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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.
411

Efficient Solutions to Autonomous Mapping and Navigation Problems

Williams, Stefan Bernard January 2002 (has links)
This thesis deals with the Simultaneous Localisation and Mapping algorithm as it pertains to the deployment of mobile systems in unknown environments. Simultaneous Localisation and Mapping (SLAM) as defined in this thesis is the process of concurrently building up a map of the environment and using this map to obtain improved estimates of the location of the vehicle. In essence, the vehicle relies on its ability to extract useful navigation information from the data returned by its sensors. The vehicle typically starts at an unknown location with no a priori knowledge of landmark locations. From relative observations of landmarks, it simultaneously computes an estimate of vehicle location and an estimate of landmark locations. While continuing in motion, the vehicle builds a complete map of landmarks and uses these to provide continuous estimates of the vehicle location. The potential for this type of navigation system for autonomous systems operating in unknown environments is enormous. One significant obstacle on the road to the implementation and deployment of large scale SLAM algorithms is the computational effort required to maintain the correlation information between features in the map and between the features and the vehicle. Performing the update of the covariance matrix is of O(n�) for a straightforward implementation of the Kalman Filter. In the case of the SLAM algorithm, this complexity can be reduced to O(n�) given the sparse nature of typical observations. Even so, this implies that the computational effort will grow with the square of the number of features maintained in the map. For maps containing more than a few tens of features, this computational burden will quickly make the update intractable - especially if the observation rates are high. An effective map-management technique is therefore required in order to help manage this complexity. The major contributions of this thesis arise from the formulation of a new approach to the mapping of terrain features that provides improved computational efficiency in the SLAM algorithm. Rather than incorporating every observation directly into the global map of the environment, the Constrained Local Submap Filter (CLSF) relies on creating an independent, local submap of the features in the immediate vicinity of the vehicle. This local submap is then periodically fused into the global map of the environment. This representation is shown to reduce the computational complexity of maintaining the global map estimates as well as improving the data association process by allowing the association decisions to be deferred until an improved local picture of the environment is available. This approach also lends itself well to three natural extensions to the representation that are also outlined in the thesis. These include the prospect of deploying multi-vehicle SLAM, the Constrained Relative Submap Filter and a novel feature initialisation technique. Results of this work are presented both in simulation and using real data collected during deployment of a submersible vehicle equipped with scanning sonar.
412

E-learning adoption in a campus university as a complex adaptive system: mapping lecturer strategies

Russell, Carol , Faculty of Engineering, UNSW January 2008 (has links)
The adoption of e-learning technologies in campus universities has not realised its potential for meeting the learning needs and expectations of 21st century students. By modelling university learning and teaching as a complex adaptive system, this thesis develops a new way of understanding and managing the adoption of new learning technologies in campus universities. The literature on learning and teaching in higher education indicates that lecturers??? ability to innovate in their teaching is constrained by tacit and discipline-specific educational knowledge. Introducing new methods and technologies into mainstream university teaching requires explicit review of educational knowledge, and requires support from departmental and institutional organizational systems. Research on organizational change in other contexts, such as manufacturing industry, has used complex adaptive systems modelling to understand the systemic interdependence of individual strategies, organizations and technologies. These models suggest that the integration of new e-learning technologies into mainstream campus university teaching will involve corresponding change processes. Part of this change requires the linking up of diverse disciplinary perspectives on learning and teaching. The thesis develops a conceptual framework for researching university learning and teaching as a complex adaptive system that includes learning technologies, people, and their organization within a university. Complex adaptive systems theory suggests that the capacity of a campus university to adapt to new e-learning technologies will be reflected in patterns in the strategies of those lecturers who are early adopters of those technologies. A context-specific study in the University of New South Wales used cognitive mapping to represent and analyse the strategies of a group of 19 early adopters of e-learning technology. These early adopters were participants in a cross-discipline Fellowship programme intended to develop their ability to act as change agents within the university. Analysis of the maps gathered before and after the Fellowship, triangulated with data on the Fellows??? participation in organizational change, leads to a new way of modelling how university learning and teaching systems, including their technologies, adapt within a complex and changing higher education context.
413

A high-resolution genetic map of human chromosome 16 and localization of the MEF gene / by Yang Shen.

