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Theory and Application of SBS-based Group Velocity Manipulation in Optical FibersZhu, Yunhui January 2013 (has links)
<p>All-optical devices have attracted many research interests due to their ultimately low heat dissipation compared to conventional devices based on electric-optical conversion. With recent advances in nonlinear optics, it is now possible to design the optical properties of a medium via all-optical nonlinear effects in a table-top device or even on a chip.</p><p>In this thesis, I realize all-optical control of the optical group velocity using the nonlinear process of stimulated Brillouin scattering (SBS) in optical fibers. The SBS-based techniques generally require very low pump power and offer a wide transparent window and a large tunable range. Moreover, my invention of the arbitrary SBS resonance tailoring technique enables engineering of the optical properties to optimize desired function performance,</p><p>which has made the SBS techniques particularly widely adapted for</p><p>various applications.</p><p>I demonstrate theoretically and experimentally how the all-optical</p><p>control of group velocity is achieved using SBS in optical fibers.</p><p>Particularly, I demonstrate that the frequency dependence of the</p><p>wavevector experienced by the signal beam can be tailored using</p><p>multi-line and broadband pump beams in the SBS process. Based on the theoretical framework, I engineer the spectral profile</p><p> to achieve two different application goals: a uniform low group velocity (slow light) within a broadband spectrum, and a group velocity with a linear dependence on the frequency detuning (group velocity dispersion or GVD).</p><p>In the broadband SBS slow light experiment, I develop a novel noise current modulation method that arbitrarily tailors the spectrum of a diode laser. Applying this method, I obtain a 5-GHz broadband SBS gain with optimized flat-topped profile, in comparison to the ~40 MHz natural linewidth of the SBS resonance. Based on the broadband SBS resonance, I build a 5-GHz optical buffer and use this optical buffer to delay a return-to-zero data sequence of rate 2.5 GHz (pulse width 200 ps). The fast noise modulation method significantly stabilizes the SBS gain and improves the signal fidelity. I obtain a tunable delay up to one pulse-width with a peak signal-to-noise ratio of 7. I also find that SBS slow light performance can be improved by avoiding competing nonlinear effects. A gain-bandwidth product of 344 dB.GHz is obtained in our system with a highly-nonlinear optical fiber.</p><p>Besides the slow light applications, I realize that group velocity dispersion is also optically controlled via the SBS process. In the very recent GVD experiment, I use a dual-line SBS resonance and obtain a tunable GVD parameter of 7.5 ns$^2$/m, which is 10$^9$ times larger than the value found in a single-mode fiber. The large GVD system is used to disperse an optical pulse with a pulse width of 28 ns, which is beyond the capability for current dispersion techniques working in the picosecond and sub picosecond region. The SBS-based all-optical control of GVD is also widely tunable and can</p><p>be applied to any wavelength within the transparent window of the</p><p>optical fiber. I expect many future extensions following this work</p><p>on the SBS-based all-optical GVD control using the readily developed SBS tailoring techniques.</p><p>Finally, I extend the basic theory of backwards SBS to describe the forward SBS observed in a highly nonlinear fiber, where asymmetric forward SBS resonances are observed at the gigahertz range. An especially large gain coefficient of 34.7 W$^{-1}$ is observed at the resonance frequency of 933.8 MHz. This is due to good overlap between the optical wave and the high order guided radial acoustic wave. The interplay from the competing process known as the Kerr effect is also accounted for in the theory.</p> / Dissertation
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Working without credit : a case study of Quebec's IPL high-school programTaylor, Meredith January 1995 (has links)
In order to accommodate the needs and abilities of all students, many high schools have designed programs for those students who are unable to cope within regular high school streams. These alternative programs have included vocational education, work experience education, various forms of tracking, and within Quebec, the Individualized Paths for Learning Program (IPL). Individualized Paths for Learning was developed to allow "at risk" students to work towards their high school diploma at a more individualised pace, and to ease their transition into the work force through job skills training and work site experience. As this case study of an Individualized Paths for Learning program suggests however, IPL in practice provides very limited work and academic preparation for the students involved. Through interviews with students and staff, and participant observation within the classroom the limitations of the program become apparent. Yet paradoxically both students and staff were committed to the program and continued to subscribe to the importance of education which is fostered both socially and by the IPL program itself. Within this case study, the students' impressions of the IPL program were of special interest. It is their words, as those most involved and affected by it, that are used in analysis. While this study is specific to its setting it hopefully will provide insight into work education programs following similar principles.
