious movements

    Resource Type:
    Article
    Creator:
    Driedger, Michael and Wolfart, Johannes
    Abstract:
    In this special issue of Nova Religio four historians of medieval and early modern Christianities offer perspectives on basic conceptual frameworks widely employed in new religions studies, including modernization and secularization, radicalism/violent radicalization, and diversity/diversification. Together with a response essay by J. Gordon Melton, these articles suggest strong possibilities for renewed and ongoing conversation between scholars of "old" and "new" religions. Unlike some early discussions, ours is not aimed simply at questioning the distinction between old and new religions itself. Rather, we think such conversation between scholarly fields holds the prospect of productive scholarly surprise and perspectival shifts, especially via the disciplinary practice of historiographical criticism.
    Date Created:
    2018-05-01

  • Continuity and change in the home literacy environment as predictors of growth in vocabulary and reading

    Resource Type:
    Article
    Creator:
    LeFevre, Jo-Anne and Sénéchal, Monique
    Abstract:
    One hundred and ten English-speaking children schooled in French were followed from kindergarten to Grade 2 (Mage: T1 = 5;6, T2 = 6;4, T3 = 6;11, T4 = 7;11). The findings provided strong support for the Home Literacy Model (Sénéchal & LeFevre, 2002) because in this sample the home language was independent of the language of instruction. The informal literacy environment at home predicted growth in English receptive vocabulary from kindergarten to Grade 1, whereas parent reports of the formal literacy environment in kindergarten predicted growth in children's English early literacy between kindergarten and Grade 1 and growth in English word reading during Grade 1. Furthermore, 76% of parents adjusted their formal literacy practices according to the reading performance of their child, in support of the presence of a responsive home literacy curriculum among middle-class parents.
    Date Created:
    2014-01-01

  • Polarization-selective grating excitation of plasmons in cylindrical optical fibers

    Resource Type:
    Article
    Creator:
    Albert, Jacques, Dakka, Milad A., Shevchenko, Yanina, and Chen, Chengkun
    Abstract:
    We show that the tilted-grating-assisted excitation of surface plasmon polaritons on gold coated single-mode optical fibers depends strongly on the state of polarization of the core-guided light, even in fibers with cylindrical symmetry. Rotating the linear polarization of the guided light by 90° relative to the grating tilt plane is sufficient to turn the plasmon resonances on and off with more than 17 dB of extinction ratio. By monitoring the amplitude changes of selected individual cladding mode resonances we identify what we believe to be a new refractive index measurement method that is shown to be accurate to better than 5 × 10-5.
    Date Created:
    2010-03-01

  • The role of invented spelling on learning to read in low-phoneme awareness kindergartners: A randomized-control-trial study

    Resource Type:
    Article
    Creator:
    Lever, Rosemary, Ouellette, Gene, Pagan, Stephanie, and Sénéchal, Monique
    Abstract:
    The goal of the present intervention research was to test whether guided invented spelling would facilitate entry into reading for at-risk kindergarten children. The 56 participating children had poor phoneme awareness, and as such, were at risk of having difficulty acquiring reading skills. Children were randomly assigned to one of three training conditions: invented spelling, phoneme segmentation, or storybook reading. All children participated in 16 small group sessions over eight weeks. In addition, children in the three training conditions received letter-knowledge training and worked on the same 40 stimulus words that were created from an array of 14 letters. The findings were clear: on pretest, there were no differences between the three conditions on measures of early literacy and vocabulary, but, after training, invented spelling children learned to read more words than did the other children. As expected, the phoneme-segmentation and invented-spelling children were better on phoneme awareness than were the storybook-reading children. Most interesting, however, both the invented spelling and the phoneme-segmentation children performed similarly on phoneme awareness suggesting that the differential effect on learning to read was not due to phoneme awareness per se. As such, the findings support the view that invented spelling is an exploratory process that involves the integration of phoneme and orthographic representations. With guidance and developmentally appropriate feedback, invented spelling provides a milieu for children to explore the relation between oral language and written symbols that can facilitate their entry in reading.
    Date Created:
    2012-04-01

