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151.
Gao-Yuan Chen John A. Cuculo Paul A. Tucker 《Journal of Polymer Science.Polymer Physics》1992,30(6):557-561
Nozzle profiles capable of generating constant extensional strain rates are termed hyperbolic dies. When used in polymer extrusion, they exhibit greater potential in inducing and retaining polymer molecular orientation than conventional capillary dies. Most mathematical expressions found in the literature involve several processing variables in describing and designing such nozzle profiles. This report reveals that a hyperbolic die profile, although rather complicated, can be expressed with equations in terms of two ordinary geometrical parameters—the exit diameter and the hyperbolic length. This finding greatly simplifies the design procedure of hyperbolic dies. The extensional strain rate of a hyperbolic die can be related to the length-to-diameter ratio for any given exit diameter. Examples of various types of die profiles are presented and their constant extensional strain-rate characteristics are discussed. 相似文献
152.
153.
154.
155.
Sheldon M Ross 《Stochastic Processes and their Applications》1976,4(2):167-173
Consider an n-component reliability system having the property that at any time each of its components is either up (i.e., working) or down (i.e., being repaired). Each component acts independently and we suppose that each time the ith component goes up it remains up for an exponentially distributed time having mean μi, and each time it goes down it remains down for an exponentially distributed time having mean υi. We further suppose that whether or not the system itself is up at any time depends only on which components are up at that time. We are interested in the distribution of the time of first system failure when all components are initially up at time zero. In section 2 we show that this distribution has the NBU (i.e., new better than used) property, and in Section 3 we make use of this and other results to obtain a lower bound to the mean time until first system failure. 相似文献
156.
The functions of the main indices of refraction n(ν) and absorption κ(ν) of uniaxial thin polyethylene terephthalate films
have been calculated by the experimental spectra of frustrated total reflection of s-and p-polarized radiation in the 700–760-cm−1 range. The κo(ν) maximum falls at the the 727-cm−1 frequency and the maximum of κe(ν) falls at the the 724-and 732-cm− 1 frequencies.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 756–759, November–December, 2005. 相似文献
157.
Analytical theory of high-power microwave propagation in waveguide filled with plasma is presented in this paper. The ponderomotive force effect of high power microwave is taken into consideration and preliminary numerical calculations are carried out, the propagation characteristics of the high-power microwave and the influence of microwave power on the distribution of plasma density are calculated and discussed. 相似文献
158.
L. V. Baev V. N. Solodovnikov 《Journal of Applied Mechanics and Technical Physics》2004,45(6):860-870
The problem of spherically symmetric, gravitational compression of an isotropic hyperelastic layered sphere which modeling the region of the Earth below the Mohorovii boundary is solved. The known mechanical characteristics of the Earth in the compressed state are used to find its characteristics in the unstrained state obtained by adiabatic or isothermal stress relief. The stress state differs significantly from the state of purely hydrostatic compression. The minimum bulk compression and maximum radial tension occur not on the boundary of the sphere but in depth at certain distances from the boundary. 相似文献
159.
Scott Kravitz 《Journal of Algebraic Combinatorics》2004,20(1):61-70
Let (B
n) be the order complex of the Boolean algebra and let B(n, k) be the part of (B
n) where all chains have a gap at most k between each set. We give an action of the symmetric group S
l on the l-chains that gives B(n, k) a Hodge structure and decomposes the homology under the action of the Eulerian idempontents. The S
n action on the chains induces an action on the Hodge pieces and we derive a generating function for the cycle indicator of the Hodge pieces. The Euler characteristic is given as a corollary.We then exploit the connection between chains and tabloids to give various special cases of the homology. Also an upper bound is obtained using spectral sequence methods.Finally we present some data on the homology of B(n, k). 相似文献
160.
S. B. Bushuk W. E. Douglas Ju. A. Kalvinkovskaya L. G. Klapshina A. N. Rubinov B. A. Bushuk A. P. Stupak 《Journal of fluorescence》2003,13(4):331-338
The spectroscopic characteristics of novel -conjugated polymers containing four-coordinated silicon, acetylene groups and either 1,4-biphenylene or 2,7-fluorene in the main chain were investigated by steady-state and picosecond laser spectroscopy. The spectral features of absorption, fluorescence excitation spectra, fluorescence lifetime, and fluorescence polarization were explained by the existence of two kinds of inhomogeneously broadened electronic states formed in the disordered polymeric chain. The dynamics of photoinduced absorption was measured in the 400–900 nm spectral range with picosecond time resolution. The long-wavelength band with max 710 nm was ascribed to excited-state absorption from higher-lying electronic states created in short polymeric segments with essential conformational distortion of the subunits. The short-wavelength band with max 580 nm and a shoulder at 500 nm was interpreted as photoinduced absorption from a lower-lying state arisen in more planar, longer -conjugated segments populated via direct excitation and energy migration between disordered segments of the polymeric chain. For the fluorene-containing polymer, the smaller Stokes shift and the greater degree of fluorescence polarization are consistent with more extensive electron delocalization along the backbone. 相似文献