Дисертації з теми "Derivators"
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Groth, Moritz [Verfasser]. "On the theory of derivators / Moritz Groth. Mathematisch-Naturwissenschaftliche Fakultät." Bonn : Universitäts- und Landesbibliothek Bonn, 2011. http://d-nb.info/1016599633/34.
Повний текст джерелаCASTAGNOLA, CHRISTIAN. "Qualite de vie et derivations urinaires cutanees : derivations non continentes versus derivations continentes : resultats d'un questionnaire adresse a 73 patients." Lyon 1, 1993. http://www.theses.fr/1993LYO1M302.
Повний текст джерелаMäkinen, Erkki. "On context-free derivations." Tampere : University of Tampere, 1985. http://catalog.hathitrust.org/api/volumes/oclc/16724479.html.
Повний текст джерелаGustafsson, Hans. "Derivatans introduktion i gymnasiematematiken." Thesis, Högskolan i Gävle, Avdelningen för elektroteknik, matematik och naturvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-32372.
Повний текст джерелаBjørk, Tina Beate. "Syntese av crocin-derivater." Thesis, Norwegian University of Science and Technology, Department of Chemistry, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10412.
Повний текст джерелаBroekhuis, Hans. "Derivations (MP) and evaluations (OT)." Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2009/3234/.
Повний текст джерелаMorris, Simon Edward. "Bounded derivations from uniform algebras." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318438.
Повний текст джерелаHeath, Matthew J. "Bounded derivations from Banach algebras." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519425.
Повний текст джерелаKnapper, Andrew. "Derivations on certain banach algebras." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368411.
Повний текст джерелаFeinstein, Joel Francis. "Derivations from Banach function algebras." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329058.
Повний текст джерелаWang, Zhiqing. "Locally nilpotent derivations of polynomial rings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0018/NQ48119.pdf.
Повний текст джерелаBoca, Paul Philip. "A framework for presenting transformational derivations." Thesis, Queen Mary, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286065.
Повний текст джерелаDavis, Colin Pierce Bryon. "The linear limitations of syntactic derivations." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129122.
Повний текст джерелаCataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 349-370).
In this dissertation, I identify and analyze several new generalizations about how phrasal displacement and discontinuity are constrained in natural language. These patterns reveal, I argue, that many limitations of syntactic derivations are attributable to the way in which syntactic operations are cyclically interleaved with the component of the grammar that establishes word order. This finding has consequences for many phenomena, and for the architecture of grammar in general. Chapter 1 introduces the theory of cyclic linearization that serves as the foundation for this work, and several principles about the locality of movement that importantly interact with it. Chapter 2 shows that these concepts predict the crosslinguistic distribution of stranding in intermediate positions. Chapter 3 extends these considerations to an analysis of possessor extraction in colloquial English, a phenomenon subject to numerous intricate but systematic limitations. Chapter 4 provides further evidence for the theory advanced here from constraints on subextraction in Russian. Chapter 5 argues that certain facts about parasitic gaps in sentences with overlapping moved phrases reveal further evidence that linearization constrains syntactic derivations, with consequences for the nature of movement more generally. Chapter 6 argues that linear order constrains extraposition, and proposes an account of this phenomenon that addresses a number of puzzles about its distribution. Chapter 7 diverges from the theme of linearization to explore parasitic gaps in relative clauses, which connect to several results from chapter 5. Chapter 8 summarizes the findings of this dissertation, and discusses several more general implications of the framework advanced here.
by Colin Pierce Bryon Davis.
Ph. D. in Linguistics
Ph.D.inLinguistics Massachusetts Institute of Technology, Department of Linguistics and Philosophy
Chitayat, Michael. "Locally Nilpotent Derivations and Their Quasi-Extensions." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35072.
Повний текст джерелаTanaka, Hidekazu. "Conditions on logical form derivations and representations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0028/NQ50266.pdf.
Повний текст джерелаSoltys-Kulinicz, Michael. "The complexity of derivations of matrix identities." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ63701.pdf.
