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Generation of Ultra-Packed Thermal Greases and Evaluation of their Effective PropertiesSukshitha Achar Puttur Lakshminarayana (5930798) 16 January 2019 (has links)
Thermal Greases are gap-filling interface materials that are used in semiconductor
packages to efficiently transfer heat from the component to the heat sink or spreader.
Thermal greases are typically particle filled composite materials comprising of highly
conducting fillers in a poorly conducting, but mechanically soft, silicone or epoxy
base matrix. Generally, the effective conductivity of the greases increases with increasing volume fractions of fillers. However, the fillers also have high elastic modulus
that induces undesirable thermal stresses on the brittle silicon device. Therefore, as
device power density increases, there is a need to increase particle volume loading,
which in turn necessitates optimally balancing the material’s thermal and mechanical
characteristics.<div><br></div><div>In this thesis, procedures are developed to simulate packed microstructures of particles so as to identify the optimal trade-off between thermal and mechanical behavior.
Experimental and numerical simulations of microstructures that have been generated
as reported in the literature were found to have volume fractions of around 60%. However, as commercially available thermal greases have volume fractions in the range of
60 − 80%, there is a need to develop an efficient algorithm to generate microstructures numerically. The particle packing is initially posed as a nonlinear programming
problem and rigorous optimization search algorithms are systematically applied to
generate particle systems that are compactly packed, but without particle overlap.
Since the packing problem is computationally expensive, the algorithms are systematically evaluated to improve computational efficiency as measured by the number of particles in the system, as well as the time to generate the microstructure. The
evaluated algorithms include the inefficient penalty function methods, best-in-class
sequential programming method, matrix-less conjugate gradient method as well as
the augmented Lagrangian method. In addition, heuristic algorithms are also evaluated to achieve computationally efficient packing. The evaluated heuristic algorithms
are mainly based on the Drop-Fall-Shake method, but modified to more effectively
simulate the mixing process in commercial planetary mixers. With the developed
procedures, Representative Volume Elements (RVE) with volume fraction as high as
74% were achieved.
<br></div><div><br></div><div>After the microstructurs were generated, the effective thermal conductivity and
effective elastic modulus were estimated using a ‘Random Network Model (RNM)’
that was previously developed. The RNM solves the near-percolation heat conduction
problem with hundreds of thousands of particles in minutes compared to hours or days
that a full-field simulation requires. The approximations inherent in the RNM are
valid if the particulate composite has widely different matrix and particle properties,
which is true in the case of thermal greases. In the present thesis, the previously
developed RNM was modified to account for the fact that the generated RVEs contain
sides with cut particles.<br></div>
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The Knowing : a Fantasy ; An epistemological enquiry into creative process, form, and genreManwaring, Kevan January 2018 (has links)
This creative writing PhD thesis consists of a novel and a critical reflective essay. Both articulate a distinctive approach to the challenges of writing genre fiction in the 21st Century that I define as 'Goldendark' - one that actively engages with the ethical and political implications of the field via the specific aesthetic choices made about methodology, content, and form. The Knowing: A Fantasy is a novel written in the High Mimetic style that, through the story of Janey McEttrick, a Scottish-Cherokee musician descended from the Reverend Robert Kirk, a 17th Century Episcopalian minister from Aberfoyle (author of the 1691 monograph, The Secret Commonwealth of Elves, Fauns and Fairies), fictionalises the diasporic translocation of song- and tale-cultures between the Scottish Lowlands and the Southern Appalachians, and is a dramatisation of the creative process. In the accompanying critical reflective essay, 'An Epistemological Enquiry into Creative Process, Form and Genre', I chart the development of my novel: its initial inspiration, my practice-based research, its composition and completion, all informed both by my practice as a storyteller/poet and by my archival discoveries. In the section 'Walking Between Worlds' I articulate my methodology and seek to defend experiential research as a multi-modal approach - one that included long-distance walking, illustration, spoken word performance, ballad-singing and learning an instrument. In 'Framing the Narrative' I discuss matters of form - how I engaged with hyperfictionality and digital technology in destabilising traditional conventions of linear narrative and generic expectation. Finally, in 'Defining Goldendark' I articulate in detail my approach to a new ethical aesthetics of the fantasy genre.
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Role of Nanoparticles in Voltammetric Signal Enhancement Exhibited by Layer-by-Layer (LbL) Gold Nanoparticle-Modified Screen-Printed Carbon Electrodes (SPCEs)Ahiadu, Ben K 01 May 2017 (has links)
Screen-printed electrodes (SPEs) have found wide use as sensing platforms due to their simple fabrication, customizability in terms of geometry and composition, and relatively low cost of production. Nanoparticles have been incorporated in or interfaced with SPEs in order to improve sensor response or provide electrocatalytic capabilities. Though nanomaterial-modified SPEs are becoming increasingly common sensing platforms, the benefits provided by nanomaterials are often determined through voltammetric studies with common redox probes, such as ferricyanide. However, recent reports have documented the ferri-/ferrocyanide redox couple to be an unreliable system for characterizing some carbon-based electrodes due to the dependence of its electrochemical response on electrode surface effects unrelated to electroactive surface area. In the current studies, we have investigated the voltammetric responses of ferricyanide and other redox probes on bare and gold nanoparticle (AuNP)-modified screen-printed carbon electrodes to determine the potential role of AuNPs in improving sensor response through electrochemical signal enhancement.
