D’après le postulat de Hebb, les circuits neuronaux ajustent et modifient durablement leurs poids synaptiques en fonction des patrons de décharges de part et d’autre de la synapse. La « spike-timing-dependent plasticity » (STDP) est une règle d’apprentissage synaptique hebbienne dépendante de la séquence temporelle précise (de l’ordre de la milliseconde) des activités appariées des neurones pré- et post-synaptiques. Le striatum, le principal noyau d’entrée des ganglions de la base, reçoit des afférences excitatrices provenant du cortex cérébral et du thalamus dont les activités peuvent être concomitantes ou décalées dans le temps. Ainsi, l’encodage temporal des informations corticales et thalamiques via la STDP pourrait être crucial pour l’implication du striatum dans l’apprentissage procédural. Nous avons exploré les plasticités synaptiques cortico- et thalamo-striatales puis leurs interactions à travers le paradigme de la STDP. Les principaux résultats sont :1. Les « spike-timing-dependent plasticity » opposées cortico-striatales et thalamo-striatales induisent des plasticités hétérosynaptiques. Si la très grande majorité des études sont consacrées à la plasticité synaptique cortico-striatale, peu ont exploré les règles de plasticité synaptique aux synapses thalamo-striatale et leurs interactions avec la plasticité cortico-striatale. Nous avons étudié la STDP thalamo-striatale et comment les plasticités synaptiques thalamo- et cortico-striatales interagissent… / According to Hebbian postulate, neural circuits tune their synaptic weights depending on patterned firing of action potential on either side of the synapse. Spike-timing-dependent plasticity (STDP) is an experimental implementation of Hebbian plasticity that relies on the precise order and the millisecond timing of the paired activities in pre- and postsynaptic neurons. The striatum, the primary entrance to basal ganglia, integrates excitatory inputs from both cerebral cortex and thalamus whose activities can be concomitant or delayed. Thus, temporal coding of cortical and thalamic information via STDP paradigm may be crucial for the role of the striatum in procedural learning. Here, we explored cortico-striatal and thalamo-striatal synaptic plasticity and their interplay through STDP paradigm. The main results described here are:1. Opposing spike-timing dependent plasticity at cortical and thalamic inputs drive heterosynaptic plasticity in striatumIf the vast majority of the studies focused on cortico-striatal synaptic plasticity, much less is known about thalamo-striatal plasticity rules and their interplay with cortico-striatal plasticity. Here, we explored thalamo-striatal STDP and how thalamo-striatal and cortico-striatal synaptic plasticity interplay. a) While bidirectional and anti-Hebbian STDP was observed at cortico-striatal synapses, thalamo-striatal exhibited bidirectional and hebbian STDP...

As the mobile electronic products development are more and more popular such as mobile phone, digital camera, PDA¡Ketc. Each of company releases variable kind of mobile products, and every portable machine has plenty of functions. A low power consumption design is a significant issue which academics and engineers concern. It would be a major progress if the approach which can drop off the power consumption successfully. The mobile electronic products have more application programs than before and the size of LCD increases continuously, so that the power consumption becomes large. Therefore, expanding the life of battery would be a significant issue. Besides, the process technology has improved day by day, and it would influence the supply voltage be declined. It represents the power management would influence the power consumption of circuit directly. Comparing to drop down the entire IC power consumption and not to influence the performance of IC, the thesis employs the algorithm that searches the Critical Path and embeds the Level Converter Logic into digital circuit. It can offer the proper supply voltage to circuits which do not want to bigger supply voltage for reduce power consumption. However, the process variation (Inter-Die or Intra-Die) may transform the original Critical Path, the Critical Path which searches through the static timing analysis would not correct. To conquer this problem, the thesis provides the statistical approach to analysis timing. It would search Path Sensitivity which is exactly equal to the probability that a path is critical. Finally, the logic gate which is designed by us would replace the UMC 90nm standard cell through Cell-Based.

