台灣自第一階段農地改革後，逐漸有為降低生產成本與提高農民收入之大規模策略出現。本研究定義出台灣歷經包括農業生產專業區、農地利用綜合規劃之共同經營班與其後之產銷班、稻米產銷專業區與農業經營專區等四種大規模策略之農地集團化利用階段，是在公共秩序之法規命令，與集團成員契約簽訂所建立之私人秩序下而得以成立運作，符合混合式治理的特徵；而此治理理念的應用，可以新制度經濟學中微觀的角度，對組成各階段公共秩序和私人秩序的規則和執行機制，進行治理結構之比較分析。此係分別展現公共秩序與私人秩序規則中，誘因和安全措施是如何的賦予，與集團運作時是藉由第三者執行或自我執行之執行機制，以分析各農地集團化利用階段所採行的混合式治理，其治理結構如何具有階層與市場屬性程度的差異，進而探討所呈現的變遷趨勢，供政府對農地集團化利用輔導之策略擬定，與營運主體設計契約化私人秩序時之參考。研究發現在市場越來越競爭之下，台灣各農地集團化利用階段之治理結構，不僅於規則中誘因的提供與安全措施的設置朝向由私人秩序賦予，更從集團之規劃召集、與集團成員行動的裁決等，都趨向依私人秩序訂定條款，由集團成員自我執行。故政府對農業經營的混合治理，在逐漸有由營運主體自發地根據公共秩序組織集團，擬定私人秩序自我執行運作的趨勢下，建議可增強公共秩序需對私人秩序治理結構之支持，並於公共秩序執行排除考量給予改善之機會，讓農地集團化利用更具競爭力與建立永續發展的空間。 / In Taiwan, after the first farmland reform, an integrated strategy has been adopted to pursue lower production cost and higher agricultural profit. This study defines four stages of integrated farmland use in Taiwan, i.e. Agricultural Production Special District, Agriculture Production Section and Production Group, Rice Production Special District, and Special Agriculture Enterprise District. Those stages of integrated farmland use have characteristics of hybrid governance which are established under laws i.e. public ordering and contracts among members of groups i.e. private ordering. The idea of hybrid governance, derived from the New Institutional Economics, is a micro-analytic point of view and can be employed to conduct a comparative study on governance structures. The governance structures, namely the rules and the enforcement mechanism in the public and private ordering of every stage, are analyzed and compared. How incentives and security measures are adopted in the rules and whether third party enforcement or self-enforcement is used in the enforcement mechanism of the public and private ordering are provided. After the analysis of hybrid governance structures, differences on their hierarchy and market orientation will be revealed. In Taiwan the governance structures of integrated farmland use has a tendency of market orientation and private ordering. The result can be considered by the government in deciding the policies for integrated farmland use, and can help the operating group to formulate private contracts for their own private ordering.

