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1.
The system damping, the system frequency, the relative building response and the base rocking response peak amplitudes are studied, as those depend on the building mass and height, the flexibility of the soil, the structural damping, the type of incident waves and their angle of incidence. A linear two-dimensional model is used, which assumes the soil to be a homogeneous isotropic half-space, the foundation supporting the building to be a rigid embedded cylinder, and in which the building model is an equivalent single-degree-of-freedom oscillator. The system frequency and the system damping ratio are determined by measuring the width and the frequency of the peak in the transfer function of the oscillator relative response, using the analogy with the half-power method for a single-degree-of-freedom fixed-base oscillator. Previous similar studies are for dynamic soil-structure interaction only, and for simplified models in which the stiffness of the soil and the damping due to radiation are represented by springs and dashpots. The study in this paper differs from the previous studies in that the wave passage effects (or the kinematic interaction) are also included, and that no additional simplifications of the model are made. Results are shown for excitation by plane P- and SV-waves. 相似文献
2.
L21雷电预警系统在呼和浩特基准地震台防雷击试运行发现,雷电到来发出预警并自动切换电源,对前兆设备防雷击起到关键作用,为替代人工断电措施提供安全保障,保证观测记录的正常运行。 相似文献
3.
A. A. Namgaladze Yu. N. Korenkov V. V. Klimenko I. V. Karpov F. S. Bessarab V. A. Surotkin T. A. Glushchenko N. M. Naumova 《Pure and Applied Geophysics》1988,127(2-3):219-254
In this paper the formulation of the problem and preliminary numerical computation results of the thermosphere-ionosphere-protonosphere system parameters are discussed.The model constructed describes time-dependent distributions of the multicomponent near-earth space plasma parameters by means of numerical integration of the appropriate three-dimensional plasma hydrodynamic equations. In the thermospheric block of the model, global distribution of neutral gas temperature and N2, O2, O concentrations, as well as three-dimensional circulation of the neutral gas are calculated in the range of height from 80 km to 520 km. In the ionospheric section of the model, global time-dependent distribution of ion and electron temperatures, as well as molecular and atomic O+, H+ ion concentrations are calculated. Global two-dimensional distribution of electric potential is calculated taking into account computed thermosphere and ionosphere parameters.The inputs needed for our global model are the solar EUV spectrum; the auroral precipitation pattern; the distribution of the field-aligned currents and the model of the geomagnetic field.Preliminary results are obtained without regard to electromagnetic plasma drift for the solar minimum, low geomagnetic activity and spring equinox conditions. Global distributions of the calculated parameters in the magnetic dipole latitude-longitude frame are presented for 1200 UT. In the summary ignored processes and future direction are discussed. 相似文献
4.
《Astronomy& Geophysics》2009,50(2):2.31-2.35
Sarah Matthews, Danielle Bewsher and Chris Davis discuss the complexities of the solar magnetic field, informed by data from Hinode and STEREO. 相似文献
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Grain growth experiments in dunite, clinopyroxenite, and wehrlites with various forsterite/diopside ratios were performed to investigate the effect of modal composition on grain growth kinetics in the Earth's uppermost mantle. The experiments were conducted using a piston-cylinder apparatus at 1200 °C and 1.2 GPa for 2-763 h under dry conditions. Normal grain growth (NGG) occurred in dunite, clinopyroxenite, and relatively forsterite-poor wehrlites (≤70 vol.% of forsterite). Grain growth rates of forsterite and diopside in relatively forsterite-poor wehrlites were much slower than those in dunite and clinopyroxenite. In the forsterite-rich wehrlites (≥80 vol.% of forsterite), NGG of diopside and abnormal grain growth (AGG) of forsterite occurred. The growth rate of diopside was significantly slower than that in clinopyroxenite, while the growth rate of forsterite by AGG was found to be similar to that by NGG in dunite. The presence of ≤20 vol.% diopside had the effect of inhibiting the forsterite grain growth during the initial stage, resulting in AGG of forsterite, thus overtaking the growth rate in dunite. Our experimental results suggest that there would be a significant difference in grain growth rate and consequently in effective viscosity between olivine-rich peridotites (depleted mantle) and relatively olivine-poor peridotites (fertile mantle) in the case of grain size-sensitive creep. Variation of mean grain sizes in the upper mantle would result not only from differences in temperature and phase assemblage, but also from the variation of modal compositions. 相似文献
7.
