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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

On the development of control systems technology for fermentation processes

Loftus, John January 2017 (has links)
Fermentation processes play an integral role in the manufacture of pharmaceutical products. The Quality by Design initiative, combined with Process Analytical Technologies, aims to facilitate the consistent production of high quality products in the most efficient and economical way. The ability to estimate and control product quality from these processes is essential in achieving this aim. Large historical datasets are commonplace in the pharmaceutical industry and multivariate methods based on PCA and PLS have been successfully used in a wide range of applications to extract useful information from such datasets. This thesis has focused on the development and application of novel multivariate methods to the estimation and control of product quality from a number of processes. The document is divided into four main categories. Firstly, the related literature and inherent mathematical techniques are summarised. Following this, the three main technical areas of work are presented. The first of these relates to the development of a novel method for estimating the quality of products from a proprietary process using PCA. The ability to estimate product quality is useful for identifying production steps that are potentially problematic and also increases process efficiency by ensuring that any defective products are detected before they undergo any further processing. The proposed method is simple and robust and has been applied to two separate case studies, the results of which demonstrate the efficacy of the technique. The second area of work concentrates on the development of a novel method of identifying the operational phases of batch fermentation processes and is based on PCA and associated statistics. Knowledge of the operational phases of a process can be beneficial from a monitoring and control perspective and allows a process to be divided into phases that can be approximated by a linear model. The devised methodology is applied to two separate fermentation processes and results show the capability of the proposed method. The third area of work focuses on undertaking a performance evaluation of two multivariate algorithms, PLS and EPLS, in controlling the end-point product yield of fermentation processes. Control of end-point product quality is of crucial importance in many manufacturing industries, such as the pharmaceutical industry. Developing a controller based on historical and identification process data is attractive due to the simplicity of modelling and the increasing availability of process data. The methodology is applied to two case studies and performance evaluated. From both a prediction and control perspective, it is seen that EPLS outperforms PLS, which is important if modelling data is limited.
142

Combinação de previsões : uma proposta utilizando análise de componentes principais

Martins, Vera Lúcia Milani January 2014 (has links)
A obtenção de previsões com maior acuracidade é uma necessidade constantemente requerida, em tempos onde há imensa disponibilidade de dados e recursos computacionais cada dia mais eficientes. Tais critérios possibilitaram o desenvolvimento de muitas técnicas de previsão individual ou de métodos de combinação que são considerados eficientes no intuito de reduzir erros. O desenvolvimento de novas técnicas, por sua vez, promove questionamentos quanto à identificação de quantas ou quais técnicas de previsão individual combinar. A literatura não é unânime ao tentar responder a estes questionamentos e indica a importância da correlação entre os erros de previsão na precisão da combinação. Posto isso, esta tese apresenta uma alternativa aos métodos atuais de combinar previsões, contemplando a correlação entre os erros de previsão, além de propor uma forma de identificar técnicas de previsão que sejam distintas quanto à modelagem de características da série de dados. Para identificar grupos de técnicas de previsão individual que sejam similares, utilizou-se a Análise de Agrupamentos em erros gerados por 15 técnicas de previsão que modelaram uma mesma série de dados real com tendência e sazonalidade. O resultado indicou a formação de 3 agrupamentos. Como alternativa aos métodos atuais de combinar previsão e selecionar a quantidade adequada de técnicas, utilizou-se a Análise de Componentes Principais. O método proposto mostrou-se viável quando comparado com outros métodos de combinação e quando submetido à modelagem de séries com maior variabilidade. / The obtaining of more accurate forecasts is a necessity often required in times where there is a huge availability of data and computing resources becoming more efficient every day. These criteria allowed the development of many individual forecasting techniques or combination methods that are considered efficient in order to reduce errors. The development of new techniques, in turn, promotes questioning as the identification of how many or which techniques to combine individual forecasts. The literature is not unanimous when trying to answer these questions and indicates the importance of the correlation between forecast errors on the accuracy of the combination. That said, this presents an alternative to current methods of combining forecasts, considering the correlation between forecast errors, and propose a way to identify predictive techniques that are different about the modeling features of the data series. To identify groups of individual forecasting techniques that are similar, it was used the cluster analysis on errors generated by 15 forecasting techniques that shaped the same series of real data with trend and seasonality. The result indicated the formation of 3 clusters. As an alternative to current methods of combining forecasting and selecting the appropriate amount of techniques, it was used the Principal Component Analysis. The proposed method has proved feasible when compared to other methods of combining and when subjected to modeling of series with greater variability.
143

