• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 162
  • 35
  • 26
  • 24
  • 24
  • 7
  • 5
  • 4
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 417
  • 56
  • 53
  • 39
  • 37
  • 30
  • 28
  • 27
  • 25
  • 25
  • 24
  • 23
  • 23
  • 22
  • 21
  • 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.
101

Usability Studies with Virtual and Traditional Computer Aided Design Environments

Ahmed, Syed Adeel 15 December 2006 (has links)
For both the CAVETM and the adaptable technology possessed by the University of New Orleans, crystal eye glasses are used to produce a stereoscopic view, and an ascension flock of birds tracking system is employed for tracking of the user's head position and position of a wand in 3D space. It is argued that with these immersive technologies along the use of gestures and hand movements should provide a more natural interface with the immersive virtual environment. This allows a more rapid and efficient set of actions to recognize geometry, interaction with a spatial environment, the ability to find errors, or navigate through an environment. The wand interface is used to provide an improved means of interaction. This study quantitatively measures the differences in interaction when compared with traditional human computer interfaces. This work uses competitive usability in four different Benchmarks: 1) navigation, 2) error detection/correction, 3) spatial awareness, and 4) a “shopping list” of error identifications. This work expands on [Butler & Satter's, 2005] work by conducting tests in the CAVETM system, rather than principally employing workbench technology. During testing, the testers are given some time to “play around” with the CAVETM environment for familiarity before undertaking a specific exercise. The testers are then instructed regarding tasks to be completed, and are asked to work quickly without sacrificing accuracy. The research team timed each task, counted errors, and recorded activity on evaluation sheets for each Benchmark test. At the completion of the testing scenarios involving Benchmarks 1, 2, 3, or 4, the subjects were given a survey document and asked to respond by checking boxes to communicate their subjective opinions.
102

Goldsmith’s: Preliminary Study of a newly discovered Pleistocene site near Sterkfontein.

Mokokwe, Winnie Dipuo 21 February 2007 (has links)
Student Number : 9903519M - MSc research report - School of Geography, Archaeology and Environmental Studies - Faculty of Science / Goldsmith’s is a newly discovered fossil and archaeological site 4km south-west of the famous Sterkfontein Cave Site, in the buffer zone of the Cradle of Humankind World Heritage Site. It preserves one of the rare occurrences in South African fossil cave sites of stone artefacts with associated fossil fauna. Thirteen artefacts from two Stone Age cultures are represented within the site: namely the Earlier Stone Age and the Middle Stone Age. Eleven stone artefacts represent the Earlier Stone Age, dated to ca, 2-1 million years within the Sterkfontein Valley sites, while two artefacts represent the MSA. The stone tools from both cultures are not embedded in breccia and may have originated from decalcified breccias, or alternatively from slope wash. Various faunal taxa were recovered including bovids, primates, carnivores and others. Carnivores are the most highly represented, followed by bovids. Analysis of bone surface modifications indicate that the majority of the bones are slightly weathered, and some bone specimens are also abraded, suggesting that they may have accumulated through slope wash. The high frequencies of carnivore remains, including Dinofelis and a representation of most carnivore body parts, support a possible death trap scenario. The fauna suggests a palaeoenvironment with open woodland or savannah within the vicinity of a closed environment.
103

Palaeoenvironments of the Middle Stone Age at Sibudu Cave, KwaZulu-Natal, South Africa: An analysis of archaeological charcoal