The hole-doped perovskite manganese oxide such as Ln1-xAxMnO3 (Ln = La, Nd, Pr, and A = Ca, Sr, Ba, Pb) is one of the most studied topics in the recent years due to the observation of colossal magnetoresistance (CMR). Basically, LaMnO3 has an almost insulating behavior and on antiferromagnetic arrangement. By substituting a divalent cation (A2+) in place of La3+, LaMnO3 can be driven into metallic and ferromagnetic state. Mixed valence of Mn 3+ / Mn4+ is needed for both metallic behavior and ferromagnetism in these materials. The CMR characteristic occurs in the ferromagnetic state. A systematic investigation of the structural, magnetic and electrical properties in the perovskite colossal magnetoresistance materials La0.7-xLnxPb0.3Mn1-yMeyO3 (Ln=Pr, Nd and Y, Me=Fe and Co) has presented in this thesis. By subatituting Nd, Pr, Y for the La and Co, Fe for the Mn, the substitution effects on the crystallographic deformation, magnetotransport behavior and electrical properties in these compounds have been studied. According to the results of this research, crystallographic distortion is induced by the substitution of smaller ions, Pr or Nd, onto the La-site. Powder $x$-ray diffraction patterns show a crystallographic transition from rhombohedral symmetry (R-3c) to orthorhombic (Pbnm) crystal structure as the doping content is increased. The increase of deformation from R-3c to Pbnm decreases the bond angle of Mn3+¡ÐO2-¡ÐMn4+ , increases the cant of Mn spin, weakens the double-exchange interaction and results in decrease of ferromagnetism, low ferromagnetic transition temperature Tc, eg electron bandwidth and conductivity. However, the great quantity of decrease in resistivity by an external field leads to the increase in the magnetoresistance ratio. We also find that the increase of saturation magnetization results from the contribution of magnetic ion of Pr or Nd. In addition. in contrast to substitution La by magnetic ion of Pr and Nd, the saturation magnetization is decreased as Y content is increased. The zero-field-cool (ZFC) and field-cool (FC) magnetic measurements indicate that the range of spin ordering for Y one is shorter than Pr one or Nd one with the same doping content. It is because of the small ionic radius of Y, which results in larger distortion, increases the bond angle of Mn3+¡ÐO2-¡ÐMn4+, and corresponds low ferromagnetic transition temperature. The distortion induced by Mn-site substitution is not obvious due to the similar radius of Mn, Co and Fe. Powder x-ray diffraction patterns show a single phase of rhombohedral symmetry (R-3c) for Co doped ststem and a slight crystallographic transition from rhombohedral (R-3c) to orthorhombic (Pbnm) symmetry for Fe doped system. Values of temperature dependence of magnetization indicate that the ferromagnetic double-exchange interaction is gradually substituted by the superexchange interaction. The ZFC-FC curves also indicate that long-range spin ordering is progressively substituted by the short-range spin ordering. The substitution of Mn by Co and Fe supresses the double-exchange interaction, decreases the ferromagnetism and the ferromagnetic transition temperature. Due to the synthesis of the substitution of Nd, Pr, Y for La and Co, Fe for Mn, the mechanism of substitution effects are proved different. The substitution of Nd, Pr and Y for La distorts the crystal, decreases the Mn3+¡ÐO2-¡ÐMn4+ bond angle, and results in the transition of properties, while the substitution of Co and Fe for Mn decrease the percentage of ferromagnetic Mn3+¡ÐO2-¡ÐMn4+. The purpose of this thesis is to clear up the role functions of all elements in these compounds and properties of these compounds. Based on the knowledge of these compounds, it would be helpful to control the physical mechanism and improve the characteristics on preparing their thin film devices.

The study of bulk and nanoparticles of perovskite rare earth manganites has been an extensive area of research in the recent past due to their rich and interesting physics and potential applications [1-5]. Manganites have potential applications in the emerging field of spintronics because of their colossal magnetoresistance (CMR) [6] and half-metallic [7] properties. Nano sized materials exhibit enhanced and different electronic and magnetic properties and expected to behave quite differently compared to their bulk counterparts due to quantum confinement effects and high surface/volume ratio. Magnetic nanoparticles in particular have great potential for use in a wide range of applications including magnetic recording media, various sensors, catalysts, magnetic refrigeration, medicine etc. In this thesis we study changes in the magnetic ordering of certain bismuth based manganites Bi1-xAxMnO3 (A = Ca and Sr) using various experimental probes when we reduce their particle size to nano