Cette thèse s’intéresse aux algorithmes adaptés aux architectures mémoire hiérarchiques, rencontrées notamment dans le contexte des processeurs multi-cœurs.Nous étudions d’abord le produit de matrices sur les processeurs multi-cœurs. Nous modélisons le processeur, bornons le volume de communication, présentons trois algorithmes réduisant ce volume de communication et validons leurs performances. Nous étudions ensuite la factorisation QR, dans le contexte des matrices ayant plus de lignes que de colonnes. Nous revisitons les algorithmes existants afin d’exploiter les processeurs multi-cœurs, analysons leurs chemins critiques, montrons que certains sont asymptotiquement optimaux, et analysons leurs performances.Nous étudions ensuite les applications pipelinées sur une plate-forme hétérogène, le QS 22. Nous modélisons celle-ci et appliquons les techniques d’ordonnancement en régime permanent. Nous introduisons un programme linéaire mixte permettant d’obtenir une solution optimale. Nous introduisons en outre un ensemble d’heuristiques.Puis, nous minimisons la mémoire nécessaire à une application modélisée par un arbre, sur une plate-forme à deux niveaux de mémoire. Nous présentons un algorithme optimal et montrons qu’il existe des arbres tels que les parcours postfixes sont arbitrairement mauvais. Nous étudions alors la minimisation du volume d’E/S à mémoire donnée, montrons que ce problème est NP-complet, et présentons des heuristiques. Enfin, nous comparons plusieurs politiques d’archivage pour BLUE WATERS. Nous introduisons deux politiques d’archivage améliorant les performances de la politique RAIT, modélisons la plate-forme de stockage et simulons son fonctionnement. / This thesis focus on memory-aware algorithms tailored for hierarchical memory architectures, found for instance within multicore processors. We first study the matrix product on multicore architectures. We model such a processor, and derive lower bounds on the communication volume. We introduce three ad hoc algorithms, and experimentally assess their performance.We then target a more complex operation: the QR factorization of tall matrices. We revisit existing algorithms to better exploit the parallelism of multicore processors. We thus study the critical paths of many algorithms, prove some of them to be asymptotically optimal, and assess their performance.In the next study, we focus on scheduling streaming applications onto a heterogeneous multicore platform, the QS 22. We introduce a model of the platform and use steady-state scheduling techniques so as to maximize the throughput. We present a mixed integer programming approach that computes an optimal solution, and propose simpler heuristics. We then focus on minimizing the amount of required memory for tree-shaped workflows, and target a classical two-level memory system. I/O represent transfers from a memory to the other. We propose a new exact algorithm, and show that there exist trees where postorder traversals are arbitrarily bad. We then study the problem of minimizing the I/O volume for a given memory, show that it is NP-hard, and provide a set of heuristics.Finally, we compare archival policies for BLUE WATERS. We introduce two archival policies and adapt the well known RAIT strategy. We provide a model of the tape storage platform, and use it to assess the performance of the three policies through simulation.

