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1.
We have developed a method for analytically solving the porous medium flow equation in many different geometries for horizontal (two‐dimensional), homogeneous and isotropic aquifers containing impermeable boundaries and any number of pumping or injection wells located at arbitrary positions within the system. Solutions and results are presented for rectangular and circular aquifers but the method presented here is easily extendible to many geometries. Results are also presented for systems where constant head boundary conditions can be emulated internal to the aquifer boundary. Recommendations for extensions of the present work are briefly discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Martin M. Roth Thomas Fechner Dieter Wolter Andreas Kelz Thomas Becker 《Experimental Astronomy》2002,14(2):99-105
PMAS, the Potsdam Multi-Aperture Spectrophotometer, is a new integral field spectrograph in the optical, which is optimized
for good transmission and high image quality from 350 nm to 1 μm. We present our plan to implement a CCD charge-shuffle mode
to allow for beam switching with a very high degree of sky subtraction accuracy for faint object 3-D spectroscopy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Lightning discharge generated in the protoplanetary nebula is viewed as a temporally isolated surge in the flow of electrically charged particles, similar to that of terrestrial lightning. If the current is intense enough, a powerful circular impulse magnetic field is generated around the instantaneous virtual electric conductor. Such magnetic field is capable of magnetizing dust grains containing ferromagnetic components present in its vicinity to their saturation levels. As a result, dust grains attract one another, forming the aggregates. This magnetically driven attraction suggests an important process possibly operational at an early stage of the planetary accretion. Based on both a classical model for electric conductor, and the theory of Lienard–Wiechert electromagnetic potentials, our calculations show that the magnetic impulse due to a discharge channel of a few cm in diameter transferring a charge of about 104 electrons reaches as high as 10 T. At these magnetic fields, the ferromagnetic dust grains, and possibly the already-formed larger aggregates as well, are easily magnetized to the saturation levels, producing compact clusters exhibiting permanent magnetic moments. 相似文献
4.
The cumulative probability distributions for stream order, stream length, contributing area, and energy dissipation per unit length of channel are derived, for an ordered drainage system, from Horton's laws of network composition. It is shown how these distributions can be related to the fractal nature of single rivers and river networks. Finally, it is shown that the structure proposed here for these probability distributions is able to fit the observed frequency distributions, and their deviations from straight lines in a log-log plot. 相似文献
5.
Ernst A. Roth 《Celestial Mechanics and Dynamical Astronomy》1981,23(1):83-87
In this note a simple formula is given for the perturbation of the anomalistic period of a highly eccentric orbit due to the zonal harmonics. This perturbation depends essentially only on the semi-major axisa, the eccentricitye (or pericentre radius r =a(1-e)) and the latitude of the pericentre. 相似文献
6.
Compositional variation in Hg-bearing sphalerite from the polymetallic Eskay Creek deposit, British Columbia, Canada 总被引:1,自引:0,他引:1
Tassos A. Grammatikopoulos Oleg Valeyev Tina Roth 《Chemie der Erde / Geochemistry》2006,66(4):307-314
The Eskay Creek, British Columbia, Canada, is a polymetallic, gold- and silver-rich, volcanic-hosted, massive sulfide deposit. The ore in the deposit is divided into subzones distinguished by mineralogy, texture, grade and metallurgical characteristics. This study presents the results of a mineralogical examination of three composite field samples, with emphasis on the chemistry of sphalerite. Sphalerite is associated with variable amounts of Hg-tetrahedrite and cinnabar, and an array of sulfides, sulphosalts and non-opaque minerals. Electron micro probe analyses of sphalerite in the three composite samples reveal wide variations in compositions. The Hg content in sphalerite in the three samples varies between 0.08 and 16.35 wt%, whereas the Fe content ranges from 0.33 to 2.29 wt%. The chemical formula of the sphalerite shows the compositional range (Zn0.89–0.98Hg0.01–0.09.Fe0.005–0.02)S. Sphalerite exhibits an almost perfect substitution of Hg and Zn, as shown by the negative covariance between them. Sphalerite with the highest Hg contents tends to have the lowest Fe concentrations. The highest Hg contents in sphalerite are recorded in the samples with the highest bulk Hg concentrations and with the highest cinnabar contents.
The compositional variations of sphalerite are important because they can be used in mapping ore forming fluids and indicate possible temporal variations. Second, determination of the compositional variation of the sphalerite in the mine has metallurgical implications because the mineral is an important Zn source. The mineralogical data indicate that non-physical processes (e.g. pyrometallurgy) must be used to separate Hg from Zn concentrates, with direct environmental implications, that is, release of metals, such as Hg, into the environment during mining and processing. 相似文献
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