This dissertation reports on a new methodology to characterize and simulate a standard cell library to be used for statistical static timing analysis. A compact variation-aware timing model for a standard cell in a cell library has been developed. The model incorporates variations in the input waveform and loading, process parameters, and the environment into the cell timing model. Principal component analysis (PCA) has been used to form a compact model of a set of waveforms impacted by these sources of variation. Cell characterization involves determining equations describing how waveforms are transformed by a cell as a function of the input waveforms, process parameters, and the environment. Different versions of factorial designs and Latin hypercube sampling have been explored to model cells, and their complexity and accuracy have been compared. The models have been evaluated by calculating the delay of paths. The results demonstrate improved accuracy in comparison with table-based static timing analysis at comparable computational cost. Our methodology has been expanded to adapt to interconnect dominant circuits by including a resistive-capacitive load model. The results show the feasibility of using the new load model in our methodology. We have explored comprehensive accuracy improvement methods to tune the methodology for the best possible results. The following is a summary of the main contributions of this work to the statistical static timing analysis: (a) accurate waveform modeling for standard cells using statistical waveform models based on principal components; (b) compact performance modeling of standard cells using experimental design statistical techniques; and (c) variation-aware performance modeling of standard cells considering the effect of variation parameters on performance, where variation parameters include loading, waveform shape, process parameters (gate length and threshold voltage of NMOS and PMOS transistors), and environmental parameters (supply voltage and temperature); and (f) extending our methodology to support resistive-capacitive loads to be applicable to interconnect dominant circuits; and (e) classifying the sources of error for our variational waveform model and cell models and introducing of the related accuracy improvement methods; and (f) introducing our fast block-based variation-aware statistical dynamic timing analysis framework and showing that (i) using compiler-compiler techniques, we can generate our timing models, test benches, and data analysis for each circuit, which are compiled to machine-code to reduce the overhead of dynamic timing simulation, and (ii) using the simulation engine, we can perform statistical timing analysis to measure the performance distribution of a circuit using a high-level model for gate delay changes, which can be linked to their parameter variation.

Background Although trainers and athletes consider ‘good timing skills’ to be critical for optimal sport performance, little is known in regard to how sport-specific skills may benefit from timing training. Thus, assuming that all motor performances are mediated by an internal timing mechanism, enhanced motor timing is expected to have positive effects on both planning and execution of movement performance, and consequently on complex sports actions as golf or soccer. Accordingly, in order to increase our knowledge of the importance of motor timing and possible effects of timing training, this thesis examines the effects of synchronized metronome training (SMT), thought to improve the execution of motor programs and to enhance motor skills in golf and soccer players. Methods Study I examined the effects of SMT on motor timing abilities and its potential effect on golf shot accuracy and consistency in 25 experienced male golfers. Additionally, Study II examined the effects of SMT on the spatiotemporal movement organisation and dynamics of the golf swing performance, as captured by kinematic measurements and analyses in thirteen male golfers. Study III examined the effect of SMT on accuracy and variability in a soccer specific, cross-pass task in elite and sub-elite female soccer players. Moreover, the underlying brain activity was assessed by means of functional magnetic resonance imaging (fMRI) to investigate the corresponding neural activity when passively observing the cross-pass task, and the possible pre- to post training effects. Results SMT was shown to improve motor timing ability, by means of less timing asynchrony and with associated changes in timing variability, in both golf- and soccer-players. Additionally, significant improvements in golf shot and soccer cross-pass performance, by means of significant increase in outcome accuracy combined with a decrease in outcome variability was found. From the kinematic investigation in Study II, results indicate that improved motor timing, as an effect of SMT, lead to a more coordinated and dynamic swing performance, and with decreased variability in the temporal structure of the swing motion. Finally, it was found that SMT induces changes in the activity of the action observation network (AON), underpinning action observation and action prediction, by means of decreased activation within bilateral cerebellum, fusiform gyrus and superior temporal gyrus. These findings hint at a more efficient pattern of neural recruitment during action observation, after SMT. Conclusion In summary, this thesis provides evidence that four weeks of SMT improved the participant’s motor timing and synchronization abilities, and showed influence on both behavioral and neurophysiological motor programs and skill performance in golf and soccer players. Thus, by improved outcome accuracy and decreased variability, affecting the coordinated movement pattern and organisation, as well as affecting the associated underlying brain activation.

