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161.
The variation with position and view direction of heliospheric H-L scattered intensity seen by a L detector in the heliosphere is re-examined. Here, a frequency- and angle-dependent multiscattering calculation (Scherer, 1994; Scherer and Fahr, 1995) is used that takes into account the local thermodynamical conditions of the scattering agent, such as temperature, density and bulk velocity of the neutral interplanetary hydrogen, as given in a recent model by Osterbart and Fahr (1992). The calculated intensity patterns show strongly pronounced dependencies of the direction of the line of sight which are explained by effects of the Doppler shift in the resonance absorption and the dipole-phase function used in the multiscattering calculation. The theoretical results obtained with these computations nicely fit the intensities measured byPrognoz 5/6 probe (Lallement, Bertaux, and Dalaudier, 1985; Bertauxet al., 1985) without, however, assuming a latitude dependence of the solar wind mass outflow. This expresses the fact that, using an adequate radiation transport calculation, it is possible to explain thePrognoz andGalileo data without the need to specify anisotropic solar wind mass outflow from the corona preferred by several authors (Lallement, Bertaux, and Dalaudier, 1985; Lallement, 1989; Broadfoot and Kumar, 1978; Bertauxet al., 1985; Ajelloet al., 1994). In view of forthcomingUlysses solar wind measurements at polar latitudes this might be of importance to know. 相似文献
162.
Within the project Morphodynamic Processes and Desertification of the Academy of Sciences in Göttingen, research has been carried out on the desertification of the Butana region in the Sahel of the Rep. of Sudan. The abolition of traditional rights of land use, with the resulting disorganized utilization of grazing lands and the self-generated sedentarization of many formerly nomadic groups, has led to a rapid desertification of the Butana, which was further accelerated by the droughts of the eighties. The combination of substratum and climatic conditions has diversified the extent of site degradation, with an accelerated development of dunes and badlands taking place due to severe vegetation transformation in areas with permanent water supply or with sandy soils. 相似文献
163.
The intrusion of granitoid magmas is understood as a lower and mid crustal process. Field observations and laboratory experiments give strong reason that most granitoid plutons are formed by diapiric ascent and emplacement of large magma bodies.On this basis, the ascent and emplacement of granitoid magmas is modelled by two-dimensional finite element calculations. The physical concept for this process provides convective transport of matter and heat, an isolated finite source region, variable source temperatures as well as variable density and viscosity contrasts.The model calculations show that the structural development of the model intrusion bodies is highly dependent on the physical properties of the magma and its surroundings. The most important among them are density and viscosity. Due to the different initial conditions, stocks of several plutons in the case of high viscosity contrast or flat magma sources as well as nappe-shaped intrusion structures as a result of low viscosity contrast can be understood by the intrusive mode of emplacement. The enlargement of the negative density contrast leads to an increase of the rate of ascent, so that more advanced intrusion structures are developed.
Notation a thermal expansion coefficient - Cp specific heat capacity - Di dissipation number (model specific) - g gravity acceleration - dynamic viscosity - h heigth of model - thermal diffusivity - Q heat flow - Ra Rayleigh number - R(v) differential operator - p density - t time - T absolute temperature - v velocity - V volume - w vertical component of velocity - x horizontal coordinate - stream function - z vertical coordinate 相似文献
Zusammenfassung Die Intrusion granitoider Magmen ist ein Prozeß der unteren und mittleren Kruste. Feldbefunde und Laboruntersuchungen geben Hinweise darauf, daß die meisten granitoiden Plutone durch diapirischen Aufstieg und Platznahme ausgedehnter Magmenkörper entstehen.Auf dieser Grundlage werden der Aufstieg und die Platznahme granitoider Magmen mit Hilfe von zweidimensionalen Finite Elemente Rechnungen modelliert. Das physikalische Konzept beinhaltet den konvektiven Transport von Masse und Energie, eine isolierte finite Quellregion, veränderliche Quelltemperaturen sowie einen variablen Dichte- und Viskositätskontrast.Die Modellrechnungen zeigen, daß die strukturelle Entwicklung der Modellmagmenkörper in hohem Maße von den physikalischen Parametern des Magmas und seiner Umgebung, vor allem Dichte und Viskosität, abhängt. Gemäß den unterschiedlichen Anfangsbedingungen können sowohl einige stockförmige Plutone im Falle eines hohen Viskositätskontrastes oder flacher Magmaquellen als auch deckenförmige Intrusionsstrukturen als Folge eines geringen Viskositätskontrastes mit Hilfe des intrusiven Einlagerungskonzeptes verstanden werden. Die Erhöhung des negativen Dichtekontrastes führt zu einer Erhöhung der Aufstiegsrate, so daß fortgeschrittenere Platznahmestrukturen erreicht werden können.
Résumé L'intrusion des magmas granitoïdes est un processus qui intéresse la croûte inférieure et moyenne. Les observations de terrain et les expériences en laboratoire fournissent des arguments très sérieux en faveur de la formation des plutons par montée diapirique et mise en place de corps magmatiques de grandes dimensions.Sur base de cette conception, la montée et la mise en place de magmas granitoïdes a fait l'objet d'une modélisation par éléments finis à deux dimensions. Un tel modèle fait appel à un transport convectif de matière et de chaleur, à une région-source isolée de dimension finie, à une source de température variable ainsi qu' à divers contrastes de densité et de viscosité.Les calculs montrent que le développement structural des corps intrusifs ainsi modélisés dépend essentiellement des propriétés physiques du magma et de son encaissant, en particulier de la densité et de la viscosité. Etant données diverses conditions initiales, la modélisation rend compte de plusieurs types de culots plutoniques dans le cas de contrastes de viscosité élevés ou de sources de magma d'extension horizontale, ainsi que d'intrusions en forme de nappe dans le cas de faibles contrastes de viscosité. L'accroissement des contrastes de viscosité négatifs contribue à augmenter la vitesse d'ascension, ce qui permet le développement de structures d'intrusion plus évoluées.
