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961.
We construct a three-parameter family of contact metric structures on the unit tangent sphere bundle T
1
M of a Riemannian manifold M and we study some of their special properties related to the Levi-Civita connection. More precisely, we give the necessary
and sufficient conditions for a constructed contact metric structure to be K-contact, Sasakian, to satisfy some variational conditions or to define a strongly pseudo-convex CR-structure. The obtained
results generalize classical theorems on the standard contact metric structure of T
1
M. 相似文献
962.
963.
M. A. Kachalova 《Journal of Mathematical Sciences》2007,140(5):699-715
The additive structure of the Hochschild cohomology ring for a Möbius algebra is described. We use the structure of the bimodule minimal projective resolution of the algebra, constructed in a previous paper. Bibliography: 4 titles. 相似文献
964.
We consider the interpolation Nevanlinna-Pick problem with infinitely many interpolation nodes in the class S[a, b] and rational matrix functions associated with this problem and orthogonal on the segment [a, b]. We obtain a criterion of complete indeterminacy of the Nevanlinna-Pick problem in terms of orthogonal rational matrix functions.
__________
Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, No. 6, pp. 764–770, June, 2007. 相似文献
965.
V. M. Budanov 《Journal of Mathematical Sciences》2007,146(3):5931-5937
This paper investigates algorithms of motion planning for a six-legged walking machine over complex terrain. Application of
the Rodrigues-Hamilton parameters for describing the orientation of the body enables one to develop algorithms of motion planning
for the body and legs in an absolute coordinate frame with automatic adaptation to the surface. Experiments with a laboratory
scale walking machine have demonstrated the efficiency of proposed algorithms.
__________
Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 7, pp. 197–206, 2005. 相似文献
966.
The classical Voigt functions occur frequently in a wide variety of problems in astrophysical spectroscopy, emission, absorption
and transfer of radiation in heated atmosphere, and plasma dispersion, and indeed also in the theory of neutron reactions.
Here, in the present paper, by applying several known upper bounds for the first-kind Bessel function J
ν
(x) given recently by (for example) Landau, Olenko and Krasikov, sharp bounding inequalities are obtained for the unified multivariable
Voigt function V
μ,ν
(x; y) in terms of the confluent Fox-Wright function 1ψ0 and its incomplete variant 1ψ0. Connections of the unified multivariable Voigt function V
μ,ν
(x; y) with other unifications and generalizations of the classical Voigt function are also briefly pointed out. 相似文献
967.
T. Schäfer 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):403-408
We review many-body calculations of the equation of state of dilute neutron matter in the context of effective-field theories
of the nucleon-nucleon interaction. 相似文献
968.
A model of a helical nanotube permitting analytical calculation of the spectrum and wave functions is proposed and studied. It is shown that the specific character of the symmetry of the Hamiltonian results in an electronic spectrum having no band structure despite the periodicity of the potential along the system axis. A two-dimensional ribbon rolled into a helix and a quasi-one-dimensional helix in a magnetic field are considered as limiting cases of the model. It is shown that the presence of additional local minima in the subbands of the electronic spectrum leads to a nonmonotonic dependence of the ballistic conductance of the system on the chemical potential. 相似文献
969.
A technique for variation of the temperature factor of free-flight models by varying their initial temperature is described. An experiment on a ballistic range is carried out with a free-flying supersonic blunt cone with a half-angle of 15° at a Mach number of 2.3. The flow at the cone base is studied in the transition range (from the laminar to turbulent flow) of Reynolds numbers. The base flow pattern is determined from the shadowgraphs of the flow about the models. The drag coefficient of the blunt cone at a zero angle of attack is found by processing trajectory data. It is found that the near wake geometries and the drag coefficients of the models tested at the laboratory temperature and a temperature of 120 K differ. Explanations of this effect are given. 相似文献
970.
W.G. Schmidt 《Applied Physics A: Materials Science & Processing》2002,75(1):89-99
There has been renewed interest in the structure of III-V compound semiconductor (001) surfaces caused by recent experimental
and theoretical findings, which indicate that geometries different from the seemingly well-established dimer models describe
the surface ground state for specific preparation conditions. I review briefly the structure information available on the
(001) surfaces of GaP, InP, GaAs and InAs. These data are complemented with first-principles total-energy calculations. The
calculated surface phase diagrams are used to explain the experimental data and reveal that the stability of specific surface
structures depends largely on the relative size of the surface constituents. Several structural models for the Ga-rich GaAs (001)(4×6)
surface are discussed, but dismissed on energetic grounds. I discuss in some detail the electronic properties of the recently
proposed cation-rich GaAs (001)ζ(4×2) geometry.
Received: 18 May 2001 / Revised version: 23 July 2001 / Published online: 3 April 2002 相似文献