scale. The general formula for doped manganites is R1-xAxMnO3 where R is a trivalent rare-earth ion such as La, Nd, Pr, Sm and A is a divalent alkaline earth ion such as Ca, Sr, Ba, Pb. They became interesting due to their many intriguing properties like CMR (Colossal Magnetoresistance), phase separation, charge ordering (CO), orbital ordering (OO) and many more. These properties depend sensitively on many factors like temperature, magnetic field, pressure and doping concentration x. There is a strong coupling of spin, orbital and lattice to each other in manganites. The complex interplay of all these couplings make them strongly correlated systems. In the parent compound RMnO3 Mn ion is in Mn3+ state while it is present as Mn4+ in the compound AMnO3. The manganites with x = 0 and x = 1 are both antiferromagnetic insulators, magnetism in them being mediated by superexchange through oxygen. On doping with a divalent alkaline earth ion in RMnO3, there is a transition The properties of nanoparticles of manganites show strong surface effects. The magnetic behavior is strongly governed by the free surface spins in nanoparticles. And as the size reduces, there is suppression of charge ordering which can also disappear in very small particles [11]. Antiferromagnetism in bulk gives way to ferromagnetism in nanoparticles [12-14]. In the following we give a chapter wise summary of the results reported in the thesis. Chapter 1: This chapter of the thesis consists of a brief introduction to the physics of manganites. Further we have written a detailed overview of bismuth based manganites, properties of nano manganites and the technique of EPR. There is a section about different line shapes observed in EPR of manganites, their origin and how to fit them to appropriate lineshape function [15]. This chapter also includes a detailed account of experimental methodologies used in thesis which are: EPR spectrometer, SQUID magnetometer, X-ray diffractometer and TEM and the analysis procedure adopted in this work. Chapter 2: This chapter deals with the magnetic and EPR studies of nanoparticles (average diameter ~ 30 nm) of Bi0.25Ca0.75MnO3 (BCMO) and their comparison with the results on bulk BCMO. Bulk Bi0.25Ca0.75MnO3 (BCMOB) shows charge ordering at 230 K followed by a transition to an antiferromagnetic phase at 130 K [16]. The bulk and the nanoparticles (D ~ 30 nm) of Bi0.25Ca0.75MnO3 were prepared by solid-state reaction method and sol-gel method respectively. The two samples were investigated by using XRD, TEM, SQUID and EPR techniques. Our magnetization and EPR results show that the charge ordering disappears in nanoparticles of this composition and there emerges a ferromagnetic phase similarly to the rare earth manganites. The nanoparticles of the rare earth based manganites are found to consist of an antiferromagnetic core and a ferromagnetic shell/surface region [3, 17] and thus are expected to exhibit the ‘exchange bias (EB) effect’ [18-22] resulting in a shift of the magnetic hysteresis loop. Indeed many nanomanganites do show EB effect. However, contrary to this expectation, we find that in BCMON samples the EB effect is absent. Chapter 3: In this chapter, we report the results of temperature dependent magnetization and electron paramagnetic resonance studies on bulk and nanoparticles of electron (x = 0. 6, BCE) and hole (x = 0.4, BCH) doped Bi1-xCaxMnO3 (BCMO) and the effect of the size reduction on the electron-hole asymmetry observed in the bulk sample. Bulk sample of Bi0.4Ca0.6MnO3is a paramagnetic insulator at room temperature with Tco = 330 K and TN ~ 120 K while BiCaMnO3 undergoes a charge ordering transition at TCO = 315 K with TN ~ 150 K [16]. All the four samples were investigated by using XRD, TEM, SQUID and EPR techniques. It is shown that antiferromagnetism and charge order persist in the hole doped nano sample while ferromagnetism has emerged in the electron doped nano sample. Our magnetization and EPR results show that spin glass phase exists in bulk BCE, bulk BCH and nano BCE whereas no sign of either spin glass state or ferromagnetism is seen in nano BCH. We have shown that electron-hole asymmetry in terms of ‘g’ parameter has reduced in the nanoparticles but it has not completely disappeared in contrast with the results on Pr1-xCaxMnO3 [23]. We understand these interesting results in terms of the presence of the highly polarizable 6s2 lone pair electrons on bismuth which is known to cause many interesting departures from the behavior of rare earth manganites. We study the temperature dependence of the linewidth behavior by fitting it to the different models [24¬27] and find that Shengelaya’s model [25, 26] fits well to all the four samples describing the spin dynamics satisfactorily in the present samples. Chapter 4: In this chapter, we present the fabrication, characterization and