Повний текст джерелаChung, Myungsuk. "Lie derivations on rings of differential operators." Diss., Virginia Tech, 1995. http://hdl.handle.net/10919/37457.
Повний текст джерелаLegault, Benoît. "Derivations partielles et totales du coeur droit." Clermont-Ferrand 1, 1994. http://www.theses.fr/1994CLF1MS08.
Повний текст джерелаDumas, François. "Corps locaux non commutatifs et hautes derivations." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21130.
Повний текст джерелаMiyagawa, Shigeru. "Blocking and causatives: unexpected competition across derivations." University of Arizona Linguistics Circle, 2011. http://hdl.handle.net/10150/139392.
Повний текст джерелаDeterding, Stephen. "Bounded Point Derivations on Certain Function Spaces." UKnowledge, 2018. https://uknowledge.uky.edu/math_etds/51.
Повний текст джерелаKhoury, Joseph. "Locally nilpotent derivations and their rings of constants." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9028.
Повний текст джерелаЧернишова, Я. "Language derivations in normative legal base of Ukraine." Thesis, Сумський державний університет, 2020. https://essuir.sumdu.edu.ua/handle/123456789/81260.
Повний текст джерелаУ дослідженні розглядаються похідні від іноземних мов до української юридичного мови. Запозичення служать важливим фактором у розвитку мови. Слова іноземного походження постійно проникають в систему національної мови, і це явище привертає увагу вчених.
В исследовании рассматриваются производные от иностранных языков юридического языка. Заимствования служат важным фактором в развитии языка. Слова иностранного происхождения постоянно проникают в систему национального языка, и это явление привлекает внимание ученых.
The study deals with foreign language derivatives in legal language. Derivations serve as an important factor in language development. Words of foreign origin constantly penetrate the national language system, and this phenomenon attracts the attention of scholars.
Trepat, Guixer Elisenda. "Aplicacions de derivats quirals de l'àcid acetoacètic." Doctoral thesis, Universitat Autònoma de Barcelona, 2001. http://hdl.handle.net/10803/3133.
Повний текст джерелаA la segona part d'aquesta tesi s'han preparat diversos precursors enantiomèricament purs de l'esfinganina que és el precursor biològic de l'esfingosina. Aquests s'han preparat partint dels 3-oxoestearats de diversos auxiliars quirals (sultama d'Oppolzer, oxazolidinona d'Evans, D-ribonolactona). La primera etapa consisteix en una addició de Michael catalitzada pel salicilaldehiat de níquel (II) i els acceptors de Michael són diversos azodicarboxilats (azodicarboxilat de dietil, de dibenzil, de di-tert-butil i de bis-tricloroetil). La segona etapa és una reducció amb BH3.SMe2 utilitzant TiCl4 com agent quelatant. S'obtenen els alcohols de configuració syn amb bones relacions diastereomèriques i rendiments correctes. A més a més s'han preparat pirazoles enantiomèricament purs que presenten un auxiliar quiral i una cadena de 15 carbonis.
a,a-disubstituted glycines present remarkable properties as enzyme inhibitors and as conformational modifiers of peptides. In the first part of this thesis we describe a new simple methodology to prepare enantiopure a,a-dialkylglycines based on the use of commercially available D-ribonolactone as a chiral auxiliary. The first step is tre preparation of 2,3-O-isopropylidene-g-D-ribonolactone acetoacetate. This product is alkylated in basic conditions with methyl iodide or butyl iodide. Dilakylated products are prepared through diastereoselective alkylation using NaH as a base and some alkyl halides (benzyl bromide, 4-bromobenzyl bromide, 2-methylnaftyl bromide). Then a transesterification step followed by a Schmidt rearrangement affords the acetamides. Finally an acid hydrolisis affords the hydrochlorides in good yields. Absolute configuration was assigned through preparation of enantiopure 4,4-disubstituted 3-methyl-2-pyrazolin-5-ones.
