More stringent Euro 6 and LEV III emission standards will immediately begin execution on 2014 and 2015 respectively. Accurate air/fuel ratio control can effectively reduce vehicle emission. The simulation of engine dynamic system is a very powerful method for developing and analysing engine and engine controller. Currently, most engine air/fuel ratio control used look-up table combined with proportional and integral (PI) control and this is not robust to system uncertainty and time varying effects. This thesis first develops a simulation package for a port injection spark-ignition engine and this package include engine dynamics, vehicle dynamics as well as driving cycle selection module. The simulations results are very close to the data obtained from laboratory experiments. New controllers have been proposed to control air/fuel ratio in spark ignition engines to maximize the fuel economy while minimizing exhaust emissions. The PID control and fuzzy control methods have been combined into a fuzzy PID control and the effectiveness of this new controller has been demonstrated by simulation tests. A new neural network based predictive control is then designed for further performance improvements. It is based on the combination of inverse control and predictive control methods. The network is trained offline in which the control output is modified to compensate control errors. The simulation evaluations have shown that the new neural controller can greatly improve control air/fuel ratio performance. The test also revealed that the improved AFR control performance can effectively restrict engine harmful emissions into atmosphere, these reduce emissions are important to satisfy more stringent emission standards.

Tobacco use is a major preventable cause of morbidity and mortality worldwide. Most smokers initiate smoking in childhood, become addicted, and continue the habit into adulthood. Various factors have been shown to impact smoking behavior. It is important to determine how these factors impact smoking behavior in developing regions of the world, such as in South Africa. This study examines the association between parental smoking status; peer smoking status; exposure to pro-tobacco marketing; and current smoking status among adolescents in South Africa. It also determines which factor is the most significant predictor of current smoking status among the study population and further examines the trends in these factors among survey populations from 1999 – 2008. Secondary analysis was conducted on data obtained from the Global Youth Tobacco Survey. Logistic regression analyses were conducted to determine the association between the independent variables; parental smoking status, peer smoking status, and exposure to pro-tobacco marketing; and the dependent variable, current smoking status, controlling for other factors. Adolescents who had at least a parent or a friend who smoked had greater odds of being current smokers as compared to those who had neither a parent nor a friend who smoked. Similarly, exposure to average and high levels of pro-tobacco marketing was associated with greater odds of an adolescent being a current smoker as compared to exposure to low levels of pro-tobacco marketing. Maternal smoking appeared to have a greater impact on adolescent smoking behavior as compared to paternal smoking. Also, peer smoking had the greatest impact on smoking behavior as compared to the other independent factors. Smoking rates among South African adolescents has decreased from 23% in 1999 to about 17% in 2008. Similarly, the proportion of adolescents who had a parent or a friend who smoked, or had been exposed to average and high levels of pro-tobacco marketing has also decreased over the same period. Programs must be implemented to educate parents on how their smoking behavior is being transmitted to their children, with a special focus on maternal influences. Tobacco use prevention campaigns aimed at the youth should also be implemented, and laws restricting tobacco marketing must be enforced.

Magister Artium - MA / Foetal Alcohol Spectrum Disorder (FASD) is a global problem that affects various communities. FASD denotes a pattern of abnormalities intermittently seen in children born to women who consume huge quantities of alcohol during pregnancy (Church & Kaltenbach, 1997). Church and Kaltenbach (1997) suggest that FAS may be one of the primary causes of hearing, speech and other language problems in children. The two main approaches used to determine the effects of FASD on language are standardised language test (using a statistical approach to test some or all four domains of language, namely, phonology, syntax, morphology and semantics) applied to close-ended questionnaire answers and, to some extent, narrative analysis (in the course of which researchers use wordless picture books to analyse narratives in order to determine the social-communicative characteristics of individuals with FASD). Although the use of standardized measures of language might be helpful to determine problematic areas in relation to the different language domains (Wyper & Rasmussen, 2011), they do not show the difficulty with social-communicative functions which these children might be facing (Coggins, Friet, & Morgan, 1998). On the other hand, while narrative analysis addresses an important level of language (discourse level), it does not foreground the inherently interactive nature of language use and the problems that may be associated with communicative interactions. These shortcomings, in turn, suggest possible limitations in the interventions intended to address the language