Le programme de réplication d’environ la moitié du génome des mammifères est caractérisé par des U/N-domaines de réplication de l’ordre du méga-base en taille. Ces domaines sont bordés par des origines de réplication maitresses (MaOris) correspondantes à des régions (~200 kb) de chromatine ouverte favorables à l’initiation précoce de la réplication et de la transcription. Grâce au développement récent de technologies à haut débit de capture de conformations des chromosomes (Hi-C), des matrices de fréquences de co-localisation 3D entre toutes les paires de loci sont désormais déterminées expérimentalement. Il est apparu que les U/N-domaines sont reliés à l’organisation du génome en unités structurelles. Dans cette thèse, nous avons effectué une analyse combinée de données de Hi-C de lignées cellulaires humaines et de profils de temps de réplication pour explorer davantage les relations structure/fonction dans le noyau. Cela nous a conduit à décrire de nouveaux domaines de réplication de grande tailles (>3 Mb) : les split-U-domaines aussi bordés par des MaOris; à démontrer que la vague de réplication initiée aux MaOris ne dépend que du temps pendant la phase S et de montrer que le repliement de la chromatine est compatible avec un modèle d’équilibre 3D pour les régions euchromatiniennes à réplication précoces et un modèle d’équilibre 2D pour les régions heterochromatiniennes à réplication tardives associées à la lamina nucléaire. En représentant les matrices de co-localisation issues du Hi-C en réseaux d’interactions structurelles et en déployant des outils de la théorie des graphes, nous avons aussi démontré que les MaOris sont des hubs interconnectés à longue portée dans le réseau structurel, fondamentaux pour l’organisation 3D du génome et nous avons développé une méthodologie multi-échelle basée sur les ondelettes sur graphes pour délimiter objectivement des unités structurelles à partir des données Hi-C. Ce travail nous permet de discuter de la relation entre les domaines de réplication et les unités structurelles entre les différentes lignées cellulaires humaines. / The replication program of about one half of mammalian genomes is characterized by megabase-sized replication U/N-domains. These domains are bordered by master replication origins (MaOris) corresponding to ~200 kb regions of open chromatin favorable for early initiation of replication and transcription. Thanks to recent high-throughput chromosome conformation capture technologies (Hi-C), 3D co-localization frequency matrices between all genome loci are now experimentally determined. It appeared that U/N-domains were related to the organization of the genome into structural units. In this thesis, we performed a combined analysis of human Hi-C data and replication timing profiles to further explore the structure/function relationships in the nucleus. This led us to describe novel large (>3 Mb) replication timing split-U domains also bordered by MaOris, to demonstrate that the replication wave initiated at MaOris only depends of the time during S phase and to show that chromatin folding is compatible with a 3D equilibrium in early-replicating euchromatin regions turning to a 2D equilibrium in the late-replicating heterochromatin regions associated to nuclear lamina. Representing Hi-C co-localization matrices as structural networks and deploying graph theoretical tools, we also demonstrated that MaOris are long-range interconnected hubs in the structural network, central to the 3D organization of the genome and we developed a novel multi-scale methodology based on graph wavelets to objectively delineate structural units from Hi-C data. This work allows us to discuss the relationship between replication domains and structural units across different human cell lines.

