• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 120
  • 63
  • 13
  • 7
  • 6
  • 5
  • 5
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 261
  • 52
  • 40
  • 40
  • 32
  • 29
  • 29
  • 26
  • 26
  • 25
  • 25
  • 25
  • 23
  • 20
  • 19
  • 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.
251

Power quality analysis using relay recorded data

Birdi, Harjit Singh 01 September 2006
Demand for electrical power is increasing everyday. Along with the increase in power demand, the characteristics of the loads are also changing. From being high power consuming, simple, robust loads, today loads are more efficient, but at the same time more sensitive. The performance and life of these highly sensitive loads depend a lot on the quality of power supplied to them. <p>Power quality is any deviation of the voltage or current waveform from its normal sinusoidal waveshape. These disturbances include, but are not limited to, sag, undervoltage, interruption, swell, overvoltage, transients, harmonics, voltage flicker and any other distortions to the sinusoidal waveform. Occurrence of one or more of such disturbances is called a power quality event. Automatic classification of these disturbances is important for quick determination of the causes and to characterize possible impacts of the disturbances.<p>Modern microprocessor based protective relays have numerous integrated functions that allow them to provide information on power quality events. It is proposed to utilize the existing numerical relays to analyze the quality of power at any point in the power system. The numerical relays can be programmed to capture the oscillographic waveform or any disturbance on the analogue signal or change of state of the digital signals and store it in the form of Common Format For Transient Data Exchange (COMTRADE) format. These records are then transferred to a central monitoring workstation for off-line analysis. <p>This thesis describes a technique to automate the classification and analysis of the power quality events using relay recorded data. The technique uses voltage duration and magnitude (as specified in the IEEE Std. 1159 - 1995, IEEE Recommended Practice for Monitoring Electric Power Quality) of three phases to detect and classify the events. The classified results are then presented in a user-friendly graphical form. Fast Fourier Transform (FFT) is used to estimate the fundamental frequency and harmonic components in power systems. The graphical user interface of the power quality analysis tool is developed using Microsoft Visual C++ IDE and the algorithms are programmed in C++. <p>The proposed technique was tested using data obtained by simulating different power system disturbances as well as on the data recorded by relays. The algorithms were able to classify the power quality events accurately. In the future, this facility will: enhance the real time monitoring of power quality and provide statistical analysis of available power quality data. From the utility viewpoint, it would allow them to monitor power quality in a cost effective manner and assist in preventive and predictive maintenance besides helping them to fix differential tariff based on the quality of the delivered power. It may also turn out to be a smart tool for them to penalize the consumer polluting the power quality.
252

Power quality analysis using relay recorded data

Birdi, Harjit Singh 01 September 2006 (has links)
Demand for electrical power is increasing everyday. Along with the increase in power demand, the characteristics of the loads are also changing. From being high power consuming, simple, robust loads, today loads are more efficient, but at the same time more sensitive. The performance and life of these highly sensitive loads depend a lot on the quality of power supplied to them. <p>Power quality is any deviation of the voltage or current waveform from its normal sinusoidal waveshape. These disturbances include, but are not limited to, sag, undervoltage, interruption, swell, overvoltage, transients, harmonics, voltage flicker and any other distortions to the sinusoidal waveform. Occurrence of one or more of such disturbances is called a power quality event. Automatic classification of these disturbances is important for quick determination of the causes and to characterize possible impacts of the disturbances.<p>Modern microprocessor based protective relays have numerous integrated functions that allow them to provide information on power quality events. It is proposed to utilize the existing numerical relays to analyze the quality of power at any point in the power system. The numerical relays can be programmed to capture the oscillographic waveform or any disturbance on the analogue signal or change of state of the digital signals and store it in the form of Common Format For Transient Data Exchange (COMTRADE) format. These records are then transferred to a central monitoring workstation for off-line analysis. <p>This thesis describes a technique to automate the classification and analysis of the power quality events using relay recorded data. The technique uses voltage duration and magnitude (as specified in the IEEE Std. 1159 - 1995, IEEE Recommended Practice for Monitoring Electric Power Quality) of three phases to detect and classify the events. The classified results are then presented in a user-friendly graphical form. Fast Fourier Transform (FFT) is used to estimate the fundamental frequency and harmonic components in power systems. The graphical user interface of the power quality analysis tool is developed using Microsoft Visual C++ IDE and the algorithms are programmed in C++. <p>The proposed technique was tested using data obtained by simulating different power system disturbances as well as on the data recorded by relays. The algorithms were able to classify the power quality events accurately. In the future, this facility will: enhance the real time monitoring of power quality and provide statistical analysis of available power quality data. From the utility viewpoint, it would allow them to monitor power quality in a cost effective manner and assist in preventive and predictive maintenance besides helping them to fix differential tariff based on the quality of the delivered power. It may also turn out to be a smart tool for them to penalize the consumer polluting the power quality.
253

