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1
Sutton, Phil J. "Saturn's turbulent F ring." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18475.
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As our abilities to utilise high performance computing to theoretically probe many astrophysical systems increases, a genuine need to relate to real systems becomes ever more important. Here, Saturn s rings can be used as a nearby laboratory to investigate in real time many astrophysical processes. One such system is the narrow F ring and its interaction with its inner shepherd moon Prometheus. Through numerical modelling and direct observations of the in-situ spacecraft Cassini we find new and exciting dynamics. These might help explain some of the asymmetries witnessed in the distribution of embedded moonlets and azimuthal ring brightness known to exist within the F ring. Spatially we find asymmetry in the Prometheus induced channel edges with regards to density, velocity and acceleration variations of ring particles. Channel edges that show fans (embedded moonlets) are also the locations of highly localised increases in densities, velocity and acceleration changes where opposing edges are considerably less localised in their distribution. As a result of the highly localised nature of the velocity and acceleration changes chaotic fluctuations in density were witnessed. However, this could seek to work in favour of creating coherent objects at this channel edge as density increases were significantly large. Thus, density here had a greater chance of being enhanced beyond the local Roche density. Accompanied with these dynamics was the discovery of a non-zero component to vorticity in the perturbed area of the F ring post encounter. By removal of the background Keplerian flow we find that encounters typically created a large scale rotation of ~10,000 km^2. Within this area a much more rich distribution of local rotations is also seen located in and around the channel edges. Although the real F ring and our models are non-hydrodynamical in nature the existence of a curl in the velocity vector field in the perturbed region could offer some interesting implications for those systems that are gas rich.
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Vosswinkel, Michael. "Ring expansion and ring opening of heteroaromatic nitrenes." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968868576.
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Gattrell, William Thomas. "Aziridines : stereocontrol of ring-making and ring-breaking." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30090.
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(S)-3-Amino-2-(1-hydroxy-2,2-dimethylprop-1-yl)-quinazolin-4(3H)-one (Q*NH2) was prepared from (L)-tert-leucine and its 3-acetoxyamino derivative (Q*NHOAc) used to aziridinate a range of alkenes. In the presence of titanium (IV) tert-butoxide, Q*NHOAc was found to convert styrene, indene, butadiene and tert-butyl acrylate with complete diastereoselectivity into the corresponding N-Q* substituted aziridines in good yield; aziridination of methyl acrylate and -methylstyrene was also highly diastereoselective. In the absence of titanium (IV) tert-butoxide, aziridination proceeded with poor diastereoselectivity in every case. The quinazolinone (Q*) ring has proved to be invaluable in directing or assisting the course of ring-opening of the N-(Q*) aziridines produced above. Thus Q* as a substituent on nitrogen was found to be sufficiently electron-withdrawing to activate the aziridine ring towards attack by nucleophiles in the absence of acid. The C-4 carbonyl oxygen of the quinazolinone (Q*) was found to participate in the aziridine ring-opening under some conditions with the result that retention of configuration was found in the alcohol product; evidence for this participation was obtained by exchange of the Q* carbonyl for a thione when the ring-opening was carried out in the presence of hydrogen sulphide. The two N-invertomers of the indene-derived aziridine were separately ring-opened by hydrogen chloride with very different stereochemistry, mediated by the Q* group. Finally, the sense of regioselectivity in the ring-opening of the methyl acrylate-derived aziridine can be changed by forming a lactone tether between the aziridine and Q* rings before ring-opening.
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Coe, Samuel. "Phyllostictine A ring assembly via ring closing metathesis." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/67101/.
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This thesis describes work focused on the chemical synthesis and herbicidal activity of the natural product phyllostictine A, a molecule of unique structure and unknown mode of action. Chapter 1 serves to introduce the natural product and describe the known activity of the natural product. Furthermore, it discusses literature methods for the construction of a-methylene-b-lactams, a key component of phyllostictine A. Chapter 2 describes work towards the construction of the macrocyclic rings found in phyllostictine A. As a result a-methylene-b-lactams have been shown, for the first time, to participate in RCM reactions. Formation of 11- and 12-membered trisubstituted membered rings was possible, however, the nature of the nitrogen substituent has a large impact. For example, 12-membered rings 124, 130 were formed in 37% yield when a para-methoxyphenyl group was utilised, while simple ethyl substitution could only achieve yields of 20%. Boc protected lactam 169 produced only linear dimer 170. The synthesis of tetrasubstituted alkenes via RCM was attempted with lactam 145, however, resulted in an unexpected rearrangement product. Not only was the RCM sensitive to the nitrogen substituent but also the size of ring being formed. For example, 11-membered rings produced significant amounts of the 22-membered dimers 89 and 87. Throughout the RCM reactions performed in this thesis held a preference for the Z-alkene. The trend was confirmed both by NMR shift analysis and X-ray crystallography. Chapter 3 describes work towards the synthesis of 4,4-disubstituted a-methylene-b-lactam subunit of phyllostictine A. Three methods: epoxide rearrangement, carbonylation of methyleneaziridines and carbonylation of 2-bromo-allyl-propenes were explored. Chapter 4 describes the herbicidal activity of phyllostictine A against the single celled algae C. reinhardtii. ED50 data was obtained for phyllostictine A against C. reinhardtii for the first time. Furthermore, it was shown to be comparable to the commercial herbicide glyphosate. Six novel a-methylene-b-lactams synthesised in Chapter 2 were tested for herbicidal activity against C. reinhardtii which has enabled us to develop preliminary structure-activity relationships.
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EPLEE, ROBERT EUGENE JR. "SPOKES IN SATURN'S B RING: DYNAMICAL AND PHYSICAL PROPERTIES DEDUCED FROM VOYAGER SATURN RING IMAGES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184056.