  • Anomalous permittivity and plasmon resonances of copper nanoparticle conformal coatings on optical fibers

    Resource Type:
    Article
    Creator:
    Shao, Li-Yang, Albert, Jacques, Coyle, Jason P., and Barry, Seán T.
    Abstract:
    The conformal coating of a 50 nm-thick layer of copper nanoparticles deposited with pulse chemical vapor deposition of a copper (I) guanidinate precursor on the cladding of a single mode optical fiber was monitored by using a tilted fiber Bragg grating (TFBG) photo-inscribed in the fiber core. The pulse-per-pulse growth of the copper nanoparticles is readily obtained from the position and amplitudes of resonances in the reflection spectrum of the grating. In particular, we confirm that the real part of the effective complex permittivity of the deposited nano-structured copper layer is an order of magnitude larger than that of a bulk copper film at an optical wavelength of 1550 nm. We further observe a transition in the growth behavior from granular to continuous film (as determined from the complex material permittivity) after approximately 20 pulses (corresponding to an effective thickness of 25 nm). Finally, despite the remaining granularity of the film, the final copper-coated optical fiber is shown to support plasmon waves suitable for sensing, even after the growth of a thin oxide layer on the copper surface.
    Date Created:
    2011-06-01

  • Towards a measure of biometric feature information

    Resource Type:
    Article
    Creator:
    Adler, Andy, Loyka, Sergey, and Youmaran, Richard
    Date Created:
    2009-01-01

  • A generalized Winternitz Theorem

    Resource Type:
    Article
    Creator:
    Morin, Pat, Hurtado, Ferran, Bose, Prosenjit, and Carmi, Paz
    Abstract:
    We prove that, for every simple polygon P having k ≥ 1 reflex vertices, there exists a point q ε P such that every half-polygon that contains q contains nearly 1/2(k + 1) times the area of P. We also give a family of examples showing that this result is the best possible.
    Date Created:
    2011-04-01

  • Atlas motion platform generalized kinematic model: Atlas motion platform

    Resource Type:
    Article
    Creator:
    Hayes, M. John, Langlois, Robert, and Weiss, Abraham
    Abstract:
    Conventional training simulators commonly use a hexapod configuration to provide motion cues. While widely used, studies have shown that hexapods are incapable of producing the range of motion required to achieve high fidelity simulation required in many applications. A novel alternative is the Atlas motion platform. This paper presents a new generalized kinematic model of the platform which can be applied to any spherical platform actuated by three omnidirectional wheels. In addition, conditions for slip-free and singularity-free motions are identified. Two illustrative examples are given for different omnidirectional wheel configurations.
    Date Created:
    2011-02-01

  • Parallel collision search with cryptanalytic applications

    Resource Type:
    Article
    Creator:
    Wiener, Michael J. and Van Oorschot, Paul C.
    Abstract:
    A simple new technique of parallelizing methods for solving search problems which seek collisions in pseudorandom walks is presented. This technique can be adapted to a wide range of cryptanalytic problems which can be reduced to finding collisions. General constructions are given showing how to adapt the technique to finding discrete logarithms in cyclic groups, finding meaningful collisions in hash functions, and performing meet-in-the-middle attacks such as a known-plaintext attack on double encryption. The new technique greatly extends the reach of practical attacks, providing the most cost-effective means known to date for defeating: the small subgroup used in certain schemes based on discrete logarithms such as Schnorr, DSA, and elliptic curve cryptosystems; hash functions such as MD5, RIPEMD, SHA-1, MDC-2, and MDC-4; and double encryption and three-key triple encryption. The practical significance of the technique is illustrated by giving the design for three $10 million custom machines which could be built with current technology: one finds elliptic curve logarithms in GF(2155) thereby defeating a proposed elliptic curve cryptosystem in expected time 32 days, the second finds MD5 collisions in expected time 21 days, and the last recovers a double-DES key from two known plaintexts in expected time 4 years, which is four orders of magnitude faster than the conventional meet-in-the-middle attack on double-DES. Based on this attack, double-DES offers only 17 more bits of security than single-DES.
    Date Created:
    1999-01-01