Simplified plasma models based on reduced kinetics

Bellemans, Aurélie 01 December 2017 (has links) (PDF)
Performing high-fidelity plasma simulations remains computationally expensive because of their large dimension and complex chemistry. Atmospheric re-entry plasmas for instance, involve hundreds of species in thousands of reactions used in detailed physical models. These models are very complex as they describe the non-equilibrium phenomena due to finite-rate processes in the flow. Chemical non-equilibrium arises because of the many dissociation, ionization and excitation reaction at various time-scales. Vibrational, rotational, electronic and translational temperatures characterize the flow and exchange energy between species, which leads to thermal non-equilibrium.With the current computational resources, detailed three-dimensional simulations are still out of reach. Detailed calculations using the full dynamics are often restricted to a zero- or one-dimensional description. A trade-off has to be made between the level of accuracy of the model and its computational cost. This thesis presents various methods to develop accurate reduced kinetic models for plasma flows. Starting from detailed chemistry, high-fidelity reductions are achieved through the application of either physics-based techniques, such as presented by the binning methods and time-scale based reductions, either empirical techniques given by principal component analysis. As an original contribution to the existing methods, the physics-based techniques are combined with principal component analysis uniting both communities. The different techniques are trained on a 34 species collisional-radiative model for argon plasma by comparing shock relaxation simulations.The best performing method is applied on the large N-N2 mechanism containing 9391 species and 23 million reactions calculated by the NASA Ames Research Center. As a preliminary step, the system dynamics is analyzed to improve our understanding of the various processes occurring in plasma flows. The reactions are analyzed and classified according to their importance. A deep investigation of the kinetics enables finding the main variables and parameters characterizing the plasma, which can thereafter be used to develop or improve existing reductions.As a result, a novel coarse grain model has been developed for argon by binning the electronic excited levels and the ionized species into 2 Boltzmann averaged energy bins. The ground state is solved individually together with the free electrons, reducing the species mass conservation equations from 34 to 4. Principal component analysis has been transferred from the combustion community to plasma flows by investigating the Manifold-Generated and Score-PCA techniques. PCA identifies low dimensional manifolds empirically, projecting the full kinetics to its base of principal components. A novel approach combines the binning techniques with PCA, finding an optimized model for reducing the N3 rovibrational collisional model. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
144

Liquidity measurements and the return-liquidity relationship : empirical evidence from Germany, the UK, the US and China

Bo, Yibo January 2017 (has links)
With reference to the existing literature on liquidity, three key questions have emerged during the last several decades: (i) How to measure liquidity in the most efficient way? (ii) What is the empirical pattern in the relation between market liquidity and stock returns? (iii) What are the determinants of the changes in the Return-Liquidity Relationship? This thesis take the above three questions as its principal focus and studies them by undertaking three separate empirical chapters, using a substantial dataset that covers all the listed firms in these four global economies – Germany, the UK, the US and China from 2001 to 2013. The empirical results imply the following: (i) The Transaction-Cost based liquidity measures, particularly the Quoted Proportional Spread, should be regarded as the most representative liquidity measurement. (ii) There is no evidence consistent with a fixed empirical pattern in the Return-Liquidity Relationship across these four countries as market liquidity is preferred in both Germany and UK, while the opposite results have been obtained for the Chinese stock market. That is, higher market leads to higher stock returns in these two European countries as the higher market liquidity facilitates capital movements to more efficient investments. However in China, the huge number of individual investors generates higher market liquidity through speculative trading rather than as a result of value-related investments, which heightens market risk and thus results in a decrease in stock prices. (iii) There is weak evidence that stock market returns have positive determinant effects on both MLIs (the market impact of liquidity on stock returns) and FLIs, (the firm-level impact of liquidity on stock returns) Return-Liquidity relation on market and firm level respectively. While only FLIs are positively correlated with stock market volatility and the inflation rate and negatively affected by the short-term interest rate.
145

Índice de sustentabilidade do perímetro irrigado Baixo Acaraú-Ceará / Sustainability index in the irrigated Baixo Acaraú -Ceará

