Two lightning detectors, of the magnetic direction finder type, form part of a two station system for determining the position of lightning strikes. The detectors are on a baseline of approximately 600 m, and the ultimate aim of the system is to accurately detect and map lightning within a radius of 30 km. Although no real time capability is present, the archive data collected from each separate station is used to find the offset errors in the azimuthal orientation, as well as in time (using processes described in Appendix A). The relative offset errors are determined by shifting the time and azimuthal information for one station’s data and calculating the maximum possible matching records (within certain time and azimuth criteria) for each incremental shift. An analysis of the peaks in total matching records, when plotted against the relevant shift increments, is performed in order to obtain the values of the offset errors. Between the two individual stations, the relative offset in orientation is found to be 24.5 degrees, and in time to be 0.001305 days (112.75 seconds). The individual stations, as well as the triangulated data calculated from matching records, can also be calibrated using data from the South African Weather Service Lightning Detection Network (SAWSLDN). Individual station calibration indicated an offset of +6.4 degrees and 0.00575 days (496.8 seconds) for Station 1, with the offsets for Station 2 determined as +29.4 degrees and −0.000105 days (9.07 seconds). Comparison of triangulated data to SAWSLDN data yields unexpected results with regard to resultant shifts, which may point to an error or anomaly in the triangulation calculations. A detailed analysis of the storm data is contained in Appendix B of the dissertation.

Nowadays, LiDAR(Light Detection And Ranging, LiDAR) is the more important and widely applicable measurement technique. The rise of visual system in 3D is very useful to the measurement of LiDAR and gets more importance value for 3D reconstruction technology, in which abundant surface features are implied in the point cloud data. Combined with the image and laser technique for real-time rendering, the LiDAR will be more functional. This thesis proposes and designs a system which combined with Laser Range Finder and 3D visual interface for vehicles, and also equipped with rotary encoder and initial measurement unit to DR(Dead Reckoning) function. Through the coordinate transform method of 2D to 3D, the 3D coordinate of each point will be calculated, and embedded with the color information which captured from the camera to take 3D color point cloud collection. This method is also called Mobile Mapping System(MMS). In addition, this mapping system uses Direct Memory Access technology to display the point cloud synchronous in 3D visual system. Except for the point cloud collection, the reconstruction of point cloud data is used in this system. The surface reconstruction is based on Nearest Neighbor Interpolation method. There are two factors to conduct the interpolation process: the angle and distance between two sample points from the points sequence. The reconstruction of point cloud and calibration of DR is not only to confirm the accuracy of 3D point cloud map but also the ¡§New Geography¡¨ of the 3D electronic map. This research will build up an independent Mobile Mapping System.

Tesis para optar al grado de Magíster en Ciencias, Mención Computación / El modelo cosmológico actual y más aceptado del universo se llama Lambda Cold Dark Matter. Este modelo nos presenta el modelo más simple que proporciona una explicación razonablemente buena de la evidencia observada hasta ahora. El modelo sugiere la existencia de estructuras a gran escala presentes en nuestro universo: Nodos, filamentos, paredes y vacíos. Los vacíos son de gran interés para los astrofísicos ya que su observación sirve como validación para el modelo. Los vacíos son usualmente definidos como regiones de baja densidad en el espacio, con sólo unas pocas galaxias dentro de ellas. En esta tesis, presentamos un estudio del estado actual de los algoritmos de búsqueda de vacíos. Mostramos las diferentes técnicas y enfoques, e intentamos deducir la complejidad algorítmica y el uso de memoria de cada void-finder presentado. Luego mostramos nuestro nuevo algoritmo de búsqueda de vacíos, llamado ORCA. Fue construido usando triangulaciones de Delaunay para encontrar a los vecinos más cercanos de cada punto. Utilizando esto, clasificamos los puntos en tres categorías: Centro, borde y outliers. Los outliers se eliminan como ruido. Clasificamos los triángulos de la triangulación en triángulos de vacíos y centrales. Esto se hace verificando un criterio de distancia, y si los triángulos contienen outliers. Este método nos permite crear un algoritmo de búsqueda de vacíos rápido y robusto. Adicionalmente, se presenta una versión paralela del algoritmo.