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The two Voyager spacecraft discovered small-scale, radially-extended features in the central region of Saturn's B Ring. These "spokes" are "clouds" of submicron-size ice grains which are electrostatically levitated above the ring plane and which appear to travel about Saturn in Keplerian orbits (Smith et al., 1981, Science 212, 163-191). This research project is a study of the dynamical and physical properties of spokes as deduced from Voyager Saturn ring images. An analysis of the orbital motion of two dynamically-anomalous spokes, in particular, has set limits on the charge-to-mass ratios of spoke particles at various times during their dynamical evolution. These two spokes have charge-to-mass ratios of at least -60 ± 3 C kg⁻¹ while corotating with Saturn, and charge-to-mass ratios of no more than -22 ± 2 C kg⁻¹ while orbiting Saturn at Keplerian velocities. Additionally, charge decay on the grains of these spokes, caused by solar UV photoemission, has allowed a lower limit of 0.10 ± 0.03 μm to be placed on the range of radii for spoke particles. In a study of spoke photometry, a single-scattering analysis of the 0.470-μm phase function for spokes has set a mean radius for the dominant scatterers (at this wavelength) of 0.22 ± 0.02 μm. Also, a multispectral analysis of spokes has determined the spectral index of the size distribution for spoke particles to be 2.1 ± 0.2. These dynamical and physical properties of spokes have been combined with theoretical explanations of spoke activity to develop a phenomenological model of spoke formation and evolution. The transport of angular momentum within the rings due to the radial motion of spoke grains is shown to be the most significant effect of spoke activity on the dynamical evolution of the B Ring, as was predicted by Goertz et al. (1986, Nature 320, 141-143). The radial mass transport velocity due to highly-charged spokes is -1 x 10⁻⁹ m s⁻¹. The subsequent spreading time for the B Ring is 600 million years, which is significantly less than the 4.6 billion-year age of the solar system.
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Hadziselimovic, Adin. "Ring Simulator." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1098.
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This report is about a Thesis for Degree of Bachelor of Science at Linköping University. It describes design of equipment which makes it possible to measure signal and noise quality during data transmission via Asymmetric Digital Subscriber Line, ADSL. The measuring instrument is HP 4934A Transmission Impairment Measuring Set. The equipment was supposed to be used for testing of ADSL systems within Solectron Sweden AB. In fact, the equipment stands for virtual Plain Old Telephone Service, POTS. That is why it simulates all three states that may come up. The states are following:"on hook", ringing,"off hook"(speech transmission). There is a control unit in the design. It changes between different circuit connections to get one of the states. You have to use a computer for control of the equipment. The computer commands are sent to equipment via its serial port via RS232 to the control unit. The equipment is driven with 48 Vdc.
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Маlenchyk, Т. V., and А. V. Bulashenko. "Ring Counters." Thesis, Sumy State University, 2018. http://essuir.sumdu.edu.ua/handle/123456789/67632.
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For the construction of ring counters, all types of shift registers can be used. The most
simple is a ring counter on D flip-flops. In the circuit, four flip-flops are closed in the ring by feedback from the output of the last flip-flop to the input of the first flip-flop. Counting pulses are fed to the clock inputs of all triggers. On this basis, all ring counters are synchronous. By the pulse of the initial setting, the first trigger is set to, the rest to.
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Thießen, Friedrich, and Sebastian Liebold. "Der Ring." Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-133479.
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Prothero, John. "Ring Width and Ring Diameter as Functions of Ring Number in Suppressed Maples and Oaks." Tree-Ring Society, 1997. http://hdl.handle.net/10150/262379.
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Phipps showed that the cross-sectional area of successive tree rings in suppressed red maples and chestnut oaks, sampled at three-foot intervals above the base, is approximately constant. I show that this invariance in cross-sectional area is consistent with ring width varying as the inverse square root of ring number and with mean ring diameter and trunk diameter each scaling as the square root of ring number. These results may be useful in formulating growth rules for tree trunks of selected species, under constant environmental conditions, in terms of a single independent variable. For example, if elastic similarity holds, trunk height is proportional to the two-thirds power of trunk diameter. This relation implies that trunk height scales as the cube root of ring number. Thus, trunk height and trunk diameter may, in principle, both be expressed in terms of one independent variable, ring number.
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Riat, D. P. S. "The ring opening polymerization of ring strained cyclic ethers." Thesis, Aston University, 1992. http://publications.aston.ac.uk/9785/.
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The kinetics and mechanisms of the ring-opening polymerization of oxetane were studied using cationic and coordinated anionic catalysts. The cationic initiators used were BF30Et2!/ethanol, BF30Et2!/ethanediol and BF30Et2/propantriol. Kinetic determinations with the BF30Et2/diol system indicated that a 1: 1 BF3:0H ratio gave the maximum rate of polymerization and this ratio was employed to detenmne the overall rates of polymerization. An overall second-order dependence was obtained when the system involved ethanediol or propantriol as co-catalyst and a 3/2-order dependence with ethanol, in each case the monomer gave a first-order relationship. This suggested that two mechanisms accounted for the cationic polymerization. These mechanisms were investigated and further evidence for these was obtained from the study of the complex formation of BF30Et2 and the co-catalysts by 1H NMR. Molecular weight studies (using size-exclusion chromatography) indicated that the hydroxyl ion acted as a chain transfer reagent when the [OH] > [BF3]. A linear relationship was observed when the number average molecular weight was plotted against [oxetane] at constant [BF3:0H], and similarly a linear dependency was observed on the BF3:0H 1:1 adduct at constant oxetane concentration. Copolymerization of oxetane and THF was carried out using BF30Et2/ethanol system. The reactivity ratios were calculated as rOXT = 1.2 ± 0.30 and rTHF = 0.14 ± 0.03. These copolymers were random copolymers with no evidence of oligomer formation. The coordinated anionic catalyst, porphinato-aluminium chloride [(TPP)AICl], was used to produce a living polymerization of oxetane. An overall third-order kinetics was obtained, with a second-order with respect to the [(TPP)AICl] and a first-order with respect to the [oxetane] and a mechanism was postulated using these results. The stereochemistry of [(TPP)AlCl] catalyst was investigated using cyclohexene and cyclopentene oxide monomers, using extensive 1H NMR, 2-D COSY and decoupling NMR techniques it was concluded that [(TPP)AlCl] gave rise to stereoregular polymers.