  • Authentication and authenticated key exchanges

    Resource Type:
    Article
    Creator:
    Wiener, Michael J., Van Oorschot, Paul C., and Diffie, Whitfield
    Abstract:
    We discuss two-party mutual authentication protocols providing authenticated key exchange, focusing on those using asymmetric techniques. A simple, efficient protocol referred to as the station-to-station (STS) protocol is introduced, examined in detail, and considered in relation to existing protocols. The definition of a secure protocol is considered, and desirable characteristics of secure protocols are discussed.
    Date Created:
    1992-06-01

  • Near infrared electrochromic variable optical attenuator based on ruthenium complex and polycrystalline tungsten oxide

    Resource Type:
    Article
    Creator:
    Yan, Donghang, Wang, Zhiyuan, Yu, Hongan, Wu, Xianguo, and Zhang, Jidong
    Abstract:
    A near infrared (NIR) electrochromic attenuator based on a dinuclear ruthenium complex and polycrystalline tungsten oxide was fabricated and characterized. The results show that the use of the NIR-absorbing ruthenium complex as a counter electrode material can improve the device performance. By replacing the visible electrochromic ferrocene with the NIR-absorbing ruthenium complex, the optical attenuation at 1550 nm was enhanced from 19.1 to 30.0 dB and color efficiency also increased from 29.2 to 121.2 cm2/C.
    Date Created:
    2005-12-01

  • Feasibility of design in stereolithography

    Resource Type:
    Article
    Creator:
    Bose, Prosenjit, Overmars, M., Wilfong, G., Toussaint, G., Garcia-Lopez, J., Zhu, B., Asberg, B., and Blanco, G.
    Abstract:
    We study the feasibility of design for a layer-deposition manufacturing process called stereolithography which works by controlling a vertical laser beam which when targeted on a photocurable liquid causes the liquid to harden. In order to understand the power as well as the limitations of this manufacturing process better, we define a mathematical model of stereolithography (referred to as vertical stereolithography) and analyze the class of objects that can be constructed under the assumptions of the model. Given an object (modeled as a polygon or a polyhedron), we give algorithms that decide in O(n) time (where n is the number of vertices in the polygon or polyhedron) whether or not the object can be constructed by vertical stereolithography. If the answer is in the affirmative, the algorithm reports a description of all the orientations in which the object can be made. We also show that the objects built with vertical stereolithography are precisely those that can be made with a 3-axis NC machine. We then define a more flexible model that more accurately reflects the actual capabilities of stereolithography (referred to as variable-angle stereolithography) and again study the class of feasible objects for this model. We give an O(n)-time algorithm for polygons and O(n log n)- as well as O(n)-time algorithms for polyhedra. We show that objects formed with variable-angle stereolithography can also be constructed using another manufacturing process known as gravity casting. Furthermore, we show that the polyhedral objects formed by vertical stereolithography are closely related to polyhedral terrains which are important structures in geographic information systems (GIS) and computational geometry. In fact, an object built with variable-angle stereolithography resembles a terrain with overhangs, thus initiating the study of more realistic terrains than the standard ones considered in geographic information systems. Finally, we relate our results to the area of grasping in robotics by showing that the polygonal and polyhedral objects that can be built by vertical stereolithography can be clamped by parallel jaw grippers with any positive-sized gripper.
    Date Created:
    1997-01-01

