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La politique monétaire dans les modèles économétriques : primat de la théorie sur l'empirie / The monetary policy in econometric models : primacy of the theory over the empiricsAttioui, Abdelali 04 December 2014 (has links)
En s'appuyant sur les limites de l'économétrie mises en évidence dans les débats sur la politique monétaire depuis les années 1960, cette thèse s'attache à montrer le primat de la théorie sur l'empirie et que l'économétrie ne peut pas être décisive dans la remise en cause de la théorie. Nous adoptons une démarche basée sur des arguments épistémologiques pour montrer que ces débat dépassent le clivage théorie/empirie et intègrent une différence de vision quant à l'utilité d'un modèle empirique. Le programme de recherche de la Commission Cowles s'est constitué autour d'une articulation particulière de trois éléments fondamentaux. Un référentiel théorique issu de la Théorie Générale de Keynes, un modèle formel s'appuyant sur le relatif consensus autour du schéma IS-LM et des techniques économétriques pour estimer les paramètres de ce modèle. C'est la nature et le degré d'interdépendance entre les trois éléments ci-dessus qui sont remis en cause par les monétaristes et les tenants de la modélisation VAR. Alors que les keynésiens établissent une nette distinction entre le modèle théorique et le modèle estimé, pour les monétaristes cette distinction n'est pas claire et ne leur semble pas pertinente. Sims (1980) reproche aux modèles structurels de la Commission Cowles de comporter trop d'hypothèses théoriques non testées empiriquement. Il propose de soumettre les hypothèses d'exogénéité à des tests économétriques directs et précis. Toutefois, l'indétermination empirique de la causalité dans un modèle VAR, liée au problème de l'équivalence observationnelle (Basmann, 1965), impose l'adoption d'un schéma d'identification sur la base d'a priori théorique pour identifier les chocs de politique monétaire. Ceci constitue un cas extrême du problème de la sous-détermination de la théorie par les données soulevé par la thèse de Duhem-Quine (Duhem, 1906, Quine, 1951). De plus, Hoover (2009) note que l'analyse des réponses impulsionnelles dans un VAR fournit un bon exemple de ce que Cartwright (2007) qualifie de ‘'contrefactuel imposteur''. Le développement des Modèles à Correction d'Erreurs et des modèles VAR cointégrés a permis de renouveler l'analyse des propositions monétaristes. Toutefois, les liens entre les propositions de cointégration, les notions d'équilibre de long terme et de déséquilibre de court terme sont rarement interprétés dans le cadre d'un modèle théorique rigoureux et complètement spécifié. Pour Faust et Leeper (1994), l'identification d'un modèle par l'imposition de contraintes peut s'avérer non fructueuse lorsque la théorie économique n'établit pas de distinction claire entre les dynamiques de court et de long terme. Faust et Whiteman (1997) relèvent l'absence d'un critère d'arbitrage dans ces démarches en présence de conflit entre le principe théorique et l'ajustement aux données, sinon une subordination de la théorie à l'économétrie. Parallèlement au problème de l'identification, la critique de Lucas (1976) constitue la seconde critique fondamentale à laquelle se heurtent les modèles économétriques. Lucas (1980, 1986) adopte une nouvelle posture épistémologique en considérant le modèle théorique comme une ‘'fiction'' et non plus comme un ensemble de propositions sur le comportement d'une économie réelle. Il défend l'idée d'une explication du cycle en termes de discipline de l'équilibre (Lucas, 1977). Les modèles DSGE, qui constituant les modèles de base de la Nouvelle Synthèse, sont fortement influencés par la méthodologie lucasienne et s'inscrivent dans la continuité des modèles RBC (Taouil, 2011). Benati et Surico (2009) ont établi la supériorité des DSGE par rapport aux VAR structurels (SVAR). Cet échec des SVAR est la conséquence directe des restrictions inter-équations imposées par l'hypothèse des anticipations rationnelles, tel que cela a été initialement soulevé par la critique de Sargent (1979). / The purpose of this thesis is to show the primacy of the theory over the empirics and prove that econometrics cannot be decisive to question the theory. For this, we rely on the limits of econometrics highlighted in discussions of monetary policy since the 1960s. We adopt an approach based on epistemological arguments to show that these debates go beyond the cleavage theory/empirics and that they integrate a difference of vision as to the usefulness of an empirical model. The research program of the Cowles Commission was formed around a particular articulation of three fundamental elements: a theoretical repository of Keynes' General Theory, a formal model based on the relative consensus on the IS-LM diagram and econometric techniques to estimate the parameters of this model. It is the nature and the degree of interdependence between these three elements that are contested by the monetarists