O objetivo deste estudo foi verificar se existe máxima fase estável de lactato (MFEL) nos exercícios LP e SR e analisar o comportamento de variáveis ventilatórias ventilação (Ve) e consumo de oxigênio (VO2), bem como lactacidemia, freqüência cardíaca (FC) e percepção subjetiva de esforço (PSE) na intensidade da MFEL e comparar as respostas entre os exercícios. Foram avaliados 12 homens jovens (20-33 anos) saudáveis e com experiência mínima de 6 meses em treinamento resistido, que passaram por teste de 1 repetição máxima (1RM), teste crescente para determinação do limiar anaeróbio (AT) e mais três sessões para a determinação da MFEL. Todas as sessões foram realizadas no mesmo horário do dia, separadas por 48 a 72 horas de intervalo. O valor de 1RM no LP foi de 298,0 ± 36,6 kg enquanto que no SR foi 93,7 ± 21,8 kg. A intensidade máxima atingida no teste crescente no LP foi 70,00 ± 12,25% de 1RM e no SR 50,00 ± 8,16% de 1RM, sendo esta diferença estatisticamente significativa (p0,05). A lactacidemia final também foi significativamente maior (p0,05) no LP comparada ao SR (8,36 ± 2,34 vs. 5,43 ± 1,12 mmol/L, respectivamente). O AT, expresso em percentual de 1RM, no LP foi de 27,9 ± 3,7% e no SR de 24,1 ± 4,4% de 1RM, porém esta diferença não foi estatisticamente significante. A lactacidemia no momento do teste crescente em que o AT era atingido também não apresentou diferença significativa, sendo 2,29 ± 0,58 mmol/L no LP e 2,52 ± 0,65 no SR. A intensidade da MFEL, no LP foi de 29,17 ± 7,02% de 1RM, enquanto que no SR a intensidade da MFEL foi de 21,67 ± 4,44% de 1RM, sendo esta diferença estatisticamente significativa (p0,05). No LP não houve diferença significativa entre as intensidades do AT e da MFEL (27,9 ± 3,7% e 29,2 ± 7,0% de 1RM, respectivamente). No SR intensidade do AT foi significativamente maior (p0,05) que a intensidade da MFEL (24,1 ± 3,4% e 21,7 ± 4,4% de 1RM, respectivamente). Durante a realização de exercício na MFEL, a ocorreu aumento de Ve, VO2, FC e PSE seguidos de estabilização, sem diferenças entre os exercícios. Estes resultados demonstram que é possível verificar MFEL nos exercícios LP e SR, e que no LP a intensidade é maior. As diferenças encontradas no teste crescente e na intensidade da MFEL são provavelmente causadas pelas características dos exercícios. / The purpose of the study was to verify if there is a maximal lactate steady state (MLSS) for the Leg Press (LP) and Bench Press (BP) exercises and to analyse ventilatory responses ventilation (Ve) and oxygen uptake (VO2), heart rate (HR), blood lactate concentration (BLC) and ratings of perceived exertion (RPE) to those exercises performed on MLSS intensity and to compare those responses for the exercises. 12 young healthy men with a minimal experience of 6 months of resistance training volunteered for the study. Volunteers underwent a 1 repetition maximum test (1RM), na incremental test to determine anaerobic threshold (AT) and three more sessions to determine MLSS. Session were performed on the same time of Day and separeted by a 48-72h interval. 1RM values for LP and BP were 298,0 ± 36,6kg and 93,7 ± 21,8 kg, respectively. The maximal intensity in the incremental test was 70 ± 12,25% of 1RM for LP and 50,00 ± 8,16% of 1RM for BP, which was a significant difference (p0,05). Post-test blood lactate concentration (BLS) was also significantly higher for LP (8,36 ± 2,34 vs. 5,43 ± 1,12 mmol/L, respectively) (p0,05). AT intensity and was not significantly different for LP and BP (27,9 ± 3,7% vs. 24,1 ± 3,6, respectively). BLC on AT was not significantly different for LP (2,29 ± 0,58 mmol/L) and BP (2,52 ± 0,65). MLSS intensity on LP (29,17 ± 7,02% of 1RM) was significantly higher (p0,05) compared to MFEL on BP (21,67 ± 4,44% of 1RM). When compared to AT, MLSS intensity for LP was not significantly different, but for BP it was significantly lower. During exercise on MLSS, oxygen uptake and ventilation, HR and RPE rose significantly compares to rest and then stabilized. There were no differences between exercises. These results show that it is possible to identify a MLSS on the LP and BP exercises, and that for LP this intensity is higher. The differences found between exercises can be atributted to the intrinsic caractheristics of each exercise.

