The Variation of Factor of Enhancement in Nucleation Rate with Electric Field for Water Vapour and Ice

the nucleation rate is the parameter to judge the effect of electric field on nucleation of water vapour and ice glaciation. In the presence of electric field the total nucleation is the sum of nucleation due to electric field and nucleation due to diffusion of water molecules. Thus we can say the nucleation rate is enhanced by the factor of RE. This is known as factor of enhancement in nucleation rate. In the present work we will calculate the factor of enhancement in nucleation rate for water vapour and ice on temperature 268 K at different electric fields as a function of super saturation ratio.

Assessment of the Influence of Water Saturation and Capillary Pressure Gradients on Size Formation of Two-Phase Filtration Zone in Compressed Low-Permeable Reservoir

The paper examines the influence of capillary pressure and water saturation ratio gradients on the size of the two-phase filtration zone during flooding of a low-permeable reservoir. Variations of water saturation ratio s in the zone of two-phase filtration are associated with the pressure variation of water injected into the reservoir; moreover the law of variation of water saturation ratio s(r, t) must correspond to the variation of injection pressure, i.e. it must be described by the same functions, as the functions of water pressure variation, but be subject to its own boundary conditions. The paper considers five options of s(r, t) dependency on time and coordinates. In order to estimate the influence of formation and fluid compressibility, the authors examine Rapoport – Lis model for incompressible media with a violated lower limit for Darcy’s law application and a time-dependent radius of oil displacement by water. When the lower limit for Darcy’s law application is violated, the radius of the displacement front depends on the value of capillary pressure gradient and the assignment of s function. It is shown that displacement front radii contain coefficients that carry information about physical properties of the reservoir and the displacement fluid. A comparison of two-phase filtration radii for incompressible and compressible reservoirs is performed. The influence of capillary pressure gradient and functional dependencies of water saturation ratio on oil displacement in low-permeable reservoirs is assessed. It is identified that capillary pressure gradient has practically no effect on the size of the two-phase filtration zone and the share of water in the arbitrary point of the formation, whereas the variation of water saturation ratio and reservoir compressibility exert a significant influence thereupon.

The role of turbulent fluctuations in aerosol activation and cloud formation

Aerosol indirect effects are one of the leading contributors to cloud radiative properties relevant to climate. Aerosol particles become cloud droplets when the ambient relative humidity (saturation ratio) exceeds a critical value, which depends on the particle size and chemical composition. In the traditional formulation of this problem, only average, uniform saturation ratios are considered. Using experiments and theory, we examine the effects of fluctuations, produced by turbulence. Our measurements, from a multiphase, turbulent cloud chamber, show a clear transition from a regime in which the mean saturation ratio dominates to one in which the fluctuations determine cloud properties. The laboratory measurements demonstrate cloud formation in mean-subsaturated conditions (i.e., relative humidity <100%) in the fluctuation-dominant activation regime. The theoretical framework developed to interpret these measurements predicts a transition from a mean- to a fluctuation-dominated regime, based on the relative values of the mean and standard deviation of the environmental saturation ratio and the critical saturation ratio at which aerosol particles activate or become droplets. The theory is similar to the concept of stochastic condensation and can be used in the context of the atmosphere to explore the conditions under which droplet activation is driven by fluctuations as opposed to mean supersaturation. It provides a basis for future development of cloud droplet activation parameterizations that go beyond the internally homogeneous parcel calculations that have been used in the past.

Drying Shrinkage and Cracking Tendency of Concrete Pavement Mixtures with Variable Packing Densities of Aggregates and Paste Contents

Excessive drying shrinkage, and associated cracking, can lead to serious durability problem in concrete pavements and bridges. In the course of this study, the magnitude of drying shrinkage and cracking potential was evaluated for several concrete pavement mixtures as a function of packing density of the aggregate and paste contents. The results indicated that both, the shrinkage and the cracking potential depend on the volume of voids between aggregate particles (packing density), paste content of concrete mixture, and the paste-aggregate void saturation ratio.

