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61.
We investigate some statistical properties of the solar soft X-ray flux and of the Auroral Electrojet (AE) index. For both these signals, the probability density functions (PDFs) of normalized differences are shown to display wide, non-Gaussian tails. The shape of the PDFs is nearly unchanged as the timelag, used to calculate differences, varies. Moreover, the two time series are characterized by a power-law distribution for waiting times between successive bursts and by a clear departure from an hypothesis of locally Poisson statistics. A similar behavior is found in a shell model of magnetohydrodynamic (MHD) turbulence. 相似文献
62.
A. Marino L. Bianchi R. Rampazzo D. Thilker F. Annibali A. Bressan L. M. Buson 《Astrophysics and Space Science》2011,335(1):243-248
We present a study of the stellar populations of ring and/or arm-like structures in a sample of S0 galaxies using GALEX far- and near-ultraviolet imaging and SDSS optical data. Such structures are prominent in the UV and reveal recent star formation.
We quantitatively characterize these rejuvenation events, estimating the average age and stellar mass of the ring structures,
as well as of the entire galaxy. The mass fraction of the UV-bright rings is a few percent of the total galaxy mass, although
the UV ring luminosity reaches 70% of the galaxy luminosity. The integrated colors of these S0s locates them in the red sequence
(NGC 2962) and in the so-called green valley. We suggest that the star formation episodes may be induced by different triggering
mechanisms, such as the inner secular evolution driven by bars, and interaction episodes. 相似文献
63.
Buckling restrained braces (BRBs) are very effective in dissipating energy through stable tension–compression hysteretic cycles and have been successfully experimented in the seismic protection of buildings. Their behavior has been studied extensively in the last decades and today the level of performance guaranteed by these devices and the technological constrains that have to be fulfilled to optimize their behavior are well known. Furthermore, several companies in the world have developed their own BRBs and are now producing them. In spite of this, many seismic codes (for instance, the EuroCode 8) do not stipulate provisions for the design and construction of earthquake‐resistant structures equipped with BRBs. This discourages the structural engineering community from using these devices and seriously limits their use in structural applications. In this paper a procedure for the seismic design of steel frames equipped with BRBs is proposed. Furthermore, the paper presents a numerical investigation aimed at validating this design procedure and proposing the value of the behavior factor q that should be used for this structural type. To this end, a set of frames with BRBs is first designed by means of several values of q. Then, the obtained frames are subjected to a set of accelerograms compatible with the elastic response spectrum considered in design. The seismic response of the frames is determined by nonlinear dynamic analysis and represented in terms of the ductility demand of BRBs and the internal force demand of nondissipative members (beams and columns). Finally, the largest value of q that leads to acceptable seismic performance of the analyzed frames is assumed as adequate. The value of q is given in the paper as a continuous function of the assumed ductility capacity of the BRBs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
64.
Mine subsidence damage from room and pillar mining in Illinois 总被引:1,自引:0,他引:1
Summary Data is presented on case histories of subsidence damage occurring over abandoned room and pillar mines in Illinois. The major modes of behaviour and damage in houses from sag-subsidence are described and summarized. The houses rested on crawl-space and basement foundations built from concrete and masonry. The prevalent mode of failure of bearing walls was inward bending. Failure is analysed and conventional design procedures are used to evaluate foundation failure. 相似文献
65.
A simple nonlinear model which describes the 11-year solar cycle can be derived from the usual – dynamo theory in the form of a Van der Pol equation. Solar activity displays also small-scale inter-cycle persistent stochastic oscillations with a Hurst exponent of the order of H0.76±0.01. The results obtained from the Van der Pol oscillator superimposed on a fractional Brownian motion which describes the stochastic fluctuations are presented. 相似文献
66.
In order to investigate how the apparent separation of jointing varies according to the distance from faults, and how the mechanical properties of rock masses depend on this distance and jointing density, a number of regression analysis were performed on the variables s (apparent joint separation), d (distance from major fault), and sh (rebound value of Schmidt hammer).The variables were measured at 380 stations distributed over a wide study area located in the Aspromonte range in Calabria, Southern Italy.The most significant results of simple regression analysis are expressed by the formulas:
s=c+Fd05