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Análise de sistemas de aterramento com hastes concretadas submetidos a correntes impulsivas.BEZERRA, Gabriel Vidal Negreiros. 25 April 2018 (has links)
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Previous issue date: 2017-03-30 / CNPq / Neste trabalho é realizada uma avaliação da resposta impulsiva de aterramento com
haste concretada, considerando o efeito da ionização do solo. Para isso, o aterramento
foi representado e simulado utilizando uma ferramenta computacional de simulação em
três dimensões por meio do método dos elementos finitos. A representação computacional, bem como a validação da mesma, foi feita tomando-se como base dados experimentais apresentados na literatura. O fenômeno da ionização do solo foi implementado ponto a ponto, utilizando o equacionamento do modelo dinâmico de ionização do solo, possibilitando que aterramentos com diferentes formatos geométricos sejam avaliados. Avaliou-se a impedância transitória de uma haste concretada padronizada para solos com diferentes resistividades. Além disso, procedeu-se com uma análise da resposta impulsiva da haste concretada para diferentes parâmetros geométricos, a saber: raio do concreto envolvente, comprimento vertical da haste concretada, comprimento vertical do concreto envolvente e profundidade da haste concretada em relação ao nível do solo. Por fim, propõem-se limites práticos e sugestões de dimensões para a haste concretada, de forma que a reposta impulsiva seja otimizada. / In this research, was performed an impulsive response evaluation of concrete encased
groundings, considering de soil ionization effect. In order to achive this, the grouding was
represented and simulated in three dimensions using a finite element method software.
The computational representation and validation were performed using experimental data
presented in the literature. The soil ionization effect was implemented in a point form,
allowing evaluate groudings with different geometric formats. It was studied the transient
impedance of a standard concrete encased rod placed in soils with different resistivity
values. Furthermore, was performed a transient response analysis for different geometric
parameters of the concrete encased rod, namely: the concrete radius, the vertical length of
the concrete encased rod, the vertical length of the concrete encased rod, the surrounding
concrete and the depth of the concrete encased rod in relation to the soil surface. Finally,
practical limits and suggested dimensions for the concrete encased rod are proposed, in
order to optimize the impulse response.
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A influência da resistência de terra nos efeitos das descargas atmosféricasSantos, Camila Guesine dos 30 May 2009 (has links)
There is great concern by the power systems utilities related to
disturbances that generate induced overvoltages in the power network, as they
reach the consumer sensitive equipment, causing damage and losses. In
consequence of this framework, the power systems utilities get large financial
losses every year due to indemnity for damage to such equipments. Among the
disturbances that lead to induced overvoltages are lightning. Thus, in this work it
was developed the study and analysis of the lightning´s effect on loads allocated
on average (11kV/15kV) and low voltage (below 600V) under the influence
caused by the resistance of grounding. For modeling and simulation of the
system under analysis, the program for transient study ATP (Alternative
Transient Program) was used. To develop the study, it was designed a system
comprising of an 88kV transmission line, a substation, a distribution line of 13.8
kV and loads representing residential consumers. It was also analyzed the use of
surge suppressor in the low voltage distribution transformers as a way to
mitigate the induced overvoltages that reach consumers. / Existe uma grande preocupação por parte das concessionárias de energia
relacionada aos distúrbios que geram sobretensões induzidas na rede elétrica,
pois estas atingem os equipamentos sensíveis dos consumidores, causando danos
e perdas. Em conseqüência deste quadro, as concessionárias contraem grandes
prejuízos financeiros todos os anos devido ao ressarcimento por danos a tais
equipamentos. Dentre os distúrbios causadores de sobretensões induzidas