Allott, Lucy Fiona 02 February 2006 (has links)
PhD - Science / Analysis of charcoal from Middle Stone Age layers at Sibudu Cave, KwaZulu-Natal, shows evidence of environmental change during the Last Glacial. Layers analysed encompass the end of the cold stadial, Oxygen Isotope Stage (OIS) 4, and the warmer interstadial, OIS 3. Layers are divided – on the basis of lithic industry associations and taxonomic content – into the Howiesons Poort (HP) (dated to ca. 61 000 years ago), and the early, middle and late post-HP assemblages (ca. 60-55 000, 55-50 000 and 50-33 000 years ago respectively). This project aims to identify evidence for environmental change, characterise this change using qualitative and quantitative analyses, and compare the results to evidence from other proxies at Sibudu Cave and elsewhere in South Africa. HP layers (GS, GR, GR2) are dominated by evergreen forest taxa, including Podocarpus spp., Buxus sp., Brachylaena sp., Sapium/Spirostachys and Ptaeroxylon obliquum. Kirkia sp. suggests a warm, woodland savanna habitat grew beyond the forest vegetation. Early post-HP layers (Eb, SPCA, BSp) contain taxa from evergreen, riverine forest communities, including Erica spp., Leucosidea sericea, and Rapanea melanophloeos. Some of the taxa in these layers suggest a shift in vegetation, possibly related to the marine regression of the Last Glacial, bringing taxa currently found further inland towards the site. Fewer evergreen forest components, and more bushveld taxa, are present in the middle post-HP (RSp, OMOD, MOD) than in the previous layers. Some of the taxa are only found in northern South Africa in regions that are significantly drier than modern KwaZulu-Natal. These layers also contain more Acacia spp. and other Fabaceae taxa and fewer Erica spp. than the samples from the early post-HP. This may be a result of environmental change, a change in wood selection, charcoal fragmentation, or sampling bias. Layer Bu, within the late post-HP, contains evergreen and deciduous taxa many of which are found in KwaZulu-Natal today. Kirkia sp. again provides evidence for a dry habitat not iv currently found in the region. Many Types were defined in Bu, which may indicate a vegetation community for which there is currently no reference material. Temperature and moisture indices produced using the Factor Analysis suggest warm and moist conditions during the HP layers. During the early post-HP conditions became cooler with intermediate moisture levels. Subsequently, conditions were warm and dry (middle post-HP) and then warm with a little more moisture indicated (late post-HP). Good fuelwoods were routinely collected during the post-HP. In contrast, the HP layers are dominated by Podocarpus spp. and many of the good fuelwoods, such as Acacia spp. and Erica spp., are absent. This pattern may be a result of changes in the environment, sample bias or a development of awareness of wood properties between the HP and post-HP occupations. The charcoal results corroborate palaeoenvironmental interpretations provided by seeds and macrofauna from Sibudu Cave. When the Sibudu Cave data are combined with data from other sites it is apparent that, although conditions in the summer rainfall region during the Last Glacial were generally dry, there is evidence for localised variation in vegetation and climate.
104

Identification of mammalian species represented by fossil hairs in Parahyaena Brunnea coprolites from middle pleistocene deposits at Gladysvale Cave, South Africa

Taru, Phillip 29 January 2013 (has links)
This research focuses on scale pattern and cross sectional morphology of hair to identify fossil hairs from Parahyaena brunnea (brown hyaena) coprolites, from Gladysvale cave in the Sterkfontein Valley, South Africa. The coprolites are part of a brown hyaena latrine preserved in calcified cave sediment dated to the Middle Pleistocene (257- 195 ka). Forty-eight fossil hairs were extracted from a 75 x 30 x 15 cm block using fine tweezers and a binocular microscope. They were ultrasonic cleaned in analar ethanol and examined using scanning electron microscopy. Hair identification was based on consultation of standard guides to hair identification and comparison with my own collection of samples of previously undocumented guard hairs, from 15 taxa of indigenous southern African mammals. Samples were taken from the back of pelts curated at the Johannesburg Zoo and Ditsong National Museum of Natural History in Tshwane (formerly Transvaal Museum, Pretoria). Based on the fossil hairs identified here, this research has established that brown hyaenas shared the Sterkfontein Valley with warthog, impala, zebra, kudu and black wildebeest. These animals are associated with savanna grasslands, much like the Highveld environment of today. Fossil human hair was also noted in the coprolites. These findings provide a new source of information, on the local Middle Pleistocene fossil mammal community, and insight into the environment in which archaic and modern humans in the interior of the African subcontinent lived. Amid a scarce fossil and archaeological record for this time period, these results make a significant contribution to the ongoing debate about the role of climate change in the evolution and success of modern humans. In accordance with modern brown hyaena feeding behaviour, the presence of medium to large-sized mammal hairs in the coprolites suggests the co-existence of large feline predators in the area, or a period of active hunting, based on the behaviour of modern brown hyaenas when rearing cubs.
105