Este trabalho consiste em realizar um estudo detalhado das vantagens e desvantagens da utilização do FDM (Filter Diagonalization Method) para a análise de dados obtidos pela sequência de Precessão Livre no Estado Estacionário (Steady State Free Precession - SSFP) para aquisição rápida de espectros de Ressonância Magnética Nuclear (RMN). No caso de RMN de baixa resolução, o procedimento de aquisição rápida, SSFP, é uma poderosa ferramenta para melhorar a relação sinal/ruído, apresentando muitas aplicações práticas. Apesar desse sucesso em baixa resolução, a SSFP não é rotineiramente utilizada para aplicações em RMN de alta resolução, provavelmente devido ao (1) artefatos provenientes do truncamento do sinal e (2) as anomalias causadas pela mistura do FID com o eco dos sinais. Existem na literatura inúmeras possíveis técnicas para suprimir este tipo de problemas, porém, nenhuma delas é capaz de realmente eliminar as anomalias geradas devido ao procedimento de aquisição rápida da SSFP. O FDM é um método paramétrico não-linear para fitar sinais no domínio do tempo. Seu objetivo fundamental é resolver o Problema da Inversão Harmônica, HIP, tornando-se robusto e adequado para a análise espectral de sinais no domínio do tempo nos casos onde a Transformada de Fourier falha. Neste trabalho, demonstramos que o FDM pode ser implementado para análises de sinais SSFP, com mais eficiência que os obtidos pelos procedimentos padrões de TF. A temperatura ambiente, espectros de RMN 13C de amostras de brucina, obtidos com tempo entre pulsos de 100ms, podem ser reproduzidos com boa relação sinal/ruído e alta resolução por meio do FDM. A limitação da análise por FDM é mais relevante nos casos de espectros com alta densidade de picos em uma determinada região espectral. Nestes casos, o curto período de observação do sinal na janela do tempo impõe uma série de limitações na resolução obtida pelo FDM. / This work consists in a detailed study of the advantages and disadvantages of the use of the Filter Diagonalization Method, FDM, for data analysis in Steady State Free Precession, SSFP, technique, usually employed to implement fast acquisition of Nuclear Magnetic Resonance, NMR, spectra. In the case of low resolution NMR using fast acquisition procedures, SSFP is a powerful tool to improve signal-to-noise ratio, presenting several important practical applications. Despite its success in the low resolution regime, SSFP is not a routine technique for high resolution applications, so far, mainly because of (1) truncation artifacts and (2) the intrinsic anomalies caused by admixture of free-induction-decay and echo signals. The literature reports many possible techniques to solve such kind of problems, but, none of them is capable to really eliminate the generated spectra anomalies caused by the fast acquisition procedure used in SSFP. FDM is a parametric method for non-liner fitting performed in the time domain. Its main goal is to solve the Harmonic Inversion Problem, HIP, making it robust and suitable for spectral analysis of time signals in the cases where the Fourier Transform, FT, technique fail. In this work we demonstrate that FDM can be used to implement the analysis of the SSFP data, with more efficiency than that achieve by appropriated FT procedures. Room temperature 13C NMR spectra of brucine samples, obtained from pulse sequences with 100 ms repetition time, can be reproduced with good signal-to-noise ratio and high resolution by means of the FDM. The limitation of the FDM analysis is more relevant in the case of spectra with a high density of peaks in a limited spectral frequency region. In these cases, the reduced short observation time window imposes serious limitation to the resolution achieved by the FDM.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-07-01T14:29:29Z No. of bitstreams: 1 paulaoliveiralagatta.pdf: 1917786 bytes, checksum: 627585584595873c205fcbcf5c79980f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T16:01:23Z (GMT) No. of bitstreams: 1 paulaoliveiralagatta.pdf: 1917786 bytes, checksum: 627585584595873c205fcbcf5c79980f (MD5) / Made available in DSpace on 2016-07-13T16:01:23Z (GMT). No. of bitstreams: 1 paulaoliveiralagatta.pdf: 1917786 bytes, checksum: 627585584595873c205fcbcf5c79980f (MD5) Previous issue date: 2012-03-05 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho são propostas duas formulações de importantes ferramentas para análise de redes em regime permanente, onde são consideradas equações que descrevem o comportamento do controle primário e secundário de frequência em sistemas elétricos de potência. A primeira proposta é baseada em uma formulação do problema de fluxo de potência convencional e a segunda uma formulação do fluxo de potência ótimo. A formulação de fluxo de potência proposta é desenvolvida a partir de uma metodologia genérica de representação de dispositivos de controle. Esta metodologia consiste em incorporar as equações que modelam dispositivos de controle ao problema básico de fluxo de potência em coordenadas polares, formando um sistema de equações de ordem (2nb+nc). O fluxo de potência desenvolvido é capaz de estimar os desvios de frequência do sistema devido a uma perturbação da carga. Por outro lado, o fluxo de potência ótimo proposto é capaz de identificar montantes e locais de corte carga, de forma a manter a frequência do sistema em uma faixa aceitável de operação. A formulação proposta de FPO consiste em incluir no problema equações de igualdade e desigualdade associadas com o controle primário de frequência e geração de potência ativa. Os desenvolvimentos propostos para o fluxo de potência convencional foram implementados no ambiente MatLab®. Para solução do fluxo de potência ótimo utilizou-se um pacote comercial de otimização, denominado LINGO®. A avaliação do fluxo de potência e fluxo de potência ótimo propostos é feita através do estudo de sistemas tutoriais e do sistema New England. A validação da análise de desvios de frequência é feita através da utilização do programa ANATEM, desenvolvido pelo CEPEL. Os