O objetivo principal desta dissertação é determinar, a partir de ensaios de laboratório, o comportamento mecânico de misturas constituídas com solos lateríticos arenoso e argiloso e emulsão asfáltica, visando a sua utilização na construção rodoviária. Utilizou-se na compactação a energia normal do Proctor, e analisaram-se os efeitos do tipo de solo, o teor e tipo de emulsão, tipo de cura pré e pós-compactação, tempo de cura e a imersão em água na resistência e rigidez das misturas. Foram realizados ensaios para a determinação da resistência à compressão simples, resistência à compressão diametral, módulo de resiliência, índice de suporte Califórnia e variação volumétrica durante a cura e imersão dos corpos-de-prova. Os resultados mostraram que as misturas com emulsão apresentaram resistência e rigidez superiores às dos solos in natura, e ainda menores variações volumétricas decorrentes da secagem e da imersão dos corpos-de-prova em água. Finalmente, concluiu-se que o uso das emulsões asfálticas é promissora na área de pavimentação, dado que proporciona às misturas propriedades físicas e mecânicas para estas serem aplicáveis na construção rodoviária. / This work has the main objective of studying, based on laboratory tests, the mechanical behavior of sand and clay lateritics soils and the asphalt emulsion in focus mixtures, seeking their utilization in road construction. Were compacted at the normal Proctor energy, analyzing the soil type, the asphaltic emulsion rate and type, the curing pre and pos- compactation, the curing time and the effect of the immersion in water to the mixtures strength and rigidity, afterwards they were submitted to tests to the determination of unconfined compressive strength, indirect tensile strength, modulus resilient, California bearing ratio and volumetric variability of specimens when immersed in water. The results showed that the addition of asphaltic emulsion to soils improve the strength and rigidity of in natura and reduction of the volumetric variability caused by drying and immersion in water soils. Finally, it concludes that bituminous emulsion provides to soils qualities that could be qualified for use in road construction.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-07-05T15:18:16Z No. of bitstreams: 1 mateusviniciusmarcial.pdf: 2235520 bytes, checksum: 25f39d17f0416ae1fc55b0285fe52d56 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-08T17:46:01Z (GMT) No. of bitstreams: 1 mateusviniciusmarcial.pdf: 2235520 bytes, checksum: 25f39d17f0416ae1fc55b0285fe52d56 (MD5) / Made available in DSpace on 2017-08-08T17:46:01Z (GMT). No. of bitstreams: 1 mateusviniciusmarcial.pdf: 2235520 bytes, checksum: 25f39d17f0416ae1fc55b0285fe52d56 (MD5) Previous issue date: 2013-07-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho é estudado uma maneira de se introduzir não-comutatividade em alguns sistemas físicos via estruturas simpléticas para se investigar as propriedades de espaços não-comutativos (NC). Inicialmente, foi discutido em detalhes uma maneira sistemática de se introduzir não-comutatividade baseado no formalismo de Faddeev-Jackiw denominada Formalismo Simplético de Indução de Não-Comutatividade (FSINC). Este formalismo foi usado pra se obter uma versão NC para o Modelo Sigma Não-linear O(3) e para o Modelo de Skyrme SU(2). Posteriormente, uma segunda lei de Newton modificada que preserva a invariância rotacional foi obtida em um espaço de fase clássico estendido NC. Entre os principais efeitos da não-comutatividade na dinâmica de um oscilador harmônico tratado nesse espaço nota-se que a não-comutatividade induz uma pertubação estável no oscilador harmônico usual e que o oscilador pode até mesmo deixar de ser periódico dependendo da relação entre as frequências de oscilação da coordenada NC e do momento linear. Em seguida, considerando um espaço de fase com estrutura simplética não-comutativa e aplicando o (FSINC), as equações Friedmann- Lemaître corrigidas foram obtidas. As correções nas equações Friedmann- Lemaître podem ser associados com um fluido perfeito NC. Finalmente, usando as equações de Friedmann-Lemaître corrigidas, o parâmetro desaceleração NC pode ser determinado em termos do redshift. Dos valores existentes na literatura para o parâmetro densidade de energia do vácuo Ω0Ʌ e para o redshift transição, estima-se que a ordem de grandeza do parâmetro densidade de matéria do fluido NC Ω0β e do parâmetro NC βsão iguais a 0,52+0,03 -0,159 e β= -0,784 +2,398 -0,453 x 10 -36s-2, respectivamente. Isso mostra que a não-comutatividade poderia ser responsável por até 8,2% da densidade de matéria do universo ou por um terço da matéria escura sem violar os valores na literatura para o redshift de transição. / In this work we have studied how to introduce noncommutativity to some physical systems through the symplectic structures to investigate the properties of the noncommutative (NC) spaces. Initially, we discussed in details one systematic way to introduce noncommutativity, based on Faddeev-Jackiw formalism, called symplectic formalism for induction of noncommutativity (SFINC). This formalism was used to obtain NC versions of the SU(2) Skyrme model and O(3) nonlinear sigma model. After that, the rotational invariant noncommutative Newton’s second law was written in the NC extended classical phase space. Among the main effects of noncommutativity in the dynamics of a harmonic oscillator treated in this space, we note that the noncommutativity induces a stable perturbation in the usual harmonic oscillator and the oscillator may even not be periodic depending on the ratio between the oscillation frequency of the position coordinate and the oscillation frequency of the NC coordinate. Subsequently, considering a phase space with NC symplectic structure and applying the SFINC we obtained the modified Friedmann-Lemaître equations, which have NC corrections. This correction can be interpreted as a NC perfect fluid, which would behave like dust during a period of radiation, preserving the law of conservation of energy. Finally, using the Friedmann-Lemaître equations the NC deceleration parameter q can be determined in terms of the redshift. From the values in literature for the vacuum-energy density parameter Ω0Ʌ and the transition redshift, the range of acceptable values of the matter density parameter of NC fluid Ω0β and the NC parameter β estimated are 0,052+0,03 −0,159 and β = −0,784+2,398−0,453 ×10−36s−2, respectively. This result shows that the NC corrections could be responsible for up to 8.2% of the matter density of the universe, or a third of the dark matter, without violating the literature values of the transition redshift.

The present work deals with developing a tribological test machine that had been built earlier but did not function properly. It was giving out abnormal noises and vibrations and was not corresponding to its desired functions. In this study, the root of these problems is analyzed and some solutions are suggested by developing a new construction concept for the machine.

L’analyse isogéométrique pour la résolution de problèmes de la mécanique du solide suscite de vifs intérêts depuis une dizaine d’année. En effet, cette méthode de discrétisation autorise la description exacte des géométries étudiées permettant ainsi de supprimer les erreurs dues à une mauvaise description du domaine spatial étudié. Cependant elle pose un problème théorique de propagation de raffinement lors de la localisation de maillage. Des méthodes pour contourner ce problème ont été proposée dans la littérature mais complexifient grandement la mise en œuvre de cette stratégie de résolution. Cette thèse propose une stratégie de raffinement localisé adaptatif en espace pour les problèmes de statique et en espace temps pour les problèmes de dynamique transitoire dans le cadre de l’analyse isogéométrique. Pour cela une méthode de localisation pour l’analyse isogéométrique en statique basée sur une résolution multigrille est tout d’abord développée pour des problèmes en deux dimensions. Elle présente l’avantage de contourner la problématique de propagation de raffinement de maillage due à l’analyse isogéométrique tout en étant plus simple à mettre en œuvre que les méthodes déjà existantes. De plus, l’utilisation de l’analyse isogéométrique permet de simplifier les procédures de raffinement lors de l’adaptation de maillage qui peuvent être complexes lors de l’utilisationd’éléments finis classiques. Une méthode de raffinement adaptatif espace temps basée sur une résolution multigrille est ensuite développée pour des problèmes en une dimension. Une étude sur la structure des opérateurs est proposée afin de choisir un intégrateur temporel adapté. Les performances de cette stratégies sont mises en évidence, puis une modification de la méthode de résolution est proposée afin de diminuer significativement les coûts de calculs associées à cette résolution. La méthode de raffinement adaptatif espace temps est appliquée à quelques exemples académiques afin de valider son bon comportement lors de la localisation. / Isogeometric analysis applied to structural mechanics problems is a topic of intense concerns for a decade. Indeed, an exact description of geometries studied is allowed by this discretization method suppressing errors due to a bad description of the spatial domain considered. However, a theoretical problem of refinement propagation appears during mesh localization. Local refinement methods for isogeometric analysis has been developed and implied a complexification of the implementation of such a resolution strategy. This PhD thesis expose a space adaptative refinement strategy for linear elastic problems and a space-time one for transient dynamic using isogeometric analysis. For this purpose, a localization method for