Relaxation of the Vela pulsar’s angular velocity following its jumps     

D. M. Sedrakian  M. V. Hairapetian 《Astrophysics》1997,40(1):39-45

The dynamics of the vortex lattice in the inner crust of a neutron star is considered. A general equation of motion is obtained and solved under the assumption that there are regions of pinned and of free vortices. By comparing these solutions with observational data for the Vela pulsar, the relative moments of inertia of regions of relaxation with the corresponding characteristic times are calculated for two model stars with different equations of state. It is shown that the theory can be reconciled with observations of the relaxation of pulsar angular velocity only for model stars with extremely stiff equations of state. Translated from Astrofizika, Vol. 40, No. 1, pp. 67–76, January–March, 1997.  相似文献   

Wave Beams in an Inhomogeneous Plasma in a Transverse Magnetic Field     

A. G. Bagdoev  D. M. Sedrakian 《Astrophysics》2002,45(1):46-51

The propagation of axisymmetric magnetohydrodynamic waves near the equatorial plane of the crust of a neutron star in a transverse magnetic field is considered. The magnetic field is perpendicular to the equatorial plane. The magnetic fields and electric currents excited by this wave beam at the stellar surface are determined.  相似文献   

Rotation of a two-component model neutron star in the GTR     

D. M. Sedrakian 《Astrophysics》1997,40(3):260-266

Equations are obtained for the dynamics of the rotation of a two-component model neutron star within the framework of the generai theory of relativity. It is shown that for steady rotation of the star’s normal component, Ω_c = const, the angular velocity Ω_s of the superfluid component depends on the coordinates and is Ω_c + ω, where ω is the nondiagonal component of the metric tensor. Translated from Astrofizika, Vol. 40, No. 3, pp. 403–412, August, 1997.  相似文献   

CQC modal combination rule for high-frequency modes     

Armen Der Kiureghian  Yutaka Nakamura 《地震工程与结构动力学》1993,22(11):943-956

The CQC rule for modal combination is extended to include the quasi-static contribution of truncated modes and the effects of input narrow-bandedness and cut-off frequency. A simple measure of the error in approximating a high-frequency modal response by its quasi-static contribution is derived. The extended rule is applicable to structures with high-frequency modes and to seismic inputs which may not be regarded as wide band. Numerical examples demonstrate the significance of input bandwidth and cut-off frequency on modal cross-correlation coefficients, and on the error resulting from truncation of high-freqeuncy modes.  相似文献   

A response spectrum method for random vibration analysis of mdf systems     

Armen Der Kiureghian 《地震工程与结构动力学》1981,9(5):419-435

A response spectrum method for stationary random vibration analysis of linear, multi-degree-of-freedom systems is developed. The method is based on the assumption that the input excitation is a wide-band, stationary Gaussian process and the response is stationary. However, it can also be used as a good approximation for the response to a transient stationary Gaussian input with a duration several times longer than the fundamental period of the system. Various response quantities, including the mean-squares of the response and its time derivative, the response mean frequency, and the cumulative distribution and the mean and variance of the peak response are obtained in terms of the ordinates of the mean response spectrum of the input excitation and the modal properties of the system. The formulation includes the cross-correlation between modal responses, which is shown to be significant for modes with closely spaced natural frequencies. The proposed procedure is demonstrated for an example structure that is subjected to an ensemble of earthquake-induced base excitations. Computed results based on the response spectrum method are in close agreement with simulation results obtained from time-history dynamic analysis. The significance of closely spaced modes and the error associated with a conventional method that neglects the modal correlations are also demonstrated.  相似文献   

Angular velocity glitches of the Vela pulsar in a model with “centrifugal buoyancy” of vortices     

D. M. Sedrakian  M. V. Hayrapetyan  L. R. Sedrakian 《Astrophysics》2007,50(2):144-156

The forces acting on the solid crust of a differentially rotating neutron star are examined when a nonuniform excess of chemical potential exists. The resultant of the external forces, a stress force, is expressed in terms of a centrifugal buoyancy force and the deformation of the star’s crust under the action of this force is calculated. It is shown that there is a region within the star where the resulting stresses lead to fracture of the crust when the difference in the angular velocities of the superfluid and normal components reaches a critical value. The “centrifugal buoyancy” mechanism for generating a glitch is used to estimate the parameters of glitches in the Vela pulsar. __________ Translated from Astrofizika, Vol. 50, No. 2, pp. 183–197 (May 2007).  相似文献   