  • Optimal parallel algorithms for rectilinear link-distance problems

    Resource Type:
    Article
    Creator:
    Sack, Jörg-Rüdiger, Maheshwari, Anil, and Lingas, A.
    Abstract:
    We provide optimal parallel solutions to several link-distance problems set in trapezoided rectilinear polygons. All our main parallel algorithms are deterministic and designed to run on the exclusive read exclusive write parallel random access machine (EREW PRAM). Let P be a trapezoided rectilinear simple polygon with n vertices. In O(log n) time using O(n/log n) processors we can optimally compute: 1. Minimum réctilinear link paths, or shortest paths in the L1 metric from any point in P to all vertices of P. 2. Minimum rectilinear link paths from any segment inside P to all vertices of P. 3. The rectilinear window (histogram) partition of P. 4. Both covering radii and vertex intervals for any diagonal of P. 5. A data structure to support rectilinear link-distance queries between any two points in P (queries can be answered optimally in O(log n) time by uniprocessor). Our solution to 5 is based on a new linear-time sequential algorithm for this problem which is also provided here. This improves on the previously best-known sequential algorithm for this problem which used O(n log n) time and space.5 We develop techniques for solving link-distance problems in parallel which are expected to find applications in the design of other parallel computational geometry algorithms. We employ these parallel techniques, for example, to compute (on a CREW PRAM) optimally the link diameter, the link center, and the central diagonal of a rectilinear polygon.
    Date Created:
    1995-09-01

  • Suburban ways of living and the geography of income: How homeownership, single-family dwellings and automobile use define the metropolitan social space

    Resource Type:
    Article
    Creator:
    Moos, Markus and Mendez, Pablo
    Abstract:
    Current research depicts suburbs as becoming more heterogeneous in terms of socio-economic status. Providing a novel analysis, this paper engages with that research by operationalising suburban ways of living (homeownership, single-family dwelling occupancy and automobile use) and relating them to the geography of income across 26 Canadian metropolitan areas. We find that suburban ways of living exist in new areas and remain associated with higher incomes even as older suburbs, as places, have become more diverse. In the largest cities the relationship between income and suburban ways of living is weaker due to the growth of condominiums in downtowns that allow higher income earners to live urban lifestyles. Homeownership is overwhelmingly more important than other variables in explaining the geography of income across 26 metropolitan areas.
    Date Created:
    2015-01-01

  • Art as a transformative practice: A participatory action research project with trans* youth

    Resource Type:
    Article
    Creator:
    Tierney, Cara, Lundy, Jess, Asakura, Kenta, and Black, Dillon
    Date Created:
    2019-10-03

  • The relationship between net energy use and the urban density of solar buildings

    Resource Type:
    Article
    Creator:
    Athienitis, Andreas K, Kesik, Ted J, Kennedy, Christopher A, and O'Brien, William
    Abstract:
    There is a paradoxical relationship between the density of solar housing and net household energy use. The amount of solar energy available per person decreases as density increases. At the same time, transportation energy, and to some extent, household operating energy decreases. Thus, an interesting question is posed: how does net energy use vary with housing density? This study attempts to provide insight into this question by examining three housing forms: low-density detached homes, medium-density townhouses, and high-density high-rise apartments in Toronto. The three major quantities of energy that are summed for each are building operational energy use, solar energy availability, and personal transportation energy use. Solar energy availability is determined on the basis of an effective annual collector efficiency. The results show that under the base case in which solar panels are applied to conventional homes, the high-density development uses one-third less energy than the low-density one. Improving the efficiency of the homes results in a similar trend. Only when the personal vehicle fleet or solar collectors are made to be extremely efficient does the trend reverse-the low-density development results in lower net energy.
    Date Created:
    2010-01-01

  • Scholarly and public engagement in Jewish politics: A journey through liminal space in ten short chapters

    Resource Type:
    Article
    Creator:
    Sucharov, Mira
    Abstract:
    This article interrogates the question of what it means to be a scholar-commentator in the digital age. Deploying an autoethnographic style, the essay asks about the role of power and responsibility in teaching, research, and public commentary, particularly in the context of studying and engaging in Jewish politics. The article addresses questions about the proper role of the scholar in the academy and the role of subjectivity and political commitments in structuring scholarship, pedagogy, and public engagement. It also examines how one’s view of the profession can seem to shift through the emergence of new writing outlets and new forums for public engagement. Finally, the author investigates how a scholar’s own political commitments can shift over time, how one seeks to shore up identification on social media while trying to change hearts and minds through the op-ed pages, and how community identification can serve as a buffer and motivator for particular forms of research and political action.
    Date Created:
    2018-12-01

