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1.
2.
Although multiple models now exist for predicting the linear viscoelasticity of a polydisperse linear polymer from its molecular
weight distribution (MWD) and for inverting this process by predicting the MWD from the linear rheology, such inverse predictions
do not yet exist for long-chain branched polymers. Here, we develop and test a method of inverting the dual-constraint model
(Pattamaprom et al., Rheol Acta 39:517–531, 2000; Pattamaprom and Larson, Macromolecules 34:5229–5237, 2001), a model that
is able to predict the linear rheology of polydisperse linear and star-branched polymers. As a first step, we apply this method
only to polydisperse linear polymers, by comparing the inverse predictions of the dual-constraint model to experimental GPC
traces. We show that these predictions are usually at least as good, or better than, the inverse predictions obtained from
the Doi–Edwards double-reptation model (Tsenoglou, ACS Polym Prepr 28:185–186, 1987; des Cloizeaux, J Europhys Lett 5:437–442,
1988; Mead, J Rheol 38:1797–1827, 1994), which we take as a “benchmark”—an acceptable invertible model for polydisperse linear
polymers. By changing the predefined type of molecular weight distribution from log normal, which has two fitting parameters,
to GEX, which has three parameters, the predictions of the dual-constraint model are slightly improved. These results suggest
that models that are complex enough to predict branched polymer rheology can be inverted, at least for linear polymers, to
obtain molecular weight distribution. Further work will be required to invert such models to allow prediction of the molecular
weight distribution of branched polymers. 相似文献
3.
V. V. Ostapenko A. A. Malysheva 《Journal of Applied Mechanics and Technical Physics》2006,47(2):157-168
The solvability of the problem of the flows resulting from the incidence of a discontinuous wave on a bottom step is studied
using a single-layer shallow water model. Solutions in which the total energy of the flow is conserved at the step and those
in which it is lost at the step are considered. Regions of double and triple hystereses in the obtained self-similar solutions
are found. An analogy is drawn with the problem of single-layer flow over a bottom obstacle.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 8–22, March–April, 2006. 相似文献
4.
M. F. Selivanov 《International Applied Mechanics》2010,46(7):799-805
The time variation in the stresses around an elliptic hole in a composite plate is studied. Solutions that characterize the
effect of the time dependence of the relaxation moduli of the composite components on stresses are obtained. The solutions
in the time domain are obtained from the elastic–viscoelastic analogy and the corresponding elastic solutions for the effective
moduli of the composite and the stress field around an elliptic hole in an anisotropic plate. The inverse Laplace transformation
is carried out by an effective numerical method 相似文献
5.
V. Sh. Shagapov A. Sh. Sultanov S. F. Urmancheev 《Journal of Applied Mechanics and Technical Physics》2006,47(5):628-636
Solutions of the problem of reflection of a stepwise pressure wave in a linearly compressed fluid from a flat boundary of
a porous medium of infinite length saturated by the same fluid are obtained in the acoustic approximation. Based on analytical
solutions, a numerical analysis is performed to reveal the specific features of the reflected and incident waves, depending
on porosity and permeability of the porous half-space.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 16–26, September–October, 2006. 相似文献
6.
B. A. Lugovtsov 《Journal of Applied Mechanics and Technical Physics》2000,41(5):870-878
The stability of steady axisymmetricMHD flows of an inviscid, incompressible, perfectly conducting fluid with respect to swirling—perturbations of the azimuthal
components of the velocity field—is studied in a linear approximation. It is shown that for flows similar to a magnetohydrodynamic
Hill-Shafranov vortex, the problem reduces to a one-dimensional problem on a closed streamline of the unperturbed flow (the
arc length of the streamline is the spatial coordinate). A spectral boundary-value eigenvalue problem is formulated for a
system of two ordinary differential equations with periodic coefficients and periodic boundary conditions. Sufficient conditions
under which swirling is impossible are obtained. Numerical solution of the characteristic equation shows that, under certain
conditions, for each streamline there is a real eigenvalue that yields monotonic exponential growth of the initial perturbations.
Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 5, pp. 120–129, September–October, 2000. 相似文献
7.
The problem of the influence of bracing struts of two types on the aeroelastic stability of a wing is studied. The formulation
of the problem follows that considered by M. V. Keldysh [1]. The behavior of the eigenvalues is studied in the complex plane
and the stability, flutter, and divergence domains are constructed.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 151–162, January–February,
1998. 相似文献
8.
D. N. Gorelov 《Journal of Applied Mechanics and Technical Physics》2007,48(2):184-191
A general formulation of a nonlinear initial-boundary problem of an unsteady separated flow around an airfoil by an ideal
incompressible fluid is considered. The problem is formulated for a complex velocity. Conditions of shedding of vortex wakes
from the airfoil are analyzed in detail. The proposed system of functional relations allows constructing algorithms for solving
a wide class of problems of the wing theory.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 48–56, March–April, 2007. 相似文献
9.
S. P. Bautin 《Journal of Applied Mechanics and Technical Physics》2000,41(3):421-428
Three initial-boundary-value problems for the equations of gas dynamics are formulated. Successive solution of these problems
yields a solution of Kraiko's problem of the isentropic transition of an ideal gas from a homogeneous state of rest to another
state of rest with higher or lower density. Solutions are constructed for plane, cylindrical, and spherical layers of an ideal
gas. The existence of locally analytic solutions is proved.
Ural State Academy of Service, Ekaterinburg 620034. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41,
No. 3, pp. 48–55, May–June, 2000. 相似文献
10.
A method of solving the problem of the motion of a cylinder of given shape below the free surface of an infinitely deep heavy
fluid is perfected for large Froude numbers. The motion of a circular cylinder is investigated at small distances from the
free surface. Solutions of the problem are given for cylinders with noncircular cross-sections.
Kazan. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 34–45, July–August, 2000.
The work was carried out with financial support from the Russian Foundation for Basic Research (projects Nos. 99-01-00169
and 99-01-00173). 相似文献
11.
V. A. Saraikin 《Journal of Applied Mechanics and Technical Physics》1999,40(5):903-907
Equations are derived for stress concentration near a crack of closed contour lying in a plane. A system of one-dimensional
integral equations for the concentration factor is obtained. The right sides of the equations contain the initial approximation—a
solution of the problem of a circular crack whose sides are acted upon by nonaxisymmetric loading.
Mining Institute, Siberian Division, Russian Academy of Sciences, Novosibirsk 630091. Translated from Prikladnaya Mekhanika
i Tekhnicheskaya Fizika, Vol. 40, No. 5, pp. 143–148, September–October, 1999. 相似文献
12.
N. F. Vorob'ev 《Fluid Dynamics》1979,14(5):726-735
A correspondence between the solutions of the direct and the inverse problem for wing theory is established for a wing of finite span in the framework of linear theory on the basis of solution of a wave equation in Volterra form for supersonic flow and solution of the Laplace equation in the form of Green's formula for subsonic flow. For the direct problem in the case of supersonic flow an expression is derived for finding the load on the wing with maximal allowance for the wing geometry. In the inverse problem for supersonic and subsonic flows, expressions are derived for finding the wing geometry from given values of the load on the wing and the variation of the load along the span of the wing. The solution of the inverse problem is presented in the form of integrals that converge for interior points of the wing surface in the sense of the Cauchy principal value, the wing surface being represented as a vortex surface of mutually orthogonal vortex lines. The conditions of finiteness of the velocities on the edges are discussed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 114–125, September–October, 1979. 相似文献
13.
A variational technique of obtaining the optimal shape of a low-aspect-ratio wing with allowance for the nonequilibrium character
of the flow is developed. The technique is applied to the problem of determining optimal wing shapes under terrestrial atmosphere
conditions. The real-gas effect on the optimal shapes and maximum lift-drag ratio is studied.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 160–170, March–April, 2000.
The study was carried out with the support of the Russian Foundation for Basic Research (project No. 96-01-00629). 相似文献
14.