The coupled upper atmospheres, ionospheres and magnetospheres of the planets were the subject of a joint RAS–G/MIST discussion meeting hosted by the RAS on 10 January 2003, organized by Ingo Mueller-Wodarg and Emma Bunce . The scientific programme consisted of 10 presentations by speakers from the UK, France, USA and Australia. 相似文献
8.
《Astronomy& Geophysics》2009,50(2):2.17-2.19
Guillermo Gonzalez notes another astronomical reason why IYA2009 is special: mutual eclipse seasons at Jupiter, Saturn and Uranus. 相似文献
9.
Summary The tidal decrease in the Earth's heliocentric longitude generated by the Sun has been computed. It represents the increase in the length of year10–7 s per century. The resonant angular velocity of the Earth's rotation is approximately equal to the present Earth's mean motion, however, for the model used, i.e., considering the Sun as the point-mass.
u u zumu ¶rt;m u, a nuuau m a. ¶rt; mmmm uu ¶rt;u z¶rt;a10–7 a mmu. a za m au u nu aa ¶rt; ¶rt;uu u, u, ¶rt;a, umam ¶rt;a ¶rt;u m a.相似文献
10.
Milan Burša 《Studia Geophysica et Geodaetica》1995,39(1):1-10
Summary The positions of the Lagrangian points of the Pluto-Charon system have been determined using the orthogonal system of cofocal ellipses-hyperbolas, the foci being situated at the centre of mass of the bodies. The tidal distortions of Pluto amount to 30 m, those of charon to 122 m. The tidal forces are believed to influence the figures of the bodies significantly. 相似文献
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A model of the carbon dioxide system in nature is derived and is used to further our understanding of the factors which control
this system in the oceans, the atmosphere, and the sediments. 相似文献
13.
Wm. Markowitz 《Surveys in Geophysics》1973,1(2):217-241
Two types of systems of units have been formed. The commercial is a system of weights and measures, such as the metric, defined by civil law. The scientific is a system of physical units generated through use of scientific laws which link corresponding quantities.The International System of units, denoted SI, was established in 1960 by the General Conference of Weights and Measures. The set of SI units included therein is the only comprehensive, coherent system of physical units. There is only one SI unit, whose value is unambiguous, for each physical quantity. Included in the SI, but not in any CGS system, are the volt, ampere, ohm, and watt, which are the only units used for measurement of the corresponding electrical quantities. Also included in the SI are prefixes used to form non-coherent, decimal multiples and sub-multiples of SI units. A few other units, such as the day, degree of arc, and degree Celsius may be used with SI units. Precepts for use of the SI, conversion tables, and geophysical constants expressed in SI units are given.Abbreviations BA
British Association for the Advancement of Science
- BIPM
Bureau Interntional des Poids et Mesures (International Bureau of Weights and Measures)
- CIPM
Comité International des Poids et Mesures (International Committee of Weights and Measures)
- CGPM
Conférence Générale des Poids et Mesures (General Conference of Weights and Measures)
- emf
electromotive force
- emu
electromagnetic unit
- esu
electrostatic unit
- G-W
Gauss-Weber
- IEC
International Electrotechnical Commission
- PE
practical electrical
- SI
Système International d'Unités (International System of Units) 相似文献
14.
Francis Graham-Smith and Maura Ann McLaughlin describe the interactions in the first double-pulsar system, which produce a comet-shaped magnetosphere with remarkable similarities to that surrounding the Earth. 相似文献
15.
