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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.
331

Auto-adaptation appliquée à un dispositif de mesure de variation de pression intra-oculaire / Self-adaptation applied to an intra-ocular pressure variation measurement device

Deluthault, Anthony 05 July 2017 (has links)
La combinaison des avancées médicales et technologiques a rendu possible le monitoring à distance des patients, introduisant le paradigme de la e-santé (e-health en anglais). Il comprend des services ou des systèmes de convergence de la médecine, la santé et l’information, avec l’e-surveillance et la télé-médecine. Le type de dispositif médical "healthcare" doit assurer une sûreté de fonctionnement optimale, que ce soit pour une analyse médicale ou l’application d’un traitement. Le niveau de sûreté et de performance est critique pour la santé du patient.Maintenant que ces dispositifs s’appliquent à un nombre croissant de patients, tous différents et vivant dans des conditions différentes, ils doivent être capables de s’adapter en termes de performances et s’adapter à l’activité, à l’environnement et au patient lui-même. Une stratégie globale et réutilisable d’auto-adaptation à été définie dans le but de mettre en place méthodiquement et de façon optimale le processus et les étapes de l’auto-adaptation. Une des pathologies importantes actuellement est le glaucome, une neuropathie oculaire détériorant le nerf optique induisant une perte du champ visuel progressive et irréversible. Le diagnostique et le suivi de cette pathologie se fait par une mesure de la Pression Intra-Oculaire(PIO). La méthode utilisée actuellement est contraignante et requière la manipulation experte d’un dispositif de mesure ponctuelle. De nouveaux capteurs biométriques ont vu le jour permettant une mesure continue et portable amenant un meilleur diagnostic ainsi qu’un suivi plus simple. Notre cas d’étude sera donc centré sur l’utilisation d’un capteur biométrique de mesure de la PIO qui servira de plate-forme de validation aux solutions proposées sachant qu’il devra être auto-adapté aux différentes anatomies, physiologies, biomécaniques et environnements du patient. Tous les indicateurs perturbateurs ou informateurs de la mesure sont regroupés en deux catégories, ceux liés à l’environnement et ceux liés aux conditions d’utilisation. Un état de l’art est proposé pour la première catégorie et un modèle analytique est proposé pour la deuxième. L’état de l’art montre que les expérimentations in vivo sont nécessaires pour compléter les connaissances sur les indicateurs majeurs dans le cas d’une mesure de la PIO faite par un capteur biométrique. Le modèle analytique inclut le couplage électromagnétique entre les deux antennes du capteur, ainsi que des phénomènes perturbateurs. Il suggère de nouveaux indicateurs indirects (Pente de la baseline et le coefficient du second ordre de la courbe de phase) pour l’adaptation aux phénomènes perturbateurs. / Thanks to the combination of medical and technological advances, it becomes feasible and relevant to operate remotely monitoring of patients, introducing e-health paradigm. It includes services or systems that are at the convergence of medicine, health and information, including e-monitoring and telemedicine. Among existing medical devices, the "healthcare" type must ensure optimum operational reliability whether it is for a medical analysis or a treatment’s application. The level of safety and performance are critical for the patient’s health. Since these devices apply to a growing number of patients, all different from each other and living under different conditions, the device must therefore be able to adapt it self to the patient’s needs, activity, his environment but also to the patient himself. A general reusable strategy of self-adaptation, aiming to define methodically and optimally the steps and processes of self-adaptation, have been defines. Diseases recognized as being of the current centuries diseases require regular medical follow. Among them is glaucoma, an ocular neuropathy that deteriorates the optic nerve leading to a progressive and irreversible loss of the vision field. To diagnose and monitor it, a measurement of the intraocular pressure (IOP) is mandatory. Current techniques are constraining and require the manipulation of punctual measurement tools by a doctor. New biometric devices have emerged allowing continuous and portable measurements to allow a better diagnostic and a simplified monitoring. Our case study will therefore rely on the use of a biometric IOP measurement device which will be used as a validation platform for the proposed solutions knowing that it must be self-adapted to the different anatomies, physiologioes, biomechanics and environments of the patient. All the disturbing or informative mesurement indicators are regrouped in two types, the environmental and the variability in operation. A state of the art is proposed for the first type and an analytical model for the second one. The state of the art shows that In-vivo experimentations are mandatory to complete the knwoledge of major indicator influencing the IOP measurement with a biometric sensor. The analytical model include the magnetic coupling between antennas and the impact of some disturbances. It suggests a new ideal indirect indicator (the slope of the baseline and second coefficient order of the Bode phase plot) for the disturbances adaptation. This model is valid for sensors with different dimensions of antennas.
332