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Sutradhar, Nitai Chandra. "The study of ring-spinning with particular reference to rotating rings." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329210.
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Steele, Brett. "Romancing the Ring : romance tropes in The Lord of the Rings." Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/53471.
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This dissertation is an exploration of the Romance tropes that exist in J.R.R. Tolkien s The
Lord of the Rings. It concentrates on the numerous Romance tropes and details evident in
Tolkien s characters and setting while focusing on how these tropes function within the
greater Romance genre. Examples from various other Romances are used to augment the
argument, but particular mention is made of the Romances or pieces of literature that
Tolkien translated and worked on in his lifetime, including: Sir Gawain and the Green Knight,
Sir Orfeo, The Pearl, The Legend of Sigurd and Gudrún, The Fall of Arthur, and Beowulf.
The dissertation focuses on Tolkien s The Lord of the Rings, which has been responsible for
the renaissance of modern fantasy in the twentieth-century. It begins by raising the
contentious issue of whether Tolkien s book may be regarded as a Romance. The work of
Helen Cooper (2009), Gillian Beer (1970) and Northrop Frye (1973 and 1976) forms the
basis of this theoretical discussion. The Romance tropes evident in the analysis of the
characters and setting of The Lord of the Rings provide an interesting starting point for
further discussion of the Romance tropes that exist elsewhere in Tolkien s work, and one
hopes that more research into this will follow.Dissertation (MA)--University of Pretoria, 2015.
English
MA
Unrestricted
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Brennan, C. M. "Ring closure reactions." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384611.
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McDonnell, P. D. "Ring closure reactions." Thesis, University of East Anglia, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378891.
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Reich, Eitan. "Deniable Ring Signatures." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41671.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 55-57).
Ring Signatures were developed by Rivest, Shamir and Tauman, in a paper titled How to Leak a Secret, as a cryptographically secure way to authenticate messages with respect to ad-hoc groups while still maintaining the signer's anonymity. While their initial scheme assumed the existence of random oracles, in 2005 a scheme was developed that does not use random oracles and meets the strongest security definitions known in the literature. We argue that this scheme is not deniable, meaning if someone signs a message with respect to a ring of possible signers, and at a later time the secret keys of all of the possible signers are confiscated (including the author), then the author's anonymity is no longer guaranteed. We propose a modification to the scheme that guarantees anonymity even in this situation, using a scheme that depends on ring signature users generating keys that do not distinguish them from other users who did not intend to participate in ring signature schemes, so that our scheme can truly be called a deniable ring signature scheme.
by Eitan Reich.
M.Eng.
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Angeltveit, Vigleik. "Noncommutative ring spectra." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34549.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2006.Includes bibliographical references (p. 87-91).
Let A be an Ax ring spectrum. We give an explicit construction of topological Hochschild homology and cohomology of A using the Stasheff associahedra and another family of polyhedra called cyclohedra. Using this construction we can then study how THH(A) varies over the moduli space of AO structures on A, a problem which seems largely intractable using strictly associative replacements of A. We study how topological Hochschild cohomology of any 2-periodic Morava K-theory varies over the moduli space of AO structures and show that in the generic case, when a certain matrix describing the multiplication is invertible, the result is the corresponding Morava E-theory. If this matrix is not invertible, the result is some extension of Morava E-theory, and exactly which extension we get depends on the AO structure. To make sense of our constructions, we first set up a general framework for enriching a subcategory of the category of noncommutative sets over a category C using products of the objects of a non-E operad P in C. By viewing the simplicial category as a subcategory of the category of noncommutative sets in two different ways, we obtain two generalizations of simplicial objects.
(cont.) For the operad given by the Stasheff associahedra we obtain a model for the 2-sided bar construction in the first case and the cyclic bar and cobar construction in the second case. Using either the associahedra or the cyclohedra in place of the geometric simplices we can define the geometric realization of these objects.
by Vigleik Angeltveit.
Ph.D.
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Gallant, Pascal. "Synthesis of oxepane nucleosides by ring expansion and ring closing routes." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103473.