Structure, Magnetic Properties and Magnetization Reversal Processes in Nanocrystalline Pr8Dy1Fe60Co7Mn6B14Zr1Ti3 Bulk Alloy

The present paper presents results concerning on structure, magnetic properties and magnetization reversal processes in the as-cast Pr8Dy1Fe60Co7Mn6B14Zr1Ti3 alloy in the form of 1 mm plate. The XRD studies revealed coexistence of three phases dominant Pr2(Fe,Co)14B and minor �-Fe and Fe3B. The remanence-to-saturation ratio Jr/Js equaled 0.66 and indicated on existence of strong exchange interactions between hard and soft magnetic phases. The analysis of Mrev vs. Mirr dependences, the pinning mechanism was detected in studied alloy.

Structure, Magnetic Properties and Magnetization Reversal Processes in Nanocrystalline Pr8Dy1Fe60Co7Mn6B14Zr1Ti3 Bulk Alloy

The present paper presents results concerning on structure, magnetic properties and magnetization reversal processes in the as-cast Pr8Dy1Fe60Co7Mn6B14Zr1Ti3 alloy in the form of 1 mm plate. The XRD studies revealed coexistence of three phases dominant Pr2(Fe,Co)14B and minor á-Fe and Fe3B. The remanence-to-saturation ratio Jr/Js equaled 0.66 and indicated on existence of strong exchange interactions between hard and soft magnetic phases. The analysis of Mrev vs. Mirr dependences, the pinning mechanism was detected in studied alloy. Keywords: bulk alloys, magnetic properties, magnetization reversal processes

Approaches to determining the critical coefficients of water saturation Burdine formulas taking into account the differences in the limits of integration

The article is devoted to the determination of the critical water saturation ratio productive reservoirs. It is necessary to have information about these coefficients in order to interpret the geophysical research wells at the stage of exploration. The print media publish Burdine formulas, which contain definite integrals, to determine the coefficients that need to be solved. In this case, the upper and lower limits of the integrals in the works of different authors don't completely coincide. The author of this article analyses Burdine formulas, which have been published in various print media, and proposes Burdine formulas without integrals. As a result, it is established that Burdine formulas, which are presented in the work [6], are suitable for real conditions; but there should be taken into account the conditions under which the relative phase permeability of oil and water is equal to 0 and 1.

Adsorption isotherms and nucleation of methane and ethane on an analog of Titan’s photochemical aerosols

In planetary atmospheres, adsorption of volatile molecules occurs on aerosols prior to nucleation and condensation. Therefore, the way adsorption occurs affects the subsequent steps of cloud formation. In the classical theory of heterogeneous nucleation, several physical quantities are needed for gas condensing on a substrate like aerosols, such as the desorption energies of the condensing gases on the substrate and the wetting parameters of the condensed phases on the substrate. For most planetary atmospheres, the values of such quantities are poorly known. In cloud models, these values are often approximately defined from more or less similar cases or simply fixed to reproduce macroscopic observable quantities such as cloud opacities. In this work, we used the results of a laboratory experiment in which methane and ethane adsorption isotherms on tholin, an analog of photochemical aerosols, are determined. This experiment also permits determination of the critical saturation ratio of nucleation. With this information we then retrieved the desorption energies of methane and ethane, which are the quantitative functions describing the adsorption isotherms and wetting parameters of these two condensates on tholin. We find that adsorption of methane on tholin is well explained by a Langmuir isotherm and a desorption energy ΔFo = 1.519 ± 0.0715 × 10−20 J. Adsorption of ethane tholin can be represented by a Brunauer-Emmett-Teller isotherm of type III. The desorption energy of ethane on tholin that we retrieved is ΔFo = 2.35 ± 0.03 × 10−20 J. We also determine that the wetting coefficients of methane and ethane on tholin are m = 0.994 ± 0.001 and m = 0.966 ± 0.007, respectively. Although these results are obtained from experiments representative of the Titan case, they are also of general value in cases of photochemical aerosols in other planetary atmospheres.