Fourier analysis of the light curves of eclipsing variables     

Zdeněk Kopal  Atsuma Yamasaki 《Astrophysics and Space Science》1980,72(1):3-14

The aim of the present paper has been to construct analytic expressions for incomplete Fourier transforms underlying Kitamura's method for an analysis of the light curves of eclipsing binary systems (Kitamura, 1965).The expansions established for Kitamura's coefficientsc _n ands _n have been used as a basis for checking numerical accuracy of these coefficients tabulated by Kitamura in 1967; and the outcome bespeaks a high quality of his tables constructed by numerical quadratures.  相似文献   

A spot model for VW Cephei     

A. Yamasaki 《Astrophysics and Space Science》1982,85(1-2):43-58

An attempt is made to interpret the variations of the light curve of VW Cephei in terms of a spot model. A light curve which is (hopefully) free from starspot effects is constructed from Kwee's (1966a) observations, and is analysed by the light-curve synthesis method. Then, Kwee's individual light curves are further analysed by assuming that starspots exist on the surface of the primary component. Properties of starspots are briefly discussed.  相似文献   

Negative detection of the four-hour periodicity of the central star of M1-2 (VV8)     

A. Yamasaki  A. Okazaki  M. Nakagiri  S. Suzuki 《Astrophysics and Space Science》1984,104(1):181-185

Four-hour (4.0002 hr) binary periodicity of the emission-line object M1-2 (=VV8), claimed by Drummond (1980), is examined on the basis of photometric and spectroscopic observations. However, neither positive variation of the light nor that of the radial velocity associated with that period has been found.  相似文献   

Geometry of stress function surfaces for an asymmetric continuum     

Takahiro Yajima  Kazuhito Yamasaki  Hiroyuki Nagahama 《Acta Geophysica》2013,61(6):1703-1721

A two-dimensional stress field of dislocation or fault is geometrically studied for an asymmetric continuum. For geometric surfaces of the stress and couple-stress functions, the mean and Gaussian curvatures are derived. The mean curvature of couple-stress function surface is connected with the asymmetric of stress tensor. Moreover, the Gaussian curvature of stress function surface is characterized by both the stress and couple-stress. On the other hand, the mean curvature of stress function surface is not affected by the asymmetry of stress. Based on these geometric expressions, the Coulomb’s failure criterion and the friction coefficient are expressed by the curvatures of couple-stress function surface. Moreover, geometric structures of stress and couple stress function surfaces are shown for edge and wedge dislocations as faults. The curvatures of these surfaces show that the effect of couple-stress is constrained around the dislocations only.  相似文献   

Short-period noncontact binaries     

Atsuma Yamasaki  Akira Okazaki  Masatoshi Kitamura 《Astrophysics and Space Science》1986,118(1-2):279-282

Five short-period noncontact binaries (GR Tau, UU Lyn, BV Eri, RU Eri, and BW Eri) are studied. It is found from photometric and spectroscopic observations that (1) both components are noncontact to each other but are very close to the respective Roche lobes; (2) period change does not appear or it is very small; and (3) component stars of UU Lyn and RU Eri are normal main sequence stars while those of GR Tau and BV Eri are smaller and less massive components indicating in an advanced evolutionary state having experienced mass reversal.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

A photometric study of the short-period eclipsing binary BW Eridani     

D. Baade  H. W. Duerbeck  M. T. Karimie  A. Yamasaki 《Astrophysics and Space Science》1982,88(1):197-204

UBV observations of the short-period eclipsing binary BW Eri are reported and analyzed. The photometric parameters are determined. BW Eri is a detached or semidetached system.  相似文献   

A photometric and spectroscopic study of the short-period eclipsing binary BV Eridani     

D. Baade  H. W. Duerbeck  M. T. Karimie  A. Yamasaki 《Astrophysics and Space Science》1983,93(1):69-77

UBV observations of the short-period eclipsing binary BV Eri are reported and analyzed. The radial velocity curve is given. The system shows a light curve distortion, making an analysis difficult. The secondary fills its critical Roche lobe. The system seems to be in an interesting evolutionary.  相似文献   

Pyroclastic flows in Japan     

Aramaki  Shigeo  Yamasaki  Masao 《Bulletin of Volcanology》1963,25(1):89-96

Bulletin of Volcanology -  相似文献   

Differential geometric approach to the stress aspect of a fault: Airy stress function surface and curvatures     

Kazuhito Yamasaki  Takahiro Yajima 《Acta Geophysica》2012,60(1):4-23

We considered the two-dimensional stress aspect of a fault from the viewpoint of differential geometry. For this analysis, we concentrated on the curvatures of the Airy stress function surface. We found the following: (i) Because the principal stresses are the principal curvatures of the stress function surface, the first and the second invariant quantities in the elasticity correspond to invariant quantities in differential geometry; specifically, the mean and Gaussian curvatures, respectively; (ii) Coulomb’s failure criterion shows that the coefficient of friction is the physical expression of the geometric energy of the stress function surface; (iii) The differential geometric expression of the Goursat formula shows that the fault (dislocation) type (strike-slip or dip-slip) corresponds to the stress function surface type (elliptic or hyperbolic). Finally, we discuss the need to use non-biharmonic stress tensor theory to describe the stress aspect of multi-faults or an earthquake source zone.  相似文献   

A quantum particle motion and thermodynamics in faults-defects field: Path integral formulation based on extended deformation gradient tensor     

Kazuhito Yamasaki 《Acta Geophysica》2009,57(3):567-582

We consider the effect of the faults-defects (FD) field on the following quantum phenomena: (i) the motion of a particle expressed by the Green function; (ii) thermodynamic phenomena expressed by the partition function. We use the path integral formulation based on the extended deformation gradient (EDG) tensor. This formulation connects the Green function of (i) with the partition function of (ii) to describe the thermodynamics in terms of a quantum particle motion. We obtain the following results: (a) The Lagrangian in the Green function includes the new potential consisting of stress functions that shift the path of the free particle from the shortest distance; (b) The solution of the partition function in one-dimensional space makes it possible to deduce the thermodynamic relations in the FD field. Such results could not be obtained by taking the traditional mechanical and quantum approaches, so the path integral formulation based on the EDG tensor is a useful tool.  相似文献