and supporters of the VAR modeling. While Keynesians make a clear distinction between the theoretical model and the estimated model, this distinction is not clear and does not seem relevant to the monetarists. Sims (1980) criticizes the structural models of the Cowles Commission for including too many theoretical hypotheses empirically untested. He proposes to review the exogeneity assumptions through direct and specific econometric tests. However, the empirical indeterminacy of causality in a VAR, linked to the problem of observational equivalence (Basmann, 1965), requires the adoption of an identification scheme on the basis of a theoretical a priori to identify the monetary policy shocks. This is an extreme case of the problem of under-determination of theory by data raised by the Duhem-Quine thesis (Duhem 1906, Quine, 1951). Furthermore, Hoover (2009) notes that the impulse response analysis in a VAR provides a good example of what Cartwright (2007) calls “counterfactual impostor”. The development of the Error Correction Models and cointegrated VAR models has renewed the analysis of monetarist proposals. However, the links between the proposals for cointégration, the notions of long-term equilibrium and short term disequilibrium are rarely interpreted in the context of a rigorous and fully specified theoretical model. According to Faust and Leeper (1994), the identification of a model by imposing constraints may not be fruitful when economic theory does not clearly distinguish the short-term and long-term dynamics. Faust and Whiteman (1997) note the absence of an arbitration criterion in these approaches apparent in the presence of conflict between the theoretical principle and the adjustment to the data; otherwise subordination of the theory to the econometrics. Alongside the issue of identification, the Lucas critique (1976) is the second fundamental criticism facing the use of econometric models. Lucas (1980, 1986) adopts a new epistemological posture considering the theoretical model as a 'fiction' and not as a set of proposals on the behavior of a real economy. He supports the idea of explaining the cycle in terms of discipline of equilibrium (Lucas, 1977). The DSGE models, that constitute the fundamental models of the New Synthesis theory, are strongly influenced by Lucas' methodology and are a continuity of the RBC models (Taouil, 2011). Benati and Surico (2009) demonstrated the superiority of a DSGE model with respect to a structural VAR (SVAR). This failure is a direct consequence of inter-equation restrictions imposed by the rational expectations hypothesis, initially raised by Sargent's critics (1979).
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Renata Lucas e os espaços públicos : intrincamento e fissura / Renata Lucas and the public spaces : intricacy and fissureVálio, Luciana Benetti Marques, 1978- 02 June 2014 (has links)
Orientador: Maria José de Azevedo Marcondes / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Artes / Made available in DSpace on 2018-08-24T17:11:03Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014 / Resumo: Pretende-se na tese "Renata Lucas e os espaços públicos: intrincamento e fissura" discutir o conjunto dos trabalhos da artista que se configuram como instalações e intervenções no espaço, com ênfase nas intervenções nos espaços públicos. Parte-se das premissas de que tais trabalhos se instituem como um intrincamento específico com o lugar onde se inserem, e de suas configurações enquanto potencial político. Assim, o objeto da pesquisa decorre das relações que o trabalho artístico estabelece com o espaço, seja em sua fisicalidade ou em sua discursividade. A análise do conjunto dos trabalhos de Renata Lucas, produzidos entre 2001 e 2013, baseia-se em teorias de áreas diversas (filosofia, antropologia, história e, fundamentalmente, nas teorias do campo da arte). Por meio de leituras distintas, tenciona-se ressaltar na poética da artista: a percepção corporal do espectador/participante no espaço; a possibilidade de irromperem-se socialidades; a tentativa de criar uma fricção com o espaço por meio da alteração dos códigos representacionais pré-ordenados. Investigam-se as problematizações decorrentes da intervenção no espaço pré-ordenado, que possibilitem novas leituras e percepções. Procura-se defender, inclusive, o potencial político do trabalho de Renata Lucas como contido em estado de latência, no sentido de um potencial a ser desencadeado para o político, tanto pela produção de novos espaços, quanto pela subversão da ordem espacial preestabelecida, assim como pela constituição de uma esfera pública. Conclui-se que os trabalhos artísticos de Renata Lucas contêm muito do estranhamento, da incerteza, da fragmentação, da irrupção. Portanto, desvelar as camadas dos trabalhos da artista possibilita também desvelar camadas subjetivas, não aparentes, aflorar a emergência da "situação na qual estamos imersos". Inferiu-se, com isso, que o trabalho de Renata Lucas concretiza-se na oscilação entre o intrincamento