Methods for determining the permeability of an orthotropic medium

Various methods are considered for determining the permeability of an orthotropic medium with a view to modeling the filtration process on the basis of the flow continuity equation and Darcy??s hypothesis of the gradient character of pressure fields in filtered flows.     

Evaporative Cooling of 3He-4He Mixture Films

Heat transport by saturated ³ He- ⁴ He films has been studied at temperatures 50..350 mK and the bulk concentration of ³ He ranging from 0.1 ppm to 5%. The cooling of the film, when locally heated above 160 mK, is mainly via 2D flow of surface ³ He from colder area followed by evaporation of ³ He. At certain heating power the 2D flow becomes a bottleneck, the heated spot runs out of ³ He and its temperature abruptly increases. The critical power is nearly proportional to the surface density of ³ He. For higher ³ He concentrations another distinct step in temperature has been observed at a lower heating power. It is attributed to the existence of an excited ³ He surface state whose population starts at ³ He surface density of 3.5×10 ¹⁴ cm^–2 . The second state is located about 1.2 K higher in energy than the ground state and provides an additional channel for the 2D flow of ³ He.     

Mathematical modeling for impregnation of reinforcing filler of fiberglasses during vacuum infusion

Composite products under vacuum infusion are formed by impregnating a reinforcing filler with resin by means of a vacuum. The task of designing the infusion process involves the development of a system of infusion. A mathematical model of the impregnation process which allows carrying out virtual technological experiments in order to find the optimal method of product impregnation is described. Examples of numerical simulation are given.     

Analytical theory of regenerative heat transfer and study of its thermodynamic efficiency

An analytical theory of the cyclic process of regenerative heat transfer is developed. Introduction of operator-valued functions of integral operators allowed the authors to formulate an equation for determination of periodic solutions. A solution of this equation is found in a linear approximation with respect to switching times. A functional — exergic efficiency — is introduced on periodic solutions. The analytical solution obtained made it possible to study the dependence of the introduced criterion on the parameters of the system and to describe the time mode of the process in which the thermodynamic efficiency is maximum. Comparison of the analytical theory and a numerical analysis of the problem showed that upon choosing an operating mode of the apparatus that fits the maximum values of the introduced criterion, one can use results of the analytical solution at all admissible values of the switching times. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 237–243, March–April, 2000.     

Pulverized-coal injection in blast furnaces at OAO Zaporozhstal’

Information is provided regarding the conversion of blast furnaces at OAO Zaporozhstal’ to pulverized-coal injection, with gradual reduction in the consumption of coke and natural gas. Since the introduction of a Kuttner pulverized-coal system in early 2013, coke consumption has decreased from 492 to 393 kg/t, with increase in productivity from 7719 to 8779 t/day.     

Doping Effects on the Properties of BaTiO3-Based Solid Solutions

The effect of Fe₂O₃ additions on the electrical properties and microstructure of yttria-doped barium titanate ceramics was studied by resistivity measurements and electron microscopy. Doping with 0.05 mol % Fe₂O₃ markedly increases the resistivity of the ceramics. The Fe atoms are nonuniformly distributed between BaTiO₃ and the grain-boundary phase Ba₆Ti₁₇O₄₀.     

Weak Password Security: An Empirical Study

ABSTRACT

Portable Document Format (PDF) is a file format developed by Adobe Systems for representing documents in a manner that is independent of the original application software, hardware, and operating system. A PDF file can describe documents containing any combination of text, graphics, and images in a device independent and/or resolution independent format. It is now used everywhere across academic, technical, and governmental institutions. For secure communication, this platform and hardware independent file can be used as a secure cover media for voluminous data concealing. The methods develop so far for data hiding in PDF files satisfy low-embedding characteristics. In this work, we have developed two techniques. The first searches trash spaces in the PDF file and replaces them with the encrypted secret data. The second technique is useful for storing voluminous encrypted secret data without disturbing any format, features, or characteristics of the file. The practical implementation of this has been done on Microsoft platform. Experimental results show the feasibility of the proposed techniques.