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1.
G.D. Hahn 《Ocean Engineering》1994,21(6)
Critical examinations are reported for the effects of wave stretching on realistic representations of the wave forces that act on offshore structures. Examinations are also made for the importance of such effects on the corresponding structural responses, and it is demonstrated that the effects of stretching on the governing wave forces and the resulting structural responses are small, indicating that they can be ignored in design practice. Valuable insight is further provided into the definition of the wave excitation, and physical interpretations are made which show that the actions of stretching cannot materially influence the governing excitation and the corresponding structural response. 相似文献
2.
G. Hahn C. -I. Lagerkvist B. A. Lindblad 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):131-141
By using theD-criterion Lindblad (1992) has identified 14 asteroid families from a sample of 4100 numbered asteroids with proper elements from Milani and Kneevi (1990). Taxonomic types and other physical properties for a significant number of objects in five of the families show strong homogeneity within each family, further strengthening their internal relationship.To test the hypothesis of a common origin in, e.g., a catastrophic collision event, we have set out to integrate the orbits of the members of the Maria, Dora and Oppavia-Gefion families over some 106 years. The mean distance for the Maria family is close to the 3:1 mean-motion resonance with Jupiter, while the other two families lie close to the 5:2 resonance.We used a simplified solar system model which included the perturbations by Jupiter and Saturn only and implemented Everhart's variable stepsize integrator RA15. All close encounters between the family members (within 0.1 AU) were recorded as well. Preliminary results from integrations over 4×105 years are presented here.The statistics of close encounters show pronounced peaks for several members within each family, while for others no significant levels above the background of random encounters or even very low frequencies were found. This indicates a subclustering within the families. Quite a lot of very close (<0.005 AU) mutual encounters are found, which suggest that, at least for the larger members in a family, the mutual gravitational interactions could be of some importance for the real orbital evolutions.The encounter statistics between the Dora and Oppavia family members suggest a possible interrelationship between this two groups. 相似文献
3.
Susanne I. Schmidt Hans J. Hahn Gerald D. Watson Robert J. Woodbury Thomas J. Hatton 《洁净——土壤、空气、水》2004,32(2):131-137
Groundwater bores act as traps. Net samplers are regularly used for sampling this type of trap for fauna. To enable direct comparisons of faunal communities in groundwater bores and stream sediments, stream sediment tubes were built similar to groundwater bores and were sampled with net samplers for fauna. These stream sediment tubes consisted of a tube anchored in the stream sediment, also called interstitial space. To test the efficacy of this trap method in stream sediments, it was compared to another type of trap, Hahn's trap. Faunal communities sampled by a net in the stream sediment tubes did not differ hugely from fauna in Hahn's trap samples. Physical and chemical factors of sampled water in both the stream sediment tubes, the surrounding interstitial sediments and the second type of traps, Hahn's traps, showed that water in both the tubes and Hahn's traps was closely related to interstitial water. The net sampler is inexpensive and easy to handle. It is suggested that sampling stream tubes with nets may be an appropriate method for long‐term monitoring studies. 相似文献
4.
The impact of uncertain emission trading markets on interactive resource planning processes and international emission trading experiments 总被引:1,自引:1,他引:0
Interactive resource planning is an increasingly important aspect of emission trading markets. The conferences of Rio de Janeiro, 1992, and Kyoto, 1997, originally focusing on environmental protection at both macro- and micro-economic levels, called for new economic instruments of this kind. An important economic tool in this area is Joint Implementation (JI), defined in Article 6 of the Kyoto Protocol. Sustainable development can be guaranteed only if JI is embedded in optimal energy management. In this contribution we describe and evaluate one international procedure within uncertain markets which helps to establish optimal energy management and interactive resource planning processes within uncertain emission trading markets. 相似文献
5.