Nonlinear Impulsive and Hybrid Dynamical Systems

Nersesov, Sergey G 23 June 2005 (has links)
Modern complex dynamical systems typically possess a multiechelon hierarchical hybrid structure characterized by continuous-time dynamics at the lower-level units and logical decision-making units at the higher-level of hierarchy. Hybrid dynamical systems involve an interacting countable collection of dynamical systems defined on subregions of the partitioned state space. Thus, in addition to traditional control systems, hybrid control systems involve supervising controllers which serve to coordinate the (sometimes competing) actions of the lower-level controllers. A subclass of hybrid dynamical systems are impulsive dynamical systems which consist of three elements, namely, a continuous-time differential equation, a difference equation, and a criterion for determining when the states of the system are to be reset. One of the main topics of this dissertation is the development of stability analysis and control design for impulsive dynamical systems. Specifically, we generalize Poincare's theorem to dynamical systems possessing left-continuous flows to address the stability of limit cycles and periodic orbits of left-continuous, hybrid, and impulsive dynamical systems. For nonlinear impulsive dynamical systems, we present partial stability results, that is, stability with respect to part of the system's state. Furthermore, we develop adaptive control framework for general class of impulsive systems as well as energy-based control framework for hybrid port-controlled Hamiltonian systems. Extensions of stability theory for impulsive dynamical systems with respect to the nonnegative orthant of the state space are also addressed in this dissertation. Furthermore, we design optimal output feedback controllers for set-point regulation of linear nonnegative dynamical systems. Another main topic that has been addressed in this research is the stability analysis of large-scale dynamical systems. Specifically, we extend the theory of vector Lyapunov functions by constructing a generalized comparison system whose vector field can be a function of the comparison system states as well as the nonlinear dynamical system states. Furthermore, we present a generalized convergence result which, in the case of a scalar comparison system, specializes to the classical Krasovskii-LaSalle invariant set theorem. Moreover, we develop vector dissipativity theory for large-scale dynamical systems based on vector storage functions and vector supply rates. Finally, using a large-scale dynamical systems perspective, we develop a system-theoretic foundation for thermodynamics. Specifically, using compartmental dynamical system energy flow models, we place the universal energy conservation, energy equipartition, temperature equipartition, and entropy nonconservation laws of thermodynamics on a system-theoretic basis.
254

Preliminary interplanetary trajectory design tools using ballistic and powered gravity assists

