Worldwide, renewable energy systems are booming with reliable distributed generation (DG) technologies to help fuel increasing global energy consumption and mitigate the corresponding environmental problems. High cost and low efficiency are major problems for such systems using traditional buck inverters with line-frequency transformers. This thesis has proposed a novel single-phase single-stage buck-boost inverter suitable for cost-effective small DG systems. The inverter was analyzed from the angle of energy exchange and transfer with two current control schemes, DCM and CCM. Sinusoidal PWM (SPWM) control method, based on DCM, was discussed in details with steady state analyses, computer simulations, and laboratory tests. A concise model with underlying equations was derived to represent the physical behavior of proposed inverter. Closed-loop SPWM control was simulated and verified to have fast dynamic response and good tracking performance with robustness and insensitivity to dc input fluctuations, ac grid variations, and component parametric uncertainties. Other control strategies were also investigated from the critical DCM, CCM, or energy approach to either increase the fundamental output or further improve the performance. Comparisons demonstrated that SPWM was preferred control method with low output THD, reduced switching losses, and simple implementation. Therefore, it is concluded the proposed inverter provides a low-cost and high-efficient solution for small DG systems with low component count, minimal dc and ac filtering requirements, and improved performance.

As the rest of the world under development catches up economically with the developed nations, adoption of western tastes is projected to lead to enormous increases in energy use. Specifically, air conditioning use within countries with low saturation rates and high cooling degree rates (India and China) have a potential demand of up to 5 times that of the U.S. market. This growth in HVAC (Heating Ventilation&Air Conditioning) means billions of tons of increased carbon dioxide emissions and trillions of dollars in investment in electricity generation and transmission infrastructure.If there is adoption of Earth sheltering and integration design within these geographical areas, then it might be possible to mitigate the need for such high increase in electricity demand.Ultimately, an estimate of how much quantifiable impact wide adoption of earth integration can have in the regions in question needs to be calculated and compared to projected energy demand if things continue as they are. To do so, parameters need to be determined to see how much of the future air conditioning demand can be met through thermal mass/earth integration. That is, how much future energy demand can be avoided through earth sheltering? To do so:1-Determine what areas account for the greatest projected demand in future air conditioning use.2-See how much of the projected demand can be met through Thermal Mass and Earth Integration (T.M./E.I.) within these areas.3-A design/energy modeling exercise showing proper use and implementation of Earth sheltering within our local climate will be carried out to prove effectiveness of varied strategic thermal mass applications.4-Compare the relative savings of different levels of Earth Integration to arrive at an average overall savings if universal adoption takes place.Top-down approach to energy savings (HVAC efficiency) is not enough to offset projected adoption and its impact on the local and global environments. Energy efficient design is necessary to deal with as much of the increase in projected demand as possible. The use of earth as a building material can be a powerful tool in the fight against increasing energy demands and accompanied destructive environmental effects and needs greater consideration and adoption.

Há décadas a comunidade científica vem alertando sobre as mudanças climáticas e a necessidade de reduzir as emissões gases de efeito estufa. Sobre dois pilares fundamentais têm se sustentado a narrativa e as ações para enfrentar a crise ecológica global (a) na desmaterialização da economia usando tecnologias e processos cada mais eficientes (b) na descarbonização da economia usando fontes renováveis. Não obstante, os resultados gerais deste trabalho não encontraram evidência empírica de desmaterialização ou descarbonização da economia mundial. Partindo deste resultado em escala global, aprofundou-se a análise empírica ao nível individual de todas as economias do planeta. Os resultados encontrados indicam que em 4 economias com elevada renda e desenvolvimento tecnológico tem havido descasamento forte (strong decoupling) do uso de energia e das emissões de CO2. Porém, este resultado contrasta com evidências compiladas que apontam que o determinante principal deste descasamento está associado a um processo de desindustrialização destas economias e, concomitantemente, uma acelerada importação de mercadorias produzidas pelas indústrias da Ásia, especialmente a chinesa (energizada a carvão). Portanto, a julgar pela dominância fóssil passada e ainda vigente, não se vislumbra um cenário no curto e médio prazos, de ruptura abrupta entre crescimento econômico futuro e o uso de energia majoritariamente produzida com fósseis. O que está em curso é a gestação de uma futura transição energética alimentada pela introdução de fontes renováveis na matriz energética mundial nos últimos anos, mas com limitações socioeconômicas importantes que são descritas neste trabalho. É mostrado que América Latina pode ter um papel crucial nesta transição, com a industrialização e sinergia regional entre seus recursos naturais (tanto renováveis como não renováveis), sendo as reservas de lítio para produção de baterias um recurso estratégico para impulsionar a mobilidade elétrica. Além da importância socioambiental e política dos padrões analisados neste trabalho, é mostrada também a relevância teórica destes, pois permitem aprofundar o questionamento da representação ortodoxa das relações entre Economia e Natureza. / For decades the scientific community has been warning about climate change and the need to reduce greenhouse gas emissions. On two fundamental pillars have been supported