isogeometric analysis based on a multigrid resolution is developed for 2D linear elastic problems. This method allow to circumvent mesh refinement propagation inherent to isogeometric analysis, and is easier to implement than existing methods. Moreover, the use of isogeometric analysis simplifies refinement procedures occuring during mesh adaptation and which can be really complex using classical finite element analysis. Then, a space-time adaptative refinement based on a multigrid resolution is developed for one dimensional in space problems. A study on operators structure is exposed in order to choose a well suited time integrator. This strategy's performances are highlighted, then an evolution of this method is set up in order to lower computational costs. The space-time adaptaptive refinement is applied to some academical examples to show it good behavior during localization.

The socioeconomic, political and cultural changes faced in recent decades, as a result of accelerated dynamics that characterize the contemporary global scenario, come changing routines and living ways. Inserted in this scope, individuals and organizations require constant adaptation to new realities imposed by external situations. Until then, the business organizations had never the necessity to transpose this sizes. In this direction, the impression is that all corporate proposals and actions undertaken do not supply completely, or at least not for a long time, the stability of a particular organization in the current market. Thus, all methodologies, tools and systems to assist employees to organizational management are valid, however, as the study authors argue that follows, without performance measurement do not exist management. In instead, is possible affirm that the main focus of this research is the proposition of organizational performance evaluation model of the metal mechanic sector. In order to achieve the objective referred to above, as well as the specific objectives was necessary to perform a theoretical and conceptual survey, to better set the author about the analyzed sector, as well as related topics such as competitiveness, strategic management, competitive strategy, competitive advantage, organizational performance assessment and critical success factors. For test the model of organizational evaluation proposed, launched a multi study procedure where two companies, located in the Rio Grande do Sul state (Vale do Rio Pardo). In this way, the model aims to provide a tool to assist administrators of metal mechanic companies in their decision making, while academically emerges a new instrument for analysis and future studies. / As mudanças socioeconômicas, políticas e culturais enfrentadas nas últimas décadas, em decorrência das aceleradas dinâmicas que caracterizam o cenário global contemporâneo, vêm alterando rotinas e formas de viver. Inseridos neste escopo, indivíduos e organizações necessitam de constantes adaptações às novas realidades impostas pelas conjunturas externas. Até então, as organizações empresariais nunca haviam tido a necessidade de transpor por tamanhos desafios. Nesta direção, tem-se a impressão de que todas as ações coorporativas propostas e realizadas não suprem por completo, ou pelo menos não por longo prazo, a estabilidade de uma determinada organização no mercado atual. Assim, todas as metodologias, ferramentas e sistemas empregados no auxílio à gestão organizacional são válidas, porém, conforme defendem autores explorados no estudo que se segue, sem medição de desempenho não há gerenciamento. Circunscrevendo o foco de análise desta pesquisa, cabe citar o objetivo geral do estudo que se apresenta, sendo este, a proposição de uma modelagem de avaliação de desempenho organizacional do setor metal mecânico. No intuito de atingir o objetivo supracitado, bem como os objetivos específicos, mostrou-se necessário realizar um levantamento teórico e conceitual para melhor ambientar o autor acerca do setor analisado, assim como de temáticas afins, como a competitividade, a gestão estratégica, estratégia competitiva, vantagens competitivas, avaliação de desempenho organizacional e fatores críticos de sucesso. São delimitadas ainda as bases para o modelo proposto, bem como os seus instrumentos e aspectos metodológicos. A fim de testar a modelagem de avaliação de desempenho organizacional do setor metal mecânico proposto, lançou-se mão do procedimento do estudo de multi casos em duas empresas do referido setor, localizadas na região Sul do Brasil Vale do Rio Pardo-RS. Tornou-se possível assim, avaliar o desempenho organizacional das empresas partícipes a partir de seus fatores críticos de sucesso. Desta forma, a modelagem visa disponibilizar uma ferramenta para auxiliar os gestores de empresas do setor metal mecânico em suas tomadas de decisões, enquanto que academicamente emerge um novo instrumento para análise e lapidações futuras.

