• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 621
  • 469
  • 301
  • 120
  • 110
  • 79
  • 25
  • 24
  • 15
  • 7
  • 7
  • 5
  • 4
  • 4
  • 3
  • Tagged with
  • 1953
  • 634
  • 578
  • 250
  • 141
  • 126
  • 125
  • 120
  • 120
  • 117
  • 108
  • 105
  • 102
  • 102
  • 100
  • 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.
1

Rocket measurements of solar and lunar ultraviolet flux and the determination of atmospheric molecular oxygen and ozone densities.

Ilyas, Mohammad. January 1976 (has links) (PDF)
Thesis (Ph.D.)-- University of Adelaide, Dept. of Physics, 1976.
2

Lunar tides in the E-region Kennelly-Heaviside layer

Niblock, Peter A. January 1952 (has links)
A number of Investigators have conducted research on the earth's atmosphere. Among them have been Laplace, Lord Kelvin and Simpson, who were interested, primarily, in pressure variations in the atmosphere; Pekeris and G. I. Taylor, who were Interested in the mechanism of atmospheric resonances; and Balfour-Stewart, Chapman, and Appleton and Weekes, who were interested in upper-atmosphere research. However, all these investigators had one idea in common; they sought to establish the presence of lunar and solar effects upon the earth's atmosphere. Even after the work which has been done on lunar tides in the E-region of the Kennelly-Heaviside layer by Appleton and Weekes and other investigators, there are still questions which remain unanswered on this subject. A description is given of an investigation performed at The University of British Columbia to determine the magnitude of a lunar tide in the E-region of the Kennelly-Heaviside layer. Details are Included of design considerations for a pulse-type communications receiver to operate in the 0.5 to 30 mc/s. band. The main differences between the unit discussed and a standard communications receiver lie in the band-pass, or selectivity characteristics and in the receiver recovery time after shock excitation by very strong radio frequency fields. Also included are details of the transmitting units, the antenna, and the calibration display unit used in the Investigation. Analysis of the data gathered during the investigation showed that there was no tide in the Kennelly-Heaviside layer Region-E of the magnitude or phase of that found by Appleton and Weekes in 1939. An analysis of the data gathered for the lunar tides Investigations produces strong evidence of daytime D-layer ionization between heights of 50 and 85 kilometers. This evidence is discussed and fields for future research are suggested. Comparisons are made between the results of Chapman's analysis of the lunar pressure oscillations at ground level and the accumulated data from the ionospheric lunar tide investigation of Appleton and Weekes and those from this investigation. The data derived from these widely differing sources are shown to be completely compatible. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
3

The fine structure of the E-region

Belrose, John Skelton January 1951 (has links)
Introduction Very little is known about the fine structure of the E-region of the ionosphere. The pulse method devised by Breit and Tuve is used to study the E-region in detail. Observations were made at Vancouver for the months of July and August 1951. The frequency 1.5 to 5 mc/s. (down to .5 mc/s. after midnight) was swept manually recording in 100 kc/s. intervals the virtual height, h’, to the nearest kilometer. Experimental (h’,t) records were also taken at 15 minute intervals throughout the day on 2 mc/s. The (h’,f) curves were analysed for fine structure details of the region which are not recorded by ionospheric equipment used for routine observations of the entire ionosphere. The following investigations were attempted: 1. Fine Structure of Night-Time E-Region. 2. Diurnal Variation of Fine Structure of E-Region. 3. Sunrise Effects of E-Region. 4. Occurrence of Echoes from Levels Below the E-Region. 5. Diurnal Variation of Critical Penetration Frequency of E-Region. 6. Determination of Scale Height of the E-Region. Results 1. Fine Structure of Night-Time E-Region Throughout the night ionization generally appears as patches from random clouds. Near sunrise short-lived echoes are found between 80 and 200 kms. Few usable results showing fine structure details are found. 2. Diurnal Variation of Fine Structure of E-Region Experimental (h',f) curves are compared to derived curves for a simple parabolic region with an E8 layer appearing as a sharp boundary embedded in the simple region. Good fits to the theoretical curves are normally found below the cusp frequency. The Hail' appearing after the cusp frequency generally has a slope greater then that predicted. Various types of ledges found in the --region are discussed. Moving ledges are often found with an approximate quasi-period (i.e. time to pass through the region) of half an hour. The variation of the penetration frequency of high smooth Es regions also appears to have a similar period. Once during the period of observation both these phenomena occurred together. Very pronounced ledges are sometimes found above the normal maximum. 3. Sunrise Effects of E-Region Day-time ionization of the E-region commences before ground sunrise. Commencement time is found to be approximately that time at which the sun*8 rays strike the E-region after grazing a spherical surface 39 kms. above the earth. 4. Occurrence of Echoes from Levels Below the E-Region Strong indications of region D are found. Often patches of ionization, as though from small ionic clouds, appear at various heights from 80 to 200 kms. No retardation effects are observed for any of these records. 5. Diurnal Variation of Critical Penetration Frequency of E-Region The critical frequency of the E-region is found to obey approximately a law fc = k oosⁿ X where X is the sun's zenith angle. The average morning value for the index, n, is .301 and the average afternoon value is .35. The average morning and afternoon value is .325. Examination of the (log fc , log cos X ) curves show that the afternoon values usually fall more nearly in a straight line. 5. Determination of Scale Height of the E-Region a. Analysis of (h',t) records From plots of the function Ln f(x) = constant + h/H H is found to be 11.3 kms. b. Analysis of (h',f) records From plots of the function h' = hN + φ(f/fc) H is found to be 9.4 kms. When this is corrected for a parabolic assumption giving the best fit to a Chapman distribution, H = 11.28 kms. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate
4