the results obtained from the magnetization and EPR measurements carried out on bulk and nanoparticles of Bi0.1Ca0.9MnO3. We prepared the nanoparticles of BCMO by standard sol¬gel technique and bulk samples by solid state reaction method. We investigated magnetic ordering by doing temperature dependent magnetic and EPR studies on both the samples and compared the properties with each other. Bulk Bi0.1Ca0.9MnO3 (BCMB) shows mixed phase of antiferromagnetism and ferromagnetism without any charge ordered state. Our results show that the ferromagnetism exists in the bulk BCMO which is present in the nano sample as well but with somewhat weakened strength with the size reduction. The nanoparticles of the rare earth based manganites are found to consist of an antiferromagnetic core and a ferromagnetic shell/surface region and thus are expected to exhibit the more uncompensated spins on the surface which reduce the magnetization in the nanoparticles. We calculated activation energy for the two samples by fitting the intensity behavior to the Arrhenius equation [28]. Activation energy was found to decrease for nano BCMO which indicates the weaker intracluster double-exchange interaction in it. Chapter 5: This chapter deals with the comparative study of the temperature dependent magnetic properties and EPR parameters of nano and bulk samples of Bi0.2Sr0.8MnO3 (BSMO). Nanoparticles and bulk sample of BSMO were prepared by sol-gel technique and solid state reaction method respectively. Bulk BSMO has high antiferromagnetic transition temperature TN ~ 260 K and robust charge ordering (TCO ~ 360 K) [29]. We confirm that the bulk sample shows an antiferromagnetic transition around ~ 260 K and a spin-glass transition ~ 40 K. For nano sample we see a clear ferromagnetic transition at around ~ 120 K. We conclude that mixed magnetic state exists in the bulk sample whereas it is suppressed in the nano sample and strong ferromagnetism is induced instead. Chapter 6: This chapter summarizes the main conclusions of the thesis, also pointing out some future directions for research in the field.

The optimum ordering strategies for the coded V-BLAST system with capacity achieving temporal codes on each stream are studied in this thesis. Mathematical representations of the optimum detection ordering strategies for the coded V-BLAST under instantaneous rate allocation (IRA), uniform power/rate allocation (URA), instantaneous power allocation(IPA) and instantaneous power/rate allocation (IPRA) are derived. For two transmit antennas, it is shown that the optimum detection strategies are based on the per-stream before-processing channel gains. Based on approximations of the per-stream capacity equation, closed-form expressions of the optimal ordering strategy under the IRA at low and high signal to noise ratio (SNR) are derived. Necessary optimality conditions under the IRA are given. Thresholds for the low, intermediate and high SNR regimes in the 2-Tx-antenna system under the IPRA are determined, and the SNR gain of the ordering is studied for each regime. Performances of simple suboptimal ordering strategies are analysed, some of which perform very close to the optimum one.

In the presented work we define non-commutative Gröbner bases including the necessary basis of non- commutative algebra theory and notion admissible ordering. We present non-commutative variant of the Buchberger algorithm and study how the algorithm can be improved. Analogous to the Gebauer-Möller criteria lead us to detect almost all unnecessary obstructions in the non-commutative case. The obstructions are graphically ilustrated. The Buchberger algorithm can be improved within redundant polynomials. This work is a summary and its specification of the results of some known authors engaged in this field. Presented definitions are ilustrated on examples. We perform proves of some of the statements which have been proven differently by other authors. Powered by TCPDF (www.tcpdf.org)

La spectroscopie est un outil primordial pour le diagnostic des plasmas, qu'il s'agisse de ceux des étoiles, permettant d'espérer comprendre toujours mieux leurs formations et leurs évolutions, ou celui des laboratoires, tout spécialement ceux rencontrés dans le cadre des expérimentations visant la fusion thermonucléaire contrôlée, telles que le projet ITER.La modélisation des profils de raie Lyman-alpha de l'hydrogène conduit à élaborer différentes approches dont le formalisme mérite d'être toujours investigué, et possiblement enrichi, en vue d'améliorer nos capacités de diagnostic. Nous avons donc successivement exploré une approche par intégrale de chemin, en vue de conserver au maximum l'information liée à la nature quantique des processus d'interaction, puis le rôle de la chronologie, le potentiel d'interaction du système atomique avec le plasma ne commutant