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A belly full of arms and legsPage, Courtney Hodges, n/a January 1997 (has links)
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The travellersPage, Sue, n/a January 1997 (has links)
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On expressive punishment and holisitic desertGreenblum, Jake 15 May 2009 (has links)
Expressive theories of punishment incorporate both deontological and consequentialist components. The deontological element claims that punishment expresses the value of both victim and wrongdoer. The consequentialist element claims that punishment restores the victim’s and wrongdoer’s worth. In contemporary literature, however, it is unclear which component is given priority and therefore expressive theories appear ambiguous at best and inconsistent at worst. My thesis argues that expressive theories are cleared up and made consistent through employing a holistic notion of punitive desert. Holism is the view that accurate desert judgments must reference an actually obtaining just distribution of punishment. In my view, the expressive function is feasible only when desert is understood holistically and in this sense expressive theories are committed to giving priority to the deontological component.
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Domestic TitusBrinkman, Ashley Marie 15 May 2009 (has links)
Critical examinations of William Shakespeare’s Titus Andronicus almost always
occlude questions of the domestic. Yet, a major portion of the play’s action takes place
in a house and the methods of the characters’ revenge can be construed as domestic.
More simply, in Titus, household properties and domestic rituals are transformed into
instruments of vengeance. With a particular focus on the cultural and historical
conditions governing literary production in early modern England, this thesis draws on
previous scholarly work and examines the intersection of domesticity and revenge in
Titus.
The thesis is divided into two sections, each of which addresses different, though
overlapping, ways in which domesticity – broadly speaking – operates in the play. The
first section examines the play’s two competing revenge plots, demonstrating that not
only are they domestic in nature, but also that many of the play’s features align closely
with generic traits and devices integral to plays classified as “Domestic Tragedies.” The
second section focuses on Titus Andronicus’ Senecan roots and examines carefully the
function(s) of the domestic setting in Titus as well as Seneca’s Thyestes, one of
Shakespeare’s sources. I explore the ways in which the play’s domestic setting is distinctly Senecan and discuss Shakespeare’s alterations to his Latin source. While the
house becomes a site of domestic and dynastic anxiety in both Seneca’s Thyestes and
Shakespeare’s Titus Andronicus, Shakespeare’s play evinces a concern with domestic
privacy that Seneca’s does not.
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On expressive punishment and holisitic desertGreenblum, Jake 15 May 2009 (has links)
Expressive theories of punishment incorporate both deontological and consequentialist components. The deontological element claims that punishment expresses the value of both victim and wrongdoer. The consequentialist element claims that punishment restores the victim’s and wrongdoer’s worth. In contemporary literature, however, it is unclear which component is given priority and therefore expressive theories appear ambiguous at best and inconsistent at worst. My thesis argues that expressive theories are cleared up and made consistent through employing a holistic notion of punitive desert. Holism is the view that accurate desert judgments must reference an actually obtaining just distribution of punishment. In my view, the expressive function is feasible only when desert is understood holistically and in this sense expressive theories are committed to giving priority to the deontological component.
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Fiscal federalism : essays on competition, equalization and cooperation /Verdonck, Magali. January 2006 (has links) (PDF)
Univ., Diss.--Louvain-la-Neuve, 2006. / Beitr. teilw. engl., teilw. franz.
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Copolymerization studies of ethylene and trimethylsilyl protected 1-alkenols using a Brookhart-type alpha-diimine nickel(II) dibromide precatalystMurray, Heidi 02 February 2009 (has links)
There has been considerable interest over the past decade in the preparation and applications of copolymers of ethylene with functionalized polar olefins. Such copolymers are expected to exhibit a variety of potentially very useful properties such as paintability, adhesion to polar surfaces, and miscibility with polar polymers such as polyesters and polyamides, but there are limitations associated with producing copolymers of ethylene with polar monomers via Ziegler-Natta processes. Many classes of Ziegler-Natta catalysts, especially those of the early transition metals (Ti and Zr), are highly oxophilic and hence are poisoned by functionalities such as -OH groups. This problem can in principle be alleviated by implementing the use of protecting groups such as –OSiMe3, which has previously been shown to be an effective masking agent both for steric reasons and because O-Si π bonding decreases the Lewis basicity of the ether oxygen atom. One can also utilize late transition metal catalyst systems, which are generally less Lewis acidic and therefore less susceptible to poisoning by functional groups.
In this thesis the results of an investigation of the copolymerization of ethylene with CH2=CH(CH2)nOSiMe3 (n = 1, 2, 8) will be presented. We have been using MAO activated dibromo[1,4-bis(2,6-diisopropylphenyl)acenaphthenediimine]nickel(II) (D) as catalyst, as this system is known to produce reasonably linear polyethylene and hence may be expected to produce essentially LLDPE containing –(CH2)nOSiMe3 branches. The latter can be hydrolyzed to give polar –(CH2)nOH branches. / Thesis (Master, Chemistry) -- Queen's University, 2009-01-31 14:43:09.93
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