Autentisiering av användare i datoriserade miljöer hos SMF - biometri kontra tokens : En jämförelse av två sätt att implementera autentisering av användare / Authentication of users in computerized environments at SME - biometrics versus tokens : A comparison of two ways to implement authentication of users

Hedberg, David January 2020 (has links)
Allt eftersom mer och mer information sparas på datorer så ökar även trycket på att denna information sparas säkert, och att endast behöriga personer kommer åt den.Syftet med arbetet var att se vilka skillnader som finns mellan biometri och tokens, och vilka skillnader som små till medelstora företag borde ta i beaktande när de väljer en autentiseringsmetod. Det förväntade resultatet var då en beskrivning, i form av ett ramverk, över vilka för- och nackdelar som finns med de två metoderna, och således vilken metod som ett enskilt företag som använder ramverket borde använda sig utav.Arbetet genomfördes via en litteraturstudie, i vilket tre databaser användes för att samla information. IEEEXplore, ACM Digital Library, och ScienceDirect var de tre databaser som användes för arbetet. I dessa identifierades ett antal artiklar, som delades upp i kodade kategorier utefter innehåll. Detta i syfte att utföra en tematisk kodad analys.Totalt identifierades 28 artiklar i de olika databaserna. I dessa artiklar identifierades kostnad, säkerhet, integritet, och användarvänlighet som några av de mesta omtalade ämnena. 7 utav de 28 artiklarna pratade om kostnad, 20 av artiklarna nämnde säkerhet, 5 nämnde integritet, och 9 pratade om användarvänlighet. Det fanns även ett antal mindre teman i tvåfaktorsautentisering, skalbarhet, typer av biometri, typer av tokens, och framtida teknologi inom biometri.Efter genomförd analys formulerades ett ramverk i vilket ett smått till medelstort företag kan se vilken metod av autentisering som passar deras företag bäst. / As technology evolves, corporations and enterprises are forced to evolve alongside it. Storing company information and data on servers and computers have become common practice.Initially, the goal with the work presented was to compare biometric authentication and token authentication in relation so SMEs. In the current landscape there is no comprehensive study in these two methods of authentication in relation to SMEs. A framework was developed for system administrators to use when choosing one of these methods of authentication. The framework is a summarization of the works analytical part.A literature study was conducted to reach the goal. Three databases were used as sources of information. These three were namely IEEEXplore, ACM Digital Library, and ScienceDirect. From these sources, literature was identified on which the study was then based. Thematic coding was used to analyze the collected data.After the process of collecting and including/excluding was complete, a total of 28 articles remained. From these articles a total of 10 themes were identified from the thematic coding. These themes were cost, integrity, usability, security pros, security cons, two-factor authentication, scalability, biometric types, token types, and future biometric technology. Four of these were more prevalent, namely cost, integrity, usability, and security.After the analysis was finished the themes that emerged as important were integrity and usability. Because of this, the framework is heavily influenced by these themes and they are particularly important for system administrators to consider.
333

Les processus métiers en tant que services - BPaaS : sécurisation des données et des services / Business process as a service - BPaaS : securing data and services