resultados obtidos mostram as vantagens da utilização das formulações propostas. / This work proposes a new formulation for both the conventional power flow and the optimal power flow formulation, in which the steady-state equations describing the primary and secondary frequency control in electrical power systems are included. The proposed power flow formulation is based on a flexible methodology for the representation of control devices. Such methodology incorporates equations that model control devices into the basic power flow formulation in polar coordinates, generating an augmented system of equations having order (2nb + nc). The developed power flow is able to estimate the system frequency deviation due to a load disturbance. On other hand, the proposed optimum power flow formulation is able to identify the minimum load shedding necessary to maintain the system frequency in an acceptable range of operation. The proposed OPF formulation includes additional equality and inequality constraints to represent the steady state primary frequency control as a function of the active power generation. The proposed development for the conventional power flow was made using the MATLAB® environment. The optimal power flow solution used a commercial optimization package called LINGO®. The evaluation of the proposed power flow and optimal power flow formulations were made through the study of small test systems and the New England test system. Validations of the frequency deviation analysis were made using the program ANATEM, developed by CEPEL. The results obtained show the advantages of using the proposed formulations.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-07-21T13:36:30Z No. of bitstreams: 1 felipedecastrobrumalmeida.pdf: 1845415 bytes, checksum: 51a0b14098a88f1127e6d6291d69e2f7 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-22T15:30:27Z (GMT) No. of bitstreams: 1 felipedecastrobrumalmeida.pdf: 1845415 bytes, checksum: 51a0b14098a88f1127e6d6291d69e2f7 (MD5) / Made available in DSpace on 2016-07-22T15:30:27Z (GMT). No. of bitstreams: 1 felipedecastrobrumalmeida.pdf: 1845415 bytes, checksum: 51a0b14098a88f1127e6d6291d69e2f7 (MD5) Previous issue date: 2011-03-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho tem por objetivo principal a avaliação do desempenho de dispositivos de controle e da modelagem da carga a partir de Regiões de Segurança Estática. Trata-se de uma importante ferramenta para avaliação da segurança de sistemas elétricos de potência, utilizadas tanto em ambiente off-line de planejamento da expansão e operação, quanto em tempo real nos centros de controle e operação (sistemas on-line VSA). Estas regiões são obtidas através de sucessivas soluções de casos de fluxo de potência e seu objetivo principal é verificar as condições de atendimento a carga (mercado) a partir de diversas condições de despacho da geração. Inicialmente, portanto, é apresentado de forma detalhada o processo de construção das Regiões de Segurança Estática, bem como os principais aspectos construtivos e considerações relevantes que podem influenciar de forma significativa a análise do desempenho do sistema. Com este objetivo, foi desenvolvido um programa para construção automática das Regiões de Segurança Estática na plataforma MatLab®. Um ambiente de processamento paralelo, intrínseco ao próprio MatLab®, foi utilizado com o intuito de aprimorar o desempenho computacional, o que permite a avaliação tanto de sistemas de pequeno porte, de valor tutorial, quanto de sistemas de médio/grande porte. Numa segunda etapa, este trabalho objetiva avaliar o desempenho de importantes dispositivos de controle e modelagem de carga a partir da construção automática das Regiões de Segurança. Os dispositivos de controle avaliados são: (i) Controle Remoto de Tensão; (ii) Controle de Tensão por Bancos Shunt Chaveados Automaticamente; (iii) Controle Automático de Tensão por Transformadores tipo LTC (Load Tap Changer); (iv) Controle Secundário de Tensão. A influência da modelagem da carga na avaliação da segurança do sistema é investigada a partir dos modelos ZIP e motor de indução. Os resultados obtidos demonstram que a representação de dispositivos de controle e da modelagem da carga podem influenciar significativamente as Regiões de Segurança Estática de sistemas elétricos de potência. / The main objective of this work is to evaluate the performance of control devices and load modelling through Static Security Regions. This is an important tool for security assessment of electric power systems, which can be used for both the operating environment (on-line systems VSA) and planning studies. These regions are obtained through successive power flow solutions and its main objective is to verify the steady-state security conditions from different configurations of generation dispatch for a given constant demand. Initially, the construction process of the Static Security Regions, as well as the key aspects of the construction and relevant considerations that may significantly impact the analysis of the system performance, is presented in detail. In this sense, a program for automatic construction of the Static Security Regions have been developed using the MatLab® platform. An intrinsic parallel processing environment was used to improve the computational performance, which allowed the evaluation of a small tutorial system and medium/large scale systems. As a second step, this work proposes the evaluation of the impact of important control devices and load modelling on the Static Security Regions construction. The control devices investigated are: (i) Remote Voltage Control; (ii) Shunt Devices with Automatic and Discrete Switching; (iii) Voltage Control by Automatic Load Tap Changing (LTC) Transformers; (iv) Secondary Voltage Control. The impact of load modelling is investigated through ZIP and induction motors models. The results obtained indicated that the representation of control devices and load modelling may significantly impact the Static Security Regions of the electrical power systems.