Brennan, Martin James 17 September 2015 (has links)
Preliminary interplanetary trajectory designs frequently use simplified two-body orbital mechanics and linked conics methodology to model the complex trajectories in multi-body systems. Incorporating gravity assists provides highly efficient interplanetary trajectories, enabling otherwise infeasible spacecraft missions. Future missions may employ powered gravity assists, using a propulsive maneuver during the flyby, improving the overall trajectory performance. This dissertation provides a complete description and analysis of a new interplanetary trajectory design tool known as TRACT (TRAjectory Configuration Tool). TRACT is capable of modeling complex interplanetary trajectories, including multiple ballistic and/or powered gravity assists, deep space maneuvers, parking orbits, and other common maneuvers. TRACT utilizes an adaptable architecture of modular boundary value problem (BVP) algorithms for all trajectory segments. A bi-level optimization scheme is employed to reduce the number of optimization variables, simplifying the user provided trajectory information. The standardized optimization parameter set allows for easy use of TRACT with a variety of optimization algorithms and mission constraints. The dissertation also details new research in powered gravity assists. A review of literature on optimal powered gravity assists is presented, where many optimal solutions found are infeasible for realistic spacecraft missions. The need was identified for a mission feasible optimal powered gravity assist algorithm using only a single impulsive maneuver. The solution space was analyzed and a complete characterization was developed for solution types of the optimal single-impulse powered gravity assist. Using newfound solution space characteristics, an efficient and reliable optimal single-impulse powered gravity assist BVP algorithm was formulated. The mission constraints were strictly enforced, such as maintaining the closest approach above a minimum radius and below a maximum radius. An extension of the optimal powered gravity assist research is the development of a gravity assist BVP algorithm that utilizes an asymptote ΔV correction maneuver to produce ballistic gravity assist trajectory solutions. The efficient algorithm is tested with real interplanetary mission trajectory parameters and successfully converges upon ballistic gravity assists with improved performance compared to traditional methods. A hybrid approach is also presented, using the asymptote maneuver algorithm together with traditional gravity assist constraints to reach ballistic trajectory solutions more reliably, while improving computational performance.
255

Tsunami wave interaction with a coastal structure: : Focus on the Tohoku tsunami case and the flip-through impact. / Étude de l'impact d'un tsunami sur une structure côtière: : Cas particulier du tsunami de Tohoku et rôle de l'impact du type " flip-through".