needs of children with FASD. There is, therefore, a need for complementary approaches that offer a more rounded picture of language impairment in children with FASD. In this study, three approaches are used in identifying features of the speech of children with FASD against the backdrop of comparisons with features in the speech of normally developing children. Firstly, conversational analysis (applied to spontaneous, open-ended speech) is introduced as a means to determine the more social-interactive aspects of speech impairment in children with FASD. Secondly, measures of linguistic aspects of speech (the mean length of utterance, Index of Productive Syntax and the number of different word roots) designed specifically for spontaneous speech are employed (they are applied to the same spontaneous data as the conversational analysis data). Thirdly, the more traditional standardized language test measures applied to non-spontaneous speech are used (covering the four domains of syntax, phonology, semantics, and pragmatics). The study’s objectives are to (1) compare patterns in the interactive speech of FASD children and normally developing children; (2) explore the relationship between FASD children and normally developing children in relation to both spontaneous speech measures and standardized measures of language; and (3) compare the impact of the primary caregiver's level of education on testing through spontaneous measures versus standardised measures. Using data from 14 children in the Bellville suburb of Cape Town, South Africa, the study finds that, on the conversational analysis measures, children with FASD, in contrast to normally developing children, tend to obey fewer rules of turn-taking, to overlap less, to engage less in self-repair and to struggle with management and maintenance of topics. The study also finds that children whose scores on the standardized language tests (with non-spontaneous data) suggest they have no language difficulty, especially in terms of phonology, obtained scores in measures of spontaneous speech that indicated language difficulty. The study also found that the socio-economic status of caregivers was a credible explanation for certain features in the speech of children with FASD is very similar to features in the speech of normally developing children. This finding highlights the role of family setting in mitigating the effects of FASD. / National Research Foundation (NRF)

Automatic Face Recognition (AFR) can be useful in the forensic field when identifying people in surveillance footage. In AFR systems it is common to use deep neural networks which perform well if the quality of the images keeps a certain level. This is a problem when applying AFR on surveillance data since the quality of those images can be very poor. In this thesis the CNN FaceNet has been used to evaluate how different quality parameters influence the accuracy of the face recognition. The goal is to be able to draw conclusions about how to improve the recognition by using and avoiding certain parameters based on the conditions. Parameters that have been experimented with are angle of the face, image quality, occlusion, colour and lighting. This has been achieved by using datasets with different properties or by alternating the images. The parameters are meant to simulate different situations that can occur in surveillance footage that is difficult for the network to recognise. Three different models have been evaluated with different amount of embeddings and different training data. The results show that the two models trained on the VGGFace2 dataset performs much better than the one trained on CASIA-WebFace. All models performance drops on images with low quality compared to images with high quality because of the training data including mostly high-quality images. In some cases, the recognition results can be improved by applying some alterations in the images. This could be by using one frontal and one profile image when trying to identify a person or occluding parts of the shape of the face if it gets recognized as other persons with similar face shapes. One main improvement would be to extend the training datasets with more low-quality images. To some extent, this could be achieved by different kinds of data augmentation like artificial occlusion and down-sampled images.

[ES] A pesar de la tendencia actual hacia la electrificación del transporte por carretera, los motores de combustión interna alternativos han sido esenciales en este sector y se espera que sigan siendo una tecnología con notable presencia durante las próximas décadas. Los vehículos de pasajeros actuales basados en motores de combustión interna son más ecológicos que los utilizados hace años, aunque todavía queda trabajo por hacer. Los sistemas de postratamiento están enfocados a minimizar tanto como sea posible el impacto de los motores de combustión interna en términos de emisiones contaminantes. En el caso de los motores de encendido provocado, los catalizadores de tres vías representan la tecnología más extendida en las últimas décadas, debido a su compacidad y buena relación precio-prestaciones. Estos convertidores son capaces de oxidar hidrocarburos y monóxido de carbono al mismo tiempo que reducen los óxidos de nitrógeno. No obstante, para lograr su mejor eficiencia, el dosado debe controlarse con precisión en torno a condiciones estequiométricas. En este sentido, los sistemas electrónicos de gestión del motor son esenciales para aprovechar las características de estos convertidores. En particular, las estrategias de control y diagnóstico desempeñan un papel clave para lograr una