DIE STRATIGRAPHISCHE UND PALAEONTOLOGISCHE BEDEUTUNG DER FOSSILEN NAGETIERE CHINAS     

VON C.C.YOUNG 《地质学报》1931,(1)

Ⅰ. VORBEMERKUNG. Die Ordnung Nagetiere umfasst sehr viele Arten und ist die verbreitetste Tiergruppe innerhalb der Saeugetiere. Sie macht mit ihren etwa 2800 Species mehr als ein Drittel der heutigen Landsaeugetiere aus. Die Nagetiere sind auf der ganzen Welt bis zu den Polen und dem vereisten Hochgebirge an-  相似文献   

Statistical downscaling of monthly mean North Atlantic air-pressure to sea level anomalies in the Baltic Sea   总被引：1，自引：0，他引：1  

HAUKE HEYEN  EDUARDO ZORITA  HANS VON STORCH 《地球，A辑:动力气象学与海洋学》1996,48(2):312-323

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Der Eukrit von Stannern     

Professor Dr. Wolf V. Engelhardt 《Contributions to Mineralogy and Petrology》1963,9(1):65-94

Zusammenfassung Die Beobachtungen beim Fall des Meteoriten von Stannern am 22. Mai 1808 werden zusammenfassend dargestellt. Der Eukrit von Stannern besitzt eine Porosität von 15 % und besteht nach mikroskopischen Beobachtungen aus ophitischen und brecciösen Partien, welche 33 Vol.-% Bytownit (An₈₄),11 Vol.-% Hypersthen (Fs₅₅), 49 Vol.-% Pigeonit (Fs₅₅En₃₅Wo₁₀), etwa 5 Vol.-% Quarz und geringere Mengen von Ilmenit, Troilit und Chromit enthalten. Alle these Mineralien werden näher beschrieben. Eine neue chemische Analyse wird mitgeteilt, die mit dem mikroskopischen Befund gut übereinstimmt. Aus einer Schmelze bildeten sick zuerst Bytownit und Hypersthen in nahezu eutektischem Mengenverhältnis. Danach wurde der Hypersthen unter gleiehzeitiger starker mechanischer Beanspruchung des ganzen Gesteins (Breccienbildung) zum größten Teil in Pigeonit umgewandelt und es kam zusätzlicher Pigeonit zur Abscheidung. Nach Abschluß der Breccienbildung entstanden als letzte Bildungen Quarz, Ilmenit und Troilit. In den letzten Phasen der Bildung spielten möglicherweise flüchtige Bestandteile eine Rolle, die heute nicht mehr im Meteoriten vorliegen. Die chemische Zusammensetzung des Eukrits von Stannern und die der übrigen Careichen Achondrite wird mit der der Chondrite und irdischen Basalte verglichen und es werden mögliche genetische Zusammenhänge diskutiert. Jedenfalls können Eukrite und Howardite nur auf nicht zu kleinen planetarisehen Körpern entstanden sein, wo Kristallisationsdifferentiation und lanusame Abkiihlung möglich waren. Die in der Atmosphäre gebildete Schmelzrinde der Steine von Stannern enthält viele Blasen, die durch des Sieden der Silikatschmelze erzeugt wurden. Aus dem Dampf schlug sick bei der Abkühlung in den Blasen und auf der Außenseite der Steine Wollastonit ab. Im Glas entstanden geringe Mengen Enstatit oder Klinoenstatit.  相似文献   

TO RADIATE OR NOT TO RADIATE     

J. P. WOLF  C. SONG 《地震工程与结构动力学》1996,25(12):1421-1432

Insight into radiation damping of an unbounded medium is developed by addressing the relative contributions of the elastic restoring force and the inertial force at infinity. When the inertial force dominates, radiation damping occurs. When the elastic restoring force dominates, no radiation damping arises. An unbounded medium with a cutoff frequency can also be identified.  相似文献   

Reduction of biosphere life span as a consequence of geodynamics   总被引：1，自引：0，他引：1  

S. FRANCK  A. BLOCK  W. VON BLOH  C. BOUNAMA  H. J. SCHELLNHUBER  Y. SVIREZHEV 《Tellus. Series B, Chemical and physical meteorology》2000,52(1):94-107

The long‐term co‐evolution of the geosphere–biospere complex from the Proterozoic up to 1.5 billion years into the planet's future is investigated using a conceptual earth system model including the basic geodynamic processes. The model focusses on the global carbon cycle as mediated by life and driven by increasing solar luminosity and plate tectonics. The main CO₂ sink, the weathering of silicates, is calculated as a function of biologic activity, global run‐off and continental growth. The main CO₂ source, tectonic processes dominated by sea‐floor spreading, is determined using a novel semi‐empirical scheme. Thus, a geodynamic extension of previous geostatic approaches can be achieved. As a major result of extensive numerical investigations, the "terrestrial life corridor", i.e., the biogeophysical domain supporting a photosynthesis‐based ecosphere in the planetary past and in the future, can be identified. Our findings imply, in particular, that the remaining life‐span of the biosphere is considerably shorter (by a few hundred million years) than the value computed with geostatic models by other groups. The "habitable‐zone concept" is also revisited, revealing the band of orbital distances from the sun warranting earth‐like conditions. It turns out that this habitable zone collapses completely in some 1.4 billion years from now as a consequence of geodynamics.  相似文献   