e a fissura, o imiscuir-se e o friccionar / Abstract: The purpose of the thesis "Renata Lucas and the public spaces: intricacy and fissure" is to discuss the collection of the artist¿s works that configure as installations and interventions of space, with emphasis on interventions of the public space. It is assumed that such works consist of specific intricacy of the space with which they deal, and of their configurations as to their political potential. Thus, the objective of the study results from the relationship that the artistic work establishes with the space, whether in its physicalness or its discursiveness. The analysis of the collective works of Renata Lucas, produced between 2001 and 2013, is based on theories in diverse areas (philosophy, anthropology, history, and, fundamentally, on theories in the field of art). By means of distinct interpretations, the aime was to highlight the poetical aspects of the artist: the corporal perception of the spectator/participant in the space; the possibility of interrupting socialities; the attempt to create a friction with the space through the alteration of pre-organized representational codes. An investigation was conducted of the problematics resulting from the intervention in the pre-organized space that permit new interpretations and perceptions. An attempt was also made to defend the political potential of Renata Lucas¿ works as contained in the latent state, in the sense of a potential to be released in its political aspect, as much through the production of new spaces as to the subversion of pre-established spacial order, as well as for the constitution of a public sphere. It is concluded that the artistic works of Renata Lucas contain much of the surprise, the uncertainty, the fragmentation, the irruption. Therefore, uncover the layers of the artist¿s works enables us also to reveal subjective layers, not apparent, to treat the emergence of the "situation in which we are immersed". It is inferred, as such, that the work of Renata Lucas is concentrated on the oscillation between intricacy and fissure, intromission and friction / Doutorado / Artes Visuais / Doutora em Artes Visuais
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Novas identidades envolvendo os números de Fibonacci, Lucas e Jacobsthal via ladrilhamentos / New identities involving Fibonacci, Lucas and Jacobsthal numbers using tilingsSpreafico, Elen Viviani Pereira, 1986- 11 November 2014 (has links)
Orientador: José Plínio de Oliveira Santos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-26T02:14:38Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014 / Resumo: Neste trabalho, colaboramos com provas combinatórias que utilizam a contagem e a q-contagem de elementos em conjuntos de ladrilhamentos com restrições. Na primeira parte do trabalho utilizamos os ladrilhamentos para demonstrar algumas identidades da teoria das partições, dentre elas, o Teorema dos Números Triangulares e o Teorema q-análogo da Série q-Binomial. Na segunda parte do trabalho apresentamos interpretações combinatórias, via ladrilhamento, para algumas identidades envolvendo os números de Jacobsthal e os números generalizados de Jacobsthal . Na terceira parte do trabalho são dadas novas identidades envolvendo os números q-análogos de Jacobsthal e encontramos generalizações para essas novas identidades. Por fim, definimos duas novas sequências: números de Fibonacci generalizados e números de Lucas generalizados e, utilizando ladrilhamentos, estabelecemos e demonstramos novas identidades envolvendo esses números / Abstract: In this work we present combinatorial proofs by making use of tilings. In the first part we use tilings to prove some identities on Partitions Theory, including Triangular Numbers' Theorem and q-analogue of q-Binomial Theorem. In the second part we present combinatorial interpretations, using tilings, for some identities involving Jacobsthal numbers and generalized Jacobsthal numbers. Next we find new identities involving an q-analogue of Jacobsthal numbers and generalizations for these new identities. Finally, we define two new sequences: generalized Fibonacci numbers and generalized Lucas numbers, and using tilings, we prove new identities involving these numbers / Doutorado / Matematica Aplicada / Doutora em Matemática Aplicada
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Quantitative Mapping of Soil Property Based on Laboratory and Airborne Hyperspectral Data Using Machine LearningLiu, Lanfa 15 February 2019 (has links)
Soil visible and near-infrared spectroscopy provides a non-destructive, rapid and low-cost approach to quantify various soil physical and chemical properties based on their reflectance in the spectral range of 400–2500 nm. With an increasing number of large-scale soil spectral libraries established across the world and new space-borne hyperspectral sensors, there is a need to explore methods to extract informative features from reflectance spectra and produce accurate soil spectroscopic models using machine learning.