the narrative and the actions to face the global ecological crisis (a) \'dematerialization\' of the economy using more efficient technologies and processes (b) decarbonization of the economy using renewable sources. Nevertheless, the overall results of this work did not find empirical evidence of dematerialization (strong decoupling) or decarbonization of the global economy. Starting from this result on a global scale, the empirical analysis was deepened including all the economies of the planet. Our findings are that in 4 high income and technological advanced economies are signs of strong decoupling between both energy use and CO2 emissions. However, these results contrasts with evidence in favor of a decoupling process associated with the deindustrialization of these economies. Simultaneously, the flux of imports produced by Asian industries, especially by coal-fired Chinese industries is increasing. Thus, judging by past and still prevailing fossil dominance, there is no indication of a short-medium term scenario with abrupt rupture between future economic growth and the use of energy (mostly produced with fossils). Currently, there is a global energy transition brewing, pushed by the efforts to insert renewable sources in the world energy matrix. However, important socioeconomic limitations described in this work remains. Latin America may be a crucial actor in the global energy transition, promoting the industrialization and synergy between natural resources (both renewable and non-renewable); being lithium reserves for the production of electric batteries one of the strategic resources to put forward the option of electric mobility. Besides the socioenvironmental and political importance of the results presented here, it was also highlight the theoretical relevance of these, since they allow to deepen in the debate about the orthodox representation of the relations between Economy and Nature.

Há décadas a comunidade científica vem alertando sobre as mudanças climáticas e a necessidade de reduzir as emissões gases de efeito estufa. Sobre dois pilares fundamentais têm se sustentado a narrativa e as ações para enfrentar a crise ecológica global (a) na desmaterialização da economia usando tecnologias e processos cada mais eficientes (b) na descarbonização da economia usando fontes renováveis. Não obstante, os resultados gerais deste trabalho não encontraram evidência empírica de desmaterialização ou descarbonização da economia mundial. Partindo deste resultado em escala global, aprofundou-se a análise empírica ao nível individual de todas as economias do planeta. Os resultados encontrados indicam que em 4 economias com elevada renda e desenvolvimento tecnológico tem havido descasamento forte (strong decoupling) do uso de energia e das emissões de CO2. Porém, este resultado contrasta com evidências compiladas que apontam que o determinante principal deste descasamento está associado a um processo de desindustrialização destas economias e, concomitantemente, uma acelerada importação de mercadorias produzidas pelas indústrias da Ásia, especialmente a chinesa (energizada a carvão). Portanto, a julgar pela dominância fóssil passada e ainda vigente, não se vislumbra um cenário no curto e médio prazos, de ruptura abrupta entre crescimento econômico futuro e o uso de energia majoritariamente produzida com fósseis. O que está em curso é a gestação de uma futura transição energética alimentada pela introdução de fontes renováveis na matriz energética mundial nos últimos anos, mas com limitações socioeconômicas importantes que são descritas neste trabalho. É mostrado que América Latina pode ter um papel crucial nesta transição, com a industrialização e sinergia regional entre seus recursos naturais (tanto renováveis como não renováveis), sendo as reservas de lítio para produção de baterias um recurso estratégico para impulsionar a mobilidade elétrica. Além da importância socioambiental e política dos padrões analisados neste trabalho, é mostrada também a relevância teórica destes, pois permitem aprofundar o questionamento da representação ortodoxa das relações entre Economia e Natureza. / For decades the scientific community has been warning about climate change and the need to reduce greenhouse gas emissions. On two fundamental pillars have been supported the narrative and the actions to face the global ecological crisis (a) \'dematerialization\' of the economy using more efficient technologies and processes (b) decarbonization of the economy using renewable sources. Nevertheless, the overall results of this work did not find empirical evidence of dematerialization (strong decoupling) or decarbonization of the global economy. Starting from this result on a global scale, the empirical analysis was deepened including all the economies of the planet. Our findings are that in 4 high income and technological advanced economies are signs of strong decoupling between both energy use and CO2 emissions. However, these results contrasts with evidence in favor of a decoupling process associated with the deindustrialization of these economies. Simultaneously, the flux of imports produced by Asian industries, especially by coal-fired Chinese industries is increasing. Thus, judging by past and still prevailing fossil dominance, there is no indication of a short-medium term scenario with abrupt rupture between future economic growth and the use of energy (mostly produced with fossils). Currently, there is a global energy transition brewing, pushed by the efforts to insert renewable sources in the world energy matrix. However, important socioeconomic limitations described in this work remains. Latin America may be a crucial actor in the global energy transition, promoting the industrialization and synergy between natural resources (both renewable and non-renewable); being lithium reserves for the production of electric batteries one of the strategic resources to put forward the option of electric mobility. Besides the socioenvironmental and political importance of the results presented here, it was also highlight the theoretical relevance of these, since they allow to deepen in the debate about the orthodox representation of the relations between Economy and Nature.