Cette thèse se compose de trois chapitres distincts. Dans le premier chapitre, nous examinons si les facteurs explicatifs de la maturité de la dette précédemment identifiés dans la littérature ont des impacts qui varient en fonction du niveau de maturité de la dette en mettant l'accent sur les cas extrêmes. Nous constatons que les effets des déterminants classiques varient sensiblement en fonction de la distribution de la maturité de la dette. Ces effets sont beaucoup plus faibles pour les percentiles les plus bas et les plus élevés. Cela indique que le risque de refinancement est beaucoup plus contraignant à très court terme et beaucoup moins à très long terme. En revanche, le fait d'avoir accès ou non au financement public accentue ce phénomène d'hétérogénéité de l'impact des déterminants en fonction du niveau de maturité de la dette. Ce dernier point peut s'expliquer par le fait que le risque de refinancement est beaucoup plus important pour les entreprises n'ayant pas accès au financement public. En résumé, nos résultats confirment notre intuition concernant les impacts hétérogènes des déterminants de la maturité de la dette en fonction du niveau de maturité de la dette et en particulier dans les cas extrêmes. Dans le deuxième chapitre, nous examinons les choix de la maturité de la dette des entreprises dans une perspective dynamique. Premièrement, nos résultats mettent en évidence des effets moutonniers. Aussi bien en termes de niveaux de la maturité de la dette qu'en termes de modifications de la maturité de la dette, les entreprises reproduisent le comportement des entreprises du même secteur. Ce comportement moutonnier explique beaucoup plus les variations de la maturité des dettes que les caractéristiques propres des entreprises. Après avoir éliminé l'impact des variations de la structure par terme des taux d'intérêt, ce comportement moutonnier en réponse aux modifications de la maturité de la dette des entreprises du même secteur est encore plus conséquent. Deuxièmement, nous constatons une persistance de niveaux de maturité de la dette dans le temps, notamment pour les entreprises ayant des maturités de la dette très faibles. Le troisième chapitre analyse l'impact du « market timing » sur la maturité de la dette. Nous affirmons que les grandes entreprises affichant des fondamentaux solides ont tendance à émettre des dettes à long terme plutôt qu'à court terme en cas de surévaluation temporaire des titres de ces entreprises. En particulier, pour ce type d'entreprises, l'effet du timing domine celui du comportement moutonnier pendant les périodes de refinancement important. Pour les petites entreprises dont les fondamentaux sont faibles, l'effet du « market timing » est faible, tandis que celui du comportement moutonnier est conséquent. / This dissertation is made of three distinct chapters. The first chapter investigates whether the effects of the previously identified factors vary along the debt maturity spectrum. Special emphasis is place on the extremely cases. Notably, we find that the effects of the conventional determinants vary substantially across the debt maturity distribution. Effect attenuation is observed at the lower and the higher debt maturity percentiles. The mechanism lies in the binding refinancing risk in the short extremes and the lessened refinancing risk in the long extremes. By contrast, the fact that a firm has access to public credit or not accentuates to a larger degree the heterogeneity in the observed effects of the included factors across the debt maturity distribution. This result can be explained by the argument that the refinancing risk is even more binding for firms without access to public credit. Altogether, our findings confirm our intuition concerning the heterogeneous effects of the conventional factors exerted along the debt maturity spectrum, especially for the extreme cases. In the second chapter, we examine debt maturity choices of firms from a dynamic perspective. Our results draw clear implications for a herding effect. Firms herd towards the levels as well as the changes of industry peers' debt maturities. Remarkably, this herding effect explains a much larger proportion of variation in debt maturity adjustment than firms' own characteristics. After eliminating the impact of changes in the yield curve, changes in peer firms' debt maturity policies drives debt maturity dynamics to a larger extent. Meanwhile, we find that debt maturity is persistent over time and that the persistence is primarily attributed to firms with short debt maturities. The third chapter analyzes the impact of market timing. We document that big firms with strong fundamentals attempt to “time” the issuance of long-term debts subsequent to temporary market mispricing. Particularly, for this type of firms, the effect of market timing dominates over that of herding during the periods firms raise large amounts of debts. For small firms with weak fundamentals, the effect of market timing is insignificant whereas the herding evidence is prominent.