Features generated from regional or large-scale soil spectral data play a key role in the quantitative spectroscopic model for soil properties. The Land Use/Land Cover Area Frame Survey (LUCAS) soil library was used to explore PLS-derived components and fractal features generated from soil spectra in this study. The gradient-boosting method performed well when coupled with extracted features on the estimation of several soil properties. Transfer learning based on convolutional neural networks (CNNs) was proposed to make the model developed from laboratory data transferable for airborne hyperspectral data. The soil clay map was successfully derived using HyMap imagery and the fine-tuned CNN model developed from LUCAS mineral soils, as deep learning has the potential to learn transferable features that generalise from the source domain to target domain. The external environmental factors like the presence of vegetation restrain the application of imaging spectroscopy. The reflectance data can be transformed into a vegetation suppressed domain with a force invariance approach, the performance of which was evaluated in an agricultural area using CASI airborne hyperspectral data. However, the relationship between vegetation and acquired spectra is complicated, and more efforts should put on removing the effects of external factors to make the model transferable from one sensor to another.:Abstract I
Kurzfassung III
Table of Contents V
List of Figures IX
List of Tables XIII
List of Abbreviations XV
1 Introduction 1
1.1 Motivation 1
1.2 Soil spectra from different platforms 2
1.3 Soil property quantification using spectral data 4
1.4 Feature representation of soil spectra 5
1.5 Objectives 6
1.6 Thesis structure 7
2 Combining Partial Least Squares and the Gradient-Boosting Method for Soil Property Retrieval Using Visible Near-Infrared Shortwave Infrared Spectra 9
2.1 Abstract 10
2.2 Introduction 10
2.3 Materials and methods 13
2.3.1 The LUCAS soil spectral library 13
2.3.2 Partial least squares algorithm 15
2.3.3 Gradient-Boosted Decision Trees 15
2.3.4 Calculation of relative variable importance 16
2.3.5 Assessment 17
2.4 Results 17
2.4.1 Overview of the spectral measurement 17
2.4.2 Results of PLS regression for the estimation of soil properties 19
2.4.3 Results of PLS-GBDT for the estimation of soil properties 21
2.4.4 Relative important variables derived from PLS regression and the gradient-boosting method 24
2.5 Discussion 28
2.5.1 Dimension reduction for high-dimensional soil spectra 28
2.5.2 GBDT for quantitative soil spectroscopic modelling 29
2.6 Conclusions 30
3 Quantitative Retrieval of Organic Soil Properties from Visible Near-Infrared Shortwave Infrared Spectroscopy Using Fractal-Based Feature Extraction 31
3.1 Abstract 32
3.2 Introduction 32
3.3 Materials and Methods 35
3.3.1 The LUCAS topsoil dataset 35
3.3.2 Fractal feature extraction method 37
3.3.3 Gradient-boosting regression model 37
3.3.4 Evaluation 41
3.4 Results 42
3.4.1 Fractal features for soil spectroscopy 42
3.4.2 Effects of different step and window size on extracted fractal features 45
3.4.3 Modelling soil properties with fractal features 47
3.4.3 Comparison with PLS regression 49
3.5 Discussion 51
3.5.1 The importance of fractal dimension for soil spectra 51
3.5.2 Modelling soil properties with fractal features 52
3.6 Conclusions 53
4 Transfer Learning for Soil Spectroscopy Based on Convolutional Neural Networks and Its Application in Soil Clay Content Mapping Using Hyperspectral Imagery 55
4.1 Abstract 55
4.2 Introduction 56
4.3 Materials and Methods 59
4.3.1 Datasets 59
4.3.2 Methods 62
4.3.3 Assessment 67
4.4 Results and Discussion 67
4.4.1 Interpretation of mineral and organic soils from LUCAS dataset 67
4.4.2 1D-CNN and spectral index for LUCAS soil clay content estimation 69
4.4.3 Application of transfer learning for soil clay content mapping using the pre-trained 1D-CNN model 72
4.4.4 Comparison between spectral index and transfer learning 74
4.4.5 Large-scale soil spectral library for digital soil mapping at the local scale using hyperspectral imagery 75
4.5 Conclusions 75
5 A Case Study of Forced Invariance Approach for Soil Salinity Estimation in Vegetation-Covered Terrain Using Airborne Hyperspectral Imagery 77