Brain-computer interface (BCI) or Brain Machine Interface (BMI) provides direct communication channel between user’s brain and an external device without any requirement of user’s physical movement. Primarily BCI has been employed in medical sciences to facilitate the patients with severe motor, visual and aural impairments. More recently many BCI are also being used as a part of entertainment. BCI differs from Neuroprosthetics, a study within Neuroscience, in terms of its usage; former connects the brain with a computer or external device while the later connects the nervous system to an implanted device. A BCI receives the modulated input from user either invasively or non-invasively. The modulated input, concealed in the huge amount of noise, contains distinct brain patterns based on the type of activity user is performing at that point in time. Primary task of a typical BCI is to find out those distinct brain patterns and translates them to meaningful communication command set. Cursor controllers, Spellers, Wheel Chair and robot Controllers are classic examples of BCI applications. This study aims to investigate an Electroencephalography (EEG) based non-invasive BCI in general and its interaction with a web interface in particular. Different aspects related to BCI are covered in this work including feedback techniques, BCI frameworks, commercial BCI hardware, and different BCI applications. BCI paradigm Steady State Visually Evoked Potentials (SSVEP) is being focused during this study. A hybrid solution is developed during this study, employing a general purpose BCI framework OpenViBE, which comprised of a low-level stimulus management and control module and a web based Google Street View client application. This study shows that a BCI can not only provide a way of communication for the impaired subjects but it can also be a multipurpose tool for a healthy person. During this study, it is being established that the major hurdles that hamper the performance of a BCI system are training protocols, BCI hardware and signal processing techniques. It is also observed that a controlled environment and expert assistance is required to operate a BCI system.

Ce travail porte sur l'étude des effets thermiques dans un palier hydrodynamique, alimentée par une rainure circonférentielle (CGJB) sous charge statique, en tenant compte des phénomènes de rupture de film dans la zone divergente. La recherche expérimentale a été réalisée à l'Université de Poitiers ; elle a permis une détermination minutieuse des champs de pression et de température sur la portée située à l’avant d’un CGJB et dans la section médiane de sa rainure. Ces mesures sous un régime stationnaire sont originales par rapport celles existantes, quel que le type de palier, de par le grand nombre de points de mesure, 180 pour la pression et 144 pour la température, l'instrumentation de haute précision, la large plage de conditions d'exploitation (pression spécifique variant de 0,125 à 2 MPa et vitesse linéaire de l’arbre allant de 5,25 à 21 m/s). Des études du régime transitoire de démarrage au régime stationnaire établi ont été effectuées pour de faibles charges. Des expériences effectuées à l'Université "Politehnica" de Bucarest ont montré une bonne corrélation entre la perte de portance, anti-portance et la rupture du film sur un patin Rayleigh (RSP), ce qui est essentiel pour l'évaluation des phénomènes de rupture dans les paliers. Quelques modèles théoriques ont été utilisés pour évaluer les risques de serrage au démarrage qui est une instabilité thermoélastique catastrophique. Les principaux résultats sont l’obtention d’une base fiable de données expérimentales permettant le développement des modèles théoriques avancés et l’infirmation d’une répartition de pression constante dans la zone divergente et de pression et température constantes dans la rainure d'alime / The main objective of the thesis is to study the thermal effects in steadily loaded circumferential groove journal bearings (CGJBs), including cavitation phenomena occurring in the divergent zone of such bearings. Experimental research