The purpose of this study has been to examine the possible relationship between patterns on the stock market and the capital structure of IT-companies. Furthermore, the study attempts to contribute a deeper understanding of the ways Chief Financial Officers (CFO) and Chief Executive Officers (CEO) handle aspects pertaining to levels of debt, solidity, the market when making investment decisions and factors that influence a company´s value. This has been done using the Market Timing Hypothesis as the main theoretical frame of reference. The study has primarily been conducted using quantitative data analysis in the form of multiple regression. Qualitative interviews have been subsequently conducted with the purpose of enhancing the statistical findings. The results from the study indicate that financial decisions largely vary depending on the situation, albeit market value being an influencing factor. Moreover, the profitability of the company and the amount of fixed assets play a role in financial decisions. The respondents further noted that the amount of equity and debt of the company does affect its value. / Studiens syfte var att undersöka sambandet mellan aktiemarknadens fluktuationer och företag i IT-branschens val av kapitalstruktur. Även att söka en djupare förståelse genom att ta del av Chief Financial Officers (CFO) och Chief Executive Officers (CEO) perspektiv på skuldsättningsgrad, soliditet, aktiemarknadens rörelser vid kapitalplacering samt vad som påverkar ett företags värde. Detta har skett med Market timing hypotesen som teoretisk utgångspunkt. Den huvudsakliga undersökningsmetoden har bestått av en kvantitativ dataanalys i form av multipel regressionsanalys. Kvalitativa intervjuer har därefter utförts i syfte att komplettera datan och för att förtydliga hur dessa aspekter hanteras i den praktiska verkligheten. Resultaten från studien indikerar att finansieringsbeslut är högst situationsbetingade men att marknadsvärdet har en viss påverkan. Utöver detta visade sig lönsamhet och andel anläggningstillgångar i förhållande till totala tillgångar väga tungt. De respondenter som intervjuades menade även att mängden eget kapital och skuld ett företaget besitter påverkar dess värde.

De acordo com a teoria de market timing, as empresas aproveitam janelas de oportunidade para a captação de recursos, com a intenção de explorar flutuações temporárias no custo de fontes alternativas de financiamento. Assim, a estrutura de capital seria determinada por tentativas passadas de emitir títulos em momentos considerados favoráveis para a emissão. O presente trabalho teve por objetivo examinar o comportamento de market timing em companhias abertas brasileiras, buscando verificar a existência e persistência de um comportamento oportunista quando da escolha dentre diferentes fontes de financiamento. Para tanto, foram desenvolvidos dois estudos complementares. Primeiramente, investiga-se o comportamento de market timing por meio da análise da influência de valores de mercado históricos sobre a estrutura de capital de companhias brasileiras que realizaram IPO no período 2001-2011. Como principal resultado, verifica-se uma relação negativa entre valores de mercado históricos e alavancagem, evidenciando que, em momentos de altos valores de mercado, as empresas reduzem o endividamento, por ser mais vantajosa a emissão de ações, e vice-versa, o que pode indicar um comportamento oportunista na captação de recursos. No entanto, o comportamento não é permanente em todo o período, a ponto de determinar a estrutura de capital destas empresas. Assim, julgou-se necessário examinar diretamente os efeitos do market timing sobre a estrutura de capital de companhias brasileiras relacionando indicadores de custo de capital (próprio e de terceiros) com os níveis de endividamento destas companhias. Para tanto, foram utilizadas duas amostras: a primeira foi composta por 235 companhias abertas ativas na BM&FBOVESPA, analisadas no período 2000-2011; a segunda foi composta por 75 companhias abertas ativas e com ratings de crédito atribuídos pelas principais agências de classificação de risco, analisadas no período 2005-2011. Foram utilizadas quatro proxies para o custo de capital próprio, baseadas no Modelo de Precificação de Ativos Financeiros - CAPM, e duas proxies para o custo de capital de terceiros, sendo uma delas baseada no custo médio do passivo