Circular source and detector trajectories in cone-beam computed tomography (CT) are known to collect insufficient data for accurate object reconstruction. One model predicts that the lacking information corresponds to a shift-variant cone of missing spatial frequency components in the local Fourier domain. These predictions were experimentally verified by imaging small, localized objects and observing their Fourier transforms. Measurements indicated that the internal angle of the ‘missing cone’ varies as the angle of locally intersecting x rays with respect to the horizontal plane, as expected. Object recovery was also found to depend greatly on the distribution of the object’s frequency spectrum relative to the missing cone, as predicted. Findings agreed with more anatomically relevant phantoms, which showed preferential intensity discrepancies at gradients oriented within or near the missing cone. Methods for artefact correction are in general limited to approximation unless a priori information is incorporated.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.

While collaborative engineering in outsourcing projects presents potential benefits to the partners, it involves some risks and reasonable concerns. First, a poor mechanism of data exchange and data communication can lead to loss of effectiveness and efficiency of the project. Second, collaborative engineering requires partners to adapt a common business process, which often means moving away from a familiar way of working. Thus, it is crucial to find an optimal way a collaboration can be achieved with the lowest waste due to changes in communication practices, and losses in efficiency due to asynchronous processes or big amount of exchange data. The main goal of this thesis is to connect two aspects in a collaboration: data-exchange and process-based execution. The main reason to do so is to resolve a problem with a weak control over information needed for successful project execution. Three research methods are used in this work: a case study to analyze how collaboration is performed in the industry and which problems exist; a literature review to understand how existing collaboration tools can be adapted to help solving the identified problems; and a prototypical implementation to show how automated versioning of engineering knowledge can be added to the union of data exchange and process-based aspects. The case study was performed and a list of business requirements was presented. Based on the list of requirements, solutions within the literature were searched. A process-based artifact-centric concept was applied to the case study scenario. Objectives are achieved, however, the problem was shown on an example of one company, which presents a limitation, as generalization has not been proved.

The technique of Raman spectroscopy was used in a study of shards of known (Ming and Meissen) and unknown (archaeological) origin. A tile shard from the Citadel of Algiers was included in this study as further confirmation of the consistency of the methods that are developed. The Citadel from which the tile shard was obtained was built in 1516 and represents a landmark from pre-colonial Algeria. The results were compared with those obtained from studies on intact museum pieces of known (Ming) origin. A consistent method of studying underglaze pigments on glazed ceramic artifacts by directing the laser beam through the predominantly silicate glaze was developed. The glaze depth profiling method developed proved to be very useful in the analysis and gives not only a detailed composition for the glaze/ceramic interfacial pigment, but also the order in which the various interfacial pigment layers were applied at the time of manufacture. The information acquired leads to an understanding of the level of technological development of the manufacturers. The detailed study and characterisation of the pigments that were analysed in this way gives insight into trade relations among ancient societies of the Mediterranean and will also assist archaeologists in establishing cut-off dates for the archaeological sites from which the artifacts were recovered. All the shards, except one from Meissen (Germany), were provided by the National Cultural History Museum of South Africa and the intact Ming dynasty plates were provided by the J.A. van Tilburg Museum of the University of Pretoria. The tile shard sample from the Citadel of Algiers was donated for the study. The results indicate that none of the archaeological shards could possibly be of Ming dynasty origin based on, firstly, the use of amorphous carbon to darken the cobalt blue (CoAl2O4) used as decoration on the shards, and secondly on the use of white (synthetic) anatase to whiten the ceramic surface before the application of the pigment since this synthetic anatase is known to have been manufactured for the first time around 1920. An ancient rediscovered ternary pigment (Pb2SnSbO6.5) previously found on Italian paintings of the 16th century, for example, “Lot and his daughters” by G.B. Langetti and “Entrance of Christ in Jerusalem” by Luca Giordano, was identified on the Citadel tile and successfully characterised. A Pb-O vibrational Raman band at 127 cm-1 for this pigment was assigned for the first time. Additional pigments identified on the tile include Naples yellow (Pb2Sb2O7), lead (II) stannate (Pb2SnO4), cobalt blue (CoAl2O4) and cassiterite (SnO2). The bulk of the tile body is composed mainly of hematite (á-Fe2O3), maghemite (ã-Fe2O3), magnetite (Fe3O4) and quartz (á-SiO2), with traces of calcite (CaCO3) and amorphous carbon. The unique non destructive depth profiling method that was developed in this study can now be applied to the study of underglaze pigments on intact porcelain artifacts in museums and private collections around the world for authentication purposes and for comparison with archaeological shard samples. / Thesis (PhD)--University of Pretoria, 2010. / Chemistry / unrestricted

