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  • 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.
71

Experimentální analýza proudu vzduchu z ofukovače osobního vozu s využitím žárového anemometru a návrh hodnocení kvality ofukovače / Experimental analysis of automobile ventilating outlet air flow using hot wire anemometry and draft of outlet quality rating

Ležovič, Tomáš January 2011 (has links)
The master’s thesis deals with air flow in the interior of automobile Škoda Octavia. The attention is focused only at a side ventilating outlet. Author’s effort was to propose the appropriate criteria for evaluation and assessment of ventilating outlet quality and elaborate the methodology of measurement for these criteria. Then follows the application of the methodology and measurement of velocity field of air flow from the outlet by the method of hot wire anemometry. The thesis also contains comparison of the results with the results attained by the smoke visualization.
72

Predictive Modeling and Statistical Inference for CTA returns : A Hidden Markov Approach with Sparse Logistic Regression

Fransson, Oskar January 2023 (has links)
This thesis focuses on predicting trends in Commodity Trading Advisors (CTAs), also known as trend-following hedge funds. The paper applies a Hidden Markov Model (HMM) for classifying trends. Additionally, by incorporating additional features, a regularized logistic regression model is used to enhance prediction capability. The model demonstrates success in identifying positive trends in CTA funds, with particular emphasis on precision and risk-adjusted return metrics. In the context of regularized regression models, techniques for statistical inference such as bootstrap resampling and Markov Chain Monte Carlo are applied to estimate the distribution of parameters. The findings suggest the model's effectiveness in predicting favorable CTA performance and mitigating equity market drawdowns. For future research, it is recommended to explore alternative classification models and extend the methodology to different markets and datasets.
73

Domain Specific Modeling Support for ArCon / Stöd för domänspecifik modellering med ArCon

Azari, Leila January 2013 (has links)
One important phase in software development process is to create a design model of the system which follows all the architectural rules. Often the architectural rules are defined by the system architect and the system model is designed by the system designer. The architect defines the rules in a text file where no standard or pattern is followed. Therefore, there is always the risk of violating the architectural rules by the designer. So manual reviews on the system model should be done by the architect to ensure the system model is valid.In order to remove this manual checking which can be erroneous and time consuming ArCon (Architecture Conformance Checker) was developed by Combitech AB. ArCon is a tool which lets the architect define the architectural rules in the format of UML (Unified Modeling Language) models where the elements of the model have different meaning than the standard UML. ArCon can read this model and extract architectural rules from it and check the system model against those rules and then print all the rule violations.ArCon is an open source tool i.e. free for everyone to download and use. Currently, it supports Papyrus as the UML modeling tool. Papyrus is integrated to Eclipse platform and is a general purpose modeling tool. It supports users with all types of UML diagrams and elements.The idea for this thesis work was to implement a new feature for ArCon in order to facilitate the design process for system designers. The feature should provide the system designers only those types of elements which they are permitted to add to a specific fraction of the system model. The list of permitted element types should be extracted from the architecture model where all the architectural rules are defined in advance. This new support in ArCon was named Domain Specific Modeling (DSM) support.To evaluate the effect of DSM support on the system designers performance a few test sessions, called usability tests, were performed. The participants in the test sessions were a representative sample of software designers. After analyzing the data collected from the test sessions, the pros and cons of the new support were discovered. Furthermore, a few new ideas for enhancing DSM support were generated.
74

Modèles de connaissance à paramètres identifiables expérimentalement pour les systèmes de refroidissement dessiccatif couplés à un système solaire / Knowledge models with identifiable parameters of solar desiccant cooling systems