oneroso e a outra no rating de crédito das companhias, esta última testada apenas para a amostra 2. Os resultados obtidos com os modelos de dados em painel indicaram que quanto maior o custo de capital próprio, maior o nível de endividamento, bem como, quanto maior o custo de capital de terceiros, menor a utilização de dívida como fonte de financiamento. Estes resultados estão de acordo com o esperado pela teoria de market timing, refletindo que as empresas estão atentas ao custo de diferentes fontes de recursos, em busca das melhores alternativas de financiamento. Este comportamento se justifica e é confirmado por meio dos resultados obtidos: no primeiro estudo, verifica-se que o valor de mercado, em média, caiu após a abertura de capital, tornando indesejável a emissão de novas ações e preferível a utilização de dívida. No segundo estudo, verifica-se que as proxies para custo de capital se mostraram as variáveis mais significativas, exercendo forte influência sobre a estrutura de capital das empresas. Assim sendo, os resultados obtidos se complementam e levam à confirmação da tese proposta: o market timing influencia a estrutura de capital de companhias abertas brasileiras, sendo que as empresas aproveitam janelas de oportunidades para a captação de recursos para financiar seus projetos de investimento. / According to market timing theory, the companies use windows of opportunity to raise funds, aiming to explore temporary fluctuations in alternative sources of capital. Thus the capital structure would be determinate by past attempts to issue securities when security issue was considered propitious. The present thesis aimed to examine the market timing behavior in Brazilian public companies, trying to verify the existence and persistence of opportunistic behavior when choosing among different sources of capital. In order to do so, we developed two complementary studies. Firstly we investigate market timing behavior by analyzing the influence of historical market value on capital structure of Brazilian companies that performed IPO from 2001 to 2011. The main result was that there is a negative relation between historical market value and leverage, evidence shows that in moments of high market value, companies reduce indebtedness because equity issue is more advantageous and vice-versa, it might indicate an opportunistic behavior when raising funds. However, the behavior is not permanent throughout the period to determine the capital structure of these companies. Therefore, it was deemed necessary to directly examine market timing effects on capital structure of Brazilian companies matching cost of capital proxies (equity and debt) with indebtedness levels of these companies. In order to do so, we used two samples: the first was composed by 235 active public companies listed at BM&FBOVESPA that were analyzed from 2000 to 2011; the second was composed by 75 active public companies with credit ratings assigned by major credit rating agencies, they were analyzed from 2005 to 2011. Four proxies were used for cost of equity capital, based on Capital Asset Pricing Model - CAPM and two proxies for cost of debt, one of them was based on average cost of book value of debt and the other on credit rating of companies, the last was tested only for sample 2. The results found with panel data model show that the higher the cost of equity, the greater the level of indebtedness, as well as the higher the cost of debt, the less the use of debt as a financing source. These results are according to the expected by market timing theory, they reflect that the companies are aware of the cost of different financing sources in the search for the best financing alternatives. This behavior is justified and confirmed by the results reached: in the first study we can see that the market value, on average, dropped after the initial public offering making it undesirable to issuing equity and preferable to using debt. In the second study we verify that the proxies for cost of capital were the most significant variables, exerting strong influence on the capital structure of companies. Thus, the results obtained are complementary and lead to the confirmation of the proposed thesis: market timing has influence on the capital structure of Brazilian public companies, and in order to raise funds to finance their investment projects they use windows of opportunity.