Martin-Medina, Manuel 20 December 2017 (has links)
Lors du tsunami de Tohoku en 2011, des relevés de terrain sur les côtes japonaises ont montré la fragilité des structures côtières, où le plus grand brise-lames du monde (brise-lames de Kamaishi) a été fortement endommagé dû à cet événement. Dans ce doctorat, l'objectif est d'étudier l'interaction entre les brise-lames , les structures côtières les plus communes protégeant les zones urbaines et les entrées des ports, et les vagues, en particulier les tsunamis.Dans la première partie de ce travail, la transformation du tsunami en bore ondulaire dans les zones côtières est étudiée numériquement avec le code de calcul BOSZ (modèle Boussinesq). Les résultats montrent que la deuxième vague générée par le tsunami de Tohoku s'est transformée en un bore ondulaire. En revanche, la première vague n'était pas assez cambrée pour permettre une telle transformation. Les forces et les moments dus aux vagues ainsi que la contrainte normale appliquée par la base arrière du caisson sur le sol de fondation sont calculés à l'aide de deux modèles numériques différents: BOSZ et THETIS (modèle Navier-Stokes). Les résultats de BOSZ sont comparés avec THETIS pour l'interaction tsunami-structure. L'étude d'impact est réalisée à relativement grande échelle dans le but d'obtenir une première estimation des efforts d'un tsunamiPar la suite, une expérience numérique utilisant le modèle THETIS a été réalisée pour étudier les impacts du type flip-through sur des brise-lames. Ces impacts de vagues sans air emprisonné sont considérés comme le type d'impact le plus extrême dans la littérature (e.g. Cooker & Peregrine (1992), Hofland et al. (2011)). L'influence de l'inclinaison de l'interface sur la dynamique d'impact et les pressions générées sont analysées dans une configuration de brise-lames réelle. Le modèle d'onde solitaire est utilisé pour générer trois impacts caractéristiques du type flip-through: peu cambré, moyen et très cambré. Le champ de vitesses et la pression à l'intérieur de la fondation sont également étudiés dans cette partie. Les forces horizontales et verticales appliquées sur le caisson sont estimées en intégrant les distributions de pression données par THETIS.La dernière partie de ces travaux montre la stabilité des caissons de brise-lames soumis à des impacts du type flip-through, qui sont ici assimilés à un jet triangulaire (e.g. Cumberbatch (1960), Kihara et al. (2015)). Cette approche simple permet de formuler un modèle semi-analytique pour prédire le mouvement des caissons dû à ce type d'impacts. Après validation avec des simulations numériques, la méthode du jet triangulaire permet d'obtenir des informations sur les forces, la durée du mouvement et le déplacement total en fonction des caractéristiques de la vague et des dimensions du caisson du brise-lames impacté. / During the Tohoku tsunami in 2011, field surveys of the east coast of Japan showed the weakness of coastal defences, as even the world largest tsunami breakwater (Kamaishi) almost completely collapsed due to this event. In this PhD, the aim is to investigate the interaction between breakwaters, the most common offshore coastal structures protecting urban areas and harbour entries, and waves and especially tsunami waves.In the first part of the work, the generation of undular bores in the near-shore area of Sendai during the Tohoku event is numerically investigated with the numerical model BOSZ (Boussinesq-type model). It is shown that the second wave, which stroke the coast during this event, transformed into an undular bore, whereas the first wave did not due to steepness differences. Tsunami loads, moments and bearing stress applied on the offshore breakwater of the Soma Port are calculated using two models: BOSZ and THETIS (Navier-Stokes VOF model). BOSZ results are compared to THETIS for the tsunami wave-breakwater interaction. The impact study is carried out