In the second part of this thesis some enantiopure precursors of sphinganine (the biosynthetic precursor of sphingosine) have been prepared. Firstly 3-oxoestearates of some chiral auxiliaries (Evans oxazolidinone, Oppolzer's sultame and D-ribonolactone acetonide) have been synthesized. The first step is a Michael addition catalyzed by nickel salicilaldehide where the Michael acceptors are some azodicarboxilates (dibenzyl, diethyl, di-tert-butyl and bis-trichloroethyl). The next step is a stereoselective reduction using BH3-SMe2 in the presence of TiCl4 (chelator Lewis acid). Alcohols with a syn configuration are obtained with good diastereomeric ratios and correct yields. Moreover enantiomerically pure pyrazoles that present a chiral auxiliary and a long chain (15 carbons)
Діденко, С. В. "Кредитні деривативи: теоретичні та емпіричні аспекти". Thesis, Українська академія банківської справи Національного банку України, 2005. http://essuir.sumdu.edu.ua/handle/123456789/62264.
Повний текст джерелаWenckens, Martin. "Synthesis and biological evaluation of novel N-alkoxypyrazoles as biomimetics for the phenoxy group in tamoxifen /." Cph : Department of Medicinal Chemistry, Royal Danish School of Pharmacy, 2002. http://www.dfh.dk/phd/defences/martinwenckens.htm.
Повний текст джерелаFarmer, Andrew Scott. "Bottom albedo derivations using hyperspectral spectrometry and multispectral video." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001054.
Повний текст джерелаAnderson, Penelope L. "Matrix based derivations and representations of Krylov subspace methods." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23766.
Повний текст джерелаSomerset, Douglas W. B. "Quasi-standard c*-algebras and norms of inner derivations." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:ab71e110-d152-473e-ad13-8f09fcd7d7c4.
Повний текст джерелаPham, Hung Le. "The functions of homomorphisms and derivations from Banach algebras." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421451.
Повний текст джерелаWeigt, Martin. "Jordan homomorphisms and derivations on algebras of measurable operators." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4944.
Повний текст джерелаIncludes bibliographical references (p.122-132) and index.
A few decades ago, Kaplansky raised the question whether unital linear invertibility preserving maps between unital algebras are Jordan homomorphisms. This question is still unanswered, and the progress that has been made has mainly been in the context of Banach algebras, including C*-algebras and von Neumann algebras. Let M be a von Neumann algebra with a faithful semifinite normal trace τ , and M~ the algebra of τ-measurable operators (measurable for short) affiliated with M. The algebra M~ can be endowed with a topology Уcm, called the topology of convergence in measure, such that M~ becomes a complete metrizable topological *-algebra in which M is dense. One of the aims of this thesis is to find answers to Kaplansky’s question in the context of algebras of measurable operators.
DUPRE, MINET MARIE. "Sensibilite, specificite et reproductibilite de l'electrocardiogramme d'effort douze derivations." Lille 2, 1991. http://www.theses.fr/1991LIL2M287.
Повний текст джерелаCatania, Jeffrey Mark. "Derivations of Tissue Slice Technology as Toxicological Screening Systems." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195419.
Повний текст джерелаBen, Abdeljelil Amine. "Generalized Derivations of Ternary Lie Algebras and n-BiHom-Lie Algebras." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7743.
Повний текст джерелаSukumaran, Murali. "Photophysical kinetics in TICT-forming compounds-derivates of DMABN." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975654411.
Повний текст джерелаDe, Matos Fernandes Susana. "Novel materialsbased in chitosan, its derivates and cellulose fibers." Pau, 2010. http://www.theses.fr/2010PAUU3010.
