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961.
应用自适应算法对BP网络进行改进,可以提高BP网络的收敛速度和全局寻优性能。在此基础上,利用多种测井数据及岩心描述资料作为网络模型的学习样本,以测井解释渗透率的神经网络模型为例,通过网络的学习、训练,建立测井解释神经网络模型。并应用此模型,定量计算出多口井的渗透率值,与常规渗透率计算结果相比,BP的解释结果及精度均令人满意,同时还取得了良好的实际应用效果。 相似文献
962.
963.
It is shown that siderite is unstable during sedimentation, diagenesis, and metamorphism of sedimentary and volcanosedimentary rocks. Regularities in the distribution of siderite in Precambrian jaspilites (iron formations), metasomatic ores of the Bakal type, continental–marine coaliferous formations, and oolitic iron ores are discussed. The genesis of the Precambrian iron formations and Riphean–Lower Paleozoic elisional–hydrothermal deposits is considered. The genetic relation of nodular siderites from coaliferous formations and oolitic iron ores with lowmoor coal-forming peat deposits is noted. 相似文献
964.
A. B. Pushkarev Yu. Yu. Kovalev I. E. Molotov M. B. Nechaeva Yu. N. Gorshenkov G. Tuccari C. Stanghellini X. Hong J. Quick S. Dougherty X. Liu 《Astronomy Reports》2004,48(11):900-908
VLBI observations of several quasars and BL Lacertae objects were carried out at 1.66 GHz in November–December 1999 using six antennas (Medvezh'i Ozera, Svetloe, Pushchino, Noto, HartRAO, and Shanghai). Maps of six sources (0420+022, 0420-014, 1308+326, 1345+125, 1803+784, and DA 193) obtained with milliarcsecond resolution are presented and discussed, together with their broad-band (1–22 GHz) spectra obtained on the RATAN-600 radio telescope at epochs close to those of the VLBI observations. Comparison of the VLBI maps with maps of these sources obtained on standard VLBI networks and with the RATAN-600 quasisimultaneous total-flux measurements indicates the reliability of the results obtained on this Low Frequency VLBI Network and the good efficiency of this network. 相似文献
965.
The paper presents the first quantitative results of a laboratory study of the velocity field in a two-arm spiral-wave pattern generated in a steady-state fashion by a hydrodynamical instability in a differentially rotating, thin layer of liquid. The liquid layer has a free surface, and the rotational profile includes an interval where the velocity drops abruptly, as in the gaseous disks of spiral galaxies. The properties of anticyclonic vortices observed between the arms of this pattern at the corotation radius are considered. 相似文献
966.
Variations in the positions of the intersection points of tangents to ray structures in the polar corona of the Sun during the solar cycle are considered. At first glance, the decrease in the distance q between the tangent intersection point and the center of the solar disk during activity maximum contradicts harmonic analyses that indicate that the relative weight of higher harmonics in the global field increases during this period. Indeed, the higher the harmonic number in an axisymmetric field, the closer the intersection point of the field-line tangents (the magnetic focus) to the solar surface. It is shown that q for a field composed of two harmonics with opposite polarities at the poles can be smaller than q for either of them taken alone. A simple model representing the global field using the third and seventh harmonics is analyzed; this model can reproduce quite satisfactorily the observed dynamics of magnetic foci of the polar field. 相似文献
967.
An analysis of the flux densities of the 51-60 A + (6.7 GHz) and 20-3?1 E (12.2 GHz) class II methanol maser lines in a large and homogeneous sample of maser sources has been carried out. For convenience, the maser lines were divided into three groups: group I contains spectral features for the lines most prominent in the 51-60 A + (6.7 GHz) transition, group II contains spectral features for the lines strongest in the 20-3?1 E (12.2 GHz) transition, group III contains spectral features for which the velocities of the emission maxima of the two lines coincide. The same dependence was found for group II and group III: log S 6.7=(0.79±0.05)×log S 12.2+(0.79±0.05). The spectral features in group I do not obey this relation, and deviations from a linear dependence are considerably greater. It is suggested that methanol class II masers be divided into a subclass IIa, which has special conditions favoring 6.7 GHz masers, and a subclass IIb, which is comprised of the 12.2 GHz masers and those 6.7 GHz masers that necessarily accompany them under the same conditions. 相似文献
968.
A.Yu. Likhacheva S. A. Veniaminov E. A. Paukshtis 《Physics and Chemistry of Minerals》2004,31(5):306-312
The thermal decomposition of ammonium-exchanged natural analcime is characterized by gas chromatography, IR spectroscopy and X-ray diffraction. The de-ammoniation and dehydroxylation proceed in parallel throughout the decomposition, which evidences the instability of the protonated analcime framework. The mechanism of degassing of NH4-analcime changes throughout its decomposition. At the initial step, the mechanism of de-ammoniation consists in thermal dissociation of NH4+ molecule onto NH3 and proton (framework OH group) and diffusion of NH3 out of the structure. Subsequent decomposition and removal of the OH groups lead to a progressive loss of crystallinity. At this step, an apparent activation energy for NH3 desorption is estimated to be 145(±13) kJ mol–1. This value is within the upper limit of the activation energy characteristic for the NH3 desorption from proton centres in large-pore zeolites. At the final step, the adsorption of NH3 and protons onto the defect centres in the amorphosed aluminosilicate framework results in a significant increase of an apparent activation energy for the de-ammoniation and dehydroxylation up to 270(±20) kJ mol–1. 相似文献
969.
Lithology and Mineral Resources - 相似文献
970.
Particles in shear enclose important information about a rock's past and can potentially be used to decipher the kinematic history and mechanical behavior of a certain outcrop or region. Isolated rigid clasts in shear zones often exhibit systematic inclinations with respect to the shear-plane at small angles, tending towards the instantaneous stretching direction of the shear zone. This shape preferred orientation cannot be easily explained by any of the analytical theories used in geology. It was recently recognized that a weak mantle surrounding the clast or a slipping clast–matrix interface might be responsible for the development of the observed inclinations. Physical considerations lead us to conjecture that such mantled, rigid clasts can be effectively treated as voids that are not allowed to change their shape. The resulting equivalent void conjecture agrees well with numerical and field data and has the following important geological implications. (i) Clasts in shear zones can have stable positions in simple shear without the requirement of an additional pure shear component. (ii) The stable orientation can be approached either syn- or antithetically; hence, the clast can rotate against the applied shear sense. (iii) The strain needed to develop a strong shape preferred orientation is small (γ≈1) and therefore evaluations based on other theories may overestimate strain by orders of magnitude. (iv) The reconstruction of far-field shear flow conditions and kinematic vorticity analysis must be modified to incorporate these new findings. 相似文献