Les matériaux céramiques sont des composants incontournables dans les blindages antibalistiques multicouches. Leur faible densité, typiquement deux à trois fois inférieure à celle de l’acier, combinée à une très haute résistance en compression les rends essentiel pour des applications d’armures légères. Le carbure de silicium est un matériau prometteur pour cette application en raison de sa faible densité et de sa dureté élevée en comparaison des autres céramiques. L’étude du lien entre la microstructure du matériau et son processus de fragmentation pendant l’impact est une étape importante afin d’optimiser les céramiques pour les applications de protection balistique.Quatre nuances de carbure de silicium denses avec différentes microstructures ont été étudiées, dont trois élaborées au cours de ces travaux. Pour cela, deux modes de frittage ont été utilisés (frittage en phase solide et frittage en phase liquide) ainsi que deux procédés de frittage (frittage naturel et frittage flash). Un soin particulier a été porté aux diverses étapes de la fabrication afin de produire des microstructures homogènes et denses. Des pièces de taille satisfaisante pour l’application ont été réalisées pour chaque nuance. Elles ont été soumises à des caractérisations microstructurales (microscopie électronique à balayage et en transmission, diffraction des rayons X, cartographie élémentaire, analyses chimiques) et mécaniques en quasi-statique (dureté, ténacité, contrainte à la rupture, module de Weibull) et en dynamique. La fragmentation dynamique des carbures de silicium a été étudiée grâce à des essais utilisant une configuration d’impact sur la tranche. Une première configuration a permis d’observer la phénoménologie et la chronologie de l’endommagement du matériau grâce à une caméra ultra-rapide. Une seconde configuration ‘sarcophage’ a permis d’observer la fragmentation des matériaux, c’est-à-dire le motif et la densité de fissuration des cibles. Il a été observé que la microstructure joue un rôle clef sur l’intensité de l’endommagement subit par la céramique pendant l’impact. Une bonne adéquation avec des simulations utilisant le modèle d’endommagement anisotrope Denoual-Forquin-Hild (DFH) a été mise en évidence. Une autre configuration expérimentale mettant en oeuvre un double impact sur une même cible a été utilisée afin de caractériser la résistance de la céramique endommagée. En parallèle, des essais balistiques avec des munitions 7,62x54mmR API B32 et 7,62x51mm AP8 ont été réalisés. La microstructure des céramiques a montré jouer un rôle important sur la performance balistique / Ceramics are a key component in multilayer armor structures. Their low density, typically two to three times lower than steel, combined with a high compressive strength make them essential materials for lightweight armor solutions. Silicon carbide is a promising material for this application due to its particularly low density and high hardness, even among other ceramics. However, armor performance is controlled by more than just the composition and understanding the link between the ceramic microstructure and the fragmentation process during the impact is essential to produce optimized and high performance materials for armor applications.Four dense silicon carbide grades with various microstructures have been used, including three produced during this work. For that, two sintering modes (solid state sintering and liquid phase sintering) and two sintering processes (pressureless sintering and spark plasma sintering) have been used. Particular care has been taken with ceramic processing