Geologic Mapping of Ice Cave Peak Quadrangle, Uintah and Duchesne Counties, Utah with Implications from Mapping Laramide Faults

Poduska, Gabriel J 01 July 2015 (has links)
Geologic mapping (1:24,000 scale) of the Ice Cave Peak quadrangle, Uintah and Duchesne Counties, Utah has produced a better understanding of the geologic structures present in the quadrangle and has increased our understanding of faulting in northeastern Utah. Map units in the quadrangle range in age from late Neoproterozoic to Quaternary and include good exposures of Paleozoic rocks (Mississippian to Permian), limited exposures of Mesozoic rocks, and good exposures of Tertiary strata (Duchesne River Formation and Bishop Conglomerate) deposited during uplift of the Uinta Mountains. Lower Mississippian strata along the south flank of the Uinta Mountains have typically been mapped as Madison Limestone. Our preliminary mapping suggested that the Madison could perhaps be subdivided into an upper unit equivalent to the Deseret Limestone, and a lower unit separated by a phosphatic interval equivalent to the Delle Phosphatic Member of the Deseret Limestone found farther west. Upon further investigation, we propose not extending the use of Deseret Limestone, with the equivalent to the Delle Phosphatic Member at its base, into the south-central Uinta Mountains. Microprobe analysis revealed no phosphorus in thin sections of this unit. Instead, the unit is composed almost entirely of calcite and dolomite. A zone of northwest-trending faults, called the Deep Creek fault zone, occurs mainly east of the Ice Cave Peak quadrangle. However, our mapping shows that this fault zone extends into the quadrangle. These faults are both strike-slip and normal/oblique faults as documented by mapping and kinematic indicators and cut the folded hanging-wall sedimentary rocks above the Uinta Basin-Mountain boundary thrust fault. These faults may be part of an en echelon fault system that is rooted in the Neoproterozoic and reactivated during Laramide deformation above a possible transfer zone between segments of the buried boundary thrust.
106

Controls on Speleogenesis in the Upper-Mississippian Pennington Formation on the Western Cumberland Plateau Escarpment

Steinmann, Hali 01 October 2018 (has links)
Much of the pioneering work on caves of the Cumberland Plateau (province spanning Tennessee, Kentucky, Alabama, and Georgia) has been stratigraphically located within the Mississippian Bangor and Monteagle Limestones, wherein some of the region’s largest and most spectacular caves occur. Of interest to the understanding of this karst landscape, but severely underrepresented in the literature thereof, are caves and karst features in a heterogeneous sequence of clastics and carbonates known collectively as the Pennington Formation (Upper Mississippian). This work consisted of a regional study of Pennington caves on the western Cumberland Plateau escarpment (Alabama and Tennessee), and a case study of Pennington caves in Savage Gulf State Natural Area (Grundy County, Tennessee). The objective of this research was to determine controls on speleogenesis in the Pennington Formation, using cave geomorphology, dye tracing, and GIS to explore lithologic, hydrologic, and structural influences on karst processes. This resulted in a conceptual model for speleogenesis in the Pennington Formation, with the major controls being: 1) direct and diffuse recharge from the caprock, undersaturated with respect to calcite; 2) thin, horizontally bedded limestones sandwiched by shales and other insoluble rocks; and 3) networks of stress release fractures oriented parallel to major stream valleys. Our present understanding of the Cumberland Plateau could be advanced by further study of karst dynamics in the Pennington Formation.
107