pas à deux instants différents, et enfin une approche modélisant le champ électrique par des processus stochastiques dont les propriétés statistiques déterminent les caractéristiques des profils de raie des plasmas étudiés. Dans ce dernier cas, le travail réalisé montre que la modélisation du champ électrique par des processus stochastiques contient de sérieuses pistes de recherche de nature à améliorer encore les résultats obtenus. / Spectroscopy is an essential tool for plasma diagnostics, especially for studying stars, allowing hope to understand always better their origin and their evolution, or for laboratory plasmas, especially those encountered in the experiments for controlled thermonuclear fusion, such as ITER.Modeling profiles of Lyman-alpha hydrogen leads to develop different approaches whose formalism deserves to still remain under investigation, and can possibly be enriched, to improve our diagnostic capabilities. We therefore explored the subject successively by a path integral approach, in order to retain maximum information related to the quantum nature of the interaction process, then the role of chronology, as the interaction potential of the atomic system with the plasma does not commute at two different times, and finally we worked on an approach modeling the electric field by stochastic processes whose statistical properties determine the characteristics of the line profiles of the studied plasmas. In the latter case, the work shows that the modeling of the electric field by stochastic processes contains serious research possibilities which should be able to further improve present results.

Cette thèse est consacrée à l'étude de deux systèmes, à la fois proches et différents par leur comportement : Co-Pt, système emblématique de l'ordre chimique, et Pt-Ag, système hybride présentant à la fois un ordre chimique et une tendance à la démixtion, ainsi qu'une forte tendance à la ségrégation. Afin de répondre à ces diverses questions, nous adoptons une approche semi-empirique à travers un potentiel à $N$-corps, permettant les relaxations atomiques, dans l'approximation du second moment de la densité d'états (SMA), couplé à des simulations Monte Carlo dans différents ensembles. Des agrégats de différentes tailles (allant de 1000 à 10000 atomes) et de différentes morphologies (octaèdre tronqué, décaèdre, ou icosaèdre) sont analysés en terme de composition chimique sur les différents sites inéquivalents (sommet, arête, facettes (100) et (111) et coeur) puis comparés aux systèmes de référence (surfaces, volume) sur toute la gamme de concentration. Pour le système Co-Pt, nous observons des structures ordonnées similaires à celles du volume pour le coeur et similaires à celles des surfaces pour les facettes. L'impact de la phase bidimensionnelle (√3×√3)R30◦ propre à la surface, est d'autant plus important sur l'ordre chimique au coeur que la nanoparticule est de petite taille. Pour le système Pt-Ag, nous observons une importante ségrégation de l'Ag en surface, ainsi qu'un enrichissement de Pt en sous-surface, et la stabilisation de la phase ordonnée L1$_{1}$ au coeur. Cette structure peut apparaître en un seul variant ou bien en adoptant tous les variants possibles, conduisant ainsi à une structure en pelures d'oignon. / Due to the correlation between atomic arrangement and physical properties, ordered nanoalloys are particularly interesting in the field of catalysis, magnetism, or optics. By reducing the system size, from alloy to nanoalloy, a lot of questions arise: Is chemical ordering conserved? What is the morphology of nanoalloys? What is the properties evolution as a size function? Is there a coupling between segregation and core ordering? This thesis is dedicated to two systems: Co-Pt, a typical example of ordering and Pt-Ag, hybrid system between ordering and demixion. To answer these questions, we performed Monte Carlo simulations in different ensembles with semi-empirical many-body potential within the Second Moment Approximation (SMA) of the density of states which allows atomic relaxations. Nanoparticles of different sizes (from 1000 to 10000 atoms) and shapes (truncated octahedra, decahedra, or icosahedra) are analyzed considering chemical composition on each site (vertex, edge, (111) and (100) facets and core) and compared to reference systems (surfaces and bulk) on the whole range of composition. For Co-Pt, we get ordered structures similar to the bulk ones and similar to surfaces for facets. The bidimensional phase (√3×√3)R30◦, purely due to surface effect, impacts core ordering, even more for small clusters. For Pt-Ag, we get a strong Ag segregation on surface coupled with a Pt sub-surface enrichment, and a stable L1$_{1}$ phase in the core. This ordered structure may appear with a single variant or with multiple variants, leading to an onion-like structure.