Made available in DSpace on 2015-04-16T14:49:06Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1152474 bytes, checksum: 26700a7c34b11ab01884eb96bde9f8b1 (MD5) Previous issue date: 2013-01-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study aimed to analyze whether the market timing and stage of life cycle influence the decision to perform a Public Seasoned Equity Offerings (SEO) in Brazilian companies traded. The analysis focused on whether the probability of a company conduct a SEO is positively related to the index MB (market-to-book), size and stock returns and profitability prior to completion of SEO, and negatively related to the stage lifecycle, profitability and stock return after completion of SEO. Initially we sought to examine the influence of the index market-tobook and returns and future steps in conducting a SEO. dditionally, we sought to examine the influence of firm age and number of years listed in BMFBOVESPA in making an SEO. And, in parallel, we attempted to verify the relationship between SEO and realization of the variables size and profitability. The population consisted of all n-financial companies, publicly traded, with shares traded on the Bolsa de Valores de São Paulo - BM & FBOVESPA, in the period from 2002 to 2010. The model follows the methodology used by H. Deangelo, L. Deangelo and Stulz (2010). Analyzing whether there is a relationship between the logistics company conduct a SEO and variable rate market-to-book, stage of life cycle, past returns and future profitability and size. About the variables we can conclude that there is a relationship between the attainment of SEO content and market-to-book, firm size and profitability after the completion of SEO. The relationships of the variables expected market-to-book and size, were confirmed as positive, however the variable profitability after completion of SEO obtained a negative relationship, thus diverging from the expected. Therefore, hypotheses 1 and 5 of the thesis, that the probability of performing SEO is positively related to the index market-to-book and size, can not be rejected. Descriptive statistics already pointed in this direction, about 81% of the operations were performed by SEO companies that presented index market-to-book more than 1, which indicates some sort of recovery, and the largest proportion, about 55% of the achievements were made by companies that were with index greater than 2.10 MB. Regarding the size, descriptive statistics already presented a preliminary support when showed that most of the offers, about 51% were held by companies that met the range of values of total assets (14 <log assets <16). Furthermore, there were no evidences that confirm the relationship of the stage of the life cycle, the stock return both the previous and subsequent to the achievement of SEO, and the operational performance before and the day of the year with the decision of SEO conduct a public seasoned equity offerings. Although the stage of the life cycle has not been found statistically significant evidence that shows that the vast majority of SEO s, about 57% were held by companies with up to 20 of the constitution, these data are confirmed when we used years BM & FBOVESPA's listing as a proxy for alternative stage of the life cycle, about 79% of SEO s were made by companies that have up to 15 years of listing. Regarding the stock performance of the ANOVA tests indicated an average return of shares a year before the superior achievement in comparison with stock returns one year after the completion of the SEO and the average stock returns in the subsequent year, the SEO companies that made and the companies that did not perform, are equal. The results point toward in favor of market timing theory as an explanation for the conduct of bids, i.e., companies realized the SEO when its shares were valued by the market, taking advantage of the time factor. / Esta dissertação teve como objetivo analisar se o market timing e o estágio do ciclo de vida influenciam na decisão de realizar uma Oferta Pública de Distribuição de Ações Subsequentes (SEO) em empresas brasileiras de capital aberto. A análise se centrou em saber se a probabilidade de uma empresa realizar uma SEO está positivamente relacionada com o índice MB (market-to-book), tamanho e ao retorno acionário anterior à realização da SEO e negativamente relacionado ao estágio do ciclo de vida e ao retorno acionário posterior a realização da SEO. Inicialmente, buscou-se analisar a influência do índice market-to-book e dos retornos acionários passados e futuros na realização de uma SEO. Adicionalmente, procurou-se analisar a influência da idade da empresa e do número de anos listados na BM&FBOVESPA na realização de uma SEO e, paralelamente, verificar a relação entre a realização da SEO e a variável tamanho. A população foi composta por todas as empresas não-financeiras, de capital aberto, com ações negociadas na Bolsa de Valores de São Paulo BM&FBOVESPA, no