The effects of rodents on ground dwelling arthropods in the Waitakere ranges

King, Peter A Unknown Date (has links)
The abundance and size classes of ground weta, cave weta, carabid beetles and prowling spiders were monitored in the La Trobe Forest Ecosystem Restoration Project, Karekare, West Auckland, where rodent populations had been reduced. These were compared with those in control sites, where the rodent populations had not been manipulated. The arthropods were sampled using pitfall traps set in young podocarp-broadleaf, mature kanuka and mature taraire forested sites, and each treatment site was matched with two control sites. Data was collected monthly from all nine sites from December to May, 2005-06. In kanuka forest, data collected during December to May, 2004-05 has also been used.Rodent populations and possum populations were monitored during the course of the study. Tracking tunnel indices indicated that rat numbers were lower in the treatment sites than the control sites during 2005-06, and that rats were low in abundance at the treatment sites, apart from the occasional spike in numbers, in the three years prior to the start of this research. Mice tracking indices were relatively high at some specific sites, mainly in spring and autumn. Evidence indicated that possum abundance was low in both the treatment and the control sites.Ground weta were more abundant at the kanuka treatment site than the control sites in 2005-06, but were rarely found in the podocarp-broadleaf and taraire forest types. Carabid beetles were trapped in greater numbers in podocarp-broadleaf and kanuka forest treatment sites in 2005-06, than in their respective control sites, and an increase in carabid beetle abundance was recorded between the 2004-05 and 2005-06 sampling seasons at the kanuka treatment site. Prowling spiders were more abundant at the podocarp-broadleaf treatment than at the control sites. Cave weta abundance at the podocarp-broadleaf and kanuka treatment sites was similar to their respective control sites. The arthropod abundance data from the taraire forest sites was confounded by many differences between the treatment and the control sites, which may have masked any effects caused by the suppression of rodent numbers at the treatment site.Ground weta and cave weta in the larger size classes appeared to be selectively preyed upon by predators, however, it was unclear whether rodents were entirely responsible because stoats and cats are also known to target larger arthropod prey, and their presence was not monitored.Ground weta in kanuka forest, carabid beetles in kanuka and podocarp-broadleaf forest and prowling spiders in podocarp-broadleaf forest are identified as potential indicators for monitoring the effects of rodent control in the Waitakere Ranges.This study was limited by a lack of knowledge of life histories and basic ecology of the arthropods. Further research at these sites is required to establish the long term population patterns of the arthropods.
108

