• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1084
  • 351
  • 333
  • 127
  • 88
  • 63
  • 46
  • 32
  • 24
  • 20
  • 12
  • 12
  • 11
  • 9
  • 8
  • Tagged with
  • 2787
  • 329
  • 276
  • 241
  • 234
  • 220
  • 182
  • 169
  • 166
  • 142
  • 127
  • 123
  • 120
  • 119
  • 117
  • 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

Shape analysis using Young's fringes

Wood, Christopher Martin January 1992 (has links)
No description available.
22

Geochemistry and stable isotope study of porphyry-related mineralisation, central Front Range, Colorado, U.S.A

Jemielita, Richard Alfred January 1987 (has links)
The central part of the Front Range mineral belt, Colorado, is a Precambrian crystalline basement terrain intruded by early Tertiary porphyries and closely associated mesothermal ore deposits. The ore deposits are gold- and silver-bearing base metal sulphide-quartz veins arranged in more or less well developed concentric mineral zones centred on concealed porphyry plutons. Central areas of pyritic mineralisation are surrounded by peripheral zone of galena-sphalerite-bearing veins, often separated by a transitional zone of composite mineralisation. Molybdenite-bearing and uraninite-bearing veins are locally abundant proximal to the central pyritic zones and are closely associated spatially and temporally with highly evolved quartz bostonite intrusions. The mineral veins are enveloped in narrow selvages of sericitized and argillized wallrock and are entirely fracture controlled. A low density lithogeochemical survey of the country rocks revealed strong lithological controls on the distributions of selected trace elements and radiation emission values. Positive Rb/Sr anomalies are tentatively linked to concealed intrusions, and corresponding positive anomalies of Pb, Zn, Mo and W are associated with known molybdenite mineralisation. Sericitized rocks are characterised by low Sr and enhanced Rb, Zn, Pb, Mo and Ag values, and areas of depleted country rock Sr values may be related to vein wallrock alteration. D/H and <SUP>18</SUP> O/<SUP>16</SUP> O signatures of fresh country rocks indicate variable magmatic water overprinting and similar analyses of sericitised rocks show that alteration was accomplished by magmatic hydrothermal fluids at 340<SUP>o</SUP> -515<SUP>o</SUP> C. Mineralisation and alteration in the area were caused by hydrothermal fluids evolved from highly differentiated Laramide quartz bostonite intrusions. K-Ar ages of ca. 62 Ma have been obtained from alteration sericites from the peripheral mineral zone. Similar studies in the central pyritic zone have yielded ages of ca. 59 Ma suggesting the existence of long lived hydrothermal activity in the area characterised by widespread high-temperature alteration, followed by thermal decay and collapse towards core zones. The ore deposits investigated during this study display numerous features in common with porphyry-style and other intrusive-related mineralisation characteristic of Cordilleran terrains, but also exhibit significant differences. The combination of these features contribute to the distinct and possibly unique character of these mineral deposits.
23

Interpretation of gravity anomalies observed in the Cascade Mountain province of Northern Oregon

Braman, Dave E. 13 January 1981 (has links)
Graduation date: 1981
24

Soil arthropods in the Central Cascades : slash burning effects and biology of some species

Estrada-Venegas, Edith G 01 May 1995 (has links)
Despite the recognized role of soil arthropod fauna on nutrient cycling and decomposition processes, many aspects of the effects of sylvicultural methods in forest ecosystems upon their biology remain poorly understood. The long term effects of prescribed fires on soil arthropods in forest ecosystems in the Pacific Northwest have never been studied. Soil samples were taken from three sites located in the Willamette National Forest in 1992: paired sites that were either clear-cut without burning and clear-cut with burning 40 years ago. One hundred and eight samples were processed; the arthropods were separated, identified and counted. To study the biology and behavior of some arthropods, eight species of oribatid mites were reared in laboratory conditions. Their life cycle, feeding behavior and reproduction were studied. Results indicated that there were no statistical significant treatment differences either in terms of total numbers of organisms or biomass. However, the majority of the commonest taxa did show offsetting treatment responses. A total of 204 taxa were found in the three sites. The most important groups included Collembola, mites, and insects. Other groups also represented, but in smaller numbers, were spiders, symphylans, pseudoscorpions, and centipedes. Of all these groups, oribatid mites was the best represented and appears to be a useful indicator of disturbances. / Graduation date: 1995
25