Повний текст джерелаThe purpose of this study was to develop new materials based on chitosan and its derivatives and cellulose, in the form of nanofibres or paper sheet. . Chitosan samples were then used to prepare transparent nanocomposite films based on different chitosan (CH) matrices (two chitosans with different DPs and corresponding water-soluble derivatives) and nanofibrillated cellulose (NFC) and bacterial cellulose (BC). The films obtained were shown to be highly transparent, displayed better mechanical properties than the corresponding unfilled chitosan films and showed increased thermal stability. Another approach involved the coating of E. Globulus based paper sheets with chitosan and two different chitosan derivatives, a fluorescent and a water-soluble derivative, on a pilot-size press machine. First, a fluorescent chitosan derivative was deposited layer-by-layer onto conventional paper sheets and its distribution was assessed. The results showed that the surface distribution was highly homogeneous and the penetration of chitosan within the paper pores ceased after a three-layer deposit, beyond coating only produced an increase in its overall thickness and film-forming aptitude. Then, the effect of chitosan and chitosan quaternization on the final properties of chitosan-coated papers was investigated. In general, both chitosan and water-soluble chitosan coatings had a positive impact on the final properties of the coated papers. Finally, chitin and chitosan were converted into viscous polyols through a simple oxypropylation reaction, with the aim of valorizing the less noble fractions or by-products of these valuable renewable resources
BRUNET, PIERRE. "Enterocystoplasties et derivations urinaires continentes : a propos de 26 observations." Lille 2, 1993. http://www.theses.fr/1993LIL2M190.
Повний текст джерелаEL, Houari Hassan. "Algorithms for locally nilpotent derivations in dimension two and three." Limoges, 2007. https://aurore.unilim.fr/theses/nxfile/default/7d0e7c9d-8bec-4ccf-af81-92abce4349cb/blobholder:0/2007LIMO4049.pdf.
Повний текст джерелаDerivations, especially locally nilpotent ones, over polynomial rings are objects of great importance in many fields of pure and applied mathematics. Nowadays, locally nilpotent derivations have made remarkable progress and became an important topic in understanding affine algebraic geometry and commutative algebra. This is due to the fact that some classic problems in these areas, such as the Jacobian conjecture, the Linearization problem and the Cancellation problem, can be reformulated in terms of locally nilpotent derivations. This thesis is about the algorithmic study of problems linked to locally nilpotent derivations and their applications to the study of polynomial automorphisms of the affine space. Its aim is to present, on one hand, some problems in which locally nilpotent derivations play a crucial role, namely, the coordinate problem and the parametrization problem. On the other hand, give some algorithms concerning locally nilpotent derivations, which may contribute in understanding locally nilpotent derivations in three dimensional case, namely, rang and triangulability algorithms of locally nilpotent derivations
Bergander, Philip. "Twisted derivations, quasi-hom-Lie algebras and their quasi-deformations." Thesis, Mälardalens högskola, Akademin för utbildning, kultur och kommunikation, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35553.
Повний текст джерелаMerighe, Liliam Carsava. "Uma introdução às derivações localmente nilpotentes com uma aplicação ao 14º problema de Hilbert." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/55/55135/tde-05082015-102547/.
Повний текст джерелаThe main objective of this thesis is to study a counterexample to the Hilberts Fourteenth Problem in dimension n = 5, which was presented by Arno van den Essen ([6]) in 2006 and that is based on a counterexample of D. Daigle and G. Freudenburg ([4]). For these purpose, we study the fundamental concepts of the theory of derivations and the basic principles of locally nilpotent derivations and their corollaries. Among these principles, Principle 13 ensures that if B is a k-algebra polynomial, say B = k[x1; ..., xn], (where k is a field of characteristic zero) and D is a locally nilpotent derivation on B, then its kernel A = ker D satisfies A = B ∩ Frac(A). Once we have proved that A is not finitely generated over k, we find the expected counterexample. In addition, in the appendix of this work is given a proof for the Hilberts Fourteenth Problemin dimension n = 1.
Gerber, Minja. "Synthesis and transdermal properties of acetylsalicylic acid derivates / Minja Gerber." Thesis, North-West University, 2003. http://hdl.handle.net/10394/281.
Повний текст джерелаThesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.
Nik, Salleh Nik Ghazali. "Photochemistry and photopolymerisation activity of novel benzophenone and thioxanthone derivates." Thesis, Manchester Metropolitan University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263447.