Spray Drying é um processo de secagem por atomização em uma câmara fechada, que visa retirar a umidade de um produto por transferência de calor e massa de água contida no produto para o ar que é previamente aquecido neste processo. Este trabalho apresenta um estudo de caso para uma indústria que produz aditivos alimentícios. O ar de entrada pode chegar à câmara com alta umidade proveniente da atmosfera, neste caso, haverá mais consumo de energia de acordo com as estações do ano. Esta pesquisa promove um estudo do processo atual, através da instalação de um equipamento de pré-desumidificação no ar de entrada do processo e mostra diferentes sistemas de desumidificação: por refrigeração e por adsorção, comparando os desempenhos sob o ponto de vista energético, ambiental e econômico com sistema original. Os objetivos deste estudo são analisar a capacidade de remoção de umidade de cada dispositivo de desumidificação, a influência de cada dispositivo e a variação da umidade do ar de entrada no processo, bem como o impacto econômico e ambiental de cada equipamento no sistema global. Além disso, promove o aumento do gradiente de umidade entre o ar de entrada e do produto otimizando o processo de secagem, aumentando a eficiência energética global do sistema e reduzindo o impacto ambiental. / Spray drying is a dehumidification process by atomization in a closed chamber that aims to remove moisture of a product by heat and mass transfer from the contained water in the product to the air which is previously heated in this process. This paper presents a case study for an industry that produces food ingredients. The inlet air can reach the chamber with high moisture from the atmosphere condition requesting, in this case, more energy consumption according to the seasons of the year. This paper promotes a study of the current process through the installation of a pre-dehumidification device of the inlet air and shows different dehumidification systems: The refrigeration and the adsorption and comparing their performance in an energetic, environmental and economic point of view. The goals of this study are to analyze the capacity of moisture removing of each dehumidification device, the influence of moisture variation of the inlet air in the process as well as the economic impact of each device in the global system. Moreover, it promotes the increasing of moisture gradient between the inlet air and the product optimizing the drying process, increasing the global energy efficiency in the global system and reducing environmental impact.

