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11.
The response of deformable fractures to changes in fluid pressure controls phenomena ranging from the flow of fluids near wells to the propagation of hydraulic fractures. We developed an analysis designed to simulate fluid flows in the vicinity of asperity‐supported fractures at rest, or fully open fractures that might be propagating. Transitions between at‐rest and propagating fractures can also be simulated. This is accomplished by defining contact aperture as the aperture when asperities on a closing fracture first make contact. Locations on a fracture where the aperture is less than the contact aperture are loaded by both fluid pressure and effective stress, whereas locations where the aperture exceeds the contact aperture are loaded only by fluid pressure. Fluid pressure and effective stress on the fracture are determined as functions of time by solving equations of continuity in the fracture and matrix, and by matching the global displacements of the fracture walls to the local deformation of asperities. The resulting analysis is implemented in a numerical code that can simulate well tests or hydraulic fracturing operations. Aperture changes during hydraulic well tests can be measured in the field, and the results predicted using this analysis are similar to field observations. The hydraulic fracturing process can be simulated from the inflation of a pre‐existing crack, to the propagation of a fracture, and the closure of the fracture to rest on asperities or proppant. Two‐dimensional, multi‐phase fluid flow in the matrix is included to provide details that are obscured by simplifications of the leakoff process (Carter‐type assumptions) used in many hydraulic fracture models. Execution times are relatively short, so it is practical to implement this code with parameter estimation algorithms to facilitate interpretation of field data. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
12.
Zamana Leonid Vasilevich 《中国地理科学(英文版)》1995,5(2):185-192
POSSIBLEHYDROGEOCHEMICALPRECONDITIONSFORKASHIN-BECKDISEASEINTRANSBAIKALIA¥ZamanaLeonidVasilevich(ChitaInstituteofNaturalResou... 相似文献
13.
Leonid S. Pilyugin Trinh X. Thuan José M. Vílchez 《Monthly notices of the Royal Astronomical Society》2007,376(1):353-360
We search for the maximum oxygen abundance in spiral galaxies. Because this maximum value is expected to occur in the centres of the most luminous galaxies, we have constructed the luminosity – central metallicity diagram for spiral galaxies, based on a large compilation of existing data on oxygen abundances of H ii regions in spiral galaxies. We found that this diagram shows a plateau at high luminosities (−22.3 ≲ M B ≲−20.3) , with a constant maximum value of the gas-phase oxygen abundance 12 + log (O/H) ∼ 8.87 . This provides strong evidence that the oxygen abundance in the centres of the most luminous metal-rich galaxies reaches the maximum attainable value of oxygen abundance. Since some fraction of the oxygen (about 0.08 dex) is expected to be locked into dust grains, the maximum value of the true gas + dust oxygen abundance in spiral galaxies is 12 + log(O/H) ∼ 8.95. This value is a factor of ∼2 higher than the recently estimated solar value. Based on the derived maximum oxygen abundance in galaxies, we found the oxygen yield to be about 0.0035, depending on the fraction of oxygen incorporated into dust grains. 相似文献
14.
Two-integral distribution functions for axisymmetric stellar systems with separable densities 总被引:1,自引:0,他引:1
Zhenglu Jiang Leonid Ossipkov 《Monthly notices of the Royal Astronomical Society》2007,382(4):1971-1981
We show different expressions of distribution functions (DFs) which depend only on the two classical integrals of the energy and the magnitude of the angular momentum with respect to the axis of symmetry for stellar systems with known axisymmetric densities. The density of the system is required to be a product of functions separable in the potential and the radial coordinates, where the functions of the radial coordinate are powers of a sum of a square of the radial coordinate and its unit scale. The even part of the two-integral DF corresponding to this type of density is in turn a sum or an infinite series of products of functions of the energy and of the magnitude of the angular momentum about the axis of symmetry. A similar expression of its odd part can be also obtained under the assumption of the rotation laws. It can be further shown that these expressions are in fact equivalent to those obtained by using Hunter & Qian's contour integral formulae for the system. This method is generally computationally preferable to the contour integral method. Two examples are given to obtain the even and odd parts of their two-integral DFs. One is for the prolate Jaffe model and the other for the prolate Plummer model.
It can be also found that the Hunter–Qian contour integral formulae of the two-integral even DF for axisymmetric systems can be recovered by use of the Laplace–Mellin integral transformation originally developed by Dejonghe. 相似文献
It can be also found that the Hunter–Qian contour integral formulae of the two-integral even DF for axisymmetric systems can be recovered by use of the Laplace–Mellin integral transformation originally developed by Dejonghe. 相似文献
15.