reducción efectiva de las emisiones en el amplio rango de condiciones de operación que se dan en condiciones de funcionamiento reales. El desarrollo de estas estrategias es fundamental, especialmente teniendo en cuenta el bajo nivel de emisiones permitido por las normativas de emisiones actuales y la tendencia hacia cero emisiones. El propósito de esta tesis doctoral es analizar el comportamiento del sistema de postratamiento en condiciones específicas pero a la vez muy comunes en conducción real, y desarrollar estrategias que proporcionen una reducción adicional de las emisiones en sistemas basados en catalizador de tres vías. Con la popularización de pequeños motores turboalimentados de encendido provocado, ha aumentado el uso de estrategias de barrido de la cámara de combustión para mitigar los típicos problemas de falta de par a bajo régimen. Esta tesis analiza el impacto de los pulsos de cortocircuito en el catalizador y en las sondas ¿. El proceso de cortocircuito de aire fresco al escape tiene un impacto importante en la dinámica intraciclo de la composición de los gases de escape. En particular, los pulsos de monóxido de carbono e hidrógeno seguidos por los pulsos de aire fresco perturban el normal funcionamiento del sensor de oxígeno. Por lo tanto, se ha propuesto un nuevo método para estimar la tasa de cortocircuito abordo. Este método permite corregir la desviación sufrida por el sensor y, por lo tanto, ayuda a reducir la penalización en emisiones de este tipo de estrategias. Para mejorar la eficiencia del catalizador en condiciones transitorias, no solo se requiere un control preciso del dosado aguas arriba del catalizador, sino que también resulta imprescindible considerar el comportamiento dinámico del convertidor en sí mismo. Por ejemplo, el almacenamiento de oxígeno es un buen indicador del estado del catalizador, pero no se puede medir directamente mediante sensores. Por lo tanto, el desarrollo de modelos es clave en las estrategias de control actuales, para poder estimar abordo diferentes parámetros relacionados con el estado del catalizador. Varios modelos de catalizador se han desarrollado en esta tesis doctoral para lidiar con diferentes cuestiones, desde la predicción de los efectos de la condensación de agua en la evolución de la temperatura del catalizador justo después del arranque en frío, a la cuantificación del nivel de envejecimiento, pasando por el control óptimo de purga del catalizador. / [CA] Malgrat la tendència actual cap a l'electrificació del transport per carretera, els motors de combustió interna alternatius han sigut essencials en aquest sector i s'espera que continuen sent una tecnologia amb notable presència durant les pròximes dècades. Els vehicles de passatgers actuals basats en motors de combustió interna són més ecològics que els utilitzats fa anys, encara que hi ha treball per fer. Els sistemes de post-tractament estan enfocats a minimitzar tant com siga possible l'impacte dels motors de combustió interna en termes d'emissions contaminants. En el cas dels motors d'encés provocat, els catalitzadors de tres vies representen la tecnologia més estesa en les últimes dècades, pel fet que són compactes i posseeixen bona relació preu-prestacions. Aquests convertidors són capaços d'oxidar hidrocarburs i monòxid de carboni al mateix temps que redueixen els òxids de nitrogen. No obstant això, per a aconseguir la seua millor eficiència, el dosatge ha de controlar-se amb precisió entorn de condicions estequiomètriques. En aquest sentit, els sistemes electrònics de gestió del motor són essencials per a aprofitar les característiques d'aquests convertidors. En particular, les estratègies de control i diagnòstic exerceixen un paper clau per aconseguir una reducció efectiva de les emissions en l'ampli rang de condicions d'operació que es donen en condicions de funcionament reals. El desenvolupament d'aquestes estratègies és fonamental, especialment tenint en compte el baix nivell d'emissions permès per les normatives actuals i la tendència cap a zero emissions. El propòsit d'aquesta tesi doctoral és analitzar el comportament del sistema de post-tractament en condicions específiques però alhora molt comunes en conducció real, i desenvolupar estratègies que proporcionen una reducció addicional de les emissions en sistemes basats en catalitzador de tres vies. Amb la popularització de xicotets motors amb sobrealimentació d'encés provocat, ha augmentat l'ús d'estratègies de curtcircuit per a mitigar els típics problemes de falta de parell a baix règim. Aquesta tesi analitza l'impacte dels polsos de curtcircuit en el catalitzador i en les sondes ¿. El procés de curtcircuit d'aire fresc té un impacte important en la dinàmica intra-cicle de la composició dels gasos. En particular, els polsos de monòxid de carboni i hidrogen seguits pels polsos d'aire fresc pertorben el normal funcionament del sensor d'oxigen. Per tant, s'ha proposat un nou mètode per a estimar la taxa de curtcircuit del motor. Aquest mètode permet corregir la desviació patida pel sensor i, per tant, ajuda a reduir la penalització en emissions d'aquest tipus d'estratègies. Per a millorar l'eficiència del catalitzador en condicions transitòries, no solament es requereix un control precís del dosatge aigües amunt del catalitzador, sinó que també resulta imprescindible considerar el comportament dinàmic del convertidor en si mateix. Per exemple, l'emmagatzematge d'oxigen és un bon indicador de l'estat del catalitzador, però no es pot mesurar directament mitjançant sensors. Per tant, el desenvolupament de models és clau en les estratègies de control actuals, per poder estimar els