Cave Aragonites of New South Wales

Rowling, Jill January 2004 (has links)
Abstract Aragonite is a minor secondary mineral in many limestone caves throughout the world. It has been claimed that it is the second-most common cave mineral after calcite (Hill & Forti 1997). Aragonite occurs as a secondary mineral in the vadose zone of some caves in New South Wales. Aragonite is unstable in fresh water and usually reverts to calcite, but it is actively depositing in some NSW caves. A review of current literature on the cave aragonite problem showed that chemical inhibitors to calcite deposition assist in the precipitation of calcium carbonate as aragonite instead of calcite. Chemical inhibitors work by physically blocking the positions on the calcite crystal lattice which would have otherwise allowed calcite to develop into a larger crystal. Often an inhibitor for calcite has no effect on the aragonite crystal lattice, thus aragonite may deposit where calcite deposition is inhibited. Another association with aragonite in some NSW caves appears to be high evaporation rates allowing calcite, aragonite and vaterite to deposit. Vaterite is another unstable polymorph of calcium carbonate, which reverts to aragonite and calcite over time. Vaterite, aragonite and calcite were found together in cave sediments in areas with low humidity in Wollondilly Cave, Wombeyan. Several factors were found to be associated with the deposition of aragonite instead of calcite speleothems in NSW caves. They included the presence of ferroan dolomite, calcite-inhibitors (in particular ions of magnesium, manganese, phosphate, sulfate and heavy metals), and both air movement and humidity. Aragonite deposits in several NSW caves were examined to determine whether the material is or is not aragonite. Substrates to the aragonite were examined, as was the nature of the bedrock. The work concentrated on Contact Cave and Wiburds Lake Cave at Jenolan, Sigma Cave, Wollondilly Cave and Cow Pit at Wombeyan and Piano Cave and Deep Hole (Cave) at Walli. Comparisons are made with other caves. The study sites are all located in Palaeozoic rocks within the Lachlan Fold Belt tectonic region. Two of the sites, Jenolan and Wombeyan, are close to the western edge of the Sydney Basin. The third site, Walli, is close to a warm spring. The physical, climatic, chemical and mineralogical influences on calcium carbonate deposition in the caves were investigated. Where cave maps were unavailable, they were prepared on site as part of the study. %At Jenolan Caves, Contact Cave and Wiburds Lake Cave were examined in detail, %and other sites were compared with these. Contact Cave is located near the eastern boundary of the Late Silurian Jenolan Caves Limestone, in an area of steeply bedded and partially dolomitised limestone very close to its eastern boundary with the Jenolan volcanics. Aragonite in Contact Cave is precipitated on the ceiling as anthodites, helictites and coatings. The substrate for the aragonite is porous, altered, dolomitised limestone which is wedged apart by aragonite crystals. Aragonite deposition in Contact Cave is associated with a concentration of calcite-inhibiting ions, mainly minerals containing ions of magnesium, manganese and to a lesser extent, phosphates. Aragonite, dolomite and rhodochrosite are being actively deposited where these minerals are present. Calcite is being deposited where minerals containing magnesium ions are not present. The inhibitors appear to be mobilised by fresh water entering the cave as seepage along the steep bedding and jointing. During winter, cold dry air pooling in the lower part of the cave may concentrate minerals by evaporation and is most likely associated with the ``popcorn line'' seen in the cave. Wiburds Lake Cave is located near the western boundary of the Jenolan Caves Limestone, very close to its faulted western boundary with Ordovician cherts. Aragonite at Wiburds Lake Cave is associated with weathered pyritic dolomitised limestone, an altered, dolomitised mafic dyke in a fault shear zone, and also with bat guano minerals. Aragonite speleothems include a spathite, cavity fills, vughs, surface coatings and anthodites. Calcite occurs in small quantities at the aragonite sites. Calcite-inhibitors associated with aragonite include ions of magnesium, manganese and sulfate. Phosphate is significant in some areas. Low humidity is significant in two areas. Other sites briefly examined at Jenolan include Glass Cave, Mammoth Cave, Spider Cave and the show caves. Aragonite in Glass Cave may be associated with both weathering of dolomitised limestone (resulting in anthodites) and with bat guano (resulting in small cryptic forms). Aragonite in the show caves, and possibly in Mammoth and Spider Cave is associated with weathering of pyritic dolomitised limestone. Wombeyan Caves are developed in saccharoidal marble, metamorphosed Silurian Wombeyan Caves Limestone. Three sites were examined in detail at Wombeyan Caves: Sigma Cave, Wollondilly Cave and Cow Pit (a steep sided doline with a dark zone). Sigma Cave is close to the south east boundary of the Wombeyan marble, close to its unconformable boundary with effusive hypersthene porphyry and intrusive gabbro, and contains some unmarmorised limestone. Aragonite occurs mainly in a canyon at the southern extremity of the cave and in some other sites. In Sigma Cave, aragonite deposition is mainly associated with minerals containing calcite-inhibitors, as well as some air movement in the cave. Calcite-inhibitors at Sigma Cave include ions of magnesium, manganese, sulfate and phosphate (possibly bat origin), partly from bedrock veins and partly from breakdown of minerals in sediments sourced from mafic igneous rocks. Substrates to aragonite speleothems include corroded speleothem, bedrock, ochres, mud and clastics. There is air movement at times in the canyon, it has higher levels of CO2 than other parts of the cave and humidity is high. Air movement may assist in the rapid exchange of CO2 at speleothem surfaces. Wollondilly Cave is located in the eastern part of the Wombeyan marble. At Wollondilly Cave, anthodites and helictites were seen in an inaccessible area of the cave. Paramorphs of calcite after aragonite were found at Jacobs Ladder and the Pantheon. Aragonite at Star Chamber is associated with huntite and hydromagnesite. In The Loft, speleothem corrosion is characteristic of bat guano deposits. Aragonite, vaterite and calcite were detected in surface coatings in this area. Air movement between the two entrances of this cave has a drying effect which may serve to concentrate minerals by evaporation in some parts of the cave. The presence of vaterite and aragonite in fluffy coatings infers that vaterite may be inverting to aragonite. Calcite-inhibitors in the sediments include ions of phosphate, sulphate, magnesium and manganese. Cave sediment includes material sourced from detrital mafic rocks. Cow Pit is located near Wollondilly Cave, and cave W43 is located near the northern boundary of the Wombeyan marble. At Cow Pit, paramorphs of calcite after aragonite occur in the walls as spheroids with minor huntite. Aragonite is a minor mineral in white wall coatings and red phosphatic sediments with minor hydromagnesite and huntite. At cave W43, aragonite was detected in the base of a coralloid speleothem. Paramorphs of calcite after aragonite were observed in the same speleothem. Dolomite in the bedrock may be a source of magnesium-rich minerals at cave W43. Walli Caves are developed in the massive Belubula Limestone of the Ordovician Cliefden Caves Limestone Subgroup (Barrajin Group). At the caves, the limestone is steeply bedded and contains chert nodules with dolomite inclusions. Gypsum and barite occur in veins in the limestone. At Walli Caves, Piano Cave and Deep Hole (Deep Cave) were examined for aragonite. Gypsum occurs both as a surface coating and as fine selenite needles on chert nodules in areas with low humidity in the caves. Aragonite at Walli caves was associated with vein minerals and coatings containing calcite-inhibitors and, in some areas, low humidity. Calcite-inhibitors include sulfate (mostly as gypsum), magnesium, manganese and barium. Other caves which contain aragonite are mentioned. Although these were not major study sites, sufficient information is available on them to make a preliminary assessment as to why they may contain aragonite. These other caves include Flying Fortress Cave and the B4-5 Extension at Bungonia near Goulburn, and Wyanbene Cave south of Braidwood. Aragonite deposition at Bungonia has some similarities with that at Jenolan in that dolomitisation of the bedrock has occurred, and the bedding or jointing is steep allowing seepage of water into the cave, with possible oxidation of pyrite. Aragonite is also associated with a mafic dyke. Wyanbene cave features some bedrock dolomitisation, and also features low grade ore bodies which include several known calcite-inhibitors. Aragonite appears to be associated with both features. Finally, brief notes are made of aragonite-like speleothems at Colong Caves (between Jenolan and Wombeyan), a cave at Jaunter (west of Jenolan) and Wellington (240\,km NW of Sydney).
109