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Modified nucleosides form an important class of antiviral and anticancer agents, and nucleic acids bearing modified nucleosides hold great promise as therapeutic agents. Oxepane nucleosides and nucleic acids are members of this important class of compounds. Oxepane nucleosides have a seven-membered carbohydrate ring instead of the canonical five-membered pentafuranose ring. This thesis describes work in the development of new synthetic approaches and routes in the synthesis of oxepane nucleosides. In chapter 2, the synthesis of oxepane nucleosides based on the ring expansion approach is described. Building on previous work in the Damha lab, studies in the synthesis of oxepane nucleosides by a ring expansion approach were carried out. In particular, oxepane nucleosides were synthesized using thioglycoside derivatives. Routes in the modification of the oxepane scaffold were explored, but later abandoned in favor of new synthetic approaches to oxepane nucleosides. In chapter 3, work towards the development of new routes in the synthesis of oxepane nucleosides by ring-closing metathesis is described. This new approach to the synthesis of oxepane nucleosides allows for the use of commercially-available nucleosides and circumvents the difficulties observed in glycosylation reaction employed in the previous approach. In chapter 3, various synthetic routes are examined, and work towards the development of viable routes is described. In particular, the direct addition of Grigard reagents to nucleosides dialdehydes, followed by Grubbs II mediated ring closing metathesis serves as a proof-of-principle of the synthesis of oxepane nucleosides by a ring closing route.Les nucléosides modifiés sont des agents thérapeutiques très efficaces contre le cancer et contre des virus. Les oxepanes font partie de ce groupe important. Au lieu d'avoir un cycle de 5 atomes, les oxepanes ont un cycle modifié de 7 atomes. Cette thèse décrit la recherche sur le développement de nouvelles méthodes pour la synthèse des oxepanes. Dans le deuxième chapitre, la synthèse des oxepanes par la méthode d'expansion de cycle est traitée. Notamment, la synthèse des oxepanes par le biais des hétérosides contenant des thiols est décrite. Dans le troisième chapitre, de nouvelles méthodes pour la synthèse des oxepanes sont étudiées. Toutes ces approches ont pour but ultime d'utiliser la métathèse d'alcènes comme l'étape clé. Notamment, l'addition directe des réactifs de Grignard à des nucléosides contenant deux aldéhydes, suivi d'une métathèse d'alcène, constitue une démonstration de faisabilité de cette approche synthétique.
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Hill, Jessica. "Medium ring nitrogen heterocycles by migratory ring expansion of metallated ureas." Thesis, University of Bristol, 2019. http://hdl.handle.net/1983/d76ea2f2-2d4a-40d9-9d50-04fde02d65c1.
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Medium ring (8-12 members) and benzannulated medium heterocycles represent a class of synthetically challenging targets. Although natural products containing medium ring N- and O- heterocycles offer beneficial biological properties, there is a stark absence of medium rings in active pharmaceutical ingredients, potentially highlighting the difficulties associated with their synthesis. Typical methods of synthesis include transition metal-catalysed processes, such as ring closing metathesis and ring expansion techniques, which require pre-organisation of the precursors to ensure a thermodynamic driving force. Research by the Clayden group has shown that the poor reactivity between carbanions and unactivated Csp2 'electrophiles' can be overcome by tethering the two through a urea linkage. The principles of this unique protocol have been applied to the research within this thesis. Firstly, the N→C rearrangement chemistry has been applied to cyclic systems where the urea nitrogen is tethered as part of a ring, ultimately resulting in ring expansion after aryl migration. This ring expansion methodology has been optimised and applied to a wide range of urea precursors, allowing access to complex structural architectures in few steps from simple starting materials. Secondly, when benzylic indole precursors were investigated, rather than obtaining the expected ring expansion products from the N→C aryl migration route, lithiation instead resulted in dearomative cyclisation, generating a range of polycyclic indoline structures. Finally, an n to n-2 ring contraction protocol has been developed to access privileged tetrahydroisoquinoline and tetrahydrobenzazepine structures from medium ring nitrogen heterocycles. Furthermore, this ring contraction methodology has been developed for applications in flow, for the efficient multigram synthesis of 1-aryl tetrahydrobenzazepine. The different synthetic methods disclosed within this thesis enables rapid access to a wide range of biologically and medicinally relevant scaffolds, from which further diversification is possible for potential library design.
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Johansson, Pontus. "New piston ring solution for Stirling engines." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75236.
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Lacroix, Jean-François. "Design and synthesis of A-ring/seco B-ring vitamin D analogues." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106520.
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A new series of vitamin D analogs were synthesized with a saturated seco B-ring and several potential aromatic A-ring mimics. These new A-ring/seco B-ring analogs examine the possibility of forming positive electrostatic interactions in the seco B-ring portion of the vitamin D nuclear receptor, the effect of increasing interactions between the ligand and Tryptophan 286 as well as the ability of aromatic rings at miming the natural A-ring. A central core based on the natural C,D-ring was developed, which allows divergent analogs synthesis for fast screening of side chain and A-ring mimics.Une nouvelle série d'analogues de la vitamine D a été synthétisée avec un cycle B secondaire saturé, ainsi qu'avec divers composés aromatiques pouvant potentiellement imiter le cycle A naturel. Cette série d'analogues évalue la possibilité de faire des interactions positive dans la région du cycle B secondaire du récepteur nucléaire de la Vitamine D, l'effet d'amplifier l'interaction entre le ligand et Tryptophane 286 ainsi que la possibilitée d'imiter le cycle A naturel avec des cycles aromatique. Un composé basé sur les cycles C et D de la vitamine D a été développé, ce composé permet l'obtention rapide d'analogues visant à évaluer des imitations de la chaine latérale et du cycle A naturel.
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Immormino, Nicholas A. "Clean Rings & Clean Group Rings." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1374247918.
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Liwag, Andra. "The Seven Day Ring." NSUWorks, 2013. http://nsuworks.nova.edu/writing_etd/8.
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O’Flaherty, Craig. "Blue ring of fire." Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/63615.
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My poems are reflections of shape, colour and emotions expressed through imagery. Their unsentimental landscape-realism echo my own feelings as well as broader human dimensions of contradiction and uncertainty, without trying to resolve them. In the same way that photography is the art of 'painting with light', my poems seek a language that evokes light and darkness. They aspire to what Keats said when writing about ‘negative capability’: “Poetical character has no self, it is anything and nothing, it has no character and enjoys light and shade”. My poems explore what I have learned about form – how line-length, syntax and musicality can add grace and energy to language. Poets that have influenced me include the classical Chinese poets such as Du Fu and Li Po, and the Generation of 27 Spanish poets, such as Antonio Machado and Leon Felipe.
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Graham, Richard Douglas. "Ring laser gain media." Thesis, University of Canterbury. Physics, 2006. http://hdl.handle.net/10092/1377.