Ghazal, Roula 12 April 2013 (has links)
La Centrale de traitement d’Air par Dessiccation (CAD) offre un contrôle complet de la température et de l'humidité dans les locaux climatisés. Son élément clé est la roue dessicante qui permet la dessiccation de l’air et une régénération continue. A travers cette étude, nous nous intéressons au développement d’une méthodologie pour obtenir un modèle dynamique de la roue utilisable dans les algorithmes de contrôle avancés de la CAD. La roue dessicante peut être considérée comme un système de type multi-entrées/multi-sorties (MIMO). La seconde partie de ce mémoire concerne l'identification expérimentale des paramètres des modèles d’état de la roue dessicante pour deux types de modèles : boîte noire et boîte grise. Dans le cas de la boîte noire, tous les paramètres du modèle sont identifiés expérimentalement. Dans le cas de la boîte grise, certains paramètres sont dérivés de considérations physiques et les paramètres restants sont identifiés en utilisant les mesures expérimentales des entrées et des sorties. Les paramètres du modèle boîte grise ont une signification physique. En comparaison avec les modèles boîte noire, les modèles boîte grises sont moins précis sur le domaine sur lequel les paramètres ont été identifiés, mais beaucoup plus précis en dehors de ce domaine. Comme les paramètres ont une signification physique, leurs valeurs ne varient pas de manière significative avec le point de fonctionnement utilisé pour l’identification. Dans l’approche boîte grise, les valeurs des paramètres obtenues pour les modèles linéaires sont presque identiques pour tous les modèles locaux du coté dessiccation et pour tous les modèles locaux du coté régénération ; cela nous a permis de considérer qu’un modèle local est valable pour tout le domaine de variation des variables d’entrée. Le modèle final de la roue dessicante se compose de deux modèles globaux : un pour le côté de la dessiccation et l'autre pour le côté de la régénération. La troisième partie de ce travail consiste dans l'identification des coefficients de transfert de masse et de chaleur au sein de la roue dessicante en utilisant un modèle boîte grise. Le coefficient de transfert de masse, le coefficient de transfert convectif et le nombre de Nusselt ont été obtenus en écrivant les paramètres du modèle d’état en fonction d’une seule variable et en exprimant les paramètres en fonction des caractéristiques géométriques et des propriétés de matériaux de la roue. Ce travail contribue au développement d’un modèle d’état utilisable pour la synthèse des algorithmes de contrôle pour la roue dessicante. / Desiccant Air Unit (DAU) offers a complete control of air temperature and humidity in the conditioned space. Its key component is the desiccant wheel which provides the functions of air desiccation and regeneration. The aim of this study is to develop a methodology for obtaining a dynamic model of the desiccant wheel which can be used for the model-based control algorithms of DAU. The desiccant wheel can be regarded as a multi-input/multi-output (MIMO) system. The first part of the thesis is devoted to the modeling of the desiccant wheel based on energy and mass balance equations. The resulting set of equations is formulated as a second order state-space system without delay. The second part of this thesis concerns the experimental identification of the parameters of the state-space model of the desiccant wheel by using a black-box and a gray-box approach. In the case of the black-box, all the parameters of the model are identified experimentally. The identified parameters have values which minimize the difference between the output of the model and the experimental values. The parameters of the black-box model do not have physical significance. Although precise in the range of variation of the inputs in which the parameters were identified, this model gives significant errors in other domains of variation of the inputs. The parameters of the gray-box model are physically significant. Compared with the black-box models, the gray-box model was less accurate for the domains for which the parameters were identified, but it was notably more robust when applied to other ranges of the inputs. Since the parameters are related to physical properties, their values do not vary significantly with changes of the operating point used for identification. For the gray-box approach, the parameter values obtained for the linear models are almost identical for all local models on the desiccation side and all the local models on the regeneration side, suggesting that a local model may be valid for all the complete range of input variables. Using the above results, a final model of the desiccant wheel was developed, comprising two global models: one for the desiccation side and another for the regeneration side. The third part of the thesis deals with the identification of mass and heat transfer coefficients of the air within the desiccant wheel using a gray-box model. The mass transfer coefficient, the convective heat transfer coefficient and the Nusselt number were obtained by defining the variable parameters of the model as a function of a single variable and by expressing the constant parameters as a function of the geometric and material properties of the wheel. This work contributes to the development of a state-space model used for the synthesis of control algorithms for the desiccant wheel.
75

The history of the teachers association of South Africa and the role it played in the develpment of education for Indians in South Africa.

Jack, Jonathan Rajmangal January 1986 (has links)
Magister Educationis - MEd / Teachers and teachers' organisations have always been an intergral part of any community. More so in the Indian Community. The Indian teacher has always commanded great respect from his community and thus he has wielded considerable influence over it. Since the early days of Indian immigration to this country, the Indian teacher has played a vital role in all but political activities. In very recent times, however, he has taken a lively interest in the political aspirations of his people within the framework permitted by his conditions of service. The Indian Teacher is a member of the largest group of highly educated men and women in his community. No wonder, then, that the community has always looked to teachers and their organisations for leadership. The establishment of the Natal Indian Teachers' Society in the 1920s arose out of a community need in that a reception committee was required for holding celebrations on the occasion of the visit of the Prince of Wales to South Africa. From then on the Natal Indian Teachers' Society continued to make representations on behalf of its members and the community for a a better deal in education. This was not always forthcoming from the authorities. Hence, the teachers and the community banded together to provide and build schools for themselves out of the monetary contributions of teachers and parents. The Natal Education Department in its biased treatment of teachers in aided schools, who it claimed were the responsibility of the grantees and managers, led teachers to form the Natal Teachers' Union which was run on trade union lines. A vigorous fight was waged by this Union for service conditions equal to those of teachers in government schools. The Education Department relented when it recognised the rights of the members of the Union. Thus the Union disbanded and its members rejoined the Natal Indian Teachers' Society. Thereafter the Natal Indian Teachers' Society grew from strength to strength. The inauguration of the branch system gave rise to broader representation and rapid growth. The formation of the Natal Indian Schools' Building Trust saw tangible evidence of of the commitment of the Society towards solving the accommodation crisis in Indian Schools. Upon the transfer of control of education to the Department of Indian Affairs in 1966, The Natal Indian Teachers' Society changed its name to the South African Indian Teachers' Association in order to enable Indian teachers throughout the Republic to become members. In 1979 the Association changed its name to the Teachers Association of South Africa, thus dropping the racial tag attached to its previous name. This meant that membership was open to all teachers. Over the twenty years of its existence as a national body the Association has developed into a vigorous institution. Its growth in stature must be measured by its multifarious activities which have benefitted Indian education. As a result of its representation in various departmental committees the Association is able to make valuable contributions where its opinions are valued. The Association's own Subject Societies make a valuable contribution towards education by means of their various publications. The Association's concern for the welfare of its members is illustrated by the representations it has made to the authorities on their behalf. In some instances legal recourse was necessary. That a great deal of success has been achieved by the Association there is no doubt. That education for Indians has made vast strides in the last 60 years there is no about. This is due in great measure to the untiring efforts of the Teachers Association of South Africa. The Association will still continue its fight for a better deal, not only for Indian teachers and Indian education, but for all South Africans.

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