in order to produce different homogenous and dense microstructures. Silicon carbide parts have been produced at a sufficient size for the application. They were submitted to microstructural characterization (scanning and transmission electronic microscopy, X-ray diffraction, elemental cartography, chemical analysis) and mechanical characterization in quasi-static mode (hardness, toughness, module of rupture, Weibull modulus) and dynamic mode. Dynamic fragmentation of silicon carbide grades has been studied by means of Edge-On Impact (EOI) experiments. A first configuration enabled the study of the damage process that spreads out within the tile thanks to an ultra-high speed camera. A second ‘sarcophagus’ configuration was used to enable observation of the target fragmentation, i.e., crack patterns and crack densities. It has been observed that the microstructure of ceramics plays a key role in the damage intensity generated during impact. A good match with a simulation using the Denoual-Forquin-Hild (DFH) anisotropic damage model has been highlighted. Another experimental configuration implying a double impact on ceramics has been used to characterize the resistance of the damaged target. In parallel, ballistic experiments with 7.62 x54mmR API B32 and 7.62x51mm AP8 threats have been performed. Microstructure of ceramics has been shown to play an important role on ballistic performance

O objetivo principal desta dissertação é determinar, a partir de ensaios de laboratório, o comportamento mecânico de misturas constituídas com solos lateríticos arenoso e argiloso e emulsão asfáltica, visando a sua utilização na construção rodoviária. Utilizou-se na compactação a energia normal do Proctor, e analisaram-se os efeitos do tipo de solo, o teor e tipo de emulsão, tipo de cura pré e pós-compactação, tempo de cura e a imersão em água na resistência e rigidez das misturas. Foram realizados ensaios para a determinação da resistência à compressão simples, resistência à compressão diametral, módulo de resiliência, índice de suporte Califórnia e variação volumétrica durante a cura e imersão dos corpos-de-prova. Os resultados mostraram que as misturas com emulsão apresentaram resistência e rigidez superiores às dos solos in natura, e ainda menores variações volumétricas decorrentes da secagem e da imersão dos corpos-de-prova em água. Finalmente, concluiu-se que o uso das emulsões asfálticas é promissora na área de pavimentação, dado que proporciona às misturas propriedades físicas e mecânicas para estas serem aplicáveis na construção rodoviária. / This work has the main objective of studying, based on laboratory tests, the mechanical behavior of sand and clay lateritics soils and the asphalt emulsion in focus mixtures, seeking their utilization in road construction. Were compacted at the normal Proctor energy, analyzing the soil type, the asphaltic emulsion rate and type, the curing pre and pos- compactation, the curing time and the effect of the immersion in water to the mixtures strength and rigidity, afterwards they were submitted to tests to the determination of unconfined compressive strength, indirect tensile strength, modulus resilient, California bearing ratio and volumetric variability of specimens when immersed in water. The results showed that the addition of asphaltic emulsion to soils improve the strength and rigidity of in natura and reduction of the volumetric variability caused by drying and immersion in water soils. Finally, it concludes that bituminous emulsion provides to soils qualities that could be qualified for use in road construction.