Shen, Yang, 1953- January 1994 (has links)
Copies of author's previously published articles inserted. / Includes bibliographic references. / vii, 200, [74] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Addresses a need for more highly informative markers to be placed on high density cytogenetic-based physical and genetic linkage maps of chromosome 16. / Thesis (Ph.D.)--University of Adelaide, Dept. of Paediatrics, Women's and Children's Hospital, 1994
414

Genetic control of hydrolytic enzymes in germinated barley (Hordeum vulgare L.) / by Cheng-dao Li.

Li, Cheng-Dao January 1997 (has links)
Bibliography: leaves 114-141. / vi, 141, [42] leaves, [19] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Using RFLP, STS-PCR and isoenzyme techniques, maps the structural genes of hydrolytic enzymes important in seed germination processes, and determines the contribution of each gene to the activity of the enzyme. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1998
415

Evaluating hyperspectral imagery for mapping the surface symptoms of dryland salinity

Dutkiewicz, Anna January 2006 (has links)
Airborne hyperspectral imagery has the potential to overcome the spectral and spatial resolution limitations of multispectral satellite imagery for monitoring salinity at both regional and farm scales. In particular, saline areas that have good cover of salt tolerant plants are difficult to map with multispectral satellite imagery. Hyperspectral imagery may provide a more reliable salinity mapping method because of its potential to discriminate halophytic plant cover from non - halophytes. HyMap and CASI airborne imagery ( at 3m ground resolution ) and Hyperion satellite imagery ( at 30 resolution ) were acquired over a 140 sq km dryland agricultural area in South Australia, which exhibits severe symptoms of salinity, including extensive patches of the perennial halophytic shrub samphire ( Halosarcia pergranulata ), sea barley grass ( Hordeum marinum ) and salt encrusted pans. The HyMap and Hyperion imagery were acquired in the dry season ( March and February respectively ) to maximise soil and perennial vegetation mapping. The optimum time of year to map sea barley grass, an annual species, was investigated through spectral discrimination analysis. Multiple reflectance spectra were collected of sea barley grass and other annual grasses with an ASD Fieldspec Pro spectrometer during the September spring flush and in November during late senescence. Comparing spectra of different species in November attempted to capture the spectral differences between the late senescing sea barley grass and other annual grasses. Broad NIR and SWIR regions were identified where sea barley grass differs significantly from other species in November during late senescence. The sea barley grass was therefore shown to have the potential to be discriminated and mapped with hyperspectral imagery at this time and as a result the CASI survey was commission for November. Other salinity symptoms were characterised by collecting single field and laboratory spectra for comparison to image derived spectra in order to provide certainty about the landscape components that were to be mapped. Endmembers spectra associated with saltpans and samphire patches were extracted from the imagery using automated endmember generation procedures or selected regions of interest and used in subsequent partial unmixing. Spectral subsets were evaluated for their ability to optimise salinity maps. The saltpan spectra contained absorption features consistent with montmorillonite and gypsum. A single gypsum endmember from one image strip successfully mapped saltpans across multiple images strips using the 1750 nm absorption feature as the input to matched filter unmixing. The individual spectra of green and red samphire are dominated by photosynthetic vegetation characteristics. The spectra of green samphire, often seen with red tips, exhibit peaks in both green and red wavebands whereas the red samphire spectra only contain a significant reflectance peak in the visible red wavelength region. For samphire, Mixture Tuned Matched Filtering using image spectra, containing all wavelength regions, from known samphire patches produced the most satisfactory mapping. Output salinity maps were validated at over 100 random sites. The HyMap salinity maps produced the most accurate results compared to CASI and Hyperion. HyMap successfully mapped highly saline areas with a good cover of samphire vegetation at Point Sturt without the use of multitemporal imagery or ancillary data such as topography or PIRSA soil attribute maps. CASI and Hyperion successfully mapped saltpan, however, their samphire maps showed a poor agreement with field data. These results suggest that perennial vegetation mapping requires all three visible, NIR and SWIR wavelength regions because the SWIR region contains important spectral properties related to halophytic adaptations. Furthermore, the unconvincing results of the CASI sea barley grass maps suggests that the optimal sensor for mapping both soil and vegetation salinity symptoms are airborne sensors with high spatial and spectral resolution, that incorporate the 450 to 1450 nm wavelength range, such as HyMap. This study has demonstrated that readily available software and image analysis techniques are capable of mapping indicators of varying levels of salinity. With the ability to map symptoms across multiple image strips, airborne hyperspectral imagery has the potential for mapping larger areas covering sizeable dryland agriculture catchments, closer in extent to single satellite images. This study has illustrated the advantage of the hyperspectral imagery over traditional soil mapping based on aerial photography interpretation such as the NLWRA Salinity 2000 and the PIRSA soil landscape unit maps. The HyMap salinity maps not only improved mapping of saline areas covered with samphire but also provided salinity maps that varied spatially within saline polygons. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2006.
416