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This thesis details the design and construction of an experiment to measure the radial distribution of laser gain in a cylindrical Helium-Neon laser gain tube. This distribution is important as it can effect the transverse mode structure of a running ring laser. Earlier theoretical models of the distribution were not supported by high quality experimental data and fail to take into account some physical processes. A resolution of 8 parts per million in gain and 50 μm in radial position has been achieved. Gain distributions have been measured and are shown to be well modeled by a 0th order Bessel function with first roots at the tube walls and a central dip depending on excitation power; except for the region very near to the tube walls where a very rapid increase in gain has been observed. Hydrogen has been identified by spectroscopic analysis as the primary constituent of gas contamination and cause of the long term reduction in gain of large ring lasers. Additional work has been done to detect a proposed non-classical Lense-Thirring field around a spinning lead superconductor. It was found that any effect is at least 20 times smaller than predicted. Techniques and tools for data acquisition programming have been reviewed focusing on difficulties with coupling of user interface and application logic, monolithicity, difficulties with scripting and algorithm implementation.
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Craig, Ian R. "Ring polymer molecular dynamics." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:f3c37800-6fc7-4d8b-b135-94d94a7cf4e1.
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This thesis presents the ring polymer molecular dynamics (RPMD) approximation to the Kubo-transformed time correlation function and shows how it may be used as the basis of an approximate quantum-mechanical method for determining the dynamical properties of condensed-phase molecular systems. The performance of the RPMD method is initially investigated by calculating the position (qˆ), and position-cubed (qˆ3), autocorrelation functions of a series of onedimensional potential wells of varying anharmonicity. It is then applied to the evaluation of the incoherent dynamic structure factors of liquid para-hydrogen at 14 K. Finally, the RPMD method is used to determine canonical rate coefficients for two onedimensional models of bimolecular chemical reactions and a multidimensional model of a solution-phase proton transfer reaction. For each application, the accuracy of the RPMD method is established by comparison with exact quantum-mechanical results and/or with experiment. Throughout this work, an emphasis is placed upon identifying the situations in which the RPMD approximation breaks down. It is found that the RPMD method is capable of providing an accurate approximation to the time correlation functions of a variety of condensed-phase molecular systems. Situations for which it is inaccurate include correlation functions which correlate highly nonlinear operators and those involving significant quantum interference effects in the real-time dynamics.
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Stones, P. A. "New ring forming reactions." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373984.
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Bourne, I. A. "Medium-ring bicyclic amines." Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375000.
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Xu, Guoda, John M. Bartha, Stuart McNamee, Larry Rheaume, and Allen Khosrowabadi. "OPTICAL SLIP-RING CONNECTOR." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/607336.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaCurrent ground-based tracking systems at the DoD test and training ranges require transmission of a variety of signals from rotating platform to fixed control and process center. Implementation of commercial off the shelf (COTS) solution for transmitting high-speed, multiple-channel data signals over a rotational platform prompt the development of an advanced electro-optic hybrid rotating-to-fixed information transmission technology. Based on current demand, an Air Force-sponsored Small Business Innovative Research (SBIR) contract has been awarded to Physical Optics Corporation (POC) to modify existing tracking mounts with a unique electro-optic hybrid rotary joint (EOHRJ). The EOHRJ under current development is expected to provide the following features: 1) include a specially designed electrical slip-ring, which is able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low-speed data signals; 2) include an optical fiber slip-ring which, by incorporating with electrical time division mulitplexing (TDM) and optical wavelength division multiplexing (WDM) technologies, is able to provide multiple channel, high data rate (over gigabits per second), and bi-directional signal transmission; and 3) is designed to be reliable for harsh environmental operation, adaptive to stringent size requirement, and accommodating to existing electrical and mechanical interfaces. Besides the military use, other possible commercial applications include on board monitoring of satellite spinners, surveillance systems, instrumentation and multi spectral vision systems, emergency/medical instruments, remote sensing, and robotics.
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Leal, João Filipe Tapadinhas Puga. "Optimization of ring oscillators." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/11361.
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Dissertação para obtenção do Grau de Mestre em
Engenharia Electrotécnica e de ComputadoresVoltage Controlled Oscillators (VCOs) are from all the building blocks of a PLL, those whose implementation is more critical, since the quality of the signal depends on its performance. The VCOs can be implemented based on LC oscillators or ring oscillators. The ring oscillators, despite of being worst when it comes to manners of phase noise, they are rather used due to lower power consumption, wider tuning range and occupying less area. Despite the fact that VCOs are widely used in last years, their designed is still a problem hard to deal with, since the ring oscillators circuits must satisfy some specifications such as area, power, speed and noise. The work proposed in this thesis aims at the development of an environment for automatic scaling of voltage-controlled oscillators with ring topology. In this work it was considered a design methodology based optimization using an analytical model of the oscillator. The oscillator model is based on the EKV model for the characterization of the transistors so as to ensure its applicability to submicron dimensions technologies. The work took place according to the following phases: - Study of ring oscillators and models proposed in the literature - Evaluation of the limitations of existing models and proposed use of EKV model. - Automatic determination of the parameters of the EKV model for UMC130 technology - Development of an analytic model for characterizing the VCO with predefined delay cell. - Use of optimization techniques for automatic sizing of the VCOs
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Thießen, Friedrich, and Sebastian Liebold. "Der Ring: Jahresausgabe 2013." RCDA Chemnitz e.V, 2013. https://monarch.qucosa.de/id/qucosa%3A20001.
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McWhorter, Suzanne D. "Ring Rust." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1430421935.
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Andersson, Pelle. "Spektrum av en ring." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297898.
