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41.
Israel Gohberg Naum Krupnik Ilya Spitkovsky 《Integral Equations and Operator Theory》1993,17(3):322-337
The Banach algebra generated by one-dimensional linear singular integral operators with matrix valued piecewise continuous coefficients in the spaceL
p
(,) with an arbitrary weight is studied. The contour consists of a finite number of closed curves and open arcs with satisfy the Carleson condition. The contour may have a finite number of points of selfintersection. The symbol calculus in this algebra is the main result of the paper. 相似文献
42.
LetP be a finite partially ordered set. The lengthl(x) of an elementx ofP is defined by the maximal number of elements, which lie in a chain withx at the top, reduced by one. Letw(P) (d(P)) be the maximal number of elements ofP which have the same length (which form an antichain). Further let
. The numbers
and
as well as all partially ordered sets for which these maxima are attained are determined. 相似文献
43.
Marcel Erné 《Order》1985,2(2):199-210
A standard extension for a poset P is a system Q of lower ends (descending subsets) of P containing all principal ideals of P. An isomorphism between P and Q is called recycling if [Y]Q for all YQ. The existence of such an isomorphism has rather restrictive consequences for the system Q in question. For example, if Q contains all lower ends generated by chains then a recycling isomorphism between P and Q forces Q to be precisely the system of all principal ideals. For certain standard extensions Q, it turns out that every isomorphism between P and Q (if there is any) must be recycling. Our results include the well-known fact that a poset cannot be isomorphic to the system of all lower ends, as well as the fact that a poset is isomorphic to the system of all ideals (i.e., directed lower ends) only if every ideal is principal. 相似文献
44.
45.
Chlorosulfonyl isocyanate adds to α-pinene in concerted fashion to give the unrearranged N-chlorosulfonyl-β-lactam 2 (75%). Thermolysis of cycloadduct 2 affords the rearranged N-chlorosulfonyl-γ-lactam 6 (60%) via a sequence of transient carbonium ions (45). Reductive hydrolysis of 2 and 6 gave, respectively, the NH-β-lactam 3 (70%) and the NH-γ-lactam 7 (70%). Proof of structure of the rearranged γ-lactams 6 and 7 are provided, respectively, by X-ray crystallographic analysis and the application of the Eu(dpm)3 NMR shift reagent. 相似文献
46.
R. C. Milward 《Fresenius' Journal of Analytical Chemistry》1973,264(3):195-199
Summary This article describes a new commercial Far-Infrared Fourier Spectrometer system which has been developed for routine spectroscopy in the 10–1000 cm–1 spectral region. The instrument incorporates real-time data processing and has been automated wherever possible for foolproof operation. A versatile sample chamber allows a wide range of spectroscopic studies to be performed, on solids, liquids and gases over a wide range of temperatures. A number of spectra are presented to illustrate the performance and typical applications of this Fourier spectrometer.
Ein neues fourier-spektrometer für das ferne infrarot
Zusammenfassung Nach einer kurzen Einführung in die Methode der Fourier-Spektroskopie wird ein neues kommerzielles Fern-Infrarot-Fourier-Spektrometer mit real-time Datenverarbeitungsanlage beschrieben. Das Gerät ist für die Spektroskopie im Bereich 10–1000 cm–1 konstruiert und weitgehend automatisiert. Eine vielseitig verwendbare Probenkammer ermöglicht umfangreiche spektroskopische Untersuchungen von Festkörpern, Flüssigkeiten und Gasen in einem sehr großen Temperaturbereich. Anhand einer Reihe von Spektren werden Leistung und typische Anwendungen dieses Fourier-Spektrometers erläutert.
Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany. 相似文献
47.
A. Gameiro Pais 《Aequationes Mathematicae》1984,27(1):49-56
This paper is concerned with the problem of solving linear difference equations of ordern with constant coefficients and with given initial conditions in which the variable runs not only through the integers but over . The main idea is the introduction of a suitable commutative ring of functions with discrete convolution as multiplication rule which works, although it is not a field. The existence of inverses is studied and, after the introduction of suitable functions, the problem is reduced by means of a Laplace-like relation to an algebraic equation. Examples of application are given. Finally some remarks make the connection with the Operational Calculus of Mikusinski and with the Operational Calculus of Fenyö. The advantages of this method lie in the fact that it is applicable to functions others than the step functions, in its simplicity from the theoretical point of view, in its usefulness even when computation is required and in its formal similarity to the classical treatment of linear differential equations with constant coefficients. 相似文献
48.
Let f C[a, b]. LetP be a subset ofC[a, b], L b – a be a given real number. We say thatp P is a best approximation tof fromP, with arc length constraintL, ifA[p]
b
a
[1 + (p(x))
2]dx L andp – f q – f for allq P withA[q] L. represents an arbitrary norm onC[a, b]. The constraintA[p] L might be interpreted physically as a materials constraint.In this paper we consider the questions of existence, uniqueness and characterization of constrained best approximations. In addition a bound, independent of degree, is found for the arc length of a best unconstrained Chebyshev polynomial approximation.The work of L. L. Keener is supported by the National Research Council of Canada Grant A8755. 相似文献
49.
Helmut Karzel 《Aequationes Mathematicae》1978,17(1):83-90
A permutation set (M, I) consisting of a setM and a set of permutations ofM, is calledsymmetric, if for any two permutations, the existence of anx M with (x) (x) and
–1
(x) =
–1
(x) implies
–1
=
–1
, andsharply 3-transitive, if for any two triples (x
1,x
2,x
3), (y
1,y
2,y
3) M
3 with|{x
1,x
2,x
3
}| = |{y
1,y
2,y
3
}| = 3 there is exactly one permutation with(x
1) =y
1,(x
2) =y
2,(x
3) =y
3. The following theorem will be proved.THEOREM.Let (M, ) be a sharply 3-transitive symmetric permutation set with |M|3, such that contains the identity. Then is a group and there is a commutative field K such that and the projective linear group PGL(2, K) are isomorphic. 相似文献
50.
B. Gyires 《Periodica Mathematica Hungarica》1978,9(1-2):109-113
This paper contains applications of theorems of [1] for quadratic statistics which have constant regression on linear statistics. Two theorems are proved. The first is a sufficient condition which assumes that the characteristic function of a sample is an entire function. The second gives a new characterization of the normal distribution. 相似文献