destacam-se as descargas atmosféricas. Sendo assim, neste trabalho foi
desenvolvido o estudo e análise do efeito de descargas atmosféricas em cargas
alocadas em média (11kV/15kV) e baixa tensão (abaixo de 600V) relacionada a
influência causada pela resistência de aterramento. Para a modelagem e
simulações do sistema sob análise utilizou-se o programa para estudo de
transitórios ATP (Alternative Transient Program). Para a realização do estudo
modelou-se um sistema composto de uma linha de transmissão de 88kV, uma
subestação, uma linha de distribuição de 13,8kV e cargas que representam os
consumidores residenciais. É analisada também a utilização de supressores de
surto na baixa tensão dos transformadores de distribuição como forma de
atenuar as sobretensões induzidas que atingem os consumidores. / Mestre em Ciências
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Contribuição ao estudo de análise de aterramento impulsivo e em altas frequências associado à avaliação da suportabilidade dos seres humanos com base no método da modelagem por linhas de transmissão (TLM)Gazzana, Daniel da Silva January 2012 (has links)
Este trabalho fundamenta-se no desenvolvimento e aprimoramento de metodologias para a melhor representação do aterramento elétrico sob uma análise transiente. O estudo concentrase no estabelecimento de contribuições ao estado da arte associadas à análise e modelagem de aterramento impulsivo e em altas frequências. O estudo vincula-se também à avaliação da suportabilidade de seres humanos submetidos a potenciais produzidos na superfície do solo, provenientes da corrente elétrica gerada por um surto atmosférico. A concepção das metodologias propostas baseou-se no uso do Método da Modelagem por Linhas de Transmissão em uma dimensão (TLM-1D). Destacam-se três grandes tópicos da pesquisa. O primeiro concentra-se no desenvolvimento de formulação para a inclusão do fenômeno de ionização do solo ao Método TLM-1D clássico. A formulação desenvolvida tem como característica ser uma técnica generalista, independente das propriedades do meio, dimensões do eletrodo e do surto atmosférico. O segundo foco concentra-se no aprimoramento e desenvolvimento de equacionamento analítico para a estimação de potenciais gerados na superfície do solo, originados pela corrente elétrica estabelecida sobre eletrodo de aterramento. Tal equacionamento tem grande aplicabilidade em conjunto com metodologias numéricas unidimensionais, as quais não são capazes de determinar diretamente os referidos potenciais. Por fim, a realização de estudo de suportabilidade e segurança de seres humanos em contato com eletrodos de aterramento submetidos a surto atmosférico, considerando modelo representativo baseado em circuitos elétricos, consolida o trabalho desenvolvido. / This work is based on the development and improvement of methodologies for the best representation of the electrical grounding under a transient analysis. The study concentrated on establishing contributions to the state of the art related to the analysis and modeling of impulsive and high frequencies grounding systems. The study is also associated to the evaluation of the supportability of human beings submitted to the potentials produced on the soil surface from the electric current generated by a lightning. The conception of the proposed methodology was based on the Transmission Line Modeling Method in one dimension (TLM- 1D). Three major research topics can be highlighted. The first involves the development of a formulation to include the soil ionization phenomenon in the classic TLM-1D algorithm. The developed formulation is a generalist technique, independent of the medium properties, characteristic of the electrode and lightning surge. The second aims at the improvement and development of analytical equations for estimating the generated potential on the soil surface, originated by the electric current calculated in the grounding electrode. Such equationing has great applicability in conjunction with one-dimensional numerical methods which are not able to determine such potential directly. Finally, the achievement of a supportability study and personal safety of humans in contact with the grounding electrodes subjected to a lightning, considering a representative model based on electrical circuits, consolidates the developed work.