conducted at University of Poitiers – Institut Pprime – France enabled a thorough determination of film pressure and temperature fields for the front land of a CGJB plus its mid-groove section, and several performance parameters. Measurements of film pressure and temperature fields under steady-state regime surpassed existing works, regardless of journal bearing design, through: sheer number of land measurement locations, 180 for pressure and for 144 temperature; high precision state of art instrumentation; broad range of operating conditions, 0.125 … 2 MPa specific bearing pressure and 5.25 … 21 m/s shaft speeds. Transient start-up to steady-statestabilization regimes have been investigated at low loads. Experiments at University "Politehnica" of Bucharest – Romania showed a correlation between the downforce thrust and film rupture for a Rayleigh step pin (RSP), important in evaluating divergent zone cavitation phenomena. Theoretical research consisted in developing simple models for evaluating CGJBs performance in steady-state and transient start-up regimes. Several theoretical models were employed for assessing start-up seizure, catastrophic transient thermoelastic instability and damage risk. The major result is a reliable experimental data collection that: enables development of advanced theoretical models; disprove flat film pressure distributions in divergent zones, and constant pressure and temperature in the bearing supply groov

The rise in the world population can be correlated with an increase in energy need. Fossil fuels are not going to able to cover this need in energy because not only are they limited, they also have a negative effect on the environment. A reason the more to switch renewable energy. One of the most popular renewable energy source is solar energy. The organic solar cell could be a low-cost, light-weight and flexible option for photovoltaics. This thesis will discuss the morphology of the active layer of an organic solar cell. The polymer poly(9,9-dioctylfluorenyl-2,7-diyl) and the fullerene derivate [6,6]-phenyl C61-butyric acid methyl ester were used as model components for the active layer. These two components were processed in different solvents, different ratios, different total concentrations and were either dip- or spin-coated on glass substrates. These samples were analyzed with atomic force microscopy, steady state and time resolved fluorescence and UV/Vis spectroscopy. The analysis show that the morphology of the films processed in chloroform and tetrahydrofuran would react very similar in α-phase and β-phase by dip- and spin-coated samples. Xylene would react the opposite as tetrahydrofuran and chloroform while ethylbenzene would react little with different samples. / De stijging in wereldpopulatie kan gelinkt worden met een stijging in energieverbruik. Het is niet aan te raden om fossiele brandstoffen te gebruiken voor deze energiestijging want niet alleen zijn ze beperkt aanwezig op aarde ook zijn ze niet goed voor het milieu. Een reden te meer om naar duurzame energie over te schakelen. Één van de meeste populaire energiebronnen is zonne-energie. Hierbij zou de organische zonnecel een goedkope, lichte en flexibele optie zijn. Deze thesis zal de morfologie van de actieve laag van een zonnecel bespreken. Het polymeer poly(9,9-dioctylfluorenyl-2,7-diyl) en het fullereen derivaat [6,6]-fenyl C61-butylzuur waren de twee model componenten voor de actieve laag. Deze twee componenten werden in verschillende oplosmiddelen, verschillende verhoudingen en verschillende totaal concentraties bereidt en werden vervolgens gedipcoated of gespincoated op glazen substraten. De stalen werden vervolgens geanalyseerd door atomic force microscopy, steady state en time resolved fluorescence en UV/Vis spectroscopy. De analyse toont dat de morfologie van de films bereidt in chloroform en tetrahydrofuraan gelijkaardig reageren in α- fase en β-fase bij gedipt- en gespincoaten stalen. Terwijl xyleen net omgekeerd reageert als chloroform en tetrahydrofuraan. Bij ethylbenzeen zou de fases maar heel weinig veranderen bij de verschillende stalen.