Nuclear divisions during sporulation of 15 predominantly two-spored and 2 predominantly four-spored yeasts were followed by Giemsa staining and light microscopy. The number of nuclei present per ascus was related to the presence or absence of conjugation at the time of germination of the spores. Plating experiments and a modification of the Finder Slide technique were used to determine whether progeny cells that developed from single spores of 2 two-spored and one four-spored strain could sporulate. The ploidy of these yeasts at different stages of their life cycles was estimated by DNA extractions. The spores of the two-spored yeasts were very difficult to separate following removal of their ascus walls, and electron microscopy was employed in an attempt to account for this. / Thesis / Master of Science (MSc)

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Personal file retrieval – the task of locating and opening files on a computer – is a common task for all computer users. A range of interfaces are available to assist users in retrieving files, such as navigation within a file browser, search interfaces and recent items lists. This thesis examines two broad goals in file retrieval: understanding current file retrieval behaviour, and improving file retrieval by designing improved user interfaces. A thorough understanding of current file retrieval behaviour is important to the design of any improved retrieval tools, however there has been surprisingly little research about the ways in which users interact with common file retrieval tools. To address this, this thesis describes a longitudinal field study that logs participants' file retrieval behaviour across a range of methods, using a specially developed logging tool called FileMonitor. Results confirm findings from previous research that search is used as a method of last resort, while providing new results characterising file retrieval. These include analyses of revisitation behaviour, file browser window reuse, and interactions between retrieval methods, as well as detailed characterisations of the use of navigation and search. Knowledge gained from this study assists in the design of three improvements to file navigation: Icon Highlights, Search Directed Navigation and Hover Menus. Icon Highlights highlight items that are considered the most likely to be accessed next. These highlights are determined using a new algorithm, AccessRank, which is designed to produce a set of results that is both accurate and stable over time. Search Directed Navigation highlights items that match, or contain items that match, a filename search query, allowing users to rehearse the mechanisms for expert performance in order to aid future retrievals, and providing greater context than the results of a traditional search interface. Hover Menus appear when hovering the mouse cursor above a folder, and provide shortcuts to highly ranked files and folders located at any depth within the folder. This allows users to reduce navigation times by skipping levels of the file hierarchy. These interfaces are evaluated in lab and field studies, allowing for both precise analysis of their relative strengths and weaknesses, while also providing a high degree of external validity. Results of the lab study show that all three techniques reduce retrieval times and are subjectively preferred by participants. For the field study, fully functional versions of Icon Highlights and Search Directed Navigation are implemented as part of Finder Highlights, a plugin to OS X's file manager. Results indicate that Icon Highlights significantly reduce file retrieval times, and that Search Directed Navigation was useful to those who used it, but faces barriers to adoption. Key contributions of this thesis include a review of previous literature on file management, a thorough characterisation of file retrieval behaviour, improved algorithms for predicting user behaviour and three improved interfaces for file retrieval. This research has the potential to improve a tedious activity that users perform many times a day, while also providing generalisable algorithms and interface concepts that are applicable to a wide range of interfaces beyond file management.

Range finding are widely used in various industrial applications, such as machine vision, collision avoidance, and robotics. Presently most range finders either rely on active transmitters or sophisticated mechanical controllers and powerful processors to extract range information, which make the range finders costly, bulky, or slowly, and limit their applications. This dissertation is a detailed description of a real-time vision-based range sensing technique and its single-chip CMOS implementation. To the best of our knowledge, this system is the first single chip vision-based range finder that doesn't need any mechanical position adjustment, memory or digital processor. The entire signal processing on the chip is purely analog and occurs in parallel. The chip captures the image of an object and extracts the depth and range information from just a single picture. The on-chip, continuous-time, logarithmic photoreceptor circuits are used to couple spatial image signals into the range-extracting processing network. The photoreceptor pixels can adjust their operating regions, simultaneously achieving high sensitivity and wide dynamic range. The image sharpness processor and Winner-Take-All circuits are characterized and analyzed carefully for their temporal bandwidth and detection performance. The mathematical and optical models of the system are built and carefully verified. A prototype based on this technique has been fabricated and tested. The experimental results prove that the range finder can achieve acceptable range sensing precision with low cost and excellent speed performance in short-to-medium range coverage. Therefore, it is particularly useful for collision avoidance.

Small signal stability has always been an important concern for analog designers. Recent advances such as the Loop Finder algorithm allows designers to detect and identify local, potentially unstable return loops without the need to identify and add breakpoints. However, this method suffers from extremely high time and memory complexity and thus cannot be scaled to very large analog circuits. In this research work, we first take an in-depth look at the loop finder algorithm so as to identify certain key enhancements that can be made to overcome these shortcomings. We next propose pole discovery and impedance computation methods that address these shortcomings by exploring only a certain region of interest in the s-plane. The reduced time and memory complexity obtained via the new methodology allows us to extend automatic stability checking to much larger circuits than was previously possible.