CONSISTENT INFINITESIMAL FINITE-ELEMENT CELL METHOD IN FREQUENCY DOMAIN     

J. P. WOLF  C. SONG 《地震工程与结构动力学》1996,25(11):1307-1327

To calculate the dynamic-stiffness matrix at the structure–medium interface of an unbounded medium for the range of frequencies of interest, the consistent infinitesimal finite-element cell method based on finite elements is developed. The derivation makes use of similarity and finite-element assemblage, yielding a non-linear first-order ordinary differential equation in frequency. The asymptotic expansion for high frequency yields the boundary condition satisfying the radiation condition. In an application only the structure–medium interface is discretized resulting in a reduction of the spatial dimension by one. The boundary condition on the free surface is satisfied automatically. The consistent infinitesimal finite-element cell method is exact in the radial direction and converges to the exact solution in the finite-element sense in the circumferential directions. Excellent accuracy results.  相似文献   

Net groundwater inflow in an enclosed lake: from synoptic variations to climatic projections     

G. Kirillin  W. Phillip  C. Engelhardt  G. Nützmann 《水文研究》2013,27(3):347-359

Using lake Stechlin in northeastern Germany as an example of a small groundwater‐feed lake without surface inflows and outflows, we estimated the temporal scales and the variability ranges of the net groundwater contribution to the lake water budget. High‐resolution water level measurements by a bottom‐mounted pressure logger provided the background for the estimation of the total lake water budget. This method has demonstrated reliability for estimation of lake level variations during periods ranging from subdiurnal to perennial. The typical amplitudes of the synoptic‐to‐perennial variability characterizing the groundwater climate of lake Stechlin are estimated by comparing the two subsequent years 2006 and 2007; one of these years shows an extremely high, and the other an extremely low, annual precipitation–evaporation balance. The net groundwater flow, estimated as the difference between the total water budget and the precipitation–evaporation balance at the surface, revealed synoptic effects of lake water exfiltration into the groundwater aquifer following strong precipitation events. Perennial variations between wet and dry years superimposed seasonal oscillations. The probable origin of the latter is seasonality in the groundwater level on the watershed, although the exact amplitudes are subject to further quantification on account of seasonality in the evaporation estimation error. The results emphasize the non‐stationary behaviour of groundwater flow on timescales shorter than climatic ones. The analysis yielded a net quantitative relationship between groundwater flow and water balance at the lake surface: The water level changes in the lake due to evaporation and precipitation are damped to 60% because of the lake–groundwater exchange by means of intermittent infiltration and exfiltration events. Assuming the remaining 40% of the surface water budget may potentially result in perennial water level variability, we estimated an effect of the precipitation decrease on the lake water budget as predicted by the regional climate scenarios for the next century. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Expert system for the selection of methods to calculate design flood flows     

EDUARDO A. VARAS  MARCELO VON CHRISMAR 《水文科学杂志》2013,58(6):739-749

Abstract

This paper presents an expert system to help select the best method to estimate design flood flows for civil engineering works based upon the procedures available, the nature and characteristics of the basin and existing hydrological records. The system presents the user with a list of possible methods ranked in descending grade order and optionally presents explanations which support the selected choices. Ordering is achieved using the knowledge base provided by the expert. The system recommends procedures for both preliminary estimates and final designs. The system also constitutes a valuable aid for junior engineers and experienced hydrologists in the selection of methods. Its conceptual structure can be easily generalized to treat other problems of a similar nature in the field of hydrology and water resources.  相似文献   

Retrieval of aerosol optical thickness for desert conditions using MERIS observations during the SAMUM campaign     

By TILMAN DINTER  WOLFGANG VON HOYNINGEN-HUENE  JOHN P. BURROWS  ALEXANDER KOKHANOVSKY  EIKE BIERWIRTH  MANFRED WENDISCH  DETLEF MÜLLER  RALPH KAHN  MOHAMMED DIOURI 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):229-238

Approximately 30% of the land surface is arid, having desert or semi-desert conditions. Aerosol originating from these regions plays a significant role in climate and atmospheric chemistry of the atmosphere. Retrieving aerosol properties from space-borne platforms above desert conditions, where the surface reflectance is usually very bright, is a challenging task. The proportion of the surface to top of atmosphere (TOA) reflectance can reach values over 90%, especially for wavelength above 500 nm. For these reasons detailed knowledge of aerosol and surface optical properties from these regions is required to separate atmosphere from intrinsically bright surfaces.
An approach to retrieve aerosol properties over arid and semi-arid regions based on the Bremen Aerosol Retrieval (BAER) has been developed and validated within the Dust Aerosol Retrievals from Space-Born Instruments (DREAMS) Project, which is part of the Saharan Mineral Dust Experiment ( SAMUM, 2006 ). Combining measurements of the backscattered radiation from the Medium Resolution Imaging Spectrometer (MERIS) instrument aboard Environmental Satellite (ENVISAT) and ground-based measurements in Morocco in radiation closure experiments yields the aerosol optical properties of mineral dust at selected locations.  相似文献   

THE INFLUENCE OF RIPARIAN VEGETATION COVER ON DIFFUSE LATERAL SEDIMENT CONNECTIVITY AND BIOGEOMORPHIC PROCESSES IN A MEDIUM‐SIZED AGRICULTURAL CATCHMENT,AUSTRIA     

RONALD E. POEPPL  MARGRETH KEILER  KIRSTEN VON ELVERFELDT  IRENE ZWEIMUELLER  THOMAS GLADE 《Geografiska Annaler: Series A, Physical Geography》2012,94(4):511-529

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