Bentounsi, Mohamed el Mehdi 14 September 2015 (has links)
Malgré les avantages économiques de l’informatique en nuage (ou cloud computing) pour les entreprises et ses multiples applications envisagées, il subsiste encore des obstacles pour son adoption à grande échelle. La sécurité des données sauvegardées et traitées dans le nuage arrive en tête des préoccupations des décideurs des directions des systèmes d'information. De ce fait, l'objectif principal de nos travaux de recherche lors de cette thèse de doctorat est de poser des bases solides pour une utilisation sûre et sécurisée du nuage. Dans un premier lieu, l’externalisation des processus métiers vers le nuage permet aux entreprises de réduire les couts d’investissement et de maitriser les couts d’exploitation de leurs systèmes d’information ; Elle permet aussi de promouvoir la réutilisation des parties (ou fragments) de ses processus métiers en tant que service cloud, éventuellement par des concurrents directs, afin de faciliter le développement de nouvelles applications orientés services ‘SOA’, ainsi la collaboration à l’échelle du nuage. Néanmoins, le fait de révéler la provenance d’un fragment réutilisé est considérée comme une brèche dans la vie privée et risque d’être dommageable pour l’entreprise propriétaire de ce fragment. Les techniques d’anonymisation des données ont fait leurs preuves dans le domaine des bases de données. Notre principale contribution dans cette partie est la proposition d’un protocole basée sur l’anonymisation des fragments de processus métiers afin de garantir à la fois, la vie privée de leurs propriétaires et la disponibilité de ces fragments pouvant être réutilisés dans le nuage. Les systèmes d’authentification biométriques permettent une authentification des individus avec une garantit suffisante. Néanmoins, le besoin en ressources informatiques ‘calcul et stockage’ de ces systèmes et le manque de compétences au sein des organismes freinent considérablement leurs utilisations à grande échelle. Le nuage offre la possibilité d’externaliser à la fois le calcul et le stockage des données biométriques à moindre cout et de proposer une authentification biométrique en tant que service. Aussi, l’élasticité du nuage permet de répondre aux pics des demandes d’authentifications aux heures de pointes. Cependant, des problèmes de sécurité et de confidentialité des données biométriques sensibles se posent, et par conséquent doivent être traité afin de convaincre les institutions et organismes à utiliser des fragments externes d'authentification biométriques dans leurs processus métiers. Notre principale contribution dans cette partie est un protocole léger ‘coté client’ pour une externalisation (sur un server distant) de la comparaison des données biométriques sans révéler des informations qui faciliteraient une usurpation d’identité par des adversaires. Le protocole utilise une cryptographie légère basée sur des algorithmes de hachage et la méthode de 'groupe de tests combinatoires', permettant une comparaison approximative entre deux données biométriques. Dans la dernière partie, nous avons proposé un protocole sécurisé permettant la mutualisation d’un Hyperviseur (Outil permettant la corrélation et la gestion des événements issus du SI) hébergé dans le nuage entre plusieurs utilisateurs. La solution proposée utilise à la fois, le chiffrement homomorphique et la réécriture de règles de corrélation afin de garantir la confidentialité les évènements provenant des SI des différents utilisateurs. Cette thèse a été réalisée à l'Université Paris Descartes (groupe de recherche diNo du LIPADE) avec le soutien de la société SOMONE et l'ANRT dans le cadre d'une convention CIFRE. / Cloud computing has become one of the fastest growing segments of the IT industry. In such open distributed computing environments, security is of paramount concern. This thesis aims at developing protocols and techniques for private and reliable outsourcing of design and compute-intensive tasks on cloud computing infrastructures. The thesis enables clients with limited processing capabilities to use the dynamic, cost-effective and powerful cloud computing resources, while having guarantees that their confidential data and services, and the results of their computations, will not be compromised by untrusted cloud service providers. The thesis contributes to the general area of cloud computing security by working in three directions. First, the design by selection is a new capability that permits the design of business processes by reusing some fragments in the cloud. For this purpose, we propose an anonymization-based protocol to secure the design of business processes by hiding the provenance of reused fragments. Second, we study two di_erent cases of fragments' sharing : biometric authentication and complex event processing. For this purpose, we propose techniques where the client would only do work which is linear in the size of its inputs, and the cloud bears all of the super-linear computational burden. Moreover, the cloud computational burden would have the same time complexity as the best known solution to the problem being outsourced. This prevents achieving secure outsourcing by placing a huge additional overhead on the cloud servers. This thesis has been carried out in Université Paris Descartes (LIPADE - diNo research group) and in collaboration with SOMONE under a Cifre contract. The convergence of the research fields of those teams led to the development of this manuscrit.
334