5.1 Abstract 78
5.2 Introduction 78
5.3 Materials and Methods 81
5.3.1 Study area of Zhangye Oasis 81
5.3.2 Data description 82
5.3.3 Methods 83
5.3.3 Model performance assessment 85
5.4 Results and Discussion 86
5.4.1 The correlation between NDVI and soil salinity 86
5.4.2 Vegetation suppression performance using the Forced Invariance Approach 86
5.4.3 Estimation of soil properties using airborne hyperspectral data 88
5.5 Conclusions 90
6 Conclusions and Outlook 93
Bibliography 97
Acknowledgements 117
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[en] CROSS-COUNTRY DIFFERENCES IN RETURNS TO CAPITAL IN THE OIL AND GAS INDUSTRY / [pt] DIFERENÇAS DE RETORNOS DE CAPITAL ENTRE PAÍSES NA INDÚSTRIA DE PETRÓLEO E GÁSOSKAR NORALD NYHEIM SOLBRAEKKE 22 January 2019 (has links)
[pt] Primeiramente, o trabalho examina em que medida os países pobres possuem retornos de capital mais elevados que os países ricos. Em segundo lugar, investiga se as diferenças nos retornos de capital entre países estão correlacionadas com fatores institucionais, variância e/ou assimetria nos retornos.
Os resultados indicam uma relação negativa entre os retornos e o PIB per capita mas com pouca significância econômica. Ademais, os resultados indicam correlações significantes entre retornos de capital e alguns fatores institucionais, embora esses também não sejam economicamente significativos. O desvio padrão ou a assimetria nos retornos não parecem estar correlacionados com os retornos. Em suma, os achados indicam que uma pior qualidade institucional é, até certo ponto, uma explicação plausível para altos retornos de capital nos países pobres. Ainda assim, a falta de significância econômica encontrada destaca a natureza idiossincrática dos retornos nesta indústria devido a independência entre retornos
e fatores específicos ao país. Os resultados indicam a necessidade de adaptar a teoria economia à differenças setoriais e também é importante na prática para empresas privadas no setor de petróleo e gás, pois os resultados indicam que estas não devem se preocupar particularmente com o PIB per capita ou as instituições dos países em que considera investir. Ao invés disso, os resultados indicam que as
empresas devem olhar principalmente para características dos poços mesmo.
Diversas explicações plausíveis para os resultados são delineadas. / [en] This thesis makes use of a unique and vast dataset of investment and production in the oil and gas industry from 1950 to 2016, to explore the Lucas Paradox and the drivers of returns to capital in the industry. Firstly, the thesis examines to what extent poor countries possess higher average returns to capital than rich countries. Secondly, it investigates whether the differences in returns between countries are correlated with institutional factors, variance and/or asymmetry in the returns. The results demonstrate that poorer countries have enjoyed significantly higher returns to capital than richer countries. Moreover, the findings show that institutional factors such as property rights protection, level of corruption and level of schooling possess a positive and statistically significant correlation with returns to capital. However, both these findings are not particularly economically significant. Variance and asymmetry of the returns appear to be an irrelevant explanation for the Lucas Paradox. On the other hand, asset-specific factors, that were, ex-ante, expected to be merely insignificant control variables, such as the size of the reservoir, or whether the asset is located onshore or offshore, have large R-squared impact on returns to capital. The findings in this thesis are important because the largely insignificant magnitude of country-specific variables highlight the importance of adapting economic development theory to account for sector-specific differences, as emphasized by Feyrer and Caselli (2008). Moreover, the results indicate that profit maximizing oil and gas companies considering new investments in a country should not be overly concerned with the GDP per capita nor the institutional quality of the country in question. Several potential explanations and paths for future studies are delineated.