Magnetic field of a neutron star with a superconducting quark core in the CFL-phase     

D. M. Sedrakian  K. M. Shahabasyan  M. K. Shahabasyan 《Astrophysics》2007,50(1):65-75

The Ginzburg-Landau equations are derived for the magnetic and gluomagnetic gauge fields in the color superconducting core of a neutron star containing a CFL-condensate of diquarks. The interaction of the diquark CFL-condensate with the magnetic and gluomagnetic gauge fields is taken into account. The behavior of the magnetic field in a neutron star is studied by solving the Ginzburg-Landau equations taking correct account of the boundary conditions, including the gluon confinement conditions. The magnetic field distribution in the quark and hadronic phases of a neutron star is found. It is shown that a magnetic field generated in the hadronic phase by the entrainment effect penetrates into the quark core in the form of quark vortex filaments because of the presence of screening Meissner currents. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 87–98 (February 2007).  相似文献   

Magnetic Field of a Neutron Star With Color Superconducting Quark Matter Core     

D. M. Sedrakian  D. Blaschke 《Astrophysics》2002,45(2):166-175

The behaviour of the magnetic field of a neutron star with a superconducting quark matter core is investigated in the framework of the Ginzburg-Landau theory. We take into account the simultaneous coupling of the diquark condensate field to the usual magnetic and to the gluomagnetic gauge fields. We solve the Ginzburg-Landau equations by properly taking into account the boundary conditions, in particular, the gluon confinement condition. We found the distribution of the magnetic field in both the quark and hadronic phases of the neutron star and show that the magnetic field penetrates into the quark core in the form of quark vortices due to the presence of Meissner currents.  相似文献   

Response spectrum analysis for floor acceleration          下载免费PDF全文

Matteo Pozzi  Armen Der Kiureghian 《地震工程与结构动力学》2015,44(12):2111-2127

The peak floor acceleration (PFA) is a critical parameter influencing the performance of non‐structural elements in buildings. This paper develops a response spectrum analysis method based on the complete quadratic combination (CQC) rule to estimate the PFA. The method accounts for the rigid contribution of truncated higher modes and the cross‐correlations between all pairs of modes. The approximation is introduced in the time domain and then formulated in the frequency domain by CQC. Application of the method to a continuous cantilever beam idealizing a building with shear walls is presented and compared with alternative formulations. The proposed method is able to provide a consistent estimation of the PFA along the entire structure, not only where the PFA is principally influenced by the first few flexible modes but also where the PFA is mainly related to the rigid response of the structure, for example, near its base. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Development and validation of nonlinear computational models of dispersed structures under strong earthquake excitation          下载免费PDF全文

Armen Derkevorkian  Sami F. Masri  Yozo Fujino  Dionysius M. Siringoringo 《地震工程与结构动力学》2014,43(7):1089-1105

Structural health monitoring of large multispan flexible bridges is particularly important because of their important role in civil infrastructure and transportation systems. In this study, the response of the Yokohama Bay Bridge (YBB), a three‐span cable‐stayed bridge, to the 2011 Great East Japan Earthquake is used to perform multi‐input multi‐output system identification studies. The extensive multicomponent measurements are also used to develop and validate data‐driven nonlinear mathematical models that can predict the response of YBB to various earthquake records and can accurately estimate its damping characteristics when the system is driven into the nonlinear response range. A combination of least‐square (parametric) and neural network (nonparametric) approaches is used to develop the mathematical models, along with time‐marching techniques for dynamic response calculations. It is shown that the nonlinear mathematical models perform better than the equivalent linear models, both for response prediction and damping estimation. The importance of having an accurate approach for quantifying the damping due to the variety of nonlinear features in the YBB response is shown. This study demonstrates the significance of constructing robust mathematical models that can capture the correct physics of the underlying system and that can be used for computational purposes to augment experimental studies. Given the lack of suitable data sets for full‐scale structures under extreme loads, the availability of the long‐duration measurements from the 2011 Great East Japan Earthquake and its many strong aftershocks provides an excellent opportunity to perform the analyses presented in this study. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献