The biogeochemical sulfur cycle in the marine boundary layer over the Northeast Pacific Ocean 总被引:1,自引:0,他引:1
T. S. Bates J. E. Johnson P. K. Quinn P. D. Goldan W. C. Kuster D. C. Covert C. J. Hahn 《Journal of Atmospheric Chemistry》1990,10(1):59-81
The major components of the marine boundary layer biogeochemical sulfur cycle were measured simultaneously onshore and off the coast of Washington State, U.S.A. during May 1987. Seawater dimethylsulfide (DMS) concentrations on the continental shelf were strongly influenced by coastal upwelling. Concentration further offshore were typical of summer values (2.2 nmol/L) at this latitude. Although seawater DMS concentrations were high on the biologically productive continental shelf (2–12 nmol/L), this region had no measurable effect on atmospheric DMS concentrations. Atmospheric DMS concentrations (0.1–12 nmol/m3), however, were extremely dependent upon wind speed and boundary layer height. Although there appeared to be an appreciable input of non-sea-salt sulfate to the marine boundary layer from the free troposphere, the local flux of DMS from the ocean to the atmosphere was sufficient to balance the remainder of the sulfur budget. 相似文献
6.
W. L. F. Brinkmann Dr. H. Hahn H. Schick J. W. Fachbereich Geowissenschaften 《GeoJournal》1987,14(3):331-338
Two lakes, Lake Gänseweiher (LGW) and Lake Fechenheimer Weiher (LFW) occupy groundwater filled abandoned gravel pits which serve as fishing grounds and are part of recreational areas, respectively.Both lakes are cut into a near-surface groundwater aquifer, which is located in the pleistocene River Main gravel terrace t6. They are sealed at the base by miocene clays and above by overlying flood deposits of the River Main. The latter provide protection from pollutants derived from wet and dry deposition of atmospheric contaminants.Groundwater chemistry determines the pool of dissolved constituents in lake water. The temporal and spatial distribution patterns of chemical compounds in lake water are brought about by endo-biogenic processes, of which the indicators are nitrate-nitrogen and dissolved silica. The latter illustrates an instantaneous response to pulses of diatom blooms.Both lakes are eutrophic (polytrophic) according to the classification guidelines presented in literature. 相似文献
7.
Dr. Lothar Hahn 《International Journal of Earth Sciences》1982,71(3):1041-1056
The tectonic movements which occurred in Thailand between the Permian and the Jurassic (Indosinian Orogeny) caused the uplifting and subsidence of areas which were dominant paleogeographic features during the Triassic. The strong orogenic movements during the Norian caused an alteration of the paleogeographic conditions.The two sedimentation cycles of the Triassic comprised a marine facies development from the Skythian to the early Norian and a terrestrial one from the later Norian to the Rhaetian/Liassic.The development of the facies and structure of the Triassic sediments, as well as the intrusion and effusion of igneous rocks, are due to the subduction of oceanic crust beginning in the Carboniferous and to the collision of the Eurasian with the Indochina Plate during the Norian.
Zusammenfassung Die zwischen Perm und Jura in Thailand auftretenden tektonischen Bewegungen (Indosinische Orogenese) führten zur Bildung von Hebungs- und Senkungsgebieten, die die Paläogeographie in der Trias beherrschten. Die starken orogenen Bewegungen im Nor führten zu einer Umgestaltung der paläogeographischen Verhältnisse.Die beiden während der Trias auftretenden Sedimentationszyklen bestehen aus einer marinen Faziesentwicklung vom Skyth bis zum unteren Nor und einer terrestrischen vom oberen Nor bis zum Rhät/Lias.Die fazielle und strukturelle Entwicklung der Triassedimente sowie die Intrusion bzw. Effusion von Eruptivgesteinen sind auf die seit dem Karbon erfolgende Subduktion ozeanischer Kruste und die Kollision der Eurasiatischen Platte mit der Indochinesischen Platte im Nor zurückzuführen.
Résumé Les mouvements tectoniques («Orogenèse Indosinienne») intervenus entre le Permien et le Trias en Thaïlande se sont traduits en soulèvements et affaissements qui ont dominé la paléogéographie du Trias. Les forts mouvements orogéniques du Norien ont conduit à transformer les rapports paléogéographiques.Les deux cycles sédimentaires du Trias consistent dans le développement d'un faciès marin du Scythien au Norien inférieur, et d'un faciès continental du Norien supérieur au Rhétien/Lias. L'évolution du faciès et de la structure des sédiments du Trias, l'intrusion et l'effusion des roches ignées sont attribuées à la subduction de la croute océanique consécutive au Carbonifère, et à la collision de la «Plaque Euroasiatique» avec la «Plaque Indochinoise» au Norien.
