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991.
A successful application of ultrasound Doppler velocimetry in liquid sodium flows is described. To obtain sufficient Doppler
signals, different problems had to be solved: the transmission of the ultrasonic beam through the channel wall made of stainless
steel, the acoustic coupling between the transducer and the channel wall, and the wetting of the inner surface of the wall
by the liquid metal, respectively. A sodium flow in a square duct exposed to a transverse magnetic field is investigated.
In accordance with the existing knowledge about MHD channel flows, we found that the velocity profiles modified to a M-shape
owing to the effect of an inhomogeneous magnetic field.
Received: 12 June 2001/Accepted: 27 October 2001 相似文献
992.
993.
994.
995.
The problem of the stability of a heavy rigid body, bounded by the surface of an ellipsoid and with a cavity in the form of a coaxial ellipsoid, rolling along a straight line on a horizontal rough plane is investigated. It is shown that in the case of a body that is close to being dynamically symmetrical, parametric resonance always occurs leading to instability of the rolling. Each ellipsoid has its own “individual” resonance angular velocity. In the general case, regions in which the necessary stability conditions are satisfied can be distinguished in parameter space. The problem of calculating the resonance coefficient corresponding to instability for parametric resonance in a reversible third-order system is solved. 相似文献
996.
Necessary conditions for the Gâteaux differentiability of the distance function to a set are considered. A series of characterizing results is obtained. 相似文献
997.
J. Matkowski 《Aequationes Mathematicae》2002,64(3):297-303
Summary. Iteration semigroups of weighted quasi-arithmetic mean-type mappings are considered. Existence and uniqueness of a mean which is invariant with respect to a continuous semigroup of mean-type mapping is proved. 相似文献
998.
W.-H. Chen 《Archiv der Mathematik》2002,79(5):396-400
Consider the class of closed Riemannian manifolds M of dimension dim(M) \geqq 3 \dim(M) \geqq 3 , Ricci curvature Ric(M) \geqq -(n - 1) \textrm{Ric}(M) \geqq -(n - 1) , diameter diam(M) < D and almost maximal volume. We show that the isomorphism types of fundamental groups characterize the diffeomorphism types of manifolds in such a class. In particular, it can be viewed as a generalization of the well-known Mostows rigidity theorem and a finiteness theorem. 相似文献
999.
P Vincent A BrioudeC Journet S RabasteS.T Purcell J Le BrusqJ.C Plenet 《Journal of Non》2002,311(2):130-137
We report here the successful inclusion of carbon nanotubes (CNs) into a TiO2 matrix prepared by a sol-gel method. The presence of CNs in the sol-gel matrix and the structure of the film were analyzed principally by transmission electron microscopy. Complementary information about the behavior of embedded carbon nanotubes versus heat treatment and ion irradiation were obtained by X-ray photoelectron spectroscopy. The elaboration of an inorganic matrix containing embedded carbon nanotubes leads to a new nanocomposite. The possible applications of this nanocomposite are discussed. 相似文献
1000.
In this paper, we explore the interplay of four different conjectures on certain zero-sum problems in Zp Zp. This study of the inter-relations between these conjectures leads to the conclusion that determining the structure of minimal zero sequences (see below for the precise definition) is crucial. Also, we study the analogous situation in Zn. 相似文献