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Ensaios em história do pensamento econômico / Essays on the history of economic thoughtAndrada, Alexandre Flávio Silva 14 September 2012 (has links)
A presente tese de doutoramento é composta de três ensaios independentes (ainda que complementares) sobre a História do Pensamento Econômico, mais especificamente, da Macroeconomia. O primeiro ensaio - \"Uma Breve História sobre a Abordagem de Desequilíbrio na Macroeconomia\" - é uma versão revista e ampliada do artigo apresentado no XXXVIII Encontro Nacional de Economia da ANPEC em 2010 (Uma Breve História sobre a Abordagem de Desequilíbrio na Economia). Nossa argumentação vai de encontro às interpretações de Romer (1989) e Mankiw (2005) sobre a compreensão histórica daquele episódio, como também a hipótese levantada por Backhouse & Boianovsky (2005) sobre o fracasso da Macroeconomia do Desequilíbrio. O segundo ensaio se chama \"Uma Análise Histórica (e Retórica) do Discurso Doutrinário de Robert E. Lucas Jr.\". Se no primeiro ensaio argumentamos que parte do \"fracasso\" da Abordagem de Desequilíbrio deveu-se ao surgimento de um método entendido como superior pela maior parte dos economistas (o método de Lucas), neste investigamos o conteúdo daqueles artigos em que Lucas busca convencer os leitores da superioridade do seu método não a partir da comparação dos resultados obtidos por seu modelo em comparação a uma estrutura alternativa, mas sim com uma retórica polemista, fazendo uso de uma série de estratagemas retóricos. Nossa intenção é checar a validade de algumas de suas teses históricas e teóricas, bem como fazer um escrutínio dos expedientes retóricos utilizados pelo autor. O terceiro ensaio - \"Tese da Ancestralidade, Reinvenção da Tradição ou Superação Positiva? Uma Investigação sobre a \"Macroeconomia\" anterior a Keynes e as Causas do Sucesso da Teoria Geral\" - é derivada do segundo ensaio. Partimos da contraposição de hipóteses históricas de dois grandes autores da Macroeconomia sobre o estado da teoria \"macroeconômica\" anterior a Keynes, e as causas do sucesso da Teoria Geral. De um lado, Robert Lucas trata a Macroeconomia fundada por Keynes como um desvio na tradição equilibrista das análises de flutuação, cujo sucesso foi um \'feliz acidente histórico\', provocado principalmente por fatores alheios as vontades e até as simpatias de Keynes. De outro, Olivier Blanchard argumenta que o que havia antes de Keynes era uma grande diversidade de métodos e ausência de um aparato hegemônico, e o sucesso de Keynes deveu-se exclusivamente aos avanços teóricos e metodológicos apresentados naquela obra. / This PhD thesis contains three independent (although complementary) essays on the History of Economic Thought, more specifically on Macroeconomics History. The first essay - A Brief History of the Disequilibrium Approach in Macroeconomics - is a revised and expanded version of paper presented at the XXXVIII Meeting of ANPEC. Our argumentation challenges Romer (1989) and Mankiw (2005) interpretations about that episode. We also disagree (at some level) with Backhouse & Boianovsky (2005) hypothesis about the so-called \"failure\" of Non-Market-Clearing Approach. The second essay - A Historical (and Rhetorical) Analysis of Robert E. Lucas Junior\'s Doctrinaire Speech - is still a work in progress. If the first essay we argue that part of the \"failure\" of Disequilibrium Approach was due to the emergence of a method perceived as superior by most economists (lucasian method), here we investigate the content of those articles where Lucas seeks to persuade its readers of the superiority of his method not from the scrutiny of the results obtained by a specific model in comparison to an alternative structure, but mainly through a polemicist rhetoric. Our intention is to check the validity of some of its historical and theoretical arguments, and make a scrutiny of rhetorical expedients used by the author. The third essay - Ancestry Thesis, Reinvention of a Tradition or Cumulative Progress? A Research on \"Macroeconomics\" before Keynes and some Speculation about the causes of General Theory\'s Success\" - is derived from the second paper. We start from the juxtaposition of historical hypotheses of two great authors about the state\'s theory of \"macroeconomic\" before Keynes, and the causes of the success of the General Theory. On one hand, Robert Lucas argues that Macroeconomics as developed by Keynes was a deviation in the tradition of equilibrist fluctuation analysis, whose success was a fortunate historical accident. On the other, Olivier Blanchard argues that what was before Keynes was a great diversity of methods and the absence of a hegemonic apparatus, and the success of Keynes was due exclusively to theoretical and methodological advances made in that work.
