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31.
32.
A macromolecular solution is represented by the simple model of rigid dumbbells suspended in a Newtonian fluid with Brownian motion included. Hydrodynamic interaction is not taken into account. It is found that for this model there will be recoil after the cessation of steady shearing flow. The ultimate shear recovery S ∞ is developed as a power series in κ?, the shear rate prior to the cessation of the steady shear flow: $$S_\infty = (\theta _0 /2\eta _0 ) \kappa ^\user1{ - } + O(\kappa ^\user1{ - } )^3$$ where η0 and θ0 values of the viscosity and primary normal stress functions respectively at zero-shear rate. The coefficient of the term in (κ?)3 is calculated. In addition, the behavior of the normal stresses during the recoil process is found; during recoil τ22?τ33 has the opposite sign from τ11?τ22. 相似文献
33.
A perturbation analysis is presented for the steady-state radial flow of a third-order fluid between two parallel disks. The
results include previous perturbation analyses in which various other rheological models were used. The pressure drop needed
to maintain the radial flow is less than that for the Newtonian creeping-flow solution because of fluid inertia and shear-thinning
viscosity, whereas the normal stresses have the opposite effect. Possible use of the “radial flow viscometer” for experimental
evaluation of second-order constants is also discussed. Finally, molecular stretching in the flow system is examined using
the elastic dumbbell model for a polymer molecule. 相似文献
34.
The phase-space kinetic theory for polymeric liquid mixtures is used to obtain an expression for the polymer contribution to the thermal conductivity of a nonflowing, dilute solution of polymers, where the polymer molecules are modeled as Fraenkel dumbbells. This theory takes into account three mechanisms for the energy transport: diffusion of kinetic energy (including the Öttinger-Petrillo term), diffusion of intramolecular energy, and the work done against the intramolecular forces. This paper is an extension of previous developments for the Hookean dumbbell model and the finitely-extensible dumbbell model. A comparison among the dumbbell results suggests that the thermal conductivity increases with chain stiffness. In addition, the zero-shear-rate viscosity and first normal-stress coefficient are also given for the Fraenkel dumbbell model.Dedicated to Prof. John D. Ferry on the occasion of his 85th birthday. 相似文献
35.
Rotationally resolved electronic spectra of several low frequency vibrational bands that appear in the S(1) ← S(0) transition of 4-fluorobenzyl alcohol (4FBA) in the collision-free environment of a molecular beam have been observed and assigned. Each transition is split into two or more components by the tunneling motion of the attached -CH(2)OH group. A similar splitting is observed in the microwave spectrum of 4FBA. Analyses of these data show that 4FBA has a gauche structure in both electronic states, but that the ground state C(1)C(2)-C(7)O dihedral angle of ~60° changes by ~30° when the photon is absorbed. The barriers to the torsional motion of the attached -CH(2)OH group are also quite different in the two electronic states; V(2) ~ 300 cm(-1) high and ~60° wide in the S(0) state, and V(2) ~ 300 cm(-1) high and ~120° wide (or V(2) ~ 1200 cm(-1) high and ~60° wide) in the S(1) state. Possible reasons for these behaviors are discussed. 相似文献
36.
Using the integral form of a nonlinear corotational model, we derive explicit analytical expressions for the zeroth, second, and fourth harmonics of the second normal stress difference in large-amplitude oscillatory shear (LAOS). This model yields an arbitrary normal stress ratio (ANSR) in any simple shearing deformation, including LAOS. This corotational ANSR model adds one parameter to the corotational Maxwell model, a time constant ?? 0 controlling the ratio ??2/??1 for both the real and imaginary parts of each harmonic of the normal stress difference. The explicit analytical expressions for all harmonics of the alternating shear stress and first normal stress difference responses in LAOS match those obtained previously for the corotational Maxwell model. We evaluate the corotational ANSR model for the case of a single Maxwell relaxation time fluid. 相似文献
37.
We report on the experimental investigation carried out in the polarisation characteristics of femtosecond pulsed and continuous wave beams propagating through a 1×2 fibre coupler. It is demonstrated that the polarisation states of pulsed and continuous wave illumination over the broad wavelength range can be preserved in a conventional fused fibre coupler. Furthermore, the fibre coupler acts as a low-pass spectral filter in the visible wavelength range with a splitting ratio between 99.6/0.4 and 99.7/0.3. The result is of importance for fibre-optic second harmonic generation microscopy which requires the polarisation preservation to extract molecular organization of a sample. 相似文献
38.
Experimental results for intrinsic viscosity and for intrinsic complex viscosity of polymer solutions were compared with the rheological predictions of the finitely extensible, nonlinear elastic (FENE) dumbbell theory of a dilute suspension. The FENE dumbbell adequately models the intrinsic viscosity of flexible polymers, but less successfully portrays the behavior in small amplitude oscillatory motion. Expressions for the high frequency asymptotic limit of the intrinsic complex viscosity of a FENE dumbbell suspension, and the mean-square end-to-end distance of FENE dumbbells in steady shear flow are given. 相似文献
39.
Summary A summary is given of some recent attempts to relate the results of the kinetic theory of rigid and flexible macromolecules to continuum mechanics results.With 1 table 相似文献
40.
The title compound has been prepared from 1,2,3,4-tetrahydroisoquinoline via successive nitration, acet-ylation, reduction and diazotisation. Earlier conflicting reports on the nitration of tetrahydroisoquinoline have been clarified. A better synthetic route, based upon reduction of the corresponding isocarbostyril, has been devised and should be applicable to the obtention of a wide range of tetrahydroisoquinolines. The structure of the neutral product of oxidative dimerisation of 2-acetyl-7-hydroxy-1,2,3,4-tetrahydroisoquinoline has been established. 相似文献