  • Ca-ATPase activity and protein composition of sarcoplasmic reticulum membranes isolated from skeletal muscles of typical hibernator, the ground squirrel Spermophilus undulatus

    Resource Type:
    Article
    Creator:
    Lopina, Olga D., Storey, Kenneth B., Rubstov, Alexander M., and Malysheva, Anna N.
    Abstract:
    Ca-ATPase activity in sarcoplasmic reticulum (SR) membranes isolated from skeletal muscles of the typical hibernator, the ground squirrel Spermophilus undulatus, is about 2-fold lower than that in SR membranes of rats and rabbits and is further decreased 2-fold during hibernation. The use of carbocyanine anionic dye Stains-All has revealed that Ca-binding proteins of SR membranes, histidine-rich Ca-binding protein and sarcalumenin, in ground squirrel, rat, and rabbit SR have different electrophoretic mobility corresponding to apparent molecular masses 165, 155, and 170 kDa and 130, 145, and 160 kDa, respectively; the electrophoretic mobility of calsequestrin (63 kDa) is the same in all preparations. The content of these Ca-binding proteins in SR membranes of the ground squirrels is decreased 3–4 fold and the content of 55, 30, and 22 kDa proteins is significantly increased during hibernation.
    Date Created:
    2001-12-01

  • Capital Intraconversion' and Canadian Literary Prize Culture

    Resource Type:
    Article
    Creator:
    Mason, Jody
    Abstract:
    This paper analyzes how the “particular symbolic fortunes” of Canada’s most widely recognized literary prize, the Scotiabank Giller Prize, undergo what James English calls “capital intraconversion”––how they are “culturally ‘laundered’” through their association with Frontier College, Canada’s longest-running adult literacy organization. While the Giller initially benefitted from fashioning itself as the private, industry-driven alternative to state-sponsored culture in Canada, increasing criticism of its corporate sponsorship has led, in the past decade, to a rebranding effort. This effort, I contend, seeks to benefit from two key terms––multiculturalism and literacy. Associated as the discourse of multiculturalism and the figure of the literate citizen are with the strong publics of the western, liberal-democratic nation-state, they possess a remarkable ability to accentuate the symbolic capital of Canada’s most widely recognized literary prize.
    Date Created:
    2017-01-01

  • Phosphorylation of H,K-ATPase α-subunit in microsomes from rabbit gastric mucosa by cAMP-dependent protein kinase

    Resource Type:
    Article
    Creator:
    Rubtsov, Alexander M., Petukhov, Sergei P., Murtazina, Dilyara A., Lopina, Olga D., and Storey, Kenneth B.
    Abstract:
    A 100-kDa protein that is a main component of the microsomal fraction from rabbit gastric mucosa is phosphorylated by cAMP-dependent protein kinase (PKA) in the presence of 0.2% Triton X-100. Microsomes from rabbit gastric mucosa possess activity of H,K-ATPase but not activity of Na,K-ATPase. Incubation of microsomes with 5 μM fluorescein 5′-isothiocyanate (FITC) results in both an inhibition of H,K-ATPase and labeling of a protein with an electrophoretic mobility corresponding to the mobility of the protein phosphorylated by PKA. The data suggest that the α-subunit of H,K-ATPase can be a potential target for PKA phosphorylation.
    Date Created:
    1999-07-27

  • The differential impact of social defeat on mice living in isolation or groups in an enriched environment: Plasma corticosterone and monoamine variations