Net energy exporting countries (NEECs) and net energy importing countries (NEICs) depend on each other for mutual gains. However, NEICs pursue strategic policies to reduce consumption of energy from conventional sources and increase that of renewable energy in order to attain energy security and macro environmental and carbon accountability. On the other hand, NEECs such as Nigeria depend heavily on oil and gas exports to NEICs to generate revenue. As a result of this inter-dependent relationship, this PhD project adopts a dependency theory and strategic issue analysis framework to underpin the study. Accordingly, the study approach is founded on the ideas of pluralism as a social reality and adopted pragmatism as the research approach. Consistent with these approaches, the study was undertaken by analysing both secondary and primary data, including macro-economic statistics of annual time-series dataset (1980-2014) and semi-structured interviews respectively. The quantitative part of the project used Auto Regressive Distributed Lag (ARDL) Bounds testing approach. This method was used to investigate and analyse the effect of renewable energy consumption and carbon emissions reduction on Nigeria’s oil and gas exports. The qualitative part involved interviews with twenty senior government officials in Nigeria from six selected Federal Ministries, Departments and Agencies (MDAs), representatives of civil society groups and academicians, to support the quantitative results and answer certain research questions. The short-run quantitative results and qualitative findings show that renewable energy consumption in developed NEICs affects Nigeria’s oil and gas exports. However, the reverse holds true for emerging NEICs. Both the quantitative results and the qualitative findings show that carbon emissions reduction in developed NEICs affects Nigerian oil and gas exports in the long run. Also, the quantitative results show that renewable energy consumption in developed and emerging NEICs does not affect Nigerian oil and gas exports in the long run. However, the qualitative findings only support the quantitative results for emerging NEICs but do not support those of developed NEICs. Similarly, the qualitative findings indicate that other external and internal factors such as discovery of shale oil and gas; improvement in energy efficient technologies; the use of long-term contract in other NEECs; stringent nature of the Nigerian Content Law and lack of passage of the Petroleum Industry Bill amongst others currently contribute in affecting Nigeria’s oil and gas exports. Moreover, the qualitative findings show that global energy transition has an impact on the Nigeria’s oil and gas revenue, savings made to the Nigerian Sovereign Wealth Fund, budget financing and will continue to affect Nigerian revenue and budget if the economy remains undiversified. Finally, the qualitative findings indicate that global energy transition has negatively affected Foreign Direct Investment flow into Nigerian petroleum industry and discoveries of new oil and gas reserves. These findings have several implications. Firstly, Nigerian oil and gas exports are affected by the carbon emissions control regime, which makes future oil and gas revenues uncertain; thereby putting pressure on budget financing and socio-economic growth and development. On this note, there is the need for Nigeria to take cautionary position in the global climate change debate in order not to adversely affect the country’s economic interest. Secondly, the consumption of energy from renewable sources in both developed and emerging NEICs is an opportunity for Nigeria to export not only its conventional energy but also renewable energy if commercially harnessed. This suggests that Nigerian should also invest heavily in renewable energy production. Thirdly, the major findings of this study provide evidence in support of the relevance of dependency theory and strategic issue analysis framework within the context of energy transition in NEICs on one hand, and Nigerian oil and gas exports to these countries on the other. This implies the need for Nigeria to focus on developing internal market trajectories to increase domestic utilisation of its conventional energy rather than being dependent on external markets for the sale of the nation’s energy resources.

Voice analysis is an important tool in the diagnosis of laryngeal disorders. Among distinct signal processing techniques employed for voice analysis, the spectrogram is commonly used, as it allows for a visualization of the variation of the energy of the signal as a function of the both time and frequency. In this context, this study investigates the use of the global energy of the voice signal, estimated through the spectrogram, as a tool for discrimination between signals obtained from healthy and pathological subjects. This research has also exploited the potential use of the global energy of the voice signal to discriminate distinct laryngeal disorders. In total, 94 subjets were involved in this study, from which 46 were dysphonic and 48 normal. The diagnosis of laryngeal disorders was confirmed by means of a videolaryngoscopic examination. Participants were also subjected to a clinical examination of vocal acoustic through the recording of the sustained vowel. The global energy allowed for the discrimination between normal and disphonic voice. Furthermore, this technique could discriminate the voice signal of patients suffering from left vocal fold paralysis from those suffering from other investigated disorders. The results suggest the global energy of the signal as an auxiliary and alternative tool for the diagnosis between normal and dysphonic voice. / A análise do sinal de voz é uma ferramenta importante no diagnóstico dos distúrbios laríngeos. Dentre as diversas