Este trabalho analisa o processo de ordenamento fiscal que ocorreu no Brasil, na década de 1990, abordando especificamente o processo de criação da Lei de Responsabilidade Fiscal (LRF). Alguns autores na Ciência Política argumentam que os projetos de lei votados no Congresso que afetam os interesses dos governadores não passam porque os governadores mobilizam suas respectivas bancadas estaduais para vetá-los. Assim, como podemos entender a aprovação da Lei de Responsabilidade Fiscal, lei complementar que afeta diretamente os interesses financeiros e fiscais dos entes federativos. Alguns autores argumentam que houve um consenso em torno da necessidade do ordenamento fiscal, na década de 1990, destacando o processo de incrementalismo das mudanças institucionais, o desenvolvimento de uma \"cultura fiscalista\"que vira consenso na opinião pública e na classe política e, as crises financeiras internacionais (México, 1995; Ásia, 1997 e Rússia, 1998) que colocaram em xeque a capacidade de reação do governo diante das ameaças à política econômica de estabilização. Este trabalho alinha-se com os que desenvolvem esses argumentos, mas enfatiza o processo de negociação, ou seja, a existência de um dissenso dentro do consenso, que caracterizou o processo de criação da LRF. Argumentamos que, a despeito da existência de um consenso em torno da idéia de promover um ordenamento fiscal, a criação e a aprovação da LRF caracterizaram-se por conflitos dentro do governo e por um processo de intensa negociação parlamentar. / The aim of this work is to investigate the Brazilian process of fiscal ordering in the 1990s. More specifically, it focuses on the creation process of Fiscal Responsibility Law. Its point of departure is some political scientists vision that legislative projects undermining the subnational governments interests are not often approved due to State governors efforts to veto them. The hypothesis is that this phenomenon happens because governors exert stronger influence on the behavior of legislators than the President and political parties. For this reason, they assume that governors are veto-players in the Brazilian political system. This is an important component of our research strategy that seeks to explain why Fiscal Responsibility Law was approved despite of the key players financial and fiscal interests. The novelty of this work is to provide an approach that unveils a little explored explanatory element by previous works: the process of negotiation of the law project in the Federal Executive and in the Federal Legislative. In tune with some authors claims that there was a consensus on the necessity of fiscal ordering, we scrutinize the incremental process of institutional change and the development of a \"fiscal culture\" in the Brazilian society and its political class. We go on to suggest that international financial international crisis (México, 1995; Ásia, 1997 e Rússia, 1998) served as tests of the government\'s capacity to deal with the challenges posed to the economic stabilization policies. Furthermore, the current work gives special attention to addressing the process of negotiation that gave rise to the Fiscal Responsibility Law. We argue that the whole process was characterized by the existence of a dissension inside of consensus. Putting somewhat different, conflicts in the Federal Executive realm and complex negotiation schemes at the Federal Legislative level characterize the creation and the approbation stages of Fiscal Responsibility Law in Brazil.

Made available in DSpace on 2016-08-10T10:40:21Z (GMT). No. of bitstreams: 1 Arineia Nogueira de Assis.pdf: 693374 bytes, checksum: dad2ec792a9f740945465bdeeb7830db (MD5) Previous issue date: 2014-02-27 / The first objective of this study is to classify the production planning and control (PPC) strategy and the ordering system (OS) of a clothing company, and the second is to propose a theoretical model based on PPC strategies and production sequencing for consequent practical implementation in industries with repetitive production system and multiple products. A study case was conducted, identifying reduction and qualification in inventory, increasing productivity as results. / O primeiro objetivo deste trabalho é classificar a estratégia de planejamento e controle de produção (PCP) e o sistema de coordenação de ordens (SCO) de uma indústria de confecção. E, o segundo, é propor um modelo teórico baseado em estratégias de PCP e sequenciamento de produção, para sua consequente implantação prática em indústrias com sistema de produção repetitivo e com múltiplos produtos. Realizou-se um estudo de caso e apresentou-se os resultados, identificando redução e qualificação de estoque, e aumento da produtividade.