    Resource Type:
    Article
    Creator:
    Anisman, Hymie, Audet, Marie-Claude, McQuaid, Robyn J., and Jacobson-Pick, Shlomit
    Abstract:
    Social defeat in mice is a potent stressor that promotes the development of depressive- and anxiety-like behaviours, as well as variations of neuroendocrine and brain neurotransmitter activity. Although environmental enrichment may protect against some of the adverse behavioural and biological effects of social defeat, it seems that, among male group-housed mice maintained in an enriched environment (EE), aggressive behaviours may be more readily instigated, thus promoting distress and exacerbating psychopathological features. Thus, although an EE can potentially have numerous beneficial effects, these may depend on the general conditions in which mice were raised. It was observed in the current investigations that EE group-housed BALB/cByJ mice displayed increased anxiety-like behaviours compared to their counterparts maintained in a standard environment (SE). Furthermore, in response to social defeat, EE group-housed male mice exhibited decreased weight gain, exaggerated corticosterone elevations and altered hippocampal norepinephrine utilization compared to their SE counterparts. These effects were not apparent in the individually housed EE mice and, in fact, enrichment among these mice appeared to buffer against serotonin changes induced by social defeat. It is possible that some potentially beneficial effects of enrichment were precluded among group-housed mice, possibly owing to social disturbances that might occur in these conditions. In fact, even if social interaction is an essential feature of enrichment, it seems that some of the positive effects of this housing condition might be optimal when mice are housed individually, particularly with regard to buffering the effects of social defeat.
    Date Created:
    2013-03-01

  • Plasmon-enhanced refractometry using silver nanowire coatings on tilted fibre Bragg gratings

    Resource Type:
    Article
    Creator:
    Bialiayeu, A., Ianoul, Anatoli, Prezgot, Dan, Bottomley, Adam, and Albert, Jacques
    Abstract:
    A novel technique for increasing the sensitivity of tilted fibre Bragg grating (TFBG) based refractometers is presented. The TFBG sensor was coated with chemically synthesized silver nanowires 100nm in diameter and several micrometres in length. A 3.5-fold increase in sensor sensitivity was obtained relative to the uncoated TFBG sensor. This increase is associated with the excitation of surface plasmons by orthogonally polarized fibre cladding modes at wavelengths near 1.5μm. Refractometric information is extracted from the sensor via the strong polarization dependence of the grating resonances using a Jones matrix analysis of the transmission spectrum of the fibre.
    Date Created:
    2012-11-09

  • Cross-section electrical resistance tomography of La Soufrière of Guadeloupe lava dome

    Resource Type:
    Article
    Creator:
    Lesparre, Nolwenn, Adler, Andy, Komorowski, Jean-Christophe, Grychtol, Bartłomiej, and Gibert, Dominique
    Abstract:
    The electrical resistivity distribution at the base of La Soufrière of Guadeloupe lava dome is reconstructed by using transmission electrical resistivity data obtained by injecting an electrical current between two electrodes located on opposite sides of the volcano. Several pairs of injection electrodes are used in order to constitute a data set spanning the whole range of azimuths, and the electrical potential is measured along a cable covering an angular sector of ≈120? along the basis of the dome. The data are inverted to performa slice electrical resistivity tomography (SERT) with specific functions implemented in the EIDORS open source package dedicated to electrical impedance tomography applied to medicine and geophysics. The resulting image shows the presence of highly conductive regions separated by resistive ridges. The conductive regions correspond to unconsolidated material saturated by hydrothermal fluids. Two of them are associated with partial flank collapses and may represent large reservoirs that could have played an important role during past eruptive events. The resistive ridges may represent massive andesite and are expected to constitute hydraulic barriers.
    Date Created:
    2014-01-01

  • Strain-optic coefficients of individual cladding modes of singlemode fibre: Theory and experiment

    Resource Type:
    Article
    Creator:
    Albert, Jacques and Chen, Chengkun
    Date Created:
    2006-09-05

  • Non-uniform-tilt-modulated fiber Bragg grating for temperature-immune micro-displacement measurement

    Resource Type:
    Article
    Creator:
    Chen, Chengkun, Guo, Tuan, and Albert, Jacques
    Date Created:
    2009-04-10

  • Single-frequency Er3+-doped silica-based planar waveguide laser with integrated photo-imprinted Bragg reflectors

    Resource Type:
    Article
    Creator:
    Hibino, Y., Kitagawa, T., Hill, K. O., Bilodeau, F., Jihnson, D. C., Malo, B., Theriault, S., Albert, Jacques, and Hattori, K.
    Abstract:
    Single-longitudinal-mode operation of Er3+-P2O5-codoped silica planar waveguide lasers which are equipped with integrated Bragg grating reflectors is demonstrated, with a polarized output of 340 μW at 1546 nm. The gratings are photo-imprinted using 193 nm light exposure through a phase mask in GeO2-free optical waveguides that have been sensitized by H2 loading.
    Date Created:
    1994-08-04