at a relatively large scale aiming to have a first estimation of tsunami efforts. Then, a numerical experiment using THETIS is carried out to investigate flip-through impacts on vertical breakwaters. This non-aerated wave impact is considered as the most severe type of impact in the literature (e.g. Cooker & Peregrine (1992), Hofland et al. (2011)) in terms of maximum pressure generated. The influence of the front interface on the impact dynamics and the pressure induced is analysed in a realistic breakwater configuration. Solitary waves are used to obtain three characteristic flip-through impacts involving least steep, medium steep and steepest wave front. The flow field and pressure inside the porous rubble mound are then investigated as well as horizontal and uplift forces applied on the breakwater caisson. The last part of this study is devoted to the stability of breakwater caissons submitted to flip-through impacts. The latter are here assimilated to water wedges (e.g. Cumberbatch (1960), Kihara et al. (2015)). This simple approach allows to formulate a semi-analytical model to predict caisson motion due to this type of impacts. After validation with numerical results, the water wedge method gives rich informations about forces, motion duration and sliding distance depending on the wave impact characteristics and breakwater caisson dimensions.
256

The modes of thinking and learning of educationally disadvantaged learners

Rosa, Cecelia Mary 30 November 2004 (has links)
The aim of this investigation was to determine the modes of thinking and learning of South African disadvantaged learners as well as to discover whether the teaching methods used by their teachers, encourage diverse cognitive skills and learning styles amongst learners. A survey of existing literature on this subject identifies a number of theories that indicate that learners come to school with diverse modes of thinking and learning. Furthermore, existing literature, indicate that educationally disadvantaged learners tend towards a Field Dependent, socially orientated mode of cognitive processing and a largely visual and kinaesthetic mode of sensory processing information. Research also reveals that teaching methods and teacher expectation of learner potential play a vital role in the academic achievement of disadvantaged learners. Teachers tend to have lower expectations of the academic potential of disadvantaged learners. Moreover, teachers tend to favour teaching methods that meet the needs of learners who use Field Independent cognitive and Auditory sensory processing. Another aspect acknowledged in existing literature that influences the academic achievement of disadvantaged learners is the role of family and the community. Disadvantaged learners generally do not have the support and security of a stable home and are frequently exposed to violence and an educationally impoverished environment. Parents and guardians tend to be less involved in the education of their children. Disadvantaged learners who were part of this empirical study conducted in the Ekhuruleni Metropolitan area, east of Johannesburg, South Africa, showed a more concrete approach to academic activities and revealed a tendency towards Field Dependency and a visual and kinaesthetic sensory approach to processing information. Learners preferred more frequent social interaction during academic activities. The study also found that the teaching method most commonly used in the geographical area mentioned above, took the form of lecturing or `chalk-and-talk' and that teaching aids generally took the form of worksheets. Hence the teaching approach most used by teachers in the study, did not address the modes of thinking and learning of disadvantaged learners in the schools that participated in the empirical study and generally did not encourage deeper cognitive structures. / Educational Studies / D. Ed. (Psychology of Education)
257

