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991.
Shengqiang Cai 《Journal of the mechanics and physics of solids》2011,59(11):2259-2278
This paper uses the thermodynamic data of aqueous solutions of uncrosslinked poly(N-isopropylacrylamide) (PNIPAM) to study the phase transition of PNIPAM hydrogels. At a low temperature, uncrosslinked PNIPAM can be dissolved in water and form a homogenous liquid solution. When the temperature is increased, the solution separates into two liquid phases with different concentrations of the polymer. Covalently crosslinked PNIPAM, however, does not dissolve in water, but can imbibe water and form a hydrogel. When the temperature is changed, the hydrogel undergoes a phase transition: the amount of water in the hydrogel in equilibrium changes with temperature discontinuously. While the aqueous solution is a liquid and cannot sustain any nonhydrostatic stress in equilibrium, the hydrogel is a solid and can sustain nonhydrostatic stress in equilibrium. The nonhydrostatic stress can markedly affect various aspects of the phase transition in the hydrogel. We adopt the Flory-Rehner model, and show that the interaction parameter as a function of temperature and concentration obtained from the PNIPAM-water solution can be used to analyze diverse phenomena associated with the phase transition of the PNIPAM hydrogel. We analyze free swelling, uniaxially and biaxially constrained swelling of a hydrogel, swelling of a core-shell structure, and coexistent phases in a rod. The analysis is related to available experimental observations. Also outlined is a general theory of coexistent phases undergoing inhomogeneous deformation. 相似文献
992.
A Discussion of the Effect of Tortuosity on the Capillary Imbibition in Porous Media 总被引:2,自引:0,他引:2
In the past decades, there was considerable controversy over the Lucas–Washburn (LW) equation widely applied in capillary
imbibition kinetics. Many experimental results showed that the time exponent of the LW equation is less than 0.5. Based on
the tortuous capillary model and fractal geometry, the effect of tortuosity on the capillary imbibition in wetting porous
media is discussed in this article. The average height growth of wetting liquid in porous media driven by capillary force
following the [`(L)] s(t) ~ t1/2DT{\overline L _{\rm {s}}(t)\sim t^{1/{2D_{\rm {T}}}}} law is obtained (here D
T is the fractal dimension for tortuosity, which represents the heterogeneity of flow in porous media). The LW law turns out
to be the special case when the straight capillary tube (D
T = 1) is assumed. The predictions by the present model for the time exponent for capillary imbibition in porous media are
compared with available experimental data, and the present model can reproduce approximately the global trend of variation
of the time exponent with porosity changing. 相似文献
993.
994.
Cai Liang Xiaoping ChenPan Xu Bo LiuChangsui Zhao Chuanlong Xu 《Experimental Thermal and Fluid Science》2011,35(6):1143-1150
During the pneumatic conveying, pulverized coal with different moisture contents may develop substantial difference in flow characteristics, whose cause is not fully understood. This study focused on influence of moisture content on conveying characteristics in an experimental test facility with the conveying pressure up to 4 MPa. The experiments included soft coal and lignite with similar density and particle size. With the increase in moisture content, the mass flow rate decreased for lignite (3.24% < M < 8.18%) but increased at first and then decreased for soft coal (0.4% < M < 6.18%) at same operating parameters. The flowability of soft coal was worse than that of lignite at similar operating parameters and external moisture content. The extremal conveying moisture contents of two coal types were obtained. The particle charge and surface moisture content were investigated to indicate influence mechanism of moisture content on mass flow rate in pneumatic conveying at high pressure. Pressure drop of soft coal was greater than that of lignite for same test section. The conveying phase diagram of dense-phase pulverized coal at high pressure was obtained and the pressure drops through different test sections were compared and analyzed. The bend loss factor rose with the increase in moisture content and was independent of conveying velocity and solid-gas ratio in dense-phase pneumatic conveying at high pressure. 相似文献
995.
Guang-hui Cai 《Czechoslovak Mathematical Journal》2011,61(1):27-40
In this paper we obtain a strong invariance principle for negatively associated random fields, under the assumptions that the field has a finite (2 + δ)th moment and the covariance coefficient u(n) exponentially decreases to 0. The main tools are the Berkes-Morrow multi-parameter blocking technique and the Csörg?-Révész quantile transform method. 相似文献
996.
We give new generalizations of some q-series identities of Dilcher and Prodinger related to divisor functions. Some interesting special cases are also deduced,
including an identity related to overpartitions studied by Corteel and Lovejoy. 相似文献
997.
In the present paper, we investigate the dual Lie coalgebras of the centerless W(2, 2) algebra by studying the maximal good subspaces. Based on this, we construct the dual Lie bialgebra structures of the centerless W(2, 2) Lie bialgebra. As by-products, four new infinite dimensional Lie algebras are obtained. 相似文献
998.
Mathematische Zeitschrift - We show that if the base frequency is Diophantine, then the Lyapunov exponent of a $$C^{k}$$ quasi-periodic $$SL(2,{\mathbb {R}})$$ cocycle is... 相似文献
999.
In this paper it is proved that every sufficiently large even integer N satisfying one of the congruence conditions N ≡ 10, 58, 130, or 178(mod 240) may be represented as the sum of one square and nine fourth powers of prime numbers. 相似文献
1000.
Science China Mathematics - Owing to its efficiency in solving some types of large-scale separable optimization problems with linear constraints, the convergence rate of the alternating direction... 相似文献