Globin gene mapping in the marsupial, Dasyurus viverrinus

Wainwright, Brandon John. January 1984 (has links) (PDF)
Bibliography: 31 unnumbered leaves at end of vol
417

Large-scale nutrient pattern in the Gulf of Bothnia with the hydrodynamic of its loads

Salawu, Lukman January 2006 (has links)
<p>Eutrophication, which is the most important degradation in water bodies, has been traced to the imposed loading of nutrients. Of interest is the fact that the process is often accompanied with undesirable effects, one of which is primarily the increased algae production at the surface and accumulation of biomass at the bottom and the secondary responses, which include a., change in species composition b. change in the biogeochemical cycle c. shift in the seasonal pattern and magnitude variability.</p><p>The biogeochemical cycle in response to hydrodynamic alterations may occur internally; however external loading often fosters the process over large spatial scales. In the quest of validating the above statement, we hypothesized that there is no difference in the mean concentration of nutrients in the Gulf of Bothnia from the overall mean concentration.</p><p>The analysis was done with a probability mapping method, in which all stations were grouped into a lattice. The cells are constructed using a grid system, i.e. x and y axis (longitude and latitude). Basically the method statistically tested for variables deviating from the over mean concentration. The variables analyzed are DIN, DSi, DIP and DIN: DSi.</p><p>Results of the analysis showed significant spatial variations in the nutrient distribution in the Gulf of Bothnia; such differences were observed in the coastal to the deep zones of the Gulf.</p>
418

Lean Remanufacturing : Material Flows at Volvo Parts Flen

Mähl, Maria, Östlin, Johan January 2007 (has links)
<p>The after market is of great importance of a company’s competitiveness and an increasing part of its revenues can be derived from it. Remanufacturing, in focus of this thesis, is a great business opportunity and the European market has an enormous growth potential. In the USA it is a major business and the automotive industry, targeted in this thesis, sells approximately 60 million remanufactured automotive products compared to 15 million products in Europe for an equivalent stock of vehicles</p><p>Compared to manufacturing, the remanufacturing environment is a more complex business due to the high degree of uncertainty in the production process, mainly caused by two factors: the quantity and quality of returned cores. Overall, seven characteristics that make the remanufacturing material flow harder to control have been identified. Emerging in the 1990’s the concept of Lean production is a well-known method for improving the manufacturing capabilities of a company. Lean production, which is said to increase productivity, decrease lead-time and costs and enhance quality, is widely adopted.</p><p>In this thesis, the purpose is to explore what characteristics of the remanufacturing environment that can hinder the implementation of Lean production principles of material flows and how Lean principles can be employed in a remanufacturing environment.</p><p>In accordance, the theories of Lean production and Remanufacturing are used and the research methodology chosen that of a case study. To assess material flow, the production flows of five major product groups in a car engine are assessed. For the collection of data, Value Stream Mapping (VSM) methodology has been used.</p><p>The main result about material flows and how Lean principles can be employed in a remanufacturing environment have resulted in eight generic proposals. The main conclusion from these proposals is that the inherent characteristics of variable processing times and uncertainty in materials recovered have major negative impact for implementing a lean production process. Vice versa, given an accurate supply of parts for reassembly, all the principles of Lean production can be fully implemented in the phases of reassembly and testing.</p>
419

Simple sequence repeat marker development and mapping in cultivated sunflower, Helianthus annuus L.