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La rationalité du jugement pratique. Perspectives kantiennes et aristotéliciennes contemporaines / The Rationality of Practical Judgment. Contemporary Kantian and Aristotelian PerspectivesBrown, Étienne 07 May 2016 (has links)
Qu’est-ce que la rationalité pratique ? Répondre à cette interrogation, c’est déterminer la nature du raisonnement pratique qu’un acteur se trouvant dans une situation concrète doit entreprendre ; comment, autrement dit, il doit délibérer, juger et agir. Afin de mener à bien ce projet, les philosophes contemporains mobilisent des héritages philosophiques distincts. Dans chacune des trois grandes traditions de la philosophie occidentale – les traditions française, allemande et anglo-américaine – des philosophes se revendiquant d’Aristote ou de Kant ont ainsi récemment débattu de la possibilité de fonder en raison des principes normatifs généraux, du rôle que de tels principes peuvent jouer au sein du raisonnement pratique et des liens que l’on doit tisser entre la rationalité pratique et les vertus. L’objectif général de notre recherche est de démontrer la fécondité des débats entre kantiens et aristotéliciens tout en défendant l’existence d’un kantisme transformé par l’aristotélisme qui nous permet aujourd’hui de mieux cerner les ressorts du raisonnement pratique. Un tel parcours nous fournira l’occasion de contribuer à la réception de travaux qui n’ont pas encore fait couler beaucoup d’encre en France, notamment ceux de Christine Korsgaard, d’Onora O’Neill, de Barbara Herman et de Nancy Sherman. / What is practical rationality? To answer this question, one must determine how an agent facing a specific challenge in a given situation should reason and determine how to act. In order to carry out this project, contemporary philosophers build on different historical perspectives. In each of the three main tradition of Western philosophy – the Anglo-American, German and French traditions – philosophers are thus rereading Aristotle and Kant to answer questions such as “Is it possible to ground general normative principles?”, “What role must principles play in our practical reasonings?” and “What is the relationship between practical rationality and virtue?”. My overall objective is to shed light on these debates, and then to defend a form of Kantianism infused with Aristotelian ideas that can help us paint a more satisfying picture of practical rationality. By doing so, I also contribute to the French reception of contemporary philosophical works such as the ones of Christine Korsgaard, Onora O’Neill, Barbara Herman and Nancy Sherman.
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Modelagens e solução de aterramentos sujeitos a surtos de corrente: respostas nos domínios da frequência e do tempo / Modeling and solution of grounding subject to current surges: responses in frequency and time domainSilva, Bárbara Pereira 29 March 2016 (has links)
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Previous issue date: 2016-03-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In the grounding systems analysis, the investigation of the effects caused by lightning
discharge is a crucial task, since it is the main electromagnetic phenomena responsible for
electricity outages which can be the cause of severe mechanical and thermal stresses on
electric installations. This dissertation presents a study of transient behavior for various
grounding configurations subject to impulsive currents originated from incident discharges.
The model is named hybrid electromagnetic model, because it is based on electromagnetic
equations and it is used concepts of electrical circuit analysis. The modeling is performed
in frequency domain considering the effects of electromagnetic propagation on the metal
electrode and into surrounding soil. In the numerical solution of model is used the method
of moments for the discretization of the electrodes and calculus of the impedances. This
methodology also considers the variation of electric soil parameters when frequency
varies. The modeling comprised the effects of propagation and electromagnetic couplings
between the grounding electrodes. Results were obtained for simple electrodes (wire
horizontally buried in the soil or a vertical rod) and grounding grid in square format from
the computational implementation of the mathematical model. This tool and the results
obtained lend itself to the determination of the grounding systems response subjected to
an injection of a typical current of lightning discharge. The validation of the tool which
resulted from this work is made by comparing the obtained results with results of similar
cases reported in the technical literature. / Na análise de sistemas de aterramento elétrico é primordial a investigação dos efeitos
causados pela incidência de descarga atmosférica, uma vez que esse é o principal fenômeno
eletromagnético responsável pelos desligamentos não programados de instalações elétricas
causando severas solicitações mecânicas e térmicas. Nesta dissertação é apresentado
um estudo do comportamento transitório para diferentes configurações de eletrodos de
aterramentos frente a descargas atmosféricas. O modelo adotado é nomeado de modelo
eletromagnético híbrido, pois baseia-se nas equações eletromagnéticas e utiliza-se conceitos
da análise de circuitos elétricos. A modelagem é realizada no domínio da frequência,
considerando-se os efeitos da propagação eletromagnética no eletrodo metálico e no
solo ao redor. Na solução numérica do modelo é empregado o método dos momentos
para a discretizacão dos eletrodos e obtenção das impedâncias. É também levada em
conta a variação dos parâmetros elétricos do solo com a frequência. São contemplados
nesta modelagem os efeitos de propagação e os acoplamentos eletromagnéticos entre os
eletrodos do aterramento. A partir da implementação computacional do modelo, foram
obtidos resultados para eletrodos simples (em posição horizontal ou vertical) e para
malhas quadradas. Esta ferramenta e os resultados obtidos permitem avaliar a resposta
do aterramento submetido a uma injeção de uma corrente impulsiva típica de descargas
atmosféricas. A validação da ferramenta desenvolvida é feita por meio de comparações dos
resultados obtidos com resultados de casos semelhantes publicados na literatura técnica.