Lopes, Fernando Bezerra January 2008 (has links)
LOPES, Fernando Bezerra. Índice de sustentabilidade do perímetro irrigado Baixo Acaraú-Ceará. 2008. 116 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Curso de Mestrado em Agronomia, Fortaleza-CE, 2008. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-06-28T14:53:36Z No. of bitstreams: 1 2008_dis_fblopes.pdf: 8811876 bytes, checksum: 201eefecde686ccd48ca07732060ab33 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-06-28T14:54:03Z (GMT) No. of bitstreams: 1 2008_dis_fblopes.pdf: 8811876 bytes, checksum: 201eefecde686ccd48ca07732060ab33 (MD5) / Made available in DSpace on 2016-06-28T14:54:03Z (GMT). No. of bitstreams: 1 2008_dis_fblopes.pdf: 8811876 bytes, checksum: 201eefecde686ccd48ca07732060ab33 (MD5) Previous issue date: 2008 / The aimed of this work was an integrated sustainability analysis of the Irrigated Perimeter of Baixo Acaraú (PIBAU) sited in Acaraú basin, Ceará, Brazil. The analysis was labeled by an agro ecological sustainability index (ASI). The approach was based on 22 cross-over form applied to small producers that live in the PIBAU. In the irrigated areas selected to perform the interviews, it was developed the irrigation system evaluation. Factory Analysis/Principal Components Analysis (FA/PCA) was employed to select the factors sustainability indicators of the irrigated perimeter as well as to define the agro ecological sustainability index. Results showed that 64% of the producers had a power education and 77% of them had no experience with irrigation agriculture before. Also, it was identified that only 18% of irrigation systems presented an excellent CUD, while 28% of them were classified with a bad performance. According to the sensitive test effectuated by FA/PCA, only 12 of 27 variables that composed the initial matrix were significant to explain the total variance of data set. The 12 variables selected by the model were grouped in five factors explaining 79.14% of the total variance. The factors loading indicated that the PIBAU sustainability is, principally, related to the lack of acknowledgment as well as the used of suitable management of agricultural practices. The sustainability index of each productive units ranges from 0.283 to 0.916 and the average was 0.538. Only 9.0% of the pooled productivity were classified as sustainable, while 18.2% of them presented a kind of sustainability. Almost the half of producers (45.5%) showed a threatened sustainability and the others (27.3%) were in unsustainable condition. Also, it was identified that some units with a good irrigation system performance, without of salinization risk presented a low sustainability index (0.371). This is explained by the fact the index express an integration of different variables. Even though, no risk of salinization was identified, this work registered an addition high of significance of salt in the irrigated area when compared to undisturbed one. / Este trabalho teve como objetivo realizar uma análise integrada da sustentabilidade do Perímetro Irrigado Baixo Acaraú (PIBAU), localizado na Bacia do Acaraú a norte do Estado do Ceará, possibilitando o desenvolvimento de um índice de sustentabilidade agro-ambiental. Para isso, aplicou-se uma amostragem exploratória, adotando um modelo de amostragem não probabilístico, obtendo uma população amostral de 22 produtores agrícolas beneficiados pelo respectivo projeto de irrigação e aplicando-se questionários do tipo “cross-over”. Nos lotes selecionados para a aplicação dos questionários, foi realizada uma avaliação dos sistemas de irrigação. Os fatores determinantes da sustentabilidade do Perímetro, bem como o índice de sustentabilidade foram identificados pelo emprego da técnica de Análise Fatorial/Análise da Componente Principal (AF/ACP). A pesquisa identificou que mais da metade dos produtores agrícolas apresentam baixo nível educacional (64%) e que 77% dos irrigantes não tinham experiência com a prática da agricultura irrigada antes de ser proprietário de um lote no Perímetro. Apenas 18% dos sistemas de irrigação localizada do Perímetro apresentam Coeficiente de Uniformidade de Distribuição (CUD) classificado como excelente e 28% apresentam CUD classificado como ruim. Pelo teste de sensibilidade, efetuado utilizando-se o modelo da AF/ACP, identificou-se que, das 27 variáveis que compunham a matriz inicial, apenas 12 delas apresentaram alguma significância na explicação da variância total dos dados. O emprego do modelo promoveu a redução de 12 características dos fatores que influenciam a sustentabilidade do Perímetro para cinco componentes, que explicam 79,14% da variância total. Os pesos atribuídos a cada fator indicaram que a sustentabilidade do Perímetro Baixo Acaraú está, principalmente, relacionada à falta de conhecimento e do uso de técnicas corretas de produção agrícola. Os índices de sustentabilidade obtidos para cada unidade produtiva variaram no intervalo de 0,283 a 0,916. A média global de sustentabilidade dos lotes foi de 0,538 representando uma condição de sustentabilidade comprometida. Apenas 9,0% das unidades produtivas estudadas encontram-se numa situação de sustentabilidade equilibrada. Outros 18,2% dos produtores ainda são considerados sustentáveis, mas em condição de ameaça, que pode advir de qualquer um dos fatores contabilizados no índice. Quase metade dos colonos (45,5%) pesquisados registrou uma sustentabilidade que já se apresenta de alguma forma comprometida e os demais (27,3%) estão em condições de insustentabilidade. A unidade produtiva em estudo não apresenta solos com problema de salinização, porém com exceção da camada inferior (0,90 a 1,20 m), para as demais camadas estudadas (0 a 0,30, 0,30 a 0,60 e 0,60 a 0,90 m) a adição de sais ao solo pelo manejo inadequado da irrigação foi altamente significativa. Apesar do solo não apresentar risco de salinização e o sistema de irrigação funcionar com uma uniformidade de distribuirão classificado como bom, a unidade em estudo apresenta índice de sustentabilidade de 0,371, devido o índice ser formado por um conjunto de variáveis.
146

