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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.
21

Defect Detection Via THz Imaging: Potentials & Limitations

Houshmand, Kaveh 22 May 2008 (has links)
Until recent years, terahertz (THz) waves were an undiscovered, or most importantly, an unexploited area of electromagnetic spectrum. This was due to difficulties in generation and detection of THz waves. Recent advances in hardware technology have started to open up the field to new applications such as THz imaging. This non-destructive and non-contact imaging technique can penetrate through diverse materials such that internal structures, in some cases invisible to other imaging modalities, can be visualized. Today, there are variety of techniques available to generate and detect THz waves in both pulsed and continuous fashion in two different geometries; transition, and reflection modes. In this thesis continuous wave THz imaging was employed for higher spatial resolution. However, with any new technology comes its challenges; automated processing of THz images can be quite cumbersome. Low contrast and the presence of a widely unknown type of noise make the analysis of these images difficult. In this work, there is an attempt to detect defects in composite material via segmentation by using a Terahertz imaging system. According to our knowledge, this is the first time that this type of materials are being tested under Terahertz cameras to detect manufacturing defects in aerospace industry. In addition, segmentation accuracy of THz images have been investigated by using a phantom. Beyond the defect detection for composite materials, this can establish some general knowledge about Terahertz imaging, its capabilities and limitations. To be able to segment the THz images successfully, pre-processing techniques are inevitable. In this thesis, a variety of different image processing techniques, self-developed or available from literature, have been employed for image enhancement. These methods range from filtering to contrast adjustment to fusion of phase and amplitude images by using fuzzy set theory, to just name a few. The result of pre-procssing and segmentation methods demonstrates promising outcome for future work in this field.
22

Tvorba geometrických schémat u žáků 1.stupně prostřednictvím podnětných geometrických prostředí / Construction of elementary pupils' geometric schemas via motivating learning environments

Kloboučková, Jaroslava January 2015 (has links)
Title: Construction of elementary pupils' geometric schemas via motivating learning environments Author: Jaroslava Kloboučková Department: Department of mathematics and mathematics education Supervisor: doc. RNDr. Darina Jirotková, Ph.D. Abstract: The aim of the dissertation is to discuss teaching geometry as integral part of mathematics education at the primary school level. The thesis also documents a longitudinal teaching study which was initiated in 2010 and which gives us a base for discussion of some fundamental questions regarding the process of learning geometry for pupils in their early school years. The main objective here is to attempt to answer the following four didactic questions: In which way do pupils learn about geometrical objects? How do they share their geometrical knowledge, experience and discoveries with one another? How much (at what level) are they able to understand mathematical concepts that the official curricular documents (the Czech Framework for Education Program) place in later years of schooling? What phenomena are they able to grasp and describe using their mother tongue? The theoretical framework focuses on the learning process and the typology of mathematical problems in geometry. Four specific engaging environments (Cube Buildings, Origami, Wooden Sticks, and Tiles) and...
23

Čichové vnímání u první epizody schizofrenie a akutních a přechodných psychotických poruch / Olfactory Perception in First-Episode Schizophrenia and Acute and Transient Psychotic Disorders

Hofmannová, Zdena January 2019 (has links)
Research suggests that olfactory perception of patients with schizophrenia differs from healthy people. In the context of previously conducted research, the present thesis addresses the differences in the abilities of identification and discrimination of odours and assessment of perceived odour qualities (pleasantness, familiarity, intensity, edibility) between patients with schizophrenia or acute and transient psychotic disorders and healthy volunteers, taking into account gender differences; in addition, the differences in the relationship between identification of odours and evaluation of the perceived qualities of odours between patients and healthy persons were explored as well as relationship between the severity of negative symptoms and olfactory perception. In line with other studies, deficits were found in patients in identification and discrimination of odours and in the assessment of odour familiarity compared to healthy subjects, with no gender differences. There were no differences in the relationship between the identification of odours and assessment of the perceived qualities of odours between patients and volunteers, and association of olfactory abilities and the assessment of perceived qualities of odours with the severity of negative symptoms was found only for identification of...

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