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Dispositivo para medição de impedância em sistemas de aterramento elétricos em alta frequência / Device for impedance measurement in high frequencies electrical grounding systemsFerraz, Rafael da Silva 04 November 2016 (has links)
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Previous issue date: 2016-11-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work presents the project and the implementation of a device that is capable of measuring the electrical effects, especially the impedance, in grounding meshes when subjected to atmospherical discharges. An analysis on the influence of the atmospheric discharges in electrical protection systems is performed and also a comparison between current and voltage impulsive circuits. The device is built of electronic circuits controlled by a microcontroller, with the possibility of parameter adjusting for shaping the generated impulse wave. The device was conceived such that it can be used for tests of soil impedance measurement and for verification of the behavior of electrical grounding systems under high frequencies. The results are presented for tests in different types of systems and there was satisfactory performance for the developed equipment when compared with a commercial device / Este trabalho apresenta o projeto e a implementação do dispositivo capaz de medir os efeitos elétricos, em especial, as impedâncias, em malha de aterramento, sujeito a descargas atmosféricas. Analisa-se as influências das descargas atmosféricas nos sistemas de proteção elétricos e desenvolve-se análise comparativa dos circuitos impulsivos de corrente e de tensão. Constrói-se o dispositivo que consiste de circuitos eletrônicos controlados por microcontrolador, com possibilidade de ajuste de parâmetros da onda gerada. O dispositivo produzido é utilizado para medição da impedância do solo e verificação do comportamento de sistemas de aterramento elétrico em baixas e altas frequências. São apresentados os resultados dos testes em diferentes tipos de sistemas, demonstrando o satisfatório desempenho quando comparado com instrumento comercial.
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Análise do problema do aterramento em modelos eletrostáticos / Problem analysis of electrical grounding in electrostatic modelsTrindade de Oliveira, Murilo 20 August 2018 (has links)
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Previous issue date: 2012 / Resumo: Nesta dissertação propomos a análise de uma idealização estabelecida dentro da teoria eletromagnética. A partir de Um Tratado sobre Eletricidade e Magnetismo, James C. Maxwell expõe alguns conceitos físicos relativos ao aterramento elétrico em condutores. Assim, ele estima que a presença de um fio condutor que estabelece a conexão entre um corpo condutor e outro, ou mesmo ao terra elétrico, perturba as características do sistema envolvido (carga, potencial e campo elétrico). Desse modo, Maxwell preconiza que para sistemas teóricos ou idealizados, quão indefinidamente fino seja o fio, indefinidamente menor será a perturbação gerada. A contextualização de uma idealização física dentro do ensino da teoria eletromagnética, especialmente para um curso de engenharia, é necessária no intuito de enfatizar as diferenças entre modelos reais e teóricos, uma vez também que os estudantes destes cursos devem estar interessados no desenvolvimento prático dos conceitos apreendidos em sala de aula. Nesse sentido, quando tratamos do método das imagens, especificamente para o problema de uma carga na presença de um condutor esférico aterrado, temos a oportunidade de explorar os limites de um modelo teórico, delimitando quais nuances podem aproximá-lo de uma aplicação no mundo real. Em vista disso, notamos que a maioria dos livros didáticos usados no ensino do eletromagnetismo, quando lidam com o problema do aterramento da esfera, simplesmente negligenciam a questão suscitada por Maxwell, de modo a transformar o problema em um exercício puramente matemático, sem necessidade de explicar os fundamentos físicos que sustentam a solução do problema. Portanto, o intuito do presente trabalho é desenvolver um modelo cuja solução defina o comportamento físico para ambos os casos (levando em consideração ou não a existência da conexão da esfera com o terra elétrico), bem como verificar os limites deste modelo teórico / Abstract: In this work, we propose the analysis about an idealized established within electromagnetic theory. From A Treatise on Electricity and Magnetism, James C. Maxwell presents some physical concepts related to electrical conductors grounded. In this direction, he estimates that the presence of a straight metallic wire which establishes the connection between a conducting body and another, or even to electrical