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Combining Partial Least Squares and the Gradient-Boosting Method for Soil Property Retrieval Using Visible Near-Infrared Shortwave Infrared SpectraLiu, Lanfa, Ji, Min, Buchroithner, Manfred F. 06 June 2018 (has links) (PDF)
Soil spectroscopy has experienced a tremendous increase in soil property characterisation, and can be used not only in the laboratory but also from the space (imaging spectroscopy). Partial least squares (PLS) regression is one of the most common approaches for the calibration of soil properties using soil spectra. Besides functioning as a calibration method, PLS can also be used as a dimension reduction tool, which has scarcely been studied in soil spectroscopy. PLS components retained from high-dimensional spectral data can further be explored with the gradient-boosted decision tree (GBDT) method. Three soil sample categories were extracted from the Land Use/Land Cover Area Frame Survey (LUCAS) soil library according to the type of land cover (woodland, grassland, and cropland). First, PLS regression and GBDT were separately applied to build the spectroscopic models for soil organic carbon (OC), total nitrogen content (N), and clay for each soil category. Then, PLS-derived components were used as input variables for the GBDT model. The results demonstrate that the combined PLS-GBDT approach has better performance than PLS or GBDT alone. The relative important variables for soil property estimation revealed by the proposed method demonstrated that the PLS method is a useful dimension reduction tool for soil spectra to retain target-related information.
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Propriedades e generalizações dos números de FibonacciAlmeida, Edjane Gomes dos Santos 29 August 2014 (has links)
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Previous issue date: 2014-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work is about research done Fibonacci's Numbers. Initially it presents a brief
account of the history of Leonardo Fibonacci, from his most famous work,The Liber
Abaci, to the relationship with other elds of Mathematics. Then we will introduce
some properties of Fibonacci's Numbers, Binet's Form, Lucas' Numbers and
the relationship with Fibonacci's Sequence and an important property observed by
Fermat. Within relationships with other areas of Mathematics, we show the relationship
Matrices, Trigonometry and Geometry. Also presents the Golden Ellipse
and the Golden Hyperbola. We conclude with Tribonacci's Numbers and some properties
that govern these numbers. Made some generalizations about Matrices and
Polynomials Tribonacci. / Este trabalho tem como objetivo o estudo dos Números de Fibonacci. Apresenta-se
inicialmente um breve relato sobre a história de Leonardo Fibonacci, desde sua obra
mais famosa, O Liber Abaci, até a relação com outros campos da Matemática. Em
seguida, apresenta-se algumas propriedades dos Números de Fibonacci, a Fórmula
de Binet, os Números de Lucas e a relação com a Sequência de Fibonacci e uma importante
propriedade observada por Fermat. Dentro das relações com outras áreas
da Matemática, destacamos a relação com as Matrizes, com a Trigonometria, com a
Geometria. Apresenta-se também a Elipse e a Hipérbole de Ouro. Concluímos com
os Números Tribonacci e algumas propriedades que regem esses números. Realizamos
algumas generalizações sobre Matrizes e Polinômios Tribonacci.
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Ensaios em história do pensamento econômico / Essays on the history of economic thoughtAlexandre Flávio Silva Andrada 14 September 2012 (has links)
A presente tese de doutoramento é composta de três ensaios independentes (ainda que complementares) sobre a História do Pensamento Econômico, mais especificamente, da Macroeconomia. O primeiro ensaio - \"Uma Breve História sobre a Abordagem de Desequilíbrio na Macroeconomia\" - é uma versão revista e ampliada do artigo apresentado no XXXVIII Encontro Nacional de Economia da ANPEC em 2010 (Uma Breve História sobre a Abordagem de Desequilíbrio na Economia). Nossa argumentação vai de encontro às interpretações de Romer (1989) e Mankiw (2005) sobre a compreensão histórica daquele episódio, como também a hipótese levantada por Backhouse & Boianovsky (2005) sobre o fracasso da Macroeconomia do Desequilíbrio. O segundo ensaio se chama \"Uma Análise Histórica (e Retórica) do Discurso Doutrinário de Robert E. Lucas Jr.