B. A. Lugovtsov 《Journal of Applied Mechanics and Technical Physics》1998,39(6):847-849
A plane analog of the problem of spontaneous swirling—the occurrence of a free transverse flow due to disturbance of the initial
plane-parallel flow—is considered. It is shown that in flows with circular streamlines between coaxial cylinders, loss of
stability can result in the occurrence of axial flow that is axisymmetric on the average (averaging over the axial coordinate
and the azimuthal angle) because of the countergradient transfer of the axial momentum component by Reynolds stresses.
Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 33–36, November–December, 1998. 相似文献
15.
The problem of stabilizing the axis of a solid by coupled perfectly rigid bodies (PRBs) is solved. The solid executes a plane-parallel
motion. The PRBs can rotate as a single rigid body about the centroidal axis of the solid and counterrotate about its transverse
axes through equal angles. There is a particle inside the solid which causes its imbalance. It is established that the principal
state (if any) of the system—rotation about the centroidal axis—is stable, whereas the rest (unwanted) states are unstable
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 8, pp. 122–129, August 2005. 相似文献
16.
An approach to the solution of problems of the statics of shallow orthotropic shells is proposed. It is based on reducing
a two-dimensional boundary value problem to a one-dimensional one using the spline-collocation method and solution of the
problem by the stable numerical method of discrete orthogonalization. Solutions are presented for problems on the stress state
of orthotropic shells of double curvature for several values of the elastic constants of the material.
Translated from Prikladnaya Mekhanika, Vol. 36, No. 7, pp. 60–66, July, 2000. 相似文献
17.
A computational thermo-metallographic and thermoelastoplastic model for the analysis of the quenching process is developed
and validated. The diffusive transfor-mations are modeled according to the Johnson–Mehl–Avrami–Kolmogorov model and the Scheil’s
additivity rule. Two different models are investigated for the non-diffusive transformation—the Koistinen–Marburger model
and the Yu model. A large displacement formulation is assumed for the deformation analysis, modeling the plastic behavior
of the material according to the Prandtl–Reuss model. Two different bilinear hardening models—the isotropic and the kinematic
hardening model—are used and compared. The model allows to evaluate the transient stress and strain distributions during the
quenching process, the final phases and hardness distributions, and to predict the residual stress and the final deformation
of the processed part. A good agreement between computational results and reference data is found 相似文献
18.
K. Cabanska-Placzkiewicz 《International Applied Mechanics》2000,36(5):673-681
Dynamic analysis of sandwich beams is performed. The external layers are modeled as beams on the basis of the Timoshenko model,
and the internal layer possesses the characteristics of Winkler's viscoelastic one-directional base. The free vibrations are
described by a homogeneous system of conjugate partial differential equations. After separation of variables in the system
of differential equations, the boundary problem is solved and four complex sequences—a frequency sequence and a sequence of
free-vibration modes—are obtained. The orthogonality of the complex modes of the free vibration is demonstrated. The free-vibration
problem is solved under arbitrary initial conditions. The results of computations conducted for different sandwich beams with
different parameters are presented.
Pedagogical University, Bydgoszcz, Poland. Published in Prikladnaya Mekhanika, Vol. 36, No. 5, pp. 122–130, May, 2000. 相似文献
19.
G. I. Maikapar 《Fluid Dynamics》1998,33(4):598-603
The shape of a waverider formed by streamsurfaces behind oblique shocks and rarefaction waves is complicated by equipping
the lifting body with a wing and fins. The joining of the wing to the body and the possibility of reducing the wave drag are
considered.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 158–165, July–August, 1998. 相似文献
20.
The convective instability of mechanical equilibrium of an inclined plane layer of fluid developing under the action of a
static gravity field and high-frequency vibration is studied. Configurations corresponding to four directions of the equilibrium
temperature gradient — vertical, longitudinal, horizontal, and transverse — are considered for an arbitrary orientation of
the vibration axis. The stability limits and the characteristics of the critical perturbations are determined.
Perm’. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 8–15, January–February,
1998.
This investigation was carried out with partial support form RSA-NASA (contract No. 920/18 — 5208/96). 相似文献