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61.
A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively. 相似文献
62.
A. I. Anfinogenov V. V. Chebykin Ya. B. Chernov 《Russian Journal of Electrochemistry》2007,43(8):968-976
Extensive material concerning the interaction of metals in ionic and ionic-electronic salt melts is presented. The mechanism and character of the phenomenon of the directed spontaneous transport of metals by their ions in salt melts are established. Examples of application of this phenomenon for depositing diffusion coatings on metals and alloys (by aluminum, beryllium, boron, zinc, titanium, chromium, silicon, and so on, as well as by two-component coatings) are presented. 相似文献
63.
A three‐dimensional extended finite element method is presented to simulate Stokes flow in complex geometries with internal moving parts. Instead of re‐meshing the flow domain, the kinematics of the internal objects are imposed on the conservation equations using a constraint, implemented with a Lagrangian multiplier. To capture discontinuities of field variables, such as pressure and velocity, on the intersected elements, XFEM is used. To validate our method, it is first applied to a relatively simple problem, that is, the flow around a cylinder in a channel. The results are verified by comparing with a boundary‐fitted solution. After validation of the model and its implementation, the three‐dimensional flow in a twin‐screw extruder is simulated and the results are compared with experimental data from literature. XFEM shows very good accuracy for complex geometries with internal moving parts and narrow gap regions where the shear rate is orders of magnitude higher than in other regions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
64.
Geometrical models have been successfully applied into the calculation of viscosity of alloys. However, traditional geometrical (TG) models are feasible only in systems with a complete solubility area. Otherwise, they will not work. In this paper, a new method has been introduced for the calculation of alloy systems with limited solubility. How the new method overcomes the drawbacks of the TG models is discussed and analysed. The viscosity of two alloy systems with limited solubility is calculated by the present model. Comparisons between the experimental viscosity and the calculated values by different models show that our model gives the best results, especially for the data nearby the limited solubility area. The introduction of this model provides a way to solve the calculation problems of ternary alloys with limited solubility, which will extend geometrical models to more practical systems. 相似文献
65.
Chao Li Feng Jiang Liheng Wu Xiaoyan Yuan Xin Li 《Journal of Macromolecular Science: Physics》2015,54(9):1029-1041
A capillary rheometer with an attached counter pressure chamber was used to determine the effect of pressure on the shear viscosity of several polymer melts, i.e., poly(?-caprolactam) (PA6), poly(ethylene terephthalate) (PET), low-density polyethylene (LDPE), and polypropylene (PP). In order to study the rheological properties of the polymer melts at a constant pressure, the measured values of shear viscosity were recalculated with respect to a series of pressures by the least square fitting based on the Barus equation. Different calculation methods were used to calculate the pressure coefficients from the recalculated viscosity values. The resulting pressure coefficients of the shear viscosity demonstrated that the degree of the pressure dependence was highest for PP, followed by PET and then LDPE. PA6 exhibited the lowest pressure coefficient. 相似文献
66.
G. Peng J.-U. Sommer A. Blumen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):73-79
We investigate numerically, using the bond-fluctuation model, the adsorption of many random AB-copolymers with excluded volume
interactions at the interface between two solvents. We find two regimes, controlled by the total number of polymers. In the
first (dilute) regime, the copolymers near the interface extend parallel to it, while in the second regime they extend perpendicular
to it. The density at the interface and the density in the bulk depend differently on the total number of copolymers: In the
first regime the density at the interface increases more rapidly than in the bulk, whereas the opposite is true in the second
regime.
Received 4 March 1998 and Received in final form 22 September 1998 相似文献
67.
Single crystals of chromium-doped LiCAF and LiSAF can be grown from nearly stoichiometric melts of the components LiF, AlF3, CrF3 and CaF2 or SrF2, respectively, by the Czochralski method. The optical quality of LiSAF crystals is usually better, as LiCAF contains more scattering particles. This different behavior can be attributed to different thermodynamic properties of both substances: The higher melting point of LiCAF leads to higher evaporation losses of volatile LiF and AlF3. Moreover, LiCAF melts incongruently. The main problem during the growth and application of LiSAF crystals is the highly anisotropic thermal expansion that may lead to thermal cracking. The extreme hygroscopicity of the doping agent CrF3 has to be considered for the growth of both substances. 相似文献
68.
O.?M.?ShabanovEmail author R.?Kachaev A.?Iskakova M.?Babaeva S.?M.?Gadzhiev 《Russian Journal of Electrochemistry》2009,45(2):231-234
It is found that conductivity of molten ZnCl2 grows at the increase of the electric field intensity and tends to the limiting values at the overintensities of the order of magnitude of MV/m. This dependence is studied in three temperature ranges characteristic of this melt. The relative conductivity growth after achieving limiting intensity values decreases at the temperature increase from 97.3% at 600 K to 28.2% at 900 K. The obtained regularities confirm the melt cluster structure of intermediate order. 相似文献
69.
Specific conductivity of molten salt mixtures of the LiF-ZrF4, NaF-ZrF4, KF-ZrF4, RbF-ZrF4, and CsF-ZrF4 systems is measured in the whole concentration range using the reference capillary technique. The results are presented in the form of equations of the χ = a + bT + cT 2 [S m?1] type. The concentration dependences of molar conductivity are calculated on the basis of the density data. The obtained regularities are explained in the terms of the complex model of ion melt structures. 相似文献
70.
The partial molar enthalpies of mixing of NaHSO4 and KHSO4 have been measured at 528 K by dropping samples of pure compounds into molten mixtures of NaHSO4 and KHSO4 in Calvet calorimeter. From these values the molar enthalpy of mixing has been deduced.
The same method has been used for the determination of the heat capacity of the two pure compounds in the solid and liquid
states.
The phase diagram of this system has been confirmed by conductometric and thermal analysis methods.
By an optimization method the excess entropy of the liquid mixtures was also calculated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献