Повний текст джерелаBenecke, Birka. "Internationale Rechnungslegung und Management approach : Bilanzierung derivater Finanzinstrumente und Segmentberichterstattung /." Wiesbaden : Wiesbaden : Deutscher Universitäts-Verlag ; Gabler, 2000. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=008939957&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Повний текст джерелаEscribà, i. Gelonch Marc. "Glicerol en la preparació d'esters de clorohidrina i derivats." Doctoral thesis, Universitat de Lleida, 2010. http://hdl.handle.net/10803/8367.
Повний текст джерелаAixí, a partir de la síntesi d'esters de dicloropropil, usant glicerol i clorotrimetilsilà com a font de clor o amb clorur d'alumini usant un líquid iònic, s'han sintetitzat esters d'al·lil, alguns d'ells amb efecte ovicida en insectes. Un dels esters de dicloropropil sintetitzat a partir d'un àcid versàtic ha estat la referència per a la preparació d'esters dessimetritzats usant iodur, hidroxils o imidazoles com a nucleòfils.
Amb la finalitat de fer les reaccions més sostenibles, s'han usat reactius provinents de subproductes industrials, tant del sector d'olis i greixos, com de la indústria del biodiesel.
S'han emprat noves tècniques en síntesi orgànica, com els líquids iònics i les microones. L'ús de microreactors en una de les reaccions ha demostrat ser efectiu per a disminuir el temps de reacció, la qual cosa hauria de facilitar el seu escalat
Se presentan diferentes reacciones de síntesis química en las cuales participa el glicerol como reactivo. La mayoría de ellas presentan altos rendimientos y buenos porcentajes de conversión. Un aspecto relevante de estas reacciones es la obtención mediante síntesis química de compuestos o precursores sintéticos de sustancias de alto valor añadido.
Así, a partir de la síntesis de ésteres de dicloropropilo, usando glicerol y clorotrimetilsilano como fuente de cloro, o con cloruro de aluminio usando un líquido iónico, se han sintetizado ésteres de alilo, algunos de ellos con efecto ovicida. Una de los ésteres de dicloropropilo obtenido a partir de un ácido versático se ha usado como referencia para la preparación de ésteres desimetrizados usando ioduro, hidroxilo o imidazole como nucleófilos.
Con la finalidad de aumentar la sostenibilidad, se han usado reactivos procedentes de subproductos industriales, tanto del sector de aceites y grasas, como de la industria del biodiesel.
Las nuevas tecnologías, como los líquidos iónicos y las microondas, también han sido aplicadas en algunas de las reacciones estudiadas. Por otra parte, el uso de microreactores ha permitido mejorar el tiempo de reacción de uno de los procesos estudiados, hecho que debería facilitar su escalado.
Different synthetic reactions are shown, where glycerol is used as a starting material. High yields and conversions are reported in many of the described reactions. One relevant aspect is that compounds or synthetic precursors with high added value can be obtained.
Thus, starting from dichloropropyl esters, allyl esters can be obtained, some of them with ovicidal effects. These esters can be synthesised using glycerol and either chlorotrimetylsilane or aluminium chloride as chlorine source. In the later case an ionic liquid is needed. A versatic dichloropropyl ester has been the reference to prepare desymmetrized esters using iodine, hydroxy ion or imidazole derivatives as nucleophilic groups.
With the aim to develop sustainable reactions, industrial byproducts from the vegetable oil and fat industries, and from the biodiesel industries have been used as reagents.
New technologies, such as ionic liquids and microwaves have also been applied. A continuous process using a microreactor has been developed, which could allow the corresponding reaction to be scaled.
González, Búrdalo Lidia. "Copolimerització de DGEBA amb Àcid de Meldrum i Derivats." Doctoral thesis, Universitat Rovira i Virgili, 2008. http://hdl.handle.net/10803/9029.