diferents paràmetres relacionats amb l'estat del catalitzador. Diversos models de catalitzador s'han desenvolupat en aquesta tesi doctoral per a tractar diferents qüestions, des de la predicció dels efectes de la condensació d'aigua en l'evolució de la temperatura del catalitzador just després de l'arrencada en fred, a la quantificació del nivell d'envelliment, passant pel control òptim de porga del catalitzador. / [EN] In spite of the current tendency towards the electrification of the road transport, internal combustion engines have been essential in this sector and it is expected to continue being a technology with a noticeable presence during next decades. Current passenger cars based on internal combustion engines are greener than those used years ago, although it is still a developing process. Aftertreatment systems are aimed to minimize as much a possible the impact of internal combustion engines in terms of pollutant emissions. In case of spark-ignited engines, three-way catalytic converters represent the most widespread technology during last decades, due to their compactness and cost-performance. These converters are capable to oxidise hydrocarbons and carbon monoxide while simultaneously reducing nitrogen oxide. Nonetheless, to achieve their best efficiency, the air-to-fuel ratio must be accurately controlled close to stoichiometric conditions. In this sense, electronic engine management systems are essential to take advantage of the features of these converters. In particular, control and diagnosis strategies play a key role to achieve an effective emissions reduction under the wide range of operating conditions that arise in real driving conditions. The further development of this strategies is fundamental, especially taking into account the low emissions level allowed by current regulatory procedures and the trend towards zero emissions. The purpose of this dissertation is to analyse the behaviour of the aftertreatment system under very specific but at the same time very common conditions, and developing strategies that provide a further emissions reduction for systems based on three-way catalyst. With the popularization of small turbocharged spark-ignited engines, the use of scavenging strategies to solve the typical low-end torque issues has increased. This dissertation analyses the impact of the short-circuit pulses on both three-way catalyst and ¿ sensors. The short-circuit process has an important effect on the in-cycle dynamics of the exhaust gas composition. In particular, the carbon monoxide and hydrogen pulses followed by fresh air pulses cause a sensor bias. Thus a new method to on-line estimate the short-circuit rate has been proposed. This method allows to correct the sensor bias and, therefore, help to reduce the emissions penalty. To improve the TWC efficiency under transient conditions, not only an accurate air-to-fuel ratio control upstream of the converter is required, but also to consider the dynamic behaviour of the converter itself. For example, the oxygen storage is the main responsible for the converter dynamics, and thus, a good indicator of the catalyst state, but it cannot be directly measured. Hence the development of models is key in current control strategies, to on-line track different parameters related with the state of the converter. Several models have been derived in this dissertation in order to fulfil different requirements, from the prediction of water condensation effects on the temperature evolution inside the converter just after cold-start, to the quantification of the ageing level, through the optimal catalyst purge control, or the air-to-fuel ratio disturbances rejection. / Real Minuesa, M. (2020). Modelling, control and diagnosis of aftertreatment systems based on three-way catalyst in spark-ignited engines [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/137040

This master's thesis deal the system, which use the Frequency Hopping (FH). Is explained principle those techniques and her benefits and disadvantages. Follows description techniques Adaptive Frequency Hopping (AFH) that used the Bluetooth. Follows description other method for setup hopset such as Dynamic Frequency Hopping (DFH), which used standards 802.22. 22. Is an emerging standard for Wireless Regional Area Networks (WRAN) operating on a license-exempt and non-interference basis in the spectrum allocated to TV broadcast services (between 47–910 MHz). Other method introduces the Adaptive Frequency Rolling (AFR), a particular instance of frequency hopping (FH) that enables the collocated WPANs to cooperate and avoid the self-interference. The AFR uses as input solely the observed packet error rate (PER) and it does not require any exchange of information among the collocated WPANs. The effect of the FR over a longer time interval is that the WPANs use the complete set of disposable channels in an implicit time-division and cooperative manner. Last method described in this Thesis is Dynamic Adaptive Frequency Hopping (DAFH). The basic strategy applied in DAFH is a binary search for a hopset that offers smaller PER. The set of admissible hopsets depends on the total number of available channels and the maximal level of binary divisions. Practical part of the master's thesis describes proposal model AFH, with usage of Matlab Simulink programme. In thesis are described function each blocks a their setting. Simulation parameters can change in simple graphic interface. The model is able to simulate influence of static and dynamic interference in transmission band of two communicating devices.

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