Predictability in dynamical systems     

Heinrich Eichhorn 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):417-420

The problem has basically three aspects: A mathematical, a physical and thirdly, an epistemological one. Even though the state of a dynamical system as a function of time may be perfectly and unambiguously determined in principle, do we at this time have the means to find out what this state is?  相似文献   

On the determination of double star orbits     

Heinrich Eichhorn 《Astrophysics and Space Science》1985,110(1):119-124

It is proposed to improve the convergence of the determination of the elements of the orbits of visual binaries by using not only first, but second-order derivatives in the development of the appropriate equations of condition. Also, some improvements of the Kowalsky-Seeliger method are suggested which improve the accuracy of the orbit used as first approximation.  相似文献   

Sulfur emissions to the atmosphere from natural sourees   总被引：1，自引：0，他引：1  

T. S. Bates  B. K. Lamb  A. Guenther  J. Dignon  R. E. Stoiber 《Journal of Atmospheric Chemistry》1992,14(1-4):315-337

Emissions of sulfur gases from both natural and anthropogenic sources strongly influence the chemistry of the atmosphere. To assess the relative importance of these sources we have combined the measurements of sulfur gases and fluxes during the past decade to create a global emission inventory. The inventory, which is divided into 12 latitude belts, takes into account the seasonal dependence of sulfur emissions from biogenic sources. The total emissions of sulfur gases from natural sources are approximately 0.79 Tmol S/a. These emissions are 16% of the total sulfur emissions in the Northern Hemisphere and 58% in the Southern Hemisphere. The inventory clearly shows the impact of anthropogenic sulfur emissions in the region between 35° and 50°N.  相似文献   

Age and evolution of scheelite-hosting rocks in the Felbertal deposit (Eastern Alps): U-Pb geochronology of zircon and titanite     

Roland Eichhorn  Urs Schärer  Rudolf Höll 《Contributions to Mineralogy and Petrology》1995,119(4):377-386

U-Pb isotope analyses of zircon and titanite extracted from different rocks of the Felbertal scheelite deposit yield the following information: (1) An age of 593±22 Ma (2) is obtained for zircon crystallization in the scheelite-bearing matrix of an eruption breccia in the western ore field. (2) Discordant zircons from an elongated, up to 8 m thick scheelite-rich quartzite body in the eastern ore field give an upper intercept age of 544±5 Ma. This quartzite contains a laminated, fine-grained scheelite mineralization. (3) Zircons from a small granitoid intrusion of the western ore field reveal an age of 336±16 Ma, and concordant titanites document an age of 282±2 Ma for Variscan amphibolite facies metamorphism. Both events, granitoid intrusion and later metamorphism caused ore re-mobilization, including the formation of yellowish fluorescent (molybdo-) scheelite porphyroblasts. (4) For a narrow lamprop-1hyric dike in the western ore field, a concordant titanite age of 283±7 Ma is obtained. This age is identical with the titanites from the amphibolite facies metamorphic intrusion. Tiny scheelite grains were tapped by the dike from pre-existing scheelite mineralizations in the truncated host rocks. (5) Alpine metamorphism at 31±4 Ma did not exceed lowermost amphibolite facies conditions, and it caused scheelite re-mobilization on a minor scale only, producing bluish fluorescent porphyroblasts in quartz veinlets and veins, as well as bluish fluorescent scheelite rims around older scheelite grains. Moreover, crosscutting Alpine fissure fillings show bluish fluorescent, inclusion-free scheelite. (6) The preservation of Variscan titanites, the absence of Alpine titanite growth, and the large degree of Variscan scheelite re-mobilization demonstrate that amphibolite facies metamorphism in the Felbertal area has a Variscan age. This result clearly documents Variscan tectono-metamorphism to be the dominant event, instead of the hitherto surmised Alpine metamorphism. This multi-stage evolution of the Felbertal ore bodies corroborates the view that tungsten deposits are conditioned by several succeeding thermal events, leading to a series of stages that ultimately produce high-grade scheelite concentrations. These high-grade ores predominately occur along shear zones of different age, accompanied by the formation of large volumes of low-grade scheelite mineralizations along host rock foliations and quartz veinlets and veins.  相似文献   

Physical time and astronomical “time”     

Heinrich Eichhorn 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):237-241

This sketch is based on the following line of thought. If we understand by (physical or dynamical) time the independent variable in the equations of motion, only quantities which are in a strictly linear relationship with this mechanical — physical time should properly be called time. This excludes therefore such concepts as e.g., sidereal time; in general that Earth Rotation Parameter which is one of the angles which define the orientation in space of a coordinate system fixed in a rigid model Earth. The relationships between these Eulerian angles and the ERP which follow from the theory of motion are discussed, also for the case that the reference system is an arbitrary noninertial system whose relationship (as a function of time) with an inertial system is known.  相似文献   

Inertial systems-definitions and realizations     

Heinrich Eichhorn 《Celestial Mechanics and Dynamical Astronomy》1984,34(1-4):11-18