Повний текст джерелаLa contracció de la xarxa polimèrica durant el procés de curat produeix tensions mecàniques internes i conseqüentment pot conduir a l'aparició d'esquerdes. Els espiroortoesters (SOEs) són monòmers considerats expansibles, que experimenten expansió durant el procés de polimerització. La síntesi dels SOEs es pot portar a terme per reacció d'epòxids amb lactones en presència d'un catalitzador àcid de Lewis. L'expansió en volum d'aquests monòmers es deguda a que en la polimerització per obertura d'anell es produeix un canvi de distancies covalents en la forma cíclica a distancies de Van der Waals en la forma oberta. La copolimerització de reïnes epoxi amb lactones en presència d'un àcid de Lewis porta a la formació "in situ" d'espiroortoesters. Un cop formats, polimeritzen i donen lloc a unitats de poli(èter-ester) a la xarxa tridimensional. Al polimeritzar generen expansió en l'última etapa del curat, precisament quan el material no té mobilitat, evitant així l'aparició de tensions internes.
D'altra banda, l'estructura típica d'un termoestable implica que aquests materials, una vegada aplicats sobre un component electrònic, no poden ser eliminats ni mitjançant dissolvents ni per escalfament. La introducció de grups ester a la xarxa, especialment si son terciaris, permet disminuir la temperatura de degradació tèrmica en comparació a la dels materials epoxídics convencionals. Sotmesos els materials a un procés tèrmic, la xarxa termoestable sofreix una degradació parcial. Aquesta és suficient perquè es puguin eliminar per dissolució o mitjançant fricció mecànica. Així, el material electrònic pot ésser reparat o reciclat.
Finalment, la introducció de restes alifàtiques a la xarxa termoestable redueix la densitat d'entrecreuament i amb ella la fragilitat dels materials, fent-los més flexibles.
S'ha utilitzat una reïna comercial, el diglicidil èter del bisfenol A (DGEBA). Com a lactones el 2,2-dimetil-4,6-dioxo-1,3-dioxà o àcid de Meldrum (MA) i tres dels seus derivats amb la posició 5 disubstituïda. L'estructura d'aquests compostos permet introduir grups ester terciaris i cadenes alifàtiques a la xarxa epoxídica.
S'ha sintetitzat una nova reïna epoxi: la 5,5-bis(2,3-epoxipropil)-2,2-dimetil-4,6-dioxo-1,3-dioxà (DGMA), on es conjuga en un mateix compost l'anell de bislactona i els grups glicidílics. Aquesta reïna s'ha homopolimeritzat i copolimeritzat amb la reïna epoxi de diglicidil èter de bisfenol A.
Com a àcids de Lewis s'han estudiat els triflats de terres rares. Aquests permeten dur a terme el curat en condicions atmosfèriques. Els materials obtinguts amb els triflats de terres rares s'han comparat amb els obtinguts amb trifluorur de bor complexat, que és un iniciador catiònic convencional.
A més, s'han obtingut materials a partir dels mateixos monòmers utilitzant un iniciador aniònic. En aquest cas, el mecanisme de curat no implica la generació de grups espiroortoester, però igualment porta a xarxes amb estructura de poli(èter-ester).
Les etapes seguides en el present treball són:
1. Síntesi i caracterització estructural dels derivats de l'àcid de Meldrum.
2. Estudi del mecanisme de les reaccions de copolimerització catiònica i aniònica de la reïna epoxi amb l'àcid de Meldrum i derivats emprant els triflats de lantànid i el BF3·MEA i la DMAP, mitjançant calorimetria i FTIR/ATR.
3. S'ha estudiat la cinètica dels processos de curat per calorimetria.
4. Caracterització estructural dels diferents materials obtinguts.
5. Avaluació de les propietats tèrmiques i mecàniques dels materials i del grau de contracció que experimenten en curar.
6. Estudi dels processos de degradació dels materials termoestables obtinguts, així com les condicions que es produeix.
De l'estudi realitzat s'ha pogut concloure que s'ha assolit una reducció global de l'encongiment al curar, s'han obtingut materials que inicien la degradació a temperatures inferiors a les de les reïnes epoxi convencionals i que van resultar ser més flexibles.