— , . , . . : , , . , , , . , , . .
Notation a thermal expansion coefficient - Cp specific heat capacity - Di dissipation number (model specific) - g gravity acceleration - dynamic viscosity - h heigth of model - thermal diffusivity - Q heat flow - Ra Rayleigh number - R(v) differential operator - p density - t time - T absolute temperature - v velocity - V volume - w vertical component of velocity - x horizontal coordinate - stream function - z vertical coordinate 相似文献
164.
Ronnie Nhr Glud Jens K. Gundersen Bo Barker Jrgensen Niels Peter Revsbech Horst D. Schulz 《Deep Sea Research Part I: Oceanographic Research Papers》1994,41(11-12)
Total O2 uptake rates were measured by the benthic flux chamber lander ELINOR, and O2 microprofiles were measured by the profiling lander PROFILUR in the eastern South Atlantic. Diffusive O2 fluxes through the diffusive boundary layer and the depth distribution of O2 consumption rates within the sediment were calculated from the obtained microprofiles. The depth integrated O2 consumption rate agreed closely with the diffusive O2 uptake at all stations. Total O2 uptake was 1.2–4.2 times the diffusive O2 uptake, and the difference correlated with the abundance of macrofauna in the sediment. Diffusive O2 uptake and O2-penetration depths correlated with the organic content of the sediments and exhibited an inverse correlation with water depth. Total and diffusive rates of in situ O2 uptake were higher than previously published data for shelf and abyssal sediments in the Atlantic, but were comparable to rates from upwelling areas in the eastern Pacific. Laboratory measurements on recovered sediment cores showed lower O2 penetration depths and higher diffusive uptake rates than in situ measurements. The differences increased with increasing water depth. We primarily ascribe this compression of O2 profiles to a transiently increased temperature during recovery and enhanced microbial activity in decompressed sediment cores. Total O2 uptake rates measured in the laboratory on macrofauna-rich stations were, in contrast, lower than those measured in situ because of underrepresentation and disturbance of the macrofauna. 相似文献
165.
166.
Correlation analysis of the mean longitude distribution of sunspot groups (taken from the Greenwich Photoheliographic Results) and high-speed solar wind streams (inferred from the C9 index for geomagnetic disturbances) with the Bartels rotation period P = 27.0 days shows anti-correlation for individual cycles.In particular, the longitudes of post-maximum stable streams of cycle 18 and 19 are well anticorrelated with the preferred longitudes of sunspot groups during the maximum activity periods of these cycles. This is further analyzed using the daily Zürich sunspot number, R, between 1932 and 1980, which reveals a conspicuous similarity of cycle 18 and 19 as well as cycle 20 and 21.We conclude that there is a solar memory for preferred longitudes of activity extending at least over one, probably two cycles (i.e. one magnetic cycle of 22 years). We conjecture that this memory extends over longer intervals of time as a long-term feature of solar activity. 相似文献
167.
168.
Suthan Suthersan John Horst Mark Klemmer Don Malone 《Ground Water Monitoring & Remediation》2012,32(3):34-40
The remediation industry has witnessed multiple innovations arising from a greater understanding of the physical, chemical, and biological processes that control the fate and transport of chemicals in the subsurface environment. In addition, increasing emphasis is being placed on remediation solutions that are greener, simpler, and more resource efficient. The positive impacts that can be derived from this emphasis include reduced energy consumption, reduced waste emissions, and lower costs. Temperature‐activated auto‐decomposition reactions represent a potentially underutilized option for the in situ remediation of certain organic contaminants, and an option that can be both highly effective and greener than other available technologies. 相似文献
169.
Horst R. Beyer Kostas D. Kokkotas 《Monthly notices of the Royal Astronomical Society》1999,308(3):745-750
We present a mathematically rigorous proof that the r-mode spectrum of relativistic stars to the rotational lowest order has a continuous part. A rigorous definition of this spectrum is given in terms of the spectrum of a continuous linear operator. This study verifies earlier results by Kojima concerning the nature of the r-mode spectrum. 相似文献
170.
Geissler Wolfram Plenefisch Thomas Kind Reiner Klinge Klaus Kämpf Horst Boušková Alena Nehybka Vladimír Skácelová Zuzana Jacob Brian 《Studia Geophysica et Geodaetica》2000,44(2):188-194
We used teleseismic recordings of a temporary deployment of seismic stations and of permanent short period stations in the western Eger Rift system to study the lithosphere with the help of Receiver Functions. The crust-mantle boundary (Moho) is observed at almost all stations by strong P-to-S converted phases. The Moho is basically flat between about 26 – 30 km depth in the entire region. At one station in the Eger Rift (BOH-1, Loket castle) no Moho is observed. We interpret this with the existence of a broad gradient zone there, instead of a sharp discontinuity. This observation, however, needs to be confirmed by more data. 相似文献