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121.
We investigate the time dynamics of monthly rainfall series intermittently recorded on seven climatic stations in northern Lebanon from 1939 to 2010 using the detrending fluctuation analysis (DFA) and the Fisher-Shannon (FS) method. The DFA is employed to study the scaling properties of the series, while the FS method to analyze their order/organization structure. The obtained results indicate that most all the stations show a significant persistent behavior, suggesting that the dynamics of the rainfall series is governed by positive feedback mechanisms. Furthermore, we found that the Fisher Information Measure (the Shannon entropy power) seems to decrease (increase) with the height of the rain gauge; this indicates that the rainfall series appear less organized and less regular for higher-located stations. Such findings could be useful for a better comprehension of the climatic regimes governing northern Lebanon. 相似文献
122.
It is shown that a strongly magnetized isothermal pair plasma near the surface of a pulsar supports low-frequency (in comparison
to electron cyclotron frequency) toroidal electrostatic plasma modes in the equatorial region. Physically, the thermal pressure
coupled with the magnetic pressure creates the low frequency oscillations which may grow for particular case of inhomogeneities
of the equilibrium magnetic field and the pair plasma density. 相似文献
123.
124.
Moment tensor inversion of nine events in Iran using INSN data 总被引:1,自引:0,他引:1
Aref Bali Lashak Mehdi Zare Gholamreza Mortezanejad Shahrokh Pour Beyranvand 《Journal of Seismology》2010,14(4):751-760
In this research, moment tensor (MT) inversion procedure in frequency domain is applied to nine events in order to evaluate
the data efficiencies in computing source parameters of earthquakes in Iran. The events are recorded by Iranian National Seismological
Network (INSN) stations, currently comprising 22 broadband stations. For the purpose of this study, first, the inversion procedure
is applied to obtain source parameters. Then, the results obtained here are compared with those of Harvard global centroid
moment tensors (GCMT) in order to estimate their reliabilities. The results show reasonable consistencies with those of Harvard
GCMT within 0.075 uncertainties in logarithmic scalar moment or 0.05 in moment magnitude and 20° in Kagan angle for focal
angles. Furthermore, according to the present research, the calculated source parameters are not significantly sensitive to
the azimuthal gap. 相似文献
125.
Adaptive multi‐rate interface: development and experimental verification for real‐time hybrid simulation 下载免费PDF全文
Amin Maghareh Jacob P. Waldbjørn Shirley J. Dyke Arun Prakash Ali I. Ozdagli 《地震工程与结构动力学》2016,45(9):1411-1425
Real‐time hybrid simulation (RTHS) is a powerful cyber‐physical technique that is a relatively cost‐effective method to perform global/local system evaluation of structural systems. A major factor that determines the ability of an RTHS to represent true system‐level behavior is the fidelity of the numerical substructure. While the use of higher‐order models increases fidelity of the simulation, it also increases the demand for computational resources. Because RTHS is executed at real‐time, in a conventional RTHS configuration, this increase in computational resources may limit the achievable sampling frequencies and/or introduce delays that can degrade its stability and performance. In this study, the Adaptive Multi‐rate Interface rate‐transitioning and compensation technique is developed to enable the use of more complex numerical models. Such a multi‐rate RTHS is strictly executed at real‐time, although it employs different time steps in the numerical and the physical substructures while including rate‐transitioning to link the components appropriately. Typically, a higher‐order numerical substructure model is solved at larger time intervals, and is coupled with a physical substructure that is driven at smaller time intervals for actuator control purposes. Through a series of simulations, the performance of the AMRI and several existing approaches for multi‐rate RTHS is compared. It is noted that compared with existing methods, AMRI leads to a smaller error, especially at higher ratios of sampling frequency between the numerical and physical substructures and for input signals with high‐frequency content. Further, it does not induce signal chattering at the coupling frequency. The effectiveness of AMRI is also verified experimentally. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
126.
Scott M. Mackaro Richard T. McNider Arastoo Pour Biazar 《Pure and Applied Geophysics》2012,169(3):401-414
Skin temperatures that reflect the radiating temperature of a surface observed by infrared radiometers are one of the most
widely available products from polar orbiting and geostationary satellites and the most commonly used satellite data in land
surface assimilation. Past work has indicated that a simple land surface scheme with a few key parameters constrained by observations
such as skin temperatures may be preferable to complex land use schemes with many unknown parameters. However, a true radiating
skin temperature is sometimes not a prognostic variable in weather forecast models. Additionally, recent research has shown
that skin temperatures cannot be directly used in surface similarity forms for inferring fluxes. This paper examines issues
encountered in using satellite derived skin temperatures to improve surface flux specifications in weather forecast and air
quality models. Attention is given to iterations necessary when attempting to nudge the surface energy budget equation to
a desired state. Finally, the issue of mathematical operator splitting is examined in which the surface energy budget calculations
are split with the atmospheric vertical diffusion calculations. However, the high level of connectivity between the surface
and first atmospheric level means that the operator splitting leads to high frequency oscillations. These oscillations may
hinder the assimilation of skin temperature derived moisture fluxes. 相似文献
127.
Litani River is the largest river in Lebanon and has been affected by several physical and anthropogenic factors that influenced its flow dynamics. By means of the Singular Spectrum Analysis (SSA), the time dynamics of the stream flow of seven sites along the course of Litani River was investigated, extracting for each site the long-term trend. A clear decreasing trend characterizes all the long-term trends of the stream flow. Furthermore, several peaks were identified, consistent with the rainfall rate and snow cover variability. 相似文献
128.
Two marine calcareous deposits as crushable soils and a siliceous sand as a noncrushable soil were used in this study to compare their monotonic response. Undrained monotonic triaxial tests were conducted on samples, which were prepared in different relative densities and consolidated under various confining pressures. The location of phase transformation point in undrained response of the sands in different initial conditions was evaluated. The effect of important parameters including relative density, confining pressure, particle shape, and particle breakage on phase transformation point was assessed. The input energy applied per unit volume of the soils was used to interpret the shearing response of crushable and noncrushable soils. The results showed that calcareous sands have more tendencies in contraction. Particle shape and breakage play a key role in engineering behavior of crushable soils. 相似文献
129.
130.
This study examines the time-dependent poromechanics behavior of a fluid-saturated spherical inclusion embedded inside a fluid-saturated
porous medium with different poroelastic properties. Both media comprise compressible constituents with distinctively defined
poroelastic parameters. It is assumed that the inclusion is subjected to a fluid source at the center. The problem is formulated
and solved using Biot theory of poromechanics. The contrasts in inclusion and the medium matrix stiffnesses and their respective
hydraulic conductivities can be recognized as two competing factors, which affect the inclusion’s rate of expansion during
fluid injection. Findings show a certain type of behavior that the inclusion exhibits at the onset of fluid injection when
having greater stiffness than the medium matrix, where the inclusion experiences some decrease in the pore pressure. Compared
to what announced as the stress redistribution due the Mandel–Cryer effect in earlier researches on dilation of free spheres,
this study shows that the associated phenomenon would be likewise attributed to the coupled nature of pressures and deformations
in the theory of poroelasticity. However, it is a consequence of the inclusion-matrix stiffness contrast where a dilating
free sphere can be regarded as a special case of this new problem. The asymptotic expansions of pressure terms verify the
existence of such an effect. The results of this study would put forward very good insight in some engineering applications. 相似文献