Leonid Pilyugin 《Astrophysics and Space Science》2003,284(2):775-778
Spiral galaxies with a reported bend in the slope of the oxygen abundance O/HR
23, derived with the traditionally used R23-method, are examined. It is shown that the artificial origin of the reported bends can be naturally explained. Two causes
of the false bend in the slope of O/HR
23 are indicated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
Jürgen Oberst Valéry Lainey Christophe Le Poncin-Lafitte Veronique Dehant Pascal Rosenblatt Stephan Ulamec Jens Biele J?rn Spurmann Ralph Kahle Volker Klein Ulrich Schreiber Anja Schlicht Nicolas Rambaux Philippe Laurent Beno?t Noyelles Bernard Foulon Alexander Zakharov Leonid Gurvits Denis Uchaev Scott Murchie Cheryl Reed Slava G. Turyshev Jesus Gil Mariella Graziano Konrad Willner Kai Wickhusen Andreas Pasewaldt Marita W?hlisch Harald Hoffmann 《Experimental Astronomy》2012,34(2):243-271
GETEMME (Gravity, Einstein??s Theory, and Exploration of the Martian Moons?? Environment), a mission which is being proposed in ESA??s Cosmic Vision program, shall be launched for Mars on a Soyuz Fregat in 2020. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive Laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine Laser range measurements to the reflectors on Phobos and Deimos. Also, asynchronous two-way Laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellite system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter ?? as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame. 相似文献
17.
Leonid S. Egorov 《Lithos》1970,3(4):341-359
The structural position, geology, petrography, petrochemistry, and petrogenesis of one of the world's greatest carbonatite provinces situated in North Siberia are recorded. Three groups of Late Permian-Early Triassic magmatites are briefly discussed: effusives, dikes, and intrusives of complex central type. Carbonatite and congenetic rocks are related to kimberlites, but are genetically unrelated to tholeiitic basalts and trachybasalts. The genetic development and diagnostic features of ultrabasic-alkaline rocks and carbonatites are formulated. 相似文献
18.
We present sub-bottom profiling (sparker and Parasound) results from the eastern Kara Sea, on the Eurasian Arctic margin, which enable the identification of the Last Glacial Maximum (LGM) ice extent. The analysed profiles show that glacigenic diamicton is ubiquitous at the seafloor, east of about 95°E and 78°N. The eastern margin of this diamicton is expressed in a conspicuous morainic ridge at the entrance to the Vilkitsky Strait, and to the south the diamicton projection aligns with the LGM limit mapped at the north-western Taymyr. The bottom of the Voronin Trough further north is also covered with diamicton and has numerous erosional bedforms, indicating a streamlined flow of grounded ice along the trough. Accurate dating of the diamicton is not attainable, but the correlation of pre-diamict sediments to well-dated sections in the Laptev Sea, and available 14 C ages from sediments on top of the diamicton, indicate its LGM age. These results support the palaeogeographic reconstruction that assumes the extension of the LGM Barents–Kara ice sheet as far east as Taymyr. This configuration implies that LGM ice blocked the drainage of the Ob and Yenisey rivers on the Kara shelf. This inference is consistent with the presence of large (>100 km wide) lenses of basin infill adjacent to the southern margin of the diamicton. However, the limited distribution of the eastern Kara ice lobe, not extending on Severnaya Zemlya, suggests that the ice was fairly thin and short-lived: insufficient for the accumulation of the gigantic proglacial lakes that occurred during earlier glaciations. 相似文献
19.
20.
Viability of pyrite pulled metabolism in the ‘iron-sulfur world’ theory: Quantum chemical assessment
Andrea Michalkova Dmytro Kosenkov Leonid Gorb Jerzy Leszczynski 《Geochimica et cosmochimica acta》2011,75(7):1933-1941
The viability of pyrite-pulled metabolism in the ‘iron-sulfur world’ theory was assessed using a simple model of iron-nickel sulfide (Fe-Ni-S) surface and data obtained from quantum chemical calculations. We have investigated how the individual reactions in the carbon fixation cycle (carboxylic acids formation) on an Fe-Ni-S surface could have operated to produce carboxylic acids from carbon oxide and water. The proposed model cycle reveals how the individual reactions might have functioned and provides the thermodynamics of each step of the proposed pathway. The feasibility of individual reactions, as well the whole cycle was considered. The reaction of acetic acid production from CH3SH and CO on an Fe-Ni sulfide surface was revealed to be endergonic with a few partial steps having positive Gibbs free energy. On the other hand, the pyrite formation was found to be slightly exergonic. The significance of the catalytic activity of transition metal sulfides in generation of acetic acid was shown. The Gibbs free energy values indicate that the acetic acid synthesis is unfavorable to proceed on the studied Fe-Ni-S model under simulated conditions. The importance of these results in terms of a primordial chemistry on iron-nickel sulfide surfaces is discussed. 相似文献