On Raynaud's phenomena of the upper extremities with special reference to sympathectomy and regeneration of the sympathetic

Katz, Arnold 16 April 2020 (has links)
Almost 100 percent of Raynaud's Phenomena of the lower extremities respond to surgical treatment. The treatment of Raynaud's Phenomena of the upper extremities, on the other hand, has occupied the attention of medical observers for over fifty years with little success. Surgeons, physicians, research workers, physicists and their associates have attempted to solve the problem and produce a rational solution.
5

Turbulent velocity distributions in the upper atmosphere

Moseley, William Battle 12 1900 (has links)
No description available.
6

Riḥla lughawīya fī il-lahajāt il-Ṣa'īdīya : a phonological description of stop variation in Upper Egyptian Arabic

Schroepfer, Jason William 16 February 2015 (has links)
It is universally accepted that the majority of Ṣa‘īdī (Upper Egyptian) and Cairene consonants correspond with each other very closely. However, the Ṣa‘īdī cognates of Cairene /tˤ/, /g/, and /ʔ/ show significant variation that has not yet been studied phonologically or mapped. The research that has been conducted on these Upper Egyptian cognate sounds is either based on a very small sample size, or lacking phonological distributions for these sounds. This paper revisits the phonological variation and distribution of the Upper Egyptian cognates for the Cairene /tˤ/, /g/, and /ʔ/. This study concludes that its Ṣa‘īdī cognate of the Cairene /tˤ/ is [ɗ] in most regions, and that the Ṣa‘īdī cognates of the /g/, and /ʔ/ differ from previous documentation. / text
7

Class relations and interclass perceptions in twentieth century Egypt (1920-1950)

Baraka, Magda S. January 1994 (has links)
No description available.
8

Tropical dynamics and transport associated with stratospheric warmings

Iwi, Alan Michael January 1998 (has links)
No description available.
9

A study of thermospheric dynamics using electron content power spectrum estimations

Low, Nam Chong January 1974 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1974. / Bibliography: leaves 310-320. / xvi, 320 leaves ill
10

Early Upper Cambrian (Marjuman) linguliformean brachiopods from the Deadwood Formation

Robson, Sean Paul 05 May 2005
The Deadwood Formation is an Upper Cambrian to Lower Ordovician succession of sandstones, shales, siltstones and limestones that blanketed central western North America during the initial Phanerozoic transgression. This transgression led to a broad, shallow epeiric sea which onlapped the Transcontinental Arch to the east and was protected on its westernseawardside by a system of carbonate platforms now exposed in the Rocky Mountains. The Deadwood Formation is mostly a subsurface unit, but several exposures exist in the northern Great Plains due to uplift by Eocene igneous intrusions. Linguliformean brachiopods were recovered from two areas: the Black Hills of South Dakota, and two subsurface cores from Alberta and Saskatchewan. Forty-five species of linguliformean brachiopods assigned to twenty-eight genera were recovered from these localities and described. Giving provisional names, one new family, Holmerellidae, one new subfamily, Neotretinae, five new genera, Amplitreta, Dianabella, Ganotoglossa, Holmerellus, and Vangaporosa, are erected and seventeen new species are described: Amplitreta cyclopis, Amplitreta elongata, aff. Anabolatreta tora, Canthylotreta parislata, Curticia pustulosa, Dianabella artemesia, Ganotoglossa leptotropis, Holmerellus convexus, Holmerellus, acuminatus, Holmerellus limbatus, Kotylotreta nupera, Linnarssonella tubicula, Opisthotreta nuda, Rhondellina albertensis, Tropidoglossa costata, Quadrisonia? sigmoidea, and Vangaporosa dakotaensis. The family Holmerellidae is distinguished by pitted larval shells and smooth postlarval shells, a feature that is unique in the Linguloidea. The composition of the new subfamily Neotretinae recognizes the evolutionary relationship of the genera Neotreta and Rhondellina, which are more closely related to each other than to any other acrotretid genera. Based on a comparison of the brachiopod assemblages with similar faunas from Australia and elsewhere in Laurentia, the sections studied are determined to be late Marjuman (early Late Cambrian) to early Sunwaptan (middle Late Cambrian) in age. The subsurface faunas provide the first biostratigraphic dates for any part of the Deadwood Formation in Canada. Faunas from South Dakota come from strata near the base of the formation and below the first trilobite occurrences, this giving a more refined age for the transgression in South Dakota. A large number of shells with perforations assumed to have been caused by predators were recovered from two localities in South Dakota, and represent the first evidence of predation of fossil lingulids. Two types of perforations were identified: round holes with sharp, non-beveled edges, and irregularly shaped holes with chipped edges. The former hole type is attributed to either steady pressure applied over time (e.g. boring) or to a swift, piercing percussive strike. The latter hole type is attributed to a smashing percussive strike with a blunt appendage. Based on criteria established by the proposed attack-mode models, various hypothetical animals are discussed as potential linguliformean predators. While the evidence for these predators is circumstantial, it indicates a more complex benthic paleoecology that had hitherto been envisaged for the Upper Cambrian.

Page generated in 0.0444 seconds