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221.
J. Vukman 《Aequationes Mathematicae》1989,38(2-3):245-254
Summary LetR be a ring. A bi-additive symmetric mappingD(.,.): R × R R is called a symmetric bi-derivation if, for any fixedy R, a mappingx D(x, y) is a derivation. The purpose of this paper is to prove some results concerning symmetric bi-derivations on prime and semi-prime rings. We prove that the existence of a nonzero symmetric bi-derivationD(.,.): R × R R, whereR is a prime ring of characteristic not two, with the propertyD(x, x)x = xD(x, x), x R, forcesR to be commutative. A theorem in the spirit of a classical result first proved by E. Posner, which states that, ifR is a prime ring of characteristic not two andD
1,D
2 are nonzero derivations onR, then the mappingx D
1(D
2
(x)) cannot be a derivation, is also presented. 相似文献
222.
Summary Motivated by different mean value properties, the functional equationsf(x) – f(y)/x–y=[(x, y)], (i)xf(y) – yf(x)/x–y=[(x, y)] (ii) (x y) are completely solved when, are arithmetic, geometric or harmonic means andx, y elements of proper real intervals. In view of a duality between (i) and (ii), three of the results are consequences of other three.The equation (ii) is also solved when is a (strictly monotonic) quasiarithmetic mean while the real interval contains 0 and when is the arithmetic mean while the domain is a field of characteristic different from 2 and 3. (A result similar to the latter has been proved previously for (i).) 相似文献
223.
Much recent work has been done to investigate convergence of modified continued fractions (MCF's), following the proof by Thron and Waadeland [35] in 1980 that a limit-periodic MCFK(a
n
, 1;x
1), with
andnth approximant
相似文献
224.
Georgi R. Grozev 《Numerische Mathematik》1989,56(4):331-343
Summary LetLM
N be the set of allL-monosplines withN free knots, prescribed by a pair (x;E) of pointsx = {x
i
}
1
n
,a <x
1 < ... <x
n
<b and an incidence matrixE = (e
ij
)
i=1
n
,
r-1
j=0
with
Denote byLM
N
O
the subset ofLM
N consisting of theL-monosplines withN simple knots (n=N). We prove that theL-monosplines of minimalL
p-norms inLM
N belong toLM
N
O
.The results are reformulated as comparison theorems for quadrature formulae. 相似文献
225.
Martin H. Gutknecht 《Numerische Mathematik》1989,56(6):547-589
Summary We discuss first the block structure of the Newton-Padé table (or, rational interpolation table) corresponding to the double sequence of rational interpolants for the data{(z
k, h(zk)}
k
=0. (The (m, n)-entry of this table is the rational function of type (m,n) solving the linearized rational interpolation problem on the firstm+n+1 data.) We then construct continued fractions that are associated with either a diagonal or two adjacent diagonals of this Newton-Padé table in such a way that the convergents of the continued fractions are equal to the distinct entries on this diagonal or this pair of diagonals, respectively. The resulting continued fractions are generalizations of Thiele fractions and of Magnus'sP-fractions. A discussion of an some new results on related algorithms of Werner and Graves-Morris and Hopkins are also given.Dedicated to the memory of Helmut Werner (1931–1985) 相似文献
226.
227.
Hadeler KP 《Acta Appl Math》1989,14(1-2):91-102
The modelling problems associated with pair formation in age-structured populations are discussed in this paper. The author also formulates a class of models for pair formation in human populations and derives some results on persistent distributions. 相似文献
228.
I. Palásti 《Periodica Mathematica Hungarica》1989,20(3):231-235
Here we establish a set of eight points in general position in the plane, i.e. no three on a line, no four on a circle, and they determine 7 distinct distances, so that, thei-th distance occursi times,i = 1, 2, , 7. The points are embedded in a triangular net, and the distances are not ordered by size or in any other way. We shall show that some known and unknown examples forn < 8 with the above properties may also be lattice points of a similar net.Research (partially) supported by the Hungarian National Foundation for Scientific Research (OTKA) grant, no. 1808. 相似文献
229.
Summary As shown in preceding papers of the authors, the verification of anR-convergence order for sequences coupled by a system (1.1) of basic inequalities can be reduced to the positive solvability of system (3.3) of linear inequalities. Further, the bestR-order
implied by (1.1) is equal to the minimal spectral radius of certain matrices composed from the exponents occuring in (1.1). Now, these results are proven in a unified and essentially simpler way. Moreover, they are somewhat extended in order to facilitate applications to concrete methods. 相似文献
230.
John Todd 《Numerische Mathematik》1988,54(1):1-18
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