ground, disturbs the properties of the system involved (charge, potential and electric field). Thus, Maxwell preconize for theoretical or idealized systems, how indefinitely thin is the wire, indefinitely lower is the disturbance created. The context of a physical idealization into the teaching of electromagnetic theory, especially for an engineering degree is required in order to emphasize the differences between real and theoretical models, since the students of these courses should be also interested in the practical development of the concepts learned in the classroom. In this sense, when we discussed the method of images, specifically to the problem of a charge point charge in the presence of a grounded conducting sphere, we have the opportunity to explore the limits of a theoretical model, outlining which nuances can approach it to a real world application. In view of this, we note that most of the textbooks used in teaching electromagnetism, when deals with the problem of grounded sphere, they simply neglect the issue raised by Maxwell. In order to transform the problem into a purely mathematical exercise, without to explain the physical foundations that support the solution of the problem. Therefore, the aim of this work is to develop a model whose solution defines the physical behavior for both cases (taking into account or not the existence of a connection of the sphere with the electrical ground), and to verify the limits of this theoretical model / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica
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The Feasibility of Rubble-Binding Sponge Propagation for Use in Reef RestorationMcGrath, Emily Christine 22 May 2012 (has links)
A common injury type associated with vessel groundings on coral reefs is generation of coral rubble. As a substrate rubble is dynamic and can be mobilized by normal wave agitation, causing secondary damage to surviving corals and preventing coral larvae and invertebrates from surviving. Typical rubble management options include offsite removal and onsite stabilization using artificial materials. Sponges show promise as a restoration tool for rubble stabilization, especially sponges that are known to have rapid regeneration rates, low mortality, and the capability to quickly form attachment points to natural and artificial substrates. As an effective restoration tool a sustainable source of sponge is required in order to minimize impact on natural populations. The purpose of this project is to evaluate the feasibility of sponge propagation for use as a restoration material following groundings on coral reefs in Biscayne National Park, FL. If small sponge fragments could be collected from donor sponges and propagated on artificial growout structures (i.e. nurseries) a sustainable source of sponge fragments could be maintained for future restoration activities. If feasible, this technique would create a continually growing sponge source that would require a single harvest, reducing pressure on the local sponge populations. Fragments of four species of native sponges, Aplysina fulva¸ Amphimedon compressa, Aplysina cauliformis, and Iotrochota birotulata, were harvested and attached to artificial growout structures composed of PVC rods and cement paver tiles. Fragment necrosis, attachment, sponge retention (persistence throughout the study), complexity, and growth rates for all four species were recorded monthly for one year. Two different PVC types were utilized to compare attachment material effects on growth. Donor sponges were monitored to assess recovery and growth after harvesting, and intact sponges in the natural population were also monitored as a control. Transplanted fragments had the highest retention of any treatment (96-100% of fragments remained), growth rates ranging from 105% to 424%, low necrosis rates, and all but one species increased in complexity. There was no significant difference in sponge growth on different PVC types or between sites. Within one month all donor wounds inflicted by harvest were completely healed, and by the end of the study donors had significantly higher growth rates than the control treatment, ranging from 400% to 781% of initial sponge volume. Donor sponges also had low necrosis rates, but were less complex than controls. This is a promising, practical and low cost method, and based on these results, is a feasible way of producing sponges for us in restoration, with little negative impact on the natural populations.
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“Dark-Skinned People Be Like”: How Colorism-Promoting Internet Memes and Audience Feedback Influence African Americans’ Intragroup Attitude and Perception of Skin – Tone BiasSmith, Marisa A. 13 August 2015 (has links)
No description available.