— — , . . - , - — . , , , , .相似文献
8.
Gerhard Hahn Claes-Ingvar Lagerkvist 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):285-302
Numerical integrations of 26 orbits of planet-crossing astetoids of Apollo-Amor type have been performed, in a solar system model including the perturbations by the planets from Venus to Neptune. The 15:th order RADAU integrator (Everhart, 1985) has been used. Orbits for the asteroids 433 Eros, 887 Alinda, 1036 Ganymed, 1221 Amor, 1580 Betulia, 1627 Ivar, 1685 Toro, 1862 Apollo, 1863 Antinous, 1864 Daedalus, 1865 Cerberus, 1915 Quetzalcoatl and 1916 Boreas have been integrated over 100 000 years forward in time and for 1866 Sisyphus, 2102 Tantalus, 2201 Oljato, 2329 Orthos, 3360 1981 VA, 3552 1983 SA, 1981 EJ30, 1985 PA, 1985 WA, 1986 DA 1986 JK and 1986 RA a period of about 33 000 years has been covered. The orbital evolutions of these asteroids are discussed. This work is part of a larger study of the long-term orbital evolution of planet-crossing asteroids and will be continued within the project SPACEGUARD (Milani et al., 1987). 相似文献
9.
A.?BoattiniEmail author G.?D’Abramo H.?Scholl O.?R.?Hainaut R.?West G.?Hahn R.?Michelsen G.?Forti P.?Pravec G.?B.?Valsecchi 《Earth, Moon, and Planets》2003,93(4):239-248
We have used the ESO Very Large Telescope (VLT) to perform as trometric observations of Near Earth Asteroids (NEAs) having
remote collision possibilities with the Earth. The observations were made for those objects which became too faint to be observed
elsewhere. Using the 4 hours allocated in the semester April–September 2003, 5 faint NEAs were observed. As a result, no NEA
that could impact the Earth was lost. 相似文献
10.
The GW-Fauna-Index: A first approach to a quantitative ecological assessment of groundwater habitats 总被引:6,自引:1,他引:6
Between June 2001 and December 2002, 18 hyporheic and groundwater bores were sampled for fauna and environmental data using phreatic traps. The bores were situated in three different natural geographic regions in Palatinate, Southwestern Germany.Faunal data correlated with the relative amount of detritus, bacterial abundances and the standard deviation of temperature, while very few and weak correlations were found with physical–chemical variables. Dissolved oxygen was assumed to be a limiting factor for most metazoans with a critical concentration at around 0.5–1 mg l−1.To quantify the strength of the hydrological exchange with surface water and its effects on fauna, a so-called GW-Fauna-Index was developed and calculated using the relative amount of detritus, standard deviation of temperature, and oxygen concentration. From all environmental data and on all spatial scales, this index best explained the total faunal abundance and taxonomic richness.To describe the availability of organic aliments in the groundwater, the terms of “alimonic” and “alimony” [from lat. alimonium=(food) supply] were proposed.Although stygofauna was different in the geographic regions investigated, the GW-Fauna-Index was independent from these regional particularities. Using the GW-Fauna-Index, three groups of groundwater habitats could be classified according to the alimonic conditions. From oligo-alimonic group I samples, fauna was mostly absent, while meso-alimonic group II samples were prevailingly populated by stygobites, and eu-alimonic group III samples by ubiquists and stygoxenes. Total abundances and taxonomic richness increased significantly from group I to group III. Group I samples were characterized by low index values, group II samples by intermediate and group III samples by high values.The GW-Fauna-Index provides promising perspectives for application, but needs some improvement. First of all, detritus should be analysed quantitatively and qualitatively, rather than semi-quantitatively. Also, a standard protocol for sampling has to be developed. 相似文献