Anställdas inställning till biometrisk autentisering : En studie på svenska små- och medelstora företag / Employees' attitude to biometric authentication

Karlsson, Jakob, Malmberg, Sebastian January 2022 (has links)
Denna studie undersöker anställdas inställning till BA som MFA-metod på svenska SMF, även vilken BA-metod som anses lämpligast för användning. Tidigare studier har främst fokuserat på större organisationer och företag med kvantitativa forskningsmetoder. Därav har denna studie valt att undersöka SMF med en kvalitativ inriktning i formen av en semistrukturerad intervjustudie. Studien genomförde totalt nio intervjuer från varierande företag med respondenter aven mängd olika arbetsroller. Utifrån dessa intervjuer kunde flera teman identifieras, dessa användes för att dra slutsatser kring användarens inställning och vilken BA-metod som föredras i företagskontext. Teman som identifierades utgjorde grunden förde anställdas inställning, exempelvis vilka positiva och negativa aspekter de anställda kunde se med BA som MFA. Resultaten visade att de anställda generellt sett var positivt inställda till BA som MFA-metod och att de flesta kunde tänka sig implementera detta på sin arbetsplats. Av fingeravtryck, röstigenkänning,ansiktsigenkänning och irisskanning föredrog respondenterna fingeravtryck som BA-metod i företagskontext. Studien valde att inte fokusera på företag som redan implementerat BA som MFA. Applikationer och program som anställda använder där BA erbjuds anses inte som att företaget implementerat BA som MFA. / This study examines employees' attitudes towards BA (Biometric Authentication) as an MFA (Multi-Factor Authentication) method at Swedish SMEs, as well as which BA method is considered most suitable for use. Previous studies have focused on larger organizations and companies with quantitative research methods. Therefore, this study has chosen to examine SMEs with a qualitative focus by conducting semistructured interviews. The study conducted a total of nine interviews from various companies with respondents from a variety of work roles. Based on these interviews, several themes could be identified, these were used to draw conclusions about the employees’ attitude and which BA method is preferred in a business context. Themes that were identified formed the basis for the employees' attitude, for example what positive and negative aspects the employees could see with BA as MFA. The results showed that the employees were generally positive about BA as an MFA method and that most could imagine implementing this in their workplace. Focusing on fingerprints, voice recognition, face recognition and iris scanning, the respondents preferred fingerprints as a BA method. The study chose not to focus on companies that have already implemented BA as MFA. Applications and programs that employees use where BA is offered are not considered that the company has implemented BA as MFA.
335

Acceptance of biometric authentication security technology on mobile devices

Malatji, W. R. January 2022 (has links)
M. Tech. (Department of Information and Communication Technology, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Mobile devices are rapidly becoming a key computing platform, transforming how people access business and personal information. Accessing business and personal data using mobile devices requires authentication that is secure. The world is rapidly becoming connected and all users of mobile devices need to be clear regarding individual data security. As a result, biometrics for mobile devices has come into existence. Biometric technology can be applied on mobile devices to improve the trustworthiness of wireless services. Furthermore, it is of great importance and necessary to start paying attention to and investing in mobile biometric technologies, as they are quickly turning into tools of choice for productivity. In the literature review, it shows that few studies measured the acceptance of biometric authentication technology on mobile devices. This study seeks to find out the perceptions as to the acceptance of biometric authentication technology on mobile devices. TAM2 was used as the foundation for generating the hypothesis and developing the conceptual framework for this study. This quantitative study used a survey-based questionnaire to collect data from 305 participants. The simple random sampling technique was used to select participants for this study. The response rate was 98% of the expected population, which was a total of 302 valid responses. A descriptive analysis was deployed to provide a description of respondents’ demographic characteristics. SPSS was used to compute the multiple regressions in order to evaluate the research hypotheses. The findings of this study revealed that perceived humanness, perceived interactivity, perceived social presence, perceived ease of use and subjective social norm, and perceived usefulness and trust are important determinants of customers’ intention to accept and use mobile biometric devices. It was found that reliability is a good predictor of trust. On the other hand privacy, identity theft and combining data are also important determinants of trust. This work can be used to strengthen biometric authentication technology in-cooperation with mobile devices for simplicity of use. Since most mobile devices are used for personal and business information, further research on the acceptance of biometric authentication technology on mobile devices is needed.
336

Developing a Computer System for the Generation of Unique Wrinkle Maps for Human Faces. Generating 2D Wrinkle Maps using Various Image Processing Techniques and the Design of 3D Facial Ageing System using 3D Modelling Tools.