La modélisation de bassin est couramment utilisée pour décrire l’évolution des bassins sédimentaires à partir d’une reconstitution de leur histoire. Durant la modélisation des processus géologiques, les propriétés de transfert des sédiments peuvent changer significativement à cause de leur fracturation naturelle. La présence de ces fractures dans le bassin peut constituer des chemins préférentiels d’écoulement ou des barrières qui contrôlent les niveaux de surpressions, l’accumulation et la migration des hydrocarbures dans le milieu ainsi que la perméabilité du milieu. Dans l’industrie pétrolière et en particulier durant l’exploration, la connaissance de l’historique des processus de fracturation naturelle permet d’améliorer la prédiction des positions de réservoirs d’hydrocarbures dans le milieu ainsi que leurs propriétés. En profondeur les fractures s’amorcent dans les roches aux niveaux des discontinuités géométriques. Cependant, les chargements à l’origine de l’initiation de ces fractures restent mal connus. Dans les bassins sédimentaires, les propriétés mécaniques et géométriques de ces fractures sont directement reliées aux processus inhérents à leur formation. Elles peuvent dériver de certains processus comme par exemple le dépôt des sédiments, les chargements tectoniques ou le processus d’érosion. Le but de cette thèse est de fournir une amélioration de la caractérisation de l’amorçage des fractures dans la modélisation de bassin à partir d’un outil numérique de simulation de réseaux de fractures et de son évolution sous chargement hydromécanique. Au cours de la sédimentation, les matériaux enfouis subissent une augmentation de la contrainte verticale. Cette augmentation de la contrainte par sédimentation entraîne une compaction mécanique et une diminution de la porosité. La compaction mécanique qui dépend du taux de sédimentation et de la perméabilité des matériaux enfouis peut générer des surpressions importantes dans le bassin. Dès lors une compétition s’établie entre la dissipation de la surpression des fluides et la vitesse de sédimentation et peut conduire à l’amorçage de fractures. Ainsi, pour étudier analytiquement l’amorçage des fractures dans le bassin, un modèle synthétique géologique est proposé. La solution analytique de l’évolution de la pression et des contraintes dans ce contexte est obtenu en superposant deux problèmes de poroélasticités. L’analyse de la solution et d’un critère de fracturation serviront de base pour prédire l’amorçage et la propagation des fractures. Pour simuler la propagation et l’évolution des fractures, un modèle numérique comportant des chemins potentiels de fracturation uniformément repartis est mis au point dans le code de calcul par éléments finis Porofis. Les fractures sont modélisées par un modèle de joints cohésifs avec endommagement et l’écoulement est décrit à partir de loi de Poiseuille. Les effets du couplage hydromécanique dans les fractures et dans la matrice poreuse sur l’évolution dynamique de l’espacement des fractures pour des cas synthétiques typiques de la modélisation de bassin sont également étudiés / Basin modeling is commonly used to describe basin's evolution from a reconstruction of its history. During the geological processes modeling, the transfer properties of sediments can change significantly due to natural fracturing and therefore may constitute preferential flow paths or barrier that control hydrocarbons migration and accumulation. In petroleum industry, and especially for exploration, the knowledge of natural fracturing processes and history enhances the prediction of overpressures, potential location of hydrocarbon storage and matrix equivalent permeability. At significant depth, nucleation of fractures and initiation are triggered at existing defects, but the loads behind its initiation are unknown or poorly characterized. In sedimentary basin, fracture mechanical and geometrical properties are directly related to the processes from which it comes. Fracture initiation at depth can arise from by many processes such as deposition, tectonic and erosion processes. The aim of the thesis is to provide an improvement in the characterization of fracture initiation in basin modeling by using a numerical modeling of fracture network and its evolution under hydro mechanical loading. During sedimentation, buried rocks are subjected to an increase in vertical stress. This increase leads to a decrease of porosity that is commonly called mechanical compaction. Indeed, the mechanical compaction depending on its rate and on the permeability of the burden rocks, can induce significant overpressures. Thus, a competition is initiated between the dissipation of fluid overpressure and sedimentation rate, and may result in fracture initiation. For analytical study of fracture initiation, a synthetic