Neues Verfahren zur Messung des Eintrages von Rührenergie in kleinen Laborflockungsreaktoren     

H.-J. Walther  N. Fichtner  R. Schott  H. Ringk 《洁净——土壤、空气、水》1973,1(4):407-409

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Zur Altersfrage der Eisenerzlagerstätte Sierra Grande/Rio Negro in Nordpatagonien Aufgrund Neuer Fossilfunde     

Dr. Horst Müller 《International Journal of Earth Sciences》1965,54(2):715-732

A small fauna is described in detail from the southern and from the eastern iron ore deposit of Sierra Grande, Prov. Rio Negro, Argentina. The southern deposit could be established to be of Silurian (Wenlockian?) age, whereas the eastern deposit seems to be younger, probably of Lower Devonian age. The rock sequence belongs to the Gondwanide system, known from the southern Sierras of the province of Buenos Aires and from the Falkland Islands (Islas Malvinas). The present study indicates a much larger extension of this system than formerly recognized.  相似文献   

Experimental evaluation of analytical and Lagrangian surface-layer flux footprint models   总被引：3，自引：1，他引：3  

D. Finn  B. Lamb  M. Y. Leclerc  T. W. Horst 《Boundary-Layer Meteorology》1996,80(3):283-308

Three surface-layer flux footprint models have been evaluated with the results of an SF₆ tracer release experiment specifically designed to test such models. They are a Lagrangian stochastic model, an analytical model, and a simplified derivative of the analytical model. Vertical SF₆ fluxes were measured by eddy correlation at four distances downwind of a near-surface crosswind line source in an area of homogeneous sagebrush. The mean fluxes were calculated for 136 half-hour test periods and compared to the fluxes predicted by the footprint models. All three models gave similar predictions and good characterizations of the footprint over the stability range -0.01 < z ₀/L < 0.005. The predictions of the three models were within the limits of the uncertainty of the experimental measurements in all but a few cases within this stability range. All three models are unconditionally recommended for determining the area defined by the footprint over short vegetative canopies in this range. They are also generally appropriate for estimating flux magnitudes within the limits of experimental uncertainties. Most of the mean differences observed between the measured and predicted fluxes at each of the four towers reflect a tendency for the measured fluxes to be greater than those predicted by the three models. Rigorous verification of the models in strongly stable conditions was complicated by the need to obtain very accurate measurements of small fluxes in only marginally stationary conditions. Verification in strongly unstable conditions was hampered by the limited number of appropriate data.  相似文献   

Downward continuation of Helmert's gravity     

P. Vaníček  W. Sun  P. Ong  Z. Martinec  M. Najafi  P. Vajda  B. ter Horst 《Journal of Geodesy》1996,71(1):21-34

. The aim of this contribution is to show that mean Helmert's gravity anomalies obtained at the earth surface on a grid of a `reasonable' step can be transferred to corresponding mean Helmert's anomalies on the geoid. To demonstrate this, we take the by mean Helmert's anomalies from a very rugged region, the south-western corner of Canada which contains the two main chains of the Canadian Rocky Mountains, and formulate the problem of downward continuation of Helmert's anomalies for this region. This can be done exactly because Helmert's disturbing potential is harmonic everywhere outside the geoid, therefore even within the topography. Then we solve the problem numerically by transforming the Poisson integral to a system of 53,856 linear algebraic equations. Since the matrix of this system is well conditioned, there is no theoretical obstacle to the solution. The correctness of the solution is then checked by back substitution and by evaluating the contribution of the downward continuation term to Helmert's co-geoid. This contribution comes out positive for all the points. We thus claim that the determination of the downward continuation of mean Helmert's gravity anomalies on a grid of a `reasonable' step is a well posed problem with a unique solution and can be done routinely to any accuracy desired in the geoid computaion. Received 27 October 1995; Accepted 9 July 1996  相似文献   

The baltic sea ferry guidance and information system (BAFEGIS)     

Horst Hecht 《Ocean Dynamics》1997,49(4):511-517

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Horst Scherer  Hans J. Fahr 《Solar physics》1995,161(2):383-392

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   

Desertification in the Butana     

Mariam Akhtar  Horst Georg Mensching 《GeoJournal》1993,31(1):41-50

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   

On the ascent and emplacement of granitoid magma bodies dynamic-thermal numerical models     

Nina Kukowski  Horst J. Neugebauer 《International Journal of Earth Sciences》1990,79(2):227-239

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.

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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.

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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.

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— , . , . . : , , . , , , . , , . .

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Notation a thermal expansion coefficient - C_p 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   

Diffusive and total oxygen uptake of deep-sea sediments in the eastern South Atlantic Ocean:in situ and laboratory measurements     

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   

Fast application of X-ray fluorescence spectrometry aboard ship: how good is the new portable Spectro Xepos analyser?     

Katharina Wien  Dirk Wissmann  Martin Kölling  Horst D. Schulz 《Geo-Marine Letters》2005,25(4):248-264

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