THE ELEMENTS OF THE CLINICAL SUPERVISION: EXPORTING CONCEPTS TO JAPAN

Miyoshi, Makoto 01 May 2016 (has links)
The current Japanese counseling profession is in the process of reforming and uniting the system and training together for counseling and related professions. Supervision is one of significant training piece in this profession; however, its familiarity among Japanese counseling professionals is very unclear. This study explored how Japanese counseling professionals conceptualize the ideal figure of a clinical supervisor based on the identified fundamental elements of clinical supervision in the US. The preliminary analysis indicates that each aspect of the U.S. clinical supervision models might be adoptable to Japanese counseling professionals. Yet the small sample size does not confirm the conceptual framework of the ideal clinical supervisor for Japanese counseling professionals, the main analysis indicated an alternative culturally appropriate conceptual framework. Further research embracing Japanese cultural characteristics and sound ethical manner in the professional counseling and supervisory relationship would enrich the clinical supervision in Japan.
147

Barreiras e fatores críticos de sucesso relacionados à aplicação da produção mais limpa no Brasil

Vieira, Letícia Canal January 2016 (has links)
Em um contexto atual de busca pelo desenvolvimento sustentável, surge a necessidade de alteração de mentalidades e práticas. A Produção mais Limpa figura como um dos exemplos de iniciativa compatível com essa demanda. Seu objetivo é que sejam considerados previamente os efeitos negativos dos processos produtivos, fazendo com que seja reduzido o desperdício e a geração de poluentes. Mesmo estando de acordo com as aspirações atuais de busca por uma produção industrial mais sustentável, sua disseminação não ocorreu de forma satisfatória. Esta dissertação visa contribuir para a compreensão das barreiras para a aplicação da Produção mais Limpa, bem como identificar quais fatores devem estar presentes para que se atinja o sucesso na sua adoção, possibilitando a geração de uma proposta de framework. Para atingir os objetivos propostos um instrumento de pesquisa foi criado com base na literatura e entrevistas com profissionais. Com esse instrumento foi executada uma survey com profissionais que possuem envolvimento com a temática de Produção mais Limpa, atingindo-se um total de 185 respondentes. A partir dos resultados da análise de componentes principais, ficou evidenciado que os fatores mais cruciais dizem respeito à organização, estando relacionados com a visão, a cultura, o planejamento estratégico e os subsídios para a implantação da Produção mais Limpa, que constituíram na primeira e segunda componentes da análise. No caso das barreiras, destaca-se a existência de uma visão e cultura organizacional inadequadas (primeira componente), seguido da falta de apoio externo (segunda componente). Também foram encontrados indícios de que pode haver uma má compreensão do conceito de Produção mais Limpa, além de uma educação ambiental inadequada. Ao analisarem-se as medidas que podem ser tomadas para que a Produção mais Limpa tenha sua aplicação de forma mais efetiva, percebe-se que o principal é o reposicionamento do ambiente externo como um forte incentivador da aplicação da Produção mais Limpa, abandonando a posição de destaque ao serem observadas as barreiras. / In t In the present context of pursuit for sustainable development, the need to alter mentalities and practices arises. Cleaner Production is an example of initiative compatible with this demand. Cleaner Production aims at considering beforehand negative effects of the productive process, reducing wastes and pollutant generation. This concept is aligned with current aspirations of pursuing for a more sustainable industrial production, but its dissemination did not occur in a satisfactory way. This dissertation seeks to contribute for comprehension of barriers to Cleaner Production application, as well as identify critical success factors that exist to achieve success in its adoption, making possible the conception of a framework proposal. To reach the proposed objectives a research instrument was created based on literature and interviews with professionals. With this instrument a survey was performed with professionals that work with Cleaner Production; a total of 185 responses were obtained. Results of the Principal Component Analysis made evident that critical factors are related with organization aspects, such as vision, culture, strategic planning and subsides for Cleaner Production implementation, that composed the first and second components. Regarding the barriers, it was emphasized the existence of an inadequate organizational vision and culture (first component), followed by lack of external support (second component). It was also found evidences that a mistaken comprehension of the Cleaner Production concept might exist, as well as an inappropriate environmental education. Considering measures that might be taken in order to disseminate Cleaner Production more effectively, it was noticed that is important to repositioning the external environment, making it a strong support in Cleaner Production applications, leaving behind a position of highlight when barriers are observed.
148

