排序方式： 共有38条查询结果，搜索用时 15 毫秒
11.
The method of singular spectral analysis (SSA) is described and used to analyze the series of Wolf numbers that characterizes solar activity from 1748 until 1996. Since this method is relatively new, we detail its algorithm as applied to the data under study. We examine the advantages and disadvantages of the SSA method and the conditions for its applicability to an analysis of the solar-activity data. Certain regularities have been found in the dynamics of this series. Both short and long (80–100-year) periodicities have been revealed in the sunspot dynamics. We predict the solar activity until 2014. 相似文献
12.
The nonlinear frequency shift arising from the interaction of the quasimono- chromatic whistler-mode wave with resonant particles in an inhomogeneous plasma is derived. The modulational instability caused by this shift is investigated. The results are applied to the propagation of long-duration VLF whistler-mode signals along the magnetic field in the magnetosphere. It is shown that the modulational instability of these waves in the equatorial region leads to pulsations very similar to those observed experimentally 相似文献
13.
The magnetic fields of soft gamma-ray repeaters and anomalous X-ray pulsars have been estimated, taking into account the appreciable increase in the deceleration of the neutron star if it is embedded in a dense interstellar medium. These estimates yield the usual values of B?1012 G. 相似文献
14.
This paper contributes to the discussion concerning the way in which Soviet state policies have influenced the lives, social organization, economy and culture of a group of indigenous Komi reindeer herders of northern Russia: its main focus is to explain how these policies have changed the herders' patterns of migration and land use. Extensive anthropological fieldwork—to determine current and past herding practices—was carried out and archives were thoroughly investigated to document land use changes in relation to state reindeer herding policies. It was found that compared with those of several decades ago, the migration routes are now much shorter, as the herders have abandoned large areas of winter pastures located in the southernmost part of their herding territory. This "abandonment" phenomenon is endemic amongst reindeer herders generally, throughout the Komi Republic. Whereas the reasons for the abandonment of winter pastures are diverse, they can be attributed mostly to the state sedentarization policy, which has modified the family structures of herders, and the continuing decreases in state subsidies that have changed the balance between state and private ownership of reindeer. Both these factors have greatly contributed to the herders' dependence on visiting towns, where they now own flats, and on selling reindeer products, upon which they are increasingly reliant for financial security. 相似文献
15.
甘肃阳坝铜多金属矿床流体包裹体及S、Pb同位素组成特征 总被引：1，自引：1，他引：0
甘肃省阳坝铜多金属矿床位于碧口地体的东北部,矿体呈层状、似层状赋存于碧口群阳坝组细碧凝灰岩和凝灰质千枚岩的过渡部位,根据矿床地质特征,将成矿期划分为海底火山喷流沉积期和变质热液叠加改造期。基于对阳坝矿床详细的野外观察和矿相学的研究,通过对矿床流体包裹体和S、Pb同位素的研究,总结矿床的成矿流体性质和成矿物质来源,探讨成矿机制。研究表明,阳坝矿床海底火山喷流沉积期流体包裹体类型主要为水溶液包裹体,成矿流体均一温度为135～336℃,盐度w(NaCl_(eq))为0.70%～10.61%,密度为0.58～0.97g/cm~3;包裹体气相成分以H_2O为主,含少量的CO_2和N_2,属于中低温、低盐度的H_2O-NaCl流体体系,与典型VMS型矿床成矿流体特征相似;变质热液叠加改造期流体包裹体类型主要为水溶液包裹体、CO_2-H_2O包裹体和纯CO_2包裹体,成矿流体均一温度为179～384℃,盐度w(NaCl_(eq))为3.39%～14.78%,密度为0.61～0.99 g/cm~3,包裹体气相成分富含CO_2及少量N_2,属于中高温、低盐度的H_2O-CO_2-NaCl±N_2流体体系,与区域上造山型金矿成矿流体特征一致,均为来自深部的变质流体。喷流沉积期矿石硫化物的δ~(34)S为-7.5‰～3.4‰,均值为-0.46‰,成矿热液δ~(34)S_(∑S)值≈3.73‰,变质热液叠加改造期硫化物的δ~(34)S为-6.7‰～3.3‰,均值-0.575‰,均显示幔源硫的特征。喷流沉积期(~(206)Pb/~(204)Pb=17.505～18.008、~(207)Pb/~(204)Pb=15.521～15.558、~(208)Pb/~(204)Pb=37.494～37.851)与变质热液叠加改造期(~(206)Pb/~(204)Pb=17.293～17.947、~(207)Pb/~(204)Pb=15.498～15.542、~(208)Pb/~(204)Pb=37.388～37.640)的矿石硫化物的Pb同位素组成相近,认为2期矿石铅具有相同来源。通过与阳坝组火山岩、阳坝岩体的Pb同位素组成对比,并结合Pb同位素源区特征值、构造模式图解和△β-△γ成因分类图解分析,认为矿石铅来自上地壳和地幔的混合。阳坝铜多金属矿床属于海底火山喷流沉积-变质热液叠加改造型矿床。 相似文献
16.
