Application of the global modal approach to the spiral galaxies     

Natalia Orlova  Vladimir Korchagin  Nobuhiro Kikuchi  Shoken. M. Miyama  Aleksei Moiseev 《Astrophysics and Space Science》2003,284(2):739-742

We have tested the applicability of the global modal approach in the density wave theory of spiral structure for a sample of spiral galaxies with measured axisymmetric background properties. We report here the results of the simulations for four galaxies: NGC 488, NGC 628, NGC 1566, and NGC 3938. Using the observed radial distributions for the stellar velocity dispersions and the rotation velocities we have constructed the equilibrium models for the galactic disks in each galaxy and implemented two kinds of stability analyses - the linear global analysis and 2D-nonlinear simulations. In general, the global modal approach is able to reproduce the observed properties of the spiral arms in the galactic disks. The growth of spirals in the galactic disks can be physically understood in terms of amplification by over-reflection at the corotation resonance. Our results support the global modal approach as a theoretical explanation of spiral structure in galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The first data on helium isotopy in a transitional clay layer at the cretaceous-paleogene boundary (Gams,Eastern Alps)     

A. F. Grachev  I. L. Kamensky  O. A. Korchagin  H. A. Kollmann 《Izvestiya Physics of the Solid Earth》2007,43(9):766-772

The paper presents preliminary results derived from the study of He isotopy in a transitional clay bed at the critical 65-Ma boundary in the Gams area (Eastern Alps). The ratio ³He/⁴He is shown to decrease from bottom to top of the transitional layer, and the difference between its values in the lower-and uppermost sublayers of the layer exceeds by more than ten times the measurement uncertainty (5%). The ratio ³He/⁴He is smallest in the upper part of the section, where all features of an impact event (spherules of pure nickel, diamonds, and awaruite) are established. The general inference of our study is that ³He enrichment in the lower part of the Gams section is related not to cosmic matter but to a change in the conditions in the source area, most likely, to volcanic activity. The effect of the latter has been established, independent of He isotopic studies, from anomalous concentrations of As, Pb, Cu, and Zn and from the presence of particles of gold, copper, and titanomagnetite similar in composition to its basaltic varieties.  相似文献   

Local manifestations of deep processes at the sea surface and in the atmospheric surface layer     

V. V. Bakhanov  Yu. N. Goryachkin  N. N. Korchagin  I. A. Repina 《Doklady Earth Sciences》2007,414(1):587-591

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Numerical simulation of the nonlinear dynamics of packets of spiral density waves     

V. I. Korchagin 《Astrophysics》1986,25(1):442-448

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俄远东、中国东北的构造特点及岩石圈深部的不均一性     

赵春荆  何国琦  段瑞焱 《国土资源》1995,(4)

俄罗斯远东和中国东北前新生代可划分为８个大地构造单元。区域地质、深部地质、地球物理及新构造研究表明，地壳和地幔深部的不均一性反映了该区主要构造单元的深部构成和大地动力学等方面的特点。地热和地磁资料表明，远东地区软流层顶部具有起伏形态的特点，最大深度２００～２５０ｋｍ，浅部仅１００～１４０ｋｍ，松辽盆地７５～１００ｋｍ；在中国东北及亚太过渡带上地幔低速层厚度在０～１００ｋｍ之间变化，计算数据表明，本区地壳厚度为３０～４４ｋｍ，变化幅度为１４ｋｍ。  相似文献   

Nonlinear oscillations in star-forming systems     

V. I. Korchagin  P. I. Korchagin  A. D. Ryabtsev 《Astrophysics and Space Science》1988,141(1):55-64

A number of analytically formulated models of star-forming systems which include nonlinear interactions of stars and interstellar medium are considered. It is shown that two conditions are essential for the development of nonlinear oscillations: namely, the induced star formation and the presence of time-delay or strong nonlinearity in interacting star-cloud systems. The three component model with time-delay reproducing the temporal behaviour obtained in numerical simulations by Seidenet al. (1982) is proposed.  相似文献   

Generation of large-scale structure by ejection of masses from the center of a galaxy     

V. I. Korchagin  V. F. Rakhimov 《Astrophysics》1981,17(2):206-213

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Formation of a steady wave of induced star formation     

V. I. Korchagin  A. D. Ryabtsev 《Astrophysics》1989,30(2):237-243

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Upper Campanian-lower Maastrichtian planktonic foraminifers and biostratigraphy of the Moni Formation,southern Cyprus     

O. A. Korchagin 《Stratigraphy and Geological Correlation》2011,19(5):526-544

The first data on the taxonomic composition and stratigraphic range of the late Campanian planktonic foraminifers encountered in the middle and upper parts of the Moni Formation, southern Cyprus, are reported. Finds of planktonic foraminifers are associated with the bentonitic clay that composes the matrix of the Moni Formation. The planktonic foraminiferal assemblages revealed are very similar to those from the Kannaviou Formation, western Cyprus, but they are more diverse and yield several key species missing in the Kannaviou sediments. The planktonic foraminiferal assemblages discussed are referred to the Globotruncana aegyptiaca Zone and to the lowermost Gansserina gansseri Zone of the upper upper Campanian of the standard scale. The intraregional correlation of the Moni sections, depth of erosion of the upper part of the formation, and its relationship with the Kannaviou Formation have been refined. When subdividing the upper Campanian sediments based on planktonic foraminifers it is suggested that additional datum planes are used, such as the FADs of Globotruncanella citae and Trinitella scotti. For tracing the Campanian-Maastrichtian boundary (GSSP), attention should be paid to the LADs of Globotruncana bulloides and Contusotruncana fornicata and the potential use of Globotruncanita (Elevatotruncana) eolita sp. nov. should be assessed. It is shown that subfamily Archaeoglobigerininae Salaj, 1987, emend. O. Korchagin is the older synonym of subfamily Archaeoglobigerininae Georgescu, 2005. Two poorly known and three new planktonic foraminiferal species are described.  相似文献   

Stratified unbounded flow past of obstacles     

I. Yu. Vladimirov  N. N. Korchagin  A. S. Savin  E. O. Savina 《Oceanology》2011,51(6):916-924

We studied the surface perturbations of a two-layer ideal fluid induced by a flow past a submerged obstacle (simulated by a point dipole) in the vicinity of the density-jump layer. It is shown that the formation of two different types of surface waves is possible behind the flowed past obstacle in the real conditions of the open sea. The comparison of the amplitudes of the surface perturbations induced by the obstacle located above and below the density jump revealed their significant differences, which seems to be important for the use of this effect in practical problems.  相似文献