  • Enhanced photosensitivity in lightly doped standard telecommunication fibre exposed to high fluence ArF excimer laser light

    Resource Type:
    Article
    Creator:
    Hill, K. O., Albert, Jacques, Bilodeau, F., Johnson, D. C., Malo, B., and Theriault, S.
    Abstract:
    The core refractive index of Corning SMF-28 optical fibre exposed to ArF laser pulses increases with the square of the fluence per pulse. Bragg gratings with a refractive index modulation amplitude higher than 10 -3 have been obtained. This is an order of magnitude improvement over previously reported values for this type of fibre in the absence of treatment to enhance the photosensitivity.
    Date Created:
    1995-05-25

  • Effective index drift from molecular hydrogen diffusion in hydrogen-loaded optical fibres and its effect on Bragg grating fabrication

    Resource Type:
    Article
    Creator:
    Johnson, D. C., Malo, B., Albert, Jacques, Bilodeau, F., and Hill, K. O.
    Abstract:
    When hydrogen loading is used to enhance the photosensitivity of silica-based optical waveguides and fibres, the presence of molecular hydrogen dissolved in the glass matrix changes the effective index of propagation of guided optical modes by as much as 0.05%. Real-time monitoring of the reflectivity spectrum of Bragg gratings written in such conditions shows that the centre wavelength follows the changes in hydrogen concentration due to diffusion and reaction with glass defects.
    Date Created:
    1994-01-01

  • Chirped in-fibre Bragg grating dispersion compensators: Linearization of dispersion characteristic and demonstration of dispersion compensation in 100km, 10 Gbit/s optical fibre link

    Resource Type:
    Article
    Creator:
    Takiguchi, K., Johnson, D. C., Hill, K. O., Hagimoto, K., Kitagawa, T., Malo, B., Bilodeau, F., Theriault, S., Albert, Jacques, and Kataoka, T.
    Abstract:
    An apodized chirped in-fibre Bragg grating that has a linear dispersion characteristic is reported. The frequency components of an optical pulse (centre wavelength 1551 nm; 10 GHz bandwidth) incident on the grating are reflected with a relative delay that varies linearly from 0 to 130 ps across the spectral width of the pulse. The dispersion compensator is used to correct for the dispersion in a 100 km link (nondispersion shifted fibre) operating at a 10 Gbit/s transmission rate and a wavelength of 1551 nm.
    Date Created:
    1994-10-13

  • Apodised in-fibre Bragg grating reflectors photoimprinted using a phase mask

    Resource Type:
    Article
    Creator:
    Johnson, D. C., Theriault, S., Malo, B., Bilodeau, F., Hill, K. O., and Albert, Jacques
    Abstract:
    An apodized in-fibre Bragg grating reflector is fabricated using the phase mask photoimprinting technique. The reflector has a centre wavelength of 1550 nm, a bandwidth of 0.22 nm and a peak reflectivity of 90%. At 0.4 nm (50 GHz) from the centre wavelength the reflectivity is 40 dB lower than the peak reflectivity; this is an improvement of more than 20 dB over an unapodized Bragg grating reflector with similar bandwidth and peak reflectivity.
    Date Created:
    1995-02-02

  • A Systematic Approach for Variable Selection With Random Forests: Achieving Stable Variable Importance Values

