Terms Of Such Properties Research Articles

Study of chemical properties of insulation mixtures to be used in high-voltage equipment

Reliable operation of high-voltage oil-filled equipment directly depends on the condition of the insulation. One of the main components of the insulation system is transformer oil, which has been used for more than 120 years. However, in the light of modern requirements for insulating materials, oil is significantly inferior to synthetic esters in terms of such properties as chemical stability, environmental safety and high fire resistance. At present, the mixing of synthetic ester and transformer oil can be considered as one of the ways to improve the properties of the latter. A change in the chemical properties of an insulating liquid during its aging, and, consequently, the formation of various impurities and a change in the structure of its component composition will also affect the electrical insulating characteristics of the liquid dielectric. And the more the liquid is oxidized, the more significantly the electrophysical parameters worsen, including the main parameter — electrical strength (or breakdown voltage).This paper presents the results of a study of the chemical properties of mixtures of oil and synthetic ester during prolonged exposure to elevated temperatures. The assessment of the quality of insulating mixtures was carried out by changing such indicators as optical turbidity, acid value, ester value, peroxide value, surface tension and corrosiveness. Fluid testing results in this study indicate that blending of synthetic ester with aromatic oil at 10% and 20% (v/v) results in mixtures that show signs of a colloidal system. This is evidenced by atypical trends in the diagrams indicating the change in peroxide value, acid value and optical turbidity during their aging at a temperature of 110ºС with free access of air to the surface of the mixture. Increasing the proportion of ester in the mixture to 30% and above leads to stabilization or slowdown of chemical reactions occurring due to thermal-oxidative effects. Under thermal exposure (without air access), the addition of synthetic ester to the aromatic oil in a volume of 30% or more significantly reduces the likelihood of sediment formation due to the destruction and polycondensation of aromatic hydrocarbons in mineral oil.

Non-normality, topological transitivity and expanding families

AbstractWe investigate the behaviour of families of meromorphic functions in the neighbourhood of points of non-normality and prove certain covering properties that complement Montel’s Theorem. In particular, we also obtain characterisations of non-normality in terms of such properties.

The Application of Oak Bark Powder as a Filler for Melamine-Urea-Formaldehyde Adhesive in Plywood Manufacturing

The woodworking industry generates a great amount of bark which has not yet found a wider industrial application. None of the previously conducted research has considered oak bark application (which is one of the most often processed wood species in Poland) as a filler for wood adhesives. Moreover, no studies have determined the properties of bark containing melamine-urea-formaldehyde resin (MUF), which increasingly replaces pure urea-formaldehyde adhesives. Thus, the aim of the study was to determine the possibility of grinded oak bark application as a filler for MUF adhesive in plywood manufacturing. The chemical composition of oak bark was evaluated. Properties of liquid resins, such as viscosity, gel time, pH, and solid content, were determined. Chemical interaction between the filler and resin was assessed with using Fourier-transform infrared (FTIR) spectroscopy. Plywood panels manufactured using MUF adhesive filled with different bark concentrations (10%, 15%, 20%, 25%) were tested in terms of such properties as formaldehyde release and bonding quality. Studies have shown an improvement in liquid resin properties. The course of FTIR spectra did not explain the chemical interaction between the polymer and the filler. The addition of oak bark at a concentration of 15% made it possible to produce plywood panels characterized by reduced formaldehyde release and improved bonding quality.

Electrochemical and Other Transport Properties of Nanoporous Track-Etched Membranes Studied by the Current Switch-Off Technique

Measurements of transient membrane potential after current switch-off have been used to study the electrochemical and other transport properties of nanoporous track-etched membranes (pore diameter of 24 nm) in KCl solutions of various concentrations. Due to their identical straight cylindrical pores within the nanorange, those membranes are a suitable object for the studies of fundamentals of nanofluidics. We have developed a theory, which enabled us to interpret the transients of membrane potential in terms of such properties as the ion transport numbers, the membrane diffusion permeability, and the specific chemical capacity. The fitted values have been further interpreted within the scope of the space-charge model and revealed good self-consistency. The dependence of fitted values of the surface charge density on salt concentration was in agreement with the mechanism of fixed charge formation due to the dissociation of weakly acidic groups, and the surface charge density corresponded well to the measurements by an independent method. Thus, our measurements have revealed a quantitative applicability of standard space-charge model to the description of electrochemical phenomena and electrolyte diffusion in straight cylindrical pores of tens of nanometers in diameter. Proceeding from our data, we could estimate the limiting current densities for our nanofluidic system. They have turned out to be more than 2 orders of magnitude lower than usually encountered in microfluidic systems with electro-osmotic fluid delivery. That finding may point to a considerable handicap in the application of such nanofluidic elements in microsystems.

