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1.
V. L. Topunov 《Acta Appl Math》1989,16(2):191-206
In this paper, an application of the Riquer-Thomas-Janet theory is described for the problem of transforming a system of partial differential equations into a passive form, i.e., to a special form which contains explicitly both the equations of the initial system and all their nontrivial differential consequences. This special representation of a system markedly facilitates the subsequent integration of the corresponding differential equations. In this paper, the modern approach to the indicated problem is presented. This is the approach adopted in the Knuth-Bendix procedure [13] for critical-pair/completion and then Buchberger's algorithm for completion of polynomial ideal bases [13] (or, alternatively, for the construction of Groebner bases for ideals in a differential operator ring [14]). The algorithm of reduction to the passive form for linear system of partial differential equations and its implementation in the algorithmic language REFAL, as well as the capabilities of the corresponding program, are outlined. Examples illustrating the power and efficiency of the system are presented. 相似文献
2.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
3.
A Volterra type integral equation in a Hilbert space with an additional linear operator L and a spectral parameter depending
on time is considered. If the parameter does not belong to the spectrum of L unconditional solvability of the considered problem
is proved. In the case where the initial value of the parameter coincides with some isolated point of the spectrum of the
operator L sufficient conditions for solvability are established. The obtained results are applied to the partial integral
equations associated with a contact problem of the theory of elasticity. 相似文献
4.
Abstract. We propose a general approach to deal with nonlinear, nonconvex variational problems based on a reformulation of the problem
resulting in an optimization problem with linear cost functional and convex constraints. As a first step we explicitly explore
these ideas to some one-dimensional variational problems and obtain specific conclusions of an analytical and numerical nature. 相似文献
5.
Dedushenko S. K. Makhina I. B. Mar'in A. A. Mukhanov V. A. Perfiliev Yu. D. 《Hyperfine Interactions》2004,158(1-4):417-421
A colourless quartz crystal doped with 57Fe3+ was obtained by hydrothermal synthesis in an NH4F solution. The crystal was transformed into violet amethyst by gamma-irradiation. The change in colour was accompanied by changes in the Mössbauer spectrum that can be interpreted as the conversion of trivalent iron into the tetravalent state: Fe3+→Fe4+.
相似文献6.
Extending to r > 1 a formula of the authors, we compute the expected reflection distance of a product of t random reflections in the complex reflection group G(r, 1, n). The result relies on an explicit decomposition of the reflection distance function into irreducible G(r, 1, n)-characters and on the eigenvalues of certain adjacency matrices.Received December 8, 2003 相似文献
7.
Walter Benz 《Monatshefte für Mathematik》2004,141(1):1-10
The lines of euclidean and hyperbolic geometries are characterized as metric lines in the sense of Blumenthal–Menger, and the lines of spherical and elliptic geometry as periodic ones. In euclidean geometries there do not exist periodic lines. 相似文献
8.
9.
A Pair of Dimeric Stilbene Epimers from Gnetum Montanum 总被引:1,自引:0,他引:1
GnetummontanumofgnetaceaisdistributedinsouthernChina.AsaChinesefOlkmedicine,itslianasareusedtotreatbronchitisandarthritis'.Previousinvestigationofthisspeciesledtotheisolationofsomealkaloidsanddibenzyletherde,i.ati.es2.lnourstudies,tenknowncomponentsincludingresveratrol,isohapontigenin,daucosterol,6-sitosterol,stearicacid,gnetifolinE,gnetol,isorhapontigenin-3-O-6-glucopyra(-)E-viniferinandgnetifolinCwereisolatedfromthesameresource.Atthesametime,apairoftraceepimerswereobtained.Thisisthefirste… 相似文献
10.
In this paper, we present a numerical scheme for solving the coupled system of compressible miscible displacement problem in porous media. The flow equation is solved by the mixed finite element method, and the transport equation is approximated by a discontinuous Galerkin method. The scheme is continuous in time and a priori hp error estimates is presented. 相似文献