Bladder artifacts during bone single photon emission computed tomography (SPECT) is a common source of errors. The extent and severity of bladder artifacts have been described for filtered back projection (FBP) reconstruction. OSEM may help to address this poor record of bladder artifacts, which render up to 20% of the images unreadable. Aims and objectives To evaluate the relationship of the bladder to acetabulum ratio in guiding the choice of the number of iterations and subsets used for OSEM reconstruction, for reducing bladder artifacts found on FBP reconstruction. Materials and Methods 105 patients with various indications for bone scans were selected and planar and SPECT images were acquired. The SPECT images were reconstructed with both filtered back projection and OSEM using four different combinations of iterations and subsets. The images were given to three well experienced Nuclear Physicians who were blinded to the diagnosis and type of reconstruction used. They then labelled images from the best to the worst after which the data was analysed. The bladder to acetabulum ratio for each image was determined which was then correlated with the different iterations and subsets used. Results The study demonstrated that reconstruction using OSEM led to better lesion detectability compared to filtered back projection in 87.62% of cases. It further demonstrated that the iterations and subsets used for reconstruction of an image correlates to the bladder to acetabulum ratio. Four iterations and 8 subsets yielded the best results in 48.5% of the images whilst two iterations and 8 subsets yielded the best results in 33.8%. The number of reconstructed images which yielded the best results with 2 iterations and 8 subsets were the same as or more than those with 4 iterations and 8 subsets when the bladder/acetabulum ratio was between 0.2-0.39. A ratio below 0.2 or above 0.39 supports the usage of 4 iterations and 8 subsets over 2 iterations and 8 subsets. Conclusion Bladder to acetabulum ratio can be used to select the optimum number of iterations and subsets for reconstruction of bone SPECT for accurate characterization of lesions. This study also confirms that reconstruction with OSEM (vs FBP) leads to better lesion detectability and characterisation. / Dissertation (MSc)--University of Pretoria, 2011. / Nuclear Medicine / unrestricted

Motion artifacts are often a significant component of the measured signal in functional near-infrared spectroscopy (fNIRS) experiments. A variety of methods have been proposed to address this issue, including principal component analyses (PCA), Kalman filtering, correlation-based signal improvement (CBSI), wavelet filtering, spline interpolation, and autoregressive algorithms. The efficacy of these techniques has been compared using simulated data; however, our understanding of how these techniques fare when dealing with task-based cognitive data is limited. Recently, Brigadoi et al. (2014) quantitatively compared 6 motion correction techniques in a sample of adult data measured during a simple cognitive task. Wavelet filtering showed the most promise as an optimal technique for motion correction. Because fNIRS is often used with infants and young children, it is critical to evaluate the effectiveness of motion correction techniques directly with data from these age groups. Here we examined which techniques are most effective with data from young children. The efficacy of each technique was compared quantitatively using objective metrics related to the physiological properties of the hemodynamic response using two different sets of parameters to ensure maximum retention of included trials. Results showed that targeted PCA (tPCA) and CBSI retained a higher number of trials. These techniques also performed well in direct head-to-head comparisons with the other approaches using both quantitative metrics and a qualitative assessment. The CBSI technique corrected many of the artifacts present in our data; however, this technique was highly influenced by the parameters used to detect motion. The tPCA technique, by contrast, was robust across changes in parameters while also performing well across all comparison metrics. We conclude, therefore, that tPCA is an effective technique for the correction of motion artifacts in fNIRS data from young children.