Mehdi, Ali January 2011 (has links)
Facial Ageing (FA) is a very fundamental issue, as ageing in general, is part of our daily life process. FA is used in security, finding missing children and other applications. It is also a form of Facial Recognition (FR) that helps identifying suspects. FA affects several parts of the human face under the influence of different biological and environmental factors. One of the major facial feature changes that occur as a result of ageing is the appearance and development of wrinkles. Facial wrinkles are skin folds; their shapes and numbers differ from one person to another, therefore, an advantage can be taken over these characteristics if a system is implemented to extract the facial wrinkles in a form of maps. This thesis is presenting a new technique for three-dimensional facial wrinkle pattern information that can also be utilised for biometric applications, which will back up the system for further increase of security. The procedural approaches adopted for investigating this new technique are the extraction of two-dimensional wrinkle maps of frontal human faces for digital images and the design of three-dimensional wrinkle pattern formation system that utilises the generated wrinkle maps. The first approach is carried out using image processing tools so that for any given individual, two wrinkle maps are produced; the first map is in a binary form that shows the positions of the wrinkles on the face while the other map is a coloured version that indicates the different intensities of the wrinkles. The second approach of the 3D system development involves the alignment of the binary wrinkle maps on the corresponding 3D face models, followed by the projection of 3D curves in order to acquire 3D representations of the wrinkles. With the aid of the coloured wrinkle maps as well as some ageing parameters, simulations and predictions for the 3D wrinkles are performed.
337

Climatic variability at Modoc Rock Shelter (Illinois) and Watson Brake (Louisiana): biometric and isotopic evidence from archaeological freshwater mussel shell

Caughron, Sarah Mistak 11 December 2009 (has links)
This thesis assesses climate change during the Hypsithermal Climatic Interval through the analysis of freshwater mussel remains from archaeological sites in Eastern North America. Modern climate data was used as a model to test the mosaic consequences of climate change. Freshwater mussels: can be used as indicators of precipitation by examining changes in overall size through time: larger mussels are found in larger streams, while smaller mussels are found in smaller streams. This study combines morphometric and isotopic data from archaeological freshwater mussels at Modoc Rock Shelter, Watson Brake, Plum Creek, Owens site, and Landerneau mounds to assess past climatic conditions. At Modoc Rock Shelter, oxygen isotopic data corroborate morphometric data and show that climate was fluctuating with a period of stability at the onset of the Hypsithermal. The oxygen isotopic data sets from the Louisiana sites show that the mid-Holocene was much warmer than the late-Holocene.
338

ESTIMATION OF EVAPOTRANSPIRATION OF COTTONWOOD TREES IN THE CIBOLA NATIONAL WILDLIFE REFUGE, CIBOLA, ARIZONA

JETTON, AMITY J. 29 May 2008 (has links)
No description available.
339

Ensemble baseado em métodos de Kernel para reconhecimento biométrico multimodal / Ensemble Based on Kernel Methods for Multimodal Biometric Recognition

Costa, Daniel Moura Martins da 31 March 2016 (has links)
Com o avanço da tecnologia, as estratégias tradicionais para identificação de pessoas se tornaram mais suscetíveis a falhas, de forma a superar essas dificuldades algumas abordagens vêm sendo propostas na literatura. Dentre estas abordagens destaca-se a Biometria. O campo da Biometria abarca uma grande variedade de tecnologias usadas para identificar e verificar a identidade de uma pessoa por meio da mensuração e análise de aspectos físicos e/ou comportamentais do ser humano. Em função disso, a biometria tem um amplo campo de aplicações em sistemas que exigem uma identificação segura de seus usuários. Os sistemas biométricos mais populares são baseados em reconhecimento facial ou de impressões digitais. Entretanto, existem outros sistemas biométricos que utilizam a íris, varredura de retina, voz, geometria da mão e termogramas faciais. Nos últimos anos, o reconhecimento biométrico obteve avanços na sua confiabilidade e precisão, com algumas modalidades biométricas oferecendo bom desempenho global. No entanto, mesmo os sistemas biométricos mais avançados ainda enfrentam problemas. Recentemente, esforços têm sido realizados visando empregar diversas modalidades biométricas de forma a tornar o processo de identificação menos vulnerável a ataques. Biometria multimodal é uma abordagem relativamente nova para representação de conhecimento biométrico que visa consolidar múltiplas modalidades biométricas. A multimodalidade é baseada no conceito de que informações obtidas a partir de diferentes modalidades se complementam. Consequentemente, uma combinação adequada dessas informações pode ser mais útil que o uso de informações obtidas a partir de qualquer uma das modalidades individualmente. As principais questões envolvidas na construção de um sistema biométrico unimodal dizem respeito à definição das técnicas de extração de característica e do classificador. Já no caso de um sistema biométrico multimodal, além destas questões, é necessário definir o nível de fusão e a estratégia de fusão a ser adotada. O objetivo desta dissertação é investigar o emprego de ensemble para fusão das modalidades biométricas, considerando diferentes estratégias de fusão, lançando-se mão de técnicas avançadas de processamento de imagens (tais como transformada Wavelet, Contourlet e Curvelet) e Aprendizado de Máquina. Em especial, dar-se-á ênfase ao estudo de diferentes tipos de máquinas de aprendizado baseadas em métodos de Kernel e sua organização em arranjos de ensemble, tendo em vista a identificação biométrica baseada em face e íris. Os resultados obtidos mostraram que a abordagem proposta é capaz de projetar um sistema biométrico multimodal com taxa de reconhecimento superior as obtidas pelo sistema biométrico unimodal. / With the advancement of technology, traditional strategies for identifying people become more susceptible to failure, in order to overcome these difficulties some approaches have been proposed in the literature. Among these approaches highlights the Biometrics. The field of Biometrics encompasses a wide variety of technologies used to identify and verify the person\'s identity through the measurement and analysis of physiological and behavioural aspects of the human body. As a result, biometrics has a wide field of applications in systems that require precise identification of their users. The most popular biometric systems are based on face recognition and fingerprint matching. Furthermore, there are other biometric systems that utilize iris and retinal scan, speech, face, and hand geometry. In recent years, biometrics authentication has seen improvements in reliability and accuracy, with some of the modalities offering good performance. However, even the best biometric modality is facing problems. Recently, big efforts have been undertaken aiming to employ multiple biometric modalities in order to make the authentication process less vulnerable to attacks. Multimodal biometrics is a relatively new approach to biometrics representation that consolidate multiple biometric modalities. Multimodality is based on the concept that the information obtained from different modalities complement each other. Consequently, an appropriate combination of such information can be more useful than using information from single modalities alone. The main issues involved in building a unimodal biometric System concern the definition of the feature extraction technique and type of classifier. In the case of a multimodal biometric System, in addition to these issues, it is necessary to define the level of fusion and fusion strategy to be adopted. The aim of this dissertation is to investigate the use of committee machines to fuse multiple biometric modalities, considering different fusion strategies, taking into account advanced methods in machine learning. In particular, it will give emphasis to the analyses of different types of machine learning methods based on Kernel and its organization into arrangements committee machines, aiming biometric authentication based on face, fingerprint and iris. The results showed that the proposed approach is capable of designing a multimodal biometric System with recognition rate than those obtained by the unimodal biometrics Systems.
340

Ensemble baseado em métodos de Kernel para reconhecimento biométrico multimodal / Ensemble Based on Kernel Methods for Multimodal Biometric Recognition

Daniel Moura Martins da Costa 31 March 2016 (has links)
Com o avanço da tecnologia, as estratégias tradicionais para identificação de pessoas se tornaram mais suscetíveis a falhas, de forma a superar essas dificuldades algumas abordagens vêm sendo propostas na literatura. Dentre estas abordagens destaca-se a Biometria. O campo da Biometria abarca uma grande variedade de tecnologias usadas para identificar e verificar a identidade de uma pessoa por meio da mensuração e análise de aspectos físicos e/ou comportamentais do ser humano. Em função disso, a biometria tem um amplo campo de aplicações em sistemas que exigem uma identificação segura de seus usuários. Os sistemas biométricos mais populares são baseados em reconhecimento facial ou de impressões digitais. Entretanto, existem outros sistemas biométricos que utilizam a íris, varredura de retina, voz, geometria da mão e termogramas faciais. Nos últimos anos, o reconhecimento biométrico obteve avanços na sua confiabilidade e precisão, com algumas modalidades biométricas oferecendo bom desempenho global. No entanto, mesmo os sistemas biométricos mais avançados ainda enfrentam problemas. Recentemente, esforços têm sido realizados visando empregar diversas modalidades biométricas de forma a tornar o processo de identificação menos vulnerável a ataques. Biometria multimodal é uma abordagem relativamente nova para representação de conhecimento biométrico que visa consolidar múltiplas modalidades biométricas. A multimodalidade é baseada no conceito de que informações obtidas a partir de diferentes modalidades se complementam. Consequentemente, uma combinação adequada dessas informações pode ser mais útil que o uso de informações obtidas a partir de qualquer uma das modalidades individualmente. As principais questões envolvidas na construção de um sistema biométrico unimodal dizem respeito à definição das técnicas de extração de característica e do classificador. Já no caso de um sistema biométrico multimodal, além destas questões, é necessário definir o nível de fusão e a estratégia de fusão a ser adotada. O objetivo desta dissertação é investigar o emprego de ensemble para fusão das modalidades biométricas, considerando diferentes estratégias de fusão, lançando-se mão de técnicas avançadas de processamento de imagens (tais como transformada Wavelet, Contourlet e Curvelet) e Aprendizado de Máquina. Em especial, dar-se-á ênfase ao estudo de diferentes tipos de máquinas de aprendizado baseadas em métodos de Kernel e sua organização em arranjos de ensemble, tendo em vista a identificação biométrica baseada em face e íris. Os resultados obtidos mostraram que a abordagem proposta é capaz de projetar um sistema biométrico multimodal com taxa de reconhecimento superior as obtidas pelo sistema biométrico unimodal. / With the advancement of technology, traditional strategies for identifying people become more susceptible to failure, in order to overcome these difficulties some approaches have been proposed in the literature. Among these approaches highlights the Biometrics. The field of Biometrics encompasses a wide variety of technologies used to identify and verify the person\'s identity through the measurement and analysis of physiological and behavioural aspects of the human body. As a result, biometrics has a wide field of applications in systems that require precise identification of their users. The most popular biometric systems are based on face recognition and fingerprint matching. Furthermore, there are other biometric systems that utilize iris and retinal scan, speech, face, and hand geometry. In recent years, biometrics authentication has seen improvements in reliability and accuracy, with some of the modalities offering good performance. However, even the best biometric modality is facing problems. Recently, big efforts have been undertaken aiming to employ multiple biometric modalities in order to make the authentication process less vulnerable to attacks. Multimodal biometrics is a relatively new approach to biometrics representation that consolidate multiple biometric modalities. Multimodality is based on the concept that the information obtained from different modalities complement each other. Consequently, an appropriate combination of such information can be more useful than using information from single modalities alone. The main issues involved in building a unimodal biometric System concern the definition of the feature extraction technique and type of classifier. In the case of a multimodal biometric System, in addition to these issues, it is necessary to define the level of fusion and fusion strategy to be adopted. The aim of this dissertation is to investigate the use of committee machines to fuse multiple biometric modalities, considering different fusion strategies, taking into account advanced methods in machine learning. In particular, it will give emphasis to the analyses of different types of machine learning methods based on Kernel and its organization into arrangements committee machines, aiming biometric authentication based on face, fingerprint and iris. The results showed that the proposed approach is capable of designing a multimodal biometric System with recognition rate than those obtained by the unimodal biometrics Systems.

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