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Denna text fungerar som en egen genomgång av spektra av matematiska ringar, inspirerad av uppgifter från Introduction to Commutative Algebra av Atiyah, MacDonald och The Geometry of Schemes av Harris, Eisenburg. Spektrumet är en struktur ur varje ring där en rings primideal ses som punkter i ett topologiskt rum. Spektrumet har alltså en geometrisk tolkning och topologin kallas Zariskitopologi. I texten presenteras en rad satser utifrån grundläggande ringlära och Zariskitopologin. Det tas upp resultat såsom att öppna mängder i spektrumet nästan alltid är mycket stora i jämförelse med det mesta, och att enskilda punkter i spektrumet inte måste vara slutna. Konkreta exempel med fallet ringar som polynomringar i två eller fler variabler tas även upp i anslutning till satsresultaten. En mycket viktig aspekt med ringspektra är att de inte har entydiga ursprungsringar, som riskerar att göra introduktionen av ringspektra ej meningsfull. För detta tillämpas kärve av ringar som är ett system där stora öppna mängder i ett topologiskt rum tilldelas mer lätthanterliga ringar. Detta visar sig lösa två problem med ringspektra. Dels blir de överväldigande stora öppna mängderna mer lättförståeliga, men det kommer också råda ekvivalens mellan paret ringspektrum-kärve - så kallat affint schema - och ursprungsringen. Faktum är att det till och med kommer vara ekvivalens mellan hela kategorierna av kommutativa ringar respektive affina scheman. Affina scheman blir inte bara en geometrisk struktur som härrör en ring, utan just den geometriska tolkningen av ringen. Även om det inte ingår i arbetssyftet så nämns det att det då blir möjligt att i stort sett göra generaliseringar av ringar genom att göra generaliseringar av affina scheman i form av att klistra ihop affina scheman till allmänna scheman. Detta hade varit mycket långsökt och svårt om endast kunskap om ringen hades, och om teorin om Zariskitopologin var okänd.
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Juglal, Shaanraj. "Prime near-ring modules and their links with the generalised group near-ring." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/714.
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In view of the facts that the definition of a ring led to the definition of a near- ring, the definition of a ring module led to the definition of a near-ring module, prime rings resulted in investigations with respect to primeness in near-rings, one is naturally inclined to attempt to define the notion of a group near-ring seeing that the group ring had already been defined and investigated into by, interalia, Groenewald in [7] . However, in trying to define the group near-ring along the same lines as the group ring was defined, it was found that the resulting multiplication was, in general, not associative in the near-ring case due to the lack of one distributive property. In 1976, Meldrum [19] achieved success in defining the group near-ring. How- ever, in his definition, only distributively generated near-rings were considered and the distributive generators played a vital role in the construction. In 1989, Le Riche, Meldrum and van der Walt [17], adopted a similar approach to that which led to a successful and fruitful definition of matrix near-rings, and defined the group near-ring in a more general sense. In particular, they defined R[G], the group near-ring of a group G over a near-ring R, as a subnear-ring of M(RG), the near-ring of all mappings of the group RG into itself. More recently, Groenewald and Lee [14], further generalised the definition of R[G] to R[S : M], the generalised semigroup near-ring of a semigroup S over any faithful R-module M. Again, the natural thing to do would be to extend the results obtained for R[G] to R[S : M], and this they achieved with much success.
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Chen, Thet-Ngian. "A new fault-tolerant configuration for the Cambridge Ring : the Hierarchical Ring-Star." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/33049.
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The primary objective of this research is to look at ways of resolving the reliability problems of the Cambridge Ring local area network system. The result is a novel design to enhance the Cambridge Ring with fault tolerance by introducing redundant communication paths with dynamic reconfiguration. The proposed Ring-Star system combines the advantages of ring and star networks to create a network which is topologically resilient while retaining the efficient communication advantage of rings.
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Guo, Boying. "New Ring Expansion and Ring Opening Reactions of Vinyl Oxetanes and Vinyl Oxiranes." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/315543.
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Three new synthetic methods employing vinyl oxetanes as substrates are presented. In Chapter 2, a new catalytic vinyl oxetane ring expansion is described. Origins, design, reaction, and optimizations are discussed. A novel asymmetric synthesis of 3,6-dihydro-2H-pyrans using chiral counterion catalysis is presented as part of these studies. In Chapter 3, the Z-selective ring opening of vinyl oxetanes using dialkyl dithiophosphate nucleophiles is described from initial discovery, through optimizations to the application towards the synthesis of thiopyrans. These insights were then utilized to develop a similar Z-selective protocol for vinyl oxiranes. In Chapter 4, a novel method to synthesize homoallylic alcohols from 3,6-dihydro-2H-pyrans using a mild and selective C-O reduction approach is described.
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Borges, Adroaldo Lazouriano Moreira. "Uma proposta de protocolo token ring sem fio." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-24032014-121359/.
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O protocolo Token Ring sem o (WTRP) é um protocolo distribuído de controle de acesso ao meio que provê qualidade de serviço em termos de uso de largura de banda e latência limitada. WTRP consiste de nós (estações) que formam topologicamente um anel. Contudo, quando o número de nós em um anel aumenta a latência aumenta e o tempo de reuso de token por parte de um nó em anel também aumenta. Neste trabalho, apresentamos uma versão extendida de WTRP com foco em reduzir a latência, tempo de reuso de token e permitir encaminhamento de dados entre anéis sem aumentar signicativamente o consumo de energia. Para provar o conceito que propomos, implementamos e testamos a nossa versão de WTRP usando simulador de rede - NS.Wireless Token Ring Protocol (WTRP) is a distributed Medium Access Control protocol that provides quality of service in terms of reserved bandwidth and limited latency]. It consists of nodes or stations structured in ring topology. However, when the number of nodes in a ring increases latency and time of a node reuse token increases. In this work, we present an extended version WTRP that focus on reducing latency, time of token reuse and data forwarding among the rings in a MANet , without suggestive increasing of energy consumption. We have implemented and tested our version of WTRP in network simulator - NS.