Seleção de variáveis para clusterização através de índices de importância das variáveis e Análise de Componentes Principais / Clustering variable selection through variable importance indices and principal component analysis

Cervo, Victor Leonardo January 2013 (has links)
A presente dissertação propõe novas abordagens para seleção de variáveis com vistas à formação de grupos representativos de observações. Para tanto, sugere um novo índice de importância das variáveis apoiado nos parâmetros oriundos da Análise de Componentes Principais (APC), o qual é integrado a uma sistemática do tipo forward para seleção de variáveis. A qualidade dos agrupamentos formados é medida através do Silhouette Index. Um estudo de simulação é projetado para avaliar a robustez e o desempenho da sistemática proposta em dados com diferentes níveis de correlação, ruído e número de observações a serem clusterizadas. Na sequência, é apresentada uma versão modificada da sistemática original, a qual utiliza funções kernel para remapeamento dos dados com vistas ao incremento da qualidade de clusterização e redução das variáveis retidas para formação dos agrupamentos. A versão modificada é aplicada em 3 bancos de dados da indústria química, aumentando a qualidade da clusterização medida pelo SI médio em 150% e utilizando em torno de 6% das variáveis originais. / This thesis proposes new approaches for variable selection aimed at forming representative groups of observations. For that matter, we suggest a new variable importance index based on parameters derived from the Principal Component Analysis (PCA), which is integrated to a forward procedure for variable selection. The quality of clustering procedure is assessed by the Silhouette Index. A simulation study is designed to evaluate the robustness of the proposed method on different levels of variable correlation, noise and number of observations to be clustered. Next, we modify the original method by remapping observations through kernel functions tailored to improving the clustering quality and reducing the retained variables. The modified version is applied to 3 databases related to chemical processes, increasing the quality of clustering measured by SI on average 150%, while using around 6% of the original variables.
149

Sistemáticas de agrupamento de países com base em indicadores de desempenho / Countries clustering systematics based on performance indexes