ENGLISH
Thermosetting polymers are interesting materials widely versatilities in the electronics industry because of their good characteristics. The present work is included in this field and it is focused in obtaining new epoxydic thermosets that may be useful as coatings for electronic devices. The objectives posed in this work were to obtain materials that: 1) undergo low shrinkage during curing process, 2) allow to be thermally degraded in a controlled way once their service life is over and 3) improve the mechanical properties with respect to the conventional epoxy materials.
The shrinkage of the polymeric network during curing process produces internal mechanical stress and consequently it can lead to the appearance of microvoids and microcracks. Spiroorthoesters (SOEs) are considered to be expandable monomers, which experience expansion during polymerization process. SOEs can be synthesized by reaction of epoxides with lactones in the presence of a Lewis acid as catalyst. The expansion in volume of these monomers is due to the ring-opening polymerization process. It produces a change in atomic distances from the cyclic form (covalent distance) to the open one (Van der Waals distance). The copolymerization of epoxy resins with lactones in the presence of a Lewis acid leads to "in situ" formation of spiroorthoesters. Once it is formed, it polymerizes yielding poly(ether-ester) unities into the three-dimensional network. On polymerizing expansion is produced, just when the material has no mobility and therefore avoiding internal stress.
The typical structure of a thermoset implies that once it is applied over an electronic device neither solvents nor heat can remove it. The introduction of ester groups into the network, especially if are tertiary, allows diminishing the temperature of thermal degradation in comparison to that of conventional epoxy materials. When these new materials are subjected to a thermal process, the thermoset network undergoes a partial degradation. This is enough to remove it by dissolution or mechanical friction. Therefore, the electronic device can be repaired or recycled.
Finally, the introduction of aliphatic moieties into the thermoset network reduces the cross-linking density and the fragility of materials, giving more flexibility to the material.
In the present work, a commercial epoxy resin, diglycidyl ether of bisphenol A (DGEBA) was used. As lactones 2,2-dimethyl-4,6-dioxo-1,3-dioxane or Meldrum acid (MA) and three of its derivatives with the five position disubstituted. The structure of these compounds allows incorporating tertiary ester groups and aliphatic chains into the epoxydic network.
A new epoxy resin was synthesized: 5,5-bis(diglycidyl)-2,2-dimethyl-4,6-dioxo-1,3-dioxane (DGMA), which present both a bislactone ring and glicydilyc groups. This resin was homopolymerized and copolymerized with the epoxy resin of diglycidyl ether of bisphenol A.
As Lewis acids triflates of rare earths were studied. These allow curing in atmospheric conditions. The materials obtained with triflates of rare earths were compared to the materials obtained with boron trifluoride complex, which is a conventional cationic initiator.
Furthermore, materials from the same monomers were obtained by using an anionic initiator. In this case, the curing mechanism does not imply the generation of spiroorthoester groups, but equally it leads to networks with a poly (ether-ester) structure.
The followed steps in the present work are:
1. Synthesis and structural characterization of Meldrum acid derivatives.
2. Study of the mechanism of cationic and anionic copolymerization reactions of the epoxy resin with Meldrum acid and its derivatives using lanthanide triflats, BF3·MEA and DMAP, by differential scanning calorimetry and FTIR-ATR.
3. The kinetics of the curing process was studied by differential scanning calorimetry.
4. Structural characterization of the materials obtained.
5. Evaluation of the thermal and mechanical properties of materials and the degree of shrinkage experimented in the curing.
6. Study of the degradation process of thermosetting materials obtained and the conditions in which it is produced.
From the study carried out it can be concluded that a global reduction in the shrinkage on curing was achieved. Also, materials that start the degradation at lower temperatures than conventional epoxy resins were obtained. These materials come to be more flexible
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數學系
90
1. On certain subrings of prime rings with derivations Let R be a noncommutative prime ring with nonzero derivation d. U is a noncentral Lie ideal of R and U^{d} is not contained in Z. If d is outer, then the subring of R generated by {[d(x),x] ;x belong to U} contains a nonzero ideal of R except charR=2 and R satisfies S_{4}. 2. Jordan generalized derivations on semiprime rings Let R be a 2-torson free semiprime ring, then every Jordan generalized derivation on R is a generalized derivation.
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