Este trabalho tem como objetivo buscar subsídios na concepção de polissemia da Semântica Cognitiva para auxiliar na disposição das acepções de itens lexicais polissêmicos em learner’s dictionaries. Para tanto, ele, inicialmente, analisa de que forma os quatro principais dicionários que compreendem esse genótipo – CALD (2008), COBUILD (2006), LDCE (2009) e OALD (2005) – apresentam suas acepções, considerando duas variáveis: (i) o emprego de uma solução homonímica ou polissêmica para a estruturação dos verbetes e (ii) a divisão e ordenação das acepções. A partir das análises, percebe-se que a solução empregada por essas obras varia, havendo a adoção tanto da solução polissêmica, com e sem divisão interna nos verbetes, quanto da solução homonímica, por critério morfológico e semântico. Quanto às acepções, por um lado, as formas como os dicionários dividem e relacionam os significados são diferentes e, por outro, os critérios utilizados pelas obras para a ordenação das acepções não se mostram plenamente satisfatórios, pois algumas delas não explicitam quais critérios são empregados na ordenação das acepções e a utilização do mesmo critério (de frequência) por diferentes obras gera resultados distintos. Além disso, para que a frequência pudesse ser empregada como critério objetivo, seria necessária a delimitação de parâmetros quantitativos ainda não disponíveis. A seguir, são levantadas questões teórico-metodológicas que surgem ao abordar a organização microestrutural, destacando que a discussão da ordenação das acepções nos dicionários é dependente de outras variáveis, como sua vinculação a uma teoria do significado lexical e da definição lexicográfica. Por fim, o trabalho busca delimitar quais das características da visão prototípica de estrutura lexical podem ser transpostas ao âmbito lexicográfico para lidar com o problema da representação da polissemia nos learner’s dictionaries.Apresentam-se propostas de verbetes criados com base em critérios estabelecidos por nós para a transposição das noções semântico-cognitivas para a ordenação das acepções. / In this thesis, we aim at contributing to sense ordering of polysemous lexical items in learner‘s dictionaries based on the conception of polysemy as developed by Cognitive Semantics. First we analyze in which way the four main dictionaries known under the label of learner‘s dictionary present their senses – CALD (2008), COBUILD (2006), LDCE (2009) e OALD (2005). We consider two variables in this analysis: (i) the use of a homonymic or a polysemous solution for structuring the entry and (ii) the sense division and ordering. From the analysis, we find out that the solutions applied in the dictionaries vary, for they adopt both a polysemous solution, with and without a division within the entry, and a homonymic solution, through morphological and semantic criteria. Regarding the senses, on the one hand, the way the dictionaries split and relate them is different. On the other hand, the criteria used in the dictionaries for ordering senses showed to be unsatisfactory, because some of the works do not explicit which criteria they apply in sense ordering, and because the use of the same criterion (frequency) in different dictionaries yields distinct results. Moreover, in order to use frequency as an objective criterion, the definition of quantitative parameters, which are still not available, would be made necessary. Hereafter, we discuss theoretical-methodological issues raised when it comes to sense ordering: this microstructural organization is dependent upon other variables, such as its relation to a theory of word meaning and a theory of lexicographical definition. At the end of this work, we present the characteristics of the prototypical conception of lexical structure that could be applied to lexicography to deal with the problem of representing polysemy in learner‘s dictionaries. We, then, propose some entries developed according to criteria we established in order to use cognitive semantic notions in sense arrangement.