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41.
Summary When measuringQ
–1 and the flexural resonance frequency of bars clamped at one end, constituted by a viscoelastic polymeric material glued to a rigid support of modulusE
1, it is possible to calculate the componentsE
2
andE
2
of the complex elastic modulus of the polymeric material examined. In this work the minimum (critical) value of the ratioa=E
2
/E
1=a
c
and the values of the ratioQ
2
–1/Q
–1=F
1 are evaluated beyond which no exact calculation ofE
2
and ofQ
2
–1 is possible.Within the confidence limits of the linear viscoelasticity theory, these values depend on the accuracy of measurement of both frequency and resonance curve, as well as on the instrument employed, on the operating temperature and on the ratio between the thicknesses of the two coupled materials.In order to keep outside the critical conditions, the most convenient method involves the use of measurements of coupled test-pieces having different ratiosz between their thicknesses and of supports having different modulusE
1, depending on the field of temperature of the analysis ofE
2
and tg 2 concerning and E.P.R. elastomer and a vulcanized cis-1,4 polyisoprene in very wide ranges of temperature comprising the glass transition. Moreover, it is demonstrated by analysis the shift on the temperature axis of the tg maximum of the composite test-piece with respect to the position of the tg maximum of the polymeric material alone.With 11 figures and 1 table 相似文献
42.
Perea-Carpio R. González-Caballero F. Bruque J. M. Pardo G. 《Colloid and polymer science》1983,261(2):183-187
Colloid and Polymer Science - Data on the surface tension of sodium alkylsulfonate solutions at different temperatures and surfactant concentrations are presented. By applying the thermodynamic... 相似文献
43.
44.
For ν≥0 let cνk be the k-th positive zero of the cylinder functionC v(t)=J v(t)cosα-Y v(t)sinα, 0≤α>π whereJ ν(t) andY ν(t) denote the Bessel functions of the first and the second kind, respectively. We prove thatC v,k 1+H(x) is convex as a function of ν, ifc νk≥x>0 and ν≥0, whereH(x) is specified in Theorem 1.1. 相似文献
45.
Given a graphG onn vertices and a total ordering ≺ ofV(G), the transitive orientation ofG associated with ≺, denotedP(G; ≺), is the partial order onV(G) defined by settingx<y inP(G; ≺) if there is a pathx=x
1
x
2…x
r=y inG such thatx
1 ≺x
j for 1≦i<j≦r. We investigate graphsG such that every transitive orientation ofG contains
2
n
−o(n
2) relations. We prove that almost everyG
n,p satisfies this requirement if
, but almost noG
n,p satisfies the condition if (pn log log logn)/(logn log logn) is bounded. We also show that every graphG withn vertices and at mostcn logn edges has some transitive orientation with fewer than
2
n
−δ(c)n
2 relations.
Partially supported by MCS Grant 8104854. 相似文献
46.
Let {ø n (dμ)} be a system of orthonormal polynomials on the unit circle with respect to a measuredμ. Szegö's theory is concerned with the asymptotic behavior ofø n (dμ) when logμ′∈L 1. In what follows we will discuss the asymptotic behavior of the ratioø n (dμ 2)/ø n (dμ 1) on the unit circle whendμ 1 anddμ 2 are close in a sense (e.g.,dμ 2=gdμ 1, where g≥0 is such thatQ(e it )g(t) andQ(e it )/g(t) are bounded for a suitable polynomialQ) and μ 1 ′ >0 almost everywhere or (a somewhat weaker requirement) lim n→∞Φ n (dμ 1,0)=0 for the monic polynomial Φ n . The asymptotic behavior of the same fraction outside the unit circle was discussed in an earlier paper. 相似文献
47.
I. Pelant M. N. Popova J. Hála M. AmbroŽ V. Lhotská K. Vacek 《Czechoslovak Journal of Physics》1987,37(10):1183-1197
Dependence of two-photon absorption (TPA) rate on the state of polarization of a laser beam is investigated in the low-temperature orthorhombic modification of Hg2Cl2 crystals. Theoretical calculations of the dependence of TPA rate on the direction of polarization vector of the beam are performed for centrosymmetric points, Y, Z, T, R andS of the Brillouin zone. The domain structure of real crystals is taken into consideration and it is shown that periodicity of the polarization dependence may indicate whether TPA is due to transitions either at, Y, Z, T orR, S points. The polarization dependence of TPA cannot, however, distinguish between points inside these two groups. Comparison of theory with a low-temperature (T 8·5 K) experimental curve of polarization dependence is discussed. It is shown that the experiment can be explained in main features by a model of noninteracting oriented linear dipoles. Further, on the basis of TPA measurements, a simple energy band structure of Hg2Cl2 is proposed regarding Hg2Cl2 crystal as a linear chain of molecules.The authors express thanks to Dr. . Barta for supplying the Hg2Cl2 crystals, Dr. Z. Bryknar for critical comments and Dr. B. Velický for stimulating discussion. We thank also Dr. V. Kohlová for assistance during measurement. 相似文献
48.
B. Barabás 《Periodica Mathematica Hungarica》1987,18(2):115-122
The properties of the empirical density function,f
n(x) = k/n(
j
+
–
j-1
+
) if
j-1
+
< x + where
j-1
+
and
j
+
are sample elements and there are exactlyk – 1 sample elements between them, are studied in that practical point of view how to choose a suitablek for a good estimation. A bound is given for the expected value of the absolute value of difference between the empirical and theoretical density functions. 相似文献
49.
L. Eckertová 《Czechoslovak Journal of Physics》1987,37(6):749-758
A simple model including different processes important for the creation of APS signals formed by electrons is proposed. Mean probabilities of elastic and inelastic interactions of electrons with individual atom layers in the solid are introduced. The contribution of different layers to the DAPS and AEPS signals and the dependence of these signals on the interaction parameters are calculated.I am indebted to dr. J. Pavluch for valuable discussions. 相似文献
50.
L. Avanov N. Borodkova Z. NĚmeček A. Omeltchenko J. Šafránková A. Skalski Yu. Yermolaev G. Zastenker 《Czechoslovak Journal of Physics》1987,37(6):759-774
The paper describes the results of investigations of the solar wind ions, carried out on board the high apogee Prognoz 7 and Prognoz 8 Earth's satellites with the aid of an SKS instrument (USSR) and a Monitor instrument (USSR-SSR). Behaviour of proton and that of components on the front of Earth's bow and interplanetary shock waves were compared by means of the energoanalysis and energy-mass analysis techniques. In several long-term periods of observation the solar wind heavy ions — oxygen, silicon and iron were determined. It enabled us to estimate the solar corona chemical composition and electron temperature.Presented at the 5th General Assembly IAGA/IAMAP August 5–17, 1985, Prague, Czechoslovakia. 相似文献