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Impacts de l'âge et du sexe sur l'amplitude et la densité des oscillations lentes en sommeilViens, Isabelle January 2009 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
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Connecting people, food & place: sustaining community, identity, and well-being through a multisensory, local food centreShwaluk, Janine 01 February 2010 (has links)
This interior design project involves investigation into the philosophies of the Slow Food Movement and how they may inspire and inform the design of a social space that fosters a connection between local people, food and place. This socio-cultural connection is implemented through the design of a concentrated, local food centre within the urban environment of Winnipeg, Manitoba. Investigation into interior design strategies which foster social interaction, taste education and sensory engagement contribute to the design of a space where the local food culture of southern Manitoba can be experienced in its authenticity. By combining the public spaces of food which contribute to the contemporary streetscape, with those that exist within the interior environment, this local food centre design aims to promote local identity and facilitate multisensory social engagement that sustains relationships, community, and the environment over time.
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Optical near-field characterization of Slow-Bloch Mode based photonic crystal devicesVo, Thanh Phong 06 September 2011 (has links) (PDF)
2D-Photonic crystal (PC) structures have enabled the fabrication of a wide variety of nanophotonic components. In perfect PCs, the exploitation of the enhanced local density of states at critical points of the band diagram has attracted considerable attention. Near these points, where the group velocity vanished, low curvature flat bands give rise to delocalized and stationary optical slow Bloch modes (or slow light modes). Properties of slow light make them good candidates to enhance Purcell or various non-linear effects or to design low-threshold lasers. Among these modes, slow Bloch modes (SBMs) emitting in the vertical direction, i.e. located at the Γ- point of the Brillouin zone are particularly interesting for integrating 2D PC architectures with free space optics. In particular, some SBMs proved to be suitable for achieving strong vertical emission with peculiar polarization properties. Other promising applications concern disorder: by introducing a controlled randomness into the PC structure, it is possible to induce a transition from slow Bloch mode (in ordered PC) to Anderson's localization (in disordered PC) as a function of disorder degree. In this PhD dissertation, Slow Bloch modes have been studied and characterized by the means of Near-field Scanning Optical microscopy (NSOM). We particularly focused on Slow Bloch laser mode at Γ- point of a honeycomb 2DPC. This NSOM technique enables to visualize the evanescent component of the mode with a spatial resolution below the diffraction limit. In this work, we showed that the far-field and the near-field image of the mode at the 2D-PC surface are different and that near-field results yield a better insight in the real mode structure inside the PC slab in agreement with theoretical prediction. The importance of the probe selection (bare silica, metallized tip and bow-tie aperture nanoantenna) for studying III-V photonic crystal structures was also demonstrated. Besides intensity measurement of the electromagnetic field, the polarization of the electric field has been measured at the nanoscale for the first time by using a bow-tie nano-antenna probe. These results enable the unambiguous identification of the modes with the 3D-FDTD simulations.In this work is also reported the first observation of two-dimensional localization of light in two types of 2D random photonic crystal lasers, where Slow Bloch Mode (SBM) is scattered by artificial structural randomness in triangular PCs. The structural randomness is introduced whether by nanometer displacements in the positions of lattice elements (air holes), whether by variation of the hole diameters. The direct near-field imaging of the lasing mode by use of NSOM for the first time, allowed us to observe the transition of the extended planar SBM to be Anderson localized.
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Modeindustrins gröna marknadsföringsstrategi : En studie om Åhléns och Filippa KMohsin, Priya January 2015 (has links)
Den senaste tiden har miljödebatten vuxit sig stor och den kopplas allt mer samman till det ohållbara konsumtionssamhället som vi lever i idag. Modeindustrin utgör en stor del i den ohållbara utvecklingen av samhället och genom ett hållbarhetsengagemang börjar många modeföretag försöka få bukt på miljöproblemet och flera andra sammanhängande globala problem. I samband med detta har det gröna marknadsföringskonceptet fått ett uppsving bland modeföretagen och företagen har börjat anamma slow fashion konceptet. Denna miljödebatt i relation till klädkonsumtion är ett väldigt viktigt ämne som behöver tas på största allvar. Med grund i denna problemdiskussion är syftet med studien att analysera grön marknadsföringsstrategi inom modebranschen och därmed bidra med kunskap och djupare förståelse för ämnet. För att utföra undersökningen har studien antagit ett företagsperspektiv och analyserat kring Åhléns och Filippa Ks hållbarhetsarbete och deras gröna marknadsföringsstrategier. Studiens frågeställningar är ”Hur arbetar Åhléns och Filippa K med hållbarhet inom deras verksamhet?” och ”Vilka likheter och skillnader går det att urskilja i företagens gröna marknadsföringsstrategi?”. Studien baserades på modellen ”The Marketing Triangle” och för att erhålla olika perspektiv av respektive företaget har därför en kvalitativ metod med en deduktiv ansats varit till grund. Det utfördes både intervjuer med respektive företag samt en personalundersökning genom ”Mystery shopping” metoden. Studien påvisade att företagen arbetar omsorgsfullt med hållbarhet inom företagen och att det finns flera likheter än skillnader i företagens gröna marknadsföringsstrategi vilket troligtvis bland annat har att göra med att de ingår i samma koncern. Utifrån ett realistiskt perspektiv har företagen en beblandning av de olika strategierna i ”The Green Marketing Strategy Matrix” och de består inte endast av en enda strategi från modellen. En skillnad i företagens marknadsföringsstrategi är att de har olika syften när de kommunicerar via marknadskommunikationen, medan Åhléns vill framhäva miljöaspekterna väljer Filippa K att avstå ifrån det. Personalundersökningen som innefattade observation av kommunikationen i butikerna påvisade att båda företagen bör arbeta mer med den interna marknadsföringen. Slutdiskussionen av studien tyder på att det för båda företagen finns brister i deras gröna arbete och det går därför att ifrågasätta hur pass miljöetiskt deras arbete är inom produktionskedjan. Det går även att konstatera att modeparadoxen är vad som hindrar arbetet mot ett hållbart konsumtionssamhälle. Som en avslutande ståndpunkt förklaras det att för att åstadkomma förändringar och bidra till ett hållbart samhälle behöver alla vi ta vårt eget ansvar.