    Resource Type:
    Article
    Creator:
    Banks, Sarah N., Millard, Koreen, Behnamian, Amir, White, Lori, Richardson, Murray, and Pasher, Jon
    Abstract:
    Random Forests variable importance measures are often used to rank variables by their relevance to a classification problem and subsequently reduce the number of model inputs in high-dimensional data sets, thus increasing computational efficiency. However, as a result of the way that training data and predictor variables are randomly selected for use in constructing each tree and splitting each node, it is also well known that if too few trees are generated, variable importance rankings tend to differ between model runs. In this letter, we characterize the effect of the number of trees (ntree) and class separability on the stability of variable importance rankings and develop a systematic approach to define the number of model runs and/or trees required to achieve stability in variable importance measures. Results demonstrate that both a large ntree for a single model run, or averaged values across multiple model runs with fewer trees, are sufficient for achieving stable mean importance values. While the latter is far more computationally efficient, both the methods tend to lead to the same ranking of variables. Moreover, the optimal number of model runs differs depending on the separability of classes. Recommendations are made to users regarding how to determine the number of model runs and/or trees that are required to achieve stable variable importance rankings.
    Date Created:
    2017-09-15

  • The Protean Challenge of Game Collections at Academic Libraries

    Resource Type:
    Article
    Creator:
    Cross, Emma, Smith, Robert, and Mould, David
    Abstract:
    The rise of game development and game studies on university campuses prompts academic libraries to consider how to support teaching and research in this area. This article examines current issues and challenges in the development of game collections at academic libraries. The gaming ecosystem has become more complex and libraries may need to move beyond collections largely based on console video games. This article will advance the discussion by considering emerging issues to support access to the full range of games. The article will use examples from Carleton University Library, Ottawa, which has been developing a game collection since 2008.
    Date Created:
    2015-01-01

  • Publishing graduate student research in geography: the fundamentals

    Resource Type:
    Article
    Creator:
    Ballamingie, Patricia and Tudin, Susan
    Date Created:
    2013-05-01

  • In the Company of my Peers: Implementation of RDA in Canada

    Resource Type:
    Article
    Creator:
    Riva, Pat, Cross, Emma, Andrews, Sue, Oliver, Chris, and Grover, Trina
    Abstract:
    This article describes the progress made toward implementing Resource Description and Access (RDA) in libraries across Canada, as of Fall 2013. Differences in the training experiences in the English-speaking cataloging communities and French-speaking cataloging communities are discussed. Preliminary results of a survey of implementation in English-Canadian libraries are included as well as a summary of the support provided for French-Canadian libraries. Data analysis includes an examination of the rate of adoption in Canada by region and by sector. Challenges in RDA training delivery in a Canadian context are identified, as well as opportunities for improvement and expansion of RDA training in the future.
    Date Created:
    2014-01-01

  • Adaptation and validation of an existing bottom-up model for simulating temporal and inter-dwelling variations of residential appliance and lighting demands

    Resource Type:
    Article
    Creator:
    Beausoleil-Morrison, Ian, Wills, A. D., and Ugursal, V. I.
    Abstract:
    The design and analysis of community-scale energy systems and incentives is a non-trivial task. The challenge of such undertakings is the well-documented uncertainty of building occupant behaviours. This is especially true in the residential sector, where occupants are given more freedom of activity compared to work environments. Further complicating matters is the dearth of available measured data. Building performance simulation tools are one approach to community energy analysis, however such tools often lack realistic models for occupant-driven demands, such as appliance and lighting (AL) loads. For community-scale analysis, such AL models must also be able to capture the temporal and inter-dwelling variation to achieve realistic estimates of aggregate electrical demand. This work adapts the existing Centre for Renewable Energy Systems Technology (CREST) residential energy model to simulate Canadian residential AL demands. The focus of the analysis is to determine if the daily, seasonal, and inter-dwelling variation of AL demands estimated by the CREST model is realistic. An in-sample validation is conducted on the model using 22 high-resolution measured AL demand profiles from dwellings located in Ottawa, Canada. The adapted CREST model is shown to broadly capture the variation of AL demand variations observed in the measured data, however seasonal variation in daily AL demand behaviour was found to be under-estimated by the model. The average and variance of daily load factors was found to be similar between measured and modelled. The model was found to under-predict the daily coincidence factors of aggregated demands, although the variance of coincident factors was shown to be similar between measured and modelled. A stochastic baseload input developed for this work was found to improve estimates of the magnitude and variation of both baseload and peak demands.
    Date Created:
    2017-09-05