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Phipps, Richard L. "Some Geometric Constraints on Ring-Width Trend." Tree-Ring Society, 2005. http://hdl.handle.net/10150/262639.
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Simulations of tree rings from trees of undisturbed forest sites are used to describe natural, long-term width trends. Ring-width trends of canopy-sized white oak are simulated from regressions of BAI (ring area) data of real trees. Examples are given of a tree from a typical re-growth forest in Illinois and of a more slowly growing tree from an old-growth forest in Kentucky. The long-term width trend was simulated as being toward constant ring width regardless of growth rate of the tree. Conditions by which either increasing or decreasing ring-width trends could be simulated from the same linear BAI trend are examined. I conclude that curvilinear width trends, either increasing or decreasing, represent width adjustments to changes in growth rate (BAI trend) after which the width trend stabilizes to a near-constant value. Interpretation of ring-width trends of trees from undisturbed stands may be useful in assessing stand disturbance history.
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Dincoflaz, Yasemin. "The Synthesis Of 6- And 7- Membered Heterocyclic Ring Systems Fused To Pyridine Ring." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615579/index.pdf.
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The synthesis of the nitrogen containing heterocyclic compounds is one of the leading research areas throughout the organic chemistry due to their significant activities in biological systems. Among the various biologically active molecules, pyridine-fused ring systems are of prime importance on the grounds of their proven clinical roles.
The coupling reactions with 6-membered heterocyclic compounds and diazepines gave rise to new pharmalogical compounds in recent years. Therefore, our object was the synthesis of pyridine-fused 6- and 7-membered heterocycles.
Starting from bromopyridine, two different methods were applied for the synthesis of target compounds. In the first part of the this thesis, coupling products were synthesized using Sonogashira coupling reaction. After synthesis of the coupling derivatives, ring-closure under the basic conditions generated the heterocyclic units without using any catalyzer. In the second part of study, nicotinic acid and pyridopyranone derivatives were synthesized by using intramolecular cyclization reactions. The formed products were conscientiously purified and characterized by means of spectroscopics method.
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White, John William. "An Evans-Tishchenko/ring closing metathesis approach towards the medium ring lactone, octalactin A." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/11557.
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Medium-ring lactones have become important targets for synthesis as they have been isolated in an increasing number of biologically active natural products. The studies towards two 8-membered ring lactone natural products, octalactins A 1 and B 2, will be described. The first section of this thesis examines the application of key methodology (anti aldol reaction, Homer Wadsworth Emmons olefination, intermolecular Evans- Tishchenko coupling and Ring Closing Metathesis) towards the octalactins via the synthesis of a model lactone 3 (Chapter 2). The second section (Chapter 3) discusses the extension of the aldol methodology from Chapter 2 towards the development of a novel chiral auxiliary 4 to mediate the anti aldol reaction. The generality of this new auxiliary in anti aldol reactions will also be discussed. The final part of this thesis describes the synthesis of the octalactins based on the application of the methodology developed from the model studies using the key functionalised fragments: aldehyde 5, 3-ketophosphonate ester 6 and aldehyde 7.
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Akurati, Parthasri, and Karan Kumar. "Development of a 3D Ring Dynamics Model For a Heavy-Duty Piston Ring-Pack." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21638.
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With the increasing restrictions in emission legislations, the automotive industry aims to improve the efficiency of the lubricating system and to decrease fuel consumption. In the power cylinder unit (PCU), the piston rings are the major contributor to these consumptions. Hence, focus on the dynamic behaviour of the rings to reduce lube oil consumption (LOC) becomes a key factor in thriving towards sustainability. Several studies have been conducted on the piston ring-pack specifically using a 2D ring dynamics approach. This study focuses on developing a 3D ring dynamics model, in the software tool AVL EXCITE™ Piston&Rings, which is capable of observing the behaviour of the ring along the third dimension i.e. circumferential direction. A coordinated approach used in the methodology gives an insight into the parameters affecting the model behaviour. Within the PCU, wear on the cylinder liner surface and in the piston ring grooves can lead to accelerated LOC. This study further focuses on using the 3D model to analyse the friction and wear on the piston rings. Factors contributing towards LOC are individually studied and the results obtained are compared to the experimental engine test data. The outcome of the 3D numerical model developed shows promising results. The model can therefore be used to simulate different piston ring-packs and analyse the behaviour of the piston ring with a better prediction of friction, wear and LOC. Thus, the model will contribute to reducing the number of physical tests conducted, the expense involved in conducting those tests and would provide satisfactory products to the customer and would manage future emission requirements.
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Engel, David B. "Syntheses and comparative studies of 5-membered ring and 6-membered ring sulfane frameworks /." Online version of thesis, 1992. http://hdl.handle.net/1850/11985.
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Esmaili, Mahyar. "Development and implementation of an apparatus for polymeric piston-ring performance tests in controlled environment." Ohio : Ohio University, 1993. http://www.ohiolink.edu/etd/view.cgi?ohiou1175286117.
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Chin, Melanie Soo, and m. chin@cqu edu au. "Towards a Reinterpretation of the Radical Theory of Associative Rings Using Base Radical and Base Semisimple Class Constructions." Central Queensland University. Computer Science, 2004. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20050411.102928.
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This research aims to refresh and reinterpret the radical theory of associative rings using the base radical and base semisimple class constructions. It also endeavours to generalise some results about ideals of rings in terms of accessible subrings. A characterisation of accessible subrings is included. By applying the base radical and base semisimple class constructions to many of the known results in established radical theory a number of gaps are uncovered and closed, with the goal of making the theory more accessible to advanced undergraduate and graduate students and mathematicians in related fields, and to open up new areas of investigation.