Over the last few years, the importance of computer science education for children has been promoted more and more vigorously. In addition, the demand for technology occupations has increased rapidly, and there are many job opportunities in computer science. However, there are not many women working in this field. One of the reasons is young women’s lack of interest in computer science. This study investigates how to attract young women to computer programming and support computational thinking through design and develop learning activities. This study’s approach includes several related researches, theories, and methodologies. Interviews, workshops, and observations were used to determine design requirements. The results demonstrate that tangible and meaningful artifacts are effective educational tools for computer programming. Based on the results, this research developed a prototype, “TomatoBox,” a do-it-yourself kit that creates toys while providing an enjoyableactivity to learn programming.

Research indicates that the application of historical empathy, defined as using historical evidence to reconstruct past perspectives, engenders critical thinking in students. There is lack of research on the level of comprehension and use of historical empathy as an instructional strategy by high school history instructors. The purpose of this qualitative study was to explore teachers' comprehension and application of historical empathy in 2 high schools. This study was grounded in Edmund Husserl's concept of intersubjectivity, which suggests that apperception facilitates the grasp of multiple perspectives. Research questions addressed history teacher comprehension and employment of historical empathy as a tool to improve students' understanding of multiple historical perspectives. All 7 local history teachers participated in this case study. Data collection included classroom observations that were followed by semi-structured teacher interviews to discuss what was observed. Six themes resulted from open, axial, and selective coding of field notes and interview transcriptions. These themes indicated that participants were unfamiliar with historical empathy, emphasized the necessity of emotion in learning, perceived the need to help students understand historical actors, stressed the need for artifacts and site visits to generate context, and used analogies to develop perspectives. These themes informed the project of a position paper recommending professional development for teachers in historical empathy. Increasing awareness of and developing empathetic instructional strategies within the classroom can foster positive social change by engendering apperceptive skills among local history students and has broader potential to increase the efficacy of museum education and heritage programs.

abstract: With the fast pace of globalization and the rise of encounters in digital spaces, CALL scholars have become increasingly interested in how digital tools mediate intercultural encounters. However, despite their evident success in connecting students from around the world, current online intercultural exchanges continue to present problems such a promotion of positive experiences over deep intercultural learning and lack of real-life value (O’ Dowd, 2018). In addition, digitally-mediated intercultural learning research is based on the same theoretical approaches to learning that guide CALL research (Firth & Wagner, 1997; Lafford, 2017). Although such frameworks are successful in allowing researchers to conceive of digital tools as mediators for human interaction, they have yet to embrace the potential of digital artifacts themselves as intercultural interlocutors. Aiming to address this gap in the research, this investigation used Atkinson’s (2010, 2014) sociocognitive approach to language learning to understand the role that digital tools have in intercultural learning. Also integrating Dervin’s (2011) liquid approach to interculturality—which focuses on understanding intercultural learning as a co-constructed process—the research questions that guided this investigation asked: (a) does film annotation mediate intercultural learning? and, (b) in what ways does film annotation mediate intercultural learning? In answering these questions, the study looked at the intercultural learning process of five advanced learners of Spanish, as they interacted with annotated film clips, and engaged in peer discussion around the themes of colonialism and coloniality presented in the film clips. Data were collected through pre and post-tests, video recordings of peer discussions, and screen recordings of participants’ interaction with the annotated film clips. Findings showed that film annotation allowed participants to notice, retrieve and take notes on important cultural information, which they later incorporated in discussion with peers. Based on this evidence, and aligned with the aforementioned theoretical frameworks, this investigation poses that intercultural learning is a fluid, iterative process. The study also suggests that digital artifacts—as well as human interlocutors—play an important role in enabling learning processes, therefore, the role of such artifacts should be studied more in depth. / Dissertation/Thesis / Doctoral Dissertation Spanish 2019

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19980号 / 工博第4224号 / 新制||工||1653(附属図書館) / 33076 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 Cruz Ana Maria , 教授 小林 潔司, 准教授 横松 宗太 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM