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Walter D. Lambert 《Journal of Geodesy》1949,23(3):274-292
If in imagination we viewed a solar eclipse or the occultation of a star from a point outside the earth, we would see the
shadow of the moon advancing across the face of the earth, the earth meanwhile turning on its axis beneath the shadow. When
some point on the advancing edge of the shadow overtook a given point on the surface of the earth, an observer at that point
would note the beginning of the eclipse or occultation. When the trailing edge of the shadow uncovered that point again, the
observer there would note the end of the eclipse or occultation.
The universal time (as distinguished from the local time) of the beginning or ending would depend on the position of the observer
with reference to the body of the earth, that is, on his ideal geodetic coordinates. These universal times would not depend
in the least on the direction of the observer’s vertical. This fact is the key to the usefulness of eclipses and occultations
for geodetic purposes.
Suppose that the prediction for the times of beginning or ending had been made on the basis of the astronomical latitude and
longitude of the observer. Since there would be in general deflections of the vertical in latitude and longitude, Δπ and Δλ,
these would bring about, even in the absence of any other source of discrepancy, diffe-
This article is at once a condensation and an expansion. It is a condensation of a series of lectures delivered in the winter
and spring of 1947 to members of the U. S. Coast and Geodetic Survey and of the Army Map Service. It is an expansion of a
very informal lecture given before Section III of the International Association of Geodesy, meeting in General Assembly at
Oslo in August, 1948. 相似文献
24.
Donald J. Walter Douglas N. Lambert David C. Young Kevin P. Stephens 《Geo-Marine Letters》1997,17(4):260-267
Real-time trackline plots of surficial sediment acoustic impedance delineate several sedimentary facies off Garden Key in
the Dry Tortugas. The sea floor within a 6×6 km surveyed area consists of carbonate muds (silts), sands and shell, rock, and
live corals. The 4-kHz acoustic data supports this finding by providing a pictographic representation of the distribution
and structure of several sediment facies types. Plotting the gridded acoustic data with commercial mapping software (Surfer)
provides a three-dimensional (3D) perspective of the bottom topography with a color contour map of surficial sediment impedance
(upper 0.4 m) draped over the 3D surface. 相似文献
25.
Bori L. Olla Allen J. Bejda Anne L. Studholme Walter H. Pearson 《Marine environmental research》1984,13(2):121-139
The burrowing and emergence behavior of sand worms, Nereis (Neanthes) virens Sars, in sediment contaminated with sublethal concentrations of Prudhoe Bay crude oil ranging from 74 to 5222 ppm, was studied in the laboratory. Initial burrowing in oiled sediment did not differ from that observed in unoiled sediment. Emergence of exposed worms was related to the oil concentration and the extent of weathering of oiled sediment. Sand worms buried in unoiled sediment did not emerge. Worms dug from oiled sediment after 12 hours' exposure and placed on unoiled sediment were impaired, resulting in a significant increase in time to burrow. However, after 12h, they recovered and burrowed at normal rates. Worms held in oiled sediment for 96 h also recovered. Possible causes for recovery are discussed. Results suggest that oil-induced aberrations may increase vulnerability to predation. 相似文献
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Walter H Pearson Stephen E Miller J.W Blaylock Bori L Olla 《Marine environmental research》1981,5(1):3-11
The ability of the blue crab, Callinectes sapidus, to detect petroleum hydrocarbons was measured with behavioural techniques. When presented with a water-soluble fraction of Prudhoe Bay crude oil, blue crabs abruptly changed antennular orientation, began rhythmic beating of the maxillipedal flagellae, and increased antennular flicking rate. The threshold concentration at which 50% of the crabs detected the water-soluble fraction was 2 × 10?6 mg/litre. The blue crab apparently can readily detect petroleum hydrocarbons at concentrations found in chronically polluted areas as well as oil spill situations. 相似文献
28.
Walter Hoppe 《Pure and Applied Geophysics》1961,50(1):129-139
Zusammenfassung Die Erzeugung von Kondensationskernen durch UV-Licht wurde mittels eines automatischenPollakschen Kernzählers und einerWilsonkammer aus Glas untersucht. Da die UV-Kerne von einem Schwebstoffilter zurückgehalten werden, ließ sich durch Verwendung zweier Bestrahlungsgefäße mit dazwischengeschaltetem Filter die Spurengashypothese bestätigen. Bestrahlungsversuche in Luft, Stickstoff, Sauerstoff, Argon und Wasserstoff ergaben, daß durch längere Bestrahlung eines abgeschlossenen Gasvolumens die kernbildende Substanz allmählich verbraucht wird. Durch Zugabe definierter Mengen gasförmigen Ammoniaks in den Bestrahlungsraum zeigte sich, daß die von verschiedenen Autoren geäußerte Ansicht, gasförmiges Ammoniak sei die kernbildende Substanz, nicht haltbar ist. Die Untersuchung des Einflusses von Schwefelwasserstoff bzw. Schwefeldioxyd ergab, daß die atmosphärische Konzentration von H2S zur Erklärung des UV-Effektes nicht ausreicht, während dies bei SO2 der Fall ist. Das Ergebnis, daß SO2 maßgebend an der Bildung der UV-Kerne in atmosphärischer Luft beteiligt ist, wird dadurch gestützt, daß der UV-Effekt einen ähnlichen Tagesgang zeigt wie das atmosphärische SO2.
Summary The production of condensation nuclei by UV light was investigated by means of an automaticPollak nucleus counter and aWilson glass-chamber. As the UV nuclei can be removed by an aerosol filter, the trace gas hypothesis could be confirmed by using two irradiation tubes separated by an aerosol filter. Irradiation experiments in air, nitrogen, oxygen, argon and hydrogen in a closed volume had the result that the nucleogenic substance gradually disappears after sufficiently long irradiation. By adding definite quantities of ammonia vapour into the irradiation tube it could be shown that ammonia is not the nucleogenic substance, as was supposed by some authors. The investigation of the influence of sulphur dioxide and hydrogen sulfide showed that the atmospheric concentration of H2S is not sufficient to explain the UV effect in atmospheric air, whereas this is true with SO2. The result that SO2 takes part in the formation of the UV nuclei is supported by the fact that SO2 and the UV effect show a similar diurnal variation.相似文献
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