Apprentissage et annulation des bruits impulsifs sur un canal CPL indoor en vue d'améliorer la QoS des flux audiovisuels / Teaching and cancelling impulsive noise on an indoor PLC channel to improve the QoS of audiovisual flows

Fayad, Farah 02 April 2012 (has links)
Le travail présenté dans cette thèse a pour objectif de proposer et d'évaluer les performances de différentes techniques de suppression de bruit impulsif de type asynchrone adaptées aux transmissions sur courants porteurs en lignes (CPL) indoor. En effet, outre les caractéristiques physiques spécifiques à ce type de canal de transmission, le bruit impulsif asynchrone reste la contrainte sévère qui pénalise les systèmes CPL en terme de QoS. Pour remédier aux dégradations dues aux bruits impulsifs asynchrones, les techniques dites de retransmission sont souvent très utilisées. Bien qu'elles soient efficaces, ces techniques de retransmission conduisent à une réduction de débit et à l’introduction de délais de traitement supplémentaires pouvant être critiques pour des applications temps réel. Par ailleurs, plusieurs solutions alternatives sont proposées dans la littérature pour minimiser l'impact du bruit impulsif sur les transmissions CPL. Cependant, le nombre de techniques, qui permettent d'obtenir un bon compromis entre capacité de correction et complexité d'implantation reste faible pour les systèmes CPL. Dans ce contexte, nous proposons dans un premier temps d'utiliser un filtre linéaire adaptatif : le filtre de Widrow, nommé aussi ADALINE (ADAptive LInear NEuron), que nous utilisons comme méthode de débruitage pour les systèmes CPL. Pour améliorer les performances du débruitage effectué à l'aide d'ADALINE, nous proposons d'utiliser un réseau de neurones (RN) non linéaire comme méthode de débruitage. Le réseau de neurones est un bon outil qui est une généralisation de la structure du filtre ADALINE. Dans un deuxième temps, pour améliorer les performances du débruitage par un réseau de neurones, nous proposons un procédé d'annulation du bruit impulsif constitué de deux algorithmes : EMD (Empirical Mode Decomposition) associé à un réseau de neurones de type perceptron multicouches. L'EMD effectue le prétraitement en décomposant le signal bruité en signaux moins complexes et donc plus facilement analysables. Après quoi le réseau de neurones effectue le débruitage. Enfin, nous proposons une méthode d'estimation du bruit impulsif utilisant la méthode GPOF (Generalized Pencil Of Function). L'efficacité des deux méthodes, EMD-RN et la technique utilisant l'algorithme GPOF, est évaluée en utilisant une chaîne de simulation de transmission numérique compatible avec le standard HPAV. / The aim of our thesis is to propose and to evaluate the performances of some asynchronous impulsive noise mitigation techniques for transmission over indoor power lines. Indeed, besides the particular physical properties that characterize this transmission channel type, asynchronous impulsive noise remains the difficult constraint to overcome on power lines communications (PLC). Usually, the impact of asynchronous impulsive disturbances over power lines is partly compensated by means of retransmission mechanisms. However, the main drawbacks of the use of retransmission solutions for impulsive noise mitigation are the bitrate loss and the induced time delays that may be prohibitive for real-time services. Although several other countering strategies are proposed in the literature, only very few of them have a good compromise between correction capability and implementing complexity for PLC systems. In this context, we proposed an adaptive linear filter, the Widrow filter, also known as ADALINE (Adaptive LInear neurons), as a denoising method for PLC systems. To improve the performance of the denoising method using ADALINE, we proposed to use a neural network (NN) as a nonlinear denoising method. The neural network is a good generalization of the ADALINE filter. In a second step, to improve the performances of denoising by NN, we proposed a combined denoising method based on EMD (Empirical Mode Decomposition) and MLPNN (Multi Layer Perceptron Neural Network). The noised signal is pre-processed by EMD which decomposes it into signals less complex and therefore more easily analyzed. Then the MLPNN denoises it. Finally, we proposed an asynchronous impulsive noise estimation method using the GPOF method (Generalized Pencil Of Function). The performances of the two methods, EMD-MLPNN and GPOF technique, are evaluated using a PLC transmission chain compatible with the HPAV standard.
258