Dunite samples from a borehole drilled in the platiniferous concentrically-zoned Kondyor Massif are studied by electron spin
resonance (ESR). The spectrum profiles, relative intensities I, and volume magnetic susceptibilities κ are analyzed. These values experience strong irregular variations, sometimes by an
order of magnitude, in the upper and medium parts of the column, at depths from 100 to 400 m; and the variations decay at
greater depths. The magnetic properties of the samples are determined by iron (II) ions in the olivine lattice and by iron
(III) ions in the magnetite and pyrrhotite microphases and in the products of breakdown of the solid solution: chromiferous
magnetite, chromoferrite, etc. The I and κ values are directly related: κmax = 27.8 × 10−3 SI units, κmin=2.63 × 10−3 SI units, and κmean = 12.7 × 10−3 SI units. The maximum κ values are found in the zones with elevated contents of magnetite and pyrrhotite particles, and the
minimum ones, in zones with few medium and small clusters with Fe3+ ions. The uneven distributions of solid solutions and magnetic phases over depths are suggested to be related to the disturbances
in the conditions of crystallization. 相似文献
17.
The concentration of rock-forming elements, the static magnetic susceptibility κ, spectra of electron paramagnetic resonance, and their relative intensities I are studied in samples from a borehole drilled in Cenozoic sedimentary deposits of southern Western Siberia. All measured values experience appreciable irregular variations with depth. A linear dependence exists between κ and I within the range of their medium and large values; κ and I have maximum values in the same sample, and κmax = 1920 × 10?6SI, κmin = 210 × 10?6 SI, and κav = 630 × 10?6 SI. The magnetic properties of the samples are controlled by Fe2+ ions present in clastic material and by microphases (clusters) with Fe3+ ions of the goethite and lepidocrocite type present in the cement. The theoretically possible magnetic susceptibility of the Fe2+ ion system (provided that all iron exists in this form) is quite comparable with κmin but, even with very high concentrations of Fe2+, does not reach half of κav: (154 < κ(Fe2+) < 254) × 10?6 SI. Anomalously high values of κ are due to a large number of clusters with Fe3+ ions if structural units FeOOH do not dissociate and the interaction of the clusters with hydroxides of aluminum and precipitation medium impedes the process of their coagulation. Otherwise, the cluster sizes gradually increase, an antiferromagnetic structure develops in clusters, and the magnetic susceptibility decreases. 相似文献
18.
We formulate the fundamentals of the geothermal method for determining the hydrate saturation of bottom sediments. According to laboratory experiments (A.A. Trofimuk Institute of Petroleum Geology and Geophysics, A.V. Nikolaev Institute of Inorganic Chemistry), detecting gas hydrates in bottom sediments requires measurement of thermal conductivity at least twice at one bottom site, using a cylindrical probe with different heater power values. Changing the latter permits controlling gas hydrate stability and instability. A low-power probe does not destroy gas hydrates and permits measuring the true thermal conductivity of the sediments. Increasing heater power destroys gas hydrates near the probe and drastically increases effective thermal conductivity. Comparison between true and effective thermal conductivity clearly shows the presence of gas hydrates in the sample or their absence from it. A technique was proposed for the quantitative interpretation of changes in the temperature field of a cylindrical probe. It permits quite a precise determination of the mass of gas hydrate that decomposed in the layer surrounding the probe over a certain period. Also, it permits a rough estimation of the gas hydrate content of the sediments. Thermal conductivity can be measured in the field with submersible multichannel thermoprobes, which are commonly used for studying the heat flow through the bottom of water basins. Now it is important to perform field experiments, so that we gain the necessary experience with the geothermal method. 相似文献
19.
20.
An exact solution is found for the interaction of a rotating magnetic field that is frozen into a star with a thin, highly conducting accretion disk. The disk pushes the magnetic-field lines towards the star, compressing the stellar dipole magnetic field. At the corotation radius, where the Keplerian and stellar rotational frequencies are equal, a current loop appears. Electric currents flow in the magnetosphere only along two particular magnetic surfaces, which connect the corotation region and the inner edge of the disk with the stellar surface. It is shown that a closed current surface encloses the magnetosphere. The disk rotation is stopped at some distance from the stellar surface, equal to 0.55 of the corotation radius. The accretion from the disk spins up the stellar rotation. The angular momentum transferred to the star is determined. 相似文献