técnicas para o processamento da voz destaca-se o espectrograma por permitir uma visualização da variação da energia do sinal em função do tempo e freqüência. Neste contexto, esta pesquisa investiga a energia global do sinal de voz, estimada a partir do espectrograma, como ferramenta capaz de discriminar esses sinais, obtidos de pacientes com diferentes doenças, daqueles coletados de sujeitos saudáveis. O estudo ainda verifica a possibilidade do uso da energia global na discriminação de distúrbios laríngeos. No total 94 indivíduos participaram desse estudo, sendo 46 disfônicos e 48 eufônicos. Inicialmente os sujeitos foram submetidos a um exame de videolaringoscopia para a determinaçãoção do diagnóstico. Posteriormente eles foram submetidos a um exame clínico de análise acústica vocal por meio da gravação da vogal sustentada. Utilizando a energia global foi possível discriminar as vozes normais das vozes disfônicas. Por meio da energia global foi possível ainda separar as vozes de pacientes portadores de paralisia da prega vocal esquerda de todas as outras doenças laríngeas investigadas. Podemos sugerir a energia global da voz como uma ferramenta auxiliar no diagnóstico diferencial entre vozes normais e disfônicas. / Mestre em Ciências

Yes / Endowed with a significant proportion of the world’s petroleum and solid mineral resources, Africa is the location of a vibrant and dynamic extractive industries sector, which today, is its chief economic mainstay. The revenue generated from the extractive industries has been a significant source of finance for public infrastructure development and investments in education, health and the development of other economic sectors across the continent. However, the African extractive industries have faced massive setbacks in recent years, in particular due to the economic disruptions caused by the coronavirus (COVID-19) pandemic, and the global transition to a low carbon economy that has formed a central part of ongoing efforts to respond to the climate change emergency. These challenges have accentuated concerns on the current and future relevance of the African extractive industries in a low-carbon economy world order. This article examines the role played by the African extractive industries in the global energy transition, contextualising these concerns against a continuum of disruption arising as a consequence of the COVID-19 pandemic and emergent efforts to redress the crisis posed by anthropogenic climate change. If well managed, extractive resources could play a crucial role in advancing energy security and transition in the African continent in the face of these challenges. In addition to its role in addressing current high levels of energy poverty across Africa in this disruptive setting, environmentally-responsible production of extractive resources can help sustain economic and social development across Africa in going forward. This article examines the current opportunities and challenges for cleaner and environmentally-responsible extractive investments in Africa in a low carbon world. It analyses the preconditions and barriers to environmentally-responsible fossil fuels developments in Africa and highlights the key considerations for African policymakers. Its analysis is informed by recognition of, and sensitivity towards, the extreme disruption to fossil fuel governance embodied by the twin concerns of the COVID-19 pandemic and the current “climate emergency.” Through a qualitative analysis, this research has found that if well-managed, African resource-rich countries could utilise the revenues from the extractive industries to invest in low carbon technologies.

全球能源消費大國之中，日本的低能源蘊藏量以及高能源利用率常引起多方研究。本文從蒐集並整理日本戰後至2011年間的能源政策、比較311前後兩個執政黨（民主黨、自民黨）的能源政策立場，到探究日本於311後能源政策轉折的方向及原因、並且進一步推敲出日本的能源治理模式。因此發現，日本在二戰之後就開始運用一系列的政策手段與能源市場干預途徑，突破低能源蘊藏量之先天不利條件，達到高能源利用率之後天技術優勢所創造的經濟成長。而當日本經歷2011年3月11日東日本大震災後，政府更強烈介入能源市場，希望進行能源結構的轉型，使得日本得以維持能源高自主率與溫室氣體低排放率的目標。本文因此結論，日本雖然身為能源匱乏國，但是它的能源政策充分體現出了國家介入能源市場由上而下治理模式的特性，使得日本得以突破能源約束，在諸多能源不利之條件下開創了近半世紀的經濟高度發展期。此外，本文亦結論日本於全球能源治理的角色可以歸納為三：（1）全球溫室氣體減量暨全球能源安全提升的追隨者；（2）區域性能源合作的示範者；（3）全球核能安全建立的示範者等三種角色。 / Japan is noted for its low energy endowment but high energy efficiency among the global top energy consuming nations. In this study, collection of the past Japanese energy policies from 1945 to 2011, comparison of the political stances on the energy strategies between the two Japanese ruling parties, Liberal Democratic Party and The Democratic Party, and investigation on factors causing a change of Japan’s energy policy post Fukushima contributed to outlining the pattern of Japan’s energy governance. This study found that Japan’s intervening in its the post-war domestic energy market by means of a string of policy instruments has successfully made Japan overcome the predicament of high energy demands out of low energy reserves, further achieve the edge of high energy efficiency, and therefore create its outstanding economic growth. Nevertheless, after experiencing another energy predicament post Fukushima, Japan made more effort on the intervention into its energy market to transform its domestic energy consumption structure with a view to maintaining high energy self-sufficient rates and low GHGs emissions. To conclude, although Japan is a nation of insufficient energy resources, its energy policies reveal the trait that the state intervenes in the energy market by the top-down governance approach to make its way to break through the energy constraints, creating a nearly half-century’s economic prosperity. Besides, we also conclude that Japan plays three major roles in the domain of global energy governance: 1. a follower of global GHGs emission abatement and global energy security enhancement, 2. a demonstrator on regional energy cooperation and, 3. a model of building global nuclear power safety.