Yu, Ju-Kyung 07 September 2001 (has links)
The cultivated sunflower (Helianthus annuus L., x=17) is one of the most important annual oilseed crops in the world. There are very few publicly shared sequence-based DNA markers and genetic maps in sunflower, even though molecular DNA markers and genetic maps have become widely used in all areas of genetic research and breeding in plant species. The objectives of this study were to develop sequence-based molecular markers and utilize the markers for genetic analyses and constructing maps in the cultivated sunflower. A total of 131 functional simple sequence repeat (SSR) markers were developed for 16 elite inbred lines using a small insert genomic library enriched for short simple sequence repeats. The polymorphism information content (PIC) estimated from 74 polymorphic SSR markers ranged from 0.0 to 0.93 with mean value of 0.55. Tetranucleotide repeats were significantly more polymorphic than dinucleotide and trinucleotide repeats, and no obvious correlation was found between repeat numbers and PIC scores. Genetic distance among 16 inbred lines, estimated from 74 polymorphic SSR markers ranged 0.175 to 0.543. Principal coordinate and cluster analyses of the genetic distance matrix well explained the difference between oilseed lines and confectionery lines, and sterility maintainer lines and fertility restorer lines. A total of 1,090 SSR markers were screened for polymorphism between the parents of two mapping populations. The two genetic maps were constructed by genotyping 94 recombinant inbred lines from a cross between PHA and PHB (276 SSR loci covering 1377.4 cM with mean distance of 4.99 cM), and 94 F��� progeny from a cross between HA370 and HA372 (122 SSR loci integrated into the existing RFLP framework map covering 1348.0 cM with mean distance of 6.77 cM). Ninety-three percent of the SSR markers were mapped to single loci and 56.5% of the loci were co-dominant. Clustering of SSR loci was observed near centromeric regions and most of the distorted loci were mapped to centromeric or distal regions. A concerted effort to develop SSR markers and generate highresolution SSR maps will enhance future fingerprinting analyses, fine-scale genome analyses and molecular breeding in the cultivated sunflower. / Graduation date: 2002
420

Patterning the zebrafish visual system requires the actions of Pbx transcription factors, and a downstream growth factor, Gdf6a

French, Curtis Robert 11 1900 (has links)
The zebrafish visual system relies on positional information in the retina and optic tectum, so that the spatial fidelity of light signals that enter the eye are preserved for visual processing. This positional information is essential for ordered topographic mapping of retinal ganglion cell axons. Spatial information in the retina and tectum relies on discrete signaling pathways that regulate polarized expression of axon guidance molecules in distinct domains in both the retina and tectum, thereby ensuring that accurate topographic maps are created. In this thesis, I have investigated the function of two families of transcription factors, Pbx and Meis, as well as a growth factor of the Bmp family, Gdf6a, in specifying positional identity in the zebrafish visual system. I demonstrate that two partially redundant pbx genes, pbx2 and pbx4, along with members of the meis family, are required for patterning of the dorsal retina and tectum in zebrafish. Embryos lacking these critical transcription factors exhibit retinal ganglion cell axon outgrowth errors, which are likely the result of tectal mis-patterning. Bone morphogenetic protein (Bmp) growth factors regulate dorsal retinal identity in vertebrate models, but the developmental timing of this signaling remains unclear. In this thesis, I investigate the functions of two zebrafish Bmps, Gdf6a and Bmp4, during initiation of dorsal retinal identity. Knockdown of zebrafish Gdf6a blocks initiation of dorsal marker expression, while knockdown of Bmp4 produces no discernable retinal phenotype. These data, combined with analyses of embryos ectopically expressing Bmps, demonstrate that Gdf6a is necessary and sufficient for initiation of dorsal retinal identity, and loss of such identity leads to errors in retinal ganglion cell topographic mapping. Finally, I demonstrate that gdf6a is required for numerous embryonic processes in addition to dorsal retina specification. Gdf6a in required for eye growth, as loss of Gdf6a function leads to microphthalmia. I have obtained preliminary evidence that this growth factor is also required for development of the lens and axial skeleton. Furthermore, many of these phenotypes are similar to those seen in human patients with mutations in GDF6, highlighting the importance of understanding the function of this growth factor in model organisms. / Molecular Biology and Genetics

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