Mello, Paula Lunardi de January 2017 (has links)
A economia mundial passou por grandes transformações no último século, as quais incluiram períodos de crescimento sustentado seguidos por outros de estagnação, governos alternando estratégias de liberalização de mercado com políticas de protecionismo comercial e instabilidade nos mercados, dentre outros. Figurando como auxiliar na compreensão de problemas econômicos e sociais de forma sistêmica, a análise de indicadores de desempenho é capaz de gerar informações relevantes a respeito de padrões de comportamento e tendências, além de orientar políticas e estratégias para incremento de resultados econômicos e sociais. Indicadores que descrevem as principais dimensões econômicas de um país podem ser utilizados como norteadores na elaboração e monitoramento de políticas de desenvolvimento e crescimento desses países. Neste sentido, esta dissertação utiliza dados do Banco Mundial para aplicar e avaliar sistemáticas de agrupamento de países com características similares em termos dos indicadores que os descrevem. Para tanto, integra técnicas de clusterização (hierárquicas e não-hierárquicas), seleção de variáveis (por meio da técnica “leave one variable out at a time”) e redução dimensional (através da Análise de Componentes Principais) com vistas à formação de agrupamentos consistentes de países. A qualidade dos clusters gerados é avaliada pelos índices Silhouette, Calinski-Harabasz e Davies-Bouldin. Os resultados se mostraram satisfatórios quanto à representatividade dos indicadores destacados e qualidade da clusterização gerada. / The world economy faced transformations in the last century. Periods of sustained growth followed by others of stagnation, governments alternating strategies of market liberalization with policies of commercial protectionism, and instability in markets, among others. As an aid to understand economic and social problems in a systemic way, the analysis of performance indicators generates relevant information about patterns, behavior and trends, as well as guiding policies and strategies to increase results in economy and social issues. Indicators describing main economic dimensions of a country can be used guiding principles in the development and monitoring of development and growth policies of these countries. In this way, this dissertation uses data from World Bank to elaborate a system of grouping countries with similar characteristics in terms of the indicators that describe them. To do so, it integrates clustering techniques (hierarchical and non-hierarchical), selection of variables (through the "leave one variable out at a time" technique) and dimensional reduction (appling Principal Component Analysis). The generated clusters quality is evaluated by the Silhouette Index, Calinski-Harabasz and Davies-Bouldin indexes. The results were satisfactory regarding the representativity of the highlighted indicators and the generated a good clustering quality.
150

Combinação de previsões : uma proposta utilizando análise de componentes principais

Martins, Vera Lúcia Milani January 2014 (has links)
A obtenção de previsões com maior acuracidade é uma necessidade constantemente requerida, em tempos onde há imensa disponibilidade de dados e recursos computacionais cada dia mais eficientes. Tais critérios possibilitaram o desenvolvimento de muitas técnicas de previsão individual ou de métodos de combinação que são considerados eficientes no intuito de reduzir erros. O desenvolvimento de novas técnicas, por sua vez, promove questionamentos quanto à identificação de quantas ou quais técnicas de previsão individual combinar. A literatura não é unânime ao tentar responder a estes questionamentos e indica a importância da correlação entre os erros de previsão na precisão da combinação. Posto isso, esta tese apresenta uma alternativa aos métodos atuais de combinar previsões, contemplando a correlação entre os erros de previsão, além de propor uma forma de identificar técnicas de previsão que sejam distintas quanto à modelagem de características da série de dados. Para identificar grupos de técnicas de previsão individual que sejam similares, utilizou-se a Análise de Agrupamentos em erros gerados por 15 técnicas de previsão que modelaram uma mesma série de dados real com tendência e sazonalidade. O resultado indicou a formação de 3 agrupamentos. Como alternativa aos métodos atuais de combinar previsão e selecionar a quantidade adequada de técnicas, utilizou-se a Análise de Componentes Principais. O método proposto mostrou-se viável quando comparado com outros métodos de combinação e quando submetido à modelagem de séries com maior variabilidade. / The obtaining of more accurate forecasts is a necessity often required in times where there is a huge availability of data and computing resources becoming more efficient every day. These criteria allowed the development of many individual forecasting techniques or combination methods that are considered efficient in order to reduce errors. The development of new techniques, in turn, promotes questioning as the identification of how many or which techniques to combine individual forecasts. The literature is not unanimous when trying to answer these questions and indicates the importance of the correlation between forecast errors on the accuracy of the combination. That said, this presents an alternative to current methods of combining forecasts, considering the correlation between forecast errors, and propose a way to identify predictive techniques that are different about the modeling features of the data series. To identify groups of individual forecasting techniques that are similar, it was used the cluster analysis on errors generated by 15 forecasting techniques that shaped the same series of real data with trend and seasonality. The result indicated the formation of 3 clusters. As an alternative to current methods of combining forecasting and selecting the appropriate amount of techniques, it was used the Principal Component Analysis. The proposed method has proved feasible when compared to other methods of combining and when subjected to modeling of series with greater variability.

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