Une vidéo est une source particulièrement riche en informations. Parmi tous les objets que nous pouvons y trouver, les visages humains sont assurément les plus saillants, ceux qui attirent le plus l’attention des spectateurs. Considérons une séquence vidéo dont chaque trame contient un ou plusieurs visages en mouvement. Ils peuvent appartenir à des personnes connues ou qui apparaissent de manière récurrente dans la vidéo Cette thèse a pour but de créer une méthodologie afin d’extraire une ou plusieurs images de visage en vue d’appliquer, par la suite, un algorithme de reconnaissance du visage. La principale hypothèse de cette thèse réside dans le fait que certains exemplaires d’un visage sont meilleurs que d’autres en vue de sa reconnaissance. Un visage est un objet 3D non rigide projeté sur un plan pour obtenir une image. Ainsi, en fonction de la position relative de l’objectif par rapport au visage, l’apparence de ce dernier change. Considérant les études sur la reconnaissance de visages, on peut supposer que les exemplaires d’un visage, les mieux reconnus sont ceux de face. Afin d’extraire les exemplaires les plus frontaux possibles, nous devons d’une part estimer la pose de ce visage. D’autre part, il est essentiel de pouvoir suivre le visage tout au long de la séquence. Faute de quoi, extraire des exemplaires représentatifs d’un visage perd tout son sens. Les travaux de cette thèse présentent trois parties majeures. Dans un premier temps, lorsqu’un visage est détecté dans une séquence, nous cherchons à extraire position et taille des yeux, du nez et de la bouche. Notre approche se base sur la création de cartes d’énergie locale principalement à direction horizontale. Dans un second temps, nous estimons la pose du visage en utilisant notamment les positions relatives des éléments que nous avons extraits. Un visage 3D a trois degrés de liberté : le roulis, le lacet et le tangage. Le roulis est estimé grâce à la maximisation d’une fonction d’énergie horizontale globale au visage. Il correspond à la rotation qui s’effectue parallèlement au plan de l’image. Il est donc possible de le corriger pour qu’il soit nul, contrairement aux autres rotations. Enfin, nous proposons un algorithme de suivi de visage basé sur le suivi des yeux dans une séquence vidéo. Ce suivi repose sur la maximisation de la corrélation des cartes d’énergie binarisées ainsi que sur le suivi des éléments connexes de cette carte binaire. L’ensemble de ces trois méthodes permet alors tout d’abord d’évaluer la pose d’un visage qui se trouve dans une trame donnée puis de lier tous les visages d’une même personne dans une séquence vidéo, pour finalement extraire plusieurs exemplaires de ce visage afin de les soumettre à un algorithme de reconnaissance du visage. / The aim of this thesis is to create a methodology in order to extract one or a few representative face images of a video sequence with a view to apply a face recognition algorithm. A video is a media particularly rich. Among all the objects present in the video, human faces are, for sure, the most salient objects. Let us consider a video sequence where each frame contains a face of the same person. The primary assumption of this thesis is that some samples of this face are better than the others in terms of face recognition. A face is a non-rigid 3D object that is projected on a plan to form an image. Hence, the face appearance changes according to the relative positions of the camera and the face. Many works in the field of face recognition require faces as frontal as possible. To extract the most frontal face samples, on the one hand, we have to estimate the head pose. On the other hand, tracking the face is also essential. Otherwise, extraction representative face samples are senseless. This thesis contains three main parts. First, once a face has been detected in a sequence, we try to extract the positions and sizes of the eyes, the nose and the mouth. Our approach is based on local energy maps mainly with a horizontal direction. In the second part, we estimate the head pose using the relative positions and sizes of the salient elements detected in the first part. A 3D face has 3 degrees of freedom: the roll, the yaw and the pitch. The roll is estimated by the maximization of a global energy function computed on the whole face. Since this roll corresponds to the rotation which is parallel to the image plan, it is possible to correct it to have a null roll value face, contrary to other rotations. In the last part, we propose a face tracking algorithm based on the tracking of the region containing both eyes. This tracking is based on the maximization of a similarity measure between two consecutive frames. Therefore, we are able to estimate the pose of the face present in a video frame, then we are also able to link all the faces of the same person in a video sequence. Finally, we can extract several samples of this face in order to apply a face recognition algorithm on them.