período de 2002 a 2010. O modelo seguiu a metodologia utilizada por Deangelo, Deangelo e Stulz (2010), analisando se há uma relação logística entre a empresa realizar uma SEO e as variáveis índice market-to-book, estágio do ciclo de vida, retornos passados e futuros e tamanho. Quanto às variáveis, conclui-se que existe relação entre a realização da SEO, o índice market-to-book e o tamanho das empresas. As relações das varáveis market-to-book e tamanho foram positivas, como esperado. Diante disso, as hipóteses 1 e 5 da dissertação, de que a probabilidade de realização de SEO é positivamente relacionada ao índice market-to-book e tamanho, não podem ser rejeitadas. A estatística descritiva apontou que cerca de 81% das operações de SEO foram realizadas por empresas que apresentavam índice market-to-book superior a 1, o que indica algum tipo de valorização e a maior proporção. Cerca de 55% das realizações foram feitas por empresas que se encontravam com índice MB maior que 2,10. No tocante ao tamanho, a estatística descritiva também apresentou um suporte preliminar, quando evidenciou que cerca de 51% das ofertas, foram realizadas por empresas que se encontraram na faixa de valores do ativo total (14< log do ativo < 16). Por outro lado, não foram observadas evidências que confirmem a relação do estágio do ciclo de vida e retorno acionário, tanto no ano anterior quanto no ano subsequente à realização da SEO com a decisão de realizar uma oferta pública de distribuição de ações subsequente. Muito embora o estágio do ciclo de vida não tenha tido significância estatística, foram encontradas evidências, apontando que a grande maioria das SEO s, cerca de 57%, foram realizadas por empresas que possuem até 20 de constituição. Esses dados são corroborados, quando utilizou-se anos de listagem da BM&FBOVESPA como proxy alternativa para estágio do ciclo de vida. No tocante ao retorno acionário, observou-se uma média do retorno das ações de um ano antes da realização superior em comparação com os retornos das ações um ano após a realização da SEO e que as médias do retorno das ações no ano posterior das empresas que realizaram SEO e das empresas que não realizaram eram iguais. Em relação ao desempenho operacional, encontraram-se evidências de diferenças entre o ROA antes e após a realização da SEO e igualdade entre o ROA posterior de empresas emissoras e não-emissoras. Os resultados obtidos apontam na direção a favor da teoria do market timing como explicação para a realização de ofertas, ou seja, as empresas realizaram a SEO quando suas ações estavam valorizadas pelo mercado.

Neste trabalho abordamos o problema de programação de tarefas em um ambiente flow shop permutacional com mais de duas máquinas. Restringimos o estudo para o caso em que todas as tarefas têm uma data de entrega comum e restritiva, e onde o objetivo é minimizar a soma total dos adiantamentos e atrasos das tarefas em relação a tal data de entrega. É assumido também um ambiente estático e determinístico. Havendo soluções com o mesmo custo, preferimos aquelas que envolvem menos tempo de espera no buffer entre cada máquina. Devido à dificuldade de resolver o problema, mesmo para instâncias pequenas (o problema pertence à classe NP-difícil), apresentamos uma abordagem heurística para lidar com ele, a qual está baseada em busca local e faz uso de um algoritmo linear para atribuir datas de conclusão às tarefas na última máquina. Este algoritmo baseia-se em algumas propriedades analíticas inerentes às soluções ótimas. Além disso, foi desenvolvida uma formulação matemática do problema em programação linear inteira mista (PLIM) que vai permitir validar a eficácia da abordagem. Examinamos também o desempenho das heurísticas com testes padrões (benchmarks) e comparamos nossos resultados com outros obtidos na literatura. / In this work we approach the permutational flow shop scheduling problem with more than two machines. We restrict the study to the case where all the jobs have a common and restrictive due date, and where the objective is to minimize the total sum of the earliness and tardiness of jobs relative to the due date. A static and deterministic environment is also assumed. If there are solutions with the same cost, we prefer those that involve less buffer time between each machine. Due to the difficulty of solving the problem, even for small instances (the problem belongs to the NP-hard class), we present a heuristic approach to dealing with it, which is based on local search and makes use of a linear algorithm to assign conclusion times to the jobs on the last machine. This algorithm is based on some analytical properties inherent to optimal solutions. In addition, a mathematical formulation of the problem in mixed integer linear programming (MILP) was developed that will validate the effectiveness of the approach. We also examined the performance of our heuristics with benchmarks and compared our results with those obtained in the literature.