There has always been a need for objective tests that assess auditory function in infants, young children, and/or any patient whose development level precludes the use of behavioral audiometric techniques. Although the Auditory Brainstem Response (ABR) is seen as the ‘gold standard’ in the field of objective audiometry, it presents with its own set of limitations. The Auditory Steady State Response (ASSR) has gained considerable attention and is seen as a promising addition to the AEP ‘family’ to address some of the limitations of the ABR. The ASSR promises to estimate all categories of hearing loss (mild to profound) in a frequency specific manner. It also indicates to the possibility to validate hearing aid fittings by determining functional gain of hearing aids by determining unaided and aided ASSR thresholds. An exploratory research design was selected in order to compare unaided thresholds, obtained through the use of three different procedures – ABR, ASSR and behavioral thresholds. Aided thresholds were also obtained and compared with two procedures – the aided ASSR (measured and predicted) and aided behavioral threshold. The results indicated that both the ABR (tone burst and click) and ASSR provided a reasonable estimation of the subsequently obtained behavioral audiograms. The ASSR, however, approximated the behavioral thresholds closer than the ABR and were furthermore able to quantify hearing thresholds accurately for subjects with severe and profound hearing losses. The result indicated further that the ASSR can be instrumental in the validation process of hearing aid fittings in infants. These results demonstrated however, that the ASSR measured thresholds underestimate the aided behavioral thresholds and the aided ASSR predicted thresholds overestimate the aided behavioral thresholds. The research concluded that the ASSR is useful in estimating frequency-specific behavioral thresholds accurately in infants and validating hearing aid fittings. Until evidence is sufficient to recommend the ASSR as primary electrophysiological measure of hearing in infants, the ASSR should be used in conjunction with the ABR – following a test battery approach in the diagnostic process of hearing loss in infants. The ASSR further shows great promise in validating hearing aid fittings, but this specific application of the ASSR needs further research evidence on large groups to validate the procedure. / Dissertation (Master of Communication Pathology)--University of Pretoria, 2007. / Speech-Language Pathology and Audiology / unrestricted

In individuals claiming compensation for occupational noise induced hearing loss, a population with a high incidence of nonorganic hearing loss, a reliable and valid behavioural pure tone (PT) threshold is not always achievable. Recent studies have compared the accuracy of behavioural PT threshold estimation using the slow cortical auditory evoked potentials (SCAEP) and auditory steady-state responses (ASSR) but there is no consensus regarding recommended technique. A review of the literature indicated that no comparison has been completed on the use of SCAEP and a single frequency ASSR technique. A research project was therefore initiated with the aim of comparing the clinical effectiveness (accuracy) and clinical efficiency (time required) of SCAEP and ASSR for behavioural PT threshold estimation in adults exposed to occupational noise. Adult participants were divided into a group with normal hearing (behavioural PT thresholds < 20 dBHL; n = 15) and a group of participants with hearing loss (n = 16 adults), the latter of which were recruited from individuals referred for audiometric screening, as part of hearing conservation programs, and who were, therefore, exposed to occupational noise. The GSI Audera electrophysiological system was used for both SCAEP and ASSR threshold measurement at 0.5, 1, 2 and 4 kHz. Use was made of tone burst stimuli for the SCAEP (rise and fall of 10 ms with 80 ms plateau), while amplitude and frequency modulated (AM/FM) stimuli was used during ASSR testing. The system’s 40 Hz protocol was chosen for use during ASSR recording while participants slept because this led to lparticipants. ASSR thresholds could not be measured in two of the three sleeping participants in the preliminary study using an 80 Hz modulation rate due to excessive noise. The mean SCAEP difference scores (SCAEP threshold minus behavioural PT threshold) for both participant groups were -0.2+10.2, 2.8+10.1,5.8+9.7, 0.5+10.4 at 0.5, 1, 2, and 4 kHz respectively, while ASSR difference scores were 25.3+12.8, 21.7+11.3,32.3+12.2, 27.1+13.8. The SCAEP correlations with behavioural PT thresholds across frequencies (r = 0.85) were also stronger than ASSR correlations (r = 0.75). Therefore, with regard to proximity of auditory evoked potentials (AEP) to behavioural PT thresholds and consistency of this relationship, the SCAEP, rather than ASSR, is the AEP of choice. However, the SCAEP took on average 10.1 minutes longer to complete than the ASSR. Clinical effectiveness was given comparably more weight than the clinical efficiency of the AEP technique to estimate behavioural PT thresholds due to the impact on overcompensation for occupational noise induced hearing loss. As such, the study acknowledged the SCAEP as the AEP of choice for the purpose of behavioural PT thresholds in adults exposed to occupational noise. It is important to note that the conclusion reached in the current study arose from the comparison of the SCAEP with a specific ASSR technique. Accuracy of ASSR estimation of behavioural PT thresholds is strongly influenced by stimulus and recording parameters of the system used, and by the participant variables. Copyright / Dissertation (MCommunication Pathology)--University of Pretoria, 2010. / Speech-Language Pathology and Audiology / Unrestricted