After a literature review and brief reminder of algebra rudiments, the useful properties of accessible subrings and the U and S operators independent from radical class connections are described. The section on accessible subrings illustrates that replacing ideals with accessible subrings is indeed possible for a number of results and demonstrates its usefulness.
The traditional radical and semisimple class definitions are included and it is shown that the base radical and base semisimple class constructions are equivalent. Diagrams illustrating the constructions support the definitions. From then on, all radical and semisimple classes mentioned are understood to have the base radical and base semisimple class form. Subject to the constraints of this work, many known results of traditional radical theory are reinterpreted with new proofs, illustrating the potential to simplify the understanding of radical theory using the base radical and base semisimple class constructions. Along with reinterpreting known results, new results emerge giving further insight to radical theory and its intricacies. Accessible subrings and the U and S operators are integrated into the development. The duality between the base radical and base semisimple class constructions is demonstrated in earnest.
With a measure of the theory presented, the new constructions are applied to examples and concrete radicals. Context is supported by establishing the relationship between some well-known rings and the radical and related classes of interest.
The title of the thesis, Towards a Reinterpretation of the Radical Theory of Associative Rings Using Base Radical and Base Semisimple Class Constructions, reflects the understanding that reinterpreting the entirety of radical theory is beyond the scope of this work. The conclusion includes an outlook listing further research that time did not allow.
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Vaughan, Stephen N. (Stephen Nick). "Some Properties of Noetherian Rings." Thesis, North Texas State University, 1986. https://digital.library.unt.edu/ark:/67531/metadc501109/.
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This paper is an investigation of several basic properties of noetherian rings. Chapter I gives a brief introduction, statements of definitions, and statements of theorems without proof. Some of the main results in the study of noetherian rings are proved in Chapter II. These results include proofs of the equivalence of the maximal condition, the ascending chain condition, and that every ideal is finitely generated. Some other results are that if a ring R is noetherian, then R[x] is noetherian, and that if every prime ideal of a ring R is finitely generated, then R is noetherian.
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Farina, John Dominic. "Stability properties in ring theory." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3237384.
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Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed December 8, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 86-90).
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Bjermo, Jonas. "The ring of entire functions." Thesis, Uppsala University, Department of Mathematics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121405.
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Alnæs, Merethe. "Integritetsevaluering av Ring Joint flensforbindelse." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produksjons- og kvalitetsteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22694.
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Med stadig høyere krav til redusert utslipp i olje- og gassindustrien er flensforbindelser en viktig komponent å sette fokus på. Flensforbindelser er blant annet brukt i subsea omgivelser til å skjøte sammen rørsystemer og komponenter. Ettersom forbindelsene eksisterer i et stort antall, og transporterer hydrokarboner under høye trykk og temperaturer er det viktig at integriteten er i behold. Standarden ASTM A182/A182M setter krav til at stålflenser skal være smidd så nært som praktisk mulig til angitt størrelse og form. Kravet eliminerer dermed muligheten for produksjon av flenshalvdelene ved andre tilvirkningsmetoder. De kan potensielt bli maskinert direkte fra smidd bar av stål. Hydrostatiske trykktester av flensforbindelser brukes til å evaluere dens integritet. Det er ikke påsatt krav til hydrostatisk trykktesting av flensforbindelser generelt, men rørsystemer er påsatt krav til å gjennomgå trykktester med dets komponenter før det er satt i driftstilstand og etter gjennomført vedlikehold. En prosedyre for trykktesting har blitt funnet i standarden ISO 10423 under litteraturstudium. Evaluering av integriteten til en Ring Joint flensforbindelse med materialegenskaper fra maskinerte flenshalvdeler av smidd bar (UNS S31803) har blitt utført med elementmetodeprogrammet Abaqus. En aksesymmetrisk elastisk-plastisk elementmetodemodell har blitt benyttet hvor en analyse med trykktestprosedyre har blitt gjennomført. Von Mises-spenningsforholdene har blitt kartlagt under påføringen av boltlasten i forbindelsen, og under resterende steg av den simulerte trykktestingen. De maksimale spenningsforholdene har blitt funnet til å ligge i ringsporet av flenshalvdelene. Plastisk tøyning har også blitt kartlagt, og maksimale verdier befinner seg i pakningen under påføring av boltlast. Kontakttrykket i flensforbindelsen mellom pakning og ringspor er av betydning for integriteten til flensforbindelsen. Kontakttrykkene har blitt kartlagt og viser seg og ligge ved verdier som ikke resulterer i svikt av integriteten.Flensforbindelsen er utsatt for flere degraderingsmekanismer. En av dem, siging, forekommer som regel etter at flensforbindelsen har gjennomgått en hydrostatisk trykktest. Det har blitt funnet at degraderingsmekanismen siging ikke er av risiko for flensforbindelsen som oppgaven omhandler. Den kritiske sigingstemperaturen vil ikke nås ved de forholdene og materialene som er betraktet i oppgaven.
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Mastine, Michael. "Atmospheric optical ring network protocols." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68044.
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The protocols used for an Atmospheric Optical Ring Network (AORN) are investigated. Performance under bad-weather conditions are of particular interest. Under these bad-weather conditions, the Gilbert-Elliott model is the fading channel model used in the simulation of the network. Appropriate channel parameters are obtained and then protocol modifications are tested. Performance plots are obtained showing the effects on performance of lowering the token timeout value and the addition of additional parity bits in the datalink layer of the network. Furthermore, the performance is plotted as function of the Trivial File Transfer Protocol (TFTP) data block length for different values of channel parameters.
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Bradley, Lisa L. "Studies in medium ring synthesis." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276522.
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Singh, Rajinder. "Free radical ring expansion reactions." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293427.
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