磁気ディスク用無電解Ｎｉ‐Ｐ皮膜に及ぼす前処理の効果

Thin-film media for increasing the recording density on magnetic hard disks have been obtained by sputtering or plating, and since these media require a comparatively flat substrate, electroless Ni-P plating is employed to harden the surface and facilitate polishing To be used successfully, the process must be satisfactory in terms of such properties as finished final surface roughness, magnetization, and adhesionThe object of the present work is to examine various pretreatments for 5086 Al-alloy, the most common material used for hard disk substrates. Results indicate that the optimum process was one consisting of alkaline non-etch cleaning, hot acid etching and double zincate treatment. This produced a homogeneous and thin zinc film. Though deeper etching improved adhesion, it also increased roughness after plating

EMPIRICAL IDENTIFICATION OF MULTIPLE TIME SERIES

Abstract. In the univariate case the problem of empirical identification consists in determining the order parameters p, d and q of ARIMA (p, d, q) processes. In this paper we introduce some new techniques for handling the corresponding problem for a multiple time series X(t) with the main emphasis on AR and MA models. Types of joint nonstationarity (or rather almost nonstationarity) are defined and a method of analyzing such structures based on the ordered eigenvalues of the function C(t) =K(t)K‐1(0) is discussed, where K(t) is the covariance function of X(t). It is proposed that the further identification procedure should be based on two X2 statistics and on the estimated trace and eigenvalues of C(t), the matrix correlation function p(t) and the matrix partial correlation function P(t). The suitability for identification purposes of each of these functions is examined in terms of such properties as scale‐invariance, existence of normalized eigenvalues and standard errors. The methods introduced are illustrated on a 5‐dimensional economic time series first studied by Quenouille and on a 4‐dimensional smulated MA series.

On the Vitali–Hahn–Saks theorem

SynopsisIn this paper, a class of Boolean rings containing the class discussed in papers by Seever (1968) and Faires (1976), is defined in such a way that an extension of the classical Vitali–Hahn–Saks theorem holds for exhausting additive set functions. Some new compact topological spaces K for which C(K) is a Grothendieck space are constructed and a Nikodym type theorem is deduced from it. The Boolean algebras of Seever and Faires and those we study here are defined by ‘interpolation properties’ between disjoint sequences in the algebra. We give an example at the end of the paper that illustrates the difficulties arising when we try to find a larger class of Boolean algebras, defined in terms of such properties, for which the Vitali–Hanh–Saks theorem holds.

Has Man an Essence?

Much of recent ethics has been thoroughly formalistic in character. In the first place it has confined itself to the investigation of the general logical properties of møral discourse and has largely ignored the broad psychological context of motives and purposes in which that kind of discourse has its life. Secondly, it has sought to distinguish the field of discourse that it takes as its subject-matter in a formalistic way, in terms of such properties as its universalisability, its autonomy and its overridingness, without reference to the concrete and specific human interests with which moral discourse is connected and which it might serve to promote.

Has Man an Essence?

Much of recent ethics has been thoroughly formalistic in character. In the first place it has confined itself to the investigation of the general logical properties of møral discourse and has largely ignored the broad psychological context of motives and purposes in which that kind of discourse has its life. Secondly, it has sought to distinguish the field of discourse that it takes as its subject-matter in a formalistic way, in terms of such properties as its universalisability, its autonomy and its overridingness, without reference to the concrete and specific human interests with which moral discourse is connected and which it might serve to promote.

An experimental computer program for hypothesis selection

An algorithm for finding the characterization of a class of objects on the basis of a randomly ordered sequence of labeled individual objects—some members of the class, some not—is described. The class is characterized as a disjunction of terms, each term being a conjunction of attributes. “All red, round objects or all square, small objects” is an example. Mechanisms based on this algorithm are described in terms of such properties as the amount of storage available for recording instances and the number of instances which had to be examined until the class was first guessed.