geologic structure is used. The analytical solution analytical solution of the pressure and stresses in a sealing formation is proposed under sedimentation by superposing two problems of poroelasticity. This analytical solution and a fracturing criterion are used to predict the initiation and propagation of the fracture. The fracture propagation and growth are studied by numerical simulations based on a finite element code dedicated to fractured porous media called Porofis. The numerical model contains defects initially closed and homogeneously distributed. The fractures are modeled with a constitutive model undergoing damage and the flow is described by Poiseuille’s law. The effect of hydromechanical coupling on dynamicevolution of fracture spacing using synthetic geological structure for basin modeling are also studied

Every living creature meets with pain up to these days. Many researches are made in labour conditions, we try to find out how the pain works and how we can suppress it or how we can utilize it in our welfare. Our work is focused on the effect of aging, season, acclimatization and ambient temperature on thermal and mechanic pain threshold in laboratory rats. We were interested how these factors affect the results of the research. Adult male Wistar rats were used in all experiments. Thermal pain thresholds were measured by withdrawal reaction of three body sites: forelimbs, hind limbs and tail. Mechanic pain thresholds were measured by von Frey filaments and a skin temperature was measured by IR thermometer, both of three body sites. Our results demonstrate that : (i) aging have effect on nociceptive pain threshold; (ii) there is presence of cranio-caudal distribution of nociceptive sensitivity in aging and in changing of ambient temperature - forelimbs have lower latency than hind limbs; (iii) thermal pain threshold depends indirectly on ambient and skin temperature; (iv) there was no effect of repeated measurement on nociceptive thresholds of the three body sites; (v) hind limbs and tails are more sensitive to changes of ambient temperature than forepaws; (vi) mechanic pain threshold not change...

Objetivo: Determinar el impacto de la nutrición enteral temprana en la unidad de cuidados intensivos pediátricos Métodos: Se realizó un estudio analítico observacional de tipo cohorte retrospectivo en los pacientes ingresados a una unidad de cuidados intensivos pediátricos (UCIP). La información fue recopilada de las historias clínicas. Nuestra variable de exposición fue nutrición enteral (NE), la cual se subdivide en inicio temprano (menor de 72 horas) y tardío (mayor o igual a 72 horas). La variable de respuesta fue tiempo de estancia hospitalaria (TEH), entendida como el periodo desde el ingreso a la UCIP hasta el alta hospitalaria. Resultados: La NE temprana se asoció a una disminución de 10.4 días en el tiempo de estancia hospitalaria. Asimismo, los pacientes que recibieron NE temprana tuvieron 7.13 días menos de tiempo de estancia en la unidad de cuidados intensivos pediátricos a comparación de quienes recibieron NE tardía. Además, la duración de la ventilación mecánica se asoció a una disminución de 5.43 días en quienes recibieron NE temprana a comparación de los pacientes que recibieron NE tardía. Finalmente, la interrupción de la NE se asoció a un aumento de 10.7 en el TEH. Conclusiones: Los pacientes con ventilación mecánica en UCIP que recibieron NE temprana tienen riesgo disminuido de tener mayor TEH, mayor tiempo de estancia en la UCIP y mayor duración de ventilación mecánica. La interrupción de la NE aumenta el TEH. / Objective: To determine the impact of early enteral nutrition in the pediatric intensive care unit. Methods: A retrospective cohort observational analytical study was performed in the patients admitted in a pediatric intensive care unit (PICU). The information in the medical records was compiled. Our exposure variable was enteral nutrition (EN) subdivided into early (<= 72 hours) and late (> 72 hours). The response variable was the length of hospital stay (LHS) understood as the period from admission to the PICU until hospital discharge. Results: Early EN is associated with a decrease of 10.4 days in the length of hospital stay. Likewise, patients who received early NE had 7.13 less days of stay in the PICU days compared to those who received late NE. In addition, the length of mechanical ventilation decrease 5.43 days in those who received early EN compared to patients who received late EN. Finally, the interruption of the NE increased the length of hospital stay by 10.7 days. Conclusions: Patients with MV in PICU who received early EN have a decreased risk of longer hospital stay, longer length of stay in the PICU, and longer duration of mechanical ventilation. The interruption of the NE increases the LHS. / Tesis