Cave swallow (Petrochelidon fulva) nest reuse in east-central Texas

Byerly, Margaret Elizabeth 17 February 2005 (has links)
Although nest reuse is most commonly associated with costs such as nest instability and increased ectoparasite loads,contrary evidence supports the possibility that nest reuse might provide an adaptive function in the form of time and energy savings. The Cave Swallow (Petrochelidon fulva), which nests under bridges and culverts in east-central Texas, chooses predominately to reuse nests when old nests are available. I conducted a field experiment involving bridge pairs and single bridges, in which I applied a treatment of nest removal to one bridge of each pair and one half of each single bridge in order to test whether control bridges and nests exhibited increased productivity from the availability of old nests. I found that a higher percentage of young fledged from control bridges and more fledged per clutch from control bridges. Small sample sizes diminished the ability to detect differences within the single bridge experiment. Results from this research support the time-energy savings concept and may be reconciled with conflicting research through fundamental differences between studies in immunity to ectoparasites, infestation type, and nest microclimate.
110

Acquisition and Modeling of Driving Skills by Using Three Dimensional Driving Simulator

TSUCHIDA, Nuio, OKUMA, Shigeru, SUZUKI, Tatsuya, HAYAKAWA, Soichiro, MATSUI, Yoshimichi, KIM, Jong-Hae 01 March 2005 (has links)
No description available.

Page generated in 0.0518 seconds