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Enhancing agent learning through world dynamics modelingSun, Zhiyuan 08 1900 (has links)
Le développement rapide de l’intelligence artificielle (IA), allant des modèles comme BERT
aux modèles de fondation à grande échelle, illustre la croissance exponentielle de la taille et
des capacités des modèles, stimulée par les avancées en puissance de calcul et la disponibilité
des données. Les modèles de fondation, qui tirent parti de l’apprentissage auto-supervisé
sur d’énormes ensembles de données non étiquetées, ont montré une polyvalence remarquable dans une large gamme de tâches, du traitement du langage à la représentation des
connaissances. Cependant, leur dépendance à des données de grande envergure, principalement issues d’Internet, introduit un « écart de connaissances »—un décalage entre les
connaissances généralisées acquises pendant l’entraînement et les connaissances spécialisées
nécessaires pour des domaines spécifiques. Cet écart est principalement causé par des informations insuffisantes, trompeuses ou superficielles disponibles lors de l’entraînement, ce
qui peut mener à des sorties peu fiables, surtout dans des contextes de données rares ou de
mauvaise qualité.
Pour relever ce défi, nous introduisons le cadre Discover, Verify, and Evolve (DiVE).
DiVE est conçu pour améliorer la compréhension des modèles de fondation en les dotant de
connaissances profondes et adaptées aux tâches en aval.
Le cadre fonctionne en trois étapes :
∙ Découvrir l’information : Extraire des informations pertinentes et utiles pour pallier le manque de données qui limite la compréhension des modèles dans des domaines
spécialisés.
∙ Vérifier l’information : Valider les informations recueillies afin de filtrer les inexactitudes et les biais, garantissant ainsi que seules des connaissances fiables sont
retenues.
∙ Faire évoluer l’information : Affiner et développer les informations vérifiées pour
obtenir des connaissances plus approfondies, améliorant ainsi la capacité du modèle
à traiter des requêtes complexes et à performer avec précision dans des tâches spécialisées.
En s’attaquant aux causes profondes de l’écart de connaissances, DiVE aide les modèles
de fondation à passer d’une compréhension générale à une expertise spécialisée, comblant
le fossé entre formation et application. Cette approche améliore la précision des modèles à
travers les domaines et renforce leurs capacités de prise de décision. Dans cette thèse, nous
démontrons l’efficacité de DiVE à travers des évaluations empiriques, soulignant son potentiel
à améliorer l’adaptabilité et la robustesse des modèles de fondation dans des scénarios réels. / The rapid evolution of artificial intelligence (AI) from models like BERT to large-scale foundation models illustrates the exponential growth in model sizes and capabilities, driven by
advances in computational power and data availability. Foundation models, which leverage self-supervised learning on vast, unlabelled datasets, have shown remarkable versatility
across a wide range of tasks, from language processing to knowledge representation. However,
their reliance on large-scale, predominantly internet-sourced data introduces a “knowledge
ga”—a mismatch between the generalized knowledge acquired during training and the specialized knowledge required for specific domains. This gap is primarily caused by insufficient,
misleading, or superficial information available during training, which can lead to unreliable
outputs, especially in low-data or poor-data settings.
To address this challenge, we introduce the Discover, Verify, and Evolve (DiVE) framework. DiVE is designed to enhance the understanding of foundation models by equipping
them with deep, tailored knowledge about downstream tasks. The framework operates in
three stages:
∙ Discover the Information: Extract relevant and useful information to address the
lack of data that limits the model’s understanding of specialized domains.
∙ Verify the Information: Validate the gathered information to filter out inaccuracies and biases, ensuring only reliable knowledge is retained.
∙ Evolve the Information: Refine and expand on verified information to gain deeper
insights, improving the model’s ability to handle complex queries and perform accurately in specialized tasks.
By addressing the root causes of the knowledge gap, DiVE helps foundation models transition from general understanding to specialized expertise, bridging the gap between training and application. This approach enhances model accuracy across domains and improves
decision-making capabilities. In this thesis, we demonstrate the efficacy of DiVE through
empirical evaluations, highlighting its potential to enhance the adaptability and robustness
of foundation models in real-world scenarios.
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