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Connecting people, food & place: sustaining community, identity, and well-being through a multisensory, local food centreShwaluk, Janine 01 February 2010 (has links)
This interior design project involves investigation into the philosophies of the Slow Food Movement and how they may inspire and inform the design of a social space that fosters a connection between local people, food and place. This socio-cultural connection is implemented through the design of a concentrated, local food centre within the urban environment of Winnipeg, Manitoba. Investigation into interior design strategies which foster social interaction, taste education and sensory engagement contribute to the design of a space where the local food culture of southern Manitoba can be experienced in its authenticity. By combining the public spaces of food which contribute to the contemporary streetscape, with those that exist within the interior environment, this local food centre design aims to promote local identity and facilitate multisensory social engagement that sustains relationships, community, and the environment over time.
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Growth Appropriate Planning in Canada: What factors lead to the implementation of progressive planning and economic development policy in Canadian Communities?Warkentin, Joshua 14 September 2012 (has links)
ABSTRACT
A key feature of Canada’s urban system is the uneven distribution of population and economic growth. The 2011 Census showed that in the past five years more than 80% of the country’s growth was concentrated in the 10 largest Canadian Metropolitan Areas. As a result, more than 33% of Canada’s population centres lost population while another 27% experienced slow growth. Despite affecting a third of the country’s communities, population loss was concentrated primarily in remote communities with a population of less than 10,000.
To better understand the processes and effects of slow growth and shrinkage in Canada this research was guided by three questions:
• How do planners, economic developers and local officials define slow growth, decline and shrinkage?
• What factors cause a community to implement growth appropriate planning tools and strategies and;
• What components should be part of growth appropriate planning and economic development strategies?
These questions were addressed using a qualitative survey which was answered by 70 participants in 51 communities.
Overall there was little variance in how respondents defined decline and shrinkage. Given their stigma, each term was primarily associated with population loss, vacant structures and a variety of problems including financial stress and the loss of employment opportunities. When asked approximately 80% of Canadian communities used at least one progressive planning tool or strategy. The implementation of these tools was largely in response to the effects of slow growth and shrinkage as well as future economic outlook, support from local actors (municipal staff and officials, residents, local businesses) and senior governments. Few communities however used these tools to acknowledge or explicitly deal with their slow growth or shrinkage as it was feared that accepting either trend would scare away future investment.
Almost all of the research participants agreed that areas of slow growth and population loss required different planning strategies than those experiencing rapid growth. These strategies included altering existing strategies to meet local needs and or creating entirely new planning tools and strategies, collaborating with other professionals, amending existing or creating new roles for planners, leverage local resources for community improvements and using an approach which equally addresses a community physical, economic, environmental and social needs. In addition, respondents noted that more research was required on how to plan in growth challenged areas and in particular, small rural communities.
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Already left behind what can be done for low achieving high school mathematics students? /Foster, Halcyon J. Presmeg, Norma C. January 2004 (has links)
Thesis (Ph. D.)--Illinois State University, 2004. / Title from title page screen, viewed Jan. 11, 2005. Dissertation Committee: Norma Presmeg (chair), Cynthia Langrall, Tami S. Martin, Amelia Adkins. Includes bibliographical references (leaves 186-192) and abstract. Also available in print.
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The relative effects of mainstream and segregated programs on the primary learning disabled students' acquisition of prerequisite reading skills and growth of self-conceptHawkins, Deborah Ann, January 1900 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 114-121).
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