Range-Based Mobile Multicast

Lee, Chung-Lai 17 June 2002 (has links)
IP multicast is an efficient means of sending to a group. Our protocol is built on top of the existing static hosts IP unicast and multicast forwarding services to avoid triangle routing which always occurs in Mobile IP. Relying only on the existing multicast service model and reconstructing the delivery tree every time a multicast member and/or source move is not always a good solution. By applying the ideas of bi-directional tunneled multicast [3], our protocol attempts to hide host mobility from all other members of the group. Therefore, the multicast distribution tree will not be updated for the sake of member location change. Furthermore, our protocol has near shortest delivery paths like remote subscription protocol [3]. Our protocol can also adapt to the fluctuation of both host movement and the number of mobile members (i.e., having mobility and scalability properties). According to our protocol, the tunnel convergence problem resulting from bi-directional tunneling will be solved. By changing service range ``R', we can trade off the advantages and disadvantages of both bi-directional tunneling and remote subscription (they are the extremes of RBMoM). We measure the system performance and cost in different service range, topology size and mobile population density through simulation. According to the results of our simulation, we believe our protocol has much better performance without using the current Mobile IP multicast solutions.
26

The economics of western juniper management on ranches located in the John Day Ecological Province of north-central Oregon /

Aldrich, Gwendolyn A. January 2002 (has links)
Thesis (M.S.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references (leaves 135-141). Also available via the World Wide Web.
27

The L-numerical range : liear image of joint unitary orbit of hermitian matrices /

Chan, Yiu-Kwong. January 2002 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 53-56).
28

Site stability assessment on a clay loam upland range site

Watters, Susan Elaine, 1959- January 1993 (has links)
Ground cover, species composition, average distance between perennial plants, standing biomass, frequency of bare quadrats, and site stability rating were evaluated as predictor variables in determining the degree of site protection from accelerated soil erosion on a clay loam upland range site. Interpretations of range condition, species diversity, and the WEPP model predicted sediment yield were analyzed to determine their usefulness in detecting a threshold of site protection. Standing biomass, basal cover, average distance between plants and frequency of bare quadrats demonstrated strong correlations to the site stability rating and were useful in examining thresholds of site protection. The WEPP model was useful in determining a threshold of protection with the site stability rating. The diversity index and range condition rating showed poor relationships with the stability indices and plant community attributes measured. Thus, individually, these ratings do not provide and adequate assessment of the degree of site protection.
29

Land-use and socio-spatial organization of female leopards in a semi-arid wooded savanna, Botswana

Steyn, V, Funston, PJ 30 September 2009 (has links)
Abstract Leopards (Panthera pardus) are the most widespread large felid, yet comparatively little is known about their fine-scale movement patterns and how these affect the risks they face. There has been much debate on the conservation status and management needs for leopards with much extrapolation from limited data. In order to gather more information on leopard movements in Botswana’s Northern Tuli Game Reserve, seven leopards were collared between February 2005 and August 2006. This allowed key aspects that affect demography, and thus resilience to anthropogenic effects, to be investigated. Generally, home ranges were typical for breeding females in woodland savanna (32.9 ± 7.3 km²) with substantial overlap (average 26.0%). Core areas though were independent and extremely small (1.9 ± 2.2 km²). These were used primarily for young cub rearing, and were characterized by rugged terrain along riverbeds. This highly localized use places leopards at potential risk of snaring as snares tend to be concentrated along these landscape features. Furthermore, hunters can conceal blinds from which to shoot leopards more easily in these areas. Further risk to adult female survival came from excursions outside the reserve boundary during which livestock was predated. Three incidences of cannibalism by adult territorial males on adult females are also reported, suggesting significant intra-specific competition.
30

The L-numerical range: liear image of joint unitary orbit of hermitian matrices

陳耀光, Chan, Yiu-Kwong. January 2002 (has links)
published_or_final_version / Mathematics / Master / Master of Philosophy

Page generated in 0.0562 seconds