R. J. Stening 《Annales Geophysicae》1995,13(6):627-632
The strength of the Sq current system is measured by taking the difference between magnetic variations on either side of the current system focus. This is carried out for several longitude sectors. A distinct semiannual variation is sometimes found but its incidence varies with longitude, local time and hemisphere. Other semiannual effects in the ionosphere are reviewed and the possibility of a diurnal modulation of the strength of the 12-h tide is suggested. 相似文献
16.
Keisuke Ito 《Earth and Planetary Science Letters》1980,51(2):451-456
The chaotic dynamics of the Rikitake two-disc dynamo system is studied for a wide range of parameters and results are compared with the sequence of geomagnetic polarity reversals. The chaos of the Rikitake system belongs to the Lorenz type, which is characterized by irregular travelling of an orbit between two unstable fixed points. Travelling corresponds to the polarity reversal. The frequency of the polarity reversals depends strongly on the parameter μ representing the resistive dissipation in the core. In the center of the chaotic regime, there is a parameter region in which reversals seldom occur and the dynamics is less disordered. The Markov entropy of the Lorenz map for the system has a sharp minimum in this parameter region named as the minimum entropy regime (M.E.R.). The average frequency of reversals in the M.E.R. is less than 0.1 per cycle of oscillation, but is not uniform even seen through a 10-m.y.-long window. The non-uniformity as well as the low rate of reversals in the M.E.R. markedly resemble the behavior of geomagnetic reversals over the past 153 m.y. It is suggested that the Earth selected the minimum entropy regime on the principle of the minimum entropy production, as is known to be the case for other dissipative dynamical systems. 相似文献
17.
This article demonstrates how system identification techniques can be successfully applied to a soil-structure interaction system in conjunction with the results of the forced vibration tests on the Hualien large-scale seismic test structure which was recently built in Taiwan for an international joint research. The parameters identified are the shear moduli of several near-field soil regions as well as Young's moduli of the shell sections of the structure. The soil-structure interaction system is represented by the finite element method combined with infinite element formulation for the unbounded layered soil medium. Preliminary investigations are carried out on the results of the static stress analysis for the soil medium and the results of the in-situ tests to divide the soil-structure system into several regions with homogeneous properties and to determine the lower and upper bounds of the parameters for the purpose of identification. Then two sets of parameters are identified for two principal directions based on the forced vibration test data by minimizing the estimation error using the constrained steepest descent method. The simulated responses for the forced vibration tests using the identified parameters show excellent agreement with the test data. The present estimated parameters are also found to be well compared with the average value of those by other researchers in the joint project. 相似文献
18.
S.K. Runcorn 《Physics of the Earth and Planetary Interiors》1979,20(1):p1-p5
The dependence of the number of days in the synodical month on the Earth-Moon distance is determined from dynamics, and its application to the discussion of palaeontological growth lines is illustrated. 相似文献
19.
本文主要介绍了一套分布式光纤振动传感系统中的数据采集及信号处理系统,该系统设计采用高性能的运算放大电路完成光电信号调理,以高精度差动模数转换器AD9246完成模数转换工作,并选用高性能FPGA作为核心逻辑控制器,并以低功耗的OMAP-L137作为CPU负责振动数据计算、网络通讯等工作,从而使该-OTDR分布式光纤振动传感系统测量范围扩展到25 km范围。本文通过计算相邻测点振动增量方法检测是否发生了振动入侵,提高了分布式光纤振动入侵检测的灵敏度。该设计方法提高分布式光纤振动传感系统的信噪比,使得该系统振动检测灵敏度提高、抗干扰能力增强,因此该分布式光纤振动传感系统可以用于实际工程的振动监控。 相似文献
20.
True polar wander(TPW), or planetary reorientation, is the rotation of solid Earth(crust and mantle) about the liquid outer core in order to stabilize Earth’s rotation due to mass redistribution. Although TPW is well-documented on Earth presently with satellites and for multiple planets and moons in the Solar System, the prevalence of TPW in Earth history remains contentious. Despite a history of controversy, both the physical plausibility of TPWon Earth and an empirical basis for it are now und... 相似文献