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71.
The majority of previous studies of the hydration of cements using heat flow calorimetry have been carried out isothermally. However, with oilwell cements the slurry is mixed on the surface at ambient temperature and then gradually increases in temperature as it is pumped down the well. A Setaram C-80 calorimeter has been used to simulate the temperature ramp in API oilwell cement test schedules. This approach has enabled cementing reactions to be studied for the first time under conditions approaching those encountered in the field, and has shown that the results obtained from isothermal experiments may be misleading.The permission of the British Petroleum Company PLC to publish this paper is gratefully acknowledged. 相似文献
72.
S. A. Savkov 《Fluid Dynamics》2003,38(3):501-506
A dependence of the heat transfer between coaxial cylinders on the energy accommodation coefficient is obtained. The known methods of solving a kinetic equation are compared. 相似文献
73.
We study elliptic systems of strongly nonlinear first-order differential equations in complex form on the plane. For such systems we develop the theory of Hilbert boundary value problems which is very much similar to the well-known theory for a holomorphic vector. Systems of nonlinear elliptic equations describe problems of interaction of several nonlinear stationary processes in the diffusive and convective mass and heat transport by hydrodynamic fluid flows. 相似文献
74.
Heat Kernel Asymptotics of Zaremba Boundary Value Problem 总被引:1,自引:0,他引:1
The Zaremba boundary-value problem is a boundary value problem for Laplace-type second-order partial differential operators
acting on smooth sections of a vector bundle over a smooth compact Riemannian manifold with smooth boundary but with discontinuous
boundary conditions, which include Dirichlet boundary conditions on one part of the boundary and Neumann boundary conditions
on another part of the boundary. We study the heat kernel asymptotics of Zaremba boundary value problem. The construction
of the asymptotic solution of the heat equation is described in detail and the heat kernel is computed explicitly in the leading
approximation. Some of the first nontrivial coefficients of the heat kernel asymptotic expansion are computed explicitly.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
75.
Finite chains of a two-state random Potts spin model with periodic boundary conditions are studied within Glauber dynamics. The spin exchange is assumed random with frustration between ferro and antiferromagnetic values (±J). Time-dependent fluctuations are induced by periodic temperature oscillations. Master type differential equations for spin correlation functions are solved within linear response theory. The spectrum of relaxation times are calculated at different temperatures. The ±J Potts glass chains undergo a zero temperature phase transition. The barriers against inversion of the spin chain take only two values; 0 and 2|J|. The temperature behaviour of specific heat is characterized by rounded peaks. The frequency dependence displays two plateaus for the real part of specific heat and two corresponding peaks for the imaginary part. The dynamic specific heat is not affected by the longest relaxing mode like susceptibility. The time separation of the modes is demonstrated by the Cole-Cole plots. 相似文献
76.
潜热型热功能流体强化换热分析 总被引:4,自引:0,他引:4
本文建立了分析带有相变微胶囊的潜热型热功能流体的流动和换热过程数理模型,应用有限差分法和移动热源法进行联合求解。计算结果表明,相变微胶囊的加入:较好地提高了流体的换热性能。获得了相变颗粒大小和体积分数对强化换热影响等结果。计算结果对该类流体的设计和应用提供了理论依据。 相似文献
77.
Taking both the heterogeneous catalytic processes, including the surface formation of particles with excited internal degrees of freedom, and the processes of multicomponent diffusion and heat transfer in the MESOX apparatus fully into account makes it possible to obtain a recombination coefficient and an accommodation coefficient of the oxygen-atoms-on-quartz recombination energy which are in good agreement with the experimental data. The heterogeneous catalysis model constructed can be used effectively for predicting the heat fluxes to the surface of reentry vehicles on their entry into the Earth’s atmosphere. 相似文献
78.
79.
80.
A 27Al nuclear magnetic resonance (NMR) investigation at room temperature of the Pb1 − xAlxF2 + x (0 ≤ x ≤ 0.12) solid solution and of the ordered Pb9Al2F24 phase is carried out. Two different types of aluminium ions are identified and their ratio is determined as a function of x. A clustering process based on the formation of column clusters, more and more extended when x increases, is proposed on the basis of results issued from the 19F (Part I) and 27Al NMR investigations. 相似文献