A frame of reference is defined asinertial if the coordinates of bodies, predicted with respect to it on the basis of some mechanical principles, agree with those actually observed. It is pointed out that within the framework of Newtonian mechanics the concept of an inertial frame of reference is global, but within the framework of general relativity only local. The relativistic local inertial frame of the Solar System moves with respect to the Newtonian global frame by the amount of geodetic precession. In all rigor, the concept of a globally privileged inertial system has been rendered meaningless by general relativity, even though the concept of an inertial reference frame remains useful in contemporary celestial mechanics. It is further pointed out that none of the practically determined approximations to an inertial frame of reference (e.g., the dynamical reference frame of celestial mechanics, the FK5) must be regarded as adefinition of an inertial system itself.  相似文献   

Methoden zur Lössuntersuchung     

Ekke Guenther 《International Journal of Earth Sciences》1955,43(2):578-578

Ohne Zusammenfassung  相似文献   

Geostatistical seismic Amplitude‐versus‐angle inversion          下载免费PDF全文

Leonardo Azevedo  Rúben Nunes  Amílcar Soares  Guenther Schwedersky Neto  Teresa S. Martins 《Geophysical Prospecting》2018,66(Z1):116-131

Seismic inversion plays an important role in reservoir modelling and characterisation due to its potential for assessing the spatial distribution of the sub‐surface petro‐elastic properties. Seismic amplitude‐versus‐angle inversion methodologies allow to retrieve P‐wave and S‐wave velocities and density individually allowing a better characterisation of existing litho‐fluid facies. We present an iterative geostatistical seismic amplitude‐versus‐angle inversion algorithm that inverts pre‐stack seismic data, sorted by angle gather, directly for: density; P‐wave; and S‐wave velocity models. The proposed iterative geostatistical inverse procedure is based on the use of stochastic sequential simulation and co‐simulation algorithms as the perturbation technique of the model parametre space; and the use of a genetic algorithm as a global optimiser to make the simulated elastic models converge from iteration to iteration. All the elastic models simulated during the iterative procedure honour the marginal prior distributions of P‐wave velocity, S‐wave velocity and density estimated from the available well‐log data, and the corresponding joint distributions between density versus P‐wave velocity and P‐wave versus S‐wave velocity. We successfully tested and implemented the proposed inversion procedure on a pre‐stack synthetic dataset, built from a real reservoir, and on a real pre‐stack seismic dataset acquired over a deep‐water gas reservoir. In both cases the results show a good convergence between real and synthetic seismic and reliable high‐resolution elastic sub‐surface Earth models.  相似文献   

Proper motion and X‐ray selected search for new members of the young TW Hya association     

K. Tachihara  R. Neuhuser  S. Frink  E. Guenther 《Astronomische Nachrichten》2003,324(6):543-551

We have searched for new members of the TWHya association (TWA) among unidentified ROSAT X‐ray sources by identifying them in proper motion catalogues and selecting those that would be consistent with kinematical membership to the TWA. Spectroscopic follow‐up observations of 19 member candidates revealed the detection of moderate lithium absorption lines for the following three stars: GSC 7206 845, TYC 7216‐55, and TYC 7247‐12. The isochronal ages of the latter TYC stars are estimated to be ∼20 Myr while the other one has ∼100 Myr age based on a kinematic distance estimate that assumes TWA membership. However, the moderately Li‐rich stars are not likely to be new pre‐main sequence members of TWA partly because of the discrepant radial velocities. Infrared follow‐up imaging in the H‐band for the 3 stars shows companion candidates near two of them.While one system (TYC 7216‐55) is probably a near‐equal‐magnitude stellar binary, our follow‐up H‐band spectrum of the faint companion candidate near GSC 7206 845 shows that it is instead a background K‐type star rather than a companion. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Correction of the Buckingham–Darcy Law for flow of high strength salts in variably saturated porous media     

Erick R. Burns  Maria I. Dragila  John S. Selker  Ronald B. Guenther  Jean-Yves Parlange  Noam Weisbrod 《Advances in water resources》2007

The Buckingham–Darcy Law is used to describe fluid flow in unsaturated porous media at low Reynolds number. In order to provide a priori corrections to this law, a process thermodynamic approach is utilized to ascertain the functional dependence. Using this knowledge, corrections to the hydraulic conductivity coefficient are proposed and compared with available data. The proposed corrections substantially predict the observed behavior of flow of high concentration (saturated) sodium chloride solutions in porous media. During the derivation, physical principles consistent with the thermodynamics of the system were utilized. A review of these principles and their results provides an alternative form of the generalized Gibbs–Duhem Relation for continuous processes, indicating that the identical equivalence to zero is unlikely to occur for dissipative processes. Further, the postulated Gibbs and Gibbs–Duhem Relations indicate that special differential operators need to be used for continuous processes rather than the usual use of a generic differential.  相似文献