\". Se no primeiro ensaio argumentamos que parte do \"fracasso\" da Abordagem de Desequilíbrio deveu-se ao surgimento de um método entendido como superior pela maior parte dos economistas (o método de Lucas), neste investigamos o conteúdo daqueles artigos em que Lucas busca convencer os leitores da superioridade do seu método não a partir da comparação dos resultados obtidos por seu modelo em comparação a uma estrutura alternativa, mas sim com uma retórica polemista, fazendo uso de uma série de estratagemas retóricos. Nossa intenção é checar a validade de algumas de suas teses históricas e teóricas, bem como fazer um escrutínio dos expedientes retóricos utilizados pelo autor. O terceiro ensaio - \"Tese da Ancestralidade, Reinvenção da Tradição ou Superação Positiva? Uma Investigação sobre a \"Macroeconomia\" anterior a Keynes e as Causas do Sucesso da Teoria Geral\" - é derivada do segundo ensaio. Partimos da contraposição de hipóteses históricas de dois grandes autores da Macroeconomia sobre o estado da teoria \"macroeconômica\" anterior a Keynes, e as causas do sucesso da Teoria Geral. De um lado, Robert Lucas trata a Macroeconomia fundada por Keynes como um desvio na tradição equilibrista das análises de flutuação, cujo sucesso foi um \'feliz acidente histórico\', provocado principalmente por fatores alheios as vontades e até as simpatias de Keynes. De outro, Olivier Blanchard argumenta que o que havia antes de Keynes era uma grande diversidade de métodos e ausência de um aparato hegemônico, e o sucesso de Keynes deveu-se exclusivamente aos avanços teóricos e metodológicos apresentados naquela obra. / This PhD thesis contains three independent (although complementary) essays on the History of Economic Thought, more specifically on Macroeconomics History. The first essay - A Brief History of the Disequilibrium Approach in Macroeconomics - is a revised and expanded version of paper presented at the XXXVIII Meeting of ANPEC. Our argumentation challenges Romer (1989) and Mankiw (2005) interpretations about that episode. We also disagree (at some level) with Backhouse & Boianovsky (2005) hypothesis about the so-called \"failure\" of Non-Market-Clearing Approach. The second essay - A Historical (and Rhetorical) Analysis of Robert E. Lucas Junior\'s Doctrinaire Speech - is still a work in progress. If the first essay we argue that part of the \"failure\" of Disequilibrium Approach was due to the emergence of a method perceived as superior by most economists (lucasian method), here we investigate the content of those articles where Lucas seeks to persuade its readers of the superiority of his method not from the scrutiny of the results obtained by a specific model in comparison to an alternative structure, but mainly through a polemicist rhetoric. Our intention is to check the validity of some of its historical and theoretical arguments, and make a scrutiny of rhetorical expedients used by the author. The third essay - Ancestry Thesis, Reinvention of a Tradition or Cumulative Progress? A Research on \"Macroeconomics\" before Keynes and some Speculation about the causes of General Theory\'s Success\" - is derived from the second paper. We start from the juxtaposition of historical hypotheses of two great authors about the state\'s theory of \"macroeconomic\" before Keynes, and the causes of the success of the General Theory. On one hand, Robert Lucas argues that Macroeconomics as developed by Keynes was a deviation in the tradition of equilibrist fluctuation analysis, whose success was a fortunate historical accident. On the other, Olivier Blanchard argues that what was before Keynes was a great diversity of methods and the absence of a hegemonic apparatus, and the success of Keynes was due exclusively to theoretical and methodological advances made in that work.
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Combining Partial Least Squares and the Gradient-Boosting Method for Soil Property Retrieval Using Visible Near-Infrared Shortwave Infrared SpectraLiu, Lanfa, Ji, Min, Buchroithner, Manfred F. 06 June 2018 (has links)
Soil spectroscopy has experienced a tremendous increase in soil property characterisation, and can be used not only in the laboratory but also from the space (imaging spectroscopy). Partial least squares (PLS) regression is one of the most common approaches for the calibration of soil properties using soil spectra. Besides functioning as a calibration method, PLS can also be used as a dimension reduction tool, which has scarcely been studied in soil spectroscopy. PLS components retained from high-dimensional spectral data can further be explored with the gradient-boosted decision tree (GBDT) method. Three soil sample categories were extracted from the Land Use/Land Cover Area Frame Survey (LUCAS) soil library according to the type of land cover (woodland, grassland, and cropland). First, PLS regression and GBDT were separately applied to build the spectroscopic models for soil organic carbon (OC), total nitrogen content (N), and clay for each soil category. Then, PLS-derived components were used as input variables for the GBDT model. The results demonstrate that the combined PLS-GBDT approach has better performance than PLS or GBDT alone. The relative important variables for soil property estimation revealed by the proposed method demonstrated that the PLS method is a useful dimension reduction tool for soil spectra to retain target-related information.
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