Perfil neuropsicológico e psiquiátrico de adolescentes submetidos a maus tratos / Neuropsychological and psychiatric profile of adolescents exposed to maltreatment

Paula Approbato de Oliveira 24 May 2013 (has links)
Introdução: Os maus tratos na infância e adolescência são considerados um problema de saúde pública devido a alta prevalência no Brasil e no mundo. A exposição a maus tratos está associada a alterações no desenvolvimento cognitivo, porém, há uma escassez de estudos brasileiros que investiguem o tema. Objetivos: Comparar o funcionamento neuropsicológico de adolescentes com e sem histórico de maus tratos, bem como estudar as relações entre essas vivências, desempenho neuropsicológico e sintomas psiquiátricos relacionados a impulsividade, oposição, hiperatividade e desatenção. Método: Cento e oito adolescentes foram selecionados em dois programas de atendimento a população em situação de vulnerabilidade e/ou risco social de São Paulo (SP). De acordo com a pontuação do Questionário de Traumas na Infância (QUESI), foram classificados em três grupos: GMT1 (grupo de maus tratos leves, n=35), GMT2 (grupo de maus tratos moderado a grave, n=19) e GC (grupo de comparação, n=54). Os adolescentes passaram por avaliação neuropsicológica com o foco na investigação de funções relacionadas a percepção visual e spam atencional (primeira unidade funcional), processamento e armazenamento de informações (segunda unidade funcional) e funcionamento executivo (terceira unidade funcional). Foram utilizadas escalas para avaliação psiquiátrica (K-SADS-PL) e investigação de sintomas de impulsividade, hiperatividade, desatenção e oposição (BIS-1, SNAP-IV). Os resultados obtidos nos grupos foram comparados com o controle estatístico de variáveis sociais (dificuldades socioeconômicas, escolaridade e abrigamento) e clínicas (transtornos psiquiátricos internalizantes e externalizantes, uso de medicação psiquiátrica e quociente intelectual estimado- QI). Por fim, foram feitas associações entre exposição a maus tratos, funcionamento neuropsicológico e sintomas psiquiátricos. Resultados: Os GMTs (grupos de maus tratos) apresentaram pior funcionamento intelectual em relação ao GC, sendo que o pior desempenho foi encontrado no GMT2 (p< 0,001). Medidas menores de QI estiveram associadas a prejuízo nas três unidades funcionais (p<= 0,049) e a mais sintomas de hiperatividade e desatenção (p <= 0,008). Foi encontrado pior desempenho dos GMTs nos testes para avaliação de segunda unidade funcional (p<= 0,001), porém, não foram encontradas diferenças entre os grupos na primeira e terceira unidades. Apesar disso, os testes de correlação indicaram que o aumento das pontuações no QUESI estava associado à piora do desempenho em todas as unidades funcionais (p<= 0,046). Os GMTs apresentaram maior impulsividade e oposição (p<= 0,008) e, quanto maior a pontuação no QUESI, maior a presença de sintomas de impulsividade, oposição, sintomas isolados de desatenção e sintomas mistos de desatenção e hiperatividade (p<= 0,006). Conclusão: Os resultados obtidos corroboram a associação entre exposição a maus tratos e dificuldades cognitivas e psiquiátricas. Os dados obtidos poderão contribuir para o planejamento de políticas públicas voltadas tanto à prevenção quanto para o tratamento de patologias associadas ao desenvolvimento neurobiológico alterado de crianças e adolescentes que crescem em condições adversas. / Introduction: Maltreatment experiences in childhood and adolescence are considered a public health problem due to high prevalence in Brazil and worldwide. The exposure to maltreatment is associated with changes in cognitive development; however, there is a shortage of Brazilian research that investigates this topic. Objectives: Comparison of neuropsychological functioning of adolescents with and without maltreatment history, as well as the research of relationships between these experiences, neuropsychological performance, and psychiatric symptoms relating to impulsivity, opposition, hyperactivity, and inattention. Methods: One hundred and eight adolescents were selected from two assistance programs for people in vulnerability and social risk situation in the city of Sao Paulo (SP). According to the Childhood Trauma Questionnaire (CTQ), three groups were classified: GMT1 Group (Mild Maltreatment, n = 35), GMT2 (group of moderate to severe maltreatment, n = 19) and GC (comparison group, n = 54). The adolescents underwent neuropsychological evaluation with a focus on the investigation of functions related to visual perception and attention spam (first functional unit), processing and retention of information (second functional unit) and executive functioning (third functional unit). Scales were used for psychiatric assessment (K-SADS-PL) and investigation of impulsivity, hyperactivity, inattention, and opposition symptoms (SNAP-IV, BIS-11). Results obtained in these groups were compared with statistical control of social variables (socioeconomic, school level, and shelter), and clinical variables (internalizing and externalizing psychiatric disorders, use of psychiatric medication, and estimated intellectual quotient - IQ). Lastly, associations between exposure to maltreatment, neuropsychological functioning and psychiatric symptoms were made. Results: The GMT (maltreatment groups) had a worse intellectual functioning compared to GC, while the worst performance was found in GMT2 (p < 0.001). Lower IQ measures were associated to impairment on the three functional units (p<= 0.049) and to more symptoms of inattention and hyperactivity (p <= 0.008). Worse performance on tests for evaluation of the second functional unit (p<= 0.001) was found for GMT, but no differences were found between the groups on the first and third units. Nevertheless, the correlation tests indicated that the increase in CTQ scores was associated to worse performance in all of the functional units (p<= 0,046). The GMT presented higher impulsivity and opposition (p<= 0,008) and the higher the CTQ score the more symptoms of impulsivity, opposition, isolated symptoms of inattention, and mixed symptoms of inattention and hyperactivity (p<= 0,006). Conclusion: The results confirm the negative association between exposure to maltreatment and psychiatric and cognitive difficulties. The data obtained will contribute to the planning of public policies for both prevention and treatment of diseases associated to altered neurobiological development of children and adolescents who grow up in adverse conditions.
259

Estudo do efeito da estimulação magnética transcraniana de repetição sobre a impulsividade na dependência de cocaína / Study of repeated transcranial magnetic stimulation on impulsivity in cocaine dependence

Adan Pelegrino Jardim 26 July 2013 (has links)
INTRODUÇÃO: A dependência química engloba alterações comportamentais, cognitivas e fisiológicas. A impulsividade está presente em muitos transtornos psiquiátricos. Sobre a impulsividade na dependência química de cocaína, os estudos existentes são relativamente novos. A Estimulação Magnética Transcraniana de repetição (EMTr) é um método capaz de neuromodular o cérebro. Este estudo avaliou os efeitos da EMTr sobre a impulsividade em dependentes de cocaína. MÉTODOS: Em um estudo randomizado, duplamente encoberto, 25 pacientes diagnosticados pelo DSM-IV-TR foram tratados com EMTr de alta frequência ativa (1250 pulsos/dia) ou EMTr placebo. O tratamento consistiu em 1 mês de aplicação de EMTr seguido de 2 meses em acompanhamento ambulatorial semanal em um grupo de prevenção de recaídas. Os pacientes foram avaliados antes do início do tratamento com EMTr (T0) e após o término das aplicações (T1), através dos instrumentos: The Shorter PROMIS Questionnaire, The Schalling Impulsivity Scale e The Leeds Dependence Questionnaire. RESULTADOS: 25 pacientes foram tratados e a análise dos dados demonstraram redução nos índices de impulsividade em ambos os grupos ao longo do tempo, porém, quando comparados entre si, os valores de interação não se mostraram significativos. CONCLUSÃO: Os efeitos da EMTr não diferiram em eficácia terapêutica na redução da impulsividade em dependentes de cocaína, com o efeito ativo correspondendo com o placebo / INTRODUCTION: Chemical addiction involves behavioral, cognitive and physiological alterations. Impulsivity is present in many psychiatric disorders. Studies about impulsivity and cocaine chemical addiction are relatively new. Transcranial Magnetic Stimulation (EMTr) is a method capable of neuromodulation the brain. This study evaluated the effects of EMTr over impulsivity in cocaine addicts. METHODS: This is a randomized doubly covert study with 25 patients diagnosed by the DSM-IV-TR who were treated with active high frequency EMTr (1250 pulses/day) or placebo. Treatment was consisted of one month of application of EMTr followed by 2 months of clinical follow-up in a relapse prevention group. Patients were evaluated before the treatment with EMTr (T0) and after the end of the applications (T1), through the instruments: The Shorter PROMIS Questionnaire, The Schalling Impulsivity Scale and The Leeds Dependence Questionnaire. RESULTS: 25 patients were treated and data analysis showed a reduction in the levels of impulsivity in both groups throughout the time. However, group comparisons did not show statistical differences. CONCLUSION: EMTr\'s effects did not differ in terms of therapeutical efficacy in the reduction of impulsivity in cocaine addicts
260

Uma contribuição ao problema de detecção de ruídos impulsivos para power line communication

Lopez, Paola Johana Saboya 03 June 2013 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-24T15:28:35Z No. of bitstreams: 1 paolajohanasaboyalopez.pdf: 1042873 bytes, checksum: a46dd95de00e062cba39ef4b9b642462 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-24T17:09:24Z (GMT) No. of bitstreams: 1 paolajohanasaboyalopez.pdf: 1042873 bytes, checksum: a46dd95de00e062cba39ef4b9b642462 (MD5) / Made available in DSpace on 2017-04-24T17:09:24Z (GMT). No. of bitstreams: 1 paolajohanasaboyalopez.pdf: 1042873 bytes, checksum: a46dd95de00e062cba39ef4b9b642462 (MD5) Previous issue date: 2013-06-03 / A presente dissertação tem por objetivo propor e avaliar cinco técnicas de detecção de ruídos impulsivos para a melhoria da transmissão digital de dados via redes de energia elétrica (do inglês, Power Line Communications) (PLC). As técnicas propostas contemplam a detecção de ruídos impulsivos no domínio do tempo discreto, no domínio da transformada wavelet discreta (do inglês, Discrete Wavelet Transform) (DWT) e no domínio da transformada discreta de Fourier (do inglês, Discrete Fourier Transform) (DFT). Tais técnicas fazem uso de métodos de extração e seleção de características, assim como métodos de detecção de sinais baseados na teoria de Bayes e redes neurais. Análises comparativas explicitam as vantagens e desvantagens de cada uma das técnicas propostas para o problema em questão, e ainda indicam que estas são bastante adequadas para a solução do mesmo. / This dissertation aims to propose and evaluate five techniques for impulsive noise detection in order to improve digital communications through power line channels. The imput signals for the proposed detection techniques are impulsive noise signals on discrete-time domain, on the Discrete Wavelet Transform domain and on the Discrete Fourier Transform domain and it makes use of feature extraction and selection techniques, as well as detection techniques supported on Bayes Theory and Multi-layer Perceptron Neural Networks. Comparative analysis show some advantages and disadvantages of each proposed technique and the relevance of them to solve the impulsive noise detection problem.

Page generated in 0.0529 seconds